FIELD OF THE INVENTION

The present invention relates to a composition comprising renewable jet fuel RJF] and an anti-oxidant component. More specifically the anti-oxidant component is a blend of phenylenediamine and hindered phenol.

BACKGROUND OF THE INVENTION

Jet fuel is a fuel intended for use in aircraft powered by gas-turbine engines. The most commonly used jet fuels Jet A and Jet A-l are produced to a standardized international specification. Jet fuel is a mixture of different hydrocarbons. The structure, molecular weights or carbon numbers of the hydrocarbons in the mixture need to be chosen such that the physical properties required by the jet fuel product specification, e.g. flash point, freezing point, boiling range, are met by the mixture. Kerosene-type jet fuel (including Jet A and Jet A-l) typically has a carbon number distribution between about 8 and 16 carbon atoms per molecule.

Fossil fuels or petroleum-based fuels may be at least partly replaced by synthesized fuel or fuel components e.g. produced from biological sources or other renewable sources. The renewable jet fuel demand is growing in the future due to global initiatives to decrease the emissions of GHG, CO2, etc. One possible solution is to increase the use of renewable fuels in jet fuels. Fuels from biological sources may include renewable lipid feedstocks such as fats and/or oils. Several types of fuels may be obtained from these triacylglycerol-containing lipid feedstocks. One example of a product that may be obtained from lipid feedstocks, is hydrocarbons produced from triacylglycerol by a hydrodeoxygenation reaction at an elevated temperature and pressure in the presence of a catalyst.

The formed hydrocarbons from the hydrodeoxygenation reaction of the triacylglycerol-containing feedstocks typically need to be isomerised before the composition fulfils fuel specification. Isomerisation of the hydrocarbons lowers the melting point of the hydrocarbons and thereby improves the cold flow properties of the composition.

The stability of any hydrocarbon composition to be used as a fuel and especially fuels for aviation use is very important. Especially, the so-called oxidation stability, i.e. capability of withstanding oxidation, is highly important. Various anti-oxidation agents or compositions are therefore used as additives in fuels, to improve the oxidation stability of the fuels. Anti-oxidation agents are also used in hydroprocessed renewable jet fuels.

Biodiesel is generally used to denote fuels based on esters of fatty acids of biological sources, such as vegetable oils and/or fats. Usually a methyl ester of the fatty acids is used, the biodiesel is then also called FAME (Fatty Acid Methyl Ester). Publication US 2011/0209390 describes an anti-oxidant for improving the oxidation stability of biodiesel (FAME), where the anti-oxidant is mixture of at least one aromatic amine, at least one sterically hindered phenol and substituted polyhydroxy phenol.

The oxidation stability is very crucial also for renewable jet fuels. Renewable jet fuel standard ASTM D7566-21c provides a list of traditional antioxidants, which are mandatory to be used in renewable fuels.

BRIEF DESCRIPTION OF THE INVENTION

An object of the present invention is to provide a composition of renewable jet fuel and an additive component comprising a blend of phenylenediamine and hindered phenol.

According to one aspect of the invention, it is provided a jet fuel composition, comprising a) a renewable jet fuel component containing hydro-processed esters and fatty acid synthetic paraffinic kerosene (HEFA-SPK), which fulfils the ASTM D7566 Annex A2 requirements for renewable jet fuel, and b) an additive component comprising a blend of phenylenediamine and hindered phenol.

Preferred embodiments of the invention are disclosed in the dependent claims.

DETAILED DESCRIPTION OF THE INVENTION

All standards referred to herein are according to the latest available revisions unless otherwise mentioned.

Hereby is disclosed a jet fuel composition comprising a renewable jet fuel component containing hydro-processed esters and fatty acid synthetic paraffinic kerosene (HEFA-SPK), which fulfils the ASTM D7566 Annex A2 requirements for renewable jet fuel blending component and an additive component comprising a blend of phenylenediamine and hindered phenol.

With the term "a renewable jet fuel component containing hydroprocessed esters and fatty acid synthetic paraffinic kerosene (HEFA-SPK)" is here meant a mixture of hydrocarbons, which is suitable as fuel for aircrafts powered by gas-turbine engines. There are strict requirements for fuels to be suitable as jet fuel or aviation fuel. The requirements for jet fuel are specified in several standards. The standards for definition of jet fuel include at least DEF STAN 91-091 Issue 12, ASTM D1655-21a (JetA-1 or Jet A) and ASTM D7566-21.

Here a renewable jet fuel component, which fulfils the ASTM D7566 Annex A2 requirements for renewable jet fuel, is any hydrocarbon component which is produced from renewable sources and meets the requirement set out in ASTM D7566 Annex A2. ASTM D7566 Annex A2 defines synthesized paraffinic kerosine (SPK) produced from hydro-processed esters and fatty acids (HEFA) for use as a synthetic blending component in aviation turbine fuels. Renewable sources as an alternative to fossil sources for fuel components have been developed to tackle the environmental challenges associated with the use of fossil-based fuels. The ASTM D7566 standard sets out the requirements for jet fuels from non- traditional sources, i.e. non-petroleum sources.

In one embodiment of the invention the renewable jet fuel component is hydro-processed esters and fatty acids (HEFA). HEFA is a collective term used e.g. by the ASTM standard to describe hydrocarbons which have been produced from mono- di and triglycerides, free fatty acids and/or fatty acid esters by hydroprocessing to remove essentially all oxygen. The paraffins need to be isomerised to meet requirements for jet fuel, such as the cold properties. Paraffins produced by hydrodeoxygenation of fatty acids are n-paraffins (straight chain paraffins) with poor cold properties. Isomerisation of paraffins produces branched paraffins, so- called iso-paraffins or i-paraffins. Iso-paraffins have better cold properties compared to n-paraffins.

In one embodiment of the invention the renewable jet fuel, which fulfils the ASTM D7566 Annex A2, is a mixture of mainly C8-C18 paraffins, i.e. at least 90 wt.% of the mixture is paraffins, preferably at least 95 wt.% is paraffins, and more preferably at least 97 wt.% of the renewable jet fuel is C8-C18 paraffins. The paraffins in the mixture comprise straight chain paraffins (n-paraffins), branched paraffins (iso-paraffins) and cycloparaffins. The paraffins mixture comprises at least 60 wt.% iso-paraffins, preferably at least 75 wt.% iso-paraffins, and more preferably at least 90 wt.% iso-paraffins and most preferably at least 95 wt.% isoparaffins as calculated on the total renewable jet fuel component.

The freezing point of the mixture of the renewable fuel paraffin mixture can be at least -30 °C, preferably at least -37 °C, and most preferably at least -40 °C. The carbon chain distribution of the hydrocarbons in the renewable fuel component can be e.g. such that hydrocarbons with carbon chain with <C15 is equal to or less than 40 wt.%, preferably from 30 wt.% to 40 wt.% or more preferably from 32 wt.% to 37 wt.%. The renewable jet fuel can comprise hydrocarbons with carbon chains C15 - C18, which is equal to or more than 55 wt.%, preferably 55 wt.% to 70 wt.%, or more preferably 60 wt.% to 67 wt.%. The hydrocarbons with carbon chains of >C18 is equal to or less than 5 wt.%, preferably from 5 wt.% to 1 wt.%. The weight percentages (wt.%) of a certain carbon number is calculated from the total carbon chain / hydrocarbon content.

It is essential to understand that a jet fuel composition comprising a renewable jet fuel component containing HEFA-SPK has a distinct composition and therefore is a different jet fuel compared to a 100% petroleum based jet fuel. The renewable component, here the HEFA-SPK component alters the chemical composition of the composition and thereby also the oxidation stability of the composition.

The jet fuel composition according to the invention comprises as an additive component a blend of phenylenediamine and hindered phenol. Here the term "additive component" denotes a component in the fuel component which is added to the fuel mixture to provide the fuel mixture certain properties. The aim of the additive component is not primarily to function as a fuel component, but to improve certain properties of the fuel. Here the additive component is primarily meant to function as an anti-oxidant in the fuel.

In one embodiment of the invention the amount of the additive component in the composition according to the invention is from 17 to 24 mg/1 based on the active material /active ingredient, i.e. the anti-oxidant of the additive.

The additive component of the current invention comprises a blend of phenylenediamine and hindered phenol. With the term "hindered phenol" is here meant a phenol in which the hydroxyl group is sterically hindered with substituents at position 2 or 6, or preferably both at position 2 and 6. The phenol substituents at positions 2 and/or 6 are generally relatively bulky inert groups such as branched alkyl groups. The hindered phenol of the current invention is preferably substituted at position 2 and/or 6 with C1-C4 branched or straight chain alkyls, preferably tert-butyl; a C5 or C6 cycloalkyl or n-nonyl. The hindered phenol is optionally also substituted at position 4 with C1-C4 branched or straight chain alkyl.

Preferably the hindered phenol has the general formula (1):

in which R ¹ and R ³ are independently selected from H, Cl -C4 branched or straight chain alkyl, a C5 - C6 cycloalkyl and n-nonyl, with the proviso that both R ¹ and R ³ are not both H;

R ² is selected from H, C1-C4 branched or straight chain alkyl and C1-C4 alkoxy.

Preferably R ¹ and R ³ in formula (1) are independently selected from H, methyl and tert-butyl, with the proviso that R ¹ and R ³ are not both H; and R ² is selected from H, methyl and tert-butyl.

In one embodiment of the invention the hindered phenol is selected from the phenols listed as anti-oxidants listed in standard DEFSTAN-91-091 Issue 12 of September 2020 or a mixture of phenols of said standard. The following antioxidant formulations are qualified according to standard DEFSTAN-91-091:

- 2,6-ditertiary-butyl-phenol RDE/A/606,

- 2,6 ditertiary-butyl-4-methyl-phenol RDE/A/607,

- 2,4-dimethyl-6-tertiary-butyl-phenol RDE/A/608,

- 75 percent minimum, 2,6-ditertiary-butyl-phenol 25 percent maximum, tertiary and tritertiary-butyl-phenols RDE/A/609,

- 55 percent minimum, 2,4-dimethyl-6-tertiary-butyl-phenol 15 percent minimum, 4 methyl-2,6-ditertiary-butyl-phenol Remainder, 30 percent maximum, as a mixture of monomethyl and dimethyl-tertiary-butyl-phenols RDE/A/610, and

- 72 percent minimum, 2,4-dimethyl-6-tertiary-butyl-phenol 28 percent maximum, mixture of tertiary-butyl-methylphenols and tertiary-butyl dimethyl phenols RDE/A/611.

In one preferred embodiment of the invention the hindered phenol is 2,6-ditertbutyl-phenol, 2,6-ditertbutyl-4-methyl-phenol, 2,4-dimethyl-6-tert- butyl-phenol or any mixture thereof. Most preferably the hindered phenol is 2,6- ditertbutyl-phenol.

The additive component also comprises phenylenediamine, which is a collective term for any compounds with a phenyl moiety, substituted with two amine-groups, preferably in para-orientation (1,4-diamine substituted phenylene).

The amine-substituents can be further substituted, preferably with Cl- C9 branched or straight alkyl or C5-C6 cycloalkyl. Preferably the phenylenediamine has the general formula (11): in which R ⁴ and R ⁵ are independently selected from H, C1-C9 branched or straight chain alkyl and C5 - C6 cycloalkyl.

In one embodiment of the invention the R ⁴ and R ⁵ are independently selected from C3 - C4 branched alkyl.

In a preferred embodiment the phenylenediamine is N,N’-di-sec-butyl- p-phenylenediamine.

In a preferred embodiment the blend of phenylenediamine and hindered phenol is a blend of 2,6-ditertbutyl-phenol, 2,6-ditertbutyl-4-methyl- phenol, 2,4-dimethyl-6-tert-butyl-phenol or any mixture thereof and N,N’-di-sec- butyl-p-phenylenediamine, and more preferably a blend of 2,6-ditertbutyl-phenol and N,N’-di-sec-butyl-p-phenylenediamine.

In one embodiment of the composition the weight percentage (wt.%) of the phenylenediamine is from 40 wt.% to 60 wt.% in the additive component and the balance up to 100 percentage being the hindered phenol. Preferably the weight percentage of the phenylenediamine and the hindered phenol is both about 50 wt.% of the additive. The weight percentages of the phenylenediamine and the hindered phenol is to be understood such that it denotes the total weight of phenylenediamines and the total weight of hindered phenol that constitute the additive composition. Therefore, if the additive composition comprises more than one type of phenylenediamines it is the total weight of these combined phenylenediamines that is meant. Similarly, if the additive component comprises more than one hindered phenol, it is the total weight of these combined hindered phenols that is meant.

The oxidative stability is important for fuels and especially for jet fuels, which possibly need to be stored for a long period of time, for several years, and for which the security of use is of outmost importance. The oxidative stability of jet fuels from renewable sources (RJFs) is very important. It has now surprisingly been found that a mixture of hindered phenols together with phenylenediamines function as an anti-oxidant additive component (anti-oxidation agent) also for RJFs and even better than the antioxidants approved by the standard.

In one embodiment of the composition, the composition further comprises a petroleum-based jet fuel component. With the term "petroleum-based jet fuel component" is here meant any such component that fulfils the requirement for jet fuel specification and is produced from fossil (petroleum) sources. Examples of jet fuel specifications are DEF STAN 91-091 Issue 12, ASTM D1655-21a (Jet A-l or Jet A) and ASTM D7566-21.

In one embodiment the jet fuel composition comprises a renewable jet fuel component containing hydro-processed esters and fatty acid synthetic paraffinic kerosene (HEFA-SPK), which fulfils the ASTM D7566 Annex A2 requirements, in an amount from 1 wt.% to 50 wt.% and the balance to 100 wt.% is petroleum based jet fuel component and additive component.

It has surprisingly been found that a combination of phenylenediamines and hindered phenols can be used as an anti-oxidation agent in renewable jet fuel (RJF). Especially it has been found that a blend of phenylenediamines and hindered phenols as presented in the current claims have superior properties as an antioxidation agent in RJFs compared to phenolic anti-oxidation agents typically used in RJF. Renewable jet fuel, like any other hydro-processed jet fuel, is susceptible to oxidative degradation and it is therefore necessary to use anti-oxidants to hinder this oxidative degradation. It has been found that the anti-oxidants hereby provided have improved anti-oxidation properties compared to the standard antioxidants currently used in jet fuels.

EXAMPLES

Example 1

Blends of renewable jet fuel and anti-oxidants were prepared. The antioxidants used were a standard anti-oxidant (AO-standard) used in jet fuels and anti-oxidant composition according to the invention (AO-1). The RJF used was a paraffinic fuel produced by hydrodeoxygenation followed by isomerisation. The RJF component used contained about 94 wt.% iso-paraffins and the rest n-paraffins and about 35 wt.% <C15 paraffins and about 65 wt.% C15 - C18 paraffins. The freezing point of the RJF was -48 °C.

The standard anti-oxidant used was 2,6-ditertiary-butyl-phenol, which is approved as anti-oxidantfor jet fuel (Defence Standard 91-091). The anti-oxidant components according to the invention were blends of 2,6-ditertbutylphenol and N,N’-di-sec-butyl-p-phenylenediamine, at about 50 wt.% each. The amount of antioxidant in the fuel samples were all the same, i.e. 20 mg/1 as per active ingredient.

The PetroOxy values of these blends were measured at the start, after 6 months, after 12 months, after 24 months, after 36 months and after 48 months. The values are compared to renewable jet fuel without anti-oxidant addition. The results of the measurements can be found in table 1.

The PetroOxy values were measured using EN16091:2011 standard. Principle of PetroOxy EN 16091 method: At ambient temperature, a known volume of a sample is placed in a reaction vessel charged with oxygen to a pressure of 700 kPa ± 5 kPa. The reaction vessel is heated to 140 C. The pressure in the vessel drops as the oxygen is consumed during the oxidation of the sample. The pressure in the vessel is recorded at intervals of 1 second until the breakpoint is reached. The elapsed time from start to the breakpoint is the induction period at the test temperature of 140 C ± 0,5 C.

Table 1; PetroOxy measures ofRJFs with various anti-oxidants

RJF = renewable jet fuel (no anti-oxidant)

AO-standard = standard anti-oxidant (RDE/A/606)

AO-1 = anti-oxidant of invention

From the results in Table 1 it can be seen that the anti-oxidants according to the invention provide higher PetroOxy values in minutes compared to the standard jet fuel anti-oxidant. A higher PetroOxy value means the oxidation of the fuel is slower, and thereby the fuel has a higher oxidation stability. Example 2

A set of blends of petroleum-based jet fuel with renewable jet fuel (JETA1 + RJF 50/50) at a proportion of 50/50 based on volume were prepared. The RJF component was prepared similarly to the RJF of Example 1 and had similar properties. A standard anti-oxidant and an anti-oxidant according to the invention were tested (same as in Example 1). Petroleum based jet fuel (JETA1) was used as a comparative example.

A set of PetroOxy measurements of the jet fuel blends were performed and the average PetroOxy value at the blending (start) is shown in Table 2.

Table 2; PetroOxy measurements of blends of JETA1 and RJF with standard antioxidant and with anti-oxidant according to invention (AO-1).

From the results in Table 2 it can be seen that the anti-oxidant component according to the invention performed better also in jet fuel blends, i.e. had a higher PetroOxy value compared to the standard anti-oxidant.

It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.