Hydrodesulfurization (HDS)

Definition - What does Hydrodesulfurization (HDS) mean?

Hydrodesulfurization (HDS) is a catalytic chemical process by which sulfur (S) is removed from natural gas and from refined petroleum products like petrol, jet fuel, kerosene, diesel fuel and fuel oils in the form of hydrogen sulfide or sulfur dioxide. This process is used to upgrade the octane rating of the naphtha streams.

Fuels obtained through hydrodesulfurization reduce sulfur dioxide emissions in automotive vehicles, aircraft, trains, ships, gas or oil burning power plants, residential and industrial furnaces and other forms of fuel combustion.

Sulfur converted to oxides causes major corrosion problems. The original organosulfur compounds in petroleum can also cause corrosion of engines.

Corrosionpedia explains Hydrodesulfurization (HDS)

Hydrodesulfurization (HDS) is a process for lowering the sulfur content of petroleum and similar products by catalytic hydrogenation, with the sulfur compounds being converted to hydrogen sulfide. Hydrodesulfurization became increasingly important following the passing, in many countries, of new regulations regarding sulfur levels in oil products in order to cut down sulfur dioxide (SO2) emissions. As a result, oil refineries usually have an HDS unit.

In addition to sulfur causing engine corrosion, sulfur in oil also reduces the effectiveness of the catalysts used to convert petroleum feedstock into other products. Sulfur in gasoline also affects catalytic converters in cars. It only requires very low levels to produce this effect, which is known as "poisoning" the catalyst.

In practice, most HDS units in petroleum refineries use catalysts based on cobalt-modified molybdenum disulfide together with smaller amounts of other metals. Aside from these catalysts, nickel and tungsten are also used, depending on the nature of the feed.

The refinery HDS feedstocks (naphtha, kerosene, diesel oil and heavier oils) contain a wide range of organic sulfur compounds, including thiols, thiophenes, organic sulfides and disulfides, and many others. When the HDS process is used to desulfurize a refinery naphtha, it is necessary to remove the total sulfur down to the parts per million range or lower in order to prevent poisoning the noble metal catalysts in the subsequent catalytic reforming of the naphthas. When the process is used for desulfurizing diesel oils, the latest environmental regulations require very deep hydrodesulfurization.

The industrial hydrodesulfurization processes include facilities for the capture and removal of the resulting hydrogen sulfide gas. In petroleum refineries, the hydrogen sulfide gas is then subsequently converted into byproduct elemental sulfur or sulfuric acid.

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