hydrodésulfuration

Hydrodesulfurization (HDS) is a catalytic chemical process used in petroleum refineries to remove sulfur from hydrocarbon streams. Sulfur compounds are present in crude oil and must be removed before further refining or combustion to prevent environmental pollution, such as acid rain, and to avoid poisoning catalysts used in downstream processes. The HDS process involves reacting the sulfur-containing feedstock with hydrogen gas at elevated temperatures and pressures in the presence of a catalyst.

The primary goal of HDS is to convert organic sulfur compounds, such as thiols, sulfides, and thiophenes, into hydrogen sulfide (H2S). The hydrogen sulfide is then separated from the hydrocarbon stream and typically processed in a Claus unit to recover elemental sulfur. The most common catalysts used in HDS are based on transition metal sulfides, such as molybdenum disulfide (MoS2) or tungsten disulfide (WS2), often supported on alumina. Promoters like cobalt or nickel are usually added to enhance the activity and selectivity of the catalyst.

The reaction conditions for HDS vary depending on the feedstock composition and the desired sulfur removal level. Typical temperatures range from 300 to 400 degrees Celsius, and pressures can be anywhere from 30 to 130 atmospheres. The effectiveness of HDS is crucial for meeting environmental regulations regarding fuel sulfur content and for ensuring the efficient operation of modern refining processes. Different sulfur compounds exhibit varying degrees of reactivity, with thiols being the easiest to remove and dibenzothiophenes being the most refractory.