Skeletal iron catalyst having improved attrition resistance and product selectivity in slurry-phase synthesis processes

Abstract

Particulate skeletal iron catalyst is provided which contain at least about 50 wt. % iron with the remainder being a minor portion of a suitable non-ferrous metal and having characteristics of 0.062-1.0 mm particle size (62-1000 micron), 20-100 m2 / g surface area, and 10-40 nm average pore diameter. Such skeletal iron catalysts are prepared and utilized for producing synthetic hydrocarbon products from CO and H2 feeds by Fischer-Tropsch synthesis process. Iron powder is mixed with non-ferrous metal powder selected from aluminum, antimony, silicon, tin or zinc powder to provide 20-80 wt. % initial iron content and melted together to form an iron alloy, then cooled to room temperature and pulverized to provide 0.1-10 mm iron alloy catalyst precursor particles. The iron alloy precursor particles are treated with NaOH or KOH caustic solution at 30-95° C. temperature to extract and / or leach out most of the non-ferrous metal portion, and then screened and treated by drying and reducing with hydrogen so as to provide smaller sized skeletal iron catalyst material. Such skeletal iron catalyst is utilized with CO+H2 feedstream for Fischer-Tropsch reactions in either a fixed bed or slurry bed type reactor at 180-500° C. temperature, 0.5-5.0 mPa pressure, and gas hourly space velocity of 0.5-3.0 L / g Fe / hr to produce desired hydrocarbon products.

Description

BACKGROUND OF INVENTION[0001] This invention pertains to skeletal iron catalyst and its preparation and use in Fischer-Tropsch and similar slurry-phase synthesis processes. More particularly, such skeletal iron catalyst utilized in slurry phase synthesis processes for H.sub.2+CO feedstreams has increased attrition resistance and improved catalyst / product liquid separation, while providing increased selectivity for producing C.sub.2-C.sub.5 light olefin products.[0002] Slurry phase Fischer-Tropsch (F-T) synthesis process technology is an important known route for indirect coal liquefaction for synthesis of liquid fuels from H.sub.2+CO feedstreams. Precipitated iron is currently a commonly used catalyst for such Fischer-Tropsch processes. However, precipitated iron catalysts are undesirably fragile and break down easily under reaction conditions into very fine particles, so that separation of such fine catalyst particles from reaction product waxes is difficult to accomplish and resul...

AI Technical Summary

Benefits of technology

[0008] The preparation method and treatment procedures for this skeletal iron catalyst are relatively simple and inexpensive. This resulting skeletal iron catalyst has good particle strength and attrition resistance, and activity equivalent to that of precipitated iron catalyst because during reactions its skeletal structure is easily accessible to H.sub.2 and produces larger yields of gasoline-diesel fuel range hydrocarbons and variable amounts of wax products. Also in F-T synthesis process it is easier to separate the skeletal iron catalyst from the reactor liquid medium and product, and thus achieves high recovery of the catalyst and thereby provides light hydrocarbon liquid products containing low concentrations of undesired catalyst fines.

Problems solved by technology

However, precipitated iron catalysts are undesirably fragile and break down easily under reaction conditions into very fine particles, so that separation of such fine catalyst particles from reaction product waxes is difficult to accomplish and results in inferior product quality and significant catalyst loss.

Such catalyst problems hinders commercial use of the process.

), thus requiring costly construction materials and consuming huge amounts of energy for feedstream heating and reaction.

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