不同催化剂对苯酚H_2O_2羟基化反应的比较

用苯酚、双氧水经羟基化反应合成邻、对苯二酚,在Fe2O3为催化剂的反应系统中,反应诱导期长,且反应剧烈;当以杂多酸盐或Fe/ZrO2为催化剂时,诱导期消失,且羟基化反应平稳。反应的诱导期可能是由铁的氧化物转化为活性物种Fe3+和Fe2+的过程引起的;在杂多酸盐或Fe/ZrO2催化剂的反应体系中,羟基化反应可能发生在催化剂表面而使反应变得缓慢平稳,反应诱导期消失。

Comparasion of Different Catalysts on Phenol Hydroxylation

Fe2O3, heteropoly salt and Fe/ZrO2 exhibited high catalytic activity toward phenol hydroxylation using H2O2 as oxidant. A rapid hydroxylation of phenol was observed after an induction period in the hydroxylation of phenol catalyzed by Fe2O3; however, a slow hydroxylation of phenol was observed and the induction period disappeared in the same system catalyzed by heteropoly salt or Fe/ZrO2. The results suggest that, first, an induction period in hydroxylation of phenol is related to the formation of active species Fe3+ and Fe2+ from Fe2O3; and second, the slow hydroxylation is related to the surface catalysis reaction on heteropoly salt or Fe/ZrO2, leading to the disappearance of the induction period.