Methods for hydrogen sulfide recycling using selective solvents in the hydroprocessing of renewable feedstocks

Abstract

Methods for hydrogen sulfide recycling using selective solvents in the hydroprocessing of renewable feedstocks are provided. An exemplary method includes the steps of combining hydrogen sulfide with renewable hydrocarbon feedstocks to form a first stream, deoxygenating the first stream to form a second hydrocarbon stream comprising deoxygenated hydrocarbons, water, carbon dioxide, and hydrogen sulfide, and separating the carbon dioxide and the hydrogen sulfide from the second hydrocarbon stream to form a third recycle stream comprising carbon dioxide and hydrogen sulfide. The method further includes the steps of selectively scrubbing the hydrogen sulfide from the third recycle stream to form a fourth recycle stream comprising carbon dioxide and a fifth recycle stream comprising hydrogen sulfide and selectively scrubbing the carbon dioxide from the fourth recycle stream.

What is claimed is: 
     
         1 . A method for hydrogen sulfide recycling using selective solvents in the hydroprocessing of renewable feedstocks comprising the steps of:
 combining hydrogen sulfide with hydrogen-rich recycle gas and renewable hydrocarbon feedstocks to form a first stream;   deoxygenating the first stream to form a second hydrocarbon stream comprising deoxygenated hydrocarbons, water, recycle gas, carbon dioxide, and hydrogen sulfide;   separating the carbon dioxide and the hydrogen sulfide from the second hydrocarbon stream to form a third recycle stream comprising recycle gas, carbon dioxide, and hydrogen sulfide;   selectively scrubbing the hydrogen sulfide from the third recycle stream to form a fourth recycle stream comprising recycle gas and carbon dioxide and a fifth recycle stream comprising hydrogen sulfide; and   selectively scrubbing the carbon dioxide from the fourth recycle stream.   
     
     
         2 . The method of  claim 1 , wherein the hydrogen sulfide comprises a portion of recycled hydrogen sulfide and a portion of make-up hydrogen sulfide. 
     
     
         3 . The method of  claim 1 , wherein the hydrogen-rich recycle gas comprises about 80% by volume of H 2 . 
     
     
         4 . The method of  claim 1 , further comprising passing the first stream to a guard reactor prior to deoxygenating the first stream. 
     
     
         5 . The method of  claim 1 , wherein deoxygenating the first stream is performed using a sulfided catalyst. 
     
     
         6 . The method of  claim 1 , wherein separating the carbon dioxide and the hydrogen sulfide from the second hydrocarbon stream comprises phase separation processes, the third recycle stream comprising a gas phase. 
     
     
         7 . The method of  claim 1 , further comprising isomerizing the deoxygenated hydrocarbons. 
     
     
         8 . The method of  claim 1 , further comprising recycling the fourth recycle stream to form the combined hydrogen-rich recycle gas of the first stream. 
     
     
         9 . The method of  claim 1 , further comprising recycling the fifth recycle stream to form the combined hydrogen sulfide of the first stream. 
     
     
         10 . A method for hydrogen sulfide recycling using selective solvents in the hydroprocessing of renewable feedstocks comprising the steps of:
 combining hydrogen sulfide with hydrogen-rich recycle gas and renewable hydrocarbon feedstocks to form a first stream;   deoxygenating the first stream to form a second hydrocarbon stream comprising deoxygenated hydrocarbons, recycle gas, water, carbon dioxide, and hydrogen sulfide;   separating the carbon dioxide and the hydrogen sulfide from the second hydrocarbon stream to form a third recycle stream comprising recycle gas, carbon dioxide, and hydrogen sulfide;   selectively scrubbing the hydrogen sulfide and the carbon dioxide from the third recycle stream to form a fourth acid gas stream comprising hydrogen sulfide and carbon dioxide and a fifth recycle gas stream comprising recycle gas; and   separating and enriching the fourth acid gas stream to form a sixth recycle stream comprising hydrogen sulfide.   
     
     
         11 . The method of  claim 10 , wherein the hydrogen sulfide comprises a portion of recycled hydrogen sulfide and a portion of make-up hydrogen sulfide. 
     
     
         12 . The method of  claim 10 , wherein the hydrogen-rich recycle gas comprises about 80% by volume of H 2 . 
     
     
         13 . The method of  claim 10 , further comprising passing the first stream to a guard reactor prior to deoxygenating the first stream. 
     
     
         14 . The method of  claim 10 , wherein deoxygenating the first stream is performed using a sulfided catalyst. 
     
     
         15 . The method of  claim 10 , wherein separating the carbon dioxide and the hydrogen sulfide from the second hydrocarbon stream comprises phase separation processes, the third recycle stream comprising a gas phase. 
     
     
         16 . The method of  claim 10 , further comprising isomerizing the deoxygenated hydrocarbons. 
     
     
         17 . The method of  claim 10 , further comprising recycling the fifth recycle stream to form the combined hydrogen-rich recycle gas of the first stream. 
     
     
         18 . The method of  claim 10 , further comprising recycling the sixth recycle stream to form the combined hydrogen sulfide of the first stream. 
     
     
         19 . A system for hydrogen sulfide recycling using selective solvents in the hydroprocessing of renewable feedstocks comprising:
 a deoxygenation reactor that deoxygenates a first stream comprising hydrogen sulfide, hydrogen-rich recycle gas, and renewable hydrocarbon feedstocks to form a second hydrocarbon stream comprising deoxygenated hydrocarbons, water, recycle gas, carbon dioxide, and hydrogen sulfide;   a phase separator that separates the carbon dioxide and the hydrogen sulfide from the second hydrocarbon stream to form a third recycle stream comprising recycle gas, carbon dioxide, and hydrogen sulfide;   a first scrubbing unit that selectively scrubs the hydrogen sulfide from the third recycle stream to form a fourth recycle stream comprising recycle gas and carbon dioxide and a fifth recycle stream comprising hydrogen sulfide; and   a second scrubbing unit that selectively scrubs the carbon dioxide from the fourth recycle stream.   
     
     
         20 . The system of  claim 19 , further comprising an isomerization reactor that isomerizes the deoxygenated hydrocarbons.