复合催化剂加氢裂化性能的研究

STUDY ON THE BEHAVIOR OF A COMPOSITE HYDROCRACKING CATALYST

本文对含焦化蜡油(50%)的大庆重瓦斯油在工业复合催化剂上加氢裂化的反应机理进行了研究。在100ml 加氢试验装置上试验了不同混合比的复合催化剂的加氢裂化活性,发现12-46和3762两种催化剂混合使用时,两者之间有一个最佳配比,使产品质量与产率均优于单一催化剂,并研究了前述焦化蜡油在复合催化剂上加氢裂化反应的表观动力学,求得的速率常数和活化能与文献值一致。应用林励吾提出的在加氢催化剂上可以同时存在强弱不同的两种活性中心的观点,我们提出;(1)在3762催化剂上的强活性中心和弱活性中心与在12-46催化剂上相反;(2)在12-46催化剂上生成的中间产物——异构化合物很不稳定,易为3762催化剂所吸附和裂化;(3)复合催化剂中两种催化剂上的活性中心在反应过程中各自独立起作用,并通过中间产物联系在一起.应用此三点假设,提出了焦化蜡油在复合催化剂上的反应机理,用焦化蜡油中的烷烃和芳烃为代表说明了其反应历程。同时还解释了复合催化剂存在最佳配比的原因,也解释了在生产过程中出现的许多现象.

A composite catalyst has been commercially used for the hydrocracking of Daqing heavy gas oil containing 50% of coking gas oil.The reaction mecha- nism on this composite catalyst has been studied,including: (1)Hydrocracking activities of composite catalyst of different blending ratios between catalyst 3762 and catalyst 12-46 were tested with a 100 ml hydrocra- cking reactor system.It was found that an optimum blending ratio exists, under which both the quality and the yield of the desired products are better than those obtained with each individual catalyst. (2)The apparent kinetics of hydrocracking reaction over the composite catalyst was studied.The rate constant and activation energy thus obtained are consistent with those in literatures. (3)Based on the experimental results and Lin's concept of the existence of both strong and weak active sites on hydrogenation catalyst,it is suggested that:(Ⅰ)The strong and weak active sites on catalyst 3762 are in the oppo- site to those on catalyst 12-46;(Ⅱ)The intermediate isomers formed on cata- lyst 12-46 are unstable and are easily adsorbed and cracked on catalyst 3762; and(Ⅲ)The active sites on the two catalyst components act separately and relate to each other by intermediates. (4)The reaction mechanism of coking gas oil over the composite hydrocra- cking catalyt was proposed and was demonstrated with reactions of the para- ffins and aromatics in coking gas oil.The existence of the optimum blending ratio of the composite catalyst as well as many phenomena occured in the com- mercial hydrocracking unit is explained.