EP1054051A1

EP1054051A1 - Diesel fuel compositions containing tertiary alkyl primary amines

Info

Publication number: EP1054051A1
Application number: EP00303880A
Authority: EP
Inventors: Rajiv Manohar Banavali; Bharati Dinkar Chheda
Original assignee: Rohm and Haas Co
Current assignee: Rohm and Haas Co
Priority date: 1999-05-19
Filing date: 2000-05-09
Publication date: 2000-11-22
Also published as: CN1274742A; JP2000345176A; CA2307821A1

Abstract

Disclosed are diesel fuel additives and diesel fuel composition containing such additives which help prevent or reduce injector nozzle fouling on diesel engines, especially indirect injection compression engines.

Description

BACKGROUND OF THE INVENTION

The present invention relates to diesel fuel additives and diesel fuel compositions containing such additives. In particular, the present invention relates to a diesel fuel additive and diesel fuel compositions containing such additives which are useful as thermal stabilizers and in reducing deposits on injection nozzles of compression ignition diesel engines.
Diesel fuel is principally a blend of petroleum-derived fractions called middle distillates (heavier than gasoline, but lighter than lube oil) and may optionally contain additional additives useful for a variety of purposes. For example, oxidation inhibitors are added to reduce the formation of gums and insoluble residues that can clog fuel filters, and detergent-dispersant additives help keep fuel-insoluble materials in suspension and are therefore helpful in maintaining a clean engine and fuel delivery system. Other additives include rust preventatives, anti-icing additives and cold-flow improvers. Ignition quality (cetane number) improvers are another type of common additive, and are added to increase the cetane number when the base fuel cetane does not meet requirements.
During operation of a diesel engine, diesel fuel is injected into the compressed, high-temperature air in the combustion chamber, where it ignites spontaneously. The most desirable fate of the carbon present in diesel fuels is to be emitted as carbon dioxide in the exhaust gas. If this is the case then the combustion is at its most efficient, which means that the maximum calorific value of the fuel is being exploited. When combustion is incomplete, then some of the carbon can be emitted as carbon monoxide (CO), hydrocarbon (HC), or as particulates. Particulates are of great concern as some studies are suggesting relationships between concentrations of fine particulates (less than 10 µ in size) in urban air and human health problems, including asthma and heart disease. Concerns over the environment and health impact of the emissions from the exhaust of automotive diesel engines have lead to several initiatives to reduce the levels of harmful pollutants. These initiatives have embraced both advancements in engine design and improvements in fuel quality. The improvements in fuel quality can be divided into two main categories: changes in certain key physical and chemical properties of the fuel; and the addition of multi-functional detergent additives packages.
Diesel fuel contains hydrocarbons having higher boiling point range than that of gasoline. Diesel fuel is designed to ignite spontaneously, quickly (within 1-2 milliseconds), and without a spark. The time lag between the initiation of injection and the initiation of combustion is known as ignition delay. In high speed diesel engines, a long ignition delay produces rough operation and knocking. To minimize ignition delay, it is necessary to maintain the fuel injector's ability to atomize a precise amount of fuel and mix it with available air. This in turn depends on the operation of the fuel injector. The performance of the fuel injector can be impaired by the build-up of deposits derived from the fuel. Thermal degradation of both fuel and crankcase lubricant components leads to the formation of deposits within fuel injectors. Deposit formation is worsened by hot combustion gases entering the nozzle. Deposits alter the close manufacturing tolerances of injectors and change fuel spray characteristics, leading to the observed degradation in engine performance.
These deposits restrict the flow of fuel through the injector and can cause needle sticking. Indirect ignition (IDI) engines with pintle-type nozzles are the more sensitive to such deposits. Engine symptoms resulting from IDI nozzle fouling are analogous to those caused by operation on fuel of inadequate cetane number. Increased noise, black smoke and exhaust emissions are all associated with severe IDI nozzle fouling, together with reduction in fuel economy.
Pintle-type nozzles are designed to release a restricted initial fuel, known as the pilot injection. This pilot injection, which occurs between needle lifts of 0 - 0.4 mm, initiates combustion ahead of the main fuel injection which occurs above 0.5 mm needle lift. This smoother, progressive combustion is both more efficient and quieter than previous type diesel engines. Deposits, which tend to form around the pintle tip, can strangulate the pilot injection by blocking the fuel flow. This results in a serious deviation from the designed combustion characteristics for the engine causing increases in noise and unburnt fuel exhaust emissions. There is published data which correlates fouling reduction with reduction of HC, CO and particulate emissions. See, for example: R. F. Haycock and R. G. F. Thatcher, "Fuel Additives and the Environment," ATC document, CEFIC, N° 52(1994); M. W. Vincent et al., "Diesel Fuel Detergent Additive Performance And Assessment," J. Soc. Automot.. Eng., SP (1994), SP-1056 (Diesel Fuel), 11-24; and K. Reading et al., "The Effect of a Fuel Detergents on Nozzle Fouling and Emissions in IDI Diesel Engines."
To counter the adverse effects of injector nozzle fouling, detergency additives are employed. The use of multi-functional detergent additive packages has become more widespread in recent years. By reducing deposit formation in the injector nozzle the detergent brings about a reduction in HC, CO and particulate emissions.
There are currently different types of chemistries which are well known to bring detergency to the diesel fuel. All are based on molecules having: a polar portion, bringing the dispersancy effect; and a lipophilic (often a polymeric) portion, allowing the entire molecule to be soluble in fuel. Most important chemistries are polybutenylsuccinic amides or imides (especially those known as PIBSA derivatives).
Surfactant molecules, frequently based on polymeric succinimide chemistry, help to control deposits within fuel injectors with significant benefits to engine performance. Detergent additives are effective in preserving an acceptable pilot flow by preventing deposit build up and removing performed deposits. Measuring the performance of detergent additive formulations is an important aspect of developing a high performance diesel fuel. Different test engines and test procedures are employed in Europe and the USA; however, the common aim is to show benefits from the use of detergent additives compared with untreated base fuels, and thereby to allow the cost effective development of improved fuels.
Another approach to the problem of injector nozzle fouling has been to blend together a number of additives to produce synergistic combinations that work to control fouling. Such additive combinations are disclosed in US 4,482,353; US 4,482,355; US 4,482,356; and US 4,482,357 (all Hanlon). However, there is still a need for simple, multifunctional diesel fuel additives, such as those capable of imparting thermal stability and preventing or reducing deposit formation in injector nozzles.

SUMMARY OF THE INVENTION

The present invention is directed to a fuel additive composition effective to provide injector deposit inhibiting properties and thermal stability to diesel fuel, such composition consisting essentially of at least one tertiary alkyl primary amine.
The present invention is also directed to diesel fuel compositions conprising a major amount of diesel fuel and a minor amount of the fuel additive composition as discussed above.

BRIEF DESCRIPTION OF THE DRAWING

Figure 1 is a cut-away side view of a typical fuel injector used in diesel engines.
Figures 2 and 3 are close-ups of the fuel injector nozzle 20 of Figure 1. Figure 2 shows the nozzle in open position, and Figure 3 shows the nozzle in closed position. Bold lines in Figures 2 and 3 indicate typical deposit formation areas.

DETAILED DESCRIPTION OF THE INVENTION

As used in this specification, the following terms have the following definitions, unless the context clearly indicates otherwise. The terminology "(C₁-C₂₁)" means a straight chain, branched chain or cyclic groups having 1 to 21 carbon atoms per group. The term "major amount" is understood to mean greater than 50 percent by weight, and the term "minor amount" is understood to mean less than 50 percent by weight. The term "TAPA" means tertiary alkyl primary amine(s). The following abbreviations are used throughout this specification: mL = milliliters; L = liters; µ - microns; mm = millimeters; mg = milligrams; g = grams; rpm = revolutions per minute. Unless otherwise specified, ranges specified are to be read as inclusive, references to percentages are by weight and all temperatures are in degrees centigrade (°C).
The tertiary alkyl primary amines useful in the present invention are tertiary alkyl primary amines according to the formula:
wherein:
R₁ and R₂ are each independently selected from: C₁-C₂₁ alkyl or substituted C₁-C₂₁ alkyl, C₁-C₂₁ alkenyl or substituted C₁-C₂₁ alkenyl; and
R₃ and R₄ are each independently selected from: hydrogen or C₁-C₂₁ alkyl, substituted C₁-C₂₁ alkyl, C₁-C₂₁ alkenyl or substituted C₁-C₂₁ alkenyl.
Suitable examples of C₁-C₂₁ alkyl include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, cyclobutyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, n-hexyl, cyclohexyl, 2-ethylhexyl, octyl cyclooctyl, nonyl, cyclononyl, decyl, isodecyl, cyclodecyl, undecyl, dodecyl (also known as lauryl), tridecyl, tetradecyl (also known as myristyl), pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, cosyl, eicosyl and heneicosyl.
Suitable examples of C₁-C₂₁ alkenyl include, but are not limited to: ethenyl, n-propenyl, isopropenyl, 1-butenyl, cis-2-butenyl, isobutylene, trans-2-butenyl, 2-3, dimethyl-2-butenyl, 3-methyl-1-butenyl, 2-methyl-2-butene, 1-pentenyl, cis-2-pentenyl, trans-2-pentenyl, 1-hexenyl, 1-heptenyl, 1-octenyl, 1-nonenyl, and 1-decenyl.
Suitable examples of C₁-C₂₁ substituted alkyl and alkenyl include, but are not limited to: the above recited alkyl and alkenyl groups substituted with hydroxy, halide such as fluorine, chlorine or bromine; cyano; alkoxy; haloalkyl; carbalkoxy; carboxy; amino; alkylamino derivatives and the like; or nitro groups.
Tertiary alkyl amines useful in the present invention include but are not limited to: 1,1,3,3-tetramethylbutylamine; an isomeric mixture of C₁₆ to C₂₂ tertiary alkyl primary amines; an isomeric mixture of C₁₀ to C₁₄ tertiary alkyl primary amines; an isomeric mixture of C₈ to C₁₀ tertiary alkyl primary amines; or mixtures thereof. In a preferred embodiment, tertiary alkyl amine is an isomeric mixture of C₈ to C₁₀ and C₁₀ to C₁₄ tertiary alkyl primary amines. In a most preferred embodiment, the tertiary alkyl primary amine is an isomeric mixture of C₁₀ to C₁₄ tertiary alkyl primary amines. Such tertiary alkyl primary amines are available from Rohm and Haas Company (Philadelphia, PA) under the PRIMENE® trademarks.
In general, the tertiary alkyl primary amines of the present invention are present in diesel fuel compositions at a concentration of 1 to 2000 mg/L, preferably 10 to 800 mg/L, more preferably 20 to 600 mg/L and most preferably 40 to 500 mg/L.
The tertiary alkyl primary amines used in the diesel fuel compositions of the present invention are prepared using substrate compounds known as substrates for the Ritter reaction and include, for example, alcohols, alkenes, aldehydes, ketones, ethers. See, generally, L. I. Krimen and D. J. Cota, "The Ritter Reaction," Organic Reactions, 17(1969), pp. 213-325. The process for preparing the amines is known in the art and is described, for instance, in US 5,527,949 and in co-pending provisional application 60/051,867.
The fuel additives of the present invention are also useful in maintaining or increasing the thermal stability of diesel fuels. Most users are knowledgeable about the fuel's primary role as an energy source; however, few are aware that diesel fuel performs multiple functions in a diesel engine and the associated fuel system. Diesel fuel is increasingly used as a circulating coolant for high pressure fuel injections systems. In addition to its primary role as an energy source, the fuel also serves as the sole lubricant of critical moving parts and as a heat-transfer fluid. Adequate thermal stability is a necessary requirement for the effective functioning of diesel fuel as a heat-transfer fluid. In modern heavy-duty diesel engines, only a portion of the fuel that is circulated to the fuel injectors is actually delivered to the combustion cylinders. The remainder is circulated back to the fuel tank carrying heat with it, consequently raising the bulk fuel temperature. Because of the recirculation of fuel through the newer engines, fuel can be exposed momentarily to temperatures as high as 350°C. This process, in some engines and fuel combinations, causes a problem in that as engine heat passes from injectors into the fuel, it can trigger a degradation process that leads to particle formation, clogging filters and injectors.
Fuels resistant to such thermal degradation must get a minimum 80% reflectance in the updated 150°C Accelerated Fuel Oil Stability Test (F21-61) at 180 minutes. Good thermal stability may become even more important in the future. Diesel engine manufacturers have indicated that engines under development to meet future exhaust emission standards will expose the fuel to more severe operating environments (stress), e.g., higher pressures and longer contact with high-temperature engine parts. the new premium diesel fuel specifications in USA will require a thermal stability and detergency pass test.
In the following Examples, performance testing of the diesel fuel detergency additives of the present invention was based on the widely used Peugeot 1.9 litre IDI engine XUD9A, in an industry standard test method developed by the Co-ordinating European Council (CEC: Working Group PF26 draft procedure). Details of the test methods used to evaluate nozzle fouling employed in the PF26 Peugeot XUD9A engine test can be found in: Vincent, M. W. et al., "Diesel Fuel Detergent Additive Performance And Assessment," J. Soc. Automot. Eng., SP (1994), SP-1056 (Diesel Fuel), 11-24; and CEC document reference CEC F-23-X-95.
The test engine is the most widely used light duty diesel engine in Europe, powering a substantial proportion of all vehicles in this class. The Peugeot engine, in common with many other IDI engines, employs a pintle type injector actuated by fuel pressure. Some of the main parameters of this test engine are provided below. Bore, mm 83.0

Stroke, mm: 88.0
No of cylinders: 4
Cubic capacity, liters: 1.9
Compression ratio: 23.5:1
Aspiration: Natural
Max Power @ rpm, kW: 4600, 48.5
Max Torque @rpm, Nm: 4000,120
Fuel injection pump: Bosch Rotary
Fuel injector type: Pintle

Referring now to the Figures, a metered quantity of fuel under pressure, delivered by the pump, lifts the injector needle 30 from its seat. The pintle type injector is normally closed by pressure from spring 20, thus preventing the flow of fuel. When the injector needle nozzle 40 is lifted from its seat by fuel pressure, a flow path is opened and a spray of small fuel droplets enters the combustion chamber. Fuel pressure under injection is typically of the order of 100 bar.
The following Examples are provided as an illustration of the present invention. Fuel samples A, B and C were, fresh test fuels without any additives and were obtained from commercial sources. The fuel samples were analyzed to ensure conformance with specifications and stored under ambient temperature, in dark, and under nitrogen atmosphere. All tests were started within a month of obtaining the fresh samples. All commercial additives used were as received without further purification. The C₉, C₁₂, and C₁₈ tertiary alkyl primary amines samples were commercial products sold by Rohm and Haas Company under the PRIMENE® trademark. The results are shown below in Table 1.

Detailed Analysis of Test Fuel Samples

Fuel # % Sulfur % Aromatics Cetane Number

A 0.033 24.5 53.2

B 0.06 39 45

C 0.051 32 47
In the Peugeot engine tests, selected pintle nozzles were flow checked and matched prior to the start of the test. The bed engine was prepared and stared from cold on "slave" injectors for 20 minutes, comprising two five minute no load idle periods, separated by operation for 10 minutes at 2000 rpm. After flushing the fuel pump with fresh test fuel to ensure thorough removal of all prior fuel, matched and flow-checked injectors were fitted for the test itself. The engine was operated for 6 hours at constant speed and load (3000 rpm, and about 50% maximum load) followed by a 5 minute idle at no load prior to shut down. Injectors were removed promptly from the engine and flows rechecked. Nozzle flows were checked both before and after the test using air. The results were expressed in terms of injector air-flow reduction measured at needle lift values of 0.05, 0.10, 0.20, 0.30, 0.40, and 0.50 mm.
In the mode tested, the engine typically undergoes severe nozzle coking on untreated base fuels. Flow loss at the onset of pilot fuel flow (0.1 mm needle lift) is typically 88-90% compared to the initial clean condition, after 6 hours test bed operation on an untreated base fuel.

Example 1: Injector Fouling Test

The efficiency of the tertiary alkyl primary amines was assessed with the Peugeot XUD-9A engine test in comparison with current commercial dispersants and detergent fuel additives (Control Reference). Table 2 contains the results of several Peugeot XUD9A engine tests at a needle lift of 0.10 mm. All the engine tests were run in a laboratory complying with IS0 14001 standard.

Percent Flow Reduction at 0.1 mm Needle Lift with Diesel Fuel A
Additive (mg/L)	% Flow Reduction
Control Reference	80.4
PRIMENE BC-9 (400)	76.7
PRIMENE 81-R (400)	75.1
C₉ - C₁₅ TAPA (250)	68.5
C₉ - C₁₅ TAPA (300)	70.5
C₉ - C₁₅ TAPA (350)	77.1
C₉ - C₁₅ TAPA (400)	69.2
C₉ - C₁₅ TAPA (420)	76.3
C₉ - C₁₅ TAPA (460)	68.1
PRIMENE JM-T (200)	80.6

One can see that the results demonstrate that tertiary alkyl primary amines provide significant reduction in injector nozzle fouling, and are comparable to or better than the combination of current commercial dispersants and fuel additives.

Example 2: Thermal Stability Tests

Samples of Fuels B and C, having a sulfur concentration of 0.06%, and 0.051%, respectively, were also evaluated by 150 °C Accelerated Fuel Oil Stability Test ("Octel F-21-61") for thermal stability improvement for 180 minutes.
The test procedure was as follows. A 50 mL sample of fuel oil in a test tube was placed in a 150 °C bath for 180 minutes. After removal from the bath the fuel was allowed to cool in air to 21 - 26 °C over a period of 90 minutes to 4 hours. The aged fuel was then filtered through 4.25 cm Whatman No 1 filter paper using vacuum filtration assembly. The paper was then washed with three portions, about 15 mL each, of iso-octane. The filter paper was dried under vacuum for one or two minutes. The filter paper was rated by measuring percent reflectance using a photovolt meter (model 577) using Search Unit Y with green filter. The filter paper was also rated for color by choosing a reference blotter which gave the best visual match. Generally, 80% or higher reflectance was considered a pass from thermal stability standpoint. Color rating of the filter paper was measured on a scale of 1 to 20, and the rating of up to 7 was considered a pass. Color rating higher than 7 is reported as poor thermal stability for the test fuel.

The data presented in the Tables 3 and 4 below show that the addition of the tertiary alkyl primary amines of the present invention to the fuel samples improved the thermal stability as seen by filter pad rating and reflection meter reading.

150°C Accelerated Fuel Oil Stability Test Results of Diesel Fuel B
Additive	Dosage (mg/L)	Filter pad rating	% Reflection meter reading
None	---	8	71
Primene 81-R	5	4	86
Commercial #1	5	7	72
Commercial #2	5	5	76
Commercial #3	5	4	84
Commercial #4	5	9	70
Commercial #5	5	8	72
Primene 81-R	10	4	89
Primene 81-R	20	2	95
Primene BC-9	20	2	97
Primene BC-9 + 81-R (1:1)	20	2	96
C₉ - C₁₅ TAPA	20	2	85
Commercial #3	20	2	94
Commercial #5	20	3	87
Commercial #6	20	4	89
Primene 81-R	40	2	96
Primene BC-9	40	2	97
Primene BC-9 + 81-R (1:1)	40	1	98
Commercial #3	40	3	92
Commercial #5	40	4	84
Commercial #1	40	3	88
Commercial #6	40	3	91

150°C Accelerated Fuel Oil Stability Test Results of Diesel Fuel #C
Additive	Dosage (mg/L)	Filter pad rating	% Reflection meter reading
None	----	13	75
Primene 81-R	10	4	84
Primene BC-9	10	3	85
Commercial #3	10	4	82
Primene 81-R	15	7	89
Primene BC-9	15	7	88
Commercial #1	15	10	72
Commercial #3	15	9	80
Commercial #4	15	8	76
Commercial #5	15	3	85
Commercial #6	15	4	87
Commercial #7	15	5	85
Commercial #8	15	5	82
Commercial #9	15	7	74

As can be clearly seen, addition of tertiary alkyl primary amines greatly improves the thermal stability of the diesel.

Claims

A fuel additive composition effective to provide injector deposit inhibiting properties and thermal stability to diesel fuel, such composition consisting essentially of at least one tertiary alkyl primary amine of formula:
wherein:

R₁ and R₂ are each independently selected from: C₁-C₂₁ alkyl or substituted C₁-C₂₁) alkyl, C₁-C₂₁ alkenyl or substituted C₁-C₂₁ alkenyl; and

R₃ and R₄ are each independently selected from: hydrogen or ₁-C₂₁ alkyl, substituted C₁-C₂₁ alkyl, C₁-C₂₁ alkenyl or substituted C₁-C₂₁ alkenyl.
The fuel additive composition of claim 1, wherein the tertiary alkyl primary amines are selected from the group consisting of: 1,1,3,3-tetramethylbutylamine; an isomeric mixture of C₁₆ to C₂₂ tertiary alkyl primary amines; an isomeric mixture of C₁₀ to C₁₄ tertiary alkyl primary amines; an isomeric mixture of C₈ to C₁₀ tertiary alkyl primary amines; or mixtures thereof.
The fuel additive composition of claim 2, wherein the tertiary alkyl primary amines are selected from the group consisting of: an isomeric mixture of C₁₀ to C₁₄ tertiary alkyl primary amines; an isomeric mixture of C₈ to C₁₀ tertiary alkyl primary amines; or mixtures thereof.
The fuel additive composition of claim 3, wherein the tertiary alkyl primary amines are selected from the group consisting of an isomeric mixture of C₁₀ to C₁₄ tertiary alkyl primary amines.
A diesel fuel composition comprising a major amount of middle distillate fuel and a minor amount of a fuel additive composition of claim 1.
The diesel fuel composition of claim 5, wherein the fuel additive composition is present in an amount between 1 and 2000 mg/L based on the weight of the diesel fuel.
The diesel fuel composition of claim 6, wherein the fuel additive composition is present in an amount between 10 and 800 mg/L based on the weight of the diesel fuel.
The diesel fuel composition of claim 7, wherein the fuel additive composition is present in an amount between 20 and 600 mg/ L based on the weight of the diesel fuel.
The diesel fuel composition of claim 8, wherein the fuel additive composition is present in an amount between 40 and 500 mg/L based on the weight of the diesel fuel.