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Applied Catalysis A, General (v.299, #)

Editorial Board (pp. co2).

Catalytic ring opening of naphthenic structures by Ulf Nyl�n; Lorenzo Sassu; Stefano Melis; Sven J�r�s; Magali Boutonnet (pp. 1-13).

The present investigation shows the most relevant results obtained during a joint academic and industrial effort to develop new effective catalysts for upgrading light cycle oil (LCO) into a high-quality diesel-blending component. Bench-scale atmospheric pressure screening with indan over 12 different Pt–Ir-based ring-opening catalysts prepared by the incipient wetness technique showed that the relative amount of iridium and the choice of support material are factors that mainly influence the activity but also the initial and final product distribution. Moreover, TPO-TG–MS analyses of the spent catalysts revealed that for ceria-based catalysts there is a correlation between the amount of iridium, the amount of coke deposits and the resulting catalytic activity: increasing the iridium load results in less carbonaceous deposits and hence higher catalytic activity due to the intrinsic hydrogenolysis/hydrogenation properties of iridium that effectively destroy coke precursors. The catalytic properties of the chosen catalyst candidate, with the formula 2wt.% Pt₅Ir₉₅/CeO₂, were examined more closely in a pilot unit under industrially employed conditions with a tetralin/cetane model feed mixture and the real feed pre-hydrotreated LCO (HDT-LCO). As the operating pressure is increased from atmospheric to industrial high-pressure conditions, i.e. 40bar, coking tendencies are supressed. Moreover, the dominating reaction pathway for the model feed changes from ring-opening to hydrogenation; still, ring-opening is gradually observed as the temperature exceeds approximately 300°C. Simultaneously with ring-opening, consecutive cracking reactions are observed and these must be closely monitored and carefully balanced in order to reduce liquid yield losses.Results obtained at high pressure employing the HDT-LCO show that catalyst performance is slightly impaired, most likely due to sulphur poisoning. In spite of this, the catalyst candidate shows very promising catalytic properties and as the majority of current and forthcoming diesel quality specifications are exceeded, implementation of this catalyst in industrial operation is feasible.

Keywords: Ring opening; Hydrogenolysis; Pt–Ir catalyst; HDT-LCO; Diesel quality improvement

Catalytic ring opening of naphthenic structures by Ulf Nyl�n; B�rbara Pawelec; Magali Boutonnet; J.L.G. Fierro (pp. 14-29).

The present paper delves into physical and chemical characterization of surface and bulk properties of the twelve 2wt.% Pt_xIr_y catalysts employed in Part I for ring opening of naphthenic structures. The support materials (ceria, alumina, silica, silica-alumina, zirconia, H-SA and magnesia) were investigated using X-ray diffraction (XRD) for phase identification and adsorption/desorption of nitrogen to obtain the specific surface area and pore size distribution. The catalyst preparation via the incipient wetness technique was closely monitored and the final catalysts were examined by means of X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS) and quantitative TPR followed by dynamic pulse chemisorption of CO, Fourier transform infrared spectroscopy (FT-IR) of adsorbed CO and NH₃-DRIFTS. The XPS analyses are particularly comprehensive and involve all the catalysts in their fresh, reduced and spent states. The combined results from TPR, XPS and FT-IR of adsorbed CO reveal that metallic Pt-Ir alloys are formed directly upon mild reduction.

Keywords: Catalyst characterization; XPS; TPR; CO chemisorption; FT-IR; Pt-Ir; Platinum; Iridium; Ceria

Catalytic autoignition of higher alkane partial oxidation on Rh-coated foams by Kenneth A. Williams; Lanny D. Schmidt (pp. 30-45).

Through online mass spectrometry it is demonstrated that steady-state production of syngas (CO and H₂) can be attained within 5s after admitting large alkanes ( i-octane, n-octane, n-decane, or n-hexadecane) and air into a short-contact-time reactor by using an automotive fuel injector and initially preheating the Rh-coated catalyst above the respective catalytic autoignition temperature for each fuel. Minimum catalytic autoignition temperatures on Rh were ∼260°C for n-octane and 240°C for i-octane and n-decane. In contrast, catalytic autoignition of n-hexadecane indirectly occurred at temperatures (>220°C) lower than those of the other fuels investigated because of exothermic homogeneous chemistry that preheated the catalyst (30–60°C) to a temperature (∼280°C) sufficient for surface lightoff.Additionally, the ignition kinetics for the large alkanes were determined and compared with those of methane. The step controlling surface ignition possessed an apparent activation energy of ∼78kJ/mol that was not significantly different between fuels ( p>0.05). However, a significant difference was found between the ignition preexponential for methane, O(10⁴s⁻¹), and the other large alkanes, O(10⁶⁻¹). The dominant energetic step for large alkane surface ignition is hypothesized to be oxygen desorption at saturation coverage as has been suggested for methane.

Keywords: Reaction kinetics; Transient experiments; Partial oxidation; Rhodium catalyst; Catalysis; Liquid fuels; Alkanes; Surface ignition; Start-up; Lightoff

Synthesis of heteropolyacid (H₃PW₁₂O₄₀)/SiO₂ nanoparticles and their catalytic properties by Hyun-Jong Kim; Yong-Gun Shul; Haksoo Han (pp. 46-51).

Heteropolyacid (H₃PW₁₂O₄₀, HPA)/SiO₂ nanoparticles were synthesized by a microemulsion technique to prevent the dissolution of HPA in polar solvents including water. The particle size was controlled within the range from 100 to 500nm. The solid-state NMR, FT-IR and the adsorption of trimethylphosphine were used to characterize the HPA/SiO₂ nanoparticles. The surface properties including the BET surface area, acidity and catalytic activity depended on the particle size of HPA/SiO₂. The reduction of particle size of HPA/SiO₂ improves the surface area and the acidity of the nanoparticles. The interaction of HPA with silica surfaces was observed by solid state NMR. Selective ethanol oxidation was tested as probe reaction on HPA/SiO₂. The catalytic activity of ethanol oxidation was enhanced with the reduction of the particle size of HPA/SiO₂. The catalytic properties of HPA in the silica nano phase might be different from those in the bulk phase due to the physico-chemical differences of nano phase.

Keywords: Heteropolyacid; Nanoparticle; Immobilization; Microemulsion; Solid-state NMR

Poisoning effect of SO₂ on the catalytic activity of Au/TiO₂ investigated with XPS and in situ FT-IR by Myoung Rae Kim; Seong Ihl Woo (pp. 52-57).

The suppression of the CO oxidation activity by SO₂ treatment in Au/TiO₂ catalyst was investigated by means of reaction experiments, in situ IR and XPS. The CO oxidation activity over Au/TiO₂ catalyst decreased after SO₂ treatment. The oxidation state of Au particles did not change after SO₂ treatment. The XP spectra in the S 2p region showed that sulfate was formed on TiO₂ supports after SO₂ treatment. The IR experiment revealed that SO₂ treatment increased the adsorption strength between Au and CO. Carbonate peak was absent for the SO₂-pretreated sample in the presence of CO. The migration of CO was completely blocked by surface sulfate compound. Strong and irreversible formation of sulfate at the perimeter is the main reason of the loss of CO oxidation activity at low temperature CO oxidation.

Keywords: Au/TiO; ₂; CO oxidation; SO; ₂; poisoning; XPS; In situ IR

Hydrogen production by oxidative methanol reforming on Pd/ZnO: Catalyst deactivation by Shetian Liu; Katsumi Takahashi; Kenji Fuchigami; Kazuo Uematsu (pp. 58-65).

The durability performance of Pd/ZnO for oxidative methanol reforming has been investigated. While Cu/ZnO lost its activity with a constant selectivity of CO formation, Pd/ZnO exhibited a more stable activity, but with increasing CO production throughout the reaction time on stream. Characterization of the catalyst using XRD and XPS revealed the formation of a Pd–Zn alloy, which was thought to be essential for the selective production of hydrogen. Based on the reaction and the catalyst characterization results, two routes were supposed for the deactivation of Pd/ZnO catalyst: surface fouling by deposited carbon and surface oxidation of the Pd–Zn alloy, breaking down the Pd–Zn alloy to produce more elemental Pd on a ZnO support. The catalyst can be regenerated in a H₂ reducing atmosphere at higher temperatures and in a diluted O₂ atmosphere at lower temperatures.

Keywords: Catalyst deactivation; Hydrogen production; Oxidative steam reforming; Methanol; Palladium; Zinc oxide

Palladium-catalyzed oxidation of geraniol in dense carbon dioxide by Marco Burgener; Tomasz Tyszewski; Davide Ferri; Tamas Mallat; Alfons Baiker (pp. 66-72).

The performance and stability of supported Pd catalysts were investigated in the partial oxidation of geraniol with molecular oxygen in dense CO₂. All catalysts deactivated to a certain extent in the continuous-flow reactor; the least stable among them was Pd/Al₂O₃. Beside oxidative dehydrogenation, isomerization and hydrogenation reactions were also catalyzed by Pd. The initial selectivity of Pd to citral formation was only 50–60% but improved up to 90% with time-on-stream. The extensive catalyst deactivation and the shift in product distribution are (partly) attributed to formation of geranic (neric) acid, and the acid-catalyzed dimerization and oligomerization of reactant and products leading to site blocking by the high molecular weight by-products. ATR-IR spectroscopy revealed that no CO was present on the Pd surface during geraniol oxidation though it appeared in the absence of oxygen. A shift from two-phase to single phase conditions diminished the reaction rate, presumably due to accumulation of water co-product on the catalyst surface. Despite of the initial deactivation of Pd/SiO₂, an outstanding TOF of 169h⁻¹ was achieved on the stabilized catalyst under steady state conditions, at 80°C and 150bar.

Keywords: Oxidation; Catalyst deactivation; Geranic acid; Geraniol; Pd/Al; ₂; O; ₃; Pd/SiO; ₂; Supercritical carbon dioxide

The influence of the support on the properties of nickel catalysts for edible oil hydrogenation by M. Gabrovska; J. Krstić; R. Edreva-Kardjieva; M. Stanković; D. Jovanović (pp. 73-83).

Two silica-containing materials, diatomite and waterglass, have been used as supports of nickel catalysts for edible oil hydrogenation. The active phase has been deposited following the precipitation–deposition method. The textural and structural characteristics of the supports and precursors have been studied by nitrogen sorption, scanning electron microscopy (SEM), infrared (IR) spectroscopy and X-ray powder diffraction (XRD). The thermogravimetric (TG) analyses have been carried out under hydrogen flow at different heating rates. Chemisorption of hydrogen has also been applied for precursor characterization and the metal particle size has been calculated from hydrogen adsorption isotherms at 25°C. The catalysts have been tested in the soybean oil hydrogenation reaction. The differences in the textural and structural properties of the catalysts under study have not been found to reflect on their activity and selectivity. However, the use of water glass as the support is considered to be preferable, because of the lower economic cost of the catalyst, related to the elimination of the mechanical, chemical and thermal treatment of the crude diatomite.

Keywords: Water glass; Diatomite; Precipitation–deposition; Textural and structural characterization; Reduction; Edible oil hydrogenation; Selectivity

The role of alkali-metal promotion on CO oxidation over PdO/SnO₂ catalysts by Burcu Mirkelamoglu; Gurkan Karakas (pp. 84-94).

Sol–gel prepared PdO/SnO₂ and Na-PdO/SnO₂ catalysts were investigated by X-ray photoelectron spectroscopy (XPS), diffuse reflectance IR (DRIFTS), temperature-programmed reaction spectroscopy (TPRS) and impulse techniques. Alkali-metal promotion was observed to enhance CO oxidation rate and decreases light-off temperatures of PdO/SnO₂. XPS analysis revealed that alkali-metal promotion resulted in the segregation of Pd atoms and promoted the oxygen storage capacity of the catalysts. The presence of super-oxide species was also observed over Na-PdO/SnO₂ catalyst and the formation of a relatively stable ternary oxide of sodium and palladium (Na_xPd₃O₄) was postulated. Surface titration experiments utilizing pulse technique showed that alkali-metal-promoted sample was able to preserve part of its CO oxidation activity even after reduction pre-treatment and that oxygen diffusion from bulk of the catalyst effectively promoted the activity of Na-PdO/SnO₂ sample at 150°C.

Keywords: Alkali-metal promotion; XPS; Carbon monoxide oxidation; Palladium oxide; Tin oxide

Synthesis and modification of ZSM-5 with manganese and lanthanum and their effects on decolorization of indigo carmine dye by I. Othman; R.M. Mohamed; I.A. Ibrahim; Mohamed Mokhtar Mohamed (pp. 95-102).

Hydrothermally synthesized ZSM-5 zeolite modified by manganese (Mn/ZSM-5) or lanthanum (La/ZSM-5) or mixture of both (Mn–La/ZSM-5) using impregnation technique was characterized by powder XRD, FTIR and N₂ adsorption measurements. These materials were tested for discoloration (adsorption) and mineralization (in the presence of UV irradiation) of indigo carmine (IC) dye. The results indicate that MnO_x incorporated ZSM-5 that showed the highest lattice volume and pore radius between all samples presented the highest photocatalytic activity, comparatively. However, the Mn-La/ZSM-5 catalyst exhibited the lowest activity even when compared with the parent ZSM-5 sample. This was in part due to evoking of Mn₃O₄ species at the expense of Mn₂O₃ ones, which were proposed to be the active sites of the reaction. This reaction was found to be acidity dependent since Mn/ZSM-5 showed significant bands at 3650 and 3619cm⁻¹ those in contrast appeared shapely in La/ZSM-5, whereas for Mn–La/ZSM-5 only a band at 3619cm⁻¹ was obtained. On the other hand, the decolorization activity showed comparable high rates for Mn/ZSM-5 and Mn–La/ZSM-5 samples (100% removal) implying that the adsorption process is more referred to acid-base site pairs where the photocatalytic activity seems to be more restricted to acidic sites. The influence of pH, catalyst amount and time on the decolorization rate of IC on Mn/ZSM-5 was thoroughly investigated and correlated with ZPC of MnO_x species, various exposed species of MnO_x and surface properties.

Keywords: Dye decolorization; Mn/ZSM-5; La/ZSM-5; Mn–La/ZSM-5; Texturing; XRD; N; ₂; adsorption

Influence of La₂O₃ and ZrO₂ as promoters on surface and catalytic properties of CuO/MgO system prepared by sol–gel method by Nagi R.E. Radwan (pp. 103-121).

The physicochemical, surface and catalytic properties of pure and doped CuO/MgO solids with La₂O₃ and ZrO₂ prepared by sol–gel method followed by calcination at 350, 500 and 650°C were investigated. The dopant concentrations of La₂O₃ and ZrO₂ were 2.0, 4.0, 6.0 and 8.0mol%. The amounts of CuO loaded were 0.1, 0.2 and 0.3mol. The techniques employed were XRD, FTIR, nitrogen adsorption at −196°C, CO oxidation by O₂ at 225–275°C and H₂O₂ decomposition in aqueous solution at 30–50°C.The results obtained revealed that the doping of CuO/MgO solids with different amounts of La₂O₃ and ZrO₂ brought about a progressive decrease in the degree of crystallinity of CuO and MgO phases and their particle size. The doping of CuO/MgO solid catalysts with La₂O₃ led to a progressive decrease in their specific surface areas, while the doping with ZrO₂ exerted opposite effect. The doping process with La₂O₃ and ZrO₂ brought about a progressive increase in the catalytic activities of the investigated solid catalysts towards CO oxidation by O₂ to an extent proportional to the amount of dopant added. The doping of solid catalysts with La₂O₃ led to a decrease in their catalytic activities towards H₂O₂ decomposition, while the doping with ZrO₂ led to an increase in the catalytic activity of the investigated solids calcined at different temperatures. The increase in the copper content of loading led to a decrease in the specific surface areas of solid catalysts, while for catalysis the increase of copper content resulted in a progressive increase in their catalytic activities towards CO oxidation for solids calcined at different temperatures and towards H₂O₂ for solids calcined at 350 and 500°C. The doping process led to an increase in the concentration of catalytically active constituents on the catalyst surface taking part in the catalytic process.

Keywords: CuO; MgO; La; ₂; O; ₃; ZrO; ₂; Sol–gel; FTIR; CO oxidation; H; ₂; O; ₂; decomposition

tert-Butylation of toluene over mordenite and cerium-modified mordenite catalysts by G. Kostrab; D. Mravec; M. Bajus; I. Janotka; Y. Sugi; S.J. Cho; J.H. Kim (pp. 122-130).

tert-Butylation of toluene with tert-butanol in the liquid phase was studied over large pore mordenite zeolite catalyst (H-MOR CBV 21A with Si/Al=10.5) and over cerium-modified parent zeolite with 1–6wt.% of cerium. The catalytic activity and para-selectivity of parent and cerium-modified H-mordenite catalysts is discussed. Non-modified H-MOR is catalytic active (66% conversion of toluene), with para-selectivity near 84% at 180°C after 8h. Cerium modification of parent mordenite by impregnation decreases catalytic activity but enhances and retains constant high para-selectivity (near 90%). Secondary reactions involved in the alkylation reaction are dealkylation of tert-butyltoluenes and isomerisation of 4- tert-butyltoluene to more stable 3- tert-butyltoluene. The positive influence of cerium modification of parent zeolite on transformation of 4- tert-butyltoluene was investigated. It was proved by¹²⁹Xe NMR spectroscopy that cerium/ceria is located on the external surface of H-mordenite, not inside the main channels. It was confirmed by XRD that after calcination at 500°C in the flow of dry air cerium is in the form of cerium/ceria. tert-Butylation of toluene with tert-butanol over shape-selective mordenite catalysts can be an ecofriendly process for industrial preparation of 4- tert-butyltoluene which is important intermediate product for fine chemicals.

Keywords: Abbreviations; TO; toluene; TBA; tert; -butanol; TBTO; tert; -butyltoluenes; X; _TO; conversion of TO; S; _4-TBTO; selectivity; =; (4-TBTO/∑TBTO); ×; 100Alkylation; tert; -Butylation; Zeolite; Mordenite; 4-; tert; -Butyltoluene; para; -Selectivity; Cerium/ceria modification

Epoxidation of alkenes by a readily prepared and highly active and reusable heterogeneous molybdenum-based catalyst by Gholamhossein Grivani; Shahram Tangestaninejad; Mohammad Hossein Habibi; Valiollah Mirkhani; Majid Moghadam (pp. 131-136).

The catalytic activity of Mo(CO)₆ supported on polystyrene in the epoxidation of alkenes with TBHP was studied in CCl₄. ▪Polymer-bound piperazine was readily prepared from Merrifield resin and was used as a robust support for immobilization of molybdenum hexacarbonyl. This polymer-supported molybdenum catalyst shows high activity in the epoxidation of various alkenes in the presence of tert-butylhydroperoxide (TBHP). This new heterogenized molybdenum catalyst can be recovered and reused for eight times without loss of its activity.

Keywords: Molybdenum carbonyl; Heterogeneous catalyst; Epoxidation; tert; -Butylhydroperoxide

Active and recyclable sulphated zirconia catalysts for the acylation of aromatic compounds by Francesco Zane; Stefano Melada; Michela Signoretto; Francesco Pinna (pp. 137-144).

Mesoporous sulphated zirconia catalysts have been prepared by precipitation of Zr(OH)₄ at constant basic pH and tested for the acylation of anisole with benzoic anhydride. All samples have been characterized by N₂ physisorption, ion chromatography and thermal analysis coupled with MS analysis of evolved gases (EGA). The samples possessed high specific surface areas and mean pore size in the mesopore range. TG/DSC/EGA analysis allowed us to observe all phenomena related to the calcination process and to better understand the catalyst behavior. Observed phenomena are physisorbed water elimination, dehydroxylation, sulphating agent decomposition, phase transitions and sulphate species removal. Catalytic tests were carried out at different temperatures (30–50°C) after a thermal treatment. The effects of the precipitation pH, calcination temperature and activation temperature on the catalytic performances were studied. Reuse of the catalyst was also appraised.

Keywords: Sulphated zirconia; Friedel–Crafts acylation; Fine chemicals; Catalyst recycling; Heterogeneous catalysis

Additive effect of noble metals on NiO-MgO solid solution in oxidative steam reforming of methane under atmospheric and pressurized conditions by Mohammad Nurunnabi; Yuya Mukainakano; Shigeru Kado; Baitao Li; Kimio Kunimori; Kimihito Suzuki; Ken-ichiro Fujimoto; Keiichi Tomishige (pp. 145-156).

The effect of noble metals (M=Rh, Pt and Pd) added to NiO-MgO solid solution catalyst on catalytic activity and carbon deposition was investigated in oxidative steam reforming of methane under atmospheric and pressurized conditions. The noble metal addition enhanced methane conversion at low W/ F condition, such as 0.13ghmol⁻¹, and the promoting effect was easily observed even for a small amount of addition, such as 0.035% Rh. This noble metal addition can maintain Ni species in a reduced state and it can enhance the methane activation ability and catalyst reducibility. Under pressurized conditions, it was found that the addition of Rh and Pt decreased carbon formation almost completely on Ni_0.2Mg_0.8O. The catalyst characterization suggests that noble metals–Ni alloy particles with the surface segregation of noble metals are formed on M/Ni_0.2Mg_0.8O. This is related to high resistance to deactivation due to oxidation and carbon formation.

Keywords: Oxidative steam reforming of methane; NiO-MgO solid solution; Rh; Pt; Pd; Deactivation; Self activation; Carbon deposition

Shape-selective alkylation and related reactions of mononuclear aromatic hydrocarbons over H-ZSM-5 zeolites modified with lanthanum and cerium oxides by Y. Sugi; Y. Kubota; K. Komura; N. Sugiyama; M. Hayashi; J.-H. Kim; G. Seo (pp. 157-166).

The La₂O₃ and CeO₂ modifications of H-ZSM-5 zeolites were examined to improve the shape-selectivity in the alkylation of mononuclear aromatic hydrocarbons and related reactions. The selectivities of p-diethylbenzene ( p-DEB) among diethylbenzene isomers were improved without significant loss of catalytic activity by the modification with these oxides in the ethylation of ethylbenzene (EB). The La₂O₃ modification enhanced the selectivities of p-DEB more effectively than the CeO₂ modification. The improvement of the selectivities over these oxides is due to the prevention of the isomerization of p-DEB at external acid sites. The para-selectivity for La₂O₃-modified H-ZSM-5 zeolites is improved due to “product selectivity�? resulting from the preferential diffusion of p-DEB by the adjustment of pore entrance as well as by the deactivation of external acid sites.The enhancement of the formation of less bulky xylene isomer was also observed in the disproportionation of toluene and the isomerization of xylene isomers over La₂O₃- and CeO₂-modified H-ZSM-5 zeolites.

Keywords: H-ZSM-5; La; ₂; O; ₃; and CeO; ₂; modification; Deactivation of external acid sites; Para; -selectivity; Alkylation

Synthesis of ZSM-48 zeolites and their catalytic performance in C₄-olefin cracking reactions by Guoliang Zhao; Jiawei Teng; Yahong Zhang; Zaiku Xie; Yinghong Yue; Qingling Chen; Yi Tang (pp. 167-174).

ZSM-48 zeolite samples with a series of SiO₂/Al₂O₃ ratios were synthesized in the hydrothermal system of Na₂O–SiO₂–Al₂O₃–H₂N(CH₂)₆NH₂ (HDA). The samples were characterized by X-ray powder diffraction, N₂ adsorption, scanning electron microscopy, temperature-programmed desorption of ammonia, thermo-gravimetric analysis and chemical analysis. Both the OH⁻/SiO₂ and SiO₂/Al₂O₃ ratios played key roles for the formation of pure ZSM-48. C₄-olefin cracking reactions were carried out on these ZSM-48 zeolites to produce propylene. Compared with currently used HZSM-5 zeolite, HZSM-48 zeolite exhibits a more excellent selectivity for the aimed olefins, especially for those with lower SiO₂/Al₂O₃ ratios. The difference of catalytic performance of HZSM-48 and HZSM-5 zeolites for the cracking of C₄-olefin can be attributed to their different acidities. The influences of reaction temperature and liquid hour space velocity on the catalytic performance of the HZSM-48 catalysts were investigated. The reasons for the deactivation of HZSM-48 zeolite in C₄-olefin cracking reactions were also studied.

Keywords: ZSM-48; Zeolite; Cracking; C; ₄; -olefin; Propylene

Activity and stability of iron-containing pillared clay catalysts for wet air oxidation of phenol by Jing Guo; Muthanna Al-Dahhan (pp. 175-184).

Catalytic wet air oxidation of an aqueous phenol solution over Fe–Al pillared catalyst was conducted in a stirred tank and packed bed reactor. Semi-batch experiments in the stirred tank reactor were designed to investigate the effects of temperature, air pressure, initial phenol concentration, catalyst loading, and catalyst size on the conversion of total organic carbon. The catalyst exhibited an important activity in degrading total organic carbon at mild conditions. Its internal mass transfer resistance was assessed over different catalyst sizes via a chosen criterion. Packed bed runs were conducted under selected temperature and pressure (170°C, 3.2MPa) over a long duration (240h). Various characterization methods were employed for fresh and aged pillared clay catalysts. Occurrence of catalyst deactivation by carbonaceous deposits during the packed bed operation was observed through scanning electron microscopy (SEM) and elemental analysis. Insignificant metal leaching was observed because trace amounts of metal elements were detected in the hot acidic liquid solution.

Keywords: Catalyst characterization; Carbon deposition; Pillared clay; Phenol treatment; Wet air oxidation

Esterification of alcohols with acetic acid over zeolites Hβ, HY and HZSM5 by Sharath R. Kirumakki; N. Nagaraju; Komandur V.R. Chary (pp. 185-192).

Kinetic studies on the liquid phase esterification of C₃ and C₄ alcohols on acetic acid were carried out over zeolites Hβ, HY and HZSM5. The aims of this study were to arrive at the reaction mechanism from the kinetic data and to investigate the effects of the type of alcohol and zeolite type on the reaction mechanism. Zeolite Hβ was found to be the most active for this reaction. The acidity of zeolite determines the extent of the esterification reaction. The esterification reaction was found to follow the Eley–Rideal pathway. Acetic acid is activated by adsorption on the zeolite acid site, which then reacts with the alcohol in the bulk to form the corresponding acetate.

Keywords: Esterification; Zeolites; Acetic acid; Reaction kinetics; Eley–Rideal mechanism

Sulfonic acid-functionalized phenylene-bridged periodic mesoporous organosilicas as catalyst materials by Bulcs� R�c; P�ter Hegyes; Peter Forgo; �rp�d Moln�r (pp. 193-201).

Three solid acids based on bridged periodic mesoporous organosilica structure (PMO) with a benzene ring as the rigid unit incorporated in the framework and functionalized with anchored sulfonic acid groups were synthesized. Samples were prepared by either sol–gel polymerization of 1,4-bis(triethoxysilyl)benzene (BTEB) or co-condensation of BTEB and 3-mercaptopropyltrimethoxysilane (MPTMS) in the presence of octadecyltrimethylammonium bromide surfactant. Physical characterization data (X-ray powder diffraction, nitrogen adsorption and desorption, and NMR spectroscopy) and acid–base titration indicate the formation of ordered structure and successful functionalization. Catalytic properties were studied in both gas-phase and liquid-phase reactions. The catalytic performance of the PMO-based samples in the isopropylation of phenol in the gas-phase, particularly their stability, exceeds markedly those of functionalized mesoporous ordered materials (MCM-41, HMS and SBA-15). Selectivities in the Fries rearrangement of phenyl acetate over the PMO-based catalysts differ significantly from that of the homogeneous reaction. The sample with benzenesulfonic acid surface functions exhibits higher activities and different selectivities in the dimerization of 2-phenylpropene and in the rearrangement–aromatization of ketoisophorone as compared to samples functionalized with propanesulfonic acid groups.

Keywords: Periodic mesoporous organosilicas; Benzene bridged; Benzenesulfonic acid; Propanesulfonic acid; Phenol isopropylation; Fries rearrangement; Shape selectivity

FTIR and mass spectrometric study of the interaction of ethanol and ethanol–water with oxide-supported platinum catalysts by J. Raskó; M. Dömök; K. Baán; A Erdőhelyi (pp. 202-211).

The formation and stability of surface species formed in the interaction of ethanol and ethanol–water mixture with Al₂O₃-, TiO₂- and CeO₂-supported Pt catalysts were studied by FTIR. The changes of the gas phase composition during the above processes were monitored by mass spectrometer. It was found that water enhanced the stability of ethoxide surface species formed in the dissociation of ethanol on Pt catalysts and suppressed the formation of CO. Dehydrogenation of molecularly adsorbed ethanol was proposed as a key reaction step. On the temperature programmed desorption (TPD) spectra of adsorbed ethanol in the case of supported Pt there is a high temperature desorption stage, which was explained by the formation and decomposition of surface acetate species. A possible mechanism of the reaction is discussed.

Keywords: Ethanol steam reforming; Surface species; TPD of ethanol; Gas phase products; Reaction of ethanol with water; Oxide-supported Pt catalysts

Heterogeneous hydroxylation catalyzed by multi-walled carbon nanotubes at low temperature by Zhenhui Kang; Enbo Wang; Baodong Mao; Zhongmin Su; Lei Gao; Li Niu; Hongyan Shan; Lin Xu (pp. 212-217).

In this paper, multi-walled carbon nanotubes (MWCNTs) were directly used as catalysts for the hydroxylation of aromatic hydrocarbons at low temperature (50–70°C). Without the assistance of any solvent or additive, high selectivity was still obtained. The catalysts were characterized by X-ray powder diffraction, infrared spectra, Raman spectra, and transmission electronic microscopy. These results prove that MWCNT was a highly-active, highly-selective, and well-reproductive heterogeneous catalyst. The curved sp²-hybridized carbon surfaces of MWCNT played an important role in these selective catalytic reactions. The reactions were proposed to occur via an oxene attacking process. The active oxygen species were generated through the interaction between the hydrogen peroxide and the MWCNTs and subsequently consumed by the aromatic hydrocarbons. This process was repeated in the catalytic reactions.

Keywords: Carbon nanotube; Heterogeneous catalysis; Hydroxylation; Aromatic hydrocarbon

Extended visible light response of binary TiO₂-Ti₂O₃ photocatalyst prepared by a photo-assisted sol–gel method by Haimei Liu; Wensheng Yang; Ying Ma; Jiannian Yao (pp. 218-223).

A new kind of binary TiO₂-Ti₂O₃ photocatalyst was successfully prepared by a simple photo-assisted sol–gel method. The as-prepared catalyst exhibited remarkable photocatalytic activity in decomposition of many organic dye pollutants, including sulforhodamine B (SRB), eosin, erythrosin B, and rhodamine B (RB) under visible light illumination. The ESR spectrum clearly showed that OH radicals were formed. These acted as an active species in the decomposition of organic dyes over as-prepared photocatalyst suspensions under visible light illumination.

Keywords: Photocatalyst; Visible light; Organic dye decomposition; ESR spectra

Influence of the acid–base properties in Si-MCM-41 and B-MCM-41 mesoporous materials on the activity and selectivity of ɛ-caprolactam synthesis by T.D. Conesa; J.M. Hidalgo; R. Luque; J.M. Campelo; A.A. Romero (pp. 224-234).

B-MCM-41 mesoporous molecular sieves have been prepared with different B contents (Si/B=40–10). Three synthesis procedures were compared: (i) direct synthesis by using tetraethyl orthosilicate as the silica source, boric acid as the boron source and the surfactant cetyl-trimethylammonium bromide, (ii) direct synthesis with a post-synthesis treatment in NH₄F solution and (iii) capillary impregnation of mesoporous Si-MCM-41. The solid structures were analysed by XRD, N₂ adsorption, TG–DTA and DRIFT. The surface acidity was determined by TPD and DRIFT by using pyridine as the probe molecule. Furthermore, the presence of acid and basic sites was shown from the conversion of 2-methyl-3-butyn-2-ol. This study indicated that samples obtained by direct synthesis had both acid and basic properties, while fluorinated samples had mainly acid properties and those synthesised by capillary impregnation exhibited predominantly basic properties. Likewise, an increase in boron content produced a decrease in both the intensity of the XRD peaks and BET surface area as well as an increase in total acidity. In the absence of deactivation processes (pulse method), at 573K, silicates and borosilicates MCM-41 catalysed the formation of by-products of ɛ-caprolactam, although this process was favoured on solids with mainly basic properties. Under continuous flow reaction conditions, at 723K, results indicated that the incorporation of boron to the Si-MCM-41 framework did not affect the activity and product distribution. Finally, when acetonitrile was used as the solvent in a continuous flow system, although selectivity to ɛ-caprolactam improved, the by-products of ɛ-caprolactam adsorption were also favoured resulting in the deterioration of catalyst life.

Keywords: Mesoporous materials; MCM-41; Beckmann rearragement; ɛ; -Caprolactam pulse method; Fluorine

Metallosalen complexes immobilized in zeolite NaX as catalysts of aerobic oxidation of cyclooctane by J. Połtowicz; K. Pamin; E. Tabor; J. Haber; A. Adamski; Z. Sojka (pp. 235-242).

Physicochemical properties of metallosalen complexes entrapped within NaX zeolite and their catalytic activities in the oxidation of cyclooctane with dioxygen in the absence of a reducing agent were studied, and compared with free metallocomplexes.Broadening of the zeolite structure-sensitive vibrations observed after the encapsulation gives the evidence of the zeolite framework changes due to the presence of the “ship-in-the-bottle�? species. EPR spectroscopy evidences the inclusion of metallosalen complexes since it distinguishes between encapsulated metallocomplexes and those adsorbed on the zeolite external surface. UV–vis spectra confirm the immobilization and stabilization of the metallocomplexes inside the zeolite structure.The most active catalysts are free metallosalen complexes. We have found that the activity of these complexes increases in the order Ni(salen), Fe(salen), Mn(salen), Cu(salen) and Co(salen) with triple difference in the catalytic activity between the most and the least active catalyst. Upon encapsulation their activity drops about two times. Only Ni(salen) after heterogenization does not change its catalytic activity. The reduction of catalytic activity of the encapsulated catalysts is probably governed by two factors: constraints in the formation of the intermediate complex and change of the redox potential of the metal in the salen complex.

Keywords: Metallosalen complexes; Cyclooctane oxidation; Encapsulated metallocomplexes; Transition metal ions; Zeolite X

Vanadium species and their effect on the catalytic behavior of an FCC catalyst by E. Tangstad; T. Myrstad; A.I. Spjelkavik; M. St�cker (pp. 243-249).

Samples of a commercial FCC catalyst impregnated with 3000ppm vanadium and subjected to oxidative and reductive treatments, were characterized by electron spin resonance (ESR) and tested in a microactivity test (MAT) to study the effect of different oxidation states of vanadium on the catalytic behavior when processing an atmospheric residue from the North Sea. MAT testing at 524�C shows that samples containing a substantial part of V⁴⁺ combined with a strong part of V³⁺ or lower oxidation states give a considerably less catalytic effect of vanadium than samples containing mainly V⁵⁺. The test results indicate that V⁴⁺ and V⁵⁺ have quite similar dehydrogenation activities, while V³⁺ or lower oxidation states have almost no dehydrogenation effect. It has been found that different oxidation states of vanadium (V³⁺ or lower, V⁴⁺ and V⁵⁺) co-exist when treating the catalyst samples in 5% hydrogen in nitrogen at elevated temperatures up to 760�C. The initial conversion to V³⁺ or lower oxidation states occurs no later than after only one-third of the vanadium is converted from V⁵⁺ to V⁴⁺. A relatively higher concentration of V⁴⁺ is allowed when treating the catalyst in 5% carbon monoxide in nitrogen.

Keywords: FCC; Vanadium; Dehydrogenation; MAT; ESR; Resid cracking

Isomerisation of n-hexane over sulphated zirconia modified by noble metals by Thomas L�ften; Edd A. Blekkan (pp. 250-257).

Isomerisation of n-hexane has been studied at industrially relevant conditions over sulphated zirconia promoted with Pt, Rh, Ir, and Ru. The Pt-promoted sample showed the highest activity, and it was considerably more active than a commercial, zeolite-based catalyst. The samples promoted with rhodium and iridium showed a lower, and similar activity, while ruthenium was less efficient and gave a less stable catalyst. The selectivities were similar for all the samples, with the methylpentanes and 2,3-dimethylbutane as main and primary products. Measured kinetic parameters for the reaction were in agreement with a conventional bifunctional mechanism: Positive order in n-hexane, negative in hydrogen and an activation energy around 90kJ/mol. Prereduction of the samples was necessary to achieve a high activity, but if the activation temperature was too high the activity was lost, probably due to the loss of sulphate groups through excessive reduction.

Keywords: Isomerisation; N; -hexane; Sulphated zirconia; Platinum; Rhodium; Iridium; Ruthenium

Kinetics for benzoylation of sodium phenoxide by liquid–liquid phase-transfer catalysis by Hung-Ming Yang; Chin-Chen Huang (pp. 258-265).

The kinetics for phase-transfer catalyzed benzoylation of sodium phenoxide (PhONa) to synthesize phenyl benzoate in a liquid–liquid system and the behaviors of the catalytic intermediate were investigated. Using tetra- n-butylammonium bromide (TBAB) as the catalyst with the molar ratio to PhONa equal to 0.1, the product yield was above 98% within 1h of reaction at 10°C and 150rpm. The benzoylation was observed strongly dependent on the agitation speed, and mainly occurred in the aqueous/organic interfacial region when non-polar organic solvent was used. The catalytic intermediate, tetra- n-butylammonium phenoxide (PhOQ), produced from PhONa with TBAB in the aqueous phase was not observed in the organic phase during the reaction using heptane as the solvent; while in dichlorobenzene, its amount was about 20–30% of the initial usage of catalyst. The concentrations of PhOQ for different agitation speeds are near constant after 20min of duration; thus the pseudo-first-order kinetics can be successfully applied to describe the reaction system. Extra additions of NaOH also affected the overall reaction rate significantly due to the extraction of PhOQ into the organic phase was influeznced by hydroxide anion. The concentration of PhOQ decreased with increasing amount of NaOH at a usage of greater than 0.025mol. The catalytic intermediate plays an important role in liquid–liquid phase-transfer catalyzed benzoylation.

Keywords: Benzoylation; Kinetics; Liquid–liquid phases; Phase-transfer catalysis; Phenyl benzoate

Highly active gold-ceria catalyst for the room temperature oxidation of carbon monoxide by Unnikrishnan R Pillai; Sarojini Deevi (pp. 266-273).

Ceria supported gold catalysts containing 0.1–5wt.% gold are prepared by deposition–precipitation technique in which the precipitate is subjected to ultrasound treatment and aging in the parent solution at 65°C for 2h prior to filtration and drying. The catalysts are found to be very active for the room temperature oxidation of CO. Au/CeO₂ catalyst containing as low as 1wt.% Au is found to be a highly active catalyst for the room temperature oxidation of CO to CO₂ with complete conversion of CO and specific activity up to 490×10⁻⁴mol_COs⁻¹g_Au⁻¹. The catalyst shows good stability and sustains its high activity for a prolonged period. Aging of the catalyst in the parent solution is found to be important in obtaining a highly active catalyst. The catalysts are characterized by XRD, SEM, TEM, XPS and TPR/TPD. TPR, TPD and XPS studies suggest that the active site for CO oxidation may be a combination of Au⁺OH⁻ and metallic gold in interface with reduced Ce³⁺ sites. In other words, the presence of highly dispersed gold particles in close contact with the ceria surface defects is vital for the superior performance of the catalyst.

Keywords: Gold-ceria catalyst; CO oxidation; Room temperature oxidation; Deposition–precipitation

The effect of acetic acid on the photocatalytic degradation of catechol and resorcinol by J. Ara�a; J.M. Do�a Rodr�guez; O. Gonz�lez D�az; J.A. Herrera Meli�n; C. Fern�ndez Rodr�guez; J. P�rez Pe�a (pp. 274-284).

The photocatalytic degradation of catechol and resorcinol with TiO₂ in presence of acetic acid has been studied. Low concentrations of the acid (30–50ppm) can modify the adsorption and degradation of the dihydroxybenzenes. However, the acetic acid concentration threshold at which effects are observed depends on the compound.FTIR analyses have shown that due to steric factors, catechol and resorcinol molecules adsorb on different TiO₂ surface centres. Additionally, acetic acid molecules are able to displace Ti⁴⁺ coordinated water molecules and those interacting by hydrogen bonds, to a lesser extent. Consequently, the catalyst surface becomes restructured, favouring the adsorption of the dihydroxybenzenes. The acetates reaction with holes and oxygen molecules with photogenerated electrons to give O₂⁻ radicals which react with OH groups with acidic character to give new radicals that enhance catechol and resorcinol degradations.

Keywords: Photocatalysis; FTIR; Acetic acid–dihydroxybenzenes interaction; TiO; ₂

Remarkable support effect for liquid phase methanol reforming with water over supported Pt–Ru catalysts by Toshihiro Miyao; Masaya Yamauchi; Hiroaki Narita; Shuichi Naito (pp. 285-291).

Support effect for the catalytic activity of liquid phase reforming of methanol with water was investigated over various supported Pt–Ru bimetallic catalysts. The SiO₂, TiO₂, Al₂O₃, MgO, CeO₂ and ZrO₂ were used as support materials by conventional impregnation method. Basic oxide supports improved the selectivity to CO₂, whereas acidic supports suppressed the catalytic activity and selectivity. The Pt–Ru/TiO₂ catalyst exhibited highest activity and selectivity for CO₂, which were improved by higher temperature reduction. The improved activity and selectivity were attributable to the occurrence of SMSI state and Pt–Ru alloy, respectively. The reforming reaction over Pt–Ru/TiO₂ catalyst proceeded through partially dehydrogenated HCOOCH₃ and HCOOH intermediate with the similar mechanism as that over SiO₂ supported Pt–Ru catalyst.

Keywords: Liquid phase reforming of methanol; Hydrogen production; Support effect; Pt–Ru/TiO; ₂; catalyst

Preparation of Fenton reagent with H₂O₂ generated by solar light-illuminated nano-Cu₂O/MWNTs composites by Lisha Zhang; Jialin Li; Zhigang Chen; Yiwen Tang; Ying Yu (pp. 292-297).

This paper introduces the preparation of needle-shaped cuprous oxide (Cu₂O) particles 3–10nm in diameter and 40–150nm in length on multiwall carbon nanotubes (MWNTs) by anodic oxidation of copper electrode in alkaline solution. Steady-state concentration of H₂O₂ as high as 0.42mM is produced in aqueous suspension of nanosized Cu₂O/MWNTs composites illuminated by simulated solar light in the presence of formate and oxygen. Assisted by Fe²⁺-EDTA, these photogenerated H₂O₂ can be used as Fenton reagent; hydroxyl radicals have been detected indirectly. The results for the degradation of brilliant red dye indicate that the effect of this new Fenton system (1g/L nanosized Cu₂O/MWNTs composites+Fe²⁺-EDTA+simulated sun light) can approach that of traditional Fenton system (4mmol/L H₂O₂+Fe²⁺-EDTA). This system is superior to the classical Fenton system in that it can act effectively for a long time.

Keywords: Nano-Cu; ₂; O/MWNTs composites; Anodic oxidation; Simulated solar light; H; ₂; O; ₂; Fenton reagent

Erratum to “Production of hydrogen via partial oxidation of methanol over Au/TiO₂ catalysts�? [Appl. Catal. A: Gen. 290 (2005) 138–147] by Feg-Wen Chang; Hsin-Yin Yu; L. Selva Roselin; Hsien-Chang Yang (pp. 298-298).

Calendar of Forthcoming Events (pp. 299-299).

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