Composite catalyst and application thereof

Abstract

The invention belongs to the field of polymer synthesis, and particularly discloses a composite catalyst and application thereof. The composite catalyst comprises a main catalyst and a cocatalyst, the chemical formula of the main catalyst is RTiX3, and R is acenaphthenyl and acenaphthenyl containing substituent groups; x is independently selected from any one of a halogen atom, a C1-8 alkyl group, a C2-8 alkenyl group, a C3-8 alkene alkyl group, a C1-8 alkoxy group, an aryl group, a C7-10 aralkyl group and a C7-10 alkaryl group; the co-catalyst comprises an aluminum alkyl catalyst and a silane catalyst. The composite catalyst provided by the invention can significantly improve the conversion rate of styrene, replaces a conventional catalyst system with high aluminum content, and reduces the aluminum content in a styrene polymerization product; the purposes of greatly improving the production efficiency and reducing the production cost are achieved by the post-treatment process of aluminum removal and purification without further solution washing of the styrene polymerization product.

Description

Technical Field

[0001] The invention belongs to the field of polymer synthesis, and in particular relates to a composite catalyst and application thereof. Background Art

[0002] Syndiotactic polystyrene (sPS) is a type of polystyrene that has the good chemical inertness, excellent electrical insulation and moisture resistance of general-purpose polystyrene. Unlike general-purpose polystyrene, the molecular chain configuration of syndiotactic polystyrene is syndiotactic, and the side groups (benzene rings) in the structural unit are arranged alternately on both sides of the macromolecular chain. Since syndiotactic polystyrene has high stereoregularity and strong crystallization ability, syndiotactic polystyrene is a crystallizable polymer with a crystalline melting point of about 270°C. The highly crystalline aggregate structure gives syndiotactic polystyrene good heat resistance and corrosion resistance, making its performance comparable to thermoplastic engineering plastics such as nylon, polyester, and polyphenylene sulfide, making it a cost-effective engineering plastic.

[0003] At present, the largest application areas of sPS are automotive connectors, high-frequency communication electronics and other products. There are high requirements for the dielectric properties and electrical insulation of materials. Due to the shielding and interference effect of metal on signals, such products require that the metal content in the materials must be very low. However, the mainstream synthesis process of sPS requires the addition of a large amount of aluminum-containing catalyst to obtain high polymerization activity. In general processes, the use of a main catalyst or a co-catalyst alone has basically no catalytic activity. Only when the main catalyst and the co-catalyst cooperate with each other can they exert good catalytic activity. In particular, the synthesis of syndiotactic polystyrene currently usually requires an alkyl aluminum catalyst that is several hundred times more than the main catalyst as a co-catalyst to assist the main catalyst in producing high activity. The large-scale use of alkyl aluminum will not only greatly increase the cost of raw materials, but also cause more aluminum metal elements to remain in the product, affecting the excellent electrical properties of syndiotactic polystyrene materials in the fields of high-frequency communication electronics and electrical. Although the polymer product can be dealuminated by solution washing, this usually requires the use of an organic solution containing a strong acid or a strong base. On the one hand, such organic solvents will cause corrosion to the equipment. On the other hand, the organic solution containing waste acid and waste alkali produced by production is also difficult to be treated and regenerated in an environmentally friendly manner, greatly increasing the production cost.

[0004] Therefore, in order to produce syndiotactic polystyrene using a low-cost non-washing process, it is necessary to find a way to solve the problem of excessively high demand for aluminum co-catalyst in the catalyst formulation. Summary of the invention

[0005] In view of the problem that in the process of synthesizing syndiotactic polystyrene involved in the above-mentioned prior art, the residual aluminum element in the product is too high due to the high amount of aluminum co-catalyst contained in the catalyst system, the present invention will provide a composite catalyst and its application.

[0006] To achieve the above purpose, the following technical solutions are specifically included:

[0007] In a first aspect, the present invention provides a composite catalyst, the composite catalyst comprising a main catalyst and a co-catalyst, the chemical formula of the main catalyst is RTiX 3 , wherein R is acenaphthenyl and acenaphthenyl containing a substituent; X is independently selected from halogen atoms, C 1-8 Alkyl, C 2-8 Alkenyl, C 3-8 Alkenyl, C 1-8 Alkoxy, aryl, C 7-10 Aralkyl, C 7-10 Any one of the alkylaryl groups; the co-catalyst includes alkyl aluminum catalysts and silane catalysts.

[0008] In the composite catalyst of the present invention, RTiX 3 The main catalyst and the two co-catalysts, the alkyl aluminum catalyst and the silane catalyst, cooperate with each other and have high catalytic styrene polymerization activity, which can significantly improve the conversion rate of styrene, can replace the conventional catalyst system with high aluminum content, reduce the aluminum content in the styrene polymerization product, and achieve the purpose of aluminum removal and purification process of the styrene polymerization product without further solution washing, greatly improve production efficiency and reduce production costs.

[0009] Specifically, the halogen atom is F, Cl or Br; 1-8 The alkyl group includes methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl or octyl; the C 2-8 Alkenyl includes but is not limited to ethenyl, propenyl or butenyl; the C 3-8 Alkenyl includes but is not limited to allyl, butyl or pentyl; the C 1-8 The alkoxy group includes but is not limited to methoxy, ethoxy or propoxy; the aryl group includes but is not limited to phenyl; the C 7-10 Aralkyl includes but is not limited to benzyl, phenethyl or phenylpropyl; the C 7-10 Alkaryl groups include, but are not limited to, 4-methyl-phenyl, 4-ethyl-phenyl or 4-propyl-phenyl.

[0010] Preferably, the substituents in the acenaphthene group containing a substituent include C 1-8 Alkyl, C 1-8 One of the alkoxy groups.

[0011] It should be understood that the “C 1-8 " means that the number of carbon atoms is any integer between 1 and 8; "C 2-8 " refers to any integer between 2 and 8 carbon atoms; "C 3-8" refers to any integer between 3 and 8 carbon atoms; "C 7-10 ” refers to any integer between 7 and 10 carbon atoms.

[0012] Preferably, the main catalyst comprises at least one of the following compounds:

[0013]

[0014] Preferably, the preparation method of the main catalyst comprises the following steps:

[0015] (1) adding acenaphthene or an acenaphthene compound containing a substituent and potassium bis(trimethylsilyl)amide to a solvent, reacting at 50 to 70° C. for 7 to 9 hours; then adding trimethylsilyl chloride, reacting at room temperature for 1 to 3 hours; then adding titanium tetrachloride, and reacting at room temperature for another 1 to 3 hours to obtain an intermediate product;

[0016] (2) mixing the intermediate product, solvent and X-ONa, and reacting them at 70-90° C. for 5-7 hours to obtain the main catalyst; X in X-ONa and the chemical formula of the main catalyst RTiX 3 The X in is the same.

[0017] Further preferably, in step (1), the room temperature is 20-30°C.

[0018] Further preferably, in step (1), the molar ratio of acenaphthene or acenaphthene-based compound containing a substituent, potassium bis(trimethylsilyl)amide, trimethylchlorosilane and titanium tetrachloride is acenaphthene or acenaphthene-based compound containing a substituent: potassium bis(trimethylsilyl)amide: trimethylchlorosilane: titanium tetrachloride = 1: (0.9-1.2): (0.9-1.2): (0.9-1.2).

[0019] Further preferably, in step (1), the solvent comprises tetrahydrofuran.

[0020] Further preferably, in step (1), the amount of acenaphthene or the acenaphthene-based compound containing a substituent is 1 mmol of acenaphthene or the acenaphthene-based compound containing a substituent in 2-10 mL of solvent.

[0021] Further preferably, in steps (1)-(2), the molar ratio of the acenaphthene or the acenaphthene-based compound containing a substituent to the X-ONa is 1:(0.9-1.2).

[0022] Further preferably, in step (2), the solvent comprises toluene.

[0023] Further preferably, in step (1), the amount of X-ONa used is 1 mmol X-ONa in 2-10 mL of solvent.

[0024] Preferably, the molar ratio of the main catalyst to the alkyl aluminum catalyst is 1: (1-10), specifically 1: 1, 1: 2, 1: 3, 1: 4, 1: 5, 1: 6, 1: 7, 1: 8, 1: 9, 1: 10, etc., as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range. In conventional styrene polymerization catalyst systems, the amount of aluminum-containing co-catalysts must reach several hundred times that of the main catalyst to effectively catalyze styrene polymerization. In the composite catalyst system of the present invention, the amount of alkyl aluminum catalysts can be selected to be only 1 to 10 times that of the main catalyst. On the basis of higher catalytic activity, the amount of aluminum-containing co-catalysts is significantly lower than that of conventional catalyst systems, greatly reducing the amount of alkyl aluminum catalysts, not only reducing the cost of raw materials, but also catalyzing styrene polymerization The effect is better than that of conventional catalyst systems, and the product contains less aluminum.

[0025] Preferably, the alkyl aluminum catalyst includes at least one of triethyl aluminum, tripropyl aluminum, triisobutyl aluminum, diisobutyl aluminum hydride, methyl aluminoxane, and modified methyl aluminoxane.

[0026] Preferably, the molar ratio of the main catalyst to the silane catalyst is 1:(50-200), specifically 1:50, 1:75, 1:100, 1:125, 1:150, 1:175, 1:200, etc., as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range. The composite catalyst of the present invention contains a silane catalyst, which can assist the main catalyst with an alkyl aluminum catalyst to improve the catalytic activity of the system, further reducing the amount of aluminum-containing co-catalyst in the system. Under the above-mentioned amount, the catalytic activity in the system is better.

[0027] Preferably, the silane catalyst includes at least one of phenylsilane, trimethylsilane, triethylsilane, trimethylchlorosilane, hexamethyldisilazane, tert-butyldimethylchlorosilane, triisopropoxysilane, trimethylhydroxyethylsilane, and methyldiphenylhydroxyethylsilane.

[0028] In a second aspect, the present invention provides an application of the composite catalyst in synthesizing syndiotactic polystyrene.

[0029] Preferably, the composite catalyst contains 3×10 -3 ~10×10 -3 mmol of main catalyst.

[0030] Preferably, the number average molecular weight of the syndiotactic polystyrene is 2×10 5 ~3×105 g / mol.

[0031] Preferably, the aluminum content in the syndiotactic polystyrene is ≤30 ppm.

[0032] In a third aspect, the present invention provides a method for synthesizing syndiotactic polystyrene, comprising the following steps:

[0033] Styrene, a solvent and the composite catalyst are added into a reactor to carry out a polymerization reaction to obtain the syndiotactic polystyrene.

[0034] The present invention adopts RTiX 3 As the main catalyst for synthesizing syndiotactic polystyrene, styrene is used as a monomer for homogeneous polymerization to synthesize syndiotactic polystyrene. On the basis of maintaining high catalytic activity, the amount of aluminum-containing additives added can be reduced to achieve the purpose of producing syndiotactic polystyrene with ultra-low aluminum content.

[0035] Preferably, the solvent is selected from at least one of toluene, xylene, ethylbenzene, n-hexane, cyclohexane, heptane, octane, tetrachloroethane and o-dichlorobenzene.

[0036] Preferably, the molar ratio of styrene to solvent is 1:(0.4-1), specifically 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, etc., as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0037] Preferably, the polymerization reaction temperature is 50-90°C, specifically 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, etc., as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0038] Preferably, the polymerization reaction time is 0.5 to 6 h, specifically 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, etc., as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0039] Compared with the prior art, the present invention has the following beneficial effects: the composite catalyst of the present invention can significantly improve the conversion rate of styrene, replace the conventional catalyst system with high aluminum content, reduce the aluminum content in the styrene polymerization product, realize the post-treatment process of aluminum removal and purification of the styrene polymerization product without further solution washing, greatly improve the production efficiency and reduce the production cost. DETAILED DESCRIPTION

[0040] In order to better illustrate the purpose, technical scheme and advantages of the present invention, the present invention will be further described below through specific examples. The test methods used in the examples and / or comparative examples are conventional methods unless otherwise specified; the materials, reagents, etc. used can be obtained from commercial channels unless otherwise specified.

[0041] Acenaphthene trimethyl titanium (denoted as A1#): homemade, the process is as follows:

[0042] In a glove box, 1mmol of acenaphthene and 1mmol of potassium bis(trimethylsilyl)amide were added to 5mL of tetrahydrofuran, and the mixture was stirred at 60°C for 8h. Then, 1mmol of trimethylsilyl chloride was added and stirred at room temperature for 2h. Then, 1mmol of titanium tetrachloride was added and stirred at room temperature for 2h to obtain a brown solid-liquid mixture. After filtering and removing the filtrate, the mixture was washed three times with tetrahydrofuran (5mL of tetrahydrofuran each time), and the solvent was drained under reduced pressure to obtain an intermediate product. 5mL of toluene and 1mmol of sodium methoxide were added to the intermediate product, and the mixture was reacted at 80°C for 6h. The solvent was drained, and the obtained yellow solid was washed three times with n-hexane (5mL of n-hexane each time), and then drained under reduced pressure to obtain a yellow powder, which is acenaphthene trimethyltitanium.

[0043] The NMR characterization results of acenaphthenyltrimethyltitanium are: δ = 7.70, 2H; δ = 7.51, 2H; δ = 7.39, 2H; δ = 3.45, 2H; δ = 1.20, 9H; elemental analysis target molecular formula C 15 H 20 Ti(%) = C: 72.61%, H: 8.05%. This indicates the successful synthesis of acenaphthene trimethyltitanium, whose chemical structure is as follows:

[0044]

[0045] Acenaphthene triallyl titanium (denoted as A2#): homemade, the process is as follows:

[0046] In a glove box, 1mmol of acenaphthene and 1mmol of potassium bis(trimethylsilyl)amide were added to 5mL of tetrahydrofuran, and the mixture was stirred at 60°C for 8h. Then, 1mmol of trimethylsilyl chloride was added and stirred at room temperature for 2h. Then, 1mmol of titanium tetrachloride was added and stirred at room temperature for 2h to obtain a brown solid-liquid mixture. After the solvent was drained, the mixture was washed three times with tetrahydrofuran (5mL of tetrahydrofuran each time), and the solvent was drained under reduced pressure to obtain an intermediate product. 5mL of toluene and 1mmol of sodium allyl alcohol were added to the intermediate product, and the mixture was reacted at 80°C for 6h. The solvent was drained again, and the obtained yellow solid was washed three times with n-hexane (5mL of n-hexane each time), and then drained under reduced pressure to obtain a yellow powder, which is acenaphthene triallyltitanium.

[0047] The NMR characterization results of acenaphthenyltriallyltitanium are: δ = 7.70, 2H; δ = 7.51, 2H; δ = 7.39, 2H; δ = 3.45, 2H; δ = 5.99, 3H; δ = 5.29, 3H; δ = 5.16, 3H; δ = 1.75, 6H; elemental analysis target molecular formula C 21 H 23 Ti(%) = C: 78.32%, H: 7.24%. This indicates the successful synthesis of acenaphthene triallyl titanium, and its chemical structure is as follows:

[0048]

[0049] Acenaphthenetribenzyltitanium (denoted as A3#): homemade, the process is as follows:

[0050] In a glove box, 1mmol of acenaphthene and 1mmol of potassium bis(trimethylsilyl)amide were added to 5mL of tetrahydrofuran, and the mixture was stirred at 60°C for 8h. Then, 1mmol of trimethylsilyl chloride was added and stirred at room temperature for 2h. Then, 1mmol of titanium tetrachloride was added and stirred at room temperature for 2h to obtain a brown solid-liquid mixture. After filtering and removing the filtrate, the mixture was washed three times with tetrahydrofuran (5mL of tetrahydrofuran each time), and the solvent was drained under reduced pressure to obtain an intermediate product. 5mL of toluene and 1mmol of sodium benzyl alcohol were added to the intermediate product, and the mixture was reacted at 80°C for 6h. The solvent was drained, and the yellow solid was washed three times with n-hexane (5mL of n-hexane each time), and then drained under reduced pressure to obtain a yellow powder, which is acenaphthenetribenzyltitanium.

[0051] The NMR characterization results of acenaphthenetribenzyltitanium are: δ = 7.70, 2H; δ = 7.51, 2H; δ = 7.39, 2H; δ = 3.45, 2H; δ = 7.20, 15H; δ = 2.40, 6H; elemental analysis target molecular formula C 33 H 29 Ti(%) = C: 83.25%, H: 6.12%. This indicates the successful synthesis of acenaphthenetribenzyltitanium, whose chemical structure is as follows:

[0052]

[0053] Methylaluminoxane (denoted as B1#), triisobutylaluminum (denoted as B2#), trimethylsilane (denoted as C1#), triethylsilane (denoted as C2#), phenylsilane (denoted as C3#) and pentamethylcyclopentadienyltrimethoxytitanium are all commercially available.

[0054] Example 1

[0055] A method for synthesizing syndiotactic polystyrene comprises the following steps:

[0056] (1) First, heat the reactor body at 100° C. by introducing heat transfer oil, evacuate the reactor body for 30 min, then introduce nitrogen to fill the cavity of the reactor body, evacuate the reactor body again, and repeat this process three times;

[0057] (2) Then, the reactor body was adjusted to the set reaction temperature (see Table 1), and styrene, toluene, 1 mL of methylaluminoxane toluene solution, 1 mL of trimethylsilane toluene solution, and 1 mL of acenaphthene trimethyltitanium toluene solution were added in sequence through the feed port according to the raw material dosage in Table 1, stirred for 1 min, and reacted for 1 h;

[0058] (2) After the reaction is completed, the temperature of the heat transfer oil in the jacket is maintained at 150° C. and vacuum devolatilization is performed for 1 hour. After the devolatilization is completed, the discharge valve at the bottom of the kettle is opened to obtain a dry product, namely, syndiotactic polystyrene.

[0059] Embodiments 2 to 12

[0060] The difference between Examples 2 to 12 and Example 1 lies in the differences in the raw materials and reaction temperatures, as shown in Table 1 in detail.

[0061] Comparative Example 1

[0062] The difference between this comparative example and Example 1 is that in this comparative example, the main catalyst A1# is replaced with an equimolar amount of pentamethylcyclopentadienyltrimethoxytitanium.

[0063] Comparative Example 2

[0064] The difference between this comparative example and Example 1 is that this comparative example does not use a silane catalyst, and the main catalyst A1# is replaced by an equal molar amount of pentamethylcyclopentadienyltrimethoxytitanium; the co-catalyst (C1#) is replaced by an equal molar amount of B2#.

[0065] Comparative Example 3

[0066] The difference between this comparative example and Example 1 is that this comparative example does not use a silane catalyst, and the main catalyst A1# is replaced by an equal molar amount of pentamethylcyclopentadienyltrimethoxytitanium; the co-catalyst (C1#) is replaced by an equal molar amount of B2#, and the amount of B1# is increased to 60 mmol, and the amount of B2# is increased to 60 mmol.

[0067] Table 1

[0068]

[0069]

[0070] Performance Testing:

[0071] The syndiotacticity, weight average molecular weight and number average molecular weight of the syndiotactic polystyrene obtained in each embodiment and comparative example were measured, and the styrene conversion rate, aluminum content and catalyst activity (catalyst activity refers to the mass of syndiotactic polystyrene generated per mole of catalyst) were calculated. The specific test method is as follows:

[0072] (1) The syndiotacticity was characterized by NMR carbon spectroscopy, the instrument model was Bruker DMX 500Hz, and the test sample was dissolved in deuterated o-dichlorobenzene. The chemical shift of the syndiotactic structure was 145.1-145.3 ppm, and the chemical shift of the random structure was 144.8-146.0 ppm. The syndiotacticity = syndiotactic structure peak area / (random structure + syndiotactic structure) peak area.

[0073] (2) Molecular weight: Characterized by gel permeation chromatography (GPC), instrument manufacturer Agilent, model PL-GPC 220, differential detector, chromatographic column using three PLgel 10um MIXED-B LS300*7.5mm in series, mobile phase: 1,2,4-trichlorobenzene, temperature: 150°C, flow rate: 1mL / min. The standard curve of the GPC test is determined by using polystyrene with a narrow molecular weight distribution as the standard sample, and the number average relative molecular weight (Mn) of the polymer is calculated. The sample syndiotactic polystyrene sample to be tested is dissolved in 1,2,4-trichlorobenzene to a concentration of 2-5mg / mL, and filtered through a 450nm organic filter to remove insoluble impurities.

[0074] (3) Monomer (styrene) conversion rate = polystyrene mass / styrene feed mass × 100%.

[0075] (4) Catalyst activity = product mass / molar amount of main catalyst.

[0076] (5) Aluminum content in syndiotactic polystyrene: The syndiotactic polystyrene product with a mass of m was decomposed by microwave digestion in an acidic aqueous solution with a volume of v (an acidic aqueous solution prepared by mixing 3 volumes of concentrated hydrochloric acid with a mass fraction of 36%-38% and 1 volume of concentrated nitric acid with a mass fraction of 65%-68%). The mass concentration c of aluminum in the acidic aqueous solution was then characterized by ICP-OES. In this way, the aluminum content in the product (ppm) = cv / m can be calculated.

[0077] The above test results are shown in Table 2.

[0078] Table 2

[0079]

[0080] The syndiotactic polystyrene of Examples 1 to 12 all had a syndiotactic degree of 100%, a styrene conversion rate of more than 75%, an aluminum content of ≤20 ppm, a number average molecular weight of syndiotactic polystyrene products of 200,000 to 278,000 g / mol, and a catalyst activity of up to 1.80×10 7 g sPS / mol Ti, indicating that the composite catalyst of the present invention has high activity and can obtain sPS products with low aluminum content.

[0081] The main catalyst used in Examples 1 to 12 is RTiX 3 , Comparative Example 1 uses the conventional main catalyst pentamethylcyclopentadienyl trimethoxytitanium. Although its catalyst content is the same as that of Example 1 of the present invention, the styrene conversion rate and catalytic activity of Comparative Example 1 are very low. It can be seen that compared with the conventional system using pentamethylcyclopentadienyl trimethoxytitanium as the main catalyst, the present invention uses RTiX 3 As the main catalyst for synthesizing syndiotactic polystyrene, it can significantly improve the activity and conversion rate of catalytic styrene conversion.

[0082] Comparative Examples 2 and 3 use pentamethylcyclopentadienyl trimethoxytitanium as the main catalyst and alkyl aluminum catalyst as the co-catalyst to form a conventional alkyl aluminum-metallocene catalyst system. Although the amount of the catalyst system in Comparative Example 2 is the same as that of Example 1 of the present invention, not only is the styrene conversion rate and catalytic activity low, but the aluminum content in the product is also high. According to the current prior art, the styrene conversion rate and catalytic activity can be improved by increasing the amount of the alkyl aluminum catalyst co-catalyst. If the content of the alkyl aluminum catalyst in Comparative Example 3 is about 3 times that in Example 1, the styrene conversion rate and catalytic activity can basically reach the actual production level, but this also causes the aluminum content of the catalyst system to increase sharply, resulting in the aluminum content in the product being as high as several hundred ppm.

[0083] It can be seen from Examples 1 to 12 and Comparative Examples 1 to 3 that the present invention uses RTiX 3 As the main catalyst for synthesizing syndiotactic polystyrene, the catalyst system of the present invention assists two co-catalysts to form a composite catalyst system. Compared with the conventional system using pentamethylcyclopentadienyltrimethoxytitanium as the main catalyst, the catalyst system of the present invention can not only significantly improve the activity and conversion rate of catalytic styrene conversion, but also significantly reduce the content of aluminum-containing catalysts in the catalyst system, thereby achieving the improvement of styrene conversion rate and catalytic activity under the condition of relatively low aluminum-containing co-catalysts, and can obtain an ultra-low aluminum-content syndiotactic polystyrene product with an aluminum content of ≤30ppm.

[0084] Examples 1 and 6-7 respectively use acenaphthenyl trimethyl titanium (A1#), acenaphthenyl triallyl titanium (A2#) and acenaphthenyl triphenyl titanium (A3#) as the main catalyst. As can be seen from Table 2, the catalytic activity of the polymerization reaction system is from high to low: acenaphthenyl triphenyl titanium (A3#), acenaphthenyl trimethyl titanium (A1#), and acenaphthenyl triallyl titanium (A2#).

[0085] The molar ratios of the main catalyst to the alkyl aluminum catalyst in Example 1 and Examples 11-12 are 1:5, 1:1, and 1:10, respectively. As the amount of the alkyl aluminum catalyst increases, the catalytic activity of the polymerization reaction system increases, but the aluminum content increases. Therefore, the molar ratio of the main catalyst to the alkyl aluminum catalyst is selected to be 1:(1-10), which can take into account both the higher catalytic activity of the system and the lower aluminum content of the product.

[0086] It can be seen from Examples 1 and 4, and Examples 8-10 that the two alkyl aluminum co-catalysts, methylaluminoxane (B1#) and triisobutylaluminum (B2#), have comparable effects in assisting the main catalyst to improve the catalytic activity of the system, and the three silane co-catalysts, trimethylsilane (C1#), triethylsilane (C2#) and phenylsilane (C3#), have comparable effects in assisting the main catalyst to improve the catalytic activity of the system.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A composite catalyst, characterized in that: The composite catalyst comprises a main catalyst and a co-catalyst. The chemical formula of the main catalyst is RTiX3, wherein R is acenaphthene and acenaphthene containing a substituent; X is independently selected from halogen atoms, C 1-8 Alkyl, C 2-8 Alkenyl, C 3-8 Alkenyl, C 1-8 Alkoxy, aryl, C 7-10 Aralkyl, C 7-10 Any one of the alkylaryl groups; the co-catalyst includes alkyl aluminum catalysts and silane catalysts.

2. The composite catalyst according to claim 1, characterized in that The main catalyst comprises at least one of the following compounds:

3. The composite catalyst according to claim 1, characterized in that The molar ratio of the main catalyst to the alkyl aluminum catalyst is 1:(1-10).

4. The composite catalyst according to claim 1, characterized in that The molar ratio of the main catalyst to the silane catalyst is 1:(50-200).

5. The composite catalyst according to claim 1, characterized in that The alkyl aluminum catalyst includes at least one of triethyl aluminum, tripropyl aluminum, triisobutyl aluminum, diisobutyl aluminum hydride, methyl aluminoxane, and modified methyl aluminoxane.

6. The composite catalyst according to claim 1, characterized in that The silane catalyst includes at least one of phenylsilane, trimethylsilane, triethylsilane, trimethylchlorosilane, hexamethyldisilazane, tert-butyldimethylchlorosilane, triisopropoxysilane, trimethylhydroxyethylsilane, and methyldiphenylhydroxyethylsilane.

7. Use of the composite catalyst according to any one of claims 1 to 6 in the synthesis of syndiotactic polystyrene.

8. The use according to claim 7, characterized in that The composite catalyst is used in the synthesis of syndiotactic polystyrene, and the composite catalyst contains 3×10 -3 ~10×10 -3 mmol of main catalyst.

9. The use according to claim 7, characterized in that The number average molecular weight of the syndiotactic polystyrene is 2×10 5 ~3×10 5 g / mol.

10. The use according to claim 7, characterized in that In the syndiotactic polystyrene, the aluminum content is ≤30ppm.

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