B2O3/TiO2-ZrO2催化环己酮肟气相Beckmann重排反应中的溶剂效应

 采用不同极性的溶剂作为环己酮肟的溶剂,考察了溶剂极性对B2O3/TiO2-ZrO2催化环己酮肟气相Beckmann重排反应性能的影响. 结果表明,除乙醇外,随着溶剂极性的增大,己内酰胺的收率逐渐提高. 在所考察的溶剂范围内,当采用极性最强的乙腈为溶剂时,B2O3/TiO2-ZrO2的催化性能最佳,连续反应9 h,环己酮肟的转化率为100%,己内酰胺的选择性高达98.6%. 极性较强的溶剂可显著改善B2O3/TiO2-ZrO2催化性能的原因主要是其有利于反应所生成的己内酰胺从催化剂表面快速脱附,从而可抑制己内酰胺进一步发生聚合及分解等副反应.

Effect of Solvents on Catalytic Performance of B2O3/TiO2-ZrO2 for Vapor-Phase Beckmann Rearrangement of Cyclohexanone Oxime

The effect of solvents with different polarity on the catalytic performance of B_2O_3/TiO_2-ZrO_2 catalyst for vapor-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam was studied. It was found that acetonitrile, having the highest polarity among the solvents used, was the most effective solvent for the formation of caprolactam with cyclohexanone oxime conversion of 100% and caprolactam selectivity of 98.6% for longer than 9 h on stream. The solvents with strong polarity increased the desorption rate of the produced caprolactam from the catalyst surface, resulting in a high selectivity for caprolactam and a low catalyst deactivation rate. The FT-IR measurements and the amounts of coke deposited on the catalyst surface determined by thermogravimetric analysis confirmed the efficient desorption of caprolactam induced by the attack of the acetonitrile molecules.