制备条件对CuO/SiO_2催化剂铜晶相的影响

采用醇盐法制备了一系列不同铜负载量及含不同助剂的SiO2 负载的铜基催化剂。考察了不同制备条件对催化剂制备过程中硅酸凝胶生成速度的影响 ,发现在其它条件相同的情况下 ,正硅酸乙酯与乙二醇的体积比起主要作用 ,与金属铜盐的浓度基本无关。用XRD测试表明 ,本实验方法所制备的催化剂中的CuO是高度分散的非晶相状态 ,极易还原。高铜负载量的催化剂在 5 0 0℃ ,空气气氛中焙烧 4h后有Cu的晶相产生 ,其中含Fe、Ni助剂的有助于铜盐在分解过程中被还原为晶相铜 ,而Zn、V助剂的存在却抑制了铜物种的还原

Influences of preparation conditions on the crystalline structure of CuO/SiO_2

A series of CuO/SiO 2 catalysts with different copper loading and containing various promoters (Fe,Ni,Zn,V) were prepared by alkoxide method.The crystalline structures were investigated by XRD.The results show that when the temperature,the mole ratio between water and ethyl silicate,and acidity in the solution keep constant,the rate of the gel formation depends only on the volume ratio between ethyl silicate and ethylene glyol,which is assumed to be related to the size of SiO 2 particle.In CuO/SiO 2 catalysts,the copper species exhibited as amorphorious or microcrystallite phase.XRD could not detect the Fe,Ni,Zn,V species after calcination.It shows that they were highly dispersed on the catalysts.It was found that in the catalysts promoted by Fe or Ni promoters the copper species were reduced to copper crystallite by ethylene glyol after calcination,and in the catalysts promoted by Ni the copper species were reduced much easier.However,the copper species in the catalysts promoted by Zn or V were not reduced and CuO formed after calcination at the same experimental conditions.