Studies On Catalyst And Catalytic Distillation Process For Alkylation Of Benzene With Ethylene To Ethylbenzene

Ethylbenzene is an important fundamental petrochemical raw-material,thedemand of which increases rapidly in recent years. It is of important meaning toproduce qualified ethylbenzene economically from cheap diluted ethylene resourcessuch as fluid catalytic cracking dry gas. This thesis studied the catalysts and processfor production ofethylbenzene from dry gas by catalytic distillation.For the first time, the role of acid strength of zeolites in liquid-phase alkylationof benzene with ethylene was studied by means of partial poisoning with ammonia.The results showed that the strong acid sites are active centers for the alkylationwhile the weak acid sites are inactive to alkylation and ethylene polymerization overzeolite beta, USY, and MCM-22. Among the active strong acid sites, difference oftheir strength leads to change in specific activity and selectivity, which followsdifferent laws over different zeolites.The concentration of strong acid sites in zeolite beta decreases only if the silicato alumina ratio rises to above 31, and leads to decrement of alkylation activity,while no evident relation is observed between the selectivity and silica to aluminaratio. Over zeolite beta, the alkylation of benzene with ethylene takes place mainlyon the strong B-acid sites, while the strong L-acid sites seem to hinder the reaction.Steaming treatment of zeolite beta can cause framework dealumination diminishingthe concentration of both strong and weak acid sites, transform some strong L-acidsites to strong B-acid sites enhancing the alkylation activity, improve the stabilitygreatly, and suppress production of by-products.Cooling at the reaction section was proposed for the first time as a measurementto enhance ethylene conversion in ethylbenzene synthesis from dry gas by catalyticdistillation through researching with zeolite beta, USY, and MCM-22. Therate-determining step in the catalytic distillation process is the liquid-phase catalyticreaction, while dissolving of ethylene in benzene reaches equilibrium essentially. Theethylene conversion is determined by macroscopic reaction rate constants of thecatalysts, partial pressure of ethylene in gas phase of the catalytic distillation column,and residence time of ethylene in the reaction section. Two zeolite catalysts, beta andY, each with unique merits, were seeked out, and proper process conditions for themwere proposed respectively. All these lay a sound basis for the coming pilotexperiments.