Heavy oil fluid catalytic cracking process

Abstract

A vacuum gas oil treated with hydrogen, with the hydrogen partial pressure higher than 80 kg/cm 2 G, is catalytically cracked in a fluid catalytic cracking apparatus having a regeneration zone, reaction zone, separation zone, and stripping zone, under conditions that a reaction zone outlet temperature is in the range of 550 to 630° C. and a contact time of hydrocarbons in the reaction zone is in the range of 0.01 to 1.0 sec. According to the fluid catalytic cracking process, a yield of light fraction olefins can be enhanced while a yield of coke can be lessened.

What is claimed is:  
     
         1 . A process for the fluid catalytic cracking of a heavy-fraction oil, which comprises the step of contacting a vacuum gas oil, which has been treated with hydrogen under the hydrogen partial pressure higher than 80 kg/cm 2 G, with a catalyst in a fluid catalytic cracking apparatus having a regeneration zone, a reaction zone, a separation zone and a stripping zone, and under the conditions that the reaction zone outlet temperature is in the range of 550 to 630° C. and the contact time of hydrocarbons in the reaction zone is in the range of 0.01 to 1.0 sec.  
     
     
         2 . The process according to  claim 1  wherein the reaction zone outlet temperature is in a range of 550 to 630° C.  
     
     
         3 . The process according to  claim 1  wherein the contact time of hydrocarbons in the reaction zone is in a range of 0.05 to 0.8 seconds.  
     
     
         4 . The process according to  claim 1  wherein the contact time of hydrocarbons in the reaction zone is in a range of 0.1 to 0.6 seconds.  
     
     
         5 . The process according to  claim 1  wherein the fluid catalytic cracking apparatus is operated at a reaction pressure of 1 to 3 kg/cm 2 G.  
     
     
         6 . The process according to  claim 1  wherein the fluid catalytic cracking apparatus is operated with a catalyst/oil ratio of 8 to 40 wt/wt.  
     
     
         7 . The process according to  claim 1  wherein the fluid catalytic cracking apparatus is operated with a catalyst/oil ratio of 12 to 30 wt/wt.  
     
     
         8 . The process according to  claim 1  wherein the reaction zone is a down flow-type reaction zone.  
     
     
         9 . The process according to  claim 1  wherein the heavy-fraction oil is a vacuum gas oil which has been treated with hydrogen under hydrogen partial pressure higher than 145 kg/cm 2 G.  
     
     
         10 . The process according to  claim 8  wherein the vacuum gas oil has been treated with hydrogen at a reaction temperature of 350 to 430° C., at an LHSV of 0.5 to 4.0 and at a H 2 /Oil of 1,000 to 4,000 scf/bbl.  
     
     
         11 . The process according to  claim 1  wherein the vacuum gas oil has a hydrogen content more than 13 wt %, a nitrogen content less than 0.01 wt %, a sulfur content less than 0.1 wt %, a specific gravity at 15° C. of 0.80 to 0.85 g/cm 3 , an aniline point of 100 to 130° C., a 10 vol % distillation point of 250 to 470° C., a 50 vol % distillation point of 300 to 520° C. and a 90 vol % distillation point of 340 to 560° C.  
     
     
         12 . The process according to  claim 10  wherein the hydrogen content is more than 13.5 wt %, the nitrogen content is less than 0.005 wt %, the 10 vol % distillation point is in the range of 340 to 420° C., the 50 vol % distillation point is in the range of 400 to 500° C., and the 90 vol % distillation point is in the range of 470 to 550° C.