Ru-Zn催化剂上苯选择加氢制环己烯中试及其N中毒和再生

Performance of Ru-Zn Catalyst for Selective Hydrogenation of Benzene to Cyclohexene in a Pilot Plant:N Poisoning and Regeneration

采用共沉淀法制备了Ru-Zn催化剂,并在连续中试装置上考察了其催化苯选择加氢制环己烯的性能。实验结果表明,Ru-Zn催化剂中Zn含量为5.4%(w),Ru微晶尺寸为5.0 nm。3480 h内该催化剂上苯转化率稳定在40%左右,环己烯的选择性和收率分别保持在80%和32%左右。苯中混有的萃取剂N,N-二甲基乙酰胺可导致催化剂中毒,因为它在酸性ZnSO4溶液中可分解为乙酸和二甲胺。二甲胺可与浆液中的ZnSO4反应生成(Zn(OH)2)3(ZnSO4)(H2O)5和二甲胺。化学吸附在催化剂表面的(Zn(OH)2)3(ZnSO4)(H2O)5对提高催化剂的环己烯选择性起关键作用,但过量的(Zn(OH)2)3(ZnSO4)(H2O)5可导致催化剂失活,向浆液中添加浓H2SO4溶液溶解部分催化剂表面的(Zn(OH)2)3(ZnSO4)(H2O)5可恢复催化剂性能。

A Ru-Zn catalyst was prepared by co-precipitation,and its catalytic activity in the selective hydrogenation of benzene to cyclohexene in a pilot plant was investigated.It was confirmed that the Zn content in the Ru-Zn catalyst was 5.4％（w） with Ru crystallite size of 5.0 nm.The benzene conversion,selectivity to cyclohexene and cyclohexene yield were about 40％,80％ and 32％ over the catalyst during running 3 480 h,respectively.The N,N-dimethylacetamine mixed in benzene could lead to catalyst poisoning since it could be decomposed into acetic acid and dimethylamine.The dimethylamine could react with ZnSO4 in the slurry to form （Zn（OH）2）3（ZnSO4）（H2O）5 and dimethylamine.The （Zn（OH）2）3（ZnSO4）（H2O）5 chemisorbed on the catalyst surface played a key role in improving the selectivity to cyclohexene.However,excess （Zn（OH）2）3（ZnSO4）（H2O）5 chemisorbed could make the catalyst inactivated.Therefore,the addition of H2SO4 into the slurry to dissolve part of （Zn（OH）2）3（ZnSO4）（H2O）5 chemisorbed could recover the catalyst activity.