Low viscosity poly-a-olefin lubricating oil and synthesis method thereof

Abstract

The present invention provides a low viscosity poly-α-olefin lubricating oil and a synthesis method thereof. The method comprises: (1) the α-olefin raw material is subjected to dehydration treatment so that the water content in the raw material is ≤10 ppm; (2) a reaction of the dehydration treated α-olefin raw material is carried out in the presence of a complex catalyst and gaseous BF.sub.3 to obtain a reaction product, wherein the pressure of the gaseous BF.sub.3 is 0.01 to 1 MPa; (3) the reaction product obtained in step (2) is sequentially subjected to flash distillation, gas stripping, centrifugation, and washing treatment to obtain an intermediate product; (4) the intermediate product obtained in step (3) is subjected to distillation under reduced pressure to separate the unreacted α-olefin raw material and α-olefin dimers, and the remaining heavy fractions are subjected to hydrogenation saturation treatment followed by fractionation and cutting-off.

Claims

1. A synthesis method for low viscosity poly-α-olefin lubricating oils, comprising the following steps: (1) dehydration treatment: an α-olefin raw material is subjected to dehydration treatment so that a water content in a dehydrated α-olefin raw material is ≤10 ppm; (2) polymerization reaction: a polymerization reaction of the dehydrated α-olefin raw material is carried out in the presence of a complex catalyst and gaseous BF.sub.3 to obtain a reaction product, wherein the pressure of the gaseous BF.sub.3 is 0.01 to 1 MPa; (3) catalyst removal: the reaction product obtained in step (2) is sequentially subjected to flash distillation, gas stripping, centrifugation, and washing treatment to obtain an intermediate product, including: a. flash distillation: the reaction product obtained in step (2) is subjected to flash distillation to obtain a first oil phase and gaseous BF.sub.3; b. gas stripping: the first oil phase obtained in step a is subjected to gas stripping to obtain a second oil phase and a stripping gas containing BF.sub.3; c. centrifugation: the second oil phase obtained in step b is subjected to separation by centrifugation using a continuous liquid-liquid separation centrifuge to obtain a recycled complex catalyst and a third oil phase; the recycled complex is dried over B.sub.2O.sub.3 so that the water content in the complex after drying is ≤100 ppm; d. washing: the third oil phase obtained in step c is subjected to alkaline washing and/or water washing to obtain an intermediate product; (4) post-treatment: the intermediate product obtained in step (3) is subjected to distillation under reduced pressure to separate the unreacted α-olefin raw material and α-olefin dimers, and the remaining heavy fractions are subjected to hydrogenation saturation treatment followed by fractionation and cutting-off to obtain poly-α-olefin synthetic oils of different viscosity grades.

2. The synthesis method according to claim 1, wherein the complex catalyst in step (2) has a water content of ≤10 ppm.

3. The synthesis method according to claim 1, wherein the complex catalyst in step (2) is consisted of replenished fresh complex catalyst and recycled complex catalyst, wherein the ratio between the fresh complex catalyst and the recycled complex catalyst is 1:20 to 1:4.

4. The synthesis method according to claim 1, wherein step (3) includes: a. flash distillation: the reaction product obtained in step (2) is subjected to flash distillation to obtain a first oil phase and gaseous BF.sub.3, the gaseous BF.sub.3 is compressed to 0.1-1.0 MPa, and 50%-98% thereof is returned to step (2) for recycled use while the remaining as purge gas is absorbed by complexation so as to provide a fresh complex catalyst; b. gas stripping: the first oil phase obtained in step a is subjected to gas stripping to obtain a second oil phase and a stripping gas containing BF.sub.3, and a portion of stripping gas containing BF.sub.3 passes through a dry recycled complex catalyst where the BF.sub.3 therein is absorbed by complexation, then is returned to a gas stripping section of step b for recycled use, while the recycled complex catalyst obtained after the absorption of BF.sub.3 by complexation returns as recycled complex catalyst to step (2) for recycled use; the remaining portion of the stripping gas containing BF.sub.3 together with the gaseous BF.sub.3 as purge gas from step a are subjected to absorption by complexation, so that a fresh complex catalyst is obtained; c. centrifugation: the second oil phase obtained in step b is subjected to separation by centrifugation using a continuous liquid-liquid separation centrifuge to obtain a recycled complex catalyst and a third oil phase; the recycled complex catalyst is dried over B.sub.2O.sub.3; d. washing: the third oil phase obtained in step c is subjected to alkaline washing and/or water washing to obtain an intermediate product.

5. The synthesis method according to claim 4, wherein the absorption by complexation in step a is absorption by complexation with a fresh initiator; the absorption by complexation in step b is absorption by complexation with the recycled complex obtained by centrifugation and drying in step c.

6. The synthesis method according to claim 5, wherein the fresh initiator is a monobasic alcohol having a carbon atom number of 1-20 or an organic monobasic acid having a carbon atom number of 1-20.

7. The synthesis method according to claim 4, wherein for the absorption by complexation in steps a and b, the temperature is each independently −50 to 50° C., and the pressure is each independently 0 to 1.0 MPa.

8. The synthesis method according to claim 4, wherein after the gaseous BF.sub.3 as purge gas and the stripping gas containing BF.sub.3 are subjected to absorption by complexation, a remaining gas is treated by alkaline washing and/or water washing before being discharged.

9. The synthesis method according to claim 8, wherein the remaining gas is treated by washing with the waste water from alkaline washing and/or water washing that is discharged from the treatment of the third oil phase by alkaline washing and/or water washing in step d.

10. The synthesis method according to claim 1, wherein the α-olefin raw material is one of or a mixture of more of straight-chain α-olefin having a carbon atom number of 8-14.

11. The synthesis method according to claim 1, wherein the complex catalyst is a BF.sub.3 complex with a monobasic alcohol having a carbon atom number of 1-20 or a BF.sub.3 complex with an organic monobasic acid having a carbon atom number of 1-20.

12. The synthesis method according to claim 1, wherein for the polymerization reaction in step (2), the reaction temperature is 0 to 100° C., the reaction duration is 0.1 to 2 h, and the reaction pressure is 0.01 to 1.0 MPa.

13. The synthesis method according to claim 1, wherein for the flash distillation in step (3), the pressure is 0 to 0.2 MPa, and the temperature is 0 to 100° C.

14. The synthesis method according to claim 1, wherein the gas used for the gas stripping in step (3) is an inert gas; and the gas for the gas stripping is used in an amount such that the volume ratio between it and the first oil phase obtained by the flash distillation treatment is 0.1:1 to 10:1.

15. The synthesis method according to claim 14, wherein the inert gas has a water content of ≤5 ppm.

16. The synthesis method according to claim 1, wherein for the gas stripping in step (3), the temperature is 0 to 100° C., and the pressure is 0 to 0.2 MPa.

17. The synthesis method according to claim 1, wherein the centrifugation in step (3) is continuous centrifugation at a temperature of 0 to 100° C., a pressure of 0 to 0.2 MPa, with a rotational speed of 50 to 3000 rotation/min and a residence time of 0.1 to 10 min.

18. The synthesis method according to claim 1, wherein the molar ratio between the complex catalyst and the dehydrated α-olefin raw material in step (2) is 1:50 to 1:1000.

19. The synthesis method according to claim 1, wherein the unreacted α-olefin raw material and α-olefin dimers obtained from separation in step (4) return to step (2) for continued reactions.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a schematic flowing chart of the processes for the synthesis of a low viscosity poly-α-olefin lubricant oil according to the present invention and recycled use of the catalyst thereof.

REFERENCE NUMBERS

(2) 1. Zeolite dehydration tower; 2. Reactor; 3. Flash distiller; 4. Gas stripping tower; 5. Centrifuge; 6. Oil product washing tower; 7. Reduced pressure distillation tower; 8. Hydrogenation rector; 9. Fractioning tower; 10. BF.sub.3 storage tank; 11. Fresh catalyst complexation tank; 12. Waste gas washing tower; 13. Stripping gas complexation absorption tank; 14. Recycled complex drying device.

DETAILED DESCRIPTION

(3) Hereinafter, the implementation and resulting advantageous effects of the present invention are described in details by means of specific examples, which is intended for readers to better understand the spirit and characteristics of the present invention, but is not to be construed as limitation to the scope of implementation of the present application.

Example 1

(4) With reference to FIG. 1, the processes for the synthesis of a low viscosity poly-α-olefin lubricant oil according to the present invention and recycled use of the catalyst thereof particularly include the following steps:

(5) 1. A Synthesis Method for Low Viscosity Poly-α-Olefin Lubricating Oils, Particularly Comprising the Following Procedures:

(6) Raw material refinement: the α-olefin raw material is subjected to dehydration refinement by using a zeolite fixed bed so that the water content in the raw material is ≤10 ppm;

(7) polymerization reaction: the α-olefin raw material and the recycled light fraction are charged into a reactor, into which a recycled complex catalyst and a replenished fresh complex catalyst (with a water content of ≤10 ppm) are added, and then BF.sub.3 is introduced to carry out a reaction, so as to obtain a reaction product;

(8) catalyst separation and removal: the reaction product is sequentially subjected to flash distillation, gas stripping, centrifugation, and washing treatment to obtain an intermediate product.

(9) (1) flash distillation: the reaction product is subjected to flash distillation to obtain a first oil phase and gaseous BF.sub.3; the gaseous BF.sub.3 is compressed, and a portion thereof is returned to the gaseous BF.sub.3 storage tank for recycled use while the remaining is discharged as purge gas into the fresh complex catalyst tank and subjected to treatment by complexation absorption;
(2) gas stripping: the first oil phase is subjected to gas stripping to obtain a second oil phase and a stripping gas containing BF.sub.3, and a portion of stripping gas containing BF.sub.3 enters the recycled complex absorption tank where the BF.sub.3 therein is separated by complexation absorption before recycling, while the recycled complex obtained after the absorption of BF.sub.3 by complexation returns to the reactor as recycled catalyst for recycled use;
(3) centrifugation: the second oil phase obtained by gas stripping is subjected to separation by centrifugation using a continuous liquid-liquid separation centrifuge to obtain a recycled complex and a third oil phase;
(4) washing: the third oil phase is subjected to alkaline washing and/or water washing to obtain a clean intermediate product.

(10) distillation under reduced pressure, hydrogenation, fractionation and cutting-off: the intermediate product is subjected to distillation under reduced pressure to separate the light fraction from the heavy fraction; the light fraction is unreacted monomers and α-olefin dimers, and are returned to the reactor as part of the reaction raw material and continue to participate in the reaction, and the heavy fraction is subjected to hydrogenation saturation treatment followed by fractionation and cutting-off to obtain poly-α-olefin synthetic oils of different viscosity grades.

Examples 1-2

(11) 1—decene refined by dehydration (with a water content of 4 ppm) was used as raw material to synthesize a low-viscocity PAO. Butanol (with a water content of 50 ppm) was used as a co-catalyst, at an amount of butanol:1-decene of 1:100 (molar ratio), and a reaction was carried out at 30° C. and a BF.sub.3 pressure of 0.2 MPa, with a retention time of 1 h. The reaction product was subjected to flash distillation.

(12) TABLE-US-00001 TABLE 1 The effect of removing BF.sub.3 by flash distillation process BF.sub.3 content in oil BF.sub.3 Temper- (g/kg) removing Exam- ature Pressure Reaction First rate ple (° C.) (MPa) product oil phase (%) 1 30 0 4.92 4.33 12.0 2 60 0 4.92 3.64 26.0

Examples 3-8

(13) The flash distilled oils obtained from the processing in Examples 1 and 2 were used as the feed for gas stripping at ambient pressure and subjected to gas stripping, respectively.

(14) TABLE-US-00002 TABLE 2 The effect of removing BF3 by gas stripping separation Gas stripping BF.sub.3 content conditions (g/kg) BF.sub.3 Temper- Gas-liquid Second removing Exam- ature ratio First oil oil rate ple (° C.) (V:V) Phase Phase (%) 3 30 1:0.1 4.33 1.93 55.4 4 30 1:1 4.33 2.09 51.7 5 30 1:10 4.33 2.42 44.1 6 60 1:0.1 3.64 0.81 77.7 7 60 1:1 3.64 1.62 55.5 8 60 1:10 3.64 1.86 48.9

Examples 9-14

(15) The second oil phase obtained in Examples 4 and 7 was subjected to centrifugal separation at ambient pressure to separate the inactive complex catalyst, and the recycled complex was subjected to dehydration.

(16) TABLE-US-00003 TABLE 3 The effect of removing BF3 by centrifugal separation Centrifuge conditions BF.sub.3 content (g/kg) Water content in the Rotational Second Third BF.sub.3 recycled complex (ppm) Temperature speed oil oil removing Before After Example (° C.) (rotation/min) phase phase rate (%) dehydration dehydration 9 30 500 2.09 0.03 98.6 416 8 10 30 1000 2.09 0.02 99.0 427 8 11 30 2000 2.09 0.01 99.5 453 11 12 60 500 1.62 0.02 98.8 379 6 13 60 1000 1.62 0.01 99.4 414 9 14 60 2000 1.62 0.01 99.4 433 9

Comparative Examples 1-2

(17) The first oil phase obtained in Examples 1 and 2 were directly subjected to centrifugal separation at ambient pressure to separate the inactive complex catalyst.

(18) TABLE-US-00004 TABLE 4 Effect of first oil phase separation by centrifugation Centrifuge conditions Com- Rotational BF.sub.3 content (g/kg) BF.sub.3 parative Temper- speed Before After removing Exam- ature (rotation/ centri- centri- rate ples (° C.) min) fugation fugation (%) 1 30 1000 4.33 0.79 81.8 2 30 1000 3.64 0.53 85.4

Example 15

(19) The resultant recycled complex catalyst was mixed with a fresh catalyst in a 9:1 mass ratio, and the catalyst was added into the reactor in an amount in accordance with a ratio between the catalyst and the olefin raw material of 1:100 (molar ratio, calculated in terms of the butanol therein). Meanwhile, the gaseous BF.sub.3 in the recycling tank was used as replenishing gas to control the pressure in the reactor at 0.2 MPa, and a PAO synthesis reaction was carried out under the condition of a reaction temperature at 30° C., and the product composition was compared with that obtained by a reaction catalyzed by the fresh catalyst under the same condition:

(20) TABLE-US-00005 TABLE 5 Impact of the times of recycled usage of the recycled catalyst on the product composition Rounds of Distribution of the polymerization product composition (wt, %) recycled Hexamer usage of or Conversion Yield the catalyst Monomer Dimer Trimer Tetramer Pentamer above rate (%) (%) Fresh 0.6 3.8 55.7 26.0 11.3 2.7 99.4 95.7 Recycled 1 0.5 3.5 56.1 26.1 11.2 2.6 99.5 96.0 catalyst 2 0.5 3.2 56.6 25.9 11.1 2.7 99.5 96.3 3 0.4 3.3 56.5 26.4 11.0 2.8 99.6 96.4

Example 16

(21) The third oil phase obtained in Example 11 was subjected to alkaline washing and water washing with an alkaline solution at a concentration of 0.01% and a volume ratio between the alkaline solution and the third oil phase of 1:1. Then, the oil after alkaline washing was subjected to washing with desalted water, and the fluoride content in the oil was determined as 0.3 ppm, with the F.sup.− concentration in the alkaline solution of 12 ppm and the F.sup.− concentration in water of 0.8 ppm.