The most common catalyst used to separate sulfur from oil is cobalt molybdate (CoMo). This compound is typically supported on an alumina oxide (Al₂O₃) base. The CoMo/Al₂O₃ catalyst is used in a process called hydrodesulfurization (HDS), which involves reacting the sulfur-containing compounds in the oil with hydrogen gas (H₂) to produce hydrogen sulfide (H₂S) and hydrocarbons. The H₂S is then removed from the oil by distillation.