Multi-olefin copolymerization catalyst, preparation method therefor, and use thereof

Abstract

The present invention relates to the field of copolymerization catalysts, and in particular to a multi-olefin copolymerization catalyst, a preparation method therefor, and a use thereof. The method comprises the following steps: mixing activated silica gel with pentane and triisobutylaluminum and then evaporating the solvent to dryness; in a protective atmosphere, adding anhydrous magnesium chloride and ethanol to hexane, reacting the mixture under heating, and then adding ethyl orthosilicate to obtain a mother solution 1; in a protective atmosphere, adding titanium tetrachloride and tetrahydrofuran to hexane and continuously stirring the mixture to obtain a mother solution 2; in a protective atmosphere, mixing the mother solution 1 with the mother solution 2, then adding a modified silica gel, and leaving the mixture to stand; after standing, taking a solid precipitate and washing same; and mixing the washed solid precipitate with hexane, diethylaluminum monochloride and ethylaluminum dichloride and then evaporating the solvent to dryness. Compared with the prior art, the present invention solves the problem of the lack of a catalyst suitable for the copolymerization of ethylene and various α-olefins in the prior art. The catalyst prepared in the present solution by adding the three alkylaluminum compounds is suitable for the copolymerization of ethylene and α-olefins.

Description

Multi-component olefin copolymerization catalyst, its preparation method and application TECHNICAL FIELD

[0001] The present application belongs to the field of copolymerization catalysts, and particularly relates to a multi-component olefin copolymerization catalyst, its preparation method and application. BACKGROUND

[0002] Linear low density polyethylene (LLDPE) is generally produced by copolymerization of ethylene and alpha-olefins at low temperature and pressure, and has excellent properties such as low temperature toughness, high modulus, bending resistance, puncture resistance and tear resistance, and can almost penetrate into all traditional markets of polyethylene, and can be used to manufacture films, moldings, pipes and wire and cable, etc.

[0003] The density of polyethylene is determined by the concentration of comonomer in the polymer chain. The higher the concentration of comonomer, the lower the density of the resin. The concentration of comonomer determines the amount of short chain branches in the polymer, and the length of the short chain branches depends on the type of comonomer. The traditional Ziegler-Natta catalyst cannot generally obtain linear low density polyethylene with high insertion rate when applied to the copolymerization of ethylene and alpha-olefins, and the copolymerization performance is even poorer for alpha-olefins with high carbon number.

[0004] US5331070A discloses a catalyst system for in-situ copolymerization of LLDPE by Phillips Company using supported chromium catalyst. A small amount of alkyl aluminum or chlorinated alkyl aluminum is added to improve the polymerization activity, and a small amount of pyrrole or its derivative is added to modify the chromium active center to produce oligomerization components, and then the unmodified chromium catalyst is used to copolymerize the oligomers with ethylene to form LLDPE.

[0005] CN1421467A discloses an in-situ copolymerization catalyst system for preparing linear low density polyethylene, which is composed of oligomerization catalyst, copolymerization catalyst and cocatalyst, wherein the copolymerization catalyst is a metallocene compound or a supported catalyst thereof, and the product has a low melting point and crystallinity, and a density range of 0.920-0.945 g / cm 3 .

[0006] CN103665206A discloses a preparation method of a multi-active center catalyst for olefin polymerization, which needs to load a second active center, and although a lower density can be achieved, the addition of the second active center greatly increases the production cost of the catalyst.

[0007] Although there are various catalysts for olefin copolymerization in the prior art, there is still a lack of catalysts suitable for copolymerization of ethylene and multiple alpha-olefins to obtain linear low density polyethylene products with very low density and wide molecular weight distribution. Therefore, it is necessary to further develop suitable catalysts. SUMMARY

[0008] The present application aims to solve at least one of the above problems by providing a multi-olefin copolymerization catalyst, a preparation method and application thereof, solving the lack of catalysts suitable for the copolymerization of ethylene and multiple alpha-olefins in the prior art.

[0009] The object of the present application is achieved by the following technical solutions:

[0010] The present application discloses a preparation method of a multi-olefin copolymerization catalyst, comprising the following steps:

[0011] S1: Silica gel modification: the activated silica gel is mixed with pentane and triisobutylaluminum to react, and then the solvent is evaporated to obtain modified silica gel;

[0012] S2: Preparation of mother liquor 1: under a protective atmosphere, anhydrous magnesium chloride and ethanol are added to hexane, heated and reacted, then tetraethyl orthosilicate is added for continuous reaction to obtain mother liquor 1;

[0013] S3: Preparation of mother liquor 2: under a protective atmosphere, titanium tetrachloride and tetrahydrofuran are added to hexane and continuously stirred to obtain mother liquor 2;

[0014] S4: Loading: under a protective atmosphere, the mother liquor 1 obtained in step S2 is mixed with the mother liquor 2 obtained in step S3 to react, then the modified silica gel obtained in step S1 is added for continuous reaction, and then it is left to stand;

[0015] S5: Washing: the supernatant obtained by standing in step S4 is washed until the titanium content in the supernatant is below the target upper limit;

[0016] S6: Preparation of catalyst: the solid precipitate after washing in step S5 is mixed with hexane, dichlorodiethylaluminum and dichloroethylaluminum and reacted, then evaporated to obtain the catalyst.

[0017] Preferably, in step S1, the molar amount ratio of the activated silica gel and triisobutylaluminum is 50:1-1:1, preferably 30:1; the reaction temperature is 20-60, preferably 40℃, and the time is 1h, and vacuum drying.

[0018] Preferably, in step S2, the molar amount ratio of the anhydrous magnesium chloride, ethanol and tetraethyl orthosilicate is 1:0.5-3.0:0.1-0.8, preferably 1:1.3:0.33; the heating reaction temperature is 60℃, and the time is 1h; the continuous reaction temperature is 60℃, and the time is 1h.

[0019] Preferably, in step S3, the volume ratio of titanium tetrachloride to tetrahydrofuran is 0.5:5.0; the time of continuous stirring is 2h.

[0020] Preferably, in step S4, the mass-volume ratio of anhydrous magnesium chloride in mother liquor 1 to tetrahydrofuran in mother liquor 2 is 1:1-1:10, preferably 1g:5mL, the mass ratio of modified silica gel to anhydrous magnesium chloride in mother liquor 1 is 4:1-10:1, preferably 4:1; the time of mixing reaction is 1h; the temperature of continuous reaction is 60℃, and the time is 1h; the time of standing is 1h.

[0021] Preferably, in step S5, hexane is used as the washing liquid, and the target upper limit is that the titanium content in the supernatant is less than 1.0mmol / L.

[0022] Preferably, in step S6, the molar ratio of tetrahydrofuran to dichloroethylaluminum and dichloroethylaluminum in the solid precipitate is 1.0:0.1-1.5:0.1-1.0, preferably 1:0.6:0.4; the time of reaction is 1h.

[0023] Preferably, the protective atmosphere is a nitrogen atmosphere.

[0024] The second aspect of the present application discloses a multi-olefin copolymerization catalyst synthesized by any of the above preparation methods.

[0025] The third aspect of the present application discloses the application of the above multi-olefin copolymerization catalyst in multi-olefin copolymerization, and the catalyst is used for the copolymerization of ethylene and at least two alpha-olefins with 3-8 carbon atoms.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] The polyethylene catalyst prepared by the method of the present application can be used to produce low-density polyethylene products;

[0028] The low-density polyethylene products prepared by using the catalyst have a density of 0.89-0.92g / cm 3 , and are suitable for the copolymerization of ethylene and two or more alpha-olefins with 3-8 carbon atoms; and can produce polyethylene products with a wide molecular weight distribution.

[0029] Compared with the prior art, the polyethylene catalyst preparation method adopted by the present application improves the preparation method of the traditional magnesium-titanium Ziegler-Natta catalyst system, three kinds of aluminum alkyl compounds are added, and the prepared catalyst is suitable for the copolymerization of ethylene and one or more than one α-olefin. In particular, the copolymerization of ethylene and α-olefin on a gas phase fluidized bed device can produce linear low density polyethylene products with very low density and wide molecular weight distribution. DETAILED DESCRIPTION

[0030] The present application will be described in detail below in conjunction with specific examples, but is by no means limited to the present application.

[0031] In the following description, if not specifically stated, the reagents used are conventional commercially available products, and the methods used are well-known means in the art.

[0032] Catalyst preparation:

[0033] (1) Thermal activation of dispersant: A certain amount of ES70W silica gel from PQ Corporation was placed in a fluidized tube, dried to remove excess hydroxyl groups, and then cooled to room temperature using flowing nitrogen at room temperature to obtain thermally activated silica gel.

[0034] (2) Silica gel modification: Then a certain amount of pentane and triisobutylaluminum was added to the thermally activated silica gel, and after sufficient reaction at 40℃ for 1 hour, the solvent was evaporated under vacuum to obtain modified silica gel.

[0035] (3) Preparation of mother liquor 1 (magnesium alcohol compound): Under nitrogen protection, 150mL of hexane was added to a 250mL three-necked flask, then 5g of anhydrous magnesium chloride was added, 3-5mL of ethanol was added under stirring, heated to 60℃, reacted for 1 hour, then 1.5mL of ethyl silicate was added, reacted for 1 hour to prepare mother liquor 1;

[0036] (4) Preparation of mother liquor 2: Under nitrogen protection, 80mL of hexane was added to a 100mL three-necked flask, 0.5mL of titanium tetrachloride and 5.0mL of tetrahydrofuran were added, and stirring was maintained for 2 hours,

[0037] (5) After mixing mother liquor 1 and mother liquor 2, loading: Under nitrogen protection, the mother liquor 2 in the 100mL three-necked flask was added to the 250mL three-necked flask and mixed for 1 hour, then it was transferred to a 500mL three-necked flask, then the modified silica gel was added, and the reaction was carried out at 60℃ for 1 hour and then stood for 1 hour.

[0038] (6) Washing: The supernatant was drawn off, and a certain amount of hexane was added for washing until the titanium content in the supernatant was less than 0.1wt%.

[0039] (7) Then add 50 mL hexane, 1.5 mL diethylaluminum chloride, 1.0 mL dichloroethylaluminum, stir for 1 hour, then evaporate to dryness to obtain the catalyst.

[0040] Example 1

[0041] (1) Weigh 30 g of ES70W silica gel into the fluidized tube, heat to 600°C for 4 hours, then cool to room temperature using flowing nitrogen at room temperature, to obtain 27 g of thermally activated silica gel.

[0042] (2) Weigh 20 g of thermally activated silica gel, add 100 mL of pentane and 2 mL of pure triisobutylaluminum, react at 40°C for 1 hour, then vacuum evaporate the solvent to dryness to obtain the modified silica gel.

[0043] (3) Preparation of mother liquor 1 (magnesium alcoholate): Under nitrogen protection, add 150 mL of hexane to a 250 mL three-necked flask, then add 5 g of anhydrous magnesium chloride, under stirring, add 5 mL of ethanol, heat to 60°C, react for 1 hour, then add 1.5 mL of tetraethyl orthosilicate, react for 1 hour to obtain mother liquor 1;

[0044] (4) Preparation of mother liquor 2: Under nitrogen protection, add 80 mL of hexane to a 100 mL three-necked flask, add 0.5 mL of titanium tetrachloride and 5.0 mL of tetrahydrofuran, keep stirring for 2 hours,

[0045] (5) After mixing mother liquor 1 and mother liquor 2, load: Under nitrogen protection, add mother liquor 2 in a 100 mL three-necked flask to a 250 mL three-necked flask, mix for 1 hour, then transfer it to a 500 mL three-necked flask, then add the modified silica gel, react at 60°C for 1 hour and stand for 1 hour.

[0046] (6) Washing: Draw off the supernatant, wash with a certain amount of hexane until the titanium content in the supernatant is less than 0.1 wt%.

[0047] (7) Then add 50 mL hexane, 1.5 mL diethylaluminum chloride, 1.0 mL dichloroethylaluminum, stir for 1 hour, then evaporate to dryness to obtain the catalyst.

[0048] Laboratory evaluation of the catalyst:

[0049] Slurry polymerization was carried out in a 2 liter reactor, 1200 mL of hexane, 40 mL of 1-hexene, 10 mL of liquid butene, 1.0 mL of triethylaluminum, 0.08 g of catalyst, total pressure 0.8 MPa, hydrogen partial pressure 0.2 MPa, ethylene partial pressure 0.6 MPa, polymerization at 80°C for 2 hours, to obtain 473 g of white polyethylene, with an activity of 5431 g PE / g Cat.

[0050] The product had an MI 2.16 kg of 2.624 g / 10 min and a density of 0.9380 g / cm 3 .

[0051] Example 2

[0052] The support activity and modification steps were the same as in Example 1, except that:

[0053] (3) Preparation of mother liquor 1 (magnesium alcoholate): 150 mL of hexane was added to a 250 mL three-necked flask under nitrogen protection, then 5 g of anhydrous magnesium chloride was added thereto, 3 mL of ethanol was added under stirring, heated to 60°C, after 1 hour of reaction, 1.5 mL of tetraethyl orthosilicate was added, and reacted for 1 hour to obtain mother liquor 1.

[0054] The laboratory evaluation conditions of the catalysts were the same:

[0055] White polyethylene 434 g was obtained, and the activity was 5344 g PE / g Cat.

[0056] The product had an MI 2.16 kg of 3.398 g / 10 min and a density of 0.9411 g / cm 3 .

[0057] Comparative Example 1

[0058] The support activity and modification steps were the same as in Example 1, except that:

[0059] (3) Preparation of mother liquor 1 (magnesium alcoholate): 150 mL of hexane was added to a 250 mL three-necked flask under nitrogen protection, then 5 g of anhydrous magnesium chloride was added thereto, 3 mL of ethanol was added under stirring, heated to 60°C, after 1 hour of reaction, 1.5 mL of 1,4-butanediol was added, and reacted for 1 hour to obtain mother liquor 1.

[0060] The laboratory evaluation conditions of the catalysts were the same:

[0061] White polyethylene 345 g was obtained, and the activity was 4312 g PE / g Cat.

[0062] The product had an MI 2.16 kg of 3.297 g / 10 min and a density of 0.9417 g / cm 3 .

[0063] Comparative Example 2

[0064] The support activity and modification steps were the same as in Example 1, except that:

[0065] (7) Then 50 mL of hexane, 0.5 ml of vanadium tetrachloride was added, stirred for 1 hour, then evaporated to obtain the catalyst.

[0066] The catalysts were evaluated in the laboratory under the same conditions:

[0067] White polyethylene was obtained, 319 g, with an activity of 3985 g PE / g Cat.

[0068] The product had an MI2.16 kg of 3.658 g / 10 min and a density of 0.9432 g / cm 3

[0069] The foregoing description of the examples has been set forth to facilitate an understanding of the application for those of ordinary skill in the technical field. Various modifications to these examples, and the generic principles under which the examples are described, can be employed without departing from the scope of the application. Accordingly, the examples are not intended to be limited to the examples described herein, but rather are to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A process for the preparation of a multi-site olefin copolymerisation catalyst characterised in that, The method comprises the following steps: S1: modification of silica gel: the activated silica gel is mixed with pentane and triisobutylaluminum to react, and then the solvent is evaporated to obtain modified silica gel; S2: preparation of mother liquor 1: under a protective atmosphere, anhydrous magnesium chloride and ethanol are added in hexane, and after heating reaction, tetraethyl orthosilicate is added to continue the reaction to obtain mother liquor 1; S3: preparation of mother liquor 2: under a protective atmosphere, titanium tetrachloride and tetrahydrofuran are added in hexane and continuously stirred to obtain mother liquor 2; S4: loading: under a protective atmosphere, the mother liquor 1 obtained in step S2 is mixed with the mother liquor 2 obtained in step S3 to react, and then the modified silica gel obtained in step S1 is added to continue the reaction, and then it is left to stand; S5: washing: the solid precipitate obtained in step S4 is washed until the titanium content in the washing liquid is lower than the target upper limit; S6: preparation of catalyst: the solid precipitate after washing in step S5 is mixed with hexane, dichlorodiethylaluminum and dichloroethylaluminum to react, and then it is evaporated to obtain the catalyst.

2. The method for preparing a multi-olefin copolymerization catalyst according to claim 1, characterized in that, In step S1, the molar ratio of the activated silica gel to triisobutylaluminum is 50:1-1:1; the reaction temperature is 20-60℃, and the reaction time is 1h.

3. The method for preparing a multi-olefin copolymerization catalyst according to claim 1, characterized in that, In step S2, the molar ratio of the anhydrous magnesium chloride, ethanol and tetraethyl orthosilicate is 1:0.5-3.0:0.1-0.8; the heating reaction temperature is 60℃, and the heating reaction time is 1h; the continuous reaction temperature is 60℃, and the continuous reaction time is 1h.

4. The method for preparing a multi-olefin copolymerization catalyst according to claim 1, characterized in that, In step S3, the volume ratio of the titanium tetrachloride to tetrahydrofuran is 0.5:5.0; the continuous stirring time is 2h.

5. The method for preparing a multi-olefin copolymerization catalyst according to claim 1, characterized in that, In step S4, the mass-volume ratio of the anhydrous magnesium chloride in the mother liquor 1 to the tetrahydrofuran in the mother liquor 2 is 1:1-1:10, and the mass ratio of the modified silica gel to the anhydrous magnesium chloride in the mother liquor 1 is 4:1-10:1; the mixing reaction time is 1h; the continuous reaction temperature is 60℃, and the continuous reaction time is 1h; the standing time is 1h.

6. The method for preparing a multi-olefin copolymerization catalyst according to claim 1, characterized in that, In step S5, hexane is used as the washing liquid, and the target upper limit is that the titanium content in the washing liquid is lower than 1.0mmol / L.

7. The method for preparing a multi-olefin copolymerization catalyst according to claim 1, characterized in that, In step S6, the molar ratio of the tetrahydrofuran in the solid precipitate to dichlorodiethylaluminum and dichloroethylaluminum is 1.0:0.1-1.5:0.1-1.0, and the reaction time is 1h.

8. The method for preparing a multi-olefin copolymerization catalyst according to claim 1, characterized in that, The protective atmosphere is nitrogen atmosphere.

9. A multi-site olefin copolymerisation catalyst characterised in that, The catalyst is synthesized by the preparation method in any one of claims 1-8.

10. Use of the multi-site olefin copolymerisation catalyst of claim 9 in the multi-site olefin copolymerisation characterised in that, The catalyst is used for the copolymerization of ethylene and at least two α-olefins with 3-8 carbon atoms.