GB2121808A - Cloud-point-lowering copolymer additives for fuel compositions - Google Patents

Abstract

Novel polymeric compounds having a number-average molecular weight in the range 2000 to 10,000 are produced by the condensation of one or more primary amine compounds of formula R-Z[-(CH2)n-NH-]m-H (I> and/or HO-CH2-R''-NH2 (II> where, in formula (I), R represents a univalent saturated C1-30 aliphatic radical, Z is an oxygen atom, an imino group or a bivalent group =NR', in which R' is a univalent C1-30 aliphatic radical, preferably straight chain and preferably containing from 12 to 24 carbon atoms; n is 2, 3 or 4 and m is 0, 1, 2, 3 or 4, provided that m is not 0 unless Z is imino; and, in Formula II, R'' is a bivalent saturated C1-18 aliphatic radical, preferably straight-chain, on a copolymer formed between: (A) vinyl acetate, and (B) at least one unsaturated alpha , beta - dicarboxylic compound that may be a dicarboxylic acid, a diester of such an acid or an anhydride. Alternatively, such copolymers may be prepared by pre-reacting (B) with the amino compound and then polymerising the product with vinyl acetate. Such compounds are added to middle hydrocarbon distillates, especially gas oils, to lower their cloud point. The compounds also have other effects on such distillates.

Description

SPECIFICATION Cloud-point-lowering copolymers and compositions containing them This invention relatesto the lowering of the cloud point of middle hydrocarbon distillates.

Novel nitrogen-bearing additives useful as agents for lowering the cloud pointofthe middle hydrocarbon distillates have now been discovered. They are described in more detail below, and constitute one embodiment ofthe present invention.

The petroleum distillates with which the present invention is concerned are middle distillates (fuel oils and gas oils) whose distillation range (standard ASTM D 86-67) is between 1 500C and 450"C. The gas oils, which are more particularly considered herein, have a distillation range from an initial temperature in the range 160"C to 190"C, to a final temperature in the range350 Cto 390 C.

There are, on the market, a large number of substances intended to improve the filterability limit temperature and the pour point of paraffin-rich petroleum cuts, such as long-chain olefin-base polymers, or-olefin-base copolymers, ethylene-(vinyl acetate) copolymers, N-acylaminoethylesters of polymers containing acids, and halocarbon compounds.

Such substances act on the kinetic crystallisation phenomena and modify the size of the crystals, enabling the suspension to be used ata lower temperature without clogging passages and filters.

The above-mentioned substances do not modify the temperature at which the first paraffin crystals appear.

In fact, it was considered hitherto thatthattemperaturn was a factor that depends on the molecular weight and the formula ofthe paraffins and the nature ofthe solvent.

A reduction in the cloud point of middle distillates (in particular gas oils) by means of an additive would be a consideration of substantial attraction from the point of view of refiners as, without modifying the distillation system, itwould make it possible to comply with the specifications which at the present time are developing in the direction of increasing severity.

The present invention provides polymericcompounds having a number-average molecularweightin the rage 2000 to 10,000 and resulting from the condensation of one or more primary amine com pounds offormula R - Z - [- (CH2)n - NH ~]m - H (I) and/or HO - CH2 - R" - NH2 (II) where, in formula (I), R represents a univalent saturated C1-30 aliphatic radical, Z is an oxygen atom, an imino group ora bivalentgroup =NR', in which R' is a u nivalent C130 aliphatic radical, preferably straight chain and preferably containing from 12 to 24 carbon atoms; n is 2,3or4and mis 0,1, 2,3or4, provided that mis not 0 unless Z is imino; and, Formula II, R" is a bivalent saturated C118 aliphatic radical, preferably straight-chain, on a copolymerformed between (A) vinyl acetate, and (B) at least one unsaturated os,ss-dicarboxyiic compound that may be a dicarboxy licacid, a diesterofsuch an acid or an anhydride.

It has been found that compounds ofthe present invention, when added to middle distillates, allow the first paraffin crystals to appear only at a lower temperature than thetemperature at which such crystals would appear without such additives. This is all the more surprising in that the property is retained after a number of heating and cooling cycles and is revealed by a mechanism that is as yet unexplained.

Compounds of the present invention also have an effect on other properties ofthe middle distallates, in particular gas oils, by modifying the performance of the medium that contains the precipitated paraffins.

Thus, compounds ofthe present invention have a substantial action on the filterability limit temperature and the pour point.

When the paraffin crystals which are caused to form by the cooling operation have appeared, their natural tendency is to gravitate to the bottom where they accumulate. That phenomenon, which is generally referred to as sedimentation, causes clogging of passages and filters and is prejudicial to satisfactory use of middle distillates and in particular gas oils.

Compounds of the present invention are capable of substantially reducing the rate of sedimentation ofthe paraffinsformed by cooling gas oils and other middle distillates.

Finally, compounds of the invention can also inhibit corrosion of metal surfaces bythe gas oils and other middle distillates to which they are added.

In theforegoing definition ofthe compounds ofthe invention, the proportions of the units corresponding to monomers (A) and (B) are preferably in the vicinity of 50%-50%, in which casethe units corresponding to the monomers (A) and (B) are distributed alternately in the copolymer.

The unsaturated oc,-dicarboxylic compound (B) may be maleic acid, an alkylmaleic acid (in particular methyl maleic or citraconic acid), an alkyl diester of the said acids (in particular a methyl, ethyl or propyl diester) ora corresponding anhydride. In accordance with the invention, anhydrides are preferred, more particularly maleic anhydride.

The compounds offormula (I) above may be primary amines havingtheformula R-NH2 (in that case, in formula (I), Z represents imino and mis zero).

Preferably, the radical R is a straight-chain C12-24 radical. The following may be mentioned as specific examples of such amines: dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, eicosylamine and docosylamine.

The compounds offormula (I) may also be polyamines derived from saturated aliphatic amines and corresponding to the formula: R - NH - [- (CH2)n - NH ]m - H which corresponds to general formula (I) in which Z is imino, mis from 1 to 4 and n is from 2 to 4, preferably 3.

Preferably, R is a C12-24 straight chain. Specific compounds include N - dodecyl -1,3 - diaminopropane, N -tetradecyl - 1,3-diaminopropane, N hexadecyl - 1,3 - diaminopropane, N - octadecyl - 1,3 - diaminopropane, N - eicoysl - 1,3 - diaminopropane, N - docosyl -1,3 - diaminopropane, N - hexadecyl dipropylenetriamine, N - octadecyl - dipropy lenetriamine, N - eicosyl - dipropylenetriamine and N docosyl - dipropylenetriamine.

The compounds offormula (I) may also be polyamines ofthe following formula: R' - N - [- (CH2)n - NH i m - H which corresponds to general formula (I) in which Z represents =NR' and each of R and R',whichare identical or different, is a C1-24 alkyl radical, preferably containing fron 8to 24 carbon atoms, and R and R' together preferably contain from 16 to 32 carbon atoms; n is from 2to 4and mis from 1 to 4.The following may be mentioned as specific compounds: N,N - diethyl -1,2 - diaminoethane, N,N - diisopropyl 1,2-diaminoethane, N,N -dibutyl - 1,2-diami- noethane, N,N - diethyl -1,4 - diaminobutane, N,N dimethyl - 1,3 - diaminopropane, N,N - diethyl -1,3 - diaminopropane, N,N - dioctyl - 1,3 - diaminopropane, N,N -didecyl - diaminopropane, N,N -didodecyl - 1,3 - diaminopropane, N,N - ditetradecyl - 1,3- diaminopropane, N,N -dihexadecyl - 1,3-diaminopro- pane, N,N - dioctadecyl -1,3 - diaminopropane, N,N didodecyl - dipropylenetriamine, N,N - ditetradecyl dipropylenetriamine, N,N - dihexadecyl - dipropylenetriamine and N,N - dioctadecyl - dipropylenetriamine.

Finally, the compounds of formula (I) may be ethers ofaminesofthefollowingformula: 90- (CH2)n - NH ]m - H which corresponds to the general formula (I) in which Z is an oxygen atom. R preferablycontainsfrom 12to 24 carbon atoms, m is an integeroffrom 1 to 4and n is a integeroffrom 2to4, preferably2 or3.

The following may be quoted as specific ether amines; 2-methoxyethylamine, 3-methoxypropylamine, 4-methoxybutylamine, 3-ethoxypropylamine, 3-octyloxypropylamine, 3-decyloxypropylamine, 3hexadecyloxypropylamine, 3-eicosyloxypropylamine, 3-docosyloxypropylamine, N-(3- octyloxypropyl)-1,3 : - diaminopropane, N - (3 - decyloxypropyl) - 1,3 diaminopropane, 3 - (2,4,6 -trimethyldecyloxy) propylamine, and N - [3 - (2,4,6 - trimethyldecyloxy) - propyl]1,3-diaminopropane.

The following may be mentioned as specific examples ofthe amino-alcohol ofthe general formula (ill): monoethanoline, 1 aminopropan - 3 - ol, 1 - aminobutan-4-ol, 1 -aminopentan -5-ol, 1 -aminohexan - 6- ol, 1 -aminoheptan -7-oIl -aminooctan-8-ol, 1 aminodecan - 10 - ol, 1 - aminoundecan - 11 - ol, 1 aminotridecan - 13 - ol, 1 - aminotetradecan -14 - ol, 1 aminohexadecan 16-ol,2-amino-2-methyl propan -1 -ol, 2-aminobutan -1 -ol and 2-aminopentan -1 ol.

Preparation ofthe additives according to the invention generally comprises two stages: preparation of the vinyl acetate - oc,P - dicarboxylic monomer copolymer, followed by condensation on the polymer formed of at least one compound offormula (I) and/or (II).

Preparation of the base copolymers is effected in the first stage by conventional methods of polymerization by a free-radical process, for example in the presence of a starter ofthe azobisisobutyronitrile or peroxide (such as lauroyl peroxide) type, in solution in a hydrocarbon solvent such as cyclohexane, isooctane, dodecane, bezene, toluene, xylene or diisopropylbenzene, or in solution in tetrahydrofuran or dioxan. Itwill be advantageous to use hydrocarbon cuts having a relatively high boiling temperature such as a kerosene ora gas oil.

The amounts ofsolvent used will usually be such thatthe concentration by weight of dry matter is in the range 25 to 70% and preferably in the vinicity of 50%.

The copolymerisation reaction in the presence of a free-radical-forming stalPer, is performed at a temper- ature in the range 40 to 1 000C, preferably 50 to 70"C.

Depending on the operating conditions, the reaction may lastforfrom 2to 10 hour?n most cases from 3 to 5 hours. The result is a solution of copolymer, in the form of a viscous liquid.

For preparation ofthe additives according to the invention, the second stage comprises condensing the compound offormula (I) or (II) on the copolymer formed in thefirststage by any usual method.

In general, the compound(s) offormula (I) and/or (Il) is/are added to the copolymer solution produced as described above, in a molar proportion that substan tially corresponds to the proportion of unsaturated diacid, diester or an hydride used in preparing the copolymer. That proportion may be for example from 0.9 to 1.1 moles of compound offormula (I) and/or (II) per mole of dicarboxylic compound. It is also possible to envisage a more substantial deficit in respect of the compound offormula (I) and/or (11). It is then possible to use a proportion which is as small for example as 0.5 mole per mole of dicarboxylic compound used in the copolymer.

The reaction is performed by heating the mixture at a temperature in the range 75 to 130"C, preferably 80 to 1 00'C, the duration ofthe reaction being from 1 to 6 hours, with a duration of about 2 hours usually being sufficient. The reaction ofthe substances offormula (I) and/or (II) on the units (B) ofthe copolymer gives rise to imide (succinimide) groups accompanied by the formation ofwater or alcohol, depending whether the dicarboxylic units (B) are diacid, an hydride or diester groups. If desired, the volatile substances formed may be removed from the reaction mixture, either by entrainmentwith an inertgassuch as nitrogen or argon, or by azeotropic distillation with a selected solvent.

Certain ofthe additives according to the invention may be synthesized by effecting radical copolymeriza tion of vinyl acetate and N-substituted maleimides, the latter being produced by preliminary reaction of the compound(s) offormula (I) and/or (II) on maleic anhydride or one of its above-mentioned derivatives.

The additives are produced in solution in the selected solvent and. may be used in that form directly in the middle petroleum distillateswhose cloud point isto be improved.

Although the mechanism by which the compounds ofthe present invention act on the temperature at which paraffin crystals appear in the middle distillate has not yet been clearly ascertained, a marked improvement in the cloud point of the middle distillates when treated by such compounds is observed when the are added in concentrations ranging forexamplefrom 0.001 to 1% by weight and preferablyfrom 0.01 to 0.2% by weight. The reduction in the cloud point may be up to 4K or in some cases even more.

A remarkablefactto be noted is that additives ofthe present invention also have the property of inhibiting sedimentation of n-paraffins in middle distillates in a rest condition, improving the filtrability limittempera ture and the pour temperature, and inhibitiing corrosion of metal surfaces in contact with such distillates.

The following examples illustrate but do not limit the invention.

EXAMPLE 1 Step a Using a reaction vessel ofthermostatically controlled double jacket type with a capacity of 1 litre and provided with an efficient mechanical agitator system, 43 g (0.5 mol) ofvinyl acetate, 49 g (0.5 mol) of maleic anhydride, 350 ml oftoluene and 2.8 g of azobisisobutyronitrile are introduced into the reaction vessel.

The agitated mixture is heated for 6 hours at a temperature of 70 C, and the resulting copolymer is filtered off, rinsed with toluene and then dried under vacuum at800C.

Stepb To the resulting 18.4 g of the copolymer is added 14 g (that isto say, 0.05 mol equivalent of primary amine) of a commercial mixture of fatty amines containing approximately 1% of C14 amine, 28% of C16 amine and 71% of C18 amine. Heptane is added so thatthe percentage of dry matter is close to 60%,then the mixture is heated under refluxfor3 hours to produce additive A in solution in heptane. The concentration of final product is adjusted to 50% by weight.

EXAMPLE2 Additive B is prepared under identical conditions to those described in Step bin Example 1 from 9.2 g of the copolymer prepared in Stepaof Example 1, and 8.1 g (that is to say, 0.027 mol equivalent of primary amine) of a mixture of primary amines having fatty chains, comprising approximately 1% of C14 amine, 5% of C16 amine, 42% of C18 amine, 12% ofC20 amine and 40% of C22 amine.

EXAMPLE3 Additive C is produced under conditions similarto those described in Step b of Example 1 bythe condensation of 16.96 g, i.e. 0.053 mol equivalent of primary amine, of a mixture of fatty amines of a composition comprising 5% of C16 amine, 15% of C18 amine, 40% of C20 amine and 40% of C22 amine, on 18.4g of copolymer produced in accordance with Example 1 Step a.

EXAMPLES 4 to 6 These Examples use a copolymer produced in accordance with Example 1 Step a and, using the mode of operation described in Example 1 Step b, condensation is effected in respect of the following, observing the molar proportions set out in Example 1 Step babove: Example 4:3 - - (2,4,6 -trimethyldecyl)oxy propyla- mine, which gives additive D.

Example 5: 1 - aminohexadecan -16 ol, which gives additive E.

Example 6: N,N-didodecyl 1,3-diaminopropane, which gives additive F.

Additives I to Ill are used in the form of solutions containing 50% ofdrymatterinheptane,while additives IV to VI are used in the form of solutions of the same content in toluene.

The degree of activity of the additives described in these Examples was tested on two cuts of gas oils of ARAMCO origin, which are referred to, hereinafter as G1 and G2 and the characteristics of which are set out in Table I below: TABLE I

ASTM distillation % distilled Density at 15 Gas oils I.P.( C) F.P.( C) at 350 C in kg/l G1 181 382 89 0.846 Go 186 385 87 0.847 AdditivesAto Fwere incorporated, in a proportion of 0.1% by weight, in the above-described gas oil cuts G1andG2.

For each of the compositions which were formed in thatway,three parameters were determined: the cloud point, using the AFNOR T 60-105 method: thefiltrability limittemperature (FLT) using the AFNOR M 07-042 method; and the pour point, using the AFNOR T 60-105 method.

The results ofthose measurement operations are set out in Table II below: TABLE n

Cloud point ( C) F.L.T. ( C) Pour point ( C) Additives G1 G2 G1 G2 G1 G2 without + 2 + 6 0 + 3 - 6 - 3 0.1% A - 1 + 2 - 4 0 - 12 - 15 0.1% B 0 + 3 - 4 0 - 9 - 9 0.1% C - 1 + 2 - 3 - 1 - 12 - 12 0.1% D 0 + 3 - 3 0 - 9 - 9 0.1% E -1 + 2 - 3 - 1 - 12 - 9 0.1% F - 1 + 2 - 4 - 1 - 12 - 9 EXAMPLE 7 This Example involves testing the anti-corrosion effect of additive A of Example 1.

This additive was used in the two gas oils G1 and G2 already described above in a level of concentration of 0.01% by weight.

The corrosion test involved studying corrosion due to artificial sea water on cylindrical testpieces of polished iron orsteel, in accordancewiththe standardASTM D 665, modified in that the temperature was 32.2 C and the period of time 20 hours.

The two gas oils G1 and G2without additive gave testpieces which are 100% rusted on their surface, whilethetwo gas oils containing 0.01% by weight of additive A gave intact testpieces with 0% rust.

Claims (16)

1. Polymericcompounds having a number-average molecularweight in the range 2000 to 10,000 and resulting from the condensation of one or more primary amine compounds offormula R - Z - [ - (CH2)n - NH - ]m - H (I) (I) and/or HO - CH2 - R" - NH2 (II) where, in formula (I), R represents a univalent saturated C 30 aliphatic radical, Z is an oxygen atom, an imino group or a bivalent group =NR', in which R' is a univalentC1 aliphatic radical; n is 2,3 or4and m is 1,2,3or4, provided that m is not 0 unlessZis imino; and, in Formula II, R" is a bivalentsaturated C1-18 aliphatic radical, on a copolymerformed between: (A) vinyl acetate, and (B) at lest one unsaturated ,ss-dicarboxylic com pound that may be a dicarboxylic acid, a diester of such an acid or an anhydride.

2. Acompound according to Claim 1 containing approximately 50 molar % of units (A) and approximately 50 molar % of units (B).

3. A compound according to Claim 1 or2inwhich the unsaturated os,ss-dicarboxylic compound from which the units (B) originate comprises at least one maleicoralkylmaleicacid, a methyl, ethyl orpropyl diester of such an acid, or a maleic or alkylmaleic anhydride.

4. A compound according to any one of Claims 1 to 3 in which the amine compound (I) comprises at least one straight-chain C12-24 primary monoamine.

5. Acompound according to any one of Claims 1 to 3 in which the amine compound (I) comprises at least one polyamine oftheformula: 9 - NH - [- (CH2)n - NH im - H in which R represents a straight-chain C12-24 alkyl radical,nis2,3or4andmisl,2,3or4.

6. A compound according to any one of Claims 1 to 3 in which the amine compound (I) comprises at least one polyamine having the formula: R - NR' - [ - (CH2)n - NH ]mH in which each of Rand R' represents a straight-chain C824alkyl radical and R and R' together contain from l6to32carbonatoms,nis2,3or4andmisl,2,3or4.

7. Acompound according to any one of Claims 1 to 3 in which the amine compound (I) comprises at least one ether amine having the following formula: R - O - [ - (CH2)n - NH im - H in which R represents a C12-24 alkyl radical, n is 2,3 or4 and m is 1, 2, 3 or 4.

8. A compound according to any one of Claims 1 to 3 in which the amine compound (II) comprises at least one amino alcohol having the following for mula: HO - CH2 - R"- NH2 in which R" represents a straight-chain C1-18 alkylene radical.

9. Acompound according to any one of Claims 1 to 8 produced by the radical copolymerisation of suitable proportions of vinyl acetate and at least one ofthe said unsaturated a,ss-dicarboxylic compounds; followed bythe condensation, on the copolymer formed, of at least one compound offormula (I) and (II) in a proportion of at least 0.5 mole per mole of unsaturated a,ss-dicarboxyliccompound used.

10. A compound according to Claim 9 in which the proportion ofthe compound offormula (I) or(ll) is from 0.9 to 1.1 mole per mole of unsaturated cx,P-dicarboxylic compound used.

11. A compound according to any one of Claims 1 to 8 produced by the radical copolymerisation of suitable proportions of vinyl acetate and at least one unsaturated a,ss-dicarboxylic compound, comprising at least one N-substituted imide produced by pre liminary reaction of an unsaturated a,ssi-dicarboxylic compound with at least one compound offormula (I) or (II).

12. A compound according to Claim 1 substantial ly as hereinbefore described in any one of Examples 1 to6.

13. A middle distillate composition comprising major proportion of middle distillate having a distilla tion range between 150 and 450 C and a minor proportion, sufficientto reduce its cloud point of at least one compound according to any one of Claims 1 to12.

14. Acomposition according to Claim 13 in which the middle distillate comprises a gas oil cut having a distillation rangefrom an initial temperature of 160 to 1900Cto a final temperature of 350 to 390 C.

15. A middle distillate composition according to Claim 13 or 14 in which the proportion of the compound according to anyone of Claims 1 to 12 is from 0.001 to 1% weight.

16. A composition according to Claim 15 in which the proportion ofthesaid compound is from 0.01% to 0.2% by weight