EP0621334A1 - Process for producing a fuel by extraction and hydrotreatment of a hydrocarboneous feed and produced gasoil - Google Patents

Abstract

Process for obtaining an internal combustion engine fuel from a hydrocarbon feedstock, including a stage a) of distillation (D1) in which a tail product (Q1) is obtained via a line 3 and a head product (T1) via a line 2, a stage b) of liquid/liquid extraction (LE) with the aid of a solvent (S1) in which an extract (E1) (line 6) and a raffinate (R1), (line 5) are obtained from the product (Q1), a stage c) of separation (D2) of the raffinate (R1) making it possible to obtain via a line 7 a product (Q2) impoverished in solvent (S1) and a stage d) of hydrotreatment (HDS) in which the mixture of the products (T1) and (Q2) is treated in hydrotreatment conditions under a partial hydrogen pressure lower than 10 megapascals and a product (P), is obtained (line 9) which has improved qualities and contains less than 500 ppm by weight of sulphur. According to a particular embodiment the extract (E1) (line 6) is distilled so as to obtain via a line 11 a tail product (Q3) which is subsequently sent to a hydrotreatment zone so as to obtain via a line 12 a product (P') containing less than 0.3% by weight of sulphur. The solvent (S1) recovered at the head of the distillations is recycled to the extraction stage b). <IMAGE>

Description

The invention relates to a petroleum product and a process for obtaining said petroleum product which can optionally be used for the formulation of a fuel for an internal combustion engine and the product obtained by the process. The gas oils that are currently found on the market, either in the form of fuels for internal combustion compression-ignition engines (diesel type), or in the form of fuel, are most often refined products which contain sulfur. in an amount (expressed by weight of sulfur) of about 0.3%. They are usually obtained following a hydrodesulfurization treatment from a feed which can come from the direct distillation of a crude oil or from a specific treatment of a crude oil (for example a pyrolysis or a distillation followed by pyrolysis of the fraction recovered during distillation, or thermal or catalytic cracking) generally containing at least 0.8% by weight of sulfur.

In a number of industrial countries, sulfur content standards are in place or will be implemented in the very near future. These standards are becoming more and more stringent, particularly for diesel oils intended to be used as fuel for engines. Thus in France, in particular from 1995, the sulfur content of these gas oils must be at most equal to 0.05% by weight (500 ppm) while the gas oils conforming to the standards in force have a content of sulfur up to 0.3%.

Likewise, the gas oils used in France as fuel for internal combustion engines must currently have a cetane number at least equal to 48 and the gas oils used as fuel, a cetane number at least equal to 40. We can expect in the near future to more stringent standards and in particular that concerning diesel fuel used as fuel in engines.

In addition, given the diversity of the charges to be treated (crudes of different origins, visbreaking, coking, hydroconversion, distillation or catalytic cracking) to produce diesel, it is desirable to be able to offer the refiner a flexible process , capable of adapting the products formed to demand and of meeting future specifications in terms of sulfur, nitrogen, cetane number, color and aromatic content.

Finally, all the existing processes such as hydrodesaromatization or hydrocracking which make it possible to obtain petroleum products with a low sulfur content and an index of relatively high cetane consumes significant amounts of hydrogen. For example, the hydrodearomatization process of a direct distillation charge whose distillation intervals (ASTM D86) are 180 ° C <T 5% <300 ° C, 260 ° C <T 50% <350, 350 ° C <T 95% <460 ° C, consumes 0.6 to 1.1% of hydrogen relative to the feed while the hydrocracking process requires more than 2% of hydrogen relative to its feed. However, the hydrogen charge in the refinery, which generally comes from the catalytic reforming unit, will tend to become insufficient in the current context of the severity of diesel standards, which results in an increase in hydrotreatments.

In addition, these existing processes lead to the production of a petroleum product whose cetane number does not exceed 63, the latter being reached only at the cost of hydrogenation of the aromatic hydrocarbons in the feed, a reaction which consumes hydrogen. (See table).

It is therefore desirable to offer the refiner a process which allows him to produce a petroleum product meeting the various standards which will come into application in the very near future and from 1995, as regards the sulfur content.

The technological background is illustrated by the following patents: US-A-4,985,139, EP-A-0,215,496, GB-A-1,006,949 and GB-A-943,239.

The present invention therefore relates to a simple implementation process, consuming little hydrogen and being able to use installations already present in the refinery, in particular the existing industrial hydrodesulfurization units, which limits the investment necessary for its implementation. . It makes it possible to improve the qualities of the diesel fuel produced and to comply with future standards and in particular that concerning the sulfur content. The process of the invention also makes it possible, as will be shown in the embodiment described below, to improve the cetane engine index of diesel, to reduce its content of aromatic compounds not containing a heteroatom of sulfur in their molecule, to reduce its content of nitrogenous compounds to improve its color and its odor and finally to decrease the formation of solid particles during its use in an internal combustion engine.

• une étape a) de distillation, de préférence à la pression atmosphérique, dans laquelle on sépare en queue un produit (Q1) contenant la majorité des composés polyaromatiques et un produit de tête (T1),
• une étape b) d'extraction liquide/liquide dans laquelle on met en contact, à une température d'au plus 140°C, de préférence de 0 à 80°C, dans des conditions d'extraction des composés polyaromatiques, le produit de queue (Q1) obtenu à l'étape a) avec un solvant ou un mélange de solvants (S1) permettant d'extraire au moins en partie les composés polyaromatiques qu'il contient, ledit solvant ayant un point initial d'ébullition inférieur d'au moins 20 °C et de préférence inférieur d'au moins 50 °C au point initial d'ébullition du produit de queue (Q1) obtenu à l'étape a), et au cours de laquelle on récupère un extrait (E1) enrichi en composés polyaromatiques et un raffinat (R1),
• une étape c) de séparation, par exemple de distillation, de préférence à la pression atmosphérique, du raffinat (R1) obtenu à l'étape b) dans laquelle on sépare un produit enrichi en solvant (S1) d'un produit (Q2) appauvri en solvant (S1),
• une étape d) d'hydrotraitement dans laquelle on introduit dans un réacteur d'hydrotraitement une partie au moins du produit de tête (T1) obtenu à l'étape a) et une partie au moins du produit (Q2) obtenu à l'étape c), puis on effectue l'hydrodésulfuration du mélange obtenu, sous une pression partielle d'hydrogène généralement inférieure à environ 10 mégapascals (MPa), avantageusement inférieure à 5 MPa et de préférence d'environ 1,5 à environ 3,5 MPa, et on récupère un produit (P) ayant des qualités améliorées et contenant moins de 500 ppm en poids de soufre, par exemple 100 à 480 ppm.

More particularly, the invention relates to a process for obtaining a petroleum product which can serve as a base in the composition of a fuel for an internal combustion engine with compression ignition, having an improved cetane number and a sulfur content, from a hydrocarbon feed having an initial boiling point of at least 150 ° C and a final boiling point of at most 500 ° C, containing from about 0.05% to about 5% by weight of sulfur , approximately 10% to approximately 60% by weight of n- and iso-alkanes, approximately 10% to approximately 90% by weight of aromatic hydrocarbons at least partly in the form of polyaromatic compounds (sulfur or not), having an index of cetane from about 20 to about 60 and a nitrogen content from about 50 to about 5,000 ppm (parts per million) by weight, said process being characterized in that it comprises the following steps:

• a distillation step a), preferably at atmospheric pressure, in which a product (Q1) containing the majority of the polyaromatic compounds and a top product (T1) are separated at the tail,
• a step b) of liquid / liquid extraction in which is brought into contact, at a temperature of at most 140 ° C., preferably from 0 to 80 ° C., under conditions of extraction of the polyaromatic compounds, the product of tail (Q1) obtained in step a) with a solvent or a mixture of solvents (S1) making it possible to extract at least in part the polyaromatic compounds which it contains, said solvent having a lower initial boiling point of at least 20 ° C and preferably at least 50 ° C lower than the initial boiling point of the bottoms product (Q1) obtained in step a), and during which an enriched extract (E1) is recovered polyaromatic compounds and a raffinate (R1),
• a step c) of separation, for example of distillation, preferably at atmospheric pressure, of the raffinate (R1) obtained in step b) in which a product enriched in solvent (S1) is separated from a product (Q2) depleted in solvent (S1),
• a hydrotreatment stage d) in which at least part of the top product (T1) obtained in stage a) and at least part of the product (Q2) obtained in stage are introduced into a hydrotreatment reactor c), then hydrodesulfurization of the mixture obtained is carried out, under a partial pressure of hydrogen generally less than about 10 megapascals (MPa), advantageously less than 5 MPa and preferably from about 1.5 to about 3.5 MPa , and we recover a product (P) having improved qualities and containing less than 500 ppm by weight of sulfur, for example 100 to 480 ppm.

For the sake of simplicity, the term hydrodesulfurization (HDS) will be used in the following description instead of hydrotreatment.

By polyaromatic compounds is meant compounds having at least two aromatic rings, sulfur or not.

The initial and final boiling point temperatures are TBP cut points.

Most often in this embodiment, at least 50% by volume of the product (Q2) is introduced and preferably at least 90%, or even all of this product, into the hydrodesulfurization reactor. Preferably, it is introduced into said reactor , the entire top product T1 from the distillation. This embodiment makes it possible to obtain a quantity of petroleum product with a very low sulfur content. In other words, a greater quantity of a recoverable product used in the composition of a fuel for internal combustion engines is thus obtained.

The hydrocarbon feedstock which is treated according to the process of the invention is most often called a diesel cutter and it preferably has an initial boiling point of approximately 150 ° C. and a final boiling point of approximately 400 ° C, its sulfur content is usually more than 0.1% and most often more than 0.5% by weight, its aromatic content at least partly in the form of polyaromatic compounds is usually about 15% to about 70% by weight and its content of n- and iso-alkanes is from 30 to 45% by weight. This charge is most often a direct distillation diesel or a pyrolysis diesel. The color of this filler measured according to the ASTM D 1500 method is usually greater than or equal to 2. The cetane number according to ISO 5165, this filler is most often less than around 60 and it is for example around 50 to about 55. The nitrogen content of this feed is usually about 20 to about 3000 ppm expressed by weight of nitrogen relative to the weight of the feed.

The product (P) obtained by the process of the present invention usually has a nitrogen content expressed by weight of nitrogen, usually 2 times less than that of the initial charge and often 4 to 5 times less. This product (P) most often has a color measured according to the Saybolt standard of approximately 10 to 30, most often 15 to 25 and the cetane number of this product is generally at least 2 points higher and often at least 5 points above the index of cetane from the initial charge (for example from 2 to 10 points). The content of aromatic compounds containing no sulfur atom in their molecule in this product (P) is usually reduced by at least 10% by weight relative to that of the initial charge and often by at least 30% by weight. weight. The sulfur content relative to that of the initial charge is less than or equal to 5% by weight. The content of n-and iso-alkanes generally increases from 4 to 15 points and most often from 6 to 11 points compared to that of the initial charge.

The invention advantageously relates to a petroleum product, usable in particular as a base used in the composition of a fuel, characterized in that the distillation cut corresponds to 95% by weight distilled between 320 ° C and 460 ° C, its cetane number is greater than 60, its content of n- and iso-alkanes is at least equal to 48% by weight, and its sulfur content less than or equal to 500 ppm (weight).

It also has a solvent content generally less than 10 ppm by weight, advantageously less than 5 ppm and most often less than 1 ppm.

The distillation is carried out under conditions making it possible to obtain a top product (T1) containing only a small proportion of compounds with at least one sulfur atom in their molecule very easily hydrotreated. When the distillation is carried out at atmospheric pressure, the top product is usually a fraction whose final boiling point is less than 360 ° C, preferably less than 330 ° C and for example about 310 ° C. The bottoms product (Q1) is usually a fraction with an initial boiling point higher than around 300 ° C, often higher than 330 ° C and sometimes higher than 360 ° C, which eliminates the refractory sulfur compounds raffinate which would require subsequent hydrotreatment at higher pressure and therefore at much higher cost.

In addition, by distilling under these preferred conditions, an amount of residue representing, for example, at most 30% of the initial charge, is sent to the extraction unit, which makes it possible to use the existing extraction units which are generally of low capacity and optimize the capacity of these units.

The liquid / liquid extraction step is a step carried out under conventional conditions. This extraction can for example be carried out against the current in a conventional device for example a filling column, trays or mechanically agitated (RDC: rotating disc contactor) generally having from 1 to 20 theoretical stages and preferably from 5 to 10 stages at a temperature generally between 0 ° C and 140 ° C, advantageously between 30 ° C and 80 ° C and under a pressure allowing to operate in the liquid phase and therefore between 0.1 and 1 MPa, preferably between 0.1 and 0.3 MPa. The volume ratio of the solvent (S1) to the volume of the bottoms product (Q1) is generally from 0.2: 1 to 5: 1, preferably from approximately 0.5: 1 to approximately 2: 1 and more often about 1: 1. The solvent is preferably chosen from the group of solvents making it possible to extract at least part of the aromatic compounds, not containing a sulfur atom in their molecule, present in the product (Q1) obtained in step a). The extraction conditions are preferably chosen so as to obtain a raffinate (R1) containing by weight at most 90% and preferably at most 70% by weight of the total weight of the aromatic compounds, not containing a sulfur atom in their molecule, present in the product (Q1) obtained in step a). The extract (E1) under these conditions will contain at least 10% and often at least 30% by weight of the total weight of the aromatic compounds, not containing a sulfur atom in their molecule, present in the product (Q1) obtained at step a).

The extraction solvent is most often a single solvent, but mixtures of solvent can also be used. This solvent generally contains less than 20% and often less than 10% by weight of water. This solvent can be an anhydrous solvent. It is most often chosen from the group formed by methanol, acetonitrile, monomethylformamide, dimethylformamide, dimethylacetamide, furfural, N-methylpyrolidone and dimethylsulfoxide. Dimethylformamide, N-methylpyrolidone or furfural are very often used.

It is also possible to add to the extraction solvent at least one cosolvent which may be, an alcohol of 1 to 6 carbon atoms, for example a linear or branched alcohol, or furfuryl alcohol.

If the feed to be treated has a high final boiling point and is particularly rich in nitrogen compounds, especially basic, it may be advantageous to introduce with the extraction solvent alone or in mixture, a minor amount of acids, in particular carboxylic (less than 1% by weight relative to the solvent for example). Among these, mention may advantageously be made of carboxylic acids of 1 to 6 carbon atoms and more particularly, acids having a boiling point below 250 ° C., in particular formic acid, acetic acid, propionic acid, butanoic acid, pentanoic acid, maleic acid, crotonic acid, isobutyric acid, valeric acid, trimethylacetic acid, benzoic acid, and 2-furoic acid .

The raffinate (R1) obtained in step b) is then sent to a distillation zone for example, in which it is distilled under conditions making it possible to recover an overhead fraction enriched, and preferably highly enriched, in solvent (S1 ) and a product (Q2) preferably highly depleted in solvent (S1). Most often the conditions of this distillation are chosen so as to obtain a top fraction containing almost all of the solvent, that is to say for example more than 95% by weight of the amount of solvent contained in the raffinate (R1 ) and introduced into this distillation zone. At least about 99% by weight of the amount of solvent contained in the raffinate (R1) is thus preferably recovered.

The raffinate, according to another mode of implementation, can be sent to at least one separation flask where a liquid-vapor equilibrium (flash) is achieved and a product (S1) enriched in solvent and a product (Q2) depleted in solvent. This or these flasks can be followed by stripping, for example with steam or nitrogen to recover the last traces of solvent.

The parameters of the hydrodesulfurization step generally chosen most often correspond to those of a hydrodesulfurization carried out under mild conditions. In other words, the space speed can be high, for example greater than 2h⁻¹. The catalyst is one of those, for example, sold by the company PROCATALYSE.

Likewise, in a particular embodiment, the extract (E1) obtained in step b) is then sent to a separation zone, for example a distillation in which it is distilled under conditions making it possible to recover an enriched fraction. , and preferably highly enriched, in solvent (S1) and a product (Q3) depleted in solvent (S1). Most often, the conditions of this separation are chosen so as to obtain a product containing almost all of the solvent, that is to say for example more than 95% by weight of the amount of solvent contained in the extract (E1) and introduced into this separation zone. At least about 99% by weight of the amount of solvent contained in the extract (E1) is thus preferably recovered.

In an advantageous embodiment of the invention, the product (Q3) is sent to a hydrodesulfurization zone in which it is subjected to hydrodesulfurization, for example in the presence of a catalyst marketed by the company PROCATALYSE under conditions generally more severe, making it possible to obtain a product (P ′) having a sulfur content less than or equal to 0.3% by weight and preferably less than or equal to 0.2% by weight, or even less than or equal to 0.1% by weight. This product (P ') will of course not be usable as fuel for the engines, since most often containing a quantity of sulfur greater than the future standard, on the other hand it will probably be able to be used as fuel.

According to another embodiment, at least part of the product (Q2) can be recovered at the end of step c) by lines (7) and (13) and be used as such as fuel or be mixed with the product (P ') resulting from the hydrodesulfurization of the product (Q3) or even be sent as a mixture with at least part of the product (Q3) to a hydrodesulfurization zone. There is then obtained, according to this embodiment, an amount of product at least partially desulphurized, usable as fuel.

In a particularly advantageous embodiment of the invention, the product or products, obtained by separation of the raffinate (R1) and optionally of the extract (E1), enriched (s) with solvent, are recycled in step b) liquid / liquid extraction.

The method of the present invention has increased flexibility over the methods described in the prior art.
It also has the following main advantages: a higher content of n- and iso-alkanes is obtained in the raffinate (table) than according to the hydrocracking or hydrodesaromatization processes, a higher cetane number, in despite an aromatic hydrocarbon content greater than 10%. In addition, the consumption of hydrogen in hydrotreatment is lower. It can be reduced for example to 0.15% by weight with respect to the charge, when the hydrogenation is limited to the maximum.

The following example illustrates the invention without limiting its scope.

EXAMPLE

The feed used in this example is a direct-distillation gas oil having a cetane number of 55, a total content of aromatic compounds, sulfur and non-sulfur, of 34% by weight, a content of n- and iso alkanes of 18% by weight and 22% by weight, a sulfur content of 1.22% by weight, a nitrogen content expressed by weight of nitrogen of 255 ppm and a color measured according to standard ASTM D 1500 equal to 2. This diesel has an initial distillation point of 150 ° C and a final distillation point of 400 ° C.

This charge is introduced via line 1 into a distillation zone from which a head fraction (T1) with a final boiling point below 320 ° C. is recovered via line 2 which contains 0.88% by weight of sulfur, and via line 3 a bottom fraction (Q1) with a final boiling point greater than 320 ° C. containing 1.7% by weight of sulfur. The top product (T1) is sent via line 2 and line 8 to a hydrodesulfurization (HDS) zone.

The bottoms product (Q1) leaving the distillation zone D1 is sent via line 3 to the extraction zone (LE) into which is introduced via line 4 an amount of dimethylformamide equal in volume to the amount of product of tail (Q1) introduced into this area. This zone is an extraction column comprising a packing formed by Pall rings corresponding to three theoretical stages. The extraction is carried out against the current, at atmospheric pressure and at a temperature of 70 ° C. A raffinate is obtained (R1) which is sent via line 5 to the distillation zone D2 in which the dimethylformamide is separated at the head which is recovered by line 10 a for possible recycling to the extraction zone and at the tail a raffinate (Q2) containing practically no more dimethylformamide, having a sulfur content of 0.51% which is sent via line 7 and line 8 to the hydrodesulfurization zone (HDS).

The products (T1) and (Q2) introduced into the hydrodesulfurization zone are subjected to a hydrodesulfurization treatment under a partial hydrogen pressure of 2.5 MPa in the presence of an industrial catalyst containing cobalt and molybdenum on an alumina support sold by the company PROCATALYSE under the reference HR 306C, the temperature is maintained at 330 ° C, the hydrogen recycling is equal to 200 liters per liter of charge and the hourly space speed is 2.5 h ⁻¹. By way of comparison, such a high-performance hydrodesulfurization carried out directly on the same diesel fuel must be carried out at an hourly space speed of 1.5 h⁻¹, all the other conditions remaining substantially equal elsewhere.

A product (P) containing 450 ppm of sulfur, 20% by weight of aromatic compounds, is recovered via line 9. This product has a color measured according to the Saybolt method equal to 20 and a nitrogen content of 50 ppm by weight. The cetane number of the product (P) is 62. This product is incorporated into the Diesel pool. The content of n- and iso-alkanes is 21% by weight and 31% by weight.

An extract (E1) is also recovered via line 6 which is sent to a distillation zone D3 in which the dimethylformamide is separated at the head which is recovered by line 10 b for possible recycling to the zone of extraction and at the tail an extract (Q3) containing practically no more dimethylformamide, having a sulfur content of 5.1% which is sent via line 11 to a hydrodesulfurization zone (HDS) distinct from that into which one has introduced the raffinate (Q2) and the top product (T1). This hydrodesulfurization is carried out in the presence of the HR 306C catalyst, under a partial hydrogen pressure of 4 MPa, at a temperature of 350 ° C. with a hydrogen recycling of 300 liters per liter of charge and an hourly space velocity of 1, 2 hrs.

A product (P ') containing 0.2% by weight of sulfur, 75% by weight of aromatic compounds is recovered via line 12. This product has a color measured according to the ASTM D-1500 method equal to 1 and a nitrogen content of 200 ppm by weight. It can be sent to the domestic fuel pool.

Claims (14)

1 - Process for obtaining a petroleum product which can serve as a base in the composition of a fuel for an internal combustion engine with compression ignition having an improved cetane number and a sulfur content, from a hydrocarbon feedstock having an initial boiling point of at least 150 ° C and an end boiling point of at most 500 ° C, containing from about 0.05% to about 5% by weight of sulfur, from about 10 to about 60% by weight of n- and iso-alkanes, about 10% to about 90% by weight of aromatic hydrocarbons at least partly in the form of polyaromatic compounds, sulfur or not, having a cetane number of about 20 to about 60 and having a nitrogen content of about 50 to about 5,000 ppm by weight, said process being characterized in that it comprises the following steps: a distillation step a) in which a product (Q1) containing the majority of the polyaromatic compounds and a top product (T1) are separated at the bottom, - a step b) of liquid / liquid extraction in which is brought into contact at a temperature of at most 140 ° C., under conditions of extraction of the polyaromatic compounds, the bottom product (Q1) obtained at step a) with a solvent or a mixture of solvents (S1) making it possible to at least partially extract the polyaromatic compounds which it contains, said solvent having an initial boiling point at least 20 ° C lower than the initial point boiling the bottom product (Q1) obtained in step a), and during which an extract (E1) enriched in polyaromatic compounds and a raffinate (R1) is recovered, a step c) of separation of the raffinate (R1) obtained in step b) in which a product enriched in solvent (S1) is separated at the head from a product (Q2) depleted in solvent (S1), a step d) of hydrotreatment in which at least part of the top product (T1) obtained in step a) and at least part of the product (Q2) obtained in the are introduced into a hydrotreatment reactor step c), then the mixture obtained is hydrotreated under a partial hydrogen pressure of less than about 10 megapascals and a product (P) having an index of cetane at least 2 points higher than that of the feed and containing less than 500 ppm by weight of sulfur. 2 - Process according to claim 1 wherein the final boiling point of the top product is less than 360 ° C and preferably at 330 ° C. 3 - Process according to claim 1 or 2 wherein step b) is carried out under conditions allowing to obtain a raffinate (R1) containing by weight at most 90% and preferably at most 70% by weight of the total weight of aromatic compounds, not containing a sulfur atom in their molecule, present in the product (Q1) obtained in step a). 4 - Method according to one of claims 1 to 3 wherein the extract (E1) obtained in step b) is sent to a separation zone so as to recover a product enriched in solvent (S1) and a product ( Q3) depleted in solvent (S1). 5 - Process according to claim 4 wherein the product (Q3) is sent to a hydrotreatment zone in which it is subjected to hydrotreatment under conditions making it possible to obtain a product (P ') having a lower sulfur content or equal to 0.3% by weight and preferably less than or equal to 0.2% by weight. 6 - Method according to one of claims 1 to 5 wherein the top product or products, obtained by separation of the raffinate (R1) and optionally the extract (E1), enriched (s) in solvent (S1), are recycled in step b) of extraction. 7 - Method according to one of claims 1 to 6 wherein the solvent is selected from the group formed by methanol, acetonitrile, monomethylformamide, dimethylformamide, dimethylacetamide, furfural, N-methylpyrolidone and dimethylsulfoxide. 8 - Process according to claim 7 wherein the solvent is chosen from the group formed by dimethylformamide, N-methylpyrolidone and furfural. 9 - Method according to one of claims 1 to 8 wherein there is introduced into another hydrotreating zone, at least part of the product (Q3) resulting from the separation of the extract and at least part of the product (Q2 ) obtained in step c), we subjects the mixture thus obtained to hydrotreatment under appropriate conditions and an at least partly desulphurized mixture which can be used as fuel is recovered. 10 - Method according to one of claims 1 to 8 wherein at least part of the product (Q2) obtained in step c) is mixed with the product (P ') resulting from the hydrotreatment of the product (Q3) and recovers an at least desulfurized mixture usable as fuel. 11 - Petroleum product characterized in that it is obtained by the process according to one of claims 1 to 10. 12 - Petroleum product according to claim 11 usable in particular as a base used in the composition of a fuel for an internal combustion engine with compression ignition having a cetane number higher by at least 3 points than that of the charge from which it comes, a content of n- and iso-alkanes greater by 4 to 15 points than that of the filler and a sulfur content relative to that of the filler less than or equal to 5% by weight. 13 - Petroleum product according to one of claims 11 to 12 characterized in that the distillation cut corresponds to 95% distilled between 320 ° C and 460 ° C, its cetane number is greater than 60, its content of n- and iso-alkanes is at least equal to 48% by weight, and its sulfur content less than or equal to 500 ppm (weight). 14 - Petroleum product according to claim 13, in which the solvent content is less than 10 ppm by weight, advantageously less than 5 ppm and most often less than 1 ppm.

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