丙烯歧化反应中CoO-MoO_3/γ-Al_2O_3催化剂的失活

Deactivation of CoO-MoO_3/γ-Al_2O_3 Catalyst in Propylene Disproportionation

在流通式加压微型反应器中,测试了（3.4％）CoO-（11.0％）MoO3/γ-Al2O3催化剂在丙烯歧化反应中的活性。在200℃,2.94×106Pa,WHSV为4.0g/h·g条件下,达到了热力学平衡转化率（43.2％）和选择性（92.7％）。红外和元素分析仪测试发现,反应以后的催化剂表面含有聚丙烯污染物和其它结焦物。运用正丁胺非水溶液回滴法,并结合Powell优化法回归了催化剂的酸度和Langmuir吸附等温方程。用少量Na2O处理载体可以提高催化剂的选择性,减少其酸度,减缓比表面下降量。认为,由催化剂酸度引起的聚合反应生成的聚丙烯污染物和部分脱氢反应生成的结焦物,是催化剂失活的主要原因。

The activity of (3.4％)CoO-(11.0％)MoO_3/γ-Al_2O_3 catalyst in propylene disproportionation was tested in a pressured continuous-flow microreactor. At 200℃, under 2.94×10~6Pa, and with a space velocity of 4.0 grams of feed per hour per gram of catalyst, propylene conversion was 43.2％(near thermodynamic equilibrium), andselectivity to ethylene and butylene-2 was 92.7. Fouling substance of polypropylene and coke deposit werediscovered on the surface of the reacted catalyst by infrared and elemental analyses, respectively. After the catalyst was measured by the n-butylamine aprotogenic solution back titration technique, the Powell optimization method was applied to regress the total acidity of the catalyst and the parameters of the Langmuir isotherm. Small amount of Na_2O in the catalyst could improve the selectivity, reduce the total acidity and slow down the descending rate of specific surface area. It was pointed out in the paper that polypropylene fouling substance from polymerization, and coke deposit from partial dehydrogenation both caused by the catalyst acidity, were the main causes of the catalyst deactivation.