EP0398100B1 - Fuel compositions containing alkoxylation products - Google Patents

Description

The invention relates to fuels for internal combustion engines with improved properties, containing alkoxylation products, by the reaction of oxo oils, fractions of these oxo oils or partially esterified carboxylic acids with oxo oils or oxo oil fractions, with alkylene oxides with 2 to 4 carbon atoms, in particular with propene oxide and / or butene oxides and / or be obtained in minor amounts of ethene oxide. In particular, the invention relates to fuel compositions for gasoline engines.

It is known that the addition of various additives to gasoline can improve the cleanliness of carburetors, injectors, intake pipes and intake valves and thereby reduce the emissions of undesirable components of the exhaust gases. In general, additive packages are added to gasoline in amounts of up to 2,500 mg / kg. These mostly consist of fuel detergents, corrosion inhibitors, oxidation inhibitors, anti-icing agents, carrier oils and solvents.

Carrier oils primarily have the task of preventing the so-called valve plugging and ensuring a better distribution of the detergents. In addition, polyethers and esters as carrier oils should reduce the increase in the octane requirement of engines with increasing number of operating hours and ultimately set the lowest possible level of octane requirement.

The use of esters as a gasoline additive has long been known and is described, for example, in DE-OS 21 29 461, DE-OS 19 64 785, DE-OS 23 16 535 or GB 21 17 468. Esters with more than 35 carbon atoms have a particularly good effect, particularly when the alcohol component is highly branched, ie has been prepared by oxidizing oligomers of propene and butenes, in particular of n-butenes. If aromatic tri- and tetracarboxylic acids are used, relatively short-chain alcohols can be used to achieve the desired molecular weight in acceptable condensation times and with normal catalyst removal. However, the high price of these poorly accessible acids is a serious economic disadvantage. The use of aromatic dicarboxylic acids such as phthalic acid is far more economical, but long-chain alcohols which are difficult to access are then required for the preparation of effective esters. High condensation temperatures give acceptable condensation times, but processing is very difficult and time-consuming.

The use of alkene oxide-based polyethers has also been known for a long time and e.g. described in DE-OS 21 29 461. Alkene oxides such as propene oxide and butene oxides are preferred here. However, only special polyethers containing predominantly butene oxides are infinitely miscible with polyisobutene and polyisobutene derivatives. Butene oxides are only available to a limited extent and the market price is correspondingly high.

The task was therefore to synthesize a highly effective, at least equivalent carrier oil at significantly lower costs and to avoid the disadvantages of ester synthesis with complete esterification or polyether production with an excess of alkoxide. Surprisingly, alkoxylation products from reaction products of alkene oxides with oxo oils, oxo oil fractions and carboxylic acids partially esterified with oxo oils combine all the advantages of esters and / or polyethers, and the cost of starting materials can be drastically reduced. The products are excellent carrier oils with partly high molecular weight, whereby up to 30% of the usual detergents can be saved without the gasoline quality, i.e. the purifying effect in the intake and mixture formation system deteriorates.

Accordingly, the invention relates to fuel compositions which contain small amounts, e.g. Contain 0.005 to 0.2% by weight of alkoxylation products, obtainable by reacting alkylene oxides with 2 to 4 carbon atoms, in particular propene oxide and / or butene oxides and / or in minor amounts of ethene oxide with oxo oils, oxo oil fractions or carboxylic acids partially esterified with oxo oils or oxo oil fractions, where the oxo oils are distillation residues from the production of oxo alcohols with more than 8 carbon atoms and the molar ratio of the alkylene oxides to the OH groups and free carboxyl groups in the oxo oil or ester is preferably from 0.2 to 30. The amount of alkoxides must be at least so large that all free carboxyl groups are alkoxylated, i.e. a molar ratio of alkene oxide to carboxyl groups of at least 2.

In the preparation of the alkoxylation products, propene oxide and butene oxides, in particular 1,2-butene oxide, are preferred as alkene oxides. However, ethene oxide can also be incorporated in minor amounts, for example up to 50 mol%, based on the total amount of carboxyl and hydroxyl groups, as long as this does not impair the compatibility of the components of gasoline additive packages. This is the case in particular in the case of production according to Example D. The use of pure ethylene oxide may even be economical here. The reaction with alkene oxides takes place in a manner known per se and is described, for example, in DE patent application P 38 26 608.3, preparation example 1.

The oxo oils or fractions used are distillation residues from the production of oxo alcohols with more than 8 carbon atoms. The oxo alcohols on which the oxo oils are based should in particular be branched with 13, 17, 21, 25, 29 and 33 carbon atoms and derive from oligomers of propene and from butenes, in particular from n-butenes, in order to ensure that the oxo oils are in a liquid state at room temperature. A low melting point well below zero ° C is an advantage, since the oxo oil behaves largely like its alcohol in this respect.

wobei n vorgenannte Bedeutung hat und in der Regel die Zahlen 9 bis 33 bedeutet. Diese Etheralkohole sind meist in Mengen von 30-60 % in den Oxoölen vorhanden und können gegebenenfalls destillativ abgetrennt werden. Aus wirtschaftlichen Gründen empfiehlt sich eine Isolierung der Etheralkohole mit nachfolgender Veresterung und/oder Veretherung für den vorliegenden Anwendungszweck jedoch nicht, es sei denn, qualitative Gründe sprechen dafür.The oxo oils, especially if they are derived from oligomers of propene or butenes, are mixtures of substances with far more than 20 compounds, some of which are only isomers. For example, the oxo oil of a di-butene contains acids, nonanols, decanediols, di-isononyl ethers, isononanoic acid nyl esters and large amounts of ether alcohols of the empirical formula C₁₉H₄₀O₂. The ether alcohols of the oxo oils have the general formula C _{2n + 1} H _{4n + 2} O₂, where n stands for the number of carbon atoms of the oxo alcohol. These ether alcohols are probably produced by etherification of a diol with an alcohol, ie in the case of dibutene from decanediol and nonanol. This leads to the presumed general formula of ether alcohol:

where n has the aforementioned meaning and generally means the numbers 9 to 33. These ether alcohols are usually present in the oxo oils in amounts of 30-60% and can optionally be separated off by distillation. For economic reasons, however, isolation of the ether alcohols with subsequent esterification and / or etherification is not recommended for the present application, unless there are qualitative reasons for this.

The partial esterification of the previously characterized oxo oils or oxo oil fractions can be carried out according to conventional esterification processes with aliphatic and aromatic carboxylic acids. Suitable aliphatic carboxylic acids are isononanoic acid, succinic acid, maleic acid and adipic acid, but also carboxylic acid mixtures, such as the dicarboxylic acid mixture of the production of adipic acid (mixture of adipic acid, succinic acid and glutaric acid) or the stripping acid of cyclohexane oxidation (mixture of adipic acid) and hydroxyapronic acid and hydroxyapronic acid. Aromatic di-, tri- or tetracarboxylic acids are o-phthalic acid, isophthalic acid, terephthalic acid, trimesic acid, trimellitic acid, pyromellitic acid and benzene tetracarboxylic acid.

Esterification with acid anhydrides, in particular phthalic anhydride, is particularly preferred. The acids or acid anhydrides are generally added during the esterification in amounts of 0.5 to 1.3 equivalents based on the hydroxyl number and with acid catalysts, such as titanium acid esters, but also without a catalyst at temperatures of 150 to 250 ° C. under vacuum or with Fumigation with nitrogen esterified. Processing by neutralization and washing is carried out according to conventional methods. In a preferred embodiment, the oxo oils are preferably esterified in the presence of KOH with 0.4 to 0.6 mol of phthalic anhydride, based on the OH number, and the condensation is terminated at acid numbers between 10 and 50 and, as described above, with alkene oxides without further KOH addition or drainage. In this way, time and cost-intensive neutralization and washing steps are avoided and alkene oxide consumption is minimized.

Fuels for internal combustion engines are organic, mostly hydrocarbon-containing liquids that are suitable for the operation of Otto, Wankel and diesel engines. In addition to fractions from crude oil processing, hydrocarbons from coal hydrogenation, alcohols of various origins and compositions and ethers such as Methyl tertiary butyl ether contained therein. The admissible mixtures are mostly nationally defined worldwide.

The alkoxylation products to be used according to the invention are usually the fuels together with fuel detergents, such as amines of oleic acid or ethylenediaminetetraacetic acid according to EP-A-6527, or the polyisobutenylsuccinic acid furthermore polyether polyamine carbamates, and in particular polybutenamines, obtained by reacting the alcohols or the corresponding halogen compounds with NH₃ , Aminoethylethanolamine, dimethylaminopropylamine, triethylene tetramine or tetraethylene pentamine, as described in US Pat. No. 3,275,354, DE-A-21 25 039, EP-A-244 616, corrosion inhibitors, which are mostly low molecular weight compounds with amide and / or ammonium and / or amine and / or acid groups or triazole and imidazole derivatives, furthermore phenolic or aminic antioxidants, such as di-tert-butylphenol or para-phenylenediamine, and finally freezing inhibitors, such as alcohols or diols. The combination of the alkoxylation products to be used according to the invention with polybutenamines is preferred, the quantitative ratio of the alkoxylation products to the polybutenamines generally being 1: 2 to 3: 1. A carrier oil combination with polyethers or mineral oil is also possible; this enables a reduction in the proportion of the alkoxylation products in relation to the polybutenamines, polyetherpolyamine carbamates or amides.

Although the reasons for the action of the alkoxylation products to be used are not known in detail, it can be stated that the effectiveness increases with increasing viscosity. As a result, the lower limit of the number of C atoms is not sharp and an upper limit solely by the viscosity, i.e. Manageability, cold stability (melting point) and the availability of the oxo oils are determined.

The following examples describe the production of some representative alkoxylation products according to the invention and their motor action in comparison to known additives.

Production example A

The distillation residue of a C₉-oxo alcohol, obtained from the cobalt-catalyzed oxidation of dibutene, is used to produce the alkoxylation product. The dibutene is produced from the so-called raffinate II, a mixture of approximately 30% butanes, 45% butene-1 and 25% cis and trans-butene-2. 1,000 g of this distillation residue, which has an OH number of 132, an acid number of 10, a density of 0.872 g / cm³ at 20 ° C and a viscosity of 27 mm² / s at 20 ° C, are in a stirred tank with 5 g of KOH flakes are added, the reaction vessel is flushed with nitrogen, evacuated to 10 mbar and heated to 120 ° C. under vacuum and the mixture is stirred for 2 hours. At 1.1 bar nitrogen pressure, the mixture is heated to 160 to 170 ° C. and 1,000 g of 1,2-butene oxide are gassed in so slowly that a pressure of 4.5 bar is not exceeded. When the gassing has ended, you wait until the pressure is constant, the pressure is released, unreacted butene oxide is distilled off and the mixture is cooled to room temperature. The KOH is then bound by customary methods, such as the addition of ion exchangers, phosphoric acid or phosphates, and the precipitate is filtered off. The polyether-containing mixture obtained has an OH number of 75, a density of 0.917 g / cm³ at 20 ° C and a viscosity of 71 mm² / s at 20 ° C.

Production example B

The procedure is as in Preparation A, but 400 g of distillation residue, 2 g of KOH flakes and 1,600 g of 1,2-butene oxide are used. The product has an OH number of 37, a density of 0.948 g / cm³ at 20 ° C and a viscosity of 385 mm² / s at 20 ° C.

Production example C

From the distillation residue of a C₁₀ oxo alcohol based on trimer propene, an ether alcohol C₂₁H₄₄O₂ is isolated by distillation and analogous to Preparation A with a mixture of 1,2-propene oxide and 1,2-butene oxide implemented. The OH number of the alcohol is 171, its density at 20 ° C 0.87 g / cm³ and its viscosity at 20 ° C 75 mm² / s. 500 g of the ether alcohol, 2.5 g of KOH, 500 g of 1,2-propene oxide and 1,000 g of 1,2-butene oxide are used for the reaction. The OH number of the reaction product is 48, its viscosity at 20 ° C was 320 mm² / s.

Production example D

400 g of a distillation residue of C₁₃-oxo alcohol synthesis from the trimers of an n-butene mixture, as described in Preparation A, with an OH number of 144, an acid number of 1.5, a density at 20 ° C of 0.863 g / cm³ and a viscosity at 20 ° C of 105 mm² / s are mixed with 75 g of phthalic anhydride and 2 g of flaky KOH and condensed at 180 ° C in a nitrogen stream for 5 hours. The acid number drops to 20. The nitrogen supply is stopped, the autoclave is closed and 150 g of 1,2-butene oxide 1,2 are added at 160 to 170 ° C. in such a way that 4.5 bar are not exceeded. After proceeding as described in Preparation A and distilling off 75 g of butene oxide, a product with a density of 0.924 g / cm³ at 20 ° C. and a viscosity of 398 mm² / s at 20 ° is obtained after removing the KOH C.

The following table shows the effect of known carrier oils and the alkoxylation products to be used according to the invention in combination with known detergents in gasoline for internal combustion engines. The quantities shown in the table were added unleaded premium petrol (RON 95; DIN 51 607) and tested in test bench tests with a 1.2 Opel Kadett engine in accordance with CEC-F-02-T-79. The reference oil RL 51 was used as engine oil.

The table shows a significantly better effect of the alkoxylation products according to the invention compared to the prior art, i.e. less deposits on the intake valves of the 1.2 l Opel Kadett engine.

Here, the carrier oils to be used according to the invention were combined with commercially available polybutenamine, produced from polybutene MG 1300 and aminoethylethanolamine, active substance content 50%. The recommended dosage of the commercial polybutenamine for formulations with mineral oil is 350 mg / kg. In contrast, the carrier oils according to the invention enable a saving of about 30% in polymeric detergents. Results with other higher viscosity detergents are comparable.

Another advantage of the new carrier oils is their compatibility with polyisobutene with a molecular weight of 800 to 2,000, which is contained in most of the detergents used for gasoline additives. Propene oxide-based polyethers are not very compatible; i.e. higher amounts of solvent are required to produce an additive package. The carrier oils according to the invention, the components of which are partly waste products or can be isolated therefrom, are significantly cheaper to produce than polyethers, especially if the latter are produced on the basis of butene oxide based on polyisobutene. Since the substance mixtures contain a number of low molecular weight compounds, particularly in the case of partial esterification, they are more suitable for combating valve plugging than pure polyethers with higher molecular weights.

Claims (11)

1. A fuel for internal combustion engines, containing small amounts of alkoxylation products, obtainable by reacting alkylene oxides of 2 to 4 carbon atoms with oxo oils or fractions of oxo oils or carboxylic acids partially esterified with oxo oils or fractions of oxo oils, wherein the oxo oils are distillation residues from the preparation of oxo alcohols of more than 8 carbon atoms.

2. A fuel for internal combustion engines, containing small amounts of alkoxylation products, as claimed in claim 1, obtainable by reacting propene oxide and/or butene oxide and/or minor amounts of ethene oxide with oxo oils or fractions of oxo oils or carboxylic acids partially esterified with oxo oils or fractions of oxo oils, wherein the oxo oils are distillation residues from the preparation of oxo alcohols of more than 8 carbon atoms.

3. A fuel as claimed in claim 1, which contains from 0.002 to 0.2% by weight of the alkoxylation products.

4. A fuel as claimed in claim 1, wherein the molar ratio of the alkylene oxides to OH groups and free carboxyl groups in the ester or oxo oil is up to 30, and the molar ratio of the alkylene oxides to the free carboxyl groups is not less than 2.

5. A fuel as claimed in claim 1, wherein the oxo oils consist of more than 50% by weight of an ether alcohol which has one ether group and one alcohol group and 2 n + 1 carbon atoms, where n is the number of carbon atoms of the oxo alcohol and is from 9 to 33.

6. A fuel as claimed in claim 1, wherein the oxo oils are distillation residues from the preparation of oxo alcohols from oligomers of propene and/or butenes.

7. A fuel as claimed in claim 1, wherein the oxo oils are distillation residues of oxo alcohols of oligomers of n-butenes.

8. A fuel as claimed in claim 1, wherein the oxo oil fractions comprise ether alcohols isolated from the oxo oil.

9. A fuel as claimed in claim 1, wherein the alkoxylation products are alkoxylation products of carboxylic acids partially esterified with oxo oils or ether alcohols obtained therefrom.

10. A fuel as claimed in claim 8, wherein carboxylic acid mixtures are used for the partial esterification.

11. A fuel as claimed in claim 1, which contains detergents, icing inhibitors, corrosion inhibitors and antioxidants in addition to the alkoxylation products.