Investigation Of Liquid-phase Alkylation Of Benzene With Ethylene Over Zeolite Catalyst

The reaction process of benzene alkylation with ethylene to form ethylbenzene was investigated under liquid-phase reaction conditions over zeolites modified β, MCM-22 and their mixture, and the performance differences among these catalysts were also investigated combining the catalytic reaction experiments and the characterization of the catalysts.At first, the effect of reaction conditions on the alkylation process for ethylbenzene synthesis over the modified β zeolite catalyst was systematically discussed and the optimal reaction conditions were researched by means of the single factor and orthogonal experiments The result shows that the appropriate operating conditions are as follows: temperature 180~220℃, benzene/ethylene molar ratio 6~8 and the weight hourly space velocity of ethylene ≤2.5h-1. Under these conditions, the ethylene conversion is more than 98.0% and the catalyst has good activity stability. In the liquid-phase products, the mounts of the by-products (C10~C13 and poly-ring aromatic alkyate) are lower, and the dimethylbenzene, which will seriously affect the quality of ethylbenzene product, and the triethylbenzene were not been detected.Combining the performance evaluation (activity, selectivity and stability) and the characterization of the catalysts (XRD, TPD, FTIR and the pore structure measure), it can be concluded that : (1)The activity of modified β is higher than MCM-22, but the selectivity of ethylbenzene is lower about 3% than that of MCM-22; (2)The mounts of diethylbenzene and the other by-products are higher 1.7 times and 1.5 times than these of MCM-22 respectively; (3)The catalytic performance of zeolite mixture is nearly equal to modified β, but the selectivity of ethylbenzene is higher about 0.5% than that of modified β; (4)The catalytic activity of zeolite is mainly correlated with the number of acid sites, strength and distribution, and the distribution of products is determined by the binding energy of ethylbenzene and the pore structure, while the stability of catalyst is affected by the amount of poly-ring aromatic alkylate and the pore structure.