邻二甲苯和苯乙烯在WO_3/ZrO_2固体超强酸的烷基化反应

ALKYLATION OF o-XYLENE WITH STYRENE ON THE WO_3/ZrO_2 SOLID SUPERACID

通过沉淀、老化、过滤、洗涤、干燥、浸渍、焙烧等过程,从ZrOCl2·8H2O和(NH4)6H2W12O40制备了WO3/ZrO2固体超强酸催化剂;用Hammett指示剂法和吡啶吸附的FT-IR光谱法测定了其酸强度和酸中心类型;研究了以邻二甲苯和苯乙烯制备1-苯基-1-(3,4-二甲基苯基)-乙烷(PXE)的烷基化反应,考察了催化剂的焙烧温度、WO3的负载量、反应温度、反应时间、催化剂用量对反应的影响以及催化剂稳定性。结果表明,在750～850℃,WO3的负载量为5%～15%的WO3/ZrO2体系可以形成超强酸,其表面上同时存在Lewis酸中心和Bronsted酸中心,并且可以相互转化;WO3/ZrO2固体超强酸催化剂在苯乙烯和邻二甲苯的烷基化反应中表现出良好的催化性能和稳定性;该反应的最佳实验条件为:反应温度为100℃,n(邻二甲苯)/n(苯乙烯)=5.0,反应时间为5h,催化剂用量为2.0g。

WO3/ZrO2 solid superacid catalysts was prepared from ZrOCl2·8H2O and (NH4)6H2W12O40 by precipitation, aging, filtering, washing, desiccation, impregnation and calcination processes, etc. Their acidic strength and type of acidic centers were determined by the methods of Hammett indicators and FT-IR spectroscopy of pyridine adsorption. The effects of the calcination temperatures, the loading amounts of WO3, reaction temperatures, reaction times, the mole ratio of reactants on the reaction and the stabilities of catalyst were studied by using alkylation of o-xylene with styrene as a probe reaction. It shows that solid superacid is formed in the WO3/ZrO2 system when the calcination temperature is in the range of 750-850°C and the loading amounts of WO3 is 5%-15%, there are Lewis and Bronsted acidic centers on their surface that can be reciprocally transformed; WO3/ZrO2 solid superacid catalyst has high catalytic activities and good stability in the alkylation of o-xylene with styrene; the optimum reaction conditions are: reaction temperature is 100°C, and n(o-xylene)/n(styrene) = 5.0, reaction time is 5 h, the quantity of catalyst is 2.0 g.