Co-processing diesel fuel with vegetable oil to generate a low cloud point hybrid diesel biofuel

Abstract

The foregoing describes methods and systems for co-processing vegetable oil and petroleum diesel to yield a hybrid diesel biofuel composition. As previously stated, in some embodiments the present invention is directed to methods/systems by/with which a mixture of vegetable oil and petroleum diesel is co-processed in two stages: the mixture is first hydrotreated to yield a reduced-sulfur hybrid intermediate, and then the hybrid intermediate is processed in an isomerization unit to yield a low cloud point hybrid diesel product that is partially derived from biomass. A notable benefit of at least some such methods/systems is that interstage removal of H 2 S and NH 3 is not required between the stages of hydrotreating and isomerizing, wherein such benefit is afforded by sulfur- and nitrogen-tolerant isomerization catalysts.

1 . A method comprising the steps of:
 a) combining vegetable oil with diesel fuel to form a first mixture, wherein the vegetable oil comprises riot more than 10 weight percent of said first mixture;   b) hydrotreating the first mixture to yield a second mixture, wherein triglyceride components of the first mixture are deoxygenated, and wherein at least 95 atomic percent of the sulfur present in the first mixture is converted to H 2 S in the second mixture;   c) isomerizing the second mixture in the presence of an isomerization catalyst to yield a third mixture comprising hybrid diesel fuel having a cloud point that is lower than that of the second mixture, wherein H 2 S in the second mixture has not been removed prior to isomerizing; and   d) isolating the hybrid diesel fuel of the third mixture to yield a hybrid diesel fuel product.   
     
     
         2 . The method of  claim 1 , wherein the first mixture comprises a nitrogen content greater than 50 ppm. 
     
     
         3 . The method of  claim 1 , wherein the first mixture comprises a nitrogen content of up to about 500 ppm. 
     
     
         4 . The method of  claim 1 , wherein the isomerization catalyst comprises Pt on an SM-7 support. 
     
     
         5 . The method of  claim 1 , wherein the isomerization catalyst comprises Pt on an SAPO-11 support. 
     
     
         6 . The method of  claim 1 , wherein the vegetable oil comprises one or more biologically-derived oils selected from the group consisting of canola, soy, rapeseed, palm, peanut, jatropha, yellow grease, algae, and combinations thereof. 
     
     
         7 . The method of  claim 1 , wherein the step of hydrotreating involves a hydrotreating catalyst comprising a metal or metal-alloy active hydrotreating catalyst component selected from the group consisting of cobalt-molybdenum (Co—Mo) catalyst, nickel-molybdenum (Ni—Mo) catalyst, noble metal catalyst, and combinations thereof. 
     
     
         8 . The method of  claim 7 , wherein the hydrotreating catalyst comprises a refractory oxide support. 
     
     
         9 . The method of  claim 7 , wherein the hydrotreating catalyst comprises a support component selected from the group consisting of Al 2 O 3  and SiO 2 —Al 2 O 3 . 
     
     
         10 . The method of  claim 1 , wherein the hydrotreating utilizes an alumina-supported nickel-molybdenum catalyst. 
     
     
         11 . The method of  claim 1 , wherein the hydrotreating is carried out at a temperature between 550° F. and 800° F. 
     
     
         12 . The method of  claim 1 , wherein the hydrotreating is carried out under a H 2  partial pressure of between 400 psig and 2000 psig. 
     
     
         13 . The method of  claim 1 , wherein the hydrotreating is carried out under a H 2  partial pressure of between 500 psig and 1500 psig. 
     
     
         14 . The method of  claim 1 , wherein the second mixture has, exclusive of H 2 S, a sulfur content of not more than 20 ppm. 
     
     
         15 . The method of  claim 1 , wherein the second mixture has cloud point of −8° C. or less. 
     
     
         16 . The method of  claim 1 , wherein the hybrid diesel fuel has, exclusive of H 2 S, a sulfur content of not more than 10 ppm. 
     
     
         17 . The method of  claim 1 , wherein the hybrid diesel fuel has a cloud point of −10° C. or less. 
     
     
         18 . The method of  claim 1 , wherein isolation of the hybrid diesel fuel is at least partly achieved by stripping the third mixture of H 2 S. 
     
     
         19 . A system for generating a hybrid diesel fuel product, said system comprising:
 a) a mixing unit for combining vegetable oil with diesel fuel so as to form a first mixture, wherein the vegetable oil comprises not more than 10 weight percent of said first mixture;   b) a hydrotreating unit for hydrotreating the first mixture to yield a second mixture, wherein said unit is operable for deoxygenating triglyceride components of the first mixture, and wherein at least 95 atomic percent of the sulfur present in the first mixture is converted to H 2 S in the second mixture; and   c) an isomerization unit for isomerizing the second mixture in the presence of an isomerization catalyst to yield a third mixture comprising hybrid diesel fuel having a cloud point that is lower than that of the second mixture, wherein H 2 S in the second mixture has not been removed prior to isomerizing.   
     
     
         20 . The system of  claim 19  further comprising an isolation unit for isolating the hybrid diesel fuel in the third mixture so as to yield a hybrid diesel fuel product. 
     
     
         21 . The system of  claim 20 , wherein the isomerization catalyst comprises Pt on an SM-7 support. 
     
     
         22 . The system of  claim 20 , wherein the isolation unit comprises an H 2 S stripping unit.