MXPA99004561A

MXPA99004561A - Fuel composition

Info

Publication number: MXPA99004561A
Application number: MXPA/A/1999/004561A
Authority: MX
Inventors: Quentin Clark Alisdair
Original assignee: Bp Oil International Limited
Priority date: 1996-11-18
Filing date: 1999-05-17
Publication date: 2000-09-04

Abstract

Unleaded aviation fuel compositions having a Motor Octane Number of at least 98, for use in piston driven aircraft comprising triptane andat least one other saturated liquid aliphatic hydrocarbon having from 5 to 10 carbon atoms. The compositions preferably contain triptane, iso-pentane and either one or any combination of iso-octane, toluene and methyl tertiary butyl ether.

Description

FUEL COMPOSITION FIELD OF THE INVENTION The present invention relates to combustible compositions and, in particular, to aviation gasoline having a high octane number suitable for use in piston-driven aircraft.

BACKGROUND OF THE INVENTION If a gasoline engine is started with a fuel having an octane lower than the minimum requirement for the engine, knocking or detonations will occur. Direct-flow gasoline with a low octane rating can be increased to the required engine octane rating of 82-88 for automotive use, by adding octane boosters such as tetraethyl lead, either alone or with refinery components such as reformate, alkylate, volatile compounds fractionated or chemical streams ^ such as toluene, xylene, tertiary methylbutyl ether or ethanol. Piston-driven aircraft engines operate under extreme conditions to provide the desired power, for example, high compression rates. Due to the severity of conditions, for example with turbo charged or supercharged engine, piston-driven aviation engines P1320 / 99MX require fuels with a minimum octane rating higher than the internal combustion gasoline engines used in automobiles, in particular at least 98-100. The basic fuel of an aviation gasoline has an engine octane of 90-93. To increase the engine octane sufficiently to the required level, aviation fuel is added to the basic aviation fuel. The fuel may contain the organoplome and also other octane enhancers, such as those described above. The publication Industrial and Engineering Chemistry Vol. 36 No. 12 pl079-1084 dated 1944, describes the use of triptan (2, 2, 3-trimethylbutane) in combination with tetraethyl lead in gasoline for aviation. However, the presence of tetraethyl lead is the key to achieving a high quality octane in gasoline for aviation. In modern formulations tetraethyl lead is always used to increase the octane quality of aviation gasoline to the desired level. However, due to environmental issues concerning the effect of lead and its compounds, attempts have been made to find an alternative to use tetraethyl lead in aviation gasoline. The conventional octane boosters P1320 / 99MX such as ethers, aromatics such as toluene and non-lead metal compounds, can increase the octane rating of unleaded gasoline to a high enough level to achieve the desired value, but do not increase the octane rating of the engine. unleaded aviation gasoline sufficiently high to ensure satisfactory performance or to have certain considerable technical limitations. US 5470358 discloses the use of aromatic amines to increase the engine octane in unleaded aviation gasoline to at least 98, but it is known that many aromatic amines are toxic. They have high boiling points, have no overload properties and have high freezing points, they are also prone to produce gums. Therefore, there is still a need for unleaded aviation gasoline with a sufficiently high octane to be suitable for use in piston-driven aircraft.

OBJECTS AND ADVANTAGES OF THE INVENTION According to the present invention, there is provided a lead-free aviation fuel composition having an engine octane of at least 98, and usually a final boiling point of less than 170 ° C and, Preferably, a Steam Pressure P1320 / 99MX Reid at 37.8 ° C of between 38-60 Pascals, comprising: component (a) consisting of at least one hydrocarbon having the following formula I R-CH2-CH (CH3) -C (CH3) 2-CH3 I wherein R is hydrogen or methyl and component (b) consisting of at least one aliphatic hydrocarbon, liquid, saturated, having from 4 to 10 carbon atoms, and in particular 5 or 6, with at least one other aliphatic, liquid, saturated hydrocarbon having from 5 to 10 carbon atoms, wherein at least 30% in volume of the total composition is a hydrocarbon of the formula I. If R is hydrogen, the hydrocarbon is triptan. If R is methyl, the hydrocarbon is 2,2,3-trimethylpentane. The triptan is especially preferred. The triptan and the 2,2,3-trimethylpentane can be used singly or in combination with each other, for example, in a weight ratio of 10:90 90:10, preferably 30:70 - 70:30. The composition may further comprise component (I), the hydrocarbon of formula I, a component (II) which is at least one of the known octane boosters described above, especially an oxygenated octane booster, typically a ether, normally of Motor Octane of at least 96-105, for example 98-103.

P1320 / 99MX The ether-based octane enhancer is usually a dialkyl ether, in particular of the asymmetric type, preferably wherein each alkyl has from 1 to 6 carbon atoms, in particular an alkyl which is a branched chain alkyl of 3. to 6 carbon atoms, in particular a tertiary alkyl, especially from 4 to 6 carbon atoms, for example tertiary butyl or tertiary amyl, and the other alkyl is from 1 to 6, for example 1 to 3 carbon atoms, in particular from linear type, for example methyl or ethyl. Examples of component (II) include tertiary methylbutyl ether, tertiary ethylbutyl ether and tertiary methylayl ether. The oxygenate can also be an alcohol of 1 to 6 carbon atoms, for example ethanol. At least one component (I) may be present together with at least one component (II) in combination. The combination may be, for example, triptan together with tertiary methylbutyl ether. The combination may be in a volume ratio of 40:60 to 99: 1, for example 50:50 to 90:10, preferably 60:40 to 85:15. The volumetric percentage of the ether can be up to 30% of the total composition, for example 1-30%, for example 1 to 5% or 5 to 25%. The octane rating of the aviation gasoline of the present invention is at least 98, for example P1320 / 99MX of 98-103, preferably from 99 to 102. The engine octane is determined according to ASTM D 2700-92 method. The hydrocarbons of the formula I can also, especially when present in an amount of at least 30% by volume, be used to provide gasolines of the invention with a performance number (according to ASTM D909) of at least 130 , for example from 130 to 170. Triptan or 2,2,3-trimethylpentane can be used with a purity of at least 95%, but preferably they are used as part of a hydrocarbon mixture obtained by distillation of a fractionated residue, which is an atmospheric or vacuum residue from a distillation of crude oil, to give a C4 fraction containing olefin and hydrocarbon, by alkylation to produce a C4_9 fraction, especially a C6_9 fraction that is distilled to give a fraction predominantly C8, which normally contains trimethylpentanes that include trimethylpentane 223 and / or trimethylpentane 233. To produce triptane, this fraction can be demethylated to give a pr crude oducts comprising at least 5% triptan, which can be distilled to increase the triptan content in the mixture, for example a distillate can comprise at least 10% or 20% of triptane and 2,2,3-trimethylpentane, but especially at least 50%, for example 50 to 90%, the rest being predominantly P1320 / 99 X other C7 and C8 aliphatic hydrocarbons, for example in an amount of 10 to 50% by volume. Alternatively, triptan and 2,2,3-trimethylpentane can be used in any commercially available form. The invention will now be described with the triptan exemplifying the compound of the formula I, but also or replacing the 2,2,3-trimethylpentane can be used. The amount of hydrocarbon of Formula I alone or with component II may be present in the composition in an amount effective to increase the Motor Octane to at least 98 and may be in a percentage of 35 to 92%, preferably at 60 to 90%, especially from 70 to 90% by volume, based on the total volume of the composition. In particular, the compound of the formula I is normally in the composition in a percentage of 5 to 90%, 10 to 80%, 20 to 60%, more especially 30 to 50% by volume, based on the total composition, although the amounts of the compounds of formula I from 10 to 45% are also valuable, 20 to 90% or 40 to 90% or 50 to 90% by volume are preferred. The composition also comprises a component (b). Component (b) is at least one liquid, aliphatic, saturated hydrocarbon having 4 to 10 carbon atoms, preferably 5 to 8 carbon atoms and P1320 / 99MX particular of 5 or 6 carbon atoms, alone or with at least one liquid, aliphatic, saturated hydrocarbon (different from component (a) having from 4 to 10 carbon atoms, in particular 5 to 10 carbon atoms , preferably of 5 to 8 carbon atoms, especially in combination with one of 4 carbon atoms Component (b) may comprise a component (III) which is more volatile and has a boiling point lower than the component (a) ), in particular a boiling point of at least 30 ° C, for example 30 to 60 ° C below the boiling point of the triptan at atmospheric pressure, and in particular has an Octane of Motor greater than 88, in particular of at least 90, for example between 88 and 93 or between 90 and 92. Examples of the component (III) include alkanes of 5 carbon atoms, in particular isopentane, which may be a substantially pure or crude hydrocarbon fraction, originating from alkylate or isomerate that contains by the men 30%, for example from 30 to 80%, that is from 50 to 70%, the main component being up to 40% of monomethylpentane of up to 50% of dimethylbutanes. The component (III) with a boiling point of 30-60 ° C less than the. boiling point of triptane can be used as a single component (III) but can be mixed with a boiling point alkane of 60 to 100 ° C less than that of triptan, for example n and / or isobutane in mixtures of 99.5: 0.5 to 70:30, for example P1320 / 99MX 88:12 to 75:25. Isopentane alone or mixed with n-butane is preferred, especially in the above proportions and, in particular, with a volumetric butane amount in the composition of up to 3.5%, for example 1 to 3.5% or 2 to 3.5 %. The component (b) can also comprise a component (IV) having a boiling point greater than the component (a), preferably the boiling point is at least 20 ° C higher than that of the compound of the formula I, example triptane, ie 20-60 ° C more than the triptan but less than 170 ° C and normally the Motor Octane is at least 92, for example from 92 to 100; these components (IV) are usually alkanes of 7 to 10 carbon atoms, especially 7 or 8 carbon atoms, and in particular have at least one branch in their alkyl chain, in particular 1 to 3 branches and, preferably, at an internal carbon atom and contain in particular at least one C (CH3) 2 group .. An example of component (IV) is iso-octane Component (b) can be a combination of at least one component (III) together with at least one component (IV) The combination may, for example, be butane or isopentane together with iso-octane, and the combination may be in a volumetric ratio of 10:90 to 90:10, preferably from 10:50 to 50:90, in P1320 / 99MX special from 15:85 to 35:65, in particular with butane or especially with isopentane together with iso-octane. Especially preferred is the combination of isopentane together with iso-octane, in particular, in the above proportions, and optionally butane. In another preferred embodiment, triptan and isopentane and, optionally, n-butane are present in the composition of the invention with 80-90% triptan and in particular in relative volume proportions of 80-90: 10-15: 0- 3.5. In a preferred embodiment of this invention, component (a) is 2,2,3-trimethylbutane and component (b) is isopentane in combination with iso-octane, preferably in relative volume proportions of 10-80: 5-25: 10. : 80, in particular 30-50: 5-25: 35-60 or 15-45: 10-18: 45-75 or 60-80: 10-18: 10-25. In particular the composition contains 30 to 80% of triptane and isopentane and iso-octane are in a volume ratio of 35-15: 65-85. In a further preferred embodiment of this invention, the composition comprises (a) as 2,2,3-trimethylbutane, tertiary methylbutyl ether and component (b) as isopentane in combination with n-butane, preferably in relative volumetric ratios of 50-90: 5-30: 10-15: 0.1-3.5 in particular 50-80: 10-25: 10-15: 0.1- 3.5. If desired, the composition may comprise P1320 / 99MX a liquid aromatic hydrocarbon of 6 to 9 carbon atoms, for example 6 to 8 or 7 to 9 carbon atoms, such as xylene or trimethylbenzene, and preferably toluene, in particular in amounts up to 30% in volume of the total composition, for example 1 to 30% or 5 to 15%. In this case, a preferred embodiment is a composition which can therefore contain 50 to 95%, for example 50 to 80% of triptan, 5 to 25%, for example 10 to 25% of component (b), for example isopentane and 5 to 30%, for example toluene. The benzene content of the composition is preferably less than 0.1% by volume. In another preferred embodiment, the composition may comprise both aromatic hydrocarbon and ether. In this case, a preferred composition may comprise 45 to 80% triptan, 5 to 30% ether (with a preferred total of both 70-85%), 10 to 25% of component (b) (III), isopentane example (optionally containing butane) and 5 to 20% toluene, all by volume. The compositions may also comprise 10 to 90%, for example 25 to 85%, 35 to 80% or 35 to 90% by volume of triptan, 5 to 75%, for example 8 to 55% by volume of a predominantly hydrocarbon mixture. iso C7 and iso C8, but usually with small amounts of iso C6 and iso C9 hydrocarbons, and 5-40%, for example 8-40% or 5-35% or 8-25% by volume of P1320 / 99MX isopentane. The triptan and the mixture can be obtained as a distillation fr ction obtained by the crude oil processing and the subsequent reactions described above. The unleaded gasoline composition for aviation of this invention typically has a calorific value (also called specific energy) of at least 42MJ / kg (18075 BTU / lb), for example of at least 43.5MJ / kg (18720 BTU / lb), such as 42-46 or 43.5-45MJ / kg. Gasoline normally has a boiling range (ASTM D86) of 25 to 170 ° C and normally "is such that 75 ° C 10 to 40% of the volume evaporates, at 105 ° C a minimum of 50% evaporates at 135 ° C a minimum of 90% evaporates, the final boiling point is usually no higher than 170 ° C, preferably 80 to 130 ° C. Gasoline normally has a maximum freezing point of -60 ° C , in particular of -40 ° C. The Reid Vapor Pressure of gasoline at 37.8 ° C measured according to the ASTM D323 method is normally 30-60kPa, preferably "of 38-60, for example 38-55 or especially 38-49 or 45-55kPa. The composition of the invention may contain at least one aviation gasoline additive, for example as those mentioned in ASTM D-910 or DEF-STAN 91-90; examples of the additives are antioxidants, corrosion inhibitors, antifreeze additives, for example glycol ethers or alcohols and P1320 / 99MX antistatic additives, especially antioxidants such as one or more hindered phenols; in particular the additives may be present in the composition in amounts of 0.1 to 100 ppm, for example 1-20 ppm, usually an antioxidant which especially consists of one or more hindered phenols. A coloring dye may also be present to differentiate aviation gasoline from the other grades of fuel. The compositions of the invention are lead free and have reduced toxicity and are suitable for use in gasoline for aviation, for aircraft with piston engines. Aromatic amines, for example m-toluidine are practically absent. The invention will be described by means of the following Examples.

Example 1 An unleaded aviation gasoline was made by mixing 2,2,3 trimethylbutane of 99% purity with isopentane and iso-octane to give a composition consisting of 2,2,3 trimethylbutane, 40%; isopentane 12%, and iso-octane 48%, expressed in percentages of volume of total gasoline. The octane number of the engine (MON-engine octane number) of gasoline was 99.9 according to the determined P1320 / 99MX by the method ASTM D2700-92 and the Steam Pressure Reid was 33kPa.

Example 2 An unleaded aviation gasoline containing the gasoline of Example 1 with 8 mg / 1 of a mixture of 75% butylphenol 2,6-diteriary and 25% tertiary and triteriary butylphenols as antioxidants.

Example 3 Unleaded aviation gasoline is made from a crude triptan fraction. A fractionated residue from the distillation of the crude oil was distilled to give a C4 fraction containing olefin and saturated. The fraction was alkylated (ie autoreacted) to form a crude C8 saturated which was distilled to give a boiling fraction of 95-120 ° C, which contained trimethylpentane 223 and 233. This fraction was demethylated by reduction to give a first fraction containing approximately 17% triptan and 83% iso C6-C9 with a majority of iso C7 and iso C8 hydrocarbons. This fraction was redistilled to produce a second fraction of 87% triptan and 13% iso C7 and C8. 90 parts by volume of this second fraction were mixed with 10 parts of isopentane to give a P1320 / 99MX unleaded aviation gasoline with a MON value of 99.1. The addition of 8 mg / 1 of the phenol mixture of Example 2 gave an unleaded aviation fuel gasoline, stabilized to oxidation.

Example 4 The process of Example 3 was repeated with the first fraction containing 17% of redistilled triptan to give a third fraction containing 37% triptan and 63% iso C7 and C8. 82 parts by volume of this third fraction were mixed with 18 parts of isopentane to give a lead-free aviation gasoline of MON value of 98.0. The addition of the phenol mixture as in Example 3 gave an aviation gasoline fuel stabilized in oxidation.

Examples 5-9 In these Examples, 2,2,3 trimethylbutane (triptan) of 99% purity was mixed with isopentane and butane and optionally toluene and / or tertiary methylbutyl ether, to produce a series of gasoline blends, for the preparation of unleaded aviation gasolines The formulated gasolines were made by mixing each of the mixtures with a phenolic antioxidant with a minimum of 55%, 2,4-dimethyl-6-butylphenol tertiary at a minimum of 15%, 4 methyl-2,6-butylphenol P1320 / 99MX diteriatrial, the rest being a mixture of monomethyl and tertiary dimethyl butylphenols (DEF STAN 91-90 RDE / A / 610). In each case the gasolines were tested in its Motor Octane and its Steam Pressure at 37.8 ° C and its calorific value, and its distillation and freezing point properties. In addition, for Example 10 an indicated mean effective pressure (IMEP) was determined (according to ASTM method D909) to give the Overload Performance Number. The results are shown in table 1.

TABLE 1 P1320 / 99MX T 10% refers to the temperature at which 10% by volume of the composition has been distilled.

P1320 / 99 X

Claims

NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following 'CLAIMS' is claimed as property: 1. A fuel composition for aviation without lead having an engine Octane of at least 98 and having a final boiling point of less than 170 ° C, comprising: component (a) comprising at least one hydrocarbon having the following formula I R-CH 2 -CH (CH 3) -C ( CH3) 2-CH3 I wherein R is hydrogen or methyl, and component (b) comprising at least one aliphatic, liquid, saturated hydrocarbon having 5 or 6 carbon atoms, wherein at least 30% by volume of the total composition is a hydrocarbon of the formula I.
2. A composition according to the claim 1, wherein the hydrocarbon of the formula I is triptan.
3. A composition according to claim 1 or 2 having a Reid Steam Pressure at 37.8 ° C of 38-60 kPascals.
4. A composition according to claim 3, with a Reid Steam Pressure of 38-49 kPascals. P1320 / 99MX
5. A composition according to any of the preceding claims, wherein the component (b) comprises a component (III) that is more volatile and has a boiling point lower than that of the triptan.
6. A composition according to the claim 5, wherein the component (III) has an Engine Octane higher than 88.
7. A composition according to any of claims 5 or 6, wherein the component (III) comprises isopentane.
8. A composition according to claim 7, wherein the fuel composition comprises from 5 to 40% by volume of isopentane.
9. A composition according to claim 8, comprising 5 to 25% by volume of isopentane.
10. A composition according to any of claims 7 to 9, wherein the component (III) comprises butane and isopentane.
11. A composition according to any of the preceding claims, wherein the fuel composition comprises 0.1 to 3.0% by volume of n-butane.
12. A composition according to any of claims 5 to 11, wherein the component (b) further comprises the component (III) a component (IV) having a boiling point higher than the triptan but lower than 170 ° C. P1320 / 99 X
13. A composition according to claim 12, wherein the component (IV) has an Engine Octane of at least 92.
14. A composition according to any of claims 12 or 13, wherein the component (IV ) is iso-octane.
15. A composition according to any of the preceding claims, wherein the composition comprises up to 30% by volume of a liquid aromatic hydrocarbon of 6 to 8 carbon atoms.
16. A composition according to claim 15, wherein the composition comprises 5 to 30% by volume of toluene.
A composition according to any of the preceding claims, comprising one comprising a component (I), the hydrocarbon having the formula I - and a component (II) which is an oxygenated agent for increasing the octane.
18. A composition according to claim 17, wherein the component (II) is an ether.
19. A composition according to claim 18, wherein the ether is tertiary methylbutyl ether.
20. A composition according to any one of the preceding claims, wherein 35 to 92% by volume of the total composition is the combined volume of hydrocarbon of the formula I and tertiary methylbutyl ether (if present). P1320 / 99MX
21. A composition according to any of claims 1 to 14, comprising 80 to 90% triptan, with isopentane 'and optionally butane.
22. A composition according to any of claims 1 to 14, comprising 30 to 80% of triptan, and also isopentane III and iso-octane IV, the volumetric ratio of III to IV is 35-15: 65-85.
23. A composition according to claim 16, comprising 50 to 90% triptan, 5 to 25% isopentane and 5 to 30% toluene.
24. A composition according to claim 23, which comprises 0 to 15% tertiary methylbutyl ether.
25. A composition according to any of the preceding claims, having a calorific value of at least 42MJ / kg.
26. A composition according to claim 25, having a calorific value of at least 43.5MJ / kg.
27. A composition according to any of the preceding claims, wherein the performance number for the overload is at least 130.
28. A lead-free aviation fuel having an Engine Octane of at least 98 and having a final boiling point of less than 170 ° C comprising ": component (a) comprising at least one hydrocarbon having the formula I P1320 / 99MX R-CH2-CH (CH3) -C (CH3) 2-CH3 I wherein R is hydrogen or methyl, and component (b) consisting of at least one aliphatic, liquid, saturated hydrocarbon having 5 or 6 carbon atoms, wherein at least 20% by volume of the total composition is a hydrocarbon of the formula I, together with at least one aviation gasoline additive selected from antioxidants, corrosion inhibitors, anti-icing additives and antistatic additives.
29. A fuel according to claim 28, wherein the antioxidant is one or more hindered phenols.
30. Use of the hydrocarbon of the formula I as an octane enhancer in an unleaded aviation gasoline, to provide a composition or fuel according to what is claimed in any of the preceding claims.
31. The use of a lead-free aviation fuel according to claims 28 or 29 in a piston-driven aircraft engine. P1320 / 99MX