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Applied Catalysis A, General (v.375, #1)

Contents (pp. iii-viii).

Editorial Board (pp. co2).

The advancements in sol–gel method of doped-TiO₂ photocatalysts by U.G. Akpan; B.H. Hameed (pp. 1-11).

A critical review on the advancements in sol–gel method of doping TiO2 photocatalysts is provided. Various sol–gel and related systems of doping were considered, ranging from co-doping, transition metal ions doping, rare earth metal ions doping to other metal ions and non-metal ions doping of TiO2. In most cases, co-doping of TiO2 increases the efficiency of the materials photocatalytic activity.A critical review on the advancements in sol–gel method of doping TiO₂ photocatalysts is provided. Various sol–gel and related systems of doping were considered, ranging from co-doping, transition metal ions doping, rare earth metal ions doping to other metals and non-metals ions doping of TiO₂. The results available showed that doping TiO₂ with transition metal ions usually resulted in a hampered efficiency of the TiO₂ photocatalyst, though in some few cases, enhancements of the photocatalytic activity of TiO₂ were recorded by doping it with some transition metal ions. In most cases, co-doping of TiO₂ increases the efficiency of its photocatalytic activity. The review reveals that there are some elemental ions that cannot be used to dope TiO₂ because of their negative effects on the photocatalytic activity of the catalyst, while others must be used with caution as their doping will create minimal or no impacts on the TiO₂ photocatalytic efficiency.

Keywords: Sol–gel; Photocatalysts; Doping; Photocatalytic efficiency

An activity and XANES study of Mn-promoted, Fe-based Fischer–Tropsch catalysts by Andrew Campos; Nattaporn Lohitharn; Amitava Roy; Edgar Lotero; James G. Goodwin Jr.; James J. Spivey (pp. 12-16).

XANES spectra for the Fe K-edge of the post-reaction [H₂ activated – 1.8atm, 280°C, 12h; syngas reaction – 2:1 H₂:CO ratio, 280°C, 1.8atm, 6h] Mn-promoted, Fe-based catalysts. The XANES spectra show a decreased reducibility of Fe (after activation+reaction) with increased Mn-metal promotion. The list is in order of decreasing reducibility (i.e. θ-Fe₃C most reduced).Iron-based Fischer–Tropsch (FT) catalysts with a mol-based formula of (100− x)Fe/ xMn/5Cu/17SiO₂ ( x≤20), were prepared using co-precipitation methods. The calcined catalysts were first activated in H₂ for 12h, then reacted in flowing syngas at 1.8atm, 280°C, and a 2:1 ratio of H₂:CO. The fresh and reacted catalysts were characterized using X-ray absorption near-edge structure (XANES) to determine changes in the oxidation state and the atomic-level environment of the Fe and Mn atoms. XANES spectra of the fresh calcined and reacted catalyst were taken using the K edges of Fe (7.112KeV) and Mn (6.540KeV) for various Mn-metal loadings ( x=0, 5, 20). The FT activity significantly increased with Mn promotion, indicating significant Fe–Mn interactions. The least squares fitting of the reacted catalyst shows that higher Mn loadings lead to decreased Fe_xC concentration and increased Fe₃O₄ concentration. Principal Component Analysis (PCA) of Fe indicates that the Fe₂O₃, Fe₃O₄, θ-Fe₃C phases were present in either the calcined or reacted catalyst. One additional Fe-containing phase was present in the catalyst but was not identified using the Fe standards. The PCA of Mn showed the presence of Mn₂O₃, as well as one additional Mn-containing phase. The Mn XANES of the reacted 95Fe5Mn and 80Fe20Mn catalysts show that Mn was a mixture of the 2+ and 3+ oxidation states. The average oxidation state of Mn in the reacted 95Fe5Mn catalyst was 2.24±0.07, consistent with the formation of an additional phase, identified as (Fe1−_yMn_y)₃O₄. FEFF calculations have shown relatively good agreement for Mn-substitution of octahedral Fe-sites in Fe₃O₄ (28664-ICSD), specifically in the pre-edge region; corresponding to the composition (Fe1−_yMn_y)₃O₄. Fe-based FT catalysts deactivate when carbon deposition occurs on larger iron carbide clusters. This study has shown less carbon deposition, Fe_xC formation, and higher CO hydrogenation activity with the Mn-promoted catalysts. This indicates that (Fe1−_yMn_y)₃O₄ was responsible for the formation of smaller clusters of Fe_xC, which were more active for CO hydrogenation and were less prone to deactivation through carbon deposition.

Keywords: Fischer–Tropsch; Iron; Manganese; XANES

Kinetics and mechanism of partial oxidation of ethane to ethylene and acetic acid over MoV type catalysts by Faizur Rahman; Kevin F. Loughlin; Muhammad A. Al-Saleh; Mian R. Saeed; Nasir M. Tukur; Mohammad M. Hossain; Khalid Karim; Agaddin Mamedov (pp. 17-25).

A kinetics study for the partial oxidation of ethane to ethylene and acetic acid is performed over MoV type catalysts. It is established that ethylene is the primary product and acetic acid and carbon oxides are secondary products. Formation of acetic acid product increases significantly with the co-feeding of water into the reactor. The elementary steps of the reaction network are formulated using a two-site Eley-Rideal-Redox (ERR) model, which includes the participation of water in the reaction scheme through surface OH⁻ groups. The derived ERR model predicts the experimental data satisfactorily.A kinetics study for the partial oxidation of ethane to ethylene and acetic acid is performed over MoV type catalysts. It is established that ethylene is the primary product and acetic acid and carbon oxides are secondary products. Formation of acetic acid product increases significantly with the co-feeding of water. The elementary steps of the reaction network are formulated using a two-site Eley-Rideal-Redox (ERR) model.

Keywords: Ethane partial oxidation; Ethylene; Acetic acid; Reaction network; Kinetic model; Eley-Rideal-Redox model; MoV type catalyst; Reaction mechanism

M₅O₁₄-like V–Mo–Nb oxide catalysts: Structure and catalytic performance by T.Yu. Kardash; L.M. Plyasova; V.M. Bondareva; T.V. Andrushkevich; L.S. Dovlitova; A.I. Ischenko; A.I. Nizovskii; A.V. Kalinkin (pp. 26-36).

Within Mo₅O₁₄-like structural type mixed V–Mo–Nb oxides are shown to be the substitution solid solutions of composition (Mo_0.6V_zNb0.4−_z)₅O₁₄ (0< z<0.2) based on the binary oxide (Mo_0.6Nb_0.4)₅O₁₄. Transformation of nanocrystalline oxides having a disordered layered structure with the interlayer distance of ca. 0.4nm into crystalline Mo₅O₁₄-like structure is accompanied by degradation of catalytic properties in relation to oxidative dehydrogenation of ethane.Within Mo₅O₁₄-like structural type for mixed V–Mo–Nb oxides, the effect of vanadium and niobium content and treatment temperature on the phase composition, structure and catalytic properties of the samples in oxidative dehydrogenation of ethane has been studied. The limits of V and Nb content in the ternary Mo₅O₁₄-like oxide are determined. V–Mo–Nb oxides are shown to be the substitution solid solutions of composition (Mo_0.6V_zNb0.4−_z)₅O₁₄ (0< z<0.2) based on binary oxide (Mo_0.6Nb_0.4)₅O₁₄. The structure of crystalline V–Mo–Nb oxides is refined. Crystallization of Mo₅O₁₄-like structure occurs at temperatures ≥550°C. Below 550°C, V–Mo–Nb oxides are nanocrystalline materials having a disordered layered structure with the interlayer distance of ca. 4Å. The structural model of nanocrystalline oxides is discussed. The role of Nb in the formation of ternary V–Mo–Nb oxide compounds is revealed, and the surface state of these oxides at different temperatures is analyzed. The low-temperature V–Mo–Nb oxides are the most active catalysts in the reaction of ethane oxidative dehydrogenation. They are characterized by the ratio V/Nb≈1 in the Mo₅O₁₄-like structure.

Keywords: Mo; ₅; O; ₁₄; V–Mo–Nb oxides; Ethane oxidative dehydrogenation

Supported gold catalysts in SBA-15 modified with TiO₂ for oxidation of carbon monoxide by C.L. Peza-Ledesma; L. Escamilla-Perea; R. Nava; B. Pawelec; J.L.G. Fierro (pp. 37-48).

A series of gold catalysts active for CO oxidation were prepared in this research. Gold catalysts supported on titania-modified SBA-15 substrate with different TiO₂ loadings (0, 10, 20, 40 and 60wt%) were prepared by the deposition–precipitation method.The experimental results revealed that the surface exposure of the Au⁺ species and the optimized TiO₂ content were the primary factors influencing the activity and stability of Au/( x)TiO₂/SBA-15 catalysts.Effect of Ti loading in the reaction of CO oxidation over gold catalysts supported on Ti-free and Ti- modified SBA-15 substrates: CO conversion as a function of the reaction temperature.This contribution describes the effect of SBA-15 support modification with variable quantity of TiO₂ (0, 10, 20, 40 and 60wt%) on the catalytic response of supported gold catalysts in CO oxidation. All gold catalysts were prepared by the deposition–precipitation method. These catalysts were characterized by chemical analysis (ICP), N₂ adsorption–desorption isotherms, X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), high resolution transmission electronic microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). Catalytic activity was found to increase with the TiO₂ loading even though this increase was not lineal: the highest catalytic activity was observed for the catalyst loaded with 10wt% TiO₂. This behavior is explained in terms of the quantity of Au⁺ species present on the surface of gold particles. In addition, an Au/TiO₂ reference sample was prepared and tested in CO oxidation reaction. This Au/TiO₂ catalyst exhibited the highest activity due to the higher gold dispersion achieved on the TiO₂ substrate. The importance of both Au⁺ and Au⁰ species present on the catalysts surface on the performance in the target reaction is discussed.

Keywords: Gold nanoparticles; SBA-15; Titania; CO oxidation

Efficient synthesis of vinyl and alkyl sulfides via hydrothiolation of alkynes and electron-deficient olefins using soluble and heterogenized gold complexes catalysts by Avelino Corma; Camino González-Arellano; Marta Iglesias; Félix Sánchez (pp. 49-54).

Soluble and heterogenized gold complexes catalyze the hydrothiolation of alkynes and electron-deficient olefins in high yields and with high anti-Markovnikov selectivity. Moreover heterogenized catalysts could be recycled in several successive runs without any loss of activity or selectivity.Soluble and heterogenized gold complexes catalyze the hydrothiolation of alkynes and electron-deficient olefins in high yields and with high anti-Markovnikov selectivity. Moreover heterogenized catalysts could be recycled in several successive runs without any loss of activity or selectivity.

Keywords: Hydrothiolation; Alkyl sulfides; Vinyl sulfides; Heterogenized catalysts; Gold catalysts

Nanoscaled rutile active phase in Mo–V–Nb–O supported catalysts for the oxidation of propane to acrylic acid by Ricardo López-Medina; J.L.G. Fierro; M. Olga Guerrero-Pérez; Miguel A. Bañares (pp. 55-62).

Niobium-promoted alumina-stabilized nanosized rutile oxide Mo–V–Nb–O phases are prepared, characterized and used for the selective oxidation of propane to acrylic acid. Segregated molybdenum oxides are not efficient while partially reduced rutile-type mixed molybdenum–vanadium oxide phases are efficient for the conversion of propane to acrylic acid. Niobium species would have a structural effect, stabilizing mixed molybdenum–vanadium oxide phases.Alumina-stabilized nanosized rutile Mo–V–Nb–O oxide phases are prepared, characterized and used for the selective oxidation of propane to acrylic acid. Coverage on alumina support, atomic Mo/V molar ratio and calcination conditions (inert vs. oxidizing) affect the structure and catalytic performance. The effect of Mo/V ratio is opposite depending on calcination atmosphere. Segregated molybdenum oxides are not efficient while partially reduced rutile-type mixed molybdenum–vanadium oxide phases are efficient for the conversion of propane to acrylic acid. Niobium species would have a structural effect, stabilizing mixed molybdenum–vanadium oxide phases.

Keywords: Propane; Acrylic acid; V–Mo–O; V–Mo–Al–O; Rutile; Oxidation; Structure–activity relationship; In situ; Raman; XRD; XPS

Hybrid catalysts used in the Catalytic Steam Cracking process (CSC): Influence of the pore characteristics and the surface acidity properties of the ZSM-5 zeolite-based component on the overall catalytic performance by H.T. Yan; R. Le Van Mao (pp. 63-69).

Both pore characteristics and surface acidity properties of the ZSM-5 zeolite that bears cracking sites for the hybrid catalyst, have great influence on the total conversion and selectivity into light olefins. Feed contamination by trimethylbenzenes is an excellent tool for providing further evidence of the coke cleaning effect by the hydrogen spilt-over species, the latter being generated by the Ni supported co-catalyst.Data of the present work show that, in order to obtain high yields in light olefins, the ZSM-5 zeolite – the cracking component of the hybrid catalyst, must have a relatively low SiO₂/Al₂O₃ mol ratio, so that its density of acid sites is high, thus resulting in a high total conversion. Such zeolite must also exhibit relatively mild acidity strength, favouring thus a high propylene/ethylene product ratio. On the other hand, these milder acid sites also lead to a lower coke deposition and thus to a greater on-stream catalyst stability because the cleaning action of the hydrogen spilt-over species is much eased.Feed contamination by trimethylbenzenes is an excellent tool for providing further evidence of the coke cleaning effect by the hydrogen spilt-over species, the latter being generated by the Ni supported co-catalyst. In the case of blending of petroleum hydrocarbon feedstocks with non-oil derived compounds, the latter should not have strong competitive adsorption properties such as those found in polymethylbenzenes (ex: 1,3,5-trimethylbenzene), otherwise rapid fouling phenomena may occur.

Keywords: Catalytic Steam Cracking; Hybrid catalysts; ZSM-5 zeolite; Acidity; Pore characteristics

Selective synthesis and the mechanism of formation of the oligoalkylnaphthenic oils by oligocyclization of 1-hexene in the presence of ionic-liquid catalysts by A.H. Azizov; R.V. Aliyeva; E.S. Kalbaliyeva; M.J. Ibrahimova (pp. 70-77).

The mechanism of selective formation of oligoalkylnaphthenic hydrocarbons by oligocyclization of α-olefins in the presence of ionic-liquid catalysts is suggested. Under the term of oligocyclization the consecutive reactions of oligomerization and cyclization, mediated by the same catalytic center or catalyst, is accepted.In the present paper, the results of 1-hexene oligomerization in the presence of recyclable chloroaluminate type ionic-liquid catalysts and their combination with Ti-containing complexes with “grafted ionic-liquid” type ligands are reported. The possibility of selective preparation of products with predominantly (∼70%) oligoalkylnaphthenic structure and narrow molecular weight distribution ( M_w/ M_n=1.03–1.55) is shown. The regulation of molecular weights of oligomer products is achieved by changing the molar ratio of the catalytic system components. The mechanism of selective formation of oligoalkylnaphthenic hydrocarbons by oligocyclization of α-olefins in the presence of ionic-liquid catalysts is suggested. The term of oligocyclization is used to indicate consecutive reactions of oligomerization and cyclization, mediated by the same catalytic center or catalyst. The oils obtained are qualified as the novel class of synthetic oils, namely as the class of synthetic oligoalkylnaphthenic oils.

Keywords: Abbreviations; ILC; ionic-liquid catalyst; ILCM; ionic-liquid catalyst modified; MWD; molecular-weight distribution1-Hexene; Oligomerization; Ionic liquids; Ti-containing complexes; Oligoalkylnaphthenic oils

Pd-catalysed oxidative carbonylation of amino alcohols to N,N′-bis(hydroxyalkyl)ureas under mild conditions using molecular oxygen as the oxidant by Potenzo Giannoccaro; Carla Ferragina; Michele Gargano; Eugenio Quaranta (pp. 78-84).

A very simple method has been developed for the selective synthesis of symmetrical N,N′ -bis(hydroxyalkyl)ureas, OC[NH-(CH₂)_x-OH]₂ ( x=3–6), by oxidative carbonylation of α,ω-amino alcohols [3-aminopropanol (3-AP), 4-aminobutanol (4-AB), 5-aminopentanol (5-APe), 6-aminohexanol (6-AH)] with CO/O₂ mixtures (O₂=5mol%) in the presence of Pd(II)/ligand/NEt₃·HI catalytic systems. The catalytic process takes place under very mild conditions ( p(CO/O₂)=0.1MPa; 303–333K). The target products can be isolated in high yield through a very simple and straightforward procedure. The catalytic system can be easily recovered and recycled for several times.The influence of a few reaction parameters (nature of ancillary ligand and iodide co-catalyst, I/Pd molar ratio, etc.) on the catalytic activity has also been investigated and the main mechanistic features of the catalytic process fully elucidated.Under very mild conditions (303–333K; p(CO/O₂)=0.1MPa; O₂=5mol%), L_nPdCl₂/NEt₃·HI systems [(L=2,2′-dipyridine (dipy) ( n=1); 2-(β-diphenylphosphine)ethylpyridine) (PN) ( n=1); PPh₃ ( n=2); CH₃CN ( n=2)] effectively promote the oxidative carbonylation of α,ω-amino alcohols to symmetrical N,N′-bis(hydroxyalkyl)ureas with high yield and selectivity.

Keywords: Oxidative carbonylation; Amino alcohols; N; ,; N; ′-bis(hydroxyalkyl)ureas; Pd-catalysts

Strong adsorption and effective photocatalytic activities of one-dimensional nano-structured silver titanates by Qiuye Li; Tetsuya Kako; Jinhua Ye (pp. 85-91).

Two kinds of one-dimensional (1D) nano-structured silver titanates (nanowires, nanorods) were prepared by the ion-exchanged method. Interestingly, they showed strong and fast adsorption for the dyes (methylene blue and Alizarin Red S dyes) and the gaseous isopropyl alcohol (IPA). Additionally, they showed remarkable photocatalytic activities for dye degradation and IPA mineralization under visible light ( λ≥410nm) irradiation. Moreover, both of the silver titanates showed good stabilities in the long-time-run photocatalytic reactions.Two kinds of one-dimensional (1D) nano-structured silver titanates, (Ag,H)₂Ti₄O₉-nanowire (ATW) and (Ag,H)₂Ti₄O₉-nanorod (ATR), were prepared by treating sodium titanate nanowires (STW) and titanic acid nanorods (TAR), respectively with molten AgNO₃ through the ion-exchanged method. STW, TAR, ATW, and ATR all belong to the monoclinic crystallinity systems, and their band gaps are 3.6, 3.5, 2.8, and 2.8eV, respectively. Interestingly, all of the four photocatalysts show strong and fast adsorption abilities for methylene blue (MB) and Alizarin Red S (ARS) dyes. MB and ARS can be adsorbed by the silver titanates completely within 5 and 10min, respectively. The photocatalytic activities of the two kinds of silver titanates were evaluated by degradation of the MB and ARS dye solutions with high concentration, and by the decomposition of gaseous isopropyl alcohol (IPA) under visible light ( λ≥410nm) irradiation. After the adsorption–desorption equilibrium, MB and ARS could be degradated almost completely within 60 and 80min, respectively. In addition, the mineralization yield of IPA on ATW reached 80% after 6.5-h irradiation. The high photocatalytic activities of the silver titanates may be due to their large BET surface areas and strong adsorption abilities. Moreover, both of the silver titanates showed good stabilities in the long-time-run photocatalytic reactions.

Keywords: Photocatalysis; Silver titanates; One-dimensional nanomaterials; Dye adsorption; IPA mineralization

Methane partial oxidation over Pt–Ru catalyst: An investigation on the mechanism by R. Lanza; P. Canu; S.G. Järås (pp. 92-100).

The relative contribution of total combustion, dry and steam reforming, and water-gas shift reactions to the methane partial oxidation has been studied by carrying out each one alone on the same bimetallic Pt–Ru catalyst. The CO and H₂ yield of partial oxidation has been quantitatively related with steam and dry reforming, while the persistent water-gas shift reaction always rearranges the products and intermediates.The mechanism of the partial oxidation of methane has been investigated over a bimetallic Pt–Ru catalyst. Dedicated experiments aimed to separate and quantify the relative contribution of single reactions included in the so-called “combustion and reforming” mechanism using the same catalyst. The catalyst is 0.5% Ru and 0.5% Pt (w/w) supported on mixture of alumina, ceria and zirconia (75/4.4/20.6%, w/w), washcoated on a ceramic monolith. Steam reforming, dry reforming, direct and reverse water-gas shift reactions were investigated. The temperature range investigated is 300< T<800°C, while the space velocity range is 25,000−1. Conditions at which single side reactions are expected to occur during the partial oxidation process, were approximated by tuning the reactant composition. The experimental results are also compared with thermodynamic equilibrium calculations. The CO and H₂ yields of partial oxidation have been quantitatively connected with steam and dry reforming, while the persistent water-gas shift reaction always rearranges the products and intermediates.

Keywords: Partial oxidation; Methane; Syngas; Mechanism

Influence of the synthesis method on structural properties and catalytic activity for oxidation of CO and C₃H₆ of pirochromite MgCr₂O₄ by K. Rida; A. Benabbas; F. Bouremmad; M.A. Peña; A. Martínez-Arias (pp. 101-106).

Pirochromite MgCr₂O₄ has been prepared by three different methods, characterized and examined for C₃H₆ and CO combustion. The work shows that novel microemulsion synthesis is able to yield high surface area material with enhanced catalytic properties for the mentioned combustion processes.The work examines comparatively MgCr₂O₄ oxide samples prepared by three methods (solid state reaction, sol–gel and co-precipitation within reverse microemulsion) with respect to their structural/morphological characteristics and catalytic properties for complete combustion of carbon monoxide and propene. For this purpose, the samples are examined by XRD, S_BET, SEM, XPS and TPR techniques. The results reveal achievement of optimum catalytic properties for the sample prepared by microemulsion, a method which apparently allows achievement of high surface area nanocrystals in this type of material.

Keywords: MgCr; ₂; O; ₄; Sol–gel; Solid state reaction; Reverse microemulsion; XRD; XPS; TPR; CO and C; ₃; H; ₆; oxidation

Zr-doped TiO₂ for enhanced photocatalytic degradation of bisphenol A by Bifen Gao; Tuti Mariana Lim; Dewi Puspitaningrum Subagio; Teik-Thye Lim (pp. 107-115).

Zr ions were successfully incorporated into the bulk lattice of TiO₂ by a multi-step sol–gel process, which induced upward shift of conduction band. The Zr-doped TiO₂ exhibited significantly higher photocatalytic degradation efficiency of bisphenol A than pure TiO₂. The influences of initial concentration, irradiation intensity, solution pH and inorganic anions on the performance of Zr-doped TiO₂ were studied.Zr ions were successfully incorporated into the bulk lattice of TiO₂ by a multi-step sol–gel process. The doping of Zr ions in TiO₂ lattice reached about 30%. The Zr-doped TiO₂ photocatalysts exhibited much higher photocatalytic efficiency than pure TiO₂ in the degradation of bisphenol A (BPA) under UV irradiation and complete mineralization of BPA was achieved. The higher photocatalytic activity of Zr-doped TiO₂ was attributed to gradually upward shift of the conduction bands with increasing Zr content, thus resulting in a stronger reduction power of photogenerated electrons and contributing to the improved photoactivity. The effects of initial BPA concentration, irradiation intensity, initial solution pH and inorganic anions on the photocatalytic performance of Zr-doped TiO₂ were studied. The photodegradation of BPA was found to be optimized under a basic condition at pH 9. The addition of PO₄³⁻and SO₄²⁻ anions enhanced the photocatalytic reaction but NO₃⁻and Cl⁻ ions showed detrimental effects.

Keywords: Bisphenol A; Zr doping; TiO; ₂; Multi-step sol–gel process

TAP investigation of hydrogen and carbon monoxide adsorption on a silica-supported cobalt catalyst by Jingping Hong; Stanislas Pietrzyk; Andrei Y. Khodakov; Wei Chu; Maria Olea; Veerle Balcaen; Guy B. Marin (pp. 116-123).

A temporal analysis of products (TAP) set-up was applied to investigate the initial elementary steps of the Fischer–Tropsch synthesis over silica-supported cobalt catalysts, i.e., hydrogen and carbon monoxide adsorption. TAP responses were successfully described assuming the presence of sites of reversible adsorption for hydrogen and both irreversible and reversible adsorption for carbon monoxide. Supporting qualitative information about reversibility of the adsorption was also obtained through alternating pulse experiments.A temporal analysis of products (TAP) set-up was applied to investigate the initial elementary steps of the Fischer–Tropsch synthesis over silica-supported cobalt catalysts, i.e., hydrogen and carbon monoxide adsorption. Single-pulse TAP experiments were performed over both reduced and passivated catalysts in order to qualitatively and quantitatively assess the mechanism and kinetics of H₂ and CO adsorption. Multi-pulse experiments were performed to change the state of the catalyst in a predefined way. Only fast and equilibrated physical hydrogen adsorption was observed over a passivated silica-supported cobalt catalyst. Over the reduced catalyst, the surface sites exhibited significant heterogeneity for adsorption. TAP responses were successfully described assuming two different reversible adsorption processes for hydrogen and both irreversible and reversible adsorption for carbon monoxide. Supporting qualitative information about reversibility of the adsorption was also obtained through alternating pulse experiments.

Keywords: Fischer–Tropsch synthesis; Clean fuels; TAP; Elementary steps; Transient kinetics; Mechanism; Adsorption; Hydrogen; Carbon monoxide

Novel carbon-based Ni/Fe catalysts derived from peat for hot gas ammonia decomposition in an inert helium atmosphere by Jaclyn Donald; Chunbao (Charles) Xu; Hiroyuki Hashimoto; Enkhsaruul Byambajav; Yasuo Ohtsuka (pp. 124-133).

Highly effective mesoporous activated carbon (AC) supported Ni/Fe catalysts were developed for catalytic decomposition of ammonia into N₂ and H₂. A new cycle mechanism, involving both metal phosphides and metal nitrides, was proposed for the NH₃ decomposition reactions over these carbon-supported Fe/Ni catalysts.Two novel carbon-based Ni/Fe catalysts were developed and tested for catalytic decomposition of ammonia into N₂ and H₂. These catalysts were prepared using a mesoporous activated carbon (AC) support derived from a Canadian peat by H₃PO₄ activation. The newly developed catalysts proved to be highly active for ammonia decomposition. The conversion of 2000ppm NH₃ diluted in helium over the Fe catalyst reached as high as 90% at 750°C and at the space velocity of 45,000h⁻¹, compared with only about 15% with the activated carbon alone without metal loading. The new catalyst of Fe/AC was also much more active than the Fe catalyst supported on a commercial activated carbon reported previously. In addition, the new Fe/Ni catalysts showed superior performance with respect to their resistance to catalyst deactivation. Both catalysts remained active as the reaction time increased up to 10h without showing a sign of deactivation. Fresh and spent catalysts were characterized by XRD and XPS. A cycle mechanism, involving both metal phosphides and metal nitrides, was proposed for the NH₃ decomposition reactions over these new Fe/Ni catalysts.

Keywords: Ammonia decomposition; Mesoporous carbon; Peat; Ni/AC; Fe/AC; Metal phosphides; Metal nitrides

Catalytic reaction pathways in liquid-phase deoxygenation of C18 free fatty acids by Jeremy G. Immer; M. Jason Kelly; H. Henry Lamb (pp. 134-139).

Deoxygenation of stearic acid (SA) under He employing a 5% Pd/C catalyst occurs via decarboxylation to n-heptadecane and heptadecenes with concomitant CO₂ and H₂ evolution. Although the initial decarboxylation rate is lower, SA deoxygenation goes to completion more rapidly under 10% H₂. Oleic acid deoxygenation under He is very slow; however, under 10% H₂ deoxygenation occurs readily via sequential hydrogenation and decarboxylation.The liquid-phase deoxygenation of stearic, oleic, and linoleic acids employing a 5wt% Pd/C catalyst was investigated using on-line quadrupole mass spectrometry (QMS). Catalytic deoxygenation of stearic acid (SA) under He occurs primarily via decarboxylation; the liquid products are n-heptadecane and heptadecenes. On-line QMS revealed concomitant CO₂ and H₂ evolution which can explain the greater than expected heptadecene yields at low to intermediate conversions. After essentially complete SA conversion, hydrogenation of heptadecenes via hydrogen transfer from the dodecane solvent results in 98% n-heptadecane yield. The initial rate of SA decarboxylation under 10% H₂ is lower than under He; however, by avoiding the formation of unsaturated products the reaction requires much less time to reach completion. The SA decarboxylation rate under 10% H₂ is 6-fold slower in heptadecane than in dodecane. This apparent solvent effect is explained by the lower vapor pressure of heptadecane resulting in greater H₂ inhibition of the decarboxylation reaction. Our results demonstrate that the unsaturated C18 free fatty acids, oleic and linoleic, must be hydrogenated to SA before decarboxylation can proceed at a significant rate. Oleic acid (OA) deoxygenation under He occurs very slowly and primarily via decarbonylation. In contrast, OA deoxygenation under 10% H₂ occurs facilely via hydrogenation to SA followed by decarboxylation. Since hydrogenation is complete during heating to reaction temperature, the decarboxylation kinetics and product yields are not affected by the initial unsaturation of the reactant.

Keywords: Biofuels; Decarboxylation; Decarbonylation; Palladium-on-carbon (Pd/C); Stearic acid; Oleic acid; Linoleic acid

An inorganic hydrothermal route to photocatalytically active bismuth vanadate by Ying Zhou; Kathrin Vuille; Andre Heel; Benjamin Probst; Roman Kontic; Greta R. Patzke (pp. 140-148).

BiVO₄ particles with high crystallinity are accessible via a straightforward and one-step hydrothermal process that offers preparative flexibility through inorganic templating. The reaction of Bi(NO₃)₃·5H₂O and V₂O₅ is steered with K₂SO₄ as an inorganic additive towards BiVO₄ materials with a high photocatalytic activity in the decomposition of MB under visible light irradiation.BiVO₄ has attracted research interest as one of the most promising visible-light-driven oxidic photocatalysts for water splitting and wastewater treatment. Highly crystalline BiVO₄ particles with a homogeneous morphology are now available from a straightforward, one-step hydrothermal protocol. The facile morphology control of BiVO₄ particles in the Bi(NO₃)₃·5H₂O/V₂O₅/K₂SO₄ hydrothermal system is achieved through K₂SO₄ as an inorganic additive that brings forward materials with a high photocatalytic activity. BiVO₄ particles generated from this inorganic additive-assisted approach outperform BiVO₄ materials obtained via other preparative routes in the decomposition of methylene blue (MB) under visible light irradiation. The relations between morphology, crystallinity and photocatalytic O₂ evolution in the presence of AgNO₃ and FeCl₃ as sacrificial reagents were studied with respect to the hydrothermal optimization of material properties. Furthermore, the Bi(NO₃)₃·5H₂O/V₂O₅/K₂SO₄ hydrothermal system brings forward potassium vanadate fibers as a second phase that also exhibits promising photocatalytic properties with respect to the decomposition of MB in the presence of visible light.

Keywords: Hydrothermal synthesis; Oxygen evolution; Bismuth vanadate; Photocatalysis

Methanol electrooxidation of Pt catalyst on titanium nitride nanostructured support by Jong-Min Lee; Sang-Beom Han; You-Jung Song; Jy-Yeon Kim; Bumwook Roh; Inchul Hwang; Woojin Choi; Kyung-Won Park (pp. 149-155).

We report a TiN nanostructured support for methanol electrooxidation prepared by heat treatment of TiO₂ under ammonium atmosphere. Compared to Pt on Vulcan XC-72, it is likely that enhanced catalytic properties of the Pt on TiO₂ heated at 900°C could be due to stability of nitride support and strong interaction between Pt catalyst and nitride support.We report nanostructured supports prepared by heat treatment of TiO₂ nanoparticles at 700, 800, or 900°C under ammonia atmosphere. From X-ray diffraction analysis, it is found that the phase transformation of the supports from antase and rutile TiO₂, TiO to TiN (TiO₂ heated at 900°C, TiO₂-900) is observed. In particular, the Pt on TiO₂-900 (Pt/TiO₂-900) exhibits such an excellent catalytic activity toward methanol electrooxidation compared to the Pt on Vulcan XC-72. It is likely that enhanced catalytic properties of the Pt/TiO₂-900 may be attributed to stability of nitride support and interaction between Pt catalyst and nitride support, which are confirmed by cycling test of supports and X-ray photoelectron spectra of Pt catalysts.

Keywords: Nanostructured support; Titanium nitride; Methanol electrooxidation; Direct methanol fuel cells

Effect of transition metal element addition upon liquid phase reforming of methanol with water over TiO₂ supported Pt catalysts by Takehiko Sakamoto; Hisashi Kikuchi; Toshihiro Miyao; Akihiro Yoshida; Shuichi Naito (pp. 156-162).

Addition effects of various transition metal elements to Pt/TiO₂ catalyst were investigated for liquid phase reforming of methanol with water. When Mo or Fe was added, a thin oxide layer was formed over TiO₂ surface. Highly dispersed cationic Pt particles on that layer exhibit remarkable activity for the reforming reaction of methanol.Addition effects of various transition metal elements were investigated upon catalysis of TiO₂ supported Pt metal for the liquid phase reforming of methanol. Addition of Mo or Fe increased the catalytic activity and selectivity of Pt/TiO₂ remarkably, while added Ni or Co showed poor improvement. The addition methods of transition metal elements, i.e. co-impregnation or successive impregnation, also exhibited significant effect on the catalytic behavior. XRD, XPS, FT-IR and XAFS measurements revealed that the added Mo or Fe species that formed a low valent thin oxide layer over TiO₂ surface and Pt metal were highly dispersed on the layer, while added Ni or Co formed alloys with Pt. Pt species on the oxide overlayer are supported as highly dispersed stable cationic particles, and their cationic state may depress the inhibition with strongly adsorbed CO for the reforming reaction.

Keywords: Liquid phase reforming; Methanol; Platinum; Addition effect; Thin layer of transition metal oxide; Hydrogen production

Self-assembled porous nano-composite with high catalytic performance by reduction of tetragonal spinel CuFe₂O₄ by Satoshi Kameoka; Toyokazu Tanabe; An Pang Tsai (pp. 163-171).

A tetragonal spinel CuFe₂O₄, which shows a self-assembled microstructure, including fine dispersion of copper nanoparticles within the porous Fe₃O₄ matrix after a H₂ treatment at 633K, is a regenerable precursor as a high performance composite catalyst. We show that metallurgical knowledge is available to tailor microstructures for designing catalysts.A tetragonal spinel CuFe₂O₄ reduced in H₂ flow at 633K shows a self-assembled microstructure that exhibits fine dispersion of copper nanoparticles within the porous Fe₃O₄ matrix and high catalytic performance. Sintering of copper particles was inhibited significantly even after H₂ reduction at 873K when CuFe₂O₄ was used as a precursor, while it readily occurred for CuO and physically mixed CuO+Fe₂O₃. The high thermal stability of copper nanoparticles from the CuFe₂O₄ after H₂ reduction is ascribed to the immiscible interaction between copper and iron (or iron oxides). The spinel CuFe₂O₄ can be regenerated after an intentional sintering treatment (e.g., in H₂ at 873K) by calcinations in air at 1273K where the activity and the morphology restored completely. We show that metallurgical knowledge is available to tailor microstructure for designing catalysts.

Keywords: Reduction of tetragonal spinel CuFe; ₂; O; ₄; Precursor; Self-assembled porous nano-composite copper–iron; Immiscible; High catalytic performance; Methanol steam reforming

On the nature of active sites and catalytic activity for OCM reaction of alkaline-earth oxides-neodymia catalytic systems by Florica Papa; Dana Gingasu; Luminita Patron; Akane Miyazaki; Ioan Balint (pp. 172-178).

The study investigates the relationship between the surface basicity and catalytic activity for C₂⁺ formation over equimolecular mixtures of alkaline-earth oxides with Nd₂O₃. The experimental results led to the idea that methane is converted to products on two distinct types of active sites by independent pathways. The synergetic effect between alkaline-earth oxide and a series of rare-oxide on the OCM catalytic activity have been also studied.The work investigates the relationship between the surface basicity and catalytic activity for C₂⁺ formation over equimolecular mixtures of alkaline-earth oxides (BeO, MgO, CaO and SrO) with Nd₂O₃. The concentration as well as the evolution of surface carbonate species with temperature, reflecting the basic properties of mixed oxides, was analyzed by TPD, XPS and IR methods to obtain information on the reaction mechanism. The concentration of surface basic sites contributing to the formation of C₂⁺ was determined by measuring the amount of evolved CO₂ in the 300–820°C temperature range. The experimental data showed that the higher was the catalyst basicity the better was the efficiency for selectively converting methane to C₂⁺. The turnover frequency (TOF) values were calculated by quantitatively determining the total number basic sites retaining CO₂. The experimental results led to the idea that methane is converted to products on two types of active sites by independent pathways. The alkaline active sites are responsible for C₂⁺ formation whereas the acidic sites with low affinity for carbonate formation are responsible for methane combustion. The synergetic effect between a selected alkaline-earth oxide (MgO) and a series of rare-oxide on the OCM catalytic activity has been also investigated.

Keywords: Oxidative coupling of methane; Methane oxidative conversion; Basicity of oxide surface; Lanthanide-alkaline-earth oxide catalysts

Corrigendum to “Naphthenic acid removal from heavy oils on alkaline earth-metal oxides and ZnO catalysts” [Appl. Catal. A: Gen. 371 (2009) 121–130] by Lianhui Ding; Parviz Rahimi; Randall Hawkins; Sooraj Bhatt; Yu Shi (pp. 179-179).

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Applied Catalysis A, General (v.375, #1)