Desulfurering

Desulfurization, sometimes spelled desulfurering in some sources, is the process of removing sulfur-containing compounds from fuels, natural gas, or chemical feedstocks. The objective is to reduce sulfur oxide emissions during combustion, protect catalysts in refineries and petrochemical processes, and meet product specifications that limit sulfur content.

The most widely used method for liquid hydrocarbon streams is hydrodesulfurization (HDS). In HDS, the feed is treated with hydrogen at high temperature and pressure in the presence of a catalyst such as cobalt-molybdenum or nickel-molybdenum supported on alumina. Sulfur compounds including mercaptans, sulfides, and thiophenes are converted to hydrogen sulfide, which is then separated and sent to a sulfur recovery unit (often a Claus plant) to recover elemental sulfur. Hydrogen consumption and catalyst life are important considerations in this process.

Complementary approaches include oxidative desulfurization (ODS), which oxidizes sulfur compounds to sulfones or sulfoxides that can be removed by extraction or catalytic methods, and adsorptive or extractive desulfurization, which remove sulfur species without hydrogen consumption. These methods are used to target stubborn sulfur compounds such as dibenzothiophenes or in fuels where HDS would be energetically or economically prohibitive.

Desulfurization is a central operation in petroleum refining, natural gas processing, and other hydrocarbon industries. The extent of sulfur removal depends on feedstock characteristics and product specifications and involves trade-offs among conversion efficiency, hydrogen use, catalyst life, and cost. Environmental policy and fuel standards continue to drive advances in desulfurization technologies and sulfur recovery.