N_2O一步氧化苯制苯酚FeZSM-5分子筛的失活与再生

Deactivation and Regeneration of FeZSM-5 Molecular Sieves for One-Step Oxidation of Benzene to Phenol by N_2O

将离子交换法制备并经水热处理的 FeZSM-5分子筛应用于 N_2O 一步氧化苯制苯酚反应中。在固定床反应器上研究了导致催化剂失活的原因,考察了失活催化剂的再生条件,并采用热重-差热综合热分析法(TG-DTA)、N_2吸附比表面测定法(BET)和程序升温氧化法(TPO)等对失活前后的催化剂进行了表征。结果表明,FeZSM-5分子筛催化剂在 N_2O 一步氧化苯制苯酚反应中具有较高的初始活性,但失活较快。失活催化剂上存在两种形式的积炭,C 与 H 比不同的低温炭和高温炭是催化剂失活的主要原因。再生实验结果表明,失活催化剂在450℃下,在 N_2O 气氛中烧炭再生处理40 min 后,催化剂的活性可完全恢复,此时催化剂表面的积炭率仍保持在30%左右。

The FeZSM-5 molecular sieves catalyst for one-step oxidation of benzene to phenol by nitrous oxide was prepared by ionexchang method and hydrothermal pretreatment. The experiments of the catalyst deactivation and regeneration were carried out in an isothermal integral reactor. The catalysts before and after deactivation were characterized by thermogravimetric analysis and differential thermal analysis （TG-DTA）, BET and temperature programmed oxidation （TPO）. The results showed that the initial activity of FeZSM-5 molecular sieves catalyst was high, but gradually decreased with run time. The main reason that resulted in the FeZSM-5 deactivating was coke forming on the activity sites, and the cokes were classified high temperature carbon and low temperature carbon. The low temperature carbon was the most important factor causing the decreasing of the FeZSM-5 activity. The investigation of regeneration indicated that the catalytic activity of deactivated FeZSM-5 could be fully restored after removing 70% coking under nitrous oxide regenerating atmosphere and 450℃ for 40 min.