Patent Application
20080295395
The present invention relates to additives for distillate fuels, and more particularly relates, in one embodiment to reducing exhaust emissions for hydro-carbon fuels using chemical additives.
It is well known that considerable effort has been expended reducing the exhaust emissions from compression ignition (e.g. internal combustion) engines. These exhaust emissions are the products of burning the fuel in the engine, emitted from an exhaust system. The major emissions include hydrocarbons, which are unburned or partially burned fuels, nitrogen oxides (generally abbreviated NOx) which are generated when nitrogen in the air reacts with oxygen under the high temperature and pressure conditions inside the engine, carbon monoxide (CO) which is a product of incomplete combustion, and carbon dioxide (CO2) which is a product of the complete combustion of hydrocarbons.
Additives to fuels are known to reduce undesirable emissions. There are many fuel additives that claim to lower emissions, such as particulate matter, unburnt hydrocarbon, and NOx. Various organo-metallic and totally organic formulations have been proposed and tried. Furthermore, diverse mechanisms have been proposed for their effectiveness.
It has been found to be difficult to simultaneously reduce particulate matter (PM) emissions and NOx emissions, particularly in diesel fuels. Unfortunately, with some additives, as the PM is lowered, NOx emissions rise, and vice versa with others. There is some promise that ethanol fuel additives may help reduce both PM and NOx simultaneously under certain conditions.
Thus, it would be desirable if other additives could be developed to reduce the emissions of distillate fuels upon combustion.
There are provided, in one non-limiting form, compositions for reducing the emissions of distillate fuels that includes a homopolymer such as polyisobutylene (PIB), polypropylene (PP), and/or a hyperbranched polymer. Combinations of these polymeric materials with an alkyl nitrate, such as 2-ethyhexylnitrate (2EHN), and/or a peroxide, such as hydrogen peroxide, are also useful.
There are further provided in another non-restrictive version distillate fuels, such as diesel fuels, gasoline, jet fuels, or kerosene, having reduced emissions, that contains an effective amount of a composition to reduce emissions of a homopolymer that may be polyisobutylene, polypropylene, and/or a hyperbranched polymer, and optionally an alkyl nitrate and/or a peroxide.
Also provided in another non-limiting embodiment are methods for reducing emissions of a distillate fuel by adding to the fuel an effective amount of a composition that includes a homopolymer that may be polyisobutylene, polypropylene, and/or a hyperbranched polymer, and optionally an alkyl nitrate and/or a peroxide.
The methods and compositions herein relate to reducing the amount of exhaust emissions resulting from the combustion of hydrocarbon fuels in compression ignition engines such as internal combustion engines. In particular, the additives reduce NOx emissions and/or particulate matter. More specifically, the methods and compositions herein concern a fuel additive formulation that includes a polymer. Suitable polymers are homopolymers including, but not necessarily limited to, polyisobutylene, polypropylene, hyperbranched polymers, and in particular hyperbranched polyalpha-olefins (PAO), and the like. In one non-restrictive version, the hyperbranched polyalpha-olefins may be hyperbranched polymers of C4-C30 alpha-olefins, where the alpha-olefins may be acid- or alcohol-functionalized, and mixtures and derivatives thereof. In one non-limiting embodiment, the polymer presence lowers NOx and in many embodiments also lowers particulate matter (PM).
The additive composition herein may also optionally contain a component that may be an alkyl nitrate and/or a peroxide. Suitable alkyl nitrates include, but are not necessarily limited to, 2-ethylhexyl nitrate (2EHN), CH3(CH2)3CH(C2H5)CH2ONO2, iso-propyl nitrate, iso-amylnitrate, iso-hexylnitrate, cyclohexyl nitrate, dodecyl nitrate, diglycol nitrate and tetraglycol nitrate and the like. Ether nitrates and fatty acid nitrates may also be useful. The alkyl nitrate may function to primarily lower the NOx emissions although reduction in PM may also be expected. Alternatively, NOx emissions may be lowered by the compositions herein without appreciably raising PM levels, which would also be an advantage and an improvement.
The additive composition may also optionally include a peroxide, in place of or in addition to the alkyl nitrate. Suitable peroxides include, but are not necessarily limited to, hydrogen peroxide, di-tertiary butyl peroxide, and benzoyl peroxide and the like. Further, some synergism has been found between the homopolymer and the alkyl nitrate and/or peroxide. Known cetane boosters for use in distillate fuels include 2-ethylhexyl nitrate, tertiary butyl peroxide, diethylene glycol methyl ether, cyclohexanol, and mixtures thereof. Conventional, known ignition accelerators include hydrogen peroxide, benzoyl peroxide, di-tert-butyl peroxide, and the like.
By hyperbranched polyalpha-olefins are meant polymers prepared by polymerizing hydrocarbons under free radical conditions at low pressures. The polymers are unique in that although hydrocarbon polymers generally have higher molecular weight, greater viscosity and greater hardness than the starting hydro-carbon these polymers generally have higher melting points and congealing points than the starting hydrocarbons. The hydrocarbons employed are primarily alpha-olefins of the formula RCH═CH2 but also include alpha-olefins having vinylidene structures, internal olefins and saturates, where R is an alkyl or alkylene group, including those having vinylidene structures. Suitable hyperbranched polyalpha-olefins are those made according to the methods described in U.S. Pat. Nos. 4,060,569; 4,239,546 and 6,776,808, all incorporated by reference herein in their entirety. The hyperbranched polyalpha-olefins are considered homopolymers herein under the classic definition because they are made from a single monomer. Suitable hyperbranched polyalpha-olefins herein may have a number average molecular weight (Mn) of from about 100 to about 275,000, alternatively a lower threshold of about 150 and independently an upper threshold of about 250,000, and in another non-limiting embodiment from about 200 independently up to about 175,000, or even up to about 125,000 The patents noted above do describe copolymers which are not encompassed by the additive compositions and methods herein.
Other polymers that may also be useful in the additive compositions herein include, but are not necessarily limited to, isotactic polypropylene (such as ones having a weight average molecular weight in the range of about 2000) or higher molecular weight hyperbranched polymer products than those described above. Polymer alone without the 2EHN may be useful.
The methods herein relate to additive compositions for distillate fuels, as contrasted with products from resid. In the context herein, distillate fuels include, but are not necessarily limited to diesel fuel, kerosene, gasoline, jet fuel, and the like. It will be appreciated that distillate fuels include blends of conventional hydrocarbons meant by these terms with oxygenates, e.g. alcohols, such as methanol, ethanol, and other additives or blending components presently used in these distillate fuels, such as MTBE (methyl-tert-butyl ether), or that may be used in the future. In one non-limiting embodiment herein, distillate fuels include low sulfur fuels, which are defined as having a sulfur content of 0.2% by weight or less, and in another non-limiting embodiment as having a sulfur content of about 0.0015 wt. % or less—such as the so-called “ultra low sulfur” fuels. Particularly preferred hydrocarbon fuels herein are diesel and kerosene. It is expected that a more conventional diesel fuel (i.e. with an aromatic content of >28%) treated with the additive composition herein will be equivalent in emissions to a Texas Low Emissions Diesel (TxLED) fuel with <10% aromatic content.
Generally, in one non-limiting embodiment herein the composition for improving the emissions of distillate fuels is a mixture or blend of 2EHN (or a peroxide component) and at least one of the homopolymers. In another non-restrictive version herein the homopolymer is present in the fuel in the range of about 20 to about 2500 ppm, in one non limiting embodiment from about 20 independently up to about 300 ppm; alternatively from about 20 independently up to about 150 ppm. The alkyl nitrate, particularly 2EHN, may be present in the fuel in the range of about 100 to about 3000 ppm, alternatively from about 500, independently up to about 1500 ppm. In one non-limiting embodiment, the volume ratio of homopolymer to the component ranges from about 1:1 to about 1:100, and alternatively the volume ratio of homopolymer to the component ranges from about 1:2 to about 1:10; and in one particularly suitable ratio, about 1:7.
Typically, a solvent may be advantageously used in the compositions herein, where the solvent may be aromatic solvents and pure paraffinic solvents. Aromatic solvents are particularly preferred. The proportion of solvent in the total fuel additive composition may range from about 0 to 90 weight %; in another non-restrictive embodiment, the solvent may range from a lower threshold of about 15 wt % independently to an upper threshold of 45 wt %. The use of a solvent is optional. In some non-limiting embodiments, no solvent is used or desired. A non-restrictive example would be 87.5% 2EHN and 12.5% HPAO with no solvent (a 7:1 ratio of active components). Specific examples of suitable solvents include, but are not limited to paraffins and cycloparaffins, aromatic naphtha, kerosene, diesel, gasoline, xylene, toluene, alcohols (e.g. 2-ethylhexanol), and the like.
It will be appreciated that the methods and compositions herein also encompass distillate fuels containing the additive compositions described herein, as well as methods of improving the emissions properties of distillate fuels using the additive compositions described herein.
Other, optional components of the distillate fuels in non-limiting embodiments may include, but are not necessarily limited to detergents, pour point depressants, cetane improvers, lubricity additives, dehazers, cold operability additives, conductivity additives, biocides, dyes, and mixtures thereof. Particularly useful components may include condensation reaction products of aldehydes and amines which are useful as antioxidants and are effective to lower PM and unburnt hydrocarbon (HC). A specific non-limiting example is the condensation reaction product between formaldehyde and di-n-butylamine. In another non-limiting embodiment, water is explicitly absent from the additive composition.
The invention will be illustrated further with respect to the following non-limiting Examples that are included only to further illuminate the invention and not to restrict it.
Additive compositions expected to be useful herein include, but are not necessarily limited to the following outlined in Table I:
The hyperbranched polymer is a polyalpha-olefin having a molecular weight of about 2800.
The 2-ethylhexanol (2EH) was added as a solvent to improve the low temperature stability of the additive formulation.
Product Q is a condensation reaction product between formaldehyde and di-n-butylamine.
Other additive compositions expected to be useful herein include, but are not necessarily limited to those outlined in Table II:
The test data in the Figures discussed below was developed using a 1991 DDC Series 60 (Serial No. 06R0038671) heavy duty diesel engine mounted in a transient-capable test cell. This engine had an in-line, six cylinder configuration rated for 365 hp at 1800 rpm, was turbocharged, and used a laboratory water to air heat exchanger for a charge air intercooler. The exhaust was routed to a full flow constant volume sampler that utilized a positive displacement pump. Total flow in the tunnel was maintained at a nominal flow rate of about 2000 SCFM. Sample zone probes for particulate matter (PM), heated oxides of nitrogen (NOx), heated hydrocarbons (HC), carbon monoxide (CO), and carbon dioxide (CO2) measurements were connected to the main tunnel. Probes for background gas measurement were connected downstream of the dilution air filter pack, but upstream of the mixing section. The dilution system was equipped with pressure and temperature sensors at various locations in order to obtain all necessary information required by the U.S. Code of Federal Regulation (40 CFR, Part 86, Subpart N).
1. All of the formulations mitigated NOx, at least to some extent.
2. PIB alone performed considerably better than HPAO alone.
3. The combinations of polymer plus EHN performed better than polymer alone or EHN alone.
4. The HPAO plus EHN combination performed better than the corresponding combination with PIB, in spite of the fact than PIB alone performed better than HPAO alone.
5. The HPAO plus EHN combination performed better at 2000 ppm than EHN alone at 3000. This point becomes even more significant when the fact is considered that the combination product at 2000 ppm has a total of 1600 ppm active components (1400 EHN and 200 HPAO). This clearly indicates a synergism between HPAO and EHN.
In addition to the effectiveness of the HPAO and HPAO-EHN combinations in mitigating NOx, there is clear evidence that these components do so without increasing particulate matter to any significant extent and, in fact, in most cases it actually lowers PM.
In the foregoing specification, the invention has been described with reference to specific embodiments thereof, and has been demonstrated as effective for reducing the emissions of fuels. However, it will be evident that various modifications and changes can be made thereto without departing from the broader spirit or scope of the invention as set forth in the appended claims. Accordingly, the specification is to be regarded in an illustrative rather than a restrictive sense. For example, specific combinations of polymers optionally together with alkyl nitrates and/or peroxides falling within the claimed parameters, but not specifically identified or tried in a particular composition to improve the emissions of fuels herein, are expected to be within the scope of this invention. Certain compositions under certain conditions may serve to lower NOx emissions without any substantial increase in PM emissions or with substantially unchanged PM emissions. It is anticipated that the compositions of this invention may also impart to the engines in which they are used as emissions reducers, greater horsepower, and better fuel economy as a result of less friction, whether they are used in diesel or gasoline engines.
The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed.
The words “comprising” and “comprises” as used throughout the claims is to interpreted “including but not limited to”.
This application claims the benefit of U.S. Provisional Patent Application No. 60/940,914 filed May 30, 2007.
| Number | Date | Country | |
|---|---|---|---|
| 60940914 | May 2007 | US |
