Lewis酸催化合成草酸二苯酯反应研究

Synthesis of Diphenyl Oxalate over Lewis Acid Catalysts

研究了Lewis酸催化剂催化苯酚和草酸二甲酯酯交换合成草酸二苯酯(DPO)反应。考察了不同Lewis酸催化剂对DPO合成反应的催化活性和Lewis酸催化剂的酸性对催化性能的影响,确定了弱酸中心促进主产物甲基苯基草酸酯(MPO)和DPO的生成,而强酸中心有利于副产物苯甲醚的生成。以弱酸TS-1分子筛为催化剂,MPO和DPO总选择性为99.2%。以强酸AlCl3为催化剂,苯甲醚选择性达到60.4%。探讨了Lewis酸催化剂催化苯酚和草酸二甲酯酯交换合成草酸二苯酯反应机理。Lewis酸催化苯酚和DMO酯交换合成MPO反应是按酰氧键断裂的反应历程进行的,DMO中和羰基相连的给电子基的-COO-基团及较大的基团体积降低了苯酚和DMO酯交换合成MPO反应的反应活性。而苯酚和DMO甲基化反应生成苯甲醚是按烃氧键断裂的反应历程进行的。

Diphenyl oxalate was prepared by the transesterification of dimethyl oxalate with phenol over Lewis acid catalysts. The activities of catalysts for the transesterification of dimethyl oxalate with phenol were evaluated. The acid strength of the catalysts had a significant influence on the selectivity of products. The weak acid sites were in favor of the production of MPO and DPO, while the strong acid sites took advantage of formation of byproduct anisole. The total selectivity of methylphenyl oxalate (MPO) and DPO was up to 99.2% over TS1, which was a weak acid. When AlCl3, as a strong acid, was used for the transesterification, selectivity of anisole was 60.4%. The reaction scheme of diphenyl oxalate synthesis by the transesterification of dimethyl oxalate was proposed.