Co/γ-Al_2O_3催化剂上CO氧化反应的研究

Studies of CO Oxidation over Co/γ-Al_2O_3 Supported Catalyst

以浸渍法与沉积沉淀法制备了不同Co负载量的Co/γ-Al2O3催化剂,研究了对CO的催化氧化行为.考察了Co含量,焙烧温度,反应温度等对催化剂氧化性能的影响,结果表明,沉积沉淀法制备400℃焙烧的负载量为10%的Co/γ-Al2O3在90℃就能够实现CO完全氧化,且热稳定性比浸渍法制得催化剂好.本文还采用XRD、TPR、XPS等技术,分别研究了Co/γ-Al2O3样品的晶相结构,还原性能及表面化学状态.XRD结果表明,以硝酸盐为前驱物的Co负载于γ-Al2O3后,Co主要以Co3O4结构存在,反应的活性相Co3O4的生成有利于CO催化氧化,且以不同制备方法得到的样品中Co3O4晶粒大小不同,催化活性也不同.TPR结果表明,以沉积沉淀法制备催化剂的还原峰向低温移动,CoOx的还原更加容易.XPS表面分析表明沉淀法制备的Co/γ-Al2O3样品中,Co3O4在载体表面富集.

A series of Co/γ\|Al\-2O\-3 supported catalysts have been prepared by impregnation and deposition\|precipitation methods. Taking CO oxidation as a probe reaction, effects of temperature, amount of Co, calcination temperature on the catalytic activity for CO oxidation have been investigated. The T100 (CO complete conversion temperature) of 10% Co/γ\|Al\-2O\-3 catalyst calcined at 400 ℃was 90 ℃. These catalysts have been characterized by means of XRD, XPS and TPR techniques to verify the species present in the catalysts. The results of XRD and XPS showed that Co\-3O\-4 phase in Co/γ\|Al\-2O\-3 catalysts was the main active phase for CO oxidation. Co particles size and reaction activities are dependent on preparation method .TPR profiles revealed that the reduction peak of the samples prepared by deposition\|precipitation shifted to the low temperature, and it resulted in that the reduction of Co species is easier. The result of XPS confirmed that the active species in catalyst was Co\-3O\-4.