EP2625252A1

EP2625252A1 - Use of rape methyl ester as precipitation- inhibiting fuel additives

Info

Publication number: EP2625252A1
Application number: EP11797048.3A
Authority: EP
Inventors: Lena HÖGGREN
Original assignee: Scania CV AB
Current assignee: Scania CV AB
Priority date: 2010-10-06
Filing date: 2011-10-03
Publication date: 2013-08-14
Anticipated expiration: 2031-10-03
Also published as: SE535227C2; EP2625252B1; BR112013008052A2; BR112013008052B1; SE1051044A1; WO2012047157A1

Abstract

The invention relates to use of a fatty acid alkyl ester or a combination of one or more such esters as fuel additive to prevent formation of sticky precipitates in an engine which is run on an ethanol-based fuel and which has a motor oil additive in the form of a dispersant. The additive preferably contains rape methyl ester.

Description

USE OF RAPE METHYL ESTER AS PRECIPITATION- INHIBITING FUEL ADDITIVES

This invention relates to use of a composition containing one or more fatty acid alkyl esters as a precipitation-inhibiting fuel additive in cases where precipitation occurs in the fuel system of ethanol-powered engines and arises from motor oils.

Background to the invention Many motor vehicles are now run on ethanol-based fuels. Certain vehicles, e.g. buses, have engines which work according to the diesel principle and use ethanol as fuel.

One of known problems with the fuel system of such ethanol buses/ ethanol engines is rapid formation of a sticky precipitate which then obstructs the fuel filter and causes blockages in the fuel return line etc. This sticky precipitate is formed as a result of motor oil additives, inter alia PIBSI (polyisobutylene succinimide) , precipitating in the ethanol system. This component is used as a dispersant in motor oil with the object of keeping particles of soot or metals floating in solution.

There is currently no substitute for PIBSI, so the formation of said sticky precipitate still occurs when motor oil and alcohols come into mutual contact.

A known practice from WO 2007053787 (Lubrizol) and WO 2008082916 (Lubrizol) is to add to a fuel, which may be ethanol, a friction modifier which contains a substance chosen from among an alkoxylated fatty amine, a fatty acid or derivatives thereof, and mixtures thereof for use in various types of fuels, including ethanol. The desired effect is that the additives result in less friction in the engine, but also that the cleaning effect and proper functioning at low temperatures are mentioned.

Prior art does however not deal with the problem of the formation of sticky precipitates pertaining to such fuel and consequently does not propose any additives specifically intended to solve the problem. Summary of the invention

The present invention aims at eliminating or in any case reducing the presence of sticky precipitates in the fuel system of engines run on ethanol-based fuels.

This object is achieved by using a fatty acid alkyl ester or a combination of one or more such esters, preferably a fatty acid methyl and/ or fatty acid ethyl ester, most preferably a fatty acid methyl ester (FAME), as a fuel additive to prevent formation of sticky precipitates in an engine which is run on an ethanol-based fuel and which has a motor oil additive in the form of a dispersant. This additive to the alcohol fuel serves as a means of dissolving or preventing sticky precipitates and may thereby reduce them.

In a preferred embodiment, the fatty acid ester is rape methyl ester (RME).

The addition of FAME is therefore not to serve as a friction modifier as in prior art.

The disadvantage of FAME is its poor solubility at low temperatures. It has now surprisingly been found that an emulsifier (Ethomeen O/ 12™; AKZO NOBEL) which is an amine and already normally present in ethanol fuels, causes FAME to

precipitate less readily at low temperatures.

In an embodiment, the additive is used in combination with an amine, preferably bis-(2-hydroxyethyl)-oleyl amine.

Combining these components in amounts corresponding to 1 wt% RME (rape methyl ester) and 1 wt% Ethomeen O / 12™, in cases where they are present in the ethanol fuel, results in an optimum combination. With this mixture, RME does not precipitate at low temperatures such as down to -28°C (RME has a cloud point of - 10 °C to - 14 °C).

Fatty acid alkyl ester contents in the fuel may range between 1 wt% and 3 wt%, with a preferred content of 1 wt%, based on the total weight of the composition. The invention thus minimises precipitation of oil additives in the fuel system of an ethanol engine which works according to the diesel principle.

A further advantage of the invention is that it works even in cold climates.

Another aspect of the invention proposes a fuel containing 91.2 - 98.5% ethanol, 0.5 - 1. 1 % bis-(2-hydroxyethyl)-oleyl amine and 1 - 2 % fatty acid methyl and fatty acid ethyl ester and possibly other additives up to 100%. A further aspect of the invention relates to a fuel additive composition comprising a mixture of one or more fatty acid alkyl esters and bis-(2-hydroxyethyl)-oleyl amine in a weight ratio of 3: 1 to 1 : 1.

Detailed description

The invention relates to use of a fatty acid methyl and fatty acid ethyl ester as additive to ethanol fuels for engines which work according to the diesel principle. This additive reduces the formation of sticky precipitates in the engine's fuel system.

For certain vehicles the fuel needs at present to contain at least 91.2 wt% ethanol, but the invention is also applicable to other ethanol contents, down to 90 wt% but even down to 85 wt%. The fuel injectors in an ethanol engine comprise a number of movable parts which need lubrication. Such lubrication is provided via ducts which are situated within the material of the injectors and which lead to the lubrication points, e.g. the piston which feeds fuel to the engine and moves to and fro in a bore. Small amounts of lubricant unavoidably pass through seals and penetrations in the movable parts. Hence additives such as PIBSI (polyisobutylene succinimide) may also enter the fuel system, in which they form sticky precipitates and may cause stoppages.

The inventors have surprisingly now discovered that a known fuel additive in the form of one or more fatty acid methyl and fatty acid ethyl esters causes said sticky precipitates to dissolve or quite simply be prevented from forming. Without wishing to tie themselves to any theory, the inventors consider it likely that PIBSI (polyisobutylene succinimide) is quite simply dissolved and kept in solution in the fuel as a result of the additive according to the invention.

The additive preferably takes the form of RME (rape methyl ester) which is a form of FAME (fatty acid methyl ester). Rape oil is made by pressing rapeseed and is a mixture of various different fatty acids. 100 grams of rape oil contains 6 g of saturated fatty acids, 62 g of monounsaturated fatty acids, 31 g of polyunsaturated fatty acids and 1 g of other fats. RME is made by esterification of rape oil with methanol and potassium hydroxide.

In a preferred embodiment, the ester is used together with an amine, preferably bis- (2-hydroxyethyl)-oleyl amine, which prevents the ester from precipitating at low temperatures.

The invention may be implemented in various ways.

In a first aspect, the ester is used alone as an additive which is provided separately and is put into a vehicle's fuel tank after it has been replenished with ethanol fuel. In this case the fuel must therefore already contain amine to ensure that low temperature operation is possible. It is here also conceivable that the fuel supplier might add RME from the outset before the fuel reaches the customer. Ethanol fuels today often already contain said amine, with the result that adding a correct amount of esters would suffice to achieve the desired effect according to the invention.

Alternatively, in a second aspect of the invention, it is possible to propose a composition comprising two components, viz. an ester and an amine in suitable proportions.

A further aspect of the invention proposes a fuel which already contains not only ethanol but also a specific amount of ester and a specific amount of amine. The table below summarises a number of experiments with different contents of the various components in an ethanol fuel, showing the compositions with which the additive does not precipitate. These experiments use rape methyl ester (RME) as precipitation-inhibiting additive and an ethanol fuel (ED 95) with an amine in the form of Ethomeen 0 / 12™ (commercially available from Akzo Nobel) with the commercial name bis-(2- hydroxyethyl)-oleyl amine.

Table 1

Table 1 shows that high ester contents do not work, but that precipitation does not occur with 1 wt% amine (Ethomeen 0/ 12) and 1 - 2 wt-% RME in ED 95 at -28°C.

Table 2

Table 2 shows that with no Ethomeen 0/ 12 in the fuel, RME precipitates in cold conditions.

Table 3 Ethomeen 0/ 12 RME wt% Temperature Precipitation content

0.25 wt% 1 wt% - 28 °C Obscure

0.50 wt% 1 wt% - 28 °C Yes

Table 3 shows a lower limit for Ethomeen 0/ 12 content in that more than 0.50 wt% Ethomeen in the fuel is required for RME not to precipitate in cold conditions. To sum up, it may be stated that in combination with 1 wt% Ethomeen 0/ 12 it is therefore possible to use RME contents of between 1 and 3 wt% in ED 95 without precipitation occurring in cold conditions.

The invention is illustrated by the following examples.

ED 95 is an ethanol fuel which contains at least 91.2 wt% ethanol, about 5.0 wt% of ignition improver and further components up to 100%.

EXAMPLE 1 (not according to the invention)

The fuel injectors (Scania Duel Rail) for an ethanol engine (Scania DC9 E02) which works according to the diesel principle are supplied with ED 95 fuel of standard type. It is found that the nozzle needle runs sluggishly in its bore because the needle becomes sticky. The deposit forms and builds up over time.

EXAMPLE 2

The same engine as in example 1 is supplied with ED 95 fuel of standard type but with an additive according to the invention. The nozzle needle is found to run easily in its bore because the needle does not become sticky.

Claims

1. Use of rape methyl ester (RME) as fuel additive in an engine which is run on an ethanol-based fuel and has a motor oil additive in the form of a dispersant, characterised in that the engine works according to the diesel principle and that the rape methyl ester prevents formation of sticky precipitates.

2. Use according to claim 1 , in combination with an amine.

3. Use according to claim 1 or 2, in which the amine is bis-(2-hydroxyethyl)-oleyl amine.

4. A fuel additive composition containing rape methyl ester (RME) and bis-(2- hydroxyethyl)-oleyl amine in a weight ratio of 3: 1 to 1 : 1.