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Applied Catalysis B, Environmental (v.107, #3-4)

Contents Continued (pp. i).

Contents (pp. co4).

Editorial Board (pp. co2).

Editorial Board (pp. i).

Surface and structural features of Pt/CeO₂-La₂O₃-Al₂O₃ catalysts for partial oxidation and steam reforming of methane by V.B. Mortola; S. Damyanova; D. Zanchet; J.M.C. Bueno (pp. 221-236).

Display Omitted► The effect of Ce(La) content on the structure and surface properties of Pt/CeO₂-La₂O₃-Al₂O₃ catalysts was studied. ► Mixed oxides supports were obtained by sol–gel method. ► High CeO₂-loaded Pt catalysts showed the best performance in POM and SMR.Mixed xCeO₂- yLa₂O₃-Al₂O₃ oxides (where x+ y=12wt%) were prepared by sol–gel method. It was shown that the mixed oxides are suitable carriers for supported Pt catalysts. The catalytic performances of the catalysts were evaluated in the reaction of stem methane reforming (SMR) and partial oxidation of methane (POM). The effect of the support kind on the surface and structural properties, as well as on the redox and catalytic behavior of the catalyst was studied. It was shown that the coexistence of the Pt⁰/Pt δ⁺ and Ce⁴⁺/Ce³⁺ redox couples leads to the increase of the CH₄ conversion and carbon resistance over Pt catalysts. The CeO₂-containing catalysts showed the highestTOFCH4 values in SMR in spite of the low metal dispersion that is related to the high capacity of the surface to carbon cleaning caused by the highest oxygen mobility at metal–support interface. The strong initial deactivation of alumina-supported Pt catalyst in POM was related to Pt sintering.

Keywords: Sol–gel method; Pt catalysts; Cerium oxide; Lanthanum oxide; Steam methane reforming; Characterization; XANES

Heterogeneous catalyst based on peroxo-niobium complexes immobilized over iron oxide for organic oxidation in water by Adilson C. Silva; Renata M. Cepera; Márcio C. Pereira; Diana Q. Lima; José D. Fabris; Luiz C.A. Oliveira (pp. 237-244).

After six reaction cycles, the Nb-NCBT catalyst presented catalytic activity loss, but after H₂O₂ solution added into de system the catalytic activity was recovered suggesting that the oxidizing sites are regenerated by the addition of H₂O₂.Display Omitted► We produced Nb-doped iron oxide with high catalytic capacity for organic oxidation. ► H₂O₂-pretreatment of the solid catalyst promotes important surface and structural changes. ► We obtained peroxo-niobium complexes, which expressively enhances the catalytic properties of the materials.Nb-doped iron oxides were used as heterogeneous catalyst to oxidize organic compounds in aqueous medium containing hydrogen peroxide. XRD data reveal that the composites contain hematite (α-Fe₂O₃), maghemite (γ-Fe₂O₃) and FeNb₂O₆. The H₂O₂ pretreatment of the solid catalyst promotes important surface and structural changes of the iron oxides mainly by peroxo-niobium complexes formation, which expressively enhances the catalytic properties of the composite. Transmission electron microscopy images show that the H₂O₂-treatment tends also to decrease the mean particle size of grains of the composite. Nb-doped iron oxides were found to impart an important role to the solid catalyst towards H₂O₂ reactions. The developed composites were confirmed to have remarkable catalytic activity on the oxidation of organic substrates and can be regenerated for several successive reaction cycles for degrading polluting organic in water.

Keywords: Hematite; Maghemite; Peroxo-niobium; Hydrogen peroxide

Influence of modification method and transition metal type on the physicochemical properties of MCM-41 catalysts and their performances in the catalytic ozonation of toluene by Maoshuai Li; K.N. Hui; K.S. Hui; S.K. Lee; Y.R. Cho; Heesoo Lee; W. Zhou; Shinho Cho; C.Y.H. Chao; Yangyang Li (pp. 245-252).

Display Omitted► Transition metal modification effectively improves the catalyst activity. ► The catalytic performance highly depends on metal type and modification method. ► High dispersion of metal oxides favors improvement of catalyst activity. ► The build-up of organic byproducts deteriorates the catalyst.The current study describes the catalytic ozonation of toluene using MCM-41 catalysts modified by different transition metals (Cu and Co) and methods (in situ synthesis and impregnation). The characteristic hexagonal channel array of the MCM-41 pore system was not destroyed by the transition metal modification, but the order and surface area were decreased. Large particles of copper oxide exposed on the (111) lattice plane, which were indicative of severe sintering, were found on the catalyst modified by Cu via in situ synthesis. Such particles were not observed on the other catalysts. Using the modified catalysts in toluene ozonation revealed that with increased reaction temperature, toluene conversion under a steady state increased, whereas ozone conversion decreased. The transition metal-modified MCM-41s also had largely improved catalytic activities compared with pure MCM-41. Catalytic performance was found to depend on the metal type and modification method. The method that resulted in improved catalytic performance was in situ synthesis for the Co-modified MCM-41, and was impregnation for the Cu-modified MCM-41. The relatively superior performance of the transition metal-modified catalysts over pure MCM-41 is attributed to two main features. One is the well dispersion of metal oxides, and the other is the strong capacity to decompose built-up organic byproducts on the catalyst surface.

Keywords: Toluene; MCM-41; Transition metal; Ozone; Catalytic oxidation

Layered double hydroxides reconstructed in NiSO₄ aqueous solution as highly efficient photocatalysts for degrading two industrial dyes by Gabriela Carja; Elena Husanu; Carmen Gherasim; Horia Iovu (pp. 253-259).

Display Omitted► LDHs reconstructed in NiSO₄ aqueous solution as highly efficient photocatalysts in degrading two industrial dyes. ► Self-assemblies of high density nanoparticles of oxidized nickel deposited on the particles of the clay. ► The composition of the clay affected the dyes photodegradation.Nanostructured photocatalysts, that can effectively photodegrade the industrial dyes drimaren red and drimaren navy (Clariant Produkte), were obtained by the structural reconstruction of MgAlLDH and MgFeAlLDH anionic clays in NiSO₄ aqueous solution. X-ray diffraction (XRD), energy dispersive X-ray (EDX) mapping, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), N₂ adsorption at 77K and UV–vis analysis were adopted to investigate the structure, surface, micromorphology and photoresponsive properties of the reconstructed clays, as oposed to the as-synthesized clays. Results show that MgAlLDH and MgFeAlLDH reconstruction in NiSO₄ aqueous solution gives rise to nanostructured enssembles defined by high density nanoparticles of oxidized nickel deposited on the larger LDHs flakes. IR spectroscopy (FTIR) results indicate that SO₄²⁻ replaced CO₃²⁻ in the interlayer space of the reconstructed clays. It was found that the dyes’ photodegradation is greatly enhanced by the deposition of nanosized nickel on the surface of the clay but is also influenced by the specific composition of the parent clay.

Keywords: Layered double hydroxides; Photodegradation; Dyes; Anionic clay

Hydroxylated magnesium fluorides as environmentally friendly catalysts for glycerol acetylation by Simona B. Troncea; Stefan Wuttke; Erhard Kemnitz; Simona M. Coman; Vasile I. Parvulescu (pp. 260-267).

Display Omitted► DAG and TAG can be formulated with petroleum-derived fuels to improve their properties. ► Hydroxylated nanoscopic fluorides have demonstrated a good catalytic behaviour in the acylation of glycerol. ► It is advantageous to use microwave or ultrasound irradiation in the synthesis.The increase of biodiesel production during the next years will result in an overproduction, and therefore, an accumulation of glycerol on the market. The use of glycerol-based additives to improve the properties of biodiesel or gasoline is one of the possibilities currently being explored to utilize this renewable feedstock. In this context, partly hydroxylated magnesium fluorides have demonstrated catalytic activity in the esterification of glycerol with acetic acid to yield diacetylglycerine (DAG) and triacetylglycerine (TAG). The catalytic activity depends on the density of acid sites at the external catalytic surface while the selectivity to different acylated products is influenced by the nature of the acid sites (Lewis and/or Brønsted). Using non-conventional activation methods of the reactant molecules, as microwave or ultrasound irradiation, optimal glycerol conversions (>90%) and selectivities to the desired compounds (over 85%) were obtained. The activities and selectivities achieved using partly hydroxylated fluorides as catalysts are comparable or even superior to those displayed by conventional oxide based acid catalysts under thermal activation.

Keywords: Glycerol; Bioadditive; Hydroxylated fluorides; Microwave; Ultrasound

CO oxidation at low temperature on Au/CePO₄: Mechanistic aspects by F. Romero-Sarria; M.I. Domínguez; M.A. Centeno; J.A. Odriozola (pp. 268-273).

Display Omitted► CePO₄ (rhabdophane structure) is used as support of gold catalysts for CO oxidation. ► Dehydration of the support during activation induces oxygen vacancies generation. ► Oxygen vacancies are able to react with gaseous oxygen to give peroxide species. ► Peroxides oxidize CO at low temperature giving carbonates that poison surface sites. ► By rising temperature, when gold is present, carbonates decompose and activity rises.This work reports the synthesis and characterization of a cerium phosphate supported gold catalyst as well as its catalytic activity for the oxidation of CO. A precipitation method in the presence of an organic modifier followed by a hydrothermal treatment was used for the support synthesis, resulting in high surface area nanometric particles. Gold/cerium phosphate catalyst with a 1% (w/w) nominal gold content was characterized using XRF, XRD, N₂ adsorption–desorption measurements, TEM and DRIFTS-MS. The catalyst shows good catalytic activity at low temperature. The activity is related to the generation of oxygen vacancies in the support caused by the elimination of structural oxygen. In situ studies revealed that the reaction of the oxygen vacancies with gaseous oxygen resulted in the formation of peroxo species. These species are responsible for the activity detected at room temperature in both the catalyst and the support. Moreover, the presence of carbonate and hydrogen carbonate acting as reaction intermediates have been observed.

Keywords: Gold; Cerium phosphate; CO oxidation; DRIFTS; Peroxides

Adsorption and heterogeneous Fenton degradation of 17α-methyltestosterone on nano Fe₃O₄/MWCNTs in aqueous solution by Xiaobin Hu; Benzhi Liu; Yuehua Deng; Hongzhe Chen; Si Luo; Cheng Sun; Po Yang; Shaogui Yang (pp. 274-283).

Display Omitted► A novel inverse-spinel Fe₃O₄/MWCNTs catalyst was prepared by in situ growth. ► The catalyst has been used to adsorb and degrade trace 17α-methyltestosterone. ► The catalyst showed higher adsorption and catalytic ability than nano Fe₃O₄. ► The enhanced ability related to the enrichment of target molecules on MWCNTs.A novel catalyst, inverse-spinel ferroferric oxide nanoparticles decorated multiwalled carbon nanotubes (Fe₃O₄/MWCNTs) was successfully prepared, and applied for the adsorption and degradation of trace artificial androgen 17α-methyltestosterone (MT) in the presence of H₂O₂. The regular growth of ferroferric oxide crystal on multiwalled carbon nanotubes was achieved by in situ oxidation of Fe²⁺ in hot alkaline solution. The catalyst was characterized by BET, XRD, TEM, XPS and Raman spectroscopy. The effects of initial pH, catalyst loading, oxidant concentration and iron leaching on the degradation of MT were investigated. The Fe₃O₄/MWCNTs showed higher ability of adsorption and degradation efficiency of MT than bare Fe₃O₄ in the batch degradation experiment. The degradation efficiencies increased with the initial pH decreasing in the wide pH range of 8.0–3.5. Further, the catalyst showed stable catalytic activity, fairly good mechanic stability and convenient recycling. Negligible iron leaching showed the reused Fe₃O₄/MWCNTs withstood the oxidation. The enhanced degradation efficiency of Fe₃O₄/MWCNTs may relate to the enrichment of trace MT molecules by MWCNTs in the vicinities of active sites.

Keywords: 17α-Methyltestosterone; Magnetite decorated multiwalled carbon nanotube; Adsorption; Heterogeneous Fenton reaction

Methanol partial oxidation over palladium-, platinum-, and rhodium-integrated LaMnO₃ perovskites by Chia-Liang Li; Yu-Chuan Lin (pp. 284-293).

. By incorporating trace Pd, Pt, or Rh ions in the B-site position, catalytic performances of methanol partial oxidation over LaMnO3 based perovskites can be varied substantially.Display Omitted► The B-site of LaMnO₃ perovskites was substituted by trace of Pd, Pt, and Rh ions. ► Catalysts for partial oxidation of methanol. ► Reducibility and oxygen mobility can be improved by the B-site-ion replacement. ► Reaction pathways can be manipulated diversely by the integrated promoter.This study investigates methanol partial oxidation over LaMnO₃ and LaMn_0.95B_0.05O₃ (B=Pd, Pt, and Rh) perovskites. Their surface and bulk properties were characterized by appropriate physicochemical techniques including BET surface area measurement, XRD, EDS, XPS, H₂-TPR, TPO, O₂-TPD, and CH₃OH-TPD. Results show significant differences in reducibility and oxygen activity between promoted and untainted LaMnO₃. Promoted perovskites showed higher reactivity than pure LaMnO₃. Results suggest that a redox pathway enhances partial oxidation to formaldehyde while oxygen activity, particularly surface chemisorbed oxygen, plays a central role in combustion. This study also reveals a plausible reaction mechanism of methanol partial oxidation over LaMnO₃-based perovskites.

Keywords: Perovskite; Noble metals; Methanol; Oxidation; Redox

Divergent catalytic behaviors of Pt and Pd films in the cathode of a sandwiched type membrane reactor by M.A. Hasnat; M. Saiful Alam; M.H. Mahbub-ul Karim; M.A. Rashed; M. Machida (pp. 294-301).

Proposed schematic representation of NO₃⁻ reduction mechanism in the membrane reactor preferentially occurred by the Ag–Pt and Ag–Pd sites. On the cathode surface, Pt particles mainly reduced nitrate ions by heterogeneous electron transfer reaction. Here the Ag acted as electron promoting particles. By contrast, Pd reduced nitrate ions mainly by hydrogenation reactions. Water is splitted on the Pt anode surface generating H⁺, which is migrated to the cathode surface through the 180μm thick H⁺ conducting.Display Omitted► In the reactor, most active cathode is Ag–Pt–Pd. ► Ag–Pt favored electron transfer reaction. ► Ag–Pd favored hydrogenation reaction.Relative electrochemical and catalytic hydrogenation responses to NO₃⁻ reduction by the Ag modified Pt, Pd and Pt–Pd cathodes, deposited on H⁺ conducting Nafion membrane, have been studied. The electrochemical investigations noticed the maximum reactivity to show by an Ag–Pt electrode exhibiting a reduction current of 24.26mAcm⁻² at −1.26V vs. Ag/AgCl reference electrode. Conversely, the catalytic hydrogenation reaction exhibited maximum nitrate reduction rate by an Ag–Pd catalyst having a rate constant of 25.1×10⁻³min⁻¹. While both electrochemical reactions and catalytic hydrogenation reactions were combined in the electrolyte reactor, the highest reduction efficiency was found to show by an Ag–Pt–Pd cathode assembly, where the reduction current was 20.12mAcm⁻² and the rate constant was 84.3×10⁻³min⁻¹ under controlled current electrolysis condition. In this paper, reasons of such divergent catalytic behaviors have been discussed.

Keywords: Nitrate reduction; Catalytic hydrogenation; Rate constant; Voltammetry, Selectivity

Comparative study on the preparation, characterization and catalytic performances of 3DOM Ce-based materials for the combustion of diesel soot by Guizhen Zhang; Zhen Zhao; Junfeng Xu; Jianxiong Zheng; Jian Liu; Guiyuan Jiang; Aijun Duan; Hong He (pp. 302-315).

Among three Ce-based materials of 3DOM CeO₂, Ce_0.7Zr_0.3O₂ and Ce_0.6Zr_0.3Pr_0.1O₂, Pr-modified ceria-zirconia solid solution of 3DOM Ce_0.6Zr_0.3Pr_0.1O₂ shows the highest thermal stability for soot combustion. Compared with the fresh sample, T₅₀ of 3DOM Ce_0.6Zr_0.3Pr_0.1O₂ after thermal treatment at 1000°C for 5h increased only by 6°C. However, for aged 3DOM CeO₂ and Ce_0.7Zr_0.3O₂, T₅₀ increased by 86°C and 21°C, respectively.Display Omitted► 3DOM Pr-modified Ce-Zr-O solid solutions were successfully prepared by colloidal crystal templating method. ► 3DOM Pr-modified Ce-Zr-O samples showed much higher catalytic activities than corresponding DM samples. ► 3DOM Ce_0.6Zr_0.3Pr_0.1O₂ exhibited the highest thermal and hydrothermal stability among 3DOM CeO₂, Ce_0.7Zr_0.3O₂ and Ce_0.6Zr_0.3Pr_0.1O₂.Three-dimensionally ordered macroporous (3DOM) praseodymium (Pr)-modified Ce-Zr solid solutions were successfully prepared by colloidal crystal templating method. They were characterized by the techniques of SEM, XRD, UV-Raman, N₂ adsorption, and H₂-TPR. 3DOM samples showed higher catalytic activities for soot combustion than corresponding disordered macroporous (DM) ones, which benefits from the enhanced contact efficiency between soot and ordered macroporous structure. In addition, the effects of Ce/Zr ratio on the phase composition and catalytic performances of Ce-Zr-O and Pr-Ce-Zr-O samples for soot oxidation were investigated. The results indicate that the phase compositions of Pr-modified ceria-zirconia solid solutions are similar to those of corresponding ceria-zirconia samples, and cubic–tetragonal phases coexist in the samples with moderate zirconia content, which is favorable for soot combustion. Furthermore, the effects of thermal and hydrothermal treatments on the catalytic properties for soot oxidation of 3DOM CeO₂, Ce_0.7Zr_0.3O₂ and Ce_0.6Zr_0.3Pr_0.1O₂ were comparatively studied. Compared with 3DOM bare CeO₂, 3DOM Ce-Zr-based solid solutions, especially Pr-modified Ce-Zr solid solution Ce_0.6Zr_0.3Pr_0.1O₂ exhibited the highest thermal and hydrothermal stability because it possesses the lowest mobility of lattice oxygen among the three samples.

Keywords: Three-dimensionally ordered macroporous materials; Ce-Zr-based solid solutions; Catalysts; Soot oxidation; Thermal and hydrothermal stability

One-pot template synthesis of Ti–Al-containing mesoporous silicas and their application as potential photocatalytic degradation of chlorophenols by Mohamed A. Betiha; Sawsan A. Mahmoud; Mohamed F. Menoufy; Ahmad M. Al-Sabagh (pp. 316-326).

Display Omitted► A new mesoporous material of Ti–Al–SiO₂ was prepared by the direct method using economic anionic surfactants, linear alkylbenzene sulfonic acid. ► The catalyst exhibited efficient activity for the degradation of 2- and 4-chlorophenol under UV irradiation. ► The photodegradation process of 4-CP is completed within 40min, while reach 67.3% for 2-CP within 130min.This article presents preparation, characterization and evaluation of heterogeneous Titanium based alumina mesoporous silica catalysts for the photo degradation of chlorophenols in aqueous solution. For more economic application, a series of silica, Al₂O₃–SiO₂ and TiO₂–Al₂O₃–SiO₂ are prepared using linear alkylbenzene sulfonic acid as a novel structure directing agent. Two Ti–Al–SiO₂ samples were prepared by direct synthesis using different titanium sources. The prepared samples are characterized by combination of various physicochemical techniques, such as XRD, N₂ physisorption, FT-IR, UV–vis, SEM and TEM. The prepared mesoporous materials are applied in the presence of UV irradiation for photodegradation of chlorophenols as pollutants in water. The results reveal that the photodegradation process of 4-chlorophenol (4-CP) is completed within 40min, while reach 67.3% for 2-chlorophenol (2-CP) within 130min. Moreover, the titanium precursor species and the catalyst dosage (0.1–0.4g/l) affect the photocatalytic activity of prepared catalysts for 2-chlorophenol degradation. Finally, the concentration of acetate and chloride ions formed during the degradation process can also affect the activity of the prepared catalysts.

Keywords: Nanocomposite; Mesoporous silica; Linear alkylbenzene; Photodegradation; Chlorophenol

Catalytic activity of Pt catalysts promoted by MnO_x for n-hexane oxidation by Mirjana Anić; Nenad Radić; Boško Grbić; Vera Dondur; Ljiljana Damjanović; Dimitar Stoychev; Plamen Stefanov (pp. 327-332).

Display Omitted► A convenient and effective deposition-precipitation method has been applied to prepare novel Mn-Pt catalysts. ► Ammonia and dimethylamine have been used as reagents for decoration of small and large Pt crystallite by Mn. ► Order of catalysts activity in n-hexane oxidation is Pt-Mn (D)>Pt-Mn (A)>Pt. ► The improvement of the catalytic activity have been attributed to the nature of MnO_x phase that is bonded with Pt.The deep oxidation of n-hexane was studied over Pt catalysts with small and large Pt crystallites, promoted by MnO_x. The Mn was deposited on the Pt/Al₂O₃ by deposition-precipitation method using two alkalis, ammonia and dimethylamine. The strength of the base influenced morphology and performances of Mn-Pt catalysts. Ammonia formed mostly spherical structure of manganese oxide, while dimethylamine created fibrous needle-like shape of MnO_x, typical for cryptomelane phase of manganese oxide. This was confirmed by XPS results that show an oxidation state of Mn close to that for cryptomelane. The Pt-Mn catalysts were more active than catalysts containing Pt only. Promoting effect of MnO_x is more pronounced for larger Pt crystallites. Among Pt-Mn samples, catalysts synthesized with dimethylamine exhibited the highest activities. Mobility and reactivity of oxygen from Pt–O–Mn sites associated with cryptomelane phase may be responsible for increased activity.

Keywords: Pt/Al; ₂; O; ₃; catalyst; Manganese oxide; Deep oxidation; n-Hexane; Promoting effect

Enhanced photocatalytic degradation of methyl red and thymol blue using titania–alumina–zinc ferrite nanocomposite by P.P. Hankare; R.P. Patil; A.V. Jadhav; K.M. Garadkar; R. Sasikala (pp. 333-339).

Photocatalytic degradation of (left) methyl red (right) thymol blue.Display Omitted► An interlayer of alumina enhances the photocatalytic activity of TiO₂–ZnFe₂O₄. ► Enhanced adsorption of dyes is observed in the TiO₂–Al₂O₃–ZnFe₂O₄ composites. ► Enhanced activity is attributed to the decreased charge transfer to zinc ferrite. ► Photocatalytic activity of TiO₂–Al₂O₃–ZnFe₂O₄ is comparable to Pd/TiO₂–ZnFe₂O₄. ► TiO₂–Al₂O₃–ZnFe₂O₄ is ferromagnetic at low applied fields.Nanocomposite of magnetically separable, TiO₂–ZnFe₂O₄ with an intermediate layer of alumina has been synthesized by a multistep wet chemical process. UV–vis absorption spectra show a red shift of the absorption edges for the composite systems compared to single phase TiO₂. Magnetic measurements indicate that the ZnFe₂O₄ is ferromagnetic at room temperature with low coercivity when the applied field is low, typical of soft magnetic materials. After TiO₂ and alumina coatings, the samples show similar magnetic behaviour. Photocatalytic activity studies for methyl red and thymol blue degradation indicate an enhanced activity for the composites when the alumina interlayer is present between TiO₂ and ZnFe₂O₄. When Pd is used as a co-catalyst in TiO₂–ZnFe₂O₄, an enhanced activity is observed, which is comparable to that of TiO₂–Al₂O₃–ZnFe₂O₄. The present study leads to a new result that an insulating interlayer like alumina can enhance the photocatalytic activity of TiO₂ coated ferrites as much as that of a noble metal co-catalyst like Pd. The enhanced photocatalytic activity of TiO₂–Al₂O₃–ZnFe₂O₄ is attributed to the decrease in the migration of photogenerated charge carriers to zinc ferrite layer and due to the increased adsorption of the reactants on the surface of TiO₂–Al₂O₃–ZnFe₂O₄.

Keywords: Alumina interlayer; Zinc ferrite; Titania; Magnetic photocatalyst; Photocatalytic degradation; Thymol blue; Methyl red

Redox behaviour of vanadium during hydrogen–oxygen exposure of the V₂O₅-WO₃/TiO₂ SCR catalyst at 250°C by Johannes Due-Hansen; Søren B. Rasmussen; Ewelina Mikolajska; Miguel A. Bañares; Pedro Ávila; Rasmus Fehrmann (pp. 340-346).

Display Omitted► Reversibility of the V₂O₅-WO₃/TiO₂ SCR catalyst in hydrogen-oxygen mixtures at 250°C is studied. ► In-situ UV–vis spectroscopy suggests the occurrence of a mild reduction of V⁵⁺ in diluted H₂/N_2. ► The isosbestic point observed at 250°C affirms that only V⁴⁺ and V⁵⁺-species is present. ► Increased VO²⁺ level (EPR) correlates with activity in the transient after H₂/O₂ treatment. ► The vanadium redox system is completely reversible upon return to normal SCR gas after reduction.A series of experiments was conducted to reveal the impact on the catalyst and NH₃-SCR activity of an industrial deNO_x catalyst from Haldor Topsøe A/S (V₂O₅-WO₃/TiO₂) by exposure to H₂ and H₂/O₂. Treatment of the SCR catalyst was done by exposure for 60min with three different concentrations of H₂ (0–2%) in an 8% O₂/N₂ mixture, where the SCR activity was measured before and after the hydrogen treatment. The results show that the activity of the SCR catalyst is only negligibly affected during exposure to the H₂/O₂ gas and in all cases it returned reversibly to the initial NO_x conversion rate after reexposure to the standard NH₃-SCR gas. In situ electron paramagnetic resonance (EPR) and UV–vis spectroscopy at 250°C suggest that a significant part of V⁴⁺ present during SCR conditions was oxidized to V⁵⁺ during exposure to 2% H₂+8% O₂. However, the distribution of vanadium in oxidation states V⁴⁺ and V⁵⁺ returned to the initial redox equilibrium in less than an hour after the hydrogen–oxygen treatment, emphasizing the reversibility of the V⁴⁺-V⁵⁺ system.

Keywords: NH; ₃; -SCR; Vanadia; Catalysis; EPR; UV–vis; Regeneration; Hydrogen; Raman; Titania

Photocatalytic oxidation of 2-propanol/toluene binary mixtures at indoor air concentration levels by Daniel Vildozo; Raquel Portela; Corinne Ferronato; Jean-Marc Chovelon (pp. 347-354).

Display Omitted► A mixture of 2-propanol and toluene, at indoor air levels, was tested by PCO. ► Almost total conversion and mineralization of the mixtures were achieved at 0% RH. ► A significant negative effect of water vapour was observed. ► Water vapour increases the number and concentration of intermediates. ► The by-products react between themselves to form new products.Photocatalytic oxidation (PCO) technology has a great potential for indoor air purification. However, the presence of humidity and different concentrations of a variety of pollutants are critical parameters that must be addressed for indoor air cleaning applications. In this work, the photodegradation over a commercial air cleaning TiO₂ filter of a mixture of two common volatile organic compounds (VOCs), 2-propanol and toluene, at indoor air concentration levels was tested and the role played by water vapour on the PCO performance was discussed. Transient and steady state experiments were performed using different inlet VOCs concentrations (80–400ppbv) and relative humidity values (RH, 0% and 60% at 25°C) in a gas flow rate of 300mLmin⁻¹. The adsorption, conversion and mineralization efficiencies were studied. The reaction products at ppbv levels were analysed by automated thermal desorption coupled to gas chromatography–mass spectrometry (ATD–GC–MS) and gas chromatography equipped with a pulsed discharge helium photoionization detector (GC–PDHID). Almost total conversion and mineralization of the less concentrated mixtures was achieved at 0% RH. A significant negative effect of water vapour was observed. This effect can be attributed to the weak adsorption and low solubility of toluene and to the fast desorption of 2-propanol reaction intermediates. The presence of different surface species, in the photocatalytic degradation tests performed in dry and humid conditions, suggests the occurrence of different reaction pathways depending on RH.

Keywords: Photocatalysis; TiO; ₂; 2-Propanol; Toluene; Indoor air; Relative humidity

Photocatalytic degradation of tetrabromobisphenol A by mesoporous BiOBr: Efficacy, products and pathway by Jian Xu; Wei Meng; Yuan Zhang; Lei Li; Changsheng Guo (pp. 355-362).

Display Omitted► Mesoporous BiOBr microspheres were synthesized via one step solvothermal method. ► BiOBr microspheres effectively and kinetically enhanced the decomposition of TBBPA. ► Hydroxylation and debromination dominated the photocatalytic degradation of TBBPA.Tetrabromobisphenol A (TBBPA) is the most widely used brominated flame retardant around the world. In the present study, for the first time we explored the photocatalytic oxidation of TBBPA by nanoarchitectural BiOBr microspheres. BiOBr photocatalysts were synthesized via solvothermal method with various preparation conditions, and the optimal synthesis condition was determined according to their characterization results and rhodamine B (RhB) removal efficiencies. The prepared optimal BiOBr was mesoporous material of pure tetragonal phase, which removed nearly 100% of RhB from solution after 60min simulated solar light irradiation. The BiOBr was adopted to decompose TBBPA, which was almost totally eliminated after 15min in the UV–vis/BiOBr system. The kinetic analysis indicated that the reaction rate constants were 0.388 and 0.101min⁻¹ for BiOBr and P25 TiO₂, respectively, suggesting that BiOBr effectively and kinetically enhanced the decomposition of TBBPA. Eight major reaction products or intermediates were identified by HPLC–MS and HPLC–SIR–MS, and a tentative degradation pathway of TBBPA was proposed. The mechanism originally illustrated that both hydroxylation and debromination played important roles in TBBPA transformation. The exceptional efficiency of mesoporous BiOBr in removing TBBPA represents a promising technique for treatment of TBBPA-containing wastewater or remediation of TBBPA-contaminated environmental matrices.

Keywords: Mesoporous BiOBr microspheres; Photocatalysis; Tetrabromobisphenol A

Photodegradation of thiacloprid using Fe/TiO₂ as a heterogeneous photo-Fenton catalyst by Nemanja Banić; Biljana Abramović; Jugoslav Krstić; Daniela Šojić; Davor Lončarević; Zara Cherkezova-Zheleva; Valéria Guzsvány (pp. 363-371).

Display Omitted► Fe/TiO₂ samples with different Fe content were prepared using deposition–precipitation method. ► Fe/TiO₂ with 7.2%, w/w Fe exhibited the highest degradation efficiency of TC under UV light irradiation in the presence H₂O₂. ► There was no loss of photocatalytic ability in three successive runs each of which lasted 5h. ► Fe/TiO₂ was stable and resistant to photocorrosion during the photocatalytic degradation of TC.Three Fe/TiO₂ photocatalysts with different content of Fe (1.9, 7.2 and 13.9%, w/w) were synthesized by a simple deposition–precipitation method and characterized by XRD, SEM, N₂ physisorption at 77K and Mössbauer spectroscopy. The characterization showed the presence of nano-sized Fe₂O₃ particles (less than 4nm) on the TiO₂ support. The photocatalytic efficiency of the catalysts was examined on the example of thiacloprid (TCL) degradation under UV light irradiation in aqueous suspension in the presence/absence of H₂O₂. Since the efficiency of TCL degradation in the presence of H₂O₂ (heterogeneous photo-Fenton process) was more than two times higher, all other investigations were conducted in the presence of H₂O₂. The photocatalyst with 7.2%, w/w Fe (denoted as 7.2Fe/TiO₂) appeared to be most efficient. The photocatalytic degradation studied under different operating conditions indicated that 0.5gL⁻¹ of 7.2Fe/TiO₂ was an optimal catalyst loading, and the optimal pH was 2.8. In the investigated range of initial concentrations of TCL (0.06–0.32mM) the photocatalytic degradation in the first stage of the reaction followed approximately a pseudo-first order kinetics. The suspended Fe/TiO₂ spontaneously precipitated once the stirring of the reaction mixture was terminated (>90% after 15min). The results clearly demonstrated that 7.2Fe/TiO₂ was stable and resistant to photocorrosion during the photocatalytic degradation of TCL. The higher efficiency of 7.2Fe/TiO₂ compared to Degussa P25 under the optimal experimental conditions of TCL photodegradation, spontaneous precipitation of the suspension, possibility of reusing the catalyst, as well as an insignificant increase in the iron concentration in water solution, all this indicates the possibility of the practical application of this photocatalyst for water treatment.

Keywords: Thiacloprid; Neonicotinoid pesticides; Fe/TiO; ₂; Heterogeneous photo-Fenton; Pollution control

PdAu/C catalysts prepared by plasma sputtering for the electro-oxidation of glycerol by M. Mougenot; A. Caillard; M. Simoes; S. Baranton; C. Coutanceau; P. Brault (pp. 372-379).

(a) Cyclic voltammograms of the co-sputtered Pd_0.7Au_0.3 catalyst, and of the 3-layer alternate sputtered Pd_0.35Au_0.3Pd_0.35 and Au_0.15Pd_0.7Au_0.15 catalysts. (b) Polarization curves of glycerol oxidation recorded (a) on sputtered Pd1 and Au1, co-sputtered Pd_0.7Au_0.3 and wet chemistry Pd_0.7Au_0.3/C catalysts, and (b) on co-sputtered Pd_0.7Au_0.3, wet chemistry Pd_0.7Au_0.3/C, and alternate sputtered Pd_0.35Au_0.3Pd_0.35 and Au_0.15Pd_0.3Au_0.15 catalysts ( v=20mVs⁻¹, N₂-saturated 1.0M NaOH electrolyte, T=293K).Display Omitted► Plasma sputtered PdAu is more active than wet chemistry PdAu. ► Modification of Pd by Au increases the catalytic activity of glycerol oxidation. ► PdAu surface alloy composition has no significant effect on catalytic activity. ► Presence of non-alloyed surface Au sites enhances the catalytic activity.Co-sputtered Pd_0.7Au_0.3 catalyst and alternate sputtered Pd_0.35Au_0.3Pd_0.35 and Au_0.15Pd_0.7Au_0.15 materials were prepared by plasma deposition of Au and Pd atoms on a carbon diffusion layer. Atomic composition and metal loadings were evaluated from EDX and RBS, respectively. The low amount of metal deposited and the resulting low metallic film thickness made TEM and XRD characterizations difficult to perform, therefore, catalyst microstructures and surface compositions were determined from electrochemical methods and compared with data obtained with Pd/C, Au/C and Pd_0.7Au_0.3/C materials synthesized via the “water in oil” microemulsion method. The surfaces of co-sputtered Pd_0.7Au_0.3 and alternate sputtered Pd_0.35Au_0.3Pd_0.35 and Au_0.15Pd_0.7Au_0.35 materials are partly composed by PdAu alloy. The plasma sputtering method leads to more active bimetallic PdAu material than the wet chemistry method. Modification of palladium surface by gold atoms leads to increase the catalytic activity toward glycerol electrooxidation. The PdAu surface alloy composition has no significant effect on the catalytic activity, however, the presence of non-alloyed gold sites on the material surface leads to the enhancement of the catalytic activity. The mechanism seems to involve glycerol adsorption on palladium surface and hydroxyl species formation on gold surface leading to catalytic activity enhancement through the bifunctional mechanism.

Keywords: Alloys; DGFC; Electro-oxidation; Glycerol; Gold; Palladium; Plasma sputtering

An investigation of the surface intermediates of H₂-SCR of NO_x over Pt/H-FER by Shufang Yang; Xinping Wang; Wenling Chu; Zhuonan Song; Shuai Zhao (pp. 380-385).

Display Omitted► High NO_x elimination level was reached in H₂-SCR at 110°C over 0.5%Pt/H-FER. ► The reaction route over the catalyst was investigated. ► NO₂ and nitrate species were demonstrated not to be intermediates of the reaction. ► NO₂ was firstly reduced to NO when it engaged in the reaction over the catalyst.Catalytic performance of platinum supported on H-ferrierite (H-FER) in selective catalytic reduction of NO and NO₂ by hydrogen (H₂-SCR) was investigated. 87.9% of the NO_x was reduced with 56% of selectivity to N₂ when a gas mixture of 910ppm NO, 90ppm NO₂, 5000ppm H₂, 10% O₂ in N₂ passed through a 0.5wt.%Pt/H-FER catalyst at 110°C and gas hourly space velocity (GHSV) of 36,000h⁻¹. It was found that the NO_x reduction sharply decreased at higher reaction temperature, accompanied by large amount of NO₂ formation. The NO_x conversion was also drastically decreased by increasing the concentration of NO₂ while holding the total concentration of NO+NO₂ in the feed gas mixture. Based on in situ Fourier transform infrared spectroscopy investigation, it was proposed that NO₂ and nitrate species were not essential intermediates of H₂-SCR over the catalyst, while NO δ⁺ species on Pt was a possible species for efficient elimination of NO.

Keywords: Reaction intermediate; NO; ₂; H; ₂; -SCR; H-ferrierite

Characterization and reactivity of Fe₃O₄/FeMnO_x core/shell nanoparticles for methylene blue discoloration with H₂O₂ by Shengtao Xing; Zicheng Zhou; Zichuan Ma; Yinsu Wu (pp. 386-392).

.Display Omitted► In this manuscript, a magnetic core/shell Fe₃O₄/FeMnO_x catalyst is prepared by a simple oxidation–precipitation method. ► Fe₃O₄/FeMnO_x is an effective and stable heterogeneous catalyst for the discoloration of methylene blue (MB) in aqueous solution at different pH. ► The catalyst shell not only increases the surface hydroxyl groups, but also enhances the electron transfer, resulting in higher activity. ► The discoloration of MB is promoted due to the decomposition of H₂O₂ intoOH and the adsorption of MB on Fe₃O₄/FeMnO_x.A magnetic core/shell Fe₃O₄/FeMnO_x catalyst was prepared by a simple oxidation–precipitation method. The catalyst was characterized by X-ray diffraction, transmission electron microscope, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and cyclic voltammetry. The characterization studies verified that Fe₃O₄ core was coated with a layer of Fe–Mn oxide. The Fe₃O₄/FeMnO_x was found to be an effective and stable heterogeneous catalyst for the discoloration of methylene blue (MB) in aqueous solution by H₂O₂. The high catalytic activity is due to the FeMnO_x shell, which not only increased the surface hydroxyl groups, but also enhanced the interfacial electron transfer. The discoloration of MB could be due to the decomposition of H₂O₂ intoOH and the adsorption of MB on Fe₃O₄/FeMnO_x.

Keywords: Core/shell nanoparticles; Magnetic catalyst; Discoloration; Surface hydroxyl; Electron transfer

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Applied Catalysis B, Environmental (v.107, #3-4)