Hydrodesulfurization is a chemical process used to remove sulfur from petroleum products. This process is essential for producing cleaner fuels, as sulfur can contribute to air pollution and acid rain when burned. During hydrodesulfurization, hydrogen gas is combined with the sulfur-containing compounds in the oil, resulting in the formation of hydrogen sulfide, which can be easily separated. The process typically occurs in a reactor at high temperatures and pressures, using a catalyst to speed up the reaction. Refineries employ hydrodesulfurization to meet environmental regulations and improve the quality of fuels like gasoline and diesel, making them more environmentally friendly.