逆水煤气变换耦合乙烷脱氢制乙烯反应的Cr/活性炭催化剂

在常压固定床微分反应器上,考察了活性炭及其负载的金属氧化物催化剂对逆水煤气变换耦合乙烷脱氢制乙烯反应的催化活性。实验结果表明,以活性炭为载体的Cr氧化物(Cr/C)催化剂具有较好的催化性能,采用5%(w)Cr/C催化剂,在700℃、原料气n(CO2)∶n(C2H6)=7∶1的条件下,乙烷转化率为56.2%,乙烯选择性和收率分别为75.0%和42.2%。反应中CO2的主要作用是通过与乙烷脱氢产物H2反应来促进乙烯的生成,提高反应活性;同时与积碳反应生成CO,消除表面积碳,提高催化剂的稳定性。通过对催化剂进行表征,研究了催化剂中活性组分的氧化还原性质和表面酸性对其催化性能的影响。XPS表征结果显示,催化剂表面存在Cr6+和Cr3+,高价态Cr有利于乙烷转化;微量吸附量热分析结果显示,催化剂表面的酸中心数量、强度及其分布与反应活性相关。

Coupling of Reverse Water-Gas Shift with Dehydrogenation of Ethane to Ethene on Cr/C Catalysts

The coupling of reverse water-gas shift with the dehydrogenation of ethane to ethylene on Cr/C(C:activated carbon) catalysts was studied.The results showed that the selectivity and yield to ethylene and the conversion of ethane were 75.0%,42.2% and 56% respectively under the conditions of 5%(w)Cr/C as the catalyst,700 ℃,and n(CO2)∶n(C2H6) 7∶1.CO2could remove the carbon deposition and react with hydrogen to accelerate the ethane dehydrogenation.The XPS results showed that Cr6+ and Cr3+ occupied the surfaces of the catalysts,which was beneficial to the ethane dehydrogenation.The microcalorimetric adsorption results indicated that the strength,number and distribution of the surface acid sites could be correlated with the reaction activity.