用不同前驱体制备的Co/SiO_2催化剂的结构及其CO_2/CH_4重整反应性能

Structure and Properties of Co/SiO_2 Catalysts Prepared from Different Cobalt Salt Precursors for Methane Reforming with Carbon Dioxide

分别采用硝酸钴、醋酸钴、硫酸钴和氯化钴为前驱体制备了Co/SiO2 催化剂 ,用XRD ,TPR ,SEM和H2 TPD等实验技术考察了钴盐前驱体对催化剂结构和二氧化碳重整甲烷反应性能的影响 ,重点考察了硝酸钴和醋酸钴的作用 .结果表明 ,由醋酸钴制备的Co/SiO2 催化剂有最佳的催化活性和稳定性 ,它在钴物种的存在状态、金属 载体相互作用、钴金属晶粒度及抗烧结、抗积炭能力等方面 ,均与由硝酸钴制备的Co/SiO2 催化剂存在显著的差别 .Co/SiO2 催化剂的反应活性和稳定性分别与其金属分散度和抗烧结、抗积炭能力密切相关 .

Co/SiO 2 catalysts are prepared by impregnation method from different cobalt salt precursors, such as Co(NO 3) 2, Co(CH 3COO) 2, CoSO 4 and CoCl 2, respectively. The effects of cobalt salts, especially Co(NO 3) 2 and Co(CH 3COO) 2, on catalyst structure and performance in CO 2/CH 4 reforming are studied using activity evaluation as well as XRD, TPR, SEM and H 2 TPD techniques. Among the catalysts investigated, Co/SiO 2 starting from Co(CH 3COO) 2 exhibits the highest activity and stability. It maintains its high activity during 10 h of reaction at 973 or 1?073 K, while the catalyst from Co(NO 3) 2 shows notable deactivation after reaction at the same temperatures for only 6 h. The higher the cobalt loading or the lower the temperature, the greater the activity difference between the two catalysts. The results of characterization show that Co/SiO 2 catalysts prepared from Co(CH 3COO) 2 and Co(NO 3) 2 are greatly different in many ways, such as existence of Co species, metal support interaction, Co 0 particle size and resistance to sintering and coking. Combining the results of the reaction with the characterization of catalysts, it is established that CO 2/CH 4 reforming over Co/SiO 2 catalyst is of structure sensitivity, and the activity and stability of the catalyst are close related to the degree of dispersion of metallic cobalt and resistance to sintering and coking, respectively.