WO2017050687A1

WO2017050687A1 - Optimal jet fuel composition with heat stability and improved oxidation

Info

Publication number: WO2017050687A1
Application number: PCT/EP2016/072146
Authority: WO
Inventors: Arij BEN AMARA; Marie-Helene Klopffer; Maira ALVES FORTUNATO; Laurie STARCK
Original assignee: IFP Energies Nouvelles
Priority date: 2015-09-22
Filing date: 2016-09-19
Publication date: 2017-03-30
Also published as: FR3041360B1; FR3041360A1

Abstract

The invention relates to a composition comprising at least one fuel and at least one additive chosen from benzenes substituted with n methyls, n being an integer between 1 and 6, tetralin and decalin, alone or as a mixture, the volume percentage of said fuel being between 75% and 98% relative to the total volume of the composition and in which: - the volume percentage of said substituted benzene, when it is present in the composition, is between 2% and 15% by volume relative to the total volume of the composition, - the volume percentage of the tetralin, when it is present in the composition, is between 2% and 10% by volume relative to the total volume of the composition and - the volume percentage of the decalin, when it is present in the composition, is between 5% and 25% by volume relative to the total volume of the composition, the sum of the volume percentages of the fuel(s) and of the additive(s) being equal to 100%.

Description

OPTIMAL CARBUREACTOR COMPOSITION WITH THERMAL STABILITY

AND IMPROVED OXIDATION

FIELD OF THE INVENTION

Environmental, economic and energy constraints have encouraged the diversification of energy resources and the development of new technologies in the field of transport and in particular aeronautical transport.

The present invention relates to the field of reactors and in particular, a new formulation, usable as a carburettor, having good thermal stability and oxidation, said composition comprising a fuel and at least one additive, in which the proportion by volume fuel relative to the total volume of the composition is higher than in the compositions of the prior art. Indeed, the molecules of the reactors are subject to autoxidation, polymerization and thermal cracking reactions. These reactions can lead to alterations in the physicochemical characteristics and change the interaction of jet fuel with its environment, in particular by the formation of sediments and / or deposits in tanks, fluid circuits and corrosion of surfaces. Thus, the stability of a jet fuel depends among other things on these parameters.

The diversification of fuel sources was necessary and led to the use of so-called synthetic fuel such as bio-fuels, synthetic paraffinic kerosenes (SPK), resulting from processes such as the Fischer Tropsch process (SPK-FT) or the hydrotreatment of esters and fatty acids (SPK-HEFA). Currently, said synthetic fuels can not be used alone because of their low oxidation stability, their low thermal stability and in some cases their low content of aromatic compounds.

Indeed, a minimum content of aromatic compounds in the carburetors is set at 8% by weight by the ASTM specification D-7655. The Aromatic compounds play a major role in the quality of a jet fuel because they make it possible to ensure the compatibility of the jet fuel with the polymers used to seal the reactor fuel lines by caking, such as for example butadiene-based copolymers. acrylonitrile (NBR: Nitrile Butadiene Rubber), fluorosilicones (FVMQ) and fluoroelastomers (FKM).

Thus, to allow the use of said synthetic fuels as a carburetor, the use of additives and in particular aromatic additives has often been considered.

PRIOR ART

The patent application CN 101 423 781 discloses an additive and fuel composition which allows the limitation of the formation of deposits. The recommended additives are terpenes, 2-propanone, glycol ethers, dimethyl esters of carboxylic acid, nonylphenol ethoxylates and mineral oils.

US Pat. Nos. 7,683,224 and 7,560,603 disclose the use of phenylalkyls and / or alkylcyclohexyls having at least one alkyl chain having 5 to 25 carbon atoms as additives for kerosene and diesel type fuels. These additives improve the properties of synthetic slices (increase flash point, density, lubricity, aerobic degradability, oxidation stability and thermal stability). US Pat. No. 8,748,678 discloses a formulation based on a blend of a high density synthetic cut composed essentially of cycloalkanes and naphthenoaromatics, preferentially tetralin and decalin, and of a low density synthetic cut, composed essentially of paraffinic compounds (SPK ) mainly of the n-alkane type and additives, making it possible to improve, among other things, the thermal stability of the jet engines and diesel engines.

The patent application WO 2012/024193 discloses a thermally stable jet fuel formulation which respects several physicochemical properties (calorific value, boiling temperature) whose content of aromatic compounds (mono and diaromatic) is between 2-25% vol. in cycloparaffins of 22-35% vol, the n-paraffin content of 20-35% vol and the iso-paraffin content of 22-35% vol.

US Pat. No. 3,703,361 discloses the use of decahydroacenaphthene as a 100% jet fuel or in a mixture with a conventional jet fuel at a decahydroacenaphthene content of between 10 and 60% by weight so as to improve the physical properties and the stability of the jet fuel.

There is therefore a real need for the development of new fuel-based and additive formulations having good thermal stability and oxidation, and also making it possible to maximize the amount of fuel that can be incorporated into the said formulation that can be used as jet fuel. .

OBJECT OF THE INVENTION

An object of the invention is a composition comprising at least one fuel and at least one additive chosen from n-methyl substituted benzenes, n being an integer between 1 and 6, tetralin and decalin alone or as a mixture, the percentage the volume of said fuel being between 75% and 98% relative to the total volume of the composition and in which:

the percentage by volume of said substituted benzene when it is present in the composition is between 2 and 15% by volume relative to the total volume of the composition,

the percentage by volume of tetralin when it is present in the composition is between 2 and 10% by volume relative to the total volume of the composition and

the percentage by volume of the decalin when it is present in the composition is between 5 and 25% by volume relative to the total volume of the composition,

the sum of the volume percentages of the fuel (s) and the additive (s) being equal to 100%.

Another object of the invention is the use of said composition as a jet fuel. An advantage of the present invention is to provide a novel jet fuel formulation whose oxidation stability, thermal stability and physical properties such as density and compatibility with materials, especially polymers, are improved.

Another advantage of the present invention is to allow the increase of the amount of synthetic fuel incorporated in a composition for use as a jet fuel with respect to the jet fuel compositions of the prior art.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a composition comprising at least one fuel and at least one additive chosen from n-methyl-substituted benzenes, n being an integer between 1 and 6, tetralin and decalin alone or as a mixture, the volume percentage of said fuel. being between 75% and 98% relative to the total volume of the composition and in which:

Preferably said fuel is selected from conventional kerosene and synthetic fuels.

Synthetic fuel is a fuel produced from non-petroleum feedstock compatible with ASTM D7566 Conventional kerosene means a fuel derived from conventional petroleum refining processes compatible with the ASTM D1 655 or DEFSTAN 91 -91 specification. In the case where said fuel is a synthetic fuel compatible with the ASTM D7566 specification, said synthetic fuel is advantageously a synthetic paraffinic kerosene (SPK) derived from a hydrotreatment of esters and fatty acids (SPK-HEFA) or from a Fischer Tropsch process (SPK-FT) or a synthetic Iso-Paraffin (S / P), also called Farnesane.

In the case where the additive is chosen from said substituted benzenes, said additive is advantageously chosen from toluene, dimethylbenzenes and trimethylbenzenes alone or as a mixture. In the case where the additive is chosen from said substituted benzenes, the volume percentage of said additive is advantageously between 3% and 12% relative to the total volume of the composition and preferably between 4% and 10% relative to the volume total of the composition. In the case where the additive is tetralin, the volume percentage of said additive is advantageously between 3% and 9% relative to the total volume of the composition and preferably between 4% and 8% relative to the total volume of the composition. In the case where the additive is decalin, the volume percentage of said additive is advantageously between 5% and 20% relative to the total volume of the composition and preferably between 10% and 15% relative to the total volume of the composition. In the case where the additives are used in a mixture, the total volume percentage of said additives is between 2% and 10% relative to the total volume of the composition, preferably between 3% and 9% relative to the total volume of the composition. the composition and even more preferably between 4% and 8% relative to the total volume of the composition. Another object of the invention is the use of said composition as a carburetor reactor. To be certified a reactor carburetor must meet different criteria and physico-chemical properties such as oxidation stability, thermal stability, density and its ability to swell the polymers ensuring the sealing of the circuits.

The oxidation stability of a jet fuel is defined by the induction period (IP) of said jet fuel, the higher the induction period, the higher the oxidation stability.

The induction period, or IP, is the time required for the jet fuel to reach a defined oxidation state. Reactors, depending on their destination and territory of use must have an IP longer than a certain time to meet the minimum required specifications.

In the standard PetroOxy method ASTM D7545, EN16091, IP595, 5mL of the jet fuel sample is introduced into a closed cell, pure oxygen is injected at 0.7 MPa. The cell is heated up to 140 ° C. The pressure within the cell decreases during the oxidation of the sample. This pressure is noted at intervals of 1 s, until the pressure readings indicate a drop of 10% compared to the maximum pressure observed (breaking point). The equipment stops the test and records the time elapsed between the start of the test and this breakpoint. This time represents the jet fuel induction period (IP) which is considered an indication of the oxidation resistance of middle distillates, fatty acid methyl esters (FAMEs) and mixtures thereof. The higher the induction period, the more the jet fuel is theoretically stable to oxidation.

The thermal stability of a jet fuel is measured by the standardized test ASTM D-3241 "Standard test method for thermal oxidation stability of aviation turbine fuels". This test method makes it possible to measure the stability of high temperature reactor carburetors. The device requires a volume of 450 ml of jet fuel for a test that lasts 2h30min. The jet fuel is pumped at a fixed volumetric flow rate through a heater and then passed through a 17 micrometer nominal porosity filter made of stainless steel where the jet fuel degradation products can be trapped. This is indicates, on the one hand, the formation of solid deposits on a heated metal tube, this is measured by visual quotation (trad: visual rating) and, on the other hand, the insoluble deposits formed in the liquid phase measured by the variation pressure gradient through a filter (dP filter). The test temperature defined by ASTM Specification D-3241 varies depending on the jet fuel tested.

The density of a jet fuel is a decisive physico-chemical parameter and must be included in a precise range because the density impacts on the amount of energy on board. If a jet fuel has a density that is too low, it is possible to have, for example, Steam plugs in the jet fuel circuit If, on the contrary, a jet fuel with too high a density, it is possible that the vaporization is not carried out optimally and therefore impacts combustion. Density is measured by ASTM methods D4052, IP365, ASTM D1298, IP1 60. Polymers such as butadiene-acrylonitrile copolymers (NBR: Nitrile)

Butadiene Rubber), fluorosilicones (FVMQ) and fluoroelastomers (FKM) are commonly used in aeronautics as a seal. The placing in contact with a jet fuel causes a setting of said polymers. The mass swelling rate of the polymers in contact with the jet fuel indicates the ability of said polymers to seal.

The swelling rate of the polymers is measured by laboratory methods. Their principle is to immerse the polymer in the jet fuel for a certain time. During this immersion phase, the polymer is regularly characterized to define its swelling through measurements of weight, and dimensions.

A compromise must be found between the different properties necessary for the good performance of a jet fuel to obtain an optimal composition. The induction period should be maximized to obtain the best oxidation stability possible, however the other parameters must meet certain standards. Thus, for thermal stability, according to ASTM Specification 7566 the visual quotation should not exceed 3 (level on a visual rating scale, the larger the figure is, the greater the amount of deposit on the tube is consistent) and the pressure difference the filter positioned after the tube shall not exceed 25 mm Hg. According to ASTM Specification D 7655, the density of the jet fuel shall be in the range of 775 to 840 gL ^"1. There is no relevant specification the ability of a jet fuel to induce polymer mass variation, however, the seal must be provided by the various seals.

The examples below illustrate the invention without limiting its scope.

EXAMPLES

Example 1: Preparation of the compositions

Synthetic paraffinic kerosene type synthetic fuel derived from the hydrotreatment of esters and fatty acids (SPK-HEFA) is mixed with an additive so as to obtain the desired percentages by volume and stirred at 25.degree. homogeneous solution. The compositions obtained are listed in Table 1 below.

Table 1

Example 2: Stability and Physicochemical Properties of the Compositions The compositions obtained in Example 1 are analyzed according to the methods described above to determine their oxidation stability, their thermal stability, their density and their ability to set a copolymer-type butadiene-acrylonitrile copolymer (NBR). : Nitrile Butadiene Rubber), fluorosilicone (FVMQ) and fluoroelastomers (FKM). The results are listed in Tables 2 and 3.

Table 2

The analyzes carried out show that the choice of additives is preponderant since 1-methylnaphthalene does not make it possible to obtain a good thermal stability, in particular regardless of the quantity added.

A compromise must be found between the different properties necessary for the good performance of a carburetor reactor.

Blends having a visual rating value greater than or equal to 3 are incompatible with ASTM 7566. Thus, xylene can not be used as an additive with a 25% by volume amount because of too much deposition. Tetralin can not be used as an additive with 15% by volume due to poor thermal stability. Decalin can be used at 25% by volume, the induction period experiencing a peak with a quantity of 15% by volume of decalin. Thus, beyond 25% by volume of decalin, the induction period becomes too low for the desired oxidation stability. 1-Methylnaphthalene can not be used as an additive given the poor thermal stability of the jet fuel regardless of the concentration of 1-methylnaphthalene.

The additives that can be used according to the invention have been tested with regard to their capacity to induce a mass variation of various polymers (butadiene-acrylonitrile copolymer (NBR: Nitrile Butadiene Rubber), fluorosilicone (FVMQ) and fluoroelastomer (FKM), the results are listed in Table 3. By increasing the concentration of the additives, the mass variation of said polymers can only be greater and since there is no upper limit, only the 5% by volume There are currently no standards for polymer mass variation, however the results can be compared to a specified jet fuel which is jet fuel called "50% JETA-1" in the table below.

Table 3

It therefore appears that the addition of the additives recommended according to the invention makes it possible to achieve or approach substantially the properties of the approved jet fuel 50% JETA-1 for the induction of polymer mass variation.

The additives according to the invention therefore make it possible both to increase the oxidation stability and the thermal stability of a jet fuel while improving the physicochemical properties. The additives according to the invention also allow to increase the proportion of synthetic fuel in a carburetor reactor composition.

Claims

Composition comprising at least one fuel and at least one additive chosen from n-methyl-substituted benzenes, n being an integer between 1 and 6, tetralin and decalin alone or as a mixture, the volume percentage of said fuel being between 75% and 98% based on the total volume of the composition and wherein:

the percentage by volume of the decalin when it is present in the composition is between 5 and 25% by volume relative to the total volume of the composition, the sum of the volume percentages of the fuel (s) and the additive (s) being equal to 100%.

The composition of claim 1, wherein said fuel or fuels are selected from conventional kerosene and synthetic fuels.

The composition of claim 2 wherein said synthetic fuel is a synthetic paraffinic kerosene derived from a hydrotreatment of esters and fatty acids or from a Fischer Tropsch process or synthetic iso-paraffin.

4. Composition according to claims 1 to 3, wherein said substituted benzene is selected from toluene, dimethylbenzenes and trimethylbenzenes alone or in admixture.

5. Composition according to claims 1 to 4 wherein said substituted benzene is present at a volume percentage of between 3% and 12% relative to the total volume of the composition.

6. Composition according to claims 1 to 3 wherein said tetralin is present at a volume percentage of between 3% and 9% relative to the total volume of the composition. 7. Composition according to claims 1 to 3 wherein said decalin is present at a volume percentage of between 5% and 20% relative to the total volume of the composition.

8. Composition according to claims 1 to 3, wherein said additives are used in a mixture, the total volume percentage of said additives being between 2% and 10% relative to the total volume of the composition.

9. Use of the composition according to one of claims 1 to 7 as a reactor fuel.