Published July 1992
In this review, we evaluate the vapor-phase hydroxylation process for the coproduction of catechol, resorcinol, and hydroquinone at a total capacity of 20 million lb/yr (9,100 t/yr). The vapor-phase zeolite-catalyzed hydroxylation process would be attractive for a total capacity of 35 million lb/yr (15,900 t/yr) or less in the coproduction of all three dihydroxybenzenes.
Phenol hydroxylation with hydrogen peroxide for commercial dihydroxybenzenes production is carried out by a liquid-phase ion-catalyzed process in agitated reactors using strong acids as catalysts. The use of heterogeneous catalysts such as titanium silicalite, titanium dioxide, or zeolites is cited in patents. To eliminate the need for removal of liquid catalyst/catalyst fines, hydrogen peroxide, and possibly solvents, from the reaction product, phenol hydroxylation can be carried out in the vapor phase according to a Rhone-Poulenc patent.
