NZ202502A - Use of tetrahydrofurfuryl nitrate as a fuel additive - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £02502 m 202502 Priority < • J • Cciripi&l-a Cpscification Fslsd: rw,.. ctoL i la a z:? v":;; * * 2 O'mar I985 Is&iC1'. ■ ■ p.C. Jer- '--al, No: .......

No.: Date: NEW ZEALAND PATENTS ACT, J 953 COMPLETE SPECIFICATION FUELS . xi/We, AECI LIMITED of 16th Floor, Office Tower, Carlton _ Centre, Commissioner Street, Johannesburg, Transvaal Province, \rtl * . J- , IfepwUlC yy Republic of South Africa, a Company registered in the Ropuplie- Vvy/ of South Africa hereby declare the invention for which jfx/ we pray that a patent may be granted to vaalus, and the method by which it is to be performed, to be particularly described in and by the following statement: - THIS INVENTION relates to ignition improvers for compression-ignition (dies-el) fuels.

Due to the increasing cost and predicted inadequate supplies of conventional diesel fuel, alternatives are being » sought by many agencies world-wide. Proposed alternatives include wider cut fractions from crude oil, products from coal liquification, materials from renewable resources such as vegetable oils and ethanol, and methanol from coal or natural gas. Many of these alternatives have a cetane number too low to enable their direct use in compression-ignition engines. Consequently the development of cetane-improving additives (ignition improvers) for such fuels is of considerable interest.

The use of methanol (cetane number approximately 3) and ethanol (cetane number approximately 8) present a particularly challenging problem, since relatively high levels of ignition improvers are required to permit these alcohols to be used as compression-ignition fuels. 202soi Various nitric acid mono-esters have been proposed as" ignition improvers, particularly the nitric-acid esters of the C2 to Cg alkanols, 2-alkoxy ethanols, and l-alkoxy-propan-2-ols. To permit methanol or ethanol to be used as a diesel 5 fuel, additions of at least 10% v/v of such compounds are required. Correspondingly lower amounts are required to upgrade base fuels of higher cetane rating.

It has now been found that the nitric acid mono-ester of tetrahydrofurfuryl alcohol (tetrahydrofurfuryl nitrate, 10 'THFN') and related compounds, are considerably more effective ignition improvers for alcohol fuels than other nitric acid mono-esters known by the inventor. In particular, an addition of between 1,0 and 7,5% THFN to methanol or ethanol was found to be sufficient to enable these alcohols to be used as diesel fuels.

The present invention provides the use of tetrahydro furfuryl nitrate as an additive to improve the compression-ignition quality of liquid fuels.

The invention also provides a liquid composition comprising from 0,01 to 99% by weight of THFN in admixture with 20 one or more combustible organic materials. Compositions containing up to about 10% by weight THFN may be used as fuels for compression ignition engines, and compositions containing higher concentrations of THFN may be used as blending stock for the preparation of compression-ignition fuels. 202507 The invention further provides a method of operating a compression-ignition engine which comprises supplying to the engine a liquid fuel comprising from 0,01 to 10% by weight of THFN, and one or more combustible organic materials.

The invention also provides a method of improving the ignition and/or combustion characteristics of a fuel which comprises admixing therewith from 0,01 to 10% by weight of THFN.

The fuels] combustible organic materials, and the like, with which the THFN is admixed, can be any suitable material. For example, one or more of an alcohol or mixture of alcohols containing from 1 to 12 carbon atoms (such as methanol or ethanol), a hydrocarbon or mixture of hydrocarbons (such as gasoline) or a low cetane diesel fuel, can be present. The THFN is especially suitable for admixing with fuels which in the absence of THFN have inadequate spontaneous ignition characteristics for use as compression-ignition fuels, but when mixed with THFN are suitable for use as fuel compositions for compression ignition engines.

THFN can be prepared by nitration of tetrahydrofurfuryl alcohol under conditions conductive to nitrate ester formation. In particular, THFN can be prepared by reacting tetrahydrofurfuryl alcohol with nitric acid in the presence of acetic anhydride at temperatures below room temperature. 202502 The following non-limiting Examples illustrate the invention: EXAMPLE 1 A mixture of 5,5 ml of 98% HNO^ and 14 ml of acetic anhydride was slowly added to 25 g of tetrahydrofurfuryl alcohol at 0°C over 30 minutes. The mixture was drowned in 300 ml of water, the organic layer separated, neutralized with aqueous ammonia solution, washed with water, and dried. 14,4 g of product were obtained, which was identified as tetrahydrofurfuryl nitrate .by * infra-red spectroscopy. The THFN so prepared can be used as an ignition improver.

The quantity of THFN to be admixed with combustible materials to provide a fuel according to the invention will be dependent on the extent of the ignition quality improvement required, and can be determined by experiment.

EXAMPLE 2 Fuels comprising 6% of the test compound, 1% of castor oil, and 93% of methanol were used to operate an instrumented single-cylinder direct-injection air-cooled diesel engine of 15,7:1 compression ratio driving a 250V, 15 A generator at 1500 rpm. The test compounds were: (a) tetrahydrofurfuryl nitrate, as well as (b) cyclohexyl nitrate, (c) ethoxy ethyl nitrate.

A fuel (d) comprising 45 cetane hydrocarbon diesel fuel was used for comparison. 202uQ2 In cases (b) and (c), the engine failed to fire even when hot, whereas in cases (a) and (d) the engine started easily from cold, idled smoothly, and ran normally under all load conditions- The display of cylinder pressure indicated that the combustion characteristics of the THFN-based fuel were 10 satisfactory for normal operation of the engine.

EXAMPLE 3 The following fuel compositions, suitable for use in a compression ignition engine, were prepared by mixing together a combustible fluid (by itself unsuitable for use as a compression ignition fuel), castor oil (as a lubricant) and THFN (to act as ignition improver). The components mixed easily to form fuels which were clear solutions.

Fuel A: 940 ml methanol ml castor oil 50 ml THFN Fuel B: 940 ml ethanol ml castor oil 50 ml THFN Fuel C: 400 ml methanol 400 ml ethanol 140 ml and higher alcohols 10 ml castor oil 50 ml THFN Fuel D: 50 0 ml methanol 440 ml gasoline 10 ml castor oil 50 ml THFN fT Fuel E: 940 ml gasoline ml castor oil 50 ml THFN EXAMPLE 4 The fuel compositions of Example 3 were used to operate the engine of Example 2. In all cases, the fuel compositions started and ran the engine in a satisfactory manner, under all speed and load conditions. This satisfactory operation i exemplified by the following ignition data, determined under the stringent condition of rated speed, no load: Fuel Firing Point Ignition Delay °BTDC m.Sec A 4,5 0,83 B 4,5 0,83 C 5,0 0,78 D 4,3 0,86 E 5,4 0,73 Fuels without addition of THFN would not ignite at all in the engine. The gasoline component of fuels D and E is used to represent a very low cetane hydrocarbon mixture, unsuitable for use alone in a compression-ignition engine.

The inventor has not been able to use low cetane fuels, such as methanol, ethanol or gasoline (on their own or mixed with

Claims (11)

20250 castor oil as a lubricant) as the fuel in a conventional compression ignition engine. However, when mixed with THFN they can be used as a fuel in such an engine, as is shown by the above examples. Thus addition of THFN to a suitable combustible material will enable that combustible material to be used as a fuel in a compression ignition engine. *02502 WHAT$1WE CLAIM IS;

1. The use of tetrahydrofurfuryl nitrate as an additive to improve the compression-ignition quality of liquid fuels.

2. The use as claimed in Claim 1, wherein tetrahydrofurfuryl nitrate is used as an additive to a compression-ignition fuel comprising one or more of an alcohol or mixture of alcohols, a hydrocarbon or mixture of hydrocarbons, or a low cetane diesel fuel.

3. A liquid composition comprising from 0,01 to 99% by weight of tetrahydrofurfuryl nitrate in admixture with one or more combustible organic materials.

4. A liquid composition as claimed in Claim 3, wherein the combustible organic material comprises an alcohol or mixture of alcohols, one or more hydrocarbons, or a low cetane diesel fuel.

5. A liquid composition as claimed in Claim 4, wherein the alcohol is methanol or ethanol.

6. A liquid composition as claimed in any of Claims 3 to 5, said composition being suitable for use as a fuel for compression-ignition engines and containing 0,01 to 10% by weight of tetrahydrofurfuryl nitrate. -10- 202502

7. A method of operating a compression-ignition engine, which comprises supplying to the engine a liquid fuel comprising from 0,01 to 10% by weight of tetrahydrofurfuryl nitrate and one or more • combustible organic materials.

8. A method of improving the ignition and/or combustion characteristics of a fuel which comprises admixing therewith from 0,01 to 10% by weight of tetrahydrofurfuryl nitrate.

9. A liquid composition, substantially as described with reference to Example 2 or Example 3.

10. A method of operating an engine, substantially as described with reference to Example 2 or Example 4.

11. ik method of improving the ignition and/or combustion characteristics of a fuel, substantially as described. DATED THIS (O1^ DAY OF A . J PARK & SON PER Q - AGENTS^OR THE APPLICANTS