Fuel Compositions

The present invention relates to a liquid fuel composition, in particular to a liquid fuel composition which provides improved engine power and which has a reduced burn duration in an internal combustion engine. The present invention also relates to methods of improving the power output of an internal combustion engine as well as increasing efficiency and reducing emissions, by fueling the internal combustion engine with the liquid fuel composition described herein below. The present invention also relates to methods of improving the burn duration of a liquid fuel composition.

In order to improve engine efficiency, power and acceleration properties of modern spark ignition internal combustion engines, these engines are increasingly being downsized and boosted as well as moving up in compression ratios.

As well as upgrading the engine hardware, it is also possible to improve engine efficiency, reduce emissions, increase power and acceleration of spark ignition engines by making changes to the fuel formulations used to fuel the engines. For example, gasoline fuel compositions containing specially formulated refinery components with high octane and good flame speed/burn duration properties can deliver increases in power and/or acceleration as well as fuel economy. However, it would be desirable to be able to use market available, standard exchange gasoline fuel for upgrading power, acceleration and fuel efficiency performance.

So-called high reactivity polybutene polymers have relatively high proportions (i.e. >30%) of polymer molecules having a terminal vinylidene group. U.S. Pat. No. 6,048,373 discloses a fuel composition comprising a spark ignition fuel, a Mannich detergent and a polybutene having a molecular weight distribution of less than 1.4 for controlling intake valve deposits and minimizing valve sticking in spark ignition internal combustion engines. Preferred polybutenes disclosed therein have a number average molecular weight (Mn) of from about 500 to about 2000, and high reactivity polyisobutylenes (PIBs) are disclosed. Preferred treat rates for the polybutene(s) having a molecular weight distribution of 1.4 or less are stated to fall within the range of about 0.5 to about 50 ptb, preferably in the range of about 1.5 to about 40 ptb. The treat rate of the high reactivity PIB used in Example 2 is 53.2 ptb which is equivalent to about 151 ppm. However, there is no teaching in this document of the use of a low molecular weight polybutene polymer at selected treat rates for providing increased engine power and reduced burn duration.

It has now surprisingly been found that the use of a a low molecular weight polybutene, such as a low molecular weight polyisobutylene (PIB), especially a low molecular weight, high reactivity, polyisobutylene (PIB), in a gasoline fuel composition, at selected additive treat rates, can provide benefits in terms of improved power output (increased P) and reduced burn duration, even when a standard exchange gasoline fuel is used. A reduction in burn duration leads to a more complete burn per cycle, which improves engine efficiency as well as lowers harmful emissions including particulate matter (PM/PN).

According to the present invention there is provided a fuel composition comprising:

It has been surprisingly found that the fuel compositions of the present invention provide improved power output as reflected in increased P, as well as reduced burn duration of the fuel. Further the fuel compositions of the present invention exhibit excellent acceleration, energy efficiency and fuel economy.

According to another aspect of the present invention there is provided a method of improving the power output of an internal combustion engine, said method comprising fueling the internal combustion engine with a liquid fuel composition comprising:

According to another aspect of the present invention there is provided a method of increasing the Pof an internal combustion engine, said method comprising fueling the internal combustion engine with a liquid fuel composition comprising:

According to yet another aspect of the present invention there is provided a method of reducing the burn duration of a liquid fuel composition in an internal combustion engine, wherein the method comprises blending a polybutene polymer with a gasoline base fuel to produce a gasoline fuel composition, wherein the polybutene polymer is blended with the gasoline base fuel at a level from 500 ppm to 5000 ppm, by weight of the gasoline fuel composition and wherein the polybutene has a molecular weight in the range from 200 to 10,000 g/mol and combusting the fuel composition in the spark ignition internal combustion, preferably wherein the polybutylene is a high reactivity polybutene wherein greater than 30% of the polymer molecules in the polybutene polymer have a terminal vinylidene group.

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

According to yet another aspect of the present invention there is provided the use of a liquid fuel composition for increasing the Pof an internal combustion engine, wherein the liquid fuel composition comprises:

According to yet another aspect of the present invention there is provided the use of a polybutene polymer in a liquid fuel composition for reducing burn duration, wherein the liquid fuel composition comprises:

The term “power output” as used herein refers to the amount of resistance power required to maintain a fixed speed at wide open throttle conditions in Chassis Dynamometer testing.

The term ‘P’ as used herein refers to the direct measurement of the force generated by decomposition of the fuel.

According to the present invention, there is provided a method of improving the power output of an internal combustion engine. Also, according to the present invention, there is a method of improving the Pof an internal combustion engine. In the context of these aspects of the present invention, the term “improving” embraces any degree of improvement. The improvement may for instance be 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 Pprovided by an analogous fuel formulation, prior to adding a low molecular weight, preferably high reactivity, polybutene to it in accordance with the present invention. The improvement in power output or Pmay even be as high as 10% of the power output or Pprovided by an analogous fuel formulation, prior to adding a low molecular weight, preferably high reactivity, polybutene to it in accordance with the present invention.

The low molecular weight, preferably high reactivity, polybutene may also be used to improve the acceleration of an internal combustion engine. The term “acceleration” as used herein refers to the amount of time required for the engine to increase in speed between two fixed speed conditions in a given gear. In the context of this aspect of the invention, the term “improving” embraces any degree of improvement, and may be improved by the same percentages as the power and or Pis increased above.

In accordance with the present invention, the power output and acceleration provided by a fuel composition may be determined in any manner known to a person skilled in the art for instance as taught in SAE Paper 2005-01-0239 and SAE Paper 2005-01-0244.

The term ‘burn duration’ as used herein means the time required (in engine crank angle degrees) for combustion to progress 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 burn duration and means the time required (in engine crank angle degrees) for combustion to progress from 50% to 90%. Investigation of combustion can be carried out by monitoring in-cylinder pressure data. The pressure data can be collected using a piezoelectric pressure transducer from which the mass fraction burn (MFB), or burn duration can be calculated. Further information on how the MFB can be calculated can be found in SAE Paper 2014-01-1336 published Apr. 1, 2014 by Ftwi Yohaness Hagos and Abd Rashid Abd Aziz entitled ‘Mass Fraction Burn Investigation of Lean Burn Low BTU Gasification Gas in Direct-injection Spark-ignition Engine’.

According to the present invention, there is provided a method of reducing the burn duration of a gasoline fuel composition wherein the method comprises adding a polybutene polymer to the gasoline fuel composition, wherein the polybutene polymer is added at a level from 500 ppm to 5000 ppm by weight of the gasoline fuel composition and wherein the polybutene has a number average molecular weight in the range from 200 to 10,000 g/mol.

In accordance with the present invention, the burn duration of a fuel composition may be determined in any known manner, for instance using the test method disclosed in the Examples section hereinbelow.

In the context of this aspect of the invention, the term “reducing the burn duration” embraces any degree of reduction. The reduction may for instance be 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 reduction of the burn duration provided by an analogous fuel formulation, prior to adding a low molecular weight, preferably high reactivity, polybutene to it in accordance with the present invention. The reduction in burn duration may even be as high as a 10% reduction of the burn duration provided by an analogous fuel formulation, prior to adding a low molecular weight, preferably high reactivity, polybutene to it in accordance with the present invention.

The term “flame speed” or ‘laminar flame speed’ (LFS) refers to laminar burning velocity. LFS is a fundamental measure of flame propagation rate without complication of mixing dynamics. However, in an engine, mixing dynamics play a role, so the measured flame speed is referred to as ‘burn rate’ and ‘burn duration’. The terms ‘burn rate’ and ‘burn duration’ are also used herein interchangeably with ‘flame speed’. Laminar Burning Velocity (LBV) is a fundamental property of a chemical component. It is defined as the rate (normal to the flame front, under laminar flow conditions) at which unburnt gas propagates to the flame front and reacts to form products.

The flame speed of a fuel composition may be determined in any known manner, for instance measurement of LFS can be performed using any one of the following three methods:

All three of these methods are described in the review publication: Egolfopoulos, F. N., Hansen, N., Ju, Y., Kohse-Höinghaus, 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.

The following method for measuring flame speed in a constant volume combustion chamber (spherical bomb), ref 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).

The following method for measuring flame speed uses a 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, Part D: J. Automobile Engineering 223 (3) (2009): 389-394.

The liquid fuel composition of the present invention comprises a base fuel suitable for use in an internal combustion engine and a low molecular weight, preferably high reactivity, polybutene. Typically, the base fuel suitable for use in an internal combustion engine is a gasoline or a diesel fuel, and therefore the liquid fuel composition of the present invention is typically a gasoline composition or a diesel fuel composition. Preferably, the base fuel is a gasoline base fuel.

The polybutene for use herein is preferably a high reactivity polybutene. A high reactivity polybutene is a polybutene having a relatively high proportion, i.e. greater than 30%, of polymer molecules having a terminal vinylidene group. The term ‘polybutene’ as used herein includes polymers made from pure or substantially pure 1-butene or isobutene, and polymers made from mixtures of two or all three of 1-butene, 2-butene and isobutene, as well as including polymers containing minor amounts, preferably less than 10% by weight, more preferably less than 5% by weight, of C2, C3, and C5 and higher olefins as well as diolefins. In a preferred embodiment, the polybutene is a 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.

In a particularly preferred embodiment, the polybutene is a high reactivity polyisobutylene.

In one embodiment, the high reactivity polybutene has greater than 40% of polymer molecules having a terminal vinylidene group.

In another embodiment, the high reactivity polybutene polymer has greater than 50% of polymer molecules having a terminal vinylidene group.

In a preferred embodiment, the high reactivity polybutene polymer has greater than 70% of polymer molecules having a terminal vinylidene group.

In another preferred embodiment, the high reactivity polybutene has more than 85% of its double bonds located in the terminal position of the molecule.

The high reactivity polybutene polymer for use herein preferably has a molecular mass distribution of 1.5 or greater, preferably 1.6 or greater, more preferably 1.7 or greater, even more preferably 1.8 or greater.

The polybutene polymer is present at a level of from 500 ppm to 5000 ppm, preferably from 1000 ppm to 5000 ppm, more preferably from 2500 to 5000 ppm, by weight of the fuel composition. Examples of preferred levels of polybutene include 2500 ppm and 5000 ppm, by weight of the fuel composition.

One or more polybutene polymer can be used in the fuel compositions herein. When more than one polybutene polymer is used herein, the total level of polybutene polymer is the same as the ranges given in the previous paragraph.

The polybutene polymer for use 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) in the range from 200 to 10,000 g/mol, preferably from 500 to 5000 g/mol, more preferably from 1000 to 5000 g/mol. In one embodiment of the invention, the polybutenes, preferably high reactivity polybutenes, for use herein have a number average molecular weight (M) from 1000 to 2300 g·mol. In another embodiment of the invention, the polybutenes for use herein have a number average molecular weight (M) from 2300 to 5000 g/mol. The number average molecular weight of the polybutene polymer can be determined using Gel Permeation Chromatography.

The high reactivity polybutenes for use herein may be bioderived or non-bioderived. In one embodiment of the invention, the polybutene is a low molecular weight, high reactivity polyisobutylene which is derived from 100% renewable feedstock.

The high reactivity polybutenes for use herein preferably contain less than 1 mg/kg of chlorine.

In one embodiment, the high reactivity polybutene polymer for use herein has a kinematic viscosity at 100° C. of 190 mm/s or greater, preferably in the range of 190 mm/s to 1500 mm/s, more preferably in the range from 430 to 1500 mm/s.

A preferred high reactivity polybutene for use herein has an alpha olefin content of greater than 85%.

Suitable high reactivity polybutenes for use herein include those commercially available from BASF under the tradename Glissopal® such as Glissopal® 1000, Glissopal® 1300 and Glissopal® 2300.

Glissopal® 1000 has a number average molecular weight (M) of 1000 g/mol, a molecular mass distribution (M/M) of 1.6, an alpha olefin content of greater than 85%, a kinematic viscosity at 100° C. of 190 mm/s and a chlorine content of less than 1 mg/kg.

Glissopal® 1300 has a number average molecular weight (M) of 1300 g/mol, a molecular mass distribution (M/M) of 1.7, an alpha olefin content of greater than 85%, a kinematic viscosity at 100° C. of 190 mm/s and a chlorine content of less than 1 mg/kg.

Glissopal® 2300 has a number average molecular weight (M) of 2300, a molecular mass distribution (M/M) of 1.6, an alpha olefin content of greater than 85%, a kinematic viscosity at 100° C. of 190 mm/s and a chlorine content of less than 1 mg/kg.

Also suitable for use herein are Glissopal® 1000, 1300 and 2300 BMBcert™ which are low molecular weight, highly reactive polyisobutenes derived from 100% renewable feedstock, commercially available from BASF.

The polybutene polymer may be blended together with any other additives e.g. additive performance package(s) to produce an additive blend. The additive blend is then added to a base fuel to produce a liquid fuel composition.

The amount of performance package(s) in the additive blend is preferably in the range of from 0.1 to 99.8 wt %, more preferably in the range of from 5 to 50 wt %, by weight of the additive blend.

Preferably, the amount of the performance package present in the liquid fuel composition of the present invention is in the range of 15 ppmw (parts per million by weight) to 10% wt, based on the overall weight of the liquid fuel composition. More preferably, the amount of the performance package present in the liquid fuel composition of the present invention additionally accords with one or more of the parameters (i) to (xv) listed below: