hydrodesulfurization

:  the process of chemically removing sulfur from raw petroleum products (such as crude oil or natural gas) in order to make them more efficient and reduce combustion byproducts Decades ago oil refineries adopted a process called hydrodesulfurization … to strip sulfur atoms from oil molecules. Sulfurous fractions are mixed with hydrogen and a cobalt-molybdenum catalyst, yielding hydrogen sulfide. — Jr Minkel, Scientific American, February 2006