Applied Catalysis B, Environmental (v.91, #1-2)
Editorial Board (CO2).
Editorial Board (i).
Progress in development of direct dimethyl ether fuel cells by Alexey Serov; Chan Kwak (1-10).
The present review summarizes recent research achievements related to the use of alternative fuel (specifically, dimethyl ether) in portable fuel cell devices. This review discusses the development of new electrocatalysts for successful dimethyl ether (DME) oxidation, the preparation and performance of membrane electrode assemblies (MEAs) and the effects of different fuel cell operation conditions The mechanisms of processes occurring at the anode and cathode are described, as shown in the literature. Different MEA structures are suggested for the purpose of altering the catalytic activity of anode catalysts and thereby improving the power output of direct DME fuel cells.
Keywords: Dimethyl ether; Fuel cell; Anode; Catalyst;
Creation of three-dimensionally ordered macroporous Au/CeO2 catalysts with controlled pore sizes and their enhanced catalytic performance for formaldehyde oxidation by Jun Zhang; Ying Jin; Changyan Li; Yuenian Shen; Li Han; Zhongxue Hu; Xiaowei Di; Zhiliang Liu (11-20).
Three-dimensionally ordered macroporous (3DOM) Au/CeO2 catalysts with controlled pore sizes are successfully created via a colloidal crystal template method, and their enhanced catalytic performance for formaldehyde oxidation is systematically investigated for the first time in this paper. The resulting Au/CeO2 catalysts possess well-defined 3DOM structures with adjustable pore sizes from 80 to 280 nm, having interconnected networks of spherical voids. Due to the uniform macroporous structures leading to good distribution of catalytic species of Au nanoparticles with less aggregation, the 3DOM Au/CeO2 catalysts are expected to have enhanced capability for formaldehyde catalytic oxidation. The formaldehyde oxidation tests reveal that the 3DOM Au/CeO2 catalysts exhibit superior catalytic activity with 100% formaldehyde conversion at ∼75 °C, a much lower temperature than previously reported powder Au/CeO2 catalysts. The superior performance of 3DOM Au/CeO2 catalysts for formaldehyde oxidation makes them potentially applicable to in-door formaldehyde decontamination and industrial catalysis.
Keywords: Three-dimensionally ordered macroporous; Au/CeO2 catalysts; Catalysis; Formaldehyde oxidation;
Intrazeolite cobalt(0) nanoclusters as low-cost and reusable catalyst for hydrogen generation from the hydrolysis of sodium borohydride by Murat Rakap; Saim Özkar (21-29).
Intrazeolite cobalt(0) nanoclusters were prepared by ion-exchange of Co2+ ions with the extraframework Na+ ions in the zeolite-Y followed by the reduction of Co2+ ions in the supercages of zeolite-Y with sodium borohydride at room temperature. The intrazeolite cobalt(0) nanoclusters were isolated as solid materials and characterized by ICP-OES, XRD, HRTEM, SEM, XPS, Raman spectroscopy and N2 adsorption technique. The catalytic activities of intrazeolite cobalt(0) nanoclusters in the hydrolysis reaction of sodium borohydride solution in the absence or presence of added base were studied. They are found to be more active in basic solution than in aqueous solution without added base. They provide 36,000 total turnovers and a turnover frequency up to 880 mol H2 (mol Co)−1 h−1 in the hydrolysis of basic sodium borohydride solution at 25.0 ± 0.1 °C. The improved hydrogen generation rate, hydrogen generation efficiency, lower activation energy and the low cost make the intrazeolite cobalt(0) nanoclusters promising candidate as catalyst for the hydrogen generation from basic sodium borohydride solution.
Keywords: Zeolite; Cobalt; Nanoclusters; Sodium borohydride; Hydrolysis; Hydrogen;
Is oxygen storage in three-way catalysts an equilibrium controlled process? by Roman Möller; Martin Votsmeier; Christopher Onder; Lino Guzzella; Jürgen Gieshoff (30-38).
Existing reaction mechanisms for three-way catalysts ignore the oxidation of Ce2O3 by H2O or CO2 and therefore treat oxygen storage on ceria as a kinetically controlled non-equilibrium process. Such mechanisms do not correctly reproduce a number of practically important phenomena.Based on transient concentration step experiments, this paper demonstrates that the oxidation of reduced ceria by H2O or CO2 plays an important role for the understanding of the oxygen storage dynamics. The results of the step experiments are well reproduced by a simple three-reaction kinetic model that takes into account the equilibrium character of oxygen storage.All these effects are explained and quantitatively predicted by the equilibrium based oxygen storage model.
Keywords: Ceria; Three-way catalyst; Oxygen storage; Simulation; Reaction mechanism;
W-doped titania nanoparticles for UV and visible-light photocatalytic reactions by Olivier Lorret; Denisa Francová; Georg Waldner; Nils Stelzer (39-46).
Nanocrystalline tungsten doped titanium dioxide powders were prepared by a sol–gel method based on hydrolysis of TiCl4 in aqueous solution. Addition of W was done to extend light absorption of the TiO2-based photocatalysts towards the visible light range. Different tungsten precursors and contents were investigated, regarding their photocatalytic properties and activity. Their photocatalytic activity was measured via degradation of methylene blue (MB) in aqueous solution under ultraviolet (UVA) or visible light. Highest activity was observed for sol–gel samples calcined at 773 K, due to full removal of chloride and increase of crystallite size by thermal treatment. Activity of Ti(W)O x sol–gel photocatalysts under UVA strongly depends on the tungsten content (maximum reached for a ratio between 1 and 2 mol%) and the precursor choice (WCl6 > (NH4)6H2W12O40 > H2WO4). Under visible-light, activity increases with W content.
Keywords: Sol–gel Ti(W)O x photocatalysts; Nanoparticles; Visible light; Methylene blue;
Detailed surface reaction mechanism for Pt-catalyzed abatement of automotive exhaust gases by J. Koop; O. Deutschmann (47-58).
A modeling and simulation study on Pt-catalyzed conversion of automotive exhaust gases is presented. The model is based on a newly developed surface reaction mechanism consisting of 73 elementary-step like reactions among 22 surface and 11 gas-phase species. Reactions for the conversion of the major pollutants CO, CH 4 , C 3 H 6 , and NO x are included. The mechanism is implemented in a two-dimensional flow field description of a single channel of the catalytic monolith. The model is evaluated by comparison with data derived from isothermal laboratory experiments in a flat bed reactor with platinum-coated monoliths using synthetic lean/rich cycling exhaust gas mixtures. The influence of CO and C 3 H 6 at lean and H 2 at rich conditions on NO conversion is investigated, both at steady-state conditions. Furthermore, the model is also applied for the simulation of emissions of hydrocarbons, CO, and NO from a gasoline engine (stoichiometric exhaust gas) in a dynamic engine test bench.
Keywords: Modeling; Platinum; Catalysis; Reaction mechanism; Automotive pollutants; Nitrogen oxides; DETCHEM;
Photocatalytic degradation of Allura red and Quinoline yellow with Polyaniline/TiO2 nanocomposite by Mohamed A. Salem; Ahmed F. Al-Ghonemiy; Ahmed B. Zaki (59-66).
A series of polyaniline/TiO2 (PANI/TiO2) composites has been prepared from aniline and TiO2 under various polymerization conditions. Among these conditions are the concentrations of aniline, ammonium persulfate, HCl, sodium dodecyl sulfate, and the amount of TiO2. More composites were obtained by replacing HCl with H2SO4, H3PO4, and HNO3 as dopant acids. Scanning electron microscopy, UV/vis-diffuse reflectance spectroscopy, FTIR and TGA were used to characterize some of these composites. The rate of degradation of dyes with these composites followed first-order kinetics in the dye concentration. The activity of the composite towards the degradation process differs according to the experimental polymerization conditions. The activity increased with the increase in the concentration of aniline monomer and persulfate, but decreased with increasing the concentration of HCl, sodium dodecyl sulfate, and the amount of TiO2. The activity of composites formed in the presence of different acids followed the order H2SO4 > H3PO4 > HCl > HNO3. The rate of composite/dye interaction was enhanced with the UV-irradiation, increasing load of composite, and temperature. It was retarded with the increase in initial dye concentration and pH. The activation parameters were determined and a plausible mechanism was proposed.
Keywords: PANI/TiO2; Nancomposite; Degradation; Kinetics; Allura red; Quinoline yellow;
Hydroxide ZnSn(OH)6: A promising new photocatalyst for benzene degradation by Xianliang Fu; Xuxu Wang; Zhengxin Ding; Dennis Y.C. Leung; Zizhong Zhang; Jinlin Long; Wenxin Zhang; Zhaohui Li; Xianzhi Fu (67-72).
Cube-shaped hydroxide ZnSn(OH)6 (ZHS) has been synthesized by a solvothermal process. The obtained sample was characterized by X-ray diffraction (XRD), N2-sorption (BET surface area), UV–vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transformation infrared spectroscopy (FTIR). Compared with commercial TiO2 (Degussa P25), the as-prepared ZHS showed much higher conversion and mineralization of benzene under 254 nm UV irradiation, and no obvious deactivation was observed during the prolonged operation of 50 h. The reasons for the high activity and long-term stability of ZHS will be discussed in terms of the population and the regeneration of surface OH groups.
Keywords: ZnSn(OH)6; Photocatalysis; Benzene degradation; OH groups;
Morphology tuning of supported MoS2 slabs for selectivity enhancement of fluid catalytic cracking gasoline hydrodesulfurization catalysts by Yu Fan; Gang Shi; Haiyan Liu; Xiaojun Bao (73-82).
A series of Co–Mo–Mg/Al2O3, K–Co–Mo–Mg/Al2O3, and Co–Mo/silica catalysts were prepared and characterized by means of N2 adsorption, temperature-programmed desorption of ammonia (NH3-TPD), high-resolution transmission electron microscopy (HRTEM), and Fourier transformed infrared (FT-IR) spectra of adsorbed NO. The physicochemical properties of the catalysts were correlated with their hydrodesulfurization and olefin hydrogenation activities. The results showed that the dispersion and stacking of supported MoS2 were more important in influencing the selectivity of FCC gasoline hydrodesulfurization than the catalyst pore diameter and acidity. The compromise between the dispersion and the stacking of supported MoS2 slabs was crucial to form the sufficient and accessible Co–Mo–S phases for achieving optimal hydrodesulfurization selectivity. The present results form a fundamental basis for developing highly effective catalysts for the selective hydrodesulfurization of fluid catalytic cracking gasoline to meet the strict regulations for ultra-low sulfur gasoline.
Keywords: Fluid catalytic cracking gasoline; Selective hydrodesulfurization; Co–Mo–Mg/Al2O3; MoS2 morphology tuning; Dispersion and stacking of supported MoS2 slabs;
Controlled synthesis of Pt-Sn/C fuel cell catalysts with exclusive Sn–Pt interaction by Sergio García-Rodríguez; Ferenc Somodi; Irina Borbáth; József L. Margitfalvi; Miguel Antonio Peña; Jose Luis G. Fierro; Sergio Rojas (83-91).
A series of Sn modified carbon supported Pt electrocatalysts displaying an increasing amount of the Pt3Sn crystalline phase within their structure has been prepared by using controlled surface reactions (CSRs). This synthetic route results in the exclusive incorporation of Sn onto the Pt sites yielding Pt(1−x)Sn x and Pt3Sn phases. As demonstrated by X-ray diffraction and transmission electron microscopy the amount of the Pt3Sn phase within the electrocatalysts can be controlled by tuning the reaction conditions in CSRs. CO and ethanol electrooxidation reactions were studied over these new type of Sn-Pt/C catalysts, demonstrating that the presence of the Pt3Sn structure effectively facilitates both processes, particularly the ethanol electrooxidation.
Keywords: PtSn/C electrocatalysts; Controlled surface reactions; Pt3Sn; Sn–Pt interaction; Ethanol; Electrooxidation;
Effect of hydrothermal treatment and silica on thermal stability and oxygen storage capacity of ceria–zirconia by Vadivukarasi Raju; Stephan Jaenicke; Gaik-Khuan Chuah (92-100).
Hydrothermal digestion of freshly precipitated cerium–zirconium hydroxides was used to synthesize nanocrystalline ceria–zirconia. This simple method produced ceria–zirconia with higher surface area and thermal stability than the untreated oxide. After calcination at 1000 °C, the surface area of the hydrothermally synthesized samples was ∼11–12 m2/g while the untreated Ce0.5Zr0.5O2 had only 4.2 m2/g. The continuous dissolution and reprecipitation of hydroxides during hydrothermal treatment is postulated to a more defect-free structure which is able to withstand loss of surface area when exposed to high temperatures. In addition, these nanocrystalline oxides were more reducible than the untreated oxide. While the addition of silica to ceria–zirconia further increased the surface area and oxygen storage capacity, the oxides suffered severe loss of surface area after calcination to 1000 °C. A silica-rich overlayer was formed which decreased the oxygen storage capacity as compared to silica-free ceria–zirconia. The oxygen storage capacity shows a strong dependence on the surface area for values below 50 m2/g but diffusion of oxygen from the bulk becomes limiting for high surface area ceria–zirconia.
Keywords: Ceria–zirconia; Hydrothermal treatment; Oxygen storage capacity; Thermal stability; Silica doping;
Oxidative methanol steam reforming on a highly dispersed CuO/CeO2/Al2O3 catalyst prepared by a single-step method by Maria Turco; Claudia Cammarano; Giovanni Bagnasco; Elisa Moretti; Loretta Storaro; Aldo Talon; Maurizio Lenarda (101-107).
A Cu/CeO2/Al2O3 catalyst (6.6% Cu, 13.8% Ce) based on a structurally organized mesoporous alumina was prepared by a new single-step sol–gel method starting from Al butoxide and Ce and Cu stearates. The sample was characterized by N2 adsorption, XRD, TPR and Cu dispersion measurements and tested as catalyst for the SRM (methanol steam reforming) and OSRM (methanol autothermal reforming) reactions. The material showed a huge surface area (360 m2 g−1) and resulted to contain very dispersed CeO2 and CuO phases on a poorly crystalline alumina matrix. A highly dispersed Cu metallic phase was obtained after a reductive treatment with H2. Catalytic tests showed that the unreduced material was fairly active for the OSRM process, but the activity increases appreciably after the pre-reduction treatment. The activity for the OSRM process resulted high, in terms of hydrogen production rate, if compared with data on similar Cu/Ce/Al systems, but the activity for SRM, in the absence of oxygen was, on the other hand, very low. This behaviour was explained either considering the occurrence of H spillover or the CeO2 assisted oxidation of Cu to Cu+.
Keywords: Oxidative methanol steam reforming; Cu/CeO2/Al2O3 catalysts; Organized mesostructured alumina; Cu dispersion;
Catalytic combustion of volatile organic compounds in binary mixtures over MnOx/Al2O3 catalyst by Fabiola N. Aguero; Bibiana P. Barbero; Luis Gambaro; Luis E. Cadús (108-112).
In this work the catalytic performance of an alumina supported manganese oxide catalyst in ethanol, ethyl acetate, toluene and mixtures of them was studied. The reactivity of each VOC investigated increased in the following order: ethanol > ethyl acetate > toluene. Toluene affects acetaldehyde yields, favoring partial combustion of ethanol and ethyl acetate. There is a competition for the adsorption sites between ethanol and ethyl acetate because both are polar molecules. Mixture effect decreases when the conversion temperature range of each component in the mixture is different, as in the case of ethanol–toluene and ethyl acetate–toluene mixture, consequently, the total conversion temperature is determined by the temperature at which the most difficult molecule is oxidized, in this case toluene.
Keywords: Alumina; Manganese oxide; VOC mixtures; Total oxidation;
Selective catalytic reduction of NO by ethanol: Speciation of iron and “structure–properties” relationship in FeSiBEA zeolite by Janusz Janas; Jacek Gurgul; Robert P. Socha; Tetsuya Shishido; Michel Che; Stanislaw Dzwigaj (113-122).
The speciation of iron in FeSiBEA zeolites is investigated in order to evidence the “structure–properties” relationship in the selective catalytic reduction (SCR) of NO by ethanol. Fe x SiBEA zeolites are prepared in acidic (pH 2.5) (x = 0.3, 0.9 and 4.2 Fe wt%) or basic (pH 10) (x = 3.6 Fe wt%) conditions by a two-step postsynthesis method which allows to incorporate Fe into zeolite, as evidenced by XRD. For low Fe content (Fe0.3SiBEA, Fe0.9SiBEA), iron incorporated as Fe(III) ions generates Brønsted acidic sites as shown by FTIR of pyridine. Framework tetrahedral Fe(III) ions are evidenced by diffuse reflectance UV–vis, XANES and EXAFS. For higher Fe content (Fe4.2SiBEA), beside tetrahedral Fe(III) ions which are dominant, octahedral Fe(III) species are also present as shown by DR UV–vis, XPS and EXAFS. In contrast, for Fe3.6SiBEA prepared in basic condition (pH 10), an extra-framework Fe(III) oxide phase is mainly observed.The catalytic activity of Fe x SiBEA in the SCR of NO by ethanol strongly depends on the speciation of iron and a structure–properties relationship has been evidenced. Fe0.3SiBEA and Fe0.9SiBEA which mainly contain framework tetrahedral Fe(III) ions are active, with selectivity toward N2 exceeding 90% for NO conversion from 25% to 55%. When additional octahedral Fe(III) species are present (Fe4.2SiBEA), the full oxidation of ethanol and NO by O2 becomes important, with CO2 and NO2, respectively, appearing at the expenses of N2. The NO conversion linearly depends on Fe concentration assuming a first order reaction, suggesting that tetrahedral and octahedral Fe(III) species are well dispersed, as confirmed by XRD. The iron oxide phase is quite inactive, the activity and selectivity of Fe3.6SiBEA being governed by the small amount of tetrahedral Fe(III) ions.
Keywords: BEA; Zeolite; Iron; SCR; NO; Ethanol; XRD; UV–vis; XPS; XAS; IR; Catalysis;
Promotional mechanism of tungstation on selective catalytic reduction of NOx by methane over In/WO3/ZrO2 by Guohua Jing; Junhua Li; Dong Yang; Jiming Hao (123-134).
The catalytic performance and promotional mechanism of tungstation for selective catalytic reduction of NO by methane over In-loaded tungstated zirconia (In/WZr) were investigated. A clear improvement of catalytic activity was found over In/WZr catalysts. The highest NO conversion of 70% was achieved over a 1% In/WZr catalyst at 450 °C and 12,000 h−1. In contrast, the maximum NO conversions of WZr, ZrO2 and In/ZrO2 were only 12%, 31% and 20%, achieved at 500, 650 and 600 °C, respectively. Tungstation was observed to influence the properties of catalysts in three aspects: (i) modify the existent state of surface indium species; (ii) determine the activation species of CH4; (iii) cooperate with the loading of indium to enhance the formation and reduction of the intermediates. Differences in the existent state of indium and the activation species of CH4 result in different catalytic activities and mechanisms for CH4-SCR of NO. X-ray photoelectron spectroscopy measurements and Py-IR analysis showed that indium species on the In/ZrO2 catalyst was in the In2O3 bulk phase due to the lack of Brønsted acid sites. However, the tungstated In/WZr catalyst possessed strong Brønsted acid sites, which was beneficial to the formation of active InO+ species. DRIFTS studies further revealed the reaction intermediates of CH4-SCR of NO on the tungstated and the untungstated catalysts. On In/ZrO2 and ZrO2, the activation species of CH4 was the fully oxidized products CO2 and H2O. While on WZr and In/WZr, HCOO−, the real reductant for CH4-SCR of NO, was detected as the main intermediate species. In addition, the formation of HCOO− and the reduction of nitrate species were greatly accelerated by the synergistic effect between InO+ and tungstation, which might explain the higher catalytic activity of In/WZr in comparison with WZr and In/ZrO2.
Keywords: DeNOx; Selective catalytic reduction; Methane; Indium; Tungstated zirconia; InO+; HCOO−;
Solvothermal preparation, electronic structure and photocatalytic properties of PbMoO4 and SrMoO4 by Jinhong Bi; Ling Wu; Yongfan Zhang; Zhaohui Li; Junqian Li; Xianzhi Fu (135-143).
PbMoO4 and SrMoO4 particles were successfully prepared via a simple solvothermal process. The obtained samples were characterized by X-ray diffraction, Brunauer–Emmett–Teller (BET) surface area analysis, UV–vis diffuse reflectance spectroscopy, scanning electron microscopy and a photoluminescence technique with terephthalic acid. The as-prepared PbMoO4 samples show different photocatalytic activities for salicylic acid under UV light irradiation. PbMoO4 exhibits relatively high photocatalytic activity for salicylic acid, Rhodamine B and benzene. While, SrMoO4 possessing a similar structure to PbMoO4 shows negligible photocatalytic activity though they exhibit similar BET surface areas and morphologies. Theoretical calculations reveal that PbMoO4 contains higher dispersive valence and conduction bands than SrMoO4. The highly dispersive valence and conduction bands can lead to higher mobility of the photo-generated carries and therefore a better photocatalytic activity.
Keywords: Solvothermal process; Photocatalytic activity; Salicylic acid; PbMoO4; SrMoO4; Electronic structure;
NH3 formation and utilization in regeneration of Pt/Ba/Al2O3 NO x storage-reduction catalyst with H2 by William P. Partridge; Jae-Soon Choi (144-151).
The nature of H2 regeneration of a model Pt/Ba/Al2O3 LNT catalyst was investigated with specific focus on intra-catalyst formation and utilization of NH3 and its role in catalyst regeneration. In situ measurements of the transient intra-catalyst species (H2, NH3, N2, NO x ) distributions at different temperatures were used to detail the reaction evolution along the catalyst axis. Comparison of the species transients identifies unique individual natures for the reductant (H2), inert product (N2) and intermediate-reductant product (NH3) which readily explain the conventional effluent species sequence as an integral effect. The data demonstrate that NH3 is created on similar timescales as the N2 product inside the catalyst, but consumed as aggressively as H2 reductant along the catalyst. This spatiotemporal NH3 behavior experimentally confirms that Intermediate-NH3 regeneration pathway is active. Analysis at 200 and 325 °C indicates equivalent local NO x storage, H2 consumption and regeneration effectiveness, but differing NH3/N2 ratio, suggesting a temperature-dependence of partitioning between Direct-H2 and Intermediate-NH3 regeneration pathways. Further experimental and numerical work is needed to more clearly understand the partitioning between the possible regeneration pathways. Nevertheless, the experimental data show that intermediate NH3 plays a significant role in LNT catalyst regeneration.
Keywords: LNT; Regeneration; NH3; Intra-catalyst measurements; SpaciMS;
Visible light responses of sulfur-doped rutile titanium dioxide photocatalysts fabricated by anodic oxidation by Yoshiteru Mizukoshi; Naofumi Ohtsu; Satoshi Semboshi; Naoya Masahashi (152-156).
Anodic oxides on pure titanium provide rutile-structured TiO2 photocatalysts with sub-micron pores. The photocatalysts effectively bleached methylene blue aqueous solution under visible light illumination with wavelengths longer than 413 nm. Auger electron spectroscopy and infrared absorption analyses revealed the presence of sulfur in the anodized oxide. The sulfur doping appears to play an important role in response to visible light by narrowing the band gap of pristine TiO2.
Keywords: Sulfur doping; Titanium dioxide; Rutile; Anodic oxidation; Visible light response;
Highly enhanced photocatalytic degradation of tetramethylammonium on the hybrid catalyst of titania and MCM-41 obtained from rice husk silica by Surachai Artkla; Wooyul Kim; Wonyong Choi; Jatuporn Wittayakun (157-164).
A hybrid photocatalyst consisting of TiO2 and the mesoporous support was prepared by loading TiO2 nanoparticles on MCM-41 which was synthesized from silica obtained from rice husk (abundant agricultural waste in Thailand). The catalysts with varying content of TiO2 were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption, high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray (EDX) analysis and UV–vis diffuse reflectance spectroscopy. The MCM-41 structure was retained after the loading of TiO2 but its surface area decreased as a result of the partial pore blocking. The TiO2 morphology and band gap were not affected by the dispersion on the support but the presence of the support prevented the TiO2 nanoparticles from agglomerating in the neutral pH range. When the TiO2 loading on the support was higher than 10 wt.%, the activity of the hybrid catalyst was saturated. The activity of TiO2/MCM-41 for the photocatalytic degradation of tetramethylammonium (TMA) in aqueous slurry was significantly higher than that of the unsupported TiO2. The optimal TiO2 loading on the support was 10 wt.% at which the complete conversion of TMA was achieved in 90 min irradiation at pH 7. The unsupported TiO2 photocatalyst could convert only 20% of TMA in the same irradiation time and condition. The photocatalytic degradation of TMA proceeded by generating demethylated intermediates such as tri-, di- and monomethylammonium ions which were finally converted to ammonium ions.
Keywords: Photocatalytic water treatment; Supported photocatalyst; TiO2; Rice husk silica; MCM-41; Tetramethylammonium;
Impact of the morphological properties of thin TiO2 photocatalytic films on the detoxification of water contaminated with the cyanotoxin, microcystin-LR by Maria G. Antoniou; Persoulla A. Nicolaou; Jody A. Shoemaker; Armah A. de la Cruz; Dionysios D. Dionysiou (165-173).
This study investigated the use of thin transparent TiO2 photocatalytic films, prepared with novel sol–gel methods containing surfactants as templating materials, for the degradation of the cyanotoxin, microcystin-LR (MC-LR). MC-LR is an emerging contaminant from the Contaminant Candidate Lists (CCLs 1–3) of the USEPA. The effects of UV-A radiation, solution pH, initial toxin concentration, coated surface area of the TiO2 films and their structural properties (porosity, crystallinity and thickness) on the degradation rate of MC-LR were investigated. Photolysis did not occur with UV-A radiation. Acidic pH was more efficient for the degradation of MC-LR due to toxin interaction with the catalyst surface and increased adsorption into the porous films. The degradation profiles of the toxin at different initial concentrations were fitted with pseudo-first order kinetics. Films prepared with three coatings (0.3 μm thickness) had the best performance at acidic and neutral pH, while the exclusion of surfactant from the preparation method resulted in non-porous films with decreased performance. The parameter that mostly affected the degradation rate was the solution pH. The toxicity of the treated samples, evaluated by an in-house protein phosphatase 1 assay, indicated that treatment with the TiO2 photocatalytic films indeed resulted in complete removal of MC-LR's toxicity.
Keywords: Cyanotoxins; Microcystin-LR; Photocatalytic; TiO2 photocatalysis; Thin films; Water treatment; Water detoxification; PP1 enzyme;
The role of α-sites in N2O decomposition over FeZSM-5. Comparison with the oxidation of benzene to phenol by L.V. Pirutko; V.S. Chernyavsky; E.V. Starokon; A.A. Ivanov; A.S. Kharitonov; G.I. Panov (174-179).
The kinetics and the mechanism of nitrous oxide decomposition (NOD) were studied using a set of FeZSM-5 samples with a wide variation in concentration of α-sites, which are special complexes of bivalent iron (FeII)α stabilized in the micropore space of the zeolite matrix. The results are compared with the N2O oxidation of benzene to phenol (OBP) studied earlier with the same set of samples. In spite of strong differences in turnover frequencies (ca. 100 times) and activation energies (92 kJ/mol), both reactions are catalyzed by the same active centers represented by α-sites. The rates of the reactions increase linearly with increasing α-sites concentration within two orders of magnitude.The NOD and OBP reactions are shown to have kindred mechanisms, which can be described by two main steps. The first step is a common one and includes oxidation of the α-site by the deposition of α-oxygen from N2O: (FeII)α + N2O → (FeIII–O−)α + N2 The α-oxygen can be safely quantified, its properties being thoroughly studied in many previous works.The second step is the reduction of the site. It proceeds due to the removal of α-oxygen by the interaction of the latter with either N2O (NOD reaction) or benzene (OBP reaction). In both cases this step is the rate determining one.Mechanistically, the OBP can be considered as an N2O reduction by benzene. One may think that fundamental role of α-sites may hold also for N2O reduction by other substrates like CO, methane, propane, etc., which are widely used for this purpose.
Keywords: N2O decomposition; N2O reduction; FeZSM-5; α-Sites; α-Oxygen; Benzene oxidation;
Wet air oxidation with tubular ceramic membranes modified with polyelectrolyte/Pt nanoparticle films by David M. Dotzauer; Ali Abusaloua; Sylvain Miachon; Jean-Alain Dalmon; Merlin L. Bruening (180-188).
Gas–liquid reactions with membrane-supported catalysts often use the interfacial contactor configuration in which the reaction occurs at the gas–liquid-catalyst interface within the membrane. Thus, control over the catalyst location in the membrane is crucial for making efficient use of expensive materials such as noble metal nanoparticles. Layer-by-layer (LBL) adsorption of polyelectrolyte/metal nanoparticle films in tubular ceramic membranes allows deposition of the catalytic nanoparticles only near the interior of the tube, where the gas–liquid interface is typically located. In wet air oxidation of formic acid, tubular membranes modified by LBL deposition of polyelectrolyte/Pt nanoparticle films show 2 to 3 times higher specific activities than similar membranes modified by traditional methods such as anionic impregnation/reduction and evaporation/recrystallization/reduction. In acetic acid and phenol oxidations, the LBL method gives order of magnitude increases in specific activity relative to the traditional membrane modification methods. The enhanced activity with LBL-modified membranes is likely due to the controlled deposition of the Pt in the catalytic inner layer of the tubes, as only the LBL method gives tubular membranes that show higher activity than pulverized membranes in stirred tank reactors.
Keywords: Catalysis; Layer-by-layer; Membrane; Wet air oxidation;
Catalytic activity of synthesized nanosized molybdenum disulfide for the hydrodesulfurization of dibenzothiophene: Effect of H2S partial pressure by Hamdy Farag; Abdel-Nasser A. El-Hendawy; Kinya Sakanishi; Masahiro Kishida; Isao Mochida (189-197).
Nanosized MoS2 catalysts with basal planes of ∼4 nm were synthesized by thermally annealing ammonium tetrathiomolybdate. The structure and morphology of the obtained phases were determined by XRD, SEM and TEM. These nanosized MoS2 clusters have a truncated hexagonal shape. The MoS2 layers in these batches were found to be curved to some extent. Catalytic performance was evaluated by the hydrodesulfurization of dibenzothiophene. We studied the effect of a wide range of H2S partial pressures on the hydrodesulfurization activity and selectivity. Catalytic activity for the hydrodesulfurization of dibenzothiophene increased remarkably when H2S was included within the reaction zone. The role of the curved MoS2 layers on activity is discussed.
Keywords: MoS2; Hydrodesulfurization; Dibenzothiophene; H2S;
High PEMFC performance by applying Ir-V nanoparticles as a cathode catalyst by Jinli Qiao; Bing Li; Daijun Yang; Jianxin Ma (198-203).
Very active catalysts Ir-V/C, as a novel suitable cathode catalyst in PEMFCs was synthesized using IrCl3 and NH4VO3 as the Ir and V precursors. By applying the ethylene glycol (EG) method, a well dispersion of Ir-V/C catalysts with mean particle size of 2 nm was obtained. The membrane–electrode assembly (MEA) fabricated with Ir-V nanoparticles exhibited the excellent catalytic activity toward the oxygen reduction reaction (ORR) and, reached 517 mW cm−2 at 0.43 V and 210 mW cm−2 at 0.30 V in a real fuel cell environment, H2/O2 and H2/air, respectively. In particular, promising results were obtained based on a low metal (Ir) loading of 0.4 mg cm−2 on the cathode which achieved 100 h durability at a constant current density of 1200 mA cm−2. The electrocatalytic effect related to a change in the electro-catalyst structure was discussed based on the XRD and TEM data. Also, for the first time, the electrochemical impedance spectra (EIS) and cyclic voltammetry (CV) techniques were used to assess the kinetics of oxygen reduction on the produced samples and the enhancement effect of V in-situ of fuel cells.
Keywords: Ir-based catalyst; Polyol process; Oxygen reduction reaction; Cathode; In-situ EIS and CV technique; PEMFC;
Promoting effect of Ce added to metal oxide supported on Al pillared clays for deep benzene oxidation by Shufeng Zuo; Qinqin Huang; Jing Li; Renxian Zhou (204-209).
Al pillared clays (Al-PILC) were used to support transition metals (M = Cr, Mn, Fe, Co, Ni and Cu) and Ce for the deep oxidation of low concentration of benzene. The effect of Ce addition to M/Al-PILC was also investigated. The catalysts were characterized by X-ray powder diffraction, N2 adsorption and H2 temperature programmed reduction techniques. Introduction of Ce into M/Al-PILC improves dispersion of transition metals, changes the redox properties of metal oxide and makes it easier to be reduced by the interaction between the two oxides, increasing lattice oxygen lability. In activity tests Mn based catalysts were observed to be the most active among the transition metals, and adding Ce obviously improved the activity and stability of M/Al-PILC. Moreover, Ce content had a great effect on the activity of MnCe/Al-PILC. MnCe (18:1)/Al-PILC exhibited the highest activity, and the temperature for complete benzene conversion using this catalyst was about 310 °C.
Keywords: Pillared clay; Transition metal; Cerium; Redox property; Benzene oxidation;
Preparation and characterization of TiO2-masked Fe3O4 nano particles for enhancing catalytic combustion of 1,2-dichlorobenzene and incineration of polymer wastes by Jin Seong Choi; Hyun Ki Youn; Bu Ho Kwak; Qiang Wang; Kyung Shik Yang; Jong Shik Chung (210-216).
Nano-sized Fe3O4 particles that were covered with a porous layer of nano-sized TiO2 (TiO2-masked Fe3O4) were prepared by simply controlling pH of aqueous slurry solution containing the two particles that have different values of isoelectric point (IEP coating method). The prepared sample showed an effective masking of red-brown color of Fe3O4 particles into a pale yellow. XPS and TEM measurements confirmed an effective covering of TiO2 particles to the Fe3O4 surface. XANES analyses revealed the transformation of some Fe2+ ions into Fe3+ in the Fe3O4 structure (formation of Fe3O4+δ ) due to a close interaction between Fe3O4 and TiO2 during the IEP coating, which was not observed in physical mixture of dry powders of Fe3O4 and TiO2. Compared with pure Fe3O4 or the physical mixture, TiO2-masked Fe3O4 particles exhibited an activity enhancement for both catalytic oxidation of 1,2-dichloro benzene and thermal incineration of catalyst-embedded polyethylene and polystyrene. Temperature-programmed reduction of CO and temperature-programmed surface reaction of CO with O2 revealed that oxygen vacancy sites on Fe3O4+δ played roles for the adsorption and reaction of CO, and close TiO2 provided oxygen to the Fe3O4+δ sites. Compared with pure Fe3O4 particles, TiO2-masked Fe3O4 particles also provided a good color-masking effect when embedded in polymers and improved the thermal stability of base polymers for high temperature fabrication.
Keywords: TiO2-masked iron oxides; Isoelectric point; 1,2-dichlorobenzene oxidation; Catalyst-embedded polymer; Polymer incineration;
Effect of Cu content on the catalytic activity of CuSiBEA zeolite in the SCR of NO by ethanol: Nature of the copper species by Janusz Janas; Jacek Gurgul; Robert P. Socha; Stanislaw Dzwigaj (217-224).
The effect of Cu content on the catalytic activity of Cu x SiBEA zeolites in the selective catalytic reduction (SCR) of NO by ethanol is investigated. The Cu x SiBEA zeolites (x = 0.3, 1.5 and 3.3 Cu wt%) are prepared by a two-step postsynthesis method which allows to control the introduction of copper into BEA zeolite and thus to obtain catalysts with isolated tetrahedral Cu(II) species. The incorporation of Cu into the vacant T-sites of SiBEA framework is evidenced by XRD. The presence of isolated tetracoordinated Cu(II) as the main copper species is evidenced by DR UV–vis and XPS investigations. Cu0.3SiBEA, Cu1.5SiBEA and Cu3.3SiBEA with isolated Cu(II) species are active in SCR of NO by ethanol with the maximum NO conversion of 33%, 45.5% and 50% and selectivity towards N2 of 90%, 97% and 75%, respectively. These results indicate that activity of Cu x SiBEA in the SCR process increases with Cu content and the main reaction route is the reduction of NO toward N2. The decreases of selectivity toward N2 and increases toward NO2 with Cu content, is probably related to formation of small amount of octacoordinated Cu(II) as suggested by XPS data. A possible pathway for the formation of tetracoordinated Cu(II) in the framework of Cu x SiBEA is proposed.
Keywords: SiBEA zeolite; Copper; NO; Ethanol; XRD; DR UV–vis–NIR; XPS; Catalysis;
Microfibrous TiO2 supported photocatalysts prepared by metal-organic chemical vapor infiltration for indoor air and waste water purification by Christos Sarantopoulos; Eric Puzenat; Chantal Guillard; Jean-Marie Herrmann; Alain N. Gleizes; Francis Maury (225-233).
The photocatalytic degradation of gaseous (toluene) and aqueous (imazapyr, malic acid, orange G) pollutants over TiO2 supported photocatalysts is investigated using a batch reactor. A strong influence of the microstructural characteristics of TiO2 on the decomposition kinetics of the pollutants is found. Well crystallized, porous TiO2-anatase films grown under low pressure at 400–500 °C by MOCVD on glass plates and by MOCVI on glass micro-fibers are the best heterogeneous photocatalysts, showing the highest activity. We demonstrate a good control of these characteristics by choosing the deposition parameters. Achieving conformal coverage (i.e. good infiltration) of glass micro-fibers by the TiO2 thin films has also a strong influence on the photocatalytic activity. A correlation between optimal infiltration, film microstructure and photocatalytic activity is established. Strong similarities between optimal photocatalytic decomposition rate in gas and liquid phase were found with respect to the film microstructure and the photocatalyst mass. The total mineralization of the toluene was prevented because of the deactivation of the photocatalyst surface. However the reactivation of the photocatalyst was achieved by UV irradiation under oxygen stream. This allows a long-term use of the photocatalyst.
Keywords: MOCVD; MOCVI; Gas phase infiltration; Titanium dioxide; Photocatalysis; Waste water treatment; Air purification;
The influence of gas phase reactions on the design criteria for catalysts for lean NO x reduction with dimethyl ether by Stefanie Tamm; Hanna H. Ingelsten; Magnus Skoglundh; Anders E.C. Palmqvist (234-241).
In the selective catalytic reduction (SCR) of NO by dimethyl ether (DME), the formation of unexpectedly high amounts of NO2 over 300 °C has previously been reported. In this study, we explain this phenomenon by radical reactions initiated by DME and O2, during which DME is partly oxidized and NO2 is formed in the presence of NO. For the design criteria of a DME-SCR catalyst, these gas phase reactions have mainly three consequences: (i) another type of reducing agent than that fed into the reactor reaches the catalyst, (ii) no activation of the reducing agent such as partial oxidation is required, and (iii) several of the proposed intermediate species for HC-SCR, e.g. NO2, HONO, CH3–NO2, and CH3–NO form already in the gas phase. An efficient DME-SCR catalyst should thus have high selectivity for reduction of NO x predominately by partially oxidized C1-compounds, and it should not have particularly strong oxidizing properties to avoid non-selective oxidation of these C1-compounds. These two requirements appear to be reasonable well met by the acidic zeolite H-ZSM-5.
Keywords: Dimethyl ether, Radical, Gas phase reaction, NO x -reduction, H-ZSM-5;
Remediation of simulated aquatic sites contaminated with recalcitrant substrates by TiO2/ozonation under natural sunlight by Toshiyuki Oyama; Ippei Yanagisawa; Masashi Takeuchi; Takayoshi Koike; Nick Serpone; Hisao Hidaka (242-246).
The fates of four aquatic contaminants, namely the 2,4-dichlorophenoxyacetic acid herbicide (2,4-D), the bisphenol A endocrine disruptor (BPA), and the sodium butylnaphthalenesulfonate (BNS) and benzyldodecyldimethylammonium bromide (BDDAB) surfactants by the TiO2-photoassisted ozonation (TiO2/O3/UV method) were investigated indoors under laboratory conditions (super-high-pressure Hg lamp) and outdoors under natural Sunlight. In laboratory experiments the TiO2/O3/UV methodology led to significant increases in degradation efficiency relative to ozonation (dark: O3; or under UV light: O3/UV) and to the TiO2-photoassisted method of oxygenated dispersions (TiO2/O2/UV). Mineralizations of the substrates were monitored by total organic carbon (TOC) assays. The BDDAB surfactant, being most recalcitrant to biodegradation and to the TiO2-photoassisted degradation, was mineralized efficiently by the TiO2/O3/UV method under natural Sunlight at relatively high concentrations of contaminants (1.0 mM) using a tubular-type photoreactor consisting of Pyrex glass tubes and a solar cell system that supplied the needed electrical power.
Keywords: Photoassisted ozonation; Titanium dioxide; Solar energy; Water pollutants; Advanced oxidation process (AOP);
Aerosol-spay assisted assembly of Bi2Ti2O7 crystals in uniform porous microspheres with enhanced photocatalytic activity by Zhenfeng Bian; Yuning Huo; Yi Zhang; Jian Zhu; Yunfeng Lu; Hexing Li (247-253).
A novel crystalline Bi2Ti2O7 in uniform porous microspheres was synthesized by aerosol-spray assisted surfactant self-assembly which displayed strong optical response in visible region owing to the narrow energy gap. During photodegradation of p-chlorophenol and rhodamine B under visible light irradiation, this photocatalyst was more active than the Bi2Ti2O7 obtained via chemical solution decomposition, apparently owing to the larger surface area and higher crystallization degree which might promote the reactant adsorption and inhibit the charge carrier recombination. The as-prepared Bi2Ti2O7 crystal also showed much higher activity than the Bi-doped TiO2 owing to the low recombination rate between photoelectrons and holes, corresponding to the higher quantum efficiency. Besides, the Bi2Ti2O7 crystal was strongly durable and could be used repetitively for more than nine times without significant deactivation, which could be attributed to the high hydrothermal stability against phase transformation and architecture damage.
Keywords: Aerosol-spray assisted assembly; Crystalline Bi2Ti2O7; Visible photocatalyst; Uniform porous microspheres; Photodegradation of p-chlorophenol (4-CP) and the rhodamine B (RhB);
UV light-activated decomposition/cleaning of concentrated biomass wastes involving also solid suspensions with remarkably high quantum efficiency by Masao Kaneko; Hirohito Ueno; Rie Saito; Saori Yamaguchi; Yuki Fujii; Junichi Nemoto (254-261).
UV light-activated decomposition/cleaning of high concentration (>103–104 ppm) biomass model and wastes in water involving also solid suspensions into CO2 and N2 were achieved by using a specially designed biophotochemical cell (BPCC) comprising a nanoporous semiconductor (TiO2) film photoanode/an O2-reducing cathode unit and a large volume bulk aqueous phase with a remarkably high internal quantum efficiency over 80 (=8000%) for pig urine.
Keywords: Biophotochemical cell (BPCC); Nanoporous titanium dioxide photoanode; O2-reducing cathode; Photodecomposition; Biomass wastes;
A comprehensive investigation of influences of NO and O2 on N2O-SCR by CH4 over Fe-USY zeolite by Qun Shen; Landong Li; Chi He; Hua Tian; Zhengping Hao; Zhi Ping Xu (262-268).
The catalytic reduction behaviors of N2O by CH4 have been investigated over Fe-USY catalyst by examining the influences of CH4, NO, O2, or their mixtures in detail. The observations show that NO and O2, which inevitably exist in the gases emitted from industrial sources, such as the nitric acid plant, inhibit the selective catalytic reduction of N2O by CH4 (N2O–CH4 SCR) to some degree, shifting the temperature for >90% N2O conversion to over 450 °C. The prohibition of O2 can be ascribed to its occupying active sites and oxidizing CH4-derived intermediates. The negative effect of NO is very prominent, inhibiting the N2O conversion by strongly occupying the active sites and gradually moving the reaction pathways from N2O–CH4 SCR to NO-assisted N2O decomposition, where the former is more efficient than the latter for N2O decomposition under the same operation conditions. In addition, the amount of reducing agent CH4 has also influenced the N2O conversion profile.
Keywords: Fe-USY zeolite; N2O–CH4 SCR; NO inhibition; NO-assisted N2O decomposition; N2O–CO SCR;
Study of different bimetallic anodic catalysts supported on carbon for a high temperature polybenzimidazole-based direct ethanol fuel cell by Justo Lobato; Pablo Cañizares; M.A. Rodrigo; Jose J. Linares (269-274).
In this work, two different catalysts, Pt–Ru (1:1), Pt–Sn (1:1), supported on both non-activated and activated carbon for the electro-oxidation of ethanol were studied in a H3PO4 doped polybenzimidazole-based fuel cell, using vapor fed ethanol and operating in the range of 150–200 °C. The catalysts were synthesized using NaBH4 as reducing agent and were characterized by X-ray diffraction, inductively coupled plasma-atomic emission spectroscopy and temperature programmed reduction. The best performance was reached at the highest temperature and with the catalyst based on Pt–Ru/Cact, using activated carbon as support. The best results for the Ru-based catalyst can be explained by the higher level of alloying reached for the Ru than that for Sn, which modifies the crystalline structure of Pt and enhances the activity oxidation of ethanol and of intermediates that can be generated during the oxidation of ethanol.
Keywords: DEFC; High temperature; Polibenzimidazole membrane; Pt–Ru/C; Pt–Sn/C;
Removal of herbicide diuron and thermal degradation products under Catalytic Wet Air Oxidation conditions by M. Carrier; M. Besson; C. Guillard; E. Gonze (275-283).
The Catalytic Wet Air Oxidation (CWAO) of diuron (N-(3,4-dichlorophenyl)-N,N-dimethylurea), a herbicide widely used in agriculture and belonging to the phenylurea family, has been investigated in aqueous solution in the presence of a Ru/TiO2 catalyst at 140–180 °C and 5 MPa total air pressure. Diuron and Total Organic Carbon (TOC) have been analyzed. Some reaction products were identified by LC–ES/MS, and the amount of the inorganic ions and organic products generated during the process have been measured. Thermal degradation is the main initial process yielding mainly 3,4-dichloroaniline (DCA) and dimethylamine (DMA). Further oxidations lead to ring opening and smaller organic molecules from DCA, but the DMA fragment was more difficult to eliminate. Reactions between DCA and carboxylic acids conducted to the formation of condensation products. On the other hand, dechlorination was fast and complete. The work points out that CWAO over Ru supported catalysts may not a viable technique for degradation of diluted aqueous solutions of diuron. The mineralization is incomplete compared to other Advanced Oxidation Processes, and a possible leaching of the metal by the amines formed by thermal degradation of diuron may be critical.
Keywords: Waste water treatment; Diuron; Catalytic Wet Air Oxidation; Degradation products; Degradation pathways;
Comparison of degradation mechanism of electrochemical oxidation of di- and tri-nitrophenols on Bi-doped lead dioxide electrode: Effect of the molecular structure by Yuan Liu; Huiling Liu; Jun Ma; Xi Wang (284-299).
In the present work, the effect of molecular structures of di- and tri- nitrophenols on electrochemical degradation has been investigated on Bi-doped lead dioxide electrodes in terms of cyclic voltammetry and bulk electrolysis. The results of SEM and AFM displayed a porous structure with small-sized crystal particles and compact crystalline structure of Ti/Bi-PbO2. These nitrophenols were believed to be mainly degraded by means of indirect oxidation due to the low anodic oxidation currents observed in cyclic voltammetries and large amount of oxidants. And the absence of polymeric adhesive compounds formed and deposited on the surface of electrodes indicated the high electrocatalytic activity of Ti/Bi-PbO2 for decomposing organics. Within the present experimental conditions used, almost complete elimination of nitrophenols was achieved. The electrochemical oxidation of them followed in the order: 2,6-dinitrophenol > 2,5-dinitrophenol > 2,4-dinitrophenol > 2,4,6-trinitrophenol. The relationship between electrochemical oxidation rate and the molecular structure of nitrophenols was discussed. The results of LC/MS and HPLC suggested that three kinds of intermediates were generated, i.e., polyhydroxylated intermediates, reduction products of nitrophenols and carboxylic acids. The possible degradation pathways of nitrophenols were proposed. The denitration and substitution by hydroxyl radicals on aromatic rings seemed to be the first stage. As a consequence, the formation of polyhydroxylated intermediates took place. These compounds were successively oxidized into catechol, resorcinol and hydroquinone, as well as reduced to aminophenols, followed by the opening of aromatic rings and the formation of a series of carboxylic acids. Finally, these carboxylic acids were oxidized into CO2 and H2O.
Keywords: Nitrophenol; Electrochemical oxidation; Mechanism; Bi-doped lead dioxide electrode; Molecular structure;
Effects of pyrolysis temperature and Pt-loaded catalysts on polar-aromatic content in tire-derived oil by Nguyễn Anh Dũng; Sujitra Wongkasemjit; Sirirat Jitkarnka (300-307).
This study investigates the influences of pyrolysis temperatures and Pt-supported catalysts on polar-aromatic content in the oils obtained from pyrolysis of waste tire. These polar-aromatic compounds are mostly the sulfur-containing aromatics since oxygen is prohibited in pyrolysis. The experimental results indicated that pyrolysis temperatures strongly affected the polar-aromatic content in the derived oils. Namely, the increase in pyrolysis temperature in the tested range produced not only a higher amount of polar-aromatics but also heavier polar-aromatic compounds. All studied catalysts decreased the polar-aromatic content in the oils drastically. In addition, it was found that the introduction of the studied catalyst also led to the production of lighter polar-aromatic compounds with respect to that produced from thermal pyrolysis. Comparing the two acid catalysts, HBETA exhibited higher activity for polar-aromatic reduction as compared to HMOR, which was ascribed to its higher medium and strong acid site density, smaller particle size and 3D-structure. The Pt supported on HMOR and HBETA catalysts showed better polar-aromatic reduction activity than their corresponding acid catalysts. And, a slightly higher catalytic activity was observed over Pt/HBETA than Pt/HMOR, which was mainly due to the higher Pt dispersion of Pt/HBETA catalyst.
Keywords: Waste tire; Pyrolysis; Polar-aromatics; Pt; Zeolite;
Complete oxidation of toluene over bimetallic Pt–Au catalysts supported on ZnO/Al2O3 by Ki-Joong Kim; Ho-Geun Ahn (308-318).
Bimetallic Pt–Au catalysts supported on ZnO/Al2O3 were prepared by the impregnation (IMP) and incipient wetness impregnation (IW-IMP) methods in air or H2 and compared with a monometallic Pt/ZnO/Al2O3 catalyst. The catalysts were characterized by ultraviolet–visible spectroscopy (UV–vis), X-ray diffraction (XRD), CO chemisorption, temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM) in conjunction with energy dispersive spectroscopy (EDS). The catalytic activity for the complete oxidation of toluene was measured using a flow reactor under atmospheric pressure. The relationship between the particle size and catalytic activity for toluene over bimetallic Pt–Au catalysts is discussed. In the results, generally, the Pt particles prepared by IW-IMP in H2 were larger than those prepared by IMP in air. On the other hand, the Au particles prepared by IW-IMP in H2 were smaller than those prepared by IMP in air, namely when using IW-IMP in H2 the Au particle size was decreased and the Pt particle size was increased. Also, the particle sizes of Pt and Au increased with increasing calcination temperature. The STEM and XRD results show that Pt and Au were simultaneously deposited as metallic particles on the ZnO/Al2O3 without forming an alloy with the Pt and Au. From the TPR results, it was found that the nanosized Au particles might promote the reduction of the surface oxygen and that the complete oxidation of toluene shows higher activity at lower temperature over the bimetallic Pt–Au catalysts as compared to the Pt/ZnO/Al2O3 catalyst. The bimetallic Pt–Au catalysts prepared by IW-IMP in H2 calcined at 400 °C showed higher activity for complete toluene oxidation.
Keywords: Bimetallic Pt–Au catalyst; Toluene oxidation; Incipient wetness impregnation; XRD; STEM; TPR;
Degradation of wastewater from terephthalic acid manufacturing process by ozonation catalyzed with Fe2+, H2O2 and UV light: Direct versus indirect ozonation reactions by K. Chandrasekara Pillai; Tae Ouk Kwon; Il Shik Moon (319-328).
In this work, terephthalic acid wastewater containing a very high chemical oxygen demand (COD = (35.0 ± 1.8) g L−1) and possessing a dark reddish brown color (platinum cobalt unit = 1400) with a pH 8.5 discharged from a terephthalic acid manufacturing plant was treated by ozonation catalyzed with Fe2+, H2O2 and UV light. To arrive at an efficient Fe2+, H2O2 and UV catalyzed ozone system (O3/H2O2/Fe2+/UV), the individual methods, viz., ozone alone (O3), UV assisted ozonation (O3/UV), H2O2 and UV assisted ozonation (O3/H2O2/UV), and Fe2+ catalyzed ozonation (O3/Fe2+) were studied to evaluate their effectiveness in decomposing the COD concentration and the three major toxic organic components, namely, terephthalic acid (TPA), isophthalic acid (IPA) and benzoic acid (BA) present in the wastewater. The first-order kinetic rate constant for the COD removal process was evaluated for comparison. The O3/H2O2/Fe2+/UV combined catalytic system showed highest oxidizing power amongst the tested methods with better COD degradation degree as high as 90% at 240 min, and TPA, IPA and BA present in TPA wastewater completely destroyed within 150 min. In order to assess the contribution to the overall COD elimination by the direct molecular oxidation and the indirect free radical oxidation, degradation studies were carried out for all the five optimized systems with tert-butyl alcohol as the •OH scavenger. Individual contributions of the two pathways to the overall global oxidation were quantified in terms of the process rate constant; and the performance evaluation of the different ozonation systems was analyzed. Finally, the potentiality of the O3/H2O2/Fe2+/UV process as a promising pre-treatment stage to obtain more easily biodegradable molecules with lower toxicity for the subsequent anaerobic digestion of the TPA wastewater was demonstrated.
Keywords: Terephthalic acid wastewater; Ozonation; Catalysis; Direct and indirect oxidation; tert-Butyl alcohol radical scavenger; Biodegradation;
NO x storage and reduction in model lean NO x trap catalysts studied by in situ DRIFTS by Yaying Ji; Todd J. Toops; Josh A. Pihl; Mark Crocker (329-338).
NO x storage and reduction on a model Pt/BaO/Al2O3 catalyst was studied by means of in situ DRIFTS measurements. To examine the effect of ceria addition, experiments were also conducted using Pt/BaO/Al2O3 to which Pt/CeO2 was added as a physical mixture in a 74:26 weight ratio. For the former catalyst, DRIFT spectra acquired during NO/O2 and NO2/O2 storage indicated the formation of nitrite at 200 °C during the initial stages of adsorption, while increasing the adsorption temperature appeared to facilitate the oxidation of nitrite to nitrate. The ceria-containing catalyst afforded similar DRIFT spectra under these conditions, although the presence of cerium nitrates was observed at 200 and 300 °C, consistent with NO x storage on the ceria phase. DRIFT spectra acquired during NO x reduction in CO and CO/H2 showed that Ba nitrate species remained on the surface of both catalysts at 450 °C, whereas the use of H2-only resulted in complete removal of stored NO x . The observation of Ba carbonates when CO was present suggests that the inferior reduction efficiency of CO may arise from the formation of a crust of BaCO3 on the Ba phase, which inhibits further NO x reduction. DRIFT spectra acquired during lean-rich cycling (6.5 min lean, 1.0 min rich) with CO/H2 as the rich phase reductants revealed that a significant concentration of nitrates remained on the catalysts at the end of the rich phase. This implies that a large fraction of nitrate is not decomposed during cycling and thus cannot participate in NO x abatement through storage and regeneration.
Keywords: DRIFTS; IR spectroscopy; Lean NO x trap; NO x adsorber catalyst; Ceria;
Calcium zincate as precursor of active catalysts for biodiesel production under mild conditions by Juan Miguel Rubio-Caballero; José Santamaría-González; Josefa Mérida-Robles; Ramón Moreno-Tost; Antonio Jiménez-López; Pedro Maireles-Torres (339-346).
This work investigates the use of calcined calcium zincate as solid base catalyst for the methanolysis of sunflower oil to FAME (biodiesel). The precursor and catalyst were characterized by XRD, XPS, SEM, EGA-MS, FTIR and N2 adsorption. The thermal treatment at temperatures as low as 400 °C leads to a base catalyst which is very active and stable in biodiesel production from different vegetable oils (sunflower and soybean). The presence of carbonate on the calcium zincate, used as precursor, is negligible after remaining in contact with air for two weeks. The catalyst obtained at 400 °C shows FAME yields higher than 90% after 45 min of reaction, and the kinetic of the heterogeneous process (60 °C, methanol:sunflower oil molar ratio of 12, 3 wt.% of catalyst) is very close to that observed under homogeneous conditions (KOH dissolved in methanol). Under these experimental conditions, the catalyst is stable against lixiviation since it can be reutilized for three catalytic runs of 1 h, reaching yields higher than 85%. Moreover, by increasing the acidity of the oil until 1.1° (typical value of fried oils), the catalytic performance is maintained. The presence of water has a negative influence on the catalytic activity, since the addition of a 0.2 wt.% of water into the reaction medium decreases the FAME yield until 80% after 3 h of reaction, although this yield is still higher than 60% after adding a 1 wt.% of water. This catalyst is also very active in the transesterification of soybean oil.
Keywords: Calcium zincate; Biodiesel; Transesterification; Sunflower oil; Soybean oil; Reutilization;
The dependence of catalytic activity for N2O decomposition on the exchange extent of cobalt or copper in Na-MOR, H-MOR and Na-MFI by Maria Cristina Campa; Valerio Indovina; Daniela Pietrogiacomi (347-354).
Catalytic decomposition of N2O was studied on Na-MOR, H-MOR, and Na-MFI samples exchanged to various extents with cobalt or copper. Co-MOR samples were characterized by FTIR and volumetric measurements of NO adsorption. The most abundant species on Co-MOR was Co2+(NO)2. In agreement, the volumetric data yielded NO/Co = 1.8 ± 0.2.On Co-MOR, N2O conversion progressively increased as the cobalt content increased. All samples yielded similar apparent activation energy, E a = 75 ± 5 kJ mol−1. The reaction order was 0.9 ± 0.1 for N2O, and 0.0 ± 0.1 for O2. For samples having a Co-exchange percentage up to 61%, the turnover frequency per total Co atom was independent of the cobalt content and was significantly lower for more extensively exchanged samples. On all Co-MOR samples, the turnover frequency per isolated Co atom was nearly constant, indicating isolated Co2+ as the active site.On Cu-MOR and Cu-MFI samples, N2O conversion markedly increased with the copper content. Samples having a Cu-exchange percentage up to 62% yielded higher E a than more extensively exchanged samples (150 ± 5 kJ mol−1 vs. 100 ± 5 kJ mol−1). The reaction order was 0.5 ± 0.1 for N2O, and 0.0 ± 0.1 for O2.We conclude that in Co-MOR and Co-MFI catalysts the active site for N2O decomposition is isolated Co2+, whereas in Cu-MOR and Cu-MFI isolated Cu2+ is nearly inactive. In extensively exchanged Cu-MOR and Cu-MFI, the active site for N2O decomposition is most probably Cu1+. A similar reaction mechanism for N2O decomposition operates over Co-zeolites and extensively exchanged Cu-zeolites.
Keywords: N2O decomposition; Co-MOR; Cu-MOR; Co-nitrosyls;
Carbon-doped TiO2 photocatalyst synthesized without using an external carbon precursor and the visible light activity by Yiseul Park; Wooyul Kim; Hyunwoong Park; Takashi Tachikawa; Tetsuro Majima; Wonyong Choi (355-361).
Carbon-doped TiO2 (C-TiO2) was successfully prepared from a conventional sol–gel synthesis without using external carbon precursors whereas all the previous reports on the synthesis of C-TiO2 utilized them. The carbons contained in titanium alkoxide precursor could be incorporated into the lattice of TiO2 with creating mid-bandgap electronic states through the controlled calcination. The level of carbon doping was changed sensitively depending on the calcination temperature, which was verified by UV–visible diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. The charge pair generation/recombination in C-TiO2 was compared under visible and UV light through a time-resolved diffuse reflectance spectroscopy study, which suggested the presence of midgap energy levels induced by the incorporation of carbon dopants. The carbon doping was maximal when the calcination temperature was around 200–250 °C and hindered at higher temperatures. The visible light activities of the prepared TiO2 samples for the conversion of 4-chlorophenol and iodide were also strongly dependent on the calcination temperature and maximized at around 250 °C. This study implies that the carbon doping in TiO2 can be obtained even unintentionally in the conventional sol–gel synthesis.
Keywords: TiO2; Carbon dopant; Visible light photocatalyst; Sol–gel synthesis; Photooxidation;
Characterization of microwave effects on metal-oxide materials: Zinc oxide and titanium dioxide by Satoshi Horikoshi; Akihiro Matsubara; Sadatsugu Takayama; Motoyasu Sato; Futoshi Sakai; Masatsugu Kajitani; Masahiko Abe; Nick Serpone (362-367).
Microwave specific effects originating from either the magnetic and/or electric field of the microwaves that may impact the photoactivity of TiO2 and ZnO have been examined in the photodegradation of the 4-chlorophenol toxin.The microwave specific effect(s) that can impact a microwave-assisted and photo-assisted reaction occurring on the surface of ZnO or TiO2 (P-25) particles was (were) examined by comparing the process occurring under rich magnetic field conditions and under magnetic/electric field conditions. The features of the photo-assisted process in the presence of microwaves rich in a magnetic field ( H ) and an electric field ( E ) are described on the basis of (i) the degradation dynamics of 4-chlorophenol (4-CP) at ambient temperatures, (ii) the number of •OH radicals produced, and (iii) the dielectric properties of the metal oxides (in pellet form). For ZnO, the photoactivity is enhanced by a microwave specific non-thermal (i.e. non-caloric) effect originating from the microwaves’ magnetic field, but decreased by the thermal (i.e. caloric) factor originating from the microwaves’ electric field. Contrary to ZnO, the photoactivity of TiO2 (P-25) was enhanced by the synergistic effect between the magnetic and electric fields of the microwave radiation. Photocorrosion of ZnO in the aqueous dispersions was negligibly small (less than 0.05%) under UV, MW- EH , and UV/MW- EH irradiation conditions.
Keywords: Microwaves; Photocatalyst; Magnetic field; Electric field; 4-Chlorophenol; ZnO; TiO2;
Preparation of magnetic cobalt-based catalyst for hydrogen generation from alkaline NaBH4 solution by Cheng-Hong Liu; Bing-Hung Chen; Chan-Li Hsueh; Jie-Ren Ku; Fanghei Tsau; Kuo-Jen Hwang (368-379).
A fast and simple fabrication process, viz. a wet-chemical reduction process, was utilized for preparation of a cobalt-based catalyst to be used for hydrogen generation from alkaline NaBH4 solution. Characteristics of this cobalt-based catalyst were carried out by using various instruments, such as SEM/EDS, XPS, ICP, VSM, BET and TGA. The surface chemistry of the obtained catalyst is mainly cobalt oxides, not cobalt borides. Ferromagnetic property of the cobalt-based catalyst makes it convenient for being recycled from spent NaBH4 solution. The rate of hydrogen generation from catalyzed hydrolysis of alkaline NaBH4 solution was determined as a function of temperature, NaBH4 concentration, and NaOH concentration in the presence of prepared catalysts. In general, stable generation rate of highly pure hydrogen near 200 mL min−1 g−1 was achieved in 100 mL of 5 wt% NaBH4 solution containing 5 wt% NaOH solution and 200 mg of Co/IR-120 catalyst, in which no temperature runoff was observed during the course of hydrogen production. The activation energy of NaBH4 hydrolysis reaction was found at 66.67 kJ mol−1, which was comparable with others reported in the open literatures.
Keywords: Hydrogen generation; Cobalt-based catalyst; Sodium borohydride; Wet-chemical reduction process; Fuel cell;
The reaction of pyrrole with dimethyl carbonate under phosphazene catalysis: N-methoxycarbonylation vs N-methylation by Eugenio Quaranta; Marianna Carafa; Francesca Trani (380-388).
Phosphazene (t-butylimino-tris(dimethylamino)phosphorane (P1-t-Bu), t-butylimino-tris(pyrrolidino)phosphorane (BTPP)) and amidine (1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)) superbases have been investigated as catalysts in the direct reaction of pyrrole with dimethyl carbonate (DMC). The system phosphazene/pyrrole/DMC proves to be a flexible synthetic tool, as it offers a solution not only for the direct and selective phosgene-free synthesis of 1-methoxycarbonyl pyrrole (1), but also for the straightforward and selective synthesis of 1-methylpyrrole (2) through a safer way which avoids the use of harmful methylating agents such as methyl halides and (MeO)2SO2. The influence of factors (temperature, catalyst loading, reaction time, etc.) affecting yields and selectivities has been investigated. We have also ascertained that a major reaction pathway to the formation of 2 involves the decarboxylation of the primary product 1. Also this process was catalytically promoted by the phosphazene catalyst. Co-generated CO2 opened a way to the deactivation of phosphazene catalyst, which converted mainly into catalytically inactive OP(NR2)3 (NR2 = NMe2, NC4H8).
Keywords: Dimethyl carbonate; Pyrrole; Carbamate; Methoxycarbonylation; Alkylation; Organo-catalysts;
Pd/Fe3O4 nano-catalysts for selective dehalogenation in wastewater treatment processes—Influence of water constituents by Heike Hildebrand; Katrin Mackenzie; Frank-Dieter Kopinke (389-396).
Palladium catalysts can be used for the selective removal of halogenated organic compounds from aqueous waste via hydrodehalogenation reactions in the presence of other omnipresent constituents of industrial wastewaters. This detoxification of the water and drastic lowering of the AOX value (adsorbable organically bound halogens) can prevent the need for further cost-intensive treatment or discharge into waste incineration plants. Often, the water can then be released to municipal sewage plants.The present paper deals with a highly active, magnetically re-extractable nanoscale Pd-on-magnetite catalyst (Pd/Fe3O4) which has been developed for application in wastewater treatment processes. The study provides insight into the performance of this catalyst and gives information about its general applicability under wastewater conditions and its sensitivity towards constituents of a wastewater matrix.The catalyst can tolerate various inorganic and organic substances in relevant concentrations. Wastewaters containing a high background concentration of organic solvents can also be cleaned from halogenated pollutants. However, waters which contain heavy metals such as lead or mercury or reduced sulphur species such as sulphides need specific pre-treatments prior to Pd-catalysed hydrodehalogenation.
Keywords: Dehalogenation; Pd catalyst; Nano-magnetite; Wastewater treatment;
One step activation of WO x /TiO2 nanocomposites with enhanced photocatalytic activity by Ahmed Khan Leghari Sajjad; Sajjad Shamaila; Baozhu Tian; Feng Chen; Jinlong Zhang (397-405).
New photocatalyst (WO x –TiO2) powder was successfully prepared by a sol–gel method with an attempt to extend light absorption of the TiO2-based photocatalyst towards the visible light range and eliminate the rapid recombination of excited electrons/holes during photoreaction. The photo composite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), BET, Raman spectra, UV–vis diffuse reflectance spectra (DRS), photoluminescence spectra (PLS) and X-ray photoelectron spectroscopy (XPS). XRD, Raman, HRTEM and XPS analysis indicated that WO x is uniformly dispersed on the surface of TiO2 probably with monolayer thickness and the mean particle size of the composite was 12 nm. XPS analysis also indicated that the vacuum activated composites contained more W in reduced form while the calcined composites showed more W in hexavalent form. The beneficial effect of W can be explained by considering the formation of W+5 species by means of a transfer of photo-generated electrons from TiO2 to W+6.Subsequently W+5 could be oxidized to W+6 by transferring electrons to adsorbed O2.DRS showed an extension of light absorption into the visible region for this WO x composite and PL analysis indicated that the electron-hole recombination rate has been effectively inhibited when WO x is deposited on the surface of TiO2.The samples activated in vacuum showed higher photocatalytic activity than calcined samples in case of MO and superior activity in case of phenol. The optimal WO3 dosage of 4.0% in WO x –TiO2 achieved the highest rate of photodegradation in this experimental condition.
Keywords: WO x /TiO2 composite; Vacuum activation; Phenol degradation; Photocatalysis;
Performance of K-promoted hydrotalcite-derived CoMgAlO catalysts used for soot combustion, NOx storage and simultaneous soot–NOx removal by Qian Li; Ming Meng; Noritatsu Tsubaki; Xingang Li; Zhaoqiang Li; Yaning Xie; Tiandou Hu; Jing Zhang (406-415).
A series of K-promoted hydrotalcite-derived CoMgAlO catalysts were synthesized by coprecipitation. Their catalytic performance for soot combustion, NOx storage and simultaneous soot–NOx removal was evaluated, respectively. The techniques of TG/DTA, BET, XRD, EXAFS, XPS and in situ DRIFTS were employed for catalyst characterization. When K is added to the catalyst CoMgAlO, soot combustion is largely accelerated, with the temperature (T m) for maximum soot conversion lowered by at least 50 °C. Moreover, the NOx reduction by soot over the catalysts calcined at 500–700 °C is also facilitated. The K-containing catalyst calcined at 600 °C shows not only the highest soot combustion rate, but also the maximum NOx reduction percentage of 32%, which is attributed to its high surface K/Co atomic ratio and the strong interaction between K and Co. In situ DRIFTS results reveal that NO is readily oxidized to NO2 and stored as nitrates over K-promoted catalysts, which could be reduced by soot more efficiently. Based on these investigations, a reaction pathway for soot combustion, NOx storage and simultaneous soot–NOx removal is proposed.
Keywords: Soot; NOx; Hydrotalcite-derived CoMgAlO catalysts; Potassium; Calcination temperature;
Glycerol acetylation over dodecatungstophosphoric acid immobilized into a silica matrix as catalyst by P. Ferreira; I.M. Fonseca; A.M. Ramos; J. Vital; J.E. Castanheiro (416-422).
The esterification of glycerol with acetic acid was carried out over dodecatungstophosphoric acid (PW) immobilized into a silica matrix. The products of glycerol acetylation were monoacetin, diacetin and triacetin. The immobilization of PW into silica was carried out by two different techniques: sol–gel and impregnation methods. The catalysts prepared by sol–gel method will be denoted as PW-in-S while the catalysts prepared by impregnation will be denoted as PW-on-S. The catalysts were characterized by nitrogen adsorption at 77 K, FTIR, XDR and ICP-AES. A series of PW immobilized into silica with different PW loading were prepared. It was observed that the catalytic activity increases with the amount of PW immobilized into silica, either by the sol–gel method or by the impregnation method.High values of selectivity to diacetin were obtained with all catalyst.The effect of various parameters, such as, reaction temperature, catalyst loading, molar ratio of glycerol to acetic acid and reusability of PW-in-S2 were studied to optimize the reaction conditions.The catalytic stability of the PW-in-S2 was evaluated by performing consecutives batch runs with the same catalyst sample. It was observed a stabilization of the catalytic activity.
Keywords: Glycerol; Esterification; Heteropolyacids; Silica;
Effect of sulphuric acid pretreatment concentration on the behaviour of CoO X /γ-Al2O3-SO4 monolithic catalysts in the lean CH4-SCR process by J.C. Martín; S.B. Rasmussen; S. Suárez; M. Yates; F.J. Gil-Llambías; M. Villarroel; P. Ávila (423-427).
The pretreatment of conformed γ-alumina monolithic supports with sulphuric acid solutions induces an increase in the activity of CoO X /γ-Al2O3 catalysts for the selective catalytic reduction of nitrogen oxides employing methane as the reductant. The improvement in the activity was related to the acid strength of the acid used in the pretreatment step, where both the activities and selectivities were found to be greatest when the monolithic supports were pretreated with a 2.5 M H2SO4 solution. The UV–vis-NIR, XRD spectroscopies, zero point charge measurements and TGA studies demonstrated that the active cobalt phase was stabilised as a tetrahedral Co(II) complex, possibly associated to sulphate ligands. UV–vis-NIR spectroscopy further revealed that pretreatment with 2.5 M H2SO4 led to the lowest ratios of crystalline Co3O4, explaining the enhanced activity and higher selectivity, since this compound is known to promote the undesirable direct methane combustion with oxygen. Furthermore, TGA analysis combined with zeta-potential measurements, lead to the conclusion that the acidity, important for the activation of methane, increased on the catalyst surface with increasing acid concentration up to 2.5 M H2SO4, whereafter formation of Al2(SO4)3 took place, that lowered the catalytic activity due to the formation of non-selective cobalt oxide clusters.
Keywords: CH4; SCR; Monolith; DeNO X ; Cobalt; Alumina; UV–vis; Zeta potential;
Composition optimization of PtRuM/C (M = Fe and Mo) catalysts for methanol electro-oxidation via combinatorial method by Ki Rak Lee; Min Ku Jeon; Seong Ihl Woo (428-433).
Ternary PtRuFe and PtRuMo alloy systems were investigated for methanol electro-oxidation reaction (MOR). Rapid optimization of the ternary alloy compositions was achieved via combinatorial synthesis and high-throughput screening method. A combinatorial library was composed of 121 different compositions of the ternary PtRuFe and PtRuMo alloys. High MOR activities were observed in Pt5Ru3Fe2, Pt4Ru3Fe3, Pt5Ru4Mo1 and Pt4Ru4Mo2 compositions (mass ratio) via quantitative analysis of each catalyst spots. Performances of these compositions were verified in their powder version catalysts: (1) on-set potential for CO electro-oxidation decreased by 0.05 V in the PtRuFe alloys and 0.15 V in the PtRuMo and (2) high MOR activities were observed in the Pt5Ru4Fe1/C (98% higher mass activity than that of commercial PtRu/C) and the Pt4Ru3Mo3/C (260% higher specific activity than that of commercial PtRu/C).
Keywords: Methanol electro-oxidation; Direct-methanol fuel cell; Combinatorial chemistry; High-throughput screening;
Reductive dechlorination of carbon tetrachloride by zero-valent iron and related iron corrosion by Yongli Jiao; Cuicui Qiu; Lihui Huang; Kuixia Wu; Houyi Ma; Shenhao Chen; Luming Ma; Deli Wu (434-440).
Electrochemical corrosion behavior of iron in aqueous solutions with and without carbon tetrachloride (CT) was investigated in a wide pH range from 0.4 to 14 using steady-state polarization curves and electrochemical impedance spectroscopy (EIS). It was found that the presence of CT significantly accelerated the hydrogen evolution reaction (HER) on the iron surface in strong acidic solutions, causing severe corrosion of iron; in return, the iron corrosion was helpful for the reductive dechlorination of CT. The inherent relationship between the dechlorination of CT and the corrosion of iron is attributed to the fact that the adsorbed hydrogen atoms produced during the iron corrosion process are necessary for the dechlorination process of CT. As a result, the removal efficiency of CT is strongly dependent on the extent of iron corrosion in aqueous solutions at different pH values.
Keywords: Dechlorination; Carbon tetrachloride (CT); Adsorbed hydrogen; Iron; Corrosion; Hydrogen evolution;
Bimetallic catalysts supported on activated carbon for the nitrate reduction in water: Optimization of catalysts composition by Olívia Salomé G.P. Soares; José J.M. Órfão; Manuel Fernando R. Pereira (441-448).
The activities and selectivities of four pairs of bimetallic catalysts (Pd–Cu, Pt–Cu, Rh–Cu and Ir–Cu) supported on activated carbon were studied in order to optimize the metals composition for the reduction of nitrate in water with hydrogen. The catalytic tests were carried out in a semi-batch reactor, working at room temperature and pressure. The activity of the catalysts is quite different depending on the copper content. The maximum activity for the catalysts with 1% of the noble metal was obtained for 1%Rh–0.6%Cu, 1%Pd–0.6%Cu, 1%Pt–0.3%Cu and 1%Ir–0.3%Cu, with nitrate conversions after 5 h of reaction of 98%, 63%, 56%, and 55%, respectively. All these weight compositions correspond to an atomic ratio noble metal/copper close to 1. With the exception of the pair Ir–Cu, where the selectivity to ammonium is almost independent of the metals composition, for all the other cases it increases with the atomic copper content up to around 75%. The pair Rh–Cu was the most active among the bimetallic catalysts tested; however, significant amounts of ammonium are obtained. The nitrate conversions for the pairs Ir–Cu and Pt–Cu are similar but the former presents higher selectivities to ammonium. The pair Pd–Cu is the most selective in the transformation of nitrate to nitrogen.
Keywords: Nitrate; Reduction; Activated carbon; Bimetallic catalysts; Formulation;
Porous clay heterostructures (PCHs) intercalated with silica-titania pillars and modified with transition metals as catalysts for the DeNOx process by Lucjan Chmielarz; Zofia Piwowarska; Piotr Kuśtrowski; Barbara Gil; Andrzej Adamski; Barbara Dudek; Marek Michalik (449-459).
Porous clay heterostructures (PCHs) intercalated with silica as well as silica-titania pillars were obtained from natural montmorillonite. The PCH samples were modified with copper or iron by an ion-exchange method. Detailed characterization of the obtained materials included: chemical (EPMA), structural (XRD) and textural (BET) analysis, determination of coordination and aggregation of transition metal species (UV–vis-DRS, EPR) as well as analysis of surface acidity (FT-IR, NH3-TPD). Titanium incorporated into the silica pillars was present mainly in the form of separated cations. Small contribution of polymeric titanium oxides was detected only for the samples with the higher Ti loading. Titanium incorporated into the silica pillars significantly increased the surface acidity of the PCH materials. Transition metals (Cu, Fe) deposited on the surface of PCHs were present mainly in the form of isolated cations and oligomeric metal oxide species. Ti-containing PCHs modified with transition metals was found to be active and selective catalysts of the DeNOx process. The Cu- and Fe-modified catalysts effectively operated in a broad temperature range of 350–550 °C and 300–500 °C, respectively. The PCH based catalysts were only slightly deactivated by water vapour and SO2.
Keywords: Porous clay heterostructures (PCHs); Montmorillonite; Silica-titania pillars; DeNOx; Ammonia;
Correlations for photocatalytic activity and spectral features of the absorption band edge of TiO2 modified by thiourea by V. Nadtochenko; N. Denisov; A. Gorenberg; Yu. Kozlov; P. Chubukov; J.A. Rengifo; C. Pulgarin; J. Kiwi (460-469).
Doping of nanocrystalline TiO2 powders with sizes ranging from 9.5 nm up to 19.1 nm was carried out with thiourea (TU) to introduce the C, N and S-species into the TiO2. The crystal size was determined by X-ray diffraction. Doped-TiO2 particles were colored while the undoped TiO2 was white. The edge of the absorption band edge was analyzed to describe the TiO2 band gap according to the indirect transitions theory of semiconductors. In the former analysis the energy distribution of the doped centers is discussed in terms of the Urbach's tail theory ( K = K 0 exp σ ( ( h ν − E g ) / k T ) ), being K the absorbance in the Kubelka–Munk equation. Evidence is presented for thiourea doped-TiO2 leading to Urbach's tail associated with the formation of states in the band-gap rather than a narrowing of the band gap. The photocatalytic activity of the doped-TiO2 was tested by the reduction of tetra-nitromethane to nitroform and by the oxidation of I− to I3 −. The rate of formation of nitroform (NF) produced under 460 nm light increased for the smaller TiO2 nanoparticles. This suggests the formation of localized centers under 460 nm light. But under 366 nm light, the highest rate of NF formation was observed for samples with the biggest nanocrystal size. Under 366 nm light, the smaller particles show a low rate of nitroform formation due to a more favorable band-gap electron-hole recombination. Lipid phosphatidyl-ethanolcholine (PE) under 460 nm visible light in the presence of doped-TiO2 led to the formation of conjugated of double bonds in PE. This implies the formation of peroxy radicals due to the TiO2 e− cb localized electronic states under visible light irradiation.
Keywords: Photocatalysis; Doped TiO2; Nitroform; Visible light; Urbach tail;
Influence of the crystalline phase and surface area of the TiO2 support on the CO oxidation activity of mesoporous Au/TiO2 catalysts by Y. Denkwitz; M. Makosch; J. Geserick; U. Hörmann; S. Selve; U. Kaiser; N. Hüsing; R.J. Behm (470-480).
The influence of the TiO2 crystalline phase and of the surface area on the activity and stability/deactivation behavior of structurally well-defined mesoporous Au/TiO2 catalysts with comparable Au loading in the CO oxidation reaction was investigated by kinetic measurements under differential reaction conditions and by in situ DRIFTS. The crystalline phase and surface area of the TiO2 substrate were controlled by the pH and the type of the structure-directing surfactants applied in the synthesis. Au loading of the mesoporous oxides was performed by the same deposition–precipitation procedure for all catalysts. The resulting trends in the CO oxidation behavior, including the TOF based activities and the stability/deactivation behavior are discussed.
Keywords: Mesoporous catalysts; Activity; Deactivation; Au/TiO2; CO oxidation;
Self-cleaning modified TiO2–cotton pretreated by UVC-light (185 nm) and RF-plasma in vacuum and also under atmospheric pressure by M.I. Mejía; J.M. Marín; G. Restrepo; C. Pulgarín; E. Mielczarski; J. Mielczarski; Y. Arroyo; J.-C. Lavanchy; J. Kiwi (481-488).
Two new innovative findings presented in this study are: (a) TiO2–cotton fabrics obtained by pretreatment with UVC-light (185 nm) at atmospheric pressure introduced functionalities into the cotton surface enabling the chelation/binding of TiO2. This was possible since the molar absorption coefficient of O2 and N2 is very low at 185 nm and (b) the radiofrequency (RF-plasma) pretreatment of cotton surface lead to the formation active binding sites on the cotton at atmospheric pressure. This unexpected RF effect was due to the drastic localized heating of the cotton leading to intermolecular H-bond breaking between the cellulose surface-OH groups of adjacent molecules with the formation of functionalized groups in the cellulose fibers. The discoloration kinetics of the wine stain on the TiO2–cotton pretreated by RF at atmospheric pressure for 10 min was the most favorable. The red wine stains discoloration under Suntest simulated light was monitored by diffuse reflectance spectroscopy (DRS) and by the CO2 evolution during the stain mineralization. By X-ray photoelectron spectroscopy (XPS) it was possible to monitor the decrease of the C, N, S-species on the textile topmost layers during the discoloration process. The XPS Ti 2p3/2 peak shifts indicating Ti4+/Ti3+ oxido-reduction taking place during the photocatalysis. X-ray diffraction showed the formation of the anatase phase on the cotton. By X-ray fluorescence the loading of TiO2 before and after the discoloration process was found to be ∼0.8%. High-resolution electron microscopy (HRTEM) shows transparent TiO2 anatase 8–18 nm coating the cotton with layers ∼31 nm (±10%). These 3–4 TiO2 layers on the cotton did not affect the touch or handling properties of the cotton enabling the potential commercial use of the TiO2–cotton fabrics.
Keywords: RF-plasma; UVC-light; Photocatalysis; Self-cleaning; Wine stains; Cotton fabrics; TiO2;
Soot combustion over silver-supported catalysts by Eleonora Aneggi; Jordi Llorca; Carla de Leitenburg; Giuliano Dolcetti; Alessandro Trovarelli (489-498).
In this study the characterization and soot oxidation activity of Ag-based catalysts deposited on alumina, ceria and zirconia have been investigated. The combustion of soot was shown to be promoted by the presence of silver, especially in a zero valent state, over all the supports investigated. Presence of silver in a positive oxidation state is favoured with CeO2, while zero valent silver dominates over alumina and zirconia. This is likely attributed to the oxygen storage capacity of ceria which stabilizes silver in an oxidized form. Soot oxidation starts at low temperature (around 500 K for Ag on ZrO2) with a T 50 in the range of 600–640 K. Deactivation under strong ageing conditions (1023 K for 12 h) is negligible with alumina and zirconia, while in the presence of ceria, which slows down formation of metallic silver from Ag2O, loss of activity following thermal treatments at high temperatures becomes more intense.
Keywords: Ceria; CeO2; Zirconia; ZrO2; Alumina; Al2O3; Silver; Ag; Ag2O; Oxygen storage; Soot oxidation; Diesel; Combustion;
CuO nanoparticles entrapped in MFI framework: Investigation of textural, magnetic and catalytic properties of Cu-ZSM-5 and Cu-S-1 catalysts by Giuseppe Fierro; Giovanni Ferraris; Giuliano Moretti (499-506).
Cu-ZSM-5 zeolites are active catalysts for both NO decomposition and selective catalytic reduction (SCR) of NO by hydrocarbons in the presence of oxygen. Unfortunately they suffer of deactivation in the presence of water vapour in the feed that is mainly due to either the segregation of the initial extra-framework copper ions, or the sintering of the entrapped CuO-like species, to form large CuO aggregates on the external surface of the zeolite crystallites. In order to acquire more information about the nature of the CuO-like species which are formed upon dehydration of these materials at high temperature and the changes occurring to these species after catalysis, we investigated some Cu-ZSM-5 and Cu-S-1 catalysts by porosimetry and magnetic susceptibility measurements. Texture analysis revealed that, with respect to the H-ZSM-5 and S-1 parent materials, in the Cu-ZSM-5 and Cu-S-1 dehydrated samples a decrease of the surface area and micropore volume occurred, suggesting that most of the CuO-like species are entrapped into the zeolites channels. Consequently, their size has to fit the channel diameter (ca. 5.5 Å). This is confirmed by the magnetic results. Indeed, differently from bulk CuO, characterized by an antiferromagnetic behaviour, the magnetic susceptibility measurements of all the Cu-ZSM-5 samples followed the Curie–Weiss law typical of paramagnetic species. The lost of the antiferromagnetic behaviour supports the idea that the CuO-like particles are entrapped in the Cu-ZSM-5 channels as nanoclusters. On the other hand, the Cu-S-1 catalyst shows a complex magnetic behaviour, and peculiar textural modifications with respect to the S-1 parent material, suggesting that, with respect to those formed in Cu-ZSM-5, the CuO nanoclusters in this case are of a higher nuclearity and in a different location in the MFI structure. Under real catalytic conditions, i.e. in the presence of ca. 12% of water vapour in the feed, some changes occur to the CuO nanoparticles. In particular their structure seems to be affected. An increase in nuclearity is suggested that should lead to a decrease of the catalytic activity, as observed in the Cu-S-1 catalyst.
Keywords: CuO nanoparticles; Cu-MFI catalysts; Textural properties; Magnetic susceptibility measurements; SCR of NO by propane;
Enhancement effect of Ag for Pd/C towards the ethanol electro-oxidation in alkaline media by Son Truong Nguyen; Hiu Mung Law; Hoa Tien Nguyen; Noel Kristian; Shuangyin Wang; Siew Hwa Chan; Xin Wang (507-515).
Carbon supported Pd–Ag/C catalyst was prepared using co-reduction method. Physicochemical characterization results revealed that alloy nanoparticles with face-centered cubic structure were successfully formed. The electrochemical studies for ethanol oxidation in alkaline media were performed with cyclic voltammetry, linear sweep voltammetry and chronoamperometry methods. The results showed that Pd–Ag/C exhibited an excellent activity, enhanced CO tolerance and better stability than Pt/C and Pd/C, making it a promising anodic catalyst for alkaline direct ethanol fuel cell.
Keywords: Ethanol oxidation; Pd–Ag; Palladium; Silver; Alkaline; Direct ethanol fuel cell;
Ethanol oxidation reaction on PtCeO2/C electrocatalysts prepared by the polymeric precursor method by R.F.B. De Souza; A.E.A. Flausino; D.C. Rascio; R.T.S. Oliveira; E. Teixeira Neto; M.L. Calegaro; M.C. Santos (516-523).
This paper presents a study of the electrocatalysis of ethanol oxidation reactions in an acidic medium on Pt-CeO2/C (20 wt.% of Pt-CeO2 on carbon XC-72R), prepared in different mass ratios by the polymeric precursor method. The mass ratios between Pt and CeO2 (3:1, 2:1, 1:1, 1:2, 1:3) were confirmed by Energy Dispersive X-ray Analysis (EDAX). X-ray diffraction (XRD) structural characterization data shows that the Pt-CeO2/C catalysts are composed of nanosized polycrystalline non-alloyed deposits, from which reflections corresponding to the fcc (Pt) and fluorite (CeO2) structures were clearly observed. The mean crystallite sizes calculated from XRD data revealed that, independent of the mass ratio, a value close to 3 nm was obtained for the CeO2 particles. For Pt, the mean crystallite sizes were dependent on the ratio of this metal in the catalysts. Low platinum ratios resulted in small crystallites, and high Pt proportions resulted in larger crystallites. The size distributions of the catalysts particles, determined by XRD, were confirmed by Transmission Electron Microscope (TEM) imaging. Cyclic voltammetry and chronoamperometic experiments were used to evaluate the electrocatalytic performance of the different materials. In all cases, except Pt-CeO2/C 1:1, the Pt-CeO2/C catalysts exhibited improved performance when compared with Pt/C. The best result was obtained for the Pt-CeO2/C 1:3 catalyst, which gave better results than the Pt-Ru/C (Etek) catalyst.
Keywords: Ethanol oxidation reaction; Electrocatalysis; Pt nanoparticles; Ceria; Polymeric precursor method;
High temperature steam reforming of methanol over Cu/ZnO/ZrO2 catalysts by Yasuyuki Matsumura; Hideomi Ishibe (524-532).
Methanol steam reforming to hydrogen and carbon dioxide is catalyzed at 400 °C over Cu/ZnO/ZrO2 (Cu content, 30 wt.%) prepared by a coprecipitation method. Conventional binary catalysts of Cu/ZnO and Cu/ZrO2 have also been prepared by the same method. The activity of Cu/ZnO/ZrO2 is stable in comparison with the binary catalysts and a commercial Cu/ZnO/Al2O3. The selectivity to carbon monoxide by-produced over Cu/ZnO/ZrO2 is fairly low. The particle sizes of Cu and ZnO for Cu/ZnO/ZrO2 are significantly smaller than those for Cu/ZnO, and the BET surface area of Cu/ZnO/ZrO2 is 2–3 times as high as that of Cu/ZnO. The Cu particle size of Cu/ZnO/ZrO2 is stable during the reaction, but growth of ZnO and ZrO2 particles is accompanied with the deactivation.
Keywords: Methanol steam reforming; Cu/ZnO/ZrO2; Hydrogen production; Stability; TEM; XRD; XPS;
Characterization and photocatalytic performance of carbon nanotube material-modified TiO2 synthesized by using the hot CVD process by Toshiki Tsubota; Asami Ono; Naoya Murakami; Teruhisa Ohno (533-538).
Carbon nanotube-modified TiO2 was synthesized by using the hot CVD process. Fe (0.13–1.9 wt%) as the catalyst for synthesis of carbon nanotubes modified on the surface of TiO2, was loaded on commercial TiO2 particles. CH4 gas was used as the carbon source in the CVD process. The color of the Fe-supported TiO2 powder changed to black when CVD treatment was performed. Nano-sized spherical carbon materials were generated on the surface of TiO2 after the CVD process. The spherical materials gradually changed to carbon nanotubes with increase in CVD treatment temperature. When the CVD process was performed under optimized conditions, the photocatalytic activity of the carbon nanotube-modified TiO2 was drastically increased. These results indicated that photoexcited electrons might pass through the carbon nanotubes on the surface of TiO2 resulting in improvement in charge separation between electrons and holes generated photocatalytically. For our system, the carbon nanotube materials were grown directly on the surface of TiO2 and this might induce strong interaction between carbon nanotubes and TiO2. Meanwhile, the long-range π electronic conjugation of nanotubes is of benefit to accelerate electron transfer. Thus, the photogenerated electrons of TiO2 are rapidly transported to the carbon nanotube materials bound to the surface of TiO2. The transfer of electrons generated in TiO2 to carbon nanotubes was confirmed by photodeposition of Pt particles by reduction of Pt4+ ions.
Keywords: Chemical vapor deposition; Doping; Composite materials; Photocatalyst; TiO2;
Photoelectrochemical degradation of anti-inflammatory pharmaceuticals at Bi2MoO6–boron-doped diamond hybrid electrode under visible light irradiation by Xu Zhao; Jiuhui Qu; Huijuan Liu; Zhimin Qiang; Ruiping Liu; Chengzhi Hu (539-545).
Bi2MoO6 particles were selectively deposited onto a boron-doped diamond (BDD) surface from amorphous complex solution via a dip-coating method followed by calcination. Its structure was confirmed via Raman and X-ray diffraction analysis. Scanning electron microscopy showed that the resulting Bi2MoO6 particles scattered on the BDD substrate. The photoelectrochemical measurement of the Bi2MoO6–BDD electrode showed a clear improvement in the photocurrent under visible light irradiation, indicating a new hybrid system. Furthermore, the hybrid electrode was applied in the degradation of ibuprofen and naproxen, two kinds of non-steroidal anti-inflammatory drugs via photocatalysis, electro-oxidation, and photoelectrocatalytic processes. It is shown that ibuprofen can be degraded via photocatalysis and electro-oxidation process with the applied bias potential of 2.0 V. By contrast, ibuprofen and naproxen can be rapidly degraded via combined electro-oxidation and photocatalysis process under visible light irradiation. Furthermore, the degradation rate in the combined process is larger than the sum of photocatalysis and electro-oxidation processes. The ibuprofen and naproxen were also efficiently mineralized in the combined process. Finally, the main intermediates of ibuprofen degradation were also identified.
Keywords: Ibuprofen; Naproxen; BDD electrode; Photoelectrocatalysis; Visible light;
M/TiO2/SiO2 (M = Fe, Mn, and V) catalysts in photo-decomposition of sulfur mustard by Ştefan Neaţu; Vasile I. Pârvulescu; Gabriel Epure; Nicoleta Petrea; Vasile Şomoghi; Gabriele Ricchiardi; Silvia Bordiga; Adriano Zecchina (546-553).
The photocatalytic decomposition of sulfur mustard (bis(2-chloroethyl)sulfide) has been examined on Fe-, Mn- and V-doped dispersed titania-silica catalysts. The catalysts were prepared by successive incipient wetness impregnation. They have been characterized by means of vibrational (FTIR) and optical (UV–vis–NIR in the DRS mode) spectroscopy. Powder XRD, XPS, and BET were used to characterize the structural morphology and texture. The reaction was carried out in two different types of reactors under both UV and visible light irradiation. The parent titania-silica catalyst showed activity only under UV irradiation, while the doped ones were active in the decontamination of the persistent sulfur mustard even under visible light irradiation.
Keywords: Photocatalysis; Titania-silica; Sulfur mustard photodegradation;
Is sulfur-doped TiO2 an effective visible light photocatalyst for remediation? by Erin M. Rockafellow; Laine K. Stewart; William S. Jenks (554-562).
Doping titania with main group elements increases the visible light absorbance by introducing a localized band of orbitals within the band gap, but the effect of such dopants on the oxidizing power of the catalysts remains ambiguous. Three aromatic organic probe molecules – 4-methoxyresorcinol, quinoline, and 1-(p-anisyl)neopentanol – have been used to evaluate the oxidative chemistry of S-doped TiO2 and test the efficacy of the catalyst with visible irradiation. With visible irradiation, a phenol is degraded efficiently, apparently through absorption by a CT band. For the other two probes, the most straightforward interpretation is that visible irradiation does not produce hydroxyl-type chemistry, but can accomplish single-electron transfers in favorable cases. The utility of sulfur-doped TiO2 as a photocatalyst over undoped titania depends entirely whether the requirement for visible-light functionality, even if at low efficiency, outweighs a modest drop in the efficiency of catalysis using UV light.
Keywords: Photocatalysis; Doped titanium dioxide; Visible light;
Electrochemical synthesis of novel structured catalysts for H2 production by Francesco Basile; Patricia Benito; Giuseppe Fornasari; Valentina Rosetti; Erika Scavetta; Domenica Tonelli; Angelo Vaccari (563-572).
Innovative catalysts supported on metallic foams (FeCrAlloy) have been prepared by electrochemical synthesis of Ni-containing hydrotalcite-type (HT) films, and used in the steam methane reforming. It consisted of a one-step synthesis and deposition of HT compounds on metallic supports after the application of a cathodic potential on the foam. The effects of synthesis parameters, applied potential (−0.9 and −1.2 V) and time (600, 1000 and 1800 s), on the properties of the supported films and catalytic performances were investigated. The potential applied mainly affected the rate of the basic media generation in the vicinity of the electrode, which is responsible for the precipitation of the HT compounds. The pulse length was the key factor to determining both the coverage of the support and the thickness of the film. Moreover, the Ni- and Al-content in the catalyst depended on both factors. The synthesis conditions affected the steam reforming tests performed under industrial-type conditions. The selection of optimum synthesis conditions (−1.2 V for 1000 s) led to a well-adhered catalyst film, showing catalytic performances close to the thermodynamic equilibrium and stable with increasing time-on-stream. Furthermore, this preparation method offers the opportunity to develop processes with increasing chemico-energetic efficiency of endothermic reactions.
Keywords: H2 production; Structured catalyst; Electrochemical synthesis; Hydrotalcite-type compound; Nickel; Metallic foam; Steam methane reforming;
Degradation of ionic liquids by Fenton reaction; the effect of anions as counter and background ions by E.M. Siedlecka; M. Gołębiowski; Z. Kaczyński; J. Czupryniak; T. Ossowski; P. Stepnowski (573-579).
The influence of counter ions (Cl−, C(CN)3 − and CF3SO3 −) and background ions (C6F11O2 −, C8F15O2 − and C10F19O2 −) on the degradation rates of 1-butyl-3-methylimidazolium cation (bmim+) in a Fenton-like system were investigated. The degradation rate of bmim+ was influenced by the particular anions as follows: Cl− > C(CN)3 − > CF3SO3 −. The inhibition of imidazolium moiety oxidation was observed in the case of counter anions in ionic liquid which entered the competition for hydroxyl radicals with bmim+ or which formed complexes with ferric and ferrous ions. The presence of perfluoric acids as a background in solution also had significance for the bmim+ degradation process. These organic anions can inhibit bmim+ oxidation through strong interactions between positively charged bmim+ and negatively charged perfluocarboxylic anions (PFCA). Additionally, bmim+ seemed to be more resistant to oxidation in the presence of a longer n-perfluoric alkyl chain anions. However, it was observed that the inhibition of bmim+ oxidation decreased when the concentration of PFCA in solution exceeded a critical micellar concentration. This fact can be explained by weaker interactions between bmim+ and perfluoric anions, stronger associated with aggregated PFCA in these experimental conditions (pH 3). Our investigations also indicated the possibility of PFCA interactions with ferric and ferrous ions.
Keywords: Ionic liquids; Perfluoric acids; Fenton reaction; Oxidation of organic matter;