Preparation of high activity cobalt catalysts, the catalysts and their use

Abstract

A method is provided for preparing a supported cobalt-containing catalyst having substantially homogeneously dispersed, small cobalt crystallites. The method comprises depositing cobalt nitrate on a support and then subjecting the support to a two-step decomposition protocol. In the first step, the support is heated in an oxygen-containing, substantially water-free atmosphere to about 160° C. to form an intermediate decomposition product. This intermediate product is then or hydrolyzed and reduced, or hydrolyzed, calcined and reduced.

1 . A method for preparing a cobalt-containing catalyst, the method comprising:
 impregnating a catalyst support with an aqueous solution of cobalt nitrate;   drying the cobalt-impregnated support;   heating the dried support in an oxygen-containing atmosphere that is substantially free of water and is free of added NO, said heating being at a temperature at which a first endotherm of nitrate decomposition occurs and for a time sufficient for the dried support to pass through the first endotherm thereby providing an intermediate material; and   subjecting the intermediate material to a step of hydrolytically decomposing the intermediate material followed by reduction whereby a cobalt-containing catalyst is obtained.   
     
     
         2 . The method of  claim 1 , further comprising a step of calcining the catalyst after hydrolytically decomposing the intermediate material and before reduction. 
     
     
         3 . The method of  claim 1  wherein the support is a titania support. 
     
     
         4 . The method of  claim 1  wherein the oxygen-containing atmosphere is dry air. 
     
     
         5 . The method of  claim 1  wherein the intermediate material is a nitrosyl species having peaks in an infrared scan in the range of 1820-1877 cm −1 . 
     
     
         6 . The method of  claim 5  wherein the nitrosyl species is present following said heating but not following said calcining. 
     
     
         7 . The method of  claim 7  wherein the dried support is heated to about 160° C. 
     
     
         8 . The method of  claim 7  wherein the heated support is held at about 160° C. for a time ranging from less than about one minute to greater than about one hour. 
     
     
         9 . The method of  claim 7  wherein the support is heated in a rotary calciner to about 160° C. and held at that temperature for about 2 to about 10 minutes. 
     
     
         10 . The method of  claim 8  including impregnating the support with a promoter metal selected from the group consisting essentially of Group IV, VII and VIII metals, and mixtures thereof before the impregnated support is heated to partially decompose the cobalt nitrate. 
     
     
         11 . The method of  claim 10  wherein the promoter metal is used in an amount sufficient to provide a loading of the metal or mixture of metals in the range of about 0.01 wt % to about 5 wt %, based on the total weight of the catalyst. 
     
     
         12 . The method of  claim 11  wherein the promoter metal is rhenium. 
     
     
         13 . The method of  claim 12  wherein the rhenium is sufficient to provide up to 0.2 wt % loading of rhenium on the catalyst, based on the total weight of the catalyst. 
     
     
         14 . A titania supported catalyst comprising: cobalt and rhenium wherein the amount of rhenium is 0.2 wt % or less based on the total weight of the catalyst and wherein the cobalt is highly dispersed as evidenced by transmission electron microscopy and wherein the cobalt has a Dsv of 10 nm or less. 
     
     
         15 . The catalyst of  claim 14  wherein the rhenium is present in an amount of about 0.01 wt % to 0.2 wt % based on the total weight of the catalyst. 
     
     
         16 . The catalyst of  claim 15  wherein the cobalt is present in an amount of about 6 wt % to about 20 wt % based on the total weight of the catalyst. 
     
     
         17 . The catalyst of  claim 16  wherein greater than 50 wt % of the titania in the support is in the rutile phase. 
     
     
         18 . Use of the catalyst of any one of  claims 14  to  17  in a Fischer-Tropsch hydrocarbon synthesis process. 
     
     
         19 . A composition formed by:
 impregnating a catalyst support with an aqueous solution of cobalt nitrate;   drying the cobalt-impregnated support; and   heating the dried support in an oxygen-containing atmosphere that is substantially free of water and is free of added NO, said heating being at a temperature and for a time sufficient to partially decompose the cobalt nitrate, through the first endotherm of the nitrate decomposition, whereby the composition is formed.   
     
     
         20 . The composition of  claim 19  wherein the oxygen-containing atmosphere is dry air and wherein the dried support is heated to 160° C.±5° C. 
     
     
         21 . The composition of  claim 20  wherein the dried support is heated for less than about 1 minute to more than about 1 hour. 
     
     
         22 . The composition of  claim 21  including impregnating the support with a promoter metal selected from the group consisting essentially of Group IV, VII and VIII metals and mixtures thereof before the impregnated support is heated to partially decompose the cobalt nitrate. 
     
     
         23 . The composition of  claim 22  wherein the promoter metal is rhenium.