HK1097567A1

HK1097567A1 - Low-sulphur diesel fuel and use of fatty acid monoalkyl esters as lubricant improvers for low-sulphur diesel fuels

Info

Publication number: HK1097567A1
Application number: HK07102628.9A
Authority: HK
Inventors: Martin Mittelbach; Michael Koncar; Helmut Gössler; Wilhelm Hammer
Original assignee: Martin Mittelbach; Bdi - Biodiesel International Ag; Michael Koncar
Priority date: 2003-07-28
Filing date: 2004-06-22
Publication date: 2007-06-29
Also published as: AU2004259773B2; AT504745B1; EP1648984A1; CN1860209A; CN1860209B; NZ545545A; WO2005010130A1; AU2004259773A1; AT504745A1; CA2533657A1; US20060213118A1

Abstract

The invention relates to a low-sulfur diesel fuel containing a maximum amount of 0.2% by weight of sulfur and fatty acid monoalkyl esters in an amount of between 10 and 50,000 ppm as lubricity improvers, with the fatty acid moieties of the fatty acid monoalkyl esters originating from saturated fatty acids by at least 50%, in particular by at least 70%. It has been shown that said fatty acid esters show a substantially better lubricity improvement in a low-sulfur diesel fuel than a biodiesel made of rape oil and soy bean oil.

Description

Low sulfur diesel fuel and use of fatty acid monoalkyl esters as lubricity modifiers for low sulfur diesel fuel

The invention relates to a low-sulfur diesel or diesel fuel containing a maximum of 0.2 wt.% of sulfur and 10 to 50000ppm of fatty acid monoalkyl esters as lubricity modifiers.

Regulations stipulate that the content of sulfur compounds in fossil fuels is always reduced as much as possible. Since 1996, sulfur content in diesel fuel was limited to 0.05 wt.% in europe. In some countries, however, for example in sweden, so-called zero-sulphur fuels with a sulphur content of less than 10ppm are used almost exclusively today. For densely populated central zones, so-called city diesel with a sulfur content of 50ppm is now being provided more.

Since sulfur compounds are removed during purification, the fuel lubricity is deteriorated. It is believed that the removal of sulphur compounds is also closely related to the reduction of polar, oxidising compounds and polycyclic aromatic compounds, and it is the latter compounds that bear the lubricating properties of the fuel itself. However, the decrease in lubricity may cause serious damage to the injection pump of the diesel engine. For this reason, it is necessary to add corresponding auxiliaries as lubricity improvers to diesel fuels. Conventional lubricity improvers or additives are synthetic mineral oil products or synthetic esters of different chemical structures. As an environmentally friendly alternative, it is currently more recommended to use some naturally occurring raw materials, such as vegetable oils or vegetable oil derivatives, for example fatty acid monoalkyl esters, as lubricant additives.

The use of esters as lubricity modifiers is described in EP 0680506B.

EP0635558a1 describes the use of fatty acid monoalkyl esters consisting of saturated and unsaturated fatty acid esters in amounts of 100 to 10000 ppm. The methyl esters are preferably used in the composition first, while the fatty acids in the composition are present in the vegetable oil, and no further pretreatment or isolation of the use is necessary.

A similar use is also described in WO 94/17160.

WO96/07632 describes a process for preparing lubricity improving agents by a secondary transesterification of vegetable oils, wherein fatty acid monoalkyl esters are prepared in a first step and then reacted with polyols in a second step. Similar compounds are also described in EP1088880a 1.

Mixtures of fatty acid esters containing dicarboxylic acid esters as lubricity improvers are described in DE 19955354.

US5891203 describes the use of a mixture consisting of biodiesel and a diethanolamine derivative as a lubricity modifier for sulfur-lean fuels. Fatty acid amides of diethanolamine and fatty acids are used, and oleic acid is used above all as the preferred fatty acid.

The use of biodiesel, which consists of a plurality of raw materials such as sunflower oil, corn germ oil, olive oil and recycled edible oils, as a lubricity improving additive is described in Energy and Fuels (2001, 15, 106-.

According to the directive of the european commission, in europe the content of biofuels should be increased to 5.75% before 2010. In order to be able to achieve this content, it is necessary in particular to make full use of all possible raw materials in the biodiesel sector. This means that more and more raw materials, such as recovered edible oils, animal fats or palm oil, have to be introduced as a source of raw materials.

A major obstacle to the use of these feedstocks as biofuels is the poor low temperature properties of the fatty acid monoalkyl esters produced therefrom, and therefore, the use of either 100% as biodiesel or as blending components is currently greatly restricted.

The present invention is therefore based on the object of producing better sulfur-lean diesel fuels having a sulfur content of at most 0.2% by weight, which contain from 10 to 50000ppm of fatty acid monoalkyl esters as lubricity improvers and which, in turn, reduce the abovementioned problems.

The inventive low-sulfur diesel fuel contains a maximum of 0.2% by weight of sulfur and 10 to 50000ppm of fatty acid monoalkyl esters as lubricity improvers and is characterized in that the fatty acid radicals of the fatty acid monoalkyl esters originate from saturated fatty acids by at least 50%, particularly preferably by at least 70%, and the fatty acid monoalkyl esters are preferably present in the form of fatty acid methyl esters.

The present invention is based on the surprising recognition that the lubricity of fatty acid monoalkyl esters is clearly dependent on the content of saturated fatty acid derivatives. That is, fatty acid esters containing saturated fatty acids in an amount of 50% or more have much higher lubricity-modifying properties in low-sulfur diesel than biodiesel made of rape oil or soybean oil.

The component containing the ester of unsaturated fatty acid can be separated off by fractional crystallization and distillation. The individual fatty acid ester fractions obtained after fractional crystallization or distillation and which have, in particular, a high saturated fatty acid content are therefore particularly suitable as lubricity improvers.

The fatty acid monoalkyl esters contained in the diesel fuel of the present invention are preferably made from vegetable fats and/or oils. All natural vegetable or animal oils and/or fats whose saturated fatty acid content already exceeds 50% or corresponding products which have been produced from the corresponding oils and fats by enriching or separating out the saturated fatty acids can be considered as starting materials. The corresponding fractions obtained from the treatment of palm oil (palm stearin) or animal fat fractions are preferably used.

A further embodiment of the diesel fuel according to the invention is characterized in that it additionally contains one or more additives for improving the cetane number or for improving the low-temperature properties.

The invention also relates to an agent for improving the lubricity of diesel fuels containing fatty acid monoalkyl esters, and is characterized in that the fatty acid radicals of the fatty acid monoalkyl esters originate from saturated fatty acids by at least 50%, particularly preferably by at least 70%.

In addition, the invention relates to a process for the preparation of fatty acid monoalkyl esters in which at least 50%, particularly preferably at least 70%, of the fatty acid radicals originate from saturated fatty acids, which process is characterized in that fatty acid monoalkyl esters in which the fatty acid radicals originate from saturated and unsaturated fatty acids are subjected to a fractional crystallization or distillation process.

Finally, the invention relates to the use of fatty acid monoalkyl esters, the fatty acid groups of which are at least 50%, particularly preferably at least 70%, derived from saturated fatty acids, as lubricity improvers for low-sulfur diesel fuels.

As a measurement method for determining lubricity, the HFRR wear test international standard according to CEC F-06-A-96 was used. Wherein the lubricity is determined by the wear of the rotating beads. In this method, the wear threshold is 460 μm. The reference fuel used in this test was a sulfur-free, additive-free diesel fuel with an abrasion value of 569 μm.

If a number of different biodiesel samples (from animal fats, rape oil, soybean oil and recovered edible oil) were used, it was surprisingly found that, at an addition level of 0.5%, although all biodiesel samples gave an improvement in lubricity, only with the reagent according to the invention a threshold value of significantly below 460 μm was obtained. The biodiesel samples consisting of rape oil and recycled edible oil were only able to fall below this threshold when the amount was 1.0%, whereas the biodiesel consisting of soybean oil itself was not able to fall below the threshold when the amount was 2.0%.

Various palm oil samples or palm oil fatty acids having a higher content of saturated fatty acids may also be cited for the preparation of fatty acid methyl esters. All samples had a content of saturated fatty acids of more than 50%. For all samples, a threshold value below 460 μm can be achieved, at least when the amount is 1.0%.

According to european standard EN 590, an allowable addition of 5.0% is made for mineral diesel. Since the price of the additives plays a decisive role when they are used and conventional lubricity improvers are available very inexpensively, the use of fatty acid alkyl esters is of economic interest only when the additives are used in as small an amount as possible.

Therefore, fatty acid monoalkyl esters having a content of saturated fatty acids of more than 50% are ideal auxiliaries for improving the lubricity of sulfur-free diesel.

Preferred embodiments of the present invention will be described in more detail below using examples.

Example 1

The starting material was animal fat having the following fatty acid composition:

lauric acid: 0.2 percent of

Myristic acid: 1.86 percent

Palmitic acid: 25.17 percent

Stearic acid: 14.47 percent

Oleic acid: 42.98 percent

Linoleic acid: 9.24 percent

The fat is converted to the corresponding fatty acid methyl ester by reacting it with methanol and potassium hydroxide according to known methods. The resulting fatty acid methyl esters are separated into two components by fractional crystallization treatment at low temperature, one of which contains high amounts of saturated fatty acids for use as a lubricity additive. The fatty acid composition of this component is as follows:

lauric acid: 2.06 percent

Myristic acid: 0.44 percent

Palmitic acid: 33.75 percent

Stearic acid: 35.00 percent

Oleic acid: 21.26 percent

Linoleic acid: 2.62 percent.

A mixture of this component with sulfur-free diesel without additives was prepared and the lubricity was determined by determining the HFRR wear test according to CEC F-06-A-96.

As a reference, various biodiesel produced from rape oil, soybean oil and recycled edible oil were also tested using the same test.

Methyl ester test sample	0.5％	1.0％	2.0％
				Fractional crystallization of methyl esters of animal fats	443	420	321
Rape oil	509	359	320
				Recovered edible oil	521	375	322
Soybean oil	540	483	487

HFRR-abrasion values are in μm; reference value of diesel without addition of auxiliary agent: 569 μm

Example 2

As a raw material for producing fatty acid methyl esters, an industrial fatty acid distillate formed from palm oil having the following fatty acid composition was used:

myristic acid: 1.59 percent

Palmitic acid: 52.07 percent

Stearic acid: 3.93 percent

Oleic acid: 33.80 percent

Linoleic acid: 8.37 percent

The fatty acid mixture is reacted with methanol and concentrated sulfuric acid as catalyst to form the corresponding fatty acid methyl esters.

A mixture of the fatty acid methyl esters and sulfur-free diesel without additives was prepared and the lubricity was determined by determining the HFRR wear test according to CEC F-06-A-96.

Amount of methyl ester	0.5％	1.0％
			HFRR	426	367

Example 3

Palm stearin, which is produced from palm oil by fractional crystallization, having the following fatty acid composition, was used as a raw material for producing fatty acid methyl esters:

myristic acid: 1.3 percent of

Palmitic acid: 73.83 percent

Stearic acid: 4.84 percent

Oleic acid: 16.56 percent

Linoleic acid: 3.52 percent

Palm stearin was subjected to a multi-step reaction using methanol and potassium hydroxide as a catalyst to form the corresponding fatty acid methyl ester.

Amount of methyl ester	0.5％	1.0％
			HFRR	534	447

HFRR-abrasion values are in μm; reference value of diesel without additive: 569 μm

Example 4

Crude palm oil having the following fatty acid composition was used as a raw material for preparing fatty acid methyl esters:

myristic acid: 1.07 percent

Palmitic acid: 44.23 percent

Stearic acid: 4.68 percent of

Oleic acid: 38.28 percent

Linoleic acid: 11.74 percent

The palm oil was subjected to a multi-step reaction using methanol and potassium hydroxide as a catalyst to form the corresponding fatty acid methyl ester.

Amount of methyl ester	0.5％	1.0％
			HFRR	477	456

Claims

1. Lean-sulfur diesel fuel containing a maximum of 0.2% by weight of sulfur and 10 to 50000ppm of fatty acid monoalkyl esters as lubricity improvers, characterized in that at least 50% of the fatty acid groups of the fatty acid monoalkyl esters originate from saturated fatty acids.

2. The diesel fuel of claim 1 wherein said fatty acid radicals are at least 70% derived from saturated fatty acids.

3. The diesel fuel of claim 1 wherein the fatty acid monoalkyl ester is present as a fatty acid methyl ester.

4. A diesel fuel according to claim 1, 2 or 3 wherein the fatty acid monoalkyl esters are prepared from vegetable fats and/or oils.

5. Process for the preparation of fatty acid monoalkyl esters wherein at least 50% of the fatty acid radicals originate from saturated fatty acids, characterized in that fatty acid monoalkyl esters wherein the fatty acid radicals originate from saturated and unsaturated fatty acids are subjected to a fractional crystallization or distillation process.

6. The method of claim 5, wherein said fatty acid moieties are at least 70% derived from saturated fatty acids.

7. Use of a fatty acid monoalkyl ester as a lubricity modifier for low-sulfur diesel fuels, characterized in that the fatty acid groups of said fatty acid monoalkyl ester are at least 50% derived from saturated fatty acids.

8. Use according to claim 7, wherein the fatty acid moieties are at least 70% derived from saturated fatty acids.