Activation, isomerization and H/D exchange of small alkanes in triflic acid

In contrast with the HF/SbF₅ superacid system and despite its strong acidity (H₀= -14.1), CF₃SO₃H is not able to protonate reversibly small alkanes. At room temperature propane and n-butane do not exchange their hydrons for deuteriums with deuterated triflic acid. The H/D exchange occurring between isobutane and the CF₃SO₃D acid is regiospecific as observed in weaker acids such as D₂SO₄ or solid acids such as sulfated zirconia or zeolites. In the same way, the formation of C₅ alkanes during C₄ isomerization is indicative of a classical bimolecular process. In the presence of carbon monoxide, isomerization as well as H/D exchange are suppressed due to chemical trapping of the carbenium intermediates. This revised version was published online in July 2006 with corrections to the Cover Date.     

BDO装置降低贫油消耗的方法

通过对100 kt/a 1,4-丁二醇(BDO)装置生产现状的研究,确定造成贫油消耗的几个主要因素,提出有效降低贫油消耗的几点措施,达到降低贫油消耗的目的。     

Synthesis of Vanadium Phosphate Catalysts by Hydrothermal Method for Selective Oxidation of n-butane to Maleic Anhydride

Two vanadium phosphate catalysts (VPH1 and VPH2) prepared via hydrothermal method are described and discussed. Both catalysts exhibited only highly crystalline pyrophosphate phase. SEM showed that the morphologies of these catalysts are in plate-like shape and not in the normal rosette-type clusters. Temperature-programmed reduction in H₂ resulted two reduction peaks at high temperature in the range of 600–1100 K. The second reduction peak appeared at 1074 K occurred as a sharp peak indicated that the oxygen species originated from V⁴⁺ phase are having difficulty to be removed and their nature are less reactive compared to other methods of preparation. Modified VPH2 gave better catalytic performance for n-butane oxidation to maleic anhydride contributed by a higher BET surface area, high mobility and reactivity of the lattice oxygen associated to the V⁴⁺ which involved in the hydrocarbon’s activation. A slight increased of the V⁵⁺ phase also enhanced the activity of the VPH2 catalyst.     

Simultaneous dehydrogenation and isomerization of η‐butane to isobutene over ZSM‐22 and zinc‐modified ZSM‐5 zeolites

Direct formation of isobutene from η‐butane was investigated over a zinc‐impregnated potassium‐ion‐exchanged ZSM‐5 dehydrogenation catalyst and an acidic shape‐selective ZSM‐22 skeletal isomerization catalyst. The experiments were performed in a fixed‐bed microreactor system operating at near‐atmospheric pressure. High selectivity to η‐butene was obtained over the zinc‐impregnated potassium‐ion‐exchanged ZSM‐5 dehydrogenation catalysts. The yield of isobutene increased after adding the acidic ZSM‐22 skeletal isomerization catalyst, although the selectivity to butene isomers slightly decreased because the skeletal isomerization of η‐butene was competing with other acid‐catalyzed reactions such as cracking and aromatization. This revised version was published online in July 2006 with corrections to the Cover Date.     

A comparison of cesium-containing heteropolyacid and sulfated zirconia catalysts for isomerization of light alkanes

The heteropolyacid H₃PW₁₂O₄₀ and its cesium salts Cs_xH_3-x PW₁₂O₄₀ (x = 1, 2, 2.5, 3) were synthesized, characterized and tested as catalysts for hydrocarbon reactions. All samples were characterized by a variety of techniques including elemental analysis, X-ray diffraction, dinitrogen adsorption, thermal gravimetric analysis and ammonia sorption. Results from these methods confirmed that pure cesium salts were prepared without significant contamination by amorphous oxide phases. Incorporation of cesium into the heteropolyacid decreased the acidic protons available for catalysis, increased the specific surface area, and increased the thermal stability. The heteropolyacids were tested as catalysts for butane skeletal isomerization, pentane skeletal isomerization and 1-butene double bond isomerization. For comparison, the activity of sulfated zirconia, a well-studied strong acid catalyst, was also evaluated for the three probe reactions. On a per gram basis, the Cs₂HPW₁₂O₄₀ sample was the most active heteropolyacid, presumably due to its high surface area. This sample was more active than sulfated zirconia for pentane skeletal isomerization and 1-butene double bond isomerization. However, sulfated zirconia was more effective for butane skeletal isomerization. Since the pentane and 1-butene reactions were monomolecular in nature, whereas butane isomerization was bimolecular, restrictions inside the micropores of the heteropolyacid may inhibit the formation of long chain intermediates. Interestingly, trace butenes were required to initiate butane isomerization reactions on sulfated zirconia, whereas heteropolyacids catalyzed the reaction in the absence of butenes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Sulfated zirconia and iron- and manganese-promoted sulfated zirconia: do they protonate alkanes?

Because of their high activities for alkane conversion, sulfated zirconia and iron- and manganese-promoted sulfated zirconia have been the objects of much recent attention as a possible next generation of solid acid catalysts for alkane conversion. These catalysts have been suggested to be superacidic on the basis of measurements with adsorbed Hammett indicator bases, but published data determined with other adsorbed bases indicate only moderately strong acid sites. The indicator methods are limited by the opaqueness of the materials and by the inability of the methods to probe a possible set of minority sites that might be responsible for the reactivity and catalytic activity for alkane conversions. Another approach to the challenge of estimating the acid strengths of the reactive and catalytic sites is to investigate the reactivities and catalytic activities of the materials for reactions which, for initiation, require donation of protons from a solid acid to a very weakly basic reactant such as an alkane. Such a test reaction is the acid-catalyzed dehydrogenation of alkanes proceeding by the Haag–Dessau mechanism (Olah type chemistry). This review includes a summary of results for conversion of ethane, propane, and n-butane that are consistent with the postulate that iron- and manganese-promoted sulfated zirconia and sulfated zirconia are capable of protonating light alkanes to give carbonium-ion transition states at temperatures as low as 200°C. The data support the postulate that these proton-donation reactions are important at low alkane conversions and in initiating alkane conversions, although conventional carbenium ion reactions predominate at high conversions. This revised version was published online in June 2006 with corrections to the Cover Date.     

甲乙酮生产技术及市场分析

介绍国内外甲乙酮生产技术及发展,并对国内外的生产现状和市场需求进行分析。2004年全球甲乙酮产能约130万t/a,总需求量约为100万t/a。截至2005年上半年,我国甲乙酮的总生产能力约为21万t/a;预计2007年我国甲乙酮的总生产能力将达30·0万t/a,总需求量将达到约29·0万t,2010年产能将达35·0万t/a,需求将达到34·5万t。     

响应面法优化亚临界丁烷萃取杏仁油工艺研究

以新疆主栽杏品种-红心杏仁为研究试材,在一定的操作条件下,采用响应面法对亚临界丁烷萃取杏仁油工艺进行优化。在单因素实验的基础上,采用Box-Behnken设计,运用SAS8.0软件回归分析了萃取时间、萃取温度、料溶比3个因素对杏仁油得率的影响,并对所得杏仁油的质量指标进行测定。结果表明:萃取时间为46min、萃取温度为42℃、料溶比为1∶6.6g/m L,此时,杏仁油的萃取率为88.58%;其质量指标均符合国家标准。      

新型惰性膜反应器中丁烷氧化脱氢制丁二烯和丁烯

The oxidative dehydrogenation of butane to butadiene and butene was studied using a conventional fixed-bed ractor (FBR), inert membrane reactor (IMR) and mixed inert membrane reactor (MIMR). When IMR and MIMR were employed, a ceramic membrane modified by partially coating with glaze was used to distribute oxygen to a fixed-bed of 24-V-Mg-O catalyst. The oxygen partial pressure in the catalyst bed could be decreased. The effect of feeding modes and operation conditions were investigated. The selectivity of C4 dehydrogenation products (bntene and bntadiene) was found to be higher in IMR than in FBR. The feeding mode with 20% of air mixing with butane in MIMR was found to be more efficient than the feeding mode with all air permeating through ceramic membrane. The MIMR gave the most smooth temperature profile along the bed.