Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Applied Catalysis A, General (v.439-440, #)
A study on the liquid-phase oxidation of toluene in ionic liquids by Yan Meng; Bin Liang; Shengwei Tang (pp. 1-7).
Display Omitted► Toluene conversion increased with the increasing hydrophilicity of ILs. ► [Emim]BF4 improved the reaction with a high conversion and high selectivities. ► The process in [Emim]BF4 was controlled by a heterogeneous L-L-G reaction. ► Coupling between reaction and extraction separation improved the process.The effect and mechanism of the hydrophilic ionic liquids (ILs) with cobalt naphthenate as catalyst on the liquid-phase oxidation of toluene were studied systematically. Five ILs with different hydrophilicities were employed as reaction media. The results showed that toluene conversion increased with increasing hydrophilicity of ILs. The toluene conversion and the corresponding selectivity of benzaldehyde reached 19.6% and 19.5%, respectively, in 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim]BF4). The solubilities of toluene, benzaldehyde, benzyl alcohol and benzoic acid in [Emim]BF4 were further measured at temperatures from 299.2K to 343.2K. The correlations between solubility and temperature were developed based on the critical point of phase separation or ideal solution model. The low solubility of toluene in [Emim]BF4 indicated a heterogeneous oxidation mechanism for toluene. The improvement of toluene conversion and product selectivity in [Emim]BF4 was attributed to the interactions between reaction and extraction separation. The sensitivity study demonstrated that the increase in oxygen pressure was beneficial to the reaction. A much lower reaction temperature of 130°C was achieved in [Emim]BF4 instead of a typical 160–170°C for current commercial plants. The high conversion, low reaction temperature and high product selectivity for the liquid-phase oxidation of toluene in [Emim]BF4 makes it a green and efficient hydrocarbon oxidation process.
Keywords: Ionic liquids; Liquid-phase oxidation; Solubility; Toluene; Benzaldehyde; Benzyl alcohol; Benzoic acid
Selective hydrogenation of acetylene in excess ethylene over SiO2 supported Au–Ag bimetallic catalyst by Xiaoyan Liu; Yanan Li; Jonathan W. Lee; Chen-Yu Hong; Chung-Yuan Mou; Ben W.L. Jang (pp. 8-14).
Display Omitted► Au–Ag/SiO2 is used in catalyzing selective hydrogenation of C2H2 in large excess of C2H4. ► O2 plasma treatment promoted the catalytic activity of Au–Ag/SiO2. ► Au–Ag/SiO2 shows better catalytic activity than Au/SiO2. ► Ag stabilizes the nanoparticles against sintering and helps to activate H2.Supported gold nanocatalysts have been reported to be active in selective hydrogenation of acetylene. In this work, SiO2 supported Au–Ag bimetallic catalyst is studied in the selective hydrogenation of acetylene in excess ethylene. Au and Ag were reductively deposited on a silica surface functionalized by APTES (3-aminopropyltriethoxysilane). They form Au–Ag alloy nanoparticles of very small size. The catalytic activity of Au–Ag bimetallic system showed better catalytic activity at high temperature than that of monometallic gold catalyst. According to the TEM and XRD results, Ag stabilized the nanoparticles against sintering during high temperature calcinations. Non-thermal O2 plasma was applied to remove the APTES under mild conditions instead of high temperature calcination. The results showed that the conversion of acetylene was much higher over Au–Ag/SiO2 catalyst pretreated by O2 plasma than that of pretreated by calcination at 500°C, although the latter catalyst had similar particle size.
Keywords: Gold; Silver; O; 2; plasma; Acetylene hydrogenation; Excess ethylene
Copper(II) complexes of arylhydrazones of β-diketones immobilized on Zn–Al layered double hydroxides as effective recyclable catalysts for peroxidative oxidation of alkanes by Tatiana C.O. Mac Leod; Maximilian N. Kopylovich; M. Fátima C. Guedes da Silva; Kamran T. Mahmudov; Armando J.L. Pombeiro (pp. 15-23).
Display Omitted► CuII-arylhydrazones of β-diketones (CuIIAHBD) complexes have been prepared. ► CuIIAHBD immobilized on ZnAl-layered double hydroxides (LDH). ► CuIIAHBD-LDH systems catalyze the peroxidative oxidation of alkanes. ► CuIIAHBD-LDH can be recycled at least five times without activity loss.New CuII complexes [Cu(H2O)(μ-L1)Na(H2O)] n·2 nH2O (4), [Cu(H2O)(μ-HL2)Na(H2O)] n·2 nH2O (5) and [Cu(H2O)(μ-L3)Na(H2O)] n·2 nH2O (6), bearing the SO3− or COO−-functionalized arylhydrazones of β-diketones (AHBDs) 3-(2-hydroxy-3-sulfo-5-nitrophenylhydrazone)pentane-2,4-dione (H3L1,1), 3-(2-hydroxy-3,5-disulfophenylhydrazone)pentane-2,4-dione (H4L2,2) or 1-ethoxy-2-(2-hydroxy-4-carboxyphenylhydrazone)butane-1,3-dione (H3L3,3), were synthesized and characterized by elemental analysis, IR spectroscopy, ESI-MS and X-ray analysis (for4).4–6 were immobilized on the layered double hydroxides (LDH) [Zn0.74Al0.26(OH)2]ǀ(NO3)0.26·0.23H2O and characterized by X-ray powder diffraction patterns (XRPD), UV–vis, IR spectroscopies, thermogravimetric (TG) and differential thermal (DTA) analyses. The heterogenized CuIIAHBD-LDH systems catalyze the peroxidative oxidation (with TBHP or H2O2 as oxidant) of alkanes (cyclohexane, n-pentane, n-hexane, n-heptane, n-octane) mainly to alcohols, under mild conditions, and can be recycled at least five times without significant loss of activity, with overall yields of 10–15% per cycle depending on the catalyst used. Regioselectivity at position 2 of the alkane is favoured by the heterogenized catalysts.
Keywords: Alkane oxidation; Immobilization of catalysts; Recycling of catalysts; Cu; II; complexes of arylhydrazones of β-diketones; Layered double hydroxides
Mesoporous carbon as an efficient catalyst for alcoholysis and aminolysis of epoxides by Inês Matos; Paulo Duarte Neves; José Eduardo Castanheiro; Elena Perez-Mayoral; Rosa Martin-Aranda; Carlos Duran-Valle; Joaquim Vital; Ana M. Botelho do Rego; Isabel M. Fonseca (pp. 24-30).
Display Omitted► Ring-opening reactions of epoxides over mesoporous carbon. ► Surface chemistry modification of the mesoporous carbon. ► Alcoholysis and aminolysis of epoxides. ► High conversion and selectivities.The ring opening reaction of epoxides by alcohols and amines using mesoporous activated carbon as efficient and environmentally friendly heterogeneous catalyst is reported. Carbon xerogels were synthesized by polymerization of resorcinol and formaldehyde. The surface of the activated carbon was oxidized in liquid phase with HNO3 and then functionalized with H2SO4.Chemical and textural characterization by elemental analysis, pHPZC, TPD, BET and XPS indicates that oxidation in liquid phase is effective in the introduction of strong acid groups in the carbon surface. The functionalization with H2SO4 led to more acid functional groups, as expected. The activated carbons were tested in alcoholysis and aminolysis of epoxides, having been obtained excellent results of conversion and selectivity, both over 95%.
Keywords: Ring opening; Mesoporous carbon; Alcoholysis of epoxides; Aminolysis of epoxides
A study of the catalytic hydroconversion of biocarboxylic acids to bioalcohols using octanoic acid as model reactant by Szabolcs Harnos; György Onyestyák; József Valyon (pp. 31-40).
Display Omitted► Supported Cu,In catalysts are active in carboxylic acid hydrodeoxygenation (HDO). ► Indium promotes alcohol selectivity of Cu catalysts in carboxylic acid HDO. ► Liquid biofuel can be generated by reducing bio-carboxylic acids to alcohols. ► Promoting effect of indium on Cu catalysts comes from alloy (Cu2In) formation.The catalytic hydrodeoxygenation (HDO) of octanoic acid (C7COOH) to octene and octane was found to proceed in consecutive reaction through octyl aldehyde and octyl alcohol intermediates. Aluminosilicate and γ-alumina supported Cu and Cu,In catalysts were applied in a fixed bed flow-through reactor at 21bar total pressure in the temperature range of 330–380°C. The feed was 7.1% C7COOH/84.3% H2/He. The WHSV of the acid was 1.82h−1. The results suggested that at lower temperatures the rate of acid hydrogenation/dehydration determined the rate of the consecutive hydroconversion process and alcohol selectivity. The reduction of aldehyde was facile, thus, the aldehyde selectivity was low under most conditions. At lower temperatures and conversions the acid coverage was high hindering the catalytic dehydration of the product alcohol. At higher temperatures and acid conversions the alcohol dehydration activity of the catalyst determined the alcohol selectivity. The indium additive was found to increase the HDO activity and the alcohol selectivity of the copper catalysts significantly. The favorable effects of indium were attributed to the formation of new catalytically active Cu2In alloy phase.
Keywords: Octanoic acid hydroconversion; Cu,In/aluminusilicate; Cu,In/γ-alumina; Supported Cu; 2; In alloy catalyst; Destruction of zeolite X and P
In situ preparation and investigation of Pd/CeO2 catalysts for the low-temperature oxidation of CO by R.V. Gulyaev; A.I. Stadnichenko; E.M. Slavinskaya; A.S. Ivanova; S.V. Koscheev; A.I. Boronin (pp. 41-50).
Display Omitted► XPS and XAS were used in situ to study the formation of Pd/CeO2 catalyst. ► Formation of mixed Pd xCe1− xO2− δ surface phase occurs during the catalyst synthesis. ► Catalytic performance depends on Pd-ceria interaction. ► Treatment of the catalysts with hydrogen leads to a sharp increase in the activity.The formation of Pd0.05Ce0.95O2 catalysts for the low-temperature oxidation of CO by the thermal decomposition of Ce(NO3)3 and Pd(NO3)2 with oxygen was studied by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) directly in the preparation chamber of a spectrometer. Palladium is represented by two species on the surface of the catalysts: solid solutions of Pd xCe1− xO2− δ and palladium clusters. Pd clusters can be formed in an oxidized or reduced state depending on the reaction conditions. Treatment of the catalysts with hydrogen leads to a sharp increase in CO conversion because of the reduction of parts of the palladium accompanying the formation of the metallic clusters. The testing of “real” and model catalysts was conducted in a light-off mode. The correlation between the activity of the Pd/CeO2 catalysts and the states of the palladium was proposed.
Keywords: Low-temperature CO oxidation; Palladium; Ceria; Pd; CeO; 2; Surface phase; XPS; XAS
Biomimetic oxidation of organosulfur compounds with hydrogen peroxide catalyzed by manganese porphyrins by S.M.G. Pires; M.M.Q. Simões; I.C.M.S. Santos; S.L.H. Rebelo; M.M. Pereira; M.G.P.M.S. Neves; J.A.S. Cavaleiro (pp. 51-56).
Display Omitted► Manganese porphyrins as catalysts and hydrogen peroxide as the oxygen source. ► A biomimetic approach for the oxidation of organosulfur compounds. ► Conversion of benzothiophene reaches 99.9% in 90min of reaction. ► Conversion of dibenzothiophene attains 99.9% after 120min of reaction. ► Total conversion of a model fuel in hexane into the corresponding sulfones after 180min.A biomimetic and environmentally benign approach, with potential application in the oxidative desulfurization procedure for several organosulfur compounds (thioanisol, diphenylsulfide, benzothiophene, 2-methylbenzothiophene, 3-methylbenzothiophene, benzothiophene-2-methanol and dibenzothiophene), is presented. The current methodology involves manganese porphyrins as catalysts, which are well-known biomimetic models of cytochrome P450 enzymes, and hydrogen peroxide as the oxygen source. [Mn(TDCPP)Cl] and [Mn(TPFPP)Cl], the manganese porphyrin complexes used in this study, proved to be very efficient catalysts, affording high conversions of all the substrates tested into the corresponding sulfones. The conversion of benzothiophene reaches 99.9% in 90min, whereas the conversion of dibenzothiophene attains 99.9% after 120min of reaction, both for a catalyst/substrate molar ratio of 150. The substituted benzothiophenes give rise to similar results, being the best conversions obtained for a catalyst/substrate molar ratio of 150. The oxidation of a model fuel (solution of benzothiophene, 3-methylbenzothiophene, 2-methylbenzothiophene, and dibenzothiophene in hexane) was performed using hydrogen peroxide and [Mn(TDCPP)Cl] as catalyst, achieving total conversion into the corresponding sulfones.
Keywords: Oxidative desulfurization; Organosulfur compounds; Manganese; Porphyrins; Hydrogen peroxide
Single and combined effects of Bottom Cracking (BCA) and Propylene Booster (PBA) separate particles additives addition to a Fluid Catalytic Cracking (FCC) catalyst on the FCC product distribution and quality by Yannick Mathieu; Avelino Corma; Michaël Echard; Marc Bories (pp. 57-73).
Display Omitted► BCA addition improves the LCO quality and limits the gasoline pool quality. ► BCA addition increases the thermal to catalytic cracking ratio. ► ZSM-5 efficiency is dependent of the feed/Ecat pair ability to yield C5+ aliphatics. ► LCO selectivity and quality is negatively affected by ZSM-5 additive. ► Beneficial effects of both additives can be simultaneously obtained.In the present work, we have investigated how the single and combined addition of commercial separate particle additives, such as Bottom Cracking additive (BCA) and Propylene Booster additive (ZSM-5 based-PBA), to a FCC USY catalyst can influence the product distribution and quality during FCC processing. Due to the relatively low catalytic activity of the BCA additive, the increasing single addition of BCA implies a higher ratio of thermal to catalytic cracking, leading in particular to higher dry-gases and coke selectivities and a lower gasoline pool quality. The Bottom Cracking ability of the BCA additive is feed dependent and starts to be representative for high addition levels of about 50–60wt%, allowing the increase of the LCO pool selectivity and quality. The single and low addition level (i.e. 10wt%) of ZSM-5 based additive allows to drastically improve the light alkenes selectivity at the expense of the gasoline selectivity, improving, due to concentration effects, the quality of the FCC gasoline pool, but generally limiting the LCO selectivity and quality while the coke selectivity is little increased. The combined use of both additives looks like an interesting upgrading strategy considering that it is possible to keep a high catalytic activity, to fully take advantage of the beneficial effects of the ZSM-5 and BCA additives, and to mitigate at the same time the increase of the coke and dry gases selectivities.
Keywords: Fluid Catalytic Cracking (FCC) catalyst; Propylene Booster additive (PBA); ZSM-5; Bottom Cracking additive (BCA); Micro-Downer (MD) unit; Micro-activity test (MAT); FCC diesel and gasoline quality; Comprehensive two-dimensional gas chromatography (GC; ×; GC FID)
Recyclable Cu(II)-macrocyclic salen complexes catalyzed nitroaldol reaction of aldehydes: A practical strategy in the preparation of ( R)-phenylephrine by Rukhsana I. Kureshy; Balchand Dangi; Anjan Das; Noor-ul H. Khan; Sayed H.R. Abdi; Hari C. Bajaj (pp. 74-79).
Display Omitted► Chiral Cu(II) macrocyclic salen catalysts with trigol linker were designed. ► These complexes were used for asymmetric nitroaldol reaction of aldehydes. ► β-nitroalcohols were achieved in high yield (92%) with 95% ee in 30h at RT. ► This protocol is used for the synthesis of ( R) phenylephrine in high yield and ee. ► The catalyst worked well up to 8 cycles with retention of catalyst performance.Chiral macrocyclic salen ligands1′–3′ derived from 1 R,2 R-(−)-1,2-diaminocyclohexane, 1 R,2 R-(+)-1,2-diphenyl-1,2-diaminoethane and ( R)-(+)-1,1′-binaphthyl-2,2′-diamine with trigol bis aldehyde were prepared and characterized by microanalysis,1H NMR, UV/Vis. spectroscopy, optical rotation and mass spectroscopy. Highly enantioselective nitroaldol reaction of various aromatic and aliphatic aldehydes with nitromethane in presence of several bases were carried out in the presence of in situ generated Cu(I)/Cu(II) complexes with chiral macrocyclic salen ligands1′–3′ at RT. Excellent yields (up to 92% with respect to the aldehyde) of β-nitroalcohols with high enantioselectivity (ee, ∼95%) was achieved in case of 3-methoxy- and 4-nitrobenzaldehyde in ca. 30h with the use of chiral macrocyclic salen ligands3′ with CuCl2·2H2O in presence of 2,6-lutidine as a base. Chiral macrocyclic salen catalyst3 mediated nitroaldol process is recyclable (up to 8 cycles with no significant loss in its performance). This protocol is also used for the synthesis of enantiomerically pure ( R)-phenylephrine (α1-adrenergic receptor agonist) via asymmetric nitroaldol reaction of 3-methoxybenzaldehyde in three steps.
Keywords: Enantioselective; Chiral Cu(II) macrocyclic complex; Chiral; β; -nitroalcohols; Aldehydes; Recyclable
Optimization of bimetallic dry reforming catalysts by temperature programmed reaction by F. Menegazzo; M. Signoretto; F. Pinna; P. Canton; N. Pernicone (pp. 80-87).
.Display Omitted► A simple temperature-programmed procedure was used. ► Both CH4/CO2 reforming and coke formation via CH4 or CO decomposition were studied. ► Bimetallic Pd(or Pt)-Ni catalysts on zirconia and alumina were investigated. ► The co-impregnated Ni-Pd/ZrO2 catalyst looks the most promising for an industrial application.Catalytic reforming of CH4 with CO2 was investigated on mono and bimetallic Pd(or Pt)-Ni based samples supported on Al2O3 and ZrO2. A simple temperature-programmed procedure was used to study both reforming and coke formation via CH4 or CO decomposition. Catalysts supported on zirconia are more active than alumina-supported samples. The addition of Pt or Pd to Ni/ZrO2, preferably by co-impregnation, prevents coke formation. The co-impregnated Ni-Pd/ZrO2 catalyst looks the most promising for a possible industrial application.
Keywords: Dry reforming; CO; 2; reforming; Ni-Pt; Ni-Pd; Temperature programmed reaction; Zirconia
Influence of the parent zeolite structure on chromium speciation and catalytic properties of Cr-zeolite catalysts in the ethylene ammoxidation by F. Ayari; M. Mhamdi; T. Hammedi; J. Álvarez-Rodríguez; A.R. Guerrero-Ruiz; G. Delahay; A. Ghorbel (pp. 88-100).
Display Omitted► Cr–S solids (S=ZSM-5, mordenite, beta, USY, Y) were tested in C2H4 ammoxidation. ► Cr species with high oxidation states play a key role in the ammoxidation. ► Agglomerated Cr2O3 and bare Cr ions should be avoided during catalyst preparation. ► Catalytic activity is highly affected by the zeolite matrix. ► Interactions between ethylamine intermediate molecules inhibit CH3CN formation.Cr-zeolites with MFI, BEA, MOR and FAU structures, prepared by solid-state ion exchange, were characterized and tested in C2H4 ammoxidation to acetonitrile in the temperature range 425–500°C. Based on characterization results, chromate and/or polychromate species, oxo-cations and small Cr2O3 oxide clusters played a key role in the ammoxidation of ethylene, while agglomerated Cr2O3 and bare Cr cations should be avoided. Cr ions sited in the sodalite and hexagonal cages of NH4+–Y are not accessible to the reactants while available catalytic sites are poorly active. However, the mesopores of the ultra stable Y zeolite (USY) favor the diffusion of reactants to the clustered Cr oxide. The corresponding catalyst is therefore active, but the presence of octahedral Al species is crucial to the ammoxidation. Cr ions in zeolites beta and mordenite led to less active catalysts when compared to ZSM-5. In zeolite beta, the micropores are small; therefore, pronounced interactions between ethylamine intermediate molecules could discourage the acetonitrile formation. In mordenite, agglomerates of Cr2O3 oxide inhibited the accessibility of active sites to the reactants and enhanced the hydrocarbon oxidation. The catalytic performance of Cr ions in ZSM-5 provided from a synergy of different parameters: structural, textural and the acid strength (Si/Al ratio).
Keywords: Ammoxidation; Solid-state exchange; Zeolite structure; Thermal analysis; H; 2; -TPR
Mn(III) based binapthyl Schiff base complex hetrogenized over organo-modified SBA-15: Synthesis, characterization and catalytic application by Priti Sharma; Anish Lazar; A.P. Singh (pp. 101-110).
Display Omitted► The synthesis of mesoporous SBA-15 was carried out hydrothermally under the autogeneous pressure in an autoclave. ► Surface modification of SBA-15 was achieved by a post synthesis grafting method. ► Neat Mn(III)-L complex and Mn(III)-L-SBA-15 were applied for sulfoxidation of thioanisole.A heterogenized organocatalyst was synthesized by the covalent anchoring of the complex chloro (S,S)(−)[N-3- tert-butyl-5-chloromethyl salicylidene]-N′-[3′,5′-di- tert-butyl salicylidene] 1,1′-binapthyl-2,2′-diamine manganese(III) over modified mesoporous surface of SBA-15 through the reactive 3-aminopropyl trimethoxysilane (3-APTMS) group. The surface properties of the functionalized catalyst were analyzed by a series of characterization techniques such as elemental analysis, XRD, N2 sorption measurement isotherm, FT-IR, TGA–DTA, XPS, and solid state13C NMR. The XRD and N2 sorption measurement, UV reflectance and CP MAS NMR spectroscopy (13C and29Si) of the catalyst confirmed the structural integrity of the mesoporous hosts and the spectroscopic characterization technique proved the successful anchoring of the metal complex over the modified mesoporous support. The screening of the catalyst Mn(III)-L-SBA-15 and neat Mn(III)-L complexes was done in the oxidation reaction of thioanisole (methyl phenyl sulfide) by using TBHP as an oxidant. Mn(III)-L-SBA-15 catalyst shows higher activities and turnover number (TON) and exhibit enhanced enantiomeric excess comparable to homogeneous catalyst [Mn(III)-L]. [Mn(III)-L-SBA-15] catalyst was found more active than homogeneous catalyst [Mn(III)-L]; Moreover bulkier alkene like 1,2-dihydronapthalene was also efficiently epoxidised with the synthesized supported catalyst.
Keywords: Chiral Schiff-base; Binaphthyl ligand; Immobilization; Post grafting synthesis
Hydrodeoxygenation of guaiacol over carbon-supported molybdenum nitride catalysts: Effects of nitriding methods and support properties by I. Tyrone Ghampson; Catherine Sepúlveda; Rafael Garcia; Ljubisa R. Radovic; J.L. García Fierro; William J. DeSisto; Nestor Escalona (pp. 111-124).
Display Omitted► Activated carbon supported-nitride catalysts favored direct conversion of guaiacol to phenol. ► Catalysts prepared using N2/H2 mixture were more highly dispersed than those prepared via ammonolysis. ► Activity difference related to molybdenum oxynitride dispersion and support porosity.Molybdenum nitride catalysts supported on activated carbon materials with different textural and chemical properties were synthesized by nitriding supported Mo oxide precursors with gaseous NH3 or N2/H2 mixtures using a temperature-programmed reaction. The supports and catalysts were characterized by N2 physisorption, XRD, chemical analysis, TPD, FT-IR and XPS. Guaiacol (2-methoxyphenol) hydrodeoxygenation (HDO) activities at 5MPa and 300°C were evaluated in a batch autoclave reactor. Molybdenum nitrides prepared using a N2/H2 mixture resulted in more highly dispersed catalysts, and consequently more active catalysts, relative to those prepared using ammonolysis. The HDO activity was also related to pore size distribution and the concentration of oxygen-containing surface groups of the different carbon supports. Increased mesoporosity is argued to have facilitated the access to active sites while increased surface acidity enhanced their catalytic activity through modification of their electronic properties. The highest activity was thus attributed to the highest dispersion of the unsaturated catalyst species and the highest support mesoporosity. Surprisingly, addition of Co did not improve the HDO activity.
Keywords: Hydrodeoxygenation; Guaiacol; Activated carbon; Mo; 2; N catalysts
Effect of H2S on selective hydrogenation of diolefins using NiPdCe( x)/Si-Al-coated structured packing catalyst by Roberto Galiasso Tailleur; Jose Ravigli Nascar (pp. 125-134).
Display Omitted► Dienes are selectively hydrogenated in presence of benzene olefins and sulfur. ► Use of stainless steel structured packing coated by a silico-aluminate. ► Ce is added to the coating to provide thioresistance. ► Pd and Ni build the hydrogenation active phase in the mesoporous coating. ► Stable operation during the hydrogenation of steam cracking C4 feed.The effect of Ce and H2S on selective hydrogenation of diolefins using NiPdCe( x)/Si-Al-coated structured packing catalyst was studied for the selective hydrogenation of butadiene in the presence of benzene. The structured packing was coated by a silico-aluminate in which Ce, Ni and Pd were incorporated during successive impregnations. The catalyst was activated in the presence of hydrogen containing 10ppm of hydrogen sulfide and tested in a continuous stirred tank reactor (CSTR) under different operating conditions. The catalysts were characterized by XRD,27Al- and29Si-NMR, TPR(H2), IR, XPS, physical and chemical analysis. The results indicated that Ce and hydrogen sulfide affect the metal dispersion, the electronic configurations of the metals on surface and the acidity of the catalyst. Therefore the activity and selectivity is modified by both Ce and H2S at constant Ni and Pd contents. The results were interpreted using a previously developed kinetics model.
Keywords: Catalytic packing; NiPdCe(; x; )/SiAl catalyst; Butadiene selective hydrogenation
Preparation and characterization of hydrotalcite-like compounds containing transition metal as a solid base catalyst for the transesterification by Sheng-Hung Wang; Yu-Bin Wang; Yong-Ming Dai; Jih-Mirn Jehng (pp. 135-141).
Display Omitted► The Mg/Fe ratio was varied from 6 to 15 in the hydrotalcite structure. ► The highest conversion of FAME (81%) was obtained after 4h reaction time when the Mg/Fe ratio is 15 and 0.3% catalyst was used. ► The conversion was affected by the basicity and Mg content, and the MgAlFe 15 showing the highest basicity among the catalysts.Hydrotalcite-like compounds (HTLCs) containing Mg2+, Fe3+ and Al3+ layered double hydroxide (LDH) were synthesized by co-precipitation method and calcined at 873K for 16h. These heterogeneous base catalysts were used for the transesterification of soybean oil with methanol to produce biodiesel. The Mg/Fe molar ratio was varied from 6 to 15, but the MgAlFe catalysts have a constant Al composition in the hydrotalcite-like structures. The catalysts were characterized by nitrogen physisorption, X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), CO2 temperature programmed desorption (CO2-TPD), field-emission scanning electron microscope (FE-SEM), and Fourier transfer infrared spectroscopy (FTIR). The conversion of fatty acid methyl ester (FAME) has been affected by the basicity and Mg content in the MgAlFe catalysts. When MgAlFe 15 was used, the highest basicity and high conversion of FAME (81%) was obtained due to the formation of Mg2+–O2−, Al3+–O2− pairs, and the higher CO2-desorption temperature.
Keywords: Heterogeneous base catalysts; Transesterification; Hydrotalcite-like compounds (HTLCs); FAME (esters of fatty acids); Biodiesel
New amphiphilic poly(quaternary ammonium) dendrimer catalyst for effective reduction of citronellal by Eagambaram Murugan; Iqbal Pakrudheen (pp. 142-148).
Display Omitted► Three types of new amphiphilic poly(quaternary ammonium) dendrimers was prepared. ► The activity of these 3 catalysts was assessed by selective reduction of citronellal. ► The 2-fold enhancement of kobs noticed in catalyst 4 than catalysts 3 & 5.Three types of new amphiphilic poly(quaternary ammonium) dendrimer catalysts were prepared from poly(propylene imine) generation-2 (PPI-G2) dendrimer with 3 types of alkyl halides having varied chain length. The CH stretching at 2922 and 2853cm−1 and CN+ stretching at 1108cm−1 confirmed the attachment of alkyl chains and generation of poly(quaternary ammonium) ions at the dendrimer surface. Their1H and13C NMR spectra also supported such confirmations. The hydrophobicity of these 3 poly(quaternary ammonium) based dendrimer catalysts was determined by the static water contact angle ( θ). The catalyst derived from attachment of long alkyl chain viz., PPI-G2-(C16H33)16 (CH3)8N+Cl− showed an increased contact angle (77.5 θ) thus proving high hydrophobicity. Their catalytic activity was evaluated through reduction of citronellal under pseudo-first order condition at ambient temperature. The rate constant ( kobs), of the catalyst containing medium length alkyl chain viz., PPI-G2-(C12H25)16 (CH3)8N+Cl− was higher than those containing short and long alkyl chains due to its well-balanced amphiphilic character. It gave 100% selectivity/activity compared to commercial single-site phase transfer catalyst for citronellal reduction. The effect of [substrate], [catalyst], [NaOH], and [NaBH4] on the rate of the reaction was studied and the results were discussed.
Keywords: Dendrimer; Amphiphilic; Quaternary ammonium; Reduction; Citronellal
Transesterification of dimethyl oxalate with phenol over nitrogen-doped nanoporous carbon materials by Xiaoling Yuan; Min Zhang; Xiaodong Chen; Nihong An; Gang Liu; Yan Liu; Wenxiang Zhang; Wenfu Yan; Mingjun Jia (pp. 149-155).
Display Omitted► Nitrogen-doped nanoporous carbon (NNC) materials were prepared by sol–gel route. ► NCC catalysts are active for transesterification of dimethyl oxalate with phenol. ► There are large amount of nitrogen-containing groups on the surface of NNC. ► Nitrogen-containing groups are main active centers for transesterification reaction.A series of nitrogen-doped nanoporous carbon (NNC) materials were prepared by directly carbonizing sol–gel composites containing aluminum phosphate, citric acid and hexamethylene tetramine (HMT). The structure and surface properties of these NNC materials were characterized by means of elemental analysis, N2 adsorption, X-ray powder diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), and X-ray photoelectron spectra (XPS). Besides possessing various oxygen-containing groups, these NNC materials also contain different types of nitrogen-containing groups, including pyridinic-N, pyrrolic-N and quaternary-N groups. The resulting NNC materials are highly active and selective heterogeneous catalysts for the transesterification of dimethyl oxalate (DMO) with phenol to produce methyl phenyl oxalate (MPO) and diphenyl oxalate (DPO), and can be easily recycled by simple filtration. The presence of suitable surface basic sites should be mainly responsible for the excellent catalytic performance of NNC materials in the transesterification reaction.
Keywords: Nitrogen-doped carbon; Transesterification; Dimethyl oxalate; Phenol
Aerobic selective oxidation of benzyl alcohols to benzaldehyde catalyzed by bidentate Schiff base dioxomolybdenum(VI) complex immobilized on CPS microspheres by Baojiao Gao; Min Wan; Jiying Men; Yanyan Zhang (pp. 156-162).
Display Omitted► We prepared new bidentate Schiff base ligand-anchored polymeric microspheres. ► A novel immobilized dioxomolybdenum(VI) complex catalyst was prepared. ► The heterogeneous catalyst was used in the oxidation of benzyl alcohol by molecular oxygen. ► The catalyst had very high catalytic activity and excellent catalytic selectivity. ► A catalytic reaction mechanism was proposed.The Schiff base reaction between aldehyde (AL) group-modified crosslinked polystyrene (CPS) microspheres, AL–CPS microspheres, and glycine (GL) was conducted, resulting in the microspheres ALGL–CPS, on which bidentate Schiff base ligand ALGL were chemically anchored. Subsequently, the coordination reaction between the ligand ALGL of ALGL–CPS microspheres and molybdenyl acetylacetonate (MoO2(acac)2) was carried out, obtaining a new immobilized dioxomolybdenum(VI) complex with bidentate Schiff base-type, CPS-[MoO2(ALGL)2] microspheres, namely a new heterogeneous dioxomolybdenum(VI) complex catalyst was prepared. The microspheres CPS-[MoO2(ALGL)2] were fully characterized by many means such as FTIR, UV/Vis absorption spectrum and AAS. They were used in the oxidation reaction of benzyl alcohol by molecular oxygen. The experimental results show that through the coordination reaction between ALGL–CPS microspheres and molybdenyl acetylacetonate (MoO2(acac)2), the immobilized Schiff base dioxomolybdenum(VI) complex can be smoothly prepared. In the oxidation reaction of benzyl alcohol with molecular oxygen as oxidant, the heterogeneous dioxomolybdenum(VI) complex catalyst, CPS-[MoO2(ALGL)2], has very high catalytic activity. Under the mild conditions such as at ordinary pressure of dioxygen and at a lower temperature of 90°C, benzyl alcohol can be transformed to benzaldehyde with a conversion of 63% in 10h. It is namely the yield of benzaldehyde because benzaldehyde is the single oxidation product. It is obvious that CPS-[MoO2(ALGL)2] has excellent catalytic selectivity, and it specially catalyzes the oxidation reaction of benzyl alcohol to benzaldehyde. It was found that the solvent polarity effects on the catalyst activity greatly. The weaker the polarity of the solvent, the higher the activity of the catalyst CPS-[VO(SAAM)2] is and the higher the yield of benzaldehyde is.
Keywords: Crosslinked polystyrene microspheres; Dioxomolybdenum(VI) complex; Schiff base; Heterogeneous catalysis; Benzyl alcohol; Dioxygen
Mechanistic study of the palladium-catalyzed ethyne hydrogenation by the Temporal Analysis of Products technique by Miguel A.G. Hevia; Blaise Bridier; Javier Pérez-Ramírez (pp. 163-170).
Display Omitted► The TAP reactor provides insights into the Pd-catalyzed partial hydrogenation of ethyne. ► The product ethene:ethane ratio is higher under the low-pressure conditions in the TAP reactor. ► The formation of subsurface hydrogen is unfavorable in the mbar pressure range. ► The influence of the H coverage is studied in the absence of unselective hydride phases. ► The Horiuti–Polanyi and Langmuir–Hinshelwood schemes were experimentally supported.The gas-phase hydrogenation of ethyne over Pd/Al2O3 is studied using the Temporal Analysis of Products (TAP) reactor, leading to valuable insights into the reaction mechanism. The exceptional time resolution of this transient technique enables to capture the hydrogenation of the carbon–carbon triple bond via the sequential addition of hydrogen. Hydrogen/deuterium exchange experiments demonstrate the dissociative and reversible adsorption of H2 on palladium. Conversion and selectivity change at early stages of the reaction as a consequence of the formation of a stable carbide layer. The alkene/alkane ratio was markedly higher in TAP compared to reported flow data, due to the mbar pressure operation of the technique. In this regime, the formation of subsurface hydrogen is unfavorable, enabling the assessment of the sole effect of reactants coverage on the product distribution, that is, in the absence of unselective hydride phases. Mechanistic aspects related to the use of carbon monoxide as a selectivity enhancer are also discussed.
Keywords: Ethyne hydrogenation; Pd catalyst; Mechanism; Selectivity; Temporal Analysis of Products; Pressure gap
Metathesis of C4 olefin over Mo-based heterogeneous catalysts: A novel route to propene and isopentene by Dazhou Zhang; Xiujie Li; Shenglin Liu; Shengjun Huang; Xiangxue Zhu; Fucun Chen; Sujuan Xie; Longya Xu (pp. 171-178).
Display Omitted► Mo/Al2O3 with suitable acidity exhibits the best catalytic performance. ► Metathesis of 2-butene and isobutene is more temperature-sensitive. ► Metathesis of 1-butene and 2-butene is more acid-sensitive. ► States of Mo species are closely related to the metathesis activation of different olefins.A novel route with high yields of propene and isopentene on the basis of consecutive metathesis of 1-butene and isobutene is proposed. Two series of Mo-based catalysts supported on γ-Al2O3 and HMOR-Al2O3 composite materials were prepared and evaluated in a fixed bed reactor. Experimental results revealed that three interesting reactions occurred on the catalysts, i.e. 1-C4=→2-C4= (Isomerization I), 2-C4=+1-C4=→C3=+2-C5= (Metathesis I), 2-C4=+ i-C4=→C3=+ i-C5= (Metathesis II). Isomerization I was the prerequisite step of the following two metathesis reactions. Metathesis I was more acidity-sensitive and it could happen at low temperatures provided that the catalyst acidity was sufficient. Metathesis II, as the targeted reaction, was proved to be more temperature-sensitive, and high reaction temperatures were preferable for the metathesis of 2-butene and isobutene. 6Mo/Al2O3 exhibited the best catalytic metathesis performance among the candidate catalysts in the consecutive metathesis of 1-butene and isobutene. Furthermore, isopentene selectivity could be highly enhanced through the steam treatment of γ-Al2O3 support. The modifications of alumina support led to the different distribution of Mo species and the formation of more Mo species in octahedral state may contribute to the preferential activation of Metathesis II.
Keywords: Propene; Isopentene; Olefin metathesis; Mo/Al; 2; O; 3; Steam treatment
Bimetallic Au–Pd/MgO as efficient catalysts for aerobic oxidation of benzyl alcohol: A green bio-reducing preparation method by Guowu Zhan; Yingling Hong; Vernon Tebong Mbah; Jiale Huang; Abdul-Rauf Ibrahim; Mingming Du; Qingbiao Li (pp. 179-186).
Display Omitted► Au–Pd bimetallic catalysts were prepared by green bio-reducing methods. ► Catalysts were characterized to understand the Au–Pd synergistic interactions. ► Bimetallic catalysts showed superior performance for benzyl alcohol oxidation. ► The effects of conditions on the catalytic performance were investigated.The oxidation of benzyl alcohol, with molecular oxygen at atmospheric pressure in an aqueous medium, is investigated using Au–Pd/MgO bimetallic catalysts to examine the effect of catalyst parameters (viz. preparation method, Au/Pd molar ratio, and calcinations temperature) and reaction conditions (viz. reaction temperature and oxygen flow rate) on conversion and selectivity. The bimetallic catalysts were prepared via two novel reduction methods with bio-reducing agents and were characterized by transmission electron microscopy, X-ray diffraction, diffuse reflectance UV–vis spectroscopy, and thermogravimetric analysis to understand synergistic interactions between Au and Pd. Under optimal conditions, the Au–Pd bimetallic catalysts, with a 1:1 molar ratio and 9.7±1.3nm particle size, exhibited remarkably enhanced catalytic activity (>52%) and selectivity (∼100%) compared with their monometallic counterparts. Moreover, the activity of the catalysts was maintained after six recycles without agglomeration.
Keywords: Benzyl alcohol; Benzaldehyde; Gold; Palladium; Oxidation
Bismuth oxychloride-mediated and laser-induced efficient reduction of Cr(VI) in aqueous suspensions by M. Qamar; Z.H. Yamani (pp. 187-191).
Display Omitted► Studied a novel combination of laser light and BiOCl. ► ∼95% Cr(VI) was reduced within 30min. ► Structural and compositional stability of BiOCl was studied in detail.The reduction of Cr(VI) was investigated in aqueous suspensions of BiOCl and Degussa P25 using a 355nm laser radiation and conventional lamp. BiOCl showed better photocatalytic activity than Degussa P25 and ∼95% Cr(VI) was reduced within short time (30min) of laser exposure in presence of BiOCl without the use of any additive. Effects of critical parameters, such as laser energy, catalyst amount and chromium concentration on the photocatalytic reduction process were investigated. The photocatalytic removal of metal was fitted to first-order kinetic and reaction rate was estimated. Structural and compositional stability of BiOCl before and after photocatalytic reaction were determined by XRD, Raman, FT-IR, TGA/DSC analyses.
Keywords: Water purification; Photocatalysis; Chromium reduction; BiOCl
Selective hydrogenation of o-chloronitrobenzene using supported platinum nanoparticles without solvent by Manhong Liu; Xinxin Mo; Yanyan Liu; Hailian Xiao; Yu Zhang; Jieying Jing; Vicki L. Colvin; William W. Yu (pp. 192-196).
Display Omitted► Nearly monodisperse Pt/γ-Fe2O3 catalysts were prepared by pre-formed Pt colloidal nanoparticles. ► Selective hydrogenation of o-CNB to o-CAN was done at 1542h−1 without using any solvent. ► 99.9% selectivity to o-CAN at 99.95% conversion of o-CNB was achieved.Colloidal platinum nanoparticles with 2.2nm were immobilized on γ-iron oxide (γ-Fe2O3) powder to make a supported catalyst (Pt/γ-Fe2O3) with controlled Pt nanoparticle size and size distribution. This catalyst was used to catalyze the selective hydrogenation of o-chlorobenzene to o-chloroaniline without using any solvent; 99.9% selectivity at 99.95% conversion was achieved.
Keywords: Chloronitrobenzene; Chloroaniline; Selective hydrogenation; Solvent-free; Nanoparticle
Polyelectrolyte encapsulated gold nanoparticles as efficient active catalyst for reduction of nitro compounds by kinetic method by Pitchaimani Veerakumar; Murugesan Velayudham; Kuang-Lieh Lu; Seenivasan Rajagopal (pp. 197-205).
Display Omitted► We have developed an environmentally benign AuNPs for the reduction of nitro group to corresponding amines. ► The advantages of this catalytic system give high product yields, short reaction time as well as improved catalytic activity. ► A new application of AuNPs in organic synthesis has been found to transformation under “green” conditions. ► Polyelectrolyte capped AuNPs is effective and stable catalytic system. ► It is a simple, convenient and novel method for the reduction of aromatic nitro groups.This paper is focused on the synthesis of gold nanoparticles (AuNPs) using highly branched polyethylenimine (PEI) and acylated polyethylenimine (PEI-C12) as reducing as well as stabilizing agent and their role as catalysts. The AuNPs are characterized by XRD, TEM, HRTEM, AFM, UV–vis and FT-IR techniques. The AuNPs, in a PEI polyelectrolyte matrix, is found to be a stable and active catalyst for the selective reduction of nitro compounds using NaBH4 under mild reaction conditions. This catalytic system is stable for several months without any obvious colloidal aggregation.
Keywords: AuNPs; Polyethylenimine; Nitrophenol; NaBH; 4; Reduction