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Applied Catalysis A, General (v.340, #2)
Low temperature synthesis, characterization and substrate-dependent photocatalytic activity of nanocrystalline TiO2 with tailor-made rutile to anatase ratio by Zoltán Ambrus; Károly Mogyorósi; Ágnes Szalai; Tünde Alapi; Kata Demeter; András Dombi; Pál Sipos (pp. 153-161).
TiO2 photocatalysts with predetermined phase composition (anatase-to-rutile ratio) have been prepared from strongly acidic aqueous HCl/TiCl4 mixtures. The phase composition of the photocatalysts was fine-tuned with systematically changing the concentration of HCl and TiCl4 in the reaction mixture. In phenol decomposition the photocatalysts containing only anatase were up to three times more efficient than rutile ones.▪TiO2 photocatalysts with predetermined phase composition (anatase-to-rutile ratio) have been prepared from strongly acidic aqueous HCl/TiCl4 mixtures with 0.1M≤[HCl]TOT≤5M and 0.05M≤[TiCl4]TOT≤3M (where the subscript TOT denotes total or analytical concentration). During the syntheses, TiCl4 was added to a cold-HCl solution. The initially precipitate free reaction mixture was boiled, resulting in the formation of large amount of solid, nanocrystalline (particle size 4–12nm) TiO2 particles with large specific surface area (up to ∼240m2/g). We found from the XRD patterns that at constant [HCl]TOT, the anatase content of the crystallized solid systematically increases with decreasing [TiCl4]TOT, while at constant [TiCl4]TOT, the rutile content was found to systematically increase with increasing [HCl]TOT. Thus the phase composition of the photocatalysts prepared was possible to be fine-tuned with the aid of these two simple initial parameters. The photocatalytic activity of the as-prepared catalysts was found to strongly correlate with the phase composition. In phenol decomposition the samples’ photocatalytic performance gradually and significantly increases with their anatase content: photocatalysts containing only anatase as crystalline phase were up to three times more efficient than rutile ones. Interestingly, in salicylic acid decomposition, rutile-only catalysts were found to show no activity at all, but some of our catalysts (both anatase-only and rutile–anatase mixtures) at pH ∼3 (but not at pH ∼7) displayed photocatalytic activity commensurable to that of Degussa P25. This can be explained in terms of the efficient surface chemisorption of salicylate ion on large specific surface area TiO2 particles in acidic solutions.
Keywords: Titania; Rutile; Anatase; Titanium tetrachloride; Hydrolysis; X-ray diffraction; Heterogeneous photocatalysis; Photocatalytic activity; Nanocrystals
Hydrogenation/hydrogenolysis of disulfides using sulfided Ni/Mo catalysts by Leanne McLaughlin; Ekaterina Novakova; Robbie Burch; Christopher Hardacre (pp. 162-168).
The mechanism of the hydrogenation/hydrogenolysis of dinitrodiphenyldisulfides using sulfided NiMo/γAl2O3 catalysts has been examined in detail. Although two routes are possible, the major pathway involves an initial SS bond cleavage followed by reduction of the nitro group. The disulfide hydrogenolysis occurs in the absence of the catalyst with the role of the catalyst thought to be to activate the hydrogen and trap the cleaved intermediate as well as facilitate the reduction of the nitro group. ▪The mechanism of the hydrogenation/hydrogenolysis of dinitrodiphenyldisulfides using sulfided NiMo/γAl2O3 catalysts has been examined in detail. Although two routes are possible, the major pathway involves an initial SS bond cleavage followed by reduction of the nitro group. Importantly, the disulfide hydrogenolysis occurs in the absence of the catalyst with the role of the catalyst thought to be to activate the hydrogen and trap the cleaved intermediate as well as facilitate the reduction of the nitro group. Monitoring the mass balance throughout the reaction demonstrates the difficulty in measuring intrinsic kinetics for gas–liquid–solid reactions. Although the mass balance is restored at the end of the reaction, up to 45% of the substrate/products is found to be adsorbed on the catalyst during the reaction.
Keywords: Disulfide; Nickel; Molybdenum; Aminothiophenol; Bond cleavage
Formation of singlet molecular oxygen associated with the formation of superoxide radicals in aqueous suspensions of TiO2 photocatalysts by Toshihiro Daimon; Tsutomu Hirakawa; Masahiro Kitazawa; Junya Suetake; Yoshio Nosaka (pp. 169-175).
The production and decay of singlet molecular oxygen (1O2) in TiO2 photocatalysis were investigated by monitoring its phosphorescence under various reaction conditions. First, the effects of additives such as KBr, KSCN, KI, H2O2, and ethanol on the amount of1O2 produced by photo excitation of P25 TiO2 were measured. The same additives were employed to investigate the effect on the amount ofO2− produced. Comparison between the effects on1O2 andO2− suggested that1O2 is formed by the electron transfer mechanism, the reduction of molecular oxygens toO2− by photogenerated electrons and the subsequent oxidation ofO2− to1O2 by photogenerated holes. The formation of1O2 decreased at pH<5 and pH>11, indicating that the intermediateO2− is stabilized at the terminal OH site of the TiO2 surface in the pH range of 52 photocatalysts were compared on the formation of1O2 andO2− in an aqueous suspension system. The formation of1O2 was increased with decreasing size of TiO2 particles, indicating that a large specific surface area causes a higher possibility of reduction producingO2− and then a large amount of1O2 is formed. The difference in the crystal phase (rutile and anatase) did not affect the formation of1O2.
Keywords: Singlet oxygen; Superoxide radical; TiO; 2; Photocatalysis; Adsorption
Highly effective P-modified HZSM-5 catalyst for the cracking of C4 alkanes to produce light olefins by Guiyuan Jiang; Li Zhang; Zhen Zhao; Xinyu Zhou; Aijun Duan; Chunming Xu; Jinsen Gao (pp. 176-182).
P-modified HZSM-5 was highly effective catalyst for the catalytic cracking of the mixed C4 alkanes to produce light olefins. The fact that P addition could modify both the acidic and basic characteristics of HZSM-5 (see figure) which in turn promoted its catalytic performance, will throw new light on the design of novel catalysts for light olefins. ▪A series of HZSM-5 zeolites modified by different amounts of phosphorus (P/HZSM-5) were prepared. The physicochemical features of P/HZSM-5 catalysts were characterized by means of XRD, BET, NH3-TPD, FT-IR spectra of adsorbed pyridine, etc., and their performances for the catalytic cracking of the mixed C4 alkanes to produce light olefins were investigated. The results indicated that phosphorus (P) modification not only modulated the amount of acidic sites and the percentage of weak acidic sites in total acidic sites, but also regulated the acid type, i.e., the ratio of L/B (Lewis acid/Brönsted acid). The introduction of P also altered the basic characteristics of HZSM-5 which was evidenced by CO2-TPD analysis. Consequently, P modification with suitable amount was favorable for enhancing the selectivity to light olefins, especially to propene. At the temperature of 650°C, the maximum yields of propene and ethene were achieved 25.6 and 33.9%, which were higher than those over parent HZSM-5 by 7 and 4.5%, respectively. Aromatics yield was found to be decreased with the increasing P loading due to the reduction of strong acid and the formation of new basic site which inhibited the hydrogen transfer reaction. All this indicates that P-modified HZSM-5 zeolites are effective catalysts for the cracking of mixed C4 alkanes to produce more light olefins.
Keywords: Catalytic cracking; C; 4; alkanes; Light olefins; HZSM-5 zeolite; Phosphorus
Coke study on MgO-promoted Ni/Al2O3 catalyst in combined H2O and CO2 reforming of methane for gas to liquid (GTL) process by Kee Young Koo; Hyun-Seog Roh; Yu Taek Seo; Dong Joo Seo; Wang Lai Yoon; Seung Bin Park (pp. 183-190).
MgO-promoted Ni/Al2O3 catalysts have been investigated with respect to catalytic activity and coke formation in combined steam and carbon dioxide reforming of methane (CSCRM) to develop a highly active and stable catalyst for gas to liquid (GTL) processes. Ni/Al2O3 catalysts were promoted through varying the MgO content by the incipient wetness method. X-ray diffraction (XRD), BET surface area, H2-temperature programmed reduction (TPR), H2-chemisorption and CO2-temperature programmed desorption (TPD) were used to observe the characteristics of the prepared catalysts. The coke formation and amount in used catalysts were examined by SEM and TGA, respectively. H2/CO ratio of 2 was achieved in CSCRM by controlling the feed H2O/CO2 ratio. The catalysts prepared with 20wt.% MgO exhibit the highest catalytic performance and have high coke resistance in CSCRM. MgO promotion forms MgAl2O4 spinel phase, which is stable at high temperatures and effectively prevents coke formation by increasing the CO2 adsorption due to the increase in base strength on the surface of catalyst.MgO-promoted Ni/Al2O3 catalysts have been investigated with respect to catalytic activity and coke formation in combined steam and carbon dioxide reforming of methane to develop a highly active and stable catalyst for gas to liquid processes. The coke formation in used catalysts was monitored by SEM. The catalysts prepared with 20wt.% MgO exhibit the highest catalytic performance and have high coke resistance in CSCRM.▪
Keywords: Gas to liquid (GTL); Combined reforming; MgO-promoted Ni/Al; 2; O; 3; Coke resistance
Synthesis, characterization and electrocatalytic activity of silver nanorods towards the reduction of benzyl chloride by T. Maiyalagan (pp. 191-195).
This paper describes a simple method of synthesizing silver nanorods using the polyol process, where propylene glycol serves both as a reducing agent and as a solvent in the presence of a capping reagent such as polyvinylpyrrolidone (PVP). The catalytic activity of a glassy carbon electrode with Ag nanorods exhibits extraordinary electrocatalytic activities towards the electro-reduction of benzyl chloride. ▪This paper describes a simple method of synthesizing silver nanorods using the polyol process, where propylene glycol serves both as a reducing agent and as a solvent in the presence of a capping reagent such as polyvinylpyrrolidone (PVP). The diameter and length of silver nanorods could be controlled by changing the AgNO3/PVP ratio. The end-to-end assembly of the silver nanorods was found. The silver nanorods were characterized by using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and absorption spectroscopy. The catalytic activity of a glassy carbon electrode with Ag nanorods exhibits extraordinary electrocatalytic activities towards the electro-reduction of benzyl chloride.
Keywords: Silver nanorods; Polyol process; Reducing agent; Capping reagent; Electro-reduction
A modified commercial DRIFTS cell for kinetically relevant operando studies of heterogeneous catalytic reactions by F.C. Meunier; A. Goguet; S. Shekhtman; D. Rooney; H. Daly (pp. 196-202).
This paper discusses a number of checks that should be carried out to ensure that the kinetic and spectroscopic measurements made using a DRIFTS cell are meaningful. The observations reported here demonstrate how an appropriately modified commercial DRIFTS cell can provide pertinent kinetic information about both gaseous products and the related surface intermediates. ▪This paper discusses a number of checks that should be carried out to ensure that the kinetic and spectroscopic measurements made using a DRIFTS cell are meaningful. The observations reported here demonstrate how an appropriately modified commercial DRIFTS cell can provide pertinent kinetic information about both gaseous products and the related surface intermediates. The oxidation of CO with O2 was used as a test to assess the catalyst bed bypass by the reaction mixture. Full CO conversion was obtained after the light-off temperature in the case of the modified cell, contrary to the case of the original cell, for which 80% of the reaction mixture bypassed the catalyst bed. The water-gas shift reaction over a Pt/CeO2 catalyst was used as a model reaction to further characterize the behavior of the cell under reaction conditions. The catalyst bed was shown not to be a dead-zone and was purged in essentially the same time as that needed to purge the cell. The reaction chamber globally operated in a quasi plug-flow mode and the gas composition in the thin catalyst bed appears to be homogeneous when operated under differential conditions. The production of the gas-phase reaction product CO2 could be simultaneously followed both by mass spectrometry and DRIFTS, both techniques leading to identical results. Various IR bands integration methods were discussed to allow a precise and accurate determination of the surface concentration of adsorbates during isotopic exchange.
Keywords: Diffuse reflectance; DRIFTS; FTIR; Operando; In situ; Spectroscopy; SSITKA
Performance and characterization of Ru/Al2O3 and Ru/SiO2 catalysts modified with Mn for Fischer–Tropsch synthesis by Mohammad Nurunnabi; Kazuhisa Murata; Kiyomi Okabe; Megumu Inaba; Isao Takahara (pp. 203-211).
The addition of Mn to γ-Al2O3-supported Ru catalyst enhanced the catalytic activity and stability for Fischer–Tropsch synthesis. According to the catalyst characterization results, moderate Ru particle size was observed and active site of Ru atoms was increased by the formation of MnCl2. ▪Mn effect and characterization on γ-Al2O3-, α-Al2O3- and SiO2-supported Ru catalysts were investigated for Fischer–Tropsch synthesis under pressurized conditions. In the slurry phase Fischer–Tropsch reaction, γ-Al2O3 catalysts showed higher performance on CO conversion and C5+ selectivity than α-Al2O3 and SiO2 catalysts. Moreover, Ru/Mn/γ-Al2O3 exhibited high resistance to catalyst deactivation and other catalysts were deactivated during the reaction. From characterization results on XRD, TPR, TEM, XPS and pore distribution, Ru particles were clearly observed over the catalysts, and γ-Al2O3 catalysts showed a moderate pore and particle size such as 8nm, where α-Al2O3 and SiO2 showed highly dispersed ruthenium particles. The addition of Mn to γ-Al2O3 enhanced the removal of chloride from RuCl3, which can lead to the formation of metallic Ru with moderate particle size, which would be an active site for Fischer–Tropsch reaction. Concomitantly, manganese chloride is formed. These schemes can be assigned to the stable nature of Ru/Mn/γ-Al2O3 catalyst.
Keywords: Fischer–Tropsch synthesis; Activity; Deactivation; Ru; Mn; γ-Al; 2; O; 3
Rhodium catalyzed hydroformylation of kaurane derivatives: A route to new diterpenes with potential bioactivity by Andreia F. Peixoto; Daniela S. de Melo; Tânia F. Fernandes; Yuraima Fonseca; Elena V. Gusevskaya; Artur M.S. Silva; Ricardo R. Contreras; Marisela Reyes; Alfredo Usubillaga; Eduardo N. dos Santos; Mariette M. Pereira; J. Carles Bayón (pp. 212-219).
Kaurenic and grandiflorenic acids are naturally occurring diterpenes whose biological activity has been described. These substrates have been hydroformylated by using unmodified Rh catalysts, as well as Rh/PPh3 and Rh/ tris-( o- t-butylphenyl)phosphite catalytic systems. For the three substrates, the two Rh catalysts modified with P-donor ligands, produced high conversions and chemo- and regioselectivities in the diastereoisomeric pair of linear aldehydes. ▪Kaurenic and grandiflorenic acids are naturally occurring diterpenes whose biological activity has been described. Both acids contain an exocyclic methylenic double bond that allows further functionalization on their structure. In an attempt to expand the number of derivatives of these two natural products, we have undertaken a study on the hydroformylation of the methyl esters of the two acids and the trimethylsilyl ether of kaurenol. These substrates have been hydroformylated by using unmodified Rh catalysts, as well as Rh/PPh3 and Rh/ tris-( o- t-butylphenyl)phosphite catalytic systems at 100°C and 20bar of CO/H2 (1:1). For the three substrates, the two Rh catalysts modified with P-donor ligands, produced high conversions and chemo- and regioselectivities in the diastereoisomeric pair of linear aldehydes. In all cases, the stereoselectivity observed is strongly dependent of the system used, being the most diastereoselective the least hindered unmodified Rh/CO catalyst. A correlation between the higher diastereoselectivity and the faster β-elimination of the metal-alkyl intermediate observed in the unmodified system is discussed.
Keywords: Diterpenes; Kauranes; Hydroformylation; Rhodium; Phosphite; Phosphine
Low-temperature prepared highly effective ferric hydroxide supported gold catalysts for carbon monoxide selective oxidation in the presence of hydrogen by Botao Qiao; Juan Zhang; Lequan Liu; Youquan Deng (pp. 220-228).
Ferric hydroxide supported Au catalysts prepared with co-precipitation method at room temperature without any heat treatment hereafter exhibited high catalytic activity and high selectivity for CO oxidation in air and CO selective oxidation in the presence of H2 at lower temperatures and both activity and selectivity decreased with calcination temperature rising. ▪Ferric hydroxide supported Au catalysts prepared with co-precipitation method at room temperature without any heat treatment hereafter exhibited high catalytic activity and selectivity for CO oxidation in air and CO selective oxidation in the presence of H2. With calcination temperature rising, both activity and selectivity decreased. X-ray Photoelectron Spectra (XPS) indicated that Au existed as Au0 and Au+ in the catalyst without heat treatment and even after being calcined at 200°C, while after being calcined at 400°C, Au existed as Au0 completely. X-ray Diffraction (XRD) and High Resolution Transmission Electron Microscopic (HRTEM) investigations indicated that both the supports and Au species were highly dispersed as nano or sub-nano particles even after being calcined at 200°C, but after being calcined at 400°C the supports transformed to crystal Fe2O3 with typical diameter of 30nm and Au species aggregated to nano-particles with typical diameter of 2–4nm. HRTEM investigations also suggested that the supports calcined at 200°C were composed of amorphous ferric hydroxide and crystal ferric oxide. Results of computer simulation (CS) showed that O2 was adsorbed on Au crystal cell and then were activated, which should be the key factor for the subsequent reaction. It also suggested that O2 species were more easily adsorbed on Au+ than on Au0, indicating that higher positive charge of the Au species possessed the higher activity for CO oxidation.
Keywords: Gold catalyst; CO selective oxidation; Preparation; Uncalcined; Low-temperature
Influence of textural properties of activated carbons on Pd/carbon catalysts synthesis for cinnamaldehyde hydrogenation by Amandine Cabiac; Thomas Cacciaguerra; Philippe Trens; Robert Durand; Gérard Delahay; Alice Medevielle; Dominique Plée; Bernard Coq (pp. 229-235).
The influence of the textural properties as well as the surface chemistry properties of a set of porous carbons has been studied and a correlation was found between the surface in the pores of the support and the Pd dispersion. The hydrogenation of cinnamaldehyde has been studied and the results obtained favourably compare with those already published.▪A set of microporous carbons have been used to prepare Pd/carbon catalysts. The properties of the raw materials have been determined in terms of texture and surface chemistry. A deposition precipitation method has been employed to prepare the final catalysts, leading to well-dispersed palladium particles. The influence of the textural properties as well as the surface chemistry properties has been studied and a correlation was found between the surface in the pores of the support and the Pd dispersion. The chemistry surface properties of the Pd/carbon catalysts were found similar, despite differences in the case of the starting raw materials. The hydrogenation of cinnamaldehyde has been studied and the results obtained favourably compare with those already published. Turnover frequencies were similar whatever the catalyst. High selectivities close to 90% in hydrocinnamaldehyde were obtained at 90% conversion.
Keywords: Carbons; Cinnamaldehyde; Hydrogenation; Texture
Homogeneous metathesis for the production of propene from butene by Wolfgang H. Meyer; M.M. Daphne Radebe; D. Wynand Serfontein; Umesh Ramdhani; Maria du Toit; Christakis P. Nicolaides (pp. 236-241).
The cross-metathesis of 1-butene and 2-butene to propene and 2-pentene using Phobcat, a homogeneous Grubbs first generation-type catalyst, is described at mild conditions and varying feed ratios. The reaction mixture composition is in fair agreement with the calculated thermodynamic equilibrium composition. Compared to heterogeneous metathesis over a WO3/SiO2 catalyst, the homogeneous reaction exhibits better reaction control and product selectivity. ▪The cross-metathesis of 1-butene and 2-butene is described for the production of propene and 2-pentene using Phobcat, a homogeneous Grubbs first generation-type catalyst bearing 9-cyclohexyl-9-phosphabicyclo-[3.3.1]-nonane as ligand. In a closed system at 20bar and 50°C, the reaction mixture composition at different 1-butene:2-butene feed ratios is in fair agreement with the calculated composition at equilibrium based on thermodynamic data. Compared to heterogeneous metathesis over a WO3/SiO2 catalyst, the homogeneous reaction exhibits better reaction control and selectivity to the desired products.
Keywords: Propene; Butene; Metathesis; Homogeneous; Ruthenium; Phoban
High-throughput preparation and screening of rhenium oxide-alumina catalysts in olefin metathesis by M. Stoyanova; U. Rodemerck; U. Bentrup; U. Dingerdissen; D. Linke; R.-W. Mayer; H.G.J. Lansink Rotgerink; T. Tacke (pp. 242-249).
High-throughput (HT) experimentation in heterogeneous catalysis exemplifies a multidisciplinary approach to address in an efficient manner different aspects of catalyst development – from synthesis to testing and characterization. The present work reports on preparation systems for rapid parallel synthesis of well defined heterogeneous catalysts and catalyst screening in olefin metathesis. Metathesis of ethene and but-2-ene to propene was chosen as a test reaction. The influences of various parameters such as rhenium oxide loading, catalyst calcination conditions, catalyst pre-treatment, as well as the reaction temperature and contact time on the catalytic performance are discussed. Sample characterization by UV–vis and FT-IR gave an evidence for the formation of active surface perrhenate species, very sensitive to humidity and pre-treatment conditions applied.▪High-throughput (HT) experimentation in heterogeneous catalysis exemplifies a multidisciplinary approach to address in an efficient manner different aspects of catalyst development – from synthesis to testing and characterization. The present work reports on preparation systems for rapid parallel synthesis of well defined heterogeneous catalysts and catalyst screening in olefin metathesis. Metathesis of ethene and but-2-ene to propene was chosen as a test reaction. The influences of various parameters such as rhenium oxide loading, catalyst calcination conditions, catalyst pre-treatment, as well as the reaction temperature and contact time on the catalytic performance are discussed. Sample characterization by UV–vis and FT-IR gave an evidence for the formation of active surface perrhenate species, very sensitive to humidity and pre-treatment conditions applied.
Keywords: Heterogeneous catalysis; Rhenium-alumina catalysts; Metathesis to propene; High-throughput preparation and screening
Novel mesoporous aluminosilicate supported palladium-rhodium catalysts for diesel upgrading by Mélanie Taillades-Jacquin; Deborah J. Jones; Jacques Rozière; Enrique Rodríguez-Castellón (pp. 250-256).
The preparation and characterisation of novel bimetallic PdRh catalysts supported on a mesoporous aluminosilicate are described. The association of a range of different techniques including adsorption from the gas-phase and element-specific spectroscopies (such as XPS and EXAFS) provide converging results indicating the existence of intermetallic particles with palladium preferentially located on the particle surfaces. ▪Bimetallic PdRh (with Pd/Rh mole ratio=2/1) catalysts supported on a mesoporous aluminosilicate have been prepared and three methods of metal incorporation in the support have been compared: direct incorporation into the synthesis gel, impregnation and ion-exchange. Physico-chemical characterisations (nitrogen adsorption–desorption, hydrogen chemisorption, transmission electron microscopy, X-ray photoelectron and extended X-ray absorption fine structure spectroscopies), as well as simulated coking and regeneration tests are described. The dispersion, metal particle size and the formation of bimetallic particles within the material depend on the method of metal incorporation. Direct incorporation and ion-exchange methods lead to co-existence of PdRh intermetallic aggregates and segregated Pd; on the other hand, the impregnation method leads to the formation of very small and well dispersed PdRh alloy particles, with Pd preferentially located on the alloy particle surface.
Keywords: Supported bimetallic palladium-rhodium catalyst; Metal dispersion; Particle size; Intermetallic aggregates; X-ray absorption spectroscopy
Novel mesoporous aluminosilicate supported palladium-rhodium catalysts for diesel upgrading by Mélanie Taillades-Jacquin; Deborah J. Jones; Jacques Rozière; Ramon Moreno-Tost; Antonio Jiménez-López; Simone Albertazzi; Angelo Vaccari; Loretta Storaro; Maurizio Lenarda; José-Manuel Trejo-Menayo (pp. 257-264).
Novel PdRh bimetallic catalysts supported on mesoporous aluminosilicates and having a range of Pd/Rh and Si/Al molar ratios are screened for their activity in hydrogenation of naphthalene and tetralin model feedstocks, at 6MPa. The most active catalyst is used for the upgrading of light cycle oil in an industrial pilot plant, when diesel of cetane index 46 is obtained. ▪Bimetallic PdRh catalysts (molar ratio Pd/Rh=1 and 2) were prepared by impregnation of a mesoporous aluminosilicate (molar ratio Si/Al=10 and 20). These materials are destined to be used in industrial processes aiming to improve diesel quality by hydrogenation and ring-opening of aromatic components. The four catalysts were examined for their activity in hydrogenation of naphthalene and tetralin model feedstocks, at 6MPa, including in the presence of sulfur containing compounds. The capacity of one of these catalysts to improve the quality of hydrogenated industrial light cycle oil containing ≤50wtppm of sulfur was evaluated in a pilot plant. In these industrial conditions, the catalyst has a higher catalytic activity at lower temperature than a reference state of-the-art catalyst, giving a seven-point improvement of the cetane number at 280–300°C and with formation of less than 10% of non-selective cracking products.
Keywords: Supported bimetallic catalyst; Hydrogenation/hydrodecyclisation; Diesel; Cetane number; Light cycle oil
Synthesis, characterization and catalytic properties of a LEV type silicoaluminophosphate molecular sieve, SAPO-35 from aqueous media using aluminium isopropoxide and hexamethyleneimine template by N. Venkatathri; J.W. Yoo (pp. 265-270).
A small-pore silicoaluminophosphate molecular sieve, SAPO-35 was synthesized using hexamethyleneimine template and aluminium isopropoxide as aluminium source in aqueous media is reported for the first time. Pure, highly crystalline samples were obtained in short period (96h). The samples crystallize at narrow silicon content (0.3M SiO2). Fourier transform Infrared spectroscopic studies reveal the presence of three different silanol groups. A comparison with multinuclear solid-state Magic angle spinning nuclear magnetic resonance spectroscopic studies with FT-IR studies shows that these groups are located at Double six member ring, near to D6R and near to single six member ring. Other characterizations and methanol to olefin reaction studies shows that the molecular sieves synthesized by aqueous and non-aqueous media are having comparable properties. It reveals a possible application of this catalyst for industrial process.A levyne type silicoaluminophosphate molecular sieve, SAPO-35 is synthesized using aluminium isopropoxide in aqueous media for the first time. The synthesized material was characterized using different physicochemical techniques and its comparison with non-aqueous media samples of same molar ratio and from same aluminium source and template, shows that it is having superior properties.▪
Keywords: SAPO-35; Aluminium isopropoxide; Aqueous media; Hexamethyleneimine
CoBr2-MnBr2 containing catalysts for catalytic oxidation of p-xylene to terephthalic acid by Kuo-Tseng Li; Shih-Wei Li (pp. 271-277).
Catalytic oxidation of p-xylene to terephthalic acid was studied with catalysts containing CoBr2 and MnBr2. The catalysts contain neither highly corrosive hydrogen bromide nor other metal ions, and have the advantage of easy catalyst recovery. The maximum product yield obtained was 93.5% at 100°C, which was much lower than the reaction temperature used for the commercial processes (175–225°C).▪Catalytic oxidation of p-xylene (PX) to terephthalic acid (TA) was studied with catalysts containing cobalt acetate, manganese acetate, CoBr2 and MnBr2. The catalysts contain neither highly corrosive hydrogen bromide nor other metal ions, and have the advantage of easy catalyst recovery. The effects of Br/Co atomic ratio, reaction time and temperature, PX concentration, oxygen pressure, and catalyst concentration on PX conversion and product/intermediate yields were investigated. The catalyst system had a suitable reaction temperature of 100°C, which was much lower than the commercial process temperature (175–225°C). The maximum product (TA) yield was 93.5%, obtained at a Br/Co atomic ratio of three. Higher Br concentration resulted in the lower TA yield, which was ascribed to the benzylic bromide formation. The synthesis of TA could be adequately described as four reaction steps in series (PX→ p-tolualdehyde→ p-toluic acid→4-carboxybenzaldehyde→TA), with a pseudo-first-order rate equation for each step, and the third step was rate-limiting. The rate constant ratios ( k j/ k3, j=1→4) obtained at 100°C were similar to the k j/ k3 values reported earlier for cobalt acetate/manganese acetate/HBr catalysts in a range of 185–191°C.
Keywords: Oxidation catalysts; Cobalt bromide; Manganese bromide; p; -Xylene; Terephthalic acid