Process for the production of kerosene and diesel fuels from light unsaturated fractions and btx-rich aromatic fractions

Abstract

Process for the production of kerosene and diesel fuels from a so-called light cracked naphtha fraction, to which can be added any quantity of an LPG fraction and a BTX-rich aromatic fraction and which uses a stage for oligomerization of olefins and alkylation of olefins on the aromatic compounds.

1 ) Process for the production of diesel fuel from a gasoline fraction that contains 5 to 10 carbon atoms and in a preferred manner 5 to 7 carbon atoms originating from a catalytic cracking unit ( 1 ), and a BTX fraction ( 9 ) that typically originates from a unit for catalytic reforming of gasolines, relying on the concatenation of the following stages:
 A stage 1 for selective hydrogenation (SHU) of the initial gasoline fraction,   A stage 2 for treatment on the acid catalyst (TR) of the effluent that is obtained from stage 1,   A stage 3 for distillation of the effluent of stage 2 that is produced in a first distillation column (CD 1 ) that makes it possible to separate at the top an olefinic fraction ( 4 ) that has a final boiling point of approximately 60°, intermediately a distillation interval fraction ( 5 ) of between 60° C. and 150° C., and at the bottom a fraction ( 6 ) with a boiling point that is greater than 150° C., which is sent to a hydrotreatment (HDT) unit,   A stage 4 for oligomerization (OLG) of the olefinic fraction ( 4 ), optionally mixed with an LPG fraction ( 10 ) that contains olefins, from which, after distillation, a stream ( 7 ) of oligomerized olefins that constitutes a “kero” fraction that is sent for a first part ( 7   a ) to the hydrotreatment (HDT) unit and for a second part ( 7   b ) to a total hydrogenation (HT) unit is extracted,   A stage 5 for alkylation of the stream ( 8 ) of olefins into C3 and C4 obtained from stage 4 for oligomerization on the BTX fraction ( 9 ) that is rich with aromatic compounds containing 6 to 12 carbon atoms, and in a preferred manner 6 to 9 carbon atoms, whereby the effluent ( 11 ) of the alkylation (ALK) unit is sent into a second distillation column (CD 2 ) from which 3 fractions are extracted:   A gasoline fraction ( 11   a ) with a boiling point that is less than 100° C., which is sent to the gasoline pool,   An intermediate fraction ( 11   b ) with a distillation interval of between 100° C. and 150° C., essentially consisting of BTX that has not reacted, which is for the most part recycled at the input of the alkylation unit, with the exception of a fraction ( 11   d ) that constitutes the purging of the (ALK) unit, and which is itself sent to the gasoline pool after stabilization,   A heavy fraction ( 11   c ) with a boiling point that is greater than 150° C. that is sent to the total hydrogenation (HT) unit from which the desired diesel fuel ( 13 ) is extracted,   
       with the oligomerization stage 4 working on a preferably zeolitic- or silica-alumina-type acid catalyst, in a temperature range of 100° C. to 350° C., and in a pressure range of 20 to 70 bar, and in a VVH range of 0.2 to 1.0 h-1, 
       and with alkylation stage 5 working on a preferably zeolitic- or silicoaluminate-type acid catalyst in a temperature range of 100 to 350° C., and in a pressure range of 20 to 70 bar, and in a VVH range of 0.1 h-1 to 2.0 h-1. 
     
     
         2 ) Process for the production of diesel fuel according to  claim 1 , in which the stage 2 for treatment on an acid catalyst relies on an ion-exchange resin-type acid catalyst, or supported phosphoric acid catalyst, or any acid catalyst previously used in the downstream stages of oligomerization (OLG) or alkylation (ALK), in a temperature range of 20° C. to 350° C., in a preferred manner of 40 to 250° C., and in a pressure range of 1 to 100 bar, in a preferred manner 10 to 30 bar, and in a VVH range of 0.1 to 5 h-1, in a preferred manner 0.3 to 2.0 h-1. 
     
     
         3 ) Process for the production of distillates according to  claim 1 , in which the hydrotreatment (HDT) stage uses a catalyst that contains at least one metal that is selected from among Ni, Co and Mo and operates in a temperature range of 50 to 400° C., in a preferred manner 100 to 350° C., and in a pressure range of 1 to 100 bar, in a preferred manner 20 to 70 bar, and in a VVH range of 0.1 h-1 to 10 h-1, in a preferred manner 0.5 h-1 to 5.0 h-1. 
     
     
         4 ) Process for the production of distillates according to  claim 1 , in which the hydrotreatment (HDT) stage uses a catalyst that contains at least one metal that is selected from among Pd and Pt and operates within a temperature range of 50 to 300° C., in a preferred manner 100° C. to 250° C., and in a pressure range of 1 to 100 bar, in a preferred manner 20 to 70 bar, and in a VVH range of 0.1 h-1 to 10 h-1, in a preferred manner 0.5 h-1 to 5.0 h-1.