Vacuum gas oil conversion process

Abstract

An integrated thermal and catalytic process for improving the yield of middle distillate from heavy petroleum oil feeds comprises cracking the heavy portion (345° C.+) of the feed in a thermal conversion zone, followed by hydrotreating the thermally cracked product and the lighter portion of the feed and then separating the hydrotreated product into a bottoms fraction which is passed to a catalytic cracking step.

1 . A thermal and catalytic process for converting a heavy petroleum oil feed into lower boiling products, comprising:
 separating a heavy hydrocarbon feed to form a light fraction boiling below about 345° C. (650° F.) and a heavy fraction boiling above about 345° C. (650° F.);   thermally cracking the heavy fraction in a thermal conversion zone to produce a thermally cracked product;   combining the light fraction with the thermally cracked heavy fraction;   hydrotreating the combined light and heavy fractions;   separating the hydrotreated product in a fractionator into a hydrotreated bottoms fraction and a hydrotreated light fraction;   catalytically cracking at least a portion of the hydrotreated bottoms fraction; and   fractionating the catalytically cracked product to separate a naphtha fraction, a distillate fraction and a bottoms fraction.   
     
     
         2 . The process according to  claim 1 , wherein the heavy hydrocarbon feed comprises a gas oil feed having a boiling point above 290° C. 
     
     
         3 . The process according to  claim 2 , wherein the gas oil feed comprises a vacuum gas oil in which at least 75 wt % of the gas oil feed boils in the range of 345° to 565° C. (ASTM D 2887). 
     
     
         4 . The process according to  claim 3 , wherein the gas oil feed comprises a vacuum gas oil in which at least 90 wt % of the gas oil feed boils in the range of 345° to 565° C. (ASTM D 2887). 
     
     
         5 . The process according to  claim 2 , wherein the gas oil feed comprises up to 10 wt % of a resid boiling above 565° C. 
     
     
         6 . The process according to  claim 4 , wherein the gas oil feed comprises up to 10 wt % of a resid boiling above 565° C. 
     
     
         7 . The process according to  claim 1 , wherein the C 4 − fraction of the combined hydrotreated light and heavy fractions is by-passed around the hydrotreating step. 
     
     
         8 . The process according to  claim 1 , wherein the severity of the thermal cracking step is from 25 to 450 equivalent seconds at 470° C. 
     
     
         9 . The process according to  claim 4 , wherein the severity of the thermal cracking step is from 25 to 450 equivalent seconds at 470° C. 
     
     
         10 . The process according to  claim 1 , wherein the hydrotreating step includes the following conditions: 6,000 to 10,000 kPag (about 870-1450 psig) hydrogen pressure, liquid hourly space velocity (LHSV) of 0.2-0.8 hr −1  and a temperature of from 355 to 455° C. (670 to 850° F.). 
     
     
         11 . The process according to  claim 10 , wherein the hydrotreating step includes a hydrotreating catalyst containing at least one Group 6 metal and at least one Group 8-10 metal on a metal oxide support. 
     
     
         12 . The process according to  claim 11 , wherein the metal oxide support is selected from silica, alumina, silica-alumina, and titania. 
     
     
         13 . The process according to  claim 1 , wherein the catalytic cracking step includes the following conditions: temperatures from about 482 to about 740° C. (900 to 1364° F.); hydrocarbon partial pressures from about 70 to 300 kPaa (about 15 to about 43 psia); a catalyst to feed (wt/wt) ratio from about 3 to about 1, and a riser reactor residence time from 1 to 5 seconds. 
     
     
         14 . The process according to  claim 13 , wherein the catalytic cracking step includes a cracking catalyst containing an amorphous, porous solid acid matrix selected from alumina, silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia, silica-titania, and silica-alumina-rare earth; and a zeolite. 
     
     
         15 . The process according to  claim 1 , wherein the distillate fraction has a Cetane Number of at least 45. 
     
     
         16 . The process according to  claim 5 , wherein the gas oil feed has a Conradson Carbon Residue (CCR) content greater than 1 wt %. 
     
     
         17 . The process according to  claim 6 , wherein the gas oil feed has a Conradson Carbon Residue (CCR) content greater than 1 wt %. 
     
     
         18 . The process according to  claim 1 , wherein at least a portion of the naphtha fraction is recycled back to the catalytic cracking step. 
     
     
         19 . The process according to  claim 1 , wherein at least a portion of the bottoms fraction is recycled back to the catalytic cracking step. 
     
     
         20 . The process according to  claim 18 , wherein at least a portion of the bottoms fraction is recycled back to the catalytic cracking step.