WO2000023542A1

WO2000023542A1 - Automotive liquefied petroleum gas (lpg) detergent additive composition

Info

Publication number: WO2000023542A1
Application number: PCT/AU1999/000887
Authority: WO
Inventors: John Norman Bennett; Stephen John Andrews
Original assignee: Mobil Oil Australia Pty Ltd
Current assignee: Mobil Oil Australia Pty Ltd
Priority date: 1998-10-16
Filing date: 1999-10-15
Publication date: 2000-04-27
Anticipated expiration: 2001-04-16

Abstract

An automotive LPG detergent additive comprising a base carrier fluid and a detergent. Generally, the base carrier fluid includes from about 35% to about 99% of a fraction which has a distillation range from about 130° to 200 °C.

Description

WO 00/23542 _^ _ PCT/AU99/00887

AUTOMOTIVE LIQUEFIED PETROLEUM GAS [LPG1 DETERGENT ADDITIVE COMPOSITION

This invention relates to detergent additive package compositions to be added to liquefied petroleum gas ("LPG").

LPG is used as an alternative fuel to petrol and diesel for internal combustion engines, such as in particular in the modern motor vehicle. The vast majority of automotive vehicles are powered by petrol.

LPG is a gas under atmospheric conditions and in storage, such as in the tank of a motor car, is maintained under pressure in liquid form. In use in motor vehicles it is flash-vaporised to a gas by an LPG converter. The resultant gas is then mixed with air by the vehicle's carburettor and then combusted in the engine in the normal way. By contrast with petrol powered vehicles the LPG fuel is presented wholly as a gas rather than as a mixture of gas and liquid droplets.

LPG inevitably has a certain level of impurities. These have the capacity to form gum like residues in those parts of the engine which come into contact with the fuel; in particular the LPG converter. Such gum residues can accumulate over time and lead to various performance problems, including loss of fuel efficiency, difficulties with ignition i.e. at start-up, and increases in maintenance and running costs. In addition compliance with emission requirements may be reduced.

A major potential source of gum forming residues in LPG is in its source raw material and previous efforts have concentrated in-part on reducing the amount of residues from that raw material; this applies equally to refinery or naturally produced product. However, at best, traces of impurities remain from the raw product. Furthermore, impurities and contaminants are encountered throughout the distribution chain where leaching of soluble organic compounds from a variety of sources, such as hoses used on tank trucks and distribution pumps, compressor oils and the like, also contribute to the accumulation of these potential gum forming materials.

It has been found that irrespective of the amount of purification of the raw materials and other elements involved in the production and distribution of LPG, inevitably some level of gum forming impurities remain in the LPG product delivered to a consumer's vehicle. Over time, even small concentrations of impurities lead to the deposition of residues throughout the engine; in particular the LPG converter.

Accordingly, it would be desirable to reduce the amount of deposition of gum forming materials in the converters of LPG powered engines.

Rather than attempt to further purify the LPG fuel itself, or further modify the distribution chain infrastructure both of which have shown in the past to be of only limited solution, the present inventors have approached the problem of residue deposit by developing an additive system which limits the ability of the potentially gum forming residues to adhere to the LPG converter and other engine fuel system surfaces, and consequently assists in keeping the engine's fuel system clean; in particular the LPG converter.

According to a first aspect, the invention provides an automotive LPG detergent additive composition comprising a base carrier fluid and a detergent.

The detergent additive composition of the invention is such that when added to LPG fuel, it is atomised into a fine liquid particle spray, which continually flushes the LPG converter and the other components of the engines fuel system, thereby reducing the formulation of gummy residues in the engines fuel system. Any heavy gum deposits that remain in the LPG converter are solubilised by the detergent additive package and can be drained from the converter via a drain plug. Base Carrier Fluid

The base carrier fluid provides a base for the carriage of the detergent through the fuel system and flushing deposits from the converter.

It is important that the complete additive composition has an appropriate distillation range. The distillation range is determined primarily by the base carrier fluid. In order for the detergent additive to work to flush the fuel system it must be in a sufficiently atomised form. The detergent component of the complete additive composition must be in liquid form, to be able to dissolve any residues that have formed and to prevent the formulation of new residues. However, unless the liquid component is in fine droplet form, it will not be transported thoroughly throughout the fuel system.

The distillation (or boiling point) range is therefore required to be such that in use the additive composition exists substantially as a fine atomised liquid particle form.

Preferably the distillation range of the base carrier fluid is between approximately 130° and 200° C. The base carrier fluid can be any fluid which has an appropriate distillation range and which is otherwise compatible with the LPG system. A suitable base carrier fluid is "low aromatic white spirit". This will usually make up from about 35% to about 99% of the final composition. Low aromatic white spirit is a C8 to C12 hydrocarbon fraction. As the person skilled will appreciate the carbon numbers and mix will determine the distillation range. Whilst it is important that a significant fraction of the base carrier fluid has a distillation range of between about 130° to 200°C other fractions can be included to extend the boiling point range as required. Generally refinery streams [fractions] with lower carbon number hydrocarbons have lesser amounts of aromatics than do higher fractions and by increasing the amount of lower boiling point fraction the aromatic content of the base carrier fluid will be reduced. The inclusion of lower boiling hydrocarbons or hydrocarbon fractions such as light alkylate (C5-C9) can be used to reduce the initial boiling point down to about 35°C. The amount of light alkylate included in the base carrier fluid may be up to about 50% or more.

To extend the upper end of the boiling point range a heavier fraction such as light heating oil (carbon fractions from about C10 to C17) may be added. This increases the final boiling point to about 250°C. A small amount of such a heavier fraction has the benefit of improving the lubricity of the composition, which aids lubrication of moving engine parts, in the LPG converter and fuel intake system, exposed to the composition such as converter valves and spindles for example. It also assists in wetting the surfaces onto which residues may otherwise form and aids the removal of those residues. The amount of such heavier fractions will usually be up to about only 20% by volume.

Larger amounts tend to result in significant condensation of that heavier fraction in the engine or fuel line componentry, such as in gas hoses and air mixers. Small amounts of still heavier fractions such as lube base stock (carbon fractions from about C18 to C31 may be included. The amount of such heavier fractions may be up to about 5% although preferably less than about 0.5%. Such heavier fractions also provide lubrication and wetting properties to the composition however an excess amount may again cause condensation problems in some converter systems.

The proportions of the fractions can be varied as required to suit different vehicles.

Detergent

As indicated above the additive composition includes a detergent. Any detergent compatible with the base carrier fraction is suitable. These include polyalkylene amines, succinimides and Mannich bases, and polyether amines, usually in a polyether carrier fluid, or other gasoline detergent. The amount of detergent will normally be up to about 3% by volume and preferably in the order of about 0.5%.

Other Components

Other components may be included as required. These include corrosion inhibitors, lubricity improvers, (such as those listed in MIL-I-25017/QPL-25017- 17) metal deactivators (such as N,N-disalicylidene-1 ,2-propane diamine or N,N- disalicylidene-1 ,2-cyclohexan diamine), antioxidants (such as blends of phenylenediamine and hindered phenols), anti-icing additives (such as diethylene glycol mono ethyl ether) and demulsifiers, (such as those based on ethoxylated alkylamines). These additives will normally be in small amounts. Typically the amount of detergents and other components will be less than 3% by volume of the total additive composition.

The detergent additive composition will normally be added to the LPG at the time of manufacturing of the LPG although it could be added at a later stage subject to appropriate vehicle fuelling adapter systems being used.

The amount of additive composition used will normally be in a range of about 1 :100 to 1:10,000, although preferably about 1 :500 to 1 :1 ,000. More or less additive may be used as appropriate. A ratio of 1 :1 ,000 is particularly preferred.

Accordingly a preferred detergent additive composition includes a base carrier fluid including;

(a) from 35% to 99% by volume of hydrocarbon fraction having a distillation range of between about 130° to about 200°C, WO 00/23542 _g_ PCT/AU99/00887

(b) up to about 50% by volume of hydrocarbon fraction having a distillation range from less than 130°C,

(c) up to about 50% by volume of hydrocarbon fraction having a distillation range up to greater than 200°C,

and a detergent.

A further preferred detergent additive composition includes;

(a) from 50% to 99% by volume of low aromatic white spirit,

(b) from 0% to 50% by volume of light alkylate,

(c) from 0% to 50% by volume of light heating oil,

(d) from 0% to 5% of light lube based stock,

(e) from 0.5% to 3% detergent.

A further preferred composition has approximately 90% low aromatic white spirit and approximately 10% light heating oil together with low amounts of detergent and other additives such as blend 13, whose composition is given in table 1.

The additive compositions of the invention in use provide a means by which the amount of residues otherwise deposited in an LPG powered engine can be substantially reduced. The composition when included with the LPG fuel solubilises long term heavy converter deposits that may be present in the converter or other parts of the engine fuel system prior to the use of the additive containing LPG fuel or those that may accumulate. The solubilised residues will remain in solution in the heavier fractions of the composition which collect at the base of the LPG converter and which can be removed as required from time to time from the engine via the converter drain plug. WO 00/23542 _y_ PCT/AU99/00887

Throughout the specification the word "comprise" and variations thereof, such as "comprising" and "comprises" do not exclude the inclusion of other components or elements.

Test Results

Tests were conducted using various formulations of detergent additive composition as described below.

The following formulations were used:

TABLE 1

Composition of Auto LP-Gas Additive Blends, vol.%

Stock 3213 - Ethyl Hitec 4961 A Multifunctional Gasoline Detergent Package

Stock 2813 - MTT 219 [Dupont DC1-4A] Corrosion Inhibitor / Lubricity Improver

Stock 6769 - Metal Deactivator UOP 3452 - Antioxidant

UOP Refining Chemicals are supplied by the UOP Chemical Des Plaines, Illinois, United States of America.

Ethyl Hitec additive is manufactured by Ethyl Corporation.

Hitec 4741 may be used as an alternative to UOP 3452. TABLE 2 PART A Physical Properties of Auto LP-Gas Additive Blends

TABLE 2 PART B

TABLE 3 PART A

Physical Properties of Auto LP-Gas Additive Blend Hydrocarbon Streams

TABLE 3 PART B

Physical Properties of Auto LP-Gas Additive Blend Hydrocarbon Streams

It is to be understood that various modifications, alterations and/or additions to the additive composition may be introduced without departing from the spirit and ambit of the invention.

Claims

1. An automotive LPG detergent additive composition comprising a base carrier fluid and a detergent.

2. A composition according to claim 1 wherein the base carrier fluid includes a fraction which has a distillation range from about 130°C to about 200°C.

3. A composition according to either of the preceding claims wherein the base carrier fluid includes from about 35% to about 99% by volume of a fraction which has a distillation range from about 130°C to about 200°C.

4. A composition according to any one of the preceding claims wherein the base carrier fluid includes a fraction which has distillation range from about 35°C.

5. A composition according to any one of the preceding claims wherein the base carrier fluid includes up to about 50% by volume of a fraction which has a distillation range from about 35°C.

6. A composition according to any one of the preceding claims wherein the base carrier fluid includes a fraction which has a distillation range up to about 250°C.

7. A composition according to any one of the preceding claims wherein the base carrier fluid includes up to about 20% by volume of a fraction which has a distillation range up to about 250°C.

8. A composition according to any one of the preceding claims wherein the base carrier fluid includes a fraction which has a distillation range which extends to greater than 250°C.

9. A composition according to any one of the preceding claims wherein the base carrier fluid includes up to about 5% of a fraction which has a distillation which extends to greater than 250°C.

10. A composition according to any one of the preceding claims further including a corrosion inhibitor.

11. A composition according to any one of the preceding claims further including a corrosion inhibitor.

12. A composition according to any one of the preceding claims further including a lubricity improver.

13. A composition according to any one of the preceding claims further including a metal deactivator.

14. A composition according to any one of the preceding claims further including an anti oxidant.

15. A composition according to any one of the preceding claims further including an anti icing additive.

16. A composition according to any one of the preceding claims further including a demulsifier.

17. A composition according to any one of the preceding claims wherein the detergent is selected from one or more of polyalkylene amines, succinimides, mannich bases and polyether amines.

18. A composition according to any one of the preceding claims wherein the amount of detergent is up to about 3% by volume.

19. A composition according to any one of the preceding claims wherein the amount of detergent is about 0.5% by volume.

20. An automotive LPG detergent additive composition comprising a base carrier fluid including:

(a) from 35% to 99% by volume of hydrocarbon fraction having a distillation range between about 130°C to about 200°C; (b) up to about 50% by volume of hydrocarbon fraction having a distillation range from less that 130°C;

(c) up to about 50% by volume of hydrocarbon fraction having a distillation range up to greater than 200°C; and a detergent additive.

21. An automotive LPG detergent additive composition including:

(a) from 50% to 99% by volume of low aromatic white spirit;

(b) from 0% to 50% by volume of light alkylate; (c) from 0% to 50% by volume of light heating oil;

(d) from 0% to 5% of light lube based stock; and

(e) from 0.5% to 3% detergent.

22. An automotive LPG detergent additive composition including:

(a) approximately 90% by volume of low aromatic white spirit;

(b) approximately 10% light heating oil; and

(c) approximately 0.5% detergent.

23. An automotive LPG detergent additive composition substantially as described in herein with reference to any one of the exemplified blends.

SUBSTITUTE SHEET (RULE 26) RO/AU