Process for the selective hydrodesulfurization of a gasoline feedstock containing high levels of olefins

Abstract

A process for selective hydrodesulfurization of a sulfur and olefin-containing hydrocarbon feedstock boiling in the naphtha or gasoline boiling range utilizing a particularly defined high activity hydrodesulfurization (HDS) catalyst composition comprising a cobalt component, a molybdenum component and little or no phosphorus, prepared on a special alumina support containing a low concentration of silica and having a high surface area of at least 280 m 2 /g. In another aspect the process involves separating the feedstock into a light and a heavy fraction, followed by selectively hydrodesulfurizing the heavy fraction using a particularly defined high activity HDS catalyst and hydrodesulfurizing the light fraction with a particularly defined high selectivity HDS catalyst. The process also includes performing the separation into fractions and the selective hydrodesulfurization of the fractions in a distillation column reactor utilizing different particularly defined HDS catalysts.

1 . A process for the selective hydrodesuilfurization of an olefin-containing gasoline feedstock, wherein said process comprises:
 contacting, under suitable hydrodesulfurization conditions, said olefin-containing gasoline feedstock, having a feed sulfur concentration exceeding 0.01 wt % and an olefin concentration, with a high activity catalyst composition comprising a support having a high surface area of at least 280 m 2 /g, a cobalt component in the amount of from 3 to 10 wt %, a molybdenum component in an amount of 12 to 30 wt %, and from 0 to 0.5 wt % of a phosphorous component, with the wt % of each component being based on the total weight of said catalyst composition and being calculated assuming each component is in its elemental form; and wherein said support consists essentially of alumina and from 0.3 to 10 wt % silica based on the total weight of said support; and   yielding a hydrotreated product having a substantially reduced sulfur concentration with no substantial reduction in olefin concentration.   
   
   
       2 . The process of  claim 1 , wherein said cobalt component is present in an amount of from 3 wt % to 8 wt %, said molybdenum component is present in an amount of from 12 wt % to 20 wt %, and said phosphorus component is present in the amount of from 0 to 0.1 wt %, with the wt % of each component being based on the total weight of said catalyst composition and being calculated assuming each component is in its elemental form. 
   
   
       3 . The process of  claim 2 , wherein said support has a surface area of from 280 to 360 m 2 /g and contains from 0.5 wt % to 6 wt % silica based on the total weight of said support. 
   
   
       4 . The process of  claim 3 , wherein said cobalt component is present in an amount of 3.4 wt % to 5 wt % and said molybdenum component is present in an amount of 14 wt % to 16 wt %, with the wt % of each component being based on the total weight of said catalyst composition and being calculated assuming each component is in its elemental form. 
   
   
       5 . The process of  claim 4 , wherein said support has a surface area of 300 to 340 m 2 /g and contains from 1.5 to 2.5 wt % silica based on the total weight of said support. 
   
   
       6 . The process of  claim 5 , wherein the sulfur concentration in the hydrotreated product is less than 30 ppmw. 
   
   
       7 . A selective hydrodesulfurization process, comprising:
 separating an olefin-containing gasoline feedstock having a feed sulfur concentration exceeding 0.01 wt % and a feed olefin concentration into a light fraction and a heavy fraction;   contacting, under suitable heavy fraction hydrodesulfurization conditions, said heavy fraction with a high activity catalyst composition comprising a support having a high surface area of at least 280 m 2 /g, a cobalt component in the amount of from 3 to 10 wt %, a molybdenum component in an amount of 12 to 30 wt %, and from 0 to 0.5 wt % of a phosphorous component, with the wt % of each component being based on the total weight of said catalyst composition and being calculated assuming each component is in its elemental form;   contacting, under suitable light fraction hydrodesulfurization conditions, said light fraction with a high selectivity catalyst composition having a low surface area of less than 125 m 2 /g and high mean pore diameter of greater than 200 Å, wherein said high selectivity catalyst composition comprises a cobalt component, a molybdenum component, a phosphorous component and a support consisting essentially of alumina; and   yielding a light hydrotreated product having a light hydrotreated product sulfur concentration below said feed sulfur concentration, and a heavy hydrotreated product having a heavy hydrotreated product sulfur concentration below said feed sulfur concentration with no substantial reduction in olefin concentration.   
   
   
       8 . The process of  claim 7 , wherein said cobalt component is present in said high activity catalyst composition in an amount of from 3 wt % to 8 wt %, said molybdenum component is present in said high activity catalyst composition in an amount of from 12 wt % to 20 wt %, and said phosphorus component is present in said high activity catalyst composition in the amount of from 0 up to 0.1 wt %, with the wt % of each component being based on the total weight of said catalyst composition and being calculated assuming each component is in its elemental form. 
   
   
       9 . The process of  claim 8 , wherein said cobalt component is present in said high activity catalyst composition in an amount of 3.4 wt % to 5 wt % and said molybdenum component is present in an amount of 14 wt % to 16 wt %, with the wt % of each component being based on the total weight of said high activity catalyst composition and being calculated assuming each component is in its elemental form. 
   
   
       10 . The process of  claim 9 , wherein the support employed in said high activity catalyst composition used to treat the heavy fraction consists essentially of gamma alumina and contains from 0.5 wt % to 6 wt % silica. 
   
   
       11 . The process of  claim 10 , wherein the alumina support employed in said high selectivity catalyst composition used to treat said light fraction consists predominantly of theta alumina and delta alumina. 
   
   
       12 . The process of  claim 11 , wherein both the light hydrotreated product and the heavy hydrotreated product have a sulfur concentration below 30 ppmw. 
   
   
       13 . A process, comprising:
 providing a distillation column reactor, wherein said distillation column reactor includes a lower distillation reaction zone containing a lower catalytic distillation structure formed with a high activity catalyst composition comprising a support having a high surface area greater than 280 m 2 /g, a cobalt component in the amount of from 3 to 10 wt %, a molybdenum component in an amount of 12 to 30 wt % , and from 0 to 0.5 wt % of a phosphorous component, with the wt % of each component being based on the total weight of said catalyst composition and being calculated assuming each component is in its elemental form, wherein said support consists essentially of alumina and from 0.3 to 10 wt % silica based on the total weight of said support;   and wherein said distillation column reactor includes an upper distillation reaction zone containing an upper catalytic distillation structure formed with high selectivity catalyst composition comprising a cobalt component, a molybdenum component and a phosphorus component on an alumina support, said high selectivity catalyst composition being characterized by having a low surface area of less than 125 m 2 /g and high mean pore diameter of greater than 200 Å, and wherein said upper distillation reaction zone is in a juxtaposed vertical relationship above said lower distillation reaction zone;   utilizing said distillation column reactor to separate an olefin-containing gasoline feedstock having a feed sulfur concentration exceeding 0.01 wt % and a feed olefin concentration into a light fraction and a heavy fraction and contacting said light fraction with at least a portion of said upper catalytic distillation structure and contacting said heavy fraction with at least a portion of said lower catalytic distillation structure; and   yielding as an overhead from said distillation column reactor a light hydrotreated product having a light hydrotreated product sulfur concentration below said feed sulfur concentration, and as a bottoms from said distillation column reactor a heavy hydrotreated product having a heavy hydrotreated product sulfur concentration below said feed sulfur concentration, with no substantial reduction in olefin concentration in either the light hydrotreated product or the heavy hydrotreated product.   
   
   
       14 . The process of  claim 13 , wherein said cobalt component is present in said high activity catalyst composition in an amount of from 3 wt % to 8 wt %, said molybdenum component is present in an amount of from 12 wt % to 20 wt %, and said phosphorus component is present in the amount of from 0 to 0.1 wt %, with the wt % of each component being based on the total weight of said high activity catalyst composition and being calculated assuming each component is in its elemental form. 
   
   
       15 . The process of  claim 14 , wherein said cobalt component is present in said high activity catalyst composition in an amount of 3.4 wt % to 5 wt % and said molybdenum component is present in an amount of 14 wt % to 16 wt %, with the wt % of each component being based on the total weight of said catalyst composition and being calculated assuming each component is in its elemental form. 
   
   
       16 . The process of  claim 15 , wherein said support for said high activity catalyst composition has a surface area of from 280 to 360 m 2 /g and contains from 0.5 wt % to 6 wt % silica based on the total weight of said support. 
   
   
       17 . The process of  claim 16 , wherein said support for said high activity catalyst composition has a surface area of from 300 to 340 m 2 /g and contains from 1.5 to 2.5 wt % silica based on the total weight of the support. 
   
   
       18 . The process of  claim 14 , wherein the alumina portion of the support employed in said high activity catalyst composition consists essentially of gamma alumina; and wherein the alumina support employed in said high selectivity catalyst composition used to treat said light fraction consists predominantly of theta alumina and delta alumina. 
   
   
       19 . The process of  claim 18 , wherein both the light hydrotreated product and the heavy hydrotreated product have a sulfur concentration below 30 ppmw.