EP0332002B2 - Use of selected acrylic and/or methacrylic acid ester copolymers as flow enhancers in paraffin-rich mineral oils and mineral-oil fractions (II) - 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 have their own pour point, which, however, is so low for many crude oils that there is no impairment in production and pipeline transport. There are also a number of petroleum qualities whose pour point is above 10 ° C. In practice, the use of flow aids based on different synthetic homopolymer and / or copolymer types can be advisable in practice.

There is extensive prior art for such auxiliaries, which are also referred to as paraffin inhibitors and are generally prepared by polymerizing olefinic 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.

Particular difficulties arise in practice 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 are exceeded in transport - for example through pipes in the seawater area with relatively low temperatures, the rapid solidification of the hydrocarbon material to a mass that is no longer pumpable and thus the blocking of pipes, pumps and the like occurs. 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. As an additional difficulty, it must be taken into account that simply increasing the amount of any pour point improver generally does not lead to a correspondingly increased decrease in the pour point. In particular, unexplained interactions between flow aids and the solidifying constituents of the crude oil are probably in the sense of a thresh hold Blame effect for the desired goal, whereby the specific constitution of the flow aid is of crucial importance for its effectiveness.

DE-A-2 264 328 describes the use of copolymers of acrylic and / or methacrylic esters of higher alcohols or alcohol cuts with at least 16 carbon atoms in the alcohol residue as additives for crude oils and petroleum fractions to reduce their flow properties.

The copolymers of DE-A-2 264 328 obviously do not contain any free acrylic acid or methacrylic acid. Example 1 of DE-A-2 264 328 expressly uses equimolar amounts of alcohol and acrylic acid.

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 an intrinsic pour point of 33 ° C. The optimum effectiveness of the copolymers used in this publication with regard to reducing 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).

JP-A-59 108 095 teaches the use of homo-, co- and / or graft polymers of monomers selected from long-chain α-olefins, unsaturated carboxylic acids and alkyl esters of unsaturated carboxylic acids to delay the phase separation in hydrocarbon mixtures, the solids as a suspension or other additives Form of liquids of higher polarity included. A solution to the pour point depression problem is not disclosed or suggested.

In contrast, the teaching of the present invention is based on knowledge. that a particularly effective lowering of the hardening temperatures - determined according to the known methods of pour point and / or pour point determination - as well as an effective improvement in the flow behavior can be obtained just in the temperature range just above the lowered pour points if the copolymer types described below in detail from acrylic and / or methacrylic acid esters of higher alcohols and free acrylic acid and / or methacrylic acid are used in limited amounts as comonomers for the purpose of lowering the pour point.

Use of copolymers of acrylic and / or methacrylic acid esters of higher alcohols or alcohol cuts with at least 16 carbon atoms in the alcohol residue and 0.5 to 15% by weight, based on the copolymer weight, of free acrylic acid and / or methacrylic acid as Additive for crude oils and petroleum fractions containing paraffins and / or asphaltenes to lower their pour point or solidification point and improve the flow properties, especially in the temperature range just above the solidification point. The teaching of the invention, characterized in that copolymers based on esters from alcohols or alcohol cuts with predominantly 18 to 24 C atoms are used, the content of C ₂₂ and higher alcohols of which is at least 45% by weight.

Particularly suitable copolymers of the type mentioned contain, together with the acrylic and / or methacrylic acid esters of higher alcohols or alcohol cuts, 1 to 10% by weight of the free acids mentioned. The most important copolymers of the type used in accordance with the invention contain acrylic acid and / or methacrylic acid as comonomers in the copolymer shown above in amounts of about 1.5 to 5.0% by weight. All these percentages by weight relate to the copolymer weight.

The additives of the invention which lower the pour point and improve the flow properties of the treated oils or oil fractions can very advantageously be used in general for crude oils or petroleum fractions of any origin. Their use is particularly helpful in the problems described at the beginning of the paraffin-rich crude oils and / or petroleum fractions with their own pour points above 20 ° C and in particular above 25 ° C. The use of the pour point improvers according to the invention in only limited quantities makes it possible to lower the pour points to values below 15 ° C. and preferably to values below 10 ° C. even with these feedstocks. This is possible even if the starting or. The self-pour points of the oils or oil fractions are at 30 ° C or above. According to the invention, it is thus possible, by adding conventional amounts of the pour point improvers, to obtain pour points in the range from about 0 to 8 ° C. even with extremely paraffin-rich starting materials. 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 amounts of copolymers containing acrylic acid and / or methacrylic acid based on esters of these acids, which have the comparatively long-chain alcohol residues with chain lengths in the range from C ₁₈ to C ₂₄ , are particularly suitable for teaching the invention. These alcohols or alcohol residues are preferably predominantly corresponding compounds with n-alkyl residues. 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 conventional solvents, for example toluene and the like, is promoted by the use of appropriate alcohol cuts in the production of the acrylic or methacrylic acid esters and their subsequent copolymerization with the corresponding free acids.

Flow improvers of the type described, which contain only or predominantly acrylic acid as free acid, are of particular importance. Likewise, esters of acrylic acid as a comonomer component are of particular importance in the sense of the action according to the invention.

It has furthermore been found that when acrylic acid and / or methacrylic acid are used as comonomers in the pour point improvers used in accordance with the invention, particularly effective copolymers are obtained if comparatively high contents of alcohol residues with at least 22 carbon atoms in the acrylate or methacrylate Component. 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 that was used for the production of the acrylate components

The application concentration of the pour point improver 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.

Examples

To produce the acrylic acid copolymers, the two acrylate ester mixtures A and B are used, which differ in 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 / acrylic acid 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 12 according to the invention are summarized in Table 2 below. The type of acrylate monomers A or B used is assigned to the respective example and the percentage (% by weight) of acrylic acid in the monomer mixture for the preparation of the pour point depressant is given. In example 1, the flow improver was produced by the batch process and in examples 2 to 12 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 1, ⌀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 so doped was quickly poured into a cylindrical glass vessel with an inside diameter of 27 mm and this immediately closed vessel was hung sufficiently deep in a water bath of + 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 content 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 acrylic acid in the copolymer specific viscosity Pour point in Bombay crude oil (° C) 1 A 2.5 0.54 6 2nd A 1.25 0.74 12th 3rd B 1.25 0.69 9 4th A 2.5 0.93 6 5 A 2.5 0.54 6 6 B 2.5 0.73 6 7 A 2.5 1.1 9 8th A 5 0.61 12th 9 B 5 0.58 6 10th A 10th 0.64 12th 11 A 20th 0.37 21 12th A 40 0.30 24th

In a further investigation, when using the pour point improver according to Example 6, the determination of the yield point is carried out with the aid of the CS 100 rotary viscometer from Carri-Med Ltd. performed. The corresponding effect of a commercially available branded product based on copolymers of long-chain acrylates and pyridine is determined in the same way. The following applies in detail to these experiments:

10.0 g of Bombay crude oil, which had been doped with a) 300 ppm of the 50% flow improver according to Example 6 and in a second sample with b) 300 ppm of a 50% known flow improver used in practice, were at 6 ° for 2 hours C cooled and then determined the yield point with the following result: according to the invention Market product Yield point after 2 hours at 6 ° C in Nm ^-2 37 1769

Were doped crudes instead of 2 hours now and 72 hours at 6 ° C held, the yield strength was in the inventive material 99 N · m ^-2, and in the branded product 1990 N · m ^-2.

The technical advantage of the flow improver according to the invention can be seen from this. The pump pressure that has to be applied to start up a pipeline filled with cooled crude oil is 48 times after 2 hours and still 20 times after working according to the teaching of the invention for the market product that has also been tested.

Claims (6)

1. Use of copolymers prepared from acrylic and/or methacrylic acid esters of higher alcohols or alcohol cuts having at least 16 C atoms in the alcohol residue and 0.5 to 15 wt.% (wt.% relative to the weight of the copolymer) of free acrylic acid and/or methacrylic acid as an additive for crude oils and petroleum fractions containing paraffins and/or asphaltenes in order to reduce their flow or setting point and to improve their flow characteristics, in particular in the temperature range just above the setting point, characterised in that copolymers based on esters prepared from alcohols or alcohol cuts predominantly having 18 to 24 C atoms are used, which copolymers have a content of C₂₂ and higher alcohols of at least 45 wt.%.
2. Use according to claim 1, characterised in that copolymers of the stated type having free acid contents in the range from approximately 1 to 10 wt.%, preferably in the range from approximately 1.5 to 5 wt.%, in each case relative to the weight of copolymer, are used.
3. Use according to claims 1 and 2, characterised in that the flow improvers are used in high-paraffin oils or oil fractions with intrinsic flow points of above 20°C, in particular of above 25°C and that the flow points are preferably reduced to values of below 15°C, in particular of below 10°C.
4. Use according to claims 1 to 3, characterised in that copolymers based on esters of alcohols or alcohol cuts are used which have a content of C₂₂ and higher alcohols of above 50 wt.%.
5. Use according to claims 1 to 4, characterised in that copolymers prepared from esters of acrylic acid with higher alcohols or alcohol cuts of the stated type and free acrylic acid are used.
6. Use according to claims 1 to 5, characterised in that the flow improvers are used, preferably dissolved in solvents, in quantities of approximately 20 to 1000 ppm.