GB2071140A - Antifreeze for fuels - Google Patents

Abstract

Fuel for internal combustion engines, particularly diesel engines, contains as a fuel antifreeze a combustible liquid which is miscible with petroleum fuel and with water, suitable antifreeze additives being methanol, 2-methoxyethanol and glycol ethers. The antifreezing additive prevents the freezing of water droplets entrained in the fuel, this ice formation being more commonly responsible for starting problems than actual freezing of the fuel itself. The fuel may also contain additives such as emulsifiers to promote dispersion of water droplets, low flash point liquid such as acetone or combustible oxidising agents such as methyl nitrate to facilitate cold starting, lubricants and corrosion inhibitors. A diesel tractor has been regularly run on the non-freezing fuel over a period of thirteen months during which time engine performance has not been affected and no starting difficulties during cold weather (down to -7 DEG C) have been experienced.

Description

SPECIFICATION Antifreeze for fuels This invention relates to an antifreeze additive for fuels, particularly but not exclusively, diesel fuel.

In cold weather difficulties encountered in starting internal combustion engines are caused by a variety of effects such as increased oil viscosity, lowering of battery power and freezing of the fuel. This latter cause is, it has been found, an over-simplification of the problem. Investigation ofthe so-called "freezing" of fuel, has revealed that it is less usual for the fuel itself to freeze, but rather that water droplets in the fuel freeze to ice particles which block the fuel lines. Additionally, engine stalling during operation in cold, damp weather can be caused by transient carburettor icing through evaporative cooling. Of course, at lower temperatures the fuel, particularly diesel, can itself solidify but temperatures low enough to achieve this are rare in an average British winter.

An object of the present invention is to provide a fuel additive which lowers the apparent freezing temperature of the fuel, i.e. the temperature at which start-up and operation of an engine is inhibited by the condition of the fuel.

According to the present invention there is provided fuel composition for an internal combustion engine comprising a combustible petroleum liquid fuel containing as an antifreezing additive a watermiscible combustible liquid.

Typical examples of the additive are, methanol and higher alcohols and glycol ethers such as dipropylene glycol methyl ether and diethylene glycol ethyl ether.

The freezing problems of fuel are initiated normally by condensation of atmospheric moisture in fuel storage tanks or in the fuel tank of a vehicle itself. It is this condensate which subsequently freezes and creates blockages in the engine fuel lines. At lower temperatures, fuel filters also become blocked by a waxy precipitate from diesel fuel itself.

The addition of a water-miscible combustible liquid to the fuel depresses the freezing point of the water therein, the degree of depression being proportional to the concentration of the added liquid in the water.

The fuel of this invention may additionally contain an emulsification or dispersion agent to promote emulsification of the entrained water with the fuel and/orto break up and disperse water droplets throughout the fuel, the object of the agent being to produce as far as possible a fuel/water emulsion since it is known that most engines can tolerate high water contents (up to 7% v/v) in the fuel provided that: (i) the water is in the emulsified state: (ii) the water contains combustible solutes: and (iii) the surface tension of the water is low enough to ensure that the fuel intake jets remain unblocked.

Condition (i) can be satisfied by the addition of an emulsifying or dispersing agent and conditions (ii) and (iii) by the presence of the water-miscible combustible liquid additive.

The emulsifying or dispersing agent may be, for example, a combustible low-foaming non-ionic surfactant such as a modified aliphatic alcohol ethoxylate.

To assist cold-starting of diesel engines it may be advantageous to add to the composition liquids of low flash-point such as acetone, miscible with fuel and water, and/or diethyl ether or petroleum spirit b.p. 40-60"C, miscible mainly with the fuel and/or a combustible (or explosive) oxidising agent such as methyl (or isopropyl or isoamyl) nitrate, miscible with the fuel.

To avoid engine wear possibly caused by dissolution of oil from cylinder bores, upper cylinder lubricant may be one constituent of the fuel composition, added in the recommended proportion. Oleophilic and/or hydrophilic corrosion inhibitors for steel, copper and aluminium may be present in the fuel composition e.g. N-acyl sarcosine (Trade Mark Sarcosyl 0), modified benzotriazoles (Trade Marks Reomet 38, Reomet 41).

The invention will now be described by way of illustration in the following Examples.

In the Examples, the symbol "p" means specific gravity.

Petrol Additive EXAMPLE 1 To 10 gallons (45.5 litres, 35 kg) petrol (p 0.77) containing water add 150 ml (118.5 g) of pure methanol (p 0.79). Methanol partitions between water and fuel layers with a preference for water (lower) layer. For 1% v/v water, the freezing point depression of water layer is found to be 15-19 (calc.

9 15 ) and the water loses its high surface tension.

For 2% and 3% v/v water, the freezing point depressions are 4-6" (calc. 9 7.6 ) and 3 (calc. > 5 ).

EXAMPLE 2 To achieve partial mixing of water with fuel, the alkyl content of the alcohol is increased by dissolving in it 0.4 to 10% w/w of a glycol ether e.g. 2 methoxy - ethanol or dipropylene glycol methyl ether (DPM) or ethyl digol (diethylene glycol ethyl ether) (ED). Viz. 498 g methanol containing 2 g DPM (or ED) to 450 g methanol containing 50 g DPM (or ED). For 10 gallons petrol containing 1%v/vwater, treated with 150 ml of a solution of DPM (2 g) in methanol (498 g), the freezing point depression of water layer is 11-14'; treated with 150 ml of a solution of DPM (509) in methanol (450 g), the freezing point depression is 12-15". For ED in methanol, the corresponding freezing point depressions are 12-16" and 11-15".

EXAMPLE 3 Emulsification of water and fuel layers may be achieved by including in the additives in Examples 1 and 2 up to 2% w/w of a combustible, low-foaming, non-ionic surfactant namely a linear aliphatic alcohol ethoxylate, modified (Trade Mark Ethylan CPG 630 or Ethylan CPG 660). 45.5 ml water treated with 15 ml of a solution of Ethylan CPG 630 (4 g) in methanol (196 g) freezes between -12"C and -14"C.

Diesel Additive Methanol (p 0.79) is immiscible with and less dense than diesel fuel (p 0.84). It is thus unsuitable as a single anti-icing additive since, without agitation, methanol and water would be the top and bottom layers of the three phase system water/ diesel i methanol. However methanol may be one compo nent of an anti-icing mixture.

EXAMPLE 4 To 10 gallons (45.5 litres, 38.2 kg) diesel fuel containing water add 300 ml (285.3 g) of pure DPM (p 0.95, mw 148). DPM partitions between water and fuel and causes some mixing of layers. For 1% v/v water, the freezing point depression of water layer is 8-10 (calc. t 7 ) and the water loses its high surface tension.

EXAMPLE5 In the composition of Example 4, to reduce the molecular weight of the additive (so asto increase its freezing point depression for the same weight of solute) and introduce a material of low flash point, up to 50% v/v DPM is replaced by acetone or methanol (flash point 12.2"C). Acetone (p 0.79, flash point -9.4 C) is less dense than diesel fuel (flash point 43-880C; ASTM D975 No. 1 -D min. 38"C) and is miscible with it in all proportions.

For 10 gallons diesel fuel containing 1 % v/v water, treated with 150mlDPM and 150 mlacetone,the freezing point depression of the water layer is 10-20" (calc. p 120).

With a sufficiently high proportion of methanol present, the separated superficial methanol layer serves to absorb moisture from the air space in the fuel tank and sweeps the sides for adhering water droplets. Both effects reduce further accumulation of water.

EXAMPLE6 Emulsification of water and fuel layers may be achieved by including in the additives in Examples 4 and 5 up to 2% wlw of a low-foaming, non-ionic surfactant e.g. Ethylan CPG 630 or Ethylan CPG 660.

45.5 ml water treated with 30 ml of a solution of Ethylan CPG 630 (6 g) in DPM (294 g) freezes between -12"Cand -22"C.

EXAMPLE 7 The viscosity increase and precipitation of actual diesel fuel in extremely cold conditions can be alleviated by replacing up to 10% v/v of fuel buy a lower-freezing hydrocarbon e.g. kerosene (freezing range -40 to -60 C), petrol (freezing range < - 100 C), heptane (freezing point - 91 C) etc. A combined treatment of diesel fuel at 10% v/v is effected as follows: In 1 gallon kerosene dissolve 300 ml of additive described in Examples 4,5 or 6. Add this solution to 9 gallons of diesel fuel. The diesel layer first shows opalescence at -5 C and remains mobile, with increased viscosity, down to -150Cto -20 C.

The freezing properties of the fuel compositions were examined in glassware. In addition, engine testing showed fuel characteristics unimpaired.

Samples of petrol and diesel, each containing varying amounts of water were progressively cooled. By - 1 C the water layer (lower layer in both cases) had frozen. Petrol showed no change to -20 C while diesel fuel on cooling below -1"C became increas ingly viscous, cloudy and set to a semi-rigid, noncrystalline mass atca. -16 C. (Temperatures referto interior of test vessels, not to exterior atmosphere.) A Ford Cortina 2000 estate car 11976) has been run almost continuously for nine months with these additives (including diesel formulations) in the fuel with no ill-effects.The fuel tank of a David Brown diesel tractor has been regularly treated with the diesel formulations over thirteen months, during which time engine performance has remained unaffected. Similarly, samples have been tested for shorter periods in other vehicles viz. Ford Cortina 2000 estate car (1973), Reliant Regal van (1971), Bedford 6 cwt. van (1974), Renault 5 (1975) and diesel tand Rover. In all cases, no difficulties in starting or running have been encountered during frequently damp and cold (down to -7 C) atmospheric conditions.

Testing with up to 7% v/v added water in petrol, containing the additives, was carried out on a 1-cylinder 4-stroke lawnmowerwith a transparent fuel pipe. This lawnmowerwas normally difficult to start from cold but when the fuel contained added water and additives (for petrol) it started cold on the second pull.

Diesel additives were tested on a cylinder portable water pump. It ran for prolonged periods on treated fuel either alone or with up to 2% added water and restarted easily when warm or cold in all cases. With the fuel tank charged with 1 litre diesel fuel containing 0.8% vivwater and 8 ml additive (Example 5, DPM-methanol 4:1 v/v) the fuel line did not freeze up when immersed for 3 hours in ice-salt (bath temp. - 1 80C). A more rigorous test, with fuel tank surrounded by solid carbon dioxide, on 1 litre fuel containing 1.2% v/v) water and 8 ml additive (Example 5, GPM-methanol 4:1 v/v) showed freezing of both layers by -18"C to -19 C (inside tank) resulting in stalling of engine. However, the engine ran efficiently on the two layers present which remained liquid down to -15" (inside tank), with the upper layer extremely cloudy.

Claims (17)

1. Fuel for an internal combustion engine comprising a combustible petroleum liquid fuel and, as an antifreezing additive, a water-miscible combustible liquid.

2. Fuel as claimed in claim 1, in which the additive is an alcohol.

3. Fuel as claimed in claim 2, in which the additive is methanol.

4. Fuel as claimed in claim 2, in which the alcohol is 2-methoxyethanol.

5. Fuel as claimed in claim 1, in which the additive is a glycol ether.

6. Fuel as claimed in claim 5, in which the glycol ether is dipropylene glycol methyl ether or diethylene glycol ethyl ether.

7. Fuel as claimed in any preceding claim which additionally contains an emulsifying or dispersing agent.

8. Fuel as claimed in claim 7, in which the emulsifying or dispersing agent is a modified aliphatic alcohol ethoxylate.

9. Fuel as claimed in any preceding claim, which additionally contains a low flash point liquid.

10. Fuel as claimed in claim 9, in which the low flash point liquid is acetone, diethyl ether or pet roleum spirit of boiling range 40 to 60"C.

11. Fuel as claimed in any preceding claim, which additionally contains a combustible oxidising agent which is miscible with the fuel.

12. Fuel as claimed in claim 11, in which the oxidising agent is methyl, isopropyl or isoamyl nitrate.

13. Fuel as claimed in any preceding claim, which additionally contains an upper cylinder lubricant.

14. Fuel as claimed in any preceding claim, which additionally contains an oleophilic or hydrophilic corrosion inhibitor for steel, copper or aluminium.

15. Fuel as claimed in claim 14, in which the inhibitor is N-acylsarcosine or a modified benzotriazole.

16. Fuel according to any one of Examples 1 to 7 hereinbefore.

17. Fuel, according to claim 1, substantially as hereinbefore described.