AlCl_3/SiO_2催化剂在二甲基直链烷基苯合成反应中的稳定性

Stability of AlCl_3/SiO_2 Catalyst for Synthesis of Dimethyl Linear Alkylbenzene

以二甲苯和工业混合烯烃(C1=4～18)为原料,AlCl3/SiO2为催化剂合成了二甲基直链烷基苯;采用N2吸附、原子吸收光谱及化学分析方法对载体的比表面积、孔分布及催化剂上氯化物的含量进行了测定;考察了载体预处理温度、载体孔径、催化剂颗粒大小、反应温度、反应时间及原料配比对催化剂稳定性的影响。实验结果表明,载体预处理温度影响催化剂上氯化物的含量,预处理温度为200℃的载体制备的催化剂稳定性最好;烯烃聚合物和二甲苯裂解、歧化产生的副产物显著影响催化剂的稳定性。使用40～60目的催化剂,在反应温度80℃、反应时间1.0h、催化剂用量1.0g、二甲苯与烯烃摩尔比为10∶1的条件下,催化剂的稳定性最好,在烯烃转化率保持100%的情况下可以循环使用11次。

Dimethyl linear alkylbenzene was synthesized by alkylation of xylene with industrial mixed olefins C14-18^= over AlCl3/SiO2 catalyst. Specific surface area and pore properties of support were determined by N2 adsorption. Chloride content on catalyst were determined by atomic absorption spectrophotometer and chemical analysis respectively. Effects of pretreatment temperature of support, its pore diameter, particle size of catalyst, reaction temperature and time, and mole ratio of xylene to olefins on stability of catalyst were investigated. Pretreatment temperature of support decides chloride content and stability of catalyst. The catalyst with active component AlCl3 immobilized into SiO2 pretreated at 200 ℃ shows best stability. Some byproducts formed due to polymerization of olefins, cracking and disproportionation of xylene obviously influence the stability of catalyst. By using catalyst with size of 40 -60 mesh, under optimal reaction conditions： reation temperature 80 ℃, reaction time 1.0 h,catalyst dosage 1.0 g, mole ratio of xylene to olefins 10 ： 1, olefins conversion keeps at 100% after being reused for 11 times.