Oxides of C are treated with H2 under high temperature and pressure in the presence of a catalyst. The deposition of solid high-molecular products on the catalyst during the reaction is prevented by the presence of a high-boiling solvent, which does not change or vaporize under the conditions of the reaction. Thus, a catalyst obtained by fusing ZnO and CaCr2O7 is used in treating CO with H2 at 400° and 200 atm. to give a mixture of higher alcohols. The catalyst is rinsed with anthracene oil to prevent inactivation by deposition of solid products.