Method for converting hydrocarbon feedstock comprising a shale oil by hydroconversion in an ebullating bed, fractionation by atmospheric distillation and liquid/liquid extraction of the heavy fraction

Abstract

Method for converting hydrocarbon feedstock comprising a shale oil, comprising a step of hydroconverting in an ebullating bed, a step of fractionating by atmospheric distillation into a light fraction, a naphtha fraction, a gas-oil fraction and a fraction heavier than the gas-oil fraction, a step of liquid/liquid extraction of the fraction heavier than the gas-oil fraction, and a dedicated hydrotreating for each of the naphtha and gas-oil fractions. The method aims to maximize the yield of fuel bases.

1 . Method for converting a shale oil or a mixture of shale oils having a nitrogen content of at least 0.1%, often at least 1% and very often at least 2% by weight, characterized in that it comprises the following steps:
 a) The feedstock is treated in a section for hydroconverting in the presence of hydrogen, said section comprising at least one ebullating bed reactor operating in gas and liquid upflow mode and containing at least one supported catalyst,   b) The effluent obtained in step a) is conveyed at least partly, and often entirely, into a fractionating zone, from which, by atmospheric distillation, a gaseous fraction, a naphtha fraction, a gas-oil fraction and a fraction heavier than the gas-oil fraction are recovered,   c) Said naphtha fraction is treated at least partly, and often entirely, in a section for hydrotreating in the presence of hydrogen, said section comprising at least one fixed bed reactor containing at least one hydrotreating catalyst,   d) Said gas-oil fraction is treated at least partly, and often entirely, in another section for hydrotreating in the presence of hydrogen, said section comprising at least one fixed bed reactor containing at least one hydrotreating catalyst,   e) The fraction heavier than the gas-oil fraction is subjected to a liquid/liquid extraction to give a raffinate and an extract.   
     
     
         2 . Method according to  claim 1 , wherein the effluent obtained in step a) is fractionated by atmospheric distillation into a gaseous fraction having a boiling point of less than 50° C., a naphtha fraction boiling at between about 50° C. and 150° C., a gas-oil fraction boiling at between about 150° C. and 370° C., and a fraction which is heavier than the gas-oil fraction and which boils generally at above 370° C. 
     
     
         3 . Method according to  claim 1 , wherein the solvent in the liquid/liquid extracting step e) is selected from the group consisting of furfural, N-methyl-2-pyrrolidone, sulpholane, dimethylformamide, dimethyl sulphoxide, phenol, or a mixture of these solvents in equal or different proportions. 
     
     
         4 . Method according to  claim 1 , wherein the liquid/liquid extracting step e) is carried out with a solvent/feedstock ratio of 1/1 to 3/1, preferably of 1/1 to 1.8/1, at a temperature of between the ambient temperature and 150° C., and at a pressure of between atmospheric pressure and 2 MPa, preferably between atmospheric pressure and 1 MPa. 
     
     
         5 . Method according to  claim 1 , wherein the fixed bed hydrotreating sections in steps c) and/or e) comprise, upstream of the catalytic hydrotreating beds, specific guard beds for arsenic compounds and silicon compounds. 
     
     
         6 . Method according to  claim 1 , wherein at least part of the raffinate obtained in liquid/liquid extracting step e) is conveyed, after solvent evaporation, into a catalytic cracking section, called step f), in which it is treated under conditions enabling production of a gaseous fraction, a petrol fraction, a gas-oil fraction and a heavy fraction. 
     
     
         7 . Method according to  claim 6 , wherein at least part of the heavy fraction, obtained in catalytic cracking step f), is recycled to the start of said step f). 
     
     
         8 . Method according to  claim 6 , wherein at least part of the gas-oil fraction, obtained in catalytic cracking step f), is recycled to gas-oil hydrotreating step d). 
     
     
         9 . Method according to  claim 1 , wherein at least part of the extract, obtained in liquid/liquid extracting step e), is recycled to the start of step a). 
     
     
         10 . Method according to  claim 1 , wherein hydroconverting step a) operates at a temperature of between 300° C. and 550° C., preferably between 400° C. and 450° C., at a total pressure of between 2 and 35 MPa, preferably of between 10 and 20 MPa, at a mass hourly velocity ((t of feedstock/h)/t of catalyst) of between 0.2 and 1.5 h −1 , preferably between 0.3 h −1  and 1 h −1 , and at a hydrogen/feedstock ratio of between 50 and 5000 Nm 3 /m 3 , preferably between 100 and 1000 Nm 3 /m 3 . 
     
     
         11 . Method according to  claim 1 , wherein step c) of hydrotreating the naphtha fraction operates at a temperature of between 280° C. and 380° C., preferably between 300° C. and 350° C., at a total pressure of between 4 and 15 MPa, preferably of between 10 and 13 MPa, at a mass hourly velocity ((t of feedstock/h)/t of catalyst) of between 0.1 h −1  and 5 h −1 , preferably between 0.5 −1  and 1 h −1 , and at a hydrogen/feedstock ratio of between 100 and 5000 Nm 3 /m 3 , preferably between 200 and 1000 Nm 3 /m 3 . 
     
     
         12 . Method according to  claim 1 , wherein step d) of hydrotreating the gas-oil fraction operates at a temperature of between 320° C. and 450° C., preferably between 340° C. and 400° C., at a total pressure of between 7 and 20 MPa, preferably of between 10 and 15 MPa, at a mass hourly velocity ((t of feedstock/h)/t of catalyst) of between 0.1 and 1 h −1 , preferably between 0.3 −1  and 0.8 h −1 , and at a hydrogen/feedstock ratio of between 100 and 5000 Nm 3 /m 3 , preferably between 200 and 1000 Nm 3 /m 3 . 
     
     
         13 . Method according to  claim 1 , wherein the catalyst in hydroconverting step a) comprises a group VIII metal selected from the group consisting of Ni and/or Co, optionally a group VIB metal selected from the group consisting of Mo and/or W, on an amorphous support selected from the group consisting of alumina, silica, silica-aluminas, magnesia, clays and mixtures of at least two of these minerals. 
     
     
         14 . Method according to  claim 1 , wherein the catalyst in hydrotreating steps c) and d) comprises a group VIII metal selected from the group consisting of Ni and/or Co, optionally a group VIB metal selected from the group consisting of Mo and/or W, on an amorphous support selected from the group consisting of alumina, silica, silica-aluminas, magnesia, clays and mixtures of at least two of these minerals. 
     
     
         15 . Method according to  claim 1 , wherein the shale oil or the mixture of shale oils is supplemented by a hydrocarbon feedstock selected from the group consisting of oils derived from coal, oils obtained from heavy tars and bituminous sands, vacuum distillates, and residues of direct distillation, vacuum distillates and unconverted residues obtained from a residue conversion process, oils deasphalted with solvents, light cycle oils, heavy cycle oils, gas-oil cuts originating from catalytic cracking and having generally a distillation range from approximately 150° C. to approximately 650° C., aromatic extracts obtained in the manufacture of lubricating oils, or mixtures of such feedstocks.