Fuel composition

Abstract

The invention provides a fuel composition comprising: (a) a gasoline base fuel suitable for use in a spark-ignition internal combustion engine; and (b) a polybutylene polymer wherein the polybutylene polymer has a number average molecular weight in the range of 200 g / mol to 10,000 g / mol, and wherein greater than 30% of the polymer molecules in the polybutylene polymer have terminal vinylidene groups; and (c) a tetraalkylethane compound of formula (I): # imgabs0 # wherein Ar represents an aryl group and each X is independently selected from the group consisting of a hydrogen atom, a substituted or unsubstituted linear or branched C1-C12 alkyl group, (CH2) nOH or (CH2) nNH2 wherein n is in the range of 1 to 9, with the proviso that at least one of the X groups in each CX3 group is a hydrogen atom. The fuel composition of the present invention provides improved engine power and reduced combustion duration.

Description

TECHNICAL FIELD

[0001] The present invention relates to a liquid fuel composition, and more particularly to a liquid fuel composition that provides increased engine power and has a reduced combustion duration in an internal combustion engine. The present invention also relates to a method for increasing the power output, improving the efficiency and reducing the emissions of an internal combustion engine by fueling the internal combustion engine with the liquid fuel composition described hereinbelow. The present invention also relates to a method for reducing the combustion duration of a liquid fuel composition. BACKGROUND ART

[0002] In order to improve the engine efficiency, power and acceleration properties of modern spark-ignition internal combustion engines, these engines are increasingly being downsized and supercharged, and the compression ratio is increased.

[0003] In addition to upgrading the engine hardware, the fuel formulation used to fuel the engine can also be changed to improve engine efficiency, reduce emissions, and increase the power and acceleration of spark-ignition engines. For example, gasoline fuel compositions containing specially formulated refining components with high octane numbers and flame speed / combustion duration properties can improve power and / or acceleration as well as fuel economy. However, it is desirable to be able to use standard exchange gasoline fuels available on the market to enhance power, acceleration and fuel efficiency performance.

[0004] So-called highly reactive polybutene polymers have a relatively high proportion (i.e., > 30%) of polymer molecules having terminal vinylidene groups. US 6,048,373 discloses a fuel composition that includes a spark-ignition fuel, a Mannich detergent, and polybutene having a molecular weight distribution of less than 1.4 for controlling intake valve deposits in a spark-ignition internal combustion engine and minimizing valve sticking. The preferred polybutene disclosed therein has a number average molecular weight (Mn) of about 500 to about 2000, and highly reactive polyisobutene (PIB) is disclosed. It is stated that the preferred treatment rate of polybutene having a molecular weight distribution of 1.4 or less falls within the range of about 0.5 ptb to about 50 ptb, preferably within the range of about 1.5 ptb to about 40 ptb. The treatment rate of the highly reactive PIB used in Example 2 was 53.2 ptb, corresponding to about 151 ppm. However, there is no teaching in this document to use low molecular weight polybutene polymers at a selected treatment rate to provide increased engine power and reduced combustion duration.

[0005] Co-pending US patent application 63 / 390715 discloses a fuel composition for providing increased engine power that includes a gasoline base fuel and a highly reactive polybutene polymer.

[0006] Co-pending US Patent Application 63 / 179,767 discloses a fuel composition comprising a base fuel and a tetraalkylethane compound such as dicumene for providing increased engine power.

[0007] It has now been surprisingly found that the use of low molecular weight polybutenes, such as low molecular weight polyisobutylene (PIB), especially low molecular weight, highly reactive polyisobutylene (PIB), preferably in combination with selected tetraalkylethane compounds at selected additive treat rates in gasoline fuel compositions can provide improved power output (increased P max ) and reduced combustion duration, even when using standard exchange gasoline fuel. The reduction in combustion duration results in a more complete combustion per cycle, which improves engine efficiency and reduces harmful emissions including particulate matter (PM / PN). Summary of the invention

[0008] According to the present invention, there is provided a fuel composition, the fuel composition comprising:

[0009] (a) a gasoline base fuel suitable for use in spark-ignition internal combustion engines; and

[0010] (b) polybutene polymers;

[0011] wherein the polybutene polymer has a number average molecular weight in the range of 200 g / mol to 10,000 g / mol, wherein greater than 30% of the polymer molecules in the polybutene polymer have terminal ethylene

[0012] alkenyl groups; and

[0013] (c) a tetraalkylethane compound having the formula (I):

[0014]

[0015] wherein Ar represents an aryl group and each X is independently selected from a hydrogen atom, a substituted or unsubstituted straight or branched C 1 -C 12 Alkyl groups, (CH 2 ) n OH or (CH 2 ) n NH 2 , where n is in the range of 1 to 9, provided that each CX 3 At least one of the X groups in the group is a hydrogen atom.

[0016] Surprisingly, it has been found that the fuel compositions of the present invention provide a maxImproved power output and reduced fuel combustion duration. In addition, the fuel compositions of the present invention exhibit excellent acceleration, energy efficiency, and fuel economy.

[0017] According to another aspect of the present invention, there is provided the use of a liquid fuel composition for improving the power output of an internal combustion engine, wherein the liquid fuel composition comprises:

[0018] (a) a gasoline base fuel suitable for a spark-ignition internal combustion engine; and

[0019] (b) a polybutene polymer;

[0020] wherein the polybutene polymer has a number average molecular weight in the range of 200 g / mol to 10,000 g / mol, preferably wherein the polybutene is a highly reactive polybutene, wherein more than 30% of the polymer molecules in the polyisobutene polymer

[0021] have terminal vinylidene groups; and

[0022] (c) a tetraalkyl ethane compound having the formula (I):

[0023]

[0024] wherein Ar represents an aryl group and each X is independently selected from a hydrogen atom, a substituted or unsubstituted straight-chain or branched-chain C 1 -C 12 alkyl group, (CH 2 ) n OH or (CH 2 ) n NH 2 , where n is in the range of 1 to 9, provided that at least one of the X groups in each CX 3 group is a hydrogen atom.

[0025] According to another aspect of the present invention, there is provided a method for improving the power output of a spark-ignition internal combustion engine, wherein the method comprises adding a polybutene and a tetraalkyl ethane compound to a gasoline base fuel to produce a gasoline fuel composition, wherein the polybutene has a number average molecular weight in the range of 200 g / mol to 10,000 g / mol, preferably wherein more than 30% of the polymer molecules in the polybutene polymer have terminal vinylidene groups; and wherein the tetraalkyl ethane compound has the formula (I):

[0026]

[0027] wherein Ar represents an aryl group and each X is independently selected from a hydrogen atom, a substituted or unsubstituted straight-chain or branched-chain C 1-C 12 alkyl group, (CH 2 ) n OH or (CH 2 ) n NH 2 , where n ranges from 1 to 9, provided that at least one of the X groups in each CX 3 group is a hydrogen atom, and burning this fuel composition in a spark-ignition internal combustion engine.

[0028] According to another aspect of the present invention, there is provided a method for reducing the combustion duration of a liquid fuel composition in an internal combustion engine, wherein the method comprises adding polybutene and a tetraalkyl ethane compound to a gasoline base fuel to produce a gasoline fuel composition, wherein the polybutene has a number average molecular weight in the range of 200 g / mol to 10,000 g / mol, preferably wherein more than 30% of the polymer molecules in the polybutene polymer have terminal vinylidene groups; and wherein the tetraalkyl ethane compound has the formula (I):

[0029]

[0030] where Ar represents an aryl group and each X is independently selected from a hydrogen atom, a substituted or unsubstituted straight-chain or branched C 1 -C 12 alkyl group, (CH 2 ) n OH or (CH 2 ) n NH 2 , where n ranges from 1 to 9, provided that at least one of the X groups in each CX 3 group is a hydrogen atom, and burning this fuel composition in a spark-ignition internal combustion engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a graph showing the P max measurement results of Example 1 and its reference base fuel.

[0032] Figure 2 is a graph showing the Pmax measurement results of Examples 2 to 4 and their reference base fuel.

[0033] Figure 3 is a graph showing the Pmax measurement results of Examples 5 to 13 and their reference base fuel.

[0034] Figure 4 Shows P between the blends (Examples 5 to 13) and their base fuel control tested at 1300 HL, IGN = 1 (IGN = ignition time)max The average % difference and the average % difference in combustion duration (AI 10 - 90).

[0035] Figure 5 It is a diagram of the Pmax measurement results of Examples 14 to 27 and their reference base fuels.

[0036] Figure 6 Shows the average % difference in Pmax and the average % difference in combustion duration (AI 10 - 90) between the blends (Examples 14 to 27) and the base fuel control tested at 1300 rpm, 15 IMEP, IGN at TDC. Detailed Description

[0037] As used herein, the term "power output" refers to the amount of drag power required to maintain a fixed speed under wide - open throttle conditions in a chassis dynamometer test.

[0038] As used herein, the term "P max " refers to a direct measurement of the force generated by fuel decomposition.

[0039] According to the present invention, a method for increasing the power output of an internal combustion engine is provided. Moreover, according to the present invention, there is a method for increasing the P max of an internal combustion engine. In the context of these aspects of the present invention, the term "increase" encompasses any degree of increase. According to the present invention, the increase can be, for example, 0.05% or more, preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.5% or more, especially 1% or more, more especially 2% or more, even more especially 5% or more of the power output or P max provided by the fuel formulation before adding low - molecular - weight, preferably highly reactive polybutene and tetraalkyl ethane compounds. According to the present invention, the increase in power output or P max can even be as high as 10% of the power output or P max provided by the fuel formulation before adding low - molecular - weight, preferably highly reactive polybutene and tetraalkyl ethane compounds.

[0040] The combination of low - molecular - weight, preferably highly reactive polybutene and tetraalkyl ethane compounds can also be used to increase the acceleration of an internal combustion engine. As used herein, the term "acceleration" refers to the amount of time required for the engine to increase speed between two fixed speed conditions in a given gear. In the context of this aspect of the present invention, the term "increase" encompasses any degree of increase, and the same percentage increase can occur when the power and / or P max is increased to the above - mentioned degree.

[0041] According to the present invention, the power output and acceleration provided by the fuel composition can be determined in any known manner, for example, using standard test methods as described in SAE paper 2005-01-0239 and SAE paper 2005-01-0244.

[0042] As used herein, the term "combustion duration" means the time (in engine crank angles) required for combustion to proceed from 10% to 90% (referred to as AI 10-90 in the examples below). The term AI 50-90 is also used in relation to the combustion duration and means the time (in engine crank angles) required for combustion to proceed from 50% to 90%.

[0043] According to the present invention, there is provided a method for reducing the combustion duration of a gasoline fuel composition, the method comprising adding a polybutene polymer and a tetraalkyl ethane compound to the gasoline fuel composition, wherein the polybutene polymer has a number average molecular weight in the range of 200 g / mol to 10,000 g / mol and wherein the tetraalkyl ethane compound has the formula (I):

[0044]

[0045] wherein Ar represents an aryl group and each X is independently selected from a hydrogen atom, a substituted or unsubstituted straight or branched chain C 1 -C 12 alkyl group, (CH 2 ) n OH or (CH 2 ) n NH 2 , where n is in the range of 1 to 9, provided that at least one of the X groups in each CX 3 group is a hydrogen atom, and combusting the fuel composition in a spark-ignition internal combustion engine

[0046] According to the present invention, the combustion duration of the fuel composition can be determined in any known manner, for example, using the test methods disclosed in the Examples section below.

[0047] In the context of this aspect of the present invention, the term "reduced combustion duration" encompasses any degree of reduction. According to the present invention, the reduction can be, for example, 0.05% or more, preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.5% or more, especially 1% or more, more especially 2% or more, and even more especially 4% or more, or 5% or more of the combustion duration provided by the fuel formulation before adding a low molecular weight, preferably highly reactive polybutene and a tetraalkyl ethane compound to a similar fuel formulation. According to the present invention, the reduction in combustion duration can even be as high as a 10% reduction of the combustion duration provided by the fuel formulation before adding a low molecular weight, preferably highly reactive polybutene and a tetraalkyl ethane compound to a similar fuel formulation.

[0048] The term "flame speed" or "laminar flame speed" (LFS) refers to the laminar burning velocity. LFS is a fundamental measure of the flame propagation rate without the complexities of mixing kinetics. However, in an engine, mixing kinetics come into play, and thus the measured flame speed is referred to as the "burning rate" and "combustion duration". The terms "burning rate" and "combustion duration" may also be used interchangeably with "flame speed" herein. The laminar burning velocity (LBV) is a fundamental property of the chemical components. It is defined as the rate at which the unburned gas propagates to the flame front and reacts to form products (perpendicular to the flame front under laminar conditions).

[0049] The flame speed of a fuel composition can be determined in any known manner. For example, the measurement of LFS can be carried out using any one of the following three methods:

[0050] 1. The stagnation flame method (up to 5 atm - 7 atm)

[0051] 2. The spherical expansion method, at constant pressure or constant volume (up to 60 atm - 80 atm)

[0052] 3. The heat flux method (up to about 5 atm).

[0053] All three of these methods are described in the review publication: Egolfopoulos, F.N., Hansen, N., Ju, Y., K., Law, C.K., and Qi, F. "Advances and challenges in laminar flame experiments and implications for combustion chemistry", Progress in Energy and Combustion Science 43(2014)36 - 67, https: / / doi.org / 10.1016 / j.pecs.2014.04.004.

[0054] The following method for measuring the flame speed in a constant volume combustion chamber (spherical bomb) is referenced from Gillespie, L.L., M., Sheppard, C.G., Wooley, R, Aspects of laminar and turbulent burning velocity relevant to spark ignition engines, Journal of the Society of Automotive Engineers, 2000(2000 - 01 - 0192).

[0055] The following method for measuring the flame speed uses the net pressure method: Mittal, M., Zhu, G., and Schock H., 'Fast mass - fraction - burned calculation using the net pressure method for real - time applications', Proc. Instn Mech Engrs, D Part: J. Automobile Engineering 223(3)(2009):389 - 394.

[0056] The liquid fuel composition of the present invention comprises a base fuel suitable for an internal combustion engine, a low molecular weight, preferably highly reactive polybutene, and a tetraalkyl ethane compound. Generally, the base fuel suitable for an internal combustion engine is gasoline or diesel fuel, and thus the liquid fuel composition of the present invention is generally a gasoline composition or a diesel fuel composition. Preferably, the base fuel is a gasoline base fuel.

[0057] The polybutene used herein is preferably highly reactive polybutene. Highly reactive polybutene is a polybutene having a relatively high proportion (i.e., greater than 30%) of polymer molecules having terminal vinylidene groups. As used herein, the term "polybutene" includes polymers made from pure or substantially pure 1-butene or isobutene and polymers made from a mixture of two or all three of 1-butene, 2-butene, and isobutene, and includes polymers containing small amounts, preferably less than 10% by weight, more preferably less than 5% by weight, of C2, C3, and C5 and higher olefins and diolefins. In a preferred embodiment, the polybutene is polyisobutene (also referred to as "polyisobutylene"), preferably wherein at least 90% by weight, more preferably at least 95% by weight, of the polymer is derived from isobutene.

[0058] In a particularly preferred embodiment, the polybutene is highly reactive polyisobutene.

[0059] In one embodiment, the highly reactive polybutene has greater than 40% of polymer molecules having terminal vinylidene groups.

[0060] In another embodiment, the highly reactive polybutene polymer has greater than 50% of polymer molecules having terminal vinylidene groups.

[0061] In a preferred embodiment, the highly reactive polybutene has greater than 85% of double bonds located at the terminal positions of the molecules.

[0062] The highly reactive polybutene polymer used herein preferably has a molecular weight distribution of 1.5 or greater, preferably 1.6 or greater, more preferably 1.7 or greater, and even more preferably 1.8 or greater.

[0063] The polybutene polymer is present in an amount of 500 ppm to 5000 ppm. In one embodiment, the polybutene polymer is present in an amount of 1000 ppm to 5000 ppm. In another embodiment, based on the weight of the fuel composition, the polybutene polymer is present in an amount of 2500 ppm to 5000 ppm. Examples of preferred contents of polybutene based on the weight of the fuel composition include 1000 ppm, 2500 ppm, and 5000 ppm.

[0064] One or more polybutene polymers can be used in the fuel compositions herein. When more than one polybutene polymer is used herein, the total content of the polybutene polymers is the same as the range given in the previous paragraph.

[0065] The polybutene polymer used herein is a low molecular weight polybutene polymer. As used herein, the term "low molecular weight polybutene" means a polybutene polymer having a number average molecular weight (M n ) in the range of 200 g / mol to 10,000 g / mol, preferably 500 g / mol to 5000 g / mol, more preferably 1000 g / mol to 5000 g / mol. In one embodiment of the present invention, the polybutene, preferably the highly reactive polybutene, used herein has a number average molecular weight (M n ) of 1000 g·mol to 2300 g·mol. In another embodiment of the present invention, the polybutene used herein has a number average molecular weight (M n ) of 2300 g / mol to 5000 g / mol. The number average molecular weight of the polybutene polymer can be determined using gel permeation chromatography.

[0066] The highly reactive polybutene used herein can be bio-derived or non-bio-derived. In one embodiment of the present invention, the polybutene is a low molecular weight, highly reactive polyisobutene derived from 100% renewable raw materials.

[0067] The highly reactive polybutene used herein preferably contains less than 1 mg / kg of chlorine.

[0068] In one embodiment, the highly reactive polybutene polymer used herein has a kinematic viscosity of 190 mm 2 / s or greater at 100 °C, preferably in the range of 190 mm 2 / s to 1500 mm 2 / s, more preferably in the range of 430 mm 2 / s to 1500 mm 2 / s.

[0069] The preferred highly reactive polybutene used herein has an alpha olefin content of greater than 85%.

[0070] Highly reactive polybutenes suitable for use herein include those polybutenes commercially available from BASF under the trade name Glissopal(RTM), such as Glissopal(RTM)1000, Glissopal(RTM)1300, and Glissopal(RTM)2300.

[0071] Glissopal(RTM)1000 has a number average molecular weight (M n ) of 1000 g / mol, a molecular mass distribution (M w / M n)、an α-olefin content greater than 85%, a kinematic viscosity of 190 mm 2 / s at 100 °C and a chlorine content of less than 1 mg / kg.

[0072] Glissopal(RTM) 1300 has a number-average molecular weight (M n ) of 1300 g / mol, a molecular mass distribution (M w / M n ) of 1.7, an α-olefin content greater than 85%, a kinematic viscosity of 190 mm 2 / s at 100 °C and a chlorine content of less than 1 mg / kg.

[0073] Glissopal(RTM) 2300 has a number-average molecular weight (M n ) of 2300, a molecular mass distribution (M w / M n ) of 1.6, an α-olefin content greater than 85%, a kinematic viscosity of 190 mm 2 / s at 100 °C and a chlorine content of less than 1 mg / kg.

[0074] Also applicable herein are Glissopal(RTM) 1000BMBcert, 1300BMBcert and 2300BMBcert(TM), which are low molecular weight, highly reactive polyisobutenes derived from 100% renewable raw materials commercially available from BASF.

[0075] The polybutene polymer can be blended with any other additives (e.g., an additive performance package) other than the tetraalkyl ethane compound to produce an additive blend. The additive blend is then added to a base fuel to produce a liquid fuel composition.

[0076] The tetraalkyl ethane compound used herein is a compound having the formula (I):

[0077]

[0078] wherein Ar represents an aryl group and each X is independently selected from a hydrogen atom, a substituted or unsubstituted straight-chain or branched C 1 -C 12 saturated or unsaturated alkyl group, (CH 2 ) n OH, (CH 2 ) n NH 2 wherein n ranges from 1 to 9, preferably from 1 to 6, more preferably from 1 to 4, and even more preferably from 1 to 3, provided that each CX 3At least one of the X groups in the group is a hydrogen atom.

[0079] Preferably, each CX 3 At least two of the X groups in the group are hydrogen atoms.

[0080] In a particularly preferred embodiment, at least three of the X groups in each CX 3 group are hydrogen atoms.

[0081] Preferably, Ar of the tetraalkyl ethane compound is a substituted or unsubstituted aromatic group such as phenyl, biphenyl, naphthyl, thienyl or anthracenyl. More preferably, Ar is an unsubstituted phenyl group. This means that for the preparation of the preferred compounds of formula (I), commercially available cumene can be used as a starting material. Starting from cumene, dicumene can be prepared by several known methods as described in US4,072,811.

[0082] Preferably, each X group is independently selected from a hydrogen atom and an unsubstituted, straight-chain or branched-chain, saturated or unsaturated C 1 -C 6 and, more preferably, C 1 -C 3 alkyl group, provided that at least one of the X groups in each CX 3 group is a hydrogen atom.

[0083] More preferably, each X group is independently selected from a hydrogen atom and an unsubstituted, straight-chain or branched-chain, saturated C 1 -C 6 and, preferably, C 1 -C 3 alkyl group, provided that at least one of the X groups in each CX 3 group is a hydrogen atom.

[0084] In one embodiment, each X group is independently selected from a hydrogen atom and an unsubstituted straight-chain saturated C 1 -C 6 and, preferably, C 1 -C 3 alkyl groups, especially methyl, ethyl and propyl.

[0085] Examples of suitable tetraalkyl ethane compounds of formula (I) include:

[0086]

[0087]

[0088]

[0089] In one embodiment of the present disclosure, the tetraalkyl ethane compound is 1,1’(1,1,2,2 - tetramethyl - 1,1 - ethanediyl) bis - benzene (di - cumene). Di - cumene is commercially available from Aldrich and various other chemical suppliers.

[0090] The tetraalkyl ethane compound is preferably present in the fuel composition in an amount of from 30 ppm to 10 wt%, preferably from 100 ppm to 5 wt%, more preferably from 100 ppm to 1 wt%, and even more preferably from 100 ppm to 5000 ppm.

[0091] In one embodiment, the tetraalkyl ethane is present in an amount of from 313 ppm to 5000 ppm by weight of the fuel composition.

[0092] The tetraalkyl ethane compound can be blended with any other additives (e.g., additive performance packages) other than polybutene polymers to produce an additive blend. The additive blend is then added to the base fuel to produce a liquid fuel composition.

[0093] The amount of the performance package in the additive blend is preferably in the range of from 0.1 wt% to 99.8 wt%, more preferably in the range of from 5 wt% to 50 wt%, based on the weight of the additive blend.

[0094] Preferably, the amount of the performance package present in the liquid fuel composition of the present disclosure is in the range of from 15 ppmw (parts per million by weight) to 10 wt%, based on the total weight of the liquid fuel composition. More preferably, the amount of the performance package present in the liquid fuel composition of the present disclosure further meets one or more of the parameters (i) to (xv) listed below:

[0095] (i) At least 100 ppmw

[0096] (ii) At least 200 ppmw

[0097] (iii) At least 300 ppmw

[0098] (iv) At least 400 ppmw

[0099] (v) At least 500 ppmw

[0100] (vi) At least 600 ppmw

[0101] (vii) At least 700 ppmw

[0102] (viii) At least 800 ppmw

[0103] (ix) At least 900 ppmw

[0104] (x) At least 1000 ppmw

[0105] (xi) At least 2500 ppmw

[0106] (xii) At most 5000 ppmw

[0107] (xiii) At most 10000 ppmw

[0108] (xiv) At most 2 wt%.

[0109] (xv) At most 5 wt%.

[0110] A further preferred additive for use in the fuel compositions herein in combination with the tetraalkyl ethane compound and the polybutene polymer is an alkylbenzene compound having the formula (II)

[0111]

[0112] wherein each of the R1-R6 groups is independently selected from hydrogen and C 1 -C 6 alkyl groups, wherein at least one of the R1-R6 groups is a C 1 -C 6 alkyl group.

[0113] In a preferred embodiment herein, three of the R1-R6 groups in the alkylbenzene compound are independently selected from C 1 -C 6 alkyl groups.

[0114] In one embodiment herein, the alkylbenzene compound is a trimethylbenzene compound. In another embodiment, the alkylbenzene compound is 1,3,5-trimethylbenzene. 1,3,5-trimethylbenzene is commercially available from Aldrich and other chemical suppliers. In another embodiment, the alkylbenzene compound is a mixture of trimethylbenzene isomers (referred to as mesitylene).

[0115] The alkylbenzene compound is preferably present in the fuel composition in an amount of 30 ppm to 2 wt%, preferably 100 ppm to 1 wt%, more preferably 100 ppm to 5000 ppm, and even more preferably 500 ppm to 2000 ppm, based on the weight of the fuel composition.

[0116] In one embodiment, the alkylbenzene compound, the tetraalkyl ethane compound, and the polybutene polymer can be blended together with any other additives (e.g., an additive performance package) to produce an additive blend. The additive blend is then added to the base fuel to produce a liquid fuel composition.

[0117] In the liquid fuel composition of the present invention, if the base fuel used is gasoline, the gasoline can be any gasoline suitable for spark-ignition (petroleum) type internal combustion engines known in the art, including automotive engines and other types of engines, such as off-road and aviation engines. The gasoline used as the base fuel in the liquid fuel composition of the present invention can also be conveniently referred to as 'base gasoline'. The gasoline can also include various contents of bio-components and bio-streams in any content while maintaining appropriate analytical specifications. The bio-components can be from any biomass conversion process, including various uncatalyzed and catalyzed biomass pyrolysis, hydrothermal liquefaction, non-thermal biomass conversion, such as microbiologically catalyzed biochemical processes, etc. Any biomass suitable as a raw material for these processes is desirable.

[0118] Gasoline generally contains a mixture of hydrocarbons having boiling points in the range of 25°C to 230°C (EN-ISO 3405), and the optimum range and distillation curve usually vary according to the climate and the season of the year. The hydrocarbons in gasoline can be obtained by any means known in the art. Conveniently, the hydrocarbons can be obtained from straight-run gasoline, synthetically produced aromatic hydrocarbon mixtures, thermally or catalytically cracked hydrocarbons, hydrocracked petroleum fractions, catalytically reformed hydrocarbons, or mixtures thereof in any known manner.

[0119] The specific distillation curve, hydrocarbon composition, Research Octane Number (RON) and Motor Octane Number (MON) of the gasoline are not critical.

[0120] Conveniently, the Research Octane Number (RON) of the gasoline can be at least 80, for example in the range of 80 to 110. Preferably, the RON of the gasoline will be at least 90, for example in the range of 90 to 110. More preferably, the RON of the gasoline will be at least 91, for example in the range of 91 to 105. Even more preferably, the RON of the gasoline will be at least 92, for example in the range of 92 to 103. Even more preferably, the RON of the gasoline will be at least 93, for example in the range of 93 to 102. And most preferably, the RON of the gasoline will be at least 94, for example in the range of 94 to 100 (EN 25164); the Motor Octane Number (MON) of the gasoline can be conveniently at least 70, for example in the range of 70 to 110. Preferably, the MON of the gasoline will be at least 75, for example in the range of 75 to 105. More preferably, the MON of the gasoline will be at least 80, for example in the range of 80 to 100. Most preferably, the MON of the gasoline will be at least 82, for example in the range of 82 to 95 (EN 25163).

[0121] Generally, gasoline contains one or more components selected from the following groups: saturated hydrocarbons, olefins, aromatic hydrocarbons, and oxygenated hydrocarbons. Conveniently, gasoline can contain a mixture of saturated hydrocarbons, olefins, aromatic hydrocarbons, and optionally oxygenated hydrocarbons.

[0122] Typically, the olefin content of gasoline ranges from 0 vol% to 40 vol% based on gasoline (ASTM D1319); preferably, the olefin content of gasoline ranges from 0 vol% to 30 vol% based on gasoline, and more preferably, the olefin content of gasoline ranges from 0 vol% to 20 vol% based on gasoline.

[0123] Typically, the aromatic content of gasoline ranges from 0 vol% to 70 vol% based on gasoline (ASTM D1319), for example, the aromatic content of gasoline ranges from 10 vol% to 60 vol% based on gasoline; preferably, the aromatic content of gasoline ranges from 0 vol% to 50 vol% based on gasoline, for example, the aromatic content of gasoline ranges from 10 vol% to 50 vol% based on gasoline.

[0124] In one embodiment herein, based on the total base fuel, the gasoline base fuel contains less than 10 vol% of aromatic compounds. In another embodiment herein, based on the total base fuel, the gasoline base fuel contains less than 2 vol% of aromatic compounds having 9 or more carbon atoms.

[0125] Based on gasoline, the benzene content of gasoline is at most 10 vol%, more preferably at most 5 vol%, and especially at most 1 vol%.

[0126] Gasoline preferably has a low or ultra-low sulfur content, such as at most 1000 ppmw (parts per million by weight), preferably not exceeding 500 ppmw, more preferably not exceeding 100 ppmw, even more preferably not exceeding 50 ppmw and most preferably not exceeding even 10 ppmw.

[0127] Gasoline also preferably has a low total lead content, such as at most 0.005 g / l, and most preferably is lead-free, without adding lead compounds thereto (i.e., unleaded).

[0128] When gasoline contains oxygenated hydrocarbons, at least a portion of the non-oxygenated hydrocarbons will replace the oxygenated hydrocarbons (matched blending) or simply be added to the fully formulated gasoline (splash blending). Based on gasoline, the oxygenate content of gasoline can be up to 85 wt% (EN 1601) (e.g., ethanol itself). For example, the oxygenate content of gasoline can be up to 35 wt%, preferably up to 25 wt%, and more preferably up to 10 wt%. Conveniently, the oxygenate concentration will have a minimum concentration selected from any one of 0 wt%, 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, 1.0 wt% and 1.2 wt%, and a maximum concentration selected from any one of 12 wt%, 8 wt%, 7.2 wt%, 5 wt%, 4.5 wt%, 4.0 wt%, 3.5 wt%, 3.0 wt% and 2.7 wt%.

[0129] Examples of oxygenated hydrocarbons that can be incorporated into gasoline include alcohols, ethers, esters, ketones, aldehydes, carboxylic acids and their derivatives, and oxygen-containing heterocyclic compounds. Preferably, the oxygenated hydrocarbons that can be incorporated into gasoline are selected from alcohols (such as methanol, ethanol, propanol, 2-propanol, butanol, tert-butanol, isobutanol and 2-butanol), ethers (preferably ethers containing 5 or more carbon atoms per molecule, such as methyl tert-butyl ether and ethyl tert-butyl ether) and esters (preferably esters containing 5 or more carbon atoms per molecule); a particularly preferred oxygenated hydrocarbon is ethanol.

[0130] When oxygenated hydrocarbons are present in gasoline, the amount of oxygenated hydrocarbons in the gasoline can vary over a wide range. For example, gasoline containing a relatively large proportion of oxygenated hydrocarbons is currently commercially available in countries such as Brazil and the United States, such as ethanol itself and E85, as well as gasoline containing a relatively small proportion of oxygenated hydrocarbons, such as E10 and E5. Thus, gasoline can contain up to 100% by volume of oxygenated hydrocarbons. Also included herein is E100 fuel as used in Brazil. Preferably, the amount of oxygenated hydrocarbons present in gasoline is selected from one of the following amounts: up to 85% by volume; up to 70% by volume; up to 65% by volume; up to 30% by volume; up to 20% by volume; up to 15% by volume; and up to 10% by volume, depending on the desired final formulation of the gasoline. Conveniently, gasoline can contain at least 0.5% by volume, 1.0% by volume or 2.0% by volume of oxygenated hydrocarbons.

[0131] Examples of suitable gasoline include gasoline having an olefin content of 0% to 20% by volume (ASTM D1319), an oxygen content of 0% to 5% by weight (EN 1601), an aromatic content of 0% to 50% by volume (ASTM D1319) and a benzene content of at most 1% by volume.

[0132] Also applicable herein are gasoline blending components, which can be derived from sources other than crude oil, such as low-carbon gasoline fuels from biomass or CO 2 and their blends with each other or with gasoline streams and components from fossil sources. Suitable examples of such fuels include:

[0133] 1) From biomass sources:

[0134] a. Hydrodeoxygenated straight-run bio-naphtha from biomass, and

[0135] b. Cracking and / or isomerization products of synthetic wax (biomass gasified to syngas

[0136] (CO / H 2 ) to obtain synthetic wax by the Fischer-Tropsch (FT) process), and then hydrocracking / hydroisomerizing it to produce a series of products including fractions within the gasoline boiling range.

[0137] 2) CO 2 Source:

[0138] a. CO 2 + H 2 Synthesis gas (CO / H 2 )(by an improved water / gas shift reaction, and then by FT process to obtain synthetic wax), and then hydrocracked / hydroisomerized to produce a series of products including fractions within the gasoline boiling range.

[0139] 3) Source from methanol:

[0140] a. Biomass gasified to synthesis gas (CO / H 2 ), then to methanol, and then to gasoline by MTG process (MTG is the'methanol - to - gasoline' process). To further reduce the carbon intensity of the fuel, the H 2 used in all processes will be renewable (green) H from water electrolysis using renewable electricity (such as from wind and solar). 2 .

[0141] Particularly suitable for use herein are gasoline blend components that can be derived from biological sources. Examples of such gasoline blend components can be found in WO2009 / 077606, WO2010 / 028206, WO2010 / 000761, European Patent Application Nos. 09160983.4, 09176879.6, 09180904.6 and US Patent Application Serial No. 61 / 312307.

[0142] Although not critical to the present invention, in addition to low molecular weight, preferably highly reactive polybutene and tetraalkyl ethane compounds, the base gasoline or gasoline composition of the present invention may conveniently contain one or more optional fuel additives. The concentration and nature of the optional fuel additives that can be included in the base gasoline or gasoline composition of the present invention are not critical. Non - limiting examples of suitable types of fuel additives that can be included in the base gasoline or gasoline composition of the present invention include antioxidants, corrosion inhibitors, detergents, demisters, anti - knock additives, metal deactivators, valve seat recession protection compounds, dyes, solvents, carrier fluids, diluents and markers. Examples of suitable such additives are generally described in US Patent No. 5,855,629.

[0143] Conveniently, the fuel additive can be blended with one or more solvents to form an additive concentrate, and then the additive concentrate can be mixed with the base gasoline or gasoline composition of the present invention.

[0144] The concentration of any optional additive (active substance) present in the base gasoline or gasoline composition of the present invention is preferably up to 1% by weight, more preferably in the range of 5 ppmw to 2000 ppmw, advantageously in the range of 300 ppmw to 1500 ppmw, such as 300 ppmw to 1000 ppmw.

[0145] Other conventional additives for gasoline are corrosion inhibitors, such as ammonium salts based on organic carboxylic acids, which tend to form films, or ammonium salts based on heterocyclic aromatic hydrocarbons for the corrosion protection of non-ferrous metals; defogging agents; anti-knock additives; metal deactivators; solvents; carrier fluids; diluents; antioxidants or stabilizers, such as those based on amines like phenylenediamines, such as p-phenylenediamine, N,N'-di-sec-butyl-p-phenylenediamine, dicyclohexylamine or their derivatives, or those based on phenols like 2,4-di-tert-butylphenol or 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid; antistatic agents; metallocenes such as ferrocene; methyl-cyclopentadienyl tricarbonyl manganese; lubricating additives, such as certain fatty acids, alkenyl succinic esters, bis(hydroxyalkyl) fatty amines, hydroxyacetamides or castor oil; and dyes (markers). Suitable such additives are disclosed in U.S. Patent No. 5,855,629. If appropriate, amines can also be added, such as those described in WO 03 / 076554. Optionally, anti-valve seat recession additives, such as sodium or potassium salts of polymeric organic acids, can be used.

[0146] The gasoline compositions herein may also contain detergent additives. Suitable detergent additives include those disclosed in WO2009 / 50287, which is incorporated herein by reference.

[0147] Preferred detergent additives for use in the gasoline compositions herein generally have at least one hydrophobic hydrocarbon group with a number average molecular weight (Mn) of 85 to 20,000 and at least one polar moiety selected from:

[0148] (A1) Monoamino or polyamino groups having up to 6 nitrogen atoms, wherein at least one nitrogen atom is basic;

[0149] (A6) Polyoxy-C 2 - to -C 4 -alkylene groups capped by a hydroxyl group, monoamino or polyamino group, wherein at least one nitrogen atom is basic, or capped by a carbamate group;

[0150] (A8) Moieties derived from succinic anhydride and having hydroxyl and / or amino and / or amide and / or imide groups; and / or

[0151] (A9) Moieties obtained by the Mannich reaction of a substituted phenol with an aldehyde and a monoamine or polyamine.

[0152] The hydrophobic hydrocarbon groups in the above detergency additives that ensure sufficient solubility in the base fluid have a number average molecular weight (Mn) of from 85 to 20,000, in particular from 113 to 10,000, especially from 300 to 5,000. Typical hydrophobic hydrocarbon groups, especially those combined with the polar moieties (A1), (A8) and (A9), include polyalkenes / polyolefins such as polypropylene-based, polybutene-based and polyisobutene-based groups, each having an Mn of from 300 to 5,000, preferably from 500 to 2,500, more preferably from 700 to 2,300, and especially from 700 to 1,000.

[0153] Non-limiting examples of the above detergency additive packages include the following:

[0154] Additives containing a monoamino or polyamino group (A1) are preferably polyolefin monoamines or polyolefin polyamines based on polypropylene or conventional (i.e., mainly having internal double bonds) polybutene or polyisobutene having an Mn of from 300 to 5,000. When polybutene or polyisobutene mainly having internal double bonds (usually in the β and γ positions) is used as a raw material for preparing the additive, possible preparation routes are by chlorination and subsequent amination, or by oxidizing the double bonds with air or ozone to obtain carbonyl or carboxyl compounds and subsequent amination under reducing (hydrogenating) conditions. The amine used for amination here can be, for example, ammonia, a monoamine or a polyamine such as dimethylaminopropylamine, ethylenediamine, diethylenetriamine, triethylenetetramine or tetraethylenepentamine. The corresponding additives based on polypropylene are described in particular in WO-A-94 / 24231.

[0155] Other preferred additives containing a monoamino group (A1) are hydrogenation products of reaction products of polyisobutene having an average degree of polymerization of from 5 to 100 with nitrogen oxides or mixtures of nitrogen oxides and oxygen, as described in particular in WO-A-97 / 03946.

[0156] Other preferred additives containing a monoamino group (A1) are compounds obtainable by reacting polyisobutene epoxide with an amine and subsequent dehydration and reduction of the amino alcohol, as described in particular in DE-A-19620 262.

[0157] Additives containing a polyoxy-C 2 -C 4 -alkylene moiety (A6) are preferably polyethers or polyetheramines, which can be obtained from C 2 - to C 60 -alkanols, C 6 - to C 30 -alkanediols, mono- or di-C 2 -C 30 -alkylamines, C 1 -C 30 -alkylcyclohexanols or C1 -C 30 - obtained by reacting an alkylphenol with 1 to 30 moles of ethylene oxide and / or propylene oxide and / or butylene oxide per hydroxyl or amino group, and in the case of polyetheramines, obtained by subsequent reductive amination with ammonia, a monoamine or a polyamine. Such products are described in particular in EP-A-310875, EP-A-356 725, EP-A-700 985 and US-A-4 877 416. In the case of polyethers, such products also have the properties of a carrier oil. Typical examples of these products are tridecanol butoxylates, isotridecanol butoxylates, isononylphenol butoxylates and polyisobutenol butoxylates and propoxylates, and the corresponding reaction products with ammonia.

[0158] The additive containing a moiety (A8) derived from succinic anhydride and having a hydroxyl and / or amino and / or amide and / or imide group is preferably a corresponding derivative of polyisobutenyl succinic anhydride, which can be obtained by reacting a conventional or highly reactive polyisobutene with a Mn of 300 to 5000 with maleic anhydride by a thermal route or via chlorinated polyisobutene. Particular interest is shown in derivatives with aliphatic polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine or tetraethylenepentamine. Such additives are described in particular in US-A-4 849 572.

[0159] The additive containing a moiety (A9) obtained by the Mannich reaction of a substituted phenol with an aldehyde and a monoamine or a polyamine is preferably a reaction product of a polyisobutene-substituted phenol with formaldehyde and a monoamine or a polyamine such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine or dimethylaminopropylamine. The polyisobutenyl-substituted phenol can be derived from a conventional or highly reactive polyisobutene with a Mn of 300 to 5000. Such "polyisobutene-Mannich bases" are described in particular in EP-A-831 141.

[0160] Preferably, the detergent additive for use in the gasoline composition of the present invention contains at least one nitrogen-containing detergent, more preferably contains at least one nitrogen-containing detergent having a hydrophobic hydrocarbon group with a number average molecular weight in the range of 300 to 5000. Preferably, the nitrogen-containing detergent is selected from the group consisting of: polyolefin monoamines, polyetheramines, polyolefin Mannich amines and polyolefin succinimides. Conveniently, the nitrogen-containing detergent can be a polyolefin monoamine.

[0161] In the above, the amounts (concentrations, volume%, ppmw, weight%) of the components are the amounts of the active substances, i.e., do not include volatile solvent / diluent materials.

[0162] The liquid fuel composition of the present invention can be produced by mixing a substantially low molecular weight, preferably highly reactive polybutene polymer and a substantially tetraalkyl ethane compound with a gasoline base fuel suitable for use in an internal combustion engine. Since the base fuel into which the basic fuel additive is incorporated is gasoline, the produced liquid fuel composition is a gasoline composition.

[0163] It has surprisingly been found that the combined use of a low molecular weight, preferably highly reactive, polybutene having a number average molecular weight of from 500 g / mol to 10,000 g / mol and a tetraalkyl ethane compound provides a synergistic benefit with respect to an internal combustion engine fueled by a liquid base fuel in terms of increasing the power of an internal combustion engine fueled by a liquid fuel composition containing said polybutene and increasing P max In a preferred embodiment herein, an increase in power can be observed under low load and low speed conditions (such as 1300 rpm and 11.5 bar) and under high load and high speed conditions (such as 3300 rpm and 12.4 bar).

[0164] It has also surprisingly been found that the combined use of a low molecular weight, preferably highly reactive, polybutene having a number average molecular weight of from 500 g / mol to 10,000 g / mol and a tetraalkyl ethane compound provides a synergistic benefit with respect to an internal combustion engine fueled by a liquid base fuel in terms of reducing the combustion duration of a liquid fuel composition containing said polybutene.

[0165] Preferably, the internal combustion engine herein is a spark-ignition internal combustion engine operating in PFI (port fuel injection) or GDI (gasoline direct injection) mode.

[0166] The present invention will be further understood by the following examples. Unless otherwise indicated, all amounts and concentrations disclosed in the examples are based on the weight of the fully formulated fuel composition.

[0167] Embodiment

[0168] Embodiments 1 to 13

[0169] The purpose of these experiments was to screen a group of additives with potential for enhanced combustion performance using a gasoline single-cylinder engine (GSCE) in PFI mode. Combustion enhancement can be manifested essentially in two modes: advanced ignition delay (octane number increase, important for reducing knocking at high compression ratios) or flame speed promoter (shortening combustion duration, resulting in improved power).

[0170] A number of fully formulated fuel compositions (Examples 1 to 13) are provided below.

[0171] All fuel compositions used were E10 base fuels (containing 10% ethanol) that met the North American mainstream specification ASTM D4814 and were free of performance additives. E10 base fuel with a RON of 92.3 was used in Example 1, E10 base fuel with a RON of 96.7 was used in Examples 2 to 4, and E10 base fuel with a RON of 96.5 was used in Examples 5 to 13.

[0172] Highly reactive polyisobutene (HR-PIB) and / or diisopropylbenzene were added to the base fuel at the treatment rates indicated in Tables 1 and 2 below. As shown, some examples also included mesitylene. Mesitylene is a mixture of trimethylbenzene isomers. Tables 1 and 2 also show the RON and MON values of each fuel formulation.

[0173] Table 1

[0174]

[0175] Table 2

[0176]

[0177]

[0178] Test Conditions

[0179] The engine used for these experiments was a gasoline single-cylinder engine in PFI mode. The engine was manufactured by AVL and based on the EA888 2.0L Audi TFSI / VW TSI (Euro 6). The details of the single-cylinder bench engine are shown in Table 3 below.

[0180] Table 3

[0181] Parameters: Details: Manufacturer AVL Displacement Volume <![CDATA[454cm 3 > Cylinder 1 Stroke 86 mm Bore 82 mm Compression Ratio Variable 8 - 12, (select 10:1) Number of Valves 2 Inlets; 2 Outlets Maximum Engine Speed 5000 rpm (select 3300 rpm) Suction Slight Lift (maximum 2.5 bar absolute) Injection PFI (Solenoid Injector) Others IMEP up to 25 bar, maximum peak pressure 130 bar continuously

[0182] The engine test conditions are detailed in Table 4 below

[0183] Table 4

[0184]

[0185] The following test protocol was performed daily with the base fuel and one test fuel (one of Examples 1 to 13):

[0186] · Preheat the engine and linearly drain the base fuel

[0187] · Run a baseline spark sweep: 1300ML, HL, 3000ML (ML = medium load;

[0188] HL = High Load)

[0189] ·Switch to the test fuel and flush 30 liters

[0190] ·Testing: Conduct spark scans under three different conditions (1300 rpm, IMEP: 11.5 bar and 8 bar; and 3300 rpm, IMEP: 12.4 bar)

[0191] ·End.

[0192] Screen each test fuel blend twice, once in each of two random loops. Conduct average maximum pressure (P max ) measurements and the results are shown in Figures 1 to 4 .

[0193] Figure 1 is a diagram showing the Pmax measurement results of Example 1 and its reference base fuel (example numbers on the x-axis and Pmax on the y-axis).

[0194] Figure 2 is a diagram showing the Pmax measurement results of Examples 2 to 4 and their reference base fuel (example numbers on the x-axis and Pmax on the y-axis).

[0195] Figure 3 is a diagram showing the Pmax measurement results of Examples 5 to 13 and their reference base fuel (example numbers on the x-axis and P max on the y-axis).

[0196] Figure 4 Shows the average % difference in P max between the test blends and their base fuel controls and the average % difference in combustion duration (AI 10 - 90) at 1300 HL, IGN = 1 (IGN = ignition timing). In Figure 4 , the example numbers are on the x-axis and the average % difference in combustion duration and the average % difference in P max are on the y-axis.

[0197] Embodiments 14 to 27

[0198] The purpose of these experiments is to screen a group of additives with potential for enhanced combustion performance using a gasoline single-cylinder engine (GSCE) in GDI mode. Combustion enhancement can be manifested essentially in two modes: advanced ignition delay (octane number increase, important for reducing knock at high compression ratios) or flame speed promoter (shortening combustion duration, resulting in improved power).

[0199] Many fully formulated fuel compositions are provided below (Examples 14 to 27).

[0200] All fuel compositions used were E10 base fuel (containing 10% ethanol) compliant with the North American mainstream specification ASTM D4814, which contained no performance additives and had a RON of 96.5.

[0201] Highly reactive polyisobutene (HR-PIB) and / or diisopropylbenzene were added to the base fuel at the treatment rates indicated in Table 5 below. As shown, some embodiments also included mesitylene. Mesitylene is a mixture of trimethylbenzene isomers. Table 5 also shows the RON and MON values of each fuel formulation.

[0202] Table 5

[0203]

[0204] Test Conditions

[0205] The engine used for these experiments was a gasoline single-cylinder engine in GDI mode. The engine was manufactured by AVL and based on the EA888 2.0L Audi TFSI / VW TSI (Euro 6). The details of the single-cylinder bench engine are shown in Table 6 below.

[0206] Table 6

[0207] Parameters: Details: Manufacturer AVL Displacement Volume <![CDATA[454cm 3 > Cylinder 1 Stroke 86 mm Bore 82 mm Compression Ratio Variable 8 - 12, (select 10:1) Number of Valves 2 Inlets; 2 Outlets Maximum Engine Speed 5000 rpm (select 3300 rpm) Suction Slight Lift (maximum 2.5 bar absolute) Injection GDI Mode Others IMEP up to 25 bar, maximum peak pressure 130 bar continuously

[0208] The engine test conditions are detailed in Table 7 below

[0209] Table 7

[0210]

[0211] The following test protocol was performed daily with the base fuel and one test fuel (one of Examples 14 to 27):

[0212] · Preheat the engine and linearly drain the base fuel

[0213] · Run a baseline spark sweep: 1300ML, 2000ML, and 3000ML (ML = medium load; HL = high load)

[0214] · Switch to the test fuel and flush 30 liters

[0215] · Test: Perform a spark sweep under three different conditions (1300 rpm, IMEP: 15 bar; 2000 rpm, IMEP: 13.5 bar; and 3300 rpm, IMEP: 16.2 bar)

[0216] · End.

[0217] Each test fuel blend was screened twice, once in each of two random loops. Average maximum pressure (P max ) measurements were made and the results are shown in Figure 5 and Figure 6 .

[0218] Figure 5 is a graphical illustration of the Pmax measurement results for Examples 14 to 27 and their reference base fuels. In Figure 5 , the example numbers are on the x-axis and Pmax is on the y-axis.

[0219] Figure 6 shows the average % difference in Pmax and the average % difference in combustion duration (AI 10 - 90) between the blend tested (Examples 14 to 27) and the base fuel control at 1300 rpm, 15 IMEP, IGN at TDC. In Figure 6 , the example numbers are on the x-axis and the average % difference in combustion duration and the average % difference in Pmax are on the y-axis.

[0220] Discussion

[0221] It has been found that under various engine conditions, i.e., both at low speed / low load and high load / high speed, the use of a combination of diisopropylbenzene and HR-PIB in the engine tests of the examples provides an increased P max (associated with increased power). This demonstrates that the fuel formulations of the present invention can be used for both retail customers and motorsport applications.

Claims

1. A fuel composition, the fuel composition comprising: (a) a gasoline base fuel suitable for a spark-ignition internal combustion engine; and (b) a polybutene polymer; wherein the polybutene polymer has a number average molecular weight in the range of 200 g / mol to 10,000 g / mol, and wherein more than 30% of the polymer molecules in the polybutene polymer have terminal vinylidene groups; and (c) a tetraalkyl ethane compound having the formula (I): wherein Ar represents an aryl group and each X is independently selected from a hydrogen atom, a substituted or unsubstituted straight-chain or branched C 1 -C 12 alkyl group, (CH 2 ) n OH or (CH 2 ) n NH 2 , where n ranges from 1 to 9, provided that at least one of the X groups in each CX 3 group is a hydrogen atom.

2. The fuel composition according to claim 1, wherein more than 40% of the polymer molecules in the polybutene polymer have terminal vinylidene groups.

3. The fuel composition according to claim 1 or 2, wherein more than 50% of the polymer molecules in the polybutene polymer have terminal vinylidene groups.

4. The fuel composition according to any one of claims 1 to 3, wherein the polybutene polymer has a number average molecular weight in the range of 500 g / mol to 5,000 g / mol.

5. The fuel composition according to any one of claims 1 to 4, wherein the polybutene polymer has a number average molecular weight in the range of 1,000 g / mol to 2,300 g / mol.

6. The fuel composition according to any one of claims 1 to 5, wherein the polybutene polymer is a polyisobutene polymer.

7. The fuel composition according to any one of claims 1 to 6, wherein the polybutene polymer is present in an amount of 1,000 ppm to 5,000 ppm by weight of the fuel composition.

8. The fuel composition according to any one of claims 1 to 7, wherein the tetraalkyl ethane compound is present in an amount of 200 ppm to 5,000 ppm by weight of the fuel composition.

9. The fuel composition according to any one of claims 1 to 8, wherein Ar of the tetraalkyl ethane compound is a substituted or unsubstituted aromatic group selected from phenyl, biphenyl, naphthyl, thienyl or anthracenyl.

10. The fuel composition according to any one of claims 1 to 9, wherein Ar is an unsubstituted phenyl group.

11. The fuel composition according to any one of claims 1 to 10, wherein each X is independently selected from a hydrogen atom, an unsubstituted straight-chain or branched C 1 -C 6 alkyl group, provided that at least one of the X groups in each CX 3 group is a hydrogen atom.

12. The fuel composition according to any one of claims 1 to 11, wherein the tetraalkyl ethane compound is 1,1’(1,1,2,2-tetramethyl-1,1-ethanediyl)bis-benzene.

13. Use of a liquid fuel composition for increasing the power output of an internal combustion engine, wherein the liquid fuel composition comprises: (a) a gasoline base fuel suitable for a spark-ignition internal combustion engine; (b) a polybutene polymer; wherein the polybutene polymer has a number average molecular weight in the range of 200 g / mol to 10,000 g / mol, and preferably wherein the polybutene is a highly reactive polybutene, and wherein more than 30% of the polymer molecules in the polyisobutene polymer have terminal vinylidene groups; and (c) a tetraalkyl ethane compound having the formula (I): wherein Ar represents an aryl group and each X is independently selected from a hydrogen atom, a substituted or unsubstituted straight-chain or branched C 1 -C 12 alkyl group, (CH 2 ) n OH or (CH 2 ) n NH 2 , where n ranges from 1 to 9, provided that at least one of the X groups in each CX 3 group is a hydrogen atom.

14. A method for increasing the power output of a spark-ignition internal combustion engine, wherein the method comprises adding polybutene and a tetraalkyl ethane compound to a gasoline base fuel to produce a gasoline fuel composition, wherein the polybutene polymer is added in an amount of 1000 ppm to 5000 ppm by weight of the gasoline fuel composition, and wherein the tetraalkyl ethane compound is added in an amount of 200 ppm to 5000 ppm by weight of the gasoline fuel composition, wherein the polybutene has a number average molecular weight in the range of 200 g / mol to 10,000 g / mol, and preferably wherein the polybutene is highly reactive polybutene, wherein more than 30% of the polymer molecules in the polybutene polymer have terminal vinylidene groups, and wherein the tetraalkyl ethane compound has the formula (I): wherein Ar represents an aryl group and each X is independently selected from a hydrogen atom, a substituted or unsubstituted straight-chain or branched C 1 -C 12 alkyl group, (CH 2 ) n OH or (CH 2 ) n NH 2 , where n ranges from 1 to 9, provided that at least one of the X groups in each CX 3 group is a hydrogen atom, and causing the fuel composition to burn in the spark-ignition internal combustion engine.

15. The method according to claim 14, wherein the spark-ignition internal combustion engine operates in PFI or GDI mode.

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