Oxidative Methylation of Toluene with Methane over Basic Zeolite Catalysts Promoted with Alkali Metal Bromides and Alkali Metal Oxides

IntroductionStyrene is one of the most important industrial monomers. At present, styrene is mainlyproduced by alkylation of benzene with ethylene followed by oxidative dehydrogenationof the resulting ethylbenzene. However, this process is very expensive and complex. Anew method of synthesizing ethylbenzene and styrene directly from toluene and methanewas discovered by Khcheyan el al. ', and Yakovich and Bakareva2. The process wouldpotentially reduce the cost because of the production of sty…     

Al2O3负载Cu,Fe或Ni掺杂氧化钼催化乙苯氧化脱氢（英文）

Molybdenum-based catalysts supported on Al2O3 doped with Ni, Cu, or Fe oxide were synthesized and used in ethylbenzene dehydrogenation to produce styrene. The molybdenum oxide was sup-ported using an unconventional route that combined the polymeric precursor method (Pechini) and wet impregnation on commercial alumina. The samples were characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherms, temperature-programmed reduction of H2 (H2-TPR), and thermogravimetric (TG) analysis. XRD results showed that the added metals were well dis-persed on the alumina support. The addition of the metal oxide (Ni, Cu, or Fe) of 2 wt% by wet im-pregnation did not affect the texture of the support. TPR results indicated a synergistic effect be-tween the dopant and molybdenum oxide. The catalytic tests showed ethylbenzene conversion of 28%–53% and styrene selectivity of 94%–97%, indicating that the addition of the dopant improved the catalytic performance, which was related to the redox mechanism. Molybdenum oxides play a fundamental role in the oxidative dehydrogenation of ethylbenzene to styrene by its redox and acid–base properties. The sample containing Cu showed an atypical result with increasing conver-sion during the reaction, which was due to metal reduction. The Ni-containing solid exhibited the highest amount of carbon deposited, shown by TG analysis after the catalytic test, which explained its lower catalytic stability and selectivity.     

Al_2O_3负载Cu,Fe或Ni掺杂氧化钼催化乙苯氧化脱氢(英文)

Molybdenum-based catalysts supported on Al_2O_3 doped with Ni, Cu, or Fe oxide were synthesized and used in ethylbenzene dehydrogenation to produce styrene. The molybdenum oxide was supported using an unconventional route that combined the polymeric precursor method(Pechini) and wet impregnation on commercial alumina. The samples were characterized by X-ray diffraction(XRD), N_2 adsorption-desorption isotherms, temperature-programmed reduction of H_2(H_2-TPR),and thermogravimetric(TG) analysis. XRD results showed that the added metals were well dispersed on the alumina support. The addition of the metal oxide(Ni, Cu, or Fe) of 2 wt% by wet impregnation did not affect the texture of the support. TPR results indicated a synergistic effect between the dopant and molybdenum oxide. The catalytic tests showed ethylbenzene conversion of 28%–53% and styrene selectivity of 94%–97%, indicating that the addition of the dopant improved the catalytic performance, which was related to the redox mechanism. Molybdenum oxides play a fundamental role in the oxidative dehydrogenation of ethylbenzene to styrene by its redox and acid–base properties. The sample containing Cu showed an atypical result with increasing conversion during the reaction, which was due to metal reduction. The Ni-containing solid exhibited the highest amount of carbon deposited, shown by TG analysis after the catalytic test, which explained its lower catalytic stability and selectivity.     

Liquid-phase epoxidation of styrene with O2 over alkali metal salt impregnated CoAPO-5

Liquid-phase epoxidation of styrene with atmospheric O₂ was conducted over CoAPO-5 molecular sieves.The catalytic performance of CoAPO-5 can be significantly improved by alkali metal salt impregnated on it,and styrene conversion and selectivity to styrene oxide reached 85%and 69%respectively when CsCl was impregnated on it.The catalyst was recyclable and exhibited similar catalytic activity and selectivity even after three catalytic reaction cycles.     

Studies of the Effects of Alkali Metal Oxides Promoter on the Oxidative Methylation of Toluene with Methane over KY Zeolite Catalysts

Methane is the most abundant component of natural gas. The direct conversion of methane into chemical feedstock or transportable liquid fuel is an attractive process. In addition to oxidative coupling of methane, oxidative methylation of toluene with methane to styrene and ethylbenzene which has been investigated by Khcheyan et al.1, provides another possibility of methane utilization. Recently, several research groups have employed some metal oxides for the oxidative methylation of toluene w…     

POLYMER-SUPPORTED RARE EARTH CATALYSTS FOR STYRENE POLYMERIZATION

The neodymium complex supported on styrene-maleic anhydride copolymer (SMA·Nd) has been prepared for the first time and found to be a highly effective catalyst for the polymerization of styrene. The SMA·Nd polymeric complex is characterized by IR and its catalytic activity, and the polymerization features have been investigated in comparison with that of the conventional Ziegler-Natta catalysts. When [Nd]=1×10~(-3) mol/L, [M]=5mol/L, Al/Nd=170(mol ratio) and CCl_4/Nd=50(mol ratio), the polymerization conversion of styrene gets to 51.6% in six hours, and the catalytic activity reaches 1852 gPS/gNd, which is much higher than that of conventional rare earth catalysts. The polymerization reaction has an induction period and shows some characteristics of chain polymerization. The polymerization rate is the first order with respect to the concentration of styrene monomer. Addition of FeCl_3 does not suppress the polymerization.     

OXIDATIVE COUPLING OF METHANE OVER SrO-La_2O_3/CaO CATALYSTS Ⅳ. EFFECT OF HOT SPOT TEMPERATURE AND CO_2 IN FEED

The phenomenon of hot spot temperature and the effect of CO_2 in thefeed on the catalytic performance were studied in the oxidative coupling ofmethane over the La_2O_3/CaO(LC)and SrO-La_2O_3/CaO(SLC)catalysts.There was an abrupt change in the activity of the catalyst when the reactiontemperature increased from 873 to 923 K if no inert gas was used in the feed.This is mainly caused by the total oxidation of methane,releasing the combus-tion heat and resulting in a local over-heated spot in the catalyst bed.Then thereaction of oxidative coupling of methane was initiated.It is found that the ad-dition of CO_2 in the feed caused a severe effect on the catalytic performances ofthe SLC catalysts,especially if the SrO content was high.But no effect couldbe detected for the LC catalyst.The deactivation of the SLC catalyst is mainlyattributed to the formation of SrCO_3,which is inactive or much less active thanthe surface SrO species and is difficult to dissociate at the reaction condition.     

氧化铝负载的银纳米颗粒高选择性催化合成亚胺(英)

The oxidative dehydrogenation of alcohols to aldehydes catalyzed by Ag nanoparticles supported on Al₂O₃ was studied.The catalyst promoted the direct formation of imines by tandem oxidative dehydrogenation and condensation of alcohols and amines.The reactions were performed under mild conditions and afforded the imines in high yield（up to 99%） without any byproducts other than H₂O.The highest activity was obtained over 5 wt%Ag/Al₂O₃ in toluene with air as oxidant.The reactions were also performed under oxidant-free conditions where the reaction was driven to the product side by the production of H₂ in the gas phase.The use of an efficient and selective Ag catalyst for the oxidative dehydrogenation of alcohol in the presence of amines gives a new green reaction protocol for imine synthesis.     

Effect of catalyst confinement and pore size on Fischer-Tropsch synthesis over cobalt supported on carbon nanotubes

This paper studies the impact of structure of cobalt catalysts supported on carbon nanotubes(CNT) on the activity and product selectivity of Fischer-Tropsch synthesis(FTS) reaction.Three types of CNT with average pore sizes of 5,11,and 17 nm were used as the supports.The catalysts were prepared by selectively impregnating cobalt nanoparticles either inside or outside CNT.The TPR results indicated that the catalyst with Co particles inside CNT was easier to be reduced than those outside CNT,and the reducibility of cobalt oxide particles inside the CNT decreased with the cobalt oxide particle size increasing.The activity of the catalyst with Co inside CNT was higher than that of catalysts with Co particles outside CNT.Smaller CNT pore size also appears to enhance the catalyst reduction and FTS activity due to the little interaction between cobalt oxide with carbon and the enhanced electron shift on the non-planar carbon tube surface.     

Selective oxidation of sulfurs and oxidation desulfurization of model oil by 12-tungstophosphoric acid on cobalt-ferrite nanoparticles as magnetically recoverable catalyst

Silica-coated CoFe2O4 nanoparticles were prepared and used as a support for the immobilization of 12-tungstophosphoric acid, to produce a new magnetically separable catalyst. This catalyst was characterized using X-ray diffraction, wavelength-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, laser par-ticle size analysis, and vibrating sample magnetometry. The catalyst showed high activity in the selective oxidation of thioethers and thiophenes to the corresponding sulfones under mild condi-tions. The catalytic activity of the nanocatalyst in the oxidative desulfurization of model oil was investigated. The effect of nitrogen-containing compounds on sulfur removal from the model oil was also evaluated. The catalyst showed high activity in the oxidative desulfurization of diesel. The cata-lyst can be readily isolated from the oxidation system using an external magnet and no obvious loss of activity was observed when the catalyst was reused in four consecutive runs.     

铁酸镍纳米微粒的固相合成及其催化性能

微波辐射;乙苯脱氢;铁酸镍纳米微粒的固相合成及其催化性能     

Niobium-containing catalysts for oxydehydrogenation of hydrocarbons and alcohols

The first methods are developed for introducing niobium(V) into Mg-Al hydrotalcites used as precursors of oxide catalysts for oxydehydrogenation (OD) of alkanes and alcohols. Samples of niobium(V)-containing oxide catalysts are synthesized. Their catalytic properties are studied in oxydehydrogenation of ethane and ethylbenzene to styrene, oxidation dehydrocyclization of octane into ethylbenzene and styrene, and oxydehydrogenation of sec-butanol to ketone (octane-(2)-one). It is ascertained that ethane transformation into ethylene is highly a selective highly process (92–97%) at low temperatures (450–500°C) in the presence of a niobium-containing catalyst; the catalyst is appreciably efficient in ethylbenzene transformation to styrene and dehydrocyclization of n-octane to ethylbenzene and styrene, and in oxydehydrogenation of secbutanol to octane-(2)-one. All the catalysts studied operate stably in OD reactions; no decrease in their activity or selectivity was detected after 50 h operation.     

Tantalum-containing catalysts for oxydehydrogenation of hydrocarbons and alcohols

The first methods were developed for introducing tantalum(V) into Mg-Al hydrotalcites, which are precursors of oxide catalysts for oxydehydrogenation of hydrocarbons and alcohols. Samples of oxide tantalum(V)-containing catalysts were synthesized. Their catalytic properties were studied in the oxydehydrogenation of ethane to ethylene and ethylbenzene to styrene, oxydehydrocyclization of octane to ethylbenzene and styrene, and oxydehydrogenation of sec-butanol to ketone (octan-2-one). The transformation of ethane to ethylene over the tantalum-containing catalyst occurs with a high selectivity (92–97%) at relatively low temperatures (500°C), and the catalyst is quite efficient in conversion of ethylbenzene to styrene, dehydrocyclization of n-octane to ethylbenzene and styrene, and oxydehydrogenation of sec-butanol to octan-2-one. Comparison with a niobium-containing catalyst showed that it ensures higher yields and selectivities in similar reactions than its tantalum-containing analogue does.     

An Overview on the Dehydrogenation of Alkylbenzenes with Carbon Dioxide over Supported Vanadium–Antimony Oxide Catalysts

Utilization of carbon dioxide as a soft oxidant for the catalytic dehydrogenation of ethylbenzene (CO₂-EBDH) has been recently attempted to explore a new technology for producing styrene selectively. This article summarizes the results of our recent attempts to develop effective catalyst systems for the CO₂-EBDH on the basis of alumina-supported vanadium oxide catalysts. Its initial activity and on-stream stability were essentially improved by the introduction of antimony oxide as a promoter into the alumina-supported catalyst. Insertion of zirconium oxide into alumina support substantially increased the catalytic activity. Modification of alumina with magnesium oxide yielded an increase of catalyst stability of alumina-supported V–Sb oxide due to the coking suppression. Carbon dioxide has been confirmed to play a beneficial role of selective oxidant in improving the catalytic performance through the oxidative pathway, avoiding excessive reduction and maintaining desirable oxidation state of vanadium ion (V⁵⁺). The positive effect of carbon dioxide in dehydrogenation reactions of several alkylbenzenes such as 4-diethylbenzene, 4-ethyltoluene, and iso- and n-propylbenzenes was also observed. Along with the easier redox cycle between fully oxidized and partially reduced vanadium species, the optimal surface acidity of the catalyst is also responsible for achieving high activity and catalyst stability. It is highlighted that supra-equilibrium EBDH conversions were obtained over alumina-supported V–Sb oxide catalyst in CO₂-EBDH as compared with those in steam-EBDH in the absence of carbon dioxide.     

乙苯脱氢氧化铁系催化剂的活性相及钾的助催作用

与机械混合法相比,用KOH水溶液浸渍法制成的K_2O-Fe_2O_3催化剂性能较佳。负载型多元催化剂的性能与C-64I相近。SEM、XPS和EDAX证实,经使用后,上述负载型多元催化剂表面形态明显改变,表面铁/钾原子比上升。连续升温XRD证实,在乙苯脱氢通常所采用的温度区间,载于表面的KOH会迅速和氧化铁相互作用生成K_2Fe_2O_4。本文认为K_3Fe_2O_4可能是活性相并据此对实验结果作出较为合理的解释。     

杂多酸催化剂上乙苯的氧化脱氢

本文研究了H₃PW₁₂O₄₀及其Na⁺、Al³⁺、Cd²⁺、La³⁺盐对乙苯氧化脱氢反应的催化活性。发现活性与酸强度和酸量之间没有直接的关系。杂多酸及其盐类在反应开始阶段均存在一段活性增长期,简称为"增活期"。增活期内催化剂表面的积炭量逐渐增加,积炭物的H/C比逐渐减小。用质谱法、薄板层析法检知了积炭物中有醌类物质存在,提出了积炭物中的醌类基团是氧化肥氢的活性中心的观点。     

Mechanism of byproduct formation in oxidative dehydrogenation of ethylbenzene to styrene on magnesium ferrite-containing catalyst

Conclusions It has been shown by application of the kinetic isotope method that in the oxidative dehydrogenation of ethylbenzene to styrene on a magnesium ferrite catalyst, benzene and toluene are formed from ethylbenzene and also from styrene. Carbon dioxide appears mainly as a result of exhaustive oxidation of the side chain of the aromatic hydrocarbon.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 778–781, April, 1986.     

Thermoregulated Phase-separable Ru_3(CO)_(12)/PETPP Complex Catalyst for Hydrogenation of Styrene

The basic problem in homogeneous catalysis is the separation of catalyst from the reaction mixtures. To overcome this drawback, a number of methods have been developed. One of them is to attach homogeneous catalyst to supports 1. An alternative and well used approach involves liquid/liquid biphasic catalysis in which the catalyst and product reside in different phases and separation of the products is achieved simply by phase separation2. Recently, a concept of thermoregulated phase transf…     

溴化锌-卤化正四丁基铵高效催化合成苯乙烯环状碳酸酯

溴化锌-卤化正四丁基铵二元催化剂高效催化合成苯乙烯环状碳酸酯, 当n-Bu4NI/ZnBr2摩尔比为2时, 在短时间内(30 min)可将苯乙烯环氧化物几乎完全转化为环状碳酸酯, 无其它副产物的生成. 在ZnBr2/n-Bu4NX的催化体系中加入Au/SiO2 氧化催化剂时, 能将苯乙烯直接氧化, 然后碳酰化实现“一锅法”制备环状碳酸酯. 在此合成路线中担载的纳米金催化第一步苯乙烯环氧化反应; ZnBr2/n-Bu4NBr催化第二步CO2环加成反应. 在温和的反应条件下(80 ℃, 1 MPa, 4 h)将环状碳酸酯的产率提高到42%.     

Influence of styrene on the oxidative dehydrogenation of ethylbenzene

The influence of styrene and by-products of side reactions on the oxidative dehydrogenation of ethylbenzene into styrene with use of the vanadia-magnesia catalyst has been investigated. Notable slowing-down influence of styrene contained in the substrates on the process has been ascertained, whereas the contamination with other products has not caused such an effect. The apparent activation energy and pre-exponential factor for the investigated reactions were calculated.