desulfurize

Desulfurize means to remove sulfur from a material, process, or mixture. It is widely practiced in energy, chemical, and metallurgical industries to reduce sulfur content for environmental, technical, or economic reasons.

In petroleum refining, desulfurization is essential to meet fuel sulfur specifications and reduce sulfur dioxide emissions. The dominant method is catalytic hydrodesulfurization (HDS), where sulfur-containing compounds react with hydrogen over a molybdenum- or cobalt-nitride catalyst under high temperature and pressure to form hydrogen sulfide, which is subsequently treated to recover elemental sulfur or sulfuric compounds. HDS effectively lowers sulfur in gasoline, diesel, and jet fuels but may be less active on some complex sulfones or aromatic sulfides, prompting complementary methods.

Alternative approaches include oxidative desulfurization (ODS), which oxidizes sulfur compounds to sulfoxides or sulfones that can be extracted with polar solvents; and adsorption or extraction techniques using specialized sorbents to remove remaining sulfur species that survive HDS. Biodesulfurization, using certain microbes, is explored for specific feedstocks but is less widely deployed.

Desulfurization also occurs in natural gas and refinery process streams to remove hydrogen sulfide, typically by amine treating or scavenging chemicals, producing sulfur for elemental recovery. In coal and solid fuels, physical cleaning and chemical treatments reduce pyritic and organic sulfur before or during combustion, improving emissions and efficiency.

In metallurgy, desulfurization of iron and steel involves slagging and the addition of calcium, silicon, or magnesium-based agents to form sulfides that are removed, enhancing ductility and toughness of the final product.

Overall, desulfurization is a common, multi-method approach to mitigate sulfur-related problems across industries.