丝光沸石的酸性对乙苯异构化反应的影响

Effect of Mordenite Zeolite Acidity on Ethylbenzene Isomerization

在微型连续流动固定床反应器上,以乙苯为原料,考察C_8芳烃异构化双功能催化剂中丝光沸石的酸性对乙苯异构化反应的影响,着重考察了丝光沸石的硅铝比、Na^+交换度和含量等对乙苯转化反应的影响;对载体预处理进行了研究,考察了氨处理和化学改性对乙苯异构化反应的影响。实验结果表明,随丝光沸石的硅锅比、Na^+交换度和含量的增大,乙苯转化率增加;但异构化选择性随硅铝比的增大而降低,随Na^+交换度和丝光沸石含量的增大先增加后下降,在一定酸性时出现峰值;适宜的硅铝比约为11,适宜的Na^+交换度约为80%,适宜的丝光沸石质量分数为30%～40%。总体上,化学改性方法可降低副反应程度,但对主反应的影响也较大;氨处理氢型载体的方法则可在降低副反应的同时,保持较高的活性,且选择性有所提高。

The bifunctional catalysts containing mordenite zeolite （MOR） used in the C8 aromatics isomerization were prepared and their ethylbenzene isomerization activities were evaluated in a fixed bed reactor. The effects of the n（ SiO2 ） ： n（ Al2O3 ）, Na^＋ exchange degree and content of MOR on the ethylbenzene isomerization were studied. The hydrogenous support pre-treatments through metallic ion exchange or ammonia passivation were investigated. The results indicated that the catalyst activity in the ethylbenzene isomerization rose along with the increases of n（ SiO2 ）： n（Al2O3 ）, Na^＋ exchange degree and MOR content, but the catalytic selectivity first increased and then decreased and the maximum value appeared at the suitable acidity. The suitable catalyst preparation conditions were as follows： n（SiO2） ： n （Al2O3） about 11, Na^＋ exchange degree about 80% and MOR mass fraction 30%- 40%. The experimental results showed that the chemical modification could synchronously restrain the side reactions and main reactions. The ammonia passivation of the hydrogenous support could decrease the formation of by-products, maintenance the main reaction activity and even heighten the selectivity to the isomerization products.