DIESEL FUEL ADDITIVES

Abstract: The invention provides the use, as an additive in a diesel fuel comprising a major proportion of a diesel oil, of an effective concentration of a polyether derivative of the general formula (I): R<1>-O-(R<3>-O)x-R<2>, wherein each of R<1> and R<2> independently represents a hydrogen atom, a C1-30 alkyl or alkenyl group optionally substituted by one or more amino or hydroxy groups, or a C2-7 alkanoyl group, x has an average value in the range 2 to 200, and each moiety R<3> is independently selected from C2-4 alkylene moieties, for reducing white smoke emissions under cold-running engine conditions, and a method of operating a diesel engine under cold-running conditions with reduced white smoke emissions.

Description: DIESEL FUEL ADDITIVES This invention relates to diesel fuel additives, and more particularly to the use of certain polyether derivatives in diesel fuel to impart improved properties, and to a method of operating a diesel engine. In I Mech E Papers presented in London, UK, 6-7 April 1993, the paper on Pages 35 to 43 by Dr. R.E. insor, "Effect of fuel modifications on Detroit diesel engine exhaust emissions" describes tests on diesel fuels including such fuels with oxygenates. On page 38 is the disclosure:- "As part of the work with Allied Petro, the LE2000 fuel was provided with 0.5% diglyme added, and this fuel (LE2500) was tested on the 6V-92TA coach engine along with the other fuels." "The addition of the diglyme appears to have reduced the particulates by about 6% compared to the original LE2000 value. Overall, on this two-stroke coach engine, the reformulated fuel with diglyme (LE2500) yielded a significant 17% reduction in particulates, but no NOx improvement, compared to the baseline #1 diesel fuel. This encouraging result with diglyme led us to conduct emission tests in a Series 60 engine with 5.0% diglyme added to low sulfur (0.1%) DF-2 fuel. The baseline fuel met EPA specifications for 1991 certification, but detailed analysis is not available. The emission testing consisted of two hot transient cycles with each fuel." "The particulate emissions decreased from 0.169 to 0.135 g/bhp-hr, a 20% reduction, while NOx showed no change. In this test hydrocarbon emissions were unchanged and carbon monoxide showed a significant reduction of 13%. In a later experiment, a Series 60 engine was tested with 3.5 weight percent dimethyl carbonate (DMC) added to low sulfur (0.1%) DF-2 fuel. Although this engine configuration gave relatively low particulate emissions with the baseline fuel, the addition of this oxygenate gave a 15% reduction in particulates and 13% reduction in carbon monoxide." The above engine tests are run under normal (hot) running conditions. Canadian Patent No. 1 273 201, and the corresponding DE-A-3 631 225, discloses a diesel fuel oil additive comprising (A) an oxyalkylene derivative of an amine having the general formula: wherein R! is an aliphatic hydrocarbon group having from 6 to 24 carbon atoms, A^ is an alkylene group having from 2 to 4 carbon atoms, 1 and m are integers of 1 or more, with 1 + m being a total of from 2 to 10; and (B) a polyoxyalkylene glycol mono-ether having the general formula: R 3 -0-(A 2 0) n —H (2) wherein R 3 IS a hydrocarbon group having from 3 to 18 carbon atoms, A 2 is an alkylene group having 3 or 4 carbon atoms and n is an integer of from 2 to 60. The utility and purpose described for this additive is ready clean-up of "deposits produced in the injector nozzle when the engine is operated under normal conditions, thus preventing the nozzle from plugging with the deposits" (Page 4, lines 34 to 37), and "the effect of improving low temperature fluidity of diesel fuel, of water draining, and of cleaning diesel engines and fuel systems (Page 5 lines 1 to 4) . GB 2 260 337 A discloses an additive concentrate for dehazing middle distillate fuels comprising (l) at least one alkoxylated amine and (n) at least one alkoxylated alcohol. Preferred alkoxylated alcohols for use as (n) have the formula R 4 (OR 5 ) w (OR 6 ) z OH wherein R is an alkyl or cycloalkyl group having from 2 to 20 carbon atoms and each of R5 and Rg is alike or different and is an alkylene, or cycloalkylene group having from 2 to 20 carbon atoms. The sum of w and z is, preferably, in the range 2 to 20. US Patent No. 4 623 362 discloses distillate fuel for indirect injection compression ignition engines containing, in an amount sufficient to minimize coking, especially throttling nozzle coking in the prechambers or swirl chambers of indirect injection compression ignition engines operated on such fuel, at least the combination of (1) organic nitrate ignition accelerator and (11) an alkoxyalkanol which, when added to said fuel in combination with said organic nitrate ignition accelerator minimizes said coking. Preferably, the alkoxyalkanol has the structure R' ( OR" ) n OH wherein R' is an alkyl group containing 1-12 carbon atoms, R" is a divalent aliphatic hydrocarbon group containing 2-4 carbon atoms and n is an integer from 1- 4. US Patent No. 4 549 884 discloses a liquid middle distillate fuel composition comprising (1) a major portion of a liquid middle distillate hydrocarbon fuel; and (11) a visible-smoke reducing portion of additive having the formula R < wherein R-"- is an alkyl, aralkyl, alkaryl, cycloalkyl, alkenyl, or alkynyl hydrocarbon group; and R 2 IS hydrogen or an alkyl, aralkyl, alkaryl, cycloalkyl, alkenyl, or alkynyl hydrocarbon group. As control examples, having inferior visible smoke performance relative to the ethoxylated phenol of the above formula are nonyltetraethoxy phenol, nonyl eicosa ethoxy phenol and Ethyl MPA-D brand of polyethoxylated alkyl phenol. The visible smoke which this patent is concerned is what is frequently termed "black smoke", arising in engines operating under load at normal (hot) operating temperatures. The present invention is concerned with a phenomenon which is entirely different from any of the phenomena described in the above prior art. This phenomenon is the problem of white smoke emissions from diesel engines under cold-running engine conditions. White smokes are typically observed from diesel engines started from cold and before the engine has reached a fully warmed condition. According to the present invention, there is provided the use, as an additive in a diesel fuel comprising a major proportion of a diesel oil, of an effective concentration of a polyether derivative of general formula Ri-O- (R 3 -0) χ -R 2 (I) wherein each of R1 and R 2 independently represents a hydrogen atom, a Cj__3o alkyl or alkenyl group optionally substituted by one or more ammo or hydroxy groups, or a C2-7 alkanoyl group, x has an average value in the range 2 to 200, and each moiety R 3 is independently selected from C2-4 alkylene moieties, for reducing white smoke emissions under cold-running engine conditions. The invention also provides a method of operating a diesel engine under cold-running conditions with reduced white smoke emissions which comprises running the engine on a diesel fuel containing a major proportion of a diesel oil and an effective concentration of a polyether derivative of formula I as defined above. The polyether of formula I may conveniently be present in the diesel fuel at a concentration in the range 0.1%w to 10%w, preferably 0.2%w to 5%w, and more preferably 0.2%w to l%w, based on the diesel fuel. Concentrations in the range 0.3% to 0.5% (3000 to 5000 ppmw) have been found to give very satisfactory results . In this specification, an alkyl, alkenyl or alkylene moiety may be straight-chain or branched, and an alkenyl group may contain more than one site of unsaturation, although it is preferably mono- unsaturated. The polyether derivatives of formula I are mostly known compounds, and they may be made by known method or by methods analogous to known methods, as will be readily appreciated by those skilled in the art. Preferred polyether derivatives accord with one or more of the following parameters :- (1) each of R^ and R 2 independently represents a hydrogen atom, a C \ -20 alkyl group optionally substituted by an ammo group, or a C2- alkanoyl group, (II) x has an average value in the range 2 to 150, (III) each of R! and R 2 independently represents a hydrogen atom or a C__20 alkyl group optionally substituted by an ammo group. The diesel oil may be a hydrocarbon fuel (a middle distilate fuel oil), which may be a conventional fuel or, preferably, a low-sulphur fuel having a sulphur concentration below 500 ppmw, preferably below 50 ppmw, advantageously below 10 ppmw. Diesel oils typically have initial distillation temperature about 160°C and 90% point of 290-360°C, depending on fuel grade and use. Vegetable oils may also be used as diesel oils per se or in blends with hydrocarbon fuels. Low-sulphur fuels will typically require a lubricity additive to reduce fuel pump wear. The polyether derivative of formula I may be incorporated directly in diesel fuel, or, more conveniently as a compound in an additive concentrate. Additive concentrates suitable for incorporating in diesel fuel compositions will contain the polyether derivative of formula I and a fuel-compatible diluent, which may be a non-polar solvent such as toluene, xylene, white spirits and those sold by member companies of the Royal Dutch/Shell Group under the Trade Mark "SHELLSOL", and/or a polar solvent such as esters and , in particular, alcohols, e.g. hexanol, 2- ethylhexanol, decanol, isotridecanol and alcohol mixtures such as those sold by member companies of the Royal Dutch/Shell Group under the Trade Mark "LINEVOL", especially "LINEVOL" 79 alcohol which is a mixture of C7_9 primary alcohols, or the C]_2-14 alcohol mixture commercially available from Sidobre Smnova, France under the Trade Mark "SIPOL". Additive concentrates and diesel fuel compositions prepared therefrom may additionally contain additional additives such as low molecular weight amine or hydrocarbyl-substituted succ imide, e.g. a polyisobutenyl succmimide, detergents, dehazers, e.g. alkoxylated phenol formaldehyde polymers such as those commercially available as "NALCO" (Trade Mark) 7D07 (ex Nalco) , and "TOLAD" (Trade Mark) 2683 (ex Petrolite) ; anti-foaming agents (e.g. the polyether-modifled polysiloxanes commercially available as "TEGOPREN" (Trade Mark) 5851 ex Th . Goldschmidt, Q 25907 (ex Dow Corning) or "RHODORSIL" (Trade Mark) (ex Rhone Poulenc) ) ; ignition improvers (e.g. 2-ethylhexyl nitrate, cyclohexyl nitrate, di-tertiary-butyl peroxide and those disclosed in US Patent No. 4,208,190 at Column 2, line 27 to Column 3, line 21); anti-rust agents (e.g. that commercially sold by Rhein Chemie, Mannheim, Germany as "RC 4801", or polyhydric alcohol esters of a succimc acid derivative, the succmic acid derivative having on at least one of its alpha-carbon atoms an unsubstituted or substituted aliphatic hydrocarbon group containing from 20 to 500 carbon atoms, e.g. the pentaerythritol diester of polyisobutylene-substituted succmic acid), reodorants, anti-wear additives; anti-oxidants (e.g. phenolics such as 2 , 6-dι-tert-butylphenol, or phenylenediamines such as N, N ' -di-sec-butyl-p-phenylenediamme) , metal deactivators and lubricity agents (e.g. those commercially available as EC831, P631, P633 or P639 (ex Paramins) or "HITEC" (Trade Mark) 580 or X9429, X4848 or X4849 (ex Ethyl Corporation), "Lubrizol" (trade mark) 539A (ex Lubrizol), "VECTRON" (trade mark) 6010 (ex Shell Additives), OLI9000 (ex Associated Octel), or ADX4101B (ex Adibis) ) . Preferred low molecular weight amme detergents are C]_Q-20 alkylamines. Aliphatic primary monoamines, particularly linear aliphatic primary monoamines, having 10 to 20 carbon atoms are particularly preferred. The alkylamme preferably has 10 to 18, e.g. 12 to 18, more preferably 12 to 16 carbon atoms. Dodecylamme is particularly preferred. Preferred hydrocarbyl-substituted succ imides, which include those described in EP-A-147 240, are the reaction product of a polyisobutylene succmic acid or anhydride with tetraethylene pentamme wherein the polyisobutylene substituent has a number average molecular weight (Mn) in the range 500 to 1200. Unless otherwise stated, the (active matter) concentration of each additive in the diesel fuel, other than the polyether derivatives of general formula I, is preferably up to 1 percent by weight, more preferably in the range from 5 to 1000 ppmw (parts per million by weight of the diesel fuel) . The (active matter) concentration of the dehazer in the diesel fuel is preferably m the range from 1 to 20, more preferably from 1 to 15, still more preferably from 1 to 10 and advantageously from 1 to 5 ppmw. The (active matter) concentrations of other additives (with the exception of the ignition improver and the lubricity agent) are each preferably in the range from 0 to 20, more preferably from 0 to 10 and advantageously from 0 to 5 ppmw. The (active matter) concentration of the ignition improver in the diesel fuel is preferably in the range from 0 to 600 and more preferably from 0 to 500 ppmw. If an ignition improver is incorporated into the diesel fuel, it is conveniently used in an amount of 300 to 500 ppmw. If a lubricity agent is incorporated into the diesel fuel, it is conveniently used in an amount of 100 to 500 ppmw . The diesel oil itself may be an additised (additive-containing) oil or an unadditised (additive- free) oil. If the diesel oil is an additised oil, it will contain minor amounts of one or more additives, e.g. one or more additives selected from anti-static agents, pipeline drag reducers, flow improvers (e.g. ethylene/v yl acetate copolymers or acrylate/maleic anhydride copolymers) and wax anti-settlmg agents (e.g. those commercially available under the Trade Marks "PARAFLOW" (e.g. "PARAFLOW" 450; ex Paramms), "OCTEL" (e.g. "OCTEL" W 5000; ex Octel) and "DODIFLOW" (e.g. "DODIFLOW" V 3958; ex Hoechst) . Use of the polyether derivatives of formula I as described above may give rise to additional benefits such as fuel injector cleanliness and reduced emissions of hydrocarbons, partially burned hydrocarbons and particulates when running at normal (hot) operating temperatures, i.e. in addition to the benefits obtained under cold-running engine conditions. The invention will be further understood from the following illustrative examples, in which temperatures are given in degrees Celsius (°C) . In the examples, in particular in Example 1, the various test materials are are available ex Aldπch, with the exception of those for which CAS Registry Numbers are quoted, and the following polyether derivatives of general formula I: R!-0- (R 3 -0) χ -R 2 (I) Polyether A is a polyoxypropylene glycol hemiether (monoether) corresponding to formula I wherein R! represents a C^2-15 alkyl group, R 2 is hydrogen, each R 3 moiety is an isopropylene group (-CH2CH (CH3 ) -) and x has an average value the range 17 to 23, prepared using a mixture of C 2-15 alcohols as initiator, and having M n in the range 1200 to 1500 and a kinematic viscosity in the range 72 to 82 mm 2 /s at 40°C according to ASTMD D 445, available under the trade designation "SAP 949" from member companies of the Royal Dutch/Shell group; Acetate ester of Polyether A is prepared by reaction of Polyether A with acetic acid at reflux temperature in the presence of toluene as solvent, together with acid catalyst, whilst removing evolved water by means of a Dean and Stark trap; so that the acetate ester differs from Polyether A itself by R 2 being an acetyl group (-COCH3) ; Polyether B is a polyoxypropylene glycol hemiether (monoether) corresponding to formula I wherein R , R 2 and R 3 are the same as for Polyether A, but x has an average value in the range 3.5 to 5.5, prepared using a mixture of C]_2-15 alkanols as initiator, and having M n in the range 435 to 505 and a kinematic viscosity in the range 16 to 21 mm 2 /s at 40°C according to ASTM D 445, available under the trade designation "OXILUBE 500" ("OXILUBE" is a registered trade mark) from member of the Royal Dutch/Shell group; Polyether C is a polyoxypropylene glycol hemiether (monoether) corresponding to formula I wherein R1, R 2 and R 3 are the same as for Polyether A, and x has an average value of about 120 prepared using a mixture of C 2-15 alkanols as initiator, having a hydroxyl value of 0.14 milliequivalents per gram according to ASTM D 4274-88 and M n calculated therefrom (on the basis of one hydroxyl group per molecule) of 7150, and a kinematic viscosity in the range of 2300 to 2400 mm /s at 40°C according to ASTM D 445; and Polyether D is a polyoxyethylene glycol hemiether (monoether) corresponding to formula I wherein R! represents a Cg-n alkyl group, R 2 is hydrogen, R 3 is an ethylene (-CH2CH2-) group and x has an average value in the range 4.5 to 5.5, prepared using a mixture of g- n alkanols as initiator, having M n 380 and a kinematic viscosity of 18 mm 2 /s at 40°C according to ASTM D 445, available under the trade designation "DOBANOL 91-5" or "NEODOL 91-5E" ("DOBANOL" and "NEODOL" are registered trade marks) from member companies of the Royal Dutch/Shell group. Example 1 The example describes tests of the above materials dissolved in automotive gasoil (diesel) fuels to examine their effectiveness in reducing exhaust emissions of white smoke from diesel engines started from cold and before the engine has reached a fully warmed condition. When a diesel engine is started from cold and allowed to idle, incomplete combustion tends to occur, leading to undesirable emissions of hydrocarbons and partially burned hydrocarbons, with the visible symptom of white smoke during the first few minutes of engine operation. The situation is similar if the engine is allowed to run at low load and higher speed during the first few minutes after starting from cold. Conventional tests of the effects of fuels and additives on cold engine performance in which a cold engine is started and run for a few minutes are recognised as being fairly inconsistent and of low repeatability. The test productivity is also very low because the engine or vehicle must usually be cooled for several hours in a refrigerated chamber between tests . The test which follows was designed to reproduce on a steady and continuous basis the conditions that exist in a cold engine during the first few minutes from start up. The test used a Cussons/Ricardo Hydra Dl single cylinder research engine with the characteristics listed in Table 1. Table 1 Hydra Test Engine Characteristics bore : 80.3 mm stroκe : 88.9 mm swept volume: 0.45 litres aspiration : natural maximum power: 8 kW approx. at 4500 r/min bowl geometry: toroidal with port-induced swirl compression ratio: 20:1 (standard) and 17:1 (some tests) fuel injection pump: Micro Bosch "A" size, Type EA4000 6900 fuel injector body: Bosch KBEL 88DV187 nozzle Bosch DLLA 155 PV 3172325 To achieve conditions representative of cold starting the engine was run on a test-bed with a dynamometer at low engine load and speed and with a continuously refrigerated coolant. The engine conditions are listed in Table 2. Table 2 Hydra Test Conditions coolant temperature, °C -10 - 0 inlet air temperature, °C -17-20 oil temperature, °C -30 speed, r/m 1200 Brake load, Nm torque 5 injection timing 4 °BTDC During the tests, m-cylinder pressure was measured as a function of crank angle by a Kistler 6121A1 piezoelectric pressure transducer from Kistler Instrumente AG, W terthur, Switzerland. Pressure, crank angle and dynamometer conditions were recorded and stored by an AVL 647 Indiskop high speed analyser with real time data analysis manufactured by AVL List GmbH, Graz, Austria. The AVL 647 analyser calculated further quantities including; IMEP (Indicated Mean Effective Pressure - a measure of the power developed in the engine cylinder) and the Coefficient of Variation of the IMEP (COV) . The COV of IMEP is a measure of degree of irregular and poor combustion. A high value indicates very irregular combustion. In the tests the COV was calculated by the AVL 647 analyser using the m-cylinder pressure measurements from a total of 500 combustion cycles. White smoke opacity was measured by a Wager Model 650 Smoke Opacity Meter manufactured by Robert H Wager Co., Inc., Passaic Avenue, Chatham, New Jersey, USA positioned approximately 0.5 m from end of the end of the exhaust pipe in the open air outside the test facility. A problem with white smoke opacity measurements is that their absolute values are affected by variations in atmospheric conditions, conditions in the engine exhaust system and the cleanliness of the instrument optical components, but COV of IMEP measurements are much more consistent both within a test and between one test and another. For these reasons COV of IMEP measurements are preferable over directly measured white smoke opacities to determine, for comparative purposes, the ability of materials dissolved in fuels to reduce white smoke emissions. To demonstrate the validity of this approach preliminary tests were carried out to establish the relationship between measured COV of IMEP and white smoke, as follows. Preliminary tests were done at the engine conditions in Table 2 with a coolant temperature of -6°C. Three fuels were tested which had different cold performances in engines. Fuel A had a natural cetane number of 41.5. Fuel B was a standard industry reference fuel RF73-T-90, ex Halterman) with a natural cetane number of 50. Fuel C comprised Fuel B with added 2-ethylhexylnιtrate at a concentration of 4.375g/kg to increase the cetane number to 57.1. The fuels properties are listed in Table 3. Table 3 The test results, COV of IMEP measurements and white smoke opacities are given in Table 4. Table 4 Relation between COV of IMEP The results demonstrate that there is a clear mter-relationship between COV of IMEP and white smoke opacity and that a reduction in COV of IMEP is an indicator of reduction also in white smoke opacity. Accordingly, the comparative tests which follow, in order to demonstrate the potential of candidate materials to reduce white smoke emissions, were based on COV of IMEP measurements. The test procedure was as follows . One material was tested per day by comparing its performance dissolved at a concentration of 4,000 ppmw (0.4% w/w) in a base fuel with that of the base fuel alone. The engine was started on a base fuel (fuel D in Table 3) with the injection timing relatively advanced. The engine coolant refrigerating system was operated to maintain the coolant temperature at 0°C. The dynamometer settings of speed and load in Table 2 were established and maintained. The cold engine running was initially unstable but stability gradually improved. Consistent with maintaining reasonable stability, the injection timing was gradually retarded to the test condition value of 4 °BTDC. The COV of IMEP initially had a very high value which decreased fairly rapidly until after about 3 hours, when the rate of decrease became slow and essentially linear. The engine was therefore run for 3 to 4 hours to allow the COV of IMEP to reach a reasonable plateau condition before taking test measurements. At this stage, the AVL 647s analyser was used to obtain three samples of the COV of IMEP. The mean of the three readings was recorded. The fuel to the engine was then changed to the additivated fuel (the base fuel previously used plus additive) by an arrangement of valves which allowed a fuel change without interrupting the fuel flow to the engine or disturbing its operation. After the fuel change, the engine was run for 15 to 20 minutes on the new fuel to ensure that a representative condition was achieved. A second set of COV of IMEP measurements was then taken. Three COV samples were taken and averaged to a single mean value. The engine fuel was then changed again, this time back to the base fuel. The engine was allowed to settle down for a further 15 to 20 minutes and a third set of base fuel COV of IMEP measurements was taken. This procedure of base fuel followed by additivated fuel measurements was repeated three times in a test and followed by a final set of measurements on the base fuel. In this way, four sets of measurements were made on base fuel and three on the additivated fuel. The latter measurements were thus always bracketed by base fuel measurements. In subsequent analysis, drifts m the engine performance were corrected for by taking the arithmetic mean of the bracketing base fuel measurements to represent what the behaviour of the engine would be during additivated fuel measurements if it were still running on the base fuel. This bracketing and interpolation method allows a clear comparison of the engine behaviour between base fuel alone and base fuel plus additive. In this way the effects of the additive are discerned. The effect of the additive material is expressed as the 'COV ratio' : CO V ratio = CO V (base fuel ) / cov (additivated fuel) where COV (base fuel ) s tne mean of the two bracketing base fuel COVs and COV ( a dditivated fuel) is that of the base fuel plus additive. An additivated fuel with a better performance (lower COV of IMEP and white smoke emissions) than the base fuel alone has a COV ratio greater than unity. A ratio of 1.0, of course, indicates that the test fuel is similar to the base fuel. Finally, at the end of each test day, the engine was run hot under moderate load for one hour to burn up any deposits formed within the previously cold combustion chamber. The hot running conditions the engine for the test on the next day and was found to reduce the severity of changes in COV of IMEP that would otherwise occur. Table 5 lists the results obtained by following the test procedure. For each material the COV ratio per 4000 ppmw test material dissolved in base fuel D is given . Table 5 Activities of Test Materials Table 3 ( continued) Example 2 This example describes tests of the effectiveness of Polyether A dissolved in a diesel fuel m reducing the opacity of white smoke emissions from a heavy-duty commercial vehicle started at a temperature of -10°C. The example used a new 1995 Mercedes-Benz L 814 D truck with a EUR02 version OM 364 LA turbo charged lntercooied engine having four cylinders and a total displacement of 4 litres. The rated power of the engine at 2600 rpm is 103 kW and the rated torque at 1200 to 1500 rpm is 500 Nm. Four fuels (E, F, G and H) were tested. The fuels properties are in Table 6. Fuels F and H were typical of commercially available diesel fuels. Fuel G was a commercially obtained advanced test fuel having a high cetane number of 58. Fuels E and F contained a conventional amount, 300 ppm w/w, of 2-ethylhexyl- nitrate ignition improver to increase their cetane numbers. Fuels E and F also contained 10 ppmw "Tegopren" (trade mark) 5851 antifoam, ex. Th Goldschmidt A.G., 5 ppm "Nalco" (trade mark) 7D07 dehazer ex. Nalco and 5 ppmw RC 4801 corrosion inhibitor ex. Rhein Chemie. Additionally, Fuel E contained 4680 ppmw (0.468 %w/w) of Polyether A to reduce white smoke opacity during cold engine running. Comparison of the performance of Fuels E and F therefore provides direct evidence of the effect of the polyether in reducing white smoke opacity. Table 6 Properties of Fuels The tests were conducted in a climate controlled chassis dynamometer facility allowing vehicle operation at a simulated road load conditions at constant temperature. The test simulated cold start procedures for medium sized trucks, for example, filling the pneumatic brake system or loading the vehicle at a loading ramp. Before tne start of the test series, the vehicle engine and exhaust system were conditioned by running for 100 km on the dynamometer under simulated road load . Before each individual test, the vehicle was conditioned hot on the dynamometer by running for 30 minutes at 60 km/h in the highest vehicle gear and at simulated road load. The purpose of the hot conditioning was to restore the vehicle to the same state before each test and to remove fuel, partially oxidised materials and deposits remaining in the cylinders and exhaust system from the previous cold start thus helping to reduce memory effects from the previous fuel. The conditioning served to improve test repeatability. After conditioning, the engine was turned off and the vehicle was left in the climate controlled facility for 15 hours with the temperature of the latter controlled at -10°C before conducting a test. The test cycle was as follows. The engine was started without using any starting aid and idled at zero applied road load for 60 s at an engine speed of 750 rpm. Still at zero applied road load the engine speed was increased to a fast idle of 1200 rpm for a further 120 s using manual control of the vehicle accelerator. Finally the engine speed was returned to an idle speed of 750 rpm for a further 60 s. The white smoke opacity during the test cycle was measured by a Celesco optical smoke meter Model 107 with a bore of 100 mm. The use of a climate controlled chamber improved test repeatability because air flows are more constant and reproducible. To help make the measurements more reliable and repeatable further precautions were taken. All the vehicle exhaust gases were collected in an open funnel (300 mm diameter reducing to 100 mm diameter over a length of 800 mm) placed directly behind the end of the unmodified vehicle exhaust pipe of 100 mm diameter to homogenise before entering the smoke meter. Flow was induced by a constant-speed fan of about 700 m3/h throughput downstream of the smoke meter. Exhaust gas: induced air ratios were about 1:2 at an idle of 750 rpm and about 1:1.2 at 1200 rpm. The engine speed, air temperature and white smoke opacity were recorded at a frequency of 10Hz in conventional manner by a computer-aided digital data logger, as will be appreciated by those skilled in the use of climate-controlled chassis dynamometers. The measurements taken during the 1200 rpm phase were processed to give opacity versus time. Repeat tests were done on each test fuel. On all the fuels, the white smoke opacities during the first 60 s period of idle at 750 rpm were insignificant, i.e. less than 1-2%. The white smoke opacities during the higher speed idle of 1200 rpm were significant, with maximum opacities up to 50%. Table 7 lists the white smoke opacities for each fuel versus time during the 1200 rpm idle phase. The opacities are tne arithmetic mean of the two tests. Table 7 White smoke opacities From commercial vehicle started at -10°C Fuel F containing added Polyether A produces significantly lower white smoke opacities than Fuel F (without the additive for the duration of the fast idle. Fuel F containing added Polyether A also produces significantly lower white smoke opacities than the advanced Fuel G with a much greater natural cetane number, or Fuel H. The maximum smoke opacity produced by Fuel F with added Polyether A was significantly less than that produced by all the other fuels. The Polyether A reduces white smoke opacities whereas changes in fuel properties, e.g. increases in cetane number - traditionally considered to be effective - have no effect. Example 3 This example describes tests of the effectiveness of two polyethers, Polyether A and Polyether B, dissolved in diesel fuel in reducing exhaust hydrocarbon emissions and the opacity of white smoke emissions from a heavy-duty diesel engine started at a temperature of -I0°C. The heavy-duty diesel engine, which was to EUR02 specification, was equipped with turbocharger and mtercooler and had 6 cylinders, a displacement of 7 litres and a rated power of 206 kW at 2600 rpm. Three fuels were tested. Fuels E and F were as in Example 2. Fuel I corresponded to Fuel F, with the additional inclusion of 4680 ppmw (0.468 %w/w) Polyether B. The tests were conducted with the engine mounted on a test bed in a climate-controlled chamber at the facilities of AVL LIST GmbH, Graz, Austria. No starting aid was used. Before tests on each fuel, the fuel system was well flushed to remove traces of the previous fuel. The lubricant and lube oil filter were also changed. The engine was then run hot for 20 minutes on the fuel to be tested at a speed of 1500 rpm and a BMEP (Brake Mean Effective Pressure) of 5 bar. The purpose of the hot conditioning was to restore the engine to the same state at the beginning of tests on each fuel. The hot running removed fuel, partially oxidised materials, and deposits remaining the cylnders and exhaust system from the previous cold start. This helped to reduce previous fuel memory effects. The engine was then left to cool for 8 hours to a temperature of -10°C. The test cycle was run and controlled automatically and consisted, after starting the engine, of running alternatively at two idle conditions 'low idle' and 'fast idle' with a five second ad j ustment period allowed for changes between the two conditions. The first running period was for 180 s, immediately after engine start, at low idle, zero applied load and 0 - throttle. The resulting engine speed is 750 rpm. The engine was then run for 25 s at 'fast idle', a throttle setting of 15% and zero applied load to produce an engine speed of 1000 rpm increasing gradually to 1300 rpm as the test proceded and the lubricant became warm. The two conditions, 25 s of slow idle followed by 25 s of fast idle were then repeated alternately a further four times. The test thus comprised an initial 180 s of slow idle followed by five periods of 25 s duration of fast idle alternating with four 25 s duration periods of slow idle. The engine exhaust was 100 mm in diameter for the first 1250 mm length from the engine, followed by a further 94 mm diameter section 485 mm in length. White smoke opacity was measured by a US-PHS-opacity meter mounted vertically m the open air above the upward facing open end of the exhaust pipe. Additionally, exhaust hydrocarbons were measured -situ at a point 640 mm from the open end of the exhaust pipe by an AVL DP482 Dynamic Particulate Analyser that used infra-red absorption simultaneously to monitor the hydrocarbon content, carbon content and water content of engine exhaust gases. During the test cycle the readings from these instruments and engine conditions were logged at frequencies of 2 Hz and 10 Hz as appropriate by an AVL "Indimaster" (trade mark) engine data recording system. Triplicate tests of good repeatability were obtained from each fuel. Tables 8 and 9 list the averaged white smoke opacities and exhaust hydrocarbon concentrations for each fuel for each fast idle section of the cycle. The exhaust hydrocarbon concentrations in the first fast idle period were not measurable because they were greater than the 1800 ppm maximum range of the AVL DP482 analyser. Smoke opacities and hydrocarbons the slow idle modes were very low. The Polyethers A and B were found to be effective in significantly reducing the white smoke opacity and exhaust hydrocarbon emissions from the cold engine. Table 8 Mean White Smoke Opacities individual fast idle periods Table 9 Mean hydrocarbon emissions individual fast idle periods

Claims: C L A I M S 1. Use, as an additive in a diesel fuel comprising a major proportion of a diesel oil, of an effective concentration of a polyether derivative of general formula R1-0- (R 3 -0) χ -R 2 (I) wherein each of R! and R 2 independently represents a hydrogen atom, a C]__3o alkyl or alkenyl group optionally substituted by one or more ammo or hydroxy groups, or a C2-7 alkanoyl group, x has an average value in the range 2 to 200, and each moiety R 3 is independently selected from C2-4 alkylene moieties, for reducing white smoke emissions under cold-running engine conditions. 2. Use according to Claim 1 wherein the polyether derivative of formula I is present in a concentration in the range 0.1%w to 10%w based on the diesel fuel. 3. Use according to Claim 1 or 2 wherein the polyether derivative of formula I is present in a concentration in the range 0.2%w to 5%w based on the diesel fuel. 4. Use according to Claim 1, 2 or 3 wherein the polyether derivative of formula I is present in a concentration in the range 0.2%w to l%w based on the diesel fuel. 5. Use according to any one of Claism 1 to 4 wherein each of R! and R 2 independently represents a hydrogen atom, a C-L_20 alkyl group optionally substituted by an ammo group, and x has an average value in the range 2 to 150. 6. Use according to any one of Claims 1 to 5 wherein diesel oil has a sulphur concentration below 500 ppmw. 7. A method of operating a diesel engine under cold running conditions with reduced white smoke emissions which comprises running the engine on a diesel fuel containing a major proportion of a diesel oil and an effective concentration of a polyether derivative of formula I as defined in any one of Claims 1 to 5. 8. A method according to Claim 7 wherein the diesel oil has a sulphur concentration below 500 ppmw.

Inventors: CLAYTON CHRISTOPHER WILLIAM, COWLEY LESLIE THOMAS, DAY JANET ANNE, CLAYTON, CHRISTOPHER, WILLIAM, COWLEY, LESLIE, THOMAS, DAY, JANET, ANNE
Applicants: SHELL INT RESEARCH, SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1997
Main classification: C10L1
IPC codes: C10L1, C10L10