EP2707462A2

EP2707462A2 - Method for the production of diesel or kerosene cuts from an olefin feed mainly having between 4 and 6 carbon atoms, using two oligomerisation units

Info

Publication number: EP2707462A2
Application number: EP12713203.3A
Authority: EP
Inventors: Pierre Alain BREUIL; Nicolas Cadran; François Hugues; Vincent Coupard
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 2011-05-12
Filing date: 2012-03-13
Publication date: 2014-03-19
Anticipated expiration: 2032-03-13
Also published as: FR2975104A1; EP2707462B1; WO2012153010A3; FR2975104B1; WO2012153010A2; FR2975103A1; WO2012153011A2; WO2012153011A3; HUE030396T2; FR2975103B1; EP2707461A2

Abstract

The invention relates to a method for the production of a diesel and middle distillate cut from an olefin feed having between 4 and 6 carbon atoms, said method including: a first purification step performed on a trapping mass formed by a molecular sieve; and two oligomerisation steps, namely one at a temperature below 120°C and another at a temperature above 120°C.

Description

PROCESS FOR PRODUCING KEROSENE OR GASOLINE CUT FROM AN OLEFINIC CHARGE HAVING A MAJORITY OF 4 TO 6 CARBON ATOMS

USING TWO UNITS OF OLIGOMERIS ATION

FIELD OF THE INVENTION

The present invention is in the field of refining processes for converting an olefinic fraction having predominantly 4 to 6 carbon atoms in a so-called middle distillate cut having predominantly 10 to 20 carbon atoms.

This middle distillate cut may be a kerosene cut or a diesel cut.

The present invention uses a first purification step to remove the nitrogen compounds contained in the feed followed by two different oligomerization,

a first oligomerization making it possible to essentially react the isoolefins and leading to a gasoline cut composed of isoolefins having predominantly from 8 to 10 carbon atoms, an excellent octane number which can be separated and recovered as such, and

a second oligomerization which makes it possible to react the normal olefins with the remaining isoolefins (of the feedstock) and the formed (non-separated) isoolefins which will predominantly be in the range of olefins with more than 8 carbon atoms.

EXAMINATION OF THE PRIOR ART

The prior art in the field of kerosene cut production is quite extensive, but it is possible to retain the patent EP 1 396 532 which describes a process for upgrading a liquid hydrocarbon feedstock comprising the following steps:

a) separating from said hydrocarbon feedstock a fraction (01) essentially comprising compounds containing 5 carbon atoms, at least 2% by weight of pentenes,

b) bringing said fraction (01) into contact with a hydrocarbon cut (02) comprising at least partly hydrocarbons having a number of carbon atoms of between 6 and 10, of which at least 2% by weight of olefins, in the presence of at least one catalyst promoting the dimerization and alkylation reactions of the species present in the mixture resulting from said contacting,

c) a separation of the effluents from step b) into at least two slices of which:

- a gasoline cut (a) whose upper distillation point is less than 100 ° C and comprising the majority of reagents unreacted and,

a kerosene fraction (β) with a distillation range of between 100 ° C. and 300 ° C. comprising the majority of the products resulting from the alkylation and dimerization reactions. This patent does not describe any pretreatment step, in particular purification of the feedstock (01).

Patent FR 2,887,555 describes a process for preparing a diesel cut from an olefinic C2 Cl 2 cut comprising the following steps:

1) an oligomerization of a C2-C12, preferably C3-C7, and more preferably still C3-C5 olefinic hydrocarbon fraction,

2) a separation of the product mixture obtained in step 1), in three sections, including an intermediate section with a final boiling point of between 200 and 220 ° C.

3) an oligomerization of the intermediate section carried out in the presence of a C4 and / or C5 olefinic hydrocarbon fraction.

This process therefore uses a very broad olefinic fraction as filler and uses two distinct oligomerizations. It does not mention the possibility of a pretreatment of said charge, including purification against any nitrogen compounds contained in said charge.

The patents FR 2 871 167 and FR 2 871 168 describe processes for producing diesel fuel cut from gasoline cuts comprising a first step of separation of the normal and isoolef, the oligomerization step relating only to the normal olefins.

The process according to the present invention does not require any prior separation of the normal and iso olefins.

Finally, the patent application filed under No. 10 / 03.559 describes a complex process using an olefinic C4 C10 cut to which is added an LPG cut and a BTX cut (abbreviation of benzene, toluene and xylenes) allowing carry out an alkylation reaction of the olefins on the BTX cut.

The process according to the present invention does not use any alkylation step and therefore does not require any BTX-type cutting.

SUMMARY DESCRIPTION OF THE FIGURES

FIG. 1 represents a diagram of the process according to the invention using two distinct oligomerization units preceded by a step of purification of the charge on a capture mass. SUMMARY DESCRIPTION OF THE INVENTION

The process according to the present invention uses two distinct oligomerization units working on different catalysts and under different operating conditions.

The process according to the invention can be defined as a process for producing an average distillate cut having predominantly from 12 to 25 carbon atoms from an olefinic feed having predominantly between 4 and 6 carbon atoms, comprising the following process: 'following steps:

1) a step of purifying (PUR) the charge on a capture mass containing at least one molecular sieve or alumina type compound, and working at a temperature below 60 ° C, for removing nitrogen compounds,

2) a step of first oligomerization (OLG1) effluents from the purification step carried out at a temperature below 120 ° C on an amorphous catalyst of silico aluminate type, from which can be extracted in part a gasoline cut predominantly consisting of C8-C12 molecules with a search octane number greater than 98,

3) a second oligomerization step (OLG2) of the remaining effluents (that is to say effluents reduced by the gasoline cut extracted in the previous step) from the first oligomerization step carried out at a temperature greater than 120 ° C on an amorphous silico aluminate catalyst, or on a zeolite catalyst,

4) a step of separating the effluents from the second oligomerization stage into at least two sections, a gasoline section having up to 12 carbon atoms, a middle distillate section (called kerosene or diesel section) having from 12 to 25 atoms of carbon,

5) a step of total hydrogenation of the middle distillate cut leading to a kerosene cut or a diesel cut to the market specifications.

In the process according to the invention, the starting olefins cut must comprise a minimum of branched olefins, called isoolefins, minimum which can be set at 10% by weight and preferably at 20% by weight, relative to all olefms of the charge.

When a petrol cut is extracted at the end of the first oligomerization step (OLG1), it is nevertheless necessary to maintain a certain proportion of the said gasoline cut in the effluents of the first oligomerization step feeding the step of seconder oligomerization (OLG2). This minimum proportion can be set at 10%, and preferably at 20% of said gasoline cut.

DETAILED DESCRIPTION OF THE INVENTION

The feed consists of a section of olefinic hydrocarbons containing from 3 to 8 carbon atoms, preferably from 4 to 6 carbon atoms. It contains from 20% to 100% of olefins, preferably from 20% to 80% of olefins, and more preferably from 40% to 60% of olefins.

It can come from a fluidized catalytic cracking unit or a naphtha steam cracking unit, or an alcohol dehydration unit or a Fischer-Tropsch synthesis unit or other available sources. from refining or petrochemical units.

The description of the process is made with reference to FIG.

The charge to be treated (1) is sent to a purification unit (PUR) using an adsorbent such as a molecular sieve (for example of the Na X or NaY type) working under the following operating conditions:

- temperature between 20 ° C and 50 ° C

pressure of 5 to 30 bar

- VVH between 0.5 and 1 h-1

Among the adsorbents used in the purification unit (PUR) include metal oxides such as aluminas, crystallized silico-aluminates such as zeolites (often called molecular sieves), or mixtures of these compounds.

Among these compounds, zeolite-based molecular sieves of the faujasite type are preferred. An example is the NaX zeolite, for example that marketed by Axens under the name SBE 13X.

This purifying unit (PUR) is mainly intended to eliminate the nitrogenous compounds contained in the feed and which constitute poisons with respect to the catalysts used in downstream oligomerization units.

The effluent (2) of the purification unit (PUR) is sent in a first oligomerization step (OLG1) working at a temperature below 120 ° C on a silica-alumina catalyst. The oligomerization catalyst for the first oligomerization step (OLG1) is an amorphous catalyst based on silico-aluminate, preferably chosen from silica-aluminas and silica aluminas, and preferably silicified alumina.

The mass ratio SiO 2 / Al 2 O 3 is between 0.05 and 10, and preferably between 0.2 and 1.

A preferred catalyst is for example that marketed by AXENS under the name IP 811.

The effluent (3) leaving the first oligomerization step (OLG1) is optionally sent to a separation unit (DISTl) for extracting a gasoline cut (3 ') with a good octane number and which can therefore join the gasoline pool (POOL). Part of this species (3 ') can also be directed to the oligomerization unit (OLG2).

The effluent (3) of the first oligomerization step (OLG1), or the effluent (4) of the optional separation step (DIST1) when it exists, is sent to a second oligomerization step (OLG2) working at a temperature above 120 ° C,

or on a silico-aluminate catalyst analogous or identical to that used in the first oligomerization stage (OLG1),

or on a zeolitic type catalyst, such as, for example, a catalyst containing a zeolite ZSM-5.

The zeolite catalyst used in the second oligomerization step (OLG2) preferably comprises at least one zeolite selected from the group consisting of aluminosilicate zeolites having an overall Si / Al atomic ratio greater than 10 and a pores 8, 10 or 12MR.

Said zeolite is even more preferably selected from the group consisting of zeolites: ferrierite, chabazite, zeolites Y and US-Y, ZSM-5, ZSM-12, NU-86, mordenite, ZSM-22, NU-10, ZBM-30, ZSM-11, ZSM-57, ZSM-35, ΓΖΜ-2, ITQ-6 and IM-5, SAPO, taken alone or in admixture.

Very preferably, said zeolite is selected from the group consisting of ferrierite zeolites, ZSM-5, Mordenite and ZSM-22, taken alone or as a mixture.

Even more preferably, the zeolite used is ZSM-5.

The effluents (5) of the second oligomerization step (OLG2) are then separated in a separation unit (DIST2) from which at least 4 sections are extracted:

a head cut (6) called raffinate, corresponding to an LPG cut, an intermediate cut (7) which corresponds to a gasoline with a number of carbon atoms of between 5 and 10,

- a bottom cut (8) called middle distillate of number of carbon atoms between 10 and 22 which is sent to the total hydrogenation unit (HT) to form the kerosene or gas oil to commercial specifications,

- A section called residue (9) of initial boiling point greater than 280 ° C if the final desired cut is kerosene, or greater than 360 ° C if the final cut desired is diesel, which joins the fuel pool of the refinery. EXAMPLES ACCORDING TO THE INVENTION

Examples 1 and 2 which follow illustrate the invention without limiting its scope.

These two examples are obtained from laboratory experiments. Example 1: Charge C5-C6 (LCN)

200 grams of NaX molecular sieve, activated by heating under a stream of dry air at 350 ° C for 16h, are arranged in a first fixed bed performing the purification step.

125 grams of catalyst IP 811 are arranged in a second fixed bed carrying out the first oligomerization step (OLG1).

75 grams of catalyst IP 811 are arranged in a third fixed bed, performing the second oligomerization step (OLG2).

The various beds are arranged in series.

The filler used is a so-called light gasoline C5-C6 cut that comes from an FCC unit, under the name LCN (Light Cut Naphta).

It is composed in mass percentages of:

1.9% butanes and butenes (0.4 and 1.5% respectively); 25% iso-pentenes;

24% n-pentenes; 28% pentanes; 11% hexenes and 7.0% hexanes.

The charge has a density of 0.6548.

It also contains organic nitrogen compounds totaling a content of 11.6 ppm by weight expressed as elemental nitrogen and 15 ppm by weight of elemental sulfur.

It is injected into the first bed (carrying out the first purification step), from bottom to top, at the rate of 36 g / h, the pressure is maintained at 50 bars effective at room temperature. The analysis of the elemental nitrogen at the end of this purification step shows a value of less than 0.5 ppm by weight.

The effluent of the first bed is sent integrally into the second bed carrying out the first oligomerization step (OLGl) in which the temperature is gradually raised between 60 ° C and 120 ° C, in order to keep constant the conversion of the iso-olefins into C5, between 80% and 85%

An average increase of 3 ° C every 100 hours is necessary to achieve this goal. Under these conditions, the conversion of n-olefins to C5 is between 10% and 20%.

The effluent from the second bed is sent integrally into the third bed carrying out the second oligomerization step (OLG2), in which the temperature is gradually raised between 150 ° C and 230 ° C, in order to keep the conversion of the olefins in C5 constant. between 75% and 80%.

An average increase of 1 ° C / 100 h is necessary to achieve this goal.

The effluent of the third stage is separated by distillation into four sections:

- a C4- cut (4% weight)

a section 15 ° C-140 ° C, (44% by weight) constituting the light gasoline cut, whose research octane number is 95.5

a 140-280 ° C. section (42% by weight) which is then hydrogenated to provide a kerosene cut, the characteristics of which are:

Smoke point: 38 mm; Flash point: 45 ° C; Crystallization point: <-65 ° C; density: 0.770. The hydrogenation is carried out with a nickel catalyst at 180 ° C. under 50 bar of hydrogen with a VVH of 0.5 and a hydrogen flow rate of 50 NL / h and a feed rate of 48 g / h.

- a residue 280+ (10% weight)

Example 2: Charge C4 ex FCC + C5-C6 (LCN)

The arrangement of the various beds, corresponding to the three purification steps, first oligomerization and second oligomerization, is the same as in Example 1.

The catalysts used in the OLG1 and OLG2 steps and the capture mass used in the PUR step are the same as in Example 1. The feedstock used is a C4 ex-catalytic cracking unit (FCC) feed to which a so-called light gasoline C5-C6 cut has been added from one FCC unit under the name LCN (Light Cut Naphtha).

It is injected into the first bed performing the purification step (PUR), from bottom to top, at a rate of 36 grams / hour.

The pressure is maintained at 50 bars effective at room temperature. '

The analysis of the elemental nitrogen at the outlet of this section shows a value of less than 0.5 ppm by weight.

The effluent from the first bed is sent integrally into the second bed carrying out the first oligomerization step (OLG1), in which the temperature gradually increases between 50 ° C and 110 ° C, in order to keep the conversion of the iso-olefins constant. C5, between 80% and 85%.

Under these conditions, the conversion of isobutene is greater than 95%.

An average increase of 2 ° C every 100 hours is necessary to achieve this goal. Under these conditions, the conversion of normal olefins to C4 and C5 is between 10 and 20%.

The conversion of olefins to C4 is greater than 80%.

An average increase of 1 ° C / 100 h is necessary to achieve this goal.

- a C4- cut (16% weight)

a 15 ° C.-140 ° C. section (42% by weight) constituting the light gasoline cut, whose research octane number (IOR) is 95.5.

a section 140 ° C.- 280 ° C. (32% by weight) which is then hydrogenated (conditions identical to those described in Example 1) to provide a kerosene cut, the characteristics of which are as follows:

Smoke point: 38 ° C; Flash point: 48 ° C; Crystallization point: <-65 ° C; density: 0.778

a 280+ residue (10% by weight).

Claims

A process for producing an average distillate fraction having predominantly from 10 to 22 carbon atoms, from an olefinic feed having predominantly 4 to 6 carbon atoms, having at least 10% by weight of branched olefins, said process comprising following steps:

1) a step of purifying (PUR) the charge on a capture mass containing at least one molecular sieve or alumina type compound, intended to remove the nitrogenous compounds from the charge, and operating at a temperature below 60 ° C.,

2) a step of first oligomerization (OLG1) effluents from the purification step carried out at a temperature below 120 ° C, on a silico aluminate catalyst,

3) a second oligomerization stage (OLG2) effluents from the first oligomerization step carried out at a temperature above 120 ° C on a silico-aluminate catalyst or on a zeolite catalyst,

4) a step of separating the effluents from the second oligomerization stage into at least two sections, a gasoline section having up to 12 carbon atoms, and a middle distillate section (called kerosene or diesel section) having from 12 to 25 carbon atoms,

5) a step of total hydrogenation of the middle distillate cut to obtain a kerosene or diesel fuel to the market specifications.

Process for the production of an average distillate cut having predominantly from 10 to 22 carbon atoms from an olefinic feedstock having mainly from 4 to 6 carbon atoms according to Claim 1, in which stage 2 of the first phase is extracted. oligomerization (OLG1) a gasoline cut having 8 to 12 carbon atoms, maintaining a minimum of 10% of said gasoline cut in the effluents of said first oligomerization step in order to feed the second oligomerization step (OLG2 ).

Process for producing an average distillate fraction having predominantly from 10 to 22 carbon atoms from an olefinic feed having predominantly between 4 and 6 carbon atoms according to claim 1, wherein the purification step (PUR) is carried out on a faujasite-type zeolite molecular sieve.

Process for the production of a medium distillate cut with predominantly 10 to 22 carbon atoms from an olefinic feedstock having predominantly 4 to 6 carbon atoms according to claim 1, wherein the first oligomerization step (OLG1) is carried out on a silico-aluminate catalyst in which the SiO 2 / Al 2 O 3 mass ratio is between 0.05 and 10 and preferably between 0.2 and 1.

Process for the production of an average distillate fraction having predominantly from 10 to 22 carbon atoms from an olefinic feed having predominantly 4 to 6 carbon atoms according to claim 1, wherein the second oligomerization step (OLG2) is carried out on a zeolite-based catalyst, the zeolite used being selected from the group consisting of: ferrierite, ZSM-5, ZSM-12, NU-86, mordenite, ZSM-22, NU-10, ZBM-30, ZSM-11, ZSM-57, ZSM-35, IZM-2, ITQ-6 and IM-5.

A process for producing a distillate cut means having predominantly 10 to 22 carbon atoms from an olefinic feedstock having predominantly 4 to 6 carbon atoms according to claim 1, wherein the step of ^'second oligomerization (OLG2 ) is carried out on a zeolite-based catalyst, the zeolite used being ZSM-5.