GB641662A - Method for making phenol - Google Patents

Abstract

In the preparation of phenol by passing benzene vapour and an oxygen containing gas at a pressure of more than 500 lbs./sq. inch through a reaction zone at a temperature between 650 DEG F. and 1225 DEG F. in the absence of solid catalyst, the yield is improved by the addition of a minor proportion, i.e. from 0.2 per cent to about 3.0 per cent by volume based on benzene, of an organic compound containing hydrogen, which under the conditions of the reaction is a better hydrogen donor than benzene and is in the gaseous phase and which has a "potential hydrogen donor ability" value, as defined in the Specification, greater than 2.5. Suitable hydrogen donors are cyclohexanol, cyclohexanone, cyclohexene, tetrahydronaphthalene, 2-ethyl-3-propyl acrolein, actaldehyde, n-hexane, diethyl ether, aniline, turpentine, n-hexene, cracked gasoline and particularly cyclohexane. The invention may also be carried out by partially hydrogenating the benzene prior to the oxidation to produce the desired proportion of hydrogen donors. Optimum reaction times, temperatures, proportions and pressures; the dimensions and construction of the reaction tube and the nature and proportion of the inductor are interdependent. Suitable values for the above are indicated. In a preferred embodiment of the invention, the benzene is separated from the phenol and other oxidation products and recycled with the addition at each recycle stage of a further small amount of the reaction promotor. This may be added as such or may be formed in situ by continuously hydrogenating a proportion of the recycled benzene prior to its admission to the reaction zone sufficient to incorporate 0.2-3.0 per cent by volume of hydrogenated benzene. Specification 459,920 is referred to.