Selective staging hydrocracking

Abstract

This invention is directed to a high conversion hydrocracking (HCR) unit to produce premium middle distillate fuel. Unconverted oil which is low in sulfur is fed to a Fluid Catalytic Cracking (FCC) unit. The process results in reduced hydrogen consumption and optimum reactor capacity. Feed is hydrotreated and separated into liquid and vapor streams. The vapor stream is passed to further processing and light ends recovery. The liquid stream is passed to a vacuum distillation column, where it is separated into at least three streams, the first stream comprising low boiling products and light ends, a second, higher boiling stream comprising the feed to a second hydroprocessing zone and third stream comprising unconverted oil. The second stream is passed to the second hydroprocessing zone, producing effluents which boil in the distillate range. The second hydroprocessing zone is generally a fuels hydrocracking unit.

1 . A method for hydroprocessing a hydrocarbon feedstock, which provides maximum flexibility in terms of feed quality variations and desired overall conversion to distillate products at minimum investment cost, said method employing multiple hydroprocessing zones within a single reaction loop, each zone having one or more catalyst beds, comprising the following steps:
 (a) passing a hydrocarbonaceous feedstock to a first hydroprocessing zone having one or more beds containing hydroprocessing catalyst, the hydroprocessing zone being maintained at hydroprocessing conditions, wherein the feedstock is contacted with catalyst and hydrogen;   (b) passing the effluent of step (a) directly to a separator, wherein the effluent is separated to produce a vapor stream comprising hydrogen, hydrogen sulfide, ammonia, and hydrocarbonaceous compounds boiling at a temperature below the boiling range of a diesel stream, and a liquid stream comprising hydrocarbonaceous compounds boiling at a temperature above the range of a diesel stream;   (c) passing the vapor stream of step (b) to further processing and light ends recovery, and passing the liquid stream of step (b) to a vacuum distillation column, where it is separated into at least three streams, the first stream comprising low boiling products and light ends, a second, higher boiling stream comprising the feed to a second hydroprocessing zone and third stream comprising unconverted oil;   (d) passing the second stream of step (c) to the second hydroprocessing zone, producing effluents which boil in the distillate range.   
   
   
       2 . The process of  claim 1 , wherein the second hydroprocessing zone of step (d) is a fuels hydrocracker. 
   
   
       3 . The process of  claim 1 , wherein production of specific products may be optimized in the distillation column by recycle between trays. 
   
   
       4 . The process of  claim 1 , wherein at least a portion of the stripped unconverted oil of step (c) is passed to a fluid catalytic cracking unit as feed. 
   
   
       5 . The process of  claim 1 , wherein the second hydroprocessing zone contains at least one bed of hydroprocessing catalyst suitable for aromatic saturation and ring opening. 
   
   
       6 . The process of  claim 1 , wherein the second stream is contacted under hydroprocessing conditions with the hydroprocessing catalyst, in the presence of hydrogen to produce middle distillate products. 
   
   
       7 . The process of  claim 1 , wherein the hydroprocessing conditions of step (a) comprise a reaction temperature of from 400° F.-950° F. (204° C.-510° C.), a reaction pressure in the range from 500 to 5000 psig (3.5-34.5 MPa), an LHSV in the range from 0.1 to 15 hr-1 (v/v), and hydrogen consumption in the range from 500 to 2500 scf per barrel of liquid hydrocarbon feed (89.1-445 m 3  H 2 /m 3  feed). 
   
   
       8 . The process of  claim 7 , wherein the hydroprocessing conditions of step 1(a) comprise a temperature in the range from 650° F.-850° F. (343° C.-454° C.), reaction pressure in the range from 1500-3500 psig (10.4-24.2 MPa), LHSV in the range from 0.25 to 2.5 hr-1, and hydrogen consumption in the range from 500 to 2500 scf per barrel of liquid hydrocarbon feed (89.1-445 m 3  H 2 /m 3  feed). 
   
   
       9 . The process of  claim 1 , wherein the hydroprocessing conditions of step 1(c) comprise a reaction temperature of from 400° F.-950° F. (204° C.-510° C.), a reaction pressure in the range from 500 to 5000 psig (3.5-34.5 MPa), an LHSV in the range from 0.1 to 15 hr-1 (v/v), and hydrogen consumption in the range from 500 to 2500 scf per barrel of liquid hydrocarbon feed (89.1-445 m 3  H 2 /m 3  feed). 
   
   
       10 . The process of  claim 1 , wherein the feed to step 1(a) comprises hydrocarbons boiling in the range from 500° F. to 1500° F. 
   
   
       11 . The process of  claim 1 , wherein the feed is selected from the group consisting of vacuum gas oil, heavy atmospheric gas oil, delayed coker gas oil, visbreaker gas oil, FCC light cycle oil, and deasphalted oil. 
   
   
       12 . The process of  claim 1 , wherein the hydroprocessing catalyst comprises both a cracking component and a hydrogenation component, wherein the cracking component may be amorphous or zeolitic. 
   
   
       13 . The process of  claim 12 , wherein the hydrogenation component is selected from the group consisting of Ni, Mo, W, Pt and Pd or combinations thereof. 
   
   
       14 . The process of  claim 12 , wherein the zeolitic component is selected from the group consisting of Y, USY, REX, and REY zeolites. 
   
   
       15 . The process of  claim 1 , wherein the hydrotreating occurs in the first reaction zone and hydrocracking occurs in the second reaction zone.