Process for removing sulfur compounds from vacuum gas oil

Abstract

A process for removing a sulfur compound from a low nitrogen content vacuum gas oil feed includes contacting the low nitrogen content vacuum gas oil feed comprising the sulfur compound with a VGO-immiscible phosphonium ionic liquid to produce a vacuum gas oil and VGO-immiscible phosphonium ionic liquid mixture, and separating the mixture to produce a vacuum gas oil effluent having a reduced sulfur compound content relative to the vacuum gas oil feed. It was found that the amount of the sulfur compound being removed was significantly improved by treating a low nitrogen content vacuum gas oil. The low nitrogen content and especially a low level of polar nitrogen compounds increases the amount of sulfur compounds that can be removed.

1 . A process for removing sulfur compounds from a low nitrogen content vacuum gas oil comprising:
 (a) contacting the low nitrogen content vacuum gas oil comprising sulfur compounds with a vacuum gas liquid-immiscible phosphonium ionic liquid to produce a mixture comprising the vacuum gas oil and the vacuum gas liquid-immiscible phosphonium ionic liquid to remove said sulfur compounds wherein said low nitrogen content vacuum gas oil contains less than 500 ppm-wt total nitrogen; and   (b) separating the mixture to produce a vacuum gas oil effluent and a vacuum gas oil-immiscible phosphonium ionic liquid effluent, the vacuum gas oil-immiscible phosphonium ionic liquid effluent comprising the sulfur compounds.   
     
     
         2 . The process of  claim 1  wherein the vacuum gas oil-immiscible phosphonium ionic liquid comprises at least one ionic liquid from at least one of tetraalkylphosphonium dialkylphosphates, tetraalkylphosphonium dialkyl phosphinates, tetraalkylphosphonium phosphates, tetraalkylphosphonium tosylates, tetraalkylphosphonium sulfates, tetraalkylphosphonium sulfonates, tetraalkylphosphonium carbonates, tetraalkylphosphonium metalates, oxometalates, tetraalkylphosphonium mixed metalates, tetraalkylphosphonium polyoxometalates, and tetraalkylphosphonium halides. 
     
     
         3 . The process of  claim 1  wherein the vacuum gas oil-immiscible phosphonium ionic liquid comprises at least one of trihexyl(tetradecyl)phosphonium chloride, trihexyl(tetradecyl)phosphonium bromide, tributyl(methyl)phosphonium bromide, tributyl(methyl)phosphonium chloride, tributyl(hexyl)phosphonium bromide, tributyl(hexyl)phosphonium chloride, tributyl(octyl)phosphonium bromide, tributyl(octyl)phosphonium chloride, tributyl(decyl)phosphonium bromide, tributyl(decyl)phosphonium chloride, tetrabutylphosphonium bromide, tetrabutylphosphonium chloride, triisobutyl(methyl)phosphonium tosylate, tributyl(methyl)phosphonium methylsulfate, tributyl(ethyl)phosphonium diethylphosphate, and tetrabutylphosphonium methanesulfonate. 
     
     
         4 . The process of  claim 1  wherein said vacuum gas oil undergoes additional steps of contact with said vacuum gas oil-immiscible phosphonium ionic liquid until said vacuum gas oil reaches a predetermined level of sulfur compound reduction. 
     
     
         5 . The process of  claim 4  wherein said predetermined reduction of sulfur compounds is at least 15 wt % 
     
     
         6 . The process of  claim 4  wherein said predetermined reduction of sulfur compounds is at least 25 wt % 
     
     
         7 . The process of  claim 1  further comprising passing at least a portion of the vacuum gas oil effluent to a hydrocarbon conversion process. 
     
     
         8 . The process of  claim 1  wherein said low nitrogen content vacuum gas oil comprises less than 300 ppm-wt nitrogen. 
     
     
         9 . A process for removing sulfur compounds from a low nitrogen content vacuum gas oil comprising:
 (a) treating a vacuum gas oil to remove nitrogen compounds thereby producing a low nitrogen content vacuum gas oil contains less than 500 ppm-wt total nitrogen;   (b) contacting said low nitrogen content vacuum gas oil comprising sulfur compounds with a vacuum gas oil-immiscible phosphonium ionic liquid to remove said sulfur compounds and to produce a mixture comprising the vacuum gas oil and the vacuum gas oil-immiscible phosphonium ionic liquid; and   (c) separating the mixture to produce a vacuum gas oil effluent and a vacuum gas oil-immiscible phosphonium ionic liquid effluent, the vacuum gas oil-immiscible phosphonium ionic liquid effluent comprising the sulfur compounds.   
     
     
         10 . The process of  claim 9  wherein the vacuum gas oil-immiscible phosphonium ionic liquid comprises at least one ionic liquid selected from the group consisting of tetraalkylphosphonium dialkylphosphates, tetraalkylphosphonium dialkyl phosphinates, tetraalkylphosphonium phosphates, tetraalkylphosphonium tosylates, tetraalkylphosphonium sulfates, tetraalkylphosphonium sulfonates, tetraalkylphosphonium carbonates, tetraalkylphosphonium metalates, oxometalates, tetraalkylphosphonium mixed metalates, tetraalkylphosphonium polyoxometalates, and tetraalkylphosphonium halides. 
     
     
         11 . The process of  claim 9  wherein the vacuum gas oil-immiscible phosphonium ionic liquid comprises at least one phosphonium ionic liquid selected from the group consisting of trihexyl(tetradecyl)phosphonium chloride, trihexyl(tetradecyl)phosphonium bromide, tributyl(methyl)phosphonium bromide, tributyl(methyl)phosphonium chloride, tributyl(hexyl)phosphonium bromide, tributyl(hexyl)phosphonium chloride, tributyl(octyl)phosphonium bromide, tributyl(octyl)phosphonium chloride, tributyl(decyl)phosphonium bromide, tributyl(decyl)phosphonium chloride, tetrabutylphosphonium bromide, tetrabutylphosphonium chloride, triisobutyl(methyl)phosphonium tosylate, tributyl(methyl)phosphonium methylsulfate, tributyl(ethyl)phosphonium diethylphosphate, and tetrabutylphosphonium methanesulfonate. 
     
     
         12 . The process of  claim 9  wherein said treatment to remove nitrogen compounds comprises an ionic liquid treatment step, a hydrotreating step or a combination of an ionic liquid treatment step and a hydrotreating step. 
     
     
         13 . The process of  claim 9  wherein said vacuum gas oil undergoes additional steps of contact with said vacuum gas oil-immiscible phosphonium ionic liquid until said vacuum gas oil reaches a predetermined reduction of sulfur compounds. 
     
     
         14 . The process of  claim 9  wherein said low nitrogen content vacuum gas liquid comprises less than 300 ppm-wt total nitrogen. 
     
     
         15 . The process of  claim 9  further comprising washing, regenerating and then drying said ionic liquid after said sulfur compounds are removed. 
     
     
         16 . A process for removing sulfur compounds from a low nitrogen content vacuum gas oil comprising:
 (a) treating a vacuum gas oil to remove nitrogen compounds thereby producing a low nitrogen content vacuum gas oil comprising less than 500 ppm-wt total nitrogen,   (b) contacting said low nitrogen content vacuum gas oil comprising sulfur compounds with a vacuum gas oil-immiscible phosphonium ionic liquid to produce a mixture comprising the vacuum gas oil and the vacuum gas oil-immiscible phosphonium ionic liquid to remove said sulfur compounds;   (c) separating the mixture to produce a vacuum gas oil effluent and a vacuum gas oil-immiscible phosphonium ionic liquid effluent, the vacuum gas oil-immiscible the vacuum gas oil-immiscible phosphonium ionic liquid effluent comprising the sulfur compounds;   (d) and then washing said vacuum gas oil-immiscible phosphonium ionic liquid, followed by regenerating said vacuum gas oil-immiscible phosphonium ionic liquid and then drying said vacuum gas liquid-immiscible phosphonium ionic liquid.   
     
     
         17 . The process of  claim 16  wherein said treatment to remove nitrogen compounds comprises an ionic liquid treatment step, a hydrotreating step or a combination of an ionic liquid treatment step and a hydrotreating step. 
     
     
         18 . The process of  claim 16  wherein said vacuum gas oil undergoes additional steps of contact with said vacuum gas oil-immiscible phosphonium ionic liquid until said vacuum gas oil reaches a predetermined reduction of sulfur compounds. 
     
     
         19 . The process of  claim 16  wherein said low nitrogen content vacuum gas liquid comprises less than 300 ppm-wt total nitrogen.