H-Beta酸改性对甲苯叔丁基化性能的影响

分别采用无机酸(磷酸、硝酸、盐酸)和有机酸(乙酸、酒石酸、柠檬酸)对H-beta分子筛进行酸处理改性,并将其用于催化甲苯叔丁基化反应.采用XRD、XRF、SEM、TEM、FT-IR、NH3-TPD、Py-IR等手段对酸改性H-beta分子筛进行表征.结果表明:无机酸对分子筛的骨架铝溶解作用较强,总酸量下降,催化活性降低...

Influence of H-Beta Acid Modification on the tert-Butylation of Toluene

H-beta zeolites were acid modified separately with inorganic acids (phosphoric acid, nitric acid and hydrochloric acid) and organic acids (acetic acid, tartaric acid and citric acid), and later used for catalyzing-tert-butylation of toluene. The acid-modified H-beta zeolites were characterized by means of XRD, XRF, SEM, TEM, FT-IR, NH₃-TPD and Py-IR, etc. The results show that inorganic acids can easily dissolve the framework aluminum of zeolites, which reduces the total acid content and catalytic activity. There is a strong complexation between organic acids and aluminum species, which can effectively regulate the acid sites of zeolites, increase the content of intermediate strong acids and B acid that are good for alkylation, and enhance the catalytic activity of H-beta zeolite to some extent. Specifically, the H beta zeolite modified with citric acid (CA/H-beta) shows the best catalytic performance in the alkylation reaction process. When the temperature is 180 ℃, the n(tert-butyl alcohol)/n(toluene) is 3, the amount of CA/H-beta zeolite is 1.0 g, the volume of cyclohexane is 60 mL and the reaction time is 4 h, the conversion rate of toluene can reach 67.1% and the selectivity of tert-butyl toluene (4-TBT) can reach up to 80.5%. Moreover, HCA/H-beta zeolite can also present a stable catalytic performance after reused for 5 times.