Abstract: A process and apparatus for converting light hydrocarbons, such as waste organic solvents, to a useful fuel having a high flash point. A mixture of light hydrocarbon and heavy oil, wherein the ratio of light hydrocarbon to heavy oil preferably lies in the range from about 10:1 to about 1:4, is forced at a pressure of preferably at least about 500 psi through a porous substrate having a catalytically effective amount of an active oxide of hexavalent group 6b metal, such as chromium, thereon. The porous substrate may comprise a sintered powder stainless steel material having an average pore size in the range from about 20 to about 2000 microns. The catalyst is prepared by wetting the porous substrate with a solution of a salt of the group 6b metal and heating the wetted substrate until a catalytically active oxide of hexavalent group 6b metal is formed thereon.