Diesel fuel additives

Abstract: The invention provides the use of an effective concentration of a nitrogen-containing compound of general formula CH₃(CH₂) n -A-NH₂ (I) wherein n is 8 to 18 and A is -CH₂- or -CO-, or a mixture thereof as an additive in a diesel fuel comprising a major proportion of a diesel oil, for reducing fouling of injectors in diesel engines.

Description: This invention relates to diesel fuel additives, and more particularly to the use of certain nitrogen-containing compounds in diesel fuel to impart improved properties. W. German Patent Application S 34337 IVC/23b (DE OS 960,920) (Socony Mobil Oil Company) describes certain distilled fuels containing linear aliphatic primary monoamines having 7 to 18 carbon atoms per molecule. These fuels may be fuel oils, gasoline, etc., e.g. heating oils or diesel oils. Such oils are described as having a tendency on storage to form precipitates or sludge and hence to block sieves or filters, and the reason for including the above monoamines in them is to prevent the blockage of sieves or filters. Tests described in the examples employ an oil having a boiling range between 160 and 340°C, and 75g per cubic meter of amine, pumped through a 0.149 mm (100- mesh) Monelmetal sieve. The amines illustrated include octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine and various mixtures of amines. German Patent 659,210 (I.G. Farbenindustrie) discloses motor fuel, e.g. benzole, gasoline, containing water-insoluble aliphatic or aliphatic-aromatic amines having a straight chain of at least 8 carbon atoms, as corrosion inhibitors against the effects of sulphuric acid produced in the engine from organic sulphur impurities in the fuel. Although n-octylamine, dodecylamine and octadecylamine are specifically named, the sole example comprises 100 parts by weight of gasoline together with 1 part by weight of dimethyldodecylamine. US Patent 4,509,952, assigned to Ethyl Corporation, discloses fuel oil compositions comprising furnace oil or diesel oil and alkyldimethylamine (a C₄₋₂₀ n-alkyl dimethylamine, preferably a C₈₋₁₄ n-alkyl dimethylamine) wherein the amine is included in order to stabilise the oil against deterioration, e.g. colour deterioration, sludge formation, filter plugging, emulsification and rusting of storage containers. N,N-dimethyl dodecylamine is sold by Ethyl Corporation under trade mark "ADMA 12". US Patent 3,707,362, assigned to Esso Research and Engineering, discloses fuel, particularly gasoline, consisting of a major proportion of volatile hydrocarbons and a minor proportion of a tertiary aliphatic amine with a C₁₂₋₂₀ n-alkyl substituent and two C₁₋₃ alkyl substituents, preferably together with a C₁₂₋₂₀ n-alkyl primary amine. The amine/amine mixture is stated to improve the distribution of air-fuel mixture in the induction system, and hence to the cylinders, of an internal combustion engine and to reduce the tendency of a film of liquid to form on the walls of the inlet manifold of the engine. Tests and comparative tests describe use of gasolines containing, variously, tertiary amines, primary amines and mixtures of such amines. US Patent 2,456,569 discloses the addition to diesel fuel of a surface active agent in an amount from about 0.01%w (100 ppmw) to about 1 or 2%w (10,000 or 20,000 ppmw) to inhibit or prevent the formation of gum deposits. As examples of surface active agents are mentioned amines of formula R-NH₂ in which R represents a hydrocarbon chain of at least 8 carbon atoms. Published French Patent Application 2,403,381 discloses the addition to diesel fuel of a composition comprising a carboxylamide of a fatty acid having a carbon chain containing between 8 and 20 carbon atoms. The carboxylamide is indicated to be useful primarily in reducing the formation of suphur trioxide formed during fuel combustion and in peptising water present in the fuel. US Patent 4,482,357, assigned to Ethyl Corporation, discloses a distillate fuel for indirect compression ignition (diesel) engines which includes (i) a hydrocarbyl-substituted succinimide or succinamide, (ii) a C₈₋₆₀, N₁₋₁₀ hydrocarbyl amine, and (iii) N,N'-disalicylidene-1,2-diaminopropane. The combination of additives (i) to (iii) is stated to minimise coking on the injector nozzles. In the combination of additives (i) to (iii), (ii) is preferably a C₈₋₁₈, more preferably C₁₂₋₁₆, tertiary-alkyl primary amine. It has now surprisingly been found that use of certain nitrogen-containing compounds in diesel fuel per se reduces fouling of injectors in diesel engines. This reduced fouling is an entirely different technological effect from the prevention of blockage of sieves or filters described in DE OS 960,920 discussed above, since the diesel fuel reaching the cylinders of a diesel engine will already have passed a fine filter, and the fouling of injectors is induced by the high temperatures to which the injectors are exposed in operation of the engine. According to the present invention there is provided the use of concentration of from 10 to 80 parts per million by weight (ppmw) of a nitrogen-containing compound of general formula CH₃(CH₂) n -CH₂-NH₂ (I) wherein n is 8 to 18, or a mixture thereof as an additive in a diesel fuel comprising a major proportion of a diesel oil, for reducing fouling of injectors, particularly injector nozzles, in diesel engines. Diesel oils are well known, and whilst different countries have different specifications, to suit climate, etc. (e.g. in UK, BS 2869), diesel oils generally have boiling ranges in the range 120°C to 370°C, with initial boiling point in the lower region of such range and final boiling point in the upper region, and 50% distillation occurring at a temperature in the range 235°C to 295°C. Density of diesel oils tends to be in the range 0.82 to 0.86 kg/dm³ at 20°C. The concentrations of the compounds of formula I are in the range 10 to 80 ppmw (parts per million by weight of the diesel fuel), preferably 20 to 80 ppmw, more preferably 30 to 80 ppmw. In formula I, n is preferably 8 to 16, e.g. 10 to 16, more preferably 10 to 14. Dodecylamine is a particularly preferred compound of formula I. The invention also provides a method of operating a diesel engine with reduced fouling of injectors which comprises running the engine on a diesel fuel containing a major proportion of a diesel oil and a concentration of from 10 to 80 ppmw of a nitrogen-containing compound of formula I as defined above. The invention will be further understood from the following illustrative examples. EXAMPLE 1 Engine tests were performed on a selection of diesel fuels all of which were based on a blended diesel oil (without additives) in accordance with BS 2869, having cetane value in the range 50 to 53 (base oil). Example 1 was a solution of 38 ppmw (parts per million by weight of the diesel fuel) dodecylamine (laurylamine) in the base oil. Comparative A was the base oil itself, Comparative B was a solution of 38 ppmw N,N-dimethyl dodecylamine in the base oil, and Comparative C was a solution of 38 ppmw "OXILUBE 40/40" (trade mark) copolymer in the base oil. "OXILUBE 40/40" copolymer is a copolymer of ethylene oxide and propylene oxide containing 40%w propylene oxide, of specific gravity at 20°C 0.98 (ASTM D.1298) and viscosity at 40°C 33 mPa (cSt) (ASTM D.445), available from member companies of the Royal Dutch/Shell Group. The above fuels were all tested according to the following method, employing a Fiat IDI (indirect injection) 1929 cc, type 149 A1.000, diesel engine as used in Fiat Regata diesel automobiles. The engine was warmed up according to the following programme: The engine was then run at 2700 rpm and 75 Nm for 8.5 hours, after which engine speed/load was quickly reduced to 1500 rpm/25Nm and the engine was switched off. Coolant oil/water temperatures were maintained at 90±2°C. Performance of each diesel fuel was assessed quantitatively by air-flow measurement of fouling levels produced in the engine's injector nozzles. The nozzles, of type Bosch DN 12 SD 1750, were placed in a Ricardo air-flow rig according to 1S0 4010, and air-flow measurements were recorded at needle lifts of 0.1, 0.2 and 0.3 mm, with a vacuum pressure 600m Bar (60,000 Pa). Build-up of deposits in the nozzles causes a reduction in measured air-flow, and degree of nozzle fouling can be quantified by the formula Nozzle Fouling = Flow (clean) - Flow (fouled) Flow (clean) × 100 where "clean" values were measured prior to engine test and "fouled" values were measured after engine test. Average fouling levels (averages of values at the three needle lift levels) were as follows: EXAMPLES 2 TO 7 Following the procedure of Example 1, using the same base oil, the same Fiat IDI diesel engine and the same engine test programme and nozzle fouling assessment criteria, tests were performed on a selection of diesel fuels containing different linear amines of formula I. Amounts of the various amines were used to give comparable nitrogen concentrations in the fuels, with the exception of Example 4, which uses the same amine as Example 3, but at half the concentration. Results are given in Table I following, the amines being defined by the value of n in general formula I, dose rate being the concentration of the amine in ppmw based on the diesel fuel, and fouling level being the fouling level in % on the same basis as Example 1. It will be noted that when n was 6, in Comparative Example D, the fouling level was similar to those of Comparative Examples A to C.

Claims: Use of concentration of from 10 to 80 parts per million by weight (ppmw) of a nitrogen-containing compound of general formula CH₃(CH₂) n -CH₂-NH₂ (I) wherein n is 8 to 18, or a mixture thereof as an additive in a diesel fuel comprising a major proportion of a diesel oil, for reducing fouling of injectors in diesel engines. Use according to Claim 1 wherein the concentration is in the range from 20 to 80 ppmw of the diesel fuel. Use according to Claim 2 wherein in formula I n is 8 to 16. Use according to Claim 3 wherein n is 10 to 14. Use according to any one of Claims 1 to 4 wherein the concentration is in the range from 30 to 80 ppmw. Use according to any one of Claims 1 to 5 wherein the compound of formula I is dodecylamine. A method of operating a diesel engine with reduced fouling of injectors which comprises running the engine on a diesel fuel containing a major proportion of a diesel oil and a concentration of from 10 to 80 ppmw of a nitrogen-containing compound of formula I as defined in any one of Claims 1, 3, 4 and 6.

Inventors: READING KEITH, TOMASSEN HENRICUS PAULUS MARIA, VAN GRIEKEN MADELINDE GERARDA, READING, KEITH, TOMASSEN, HENRICUS PAULUS MARIA, VAN GRIEKEN, MADELINDE GERARDA FRANCISCA MARGA
Applicants: SHELL INT RESEARCH, SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1991
Main classification: C10L1
IPC codes: C10L1, F02B3, C10L10