NL1036154C

NL1036154C - A motor fuel additive with enhanced properties, and processes for the production thereof.

Info

Publication number: NL1036154C
Application number: NL1036154A
Authority: NL
Inventors: Hendrik Adriaan Cornelis Groeneveld
Original assignee: Criss Cross Technology B V
Priority date: 2008-11-05
Filing date: 2008-11-05
Publication date: 2010-05-06
Also published as: NL1037447C2; NL1038546A; WO2010053354A2; NL1037447A; WO2010053354A3; NL1038546C2; EP2364349A2

Abstract

The invention relates to motor fuel additives with enhanced properties. More specifically, the present additives improve the total fuel efficiency, and reduce the soot reduction of a motor fuel. The additives are based on at least partially esterified and/or partially etherified di- or polyhydroxy hydrocarbon compounds. In a gasoline/ethanol mixture, the additive acts as a co-solvent. Further, the present additives act as octane number improving compositions. Processes for the production of the present additives are also described.

Description

5

Title: A motor fuel additive with enhanced properties, and processes for the production thereof.

Background

The use of biofuel components as such or as admixture in fossil fuels is an ongoing hot topic.

A recent snapshot is that the classic routes using 10 renewable resources at the cost of edible crops production will cause delays in developing the biodiesel potential.

At the same time the efficiency of reducing C02~emissions is doubted and feedstock like rapeseed oil, palm oil etc. are derogatorily treated as first generation options without a 15 clear definition of what is meant and how to improve on the overall efficiency, ecology and economy of the production and application chain.

Used vegetable oils and fats are also being considered as very attractive feedstocks for the production of biodiesel due 20 to their lower market value compared to virgin oils and their fact of being recycled materials from other industrial sectors. The processing of the oil often requires a reduction of the high FFA content via acid catalysed esterification before the actual raw material can be transesterified to 25 biodiesel (see R. Luque et al, Energy Environ. Sci.,, 2008, Biofuels: a technological perspective (DOI: 10.1039/b807094f) ) .

To meet the present new clean air standards, a high quality diesel fuel is required, which can improve the overall 30 fuel efficiency, and reduces the soot generation.

Reduction of particulate matter by means of, for example, ether derivatives of glycerol, is claimed in US 5.308.365.

The production of biodiesel fuels with improved properties at low temperature is known from EP-A-1.331.260.

35 This reference discloses, more specifically, a freezing point 1036154 <* *· 2 lowering effect of a mixture of methyl esters of fatty acids, such as sunflower oil and soya oil, and glycerine (di- or tri)acetate (also called diacetin and triacetin respectively) in mixtures with diesel fuels of fossil origin. It is further 5 suggested that methyl acetate possibly reacts with fatty acid triglyceride esters, to produce glycerol acetyl esters and fatty acid esters according to a transesterification reaction, at a higher rate than methanol to generate glycerine acetate and methyl esters of the fatty acids. The production process 10 is, according to this reference, effected with a large excess of methanol and of methyl acetate.

EP 1.331.260 thus relates to mixtures of biodiesel and diesel fuel compositions based on fossil components, to which said glycerine triacetate has been added.

15 It has, nevertheless, been found by applicant that the biodiesel component in such mixtures is necessary to obviate the phase separation observed between triacetin and diesel of fossil origin, and must be present in quite large amounts; the biodiesel component thus acts in such mixtures as a 20 compatabilizer.

Applicant now found an additive which, when used in small amounts in a diesel fuel of fossil origin, acts as a plasticizer, and therefore obviates the necessary presence of biodiesel, as disclosed in EP 1.331.260.

25 Although applicant does not want to be bound by any theory, it is assumed that the additive according to the invention has the effect that the intramolecular distance of the different fuel components is enlarged. Such an effect could explain the remarkable fuel efficiency improvement, seen 30 when added to different diesel formulations, also when the additive was added in a small proportion.

The additive according to the invention has a further benificial effect, in that it also reduces the soot generation of diesel fuel, while the produced soot particles it-self are 35 larger than the soot particles produced in the absence of the « 3 additive according to the invention. It thus reduces the amount of fine dust, produced along with the combustion of diesel fuel, considerably.

The additive according to the invention is further based 5 on the use of oils of vegetable or animal origin, including waste materials consisting of such oils. The invention is nevertheless not restricted to such oils.

Description of the invention.

10

Whilst businesswise we saw ample scope in using waste materials (used cooking oils etc.) we also did find out that there are ample opportunities to improve on conversion processes (i.e. routes to convert the oils into biodiesel 15 components) and the use of products in a way that the product characteristics are tuned to achieve enhanced fuels based on reducing C02-emissions, soot repression and fuel economy as well as compatibility with other (fossil) fuels.

This approach brought us novel ideas and novel 20 combinations in this field, dealing with the best use of the oil in terms of overall yield and performance based on a combination of properties. In this context fossil fuels are not treated as the adversary, but as a useful partner for mixed fuels in the gradual transition to a more sustainable 25 future.

It is in this context that fossil ethers and esters as reactive components with the oils, the use of novel catalysts for process intensification, reactive destillation/extraction principles and product mixture optimization were put to work. 30 As a result we have achieved much enhanced efficiency, much lower costs, better logistics and improved contributions to fuel efficiency and soot suppression.

Whilst the political debate goes on with regard to the introduction of biofuels, air quality standards etc. we are 35 confident that the novel feedstock/process/application

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4 combinations we set out below can make a considerable contribution by providing feasible options.

Although most of the benefits of oxygenated compounds to be added to diesel fuel mixtures are known, we have discovered 5 that some classes of these compounds show a most remarkable fuel efficiency improvement even in those cases where the components were added in a small proportion, either in combination with Biodiesel (FAME type of products) or added to diesel formulations purely based on fossil components.

10 The invention thus relates, in a first aspect, to an additive for a motor fuel for the improvement of the total combustion efficiency of the motor fuel, selected from oxygenated compounds, obtainable by the at least partial esterification and/or etherification of di- and poly-hydroxy 15 hydrocarbon compounds. The additive contains preferably a mixture of such esters and/or ethers.

It is observed that said hydrocarbon compounds comprise biogenic as well as fossil compounds, which are preferably derived from waste or used materials, such as vegetable oils 20 or animal fats.

It has been found that oxygenated compounds derived from di- and polyhydroxy compounds, being esterified or etherified (at least partially) to their corresponding esters and/or ethers have the effect of improving the overall fuel 25 efficiency as tested under realistic conditions by a value of some 10%. Thus a 2% addition of an additive according to the invention, with a lower energy content than the fuel itself, does improve energy to this level of 10%, which is based on an average of 7 - 13%.

30 The invention relates, in a second aspect, to an additive for a motor fuel for the reduction of soot emission at combustion, selected from oxygenated compounds, obtainable by the at least partial etherification and/or esterification of di- and polyhydroxy hydrocarbon compounds. The additive could 35 contain a mixture of such esters and/or ethers. It is 1 5 observed, that for reduction of the soot emission, the oxygenated compounds will, preferably, not contain any non-derivatised OH-groups.

It has been found that the present esters, or ethers, of 5 said oxygenated compounds reduce soot generation by more than 25%, whilst the amount of the smaller soot particles (the so-called fine dust particles) was reduced by 80% or more. As the latter exhibits a very high health risk, and the larger particles can easily be removed by relatively simple filters, 10 a very realistic solution is provided for air pollution problems related to all kinds of car engines.

The di- or polyhydroxy hydrocarbon compound, which is part of the present additive, is preferably selected from ethylene glycol, diethylene glycol, glycerol, diglycerol, 15 pentaerythritol, sugars such as tetroses, pentoses, hexoses, for example glucose, fructose, xylose, mannose; sorbitol, and mannitol, and the like. Said di- or polyhydroxy hydrocarbon compound can, of course, be obtained from a "green", renewable, feedstock.

20 The additive according to the invention consists preferably of a di- or polyhydroxy hydrocarbon compound, which is at least partially esterified with a straight or branched Ci - C5 alkyl carboxylic acid. Said carboxylic acid is preferably selected from formic acid, acetic acid, propionic acid, and 25 (iso-)butyric acid. This list must nevertheless not deemed to be exhaustive; other carboxylic acids can be used as well.

The additive according to the invention is preferably selected from the group, consisting of the mono-, di-, and triacetylesters of glycerol, the acetyl esters of sorbitol, 30 and of diethylene glycol, and any mixture of these compounds, preferably diacetin, triacetin, mono-acetyl isosorbide and diacetyl isosorbide, or any mixture of these compounds.

Testing these isosorbide esters as fuel additives confirmed our observations as made with the glycerol esters.

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An energy efficiency improvement of 10%, and a soot emission reduction of over 25% were achieved.

We have also found that ethers from glycerol have similar properties, although the fuel efficiency is not so much 5 improved. Therefore, combinations of ether and ester functionality still have a good fuel performance. This was confirmed in engine tests. The additive according to the invention thus also consists of a di- or polyhydroxy hydrocarbon compound, which is at least partially etherified 10 with tert.butyl- or tert.amyl groups.

The motor fuel composition utilized in the present invention, generally consists of hydrocarbons which fall within the diesel fuel boiling range, typically from about 160° C to about 370° C. These fuels are often referred to as middle 15 distillate fuels since they comprise the fractions which distill after gasoline.

In another embodiment of the invention, the motor fuel composition consists of a gasoline/ethanol mixture. The additive of the invention, which will still contain remaining 20 OH-functionality, will, when used in a gasoline/ethanol mixture, improve the fuel efficiency of such a mixture, if added in a certain amount. Such a motor fuel composition contains an ethanol phase, which may contain from 1 to 7% of water, for example 4% of water, which will allow the use of an 25 ethanol/water azeotropic mixture in gasoline. It is assumed that the presence of the additive according to the invention has a favourable influence on the mutual miscibility of the gasoline phase and the ethanol phase. It is well known that, upon contact with humid air, a gasoline/ethanol mixture 30 usually takes up more water, resulting into undesirable phase separation. Because the additive according to the invention acts as a co-solvent, phase separation of a gasoline/ethanol mixture due to the presence of water can be prevented, or reduced.

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The amount of the additive added to a gasoline formulation is generally from about 1 to 10 vol.%, preferably from about 2 to 3 vol.%.

It has also been found that the additives of the invention 5 are octane number improving agents.

The invention further relates to a process for the preparation of an additive, as mentioned above, wherein a fatty acid triglyceride having formula (CH2 - ORi) ((¾ -OR2) (CH2 - OR3) , wherein Ri, R2, and R3 each independently 10 represent a straight or branched, C5 - C30 alkyl carboxylic group, is reacted with a stoichiometric excess of a lower alkyl ester of a lower carboxylic acid, preferably a Ch - C5 alkyl acetate, more preferably methyl acetate or ethyl acetate, in the presence of a catalyst, to obtain said 15 additive as a mixture of glyceryl carboxylic esters, preferably glyceryl acetate esters, and Ci - C5 alkyl esters of C5 - C30 fatty acids, preferably methyl or ethyl esters of C5 -C30 fatty acids.

Δ special embodiment of such a mixture consists of FAME 20 (fatty acid methyl esters) and triacetin, which mixture can for example be produced starting from some used vegetable oil. We found that the production of FAME and triacetin can be combined into one step, whithout the intermediate glycerol formation. To that extent, e.g. methyl acetate, is reacted 25 with the triglyceride oil, using a basic catalyst such as potassium methanolate, or a solid or liquid acid catalyst such as PTSA or H2SO4. The solid acid catalyst is preferably selected from the group, consisting of a zeolite, preferably H-ZSM-5, Y and Beta; and a mixed metal oxide, preferably 30 sulphated zirconia. An enzymatic catalyst can also be used in this reaction. The reaction rates appeared to be higher than normal due to the solvency of the excess of methyl acetate.

Also a heterogeneous catalyst such as an acid ion exchanger, such as Amberlyst-15, does result in good conversions, 35 yielding a product that, depending on the excess of methyl 8 acetate, approaches the composition of a diesel plus mix, which can also be produced according to the two-step process to be discussed hereafter.

The above-mentioned reaction is preferably executed with 5 a molar ratio of 1 - 10 moles of Οχ - C5 alkyl acetate, preferably methyl acetate, to 1 mole of fatty acid triglyceride, preferably from 4-8 moles of methyl acetate to 1 mole of fatty acid triglyceride; we found more particularly that using a molar ratio of from about 6 moles of methyl 10 acetate to 1 mole of triglycerides yields a product that will meet the requirements set for additives for a diesel fuel.

When preparing biodiesel, a typical route for transesterification is one that is catalysed by, for example, potassium methanolate, in a 2-step process.

15 More specifically relates the invention, in such an embodiment, to a process for the preparation of an additive, as disclosed above, wherein a fatty acid triglyceride of formula (CH2 - ORi) (CH2 - OR2) (0¾ - OR3) , wherein Ri, R2/ and R3 each independently represent a straight or branched C5 - C30 20 alkyl carboxylic group, is reacted with a Ci - C5 alkanol, preferably methanol, in the presence of a catalyst, preferably potassium methanolate, to obtain a 2-phase mixture, consisting of a glycerol containing, aqueous phase, and a Ci - C5 alkyl esters of C5 - C30 fatty acids containing phase; the 2-phase 25 mixture is, if desired, dried; and the glycerol containing phase is reacted with a Cj - C5 alkyl acetate, preferably methyl acetate or ethyl acetate, to produce a glycerol acetyl esters containing phase and an alkanol, preferably ethanol, containing phase, which, if desired, is subjected to phase 30 separation; the phases thus obtained are purified according to a process known as such; to obtain an additive for a motor fuel composition.

In a preferred embodiment, said reaction is executed with a stoichiometrically insufficient amount of Ci - C5 alkanol, 9 preferably methanol. Said mixture is expediently dried by azeotropic distillation.

It is observed that it is known from EP 1.331.260 to prepare a mixture of glycerin acetate an and methyl esters of 5 sunflower, by heating a mixture of sunflower oil, methanol and methyl acetate, in the presence of NaOH. More specifically, large excesses of methanol and of methyl acetate are used in this known process, to obtain a completely esterified product, i.e. the methyl esters of sunflower oil.

10 According to the process of the invention, nevertheless, a criss-cross reaction is effected with only an ester, and some (small amount of) methanol, which results in a mixture of products, which will dissolve better in a diesel fuel composition of fossil origin, than the mixture according to EP 15 1.331.260.

Similar to the above, etherification can be made part of the process of the invention: in that case, a catalyst switch will be necessary (neutralising KOH, etc.) and preferably an acid catalyst, e.g. Amberlyst-15, is applied in order to 20 obtain glycerol ethers and glycerol ethers/esters.

Similar to the above, a criss-cross etherification can be carried out using MTBE ( methyl tert.butyl ether) or methyl tert.amylether as agent, to produce a product mix that will contain GTBE (glyceryl tert.butyl ether)-type or GTAE 25 (glyceryl tert.amyl ether)-type of components, along with FAME and intermediate products.

In a preferred embodiment of the invention, it is thus possible to convert the glycerol moiety of the natural (waste) oils into a mixture of glycerol ethers, by using ethers (such 30 as MTBE, or ETBE, but not limited to these) instead of alkanols. The use of MTBE (which is amply available and more easily to handle than isobutylene as etherifying component) obviates the production of glycerol as a low-priced unpure bulk product, but produces an additional mass a suitable 35 diesel components.

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Such an embodiment comprises that a fatty acid triglyceride of formula (CH2 - ORi) (CH2 - OR2) (CH2 - OR3) , wherein Rj, R2, and R3 each independently, represent a straight or branched, C5 - C30 alkyl carboxylic group, is reacted with a 5 stoichiometric insufficient amount of a Ci - C5 alkyl ether, preferably MTBE or ETBE, in the presence of a catalyst, to obtain an additive as a mixture of glyceryl ethers and Ci - C5 alkyl esters of C5 - C30 fatty acids. This reaction is expediently executed in the presence of a heterogeneous 10 catalyst, such as an acid ion exchanger, preferably Amberlyst- 15.

The above embodiment is a one-step process. It is nevertheless also possible to effect the aimed process in two steps. In that case, the additive according to the invention 15 is prepared in that a fatty acid triglyceride of formula (CH2 -ORi) (CH2 - OR2) (CH2 - OR3) , wherein Ri, R2, and R3 each independently represent a branched or straight, C5 - C30 alkyl carboxylic group, is reacted with a lower alkanol, preferably a Ci - C5 alkanol, especially methanol, in the presence of a 20 catalyst, preferably a basic catalyst, especially KOH, to obtain a 2-phasic mixture, consisting of a glycerol and alkali containing phase, on the one hand; and a Ci - C5 alkyl esters of C5 - C30 fatty acids containing phase, on the other hand.

The 2 phases are thereafter separated and, if desired, dried.

25 The glycerol containing phase is neutralised, and is thereafter reacted with a Ci - C5 alkyl ether, preferably methyl tert.butyl ether (MTBE), or methyl tert. amyl ether (MTAE), in the presence of an acid catalyst, such as an acid ion exchanger, preferably Amberlyst-15, to obtain an alkyl 30 ether containing fraction, preferably a glyceryl tert.butyl ether or glyceryl tert.amyl ether containing fraction. The thus obtained phases are, if desired, purified according to a process known as such, and, if desired, mixed together, to obtain the additive of the invention as a mixture of Ci - C5 35 alkyl esters of C5 - C30 fatty acids and C3 - C5 alkyl ethers of » 11 glycerol. The mixture will preferably contain glyceryl t.butyl ethers(GTBE) and glyceryl t.amyl ethers(GTAE).

As indicated above, GTBE and GTAE also act as plastizisers in a motor fuel composition of fossil origin, but 5 in a lesser degree than the abovementioned esters, and thus also effect the improvement of the fuel efficiency. The present ether derivatives can, in fact, be regarded as pour points depressants when used in a motor fuel composition.

It will be obvious that glycerol, being a polyhydroxy 10 hydrocarbon compound, can be replaced by other polyhydroxy compounds, such as diethylene glycol, ethylene glycol, diglycerol, pentaerythritol, and sugars such as tetroses, pentoses, hexoses, preferably glucose, fructose, xylose, sorbitol, and mannitol, to mention some from a non-exhaustive 15 list, which will show the same favourable final result.

It is observed that the use of esters, like methylacetate, ethylacetate etc., and ethers like MTBE and MTAE do provide various options for azeotropic drying, and thus improve phase separation, enhancing the rate of reaction, reactive 20 distillation, etc.

These types of process variants, as they are related to the product classes claimed in this invention, are part of the invention.

The invention is further explained in the following 25 example.

Example 1.

A testrun was executed with a standard diesel engine. The fuel 30 savings were measured at an electronically controlled constant load in a testrun in the stationary phase.

In this motor test, 4% (v/v)normal biodiesel fuel (EN14214) and 1% (v/v) GTAE were added to normal standard fossil diesel fuel.

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This mixture gave a soot reduction of about 25%, compared with the standard diesel fuel, without the additives.

The fuel savings were 13,8% and 9,7%.

Almost the same results were obtained when the normal 5 biodiesel fuel was not added.

Example 2.

The same standard diesel engine, as used in example 1, was 10 used for effecting a testrun for the determination of the effect on the soot production of a standard fossil diesel fuel composition, to which 2% (v/v) diacetin was added.

This mixture also gave a soot reduction of about 25%, while the amount of fine dust particles was reduced by 85%.

1036154

Claims

A motor fuel additive for improving the total combustion efficiency of the motor fuel selected from oxygenated compounds obtainable by partial esterification and / or etherification of di- or polyhydroxy hydrocarbon compounds.

2. Additive for a motor fuel for reducing soot emissions during combustion, selected from oxygenated compounds, obtainable by at least partial etherification and / or esterification of di- or polyhydroxy hydrocarbon compounds.

3. The additive according to claim 1 or 2, wherein the di- or polyhydroxy hydrocarbon compound is selected from the group consisting of ethylene glycol, diethylene glycol, glycerol, diglycerol, pentaerythritol, sugars such as tetroses, pentoses, hexoses, for example glucose, fructose, xylose , mannose, sorbitol and mannitol.

The additive according to one or more of claims 1 to 3, consisting of at least one, straight or branched, C 1 -C 5 alkyl carboxylic acid, at least partially esterified, di- or polyhydroxy hydrocarbon compound.

The additive of claim 4, wherein the C 1 -C 5 alkylcarboxylic acid is selected from formic acid, acetic acid, and propionic acid.

6. The additive as claimed in one or more of claims 1 to 3, consisting of a di- or polyhydroxy hydrocarbon compound which is at least partially etherified with tert-butyl or tert-amyl groups. 1036154

The additive according to one or more of claims 1 to 5, selected from the group consisting of the mono-, di- and triacetyl esters of glycerol, the acetyl esters of sorbitol, and 5 of diethylene glycol, and any mixture of these compounds, at preferably diacetin, triacetin, monoacetyl isosorbide, and diacetyl isosorbide.

The additive of any one of claims 1 to 7, wherein the motor fuel is a fuel composition consisting of hydrocarbons boiling in the diesel fuel trajeet at about 160 ° C to about 370 ° C.

9. Motor fuel composition consisting of 15 hydrocarbons boiling in the diesel fuel boiling range from about 160 ° C to about 370 ° C, containing a soot-reducing or combustion-efficiency-improving amount of an additive according to one or more of claims 1 to 7. 20

A gasoline fuel composition consisting of a gasoline / ethanol mixture containing a combustion efficiency improving amount of an additive according to one or more of claims 1 to 7, wherein the additive remains

25 has OH functionality.

A gasoline fuel composition according to claim 10, wherein the ethanol phase contains 1% to 7% water, preferably 4% water. 30

Fuel composition according to one or more of claims 9 to 11, wherein the composition contains 1-10% by volume, preferably 2-3% by volume, of an additive according to one or more of claims 1 to 7. 35

Co-solvent for a fuel composition based on a gasoline / ethanol mixture consisting of an additive according to one or more of claims 1 to 7.

Use of an additive as claimed in one or more of claims 1 to 7 as an octane-increasing agent for a fuel composition.

Process for the preparation of an additive according to claim 7, wherein a fatty acid triglyceride of formula (CH 2 -OR 1) (CH 2 -OR 2) (CH 2 -OR 3), wherein R 1, R 2, and R 3 are each independently, a straight or branched, C 5 -C 30 alkyl carboxyl group, reacts with a stoichiometric excess of a lower alkyl ester of a lower carboxylic acid, preferably a C 1 -C 5 alkyl acetate, more preferably methyl acetate or ethyl acetate, in the presence of a catalyst, to obtain the additive as a mixture of glyceryl carboxyl esters, preferably glyceryl acetyl esters, and C 1 -C 5 alkyl esters of C 5 -C 30 fatty acids, preferably methyl or ethyl esters of C 5 -C 30 fatty acids.

16. The method of claim 15, wherein the catalyst is selected from the group consisting of a basic catalyst, preferably potassium methanolate; a solid or liquid acid catalyst, preferably sulfuric acid; a heterogeneous catalyst, preferably Amberlyst-15; or an enzymatic catalyst.

The method of claim 16, wherein the solid acid catalyst is selected from the group consisting of a zeolite, preferably H-ZSM-5, Y and Beta; and a mixed metal oxide, preferably sulfated zirconium oxide.

A process according to any one of claims 15 to 17, wherein the reaction is carried out with a molar ratio of 1-10 moles of C 1 -C 5 alkyl acetate, preferably methyl acetate, up to 1 mole of fatty acid triglyceride, preferably of 4-8 moles of 5 methyl acetate up to 1 mole of fatty acid triglyceride, in particular 6 mole of methyl acetate to 1 mole of fatty acid triglyceride.

A process for the preparation of an additive according to claim 7, wherein a fatty acid triglyceride of formula 10 (CH 2 - OR 2) (CH 2 - OR 2) (CH 2 - OR 3), wherein R 1, R 2, and R 3 are each independently, a straight or branched C 5 -C 30 alkyl carboxyl group, react with lower alkanol, preferably a C 1 -C 5 alkanol, more preferably methanol, in the presence of a catalyst, preferably 15 potassium methanolate, to obtain a 2-phase mixture consisting of an aqueous phase containing a glycerol and a phase containing a C 1 -C 5 alkyl esters of a C 5 -C 30 fatty acids; the 2-phase mixture dries if desired; and reacting the glycerol-containing phase with C 1 -C 5 alkyl acetate, preferably methyl acetate or ethyl acetate, to form a phase containing a glycerol acetyl ester and an alkanol, preferably methanol-containing phase, which may be subjected to phase separation if desired; the phases thus obtained may, if desired, be purified in a manner known per se, to obtain an additive for a motor fuel composition.

20. Process according to claim 19, wherein the reaction is carried out with a stoichiometric deficiency of C 1 -C 8 alkanol, preferably methanol.

The method according to claim 19 or 20, wherein the 2-phase mixture is dried by azeotropic distillation.

A method for the preparation of an additive according to claim 6, wherein a fatty acid triglyceride of formula (CH 2 - OR 1) (CH 2 - OR 2) (CH 2 - OR 3), wherein R 1, R 2, and R 3 are each independently, straight or branched C 5 -C 18 alkyl carboxyl group, react with a stoichiometric excess of C 1 -C 5 alkyl ether, preferably MTBE or ETBE, in the presence of a catalyst, to obtain an additive as a mixture of glycerol ethers and C 1 -C 5 alkyl esters of C 5 - C30 fatty acids. 10

23. Process according to claim 22, wherein the reaction is carried out in the presence of a heterogeneous catalyst, preferably an acid ion exchanger, in particular Amberlyst-15.

Process for the preparation of an additive according to claim 6, wherein a fatty acid triglyceride of formula (CH 2 - OR 1) (CH 2 - OR 2) (CH 2 - OR 3), wherein R 1; R 2 / and R 3 each independently represent a straight or branched C 5 -C 30 alkyl carboxyl group, react with a lower alkanol, preferably a C 1 -C 5 alkanol, more preferably methanol, in the presence of a catalyst, preferably a basic catalyst, in particular KOH, to obtain a 2-phase mixture consisting of, on the one hand, a phase containing a glycerol and a lye; and on the other hand a phase containing C 1 -C 5 alkyl esters of C 5 -C 30 fatty acids; separates the 2 phases and dries if desired; neutralize the catalyst, and add an acid catalyst, and the glycerol-containing phase, in the presence of an acid catalyst, preferably an acid ion exchanger, such as Amberlyst-15, react with a C 1 -C 5 alkyl ether, preferably methyl tert-butyl ether ( MTBE), or methyl tert-amyl ether (MTAE), to obtain an alkyl ether-containing fraction, preferably a glyceryl tert-butyl ether or glyceryl tert-amyl ether-containing fraction; Optionally purifies the phases thus obtained in a manner known per se; the phases are optionally combined to obtain an additive for a motor fuel composition in the form of a mixture of C1 -C5 alkyl esters of C5 -C30 fatty acids, and C3 C 5 alkyl ethers of glycerol, preferably glyceryl t-butylethers and glyceryl t-amylethers.

25. A method according to any one of claims 15 to 24, wherein the fatty acid triglyceride is replaced by a corresponding ester of a di- or polyhydroxy hydrocarbon compound selected from the group consisting of diethylene glycol, ethylene glycol, glycerol, diglycerol, pentaerythritol, and sugars such as tetroses, pentoses, hexoses, preferably glucose, fructose, xylose, sorbitol, and mannitol. 1036154