ETHANOL FUEL AND ITS USE AS A DIESEL FUEL

Abstract: The present invention relates to a fuel having the form of a solution and containing 62-94% by weight of ethanol, 2-8% by weight of water and at least 1%, preferably 2-30% by weight of a water-soluble polyalkylene glycol compound which contains 6-50 alkylene oxide units having 2-4 carbon atoms and which has a molecular weight of less than 2500. The fuel is suitable for use in diesel engines.

Description: ETHANOL FUEL AND ITS USE AS A DIESEL FUEL The present invention relates to an ethanol fuel which contains polyalkylene glycol compounds as ignition- improving agent. In a diesel engine, the combustion air is com- pressed to about 40 bars, the air reaching a temperature sufficiently high to ignite the diesel oil which is being injected. For gas oil, the temperature of use is specified at 336°C, and for kerosene at 295°C. For anhydrous ethanol, the ignition temperature in air is specified at 558°C, and in oxygen gas at 425°C. Morover, the evaporation of ethanol corresponds to a cooling of air by about 125°C in a stoichiometric relationship between ethanol and air. Because of the high ignition temperature of the ethanol , it is not possible to use pure ethanol as fuel in a conventional diesel engine. One way of igniting the ethanol fuel is to provide the diesel engine with spark plugs, but this necessi¬ tates extensive modifications to the engine construction. For conventional diesel engines, a so-called ignition- improving agent, i.e. an agent which serves to lower the ignition temperature of the fuel , has been added to the ethanol . The predominant ignition-improving agent is the group consisting of alkyl nitrates, and the most used substrate is 2-ethylhexyl nitrate, generally abbreviated EHN. EHN which has a rather strong and disagreeable odour, is toxic and can be hydrolysed to nitric acid and 2-ethylhexanol when stored for longer periods of time, especially at elevated temperature. The hydro¬ lysis causes a marked lowering of the pH, implying a serious risk of corrosion. A further serious objection to EHN is that the substance contains nitrogen which may increase the emission of nitrogen oxides with thr* exhaust gases. Therefore, it is generally desirable that EHN and other nitrate-based ignition-improving agents can be replaced by an agent which is less hazardous to the environment and has higher stability. It is also known to add corrosion inhibitors and lubricants to fuels. German Patent Application A1 , 3,628,504 describes a fuel mixture of hydrocarbons, an alcohol and a corrosion inhibitor in an amount of up to 5000 ppm. This inhibitor contains a surface active agent, e.g. block polymers of alkylene oxides. British Patent Application A2, 143,846 discloses the use of 0.005-0.05% by weight of a polyalkylene glycol as a lubricity improver in a diesel fuel based on methanol and/or ethanol. It has been found that the above-mentioned dis¬ advantages of EHN can be eliminated if polyalkylene glycol compounds are used as ignition-improving agent in ethanol fuel. The ethanol fuel according to the invention is characterised in that it is in the form of a solution and contains 62-94%, preferably 70-85% of ethanol, 2-8%, preferably 3-6% of water, and at least 1%, suitably 2-30%, and preferably 8-25% of a water-soluble polyalkylene glycol compound which contains 6-50 alkylene oxide units having 2-4 carbon atoms and which has a molecular weight of less than 2500. Specific examples of such polyalkylene glycol compounds are those which can be expressed by the general formula R 0(A) H, wherein R is hydrogen or a hydrocarbon group having 1-30 carbon atoms, A is an alkylene oxide group having 2-3 carbon atoms, at least 20% of all alkylene oxide groups being ethylene oxide groups, and n is an integer selected such that the polyalkylene glycol compound has a molecular weight of from 300 to 2000, preferably from 400 to 1000. Other useful polyalkylene glycol compounds are compounds in which alkylene oxide having 2-1 carbon atoms has been combined with a thiol compound, a carboxy- lic acid, a primary or secondary amine, or an alkanol amine in such an amount that the polyalkylene glycol compound will obtain the required molecular weight. In the conventional diesel engine, the addition of the polyalkylene glycol coumpound preferably amounts to 12-20% by weight, but by optimising the engine, e.g by increasing the compression ratio and/or pre- heating of inlet air, the addition can be reduced, preferably to 2-12% by weight. The ethanol composition of the present invention has an excellent inflammability, and the polyalkylene glycol compounds are odourless, nontoxic and stable in storage. Since they can easily be chosen in such a manner that they only contain carbon, oxygen and hydrogen, their combustion con¬ stitutes no hazard to the environment, and tests have shown that the ethanol fuel according to the invention has excellent combustibility, and that the content of organic hydrocarbons is low, usually far below 1000 ppm. It is important that the polyalkylene glycol compounds have a molecular weight higher than 300, because compounds of lower molecular weight have an ignition-improving effect which is far too low, whereas compounds having a molecular weight higher than about 2500 are not sufficiently soluble in the ethanol fuel. If large amounts of polyalkylene glycol compound are added, the molecular weight thereof should not exceed 1000 in order to ensure satisfactory solubility in the ethanol fuel. The polyalkylene glycol compounds according to the invention may be derived from both ethylene oxide and mixtures of ethylene oxide and propylene oxide. If mixtures of ethylene oxide and propylene oxide are used, these may be both randomly combined and combined in one or several blocks. The alkylene oxides can also be combined with a compound containing active hydrogen, such as an alcohol, carbo- xylic acid, amine, thiol or a phenol compound. 'I'ho alco ¬ hol, carboxylic acid, amine or thiol is preferably selected such that it contains 1-16 carbon atoms, and the phenol compound such that it contains 6-15 carbon atoms. Preferably, the polyalkylene glycol compounds are essentially free from ashes, e.g. lower than 0.02%, in order to minimise deposits in cylinders and exhaust catalytic converter. Normally, the polyalkylene glycol compounds contain ashes derived from the metal compounds used in the production. These metal compounds may be removed by ionic exchange or by precipitation followed by filtration. Another method to obtain ash-free poly¬ alkylene glycols is to use organic ash-free compounds as catalysts in the production. Besides ethanol, water and the polyalkylene glycol compounds, the fuel according to the invention may also contain a number of conventional additives, such as corrosion inhibitors, lubrication-improving agents and denaturants. To further illustrate the present invention, the following Examples are given. Example 1 Different ethanol fuels were tested in a six- cylinder supercharged laboratory diesel having a com¬ pression ratio of 18:1. The fuel injectors had five holes with a diameter of 0.42 mm. During the test, the content of organic hydrocarbons in the exhaust gases at different engine speeds and at a load of 2% was determined. The ethanol fuels tested contained 60.8 parts by weight of ethanol, 3.2 parts by weight of water and 22 parts by weight of polyethylene glycol of molecular weight by 400 (PEG 400), or 20 parts by weight of an adduct consisting of nonyl phenol combined with 16 mols of EO (NF + 16 EO), or of dinonyl phenol combined with 20 mols of alkylene oxide con- sisting of a mixture of 30% ethylene oxido and 70% propylene oxide (DNF+(6 EP+14 PO)). The followinq results were obtained. The results show that the ethanol fuel according to the invention can advantageously be used as a diesel fuel, and that the hydrocarbon content in the exhaust gases is essentially below 1000 ppm. Contents above 1000 ppm in the exhaust gases are unacceptable for environmental reasons. Example 2 Test were conducted with the same diesel engine as in Example 1. The diesel engine was warmed up at 1300 rpm at a load of 550 Nm, whereupon the engine was run for ten minutes at idle speed. The diesel fuel consisted of 60.8 parts by weight of ethanol, 3.2 parts by weight of water, and 14 or, alternatively, 17 parts by weight of polyalkylene glycol coumpound consisting of nonyl phenol combined with 16 mols of ethylene oxide per mol of nonyl phenol (NF+16 EO). For some tests, the engine was also equipped with a catalyser for exhaust purification. The results show that also during idling, when they hydrocarbon emission of a diesel engine normally is very high, the hydrocarbon content will stay well below 1,000 ppm when an ethanol fuel according to the present invention is used. Example 3 In the same way as in Example 1 , a ethanol fuel was tested at 2,000 rpm. The ethanol fuel contained 60.8 parts by weight of ethanol, 3.2 parts by weight of water and 18.7 parts by weight of polyethylene glycol having a molecular weight of 600. The exhaust gases were found to contain 650 ppm of organic hydro¬ carbon.

Claims: CLAIMS 1. A fuel, c h a r a c t e r i s e d in that it is in the form of a solution and contains 62-94% by weight of ethanol, 2-8% by weight of water and at least 1%, preferably 2-30% of weight of a water-soluble polyalkylene glycole compound containing 6-50 alkylene oxide units having 2-4 carbon atoms and which has a molecular weight less than 2500. 2. A fuel as claimed in claim 1, c h a r a c¬ t e r i s e d in that the water-soluble polyalkylene glycol compound has the general formula R 0(A) H, wherein R is a hydrogen or a hycrocarbon group having 1-30 carbon atoms, A is an alkyleneoxy group having 2-3 carbon atoms, at least 20% of all alkyleneoxy groups being ehtyleneoxy groups, and n is an integral selected such that the polyalkylene glycol compound has a molecular weight of from 300 to 2,000. 3. A fuel as claimed in claim 1 and 2, c h a ¬ r a c t e r i s e d in that it contains 70-85 % by weight of ethanol, 3-6 % by weight of water, and 2-20% by weight of the polyalkylene glycol compound. 4. Fuel as claimed in claim 1, 2 or 3, c h a ¬ r a c t e r i s e d in that the polyalkylene glycol compound has a molecular weight of 400-1000. 5. Fuel as claimed in claim 1, 2, 3 or 4 , c h a r a c t e r i s e d in that the polyalkylene glycol has an ash content of less than 0.02%. 6. Use of a composition having the form of a solution and contains 62-94 % by weight of ethanol, 2-8 % by weight of water and 2-30 % of weight of a water-soluble polyalkylene glycol compound containing 6-50 alkyleneoxy units having 2-4 carbon atoms and a molecular weight less than 2500, as a diesel engine fuel . 7. Use as claimed in claim 6, c h a r a c ¬ t e r i s e d in that the water-soluble polyalkylene glycol compound has the general formula R 0(A) H, wherein R is hydrogen or a hydrocarbon group having 1-30 carbon atoms, A is an alkyleneoxide group having 2-3 carbon atoms, at least 20% of all alkylene oxide groups being ethylene oxide groups, and n is an integer selected such that the polyalkylene glycol compound has a molecular weight of from 300 to 2000. 8. Use as claimed in claim 6 or 7, c h a r a c ¬ t e r i s e d in that the composition contains 70-85% by weight of ethanol, 3-6% by weight of water and 2-20% by weight of the polyalkylene glycol compound. 9. Use as claimed in claim 6, 7 or 8, c h a ¬ r a c t e r i s e d in that the polyalkylene glycol compound has a molecular weight of 400-1000. 10. Use as claimed in claim 6, 7 or 8, c h a ¬ r a c t e r i s e d in that the polyalkylene glycol has an ash content of less than 0.02%.

Inventors: CARLSSON GOERAN, HELLSTEN MARTIN, CARLSSON, GOERAN, HELLSTEN, MARTIN
Applicants: BEROL NOBEL STENUNGSUND AB
Application year: 1989
Main classification: C10L1
IPC codes: C10L1, F02B3