DE69310766T2 - A COMPOSITION CONTAINING PETROLEUM DISTILLATE LIMITING SPEED OF PARAFFINS - Google Patents

Abstract

A middle petroleum distillate composition containing a major proportion of middle petroleum distillate and a minor proportion of an additive in a sufficient amount to limit the settling speed of paraffins contained in said middle distillate. Said additive consists of a product resulting from a reaction between at least one aliphatic dicarboxylic compound and at least one primary amine functional compound of general formula (I), wherein R<1> is a monovalent saturated aliphatic radical, Z is selected from -NR'- groupings in which R' is a hydrogen atom or a monovalent saturated aliphatic radical, n is an integer between 2 and 4, and m is an integer between 1 and 4; said primary amine functional compound being used in a ratio of 0.3-0.8 mols per mol of said dicarboxylic compound.

Description

The invention relates to petroleum middle distillates (heating oils, gas oils) in which the rate of paraffin sedimentation is slowed down by the addition of nitrogen-containing additives. It also relates to a process in which the precipitation or sedimentation of the paraffins of a petroleum middle distillate is slowed down by the addition of a minor proportion of at least one nitrogen-containing additive.

The invention applies to petroleum distillates, which are paraffin-containing middle distillates (heating and gas oils) whose distillation process (ASTM D 86-67 standard) is between 150º C and 450º C. The invention applies in particular to gas oils whose distillation process begins at a temperature of 160º C to 190º C and ends at a temperature of 350º C to 390º C.

The market offers a large number of products designed to improve the filterability limit temperature and the pour point of paraffin-rich petroleum fractions, such as:

- Polymers based on long-chain olefins

- Copolymers based on alpha-olefins

- Vinylethylene acetate copolymers

- Acidic polymer N-acylaminoethyl esters or

- Components containing halogenated hydrocarbons.

These products, which influence the kinetic crystallization processes and change the crystal size, make it possible to use suspensions at lower temperatures without clogging pipes and filters.

There are also products on the market that lower the cloud point of petroleum fractions by changing the temperature at which the first paraffin crystals form.

The reduction of the distillate cloud point by means of an additive (especially in gas oils) is of great interest to refiners, as it enables them to comply with increasingly strict regulations without changing the distillate process.

When paraffin crystals have formed due to the cold, they tend to collect in the lower part of the vessel due to gravity. This process, which is generally known as subsidence, causes pipes and filters to become blocked and, at low temperatures, has a negative effect on the good utilization of middle distillates - especially gas oils.

Patent EP-B-71513 describes a certain class of chemical compounds as additives capable of lowering the cloud point of petroleum middle distillates and having an important influence on the filterability limit temperature and the flow temperature, and indicates that they also influence the rate of reduction of the paraffins resulting from the cooling of gas oils and other middle distillates.

The additives considered in the present patent application and described below are similar to the additives described in patent EP-B-71513 and belong to the same class of compounds. Surprisingly, it has been discovered that the class of compounds generally described in patent EP-B-71513 contains some compounds not described therein which have far better properties with regard to influencing the rate of paraffin sedimentation and are more effective sedimentation inhibitors even under stricter test conditions.

Furthermore, the products preferred in the present invention for their above-mentioned anti-settlement properties impart corrosion-inhibiting properties to metal surfaces to gas oils and other middle distillates to which they are added.

It should be noted here that N-alkyl polyalkylene polyamine and alkenyl succinic anhydride derivatives are known from patent US-A-2 638 450 as corrosion-inhibiting additives in mineral oils, gasolines and light petroleum products. These components are obtained in a two-stage process.

1) Alkylation of a polyalkylenepolyamine using a monohalogen derivative with 4 to 31 carbon atoms. The alkyl-containing polyalkylenepolyamine obtained in this way can have a very diverse structure, with derivatives from C-alkylation and N-alkylation being permissible.

2) Reaction of the alkyl-containing polyalkylenepolyamine with an alkenylsuccinic anhydride. The molar ratio of polyamine to anhydride depends on the alkylation rate of the anhydride, i.e. on the molar ratio of polyamine/alkylmonohalogen derivative used in the alkylation step. It can be less than 1 or equal to 1.

Due to the pre-alkylation of the polyamine, which probably gives rise to derivatives from the C-alkylation and from the N-alkylation of the various amino groups, these additives differ from those claimed for use in the present application. In addition, this older patent discloses the use of these products as anti-corrosive agents for petroleum derivatives, although it is not certain whether paraffin crystallization even takes place in these derivatives. This particular problem is not even addressed in the patent.

In general, the petroleum middle distillate compositions of the present invention consist of a major portion of a paraffinic petroleum middle distillate and a minor portion large enough to limit the rate of sedimentation of its paraffins, of at least one active ingredient consisting of a product with an average molecular weight of about 300 to 10,000 and resulting from the reaction of at least one aliphatic dicarboxylic compound selected from maleic and alkylmaleic anhydrides, alkenylsuccinic anhydrides containing 10 to 32 carbon atoms in the alkenyl radical, dicarboxylic acids and the corresponding light alkyl diesters, with at least one compound having primary amine activity, according to the empirical formula (1)

in which R¹ represents a monovalent saturated aliphatic radical having 1 to 32 carbon atoms, Z is selected from the -NR' groups, where R' represents a hydrogen atom or a monovalent saturated aliphatic radical having 1 to 32 carbon atoms, n is an integer between 2 and 4, m is an integer between 1 and 4; said compound with primary amine activity is used in a ratio of 0.3 to 0.8 moles per mole of said dicarboxylic compound; said reaction is carried out at a temperature of between 120 and 200º C and continues until the volatile products formed during the reaction, consisting of water and/or alcohol, have been completely separated. In most cases, the reaction is continued until the theoretical amount of volatile products - water and/or alcohol - which are then removed is produced.

The present invention also relates to a process for slowing down the rate of paraffins contained in a hydrocarbon mixture, wherein a sufficient amount of a minor proportion of at least one active ingredient, consisting of a product with an average molecular weight of about 300 to 10,000, resulting from the reaction of at least one aliphatic dicarboxylic compound selected from maleic and alkylmaleic anhydrides, alkenylsuccinic anhydrides with 10 to 30 carbon atoms in the alkenyl radical, dicarboxylic acids and the corresponding light alkyl diesters, with at least one compound with primary amine activity, according to the empirical formula (1)

in which Z, R¹, n and m correspond to the definition given above, said compound with primary alkene activity being used in a ratio of 0.3 to 0.8 moles per mole of said dicarboxylic compound, and said reaction, carried out at a temperature of between 120 and 200ºC, being continued until the end of the separation of the volatile products consisting of water and/or alcohol which are formed during the reaction.

The compounds according to formulation (I) may be polyamines derived from saturated aliphatic amines and corresponding to the following formula

which corresponds to the empirical formula (I) in which represents the -NH group; m can have a value of 1 to 4, n a value of 2 to 4, preferably m has a value of 2 to 4 and n is 3; R¹ is preferably a saturated, monovalent, straight-chain aliphatic radical having 12 to 32 carbon atoms, in particular 16 to 24 carbon atoms.

The following can be mentioned as specific compounds: N-dodecyldiamino-1,3-propane, N-tetradecyldiamino-1,3-propane, N-hexadecyldiamino-1,3-propane, N-octadecyldiamino-1,3-propane, N-eicosyldiamino-1,3-propane, N-docosyldiamino-1,3-propane, N-hexadecyldipropylenetriamine, N-octadecyldipropylenetriamine, N-eicosyldipropylenetriamine and N-docosyldipropylenetriamine. It is recommended to use N-docosyl, N-eicosyl, N-octadecyl, N-hexadecyl or N-dodecyl-diamino-1,3-propane, with dipropylenetriamines such as N-hexadecyl or N-octadecyl-dipropylenetriamine being preferred.

The compounds of formula (I) can also consist of polyamines according to the following formula

which corresponds to the empirical formula (1), in which Z represents the -NR²R³- group, R² and R³ - whether identical or not identical - are defined as R1 and preferably each represent an alkyl radical having 1 to 24 carbon atoms, preferably 6 to 24 carbon atoms, R² and R³ together preferably contain 12 to 32 carbon atoms, n has a value of 2 to 4, preferably 3, and m has a value of 1 to 4, preferably 2 to 4.

As specific compounds one can mention the following: N,N-diethyl-diamino-1,2-ethane, N,N-diisopropyldiamino-1,2-ethane, N,N-dibutyl-diamino-1,2-ethane, N,N-diethyl-diamino-1,4-butane, N,N-dimethyl-diamino-1,3-propane, N,N-diethyl-diamino-1,3-propane, N,N-dioctyl-diamino-1,3-propane, N,N-didecyldiamino-1,3-propane, N,N-didodecyl-diamino-1,3-propane, N,N-ditetradecyl-diamino-1,3-propane, N,N-dihexadecyldiamino-1,3-propane, N,N-dioctadecyldiamino-1,3-propane and as more preferred products: N,N-didodecyldipropylene- triamine, N,N-ditetradecyldipropylenetriamine, N,N-dihexadecyldipropylenetriamine and N,N-dioctadecyldipropylenetriamine.

Of course, one or more compounds according to the formula (I) can be used according to the invention.

The dicarboxylic acids described above on which the condensation of a compound of formula (I) is carried out are chosen in particular from maleic anhydride, alkylmaleic anhydrides such as methylmaleic anhydride, or also from alcenylsuccinic anhydrides such as those obtained by the reaction of at least one olefin, preferably a linear olefin (for example having 10 to 32 carbon atoms), with maleic anhydride. Mention may be made in particular of n-octadecenylsuccinic anhydride or dodecenylsuccinic anhydride. It is of course possible to use mixtures of two (or more) of these compounds.

Instead of the above-mentioned anhydrides, the corresponding dicarboxylic acids such as their light dialkyl esters (such as the methyl, ethyl, propyl and butyl esters) can be used.

The compounds with primary amine function according to formula (I) are usually used in amounts of 0.3 to 0.8 mol, preferably 0.4 to 0.7 mol, per mole of the dicarboxylic compound.

The condensation of the compounds according to formula (I) on dicarboxylic compounds (for example dicarboxylic acids, esters or preferably anhydrides) can be carried out without solvent, but it is preferred to use a hydrocarbon solvent whose boiling point is between 70ºC and 250ºC, which in particular consists of an aromatic or a naphthenic aromatic hydrocarbon such as toluene, xylenes, diisopropylbenzene or a petroleum fraction with the appropriate distillation process.

In practice, the additive formulations according to the invention can be prepared as follows: The compound according to formula (I) is added to a reaction vessel containing the dicarboxylic compound and kept at a temperature of 30°C to 80°C. The temperature is then increased to 120°C - 200°C, whereby the volatile products formed (water or alcohols) are removed either via an inert gas stream or by azeotropic distillation with the selected solvent. The dry matter concentration is, for example, 40 to 70%, usually about 60%.

After addition of additives, the reaction takes between 1 and 8 hours, preferably between 3 and 6 hours.

The additives according to the invention prove to be particularly interesting for slowing down the rate of wax decomposition in petroleum middle distillates (in particular in gas oils).

Although the mechanism of action of these additives on the rate of wax crystal formation in middle distillates has not yet been fully elucidated, a clear slowing down of wax precipitation is observed in middle distillates treated with these additives when the additives are added in concentrations of, for example, 20 to 2 000 grams per tonne (g/t) of petroleum middle distillate. The preferred concentrations are 100 to 200 g/t.

It is also noteworthy that the additives according to the invention are able to prevent both the reduction in n-paraffin content in quiescent petroleum middle distillates and the corrosion of the metal surfaces that come into contact with these distillates.

In the additive concentration range of 20 g to 2 000 g/t, the proportion of paraffins reduced obviously decreases, and this decrease can be as high as 100% under the conditions described in patent EP-B-7 1513, but also under more severe temperature conditions in the range of 5 to 10ºC. Furthermore, a clear anti-corrosive effect is observed, particularly on ferrous metals.

To formulate the middle distillate compositions of the invention, the additives can be added to the petroleum middle distillate by simple mixing.

However, it is often advantageous to introduce them as "mother solutions" prepared in advance in the above solutions. The "mother solutions" can contain, for example, 20 to 60% by weight of additives.

The petroleum middle distillate compositions of the present invention (for example in the case of gas oils) may also contain other additives which in particular improve the cold behavior, for example those which reduce the pour point or the filterability limit temperature of the middle distillates (for example the gas oils).

The present invention also relates to the use of at least one compound according to formula (I):

in which Z, R¹, n and m are defined above and are present as an additive to limit the rate of paraffin reduction in a hydrocarbon-containing composition consisting mainly of a paraffin-containing petroleum middle distillate, in a proportion of 20 to 2 000 ppm of the total weight of the composition. It also relates to the use of at least one compound according to the above-mentioned empirical formula (I) as a corrosion-preventing additive in a hydrocarbon-containing Composition consisting of a major portion of a paraffinic petroleum middle distillate in a proportion of 20 to 2 000 ppm of the total weight of the composition.

Particular advantages arise from the use of at least one compound according to formula (I), which consists of at least one polyamine according to one of the following formulas

in which R¹, R², R³, n, m correspond to the definition given above.

The following examples are intended to illustrate the invention, but in no way exclude other embodiments.

Example 1 (comparative formulation)

2700 g of a commercial polyamine (containing a mixture of about 27% palmityl-1,3-propanediamine and about 70% stearyl-1,3-propanediamine, said mixture corresponding to 370 g of a primary amine group) and 2700 g of xylene are introduced into a 20-litre reaction vessel with a good stirring system; the amine is dissolved at 50ºC, cooled to 30ºC; then a solution of 699 g of maleic anhydride in 1050 g of xylene is added, maintaining the internal temperature at 40ºC. The addition takes one hour, then the reflux temperature of the xylene is maintained for 3 hours, the internal temperature of the reaction vessel being 144ºC. 157 g of water are removed by distillation, consisting of 128 g of reaction water and 29 g of water from the reactant amine. At the end of the reaction, 500 g of xylene are distilled to obtain a solution with 50% by weight of additive I in the xylene.

Additive I was analyzed after evaporation of the solvent. It has a molecular weight of 1 800 measured by tonometry. The infrared spectrum shows the presence of of imide bands at 1 700 and 1 780 cm⁻¹, secondary amine bands at 1 635 and 1 560 cm⁻¹ and a secondary amine band at 3 300 cm⁻¹. This addition was described in Example 1 of patent specification EP-B-7 1513.

Example 2

Example 1 is repeated, using N-stearyldipropylenetriamine as the amine in a ratio of 0.75 moles of amine per mole of anhydride. The reaction vessel is kept at the xylene reflux temperature for 3.5 hours, after which no more water is produced. The amount of xylene is adjusted so that a solution with 50% by weight of additive II in the xylene is produced.

Additive II was analyzed after evaporation of the solvent. It has a molecular weight of 1 600 as measured by tonometry. The infrared spectrum shows the presence of imide bands at 1 700 and 1 780 cm⁻¹, secondary amine bands at 1 635 and 1 560 cm⁻¹ and a secondary amine band at 3 300 cm⁻¹.

Example 3

Example 2 is repeated using N-stearyldipropylenetriamine as the amine and N-octadecenylsuccinic anhydride as the anhydride in a ratio of 0.70 moles of amine per mole of anhydride. The reaction vessel is kept at the xylene reflux temperature for 4 hours, after which no more water is produced. The amount of xylene is adjusted so that a solution with 50% by weight of additive III in the xylene is formed.

Additive III was analyzed after evaporation of the solvent. It has a molecular weight of 1 700 measured by tonometry. The infrared spectrum shows the presence of of imide bands at 1700 and 1780 cm⁻¹, secondary amine bands at 1635 and 1560 cm⁻¹ and a secondary amine band at 3300 cm⁻¹.

Example 4

Example 2 is repeated using N-stearyldipropylenetriamine as the amine and N-octadecenylsuccinic anhydride as the anhydride in a ratio of 0.5 moles of amine per mole of anhydride. The reaction vessel is kept at the xylene reflux temperature for 3 hours, after which no more water is produced. The amount of xylene is adjusted so that a solution with 50% by weight of additive IV in the xylene is formed.

Additive IV was analyzed after evaporation of the solvent. It has a molecular weight of 1 700 as measured by tonometry. The infrared spectrum shows the presence of imide bands at 1 700 and 1 780 cm⁻¹, secondary amine bands at 1 635 and 1 560 cm⁻¹ and a secondary amine band at 3 300 cm⁻¹.

Example 5

The anti-seeding effect of Additive I and Additives II to IV - as described in the invention - was investigated on n-paraffins crystallising in two commercial winter gas oils, the characteristics of which are given in Table I below: TABLE 1

These commercial gas oils contain 500 ppm by weight of a polymer such as vinyl ethylene acetate (EVA) to improve the pour point.

Two 250 cm³ test tubes are filled with gas oil No. 1. No additive is added to the first test tube. 0.1% by weight of one of the additives is added to the second test tube.

The two test tubes are sealed hermetically and stored in a cold room at -15º C for 24 hours. After 24 hours, the degree of sedimentation of the precipitated paraffins is expressed in the volume of the different phases in the test tube (amount of precipitate, slightly cloudy phase, cloudy phase, clear or transparent phase).

The following results were obtained and are shown in Tables II, IV and VI below.

The same test was carried out with gas oil No. 2 at -20ºC for 24 hours. The results are given in Tables III, V and VII below.

The quality of the upper phase is crucial for the sediment-inhibiting effect of the product. If the upper phase is cloudy, a large proportion of the paraffin is still in suspension. If this phase is clear, almost all of the paraffin has precipitated. If the upper phase is slightly cloudy, the sediment-inhibiting effect is mediocre.

Let us now consider the amount of paraffins precipitated: the more paraffin-free the upper phase has become, the denser the precipitate phase is, making it difficult to pump the gas oil. The amounts of paraffins precipitated can only be compared if they have the same density, i.e. if the upper phases are the same.

Tables II and III give the results obtained with Addition 1, Tables IV and V give the results obtained with Addition II and Tables VI and VII give the results obtained with Additions III and IV. TABLE II TABLE III

It can be stated here that additive I, which was presented in EP-B-71513 as an example of its anti-settlement effect at -10ºC, is less effective at -15ºC and not effective at all at -20ºC. TABLE IV TABLE V

The anti-sediment effect of Additive II is stronger than that of Additive I, especially at -20º C. TABLE VI TABLE VII

With Additive III, a better paraffin dispersion is obtained than with Additive II, but the active ingredient ratio is an important factor with regard to the anti-sagging effect of the additives: Additive IV ensures the best gas oil homogeneity during cold storage.

Example 6

The corrosion-inhibiting effect of the additives I to IV described above is tested.

Each additive is used in the two gas oils No. 1 and 2 as described above at a concentration of 0.01% by weight.

The corrosion test consists in investigating the corrosion of cylindrical test bars made of polished steel or iron by synthetic sea water according to ASTM D 65, modified so that the temperature is 32.2ºC and the test duration is 20 hours.

For the two gas oils No. 1 and 2 without additives, the test bars rust on 100% of their surfaces, while the samples for the same two gas oils with 0.01% by weight of one of the additives described above show 0% rust.

Claims (1)

1- Petroleum middle distillate composition consisting of a major proportion of paraffinic petroleum middle distillate, the distillation process of which (see standard ASTM D 86-67) takes place between 150 and 450ºC, and a minor proportion of at least one active ingredient consisting of a product with an average molar mass of approximately 300 to 10 000 and resulting from the reaction of at least one aliphatic dicarboxylic compound (a) selected from maleic and alkylmaleic anhydrides, alkenylsuccinic anhydrides containing 10 to 32 carbon atoms in the alkenyl radical, dicarboxylic acids and the corresponding light alkyl diesters, with at least one compound having a primary amine action (b), according to the generalized formula (1): in which R¹ represents a monovalent saturated aliphatic radical containing 1 to 32 carbon atoms, Z is chosen from -NR'-amino groups, R' representing a hydrogen atom or a monovalent saturated aliphatic radical containing 1 to 32 carbon atoms, n is an integer between 2 and 4, m is an integer between 1 and 4; characterized in that, in order for said active ingredient to regulate the paraffin reduction with sufficient efficiency, said compound with primary amine activity (b) is used in a ratio of 0.3 to 0.8 moles per mole of said dicarboxylic compound (a); said reaction is carried out at a temperature of between 120 and 200ºC and is continued until the end of the separation of the volatile products consisting of water and/or alcohol which are formed during the reaction. 2- Composition according to claim 1, characterized in that the active ingredient used results from the reaction of 0.4 to 0.7 moles of compound (b) per mole of compound (a). 3- Composition according to one of claims 1 and 2, characterized in that the compound with primary amine action (b) consists of at least one polyamine having the formula which corresponds to the generalized formula (1) in which Z represents the -NH- group, m has a value between 1 and 4, n has a value between 2 and 4, R¹ is a straight-chain, monovalent, saturated, aliphatic radical with 12 to 32 carbon atoms. 4- Composition according to one of claims 1 and 2, characterized in that the compound with primary amine action (b) consists of at least one polyamine having the formula which corresponds to the generalized formula (1) in which Z represents the -NR²R³ group, R² and R³ are identical or not identical and are each an alkyl radical with 1 to 24 carbon atoms, n has a value of 2 to 4 and m has a value of 1 to 4. 5- Composition according to one of claims 1 to 4, characterized in that the dicarboxylic compound (a) is selected from the group consisting of maleic anhydride, methylmaleic anhydride, n-octadecenylsuccinic anhydride and dodecenylsuccinic anhydride. 6- Composition according to one of claims 1 to 5, characterized in that the reaction takes place within a tar-containing solvent whose boiling point is between 70º and 250º C, and the mixing at a temperature of 30 to 80º C of said dicarboxylic compound (a) with said compound (b) according to formula (1) and the heating of the resulting mixture at a temperature of 120 to 200º C for 1 to 8 hours. 7- Composition according to one of claims 1 to 6, characterized in that the middle distillate is a gas oil fraction whose distillation course begins at a temperature of 160 to 190ºC and ends at a temperature of 350 to 390ºC. 8- Composition according to one of claims 1 to 7, characterized in that the ratio between said active ingredient and the middle distillate is between 20 and 2,000 grams per tonne. 9- Process for regulating the reduction in paraffin content in a paraffinic petroleum middle distillate, the distillation process of which (see standard ASTM D 86-67) takes place between 150 and 450ºC, characterized in that an effective minority of at least one active ingredient is added to said middle distillate, which consists of a product with an average molar mass of about 300 to 10,000 resulting from the reaction of at least one aliphatic dicarboxylic compound (a) selected from maleic and alkylmaleic anhydrides, alkenylsuccinic anhydrides containing 10 to 32 carbon atoms in the alkenyl radical, dicarboxylic acids and the corresponding light alkyl diesters, with at least one compound with primary amine activity (b), according to the generalized formula (1): in which R¹ represents a monovalent, saturated, aliphatic radical having 1 to 32 carbon atoms, Z is selected from the -NR'-amino groups, where R' represents a hydrogen atom or a monovalent, saturated, aliphatic radical having 1 to 32 carbon atoms, n is an integer comprised between 2 and 4, m is an integer comprised between 1 and 4; said compound having primary amine activity (b) is used in a proportion of 0.3 to 0.8 moles per mole of said dicarboxylic compound (a); said reaction is carried out at a temperature comprised between 120 and 200ºC and is continued until the end of the separation of the volatile products consisting of water and/or alcohol formed during the reaction. 10- Process according to claim 9, characterized in that the active ingredient used is formed by the reaction of 0.4 to 0.7 moles of compound (b) per mole of compound (a).