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Applied Catalysis A, General (v.334, #1-2)

Contents (pp. iii-xiv).

Editorial Board (pp. co2).

Propane reforming on Ni–Ru/GDC catalyst: H₂ production for IT-SOFCs under SR and ATR conditions by V. Modafferi; G. Panzera; V. Baglio; F. Frusteri; P.L. Antonucci (pp. 1-9).

Steam and auto-thermal reforming of propane over a Ni–Ru/GDC catalyst prepared by hydrothermal method were investigated under intermediate temperature solid oxide fuel cell (IT-SOFC) operating conditions. Such an approach is propaedeutical for the application of the catalyst in IT-SOFC.At reaction temperature higher than 700°C, under both steam reforming (SR) and auto-thermal reforming (ATR), high propane conversion and syngas (H₂+CO) productivity were obtained. In SR significant amount of filamentous carbon was formed mainly at 600°C, with subsequent catalyst deactivation. In ATR, coke formation was completely depressed and the catalyst resulted to be very stable in all investigated reaction conditions. Notwithstanding the oxygen storage capability and redox properties of ceria in promoting both oxygen activation and carbon residues gasification, without oxygen in gas phase the concentration of oxygen vacancies itself were not able to inhibit carbon deposition. On the other hand, the presence of oxygen in the reaction stream slightly negatively reflects on syngas production, since it promotes CO₂ and H₂O formation; however, the loss in selectivity is widely compensated by the absence of deactivation phenomena.Steam and auto-thermal reforming of propane over a Ni–Ru/GDC catalyst prepared by hydrothermal method were investigated under intermediate temperature solid oxide fuel cell (SOFC) operating conditions. High propane conversion and syngas (CO+H₂) productivity were obtained both in SR and ATR conditions. In SR significant amount of filamentous carbon was formed mainly at 600°C, with subsequent catalyst deactivation, while in ATR coke formation was completely depressed. The oxygen storage capability and redox properties of ceria were indicated to be responsible for promoting both oxygen activation and carbon residues gasification. The presence of oxygen in the reaction stream slightly negatively reflects on syngas production, since it promotes CO₂ and H₂O formation, however, the loss in selectivity is widely compensated by the absence of deactivation phenomena. ▪

Keywords: Hydrogen production; SOFC; Propane reforming; Ni–Ru/GDC catalyst

Effect of P/Fe ratio on the structure and ammoxidation functionality of Fe-P-O catalysts by P. Nagaraju; Ch. Srilakshmi; Nayeem Pasha; N. Lingaiah; I. Suryanarayana; P.S. Sai Prasad (pp. 10-19).

Bulk FePO₄ catalysts, with varying P/Fe atomic ratio in the range of 1–1.6, were prepared and characterized by XRD, FT-IR, TPR, Potentiometric titration, Laser Raman, TEM, XPS and TG/DTA techniques in order to study the influence of P/Fe atomic ratio on the nature and extent of the active phase formation. The data obtained from XRD and Laser Raman techniques suggested predominant formation of the quartz type iron phosphate at close to stoichiometric P/Fe ratio, but as the ratio increased beyond 1.4 a progressive transformation of monomeric phosphate into its polymeric form was observed. XPS spectra reflected the presence of iron in its 3+ state when P/Fe≤1.2 and exists as Fe²⁺ and Fe³⁺ when P/Fe≥1.4. The catalytic properties of these iron phosphates were studied in the vapor phase ammoxidation, taking 2-methylpyrazine (MP) to 2-cyanopyrazine (CP) as an example. The ammoxidation activity of the catalysts was found to be proportional to the extent of quartz phase formed which in turn was proportional to the redox property, as observed by the oxidation functionality of the catalysts in benzyl alcohol transformation. However, the selectivity to nitrile was found to be dependent on the acid strength of the catalysts.

Keywords: Iron phosphate; Ammoxidation; 2-Methyl pyrazine; 2-Cyano pyrazine

Influence of the final “ageing” temperature on the regeneration behaviour and location of the coke obtained in the HZSM-5 and USY zeolites during the LDPE cracking by A. Marcilla; A. Gómez-Siurana; F.J. Valdés (pp. 20-25).

In this work, the influence of the “ageing” temperature on the location and regeneration behaviour of the coke obtained in the cracking of LDPE in the presence of HZSM-5 and USY zeolites is studied. The coke content in the zeolites is influenced by the thermal treatment, and for both zeolites studied, the higher the final cracking temperature the lower the coke content. The nitrogen adsorption isotherms have shown the different deactivation mechanisms, related to the possible different locations of the coke on each zeolite and the influence of the final cracking temperature on these parameters. The regeneration study of the coked zeolites has shown that the coke combustion process strongly depends on the insoluble content of the coke (i.e., of the presence of bulky polyaromatic compounds) and of the zeolite framework.The work shows the influence of the final “ageing” temperature on the nitrogen adsorption isotherms which shows the possible deactivation mechanisms and the location of the coke on each zeolite. The regeneration study of the coked zeolites has shown that the coke combustion process strongly depends on the insoluble content of the coke and of the zeolite framework. ▪

Keywords: LDPE; deactivation; HZSM-5; USY

Structural, acidic and redox properties of V₂O₅-TiO₂-SO₄²⁻ catalysts by Qing Sun; Yuchuan Fu; Jingwei Liu; Aline Auroux; Jianyi Shen (pp. 26-34).

A series of V₂O₅-TiO₂ catalysts were prepared by the co-precipitation method and doped with SO₄²⁻ ions. The results showed that V₂O₅ could be well dispersed with a V density of 11.5Vnm⁻². The surface acidities of V₂O₅-TiO₂ catalysts were greatly enhanced by the addition of SO₄²⁻, as indicated by the results of isopropanol (IPA) conversion and methanol oxidation reactions. In the methanol oxidation, a high yield of dimethoxymethane (DMM) was found on the SO₄²⁻ modified 25wt%V₂O₅-75wt%TiO₂ catalyst, with 54% methanol conversion and 90% DMM selectivity at low temperature (413K).▪A series of V₂O₅-TiO₂ (VT) catalysts with V₂O₅ contents from 15 to 75wt% were prepared by the co-precipitation method and doped with SO₄²⁻ ions. The structural properties were characterized by X-ray diffraction (XRD), Raman spectroscopy (LRS) and X-ray photoelectron spectroscopy (XPS). The surface acidity was determined by the techniques of NH₃ adsorption microcalorimetry and pyridine adsorption infrared spectroscopy (FT-IR). Isopropanol (IPA) and methanol probe reactions in the presence of O₂ were employed to provide the information about surface acidity and redox properties simultaneously. The results from XRD and LRS showed that V₂O₅ was well dispersed on the surface of TiO₂ when the vanadia content was below 25wt%. XPS showed that both vanadium and titanium were present in their fully oxidized states in all the samples. The SO₄²⁻ doped VT samples had the sulfur oxidation state of +6. The results of NH₃ adsorption microcalorimetry and pyridine adsorption FT-IR indicated that the VT catalysts possessed identical surface acid densities independently of the V₂O₅ content, and that both Brønsted and Lewis acid sites were present on their surfaces. The results of isopropanol probe and methanol oxidation reactions suggested that the surface acidity of VT catalysts was improved upon SO₄²⁻ doping, as evidenced by the simultaneous decrease in the amounts of oxidation products and increase in the amounts of dehydration products. A high selectivity of 90% to dimethoxymethane (DMM) was measured on the SO₄²⁻ modified 25%V₂O₅-75%TiO₂ catalyst, with 54% conversion of methanol at 413K.

Keywords: V; ₂; O; ₅; -TiO; ₂; -SO; ₄; ²⁻; Adsorption microcalorimetry; Acidic and redox properties; Isopropanol probe reaction; Methanol probe reaction

CaO supported on mesoporous silicas as basic catalysts for transesterification reactions by Mônica C.G. Albuquerque; Inmaculada Jiménez-Urbistondo; José Santamaría-González; Josefa M. Mérida-Robles; Ramón Moreno-Tost; Enrique Rodríguez-Castellón; Antonio Jiménez-López; Diana C.S. Azevedo; Célio L. Cavalcante Jr.; Pedro Maireles-Torres (pp. 35-43).

CaO supported on mesoporous SBA-15 silicas were prepared and characterized. The transesterification activity of vegetable oils confirms the results obtained with ethyl butyrate and methanol, reaching conversion as high as 95% with sunflower oil (5h) and 65% (1h) for castor oil. Moreover, unlike commercial CaO, no lixiviation of the active phase was detected.▪A new group of basic catalysts supported on mesoporous solids has been prepared with the aim of being used as heterogeneous catalysis in biodiesel production. These catalysts based on calcium oxide supported on porous silica (SBA-15, MCM-41 and fumed silica) have been characterized and evaluated in transesterification processes. They were characterized by DRX, XPS, SEM, FT-IR, CO₂-TPD and N₂ adsorption. The catalytic activity was evaluated in the transesterification of ethyl butyrate with methanol, and different reaction parameters were optimized by a factorial design response surface methodology. Thus, a sample containing 14wt.% of CaO supported on SBA-15 was the most active, and, unlike commercial CaO, no lixiviation of the active phase was detected in the reaction medium. The transesterification activity of vegetable oils confirms the results obtained in the reaction of ethyl butyrate with methanol, reaching conversion as high as 95% with sunflower oil (after 5h of reaction) and 65% (after 1h) for castor oil.

Keywords: Transesterification; SBA-15; CaO; Biodiesel; Heterogeneous catalysis

Selective oxidation of spirolactone-related sulfides to corresponding sulfoxides and sulfones by hydrogen peroxide in the presence of N-hydroxysuccinimde by Zhi-Gang Xiong; Jun Zhang; Xian-Ming Hu (pp. 44-50).

Spirolactone-related sulfides were oxidized to corresponding sulfoxides and sulfones selectively and in high yield by hydrogen peroxide using N-hydroxysuccinimide as an efficient catalyst under metal-free conditions. Sulfoxides were obtained without over-oxidation to sulfones in acetone under reflux condition whereas sulfones were obtained in methanol at room temperature.▪Spirolactone-related sulfides were oxidized to corresponding sulfoxides and sulfones selectively and in high yield by hydrogen peroxide using N-hydroxysuccinimide as an efficient catalyst under metal-free conditions. Sulfoxides were obtained without over-oxidation to sulfones in acetone under reflux condition whereas sulfones were obtained in methanol at room temperature. Both processes were compatible with the presence of sensitive groups including ketones, alkenes, hydroxyl groups and benzylic carbons under our conditions.

Keywords: Spirolactone-related sulfides; Sulfoxides; Sulfones; Catalytic oxidation; Hydrogen peroxide; N; -hydroxysuccinimide

Novel Ag₂ZnGeO₄ photocatalyst for dye degradation under visible light irradiation by Xiukai Li; Shuxin Ouyang; Naoki Kikugawa; Jinhua Ye (pp. 51-58).

A cristobalite structure-related multiple-metal oxide, viz. Ag₂ZnGeO₄, had been developed as a visible light-sensitive photocatalyst with the band gap of 2.29eV. The Ag₂ZnGeO₄ photocatalyst showed good activity for RhB and Orange II photodegradation. Under typical reaction conditions and after 360min of visible light ( λ>420nm) irradiation, RhB could be completely degraded and 69.2% of Orange II was converted. The unique energy band structure and crystal structure determined the overall photocatalytic performance of Ag₂ZnGeO₄.▪We report a multiple-metal oxide Ag₂ZnGeO₄ with cristobalite-related structure as a visible light-sensitive photocatalyst (Eg 2.29eV) for dye degradation. The physical characteristics of the samples were examined by techniques such as XRD, UV–vis diffuse reflectance spectroscopy and SEM. The photocatalytic activity of Ag₂ZnGeO₄ was confirmed by Rhodamine B (RhB) and Orange II photodegradation in aqueous phase. After 360min of visible light ( λ>420nm) irradiation, the conversions of RhB and Orange II reached 100% and 69.2%, respectively. The electronic structure of Ag₂ZnGeO₄ was investigated by band structure calculation based on the density function theory (DFT). Results revealed that the hybridized Ag 4d¹⁰ and O 2p⁶ orbitals form the valence band top of Ag₂ZnGeO₄, which leads to a much narrowed band gap as compared with that of the Na₂ZnGeO₄ parent sample. We propose that the specific cristobalite structure of Ag₂ZnGeO₄ favors the mobility of photo-generated carriers, and that this contributes positively to the observed photocatalytic activity for dye degradation.

Keywords: Photocatalysis; Visible light; Ag; ₂; ZnGeO; ₄; Dye degradation; Rhodamine B; Orange II

Synthesis of camphene from α-pinene using SO₃²⁻ functionalized MCM-41 as catalyst by M. Román-Aguirre; Y.P. Gochi; Alejandro Robau Sánchez; Luis de la Torre; A. Aguilar-Elguezabal (pp. 59-64).

MCM-41 and Aerosil-200 functionalized with different quantity of SO₃⁻ groups were used as catalysts for the synthesis of camphene from α-pinene. Three types of acid sites were found on the functionalized MCM-41, whereas on Aerosil-200 mainly strong acid sites were formed. Conversion of α-pinene increased with the quantity of medium strength acid sites. ▪MCM-41 and Aerosil-200 functionalized with different quantity of SO₃⁻ groups were used as catalysts for the heterogeneous synthesis of camphene from α-pinene. The characterization of the catalysts was made by thermodesorption of NH₃ and physisorption of nitrogen. Three types of acid sites were found on the functionalized MCM-41, whereas on Aerosil-200 mainly strong acid sites were found. The conversion of α-pinene increased with the quantity of medium strength acid sites. The highest conversion was 100% with yield to camphene of 39.3% for catalyst with the higher content of SO₃⁻. The highest yield to camphene was 42.2% with a conversion of 95% and was reached for moderate acid treatment of catalyst. The Aerosil-200 based catalyst did not show conversion of α-pinene. Other terpenes as limonene, terpinolene and δ-terpinene were obtained as by products.

Keywords: MCM-41; Sulfonic acid; Pinene; Camphene

Kinetic modeling of enzymatic ethyl oleate synthesis carried out in biphasic systems by M.L. Foresti; M. Pedernera; M.L. Ferreira; V. Bucalá (pp. 65-72).

In the lipase-catalyzed solvent free esterification of oleic acid and ethanol thermodynamic calculations revealed that the addition of water to hydrate the biocatalyst, or the production of water during reaction leads to a biphasic reaction medium, due to the formation of a second aqueous phase. An rigorous reactor model is proposed to calculate compositions over time, and to fit kinetic parameters, considering chemical reaction and mass transfer between both liquid phases simultaneously.▪This work presents a new approach for the kinetic modeling of solvent free ethyl oleate synthesis, catalyzed by an enzymatic catalyst. The biocatalyst used was the lipase from Candida antarctica B immobilized onto chitosan powder. Thermodynamic calculations revealed that the addition of water to hydrate the biocatalyst, or the production of water during esterification leads to a biphasic reaction medium, due to the formation of a second aqueous phase. A rigorous reactor model is proposed to calculate compositions over time, and to fit kinetic parameters, considering mass transfer and chemical reaction simultaneously. The biphasic model presented, which explicitly considers the presence of a second phase, is compared with the traditional monophasic approach that ignores the biphasic nature of reaction medium. The best-fitted monophasic model is not able to represent experimental data. On the other hand, the biphasic model allows to accurately fit experimental data, indicating the importance of modeling two-phase systems properly.

Keywords: Ethyl oleate synthesis; Solvent free; Kinetics; Enzyme; Phase equilibria; Biocatalysis

New catalytic materials for the high-temperature synthesis of hydrocyanic acid from methane and ammonia by high-throughput approach by S. Moehmel; N. Steinfeldt; S. Engelschalt; M. Holena; S. Kolf; M. Baerns; U. Dingerdissen; D. Wolf; R. Weber; M. Bewersdorf (pp. 73-83).

For converting methane and ammonia to hydrocyanic acid, improved catalyst formulations were obtained using high-throughput experimentation (preparation and testing) and a genetic algorithm as design tool. Furthermore, multi-way analysis of variance and regression trees were applied to establish correlations between HCN yield and catalyst composition.▪For converting methane and ammonia to hydrocyanic acid, catalysts were prepared and tested in a 48-parallel channel fixed-bed reactor unit operating at temperatures up to 1373K. The catalysts were synthesized with a robot applying a genetic algorithm as the design tool. New and improved catalyst compositions were discovered by using a total of seven generations each consisting of 92 potential catalysts. Thereby, the catalyst support turned out as an important input variable. Furthermore, platinum, which is well known as a catalytic material was confirmed. Moreover, improvements in HCN yield were achieved by addition of promoters like Ir, Au, Ni, Mo, Zn and Re. Multi-way analysis of variance and regression trees were applied to establish correlations between HCN yield and catalyst composition (support and metal additives). The obtained results are considered as the base for future even more efficient screening experiments.

Keywords: High-throughput experimentation; Evolutionary catalyst development; Genetic algorithm; Hydrocyanic acid; High-temperature equipment; Multi-way analysis of variance; Regression trees

Vapor-phase dehydration of 1,5-pentanediol into 4-penten-1-ol by Satoshi Sato; Ryoji Takahashi; Naoki Yamamoto; Eiji Kaneko; Hirotomo Inoue (pp. 84-91).

Dehydration of 1,5-pentanediol was investigated over ZrO₂ and Yb₂O₃ catalysts at 300–450°C. 1,5-Pentanediol was converted into 4-penten-1-ol together with tetrahydropyran. Modification of ZrO₂ with Li ions increased the selectivity to 4-buten-1-ol up to 70mol%. Yb₂O₃ also effectively worked as a catalyst: Yb₂O₃ with cubic structure showed higher than 75mol% selectivity to 4-penten-1-ol.▪Dehydration of 1,5-pentanediol was investigated over ZrO₂ and Yb₂O₃ catalysts at 300–450°C. 1,5-Pentanediol was converted into 4-penten-1-ol together with tetrahydropyran over monoclinic ZrO₂ at temperatures <400°C, and the selectivity to 4-penten-1-ol exceeded 50mol%. Modification of ZrO₂ with Li ions increased the selectivity to 4-buten-1-ol up to 70mol%. Yb₂O₃ also effectively worked as a catalyst in the dehydration of 1,5-pentanediol into 4-buten-1-ol at temperatures <425°C. Especially, Yb₂O₃ with cubic structure showed higher than 75mol% selectivity to 4-penten-1-ol.

Keywords: Homoallyl alcohol; 4-Penten-1-ol; Dehydration; 1,5-Pentanediol; CeO; ₂; ZrO; ₂; Yb; ₂; O; ₃

Complete oxidation of 2-propanol over gold-based catalysts supported on metal oxides by Shih Yin Liu; Sze Ming Yang (pp. 92-99).

Catalytic oxidation of 2-propanol was investigated on Au/CeO₂, Au/Fe₂O₃, Au/TiO₂ and Au/Al₂O₃ catalysts prepared from the deposition–precipitation method. The catalytic activity of Au/metal oxide samples towards the deep oxidation of 2-propanol to CO₂ and water has been found to be strongly dependent on the kind of supports, the amount of gold loading, the calcination temperature and the moisture content in the feed.▪This paper concerns the preparation of metal oxide-supported gold catalysts and their application to 2-propanol abatement in order to lower the light off temperature. Catalytic oxidation of 2-propanol was investigated on Au/CeO₂, Au/Fe₂O₃, Au/TiO₂ and Au/Al₂O₃ catalysts prepared from the deposition–precipitation (DP) method. The catalysts are characterized by XRD (X-ray diffraction), BET (Brunner–Emmett–Teller), TEM (transmission electron microscopy), NH₃-TPD (NH₃-temperature programmed desorption), H₂-TPR (H₂-temperature programmed reduction), ICP-AES (inductively coupled plasma-atomic emission spectroscopy) and XPS (X-ray photoelectron spectroscopy) techniques. The catalytic activity of Au/metal oxide samples towards the deep oxidation of 2-propanol to CO₂ and water has been found to be strongly dependent on the kind of supports, the amount of gold loading, the calcination temperature and the moisture content in the feed.

Keywords: Complete oxidation; Au catalyst; 2-Propanol; Cerium oxide; Volatile organic compounds

Ionic liquid as an efficient promoting medium for synthesis of dimethyl carbonate by oxidative carbonylation of methanol by Wen-Sheng Dong; Xianshu Zhou; Chunsheng Xin; Chunling Liu; Zhaotie Liu (pp. 100-105).

The N-butylpyridinium tetrafluoroborate-meditated CuCl catalyst system could be a very effective catalyst system for oxidative carbonylation of methanol to give dimethyl carbonate. The catalyst system could be reused at least five recycles with the same selectivity and only a slight loss of catalytic activity due to loss of the catalyst during handling and transferring the reaction mixture. ▪The synthesis of dimethyl carbonate by oxidative carbonylation of methanol using Cu salt catalysts in the presence of various room temperature ionic liquids (RTILs) was reported. Among the ionic liquids used, N-butylpyridinium tetrafluoroborate was the most effective promoter in terms of the conversion of methanol and the selectivity to dimethyl carbonate (DMC). The influences of reaction temperature, pressure, time, molar ratio of CO/O₂, and amount of the ionic liquid on the oxidative carbonylation of methanol were investigated. The results indicated that under the reaction conditions of 120°C and 2.4MPa of a 2:1 mixture of CO and O₂, 17.2% conversion of methanol, 97.8% selectivity of DMC and a DMC productivity of 4.6gg⁻¹cath⁻¹ were achieved. The N-butylpyridinium tetrafluoroborate-meditated CuCl catalyst system could be reused at least five recycles with the same selectivity and a slight loss of catalytic activity due to loss of the catalyst during handling and transferring the reaction mixture.

Keywords: Ionic liquids; Dimethyl carbonate; Cu-based catalysts; oxidative carbonylation; Methanol

Catalytic epoxidation of olefins with hydrogen peroxide by hybrid complex containing nickel(III) Schiff base complex covalently linked to polyoxometalate by Valiollah Mirkhani; Majid Moghadam; Shahram Tangestaninejad; Iraj Mohammadpoor-Baltork; Esmaeil Shams; Nahid Rasouli (pp. 106-111).

The catalytic activity of a hybrid compound, nickel(salen)–POM (1), consisting of nickel(salen) [salen= N, N′-bis(salicylidene)ethylenediamine] complex covalently linked to a lacunary Keggin-type polyoxometalate, K₈[SiW₁₁O₃₉] (POM), was studied in the epoxidation of various olefins in acetonitrile, using hydrogen peroxide as an oxygen source. This is the first time that nickel(salen)–POM has been used as a catalyst for the liquid phase epoxidation of olefins. The complex (1) can catalyze epoxidation of various olefins including non-activated terminal olefins. The effect of reaction parameters such as temperature, solvent and oxidant on the epoxidation of styrene were investigated. In comparison with the corresponding Ni(salen), the higher yields obtained in the epoxidation of olefins catalyzed by nickel(salen)–POM.The catalytic activity of a hybrid compound, nickel(salen)–POM (1), consisting of nickel(salen) complex covalently linked to a Keggin-type polyoxometalate (POM) was studied in the epoxidation of various olefins in acetonitrile, using hydrogen peroxide as an oxygen source. The effect of parameters such as temperature, solvent and oxidant in the epoxidation of styrene were also investigated. ▪

Keywords: Nickel(salen); Hybrid complex; Polyoxometalate; Epoxidation; Hydrogen peroxide

Rearrangement of glucose to mannose catalysed by polymer-supported Mo catalysts in the liquid phase by Angela Köckritz; Michael Kant; Martin Walter; Andreas Martin (pp. 112-118).

The rearrangement of glucose to mannose was accomplished by ion exchanger-supported molybdate catalysts. The experiments were carried out in the batch as well as in the continuous mode. A “molybdic acid”-based catalyst was active during an 800h run. ▪The rearrangement of glucose to mannose was accomplished by ion exchanger resin supported molybdate catalysts in the liquid phase. Sodium molybdate and “molybdic acid” were used as catalyst precursor compounds. The fresh catalysts differ in their content of oligomer Mo species, as could be shown by UV–vis spectroscopy. The catalytic experiments were carried out in batch as well as in continuous mode. The highly selective rearrangement yielded up to 28.4% mannose in the batch and 27.2% in the continous reactor. A “molybdic acid”-based catalyst was tested during a long-term run over 800h, however deactivation was observed to a certain extent as indicated by decreasing activity. The main cause for deactivation was Mo leaching. A method for the reactivation of used catalysts was elaborated. The initial activity could be received by reloading with fresh molybdate precursor and by reoxidation of reduced Mo species with 1% H₂O₂.

Keywords: Mannose; Glucose; Rearrangement; Molybdate; Bílik reaction; Supported Mo catalysts

A novel photocatalytic monolith reactor for multiphase heterogeneous photocatalysis by Peng Du; Joana T. Carneiro; Jacob A. Moulijn; Guido Mul (pp. 119-128).

A novel reactor for multi-phase photocatalysis is presented, the so-called internally illuminated monolith reactor (IIMR). In the concept of the IIMR, side light emitting fibers are placed inside the channels of a ceramic monolith, equipped with a TiO₂ photocatalyst coated on the wall of each individual channel. The photonic efficiency achieved with the IIMR reactor in the selective photo-oxidation of cyclohexane is 0.062, which is lower than obtained with a top illumination slurry reactor (0.151), but higher than the efficiency of an annular slurry reactor and reactor configuration with side light fibers immersed in a TiO₂ slurry, reaching a photonic efficiency of 0.008 and 0.002, respectively. The results are discussed on the basis of differences in photon flows entering the reactors, and the related magnitude of product concentrations.

Keywords: Photoreactor; Monolith; Optical fiber; Cyclohexane; Photocatalysis; Selective oxidation; UV light; TiO; ₂; Coating

Adsorptive removal of tetrahydrothiophene (THT) and tert-butylmercaptan (TBM) using Na-Y and AgNa-Y zeolites for fuel cell applications by Doohwan Lee; Eun-Yong Ko; Hyun Chul Lee; Soonho Kim; Eun Duck Park (pp. 129-136).

Adsorptive removal of tetrahydrothiophene (THT) and tert-butylmercaptan (TBM) was studied using AgNa-Y zeolites. THT adsorption strength on these sites follow an order of Ag⁺>Na⁺∼Ag⁰>H⁺>Ag₂O. The adsorption strength of THT on the Na⁺ sites was sufficiently high, and an increase in the Ag⁺-exchange level did not lead to a notable increase in the breakthrough THT uptake. Differently, adsorption of TBM on the Na⁺ sites was weak, whereas that on the Ag⁺ site was strong. This resulted in a marked increase in the breakthrough TBM adsorption uptake with an increase in the Ag⁺-exchange level, showing an order of magnitude higher uptake on AgNa-Y compared with that on Na-Y. Noticeably, an almost 100% adsorption selectivity for THT over TBM was observed over AgNa-Y when these two sulfur species coexisted in the feed stream. ▪Adsorptive removal of tetrahydrothiophene (THT) and tert-butylmercaptan (TBM) that are widely used sulfur odorants in pipeline natural gas was studied using AgNa-Y zeolites at ambient temperature and atmospheric pressure. The AgNa-Y were obtained via Ag⁺-exchange with Na⁺ of Na-Y at various exchange levels, and the contributions of formed adsorption sites (Ag⁺, Na⁺, Ag⁰, H⁺, and Ag₂O) in the THT and TBM adsorption uptake and selectivity were characterized. THT adsorption strength on these sites followed an order of Ag⁺>Na⁺∼Ag⁰>H⁺>Ag₂O. The adsorption strength of THT on Na⁺ sites was sufficiently high, thus an increase in the Ag⁺-exchange level did not lead to a notable increase in the breakthrough THT uptake. Differently, adsorption of TBM on Na⁺ sites was weak, whereas that on Ag⁺ sites was strong. This resulted in a marked increase in the breakthrough TBM uptake with an increase in the Ag⁺-exchange level, showing an order of magnitude higher uptake on AgNa-Y compared with that on Na-Y. Noticeably, the adsorption strength of THT on these adsorption sites was higher than that of TBM. This resulted in an almost 100% adsorption selectivity for THT over TBM, when these two sulfur species coexisted in the feed stream.

Keywords: Adsorption; Desulfurization; Tetrahydrothiophene; tert; -Butlymercaptan; Ag-Y; Na-Y; Fuel cell

Zr/HZSM-5 catalyst for NO reduction by C₂H₂ in lean-burn conditions by Chong Wang; Xinping Wang; Na Xing; Qing Yu; Yijing Wang (pp. 137-146).

Zr-based zeolite catalysts were investigated for the first time in selective catalytic reduction of NO by hydrocarbon (HC-SCR). Highly dispersed zirconium species, especially the amorphous ultrafine zirconium oxide in the catalyst, considerably enhanced the activity for selective catalytic reduction of NO by acetylene (C₂H₂-SCR), both by accelerating the NO oxidation to NO₂ and enlarging the NO₂ adsorption capacity of the catalyst under the reaction conditions. Thus a durable and active Zr/HZSM-5 catalyst giving 89% of NO conversion to N₂ at 350°C in 1600ppm NO, 800ppm C₂H₂, and 9.95% O₂ in helium was obtained. For the C₂H₂-SCR of NO, it was suggested that acidic sites with strong acidity on the Zr-based HZSM-5 catalysts are indispensable to initiate the aimed reaction via the route of NO oxidation to NO₂, which explains the higher activity for the reaction obtained over the Zr/HZSM-5 catalyst sample with lower SiO₂/Al₂O₃ ratio. The zirconium species could only functioned in the presence of protons in the C₂H₂-SCR of NO, so a synergistic effect between the zirconium species and protons of the Zr/HZSM-5 catalyst was proposed.

Keywords: Zirconium; HZSM-5; SCR; NO; Acetylene

Hydrogen production by partial oxidation of methanol over bimetallic Au–Ru/Fe₂O₃ catalysts by Feg-Wen Chang; L. Selva Roselin; Ti-Cheng Ou (pp. 147-155).

Hydrogen production by partial oxidation of methanol (POM) was investigated over Fe₂O₃, Au/Fe₂O₃, Ru/Fe₂O₃ and Au–Ru/Fe₂O₃ catalysts. The bimetallic Au–Ru/Fe₂O₃ catalysts exhibited higher activity towards hydrogen formation compared to the monometallic Au/Fe₂O₃ and Ru/Fe₂O₃ catalysts. Bulk Fe₂O₃ showed negligible activity. The enhanced activity of the bimetallic Au–Ru/Fe₂O₃ catalysts is explained by the strong metal–metal and metal–support interactions. ▪Hydrogen production by partial oxidation of methanol (POM) was investigated over Au–Ru/Fe₂O₃ catalyst, prepared by deposition–precipitation. The activity of Au–Ru/Fe₂O₃ catalyst was compared with bulk Fe₂O₃, Au/Fe₂O₃ and Ru/Fe₂O₃ catalysts. The reaction parameters, such as O₂/CH₃OH molar ratio, calcination temperature and reaction temperature were optimized. The catalysts were characterized by ICP, XRD, TEM and TPR analyses. The catalytic activity towards hydrogen formation is found to be higher over the bimetallic Au–Ru/Fe₂O₃ catalyst compared to the monometallic Au/Fe₂O₃ and Ru/Fe₂O₃ catalysts. Bulk Fe₂O₃ showed negligible activity towards hydrogen formation. The enhanced activity and stability of the bimetallic Au–Ru/Fe₂O₃ catalyst has been explained in terms of strong metal–metal and metal–support interactions. The catalytic activity was found to depend on the partial pressure of oxygen, which also plays an important role in determining the product distribution. The catalytic behavior at various calcination temperatures suggests that chemical state of the support and particle size of Au and Ru plays an important role. The optimum calcination temperature for hydrogen selectivity is 673K. The catalytic performance at various reaction temperatures, between 433 and 553K shows that complete consumption of oxygen is observed at 493K. Methanol conversion increases with rise in temperature and attains 100% at 523K; hydrogen selectivity also increases with rise in temperature and reaches 92% at 553K. The overall reactions involved are suggested as consecutive methanol combustion, partial oxidation, steam reforming and decomposition. CO produced by methanol decomposition is subsequently transformed into CO₂ by the water gas shift and CO oxidation reactions.

Keywords: Gold; Ruthenium; Iron oxide; Partial oxidation of methanol; Hydrogen

Hydrodechlorination of CCl₄ over Pt/γ-Al₂O₃ prepared from different Pt precursors by Jong Wook Bae; Jae Sung Lee; Kyung Hee Lee (pp. 156-167).

The platinum particle size on γ-Al₂O₃ prepared from different platinum precursors such as Pt(NH₃)₂(NO₂)₂, H₂PtCl₆, and K₂PtCl₆, and its effect on hydrodechlorination (HDC) of CCl₄ with the variation of calcination temperatures was investigated. It concomitantly affects the products distribution and catalytic stability in HDC of CCl₄. To verify the effects of platinum particle size with different platinum precursors on the product distribution, the catalysts have been characterized by HRTEM and CO chemisorption, FT-IR, and TP methods (TPR, TPD and TPSR). The catalysts with small platinum particles, which possess low coordination number and electron-deficient character, favor the complete dechlorination of CCl₄ and produce CH₄ more selectively. It could be due to the strong adsorption strength of CCl₄ or the decreased activation energy of surface intermediates on small platinum particles. FT-IR studies reveal that the maximum peak position of linear-bonded CO shifted to the higher frequency with the increase of platinum particle size in all catalysts prepared from three different platinum precursors. While the selectivity to CH₄ increased with the decrease in the platinum particle size, the total amount of carbonaceous species on the platinum particles was enhanced. The larger the platinum particle, the higher the selectivity to CHCl₃ was obtained in all tested catalysts under the non-deactivating condition.The maximum peak position of linear-bonded CO shifted to the higher frequency with the increase of platinum particle size in all catalysts prepared from three different platinum precursors. The small platinum particles, which possess low coordination number and electron-deficient character, favor the complete dechlorination of CCl₄ and produce CH₄ more selectively.▪

Keywords: Hydrodechlorination; CCl; ₄; Platinum particle size; γ-Al; ₂; O; ₃; Product distribution

A study on Al and Al–Ce–Fe pillaring species and their catalytic potential as they are supported on a bentonite by J.G. Carriazo; R. Molina; S. Moreno (pp. 168-172).

This work describes the synthesis and characterization by XRD of pillaring species in solid state, obtained from Al or Al–Ce–Fe polyhydroxocationic solutions, the modification of a bentonite via pillaring and the catalytic activity of the pillared clays in the total oxidation reaction of phenol. Results indicate the formation of boehmite from the Al³⁺ polyhydroxocationic solution and the presence of three different crystalline structures (boehmite, α-Fe₂O₃ and CeO₂) into the solid synthesized from the Al–Ce–Fe polyhydroxocationic solution.▪This work describes the synthesis and characterization by XRD of pillaring species in solid state, obtained from Al or Al–Ce–Fe polyhydroxocationic solutions, the modification of a bentonite via pillaring by ionic exchange with such solutions and the catalytic activity of the pillared clays in the phenol oxidation reaction in diluted aqueous medium with hydrogen peroxide. Results indicate the formation of boehmite from the Al³⁺ polyhydroxocationic solution and the presence of three different crystalline structures (boehmite, α-Fe₂O₃ and CeO₂) into the solid synthesized from the Al–Ce–Fe polyhydroxocationic solution. The EPR analysis confirms the formation of iron oxide particles and the likely inclusion of isolated Fe³⁺ species into the alumina matrix. On the other hand, the clay modified with Al–Ce–Fe is a very active (100% of phenol conversion in the first hour of reaction) and selective (55% of selectivity to CO₂) catalyst in the total oxidation of phenol, at 20°C and atmospheric pressure.

Keywords: Pillared clay; Phenol oxidation; Wastewater treatment; Al–Ce–Fe polyoxocation

Isomerization of 1-butene catalyzed by ion-exchanged, pillared and ion-exchanged/pillared clays by Alexander Moronta; Tania Oberto; Gabriela Carruyo; Roger Solano; Jorge Sánchez; Eduardo González; Lenin Huerta (pp. 173-178).

A natural smectite clay (STx-1, USA) was ion-exchanged with Al, Fe or pillared with polyoxocations of the same metals. Samples were also prepared by combining these two treatments. The prepared solids were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), thermogravimetric analysis (TGA), TPD of ammonia and N₂ adsorption. The catalytic activity was evaluated by using the isomerization of 1-butene at 300°C. XRF results showed an increase in the content of Al or Fe thus giving evidence that these metals were effectively exchanged or deposited over the starting material. Al- and Fe-pillared clays showed a significant increase of the surface area. Ion-exchanged clays showed similar surface areas to that of the starting clay. From XRD patterns only the Al-pillared clay gave an increase of the d-spacing. The synthesized pillared clays were superior catalysts for the isomerization of 1-butene than the ion-exchanged clays; the ion-exchanged/pillared clays showed the same catalytic behavior as that of the parent pillared clays. The Al-pillared clay was the best catalyst for the reaction and its efficiency was related to its high acidity and high surface area. The total conversion correlated well with the acidity values determined by the desorption of cyclohexylamine and TPD of ammonia.▪A natural smectite clay (STx-1, USA) was ion-exchanged with Al, Fe or pillared with polyoxocations of the same metals. Samples were also prepared by combining these two treatments. The prepared solids were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), thermogravimetric analysis (TGA), TPD of ammonia and N₂ adsorption. The catalytic activity was evaluated by using the isomerization of 1-butene at 300°C. XRF results showed an increase in the content of Al or Fe thus giving evidence that these metals were effectively exchanged or deposited over the starting material. Al- and Fe-pillared clays showed a significant increase of the surface area. Ion-exchanged clays showed similar surface areas to that of the starting clay. From XRD patterns only the Al-pillared clay gave an increase of the d-spacing. The synthesized pillared clays were superior catalysts for the isomerization of 1-butene than the ion-exchanged clays; the ion-exchanged/pillared clays showed a similar catalytic behavior as that of the parent pillared clays. The Al-pillared clay was the best catalyst for the reaction and its efficiency was related to the high acidity and high surface area.

Keywords: 1-Butene; Clays; Ion-exchanged clays; Isomerization; Pillared clays

Partial oxidation and water–gas shift reaction in an integrated system for hydrogen production from ethanol by Adriana M. Silva; Andréa M. Duarte de Farias; Lídia O.O. Costa; Ana P.M.G. Barandas; Lisiane V. Mattos; Marco A. Fraga; Fábio Bellot Noronha (pp. 179-186).

A fuel processing system using ethanol as a renewable feedstock is proposed to produce highly pure hydrogen to feed a fuel cell for power generation. Hydrogen production was accomplished through partial oxidation of ethanol over Rh/CeO₂ catalyst. The reformate was admitted into a water–gas shift reactor for primary CO clean-up. ▪A fuel processing system using ethanol as a renewable feedstock is proposed to produce highly pure hydrogen to feed a fuel cell for power generation. Hydrogen production was accomplished through partial oxidation of ethanol over Rh/CeO₂ catalyst. The reformate was admitted into a water–gas shift reactor for primary CO clean-up. In this purification stage two different CeO₂-supported catalysts were investigated. The results from partial oxidation reaction revealed that hydrogen production is strongly affected by the reaction temperature. Therefore, it was clear that the operating condition must be adjusted to reach a more efficient process focused on maximizing the hydrogen production and deplete the CO formation. The catalyst behavior and infrared analyses showed that the mechanism of ethanol partial oxidation follows a different pathway over Rh-based catalysts. Regarding the water–gas shift step, it was seen that higher catalytic activities were reached over the vanadium-modified Pt/CeO₂ catalyst within a wide range of temperature. Such improvement was suggested to be related to the presence of a V₂O₅ phase, much probably due to its redox properties. The results suggest that the catalysts presented in this contribution may be used as a fuel processor system for fuel cell applications.

Keywords: Ethanol partial oxidation; Water–gas shift; Fuel cell; CeO; ₂; V; ₂; O; ₅

Effect of iron on the properties of sulfated zirconia by Amalia Luz Costa Pereira; Sergio Gustavo Marchetti; Alberto Albornoz; Patrício Reyes; Marcelo Oportus; Maria do Carmo Rangel (pp. 187-198).

The effect of iron on sulfated zirconia was studied in this work. When Fe/Zr≤0.4 all iron ions go into zirconia but higher amounts (Fe/Zr≥0.8) leads to segregation of hematite. Iron increases the specific surface areas, makes the solids thermally more stable and creates acidic sites with medium strength. All these changes are very useful for catalytic applications.▪Sulfated zirconia has found several industrial applications, mainly for catalyzing reactions which require acidic sites. In order to control the properties of this solid, the effect of iron on the sulfated zirconia properties was studied in this work. Samples with different iron to zirconium molar ratios were prepared by the sol–gel method, followed by sulfation and characterization by several techniques. It was found that all iron ions go into zirconia when Fe/Zr≤0.4. However, when higher amounts of iron (Fe/Zr≥0.8) are added, hematite is segregated. Different phases can be obtained depending on the iron content and on the sulfur presence. Iron increases the specific surface areas of both sulfated and pure zirconia but does not affect the incorporation of sulfate groups as compared to pure zirconia. Iron also makes the solids thermally more stable and modifies the sulfated zirconia surface creating acidic sites with medium strength. Therefore, it is possible to control the acidity of the solid doping the sulfated zirconia with iron. All these changes are very useful for catalytic applications.

Keywords: Iron-doped zirconia; Sulfated iron oxide; Sulfated zirconia

Clean production of chloroanilines by selective gas phase hydrogenation over supported Ni catalysts by Fernando Cárdenas-Lizana; Santiago Gómez-Quero; Mark A. Keane (pp. 199-206).

We have established for the first time 100% selectivity in the continuous gas phase hydrogenation of p-chloronitrobenzene ( p-CNB) to p-chloroaniline for reaction over a series of oxide and carbon supported Ni catalysts (6±2%, w/w) under mild reaction conditions ( T=393K, P=1atm). Catalyst activation by temperature programmed reduction (TPR) is addressed, BET area and H₂ uptake measurements provided and mean metal particle sizes evaluated by transmission electron micrographic (TEM) analysis. The following activity sequence has been determined: Ni/Al₂O₃>Ni/SiO₂>Ni/Activated Carbon>Ni/graphite. Pd/Al₂O₃, as an alternative catalyst, delivered an appreciably higher activity but with the production of nitrobenzene (principal product) and aniline (secondary product), i.e. hydrodechlorination with subsequent –NO₂ reduction prevailed. Exclusive formation of the corresponding haloaniline is also demonstrated for the hydrogenation of o-chloronitrobenzene, m-chloronitrobenzene and p-bromonitrobenzene over Ni/Al₂O₃. A lower hydrogenation rate is established for p-CNB relative to nitrobenzene, consistent with a halogen substituent deactivation effect. While the Ni catalysts suffered a loss of activity with time-on-stream, exclusive selectivity to the haloamine product was maintained. These preliminary results can serve as a basis for the development of a cleaner, high throughput production of commercially important haloamines.The catalytic reduction of p-chloronitrobenzene ( p-CNB) to commercially important p-chloroaniline ( p-CAN) can generate a range of intermediates and unwanted by-products (see figure); we have established 100% selectivity to p-CAN in continuous gas phase reaction over oxide and carbon supported Ni catalysts under mild reaction conditions ( T=393K, P=1atm).▪

Keywords: Selective hydrogenation; p; -Chloronitrobenzene; p; -Chloroaniline; Carbon and oxide supported Ni

Mechanism of n-butane oxidative dehydrogenation over tetravalent pyrophosphates catalysts by Ioan-Cezar Marcu; Ioan Sandulescu; Yves Schuurman; Jean-Marc M. Millet (pp. 207-216).

The reaction mechanism of the oxidative dehydrogenation of n-butane has been studied over titanium and zirconium pyrophosphates between 683 and 843K. Two reaction mechanisms are involved, one common to ZrP₂O₇ and TiP₂O₇ at low temperature and a second specific to TiP₂O₇ at high temperature. The initial step of these mechanisms would correspond to the attack of the alkane molecules by O⁻ species.▪The reaction mechanism of the oxidative dehydrogenation of n-butane has been studied over titanium and zirconium pyrophosphates between 683 and 843K, at atmospheric pressure. The catalytic results obtained in both stationary and transient conditions clearly showed that two reaction mechanisms occur on these pyrophosphates. The first mechanism is common to both ZrP₂O₇ and TiP₂O₇ at low temperature whereas the second mechanism is specific to TiP₂O₇ at high temperature. Catalyst characterization by techniques like ESR and electrical conductivity measurements together with TAP experiments allow proposing different elementary steps for these mechanisms. The initial step of activation of n-butane would correspond to the attack of the alkane molecules by O⁻ species giving radicals on both catalysts. On ZrP₂O₇, the radical formed should rapidly undergo a second hydrogen abstraction according to a similar mechanism leading to butene. On TiP₂O₇, it should transfer an electron to a reducible Ti^IV or to an anionic vacancy, transforming to an alkoxide intermediate before a subsequent dehydrogenation. In the first case the rate-limiting step would be the attack of the alkane by the O⁻ species whereas in the second one it would be the re-oxidation of the catalytic site by diffusion of the lattice oxygen or directly by gas phase oxygen. These hypotheses are discussed in relation with all the catalytic data obtained and the physicochemical properties of the solids.

Keywords: n; -Butane; Oxidative dehydrogenation; Pyrophosphates; Reaction mechanism

Size dependence in solvent-free aerobic oxidation of alcohols catalyzed by zeolite-supported palladium nanoparticles by Feng Li; Qinghong Zhang; Ye Wang (pp. 217-226).

Studies using NaX-supported palladium catalysts with mean sizes of Pd particles ranging from 2.0 to 10.5nm reveal that the turnover frequency for benzyl alcohol oxidation exhibits a maximum at a medium Pd size of 2.8nm, whereas the turnover frequency for the oxidation of geraniol or 2-octanol is almost independent of the size of Pd.▪The size dependence in the palladium nanoparticle-catalyzed solvent-free aerobic oxidation of alcohols was studied. Palladium nanoparticles with tunable mean sizes in a range of 2.0–10.5nm were prepared over NaX zeolite by ion exchange of Na⁺ with an ionic Pd precursor followed by calcination and H₂ reduction. The calcination temperature was found to be a crucial factor in determining the mean size of Pd nanoparticles. Pd/NaX catalysts with proper mean sizes of Pd could catalyze the solvent-free aerobic oxidation of various alcohols, and were particularly efficient for the oxidation of benzylic alcohols without substituents in benzene ring. Detailed studies using the Pd/NaX catalysts with different mean sizes of Pd revealed that the solvent-free aerobic oxidation of benzyl alcohol was structure-sensitive, and the intrinsic turnover frequency (TOF) reached a maximum at a medium mean size of Pd (2.8nm). On the other hand, for the oxidation of geraniol or 2-octanol without delocalized π-ring, the reaction was structure-insensitive, and the intrinsic TOF did not change significantly with the mean size of Pd particles.

Keywords: Aerobic oxidation; Alcohols; Palladium; Size dependence; Structure sensitivity

Efficient photocatalytic degradation of organic dyes over titanium dioxide coating upconversion luminescence agent under visible and sunlight irradiation by Jun Wang; Ronghe Li; Zhaohong Zhang; Wei Sun; Rui Xu; Yingpeng Xie; Zhiqiang Xing; Xiangdong Zhang (pp. 227-233).

In this work, an upconversion luminescence agent, crystallized Er³⁺:Y₃Al₅O₁₂, which can emit three upconversion fluorescent peaks below 387nm under the excitation of 488nm visible light, was synthesized and characterized. Meanwhile, the prepared TiO₂ photocatalysts coating upconversion luminescence agent were characterized by XRD and TEM. The experimental results proved that the prepared TiO₂ photocatalyst coating crystallized Er³⁺:Y₃Al₅O₁₂ showed much higher photocatalytic activity under visible and sunlight irradiation. ▪In order to use the sunlight efficiently, a new titanium dioxide (TiO₂) photocatalyst with high catalytic activity under visible light irradiation was prepared with sol–gel technique. In this work, an upconversion luminescence agent, crystallized Er³⁺:Y₃Al₅O₁₂, was synthesized and its characters were determined. It is found that this crystallized Er³⁺:Y₃Al₅O₁₂ can emit three upconversion fluorescent peaks below 387nm under the excitation of 488nm visible light. Hence, this upconversion luminescence agent could transform visible light into ultraviolet light, which could satisfy the genuine requirement of TiO₂ photocatalyst. Additionally, the upconverison mechanisms were also discussed. Meanwhile, the prepared TiO₂ photocatalysts coating upconversion luminescence agent were characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The photocatalytic activity of prepared TiO₂ powder was tested through the degradation of congo red in aqueous solution as a model compound under visible and sunlight irradiation. To affirm the complete mineralization, the ion chromatography and total organic carbon (TOC) were used to observe the mineralized anions and organic residues. The experimental results proved that the prepared TiO₂ photocatalyst coating crystallized Er³⁺:Y₃Al₅O₁₂ behaved much higher photocatalytic activity under visible light and sunlight irradiation, and was able to decompose the congo red in aqueous solution efficiently. Therefore, this method may be envisaged as a novel technology for treating dyes wastewater using solar energy, especially for textile industries in developing countries.

Keywords: Upconversion luminescence agent; TiO; ₂; photocatalyst; Sunlight; Visible light; Congo red

Oxygen evolution over Ag/Fe_xAl2−_xO₃ (0.0≤ x≤2.0) catalysts via N₂O and H₂O₂ decomposition by Bahaa M. Abu-Zied (pp. 234-242).

In this paper, a series of silver-aluminum-iron catalysts were prepared via the using urea as a combustion fuel with the corresponding nitrates at the 400–700°C temperature range. Phase analysis revealed that silver metal supported on Al₂O₃ and/or Fe₂O₃ represent the major constituents of all the calcinations products, i.e. Ag/Fe_xAl2−_xO₃. All the catalysts were able to decompose N₂O and H₂O₂ yielding oxygen as a joint product. Meanwhile, it was found nitrous oxide destruction activity increases with decreasing both silver particles size and iron content in the catalysts substrate. On the contrary, increasing iron content in the different catalyst was found to enhance hydrogen peroxide decomposition activity.▪In this paper, a comparative study between nitrous oxide and hydrogen peroxide decomposition over a series of catalysts prepared via the combustion of silver, aluminum, and iron nitrates (with different aluminum: iron ratios). Urea was used as a combustion fuel. The calcinations were affected at the 400–700°C temperature range. The produced catalysts were characterized by using XRD and SEM analyses. The obtained results revealed that silver metal supported on Al₂O₃ and/or Fe₂O₃ represent the major constituents of all the calcinations products, i.e. Ag/Fe_xAl2−_xO₃. However, two different interfaces are involved in the two test reactions, all the catalysts were able to decompose both reactants yielding oxygen as a joint product. Meanwhile, it was found nitrous oxide destruction activity increases with decreasing both silver particles size and iron content in the catalysts substrate. On the contrary, increasing iron content in the different catalyst was found to enhance hydrogen peroxide decomposition activity. Moreover, a synergic effect was observed for the catalysts having Al:Fe ratio of 0.5:1.5.

Keywords: N; ₂; O decomposition; H; ₂; O; ₂; decomposition; Silver catalyst; Alumina; Iron oxide

Autothermal reforming of methane over Ni/γ-Al₂O₃ promoted with Pd by Joelmir A.C. Dias; José M. Assaf (pp. 243-250).

The effect of adding small amounts of palladium to Ni/γ-Al₂O₃ catalysts for the autothermal reforming of methane is mainly the promotion of reduction of nickel. The promotion of the reduction increases the number of active sites available for steam reforming and oxidation of methane, allowing both reactions to occur simultaneously.▪The effects of adding small amounts of palladium to Ni/γ-Al₂O₃ catalysts for the autothermal reforming of methane, in terms of activity, reducibility, capacity of repeated ignition and temperature profile of the reactor are described. The effect of different Pd sources was also studied. The Pd addition favors nickel reduction at lower temperatures. When the palladium is added as PdCl₂ (PdNiAl-Cl) it exhibits a higher reduction temperature than when Pd(NO₃)₂ (PdNiAl-N) is used, an this can be attributed to the formation of Pd_xCl_yO_z species. Palladium strongly increases the activity of the Ni catalyst in autothermal reforming of methane, which is proportional to an increase in metal surface area. The addition of palladium to the catalyst also leads to a flatter temperature profile through the catalytic bed in the autothermal reforming of methane, and this is assigned to the high surface metal area of the catalyst. Only PdNiAl-N catalyst catalyzes the autothermal reforming of methane without previous reduction, while the PdNiAl-Cl catalyst only catalyzes the methane combustion and the unpromoted catalyst was inactive.

Keywords: Reforming reactions; Bimetallic catalyst; Nickel; Palladium; Light-off

Dry reforming of methane over LaNi1−_yB_yO3±_δ (B=Mg, Co) perovskites used as catalyst precursor by Germán Sierra Gallego; Catherine Batiot-Dupeyrat; Joël Barrault; Elizabeth Florez; Fanor Mondragón (pp. 251-258).

Perovskites LaNi1−_xB_xO3−_δ (B=Mg,Co) were evaluated as catalyst precursors in the dry reforming of methane. LaNi1−_xMg_xO3−_δ perovskite had the highest catalytic activity at 700°C using drastic reaction conditions without dilution gas. CH₄ and CO₂ conversions were 57% and 67%, respectively, with a H₂/CO ratio equal to 0.47. The partial substitution of Ni by Co leads to a decrease of the catalytic activity.▪Perovskites LaNiO₃, LaNi1−_xMg_xO3−_δ and LaNi1−_xCo_xO3−_δ were synthesized by auto combustion method. TPR analysis reveled that Mg or Co substituted perovskites were more difficult to reduce. The perovskites were evaluated as catalyst precursors in the dry reforming of methane. Catalysts obtained by reduction of LaNiO₃ and LaNi1−_xMg_xO3−_δ perovskite had the highest catalytic activity for CO₂ reforming of CH₄ at 700°C using drastic reaction conditions (10mg of catalyst, a mixture of CH₄/CO₂ without dilution gas). Methane and carbon dioxide conversions were 57% and 67%, respectively, with a H₂/CO ratio equal to 0.47.The presence of cobalt leads to a decrease of the catalytic activity. This decreasing of activity may be attributed to the Co–Ni alloy formation. Computational calculations revealed that Ni atom cleaves the C–H atom while Co is not able to activate the CH₄ molecule. The interaction energy of CH₄ with the Ni and CO atom was 18kcal/mol and 0.7kcal/mol, respectively.The catalysts were characterized by TPR, TEM and in situ XRD.

Keywords: CO; ₂; reforming of CH; ₄; Ni perovskites; Auto combustion method; Cation substitution

Syngas production by autothermal reforming of methane on supported platinum catalysts by Juan A.C. Ruiz; Fabio B. Passos; José M.C. Bueno; Eduardo F. Souza-Aguiar; Lisiane V. Mattos; Fabio B. Noronha (pp. 259-267).

The performance of supported platinum catalysts on the autothermal reforming of methane was evaluated. The effect of the calcination temperature of the CeZrO₂ support and of the reaction conditions (reaction temperature, presence of CO₂ in the feedstock, and H₂O/CH₄ molar ratio) was studied. The catalysts were characterized by BET, XRD, and OSC analyses and the reaction mechanism was determined by TPSR experiments. The TPSR analyses indicate that autothermal reforming of methane proceeds through a two-step mechanism (indirect mechanism) over all catalysts studied. The Pt/Ce_0.75Zr_0.25O₂ catalyst presented the best stability, which depends not only on the amount of oxygen vacancies of the support but also on the metal particle size. The higher reducibility and oxygen storage/release capacity of Pt/Ce_0.75Zr_0.25O₂ catalyst promote the mechanism of continuous removal of carbonaceous deposits from the active sites, which takes place at the metal-support interfacial perimeter. The water also participates in this mechanism, favouring the carbon removal of metal particle. Furthermore, the reaction conditions influenced significantly the behaviour of Pt/Ce_0.75Zr_0.25O₂ catalysts. The increase of H₂O/CH₄ molar ratio had a beneficial effect on the methane conversion and on the H₂/CO molar ratio. However, the increase of the reaction temperature had an opposite effect. Both the methane conversion and H₂/CO molar ratio decreased with the increasing of reaction temperature. Moreover, the addition of CO₂ to feedstock increased the initial methane conversion, but decreased the stability of the catalyst.The performance of supported Pt catalysts on the autothermal reforming of methane was evaluated under different reaction conditions. The TPSR analyses indicate that autothermal reforming of methane proceeds through a two-step mechanism over all catalysts studied. The Pt/Ce_0.75Zr_0.25O₂ catalyst presented the best stability, which depends not only on the amount of oxygen vacancies of the support but also on the metal particle size. ▪

Keywords: GTL technology; Synthesis gas; Natural gas; Autothermal reforming (ATR); Pt/CeZrO; ₂; catalysts

Effects of support on hydrogen adsorption/desorption on nickel by Leszek Znak; Jerzy Zieliński (pp. 268-276).

The effects of alumina, silica and carbon on hydrogen adsorption on nickel were studied by the temperature-programmed desorption (TPD) method. The examinations were carried out in the flow system, starting TP measurement at 100K, which resulted in the formation of complete characteristics of the interaction of hydrogen with supported nickel. The examinations have shown that each support modifies in its own way the state of hydrogen adsorbed on nickel.▪The effects of alumina, silica and carbon on hydrogen adsorption on nickel were studied by the temperature-programmed desorption (TPD) method. The examinations were carried out in the flow system, starting TP measurement at 100K, which resulted in the formation of complete characteristics of the interaction of hydrogen with supported nickel. The examinations have shown that each support modifies in its own way the state of hydrogen adsorbed on nickel. Alumina and silica insignificantly affect hydrogen strongly adsorbed on nickel, but significantly affect hydrogen weakly adsorbed; in particular, the effect of silica depends qualitatively on the way of preparation of the examined sample. Carbon affects significantly both strongly and weakly adsorbed hydrogen.

Keywords: Hydrogen adsorption; Hydrogen desorption; Hydrogen on nickel; TPD examination; Effect of support

n-Dodecane reforming over nickel-based monolith catalysts: Deactivation and carbon deposition by Benjamin D. Gould; Xiaoyin Chen; Johannes W. Schwank (pp. 277-290).

The carbon deposition behavior of Ni-based monolith reforming catalysts was studied during n-dodecane autothermal reforming, partial oxidation, and steam reforming. One catalyst formulation was nickel deposited on cerium zirconium oxide (CZO) coated monolith, while the second formulation was nickel directly deposited on bare monolith. In both formulations, a series of catalysts with a range of nickel loadings (0–16wt.%) were prepared to examine the influence of nickel loading on carbon deposition and to elucidate the benefits of the reducible oxide support CZO on carbon deposition. Carbon deposition was generally more pronounced at higher nickel loadings and on catalysts lacking CZO. Nickel supported on bare monolith suffered from excessive carbon deposition and carbon-induced monolith disintegration. The morphologies of carbon were determined by scanning electron microscopy (SEM). Temperature programmed oxidation (TPO) indicated the presence of two types of carbon. The low-temperature TPO peak can be attributed to coating carbon, while the high-temperature peak corresponds to filamentous carbon structures, including large whiskers and smaller filaments. Accumulation of whisker carbon had a deleterious effect on the monolith substrate resulting in the physical destruction of some samples. X-ray diffraction (XRD) gave no evidence for the presence of graphite or carbide species in carbon-deposited catalysts. The experimental results of this study are used to diagnose the causes for nickel catalyst deactivation during autothermal reforming and for proposing strategies to mitigate the deactivation.Deactivation of Ni-based monolith reforming catalysts from carbon deposition was studied during autothermal reforming, partial oxidation, and steam reforming of n-dodecane. The influence of Ni loading, Ni particle size, and support material on carbon formation is determined and strategies to minimize carbon deposition are proposed. ▪

Keywords: Dodecane; Carbon; ATR; Nickel; Monolith; Ceria; TPO; TGA; SEM; Jet fuel

Kinetic modeling of the homogeneous hydrogenation of avermectins catalyzed by in situ formed RhCl(Ph₃P)₃ complexes by María I. Cabrera; Patricia D. Zgolicz; Ricardo J. Grau (pp. 291-303).

On the basis of kinetic modeling, this study provides some insight into the hydrogenation kinetics of avermectins B1_a and B1_b (Av_i, i=B1_a and B1_b) with the in situ formed Wilkinson's catalyst from the dinuclear chloro-bridged Rh(I) complex [RhCl(COD)]₂ (COD=1,5-cyclo-octadiene) and triphenylphosphine (Ph₃P). More significantly, this paper is the first attempt to derive describing kinetic models. The kinetic behavior was studied in a temperature range of 313–343K, at a hydrogen pressure of 275.7kNm⁻². A significant induction period strongly dependent on the temperature was noticed during the in situ generation of the catalytic species. After improving a previous kinetic model describing Wilkinson's hydrogenation catalytic cycle, kinetic models for the in situ synthesis of the catalytic species were developed on the basis of reaction pathways assuming that the COD ligand replacement occurs via substitution by PPh₃ or via reductive elimination of COE (COE=cyclo-octene). Estimates of the kinetic parameters characterizing both reaction routes were uncoupled from those of the catalytic cycle steps. Among the rival kinetic models tested, a simple model featuring the PPh₃ insertion in the bidentate COD ligand as rate determining step (RDS) and the competitive replacement of the COD ligand by both PPh₃ and Av_i proved fair enough to describe the synthesis process in the presence of these macrocyclic lactones. A very high activation barrier characterizes the in situ synthesis of the catalytic complexes, and the presence of avermectins in the reaction medium interferes with the course of the catalytic species synthesis due to the formation of too stable intermediate complexes. From these observations, high reaction temperature and the absence of avermectins in the synthesis medium of the species responsible for the catalysis are two necessary conditions for improving the performance of this catalytic hydrogenation system.This study provides some insight into the hydrogenation kinetics of avermectins B1_a and B1_b with the in situ formed Wilkinson's catalyst from the dinuclear chloro-bridged Rh(I) complex [RhCl(COD)]₂ and triphenylphosphine. More significantly, this paper is the first attempt to derive describing kinetic models. The kinetic behavior was studied in a temperature range of 313–343K, at a hydrogen pressure of 275.7kNm⁻². ▪

Keywords: Hydrogenation; Kinetic modeling; Rhodium; In situ; synthesis; Avermectins

Effect of hydrochlorination and hydrofluorination of Pt/H-ZSM-5 and Pt–Ir/H-ZSM-5 catalysts for n-hexane hydroconversion by Ahmed K. Aboul-Gheit; Ahmed E. Awadallah; Noha A.K. Aboul-Gheit; El-Sayed A. Solyman; Mohammed A. Abdel-Aaty (pp. 304-310).

Pt and Pt–Ir/H-ZSM-5 catalysts doped with HCl or HF were used to produce iso-C₆ and benzene from n-C₆. HCl was enhancing, but HF was inhibiting.▪Pt/H-ZSM-5 and Pt–Ir/H-ZSM-5 catalysts were hydrochlorinated or hydrofluorinated with 3.0wt%HCl or HF, respectively. These mono- and bimetallic catalysts were tested for n-hexane hydroconversion in a pulsed microcatalytic reactor in a flow of H₂ gas. The catalysts were characterized via XRD, metal dispersion via H₂ chemisorption and acid site strength distribution using temperature programmed desorption of ammonia (TPD). Although metallic promoters frequently cause inhibition of the catalytic activities of Pt and since iridium is less active than platinum, fortunately, Ir was found to enhance the hydroconversion activities of the current catalysts, particularly after hydrochlorination.

Keywords: n; -Hexane; Hydroconversion; Hydroisomerization; Hydrocracking; Dehydrocyclization; Hydrochlorinated; Hydrofluorinated; Platinum; Iridium; H-ZSM-5 zeolite

Rare earth-first-row transition metal perovskites as catalysts for the autothermal reforming of hydrocarbon fuels to generate hydrogen by Jennifer R. Mawdsley; Theodore R. Krause (pp. 311-320).

Perovskite oxides (ABO₃) containing rare earth elements on the A-site and first-row transition metal elements on the B-site were studied as catalysts for autothermal reforming of liquid hydrocarbon fuels to produce hydrogen for fuel cell systems. Experiments were conducted in a fixed bed microreactor at temperatures of 600–800°C and gas-hourly space velocities (GHSV) ranging from 4600 to 28,000h⁻¹ using 2,2,4-trimethylpentane (isooctane) as a surrogate fuel. We have found that the two binary oxides, LaNiO₃ and LaCoO₃, produced high yields of H₂, but were not structurally stable. These perovskites decomposed to La₂O₃ and Ni/NiO or Co/CoO under the reducing conditions present in the reformer. Three other binary oxides, LaCrO₃, LaFeO₃, and LaMnO₃, were structurally stable but significantly less active than LaNiO₃ and LaCoO₃. The partial substitution of chromium, iron, aluminum, gallium, or manganese on the B-site of LaNiO₃ to yield LaB_xNi1−_xO₃ was shown to improve the structural stability without a significant decrease in the H₂ yield. The effects of substituting rare earth elements for La and the substitution of alkaline earth elements on the A-site (La1−_yA_yB_xNi1−_xO₃) on catalyst performance and stability were also investigated. Finally, La_0.8Sr_0.2M_0.9Ni_0.1O₃ catalysts (where M=Cr, Mn, or Fe) were tested with a “benchmark fuel” mixture containing from 0 to 50ppmw sulfur. These tests showed that using chromium as a stabilizing element in LaNiO₃ imparts the most sulfur tolerance.Perovskite oxides (ABO₃) were studied as catalysts for autothermal reforming of liquid hydrocarbon fuels to produce hydrogen. LaNiO₃ and LaCoO₃ produced high yields of H₂, but were not structurally stable. LaCrO₃, LaFeO₃, and LaMnO₃ were structurally stable but were less active. The partial substitution of chromium, iron, aluminum, gallium, or manganese for nickel in LaNiO₃ improved the structural stability without a significant decrease in the H₂ yield.▪

Keywords: Autothermal reforming; Perovskite; Catalyst; Sulfur tolerance

Influence of zirconia crystal phase on the catalytic performance of Au/ZrO₂ catalysts for low-temperature water gas shift reaction by Juan Li; Junli Chen; Wei Song; Junlong Liu; Wenjie Shen (pp. 321-329).

The influence of crystal phase of zirconia on the performance of Au/ZrO₂ catalysts for low temperature water gas shift reaction was investigated. Au/ZrO₂ catalysts with pure tetragonal and monoclinic phases of ZrO₂ were prepared by the deposition-precipitation method with similar gold loading and dispersion. It was found that the Au/m-ZrO₂ catalyst showed much higher activity than that of the Au/t-ZrO₂ catalyst, which could be attributed to the higher CO adsorption capacity of the Au/m-ZrO₂ catalyst. The chemical state of gold that was strongly related to the pretreatment atmosphere also played an essential role in determining the catalytic activity for water gas shift reaction. Hydrogen and/or helium pretreated samples only contained Au⁰ species and exhibited higher activity than that of the sample pretreated with oxygen-containing atmosphere which resulted in the co-existence of Au⁰ and Au⁺ species. FTIR study further revealed that the formate species formed by the reaction of the adsorbed CO on gold nanoparticle with the hydroxyl groups on the surface of m-ZrO₂ acted as the most important intermediates for the water gas shift reaction.Au nanoparticles on monoclinic ZrO₂ could show much higher catalytic activity for low-temperature water gas shift reaction than those on tetragonal zirconia, mainly due to the high CO adsorption capacity of monoclinic ZrO₂. Formate species formed by the reaction of adsorbed CO on gold nanoparticle with hydroxyl groups on ZrO₂ acted as the most important reaction intermediates.▪

Keywords: Au/ZrO; ₂; Crystal phase; Low-temperature; Water gas shift; FTIR

Influence of reduction temperature and metal loading on the performance of molybdenum phosphide catalysts for dibenzothiophene hydrodesulfurization by A. Montesinos-Castellanos; T.A. Zepeda; B. Pawelec; E. Lima; J.L.G. Fierro; A. Olivas; J.A. de los Reyes H. (pp. 330-338).

Two series of alumina-supported molybdenum phosphide (MoP) catalysts with low and high metal loadings were prepared by temperature-programmed reduction of the oxidic catalyst precursors in hydrogen to different temperatures (823, 923, 1023 and 1123K, respectively). Effects of reduction temperature and metal loading on the surface distribution and the type of species formed were studied by TPR, S_BET, XRD, HRTEM,³¹P NMR,²⁷Al NMR and in the reaction of dibenzothiophene (DBT) hydrodesulfurization (HDS) performed in a flow reactor at 553K and total hydrogen pressure of 3.4MPa. HRTEM and³¹P NMR confirmed formation of MoP phase on all catalysts. The 9.9wt% Mo catalyst activated at lowest reduction temperature (823K) was found to be most active among the catalysts studied. The presence of a low amount of Mo⁰ species on the surface of this catalyst does not appear to be a drawback for the catalytic activity. The increase in both metal loading (from 9.9 to 15wt% Mo and from 3.2 to 4.8wt% P) and reduction temperature (from 823 to 1123K) was found to be detrimental for HDS activity due to sintering of active phase, and also to decrease in specific area and formation of phosphate species.Two series of alumina-supported molybdenum phosphide (MoP) catalysts with low and high metal loadings were prepared by temperature-programmed reduction of the oxidic catalyst precursors in hydrogen to different temperatures (823, 923, 1023 and 1123K, respectively). Effects of reduction temperature and metal loading on the surface distribution and the type of species formed were studied.▪

Keywords: Hydrodesulfurization; Dibenzothiophene; Supported molybdenum phosphide; Alumina

Support and promoter effects in the selective oxidation of ethane to acetic acid catalyzed by Mo-V-Nb oxides by Xuebing Li; Enrique Iglesia (pp. 339-347).

The rate and selectivity of acetic acid synthesis from ethane-O₂ reactants were markedly increased by depositing active Mo_0.61V_0.31Nb_0.08O_x onto colloidal TiO₂ and combining them with a Pd/SiO₂ co-catalyst (≤0.01wt.% Pd). TiO₂ leads to active structures with higher area but surface reactivity similar to that on bulk powders. PdO_x species catalyze selective oxidation of ethene intermediates to acetic acid.▪Catalysts based on Mo-V-Nb oxides were examined in bulk and supported forms for the oxidation of ethane to ethene and acetic acid. Bulk Mo_0.61V_0.31Nb_0.08O_x powders showed rates and selectivities similar to those in previous reports. Precipitation in the presence of colloidal TiO₂ led to a 10-fold increase in ethene and acetic acid rates (per active oxide) without significant changes in selectivity relative to unsupported samples. Precipitation in the presence of colloidal ZrO₂ and Al₂O₃ suspensions, however, introduced unselective combustion sites without improving ethane oxidation rates. Mo₅O₁₄ structures, containing low-valent metal cation centers were detected in bulk Mo_0.61V_0.31Nb_0.08O_x and TiO₂-supported samples by Raman and UV–visible spectra and consistent with X-ray diffraction patterns, but not in Al₂O₃- or ZrO₂-containing catalysts. The introduction of trace amounts of Pd (0.0025–0.01wt.%), as a physical mixture of separate 0.3wt.% Pd/SiO₂, led to the near complete depletion of ethene intermediates and to a significant increase in acetic acid synthesis rate. Small PdO_x catalyze ethene oxidation to acetaldehyde, but require the rapid scavenging of these molecules by Mo-V-Nb oxides to prevent acetaldehyde combustion and loss of selectivity. Dispersed VO_x domains on TiO₂ were able to catalyze all steps required for ethane oxidation to acetic acid. CO_x selectivities, however, were much higher than on bulk and TiO₂-supported Mo_0.61V_0.31Nb_0.08O_x catalysts. Dispersed MoO_x domains were essentially inactive at these reaction conditions but their concurrent presence with VO_x increased acetic acid selectivity by titrating unselective sites and stabilizing more reducible VO_x species.

Keywords: Ethane; Oxidation; Metal oxide; Ethene; Acetic acid

Multicomponent Au/MgO catalysts designed for selective oxidation of carbon monoxide by András Tompos; Mihály Hegedűs; József L. Margitfalvi; Ervin Gy. Szabó; Lajos Végvári (pp. 348-356).

Combinatorial approach using both library optimization and information mining tools was applied in designing multicomponent Au/MgO catalysts for CO oxidation in the presence of hydrogen. High activity ( α_CO) and selectivity ( S_CO) required the modification of both gold and the support. Different optimum gold and modifier concentrations were found depending on the mode of catalyst pretreatment prior to the use of catalysts.▪A complex combinatorial approach has been applied for the design of multicomponent Au/MgO catalysts for CO oxidation in the presence of hydrogen. The combinatorial library design led to unique earlier unknown catalyst compositions. The best catalysts contained significant amount of Pb and Sm, which had never been reported before as useful components of PROX catalysts. In order to increase the diversity of experimental space different pretreatment conditions have been applied prior to catalytic tests. Actually, two catalyst libraries have been tested after (i) a reductive, and (ii) a combined reductive pretreatment. Significantly different optimum compositions have been obtained upon using these two pretreatment procedures. The combined reductive treatment resulted in a more cost effective optimum composition with significantly less components and smaller gold content in comparison to the best catalyst obtained upon using a simple reductive treatment. Further studies showed different ways of promoting action of modifiers. After reductive pretreatment the modifiers suppress the hydrogen consumption, while after combined reductive pretreatment the modifiers lead to the promotion of both oxidation reactions.

Keywords: Au/MgO; Modification of gold; PROX; Combinatorial catalysis; Catalyst library design; High throughput experimentation; Artificial neural networks; Information mining; Multicomponent catalysts

Active phase of calcium oxide used as solid base catalyst for transesterification of soybean oil with refluxing methanol by Masato Kouzu; Takekazu Kasuno; Masahiko Tajika; Shinya Yamanaka; Jusuke Hidaka (pp. 357-365).

By characterizing the catalyst collected after achieving the conversion of edible soybean oil into its methyl ester at reflux of methanol in a glass batch reactor, the active site of calcium oxide was investigated Calcium oxide combined with the by-produced glycerol, so that the collected catalyst consisted of calcium diglyceroxide (Ca(C₃H₇O₃)₂). Calcium diglyceroxide functioned as the solid base catalyst in actual fact, and was tolerant to air-exposure.▪For developing a process of biodiesel production with environmental benignity, much interest has been focused on solid base catalysts such as calcium oxide for transesterification of vegetable oils with methanol. In this paper, the active phase of calcium oxide was investigated by characterizing the catalyst collected after achieving the conversion of edible soybean oil into its methyl ester at reflux of methanol in a glass batch reactor. Calcium oxide combined with the by-produced glycerol, so that calcium diglyceroxide was a major constituent of the collected catalyst. The absence of calcium methoxide was clear from the spectrum of solid-state¹³C-NMR. The chemical change of calcium oxide was not observed, when the yield of FAME reached 30%. The collected catalyst was not as active as the fresh one (calcium oxide), but was reused without any deactivation. In order to identify the active phase of the collected catalyst, we prepared calcium diglyceroxide by immersion of calcium oxide with refluxing methanol in the presence of glycerol. Calcium diglyceroxide prepared as the reference sample was as active as the collected catalyst in the transesterification, and was tolerant to air-exposure.

Keywords: Biodiesel; Calcium oxide; Calcium diglyceroxide; Transesterification; Solid base catalyst

Ultra-deep oxidative desulfurization of diesel fuel by the Mo/Al₂O₃-H₂O₂ system: The effect of system parameters on catalytic activity by José Luis García-Gutiérrez; Gustavo A. Fuentes; Maria Eugenia Hernández-Terán; Ponciano García; Florentino Murrieta-Guevara; Federico Jiménez-Cruz (pp. 366-373).

Mo/γ-Al₂O₃ catalysts were evaluated in the oxidative desulfurization (OD) process of diesel fuel using hydrogen peroxide as the oxidizing reagent. On the basis of the results obtained a mechanistic proposal for this reaction is described, as an oxidation mechanism by nucleophilic attack of the sulfur atom on peroxo species of hepta- and octamolybdates, but a mechanism involving the singlet oxygen presence can be discarded.▪This work presents the results obtained in the development of Mo/γ-Al₂O₃ catalysts and their evaluation in the oxidative desulfurization (OD) process of diesel fuel using hydrogen peroxide as the oxidizing reagent. The catalysts were prepared by equilibrium adsorption using several molybdenum precursors and aluminas with different acidity values. They were characterized by Raman spectroscopy. The effect of the reaction time, reaction temperature, nature of solvent, concentration of solvent and hydrogen peroxide, content of molybdenum and phosphate in the catalysts were investigated. The results showed that the activity for sulfur elimination depends mainly on the presence of hepta- and octamolybdates species on the catalyst support and the use of a polar aprotic solvent. Likewise, the presence of phosphate markedly increases the sulfur elimination. In this way, it is possible to reduce sulfur level in diesel fuel from about 320 to less than 10ppmw at 333K and atmospheric pressure. Additionally, on the basis of the results obtained a mechanistic proposal for this reaction is described, as an oxidation mechanism by nucleophilic attack of the sulfur atom on peroxo species of hepta- and octamolybdates, but a mechanism involving the singlet oxygen presence can be discarded.

Keywords: Desulfurization; Oxidation; Sulfur; Sulfone; Hydrogen peroxide; Catalysis; Molybdenum; Diesel fuel; 4,6-dimethyldibenzothiophene

Supported heteropolycompounds as ecofriendly catalysts for 2,6-dimethylphenol oxidation to 2,6-dimethyl-1,4-benzoquinone by P. Villabrille; G. Romanelli; P. Vázquez; C. Cáceres (pp. 374-380).

Different heteropolycompounds were used as catalysts in the synthesis of coumarins from phenols and ethyl acetoacetate. Keggin heteropolyacids were supported on silica and the aluminium salts of these heteropolyacids were prepared. The catalytic activity using several phenols were determined and high yield of product was obtained in the case of 4-methyl-7-hydroxycoumarin, 4-methyl-5,7-dimethoxycoumarin and 4-methyl-7,8-benzocoumarin. The use of microwave radiation increases the reaction yield and mainly decreases the reaction time.▪Supported catalysts were prepared by in situ deposition of the cesium salt of H₄PMo₁₁VO₄₀. Commercial silica was impregnated to incipient wetness with an aqueous solution of CsNO₃. The dried and calcined solid was then impregnated an aqueous solution of H₄PMo₁₁VO₄₀. Solids with 40% and 7% (w/w) of Cs₃HPMo₁₁VO₄₀ were obtained. To compare on behavior catalytic, a catalyst was prepared by silica impregnation with an aqueous solution of H₄PMo₁₁VO₄₀ (40%, w/w), using the incipient wetness technique. Impregnated silica particles showed a homogeneous distribution by scanning electron microscope (SEM). The Keggin structure was preserved for the salt in those catalysts according to the FT-IR and DRS characterization. The acidity of the solids with 40% and 7% (w/w) of Cs₃HPMo₁₁VO₄ was greater than that of the silica but lower than that of bulk salt. The catalysts were used in the oxidation of 2,6-dimethylphenol with aqueous hydrogen peroxide, in acetonitrile at 20°C. The reaction was followed by UV–vis spectroscopy. The phenol conversion was 35% at 4h for H₄PMo₁₁VO₄₀/SiO₂, 20% at 2h and 29% at 135h for 7% Cs₃HPMo₁₁VO₄/SiO₂, and 83% at 98h for 40% Cs₃HPMo₁₁VO₄/SiO₂. The behavior of the latter was also studied by HPLC technique. Similar results were achieved with both techniques. The Cs₃HPMo₁₁VO₄/SiO₂ catalysts were almost totally insoluble in the reaction mixture.

Keywords: Supported heteropolycompounds; Ecofriendly catalysts; 2,6-dimethylphenol oxidation; 2,6-dimethyl-1,4-benzoquinone

Identification versus generalization by Martin Holeňa (pp. 381-385).

Artificial neural networks; Identification; Generalization; Universal approximation capability

Photodegradation of 2-naphthol in water by artificial light illumination using TiO₂ photocatalyst: Identification of intermediates and the reaction pathway by S. Qourzal; N. Barka; M. Tamimi; A. Assabbane; Y. Ait-Ichou (pp. 386-393).

The photo catalytic degradation of 2-naphthol was investigated in aqueous suspensions of TiO₂ under a variety of conditions. An analysis of total organic carbon (TOC) showed that a complete mineralization of 2-naphthol can be easily achieved. The intermediate products were identified. A detailed degradation pathway was proposed.▪The kinetics of the photocatalytic degradation of 2-naphthol has been investigated in aqueous suspensions of titanium dioxide (TiO₂) under a variety of conditions, which is essential from application point of view. The degradation was studied using different parameters such as types of TiO₂, catalyst concentration, substrate concentration, reaction pH and in the presence of different electron acceptors such as hydrogen peroxide (H₂O₂), potassium bromate (KBrO₃) and potassium persulphate (K₂S₂O₈) besides molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst “Degussa P-25” was found to be more efficient as compared with other photocatalysts. The degradation kinetics fit well to the Langmuir–Hinshelwood rate law. It was found that an optimal concentration of 5×10⁻⁴mol/l Ag⁺ in TiO₂ achieved the fastest 2-naphthol degradation under the experimental conditions. However, with the addition of Na⁺, K⁺, Mg²⁺, Ca²⁺, Zn²⁺, Co²⁺ and Ni²⁺, there are no obvious effects on the reactions. An analysis of total organic carbon (TOC) showed that a complete mineralization of 2-naphthol can be easily achieved. The intermediate products were identified by HPLC–MS technique. A detailed degradation pathway could be proposed.

Keywords: Photocatalysis; Kinetics; TiO; ₂; 2-Naphthol; Mechanism; Water treatment

Re: “Identification versus generalization. Comment on the criticism of indeterminacy of artificial neural networks” by Martin Holeňa [Appl. Catal. A: Gen., 334 (2008) 381] by W. Sha (pp. 394-394).

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Applied Catalysis A, General (v.334, #1-2)