Desulfurization of naphtha blends

Abstract

A process for desulfurizing a delayed coker naphtha in a catalytic naphtha desulfurization process in which the feed comprising the delayed coker naphtha is passed over a silicon trap comprising a high surface area inert alumina of low metals content prior to being hydrodesulfurized in an olefin-retentive, catalytic naphtha hydrodesulfurization process. Unpromoted (no intentional metals content), inert alumina is preferred for the silicon trap since it will not affect the olefin-retentive qualities of the hydrodesulfurization catalyst and for maximal silicon capture, a high surface area alumina is employed.

1 . A process for desulfurizing a delayed coker naphtha in a catalytic naphtha hydrodesulfurization process which comprises:
 passing a naphtha boiling range feed comprising delayed coker naphtha containing silicon compounds over a silicon trap comprising a high surface area inert alumina of low metals content to trap silicon compounds and form a naphtha boiling range effluent, and   hydrodesulfurizing the naphtha boiling range effluent in an olefin-retentive, catalytic naphtha hydrodesulfurization process.   
     
     
         2 . A process according to  claim 1  in which the naphtha boiling range feed is hydrogenatively treated to remove diolefins. 
     
     
         3 . A process according to  1  in which the naphtha boiling range feed comprises catalytically cracked naphtha and delayed coker naphtha. 
     
     
         4 . A process according to  3  in which the naphtha boiling range feed comprises catalytically cracked naphtha and up to 20% v/v delayed coker naphtha. 
     
     
         5 . A process according to  3  in which the naphtha boiling range feed comprises catalytically cracked naphtha and 5 to 10% v/v delayed coker naphtha. 
     
     
         6 . A process according to  1  in which the silicon trap comprises a particulate inert alumina. 
     
     
         7 . A process according to  1  in which the silicon trap comprises a particulate inert alumina having a base metals content of not more than 1 wt. pct. Group VIII metals and not more than 5 wt. pct. Group VI metals. 
     
     
         8 . A process according to  1  in which the silicon trap comprises a particulate inert alumina having a base metals content of not more than 1 wt. pct. Ni or Co and not more than 5 wt. pct. Mo. 
     
     
         9 . A process according to  1  in which the silicon trap comprises a particulate inert alumina having a surface area of at least 250 m 2 /g. 
     
     
         10 . A process according to  1  in which the silicon trap comprises a particulate inert alumina having a surface area of at least 300 m 2 /g 
     
     
         11 . A process according to  1  in which the silicon trap comprises a particulate inert alumina having a surface area of at least 350 m 2 /g. 
     
     
         12 . A process according to  1  in which the silicon trap comprises a particulate inert alumina having a particle size less than 1.6 mm. 
     
     
         13 . A process according to  1  in which the olefin-retentive hydrodesulfurization is carried out at a temperature of 250-325° C., a total system pressure of 1000-3500 kPag, a hydrogen partial pressure of 600-2500 kPa and 1-10 hr. −1  LHSV. 
     
     
         14 . A process according to  1  in which the olefin-retentive hydrodesulfurization is carried out in contact with a catalyst comprised of about 1 to 10 wt. % Mo0 3 ; and about 0.1 to 5 wt. % CoO; a Co/Mo atomic ratio of about 0.1 to 1.0; a median pore diameter of 6 to 20 nm; a Mo0 3  surface concentration in g Mo0 3 /m2 of 0.5×10 −4  to 3×10 −4 ; and an average particle size diameter of less than about 2.0 mm. 
     
     
         15 . A process according to  14  in which the olefin-retentive hydrodesulfurization is carried out in a two stage process in which the naphtha boiling range feed is contacted with hydrogen over a first hydrotreating catalyst in the vapor phase to remove at least 70 wt. % of the sulfur, to produce a first stage effluent which is cooled to condense the naphtha vapor which is then separated from the H 2 S containing gas and passed with hydrogen into the a second vapor phase stage at a temperature at least 10 C greater than in the first stage and at a space velocity at least 1.5 times greater than in the first stage, to remove at least 80 wt. % of the remaining sulfur from the naphtha and form a desulfurized naphtha vapor. 
     
     
         16 . A process according to  15  in which the effluent of the second stage comprises a naphtha which contains less than 5 wt. % of the amount of sulfur present in the feed but retaining at least 40 vol. % of the olefin content of the feed. 
     
     
         17 . A process according to  15  in which the catalyst in both stages comprises Co and Mo on a support in an amount of less than a total of 12 wt. % calculated as the respective metal oxides CoO and MoO 3  with a Co to Mo atomic ratio from 0.1 to 1.0. 
     
     
         18 . A process according to  15  in which the olefin-retentive hydrodesulfurization is carried out in each stage normally range from 230-400 C, a pressure of from 400-34000 kPag, and a space velocity of from 1-10 v/v/hr-1 and with a space velocity in the second stage greater than that in the first stage. 
     
     
         19 . A process according to  18  in which the percent desulfurization in the second stage is typically at least 90%. 
     
     
         20 . A process according to  1  in which the effluent of the second stage is blended into the gasoline product pool for ethanol blending.