Process and apparatus for hydrocracking a residue stream in two stages with aromatic saturation

Abstract

A process and apparatus for two stage hydrocracking of resid feed saturates aromatics including PNA's from the first stage hydrocracking unit to prevent production of HPNA's. The saturated aromatics including PNA's can be hydrocracked in the second stage to minimize or eliminate purged unconverted oil to approach or obtain maximum conversion. In an aspect, a separator and a first hydrocracking reactor may be located in the same vessel.

1 . A process for hydrocracking a hydrocarbon resid stream comprising:
 hydrotreating a resid stream over a demetallization catalyst and a desulfurization catalyst in the presence of hydrogen to provide a hydrotreated resid stream reduced in metals and sulfur concentration;   hydrocracking said hydrotreated resid stream over a first hydrocracking catalyst and hydrogen to provide a first hydrocracked stream;   fractionating said hydrocracked stream at a pressure of at least atmospheric to provide a fractionated stream;   fractionating said fractionated stream at a pressure below atmospheric to provide a recycle oil stream;   hydrotreating said recycle oil stream over a hydrotreating catalyst to provide a second hydrocracking feed stream; and   hydrocracking said second hydrocracking feed stream over a second hydrocracking catalyst in the presence of hydrogen to provide a second hydrocracked stream.   
     
     
         2 . The process of  claim 1  wherein said hydrotreating said recycle oil stream comprises hydrotreating said recycle oil stream over a noble metal catalyst. 
     
     
         3 . The process of  claim 1  wherein said hydrotreating said recycle oil stream comprises hydrotreating said recycle oil stream to saturate at least 40 wt % of aromatics in said recycle oil stream. 
     
     
         4 . The process of  claim 1  further comprising hydrotreating said resid stream includes hydrotreating said resid stream over a denitrogenation catalyst in the presence of hydrogen to provide a hydrotreated resid stream reduced in nitrogen concentration. 
     
     
         5 . The process of  claim 4  wherein a hydrotreating catalyst in said first hydrotreating step is different than a hydrotreating catalyst in said second hydrotreating step. 
     
     
         6 . The process of  claim 1  further comprising separating a gas hydrotreated resid stream from said hydrotreated resid stream before hydrocracking said hydrotreated resid stream. 
     
     
         7 . The process of  claim 6  further comprising separating said gas stream in a cold separator to provide a recycle gas stream. 
     
     
         8 . The process of  claim 7  further comprising separating said hydrocracked stream in a hot separator into a hot vapor stream and a hot liquid stream and separating said hot vapor stream in said cold separator. 
     
     
         9 . The process of  claim 8  further comprising separating said second hydrocracked stream in said hot separator to provide a liquid hydrocracked stream for fractionation. 
     
     
         10 . The process of  claim 1  further comprising separating said first hydrocracked stream and said second hydrocracked stream in said hot separator to provide a liquid hydrocracked stream for fractionation. 
     
     
         11 . A process for hydrocracking a hydrocarbon resid stream comprising:
 hydrotreating a resid stream over a demetallization catalyst, a desulfurization catalyst and a denitrogenation catalyst in the presence of hydrogen to provide a hydrotreated resid stream reduced in metals, sulfur and nitrogen concentration;   hydrocracking said hydrotreated resid stream over a first hydrocracking catalyst and hydrogen to provide a first hydrocracked stream;   fractionating said hydrocracked stream at a pressure of at least atmospheric to provide a fractionated stream;   fractionating said fractionated stream at a pressure below atmospheric to provide a recycle oil stream;   hydrotreating said recycle oil stream over a hydrotreating catalyst to provide a second hydrocracking feed stream; and   hydrocracking said second hydrocracking feed stream over a second hydrocracking catalyst in the presence of hydrogen to provide a second hydrocracked stream.   
     
     
         12 . The process of  claim 11  wherein said hydrotreating said recycle oil stream comprises hydrotreating said recycle oil stream over a noble metal catalyst. 
     
     
         13 . The process of  claim 11  wherein said hydrotreating said recycle oil stream comprises hydrotreating said recycle oil stream to saturate at least 60 wt % of aromatics in said recycle oil stream. 
     
     
         14 . The process of  claim 11  wherein a hydrotreating catalyst in said first hydrotreating step is different than a hydrotreating catalyst in said second hydrotreating step. 
     
     
         15 . The process of  claim 11  further comprising separating a gas hydrotreated resid stream from said hydrotreated resid stream before hydrocracking said hydrotreated resid stream. 
     
     
         16 . The process of  claim 15  further comprising separating said gas stream in a cold separator to provide a recycle gas stream. 
     
     
         17 . An apparatus for hydrocracking a hydrocarbon stream comprising:
 a first hydrotreating unit for demetallizing and desulfurizing a first resid stream;   a first separator in communication with said first hydrotreating reactor;   a first hydrocracking reactor in downstream communication with said first separator;   a first fractionation column in downstream communication with the first hydrocracking reactor;   a second fractionation column in downstream communication with said first fractionation column;   a second hydrotreating reactor in downstream communication with said second fractionation column; and   a second hydrocracking reactor in downstream communication with said second hydrotreating reactor.   
     
     
         18 . The apparatus of  claim 17  wherein said first separator and said first hydrocracking reactor are in the same vessel. 
     
     
         19 . The apparatus of  claim 17  wherein a cold separator is in downstream communication with an overhead line of said separator and an effluent line of said first hydrocracking reactor. 
     
     
         20 . The apparatus of  claim 19  wherein a hot separator is in downstream communication with said first hydrocracking reactor and said second hydrocracking reactor.