JP2010013665A - Fuel composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel composition containing a large quantity of gasoline fuel having a maximum sulfur content of 150 ppm by mass, and a small quantity of at least one gasoline fuel additive having a cleaning effect or an effect to prevent seat valve abrasion. <P>SOLUTION: The gasoline fuel additive has at least one hydrophobic hydrocarbon group having a number average molecular weight (MN) of 85 to 20,000 and at least one polar unit. The fuel composition contains at least one lower alkanol by about 5 to 75 vol.%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel composition containing a large amount of a particular lower alkanol and a small amount of selected gasoline fuel additives.

  Carburetor and gasoline engine intake and fuel delivery injectors are increasingly polluted by dust particles from the air, unburned hydrocarbon residues from the internal combustion engine, and impurities generated by crankcase exhaust gases introduced into the carburetor .

  These residues shift the air-fuel ratio in the case of idling and at low partial load ranges, the mixture becomes leaner, the combustion is more incomplete, and the proportion of unburned or partially burned hydrocarbons in the exhaust gas is reduced. Increases and increases gasoline consumption.

  It is known that these drawbacks can be prevented by using fuel additives that keep valves and carburetors or gasoline engine injectors clean (eg M. Rossenbeck in Katalysatenen, Tenside, Mineraloidadditives [Catalysts surfactants minor illuminants] Eds J. Farbe, U. Hasserodt, p.223, G. Thieme Verlag, Stuttgart 1978).

  In older gasoline engines, valve seat wear problems arise when operating with lead-free gasoline fuel. In order to prevent this, additives have been developed that prevent wear of valve seats based on alkali metals or alkaline earth metal compounds.

  For trouble-free use, modern gasoline engines require fuels with complex characteristic profiles that can only be guaranteed in combination with suitable gasoline fuel additives. These gasoline fuels generally consist of a mixture of complex compounds and are characterized by physical quantities. However, the interaction of gasoline fuel with suitable additives still requires improvements in known fuel compositions with regard to cleaning and maintaining cleanliness and preventing valve seat wear.

European Patent No. 244616 WOA94 / 2431 WOA97 / 03946 German Patent No. 19620262 WOA-96 / 03367 WOA96 / 03479 European Patent No. 476485 European Patent No. 307815 WOA87 / 01126 European Patent No. 639632 European Patent No. 310875 European Patent No. 356725 European Patent No. 7000985 U.S. Pat. No. 4,877,416 German patent 3838918 U.S. Pat. No. 4,849,572 European Patent No. 8111141

M.M. Rossenbeck in Katalysatoren, Tenside, Mineraloleadditive [Catalysts surfactants mineral oil additives] Eds. Farbe, U.S. Hasserodt, p.223, G.G. Thiemme Verlag, Stuttgart 1978

  The object of the present invention is to find a more effective gasoline fuel-gasoline fuel additive composition. The object of the present invention is to find a particularly effective additive composition.

  The object is to provide a large amount of gasoline fuel having a sulfur content of up to 150 ppm by mass and a fuel composition containing a small amount of at least one gasoline fuel additive having a cleansing action or a valve seat antiwear action. The gasoline fuel additive has been found to be solved and has at least one hydrophobic hydrocarbon group having a number average molecular weight (MN) of 85-20000 and at least one polar unit, the fuel composition comprising: About 5 to 75% by volume of at least one lower alkanol is contained.

The polar unit is selected from:
(A) a monoamino or polyamino group having up to 6 nitrogen atoms, wherein at least one nitrogen atom has basic properties (b) a nitro group optionally in combination with a hydroxyl group (c) at least one nitrogen atom A hydroxyl group in combination with a monoamino group or a polyamino group (d) a carboxyl group or its alkali metal salt or alkaline earth metal salt (e) a sulfonic acid group or its alkali metal salt or alkaline earth metal salt (f ) From a hydroxyl group, a polyoxy-C2-C4-alkylene unit in which at least one nitrogen atom is terminated by a monoamino group or polyamino group or carbamate group having basic properties (g) a carboxylic ester group (h) from succinic anhydride A hydroxyl group and / or an amino group and / Or amide groups units and having and / or imido groups (i) substituted phenols with aldehydes and monoamines or units obtained by Mannich reaction with a polyamine.

The alkanols used according to the invention are preferably linear or branched, saturated C ₁ -C ₆ -monools or diols, in particular C ₁ -C ₃ -monoalkanols such as methanol, ethanol, n-propanol, isopropanol Or a mixture of a plurality of these alkanols.

  The alkanol content relative to the total volume of the fuel composition is at most 75% by volume, such as 5 to 75% by volume, preferably 10 to 65% by volume, in particular 20 to 55% by volume, for example 30 to 40% by volume, or 40 to 50% by volume. %.

  The content of other alcohols and ethers in gasoline fuels is generally quite low. Typical maximum contents are 7% by volume for t-butanol, 10% by volume for isobutanol and 15% by volume for ethers having 5 or more carbon atoms in the molecule.

  The aromatics content of the gasoline fuel is preferably at most 40% by volume, in particular at most 38% by volume. The preferred range of aromatic compounds is 20 to 42% by volume, in particular 25 to 40% by volume.

  The sulfur content of the gasoline fuel is preferably at most 100 ppm by weight, in particular at most 50 ppm by weight. An advantageous range for the sulfur content is 0.5 to 150 ppm by weight, in particular 1 to 100 ppm by weight.

  In one advantageous configuration, the gasoline fuel has an olefin content of up to 21% by volume, preferably up to 18% by volume, in particular up to 10% by volume. An advantageous range for the olefin content is 6 to 21% by volume, in particular 7 to 18% by volume.

  In another advantageous configuration, the gasoline fuel has a benzene content of up to 1.0% by volume, in particular up to 0.9% by volume. An advantageous range for the benzene content is 0.5 to 1.0% by volume, in particular 0.6 to 0.9% by volume.

  In another advantageous configuration, the oxygen content of the gasoline fuel is up to 2.7% by weight, preferably 0.1 to 2.7% by weight, in particular 1.0 to 2.7% by weight, in particular 1.2%. It is -2.0 mass%.

  A gasoline fuel having an aromatic compound content of up to 38% by volume, an olefin content of up to 21% by volume, a sulfur content of up to 50 ppm by mass, a benzene content of up to 1.0% by volume and an oxygen content of 1.0 to 2.7% by mass It is advantageous.

  The above volume percent indications for olefin, benzene, aromatics and oxygen content are each related to the volume of the mineral gasoline fuel component, i.e. without additives and alkanols.

  The summer vapor pressure of gasoline fuel is typically up to 70 kPa, especially 60 kPa (each at 370 ° C.).

  The research octane number (RON) of gasoline fuel is generally 90-100. A typical range for the corresponding motor octane number (MON) is 80-90.

  The standard is determined by a general method (DINEN228).

  Hydrophobic hydrocarbon groups in gasoline fuel additives that ensure sufficient solubility in gasoline fuel have a number average molecular weight (Mn) of 85-20000, in particular 113-10000, in particular 300-5000. Typical hydrophobic hydrocarbon groups which can be used in combination with the polar units (a), (c), (h) and (i) are polypropenyl, polybutenyl and polyisobutenyl groups, respectively, Mn = 300-50000, in particular 500 ˜2500, in particular 750˜2250.

  Examples of individual gasoline fuel additives that have a cleaning action or a valve seat wear prevention action include the following.

  Additives containing monoamino groups or polyamino groups (a) are preferably polypropenes or highly reactive (ie generally having predominantly double terminal bonds at the α and β positions) or common (ie mainly internal) Polyalkene monoamines or polyalkene polyamines based on polybutene or polyisobutene with Mn = 300-5000 (with double bonds). Polyisobutenes which can contain up to 20% by weight of n-butene units by hydroformylation and reductive amination with ammonia, monoamines or polyamines such as dimethylaminopropylamine, ethylenediamine, diethylenetriamine, triethylenetetramine or tetraethylenepentamine These additives based on highly reactive polyisobutenes which can be produced from are described in particular in EP 244616. When using polybutenes or polyisobutenes with internal double bonds mainly as starting materials for the production of additives (generally in the β and γ positions), possible production methods are chlorination and subsequent amination, or air or ozone Formation of a carbonyl or carbonyl compound by oxidation of a double bond at and subsequent amination under reducing (hydrogenation) conditions. The amine used for the amination may be the same amine as described above for the reductive amination of the hydroformylated highly reactive polyisobutene. Corresponding additives based on polypropene are described in particular in WOA 94/2431.

  Other advantageous additives containing monoamino groups are those of the reaction product of polyisobutene with a mean degree of polymerization P = 5-100 and a mixture of nitric oxide or nitric oxide and oxygen, in particular described in WOA 97/03946. Hydrogenated product.

  Other advantageous additives having a monoamino group (a) are compounds obtained by reaction with amines from polyisobutene epoxides and subsequent dehydration and reduction of aminoalcohols, in particular described in DE 19620262.

  Additives having a nitro group optionally combined with a hydroxyl group (b) preferably have an average degree of polymerization P = 5 to 100 or 10 to 100, as described in particular in WOA-96 / 03367 and WOA 96/03479 It is a reaction product of polyisobutene and nitric oxide or a mixture of nitric oxide and oxygen. These reaction products are generally a mixture of hydroxynitropolyisobutane (eg, α-nitro-β-hydroxypolyisobutane) mixed with pure nitropolyisobutane (eg, α, β-dinitropolyisobutane).

  Additives containing hydroxyl groups (c) in combination with monoamino groups or polyamino groups are described in particular in EP 476485, preferably polyisobutene epoxides obtained mainly from polyisobutenes having terminal double bonds and Mn 300 to 5000 Reaction product of ammonia with ammonia, or monoamine or polyamine.

The additive containing a carboxyl group or an alkali metal salt or alkaline earth metal salt (d) thereof preferably has a total molecular weight of 500 to 20000, and the carboxyl group is partially or fully converted into an alkali metal salt or alkaline earth metal salt. is converted, the remaining carboxyl groups are reacted with alcohols or amines, C 2 _-C 40 _- is a copolymer of an olefin and maleic anhydride. These additives are described in particular in EP 307815. These additives are used to prevent valve seat wear and are preferably used in combination with common fuel detergents such as poly (iso) butenamine or polyetheramine, as described in WOA 87/01126. be able to.

  The additive containing a sulfonic acid group or an alkali metal salt or alkaline earth metal salt thereof is preferably an alkali metal salt or alkaline earth metal salt of a sulfosuccinic acid alkyl ester as described in EP 639632. These additives are primarily used to prevent valve seat wear and can be used in combination with common fuel detergents such as poly (iso) buteneamine or polyetheramine.

Additives containing polyoxy-C ₂ -C ₄ -alkylene units (f) are preferably C ₂ -C ₆₀ -alkanols, C ₆ -C ₃₀ -alkanediols, mono- or di-C ₂ -C ₃₀ -alkyls. Reactions of amines, C ₁ -C ₃₀ -alkylcyclohexanols or C ₁ -C ₃₀ -alkylphenols with 1 to 30 mol of ethylene oxide and / or propylene oxide and / or butylene oxide per hydroxyl group or amino group and polyether amines In the case of polyether or polyetheramine obtained by subsequent reductive amination with ammonia, monoamine or polyamine. These products are described in particular in EP 310875, EP 356725, EP 700755 and US Pat. No. 4,877,416. In the case of polyethers, these products have carrier oil properties. Typical examples of these are tridecanol butoxylate, isotridecanol butoxylate, isononylphenol butoxylate, polyisobutenol butoxylate and propoxylate and the corresponding reaction products with ammonia.

Additives containing carboxylic ester groups (g) advantageously, mono -, di - or esters of tricarboxylic acids with long-chain alkanols or polyols, in particular described in German Patent No. 3,838,918, 2 mm at 100 ° C. ² / It has a minimum viscosity of s. The mono-, di- or tricarboxylic acids used can be fatty acids or aromatic acids, and particularly suitable ester alcohols or ester polyols are long-chain ones having, for example, 6 to 24 carbon atoms. Exemplary esters are adipate, phthalate, isophthalate, terephthalate, and trimellitate of isooctanol, isononanol, isodecanol, and isotridecanol. These products have carrier oil properties.

  Additives derived from succinic anhydride and containing units (h) having hydroxyl groups and / or amino groups and / or amide groups and / or imide groups are preferably obtained by thermal methods or via chlorinated polyisobutenes. It is a corresponding derivative of polyisobutenyl succinic anhydride obtained by reaction of a general or highly reactive polyisobutene with Mn = 300 to 5000 and maleic anhydride. Of particular interest are derivatives having aliphatic polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, or tetraethylenepentamine. These gasoline fuel additives are described in particular in US Pat. No. 4,849,572.

  Additives containing units (i) obtained by Mannich reaction of substituted phenols with aldehydes and monoamines or polyamines are preferably polyisobutene-substituted phenols with formaldehyde and ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine or dimethylaminopropylamine. Reaction products with such monoamines or polyamines. Polyisobutenyl substituted phenols can be generated from common or highly reactive polyisobutenes having Mn = 300-5000. These polyisobutene Mannich bases are described in particular in EP 831141.

  Detailed individual descriptions of further definitions of gasoline fuel additives are disclosed in the state of the art publications.

  The fuel composition of the present invention may additionally contain other common components and additives. These include premier carrier oils, such as mineral carrier oils (base oils), which have no significant cleaning action, in particular olefin polymers having a viscosity type of Solvent Neutral (SN) 500-2000 and Mn = 400-1800, in particular polybutene or polyisobutene Synthetic carrier oils based on (hydrogenated or non-hydrogenated) or poly-α-olefins or poly (internal olefins) are included.

  Useful solvents or diluents (when preparing additive packs) are aliphatic and aromatic hydrocarbons such as Solvent Naphtha.

  Other common additives are, for example, corrosion inhibitors based on ammonium salts of organic carboxylic acids or ammonium salts of heterocyclic aromatics for corrosion protection of non-ferrous metals, which tend to form films, Antioxidants or stabilizers, for example based on amines such as p-phenylenediamine, dicyclohexylamine or their derivatives or 2,4-di-tert-butylphenol or 3,5-di-tert-butyl-4- Those based on derivatives of phenols such as hydroxyphenylpropionic acid, demulsifiers, antistatic agents, metallocenes such as ferrocene or methylcyclopentadienyl manganese tricarbonyl, some fatty acids, alkenyl succinates, bis ( Hydroxyalkyl) fatty amine, hydroxyacetamide or Lubricating additives, such as with oil and a dye (marker). An amine is optionally added to lower the pH value of the fuel.

  Mixtures of said gasoline fuel with lubricating additives based on carboxylic acids or fatty acids which can be present as gasoline fuel additives having a polar unit (f) and corrosion inhibitors and / or monomer and / or dimer types Are particularly useful in the fuel composition of the present invention. Typical mixtures of this type are alkanols such as polyisobutanamine, tridecanol or isotridecanol butoxylate-ammonia reaction products in combination with alkanol-initiated polyethers such as tridecanol or isotridecanol butoxylate or propoxylate. An alkanol-initiated polyether, such as a tridecanol or isotridecanol butoxylate reaction product, in combination with an alkanol-initiated polyether such as tridecanol or isotridecanol butoxylate or propoxylate in combination with an initiating polyetheramine Contains an amine and is used in conjunction with the corrosion inhibitor and / or lubricating additive.

  The gasoline fuel additive having the polar units (a) to (i) and the other components is supplied to the gasoline fuel and exhibits its function there. The components and / or additives can be added to the fuel individually or as a concentrate (additive pack) produced as described above.

  The gasoline fuel additive having the polar units (a) to (i) is typically added to the gasoline fuel in an amount of 1 to 5000 ppm by weight, in particular 5 to 3000 ppm by weight, in particular 10 to 1000 ppm by weight. The other ingredients and additives mentioned above are added in conventional amounts for this purpose if necessary.

  Surprisingly, the fuel composition of the present invention uses the apparently less detergent or valve antiwear agent to achieve the same cleaning or cleansing action as a comparable fuel composition without the addition of a lower alkanol or It is possible to achieve a valve seat wear prevention effect. Furthermore, the fuel composition of the present invention uses the same amount of detergent or anti-skid antiwear agent as compared to conventional fuel compositions, and surprisingly has a clearly better cleaning action or cleaning. Maintains and prevents valve seat wear.

  Furthermore, the fuel composition of the present invention additionally has the advantage that less deposits are formed in the combustion chamber of the gasoline engine and less additive is carried to the engine oil due to fuel dilution.

The present invention further provides i) the use of lower alkanols in low sulfur gasoline fuels to improve the action of additives having the above-described cleaning or anti-valve wear effects ii) mixing gasoline fuel with an effective amount of lower alcohol A method for improving the additive action of additives having the above-mentioned cleaning action or valve seat wear prevention action in low-sulfur gasoline fuels iii) Reduction of combustion chamber deposits and / or deposition of intake devices of gasoline engines Use of a combination of at least one additive having a cleaning action or a valve seat wear prevention action and a lower alcohol to reduce the matter iv) Valve seat wear prevention as a valve seat wear prevention agent for gasoline fuel It relates to the use of a combination of an additive having an action and a lower alcohol.

  The following examples illustrate the present invention and are not limited thereto.

EXAMPLE The gasoline fuel additive used is a commercial product consisting of detergent additive, 60% by weight of polyisobuteneamine (Mn = 1000 g / mol) and 32% by weight of carrier oil (tridecanol etherified with 22 units of butylene oxide). It was an additive pack.

  The gasoline fuel used is a fuel having the specific specifications described below, and GF1 (see Table 1 for parameters) is a typical commercially available fuel.

ＧＦ２＝ＧＦ１＋ＥｔＯＨ１０体積％
ＧＦ３＝ＧＦ１＋ＥｔＯＨ５０体積％。

GF2 = GF1 + EtOH 10% by volume
GF3 = GF1 + EtOH 50% by volume.

Production of fuel composition Example 1 (comparative example)
Additive pack 150 mg or 200 mg was dissolved in 1 kg GF1 according to Table 1.

Example 2 (Invention)
Example 1 was repeated, but using GF2 instead of GF1.

Example 3 (Invention)
Example 1 was repeated, but using GF3 instead of GF1.

Performance Test Example 4
The effects of gasoline fuel according to Examples 1 to 3 on the intake valve deposit (IVD) and total combustion deposit (TCD) were investigated. This was done according to CECF-05-A-93 using the engine test carried out in the automotive test using the Mercedes-Benz engine M102E. The IVD values for added and unadded fuel are listed in Table 2 below.

  In addition, the amount of total combustion deposit (TCD) was measured in the same test for each of the four cylinders of the engine. Individual average values are also shown in Table 2. In order to determine the TCD value, it was carried out analogously to the method of CECF-20-A-98.

  As can be seen from Table 2, unexpectedly less formation of valve or combustion chamber (cylinder) deposits is observed where a significant amount of ethanol (ie, greater than 10%) is mixed with the gasoline fuel.

Claims (20)

A large amount of gasoline fuel having a sulfur content of up to 150 ppm by weight and a fuel composition comprising a small amount of at least one gasoline fuel additive having a cleaning action or a valve seat antiwear action. The additive has at least one hydrophobic hydrocarbon group having a number average molecular weight (MN) of 85-20000 and at least one polar unit, and the fuel composition further comprises about 10-75% by volume of at least one kind C 3 _-C 6 _- fuel composition characterized by containing a mono-alkanol. Polar unit is
(A) a monoamino or polyamino group having up to 6 nitrogen atoms, wherein at least one nitrogen atom has basic properties (b) a nitro group optionally in combination with a hydroxyl group (c) at least one nitrogen atom A hydroxyl group in combination with a monoamino group or a polyamino group (d) a carboxyl group or its alkali metal salt or alkaline earth metal salt (e) a sulfonic acid group or its alkali metal salt or alkaline earth metal salt (f ) From a hydroxyl group, a polyoxy-C2-C4-alkylene unit in which at least one nitrogen atom is terminated by a monoamino group or polyamino group or carbamate group having basic properties (g) a carboxylic ester group (h) from succinic anhydride A hydroxyl group and / or an amino group and / Or units and (i) fuel composition of claim 1 wherein is selected from units obtainable by Mannich reaction of substituted phenols with aldehydes and mono- or polyamines having an amide group and / or imide groups.   3. The fuel composition according to claim 2, comprising a polyalkene mono- or polyalkylene polyamine based on polypropylene, polybutene or polyisobutene having Mn = 300 to 5000 as gasoline fuel additive having polar units (a).   The fuel composition according to claim 2, wherein the gasoline fuel additive having a polar unit (b) contains a reaction product of polyisobutene having an average degree of polymerization P of 5 to 100 and nitrogen oxide or a mixture of nitrogen oxide and oxygen. .   As a gasoline fuel additive having a polar unit (c), mainly contains a reaction product of polyisobutene epoxide obtained from polyisobutene having a terminal double bond and Mn = 300 to 5000 and ammonia, monoamine or polyamine The fuel composition according to claim 2. As a gasoline fuel additive having a polar unit (d), it has a total molecular weight of 500 to 20000, part or all of the carboxyl groups are converted to alkali metal salts or alkaline earth metal salts, and the remaining carboxyl groups are alcohol or reacted with an amine, C 2 _-C 40 _- olefin with claim 2 fuel composition according containing copolymer of maleic anhydride.   The fuel composition according to claim 2, comprising an alkali metal salt or alkaline earth metal salt of sulfosuccinic acid alkyl ester as a gasoline fuel additive having a polar unit (e). As gasoline fuel additive having polar units _{(f), C 2 ~C 30} - _alkanols, C 6 _{-C 60} - alkanediol, mono- - or di _-C 2 _{-C 30} - alkyl _amines, C 1 _{-C 30} - Alkylcyclohexanol or C ₁ -C ₃₀ -alkylphenol is reacted with 1 to 30 mol of ethylene oxide and / or propylene oxide and / or butylene oxide per hydroxyl group or amino group, and in the case of polyetheramine, ammonia, monoamine 3. The fuel composition according to claim 2, further comprising a polyether obtained by reductive amination with a polyamine or a polyetheramine.   3. The fuel composition according to claim 2, comprising a mono-, di- or tricarboxylic acid and a long-chain alkanol or polyol ester as a gasoline fuel additive having a polar unit (g).   As a gasoline fuel additive having polar units (h), obtained by reacting a general or highly reactive polyisobutene with Mn = 300-5000 with maleic anhydride by thermal methods or via chlorinated polyisobutene The fuel composition according to claim 2, comprising a derivative of polyisobutenyl succinic anhydride.   The fuel composition according to claim 2, comprising a reaction product of polyisobutene-substituted phenol, formaldehyde and monoamine or polyamine as a gasoline fuel additive having polar unit (i).   The fuel composition according to any one of claims 1 to 11, comprising a gasoline fuel having an olefin content of at most 21% by volume based on the volume of the non-added lower alkanol-free gasoline fuel.   13. The fuel composition according to any one of claims 1 to 12, comprising a gasoline fuel having a benzene content of at most 1.0% by volume with respect to the volume of the non-added lower alkanol-free gasoline fuel.   14. The fuel composition according to any one of claims 1 to 13, comprising a gasoline fuel having an oxygen content of up to 2.7% by volume relative to the volume of the non-added lower alkanol-free gasoline fuel.   The fuel composition according to any one of claims 1 to 14, comprising a gasoline fuel having an aromatic compound content of up to 42% by volume relative to the volume of the non-added lower alkanol-free gasoline fuel.   The fuel composition according to any one of claims 1 to 15, which contains a gasoline fuel additive having polar units (a) to (i) in an amount of 1 to 5000 ppm by mass.   Improves the action of additives having a cleansing or anti-valve wear effect, wherein the additive has at least one hydrophobic hydrocarbon group having a number average molecular weight (MN) of 85-20000 and at least one polar unit Use of lower alkanols in low sulfur gasoline fuels having a sulfur content of up to 150 ppm by weight.   The method for improving the additive action of additives having a cleansing action or valve seat wear prevention action according to claim 1 in low sulfur gasoline fuel by mixing gasoline fuel with an effective amount of lower alcohol.   At least one hydrophobic hydrocarbon group with an additive having a number average molecular weight (MN) of 85 to 20000 for reducing combustion chamber deposits and / or reducing deposits in a gasoline engine inhaler And the use of a combination of at least one additive having a cleaning action or anti-valve wear action and a lower alcohol having at least one polar unit.   As a valve seat antiwear agent for gasoline fuel, the additive has at least one hydrophobic hydrocarbon group having a number average molecular weight (MN) of 85 to 20000 and at least one polar unit, and has a valve seat antiwear effect Use of a combination of additives and lower alcohols.