Applied Catalysis B, Environmental (v.91, #3-4)

Contents (CO4).

Synthesis and thermal treatment of cu-doped goethite: Oxidation of quinoline through heterogeneous fenton process by Iara R. Guimaraes; Amanda Giroto; Luiz C.A. Oliveira; Mario C. Guerreiro; Diana Q. Lima; José D. Fabris (581-586).
Samples of Cu-doped goethites were prepared and characterized by Mössbauer spectroscopy, XRD, TPR and BET surface area measurements. Mössbauer data showed the incorporation of Cu2+ in the goethite structure, and this cation-doping caused a significant decrease of the chemical reduction temperature in the TPR process. The catalytic behavior of these Fe1−x Cu x OOH materials was investigated for the H2O2 decomposition to O2 and the Fenton-like reaction to oxidize quinoline. It was observed that Cu2+ in this goethite and also the thermal treatment with H2 produced a strong increase in the catalytic activity during the quinoline oxidation. The successive hydroxylation of quinoline during this oxidation strongly suggests that highly reactive hydroxyl radicals are generated during the reaction involving H2O2 on the Cu-goethite grain surface, also confirming that these materials are efficient heterogeneous Fenton catalysts.
Keywords: Goethite; Copper; Oxidation; Fenton-like reaction;

Study of the selective catalytic reduction of NO x on an efficient Fe/HBEA zeolite catalyst for heavy duty diesel engines by Peter Balle; Bastian Geiger; Dirk Klukowski; Matias Pignatelli; Stefan Wohnrau; Michael Menzel; Ingo Zirkwa; Gunther Brunklaus; Sven Kureti (587-595).
The present paper addresses the removal of NO x from the exhaust of heavy duty vehicles using the SCR technique. The studies were conducted with a highly active H-BEA zeolite exhibiting a molar Si/Al ratio of 12.5 and a Fe load of 1.0 wt.% (1Fe/HBEA). The pronounced efficiency of 1Fe/HBEA is reflected by the apparent turnover frequency being superior to traditional V2O5/WO3/TiO2. The nature of the Fe sites was investigated with high resolution transmission electron microscopy (HRTEM), 57Fe Mössbauer spectroscopy and powder X-ray diffraction (PXRD). In connection with previous examinations it is deduced that the iron sites represent octahedrally coordinated high spin Fe3+ cations. Furthermore, highly dispersed species, which are the most active sites, are supposed to be paramagnetic, while oligomeric and particulate structures indicate superparamagnetic behaviour.The practical evaluation of the 1Fe/HBEA catalyst was systematically carried out including laboratory studies of granulated powder and honeycomb samples as well as engine bench tests. For the latter studies a coated honeycomb prototype was employed showing very similar efficiency as referred to a commercial V2O5/WO3/TiO2 pattern.Furthermore, 1Fe/HBEA exhibits pronounced hydrothermal stability after aging at 550 °C which represents an elevated exhaust temperature of heavy duty vehicles. The aging caused no change in fast SCR, i.e. when a c(NO2)/c(NO x ) ratio of 0.5 was used, and only minor decline in standard SCR. The slight aging effect is mainly referred to little decrease in BET surface area and NH3 uptake, respectively. PXRD indicated maintenance of the BEA structure, whereas 27Al nuclear magnetic resonance spectroscopy showed removal of some Al from the zeolite framework. Contrary, UV–vis spectroscopy evidenced no effect of hydrothermal aging on the composition of the Fe sites. Finally, the catalyst also maintained its efficiency after SO2 aging at 300 °C. Diffuse reflectance infrared Fourier transform spectroscopic studies showed adsorption of molecular SO2 on the zeolite substrate releasing already at about 400 °C.
Keywords: SCR; BEA; Zeolite; Fe; Active sites; Diesel engine; Hydrothermal aging; SO2 stability;

Influence of preparation methods of LaCoO3 on the catalytic performances in the decomposition of N2O by J.P. Dacquin; C. Lancelot; C. Dujardin; P. Da Costa; G. Djega-Mariadassou; P. Beaunier; S. Kaliaguine; S. Vaudreuil; S. Royer; P. Granger (596-604).
This study reports the potential interest of LaCoO3 in the catalytic decomposition of N2O from nitric acid plants. Typically, the exhaust gas contains NO, water and O2 which usually induce strong inhibiting effects depending on the surface properties of the solids particularly the surface mobility of oxygen from LaCoO3. Different preparation methods have been implemented, involving citrate route, reactive grinding and the use of templates, which lead to different structural and textural properties examined by X-ray diffraction, transmission electron microscopy and N2 physisorption. EDX analysis and XPS measurements also revealed that different surface composition may alter subsequent interactions between the surface and the reactants and related catalytic performances. LaCoO3 prepared by reactive grinding was found to be the most active catalyst due to a high specific surface area but the presence of Fe and Zn impurities inherent to the preparation method were suggested to interfere on the catalytic performances.
Keywords: Nitrous oxide; N2O decomposition; Perovskite; XPS; LaCoO3;

Environmentally friendly phthalocyanine catalysts for water decontamination—Non-photocatalytic systems by P. Kluson; M. Drobek; A. Zsigmond; J. Baranyi; P. Bata; S. Zarubova; A. Kalaji (605-609).
Macrocyclic porphyrin-like compounds known as phthalocyanines (Pcs) have been shown to produce singlet oxygen species upon illumination with light of an appropriate wavelength. Singlet oxygen is an effective agent for complete oxidation of common water-soluble pollutants including chlorinated phenols. The most active are, in this respect, phthalocyanines bearing Al, Zn and Si central atoms. Although these compounds were proofed to be virtually non-toxic, the presence of the Al3+ and Zn2+ ions may contradict this. On the other hand e.g. iron phthalocyanine (FePc) does not represent any danger from this point of view. However, due to the specific coordination of its central metal ion and also because of the number of electrons occupying its valence orbitals, the FePc cannot be effectively activated by the photon flux. Here we report on an alternative system in the dark. It is based on the initial catalytic decomposition of various peroxo substances by metal Pc, producing oxidising species which can decompose chlorinated phenols. A series of Pcs and peroxo substances were compared and the reaction system optimised. It was shown that the highest activity was revealed for the system comprising of FePc and tert-butylhydroperoxide. Iron phthalocyanine was also successfully immobilised on an Al2O3 solid matrix, and this heterogeneous system was tested analogously to the homogeneous one. Virtually zero leaching of the anchored complex was detected and the activity was found to be comfortably high.
Keywords: Phthalocyanines; Iron phthalocyanine; Chlorinated phenols; Water purification;

Support effect on the low-temperature hydrogenation of benzene over PtCo bimetallic and the corresponding monometallic catalysts by Shuliang Lu; William W. Lonergan; Yuexiang Zhu; Youchang Xie; Jingguang G. Chen (610-618).
PtCo bimetallic and Co, Pt monometallic catalysts supported on γ-Al2O3, SiO2, TiO2 and activated carbon (AC) were prepared and evaluated for the hydrogenation of benzene at relatively low temperatures (343 K) and atmospheric pressure. Results from flow reactor studies showed that supports strongly affected the catalytic properties of different bimetallic catalysts. AC supported PtCo bimetallic catalysts exhibited significantly better performance than the other bimetallic catalysts, and all the bimetallic catalysts possessed higher activity than the corresponding monometallic catalysts. Results from CO chemisorption and H2-temperature-programmed reduction (H2-TPR) studies suggested that different catalysts possessed different properties in chemisorption capacity and reduction behavior, and AC supported PtCo catalysts possessed significantly higher CO chemisorption capacity compared to the other catalysts. Extended X-ray absorption fine structure (EXAFS) and transmission electron microscopy (TEM) analysis provided additional information regarding the formation of Pt–Co bimetallic bonds and metallic particle size distribution in the PtCo bimetallic catalysts on different supports.
Keywords: Benzene; Hydrogenation; Bimetallic; PtCo; EXAFS;

In this study, we investigated the photocatalytic kinetics and mechanisms of trioctylphosphine oxide-capped titanium dioxide (TOPO-capped TiO2) for degradation of two endocrine disrupting chemicals (EDCs), phenol and bisphenol A, which contained different hydrophobicity, chemiadsorbability, and degradable capacity. The TOPO-capped TiO2 exhibited high partition coefficients of 2.00 × 10−4 and 3.42 × 10−3  l/mg for phenol and bisphenol A, respectively. In addition, the bonded TOPO introduced substantial amounts of trapped holes at the surface. The high affinity toward the target compounds and stabilized charge carriers resulted in high photocatalytic activity of the modified TiO2. The TOPO-capped TiO2 exhibited 12- and 3-fold higher photocatalytic activities than P25 for decomposition of bisphenol A and phenol, respectively. The presence of the hydrophobic modifier inhibited the generation of hydroxyl radicals and led to the photocatalysis undergoing mainly from partition followed by chemisorption and interfacial charge transfer. Partition and interfacial charge transfer were the rate determining steps for the degradation of phenol and bisphenol A, respectively. According to the Langmuir–Hinshelwood model, the adsorption coefficient (K a) and intrinsic rate constant (k r) for phenol were 4.17 × 10−2  l/mg and 5.60 × 10−2  mg-g/l-min-m2, respectively, while they were 2.91 × 10−2  l/m and 2.18 × 10−1  mg-g/l-min-m2, respectively for bisphenol A degradation. The product of the k r and K a for bisphenol A was 2.7 times higher than that for phenol, revealing that the modified TiO2 favored decomposition of the compound which contains high chemiadsorbability and direct photocatalytic tendency in their individual systems. In contrast, the high degradable capability of phenol resulted in its preferential degradation in the competitive system.
Keywords: Ligand-capped TiO2; Endocrine disrupting chemicals; Photocatalytic degradation;

Photocatalytic functional coatings of TiO2 thin films on polymer substrate by plasma enhanced atomic layer deposition by Chang-Soo Lee; Jungwon Kim; J.Y. Son; Wonyong Choi; Hyungjun Kim (628-633).
We prepared photocatalytic TiO2 thin films which exhibited relatively high growth rate and low impurity on polymer substrate by plasma enhanced atomic layer deposition (PE-ALD) from Ti(NMe2)4 [tetrakis (dimethylamido) Ti, TDMAT] and O2 plasma to show the self-cleaning effect. The TiO2 thin films with anatase phase and bandgap energy about 3.3 eV were deposited at growth temperature of 250 °C and the photocatalytic effects were compared with commercial Activ glass. From contact angles measurement of water droplet and photo-induced degradation test of organic liquid, TiO2 thin films with anatase phases showed superhydrophilic phenomena and decomposed organic liquid after UV irradiation. The anatase TiO2 thin film on polymer substrate showed highest photocatalytic efficiency after 5 h UV irradiation. We attribute the highest photocatalytic efficiency of TiO2 thin film with anatase structure to the formation of suitable crystalline phase and large surface area.
Keywords: TiO2; Photocatalyst; Plasma enhanced atomic layer deposition; Self-cleaning effect; Polymer substrate;

Rutile TiO2 particles with specific exposed crystal faces were prepared by hydrothermal treatment of titanium trichloride (TiCl3) solution with poly(vinyl pyrrolidone) (PVP) as a shape-control reagent. Crystal phase, shape, and size of TiO2 particles were found to be greatly dependent on the concentration of PVP in the solution. The exposed crystal surface of TiO2 was controlled by changing the concentration of PVP in TiCl3 and NaCl solutions. The prepared TiO2 particles were characterized by TEM, SEM, XRD, and specific surface area measurements. The photocatalytic activity of the synthesized TiO2 particles was evaluated by decomposition of acetaldehyde and toluene in gas phase. The synthesized TiO2 particles showed higher photocatalytic activity for degradation of acetaldehyde and toluene than did commercial TiO2 particles (MT-600B). However, the tendency of photocatalytic activities of the synthesized TiO2 particles for degradation of acetaldehyde in gas phase was different from that for degradation of toluene. From the photodeposition of Pt and PbO2, we propose that the (1 1 0) face provides reductive sites and that the (1 1 1) face provides oxidative sites. The results suggest that the crystal faces facilitate the separation of electrons and holes, resulting in improvement in photocatalytic activity.
Keywords: Photocatalyst; PVP; Rutile; Exposed crystal surface; Hydrothermal treatment;

Silver supported mesoporous SBA-15 as potential catalysts for SCR NO x by ethanol by Maya Boutros; Jean-Michel Trichard; Patrick Da Costa (640-648).
Reduction of nitrogen oxides (NO x ) in a lean exhaust gases has become one of the most important environmental concerns. This study compared the performances of DeNO x and the properties of silver/mesoporous aluminosilica synthesized by different methods. Silver nanoparticles were obtained after calcination of the materials prepared by incipient wetness or by the excess solvent impregnation of Al-SBA-15 support by silver nitrate. On the other hand, the silver nitrate was introduced on the synthesis gel of SBA-15. The solid product was used as support to deposit aluminium. The effect of synthesis method on silver incorporation and the porous structure of the resulting solids has been examined. Some techniques had been applied, such as: elemental analysis, X-ray diffraction (XRD), N2 sorption measurements and Transmission Electron Microscopy (TEM). The nature of silver species in these catalysts was investigated by XPS measurements, high angle XRD, high resolution TEM and TPR/H2 (temperature-programmed reduction). The resulting materials were tested in the selective catalytic reduction of NO x by ethanol in the presence of oxygen. Finally, the effect of H2 on the DeNO x activity was also investigated.The impregnation method of Al-SBA-15 by silver nitrate influences the size, the location of the particles and the catalytic activity. To maintain a higher DeNO x activity, the percentage of aluminium loading and the feed of H2 gases should be increased.
Keywords: Silver; Mesoporous silica or aluminosilica; NO x ; Ethanol;

Effect of ceria on the structure and catalytic activity of V2O5/TiO2–ZrO2 for oxidehydrogenation of ethylbenzene to styrene utilizing CO2 as soft oxidant by Komateedi N. Rao; Benjaram M. Reddy; B. Abhishek; Yeong-Hui Seo; Nanzhe Jiang; Sang-Eon Park (649-656).
The present study was undertaken to investigate the influence of ceria on the physicochemical and catalytic properties of V2O5/TiO2–ZrO2 for oxidative dehydrogenation of ethylbenzene to styrene utilizing CO2 as a soft oxidant. Monolayer equivalents of ceria, vanadia and ceria–vanadia combination over TiO2–ZrO2 (TZ) support were impregnated by a coprecipitation and wet impregnation methods. Synthesized catalysts were characterized by using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, temperature programmed reduction, transmission electron microscopy and BET surface area methods. The XRD profiles of 550 °C calcined samples revealed amorphous nature of the materials. Upon increasing calcination temperature to 750 °C, in addition to ZrTiO4 peaks, few other lines due to ZrV2O7 and CeVO4 were observed. The XPS V 2p results revealed the existence of V4+ and V5+ species at 550 and 750 °C calcinations temperatures, respectively. TEM analysis suggested the presence of nanosized (<7 nm) particles with narrow range distribution. Raman measurements confirmed the formation ZrTiO4 under high temperature treatments. TPR measurements suggested a facile reduction of CeO2–V2O5/TZ sample. Among various samples evaluated, the CeO2–V2O5/TZ sample exhibited highest conversion and nearly 100% product selectivity. In particular, the addition of ceria to V2O5/TZ suppressed the coke deposition and allowed a stable and high catalytic activity.
Keywords: Oxidative dehydrogenation; Ethylbenzene; Carbon dioxide; V2O5/TiO2–ZrO2; Styrene;

Photo-catalytic degradation of Rhodamine B on C-, S-, N-, and Fe-doped TiO2 under visible-light irradiation by Xiangxin Yang; Chundi Cao; Larry Erickson; Keith Hohn; Ronaldo Maghirang; Kenneth Klabunde (657-662).
C-, S-, N-, and Fe-doped TiO2 photocatalysts were synthesized by a facile sol–gel method. The structure and properties of catalysts were characterized by N2 desorption–adsorption, X-ray diffraction (XRD), UV–vis spectroscopy, and X-ray photoelectron spectroscopy (XPS). Results revealed that the surface area of the multi-doped TiO2 was significantly increased and the crystallite size was smaller than the pure TiO2 obtained by a similar route. Compared with TiO2, the peak position in doped-TiO2 XRD patterns was slightly shifted, which could be attributed to the distortion by the substitution of carbon, nitrogen, and sulfur dopants for some oxygen atoms and Fe3+ for Ti4+ in the lattice of TiO2. These substitutions were confirmed by XPS. In addition, these dopants were responsible for narrowing the band gap of TiO2 and shifting its optical response from ultraviolet (UV) to the visible-light region. The photocatalytic reactivities of these multi-doped TiO2 catalysts were investigated by degrading Rhodamine B (RB) in aqueous solution under visible-light irradiation (λ > 420 nm). It was found out that the reactivity was significantly enhanced and the catalyst doped with nitrogen, carbon, sulfur, and 0.3 wt% iron had the highest photocatalytic activity.
Keywords: Carbon; Nitrogen; Sulfur; Iron; Dopants; TiO2; Photocatalyst;

Porous TiO2 thin films were prepared on the Si substrate by hydrothermal method, and used as the Pt electrocatalyst support for methanol oxidation study. Well-dispersed Pt nanoparticles with a particle size of 5–7 nm were pulse-electrodeposited on the porous TiO2 support, which was mainly composed of the anatase phase after an annealing at 600 °C in vacuum. Cyclic voltammetry (CV) and CO stripping measurements showed that the Pt/TiO2 electrode had a high electrocatalytic activity toward methanol oxidation and an excellent CO tolerance. The excellent electrocatalytic performance of the electrode is ascribed to the synergistic effect of Pt nanoparticles and the porous TiO2 support on CO oxidation. The strong electronic interaction between Pt and the TiO2 support may modify CO chemisorption properties on Pt nanoparticles, thereby facilitating CO oxidation on Pt nanoparticles via the bifunctional mechanism and thus improving the electrocatalytic activity of the Pt catalyst toward methanol oxidation.
Keywords: Porous TiO2; Platinum; Hydrothermal method; CO oxidation; Methanol electro-oxidation;

Colloidal Co nanoparticles supported on SiO2: Synthesis, characterization and catalytic properties for steam reforming of ethanol by Renata U. Ribeiro; Janete W.C. Liberatori; Herbert Winnishofer; José Maria C. Bueno; Daniela Zanchet (670-678).
Colloidal Co nanoparticles with sizes in the 3–8 nm range were obtained by thermal decomposition of Co2(CO)8 in the presence of ligands and impregnated on SiO2 to prepare SiO2-supported Co nanocatalysts. The catalysts showed activity for the steam reforming of ethanol with higher values for smaller Co particles. H2 adsorption results and Fourier transform infrared spectroscopy of adsorbed CO suggested that the fraction of accessible Co sites also depended on the synthesis conditions. Precipitation of the Co nanoparticles with methanol instead of ethanol before impregnation had a positive effect on the density of accessible Co sites to catalysis; similar result was verified by increasing the thermal treatment temperature under H2 flow before the reaction. Based on the distribution of products with temperature of reaction, a mechanism for steam reforming of ethanol on SiO2-supported Co nanocatalysts is suggested.
Keywords: Cobalt; Nanoparticles; Steam reforming of ethanol;

SO x storage and release kinetics for ceria-supported platinum by Markus Happel; Lisa Kylhammar; Per-Anders Carlsson; Jörg Libuda; Henrik Grönbeck; Magnus Skoglundh (679-682).
The SO x storage and release kinetics on CeO2 have been studied by lean SO x adsorption and temperature programmed desorption for different pairwise configurations of individual monolith samples, i.e., Pt/CeO2  + SiO2, Pt/SiO2  + CeO2, CeO2  + Pt/SiO2 and CeO2  + SiO2. In the case of sole ceria, SO x adsorption proceeds both via SO2 and SO3 adsorption although the latter channel is kinetically favored. Hence, the rate of SO2 oxidation is crucial for the overall SO x storage kinetics. It is also found that physical contact between Pt and ceria is important for the storage process. This is attributed to efficient transport routes for SO x (surface diffusion and spill-over processes) and/or specific adsorption sites at the platinum–ceria interface. The main route for SO x release is found to be thermal decomposition where the effect of platinum is minor, although an indirect effect cannot be ruled out. Different mechanistic scenarios for SO x adsorption are discussed, which may serve as a guide for future experiments.
Keywords: Sulfur trap; Adsorption; Desorption; SO2 oxidation; Noble metal–support interaction; CeO2; Pt;