Ni-Sn-Cr/AC催化剂上乙酸甲酯气相羰基化合成醋酐反应的研究

Vapor phase carbonylation of methyl acetate to acetic anhydride over Ni-Sn-Cr/AC catalyst

以活性炭为载体,采用浸渍法制备Ni-Sn-Cr/AC催化剂,在连续流动固定床反应器上研究其对乙酸甲酯气相羰基化合成醋酐反应的催化性能。分别考察了Ni、Sn、Cr三种金属组分的负载量对催化活性的影响,进一步考察了反应压力、反应温度、反应时间对反应的影响。实验结果表明,在Ni9%-Sn12%-Cr6%/AC催化剂上,当反应温度205℃,压力5.5 MPa,催化剂焙烧温度600℃,催化剂焙烧时间为4 h的条件下,乙酸甲酯的转化率为38.8%,醋酐的选择性为81.1%。采用X射线衍射和元素分析技术分别对反应前和不同反应时间后的催化剂进行了表征。分析结果表明,Ni0是催化剂的主要活性中心,随着反应时间的延长,活性组分镍的流失现象比较严重,同时催化剂上出现积炭及载体骨架遭到破坏,是导致催化剂失活的主要原因。

Ni-Sn-Cr/AC catalyst was prepared through impregnation with Ni（NO3）2·6H2O,SnCl4·5H2O and Cr（NO3）3·9H2O as precursors and activated carbon as support;it was used in vapor phase carbonylation of methyl acetate to proroduce acetic anhydride in a continuous flow type fixed-bed reactor.The effects of each metal loading on the catalytic activity as well as the influence of reaction temperature,pressure,and time on the reaction behavior were investigated.The results showed that the Ni9%-Sn12%-Cr6%/AC catalyst calcined at 600 ℃ for 4 h exhibits excellent performance in the carbonylation;over it under the optimized reaction conditions of 5.5 MPa and 205 ℃,the conversion of methyl acetate and the selectivity to acetic anhydride reach 38.8% and 81.1%,respectively.The fresh catalyst and spent catalysts after reaction for different times on stream were characterized by means of X-ray diffraction and element analysis;the results suggested that Ni0 is main active sites.During the test,the activity of the catalyst is decreased dramatically with the time on stream,which could be ascribed to the loss of active component Ni,carbonaceous deposition and destruction of activated carbon framework.