New Way of Hydroquinone and Catechol Synthesis using Nitrous Oxide as Oxidant

Abstract

The synthesis of dihydroxybenzenes (DHB) via the gas-phase oxidation of phenol with nitrous oxide in the presence of benzene was studied. Addition of benzene to the feed mixture greatly improves the selectivity and catalytic stability of the Fe-containing ZSM-5 zeolite, that was previously considered to be a main obstacle to the development of a new process. Reaction conditions strongly affect the distribution of the DHB isomers: the ratio of hydroquinone to catechol may vary from 1.4 to 10, with the resorcinol fraction being nearly constant and comprising 3 ± 5%. Some 40h experiments on the oxidation of a phenol-benzene mixture demonstrated the high efficiency of the formed FeZSM-5 catalyst. With a good stability, the catalyst provides 97% phenol selectivity referred to DHB and 85 ± 90% N2O selectivity referred to the sum of DHBs and phenol. A new process for hydroquinone and catechol synthesis based on the neat oxidation of benzene with recycling of the phenol as an intermediate product is suggested.