A process for treating a hydrocarbon-containing feedstock is provided in which a hydrocarbon-containing feed comprising at least 20 wt. % of heavy hydrocarbons is mixed with hydrogen, hydrogen sulfide, and a metal-containing catalyst to produce a hydrocarbon-containing product. The hydrocarbon-containing feedstock, the catalyst(s), the hydrogen sulfide, and the hydrogen are provided to a mixing zone and blended in the mixing zone at a temperature of from 375° C. to 500° C. and a total pressure of from 6.9 MPa to 27.5 MPa, where hydrogen sulfide is provided at a mole ratio of hydrogen sulfide to hydrogen of at least 0.5:9.5 and the combined hydrogen sulfide and hydrogen partial pressures provide at least 60% of the total pressure. A vapor comprised of hydrocarbons that are vaporizable at the temperature and pressure within the mixing zone is separated from the mixing zone, and, apart from the mixing zone, the vapor may be condensed to produce a liquid hydrocarbon-containing product.