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Applied Catalysis A, General (v.279, #1-2)

EDITORIAL BOARD (pp. iii).

NEWSBRIEF (pp. n1-n6).

CONTENTS LIST (pp. v-vi).

Utilization of electromagnetic and acoustic irradiation in enhancing heterogeneous catalytic reactions by B. Toukoniitty; J.-P. Mikkola; D.Yu. Murzin; T. Salmi (pp. 1-22).

Process intensification has become a very interesting approach, transforming current practices in chemical engineering and bringing forth new developments in equipment, processing techniques and operational methods. This development aims at more compact, safe, energy efficient and environmentally friendly process.Several unconventional processing techniques rely on alternative forms of energy. Chemistry under extreme and non-conventional conditions is an actively studied topic in applied research and industry. Alternatives to conventional synthetic procedures promise enhancement of reaction rates, yields, selectivity and also bear promise of milder reaction conditions in chemical synthesis. During the last few decades, chemical application of ultrasound (US) and microwave (MW) irradiation has received a lot of attention and widespread research is going on in these areas. Significant enhancement of selectivities, rates and yields in chemical reactions has been achieved by means of US and MW irradiation. The popularity of US and MW irradiation as chemical laboratory techniques is rapidly growing, based on the number of publications, presentations and meetings, demonstrating their vast potential. Other less exploited methods are solar and plasma reactors. These, however, will not be touched in the present review, which focuses on the use of ultrasound and microwaves as sources of energy, mainly in catalytic applications.

Keywords: Ultrasound irradiation; Microwave irradiation; Hetrogeneous catalytic reaction

Low temperature water-gas shift reaction on cerium containing mordenites prepared by different methods by M.M. Mohamed; T.M. Salama; A.I. Othman; G.A. El-Shobaky (pp. 23-33).

Cerium containing mordenites catalysts were prepared by impregnation (CeM_imp), solid-state ion exchange (CeM_ss) and in situ incorporation during synthesis (CeM_in). The structure of the samples has been investigated by X-ray diffraction, FT-IR, N₂ adsorption, thermal analyses (TG and DTA) and pyridine-FT-IR. Water-gas shift reaction (WGSR) was carried out over various catalysts and the catalytic reaction was monitored using in situ FT-IR. The results obtained showed the presence of cerium silicate phase in case of CeM_in sample as evidenced by XRD and FT-IR spectroscopy. In case of CeM_imp and CeM_ss, a separate CeO₂ phase was observed in a highly dispersed state in the former than in the latter, which measured the highest specific surface area. FT-IR results of pyridine adsorption indicate the presence of acid–base site pairs on the surface of CeM_imp and CeM_ss samples where only Lewis acidity was found on CeM_in, reflecting the presence of Ce³⁺ with Si⁴⁺ cations at tetrahedral lattice sites in mordenite. CeM_imp showed the highest catalytic activity followed by CeM_ss. It has been shown that reduction by H₂ carried out at 500°C was responsible for activating different carbonyls attached to Ce³⁺; such as Ce³⁺–CO and Ce³⁺–(CO)₂ which decomposed into CO2_ads. The role of basicity, Ce dispersion and surface texture of reduced Ce–mordenites on their catalytic activity in CO oxidation by H₂O was evaluated and discussed.

Keywords: Water-gas shift reaction; Ce-containing mordenite catalysts monitored by FT-IR

Hydrazine decomposition over iridium supported on carbon nanofibers composite for space applications: near actual flight conditions tests by Ricardo Vieira; Dem�trio Bastos-Netto; Marc-Jacques Ledoux; Cuong Pham-Huu (pp. 35-40).

Hydrazine-type monopropellant propulsion is well suited to attitude and orbit control systems on satellites. These systems are powered by micro thrusters with 30–40wt.% iridium supported on alumina as catalyst for hydrazine decomposition. Carbon nanofibers with macroscopic shaping can be used as an alternative to the traditional support. This new material is prepared by chemical vapor deposition of ethane on nickel particles dispersed upon the surface of the graphite felt. The carbon nanofiber-based composite was impregnated with 30wt.% of iridium. The overall performances of these catalysts have been evaluated for the hydrazine catalytic decomposition reaction in a 2N micro thruster into a vacuum chamber, i.e., under near actual flight conditions. The results obtained were compared with those of a commercial catalyst (Shell 405). The carbon nanofibers-based catalysts showed far better performance than the commercial catalyst from a standpoint of activity due to its texture and its high thermal conductivity.

Keywords: Carbon nanofiber; Catalytic support; Hydrazine decomposition; Satellite propulsion

Novel and effective surface enrichment of active species in Ni-loaded catalyst prepared from Mg–Al hydrotalcite-type anionic clay by Katsuomi Takehira; Tetsuya Shishido; Daisuke Shouro; Kazuhiro Murakami; Masahide Honda; Tomonori Kawabata; Ken Takaki (pp. 41-51).

Egg shell-type Ni loaded catalysts have been prepared by adopting the “memory effect�? of Mg–Al hydrotalcite and have been successfully used in the steam reforming of CH₄. Mg–Al(3/1) mixed oxide particles were first prepared as the catalyst support by the thermal decomposition of Mg–Al hydrotalcite. When the particles were dipped in aqueous solution of Ni(II) nitrate, Mg–Al hydrotalcite was reconstituted in the surface layer of the particles, and simultaneously Ni(II) substituted for the Mg(II) sites, leading to the formation of egg shell-type Ni-loading. The conditions of both preparation of Mg–Al(3/1) mixed oxide and dipping in Ni(II) nitrate solution were varied, and their influences on egg shell-type Ni-loading and on the catalytic activity were studied. The shape of egg shell-type Ni-loading was significantly affected by the rate of heating, the final calcination temperature of Mg–Al(3/1) mixed oxide, the pH of Ni(II) nitrate aqueous solution, and the dipping time of the mixed oxide in the aqueous solution. The smaller heating rate, the lower temperature calcination, and a dipping in the aqueous solution at the lower pH were preferable for the Ni-loading in egg shell-type. Under the mild heating conditions, periclase-like MgO structure was formed, on which the reconstitution of Mg–Al hydrotalcite was preferentially provoked in the surface layer of the particle by “memory effect�? during the dipping at the lower pH. It is concluded that the activity of egg shell-type Ni-loaded catalyst was enhanced by the surface enrichment of well-dispersed Ni metal particles.

Keywords: CH; ₄; reforming; H; ₂; production; Egg shell-type Ni-loaded catalyst; Mg–Al hydrotalcite; High dispersion; Stable Ni metal particles

Hydrocracking of n-decane on a bifunctional sulfided NiW/silica–alumina catalyst: effect of the operating conditions by Martial Roussel; S�bastien Norsic; Jean-Louis Lemberton; Michel Guisnet; Tivadar Cseri; Eric Benazzi (pp. 53-58).

Hydrocracking of n-decane was carried out on a sulfided NiW/silica–alumina catalyst in a fixed-bed reactor, in the presence of hydrogen sulfide and ammonia. The effect of the reaction temperature and of the partial pressures of n-decane, hydrogen, hydrogen sulfide and ammonia was determined. The transformation of n-decane occurred through two reactions: a bifunctional transformation and a “direct cracking�? reaction. Whatever the operating conditions, the main reaction observed was the bifunctional transformation of n-decane into monobranched isomers. At low reaction temperature or in the presence of ammonia, the bifunctional transformation of the monobranched isomers into multibranched isomers and into cracking products was very slow. This can be related to the weak acidity of the silica–alumina support which was moreover strongly poisoned by ammonia. Consequently, the acidic step of n-decane hydrocracking was clearly rate-determining, which was in agreement with the kinetic reaction orders measured. The “direct cracking�? reaction always existed, whatever the operating conditions, and yielded linear C₂–C₈ alkanes. The kinetic orders measured for this reaction confirmed that it occurred on exposed W atoms in the sulfide phase of the catalyst.

Keywords: Hydrocracking; n; -Decane; Bifunctional catalyst; Silica–alumina; NiW sulfides; Kinetics

Influence of preparation method and additive for Cu–Mn spinel oxide catalyst on water gas shift reaction of reformed fuels by Yohei Tanaka; Tatsuya Takeguchi; Ryuji Kikuchi; Koichi Eguchi (pp. 59-66).

Higher CO conversions were achieved over Cu–Mn spinel catalysts prepared by citric acid complex method (CIT), urea homogenous coprecipitation (URE) and Pechini method (PEC) than by coprecipitation with NH₃ (COP(NH₃)). Higher reducibility was attained by CIT, URE and PEC than by COP(NH₃). The citric acid method was a simple way to produce a catalyst with high activity. CO conversion was enhanced with a rise in calcination temperatures over the Cu–Mn spinel catalyst prepared by the citric acid method. Partial substitution of Fe or Al for Mn enhanced the catalytic activity of Cu–Mn spinel. Optimized Cu/Mn/Fe ratio was 1:1:1 in terms of catalytic activity.

Keywords: Water gas shift reaction; CO; Cu spinel-type oxide; Preparation methods; Cu–Mn–Fe spinel oxide

Bulk oxidation state of the different cationic elements in the MoVTe(Sb)NbO catalysts for oxidation or ammoxidation of propane by Manuel Baca; Jean-Marc M. Millet (pp. 67-77).

Different spectroscopic techniques like XANES, ESR, XPS and Mössbauer spectroscopy have been used to determine the oxidation state of the various cations in the M1 and M2 phases of the MoVTe(Sb)NbO catalysts used for the oxidation or ammoxidation of propane. It was observed that the tellurium or antimony M1 or M2 phases contained mainly Te^IV, and Nb^V. Molybdenum, vanadium and antimony were shown to be present as Mo^VI and Mo^V, V^V and V^IV and Sb^V and Sb^III. The M1 phase which is responsible for the high efficiency of catalysts, corresponds to the total stoichiometry (AO)2−_x(A₂O)_xM₂₀O₅₆ with A=Sb or Te, M=Mo, V and Nb and 0≤ x≤1. It has a structure with hexagonal channels occupied by the A cations and oxides. This channel may contain an excess of oxygen which constitutes a reservoir for the catalysts and which likely plays a role in the reoxidation of the catalytic sites. The balance of the charges introduced by these oxides anions was achieved by the partial oxidation of Sb^III to Sb^V in M1(Sb) and by the oxidation of Mo^V to Mo^VI in M1(Te), Te remaining always Te^IV as shown from Mössbauer spectroscopy data. The characterization of the solids after catalytic test showed very few changes in the solids structures and compositions. The study allowed concluding that the lone pair elements does not have only a role as constituents of the surface catalytic sites but also as bulk components to store oxygen in the hexagonal channels and contributes to its rapid diffusion to the surface.

Keywords: Propane mild oxidation and ammoxidation; Cationic oxidation state; MoVTeNb and MoVSbNb oxide catalysts

Acidic and catalytic properties of MCM-22 and MCM-36 zeolites synthesized from the same precursors by S. Laforge; P. Ayrault; D. Martin; M. Guisnet (pp. 79-88).

Samples of MCM-22 and MCM-36 (the pillared MCM-22 analog), synthesized from the same precursors were characterized by various techniques: XRD, N₂ adsorption, pyridine and 2,4-dimethylquinoline adsorption followed by IR spectroscopy, m-xylene transformation at 350�C in absence or in presence of 2,4-dimethylquinoline. The MCM-36 samples were shown to present sinusoidal channels, mesopores and/or supermicropores containing cups but also a small amount of undesired supercages. The method previously developed to estimate the activity and selectivity of the three MCM-22 pore systems (sinusoidal channels, supercages and external cups) was adapted to the characterization of the MCM-36 pore systems. Pillaring causes a large change in the distribution of the activity: approximately 15% of m-xylene transformation occurs in the inner micropores of the synthesized MCM-36 against more than 70% in the corresponding MCM-22 sample. Hence, 85% of the activity of MCM-36 (against 30% in MCM-22) is due to the protonic sites located in cups which are accessible to bulky molecules.

Keywords: MCM-22 zeolite; MCM-36 zeolite; Pore systems; Acid sites; Activity; m; -Xylene

C₂H₆ as an active carbon source for a large scale synthesis of carbon nanotubes by chemical vapour deposition by Giuseppe Gulino; Ricardo Vieira; Julien Amadou; Patrick Nguyen; Marc J. Ledoux; Signorino Galvagno; Gabriele Centi; Cuong Pham-Huu (pp. 89-97).

Ethane was successfully used as an active and efficient carbon source in a large scale synthesis of high quality carbon nanotubes by chemical vapour deposition (CVD) over Fe/Al₂O₃ catalyst with an iron loading of 20wt.%. The carbon nanotubes yield of 20g per gram of catalyst per hour was obtained at a synthesis temperature of 660°C. The active phase for growing carbon nanotubes is a mixture of a metastable iron carbide (Fe₃C) and α-Fe which were formed in situ by the ethane dissociation followed by carbon diffusion through the starting α-Fe phase similarly to that reported in the literature. The reaction products only contained multi-walled carbon nanotubes with very homogeneous diameters between 20 and 40nm and lengths up to several hundred nanometers without any trace of other impurities such as nanoparticles or amorphous soot. The high yield of the MWNT significantly decreases the amount of the catalyst in the final product and the product can be used directly without need for post-synthesis treatment in order to remove the catalyst. Ethane is an active carbon source for growing MWNTs with high yield and selectivity. The reaction temperature should be keep ≤750°C as synthesis carried out at 800°C under similar reaction conditions led to the formation of amorphous soot and carbon nanoparticles mixed with nanotubes.

Keywords: Carbon nanotube; Iron carbide; Vapour deposition; Ethane; High yield

Kinetic peculiarities of cis/ trans methyl oleate formation during hydrogenation of methyl linoleate over Pd/MgO by I.V. Deliy; N.V. Maksimchuk; R. Psaro; N. Ravasio; V. Dal Santo; S. Recchia; E.A. Paukshtis; A.V. Golovin; V.A. Semikolenov (pp. 99-107).

Kinetic peculiarities of cis and trans methyl oleate formation in the course of methyl linoleate hydrogenation over Pd/MgO were studied. Liquid phase hydrogenation was carried out in temperature range of 303–323K and under hydrogen pressure within 1–10bar. Gas–liquid chromatography, IR and¹³C NMR techniques were employed to characterize the reaction products. Effects of hydrogen pressure and reaction temperature on cis and trans methyl oleate formation were studied. The general kinetic scheme and reaction mechanism of methyl linoleate hydrogenation and cis– trans methyl oleate isomerization have been proposed.

Keywords: Cis; –; trans; isomerization; Partial hydrogenation; Pd/MgO; Kinetics

Regeneration of a deactivated USY alkylation catalyst using supercritical isobutane by David N. Thompson; Daniel M. Ginosar; Kyle C. Burch (pp. 109-116).

Off-line, in situ alkylation activity recovery from a completely deactivated solid acid catalyst was examined in a continuous-flow reaction system employing supercritical isobutane. A USY zeolite catalyst was initially deactivated during the liquid phase alkylation of butene with isobutane in a single-pass reactor and then varying amounts of alkylation activity were recovered by passing supercritical isobutane over the catalyst bed at variable reactivation conditions. Temperature, pressure and regeneration time were found to play important roles in the supercritical isobutane regeneration process when applied to a completely deactivated USY zeolite alkylation catalyst. Manipulation of the variables that influence solute solubility, diffusivity, surface desorption, hydride transfer rates, and coke aging, strongly influences regeneration effectiveness.

Keywords: Alkylation; Isoparaffin; Trimethylpentane; Solid acid catalyst; Supercritical fluid; Regeneration

Impact of the preparation method and iron impurities in Fe-ZSM-5 zeolites for propylene production via oxidative dehydrogenation of propane with N₂O by Javier P�rez-Ram�rez; Amalia Gallardo-Llamas (pp. 117-123).

The performance of differently prepared Fe-ZSM-5 zeolites in the N₂O-mediated propane oxidative dehydrogenation to propylene has been investigated at 723K using a tapered element oscillating microbalance (TEOM) coupled to on-line GC analysis. Catalysts were prepared by hydrothermal synthesis followed by calcination and steam treatment, liquid-ion exchange, and chemical vapor deposition, and contain molar Fe/Al ratios in the range of 0.26–1. Propylene yields in the range of 22–25% were attained over steam-activated Fe-ZSM-5, much higher over the iron zeolites prepared by post-synthesis methods (9–16%), with propylene selectivities around 40%. The deactivation behaviour due to coking differs among the catalysts investigated. Calcined H-ZSM-5 with impurities of iron (Fe/Al=0.007) leads to an initial yield of propylene of 8%, and is increased to 16% upon steam treatment, obtaining a selectivity to propylene of 90%. The turnover frequency for propylene production is up to three orders of magnitude higher in steamed H-ZSM-5 than in the synthesized iron zeolites. Our results suggest that traces of well-isolated (mononuclear) Fe species released from framework positions by steaming are extremely active in the oxidative dehydrogenation of propane to propylene, while large iron clusters enhance deep oxidation of important reaction intermediates to CO_x.

Keywords: Oxidative dehydrogenation; Propane; N; ₂; O; Propylene; Fe-ZSM-5; Preparation method; Commercial zeolite; Iron impurities; Steaming; Deactivation; Coke formation; TEOM

An easily recoverable and efficient natural biopolymer-supported zinc chloride catalyst system for the chemical fixation of carbon dioxide to cyclic carbonate by Lin-Fei Xiao; Fu-Wei Li; Chun-Gu Xia (pp. 125-129).

Chemical fixation of carbon dioxide with epoxides to form cyclic carbonates proceeds very effectively under mild conditions by using a chitosan-supported zinc chloride catalyst in conjunction with 1-butyl-3-methylimidazole halides (BMImX) without any organic solvents. Reaction temperature, carbon dioxide pressure, effects of co-catalysts and the molar ratio of catalyst to co-catalyst were investigated. The optimum reaction conditions were 110�C and 1.5MPa, and BMImBr was the best co-catalyst. The catalyst system was recycled and reused.

Keywords: Chitosan; Carbon dioxide; Cyclic carbonates; Epoxides; Green chemistry

Photo-stability of surface chromate species on Phillips CrO_x/SiO₂ catalysts isothermally calcined at various temperatures, probed by high resolution X-ray photoelectron spectroscopy by Yuwei Fang; Boping Liu; Minoru Terano (pp. 131-138).

Phillips CrO_x/SiO₂ catalyst is still an important industrial catalyst for ethylene polymerization. Poor understanding of the electronic states of surface chromate species has hindered further mechanistic exploration and improvement of this catalyst system. The objective of this work is to systematically study the photo-stability of Phillips catalyst by X-ray photoelectron spectroscopy (XPS) method, since such photo-stability has not been well documented yet in the literature. Five catalysts: namely, PC200, PC300, PC400, PC600 and PC800 with 1.0wt.% of Cr loading were prepared from the industrial Phillips catalyst precursor PCP120 at 200, 300, 400, 600 and 800°C, respectively. The photo-stability in terms of electronic stability for the surface chromate species (Cr(VI)O x_,surf) on these catalysts was investigated by a high resolution XPS method. The resistance to photo-reduction into supported Cr(III)O_x,_surf species induced by X-ray irradiation during XPS measurement was studied. The photo-stability of surface chromate species on Phillips catalyst was found to be significantly dependent on the calcination temperature for preparation of the catalysts. A correlation between the photo-stability of surface chromate species and the calcination temperatures for catalyst preparation has been established. Deeper insight on the electronic states of surface chromate species on Phillips type catalysts has been achieved by high resolution XPS methods.Photo-stability of surface chromate species (Cr(VI)O_x,_surf) on Phillips catalysts isothermally prepared from PCP120 precursor at various temperatures between 200 and 800°C was investigated by high resolution XPS method. The photo-stability of Cr(VI)O_x,_surf was found to be significantly dependent on the calcination temperature for preparation of the catalysts. A correlation between the photo-stability of surface chromate species and the calcination temperatures has been successfully established. ▪

Keywords: Photo-stability; Chromate species; X-ray photoelectron spectroscopy (XPS); Phillips CrO; _x; /SiO; ₂; catalyst; Ethylene polymerization; Chromium(III) acetate

Tunable dimerization of α-methylstyrene catalyzed by acidic ionic liquids by Qinghai Cai; Jing Li; Fuxing Bao; Yongkui Shan (pp. 139-143).

Dimerization of α-methylstyrene (AMS) catalyzed by ionic liquids and the effects of different organic solvents on the catalytic reaction were investigated. The results show that ionic liquids such as alkylaminium-chloroaluminate and alkylaminium-ferric chloride are effective catalysts for the dimerization. AMS conversion of 100% was achieved when using alkylaminium-chloroaluminate chloride as catalyst. The selectivity of saturated dimer 1,1,3-trimethyl-3-phenylindan is as high as about 97% in the absence of organic solvents. Moreover, the raw material was mainly converted to unsaturated dimers 4-methyl-2,4-diphenyl-1-pentene and 4-methyl-2,4-diphenyl-2-pentene in the presence of several polar solvents such as tertiary amyl alcohol or tertiary butanol, although the reaction rate of the AMS conversion became much lower. Thus, AMS dimerization can be tuned to produce either cyclic dimers or linear dimers by adding polar solvents or omitting them.

Keywords: α-Methylstyrene; Dimerization; Effect of solvent; Catalysis; Ionic liquids; Alkylaminium-chloroaluminate; Alkylaminium-ferric chloride

Vapor-phase Beckmann rearrangement of cyclohexanone oxime over B₂O₃/TiO₂–ZrO₂: the effect of catalyst calcination temperature and solvent by Dongsen Mao; Guanzhong Lu; Qingling Chen (pp. 145-153).

The effect of calcination temperature (500–700°C) on the performance of B₂O₃/TiO₂–ZrO₂ catalyst for vapor-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam was investigated. Catalysts were characterized by adsorption of nitrogen, X-ray diffraction and ammonia temperature-programmed desorption. The results indicated that the percent of acid sites of medium strength within the total acid sites and the pore size both increased with calcination temperature. Such increases led to increases of the oxime conversion and caprolactam selectivity. However, a large amount of crystalline B₂O₃ appeared after calcination at 700°C and caused the decrease of the total amount of acid sites, which resulted in remarkable decrease in the activity of the catalyst. Another part of this work focused on the effect of solvent on the catalytic performance of B₂O₃/TiO₂–ZrO₂. Solvents with various polarities were investigated for the reaction. It was found that acetonitrile, which has the highest polarity for solvents examined here, was the most effective for the formation of caprolactam. The solvent with high polarity increases the desorption rate of produced caprolactam from catalyst surface, resulting in a high selectivity to caprolactam and low catalyst deactivation rate. FT-IR measurements confirmed the efficient desorption of caprolactam induced by the attack of the acetonitrile molecule.

Keywords: Beckmann rearrangement; Cyclohexanone oxime; Caprolactam; TiO; ₂; –ZrO; ₂; mixed oxide; Boria catalyst; Calcination temperature; Acetonitrile

H₂ production by steam reforming of methanol over Cu/ZnO/Al₂O₃ catalysts: transient deactivation kinetics modeling by V. Agarwal; Sanjay Patel; K.K. Pant (pp. 155-164).

Steam reforming of methanol over a Cu/ZnO/Al₂O₃ catalyst has been investigated over the temperature range of 493–573K at atmospheric pressure in a fixed bed reactor. A series of catalysts were prepared by wet impregnation and characterized by atomic absorption spectroscopy, surface area, pore volume, pore size and X-ray diffraction technique. The X-ray photoelectron spectroscopy and thermogravimetry analysis of deactivated catalyst was done to investigate the nature of coke deposited on catalyst surface. The rate of coke formation and its influence over catalyst deactivation have also been studied. A monolayer–multilayer mechanism is proposed to model the coke formation with time and to study its effect on methanol conversion. Deactivation model was coupled with the kinetic model available in the literature to study the effect of coke formation on activity. The parameters of deactivation model for the Cu/ZnO/Al₂O₃ (10/5/85wt.%) catalyst have been determined by fitting the experimental data for methanol conversion and coke deposition. This model achieved the key objective of predicting the experimental observation with 95% accuracy.

Keywords: Cu/ZnO/Al; ₂; O; ₃; catalyst; Hydrogen production; Kinetics; Deactivation; Coke

Catalytic properties and structures of nano-amorphous Ni–B alloys affected by annealing temperatures by Zheng Jiang; Hongwei Yang; Zheng Wei; Zhi Xie; Wenjie Zhong; Shiqiang Wei (pp. 165-171).

The catalytic activities of nano-amorphous Ni–B alloy catalysts prepared by chemical reduction and then annealed at various temperatures were investigated by using the benzene hydrogenation as a probe reaction. The results indicated that the benzene conversion (63%) and turnover frequency (0.67s⁻¹) reached a maximum for the nano-amorphous Ni–B alloy catalyst annealed at an optimized temperature of 623K. Such values were about 110 and 70% higher than those of the as-prepared one. A high annealing temperature of 773K led to a dramatic decrease in the catalytic activity of Ni–B alloy. From the XAFS and XRD results, we confirmed that the nano-amorphous Ni–B alloy annealed at 573 or 623K was composed of nano-crystalline Ni and crystalline Ni₃B. After being annealed at the higher temperature of 773K, the Ni–B alloy may result in the decomposition of crystalline Ni₃B into crystalline Ni and aggregation of nano-crystalline Ni into crystalline Ni with a large size. Our results indicated that the nano-crystalline Ni showed higher activity and turnover frequency than nano-amorphous Ni–B alloy did. We propose that the order of catalytic activity of benzene hydrogenation for various phases in the amorphous Ni–B alloy is as follows: nano-crystalline Ni>nano-amorphous Ni–B alloy>crystalline Ni≈crystalline Ni₃B.

Keywords: Nano-amorphous Ni–B alloy; XAFS; XRD; Catalytic activity; Structure

Fischer–Tropsch synthesis on RuTi intermetallic compound catalyst by Takayuki Komatsu; Yukino Fukui (pp. 173-180).

Catalytic properties of Ru-based intermetallic compounds are studied for Fischer–Tropsch synthesis. Among unsupported compounds between ruthenium and other transition metals, RuTi gave the highest selectivity to higher hydrocarbons. Preparation of fine particles of RuTi on silica gel was tried by co-impregnation and chemical vapor deposition methods. The latter method using the vapor of titanocene dichloride and ruthenium supported on silica gel gave fine particles of RuTi intermetallic compound. This supported RuTi catalyst showed higher selectivity than that of Ru/SiO₂ for the formation of higher hydrocarbons. H₂–D₂ equilibration indicated that RuTi has low hydrogen dissociation activity compared with that of Ru. IR spectra indicated that RuTi particles adsorbed carbon monoxide more strongly than Ru particles on silica gel.

Keywords: Intermetallic compound; Ruthenium; Fischer–Tropsch synthesis; Chemical vapor deposition

Oscillation theory by Leonid B. Datsevich (pp. 181-185).

In previous papers [L.B. Datsevich, Appl. Catal. A 250 (2003) 125–141; L.B. Datsevich, Catal. Today 79–80 (2003) 341–348; L.B. Datsevich, Appl. Catal. A 247/1 (2003) 101–111] devoted to the oscillatory motion of liquid in catalyst pores in gas–liquid reactions with gas and/or heat production, some directions of catalyst and process development have been discussed. It has been supposed that modification of the pore structure of catalysts can provoke oscillations in pores, leading to an acceleration of internal mass transfer and to an increase in the overall reaction rate. The present paper deals with a confirmation of this theoretical conclusion. It shows that an unsophisticated change in the pore structure can intensify the process of 1-octene hydrogenation to n-octane on a Ni tablet catalyst up to three times.

Keywords: Multiphase catalysis; Oscillation model; Pore optimisation; Process intensification

Catalytic oxidation with air of cyclododecanone and 3,3,5-trimethylcyclohexanone to the corresponding linear dicarboxylic acids over synthetic carbons by Florence Gauthard; Blazej Horvath; Pierre Gallezot; Mich�le Besson (pp. 187-193).

Cyclododecanone and 3,3,5-trimethylcyclohexanone were oxidised with air in an attempt to prepare 1,12-dodecanedioic and 2,2,4- or 2,4,4-trimethyladipic acids, respectively. These long-chains dicarboxylic acids are useful for polymer synthesis. Oxidation was conducted on metal-free and platinum-loaded carbon catalysts activated in air or CO₂. The influence of catalyst preparation and of reaction parameters on the activity and selectivity to the corresponding linear diacids has been studied. In parallel with oxidation reaction giving the long-chain C₁₂ diacids, oxidative cleavage reactions occur leading to C₄–C₁₁ dicarboxylic acids. The air-activated carbon SA yielded the best selectivity to the desired long-chains diacids (25–30%). Selectivity was also improved by operating at 125°C and 40bar of total air pressure and by diluting the cyclic ketones in acetic acid, pure or containing 20% water.

Keywords: Synthetic carbon; Activation; Catalytic oxidation; Cyclic ketones

Low-temperature water-gas shift reaction of plate-type copper-based catalysts on an aluminum plate prepared by electroless plating by Choji Fukuhara; Hiromichi Ohkura; Kaichi Gonohe; Akira Igarashi (pp. 195-203).

The water-gas shift reaction at low-temperature is an important chemical reaction for the manufacture of hydrogen. In view of increasing demands for hydrogen in the future hydrogen-oriented society, the CO shift converter requires a quick load response, downsized reactor dimensions, and an effective exchange of heat energy. The wall-type reactor can respond to such demands. This study investigated the CO shift performance of a copper-based catalyst, which was prepared by electroless plating consisting of zinc plating and copper plating, as a plate-type catalyst for the wall-type CO shift converter. The shift properties of the prepared catalyst varied according to metal species used in the intermediate plating prior to the copper plating. The plate-type Cu–Fe/Zn catalyst using iron for the intermediate plating presented superior shift performance. This catalyst had increased activity when oxidized prior to reaction, and was comparable or, at higher temperatures, superior to a commercial granular catalyst. Results also showed that the activity deterioration of the Cu–Fe/Zn catalyst at 250°C was relatively low, although an ordinary copper-based catalyst suffers a high deterioration of activity during a reaction. Physicochemical measurement of the plated layer showed that it contained a large quantity of zinc derived from the displacement plating. Such zinc would move from the bulk layer to the surface layer if the catalyst drying process after plating and the pretreatment before reaction were performed in an oxidative atmosphere. The existence of zinc in proximity to copper appeared to form some reaction sites with high shift activity.

Keywords: Structured catalyst; Copper-based catalyst; Water-gas shift reaction; Electroless plating; Physicochemical property; Oxidation

Synthesis of dimethyl carbonate from methanol, propylene oxide and carbon dioxide over KOH/4A molecular sieve catalyst by Yuan Li; Xin-qiang Zhao; Yan-ji Wang (pp. 205-208).

The synthesis of dimethyl carbonate (DMC) from methanol, propylene oxide (PO) and carbon dioxide (CO₂) over supported catalysts was studied for the first time. A series of supported solid base catalysts were prepared by impregnation and their catalytic activities were evaluated. It was found that KOH/4A molecular sieve was the most effective catalyst. The effects of various conditions, such as reaction time, reaction temperature, molar ratio of the reactants and KOH loading, on the yield of DMC was investigated. It was proposed that DMC was formed from the transesterification of propylene carbonate (PC) with methanol, where PC was synthesized from PO and carbon dioxide. Methanol was favorable to such cycloaddition of PO with CO₂. Under the optimized conditions, PO was converted completely and the yield of DMC was up to 16.8%.

Keywords: Dimethyl carbonate; Propylene oxide; Methanol; Carbon dioxide; Supported catalyst

Ru, Os and Ru–Os supported on mesoporous silica doped with zirconium as mild thio-tolerant catalysts in the hydrogenation and hydrogenolysis/hydrocracking of tetralin by D. Eliche-Quesada; J.M. M�rida-Robles; E. Rodr�guez-Castell�n; A. Jim�nez-L�pez (pp. 209-221).

Monometallic Ru and Os catalysts and bimetallic Ru–Os catalysts with molar ratios (8:1, 4:1 and 1:1) supported on a mesoporous silica doped with zirconium (molar ratio Si/Zr=5) with a total metal loading of 5wt.% were prepared by the wet incipient impregnation method, then dried at 120°C and finally reduced with hydrogen at 400°C. After a complete characterisation with XRD, XPS, N₂ adsorption–desorption volumetry, H₂-TPR and NH₃-TPD, the catalysts were tested in the hydrogenation and ring opening of tetralin at high hydrogen pressure. Catalysts with a high Ru content display excellent hydrogenation properties even at low reaction temperatures (200–295°C). However, catalysts with a high Os content display weak hydrogenation activity but a very good hydrogenolysis/hydrocracking activity (30–40% of cracking compounds). This high level of activity is explained by the strength of the acid centres. Catalysts with a high Ru content maintain their catalytic performance in the presence of 600ppm of dibenzopthiophene in the feed at 320°C, but all other catalysts are partially or totally deactivated. All catalysts are irreversibly poisoned with a feed containing 1000ppm of dibenzothiophene.

Keywords: Ruthenium; Osmium; Hydrogenation; Hydrogenolysis/hydrocracking; Tetralin; MCM-41; XPS

Catalytic engineering of carbon nanotube production by Zhixin Yu; De Chen; B�rd T�tdal; Tiejun Zhao; Yingchun Dai; Weikang Yuan; Anders Holmen (pp. 223-233).

The impact of some engineering aspects such as space velocity, catalyst metal loading, hydrogen, and temperature on carbon nanotube (CNT) production rate, productivity, and morphology in carbon monoxide disproportionation has been studied. The morphology and quality of the CNTs produced were examined by high resolution transmission electron microscopy (TEM). It was found that space velocity and metal loading have significant effects on the production rate and CNT productivity. The presence of H₂ dramatically increased the productivity, but altered the CNT structure. The synthesis temperature also influenced the carbon productivity and structure. The results were interpreted according to the traditional model for CNT growth, and the implications for large-scale CNT production were suggested.

Keywords: Space velocity; Metal loading; Production rate; Productivity; Large-scale synthesis

Contrast activities of four alumina and alumina–silica-supported nickel–molybdenum sulfide catalysts for deep desulfurization of gas oils by Naoyuki Kunisada; Ki-Hyouk Choi; Yozo Korai; Isao Mochida; Koji Nakano (pp. 235-239).

Four NiMoS catalysts on conventional alumina (NMA-1), acidified alumina (NMA-2), and on two alumina–silica mixtures of different preparation procedures with 70% (NMASA1-70) and 50% (NMASA2-50) silica supports were prepared. In HDS and HDN of straight run gas oil (SRGO) and its desulfurized oil (HSRGO), their selective activities toward above reactions were compared since the best combination of two catalysts in two-layer bed was expected to achieve deep HDS of SRGO rather easily. NMA-1 removed reactive sulfur species effectively and refractory sulfur species moderately but failed to remove nitrogen species in SRGO. The catalyst was not effective to remove refractory sulfur species in HSRGO to achieve the total sulfur level of less than 10ppm S in the second layer. NiMoS on acidified alumina (NMA-2) and NMASA1-70 removed nitrogen species very effectively but sulfur species in SRGO were not so efficiently removed. Both catalysts were very active for HSRGO to attain 10ppm sulfur level. Rapid HDN in SRGO over the catalysts appears to retard HDS of SRGO, leaving even reactive sulfur species unreacted. Among the catalysts, NiMoASA2-50 was very active for all reactions to achieve less than 10ppm from SRGO via two stages. The rapid HDN over the particular catalyst allowed the effective HDS after the rapid completion of HDN. Such contrast activities of four catalysts are compared as regards their surface area, acidity and NiMoS location on the support particles. NiMo on alumina or on the border of acidified alumina and silica of right content is most activated for HDN as well as HDS. Acidity appears essential for HDN. Larger surface area of the particular alumina–silica support is certainly favorable for both HDS and HDN. The larger content of silica in NMASA1-70 may not be favorable for high dispersion of NiMoS to show higher activity for HDS while HDN progresses.

Keywords: Hydrodesulfurization; NiMo catalyst; Acidity; Gas oil

Nanocrystalline zirconia as catalyst support in methanol synthesis by Xin-Mei Liu; G.Q. Lu; Zi-Feng Yan (pp. 241-245).

Nanocrystalline zirconia was synthesized and used as catalyst support for methanol synthesis. The nanocrystallite particles have new physical and textural properties which are critical in determining the catalytic performance. Nanocrystalline zirconia changes the electronic structure and affects the metal and support interactions on the catalyst, leading to facile reduction, intimate interaction between copper and zirconia, more corner defects and oxygen vacancies on the surface of the catalyst. All these changes are beneficial to the reaction of methanol synthesis from hydrogenation of CO₂. As a result, higher conversion of CO₂ and selectivity of methanol are achieved compared to the catalysts prepared by conventional co-precipitation method.

Keywords: Hydrogenation of CO; ₂; Nanocrystalline zirconia; Methanol synthesis; Solid-state reaction

Photoelectrocatalytic degradation of oxalic acid in aqueous phase with a novel three-dimensional electrode-hollow quartz tube photoelectrocatalytic reactor by Taicheng An; Guiying Li; Xihai Zhu; Jiamo Fu; Guoying Sheng; Zhu Kun (pp. 247-256).

Taking oxalic acid as an index, we investigated photoelectrocatalytic degradation of organic pollutants by using a newly designed photoelectrocatalytic reactor coupled by a three-dimensional electrode reactor with a packed-bed hollow quartz tube photocatalytic reactor. The efficiency of the photoelectrocatalytic degradation was determined with COD removal from the tested wastewater; the COD removal efficiencies were considerably dependent on the cell voltage and the concentration of the supporting electrolyte. The experimental results showed that oxalic acid could be degraded more efficiently by photoelectrocatalytic process than individually by photocatalytic or electrochemical oxidation in the photoelectrocatalytic reactor. The introduction of hollow quartz tubes into the three-dimensional electrode – packed-bed photoelectrocatalytic reactor could provide a solution to the earlier drawbacks: the inability to treat the high concentration and low-transmittance wastewater by photocatalytic technology.

Keywords: Photoelectrocatalytic; Photocatalytic; Three-dimensional electrode; Reactor; Oxalic acid

Synthesis of β-Mo₂N_0.78 hydrodesulfurization catalyst in mixtures of nitrogen and hydrogen by Shuwen Gong; Haokan Chen; Wen Li; Baoqing Li (pp. 257-261).

β-Mo₂N_0.78 catalyst was synthesized via the temperature-programmed reaction between N₂–H₂ mixture gases and molybdenum oxide. The influences of the synthesis conditions on catalyst structure and catalyst hydrodesulfurization (HDS) behavior were also studied. H₂-TPR experiment was used to investigate the structure changes of catalyst before and after HDS reaction. Preparation results showed that β-Mo₂N_0.78 can be formed at a final nitriding temperature of 923–1023K and N₂/H₂ ratios of 1/4–1/1. The formation of MoO₂ intermediate results in the low surface area β-Mo₂N_0.78 product. The thiophene HDS result indicated that β-Mo₂N_0.78 also has HDS catalytic activity. Its bulk structure is retained after HDS reaction although sulfur replaces the surface oxygen as determined by TPR examination. Pre-reduction does not improve the HDS activity of passivated β-Mo₂N_0.78 although hydrogen reduction can remove the oxygen from surfaces. The catalytic activity of passivated nitride decreases with the increasing of final nitriding temperature from 923 to 1123K, and there is a suitable N₂–H₂ ratio to prepare high activity β-Mo₂N_0.78 catalyst.

Keywords: Catalyst; β-Mo; ₂; N; _0.78; Hydrodesulfurization

CO₂CH₄ reforming over NiO/γ-Al₂O₃ in fixed/fluidized-bed multi-switching mode by Xin Chen; Kazunori Honda; Zhan-Guo Zhang (pp. 263-271).

CO₂ reforming of methane over NiO/γ-Al₂O₃ catalyst was investigated in a fixed/fluidized-bed multi-switching mode at 1073K, 1atm, a GHSV of 93,750h⁻¹ and a fixed ratio of CO₂/CH₄=1.5. When the mode-switching reforming test was carried out in the following mode order: fixed-, fluidized-, fixed-bed again, and finally fluidized-bed, the CH₄ conversion alternated between low and high (48, 92, 75, 89%). The form and amount of carbon deposited on the spent catalysts recovered from the mode-switching experiments that ended at different times of the different modes were evaluated by TG, TPO and XPS analyses. The results showed that not only was less carbon formed in the fluidized-bed reforming, but gasification of the carbon, especially the CC species, was also more significant under the fluidized-bed operation. Furthermore, the H₂-TPR, H₂-TPD and XPS analyses of the spent catalysts showed that fluidizing the catalyst particles in the bed under the reforming reaction conditions is favorable to improve the reduction extent of the catalyst and to increase the surface area of active metallic nickel. Possible reasons for all these observations were explored and are discussed in this paper.

Keywords: CO; ₂; CH; ₄; reforming; Fixed/fluidized multi-mode-switching; NiO/γ-Al; ₂; O; ₃; catalyst

Catalytic steam reforming of ethanol to produce hydrogen and acetone by Toshiya Nishiguchi; Tomoaki Matsumoto; Hiroyoshi Kanai; Kazunori Utani; Yasuyuki Matsumura; Wen-Jie Shen; Seiichiro Imamura (pp. 273-277).

Steam reforming of ethanol over CuO/CeO₂ was studied. Acetaldehyde and hydrogen were mainly produced at 260°C. At 380°C, acetone was the main product, and 2mol of hydrogen was produced from 1mol of ethanol. The formation of hydrogen accompanied by the production of acetone was considered to proceed through the following consecutive reactions: dehydrogenation of ethanol to acetaldehyde, aldol condensation of the acetaldehyde, and the reaction of the aldol with the lattice oxygen [O_(S)] on the catalyst to form a surface intermediate, followed by its dehydrogenation and decarboxylation. The overall reaction was expressed by 2C₂H₅OH+H₂O→CH₃COCH₃+CO₂+4H₂. Ceria played an important role as an oxygen supplier. The addition of MgO to CuO/CeO₂ resulted in the production of hydrogen at lower temperatures by accelerating aldol condensation.

Keywords: Ethanol; Steam reforming; Acetone; Hydrogen; CuO/CeO; ₂

Oxidative desulfurization and denitrogenation of a light gas oil using an oxidation/adsorption continuous flow process by Atsushi Ishihara; Danhong Wang; Franck Dumeignil; Hiroshi Amano; Eika Weihua Qian; Toshiaki Kabe (pp. 279-287).

The oxidation of undesirable sulfur compounds present in a desulfurized light gas oil (LGO; sulfur content: 39ppm) was performed with tert-butyl hydroperoxide ( t-BuOOH) as the oxidant in the presence of a 16wt.% MoO₃/Al₂O₃ catalyst. The oxidation activity of the sulfur compounds in the light gas oil increased when the O/S molar ratio increased up to 15; the activity slightly decreased for higher ratios. This optimal ratio was significantly higher that the stoichiometric one (=2) due to parallel oxidation reactions of olefins, etc., in the LGO. Further, we compared the oxidation reactivity of dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT), and trimethyldibenzothiophene (C₃-DBT), which are refractory compounds present in the light gas oil. The reactivity decreased in the order DBT≫4,6-DMDBT>C₃-DBT, irrespective of the WHSV and the temperature. Subsequent mathematical treatment revealed that the oxidative reaction of each sulfur compound follows a first-order kinetics. We found an activation energy of 32±2kJmol⁻¹, whatever the compound, suggesting that the oxidation mechanism was the same for these compounds. Then, according to the proposed global process, the previously oxidized molecules in the treated light gas oil were further removed by adsorption over a silica gel at ambient temperature. As a result, the total sulfur content could be decreased after oxidation/adsorption to less than 5ppm. Further, N-containing model compounds were also treated according to the same procedure and the denitrogenation performance decreased in the order indole>quinoline>acridine>carbazole. Subsequently, the same process allowed decreasing the N content in the LGO from an initial value of 13.5ppm to a value of 0.8ppm, which is a remarkable result.

Keywords: Oxidative desulfurization; Oxidative denitrogenation; t; -BuOOH; DBTs; Mo/Al; ₂; O; ₃; catalyst

CALENDER (pp. 289-289).

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Applied Catalysis A, General (v.279, #1-2)