Study On The Byproduct Xylene Formation In Benzene Alkylation With Ethanol

Vapor-phase alkylation of benzene with ethanol was investigated in a small fixed-bed reactor over DRF catalyst. The influence of process conditions and catalyst modification was studied on the formation of main byproduct xylene. The paralleled stability test of DRF and referential catalysts was carried out and the catalystic performance differences among these catalysts were also investigated combining the catalytic reaction experiments and the characterization of the catalysts, and the performance of regeneration for two catalysts were studied via coke-burning regeneration methods. The results can be concluded as follow:(1) DRF catalyst has the good ethylbenzene selectivity, stability and the relative low content of xylene to the benzene alkylation with ethanol to form ethylbenzene. The results shows that the appropriate operating conditions are as follows:temperature,360～400℃; benzene/ethanol molar ratio,5～7; the weight hourly space velocity of benzene and ethanol, 12.(2) The decrease of reaction temperature and increase feed ratio can restrain the formation of xylene. The enhance of feed ratio of benzene to ethanol is beneficial to increase the ethylbenzene selectivity and reduce the diethylbenzene selectivity. Under the relatively big weight hourly space velocity, the retention time of the reactant is shortened, the coked degree of the catalyst is reduced and the probability of xylene generation is decreased.(3) The total acid quantity of modified DRF catalyst is larger than before, but the relative content of xylene is not reduced. Besides, the ethylbenzene selectivity is improved and the relative content of diethylbenzene is reduced over the modified catalyst.(4) The relative content of xylene is lower and selectivity of ethylbenzene is higher over DRF catalyst than referential catalyst in reaction for 2000 hours under the same conditions. The comprehensive performance has exceeded the level of referential catalyst. The results indicat that the DRF catalyst has good prospect of industrial application.