hydrodesulfurizacji

Hydrodesulfurization, often abbreviated as HDS, is a crucial catalytic chemical process used in petroleum refineries. Its primary purpose is to remove sulfur compounds from crude oil and its various fractions, such as gasoline, diesel fuel, and kerosene. Sulfur is an undesirable element in fuels because its combustion produces sulfur dioxide (SO2), a major air pollutant contributing to acid rain and respiratory problems. HDS achieves sulfur removal by reacting sulfur-containing organic molecules with hydrogen gas at elevated temperatures and pressures in the presence of a catalyst.

The most common catalysts used in HDS are based on transition metal sulfides, typically molybdenum sulfide (MoS2) or tungsten sulfide (WS2), supported on an alumina (Al2O3) base. During the process, the sulfur atoms in the hydrocarbon molecules are hydrogenolyzed, meaning they are cleaved from the carbon chain and react with hydrogen to form hydrogen sulfide (H2S). The hydrocarbons are simultaneously hydrogenated, meaning they gain hydrogen atoms. The overall reaction can be generalized as R-S-R' + 2H2 -> 2RH + H2S, where R and R' represent hydrocarbon fragments.

The H2S produced is then separated from the hydrocarbon stream and typically converted into elemental sulfur through the Claus process, a valuable byproduct. HDS is essential for meeting increasingly stringent environmental regulations regarding fuel sulfur content and for preventing catalyst poisoning in downstream refining processes. The efficiency of HDS varies depending on the type of sulfur compound present; some, like thiophenes, are more difficult to remove than others, like mercaptans.