FR2821852A1 - PROCESS FOR PRODUCING A DESULFURIZED ESSENCE FROM A PETROL CUTTING CONTAINING CONVERSION ESSENCE - Google Patents

Abstract

The invention relates to a method for producing low-sulphur petrol from an initial petrol containing sulphur compounds comprising the following steps: a) the selective hydrogenation of the non-aromatic polyunsaturated compounds present in the initial petrol; b) increasing the molecular weight of the light sulphur products that were initially present in the petrol at the beginning of step b); c) the alkylation of at least part of the sulpur compounds present in the product resulting from step b); d) the fractionation of the petrol resulting from step c) into at least two fractions, one of said fractions being practically free of sulphur compounds and the other containing a larger proportion of sulphur compounds (heavy petrol); e) the catalytic treatment of the heavy petrol to transform the sulphur compounds in conditions that allow the, at least partial, decomposition or hydrogenation of said sulphur compounds.

Description

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L'invention concerne un schéma de désulfuration d'essences de conversion et en particulier d'essences en provenance du craquage catalytique, du craquage catalytique en lit fluide (FCC), d'un procédé de cokéfaction (coking dans la langue de Shakespeare), d'un procédé de viscoréduction (visbreaking dans la langue de Shakespeare), d'un procédé de pyrolyse. Ce procédé pourra également traiter des essences de distillation directe (straight run en anglais) en mélange avec au moins une

des essences citées ci-dessus. Le procédé de la présente invention permet d'atteindre de forts taux de désulfuration en limitant la perte en octane due à la saturation des oléfines observées lors des réactions d'hydrodésulfuration. L'invention concerne un procédé de production d'essence à faible teneur en soufre comprenant une hydrogénation, une étape de transformation des composés soufrés, une étape d'alkylation des composés soufrés non transformés dans l'étape précédente, un fractionnement en une fraction légère et en au moins une fraction lourde et éventuellement une ou plusieurs fractions intermédiaires, et une hydrodésulfuration d'une fraction lourde etlou d'une fraction intermédiaire. Ce procédé permet de valoriser une coupe essence comprenant éventuellement en outre des hydrocarbures à deux trois ou quatre atomes de carbone, en réduisant la teneur en soufre total de ladite coupe à de très faibles niveaux compatibles avec les spécifications actuelles ou à venir. Technical field of the invention

The invention relates to a desulfurization scheme of conversion gasolines and in particular of gasoline from catalytic cracking, fluid catalytic cracking (FCC), a coking process (coking in the language of Shakespeare), of a visbreaking process (visbreaking in the language of Shakespeare), a pyrolysis process. This process can also treat straight-run gasolines in a mixture with at least one

species listed above. The method of the present invention achieves high desulfurization rates by limiting the octane loss due to the saturation of olefins observed during hydrodesulfurization reactions. The invention relates to a process for the production of low-sulfur gasoline comprising a hydrogenation, a step of converting the sulfur compounds, a step of alkylation of the unprocessed sulfur compounds in the previous step, fractionation into a light fraction. and at least one heavy fraction and optionally one or more intermediate fractions, and a hydrodesulfurization of a heavy fraction and / or an intermediate fraction. This method makes it possible to upgrade a gasoline cutoff optionally further comprising hydrocarbons having two three or four carbon atoms, reducing the total sulfur content of said cut to very low levels compatible with current or future specifications.

ou craquage catalytique en lit fluidisé). La désuifuration (l'hydrodésulfuration) des essences et principalement des essences de FCC est donc d'une importance évidente pour l'atteinte des spécifications. This desulphurization is also carried out without substantial reduction in the yield of gasoline and minimizing the reduction of the octane number. The production of reformulated gasolines that meet the new environmental standards notably requires that their concentration be reduced slightly. in olefins but significantly their concentration of sulfur. The conversion gasolines and more particularly that resulting from catalytic cracking, which can represent 30 to 50% of the gasoline pool, have high olefin and sulfur contents. The sulfur present in the reformulated gasolines is attributable, to nearly 90%, to the catalytic cracking gasoline (FCC, Fluid Catalytic Cracking

or catalytic cracking in a fluidized bed). The desulphurisation (hydrodesulfurization) of the species and mainly FCC species is therefore of obvious importance for the achievement of the specifications.

The hydrodesulfurization of the feedstock sent to catalytic cracking leads to gasolines typically containing 100 ppm of sulfur. However, the catalytic cracking feed hydrotreating units operate under severe conditions.

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 temperature and pressure, which implies a high consumption of hydrogen and a high investment. In addition, the entire charge must be desulfurized, resulting in the processing of very large load volumes.

The hydrodesulphurization of cracking gasolines, when it is carried out under standard conditions known to those skilled in the art, makes it possible to reduce the sulfur content of the cut. However, this method has the major disadvantage of causing a very significant drop in the octane number of the cut, due to the saturation of all the olefins during the hydrotreatment.

The teaching of the prior art is extremely diffuse and a great many solutions have been envisaged to obtain a desulphurised gasoline that meets the standards currently in force and the foreseeable future standards for the years 2005-2010 both in terms of sulfur content. as regards the content of aromatic compounds and value of the desired octane number. Thus, for example, the process described in US Pat. No. 4,131,537, which teaches the advantage of splitting gasoline into several cuts, preferably three, depending on their point of contact. boiling, and desulfurize under conditions that may be different and in the presence of a catalyst comprising at least one Group VIB metal and / or Voll group. It is stated in this patent that the greatest benefit is obtained when the gasoline is split into three cuts, and when the cut having intermediate boiling points is treated under mild conditions.

It is also possible to cite the teaching of patent application EP-A-0 725 126 which describes a process for the hydrodesulfurization of a cracking gasoline in which the gasoline is separated into a plurality of fractions comprising at least a first fraction. rich in easily desulfurized compounds and a second fraction rich in compounds difficult to desulphurize. Before carrying out this separation, it is first necessary to determine the distribution of the sulfur compounds by means of analyzes. These analyzes are necessary to select the equipment and the separation conditions.

In this application it is thus indicated that a light fraction of cracking gasoline sees its olefin content and octane drop significantly when it is desulfurized without being fractionated. On the other hand, the fractionation of said light fraction in 7 to 20 fractions followed by analyzes of the sulfur and olefin contents of these fractions makes it possible to determine the fraction or fractions richest in sulfur compounds which are then desulfurized simultaneously or separately and mixed. other desulfurized fractions or not. Such a procedure is complex and must be reproduced with each change in the composition of the gasoline to be treated.

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Il a également été proposé, par exemple dans le brevet US-A-5, 290, 427, des procédés d'hydrotraitement des essences consistant à fractionner l'essence, puis à introduire les fractions à différents niveaux d'un réacteur d'hydrodésulfuration et à convertir les fractions désulfurées sur une zéolithe ZSM-5, afin de compenser la perte d'octane enregistrée au moyen d'une isomérisation. Cette isomérisation est accompagnée d'un craquage de l'essence vers des composés plus légers.

It has also been proposed, for example in US Pat. No. 5,290,427, methods for hydrotreating gasolines consisting of splitting the gasoline and then introducing the fractions at different levels of a hydrodesulfurization reactor. and converting the desulfurized moieties to a ZSM-5 zeolite to compensate for the recorded octane loss by means of isomerization. This isomerization is accompanied by a cracking of gasoline towards lighter compounds.

In these processes, the gasolines to be treated generally have an initial point greater than 70 ° C., and again it is necessary to treat the light gasoline separately (fraction corresponding to compounds with a boiling point of between C5 hydrocarbons having 5 atoms. of carbon and 70 C) for example by means of a softening.

According to the teachings of US Pat. No. 5,599,441, the process for the desulphurization of a naphtha fraction comprising an olefinic gasoline comprises a step of increasing the weight of sulfur compounds by alkylation followed by a step of splitting the gasoline into two slices. light petrol being depleted of sulfur.

According to the teachings of US Pat. No. 6,024,865, the process for producing desulphurized gasoline comprises separating the gasoline into a light gasoline and a heavy gasoline. The light gasoline is sent to a reactor for increasing the sulfur compounds by alkylation. The heavy gasoline additive reactive olefins is sent to a reactor for increasing the sulfur compounds by alkylation.

The heavy gasoline and the light gasoline are mixed and then sent to a distillation which makes it possible to recover, at the head, a gasoline depleted in sulfur.

According to the teaching of EP-A-1,077,247 of the Applicant the gasoline to be desulphurized is treated in a process comprising a step a1) of selective hydrogenation of the diolefinic compounds, optionally at least a step a2) aimed at increasing the molecular weight of the light sulfur products present in the initial gasoline to be desulphurized, at least one step b) of separation of the gasoline obtained at the exit of step a1) and / or a2) in two distinct sections, one of which is lightly practically free from sulfur and containing the lighter olefins of the initial gasoline and the other heavy cut containing most of the sulfur compounds present in the initial gasoline and / or sulfur compounds from step a2), at least one c) treatment step of the heavy cut to break down or hydrogenate unsaturated sulfur compounds present in this section and in particular cyclic sulfur compounds or aromatic under limited hydrogenation conditions of the olefins present in this section and at least one step

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d) de l'essence issue de l'étape c) permettant de décomposer les composés soufrés insaturés non transformés dans l'étape c) et les composés soufrés saturés linéaires et/ou cycliques présents dans cette essence issue de l'étape c) avec une hydrogénation limitée des oléfines présentes. L'application de ce procédé entraîne une limitation de la température en tête de la colonne de fractionnement pour pouvoir obtenir une fraction de tête ne contenant pratiquement pas de soufre et en particulier ne contenant pas de thiophène. Cette limitation est ainsi largement pénalisante au niveau de la mise en oeuvre de l'ensemble du procédé puisque la fraction récupérable en tête de la colonne de fractionnement est limitée en température et donc en quantité ce qui, par ailleurs entraîne une augmentation de la fraction lourde à retraiter ensuite en vue de diminuer sa teneur en soufre.

d) gasoline from step c) for decomposing unsubstituted sulfur compounds not transformed in step c) and saturated sulfur compounds linear and / or cyclic present in this gasoline from step c) with limited hydrogenation of the olefins present. The application of this process results in a temperature limitation at the top of the fractionation column to obtain a head fraction containing substantially no sulfur and in particular not containing thiophene. This limitation is thus largely disadvantageous in the implementation of the entire process since the fraction recoverable at the top of the fractionation column is limited in temperature and therefore in quantity which, moreover, causes an increase in the heavy fraction. to be reprocessed in order to reduce its sulfur content.

The present invention makes it possible to produce a desulphurized gasoline while limiting the octane loss by desulfurization. The scheme of the present invention differs from conventional desulfurization schemes which are based on total gasoline desulfurization. In some cases these schemes provide for a separation of the gasoline into at least two sections: a section containing light gasoline and a section containing heavy gasoline, that is to say a gasoline with a final boiling point greater than that of light petrol.

The heavy gasoline is desulfurized, for example by treatment with hydrogen or by absorption of sulfur compounds. The schemes comprising a hydrogen treatment lead to a high saturation of the olefins, and consequently to a high loss of octane. The light gasoline can be desulphurized under mild conditions by hydrodesulfurization, washing with a basic solution or adsorption on solid, or softened by an oxidation process such as for example the Merox process of Universal Oil Product (UOP) which can be extractive.

Some schemes only desulphurize heavy gasoline, the sulfur compounds usually present in light gasoline (mercaptans) having been previously weighed upstream of a distillation or fractionation zone (splitter in the language of Shakespeare).

As regards the processes for increasing the sulfur compounds by alkylation presented above, they make it possible to produce a light desulfurized gasoline, the heavy gasoline concentrating the heavy sulfur compounds and increased by alkylation.

These processes therefore do not make it possible to desulphurize the entire gasoline cut of

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 conversion and particularly that resulting from catalytic cracking units. In addition, the processes for increasing the weight of sulfur compounds by alkylation are based on acid catalysis. The life of the catalyst can be limited by the presence of diolefins and basic compounds (mainly nitrogen) in the gasoline to be treated.

SUMMARY OF THE INVENTION The present invention relates to a process for the production of gasolines with a low sulfur content, which makes it possible to recover the whole of a petrol fraction containing sulfur, preferably a gasoline catalytic cracking or coking fraction (coking). according to English terminology), or pyrolysis, or visbreaking (visbreaking according to English terminology), possibly mixed with a straight-run gasoline, and reduce the sulfur content in said gasoline cut at very low levels, without decreasing gasoline yield while minimizing the octane reduction due to the hydrogenation of olefins.

The feedstock of the process according to the invention may also optionally comprise, in addition to a gasoline cut, a C4-cut comprising hydrocarbons containing two, three or four carbon atoms.

The present invention relates to a process for producing low sulfur gasolines from an initial gasoline containing at least 150 parts per million by weight (ppm), often at least 200 ppm and most often at least 300 ppm of sulfur compounds comprising at least the following steps: a step a) of selective hydrogenation of the nonaromatic polyunsaturated compounds present in the initial gasoline, at least one step b) aimed at increasing the molecular weight of light sulfur products mainly from those which are in the form of mercaptans having 1 to 6 carbon atoms in their molecules and sulfides often having 2 to 6 carbon atoms in their molecules initially present in the gasoline introduced in step a) and / or those contained in the product resulting from step a), at least one step c) of alkylation of at least a part of the sulfur compounds, mainly of those in the form of thiophé compounds present in the product from step b) to obtain sulfur compounds of higher molecular weight,

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au moins une étape d) de fractionnement de l'essence issue de l'étape c) en au moins deux fractions, une première fraction pratiquement dépourvue de soufre et contenant les oléfines les plus légères de l'essence initiale non converties à l'étape c), (essence légère), au moins une autre fraction, plus lourde que ladite première fraction, enrichie en composés soufrés et de préférence au moins une fraction dite lourde contenant la majeure partie des composés soufrés présents dans l'essence issue de l'étape c) (essence lourde), et au moins une étape e) de traitement d'au moins l'une des fractions plus lourde issue de l'étape d) sur un catalyseur permettant de décomposer au moins partiellement les composés soufrés. De préférence au cours de cette étape e) on traite la fraction

dite lourde séparée à l'étape d) Dans les étapes b) et c), le terme"principalement"signifie qu'au cours de l'étape concernée on convertit au moins 50 % des composés soufrés qui sont sous la forme des composés de type indiqué.

at least one step d) fractionation of the gasoline from step c) into at least two fractions, a first fraction substantially free of sulfur and containing the lighter olefins of the original gasoline not converted to step c), (light gasoline), at least one other fraction, heavier than said first fraction, enriched in sulfur compounds and preferably at least one so-called heavy fraction containing most of the sulfur compounds present in the gasoline resulting from the step c) (heavy gasoline), and at least one step e) of treating at least one of the heavier fractions resulting from step d) on a catalyst for at least partially decomposing the sulfur compounds. Preferably during this step e) the fraction is treated.

In step b) and c), the term "mainly" means that during the step in question at least 50% of the sulfur compounds which are in the form of type indicated.

Often step e) is a step of treating at least one of the heavier fractions separated in step d) on a catalyst for at least partially decomposing the sulfur compounds carried out under conditions where the hydrogenation of the olefins on this catalyst is limited.

permettant de décomposer au moins partiellement les composés soufrés non transformés au cours de l'étape e) avec une hydrogénation limitée des oléfines, et préférentiellement de décomposer les composés soufrés insaturés et les composés soufrés saturés linéaires et/ou cycliques non transformés au cours de l'étape e) avec une hydrogénation limitée des oléfines. According to a preferred embodiment of the invention, the treatment of at least one of the heavier fractions resulting from step d) and preferably heavy gasoline is carried out in two steps: at least one step e) treating at least one of the heavier fractions and preferably heavy gasoline separated in step d) on a catalyst for at least partially decomposing the sulfur compounds, under conditions where the hydrogenation olefins on this catalyst is limited, and at least one step f) of treating the product obtained in step e), without removing the H 2 S formed during this step e), on a catalyst and under conditions

for at least partially decomposing the non-transformed sulfur compounds in step e) with a limited hydrogenation of the olefins, and preferentially decomposing the unsaturated sulfur compounds and the saturated linear and / or cyclic sulfur compounds which are not converted during the course of the process. step e) with limited hydrogenation of the olefins.

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 For the purposes of the present description, the term "polyunsaturated compounds" covers diolefinic hydrocarbon compounds, that is to say compounds containing two double bonds, hydrocarbon compounds containing more than two double bonds but not aromatic, and hydrocarbon compounds containing at least one triple bond present. in the initial essence. Most often the initial gasoline contains as polyunsaturated compounds essentially diolefinic compounds. As used herein, the low sulfur gasoline that is obtained is a gasoline containing less than 150 ppm by weight, often less than 100 ppm and most often less than 80 ppm by weight sulfur.

Stage (b) of transformation of the light sulfur compounds usually mainly concerns the conversion of saturated sulfur compounds having a boiling point below 120oC. This step may optionally be carried out simultaneously in step a) on all or part of the initial gasoline, in the same reactor or in a different reactor. It can also be carried out separately on all or part of the hydrogenated gasoline in step a). In this step b), thiophene and thiophene compounds are poorly processed. Thus, this step a) of hydrogenation of the unsaturated compounds and step b) aimed at increasing the molecular weight of the saturated light sulfur compounds initially present in the gasoline introduced in step a) are optionally carried out simultaneously in a single reaction zone. containing one or more beds of a single catalyst.

Step c) is an alkylation step of the sulfur compounds usually belonging to the group comprising thiophene, the thiophene compounds and the mercaptans present in the product resulting from step b). The mercaptans possibly present are either those formed in step a) and / or b), or those present in the initial gasoline and not converted in step a) and / or b). This step can be carried out in one or more reactors in series or in parallel. In the case of a device comprising several reactors in series, the first reactor can act as a guard bed intended to retain the basic compounds possibly present in the starting gasoline. These basic compounds can also be at least partly removed before the introduction of the gasoline in the hydrogenation step a) of the polyunsaturated compounds.

This removal is preferably carried out by treatment with an acidic aqueous solution. The operating conditions can be adjusted so that a portion of the olefins of the starting gasoline is converted into branched long olefins by addition reactions between olefins. Similarly, the operating conditions can be adjusted so that a portion of the aromatics are increased by alkylation with olefins.

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 Step d) fractionation of the gasoline obtained at the end of step c) comprises the fractionation into at least two fractions (or cuts), a light fraction preferably substantially free of sulfur and containing the olefins most light weight of the initial gasoline (light gasoline or light fraction), and a heavy fraction in which preferably most of the sulfur compounds initially present in the initial gasoline and / or formed during steps a), b) and c ) is concentrated (gasoline or heavy fraction). It is also possible to separate the gasoline obtained in step c) in addition to two fractions, that is to say for example a light fraction, at least an intermediate fraction and a heavy fraction. In this case, the intermediate fraction (s) can be sent to a catalytic reforming unit usually after a thorough desulfurization step.

Stage e) of treatment of the heavy gasoline and / or of an intermediate fraction containing a proportion of sulfur compounds very much greater than that contained in the light fraction is a step of treating this fraction on a catalyst for decomposing at least partially sulfur compounds, especially cyclic sulfur compounds, or even aromatic such as for example thiophene compounds, by placing under conditions where the hydrogenation of olefins on this catalyst is limited.

Stage f) is a stage of treatment of the product obtained in stage e), without elimination of the H 2 S formed during this stage e), on a catalyst and under conditions making it possible to decompose or hydrogenate at less partially sulfur compounds not transformed during step e), and preferably to decompose or hydrogenate unsaturated sulfur compounds and saturated sulfur compounds linear and / or cyclic unprocessed during step e) and particularly thiophene compounds and mercaptans, with limited hydrogenation of olefins.

Steps e) and f) are most often carried out in at least two successive and distinct reaction zones. The catalytic treatments carried out during steps e) and f) can be carried out either in a single reactor containing the two catalysts, or in at least two different reactors. When the treatment is carried out using two reactors, the latter two are placed in series, the second reactor preferably treating integrally the effluent at the outlet of the first reactor, preferably without separation of the liquid and the gas between the first and the second reactor. the second reactor. It is also possible to use several reactors in parallel or in series for one and / or the other of the steps e) and / or f).

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Par ailleurs, il n'est pas nécessaire d'éliminer l'H2S formé au cours de l'étape e) avant d'envoyer l'effluent de cette étape e) à l'entrée du ou des réacteurs d'hydrodésulfuration de l'étape f).

Moreover, it is not necessary to remove the H2S formed during step e) before sending the effluent of this step e) to the inlet of the hydrodesulfurization reactor or reactors of the step f).

One of the advantages of the process according to the invention therefore lies in the fact that it is not necessary to adjust the H2S content between step e) and step f). Furthermore, a step g) is preferably carried out after step f), this step consists in mixing the light gasoline separated in step d) and at least part of the heavy gasoline resulting from step f). to form the desulfurized global essence sought.

Preferably, all the desulphurized heavy gasoline resulting from stage f) is mixed with the light gasoline resulting from stage d), without separation of the liquid and the gas contained in the heavy gasoline after desulfurization, possibly a simple stripping with at least one inert gas can be carried out to remove 1H2S from the largely desulphurized heavy gasoline that is to say usually containing less than 50% by weight and often less than 20% by weight of residual sulfur compounds by relative to the sulfur compound content of the heavy gasoline leaving step d).

In certain specific cases, recovery of light petrol and desulphurised heavy gasoline is carried out separately. It is then unnecessary to perform step g).

For gasolines with a boiling point greater than 130 ° C., two additional steps may be necessary: an additional step of removing basic compounds which may be carried out by washing with an aqueous acidic solution intended to eliminate the basic compounds may be necessary before step c) a step of fractionation of the gasoline from steps d), fractionation or one of the steps e) or f) hydrodesulphurization for to separate from the gasoline produced a heavy fraction whose initial point would be for example 210C and a lighter fraction whose end point would be for example 210 C.

 In the case where this fractionation is performed on the gasoline from step d), the light fraction is sent in step e).

The feedstock of the process according to the invention is a gasoline cutter containing sulfur, preferably a gasoline cutoff from a cracking unit, most often a

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 catalytic cracking unit, whose range of boiling points typically extends from about the boiling points of the hydrocarbons with 2 or 3 carbon atoms (C2 or C3) up to about 250 C, preferably since about boiling point of hydrocarbons with 2 or 3 carbon atoms (C 2 or C 3) up to about 220 ° C., more preferably from about 5 carbon atoms (C 5) hydrocarbon boiling points to about C. The process of the present invention is more particularly applicable to catalytic cracking gasolines whose final boiling temperatures are from about 120 ° C. to about 230 ° C.

The advantages of this scheme over those of the prior art are as follows: 1-Removal of the diene compounds, and possibly acetylenic compounds contained in the initial gasoline in order to limit the deactivation of the alkylation catalyst of the step c) subsequent sulfur compounds as well as the formation of gums in gasolines.

2-Elimination of light mercaptans to produce a softened light species that does not require further purification or desuifuration.

3-Increase in the production of light desulfurized gasoline recovered at the top of the fractionation column, which induces a minimization of the quantity of gasoline to be treated by hydrodesulfurization 4-Production, by fractionation of a heavy gasoline rich in branched olefins whose the octane is not very sensitive to the saturation of olefins. 5-Selective desulphurisation of heavy gasoline (or from lateral drawdowns) to limit the saturation of olefins and the octane loss of heavy gasoline.

6-Overall reduction of the vapor pressure of the gasoline produced compared to the initial gasoline.

DETAILED DESCRIPTION The invention is described in the present invention a process for obtaining a desulfurized gasoline from a conversion gasoline and preferably a gasoline from a catalytic cracking unit, coking, visbreaking or pyrolysis optionally mixed with a saturated gasoline and having a limited sulfur content in which the gasoline is first subjected to a selective hydrogenation treatment of diolefins, then a step of transformation of the sulfur compounds of gasoline present under form of mercaptans having 1 to 6 carbon atoms in their molecule and sulphides often having 2 to 6 carbon atoms which should after fractionation be in the light gasoline so that they are essentially in the heavy fraction after the fractionation step of the process according to the invention, a step of alkylation of the sulfur compounds present s form of thiophenic compounds in gasoline from

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 the stage of transformation of the sulfur compounds in the form of mercaptans and sulphides. In this step, the operating conditions can be adjusted to promote olefin alkylation reactions on olefins and aromatics, which results, in particular, in a lowering of the vapor pressure of the gasoline. At least one fraction resulting from the fractionation step, preferably the heavy fraction or an intermediate fraction, may be treated in a step of converting these sulfur compounds into H 2 S (hydrogen sulphide) with or without minimization of the saturation of the olefins.

After said fractionation, the heavy gasoline or at least one intermediate fraction is treated in a hydrodesulfurization section, preferably in the presence of a hydrodesulfurization catalyst or optionally an absorbent. Preferably, no desulphurization of the light fraction is necessary in the process according to the invention, since most of the sulfur compounds initially present in the gasoline are found in the heavy fraction and optionally in the intermediate fraction or fractions. fractionation step d) which is carried out after the steps of hydrogenation, transformation of the sulfur compounds (step b), transformation of the thiophenic compounds and optionally mercaptans, in particular residual mercaptans which are not converted and / or formed in the steps a) and b) (step c) by alkylation of at least a portion of the sulfur compounds not converted in step b) (step c).

This sequence makes it possible ultimately to obtain a desulfurized gasoline without significant reduction in the olefin content or the octane number, even for high desulfurization rates, without the need to treat the gasoline. by means of a hydrodesulphurization or softening section, or using methods to restore the octane number of gasoline. Thanks to this process, significant deuifuration rates are achieved under reasonable operating conditions specified below.

hétérocycliques, tels que par exemple le thiophène ou les alkyl-thiophènes, ou des composés plus lourds, comme par exemple le benzothiophène et/ou le dibenzothiophène. The sulfur species contained in the fillers treated by the process of the invention may be mercaptans, sulphides, disulfides and / or compounds

heterocyclic compounds, such as, for example, thiophene or alkyl-thiophenes, or heavier compounds, for example benzothiophene and / or dibenzothiophene.

The fractionation point of the gasoline is preferably limited to avoid the presence of sulfur compounds in the light gasoline. In the absence of the alkylation reactor of the sulfur compounds, it would be possible to separate in the light gasoline only

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 CS olefins and a small part of the C6 olefins, as this would cause an excessive fraction of thiophene in this section. Thus the process according to the invention is advantageous by carrying out a step of transformation of thiophene and more generally of thiophene compounds, for example by means of an alkylation section upstream of the fractionation section or integrated in said section. according to a detailed mode in the following description.

désulfuration élevés tout en limitant le taux d'hydrogénation des oléfines et donc la perte en octane. In order to recover a larger fraction of the light gasoline while limiting the sulfur content of this fraction without further treatment, it is preferably proposed to treat the feed in step b) under conditions and on catalysts. which make it possible to convert the light sulfur compounds present in the form of mercaptans and sulphides most often having from 2 to 6 carbon atoms in their molecule into sulfur compounds with a higher boiling point found after the separation, possibly in at least an intermediate fraction or in heavy gasoline. These intermediate and / or heavy cuts can then be desulfurized. This desulphurisation is carried out under defined conditions and by means of a hydrodesulphurization catalyst which can optionally limit the saturation of the olefins or according to a preferred embodiment of the invention, by means of a series of catalysts making it possible to reach of

high desulfurization while limiting the hydrogenation rate of the olefins and thus the octane loss.

The sulfur content of gasoline fractions produced by catalytic cracking and in particular fluid-bed catalytic cracking (FCC) depends on the sulfur content of the FCC-treated feed, whether or not the FCC feed pretreatment, as well as the end point of the cut. Generally, the sulfur contents of the entirety of a petrol cut, in particular those coming from the FCC, are greater than 150 ppm by weight and most of the time greater than 500 ppm by weight. For gasolines with end points greater than 200oC, the sulfur contents are often greater than 1000 ppm by weight, they can even in some cases reach values of the order of 4000 to 5000 ppm by weight.

The method according to the invention is particularly applicable when high desulphurization rates of gasoline are required, ie when the desulphurized gas must contain at most 10% of the sulfur of the initial gasoline and possibly at most 5% or even more than 2% of the sulfur of the initial gasoline which corresponds to desulfurization rates greater than 90% or even greater than 95 or 98%.

The method according to the invention comprises at least the following steps a) to e):

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 The step a) of selective hydrogenation of diolefins: this step is intended to eliminate diolefins which are likely to cause premature deactivation of the sulfurization catalysts of compounds sulfurized by alkylation in step c) below , and to form gums in desulfurized gasolines. This step is carried out by passing the filler, preferably consisting of the entire gasoline cut, on a catalyst for selectively hydrogenating the diolefins of the gasoline without hydrogenating the olefins.

Stage b) of increasing the mercaptans and light sulfides on a supported metal catalyst: this reaction can be carried out in the reactor for the selective hydrogenation of diolefins. This step consists in passing all or part of the initial gasoline or hydrogenated gasoline in step a), preferably all of the initial gasoline or hydrogenated gasoline in step a), on a catalyst allowing at least partly converting the light sulfur compounds (for example: ethyl mercaptan, propyl mercaptan), by reaction with all or part of the olefins, into heavier sulfur compounds. This step is for example carried out simultaneously with step a), for example by passing the initial gasoline over a catalyst that is capable of both hydrogenating the diolefins and converting the light sulfur compounds, preferably with the olefins, into sulfur compounds. heavier, or on a separate catalyst but making it possible to carry out this transformation in the same reactor as that used for carrying out step a) Step c) is a step of increasing the sulfur compounds by alkylation. This step makes it possible to eliminate most of the sulfur compounds present in the form of thiophenics by an addition reaction on the olefins. This step consists in passing all or part of the gasoline resulting from stage b) on a catalyst having an acid function which makes it possible to carry out the addition of the sulfur compounds in the form of mercaptans and sulphides to the olefins and the reaction of alkylation of thiophene and thiophene derivatives by these same olefins.

Stage d) fractionation of the gasoline obtained at the end of stage c): this stage is intended to produce a light desulfurized gasoline at the top of the distillation column. The gas thus recovered is low in sulfur and most often does not require additional treatment. This light sulfur-poor gasoline is most often directly sent to the gasoline storage area (gasoline pool according to the terminology most frequently employed in the art), preferably without additional post-processing. Gasoline recovered at the bottom of the column concentrates the sulfur compounds initially present in the feedstock. This column may comprise lateral withdrawals allowing for example to obtain one or more intermediate fractions.

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Dans l'étape e) l'essence de fond de colonne et/ou celle contenue dans une fraction intermédiaire issue de l'étape d) est désuifurée par hydrotraitement.

In step e) the essence of the column bottom and / or that contained in an intermediate fraction resulting from step d) is desulphurized by hydrotreatment.

According to a preferred embodiment of the invention, the column bottom gasoline and / or that contained in an intermediate fraction resulting from stage d) is desulfurized in stage e) on a catalyst and under conditions such that Olefin saturation is partial in order to limit the octane loss.

la saturation des oléfines. En effet, la mise en oeuvre d'une hydrodésulfuration sélective permet de limiter la saturation des oléfines et de limiter, ainsi, la perte en octane de l'essence. L'essence lourde et/ou au moins une essence intermédiaire ainsi désulfurée peut ensuite être éventuellement strippée (c'est-à-dire qu'un courant gazeux, de préférence contenant un ou des gaz inertes est passé au travers de cette essence), afin d'éliminer l'H2S éventuellement produit lors de la désulfuration. According to a more preferred embodiment of the invention, in the successive steps e) and f) the essence of the column bottom and / or that contained in an intermediate fraction resulting from stage d) is desulphurized by hydrotreatment according to a process which allows to limit

the saturation of olefins. Indeed, the implementation of a selective hydrodesulphurization can limit the saturation of olefins and thus limit the octane loss of gasoline. The heavy gasoline and / or at least one intermediate gas thus desulphurized may then optionally be stripped (that is to say a gaseous stream, preferably containing one or more inert gases, is passed through this gasoline), to remove any H2S produced during the desulphurization.

. transformation des composés soufrés par alkylation tels que par exemple le thiophène, les composés thiophèniques et éventuellement les mercaptans (étape c) désulfuration des fractions intermédiaires et/ou désulfuration de la fraction lourde ( (étape e) et/ou étape f)) De tels dispositifs comprenant une colonne de fractionnement associés à un réacteur externe et utilisables dans le procédé selon l'invention ont été par exemple décrits pour des applications dans le domaine du raffinage et de la pétrochimie dans les brevets US 5,1777, 283, US 5,817, 227 et US 5,888, 355 Selon d'autres variantes du procédé selon l'invention, il est également possible d'utiliser une colonne réactive à la place de la colonne de fractionnement, c'est-à-dire de placer au moins une desdites sections réactionnelles dans la colonne de fractionnement According to a variant of the process according to the invention, it is possible to associate at least one reaction section with the fractionation column. Said said reaction section or sections then operate on at least one fraction taken from the inside of the fractionation column and the effluent from the reaction section is returned to the fractionation column. The reaction section or sections thus coupled to the fractionation column of step d) may be chosen from the group consisting of the reaction sections of the following steps:

. transformation of sulfur compounds by alkylation, such as, for example, thiophene, thiophenic compounds and optionally mercaptans (step c) desulfurization of the intermediate fractions and / or desulfurization of the heavy fraction ((step e) and / or step f)). devices comprising a fractionation column associated with an external reactor and usable in the process according to the invention have for example been described for applications in the field of refining and petrochemistry in US Patents 5,1777, 283, US 5,817, According to other variants of the process according to the invention, it is also possible to use a reactive column instead of the fractionation column, that is to say to place at least one of said reaction sections in the fractionation column

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 (column internal reaction section), preferably in a zone where the reagent concentration is maximum. Thus, for example, in the case of step c) of conversion of the sulfur compounds by alkylation such as for example the thiophene compounds, the reaction section will preferably be placed in an area having the maximum concentration of these compounds.

According to a preferred variant of the process according to the invention, the reaction section internal to the column is chosen from the group consisting of the following reaction sections: transformation of sulfur compounds such as thiophene, thiophenic compounds and optionally mercaptans by alkylation (step c)), desulfurization of the intermediate fractions and / or desulfurization of the heavy fraction ((step e) and / or step f).

alors traitée dans un réacteur externe associé ou non à la colonne de fractionnement. De telles colonnes réactives sont connues de l'homme du métier et ont été par exemple décrites dans les brevets ou demandes de brevet US 5,368, 691, US 5,523, 062, FR 2,737, 131, FR 2,737, 132, EP-A-O 461 855. In a very preferred embodiment of the process according to the invention, the reaction section is placed in the middle of a fractionation column, so as to treat the compounds having the intermediate boiling points, that is to say the compounds which can constitute a intermediate cut and which are recovered alone or with the heavy fraction at the bottom of the column, at the end of the fractionation step. The heavy fraction is

then treated in an external reactor associated or not with the fractionation column. Such reactive columns are known to those skilled in the art and have been described, for example, in patents or patent applications US Pat. Nos. 5,368,691, 5,523,062, 2,737,131, 2,737,132 and EP-AO 461,855. .

Another variant of the process according to the invention consists both in using a reactive column comprising at least one reaction section and an external reactor coupled or not to said column. Such variants are for example described in the patent application WO00 / 15319.

The variants described above are only illustrations of the possible variants of the method according to the invention. The process according to the invention can indeed be carried out by combining reaction sections (steps a), b), c), e) or f)) associated with the fractionation column of step d. ), either internal to said column or external and non-coupled to said column in the sense that the effluent of said reaction section (s) is not recycled. to the fractionation column.

One of the advantages of the process according to the invention lies in the fact that it is most often not necessary to desulphurize the light fraction of the gasoline resulting from the fractionation. The transformation of sulfur and / or thiophene compounds (steps

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 b) and / or c)) makes it possible to considerably reduce the content of sulfur compounds in the light cut and possibly at least one intermediate cut, and generally to recover the bulk of these compounds in the heavy fraction, and possibly in the intermediate fraction (s).

Steps b) and c) are distinguished, inter alia, by the fact that the conversion of the thiophene compounds is generally less than 60% by weight, or even less than 40% by weight in stage b), whereas the conversion is usually greater than at 80% by weight, preferably greater than 90% by weight, very preferably greater than 95% by weight in stage c). Step b) essentially increases the mercaptans and light sulphides while step c) essentially increases the weight of the thiophene compounds.

This operation is carried out while maintaining most of the olefins in the light fraction, optionally in at least one intermediate fraction that does not require extensive desulfurization. The content of sulfur compounds in the light fraction thus obtained is usually less than 100 ppm, preferably less than 50 ppm, more preferably less than 20 ppm and very preferably less than 10 ppm.

Another advantage lies in the fact that the residual content of sulfur compounds of the desulfurized gasoline by means of the process according to the invention is particularly low, and that the octane number of the gasoline is maintained at a high level.

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

tel que par exemple de l'alumine, de la silice ou un support contenant au moins 50 % d'alumine. - Hydrogenation of diolefins (step a): The hydrogenation of dienes is a step which eliminates, before hydrodesulfurization, almost all the dienes present in the petrol fraction containing sulfur to be treated. It is preferably carried out in the first step (step a) of the process according to the invention, generally in the presence of a catalyst comprising at least one metal of the Voll group, preferably selected from the group consisting of platinum, palladium and nickel. , and a support. For example, 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% alumina.

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The pressure employed is sufficient to maintain more than 60%, preferably 80%, and more preferably 95% by weight of the gasoline to be treated in the liquid phase in the reactor; it is most generally between about 0.4 and about 5 MPa and preferably greater than 1 MPa, more preferably between 1 and 4 MPa. The hourly space velocity of the liquid 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 3 and 8 h -1. The temperature is most generally between about 50 and about 250 C, and preferably between 80 and 220 C, and more preferably between 100 and 200 C, to ensure a sufficient conversion of diolefins. Very preferably it is limited to 180 ° C. The hydrogen / charge ratio expressed in liters is generally between 1 and 50 liters per liter, preferably between 2 and 30 liters, more preferably between 3 and 25 liters per liter.

The choice of operating conditions is particularly important. It will operate most generally 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 preferably comprising a fixed bed of catalyst.

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 patent FR 2 764 299.

The catalytic cracked gasoline may contain up to a few percent (%) by weight of diolefins. After hydrogenation, the diolefin content is generally reduced to less than 3000 ppm, or even less than 2500 ppm and more preferably less than 1500 ppm. In some cases, it can be obtained less than 500 ppm. The diene content after selective hydrogenation can even if necessary be reduced to less than 250 ppm.

According to a particular embodiment of the process according to the invention, the hydrogenation stage of the dienes takes place in a catalytic hydrogenation reactor which comprises a catalytic reaction zone traversed by the entire charge and the quantity of hydrogen necessary to effect the desired reactions.

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transformation of light sulfur compounds (step b): This step consists in transforming the light sulfur compounds. That is to say the compounds which at the end of the diene hydrogenation step a) would be (after fractionation in step d)) in the light gasoline, into heavier sulfur compounds entrained in heavy gasoline. Preferably, the light sulfur compounds are selected from the families of mercaptans of 1 to 6 carbon atoms and sulfides of 2 to 6 carbon atoms. This transformation is preferably carried out on a catalyst comprising at least one element of group VIII of the periodic table of elements (Handbook of Chemistry and Physics 45 th edition 1964-1965) (groups 8, 9 and 10 of the new periodic table). The choice of the catalyst is carried out in particular so as to promote the reaction between light mercaptans and olefins, which leads to heavier sulphides or mercaptans. Other compounds such as COS or CS2 may optionally also be converted.

de mercaptan soit transformée. Ainsi une certaine réduction de la teneur en mercaptans est obtenue. Pour ce faire, on peut utiliser la procédure d'hydrogénation des diènes décrite dans la demande de brevet EP-A-O 832 958, qui utilise avantageusement un catalyseur à base de palladium, ou celle décrite dans le brevet FR 2 720 754. This step may possibly be performed at the same time as step a). For example, it may be particularly advantageous to operate, during the hydrogenation of the diolefins, under conditions such that at least a part of the compounds in the form of

of mercaptan is transformed. Thus some reduction of the mercaptan content is obtained. For this purpose, it is possible to use the diene hydrogenation procedure described in patent application EP-A-0 832 958, which advantageously uses a catalyst based on palladium, or that described in patent FR 2 720 754.

Another possibility is to use a nickel-based catalyst that is identical to or different from the catalyst of step a), such as, for example, the catalyst recommended in the process of US-A-3,691,066, which makes it possible to transform the mercaptans (butyl mercaptan) to heavier sulfur compounds (sulphides).

Another possibility for carrying out this step consists in hydrogenating thiophene at least in part to thiophane whose boiling point is greater than that of thiophene (boiling point 121 ° C.). This step can be carried out on a catalyst based on nickel, platinum or palladium. In this case, the temperatures are generally between 100 and 300 ° C. and preferably between 150 and 250 ° C. The ratio H2 / charge is adjusted to between 1 and 20 liters per liter, preferably between 3 and 15 liters per liter, to favor if additionally possible hydrogenation of the thiophene compounds and minimize the hydrogenation of olefins present in the feed. The space velocity is generally between 1 and 10 h -1, preferably between 2 and 4 h -1 and the pressure between 0.5 and 5 MPa, preferably between 1 and 3 MPa.

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transformation of the sulfur compounds by alkylation (step c): This step consists in passing preferably all of the fraction resulting from step b) on a catalyst having an acid function which makes it possible to carry out the addition of the sulfur compounds under form of mercaptans on olefins and the alkylation reaction of thiophene and thiophene derivatives with these same olefins. The operating conditions are adjusted to achieve the desired conversion with conversion rates of thiophene and / or thiophene compounds, greater than 80% by weight, preferably greater than 90% by weight, very preferably greater than 95% by weight. Other compounds such as COS or CS2 may optionally also be converted.

During this step, a portion of the olefins of the starting gasoline can be converted into branched long olefins, by addition reactions (oligomerization) between olefins, and a portion of aromatics increased by alkylation with olefins.

des catalyseurs acides tel que les alcools, les éthers ou l'eau. Lors de l'alkylation, les composés thiophéniques dont le point d'ébullition est d'environ 60 C à environ 160 C vont réagir avec des taux de conversion supérieurs à 80 % poids, de préférence supérieurs à 90 % poids, avec les oléfines pour former des alkyls thiophènes dont la température d'ébullition est largement supérieure à celle des composés thiophèniques de départ. To minimize the oligomerizing activity of the acid catalyst optionally used, the gasoline may be additive of a compound known to inhibit the oligomerizing activity

acidic catalysts such as alcohols, ethers or water. During the alkylation, the thiophene compounds whose boiling point is from about 60 ° C. to about 160 ° C. will react with conversion levels of greater than 80% by weight, preferably greater than 90% by weight, with the olefins for to form thiophene alkyls whose boiling temperature is much higher than that of the starting thiophene compounds.

Some or all of the benzene may also be removed by alkylation with the olefins.

températures d'ébullition plus élevées que celles qu'ils avaient avant alkylation. Ainsi la température théorique d'ébullition du thiophène qui est de 84 C se trouve déplacée vers 150 C pour les alkyls thiophènes. Cette réaction est couplée à des réactions d'addition des oléfines qui conduisent donc le plus souvent à un alourdissement de l'essence, notamment dans le cas où la fraction d'essence et/ou l'essence de départ sont légères, et à une diminution de sa tension de vapeur. These compounds of higher molecular weight are mainly characterized by

boiling temperatures higher than those they had before alkylation. Thus the theoretical boiling temperature of thiophene which is 84 C is shifted to 150 C for thiophene alkyls. This reaction is coupled with olefin addition reactions, which therefore most often lead to an increase in gasoline, especially in the case where the gasoline fraction and / or the starting gasoline are light, and at a lower temperature. decrease of its vapor pressure.

This alkylation step is carried out in the presence of an acid catalyst. This catalyst may be indifferently a resin, a zeolite, a clay, any functionalized silica or any silico-aluminate having acidity, or any grafted support of acidic functional groups. The ratio of the volume of charge injected into the volume of

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ou en mélange) la silice, les silices alumines, les silices titane, les silices zircone ou tout autre solide présentant une acidité quelconque. Un mode particulier de l'invention peut consister à mettre en oeuvre un mélange physique d'au moins deux des catalyseurs ci- devant dans des proportions variant de 95/5 à 5/95, préférentiellement de 85/15 à 15/85 et très préférentiellement de 70/30 à 30/70. The catalyst is between 0.1 and 10 liter / liter / hour and preferably between 0.5 and 4 liter / liter / hour. More specifically, this alkylation step is carried out in the presence of at least one acidic catalyst selected from the group consisting of Bronsted acids (including phosphoric, sulfuric, boric, fluoridic acids) supported for example on silica, alumina or silica. alumina, silicoaluminates, titanosilicates, mixed titanium alumina, clays, resins, mixed oxides obtained by grafting at least one organo-metallic organosoluble or water-soluble compound (chosen from the group consisting of alkyls and / or alkoxy compounds. metals of at least one element such as titanium, zirconium silicon, germanium, tin, tantalum, niobium ...) on at least one oxide such as alumina (gamma, delta, eta forms, alone

or in admixture) silica, silica aluminas, titanium silicas, zirconia silicas or any other solid having any acidity. A particular embodiment of the invention may consist in using a physical mixture of at least two of the catalysts above in proportions ranging from 95/5 to 5/95, preferably from 85/15 to 15/85 and very preferably preferably from 70/30 to 30/70.

The temperature for this step is generally from about 10 to about 350 C depending on the type of catalyst or the strength of the acidity. Thus, for a supported phosphoric acid type catalyst, the temperature is usually from about 50 to about 250 ° C., preferably from about 100 to about 210 ° C. The molar ratio of olefins to thiophene compounds is greater than 10 mol / mol, preferably greater than 10 mol / mol. 100 mole / mole.

The operating pressure of this step is generally between 0.1 and 3 MPa and preferably such that the filler is in liquid form under the conditions of temperature and pressure, ie at a pressure greater than 0.5 MPa.

The effluent from step c) of transformation of the sulfur compounds is at least partially and preferably entirely sent to a fractionation unit (step d)) to be separated into at least two fractions, a light fraction and a fraction. heavy which is preferably sent in full optionally after mixing with an intermediate fraction in a desulfurization zone operating in one (step e) or two successive desulfurization steps (step e) and step f)).

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 separation of the gasoline resulting from stage c) into at least two fractions (stage d): According to a first variant of the process according to the invention, the gasoline is divided into two fractions: a light fraction containing a content of limited residual sulfur, preferably less than about 100 ppm, very preferably less than about 20 ppm, and most often allowing to use this cup without performing other treatment to reduce its sulfur content, * a heavy fraction wherein preferably most of the sulfur initially present in the feed is concentrated.

This separation is preferably carried out by means of a conventional distillation column also called a splitter according to the English name. This fractionation column must make it possible to separate a light fraction of the gasoline containing a small sulfur fraction and a heavy fraction preferably containing most of the sulfur initially present in the initial gasoline.

This column generally operates at a pressure of between 0.1 and 2 MPa and preferably between 0.2 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 flow rate in the column divided by the distillate flow rate expressed in kg / h, is generally less than unity and preferably less than 0.8.

The light gasoline obtained after the separation is generally composed of hydrocarbon cuts with 5.6 and 7 carbons. Generally, this light fraction has a low sulfur content, i.e. it is not generally necessary to treat the light cut before using it as fuel.

In this case, the gasoline is preferably fractionated into at least two sections having the following properties: a so-called light section (L section) whose boiling points are preferably less than about 120 C. This temperature is given as an indication, it generally corresponds to the maximum temperature for which the sulfur content is less than 20 ppm,

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au moins une coupe dite lourde (coupe H1) dont les points d'ébullition sont supérieurs à environ 100 C.

at least one so-called heavy cup (H1 section) whose boiling points are greater than about 100 C.

The light cut L is preferably injected into a liquid gas separation tank in order to separate the unconsumed hydrogen and the H2S formed during step a) and / or b) and / or c), olefins having generally from 5 to 7 carbon atoms.

The so-called heavy cut H1, that is to say the cut whose temperatures are greater than about 100 ° C., is sent to the desulfurization zone step e) and preferably steps e) and f).

According to a second variant of the process according to the invention, the essence is fractionated into at least 3 fractions: a light fraction, a heavy fraction and at least an intermediate fraction.

est équivalent à la fraction lourde H1 du cas où le fractionnement est limité à deux fractions. The light fraction is identical to that described above. Intermediate fraction 12 whose boiling points by way of example are at least 100 ° C. and at most about 140 ° C. or even about 160 ° C. This cut can be treated in step e) and then optionally in step f) of the process according to the invention. The heavy fraction H2 is then a fraction whose boiling points are generally greater than about 160 ° C. or about 140 ° C. In this case the whole intermediate fraction plus heavy fraction

is equivalent to the heavy fraction H1 of the case where the fractionation is limited to two fractions.

The heavy cut H2 whose boiling temperatures are generally greater than about 160 ° C. or about 140 ° C. is sent to the desulfurization zone.

In another version of the process according to the invention, it is also possible to fractionate the product resulting from stage c) in at least three sections, a light section (L), at least one intermediate section (12) and at least one heavy cut (H2) having the properties described above.

Intermediate section 12, whose boiling points are between about 100 ° C. and about 120 ° C. or about 160 ° C., can be sent to a sulfur compound conversion unit according to step c) or recycled in this step c).

After step d), the section or sections 12 may again be fractionated into an intermediate section 13 and a heavy section H3. The section H3 thus obtained may optionally be mixed with the section H2, preferably before desulfurization and the

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coupe 13 peut être envoyée dans une unité de transformation des composés soufrés selon l'étape c) ou recyclée dans cette étape c).

section 13 can be sent to a conversion unit sulfur compounds according to step c) or recycled in this step c).

In the rest of the description, the conditions given for step e) include those in which a single desulfurization step is carried out and those of a preferred embodiment of the invention in which the hydrodesulphurization is carried out in two successive stages. and F).

- Decomposition of sulfur compounds of heavy and / or intermediate fractions from step d) (step e): This step, which applies to heavy gasoline (heavy fractions and / or intermediate fractions) obtained at the end the fractionation step d) consists of at least partially hydrogenolysis of the sulfur compounds to form H 2 S. The fraction of the sulfur compounds thus transformed is a function of the desired desulphurization rate.

une température comprise entre environ 210 C et environ 350 C, de préférence entre 220 C et 320 C, sous une pression généralement comprise entre environ 1 et environ 4 MPa, de préférence entre 1, 5 et 3 MPa. La vitesse spatiale du liquide est comprise entre environ 0, 5 et environ 20 h-1 (exprimée en volume de liquide par volume de catalyseur et par heure), de préférence entre 0,5 et 10 h-1, de manière très préférée entre 1 et 8 h-1. Le rapport Hz/HC est compris entre 100 à 600 litres par litre et préférentiellement entre 200 et 500 litres par litre. This step may, for example, be carried out by passing heavy gasoline, in the presence of hydrogen, over a catalyst comprising at least one element of group VIII and / or at least one element of group VIB at least partly in sulphide form, at

a temperature of between about 210 ° C. and about 350 ° C., preferably between 220 ° C. and 320 ° C., under a pressure generally of between about 1 and about 4 MPa, preferably between 1.5 and 3 MPa. The space velocity of the liquid is between about 0.5 and about 20 h -1 (expressed as volume of liquid per volume of catalyst per hour), preferably between 0.5 and 10 h -1, very preferably between 1 and 8 h-1. The Hz / HC ratio is between 100 to 600 liters per liter and preferably between 200 and 500 liters per liter.

(métaux du groupe 6 de la nouvelle classification, c'est-à-dire le chrome, le molybdène ou le tungstène), sur un support approprié. La teneur en métal du groupe VIII exprimée en oxyde est généralement comprise entre 0,5 et 15 % poids, préférentiellement entre 1 et 10 % poids. La teneur en métal du groupe VIB est généralement comprise entre 1,5 et 60 % poids, préférentiellement entre 3 et 50 % poids. L'élément du groupe Voll, lorsqu'il est présent, est de préférence To achieve, at least in part, the hydrogenolysis of the unsaturated sulfur compounds of gasoline according to the process of the invention, use is generally made of at least one catalyst, comprising at least one element of group VIII (Group 8 metals, 9 and 10 of the new classification, i.e., iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium or platinum) and / or at least one group VIB element

(Group 6 metals of the new classification, ie chromium, molybdenum or tungsten), on a suitable support. The content of Group VIII metal expressed as oxide is generally between 0.5 and 15% by weight, preferably between 1 and 10% by weight. The metal content of group VIB is generally between 1.5 and 60% by weight, preferably between 3 and 50% by weight. The element of the Voll group, when present, is preferably

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 cobalt, and the group VIb element, when present, is usually molybdenum or tungsten. Combinations such as cobalt-molybdenum are preferred. The catalyst support is usually a porous solid, such as for example an alumina, a silica-alumina or other porous solids, such as, for example, magnesia, silica or titanium oxide, alone or in mixture with alumina or silica-alumina. To minimize the hydrogenation of the olefins present in heavy gasoline, it is advantageous to preferentially use a catalyst in which the density of molybdenum, expressed in% by weight of MoO 3 per unit area, is greater than 0.07 and preferably greater than 0.07. at 0.10. The catalyst according to the invention preferably has a specific surface area of less than 190 m 2 / g, more preferably less than 180 m 2 / g, and very preferably less than 150 m 2 / g.

The catalyst is preferably used at least in part in its sulfurized form.

The suifuration step may be carried out by any technique known to those skilled in the art, in situ or ex situ.

In the process according to the invention the conversion of the sulfur compounds is greater than 50% and preferably greater than 90%.

Step e) is carried out under conditions such that the transformation of at least a portion of the unsaturated sulfur compounds, such as the thiophene compounds, into saturated compounds, for example into thiophanes (or thiacyclopentanes) or into mercaptans, or to hydrogenolize at least partially these unsaturated sulfur compounds to form H2S.

In the process according to this preferred embodiment of the invention, the conversion of the unsaturated sulfur compounds is greater than 15% and preferably greater than 50%. At the same time, the degree of hydrogenation of the olefins is preferably less than 50%, more preferably less than 40%, and very preferably less than 35%, during this step. The effluent resulting from this first hydrogenolysis step is then sent, preferably without any separation of the liquid and the gas, to step f) which makes it possible to decompose the saturated sulfur compounds with H2S.

- Decomposition of the sulfur compounds contained in the product from step e) (step f): In this step, the saturated sulfur compounds are converted in the presence of hydrogen, on a suitable catalyst. The decomposition of non unsaturated compounds

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 hydrogenated during step e) can also take place simultaneously. This transformation is carried out without substantial hydrogenation of the olefins, that is to say during this step the hydrogenation of the olefins is generally limited to 20% by volume relative to the olefin content of the initial gasoline. and preferably limited to 10% by volume based on the olefin content of the initial gasoline.

de manière très préférée entre 10 et 25 % poids. De façon préférée, le catalyseur est généralement mis en forme, de préférence sous forme de billes, de pastilles, d'extrudés, par exemple de trilobes. Le métal peut être incorporé au catalyseur par dépôt sur le support préformé, il peut également être mélangé avec le support avant l'étape de mise en forme. Le métal est généralement introduit sous forme d'un sel précurseur, généralement soluble dans l'eau, tel que par exemple les nitrates, les heptamolybdates. Ce mode d'introduction n'est pas spécifique à l'invention. Tout autre mode d'introduction connu de l'homme du métier peut convenir. On utilise très avantageusement un catalyseur contenant au moins un élément du groupe Vttt et en particulier du nickel. The catalysts which may be suitable for this stage of the process according to the invention, without this list being limiting, are catalysts generally comprising at least one base element chosen from Group VIII and Group VIB elements, and preferably chosen from the group formed by nickel, cobalt, iron, molybdenum and tungsten. These metals can be used alone or in combination, they are preferably supported and used in their sulfurized form. The catalyst of step f) is preferably of a different nature and / or composition than that used in step e). The base metal content of the catalyst according to the invention is generally between about 1 and about 60% by weight, preferably between 5 and 30% by weight, and

very preferably between 10 and 25% by weight. Preferably, the catalyst is generally shaped, preferably in the form of beads, pellets, extrudates, for example trilobes. The metal may be incorporated into the catalyst by deposition on the preformed support, it may also be mixed with the support before the shaping step. The metal is generally introduced in the form of a precursor salt, generally soluble in water, such as for example nitrates, heptamolybdates. This mode of introduction is not specific to the invention. Any other mode of introduction known to those skilled in the art may be suitable. Very advantageously a catalyst containing at least one element of the group Vttt and in particular nickel is used.

exemple, les alumines, les silices et les silices-alumines, la magnésie, ainsi que l'oxyde de titane et l'oxyde de zinc, ces derniers oxydes pouvant être utilisés seuls ou en mélange avec de l'alumine ou de la silice-alumine. De préférence, les supports sont des alumines de transition ou des silices dont la surface spécifique est comprise en 25 et 350 m2/g. Les composés naturels, tels que par exemple le kieselgur ou le kaolin, peuvent également convenir comme supports des catalyseurs utilisés dans cette étape du procédé. The supports of the catalysts used in this step of the process according to the invention are generally porous solids chosen from refractory oxides, such as by

for example, aluminas, silicas and silica-aluminas, magnesia, as well as titanium oxide and zinc oxide, these latter oxides being able to be used alone or in admixture with alumina or silica-alumina. alumina. Preferably, the supports are transition aluminas or silicas whose specific surface area is between 25 and 350 m 2 / g. Natural compounds, such as, for example, kieselguhr or kaolin, may also be suitable as supports for the catalysts used in this stage of the process.

The catalyst is preferably used at least in part in its sulfurized form. This has the advantage of minimizing the risks of hydrogenation of unsaturated compounds such as olefins or aromatic compounds during the cooling phase.

<Desc / Clms Page number 26>

 start-up. The sulphurization step may be performed by any technique known to those skilled in the art, in situ or ex situ.

cobalt, le fer, le molybdène, le tungstène, à une température comprise entre environ 280 C et environ 400 C, de préférence entre environ 290 C et environ 380 C, de manière plus préférée entre 310 C et 360 C, et de manière très préférée entre 320 C et 350 C, sous une pression généralement comprise entre environ 0, 5 et environ 5 MPa, de préférence comprise entre 1 et 3MPa, de manière plus préférée entre 1, 5 et 3 MPa. La vitesse spatiale du liquide est comprise entre environ 0, 5 et environ 10 h-1 (exprimée en volume de liquide par volume de catalyseur et par heure), de préférence entre 1 et 8 h-1. Le rapport H2/HC est ajusté en fonction des taux d'hydrodésulfuration désirés dans la gamme comprise entre environ 100 et environ 600 litres par litres, de préférence entre 100 et 300 litres par litres. Tout ou partie de cet hydrogène peut éventuellement provenir de l'étape e) (hydrogène non converti) ou d'un recyclage de l'hydrogène non consommé dans les étapes a), b) ou c). Il a été trouvé que la mise en oeuvre de ce second catalyseur dans cette étape, dans des conditions opératoires particulières, permet de décomposer les composés saturés, contenus dans l'effluent issu de l'étape c, en H2S. Cette mise en oeuvre permet d'atteindre un niveau global élevé d'hydrodésulfuration à l'issu de l'ensemble des étapes du procédé selon l'invention, tout en minimisant la perte en octane résultant de la saturation des oléfines, car la conversion des oléfines au cours de l'étape e) est généralement limitée à au plus 20 % en volume des oléfines, de préférence au plus 10 % en volume. After the suifuration, the sulfur content of the catalyst is generally between 0.5 and 25% by weight, preferably between 4 and 20% by weight and very preferably between 4 and 10% by weight. The hydrodesulphurization carried out during this step is intended to convert into H2S saturated sulfur compounds of gasoline which have already undergone at least one prior hydrogenation of unsaturated sulfur compounds in step e). It makes it possible to obtain an effluent that meets the desired specifications in terms of sulfur compound content. The gasoline thus obtained has only a low octane loss. The process for decomposing the saturated sulfur compounds from step e) of the process is carried out in the presence of hydrogen, with the catalyst comprising at least one base metal selected from the group consisting of nickel,

cobalt, iron, molybdenum, tungsten, at a temperature of between about 280 ° C. and about 400 ° C., preferably between about 290 ° C. and about 380 ° C., more preferably between 310 ° C. and 360 ° C., and very preferably preferred between 320 C and 350 C, at a pressure generally between about 0.5 and about 5 MPa, preferably between 1 and 3MPa, more preferably between 1, 5 and 3 MPa. The space velocity of the liquid is between about 0.5 and about 10 h -1 (expressed as volume of liquid per volume of catalyst per hour), preferably between 1 and 8 h -1. The H2 / HC ratio is adjusted according to the desired hydrodesulphurization rates in the range of from about 100 to about 600 liters per liter, preferably from 100 to 300 liters per liter. All or part of this hydrogen may possibly come from step e) (unconverted hydrogen) or a recycling of the hydrogen not consumed in steps a), b) or c). It has been found that the use of this second catalyst in this step, under particular operating conditions, makes it possible to decompose the saturated compounds, contained in the effluent from step c, into H 2 S. This implementation makes it possible to achieve a high overall level of hydrodesulfurization at the end of all the steps of the process according to the invention, while minimizing the octane loss resulting from the saturation of the olefins, because the conversion of the olefins in step e) is generally limited to at most 20% by volume of the olefins, preferably at most 10% by volume.

moins une partie des composés soufrés présents dans le produit issu de l'étape b). Selon une réalisation préférée les composés azotés basiques contenus dans l'essence initiale sont au moins en partie éliminés avant son introduction dans l'étape a) In a particular form used, according to the characteristics of the initial gasoline filler, the latter is freed from most of its basic nitrogen compounds which are at least partially removed before step c) alkylation of at

at least a portion of the sulfur compounds present in the product from step b). According to a preferred embodiment, the basic nitrogen compounds contained in the initial gasoline are at least partially removed before being introduced in step a)

<Desc / Clms Page number 27>

d'hydrogénation des composés polyinsaturés. Le plus souvent l'élimination des composés azotés basiques est effectuée par un traitement (un lavage) à l'aide d'une solution aqueuse acide. Ainsi lorsque l'essence initiale contient des composés azotés basiques ceux-ci sont au moins en partie éliminés par un traitement à l'aide d'une solution aqueuse acide effectué avant l'étape c) d'alkylation d'au moins une partie des composés soufrés présents dans le produit issu de l'étape b). Ce lavage est habituellement effectué avant ou après le traitement d'hydrogénation sélective dans l'étape a) des composés polyinsaturés contenus dans l'essence initiale.

hydrogenation of polyunsaturated compounds. Most often the removal of basic nitrogen compounds is carried out by treatment (washing) with an acidic aqueous solution. Thus, when the initial gasoline contains basic nitrogen compounds these are at least partially removed by treatment with an acidic aqueous solution carried out before step c) alkylation of at least a portion of sulfur compounds present in the product from step b). This washing is usually carried out before or after the selective hydrogenation treatment in step a) of the polyunsaturated compounds contained in the initial gasoline.

The catalysts used in steps e) and f) are most often separate sulfurized catalysts.

Description of the single figure (schematically illustrating, without limitation, an embodiment of the invention) The gasoline (a) containing sulfur compounds, diolefins and olefins is injected into the line (1). The hydrogen is injected into the line (2) in such a quantity that the hydrogen / diolefin molar ratio is greater than 1. The gasoline and the hydrogen are brought into contact in a reactor (A) for selective hydrogenation of the diolefins, under conditions optimized to limit the saturation of olefins while hydrogenating the diolefins.

The effluent from the reactor (A) is sent via line (3) to a unit for increasing the weight of sulfur compounds (B). The reactions used in this reactor (B) are essentially weighting reactions of the mercaptans of 1 to 6 carbon atoms as well as sulphides of 2 to 6 carbon atoms. Partial conversion of the compounds such as CS2 and COS is also observed. The gasoline produced is introduced via line (4) into a reactor (C) for increasing the weight of sulfur compounds by addition to the olefins. The sulfur compounds mainly weighed down in this reactor are the thiophene compounds. In this reactor (C), reactions of oligomerization of olefins and partial alkylation of benzene compounds are also observed. The gasoline produced in this reactor (C) is therefore both heavier than gasoline (cc) and depleted in light sulfur compounds. The gasoline produced in the reactor (C) is injected via the line (5) into a fractionation column (D) which separates the gasoline into at least two sections.

Light gasoline whose end point can be between 55 C and 160C is recovered at the top of the column. This essence is desulfurized and does not require

<Desc / Clms Page number 28>

traitement supplémentaire. La température finale de cette essence légère est fixée par la quantité maximale de soufre autorisée.

additional treatment. The final temperature of this light gasoline is set by the maximum amount of sulfur allowed.

The heavy gasoline recovered at the bottom of the column via line (7) is sent after mixing with hydrogen introduced via line (8) to a desulfurization section (E + F). This essence has an initial distillation point between 50 C and 130 C.

The hydrodesulphurization section (E + F) is designed to desulphurize gasoline while limiting the hydrogenation of olefins, thereby limiting octane loss. It consists of at least two reactors in series, the first of which (E) comprises a catalytic system optimized to saturate the thiophene compounds and partially convert the sulfur compounds into H2S. The second contains a catalyst which is an optimized catalyst for converting mercaptans to H 2 S, limiting the hydrogenation of olefins present in gasoline. This desulfurization scheme has been described in patent application EP 1 077 247. The heavy gasoline recovered by line (10) and the light gasoline recovered by line (6) can be mixed to produce a total desulfurized gasoline recovered by the line (11).

Example 1 (Comparative) A cracking gasoline is subjected to a hydrogenation treatment of diolefins under conditions where the sulfur-containing light sulfur compounds present in the feed are partly converted into heavier compounds.

This treatment is carried out in a reactor operating continuously. The catalyst is based on nickel and molybdenum (catalyst marketed by Procatalyse under the reference HR945). The reaction is conducted at 180 ° C. under a total pressure of 2.6 MPa, with a space velocity of 6 h -1. The H2 / filler ratio, expressed in liters of hydrogen per liter of filler, is 10.

The characteristics of catalytic cracking gasoline and effluent after hydrogenation of diolefins and conversion of light compounds are shown in Table 1.

<Desc / Clms Page number 29>

Table 1

<Tb>
<tb> Gasoline <SEP> Gasoline <SEP> after
<tb> initial <SEP> hydrogenation <SEP> (steps <SEP> a <SEP> and <SEP> b)
<tb> density <SEP> 15/4 <SEP> 0, <SEP> 7215 <SEP> 0, <SEP> 7237
<tb> Index <SEP> of <SEP> brome <SEP> 78 <SEP> 74
<tb> (gBr / 100g)
<tb> Olefins <SEP> (GC) <SEP>% <SEP> Weight <SEP> 43 <SEP> 40, <SEP> 5
<tb> MAV <SEP> (mg / g) <SEP> 10 <SEP> 0, <SEP> 2
<tb> Octane <SEP> Index <SEP> 93 <SEP> 92.5
<tb> search
<tb><SEP> octane number <SEP> engine <SEP> 79, <SEP> 6 <SEP> 79, <SEP> 4
<tb> mercaptans <SEP> (ppm) <SEP> 26 <SEP> 4
<tb> S <SEP> Total <SEP> (ppm) <SEP> 350 <SEP> 350
<tb><SEP> points of <SEP><SEP> cut (of)
<tb> 0.5% <SEP> 2 <SEP> 2
<tb> 5% <SEP> 23 <SEP> 24
<tb> 10% <SEP> 30 <SEP> 31
<tb> 50% <SEP> 86 <SEP> 87
<tb> 90% <SEP> 141 <SEP> 143
<tb> 95% <SEP> 152 <SEP> 151
<tb> 99.5% <SEP> 175 <SEP> 175
<Tb>
At the end of this treatment, the gasoline is separated into two fractions, a light fraction representing 65% by weight of the distilled gasoline whose cutting point corresponds to a temperature of 100 C and a heavy fraction. The separation is carried out on a discontinuous distillation column composed of 30 theoretical plates. The characteristics of the two fractions obtained are given in Table 2.

<Desc / Clms Page number 30>

Table 2

<Tb>
<tb> Fraction <SEP> Fraction
<tb> slight <SEP> heavy
<tb> Ph-100 <SEP> 100-175
<tb> density <SEP> 15/4 <SEP> 0, <SEP> 6826 <SEP> 0.7712
<tb> Index <SEP> of <SEP> brome <SEP> (gBr / 100g) <SEP> 91 <SEP> 48
<tb> MAV <SEP> (mg / g) <SEP><0,<SEP> 2 <SEP><<SEP> 0, <SEP> 2
<tb><SEP> octane number <SEP> search <SEP> 93.4 <SEP> 91.8
<tb><SEP> octane number <SEP> engine <SEP> 79, <SEP> 9 <SEP> 79
<tb> mercaptans <SEP> (ppm) <SEP> 3 <SEP> 4
<tb> S <SEP> Total <SEP> (ppm) <SEP> 62 <SEP> 885
<tb><SEP> points of <SEP> cut <SEP> (DS)
<tb> 0, <SEP> 5% <SEP> 4 <SEP> 93
<tb> 5% <SEP> 20 <SEP> 99
<tb> 10% <SEP> 22 <SEP> 108
<tb> 50% <SEP> 60 <SEP> 128
<tb> 90% <SEP> 96 <SEP> 145
<tb> 95% <SEP> 99 <SEP> 152
<tb> 99.5% <SEP> 110 <SEP> 177
<Tb>
The light fraction has diolefin, mercaptan and sulfur contents such that it can be used directly, provided that the sulfur content specification is greater than 60 ppm.

Heavy gasoline must be desulphurized before use. In any case, this scheme does not make it possible to produce a desulfurized gasoline, containing less than 40 ppm of sulfur, by recombination of light gasoline and heavy gasoline. Example 2 (comparative) The catalytic cracking gasoline obtained in Example 1 after the hydrogenation treatment is separated into two fractions, a light fraction representing 20% by weight of the distilled gasoline whose cutting point corresponds to a temperature of 55 C and a heavy fraction. The separation is carried out on the same column as in Example 1. The characteristics of the two fractions obtained are given in Table 3.

<Desc / Clms Page number 31>

Tableau 3

Table 3

<Tb>
<tb> Fraction <SEP> Fraction
<tb> slight <SEP> heavy
<tb> Ph-55 <SEP> 55-175
<tb> density <SEP> 15/4 <SEP> 0, <SEP> 65 <SEP> 0, <SEP> 77
<tb> Index <SEP> of <SEP> bromine <SEP> (gBr / 100g) <SEP> 130 <SEP> 65
<tb> Olefins <SEP> (GC) <SEP> 60 <SEP> 36
<tb> MAV <SEP> (mg / g) <SEP><<SEP> 0.2 <SEP><SEP> 0.2
<tb> Octane <SEP> Octane <SEP> Search <SEP> 95 <SEP> 90, <SEP> 5
<tb><SEP> octane number <SEP> engine <SEP> 81, <SEP> 5 <SEP> 80
<tb> mercaptans <SEP> (ppm) <SEP><1<SEP> 4
<tb> S <SEP> Total <SEP> (ppm) <SEP> 2 <SEP> 437
<tb><SEP> points of <SEP> cut <SEP> (DS)
<tb> 0.5% <SEP> 4 <SEP> 52
<tb> 5% <SEP> 20 <SEP> 54
<tb> 10% <SEP> 22 <SEP> 67
<tb> 50% <SEP> 36 <SEP> 102
<tb> 90% <SEP> 41 <SEP> 138
<tb> 95% <SEP> 54 <SEP> 151
<tb> 99, <SEP> 5% <SEP> 72 <SEP> 176
<Tb>

L'essence légère produite par distillation présente des teneurs en mercaptans, dioléfines et soufre telles qu'elle peut être utilisée directement.

The light gasoline produced by distillation has mercaptan, diolefin and sulfur contents such that it can be used directly.

Heavy gasoline requires additional desulphurization.

The heavy gasoline is therefore subjected to hydrodesulphurization on a series of catalysts in an isothermal tubular reactor.

The first catalyst (catalyst A) is obtained by impregnation without excess solution of a transition alumina, in the form of beads, with a specific surface area of 130 m 2 / g and a pore volume of 0.9 ml / g, by an aqueous solution containing molybdenum and cobalt in the form of ammonium heptamolybdate and cobalt nitrate. The catalyst is then dried and calcined in air at 500 ° C. The cobalt and molybdenum content of this sample is 3% of CoO and 14% of MioO 3.

The second catalyst (catalyst B) is prepared from a transition alumina of 140 m 2 / g in the form of beads 2 mm in diameter. The porous volume

<Desc / Clms Page number 32>

est de 1 ml/g de support. Un kilogramme de support est imprégné par 1 litre de solution de nitrate de nickel. Le catalyseur est ensuite séché à 120 C et calciné sous courant d'air à 400 C pendant une heure. La teneur en nickel du catalyseur est de 20 % poids.

is 1 ml / g of support. One kilogram of support is impregnated with 1 liter of nickel nitrate solution. The catalyst is then dried at 120 ° C. and calcined under a stream of air at 400 ° C. for one hour. The nickel content of the catalyst is 20% by weight.

traitement pendant 4 heures sous une pression de 3, 4 MPa à 350 C, au contact d'une charge contenant 2 % en poids de soufre sous forme de diméthyldisulfure dans du n-heptane. 100 ml of catalyst A and 200 ml of catalyst B are placed in two reactors in series, so that the charge to be treated (heavy fraction) first meets catalyst A and then catalyst B. A sampling zone of the effluent from step e is provided between catalysts A and B. The catalysts are first sulphurized by

treatment for 4 hours under a pressure of 3, 4 MPa at 350 ° C., in contact with a feedstock containing 2% by weight of sulfur in the form of dimethyl disulphide in n-heptane.

The operating conditions of the hydrodesulfurization are as follows: VVH = 1.33 h -1 relative to the entire catalytic bed H2 / HC = 300 1/1, P = 2.0 MPa. The temperature of the catalytic zone comprising catalyst A is 280 ° C., the temperature of the catalytic zone containing catalyst B is 330 ° C.

The characteristics of the effluents thus obtained are presented in Table 4.

<Desc / Clms Page number 33>

Tableau 4.

Table 4.

<Tb>
<Tb>

Fraction <SEP> Fraction <SEP> SEP Blend of
<tb> heavy <SEP> initial <SEP> heavy <SEP> light <SEP> gasoline
<tb> desulfurized <SEP> and <SEP> from
<tb> heavy <SEP> gasoline
<tb> desulfurized
<tb> 55-175 <SEP> 55-175 <SEP> Ph-175
<tb> density <SEP> 15/4 <SEP> 0, <SEP> 7732 <SEP> 0, <SEP> 7696 <SEP> 0, <SEP> 7228
<tb><SEP> Index of <SEP> Bromine <SEP> 65 <SEP> 38.5 <SEP> 56.2
<tb> (gBr / 1 <SEP> OOg)
<tb> Olefins <SEP> (GC) <SEP>% <SEP> Weight <SEP> 36 <SEP> 25 <SEP> 32
<tb> MAV <SEP> (mg / g) <SEP><<SEP> 0.2 <SEP><<SEP> 0.2 <SEP><SEP> 0.2
<tb> Octane <SEP> Index <SEP> 90.5 <SEP> 85.4 <SEP> 88.9
<tb> search
<tb><SEP> octane number <SEP> engine <SEP> 80 <SEP> 76 <SEP> 78, <SEP> 2
<tb> mercaptans <SEP> 4 <SEP> 12 <SEP> 10.4
<tb> S <SEP> 25
<tb><SEP> points of <SEP><SEP> cut (of)
<tb> 0.5% <SEP> 52 <SEP> 2
<tb> 5% <SEP> 54 <SEP> 23
<tb> 10% <SEP> 67 <SEP> 30
<tb> 50% <SEP> 102 <SEP> 86
<tb> 90% <SEP> 138 <SEP> 141
<tb> 95% <SEP> 151 <SEP> 152
<tb> 99, <SEP> 5% <SEP> 176 <SEP> 175
<Tb>
This scheme as described in patent application EP 1 077 247 makes it possible to produce a desulfurized gasoline, the mercaptan and diolefin content of which are compatible with the qualities required for gasolines.

In the particular case of this example, the desulfurization rate is 92.8%, the residual sulfur content is 25 ppm and the octane loss calculated by the formula (RON + MON) / 2 is 2.75 points.

Example 3 (According to the Invention) The catalytic cracking gasoline obtained in Example 1 after the hydrogenation treatment (steps a) and b) according to the invention is sent to a reactor for increasing the weight of compounds sulfurized by alkylation with olefins (step c) according to

<Desc / Clms Page number 34>

l'invention). Cette étape est mise en oeuvre dans un réacteur tubulaire contenant du catalyseur à base d'acide phosphorique supporté sur silice contenant 20 % poids d'acide phosphorique (catalyseur C), dans les conditions opératoires suivantes : VVH = 1h-1, Pression = 2,0 MPa, Température = 180 C. Avant injection dans le réacteur, la charge est additivée en isopropanol à hauteur de 500 ppm, destiné à hydrate le catalyseur en continu dans le réacteur.

the invention). This step is carried out in a tubular reactor containing phosphoric acid catalyst supported on silica containing 20% by weight of phosphoric acid (catalyst C), under the following operating conditions: VVH = 1h-1, pressure = 2 , 0 MPa, Temperature = 180 ° C. Before injection into the reactor, the feedstock is additivated with isopropanol at a level of 500 ppm, intended to hydrate the catalyst continuously in the reactor.

The effluent thus produced is separated in two sections using a distillation column as described in Example 1. The cutting point of the distillation is set at 100 ° C., the light fraction represents 50% by weight of the starting essence.

The characteristics of the gasoline produced during steps c) alkylation and d) fractionation are given in Table 5. Table 5

<Tb>
<tb> Gasoline <SEP> after <SEP> Fraction <SEP> Fraction
<tb> weight loss <SEP> by <SEP> slight <SEP> heavy
<tb> alkylation <SEP> (step <SEP> d) <SEP> (step <SEP> d)
<tb> (step <SEP> c)
<tb> PI-240 <SEP> PI-100 <SEP> 100-240
<tb> density <SEP> 15/4 <SEP> 0, <SEP> 7641 <SEP> 0.6921 <SEP> 0.8124
<tb> Index <SEP> of <SEP> bromine <SEP> 62 <SEP> 53 <SEP> 72
<tb> (gBr / 100o)
<tb> MAV <SEP> (mg / g) <SEP><<SEP> 0.2 <SEP><<SEP> 0.2 <SEP><SEP> 0.2
<tb> Octane <SEP> Index <SEP> 91.4 <SEP> 86.2 <SEP> 93.6
<tb> Search
<tb> Octane <SEP> Index <SEP> 80.7 <SEP> 79.5 <SEP> 81.7
<tb> Engine
<tb> mercaptans <SEP> (ppm) <SEP> 5 <SEP> 4
<tb> S <SEP> Total <SEP> (ppm) <SEP> 350 <SEP> 18 <SEP> 670
<tb><SEP> points of <SEP> cut <SEP> (DS)
<tb> 0.5% <SEP> 6 <SEP> 6 <SEP> 94
<tb> 5% <SEP> 23 <SEP> 19 <SEP> 102
<tb> 10% <SEP> 30 <SEP> 24 <SEP> 108
<tb> 50% <SEP> 105 <SEP> 61 <SEP> 154
<tb> 90% <SEP> 206 <SEP> 97 <SEP> 210
<tb> 95% <SEP> 215 <SEP> 100 <SEP> 219
<tb> 99, <SEP> 5% <SEP> 240 <SEQ> 111 <SEP> 238
<Tb>

<Desc / Clms Page number 35>

 The light gasoline recovered at the exit of the fractionation stage has diolefin, mercaptan and total sulfur content such that it can be used without additional treatment. Heavy gasoline requires a desulfurization step.

les suivantes : VVH = 1, 33 h-1 par rapport à l'ensemble du lit catalytique H2/HC = 300 1/1, P = 2, 0 MPa. La température de la zone catalytique comprenant le catalyseur A est de 290 C, la température de la zone catalytique contenant le catalyseur B est de 340 C. L'essence ainsi produite ne présente plus qu'une teneur en soufre de 26 ppm. Elle peut être utilisée sans traitement supplémentaire. Cette essence est recombinée à l'essence légère récupérée à l'étape d). The desulfurization of the heavy gasoline (steps e) and f) of the process according to the invention) is carried out using the device described in Example 2. The operating conditions are

the following: VVH = 1.33 h-1 relative to the entire catalytic bed H2 / HC = 300 1/1, P = 2.0 MPa. The temperature of the catalytic zone comprising catalyst A is 290 ° C., the temperature of the catalytic zone containing catalyst B is 340 ° C. The gasoline thus produced has only a sulfur content of 26 ppm. It can be used without additional treatment. This species is recombined with the light gasoline recovered in step d).

The characteristics of desulphurised heavy gasoline and recombinant gasoline are given in Table 6. Table 6

<Tb>
<tb> Gasoline <SEP> Gasoline <SEP> Gasoline <SEP> Heavy <SEP> Gasoline <SEP> Light
<tb> initial <SEP> mild <SEP> desulphurized <SEP> and
<tb> (step <SEP> d) <SEP> (steps <SEP> e) <SEP> and <SEP> essence <SEP> heavy
recombinant <tb> f) <SEP>
<tb> PI-175 <SEP> PI-100 <SEP> 100-240 <SEP> PI-240
<tb> density <SEP> 15/4 <SEP> 0, <SEP> 7215 <SEP> 0, <SEP> 6921 <SEP> 0.8134 <SEP> 0.7683
<tb> Index <SEP> of <SEP> bromine <SEP> (gBr / 100g) <SEP> 80 <SEP> 53 <SEP> 37 <SEP> 45
<tb> Olefins <SEP> (GC) <SEP>% <SEP> Weight <SEP> 44
<tb> MAV <SEP> (mg / g) <SEP> 12 <SEP><SEP> 0, <SEP> 2 <SEP><SEP> 0, SEP> 2 <SEP><SEP> 0 , <SEP> 2
<tb> Octane <SEP><SEP> Search <SEP> 93 <SEP> 86.2 <SEP> 90.4 <SEP> 88.8
<tb> Octane <SEP>SEP> Motor <SEP> 79.8 <SEP> 79.5 <SEP> 80.2 <SEP> 79.7
<tb> mercaptans <SEP> (ppm) <SEP> 20 <SEP> 4 <SEP> 12 <SEP> 9
<tb> Sulfur <SEP> 14 <SEP> 24 <SEP> 17
<tb> S <SEP> 26
<Tb>
This scheme made according to the invention makes it possible to produce a desulfurized gasoline with a limited octane loss, the mercaptan and diolefin contents of which are compatible with the qualities required for gasolines.

In the particular case of this example, the desulfurization rate is 92.6%, the residual sulfur content is 26 ppm and the octane loss calculated by the formula (RON + MON) / 2 is 2.15. points.

Claims (17)

 A process for the production of low sulfur gasolines from an initial gasoline containing at least 150 ppm by weight of sulfur compounds, comprising at least the following steps: a step a) of selective hydrogenation of the nonaromatic polyunsaturated compounds present in the initial gasoline, at least one step b) aimed at increasing the molecular weight of the light sulfur products, principally from those in the form of mercaptans having from 1 to 6 carbon atoms in their molecules and sulfides initially present in the gasoline introduced in step a) and / or those contained in the product from step a), at least one step c) alkylation at least a part of the sulfur-containing compounds, principally those in the form of thiophene compounds present in the product resulting from step b) aimed at obtaining sulfur compounds of higher molecular weight, at least one step d) of fractionation of the gasoline from step c) into at least two fractions, a first fraction substantially free of sulfur and containing the lighter olefins of the original gasoline not converted to the c), (light gasoline), at least one other fraction, heavier than said first fraction, enriched with sulfur compounds, and at least one step e) of treating at least one of the heavier fractions resulting from step d) on a catalyst for at least partially decomposing the sulfur compounds. 2-Process according to claim 1 wherein the step e) of treating at least one of the heavier fractions separated in step d) on a catalyst for at least partially decomposing the sulfur compounds is carried out in conditions where the hydrogenation of olefins on this catalyst is limited. 3-Process according to claim 1 or 2 comprising at least one step f) of treating the product obtained in step e), without removing the H2S formed during this step e), on a catalyst and under conditions to break down at <Desc / Clms Page number 37>  less partially unsubstituted sulfur compounds in step e) with limited hydrogenation of olefins. 4-Process according to one of claims 1 to 3 wherein the initial gasoline is a catalytic cracking gasoline whose final boiling temperatures are from about 120 C to about 230 C. 5-Process according to claim 3 or 4 wherein the conditions of step f) are chosen so as to decompose the unsaturated sulfur compounds and saturated sulfur compounds linear and / or cyclic unprocessed during step e), with limited hydrogenation of olefins. 6-Process according to one of claims 1 to 5 wherein the step a) of hydrogenation of unsaturated compounds and step b) to increase the molecular weight of light sulfur products initially present in the gasoline introduced into the step a) are carried out simultaneously in a single reaction zone containing one or more beds of a single catalyst. 7-Process according to one of claims 1 to 6 wherein the initial essence contains basic nitrogen compounds which are at least partly removed before step c) alkylation of at least a portion of the sulfur compounds present in the product from step b) 8-Process according to claim 7 wherein the basic nitrogen compounds contained in the initial gasoline are at least partly removed before its introduction in step a) of hydrogenation of the polyunsaturated compounds. 9-Process according to claim 6 or 7 wherein the removal of basic nitrogen compounds is carried out by treatment with an acidic aqueous solution. 10-Process according to one of claims 3 to 9 wherein the desulfurized heavy gasoline from step f) is subjected to a stripping treatment using an inert gas. 11-Process according to one of claims 3 to 10 wherein steps e) and f) are carried out in at least two successive and distinct reaction zones. <Desc / Clms Page number 38> 12-Process according to one of claims 3 to 11 wherein the light gasoline from step d) and at least a portion of the heavy gasoline from step f) are mixed to form the overall gasoline Desulfurized sought. 13-Process according to one of claims 1 to 12 wherein the catalyst of step e) comprises at least one element of group VIII and at least one element of group VIB. 14-Process according to one of claims 3 to 13 wherein the catalyst of step f) comprises at least one member of the group Voll. 15-Process according to one of claims 3 to 14 wherein the catalysts used in steps e) and f) are separate sulfurized catalysts. 16-Process according to one of claims 3 to 15 wherein the steps e) and f) are carried out in two reactors placed in series, the second reactor integrally treating the effluent of the first reactor. 17. The process as claimed in claim 1, in which the alkylation step c) is carried out under conditions such that a portion of the olefins of the starting gasoline is converted into branched long olefins by reaction reactions. addition between olefins and a part of the aromatics is increased by alkylation with olefins. 18-Process according to one of claims 1 to 17 wherein wherein the heavy fraction from step d) is sent to a fractionation zone to obtain a sulfur-enriched heavy fraction and a lighter fraction depleted in sulfur. 19-Process according to one of claims 1 to 17 wherein the gas from the hydrodesulphurization step e) or f) is sent to a fractionation zone to obtain a sulfur-enriched heavy fraction and a fraction lighter in sulfur.