Method for dewaxing mineral oil compositions

Abstract

The present invention relates to a lubricant composition for a process for reducing the paraffin content of mineral oil compositions, by providing a mineral oil composition with a dewaxing aid, cooling to form a paraffin precipitate and at least partly removing the paraffin precipitate formed. The dewaxing aid used is a copolymer mixture comprising at least three copolymers, the copolymers differing in the composition of the repeat units.

Claims

1. A process for reducing a paraffin content of a mineral oil composition, the process comprising: adding a dewaxing aid to a mineral oil composition to obtain a mixture, cooling the mixture to form a paraffin precipitate, and at least partly removing the paraffin precipitate, wherein the dewaxing aid is a copolymer mixture comprising at least four copolymers, the copolymers of the copolymer mixture differ in composition of repeat units, and have repeat units derived from one or more alkyl methacrylates having 16 to 18 carbon atoms, and repeat units derived from one or more alkyl acrylates having 19 to carbon atoms, wherein the copolymer mixture is obtained by copolymerization of a monomer mixture consisting of at least one alkyl acrylate and at least one alkyl methacrylate in one polymerization step.

2. The process of claim 1, wherein the copolymer mixture comprises at least five copolymers which differ in composition of repeat units.

3. The process of claim 2, wherein a proportion of any copolymer in the copolymer mixture is not more than 50% by weight.

4. The process of claim 1, wherein: at least three of the copolymers comprise at least two different repeat units derived from alkyl (meth)acrylates having 16 to 18 carbon atoms and repeat units derived from alkyl acrylates having 19 to 22 carbon atoms; at least one first copolymer having a higher proportion of repeat units derived from alkyl acrylates having 19 to 22 carbon atoms in an alkyl radical than at least two of the other copolymers; at least one second copolymer has a higher proportion of repeat units derived from alkyl methacrylates having 16 to 18 carbon atoms in an alkyl radical than at least two of the other copolymers; and at least one third copolymer has repeat units deprived from alkyl acrylates having 19 to 22 carbon atoms in an alkyl radical and having repeat units derived from alkyl methacrylates having 16 to 18 carbon atoms in an alkyl radical, the proportion in the third copolymer of repeat units derived from alkyl acrylates having 19 to 22 carbon atoms in the alkyl radical being lower than the proportion of these repeat units in the first copolymer, and the proportion in the third copolymer of repeat units derived from alkyl methacrylates having 16 to 18 carbon atoms in the alkyl radical being lower than a proportion of these repeat units in the second copolymer.

5. The process of claim 4, wherein a proportion of any copolymer in the copolymer mixture is not more than 50% by weight.

6. The process of claim 1, wherein a proportion of any copolymer in the copolymer mixture is not more than 50% by weight.

7. The process of claim 1, wherein the copolymer mixture has a crystallization transition in a range from 30 C. to 50 C.

8. The process of claim 1, wherein the copolymer mixture has a crystallization transition whose half-height width is at least 8 C.

9. The process of claim 1, wherein a copolymer of the copolymer mixture comprises at least 30% by weight of repeat units derived from the alkyl acrylates having 19 to 22 carbon atoms.

10. The process of claim 1, wherein the copolymer mixture has a weight-average molecular weight in a range from 200 000 to 500 000 g/mol.

11. The process of claim 1, wherein the process is performed in the presence of a solvent.

Description

EXAMPLES AND COMPARATIVE EXAMPLES

General Preparation Method for the Polymers

(1) In a 2 L reaction flask of an apparatus with sabre stirrer, condenser, temperature regulator with PT100, syringe pump and N.sub.2 feed line, 850.0 g of monomers, 143.6 g of 100N oil and 1.0 g of dodecyl mercaptan were weighed in. The apparatus was inertized and heated to 110 C. A further 6.4 g of 100N oil were admixed with 2.1 g of tert-butyl per-2-ethylhexanoate. After the mixture in the reaction flask had reached a temperature of 110 C., the feed of the oil/initiator mixture was started by means of the pump.

(2) The addition was effected at 110 C. over 3 h. 5% of the solution was metered in within the first hour, 25% within the second hour and 70% of the mixture in the last hour. 2 h after the end of the feed, another 1.7 g of tert-butyl per-2-ethylhexanoate were added and the mixture was stirred at 110 C. for 1 h. This gave an 85.0% clear solution or colorless waxy solid (examples 1 and 2 and comparative examples 1 and 2).

(3) The process described above was used to polymerize the monomer mixtures described in table 1. In the case of use of acrylates and methacrylates, copolymer mixtures whose individual copolymers feature a continuously changing composition with regard to the repeat units were obtained.

(4) TABLE-US-00001 TABLE 1 BehA SMA DPMA Styrene [% by wt.] [% by wt.] [w % by wt.] [% by wt.] Example 1 68.0 32.0 Example 2 60.0 40.0 Comparative 90.0 10.0 example 1 Comparative 100.0 example 2 Comparative 30.0 70.0 example 3 Comparative 90.0 10.0 example 4 Comparative 100.0 example 5 BehA: behenyl acrylate (acrylate having 18 to 22 carbon atoms in the alkyl radical, average of 20 carbon atoms) SMA: stearyl methacrylate (methacrylate having 16 to 18 carbon atoms in the alkyl radical, average of 17.3 carbon atoms) DPMA: dodecyl-pentadecyl methacrylate (Alcohol: Neodol 25)

(5) The polymers obtained were additionally used to make up the mixtures described in table 2. The percentages are based on the polymers containing.

(6) TABLE-US-00002 TABLE 2 Polymers used for preparation of the mixture Comparative 55% by wt. of 45% by wt. of example 6 comparative comparative example 2 example 3 Comparative 60% by wt. of 20% by wt. of 20% by wt. of example 7 comparative comparative comparative example 3 example 1 example 4 Comparative 60% by wt. of 40% by wt. of example 8 comparative comparative example 2 example 5

(7) To distinguish the performance of the dewaxing aids produced, a laboratory filtration test which allows the measurement of oil yield and filtration rate was used. Especially in the case of the latter, great differences can be elucidated among the examples.

(8) Performance of the Filtration Test

(9) The filtration apparatus consisted of a steel filter with a lid and cooling jacket, and was cooled with the aid of a cryostat in circulation. A customary filter cloth from a dewaxing plant in a refinery was used. The filter volume was 100 ml. The filter was connected to a measuring cylinder via a glass attachment with a 2-way tap. By means of a rotary-vane oil pump, a pressure-reducing valve and a manometer, it was possible to apply a defined vacuum to the filtration apparatus. The mineral oil distillate to be dewaxed was admixed under hot conditions, typically at 70 C., but in each case above the cloud point, with the dewaxing solvents and the dewaxing aids, and stirred until a clear solution resulted. Then the mixture was cooled to the desired filtration temperature at a defined rate with temperature control. The filter was precooled to this temperature. All filtration conditions, such as solvent, feedstock ratio, ratio of the solvents in the case of use of solvent mixtures, cooling rates and filtration temperatures, corresponded to the conditions employed in the respective refinery.

(10) After the filtration temperature had been attained, the mixture was transferred to the precooled filter and the vacuum was applied. Typically, a reduced pressure of 300 to 700 mbar was employed. The filtration volume was then determined as a function of time. The filtration was ended when no further liquid penetrated through the filter cloth.

(11) In all filtration tests, an additization rate of 350 ppm based on polymers was employed.

Use Example 1

(12) To determine the performance of the individual dewaxing aids, a 650N feedstock from an east European refinery was used, and the filtration volumes in ml were determined after the times shown in table 3.

(13) Solvent system: 45% methyl ethyl ketone/55% toluene

(14) Feedstock: solvent ratio=1:4.65

(15) Procedure: 1) mixing at 70 C., 2) 30 min in a bath at 25 C., 3) 60 min in a bath at 25 C., filtration temperature: 25 C.

(16) TABLE-US-00003 TABLE 3 Filtration volume [ml] Com- Com- Filtration Example parative parative time [s] No additive 1 example 1 example 2 5 4 13 5 4 10 7 19 8 8 15 9 24 10 10 20 11 28 12 11 25 12 32 13 13 30 13 35 15 15 35 15 38 16 16 40 16 41 17 17 45 17 44 18 18 50 18 47 19 19 55 19 50 20 20 60 20 52 21 21 65 21 54 22 22 70 22 57 23 23 75 22.5 59 24 23.5 80 23 61 25 24 85 24 63 26 25 90 24.5 65 27 26 100 25.5 69 28 27 110 27 71 30 29 120 28 72 31 30 130 29.5 73 33 32 140 31 73 34 33 150 32 35 34 160 33 37 35 170 34 38 37 180 35 39 38 190 36 40 39 200 37.5 42 40 240 42 46 44 270 44 49 47 300 47 52 50 360 52 57 55 420 57 62 59 480 61 66 63 540 65 70 67 600 68 70 660 70 72 720 71 Filtration volume [ml] Filtration Comparative Comparative Comparative time [s] example 6 example 7 example 8 5 3 5 5 10 8 9 9 15 12 12 13 20 14 14 16 25 17 16 18 30 19 18 20 35 21 20 22 40 23 21 24 45 25 23 26 50 26.5 24 27 55 28 25 29 60 29.5 27 30 65 31 28 32 70 32.5 30 33 75 34 31 34 80 35 32 36 85 36.5 34 37 90 38 35 38 100 40.5 37 40 110 43 39 43 120 45 41 45 130 48 43 47 140 50 45 50 150 52 47 52 160 54 48 54 170 56 50 56 180 57 52 58 190 59 54 60 200 61 55 62 240 67 61 69 270 72 65 73 300 74 67 73 360 76 420

Use Example 2

(17) To determine the performance of the individual dewaxing aids, a 500SN feedstock from a south-west European refinery was used, and the filtration volumes in ml were determined after the times shown in table 4.

(18) Solvent system: 50% methyl ethyl ketone/50% toluene

(19) Feedstock: solvent ratio=1:2.91

(20) Procedure: 1) mixing at 60 C., 2) 15 min in a bath at 20 C., 3) 60 min in a bath at 22 C. filtration temperature: 22 C.

(21) TABLE-US-00004 TABLE 4 Filtration volume [ml] Filtration Com- Com- time No Example parative parative [s] additive 1 example 1 example 3 example 4 5 4 13 13 6 5 10 8 23 21 11 8 15 11 28 28 15 12 20 13 34 35 18 14 25 15 39 39 20 15 30 17 43 43 23 17 35 19 47 47 25 18 40 20 51 50 27 21 45 22 54 53 29 22 50 23 58 57 31 23 55 25 61 60 33 25 60 26.5 64 63 34 26 65 28 67 66 36 27 70 29 71 68 37 28 75 31 72 70 38 30 80 32 72 71 40 31 85 33 73 72 42 32 90 34 73 73 43 33 100 36 74 74 45 35 110 39 74 48 37 120 41 50 39 130 42.5 53 41 140 45 55 42 150 47 58 44 160 49 60 46 170 51 62 47 180 52 64 49 190 54 66 51 200 56 68 52 240 62 74 58 270 65 75 62 300 67 66 360 71

Use Example 3

(22) To determine the performance of the individual dewaxing aids, a brightstock from a south European refinery was used, and the filtration volumes in ml were determined after the times shown in table 5.

(23) Solvent system: 50% methyl ethyl ketone/50% toluene

(24) Feedstock: solvent ratio=1:3.80

(25) Procedure: 1) mixing at 52 C., 2) 30 min in a bath at 5 C., 3) 60 min in a bath at 18 C., filtration temperature: 18 C.

(26) TABLE-US-00005 TABLE 5 Filtration Filtration volume [ml] time No Comp. Comp. Comp. [s] additive Example 1 Example 2 ex. 1 ex. 3 ex. 4 5 6 11 14 8 9 5 10 9 24 26 14 14 8 15 12 35 36 18 19 11 20 15 43 44 24 23 13 25 17 51 52 26 26 15 30 19 59 58 29 30 17 35 21 65 65 31 33 19 40 22 71 72 33 36 20 45 24 76 77 35 39 21.5 50 26 79 80 37 41 23 55 27 80 81 39 43 24.5 60 28 80 81 41 45 26 65 30 42 48 27 70 31 44 50 28 75 32 45 52 29 80 34 47 54 30 85 36 49 56 31 90 37 51 58 32 100 39 53 61 34 110 41 56 64 36 120 43 59 67 38 130 46 61 71 40 140 48 63 74 42 150 50 66 76 43 160 52 68 79 45 170 54 71 80 47 180 56 72 81 49 190 57 74 81 50 200 59 79 82 52 240 66 80 57 270 70 61 300 72 65 360 75 70 420 76 71

Use Example 4

(27) To determine the performance of the individual dewaxing aids, a 500SN raffinate from a south European refinery was used, and the filtration volumes in ml were determined after times shown in table 5.

(28) Solvent system: 45% methyl ethyl ketone/55% toluene

(29) Feedstock: solvent ratio=1:2.3

(30) Procedure: 1) mixing at 25 C., 2) 30 min in a bath at 5 C., 3) 60 min in a bath at 19 C., filtration temperature: 18 C.

(31) TABLE-US-00006 TABLE 5 Filtration volume [ml] Filtration Comparative Comparative time [s] No additive Example 1 example 1 example 5 5 1 4 1 2 10 5 8 3 4 15 6 11 5 7 20 6.5 13 7 8 25 7 15 9 10 30 9 17 11 11 35 10 18 12 12 40 11 19 13 12.5 45 12 21 13.5 14 50 13 22 14 14.5 55 13.5 23 15 15.5 60 14 25 15.5 16.5 65 15 26 16 17 70 15.5 27 17 18 75 16 28 18 19 80 17 30 19 19.5 85 17.5 31 19.5 20 90 18 32 20 20.5 100 19 33 21 22 110 20 35 22 23 120 22 37 23 24 130 23 39 24 25.5 140 24 41 25 26.5 150 24.5 42 26 27.5 160 25 44 27 29 170 26 45 28 30 180 27 47 29 31 190 28 48 30 31.5 200 28.5 50 31 33 240 31 55 34 36 270 32.5 59 37 39 300 35 61 39.5 41 360 38 62 44 46 420 42 48 50 480 45 52 54 540 48 56 57 600 51 57 59 900 58 59 Filtration volume [ml] Filtration Comparative Comparative Comparative time [s] example 6 example 7 example 8 5 3 2 1 10 6 5 6 15 9 9 8 20 11 12 10 25 13 13 11.5 30 14 14 13 35 17 16 14.5 40 18 17 15.5 45 19 18 17 50 20 19.5 18 55 21 21 19 60 22 22 21 65 23 23 22 70 24 24 22.5 75 25 25 23 80 26 26 25 85 27 27 25.5 90 28 28 26 100 30.5 29 28 110 32 30 29 120 33 31 30.5 130 35 32.5 32 140 36.5 34 33 150 38 35 34 160 39 36 35.5 170 41 38 37 180 42 39 38 190 43 40 39 200 44 42 40 240 49 45 44.5 270 53 48 47 300 56 53 50 360 58 57 55 420 61 60 59 480 62 60

(32) In the filtration tests, it is clear that the filtrations using inventive examples 1 and 2 had ended significantly more rapidly than using the comparative examples. Surprisingly, it was also possible to increase the volume of oil filtered off. In addition, the use examples show that the inventive dewaxing aids can be used in a multitude of different starting compositions with great success with regard to filtering time and the yield of upgraded mineral oil obtained.