Process for conversion of hydrocracked pitch

Abstract

The present disclosure relates to a process for conversion of hydrocracked pitch into distillates in a slurry hydro-conversion reactor in presence of hydrogen gas with recycling of a hydrocracked pitch residue to achieve improved overall conversion and minimize fresh addition of catalyst. The slurry hydro-conversion of hydrocracked vacuum residue along with recycle of hydrocracked pitch residue (4d) provides improved overall conversion of >97% with very less yield of <3 wt. % pitch (>540° C.) along with distillates (C6+−370° C.) in a yield of 55 wt. % and VGO (370-540° C.) in a yield of 28.3 wt. %. The recycling of hydrocracked pitch residue back to slurry hydro-conversion reactor facilitates the minimization of the addition of fresh catalyst to the reactor section.

1 . A process for conversion of hydrocracked pitch, said process comprising:
 a) hydrocracking a virgin vacuum residue feed stream in a hydro-conversion reactor to obtain a hydrocracked effluent stream;   b) fractionating the hydrocracked effluent stream in a fractionator to obtain a hydrocarbon fraction and a hydrocracked vacuum resid fraction as bottom stream;   c) splitting the hydrocracked vacuum resid fraction into a first portion of hydrocracked stream and a second portion of hydrocracked stream;   d) sending the first portion of hydrocracked stream to a Solvent De-asphalting unit which provides a stream of asphaltenic pitch;   e) mixing the second portion of the hydrocracked stream, a virgin vacuum residue and the asphaltenic pitch to obtain a mixed feed stream;   f) processing the mixed stream in presence of hydrogen and a catalyst in a slurry hydro-conversion reactor to obtain an effluent stream;   g) separating the effluent stream in a separation zone, to obtain a vapour effluent and a liquid effluent;   h) fractionating the liquid effluent in a fractionator to obtain lighter hydrocarbon fractions and unconverted hydrocracked pitch residue which contains active metal sulfide catalyst particles along with hydrocarbon fractions;   i) separating the unconverted hydrocracked pitch in a catalyst recovery zone to obtain a purge stream and a hydrocarbon stream containing highly active metal sulfide catalyst particles with recovered hydrocarbons;   j) recycling the hydrocarbon stream to the mixed stream to obtain a hydrocracked pitch residue; and   k) processing the hydrocracked pitch residue in the slurry hydro-conversion reactor.   
     
     
         2 . The process as claimed in  claim 1 , wherein the virgin vacuum residue feed stream is selected from a group consisting of hydrocarbon fractions having boiling points above 540° C., heavy deasphalted oil, extra heavy oils, tar sands bitumen, containing high-metal and impurity streams resulting as bottom streams from hydrocracked atmospheric tower or vacuum tower. 
     
     
         3 . The process as claimed in  claim 1 , wherein the hydro-conversion reactor is selected from a group consisting of a fixed bed reactor, a moving bed hydroconversion unit, and an ebullated bed hydroconversion unit, or combination thereof. 
     
     
         4 . The process as claimed in  claim 3 , wherein the hydro-conversion unit can co-exist with a thermal cracking unit, or a solvent extraction unit. 
     
     
         5 . The process as claimed in  claim 1 , wherein the hydrocarbon fraction comprises a light naphtha fraction, a heavy naphtha fraction, a kerosene fraction, a diesel fraction, a light vacuum gas oil fraction, and a heavy gas oil fraction. 
     
     
         6 . The process as claimed in  claim 1 , wherein the slurry hydro-conversion reactor is selected from a group consisting of a bubble column reactor, a tubular reactor, a fixed bed reactor and a loop reactor. 
     
     
         7 . The process as claimed in  claim 5 , wherein the slurry hydro-conversion reactor comprises of an assembly of multiple reactors. 
     
     
         8 . The process as claimed in  claim 1 , wherein the slurry hydro-conversion reactor is operated at a temperature in the range of 380-500° C., at a hydrogen pressure in the range of 2-20 MPa, and at a liquid hourly space velocity in the range of 0.1-8 hr −1 . 
     
     
         9 . The process as claimed in  claim 7 , wherein the slurry hydro-conversion reactor is operated at a temperature in the range of 420-460° C., at a hydrogen pressure in the range of 10-19 MPa, and at a liquid hourly space velocity in the range of 0.5-6 hr −1 . 
     
     
         10 . The process as claimed in  claim 1 , wherein the catalyst is present in a concentration in the range of 0.01-10 wt. %. 
     
     
         11 . The process as claimed in  claim 1 , wherein the catalyst is selected from a group consisting of a metal based oil soluble catalyst, solid dispersed nano particle supported catalyst, and metal oxide based supports or a combination of thereof. 
     
     
         12 . The process as claimed in  claim 9 , wherein the metal based oil soluble catalyst comprises mono metallic or bimetallic or trimetallic liquid catalyst with metal selected from group consisting of molybdenum, nickel, cobalt, and tungsten or combination thereof. 
     
     
         13 . The process as claimed in  claim 1 , wherein the separation zone comprises of separators, selected from a group of high pressure high temperature (HPHT) separator, high pressure Low temperature (HPLT) separator, Low pressure high temperature (LPHT) separator, and Low pressure low temperature (LPLT) separator for separating liquids with catalyst from the vapors or liquids. 
     
     
         14 . The process as claimed in  claim 1 , wherein the hydrocracked pitch residue ( 4   d ) processed in slurry hydro-conversion reactor has asphaltene content in the range of 1-70 wt. %. 
     
     
         15 . The process as claimed in  claim 13 , wherein the hydrocracked pitch residue processed in slurry hydro-conversion reactor has asphaltene content in the range of 5-30 wt. %. 
     
     
         16 . The process as claimed in  claim 1 , wherein the hydrocracked pitch residue has a Conradson Carbon residue in the range of 1-60 wt. %. 
     
     
         17 . The process as claimed in  claim 15 , wherein the hydrocracked pitch residue has a Conradson Carbon residue in the range of 5-40 wt. %. 
     
     
         18 . The process as claimed in  claim 1 , wherein the catalyst recovery section is selected from a group comprising of a centrifugal separator, a settler for phase separation, a vacuum separator, and a filtration setup.