添加聚乙二醇对CuZnAl浆状催化剂结构和性能的影响

首先利用共沉淀沉积法制备CuZnAl催化剂前驱体,并且通过添加聚乙二醇(PEG600)对其进行改性,最后采用完全液相法对前驱体进行热处理制得浆状催化剂,考察了其在浆态床合成气一步法制二甲醚反应中的催化性能,采用X射线粉末衍射、程序升温还原、氨程序升温脱附和X射线光电子能谱对其进行了表征.结果表明,PEG600的添加促进了催化剂中铜组分在热处理过程中被还原成低价铜,提高了催化剂中Cu2O的分散性,改变了催化剂表面酸量和酸强度的分布,同时PEG600的添加方式对催化剂的甲醇合成和甲醇脱水能力有显著影响.在硝酸铜和硝酸锌水溶液中添加0.5 wt%的PEG600时,在热处理过程中形成的Cu2O最稳定,不易被还原,其晶粒度小,进而使CO转化率大幅度提高.

Effect of Polyethylene Glycol on Structure and Performance of CuZnAl Slurry Catalyst

CuZnAl precursor was prepared by coprecipitation sedimentation method and modified by addition of polyethylene glycol(PEG600).Slurry catalyst was then obtained by heat-treatment using complete-liquid phase technology.The performance of the catalysts for the direct synthesis of dimethyl ether from syngas was evaluated in a slurry reactor.Characterization of the catalysts was carried out by powder X-ray diffraction,H2 temperature-programmed reduction,temperature-programmed desorption of ammonia and X-ray photoelectron spectrometry.The results indicated that PEG600 could effectively promote the reduction of the copper species in catalysts and improve the Cu2O dispersion.The amount of acid and the acidic distribution of catalyst were also changed due to addition of PEG600.Moreover,marked influences were found on methanol synthesis and dehydration capability when PEG600 was added in different way.A significant increase of activity was achieved when the catalyst was prepared in the condition of adding 0.5 wt% PEG600 into the solution of copper nitrate and zinc nitrate.This was attributed to the stable Cu2O with small grain size formed during the heat-treatment process.