Method for the production of very low sulfur diesel

Abstract

A process for the deep desulfurization of diesel range feedstock to produce low sulfur diesel fuels by contacting a sulfur containing diesel range feedstock with a cobalt molybdenum (CoMo) catalyst followed by a nickel containing catalyst, such as nickel molybdenum (NiMo), nickel tungsten (NiW), nickel tungsten molybdenum (NiWMo) and nickel cobalt molybdenum (NiCoMo), under a combination of elevated temperature and superatmospheric hydrogen pressure to convert the sulfur in the sulfur-containing feedstock to inorganic sulfur compounds and produce a desulfurized product having a sulfur content below SO ppm by weight. The process can include a dual catalyst system, wherein the sulfur containing diesel range feedstock is desulfurized with a cobalt molybdenum (CoMo) catalyst and then the sulfur compounds can optionally be stripped from the stream prior to contacting with the nickel containing catalyst. The preferred desulfurized product contains less than 11 wt. % polycyclicaromatics and has an increased cetane number.

1 . A process for the desulfurization of diesel boiling range feedstocks to produce low sulfur, low polynuclear diesel fuels comprising: 
 contacting a sulfur-containing diesel boiling range feedstock with a refractory supported cobalt molybdenum containing catalyst, then stripping said feedstock, followed by a second stage containing a refractory supported nickel cobalt molybdenum catalyst under a combination of elevated temperature and superatmospheric hydrogen pressure, to convert said sulfur in said sulfur-containing feedstock to inorganic sulfur compounds and produce a desulfurized product having a sulfur content below 50 ppm by weight,    wherein 
 (i) the first stage's temperature ranges from about 150° C. to about 455° C. and the first stage's pressure ranges from about 50 to 1500 psig, and  
 (ii) the second stage's temperature ranges from about 220° C. to about 454° C. and the second stage's pressure ranges from about 50 psig to about 1500 psig.  
   
     
     
         2 . The process of  claim 1 , wherein said process is carried out in one reactor vessel.  
     
     
         3 . The process of  claim 1 , wherein said diesel boiling range feedstock has a first cetane number and said desulfurized product has a second cetane number, and wherein said second cetane number is greater than said first cetane number.  
     
     
         4 . The process of  claim 1 , wherein said desulfurized product contains less than 11 wt. % polyaromatics.  
     
     
         5 . The process of  claim 1 , wherein said diesel range feedstock contains less than 0.05 wt. % sulfur.  
     
     
         6 . The process of  claim 3 , wherein said diesel range feedstock has a polycyclicaromatics content of less than 11 wt. %.  
     
     
         7 . The process of  claim 5 , wherein said desulfurized product contains less than 11 wt. % polycyclicaromatics.