FR2731010A1 - Multifunctional additive for petrol or diesel motor fuels - Google Patents

Abstract

Fuel additive comprises a 3-alkyloxy-1-alkylamino propan-2-ol, or dimer, of which one alkyl is 2-18C alkyl. Also claimed are the method of prepn. of the prod., and the fuel compsn. contg. the additive.

Description

FUEL ADDITIVE BASED ON 3-ALKYLOXY-1
ALKYLAMINO PROPAN-2-OL OR ITS DIMER AND METHOD
FOR PREPARING THE ADDITIVE
The invention relates to a fuel additive for a gasoline or diesel engine and to a process for its preparation.

 It is known to add certain oxygenates in conventional fuels of fossil origin in order to increase their octane number, particularly when using fuel alcohol mixtures for fuels not using tetraethyl lead.

However the use of alcohol is limited. Indeed, methanol generates toxic formaldehyde and causes demixing of the alcohol-fuel mixture in the presence of water and at low temperature, its use therefore requires the use of a cosolvent while ethanol can be used without cosolvent but generates a cost very high purification.

Thus ethanol is generally used in the so-called "ETBE" form (Ethyl
Tertio Butyl Ether) which still contains water. The presence of this water causing a demixing between the ethanol / water mixture and the fuel, it is important that the additive can in addition to its action on the octane number, avoid such demixing.

Publications EP-BO 303 862 and EP-BO 255 115 disclose alcohol-containing fuel additive compositions comprising an organic peroxide, a detergent selected from amines, diamines, fatty imidazolines, polymeric amines and the like. combinations of these substances with carboxylic acids, and a hydrocarbon solvent. The presence of these numerous compounds causes on the one hand handling difficulties and on the other hand high manufacturing costs.

One solution to these problems seemed to be the development of molecules that alone could increase the octane number of a fuel containing alcohol and to avoid a possible demixtion within it. Such molecules, including triethylene glycol dinitrate, have been studied, however, they are difficult to use because of the very delicate reaction conditions that their synthesis implies, which, moreover, is particularly expensive.

However, some compounds of the hexyl nitrate type have also been tested as an additive. The result of these tests reveals an effectiveness of the additive subordinate to a minimum concentration of more than 10% in ethanol, which constitutes too much.

The use instead of these additive compositions of polyfunctional compounds has not led to real solutions, the many prejudices on the use of a single compound is also supported by its poor results.

The invention relates to a fuel additive consisting of a single organic compound, which even allows in low concentration in ethanol to avoid demixing between the water / ethanol mixture and the fuel and increase the index of octane of the latter.

The invention also relates to an additive whose handling is easy and whose preparation is easily achievable by obtaining a good yield.

The invention finally relates to a fuel containing an additive according to the invention.

According to the invention, the fuel additive is constituted by a 3-alkyloxy 1-alkylamino propan-2-ol or its dimer, an alkyl radical of which is in C 2 -C 8 alkyl: the allyl radical can be in C 2 -C 8 to function terminal hydroxyl, the amine function is constituted by a mono or di-substituted amine C2 to C18 or by a C2 to C8 alkanolamine.

Preferably, the alkyl radical is C8.

The invention also relates to a fuel containing alcohol and an additive according to the invention which constitutes about 2% to 5% by weight of the fuel.

The invention also relates to a process for the preparation of 3-alkyloxy-1-alkylamino propan-2-ol and their dimers which consists of a first step of alkylation of epihalohydrins with fatty alcohols in solidelliquid heterogeneous medium, and in a second step of condensation of fatty amines on the alkyl glycidyl ethers obtained in the first step.

According to different variant embodiments of the process: the fatty alcohols are monoalcohols or diols; the solid phase of the heterogeneous alkylation medium consists of potassium hydroxide which may be combined with tetraethylene glycol; the liquid phase of the heterogeneous alkylation medium consists of either hexane, propylene glycol or tetrahydrofuran.

the condensation is carried out in ethanol or in tert-butanol.

The second step is optionally followed by extraction in pentane in order to separate the monoadditioned and bi-added products obtained.

Other advantages and characteristics of the invention will appear on reading the description of an example of an additive for fuels based on diesel fuel and ethanol and its preparation.

The new use of polyfunctional compounds known as fuel additives assumes certain constraints: their properties must be compatible with those required for an additive and likely to play certain precise roles. Indeed, it is a question of preventing the demixing of ethanol and diesel fuel, on the other hand of increasing the octane number or even of obtaining other desired properties for fuels such as lubricating properties, antifreeze, corrosion inhibitors and oxidation while ensuring good fuel mixing viscosity. Of course, such additives must allow the realization of a uniform ternary mixture of fuel.

The idea was to use 3-alkyloxy-1-alkylamino propan-2-ol or their dimers N, N-di- (3-alkyloxy-2-hydroxy-propyl) alkylamine, known for their surfactant properties .

Moreover, these compounds have good wetting powers as well as properties of anti-freeze and anti-corrosion agents. In addition, with good thermal stability, these compounds are prepared and easy to handle.

où : - Nu est une amine mono ou di-substituée en C2 à C18 ou une alcanolamine en C2 à C8,
- R est un radical alkyle en C2 à C18 ou en C2 à C8 à fonction hydroxyle terminale.Polyfunctional structures: 3alkyloxy-1-alkylamino propan-2-ol or
N, N-di- (3-alkyloxy-2-hydroxypropyl) are represented by the following general formulas:

where: - Nu is a mono or di-substituted C2 to C18 amine or a C2 to C8 alkanolamine,
- R is a C2-C18 or C2-C8 alkyl radical with terminal hydroxyl function.

These structures are particularly interesting at the functional level because they have at least one labile hydrogen (that of the hydroxyl group) and an amine which will allow the establishment of hydrogen bonding with ethanol and water, fatty chains (function ether and amine) that create the affinity between these molecules and diesel. Thus all of these functions make it possible to avoid the separation between water methanol and diesel.

danslesquelsm est compris entre 1 et 17 et n entre 2 et 8.Such properties have been demonstrated in particular on the three compounds represented below, and which will be identified by references 1, 2 and 3 where 1 and 3 are 3-alkyloxy-1-alkylamino propan-2 and 2 is a
N, N-di- (3-alkyloxy-2-hydroxy-propyl):

wherem is between 1 and 17 and n is between 2 and 8.

The properties of these compounds, thermal stability, viscosity, suuiactant power, are accompanied by a property essential to the interest of the study: the very good chemical compatibility with fuels in particular consisting of a methanol gas oil mixture.

As shown in Table 1 in which characteristic temperatures of the above-listed organic compounds (such as melting point, thermal decomposition temperature, oxidative decomposition temperature, polycondensation temperature, and mass loss stages) are given, these compounds exhibit good thermal stability up to about 300 C.

The viscosity of these molecules was measured with a rheometer-Viscometer imposed stress, varies between 50 and 75 mPa.s at 20 C which corresponds to the viscosity range of a lubricant. In gasoethanol mixtures; these compounds improve the viscosity of the mixtures as shown in Table 2 which represents the viscosity measurement for several fuel mixtures and the viscosity gain obtained by the presence of additive.

Similarly, the lubricating properties of certain molecules such as compound 2 have been demonstrated for temperatures above 30 ° C as shown in Table 1. In fact these compounds give rise to polycondenadon reactions under the effect of temperature.

Finally, the surfactant power of these molecules is very interesting since it consists in forming a clear microemulsion in the gasolelethanol hydrate mixture (the oily phase being constituted by the hydrocarbon, the surfactant by the additive and the ethanol over-reactant). ):
- This property has been highlighted on the one hand in the molecules
pure by the determination of micellar concentrations
CMC, presented in Table 3 and carried out by
surface tension with a self-balancing sphygmomanometer. These
values of CMC are actually in the field of "good"
surfactants that is to say between 104 and 10-3 mol.ll.

- On the other hand the surfactant power has been highlighted in a
gasolethanol mixture by measuring the time after which the mixture
with additive left in the air gets cloudy: the effectiveness of the molecule
being proportional to the time of onset of the disorder. Table 4
underlines the interest of this property for mixtures M1, M2 and M3
including 2% of additive 1, 2 and 3 respectively.
compound 1, it is possible to use ethanol at 97 C while
keeping the clarity of the 85/15 mixture.

Moreover the role of these compounds as an additive allows of course
an increase in the octane number of the fuel; some posssdent
also interesting anti-freezing properties, other anti-corrosion or
antioxidant.

However syntheses of these compounds offering only a very weak
yield, their use as an additive at an industrial level
required the development, if possible, of a simple process
to obtain a good return.

The process for the preparation of these compounds will be described in what follows.
polyfunctional organic.

The starting reagent common to these molecules is an epihalohydrin (1
halo-2,3 * oxypxpane) of petrochemical origin or prepared from
natural glycerol itself from the processing of oils
plant.

The first step of the synthesis consists in producing alkyl glycidyl ethers by condensing the epihalohydrin on an alcohol according to the following reactions:

X = Cl. Br R '= (CH3) nOH
n = 2 to S

The known methods for carrying out such a reaction are either in two stages with an acid then basic catalyst, or in a single step with a basic metal hydroxide agent. However, these processes lead to poor performance, very long reaction times and constraining synthesis conditions.

The process which has been developed here performs the alkylation reaction of a monoalcohol or a diol with a heterohydrin in a solid-heterogeneous heterogeneous medium in a single step. In the biphasic systems studied were selected in particular KOHihexane for monoalcohols and KOH / THF for diols. Under these conditions the glycidyl ether is obtained after a few hours of reaction (6h) at a temperature of about 70 C with a yield of 90% and a selectivity of 95%. The hydroxylated glycidyl ether and its dimer are also obtained in 70130 proportions and are easily separated at the end of the reaction.

An improvement in the selectivity of the process for the monohydric alcohols consists in using a heterogeneous system of potassium hydroxide propylene glycol, KOH-PEG, in hexane or potassium hydroxide, KOH, in tetraethylene glycol dimethyl ether, TEGDME, which allows to obtain the same yield at room temperature with total selectivity after about ten hours. Indeed the PEG or the
TEGDME are good complexing agents of the potassium cation and thus promote O-alkylation by activating the nucleophilic character of hydroxide anions and alcoholates generated in situ.

The second step of the reaction consists in synthesizing the 3-alkyloxy-1-alkylamino propan-2-ols and their dimers respectively from the glycidyls ethers and glycidyls hydroxyl ethers.

It consists in carrying out an addition on these products of a primary amine or a secondary amine which causes the opening of the glycidyl ring by the aliphatic amine according to the following reaction:

The selectivity of the reaction towards a mono-added or bioadditioned product is facilitated by the choice of the alcoholic medium. Thus, the mono-added product will be selectively obtained by carrying out the condensation in ethanol, and the bi-addition product in tert-butanol, respectively, with a selectivity of 95% with a good choice of glycidyl ether / amine molar ratio.

Purification of the final product irrespective of the relative proportions of the two constituents, occurring by crystallization in pentane of the mono-added product, the bi-added product being solubilized in the same solvent.

From the glycidyl ether with a primary amine three compounds 1, 2 and 3 are obtained.

This second step carried out from the glycidyl ether hydroxyl and its dimer with a primary amine leads to the following three compounds.

Similarly for a secondary amine in an ethanolic medium, selectively:

Examples 1 and 2 which follow illustrate the invention without limiting it. In particular, these relate to processes for the preparation of compounds 1 and 2 in the case of a C 8 radical, which have been demonstrated by conventional characterization tests.

EXAMPLE 1 PROCESS FOR THE PREPARATION OF 1-OCTYLAMINO
3-OCTYLOXY PROPAN-2-OL -First step: preparation of glycidyl octyl ther (la)
Reaction medium
- 84 g (1.5 mol) of potash in flakes,
-118 ml (0.75 mol) octanol,
78 ml (1 mol) of epichlorohydrin or 82 ml (1 mol) of epibromohydrin,
400 ml of hexane.

Operating procedure
In a reactor of one liter, equipped with a refrigerant and a mechanical stirrer with broad starry pale, are introduced the constituents of the reaction medium. The latter is stirred (600 rpm) at reflux of the solvent (700 C) for 6 hours.

After cooling, the solid residue is removed by sinter filtration.

The organic phase (hexane), introduced into a separatory funnel, is washed twice with 60 ml of water and then dried over MgSO 4. The solvent is then evaporated under reduced pressure (15 mmHg, ie approximately 2.103 Pa).

There is then obtained 130 g of glycidyl octyl ether containing 5 to 8% octanol, directly usable for the second step.

The substitution of hexane by tetraethylene glycol dimethyl ether (IEGDME) or the introduction into the medium of 84 g of polyethylene glycol PEG 3400 type, offers the advantage of operating at room temperature respectively for 8 or 15 hours . After washing with water the organic phase, it is preferable to distill the glycidyl ether obtained to remove any traces of PEG or TEGDME.

second step: Synthesis of 1-octylamino-3-octyloxy propaneNol (1)
Reaction medium
- 330 ml (2 mol) of octylamine
- 150 ml of ethanol
- 200 g (-1mol) of glycidyl octyl ether obtained in step 1.

Operating procedure
In a one-liter reactor equipped with a condenser, a mechanical stirrer and a dropping funnel, octylamine and ethanol are introduced.

At reflux of the solvent (80 ° C.), the solution of glycidyl octyl ether is then added dropwise (for 2 hours).

The reaction medium is kept under reflux with methanol (80 ° C.) with stirring for an additional 2 hours until the glycidyl ether is completely consumed.

 After evaporation of the ethanol, the excess octylamine and the octanol are distilled off under reduced pressure (60 ° C. under 0.3 mmHg, ie approximately 40 Pa). The distilled octylamine may be retained for later use.

Once cooled, the solidified medium is dispersed in 50 ml of pentane and sintered. The operation is repeated until the solid (270 g) has become totally white. The secondary bioaddition compound (yellow-orange oil) is driven by pentane (filtrate).

Recrystallization can be carried out in petroleum ether to obtain fine white flakes (final yield 90%).

EXAMPLE 2: PROCESS FOR THE PREPARATION OF N, N-DI- (2-
HYDROXY-3-OCTYLOXY PROPYL) OCRYLAMINE -First step: preparation of the glycidyl octyl ether iderite in Example 1 -Second step: Synthesis of N, N-di- (2-hydroxy-3-octyloxypropyl) octylamine.

Reaction medium
82.5 ml (2 mol) of octylamine
- 250 ml of tert-butanol
200 g (-1 μmol) of glycidyl octyl ether obtained in stage 1.

Operating procedure
In a 1-liter reactor equipped with a condenser, a mechanical stirrer and a dropping funnel, 150 ml of t-butanol, glycidyl octyl ether, are introduced.

At reflux of the solvent (85 ° C.), a solution of 82.5 ml (0.5 mol) of octylamine in 100 ml of tert-butanol for 2 hours is then added dropwise.

The medium is kept at reflux of the solvent with stirring for an additional 2 hours until total consumption of octyline.

After evaporation of tertiobutanol, the octanol and traces of excess glycidyl ether are distilled under reduced pressure (60 C under 0.3 mmHg or about 40 Pa).

The resulting compound is an orange colored oil which will be placed at refrigerator temperature to more easily crystallize the 5% of the mono-add product. The majority biaddition product is then solubilized in 80 ml of pentane, which makes it possible to isolate the monoaddition product by porosity filtration with a porosity 2. After evaporation of the pentane, 450 g of bi-addition product is recovered. in the form of an orange oil (yield 90%). -
Table 1

<SEP> Compound <SEP> Fusion <SEP> Decomposition <SEP> Decomposition <SEP> Poly- <SEP> Tier <SEP> of
<tb><SEP> thermal <SEP> by <SEP> oxidation <SEP> condensation <SEP> loss <SEP> of
<tb> mass
<tb><SEP> 1 <SEP> 48 C <SEP> 320 C <SEP> 290 C
<tb><SEP> 2 <SEP> 385 C <SEP> 340 C
<tb><SEP> 3 <SEP> 47 C <SEP> 275 C <SEP> 265 C
<Tb>
Table 2

<tb><SEP> [to <SEP> 20 C]
<tb><SEP> Viscosity <SEP> Gain
<tb><SEP> of <SEP> viscosity
<tb> in <SEP> mPa.s
<tb><SEP> Gas Oil <SEP> 3.36
<tb><SEP> Gas oil + 15% <SEP> ethanol <SEP> 2.84
<tb> 34 <SEP>%
<SEP> Gas oil + 15% <SEP> ethanol + Ad <SEP> 3.02
<tb><SEP> Gas oil + 10% <SEP> ethanol <SEP> 2.87
<tb><SEP> 38 <SEP>%
<tb><SEP> Gas oil + 10% <SEP> ethanol + Ad <SEP> 3.06
<tb><SEP> Gas oil + 5% <SEP> ethanol <SEP> 2.98
<tb> 47%
<tb><SEP> Gas oil + 5% <SEP> ethanol + Ad <SEP> 3.16
<Tb>
Ad: addition of 2% by weight of additive.

Table 3

<tb> Compound <SEP> CMC <SEP> (mol <SEP> I-1)
<tb><SEP> 1 <SEP> 1.5 <SEP> - <SEP> 10-3 <SEP> to <SEP> 25 C
<tb><SEP> 3 <SEP> 9.5 <SEP> - <SEP> 10-3 <SEP> in <SEP> EtOH / H2O
<tb><SEP> (1 <SEP>: <SEP> 1)
<Tb>
Table 4

<tb><SEP> Power <SEP> +++ <SEP> ++ <SEP> +
<tb> Surfactant
<Tb>

Claims (19)

 1) Fuel additive characterized in that it is constituted by a 3  alkyloxy-1-alkylamino propan-2-ol of which an alkyl radical is C2 to  C18. 2) Fuel additive characterized in that it consists of the  of a 3-alkyloxy-1-alkylamino propan-2-ol of which a radical  alkyl is C 2 to C 18. 3) Additive according to any one of claims 1 or 2, characterized  in that the acyl radical is C 2 -C 8 hydroxyl-functional  terminal. 4) Additive according to any one of claims 1 to 3, characterized  in that the amine function is constituted by a mono amine  substituted in C2 to C18. 5) Additive according to any one of claims 1 to 3, characterized  in that the amine function is an amine di  substituted in C2 to C18. 6) Additive according to any one of claims 1 to 3, characterized  in that the amine function is an alkanolamine  in C2 to C8. 7) Additive according to any one of claims 1 to 6, characterized  in that the alkyl radical is C8. 8) Fuel containing an additive according to any one of  Claims 1 to 7, characterized in that the additive  approximately 2% to 5% by mass of the fuel and that the fuel contains  alcohol. 9) Process for preparing 3-alkyloxy-1-allylamino propan-2-ol and  of their dimers which consists of a first stage of alkylation  of epihalohydrins with fatty alcohols in a heterogeneous medium  solidelliquide, and in a second stage of condensation of amines  fatty acids on the alkyl glycidyl ethers obtained in the first step. 10) Process according to claim 9, characterized in that the alcohols  fat are mono-alcohols. 11) Process according to claim 9, characterized in that the alcohols  fatty are diols, 12) Process according to any one of claims 9 to 11, characterized  in that the solid phase of the heterogeneous alkylation medium is  consisting of potassium hydroxide. 13) Process according to all of claims 10 and 12, characterized by  the fact that potassium hydroxide is associated with tetraethylene  glycol. 14) The method of claim 10 and any one of  12 or 13, characterized in that the liquid phase of the  Heterogeneous alkylation medium consists of hexane. 15) Process according to all of claims 10 and 12, characterized by  the fact that the liquid phase of the heterogeneous medium consists of  propylene glycol. 16) Process according to the set of claims 1 1 and 12, characterized by  the fact that the liquid phase of the heterogeneous alkylation medium is  consisting of tetrahydrofuran. 17) Method according to any one of claims 9 to 16, characterized  in that the condensation is carried out in ethanol. 18) Method according to any one of claims 9 to 16, characterized  in that the condensation is carried out in tertiobutanol. 19) Method according to any one of claims 9 to 18, characterized  in that the second step is followed by an extraction in  pentane in order to separate monoadditioned and bi products  obtained.