Process for adsorption of sulfur compounds from hydrocarbon streams

Abstract

The present invention provides a high capacity adsorbent for removing sulfur from hydrocarbon streams. The adsorbent comprises a composite material containing particles of a nickel phosphide complex Ni x P. The adsorbent is utilized in a sulfur removal process that does not require added hydrogen, and run at relatively low temperatures ranging from about 150° C. to about 400° C. The process of this invention enables “ultra-deep” desulfurization down to levels of about 1 ppm and less.

1 . An adsorbent composite for removing sulfur from a hydrocarbon stream comprising: 
 i. a high surface area support comprising silica, alumina, carbon, or a combination thereof,    ii. nickel phosphide particles disposed on the support, said particles comprising Ni 2 P, Ni 12 P 5 , Ni 3 P, or mixtures thereof.    
     
     
         2 . The adsorbent of  claim 1  wherein said particles range in size from about 2 nm to about 30 nm.  
     
     
         3 . The adsorbent of clam  1  wherein said particles comprise from about 15 wt % to about 80 wt % of the adsorbent.  
     
     
         4 . The adsorbent of  claim 3  wherein said particles comprise from about 20 wt % to about 60 wt % of the adsorbent.  
     
     
         5 . The adsorbent of  claim 2  wherein said particles range in size from about 2 nm to about 30 nm.  
     
     
         6 . The adsorbent of  claim 1  wherein said support comprises silica, mesoporous silica, silica-alumina, carbon, or a mixture thereof.  
     
     
         7 . The adsorbent of  claim 6  wherein said support is further characterized as having a surface area ranging from about 200 m 2 /g to about 800 m 2 /g.  
     
     
         8 . The adsorbent of  claim 7  wherein said surface is further characterized as having pores having average pore diameters ranging from about 5 nm to about 50 nm.  
     
     
         9 . The adsorbent of  claim 3  wherein said particles comprise greater than about 45 wt % of the adsorbent.  
     
     
         10 . A process for making an adsorbent for removing sulfur from a hydrocarbon stream, said process comprising: 
 (a) providing a support comprising silica, alumina, or a combination thereof,    (b) depositing Ni x P y O z  complexes on the support,    (c) reducing the Ni x P y O z  complexes to form Ni x P nanoparticles on the support comprising Ni 2 P, Ni 12 P 5 , Ni 3 P, or a combination thereof.    
     
     
         11 . The method of  claim 10  wherein the support comprises mesoporous silica, alumina, or a combination thereof.  
     
     
         12 . The method of  claim 11  wherein the mesoporous support has a surface area of about 200 m 2 /g to about 800 m 2 /g and an average pore size ranging from about 5 nm n to about 50 nm.  
     
     
         13 . The method of claims  10  or  12  wherein the nickel phosphide particle is prepared by reduction of nickel phosphate, or a combination of nickel oxide, and ammonium phosphate.  
     
     
         14 . The method of  claim 10  or  12  wherein NiP x  content of the adsorbent is increased by extraction of silica from the composite.  
     
     
         15 . The method of  claim 14  wherein said silica extraction comprises contacting the composite with sodium hydroxide, or hydrofluoric acid.  
     
     
         16 . The method of claims  10  or  12  wherein the nickel phosphate Ni x P y O z  complex is deposited on support by deposition-precipitation method in presence of urea from aqueous solution of nickel salt and ammonium phosphate stabilized with acid (preferably nitric acid)_at pH of 0.2-3, preferably 0.8-1.2.  
     
     
         17 . A method for removing sulfur from a hydrocarbon stream comprising contacting said stream with a composite adsorbent comprising a nickel phosphide complex having particles of Ni 2 P, Ni 12 P 5 , Ni 3 P phase, or a mixture thereof deposited on a silica, mesoporous silica, silica-alumina, or carbon support.  
     
     
         18 . The method of  claim 17  wherein the particles range in size from about 2 nm to about 30 nm.  
     
     
         19 . The method of  claim 17  wherein said particles comprise between about 15 wt % to about 80 wt % of the adsorbent.  
     
     
         20 . The method of  claim 16  wherein the adsorbent, after contacting the hydrocarbon stream, is regenerated by exposing the adsorbent to hydrogen at temperatures 450-580° C. and time of 3-6 hours sufficient to reduce adsorbed sulfur species.  
     
     
         21 . The method of  claim 16  wherein sulfur is reduced from about 20 ppm to less than about 1 ppm.  
     
     
         22 . The method of  claim 16  wherein said sulfur removal is accomplished without added hydrogen.  
     
     
         23 . The method of  claim 17  wherein said sulfur atom is removed from a variety of organo-sulfur compounds (including but not limited to mercaptans, sulfides, disulfides, thiophenes, benzothiphenes (BT), dibenzothiophenes (DBT) and other substituted DBTs) typically present in hydrocarbon fuel mixtures.  
     
     
         24 . The method of  claim 17  wherein the sorbent maintains its capacity over a range of flowrates from 0.5/hr to 30/hr, preferably from 1-20/hr and most preferably from 3-15/hr.  
     
     
         25 . The method of  claim 17  wherein the sorbent maintains robust reactivity over a wide temperature range from 150-400° C., preferably from 200-375° C. and most preferably from 275 to 350° C.  
     
     
         26 . The method of  claim 17  wherein the desulfurization process does not significantly change any bulk properties of the unadditized diesel fuel.