【作者】 张萍波；

【导师】 马新宾；

【作者基本信息】 天津大学 ， 化学工艺， 2007， 硕士

【摘要】 碳酸二乙酯（DEC）是环境友好的绿色化学品,是重要的有机合成中间体,特别是近年来发现DEC可以作为油品的含氧添加剂,取代MTBE的使用,应用前景广阔。本文对乙醇氧化羰基合成碳酸二乙酯（DEC）负载型铜钯系催化剂体系进行了研究。本工作分别以HMS和Cu-HMS为载体,通过浸渍活性组分的方法制备了新型的催化剂CuCl₂-PdCl₂/HMS与PdCl₂/Cu-HMS。首先研究了CuCl₂-PdCl₂/HMS催化剂乙醇氧化羰基合成碳酸二乙酯（DEC）反应性能的影响,并考察了助剂对催化剂的影响。助剂的加入在不同程度上提高了CuCl₂-PdCl₂/HMS的催化活性,其中四乙基溴化胺（TEAB）的效果最为理想,产物DEC的时空收率达到210.9g /（L·h）,转化率达到13.6%。XRD、XPS、IR与ESR等分析表明,助剂TEAB对载体的有序度起到一定的改善作用,进而提高了催化剂的催化活性。另外,通过焙烧脱除模板剂的方法合成了含铜的中孔杂原子分子筛Cu-HMS,并对催化剂的结构及活性进行了探讨。采用XRD、XPS、ICP-AES、IR等表征手段,表明铜离子以高度分散的状态进入HMS骨架,并保持了良好的介孔结构的有序性,同时PdCl₂的负载一定程度上提高了Cu-HMS的介孔规整度。通过催化剂活性的考察发现,PdCl₂/Cu-HMS表现出较佳的选择性,助剂的加入在不同程度上提高了PdCl₂/Cu-HMS催化剂的活性,其中四乙基溴化胺（TEAB）的效果最为理想,产物DEC的时空收率达到187.93g /（L·h）,其最佳修饰量为TEAB/Pd=12/1。不同Si/Cu比合成的Cu-HMS催化剂对于合成DEC催化活性具有一定影响,适宜的Si/Cu比为50/1时,可以有效提高催化剂的活性中心,同时保持介孔有序度性,从而提高催化活性。最后通过对PdCl₂/Cu-HMS催化剂体系反应机理的探讨,解释了表面的Pd与骨架中Cu之间的协同作用有利于该反应体系活性中心的形成。更多还原

【Abstract】 Diethyl carbonate （DEC） is a versatile compound that represents an attractive eco-friendly alternative to both ethyl halides and phosgene for ethylation and carbonylation processes, respectively. In recent years, diethyl carbonate is found to substitute for methyl tert-butyl ether （MTBE）, which is used as an oxygen-containing fuel additive. In this paper, supported PdCl₂-CuCl₂ catalysts for the vapor phase synthesis of DEC by the oxidative carbonylation of ethanol in the gas phase were studied.Diethyl carbonate （DEC） has been produced by the oxidative carbonylation of ethanol in the gas phase over a heterogeneous PdCl₂-CuCl₂ catalyst supported on mesoporous HMS silica. The effects of the various quaternary ammonium salt （QAS） promoters and the promoter loading level were investigated. The catalytic performance of the PdCl₂-CuCl₂/HMS catalyst was greatly improved by the addition of promoter tetraethyl ammonium bromide （TEAB）. Under the PdCl₂- CuCl₂-TEAB/HMS catalyst system, space time yield （STY） of DEC is 210.9 g /（L·h） , and conversion of EtOH is 13.6%. The functions of promoters were investigated on the basis of catalyst characterization and activity by means of X-ray powder diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, low-temperature electron spin resonance （ESR） spectroscopy, and infrared resonance （IR） spectroscopy. It can be concluded that the essential role of TEAB promoter is to improve the order degree of mesoporous structure, which is interrelated with the concentration of surface Si species.PdCl₂/Cu-HMS has been investigated, which demonstrated excellent selectivity to DEC by oxidative carbonylation of ethanol in the gas-phase reaction. The effects of various quaternary ammonium salt （QAS） promoters and promoter loading amounts were investigated. The catalytic performances of the PdCl₂/Cu-HMS catalyst were significantly improved by the addition of a promoter tetraethyl ammonium bromide （TEAB）. From XRD, XPS, ICP and IR characterization and analysis, it can be concluded that copper species incorporated into HMS frame and was highly dispersed in the frame of silica. An optimized Si/Cu ratio exists for catalytic activity, which is about 50/1. The catalytic performances of PdCl₂/Cu-HMS with the different Si/Cu ratio of the Cu-HMS support are related with both Cu content in the Cu-HMS and the order degree of mesoporous structure for Cu-HMS. The catalytic reaction mechanism was illuminated by the interaction between Pd²⁺ loaded on the surface and Cu²⁺ in Cu-HMS frame.更多还原