1. A rare earth catalyst having the structure of formula I:

wherein Ln is a group IIIB transition metal element;

Z₁and Z₂Identical or different, independently is a substituent of Ln;

d is a neutral ligand coordinated with Ln, and n is an integer greater than or equal to 0;

l is a group formed by a compound of formula II:

wherein R is¹、R²、R³、R⁴The same or different, and is independently selected from hydrogen, C1-C10 alkyl, C6-C30 aryl.

2. The rare earth catalyst as set forth in claim 1, wherein Ln is one of scandium, yttrium, lanthanoid rare earth metal elements; or Z₁And Z₂Independently selected from one of trimethylsilylmethyl, bis (trimethylsilyl) methyl, tris (trimethylsilyl) methyl, o- (N, N-dimethylamino) benzyl, N-bis (trimethylsilyl) amino; or D is one of tetrahydrofuran, diethyl ether, thiophene, pyridine, pyrrole and triphenylphosphine.

3. A rare earth catalyst composition characterized by comprising the rare earth catalyst according to claim 1 or 2 as a main catalyst, and further comprising a co-catalyst and a chain transfer agent.

4. The rare earth catalyst composition of claim 3, wherein the promoter is selected from at least one of the following formulas III and IV:

formula III: [ EH]⁺[BA₄]^-、[E]⁺[BA₄]^-Or BA₃Wherein E is neutral or cationic Lewis acid containing nitrogen or carbon, B is boron element, H is hydrogen element, A is selected from aryl or halogenated aryl of C6-C30, alkyl or halogenated alkyl of C1-C10;

formula IV: - [ Al (R)⁵)O]_n ^-Wherein Al is aluminum element, R⁵Is C1-C20 alkyl or C1-C20 haloalkyl, O is oxygen, and n is an integer greater than or equal to 2.

5. The rare earth catalyst composition as claimed in claim 4, wherein the formula III is one selected from triphenyl (methyl) -tetrakis (pentafluorobenzene) borate, phenyl-dimethylamino-tetraphenylborate, tris (pentafluorobenzene) boron, triphenylboron; the formula IV is selected from chain aluminoxane or cyclic aluminoxane containing repeating units.

6. The rare earth catalyst composition of claim 5, wherein the formula IV is selected from methylaluminoxane MAO or modified methylaluminoxane MMAO.

7. The rare earth catalyst composition of claim 3, wherein the chain transfer agent has the structure of formula V:

formula V: al (R)⁶)(R⁷)(R⁸) Wherein Al is aluminum element, R⁶、R⁷、R⁸The same or different, is independently selected from hydrogen, halogen, alkyl of C1-C10 or halogenated alkyl of C1-C10.

8. The rare earth catalyst composition as claimed in claim 7, wherein the chain transfer agent is at least one selected from the group consisting of trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, triisopropylaluminum, triisobutylaluminum, trihexylaluminum, tricyclohexylaluminum, and diisobutylaluminum hydride.

9. The rare earth catalyst composition as set forth in claim 4, wherein the molar ratio of the formula III to the procatalyst is from 0.1/1 to 10/1; the molar ratio of the formula IV to the procatalyst is from 10/1 to 1000/1; the molar ratio of the chain transfer agent to the procatalyst is from 10/1 to 10000/1.

10. A method for preparing a rare earth catalyst, comprising: reacting a compound of formula II with compound LnZ₁Z₂Z₃Carrying out acid-base reaction in an organic solvent to obtain a rare earth catalyst shown in a formula VI;

wherein Ln is a group IIIB transition metal element;

Z₁、Z₂identical or different, independently a substituent of Ln, Z₃And Z₁、Z₂Identical or different, are substituents;

d is a neutral ligand coordinated with Ln, and n is an integer greater than or equal to 0;

R¹、R²、R³、R⁴the same or different, and is independently selected from hydrogen, C1-C10 alkyl, C6-C30 aryl.

11. The method for preparing a rare earth catalyst according to claim 10, wherein the organic solvent is at least one of toluene, hexane, diethyl ether, and tetrahydrofuran; the temperature of the acid-base reaction is 0-60 ℃.

12. Use of the rare earth catalyst composition of any of claims 3-9 in olefin polymerization.

Background

The catalyst system for olefin rubber is the key of the olefin rubber production technology (Zingiber officinale, rare earth cis-butadiene rubber, metallurgy industry publishers, 2016, 39), wherein the cis-1, 4 content of the olefin rubber product prepared by adopting a Ziegler-Natta catalyst system of titanium, cobalt, nickel and rare earth can reach more than 95%. Among the catalytic systems, the rare earth catalyst is the most distinctive variety with excellent comprehensive performance, and the olefin rubber produced by the rare earth catalyst has high cis-structure content, high linear structure regularity, high molecular weight and narrow distribution.

The Changchun acclimatization institute of Chinese academy of sciences in 1970 successfully developed a ternary catalytic system of rare earth carboxylate, alkylaluminum and alkylaluminum chloride for preparing high cis-polybutadiene rubber (rare earth catalytic synthetic rubber article [ C ]. scientific Press, 1980, 25). In the 80 s of the 20 th century, Bayer AG (At 133rd meeting of the Rubber Division of ACS, 1988, 4, 19; At 133rd meeting of the Rubber Division of ACS, 1988, 10, 18) in Germany and Enichem AG (Kautschuk Gummi Kunststiffe, 1993, 6, 458) in Italy realized the industrialization of rare earth polybutadiene Rubber successively. The rare earth catalysts currently used in industry are mainly ternary neodymium catalysts, and the core technology thereof is mainly mastered by Lanxess company in Germany (EP2311889, EP2363303, EP2676968, EP3057998, CN102574955, CN102762613, CN104395351 and CN107254008) and by the research groups of Changchun nationality institute (CN01128284, CN01128287, US7288611, CN01128289, CN03127180 and CN 200610016949).

Currently, the research on single-site rare earth metal catalysts with specific structures for the directional polymerization of conjugated dienes has been well developed, which are characterized by high activity and narrow molecular weight distribution in the catalytic diene polymerization reaction (J. Organomet. chem., 2001, 621, 327; Macromol. chem. Phys., 2003, 204, 1747; Macromol. chem. Phys., 2004, 205, 737; Angel. chem., 2005, 117, 2649; Angel. chem. Ed., 2005, 44, 2593; Macromolecules1999, 32, 9078; Macromolecules 2001, 34, 1539; Macromolecules 2003, 36, 7923; Macromolecules 2004, 37, 5860; Macromolecules 2006, 39, 1359-3; Dalton. Trans, 2531; Angel. chem. 2007, 19024, 2007, 13660; Morel. Ed. 130, 130. It et al., CN.35, published by Sophor.

However, the current catalysts have the defects that most homogeneous single-center rare earth metal catalysts need to be cationized by expensive borate reagents; kaita uses MMAO to replace borate reagent in indenyl rare earth catalyst, but the activity is still low, and the industrial application condition is not met; in addition, the stereoregularity of the polymerization reaction is greatly affected by temperature, and the cis-1, 4 content under high temperature conditions is not easily controlled (CN104379613B, CN104995217B, US2008114136a1, CN 106661140B). In view of this, the search for homogeneous single-site rare earth metal catalyst systems with more controllable polymerization activity and stereoregularity and the reduction of cocatalyst cost are the key to the realization of industrial applications of these catalysts.

Disclosure of Invention

The invention mainly aims to provide a rare earth catalyst, a preparation method thereof, a rare earth catalyst composition containing the rare earth catalyst and application of the rare earth catalyst composition, so as to overcome the defects of poor polymerization activity of a homogeneous single-center rare earth metal catalyst and stereo regularity of the obtained polymer or high cost of a cocatalyst in the prior art.

In order to achieve the above object, the present invention provides a rare earth catalyst having the following structure of formula I:

wherein Ln is a group IIIB transition metal element;

Z₁and Z₂Identical or different, independently is a substituent of Ln;

d is a neutral ligand coordinated with Ln, and n is an integer greater than or equal to 0;

l is a group formed by a compound of formula II:

wherein R is¹、R²、R³、R⁴The same or different, and is independently selected from hydrogen, C1-C10 alkyl, C6-C30 aryl.

In the rare earth catalyst, Ln is one of scandium, yttrium and lanthanide rare earth elements; or Z₁And Z₂Independently selected from one of trimethylsilylmethyl, bis (trimethylsilyl) methyl, tris (trimethylsilyl) methyl, o- (N, N-dimethylamino) benzyl, N-bis (trimethylsilyl) amino; or D is one of tetrahydrofuran, diethyl ether, thiophene, pyridine, pyrrole and triphenylphosphine.

In order to achieve the purpose, the invention also provides a rare earth catalyst composition, which takes the rare earth catalyst as a main catalyst and also comprises a cocatalyst and a chain transfer reagent.

The rare earth catalyst composition of the invention, wherein the cocatalyst is selected from at least one of the following formulas III and IV:

formula III: [ EH]⁺[BA₄]^-、[E]⁺[BA₄]^-Or BA₃Wherein E is neutral or cationic Lewis acid containing nitrogen or carbon, B is boron element, H is hydrogen element, and A is selected from aryl of C6-C30Or a haloaryl, C1-C10 alkyl or haloalkyl;

formula IV: - [ Al (R)⁵)O]_n ^-Wherein Al is aluminum element, R⁵Is C1-C20 alkyl or halogenated alkyl, O is oxygen element, and n is an integer greater than or equal to 2.

The rare earth catalyst composition of the invention, wherein the formula III is one selected from triphenyl (methyl) -tetra (pentafluorobenzene) borate, phenyl-dimethylamino-tetraphenylborate, tris (pentafluorobenzene) boron and triphenylboron; the formula IV is selected from chain aluminoxane or cyclic aluminoxane containing repeating units.

The rare earth catalyst composition of the present invention, wherein the formula IV is selected from methylaluminoxane MAO or modified methylaluminoxane MMAO.

The rare earth catalyst composition of the invention, wherein the chain transfer agent has the following structure V:

formula V: al (R)⁶)(R⁷)(R⁸) Wherein A1 is aluminum element, R⁶、R⁷、R⁸The same or different, are independently selected from hydrogen, halogen, alkyl or halogenated alkyl of C1-C10.

The rare earth catalyst composition of the present invention, wherein the chain transfer agent is at least one selected from trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, triisopropylaluminum, triisobutylaluminum, trihexylaluminum, tricyclohexylaluminum, and diisobutylaluminum hydride.

The rare earth catalyst composition of the invention, wherein the molar ratio of the formula III to the main catalyst is 0.1/1 to 10/1; the molar ratio of the formula IV to the procatalyst is from 10/1 to 1000/1; the molar ratio of the chain transfer agent to the procatalyst is from 10/1 to 10000/1.

In order to achieve the above object, the present invention further provides a method for preparing a rare earth catalyst, comprising: reacting a compound of formula II with compound LnZ₁Z₂Z₃Carrying out acid-base reaction in an organic solvent to obtain a rare earth catalyst shown in a formula VI;

wherein Ln is a group IIIB transition metal element;

Z₁、Z₂identical or different, independently a substituent of Ln, Z₃And Z₁、Z₂Identical or different, are substituents;

d is a neutral ligand coordinated with Ln, and n is an integer greater than or equal to 0;

R¹、R²、R³、R⁴the same or different, and is independently selected from hydrogen, C1-C10 alkyl, C6-C30 aryl.

The preparation method of the rare earth catalyst comprises the following steps of (1) preparing an organic solvent, wherein the organic solvent is at least one of toluene, hexane, diethyl ether and tetrahydrofuran; the temperature of the acid-base reaction is 0-60 ℃.

In order to achieve the above object, the present invention further provides the use of the above rare earth catalyst composition in olefin polymerization.

The invention has the beneficial effects that:

the rare earth catalyst composition can be used for preparing conjugated diene polymers, and is a homogeneous solution polymerization process; compared with the mononuclear rare earth catalyst in the prior art, the rare earth catalyst composition has higher catalytic activity, and the obtained olefin polymer has higher stereoregularity.

Detailed Description

The following examples of the present invention are described in detail, and the present invention is carried out on the premise of the technical scheme of the present invention, and detailed embodiments and procedures are given, but the scope of the present invention is not limited to the following examples, and the following examples are experimental methods without specific conditions noted, and generally follow conventional conditions.

The invention relates to a rare earth catalyst, which is a rare earth metal compound stabilized by a monovalent anion ligand and has the following structure of formula I:

wherein Ln is a group IIIB transition metal element;

Z₁and Z₂Identical or different, independently is a substituent of Ln;

d is a neutral ligand coordinated with Ln, and n is an integer greater than or equal to 0;

l is a group formed by a compound of formula II:

for example, L is

Wherein R is¹、R²、R³、R⁴The same or different, are independently selected from hydrogen, C1-C10 alkyl, C6-C30 aryl and derivatives thereof.

The short transverse line "-" of the formula I in the invention only represents the connection between groups, and does not refer to a single bond, for example, the connection relationship between the groups can be single bond connection, coordination connection and the like, and can also be a combination of single bond connection and coordination connection and the like.

In one embodiment, Ln is selected from at least one of scandium, yttrium, lanthanide rare earth elements; in another embodiment, Ln is selected from at least one of Y, Gd.

In one embodiment, Z₁And Z₂Examples of the hetero atom include silicon and nitrogen. In another embodiment, Z₁And Z₂Independently selected from one of trimethylsilylmethyl, bis (trimethylsilyl) methyl, tris (trimethylsilyl) methyl, o- (N, N-dimethylamino) benzyl, N-bis (trimethylsilyl) amino; in yet another embodiment, Z₁And Z₂Is o- (N, N-dimethylamino) benzyl.

In one embodiment, D is one selected from tetrahydrofuran, diethyl ether, thiophene, pyridine, pyrrole and triphenylphosphine, and n is an integer greater than or equal to 0; in another embodiment, D is tetrahydrofuran.

In one embodiment, the rare earth catalyst of the present invention has the following structure VI:

the meaning of each symbol is described in detail above, and is not described herein again. In the formula, the dash "-" represents a single bond linkage, and the arrow indicates a coordinate linkage.

The invention also provides a preparation method of the rare earth catalyst, which comprises the following steps: reacting a compound of formula II with compound LnZ₁Z₂Z₃Carrying out acid-base reaction in an organic solvent to obtain a rare earth catalyst shown in a formula VI;

wherein Ln is a group IIIB transition metal element;

Z₁、Z₂identical or different, independently a substituent of Ln, Z₃And Z₁、Z₂Identical or different, are substituents;

d is a neutral ligand coordinated with Ln, and n is an integer greater than or equal to 0;

R₁、R₂、R₃、R₄the same or different, and is independently selected from hydrogen, C1-C10 alkyl, C6-C30 aryl.

In the above reaction formulae, the meanings of the symbols are the same as above, and are not described herein again. Wherein Z is₁、Z₂And Z₃Same or different, in one embodiment, Z₁、Z₂And Z₃And may independently be an alkyl substituent or a substituted amine group containing a heteroatom such as silicon, nitrogen, or the like. In another implementationIn the mode (Z)₁、Z₂And Z₃Independently selected from one of trimethylsilylmethyl, bis (trimethylsilyl) methyl, tris (trimethylsilyl) methyl, o- (N, N-dimethylamino) benzyl, N-bis (trimethylsilyl) amino; in yet another embodiment, Z₁、Z₂And Z₃Is o- (N, N-dimethylamino) benzyl.

In detail, the preparation method of the rare earth catalyst comprises the following steps: the rare earth metal complex is prepared through acid-base reaction between univalent anion ligand and homoleptic trisubstituted rare earth metal compound. The reaction temperature can be selected from 0-60 ℃, preferably 25-40 ℃, and the reaction temperature is preferably selected according to different types of substituent groups and rare earth metals; the reaction solvent can be selected from toluene, hexane, diethyl ether, tetrahydrofuran, preferably toluene.

The invention also provides a rare earth catalyst composition, which takes the rare earth catalyst as a main catalyst and also comprises a cocatalyst and a chain transfer reagent.

In one embodiment, the cocatalyst is selected from at least one of the following formulas III and IV:

formula III: [ EH]⁺[BA₄]^-、[E]⁺[BA₄]^-Or BA₃Wherein E is neutral or cationic Lewis acid containing nitrogen or carbon, B is boron element, H is hydrogen element, A is selected from aryl or halogenated aryl of C6-C30, alkyl or halogenated alkyl of C1-C10;

formula IV: - [ Al (R)⁵)O]_n ^-Wherein Al is aluminum element, R⁵Is C1-C20 alkyl or halogenated alkyl, O is oxygen element, and n is an integer greater than or equal to 2.

In another embodiment, the compound of formula III is selected from one of triphenyl (methyl) -tetrakis (pentafluorobenzene) boron salt, phenyl-dimethylamino-tetraphenylboron salt, tris (pentafluorobenzene) boron salt, triphenyl boron salt; further preferred is phenyl-dimethylamino-tetraphenylboron salt; the compound of formula IV is selected from a chain aluminoxane or a cyclic aluminoxane containing repeating units. In yet another embodiment, the compound of formula IV is selected from methylaluminoxane MAO or modified methylaluminoxane MMAO; further preferred is Modified Methylaluminoxane (MMAO).

In one embodiment, the chain transfer reagent has the following structure of formula V:

formula V: al (R)⁶)(R⁷)(R⁸) Wherein Al is aluminum element, R⁶、R⁷、R⁸The same or different, is independently selected from hydrogen, halogen, alkyl of C1-C10 or halogenated alkyl of C1-C10.

In another embodiment, the chain transfer agent is selected from at least one of trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, triisopropylaluminum, triisobutylaluminum, trihexylaluminum, tricyclohexylaluminum, diisobutylaluminum hydride; further preferred is diisobutylaluminum hydride.

In one embodiment, the rare earth catalyst composition of the present invention has a molar ratio of formula III to the procatalyst of 0.1/1 to 10/1, more preferably 1.0/1 to 2.0/1; the molar ratio of formula IV to the procatalyst is from 10/1 to 1000/1, more preferably from 20/1 to 40/1.

In one embodiment, the molar ratio of the chain transfer reagent of the present invention to the procatalyst is from 10/1 to 10000/1, more preferably from 10/1 to 1000/1. The chain transfer agent is mainly used as a polymer chain transfer agent, and the dosage of the chain transfer agent has great influence on the molecular weight of a polymer. In addition, the chain transfer reagent is also used as a main impurity removal reagent to react with impurities in the polymerized monomers for impurity removal. Therefore, when the molar ratio of the chain transfer agent/the main catalyst is in the above range, the problem of partial deactivation of the catalyst due to incomplete removal of impurities from the polymerized monomer can be avoided; the polymer molecular weight distribution can also be controlled within a suitable range. In one embodiment, the chain transfer agent of the present invention may be added to the reaction system in advance to be mixed with the polymerization monomer.

The rare earth catalyst composition can be used for preparing conjugated diene polymers, and is a homogeneous solution polymerization process; compared with the mononuclear rare earth catalyst in the prior art, the rare earth catalyst composition has higher catalytic activity, and the obtained olefin polymer has higher stereoregularity.

In the present invention, rare earth metal precursor compound LnZ₁Z₂Z₃(e.g. rare earth tribenzyl compound Ln (CH)₂C₆H₄NMe₂-o)₃) The synthesis of (c) can be performed as described in reference (chem. eur. j.2008, 14, 2167-2179). The synthesis of the rare earth catalyst and the catalytic olefin polymerization reaction are carried out under the anhydrous and oxygen-free conditions unless specially stated, and are realized by an inert gas glove box or a Schlenk technology. All solvents used in the experiment are subjected to anhydrous and anaerobic treatment.

Furthermore, nuclear magnetic resonance of rare earth catalysts¹H-NMR spectrum is tested by Bruker Ascend 600MHz, and part of complexes cannot be tested due to paramagnetic property¹And H-NMR characterization. Cis-1, 4 selective passage of polymers¹³C-NMR spectrum determination is carried out, and an inverse gating decoupling mode is adopted; the molecular weight and molecular weight distribution of the polymer were measured by PL-GPC50 gel permeation chromatography.

The technical solution of the present invention will be further illustrated by the following specific examples.

Example 1

Preparation of the procatalyst 1

At room temperature, a toluene solution of NNN ligand (1.00g, Fw ═ 503.24, 2mmol) was slowly added to a toluene solution of Y tribenzyl compound (0.98g, Fw ═ 491.20, 2mmol), the reaction was continued at room temperature for 24 hours, the toluene solvent was drained, and 20mL of hexane solvent was added to wash the mixture, and the obtained pale yellow powdery solid was rare earth metal complex 1 (main catalyst 1), with a yield of 1.43g and a yield of 83%, and characterized by NMR.

Nuclear magnetic data:¹H-NMR(600MHz，C6D6)：1.87(s，4H，Y-CH₂)，2.37(s，12H，N-Me)，2.56(s，6H，N-Me)，6.53(m，2H，Ar-H)，6.61(m，2H，Ar-H)，6.73(m，2H，Ar-H)，6.85(m，4H，Ar-H)，7.01(m，4H，Ar-H)，7.07(m，2H，Ar-H)，7.30(m，5H，Ar-H)，8.31(s，1H，N＝CH).

examples 2 to 6

Synthesis of the complexes shown in examples 2 to 6 referring to the synthesis of the main catalyst 1, the rare earth central metals in the raw materials are respectively replaced by La, Pr, Nd, Sm and Gd, the experimental procedures are consistent, the obtained products are respectively light yellow (La), dark green (Pr), purple (Nd), brown black (Sm) and light yellow (Gd) powder solids, and the yield is 70 to 85 percent; due to the paramagnetic characteristics of the +3 La, Pr, Nd, Sm, Gd compounds, NMR characterization could not be performed.

Examples 7 to 11

Synthesis of Main catalyst shown in examples 7 to 11 referring to the synthesis of the Main catalyst 1, the alkyl group in the rare earth trialkyl compound in the raw material is changed to-CH₂SiMe₃And replacement of the substituent R¹-R⁴(ii) a NMR characterization was not possible due to the paramagnetic nature of the +3 valent Gd compound.

Example 12

Evaluation of catalyst polymerization:

in an inert gas glove box, 14.4g (2.16g, 40mmol) of a hexane solution (mass fraction 15%) of 1, 3-butadiene was weighed in a 100mL round-bottomed flask, 0.2mL (1M, 0.2mmol) of a hexane solution of triisobutylaluminum was added, and stirred at room temperature for 30min, and a toluene solution of rare earth metal complex 1(0.02mmol) of example 1 and [ PhNHMe were added to the polymerization solution₂][B(C₆F₅)₄]A toluene suspension of (2). After polymerization at room temperature for 45min, the polymerization system became viscous and the polymerized monomers were completely consumed. After the polymerization was completed, the reaction flask was taken out of the inert gas glove box, anhydrous methanol was slowly added with stirring until the polymer was completely precipitated, 0.02g (1% by mass of the polymer) of BHT antioxidant was added, and the polymer was washed with anhydrous methanolThe mixture was dried 3 times in a vacuum oven at 70 ℃ for 5 hours and weighed.

The polymerization results are shown in Table 1.

Examples 13 to 22

Evaluation of catalyst polymerization:

butadiene polymerization was performed according to the same method as in example 12, except that the rare earth metal complexes of examples 2 to 11 were used in order.

The polymerization results are shown in Table 1.

TABLE 1 polymerization results of examples 12-22

Description of the drawings: (1) [ B ]]_N＝[PhNHMe₂][B(C₆F₅)₄]，[B]_N/[Ln]The ratio is a molar ratio, and the ratios in table 1 are all molar ratios.

Among them, the catalyst in example 13 has no catalytic activity and may have too large a central ionic radius of the contained metal La.

Examples 23 to 29

Butadiene polymerization was carried out in the same manner as in example 17 except that the molar ratio of 1, 3-butadiene monomer to the catalyst site metal was changed, and the amount of triisobutylaluminum used was adjusted, and the specific amount and polymerization results are shown in Table 2.

Table 2 polymerization results of examples 23 to 29

Description of the drawings: (1) [ B ]]_N＝[PhNHMe₂][B(C₆F₅)₄]，[B]_N/[Ln]The ratio is a molar ratio, and the ratios in table 2 are all molar ratios.

As shown in table 2, when Gd is the central metal and borate is used as the co-catalyst, the catalyst system showed very high catalytic activity, and the molecular weight was adjusted by changing the amount of triisobutylaluminum, and the molecular weight distribution was narrow. When the molar ratio of the 1, 3-butadiene monomer to the catalyst-center metal is relatively high, a series of problems such as thickening of the system results in a decrease in the conversion per unit Time (TOF).

Examples 30 to 37

Ethylene polymerization was carried out in the same manner as in example 12, using as the main catalyst a rare earth complex 6 whose central metal was Gd, except that the molar ratio of 1, 3-butadiene monomer to the catalyst central metal was different, using triisobutylaluminum or diisobutylaluminum hydride as the chain transfer agent, the amount being adjusted depending on the molar ratio of 1, 3-butadiene monomer to the catalyst central metal; in addition, the cocatalyst species were also adjusted from the borate reagent to Methylaluminoxane (MAO) or Modified Methylaluminoxane (MMAO), and the polymerization results are shown in Table 3.

Table 3 examples 30-37 polymerization results

Description of the drawings: (1) MMAO/[ Ln ] is 20, the ratio is a molar ratio, and the ratios in table 3 are all molar ratios.

As shown in Table 3, when the cocatalyst is MMAO replaced by borate reagent, the catalytic activity of the rare earth catalyst system is greatly improved, and the cis-1, 4 selectivity is still maintained above 98%; however, when triisobutylaluminum is used as a chain transfer agent, the chain transfer effect is not good and the molecular weight is too high. When diisobutylaluminum hydride is used as the chain transfer agent, the chain transfer effect is obviously improved, and the molecular weight is reduced more quickly.

Comparative examples 1 to 2

Comparative examples 1-2 according to the technical scheme of CN201580044464, Gd [ N (SiMe) is used as a rare earth metal catalyst₃)₂]₃The polymerization results of + 3-benzylidene, MMAO and TMAO as co-catalysts, and alkylaluminum as a chain transfer agent are shown in Table 4. The system requires higher MMAO amounts (500 molar ratio to rare earth) than the rare earth catalyst system of the present invention, andthe activity was also lower.

TABLE 4 polymerization results of comparative examples 1 and 2

As described above, the present invention provides a rare earth catalyst, a method for preparing the same, a rare earth catalyst composition comprising the same, and applications thereof. Compared with the mononuclear rare earth catalyst in the prior art, the rare earth catalyst composition has higher catalytic activity, and the obtained olefin polymer has higher stereoregularity.

The present invention is capable of other embodiments, and various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.