EP0773981B1 - Jet fuel and method for producing same - Google Patents

Abstract

PCT No. PCT/FR96/00762 Sec. 371 Date Apr. 28, 1997 Sec. 102(e) Date Apr. 28, 1997 PCT Filed May 22, 1996 PCT Pub. No. WO96/37577 PCT Pub. Date Nov. 28, 1996The invention concerns a jet engine fuel having the following characteristics: i) distilling range from 140 to 300 DEG C.; ii) cis-decalin/trans-decalin ratio greater than 0.2; iii) aromatics content less than 22% by volume; iv) sulfur content less than 100 ppm, and v) lower heating value per unit volume greater than 34.65 Mj/liter. Also process for making the same wherein for example a cut from catalytic cracking distilling between 140 and 300 DEG 0 C. is subjected to a hydrotreatment step and then to a dearomatization step.

Description

The present invention relates to jet fuels, or fuels for jet engines, and their process preparation.

Many methods have been proposed for the manufacture of fuels for jet engines, from a wide range of raw materials.

In general, fuel for jet engines or jet fuel is produced from a fraction of kerosene obtained directly from atmospheric distillation crude oil and whose distillation points are between 140 and 300 ° C and, more typically, between 150 and 270 ° C. This fraction is then either processed in a desulfurization unit, or treated in a unit of transformation of mercaptans into disulfides.

Another production route is that consisting of hydrocracking a fraction of the distillate under vacuum. The effluent fractionation provides a jet fuel which does not require further treatment. However, the jet fuel thus obtained has a power very weak lubricant and insufficient for its use at pure state in jet engines. Therefore, he must be mixed with other jet fuels, especially direct distillation jet fuels, which have a better lubricity and thus compensate for this insufficiency.

Jet fuels are used to power aircraft turbojet and propellant burners. In this Indeed, jet fuels must have certain characteristics. In particular, Jet A1 jet fuel, which is the most commonly used jet fuel in civil aviation, must imperatively have a content of sulfur less than 0.30% by weight, a content of compounds aromatics less than 22% by volume, a flash point greater than 38 ° C, a smoke point greater than 25 mm, and a defrost point below - 47 ° C. According to the ways of production of the prior art, jet fuels have similar energy qualities and calorific value lower volume whose value is less than 34.60 Mj / liter. Other characteristics of jet fuel Jet A1 are given in Table 6 appearing in the continuation of this description, after examples of setting of the invention, this Table 6 also bringing together characteristics of the jet fuels produced in these examples.

i) un point de distillation compris entre 176,7 et 218 °C

ii) une teneur en aromatiques de 1,9% en volume,

iii) un pouvoir calorifique inférieur volumique qui est de 36,521 Mj/litre,

iv) une teneur en soufre inférieure à 150 ppm (cf. col.2, ligne 5).

American patent US-A-3 175 970 reports (cf. Table in column 3) a jet fuel having the following characteristics:

i) a distillation point between 176.7 and 218 ° C

ii) an aromatic content of 1.9% by volume,

iii) a lower calorific value which is 36.521 Mj / liter,

iv) a sulfur content of less than 150 ppm (cf. col. 2, line 5).

This jet fuel is present (see Table in column 3) a freezing point below -76 ° F, or -60 ° C. This value is however still too high.

The demand for jet fuel is growing and the means of jet fuel production are limited within of a classic refinery. Hydrocracking units are extremely expensive and the quantities of jet fuel from atmospheric crude oil distillation are limited and depend on the quality of crude oils.

In addition, refineries whose conversion mode is consisting of catalytic cracking, have only jet fuel from direct distillation.

Indeed, the catalytic cracking effluents contain very large quantities of aromatics, olefins, and sulfur products.

Since the dearomatization catalysts, which are based on platinum, are very sensitive to sulfur, it is necessary to remove the sulfur products by a prior hydrotreatment.

However, this hydrotreatment operation is made very difficult due to its exothermicity.

When trying to solve this problem encountered in prior art, the Applicant has discovered that it is possible to produce jet fuel from a cut from catalytic cracking.

i) un point de distillation compris dans l'intervalle de 140 à 300°C ;

ii) un rapport cis décaline/trans décaline supérieur à 0,2;

iii) une teneur en aromatiques inférieure à 22% en volume ;

iv) une teneur en soufre inférieure à 100 ppm ; et

v) un pouvoir calorifique inférieur volumique qui est supérieur à 34,65 Mj/litre.

The Applicant has also discovered that, surprisingly, the jet fuel produced by catalytic cracking (that is to say a cracking at high temperature, in the presence of a catalyst and without hydrogen) then hydrotreatment, was different from that obtained. by cracking in the presence of hydrogen (hydrocracking) and of higher quality than the latter.
Thus, the Applicant has developed a jet fuel characterized in that it has:

i) a distillation point in the range of 140 to 300 ° C;

ii) a cis decaline / trans decaline ratio greater than 0.2;

iii) an aromatic content of less than 22% by volume;

iv) a sulfur content of less than 100 ppm; and

v) a lower calorific value which is greater than 34.65 Mj / liter.

Preferably, the jet fuel according to the invention has a lower calorific value between 34.65 and 35.30 Mj / liter.

The jet fuel according to the invention is therefore different from the jet fuels of the prior art, in especially regarding its higher calorific value high, so that it allows volume consumption lower than that of jet fuel of the prior art.

The invention also aims to provide a new method for the manufacture of this jet fuel with properties improved. This process is new and original by the fact that it does not use the conventional production lines of jet fuel. It allows additional production jet fuel in a refinery, in addition to to that produced by atmospheric distillation cutting crude oil.

This process makes it possible to obtain a jet fuel from a cut from the fractionation of the effluent from a catalytic cracking unit. Thus, the valuation in jet fuel from a catalytic point cracking cup distillation between 140 and 300 ° C is possible.

However, this cut from a cracking unit catalytic generally requires a number of specific treatments before becoming a jet fuel having the characteristics required for its approval.

Different treatments of the cracked cut catalytic can be considered to obtain the jet fuel. However, in accordance with the invention, the catalytic cracking cut is preferably treated in two stages: a hydrotreatment stage and a aromatization.

Usually this catalytic cracking cut has an olefin content of between 20 and 45% and a aromatic content between 40 and 70%, by compared to the total volume.

However, the specifications of jet fuels limit this aromatic content up to 22%, which requires a flavoring. In addition, since the catalyst is particularly sensitive to pollutants, it is necessary to operate a hydrotreatment prearromatization.

The purpose of the hydrotreatment step is to desulfurize, de-nitrogen and hydrogenate olefins from the cracked cut catalytic. If the denitrogenation of the charge caused during of the hydrotreatment step is weak or insufficient, a additional denitrogenation step will be incorporated into process diagram.

The cut resulting from catalytic cracking has properties very different from those that allow obtaining jet fuels of the prior art.

Thus, it contains more olefins than the cut from direct atmospheric distillation, and further differs of the hydrocracking charge cut which is a distillate under vacuum with higher boiling point.

This explains why the jet fuel of the invention has characteristics that stand out from those of jet fuels obtained by the usual routes.

The jet fuel according to the invention thus exhibits improved combustion properties in engines with reaction. Indeed, it has a high concentration of polycyclic naphthenes versus concentration total in naphthenes of jet fuel, which results in a substantial gain in volume energy and greater than 0.5%. Consequently, under identical conditions, the volume consumed of jet fuel according to the invention will be lower than that of a jet fuel of the prior art.

The jet fuel according to the invention generally has a cis decaline / trans decaline ratio greater than 0.2, and preferably greater than 0.3.

This is because the cracked cut catalytic from which the jet fuel is derived, is rich in olefins, and in particular dicycloolefins, which are precursors of cis decalin.

The jet fuel according to the invention also has preferably a naphthalene / trans decaline ratio lower than 0.05. Indeed, the hydrogenation step in accordance with the process according to the invention, transforms the vast majority of Naphthalenes present in decalins.

The jet fuel according to the invention has a naphthenes / paraffins ratio of between 1.2 and 2.

In addition, the jet fuel according to the invention has very good cold resistance properties and higher than that required for Jet A1 jet fuel. Therefore, the jet fuel according to the invention can be advantageously used in severe conditions of cold, especially in the field of military aviation.

In addition, the jet fuel of the invention can be mixed to other jet fuel bases, which allows the if necessary, to improve the properties of carburetors, including their energy qualities, while respecting the standards required for a Jet A1 jet fuel.

The process for the preparation of jet fuel in accordance with the invention will now be explained.

The hydrotreatment step of the cracked cup catalytic is carried out in the presence of a catalyst arranged as one or more fixed beds in a reactor. The catalyst consists of at least one metal hydrogenating and / or hydrogenolysing deposited on a support substantially neutral, for example catalysts based on nickel and molybdenum such as catalyst TK 525 of the Haldor Topsoe or HR 348 catalyst from the company Procatalysis.

Other types of catalysts can be used, in particular cobalt and molybdenum catalysts HR 306 and HR 316 from the company Procatalyse, KF 752 from the company Akzo, and TK 524 and TK 554 from the company Haldor Topsoe. The reaction temperature is generally between 250 and 350 ° C, under a minimum pressure of 30.10 ⁵ Pascals (30 bars), with an hourly volume speed of approximately 1 to 5 h ^-1 , the volume ratio hydrogen / hydrocarbons to l 'reactor inlet being between 100 and 500 Nm ³ / m ³ and preferably between 200 to 300 Nm ³ / m ³ . Advantageously, the temperature is around 280 ° C, under a pressure of 35.10 ⁵ Pascals.

The hydrotreatment step generates reactions strongly exothermic. In order to control this phenomenon, a person skilled in the art will adjust various factors, in particular, the temperature at the reactor inlet, the hydrogen / hydrocarbons, and the amount of olefins in the feed. A diluent such as a reactor recycle or, preferably kerosene from distillation atmospheric crude oil can be optionally mixed with the filler to decrease its concentration in olefins.

In the case of a reactor where the catalyst is placed in several fixed beds, a quenching fluid can be injected between said beds, its nature, its flow and its temperature being selected to control the exothermicity of the reactions of this hydrotreatment step. A recycle of the unit, hydrogen or, preferably atmospheric distillation kerosene, can constitute the quenching fluid.

The partial aromatization reaction of the effluent from the desulfurization unit is carried out in the presence of a catalyst, for example in the form of one or several fixed beds in a reactor. The catalyst used is selected according to the operating conditions of reactor.

The catalyst can be a thioresistant catalyst, consisting of at least one noble hydrogenating metal deposited on a substantially acid support, this noble metal possibly being in particular platinum or palladium. As examples, thioresistant catalysts such as LD 402 catalysts from Procatalyse, AS-100 from Criterion and TK 908 by Haldor Topsoe can be used for this purpose.

The catalyst used can also be a catalyst based on nickel, which turns out to be an interesting route, because more economical than that using catalysts containing platinum or palladium. As examples, catalysts such as HTC 400 and HTC 500 from Crosfield and C46-7-03 and L3427 from Süd-Chemie can be used. Preferably Crosfield's HTC 400 catalyst is employed.

In the case of a catalyst containing a noble metal, the reaction temperature is generally between 200 and 300 ° C, under a minimum pressure of 30.10 ⁵ Pa, with an hourly volume speed of 1 to 5 h ^-1 , the ratio volume hydrogen / hydrocarbons at the inlet of the reactor being between 500 and 900 Nm ³ / m ³ , preferably 600 Nm ³ / m ³ (Nm ³ here means Normal m ^3. 1 Normal m ³ corresponds to 1m ³ of gas in standard conditions of temperature and pressure, i.e. 0 ° C and 1 atmosphere - 1.01325.10 ⁵ Pa). Advantageously, the temperature is approximately 240 ° C., under a pressure substantially of 50 × 10 ⁵ Pa.

In the case of a nickel-based catalyst, the reaction temperature is generally between 100 and 200 ° C, under a minimum pressure of 30.10 ⁵ Pa, with an hourly volume speed of 1 to 5 h ^-1 , the ratio volume hydrogen / hydrocarbons at the inlet of the reactor being between 600 and 1000 Nm ³ / m ³ , preferably equal to 800 Nm ³ / m ³ . Advantageously, the temperature is approximately 160 ° C., under a pressure substantially of 50 × 10 ⁵ Pa.

Preferably, the catalyst of the stage of aromatherapy is arranged in several beds, between which is injected with a quenching fluid to control the exothermicity of the aromatization reaction.

Depending on the types of catalysts used for both steps described above, a complementary step of denitration can be carried out before that of aromatization. Indeed, certain catalysts of aromatics are sensitive to nitrogen, which causes their deactivation. Therefore, if the catalyst selected hydrotreatment did not reduce the nitrogen content of the feed, it must be treated in order to have a very low nitrogen content of the order of 10 ppm. This treatment can be carried out by different means such as a conventional nitrogen trap containing a mass denim.

Depending on the type of catalyst used in the aromatization, washing of the step effluent hydrotreatment is required to remove ammonia and dissolved hydrogen sulfide which are factors limiting or poisoning for certain types of dearomatization catalysts.

The examples below illustrate different modes of preparation of jet fuel according to the prior art and according to the invention. They are not limiting in nature and are intended to illustrate the advantages of jet fuels according to the invention as defined in the claims.

In these examples, we will refer to the single figure of attached drawing, which represents various curves of distillation of jet fuels described in the examples.

Example 1

One charge, at distillation points between 150 and 250 ° C, coming directly from the fractionation of a catalytic cracking unit, has been treated in accordance with the method according to the invention.

Initially, the feed was treated in a hydrotreating unit. An alumina catalyst is used having a specific surface of 220 m ² / g, a pore volume of 0.5 cm ³ / g, containing, in% by weight, 4.2% of nickel oxide and 16 , 5% molybdenum. The operation is carried out at an average temperature of 325 ° C. under approximately 35.10 ⁵ Pa, with an hourly volume speed of 3 h ^-1 and a hydrogen / hydrocarbon ratio of 200 Nm ³ / m ³ .

For the dearomatization stage, the catalyst TK 908 from Haldor Topsoe is used. The operation is carried out at an average temperature of 240 ° C. under approximately 50 × 10 ⁵ Pa, with an hourly volume speed of 1 h ^-1 and a hydrogen / hydrocarbon ratio of 600 Nm ³ / m ³ .

The characteristics of the feedstock, of the effluent after hydrotreatment and of the jet fuel obtained after dearomatization, are collated in Table 1 below:

The distillation curve is shown in the figure single annexed.

Example 2 (Comparative)

A mass mixture composed of 50% of a fraction kerosene from distillation points between 140 and 270 ° C from direct distillation of crude oil, and at 50% of a load of distillation points of 160 and 240 ° C, coming directly from the fractionation of a unit of catalytic cracking, has been treated in accordance with the method according to the invention.

Initially, the feed was treated in a hydrotreating unit. A catalyst identical to that of Example 1 is used. The operation is carried out at an average temperature of 300 ° C., under approximately 35 × 10 ⁵ Pa, with an hourly volume speed of 4 h ^-1 and a hydrogen / hydrocarbon ratio of 200 Nm ³ / m ³ .

For the dearomatization stage, the catalyst TK 908 from Haldor Topsoe is used. The operation is carried out at an average temperature of 270 ° C., under approximately 50 × 10 ⁵ Pa, with an hourly volume speed of 3 h ^-1 and a hydrogen / hydrocarbon ratio of 600 Nm ³ / m ³ .

La courbe de distillation est reproduite sur la figure unique annexée.The characteristics of the feed, of the effluent after hydrotreatment and of the jet fuel obtained after dearomatization, are collated in Table 2 below:

The distillation curve is reproduced in the attached single figure.

This example illustrates the use of a fraction kerosene from the direct distillation of crude oil as a diluent, which allows both to control the exothermicity of the hydrotreatment reactions and to improve the basic qualities of the said fraction kerosene (including thawing point and power lower heat).

Example 3

A load at distillation points between 150 and 270 ° C, coming directly from the fractionation of a unit catalytic cracking, has been treated in accordance with the method according to the invention.

Initially, the feed was treated in a hydrotreating unit. An alumina catalyst is used having a specific surface of 210 m ² / g, a pore volume of 0.6 cm ³ / g, and containing 2.8% of cobalt oxide and 13.8% of molybdenum oxide. The operation is carried out at an average temperature of 325 ° C., under approximately 35 × 10 ⁵ Pa, with an hourly volume speed of 3 h ^-1 and a hydrogen / hydrocarbon ratio of 300 Nm ³ / m ³ .

For the dearomatization stage, the catalyst HTC 400 Crosfield is used. The operation is carried out at an average temperature of 160 ° C. under approximately 50 × 10 ⁵ Pa, with an hourly volume speed of 3 h ^-1 and a hydrogen / hydrocarbon ratio of 800 Nm ³ / m ³ .

La courbe de distillation est représentée sur la figure unique annexée.The characteristics of the feedstock, of the effluent after hydrotreatment, and of the jet fuel obtained after dearomatization are set out in Table 3 below:

The distillation curve is shown in the attached single figure.

Example 4 (Comparative)

A load at distillation points between 140 and 250 ° C, from the atmospheric distillation of a crude oil, is processed in a softening unit of "KEROX" type mercaptans, the principle of which is described succinctly page 877 of the book "Refining and engineering chemical "by P. Wuithier, IFP, volume 1, 1972 edition.

The operation is carried out in a manner known per se, in the presence of a catalyst based on cobalt phthalocyanine, at a pressure of 8.10 ⁵ Pa and at a temperature of 50 ° C.

La courbe de distillation est reproduite sur la figure unique annexée.The characteristics of the charge and of the carburetor obtained are collated in Table 4 below:

The distillation curve is reproduced in the attached single figure.

Example 5 (Comparative)

A load at distillation points between 350 and 560 ° C, from vacuum distillation, is processed in a Unicracking type double-hydrocracker, developed by UNOCAL and UOP. For reference, this device hydrocracking is briefly described on page 761 of the book "Refining and chemical engineering" by P. Wuithier, IFP, volume 1, 1972 edition.

The vacuum distillate charge is pretreated in a first reactor in the presence of a denitrogenation catalyst. Then, the effluent obtained is treated in the reactor cracked. The operating conditions are appreciably similar to those indicated on page 764 of the book "Refining and chemical engineering "by P. Wuithier, IFP, volume 1, edition of 1972.

La courbe de distillation est reportée sur la figure unique annexée.The characteristics of the charge and of the jet fuel obtained by fractionation are presented in Table 5 below:

The distillation curve is shown in the attached single figure.

All the characteristics of JET Al and jet fuels of examples 1, 2, 3, 4 and 5 is described in Table 6 below.

The freezing points of Examples 1 and 3 are, in particular, much lower than the minimum required, that is to say less than -47 ° C, and therefore allow potential use of these jet fuels in extreme cold conditions. In addition, it should be noted that the lower calorific power of the jet fuels obtained according to the invention is particularly high compared to those of the prior art.

Claims (11)

1. A jet fuel having a combination of the following characteristics:

   i) a distillation point in the range between 140 and 300°C;

   ii) a content of aromatic hydrocarbons of less than 22 % by volume;

   iii) a lower volumetric calorific value above 34.65 Mj/litre;

   characterised in that it additionally has:

   iv) a cis decalin/trans decalin ratio higher than 0.2;

   v) a sulphur content of less than 100 ppm, and

   vi) a ratio of naphtenes / paraffins of between 1.2 and 2.
2. A jet fuel according to claim 1, characterised in that its calorific value is between 34.65 and 35.30 Mj/litre.
3. A jet fuel according to claim 1 or 2, characterised in that its cis decalin/trans decalin ratio higher than 0.3.
4. A jet fuel according to any one of the preceding claims, characterised in that its naphthalene/trans decalin ratio is lower than 0.05.
5. A process for preparing a jet fuel according to any one of claims 1 to 4, characterised in that a catalytic cracking fraction distilling between 140 and 300°C is subjected to a hydrotreatment stage, then to a dearomatisation stage.
6. A process according to claim 5, characterised in that the hydrotreatment stage is carried out on at least one fixed catalyst bed containing at least one hydrogenating and/or hydrocracking metal, at an average temperature of between 250 and 350°C, at a minimum pressure of 30.10⁵ Pa, with an hourly spacial velocity of 1 to 5 h^-1 and a hydrogen/hydrocarbon ratio of between 100 and 500 Nm³/m³.
7. A process according to claim 6, characterised in that the catalyst contains cobalt and molybdenum or nickel and molybdenum.
8. A process according to any one of claims 5 to 7, characterised in that the dearomatisation stage is carried out in the presence of a catalyst containing at least one noble metal disposed on at least one fixed bed, at a temperature of between 200 and 300°C and at a minimum pressure of 30.10⁵ Pa, with an hourly spatial velocity of 1 to 5 h^-1 and a hydrogen/hydrocarbon ratio of between 500 and 900 Nm³/m³.
9. A process according to any one of claims 5 to 8, characterised in that the dearomatisation stage is carried out in the presence of a nickel-based catalyst disposed on at least one fixed bed, at a temperature of between 100 and 200°C and at a minimum pressure of 30.10⁵ Pa, with an hourly spatial velocity of 1 to 5 h^-1 and a hydrogen/hydrocarbon ratio of between 600 and 1000 Nm³/m³.
10. A process according to any one of claims 5 to 9, characterised in that a diluent is used in at least one of the stages of said process to control the exothermic nature of the reaction.
11. A process according to claim 10, characterised in that a diluent is mixed with the catalytic cracking fraction before hydrotreatment, said diluent being a kerosene fraction formed in the atmospheric distillation of crude petroleum.

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