Bonyan

HDS catalyst /BNS/14/2015

HDS Catalyst.

Hydrodesulfurization (HDS) is a catalytic chemical process widely used to remove sulfur (S) from natural gas and from refined petroleum products, such as gasoline or petrol, jet fuel, kerosene, diesel fuel, and fuel oils. The purpose of removing the sulfur is to reduce the sulfur dioxide (SO2) emissions that result from using those fuels in automotive vehicles, aircraft, railroad locomotives, ships, gas or oil burning power plants, residential and industrial furnaces, and other forms of fuel combustion.

Another important reason for removing sulfur from the naphtha streams within a petroleum refinery is that sulfur, even in extremely low concentrations, poisons the noble metal catalysts (platinum and rhenium) in the catalytic reforming units that are subsequently used to upgrade the octane rating of the naphtha streams.

Hydrogenation of the sulfur compounds results in the formation of undesirable, toxic gaseous hydrogen sulfide. The industrial hydrodesulfurization processes include facilities for the capture and removal of the hydrogen sulfide gas. In petroleum refineries, the hydrogen sulfide gas is then subsequently converted into byproduct elemental sulfur. In fact, the vast majority of the 68,000,000 metric tons of sulfur produced worldwide in 2010 was byproduct sulfur from petroleum refining and natural gas processing plants.

The process chemistry

Hydrogenation is a class of chemical reactions that results in the addition of hydrogen. Hydrogenolysis is a type of hydrogenation that results in the cleavage of the C-X chemical bond, where C is a carbon atom and X is a sulfur, nitrogen or oxygen atom. The net result of a hydrogenolysis reaction is the formation of C-H and H-X chemical bonds. Thus, hydrodesulfurization is a hydrogenolysis reaction. Using ethanethiol (C₂H₅SH), a sulfur compound present in some petroleum refining streams, as an example, the hydrodesulfurization reaction can be expressed as:

Ethanethiol + Hydrogen ⇒ Ethane + Hydrogen Sulfide

C₂H₅SH + H₂ ⇒ C₂H₆ + H₂S

Catalysts

Many metals catalyze the HDS reaction, but it is those at the middle of the transition metal series that are most active. Ruthenium disulfide (RuS₂) appears to be the single most active catalyst, but binary combinations of cobalt and molybdenum are also highly active.

In practice, most HDS units in petroleum refineries use catalysts based on cobalt-modified molybdenum disulfide (MoS₂) together with smaller amounts of other metals. Aside from the MoS₂ catalysts, nickel and tungsten are also used, depending on the nature of the feed. For example, nickel-wolfram (Ni-W) catalysts are more effective for the hydrodenitrification (HDN) which is also desired in many HDS units.

Metal sulfides are supported on materials with high surface areas. A typical support for HDS catalyst is alumina. The support allows the more expensive catalyst to be more widely distributed, giving rise to a larger fraction of the MoS₂ that is catalytically active.

Bonyan Shimi and HDS

The Bonyan Shimi's main market for HDS was aimed at the Iranian petrol-chemical industry but since the HDS can be produced to any customers wishes Bonyan Shimi is actively approaching other market segments as well. The target group is set to the food industry as we strongly believe that we can serve that market successfully with full adaptation of the customers specifications.

Feel free and request a quotation.