Heavy oil desulfurization is a key process for the purpose of reducing the sulfur content in heavy crude oil, which is necessary to comply with environmental regulations and to improve oil product quality. This process primarily involves converting sulfur compounds to hydrogen sulfide which can then be easily separated from the oil. Technological attributes of desulfurization include the use of catalysts, such as hydrodesulfurization, and advanced tecniques like oxidative desulfurization and biodesulfurization. These methods are used in oil refineries to produce cleaner fuels that emit less pollution into our atmosphere. The objectives are to improve the value of heavy oils, meet the emissions regulations, and raise the efficiency of downstream processes.