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 H 2 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+H 2 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.

We claim:  
     
         1 . A method for preparing of a skeletal iron catalyst useful for Fischer-Tropsch synthesis processor, comprising the steps of: 
 a) preparing catalyst precursor metal alloy by providing iron powder together with a non-ferrous metal powder selected from aluminum, antimony, silicon, tin or zinc powder sufficient to provide iron content 20-80 wt % and 0.01-5.0 wt % of promotor metal selected from calcium, copper, chromium, magnesium, or potassium, heating the powder in an electric arc induction furnace under inert gas protection and stirring said powder uniformly by magnetic stirring while melting the metal powders, then cooling the melted iron alloy to room temperature and mechanically pulverizing the resulting metal alloy to provide iron alloy precursor particles having 0.1-10 mm particle size;    b) treating the catalyst precursor metal alloy particles by contacting it with NaOH or KOH solution having 10-50% concentration under hydrogen atmosphere and heating the mixture to temperature of 30-95° C., while maintaining reaction condition for 5-150 minutes for extracting or leaching out a major portion of the non-ferrous metal from the iron alloy particles, then washing with deionized water until pH=7, displacing water with alcohol, and placing the resulting skeletal iron catalyst particles in ethanol; and    c) pre-treating the skeletal iron catalyst by drying it with hydrogen at high space velocity at 200-500° C. for 2-12 hours, then transferring the dried skleletal iron catalyst into water-free ethanol or liquid paraffin for storage.    
     
     
         2 . The catalyst preparation method of  claim 1 , wherein step (b) is treating the skeletal iron catalyst precursor metal alloy particles by adding sufficient NaOH or KOH solution having 10-50% concentration into a stirred container under hydrogen atmosphere, and heating the solution to temperature of 30-95° C., then adding the iron-metal alloy particles into the caustic solution at suitable time intervals, while maintaining reaction condition for 5-150 minutes after alloy particle addition for extracting or leaching out a major portion of the non-ferrous metal from the iron, then washing with deionized water until pH=7, displacing water with alcohol, and placing the resulting skeletal iron alloy catalyst particles in ethanol.  
     
     
         3 . The catalyst preparation method of the  claim 1 , wherein step (b) is mixing the iron alloy precursor particles with solid sodium hydroxide powder at weight ratio of sodium hydroxide to the metal alloy of 510:1, then adding deionized water drop-wise to wet the mixture to provide a paste but not a fluid state while stirring so that reaction proceeds under a wet state; after reaction has proceeded 5-30 minutes while gas release gradually decreases, adding to said mixture fresh NaOH or KOH of 10-50% concentration solution and maintaining for 2-60 minutes at 50-95° C.; then washing with deionized water to pH=7, displacing water with water-free ethanol and store in ethanol.  
     
     
         4 . The catalyst preparation method of  claim 1 , wherein step (b) includes placing the iron alloy precursor particles in a well-stirred container, spraying the particles with a 40-60% concentration NaOH or KOH solution, maintaining reaction in a wet but not fluid state for 5-30 minutes, adding NaOH or KOH solution of 10-50% concentration, maintaining for 2-60 minutes at 50-95° C., then washing with deionized water to pH=7, then replacing water with water-free ethanol and store in ethanol.  
     
     
         5 . The catalyst preparation method of  claim 1 , wherein said metal powders are iron aluminum and copper having an initial respective weight ratio of 49:50:1.  
     
     
         6 . The catalyst preparation method  claim 1 , wherein the metal powders are iron, aluminum and copper having an initial weight ratio of 25:74:1.  
     
     
         7 . The catalyst preparation method  claim 1 , wherein the metal powders are iron, aluminum and copper having an initial respective weight ratio of 33:66:1.  
     
     
         8 . A Fisher-Tropsch catalytic synthesis process utilizing skeletal iron catalyst in a reactor, the process comprising: 
 (a) feeding CO and H 2  gas having H 2 /CO molar ratio of 0.5-2.5 into a reactor containing a skeletal iron catalyst as defined by claim  1 ;    (b) maintaining said reactor at conditions of 200-350° C. temperature, 1.0-2.0 mPa pressure and gas hourly space velocity of 0.5-3.0 L/g Fe/h; and    (c) withdrawing a hydrocarbon gas product and hydrocarbon liquid containing particles of said catalyst from the reactor.    
     
     
         9 . The catalytic synthesis process of  claim 8 , wherein the H 2 /CO molar ratio is 2.0, reaction temperature is 270° C., pressure is 1.6 mPa and gas hourly space velocity is 1.0 L/g Fe/h.  
     
     
         10 . The catalytic synthesis process of  claim 8 , wherein the skeletal iron catalyst in ethanol having particle size of 0.1-10 mm is utilized in a fixed bed reactor.  
     
     
         11 . The catalytic synthesis process of  claim 8 , wherein the skeletal iron catalyst having particle size of 20-200 micron is mixed with liquid paraffin and utilized in a slurry phase reactor.