Internal combustion engines suffer from deterioration in performance and corrosion of their internal parts from the ingestion of impurities either within the fuel source or from atmospheric soils arriving through the airflow. The efficiency of turbocharged and normally aspirated engines gradually deteriorates as efficiency reducing deposits of carbons; silicates and airborne contaminants build up on the engine surfaces. The delicate air to fuel mixture is disturbed and the engine runs less efficiently than its design. This can be ameliorated by regular cleaning, but such activity is time-consuming and complex if, in order to clean the engine, it has to be disassembled, the parts cleaned, and the engine reassembled.

It is well-know that on line cleaning of metallic surfaces of engine components, particularly of aluminium and steel may be carried out by injecting cleaning compositions into an air inlet of a running engine, e. g. a static gas fuelled generating engine or automobile engine powered by gas, diesel or petrol. By injecting the invention into the engine via the airways the

engine will be cleaned in place and on line, as the cleaning product passes the sites of contamination, operation of the engine will be restored to optimum operating conditions.

Cleaning compositions and their use in this area are disclosed in UK-A- 1342077 and UK-A-2352730.

For all engines the product is delivered into the engine through the airways as an atomised spray either from a fixed automatic spray device or from a mobile hand held spray device, In each application, the product is atomised by a pressure pump to allow the delivery of the product throughout the combustion surfaces.

Cleaning an engine in this way reduces operational costs of running engines, whether fuelled by petrol, diesel or gas, by the in line removal of efficiency reducing deposits from the air intake, combustion surfaces and exhaust system. Once injected, the cleaning compound is carried into and through the engine by the air stream and out through the exhaust system.

While in many cases the deterioration in engine performance due to the build-up of deposits is generally slow, there are instances where, because of adverse environmental conditions, it occurs rapidly. One particular example is the use of diesel engines for generating electricity on landfill waste biomass or sewage sites, where operating efficiency deteriorates markedly accompanied by the erosion of engine parts by chemical contaminants derived from the waste. Typically in such circumstances, chlorides, fluorides, silicates and other silica based materials tend to form matrices with atmospheric contaminants and corrode engine parts over short periods of time. Compositions as disclosed in the specifications referred to above do not provide adequate cleaning in such cases.

A second example is found in automobile engines where incoming airborne contaminants including silica forms a matrix deposit under the valve seats;

such deposits have an adverse effect on the combustion process and can contribute to inefficient engine performance.

According to the present invention, there is provided an engine cleaning composition comprising, in an aqueous medium, at least one primary surfactant selected from non-ionic surfactants, and at least one glycol, and which includes catechol or a catechol derivative.

The composition may also include ingredients known for use in such compositions as a further aid to the removal of tightly bound carbon-and silica-based deposits. These include tar acids and dispersants for corrosion prevention. Uric acid is useful as a pH adjuster, and is found to improve cleaning penetration, as well as to assist stabilisation of the composition.

Acrylic acid may be included, and this is found to improve the attack of the composition on some types of silica deposits.

In such compositions, the surfactant is a main cleaning and dispersing component. Thermal stability is an important property to facilitate the product remaining fluid within the engine at temperatures above 350 degrees Celsius. The surfactant should not contain corrosive trace elements, particularly sodium, potassium and chlorine, as these encourage corrosion at high temperatures.

A preferred group of primary surfactants comprises the primary alcohol ethylene oxide condensates, for example those commercially available under the trade designation of Ethylan synthetic C12 surfactants (Akcros chemicals of Trafford Park, Manchester England). These give particularly good removal of. engine debris, especially of hydrocarbon based deposits, and have excellent soil penetration characteristics. The condensates have typically 6 to 15 moles of ethylene oxide per mole of alcohol.

Other suitable alcohol ethylene oxide condensates for use as the main surfactant may be obtained from a large number of commercial suppliers,

e. g. Libra Chemicals, Irlam, Manchester, England.

Preferably, in addition to the primary surfactant, the composition contains a second surfactant to enhance the attack on the build-up of contamination on engine components. A combination of primary alcohol/ethylene oxide condensates and ethoxylated amine surfactants is found to work well.

The glycols act as high temperature carriers, which are stable and able to remain as a fluid or in an active gaseous form so as to remain effective even at high temperatures. The glycol component may have additional surfactant properties to assist in cleaning and dispersion; it may also break down organic soils. Suitable glycols include mono propylene, polyethylene and triethylene glycols.

The inclusion of tar acid in the composition assists it in being able to penetrate and disperse carbon deposits commonly found within engines.

Tar acids generally have boiling points in the range of 230-280 degrees Celsius. A preferred tar acid ingredient for use in the composition is cresylic acid.

The water used in the formulation is preferably deionised water, with a conductivity of less than 10 microsiemen. The pH of the composition is preferably 6.0 to 9.5.

A further preferred inclusion in the composition is a proportion of long chain fatty acid amides. These assist the dispersion of the composition within the engine and also have corrosion-protecting effect.

The composition may also contain glacial acrylic acid. In addition to the buffering properties of this acid, its presence enhances the ability of the composition to remove silica from engine parts when deposited as a matrix with other engine contaminants.

Ammonia may be included in the composition to aid the removal of contaminants particularly chlorides, fluorides, silicates, and other corrosion producing contaminants. These impurities are particularly found in engines used for generating electricity and located on waste sites where deposited household waste degrades into a variety of chemical compounds which cause erosion within engine parts.

In accordance with the invention, the composition includes catechol or a catechol derivative, for example 4-t-butyl catechol which is commercially available from Coalite Products, Bolsover, Derbyshire and other suppliers (it is used as an antioxidant and polymerisation inhibitor). This is particularly useful in aiding the removal of silicates that may have deposited within an engine. Silicate is deposited as a result of impurities in the fuel being used in the engine; the silicate binds other erosion producing materials to the surfaces within the engine. To remove these deposits it is necessary to remove the silica thus breaking down the matrix and releasing the corrosion producing contaminants which are then removed via the engine exhaust.

The proportions of components in the cleaning compositions of the present invention are preferably in the following ranges expressed as percent by volume 0.5 to 15% primary surfactant, 15 to 35% of glycol, from 0.1 to 3.0% of tar acid, up to 5% by volume of acids selected from acrylic acid, uric acid and phosphonic acid, 0.5 to 2.0% catechol or derivative and up to 3.0% ammonia.

The composition may be initially formulated as a concentrate which is to be diluted appropriately with preferably deionised water before use.

We have found that the cleaning compositions according to the invention when injected into the air intake of a running engine, can penetrate and disperse carbon, silica, scale and hardened deposits of hydrocarbons as well as deposits of atmospheric contaminants. The deposits are converted to a fine dry powder that is carried out through the exhaust system.

In tests on static diesel engines on landfill sites, we have found that cleaning an engine with the composition according to the invention can reduce the erosion caused by contamination sufficiently to prolong the service life of the engine between overhauls by up to twenty times, The use of the composition according to the invention in individual combustion engines generally can also lead to a reduction in exhaust emissions of hydrocarbons, nitrous oxides, carbon dioxide and carbon monoxide by up to 80%, while increasing the power output of the engine, either for generating power or to drive a vehicle, by up to 20%.

The frequency and application rate of cleaning compositions when used to improve engine performance may vary widely, depending on the acceptable degradation in performance before cleaning is carried out. How rapidly performance degrades will vary with both operating and environmental conditions. For example, in a static diesel engine running on waste gas, typically methane, located on a landfill site, cleaning should be carried out at least every other day by spraying up to 5 litres of the composition into the air intake over a period of 1 to 24 hours In other engines either running on diesel, petrol or natural gas the product should be injected into the air intake at up to 1.5 litres per 2 litres of engine capacity as often as required.

Injection of the composition into the engine may be effected by fitting spray nozzles within the air intake.

The following are examples of preferred cleaning compositions according to the invention. In each case the deionised water has a conductivity of less than 10 microsiemen.

EXAMPLE 1 1. 5kg Ethoxylated Amine surfactant (Imbentin, ex Libra Chemicals) 24.5kg Alcohol Ethoxylate surfactant (UN65, ex Sufachem Group)

2.0kg Dimethylamides of long chain fatty acids (DMAD ex Buckman Laboratories) 1.5kg Tar Acid 0.5kg 4-t-butyl Catechol 200kg Mono Propylene Glycol 25 mi Ammonia 770 litres deionised water EXAMPLE 2 1. 5kg Ethoxylated Amine surfactant (Imbentin, ex Libra Chemicals) 24.5kg Alcohol Ethoxylate surfactant (UN65, ex Sufachem Group) 2.0kg Dimethylamides of long chain fatty acids (DMAD ex Buckman Laboratories) 1. 5kg Tar Acid 0.5kg 4-t-butyl Catechol 70kg Mono Propylene Glycol 25 ml Uric Acid 900 litres deionised water EXAMPLE 3 26kg Alcohol Ethoxylate surfactant (UN65, ex Sufachem Group) 1. 5kg 4-t-butyl Catechol 0.5kg Tar Acid 2.0kg Dimethylamides of long chain fatty acids (DMAD ex Buckman Laboratories) 70kg Mono Propylene Glycol 30 ml Ammonia 900 litres deionised water

EXAMPLE 4 26kg Ethoxylated Amine surfactant (Imbentin, ex Libra Chemicals) 2.0kg 4-t-butyl Catechol 2.0kg Dimethylamides of long chain fatty acids (DMAD ex Buckman Laboratories) 200 litres Mono Propylene Glycol 25 mi Glacial Acetic Acid 770 litres deionised water In each of examples 1 to 3, part or all of the tar acid can be replaced by the 4-t-butyl catechol. In each example, the mono propylene glycol can be partly or wholly replaced by a polyethylene glycol of molecular weight in the range 300 to 1500.

Example 5 26 kg Ethoxylated Amine (Imbentin) 0.5kg Catechol 1. 5kg Tar Acid 2.0kg DMAD 70.0kg Monopropylene Glycol 20. Omls Acrylic Acid 900 litres Deionised water Example 6 24kg Alcohol Ethoxylate (Sufachem) 2kg Ethoxylated Amine (Imbentin) 0.5kg Catechol 1.5kg Tar Acid 2.0kg DMAD 70.0kg Monopropylene Glycol 15mls Acrylic Acid 900 litres Deionised water