碱处理和Fe改性制备多级孔ZSM-5催化剂及其催化合成二苯甲烷的性能

PREPARATION OF ZSM-5 WITH HIERARCHICAL PORES BY ALKALI TREATMENT AND Fe-MODIFIED AND ITS CATALYTIC PERFORMANCE FORSYNTHESIS OF DIPHENYLMETHANE

采用碱处理ZSM-5并通过浸渍法制备Fe改性多级孔ZSM-5分子筛催化剂Fe-ZSM-5。通过X射线衍射、N_(2)吸附-脱附、NH_(3)程序升温脱附对催化剂进行表征。结果表明,采用0.05 mol/L氢氧化钠处理ZSM-5,扩大了分子筛的孔径,Fe改性后ZSM-5仍保持原有结构,弱酸酸量显著增大,弱酸酸强度变高,强酸酸量减少。以苯和氯化苄为原料进行烷基化反应,考察碱处理浓度、金属负载量、焙烧时间、焙烧温度对催化剂催化合成二苯甲烷性能的影响。试验结果表明,当Fe与分子筛质量比为5%、氢氧化钠溶液浓度为0.05 mol/L、碱处理时间为30 min、焙烧温度为450℃、焙烧时间为4 h时,制备的催化剂活性最高,氯化苄转化率为96.2%,二苯甲烷选择性为84.9%。

Fe-ZSM-5 molecular sieve with hierarchical pore structure was prepared by alkali treatment of ZSM-5 and impregnation method.The catalyst samples were characterized by X-ray diffraction,N_(2) adsorption-desorption and NH_(3) temperature programmed desorption.The results showed that the pore size of the zeolite was enlarged,the amount of weak acid sites increased significantly,the strength of weak acid became stronger,and the amount of strong acid sites decreased when ZSM-5 was treated with 0.05 mol/L of sodium hydroxide solution.After loading Fe,the structure of ZSM-5 was still maintained.The alkylation of benzene with benzyl chloride was carried out to investigate the effects of alkali concentration,metal loading,calcination time and temperature on the catalytic performance of the catalyst for the synthesis of diphenylmethane.The experimental results indicated the prepared catalyst had the high catalytic performance for the alkylation reaction when the Fe to molecular sieve mass ratio was 5%,the sodium hydroxide concentration was 0.05 mol/L,the alkali treatment time was 30 minutes,the calcination temperature was 450℃,and the calcination time was 4 h.The conversion rate of benzyl chloride was 96.2%,and the selectivity of diphenylmethane was 84.9%.