FIELD OF THE INVENTION
The field of the invention is that of high-octane gazoline production and the co-production of aromatic bases for petrochemistry (xylenes, toluene, benzene).

The arrangement described in the present invention makes use of an aromatics separation unit (SEP), a catalytic reforming unit (RC) for producing a high-octane gazoline (octane number NO of above 95), and a hydrogen-rich gas, and a unit known as an aromatics complex (CA) which essentially permits the production of aromatic bases, such as xylenes, benzene, toluene.

The present invention also enables catalytic reforming operating conditions to be optimised, so that for a given capacity, more high-octane gasoline will be produced than with prior art arrangements.

Another advantage of the arrangement according to the present invention is that according to one of the variants thereof it permits an increase in the production of para-xylene for a given amount of charge in the aromatics complex.

Finally, and this is essential to the overall economy of the refining arrangement where the hydrogen requirements are ever-increasing in order to achieve the various hydrotreatings and hydrogenations, the overall hydrogen yield of the process is clearly improved over prior art arrangements.

STUDY OF THE PRIOR ART
Conventionally, the purpose of a catalytic reforming unit is to convert naphthenic and paraffinic compounds (n-paraffins and iso-paraffins) into aromatic compounds. The main reactions employed are dehydrogenation of the naphthenes and dehydrocyclisation of the paraffins into aromatics, and isomerisation of the paraffins and naphthenes. Other, so-called "parasite" reactions, can occur, such as hydrocracking and hydrogenolysis of the paraffins and naphthenes, hydro-dealkylation of the alkyl-aromatics giving rise to light compounds and lighter aromatics, and coke formation at the surface of the catalyst.

The performances which are to be optimised for a gasoline application are the yield of liquid reformate and the octane number of said reformate, whereas in a petrochemical application the performances sought are the aromatics yield and the distribution of the aromatics produced. The aromatics are generally treated in an aromatics complex in order to maximise production of one or more products, most frequently the xylenes and benzene. Toluene and heavier aromatics can be upgraded to constitute gasoline stock, or to produce xylene mixtures.

The conventional charges of a catalytic reforming unit are rich in paraffinic and naphthenic compounds and relatively poor in aromatic compounds. These are typically naphthas coming from crude distillation or natural gas condensates.

In addition to conventional charges, other available charges are to be found in a refinery, containing variable contents of aromatics, namely heavy naphthas from catalytic cracking (FCC), coking, hydrocracking, or gasoline from steam cracking. These charges, which vary in respect of their content in aromatic compounds, can be used for feeding a catalytic reforming unit for the production of gasoline bases or aromatic bases.
There are certain drawbacks in sending charges containing significant amounts of aromatics directly to a catalytic reforming unit. Firstly, the increase in capacity of the unit is unusefull since the aromatic compounds do not need to undergo reforming reactions. Secondly, these aromatic species can undergo "parasite" reactions of hydro-dealkylation which give rise to a loss in the yield of aromatics, or polycondensation reactions which cause coke deposits on the catalyst.

The presence in the charge of these species with a high coking capacity generally gives rise to an increase in the intensity of the reforming, which is manifested by an increase in investment costs and operating costs.

Proposals have been made for modifications in the conventional arrangement for recovering the aromatic compounds contained in the charge of a reformer.

Thus, according to one approach for the production of benzene, US 2007/0129590 proposes a method which applies to the naphthas which feed conventional reformers employing platinum- and/or rhenium-based catalysts, which may, or may not, be doped.

The proposed arrangement consists in recovering, in a unit for the extraction of aromatics, 3 fractions from a C6-C11 naphtha cut; an aromatic fraction, a fraction of aromatic precursors, and a raffmate fraction.

The raffinate fraction is an end product, whereas the aromatic precursor fraction is sent to a reforming unit operating at low intensity to convert the aromatic precursors into aromatics. The effluent from the reforming unit is sent, together with the naphtha, to the extraction unit in order to recover the aromatics and unconverted aromatic precursors. These latter are recycled to the low intensity reforming unit until they are exhausted.

The arrangement described in the cited document requires an extraction unit which is capable of recovering the non-aromatic compounds in two separate cuts; namely, the fraction of aromatic precursors and the raffinate fraction. Separation of this kind necessitates additional distillation and/or adsorption stages in order to obtain a naphthene-rich flow in the aromatic precursor fraction, and a second, paraffin-rich flow in the raffmate fraction.

Moreover, the arrangement described in the cited document does not employ the paraffins available in the charge for the purpose of producing aromatics, which is not very adequate when the aim is to maximise aromatics production, or gasoline production. In fact, the paraffins recovered in the raffinate fraction are mainly n-paraffins or mono-branched paraffins which are not the most interesting species for a gasoline application.

The aim of the arrangement according to the present invention is to provide a very flexible process arrangement allowing the effluents to be directed towards the production of gasoline bases, or towards the production of aromatic bases. Furthermore, the arrangement according to the present invention makes it possible to avoid the drawbacks caused as a result of converting the aromatics-rich charges in the catalytic reforming unit, and to improve yields in favour of the products sought.

Moreover, the arrangement according to the invention makes it possible to increase the flexibility of the catalytic reforming unit, by improving its adaptation to variations in respect of the composition of the charges, or to an enlargement of the origins, with limited impact upon the operating conditions and intensity.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a diagram showing the process arrangement according to the invention in a very generalised way, with an aromatics separation unit (SEP), a catalytic reforming unit (RC), and a so-called aromatics complex unit (CA). In Figure 1, the units or lines indicated by dashes denote components which are optional.

Figure 2 shows one particular arrangement according to the invention whereof the objective is to maximise para-xylene production.

Figure 3 shows an arrangement of the prior art which does not comprise an aromatics separation unit.

BRIEF DESCRIPTION OF THE INVENTION
To facilitate comprehension of the text, "naphtha" should be understood hereinafter as a gasoline cut of any random chemical composition, and with a distillation range of between 50°C and 250°C. The chemical family distribution, denoted by the letters PONA (P for Paraffins, O for Olefins, N for Naphthenes, and A for Aromatics) can be arbitrary.

Aromatic bases in the broad sense are xylenes (para-xylene, meta-xylene, ortho-xylene), ethylbenzene, toluene and benzene, and, possibly, heavier aromatics such as monomer styrene, cumene or linear alkylbenzenes.

The reformate is the high-octane gasoline cut with an octane number above 95, produced by the catalytic reforming unit.

A high-octane gasoline is a high-octane gasoline with an octane number of above 95, and preferably above 98.
The present invention can be defined according to Figure 1 as a process for the production of a high-octane gasoline with an octane number of above 95, and preferably of above 98, and a process for the co-production of aromatic bases firom one or more naphtha cuts coming firom one or more of the following units: atmospheric distillation-, FCC, coking, steam cracking unit, hydro cracking unit, or resulting firom the fractionation of natural gas condensates.
In the process according to the present invention, the naphtha charge (1) is generally sent to an aromatics separation unit (SEP) which produces a so-called "extract" cut (3) containing most of the aromatics, and a so-called "raffinate" cut (2) containing most of the non-aromatic compounds.
In some instances, if the aromatics content of the naphtha charge is low, say less than 30% by weight, preferably less than 20% by weight, and, still more preferably, less than 10% by weight, the aromatics separation stage can be eliminated, and said naphtha which is "low in aromatics" can be sent directly to the catalytic reforming unit (RC).
Most generally, when the charge is constituted by naphtha with a high aromatics content (let's say above 30% by weight), and by naphtha with a low aromatics content, the resulting arrangement corresponds to that of Figure 2 where there is a distinction between the part of the naphtha charge with a low aromatics content which is sent direct to the catalytic reforming unit (RC), and the part of the naphtha charge with a high aromatics content which is sent to the aromatics separation unit (SEP).
The aromatics separation unit (SEP) produces a raffinate (14) which contains almost no more aromatics, and an extract (3) which is rich in aromatics.
- At least part of the raffinate (14), possibly mixed with part of the charge (11) constituted by naphthas with a low content of aromatics, is sent to a catalytic reforming unit (RC) from which a hydrogen flow (5) and a high-octane gasoline cut (4) are produced, forming part of

the gasoline pool, said gasoline possibly being recycled either partially or completely to the aromatics separation unit (flow 9'), or being sent to the aromatics complex unit (CA) via the flow (6), and
- all, or part of, the extract (3) is sent to a so-called aromatics complex unit (CA) permitting the production of aromatic bases (flows (7) and (8)), the other part of the extract (3), if there is one, i.e. flow (9), being sent to the gasoline "pool" via the flow (9).
When the raffmate (14) is not entirely sent to the catalytic reforming unit (RC), the part (2') which is not sent to the catalytic reforming unit (RC) can form part of the gasoline pool, or be sent to a conversion unit, like a steam cracking unit.
The process according to the invention, in its most general form, includes all possible distributions between the production of high-octane gasoline (4) and the production of aromatic bases (flows 7 and 8), including the two extreme cases, namely the production of high-octane gasoline only, and the production of aromatic bases only.
These two extreme cases are perfectly well within the scope of the invention.
According to one variant of the process for production of high-octane gasoline with an octane number of above 95, and for the co-production of aromatic bases according to the invention, shown in Figure 2, the charge which is to be treated is composed of at least one naphtha cut from direct distillation (10) and a naphtha cut (12) from a catalytic cracking unit (not shown in Figure 2),
- the naphtha cut ex FCC (12) is sent to a hydrotreatment unit (HDTl), and the resultant hydrotreated cut (13) is sent to the aromatics separation unit (SEP) which produces a flow of extract (3) which is sent to the aromatics complex unit (CA).
- the naphtha cut (10) from direct distillation is sent to a hydrotreatment unit (HDT2), and the resultant hydrotreated cut (11) is mixed with the raffinate (14) resulting from the aromatics separation unit (SEP), in order to constitute the charge (2) of the catalytic reforming unit
(RC).

The catalytic reforming unit (RC) produces a reformate (4) which is sent, at least partially, (flow 6) to the aromatics complex (CA) which permits the production of the aromatic bases (7) and (8).
The catalytic reforming unit (RC) also produces a flow of hydrogen (5).
A part of the extract (3) can be blent with the reformat (4) and the resulting flux (6') can be directed to the gasoline pool.
According to another variant of the process of the present invention, the charge (1) which is to be treated is constituted by a random mixture of the various cuts resulting from the following operations: direct distillation of crude, catalytic cracking, coking, hydrocracking, steam cracking, or natural gas condensate, the charge to be treated being able to be sent, as a mixture, to a hydrotreatment unit (HDT) located upstream of the aromatics separation unit (SEP).
In other instances, depending on the impurities content in the various cuts constituting the charge which is to be treated, in particular sulphur and nitrogenous compounds, or unsaturated compounds, certain cuts constituting the charge can be sent to separate hydrotreatment units.
According to another variant of the process of the present invention, all of the extract (3) coming from the aromatics separation unit (SEP) can be sent to the aromatics complex unit (CA).
According to another variant of the process according to the present invention, all of the high-octane gasoline produced as a result of catalytic reforming (RC) can be sent to the aromatics complex (CA).
In some configurations, which form part of the arrangement of the present invention, the catalytic reforming unit (RC) operates at high intensity, i.e.:
- with an average reactor inlet temperature of between 450 and 560°C,

- a H2/HC ratio of between 1 and 5 mole/mole,
- an average reactor pressure of between 3 and 16 bar (1 bar -105 pascal)
- a mass space velocity of between 1 and 5 kg charge/(kg catalyst.h).
DETAILED DESCRIPTION OF THE INVENTION
The detailed description given hereinafter will permit a better understanding of the operation of the units used in the arrangement according to the invention. The description is made with reference to Figure 1.
The present invention consists of a arrangement of at least 3 units, namely an aromatics separation unit (SEP), a catalytic reforming unit (RC) and a so-called aromatics complex unit (CA) for obtaining a) a high-octane gasoline, i.e. with an octane number of above 95 and, simultaneously, b) aromatic bases, mainly xylenes, benzene and toluene, in amounts which can vary, as desired.
The naphtha charge (1), possibly following hydrotreatment shown by the unit denoted as (HDT) in Figure 1, is sent to an aromatics separation unit (SEP) which produces a so-called "extract" cut (3) containing most of the aromatics, and a so-called "raffmate" cut (2) containing most of the non-aromatic compounds, at least part of the raffinate (2) being sent to a catalytic reforming unit (RC) from which are produced a hydrogen flow (5) and a high-octane, so-called "reformate" gasoline cut (4) constituting part of the gasoline pool, said gasoline being able to be completely or partially recycled to the aromatics separation unit (flow 9'), or being sent to the aromatics complex unit (CA) via the flow (6), and the extract (3) being sent either completely or partially to a so-called aromatics complex unit (CA) from which aromatic bases (flows (7) and (8)) are produced, the other part of the extract (3), if there is one, being sent to the gasoline "pool" via the flow (9).
When a part (9') of the reformat (4) is recycled to the aromatics separation unit (SEP), the so called part (9') is preferentially constituted of the fraction in C6, C7 or C8 contained in the reformat (4).

When the raffinate (2) is not entirely sent to the catalytic reforming unit (RC), the part (2') which is not sent to the catalytic reforming unit (RC) can constitute part of the gasoline pool, or be sent to the conversion unit, such as a steam cracking unit.
In one particular case a) of the process according to the invention, it is possible to maximise the production of aromatic bases (flows (7) and (8)) by sending all of the extract (3) to the aromatics complex (CA) and by recycling a major part of the reformate (4) to said aromatics complex (CA) via the flow (6).
In another particular case b) of the process according to the invention, it is possible to maximise the production of high-octane gasoline (flow 4)) by sending a major part of the extract (3) to the gasoline pool via the flow (9), and by sending all of the reformate (4) to the gasoline pool.
All the intermediate variants between the afore-mentioned examples a) and b) are obviously possible, and depend upon the level of recycling of the extract (3) to the gasoline pool via the flow (9), and on the level of recycling of the reformate (4) to the aromatics complex (CA) via the flow (6).
In another particular instance of the process according to the invention, it is possible to obtain reformate (4) and an extract (3) only. This happens, in practice, when the extract (3) produced in the aromatics separation unit (SEP) is sent to an aromatics complex which cannot be present on the site where the aromatics separation unit and catalytic reforming unit are located, but which can be provided on a different site.
The case when the aromatics complex is located on a separate site from the aromatics separation unit and the catalytic reforming unit, is considered as equivalent to the case when all the units are located on the same site and thus remains perfectly well within the scope of the invention.
In another variant of the process of the invention, it is possible to send all of the reformate (4) to the gasoline pool, and all of the extract (3) to the aromatics complex.

The flexibility of the arrangement according to the invention is an important aspect which distinguishes it from prior art arrangements.
Hereinafter in the description, information will be given concerning 1) the aromatics separation unit, 2) the catalytic reforming unit, and 3) the aromatics complex.
1) The separation unit (SEP) for aromatic compounds which generally have from 6 to 11 carbon atoms can be made up by processes known to the skilled person, based on an absorption system such as liquid-liquid extraction, or extractive distillation employing one or more solvents, or based on an adsorption system. The process according to the invention is not associated with any particular technology as far as the aromatics separation unit is concerned.
The aromatics separation unit can be designed in such a way that it only extracts part of the aromatic compounds contained in the charge, e.g. the compounds which have from 6 to 10, from 6 to 9, or from 6 to 8 carbon atoms. The complementary part of the aromatic compounds, namely Cll, C10 to Cll, or C9 to Cll aromatic compounds, are thus to be found in the raffinate.
In the following example, the aromatic compounds are separated in accordance with liquid-liquid exfraction technology. The exfraction is carried out by the use of a solvent of the sulfolane type, of the chemical formula C4 H8 02 S, which has a sfrong affinity with aromatic compounds. The products issuing from the aromatics separation unit are a "raffinate" (2) which is rich in non-aromatic compounds, and an "extract" (3) which concentrates the aromatic compounds contained in the charge (1).
The charge (1), possibly following hydrotreatment, is contacted with the solvent in a first exfraction column from which a solvent is recovered which is rich in aromatic compounds, and a raffinate (2) which is constituted by non-aromatic compounds. The raffinate (2) is then purified in a washing column in order to remove residual fraces of solvent.

The solvent which is rich in aromatic compounds is firstly stripped of these latter non-aromatic compounds in a "stripping" column, and is then sent to a column for the recovery of aromatic compounds. Following regeneration, the solvent is recycled, whilst the aromatic compounds are recovered in the extract (3).
2) The catalytic reforming unit (RC) operates under operating conditions which are dependent upon the charge which is to be converted and the sought products in order to optimise the yield of them.
If necessary, the charge arriving for catalytic reforming can be hydrotreated in order to attain the required specification in terms of the content of sulphur, nitrogen and olefinic and diolefinic compounds.
There are generally 3, 4 or 5 reactors constituting the catalytic reforming unit. The catalysts used are also catalyst systems selected in accordance with operating conditions. They are typically promoted platinum-based, the promoter being able to be Re, Sn, In, P, Ge, Bi, boron, iridium, rare earths, or any random combination of those elements. Preferably, the catalyst promoters of the catalytic reforming unit will be selected from the following list: Sn, In, P.
The catalytic reforming unit can call upon the fixed bed, or moving bed, technology.
A catalytic reforming unit in fixed bed, or in moving bed, or as a combination of the two technologies, typically operates within the following operating ranges:
- with an average reactor inlet temperature of between 400 and 560°C,
- a H2/HC ratio of between 1 and 10 mole/mole,
- an average reactor pressure of between 3 and 37 bar (1 bar = 105 Pascal),
- a mass space velocity of between 1 and 5 kg charge/(kg catalyst.hour).
The catalytic reforming unit preferably operates within the range of the so-called continuous regeneration processes for which the operating ranges are stricter, namely

- an average reactor inlet temperature of between 450 and 560°C,
- a H2/HC ratio of between 1 and 5 mole/mole,
- an average reactor pressure of between 3 and 16 bar,
- a mass space velocity of between 1 and 5 kg charge/(kg catalyst.h).
3) The aromatics complex denotes a combination of different fractionation units, for example adsorption, distillation, extractive distillation, liquid-liquid extraction, or crystallisation units, and/or conversion units, these units being possibly for the re-arrangement of aromatics, such as transalkylation or disproportionation processes, selective or not, aromatics dealkylation or alkylation units, or units for the isomerisation of the xylenes with or without dealkylation of ethylbenzene.
The products from an aromatics complex are mainly intermediate petrochemicals, referred to here as "aromatic bases", such as benzene, para-xylene, ortho-xylene, meta-xylene, xylene cuts, ethylbenzene, styrene monomer, cumene or linear alkylbenzenes, or ingredients for constituting gasoline bases, such as toluene, or a cut of heavy aromatics.
If so required, the charge arriving at the aromatics complex can be hydrotreated.
EXAMPLE
The following example compares the arrangements of two processes: one arrangement is in accordance with the invention (as in Figure 2), and one arrangement is in accordance with the prior art and is without an aromatics separation unit (as in Figure 3).
In both the prior art arrangement and the arrangement according to the invention, the catalytic reforming unit (RC) and the aromatics complex (CA) are identical.
In both cases, the charges under consideration are:
- a heavy naphtha cut resulting from the direct distillation of crude (10) with a distillation
range of between 60° and 165°C along the true distillation curve (so-called "TBP" curve).

- a naphtha curve (12) resulting from a catalytic cracking unit (FCC), rich in aromatic compounds.
A charge of this kind can come from a catalytic cracking unit (denoted as FCC) which is dedicated to the production of gasoline or light olefins for the petrochemicals industry, operating at high intensity (reactor outlet temperature of 550°C, or above, and a ratio of catalyst flow rate to charge flow rate of above 10), and employing catalysts with specific formulations doped, or not, with one or more zeolites.
The content of aromatic compounds in the naphtha cut produced in the FCC is actually considerably increased when the intention is to maximise the propylene yield of said FCC, as is the case in this example.
The chemical family distribution (PONA) of the two charges is given in Table I hereinbelow:


Description of the prior art arrangement
The prior art arrangement is as shown in Figure 3.
In the prior art arrangement, the charge (21) constituted by the mixture of the two cuts shown in Table 1 (a naphtha cut resulting from direct distillation of crude (10) and a naphtha cut coming from an FCC unit (12)) is sent to a hydrotreatment unit (HDT) whence a hydrotreated effluent (22) issues. This hydrotreatment is needed in order to permit feeding of the catalytic reforming unit (RC) so that requirements are observed in respect of the impurities which it can contain (Bromine index of olefins and diolefins of <100, sulphur < 1 ppm wt. and nitrogen < 1 ppm wt.).
The hydrotreated flow (22) constitutes the charge of a catalytic reforming unit (RC) which produces a reformate (24), all of which is sent to an aromatics complex (CA), and a hydrogen-rich gas (23).
The catalytic reforming unit (RC) operates under the following conditions:
Reactor inlet temperature : 510°C
Pressure : 4.5 bar
H2/HC ratio: 3.0
A description of the aromatics complex, which is identical to that used in the arrangement of
the process according to the invention, will be given hereinafter.
This aromatics complex (CA) produces para-xylene (27) and benzene (28). Description of the arrangement according to the invention
The arrangement of the process according to the present example is as shown in Figure 2.
The charge is the same as that of the prior art arrangement, that is to say:
- a naphtha cut from direct distillation of crude (10)
- a naphtha cut from an FCC unit (11) rich in aromatic compounds.

1) Initial hydrotreatment of the naphtha charge ex FCC is needed in order to permit feeding of the catalytic reforming unit (RC) so that requirements are observed in respect of the impurities which it can contain (Bromine index of olefins and diolefins of <100, sulphur < 1 ppm wt. and nitrogen < 1 ppm Avt.).
Only the gasoline resulting firom the FCC following hydrotreatment is sent to the aromatics extraction unit, since it contains about 67% aromatic compounds, in comparison with only 7% for the gasoline fi-om direct distillation.
The effluents from the aromatics extraction unit (SEP) are:
- an extract (3), all of which is sent to the aromatics complex (CA), and
- a raffmate (14) which is mixed with the heavy naphtha (11) from direct distillation which has been hydrotreated in order to constitute the charge (2) of the catalytic reforming unit (RC).
The chemical family distribution (PONA) of the charge of the catalytic reforming unit is given in Table 2 hereinbelow for the prior art and for the present invention.


2) The catalytic reforming unit (RC) operates under the following conditions:
Reactor inlet temperature : 520°C
Pressure : 4.5 bar
H2/HC ratio: 1.5
The reformate (4) produced by the catalytic reforming unit is all sent (flow 6) to the aromatics
complex unit (CA) from which para-xylene (7) and benzene (8) are produced.
Table 3 hereinafter compares the capacity of the catalytic reforming unit (RC) and the operating conditions thereof, the average pressure of the reactors (P), the average reactor inlet temperature (T), and the rate of recycling ({H2/HC} ratio) in 3 cases:
- in the case of the invention,
- in the 2 prior art cases, referred as case a) and case b), which have the following meaning:
- case A corresponds to the prior art arrangement with a catalytic reforming unit which has the same charge of catalyst as that used according to the invention.
The capacity of the catalytic reforming unit is 77 (arbitrary units) for the arrangement according to the invention, and is 100 (arbitrary units) for the prior art arrangement due to the aromatics having been drawn off upstream of the catalytic reforming unit.
The space velocity is therefore in the same ratio as that of the charges, i.e. 77 according to the invention, and 100 according to the prior art.
- Case B corresponds to the prior art arrangement with a reforming unit which operates with
a larger catalyst charge, in order to permit a comparison between the prior art arrangement
and the arrangement according to the invention, given the same catalytic reforming space
velocity.


TABLE 3
The arrangement according to the invention permits operation under optimum catalytic reforming conditions because they are more favourable towards improved selectivity of aromatic compounds: specifically, the H2/HC ratio is divided by 2, and the temperature is increased by l0°C.
3) The aromatics complex, which is identical in the prior art arrangement and in the arrangement according to the invention, is made up of the following units:
Two conversion units:
- one unit for the transalkylation of toluene and C9+ aromatics so as to produce C8 aromatics and benzene.
- one unit for the isomerisation of xylenes and for the dealkylation of ethylbenzene.

Various Fractionation units:
- A fractionation column for all of the reformate into a light (C7-) reformate, and a C8+
reformate,
- A fractionation column for the C8+ aromatic cut into a C8 cut and a C9+ aromatic cut,
- A fractionation column for the C9+ aromatic cut and a cut rich in C9-C10 and a cut of heavier aromatics,
- An extractive distillation unit for separating from the non-aromatic compounds an aromatic cut which is rich in benzene and toluene,
- A BT fractionation section made up of a column of benzene and a column of toluene,
- A unit for the separation, by adsorption, of the para-xylene from a C8 aromatic cut.
To be more specific, the aromatics complex operates in the following way, with reference to Figure 2:
The reformate (6) is sent to a fractionation column which separates a light reformate (C7-) from a C8+ reformate. The light reformate is sent to ein extractive distillation unit for separating from the non-aromatic compounds an aromatic cut which is rich in benzene and toluene. This latter is sent to a fractionation column for separating the Benzene as the end product of the complex from the toluene used as reagent in a transalkylation unit. The heavier aromatics (C8+) are mixed with the C8+ reformate.
The C8+ reformate is sent to a fractionation column (column of xylenes) which separates the C8 aromatics from the heavier aromatics. These latter are subsequently fractionated in order to send an aromatic cut rich in C9-C10 type carbon atoms as reagents into the transalkylation unit.
In that unit, the toluene reacts with the heavier aromatics in order to produce C8 aromatics and also benzene. Recycling of the effluent to the BT fractionation section permits fractionation of the unconverted products and reagents, so that they rejoin the C8 aromatics at the top of the column of xylenes. That C8 cut is then converted into para-xylene: this latter is separated from the other isomers by way of an adsorption process. The effluent is then sent to a unit for the isomerisation of xylenes, where equilibrium is restored between the various

xylene isomers, and where the ethylbenzene is converted into benzene by dealkylation. The isomerisation effluent is then recycled to the column of xylenes until the fresh charge has been depleted of all the xylenes. As a result, the Para-xylene (7) is the main product of the complex, benzene (8) being the main co-product.
Taking into consideration the assembly comprising "aromatics separation unit + catalytic reforming unit". Table 4 hereinafter compares the production of hydrogen (H2), liquid reformate (C5+) and the products described as aromatic compounds.
Table 4 hereinbelow compares the performance of the catalytic reforming catalyst in terms of aromatics selectivities (STA) and the conversion of non-aromatics (C6+ NA) in the prior art and according to the invention.
In comparison with A of the prior art, the arrangement according to the invention permits greater production of liquid reformate, of hydrogen and of aromatic compounds, but also better retention of heavy aromatics (C8+).
Although the arrangement B of the prior art does make it possible to produce more hydrogen and aromatic compounds (at the expense of the yield of liquid reformate) than prior art case A, the yields remain less than those obtained with the arrangement according to the invention.
Moreover, the distribution of the aromatic compounds produced is different from that of the arrangement according to the invention: the more benzene and toluene, fewer C9+ aromatics are produced, which has an impact upon the performance of the aromatics complex downstream.
From studying the performances of the catalytic reforming unit it can be seen that the conversion of non-aromatic C6+ compounds is certainly increased in case B compared with case A, but the selectivity towards aromatic compounds remains clearly less than that which is achieved with the arrangement according to the invention.

Neither case A nor case B of the prior art is able to achieve the yields of the present invention.
NOTE:
The selectivity towards aromatic compounds (mol/mol) is defined as the ratio of moles of
aromatic compounds produced to moles of non-aromatic C6+ compounds converted.
The conversion of C6+ non-aromatics in the charge is defined as the ratio of moles of converted non-aromatic C6+ compounds to moles of non-aromatic C6+ compounds at the inlet.
Table 5 hereinafter compares the production of para-xylene and benzene at the outlet from the aromatics complex unit (CA).

The production of para-xylene in the arrangement according to the invention is increased by 2.5 units of weight/hour in comparison with case A, and by 2.2 units of weight/hour in comparison with case B, which is quite meaningful.
In comparison with case A, prior art arrangement B certainly does produce slightly more para-xylene. However, the ratio of para-xylene produced / benzene produced is reduced overall.
The arrangement according to the invention therefore makes it possible to maximise para-xylene production.

CLAIMS

1) A process for the production of gasoline with an octane number of above 95, and for the co-production of aromatic bases in which the charge (1) to be treated is composed of various naphtha cuts of diverse origin (direct distillation, catalytic cracking unit, coker, steam reforming unit, or fractionation of natural gas condensates),

- the part of the charge with a high aromatic content (above 30% by weight), represented by the flow (12), is sent to a hydrotreatment unit (HDTl), and the resultant hydrotreated cut (13) is sent to an aromatics separation unit (SEP) which produces a raffinate (14),

- the part of the charge with a low aromatic content (less than 30% by weight, and preferably less than 20% by weight), represented by the flow (10), is sent to a hydrotreatment unit (HDT2), and the resultant hydrotreated cut (11) is mixed with the raffinate (14) coming from the aromatics separation unit (SEP), so as to constitute the charge (2) of a catalytic reforming unit (RC),

- at least part of the extract (3) coming from the aromatics separation unit (SEP) is sent to an aromatics complex unit (AC) which produces aromatic bases (7) and (8), the other part of the extract (3) being sent via the flow (9) to the gasoline pool,

- the catalytic reforming unit (RC) produces a reformate (4), at least part of which is sent to the aromatics complex (CA) via the flow (6), the other part of the reformate (4) being sent to the gasoline pool by the flow (6'), and a hydrogen flow (5).

2) A process for the production of gasoline with an octane number of above 95, and for the co-production of aromatic bases according to Claim 1, wherein all of the extract (3) coming from the aromatics separation unit (SEP) is sent to the aromatics complex unit (CA).

3) A process for the production of gasoline with an octane number of above 95, and for the co-production of aromatic bases according to Claim 1, wherein all of the reformate (4) produced by catalytic reforming (RC) is sent to the aromatics complex (CA).

4) A process for the production of gasoline with an octane number of above 95, and for the co-production of aromatic bases according to Claim 1, wherein the catalytic reforming unit (RC) operates at high intensity, that is to say.

- with an average reactor inlet temperature of between 450 and 560°C,

- a H2/HC ratio of between 1 and 5 mole/mole,

- an average reactor pressure of between 3 and 16 bar,

- a mass space velocity of between 1 and 5 kg charge/(kg catalyst.h).

5) A process for the preparation of gasoline with an octane number of above 95, and for the co-production of aromatic bases according to Claim 1, wherein the catalytic reforming unit (RC) makes use of a Pt-based catalyst promoted with one of the following elements: Re, Sn, In, P, Ge, Bi, boron, iridium, rare earths, and preferably selected from the sub-list Sn, In, P.

6) A process for the production of gasoline with an octane number of above 95, and for the co-production of aromatic bases according to Claim 1, wherein a part (9') of the reformate (4) coming from the catalytic reforming unit (RC) is recycled to the aromatics separation unit.