Naphtha hydroprocessing with mercaptan removal

Abstract

This invention relates to the hydroprocessing of naphtha with removal of mercaptan from product. Naphtha feedstock is hydrotreated and hydrocracked. Sulfur-containing contaminants, notably C 5 + recombinant mercaptans, are then selectively removed from the hydrocracked naphtha by selective extraction or adsorption.

1 . A process for removing C 5 + mercaptans from a hydrotreated naphtha which comprises: 
 (a) hydrotreating a naphtha feed in at least one hydrotreating step under catalytic hydrotreating conditions to form a hydrotreated naphtha,    (b) conducting at least a portion of the hydrotreated naphtha to a cracking zone and hydrocracking the hydrotreated naphtha with a hydrocracking catalyst under hydrocracking conditions to form a hydrocracked naphtha and C 5 + recombinant mercaptans, and    (c) separating C 5 + recombinant mercaptans from hydrocracked naphtha by selective extraction or adsorption.    
   
   
       2 . The process of  claim 1  wherein the selective extraction comprises contacting the hydrocracked naphtha and C 5 + recombinant mercaptans with a composition comprising water, alkali metal hydroxide, cobalt phthalocyanine sulfonate and alkylphenols.  
   
   
       3 . The process of  claim 2  wherein the composition comprises a first and second phase.  
   
   
       4 . The process of  claim 3  wherein the first phase contains dissolved alkali metal alkylphenylate, dissolved alkali metal hydroxide, dissolved sulfonated cobalt phthalocyanine and water and the second phase contains water and dissolved alkali metal hydroxide.  
   
   
       5 . The process of  claim 2  wherein the contacting is under substantially anaerobic conditions.  
   
   
       6 . The process of  claim 3  wherein the first and second phases are substantially immiscible.  
   
   
       7 . The process of  claim 3  wherein the first phase is separated into an upgraded naphtha and an extractant containing recombinant C 5 + mercaptans.  
   
   
       8 . The process of  claim 7  wherein the extractant is contacted with an oxidizing amount of oxygen and the recombinant mercaptans are oxidized at least in part to disulfides.  
   
   
       9 . The process of  claim 1  wherein the naphtha feed is fractionated into a lower boiling fraction containing mercaptans and a higher boiling fraction containing sulfur heterocyclic compounds prior to hydrotreating.  
   
   
       10 . The process of  claim 1  wherein hydrotreating conditions include temperatures of from 150° C. to 400° C., pressures of from 790 to 20786 kPa, a liquid hourly space velocity of 0.1 to 10, and a hydrogen to feed ratio of from 89 to 1780 m 3 /m 3 .  
   
   
       11 . The process of  claim 1  wherein the adsorption is by chemisorption using metals or metal oxides.  
   
   
       12 . The process of  claim 11  wherein the metals are from Groups 7-12 of the IUPAC periodic table.  
   
   
       13 . The process of  claim 12  wherein the metals include at least one of Ni, Co, Cu, Pt, Zn, Mn, and Cd.  
   
   
       14 . The process of  claim 1  wherein the adsorption is by physical adsorption using molecular sieves.  
   
   
       15 . The process of  claim 14  wherein the molecular sieve is a zeolite.  
   
   
       16 . The process of  claim 1  wherein the adsorption is by physical adsorption using ion-exchange resins.  
   
   
       17 . The process of  claim 2  wherein the selective extraction comprises a single phase.  
   
   
       18 . A process for removing C 5 + mercaptans from a hydrotreated naphtha which comprises: 
 (a) hydrotreating a naphtha feed in at least one hydrotreating step under catalytic hydrotreating conditions to form a hydrotreated naphtha,    (b) conducting at least a portion of the hydrotreated naphtha to a cracking zone and hydrocracking the hydrotreated naphtha with a hydrocracking catalyst under hydrocracking conditions to form a hydrocracked naphtha and C 5 + recombinant mercaptans,    (c) contacting at least a portion of hydrocracked naphtha with a first phase of a treatment composition having at least two phases, said treatment composition containing water, alkali metal hydroxide, cobalt phthalocyanine sulfonate, and alkyl phenols, wherein 
 (i) the first phase contains dissolved alkali metal alkylphenylate, dissolved alkali metal hydroxide, water and dissolved sulfonated cobalt phthalocyanine, and  
 (ii) the second phase contains water and dissolved alkali metal hydroxide, and  
   (d) separating from the first phase an upgraded naphtha having less mercaptans than the hydrocracked naphtha from step (b).