EP0410202B1 - Additive for liquifiedgas-fuel - Google Patents

Abstract

An additive for liquefied-gas fuels for corrosion protection, ageing protection, prevention of the precipitation of deposits on engine components and maintaining cleanliness of the exhaust gas from internal combustion engines run with the liquefied gas is characterised by a content of a) 30 to 60 % by volume of at least one nitrogen-containing solvent, b) 30 to 60 % by volume of at least one nitrogen-containing dispersant, c) 0.5 to 10 % by volume of at least one nitrogen-containing corrosion inhibitor and d) 0.5 to 10 % by volume of at least one oxidation inhibitor. <IMAGE>

Description

The invention relates to an additive for liquid gas fuels for corrosion protection, aging protection, preventing the deposition of deposits on engine parts and keeping the exhaust gas clean from internal combustion engines operated with the liquid gas, in particular gas engines.

In view of dwindling resources and increased environmental awareness, there is a strong need to use not only liquid mineral oil components, such as the gasoline normally used, as fuels for internal combustion engines, but also on the large quantities of natural gas that are present to fall back on, in particular in the form of liquefied natural gas, hereinafter referred to as liquefied gas. The normally available liquid gases contain mixtures of C⁷- and / or C⁸-alkanes, such as propane, butane or isobutane, which products in oil refineries as a by-product in the distillation and cracking of natural gas as well as in the processing of natural gas attack. The constituents propane, butane and isobutane can be contained in any proportions in the liquid gas and, because they contain little or no sulfur-containing or nitrogen-containing constituents, only give water and carbon dioxide as combustion products.

When storing fuels such as petrol, diesel oil and liquid gas, both in the storage tanks of the refineries, the petrol stations and the motor vehicles operated with them, polymerisation and oxidation reactions can occur, in which resinous or rubber-like precipitates are formed, which cause the Transport of the liquid gas through fuel lines, carburettors, injection pumps, injectors and vaporizers can impair and cause deposits in these devices. It is known that this problem can be counteracted in the case of liquid mineral petroleum fuels by adding additives, for which purpose in particular oxidation stabilizers, such as long-chain fatty amines, and dispersants, in particular surface-active agents, which stabilize the insoluble constituents, are used.

From DE-PS 33 01 840, an additive for liquid hydrocarbon fuels is already known which contains an alcohol with no more than 4 carbon atoms, an aliphatic ester with no more than 6 carbon atoms, an aromatic hydrocarbon, a halogenated alkene Contains 3 or fewer carbon atoms in the alkene chain, an aliphatic hydrocarbon with a 50% boiling point between 115 ° and 182 ° C and a hydroxy-substituted, unsaturated acid with 16 to 24 carbon atoms. This additive can be used especially for petrol and diesel ωl to improve combustion efficiency and for clean combustion.

The liquid gas available from the refineries contains small amounts of unsaturated compounds which, as a result of polymerization and oxidation reactions, form resinous, lacquer-like and also acidic substances which are deposited in the entire liquid gas system and cause corrosion can. In particular, these substance mixtures accumulate in the evaporator system of the liquid gas internal combustion engine and are solidified there due to the high temperatures and a sufficiently long dwell time, and are deposited in the form of solid, hard-to-remove deposits. In addition, engine pollution from the aged liquefied petroleum gas increases in the area of the intake system, which also has an unfavorable influence on the exhaust gas composition with regard to hydrocarbons and carbon monoxide.

For liquid gas with its relatively low temperature, which can reach as low as -50 ° C when evaporating, the additives used for the normal fuels which are liquid under ambient conditions have proven to be unsuitable because, due to their insufficient volatility does not evaporate with the liquid gas and accumulate in the fuel tank.

From US-A-2 641 539 a method for preventing the discoloration of fuel oils with boiling points above the gasoline range is known, which consists in adding a certain additive mixture which is a condensation product of a benzaldehyde and an alkanolamine, an alkanolamine with 8 contains up to 40 carbon atoms per molecule, an alkylamine with 6 to 20 carbon atoms per molecule and a metal deactivator.

US-A-3 860 430 describes film-forming amine emulsions which contain an aliphatic film-forming amine and a tertiary amine containing polyoxyalkylene groups as the dispersant. These emulsions serve to form a protective coating against the corrosive attack of metal surfaces exposed to aqueous media.

The object of the present invention is now to provide an additive for liquid gas fuels with which these problems can be solved, that is to say the formation of resin-like or rubber-like precipitates during the storage of the liquid gas and the deposition of these products in the fuel lines, the evaporator system, the injectors and the valves can be prevented and the exhaust gas quality can be improved.

This task is now solved by the additive according to the main claim. The subclaims relate to particularly preferred embodiments of this subject matter of the invention.

• a) 30 bis 60 Vol.-% mindestens eines stickstoffhaltigen Lωsungsmittels, ausgew{hlt aus der Gruppe, die Formamidderivate, Thioformamidderivate, N-Alkylpyrrolidonderivate mit 1 oder 2 Kohlenstoffatomen im Alkylrest, Acetamidderivate, sek.-N-Alkanolamine, tert.-N-Alkanolamine mit jeweils 1 bis 4 Kohlenstoffatomen im Alkylrest und Nitroparaffine mit 1 bis 8 Kohlenstoffatomen umfaßt,
• b) 30 bis 60 Vol.-% mindestens eines stickstoffhaltigen Dispergiermittels, ausgew{hlt aus der Gruppe, die Morpholin, Morpholinderivate, Thiomorpholin, Thiomorpholinderivate und Cyclohexylamin umfaßt,
• c) 0,5 bis 10 Vol.-% mindestens eines stickstoffhaltigen Korrosionsschutzmittels, ausgew{hlt aus der Gruppe, die prim{re, sekund{re und terti{re Alkylamine mit 6 bis 14 Kohlenstoffatomen in den Alkylgruppen und Alkylendiamine mit 3 bis 6 Kohlenstoffatomen im Alkylenrest und
• d) 0,5 bis 10 Vol.-% mindestens eines Oxidationsinhibitors, mit der Maßgabe, daß die Summe der Bestandteile 100 Vol.-% betr{gt.

The invention thus relates to an additive for liquid gas fuels, which is characterized by a content of

• a) 30 to 60% by volume of at least one nitrogenous solvent, selected from the group consisting of the formamide derivatives, thioformamide derivatives, N-alkylpyrrolidone derivatives with 1 or 2 carbon atoms in the alkyl radical, acetamide derivatives, sec.-N-alkanolamines, tert.-N Alkanolamines each having 1 to 4 carbon atoms in the alkyl radical and nitroparaffins having 1 to 8 carbon atoms,
• b) 30 to 60% by volume of at least one nitrogenous dispersant selected from the group comprising morpholine, morpholine derivatives, thiomorpholine, thiomorpholine derivatives and cyclohexylamine,
• c) 0.5 to 10% by volume of at least one nitrogen-containing corrosion inhibitor, selected from the group consisting of primary, secondary and tertiary alkylamines with 6 to 14 carbon atoms in the alkyl groups and alkylene diamines with 3 to 6 Carbon atoms in the alkylene radical and
• d) 0.5 to 10% by volume of at least one oxidation inhibitor, with the proviso that the sum of the components is 100% by volume.

According to a preferred embodiment of the invention, the additive contains 40 to 50% by volume of the nitrogenous solvent, 40 to 50% of the nitrogenous dispersant, 1 to 5% by volume of the nitrogenous corrosion inhibitor and 1 to 5% by volume .-% of the oxidation inhibitor.

It is advantageous to use a material with a maximum molecular weight of 120 as the nitrogen-containing solvent a) or as the nitrogen-containing dispersant b), since this ensures that these constituents are not present in the liquid gas container when the liquid gas evaporates from it Collect containers. The nitrogen-containing corrosion inhibitor c) and the oxidation inhibitor d) generally have higher boiling points, but are contained in such small amounts in the additive and in particular in the liquid gas that they are entrained by the liquid gas and likewise do not accumulate.

In addition to the essential constituents a) to d), the additive according to the invention may also contain additional constituents, such as dyes, odor improvers and agents for inhibiting heavy metals, such as for example copper, in each case in amounts of 0.1 to 5% by weight, based on the mixture of components a) to d).

The additive is either in the form of a mixture of the essential components or in the form of a solution in an alkanol having 1 to 4 carbon atoms, preferably with a content of 50 to 200% by volume of the alkanol, based on 100% by volume of the components a) to d), in particular in the form of a 1: 1 solution in methanol, ethanol, propanol, isopropanol and / or butanol.

The additive according to the invention is added to the liquid gas in an amount of 25 to 1000 ppm, more preferably 50 to 400 ppm, calculated as a mixture of the components a) to d).

The additive according to the invention contains as nitrogen-containing solvent a) at least one compound selected from the formamide derivatives, thioformamide derivatives, N-alkyl-pyrrolidone derivatives with 1 or 2 carbon atoms in the alkyl radical, acetamide derivatives, sec. -N-alkanolamines and tert. -N-alkanolamines each having 1 to 4 carbon atoms in the alkyl radical and nitroparaffins having 1 to 8 carbon atoms. Particular preference is given to using the nitrogen-containing solvent a) methylformamide, dimethylformamide, ethylformamide, diethylformamide, methylethylformamide, ethylpropylformamide, methylthioformamide, dimethylthioformamide, ethylthioformamide, diethylthioformamide, methylethylthioformamide, ethylpropylthioformamide, 2-methyl-n-solid, N-methyl-n-methyl-N-methyl-N-methyl-N-methyl -Ethyl-2-pyrrolidone, methylacetamide, dimethylacetamide, ethyl acetamide, diethylacetamide, bis (2-hydroxyethyl) amine, bis (3-hydroxypropyl) amine, bis (4-hydroxybutyl) amine, 2-hydroxyethyl-3-hydroxypropylamine, Hydroxymethyl-4-hydroxybutylamine, 2-hydroxyethyl-4-hydroxybutylamine, tris (2-hydroxyethyl) amine, tris (3-hydroxypropyl) amine, tris (4-hydroxybutyl) amine, 2-hydroxyethyl-3-hydroxypropyl -4-hydroxybutylamine, bis (2-hydroxyethyl) -3-hydroxypropylamine, nitromethane, nitroethane, nitropropane, nitrobutane, nitropentane, nitrohexane, nitroheptane and nitrooctane, as well as the nitroderivatives of the corresponding isomers of these compounds.

The additive claimed contains, as nitrogenous dispersant b), morpholine, morpholine derivatives, thiomorpholine, thiomorpholine derivatives and cyclohexylamine. Examples of morpholine derivatives are N-methylmorpholine, N-ethylmorpholine, N-propylmorpholine, N-formylmorpholine, N-acetylmorpholine, N-propionylmorpholine, N-methylthiomorpholine, N-ethylthiomorpholine, N-formylthiomorpholine and N-acetylthiomoline. More preferred nitrogen-containing solvents a) are dimethylformamide and dimethylacetamide.

Morpholine is particularly preferred according to the invention.

As a nitrogen-containing corrosion inhibitor c), the additive claimed contains primary, secondary and tertiary alkylamines with 6 to 14 carbon atoms in the alkyl groups and alkylenediamines with 3 to 6 carbon atoms in the alkylene radical. Primary alkylamines having 12 to 14 carbon atoms in the alkyl radicals, and also propylenediamine, ethylenediamine and hexylenediamine are particularly preferred.

As a nitrogen-containing oxidation inhibitor d), the additive of the invention can preferably be representatives from the diphenylamine, alkyl-diphenylamine derivatives with 3 to 6 carbon atoms in the alkyl radical, thiodiphenylamine, alkylthiodiphenylamine derivatives with 3 to 6 carbon atoms in the alkyl radical, diaminobenzene derivatives and diaminoalkylbenzene derivatives with 3 to 8 carbon atoms in the alkyl radical , specifically 2,4,6-tri-tert-butylphenol, 2,4-di-tert-butylphenol, 2-tert-butylphenol or mixtures thereof, and 2,4,6, -tri-tert-octyl- phenol, and alkyl salicylates containing 3 to 6 carbon atoms in the alkyl group.

The nitrogen-containing solvent a) used according to the invention brings about the solution of the possibly formed, insoluble oxidation products and prevents their deposition on the surfaces which come into contact with the liquid gas.

The nitrogen-containing dispersing or wetting agent b) keeps the possibly present impurities, which are not or only colloidally soluble, in suspension or in the form of an emulsion, influences the surface tension and promotes combustion and provides vapor phase corrosion protection.

The nitrogen-containing corrosion inhibitor c) prevents the corrosion of the surfaces coming into contact with the liquid gas by cation activity on the surfaces and by binding of oxygen, carbon dioxide and moisture and by neutralization of acidic groups such as sulfate groups or reactive functional groups.

The oxidation inhibitor d) serves to suppress polycondensation and to polymerize the portions with double bond and multiple double bond present in the liquid gas.

It has been shown that the combination of active ingredients according to the invention a) to d) have a synergistic effect in which not only the corrosion of metal parts in contact with the liquid gas is prevented and the deposition of resinous deposits in the evaporator and on the valves of the internal combustion engine are prevented, but that one unexpectedly significant improvement in the exhaust gas composition is achieved.

The following example serves to further explain the invention and to prove this fact. The invention is therefore explained in more detail below with reference to the following example and the attached drawing.

• Fig. 1 die Wirkung des erfindungsgem{ßen Additivs auf den CO-Ge halt des Abgases eines mit einem Fl}ssiggas betriebenen Verbrennungsmotors
  und
• Fig. 2 die Wirkung des erfindungsgem{ßen Additivs auf den Kohlenwasserstoff-Gehalt (HC) des Abgases eines mit einem Fl}ssiggas betriebenen Verbrennungsmotors.

The drawing shows:

• 1 shows the effect of the additive according to the invention on the CO content of the exhaust gas of an internal combustion engine operated with a liquid gas
  and
• 2 shows the effect of the additive according to the invention on the hydrocarbon content (HC) of the exhaust gas of an internal combustion engine operated with a liquid gas.

example

An additive is formed by mixing the following components:
44.5% by volume of dimethylformamide
47.5 vol% morpholine
4.0% by volume of a mixture of primary alkylamines having 12 to 14 carbon atoms in the alkyl radical (Primene 81-R) and
4.0% by volume of a mixture of 75% 2,6-di-tert-butylphenol and 25% of a mixture of 2,4,6-tri-tert-butylphenol, 2,4-di- tert-butyl phenol and 2-tert-butyl phenol.

This additive mixture is added to a commercially available liquid gas in an amount of 250 ppm. A test engine based on the Euro standard CECT-02-T79 is operated with the liquid gas treated in this way with the additive. Even after a 40-hour engine run, no deposits can be found on the surface of the evaporator or on the valve plates.

During the operation, the exhaust gas composition with regard to the content measured on carbon monoxide (CO in vol .-%) and on hydrocarbons (HC in ppm). During the measurements, the oil temperature was kept constant at 90 ° C and the cooling temperature between 92 ° and 96 ° C.

The results obtained are summarized in the table below:

A graphic representation of these results is shown in the drawing. 1 shows the influencing of the CO content of the exhaust gas by the additive according to the invention and FIG. 2 shows the influencing of the hydrocarbon content of the exhaust gas by the additive according to the invention. As can be seen, there is a surprising improvement in the exhaust gas composition Use of the additive according to the invention.

In further investigations, it was found that after storage of the additive-containing liquid gas in comparison with the additive-free liquid gas, storage was prevented for 48 hours and corrosion caused by contact with a liquid gas with a content of 0. 2% water with a pH of 5.0 is prevented.

Claims (10)

1. Additive for liquefied gas fuels, characterized by containing

   a) 30 to 60 vol.-% of at least one nitrogen-containing solvent selected from the group comprising formamide derivatives, thioformamide derivatives, N-alkyl-pyrrolidone derivatives with 1 or 2 carbon atoms in the alkyl residue, acetamide derivatives, sec.-N-alkanolamines, tert.-N-alkanolamines with 1 to 4 carbon atoms each in the alkyl residue, and nitroparaffins with 1 to 8 carbon atoms,

   b) 30 to 60 vol.-% of at least one nitrogen-containing dispersing agent selected from the group comprising morpholine, morpholine derivatives, thiomorpholine, thiomorpholine derivatives, and cyclohexylamine,

   c) 0.5 to 10 vol.-% of at least one nitrogen-containing corrosion inhibitor selected from the group comprising primary, secondary and tertiary alkylamines with 6 to 14 carbon atoms in the alkyl groups and alkylenediamines with 3 to 6 carbon atoms in the alkylene residue, and

   d) 0.5 to 10 vol.-% of at least one oxidation inhibitor, with the condition that the sum of the constituents is 100 vol.-%.
2. The additive according to claim 1, characterized by containing

   a) 40 to 50 vol.-% of the nitrogen-containing solvent,

   b) 40 to 50 vol.-% of the nitrogen-containing dispersing agent,

   c) 1 to 5 vol.-% of the nitrogen-containing corrosion inhibitor, and

   d) 1 to 5 vol.-% of the oxidation inhibitor.
3. The additive according to claim 1, characterized in that the nitrogen-containing solvent a) has a maximum molecular weight of 120.
4. The additive according to claim 1 or 2, characterized in that the nitrogen-containing dispersing agent b) has a maximum molecular weight of 120.
5. The additive according to claim 1, characterized in that the nitrogen-containing solvent a) is selected from the group comprising methylformamide, dimethylformamide, ethylformamide, diethylformamide, methylethylformamide, ethylpropylformamide, methylthioformamide, dimethylthioformamide, ethylthioformamide, diethylthioformamide, methylethylthioformamide, ethylpropylthioformamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, methylacetamide, dimethylacetamide, ethylacetamide, diethylacetamide, bis(2-hydroxyethyl)amine, bis(3-hydroxypropyl)amine, bis(4-hydroxybutyl)amine, 2-hydroxyethyl-3-hydroxypropylamine, hydroxymethyl-4-hydroxybutylamine, 2-hydroxyethyl-4-hydroxybutylamine, tris(2-hydroxyethyl)amine, tris(3-hydroxypropyl)amine, tris(4-hydroxybutyl)amine, 2-hydroxyethyl-3-hydroxypropyl-4-hydroxybutylamine, bis(2-hydroxyethyl)-3-hydroxypropylamine, nitromethane, nitroethane, nitropropane, nitrobutane, nitropentane, nitrohexane, nitroheptane and nitrooctane, as well as the nitro derivatives of the corresponding isomers of these compounds.
6. The additive according to at least one of the preceding claims, characterized in that it contains as dispersing agent b) at least one representative of the group comprising N-methylmorpholine, N-ethylmorpholine, N-propylmorpholine, N-formylmorpholine, N-acetylmorpholine, N-propionylmorpholine, N-methylthiomorpholine, N-ethylthiomorpholine, N-formylthiomorpholine, and N-acetylthiomorpholine.
7. The additive according to claim 1, characterized in that it contains as nitrogen-containing corrosion inhibitor c) at least one primary alkylamine with 12 to 14 carbon atoms in the alkyl radical, propylene diamine, ethylene diamine and/or hexylene diamine.
8. The additive according to at least one of the preceding claims, characterized in that it contains as oxidation inhibitor d) at least one representative from the group comprising diphenylamine, alkyl-diphenylaminederivatives with 3 to 6 carbon atoms in the alkyl residue, thiodiphenylamine, alkyl-thiodiphenylamine derivatives with 3 to 6 carbon atoms in the alkyl residue, diaminobenzene derivatives and diaminoalkylbenzene derivatives with 3 to 8 carbon atoms in the alkyl radical, alkylphenol derivatives, namely 2,4,6-tri-tert.-butylphenol, 2,4-di-tert.-butylphenol, 2-tert.-butylphenol or mixtures thereof, as well as 2,4,6-tri-tert.-octyl-phenol, and alkylsalicylates with 3 to 6 carbon atoms in the alkyl residue.
9. The additive according to at least one of the preceding claims, characterized by containing as additional constituents colorants, deodorants and/or agents to inhibit heavy metals in amounts of 0.1 to 5 wt.-% each relative to the mixture of constituents a) to d).
10. The additive according to at least one of the preceding claims, characterized by containing as a solvent 50 to 200 vol.-% of a C⁵-C⁸ alkanol relative to 100 vol.-% of the constituents a) to d).

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