Composite catalyst and use thereof

Abstract

The present invention relates to the field of polymer synthesis, and specifically, to a composite catalyst and use thereof. The composite catalyst of the present invention comprises a main catalyst and a co-catalyst. The main catalyst has a chemical formula of RTiX3, where R is an acenaphthenyl group or an acenaphthenyl group containing a substituent; each X is independently selected from any one of halogen atom, C1-8 alkyl, C2-8 alkenyl, C3-8 alkenylalkyl, C1-8 alkoxy, aryl, C7-10 aralkyl, and C7-10 alkaryl. The co-catalyst comprises an alkylaluminum catalyst and a silane catalyst. The composite catalyst of the present invention can significantly improve the conversion rate of styrene, replace conventional catalyst systems with a high aluminum content, and reduce the aluminum content in styrene polymerization products, thereby achieving the purpose of eliminating the need for a post-treatment process of aluminum removal and purification by solution washing for the styrene polymerization product, greatly improving production efficiency, and reducing production costs.

Description

A composite catalyst and its application

[0001] This application claims priority to Chinese Patent Application No. 202510201930.1, filed on February 24, 2025, entitled “A Composite Catalyst and Its Application”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention belongs to the field of polymer synthesis, specifically relating to a composite catalyst and its application. Background Technology

[0003] Syndiotactic polystyrene (SPS) is a type of polystyrene that possesses the good chemical inertness, excellent electrical insulation, and moisture resistance of general-purpose polystyrene. Unlike general-purpose polystyrene, SPS has a syndiotactic stereostructure, with side groups (benzene rings) alternating on both sides of the macromolecular chain in its structural units. Due to its high stereoregularity, SPS has a strong crystallization ability, making it a crystallizable polymer with a high melting point of approximately 270°C. This highly crystalline aggregated structure endows SPS with good heat resistance and corrosion resistance, making its performance comparable to thermoplastic engineering plastics such as nylon, polyester, and polyphenylene sulfide, thus making it a cost-effective engineering plastic.

[0004] Currently, the largest application areas for sPS are automotive connectors and high-frequency communication electronics, which require high dielectric and electrical insulation properties. Due to the shielding and interference effects of metals on signals, these products require very low metal content in the materials. However, mainstream sPS synthesis processes require the addition of large amounts of aluminum-containing catalysts to achieve high polymerization activity. In general processes, using a main catalyst or co-catalyst alone yields virtually no catalytic activity; only when the main catalyst and co-catalyst work together can good catalytic activity be achieved. In particular, the synthesis of syndiotactic polystyrene typically requires an alkylaluminum catalyst in hundreds of times excess compared to the main catalyst as a co-catalyst to assist the main catalyst in achieving high activity. The extensive use of alkylaluminum not only significantly increases raw material costs but also results in a large amount of residual aluminum metal in the product, affecting the excellent electrical properties of syndiotactic polystyrene in high-frequency communication electronics. Although aluminum can be removed from the polymerization product through solution washing, this usually requires organic solutions containing strong acids or bases. On the one hand, these organic solvents can cause equipment corrosion; on the other hand, the resulting organic solutions containing waste acids and bases are difficult to treat environmentally and regenerate, greatly increasing production costs.

[0005] Therefore, in order to produce syndiotactic polystyrene using a low-cost, non-washing process, it is necessary to address the problem of excessively high demand for aluminum-containing co-catalysts in the catalyst formulation. Summary of the Invention

[0006] In view of the problem that the high aluminum content in the catalyst system leads to excessive residual aluminum in the product during the synthesis of syndiotactic polystyrene in the above-mentioned prior art, the present invention will provide a composite catalyst and its application.

[0007] To achieve the above objectives, the following technical solutions are specifically included:

[0008] A composite catalyst includes a main catalyst and a co-catalyst, wherein the main catalyst has the chemical formula RTiX3, wherein R is an acenaphthenic group or an acenaphthenic group containing substituents; and 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 Aryl alkyl, C 7-10 Any one of alkylaryl groups; the co-catalyst includes alkylaluminum catalysts and silane catalysts.

[0009] In some embodiments, the halogen atom is F, Cl, or Br.

[0010] In some implementations, the C 1-8 Alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, or octyl.

[0011] In some implementations, the C 2-8 Alkenyl groups include vinyl, propenyl, or butenyl.

[0012] In some implementations, the C 3-8 Alkenyl groups include allyl, allyl, or allyl.

[0013] In some implementations, the C 1-8 Alkoxy groups include methoxy, ethoxy, or propoxy.

[0014] In some embodiments, the aryl group includes a phenyl group.

[0015] In some implementations, the C 7-10 Aryl groups include benzyl, phenethyl, or phenylpropyl.

[0016] In some implementations, the C 7-10 Alkyl groups include 4-methyl-phenyl, 4-ethyl-phenyl, or 4-propyl-phenyl.

[0017] In some embodiments, the main catalyst comprises at least one of the following compounds:

[0018] In some embodiments, the preparation method of the main catalyst includes the following steps:

[0019] (1) Add acenaphthene or a acenaphthene compound containing a substituent to potassium bis(trimethylsilyl)amide in a solvent and react at 50-70°C for 7-9 hours; then add trimethylchlorosilane and react at room temperature for 1-3 hours; then add titanium tetrachloride and react at room temperature for 1-3 hours to obtain an intermediate product;

[0020] (2) The intermediate product, solvent and X-ONa are mixed and reacted at 70-90°C for 5-7 hours to obtain the main catalyst; the X in X-ONa is the same as the X in the chemical formula RTiX3 of the main catalyst.

[0021] In some implementations, the room temperature in step (1) is 20-30°C.

[0022] In some embodiments, in step (1), the molar ratio of acenaphthene or a substituent-containing acenaphthene compound, potassium bis(trimethylsilyl)amide, trimethylchlorosilane, and titanium tetrachloride is acenaphthene or a substituent-containing acenaphthene compound: potassium bis(trimethylsilyl)amide: trimethylchlorosilane: titanium tetrachloride = 1:(0.9-1.2):(0.9-1.2):(0.9-1.2).

[0023] In some embodiments, in step (1), the solvent comprises tetrahydrofuran.

[0024] In some embodiments, in step (1), the amount of acenaphthene or acenaphthene compound containing a substituent is 2-10 mL of solvent containing 1 mmol of acenaphthene or acenaphthene compound containing a substituent.

[0025] In some embodiments, in steps (1)-(2), the molar ratio of the acenaphthene or the acenaphthene compound containing a substituent to the X-ONa is 1:(0.9-1.2).

[0026] In some embodiments, in step (2), the solvent includes toluene.

[0027] In some embodiments, in step (1), the amount of X-ONa used is 2-10 mL of solvent containing 1 mmol of X-ONa.

[0028] In some embodiments, the composite catalyst as described in claim 1 is characterized in that the molar ratio of the main catalyst to the alkylaluminum catalyst is 1:(1-10).

[0029] In some embodiments, the composite catalyst as described in claim 1 is characterized in that the molar ratio of the main catalyst to the silane catalyst is 1:(50-200).

[0030] In some embodiments, the composite catalyst according to claim 1 is characterized in that the alkylaluminum catalyst includes at least one of triethylaluminum, tripropylaluminum, triisobutylaluminum, diisobutylaluminum hydride, methylaluminoxane, and modified methylaluminoxane.

[0031] In some embodiments, the composite catalyst according to claim 1 is characterized in that the silane catalyst comprises at least one of phenylsilane, trimethylsilane, triethylsilane, trimethylchlorosilane, hexamethyldisilazane, tert-butyldimethylchlorosilane, triisopropoxysilane, trimethylhydroxyethylsilane, and methyldiphenylhydroxyethylsilane.

[0032] The present invention also provides an application of the aforementioned composite catalyst in the synthesis of syndiotactic polystyrene.

[0033] In some embodiments, the composite catalyst, in the synthesis of syndiotactic polystyrene, contains 3 × 10⁻⁶ molecules per mole of styrene. -3 ~10×10 -3 millimolecular main catalyst.

[0034] In some embodiments, the number-average molecular weight of the syndiotactic polystyrene is 2 × 10⁻⁶. 5 ~3×10 5 g / mol.

[0035] In some embodiments, the mass content of aluminum in the syndiotactic polystyrene is ≤30 ppm.

[0036] This invention also provides a method for synthesizing syndiotactic polystyrene, comprising the following steps:

[0037] Styrene, solvent, and the composite catalyst according to any one of claims 1 to 9 are added to a reactor to carry out a polymerization reaction to obtain the syndiotactic polystyrene.

[0038] In some embodiments, the solvent is selected from at least one of toluene, xylene, ethylbenzene, n-hexane, cyclohexane, heptane, octane, tetrachloroethane, and o-dichlorobenzene.

[0039] In some embodiments, the molar ratio of styrene to solvent is 1:(0.4-1).

[0040] In some embodiments, the polymerization reaction is carried out at a temperature of 50–90°C.

[0041] In some embodiments, the polymerization reaction takes 0.5 to 6 hours.

[0042] 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 styrene polymerization products, realize the purpose of styrene polymerization products without further aluminum removal purification process by solution washing, greatly improve production efficiency and reduce production costs. Detailed Implementation

[0043] In a first aspect, the present invention provides a composite catalyst comprising a main catalyst and a co-catalyst, wherein the main catalyst has the chemical formula RTiX3, wherein R is an acenaphthenic group or an acenaphthenic group containing substituents; and 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 Aryl alkyl, C 7-10 Any one of alkylaryl groups; the co-catalyst includes alkylaluminum catalysts and silane catalysts.

[0044] In the composite catalyst of this invention, the RTiX3 main catalyst and the two co-catalysts, alkylaluminum catalyst and silane catalyst, work together to exhibit high catalytic activity for styrene polymerization. This can significantly improve the conversion rate of styrene and replace conventional catalyst systems with high aluminum content. It can reduce the aluminum content in styrene polymerization products, thereby achieving the goal of eliminating the need for further aluminum removal and purification processes for styrene polymerization products through solution washing, greatly improving production efficiency, and reducing production costs.

[0045] Specifically, the halogen atom is F, Cl, or Br; the C 1-8 Alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, or octyl; the C 2-8 Alkenyl groups include, but are not limited to, vinyl, propenyl, or butenyl groups; the C 3-8 Alkenyl groups include, but are not limited to, allyl, allyl, or allenyl; the C 1-8 Alkoxy groups include, but are not limited to, methoxy, ethoxy, or propoxy groups; the aryl group includes, but is not limited to, phenyl groups; the C group... 7-10 Aryl groups include, but are not limited to, benzyl, phenethyl, or phenylpropyl; the C 7-10 Alkyl groups include, but are not limited to, 4-methyl-phenyl, 4-ethyl-phenyl, or 4-propyl-phenyl.

[0046] Preferably, the substituents in the acenaphthene group containing substituents include C 1-8 alkyl, C 1-8One of the alkoxy groups.

[0047] It should be understood that the "C" appearing in this invention 1-8 "C" refers to any integer between 1 and 8 carbon atoms; 2-8 "C" refers to any integer between 2 and 8 carbon atoms; 3-8 "C" refers to any integer between 3 and 8 carbon atoms; 7-10 "" refers to any integer between 7 and 10 carbon atoms.

[0048] Preferably, the main catalyst comprises at least one of the following compounds:

[0049] Preferably, the preparation method of the main catalyst includes the following steps:

[0050] (1) Add acenaphthene or a acenaphthene compound containing a substituent to potassium bis(trimethylsilyl)amide in a solvent and react at 50-70°C for 7-9 hours; then add trimethylchlorosilane and react at room temperature for 1-3 hours; then add titanium tetrachloride and react at room temperature for 1-3 hours to obtain an intermediate product;

[0051] (2) The intermediate product, solvent and X-ONa are mixed and reacted at 70-90°C for 5-7 hours to obtain the main catalyst; the X in X-ONa is the same as the X in the chemical formula RTiX3 of the main catalyst.

[0052] More preferably, in step (1), the room temperature is 20-30°C.

[0053] More preferably, in step (1), the molar ratio of acenaphthene or a acenaphthene compound containing a substituent, potassium bis(trimethylsilyl)amide, trimethylchlorosilane, and titanium tetrachloride is acenaphthene or a acenaphthene compound containing a substituent: potassium bis(trimethylsilyl)amide: trimethylchlorosilane: titanium tetrachloride = 1:(0.9-1.2):(0.9-1.2):(0.9-1.2).

[0054] More preferably, in step (1), the solvent includes tetrahydrofuran.

[0055] More preferably, in step (1), the amount of acenaphthene or acenaphthene compound containing a substituent is 2-10 mL of solvent containing 1 mmol of acenaphthene or acenaphthene compound containing a substituent.

[0056] More preferably, in steps (1)-(2), the molar ratio of the acenaphthene or the acenaphthene compound containing a substituent to the X-ONa is 1:(0.9-1.2).

[0057] More preferably, in step (2), the solvent includes toluene.

[0058] More preferably, in step (1), the amount of X-ONa used is 1 mmol of X-ONa in 2-10 mL of solvent.

[0059] Preferably, the molar ratio of the main catalyst to the alkylaluminum 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., and any value between these ranges. For space limitations and for the sake of brevity, this invention will not exhaustively list all the values ​​within the range. In conventional styrene polymerization catalyst systems, the amount of aluminum-containing co-catalyst must be several hundred times that of the main catalyst to effectively catalyze styrene polymerization. However, in the composite catalyst system of this invention, the amount of alkylaluminum catalyst can be selected to be only 1-10 times that of the main catalyst. While maintaining high catalytic activity, the amount of aluminum-containing co-catalyst is significantly lower than in conventional catalyst systems, greatly reducing the amount of alkylaluminum catalyst. This not only reduces raw material costs but also provides a better styrene polymerization effect than conventional catalyst systems, resulting in a lower aluminum content in the product.

[0060] Preferably, the alkylaluminum catalyst includes at least one of triethylaluminum, tripropylaluminum, triisobutylaluminum, diisobutylaluminum hydride, methylaluminoxane, and modified methylaluminoxane.

[0061] 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., and any value between these ranges. For space limitations and for the sake of brevity, this invention will not exhaustively list all the values ​​included in the range. The composite catalyst of this invention contains a silane catalyst, which can assist the main catalyst with an alkylaluminum catalyst to improve the catalytic activity of the catalyst system, further reducing the amount of aluminum-containing co-catalyst in the catalyst system. Under the above-mentioned amounts, the catalytic activity of the catalyst system is even better.

[0062] Preferably, the silane catalyst includes at least one of phenylsilane, trimethylsilane, triethylsilane, trimethylchlorosilane, hexamethyldisilazane, tert-butyldimethylchlorosilane, triisopropoxysilane, trimethylhydroxyethylsilane, and methyldiphenylhydroxyethylsilane.

[0063] Secondly, the present invention provides an application of the composite catalyst described above in the synthesis of syndiotactic polystyrene.

[0064] Preferably, in the synthesis of syndiotactic polystyrene, the composite catalyst contains 3 × 10⁻⁶ molecules per mole of styrene. -3 ~10×10 -3 millimolecular main catalyst.

[0065] Preferably, the syndiotactic polystyrene has a number-average molecular weight of 2 × 10⁻⁶. 5 ~3×10 5 g / mol.

[0066] Preferably, the aluminum content in the syndiotactic polystyrene is ≤30ppm by mass.

[0067] Thirdly, the present invention provides a method for synthesizing syndiotactic polystyrene, comprising the following steps:

[0068] Styrene, solvent, and the composite catalyst are added to a reactor to carry out a polymerization reaction to obtain the syndiotactic polystyrene.

[0069] This invention uses RTiX3 as the main catalyst for synthesizing syndiotactic polystyrene, and uses styrene as a monomer to carry out homogeneous polymerization to synthesize syndiotactic polystyrene. While maintaining high catalytic activity, it can reduce the amount of aluminum-containing additives added, thereby achieving the goal of producing syndiotactic polystyrene with ultra-low aluminum content.

[0070] Preferably, the solvent is selected from at least one of toluene, xylene, ethylbenzene, n-hexane, cyclohexane, heptane, octane, tetrachloroethane, and o-dichlorobenzene.

[0071] 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 any value between the above points. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the points included in the range.

[0072] Preferably, the temperature of the polymerization reaction is 50 to 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 any value between the above points. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the points included in the range.

[0073] Preferably, the polymerization reaction time is 0.5 to 6 hours, specifically 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, etc., as well as any value between the above points. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the points included in the range.

[0074] To better illustrate the purpose, technical solution, and advantages of this invention, specific embodiments will be used to further explain the invention below. Unless otherwise specified, the test methods used in the embodiments and / or comparative examples are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available.

[0075] Acenamethanetrimethyltitanium (denoted as A1#): Self-made, the process is as follows:

[0076] In a glove box, 1 mmol of acenaphthene and 1 mmol of potassium bis(trimethylsilyl)amide were added to 5 mL of tetrahydrofuran and stirred at 60 °C for 8 h. Then, 1 mmol of trimethylchlorosilane was added and stirred at room temperature for 2 h. Next, 1 mmol of titanium tetrachloride was added and stirred at room temperature for 2 h to obtain a brown solid-liquid mixture. After filtering to remove the filtrate, the mixture was washed three times with tetrahydrofuran (5 mL each time), and the solvent was dried under reduced pressure to obtain an intermediate product. 5 mL of toluene and 1 mmol of sodium methoxide were added to the intermediate product, and the mixture was reacted at 80 °C for 6 h. The solvent was then dried under reduced pressure, and the resulting yellow solid was washed three times with n-hexane (5 mL each time) and dried under reduced pressure to obtain a yellow powder, which is acenaphthene-trimethyltitanium.

[0077] The NMR characterization results of acenaphthene-trimethyltitanium were as follows: δ = 7.70, 2H; δ = 7.51, 2H; δ = 7.39, 2H; δ = 3.45, 2H; δ = 1.20, 9H; the deuterated solvent was deuterated acetone. The target molecular formula for elemental analysis is C1. 15 H 20 Ti (%) = C: 72.61%, H: 8.05%. This indicates the successful synthesis of acenaphthene-trimethyltitanium, whose chemical structure is as follows:

[0078] Acenamethurized triallyl titanium (denoted as A2#): Self-made, the process is as follows:

[0079] In a glove box, 1 mmol of acenaphthene and 1 mmol of potassium bis(trimethylsilyl)amide were added to 5 mL of tetrahydrofuran and stirred at 60 °C for 8 h. Then, 1 mmol of trimethylchlorosilane was added and stirred at room temperature for 2 h. Next, 1 mmol of titanium tetrachloride was added and stirred at room temperature for 2 h to obtain a brown solid-liquid mixture. After the solvent was removed, the mixture was washed three times with tetrahydrofuran (5 mL each time), and the solvent was removed under reduced pressure to obtain an intermediate product. 5 mL of toluene and 1 mmol of sodium allyloxide were added to the intermediate product and reacted at 80 °C for 6 h. The solvent was then removed, and the resulting yellow solid was washed three times with n-hexane (5 mL each time) and then removed under reduced pressure to obtain a yellow powder, which is acenaphthene-triallyl titanium.

[0080] The NMR characterization results of acenaphthene-triallyl titanium were as follows: 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; the deuterated solvent was deuterated acetone. The target molecular formula for elemental analysis is C1. 21 H 23 Ti (%) = C: 78.32%, H: 7.24%. This indicates the successful synthesis of acenaphthenic triallyl titanium, whose chemical structure is as follows:

[0081] Acenamethanil tribenzyl titanium (denoted as A3#): Self-made, the process is as follows:

[0082] In a glove box, 1 mmol of acenaphthene and 1 mmol of potassium bis(trimethylsilyl)amide were added to 5 mL of tetrahydrofuran and stirred at 60 °C for 8 h. Then, 1 mmol of trimethylchlorosilane was added and stirred at room temperature for 2 h. Next, 1 mmol of titanium tetrachloride was added and stirred at room temperature for 2 h, resulting in a brown solid-liquid mixture. After filtering to remove the filtrate, the mixture was washed three times with tetrahydrofuran (5 mL each time), and the solvent was removed under reduced pressure to obtain an intermediate product. 5 mL of toluene and 1 mmol of sodium benzyloxide were added to the intermediate product, and the mixture was reacted at 80 °C for 6 h. The solvent was then removed under reduced pressure, and the resulting yellow solid was washed three times with n-hexane (5 mL each time) and then removed under reduced pressure to obtain a yellow powder, which is acenaphthene-tribenzyl titanium.

[0083] The NMR characterization results of acenaphthene-tribenzyltitanium were as follows: δ = 7.70, 2H; δ = 7.51, 2H; δ = 7.39, 2H; δ = 3.45, 2H; δ = 7.20, 15H; δ = 2.40, 6H; with deuterated solvent being deuterated acetone. The target molecular formula for elemental analysis is C1. 33 H 29 Ti (%) = C: 83.25%, H: 6.12%. This indicates the successful synthesis of acenaphthene-tribenzyl titanium, whose chemical structure is as follows:

[0084] 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.

[0085] Example 1

[0086] A method for synthesizing syndiotactic polystyrene includes the following steps:

[0087] (1) First, heat transfer oil is introduced to heat the reactor body at 100°C, and vacuum is applied for 30 minutes. Then, nitrogen is introduced to fill the cavity of the reactor body, and vacuum is applied again. This process is repeated three times.

[0088] (2) Then adjust the reactor body to the set reaction temperature (see Table 1), and add styrene, toluene, 1 mL of methylaluminoxane toluene solution, 1 mL of trimethylsilane toluene solution and 1 mL of acenaphthene trimethyltitanium toluene solution through the feed port in sequence according to the raw material dosage in Table 1. Stir for 1 min and react for 1 h.

[0089] (2) After the reaction is completed, the jacket heat transfer oil temperature is kept at 150℃ and vacuum is applied for 1 hour. After the desizing is completed, the bottom discharge valve of the reactor is opened to obtain the dried product, i.e., syndiotactic polystyrene.

[0090] Examples 2-12

[0091] The difference between Examples 2-12 and Example 1 lies in the differences in raw materials and reaction temperature, as detailed in Table 1.

[0092] Comparative Example 1

[0093] The difference between this comparative example and Example 1 is that the main catalyst A1# is replaced with an equimolar amount of pentamethylcyclopentadienyltrimethoxytitanium.

[0094] Comparative Example 2

[0095] 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 with an equimolar amount of pentamethylcyclopentadienyltrimethoxytitanium; the co-catalyst (C1#) is replaced with an equimolar amount of B2#.

[0096] Comparative Example 3

[0097] 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 with an equimolar amount of pentamethylcyclopentadienyltrimethoxytitanium; the co-catalyst (C1#) is replaced with an equimolar amount of B2#, and the amount of B1# is increased to 60 mmol, and the amount of B2# is increased to 60 mmol.

[0098] Table 1

[0099] Performance testing:

[0100] The degree of syndiotacticity, weight-average molecular weight, and number-average molecular weight of the syndiotactic polystyrene prepared in each example and comparative example were determined. Simultaneously, the styrene conversion rate, aluminum mass content, and catalyst activity (catalyst activity refers to the mass of syndiotactic polystyrene produced per mole of catalyst) were calculated. Specific testing methods are as follows:

[0101] (1) Syndiotacticity was characterized by carbon NMR spectroscopy using a Bruker DMX 500Hz instrument. The test samples were prepared by dissolving in deuterated o-dichlorobenzene. The chemical shifts of the syndiotactic structure were 145.1-145.3 ppm and the chemical shifts of the random structure were 144.8-146.0 ppm. Syndiotacticity = peak area of ​​syndiotactic structure / (peak area of ​​random structure + peak area of ​​syndiotactic structure).

[0102] (2) Molecular weight: Characterized by gel permeation chromatography (GPC) using an Agilent PL-GPC 220 instrument with a differential detector. Three PLgel 10µm MIXED-B LS300*7.5mm columns were used in series. The mobile phase was 1,2,4-trichlorobenzene, the temperature was 150℃, and the flow rate was 1mL / min. The standard curve for GPC testing was determined using polystyrene with a narrow molecular weight distribution as a standard, and the number-average relative molecular weight (Mn) of the polymer was calculated. The syndiotactic polystyrene sample was dissolved in 1,2,4-trichlorobenzene to a concentration of 2-5 mg / mL, and filtered through a 450nm organic filter to remove insoluble impurities.

[0103] (3) Monomer (styrene) conversion rate = mass of polystyrene / mass of styrene added × 100%.

[0104] (4) Catalyst activity = product mass / molar amount of main catalyst.

[0105] (5) Mass content of aluminum in syndiotactic polystyrene: The mass of syndiotactic polystyrene product with mass m was decomposed in an acidic aqueous solution with volume v (an acidic aqueous solution prepared by mixing 3 volumes of concentrated hydrochloric acid with mass fraction of 36%-38% and 1 volume of concentrated nitric acid with mass fraction of 65%-68%) by microwave digestion. The mass concentration c of aluminum in the acidic aqueous solution was then characterized by inductively coupled plasma optical emission spectrometry (ICP-OES). The mass content of aluminum in the product (ppm) can be calculated as cv / m.

[0106] The test results are shown in Table 2.

[0107] Table 2

[0108] The syndiotactic polystyrene in Examples 1-12 all had a syndiotactic degree of 100%, a styrene conversion rate of over 75%, an aluminum mass content of ≤20 ppm, a number-average molecular weight of 200,000 to 278,000 g / mol, and a catalyst activity of up to 1.80 × 10⁻⁶. 7 The g sPS / mol Ti indicates that the composite catalyst of the present invention has high activity and can obtain sPS products with low aluminum content.

[0109] In Examples 1-12, the main catalyst used was RTiX3. Comparative Example 1 used a conventional main catalyst, pentamethylcyclopentadienyltrimethoxytitanium. Although its catalyst content was the same as in Example 1 of this invention, the styrene conversion rate and catalytic activity in Comparative Example 1 were very low. It is evident that, compared to the conventional catalyst system using pentamethylcyclopentadienyltrimethoxytitanium as the main catalyst, the use of RTiX3 as the main catalyst for the synthesis of syndiotactic polystyrene in this invention can significantly improve the activity and conversion rate of styrene conversion.

[0110] Comparative Examples 2 and 3 used pentamethylcyclopentadienyltrimethoxytitanium as the main catalyst and alkylaluminum catalysts as co-catalysts, forming conventional alkylaluminum-metallocene catalyst systems. Although the amount of catalyst in Comparative Example 2 was the same as that in Example 1 of this invention, it not only had low styrene conversion and catalytic activity, but also a high aluminum content in the product. According to current technology, the styrene conversion and catalytic activity can be improved by increasing the amount of alkylaluminum catalyst co-catalysts. For example, in Comparative Example 3, the content of alkylaluminum catalyst was about three times that in Example 1, and the styrene conversion and catalytic activity could basically reach the actual production level. However, this also caused a sharp increase in the aluminum content of the catalyst system, resulting in an aluminum content in the product of several hundred ppm.

[0111] As can be seen from Examples 1-12 and Comparative Examples 1-3, the present invention uses RTiX3 as the main catalyst for the synthesis of syndiotactic polystyrene, and supplements it with two co-catalysts to form a composite catalyst system. Compared with the conventional catalyst system that uses pentamethylcyclopentadienyltrimethoxytitanium as the main catalyst, the catalyst system of the present invention can not only significantly improve the activity and conversion rate of styrene conversion, but also significantly reduce the content of aluminum-containing catalysts in the catalyst system. It can improve the styrene conversion rate and catalytic activity under the condition of low aluminum-containing co-catalysts, and obtain syndiotactic polystyrene products with ultra-low aluminum content ≤30ppm.

[0112] In Examples 1 and 6-7, acenaphthene trimethyl titanium (A1#), acenaphthene triallyl titanium (A2#), and acenaphthene tribenzyl titanium (A3#) were used as the main catalysts, respectively. As shown in Table 2, the catalytic activity of the polymerization catalyst system from high to low is acenaphthene tribenzyl titanium (A3#), acenaphthene trimethyl titanium (A1#), and acenaphthene triallyl titanium (A2#).

[0113] In Examples 1 and 11-12, the molar ratios of the main catalyst to the alkylaluminum catalyst were 1:5, 1:1, and 1:10, respectively. As the amount of alkylaluminum catalyst increased, the catalytic activity of the polymerization catalyst system increased. However, the aluminum content in the product also increased. Therefore, selecting a molar ratio of 1:(1-10) for the main catalyst to the alkylaluminum catalyst can balance the high catalytic activity of the catalyst system with the low aluminum content in the product.

[0114] As can be seen from Examples 1 and 4, and Examples 8-10, the two alkylaluminum co-catalysts, methylaluminoxane (B1#) and triisobutylaluminum (B2#), have comparable effects in improving the catalytic activity of the catalyst system by assisting the main catalyst. Similarly, the three silane co-catalysts, trimethylsilane (C1#), triethylsilane (C2#), and phenylsilane (C3#), have comparable effects in improving the catalytic activity of the catalyst system by assisting the main catalyst.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A composite catalyst, characterized in that, The composite catalyst comprises a main catalyst and a co-catalyst. The main catalyst has the chemical formula RTiX3, wherein R is an acenaphthene group or an acenaphthene group containing substituents; 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 Aryl alkyl, C 7-10 Any one of alkylaryl groups; the co-catalyst includes alkylaluminum catalysts and silane catalysts.

2. The composite catalyst as described in claim 1, characterized in that, At least one of the following must be met: 1) The halogen atom is F, Cl, or Br; 2) The C 1-8 Alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, or octyl; 3) The C 2-8 Alkenyl groups include vinyl, propenyl, or butenyl groups; 4) The C 3-8 Alkenyl groups include allyl, allyl, or allyl; 5) The C 1-8 Alkoxy groups include methoxy, ethoxy, or propoxy groups; 6) The aryl group includes phenyl; 7) The C 7-10 Aryl groups include benzyl, phenethyl, or phenylpropyl; 8) The C 7-10 Alkyl groups include 4-methyl-phenyl, 4-ethyl-phenyl, or 4-propyl-phenyl.

3. The composite catalyst as described in claim 1 or 2, characterized in that, The main catalyst includes at least one of the following compounds:

4. The composite catalyst as described in claim 1 or 2, characterized in that, The preparation method of the main catalyst includes the following steps: (1) Add acenaphthene or a acenaphthene compound containing a substituent to potassium bis(trimethylsilyl)amide in a solvent and react at 50-70°C for 7-9 hours; then add trimethylchlorosilane and react at room temperature for 1-3 hours; then add titanium tetrachloride and react at room temperature for 1-3 hours to obtain an intermediate product; (2) The intermediate product, solvent and X-ONa are mixed and reacted at 70-90°C for 5-7 hours to obtain the main catalyst; the X in X-ONa is the same as the X in the chemical formula RTiX3 of the main catalyst.

5. The composite catalyst as described in claim 4, characterized in that, At least one of the following must be met: a. In step (1), the room temperature is 20-30℃; b. In step (1), the molar ratio of acenaphthene or a acenaphthene compound containing a substituent, potassium bis(trimethylsilyl)amide, trimethylchlorosilane, and titanium tetrachloride is acenaphthene or a acenaphthene compound containing a substituent: potassium bis(trimethylsilyl)amide: trimethylchlorosilane: titanium tetrachloride = 1:(0.9-1.2):(0.9-1.2):(0.9-1.2); c. In step (1), the solvent includes tetrahydrofuran; d. In step (1), the amount of acenaphthene or acenaphthene compound containing a substituent is 2-10 mL of solvent containing 1 mmol of acenaphthene or acenaphthene compound containing a substituent; e. In steps (1)-(2), the molar ratio of the acenaphthene or the acenaphthene compound containing a substituent to the X-ONa is 1:(0.9-1.2); f. In step (2), the solvent includes toluene; g. In step (1), the amount of X-ONa used is 2-10 mL of solvent containing 1 mmol of X-ONa.

6. The composite catalyst as described in claim 1, characterized in that, The molar ratio of the main catalyst to the alkylaluminum catalyst is 1:(1-10).

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

8. The composite catalyst as described in claim 1, characterized in that, The alkylaluminum catalyst includes at least one of triethylaluminum, tripropylaluminum, triisobutylaluminum, diisobutylaluminum hydride, methylaluminoxane, and modified methylaluminoxane.

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

10. The application of the composite catalyst according to any one of claims 1 to 9 in the synthesis of syndiotactic polystyrene.

11. The application as described in claim 10, characterized in that, In the synthesis of syndiotactic polystyrene, the composite catalyst contains 3 × 10⁻⁶ molecules per mole of styrene. -3 ~10×10 -3 millimolecular main catalyst.

12. The application as described in claim 10, characterized in that, The number-average molecular weight of the syndiotactic polystyrene is 2 × 10⁻⁶. 5 ~3×10 5 g / mol.

13. The application as described in claim 10, characterized in that, The mass content of aluminum in the syndiotactic polystyrene is ≤30ppm.

14. A method for synthesizing syndiotactic polystyrene, comprising the following steps: Styrene, solvent, and the composite catalyst according to any one of claims 1 to 9 are added to a reactor to carry out a polymerization reaction to obtain the syndiotactic polystyrene.

15. The synthesis method according to claim 14, characterized in that, The solvent is selected from at least one of toluene, xylene, ethylbenzene, n-hexane, cyclohexane, heptane, octane, tetrachloroethane, and o-dichlorobenzene.

16. The synthesis method according to claim 14, characterized in that, The molar ratio of styrene to solvent is 1:(0.4-1).

17. The synthesis method according to claim 14, characterized in that, The polymerization reaction is carried out at a temperature of 50–90°C.

18. The synthesis method according to claim 14, characterized in that, The polymerization reaction takes 0.5 to 6 hours.

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