Skip to content. Skip to navigation
Sections
Personal tools
You are here: Home
Featured Journal
Navigation
Site Search
 
Search only the current folder (and sub-folders)
Log in


Forgot your password?
New user?
Check out our New Publishers' Select for Free Articles
Journal Search

Applied Catalysis A, General (v.287, #1)

Newsbrief (pp. n1-n2).

C-alkylation reactions catalyzed by silica-supported Keggin heteropolyacids by L.R. Pizzio; P.G. Vázquez; C.V. Cáceres; M.N. Blanco; E.N. Alesso; M.R. Torviso; B. Lantaño; G.Y. Moltrasio; J.M. Aguirre (pp. 1-8).
Aromatic alkylation reactions were studied using molybdophosphoric and tungstophosphoric acids supported on silica as catalysts. Benzene and toluene alkylation was carried out with benzyl chloride or benzyl alcohol. Also, cyclohexene and cyclohexanol were used as alkylating agents of toluene. These catalysts allow quantitative conversions in short times, with very good yields in monoalkylation products and minimal formation of polyalkylation products. Regioselectivity in these reactions is similar to that described in literature for different catalysts but the latter are markedly less efficient. In the reaction of formal [3+2] cycloaddition with benzyl alcohols catalyzed by silica-supported molybdophosphoric acid, the results are similar to those previously obtained using SnCl4 as catalyst.

Keywords: Supported Keggin heteropolyacids; Silica; C-alkylation; Formal [3; +; 2] cycloaddition


Ethylbenzene dehydrogenation on Fe2O3-Cr2O3-K2CO3 catalysts promoted with transitional metal oxides by Nicu Dulamiţă; Andrada Măicăneanu; Dean C. Sayle; Maria Stanca; Radu Crăciun; Maria Olea; Cerasella Afloroaei; Alexandrina Fodor (pp. 9-18).
The effect of titanium, vanadium and cerium oxides on the activity and selectivity of Fe2O3-based catalysts for ethylbenzene (EB) dehydrogenation reaction has been examined in an integral fixed bed reactor. For all single- or double-promoted catalysts, the selectivity to styrene was higher than that for the unpromoted catalyst. For the V2O5-promoted catalyst, an optimum content of 3wt.% was found with respect to the selectivity to styrene. Moreover, by promoting the standard catalyst with a combination of TiO2/CeO2 up to 6wt.%, the activation energy decreased by 10kJ/mol. The physicochemical properties of the promoted Fe2O3-Cr2O3-K2CO3 catalysts were examined using N2 adsorption, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. All catalysts were macroporous, 65–75% of pores having a radius larger than 150Å. No diffraction patterns specific to TiO2 or V2O5 were observed. A CeO2 crystalline phase was present in the single promoted catalyst and in the double promoted with TiO2 as well. The average size of crystals was 48.6nm for single and 21.4nm for the double one. The XPS results confirmed the better dispersion of CeO2 in the presence of TiO2. Based on experimental data several kinetic models were proposed and kinetic parameters were estimated using a non-linear least squares optimization procedure. The Langmuir–Hinshelwood–Hougen–Watson (LHHW) kinetic model with surface reaction rate-determining step better described the experimental data.

Keywords: Dehydrogenation; Ethylbenzene; Styrene; Fe; 2; O; 3; -Cr; 2; O; 3; -K; 2; CO; 3; Transitional metal oxides; LHHW kinetic model


Combustor of ceramic Pt/alumina catalyst and its application for micro-thermoelectric hydrogen sensor by Y. Choi; K. Tajima; W. Shin; N. Izu; I. Matsubara; N. Murayama (pp. 19-24).
A combustor of Pt/alumina catalyst was developed for the integration on a micro-thermoelectric hydrogen sensor (μ-THS) with a dispenser technique. The Pt/alumina catalyst was deposited on Si substrate and the hydrogen/air mixture gas was flowed to test the combustion performance. The temperature difference, developed by the heat generated from hydrogen oxidation on the catalyst, between the catalyst surface and the Si substrate showed its maximum at the Pt content of 40wt.% in the catalyst. The effect of the catalyst size on the thermoelectric voltage (Δ Vs) of μ-THS was investigated. The catalyst ( ϕ=0.8mm) smaller than the membrane developed the highest Δ Vs because of its good thermal insulation. For the gas mixture of hydrogen/air, the μ-THS showed a wide range of hydrogen detection, 50ppm-3%, with the Δ Vs of 0.03–31.74mV, respectively, at room temperature.

Keywords: Micro-thermoelectric hydrogen sensor; Pt/alumina catalyst; Dispenser technique


Selective catalytic oxidation (SCO) of ammonia to nitrogen over Fe/ZSM-5 catalysts by Gongshin Qi; Ralph T. Yang (pp. 25-33).
In this paper, we report a Fe/ZSM-5 catalyst that has superior catalytic activities for the selective catalytic oxidation (SCO) of ammonia to nitrogen as compared to all previously known catalysts. This Fe/ZSM-5 catalyst was prepared by a simple impregnation method using NH4-ZSM-5 and FeCl2. The performance of the catalyst showed that the impregnation method based on NH4-ZSM-5 and FeCl2 is a surprisingly effective process for the preparation of Fe/ZSM-5 catalyst, which has superior catalytic activities for the SCO of ammonia in the presence of excess oxygen. This preparation process is in fact a combination of the conventional impregnation and solid-state ion-exchange processes. Two different procedures were used to prepare Fe/ZSM-5, which is referred to 1-step and 2-step method, respectively. The SCO activity results show that the Fe/ZSM-5 prepared by 2-step method using FeCl2 has the highest activity compared to other catalysts studied. For the Fe/ZSM-5 catalyst, there existed a good correlation between the N2 selectivity for the SCO reaction and the activity for the selective catalytic reduction (SCR) of NO with ammonia, i.e., the higher the SCR activity, the higher N2 selectivity for SCO reaction. The study of the effect on H2O and SO2 indicated that although SO2/H2O decreased the NH3 conversion, a high conversion was still obtained at 400°C at a high space velocity, so the Fe/ZSM-5 prepared by NH4-ZSM-5 and FeCl2 should be a promising catalyst for the selective oxidation of NH3 to N2.

Keywords: Selective catalytic oxidation (SCO); Selective catalytic reduction (SCR); SCO of ammonia; SCR of NO with ammonia; Fe/ZSM-5


Kinetic and decay cracking model for a MicroDowner unit by Avelino Corma; Francisco V. Melo; Laurent Sauvanaud (pp. 34-46).
A vacuum gasoil was cracked in the MicroDowner at various operating conditions. Cracking yields were simulated with a one-dimensional hydrodynamic model and pseudo-homogeneous kinetics. A new model for describing catalyst deactivation in gasoil cracking has been used, and compared with a more traditional model based on coke-deactivation. The new model includes a fraction named strippable coke that refers to molecules that are strongly adsorbed on catalyst surface (active site coverage), but which can be stripped out of the catalyst and recovered into the heavy cycle oil fraction after the reaction. At short time-on-stream this fraction represents the major cause of deactivation, and is slowly replaced by coke-based deactivation as coke yield increases on catalyst surface.

Keywords: Catalytic cracking; Deactivation; Adsorption; Kinetics; Modelling; MicroDowner


Synergism between unsupported Re and Co or Ni sulfide catalysts in the HDS and HDN of gas oil by N. Escalona; J. Ojeda; P. Baeza; R. García; J.M. Palacios; J.L.G. Fierro; A. López Agudo; F.J. Gil–Llambías (pp. 47-53).
Two series of unsupported Co–Re and Ni–Re binary sulfide catalysts with variable atomic ratio α=Me/(Me+Re) from 0 to 1 were prepared by the co-maceration method. The catalysts were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and evaluated in the simultaneous hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) reactions of a real gas oil feed under industrial relevant conditions. The results showed a synergetic effect of the Co or Ni sulfide on the ReS2 in both HDS and HDN reactions. A maximum in activity at the same atomic ratio α∼0.5 was observed for both reactions and both Co–Re and Ni–Re catalysts. The magnitude of the synergy was generally superior for HDS than for HDN, and at low reaction temperature (598K) larger for Ni–Re than for Co–Re catalysts, especially in HDS, while at high temperature (648K) it was reverse. Moreover, the Co–Re catalysts exhibited higher HDN/HDS selectivity than the Ni–Re catalysts. Neither XRD nor XPS results evidenced the presence of a “Co–Re–S� or “Ni–Re–S� like phase. It is suggested that the synergism could be associated to the hydrogen activation and spillover from the Co or Ni sulfide to ReS2.

Keywords: Hydrodesulfurization (HDS); Hydrodenitrogenation (HDN); ReS; 2; Co sulfide; Ni sulfide


Tris(silyl)trifluoromethanesulfonates and their tetrakis(silyl) analogues as potential catalysts in photoinitiated cationic polymerization by Anna Kowalewska; Włodzimierz A. Stańczyk; Richard Eckberg (pp. 54-59).
UV initiated cationic photo-curing is commonly carried out in the presence of photo-sensitive onium salts as acid generators. The performance of this class of compounds can be improved by addition of a catalyst (acid) precursor (acid amplifier, AA), prone to acid catalyzed decomposition (also in an autocatalytic sequence). “Trisyl� or “tetrakis�-type esters of strong acids were studied as potential candidates for such a photo-curing purpose. (PhMe2Si)(Me3Si)2CSiMe2OSO2CF3 and [( p-MeC6H4O2SO)Me2Si]4C were found to be the most promising systems. They are more compatible with silicone materials than currently used AAs and can be embedded in the cured resin, thus limiting the post-curing evolution of low molecular weight photolytic decomposition products. They can additionally improve thermal stability of the resin.

Keywords: Catalytic cross-linking; Acid amplifier; Photoinitiated cationic polymerization; Trifluoromethanesulfonate; Trisyl


Fischer–Tropsch synthesis over iron catalysts supported on carbon nanotubes by Munga C. Bahome; Linda L. Jewell; Diane Hildebrandt; David Glasser; Neil J. Coville (pp. 60-67).
Carbon nanotubes (CNTs) were synthesized in a catalytic reaction over an iron catalyst using CaCO3 as a support. The purification of the carbon nanotubes (CNTs) and the oxidation of the CNTs surfaces were performed with HNO3. Iron-based catalysts supported on carbon nanotubes for use in the Fischer–Tropsch (FT) reaction were prepared either by incipient wetness or a deposition precipitation method using urea and then promoted with potassium and/or copper. The FT synthesis was carried out in a fixed-bed micro reactor (275°C, 8bar, CO/H2=2). The effect of Cu and promoters on CO conversion, product selectivity and FT synthesis activity were investigated and compared with data reported on other carbon-based supports. The potassium promoted catalysts gave higher yields of CO2 and C2 olefins and the lowest methane selectivity when compared to the unpromoted catalysts. Copper, while enhancing catalyst activity, did not have an effect on the FT product selectivity.

Keywords: Carbon nanotubes; Fischer–Tropsch; Iron-based catalyst; Cu and K promoters


Copper(II) chloride/tetrabutylammonium bromide as a catalytic system for the oxidation of 2-isopropylnaphthalene with oxygen by Beata Orlińska; Jan Zawadiak; Danuta Gilner (pp. 68-74).
The catalytic oxidation of 2-isopropylnaphthalene with oxygen was studied. The system composed of copper(II), cobalt(II) or manganese(II) chloride with tetrabutylammonium bromide was used as catalysts. Depending on the metal ion as well as process conditions, different compositions of products were obtained. The mixture of 2-(2-naphthyl)-2-propanol, 2-acetylnaphthalene, bis(1-methyl-1-(2-naphthyl)ethyl) peroxide as well as a small amount of 1-methyl-1-(2-naphthyl)ethyl hydroperoxide was obtained in the presence of copper(II) chloride and tetrabutylammonium bromide.

Keywords: Oxidation; 2-Isopropylnaphthalene; Chlorides of transition metal; Tetrabutylammonium bromide


Unsupported Fe–V mixed sulfides: Characterization and VOOEP hydrodeporphyrinization by B.P. Embaid; F. Gonzalez-Jimenez; C.E. Scott (pp. 75-82).
Bulk Fe–V mixed sulfide catalysts prepared by the co-precipitation method were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fe57 Mössbauer spectroscopy. Hydrodeporphyrinization (HDP) of vanadyl octaetil porphyrine (VOOEP) was used as a catalytic test. XRD and Mössbauer analysis showed the existence of two structural phases based on NiAs sub-cell, i.e. monoclinic (Fe, V)3S4 and hexagonal (Fe, V)1− xS. TEM micrographs reveal similar morphology (particle size and shape) for all the catalysts except for pure iron sulfide, which presented larger particle size. Mössbauer spectra of fresh and used catalysts indicate that phases are rather stable at reaction conditions. A correlation between specific HDP activity and the amount of monoclinic (Fe, V)3S4 phase is evidenced.

Keywords: Fe–V sulfides; Characterization; VOOEP hydrodeporphyrinization


Vapor-phase Beckmann rearrangement of cyclohexanone oxime over H3PO4/ZrO2–TiO2 by M. Ghiaci; A. Abbaspur; R.J. Kalbasi (pp. 83-88).
ZrO2–TiO2 mixed oxides with a Ti and Zr molar ratio of 1/1 were prepared under various conditions by the sol–gel method. Catalysts containing 5–35% H3PO4 were prepared using these oxides and the catalytic performance of each material for vapor-phase Beckmann rearrangement of cyclohexanone oxime to ɛ-caprolactam was determined. As the H3PO4 content in the mixed oxide increased, the specific surface area decreased; XRD results indicated that ZrO2–TiO2 became amorphous after calcinations at 700°C. The yield of lactam increased with increasing the H3PO4 content in the mixed oxide and reached a maximum value for the 15wt.% H3PO4 on the ZrO2–TiO2 (1/1) support. With further increase in H3PO4 content, the lactam yield decreased; the lowest value was observed for the 35wt.% H3PO4 on the ZrO2–TiO2 (1/1) support. The acidic properties and the pore characteristics of the catalysts were key factors that affected its performance. The influences of the operating parameters on the performance of H3PO4/ZrO2–TiO2 (1/1) catalyst were also investigated. The interaction of H3PO4 with ZrO2–TiO2 (1/1) support has been investigated by FT-IR, for characterization of the interaction of H3PO4 with the support.

Keywords: Beckmann rearrangement; É›-Caprolactam; Cyclohexanone oxime; H; 3; PO; 4; TiO; 2; ZrO; 2


Low-temperature hydrodechlorination mechanism of chlorobenzenes over platinum-supported and palladium-supported alumina catalysts by Yoshihito Hashimoto; Yoshio Uemichi; Akimi Ayame (pp. 89-97).
Hydrodechlorination of monochlorobenzene was carried out on Pt-supported and Pd-supported alumina, silica, titania, and silica-alumina catalysts at 298K using a gas-phase fixed bed flow reactor. The Pt and Pd catalysts supported on alumina with Lewis acid sites indicated higher activity than those supported on silica-alumina and titania that have Brønsted acid sites. The activities of the Pt-supported and Pd-supported silica lay between those of the alumina and the silica-alumina catalysts. On each carrier, the Pd catalysts resulted in higher activity than the Pt ones. The pure Pt and Pd powder catalysts indicated less activities than the metal-supported alumina catalysts. Reaction products were only benzene and cyclohexane; on the Pd catalysts, cyclohexane was a minor product. No cleavage or decomposition of aromatic structure occurred. All the catalysts showed gradual activity decrease with process time, which originated from the accumulation of chlorines or chloride ions on the catalyst surfaces. The accumulation took place on both the metal and carrier surfaces, but the contribution of the latter was much larger than that of the former. In the reactions of 1,4-dichlorobenzene and 1,3,5-trichlorobenzene, similar results were also obtained. Furthermore, the conversion of 1,4-dichlorobenzene increased with increasing the amount of supported Pd at a constant amount of alumina carrier and with increasing the amount of alumina at a constant amount of supported Pd. Based on the above experimental results, the mechanism of the hydrodechlorination on the Pt-supported and Pd-supported alumina catalysts was discussed.

Keywords: Chlorobenzene; Hydrodechlorination; Ambient temperature; Platinum; Palladium; Alumina; Fixed bed flow reactor; Benzene; Cyclohexane


Ethylene oligomerizations to low-carbon linear α-olefins by structure modulated phenoxy-imine nickel(II) complexes combined with aluminum sesquichloride by Il Kim; Chang Hun Kwak; Jae Sung Kim; Chang-Sik Ha (pp. 98-107).
A series of ethylene oligomerization catalysts based on bidentate phenoxy-imine ligands coordinated to nickel is reported. The phenoxy-imine nickel(II) complexes of the general structure, [(2,6-R2C6H3N=C-3-R′C6H3O)2Ni] (R′=H,1; tBu=2; R=Me,a; Et,b; iPr,c), modifying their structural characteristics by changing the nature of the ligand substituents on the imino and aromatic moieties were prepared by using one shot synthesis. The formation of active species in the reaction of1c complexes with ethylaluminum sesquichloride (EAS) was investigated UV–vis spectroscopy. At Al/Ni molar ratio >25, the formation of a cationic nickel species, active in the oligomerization of ethylene, was supposed to occur and this result was in agreement with the actual oligomerization results. In the presence of ethylene and EAS cocatalyst, all complexes are extremely active for the ethylene oligomerization, with activities greater than 5×108goligomer/molNihatm, regardless of the catalyst structure. All catalysts yielded butenes as major products. The catalytic behavior of the homogeneous systems prepared in situ from1c and different organoaluminum co-catalysts in the activation of ethylene was also investigated. In particular, the effect of reaction parameters, such as temperature, the Al/Ni molar ratio and the type of solvent, was studied. Changing the reaction parameters it was possible to modify the chemo- and regioselectivity of the catalytic process towards the formation of target olefin products, even if they were not decisive factors to control product distribution.

Keywords: Ethylene; Ethylaluminum sesquichloride; Homogeneous catalysis; Nickel; Oligomerization; Phenoxy-imine ligands


Chemical fabrication of Al2O3 nano-trilobes by S.M. Liu; W.D. Zhang; Z.L. Liu; L.H. Liu (pp. 108-115).
The recent development of silicon-based microreactors requires conventional catalyst carriers to be trimmed down to the sub-micrometer regime while keeping their complex geometrical shapes unchanged. In this work, we use a “top-down� etching approach to fabricate Al2O3 nano-trilobe carriers from the inter-channel parts of pseudo-hexagonally arranged one-dimensional channels of anodic alumina membranes. With a dilute NaOH (0.04M) etchant and prolonged etching time (1.5h), highly regulated Al2O3 nanocarriers have been prepared into two major forms: well-aligned (bundles) and freestanding trilobes. It has been found that the Al2O3 nano-trilobes are generated only on the upward facing of the membranes owing to the support provided by less etched membrane underneath and a less vibrant region in fluid exchange. The etching process can be described as a nucleophilic reaction that involves an attachment of hydroxyl ions to Lewis acid sites of aluminum cations. The amorphous as-prepared nano-trilobes can be further heat-treated to any crystallographic phases. For example, phase pure polycrystalline θ-Al2O3 nano-trilobes have been prepared at 1000°C in laboratory air. Future applications of these nanocarriers have also been discussed.

Keywords: Al; 2; O; 3; Nano-trilobes; Etching; Alumina membrane


Mild acid MCM-41 promotes para-isomer in the vapour phase alkylation of isopropylbenzene with diethyl carbonate by Seshachalam Udayakumar; Arumugam Pandurangan; Pradeep Kumar Sinha (pp. 116-128).
Ethylation of isopropylbenzene (IPB) with diethyl carbonate (DEC) was studied using Al-MCM-41 molecular sieves with Si/Al ratios of 33, 52, 75 and 114 at temperatures ranging from 200 to 350°C. Both mono-ethylated and diethylated isomers were obtained. The products obtained were 2-ethyl-isopropylbenzene (2-EIPB), 3-ethyl-isopropylbenzene (3-EIPB), 4-ethyl-isopropylbenzene (4-EIPB), 2,4-diethyl-isopropylbenzene (2,4-DEIPB), 2,6-diethyl-isopropylbenzene (2,6-DEIPB) and ethylbenzene (EB). The Al-MCM-41 mesoporous materials were characterized using powder X-ray diffraction (XRD), nitrogen adsorption measurements (BET) and thermogravimetric-differential thermogravimetric analysis (TGA-DTG). XRD studies indicated that the calcined and as-synthesized materials had the standard MCM-41 structure. Nitrogen adsorption was used to determine specific surface area, pore volume, and pore size distribution in the Al-MCM-41 (33), Al-MCM-41 (52), Al-MCM-41 (75) and Al-MCM-41 (114) mesoporous molecular sieves. FT-IR studies showed that Al ions were incorporated into the hexagonal mesoporous structures of Al-MCM-41. The thermal stability of the as-synthesized materials was studied using TGA-DTG. The effects of reaction temperature, WHSV and feed ratios on the selectivity of 4-EIPB were studied.

Keywords: Ethylation of isopropylbenzene; Mild acidity; Selectivity of isopropylbenzene; Al-MCM-41


Hydrothermal synthesis of molybdenum oxide catalyst: Heteropoly acids encaged in US-Y by Mai Huong Tran; Hironobu Ohkita; Takanori Mizushima; Noriyoshi Kakuta (pp. 129-134).
Molybdenum oxide was encaged into the supercages of US-Y by using a hydrothermal synthesis technique. Silicomolybdic acid (SMA), and phosphomolybdic acid (PMA), heteropoly acids (HPAs) with a Keggin structure, were synthesized by refluxing treatments with phosphoric or nitric acids. FT-IR, and EXAFS analyses revealed the presence of HPAs even after washing several times in hot water, indicating that the HPA molecules were anchored in the supercages. In addition, not only PMA but also SMA were detected after the treatment with phosphoric acid, suggesting that the refluxing induced the reaction of Si species of US-Y. The catalytic activity of PMA encaged in US-Y demonstrated that both the dispersion of PMA and the presence of SMA acted synergistically as active sites for partial oxidation of methane.

Keywords: Heteropoly acid; Zeolite Y; Supercage; Methane oxidation (partial); Formaldehyde


Characterization and hydrodesulfurization activity of CoMo catalysts supported on sol–gel prepared Al2O3 by Franck Dumeignil; Koichi Sato; Motoyasu Imamura; Nobuyuki Matsubayashi; Edmond Payen; Hiromichi Shimada (pp. 135-145).
A series of CoMo/Al2O3 catalysts was prepared by impregnation on a series of alumina powders synthesized by the sol–gel method with different hydrolysis ratios R (defined as [H2O]/[aluminum-tri-sec-butoxide (ASB)]; R=3,4,…,12,13). The oxide precursors were characterized and subsequently tested in the hydrodesulfurization (HDS) of thiophene, dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT). Mainly due to their large pore diameters of ca. 6nm, the catalysts prepared from the alumina with hydrolysis ratio R=7–10 showed higher HDS activity compared with the activities of the other prepared catalysts. The effect of the pore diffusional limitation was more significant than expected, due to the ink-bottle shape of the pores of the prepared catalysts with hydrolysis ratio R<8 and R>10. Due to highly dispersed CoMo active phase, the HDS activity of the prepared catalysts with hydrolysis ratio R=8 and 9 for thiophene was similar to that of a reference industrial catalyst that was designed and manufactured for deep HDS of diesel fuel fractions. Furthermore, the HDS activity of the prepared catalysts with hydrolysis ratio R>5 for DBT was higher than that of the reference industrial catalyst. For 4,6-DMDBT, however, the reference industrial catalyst showed higher HDS activity compared with the activities of the prepared catalysts. Relatively high HDS activity was observed for the prepared catalysts with R=9 and 10 with cylindrical pore shape and with a high proportion of strong acid sites. The strong acidity supposedly enhanced the hydrogenation activity of the catalysts that was essential for the HDS of 4,6-DMDBT.

Keywords: Catalysis; Sol–gel; Alumina; CoMo; HDS; Porosity; Acidity; Thiophene; DBT; 4,6-DMDBT
Featured Book
Web Search
Powered by Plone CMS, the Open Source Content Management System

This site conforms to the following standards: