HZSM-5分子筛催化苯与碳酸二乙酯烷基化合成乙苯

在连续流动固定床反应器上,用HZSM-5分子筛催化苯与碳酸二乙酯(DEC)进行烷基化反应合成乙苯;采用X射线衍射、NH3程序升温脱附和吡啶吸附红外光谱等手段对HZSM-5分子筛进行了表征;考察了HZSM-5分子筛的硅铝比n(SiO2)∶n(Al2O3)、反应温度和原料配比对烷基化反应的影响。实验结果显示,随硅铝比的增加,HZSM-5分子筛的酸量减少,酸强度减弱;硅铝比为200的HZSM-5分子筛的催化活性最高。以硅铝比200的HZSM-5分子筛为催化剂,适宜的烷基化反应条件为:反应温度653K、反应压力0.5MPa、n(苯)∶n(DEC)=4、重时空速1h-1、催化剂用量5mL。在此条件下,苯的转化率为42.5%,乙苯的选择性达到85.5%。

Synthesis of Ethylbenzene by Alkylation of Benzene with Diethyl Carbonate over HZSM-5 Molecular Sieve

Synthesis of ethylbenzene by alkylation of benzene with diethyl carbonate(DEC) was carried out in a continuous flow fixed-bed reactor over HZSM-5 molecular sieves.The molecular sieves in use were of different n(SiO2)∶n(Al2O3) ratios.The HZSM-5 molecular sieves were characterized by means of XRD,NH3-TPD and pyridine-IR.With increasing of n(SiO2)∶n(Al2O3) in HZSM-5 molecular sieves,the amount and strength of acidic sites on HZSM-5 molecular sieves decreased,but the conversion of benzene and selectivity to ethylbenzene increased.Maximum conversion of benzene and maximum selectivity to ethylbenzene could be obtained when n(SiO2)∶n(Al2O3) in HZSM-5 molecular sieves was 200.Further increasing of n(SiO2)∶n(Al2O3) tended to a lowering of both.Effects of reaction temperature and n(benzene): n(DEC) in feed on the alkylation were also studied.Under optimal conditions:reaction temperature 653 K,reaction pressure 0.5 MPa,n(benzene)∶n(DEC) 4,WHSV 1 h-1,catalyst dosage 5 mL,conversion of benzene and selectivity to ethylbenzene were 42.5% and 85.5%,respectively.