VOx/AlPO4催化剂合成及其催化苯羟基化反应性能

Synthesis of VOx/AlPO4 catalyst and its catalytic performance in hydroxylation of benzene

摘要:

以异丙醇铝与磷酸为原料，以离子液体[Bmim]Br与二正丙胺为共模板剂合成了AlPO4，进而以AlPO4为载体制备了VOx/AlPO4催化剂。采用XRD、SEM、TEM、Mapping、FTIR、N2吸/脱附、XPS等对催化剂物化性质进行表征，同时考察钒基催化剂在苯羟基化反应中的催化性能。结果表明，钒氧化物负载量为16%（以V2O5和AlPO4的总质量为基准，下同）的催化剂具有最多且分布均匀的V4+活性中心、契合反应的酸性微环境，在催化剂用量0.2 g，苯用量4 mL，质量分数30%的H2O2用量12.5 mL，乙腈用量15 mL，反应温度70 ℃，反应时间7 h的条件下，苯转化率为53.4%，苯酚选择性为98.4%。基于催化剂表征分析及性能评估，推测反应机理是由亲核氧化催化机理为主，自由基机理为辅。

Abstract:

AlPO4 was synthesized by ionic liquid and aluminium isopropoxide, which was employed as carrier to support V2O5 for synthesizing the highly active catalysts of benzene hydroxylation. Physicochemical properties of catalysts were characterized by XRD, SEM, TEM, Mapping, FT-IR, XPS and N2 adsorption/desorption. And the catalytic performance of vanadium-based catalysts in the hydroxylation of benzene were investigated. Catalyst with 16% (based on the total mass of V2O5 and AlPO4, the same below) vanadium oxide loading would own the most and evenly distributed V4+ active centers, the acidic microenvironment that fitted the reaction. Under the following conditions: catalyst dosage 0.2 g, mass fraction 30% hydrogen peroxide 12.5 mL, benzene 4 mL, acetonitrile 15 mL, reaction temperature 70 ℃ and reaction time 7 h, the conversion of benzene was 53.4% and the selectivity of phenol was 98.4%. Based on the analysis of characterization and performance evaluation, it was concluded that the reaction mechanism might be mainly nucleophilic oxidation catalytic mechanism, supplemented by free radical mechanism.