Abstract: A heavy hydrocarbon oil, a substantial portion of which boils above 524.degree. C., is subjected to hydrocracking with a fractionated heavy oil recycle stream containing active additive particles. In the process, a slurry feed of (1) fresh heavy hydrocarbon oil feedstock and a heavy hydrocarbon recycle and (2) from about 0.01-4% by weight (based on fresh feedstock) of iron sulphate additive particles having sizes less than 45 .mu.m, is passed upwardly through a confined vertical hydrocracking zone. A mixed effluent is removed from the top of the hydrocracking zone, which is then passed through a hot separator vessel. From the bottom of the separator is withdrawn a liquid heavy hydrocarbon stream comprising heavy hydrocarbons and particles of the iron sulphate additive converted mainly to an iron sulphide phase. This separated liquid heavy hydrocarbon stream is fractionated to obtain a heavy oil which boils above 450.degree. C., containing the additive particles.

Abstract: A process is described for reducing the viscosity of heavy hydrocarbon oils which comprises separately heating a stream of heavy hydrocarbon oil and a stream of gas, mixing the hot gas and hot heavy hydrocarbon oil under pressure and immediately thereafter passing the heavy oil/gas mixture through a small nozzle or orifice such that a substantial pressure drop occurs across the orifice and the heavy oil/gas mixture is ejected from the orifice as a spray in the form of fine oil droplets entrained by highly turbulent gas flow. This spray is discharged into a confined reaction zone from which the oil of reduced viscosity is collected.