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Applied Catalysis A, General (v.319, #)

Editorial Board (pp. co2).

Contents (pp. iii-x).

Zeolite supported Pt-Ni catalysts in n-hexane isomerization by Maura H. Jordão; Vicemario Simões; Dilson Cardoso (pp. 1-6).

Bifunctional catalysts containing Ni and Pt supported in HUSY zeolite were prepared by competitive ion exchange method. The catalysts were characterized and evaluated in the n-hexane isomerization reaction. The Pt monometallic catalysts were more stable, active and selective in this reaction than that containing only Ni. However, the Pt-Ni bimetallic catalysts presented higher activity than the Pt monometallic catalyst. In addition, the bimetallic catalysts were more selective to the formation of di-branched alkanes. ▪Bifunctional catalysts containing 1–4wt.% of Ni and Pt in a metallic form supported in an ultrastabilized HUSY zeolite were prepared by competitive ion exchange method. The catalysts were characterized by ICP and TPR techniques to obtain metal contents and conditions for the reduction steps, respectively, and evaluated in the n-hexane isomerization reaction. The Pt monometallic catalysts were more stable, active and selective in this reaction than that containing only Ni. However, it was observed that maintaining the same total metal loading (1 or 2wt.%) and varying the proportion of these metals, the Pt-Ni bimetallic catalysts containing 20–30% Pt presented higher activity in the mentioned reaction than the Pt monometallic catalyst. In addition, the bimetallic catalysts were more selective to the formation of di-branched alkanes, that is, products with higher octane number.

Keywords: Bimetallic catalyst; Zeolite; Di-branched alkanes; n; -Hexane isomerization; TPR

A new fast method for ceramic foam impregnation: Application to the CCVD synthesis of carbon nanotubes by Anne Cordier; Fabrice Rossignol; Christophe Laurent; Thierry Chartier; Alain Peigney (pp. 7-13).

A new process that allows to prepare, in a single step, good washcoats of catalytic materials in reticulated ceramic foams is reported. Viscous slurries made of finely divided powders dispersed in different media are used to obtain deposits which cover the total surface of foams with good adhesion. Their catalytic activity towards the CCVD synthesis of CNT is verified. ▪A new process that allows preparing, in a single step, good washcoats of catalytic materials for the catalytic chemical vapour deposition (CCVD) synthesis of carbon nanotubes (CNTs) in reticulated ceramic foams is reported. It is shown that the washcoats, obtained by impregnation using viscous slurries made of finely divided powders dispersed in different media, cover the total surface of foams with good adhesions. The catalytic activity with regards to the CNT synthesis is finally verified, showing that our new fast impregnation process makes possible to get materials with final architectures suitable for heterogeneous catalysis applications.

Keywords: Ceramic foam; Impregnation process; Washcoat; Synthesis of carbon nanotubes

The surface and catalytic properties of titania-supported mixed PMoV heteropoly compounds for total oxidation of chlorobenzene by Albena Predoeva; Sonia Damyanova; Eric M. Gaigneaux; Lachezar Petrov (pp. 14-24).

The catalytic behavior of heteropoly catalysts based on supported PMoV heteropoly compounds with Keggin structure was evaluated in the reaction of total oxidation of Cl-benzene. Increasing the number of introduced V atoms in heteropolyanion leads to increasing its thermal stability. The presence of vanadium centers is responsible for the increased activity of titania-supported catalysts, being seen in the figure. ▪Heteropoly catalysts based on the mixed PMoV heteropoly compounds (HPC) with Keggin structure were prepared. The behaviors of the samples (in bulk and in titania-supported form) as a function of temperature treatment in the range of 343–923K and the number of introduced V atoms into the heteropoly anions were studied. The catalytic activity of titania-supported catalysts was evaluated in the reaction of total oxidation of Cl-benzene at 473K. The samples were characterized by S_BET method, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The XRD, IR and Raman results provided clear evidence that V indeed is incorporated into the Keggin unit. Introduction of one V atom into heteropolyanion leads to a significant increase of its thermal stability. On the other hand, the presence of the vanadium centers appears to be responsible for the increased activity of the titania-supported samples in the reaction of total oxidation of chlorobenzene.

Keywords: Mixed PMoV heteropoly compounds; Total oxidation of Cl-benzene; XRD; FT-IR; Raman spectroscopy; XPS

HDS, HDN, HDA, and hydrocracking of model compounds over Mo-Ni catalysts with various acidities by Lianhui Ding; Ying Zheng; Zisheng Zhang; Zbigniew Ring; Jinwen Chen (pp. 25-37).

The hydrogenation and hydrocracking performances of a series of MoNi/Al₂O₃ catalysts were studied. The addition of zeolites to the catalysts can greatly improve the hydrodesulfurization and hydrodenitrogenation activities, while the hydrocracking of hexadecane also increased proportionally with the zeolite content. The performance of the catalysts is closely associated with the morphology of sulfided catalysts. The figure shows the distribution of the length of MoS₂ slabs for the four sulfided catalysts. ▪The hydrogenation and hydrocracking performances of a series of MoNi/Al₂O₃ catalysts were evaluated with 4,6-dimethyl dibenzothiophene (4,6-DMDBT), 1-methylnaphthalene, pyridine, and hexadecane as model compounds. Different materials which involved amorphous silica–alumina, and hydrothermally treated zeolite beta and zeolite Y were introduced as part of the catalyst supports. The catalysts were characterized by BET, NH₃ temperature programmed desorption (NH₃-TPD), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The addition of zeolites in the catalysts could greatly improve the hydrodesulfurization and hydrodenitrogenation activities, but it had have little enhancement in the hydroconversion of 1-methylnaphalene. The comparison among zeolite beta containing catalysts with various zeolite content (5–20wt%) indicated that the optimum hydrogenation activity was achieved by the catalyst containing 10wt% zeolite beta. A considerable amount of hexadecane was hydrocracked on zeolite containing catalysts. The hydrocracking of hexadecane proportionally increased with the zeolite content. Zeolite Y appeared to be more effective in enhancing the hydrotreating activity than zeolite beta. The high hydrogen pressure not only considerably increased hydrodearomatization activity, but also greatly suppressed the cracking of hexadecane in the feed.

Keywords: HDS; HDN; Zeolite beta; Hydrocracking; Mo-Ni; Zeolite Y

Production of ultrapure hydrogen in a Pd–Ag membrane reactor using Ru/La₂O₃ catalysts by B. Faroldi; C. Carrara; E.A. Lombardo; L.M. Cornaglia (pp. 38-46).

Ru/La₂O₃ catalysts were prepared by wet impregnation. In the Pd–Ag membrane reactor, both Ru(0.6) and Ru(1.2) catalysts were able to restore the equilibrium for the dry reforming reaction; Ru(0.6) was the most effective catalyst. The characterization data yielded clues to understand the interplay of Ru oxidation states, varying H₂ partial pressures and Ru concentration with the slight deactivation observed for Ru(1.2). ▪Ru catalysts supported on lanthanum oxide with different loadings were prepared by wet impregnation. These solids were characterized by laser Raman spectroscopy (LSR), XPS, XRD and TPR. The catalytic activity toward hydrogen production through the dry reforming of methane was determined in a fixed-bed reactor and a membrane reactor. The reaction rate expressed per gram of Ru decreased when the metal loading increased.In the Pd–Ag membrane reactor, when the sweep gas flow rate (SG) increased, the conversions overcame the equilibrium values and the difference between CH₄ and CO₂ conversions decreased. Both Ru(0.6) and Ru(1.2) catalysts were able to restore the equilibrium for the dry reforming reaction up to values of SG=30mlmin⁻¹; Ru(0.6) was the most effective catalyst. By employing a CO₂/CH₄=1 and a SG of 0.05mmols⁻¹, both a high H₂ permeation flux of 5.68×10⁻⁷mols⁻¹m⁻² and a hydrogen recovery of 80% were obtained.Both the TPR and the Raman spectroscopy data indicated the presence of Ru(III) strongly interacting with La. Significantly, this observation was further confirmed by the appearance of Ru(III) on the surface. When the Ru content increased, the higher Ru 3d binding energy component was proposed as arising from Ru(IV). Concerning the Ru(1.2) solid, the presence of Ru(IV) was detected by means of TPR experiments, in agreement with the high proportion of Ru(IV) on the surface. Therefore, a fraction of Ru loading was present in this solid as species with weaker metal–support interaction leading to the slight deactivation of this catalyst in the membrane reactor.

Keywords: Membrane reactor; Hydrogen production; Ru/La; ₂; O; ₃; CO; ₂; reforming

Low temperature water-gas shift: Characterization of Pt-based ZrO₂ catalyst promoted with Na discovered by combinatorial methods by John M. Pigos; Christopher J. Brooks; Gary Jacobs; Burtron H. Davis (pp. 47-57).

Addition of Na to Pt/ZrO₂ low temperature water-gas shift catalysts led to an important weakening of the formate CH bond, as indicated by a shift to lower wavenumbers in infrared spectroscopy. In one view, formate CH bond breaking is proposed to be the rate-limiting step of the cycle. Enhanced WGS rates and formate decomposition rates are demonstrated with Na doping. ▪In one view, CH bond breaking of the formate has been proposed to be the rate-limiting step of the low temperature water-gas shift mechanism. In combinatorial catalytic testing, enhanced water-gas shift rates were observed by incorporating Na to Pt/ZrO₂ catalysts. DRIFTS investigations suggest that electronic modification of formate was achieved, leading to an important weakening of the formate CH bond. Three separate DRIFTS investigations were carried out, including (1) dynamic formate coverage studies during steady state water-gas shift, (2) transient forward formate decomposition tests at low temperature in steam, and (3) formate H–D exchange studies in the absence of steam (i.e., reverse decomposition). In each investigation, the decomposition rate of formate was much more facile for the Na promoted catalyst relative to Pt/ZrO₂ alone.

Keywords: Zirconia (ZrO; ₂; ); Platinum (Pt); Sodium (Na); Water gas shift; Fuel processor; Hydrogen; Formate; Carbonate

The effect of MgO coating on photocatalytic activity of SnO₂ for the degradation of chlorophenol and textile colorants; the correlation between the photocatalytic activity and the negative shift of flatband potential of SnO₂ by J. Bandara; R.A.S.S. Ranasinghe (pp. 58-63).

Coating of a thin MgO layer on SnO₂ nanocrystalline particles transforms photocatalytically inactive SnO₂ to an active photocatalyst. Negative shift of flatband (FB) potential of SnO₂ and retardation of charge recombination were observed with coating of a thin MgO layer on SnO₂ particles. Hence, the promoting effects of MgO layer on SnO₂ catalyst for the degradation of colorants and chlorophenol in aqueous phase were assigned to both slow charge recombination and to the negative shift of FB potential.▪SnO₂ is a totally inactive photocatalyst for the degradation of 2-chlorophenol (2CP) and textile colorant Mercurochrome (MC) at acidic pH values, but shows feeble photocatalytic activity for the degradation of said pollutants at basic pH values. However, coating of a thin MgO layer on SnO₂ nanocrystalline particles transforms photocatalytically inactive SnO₂ to an active photocatalyst. A negative shift of the flatband (FB) potential of SnO₂ was observed with the increase of pH values and coating of a thin MgO layer on SnO₂ particles. Further we noticed the retardation of charge recombination on SnO₂ upon MgO coating and increase in pH values. Hence, the promoting effects of MgO layer on SnO₂ catalyst for the sensitized degradation of colorants and chlorophenol degradation in aqueous phase were assigned to both slow charge recombination and to the negative shift of FB potential.

Keywords: Photodegradation; Charge recombination; MgO; SnO; ₂; Mercurochrome; Chlorophenol; Flatband

Basic sites in zeolites followed by IR studies of NO⁺ by Barbara Gil; Karolina Mierzyńska; Monika Szczerbińska; Jerzy Datka (pp. 64-71).

Basic properties of zeolites of faujasite type in sodium and protonic forms as well as in zeolites steamed and dehydroxylated was investigated. NO⁺ was used as a probe for basic sites. Three kinds of basic sites (framework oxygens) of various basicity were found in zeolite NaY. The basicity of framework oxygens was modified by the adsorption of electrondonor organic molecules. Spectra of increasing amount of NO⁺ and of NO₃⁻ (spectra a–d) formed in zeolite NaY. ▪The basic properties of zeolitic oxygens were examined by IR studies of NO⁺ ions. NO⁺ were formed by the disproportionation of N₂O₄ (N₂O₄→NO⁺+NO₃⁻). NO⁺ were stabilized by zeolitic oxygens and NO₃⁻ by the zeolitic cations or positively charged extraframework Al species. The spectra of NO⁺ in zeolite NaY show three maxima that indicate the presence of oxygens of various negative charges (of various basicity). These oxygens may have various numbers of AlO₄⁻ and/or various numbers of Na⁺ in close vicinity. The basic oxygen content was estimated as 15sites/u.c. which is less than 5% of all the oxygen atoms in faujasite-type zeolite. In the presence of water, N₂O₄ disproportionates producing: NO₃⁻, NO₂⁻ and strongly acidic Si–OH–Al groups. Similarly, NO⁺ reacts with water, forming NO₂⁻ and Si–OH–Al. The presence of strongly acidic Si–OH–Al decreases the basicity of the zeolitic oxygens. The basicity of the zeolitic oxygens diminishes also with the Si/Al, due to the decreased amount of AlO₄⁻. NO⁺ were also formed in zeolites NaHY but like NO₃⁻, their amount decreased with the degree of Na/H exchange, i.e., with the amount of Na⁺ cations, which are supposed to stabilize NO₃⁻ ions. In zeolites NaHY the basicity of oxygens decreased with the degree of Na/H exchange, due to replacement of Na⁺ cations by more electronacceptor H⁺ ions, but this effect is smaller than the variation of Si/Al The basicity of the oxygens in dehydroxylated zeolite NaHY was found to be comparable (but somewhat lower) to that in zeolite NaY. Steamed zeolite HY (which is known to contain the most strongly acidic hydroxyls) showed the lowest basicity of the zeolitic oxygens. IR studies showed also that the basicity of the zeolitic oxygens in zeolite NaY increased in the presence of electrondonor organic molecules such as CCl₄ and chloroform, which we relate to some “neutralization” of the zeolitic cations.

Keywords: Zeolite basicity; IR spectroscopy; NO; ⁺

Synthesis and characterization of novel bead-shaped insoluble polymer-supported tri-site phase transfer catalyst and its efficiency in N-alkylation of pyrrole by Eagambaram Murugan; Prakash Gopinath (pp. 72-80).

New bead-shaped insoluble polymer-supported multi-site (tri-site) phase transfer catalyst (PS-MPTC) viz., polymer-supported 4-(2,2,2-tris[triethylammoniummethylene chloride]-1-hydroxy ethyl) phenylether (PSTTEACHPE) has been synthesized and its catalytic efficiency was ascertained by N-alkylation of pyrrole with benzylchloride using 30% (w/v) aqueous sodium hydroxide at 60°C. Investigations were also made on kinetic variables such as stirring speed, [substrate], [catalyst], [NaOH] and temperature. Based on the observed kinetic and thermodynamic results, an interfacial mechanism was proposed for the N-alkylation of pyrrole.▪A new bead-shaped insoluble polymer-supported multi-site (tri-site) phase transfer catalyst (PS-MPTC) viz., polymer-supported 4-(2,2,2-tris[triethylammoniummethylene chloride]-1-hydroxy ethyl) phenylether (PSTTEACHPE) has been synthesized by following a simplified procedure. Initially, polystyrene-based cross-linked beads was prepared by allowing the reaction using 2% divinylbenzene (as a cross linking monomer), 25% vinylbenzyl chloride (as a functional monomer) and styrene (as supporting monomer) to proceed through a suspension copolymerization method. The obtained terpolymer beads containing pendant benzyl chloride groups were condensed with 4-(2,2,2-tris[triethylammonium methylene chloride]-1-hydroxy ethyl) phenol, followed by quaternization using triethylamine, resulting in the formation of polymer-supported 4-(2,2,2-tris[triethylammoniummethylene chloride]-1-hydroxy ethyl) phenyl ether (PSTTEACHPE). Then the presence of tri-active site in PSTTEACHPE was examined by FT-IR,¹H NMR,¹³C NMR, [chloride ion] and SEM analyses. The comparative results of [chloride ion] and the peak intensity of C–N stretching (quaternary onium group) in FT-IR were found to increased three fold in PSTTEACHPE on comparing with their similar types of polymer-supported bead-shaped single-site PTC (PS-BSPTC); thus we confirmed the presence of three active sites. The surface morphology study through SEM shows that the PSTTEACHPE is heterogeneous in nature with tiny nodules; whereas the single-site PS-BSPTC shows smooth homogeneous nature; this is an another piece of evidence for the availability of more numbers of active sites in PSTTEACHPE. Further, the catalytic efficiency of this new PSTTEACHPE was ascertained by N-alkylation of pyrrole with benzylchloride using 30% (w/v) aqueous sodium hydroxide at 60°C. The pseudo-first order rate constants were calculated by following the disappearance of pyrrole through gas chromatography. The observed rate constants were found to be three-fold higher for PSTTEACHPE than with PS-BSPTC, which again confirmed the presence of three active-sites. Investigations were also made on kinetic variables such as stirring speed, [substrate], [catalyst], [NaOH] and temperature; it is observed that each variable is influenced the rate of reaction. From the Arrhenius plot, the activation energy and thermodynamic parameters were evaluated as 12.44, −7.99, 10.99 and 13.25kcalmol⁻¹ for E_a, Δ S^#, Δ H^# and Δ G^# respectively. Based on the observed kinetic and thermodynamic results, an interfacial mechanism was proposed for the N-alkylation of pyrrole.

Keywords: Polymer-supported multi-site PTC; N; -Alkylation; Interfacial mechanism

Pt-Ru fuel cell catalysts subjected to H₂, CO, N₂ and air atmosphere: An X-ray absorption study by C. Roth; N. Benker; M. Mazurek; F. Scheiba; H. Fuess (pp. 81-90).

A novel reactor/furnace set-up has been used for in situ XANES and EXAFS measurements of Pt-Ru fuel cell catalysts in different atmospheres at elevated temperatures resembling fuel cell conditions, but without the electrochemical potential. The results obtained have certain implications for the catalysts long-term stability and enhanced CO tolerance in the different bimetallic systems. ▪ In situ X-ray absorption spectroscopy (XAS) measurements were carried out on commercial carbon-supported Pt, Ru and Pt-Ru alloy electrocatalysts as well as a Pt/Ru mixture electrocatalyst in a specifically designed reactor/furnace set-up at the Pt L₃ and the Ru K edge. The catalysts were heated to 100°C and subjected to different atmospheres – 5% H₂/N₂, 5% CO/N₂, N₂, air – of interest for fuel cell operation. X-ray absorption spectroscopy was used to follow changes in the catalyst structure, most importantly particle growth, oxidation, and (de-)alloying. Alloying is observed to be advantageous, as it decreases particle growth and oxidation tendency in the catalysts. Initially, all electrocatalysts contained large amounts of the respective oxides, as indicated by pronounced white-line intensities in the XANES spectra, whereas the catalysts were reduced to the metallic state upon exposure to hydrogen. In CO atmosphere, however, ruthenium oxides remain stable, depending on the Pt to Ru site distribution: it is assumed that Pt in contact with Ru acts as a “catalyst” for the reduction of ruthenium oxides and strengthens the Ru–CO bond favouring it over Ru-O (ligand effect). Consequently, the share of ruthenium oxides in the Pt-Ru alloy decreases in 5% CO/N₂, whereas for the Pt/Ru mixture and the pure Ru it does not change significantly.

Keywords: Electrocatalysts; Fuel cell; Heat-treatment; In situ; Pt; Pt-Ru; X-ray absorption spectroscopy

Homogeneous catalytic oxidation of propene to acetone and butene-1 to butanone in the presence of palladium and molybdovanadophosphoric heteropoly acid by Elena G. Zhizhina; Marina V. Simonova; Viktor F. Odyakov; Klavdii I. Matveev (pp. 91-97).

Oxidation of propene to acetone and butene-1 to butanone in aqueous solutions was studied in the presence of homogeneous catalysts Pd+HPA- x (HPA- x=H3+_xPV_xMo12−_xO₄₀ having Keggin composition, x=1−4). The selectivity of oxidation of propene is >99%, and butene-1 is >98%. Alkenes are also successfully oxidized in the presence of solutions of modified high-vanadium non-Keggin HPA- x′ ( x′>4). The HPA- x′ solutions have improved thermal stability and are very promising for the processes of oxidation of the lower alkenes. Kinetic peculiarities of oxidation of both alkenes in the presence of solutions of HPA- x′ and HPA- x are similar.▪Oxidation of propene to acetone and butene-1 to butanone in aqueous solutions was studied in the presence of homogeneous catalysts Pd+HPA- x (HPA- x=H3+_xPV_xMo12−_xO₄₀ having Keggin composition, x=1–4). The reaction order with respect to alkenes is 1, to palladium is 0.5 for propene and 0.66 for butene-1, respectively. The rate of alkene oxidation does not depend on concentration of HPA- x and acidity of catalyst solution. Alkenes are also successfully oxidized in the presence of new catalysts Pd+HPA- x′ containing modified high-vanadium non-Keggin HPA- x′ ( x′>4). The HPA- x′ solutions have improved thermal stability and are very promising for oxidation of the lower alkenes. Kinetic peculiarities of oxidation of both alkenes in the presence of solutions of HPA- x′ and HPA- x are similar.

Keywords: Catalytic oxidation; Propene; Acetone; Butene-1; Butanone; Heteropoly acids

Influence of reaction conditions on catalyst composition and selective/non-selective reaction pathways of the ODP reaction over V₂O₃, VO₂ and V₂O₅ with O₂ and N₂O by Evgenii V. Kondratenko; Olga Ovsitser; Joerg Radnik; Matthias Schneider; Ralph Kraehnert; Uwe Dingerdissen (pp. 98-110).

The effect of reaction conditions on catalytic performance and composition of individual vanadium oxides (V₂O₃, VO₂, and V₂O₅) in the oxidative dehydrogenation of propane (ODP) at 773K was investigated by means of steady-state catalytic experiments with¹⁶O₂,¹⁸O₂ and N₂O in combination with in situ XRD, in situ UV–vis, and ex situ XPS analysis. Steady-state product selectivities over these oxides are not determined by their initial (fresh) composition but a new catalyst composition created under the reaction conditions. At similar degrees of propane conversion, this steady-state composition depends on the oxidizing agent (O₂ or N₂O). For an oxygen (C₃H₈/O₂=2) containing mixture ( X(C₃H₈)<5%, X(O₂)<10%), vanadium species are stabilized in penta- and tetravalent oxidation states, with the former being the main one. In the presence of N₂O, the oxidation state of vanadium is lower under controlled degrees of propane and oxidant conversion ( X(C₃H₈)<5%, X(N₂O)<10%). It is suggested that the difference in the oxidation state of vanadium with O₂ and N₂O is related to the lower ability of N₂O for reoxidation of reduced VO_x species as compared to O₂. Moreover, individual vanadium oxides poorly performing with O₂ become selective in the ODP reaction using N₂O. This improving effect of N₂O on the catalytic performance of vanadium oxides is related to the degree of catalyst reduction under reaction conditions and to the nature of oxygen species originated from O₂ and N₂O.Catalytic performance of V₂O₅, VO₂ and V₂O₃ in the ODP reaction is determined by a new catalyst composition created under the reaction conditions. This steady-state composition depends on the oxidizing agent (O₂ or N₂O). The oxidation state of vanadium in V₂O₅, VO₂ and V₂O₃ reduces from +5 to ca. +4, when O₂ is replaced by N₂O. This is due to the lower oxidizing ability of N₂O as compared to O₂. Moreover, propene selectivity is significantly improved in the presence of N₂O. This improving effect of N₂O is related to the degree of catalyst reduction and to the nature of oxygen species. ▪

Keywords: Propane; Propene; N; ₂; O; Reaction mechanism; ODP; XRD; XPS; UV–vis; SSITKA

Preparation of Cu/SiO₂ catalysts with and without tartaric acid as template via a sol–gel process by Esther M. Fixman; M. Cristina Abello; Osvaldo F. Gorriz; Luis A. Arrúa (pp. 111-118).

Cu/SiO₂ catalysts were prepared via a sol–gel process in the presence and absence of a hydroxy-carboxylic acid (tartaric acid) as a non-surfactant template or pore-forming agent. These catalysts were characterized by means of nitrogen sorption, X-ray diffraction, Fourier transformed infrared spectrometry, thermal gravimetric analysis, temperature programmed reduction, N₂O dissociative chemisorption, and transmission electron microscopy. They were evaluated in the partial oxidation of methanol (POM). The addition of tartaric acid showed two major and opposite effects on the final catalyst. On the one hand, tartaric acid has the ability to increase the pore size and specific surface area generating a mesoporous material without long-range ordering channel arrangements. On the other hand, the presence of tartaric acid contributes to decreasing the copper dispersion by aggregation of Cu species. The catalyst prepared in the presence of TA was much more active in POM than that prepared in the absence of TA. However, the last one showed a higher yield to hydrogen(YH2≈49%) with a very good selectivity(SH2≈99%). ▪Cu/SiO₂ catalysts were prepared via a sol–gel process in the presence and absence of a hydroxy-carboxylic acid (tartaric acid) as a non-surfactant template or pore-forming agent. These catalysts were characterized by means of nitrogen sorption, X-ray diffraction, Fourier transformed infrared spectrometry, thermal gravimetric analysis, temperature programmed reduction, N₂O dissociative chemisorption, and transmission electron microscopy. They were evaluated in the partial oxidation of methanol (POM). The addition of tartaric acid showed two major and opposite effects on the final catalyst. On the one hand, tartaric acid has the ability to increase the pore size and specific surface area generating a mesoporous material without long-range ordering channel arrangements. On the other hand, the presence of tartaric acid contributes to decreasing the copper dispersion by aggregation of Cu species. The catalyst prepared in the presence of TA was much more active in POM than that prepared in the absence of TA. However, the last one showed a higher yield to hydrogen(YH2≈49%) with a very good selectivity(SH2≈99%).

Keywords: Cu/SiO; ₂; catalysts; Sol–gel process; Non-surfactant template; Methanol partial oxidation

Properties of Sm₂O₃–ZrO₂ composite oxides and their catalytic performance in isosynthesis by Yingwei Li; Dehua He; Zhihui Zhu; Qiming Zhu; Boqing Xu (pp. 119-127).

Sm₂O₃ doped ZrO₂-based catalysts (Sm₂O₃–ZrO₂ composite oxide) were prepared by co-precipitation and their physical properties (texture and structure) and chemical properties (acid–base and redox) were characterized with the methods of N₂ adsorption–desorption isotherm, powder X-ray diffraction, Raman spectroscopy, NH₃ and CO₂ temperature programmed desorption and H₂ temperature programmed reduction. The catalytic performances of the catalysts (activity and selectivities) were evaluated in the CO hydrogenation to isobutene and isobutane (isosynthesis) under the reaction conditions of 673K, 5.0MPa, and 650h⁻¹. The relationship between the catalytic performance and the physical/chemical properties of Sm₂O₃–ZrO₂ catalysts were also examined. The catalytic activity and selectivity of the Sm₂O₃–ZrO₂ catalysts varied with Sm₂O₃ doping. The physical properties of the catalysts, such as cumulative pore volumes, average pore diameters and crystal sizes had some influences on the activity and selectivity in the isosynthesis. CO conversion increased with an increase in the amount of the acidic sites on the surface of Sm₂O₃–ZrO₂ catalysts, while iso-C₄ percentage in total hydrocarbons increased with an increase in the amount of the basic sites. The addition of Sm₂O₃ into ZrO₂ enhanced the reducibility of Sm₂O₃–ZrO₂ catalysts. The highest CO conversion (21.6%) and C₄ selectivity (41.8%) were obtained over the catalyst that had a maximum amount of H₂ consumptions (57.7μmolg⁻¹) in the TPR measurement for Sm₂O₃–ZrO₂ catalysts. A coordination of the acid–base properties and the redox property may play important role for the improvement of the catalytic performances of the isosynthesis.Sm₂O₃–ZrO₂ composite oxides were prepared by co-precipitation, characterized with the methods of N₂ adsorption desorption isotherm, powder X-ray diffraction, Raman spectra, NH₃ and CO₂ temperature programmed desorption and H₂ temperature programmed reduction, and evaluated as the catalysts in the isosynthesis under the reaction conditions of 673K, 5.0MPa and 650h⁻¹. ▪

Keywords: Isosynthesis; CO hydrogenation; Sm; ₂; O; ₃; –ZrO; ₂; composite oxide; Acid–base; Redox

Benzene to phenol hydroxylation with N₂O over Fe-Beta and Fe-ZSM-5: Comparison of activity per Fe-site by Igor Yuranov; Dmitri A. Bulushev; Albert Renken; Lioubov Kiwi-Minsker (pp. 128-136).

Fe-Beta and Fe-ZSM-5 were studied in the benzene to phenol transformation with N₂O. The activity of isomorphously substituted Fe-ZSM-5 catalysts calculated per a Fe(II) site active in CO oxidation (TOF) was ∼2-fold higher as compared to the TOF of Fe-Beta catalysts. This was attributed to the geometry of Fe(II) active sites which may vary depending on the zeolite host.▪Fe-Beta catalysts with iron content of 0.045–2.0wt.% were studied in the benzene to phenol transformation with N₂O and compared to similar Fe-ZSM-5 catalysts to understand the influence of zeolite structure on the Fe-sites activity. The Fe-containing zeolites were prepared either by a direct hydrothermal synthesis or by a post-synthesis Fe deposition followed by activation (steaming or high temperature treatment in He). Total amount of Fe(II) active sites able to form atomic oxygen (O)_Fe, from N₂O, was quantified by the transient response method at 523K measuring the released N₂. The fraction of the (O)_Fe active in CO oxidation was determined via the amount of CO₂ released. The catalyst activity in the benzene to phenol transformation over the activated isomorphously substituted Fe-Beta and Fe-ZSM-5 zeolites was directly proportional to the amount of the (O)_Fe active in CO oxidation. The turnover frequency (TOF) over Fe-Beta and Fe-ZSM-5 catalysts was found to be close indicating a similarity in the structures of Fe active sites. The observed ∼2-fold difference can be attributed to the influence of the zeolite host lattices. The difference between Fe-Beta and Fe-ZSM-5 was also observed in DRIFT spectra of NO adsorbed on iron sites at room temperature. The bands of NO adsorbed on Fe-Beta and Fe-ZSM-5 were at 1873 and 1878/1891cm⁻¹, respectively. The areas of these bands correlate with the amount of (O)_Fe active in CO oxidation. Comparison of the DRIFT spectra of adsorbed NO on the zeolites with the spectra on some iron containing compounds allowed to attribute the adsorption sites to Fe(II) sites and not to Fe(III) sites.

Keywords: Fe-ZSM-5; Fe-Beta; Zeolites; N; ₂; O; Benzene hydroxylation; Phenol; Fe active species

BEA and MOR as additives for light olefins production by Alexandre F. Costa; Henrique S. Cerqueira; José Marcos M. Ferreira; Naira M.S. Ruiz; Sonia M.C. Menezes (pp. 137-143).

Beta (BEA) or mordenite (MOR) zeolites were combined with conventional MFI-based additive. After H₃PO₄ impregnation and hydrothermal treatment, both zeolites presented tetrahedral aluminum and phosphorus in AlPOs-like crystalline structures. Laboratory performance of samples treated with phosphorus showed an expressive increase in lighter products yields in detriment of naphtha. Besides tetrahedral aluminum in framework other aluminum species are also important for performance. ▪The use of MFI-based additives in the fluid catalytic cracking (FCC) process in order to increase both – the production of light olefins and gasoline octane number – has been commercially proven. It is well known that impregnation by phosphorus increases the stability of aluminum atoms of H-MFI zeolite framework, resulting in higher yields of desired products. This paper discusses the possibility of combining either beta (BEA) or mordenite (MOR) zeolites – before and after treatment – with phosphoric acid (P/Al ratio of 1) with the conventional MFI-based additive. Zeolite samples were characterized by nitrogen adsorption, X-ray diffraction (XRD) and²⁷Al and³¹P solid state NMR before and after hydrothermal treatment. Such treatment was responsible for decreases in zeolite surface area, crystallinity and also in the number of framework tetrahedral aluminum species of all samples. After impregnation with phosphoric acid and hydrothermal treatment, besides other species, both H-MOR/P/St and H-BEA/P/St presented resonance signals at 38 and −30ppm at the²⁷Al and³¹P MAS NMR spectra, respectively, which can be attributed to tetrahedral aluminum and phosphorus in AlPO's-like crystalline structures. After being mixed with an equilibrium FCC catalyst, the laboratory performance of the different additives was investigated using a gasoil feedstock and a fixed-bed micro activity test unit. Similarly to what was previously reported for H-MFI/P/St, the phosphoric acid treatment improved the performance of H-MOR/P/St and H-BEA/P/St zeolites with an expressive increase in lighter products yields in detriment of naphtha. The results suggest that, besides classical tetrahedral aluminum in the framework (Al_tet-f), other aluminum species also take part in the improvement of the zeolites performance.

Keywords: MFI; BEA; MOR; NMR; Phosphorus; Additive

Preparation of NiB nanoparticles in water-in-oil microemulsions and their catalysis during hydrogenation of carbonyl and olefinic groups by Shu-Jen Chiang; Biing-Jye Liaw; Yin-Zu Chen (pp. 144-152).

Surfactant-stabilized NiB catalysts (ME-NiB) were prepared using the chemical reduction method in the ternary microemulsion system of water/cetyl-trimethyl-ammonium bromide (CTAB)/ n-hexanol. The surfactant molecules could adsorb onto the surface of the formed particles, and acted as a protective agent to stabilize and restrict the growth of particles. The size of the nanoparticles was not fully determined by the size of the microemulsion droplets, which depended on the composition of the microemulsion system. Additionally, the particle sizes and the reactivities of the ME-NiB nanoparticles depended on the concentration of nickel salt, the amount and speed of addition of NaBH₄ and the temperature. The ME-NiB samples were characterized by X-ray diffraction (XRD) as an amorphous structure and by transmission electron microscopy (TEM) as having particle size distributions in the range 3–8nm, which was much smaller than that of NiB (20–50nm) prepared by the typical chemical reduction method. The ultrafine catalyst of ME-NiB was markedly more active than NiB in the hydrogenation of carbonyl and olefinic groups. A good yield of citronellal/citronellol was obtained from the selective hydrogenation of citral at a low temperature of 30°C over the ME-NiB catalyst.The surfactant-stabilized nanoparticles (3–4nm) of NiB (ME-NiB) were prepared by reducing nickel acetate with sodium borohydride in the water/CTAB/ n-hexanol microemulsion system. The ME-NiB catalysts were characterized as amorphous and markedly more active than NiB prepared by the typically chemical reduction method. The ME-NiB catalysts could selectively hydrogenate citral to obtain citronellal yield about 84% and citronellal/citronellol yield about 95% at a low temperature of 30°C. ▪

Keywords: Chemical reduction; Microemulsion; NiB; Nanoparticle; Hydrogenation; Butyraldehyde; Furfural; Crotonaldehyde; Citral

Preparation and characterization of new Ni-aluminosilicate catalysts and their performance in the epoxidation of ( Z)-cyclooctene by K.J. Ciuffi; E.J. Nassar; L.A. Rocha; Z.N. da Rocha; S. Nakagaki; G. Mata; R. Trujillano; M.A. Vicente; S.A. Korili; A. Gil (pp. 153-162).

This work reports the preparation of two series of Ni-aluminosilicates by the sol–gel and the co-precipitation methods. The main difference between the two processes of synthesis is the pH of the initial mixture, 2 for the sol–gel and 11 for the co-precipitation method, respectively. The obtained solids are heat-treated at various temperatures in the range of room temperature to 1000°C, and the resulting materials are characterized by X-ray diffraction, thermogravimetric and differential thermal analysis, ultraviolet–visible spectroscopy, nitrogen adsorption, and transmission electron microscopy. Various nickel compounds crystallize under the sol–gel reaction conditions, as well as, amorphous silica and crystalline 2NaAlO₂·3H₂O. Ni–Al hydrotalcite, takovite, and amorphous silica are obtained when the samples from the co-precipitation method are analysed. A maximum of 302m²/g of specific surface area shows the co-precipitation samples series, with only 32m²/g in the case of the sol–gel samples series. The catalytic performance in the epoxidation of ( Z)-cyclooctene at room temperature and atmospheric pressure is evaluated using aqueous hydrogen peroxide as oxidant.

Keywords: Nickel aluminosilicate; Saponite; Sol–gel synthesis; Co-precipitation synthesis; Epoxidation

Mechanistic studies for the polymerization of 2,6-dimethylphenol to poly(2,6-dimethyl-1,4-phenylene ether): LC–MS analyses showing rearrangement and redistribution products by Sunita Gupta; John A.P.P. van Dijk; Patrick Gamez; Ger Challa; Jan Reedijk (pp. 163-170).

In order to understand the mechanism of oxidative coupling polymerization of 2,6-dimethylphenol to poly(2,6-dimethyl-1,4-phenylene ether), reactions have been carried out for very short time by taking a mixture of dimer of 2,6-dimethylphenol and 2,4,6-trimethylphenol (monomer) as substrate and Cu–NMeim system as catalyst. The LC–MS chromatograms reveal peaks corresponding to rearrangement (hybrid trimer) and redistribution (DMP monomer and hybrid dimer) products.▪For a detailed investigation of the mechanism of the oxidative coupling polymerization of 2,6-dimethylphenol (DMP) to poly(2,6-dimethyl-1,4-phenylene ether) (PPE), reactions were carried out with a mixture of 4-(2′,6′-dimethylphenoxy)-2,6-dimethylphenol (DMP-dimer) and 2,4,6-trimethylphenol, under a dioxygen atmosphere using a copper(II)–NMeim catalyst (NMeim= N-methylimidazole).Oxidative coupling experiments were performed for very short reaction times in order to detect any intermediate or hybrid compounds (i.e. when starting from mixtures of the parent phenols) generated during the early stages of the polymerization process. The LC–MS chromatograms of the samples collected reveal peaks which indicate the formation of (i) DMP-monomer; (ii) dimer which is a hybrid of the parent phenols; (iii) DMP-trimer; (iv) trimer which is a hybrid of parent phenols. Formation of DMP monomer and these oligomers are in support of the formation of a quinone-ketal during the reaction. The phenol-ketal further undergoes redistribution (to form monomer and hybrid dimer) and rearrangement (to form trimers). So, these studies further corroborate the formation of a quinone-ketal already during the first steps of the polymerization process.

Keywords: Poly(2,6-dimethyl-1,4-phenylene ether); Quinone-ketal; Rearrangement; Redistribution; LC–MS technique

Effect of the Al-MCM-41 properties on the catalytic liquid phase rearrangement of 1,2-epoxyoctane by David P. Serrano; Rafael van Grieken; Juan Antonio Melero; Alicia García (pp. 171-180).

Liquid phase rearrangement of 1,2-epoxyoctane has been investigated over Al-MCM-41 type mesostructured materials prepared by a sol–gel route with different Si/Al molar ratios. The main reaction product is the corresponding aldehyde, although other rearrangement products, allylic alcohols and diol, are also obtained. Catalysts having a Si/Al molar ratio around 40 combine the best catalytic performance in regards to substrate conversion and a valuable product selectivity. ▪Liquid phase rearrangement of 1,2-epoxyoctane has been investigated over Al-MCM-41 type mesostructured materials prepared by a sol–gel route with different Si/Al molar ratios. The main reaction product is the corresponding aldehyde, although other rearrangement products, mainly allylic alcohols and diol, are also obtained. The pore size and acidic properties of the Al-MCM-41 catalysts strongly depend on the aluminium content, which affects both the extent and selectivity of 1,2-epoxyoctane rearrangement reaction. A clear lowering of the epoxide conversion with the increase of aluminium content is observed. This fact arises probably from the change from mesoporous to microporus materials as the molar Si/Al ratio of Al-MCM-41 decreases, which leads to diffusional limitations. However, the increase of aluminium content yields high selectivities towards valuable products (octaldehyde and octen-ols) with a low formation of 1,2-octanediol. Catalysts having a Si/Al molar ratio around 40 combine the best catalytic performance in regards to substrate conversion and a valuable product selectivity. TG analyzes of used catalysts indicate that the occupation degree of the pores by occluded organic molecules increases with the aluminium content, as a consequence of the increase in the number of acid sites and the decrease in the pore size of these materials. This fact is in agreement with the lower activity exhibited by the samples having high aluminium contents as it may enhance the diffusional limitations and favour the catalyst deactivation. Nevertheless, the catalytic performance of Al-MCM-41 materials is completely recovered after thermal treatment of the used catalysts.

Keywords: Al-MCM-41; Linear epoxides; Mesoporous materials; Rearrangement

Hydrodechlorination of 1,2-dichloroethane and dichlorodifluoromethane over Ni/C catalysts: The effect of catalyst carbiding by Anna Śrębowata; Wojciech Juszczyk; Zbigniew Kaszkur; Janusz W. Sobczak; Leszek Kępiński; Zbigniew Karpiński (pp. 181-192).

In spite of previous reports, nickel catalysts appeared active in hydrodechlorination of 1,2-dichloroethane, producing ethylene with very high selectivity (up to 97%) at low temperatures of reaction (210–230°C). In addition, at these temperatures, nickel deactivation by surface chloriding, observed by others, does not practically occur. The use of different nickel salts (chloride, nitrate, acetate) as catalyst precursors makes it possible to obtain different metal dispersions, reflected in variations of overall catalytic activity expressed per mass of nickel. The conditions of catalyst reduction led to a complete reduction of nickel precursor and effective removal of the counterion (Cl⁻ or NO₃⁻). Interestingly, in the case of the chloride- and acetate-derived catalysts, the selectivity to vinyl chloride increases gradually with time on stream, at the expense of ethylene, even up to 30%. The appearance of fcc NiC_x solutions ( x≤0.1) and an hcp Ni₃C phase in Ni/C catalysts used results from a massive production of ethylene, which is an efficient carbiding agent. An increasingly deeper transformation of Ni to Ni₃C led to a higher selectivity to vinyl chloride. Alternatively, the Ni/C samples which were most selective toward ethylene (and characterized by a smaller Ni particle size) contained only tiny amounts of carbon in the form of NiC_x solution. The behavior of Ni/C catalysts seems to be largely regulated by the population of surface carbon species. A higher surface carbon content (implied by a higher carbon content in Ni₃C than in NiC x≤_0.1) creates an undeniable difficulty in removal of the second chlorine atom from 1,2-dichloroethane. It is suggested that, in such conditions, a new reaction route leading to vinyl chloride via a concerted elimination of HCl is feasible. The Ni/C catalysts subjected to CCl₂F₂ hydrodechlorination contained even higher amounts of Ni₃C than the analogous samples screened in the reaction of 1,2-dichloroethane.Ni/C appeared active in hydrodechlorination of 1,2-dichloroethane, producing ethylene with very high selectivity (up to 97%) at low temperatures of reaction (210–230°C), without catalyst deactivation. The appearance of fcc NiC_x solutions ( x≤0.1) and an hcp Ni₃C phase in Ni/C catalysts used results from a massive production of ethene, which is an efficient carbiding agent, however a deeper transformation of Ni to Ni₃C led to a higher selectivity to vinyl chloride, at the expense of ethene, even up to 30%. It is suggested that a new reaction route leading to vinyl chloride via a concerted elimination of HCl is feasible. ▪

Keywords: Hydrodechlorination; Nickel/Sibunit carbon; 1,2-Dichloroethane; Dichlorodifluoromethane; Selectivity to ethylene; Selectivity to vinyl chloride; Ni; ₃; C; NiC; _x

Enantioselective hydrogenation of itaconic acid over cinchona alkaloid modified supported palladium catalyst by György Szöllősi; Katalin Balázsik; Mihály Bartók (pp. 193-201).

The enantioselective hydrogenation of itaconic acid was studied over cinchona alkaloid-modified supported palladium catalyst in the presence of benzylamine as achiral base additive. The effect of several reaction parameters was investigated, such as the addition order of the additive, modifier and itaconic acid, hydrogen pressure, reaction temperature, amount of additive and modifier. Enantioselectivities up to 58% could be obtained by setting the appropriate conditions. The above results along with studies on the structure of the achiral amine additive, the chiral modifier and the substrate led to an interpretation of the increased enantioselection observed in the hydrogenation of itaconic acid in presence of benzylamine. According to this benzylamine plays role both on the surface of the catalyst and in the liquid phase by transforming the acid in bis-benzylammonium salt. Due to the salt formation the interaction with cinchonidine occurred through the conjugated carboxylic group, which led to increased enantioselectivity. Based on modifications in the substrate structure the effect of the unconjugated carboxylic group was also discussed.The enantioselective hydrogenation of itaconic acid was studied over cinchona alkaloid-modified supported palladium catalyst in the presence of benzylamine. Benzylamine plays role both on the surface of the catalyst and in the liquid phase. It was shown that, by transforming the acid in bis-benzylammonium salt, the interaction with cinchonidine occurred through the conjugated carboxylic group, resulting in increased enantioselectivity. ▪

Keywords: Benzylamine; Cinchona alkaloid; Enantioselective; Heterogeneous catalyst; Hydrogenation; Palladium; Itaconic acid

The use of hydrogen chemisorption for the determination of Ru dispersion in Ru/γ-alumina catalysts by J. Okal; M. Zawadzki; L. Kępiński; L. Krajczyk; W. Tylus (pp. 202-209).

Ru nanoparticles supported on γ-Al₂O₃, prepared by reduction of RuCl₃ in ethylene glycol with using microwave irradiation, were thoroughly characterized by ICP-AES, BET, XRD, TEM, XPS and H₂ chemisorption. Structure and chemisorptive properties of the supported colloidal Ru nanoparticles were compared with those of the Ru/γ-Al₂O₃ catalyst prepared by the incipient wetness impregnation method, using the same RuCl₃ precursor. Results obtained by volumetric H₂ chemisorption performed at different temperatures 20–200°C, showed that the irreversible H₂ adsorption onto colloidal Ru/γ-Al₂O₃ catalyst is a nonactivated process. For this catalyst saturation of the ruthenium surface with hydrogen was achieved already at room temperature. Ruthenium dispersion and particle sizes obtained from H₂ measurements agreed well with the results of TEM and XRD methods. In contrast, activated chemisorption behavior has been observed on traditionally prepared Ru/γ-Al₂O₃ catalyst. Even at 100°C, irreversible H₂ uptake was lower then expected as evidenced by the large discrepancies between the mean particle sizes obtained from H₂ chemisorption and TEM. Superior chemisorptive properties of the Ru nanoparticles supported on γ-Al₂O₃ are assigned to the higher dispersion of the smaller ruthenium particles and also their weaker interaction with the support. The colloidal catalyst, in contrast to traditionally prepared one, is free of chlorine contamination. Also, contamination of Ru by aluminum ions, possible during the catalyst preparation by conventional impregnation with acidic solution, was avoided.Ru nanoparticles on γ-Al₂O₃ were prepared by reduction of RuCl₃ in ethylene glycol with using microwave irradiation. Chemisorptive properties of this system were compared with those of the Ru/γ-Al₂O₃ catalyst prepared by impregnation. Superior chemisorptive properties of the former system are assigned to the higher dispersion of the smaller ruthenium particles and weaker interaction of Ru nanoparticles with the support. ▪

Keywords: Metal nanoparticles; Chemisorption of hydrogen; Polyol method; Ru/γ-Al; ₂; O; ₃; catalyst

Preparation of trimetallic Pt–Re–Ge/Al₂O₃ and Pt–Ir–Ge/Al₂O₃ naphtha reforming catalysts by surface redox reaction by Viviana Benitez; Marieme Boutzeloit; Vanina A. Mazzieri; Catherine Especel; Florence Epron; Carlos R. Vera; Patrice Marécot; Carlos L. Pieck (pp. 210-217).

Pt–Re–Ge/Al₂O₃ and Pt–Ir–Ge/Al₂O₃ naphtha reforming catalysts of varying Ge content were prepared by means of catalytic reduction. The results indicate that the method is suitable for preparing trimetallic catalysts and that Ge addition modified the properties of both the metal and acid functions of the bimetallic catalysts. ▪Preparation of trimetallic Pt–Re–Ge/Al₂O₃ and Pt–Ir–Ge/Al₂O₃ naphtha reforming catalysts by means of a surface redox reaction (namely the catalytic reduction method), was studied by varying the concentration of Ge. The catalytic reduction method was chosen in order to favor the interaction of Ge with the active Pt–Re and Pt–Ir phases.The results shows that the deposition of Ge on the bimetallic catalysts does not seemingly depend on the nature of the metal phase (Pt–Ir or Pt–Re).The test reactions indicated that Ge addition modified the properties of both the metal and acid functions of the bimetallic catalysts. The modification of the acidity is due to the deposition of part of Ge on the support.The n-C₇ reforming results show that Pt–Re–Ge/Al₂O₃ and Pt–Ir–Ge/Al₂O₃ catalysts with low Ge contents (≤0.3%) have similar catalytic performances (toluene yield, C₁–C₄ formation, coke deposit) as the presulfided bimetallic samples. This effect is attributed to an efficient passivation of hydrogenolytic activity at low Ge contents. At higher Ge contents a drastic decrease of the toluene yield is observed due to a strong poisoning of the metal phase and the formation of isolated Ge species.

Keywords: Trimetallic reforming catalysts; Catalytic reduction method

Promotion of Re/Al₂O₃ and Re/C catalysts by Ni sulfide in the HDS and HDN of gas oil: Effects of Ni loading and support by N. Escalona; J. Ojeda; J.M. Palacios; M. Yates; J.L.G. Fierro; A. López Agudo; F.J. Gil-Llambías (pp. 218-229).

Two series of NiRe catalysts supported on γ-Al₂O₃ and activated carbon having constant renium content and various Ni/Re atomic ratios were prepared to investigate the promoting action of Ni on Re in the simultaneous hydrodesulfurization and hydrodenitrogenation of gas oil at 325, 350 and 375°C. On both supports, the dependence of activities showed initially an increase and subsequent decrease with increasing Ni content, with optimum Ni/Re atomic ratios of ∼0.94 for Ni( x)Re/Al₂O₃ catalysts and ∼1.25 for Ni( x)Re/C catalysts. ▪Two series of NiRe catalysts supported on γ-Al₂O₃ and activated carbon having constant wt.% Re₂O₃ content (3.51 and 1.97, respectively) and various Ni/Re atomic ratios were prepared to investigate the promoting action of Ni on sulfided Re catalysts in the simultaneous hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) of gas oil. The catalysts were characterized using textural analysis, X-ray diffraction, diffuse reflectance spectroscopy, energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy. On both Ni( x)Re/Al₂O₃ and Ni( x)Re/C catalysts, the dependence of HDS and HDN activities showed initially an increase and subsequent decrease with increasing Ni content, with optimum Ni/Re atomic ratios of ∼0.94 for Ni( x)Re/Al₂O₃ catalysts and ∼1.25 for Ni( x)Re/C catalysts. The decline in activity was attributed to a reduction in Re dispersion and a low Ni sulfidation for the alumina-supported catalysts, and to a separate location of Re and Ni on the support surface, as well as to an incomplete Ni sulfidation for the carbon-supported catalysts. The synergetic effect in activity observed between Ni and Re was slightly higher for HDS than for HDN, especially at low reaction temperature (325°C) and on carbon-supported catalysts. On the basis of these promotional effects on catalytic activities and HDN/HDS selectivity, and the characterization results, the nature of the promotion observed on NiRe supported catalysts was discussed.

Keywords: Hydrodesulfurization (HDS); Hydrodenitrogenation (HDN); Re sulfide catalyst; Ni-Re catalyst

Improved photocatalytic activity of Sn⁴⁺-doped and undoped TiO₂ thin film coated stainless steel under UV- and VIS-irradiation by Hikmet Sayılkan (pp. 230-236).

TiO₂ can be used as a photocatalyst because of its semiconductor property. If TiO₂ is doped with transition metal ions, its electronic properties are modified. In this work, nanosized Sn⁴⁺-doped and undoped TiO₂ (TiO₂–Sn⁴⁺ and TiO₂) particles have been synthesized without organic solvent by hydrothermal process at low temperature. Nano-TiO₂ particulates having a doping ratio of about 5 [Sn⁴⁺/Ti(OBuⁿ)₄; mol/mol%] allowed to coat the stainless steel substrate by spin-coating technique. The particles and the films were characterized by XRD, SEM, BET and UV/VIS/NIR techniques. The photocatalytic performance of the films were tested for degradation of Malachite Green dye in solution under UV and VIS-lights. The results reveal that (a) nano-TiO₂ particles are fully anatase crystalline form and are easily dispersed in water, (b) the coated surfaces are hydrophilic, (c) the photocatalytic activity of the TiO₂–Sn⁴⁺ film is higher than that of the undoped TiO₂ film under UV and VIS-light irradiation and, (d) TiO₂–Sn⁴⁺ film can be repeatedly used with increasing photocatalytic activity compared to undoped TiO₂ film.

Keywords: Nano-TiO; ₂; Sn; ⁴⁺; -doping; Hydrothermal process; Thin film; Photocatalysis

Enhance efficiency of tetraoctylammonium fluoride applied to ultrasound-assisted oxidative desulfurization (UAOD) process by Meng-Wei Wan; Teh-Fu Yen (pp. 237-245).

The UAOD process, applied to diesel fuels with varying sulfur contents. The transition metal complex and quaternary ammonium salts (QAS) phase transfer agents have been applied with aqueous hydrogen peroxide. No contaminates such as bromo compound derivates are isolated when the new fluoride phase transfer agents were used. Selectivity is higher and catalyst is recovered for reuse. ▪The ultrasound-assisted oxidative desulfurization (UAOD) process has been applied to a number of diesel fuels containing varying amounts of sulfur content. The transition metal complex and quaternary ammonium salts (QAS) phase transfer agents have been applied with aqueous hydrogen peroxide as oxidizing agent. High yield of 3-bromobenzothiophene, and 2-bromobenzothiphene sulfone has been found from phase transfer agents containing tetraoctylammonium bromide. No contaminates such as bromo compound derivates had been isolated when the new fluoride phase transfer agent was used. Selectivity was particularly high for this process as demonstrated by selective ions mass spectrometry. The experiment also demonstrated that the catalyst could be recovered for reuse. Furthermore, the hydrogen peroxide provides a good performance, and the oxidation will proceed as low as 0.25%.

Keywords: Desulfurization; Phase transfer agent; Tetraoctylammonium fluoride; Ultrasound-assisted oxidative desulfurization; Diesel fuel

The influence of operating conditions on the growth of carbon nanofibers on carbon nanofiber-supported nickel catalysts by Amaya Romero; Agustín Garrido; Antonio Nieto-Márquez; Ana Raquel de la Osa; Antonio de Lucas; José Luís Valverde (pp. 246-258).

Carbon nanofibers (CNFs) were prepared by the catalytic decomposition of ethylene over Ni/Y-zeolite at 550°C, followed by catalyst removal with hydrofluoric acid. The demineralised CNFs were impregnated in an aqueous solution of Ni(II) nitrate. The CNF-supported Ni exhibited high catalytic activity in the CVD synthesis of CNFs, proving that the structured CNF support served to stabilize Ni activity. Results clearly indicated that careful control of temperature and H₂ content was important to achieve the desired product. Changing the total flow rate did not seem to alter the type of carbon deposited but did change the deposition rate. ▪Carbon nanofibers (CNFs) were prepared by the catalytic decomposition of ethylene over Ni/Y-zeolite at 550°C, followed by catalyst removal with hydrofluoric acid. The demineralised CNFs were impregnated in an aqueous solution of Ni(II) nitrate. The CNF-supported Ni exhibited high catalytic activity in the CVD synthesis of CNFs, proving that the structured CNF support served to stabilize Ni activity. Results clearly indicated that careful control of temperature and H₂ content was important to achieve the desired product. Changing the total flow rate did not seem to alter the type of carbon deposited but did change the deposition rate.

Keywords: Carbon nanofiber; Chemical vapour decomposition; Nickel; Carbon yield

Benzylation of aromatics on tin-containing mesoporous materials by K. Bachari; O. Cherifi (pp. 259-266).

The benzylation of benzene and substituted benzenes reaction employing benzyl chloride as the alkylating agent over a series of tin-containing mesoporous silicas (Sn-HMS- n) with different Sn contents ( n=Si/Sn) has been investigated. These materials have been characterized by elemental analysis, DRX method, N₂ adsorption measurements (BET and BJH theory), XPS, UV–vis, FTIR and Mössbauer spectroscopic methods.Display OmittedThe benzylation of benzene and substituted benzenes reaction employing benzyl chloride as the alkylating agent over a series of tin-containing mesoporous silicas with different Sn contents has been investigated. These materials (Sn-HMS- n) have been characterized by elemental analysis, DRX method, N₂ adsorption Measurements (BET and BJH theory), XPS, UV–vis, FTIR and Mössbauer spectroscopic methods. The mesoporous tin-containing materials showed both high activity and high selectivity for benzylation of benzene. The activity of these catalysts for the benzylation of different aromatic compounds is in the following order: benzene>toluene> p-xylene>anisole. More interesting is the observation that this catalyst is always active and selective for large molecules like naphthenic compounds such as methoxynaphthalene and he can also be reused in the benzylation of benzene for several times. Kinetics of the benzene benzylation over these catalysts has also been investigated.

Keywords: Benzylation of aromatics; Benzyl chloride; Tin-mesoporous materials; Diphenylmethane

Tuning the morphology of monolith coatings by Agustín F. Pérez-Cadenas; Freek Kapteijn; Jacob A. Moulijn (pp. 267-271).

The morphology of monolithic channels can be tuned by coating with α-Al₂O₃. Two coating geometries, the extremes for square channels, round and quasi-square ones, have been obtained. So, an optimal coating morphology can be chosen depending on the application. Finally, γ-Al₂O₃ has been used as example of final catalyst support coating with a uniform thickness over the whole channel perimeter.▪Well-defined α-Al₂O₃-coated monoliths with different channel geometries to be used in the preparation of structured catalysts or sorbents have been prepared by dipping cordierite monoliths in α-Al₂O₃/water suspensions.Tuning the morphology of α-Al₂O₃-coated monoliths can be carried out fixing different factors, like pH, α-Al₂O₃ concentration in the suspension and using dry or pre-wetted monoliths. Two coating geometries, the extremes for square channels, round and quasi-square ones, have been obtained. So, an optimal coating morphology can be chosen depending on the application. Finally, γ-Al₂O₃ has been used as example of final catalyst support coating with a uniform thickness over the whole channel perimeter.

Keywords: Monolith; Alumina; Coating; Catalyst support; Geometry

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Applied Catalysis A, General (v.319, #)