Nickel sulfide catalysts useful life

The Ni3S2 catalyst on china clay used for the catalytic removal of organic sulfur compounds from coal gas has an average life of three months (8). Nickel sulfide catalysts lose activity, as a rule, because they become coated with reaction products which are insufficiently volatile or soluble under the prevailing conditions. However, a nickel sulfide... 

Nearly all fuels used to operate carbonate fuel cell power plants contain sulfur. Sulfur compounds deactivate nickel-based catalysts used in the carbonate fuel cell anode. Sulfur has a tendency to be chemisorbed on active nickel, forming nickel sulfide (as shown in Reactions 4-6). The catalyst deactivation causes loss of reforming activity and hence limits the catalyst life. For stable long-term carbonate fuel cell operation, the sulfur concentration in fuel needs to be reduced to a lower level prior to introduction to the anode by utilizing an efficient fuel desulfurization system. As a rule-of-thumb, sulfur should be removed to bring the concentration down to the sub-ppm level. 

The usual catalysts are based on cobalt, nickel, molybdenum and tungsten sulfides, generally combined and deposited on alumina. The most widely used formula is a composite sulfide of molybdenum and colbalt oo alumina. Run length and catalyst life are longer than those of tbe catalytic systems employed in brst step hydrogenation, Le. 6 to 12 months and 3 to 5 years, and the regeneration method is identical... 

The BASF15 and IFP12 processes are reported to use sulfided NiO/MoO catalysts, and catalysts of this general sulfided base metal type can be expected to be employed by all licensors. While noble metal or nickel catalysts result in low reactor temperatures, their use is unlikely in this application. Sulfur levels in the feeds make for short catalyst life unless they are from dewaxing a hydro-crackate. 

Impurities such as chlorine, arsenic, and nickel used in the manufacturing process tend to shorten the life of the catalyst. The usual methods for desulfurization are by activated carbon adsorption at about 15 to 50°C or oxidation with zinc oxide or both. The use of zinc oxide is often preferred when large quantities of mercaptans and highly condensable hydrocarbons are present, which may quickly saturate the catalysts. The main function of the zinc oxide is to remove the hydrogen sulfide, mercaptans and chlorine. Combining activated carbon and zinc oxide is very effective in removing the different types of sulfide compounds. 

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