DD297440A5 - FUEL ADDITIVE - Google Patents

Abstract

The invention relates to the use of a compound having at least two substituents and a space filling and configuration such that it can adopt the positions of wax molecules at the interfaces of the plane (001) and the planes (110) and / or (111) in wax crystals, wherein the substituents are alkyl, alkoxyalkyl or polyalkoxyalkyl groups having at least 10 carbon atoms in the main chain, as additives to wax-containing distillates used as propellants. mineral oils; additives; molecular geometry; Wax crystals; Fuel distillates; Turbidity point}

Description

For this 8 pages drawings

Field of application of the invention

The invention relates to the use of specifically substituted compounds as additives for wax-containing distillates used as propellants.

Characteristic of the known state of the art

Mineral oils containing waxy paraffins, such as petroleum distillates used as diesel fuel or fuel oil, have the property of becoming less liquid as the temperature of the oil decreases. The cause of this loss of fluidity is the crystallization of wax into plate-like crystals, which can eventually form a sponge-like mass, in which the oil is trapped. The temperature at which wax crystals start to form is known as the cloud point, and the temperature at which the oil is no longer flowable by the wax is known as the pour point.

It has long been known that a number of additives act as a pour point depressant when blended with waxy mineral oils. These compositions modify the size and shape of the wax crystals and reduce the cohesive forces between the crystals and between the wax and the oil in such a way that the oil remains liquid at a lower temperature so that it remains pourable and capable of being rendered to pass rough filters.

The literature describes a number of means for lowering the pour point, and several of them are used industrially. So z. For example, in US Patent 3,048,479 the use of copolymers of ethylene and of Ci-C ₆ vinyl esters, eg. As vinyl acetate, taught as a means for lowering the pour point of fuels, especially fuel oils, diesel fuels and jet fuels. Polymeric hydrocarbons based on ethylene and higher alpha olefins, eg propylene, are also known. U.S. Patent 3,252,771 discloses the use of polymers of cis to cis alpha-olefins made with aluminum trichloride / alkyl halide catalysts as a pour point depressant in wide boiling range types of petroleum distillates were easy to treat and were commercially available in the US in the early 1960's.

In the late '60s and early' 70s, the improvement in filterability of oils at temperatures between the cloud point and pour point, as evidenced by the more difficult to use "Cold Filter Plugging Point (CFPP) Test." In the US Pat. No. 3,961,916, the use of a mixture of copolymers to control the. (IP309 / 80) has become more important and since then many patents have been published which have dealt with improving the behavior of fuels in this test It is proposed in GB 1,263,152 to control the size of the wax crystals by using a copolymer having a lower side chain branching content.

It has also been proposed, for. In GB-PS 1,469,016 that the copolymers of di-n-alkylfumarates and vinylacetate hitherto used as agents for lowering the pour point of lubricating oils, as a further additive to ethylene / vinyl acetate copolymers in the treatment of petroleum distillates be used with a high boiling point to improve their flow properties at low temperatures.

It has also been proposed to use additives based on olefin / maleic anhydride copolymers. So z. For example, in US Patent 2,542,542 copolymers of olefins, ζ. From octadecene, and maleic anhydride esterified with an alcohol, such as lauryl alcohol, as a pour point depressant; and in GB-PS 1,468,588 copolymers of C ₂₂ -C _2a olefins with maleic anhydride esterified with behenyl alcohol are used as further additives for petroleum distillates.

According to Japanese Unexamined Patent Publication No. 56-54,037, olefin / maleic anhydride copolymers reacted with amines are similarly used as a pour point depressant.

In JP-OS 56-54,038 the use of derivatives of olefin / maleic anhydride copolymers together with conventional means for improving the flow behavior of middle petroleum distillates, z. B. of ethylene-vinyl acetate

-2- 237 440

Copolymers described. In JP-OS 55.40.640, the use of olefin-maleic anhydride copolymers (not esterified) is published and found that the olefins used should not have more than 20 carbon atoms in order to achieve a CFPP activity. According to GB-OS 2,192,012, mixtures of certain esterified olefin · malonic anhydride copolymers and low molecular weight polyethylenes are used, the ve. esterified copolymers are ineffective when used as a single additive.

The enhancement of CFPP activity by the addition of the additives disclosed in these patents is achieved by modifying the size and shape of the wax crystals which form, usually using acicular crystals generally of a particle size of 10 microns or larger, generally from 30 to 100 microns. When operating diesel engines at low temperatures, these crystals can not pass the paper filters in the fuel system of the vehicles, but form a permeable filter cake on the filter so that the liquid fuel can pass, the wax crystals gradually dissolving as machine and fuel, which can be done by recirculating fuel that heats the fuel supply. However, the formation of wax can block the filters, which can lead to problems with the start of diesel vehicles and problems at the start of operation in cold weather or failure of heating systems.

With the aid of a computer, it is possible to precisely calculate the geometry of the lattice of n-alkane wax crystals and the energetically preferred geometry of a possible additive molecule in a simple and very convenient way. The results of such calculations become particularly thin when subsequently visualized with the aid of a plotter or graphic terminal. This method is known as "molecular modeling." Computer programs for this purpose are already available.

The growth of paraffin crystals proceeds in such a way that individual paraffin molecules attach with their long side to the edge of an existing paraffin platelet, as shown schematically in FIG. The association to the upper or lower side of the platelet is energetically unfavorable, since in this case only one end of the chain-shaped paraffin molecule interacts with the existing crystal. The association occurs mainly at the crystallographic level (001) (see Fig. 1). The plane (001) contains the greatest number of strong intermolecular conditions and thus causes the crystal to form large, flat, rhombohedral plates (Figure 3). The most stable plane on the crystal closest to this shape is the (11x) (eg, the [110]). The intermolecular association is strongest where the n-alkane molecules are densely packed so that the (1 J0) plane binds more strongly than the (100) plane. The crystal grows by widening the (001!) Plane, so it is important to note that the edges of this plane are the rapidly expanding surfaces and that these (11x) (eg, the [110) plane) and to a lesser extent the (100). It follows that growth is mainly controlled by the extension of the (11x) plane.

Since the head-to-head bindings are relatively weak, we generally consider only one molecular level (001), so we can assume that the levels (110), (111), and so on, are equivalent in our view Figure 4, which is a photograph of a wax-crystal plate, shows that the macroscopic appearance of the platelets is indicated by the plane (001) of the lattice and the relative orientations of adjacent molecules supported side by side It is these plates that can block the filtor in fuel lines Fahrzeugen. von of vehicles.

Object of the invention

The aim of the invention is to substantially eliminate the disadvantages described in detail above.

Explanation of the essence of the invention

According to the invention, the described problem is solved in that the crystal growth in the plane (001) and in the directions (110) and (111) is prevented or at least greatly reduced.

This can produce waxy fuels having crystals that are sufficiently small at low temperatures to pass through the filters commonly used in diesel engines and fuel oil systems. This is achieved by the addition of certain additives.

By this invention, therefore, there is provided a compound for use as an additive for wax-containing petroleum distillate fuels which has at least white substituents of such a configuration and spatial arrangement as to occupy the locations of wax molecules in the plane (001) occupying themselves with the planes (110) and / or (111) in crystals of the wax, the substitutes being alkyl, alkoxyalkyl or polyalkoxyalkyl groups having at least 10 carbon atoms in the main chain.

The taking of the planes in the crystal can be explained with reference to FIG. 4, which shows an enlarged plan view of the crystal lattice of a paraffin plate. The viewing direction corresponds to the long axis of the paraffin chains. Each of them has only two carbon atoms and four hydrogen atoms (the latter being shown only once), since the other atoms are below the represented atoms, since all the carbon atoms are in a plane of symmetry of the molecule. In Figure 4 it can be seen that the distances between two molecules in the plane (100) and in the plane (110) are substantially equal.

These distances are denoted by "b" and "d" in FIG. 4 and the values are b = 4.9 A and d = 4.5 A. The main difference between the planes (100) and (110) (or more broadly, the planes [11x] in which χ represents 0 or an integer) consists in the relative orientation of the adjacent paraffin molecules. Within plane (100), the planes of symmetry of the molecules are parallel to each other, i. H. that the dihedral angle is 0 °. In the crystalline plane (110), the dihedral angle between the planes of symmetry of adjacent molecules is about 82 °. According to the invention, the additives are said to occupy the positions on the paraquine molecules which have been designated "C" and "D" in Fig. 4. This is possible only if the distance between the substituents is about 4.5 to 5.0 Å in one

is energetically available conformation and when the dihedral angle between the localon symmetry planes of the two substituents is about 82 °, preferably between 75 ° and 90 °.

A molecule can be modeled by either entering its known atomic coordinates into a computer or by building its structure according to the rules of chemical physics using a computer. Subsequently, the structures can be refined, for. B. by

a) Calculation of the partial charges at each atom from differences in electronegativity (force field method) or by quantum mechanical techniques (e.g., CNOO, Q.C.P.E. 141, Indiana University);

b) optimization of the structure using molecular mechanics (see "Modular Mechanics", U. Burkert and N. L. Alinger, ACS, 1982);

c) minimizing the total energy by optimizing the conformation, i. H. by rotation about the rotatable bonds. In this case, it should be noted that the environment on the wax crystal surface differs from that in the gas phase or in solution and it is possible that the molecule of the additive crystallizes together with the paraffin in a conformation which is not the most energetic favored conformation in the gas phase. Furthermore, it should be noted that the additive can not adopt a conformation that is hindered by steric or electronic factors.

By using the following criteria, it can be checked whether the molecule of an additive fits into the plane (001) of the paraffin crystal lattice in the desired positions C and O, because

(1) the distance between the substituents on the molecule must be approximately equal to the distance between two adjacent paraffin molecules in the plane (001) which intersects with the plane (11x), i. H. must be about 4.5A. The relative orientation of the substituents should match the arrangement of the n-alkanes in the direction (110), i. H. that the dihedral angle between the local symmetry planes of the substituents should be about 82 °. This distance and angle can be easily determined using computer programs.

(2) the molecule of the additive should fit into the lattice structure of the wax crystal and fit into two vacant lattice sites.

Compounds which have hitherto been proposed as additives are certain derivatives of phthalic acid, maleic acid, succinic acid and vinylidene olefins. None of these compounds meet criterion (1), as described above. This is explained by the following selected examples.

(a) Phthalic acid diamide, in the most favorable case, has the conformation shown in (5), where the distance between the substituents and the dihedral angle is too small, and this conformation is not energetically favored because it is sterically hindered The re-minimization leads to the disturbed Konformatioo, which is shown in Fig.6.

(b) In the case of maleic acid diamide, the situation is similar, as can be seen from Fig. 7. Because of the steric hindrance, the re-minimization leads to the disordered conformation as shown in FIG.

(c) Due to steric hindrance, succinic acid can not adopt a conformation close to the particular arrangement of the invention (see Fig. 9). By rotation about the C-C single bond, the succinic acid converts to the conformation shown in FIG.

The improvement in CFPP performance by incorporating the additives heretofore used in these patents is achieved by modifying the size and shape of the wax crystals that form, by adding substantially acicular crystals having a particle size of generally 10000 nm or larger, typically 30,000 to 100,000 nm, are produced. When operating diesel engines at low temperatures, these crystals do not pass through the paper fuel filters of these vehicles, but form a penetrable cake on the filter through which the liquid fuel can pass through, with continued warming of the engine and fuel causing the wax crystals to wane and dissolve and this heating of the fuel can be done by recirculating fuel into the fuel tank. However, the deposition of the wax can clog the filters, which can lead to problems in starting the diesel engines and starting the operation in cold weather. Likewise, this can lead to the failure of heating systems with fuels.

In this application, the following test methods are used:

The wax exfoliation temperature (WAT) of the fuel is determined by Differential Scanning Calorimetry (DSC). In this test, a small sample of the fuel (25 microliters) is cooled at a rate of 2 ° C / minute along with a reference sample of similar heat capacity, but which does not deposit wax within the temperature range of interest (eg, kerosene). As soon as crystallization occurs in the sample, an exothermic peak is observed. The WAT of the fuel can z. Example by the extrapolation technique using a Mettler TA2000B warden. The wax content of the fuel is obtained from the OSC curve by integrating the area enclosed by the baseline and the exothermic up to the determined temperature. The calibration was previously carried out on a known amount of crystallizing wax.

The average particle size of the wax crystals is determined by analyzing a recording electron micrograph of a fuel sample at a magnification of between 4,000 and 8,000, with the largest linear expansion of at least 40 out of 88 points measured in a predetermined grid. that at an average size of less than 4000 nanometers, the wax begins to flow along with the fuel through the commonly used paper filters used in diesel engines, although it is preferred that the particle size be less than 3000 nanometers, more preferably less than 2500 and most preferably less than 2000 nanometers, and more preferably less than 1000 nanometers, which then achieves the true merits of passing de <- crystals through the paper filters for the fuel. The actual size to be achieved depends on the original type of fuel and on the type and amount of additive used; however, we have found that these particle sizes and smaller ones can be achieved.

The use of the additive according to the invention results in that such small wax crystals can be produced in the fuel, which leads to significant advantages in the operation of diesel engines. This can be demonstrated by flowing fuel through a filter paper for diesel engines as used in a VW Golf or a Cummins diesel engine at a rate between 8 and 15 ml / sec and 1.0 to 2.4 liters per minute and per square meter

Filter surface at a temperature of at least 5 ° C below the temperature of the beginning of the deposition of wax crystals with at least 0.5 wt .-% of the fuel in the form of solid wax, is pumped through. The assessment as to whether both fuel and wax have successfully passed the filter is made by satisfying one or more of the following criteria: (i) When 18 to 20 liters of fuel have been pumped through the filter, the pressure drop exceeds that Filter not 50 kilopascals (kPa), preferably not more than 25 kPa, more preferably not more than 10 kPa, and most preferred

not more than 5kPa

 (ii) At least 60%, preferably 80% and more preferably at least 90% by weight of the wax present in the starting propellant, as determined by the DSC test described hereinbefore, is present in the fuel,

(iii) While 18 to 20 liters of fuel are pumped through the filter, the flow rate will always remain above 60% of the original flow rate and preferably above 80% of the same.

The amount of crystals passing through the filters of automobiles and the advantages of operating motors resulting from the small crystals are highly dependent on the length of the crystals, although the shape of the crystals is also important. We assume that cube-shaped crystals can pass the filters slightly more easily than flat crystals, and if they do not pass the filter, they offer less resistance to the fuel flow. Nevertheless, the preferred crystal form is a flat shape which, in principle, allows a greater amount of wax to be deposited on the filter as the temperature is lowered and allows a larger amount of wax to be deposited before the critical length of crystal is reached than for cube-shaped crystals of the same length Case would be.

The fuels produced by the process according to the invention have outstanding advantages compared to conventional fuels from petroleum distillates, when the latter improve the flow properties at low temperatures by adding conventional additives. So these fuels z. At temperatures closer to the pour point, and are not limited in their use in that they do not pass the CFPP test, either because they satisfy the CFPP test at significantly lower temperatures or it is not necessary at all Test. These fuels also have improved low temperature cold start properties and are not dependent on the circulation of warm fuel, by which means undesirable wax deposits are to be eliminated. Furthermore, the wax crystals tend to remain in suspension and do not settle, thereby forming wax layers in storage tanks, which occurs when fuels are added with conventional additives. Used as fuels petroleum distillates of the general class, the C boiling in the range of 120 ° C to ⁰ SOO differ significantly in their boiling characteristics, their distribution in the n-alkanes and the wax content. Fuels from Northern Europe generally have a lower upper boiling limit and cloud points than those from southern Europe. The contents of wax are generally above 1.5% (at 1O ⁰ C below the WAT).

Likewise, fuels from other countries in the world differ in the same way with respect to their respective climatic conditions, but the wax content is also dependent on the supplier of the crude oil. A fuel made from a Middle East crude oil is likely to have a lower wax content than a fuel derived from the typical crudes, e.g. from China and Australia.

The extent to which it is possible to obtain these very small crystals depends on the nature of the fuel itself, and for some fuels it may well be possible to produce extremely small crystals. When such a situation occurs, the characteristic properties of the fuel can be changed to allow the production of such small crystals, e.g. B. by adjusting the refining conditions or by mixing to make the use of suitable additives possible.

Since the wax precipitated from petroleum distillates used as fuels consists essentially of n-alkanes, which crystallize in an orthorhombic unit cell via a rotator or a hexagonal shape, as described in the literature z. From A. Muller in Proc. Roy. Soc A114,542 (1927), ibid. 120,437 (1928 ibid.), 127,417 (1930), ibid. 138,514 (1932); by A.E. Smith in J. Chem. Phys. 21,2229 (1953) and P.W. Teare in Acta Cryst. 12,294 (1955). As already mentioned, the two factors that are important for matching the additional micelle molecule to the wax crystal structure are, firstly, the separation between the n-alkane chains in selected crystal planes, in which the critical distances are those in the planes or directions (110) and (111), etc., and to a lesser extent those at level (100).

The chains of the admixture must occupy the lattice sites (more than one) in positions on the axes which are at right angles to the axis of the n-alkane chains in the crystal. These separations are on the order of 4.5 to 5.5A, and the closer the chains of admixtures are to these ranges, the more effective the additive. Second, although perhaps less important, the relative orientations of the A additive molecule chains are preferably consistent with those of the n-alkanes in the crystal. The n-alkyl chains of the admixture must be able to exactly match the intermolecular distances of the n-alkanes in the wax crystals along the planes (100) and / or (110) and (111) where they align with the plane ( 001), and they must be able to adopt conformations that allow the chains to arrange themselves at similar angles to those of those alkanes in the above crystal planes. It has been found that these spacings and orientations of the chains of the additive molecule can best be adjusted by being located on adjacent carbon atoms in a cyclic or ethylenically unsaturated compound, provided they are substituted in the cis orientation.

Preferably, this mating is also achieved by utilizing the entire length of the n-alkane chain of the wax, and the total chain length of the additive is preferably of the same order of magnitude as the average chain length in the wax. The wax deposition in the fuel or oil is generally a mixture of n-alkanes, and therefore the reference to average dimensions.

The additives therefore generally contain alkyl, preferably n-alkyl chains or chain segments which can crystallize together with the wax. We have found that one molecule should have two or more such chains and that they should be located on the same side of the additive molecule. It is desirable that the additive molecule have two distinct sides. A "side" should be the jointly crystallizing alkyl chains

and the other "side" should have the smallest possible number of hydrocarbon groups necessary to block or prevent further crystallization after co-crystallization of the additive molecule into the n-alkane sites of the wax crystal "Blocking" group is located halfway or approximately halfway along the co-crystallizing n-alkyl chains of the additive

 The preferred additives in this use have the formula

on, in the

-YR ² SO ₃ ⁽ - ^{| (+ 1} NRlR ² , -SO 3 ^l " ^{1 (+ 1} HNRiR ² , -SO 3 ⁽ " ^{1 (+ 1} HaNR ³ R ² , -SO 3 ⁽ - " ^{+ 1} H 3 NR ² , -SO ₂ NR ³ R ² OdBr-SO ₃ R '; - XR ¹ -YR ² or -CONR ³ R', - CO ₂ ⁽ - ^{H + 1} NRiR ¹ , -CO ₃ ^| - ^{| <+1} NHiR ¹ , -CO ₂ ⁽ - ^{1 (+} 1H 2NR ³ R ¹ , -CO ₂ ¹ - ^{| (+)} H ³ NR ¹ ₍ -R ⁴ -COOR ^I ,

-NR ^ OR'.R'OR '.- R ^ COR' .- R'R '.- NICOR'm' or Z ¹ ^ ⁺¹ NR ₃ ¹ R ¹ ; -Z ¹ " ¹ SO ₃ ^1- OdOr-COO ¹ " ¹ and

R ¹ and R ^{2 represent} alkyl, alkoxyalkyl or polyalkoxyalkyl groups having at least 10 carbon atoms in the main chain;

wherein R ^{3 is} a hydrocarbyl radical and each R ³ may be the same or different and R ⁴ is nothing or a C 1 - to (C 1-4 alkylene group and in

The ring atoms in such ring compounds are preferably carbon atoms, but may also include a ring nitrogen, sulfur or oxygen to give a heterocyclic compound. Examples of aromatic compounds from which the additives can be prepared are

in which the aromatic group may be substituted.

On the other hand, they can also be derived from polycyclic compounds, i. those which have two or more ring structures and which can take various forms. They may be (a) condensed benzene structures, (b) fused ring structures in which none or not all rings are benzene rings, (c) fused rings, (d) heterocyclic compounds, (e) non-aromatic or partially saturated ring systems or ( f) be three-dimensional structures. Condensed benzene structures from which these compounds are derived include e.g. Naphthalene, anthracene, phenanthrene and pyrene.

The condensed ring structures in which no or not all rings are benzene rings are, for. As azulene, indene, hydroindene, fluorene or diphenylene. Compounds in which the rings are annelated, z. B. diphenyl. Suitable heterocyclic compounds from which they can be derived are u. a. z. Quinoline, pyridine, indole, 2,3-dihydroindole, benzofuran, coumarin, isocoumarin, benzthiophene, carbazole and thiodiphenylamine. Suitable non-aromatic or partially saturated ring systems include i.a. Decalin (decahydronaphthalene), α-pinene, cadins, bornylene. Suitable three-dimensional compounds are, for. Norbornene, bicycloheptane (norbornane), bicyclooctane and bicyclooctene.

The two substituents X and Y must be attached to adjacent ring atoms in the ring if there is only one ring or to adjacent ring atoms in one of the rings if the compound is polycyclic. In the latter case, this implies that these substituents, if one were to use naphthalene, could not be attached in the 1,8 or 4,5 position but in the 1,2,3,3,4- , 5,6-, 6,7- or 7,8-pos.

These compounds are reacted to produce the esters, amines, amides, half-esters / hemiamides, hemi-ethers or salts thereof, which are used as the additives. Preferred additives are the salts of a secondary amine having hydrogen and carbon containing groups or groups having at least 10, preferably at least 12 carbon atoms. Such amines or salts can be prepared by reacting the acid or anhydride, as previously described, with an amine, or by reacting a secondary amine with carboxylic acids or anhydrides. In general, it is necessary to remove and heat water in the production of amides from acids. On the other hand, the carboxylic acid may be reacted with an alcohol having at least 10 carbon atoms or with a mixture of an alcohol and an amine.

The hydrogen and carbon-containing groups in the substituents are preferably hydrocarbon groups, although halogenated hydrocarbon groups may also be used, with only a small proportion of halogen atoms being preferred (e.g., chlorine atoms), e.g. B. less than 20Gew .-%. The hydrocarbon groups are preferably aliphatic, ζ. B. Alkylenegruppon. They are preferably straight-chain groups. Unsaturated hydrocarbon groups, e.g. Alkenyl groups may also be used, but are not preferred. The alkyl groups preferably have at least 10 carbon atoms, preferably 10 to 22 carbon atoms, e.g. 14 to 20 carbon atoms, and are preferably straight-chain or branched in the 1- or 2-position. If more than 20% of the alkyl chains are branched, then the branching groups must be methyl groups. The other groups containing hydrogen and carbon may be shorter, e.g. Having less than 6 carbon atoms or, if desired, may have at least 10 carbon atoms. Suitable alkyl groups include i.a. Methyl, ethyl, propyl, hexyl, decyl, dodecyl, tetradecyl, eicosyl and docosyl (behenyl) groups. Suitable alkylene groups include, but are not limited to, hexylene, octylene, dodecylene and hexadecylene groups. In the preferred embodiment in which the intermediate is reacted with a secondary amine, one of the substituents is preferably an amide and the other is an amine or a dialkyl ammonium salt of a secondary amine

 The most preferred additives are the amides and amine salts of secondary amines. To obtain the fuels of this invention, these additives will generally be used in conjunction with other additives; Examples of other additives are those referred to as "comb polymers" having the general formula:

D H* - J H I I I I  0- -C- I ra -Ο ι -C- I I E I G I K I L  J

wherein D = R, CO.OR, OCO.R, R'CO.OR or OR E = H or CH ₃ or D or R 'G = H or D

m = 1.0 (homopolymer) to 0.4 (molar ratio) J = H, R ', aryl or heterocyclic group, R'CO.OR K = H, CO.OR ·, OCO.R', OR ', COOH L = H, R ', CO.OR', OCO.R ', aryl, COOH η = 0.0 to 0.6 (molar ratio) Rs = Ct ₀ R' = sC,

Another monomer can be terpolymerized if it proves necessary.

In case these other additives are copolymers of alpha-olefins and maleic anhydride, they can easily be prepared by reacting the monomers in the solvent-free process or in solution in a hydrocarbon, e.g. For example, heptane, benzene, cyclohexane or paraffin oil at a temperature generally in the range of 20 ° C to 15O ⁰ C and usually accelerated with a catalyst of the peroxide or azo type, for. Benzoyl peroxide or azobis (isobutyronitrile), under a protective layer of an inert gas, e.g. B. of nitrogen or carbon dioxide to exclude oxygen, are polymerized. It is preferred, but not essential, that equimolar amounts of the olefin and maleic anhydride be used, although molar ratios in the range of 2: 1 to 1: 2 are suitable. Examples of olefins which can be copolymerized with maleic anhydride are 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene and 1-octadecene.

The copolymer of olefin and maleic anhydride may be esterified by any suitable technique, and although it is preferred, it is not essential that the maleic anhydride is at least 50% esterified. Examples of alcohols that can be used include n-decane-1-oil, n-dodecan-1-ol, n-tetradecane-1-oil, n-hexadecane-1-oil, n-octadecan-1-ol , The alcohols may also have up to one methyl group branch per chain, ζ. For example, 1-methylpentadecan-1-ol, 2-methyltridecan-i-ol. The alcohol may be a mixture of normal and methyl branched alcohols. Any of these alcohols can be used to esterify the copolymers of maleic anhydride with one of said olefins. It is preferred to use pure alcohols and not the commercial alcohol mixtures, but when mixtures are used, then R ¹ refers to the average number of carbon atoms in the alkyl groups; when alcohols having a branch at the 1- or 2-position are used, R ¹ refers to the straight-chain chain segment of the alcohol. When mixtures are used, it is important that no more than 15% of the groups R 'have the value r ¹ + 2. The choice of alcohol is, of course, dependent on the choice of olefin copolymerized with maleic anhydride, so that R + R 'is within the range of 18 to 38. The preferred value of the sum R + R ¹ will depend on the boiling characteristic of the fuel in which the additive is to be used.

These comb polymers may also be fumaric acid polymers and copolymers as described in our European Patent Applications Nos. 0153176, 0153177, 85301047 and 85301048. Other suitable comb polymers are copolymers of alpha olefins and polymers thereof and the esterified copolymers of styrene and maleic anhydride.

Examples of other additives which may be used in conjunction with the cyclic compounds are the polyoxyalkylene esters, ethers, ethers / ethers and mixtures thereof, especially those containing at least one, preferably at least two C ₁ O to C ₃₀ linear, saturated alkyl groups and a polyoxyalkylene glycol group of molecular weight 100 to 5000, preferably 200 to 5000, wherein the alkyl group in said polyoxyalkylene glycols contains 1 to 4 carbon atoms. These fabrics are the subject of European Patent 0,061,395 B. Other such additives are described in U.S. Patent 4,491,455. The preferred esters, ethers or ester ethers which can be used in this process according to the invention can be represented by the following formula in their structure:

, R-O (A) -O-R "

wherein R and R "may be the same or different and have the following meaning: i) n-alkyl groups H) n-alkyl-C

III) n-AlkycO-C- (CH ₂ ) _n -

iv) n-alkyl-OC- (CH ₂ ) "- C-

Il

O O

wherein the alkyl groups are to be linear and saturated and have from 10 to 30 carbon atoms, and wherein A represents the polyoxyalkylene segment of the glycol in which the alkylene group has from 1 to 4 carbon atoms, e.g. Polyoxymethylene, polyoxyethylene or polyoxytrimethylene, which are substantially linear; a low degree of branching with lower alkyl side chains (as is the case, for example, in poloxypropylene glycol) can be tolerated, but it is preferred that the glycol be substantially linear. A may also contain nitrogen.

Suitable glycols are the substantially linear polyethylene glycols (PEG) and polypropylene glycols (PPG) having molecular weights of about 100 to 5,000, preferably 200 to 2,000. Esters are preferred, and fatty acids of 10 to 30 carbon atoms are suitable for reaction with the glycols whereby the esters used as additives are prepared, and it is preferred to use C ₁₈ -C ₂ 4 fatty acids, in particular behenic acid. The esters can also be prepared by esterifying polyethoxylated fatty acids or polyethoxylated alcohols. Polyoxyalkylene diesters, diethers, ester ethers and mixtures thereof are useful as additives with the diesters being preferred for use in narrow boiling distillates, while small amounts of monoethers and monoesters may also be present. These are often produced during the manufacturing process. For the performance as an additive is important that the majority is in the form of the dialkyl compound. In particular, diesters of stearic acid or behenic acid with polyethylene glycol, polypropylene glycol or polyethylene-polypropylene glycol mixtures are preferred.

The additives used may also contain copolymers of ethylene and ethylenically unsaturated esters as improvers of Feüesverhaltens. The unsaturated monomers which can be copolymerized with ethylene are e.g. B. unsaturated mono- and diesters of the general formula:

C = G

wherein R _{6 is} hydrogen or a methyl group, R _{6 is} an -OOCRs group in which R _{8 is} hydrogen or a C) -C ₂₈ -, usually a C) -C) ₇ - and preferably a C) -C ₈ - straight-chain or branched alkyl group, or wherein Rs is a -COORa grouping in which R _{8 is} as described above, but not hydrogen, and R _{7 is} hydrogen or a -COOR ₈ grouping, as has already been defined. This group of monomers, when R ₆ and R _{7 are} hydrogen and R _{6 is} an -OOCRs moiety, includes vinyl alcohol esters of C 1 -C ₂₉ , conventional C 1 -C 4 monocarboxylic acids and preferably C ₂ to C ₂₉ , usually C ₁ - to C) ₈ monocarboxylic acids and preferably C ₂ - to Ce monocarboxylic acids. Examples of vinyl esters that can be copolymerized with ethylene include vinyl acetate, vinyl propionate, and vinyl butyrate or isobutyrate, with vinyl acetate being preferred. When these compounds are used, it is preferred that the copolymer contain between 5 and 40% by weight of the vinyl ester, more preferably between 10 and 35% by weight of the vinyl ester. They may also be blends of two copolymers as described in U.S. Patent 3,961,916. It is preferred that these copolymers have a number average molecular weight as determined by vapor pressure osmometry of from 1,000 to 10,000, preferably from 1,000 to 5,000.

The additives used may also contain other polar compounds, which may be either ionic or nonionic, and which have the property of being effective in fuels as inhibitors of crystal growth. It has been found that polar nitrogen-containing compounds are particularly effective when used in conjunction with glycol esters, ethers or ether esters. These polar compounds are generally amine salts and / or amides prepared by the reaction of at least a molar proportion of substituted hydrocarbyl radicals with a molar proportion of a hydrocarbylic acid having from 1 to 4 carboxylic acid groups or their anhydrides; however, it is also possible to use ester amides which contain from 30 to 300, preferably from BO to 150, total carbon atoms. These nitrogen compounds are described in US Pat. No. 4,211,534. Suitable amines are generally long chain

e, secondary, tertiary or quaternary amines or mixtures thereof, however, shorter chain amines can also be used, provided that the nitrogen compound thus obtained is oil soluble so that it normally contains a total of 30 to 300 carbon atoms. The nitrogen compound preferably contains at least one straight chain C ₈ to C ₂ 4 alkyl segment.

Suitable amines are primary, secondary, tertiary or quaternary, but secondary ones are preferred. Tertiary and quaternary amines can only form amine salts. Examples of suitable amines are tetradecylamine, cocoamine, hydrogenated tallow amine and the like. Examples of secondary amines are dioctadecylamine, methyl-phenylamine and the like, amine mixtures are also suitable as well as many amines derived from naturally occurring substances which are also mostly mixtures. The preferred amine is a secondary hydrogenated tallow amine of the formula HNR ₁ R ₂ wherein R 1 and R _{2 are} alkyl groups derived from the hydrogenated tallow fat consisting of approximately 4% C ₁₄ , 31% C ₁₈ and 59% C _{) e} .

Examples of suitable carboxylic acids (and their anhydrides) for preparing these nitrogen-containing compounds include cyclohexane-1-dicarboxylic acid, cyclohexene-1-dicarboxylic acid, cyclopentane-1-dicarboxylic acid, naphthalenedicarboxylic acid and the like. In general, these acids have 5 to 13 carbon atoms in the cyclic unit. Preferred acids for the process according to the invention are the benzene-dicarboxylic acids, eg. As phthalic acid, isophthalic acid and terephthalic acid. Particularly preferred is phthalic acid or its anhydride. The most preferred compound is the amide-amine salt prepared by the reaction of 1 molar portion of phthalic anhydride with 2 molar proportions of dihydrogenated tallow amine. Another preferred compound is the diamide prepared by dehydration of this aminamide salt.

Hydrocarbon polymers may also be used as part of the additive composition in the preparation of the fuels of this invention. These can be represented by the following general formula:

T H

I I • C-C

I i

T T

U H

-0-Oj - I

^HU w

where T is H or R '

U is H, T or aryl,

ν 1.0 to 0.0 (molar ratio)

w 0.0 to 1.0 (molar ratio)

R'alkyl mean.

These polymers can be directly: from ethylenically unsaturated monomers or indirectly z. By hydrogenation of the polymer prepared from other monomers such as isoprene or butadiene.

A particularly preferred hydrocarbon polymer is a copolymer of ethylene and propylene having an ethylene content preferably between 50 and 60% by weight.

The amount of additive needed to heat the distilled fuel oils of the present invention depends on the type of propellant used, but is generally between 0.001 and 0.5% by weight, e.g. B. between 0.01 and 0.1 wt .-% of active Stofie, based on the weight of fuel. The additive may be best dissolved in a suitable solvent to produce a concentrate containing from 20 to 90, e.g. B. 30 to 80Gew .-%, in the solvent. Suitable solvents include kerosene, aromatic petroleum fractions, mineral lubricating oils, etc. This invention is illustrated by the following examples, in which the size of the wax crystals in the fuel is measured by driving stole samples in 2-oz bottles in coolers, approximately 8 ° C were kept above the cloud point of the fuel, one hour were adjusted so that the temperature of the fuel stabilized. The icebox is then cooled to the test temperature at a rate of 1 "C / hour, which is then held: a prepared filter carrier consisting of a 10mm diameter sintered ring surrounded by a 1mm wide circular metal ring and carrying a 200nni mesh silver membrane filter held in position by two vertical pins is placed on a vacuum unit, a vacuum of at least 8OkPa is applied, and the cooled fuel is dropped from a clean dropper pipette onto the membrane, The fuel is slowly further dripped so that the dtase layer is maintained for a few minutes, and after 10 to 20 drops of fuel have been applied, the layer is aspirated, producing a very thin, dull, layer of Fuel moist wax cake layer is left on the membrane A thick Wachsschic ht can not be sufficiently washed, and a very thin layer of wax can be washed out. The optimum thickness of the layer is a function of crystal form, with "sheet-like" crystals requiring thinner layers than "square" crystals. It is important that the finally obtained crystal cake has a dull appearance. A "shiny" filter cake indicates excess, residual fuel and "smudging" of the crystals and should be discarded. The filter cake is then washed with a few drops of methyl ethyl ketone, which are completely sucked off. This process is repeated a few times. When the washing process is complete, the methyl ethyl ketone disappears very rapidly leaving a "bright matte white" surface, which turns gray upon addition of another drop of methyl ethyl ketone, The washed sample is then placed in a refrigerated desiccator and stored there until all is ready for coating SEM

ready. It may be necessary to keep the sample deeply chilled to obtain the wax. In this case, the sample should be stored in a refrigerator until transfer (in a suitable sample transport container) to avoid the formation of ice crystals on the sample surface. During coating, the sample must be kept as cold as possible to minimize damage to the crystals. The electrical contact with the device is best made by pressing the circular ring against the side of a counterbore in the device designed so that the sample surface lies in the focal plane of the instrument. Electrically conductive paint can also be used.

Once the samples are coated, the photographs are obtained in the usual manner by the recording electron microscope. The electron micrographs are evaluated to determine the average crystal size by attaching a transparent trap with 88 marked dots (as dots) at the intersections of a regular, evenly-spaced, 8-row, 11-column grid on a suitable electron micrograph. The magnification should be chosen such that only some of the largest crystals are touched by more than one point; and it turns out that 4000 to 8000 times are suitable. At leather lattice point, if the point touches a crystal dinion whose shape can be defined kl & ^r , the crystal can be measured. A measure of the variance in the form of the Gaussian standard deviation with the Besset correction is also calculated.

The wax content before and after the filtering process is measured by means of a DSC differential scanning calorimeter (e.g., one of the duPont 9900 series) which is capable of producing a curve having an area of about 10 10% by volume of fuel in the form of wax with an instrument-induced noise deviation with a standard deviation of less than 2% of the main output signal.

The DSC is calibrated by using an additive that causes large crystals to be safely retained by the filter, that is fed through the experimental set-up at the test temperature, and that the WAT of the dewaxed fuel is measured by DSC , The samples of fuel taken out of the tank and the filtered pulp to be tested are then analyzed by DSC; for each fuel, the area above the baseline is determined up to the WAT of the Eichtreibstoffes. The ratio of

DSC area for the sample after filtration χ 100

DSC area for the sample from the tank

corresponds to the percentage of wax remaining after filtration.

The turbidity points of the distilled fuels were determined by the standard cloud point experiment (IP-219 or ASTM-D 2500); other measures to characterize the onset of crystallization are the Wax (WAP) Deposition Start Point Test (ASTM D-3117-72) and the "on-growth" temperature are determined by using Differential Scanning Calorimetry using a recording The ability of the fuel to pass the main filter of a diesel engine was determined in an apparatus consisting of a typical main diesel engine filter housed in a standard housing in a fuel line Type Bosch used in a passenger car type VW Golf Diesel, model 1980, and a filter type Cummins FF 105 in a Cummins NTC series engine, which are suitable for the experiment A reservoir and a supply system, which are able Half of the usual filling of the fuel tank available Used in conjunction with an injection pump for fuel, as used in the VW Golf are used to pull the fuel from the tank at a constant speed through the Filtei, as is the case in the vehicle. Indicators are provided to measure the pressure drop across the filter, the flow rate from the injection pump and the temperature of the units. Templates are provided to catch the pumped fuel, both the injected fuel and the excess fuel. In the experiment, the tank is filled with 19kg of fuel and inspected for leaks. When this test has been satisfactory, the temperature is stabilized at an air temperature of 8 ° C above the cloud point of the fuel. The unit is then cooled to the desired test temperature at a rate of 3 ° C / hour and held there for at least 3 hours to stabilize the temperature of the fuel. The tank is shaken vigorously to completely disperse the wax present; A sample is taken from the tank and 11 fuel is withdrawn through the sample port in the drain line just past the tank and returned to the tank. Thereafter, the pump is put into operation with the pumping speed set to be equal to that at a speed of 110km / h on the road. In the case of the VW Golf, it is 1900 rpm, corresponding to a motor rotation speed of 3800 rpm. The pressure drop across the filter and the flow rate of fuel from the injection pump are recorded until the fuel is exhausted, which is usually F.I.I. within 30 to 35 minutes.

Assuming that the fuel supply to the injection pumps can be maintained at 2 ml / s (with the excess fuel flowing at a rate of about 6.5 to 7 ml / s), the result is "pass" the flow velocity to the injection pumps shows a "Grenzfal!" on; no flow means "failed test." Typical of this experiment is that a "pass" test result may be associated with an increased pressure drop across the filter surface, which may increase to 6OkPa. In general, considerable amounts of wax must pass through the filter to obtain such a result. A "Well Passed" test result is characterized by a test in which the pressure drop across the filter does not rise above 10 kPa, and this is the first indication that most of the filter's wax has passed. Excellent test results indicate a pressure drop below 5kPa on.

In addition, samples of the fuel are taken from the excess fuel and fuel at the inflow of the injection pumps, ideally every four minutes throughout the experiment. These samples are compared with the samples from before the trial by DSC to determine the proportion of wax in the influent that has passed through the filter. From pre-run fuel samples, samples are also prepared for the SEM after the trial to compare the crystal size of the wax and its type to actual behavior. The additives used were as follows:

Additive 1

The Ν, Ν-dialkylammonium salt of 2-dialkylamidobenzene-sulfonate, wherein the alkyl groups nCis_ | ₈ H ₃ 3-37 were prepared by reacting 1 mole of the cyclic anhydride of o-sulfobenzoic acid with 2 moles of dihydrogenated tallow amine in xylene as a solvent at a concentration of 50% by weight. The reaction mixture was stirred between 100 ° C and the reflux temperature. The solvent and starting materials should be as dry as possible so that hydrolysis of the anhydride does not occur.

The reaction product was analyzed by nuclear magnetic resonance spectroscopy at 500 MHz, confirming the following structure:

The molecular model of this compound is shown in Figure 11.

Additive 2

A copolymer of ethylene and 17 weight percent vinyl acetate, molecular weight 3500 and side chain branching 8 methyl groups per 100 methylene groups as determined by 500 MHz NMR.

Additive 3

A styrene-dialkyl maleate copolymer, dos by Verester ung a styrene-maleic anhydride copolymers the molar ratio of 1: 1 with 2 moles of a 1: 1molaien mixture of C ₂ H ₂ BOH and CuH was prepared ₂₉ OH per mole of anhydride groups, wherein in the esterification a small excess of 5% alcohol and p-toluensuifonic acid was used as catalyst (via mole) in xylene as solvent. The product had a molecular weight of 50,000 (M _n) and did not contain 3 wt .-% unreacted alcohol.

Additive 4

The dialkyl ammonium salts of 2-N, N-dialkyl amidobenzoate prepared by mixing one molar portion of phthalic anhydride with two molar proportions of dihydric talganine at 60 ° C.

embodiments

The results were the following.

example 1 -14 ⁰ C Characteristic of the fuel: + 18.6 ⁰ C cloud point 178 ⁰ C Temperature of occurrence of wax 23O ⁰ C Beginning of the boiling range 318 ⁰ C 20% 355 ⁰ C 90% 1.1% by weight End of the boiling range Wax content at -25 ⁰ C.

250ppm of each of the admixtures 1,2 and 3 were Zune sets the fuel, the test temperature was -25 ⁰ C. It has been found that the size of the wax crystals was 1,200 nm in the Länpa and that more than 90% of the wax passed through the Cumminsfilter FF105 , During the experiment, the passage of the wax was further confirmed by observing the pressure drop across the filter, which increased only by 2.2 kPa.

Example 2

Example 1 was repeated. It was found that the crystal size of the wax was 1300 nm and that the largest pressure drop at the end of the test over the filter was 3.4 kPa.

Example 3

Characteristic of the fuel:

Cloud point ⁰ C

Temperature of appearance of wax -2.5 ⁰ C

Beginning of the boiling range 182 ⁰ C

20% 22O ⁰ C

90% 354 ° C

End of the boiling range 385 ° C

Wax content at the test temperature 1.6% by weight

250ppm of each of the admixtures 1,2 and 3 were used, the crystal size of the wax crystals was determined to be 1500 nm and about 75Gew .-% of the wax passed through the Bosch 145434106 filter type at the experimental temperature of ⁰ -8.5 C. The maximum pressure drop across the filter was 6.5kPa.

Example 4

Example 3 was repeated. Wax crystals of 2000 nm in length were obtained, of which approximately 50% by weight passed through the filter, the maximum pressure drop being 35.3 kPa.

Example 5

The fuel used in Example 3 was added with 400 ppm of additive 1 and 100 ppm of a mixture of additive 2 and tested as in Example 3 at a temperature of -8 ° C; at this temperature, the wax content was 1.4% by weight. It was found that the crystal size of the wax was 2500 nm and that 50% by weight of the wax passed through the filter, with a maximum final pressure drop of 67.1 kPa.

When this fuel was used in the test setup, the pressure drop increased relatively quickly and the test failed. It is believed that the cause, as shown in the photograph, is that the crystals are shallow and that flat crystals that do not pass the filter tend to have the filter with a thin, non-transmissive layer cover .ui. On the other hand, "cube-shaped" (or "edgy") crystals accumulate, if they do not pass through the filter, in the form of a relatively loose cake through which the fuel can still flow until the tube becomes so large that the filter fills and the total thickness of the wax cake becomes so great that the pressure drop again becomes too great.

Example 6 (comparative example)

The fuel used in Example 3 was admixed with 500 ppm of a mixture of 4 parts of Additive 4 and 1 part of Additive 2 and tested at -8 ^0C. It was found that the crystal size of the wax was 6300 nm and that 13% by weight of the wax passed through the filter.

This example represents one of the best examples in the prior art, according to which excellent experimental results are achieved without passing the crystals.

Electron micrographs of the wax crystals forming in the fuels of Examples 1 to 6 are Figures 1 to 6 attached hereto.

Examples 1 to 4 therefore show that, when the crystals reliably pass through the filter, the excellent properties of the fuel at low temperatures can be extended to substantially higher wax contents than heretofore practicable and also to temperatures still below the point of onset The wax deposition in the fuel were, as was previously practicable. This applies without reference to the fuel system to, ζ. For example, the ability to return fuel from the engine to the tank to heat the fuel removed from the fuel tank; dao ratio of the supplied to the returned fuel; the ratio of the surface of the main filter to the flow of fuel supplied; and the size and arrangement of prefilters and sieves.

These examples show that for the investigated filters, significantly better behavior of the fuel is achieved at crystal lengths below about 1800 nm.

Example 7

In this example, additive 1 was added to a distilled fuel having the following characteristics:

Start of the boiling range (IBP) 180 ⁰ C

20% 223 ⁰ C

90% 336 ⁰ C

End of the boiling range (FBP) 365 ⁰ C

Temperature of appearance of wax 5.5 ⁰ C

Cloud point -3.5 ⁰ C

For comparison purposes, the following additives were also added to the distilled fuel:

Additive A: A blend of ethylene-vinyl acetate copolymers, one additive 2 (1 part by weight) and the other (3 parts by weight) a copolymer having a vinyl acetate content of 36% by weight, molecular weight 2000, and side chain branching ranging from 2 to 3 Methyl groups per 100 methyl groups as measured by 500 MHz NMR,

Additive B: A mixture of additives 4 and 2 with a 4: 1 molar ratio.

Additive C: the dibehenic acid ester of a polyethylene glycol mixture having the average molecular weight of 600.

Additive D: A ethylene-propylene copolymer in which the ethylene content was 56 wt%, the number average molecular weight was about 60,000.

The additives were added in the amounts listed in the following tables and the tests were carried out according to the PCT, which is described in detail below:

Programmed Cooling Test (PCT)

This is a slow cooling test designed to correlate with the pumping of stored fuel oil. The flow properties of the fuels containing the additives at low temperatures are determined by the PCT as follows. 300 ml of fuel are cooled linearly at 1 ° C / hour to the test temperature, then the temperature is kept constant. After two hours at the test temperature, about 20 ml of the surface layer is removed by suction to prevent the experiment from being caused by unusually large wax crystals that readily adhere to the surface

Boundary layer oil / air on cooling form, is disturbed.

Wax that has settled in the bottle is spread by gentle stirring and finally the CFPPT filter assembly (1) is inserted. The cock v. : open to allow a vacuum of 500mm of mercury to be applied, and it will be closed again if 200ml of the fuel passed the filter and run into a graduated template: the test is considered to be "pass" if the 200ml is within has been collected for a given pore width of the filter for ten seconds, and it is considered Fail if the flow rate is too slow, indicating that the filter has been blocked.

The pore width of the filter (mesh number) at the test temperature is recorded.

(1) CFPPT = Cold Filter Plugrjing Po; > ST (CFPPT) experiment to investigate the point of clogging a cold filter is described in detail in "Journal of the Institute of Petroleum", Vol. 52, No. 510, June 1966, pages 173-185.

Example 8

The fuel used in this example had the following characteristics: (ASTM-D86):

Start of the boiling range (IBP) 19O ⁰ C

20% 246 ° C

90% 346 ⁰ C

End of the boiling range (FBP) 374 ° C

Temperature of occurrence of wax (WAT) -1.5 ⁰ C

Cloud point + 2.0 ° C

(E) A mixture of additive 2 (1 part by weight) and additive 4 (9 parts by weight);

(F) A commercial ethylene-vinyl acetate copolymer used as an additive sold by Exxon Chemicals under the name ECA 5920;

(G) A mixture of: 1 part by weight of additive 1

1 part by weight of additive 3 1 part by weight of additive D 1 part by weight of additive K

(H) The commercially available ethylene-vinyl acetate copolymer 2042 E marketed by Amoco as an additive.

(I) The commercial ethylene-vinyl acetate copolymer sold as an additive by BASF under the name Keroflux 5486.

(J) No additive.

(K) The reaction product of 4 moles of dihydrogenated tallow amine and 1 mole of pyromellitic anhydride. The reaction is carried out without solvent at 150 ° C with stirring and under nitrogen within ¹ 'of 6 hours.

Subsequently, the following performance parameters of these drive offs were measured:

(i) The ability of the fuel, pass therethrough at -9 C ⁰ through the main filter of a diesel engine and the percentage of wax passing through the filter, whereby the following results were obtained: Additive Time to failure (min)% wax pass

E 11 18-30

F 16 30

G no failure 90-100

H 15 25

I 12 25

J 9 10

(ii) the pressure drop across the main filter over time; The results are shown graphically in Figure 12.

(iii) The wax separation in the fuels was measured by cooling 100 ml of the fuel into a graduated graduated cylinder. The cylinder is at a rate of 1 ° C / hour from a temperature preferably 10 ⁰ C above the Trübuugspunktes of the fuel, but not less than 5 ° C above the cloud point of the fuel is cooled to the test temperature, which is then held for a predetermined time becomes. The test temperature and time will depend on the type of application, ie diesel fuel and fuel oil. It is preferred that the test temperature is at least 5 ° C below the cloud point and the minimum cooling time at the test temperature is at least four hours. Preferably, the test temperature should be 10 ° C or more below the cloud point of the fuel, and the cooling period should be 24 hours or more.

Upon completion of the cooling time, the graduated cylinder is observed and the extent of wax deposition visually determined as the height of any wax layer above the bottom of the cylinder (0 ml) and expressed as% of the total volume (100 ml). Clear fuel can be observed above the settled wax crystals, and this form of measurement is often sufficient to form an opinion on the wax deposit, in some cases the fuel is cloudy over the deposited wax crystals or it can be observed that the wax crystals coexist with the wax crystals Increasing reduction to the bottom of the measuring cylinder visible turn denser. In

In such cases, a more quantitative analysis method is used. In this, the top 5% (5ml) are carefully aspirated and stored, the following 45% aspirated and discarded, the subsequent 5% aspirated and stored, the subsequent 35% aspirated and discarded and then stored the lowest 10%,

Vacuum is quite low, ie 200 mm of water, and that the tip of the pipette is placed exactly on the surface of the fuel, so that flows in the liquid / which could interfere with the concentration of the wax in the different layers within the cylinder . The samples are subsequently

'As previously described .

In this case an OSC device of the type Mettler TA 2000 B was used. A sample of 25 μΙ is placed in the sample pan and the ref erenzzelle filled with normal kerosene, then both at a rate of 22 ° C / minute from 6O ⁰ C to at least 10 ° C, but preferably 2O ⁰ C above the temperature of Occurrence of wax IWAT), cooled; then it is further cooled at a rate of 2 ° C / minute to a temperature of about 20 ° C below the WAT. A control sample must also be measured with untreated , uncooled, treated fuel. The extent of wax deposition then correlates with the WATI or AAWAT = WAT with wax deposition - WAT of the original).

Negative values indicate a reduction in the wax content in the fuel, positive values indicate a wax accumulation by settling. From these samples, the wax content in the samples can also be obtained as a measure of wax deposition. This is illustrated by the values% WAX or A% WAX (A% WAX =% wax in a sample with deposition -% wax in the original), and here again negative values indicate a reduction of the wax content in the fuel and positive values an enrichment by settling out. In this example, the fuel at a rate of 1 ° C / hour from + 1O ⁰ C to -9 ⁰ C was cooled and stabilized in the cold before the experiment 48 hours. The following results were obtained:

Additive Wax separation, WAT data in samples with wax deposition ( ⁰ C)

visually upper 5% middle 5% lower 10; o

e consistently cloudy -10.80 -4.00 -3.15 X) in samples with wax deposition lower 10% F 50%, closer to the ground, -13.35 -0.80 -0.40 (Fuel without separation upper 5% middle 5% clear about G 100% -7.85 -7.40 -7.50 H 35%, plain -13.05 -8.50 +0.50 I 65%, plain J 100%, half gelled -6.20 -6.25 -0.40 (The results are also shown graphically in Figure 13). WAT in the original WAT (

E -6.00 -4.80 + 2.00 + 2.85

F -5.15 -8.20 + A 35 +4.75

G -7.75 -0.10 + 0.35 + 0.25

H -5,00 -8,05 -3,50 +4,50

J -6.20 0.00 -0.05 -0.20

(Note that a significant decrease in WAT can be achieved by the most effective additive [G].)

% WAT (samples with separation)

upper 5% middle 5% lower 10%

E F G H J

These results show that as the crystal size decreases, the addition of the additives causes the wax crystals to settle faster. To show z. For example, untreated fuels, when cooled below their cloud points, have a low degree of wax deposition because the platelet-like crystals combine with one another and can not move freely in the liquid, forming a gel-like structure; however, when a fluidity improver is added, the crystals may be modified to be less platelike in appearance and to form needles of the order of tens of microns, which are then freely movable in the liquid and relatively free settle quickly. This settling of the wax crystals can lead to problems in storage tanks and fuel systems of vehicles. Concentrated layers of wax can be withdrawn suddenly, especially if the fill level of fuel is low or the tank is disturbed (eg, when the vehicle turns around), which may then cause the filter to lock.

If the size of the wax crystals can be reduced even further, to below 10 nanometers, then the crystals settle relatively slowly so that an anti-wax settling process can result, which can then lead to the advantages in fuel performance over one Fuel can be obtained with wax crystals deposited. If the size of the

-0.7 +0.8 +0.9 -0.8 +2.1 +2.2 ± 0.0 +0.3 +0.1 -1.3 -0.2 + 1.1 -0.1 ± 0.0 ± 0.1

Wax crystals can be further reduced to a size below about 4 nanometers, the tendency of the crystals to settle is almost excluded within the period of storage of the fuel.

If the size of the crystals is reduced to the preferred size of less than 2 nanometers that is claimed, the wax crystals remain suspended in the fuel for many weeks, which is a tent needed in some storage systems, and then the problems of settling the crystals are essentially eliminated.

(iv) The results of CFPP were as follows:

additive CFPP temperature ( ⁰ C) CFPP depression Size (nm) e -14 11 4400 F -20 17 10400 G -20 17 2600 H -20 17 10800 I -19 16 8400 J -3 - (v) The average crystal size found was as follows: additive e F G H thin platelets above 50,000 I J

Claims (4)

1. Use of a compound having at least 2 substituents having such space filling and configuration as to adjust the positions of wax molecules at the intersections of plane (001) and (11x) planes, e.g. B. the (110) and / or (111) levels in wax crystals, said substituents are alkyl, alkoxyalkyl or polyalkoxyalkyl groups having at least 10 carbon atoms in the main chain, characterized in that it is used as an additive for waxy fuel distillates , 2. Use according to claim 1, characterized in that the compound at least Contains 2 n-alkyl groups having more than two carbon atoms, whose spatial separation is in the order of 4.5 to 5.5A. 3. Use according to claim 1 or 2, characterized in that the dihedral angle between the local planes of symmetry of the two alkyl groups is between 75 ° and 90 °. 4. distillates used as propellants, characterized in that they contain an additive according to claim 1.