FR2686094A1 - Production of base for benzene-free motor fuel exhibiting a high octane number - Google Patents

Abstract

Reduction in the benzene content in the gasoline pool, in which hydrogenation is carried out of the feedstock characterised by a weight composition included within the following ranges: - between 40 and 80 % of paraffins - between 0.5 and 7 % of naphthenes - between 6 and 45 % of aromatics and a maximum distillation temperature of between 70 and 90@C, then an isomerisation of the said feedstock is carried out, the process being characterised in that the said feedstock has been mixed with a C5-C6 direct distillation cut at at least one of the following times: - just before the hydrogenation, - just before the isomerisation and after the hydrogenation of the said feedstock.

Description

The invention relates to a method for reducing the benzene content in the gasoline pool by a process combining the hydrogenation of benzene contained in the light reformate and optionally the C5 / C6 direct distillation cut and the isomerization of the effluent from the hydrogenation and optionally of said cut.

PRIOR ART
Environmental problems will lead to the reduction of lead content and the reduction of benzene content in the gasoline pool, preferably without a decrease in octane number.

This leads to the need for a rearrangement of the various hydrocarbons present in the gasoline pool, in order to obtain high octane numbers. Catalytic reforming used under conditions of high severity, and isomerization of normal low-octane C5 / C6 paraffins are the most commonly used methods for obtaining high octane numbers without the addition of lead.

However, the catalytic reforming process produces large amounts of high octane benzene. It now appears that the legislation of different countries envisages, in the more or less short term, to reduce the benzene content in the species. This is why it is necessary to develop new processes to reduce the benzene content of fuels while meeting the specifications on the octane number.

The combination of catalytic reforming and isomerization processes, consisting of separating the C5 / C6 fraction from the reformate, isomerizing it and introducing it directly into the gasoline pool to improve the octane number, is well known: is described for example in US-A-4,457,832, US-A-4,181,599, US-A-3,761,392. The isomerization treatment of the C5 / C6 cut resulting from the direct distillation of crude oil is also well known. It leads to a considerable improvement in the octane number of this pair. The reduction of the benzene content of the reformate can also be carried out in various ways, such as for example the modification of the cutting point of the naphtha between the reforming and isomerization, or the separation of the reformate into two fractions: a heavy reformate and a light reformate in which all the benzene is concentrated. This light fraction is then sent to a hydrogenation unit which converts benzene to naphthenes, which are then ring-opened in an isomerization unit operating under severe conditions. The paraffins thus formed are isomerized by a conventional isomerization process (US-A 5,003,118). In the case of an isomerization catalyst based on chlorinated alumina, the naphthenes are adsorbed on the catalyst and thus contribute to deteriorate its activity.

US-A-3,611,117 also discloses a process for the hydroisomerization of cyclic hydrocarbons which uses a zeolite-supported Group VIII metal as a ring-opening catalyst under severe operating conditions and as an isomerization catalyst in mild operating conditions.

One of the major problems in reducing the benzene content by saturation followed by ring opening and isomerization of the paraffins formed is the possible reduction of the octane number of the cut.

The object of the present invention is to jointly carry out the reduction of the benzene content contained in the light reformate and the isomerization of the paraffins contained on the one hand in this light reformate and on the other hand in the C5 / C6 paraffinic fraction. from the direct distillation, by prior hydrogenation of benzene in a hydrogenation unit and then by isomerization.

 Surprisingly, it has been shown that the joint treatment of these two feeds led to the production of an effluent that is preferably completely benzene-free and has a sufficiently high octane number so that it can be directly incorporated into the gasoline pool. after stabilization.

DETAILED DESCRIPTION OF THE INVENTION
The feeds concerned by the present invention are: 1) the light fraction of the reformate, 2) the C5 / C6 cut resulting from the direct distillation.

The light fraction of the reformate is obtained by distillation of said reformate. The maximum distillation temperature of this fraction is between 70 and 90 ° C, preferably between 77 and 83 ° C. The weight composition by hydrocarbon families of this light fraction of the reformate is variable according to the following intervals: - paraffins: between 40.0 and 80.0%, - naphthenes: between 0.9 and 7.0%, - aromatics: between 6.0 and 45.0%.

The family of aromatic hydrocarbons consists essentially of benzene; in addition, between 1.0 and 3.0% of olefinic hydrocarbons may be present in this light fraction. The average molecular weight of this filler is between 70 and 90 g / mol and its density measured at 15 ° C is between 0.670 and 0.780 g / cm 3. The value of the octane number search for this charge is included. generally between 75 and 90.

Any other hydrocarbon feedstock from another process or set of processes and having characteristics similar to those described above may also be used.

The weight composition of the C5 / C6 cut resulting from the direct distillation depends on the nature of the crude to be treated.

It may contain very low levels of compounds having 4 carbon atoms per molecule (less than 0.5% by weight).

The paraffin content is generally greater than 90% by weight, the naphthene content is less than 10% by weight and the benzene content is less than 1.5% by weight. Its research octane number is between 60 and 75.

These two types of charges can be sent together to the hydrogenation unit, the light reformate content varying from 10 to 90% and preferably from 20 to 80%.

Preferably, the charge resulting from the direct distillation is mixed with the saturated light reformate at the outlet of the hydrogenation unit, the content of saturated reformate ranging from 10 to 90% and preferably from 20 to 80%.

Whatever the charge envisaged, the pressure required for this hydrogenation stage is between 1 and 60 bar absolute, particularly between 2 and 50 bar and more advantageously between 5 and 45 bar.
The operating temperature is between 100 and 400 ° C, more preferably between 150 and 350 ° C and preferably between 160 and 320 ° C.

The space velocities calculated relative to the catalyst are between 1 and 50 h -1 and more particularly from 1 to 30 h -1 (charge volumes per volume of catalyst per hour).

The flow rate of hydrogen, relative to the catalyst, is between 1 and 2000 volumes (gas under normal conditions) per volume of catalyst and per hour.

The heat released at this stage is advantageously used to preheat the isomerization charge.

The catalyst used in the hydrogenation step forming the subject of the present invention comprises at least one metal M chosen from the group formed by nickel, platinum and palladium, used as such or preferably deposited on a support. The metal M must be in reduced form for at least 50% of its totality. Nickel or platinum is preferably used.

The support may be chosen from the group formed by alumina, silicalumines, silica, zeolites, activated carbon, clays and aluminous cements.

In the case of the use of nickel, the proportion of metal M relative to the total weight of catalyst is between 0.1 and 60%, more particularly between 5 and 60% and preferably between 5 and 30%. In the case of the use of platinum and / or palladium, the total proportion of the metal M relative to the total weight of catalyst is between 0.1 and 10% and preferably between 0.05 and 5%.

The solid mineral dispersant may advantageously be an alumina. It preferably has a large surface and a sufficient pore volume, that is to say at least 50 m 2 / g and at least 0.4 cm 3 / g for example between 50 and 350 m 2 / g and between 0.4 and 1.2 cc / g.

When using platinum or palladium the catalyst may advantageously contain at least one halogen in a proportion by weight relative to the catalyst of between 0.5 and 2%. Preferably, chlorine or fluorine or a combination of both is used in a proportion relative to the total catalyst weight of between 0.5 and 1.5%.

The effluent from the hydrogenation unit contains less than 0.1% aromatics and has lost between 4 and 6 octane points.

The isomerization unit fed by the effluent of the hydrogenation unit alone, comprising the light reformate mixture plus the C5 / C6 hydrogenated straight-run cutting or by a light reformed mixture plus C5 / C6 straight-run distillation. treated, is carried out under the usual conditions of isomerization: the temperature is between 150 OC and 300 "C and preferably between 230 and 280" C, and the partial pressure of hydrogen is between atmospheric pressure and 70 bars and preferably between 5 and 50 bars. The space velocity is between 0.2 and 10 liters and preferably between 0.5 and 5 liters of liquid hydrocarbons per liter of catalyst and per hour. The molar ratio of hydrogen / charge is normally between 0.5 and 10 and preferably between 1 and 3.

It is possible to use a chlorinated alumina-based platinum catalyst containing from 1 to 10% of chlorine and preferably from 2 to 9% of chlorine, but preferably a catalyst comprising at least one Group VIII metal and a zeolite is used. . Different zeolites can be used to make the catalyst such as, for example, mordenite or zeolite Q. Preferably, a mordenite having a ratio is used.
If / Al (atomic) between 5 and 50 and preferably between 5 and 30, a sodium content of less than 0.2% and preferably less than 0.1% (based on the weight of dry zeolite), a V mesh volume of the elementary mesh between 2.78 and 2.73 nm 3 and preferably between 2.77 and 2.74 nm 3, a benzene absorption capacity greater than 5% and preferably greater than 8% (relative to the weight of dry solid).

The mordenite thus prepared is then mixed with a generally amorphous matrix (alumina, silica alumina, kaolin, etc.) and shaped by any method known to those skilled in the art (extrusion, pelletizing, coating). The mordenite content of the support thus obtained must be greater than 40% and preferably greater than 60% by weight.

At least one Group VIII hydrogenating metal, preferably selected from the group formed by platinum, palladium, and nickel, is then deposited on this support, either in the form of a tetramine complex by cation exchange, or in the form of an acid. hexachloroplatinic in the case of platinum or in the form of palladium chloride by anion exchange.

In the case of platinum or palladium, the content by weight is between 0.05 and 1% and preferably between 0.1 and 0.6%. In the case of nickel the weight content is between 0.1 and 10% and preferably between 0.2 and 5%.

The stabilized effluent thus obtained then has an octane number sufficiently high to be incorporated into the gasoline pool after stabilization and comprises a maximum benzene content equal to 0.1% by weight. Preferably, it is completely free of benzene.

The single figure shows a preferred arrangement of the various methods for the invention.

The stabilized reformate (1) is sent to a distillation column (6) from which a heavy reformate (3) which can be used directly in the fuel pool and at the top a light reformate (2) is discharged. The latter is sent to a hydrogenation unit (7), alone or after mixing with a cut (9) resulting from the direct distillation. The resulting cut (4) is processed in an isomerization unit (8) giving the final product (5) which after stabilization can be used in the gasoline pool. The straight-run C5 / C6 cut (10) can advantageously be mixed with the saturated light reformate (4) just before the isomerization unit (10).

The following examples specify the invention without limiting its scope.

Example 1 (according to the invention)
The light reformate obtained after distillation at 85 ° C, containing 21.5% benzene and having an octane number of 80.3 is mixed at a rate of 50% by weight with a straight-run C5 / C6 cut containing 0.7 % of benzene and having an octane number of 65. The compositions of these two products are shown in Table I. The feedstock resulting from the mixture, the composition of which is also given in Table I, is sent to a hydrogenation unit. a temperature of 110 ° C. and a pressure of 40 bars The molar ratio of hydrogen to hydrocarbons contained in the feed is equal to 0.85 and the liquid space velocity is equal to 4 h -1. Hydrogenation consists of 15% of Ni deposited on alumina.

The effluent from the hydrogenation unit, the composition of which is shown in Table I, no longer contains benzene but has an octane number of 70.9. It is then sent to an isomerization unit operating at a temperature of 260 ° C, a pressure of 30 bar with a LHSV equal to 2 h -1 and a molar ratio of hydrogen to hydrocarbons of the load equal to 4. The catalyst used in the isomerization unit contains 0.3% of Pt deposited on a support composed of 80% mordenite of Si / Al = 11 ratio and 20% of alumina The effluent discharged from the isomerization unit the composition given in Table I, it contains no more benzene and has an octane number of 78.1, so it is directly incorporated into the gasoline pool.

<Tb>

<SEP> Reformat <SEP> Cut <SEP> Load <SEP> Effluent <SEP> Output <SEP> Effluent <SEP> Output
<tb><SEP> C5 / C6 <SEP> of <SEP> Hydrogenation <SEP> Hydrogenation <SEP> Isomerization
<tb><SEP> distillation
<tb> mild <SEP> 6.5 <SEP> 1.0 <SEP> 3.7 <SEP> 3.7 <SEP> 4.6
<tb> 105 <SEP> 9.9 <SEP> 18.9 <SEP> 14.4 <SEP> 14.4 <SEP> 18.8
<tb> nC5 <SEP> 7.1 <SEP> 25.4 <SEP> 16.25 <SEP> 16.25 <SEP> 12.5
<tb> 22DMC4 <SEP> 3.0 <SEP> 0.4 <SEP> 1.7 <SEP> 1.7 <SEP> 6.3
<tb> 23DMC4 <SEP> 4.1 <SEP> 1.85 <SEP> 3.0 <SEP> 3.0 <SEP> 4.8
<tb> 2MC5 <SEP> 15.8 <SEP> 11.1 <SEP> 13.45 <SEP> 13.45 <SEP> 17.6
<tb> 3MG5 <SEP> 12.5 <SEP> 9.4 <SEP> 11.0 <SEP> 11.0 <SEP> 11.55
<tb> nC6 <SEP> 12.1 <SEP> 19.6 <SEP> 15.9 <SEP> 15.9 <SEP> 8.75
<tb> C7 <SEP> 3.5 <SEP> 4.4 <SEP> 3.9 <SEP> 3.9 <SEP> 1.9
<tb> CC5 <SEP> 0.4 <SEP> 1.4 <SEP> 0.9 <SEP> 0.9 <SEP> | <SEP> 0.9
<tb> MCC5 <SEP> 3.6 <SEP> 4.1 <SEP> 3.85 <SEP> 3.85 <SEP> 9.9
<tb> Benzene <SEP> 21.5 <SEP> 0.7 <SEP> 11.1 <SEP> - <SEP> j <SEP>
<tb> CC6 <SEP> 0 <SEP> 1.75 <SEP> 0.85 <SEP><SEP> 11.95 <SEP> 2.4 <SEP>
<tb> RON <SEP> 80.3 <SEP> 65 <SEP> 72.9 <SEP> 70.9 <SEP> 78 <SEP> 1 <SEP>
<Tb>
Table I
Example 2 (according to the invention)
The light reformate obtained after distillation at 85 OC containing 21.5% of benzene, having an octane number of 80.3 and whose detailed composition is given in Table II, is sent to a hydrogenation unit at a temperature of 110.degree. C. and a pressure of 40 bar. The molar ratio of hydrogen to hydrocarbons contained in the feed is 0.85, and the liquid space velocity is equal to 4 h -1. The catalyst used in the hydrogenation section consists of 15% of Ni deposited on alumina.

The effluent from the hydrogenation unit, the detailed composition of which appears in Table II, no longer contains benzene but has an octane number of 76.5. It is then mixed at a rate of 50% by weight with a straight-run C5 / C6 cut containing 0.7% of benzene and having an octane number of 65. The composition of this section as well as the composition of the mixture which constitutes the The charge of the isomerization unit is given in Table II. The isomerization unit operates at a temperature of 260 ° C., a pressure of 30 bars with an LHSV equal to 2 and a molar ratio of hydrogen to hydrocarbons of the feed equal to 4. The catalyst used in this isomerization unit contains 0.3% of Pt deposited on a support composed of 80% mordenite Si / Al = 11 ratio and 20% alumina.

The effluent discharged from the isomerization unit has the composition given in Table II; it no longer contains benzene and has an octane number of 78.1. This effluent is directly incorporated into the gasoline pool.

<Tb>

<SEP> Reformat <SEP> Cut <SEP> Effluent <SEP> Output <SEP> Load <SEP> Effluent
<tb><SEP> Cs / C6 <SEP> of <SEP> Hydrogenation <SEP> Isomerization <SEP> Isomerization
<tb><SEP> distillation
<tb> mild <SEP> 6.5 <SEP> 1.0 <SEP> 6.5 <SEP> 3.7 <SEP> 4.6
<tb> iC5 <SEP> 9.9 <SEP> 18.9 <SEP> 9.9 <SEP> 14.4 <SEP> 18.8
<tb> nC5 <SEP> 7.1 <SEP> 25.4 <SEP> 7.1 <SEP> 16.25 <SEP> 12.5
<tb> 22DMC4 <SEP> 3.0 <SEP> 0.4 <SEP> 3.0 <SEP> 1.7 <SEP> 6.3
<tb> 23DMC4 <SEP> 4.1 <SEP> 1.85 <SEP> 4.1 <SEP> 3.0 <SEP> 4.8
<tb> 2MC5 <SEP> 15.8 <SEP> 11.1 <SEP> 15.8 <SEP> 13.45 <SEP> 17.6
<tb> 3MO5 <SEP> 12.5 <SEP> 9.4 <SEP> 12.5 <SEP> 11.0 <SEP> 11.55
<tb> nC6 <SEP> 12.1 <SEP> 19.6 <SEP> 12.1 <SEP> 15.9 <SEP> 8.75
<tb> C7 <SEP> 3.5 <SEP> 4.4 <SEP> 3.5 <SEP> 3.9 <SEP> 1.9
<tb> CC5 <SEP> 0.4 <SEP> 1.4 <SEP> 0.4 <SEP> 0.9 <SEP> 0.9
<tb> MCCS <SEP> 3.6 <SEP> 4.1 <SEP> 3.6 <SEP> 3.85 <SEP> 9.9
<tb> Benzene <SEP> 21.5 <SEP> 0.7 <SEP> - <SEP> 0.35
<tb> CC6 <SEP> 0 <SEP> 1.75 <SEP> 21.5 <SEP> 11.6 <SEP> 2.4
<tb> RON <SEP> 80 <SEP> 3 <SEP> 65 <SEP> 76.5 <SEP> 71 <SEP> 2 <SEP> 78.1
<Tb>
Table II

Claims (7)

 just before isomerization and after the hydrogenation of said feedstock.  just before the hydrogenation,  between 6 and 45% of aromatics and a maximum distillation temperature of between 70 and 90 OG, then with an isomerization of said filler, the process being characterized in that said filler is mixed with a C5-C6 cut direct distillation to at least one of the following  between 0.5 and 7% of naphthenes  o between 40 and 80% of paraffins  a weight composition included in the following intervals  which is carried out a hydrogenation of the load characterized by:  CLAIMS 1 - Process for reducing the benzene content in the gasoline pool in 2 - Process according to claim 1 wherein the mixture comprises 10 to  90% of said charge. 3 - Process according to one of claims 1 or 2 wherein the catalyst  of hydrogenation comprises at least one metal selected from the group  formed by nickel, platinum and palladium. 4- Method according to one of claims 1 to 3 wherein the catalyst  isomerization comprises a mordenite of Si / Al ratio of between  and 50 and at least one Group VIII metal. The process of claim 4 wherein the Group VIII metal is  selected from the group consisting of platinum, palladium and nickel. 6. Process according to one of claims 1 to 5 wherein the step  hydrogenation is carried out according to the following operating conditions:  temperature is between 100 and 400 ° C, pressure is included  between 1 and 60 bar, the space velocity is between 1 and 50 volumes  of charge per volume of catalyst and per hour and the flow of hydrogen  is between 1 and 2000 volumes per volume of catalyst and  hour. 7- Method according to one of claims 1 to 6 wherein the step  Isomerisation is carried out according to the following operating conditions:  temperature is between 150 and 300 "C, the partial pressure  hydrogen is between atmospheric pressure and 70 bar, the  space velocity is between 0.2 and 10 liters of charge per liter of  catalyst and per hour, and the molar ratio hydrogen on charge is  between 0.5 and 10.