NO801833L - PROCEDURE FOR AA PREVENTING SEPARATION OF PARAFFINES IN PARAFFIN CONTAINING RAIL OILS, AND CRYSTALLIZATION INHIBITOR FOR EXECUTION OF THE PROCEDURE - Google Patents

Description

The present invention relates to a method for preventing paraffin separation in paraffin-containing crude oils during the extraction and transport of crude oil, as well as means for carrying out the method.

Depending on the petroleum extraction field in question, the crude oils may contain significant amounts of paraffins. When cooled below a certain temperature, the paraffins crystallize and thereby form a three-dimensional network of scales and/or needles, which are filled with oil. Such a structure gives the crude oil unfavorable properties with regard to fluidity and handling of the oil.

Crystallized paraffin in the crude oil causes the oil to hardly or not flow anymore, cannot be pumped or only very difficult and forms deposits in pipelines and oil pipelines,

in storage containers or in ship tanks, which leads to significant production and capacity losses.

It appears from this that the flow properties of the crude oil both during extraction and storage as well as during transport and even during refining play a major role and that the things that affect the flow properties must be counteracted.

The crude oils found in oil-bearing layers have a temperature that depends on the depth. In the deeper layers, from which oil is extracted, higher temperatures prevail, at which the paraffins are still liquid and are dissolved in the crude oil. If crystallization inhibitors are added to a paraffin-containing crude oil in this state, on the one hand, the freezing point of the crude oil is lowered. On the other hand, the crystal structure of the separated waxes is changed by the addition of the crystallization inhibitors in such a way that the oil's flow characteristics are improved.

When it comes to crystallization inhibitors, it mostly concerns polymers produced by polymerizing ole-finically unsaturated compounds, which at least partially contain an unbranched, saturated hydrocarbon chain with at least 18 C atoms. Such products are, for example, described in: BRD expl. documents no.:

From US patent 3,340,030 it is known the use of a copolymer of alkyl acrylates and dialkylaminoalkyl acrylates in a synergistic mixture with salts of alkylbenzenesulfonic acid in fuel oils, which contain catalytically cracked material, for improving stabilization, filterability and water separation properties.

Practice shows, however, that there are drawbacks to many well-known products. For example, it has been shown that many products do not

can be used universally on all types of oil and loses its effect with different oils.

Another disadvantage of many products lies in their

high sensitivity to shear forces. It has been shown in practice that many known products only fulfill their task as crystallization inhibitors for paraffin-containing crude oils when the treated oils are not subjected to shear forces. Normally, however, crude oil is transported in oil pipelines, whereby the transport is effected by pumps.

Hereby, the shear force exerted by the pumps completely destroys the effect of many crystallization inhibitors.

It was therefore the task of the invention to produce crystal ice ion inhibitors which

- in a majority of the occurring paraffinic oils-

types lead to a clear lowering of the solidification point,

- besides the lowering of the solidification point also causes

a reduction of the paraffin deposit,

- lowers the crude oil's viscosity and

- maintains its effectiveness under shear stress (pumps).

The task is solved by crystallization inhibitors which consist of

of a copolymer of n-alkyl acrylates and dialkylaminoalkyl acrylates or containing such copolymers.

The object of the invention is a method for preventing the separation of paraffins in paraffin-containing crude oils by adding crystallization inhibitors based on polymers of olefinically unsaturated compounds, characterized in that crystallization inhibitors are used which consist of a copolymer of n-alkyl acrylates with the general formula: and dialkylaminoalkyl acrylates with the general formula formula:

eeler contains such a copolymer, whereby R, stands for hydrogen or methyl, R 2 for an n-alkyl radical with at least 16 C atoms R_ and , which may be the same or different, for a lower

linear or branched alkyl radical with 1-8 C atoms, and X is a linear or branched alkylene radical with 2-5 C atoms in the general formulas A and B. Preferably R216-30 C atoms, especially at least

20 C atoms. R^ and R^ preferably have 1-4 C atoms.

Examples of the residue X are the linear 1,2-ethylene, 1,3-propylene, 1,4-butylene and 1,5-pentylene residues, as well as the corresponding branched residues such as e.g. 1,1-ethylene (= methyl-methylene), 1,1-propylene residue (= ethyl-methylene), 1-methyl-1,2-ethylene or 2-methyl-1,2-ethylene residue as branched residues with 3 C atoms, a 1,2- or 1,3-butylene residue such as the 2-methyl-1,3-propylene residue, the 1,2-dimethyl-1,2-ethylene residue or also the 1,1-butylene residue (propyl-methylene ) and finally the neopentyl residue.

The molar ratio between the n-alkyl acrylates (A) and the dialkylamino-alkyl acrylates (B) is generally from 20:1 to 1:10, preferably from 16:1 to 1:5 and especially from 4:1 to 1:1.

The intrinsic viscosity of the copolymer amounts to 8 to 100 ml/g, preferably 10 to 50 ml/g, measured in toluene at 20°C.

The compounds with formula A are esters of acrylic acid acc. Methacrylic acid with linear alcohols containing at least 16 C atoms. The upper limit for the number of C atoms is not critical. It depends on the technical availability of alcohol. Such alcohols can be of native or synthetic origin. These are usually alcohol mixtures with a broad C chain distribution. The rest R ? then stands for the average chain length, which follows from the C chain distribution of the alcohol mixture. R2 is preferably in the range from 20 to 22 C atoms.

The C-chain distribution in the alcohol mixture should correspond approximately to the following composition:

Certain fractions of the synthetic alcohols following the Ziegler synthesis have proven particularly suitable, whereby a preferred average shows the following composition:

A particularly preferred fraction of synthetic alcohols exhibits an even lower content of C,,-C,„- alcohols and has the following

-L o -L o

composition:

Admittedly, this alcohol fraction also contains dependent

of the production still low proportions of up to approx. 3% of lower C^g- to C^g- alcohols.

According to their synthetic method of production, the alcohols may also contain a small percentage of neutral parts, e.g. paraffin, which, however, does not interfere with the properties of the products manufactured according to the invention.

From the alcohols and the acrylic acid acc. methacrylic acid, the monomeric esters are prepared in the usual and known manner, the alcohol mixture being heated with acrylic acid or methacrylic acid in the presence of an esterification catalyst, such as e.g. sulfuric acid or p-toluenesulfonic acid, and a polymerization inhibitor, such as e.g. hydroquinone, suitably in the presence of an azeotropic solvent, such as e.g. benzene, toluene or xylene, until the water of reaction is removed. The esterification is carried out at a temperature between 70 and 170°C, depending on the solvent.

The compounds of formula B are dialkylaminoalkyl esters of acrylic acid or methacrylic acid. This mostly concerns technically available raw materials, which are extracted by transesterification of methyl acrylate according to methyl methacrylate with dialkylamino alcohols.

Products in which the alkyl residues in the dialkylamino group are the same are preferred as dialkylamino alcohols. As dialkylamino alcohols, the dialkylamino derivatives of ethanol, propanol, butanol and neopentyl glycol are suitable.

Suitable products with formula B are, for example:

Dimethylaminoethyl acrylate,

Dimethylaminoethyl methacrylate,

Diethylaminoethyl acrylate,

Diethylaminoethyl methacrylate,

Dimethylaminopropyl acrylate,

Dimethylaminopropyl methacrylate,

Dimethylaminobutyl acrylate,

Diisopropylaminoethyl acrylate,

Dibutylaminoethyl methacrylate oder

Diisobutylaminoethyl methacrylate,

Dimethylaminoneopentyl acrylate.

For technical and economic reasons, dimethylaminoethyl methacrylate is preferred as comonomer.

The copolymers are produced by copolymerization of the monomers denoted by the formulas A and B. The polymerization can either be carried out without a solvent (substance polymerization) or in an organic solvent, in which the monomers and the copolymer are soluble according to known methods. In this way, the polymer is obtained either in solid form or as a solution. The solvent must be inert towards the monomers and the copolymer. It is preferably an aromatic or aliphatic hydrocarbon, whereby, however, any other solvent as well as technical solvent mixtures that correspond to the requirements stated above can also be used. Suitable solvents include, for example, benzene, toluene, liquid paraffins, chlorohydrocarbons (e.g. trichloroethene, tetrachloroethylene), etc. Preferred solvents are toluene or an aromatic solvent mixture with the following composition:

The monomer concentration in the solvent amounts to 20 to 100, preferably 50 to 100, % by weight, so that after the polymerisation an essentially waxy product or a solution is obtained.

At higher monomer concentrations, the reaction is admittedly highly exothermic, but on the other hand, the reaction rate is not very high, so that control of the polymerization process can be maintained without difficulty.

The polymerization can be carried out at a temperature within the range from 50 to 150°C, whereby the preferred temperatures are in the range from 80 to 120°C.

According to the method in the invention, the reaction time at 85 to 95°C amounts to 4 hours.

An organosoluble, radical-forming catalyst is required for the polymerization. Suitable catalysts include benzoyl peroxide, capryl peroxide, acetyl peroxide, acetyl benzoyl peroxide, di-tert-butyl peroxide, azoisobutyronitrile, dimethyl azoisobutyrate and many others. Mixtures of such catalysts are also suitable in the polymerization method of the present invention.

The copolymers used according to the invention as crystallization inhibitors are waxy. Solid products, which dissolve easily in organic solvents, such as e.g. toluene, and somewhat slower in lubricating oils and in crude oils. It is therefore appropriate for the application to prepare the products directly in solution, or if it concerns substance polymerization, to prepare the solution immediately after the copolymerization by mixing the molten copolymer with suitable solvents, so that the finished products are available as solution or dispersion.

The degree of polymerization, which is important for characterization

of the copolymers, cannot be determined directly, because the consts

in the Mark-Houwink relationship is not yet known for such copolymers. There is therefore only the possibility of drawing conclusions about the relative degree of polymerization from the limiting viscosity determined according to usual methods (in toluene at 20°C). The limiting viscosity of the copolymer is, depending on the manufacturing conditions, 8 to 100 ml/g, whereby the preferred limiting viscosity amounts to 10 to 50 ml/g.

Subject matter of the invention are further means for carrying out the method. These agents consist of or contain mixed polymers of n-alkyl acrylates with the general formula A: and dialkylaminoalkyl acrylates with the general formula B:

where is hydrogen or methyl, R2 an n-alkyl radical of at least 16 C atoms, R^ and R^, which may be the same or different, a lower linear or branched alkyl radical of 1 to 8 C atoms and X a linear or branched alkylene radical with 2 to 5 C atoms.

The preferred products, where R2 in the general formula A stands

for an alkyl residue with at least 20 C atoms, are new, whereby the upper limit is not critical, but this usually amounts to 30 C atoms. Particularly preferred are products where R 2 exhibits 20 to 22 C atoms. R^ and R^ in the general formula B preferably have 1 to 4 C atoms.

The application concentration for the crystallization inhibitors in the invention is different from crude oil to crude oil and must be calculated for the relevant oil type in advance by solidification point determination and sedimentation tests.

In general, the application concentrations for the crystallization inhibitors in the invention are at 20 to 1000 ppm, whereby concentrations from 50 to 350 ppm are preferred.

The crystallization inhibitors according to the invention are added

preferably already in the borehole.

Determining the solidification point is generally carried out

according to ASTM-D97 B Section 6 f, whereby a distinction is made between four different types of solidification point determination:

a) The actual pourpoint

b) The minimum pourpoint

c) The maximum pourpoint

d) The 'true' maximum pourpoint

pour point)

The activity of the compound by paraffin deposition is tested according to a method developed by the company SERVO, which is described

in the company brochure "Servo paraffin inhibitors for paraffin deposit prevention", SERVO bv, Delden/The Netherlands. According to this method, a paraffin-containing crude oil is conditioned in an insulated vessel to a temperature T0. Two metal discs inserted in a holder are then cooled

to a temperature Tc, while they are immersed in the oil.

By simultaneously gradually lowering the temperatures TQ and Tco, it is achieved

a fast path. simulation of practical conditions. The paraffin deposit is determined by weighing the metal disks, and the deposit reduction can be calculated as a percentage compared to a blank test without the addition of crystallization inhibitors.

In the following examples, the production of

the monomeric and polymeric products as well as their use:

Example 1.

Composition and properties of the starting alcohols:

Alcohols A and B are synthetic, primary, linear alcohols, which are produced according to the Ziegler process ("Alfole"), while alcohol C is a product based on vegetable and animal oils and fats.

For the synthesis of the monomeric alkyl acrylates, the following materials were used:

The alcohol components were dissolved while heating to approx. 60°C in toluene. After addition of hydroquinone and acrylic acid, the esterification was catalyzed with sulfuric acid. The reaction mixture was heated to reflux and the water of reaction separated azeotropically. About. 98% of the theoretical amount of water was removed in 6 hours. The solvent and unreacted acrylic acid were then removed from the reaction mixture by vacuum distillation. The monomeric acrylic acid ester showed the following data:

Example 2.

80.0 g of acrylic acid ester were introduced into a polymerization vessel

A, 1.8 g of dimethylaminoethyl methacrylate (DMAEMA) in the molar ratio 16:1

and 0.6 ml of dodecyl mercaptan and the mixture was heated under a nitrogen atmosphere to 85°C. At this temperature, 0.15 g of azoisobutyronitrile (AIBN) in 3.0 ml of toluene was added. The temperature rose within 6 minutes to 105°C. After cooling to 85°C

further amounts of the catalyst were added as long as there was a noticeable exothermic reaction. A total of 0.55 g of AIBN was consumed. The reaction time was 4 hours, and the polymerization temperature was 85 to 105°C.

The copolymer exhibits a limiting viscosity (in toluene

at 20°C) of 12.7 ml/g and its technical application characteristics are listed in Tables 1, 2, 3 and 5.

Example 3.

In a polymerization vessel, 80 g of acrylic acid ester A and 7.94 g of DMAEMA were placed in the molar ratio of 4:1, and the mixture was heated under a nitrogen atmosphere to 85°C. By adding 0.15 g of AIBN in 3.0 ml of toluene, the polymerization was started. During the first 25 minutes the temperature rose to 92°C. As long as an exothermic reaction could be established, initiator solution was added in several portions (in total 0.65 g AIBN). The total reaction time amounted to 4 hours. The polymerization temperature was 85 to 92°C. The copolymer has an intrinsic viscosity of 4 2.3 ml/g and

its technical application characteristics are indicated in tables 1, 2,

3 and 5.

Example 4.

According to the method described in example 3, the copolymerization of the acrylic acid ester B (105.3 g) with DMAEMA (8.8 g) in the molar ratio 4:1 was carried out. In total, 0.9 g of AIBN was added in several portions to the reaction mixture during the polymerization. The reaction time was 4 hours at 84 to 91°C. The copolymer has an intrinsic viscosity of 12.5 ml/g. Its technical application characteristics are shown in tables 1 and 2.

Example 5.

According to the method described in example 3, the copolymerization of the acrylic acid ester B (83.3 g) with DMAEMA (31.6 g) in the molar ratio 1:1 was carried out. A total of 0.75 g of AIBN was added

in several portions to the reaction mixture during the polymerization. The reaction time was 4 hours at 85 to 95°C. The copolymer has an intrinsic viscosity of 30.8 ml/g. Its technical application characteristics are shown in tables 1 and 4.

Example 6.

According to the method described in example 4, the copolymerization of the acrylic acid ester C (80.0 g) with DMAEMA (9.0 g) in the molar ratio 4:1 was carried out. In total, 0.60 g of AIBN was added in several portions to the reaction mixture during the polymerization. The reaction time was 4 hours at 85 to 115°C. Its technical application characteristics are shown in tables 1 and 2.

Example 7.

According to the method described in examples 2 and 3

the copolymerization of the acrylic acid ester A with DMAEMA in different molar ratios was carried out:

Example 8.

393.6 g acrylic acid ester A, 39.7 g DMAEMA and 206 g aromatic solvent mixture (composition see page 6) were added to a polymerization vessel, and the mixture was heated to 85°C. At this temperature, 0.25 g of AIBN was added in 5 ml of toluene and further a total of 4.0 g of AIBN (dissolved in toluene) was added.

in several portions over the course of 2 hours. During the addition of initiator, the temperature rose to 100°C. After the exothermic reaction, the mixture was stirred for a further 4 hours at 85°C.

Example 9.

According to the method described in example 8, copolymerization of the acrylic acid ester A (95.4 g) was carried out with DMAEMA (16.9 g) in the molar ratio 2.3:1. 50 ml of toluene was used as diluent. In total, 0.5 g of AIBN was added to the reaction mixture in several portions during the polymerization. The reaction time was 4 hours at 90 to 110°C. The effect of the product attributed to 72% active substance can be seen from tables 1 and 4.

Example 10.

According to the method described in example 3, the copolymerization of the acrylic acid ester A (80 g) was carried out with dibutylaminoethyl methacrylate (12.2 g) in the molar ratio 4:1. In total, 0.9 g of AIBN was added to the reaction mixture in several portions during the polymerization. The reaction time was 4 hours at 85 to 95°C. The copolymer has a limiting viscosity of 20 ml/g. Its characteristics are shown in tables 1 and 2.

Example 11.

According to the method described in example 1, an ester was prepared from 1003 g (3 mol) of alcohol A and 258 g (3 mol) of methacrylic acid.

80 g of this ester and 8.6 g of diethylaminoethyl acrylate were

copolymerized in an approximate molar ratio of 4:1 analogous example

3. A total of 0.9 g of AIBN was added in several portions during the polymerization. The effect of the product can be seen from tables 1 and 3.

92.5% by weight of a Petrol fraction with a boiling range of 161-197°C

and additional data:

The special activity of the crystallization inhibitors according to the invention is confirmed by means of the following comparative examples.

Comparison example 1.

With a copolymer according to BRD-off, letter 2,210,431 of 4-vinylpyridine and acrylic acid ester A (alcohol mixture with an average C chain of 21 C atoms) in the molar ratio 1:1, the following freezing point reductions were achieved:

Comparison example 2.

With a copolymer according to BRD-off, document 2,210,431 of 2-vinylpyridine and acrylic acid ester A (alcohol mixture with an average C chain of 21 C atoms) in the molar ratio 1:1, the following freezing point reductions were achieved:

The crude oils used in the listed examples are characterized by the following properties listed in Table 6:

Claims (17)

1. Process for preventing the separation of paraffins in paraffin-containing crude oils by adding crystallization inhibitors based on polymers of olefinically unsaturated compounds, characterized in that crystallization inhibitors are used which consist of a copolymer of at least one n-alkyl acrylate with the general formula: and at least one dialkylaminoalkyl acrylate of the general formula: or contains such a copolymer, whereby in the general formulas A and B R^ stands for hydrogen or methyl, R2 for an n-alkyl radical with at least 16 C atoms, R^ and R^, which may be the same or different, for a lower, linear or branched alkyl radical of 1 to 8 C atoms and X is a linear or branched alkylene radical of 2 to 5 C atoms. 2. Method according to claim 1, characterized in that crystallization inhibitors are used where the radical R2 in the general formula A has 16 to 30 C atoms. 3. Method according to claim 1, characterized in that crystallization inhibitors are used where the radical R2 in the general formula A has 20 to 22 C atoms. 4. Method according to claims 1 to 3, characterized in that crystallization inhibitors are used where R 1 and R 2 in the general formula B is an alkyl residue with 1 to 4 C atoms. 5. Method according to claims 1 to 4, characterized in that crystallization inhibitors are used where the molar ratio between n-alkyl acrylate and dialkylaminoalkyl acrylate is 20:1 to 1:20. 6. Method according to claims 1 to 4, para terized in that crystallization inhibitors are used where the molar ratio between n-alkyl acrylate and dialkylaminoalkyl acrylate is from 16:1 to 1:5. 7. Method according to claims 1 to 4, characterized in that crystallization inhibitors are used where the molar ratio between n-alkyl acrylate and dialkylaminoalkyl acrylate is from 4:1 to 1:1. 8. Method according to claims 1 to 7, characterized in that the limiting viscosity of the copolymer (measured in toluene at 20°C) lies in the range from 8 to 100 ml/g. 9. Method according to claims 1 to 7, characterized in that the limiting viscosity of the copolymer (measured in toluene at 20°C) is in the range from 10 to 50 ml/g. 10. Method according to claims 1 to 9, characterized in that crystallization inhibitors obtained by radical polymerization are used. 11. Method according to claims 1 to 10, characterized in that the crystallization inhibitors are used as a solution or dispersion in a solvent. 12. Method according to claims 1 to 11, characterized in that the crystallization inhibitors are used in concentrations from 20 to 1000 ppm of active substance, calculated on paraffin-containing crude oil. 13. Method according to claims 1 to 11, characterized in that the crystallization inhibitors are used in concentrations of 50 to 350 ppm, calculated on paraffinic crude oil. 14. Method according to claims 1 to 13, characterized in that the crystallization inhibitors are added to the borehole. 15. Crystallization inhibitors for use in the method according to claims 1 to 14, characterized in that they consist of or contain copolymers of n-alkyl acrylates with the general formula: and dialkylaminoalkyl acrylates of the general formula: where R^ stands for hydrogen or methyl, R 2 for an n-alkyl radical with at least 20 C atoms, R 2 and R 4 , which may be the same or different, for a lower, linear or branched alkyl radical with 1 to 8 C atoms and X is a linear or branched alkylene radical with 2 to 5 C atoms. 16. Crystallization inhibitor according to claim 15, characterized in that the radical R2 in the general formula A has 20 to 22 C atoms. 17. Crystallization inhibitor according to one of claims 15 and 16, characterized in that the residues R 3 and R 4 . in the general formula B has 1 to 4 C atoms.