Process for the conversion of heavy charges such as heavy crude oils and distillation residues

Abstract

Process for the conversion of heavy charges such as heavy crude oils, tars from oil sands and distillation residues, by the combined use of the following three process units: hydroconversion with catalysts in slurry phase (HT), distillation or flash (D), deasphalting (SDA), characterized in that the three units operate on mixed streams consisting of fresh charge and recycled streams, by the use of the following steps: sending at least one fraction of the heavy charge to a deasphalting section (SDA) in the presence of hydrocarbon solvents obtaining two streams, one consisting of deasphalted oil (DAO), the other of asphalts; mixing the asphalt with a suitable hydrogenation catalyst and optionally with the remaining fraction of heavy charge not sent to the deasphalting section and sending the mixture obtained to a hydro-treatment reactor (HT) into which hydrogen or a mixture of hydrogen and H 2 S is charged; sending the stream containing the hydro-treatment reaction product and the catalyst in dispersed phase to one or more distillation or flash steps (D) whereby the most volatile fractions are separated, among which the gases produced in the hydro-treatment reaction; recycling at least 60% by weight, preferably at least 80%, more preferably at least 95%, of the distillation residue (tar) or liquid leaving the flash unit, containing the catalyst in dispersed phase, rich in metallic sulfides produced by demetallation of the charge and possibly coke, to the deasphalting zone.

1 . A process for the conversion of heavy charges selected from heavy crude oils, distillation residues, “heavy oils coming from catalytic treatment, “thermal tars”, tars from oil sands, various kinds of coals and other high-boiling charges of a hydrocarbon origin known as “black oils”, by the combined use of the following three process units: hydroconversion with catalysts in slurry phase (HT), distillation or flash (D), deasphalting (SDA), characterized in that the three units operate on mixed streams consisting of fresh charge and recycled streams, with the use of the following steps: 
 sending at least one fraction of the heavy charge to a deasphalting section (SDA) in the presence of hydrocarbon solvents obtaining two streams, one consisting of deasphalted oil (DAO), the other of asphalts;    mixing the asphalt with a suitable hydrogenation catalyst with the remaining fraction of heavy charge not sent to the deasphalting section and sending the mixture obtained to a hydro-treatment reactor (HT) into which hydrogen or a mixture of hydrogen and H 2 S is charged;    sending the stream containing the hydro-treatment reaction product and the catalyst in dispersed phase to one or more distillation or flash steps (D) whereby the most volatile fractions are separated, among which the gases produced in the hydro-treatment reaction;    recycling at least 60% by weight of the distillation residue (tar) or liquid leaving the flash unit, containing the catalyst in dispersed phase, rich in metallic sulfides produced by demetallation of the charge and possibly coke, to the deasphalting zone.    
   
   
       2 . The process according to  claim 1 , wherein at least 80% by weight of the distillation residue or liquid leaving the flash unit is recycled to the deasphalting zone.  
   
   
       3 . The process according to  claim 2 , wherein at least 95% by weight of the distillation residue or liquid leaving the flash unit is recycled to the deasphalting zone.  
   
   
       4 . The process according to  claim 1 , wherein at least part of the remaining part of distillation residue (tar) or liquid leaving the flash unit, not recycled to the deasphalting zone, is recycled to the hydro-treatment section.  
   
   
       5 . The process according to  claim 1 , wherein the recycling ratio between the streams containing asphaltenes, or fresh charge, tar and asphalts, must be such that:  
       (ν mix   /RT )(δ asph −δ mix ) 2   <k    wherein:    δ asph  is the highest value among the solubility parameters of the two C 7  asphaltenes of the mixture (highest value)    ν mix  is the molar average of the molar volumes of the maltene components    δ mix  is the volumetric average of the solubility parameters of the maltene components    k is a constant whose value ranges from 0.2 to 0.5;    R is the gas constant with a value of 1.987 cal/mol K; and    T is the temperature with units of K.    
   
   
       6 . The process according to  claim 1 , wherein the distillation step is carried out at a reduced pressure ranging from 0.001 to 0.5 MPa.  
   
   
       7 . The process according to  claim 6 , wherein the distillation step is carried out at a reduced pressure ranging from 0.05 to 0.3 MPa.  
   
   
       8 . The process according to  claim 1 , wherein the hydro-treatment step is carried out at a temperature ranging from 370 to 450° C. and a pressure ranging from 30 to 300 Atm.  
   
   
       9 . The process according to  claim 8 , wherein the hydro-treatment step is carried out at a temperature ranging from 380 to 440° C. and a pressure ranging from 100 to 200 Atm.  
   
   
       10 . The process according to  claim 1 , wherein the deasphalting step is carried out at temperatures ranging from 40 to 200° C. and a pressure ranging from 1 to 70 Atm.  
   
   
       11 . The process according to  claim 1 , wherein the deasphalting solvent is a light paraffin with from 3 to 6 carbon atoms.  
   
   
       12 . The process according to  claim 1 , wherein the deasphalting step is carried out by means of extraction with a solvent operating in supercritical phase.  
   
   
       13 . The process according to  claim 1 , wherein the stream consisting of deasphalted oil (DAO) is fractionated by conventional distillation.  
   
   
       14 . The process according to  claim 1 , wherein the stream consisting of deasphalted oil (DAO) is mixed with the products separated in the flash step after being condensed.  
   
   
       15 . The process according to  claim 1 , wherein the hydrogenation catalyst is an easily decomposable precursor or a preformed compound based on one or more transition metals.  
   
   
       16 . The process according to  claim 15 , wherein the transition metal is molybdenum.  
   
   
       17 . The process according to  claim 1 , wherein the concentration of catalyst in the hydroconversion reactor, defined on the basis of the concentration of the metal or metals present, ranges from 350 to 10000 ppm.  
   
   
       18 . The process according to  claim 17 , wherein the concentration of catalyst in the hydroconversion reactor ranges from 1000 to 8000 ppm.  
   
   
       19 . The process according to  claim 18 , wherein the concentration of catalyst in the hydroconversion reactor ranges from 1500 to 5000 ppm.