EP0464489B1 - Ester containing fuels, for spark ignition- and diesel engines - Google Patents

Description

The invention relates to fuels for gasoline engines or diesel engines which contain small amounts of esters of alkylalkanolamines or alkylaminopolyalkylene glycols with polycarboxylic acids as additives.

Carburetors and lapping systems of gasoline engines, but also injection systems for fuel metering in gasoline and diesel engines, are increasingly contaminated by contaminants caused by dust particles from the air, unburned hydrocarbon residues from the combustion chamber and the crankcase ventilation gases that are led into the carburetor.

These residues shift the air-fuel ratio at idle and in the lower part-load range, so that the mixture is richer, the incomplete combustion and, in turn, the proportions of unburned or partially burned hydrocarbons in the exhaust gas increase and the gasoline consumption increases.

It is known that in order to avoid these disadvantages, fuel additives are used to keep valves and carburetor or injection systems clean (see, for example: M. Rossenbeck in catalysts, surfactants, mineral oil additives, ed. J. Falbe, U. Hasserodt, p. 223 f ., G. Thieme Verlag, Stuttgart 1978).

Depending on the mode of action, but also on the preferred place of action of such detergent additives, a distinction is made between two generations.

The first additive generation could only prevent the formation of deposits in the intake system, but not remove existing deposits, whereas the modern additives of the second generation can do both ("keep-clean" and "clean-up effect"), in particular due to their improved thermostability in zones of higher temperatures, namely in the in-valve.

In addition to products based on polyisobutenes, amides, imides and imide / amides of various carboxylic acids and polycarboxylic acids have proven themselves as representatives of the second generation of additives.

Of particular note here are the known active ingredients based on certain amino acid derivatives (for example ethylenediaminetetraacetic acid) and higher amines (EP 0 006 527).

These products are often difficult to handle due to their consistency; it is mostly highly viscous, pasty or even solid substances that almost always have to be formulated in conjunction with a suitable solvent.

Esters of such, in particular higher, carboxylic acids with aliphatic alcohols are used less frequently because of their often difficult preparative accessibility.

EP-A-117 108 discloses esters of monocarboxylic acids which are suitable as a "cold flow improver".

No. 3,426,062 describes esters of special halogen-containing polycyclic dicarboxylic acids which are already unfavorable as fuel additives due to their halogen content. US 3 183 070 and US 3 088 815 disclose esters of monoalkyl dihydroxyalkyl amines.

In other cases, e.g. When using certain polymer-based active ingredients, the formulations must contain higher-boiling, thermostable solvent components (e.g. mineral oils or synthetic oils) that facilitate the drainage of the products from the inlet valves.

Effects such as valve sticking and valve sticking have been observed in formulations without such additives.

It was therefore an object to provide fuel additives which outperform the known additives or which achieve the same effect with a lower dose and which are easy to handle at the same time.

in der
R₁ und R₂ einen C₆- bis C₃₀-Alkylrest,
R₃ den Hydroxylalkylrest der allgemeinen Formel II

   worin R₄ Wasserstoff oder einen C₁- bis C₆-Alkylrest und m die Zahlen von 0 bis 100 bedeuten,
wobei Kraftstoffe mit Reaktionsprodukten von Polyhalogenpolyhydropolycyclodicarbonsäuren, -anhydriden oder -estern mit N,N-Dicycloalkyl-alkanolaminen ausgeschlossen sind,
enthalten.It has now been found that fuels for gasoline engines and diesel engines have a very good cleaning effect for valves and carburetors of gasoline engines and injection systems for fuel metering in gasoline and diesel engines if they contain small amounts of esters of polycarboxylic acids with alkylalkanolamines or alkylaminopolyalkylene glycols as additives general formula I.

in the
R₁ and R₂ are a C₆ to C₃₀ alkyl radical,
R₃ is the hydroxylalkyl radical of the general formula II

in which R₄ is hydrogen or a C₁- to C₆-alkyl radical and m is the number from 0 to 100,
fuels with reaction products of polyhalopolyhydropolycyclodicarboxylic acids, anhydrides or esters with N, N-dicycloalkylalkanolamines are excluded,
contain.

The amount of the ester according to the invention contained in the fuels is generally 10 to 5000 mg, preferably 50 to 2000 mg, in particular 100 to 1000 mg, of the ester per kg of fuel.

in der R₁ einen C₆- bis C₃₀-Alkylrest, vorzugsweise einen C₆- bis C₂₄-Alkylrest, insbesondere einen C₆- bis C₂₀-Alkylrest, und R⁵ einen C₆-bis C₃₀-Alkylrest, vorzugsweise einen C₆- bis C₂₄-Alkylrest, insbesondere einen C₆- bis C₂₀-Alkylrest, bedeuten, wobei R₁ und R₅ als Alkylreste gleich oder verschieden sein können, in an sich bekannter Weise die Alkylalkanolamine bzw. Alkylaminopolyalkylenglykole der allgemeinen Formel I her. Die Alkoxylierung wird gegebenenfalls in Gegenwart von Alkali wie Kalilauge, Natronlauge, Natriummethylat, zweckmäpig bei erhöhten Temperaturen, beispielsweise bei Temperaturen von 80 bis 160°C, vorzugsweise 100 bis 160°C durchgeführt.The ester additives to be used according to the invention are generally synthesized in several stages. In a first step, the mixture is expediently prepared by alkoxylation with alkylene oxides having 2 to 8 carbon atoms, preferably 2 to 6 carbon atoms, in particular 2 to 4 carbon atoms, or mixtures of these alkylene oxides of secondary amines of the general formula III

in which R₁ is a C₆ to C₃₀ alkyl radical, preferably a C₆ to C₂₄ alkyl radical, in particular a C₆ to C₂₀ alkyl radical, and R⁵ is a C₆ to C₃₀ alkyl radical, preferably a C₆ to C₂₄ alkyl radical, in particular one C₆- to C₂₀-alkyl radical, where R₁ and R₅ as alkyl radicals can be the same or different, the alkylalkanolamines or alkylaminopolyalkylene glycols of the general formula I in a manner known per se. The alkoxylation is optionally carried out in the presence of alkali such as potassium hydroxide solution, sodium hydroxide solution, sodium methylate, expediently at elevated temperatures, for example at temperatures from 80 to 160 ° C., preferably 100 to 160 ° C.

Suitable alkylene oxides are, for example, ethylene oxide, propylene oxide, 1,2-butylene oxide, isobutylene oxide, 1,2-pentene oxide, ethylene oxide being preferred.

Examples of amines III which may be mentioned are dihexylamine, dicyclohexylamine, dioctylamine, didecylamine, diisotridecylamine, dicetylamine, distearylamine, dicerylamine.

To prepare the alkylalkanolamines I, the amine is reacted in a manner known per se, for example in the presence of water, with 1 mol of alkylene oxide or a mixture of alkylene oxides per 1 mol of secondary amine III (see, for example, SP McManus et al. Synth. Commun. 1973, 177).

To prepare the alkylaminopolyalkylene glycols I, the alkylalkanolamines obtained in this way are expediently reacted with an amount of alkylene oxides such that m in the hydroxyalkyl radicals of the alkylaminopolyalkylene glycols obtained means the numbers 1 to 100, preferably 1 to 50, in particular 1 to 30.

The compounds of formula I obtained are then in a further step to the esters of polycarboxylic acids according to known methods of ester formation, e.g. implemented by esterification processes or transesterification processes. The methods of ester formation are e.g. in Houben-Weyl, Methods of Organic Chemistry, Volume VIII, Oxygen Compounds III (1952), pages 516 to 555.

The ester formation is generally carried out at temperatures from 40 to 220 ° C., preferably 50 to 200 ° C., in particular 60 to 180 ° C. The esterification can be carried out with and without a catalyst. The esterification is preferably carried out in the presence of acidic catalysts, e.g. Mineral acids such as sulfuric acid, phosphoric acid, p-toluenesulfonic acid, and Lewis acids such as BF₃, dibutyltin dilaurate. It may be advantageous to remove the water formed during the esterification by azeotropic distillation by carrying out the esterification in the presence of a volatile, water-insoluble diluent such as benzene, toluene, xylene or else chloroform and carbon tetrachloride.

The esters are conveniently prepared via transesterification, starting from the esters of polycarboxylic acids with lower alcohols such as methanol, ethanol, propanol, by reacting them with the compounds of the general formula I in the presence of basic or acidic catalysts, preferably Lewis acidic catalysts, with expedient removal by distillation of the lower alcohol released.

Suitable carboxylic acids on which the esters are based are, for example, aliphatic, cycloaliphatic and aromatic polycarboxylic acids, which can also be substituted, for example as hydroxypolycarboxylic acids or amino, imino and nitrilopolycarboxylic acids. In general, the carboxylic acids have 4 to 26, preferably 5 to 20, carbon atoms. The polycarboxylic acids which are preferably used are generally those having 2 to 6, preferably 2 to 4, carboxyl groups.

Suitable aliphatic polycarboxylic acids are e.g. Dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and citric acid. Aromatic polycarboxylic acids include e.g. Phthalic acid, terephthalic acid, isophthalic acid, trimellitic acid, hemimellitic acid, trimesic acid, pyromellitic acid, mellitic acid into consideration.

Other suitable polycarboxylic acids are nitrilotriacetic acid and ethylenediaminetetraacetic acid.

The esters according to the invention are generally obtained as colorless to light yellow, in some cases. viscous, oily products, which are often similar to lubricants in their physical properties.

The most striking and surprising property of the esters according to the invention is their excellent thermal stability, which results from the results of thermogravimetric or differential thermal analysis.

It was surprising that the esters according to the invention can be prepared in a simple manner in good yield from the higher carboxylic acids and the aminoalkanol compounds I, since it was known that esters of such carboxylic acids with aliphatic alcohols, i.e. Alcohols that do not contain amino groups are often difficult to obtain from a preparative perspective.

It can be advantageous to combine the esters added as detergent additives with so-called carrier oils. The carrier oils have an additional washing function, often also a synergistic effect in combination with the detergents. The carrier oils are usually high-boiling, viscous, thermostable liquids. They coat the hot metal surface (e.g. the inlet valves) with a thin film of liquid and thereby prevent or delay the formation or deposition of decomposition products on the metal surfaces. In practice, high-boiling, refined mineral oil fractions (mostly vacuum distillates) are often used as carrier oils. A particularly good carrier oil is Brightstock in combination with low-boiling, highly refined lubricating oil fractions. Synthetic components have also been used as carrier oils. Esters in particular have been described as suitable carrier oils (e.g. DE 10 62 484, DE 21 29 461 and DE 23 04 086).

The carrier oils are generally added to the fuels in an amount of 50 to 5000 mg, preferably 100 to 2000 mg, of carrier oil per kg of fuel.

The ester is tested as an additive, particularly for its suitability as a valve and carburetor cleaner, by means of a motor test according to CEC-F-02-T 79 in an Opel Kadett 1.2-1 engine.

A) Manufacturing examples

• 1. Production of alkyl dialkanolamines or dialkylalkanolamines
  The alkylamine or dialkylamine together with 5% by weight of water are placed in a pressure vessel. It is purged several times with nitrogen and, depending on the type of alkyl oxide used, is preheated to the appropriate temperature, for example:
  for ethylene oxide at 120 to 125 ° C,
  for propylene oxide at 130 to 135 ° C,
  for butylene oxide at 140 to 150 ° C.
  Then, with stirring, the alkylene oxide in a 10 mol% excess, based on the NH bonds of the amine to be reacted, is fed in at a pressure of 10 to 30 bar. Primary amines are alkoxylated twice.
  After the reaction has ended i.Vac. volatile components and water completely removed.
  The β-aminoalkanols thus obtained are used for the esterification.
• 2. Production of alkylamino-bis-polyalkylene glycols or dialkylamino-polyalkylene glycols
  A dewatered mixture of the β-aminoalkanol from Example 1 and KOH used as starter is placed in a pressure vessel, the amount of KOH used being approximately 0.1% of the total weight of the reaction product to be expected. It is flushed with nitrogen several times, preheated to the temperatures given in Example 1 and then, with stirring at constant temperature and a pressure between 10 and 30 bar, the alkylene oxide is fed in continuously or batchwise, via an immersion tube or onto the surface, until the desired viscosity is reached is.
  Volatile constituents are removed completely in vacuo and, if necessary, the reaction product is clarified by filtration.
• 3. Implementation of adipic acid with diisotridecylethanolamine
  1 mole of adipic acid, 2.1 moles of diisotridecylethanolamine obtained according to the preparation method of Example 1, 1 g of dibutyltin dilaurate and 1.5 l of xylene are mixed and heated under reflux using a water separator until the theoretical amount of water has separated.
  The solvent is removed by distillation, lastly by applying a water jet vacuum; if necessary, filter. The adipic acid diester is obtained as a yellow oil.
• 4. Implementation of trimellitic anhydride with diisotridecylethanolamine
  In an analogous manner as described in Example 3, the corresponding trimellitic acid triester is obtained from 1 mol of trimellitic anhydride and 3.1 mol of diisotridecylethanolamine.
• 5. Implementation of ethylenediaminetetraacetic acid with diisotridecylethanolamine
  In an analogous manner as described in Example 3, the corresponding tetraester is obtained from 1 mol of ethylenediaminetetraacetic acid and 4.2 mol of diisotridecylethanolamine.

B) Examples of use

The following table shows the results of the application tests. The effect of known detergents and the carboxylic acid alkanolamine esters used according to the invention are also compared here, also in combination with synthetic carrier oils in gasoline for internal combustion engines. The amounts of detergents and carrier oils specified in the table were added to premium petrol (unleaded, RON 95) according to DIN 51607, which was used in test bench tests with a 1.2-1 Opel Kadett engine according to CEC-F-02-T-79 were. The reference oil RL 51 was used as engine oil.

The amounts of detergents refer to pure active substances without solvents.

Claims (3)

1. A fuel for gasoline and diesel engines, comprising small amounts of esters of polycarboxylic acids with alkylalkanolamines or alkylaminopolyalkylene glycols of the general formula I

   

   where R₁ and R₂ are each C₆-C₃₀-alkyl and
   R₃ is the hydroxyalkyl radical of the general formula II

   

   where R₄ is hydrogen or C₁-C₆-alkyl and m is from 0 to 100,
   subject to the proviso that fuels comprising reaction products of polyhalopolyhydropolycyclodicarboxylic acids, anhydrides or esters with N,N-dicycloalkylalkanolamines shall be excluded.
2. A fuel as claimed in claim 1 comprising esters which are derived from polycarboxylic acids having from 2 to 4 carboxyl groups.
3. A fuel as claimed in claims 1 and 2 comprising from 10 to 5000 mg of the ester per kg of fuel.