Mesoporous siliceous SBA-15-supported Cu catalysts have been prepared by different methods and systematically characterized. The results revealed that the incipient wetness impregnation (IWI) method gives poor dispersion of copper species, whereas much better dispersion is found in catalysts prepared by the deposition precipitation (DP), grafting, and homogeneous deposition precipitation (HDP) methods. The Cu/SBA-15 catalyst prepared by the grafting method is rich in Cu+, while a partial destruction of the hexagonal mesostructure of SBA-15 occurs in the catalyst prepared by the HDP method. In gas phase hydrogenolysis of dimethyl maleate (DMM) to 1,4-butanediol (BDO), the hydrogenolysis activities of the catalysts follow the sequence of the metallic Cu surface areas; the catalyst prepared by the HDP method exhibits the highest activity and selectivity. Irrespective of the much smaller metallic Cu surface area of the catalyst prepared by the grafting method, this catalyst exhibits only slightly lower activity than that prepared by the DP method, suggesting that Cu+ also participates in DMM hydrogenolysis. The reaction conditions are further investigated over the Cu/SBA-15 catalyst prepared by the HDP method, aiming to obtain a high yield of BDO. (C) 2008 Elsevier B.V. All rights reserved.

The water–gas shift performances of Cu/ZnO and Cu/ZnO/Al2O3 catalysts in the challenging shut-down/start-up operation were investigated. The Cu/ZnO catalyst showed comparable activity to the Cu/ZnO/Al2O3 catalyst but better stability in shut-down/start-up cycles, although the latter had much higher Cu surface area and smaller Cu crystallite size. The Cu–ZnO interface sites were thus suggested to participate directly in the reaction. Based on the characterizations, the deactivation of the Cu/ZnO/Al2O3 catalyst was mainly attributed to the loss of active sites due to the formation of carbonate species rather than the sintering of Cu crystallites.

Cu/SiO2 catalysts have been prepared by the chemisorption-hydrolysis (CH), ammonia evaporation (AE) and wetness impregnation (WI) methods, and evaluated in gas phase hydrogenolysis of dimethyl oxalate (DMO) to ethylene glycol (EG). The Cu/SiO2 catalyst prepared by the CH method showed the highest hydrogenolysis activity and selectivity to EG, giving an EG yield of 92.6%. Characterizations disclosed that Cu species were poorly dispersed on the catalyst prepared by the WI method, which accounts for its poor activity. CH and AE methods could well disperse Cu species, but the CH method resulted in higher Cu0 surface area and comparable Cu+ surface area as compared to the AE method. As a result, the Cu/SiO2 catalyst prepared by the CH method exhibits the higher hydrogenolysis activity than that by the AE method.

The advances in studies of preparation of ethylene glycol by catalytic hydrogenation of oxalate esters via the C_1 route were reviewed.According to the reaction type,the catalysts were sorted into two types,one was ruthenium based catalyst used in the liquid phase homogeneous catalytic hydrogenation,and the other was copper based catalyst used in the vapor phase heterogeneous hydrogenation. Besides the typical characters of the two type catalysts used in the catalytic hydrogenation of oxalate esters were introduced in detail,kinetic studies on the preparation of ethylene glycol by catalytic hydrogenation of oxalate esters were also summarized.Finally,the merits and demeits of the dimethyl oxalate(DMO) route and the diethyl oxalate(DEO) route to ethylene glycol were compared.

Cu/SiO2 catalysts prepared by the ammonia-evaporation (AE) method have been systematically characterized focusing on the effect of the AE temperature during catalyst preparation. It is found that the texture, composition, and structure of the calcined and reduced Cu/SiO2 catalysts were profoundly affected by the AE temperature. Based on characterizations and previous findings, the copper species on calcined Cu/SiO2 samples and reduced Cu/SiO2 catalysts were assigned. In gas-phase hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG), the evolution of the catalytic activity with the Cu0 and Cu+ surface areas suggested that Cu+ also participated in the hydrogenation process. The cooperative effect between Cu0 and Cu+ is proposed to be responsible for the highest hydrogenation activity of the Cu/SiO2 catalyst prepared at the AE temperature of 363 K, on which an EG yield of 98% was obtained under the optimized hydrogenation conditions.

A novel flow-injection irreversible biamperometric method is described for the determination of ethamsylate. The proposed method is based on the oxidation of ethamsylate at one platinum electrode and the reduction of permanganate at another to form an irreversible biamperometric detection system. Ethamsylate can be determined over the range 1.0×10−6–1.0×10−4 mol l−1 with a sample measurement frequency of 180 samples h−1. The detection limit for ethamsylate is 4.0×10−7 mol l−1. The stability of the proposed method is shown by a RSD of 0.52% for 11 replicate determinations of 2.0×10−5 mol l−1 ethamsylate. The proposed method was applied to the determination of ethamsylate in pharmaceutical preparations.

采用浸渍-化学还原法制备了不同载体负载的Cu-B催化剂,并用于马来酸二甲酯气相加氢反应中.用N2物理吸附研究了催化剂的比表面积、孔型和孔径分布,用X射线光电子能谱(XPS)分析了催化剂中Cu组分的化学状态.实验结果表明,MgO负载的Cu-B催化剂由于Cu仅被还原为Cu+,所以加氢活性极差;而孔径单一的Cu-B催化剂可能并不利于目标产物四氢呋喃的生成.以ZrO2、γ-Al2O3和TiO2为载体有利于DMM选择加氢生成四氢呋喃,其中以γ-Al2O3为最优.

The polarographic response characteristics of diclofenac sodium were investigated in 0.25M HAc-NaAc (pH 5.0) supporting electrolyte in the absence and the presence of dissolved oxygen. The results demonstrate that the reduction peak at ca. −1.10V is a catalytic hydrogen wave after deaeration, and the reduction peak in the presence of dissolved oxygen is a so-called parallel catalytic hydrogen wave. Based on the parallel catalytic hydrogen wave, a novel method has been proposed for the determination of diclofenac sodium by single-sweep polarography. The calibration curve is linear in the range 1.2×10−7–2.6×10−6M and the detection limit is 6.0×10−8M. The proposed method is applied to the direct determination of diclofenac sodium in tablet forms and biological samples.