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Applied Catalysis B, Environmental (v.121-122, #)
Hydrogen production through oxidative steam reforming of ethanol over Ni-based catalysts derived from La1− xCe xNiO3 perovskite-type oxides by Sania M. de Lima; Adriana M. da Silva; Lídia O.O. da Costa; José M. Assaf; Lisiane V. Mattos; Reema Sarkari; A. Venugopal; Fábio B. Noronha (pp. 1-9).
Display Omitted► The incorporation of Ce into the LaNiO3 structure affected the catalyst stability. ► La0.90Ce0.10NiO3 catalyst exhibited better stability in OSR of ethanol. ► No carbon formation was observed on La0.90Ce0.10NiO3 catalyst. ► La0.90Ce0.10NiO3 has smaller Ni particle size and higher amount of oxygen vacancies.This paper investigates the effect of lanthanum substitution by cerium oxide on the performance of La1− xCe xNiO3 ( x=0, 0.05, 0.1, 0.4, 0.7 and 1.0) perovskite-type oxide precursor for the oxidative steam reforming of ethanol. All catalysts are active and selective to hydrogen but carbon deposition occurs except for La0.90Ce0.10NiO3. Increasing the Ce content decreases the amount of carbon deposited, which passes through a minimum at around 10wt% of Ce and then increases. The higher resistance to carbon formation on La0.90Ce0.10NiO3 catalyst is due to the smaller Ni crystallite size. Furthermore, the support also plays an important role on catalyst stability during ethanol conversion reaction. The reduced La0.9Ce0.1NiO3 sample exhibits the highest amount of oxygen vacancies, which decreases as ceria content increases. This highly mobile oxygen reacts with carbon species as soon as it forms, and thus keeps the metal surface free of carbon, inhibiting deactivation.
Keywords: Perovskite-type oxides; Hydrogen production; Ethanol oxidative steam reforming; Deactivation mechanism; Nickel catalyst
A lumped kinetic model based on the Fermi's equation applied to the catalytic wet hydrogen peroxide oxidation of Acid Orange 7 by Adrián M.T. Silva; J. Herney-Ramirez; Umut Söylemez; Luis M. Madeira (pp. 10-19).
Display Omitted► Acid Orange 7 is completely degraded by a catalytic wet hydrogen peroxide process. ► Mineralization of up to 80% was reached in less than 4h. ► The 21wt.% Fe-pillared saponite clay catalyst is very active and quite stable. ► Models were developed to describe both dye and TOC concentration histories. ► Kinetics is based on Fermi's equation, with remarkable adherence to the data.A catalytic wet hydrogen peroxide process was applied for the degradation of an azo dye – Acid Orange 7, also called Orange II (OII) – using as catalyst a pillared saponite clay impregnated with 21wt.% of iron. Tests were carried out in a slurry batch reactor, following along time the OII degradation, the dye mineralization and the iron leaching from the support. A detailed parametric study was done, changing one variable at a time, while keeping the others constant. Among the variables studied (temperature, catalyst dose, and initial concentration of oxidant – H2O2 – or dye), temperature revealed to have a marked effect, increasing reaction rate but also iron leaching from the support (which was in all cases still negligible, thus allowing to comply with legislated standards and evidencing the heterogeneous character of the process). A previously developed semi-empirical kinetic model, based on the Fermi's equation (the mirror image of the logistic function), was used to successfully describe the evolution of the OII concentration in this complex process. Such equation was extended in the present work by developing a lumped model proposed to predict the evolution of the total organic carbon along time; this model also showed very good adherence to the experimental data.
Keywords: Acid Orange 7 (Orange II); Catalytic wet hydrogen peroxide oxidation; Fe-containing pillared clay; Reaction kinetic model; Fermi's equation; Total organic carbon
Bacteria and fungi inactivation using Fe3+/sunlight, H2O2/sunlight and near neutral photo-Fenton: A comparative study by I. García-Fernández; M.I. Polo-López; I. Oller; P. Fernández-Ibáñez (pp. 20-29).
.Display Omitted► The inactivation of a bacterium and a fungus was evaluated under sunlight with H2O2, Fe3+ and H2O2/Fe3+. ► The inactivation pattern and rate is observed to be highly dependent on the type of microorganism. ► The order of disinfecting efficacy was: photo-Fenton>H2O2/sunlight>Fe3+/sunlight.Wastewater reuse is becoming increasingly important for water sustainability, and is essential for the enhancement of access to safe water for human needs like drinking water and crop irrigation. The adequate treatment of contaminated wastewater is needed so that it may be used to recharge water resources. Therefore, reduction and control of waterborne pathogens are required for appropriate water reuse. Advanced Oxidation Processes, which generate hydroxyl radicals, are promising treatments for water disinfection. The purpose of the current study was to evaluate and compare the effectiveness of three solar treatments; Fe3+/sunlight, H2O2/sunlight, and solar photo-Fenton at near-neutral pH, for the inactivation of Fusarium solani and Escherichia coli in water. Different concentrations of Fe3+ (0–50mg/L), H2O2 (0–10mg/L) and Fe3+/H2O2 (1/2.5, 5/10, 10/10, 50/10mg/L) were evaluated in bottle reactors (200mL) for 5h under natural solar light in the Southeast of Spain. The order of efficacy for disinfection of both kinds of microorganisms was: photo-Fenton>H2O2/sunlight>Fe3+/sunlight.The results for bacteria inactivation show that the highest rate was observed using photo-Fenton system with 5mg/L of Fe3+ and 10mg/L of H2O2, which gave a 5-log inactivation of E. coli in 10min (0.96kJ/L). The best results for Fusarium inactivation were found using 2.5mg/L of Fe3+ and 5mg/L of H2O2, which gave a 3.4-log decrease in 3h of solar exposure (14.47kJ/L). Moreover, sunlight with H2O2 alone showed good potential for water disinfection with only low doses of H2O2 (10mg/L) required for 6-log inactivation of E. coli and a 3-log inactivation of F. solani.In all cases studied, the inactivation pattern and rate is observed to be highly dependent on the type of microorganism. The spores of F. solani were more resistant than the vegetative cells of E. coli to the solar treatments.
Keywords: Fusarium solani; Escherichia coli; Solar photo-Fenton; Solar disinfection; Hydrogen peroxide
A comparative study on the removal of cylindrospermopsin and microcystins from water with NF-TiO2-P25 composite films with visible and UV–vis light photocatalytic activity by Miguel Pelaez; Polycarpos Falaras; Athanassios G. Kontos; Armah A. de la Cruz; Kevin O'shea; Patrick S.M. Dunlop; J. Anthony Byrne; Dionysios D. Dionysiou (pp. 30-39).
Display Omitted► Improved physicochemical properties and photocatalytic activity of NF-TiO2 with the addition of P25-TiO2 nanoparticles. ► The optimum P25-TiO2 loading was 5gL−1 in the modified sol. ► The general reactivity of the microcystins with the composite films at pH 3.0 was MC-LA>MC-LR≥MC-YR>MC-RR. ► Cylindrospermopsin was efficiently removed under UV–vis light despite negligible adsorption at pH 3.0.In this investigation, in order to develop photocatalyst materials with improved photo-efficiency and visible light response compared to the state of the art materials, the role of Evonik Aeroxide® P25-TiO2 (P25) nanoparticles incorporated in a modified sol–gel process to yield composite nitrogen and fluorine doped TiO2-P25 (NF-TiO2-P25) films was investigated. The addition of P25 nanoparticles in the sol leads to higher BET surface area, pore volume, porosity and total TiO2 mass, as well as larger thickness and roughness of the films after heat treatment. Microscopy techniques confirmed partial sintering of NF-TiO2 sol–gel formed and P25 nanoparticles having different average size. The existence of well defined regions of only anatase from NF-TiO2 and anatase–rutile mix from P25 was verified in the micro-Raman spectra. The photocatalytic degradation of four microcystins (microcystin-LR, -RR, -LA and -YR) and cylindrospermopsin was evaluated with NF-TiO2 and NF-TiO2-P25 films under visible and UV–vis light. The general reactivity for the microcystins under acidic conditions (pH 3.0) was: MC-LA>MC-LR≥MC-YR>MC-RR where the highest initial degradation rate was achieved with the NF-TiO2-P25 films (5gL−1 of P25 in sol when irradiated with visible light and 15gL−1 of P25 in sol when irradiated with UV–vis light). Cylindrospermopsin showed negligible adsorption at pH 3.0 for all films. Nevertheless, significant photocatalytic removal was found under UV–vis light with maximum P25 loaded films indicating that the degradation was mediated by the involvement of photogenerated reactive oxygen species and not by the trapping reaction of the positive hole.
Keywords: Nitrogen doping; Fluorine doping; P25; TiO; 2; Photocatalysis; Photocatalytic; Cylindrospermopsin; Microcystins; Visible; UV–vis; Water treatment
Influence of reaction parameters on the activity of ruthenium based catalysts for glycerol steam reforming by Alessandro Gallo; Claudio Pirovano; Paola Ferrini; Marcello Marelli; Rinaldo Psaro; Saveria Santangelo; Giuliana Faggio; Vladimiro Dal Santo (pp. 40-49).
Display Omitted► Low loaded ruthenium based catalyst supported on magnesium aluminum mixed oxide. ► Heterogeneous catalysts for glycerol steam reforming to hydrogen rich mixtures. ► High temperature and low glycerol concentrations result in highest performances. ► High glycerol concentrations result in low, but stable, activity. ► Coke and by-products are formed at low temperatures and high glycerol concentrations.Mg(Al)O supported Ru catalysts with low loading of active metal (0.6wt.%), obtained from simple inorganic salts, were tested, for the first time, in the steam reforming (SR) of glycerol to hydrogen rich mixtures. The catalysts, obtained by simple wet impregnation of Ru salts on a Mg(Al)O mixed oxide followed by high temperature oxidation/reduction treatments, were systematically characterized by numerous complementary techniques, both before and after their use in SR reaction. The changes of the performances (activity, selectivity and stability) of Ru/Mg(Al)O catalysts were studied, produced by varying reaction temperature (450–650°C) at fixed glycerol concentration (10wt.% in water), and by varying glycerol concentration (10–40wt.% in water) at fixed reaction temperature (550°C). The best performances (in terms of glycerol conversion, H2 yield and CO2 selectivity), at lowest reaction temperature, were obtained operating at 10wt.% glycerol and 550°C. Correspondingly, catalysts showed glycerol conversion, H2 yield and CO2 selectivity close to 100%. Methane was practically absent, CO selectivity was lower than 3.5% and coke deposition quite scarce (1.1mgCgcat−1h−1). However, at this temperature, catalysts exhibited stable, although lower, performances up to 40wt.% glycerol concentrations. Significantly, catalytic performances could be improved increasing reaction temperature up to 650°C keeping other advantages.
Keywords: Steam reforming; Glycerol; Hydrogen; Ruthenium; Magnesium aluminum mixed oxide; Coke
Facile route to prepare bimodal mesoporous γ-Al2O3 as support for highly active CoMo-based hydrodesulfurization catalyst by Xinmei Liu; Xiang Li; Zifeng Yan (pp. 50-56).
In the presence of polyethylene glycol(PEG), bimodal mesoporous nanorod γ-Al2O3 was successfully synthesized via hydrothermal method. The introduction of the novel structure alumina to the hydrodesulfurization catalyst can significantly change it's physically properties and improve the performance in reaction. There is apparently pore confinement effect and nanosized effect in the hydrodesulfurization catalyst.Display Omitted► Bimodal mesoporous nanorod γ-Al2O3 was successfully synthesized. ► The formation of novel structure of alumina was investigated. ► The effects of the novel structure of alumina on the HDS catalyst were discussed. ► The reasons of optimum catalytic performance were also exhibited.In the presence of polyethylene glycol (PEG), bimodal mesoporous nanorod γ-Al2O3 was successfully synthesized via hydrothermal method. The pore structure, crystal parameters and morphology of the alumina can be controlled by PEG. The more PEG can facilely induce the formation of bimodal mesoporous skeletal nanorod structure and lead to the relatively higher crystallinity to the alumina. This novel structure alumina result in the catalysts for hydrodesulfurization (HDS) possessing lower metal–support interaction and higher crystal phase dispersion. The nanorod structure of alumina contributes shorter crystallite length and higher staking degree to the catalysts. Of note is that there is apparently pore confinement effect on the HDS process. The catalysts with bimodal mesoporous structure indicate the higher HDS activity than that of catalyst with mono-modal structure.
Keywords: Bimodal mesoporous alumina; Nanorod; Hydrodesulfurization catalyst; HDS activity
A linear molecule functionalized multi-walled carbon nanotubes with well dispersed PtRu nanoparticles for ethanol electro-oxidation by Xiulin Yang; Junpeng Zheng; Mingming Zhen; Xiangyue Meng; Feng Jiang; Taishan Wang; Chunying Shu; Li Jiang; Chunru Wang (pp. 57-64).
Display Omitted► PtRu nanoparticles with 1–3nm size uniformly deposited on MWCNTs wrapped by linear POB. ► POB is used as an effective cross linker between MWCNTs and precursors of Pt and Ru ions. ► POB can preserve the integrity and the electronic structure of MWCNTs. ► The PtRu/POB-MWCNTs catalyst shows excellent performance for ethanol electro-oxidation.The performance-enhanced PtRu electrocatalysts derived from polyoxyethylene bis(amine) functionalized multi-walled carbon nanotubes (POB-MWCNTs) were fabricated by electrostatic self-assembly technology, in which Pt and Ru precursors were first uniformly distributed on the POB-functionalized MWCNT surface via the electrostatic interaction and then reduced in situ to PtRu nanoparticles in ethylene glycol-water solution. In this process, POB as the wrapping molecule not only preserves the integrity and well dispersion of MWCNTs, but also facilitates the even distribution of PtRu nanoparticles on the surface of MWCNTs. The structure and catalytic properties of the PtRu catalysts were characterized by various spectroscopic techniques such as FT-IR, Raman, TGA, XPS, TEM and XRD spectrometry, and the electrocatalytic properties for ethanol oxidation were investigated by cyclic voltammetry and chronoamperometry. It was revealed that the as-prepared PtRu catalysts possess a high electrocatalytic activity and stability for the electro-oxidation of ethanol, and it provides a facile and eco-friend approach to large-scale production of high performance fuel cell eletrocatalysts.
Keywords: Multi-walled carbon nanotubes; Polyoxyethylene bis(amine); Self-assembly; Electrocatalyst; Direct alcohol fuel cells
Highly efficient multifunctional dually-substituted perovskite catalysts La1− xK xCo1− yCu yO3− δ used for soot combustion, NO x storage and simultaneous NO x-soot removal by Zhaoqiang Li; Ming Meng; Yuqing Zha; Fangfang Dai; Tiandou Hu; Yaning Xie; Jing Zhang (pp. 65-74).
Display Omitted► La1− xK xCo1− yCu yO3− δ is highly efficient for soot combustion and NO x-soot removal. ► More Co4+ ions and oxygen vacancies are formed in La1− xK xCo1− yCu yO3− δ catalysts. ► Substituted La1− xK xCo1− yCu yO3− δ possesses larger amount of adsorbed oxygen species. ► Dual substitution by K/Cu obviously decreases the soot combustion activation energy. ► Reaction pathways for soot combustion and simultaneous NO x-soot removal are proposed.A series of K/Cu simultaneously substituted nanometric perovskite catalysts La1− xK xCo1− yCu yO3− δ ( x=0, 0.1; y=0, 0.05, 0.1, 0.2, 0.3) were synthesized by citric acid complexation, which were employed for soot combustion, NO x storage and simultaneous NO x-soot removal. The physico-chemical properties of the catalysts were characterized by XRD, FT-IR, EXAFS, SEM, H2-TPR, Soot-TPR, TG/DTA, XPS and in situ DRIFTS techniques. When K and Cu are simultaneously introduced into LaCoO3, soot combustion is largely accelerated, decreasing the characteristic temperature ( Tm) corresponding to the maximal soot combustion rate at least 80°C; moreover, NO x reduction by soot is also remarkably facilitated. Among all the catalysts La0.9K0.1Co0.9Cu0.1O3− δ shows the lowest Tm of 360°C, the highest NO x storage capacity (NSC) of 284μmolg−1 and the largest NO x reduction percentage of 32%; for soot combustion, it also exhibits the lowest activation energy (80.04kJmol−1). The XPS and Soot-TPR results reveal that the catalyst La0.9K0.1Co0.9Cu0.1O3− δ possesses more active and larger amount of surface oxygen species (O2− and O−), more tetravalent cobalt ions and better reducibility than others, which determines its better catalytic performance. Based on in situ DRIFTS and other characterization results, the potential mechanisms for soot combustion, NO x storage and simultaneous NO x-soot removal are proposed.
Keywords: Soot combustion; NO; x; reduction; Perovskite; Dual substitution; Mechanism
Activity and thermal stability of Rh-based catalytic system for an advanced modern TWC by Iljeong Heo; Dal Young Yoon; Byong K. Cho; In-Sik Nam; Jin Woo Choung; Seungbeom Yoo (pp. 75-87).
Display Omitted► ZrO2 is a promising support for preparing a thermally stable Rh TWC. ► The sintering and burial of Rh are primary causes for the catalyst deactivation. ► Rh-tetragonal ZrO2 interaction prevents a burial of Rh into ZrO2 support.The catalytic activity and thermal durability of Rh supported on a variety of metal oxides for removing NO x in the three-way catalyst (TWC) converter have been investigated under realistic gasoline engine exhaust conditions. Among the Rh/metal oxide catalysts examined, the Rh/ZrO2 catalyst has the best thermal durability. The catalytic activity and thermal stability of the Rh/ZrO2 catalysts have shown strong dependence on the ZrO2 support employed, with the ZrO2 prepared by the sol–gel (SG) and precipitation (P) methods exhibiting the most favorable catalytic performance. The improved TWC performance and thermal stability of the Rh/ZrO2 (SG and P) catalysts compared to other Rh/ZrO2 catalysts are mainly due to the structural difference in the underlying ZrO2 supports. Both ZrO2 (P) and ZrO2 (SG) contain the tetragonal as well as the monoclinic phase of ZrO2, whereas the others are primarily in the monoclinic phase. Deactivation of the Rh/ZrO2 upon thermal aging is mainly caused by the loss of the active metal surface area of Rh due to sintering and/or burial of Rh into the sublattice of ZrO2. The strong interaction of Rh with the tetragonal phase of ZrO2 appears to prevent the burial of Rh into ZrO2 lattice during the thermal aging. A series of comparative kinetic experiments revealed that the Rh/ZrO2 (SG and P) catalysts among other Rh/metal oxide catalysts produce the least amount of harmful NH3, which can be subsequently oxidized to hazardous NO x over the Pd-based oxidation catalyst co-existing in the TWC converter. A dual-brick monolith system washcoated with Rh/ZrO2 (P) and Pd/Al2O3 in the front and the rear bricks, respectively, has shown superior thermal durability over monolith configurations investigated in the present study.
Keywords: TWC; Rh/ZrO; 2; Catalyst deactivation; NH; 3; formation; TWC monolith
A non-acid-assisted and non-hydroxyl-radical-related catalytic ozonation with ceria supported copper oxide in efficient oxalate degradation in water by Tao Zhang; Weiwei Li; Jean-Philippe Croué (pp. 88-94).
Display Omitted► A non-acid-assisted and non-hydroxyl-radical-related catalytic ozonation. ► Highest activity at neutral pH. ► Significant promotion by bicarbonate, a hydroxyl radical scavenger in water. ► Molecular ozone is the principal oxidant in the catalytic degradation. ► Multidentate Cu(II)–oxalate complex is formed on new Cu(II) sites.Oxalate is usually used as a refractory model compound that cannot be effectively removed by ozone and hydroxyl radical oxidation in water. In this study, we found that ceria supported CuO significantly improved oxalate degradation in reaction with ozone. The optimum CuO loading amount was 12%. The molar ratio of oxalate removed/ozone consumption reached 0.84. The catalytic ozonation was most effective in a neutral pH range (6.7–7.9) and became ineffective when the water solution was acidic or alkaline. Moreover, bicarbonate, a ubiquitous hydroxyl radical scavenger in natural waters, significantly improved the catalytic degradation of oxalate. Therefore, the degradation relies on neither hydroxyl radical oxidation nor acid assistance, two pathways usually proposed for catalytic ozonation. These special characters of the catalyst make it suitable to be potentially used for practical degradation of refractory hydrophilic organic matter and compounds in water and wastewater. With in situ characterization, the new surface Cu(II) formed from ozone oxidation of the trace Cu(I) of the catalyst was found to be an active site in coordination with oxalate forming multi-dentate surface complex. It is proposed that the complex can be further oxidized by molecular ozone and then decomposes through intra-molecular electron transfer. The ceria support enhanced the activity of the surface Cu(I)/Cu(II) in this process.
Keywords: Catalytic ozonation; Acid assistance; Hydroxyl radical oxidation; Bicarbonate; Oxalate
Catalyst property of Co–Fe alloy particles in the steam reforming of biomass tar and toluene by Lei Wang; Yuji Hisada; Mitsuru Koike; Dalin Li; Hideo Watanabe; Yoshinao Nakagawa; Keiichi Tomishige (pp. 95-104).
Display Omitted► The optimized Co–Fe/Al2O3 showed high activity and stability in tar steam reforming. ► The optimized Co–Fe/Al2O3 has high catalytic activity and stability in the toluene steam reforming with H2 addition. ► Most Co and Fe species were reduced to form fcc Co–Fe and bcc Co–Fe alloy. ► The bcc Co–Fe alloy at the suitable composition has high catalytic activity.Performance of Co–Fe/Al2O3 catalysts with the optimum composition (Fe/Co=0.25) was much higher than corresponding monometallic Co and Fe catalysts in the steam reforming of tar from the pyrolysis of cedar wood in terms of the catalytic activity and the suppression of coke deposition. According to the catalyst characterization, the fcc and bcc Co–Fe alloys were formed by H2 reduction on the Co–Fe/Al2O3 catalyst. In the steam reforming of toluene, the addition of H2 to the reactant gas enhanced the activity of Co–Fe/Al2O3 remarkably. Without H2 addition, bcc Co–Fe alloy particles were oxidized and this is connected to the deactivation. With H2 addition, the bcc Co–Fe alloy with an appropriate composition is maintained in metallic state and it contribute to high activity in the steam reforming of toluene.
Keywords: Cobalt; Iron; Alloy; Steam reforming; Biomass; Tar
Synthesis of Pt-Cu/SiO2 catalysts with different structures and their application in hydrodechlorination of 1,2-dichloroethane by Xing Wei; Ai-Qin Wang; Xiao-Feng Yang; Lin Li; Tao Zhang (pp. 105-114).
Display Omitted► Pt-Cu/SiO2 catalysts with core–shell structures. ► Controllable particle sizes and chemical compositions. ► High selectivity to ethylene for hydrodechlorination of 1,2-dichloroethane.Pt-Cu/SiO2 catalysts with different structures and chemical compositions were prepared using a two-step method. For the series of Pt xCu100− x/SiO2 catalysts, Pt was deposited in the first step with H2PtCl6 as the precursor and Cu was deposited subsequently with Cu(NH3)42+ as the precursor. For the Cu100− xPt x/SiO2 catalyst, the deposition sequence was reversed accompanied with galvanic displacement of Cu0 by Pt4+. All the samples were characterized by XRD, TEM, H2-TPR, H2 chemisorption, and DRIFT of CO adsorption, and evaluated for the catalytic hydrodechlorination of 1,2-dichloroethane. The results show that the Pt xCu100− x/SiO2 catalysts exhibit core–shell structures with Pt-rich alloy cores and Cu-rich alloy shells, while the Cu100− xPt x/SiO2 catalyst shows a Pt–Cu alloy core and a Pt rich alloy shell. Different structures and chemical compositions lead to quite different performances in catalyzing the hydrodechlorination of 1,2-dichloroethane. The Pt16Cu84/SiO2 catalyst gave a high selectivity to ethylene over 90% and an excellent stability over 18h run due to the Cu-rich shell structure, while the Cu44Pt56/SiO2 catalyst produced predominantly ethane due to the Pt rich shell.
Keywords: Platinum; Copper; Hydrodechlorination; Bimetallic; Dichloroethane
Chloride-free Cu-modified SAPO-37 catalyst for the oxidative carbonylation of methanol in the gas phase by Thi Thuy Hanh Dang; Michael Bartoszek; Matthias Schneider; Dang-Lanh Hoang; Ursula Bentrup; Andreas Martin / (pp. 115-122).
Display Omitted► Zeolite Y analogue FAU structure SAPO-37 could be used for MeOH oxycarbonylation in the gas phase. ► No destruction of the crystallinity during template removal and loading with Cu can be detected. ► Cu-modification of SAPO-37 has been carried out by solid state ion exchange using Cu acetyl acetonate. ► The application of Cu-SAPO-37 offers an alternative to the commonly used CuY catalyst.The substitution of harmful phosgene or chloride-containing catalysts in the synthesis of dimethyl carbonate (DMC) and its use as “green solvent” or polycarbonate building block direct its manufacture towards environmental benign syntheses. Thus, copper was introduced into silicoaluminophosphate structure SAPO-37 (belonging to the same FAU structure family like aluminosilicate zeolites Y and X) by solid state ion exchange (SSIE) using Cu(II) acetyl acetonate. This strategy circumvented structural breakdown being observed when using aqueous copper solutions for impregnation or ion exchange. The SSIE efficiently ran when the organic template is widely extracted from the synthesis form of SAPO-37, e.g. through treatment with methanolic HCl. The parent SAPO-37, template-free SAPO-37 and Cu-SAPO-37 materials were characterized by XRD, TG, temperature programmed reduction (TPR), temperature programmed desorption of ammonia (TPDA) and FTIR spectroscopy of adsorbed pyridine and CO. The Cu-SAPO-37 catalyst pre-treated in inert gas exhibits a high selectivity for DMC and dimethoxymethane (DMM) in the oxidative carbonylation of methanol (OCM). The catalytic behavior of Cu-SAPO-37 is shown to be comparable with those of a Cu-containing Y zeolite catalyst that is so far regarded as one of the best chloride-free catalyst for the OCM reaction in the gas phase.
Keywords: SAPO-37; Cu-modified SAPO-37; Dimethyl carbonate; Oxidative carbonylation of methanol; Solid state ion exchange
Modulating the copper oxide morphology and accessibility by using micro-/mesoporous SBA-15 structures as host support: Effect on the activity for the CWPO of phenol reaction by Xin Zhong; Jacques Barbier Jr.; Daniel Duprez; Hui Zhang; Sébastien Royer (pp. 123-134).
Display Omitted► Mesoporous supported CuO nanoparticles are prepared by in situ autocombustion method. ► Removal of phenol by CWPO is investigated using SBA-15 supported copper oxide. ► Mesoporous supported CuO are efficient but present limited stability in reaction. ► Pore structure affects CuO dispersion which results in different catalytic activity.This study presents an original approach to the improvement of advanced oxidation process (AOP) efficiencies through the design of highly active catalysts. Then, removal of phenol was obtained under mild conditions by catalytic wet peroxide oxidation (CWPO) process over silica supported micropore and/or mesopore confined copper oxide nanoparticles. The materials, i.e. y wt.% CuO ( y ranging from 4 to 10) on SBA-15 exhibiting different pore structure properties, were entirely characterized. In this study, we took advantage from the evolution of the micropore fraction in the mesoporous silica with the autoclaving temperature of synthesis. While only mesopore nanocasted copper oxide nanoparticle formed when the support exhibits only mesoporosity, micropore silica confined nanoparticles other formed the two supports exhibiting both micropores and mesopores. In this case, mesopore nanocasted nanoparticles can be only observed when copper oxide loading reaches 10wt.%. As a consequence, the copper active surface is suggested to be higher when copper incorporates interconnected micropores, without limited pore plugging issued from mesopore confined nanoparticle formation.For the phenol removal reaction, all the materials are exhibiting interesting activity, with a complete conversion of phenol and almost 60–80% of mineralization obtained in less than 2h at 60°C. Nevertheless, the results showed that the increase in copper loading up to high values is not needed to achieve high mineralization degree, due to the typical morphology of the materials, i.e. confinement of nanoparticles inside micropores or mesopores. In addition, the prepared materials allow a continuous use in reaction with leaching of active phase (≤4.4mgL−1) which also results in no water post-purification for cation removal as in the case of the classical homogeneous Fenton process.
Keywords: SBA-15; x; CuO/SBA-15(; y; ); Auto-combustion; Catalytic wet peroxide oxidation (CWPO) process
Ceria–gadolinia supported NiCu catalyst: A suitable system for dry reforming of biogas to feed a solid oxide fuel cell (SOFC) by G. Bonura; C. Cannilla; F. Frusteri (pp. 135-147).
Display Omitted► Design an efficient system suitable for dry reforming of a simulated biogas mixture. ► The formation of a nickel–copper solid solution results to be fundamental. ► Copper addition promotes the kinetics of nickel reduction. ► The decay kinetics is fundamentally ruled out by the coking rate. ► By feeding CO2-lean biogas mixtures, carbon considerably forms also at 800°C.NiCu/Ce0.9Gd0.1O2− δ (CGO) catalysts were prepared by different techniques with the aim to develop a bifunctional catalyst, characterized both by catalytic and anodic properties for integrated biogas SOFC process. Catalytic measurements have been performed in CO2 reforming of CH4, using a fixed bed reactor at a reaction temperature ranging from 650 to 800°C. Results revealed that NiCu/CGO system is a promising catalyst for the conversion of biogas mixtures at temperature suitable to be used in low temperature solid oxide fuel cell (LT-SOFC). Characterization data clearly demonstrated that NiCu alloy forms by reduction of NiCuO x mixed oxide patches, while catalytic testing showed carbon-free operation at 800°C (GHSV=6600h−1) when “CO2-rich” biogas mixtures are used. By a thermodynamic evaluation of the different reaction kinetics, the poor efficiency of the catalyst in promoting the carbon gasification by CO2 reaction has been assessed. Characterization of spent catalysts shed light both on the reasons of deactivation phenomena occurring with time over the catalysts and on the deactivation kinetics under the adopted experimental conditions.
Keywords: Biogas conversion; Dry reforming; Solid oxide fuel cells; NiCu alloy
Synthesis of porous platinum-ion-doped titanium dioxide and the photocatalytic degradation of 4-chlorophenol under visible light irradiation by Suzuko Yamazaki; Yuhei Fujiwara; Shinya Yabuno; Kenta Adachi; Kensuke Honda (pp. 148-153).
Display Omitted► Pt-ion doped TiO2 was synthesized by the modified sol–gel method. ► Pt-TiO2 has mesopores and BET surface area higher than 200m2g−1. ► Pt-TiO2 shows a superior activity to TiO2 under UV and visible light irradiation. ► Kinetic studies for degradation of 4-chlorophenol were performed under visible light. ► Reaction rate law was proposed.Porous platinum-ion-doped TiO2 (Pt-TiO2) with BET surface area higher than 200m2g−1 was prepared by using water as solvent and conducting dialysis in a sol–gel method and demonstrated to have superior photocatalytic activity for the photodegradation of 4-chlorophenol (4-CP) under both ultraviolet and visible light (VL) irradiation. During dialysis, 76.5% of Cl− was removed and mesopores were formed in Pt-TiO2. Measurements of pore-size distribution indicated a peak at ca. 3nm after the calcination of Pt-TiO2 at 200°C. Optimal conditions to prepare Pt-TiO2 acting under VL were 0.5at.% as the Pt-doping content and 200°C as the calcination temperature in the range of 200–500°C. Kinetic studies were performed to clarify the effect of the amount of Pt-TiO2, initial concentration of 4-CP, intensity and wavelength of the incident light, pH and temperature on the reaction rate and to obtain the rate law under VL irradiation. Formation of benzoquinone and hydroquinone as intermediates was observed. They were further photodegraded on Pt-TiO2 and 90.7% of 4-CP was completely mineralized at the VL irradiation of 390min.
Keywords: Visible-light responsive photocatalyst; Titanium dioxide; Platinum-doping; Kinetics
Electrooxidation of methanol on highly active and stable Pt–Sn–Ce/C catalyst for direct methanol fuel cells by Arun Murthy; Eungje Lee; Arumugam Manthiram (pp. 154-161).
Display Omitted► Pt–Sn–Ce catalysts exhibit superior catalytic activity for methanol oxidation. ► Pt–Sn–Ce catalysts exhibit better stability than the conventional Pt–Ru catalysts. ► The addition of Ce into Pt–Sn enhances the oxidation of CO to CO2.Carbon supported Pt–Sn–Ce and Pt–Sn catalysts have been synthesized by a polyol reduction method and compared for methanol oxidation reaction (MOR). X-ray photoelectron spectroscopic (XPS), X-ray diffraction (XRD), and transmission electron microscopic (TEM) analyses reveal the beneficial effects of the Ce component in Pt–Sn–Ce/C for MOR, despite its low content. Electrochemical techniques such as COad stripping, linear scan, and derivative voltammetries along with electrochemical impedance spectroscopy (EIS) were employed to analyze MOR on Pt–Sn–Ce/C and Pt–Sn/C from a mechanistic point of view. Accelerated durability test (ADT) and single cell test of Pt–Sn–Ce/C in comparison to a commercial PtRu/C catalyst demonstrate the superior performance of Pt–Sn–Ce/C from stability and activity points of view.
Keywords: Methanol oxidation reaction; Pt–Sn catalyst; Pt–Sn–Ce catalyst; Electrochemical stability; Direct methanol fuel cell
Activity, selectivity and stability of praseodymium-doped CeO2 for chlorinated VOCs catalytic combustion by B. de Rivas; N. Guillén-Hurtado; R. López-Fonseca; F. Coloma-Pascual; A. García-García; J.I. Gutiérrez-Ortiz; A. Bueno-López (pp. 162-170).
Pure and mixed oxides of Ce and/or Pr were prepared and evaluated for the catalytic combustion of 1,2-dichloroethane. Ce0.5Pr0.5O2 is the most active and stable catalyst, while other formulations suffer deactivation by chlorination.Display Omitted► Ce0.5Pr0.5O2 is an active and stable catalyst for chlorinated VOC combustion. ► Ce0.5Pr0.5O2 activity was constant in a 115h VOC-Cl combustion test at 350°C. ► Ce0.5Pr0.5O2 activity was constant after three VOC-Cl combustion tests (150–500°C). ► Pure and mixed oxides with Ce:Pr ratio different to 1 suffer partial deactivation. ► Deactivation is attributed to chlorination.Ce–Pr mixed oxides, namely Ce0.8Pr0.2O2, Ce0.5Pr0.5O2 and Ce0.2Pr0.8O2, were prepared by conventional coprecipitation and evaluated for the catalytic combustion of 1,2-dichloroethane, which was selected as a model reaction for chlorinated VOC abatement. For comparison purposes, the pure oxides were also prepared and catalytically tested. A certain decrease in catalytic activity was observed after three consecutive temperatures cycles from 150 to 500°C for all catalysts, except for Ce0.5Pr0.5O2. This deactivation was particularly noticeable for pure praseodymia and Ce0.2Pr0.8O2, while Ce0.8Pr0.2O2 and Ce0.5Pr0.5O2 exhibited a superior stability. The catalysts deactivation was attributed to bulk and/or surface chlorination, as revealed by X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy. Interestingly, the Ce0.5Pr0.5O2 mixed oxide, which converted the chlorinated feed at the lowest temperature due to its substantial resistance to chlorination, showed a constant activity in a 115h lifetime test at 335°C.
Keywords: Chlorinated VOC combustion; 1,2-Dichloroethane; Ce; x; Pr; 1−; x; O; 2; Cerium–praseodymium mixed oxide
Comparison of the efficiency and mechanism of catalytic ozonation of 2,4,6-trichloroanisole by iron and manganese modified bauxite by Fei Qi; Bingbing Xu; Lun Zhao; Zhonglin Chen; Liqiu Zhang; Dezhi Sun; Jun Ma (pp. 171-181).
Reaction mechanism of modified raw bauxite catalytic ozonation of 2,4,6-trichloroanisole. The adsorption of both ozone and TCA in the micropores resulted in the subsequent interaction (direct and indirect oxidation) between them. This was followed by diffusion of ozone and TCA on the mesoporous surface. Surface hydroxyl groups covering mesoporous surface initialed ozone decomposition to generateOH, resulted in TCA degradation.Display Omitted► Iron and manganese-modified bauxite was used as catalyst in catalytic ozonation. ► The role of surface chemical properties of modified bauxite in catalytic ozonation for removal trichloroanisole was confirmed. ► Different role of micropores and mesoporous in catalytic ozonation was determinate.The efficiency and mechanism of catalytic ozonation of 2,4,6-trichloroanisole (TCA) by metal oxide modified bauxite were studied. TCA was effectively degraded by catalytic ozonation in the presence of iron- or manganese-modified bauxite (IMB or MMB). The effect of water pH on catalytic ozonation indicated that surface property was the key factor that influenced the activity of catalyst. Analysis results of the isoelectric point (IEP) and zeta potential for catalyst further confirmed that a lower zeta potential for modified bauxite enhanced catalytic activity. Results of both catalytic ozone decomposition and radical scavengers experiments indicated that catalytic ozonation by IMB or MMB followed a hydroxyl radical (OH) reaction pathway. The main reaction pathway was proposed that adsorption of both ozone and TCA in the micropores and subsequent interaction (direct and indirect oxidation) between them that was confirmed by the analysis of the surface pore volume and surface hydroxyl groups, being followed by the diffusion of ozone and TCA on the mesoporous surface, in which surface hydroxyl groups covering mesoporous surface initialed ozone decomposition to generateOH, resulted in TCA degradation.
Keywords: Catalytic ozonation; Bauxite; Iron modification bauxite (IMB); Manganese modification bauxite (MMB); 2,4,6-Trichloroanisole
High efficiency of the cylindrical mesopores of MWCNTs for the catalytic wet peroxide oxidation of C.I. Reactive Red 241 dissolved in water by M. Soria-Sánchez; E. Castillejos-López; A. Maroto-Valiente; M.F.R. Pereira; J.J.M. Órfão; A. Guerrero-Ruiz (pp. 182-189).
Display Omitted► Carbons as catalysts for removing a dye from wastewaters by peroxidation with H2O2. ► Evaluation of reactant adsorption, decomposition of H2O2 and catalytic oxidation. ► Textural and surface properties of carbon materials are considered. ► The role of inorganic impurities of activated carbon is studied. ► Hydrophobic carbon nanotubes appear as the more efficient catalysts.A study of the catalytic decolourisation of one textile dye by oxidation with H2O2, using different carbon materials as catalysts, is reported. Ten carbon solids, differing both in their texture–structure features and in their surface chemistry properties, were used for this purpose. These are two activated carbons, a high surface graphite, two structured nanomaterials (carbon nanofibres and carbon nanotubes), and the derivative samples prepared by oxidation of the pristines with nitric acid solutions. All these samples were characterised by determination of the nitrogen adsorption isotherms, thermogravimetric data, transmission electron microscopy, pH at the point of zero charge and chemical composition based on the X-ray photoelectron spectra. These carbon materials were evaluated as catalysts for the catalytic wet peroxide oxidation of C.I. Reactive Red 241 dissolved in water. Carbon nanotubes (CNTs) exhibit the highest performance in terms of activity for the catalytic wet peroxide oxidation, achieving a total removal of the dye after 90min in process. It appears that catalytic activity for this reaction is improved by the internal cylindrical mesopores of CNTs. However, when these hydrophobic CNTs are treated by incorporation of oxygen surface groups which increase their hydrophilic character, the high catalytic performance of CNTs largely disappears.
Keywords: Carbon materials; Hydrogen peroxide; Adsorption; Catalytic decomposition
Nanocrystalline TiO2 based films onto fibers for photocatalytic degradation of organic dye in aqueous solution by A. Panniello; M.L. Curri; D. Diso; A. Licciulli; V. Locaputo; A. Agostiano; R. Comparelli; G. Mascolo (pp. 190-197).
Display Omitted► Nanosize TiO2 was deposited onto commercially available silica and alumina fibers. ► Supported catalysts showed high photocatalytic activity. ► Performance of obtained coated fibers was compared with that of suspended P25 TiO2.Nanocrystalline titania (TiO2) synthesized via sol–gel, by using an alkoxide precursor were deposited onto commercially available silica and alumina fibers, namely E-Glass and Nextel 650, respectively. Different processing conditions and material preparation parameters, such as amount of TiO2, film composition and annealing temperature were tested in order to obtain nanocrystalline TiO2 with different morphological and structural characteristics. The materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and the Brunauer, Emmett, and Teller (BET) surface area measurements. The photocatalytic activity of the obtained coated fibers was investigated by monitoring the degradation of a model molecule, an azo dye (Methyl Red), under UV irradiation in aqueous solution. The detected photocatalytic performance of the sol–gel derived nanocrystalline TiO2 was explained on the basis of mechanism associated to the photocatalytic decomposition of organic molecules using semiconductor oxides and accounted for the structural and morphological characteristics of the TiO2 based coating. The materials with the most suited characteristics for photocatalysis were used to scale up the deposition onto a larger sample of fiber and then tested in a photocatalytic reactor. A commercially available TiO2 standard material (TiO2 P25 Degussa) was used as reference, in order to ultimately assess the viability of the coating process for real application.
Keywords: TiO; 2; colloidal nanocrystals; TiO; 2; Degussa P25; Supported nano-sized TiO; 2; Degradation of organic dye
Significant enhanced performance for Rhodamine B, phenol and Cr(VI) removal by Bi2WO6 nancomposites via reduced graphene oxide modification by Hongwei Ma; Jianfeng Shen; Min Shi; Xin Lu; Zhiqiang Li; Yu Long; Na Li; Mingxin Ye (pp. 198-205).
Display Omitted► Photocatalysts were prepared by a simple and green hydrothermal way. ► Reduced graphene oxide sheets (RGO) acts as a nanostructure growth-directing template. ► Small amount of RGO modified Bi2WO6 nanocomposites could enhance photocatalytic performance. ► The photocatalyst shows good stable and regeneration property.A series of reduced graphene oxdie(RGO) modified Bi2WO6 nanocomposites were synthesized by hydrothermal method and characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and Brunauer–Emmett–Teller (BET) specific surface areas analysis. The results indicated that the RGO could be used as structure-directing agent in the process of formation of the RGO/Bi2WO6 nanocomposites. The as-prepared RGO/Bi2WO6 nanocomposites can effectively remove Rhodamine B, phenol and Cr(VI) from water under UV and visible light irradiation. Therefore, the amount of RGO in the composite is an important factor affecting photocatalytic activity of RGO/Bi2WO6 nanocomposites. Therefore, the optimum amount of RGO is 20mg, at which the RGO/Bi2WO6 sample displays the highest reactivity. Furthermore, the as-prepared photocatalyst has its prominent potential as a readily separable and recoverable one. Our findings demonstrated that RGO could be utilized as a modified and structure-directing agent for promising development of high-performance photocatalysts in the environmental applications.
Keywords: Reduced graphene oxide; Hydrothermal; Bi; 2; WO; 6; Degradation; Cr(VI) reduction
Organic dye-sensitized TiO2 as a versatile photocatalyst for solar hydrogen and environmental remediation by Sung Kyu Choi; Hyun Sik Yang; Jae Hong Kim; Hyunwoong Park (pp. 206-213).
Display Omitted► Ru-free organic dyes with different numbers of carboxylate groups are anchored to TiO2. ► All dyes are effective in producing H2 in the presence of electron donors. ► The sensitization effects change due to switched binding modes of the organic dyes. ► The dye structure is less important in the remediation of pollutants.This study explores the applicability of organic dye-sensitized TiO2 particles in the production of molecular hydrogen and remediation of environmental pollutants (4-chlorophenol and Cr(VI)) under visible light ( λ>420nm). In order to examine the effect of number of anchoring groups, Ru-free organic dyes of donor–π–acceptor configuration are prepared with different numbers ( n) of carboxylate anchoring groups ( n=1, 2, and 3; referred to as D1, D2, and D3, respectively). All the three dyes are found to be effective at producing H2 in the presence of electron donors (triethanolamine (TEOA) and ethylenediaminetetra-acetic acid (EDTA)) with the following orders: D3–D2>D1 (TEOA) and D3>D2–D1 (EDTA). FTIR studies reveal that D1 and D3 are anchored to the TiO2 surface primarily via bidentate modes with a single carboxylate and two carboxylates, respectively. D2, in contrast, is anchored with one or two carboxylates, depending on the competing electron donors. The number of carboxylates is less important in the sensitized remediation of pollutants likely due to different photochemical conditions (oxic vs. anoxic) and various reaction pathways. A detailed systematic study is performed, including the UV–vis absorption characterization of free dyes and dye/TiO2 samples, the photoelectrochemical behaviors of dye/TiO2 electrodes, and the effects of dye concentrations, solution pH, and TiO2 kind (Degussa P25 vs. Hombikat UV-100).
Keywords: Water splitting; Artificial photosynthesis; Dye structure; Cr reduction; Electron donors
Effect of Fe–olivine on the tar content during biomass gasification in a dual fluidized bed by M. Virginie; J. Adánez; C. Courson; L.F. de Diego; F. García-Labiano; D. Niznansky; A. Kiennemann; P. Gayán; A. Abad (pp. 214-222).
Display Omitted► Fe/olivine has suitable properties for tar primary reduction in biomass gasification. ► Fe/olivine is an inexpensive and non-toxic material. ► Important improvements in comparison to olivine and silica sand were found. ► The dual effect as catalyst and oxygen carrier produces an increased tar destruction. ► Catalyst has a good aging in the operating conditions.The Fe/olivine catalyst effectiveness regarding tar primary reduction during biomass gasification in dual fluidized beds has been investigated. The use of Fe/olivine instead olivine leads to an important decrease in the amount of produced tar, which was reduced by up to 65% at 850°C, naphthalene being the most stable molecule. It has been found that Fe/olivine materials have a double effect on tar destruction. On the one hand, they act as a catalyst for tar and hydrocarbon reforming. On the other hand, they can act as an oxygen carrier that transfers oxygen from the combustor to the gasifier, and part of the oxygen is used to burn volatile compounds. The catalyst was fairly stable because the result was confirmed during 48h of continuous operation. The Fe/olivine material characterization (X-ray diffraction, Mössbauer spectroscopy, temperature programmed reduction and oxidation, etc.) revealed that the catalyst structure was maintained despite the large number of oxidizing–reducing cycles. The carbon that formed on the catalyst surface was low and easily oxidized in the combustion zone. Therefore, the inexpensive and non-toxic Fe/olivine catalyst is a material suitable for use as primary catalyst in a fluidized bed gasification of biomass.
Keywords: Fe/olivine catalyst; Biomass gasification; Tar removal; Dual fluidized bed
CeO2/H2O2 system catalytic oxidation mechanism study via a kinetics investigation to the degradation of acid orange 7 by Feng Chen; Xingxing Shen; Yongchuan Wang; Jinlong Zhang (pp. 223-229).
Display Omitted► The catalytic oxidation reactivity of CeO2/H2O2 system is related to surface Ce3+. ► H2O2 over-complexation decreases the catalytic reactivity of CeO2. ► Adsorbed organics occupy the Ce3+ sites, and protect Ce3+ from H2O2 complexation. ► Degradation of AO7 shows an apparent reaction order of 2.40 to its adsorption on CeO2.Nano ceria with cubic lattice was prepared and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Degradation kinetics of acid orange 7 (AO7) was investigated to understand the catalytic oxidation mechanism of the CeO2 with H2O2. The degradation of AO7 relies significantly on its adsorption on the surface of CeO2 with an apparent order of 2.40. Increasing the concentration of H2O2 increases the degradation reaction rate constant of AO7 in a positive linear relationship at the initial stage, but later hinders further degradation of AO7 due to over-complexation of Ce3+ with H2O2. The catalytic kinetics of CeO2 in pre-adsorbed mode (AO7 pre-adsorbed on CeO2 before the addition of H2O2) and pre-mixed mode (CeO2 pre-mixed with H2O2 before the addition of AO7) is quite different. The pre-mixed mode is unfavorable for AO7 degradation, as almost all of surface Ce3+ are pre-oxidized into surface peroxide species with H2O2 and hence reduces adsorption of AO7 as well as the activation of AO7 degradation. Reversely, the reactivity of CeO2 can slowly be recovered by adsorption of AO7, which competitively adsorbs on the CeO2 and gradually initiates the release of the surface Ce3+ by consuming the surface peroxide species. The AO7 degradation kinetics investigation in this work verifies that the degradation of organics in CeO2/H2O2 system is adsorption-triggered and the Ce3+ in reduced state is essential for activating the catalytic oxidation activity of surface peroxide species. EPR studies show that the surface peroxide species oxidizes the organics via hydroxyl adduct route.
Keywords: Ceria; Hydrogen peroxide; Peroxide species; Adsorption; Kinetics; Ce; 3+
Kinetics of photocatalytic disinfection in TiO2-containing polymer thin films: UV and visible light performances by Anna Kubacka; Manuel Ferrer; Marcos Fernández-García (pp. 230-238).
Display Omitted► Inactivation of 5 microorganisms is essayed with Ag–, Cu– and Zn–TiO2 containing polymer thin films. ► TiO2-polymer thin films present high activity irrespective of the microorganism nature. ► UV and visible light maximum activity is obtained using Ag and Zn-promoted TiO2 biocidal agents. ► The active species of the disinfection process is a hole-related radical.The photocatalytic disinfection potential of TiO2- and Cu-, Zn- and Ag-promoted TiO2 embedded in polymer-based materials has been analyzed upon both ultraviolet and visible light excitations. A complete set of microorganisms including two Gram-negative ( Escherichia coli and Pseudomonas earuginosa) and two Gram-positive ( Staphylococcus aureus and Enterococcus faecalis) bacteria and a yeast ( Pichia jadinii) was used throughout the study. This series covers clinically and food derived infection relevant pathogens. A kinetic modeling using an “adsorption Langmuir–Hinshelwood” type mechanism was used to interpret the disinfection tests and the performance of the different TiO2 photo-biocide agents. The results clearly indicate that Ag- and Zn-containing materials are the most effective in all conditions tested (e.g. irrespective of the microorganism nature and light energy) and this seems intimately linked with intrinsic characteristics of the radical species reaching the surface of the polymer-oxide nanocomposite films as detected by electron paramagnetic resonance.
Keywords: Photocatalysis; Titania; Anatase; Metal and oxide promotion; Silver; Copper; Zinc; EVOH polymer; Biocidal; Germicidal; EPR
Coupled NO x storage and reduction and selective catalytic reduction using dual-layer monolithic catalysts by Yi Liu; Michael P. Harold; Dan Luss (pp. 239-251).
Display Omitted► Dual layer SCR (top)/LNT (bottom) monolithic catalysts synthesized for lean NO x reduction. ► Rich-lean period switching generates NH3 in LNT layer and reduces NO x in SCR layer. ► Dual-layer catalysts achieve higher N2 selectivity than LNT-only catalyst at same NO x conversion. ► Dual-layer catalyst has higher NO x conversion than LNT-only catalyst in presence of CO2 and H2O. ► Ceria improves NO x reduction below 250°C and mitigates PGM migration.Lean reduction of NO x (NO and NO2) was studied using monolith-supported catalysts consisting of a layer of a metal-exchanged (Fe, Cu) zeolite (ZSM-5) selective catalytic reduction (SCR) catalyst deposited on top of a Pt/Rh/BaO/CeO2 lean NO x trap (LNT) catalyst. During periodic switching between lean and rich feeds, the LNT layer reduces NO x to N2 and NH3. The SCR layer traps the latter, resulting in additional NO x reduction. The dual-layer catalysts exhibited high N2 selectivity and low NH3 selectivity over the temperature range of 150–300°C. The NO x conversion was incomplete due to undesired side reactions in the LNT layer, such as NH3 oxidation to N2O at low temperature and NO x at high temperature. The NO x conversion and N2 selectivity of the Cu-exchanged ZSM-5 was higher than that of the Fe-exchanged ZSM-5. This was due to a higher low temperature SCR activity and a higher NH3 storage capacity on the Cu-zeolite. The dual-layer catalyst had a higher NO x conversion than the LNT catalyst below 300°C and a higher N2 selectivity over the entire temperature range when H2O and CO2 were present in the feed. The NO x storage capacity and NH3 generation increased upon addition of CeO2 to the LNT layer below 250°C. It also led to increased NH3 oxidation at high temperatures. The addition of ceria mitigated the undesirable migration of Pt between the LNT and SCR layers. Hydrothermal aging had a smaller effect on dual-layer catalysts containing ceria.
Keywords: Dual-layer catalyst; Monolith; Lean NO; x; Trap; NO; x; storage and reduction; Selective catalytic reduction; Ceria; Cu; Fe; ZSM-5; NH; 3; Lean NO; x; reduction; Pt