摘要
利用等体积浸渍法制备了氧化硅负载钴催化剂 .通过程序升温还原、氢化学吸附、氧滴定和催化活性评价等手段研究了氧化钡对Co/SiO2 的还原性能、钴分散度和颗粒度、分解甲烷活性及其稳定性等的影响 .研究结果表明 ,氧化钡明显地影响Co/SiO2 的还原性能 ;添加 2 %氧化钡提高了Co/SiO2 在中温 (4 5 0℃ )条件下的还原度 ;氧化钡的还原对Co/SiO2 还原的诱导、氧化钡与氧化硅及与氧化钴之间的相互作用是导致Co/SiO2 还原性能变化的原因 .氧化钡提高了Co/SiO2 的初活性和钴的分散度 ,降低了钴的颗粒度 ;添加 0 5 %～ 1 5 %氧化钡有利于提高Co/SiO2 的稳定性 .钴的分散度和颗粒度影响Co/SiO2的活性和稳定性 ;氧化钡的强供电效应也是提高Co/SiO2 活性和稳定性的重要因素 .甲烷分解生成的碳物种覆盖了钴活性中心 ,导致Co/SiO2 初活性下降 ;但大部分碳物种并不沉积在钴活性中心上 。
Co/SiO_2 promoted by BaO was prepared by the method of incipient wetness impregnation. CH_4 decomposition on the catalyst was performed in a fixed-bed reactor under the conditions of reactant gas (5%CH_4-95%Ar) flow rate of 142 ml/min and 450 ℃. TPR, hydrogen chemisorption, and oxygen titration were employed to study the influence of BaO on the reduction performance, Co dispersion and particle size of the Co/SiO_2 catalyst. The presence of BaO affected the TPR performance of Co/SiO_2, and Ba loading of 2% increased the reduction degree of Co/SiO_2 at the moderate temperature (450 ℃). The difference of the TPR performance between unpromoted and promoted catalyst samples could be ascribed to the induction of the reduction of BaO,and the interactions between barium oxide and silica, barium oxide and cobalt oxide. Compared with the unpromoted catalyst, the presence of BaO increased the initial activity and Co dispersion, but decreased the Co particle size. During CH_4 decomposition the deactivation rate of Co/SiO_2 promoted by BaO was dependent upon the Ba loading, and a slower deactivation rate could be achieved whenw(BaO)=0.5%～1.5%. Although the carbon species formed from CH_4 decomposition resulted in the decrease of the initial activity of Co/SiO_2, the majority of carbon species might yield the filamentous carbon during reaction.
出处
《催化学报》
SCIE
EI
CAS
CSCD
北大核心
2003年第1期61-66,共6页
基金
浙江省"15 1"人才专项资金资助项目
