Skeletal iron catalyst and its preparation for fischer-tropsch synthesis processes

Abstract

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 aluminum, antimony, silicon, tin or zinc powder and 0.01-5 wt. % metal promotor powder to provide 20-80 wt. % iron content, then melted together, 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. to extract or leach out a major portion of the non-ferrous metal portion from the iron and provide the skeletal iron catalyst material. Such skeletal iron catalyst is utilized with CO+H2 feedstream in either fixed bed or slurry bed type reactor at 200-350° C. temperature, 1.0-3.0 mPa pressure and gas hourly space velocity of 0.5-3.0 L / g Fe / h to produce desired hydrocarbon products.

Description

BACKGROUND OF INVENTION[0001] This invention pertains to skeletal iron catalysts, and particularly pertains to catalyst preparation methods and process for use of such catalysts in Fischer-Tropsch synthesis processes for CO and H.sub.2 feeds to produce hydrocarbon products.[0002] As a basic technology for producing synthetic liquid fuels from CO+H.sub.2 feedstreams, the Fischer-Tropsch catalytic synthesis process has undergone worldwide development and use since the 1920s. Iron-based catalysts have been widely investigated and used and precipitated iron catalyst and fused iron catalyst have been the commonly used catalysts in such F-T synthesis processes. However, the preparation procedure for the precipitated iron catalyst is undesirably complicated and includes several steps of precipitation, washing, filtration, drying, formation, calcination, pulverization, and reduction. Also, the precipitated iron catalyst is significantly influenced by various parameters, including precipitat...

AI Technical Summary

Benefits of technology

[0004] The resulting skeletal iron catalyst has high activity and provides good selectivity towards the formation of desirable low-molecular-weight hydrocarbon products from the CO and H.sub.2 feedstreams. This catalyst has catalytic activity equivalent to that of precipitated iron catalyst and product selectivity exceeding that of either precipitated or fused iron catalysts,and can be utilized in either fixed bed or slurry bed type reactors for Fischer-Tropsch synthesis reaction processes.

[0006] (a) The preparation method and pretreatment procedures for skeletal iron catalyst are relatively simple and inexpensive.

[0009] (d) For slurry-phase Fischer-Tropsch synthesis processes, the skeletal iron catalyst has stable activity and significant selectivity for low molecular weight hydrocarbons (C.sub.4 selectivity>10%).

Problems solved by technology

However, the preparation procedure for the precipitated iron catalyst is undesirably complicated and includes several steps of precipitation, washing, filtration, drying, formation, calcination, pulverization, and reduction.

Also, the precipitated iron catalyst is significantly influenced by various parameters, including precipitating agent, solution concentration, precipitation temperature, solution pH value, pretreatment temperature, and atmosphere, and such catalyst is undesirably expensive.

Furthermore, the fused iron catalyst has undesirably low active surface area (.about.10 m.sup.2 / g) that is difficult to increase, and it also has low catalytic activity and minimal economic advantage.