EP2707462B1 - 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 - Google Patents

Description

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.

• une première oligomérisation permettant de faire essentiellement réagir les isooléfines et conduisant à une coupe essence composée d'isooléfines ayant majoritairement de 8 à 10 atomes de carbone, d'excellent indice d'octane qui peut être séparée et valorisée en tant que telle, et
• une seconde oligomérisation qui permet de faire réagir les normales oléfines avec les isooléfines restantes (de la charge) et les isooléfines formées (non séparées) qui seront majoritairement situées dans la gamme des oléfines à plus de 8 atomes de carbone.

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

1. a) la séparation à partir de ladite charge d'hydrocarbures d'une fraction (O1) comprenant essentiellement des composés contenant 5 atomes de carbone dont au moins 2% poids de pentènes,
2. b) une mise en contact de ladite fraction (O1) avec une coupe d'hydrocarbures (O2) comprenant au moins en partie des hydrocarbures présentant un nombre d'atomes de carbone compris entre 6 et 10, dont au moins 2 % poids d'oléfines, en présence d'au moins un catalyseur favorisant les réactions de dimérisation et d'alkylation des espèces présentes dans le mélange issu de ladite mise en contact,
3. c) une séparation des effluents issus de l'étape b) en au moins deux coupes dont :
   • une coupe essence (α) dont le point supérieur de distillation est inférieur à 100°C et comprenant la majorité des réactifs n'ayant pas réagi et,
   • une coupe kérosène (β) d'intervalle de distillation compris entre 100°C et 300°C comprenant la majorité des produits issus des réactions d'alkylation et de dimérisation.

The prior art in the field of kerosene cut production is quite extensive, but the patent can be retained. EP 1 396 532 which describes a method of upgrading a liquid hydrocarbon feedstock comprising the following steps:

1. a) separating from said hydrocarbon feedstock a fraction (O1) essentially comprising compounds containing 5 carbon atoms, at least 2% by weight of pentenes,
2. b) contacting said fraction (O1) with a hydrocarbon fraction (O2) 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,
3. c) a separation of the effluents from step b) into at least two slices of which:
   • a gasoline cut (α) whose upper distillation point is less than 100 ° C and comprising the majority of unreacted reagents and,
   • a kerosene cut (β) distillation range of between 100 ° C and 300 ° C including the majority of products from the alkylation and dimerization reactions.

This patent does not describe any pretreatment step, in particular purification of the feedstock (O1).

1. 1) une oligomérisation d'une coupe d'hydrocarbures oléfiniques en C2-C12, de préférence en C3-C7, et plus préférentiellement encore en C3-C5,
2. 2) une séparation du mélange de produits obtenu lors de l'étape 1), en trois coupes dont une coupe intermédiaire de point d'ébullition final compris entre 200 et 220°C
3. 3) une oligomérisation de la coupe intermédiaire réalisée en présence d'une coupe d'hydrocarbures oléfiniques en C4 et/ou en C5.

The patent FR 2,887,555 discloses a process for preparing a diesel cut from a C2 C12 olefinic cut comprising the steps of:

1. 1) an oligomerization of a C2-C12, preferably C3-C7, and more preferably still C3-C5 olefinic hydrocarbon fraction,
2. 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. 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.

Licences 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 isoolefins, 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 a 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 patent US 2007/0213575 discloses a process for producing a distillate cut from an olefinic C4 - C6 feedstock comprising a feed purification step, one or more oligomerization steps, a separation step, and a hydrogenation step.

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

The figure 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 a medium 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: steps described by claim 1.

In the process according to the invention, the olefins starting cut must comprise a minimum of branched olefins, called iso olefins, minimum which can be set at 10% by weight and preferably at 20% by weight, based on all the olefins from 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 second 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 based on the figure 1 .

• température comprise entre 20°C et 50°C
• pression de 5 à 30 bars
• VVH entre 0,5 et 1 h-1

The charge to be treated (1) is sent to a purifying unit (PUR) using a molecular sieve based on faujasite-type zeolite (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

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 stage (OLG1) is an amorphous catalyst based on silico-aluminate, preferably chosen from silica-aluminas and silica aluminas, and preferably silicified aluminas.

The weight ratio SiO2 / Al2O3 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 sent to a separation unit (DIST1) 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 ') is directed to the oligomerization unit (OLG2). The effluent (4) of the separation step (DIST1) is sent to a second oligomerization step (OLG2) operating at a temperature above 120 ° C. on a zeolite type catalyst, such as, for example, a catalyst containing 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, IZM-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.

• une coupe de tête (6) dite raffinat, correspondant à une coupe LPG,
• une coupe intermédiaire (7) qui correspond à une essence de nombre d'atomes de carbone compris entre 5 et 10,
• une coupe de fond (8) appelé distillat moyen de nombre d'atomes de carbone compris entre 10 et 22 qui est envoyé à l'unité d'hydrogénation totale (HT) pour constituer le kérosène ou le gazole aux spécifications commerciales,
• une coupe dite résidu (9) de point d'ébullition initial supérieur à 280°C si la coupe finale recherchée est le kérosène, ou supérieur à 360°C si la coupe finale recherchée est le gazole, qui rejoint le pool fuel de la raffinerie.

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 section (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 the average number of carbon atoms distillate between 10 and 22 which is sent to the total hydrogenation unit (HT) to form the commercial specification kerosene or gas oil,
• a section called residue (9) of initial boiling point greater than 280 ° C if the final cut desired is kerosene, or greater than 360 ° C if the final cut desired is diesel, which joins the fuel pool of the refinery .

EXAMPLES

Examples 1 and 2 which follow do not illustrate the invention.

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).

• 1,9 % de butanes et butènes (0,4 et 1,5% respectivement); 25 % d'iso-pentènes;
• 24% de n-pentènes; 28% de pentanes ; 11% d'hexènes et 7,0% d'hexanes.

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 to the second bed carrying out the first oligomerization step (OLG1) in which the temperature is gradually raised between 60 ° C and 120 ° C, in order to keep the conversion of the iso-olefins constant. 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.

• une coupe C4-(4% poids)
• une coupe 15°C-140°C, (44% poids) constituant la coupe essence légère, dont l'indice d'octane recherche est de 95,5
• une coupe 140-280°C, (42% poids) qui est ensuite hydrogénée pour fournir une coupe kérosène, dont les caractéristiques sont:
  • Point de fumée : 38 mm; Point d'éclair : 45°C; Point de cristallisation : < -65°C ; densité : 0,770. L'hydrogénation est réalisée avec un catalyseur au nickel à 180°C sous 50 bar d'hydrogène avec une VVH de 0,5 et un débit d'hydrogène de 50 NL/h et un débit de charge de 48 g/h.
• un résidu 280+ (10% poids)

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

• a cut C4- (4% weight)
• a section 15 ° C-140 ° C, (44% by weight) constituting the light gasoline cut, whose research octane number is 95.5
• a cut 140-280 ° C, (42% 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 280+ residue (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 stage are the same as in Example 1

The filler used is a C4 ex catalytic cracking unit (FCC) to which a C5-C6 so-called light gasoline fraction was added from an FCC unit under the name LCN (Light Cut Naphta).

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 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%.

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

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

• une coupe C4-(16% poids)
• une coupe 15°C-140°C, (42% poids) constituant la coupe essence légère, dont l'indice d'octane recherche (IOR) est de 95,5.
• une coupe 140°C- 280°C, (32% poids) qui est ensuite hydrogénée (conditions identiques à celles décrites dans l'exemple 1) pour fournir une coupe kérosène, dont les caractéristiques sont les suivantes:
  • Point fumée : 38°C; Point d'éclair : 48°C; Point de cristallisation : < -65°C ; densité : 0,778
• un résidu 280+ (10% poids).

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

• a C4- cut (16% weight)
• a section 15 ° C-140 ° C, (42% 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% weight).

Claims (3)

1. A process for the production of a middle distillate cut having mainly from 10 to 22 carbon atoms from an olefinic feed having mainly between 4 and 6 carbon atoms, comprising at least 10% by weight of branched chain olefins, said process comprising the sequence of following steps:

   1) a purification step (PUR) for the feed carried out on a molecular sieve based on zeolite of faujasite type, intended to remove the nitrogenous compounds from the feed, and operating at a temperature lower than 60°C,

   2) a step for first oligomerisation (OLG1) of the effluents issuing from the purification step, that is carried out at a temperature lower than 120°C, on an amorphous catalyst of silico aluminate type in which the SiO2/Al2O3 ratio by mass is between 0.05 and 10 and preferably between 0.2 and 1, from which first oligomerisation step there is extracted a petrol cut having from 8 to 12 carbon atoms, while maintaining a minimum of 10% of said petrol cut in the effluents from said first oligomerisation step,

   3) a step for second oligomerisation (OLG2) of the effluents issuing from the first oligomerisation step, that is carried out at a temperature higher than 120°C on a zeolitic catalyst,

   4) a step for separation of the effluents from the second oligomerisation step into at least two cuts, a petrol cut having up to 12 carbon atoms and a middle distillate cut (referred to as a kerosene or diesel cut) having from 12 to 25 carbon atoms, and

   5) a step for total hydrogenation of the middle distillate cut making it possible to obtain a kerosene or a diesel in accordance with the specifications of the market.
2. A process for the production of a middle distillate cut having mainly from 10 to 22 carbon atoms from an olefinic feed having mainly between 4 and 6 carbon atoms according to claim 1 wherein the second oligomerisation step (OLG2) is carried out on a zeolite- based catalyst, the zeolite used being selected from the group formed by: 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.
3. A process for the production of a middle distillate cut having mainly from 10 to 22 carbon atoms from an olefinic feed having mainly between 4 and 6 carbon atoms according to claim 1 wherein the second oligomerisation step (OLG2) is carried out on a zeolite-based catalyst, the zeolite used being ZSM-5.

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