强化直馏石脑油催化裂解过程中链烷烃选择性催化裂解反应研究

摘要

在直馏石脑油催化裂解(SNCC)技术开发过程中,发现原料中链烷烃转化率始终难以大幅提高,仅保持在52.58％～77.07％,对低碳烯烃产率存在较明显的限制.本研究采用基于密度泛函理论的分子模拟计算方法,构建了正辛烷、2-甲基庚烷和2,5-二甲基己烷3种直馏石脑油馏分链烷烃模型化合物的催化裂解反应网络,并分别提出了正构烷烃和异构烷烃理想的链反应引发途径和反应方向,发现反应体系中存在的高供氢活性的环烷烃等烃类会通过负氢离子转移反应抑制链烷烃转化,从而导致链烷烃转化率较低.通过引入新型有特定孔道结构的IM-5分子筛催化剂,可有效强化SNCC过程中链烷烃的选择性催化裂解.%The low conversion rate of paraffins,52.58％-77.07％,limits the light olefins yield in straight-run naphtha catalytic cracking(SNCC).Reaction networks of n-octane,2-methyl heptanes and 2,5-dimethyl hexane as models were established by DFT methods to investigate the initiative ways of ideal chain reaction and reaction direction.It is found that the existing naphthenic hydrocarbon with higher hydrogen donating ability in naphtha is the key reason for limited conversion of paraffins due to the hydride transfer reaction.The addition of IM-5 zeolite with specific microporous structure in catalyst can rationally strengthen the selective catalytic cracking reactions of paraffins in SNCC process.