GB378501A - Improvements in and relating to the production of aromatic hydrocarbons from phenols - Google Patents

Abstract

In the manufacture of aromatic hydrocarbons by the catalytic hydrogenation of phenols at 400-500 DEG C., the phenol is preheated to a temperature of at least 375 DEG C., preferably to the reaction temperature, prior to the reaction, whereby the reaction is effected with little or no formation of hydroaromatic hydrocarbons. The conversion is best carried out under elevated pressures, e.g. 5-500 atmospheres, preferably 50-250 atmospheres, but may also be carried out at pressures lower than 5 atmospheres or at ordinary pressure. The preferred catalysts are molybdenum compounds, particularly the oxide or sulphide, which may be employed alone or associated with promoters, such as silica or zinc oxide and with or without carriers, such as pumice. The catalysts may be revivified, in the case of molybdenum oxide by treatment with air or oxygen at 400-450 DEG C., and in the case of the sulphide by treatment with hydrogen sulphide, or, in the latter case, the hydrogenating gas may contain hydrogen sulphide. In examples: (1) phenol is introduced with molybdenum oxide into a mild steel rotary converter which is then swept out with hydrogen at atmospheric pressure, heated to 450 DEG C. and hydrogen, which may also be preheated, is introduced until the pressure rises to 100 atmospheres; the product contains 90 per cent of benzene; a comparative experiment without preheating is described; (2) o-cresol is similarly treated with a hydrogen pressure of 125 atmospheres, the product containing 90 per cent of toluene; (3) through an iron tube at 430 DEG C., containing a catalyst prepared by heating pumice impregnated with ammonium molybdate, are passed hydrogen and cresol vapour, both heated to a temperature close to the conversion temperature; the product contains 89 per cent of toluene; alternatively molybdenum trisulphide is used as catalyst and hydrogen sulphide is added to the hydrogen. The process is applicable to the treatment of individual phenols or to mixtures thereof, including technical phenol mixtures from coal hydrogenation or coal carbonization processes. Specification 273,493, [Class 2 (iii), Dyes &c.], is referred to.