Process for the hydrotreatment of diesel employing a concatenation of catalysts

Abstract

A process for the hydrotreatment of a diesel type hydrocarbon feed containing nitrogen-containing compounds is described, comprising a first step in which the feed is brought into contact with a catalyst in its oxide form, then a second step in which the feed is brought into contact with a dried catalyst comprising at least one organic compound containing oxygen and/or nitrogen.

1 . A process for the hydrotreatment of a hydrocarbon feed containing nitrogen-containing compounds in an amount of more than 150 ppm by weight and having a weighted average temperature in the range 250° C. to 380° C., comprising the following steps:
 a) bringing said hydrocarbon feed into contact, in the presence of hydrogen, with at least one first catalyst comprising an alumina support, phosphorus, and an active phase formed by at least one metal from group VIB in the oxide form and at least one metal from group VIII in the oxide form, said first catalyst being prepared in accordance with a process comprising at least one calcining step; 
 b) bringing the effluent obtained in step a) into contact, in the presence of hydrogen, with at least one second catalyst comprising an alumina support, phosphorus, an active phase formed by at least one metal from group VIB and at least one metal from group VIII, and at least one organic compound containing oxygen and/or nitrogen, said second catalyst being prepared in accordance with a process comprising the following steps: 
 i) bringing at least one component of a metal from group VIB, at least one component of a metal from group VIII, phosphorus and at least one organic compound containing oxygen and/or nitrogen into contact with the support, so as to obtain a catalyst precursor; 
 ii) drying said catalyst precursor obtained from step i) at a temperature of less than 200° C., without subsequent calcining; 
 in order to obtain a hydrotreated effluent. 
 
     
     
         2 . The process according to  claim 1  in which, for the catalyst of step a) or b), the metal from group VIB is molybdenum and the metal from group VIII is selected from cobalt, nickel and a mixture of these two elements. 
     
     
         3 . The process according to  claim 1  in which, for the catalyst of step a) or b), the quantity of metal from group VIB is in the range 5% to 40% by weight of oxide of the metal from group VIB with respect to the total catalyst weight, the quantity of metal from group VIII is in the range 1% to 10% by weight of oxide of the metal from group VIII with respect to the total catalyst weight, and the quantity of phosphorus is in the range 0.1% to 10% by weight of P 2 O 5  with respect to the total catalyst weight. 
     
     
         4 . The process according to  claim 1 , in which the catalyst of step a) or b) further contains at least one dopant selected from boron and fluorine and a mixture of boron and fluorine. 
     
     
         5 . The process according to  claim 1 , in which the organic compound is one or more selected from a carboxylic acid, an alcohol, an aldehyde, an ester, an amine, an aminocarboxylic acid, an aminoalcohol, a nitrile or an amide. 
     
     
         6 . The process according to  claim 5 , in which the organic compound is one or more selected from ethylene glycol, glycerol, polyethylene glycol (with a molecular weight of 200 to 1500), acetophenone, 2,4-pentanedione, pentanole, acetic acid, maleic acid, oxalic acid, tartaric acid, formic acid, citric acid and C1-C4 dialkyl succinate. 
     
     
         7 . The process according to  claim 5 , in which the organic compound comprises at least the combination of C1-C4 dialkyl succinate and acetic acid. 
     
     
         8 . The process according to  claim 5 , in which the organic compound comprises at least citric acid. 
     
     
         9 . The process according to  claim 1 , in which the catalyst of step a) or b) has also undergone a sulphurizing step. 
     
     
         10 . The process according to  claim 1 , in which the quantity of basic nitrogen in the feed is 50 ppm or more. 
     
     
         11 . The process according to  claim 1 , in which the feed is a feed obtained from catalytic cracking, a coker or from visbreaking. 
     
     
         12 . The process according to  claim 1 , in which each of steps a) and b) is carried out at a temperature in the range 180° C. to 450° C., at a pressure in the range 0.5 to 10 MPa, at an hourly space velocity in the range 0.1 to 20 h −1  and with a hydrogen/feed ratio, expressed as the volume of hydrogen measured under normal temperature and pressure conditions, per volume of liquid feed in the range 50 L/L to 2000 L/L. 
     
     
         13 . The process according to  claim 1 , in which step a) is carried out in a first zone containing the first catalyst which occupies a volume V1, and step b) is carried out in a second zone containing the second catalyst which occupies a volume V2, the distribution of the volumes, V1/V2, being in the range 10% by volume/90% by volume to 50% by volume/50% by volume for the first and second zone respectively. 
     
     
         14 . The process according to  claim 1 , in which step i) of step b) comprises the following steps in succession:
 i′) impregnating an alumina support with at least one solution containing at least one metal from group VIB, at least one metal from group VIII and said phosphorus in order to obtain an impregnated support;   i″) drying the impregnated support obtained in step i′) at a temperature of less than 180° C. without subsequent calcining in order to obtain a dried impregnated support;   i′″) impregnating the dried impregnated support obtained in step i″) with an impregnation solution comprising at least one organic compound containing oxygen and/or nitrogen in order to obtain an impregnated catalytic precursor;   i″″) allowing the impregnated catalytic precursor obtained in step i′″) to mature, in order to obtain said catalyst precursor.   
     
     
         15 . The process according to  claim 1 , in which the effluent obtained in step a) undergoes a separation step in order to separate a heavy fraction and a light fraction containing the H 2 S and NH 3  formed during step a), said heavy fraction then being introduced into step b).