EP2256179B1 - Method for producing a hydrocarbon cut with a high octane level and low sulphur content - Google Patents

Description

The present invention relates to the field of improving the octane number of a hydrocarbon fraction, and more particularly to a process for producing a high octane and low sulfur hydrocarbon fraction, which makes it possible to value the entire cut, reduce the total sulfur content of the cut to very low levels, while increasing the octane number of the cut.

Petroleum refining and petrochemicals are now subject to new constraints. Indeed, all countries are gradually adopting strict specifications of sulfur, the goal is to reach between 5 to 10 ppm of sulfur. The problem of reduction of sulfur contents is essentially concentrated on the species obtained by cracking, whether catalytic (FCC Fluid Catalytic Cracking according to the English terminology) or non-catalytic (coking, visbreaking, steam cracking), main sulfur precursors. in the gasoline pools. Today there are sulfur specification schemes for catalytic cracking gasoline. Although these schemes attempt to limit the loss of olefins, they inevitably imply octane loss irrespective of the technology used, which is problematic at a time when the octane constraints imposed by car manufacturers are becoming stronger.

A second constraint comes from the fact that the fuel market shows a steady decline in the demand for gasoline in favor of diesel while maintaining a high demand of gasoline quality in terms of octane, vapor pressure Reid and sulfur content. It is therefore important to produce gasoline of improved quality but in reduced quantity for the benefit of distillates (kerosene and diesel).

A third constraint comes from the petrochemical industry and in particular the steam cracking and catalytic reforming processes which produce the highest value of olefins and aromatics (ethylene and propylene) respectively, and the price of its raw materials (especially naphthas). alarmingly, and this in the long term because of future resource constraints and which require low aromatic loads.

One solution, well known to those skilled in the art, for reducing the sulfur content is to perform hydrotreating (or hydrodesulfurization) of the slices. hydrocarbons and in particular catalytic cracking gasolines. However, this process has the major disadvantage of causing a very large drop in the octane number.

Other methods for desulfurizing olefinic species by limiting the hydrogenation of olefins, and therefore minimizing the decrease in octane number, are described in numerous patents.

The patent EP1370627 , for example, discloses a process for producing low sulfur gasoline comprising at least one selective hydrogenation of the diolefins present in the initial gasoline, a step of transforming the light sulfur compounds present in the gasoline, a fractionation of the gasoline obtained in at least two fractions, a light fraction and a heavy fraction, and a desulfurization treatment in one step of at least a portion of the heavy fraction resulting from the fractionation. This process thus makes it possible to reduce the amount of sulfur present in gasoline and to obtain gasolines whose octane number is better than that which could be obtained simply by hydrotreatment. However, even if the octane number is improved, compared to that obtained with a hydrotreatment, it is ultimately degraded, ie less than that of the treated feedstock.

The patent US 3044950 discloses a process for upgrading an essence of FCC to the gasoline pool which comprises a step of distilling said gasoline into two or three slices and a hydrotreating step (HDS and total hydrogenation of olefins) of the heaviest cut resulting from distillation. Finally, the heavy desulfurized cut is subjected to a step of extraction of the aromatic compounds from which is recovered an aromatic enriched extract and a paraffin-rich raffinate. According to the patent US 3044950 , the paraffinic raffinate is fully processed in a catalytic reforming unit to produce a rich aromatic effluent that is sent to the gasoline pool.

• mise aux spécifications en soufre de la charge hydrocarbonée avec un indice d'octane du produit supérieur ou égal à celui de la charge et une réduction substantielle de la teneur en oléfines,
• conversion d'une partie de la charge hydrocarbonée en base pour la pétrochimie.
• et dans certains cas, conversion d'une partie de la charge hydrocarbonée en distillats moyens à basse teneur en soufre.
• envoi d'une partie seulement de l'essence d'origine vers un pool essence.

It is therefore an object of the present invention to overcome one or more of the disadvantages of the prior art by proposing a method for producing a hydrocarbon fraction from a hydrocarbon feedstock and for example a fraction of catalytic cracking gasoline. to meet the aforementioned constraints:

• setting the sulfur content of the hydrocarbon feedstock with an octane number of the product greater than or equal to that of the feedstock and a substantial reduction in the olefin content,
• conversion of a portion of the hydrocarbon feedstock to a base for petrochemicals.
• and in some cases conversion of a portion of the hydrocarbon feedstock to low sulfur middle distillates.
• sending only a portion of the original gasoline to a gasoline pool.

For this, the present invention provides a process for producing a hydrocarbon fraction with a high octane number and a low sulfur content from a hydrocarbon feedstock, according to claim 1.

In one embodiment of the invention, the hydrocarbon feedstock is derived from a catalytic cracking unit or a thermal cracking unit or a coker unit or a visbreaking unit.

According to one embodiment of the invention, the hydrodesulfurization step is selective and carried out in one step in one or two reactors or in two stages.

According to another embodiment of the invention, the hydrodesulfurization step is non-selective.

In one embodiment of the invention, at least a portion of the paraffinic raffinate is sent to a separation step which leads to a light raffinate sent to the gasoline pool, in admixture with the aromatic extract, and / or to a unit steam cracking or a catalytic reforming unit and a heavy raffinate sent to the diesel pool or to the kerosene pool.

In one embodiment of the invention, the light hydrocarbon fraction is sent in admixture with the aromatic extract and a part of the paraffinic raffinate to the gasoline pool.

In one embodiment of the invention, the aromatic extraction step is a liquid-liquid extraction or an extractive distillation.

In one embodiment of the invention, the step of extracting the aromatic compounds is a liquid-liquid extraction with a solvent level of between 1.5 and 5.

• la figure 1 est une représentation schématique du procédé de production de coupe hydrocarbonée non conforme à l'invention.
• la figure 2 est une représentation schématique d'une variante du procédé de production de coupe hydrocarbonée selon l'invention,
• la figure 3 est une représentation schématique d'une autre variante du procédé de production de coupe hydrocarbonée selon l'invention.

Other features and advantages of the invention will be better understood and will appear more clearly on reading the description given hereinafter with reference to the appended figures given by way of example:

• the figure 1 is a schematic representation of the hydrocarbon cutting production process not according to the invention.
• the figure 2 is a schematic representation of a variant of the hydrocarbon cutting process according to the invention,
• the figure 3 is a schematic representation of another variant of the hydrocarbon cutting process according to the invention.

The process, illustrated on figures 1 , 2 and 3 consists in producing a hydrocarbon fraction with high octane number and low sulfur content.

The filler used in the process according to the invention is a sulfur-containing hydrocarbon feedstock whose boiling point extends from the boiling point of the hydrocarbon feeds containing 4 carbon atoms (C ₄ ) up to the point of boiling point. 300 ° C final boiling according to ASTM D86. The hydrocarbon feedstock used in the process according to the invention may be, for example, a petrol cut from a catalytic cracking unit, a thermal cracking unit (Steam Cracker), a coker unit (coker according to the English terminology) or a visbreaking unit (visbreaker according to the English terminology).

• une fraction d'oléfine supérieure à 5% poids et le plus souvent supérieure à 10% poids
• une fraction d'aromatiques supérieure à 5% poids et le plus souvent supérieure à 10% poids
• au moins 50 ppm poids de soufre

The filler used in the process according to the invention generally comprises:

• an olefin fraction greater than 5% by weight and most often greater than 10% by weight
• an aromatic fraction greater than 5% by weight and most often greater than 10% by weight
• at least 50 ppm by weight of sulfur

In the process, illustrated on the figure 1 the hydrocarbon feedstock is subjected to at least one hydrodesulfurization treatment and an extraction treatment of the aromatic compounds. For this, the charge is sent via line (1) to a hydrodesulfurization unit (C). The effluent from the hydrodesulfurization unit (C) flows via line (4) before being sent to the aromatics extraction unit (D). The aromatic extract (also called extract enriched in aromatics by contribution to the charge) then circulates via line (9). The paraffinic raffinate (also called paraffin enriched raffinate with respect to the feedstock) obtained at the outlet of the aromatics extraction unit (D) circulates via the line (6). Part of this paraffinic raffinate is sent via line (7) to a steam cracking unit. The other part of this paraffinic raffinate is sent via line (8) to the gasoline pool. The mixture of effluents (aromatic extract and paraffinic raffinate) flowing in lines (9) and (8) is sent via line (10) to the gasoline pool.

The sequencing of the hydrodesulphurization and extraction stages of the aromatic compounds makes it possible to valorise the totality of a hydrocarbon feedstock and in particular of a gasoline cut by reducing the sulfur content and maximizing the octane number of the feedstock. petrol. Part of the gasoline can be converted into medium distillate with low sulfur content. Another part of the gasoline can be used as a petrochemical base by being sent to a steam cracking unit.

The process thus makes it possible to meet the abovementioned constraints by reducing the quantity of gasoline produced from a hydrocarbon feedstock in favor of a better raffinate for petrochemicals.

According to a variant of the process according to the invention (illustrated on the figure 2 the steps of hydrodesulphurization and extraction of the aromatic compounds are preceded by a selective hydrogenation step itself followed by a separation step. In this variant the charge is sent via line (1) to a selective hydrogenation unit (A). The effluent from the selective hydrogenation unit (A) flows via the line (2) and is then injected into a separation column (B) which leads to at least two cuts: a light gasoline cut sent to the gasoline pool via line (5); this light cut will have a maximum ASTM D86 end point of 160 ° C, preferably 120 ° C and very preferably 90 ° C, a heavy gasoline cut flowing via the line (3) and possibly an intermediate gasoline cut flowing via the line (18). This intermediate slice generally has an ASTM D86 boiling point of less than or equal to 220 ° C, preferably less than or equal to 180 ° C and very preferably less than or equal to 160 ° C. When an intermediate cut (18) is produced, it is sent to the hydrodesulfurization unit (C) via the line (18). The heavy cut flowing via the line (3) is sent to the middle distillates after hydrotreatment if necessary. In the case where there is no intermediate cut, it is the heavy cut that is sent to the hydrodesulfurization unit (C) via the line (3).

The effluent from the hydrodesulfurization unit (C) flows via line (4) before being sent to the aromatics extraction unit (D). The paraffinic raffinate circulates via line (6). Part of this paraffinic raffinate is sent via line (7) to a steam cracking unit. The other part of this paraffinic raffinate is sent via line (8) to the gasoline pool. The effluents (light gasoline and aromatic extract) circulating in the lines (9) and (5), are mixed via the line (11), before being sent in mixture with the effluent (paraffinic raffinate) circulating via the line ( 8) to the gasoline pool.

This variant of the process according to the invention makes it possible, at the moment of the separation step, to obtain a cut of light petrol containing less than 10 ppm of sulfur and a cut of heavy gasoline with a controlled olefin content, which implies a 15 to 85% decrease in olefins sent to the hydrodesulfurization unit.

• une étape de d'hydrogénation sélective,
• une étape de séparation,
• une étape d'hydrodésulfuration sur la coupe d'essence lourde et une partie de la coupe d'essence légère,
• une étape d'extraction des aromatiques sur la totalité de l'effluent issu de l'unité d'hydrodésulfuration,
• envoi de la totalité du raffinat paraffinique obtenu vers le vapocraqueur.

In the case where it is desirable to maximize the steam cracker charge, the proposed configuration may consist of:

• a step of selective hydrogenation,
• a separation step,
• a hydrodesulphurization step on the heavy gasoline cut and a part of the light petrol cut,
• a step of extraction of the aromatics on the totality of the effluent resulting from the hydrodesulfurization unit,
• sending all the paraffinic raffinate obtained to the steam cracker.

It is also possible to separate the paraffinic raffinate in two cuts, a light cut low in sulfur and octane returned to the gasoline pool if there is a margin in terms of octane number or in the opposite case to the steam cracker and a heavy low sulfur cut and controlled flash point sent to the kerosene pool or diesel pool.

According to another variant of the process according to the invention (illustrated on the figure 3 ), the aromatics extraction step may be followed by a separation step. The feed is sent via line (1) to the selective hydrogenation unit (A). The effluent from the selective hydrogenation unit (A) flows via the line (2) and is then injected into a separation column (B) which leads to two cuts: a gasoline cut lightly sent to the gasoline pool via line 5 and a heavy gasoline cut sent to the hydrodesulfurization unit (C) via line (3). The effluent from the hydrodesulfurization unit (C) flows via line (4) before being sent to the aromatics extraction unit (D).

The paraffinic raffinate circulates via line (6). The effluents (light gasoline and aromatic extract) circulating in lines (9) and (5) are mixed via line (11).

The paraffinic raffinate circulating via the line (6) is sent to a separation column (E). The heavy raffinate is sent to the diesel cut via line (13). The light raffinate flows via line (14). Part of this light raffinate is sent via line (15) to the gasoline pool and the other part is sent via line (16) to the steam cracker. The effluent circulating via the line (11) is mixed with the effluent circulating via the line (15) to give the effluent circulating via the line (17) which is sent to the gasoline pool.

This variant can be used in the case where it is desirable to maximize the production of distillates, without sending product to the petrochemical industry.

According to another variant (not shown), the hydrocarbon feedstock, without any selective hydrogenation step or separation, is subjected to at least one hydrodesulfurization treatment and an extraction treatment of the aromatic compounds which can be followed by a step of seperation. For this, the charge is sent to a hydrodesulfurization unit. The effluent from the hydrodesulfurization unit is sent to the aromatics extraction unit. The paraffinic raffinate obtained at the outlet of the aromatics extraction unit is sent to a separation column. The heavy raffinate is sent to the diesel cutter. Some of the light raffinate is sent to the gasoline pool and the other part is sent to the steam cracker. The aromatic extract from the extraction unit is mixed with the other part of the light raffinate, and then sent to the gasoline pool.

The different steps of the process according to the invention are described in more detail below.

Selective hydrogenation step

The process according to the invention comprises a step of selective hydrogenation. This step is intended to convert the diolefins, present in the hydrocarbon feedstock, into olefins. During this stage it is also possible to weigh down the light sulfur products present in the hydrocarbon feedstock.

This selective hydrogenation step takes place in a reactor generally in the presence of a catalyst containing at least one Group VIII metal, preferably selected from the group formed by platinum, palladium and nickel, and a support. It is possible, for example, to use a catalyst based on nickel or palladium deposited on an inert support, such as, for example, alumina, silica or a support containing at least 50% of alumina.

Another metal may be associated with the main metal to form a bimetallic catalyst, such as, for example, molybdenum or tungsten. The use of such catalytic formulas has for example been claimed in the patent FR 2,764,299 .

The choice of operating conditions is particularly important. In general, the step is carried out under pressure and in the presence of a quantity of hydrogen in small excess relative to the stoichiometric value necessary to hydrogenate the diolefins. The hydrogen and the feedstock to be treated are injected in ascending or descending streams into a reactor generally comprising a fixed bed of catalyst.

The pressure employed during the selective hydrogenation reaction must be sufficient to maintain more than 60% by weight of the batch to be treated in the liquid phase in the reactor, preferably more than 80%, and more preferably more than 95% . The pressure is thus generally between, for example, 0.4 and 5 MPa, preferably greater than 1 MPa, and more preferably between 1 and 4 MPa. The hourly space velocity of the charge to be treated is between about 1 and about 20 h ^-1 (volume of charge per volume of catalyst per hour), preferably between 2 and 10 h ^-1 , very preferably between 2 and 10 h ^-1. 8 h ^-1 .
The temperature is most generally between about 50 ° C and about 250 ° C, and preferably between 80 ° C and 220 ° C, and more preferably between 100 ° C and 200 ° C, to ensure a sufficient conversion of diolefins.

The ratio of hydrogen on charge expressed in liters is generally between 3 and 50 liters per liter, preferably between 3 and 20 liters per liter.

In the case of the treatment of a catalytic cracking gasoline, it may contain up to a few% by weight of diolefins (from 0.1% to 5%). After hydrogenation, the diolefin content is generally reduced to less than 3000 ppm, and preferably less than 1500 ppm.

In order to transform the light sulfur compounds into heavy sulfur compounds, this hydrogenation step can be carried out by passing, for example, the initial carbonaceous feedstock over a catalyst capable of both hydrogenating the diolefins and converting the light sulfur compounds or the olefins into heavier sulfur compounds, or on a separate catalyst (same or different) but to achieve this transformation in the same reactor as the hydrogenation step.

Separation step of the effluent resulting from the hydrogenation step

• une coupe légère contenant une teneur en soufre résiduelle limitée et contenant les oléfines pouvant être utilisé comme charge de la pétrochimie ou incorporé dans le pool essence sans autre traitement aval visant à diminuer sa teneur en soufre,
• une coupe lourde enrichie en aromatiques par rapport à la charge et dans laquelle la majeure partie des composés soufre, initialement présent dans la charge, est concentrée.
• éventuellement une coupe intermédiaire contenant la majeure partie des produits BTX (benzène, toluène et xylène) initialement présents dans la charge.

The process according to the invention generally comprises a step of separating the effluent obtained in the hydrogenation stage in at least two sections. These cuts are:

• a light cut containing a limited residual sulfur content and containing the olefins that can be used as a petrochemical feedstock or incorporated into the gasoline pool without further downstream treatment to reduce its sulfur content,
• a heavy cut enriched in aromatics with respect to the feedstock and in which the major part of the sulfur compounds, initially present in the feed, is concentrated.
• optionally an intermediate cut containing most of the BTX products (benzene, toluene and xylene) initially present in the feed.

This separation step is preferably carried out by means of a conventional distillation / fractionation column. This fractionation column must make it possible to separate at least the light fraction of the feedstock resulting from the hydrogenation containing a small fraction of sulfur and the heavy fraction containing most of the sulfur initially present in the initial charge.

This column generally operates at a pressure of between 0.1 and 2 MPa and preferably between 0.1 and 1 MPa. The number of theoretical plates of this separation column is generally between 10 and 100 and preferably between 20 and 60. The reflux ratio, expressed as the ratio of the liquid traffic in the column divided by the distillate flow rate expressed in kg / h, is generally between 0.1 and 2, preferably greater than 0.5.

The light gasoline obtained after the separation generally contains at least 50% of C 5 olefins, and preferably at least 90%, optionally of C5 compounds, C6 olefins and C ₇ compounds.

Generally, this light fraction has a low sulfur content, ie it is not generally necessary to treat the light cut before using it as fuel.

However, in some extreme cases, softening of light gasoline may be considered.

Hydrodesulphurization step

The process according to the invention comprises a hydrodesulfurization step. This step can be carried out either directly on the initial charge or on the heavy cut obtained at the end of the separation step.

The hydrodesulfurization carried out as part of the process may be selective (with a controlled olefin saturation rate, that is to say the conservation of a portion of the olefins) or non-selective (saturation of the olefins). This step is generally carried out in at least one reactor in the presence of a catalyst comprising at least one element of group VIII.

Selective hydrodesulfurization:

Selective hydrodesulfurization can be carried out either in one step or in two steps.

We designate with 2 stages the schemes with intermediate removal of H ₂ S

• Cas d'un seul réacteur :

In the case of a one-step scheme, this step may contain one or two reactors at different operating conditions

• Case of a single reactor:

• Cas de 2 réacteurs :

The catalyst used is generally a catalyst comprising cobalt or nickel and molybdenum. This step is carried out in the presence of hydrogen, at a temperature for example between 200 ° C and 400 ° C, preferably between 220 ° C and 350 ° C under a pressure generally between 0.5 and 5 MPa, preferably between 1 and 3 MPa, and very preferably between 1.5 and 3 MPa. The The space velocity of the liquid is for example between 0.5 and approximately 10 h ^-1 (expressed in volume of liquid per volume of catalyst per hour), and preferably between 1 and 8 h ^-1 . The H ₂ / HC ratio is adjusted according to the desired hydrodesulphurization rates in the range of, for example, between 100 and 600 liters per liter, and preferably between 100 and 350 liters per liter.

• Case of 2 reactors:

The catalyst and process conditions used in the reactor ¹ are similar to that described in the case of a single reactor

In the ^2nd reactor, the catalysts used are generally catalysts comprising cobalt and molybdenum or catalysts comprising nickel.

The temperature in the 2 ^nd reactor is generally between 250 and 400 ° C and preferably between 300 and 370 ° C. The space velocity of the liquid is for example between 0.5 and about 10 h ^-1 (expressed in volume of liquid per volume of catalyst per hour), and preferably between 1 and 8 h ^-1 .

The conditions of pressure and H ₂ / HC are similar to those of the reactor ¹ to the 1 ^st step.

This configuration (and in particular the decoupling of temperatures and the use of catalyst sequencing) makes it possible to be more selective than in the configuration with a single reactor. The preservation of olefins through the HDS stage is therefore better.

• une première étape : opérée à des conditions de pression, température, LHSV et H₂/HC similaire à celle d'un schéma 1 étape avec 1 réacteur
• une deuxième étape : traite l'effluent de la 1^ére étape après élimination de l'H₂S, opérée à des conditions se situant dans les mêmes gammes que celle de la 1^ère étape.

In the case of two stages, these are:

• a first step: operated under conditions of pressure, temperature, LHSV and H ₂ / HC similar to that of a 1 stage diagram with 1 reactor
• a second step: treats the effluent of the 1 ^st step after removal of H ₂ S, operated at conditions in the same ranges as that of the 1 ^st step.

The catalyst used is generally a catalyst comprising cobalt and molybdenum in the two steps.

This configuration makes it possible to be even more selective thanks to the intermediate elimination of H ₂ S between the two stages, which reduces the partial pressure of H ₂ S.

In the case of the selective hydrodesulfurization, the conversion of the olefins by hydrogenation observed is from 5 to 95%, preferably from 15 to 85%, and very preferably from 15 to 50%.

Non-selective hydrodesulfurization:

This step is carried out in the presence of hydrogen, at a temperature for example between 200 ° C and 400 ° C, preferably between 220 ° C and 350 ° C under a pressure generally between 0.5 and 5 MPa, preferably between 1 and 3 MPa, and very preferably between 1.5 and 3 MPa. The space velocity of the liquid is for example between 0.5 and about 10 h ^-1 (expressed in volume of liquid per volume of catalyst per hour), and preferably between 1 and 8 h ^-1 . The H ₂ / HC ratio is adjusted according to the desired hydrodesulphurization rates in the range of, for example, between 100 and 600 liters per liter, and preferably between 100 and 350 liters per liter.

The main difference from selective hydrodesulphurization is the choice of catalyst. The catalyst used is generally a catalyst comprising cobalt and molybdenum or nickel and molybdenum. The catalysts used have a higher hydrogenating activity than in the case of a selective hydrodesulfurization

In the process according to the invention, the conversion of unsaturated sulfur compounds is greater than 15% and preferably greater than 90%.

In the case of non-selective hydrodesulfurization, the reduction in olefins observed is greater than 50%, preferably greater than 85%, and very preferably greater than 95%.

Step extraction of aromatic compounds:

The process according to the invention comprises a step of extracting the aromatic compounds. This extraction is either a liquid-liquid extraction or an extractive distillation using one or more solvents.

In the case of a conventional liquid-liquid extraction, the extraction is carried out using any type of solvent well known to those skilled in the art to carry out such extractions and for example solvents of sulfolane type, dimethylsulfoxide. (DMSO), dimethylformamide (DMF), N-methylpyrrolidone (NMP), N-formylmorpholine (NFM), methanol, acetonitrile and mixtures of these various solvents. The effluent obtained after the hydrodesulfurization step is contacted with the solvent in a first extraction column from which are recovered a solvent rich in aromatic compounds, and a raffinate consisting of non-aromatic compounds. The raffinate is subsequently purified in a washing column to remove residual traces of solvent. The solvent rich in aromatic compounds is conventionally first freed of the last nonaromatic compounds in a separation column, then sent to a column for recovering aromatic compounds. The solvent is recycled after regeneration while the aromatic compounds are recovered as an extract.

In the case of an extractive distillation, a non-volatile and miscible high-boiling separation solvent is used to modify the relative volatility (vapor pressure) of the constituents of a mixture whose volatility is very close. The solvent interacts differently with the different components of the mixture, thus causing a difference in the relative volatility of each component and making it possible to separate them. The technique involves sending the stream comprising the aromatic compounds with a solvent into an extractive distillation column. The non-aromatic compounds are removed from the top of the column with a small amount of solvent (which is then regenerated). The aromatic compounds are removed from the bottom of the column with the solvent. The solvent / aromatic compounds group is sent to a separation column or the purified aromatic compounds are separated from the solvent. The solvent employed is well known to those skilled in the art such as N-formylmorpholine.

• la colonne de séparation est supprimée ou alors elle comprend moins de plateaux,
• le taux de solvant /charge est compris entre 1 et 10, de préférence entre 1 et 6, et de manière très préférée entre 1 et 3,5, contrairement à une extraction classique ou le taux est compris entre 3 et 10.

One of the advantages of the invention stems from the fact that it is not necessary to have an excellent yield or a very high purity at the end of the extraction step of the aromatic compounds, contrary to the conditions of application of these technologies. in the petrochemical environment to produce aromatics with high purity and high yield. Although the octane number is better with a higher solvent rate, the quality of the products is acceptable with a lower solvent rate than that usually used by those skilled in the art. It is therefore possible to use a simplified aromatics extraction unit with respect to a conventional extraction unit. In this case preferably:

• the separation column is deleted or it has fewer trays,
• the solvent / filler content is between 1 and 10, preferably between 1 and 6, and very preferably between 1 and 3.5, unlike a conventional extraction or the rate is between 3 and 10.

The aromatic extract obtained makes it possible to remove the low octane molecules present in the feedstock and thus generally contributes to exceeding the required specifications of Octane Research Index (or RON for Research Octane Number, according to the English thermology Saxon) of 95 and Octane Engine Index (or MON for Motor Octane Number according to English terminology) 85 of the gasoline pool after remixing with other typical constituents (reformate, isomerate, ethers, ...).

The paraffinic raffinate obtained generally constitutes an excellent feedstock for a steam cracking or catalytic reforming unit and thus replaces the very expensive naphtha.

Step of separation of the raffinate obtained after extraction of the aromatic compounds

The process according to the invention may comprise a step of separating the raffinate, obtained at the step of extracting the aromatic compounds, in at least two cuts, a light cut that can be sent to the gasoline pool or to the petrochemical and a cut. heavy that can be sent to the kerosene or diesel pool.

This separation is preferably carried out by means of a conventional distillation column.

This column generally operates at a pressure of between 0.01 and 2 MPa and preferably between 0.01 and 0.5 MPa. The number of theoretical plates of this separation column is generally between 10 and 100 and preferably between 20 and 60. The reflux ratio, expressed as the ratio of the liquid traffic in the column divided by the distillate flow expressed in kg / h, is generally greater than 0.2 and preferably greater than 0.4

The following comparative examples illustrate the present invention.

Examples Example 1 (Figure 1) a) Production of a Desulphurized Catalytic Cracking Gasoline

It starts from a catalytic cracking gasoline to produce a quality gasoline at least similar to the load and a raffinate that can supply a steam cracking unit.

Catalytic cracking gasoline has the following characteristics: ASTM D86 distillation: Starting point: 35 ° C End point: 220 ° C Olefin content: 33.6% by weight
Aromatic content: 34.6% by weight
RON = 93.00
Sulfur = 3278 ppm

The initial charge (1) is desulfurized selectively on a Cobalt / Molybdenum catalyst (HR 806 type) under the following conditions: temperature: 260 ° C .; P = 2MPa, VVH = 4h ^-1 with a H ₂ / HC ratio of 200 l / l in the hydrodesulfurization unit (C).

b) Extraction of desulphurised gasoline

The effluent obtained in the hydrodesulfurization stage is sent via line (4) to an aromatic extraction unit (D) with sulfolane.

• la colonne de séparation est supprimée,
• le taux de solvant / charge est réduit à 2,7.

The unit is simplified compared to a conventional extraction unit:

• the separation column is deleted,
• the solvent / charge ratio is reduced to 2.7.

The paraffinic raffinate that circulates via the line (6) is sent partially to the gasoline pool via line (8) until an octane gasoline equal to or greater than the charge.

The excess is sent to the steam cracker via line (7).

c) Quality of products

Effluent 1 4 9 6 8 7 10 olefins
%weight 33.60 16.80 12.50 17.78 17.78 17.78 14.33 aromatic
%weight 34.60 34.60 61,00 28.61 28.61 28.61 49.80 compounds
saturated
%weight 31.80 48.60 26.50 53.62 53.61 53.61 35.90 RON 93,00 85.90 98.40 83,00 83,00 83,00 93.10 MY 81.60 80.30 87,00 78.80 78.80 78.80 84.18 Sulfur (ppm) 3278.0 7.0 11.3 6.0 6.0 6.0 9.5 Flow rate (kg / h) 100000 100000 18500 81500 9780 71720 28280 Density 0761 0761 0757 0762 0762 0762 0758

Under these conditions, a gasoline is obtained whose octane number is slightly increased (RON: 93.10) relative to that of the starting charge (RON: 93.00). The sulfur content is very low (9.5 ppm) and has greatly decreased compared to that of the feedstock (3278 ppm). The raffinate is a good steam cracker load.

Example 2 (Figure 2 - selective mode) a) Production of a Desulphurized Catalytic Cracking Gasoline

It starts from a catalytic cracking gasoline on which it is desired to recover a raffinate for sending to steam cracking while improving the quality of the gasoline produced.

The catalytic cracking gasoline circulating via line (1) has the following characteristics: ASTM D86 distillation: Starting point: 35 ° C End point: 140 ° C Olefin content: 34.5% by weight
Aromatic content: 19.2% by weight
RON = 91.40
Sulfur = 1112 ppm

It is treated on a nickel-Molybdenum selective hydrogenation catalyst (HR 845).

• Température : 160°C ; Pression : 2MPa ;VVH=4h^-1 avec un rapport H₂/HC de 5 l/l.
• L'effluent circulant via la ligne (2) est ensuite fractionné sur une colonne (étape B).

Gasoline is treated under the following conditions:

• Temperature: 160 ° C; Pressure: 2MPa; VVH = 4h ^-1 with a H ₂ / HC ratio of 5 l / l.
• The effluent flowing via the line (2) is then fractionated on a column (step B).

A cut with a boiling point ASTM D86 of 60 ° C desulphurated circulating via the line (5) is recovered at the top. In bottom, the ASTM D86 distillation interval cut 60-140 ° C (3) flowing via line (3) is desulphurized selectively over a CoMo catalyst (HR 806) under the following conditions: Temperature: 260 ° C; P = 2MPa, VVH = 4h ^-1 with an H ₂ / HC ratio of 200 l / l.

b) Extraction of desulphurised gasoline

The effluent of the hydrodesulfurization flowing via line (4) is sent to an extraction of sulfolane aromatic.

• la colonne de séparation est supprimée,
• le taux de solvant /charge est réduit à 2,7

The unit is simplified compared to a conventional extraction unit:

• the separation column is deleted,
• the solvent / charge ratio is reduced to 2.7

The raffinate flowing via the line (6) is sent is sent partly to the gasoline pool via the line (8) to obtain an octane gasoline equal to or greater than the load. The excess is sent to the steam cracker via line (7). Extract (9) is sent to the essence pool.

c) Quality of products

Effluent 1 5 3 4 9 6 8 7 12 olefins
%weight 34.50 46.40 28.09 14,05 9.30 15.28 15.28 15.28 31.74 aromatic
%weight 19.2 0.9 29.1 29.1 60.0 21.0 21.0 21.0 18.1 compounds
saturated
%weight 46.3 52.7 42.9 56.9 30.7 63.7 63.7 63.7 50.2 RON 91.40 94,40 89.60 83.90 95.90 81,00 81,00 81,00 92,00 MY 81,00 83.50 79.50 77.60 83.50 76.20 76.20 76.20 82,00 Sulfur (ppm) 1,112.0 9.0 1705.0 9.0 13.1 7.9 7.9 7.9 9.7 Flow rate (kg / h) 100000 35000 65000 65000 13390 51610 12902.5 38707.5 61293 Density 0.74 68 0.78. 0.78 0.82 0.76 0.76 0.76 0.73

Under these conditions we obtain a gasoline whose octane number is slightly increased (RON: 92.00) compared to that of the starting charge (RON: 91.40). The sulfur content is very low (<10 ppm) and has greatly decreased compared to that of the feedstock (1112 ppm). The raffinate is a good steam cracker load.

Example 3 (Figure 2 - non-selective mode) a) Production of a Desulphurized Catalytic Cracking Gasoline

It starts from a catalytic cracking gasoline on which it is desired to recover a raffinate for sending to steam cracking while improving the quality of the gasoline produced.

The catalytic cracking gasoline circulating via line (1) has the following characteristics: ASTM D86 distillation: Starting point: 35 ° C End point: 140 ° C Olefin content: 34.5% by weight
Aromatic content: 19.2% by weight
RON = 91.40
Sulfur = 1112 ppm

It is treated on a nickel-Molybdenum selective hydrogenation catalyst (HR 845).

• Température : 160°C ; Pression : 2MPa ;VVH=4h^-1 avec un rapport H₂/HC de 5 l/l.
• L'effluent (2) est ensuite fractionné (unité B). On récupère en tête une coupe avec un point final d'ébullition ASTM D86 de 60°C désulfurée circulant via la ligne (5). En fond, la coupe d'intervalle de distillation ASTM D86 60-140°C circulant via la ligne (3) est désulfurée (unité C) et hydrogénée totalement sur un catalyseur CoMo dans les conditions suivantes :Température :260°C ; P=2MPa, VVH=4h^-1 avec un rapport H₂/HC de 200 l/l.
• Les oléfines de l'essence lourde de craquage catalytique ont été pratiquement totalement hydrogénées.

Gasoline is treated under the following conditions:

• Temperature: 160 ° C; Pressure: 2MPa; VVH = 4h ^-1 with a H ₂ / HC ratio of 5 l / l.
• The effluent (2) is then fractionated (unit B). A cut with a boiling point ASTM D86 of 60 ° C desulphurated circulating via the line (5) is recovered at the top. In the bottom, the ASTM D86 60-140 ° C distillation gap section flowing via line (3) is desulphurized (unit C) and completely hydrogenated over a CoMo catalyst under the following conditions: Temperature: 260 ° C; P = 2MPa, VVH = 4h ^-1 with an H ₂ / HC ratio of 200 l / l.
• The olefins of the catalytic cracked heavy gasoline were virtually completely hydrogenated.

b) Extraction of desulphurised gasoline

The effluent of the hydrodesulfurization flowing via line (4) is sent to an extraction of sulfolane aromatic.

• la colonne de séparation est supprimée,
• le taux de solvant /charge est réduit entre 2 et 3. Il est fixé ici à 2,5.

The unit is simplified compared to a conventional extraction unit:

• the separation column is deleted,
• the solvent / charge ratio is reduced between 2 and 3. It is set here at 2.5.

The raffinate flowing via the line (6) is sent is sent partly to the gasoline pool via the line (8) to obtain an octane gasoline equal to or greater than the load. The excess is sent to the steam cracker via line (7). Extract (9) is sent to the essence pool.

c) Quality of products

Effluent 1 5 3 4 9 6 8 7 12 Effluent 34.50 46.40 28,10 2.80 1.80 3.10 3.10 3.10 28,70 olefins
%weight 19.2 0.9 29.1 29.1 68.3 19.1 19.1 19.1 19.3 aromatic
%weight 46.3 52.7 42.9 68.1 29.9 77.9 77.9 77.9 52.0 RON 91.40 94,40 89.60 78.20 96.50 73.90 73.90 73.90 91.40 MY 81,00 83.50 79.50 75.70 84,00 73.70 73.70 73.70 82,00 Flow rate (kg / h) 1,112.0 9.0 1705.9 9.0 13.3 7.9 7.9 7.9 9.8 Effluent 100000 35000 65000 65000 13195 51805 10361 41444 58556 olefins
%weight 135.1 51.4 83.8 83.8 15.9 67.9 13.6 54.0 81.0 compounds
saturated
%weight 0.74 0.68 0.78 0.78 0.83 0.76 0.76 0.76 0.72

Under these conditions, a gasoline with the same octane number as the charge (RON: 91.4) is obtained. The sulfur content is very low (<10 ppm) and has greatly decreased compared to that of the feedstock (1112 ppm).

Raffinate is a good steam cracker feed and even better than in the previous example because it contains less olefins.

Example 4 (Figure 2 - non-selective mode) a) Production of a Desulphurized Catalytic Cracking Gasoline

It starts from a catalytic cracking gasoline on which it is desired to recover a gasoline of maximum octane number and a raffinate of very good quality for sending to the steam cracker while improving the quality of the gasoline produced.

Catalytic cracking gasoline has the following characteristics: ASTM D86 distillation: Starting point: 35 ° C End point: 140 ° C Olefin content: 34.5% by weight
Aromatic content: 19.2% by weight
RON = 91.40
Sulfur = 1112 ppm

• Température : 160°C ;Pression : 2MPa ;VVH=4h^-1 avec un rapport H₂/HC de 5l/l.
• L'effluent (2) est ensuite fractionné (unité B). On récupère en tête une coupe avec un point final d'ébullition ASTM D86 de 60°C désulfurée circulant via la ligne (5). En fond, la coupe d'intervalle de distillation ASTM D86 60-140°C circulant via la ligne (3) est désulfurée (unité C) et hydrogénée totalement sur un catalyseur CoMo dans les conditions suivantes : température : 260°C ; P=2MPa, VV/H=4h^-1 avec un rapport H₂/HC de 200 l/l.
• Les oléfines de l'essence lourde de craquage catalytique ont été pratiquement totalement hydrogénées.

It is treated on a nickel-Molybdenum selective hydrogenation catalyst (HR 845) under the following operating conditions:

• Temperature: 160 ° C, Pressure: 2MPa, VVH = 4h ^-1 with a H ₂ / HC ratio of 5l / l.
• The effluent (2) is then fractionated (unit B). A cut with a boiling point ASTM D86 of 60 ° C desulphurated circulating via the line (5) is recovered at the top. In bottom, the ASTM D86 60-140 ° C distillation gap section flowing via line (3) is desulphurized (unit C) and fully hydrogenated on a CoMo catalyst under the following conditions: temperature: 260 ° C; P = 2MPa, VV / H = 4h ^-1 with a H ₂ / HC ratio of 200 l / l.
• The olefins of the catalytic cracked heavy gasoline were virtually completely hydrogenated.

b) Extraction of desulphurised gasoline

The effluent of the hydrodesulfurization flowing via the line (4) is sent to a sulfolane aromatic extraction (unit D).

The unit is identical to conventional aromatic extraction units. The solvent / charge ratio is 6

The raffinate (7) is sent to steam cracking. Because of its almost completely paraffinic nature, it is an excellent steam cracker feedstock.

Extract (9) is sent to the essence pool.

The gasoline produced has an octane number which is very much improved with respect to the charge.

c) Quality of products

Effluent 1 5 3 4 9 7 12 Olefins% by weight 34.5 46.4 28.1 2.8 1.3 3.37 31.3 Aromatic% weight 19.2 0.9 29.0 29.0 85.2 8.12 29.2 saturated compounds% weight 46.3 52.7 42.8 68.1 13.5 88.51 39.6 RON 91.40 94,40 89.60 78.20 102.80 69.70 96.90 MY 81,00 83.50 79.50 75.70 91.80 70,10 85.90 Sulfur (ppm) 1112 10 1705 10 11 10 10 Flow (kg / h) 100000 35000 65000 65000 17654 47346 52654 Density 0.74 0.682 0.776 0.776 0.823 0.760 0.723

Under these conditions, a gasoline is obtained whose octane number is higher (RON: 96.90) than that of the starting charge (RON: 91.40). The sulfur content is very low (<10 ppm) and has greatly decreased compared to that of the feedstock (1112 ppm).

Example 5 (Figure 3) a) Production of a Desulphurized Catalytic Cracking Gasoline

It starts from a catalytic cracking gasoline on which we want to send 20% to the diesel pool while producing a gasoline quality at least similar to the load and producing a raffinate that can supply a steam cracker.

Catalytic cracking gasoline has the following characteristics ASTM D86 distillation: Starting point: 35 ° C End point: 220 ° C Olefin content: 33.6% by weight
Aromatic content: 34.6% by weight
RON = 93.00
Sulfur = 3278 ppm

• Température : 160°C ; Pression : 2MPa ;VVH=4h^-1 avec un rapport H₂/HC de 5l/l.

It is treated on a nickel-molybdenum selective hydrogenation catalyst (type HR 845) under the following operating conditions

• Temperature: 160 ° C; Pressure: 2MPa; VVH = 4h ^-1 with a H ₂ / HC ratio of 5l / l.

The effluent obtained at the end of the selective hydrogenation circulating via line (2) is then fractionated on a fractionation column (B). At the top of the column is recovered a section with a boiling point ASTM D86 of 60 ° C desulfurized circulating via the line (5).

In bottom, the section with a distillation interval ASTM D86 60-220 ° C flowing via the line (3) is desulfurized (unit C) selectively on a cobalt / molybdenum catalyst (HR 806 type) under the following operating conditions: 260 ° C; P = 2MPa, VV / H = 4 ^-1 with a H ₂ / HC ratio of 200 l / l

b) Extraction of desulphurised gasoline

• le taux de solvant / charge est réduit à 3,5.

The effluent of the hydrodesulfurization step (4) is sent to an aromatic sulfolane extraction. The unit is simplified compared to a conventional extraction unit:

• the solvent / charge ratio is reduced to 3.5.

The extraction raffinate circulating via the line (6) is then distilled. The heaviest fraction (with a desulfurized ASTM D86 150-220 ° C distillation range) is sent to the diesel pool via line (13).

The light raffinate (having an ASTM D86 distillation endpoint of 150 ° C) flowing via the line (14) is partially sent to the gasoline pool (15) until an octane gasoline equal to or greater than the charge.

The excess is sent to the steam cracker (16).

c) Quality of products

Effluent 1 5 3 4 9 6 14 13 15 16 17 Olefin olefins 33.6 61.6 26.6 13.3 8.3 14.8 18.1 8.0 18.1 18.1 32.1 aromatic
%weight 34.6 0.0 43.3 43.3 82.9 31.1 12.9 68.9 12.9 12.9 34.4 compounds
saturated
%weight 31.8 38.4 30.2 43.5 8.8 54.1 69.0 23.1 69.0 69.0 33.5 RON 93,00 95,00 92.40 87,00 103.40 81.80 83,00 79.10 83,00 83,00 95.70 MY 81.60 83.20 81.10 79.30 92,00 75.30 75.00 76,00 75.00 75.00 84.80 Sulfur (ppm) 3278 8 4096 8 10 7 11 <10 11 11 9 Flow rate (kg / h) 100000 20000 80000 80000 18800 61200 41347 19853 10337 31010 49137 Density 0.76 0.66 0.79 0.79 0.77 0.79 0.77 0.85 0.77 0.77 0.72

Under these conditions, a gasoline is obtained whose octane number is increased (RON: 95.70) relative to that of the starting charge (RON: 93.00). The sulfur content is very low (<10 ppm) and has greatly decreased compared to that of the feedstock (3278 ppm).

The cut with a distillation interval ASTM D86 150-220 will be sent to the diesel pool or kerosene with if necessary a hydrotreatment.

The light raffinate is a good load of steam cracker

The set of examples, illustrating the various variants of the invention, demonstrates that the process according to the invention makes it possible to conserve and in certain cases increase the octane number of the hydrocarbon feed obtained, while by significantly decreasing its sulfur content.

The quantity of gasoline is also greatly reduced in favor of a better raffinate for petrochemicals.

It should be obvious to those skilled in the art that the present invention should not be limited to the details given above and allow embodiments in many other specific forms without departing from the scope of the invention. . Therefore, the present embodiments should be considered by way of illustration, and may be modified without departing from the scope defined by claims.

Claims (8)

1. Process for the production of a hydrocarbon fraction with a high octane number and a low sulfur content from a hydrocarbon feedstock, comprising at least the following stages:

   - a stage for selective hydrogenation of diolefins of the hydrocarbon feedstock,

   - a stage for separating the effluent that is obtained in the selective hydrogenation stage that leads to at least two fractions, a light hydrocarbon fraction and a heavy hydrocarbon fraction,

   - a hydrodesulfurization stage of the heavy hydrocarbon fraction,

   - at least one stage for extracting aromatic compounds over all or part of the effluent that is obtained from the hydrodesulfurization stage, whereby said extraction leads to a paraffin-enriched raffinate relative to the feedstock and an aromatic compound-enriched extract that is sent to a gasoline pool, in which the light hydrocarbon fraction is sent in a mixture with the aromatic extract and a portion of the paraffinic raffinate to the gasoline pool and in which another portion of the paraffinic raffinate is sent to a steam-cracking unit to produce light olefins.
2. Process according to claim 1, in which the hydrocarbon feedstock is obtained from a catalytic cracking unit or a thermal cracking unit or a coking unit or a visbreaking unit.
3. Process according to one of claims 1 or 2, in which the hydrodesulfurization stage is selective and carried out in one stage in one or two reactors or in two stages.
4. Process according to one of claims 1 or 2, in which the hydrodesulfurization stage is non-selective.
5. Process according to claim 1, in which at least a portion of the paraffinic raffinate is sent to a separation stage that leads to a light raffinate that is sent to the gasoline pool, in a mixture with the aromatic extract, and to a steam-cracking unit and to a heavy raffinate that is sent to the diesel pool or to the kerosene pool.
6. Process according to one of claims 1 to 5, in which the separation step further leads to an intermediate hydrocarbon fraction which is sent as a feedstock to the hydrodesulfurization stage.
7. Process according to one of claims 1 to 6, in which the aromatic extraction stage is a liquid-liquid extraction or an extractive distillation.
8. Process according to claim 7, in which the stage for extracting aromatic compounds is a liquid-liquid extraction with a solvent ratio of between 1.5 and 5.

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