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Applied Catalysis A, General (v.328, #2)

Contents (pp. iii-viii).

Editorial Board (pp. co2).

Highly active NiMo/TiO₂–Al₂O₃ catalysts: Influence of the preparation and the activation conditions on the catalytic activity by A. Guevara-Lara; Robert Bacaud; M. Vrinat (pp. 99-108).

NiMo/TiO₂–Al₂O₃ catalysts were prepared over a TiO₂–Al₂O₃ mixed oxide (5% of Al₂O₃) by impregnation with nickel and molybdenum salts precursors at different pH solution and the catalysts have been activated by several calcination–sulfidation procedures. Evaluation of the catalysts in tetraline hydrogenation under pressure indicated that the sample obtained after impregnation under basic condition and sulfided without any previous calcination presents the highest activity. Characterizations of the samples by Raman and UV–vis diffuse reflectance spectroscopies, XPS and HRTEM allowed to follow the evolution of the Ni and Mo species along the different steps of the preparation and to understand how to get a high promoting effect of Ni over such a TiO₂ rich support.▪NiMo/TiO₂–Al₂O₃ catalysts were prepared over a TiO₂–Al₂O₃ mixed oxide (5% of Al₂O₃) by impregnation with nickel and molybdenum salts precursors at different pH solution and the catalysts have been activated by several calcination–sulfidation procedures. Evaluation of the catalysts in tetraline hydrogenation under pressure indicated that the sample obtained after impregnation under basic condition and sulfided without any previous calcination presents the highest activity. Characterizations of the samples by Raman and UV–vis diffuse reflectance spectroscopies, XPS and HRTEM allowed to follow the evolution of the Ni and Mo species along the different steps of the preparation and to understand how to get a high promoting effect of Ni over such a TiO₂ rich support.

Keywords: Hydrotreating; TiO; ₂; –Al; ₂; O; ₃; support; Raman spectroscopy; UV–vis; NiMoO; ₄

Catalytic reaction of 1,3-butanediol over rare earth oxides by Satoshi Sato; Ryoji Takahashi; Toshiaki Sodesawa; Ai Igarashi; Hirotomo Inoue (pp. 109-116).

In the reaction of 1,3-butanediol, dehydration and decomposition occurred simultaneously. The formation of unsaturated alcohols was predominant over CeO₂, Sc₂O₃, and Tm₂O₃, while 1,3-butanediol was decomposed over the other rare earth oxides. Basicity of rare earth oxides increased with increasing ionic radius of the cations, and light rare earth oxides such as La₂O₃, Pr₆O₁₁, Nd₂O₃, and Sm₂O₃ catalyzed decomposition of 1,3-butanediol into 2-propanol, propanone, methanol, and ethanol. ▪Vapor-phase reaction of 1,3-butanediol was investigated over rare earth oxide (REO) catalysts. In the reaction of 1,3-butanediol, dehydration and decomposition of 1,3-butanediol occurred simultaneously at 325°C. The formation of unsaturated alcohols such as 3-buten-2-ol and trans-2-buten-1-ol was predominant over CeO₂, Sc₂O₃, and Tm₂O₃, while 1,3-butanediol was preferentially decomposed over the other REOs. Especially, light REOs such as La₂O₃, Pr₆O₁₁, Nd₂O₃, and Sm₂O₃, catalyzed decomposition of 1,3-butanediol into 2-propanol, propanone, methanol, and ethanol. Basic and acidic properties of REOs were measured with temperature-programmed desorption (TPD) of adsorbed CO₂ and NH₃, respectively. The surface character of REOs was basic but not acidic. Both strength and number of basic sites of REOs increased with increasing ionic radius of rare earth cation in the REO except CeO₂: light REOs were more basic. The decomposition of 1,3-butanediol would be attributed to the basicity of catalyst. In the reaction of 1,3-butanediol as well as 1,4-butanediol, the catalytic function of REOs will be discussed in connection with lanthanide contraction.

Keywords: Dehydration; Rare earth oxide; 1,3-Butanediol; 1,4-Butanediol

Studies on catalytic performance of precipitated iron/silica catalysts for Fischer–Tropsch Synthesis by Hiroshi Hayakawa; Hisanori Tanaka; Kaoru Fujimoto (pp. 117-123).

The effects of coprecipitated silica were investigated in iron-based catalysts for Fischer–Tropsch Synthesis (FTS). Silica-containing catalysts exhibited micro pores (<10nm) and large specific surface areas, while the silica-free catalyst had large pores (10–100nm) and low specific surface area.Coprecipitated silica enhances the productivity of hydrocarbon for FTS, especially C5+ hydrocarbon selectivity. Silica-free and silica-containing iron catalyst showed high activity and stability over 100h test. ▪The effects of coprecipitated silica were investigated in iron-based catalysts for Fischer–Tropsch Synthesis (FTS). Silica-containing catalysts exhibited micro pores (<10nm) and large specific surface areas, while the silica-free catalyst had large pores (10–100nm) and low specific surface area.Coprecipitated silica enhances the productivity of hydrocarbon for FTS, especially C5+ hydrocarbon selectivity.Silica-free and silica-containing iron catalyst showed high activity and stability over 100h test, and exhibited little difference of the product selectivity (olefin/paraffin ratio) over the temperature range of 513–553K.An iron catalyst has higher activity with the low H₂/CO ratio (0.4–1.0). Thus, an iron catalyst has the advantage in applications to coal-derived gas, as compared to the cobalt-based catalyst.

Keywords: Fischer–Tropsch Synthesis; Iron catalyst; Catalytic performance; 1-Olefin selectivity

A global kinetic model as a tool to reproduce the deactivation behaviour of the HZSM-5 zeolite in the catalytic cracking of low-density polyethylene by A. Marcilla; M.I. Beltrán; A. Gómez-Siurana; R. Navarro; F. Valdés (pp. 124-131).

The experimental study of the deactivation behaviour of HZSM-5 during the catalytic cracking of LDPE has permitted a new and simple kinetic model to be developed that takes into account the effect of the coke formation on the catalytic activity decay and the acid and surface properties of the zeolite. Very good correlation results have been obtained, proving that the method suggested allows a quantitative and simultaneous correlation of the global deactivation behaviour of the HZSM-5 in the catalytic cracking of LDPE.▪The deactivation behaviour of the HZSM-5 zeolite in the catalytic cracking of LDPE has been analysed. Four important properties of the partly deactivated catalysts have been measured: firstly, the activity of the fresh and partly coked zeolites in the pyrolysis reactions in TG; secondly, the amount of coke deposited on the catalysts after each reaction; thirdly the effect of the coke content of the catalyst on their acid properties and in the fourth place the effect of the coke content on their surface properties. The experimental study of the deactivation behaviour of HZSM-5 during the catalytic cracking of LDPE has permitted a new and simple kinetic model to be developed that takes into account the effect of the coke formation on the catalytic activity decay and the acid and surface properties of the zeolite. The model considered in the present work has been applied to simultaneously correlate the TG data of the successive reaction cycles, the NH₃ TPD experimental curves and the nitrogen adsorption isotherms as a function of the amount of coke in the catalyst. Very good correlation results have been obtained, proving that the method suggested allows a quantitative and simultaneous correlation of the global deactivation behaviour of the HZSM-5 in the catalytic cracking of LDPE.

Keywords: LDPE; HZSM-5; Deactivation; Kinetic model; Coke

Catalytic pyrolysis of polyolefin waste into valuable hydrocarbons over reused catalyst from refinery FCC units by Y.-H. Lin; M.-H. Yang (pp. 132-139).

A commingled polyethylene/polypropylene (PE/PP) mixture was pyrolysed over used fluid catalytic cracking (FCC) commercial equilibrium catalyst (RCat-c1) using a laboratory fluidised-bed reactor operating isothermally at ambient pressure. The conversion at 390°C for RCat-c1 catalyst (81.5wt%) gave much higher yield than silicate (only 18.3wt%). Greater product selectivity was observed with RCat-c1 as a post-use catalyst with about 53wt% olefins products in the C₃–C₆ range. The selectivity could be further influenced by changes in reaction conditions. Valuable hydrocarbons of olefins and iso-olefins were produced by low temperatures and short contact times used in this study. It is demonstrated that the use of spent FCC commercial catalyst and under appropriate reaction conditions can have the ability to control both the product yield and product distribution from polymer degradation, potentially leading to a cheaper process with more valuable products.An in-house designed fluidised-bed reactor has been successfully used to obtain a range of valuable hydrocarbons by catalytic degradation of polyolefin waste in the temperature range 330–450°C. In particular, it is interesting that a post-use catalyst system under appropriate conditions the resource potential of polymer waste can be economically recovered and also can provide an alternative practically to solve a major environment problem. ▪

Keywords: Pyrolysis; Polyolefin; Catalyst; FCC; Selectivity

Comparative study between methane and ethane in catalytic partial oxidation over Pt and Rh foils using molecular-beam technique by Toshiaki Sasaki; Kenji Nakao; Keiichi Tomishige; Kimio Kunimori (pp. 140-149).

The effect of energetic activation of methane and ethane using molecular-beam techniques in catalytic partial oxidation under steady-state condition was investigated over Pt and Rh foils. Energetic activation of methane and ethane by heating and seeding promoted the catalytic partial oxidation and enhanced hydrogen formation in particular.▪The effect of energetic activation of methane and ethane using molecular-beam techniques in their oxidation with O₂ under steady-state condition was investigated over Pt and Rh foils. Energetic activation of methane and ethane by heating and seeding promoted the catalytic partial oxidation and enhanced hydrogen formation in particular. Based on the results on the reaction order measurements over Pt foil, one possible explanation for the promotion is that the energetically activated methane and ethane react with adsorbed oxygen and produce methoxy and ethoxy species, which are regarded as precursors for hydrogen formation. The production rates over Rh foil were smaller then over Pt foil, and lower O₂ partial pressure was required to produce CO and hydrogen, which is related to the higher oxygen affinity of Rh.

Keywords: Partial oxidation; Methane; Ethane; Energetic activation; Molecular-beam

Selective hydroxylation of benzene using dioxygen activated by vanadium–copper oxide catalysts supported on SBA-15 by Ying-Ying Gu; Xin-Hua Zhao; Gui-Rong Zhang; Han-Ming Ding; Yong-Kui Shan (pp. 150-155).

Phenol was synthesized through directly hydroxylation reaction of benzene over VO_x/CuSBA-15 catalyst using molecular dioxygen as an oxidant in the presence of ascorbic acid. A high yield of phenol was achieved at ca. 27% with the selectivity of nearly 100%. ▪The vanadium and copper oxide species supported catalyst, VO_x/CuSBA-15, was synthesized to catalyze the hydroxylation reaction of benzene to form phenol using molecular dioxygen in the presence of ascorbic acid. A high yield of phenol was achieved at ca. 27% with the selectivity of nearly 100%. The VO_x/CuSBA-15 has two characteristics that it can selectively activate dioxygen molecules rather than H₂O₂, and it can selectively catalyze benzene hydroxylation to form phenol, but can hardly catalyze phenol for further oxidation under the same reaction conditions. Both copper and vanadium oxide species supported on a mesoporous silicate has a prominent catalytic performance toward the benzene hydroxylation reaction comparing to the other bi-transition metal oxides or monometallic catalysts on the same support. The results suggest that there might be a synergy between copper and vanadium oxide species on the support. It is believed that benzene hydroxylation over the VO_x/CuSBA-15 catalyst occurs through the hydroxyl radical pathway, and the catalytic activation of molecular oxygen to form hydroxyl radical would be a rate determining step.

Keywords: Benzene; Phenol; Hydroxylation; Oxidation; Vanadium oxide; Copper oxide; SBA-15

Preparation of LaSrCuO₄ nanowires by carbon nanotubes and their catalytic and chemiluminescence properties for CO oxidation by Fei Teng; Bulgen Gaugeu; Shuhui Liang; Yongfa Zhu (pp. 156-162).

Single-phase LaSrCuO₄ nanowires were prepared using carbon nanotubes in the presence of citrate. After being calcined at 750°C for 48h, LaSrCuO₄ nanowires showed a higher thermal stability and a higher activity for CO oxidation than the nanoparticle counterpart. ▪LaSrCuO₄ nanowires were synthesized using carbon nanotubes (CNTs) in the presence of citrate; LaSrCuO₄ nanoparticles were also prepared by a conventional citrate route in order to compare with the nanowires. The samples were characterized by transmission electron microscopy (TEM), high-resolution electron microscopy (HRTEM), frontier-transformed electron diffraction (FT-ED), X-ray diffraction (XRD), N₂ adsorption isotherm and CO-TPD (temperature-programmed desorption) methods. The catalytic and chemiluminescence (CL) properties for CO oxidation over LaSrCuO₄ catalysts with different morphologies were investigated further. The results revealed that CNTs and citrate played the key roles in controlling the morphology, crystallization and phase compositions of LaSrCuO₄ catalyst; a high thermal stability of LaSrCuO₄ nanowires against calcination was observed, and a high activity for CO oxidation was maintained.

Keywords: Carbon nanotubes; Citrate; LaSrCuO; ₄; Nanowires; CO oxidation; Chemiluminescence

A mechanistic investigation of the coupled reaction of n-hexane and methanol over HZSM-5 by Fuxiang Chang; Yingxu Wei; Xianbin Liu; Yinfeng Zhao; Lei Xu; Ying Sun; Dazhi Zhang; Yanli He; Zhongmin Liu (pp. 163-173).

Conversions of n-hexane without methanol coupling (▵) and with methanol coupling (□) and ratio of coupled n-C₆ conversion and uncoupled n-C₆ conversion (●) versus contact time at 400°C over HZSM-5 zeolite (Si/Al=19). ▪The coupled reaction of n-hexane and methanol was studied and compared with the reactions of individual reactants over HZSM-5 zeolite catalyst. The catalytic reaction test results and the temperature-programmed surface reaction (TPSR) results showed an improvement of the initial n-hexane activity when methanol was used as co-reactant. The FT-IR analysis indicated that methanol was adsorbed on acid sites prior to n-hexane and immediately transformed into surface methoxy groups. These species acted as the active sites for the conversion of n-hexane and improved the initial activity of n-hexane by bimolecular hydride transfer. The catalytic test also suggested that alkenes resulting from the transformation of methanol further enhance the conversion of n-hexane, in addition to the improvement by methoxy groups. A faster conversion of methanol was also observed in the coupled system, which highlights a bidirectional promotion effect of the coupled reaction. A reaction mechanism is proposed to explain all observations.

Keywords: Coupled reaction; n; -Hexane; Methanol; ZSM-5; Mechanism

The acid properties of H-ZSM-5 as studied by NH₃-TPD and²⁷Al-MAS-NMR spectroscopy by Luz Rodríguez-González; Florian Hermes; Marko Bertmer; Enrique Rodríguez-Castellón; Antonio Jiménez-López; Ulrich Simon (pp. 174-182).

The acid properties of H-ZSM-5 zeolites with different SiO₂/Al₂O₃ ratios (30, 50, 80, 150, 280 and 1000) were examined by means of the temperature programmed desorption of ammonia (NH₃-TPD). The strength of the Brønsted acid sites, determined by a theoretical model assuming the free readsorption of ammonia, is found to be in the range of Δ H=129–161kJmol⁻¹ and shows variations in the acid strength to be less than σ=12kJmol⁻¹. ▪The acid properties of H-ZSM-5 zeolites with different SiO₂/Al₂O₃ ratios (30, 50, 80, 150, 280 and 1000) were examined by means of the temperature programmed desorption of ammonia (NH₃-TPD). Different pretreatments together with a comparison of different curve-fitting methods after desorption of ammonia were used to differentiate between different adsorption sites.²⁷Al-MAS-NMR spectroscopy was applied to distinguish the framework (Al_F) from the extra-framework aluminum (Al_EF). Both techniques reveal that the concentration of Brønsted acid sites is lower than expected when considering the aluminum content. The strength of the Brønsted acid sites, determined by a theoretical model assuming the free readsorption of ammonia, is found to be in the range of Δ H=129–161kJmol⁻¹ and shows variations in the acid strength to be less than σ=12kJmol⁻¹.

Keywords: NH; ₃; -TPD; H-ZSM-5; ²⁷; Al-MAS-NMR; Brønsted acidity; Zeolite

Gas-phase dehydrocyclization of diphenylamine by Miroslav Vlčko; Zuzana Cvengrošová; Milan Hronec; Piyasan Praserthdam (pp. 183-188).

The gas-phase dehydrocyclization of diphenylamine to carbazole was studied in a fix-bed reactor over Pt and Pd catalysts. Alumina, magnesium oxide and silica were used as supports. The reaction was carried out at a temperature of 560°C in the presence of hydrogen. Pd catalysts are reasonably active but not selective compared to Pt catalysts which possess very high activity and selectivity. For supporting active metal, proper alumina has advantages compared to silica and magnesium oxide. This is due to its acid sites which accelerate the isomerization step. Though higher loading of Pt has a positive influence on the carbazole formation, at a Pt content higher than 0.6wt.% this effect is negligible. In the presence of catalyst with 0.6wt.% Pt deposited on alumina, carbazole is produced with a selectivity of about 90% at a conversion of diphenylamine about 97%.

Keywords: Diphenylamine; Carbazole; Dehydrocyclization; Platinum catalysts; Gas-phase

Benzene transalkylation with C9+ aromatics over supported 12-tungstophosphoric acid on silica catalysts by José A. Dias; Maria do Carmo Rangel; Sílvia C.L. Dias; Ednéia Caliman; Fillipe A.C. Garcia (pp. 189-194).

H₃PW₁₂O₄₀/SiO₂ (8–25wt.%) were prepared and evaluated in benzene transalkylation with C9+ aromatics. The activity and selectivity to xylenes changed with the acid loading and was related to optimum acid strength and dispersion as well as specific surface area of the solids. The most active (15wt.%) showed the adequate combination of those parameters representing a promising catalyst for industrial applications.▪Silica-supported H₃PW₁₂O₄₀ (H₃PW) catalysts (8, 15, 20 and 25wt.% H₃PW) were prepared and their catalytic activities were evaluated in benzene transalkylation with C9+ aromatics, using an industrial stream. This reaction is a convenient way to upgrade the low value of the stream produced in naphtha reforming and gasoline pyrolysis, by improving the production of xylenes. It was found that the activity and selectivity to xylenes changed with the acid loading and this was related to optimum acid strength and dispersion as well as specific surface area of the solids. The most active catalyst was the sample with 15wt.% H₃PW, which showed the adequate combination of the three parameters cited above. This solid was also the most stable, showing the lowest rate of deactivation under the reaction conditions, producing the least amount of coke. In addition, it presented the highest activity and selectivity to xylenes, even when compared to a mordenite commercial catalyst. Consequently, this catalyst represents a promising catalyst for industrial applications.

Keywords: Benzene transalkylation; 12-Tungstophosphoric acid; Silica; Supported heteropoly acid

Effect of oxalic acid content and medium of thermal treatment on physicochemical and catalytic properties of MoVTeNb oxide catalysts in propane ammoxidation by G.Ya. Popova; T.V. Andrushkevich; G.I. Aleshina; L.M. Plyasova; M.I. Khramov (pp. 195-200).

Catalytic characteristics of MoV_0.3Te_0.23Nb_0.12O_x catalysts in propane ammoxidation depend strongly on the quantity of oxalic acid present during slurry preparation and on the redox conditions during thermal treatment of the catalyst. Two stage thermal treatment (320°C in air, 600°C in He) and oxalate anion to niobium ratio in the slurry С₂О₄²⁻/Nb=3–5 have been shown to result in the catalysts with the best catalytic properties. Optimal catalysts have been found to contain M1 and M2 crystalline phases in the ratio of 3:1 or more. When the molar ratio С₂О₄²⁻/Nb exceeds 3.5, tellurium is lost during calcination in He and other phases beside M1 and M2 are formed. ▪Catalytic characteristics of MoV_0.3Te_0.23Nb_0.12O_x catalysts in propane ammoxidation depend strongly on the quantity of oxalic acid present during slurry preparation and on the redox conditions during thermal treatment of the catalyst. Two stage thermal treatment (320°C in air, 600°C in He) and oxalate anion to niobium ratio in the slurry С₂О₄²⁻/Nb=3–5 have been shown to result in the catalysts with the best catalytic properties. Optimal catalysts have been found to contain M1 and M2 crystalline phases in the ratio of 3:1 or more. When the molar ratio С₂О₄²⁻/Nb exceeds 3.5, tellurium is lost during calcination in He and other phases beside M1 and M2 are formed.

Keywords: MoVTeNb mixed oxide; Phase structure; M1; M2; Propane; Ammoxidation; Acrylonitrile

Effect of the modified support γ-Al₂O₃-CaO on the structure and hydrodesulfurization activity of Mo and Ni-Mo catalysts by S. Andonova; Ch. Vladov; B. Pawelec; I. Shtereva; G. Tyuliev; S. Damyanova; L. Petrov (pp. 201-209).

The effect of the support γ-Al₂O₃ modified with CaO by deposition–precipitation method on the structure, catalytic activity and resistance to coke formation of Mo and Ni-Mo catalysts for HDS was investigated. The synthesized catalysts deposited on the modified support have higher HDS activity and resistance to coke formation. This is as a result of the presence of Ca²⁺ ions which hinders the formation of MoO₃ crystallites on the catalytic surface.▪The effect of the support γ-Al₂O₃ modified with CaO by deposition–precipitation method on the structure, catalytic activity and selectivity of Mo and Ni-Mo catalysts for HDS was investigated. The resistance of the catalysts to deactivation by coke formation was also investigated. The samples have been characterized by means of XRD, DRS, XPS, Al²⁷ NMR, TPR, and specific surface area and pore size distribution. The reaction of thiophene hydrodesulphurization, carried out at atmospheric pressure, was used as a model reaction for estimating the activity of the catalyst samples.The obtained results show that the applied method of modification with CaO leads to the formation of support with mesoporous structure and a considerable higher mechanical strength than that of the pure γ-Al₂O₃. Mo and Ni-Mo catalysts deposited on the modified support have higher HDS activity and resistance to coke formation. The presence of Ca²⁺ ions in the lattice of the support hinders the formation of crystallites of MoO₃ and Al₂(MoO₄)₃ phase. The higher catalytic activity of the samples with modified support is due to the higher degree of their sulfidation.

Keywords: Alumina; Ni-Mo catalysts; Thiophene hydrodesulphurization

Extrusion of zeolites: Properties of catalysts with a novel aluminium phosphate sintermatrix by Jens Freiding; Florina-Corina Patcas; Bettina Kraushaar-Czarnetzki (pp. 210-218).

A novel type of mechanically strong zeolite extrudates is introduced, in which the zeolite crystals, here ZSM-5, are embedded in a sintermatrix of aluminium phosphate with the crystal structure of tridymite. The pore size distribution in the matrix can be tailored through both, the choice of the size of the embedded particles and their amount in the extrudates. At zeolite concentrations of 50% (w/w) or higher, the mean pore diameter of the matrix ( D_pore) depends on the zeolite crystal size only, and amounts to D_pore≈0.25 D_particle. Other than conventional matrices on alumina basis, the AlPO₄ matrix does neither provide catalytic self-activity, nor does cause any alumination of the zeolite framework.A novel type of strong zeolite extrudates is introduced, in which the zeolite crystals are embedded in a sintermatrix of AlPO₄ with tridymite structure. The pore size distribution can be tailored through choice of the size of the embedded particles and their amount in the extrudates. Other than alumina matrices, the AlPO₄ matrix does neither provide catalytic self-activity, nor does is cause alumination of the zeolite.▪

Keywords: Extrusion; Aluminium phosphate; Zeolites; Alumination; Macropores

Effect of phosphorus addition on the active sites of a Co-Mo/Al₂O₃ catalyst for the hydrodesulfurization of thiophene by Usman; Tomoya Yamamoto; Takeshi Kubota; Yasuaki Okamoto (pp. 219-225).

The effect of phosphorus addition was studied on the hydrodesulfurization (HDS) of thiophene over Co-MoS₂/P/Al₂O₃, which was prepared by a chemical vapor deposition (CVD) technique using Co(CO)₃NO as a precursor of Co. The catalysts were characterized by means of NO adsorption, FTIR and Raman spectroscopy. The HDS activity of Co-MoS₂/Al₂O₃ was slightly increased by the addition of 0.2wt% P, followed by a slight decrease with a further addition of phosphorus. In spite of the activity increase, the amount of NO adsorption on MoS₂/P/Al₂O₃ steadily decreased with increasing phosphorus loading, suggesting that the dispersion of MoS₂ particles is decreased by the addition of phosphorus. The TOF of the HDS over CVD-Co/MoS₂/P/Al₂O₃ catalysts, defined by the activity per Co atom forming the Co-Mo-S phase, increased as much as 1.3 times by the addition of phosphorus, indicating that the active phase of the catalysts shifts from less active Co-Mo-S Type I to more active Co-Mo-S (pseudo) Type II. FTIR results showed that phosphoric acid reacts with the surface OH groups of Al₂O₃, resulting in weakened interactions between molybdenum oxides and Al₂O₃ surface and thus in less abundant Mo–O–Al bonds in MoS₂–Al₂O₃ interactions.

Keywords: Hydrodesulfurization; Co-Mo/Al; ₂; O; ₃; Phosphorus addition; TOF; Laser Raman spectroscopy; FTIR spectroscopy; XPS; Intrinsic activity; HDS

New green catalytic manufacture of glutaric acid from the oxidation of cyclopentane-1,2-diol with aqueous hydrogen peroxide by Hui Chen; Wei-Lin Dai; Ruihua Gao; Yong Cao; Hexing Li; Kangnian Fan (pp. 226-236).

Selective oxidation of cyclopentane-1,2-diol to glutaric acid with aqueous hydrogen peroxide was carried out over different kinds of materials: the homogeneous H₂WO₄, the heterogeneous W-MCM-41 and the phase-transfer catalysts. The homogeneous and phase-transfer catalysts showed very high activity that the GAC yields were higher than 90% while the heterogeneous and phase-transfer catalysts were convenient to be recovered and reused. ▪Selective oxidation of cyclopentane-1,2-diol to glutaric acid (GAC) over different kinds of materials has been carried out with aqueous hydrogen peroxide. The homogenous tungstic acid catalyst was tried first, which showed a yield of GAC as high as 91.2%. However, the separation, recovering and reusing of the homogeneous catalyst are very difficult, thus restricting its further application in industry. Then tungsten-containing mesoporous silica (W-MCM-41) was next tried as a heterogeneous catalyst. Although the activity was about 20% lower than that of the homogeneous one, it was much more easily to be separated, recovered and reused. It is interesting to find that the phase-transfer material shows the best performance in the reaction, during which the yields of GAC on [π-C₅H₅NC₁₆H₃₃]₂{W₂O₃[O₂]₄} (CW) and [π-C₅H₅NC₁₆H₃₃]₃{PO₄[WO₃]₄} (CPW) were 91.3 and 94.3%, respectively. These two materials demonstrated the characteristic features of “reaction-controlled phase-transfer”; the samples dissolved during the reaction and precipitated after the reaction. Therefore, these materials show the advantages of both homogeneous and heterogeneous catalysis and can easily be recovered and reused. The fresh samples and the recovered ones were all characterized by FT-IR, Raman,³¹P NMR and XPS spectroscopy. The structures of these two materials all changed after the reaction, polymerizing by forming W–O_c–W (edge-sharing) bonds. XPS results revealed that the recovered samples of CW and CPW are all more stable than the corresponding fresh ones due to the changes of the coordination circumstances.

Keywords: Cyclopentane-1,2-diol; Glutaric acid; Selective oxidation; Hydrogen peroxide; Homogeneous catalyst; Heterogeneous catalyst; Phase-transfer catalyst

Water–gas-shift kinetics in the iron-based low-temperature Fischer–Tropsch synthesis by F. Gideon Botes (pp. 237-242).

The kinetic modelling of the water–gas-shift (WGS) reaction in the iron-based low-temperature Fischer–Tropsch synthesis was investigated. First order kinetics in CO is a reasonable description of the CO₂ formation rate, but it appears to be essentially an empirical relationship. WGS rate expressions based on the formate mechanism were found to provide an improved description of the WGS kinetic data.▪The kinetic modelling of the water–gas-shift (WGS) reaction in the iron-based low-temperature Fischer–Tropsch synthesis was investigated. It was found that first order kinetics in CO is a reasonable description of the CO₂ formation rate, but (due to systematic errors in this model) it appears to be essentially an empirical relationship. WGS rate expressions based on the formate mechanism were found to provide an improved description of the WGS kinetic data. By considering rate data measured over a wide range of reactor pressures, it was possible to discriminate between the various formate-based rate equations considered during this study.

Keywords: Iron; Water–gas-shift; Fischer–Tropsch; Kinetics

Fe-Ru small particle bimetallic catalysts supported on carbon nanotubes for use in Fischer–Tröpsch synthesis by Munga C. Bahome; Linda L. Jewell; Kamentheren Padayachy; Diane Hildebrandt; David Glasser; Abhaya K. Datye; Neil J. Coville (pp. 243-251).

Fe-Ru catalysts for Fischer–Tröpsch synthesis were prepared by co-impregnation of Fe nitrate and Ru acetate on purified carbon nanotubes. The catalysts were promoted with K and Cu. HAADF-STEM evidenced metal particles with an average size of 2.1nm. The catalysts show behaviour typical of Ru:Fe catalysts, with remarkable stability. Moreover the support interaction with the carbon does not hinder reduction and produces a catalyst which does not sinter.▪Fe-Ru bimetallic catalysts for Fischer–Tröpsch (FT) synthesis were prepared by co-impregnation of Fe nitrate and Ru acetate salts on purified carbon nanotube (CNT) supports. The Fe-Ru/CNT catalysts were promoted with potassium and/or copper using an incipient wetness procedure in which the promoter was added at the same time as the Fe-Ru. The structures of the CNTs and sizes of the Fe-Ru metal particles (on average 2.1nm) were determined by high-resolution TEM and HAADF-STEM. The reducibility of the catalysts was studied by temperature-programmed reduction (TPR) and the expected promoter effects (K, Cu on Fe) were observed. All the catalysts were used for the FT synthesis in a fixed-bed microreactor (275°C, 8bar, H₂/CO=2/1). The effect of Cu and K on CO conversion, product selectivity and FT synthesis activity was investigated. The observed behaviour of the small particles obtained in this study followed similar trends to what has been observed before for Fe promoted catalysts suggesting that support interactions do not strongly affect the promoter properties of the metals. All the catalysts were found to be stable in the FT reaction (ca. 120h) indicating that the Fe-Ru clusters possess remarkable stability in the FT reaction when supported on carbon nanotubes. This resistance to sintering is attributed to the metal support interaction characteristic of CNT supports.

Keywords: Fischer–Tröpsch; Fe-Ru bimetallic catalysts; Carbon nanotubes; Promotion

Molecularly imprinted soluble nanogels as a peroxidase-like catalyst in the oxidation reaction of homovanillic acid under aqueous conditions by Zhiyong Chen; Zhendong Hua; Jun Wang; Yuan Guan; Meiping Zhao; Yuanzong Li (pp. 252-258).

A novel type of soluble peroxidase-like imprinted nanogels incorporating hemin, acrylamide and 4-vinylpyridine as functional monomers was prepared by solution polymerization method. Such highly crosslinked molecularly imprinted nanogels showed greater catalytic activity in DMSO–Tris–HCl buffer than in pure Tris–HCl buffer mainly because it could behave as a homogeneous catalyst under appropriate DMSO–Tris–HCl system. ▪A novel type of soluble peroxidase-like imprinted nanogels incorporating hemin, acrylamide and 4-vinylpyridine as functional monomers was prepared by solution polymerization method. Such highly crosslinked nanogels could be conveniently separated from the reaction mixture through precipitation, ultracentrifugation or ultrafiltration, whereby they could be analyzed by gel permeation chromatography (GPC), transmission electron microscopy (TEM), dynamic light scattering (DLS) and environmental scanning electron microscope (ESEM). More importantly, the molecularly imprinted polymers (MIP) showed greater catalytic activity in DMSO–Tris–HCl buffer than in pure Tris–HCl buffer mainly because it could behave as a homogeneous catalyst under appropriate DMSO–Tris–HCl system. The results suggested that the unavoidably restrained transport properties inside conventional insoluble imprinted polymers might be overcome. Additionally, the MIP showed higher adsorption towards substrate under aqueous conditions compared with its corresponding blank polymer, which was due in part to its higher catalytic activity.

Keywords: Molecularly imprinted polymers; Enzyme mimic; Nanogel; Peroxidase

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Applied Catalysis A, General (v.328, #2)

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Applied Catalysis A, General (v.328, #2)