Zhai Yunping, Chen Junwen, Wang Yongrui, Luo Yibin, Shu Xingtian
State Key Laboratory of Catalytic Material and Reaction Engineering, Research Institute of Petroleum Processing, Sinopec Beijing 100083 China
RSC Adv. 2021 May 20;11(30):18288-18298. doi: 10.1039/d1ra02427b. eCollection 2021 May 19.
Ethylbenzene (EB) is an important bulk chemical intermediate. The vapor-phase process is considered to be more efficient than the liquid-phase process when using dilute ethylene ( FCC or DCC off-gas) as the feed due to its high ethylene space velocity. However, realizing a balance between reducing the xylene formation and enhancing the EB selectivity is still a challenge due to the poor performance of ZSM-5 at low reaction temperature. This study concerns an IM-5 zeolite (IMF topology) modified by HSiF, with 89% ethylbenzene selectivity, 98.6% total EB + DEB selectivity and only 540 ppm of xylene at 330 °C. IM-5 zeolites with different Si/Al ratios (40-170) were prepared by HSiF modification and their catalytic performance in vapor phase alkylation of benzene with ethylene was investigated. There was an obvious decrease in the acid sites and acid strength of IM-5 in the HSiF treatment process, which led to a slight decrease in ethylbenzene selectivity and a significant decline in xylene yield. Under the conditions of complete ethylene conversion, the selectivity to EB + DEB increased from 96.1% to 98.6% in the parent I-40 and modified IM-5. Compared with ZSM-5 that has a similar acidity, the slightly bigger channel opening makes IM-5 more conductive to the formation and diffusion of DEB while xylene may present adverse effects. The 120 hour-lifetime test showed that IM-5 (I-110) has superior activity, equivalent stability, higher DEB selectivity and a much lower xylene selectivity in comparison with ZSM-5. The catalytic performance of the IM-5 zeolite in the vapor phase process provides a new choice for the production of ethylbenzene.
乙苯（EB）是一种重要的大宗化学中间体。当使用稀释乙烯（催化裂化或催化裂解尾气）作为原料时，由于其高乙烯空速，气相法被认为比液相法更高效。然而，由于ZSM - 5在低反应温度下性能不佳，要在减少二甲苯生成和提高EB选择性之间实现平衡仍是一项挑战。本研究涉及一种经HSiF改性的IM - 5沸石（IMF拓扑结构），在330℃时具有89%的乙苯选择性、98.6%的EB + DEB总选择性以及仅540 ppm的二甲苯。通过HSiF改性制备了不同硅铝比（40 - 170）的IM - 5沸石，并研究了它们在苯与乙烯气相烷基化反应中的催化性能。在HSiF处理过程中，IM - 5的酸位点和酸强度明显降低，这导致乙苯选择性略有下降，二甲苯产率显著下降。在乙烯完全转化的条件下，母体I - 40和改性IM - 5中EB + DEB的选择性从96.1%提高到了98.6%。与具有相似酸度的ZSM - 5相比，稍大的孔道开口使IM - 5更有利于DEB的形成和扩散，而二甲苯可能产生不利影响。120小时的寿命测试表明，与ZSM - 5相比，IM - 5（I - 110）具有优异的活性、相当的稳定性、更高的DEB选择性和低得多的二甲苯选择性。IM - 5沸石在气相法中的催化性能为乙苯生产提供了一种新选择。
