二氧化硅负载磷钨酸铵催化苯酚氧化溴代反应

Oxidative Bromination Reaction of Phenol Catalyzed by Ammonium Tungstophosphate Catalyst Supported on Silica

以溶胶-凝胶法制备的二氧化硅负载磷钨酸铵为催化剂,溴化钾为溴源,双氧水为氧化剂,冰醋酸为溶剂,实现了苯酚的催化氧化溴代反应。探讨了催化剂负载量、催化剂用量和反应时间等反应参数对氧化溴代反应的影响。结果表明,溶胶-凝胶法制备的负载磷钨酸铵仍具有典型的Keggin结构;在室温的温和条件下,该催化剂表现出较强的催化苯酚氧化溴代反应活性和较高的对溴苯酚选择性,在实验优化条件下,苯酚转化率达到95.4%,对邻比达到3.2;而且催化剂易回收,重复4次使用后,催化活性有所降低,苯酚转化率为87.4%,对邻比为1.6。

An efficient presence of ammonium oxidative bromination reaction of phenol by KBr-H2 02 has been achieved in the tungstophosphate catalyst supported on silica with different loadings, which were synthesized by sol-gel method. The effects of the reaction time and catalyst amount on the oxidative bromination reaction were also investigated. The results indicated that the Keggin structure of ammonium tungstophosphate could be retained after supported on silica, and these catalysts exhibited high bromination reaction catalytic activity with a yield of 96. 4% and high selectivity ofp-bromophenol with a p/o ratio of 3. 2. After reaction, these catalysts can be recycled and still exhibited catalytic activity with a yield of 87.4% and a p/o ratio of 1.6 after four cvcle reactions.