EP0332000B1 - Use of selected acrylic and/or methacrylic acid ester copolymer versions as flow enhancers in paraffin-rich mineral oils and mineral-oil fractions (I) - Google Patents

Description

It is known to improve the flow properties of crude oils and / or petroleum fractions by using limited amounts of synthetic flow aids. As is known, the task of these flow aids is to lower the respective temperature below those in the liquid hydrocarbon mixture of solid constituents - in particular higher paraffins, if appropriate in combination with asphaltenes or other poorly soluble constituents - in such amounts that the flowability of the hydrocarbon mixtures is permanently impaired. The temperature range mentioned here is determined by the known methods of determining the pour point or pour point. Due to its specific composition, each crude oil or the petroleum fractions obtained from it has its own pour point, which, however, is so low for many crude oils that there is no impairment in production and pipeline transport. But there is also a whole range of petroleum qualities with a pour point above 10 ° C. In practice, the use of flow aids based on different synthetic homopolymer and / or copolymer types can be advisable.

There is extensive prior art for such auxiliaries, which are also referred to as paraffin inhibitors are and are usually prepared by polymerizing olefinically unsaturated compounds which contain at least partially unbranched saturated hydrocarbon chains with at least 18 carbon atoms. Reference is made, for example, to DE-AS 22 10 431 and DE-OSs 26 12 757, 22 64 328, 20 62 023, 23 30 232, 19 42 504 and 20 47 448.

In practice, particular difficulties arise when the intrinsic pour point of the crude oil or the petroleum fraction to be processed reaches extremely high values, which in particular can be at least 25 ° C and can be 30 ° C and above. Petroleum materials of this type tend to solidify rapidly even at ambient temperature. If, for example, pumping processes are interrupted even for a short time or if temperature ranges - for example through pipes in the seawater area - are crossed with relatively low temperatures, the rapid solidification of the hydrocarbon material to a mass that is no longer pumpable and thus blockage of pipes, pumps and the like. The situation is made more difficult by the fact that, in order to reliably rule out malfunctions of the type described, practice is often required to lower the pour points of the oils or oil fractions to values below 15 ° C and in particular to values below 12 ° C or even below 10 ° C . It is immediately apparent that there are very special technological difficulties when, for example, it is necessary to lower the crude oil's own pour point from around 33 ° C to values well below 10 ° C. An additional difficulty to be taken into account here is that simply increasing the amount of any pour point improver generally does not lead to a correspondingly increased decrease in the pour point. Interactions between flow aids and the solidifying that have not yet been elucidated Components of the crude oil are probably responsible for the desired goal in the sense of a thresh-hold effect, with the specific constitution of the flow aid being of decisive importance for its effectiveness.

DE-PS 30 31 900 describes copolymers of n-alkyl acrylates with at least 16 carbon atoms in the alcohol residue and maleic anhydride with molar ratios of n-alkyl acrylate to maleic anhydride from 20: 1 to 1:10. Compounds of this type are said to be used as crystallization inhibitors for paraffin-containing crude oils. Examples shown numerically relate to the use of corresponding copolymers in the molar ratio of the acrylic acid ester to maleic anhydride in the range from 1: 1 to 8: 1. Crude oils with intrinsic pour points below 20 ° C. are predominantly used. A table of values deals with India crude oil, which is known to be a particularly paraffin-rich starting material (disruptive paraffin content 15%) and has its own pour point of 33 ° C. The optimum effectiveness of the copolymers used in this publication with regard to lowering the pour point on this starting material is at the molar ratio of acrylic acid ester / maleic anhydride of 4: 1. The lowest pour points set here are at 12 ° C. If the proportion of maleic anhydride in the copolymer is further reduced, then the pour points of the India crude oil thus added rise again with the addition of the same amount (cf. in particular Table 2 of the cited literature reference).

Starting from the problems, in particular in the production of inhibitors of the type described above, with higher contents of dicarboxylic acid residues in the polymer molecule, the teaching of GB 2 160 536 aims to provide improved crystallization inhibitors by building up ternary copolymers. To build up the polymer molecule, it is proposed here to use, as the third monomer component, ethylenically unsaturated compounds of the formula CH ₂ = CZ ₁ Z ₂ , where the radicals Z ₁ and Z _{2 are the} same or different and are hydrogen, halogen, saturated, unsaturated or aromatic C _{1 -30-} hydrocarbon residues, ester residues or ether residues. Comparative Example 5 of this publication describes a binary copolymer of n-alkyl acrylate with an average chain length C ₂₀ to C ₂₂ and maleic anhydride with a MAH content of 1.9% in the polymer molecule. The use of the flow improver of Comparative Example 5 in crude oils with their own pour points above 25 ° C does not lead to a reduction in the pour points to values below 15 ° C in any of the cases shown in the publication.

In contrast, the teaching of the present invention is based on the surprising finding that a particularly effective lowering of the solidification temperatures determines According to the known methods of pour point and / or pour point determination - with starting materials with a high paraffin content and correspondingly particularly high self-solidification temperatures can be effectively obtained if selected types of copolymers of the type described below are used as flow aids. It has surprisingly been found that selected copolymers with extremely low maleic anhydride contents can be particularly suitable for effectively lowering the limit temperatures of the flowability of crude oils containing high paraffin or corresponding petroleum fractions.

The invention accordingly relates to the use of copolymers consisting of acrylic and / or methacrylic acid esters of higher alcohols or alcohol cuts with at least 16 carbon atoms in the alcohol residue, the content of C ₂₂ - and optionally higher alcohols - based on that for the preparation of the acrylate or methacrylate components used alcohol mixture - is at least 45 wt .-%, and not more than 5 wt .-%, preferably 0.5 to 2.5 wt .-% maleic anhydride - wt .-% based on copolymer weight - as a flow improver in paraffin-rich crude oils and / or petroleum fractions with their own pour points above 25 ° C to lower their pour points to values below 15 ° C, preferably below 10 ° C.

Copolymers of the type mentioned whose content of maleic anhydride is in the range from approximately 0.5 to 2.5% by weight and in particular in the range from approximately 1 to 2% by weight are particularly suitable for the inventive action. Here, too, the percentages by weight relate to the proportion of total monomer. It is part of the teaching according to the invention that the pour points of the crude oils and / or petroleum fractions used with their starting or intrinsic pour points above 25 ° C. and in particular above 30 ° C. by adding the flow improvers defined according to the invention to values below 15 ° C. and preferably below 10 ° C. According to the invention it is possible, for example, by adding conventional amounts of the pour point improvers in the sense of Invention to come to pour points of the extremely paraffin-rich starting materials in the range of about 0 to 8 ° C. This ensures trouble-free handling of these crude oils and oil fractions under normal everyday conditions. In particular, it is ensured that lines, distributors and the like which are guided under water can be operated without problems.

Small quantities of copolymers containing maleic anhydride based on the esters of acrylic acid are particularly suitable for teaching the invention. The further particularly preferred acrylic acid esters contain comparatively long-chain alcohol residues, which can be at least predominantly n-alkyl residues and have preferred chain lengths in the range from C ₁₈ to C ₂₄ . Proportions of alcohols with a higher carbon number, in particular up to about C ₃₀ and / or alcohols with a lower carbon number up to about C ₁₆ , can also be used. In particular, the dissolution behavior of the copolymers in customary solvents, for example toluene and the like, is promoted by the use of appropriate alcohol cuts in the production of the acrylic acid esters and their subsequent copolymerization with maleic anhydride.

It has further been shown that when only small amounts of maleic anhydride are used as comonomers in the sense of the teaching according to the invention, particularly effective copolymers are obtained in the pour point improvers if comparatively high contents of alcohol residues with at least 22 carbon atoms in the acrylate or Methacrylate component are present. The teaching of the invention thus provides for the use of alcohol cuts for the production of the acrylate component (s) whose content of C ₂₂ alcohol makes up at least 45% by weight. Particularly good pour point improvers are obtained if these long-chain alcohol components in the alcohol cuts used to produce the (meth) acrylate component are above 50% by weight. The weight percentages given here relate to the content of C ₂₂ alcohol - and possibly higher alcohols - in the alcohol mixture which was used for the production of the acrylate or methacrylate components.

The application concentration of the pour point improvers according to the invention is in the conventional range and is, for example, 20 to 1000 ppm, with amounts in the range from 100 to 500 ppm being preferred. The pour point improvers are expediently used in suitable solvents. Details on this and on the preparation of the copolymers can be found in the relevant prior art, for example in DE-PS 30 31 900 already cited.

The alcohols or alcohol cuts used for the production of the acrylate components can be of native or synthetic origin. Alcohol cuts with a predominant proportion of components with at least 22 carbon atoms, but at the same time also minor amounts of alcohol components in the range C ₁₆ to C ₂₀ , are the preferred starting materials. In a particular embodiment of the invention, acrylates or methacrylates selected in this way are copolymerized with maleic anhydride in such mixing ratios that the molar ratio of alkyl acrylate or methacrylate to maleic anhydride is greater than 20: 1.

Examples

The two acrylate ester mixtures A and B are used to prepare the maleic anhydride copolymers Distinguish by the C chain distribution of the fatty alcohol mixture used for the acrylic acid esterification. The two types of acrylate are characterized as follows: Table 1 C chain distribution of fatty alcohol /% C ₁₆ C ₁₈ C ₂₀ C ₂₂ Acrylate A 16.3 22.9 10.7 46.9 Acrylate B 1.5 8.6 15.2 68.8

Two types of processes are used to produce the acrylate / MAH copolymers, the batch process and the feed process.

Carrying out experiments in the batch process

The monomers, initiator and solvent are weighed into a three-necked flask.

At a stirrer speed of 70 rpm, the batch is evacuated for 10 × 1 min and the vacuum is released again with 99.999% nitrogen. At a stirrer speed of 50 rpm and under a slight stream of N _{2, the} batch is heated to 90 ° C. and kept at this temperature. The entire reaction is carried out under inert conditions. The start of the reaction manifests itself in a temperature rise to 93 to 96 ° C. The mixture is kept at 90 ° C ± 1 ° C for 3 h. After this time, the mixture is cooled to room temperature within 45 minutes and the product is filled.

Toluene is used as the solvent here and in the subsequent feed process. The polymerization initiator used is dibenzoyl peroxide or azoisobutyronitrile as indicated below. The mixing ratio of solvent to monomer mixture is 1: 1 (parts by weight).

Carrying out the experiment in the feed process:

The monomers are dissolved in toluene in the desired mixing ratio at 45 to 50 ° C. and the solution is then cooled to 25 ° C. The initiator is also used in solution in toluene. About 20% of the monomer solution determined per batch is placed in a reactor. The reactor is flushed three times with nitrogen and heated to 90 ° C. while stirring under a gentle stream of N ₂ . The initiator solution is now metered in so that the total metering time is 2.5 hours.

Approx. A temperature increase occurs 20 minutes after the initiator has been added. The temperature is kept at 90 ± 3 ° C by cooling the reactor jacket.

30 minutes after the initiator has been added, the remaining monomer solution is metered into the reactor in such a way that the total metering time is 2 h. The temperature is kept at 90 ± 3 ° C throughout the reaction time. The reaction mixture is then kept at the same temperature for a further 60 min. The reaction product is then cooled and filled at 30 ° C.

Examples 1 to 10 according to the invention are summarized in Table 2 below. The type of acrylate monomers A or B used is used in the respective example assigned and the percentage (wt .-%) of maleic anhydride in the monomer mixture for the preparation of the pour point depressant stated. In Examples 1 and 2, the flow improver was produced by the batch process and in Examples 3 to 10 by the feed process.

In Examples 1 and 7, azoisobutyronitrile was used as the initiator, and dibenzoyl peroxide was used as the initiator in all other examples.

Table 2 finally shows the specific viscosity of the copolymer solutions prepared in each case. The viscosity is measured using an Ubbelohde viscometer capillary I, ⌀ 0.63 mm. The measured toluene solutions are 3% solutions in toluene. The measurement is carried out at 20 ° C after a temperature adjustment of 10 min.

Finally, Table 2 contains the pour point values which were obtained when the pour point improvers according to the invention were added to an India crude (Bombay crude oil) in accordance with the following working instructions.

Determination of the pour point

The pour point was determined in accordance with ASTM D 97-66 and DIN 51597 as follows:

25.0 g of Bombay crude oil, together with 800 ppm of the 50% strength by weight solution of the flow improver, were kept in a closed vessel at 50 ° C. for 15 minutes and vigorously shaken 5 times at regular intervals. The crude oil doped in this way was quickly poured into a cylindrical glass vessel with an inside diameter of 27 mm and this immediately sealed vessel was hung sufficiently deep in a water bath at + 36 ° C.

After 30 minutes the glass was tilted slightly to the side and observed whether the contents were flowing. The sample was then gradually cooled by 3 ° C and the test procedure was carried out each time. 3 ° C was added to the temperature at which the contents no longer flowed, even when the test glass was inclined by 90 °, and this temperature was defined as the pour point.

The pour point of the untreated Bombay crude oil is 30 ° C according to this determination method. Table 2 E.g. Acrylic type % By weight of MAH in the copolymer Specific viscosity Pour point in Bombay crude oil (° C) 1 A 1.25 0.657 6 2nd A 5 1.17 9 3rd A 0.25 0.56 12th 4th A 0.5 0.65 12-15 5 A 1.25 0.65 6 6 B 1.25 0.64 3rd 7 A 1.25 0.37 9 8th A 2.5 0.83 9 9 A 2.5 0.61 9 10th B 5 0.52 12th

Claims (4)

1. The use of copolymers consisting of acrylates and/or methacrylates of higher alcohols or alcohol cuts containing at least 16 C atoms in the alcohol radical, of which the content of C₂₂ and optionally higher alcohols - based on the alcohol mixture used to produce the acrylate or methacrylate components - is at least 45% by weight, and no more than 5% by weight and preferably 0.5 to 2.5% by weight of maleic anhydride (% by weight here based on the weight of the copolymer) as flow improvers in paraffin-rich crude oils and/or petroleum fractions with self-pour points above 25°C for reducing their pour points to values below 15°C and preferably below 10°C.
2. The use claimed in claim 1, characterized in that the flow improvers are used in crude oils or in petroleum fractions with self-pour points of at least 30°C.
3. The use claimed in claims 1 and 2, characterized in that maleic anhydride copolymers based on esters of acrylic acid with predominantly C_18-24, alcohols are used, corresponding alcohol cuts with a content of C₂₂ and optionally higher alcohols of more than 50% by weight being preferred.
4. The use claimed in claims 1 to 3, characterized in that copolymers with a maleic anhydride content of 1 to 2% by weight are used.