Tailored Fischer-Tropsch synthesis product distribution

Abstract

Novel methods of Fischer-Tropsch synthesis are described. It has been discovered that conducting the Fischer-Tropsch synthesis over a catalyst with a catalytically active surface layer of 35 microns or less results in a liquid hydrocarbon product with a high ratio of C 5 -C 20 :C 20+ . Descriptions of novel Fischer-Tropsch catalysts and reactors are also provided. Novel hydrocarbon compositions with a high ratio of C 5 -C 20 :C 20+ are also described.

1 . A method of decoupling methanation from synthesis of liquid hydrocarbons in a Fischer-Tropsch process, comprising: 
 contacting H 2  and CO in a reaction microchannel over a catalyst at a temperature sufficient to convert the CO to hydrocarbons;    wherein there is a bulk flow path past the catalyst and the catalyst has a thickness of catalytically active component that is less than 35 μm;    wherein the catalytically active component comprises a Fischer-Tropsch catalytic metal; and    wherein the method has the characteristic that, while maintaining other reaction conditions, adjusting reaction temperature can increase CO conversion (absolute) from 25% to 60% while methane selectivity increases by less than 80% (relative) over the same temperature range and conditions.    
     
     
         2 . A reactor for Fischer-Tropsch synthesis, comprising: 
 a microchannel; and    a catalytically active surface layer disposed over at least a portion of the surface of the microchannel;    wherein the catalytically active surface layer comprises a Fischer-Tropsch catalytic metal and wherein the thickness of the catalytically active surface layer is less than 35 μm.    
     
     
         3 . The reactor of  claim 2  wherein the catalytically active surface layer comprises a Fischer-Tropsch catalytic metal selected from the group consisting of Fe, Co, Ni, Ru, Re, Os, and combinations thereof.  
     
     
         4 . The reactor of  claim 2  comprising a bulk flow path through the microchannel.  
     
     
         5 . The reactor of  claim 3  wherein the catalytically active surface layer further comprises a promoter.  
     
     
         6 . The reactor of  claim 4  wherein the catalytically active surface layer further comprises a metal oxide.  
     
     
         7 . The reactor of  claim 3  wherein the thickness of the catalytically active surface layer is less than 20 μm.  
     
     
         8 . The reactor of  claim 4  wherein the thickness of the catalytically active surface layer is between 2 and 20 μm.  
     
     
         9 . The reactor of  claim 3  wherein the microchannel is in a honeycomb.  
     
     
         10 . The reactor of  claim 3  wherein the surface layer comprises a porous catalyst material.  
     
     
         11 . The reactor of  claim 3  having methane decoupling selectivity such that when hydrogen and carbon dioxide are fed into the reactor at a H 2 :CO ratio of 2 and a weight hourly space velocity of 3.73 g CO/g catalyst/hr, a combined (H 2  +CO) feed pressure of 40 atm, and temperature is increased from 224° C. to 260° C., 
 the CO conversion more than doubles while the methane selectivity increases by 70% or less.    
     
     
         12 . A method of making a hydrocarbon composition via Fischer-Tropsch synthesis, comprising: 
 contacting H 2  and CO over the catalytically active surface layer that is in the microchannel of the reactor of  claim 2 , at a temperature sufficient to convert the CO to hydrocarbons.    
     
     
         13 . The method of  claim 12  wherein the catalytically active surface layer comprises a wachcoat on at least a portion of the microchannel.  
     
     
         14 . The method of  claim 12  wherein there is a contiguous bulk flow path through the microchannel having an open dimension of at least 0.1 mm.  
     
     
         15 . The method of  claim 12  wherein at least a portion of the heat generated by the Fischer-Tropsch synthesis is transferred to an adjacent microchannel that contains a heat exchange fluid.  
     
     
         16 . A hydrocarbon composition, comprising: 
 C5 to C20 hydrocarbons    wherein the amounts (by weight) of hydrocarbons decrease in the order C5>C6>C7>C8>C9>C10>C11>C12>C13>C14>C15>C16>C17>C18>C19>C20;    wherein C5, C6, C7, and C8 are each present in at least 5 wt %; and    wherein C20 is present in the range of 0.3 to 2.0 wt %.    
     
     
         17 . The hydrocarbon composition of  claim 16  wherein C9 is present in at least 5 wt %; and C20 is present in the range of 0.4 to 1.5 wt %.  
     
     
         18 . The hydrocarbon composition of  claim 16  wherein C5, C6, and C7 are each present in a range of 6 to 10%.  
     
     
         19 . The hydrocarbon composition of  claim 16  having the composition substantially as shown in  FIG. 5  (15 μm coating).  
     
     
         20 . A method of making the hydrocarbon composition of  claim 16  comprising reacting CO and H 2  in the reactor of  claim 2 .  
     
     
         21 . The method of  claim 16  wherein said hydrocarbon composition is obtained from a Fischer-Tropsch reaction without additional refining steps.  
     
     
         22 . A method of formulating a fuel comprising combining the hydrocarbon composition of  claim 16  with a hydrocarbon or a diesel fuel additive.  
     
     
         23 . The hydrocarbon composition of  claim 16  further comprising a trace amount (0.1 ppb to 10 ppm) of at least one element selected from the group consisting of Co, Ni, Ru, and Re.  
     
     
         24 . The hydrocarbon composition of  claim 23  having a composition wherein each C5-C20 component is present within ±1% of the value shown in  FIG. 5  (15 μm coating).  
     
     
         25 . The hydrocarbon composition of  claim 16  having a composition wherein each C5-C20 component is present within ±0.5% of the value shown in  FIG. 5  (15 μm coating).