FR3034764A1 - PROCESS FOR ISOMERIZING A C7 TO C11 HYDROCARBON LOAD - Google Patents

Abstract

The present invention relates to a process for producing gasoline bases from a hydrocarbon feedstock comprising paraffinic, naphthenic and aromatic hydrocarbons having 7 to 11 carbon atoms per molecule, including the following steps: a) the feed is sent of hydrocarbons and a recycle stream in a separation column configured to separate at least three slices: • a top slice containing branched C7 paraffinic hydrocarbons; An intermediate cut containing predominantly linear C7 paraffinic hydrocarbons which is withdrawn at a level of the column located above the point of injection of the feedstock and below the point of injection of the recycle stream; • a bottom section containing naphthenic and aromatic C7 hydrocarbons and C8 + hydrocarbons. b) treating the intermediate slice in an isomerization unit external to the separation column to produce an effluent containing branched C7 paraffinic hydrocarbons; c) recycling said effluent into the separation column and at the top thereof as a recycle stream in step a).

Description

The present invention relates to a process for refining a hydrocarbon feedstock comprising paraffinic, naphthenic and aromatic hydrocarbons having 7 to 11 carbon atoms per molecule to produce bases useful for fuel type fuel formulation.

State of the art Safety and environmental concerns have changed the specification of fuels of the gasoline type towards increasingly stringent standards, particularly with regard to the levels of olefinic and aromatic compounds, in particular benzene, and this while imposing a high octane number. For example in Europe, the standards set aromatic levels of less than 35% volume and with a benzene level below 1% volume and a maximum olefin content of 10% volume. As a result, refineries can no longer use significant proportions of aromatics as an octane source in the gasoline pool.

The process for generating aromatic compounds is catalytic reforming which is carried out on naphtha cuts from 07 to 01/0/011. As the aromatics content of petrol fuels is increasingly limited, the proportion of reformate in petrol bases is therefore reduced in the future. An alternative means to compensate for this loss of octane source is to increase the proportion of branched alkanes, which have high octane numbers, in the gasoline formulations. Thus the isomerization processes of linear alkane compounds into their branched isomers are becoming more and more essential for refiners. A particularly interesting solution is to carry out the isomerization only of the fraction at 07 of the naphtha section, which generally goes to reforming. Indeed, this solution makes it possible to produce branched compounds while reducing the amount of aromatic compounds that are produced by catalytic reforming so as to produce high octane fuel bases with less aromatics. It should be noted that the isomerization processes are generally carried out on 05/06 fillers. These units can not convert at the same time the longer paraffinic compounds, for example to 07, because the latter are very sensitive to cracking which then generates coke precursors responsible for the deactivation of the isomerization catalyst and is responsible for the losses. in yield. Therefore, special attention should be paid to the operating conditions of isomerization of these cuts of longer chain paraffinic hydrocarbons. US 4,834,866 discloses a process for converting a hydrocarbon feed containing linear and cyclic paraffins having 6 and more than 6 carbon atoms which comprises fractioning the feedstock and withdrawing an intermediate fraction containing predominantly 06 cyclical. The intermediate fraction is then treated in an isomerization reactor in the presence of an isomerization catalyst so as to isomerize and uncyclize the compounds at 06. The effluent from the isomerization reactor, after stabilization, is recycled to the column of fractionation which allows to recover at the top of said column a cut containing light hydrocarbons, at the bottom of the column a cut containing hydrocarbons having 7 or more carbon atoms and the intermediate fraction. Also known is US 2,443,607 which relates to a process of isomerization of heptane from a naphtha hydrocarbon feedstock. The process comprises fractionating the feed in a distillation column and recovering an intermediate cut containing n-heptane. The n-heptane cut is then mixed with methyl hexane and the resulting mixture is processed in an isomerization unit. which comprises two isomerization reactors in series and separation columns. According to the method US Pat. No. 2,443,607, the effluent of the isomerization reaction, after stripping, is sent to a de-hexanizer separation column from which a hexane-containing cup and lighter-weight compounds are recovered at the top. hexane and in bottom a section in 07. The cut in 07 is sent in a separation column which is configured to separate at the top a cut containing dimethyl pentane and trimethyl butane and in bottom a cut containing n-heptane, the methyl hexane and naphthenes which is recycled to the distillation column.

US 2007/0167663 discloses a process for isomerizing n-heptane contained in a 06-08 naphtha section which comprises a first fractionation in a first column to produce a first top fraction comprising n-heptane and more compounds. and a first bottoms fraction comprising naphtha 08. The first top fraction is fed into a second fractionation stage in a second column to produce a second top fraction containing branched heptanes and a second bottom fraction containing n-form. heptane. The second bottom fraction is treated in an isomerization zone to produce an effluent containing branched heptanes which is returned to the second column so that the branched heptanes and unconverted n-heptane are respectively recovered at the top and bottom. bottom of the second column. US 2006/0270885 teaches a process for isomerizing a c7 + hydrocarbon cut in which said cut is treated in a reactive distillation column comprising an isomerization catalyst bed which concomitantly enables the conversion of linear heptanes in branched heptanes and separating, respectively at the top and at the bottom of the reactive column, a cross-section containing the branched-chain compounds and a C8 + cut. US 8,808,534 discloses a process for refining a c7 + naphtha section which comprises a step of separating said section into a section containing linear paraffins and a paraffin-free section. Said cut containing linear paraffins is then treated in an isomerization unit. For example, the linear paraffin-containing cut that is isomerized is a cut containing hydrocarbons having 7 to 10 carbon atoms.

It is an object of the invention to provide an alternative method of isomerizing a hydrocarbon cut containing essentially linear paraffins at 07 to produce high octane gasoline bases which is advantageous from the point of view of yield. This can be advantageously incorporated into a branched compound, prior to a catalytic reforming process so as to provide a less energy consuming process. SUMMARY OF THE INVENTION The invention relates to a process for producing gasoline bases from a hydrocarbon feedstock comprising paraffinic, naphthenic and aromatic hydrocarbons having 7 to 11 carbon atoms per molecule, including the steps following: a) the hydrocarbon feedstock and a recycle stream are fed into a separation column configured to separate at least three slices: - a top slice containing branched branched paraffinic hydrocarbons; an intermediate cut consisting essentially of linear paraffinic hydrocarbons which is withdrawn at a level of the column above the point of injection of the feed and below the point of injection of the recycle stream; a bottom section containing aromatic and naphthenic hydrocarbons and hydrocarbons at 08k, b) the intermediate section is treated in an isomerization unit external to the separation column in order to produce an effluent containing paraffinic hydrocarbons; 07 branched; c) recycling said effluent into the separation column and at the top thereof as a recycle stream in step a). The process according to the invention has the advantage of using only one separation column which makes it possible not only to separate the paraffinic hydrocarbons from the naphthenic and aromatic hydrocarbons and the C8 + hydrocarbons, but also from the conversion of linear paraffinic hydrocarbons which have not been converted to their isomers by the recycling of the effluent (isomerate) from the isomerization unit in the separation column. Operating with an isomerization unit outside the separation column is operationally favorable since the temperature and pressure conditions of this step can be controlled to optimize conversion, limit taping reactions. and chosen independently of the conditions used for in the separation column. Advantageously, the separation column is configured and operated in such a way as to provide an intermediate cut containing predominantly mono-branched linear and mono-branched paraffinic hydrocarbons and a top cut containing mainly paraffinic hydrocarbons in 07 di and tri- and more volatile products than the latter. This embodiment substantially improves the octane number of the cut recovered at the top of the separation column since the di- and tri-branched paraffins have better octane numbers than their mono-branched counterparts. . Within the meaning of the invention, the mono-branched paraffins en 7 include 2-methylhexane, 3-methylhexane and 3-ethylpentane. In the context of the invention, the di- and tri-branched paraffins are 2,2-dimethylpentane, 2,3-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane and 2-dimethylpentane. , 2,3-trimethylbutane.

It is known to those skilled in the art that a column separation is not perfect and therefore some overlap in the boiling points of the head and intermediate cups occurs near the cutting point.

According to the invention, the heavy cut containing naphthenic and aromatic hydrocarbons and C8 + hydrocarbons is advantageously treated in a catalytic reforming unit to produce aromatic compounds. By way of indication, the naphthenic hydrocarbons include in particular dimethylcyclopentane and methylcyclohexane. The advantage of the process according to the invention is that by removing the paraffinic section, the quantity of aromatic compounds produced (in particular toluene) is reduced by reforming.

According to one embodiment, the effluent from the isomerization unit is sent to a stabilization column in order to separate, respectively at the top and at the bottom of the stabilization column, a light cut 06 and a cut of stabilized branched paraffinic hydrocarbons and said branched stabilized branched paraffinic hydrocarbon fraction is recycled to the separation column in accordance with step c).

The separation column is operated, for example, under the following operating conditions: at an absolute pressure at the reflux flask of between 1.1 and 2 bar (0.11 and 0.2 MPa) in order to limit the energy consumption. with a temperature at the top of the column which depends primarily on the target in terms of the RON index of the head cut. For example, the temperature can vary between 100 and 108 ° C for an absolute pressure at the top of the column of 1.7 bar (0.17 MPa). with a temperature at the bottom of the column which depends on the final boiling point of the treated feedstock. Generally it varies between 140 and 200 ° C.

Those skilled in the art can readily modify the parameters described above depending on the load being processed and the required performance without being inventive. Advantageously, the bottom cut is treated in a catalytic reforming unit.

In a preferred embodiment, the effluent from the isomerization unit is sent to a stabilization column in order to separate, at the top and at the bottom of the stabilization column, a light cut at 04.degree. stabilized branched paraffinic hydrocarbon fraction and said branched stabilized branched paraffinic hydrocarbon fraction is recycled to the separation column in accordance with step c). Preferably, in step b), the intermediate cut is treated in a reactor in the presence of isomerization catalysis under the following operating conditions: at a temperature of between 70 and 100 ° C., preferably between 80 and 100 ° C. and 90 ° C; at an absolute pressure of between 2 and 5 MPa, preferably of between 2.5 and 3.5 MPa; With a mass space velocity, expressed as the ratio of the mass flow rate of the feedstock to the catalyst mass of between 1 and 1.6 h -1, preferably of between 1.2 and 1.4 h -1; with a molar ratio H 2 / charge of between 0.1 mol / mol to 1 mol / mol.

The feed containing paraffinic, naphthenic and aromatic hydrocarbons generally has a distillation range measured according to ASTM D86 which is between an initial point of 80 ° C and an end point of 200 ° C. Preferably the distillation range is between an initial point of 80 ° C and an end point of 185 ° C.

The hydrocarbon feedstock generally contains: 20 to 75 wt% paraffins 15 to 55 wt% naphthenes 5 to 30 wt% aromatics For example the hydrocarbon fraction in which the charge which is treated contains: 20 to 80 wt.% paraffinic weight, 20 to 55 wt.% naphthenic weight, 5 to 25 wt. .

DETAILED DESCRIPTION OF THE INVENTION The other features and advantages of the invention will appear on reading the following description, given by way of illustration only and without limitation, and with reference to the drawings, among which: FIG. 1 is a first block diagram of the method according to the invention; FIG. 2 is a second block diagram of the method according to the invention; FIG. 3 is a block diagram of a petrol processing unit A according to the prior art; FIG. 4 is a block diagram of a gas treatment unit B incorporating the method according to the invention. Similar items are generally referred to as identical reference signs.

According to the invention, the hydrocarbon feedstock which is capable of being treated by the process is a naphtha-type cut containing hydrocarbons having 7 to 11 carbon atoms per molecule. Said feed thus contains paraffinic, naphthenic and aromatic hydrocarbons and generally has a distillation range measured according to ASTM D86 which is between an initial point of 80 ° C and an end point of 200 ° C. Preferably the distillation range is between an initial point of 80 ° C and an end point of 185 ° C. Said cut can be obtained by direct distillation of the crude oil or also after distillation of a gasoline derived from a unit of catalytic cracking (Fluid Catalytic Cracking 20 according to the English terminology, which can be translated by catalytic cracking into fluidized bed). The hydrocarbon feedstock thus generally contains: 20 to 75% by weight of paraffins; 15 to 55% by weight of naphthenes; - 5 to 30% by weight of aromatics.

The C7 hydrocarbon fraction that composes the feed typically contains: 20 to 80 wt% of paraffinic C7; 20 to 55% by weight of C7 naphthenic; - 5 to 25% by weight of aromatic C7.

For example, the feed is a so-called "total" naphtha cut which has undergone a separation step in order to subtract the C 5 and C 6 hydrocarbon fraction, this operation being carried out by means of a "naphtha splitter".

With reference to FIG. 1, the hydrocarbon feedstock described above is fed through line 1 into a separation column 2 (or distillation column). In accordance with the invention, the C7 (i.e. hydrocarbons containing 7 carbon atoms per molecule) to C11 hydrocarbon feed (hydrocarbons containing 11 carbon atoms per molecule) is fractionated into three hydrocarbon cuts. The distillation column 2 is divided along its vertical axis into at least: - a concentration section located between the head of the column and the feed point of the load; a depletion section situated between the feed point of the load and the bottom of the column. The concentration and exhaustion sections are equipped with internal contact / gas-liquid exchange means. In the case of Figure 1, these internals are in distillation trays 3 known to those skilled in the art. A distillation tray 3 may take the form of a metal flat plate on which bubbler, barrier and overflow elements are located or alternatively it may be a plate having holes or slots. As shown in FIG. 1, a vapor phase whose composition is detailed below is extracted at the top of the column by line 4 while a liquid phase is recovered at the bottom of the column in the exhaustion section. line 5. In accordance with the invention, the column has a lateral withdrawal 6 which makes it possible to separate, from the product distilling at the top of the column, a fraction of volatile hydrocarbons in the liquid phase (or so-called intermediate cup). In operation, the C7 to C11 hydrocarbon feed is fed into the column which is configured and operated to separate three hydrocarbon cuts, namely: at the top of the column, a vapor phase containing essentially branched C7 paraffinic hydrocarbons (mono, di and tri-branched) and more volatile hydrocarbons; at the bottom of the column, a liquid phase containing naphthenic C7 hydrocarbons (for example dimethylcyclopentane and methylcyclohexane) and aromatic hydrocarbons (toluene) and C8 + hydrocarbons (i.e. hydrocarbons containing 8 to 11 carbon atoms per molecule); - At the side withdrawal, an intermediate section containing linear paraffins (n-heptane). Such a separation column is characterized generally comprises a number of trays of between 60 and 140, preferably between 80 and 110. Correctly used, the column provides a head cup containing at least 90% by weight of paraffins. C7 branched and with less than 1% by weight of paraffins C7 of the feed entering the column which are lost in the bottom cut.

Typically the recovery and conversion rate of linear paraffins is greater than 98% by weight. According to an alternative embodiment, the column is configured and operated under more severe conditions to separate: at the top of the column, a vapor phase containing essentially branched and tri-branched branched-chain hydrocarbons (2.2 dimethylpentane, 2,3-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane and 2,2,3-trimethylbutane) and more volatile hydrocarbons; at the bottom of the column, a liquid phase containing naphthenic hydrocarbons at 07 (for example dimethyl cyclopentane, ethylcyclopentane and methylcyclohexane) and aromatic at 07 (toluene) and C8 + hydrocarbons (c. that is, hydrocarbons containing between 8 and 11 carbon atoms per molecule). at the side draw, an intermediate cut containing linear paraffins (n-heptane) and mono-branched branched paraffins (2-methylhexane, 3-methylhexane and 3-ethylpentane). FIG. 1, the intermediate section which is withdrawn via line 6, situated a few trays below the head of the column, is sent to an isomerization unit 7 which comprises at least one reactor equipped with a reaction section 30 containing isomerization catalyst. The liquid intermediate section is thus brought into contact with the hydrogen supplied via line 8. The reaction involved makes it possible to isomerize linear paraffins in branched paraffins (mono, di and tri-branched).

The isomerization catalyst may comprise, for example, platinum deposited on a chlorinated alumina. The catalytic isomerization reaction is generally carried out under the following operating conditions: at a temperature of between 70 and 100 ° C., preferably between 80 and 90 ° C .; at an absolute pressure of between 2 and 5 MPa, preferably of between 2.5 and 3.5 MPa; with a mass space velocity, expressed as the ratio of the mass flow rate of the feedstock to the catalyst mass of between 1 and 1.6 h -1, preferably of between 1.2 and 1.4 h -1; with an H 2 / feed molar ratio of between 0.1 mol / mol to 1 mol / mol These operating conditions are chosen so as to limit the cracking reactions which form coke precursors which deactivate the isomerization catalyst. The effluent (or isomerate) extracted from the isomerization unit 7 is entirely recycled in the separation column 2, via the line 9 located between the lateral withdrawal line 6 and the injection point of the reflux liquid supplied by line 10.

Recycling the isomerate thus returns to the column the unconverted n-heptane contained in the isomerate so as to improve the isomer yield. In the separation column 2, branched paraffins are separated and recovered in the gaseous phase withdrawn at the top of the column via line 4. The gaseous phase undergoes a condensation step which involves cooling by means of an exchange device And a liquid / vapor phase separation with a phase separation device 12 (for example a separator flask). The residual vapor phase is discharged from the separation device 12 via line 13. The liquid phase (or condensate) is partly returned to the top of the column, through line 10, as a reflux liquid while the remainder of the liquid phase is The liquid phase of line 30 which contains essentially branched paraffins is a high octane base for the gasoline fuel formulation. Before being used as a gasoline base, the liquid phase undergoes a stabilization step (or debunatization) in order to remove the O 4 - hydrocarbons possibly present in the liquid phase.

As shown in FIG. 1, the liquid bottom slice which contains hydrocarbons boiling at a temperature above n-heptane (i.e., aromatic and aromatic C 7 hydrocarbons and C 8 + hydrocarbons) is drawn off. of the column through line 5. A portion of the bottom cut is fed through line 17 into a reboiler system 16 configured to vaporize and recycle the bottom cut into distillation column 2. The other part of the Bottom section is conveniently treated in a catalytic reforming unit (not shown) to produce a high octane reformate that can enter the gasoline fuel formulation.

FIG. 2 represents a second embodiment of the process which differs from that of FIG. 1 in that the effluent withdrawn from the isomerization unit 7 is sent to a debutanizer 20 in order to separate a hydrocarbon fraction in FIG. C4- (extracted via line 21) and a section of stabilized branched C7 paraffinic hydrocarbons which is recycled to the top of the separation column 2 via the line 22. The cooled vapor in the condenser 11 can then be completely liquefied with temperatures of the order of 40 ° C and the product extracted by the line 15 is then stabilized and can be used directly as a mixing base for gasolines. The process according to the invention can be integrated upstream of a conventional catalytic reforming unit which processes a C7 to C10 / C11 naphtha feedstock.

The method according to the invention also has the advantage of using a separation column already available on the refinery site when the latter already has an isomerization unit of the C7 cut, for example an Isomalk unit. -4 "of GTC Technology, which comprises a separation column designated by the term" deheptanizer ", for separating the C7 paraffins from the c7 + cut that is usually sent to the reforming when the gasolines are produced without isomerization of the C7 cut . Example In the example below, the operation of two treatment units A (comparative) and B (which comprises an isomerization unit C7 according to the invention) of a C5 to C11 naphtha fraction which comprises a C5 / C6 isomerization unit, a C7 isomerization unit and a catalytic reforming unit. Units A and B are shown in Figures 3 and 4, respectively. Processing units A and B are operated to produce a gasoline with an RON of 95.

Table 1 gives the composition of the treated naphtha fraction: Composition Paraffins 87% by weight Naphthenes 7% by weight Aromatics 6% by weight C4 0.4% by weight C5 12.4% by weight C6 20.2% by weight C7 21.2% weight C8 20.8% weight C9 16.3% weight Cl 0+ 8.7% weight Table 1 5 The charge rate treated by units A and B is set at 200 tonnes / hour. More specifically, the unit A is operated as follows: The naptha charge (05 - C11) is sent via the line 30 in a first separation column 31 (or splitter according to the English terminology) to separate at the top from the column a hydrocarbon cut 05/06 and in bottom a C7 + hydrocarbon cut. Hydrocarbon cutting 05/06 is sent via line 32 to an isomerization unit which comprises a reactor 33 employing ATIS-2L catalyst from AXENS. The reactor is operated at 3 MPa at 110 ° C. with a specific space velocity of 1.3 h -1 and a molar ratio H2 / feed of 0.2 mol / mol. The effluent extracted from the isomerization reactor 33 is "debutanized" in a debutanizer 34 from which a stabilized 05/06 isomerate is extracted via line 35. The stabilized isomerate 05/06 is treated in a separation column 36 (or dehexanizer) which makes it possible to recover at the top by line 37 an isomerate at 05, at the bottom by line 38 a isomerate at 06 and a lateral section containing essentially non-isomerized hexane which is recycled to the reactor 33 via the line 39. The recycle rate 20 is fixed in this case at 100%. The top and bottom products of the separation column 36 are mixed to form the 05/06 isomer which is then stored.

The c7 + hydrocarbon fraction withdrawn at the bottom of the column 31 via the line 40 is fractionated in a column 41 configured to separate at the top a paraffinic hydrocarbon fraction at 07 and in bottom a C8 hydrocarbon fraction. . As indicated in FIG. 3, the C7 paraffinic hydrocarbon fraction is sent via line 42 to the C7 isomerization unit using a reactor 43 loaded with ATIS-2L catalyst from AXENS. The C7 isomerization reactor is operated under the following conditions: 3 MPa, at 90 ° C. with a mass space velocity of 1.2 h -1 and a molar ratio of H 2 / feed of 0.2 mol / mol. The effluent extracted from the isomerization reactor 43 is "debutanized" in a debutanizer 44 which makes it possible to extract via line 45 a stabilized C7 isomer. The stabilized isomerate 07 is treated in a separation column 46 (or deheptanizer) which makes it possible to recover at the top by the line 47 a light isomerization at 07, in bottom by the line 48 a heavy isomerate at 07 and a lateral cut containing essentially non-isomerized n-heptane which is recycled to the reactor 43 via line 49. The recycle rate required in this case is 500% (ie a reactor 32 capable of treating six times the fresh charge rate). As for the hydrocarbon fraction discharged at the bottom of column 41 via line 50, it is treated by catalytic reforming in a unit 51 of catalytic reforming. In the example, the unit 51 used is a so-called "continuous regeneration" unit (or COR for Continuous Catalyst Regeneration) comprising four reactors in series using a catalyst comprising platinum and chlorine with an alumina support. The catalytic reforming unit is operated under the following conditions: T ° entry of the reactors: 520 ° C. Absolute mean inlet pressure of the four reactors: 0.5 MPa -special mass velocity: 2.1 h -1. note that the ratio (mass flow rate / mass of catalyst) is the adjustment variable allowing to reach a RON equal to 95 at the level of the mixture of the 3 products generated by the unit (isomerate 05/06 + isomerate 07 + reformat) Unit B differs from unit A in that the cut c7 + withdrawn at the bottom of the first separation column 31 is sent via line 40 to an isomerization unit according to the invention which is represented in Figure 2. As shown in Figure 4, the c7 + cut is split into three sections of hydrocarbons. Thus, at the top of the column, an isomerate containing branched and branched hydrocarbons is withdrawn at the bottom of the column, a section comprising aromatic and aromatic hydrocarbons and C8 + hydrocarbons and an intermediate section comprising the paraffinic hydrocarbons. In the example, the pressure at the top of the column 2 is set at 0.17 MPa absolute. The operating conditions of the isomerization reactor of the section 07 are identical to the case A. The flow rate drawn off in the column is equal to 6 times the paraffin flow rate at 07 present in the c7 + section entering the recycle column. The bottom section of column 2 which contains C8 + hydrocarbons but also toluene and most of the naphthenes with 7 carbon atoms is sent to the reforming, the operating conditions of which are as follows: reactor inlet temperature: 520 ° C. - absolute mean pressure at the inlet of the 4 reactors: 0.5 MPa - a mass space velocity: 2.9 h-1.

It should be noted that the mass spatial velocity is the adjustment variable making it possible to reach an RON equal to 95 at the level of the mixture of the 3 products generated by the unit (isomerate 05/06 + isomerate 07 + reformate). Note that for both examples, the isomerization units of the 07 have been adjusted so as to ensure in the isomerization reactor: the presence of less than 0.5% by weight of toluene because the exothermicity generated by the hydrogenation of this compound promotes cracking the presence of less than 25% by weight of naphthenes whose presence penalizes the conversion of paraffins.

The performances of the units A and B are presented in the tables below: Unit A Unit B (Scheme of (according to reference) the invention) Isomerisation unit section 07 Aromatic content [`) / 0 weight] 0.5% 0.4% of the feedstock entering the reactor Naphtgen content of the feed entering the reactor [`] / 0 wt.] 9% 22% RON isomerate 07 [-] 80.8 84.5 Petrol pool RON mixture [-] 95.0 95.0 Flow [standard m3.11-1] 250.9 252.5 [kg / h] 187575 188479 Yield [`) / 0 vol] 89.6% 90.2% [% wt] 93.8% 94.2% Aromatic content [% vol] 38.2% 38.0% Energy consumption specific to Unit Column deheptanizer [MW] 32.0 isomerization of (reference 41 Fig. 3) C7 Recycle column [MW] 38.6 46.5 (reference 46 Fig. 3, reference 2 Fig. 4) Stabilization column [MW] 12.0 12.0 (reference 44 Fig. 3, reference 20 Fig. 4) Total [MW] 82.6 58.5 As can be seen, the present invention substantially improves the efficiency of e conversion of the charge (0.4% wt and 0.6% vol gain) while slightly reducing the aromatics content in the gasoline pool (gain of 0.2% vol). The most significant effect is on the energy consumption specific to the isomerization part of the C7 cut, which is reduced by almost 30%.

Claims (9)

CLAIMS1) A process for producing gasoline bases from a hydrocarbon feedstock comprising paraffinic, naphthenic and aromatic hydrocarbons having 7 to 11 carbon atoms per molecule, including the following steps: a) the hydrocarbon feed is sent and a recycle stream in a separation column configured to separate at least three slices: - a top slice containing branched paraffinic hydrocarbons; an intermediate cut containing predominantly linear paraffinic hydrocarbons which is withdrawn at a level of the column located above the point 10 of injection of the feedstock and below the point of injection of the recycle stream; a bottom section containing naphthenic and aromatic hydrocarbons and C8 + hydrocarbons. b) treating the intermediate cut in an isomerization unit external to the separation column to produce an effluent containing branched paraffinic hydrocarbons; c) recycling said effluent into the separation column and at the top thereof as a recycle stream in step a). 2) Process according to claim 1, wherein the separation column is configured so as to provide an intermediate slice containing predominantly linear and mono-branched 07 paraffinic hydrocarbons and a top slug containing predominantly paraffinic hydrocarbons in the following manner. di and tri-connected. 3. The process according to claim 1, wherein the bottom cut is treated in a catalytic reforming unit. 4) Method according to one of the preceding claims, wherein the effluent from the isomerization unit is sent to a stabilization column to separate, respectively at the head and bottom of the stabilization column, a light cut at 04- and 30 a branched stabilized branched paraffinic hydrocarbon fraction and said stabilized branched branched paraffinic hydrocarbon fraction being recycled to the separation column in accordance with step c). 3034764 17 5) Method according to one of the preceding claims, wherein in step b) the intermediate cut is treated in an isomerization reactor under the following operating conditions: - at a temperature between 70 and 100 ° C; at an absolute pressure of between 2 and 5 MPa; with a mass space velocity, expressed as the ratio of the mass flow rate of the feedstock to the catalyst mass of between 1 and 1.6 h -1; with a molar ratio H 2 / charge of between 0.1 mol / mol to 1 mol / mol. 10 6) The method of claim 5, wherein step b) is operated: - at a temperature between 80 and 90 ° C; at an absolute pressure of between 2.5 and 3.5 MPa; with a mass space velocity, expressed as the ratio of the mass flow rate of the feedstock to the catalyst mass of between 1.2 and 1.4 h -1. 7) A process according to any one of the preceding claims wherein the feed containing paraffinic, naphthenic and aromatic hydrocarbons has a distillation range measured according to ASTM D86. which is between an initial point of 80 ° C and an end point of 200 ° C, and a deference of between 80 and 185 ° C. 8. Process according to one of the preceding claims, in which the treated hydrocarbon feed contains: 20 to 75 wt% paraffins 25 to 55 wt% naphthenes 5 to 30 wt. 0 weights of aromatics. 9) The process according to one of the preceding claims, wherein the hydrocarbon fraction at 07 which makes up the treated hydrocarbon feed contains: 30 - 20 to 80 (3/0 weight of paraffinic 07 - 20 to 55 (3) Naphthenic weights, 5 to 25 wt.