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Applied Catalysis B, Environmental (v.126, #)

Editorial Board (pp. co2).

Contents (pp. co4).

Editorial Board (pp. i).

Contents (pp. ii).

Effect of copper surface area and acidic sites to intrinsic catalytic activity for dimethyl ether synthesis from biomass-derived syngas by Ji Woo Jung; Yeong Jun Lee; Soong Ho Um; Pil J. Yoo; Dong Hyun Lee; Ki-Won Jun; Jong Wook Bae (pp. 1-8).

.Display Omitted► The intrinsic activity is well correlated with the copper surface area and acidic sites. ► The small copper particles and large amount of acidic sites are responsible for high activity. ► The intrinsic activity keeps constant irrespective to the values of copper surface area multiplied by acidic sites.The crucial effects of copper surface area and acidic sites to intrinsic catalytic activity on the bifunctional catalysts such as Cu-ZnO/Al₂O₃ and Cu-ZnO-Al₂O₃/Zr-modified ferrierite catalysts have been investigated to find out the correlation between these two characteristics for the direct synthesis of dimethyl ether (DME) from biomass-derived syngas. The well-dispersed copper particles with a high reducibility as well as a large amount of weak acidic sites on bifunctional catalysts are responsible for their high catalytic performance. The high activity for methanol synthesis could be obtained by designing a high surface area of metallic copper with a low aggregation character, however, the quantity of the acidic sites on solid-acid components is also crucial factor for a high DME yield than the surface area of copper, which could be obtained by preparing proper bifunctional catalysts. It is mainly due to the fast reaction rate of methanol dehydration to DME compared to CO hydrogenation to methanol. The two important characteristics of the metallic surface area of copper and the amount of acidic sites are well correlated with the intrinsic catalytic activity on this consecutive reaction. The intrinsic activity for the direct DME synthesis from syngas on bifunctional catalysts initially decreases and maintains at constant value with the increase of the values of the copper surface area multiplied by the amount of acidic site.

Keywords: Dimethyl ether; Biomass-derived syngas; Bifunctional catalyst; Copper surface area; Acidic site; Intrinsic activity (TOF)

Mn–Fe/ZSM5 as a low-temperature SCR catalyst to remove NOx from diesel engine exhaust by Young Jin Kim; Hyuk Jae Kwon; Iljeong Heo; In-Sik Nam; Byong K. Cho; Jin Woo Choung; Moon-Soon Cha; Gwon Koo Yeo (pp. 9-21).

Display Omitted► Mn–Fe/ZSM5 exhibits excellent low-temperature deNOx activity and N₂ selectivity. ► Its hydrothermal stability is enhanced by addition of Mn and Er. ► Mn–Fe/ZSM5 has excellent durability toward K⁺, Ca²⁺ as well as C₃H₆. ► Mn–Fe/ZSM5 is deactivated by SO₂ due to the formation of MnSO₄.A Mn–Fe/ZSM5 catalyst has been developed for removing NOx from diesel engine exhausts and its excellent low-temperature SCR activity and N₂ selectivity demonstrated in comparison with other representative SCR catalysts including CuZSM5 and a Cu-based commercial catalyst (COM). The well-dispersed MnO₂ and the high NH₃ adsorption capacity of the Mn–Fe/ZSM5 catalyst have been identified as the primary sources for its high deNOx activity for NH₃/SCR. Hydrothermal stability and durability of the Mn–Fe/ZSM5 catalyst have been examined and compared to those of the CuZSM5 and COM catalysts. The hydrothermal stability of the catalyst improved upon the increase of Mn content and/or the addition of Er, the latter of which helps to stabilize the dispersion of MnOx on the catalyst surface during hydrothermal aging. The deNOx activity of the Mn–Fe/ZSM5 and its Er-promoted counterpart was less affected by HC poisoning, C₃H₆ poisoning in particular, compared to the CuZSM5 and COM catalysts, mainly due to the excellent C₃H₆ oxidation activity of MnO₂. No poisoning of the Mn-based ZSM5 and CuZSM5 catalysts has been observed upon the addition of 2wt.% of K⁺ and Ca²⁺ to their surface, primarily due to the high NH₃ adsorption capacity of the ZSM5 support, whereas the COM catalyst has been severely deactivated by the deposition of K⁺ and Ca²⁺. The deNOx activity of the Mn-based ZSM5 catalyst, particularly the Er-promoted one, was less affected by SO₂ compared to the CuZSM5 and COM catalysts, although it was hardly regenerated at 500°C. Formation of MnSO₄ on the catalytic surface appears to be the primary cause for the deactivation of the Mn-based ZSM5 catalysts in the presence of SO₂ in the feed gas stream.

Keywords: Selective catalytic reduction; Manganese; Hydrothermal aging; Sulfur poisoning; HC inhibition

Carbon xerogels and ceria–carbon xerogel materials as catalysts in the ozonation of organic pollutants by C.A. Orge; J.J.M. Órfão; M.F.R. Pereira (pp. 22-28).

Display Omitted► Carbon xerogels (XC) and various ceria–XC materials are tested as ozonation catalysts. ► The pore size of XC plays a key role in the degradation of pollutants. ► Ceria–XC catalysts present higher performance than ceria and XC. ► The reaction mechanism involves surface reactions. ► A new and highly active ceria–XC catalyst was prepared by one-pot synthesis.Carbon xerogels prepared at different pH and ceria–carbon xerogel materials with different compositions and synthesized by different procedures were evaluated as catalysts in the ozonation of oxalic acid and the textile dye CI Reactive Blue 5. The prepared samples were characterized by N₂ adsorption at −196°C, X-ray diffraction and scanning electronic microscopy. All the catalysts containing both cerium oxide and carbon xerogel removed all oxalic acid in solution after 1h of reaction. Cerium oxide supported on carbon xerogel and carbon xerogel containing 1% of cerium oxide prepared by one-pot synthesis were the most active catalysts for the ozonation of the dye solution. Considering the catalytic activity and the steps involved in the preparation of materials, the carbon xerogel containing 1% of cerium oxide prepared by one-pot synthesis is the most promising catalyst.

Keywords: Catalytic ozonation; Cerium oxide; Carbon xerogel; Oxalic acid; Textile dye

Effect of FeCl₃ on sulfonamide removal and reduction of antimicrobial activity of wastewater in a photocatalytic process with TiO₂ by Ewa Adamek; Wojciech Baran; Justyna Ziemiańska; Andrzej Sobczak (pp. 29-38).

Display Omitted► The most active catalyst for photodegradation of sulfa drugs in sewage was a mixture of TiO₂/FeCl₃. ► The optimum pH for this process was ≤3. ► Excess of FeCl₃ (>1.0mmoll⁻¹) was an inhibitor of the process. ► Products of sulfonamides photodegradation did not cause an increase in microbial activity. ► Ionic contaminants in sewage probably acted as an inhibitor of photodegradation of sulfonamides.The aim of the study was to investigate the degradation of sulfonamides (SNs) in real wastewater samples using photocatalytic processes performed in the presence of a commercial TiO₂ catalyst (Degussa Aeroxide P25), FeCl₃ and a TiO₂/FeCl₃ mixture. The dynamics of the photodegradation of a mixture containing sulfadiazine, sulfamethoxazole and sulfathiazole in distilled water and in synthetic, municipal (raw and after treatment) wastewater, in wastewater from septic tank and in landfill leachate were compared during the study. The changes in the antimicrobial activity of the samples containing SNs and the photodegradation products were also assessed using the MARA^® test.It was observed that the photocatalytic degradation rate of SNs was primarily dependent on the environmental pollution degree, the catalytic system composition and pH values. In a landfill leachate the SNs photodegradation practically did not proceed. The inhibitors of the process were primarily soluble wastewater components.The decomposition products of the SNs did not cause an increase in the antimicrobial activity of the reaction medium. The highest effectiveness for the photodegradation of SNs was obtained using the mixture containing TiO₂ (∼0.5gl⁻¹) and FeCl₃ (∼0.5mmoll⁻¹) at pH ∼3.0. The activity of this catalyst system estimated based on the half-life values of the SNs in the investigated samples were approximately 4.5 times greater than that in the presence of TiO₂ alone. Its high activity at pH ∼3 primarily resulted from the decrease in the dissociation degree of other wastewater components in acidic medium, rather than the synergism of both photocatalyst components.

Keywords: Photocatalysis; Sulfonamides; Wastewater treatment; Antimicrobial activity; Photochemical treatment

Stainless steel wire mesh-supported potassium-doped cobalt oxide catalysts for the catalytic decomposition of nitrous oxide by Laura del Río; Gregorio Marbán (pp. 39-46).

Display Omitted► Dropwise impregnation with K₂CO₃ solutions provides the best results. ► Catalytic activity is restored when the water is removed from the reaction stream. ► Results showed a compensation effect, explained by assuming dual site catalysts. ► The catalysts are among the most active and stable catalysts in the literature. ► The catalysts have superior performance in terms of pressure drop and heat transfer.Structured catalysts consisting of potassium-doped cobalt oxide supported on stainless steel wire mesh were tested for the decomposition of N₂O under dry and wet conditions. The cobalt oxide catalysts were prepared by the ammonia-evaporation-induced method. Of the several doping procedures tested, dropwise impregnation with potassium carbonate solutions provided the best catalytic results at lower K/Co molar ratios. Kinetic analysis of a potassium-doped catalyst yielded a reaction order on the N₂O partial pressure slightly below unity (0.87). The activation energy values and the natural logarithms of the pre-exponentials factors for the different catalysts followed the classical compensation effect. This effect may be the result of a combination of competing reactions on different groups of active centers. Thus, cobalt ions affected by potassium display a low activation energy (∼40kJ/mol), whereas cobalt atoms unaffected by potassium display a higher activation energy equal to that of the undoped catalysts (∼106kJ/mol). The catalytic activity of the catalysts in N₂O decomposition increases with the amount of reducible Co³⁺ ions, although there does not appear to be a direct relation between the amount of Co³⁺ ions and the textural and crystal properties of the catalysts. The addition of water produces some inhibition of the N₂O decomposition reaction on K-doped catalysts, although catalytic activity is completely restored when the water is removed from the reaction stream. The catalysts prepared in this work were found to be among the most active, selective and stable catalysts reported in the literature.

Keywords: Co; ₃; O; ₄; N; ₂; O decomposition; Stainless steel mesh; Potassium

Improved visible light photocatalytic activity of TiO₂ co-doped with Vanadium and Nitrogen by R. Jaiswal; N. Patel; D.C. Kothari; A. Miotello (pp. 47-54).

Display Omitted► V-N-codoped TiO₂ nano-photocatalyst with average size of 7nm was synthesized. ► The TiO₂ band gap was narrowed up to 2.3eV when 2% of V and 4% of N are incorporated in TiO₂. ► Increased visible light absorption and charge separation creates synergistic effect. ► Significantly higher photocatalytic activity was obtained with V-N-codoped-TiO₂.V- and N-codoped TiO₂ photo-catalyst is synthesized by sol–gel method to sensitize TiO₂ to visible light. The concentrations of V and N were varied and optimized to enhance photo-catalytic activity. In order to increase the active surface area, the crystalline powder was ball milled to obtain nanosized particles. The photo-catalysts were characterized by Micro-Raman, TEM, XPS and UV–vis (in diffused reflectance mode) techniques. The co-doped TiO₂ photocatalyst displayed narrower band gap (2.3eV) compared to singly doped TiO₂ catalyst, namely V (2at.%)-doped (2.42eV), N (4at.%)-doped (2.95eV), and undoped TiO₂ (3.13eV). The photocatalytic activity for the degradation of Rhodamine B (an organic dye) under visible light irradiation obtained with co-doped TiO₂ photo-catalyst is significantly better as compared to the undoped, V-doped, and N-doped TiO₂. The incorporation of V and N in TiO₂ lattice induces isolated energy levels near the conduction and valence bands, respectively, causing an effective narrowing of the band gap. In addition, due to the low dopants concentrations, these energy levels can also act as traps for photoexcited holes or electrons thus reducing the recombination between photo-generated charges. Both these effects, namely band narrowing and enhanced charge separation produce synergistic effects to increase the photocatalytic activity of V-N-codoped TiO₂.

Keywords: Photocatalytic degradation; Rhodamine B; Codoping TiO; ₂; Sol–gel method; Ball milling

Active phase genesis of NiW hydrocracking catalysts based on nickel salt heteropolytungstate: Comparison with reference catalyst by Karima Ben Tayeb; Carole Lamonier; Christine Lancelot; Michel Fournier; Audrey Bonduelle-Skrzypczak; Fabrice Bertoncini (pp. 55-63).

.Display Omitted► Study of HCK catalysts sulfidation by Raman, XPS, HRTEM and EPR. ► Higher quantity of NiWS for HPA based catalyst than for conventional NiW catalysts. ► Evidence of sulfidation intermediates WS₃ and WO_xS_y. ► Ni-WO_xS_y species proposed as NiWS phase precursors.The sulfidation of supported NiW hydrotreating catalysts is followed by a combination of X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM), Raman and electron paramagnetic resonance (EPR) spectroscopy. In this work, we compared two catalysts prepared by incipient wetness impregnation from different precursors. The first one is an innovating catalyst prepared with the nickel salt of the derived lacunary Keggin heteropolyanion (HPA) Ni₄SiW₁₁O₃₉ and the second one is a conventional catalyst synthesized from ammonium metatungstate and nickel nitrate. The results show for both catalysts that the sulfidation of nickel and tungsten elements does not occur at the same temperature. However, a better sulfidation of tungsten and nickel atoms respectively to WS₂ and NiWS phases is observed at 400°C for HPA precursor compared to conventional catalyst, highlighting the benefit of HPA starting material.

Keywords: Sulfidation; WS; ₂; NiW catalysts; Heteropolyanion; XPS; HRTEM; Raman; EPR

Catalytic combustion of chlorobenzene over Ru-doped ceria catalysts by Qiguang Dai; Shuxing Bai; Zhengyi Wang; Xingyi Wang; Guanzhong Lu (pp. 64-75).

Ru doped CeO₂ catalysts were prepared by a simple coprecipitation method and 10wt.% NaOH solution as the precipitating agent. It was found that the Ru-CeO₂ catalysts showed an outstanding catalytic activity ( T_90% below 250°C and stability (at least 80h at 275°C for catalytic combustion of chlorobenzene. The better stability of the Ru based catalysts can be ascribed to the inorganic chlorine species adsorbed on active sites can be removed rapidly via the Deacon process catalysized by RuO₂ component.Display Omitted► Ru doped CeO₂ was prepared by a coprecipitation method and 10wt.% NaOH as the precipitating agent. ► The catalytic combustion of chlorobenzene was investigated over Ru-CeO₂ for the first time. ► Ru-CeO₂ showed an outstanding activity and stability for chlorobenzene decomposition. ► The better stability can be ascribed to the dissociactive Cl can be removed via the Deacon process.CeO₂ and Ru doped CeO₂ nanoparticles with small particle sizes (∼7nm) and high surface area (∼100m²g⁻¹) were prepared by a simple precipitation/coprecipitation method and aqueous NaOH solution (10wt%) as the precipitating agent, and characterized by XRD, N₂ adsorption, TEM/HRTEM, Raman, XPS and H₂-TPR. The catalytic combustion of chlorobenzene (CB) was investigated for the first time. The results revealed that the Ru doped CeO₂ catalysts exhibit an outstanding catalytic activity ( T_90% below 250°C) and stability (at least 82h at 275°C) for CB decomposition. The better stability of the Ru-CeO₂ catalysts can be ascribed to the inorganic chlorine species or dissociative Cl adsorbed on active sites can be removed rapidly via the Deacon process catalysized by RuO₂ component with extraordinary stability (limited chlorination and easier Cl₂ evolution).

Keywords: Chlorobenzene; Ceria; Ru; Catalytic combustion; Chlorinated hydrocarbons

Insights towards the influence of Pt features on the photocatalytic activity improvement of TiO₂ by platinisation by J.J. Murcia; J.A. Navío; M.C. Hidalgo (pp. 76-85).

Display Omitted► Pt deposit size was precisely tuned with sizes ranging from 3 to 6nm. ► Pt oxidation state depended strongly on photodeposition time. ► Fraction of metallic platinum (Pt⁰) was crucial for activity improvement. ► At similar fraction of Pt⁰, metal deposit size became the key parameter for activity. ► The influence of substrate to be degraded (phenol or methyl orange) was studied.The influence of Pt features, such as particle size, dispersion, oxidation state and amount of metal, on the improvement of the photoactivity of TiO₂ for phenol and methyl orange degradation was studied.The size of Pt deposits was precisely controlled by changing deposition time under medium light intensity during the photodeposition, with sizes ranging from 3 to 6nm. Pt oxidation state was also strongly dependent on the photodeposition time.Photocatalytic activity results showed that the fraction of metallic platinum (Pt⁰) was the crucial factor for the improvement of the activity. When the fraction of Pt⁰ was similar, metal deposit size became the dominant parameter influencing the activity.The influence of the substrate to be degraded (phenol or methyl orange) was also studied.

Keywords: Pt-TiO; ₂; Platinisation; Photodeposition; Photocatalysis; Phenol oxidation; Methyl orange oxidation

Isotope tracing study on oxidation of water on photoirradiated TiO₂ particles by Thuan Duc Bui; En Yagi; Takashi Harada; Shigeru Ikeda; Michio Matsumura (pp. 86-89).

Display Omitted► Water is oxidized on TiO₂ photocatalysts using O₂ as the electron acceptor. ► As a result, O₂ is produced using O atoms supplied solely from water. ► Rutile particles showed 3-times higher quantum efficiencies than anatase particles. ► Larger particles showed higher efficiency for both rutile and anatase particles.Water is oxidized to molecular oxygen on a TiO₂ photocatalyst using electron acceptors such as Ag⁺ and Fe³⁺ ions. However, there has been no information about whether this reaction occurs or not using molecular oxygen as the electron acceptor. We found by analysis of oxygen in the gas phase using¹⁸O-enriched water that this reaction does in fact occur. The quantum efficiency was higher with rutile-form particles than with anatase-form particles. O₂ was photocatalytically produced using O atoms supplied solely from water even in the presence of O₂ in the system. These results are important for deepening the understanding of TiO₂ photocatalysts because molecular oxygen is used most frequently as the electron acceptor and the intermediates of oxidation of water are involved in various kinds of photocatalytic reactions.

Keywords: Photocatalysis; Titanium dioxide; Oxidation of water; Labeled water

Photocatalytic degradation of imazalil in an aqueous suspension of TiO₂ and influence of alcohols on the degradation by R. Hazime; C. Ferronato; L. Fine; A. Salvador; F. Jaber; J.-M. Chovelon (pp. 90-99).

Display Omitted► Imazalil was totally degraded in an aqueous TiO₂ suspension. ► Alcohols were used as hydroxyl radical scavenger, to assess the role of the latter in the degradation. ► Hydroxyl radicals play a major role in the degradation of imazalil. ► Nine intermediates were identified by HPLC–MS/MS. ► A mechanism of degradation has been tentatively proposed.The photocatalytic degradation of imazalil, a probably carcinogen fungicide, was carried out in an aqueous suspension of titanium dioxide under UV irradiation. The influence of alcohols as hydroxyl scavengers (isopropanol, methanol) on the degradation was studied and different concentrations were used. We conclude that the degradation of imazalil occurs mainly by OH attack, since 80% of the degradation was inhibited in the presence of isopropanol [isopropanol]=1000[imazalil]. Using HPLC/DAD and LC–MS/MS analysis, nine intermediates were identified giving monohydroxylated, dihydroxylated and mostly a hole attack for other products. Their kinetic evolution profiles were plotted and compared to those with isopropanol. The quantity of photoproducts formed by OH radicals was decreased in the presence of isopropanol. After that a tentative pathway mechanism was proposed including mainly hydroxyl radical attack with the participation of holes in the degradation. Ion chromatography showed that nitrogen groups in imidazole were converted to both NH₄⁺ and NO₃⁻. In addition, TOC was examined in details and total mineralization was reached.

Keywords: Imazalil degradation; Hydroxyl scavengers; Alcohols; Photocatalysis; HPLC–MS/MS

Role of activated carbon in the photocatalytic degradation of 2,4-dichlorophenoxyacetic acid by the UV/TiO₂/activated carbon system by J. Rivera-Utrilla; M. Sánchez-Polo; M.M. Abdel daiem; R. Ocampo-Pérez (pp. 100-107).

Display Omitted► The degradation of 2,4-D with the UV/TiO₂/activated carbon (AC) system was studied. ► The presence of ozonated AC enhances 2,4-D photodegradation by the UV/TiO₂ system. ► Carboxyl groups of AC participate in the additional generation of HO radicals. ► The UV/TiO₂/AC-ozonated system mineralized 40% of the organic matter. ► The toxicity of the degradation byproducts was much lower than that of 2,4-D.The objective of this study was to photocatalytically degrade the pesticide 2,4-dichlorophenoxyacetic acid (2,4-D) by using the integrated UV/TiO₂/activated carbon system and to study the degradation kinetics and the role of the chemical and textural properties of activated carbon in this process. Results obtained show that the presence of activated carbon during the catalytic photodegradation (UV/TiO₂) of 2,4-D considerably increases its percentage removal. After 60min of treatment, the highest percentage 2,4-D degradation is obtained in the presence of the activated carbons with the greatest content of carboxyl groups. In order to determine the role of activated carbon in this process, we determined the adsorptive and photocatalytic contribution (UV/TiO₂) to the overall 2,4-D removal. The total percentage removal by the UV/TiO₂/activated carbon system is much higher than the value obtained by summing the adsorptive and catalytic contributions, mainly when the carbon has an elevated carboxyl group content. No relationship was observed between the textural properties of activated carbons and their synergistic activity; however, the carbons with the greatest carboxyl group content showed the highest synergistic activity. Together with the results of chemical and superficial characterization of the carbon samples after their utilization in the photocatalytic process (UV/TiO₂), these findings demonstrate that the reduction of superficial carboxyl groups to alcohol groups is the main pathway by which activated carbon enhances the additional generation of HO radicals in the medium. Experiments conducted in the presence of radical scavengers (carbonate ions, sulfate ions, and t-butanol) revealed that H, e_aq⁻, and HO species participate in the 2,4-D photodegradation. According to the time course of total organic carbon and toxicity during 2,4-D photodegradation, its complete mineralization is not achieved, and the toxicity of the degradation compounds is lower than that of 2,4-D.

Keywords: 2,4-Dichlorophenoxyacetic acid; Photodegradation; Titanium dioxide; Ozonated activated carbon

Insights into the effect of surface hydroxyls on CO₂ hydrogenation over Pd/γ-Al₂O₃ catalyst: A computational study by Riguang Zhang; Hongyan Liu; Baojun Wang; Lixia Ling (pp. 108-120).

CO₂ hydrogenation on Pd/γ-Al₂O₃ catalyst with both the dry and the hydroxylated γ-Al₂O₃ support suggest that the hydroxylation of γ-Al₂O₃ support can alter the interaction of metal–support, and ultimately, the selectivity of CO₂ hydrogenation.Display Omitted► CO is favorably formed on Pd/γ-Al₂O₃ catalyst with dry support. ► HCOO is preferred on Pd/γ-Al₂O₃ catalyst with hydroxylated support. ► Hydroxylation of support can alter the selectivity of CO₂ hydrogenation. ► The migration of H adatom on Pd is an essential step of CO₂ hydrogenation. ► Pd/γ-Al₂O₃ catalyst must get help from additives to achieve high selectivity.The elementary steps leading to the formation of HCOO and CO via CO₂ hydrogenation, two important intermediates contributing to methanol and methane formation, respectively, have been explored to identify hydroxylation effect of the oxide support on the selectivity in CO₂ hydrogenation on Pd/γ-Al₂O₃ catalyst by the density functional theory together with slab model calculations. Two models: tetramer Pd4 cluster supported on the dry γ-Al₂O₃(110) surface, D(Pd4), and on the hydroxylated γ-Al₂O₃(110) surface, H(Pd4), have been employed to model Pd/γ-Al₂O₃ catalyst. Meanwhile, Pd(111) surface is used to model the unsupported large Pd particle sizes. On D(Pd4), the formation of CO is preferred both kinetically and thermodynamically. On H(Pd4), HCOO formation becomes more favorable kinetically while CO formation is more facile thermodynamically. However, Pd(111) surface has not shown strong selectivity and activity for CO₂ hydrogenation to HCOO or CO. These results show that varying the properties of γ-Al₂O₃ support can alter the selectivity of CO₂ hydrogenation, moreover, the presence and number of low-coordinated Pd particles is of great importance to improve the overall activity and selectivity of CO₂ hydrogenation. Our results also show that to achieve high selectivity of CO₂ hydrogenation, Pd/γ-Al₂O₃ catalyst has to get help from additives, which should be able to improve its dispersion or to control the hydroxylation. The present study provides the basis and one of the directions to the design of improved catalysts in CO₂ hydrogenation for methanol, methane and other products.

Keywords: Pd/γ-Al; ₂; O; ₃; CO; ₂; hydrogenation; Hydroxylation; Support; Density functional theory

Preparation of carbon-sensitized and Fe–Er codoped TiO₂ with response surface methodology for bisphenol A photocatalytic degradation under visible-light irradiation by Dianxun Hou; Ronn Goei; Xiaoping Wang; Penghua Wang; Teik-Thye Lim (pp. 121-133).

Display Omitted► Fe/Er–TiO₂ was prepared via a facile solvothermal method. ► RSM was used to obtain the optimum synthesis conditions for this novel Fe/Er–TiO₂. ► RSM was used to examine the main and interactive effects of the synthesis parameters. ► Photocatalytic degradation of BPA under various conditions was investigated. ► Photocatalytic mechanism on Fe/Er–TiO₂ under visible light irradiation was proposed.The carbon-sensitized and Fe–Er codoped TiO₂ (Fe/Er–TiO₂) was synthesized by a facile solvothermal method using titanium isopropoxide both as titanium precursor and carbon source, as well as ferric nitrate and erbium nitrate as dopants source. The response surface methodology (RSM) with central composite design (CCD) model was used to obtain the optimum synthesis conditions for this novel Fe/Er–TiO₂. The RSM was also applied to study the main and interactive effects of the parameters (Er concentration [Er], Fe concentration [Fe] and calcination temperature [CT]) investigated. The experimental results indicated an improved photocatalytic activity of Fe/Er–TiO₂ for bisphenol A (BPA) degradation compared to the pristine TiO₂, Er–TiO₂, Fe–TiO₂ and Degussa P25 (P25) under visible light irradiation. In addition, the RSM model obtained ( R²=0.929) showed a satisfactory correlation between the experimental results and predicted values of BPA removal efficiency. The identified optimum condition for preparing Fe/Er–TiO₂ was 1.5mol%, 1.25mol% and 450°C for [Er], [Fe] and [CT], respectively. Moreover, the photocatalytic activity of the optimized Fe/Er–TiO₂ was preserved effectively even after ten cycles of use. The possible photocatalytic mechanisms induced by the Fe/Er–TiO₂ under visible light irradiation are proposed. The enhanced photocatalytic activity of Fe/Er–TiO₂ can be attributed to the synergistic effects of photosensitizing (CO band), narrowed band gap and enhanced e⁻/h⁺ separation (Ti–O–Fe linkage), and upconversion luminescence property (Ti–O–Er linkage).

Keywords: Carbon-sensitizing; Fe–Er codoping; Response surface methodology; Photocatalytic degradation; Upconversion luminescence

Influence of lanthanum stoichiometry in La1−_xFeO3−_δ perovskites on their structure and catalytic performance in CH₄ total oxidation by Jérémy Faye; Alexandre Baylet; Martine Trentesaux; Sébastien Royer; Franck Dumeignil; Daniel Duprez; Sabine Valange; Jean-Michel Tatibouët (pp. 134-143).

Display Omitted► La1−_x FeO 3_−δ perovskites were prepared by the auto-ignition procedure. ► XPS analyses allowed to clearly describe the surface composition evolution. ► Enrichment in Fe₂O₃ on the surface was evidenced when decreasing La content. ► The closer the stoichiometry, the more efficient the catalyst in methane oxidation.A series of iron-based La1−_xFeO3−_δ perovskites (with x=0, 0.1, 0.2, 0.3 and 0.4) was prepared by the so-called self-combustion method using glycine as an ignition promoter. The chemical, structural and surface properties of these mixed oxides were thoroughly characterized before the determination of their activity in the total oxidation of methane. The catalytic data indicated a strong dependence of the methane conversion towards the catalyst elemental composition. A progressive Fe₂O₃ enrichment of the perovskite surface was clearly evidenced by XPS characterization when decreasing the lanthanum content of the solid. Such additional undesirable surface iron oxide induced an inhibiting effect on the catalytic activity. As a result, while the La1−_xFeO3−_δ ( x=0, 0.1, 0.2, 0.3, 0.4) perovskites presented moderated performances in methane total oxidation, the most efficient lanthanum iron-based perovskite is the stoichiometric LaFeO₃ mixed-oxide that exhibits the most adapted surface and global composition, resulting in a CH₄ conversion of 86% at 873K.

Keywords: CH; ₄; total oxidation; Non-stoichiometric perovskite; XPS; Redox properties; Iron oxide

Local ammonia storage and ammonia inhibition in a monolithic copper-beta zeolite SCR catalyst by Xavier Auvray; William P. Partridge; Jae-Soon Choi; Josh A. Pihl; Aleksey Yezerets; Krishna Kamasamudram; Neal W. Currier; Louise Olsson (pp. 144-152).

Display Omitted► We characterize the transient distributed performance of a Cu-beta SCR catalyst. ► The intra-SCR zone can vary dramatically with constant integral performance. ► The NH₃ capacity is practically saturated over the SCR zone. ► Fast NH₃ coverage buildup drives dynamic inhibition conversion inflections. ► Inhibited conditions can be accessed without experiencing dynamic inhibition.Selective catalytic reduction of NO with NH₃ was studied on a Cu-beta zeolite catalyst, with specific focus on the distributed NH₃ capacity utilization and inhibition. In addition, several other relevant catalyst parameter distributions were quantified including the SCR zone, or catalyst region where SCR occurs, and NO and NH₃ oxidation. We show that the full NH₃ capacity (100% coverage) is used within the SCR zone for a range of temperatures. By corollary, unused NH₃ capacity exists downstream of the SCR zone. Consequently, the unused capacity relative to the total capacity is indicative of the portion of the catalyst unused for SCR. Dynamic NH₃ inhibition distributions, which create local transient conversion inflections, are measured. Dynamic inhibition is observed where the gas phase NH₃ and NO concentrations are high, driving rapid NH₃ coverage buildup and SCR. Accordingly, we observe dynamic inhibition at low temperatures and in hydrothermally aged states, but predict its existence very near the catalyst front in higher conversion conditions where we did not specifically monitor its impact. While this paper addresses some general distributed SCR performance parameters including Oxidation and SCR zone, our major new contributions are associated with the NH₃ capacity saturation within the SCR zone and dynamic inhibition distributions and the associated observations. These new insights are relevant to developing accurate models, designs and control strategies for automotive SCR catalyst applications.

Keywords: SCR; Ammonia; NO; NH; ₃; capacity; NH; ₃; inhibition; Distributed reactions; Cu-beta; Zeolite

Outstanding activity of sub-nm Au clusters for photocatalytic hydrogen production by Peichuan Shen; Shen Zhao; Dong Su; Yan Li; Alexander Orlov (pp. 153-160).

Display Omitted► This work is the first ever application of sub-nm Au co-catalysts for water splitting. ► Sub-nm gold particles are extraordinarily active for hydrogen production under visible light. ► This activity was much higher than that of any other co-catalysts tested. ► The activity of sub-nm Au was also much better than that of CdS modified with larger Au particles.Developing sustainable methods of hydrogen production can have significant environmental and energy efficiency benefits. A potentially viable way forward is to produce hydrogen from water by combining solar energy and heterogeneous catalysts. Our results indicate that sub-nm gold particles can provide an enormous enhancement in photocatalytic hydrogen production under visible light. We have observed a 35 times increase in activity for Au modified CdS as compared to that of unmodified catalyst. This activity was much higher than that of any other co-catalysts tested, which included 2–4nm Pt, Ru, Pd and Rh nanoparticles modified CdS. The activity of sub-nm Au was also much better than that of CdS modified with larger Au particles. Our first-principles calculations of unsupported Au clusters indicated that there is a substantial difference in both shape and electronic properties between charged and neutral bare Au clusters as well as between bare and ligand-protected ones. This is the first ever demonstration of the remarkable potential of sub-nm Au particles for H₂ production.

Keywords: Photocatalytic; Water splitting; Au clusters; Hydrogen production; Catalyst; TDDFT; CdS

Size controlled copper nanoparticles hosted in mesoporous silica matrix: Preparation and characterization by Alessandro Gallo; Tanya Tsoncheva; Marcello Marelli; Mihail Mihaylov; Momtchil Dimitrov; Vladimiro Dal Santo; Konstantin Hadjiivanov (pp. 161-171).

Display Omitted► Novel method for synthesis of supported copper nanoparticles with tailored size. ► Size dependent effects of the redox and catalytic properties. ► Catalysts formation by the influence of reaction medium. ► Size dependent effects are controlled by the support porous structure.A novel preparation strategy was performed to obtain uniform and size controlled, in a large scale, copper nanoparticles, hosted into mesoporous silica matrix. The method includes the initial deposition of finely dispersed copper nanoparticles, using a conventional incipient wetness impregnation of silica matrix with small amount of nitrate precursor and consecutive pretreatment in oxidation and reduction atmosphere. The further controlled growing of the loaded copper particles was performed in rotary bed reactor by step-wise deposition of copper over them by OMCVD techniques, using bis- (hexafluoroacetylacetonate) copper (II) hydrate as a precursor. A complex of physicochemical methods (TEM, Nitrogen physisorption, TPR and TPRD-MS measurements, UV-Vis and FTIR spectroscopy of adsorbed CO) was used for characterization of the samples. The catalytic properties of the obtained materials were investigated in methanol decomposition to CO and hydrogen. A mechanism of the copper particles growing was discussed. Size dependent effects of the redox and catalytic properties of the loaded copper particles which are strongly affected by their location in the silica porous structure are assumed.

Keywords: OMCVD technique; Copper nanoparticles supported on mesoporous silica; Methanol decomposition; Size dependent effects; FTIR spectroscopy

Performance comparison of CO₂ conversion in slurry and monolith photoreactors using Pd and Rh-TiO₂ catalyst under ultraviolet irradiation by Oluwafunmilola Ola; Mercedes Maroto-Valer; Dong Liu; Sarah Mackintosh; Chien-Wei Lee; Jeffrey C.S. Wu (pp. 172-179).

.Display Omitted► Novel combination of metal coated TiO₂ nanoparticles and monoliths were prepared. ► The photocatalytic properties were studied upon UV irradiation. ► The metal coated TiO₂ monoliths show superior photocatalytic activity. ► We report improved quantum efficiency due to the reactor's flexible configuration.Anthropogenic activities are causing an increase in greenhouse gases in the atmosphere, with carbon dioxide (CO₂) being the key cause of global warming. The conversion of CO₂ into valuable hydrocarbons serves as a promising route for mitigating the effects of global warming and meeting future energy demands. Herein, we show the comparison between the photocatalytic reduction of CO₂ for metal coated TiO₂ nanoparticles in a slurry batch annular reactor system and metal coated TiO₂ monoliths in an internally illuminated photoreactor system using the 1wt% Pd/0.01wt% Rh-TiO₂ catalyst. Carbon based fuels, such as methane, methanol or acetaldehyde were produced in the gas phase from the CO₂ reduction with water by titania nanoparticles modified by Pd and Rh for improved reactivity. The modified photocatalysts synthesized by the improved sol–gel method were tested under UV light irradiation. The quantum efficiency of the internally illuminated monolith reactor was near one order of magnitude higher than the slurry batch annular reactor. This efficiency was due to the reactor's flexible configuration; which allows maximum exploitation of the combined advantages of the high surface area of the monolith and the elimination of uneven light distribution via the optical fibres.

Keywords: Slurry reactor; Photocatalysis; Monolith photoreactor; Titanium dioxide

Simultaneous production of glyceric acid and hydrogen from the photooxidation of crude glycerol using TiSi₂ by Narasimharao Kondamudi; Mano Misra; Subarna Banerjee; Srikanta Mohapatra; Susanta Mohapatra (pp. 180-185).

Waste glycerol and water are converted to two value added products under mild conditions with sun light.Display Omitted► For the first time, waste glycerol from the biodiesel process is converted to two value added products, glyceric acid and hydrogen. ► 98% conversion and 100% selectivity were achieved under mild reaction conditions. ► This process needs, solid TiSi₂ catalyst, solar light and water.The biodiesel industry is facing a problem with glycerol market saturation due to the large amounts of glycerol co-product that are produced during biodiesel processing. This is also having a negative impact on our environment. The crude glycerol obtained from biodiesel industry is at basic pH (∼12–14) because of soluble bases such as potassium hydroxide (KOH) or sodium hydroxide (NaOH). In this work, the use of solid photo catalyst, titanium disilicide (TiSi₂) is investigated for glycerol oxidation in basic aqueous solution under mild conditions. The oxidation in a batch reactor at 65°C and atmospheric pressure using in situ oxygen as oxidant showed 100% selectivity toward glyceric acid. Conversion efficiency of glycerol was observed around 64% over 6h. Higher conversion (97.6%) was also observed over prolonged reaction conditions (∼12h).

Keywords: Glyceric acid; Titanium disilicide; Photo catalysis; Glycerol oxidation

Effect of H₂S on the behaviour of an impregnated NiO-based oxygen-carrier for chemical-looping combustion (CLC) by Cristina Dueso; María T. Izquierdo; Francisco García-Labiano; Luis F. de Diego; Alberto Abad; Pilar Gayán; Juan Adánez (pp. 186-199).

Display Omitted► H₂S in the fuel affects the reactivity and the oxygen transport capacity of NiO-based oxygen-carriers. ► Sulphur reacts preferentially with NiO in the particles instead of NiAl₂O₄>Ni₃S₂ and small amounts of NiS and NiSO₄ were found in the fuel-reactor particles. ► NiSO₄ and small amounts of Ni₃S₂ were found in the air-reactor particles. ► Total regeneration of the accumulated sulphur in the particles was not possible.Gaseous fuels for chemical-looping combustion (CLC) process may contain sulphur-compounds which could affect the oxygen-carrier behaviour, especially if NiO is used as active phase. In this work, several samples of a NiO-based oxygen-carrier prepared by impregnation (18wt.%) on α-Al₂O₃, so-called NiO18-αAl, were extracted from a CLC unit after continuous operation with CH₄ containing 500vppm of H₂S and characterized subsequently. Part of the sulphur fed to the system was release as SO₂ in the air-reactor during the CLC experiments while the rest remained in the solid particles. Ni₃S₂ was found in the oxygen-carrier extracted from the fuel-reactor, although small amounts of NiSO₄ were also detected. On the contrary, NiSO₄ was the main sulphur compound in the oxygen-carrier from the air-reactor while a low concentration of Ni₃S₂ was present. Despite the accumulated sulphur and the oxygen transport capacity loss during the operation, the oxygen-carrier was capable of recovering the initial reactivity for the CH₄ combustion after some time without H₂S feeding to the CLC system. In addition, a study about the possible regeneration of the oxygen-carrier in the air-reactor working at different temperatures and oxygen concentrations was performed. Independently of the operating conditions, part of the sulphur remained in the solid and total regeneration was not possible. The analysis of the NiO18-αAl oxygen-carrier after the CLC operation using TPR and XPS techniques revealed that sulphur reacted preferably with free NiO instead of NiAl₂O₄. Although Ni₃S₂ was the majority sulphide in the fuel-reactor, minor amounts of other sulphides such as NiS were detected. Sulphur was preferably concentrated in the outer surface of the particles. Taking into account all these results, a previous desulphuration process of the fuel would be necessary when NiO-based oxygen-carriers are used in a CLC system.

Keywords: Chemical-looping combustion (CLC); Oxygen-carrier; Nickel oxide; Sulphur

Manganese- and copper-doped titania nanocomposites for the photocatalytic reduction of carbon dioxide into methanol by P.L. Richardson; Marisa L.N. Perdigoto; W. Wang; Rodrigo J.G. Lopes (pp. 200-207).

Display Omitted► We investigate the photocatalytic reduction of carbon dioxide into methanol. ► Mn- and Cu-doped catalysts were characterized by means of XRD, TEM, BET/BJH, and XPS. ► Metal dopants acted as electron trappers as to avoid the recombination of hole and electron. ► Laboratory-made catalysts exhibited bandgaps lower than 3eV. ► Mn_0.22–Cu_0.78/TiO₂ was photocatalytically the most active with the highest energy/quantum efficiencies.In this work, the photocatalytic reduction of CO₂ is comprehensively investigated with commercial and laboratory-made catalysts by doping their surface with an electron acceptor based on Mn and Cu metals. Manganese- and copper-doped titania has been prepared via the sol–gel route as to obtain different nanocomposites for the CO₂ conversion to methanol. First, the XRD characterization demonstrated that both Mn and Cu were finely dispersed on the surface of the titanium oxide support preserving the crystalline structure. Second, the TEM morphological characterization pointed out representative titania grain sizes 15–25nm as to avoid the surface recombination of electron–hole pairs and concomitantly enhancing the photoactivity. The structural analyses provided by BET and BJH techniques revealed a considerable shrinkage of the volume absorbed for both fresh and used titania specimens when increasing the Mn loading on the TiO₂ substrate, and all the sol–gel derived titania photocatalysts exhibited a mesoporous structure for Mn- and Cu-dopped formulations. Afterwards, XPS spectra presented equivalent binding energies characteristic of pure Mn, Cu and Ti (2p_3/2, 2p_1/2) by underlining the chemical composition and crystallographic structure of laboratory-made photocatalysts. Finally, several photocatalytic reductions of CO₂ were performed with Mn- and Cu-doped titania catalysts by evaluating the methanol production. The Mn_0.22–Cu_0.78/TiO₂ specimen was found to yield a maximum of 238.6μmol-MeOH/g_cat with the highest energy (18.4%) and quantum (26.5%) efficiencies thereby acting as a potential candidate catalyst for the photocatalytic conversion of carbon dioxide.

Keywords: Photoreduction; Carbon dioxide; Methanol; XRD; TEM; XPS

Novel synthesis of N-doped porous carbons from collagen for electrocatalytic production of H₂O₂ by Ying-Hui Lee; Feng Li; Kuo-Hsin Chang; Chi-Chang Hu; Takeo Ohsaka (pp. 208-214).

The collagen-derived carbon synthesized at 800°C for 6h (i.e., CG 800-6) shows a good electrocatalytic activity for the four-electron oxygen reduction reaction (ORR). On the other hand, the carbons prepared at 400–800°C for 4h (i.e., CG400, CG600, CG800) possess a high selectivity for the H₂O₂ production at potentials more negative to 0.6V through a near constant two-electron transfer reaction. The H₂O₂ production percentage for the carbon synthesized at 400°C reached even 93%. In comparison with the undoped carbon (i.e., SWCNT), the much more positive onset potential and the nearly two-electron process of the ORR on these collagen-derived porous carbons reveal their unique electrocatalytic activity for H₂O₂ production.Display Omitted► N-doped carbons from collagen were developed for either two-electron or four-electron transfer reaction of ORR. ► The N-doped carbon (i.e., CG800-6) shows a good electrocatalytic activity for the four-electron ORR. ► The N-doped carbons (i.e., CG400, CG600, CG800) show an excellent electrocatalytic activity for H₂O₂ production. ► The efficiency of H₂O₂ production is higher than 80% over a wide potential range of ca. 0.17–0.6V (vs. RHE).Highly porous N-doped carbons for the electrocatalytic production of H₂O₂ via oxygen reduction were synthesized from paraformaldehyde cross-linked collagen through heating in vacuum at different temperatures (400–800°C). SEM images and N₂ adsorption/desorption isotherms of such collagen-derived carbons reveal the formation of a sheet-like porous structure with increasing the carbonization temperature. A higher carbonization temperature favors the formation of a quaternary-N structure and the removal of oxygen-containing functional groups and therefore enhances the graphitic crystallinity, which were confirmed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The collagen-derived carbon synthesized at 800°C for 6h shows a good electrocatalytic activity for the four-electron oxygen reduction reaction (ORR). On the other hand, the carbons prepared at 400–800°C for 4h possess a high selectivity for the H₂O₂ production at potentials more negative than 0.6V. The H₂O₂ production percentage for the carbon synthesized at 400°C even reached 93%. In comparison with undoped carbons, the much more positive onset potentials and the nearly two-electron process of the ORR on these collagen-derived porous carbons reveal their unique electrocatalytic activity for H₂O₂ production.

Keywords: Carbons; Nitrogen-doping; Collagen; H; ₂; O; ₂; generation; Oxygen reduction

Oxidation of perchloroethylene—Activity and selectivity of Pt, Pd, Rh, and V₂O₅ catalysts supported on Al₂O₃, Al₂O₃–TiO₂ and Al₂O₃–CeO₂. Part 2 by Satu Pitkäaho; Lenka Matejova; Kvieta Jiratova; Satu Ojala; Riitta L. Keiski (pp. 215-224).

Display Omitted► The total acidity did not correlate with the oxidation activity of the catalysts. ► The enhanced reducibility was the key property of the catalyst in PCE oxidation. ► After 40.5h in PCE oxidation the Pt/Al₂O₃–CeO₂ catalyst proved to be stable. ► In destructive adsorption water enhanced the HCl yield and catalysts’ stability. ► PCE decomposed by detaching the chlorine atoms prior carbon–carbon bond breakage.Pt, Pd, Rh and V₂O₅ metallic monolith catalysts supported on Al₂O₃, Al₂O₃–CeO₂ and Al₂O₃–TiO₂ were examined in the oxidation of perchloroethylene (PCE). The H₂-TPR experiments proved that the enhanced reducibility is the key feature of the catalyst in PCE oxidation: both the activity and the selectivity followed the orders of catalysts’ reducibility. The NH₃-TPD measurements showed that the acidity is not the determining property of the catalyst in the PCE oxidation. After the 40.5h stability test, no carbonaceous species were seen on the Pt/Al₂O₃–CeO₂ catalyst's surface. Instead, some chlorine was detected on the surface which at this point did not alter the catalysts’ performance. During the oxidation strong correlation between the water concentration in the feed and the HCl yield was seen. In the absence of oxygen, i.e. during destructive adsorption, the presence of water had even more pronounced effect on the HCl formation and on the catalysts’ stability. The oxidation of PCE over the Pt/Al₂O₃ and Pt/Al₂O₃–CeO₂ catalysts and in the presence of excess hydrogen proceeds via detaching the chlorine atoms before the breakage of the carbon–carbon double bond, and hence following the order of the lowest bond energy in each step.

Keywords: Catalytic oxidation; Emission abatement; Chlorinated volatile organic compounds (CVOCs); PCE; Tetrachloroethylene; Reducibility; Acidity; Destructive adsorption

Comparative study of IVB–VIB transition metal compound electrocatalysts for the hydrogen evolution reaction by Sebastian Wirth; Falk Harnisch; Markus Weinmann; Uwe Schröder (pp. 225-230).

Display Omitted► 21 non-noble hydrogen evolution electrocatalysts are systematically studied. ► Emphasis are 18 IVB–VIB transition metal carbides, nitrides, borides etc. ► The voltammetry of immobilised microparticles is used for rapid characterisation.A systematic and comparative investigation of 18 different IVB–VIB transition metal carbides, nitrides, sulfides, silicides and borides as well as of the three main group element ceramics AlN, B₄C and h-BN for their electrocatalytic performance towards the hydrogen evolution reaction (HER) is presented. We exploited the voltammetry of immobilised particles as a method that allows a rapid electrocatalyst screening and characterisation. The performances of the electrocatalysts – by means of the overpotential of the hydrogen evolution reaction in 100mM H₂SO₄ – were compared with platinum and nickel as benchmarks. Although none of the catalyst materials investigated reached the performance of platinum with respect to overpotential and stability, the electrocatalytic properties of several compounds, i.e. tungsten and molybdenum carbide but also of tungsten boride calls for continuative work.

Keywords: Hydrogen evolution reaction; Tungsten carbide; Transition metal carbides; Nitrides; Voltammetry of immobilised particles

Facile synthesis of highly active LaCoO₃/MgO composite perovskite via simultaneous co-precipitation in supercritical water by Jingyi Zhang; Xiaole Weng; Zhongbiao Wu; Yue Liu; Haiqiang Wang (pp. 231-238).

Display Omitted► A facile continuous hydrothermal flow synthesis route (CHFS) had been utilized. ► The CHFS made LaCoO₃/MgO had high surface area. ► The CHFS made LaCoO₃/MgO had good oxygen reduction and desorption capability. ► The LaCoO₃/MgO show good performance in catalytic oxidation toluene and methane. ► A “support dispersion” model was proposed to design better composite perovskites.In this paper, LaCoO₃/MgO composite perovskites were synthesized via a facile route using supercritical water and a more conventional citrate route. The resultant samples were denoted as sc-LCM and cr-LCM, respectively, which were subsequently subjected to a range of analytical techniques, including XRD, HAADF-STEM, HR-TEM, BET, H₂-TPR, O₂-TPD, etc. Experimental results showed that the sc-LCM sample had a well dispersed “support dispersion” feature (i.e. perovskites were dispersed on MgO supports), which yielded higher surface area and better oxygen desorption and reduction capability than the cr-LCM sample (with “among dispersion” feature, i.e. perovskites were dispersed among MgO particles), hence showing good performance in toluene and methane oxidation tests. We proposed that the “support dispersion” model in the sc-LCM sample could be more beneficial for the design of composite perovskites, which could not only ensure the functioning of MgO as sintering barriers but also provide sufficient contacting of LaCoO₃ particles with MgO support, leading to more oxygen deficiency in the structure as well as abundant weakly chemisorbed oxygen. We expect that the results present herein could give a new thought for the syntheses of composite perovskites with higher surface area and better catalytic activity.

Keywords: Abbreviations; CHFS; continuous hydrothermal flow synthesis; A-sc-LCM; As-prepared mixture that was synthesized via CHFS route; A-cr-LCM; As-prepared mixture that was synthesized via citrate route; sc-LCM; LaCoO; ₃; /MgO composite perovskite that was synthesized via CHFS route; cr-LCM; LaCoO; ₃; /MgO composite perovskite that was synthesized via citrate routeSupercritical water; VOCs; Perovskite; Catalytic oxidation; Composite

TAP investigation on methane conversion on supported Pd and Rh based catalysts – 1. Kinetics of methane adsorption by Y. Renème; F. Dhainaut; S. Pietrzyk; M. Chaar; A.C. van Veen; P. Granger (pp. 239-248).

Display Omitted► TAP as a powerful approach for the quantification of support induced effect on CH₄ adsorption. ► Evidence from TAP of the detrimental effect of sintering via accurate calculation of activation barrier for CH₄ adsorption. ► A detail approach in modeling outlet flow rate of CH₄ accounting for the porous structure of NGV Pd–Rh/Al₂O₃ catalysts. ► Beneficial effect of Rh limiting the loss of CH₄ adsorption on aged-NGV Pd-Rh/Al₂O₃.The adsorption of methane on supported Pd- and Rh-based catalysts has been investigated by TAP experiments in the temperature range of 400–550°C. Particular attention was paid to the effects related to thermal aging causing significant particle growth which strongly alters the adsorptive properties of noble metals. In the temperature range 400–550°C, most of CH₄ is irreversibly adsorbed and converted into CO, H₂, CO₂ and H₂O at selectivities depending on the pre-reductive or oxidative thermal treatment prior to TAP measurements. Responses of single pulse experiments were modeled in order to determine the rate constant values for methane adsorption and the related activation barriers. The employed model uses diffusivities for gas phase species determined separately in the different zones of the micro-reactor assuming a Knudsen diffusion. A significant increase in the activation energy values on aged catalysts is noted suggesting drastic changes in the nature of the reaction pathways for the dissociation of methane and/or in the extent of interaction between noble metals and the support. Such observations are discussed in view of a possible involvement of spill-over effects from alumina support onto noble metal particles partly suppressed after aging because of significant alterations of the metal/support interface.

Keywords: TAP reactor; Methane activation; Palladium; Metal/support interface; NGV catalyst; Thermal aging

Hydrogen from scrap tyre oil via steam reforming and chemical looping in a packed bed reactor by Nikolaos Giannakeas; Amanda Lea-Langton; Valerie Dupont; Martyn V. Twigg (pp. 249-257).

Display Omitted► Steam reforming of scrap tyre pyrolysis oil demonstrated with Ni catalyst. ► Highest hydrogen yield reported on basis on scrap tyre feedstock (11.8wt%). ► Optimum conditions at 750°C, molar steam to carbon ratio of 4. ► Deactivation during chemical looping reforming by C, S deposits and Ni crystal growth. ► Potentially higher H₂ yield if desulphurisation of oil and controlled steam addition.The production of hydrogen from scrap tyre pyrolysis oil (STPO) was investigated using catalytic steam reforming. STPO is difficult to upgrade to cleaner fuels due to its high sulphur content, complex organic composition, acidity and viscosity, which contribute to catalyst deactivation. The effects of temperature and steam to carbon ratio were investigated through thermodynamic equilibrium calculations of the main aromatic, aliphatic and hetero-N and -S compounds known to be present in STPO. The optimum operating conditions in a packed bed reactor with a Ni/Al₂O₃ catalyst at atmospheric pressure and molar steam to carbon ratio of 4:1 were 750°C at a WHSV of 0.82h⁻¹. The maximum hydrogen yield was 26.4wt% of the STPO feedstock, corresponding to 67% of the maximum theoretical yield, compared to 79.4% predicted at equilibrium for a model mixture of 22 STPO compounds in the same conditions. The selectivity to the H-containing products was 98% H₂ and 2% CH₄, respectively, indicating little undesirable by-product formation, and comparable to equilibrium values. The potential to optimize the process to enhance further the H₂ yield was explored via feasibility tests of chemical looping reforming (CLR) aimed at lowering the heating and purification costs of the hydrogen production from STPO. However, the hydrogen yield decreased with each cycle of CLR. Analysis of the catalyst indicated this was most likely due to deactivation by carbon accumulation and sulphur originally present in the oil, and possibly also by trace elements (Ca, Na). The NiO particles in the catalyst were also shown to have grown after CLR of STPO. Hence further development would require pre-treating the oil for removal of sulphur, and use of a catalyst more tolerant to carbon formation.

Keywords: Scrap (waste) tyre oil; Steam reforming; Hydrogen; Chemical looping; Nickel

Dissolution of mesoporous silica supports in aqueous solutions: Implications for mesoporous silica-based water treatment processes by Anh Le-Tuan Pham; David L. Sedlak; Fiona M. Doyle (pp. 258-264).

Display Omitted► Dissolution of mesoporous silica supports in aqueous solution was investigated. ► Both as-synthesized and modified supports dissolve quickly in neutral pH solutions. ► Dissolved silica released from the support poisoned FeOOH catalyst. ► The merits of using mesoporous silica supports in water are discussed.Under pH 7–10 conditions, the mesoporous silica supports proposed for use in water treatment are relatively unstable. In batch experiments conducted in pH 7 solutions, the commonly used support SBA-15 dissolved quickly, releasing approximately 30mg/L of dissolved silica after 2h. In column experiments, more than 45% of an initial mass of 0.25g SBA-15 dissolved within 2 days when a pH 8.5 solution flowed through the column. In a mixed iron oxide/SBA-15 system, the dissolution of SBA-15 changed the iron oxide reactivity toward H₂O₂ decomposition, because dissolved silica deposited on iron oxide surface and changed its catalytic active sites. As with SBA-15, other mesoporous silica materials including HMS, MCM-41, four types of functionalized SBA-15, and two types of metal oxide-containing SBA-15 also dissolved under circumneutral pH solutions. The dissolution of mesoporous silica materials raises questions about their use under neutral and alkaline pH in aqueous solutions, because silica dissolution might compromise the behavior of the material.

Keywords: Mesoporous silica; Hydrogen peroxide; Fenton reaction; Advanced oxidation process; Silica solubility in water

Single-source precursor approach for the preparation of CdS nanoparticles and their photocatalytic and intrinsic peroxidase like activity by Swarup Kumar Maji; Amit Kumar Dutta; Supriya Dutta; Divesh N. Srivastava; Parimal Paul; Anup Mondal; Bibhutosh Adhikary (pp. 265-274).

Nanorods and nanospheres of CdS have been synthesized through decomposition of a precursor complex [Cd(SOCPh)₂Lut₂]. As prepared CdS NPs show excellent catalytic, photocatalytic properties.Display Omitted► A novel precursor complex [Cd(SOCPh)₂Lut₂] with crystal structure. ► CdS NPs obtained by thermal and solvothermal decomposition of precursor complex. ► Superior photocatalytic activity toward the decomposition of Rose Bengal dye. ► Terephthalic acid photoluminescence probing technique to establish the degradation mechanism. ► Intrinsic peroxidase-like behavior.CdS nanoparticles (NPs) with different shapes and sizes (rods and spheres) have been synthesized through decomposition of a newly synthesized precursor complex [Cd(SOCPh)₂Lut₂] using structure-directing solvents such as ethylenediamine (EN), dimethylsulfoxide (DMSO) and ammonia (NH₃). In addition, CdS NPs is also prepared by thermal decomposition of the precursor complex under N₂ atmosphere. The precursor complex is characterized by elemental analyses, TGA, FTIR, UV–vis spectroscopy and single crystal X-ray diffraction. The distorted tetrahedron geometry of the precursor complex has been determined by X-ray diffraction, which crystallizes in monoclinic crystal system of P2(1)/n space group with a=11.0487(17)Å, b=16.396(3), c=15.413(2)Å, α=90.00°, β=109.708(4)°, γ=90.00° and Z=4. The CdS NPs are characterized using powder X-ray diffraction, transmission electron microscopy, BET analyses, UV–vis absorption and photoluminescence spectroscopy. The photo-catalytic activity of CdS NPs is studied by the degradation of Rose Bengal (RB) dye, indicating an excellent photocatalytic activity compared to that of commercial TiO₂. The mechanism behind photocatalytic degradation of RB in presence of CdS NPs is elucidated using terephthalic acid photoluminescence probing technique and evidence have shown that the photogenerated holes to be the predominant active species. This paper also demonstrates the intrinsic peroxidase like activity of CdS NPs toward peroxidase substrates 3,3′,5,5′-tetramethyl benzidine (TMB) and hydrogen peroxide. Kinetic analysis indicates that the catalysis by CdS NPs show typical Michaelis–Menten kinetics. Moreover, our synthesized CdS NPs show higher catalytic performances with a higher binding affinity for the substrate TMB than horseradish peroxidase (HRP) and other recently reported nano-mimitics.

Keywords: CdS nanoparticles; Single-source precursor; Crystal structure; Photocatalytic activity; Peroxidase-like behavior

High-surface-area zinc aluminate supported silver catalysts for low-temperature SCR of NO with ethanol by Aurélien Flura; Fabien Can; Xavier Courtois; Sébastien Royer; Daniel Duprez (pp. 275-289).

Display Omitted► NO_x SCR by ethanol were performed over Ag/Zn_x-Al₂O₃ with x=10, 20 or 33 at.%. ► Zn incorporation leads to changes the Lewis acid sites strength and silver state. ► Best N₂ yield at 250°C and 300°C were obtained with Ag/Zn_0.33-Al₂O₃ C800. ► N₂ formation depends on both the acetaldehyde formation and the NO₂+NH₃ reactivity.The NO_x selective catalytic reduction of ethanol (EtOH-SCR) was studied using a complex gas mixture representative of a diesel exhaust, over zinc alumina mixed oxide supported silver catalysts (2wt.% Ag/Zn_x-Al₂O₃, with x=10–20–33at.%). The supports were obtained using a template assisted sol–gel route in order to achieve high surface areas. For the higher Zn loading (33%), the calcination temperature has been raised from 600°C to 800°C then 1000°C in order to evaluate thermal stability of these materials. Addition of zinc in alumina network leads to the formation of the spinel-type zinc aluminate structure. Chemical and physical characterizations of the catalysts have been confronted with the EtOH-SCR results, in order to understand the respective influence of the metal and support in nitrogen formation. This study shows that addition of zinc and modification of the support calcination temperature both play upon the Lewis acidic sites (LAS) concentration and density, determined by pyridine adsorption monitored by FTIR spectroscopy. This parameter is shown to be related with ammonia emission at T≥350°C. Besides, formation of nitrogen at T≤350°C is shown to be dependent on (i) the rate of acetaldehyde formation and (ii) the reactivity of acetaldehyde in SCR of NO reaction. Modification of the alumina support directly impacts these parameters. Finally, it is demonstrated that Zn is a hopeful candidate to increase the EtOH-SCR activity at low temperature ( T≤300°C).

Keywords: Ag/Zn-Al; ₂; O; ₃; Ethanol; SCR; NO; _x; NH; ₃

Exploring the relationship between surface structure and photocatalytic activity of flame-made TiO₂-based catalysts by Yijiao Jiang; Jason Scott; Rose Amal (pp. 290-297).

Display Omitted► TiO₂-based nanoparticles were controllably synthesized by one-step flame spray pyrolysis. ► Cu- or F-TiO₂ gave comparable textural and morphological properties. ► Surface hydroxyl groups on the TiO₂ play a key role in defining their activity. ► Low terminal hydroxyl group content is congruent with a high photocatalytic activity.Bare titanium dioxides (TiO₂) and doped with metal (Cu) or non-metal ion (F) were synthesized by a single-step flame spray pyrolysis (FSP) method. According to the BET, XRD, and TEM results, the Cu- and F-doped TiO₂ nanoparticles synthesized by FSP possess comparable features in terms of surface area, crystallite size and phase composition, and morphology. However, the F-doped TiO₂ exhibited the highest photocatalytic activity for the complete oxidation of acetaldehyde (ACE) even surpassing benchmarking Aeroxide TiO₂ (P25). In contrast, Cu-doped TiO₂ had a detrimental effect on the ACE photocatalytic oxidation. The proportion of native terminal hydroxyl groups, evaluated using high-field¹H MAS NMR, on the particle surface was varied by doping the TiO₂ with either Cu or F ions during FSP synthesis. A relationship, whereby decreased terminal hydroxyl group content corresponded to elevated acetaldehyde photodegradation, was subsequently uncovered. The findings were reinforced by studying the XPS O 1s photopeaks in the region attributed to surface hydroxyl groups.

Keywords: Photodegradation; Acetaldehyde; Titanium dioxide; Dopants; Flame spray pyrolysis; Surface hydroxyl groups; ¹; H MAS NMR

Ag/ZnO flower heterostructures as a visible-light driven photocatalyst via surface plasmon resonance by Zhizhong Han; Lili Ren; Zhihui Cui; Chongqi Chen; Haibo Pan; Jianzhong Chen (pp. 298-305).

Display Omitted► Ag/ZnO flower heterostructures was synthesized via facile photoreduction method. ► It is the first work about Ag/ZnO flower used as a photocatalytic device. ► Ag/ZnO flower heterostructures exhibit excellent visible-light catalytic activity. ► This photocatalysts based on ITO is convenient to recycle without centrifugation. ► The photo-induced electrons transfer from Ag to ZnO due to surface plasmon resonance.Visible-light driven photocatalyst, Ag/ZnO flower (ZnO Fl) heterostructures, was prepared on indium doped tin oxide (ITO) glass via a simple photoreduction method without surfactants. The samples are characterized by X-ray diffraction, scan electron microscopy, X-ray photoelectron spectroscopy, UV–vis spectroscopy, photoluminescence spectra and photocurrent response. The results show that ZnO FRs are wurtzite phase with single crystalline grown along the [001] direction and Ag nanoparticles (NPs) located on the surface are metallic. The binding energy of Ag 3d for the Ag/ZnO Fls sample shifts remarkably to the lower binding energy compared with the corresponding value of pure metallic Ag attribute to the interaction between Ag and ZnO Fls. Ag/ZnO Fl heterostructures exhibit higher visible-light driven photocatalytic activity. It is suggested that photo-induced electrons are generated from Ag due to surface plasmon resonance, and transfer from Ag to ZnO Fls. Then the electrons interact with adsorbed oxygen, finally forming hydroxyl radicals (OH), and the visible-light driven photocatalytic efficiency is enhanced. The proposed mechanism is further confirmed by the photoluminescence and transient photocurrent response. Additionally, the as-prepared Ag/ZnO Fls/ITO as a convenient photocatalytic device can be recycled without centrifugation.

Keywords: ZnO; Ag nanoparticles; Photoreduction; Surface plasmon resonance; Visible-light driven photocatalyst

Effect of support for PtCu bimetallic catalysts synthesized by electron beam irradiation method on preferential CO oxidation by J. Kugai; T. Moriya; S. Seino; T. Nakagawa; Y. Ohkubo; H. Nitani; Y. Mizukoshi; T.A. Yamamoto (pp. 306-314).

Display Omitted► PtCu/CeO₂ shows uniquely high selectivity at low CO coverage region. ► Support material has a major impact on selectivity in PROX. ► PtCu on CeO₂ of small crystallite size shows high capacity for oxygen transport. ► PtCu shows higher activity than Cu and higher selectivity than Pt. ► Arrangement of Pt on the PtCu surface greatly improves low temperature activity.Supported bimetallic catalysts have been shown to improve properties and catalytic performance of monometallic catalysts in various fuel conversion reactions. To investigate the effect of support on bimetallic PtCu system, PtCu supported on γ-Fe₂O₃ and CeO₂ were synthesized using electron beam irradiation method and preferential CO oxidation (PROX) performance was investigated in relation to structural and chemical properties of the catalysts. The difference in performance among the catalysts existed in both oxygen transport ability and selectivity. While oxygen transport ability was influenced by support property such as crystallite size (within the comparison among catalysts supported on CeO₂ and γ-Fe₂O₃), selectivity was rather influenced by support material which led to clear differences in reducibility, reduction degree of catalyst, and alloying extent of PtCu. CeO₂-supported catalysts are unique in the view point that they were able to convert CO selectively in high CO conversion region compared to Fe₂O₃-supported catalyst. PtCu with small CeO₂ crystallite maintained high O₂ conversion (high capacity for oxygen transport) in O₂-rich atmosphere in addition to high selectivity. Compared to monometallic Cu which lost its activity in the O₂-rich wet condition, or compared to monometallic Pt which exhibited poor selectivity, PtCu realized both high activity and selectivity on CeO₂ of small crystallite size, leading to more than 99% of CO conversion at 100°C. By modifying the structure, it was demonstrated that PtCu/CeO₂ system can be improved to have low-temperature activity comparable to monometallic Pt while keeping high selectivity of the original PtCu catalyst in the practical PROX condition.

Keywords: Pt; Cu; Bimetallic catalyst; Preferential oxidation; CeO; ₂; support; Electron beam irradiation

Structure–activity relationships of Pt/Al₂O₃ catalysts for CO and NO oxidation at diesel exhaust conditions by Alexey Boubnov; Søren Dahl; Erik Johnson; Anna Puig Molina; Søren Bredmose Simonsen; Fernando Morales Cano; Stig Helveg; Lived J. Lemus-Yegres; Jan-Dierk Grunwaldt (pp. 315-325).

Display Omitted► Lean CO and NO oxidation studied over Pt/Al₂O₃ catalysts with 1–10nm Pt particles. ► CO oxidation fastest over 2–3nm Pt particles with low-coordinated Pt atoms as dominant surface species. ► NO oxidation fastest over largest Pt particles where surface is dominated by planar facets. ► Pt surface oxidation promotes CO oxidation but deactivates NO oxidation. ► Strong promotional effect of CO on NO oxidation.Structure–performance relationships for Pt/Al₂O₃ catalysts with mean Pt particle sizes of 1, 2, 3, 5 and 10nm are investigated for the catalytic oxidation of CO and NO under lean-burning diesel exhaust conditions. The most active catalysts for CO oxidation exhibit Pt particles of 2–3nm, having a large fraction of low-coordinated and reactive surface Pt atoms. Exploiting in situ XAFS, we find that a reversible Pt surface oxidation is connected to high CO conversion. NO oxidation is most efficient over the catalysts with the largest Pt particles mainly exhibiting surface Pt atoms on planar facets. An irreversible Pt oxide formation observed during NO oxidation is a possible deactivation route and we suggest that the most active sites for NO oxidation are the ones least prone to surface oxidation. When both CO and NO are present in the reaction mixture, activity is increased for both reactions, suggesting that CO oxidation actively regenerates the Pt surface for NO oxidation and vice versa. The effect is strongest for the NO oxidation activity.

Keywords: Platinum; Alumina; Particle size; CO oxidation; NO oxidation; Lean burn; Surface oxide; TEM; Chemisorption; In situ; XAFS

Degradation of methylene blue by catalytic and photo-catalytic processes catalyzed by the organotin-polymer³_∞[(Me₃Sn)₄Fe(CN)₆] by Safaa El-din H. Etaiw; Mohamed M. El-bendary (pp. 326-333).

Display Omitted► The [(Me₃Sn)₄Fe(CN)₆],1 has been tested as catalyst. ► Fenton and photo-Fenton discoloration of MB investigated by H₂O₂ catalyzed with1. ► Mineralization of MB was investigated by FT-IR spectra. ► NaTA photoluminescence probing technology was carried out to identify oxygen species.The organotin-polymer [(Me₃Sn)₄Fe(CN)₆],1, has been synthesized and characterized to test its potential application as catalyst. The structure of1 consists mainly, of [Fe(CN)₆]⁴⁻ building blocks connected by the Me₃Sn cations forming 3D-polymeric network. The iron (II) sites acquire distorted octahedral geometry while the tin atom exhibits TBPY-5 configured [Me₃Sn(CN…)₂] fragments. Fenton and photo-Fenton oxidative discoloration of methylene blue (MB) has been investigated by hydrogen peroxide catalyzed with the metal–organic framework, (MOF)1. The reaction is first order with respect to MB dye. The irradiation of the reaction with UV-light enhanced the rate of MB mineralization. Mineralization of MB was investigated by FT-IR spectra. Disodium salt of terephthalic acid photoluminescence probing technology was carried out to identify the reactive oxygen species. The different parameters that affect MB degradation rate were evaluated. Moreover, the efficiency of recycled the catalyst1 and the mechanism of degradation of MB dye were investigated.

Keywords: Fenton and photo-Fenton reaction; Catalysis; Kinetics; Organotin-polymer; Methylene blue

Photocatalytic properties of TiO₂/WO₃ coatings formed by plasma electrolytic oxidation of titanium in 12-tungstosilicic acid by S. Stojadinović; N. Radić; R. Vasilić; M. Petković; P. Stefanov; Lj. Zeković; B. Grbić (pp. 334-341).

Display Omitted► Plasma electrolytic oxidation (PEO) of titanium in 12-tungstosilicic acid. ► Preparation of TiO₂/WO₃ coatings by PEO process. ► Photocatalytic activity (PA) of TiO₂/WO₃ coatings varies with duration of PEO. ► PA of TiO₂/WO₃ is related to morphology, phase and elemental composition of coatings. ► The increase of photoluminescence corresponds to decrease of PA of TiO₂/WO₃ coatings.In this paper, we have investigated photocatalytic properties of TiO₂/WO₃ coatings formed by plasma electrolytic oxidation (PEO) of titanium in 12-tungstosilicic acid water solution and compared with photocatalytic activity of pure TiO₂ coatings. The photocatalytic activity of the coatings is evaluated by measuring the degradation of methyl orange under simulated sunlight conditions. Photocatalytic activity of TiO₂/WO₃ coatings varied with duration of PEO process and higher photoactivity is obtained for a shorter process time. Photocatalytic activity of TiO₂/WO₃ coatings is related to morphology and phase and elemental composition of coatings. The oxide coatings morphology is strongly dependent on PEO time. The elemental components of the coatings are Ti, W and O. The oxide coatings are partly crystallized and mainly composed of WO₃ and anatase. Decrease in the number of microdischarge channels and agglomeration of particles on the surface leads to a decrease in photocatalytic activity. The reduction of the photocatalytic activity with increased time of PEO process is accompanied with the increase of WO₃ concentration on the coatings’ surface. Diffuse reflectance spectroscopy has shown that coatings enriched with tungsten oxide exhibit significant red shift with respect to the pure TiO₂ coatings. TiO₂/WO₃ coatings with improved catalytic activity, compared to pure TiO₂ coatings, are grouped around energy band gap of 2.6eV. The results of PL measurements of TiO₂/WO₃ coatings are in agreement with photocatalytic activities. The increase of PL intensity corresponds to decrease of photocatalytic activity of the coatings, indicating fast recombination of electron–hole pairs.

Keywords: Photocatalysis; Plasma electrolytic oxidation; TiO; ₂; /WO; ₃; TiO; ₂

Determination of reaction orders for the transesterification of canola oil with methanol by using KOH/MgO as a heterogeneous catalyst by Oguzhan Ilgen; A. Nilgun Akin (pp. 342-346).

Display Omitted► The reaction orders with respect to the reactants were determined. ► The method of initial rates was used to determine the reaction rate. ► The proposed Power Law rate equation fits very well with experimental observations. ► The results support the validity of Eley–Rideal mechanism.The reaction orders with respect to the reactants were determined for the reaction of canola oil with methanol catalyzed by KOH/MgO. The method of initial rates was used to determine the reaction rate. The experiments were carried out with different initial concentrations of methanol and canola oil. A very good correlation was found between the experimental and calculated reaction rates using the proposed equation. The reaction rate equations derived from Eley–Rideal and Langmuir–Hinshelwood mechanisms were discussed. As a result, the orders of reaction respect to both oil and methanol are concordant with the suggestion that the reaction takes place both homogeneously and heterogeneously.

Keywords: Biodiesel; Canola oil; Transesterification; Kinetics

Electrocatalytic dechlorination of volatile organic compounds at a copper cathode. Part I: Polychloromethanes by Abdirisak Ahmed Isse; Binbin Huang; Christian Durante; Armando Gennaro (pp. 347-354).

Display Omitted► Like Ag, Cu is a good electrocatalyst for the reduction of polychloromethanes, PCMs. ► Complete dechlorination of any PCM can be achieved at Cu without electrode fouling. ► Both potentiostatic and galvanostatic electrolyses give high yields of methane. ► Addition of a good proton donor highly favors the hydrodehalogenation reaction route. ► Cu is a promising cathode for large scale applications and pollution remediation.The electrochemical reductive dehalogenation of CCl₄, CHCl₃, CH₂Cl₂ and CH₃Cl was investigated at Cu in dimethylformamide (DMF). The principal aim of the study was to check whether Cu has good electrocatalytic properties and is stable to fouling in preparative-scale electrolyses. All polychloromethanes (PCMs) have been investigated by cyclic voltammetry in DMF+0.1M Pr₄NBF₄ in order to evaluate the reduction mechanism and the catalytic activity of Cu. The electrochemical reduction of CCl₄ and CHCl₃ has also been studied by controlled-potential electrolysis in DMF+0.1M Pr₄NBF₄ both in the absence and presence of H₂O or CH₃CO₂H, using chromatographic techniques to determine the intermediates and final products of the process. Cu exhibits a good electrocatalytic activity, in some cases the positive shifts of the reduction potentials with respect to GC being comparable with those at Ag, which is considered to be one of the best candidates for environmental applications in dehalogenation reactions. The results point out that the reduction mechanism at Cu is similar to what was already observed for Ag on which reduction of PCMs takes place through two competing reaction pathways: hydrodehalogenation and hydrogenolysis of carbenes. The proton availability of the medium affects drastically both the catalytic effect of Cu and the distribution of reduction products. The presence of an added proton donor promotes the hydrodehalogenation pathway, enhancing the concentration of intermediate PCMs and the final yield of methane, which is the main product of the exhaustive electrolysis.

Keywords: Polychloromethanes; Copper cathode; Electrocatalysis; Pollutant degradation; Hydrodehalogenation

Electrocatalytic dechlorination of volatile organic compounds at copper cathode. Part II: Polychloroethanes by Christian Durante; Binbin Huang; Abdirisak Ahmed Isse; Armando Gennaro (pp. 355-362).

Display Omitted► Cu shows catalytic activity for the reduction of polychloroethanes, PCAs. ► The H⁺ availability and the PCA structure influence the catalytic activity of Cu. ► Added or electro-generated bases prompt a dehydrodehalogenation pathway. ► Hydrodehalogenation is favored in the presence of a good proton donor. ► Cu is a hopeful cathode for selective activation of R-X bond in industrial processes.Copper is considered as a catalytic electrodic material for the reduction of organic halides for possible application in environmental remediation. In Part I, we have demonstrated that Cu is a good electrodic material in the reduction of polychloromethanes (PCMs). In this second part, we extended the study to geminal polychloroethanes (PCAs) with the aim of understanding whether the catalytic activity and the reduction mechanism observed for PCMs are maintained or significantly affected by molecular structure. To this end, we considered the electroreduction of 1,1,1-trichloroethane (TCA) and 1,1-dichloroethane (DCA), which are the simplest molecules belonging to the homologous series of chloroform and dichloromethane, respectively, at a Cu electrode in DMF under controlled proton availability. Voltammetric investigations point out that PCAs can be sequentially reduced at both GC and Cu. Copper shows modest catalytic effects for TCA and DCA; with respect to GC, E_p at Cu anodically shifts by 210mV and 76 for TCA and DCA, respectively. In contrast to the reduction of PCMs, Cu exhibits a good electrocatalytic activity only in the presence of acetic acid, HAc, indicating a strong influence of the structure of the polychlorinated molecule. Controlled-potential electrolyses have shown that the reduction mechanism and therefore the intermediates and final products of the reduction process are profoundly affected by the presence of H₂O or HAc. In analogy to what was previously observed for PCMs, sequential hydrodehalogenation leading to ethane as the final product becomes the principal reaction pathway in the presence of HAc. In the presence of H₂O both hydrodehalogenation and dehydrodehalogenation mechanisms are possible. In the latter case the mechanism involves α,β-elimination of H⁺ and Cl⁻ and leads to the formation of chlorinated olefins and acetylene.

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Applied Catalysis B, Environmental (v.126, #)