Composite catalyst and application thereof

Abstract

The invention belongs to the field of polymer synthesis, and particularly discloses a composite catalyst and application thereof. According to the invention, RTiX3 is used as a main catalyst for styrene polymerization, under the assistance of a cocatalyst, very high catalytic polymerization activity can be exerted at a high temperature, and a generated polymer product can be dissolved in a reaction solvent at a high temperature and cannot be separated out, so that a uniform liquid phase state is always kept, heat and mass transfer is relatively easy, and the catalyst is suitable for industrial production. The conversion rate and the single-kettle efficiency can be greatly improved, and the purposes of improving the production efficiency and reducing the production cost are achieved.

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] The biggest difficulty in the synthesis of syndiotactic polystyrene lies in its heterogeneous characteristics. Usually, the optimal activity temperature of the catalyst of syndiotactic polystyrene is below 100 degrees, such as the commonly used cyclopentadienyl or alkyl-substituted cyclopentadienyl metallocene catalysts, which have the optimal activity temperature of 50-90°C, and their activity decreases at higher temperatures. However, due to the fast crystallization rate and high solvent resistance of syndiotactic polystyrene, the polymer will inevitably precipitate from the liquid phase once it is transformed and formed at a polymerization temperature of 50-90°C. During this period, the syndiotactic polystyrene precipitate easily absorbs the monomer to form a swollen body, which adheres to the inner wall surface of the reactor and the stirring paddle. Once there is a stirring dead zone, or the crushing and dispersion refinement are not timely and sufficient, the swollen body will gradually accumulate and agglomerate and harden to form waste, which is not only difficult to be sheared and crushed, but also greatly increases the stirring power. Therefore, the heterogeneous characteristics greatly affect the heat and mass transfer of the polymerization process, not only making stirring extremely difficult, but also extremely difficult to remove heat, and also making the heat transfer efficiency in the middle and late stages of polymerization very low, so that polymerization is difficult to carry out. Therefore, the current production process of syndiotactic polystyrene is mainly solution polymerization. The solution polymerization method requires the addition of a solvent of equivalent mass to the styrene monomer for dilution. This method can well solve the swelling and agglomeration problem in the production process of syndiotactic polystyrene. However, even if the solution content reaches 80%, the system solid content will turn into a very viscous heterogeneous state after reaching 10%, resulting in greater difficulty in stirring and heat transfer in the later stage of polymerization, and the styrene conversion rate is difficult to exceed 80%. Therefore, the single-pot yield of syndiotactic polystyrene produced by the solution polymerization method is very low (single-pot yield = monomer concentration × monomer conversion rate), which is not conducive to the control of enterprise production costs and the improvement of production efficiency. In addition, solution polymerization also involves the distillation separation and recovery of solvent and unreacted styrene, and the process is relatively complicated. It is possible to improve the heat and mass transfer problem only when very complex reaction equipment is required, but it will also bring huge production investment.

[0004] Therefore, it is necessary to solve the problem of heterogeneous polymerization under low solvent dosage, especially to improve the heat and mass transfer efficiency in the styrene solid content system, in order to obtain high production efficiency. Summary of the invention

[0005] In view of the problems of swelling, low conversion rate, low production efficiency and the like caused by heterogeneous polymerization in the synthesis of syndiotactic polystyrene involved in the above-mentioned prior art, the present invention provides a composite catalyst and its application.

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

[0007] A composite catalyst, comprising a main catalyst and a co-catalyst, wherein the chemical formula of the main catalyst is RTiX 3 , wherein R is indeno(1,2,3-cd)pyrene and indeno(1,2,3-cd)pyrene containing a substituent; X is independently selected from a halogen atom, 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 a first co-catalyst and a second co-catalyst; the first co-catalyst includes an alkyl aluminum catalyst; the second co-catalyst includes at least one of a borate catalyst and a phenyl catalyst.

[0008] Compared with the catalysts in the prior art, the present invention uses RTiX 3 As the main catalyst for styrene polymerization, with the assistance of a co-catalyst, it can exert a very high catalytic polymerization activity at a high temperature of 130-170°C, and the syndiotactic polystyrene product produced by the reaction can be dissolved in the reaction solvent at high temperature, and the syndiotactic polystyrene product will not precipitate, so that the polymerization reaction system always maintains a uniform liquid phase state, heat and mass transfer is relatively easy, and the conversion rate and single-pot efficiency can be greatly improved, thereby achieving the purpose of improving production efficiency and reducing production costs.

[0009] Specifically, the halogen atom is F, Cl or Br; 1-8 The alkyl group is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl or octyl; 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 7-10Aralkyl 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 indeno(1,2,3-cd)pyrene 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 1-9 ” refers to any integer between 1 and 9 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 indeno(1,2,3-cd)pyrene or an indeno(1,2,3-cd)pyrene compound containing a substituent and potassium bis(trimethylsilyl)amide to a solvent, and reacting at 50 to 70° C. for 7 to 9 hours; then adding trimethylsilyl chloride, and 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 indeno(1,2,3-cd)pyrene or an indeno(1,2,3-cd)pyrene-based compound containing a substituent, potassium bis(trimethylsilyl)amide, trimethylsilyl chloride and titanium tetrachloride is indeno(1,2,3-cd)pyrene or an indeno(1,2,3-cd)pyrene-based compound containing a substituent: potassium bis(trimethylsilyl)amide: trimethylsilyl chloride: 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 indeno(1,2,3-cd)pyrene or the indeno(1,2,3-cd)pyrene-based compound containing a substituent is 1 mmol of indeno(1,2,3-cd)pyrene or the indeno(1,2,3-cd)pyrene-based compound containing a substituent in 2-10 mL of solvent.

[0021] Further preferably, in steps (1)-(2), the molar ratio of the indeno(1,2,3-cd)pyrene or the indeno(1,2,3-cd)pyrene 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 co-catalyst is 1:(1-150), specifically 1:1, 1:25, 1:50, 1:75, 1:100, 1:125, 1:150, 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.

[0025] The main catalyst and the co-catalyst cooperate with each other to have a higher activity in catalyzing the polymerization of styrene. Since the catalytic activity of the co-catalyst is lower than that of the main catalyst, when the amount of the co-catalyst added is greater than that of the main catalyst, the catalytic activity is better.

[0026] Preferably, the co-catalyst includes a first co-catalyst and a second co-catalyst; the first co-catalyst includes an alkyl aluminum catalyst; and the second co-catalyst includes at least one of a borate catalyst and a phenyl catalyst.

[0027] The inventors of the present invention have found that when the above two types of catalysts are selected as co-catalysts, they can better cooperate with the main catalyst to improve the catalytic activity of the system.

[0028] Preferably, the molar ratio of the first co-catalyst to the second co-catalyst is (1-50):1, specifically 1:1, 10:1, 20:1, 30:1, 40:1, 50:1, 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.

[0029] Preferably, the alkyl aluminum catalyst is selected from at least one of triethyl aluminum, tripropyl aluminum, triisobutyl aluminum, diisobutyl aluminum hydride, methyl aluminoxane, and modified methyl aluminoxane.

[0030] Preferably, the borate catalyst is selected from at least one of trityl-tetrakis(pentafluorophenyl)borate, N,N-dimethylaniline-tetrakis(pentafluorophenyl)borate, and N,N-dimethylaniline-tetraphenylborate.

[0031] Preferably, the phenyl-based catalyst includes at least one of diphenylzinc and phenylsilane.

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

[0033] In addition, the present invention also provides a method for preparing syndiotactic polystyrene, comprising the following steps:

[0034] Styrene, solvent and the composite catalyst are added into a reactor to carry out polymerization reaction to obtain the syndiotactic polystyrene; the solvent is a halogenated benzene or a halogenated hydrocarbon with a boiling point greater than 130°C.

[0035] Preferably, the temperature of the polymerization reaction can be specifically 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, etc., as well as specific point values ​​between the above point values. Due to limited space and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0036] In the method for preparing syndiotactic polystyrene of the present invention, the main catalyst RTiX 3The special cyclopentadienyl chemical structure can stably exist at 130-170°C. Therefore, during the polymerization reaction, the composite catalyst can maintain a high activity at 130-170°C, and the polymer formed by the polymerization of styrene at this temperature can be dissolved in a small amount of non-toluene solvent, so that the entire polymerization reaction maintains a uniform liquid phase. The use of conventional reactors (such as single-axis anchor-type stirring paddle reactors) can meet its stirring and heat transfer requirements, overcoming the defects of easy swelling and low mass and heat transfer efficiency caused by the heterogeneous phase in conventional processes, obtaining a styrene conversion rate of more than 90%, significantly improving production efficiency, and having broad prospects in industrial applications.

[0037] Preferably, the main catalyst is used in an amount of 0.004 to 0.03 mmol / 1 mol of styrene.

[0038] Preferably, the solvent is selected from at least one of o-dichlorobenzene, trichlorobenzene and tetrachloroethane.

[0039] Preferably, the mass ratio of styrene to solvent is 1:(0.1-0.5), specifically 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 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.

[0040] In the polymerization reaction system of the present invention, the polymer formed by polymerization of styrene can be dissolved in a small amount of non-toluene solvent, so that the entire polymerization reaction maintains a uniform liquid phase. Therefore, the amount of solvent required for the reaction system can be less than the amount of styrene raw material, thereby improving the single-pot yield. In addition, the amount of solvent in the reaction product is small, and no further distillation separation and recovery are required, thereby simplifying the process flow, improving production efficiency and reducing production costs.

[0041] Preferably, the number average molecular weight of the syndiotactic polystyrene is 2×10 5 ~3×10 5 g / mol.

[0042] Compared with the prior art, the present invention has the following beneficial effects: 3 As the main catalyst for styrene polymerization, it can exert a very high catalytic polymerization activity at high temperature with the assistance of a co-catalyst. The produced polymer product can be dissolved in the reaction solvent at high temperature without precipitation, thereby always maintaining a uniform liquid phase state. Heat and mass transfer are relatively easy, which can greatly improve the conversion rate and single-pot efficiency, thereby achieving the purpose of improving production efficiency and reducing production costs. DETAILED DESCRIPTION

[0043] 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.

[0044] Some of the reagents selected in the embodiments and comparative examples of the present invention are described as follows:

[0045] Indeno (1,2,3-cd) pyrene trimethyl titanium (denoted as A1#): homemade, the process is as follows:

[0046] In a glove box, 1 mmol of indeno(1,2,3-cd)pyrene and 1 mmol of potassium bis(trimethylsilyl)amide were added to 5 mL of tetrahydrofuran, and the mixture was stirred at 60°C for 8 h. Then, 1 mmol of trimethylsilyl chloride was added and stirred at room temperature for 2 h. Then, 1 mmol of titanium tetrachloride was added and stirred at room temperature for 2 h to obtain a brown solid-liquid mixture. After filtering and removing the filtrate, the mixture was washed three times with tetrahydrofuran (5 mL of tetrahydrofuran each time), and the solvent was drained 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 drained, and the yellow solid was washed three times with n-hexane (5 mL of n-hexane each time), and then drained under reduced pressure to obtain a yellow powder, i.e., indeno(1,2,3-cd)pyrene trimethyltitanium.

[0047] The NMR characterization results of indeno(1,2,3-cd)pyrenetrimethyltitanium are: δ=7.78, 2H; δ=7.72, 2H; δ=7.64, 1H; δ=7.55, 1H; δ=7.55, 1H; δ=7.51, 1H; δ=7.43, 1H; δ=7.40, 1H; δ=7.35, 1H; δ=7.31, 1H; δ=1.20, 9H; elemental analysis target molecular formula C 25 H 24 Ti(%) = C: 80.61%, H: 6.45%. This indicates the successful synthesis of indeno(1,2,3-cd)pyrenetrimethyltitanium, whose chemical structure is as follows:

[0048]

[0049] Indeno (1,2,3-cd) pyrene triallyl titanium (denoted as A2#): homemade, the process is as follows:

[0050] In a glove box, 1 mmol of indeno(1,2,3-cd)pyrene and 1 mmol of potassium bis(trimethylsilyl)amide were added to 5 mL of tetrahydrofuran, and the mixture was stirred at 60°C for 8 h. Then, 1 mmol of trimethylsilyl chloride was added and stirred at room temperature for 2 h. Then, 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 drained, the mixture was washed three times with tetrahydrofuran (5 mL of tetrahydrofuran each time). The solvent was drained under reduced pressure to obtain an intermediate product. 5 mL of toluene and 1 mmol of sodium allyl alcohol were added to the intermediate product, and the mixture was reacted at 80°C for 6 h. The solvent was drained again. The yellow solid was washed three times with n-hexane (5 mL of n-hexane each time), and then drained under reduced pressure to obtain a yellow powder, which is indeno(1,2,3-cd)pyrene triallyltitanium.

[0051] The NMR characterization results of indeno(1,2,3-cd)pyrenetriallyltitanium are: δ=7.78, 2H; δ=7.72, 2H; δ=7.64, 1H; δ=7.55, 1H; δ=7.55, 1H; δ=7.51, 1H; δ=7.43, 1H; δ=7.40, 1H; δ=7.35, 1H; δ=7.31, 1H; δ=5.99, 3H; δ=5.29, 3H; δ=5.16, 3H; δ=1.75, 6H; elemental analysis target molecular formula C 31 H 27 Ti(%) = C: 83.32%, H: 6.08%. This indicates the successful synthesis of indeno(1,2,3-cd)pyrenetriallyltitanium, whose chemical structure is as follows:

[0052]

[0053] Indeno (1,2,3-cd) pyrene tribenzyl titanium (denoted as A3#): homemade, the process is as follows:

[0054] In a glove box, 1 mmol of indeno(1,2,3-cd)pyrene and 1 mmol of potassium bis(trimethylsilyl)amide were added to 5 mL of tetrahydrofuran, and the mixture was stirred at 60°C for 8 h. Then, 1 mmol of trimethylsilyl chloride was added and stirred at room temperature for 2 h. Then, 1 mmol of titanium tetrachloride was added and stirred at room temperature for 2 h to obtain a brown solid-liquid mixture. After filtering and removing the filtrate, the mixture was washed three times with tetrahydrofuran (5 mL of tetrahydrofuran each time), and the solvent was drained under reduced pressure to obtain an intermediate product. 5 mL of toluene and 1 mmol of sodium benzyl alcohol were added to the intermediate product, and the mixture was reacted at 80°C for 6 h. The solvent was drained, and the yellow solid was washed three times with n-hexane (5 mL of n-hexane each time), and then drained under reduced pressure to obtain a yellow powder, i.e., indeno(1,2,3-cd)pyrenetribenzyltitanium.

[0055] The NMR characterization results of indeno(1,2,3-cd)pyrenetribenzyltitanium 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 43 H 33 Ti(%) = C: 86.25%, H: 5.38%. This indicates the successful synthesis of indeno(1,2,3-cd)pyrenetribenzyltitanium, whose chemical structure is as follows:

[0056]

[0057] Methylaluminoxane (denoted as B1#), triethylaluminum (denoted as B2#), N,N-dimethylaniline-tetrakis(pentafluorophenyl)borate (denoted as B3#), diphenylzinc (denoted as B4#), phenylsilane (denoted as B5#) and pentamethylcyclopentadienyltrimethoxytitanium are all commercially available.

[0058] The following examples and comparative examples all use a vertical single-shaft anchor-type stirring paddle reactor as a reactor.

[0059] Example 1

[0060] A method for synthesizing syndiotactic polystyrene comprises the following steps:

[0061] (1) First, heat transfer oil was introduced into the heating reactor body at 100° C., and vacuum was applied for 30 min. Then, nitrogen was introduced to fill the cavity of the reactor body, and vacuum was applied again. This process was repeated three times.

[0062] (2) Then, the reactor body was adjusted to the set reaction temperature (see Table 1), and 4500 g of styrene, 1250 g of o-dichlorobenzene, 1 mL of a toluene solution of methylaluminoxane (containing 10 mmol of methylaluminoxane), 1 mL of a toluene solution of N,N-dimethylaniline-tetrakis(pentafluorophenyl)borate (containing 0.2 mmol of N,N-dimethylaniline-tetrakis(pentafluorophenyl)borate) and 1 mL of a toluene solution of indeno(1,2,3-cd)pyrenetrimethyltitanium were added in sequence through the feed port. The detailed amounts are shown in Table 1. The mixture was stirred for 1 min and the reaction was continued for 1 h.

[0063] (3) 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.

[0064] Embodiments 2 to 12

[0065] 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.

[0066] Comparative Example 1

[0067] 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.

[0068] Comparative Example 2

[0069] The difference between this comparative example and Example 1 is that in this comparative example, the main catalyst A1# is replaced by an equal molar amount of pentamethylcyclopentadienyltrimethoxytitanium; the co-catalyst (B3#) is replaced by triisobutylaluminum, and the molar amount is increased to 60 mmol; and the molar amount of B1# is increased to 60 mmol.

[0070] Comparative Example 3

[0071] The difference between this comparative example and Example 1 is that in this comparative example, the solvent o-dichlorobenzene is replaced with toluene of the same mass.

[0072] Comparative Example 4

[0073] The difference between this comparative example and Example 1 is that the reaction temperature in this comparative example is set to 120°C.

[0074] Table 1

[0075]

[0076]

[0077] Performance Testing:

[0078] The syndiotacticity and number average molecular weight of the syndiotactic polystyrene prepared by the preparation methods of each embodiment and comparative example were measured, and the styrene conversion rate, swelling body content and catalyst activity were calculated at the same time. The test method is as follows:

[0079] (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.

[0080] (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 LS 300*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.

[0081] (3) Styrene monomer conversion rate = polystyrene mass / styrene feed mass × 100%.

[0082] (4) Swelling body content = swelling body mass / styrene feed mass × 100%, wherein the dried product is passed through a 18-mesh (mesh diameter 1 mm) vibrating sieve, wherein the powder passing through the sieve is polystyrene, and the powder retained on the sieve is the swelling body.

[0083] (5) Catalyst activity = product mass / main catalyst molar amount, where catalyst activity refers to the mass of syndiotactic polystyrene generated per mole of catalyst.

[0084] The test results are shown in Table 2.

[0085] Table 2

[0086]

[0087]

[0088] Comparative Example 1 uses the existing conventional main catalyst pentamethylcyclopentadienyl trimethoxytitanium, and the styrene conversion rate of its preparation method is very low. Comparative Example 2 uses the existing conventional metallocene catalyst system, and its formula uses pentamethylcyclopentadienyl trimethoxytitanium as the main catalyst. In order to improve the catalytic activity, a co-catalyst is added that is about 300 times more than the main catalyst, but its styrene conversion rate under high temperature conditions is still very low. The solvent of Comparative Example 3 uses toluene, and the system forms a large-area swelling body, and almost no powder product is obtained. Comparative Example 4 sets the reaction temperature to 120°C. Although there is a small amount of conversion, the actual conversion rate and apparent activity are very low because the polymerization product cannot be well dissolved at this temperature, causing heterogeneous swelling. A large amount of swelling is also generated, indicating that at high temperature, dissolving with a specific solvent to form a homogeneous system is the key to avoiding swelling and obtaining a high conversion rate.

[0089] It can be seen from Examples 1 to 12 and Comparative Examples 1 to 2 that the composite catalyst of the present invention has high catalytic activity at a high temperature of 130 to 170°C, and the activity of the composite catalyst is ≥ 2×10 7 g sPS / mol Ti, so that the styrene conversion rate is ≥90%, and the number average molecular weight is 198,000 to 259,000 g / mol; at the same time, in the reaction systems of Examples 1 to 12, the weight ratio of styrene to solvent is in the range of 1:(0.1-0.5), the styrene solid content in the system is ≥50%, which belongs to a high solid content or low solvent system, and the swelling body content is ≤0.1%. It can be seen that the synthesis method of the present invention well achieves high conversion rate, high catalytic activity and high single-pot yield at low solvent content in the process of producing syndiotactic polystyrene.

[0090] The main catalysts in Examples 1 and 6-7 are indeno(1,2,3-cd)pyrenetrimethyltitanium (A1#), indeno(1,2,3-cd)pyrenetriallyltitanium (A2#) and indeno(1,2,3-cd)pyrenetribenzyltitanium (A3#), respectively. The conversion rates of styrene of the three main catalysts can reach more than 90%. Among them, the catalytic effect of indeno(1,2,3-cd)pyrenetrimethyltitanium is the best, and the catalytic effects of indeno(1,2,3-cd)pyrenetriallyltitanium (A2#) and indeno(1,2,3-cd)pyrenetribenzyltitanium (A3#) are equivalent.

[0091] The polymerization reaction temperatures in Examples 1 and 11-12 are 150°C, 130°C and 170°C, respectively. At a reaction temperature of 130-170°C, the conversion rate of styrene can reach more than 90%. In this range, as the reaction temperature increases, the styrene conversion rate and the catalyst activity first increase and then slightly decrease. It can be seen that the polymerization reaction temperature of the present invention can be selected to be 130-170°C, at which time the catalytic activity of the reaction system and the styrene conversion rate are both high. At the same time, combined with the analysis of Examples 2, 6 and Examples 3, 7, the results show that the most suitable temperatures of different main catalysts are different, and a higher conversion rate and catalyst activity can be obtained with less co-catalyst at the optimal temperature.

[0092] The results of Examples 1, 8, 9, and 10 show that different combinations of co-catalysts will also have differences in activity; but in general, higher conversion rates, number average molecular weights, and catalyst activities can be obtained. Among them, the first type of co-catalysts in Examples 1 and 9 are methylaluminoxane (B1#) and triethylaluminum (B2#), respectively, and the catalytic effects of the two first co-catalysts in assisting the main catalyst are equivalent; the second type of co-catalysts in Examples 1, 8, and 10 are N, N-dimethylaniline-tetrakis (pentafluorophenyl) borate (B3#), diphenylzinc (B4#), and phenylsilane (denoted as B5#), respectively. The styrene conversion rate and catalyst activity of Example 1 are higher than those of Examples 8 and 10, which shows that the catalytic effect of N, N-dimethylaniline-tetrakis (pentafluorophenyl) borate (B3#) in assisting the main catalyst is better.

[0093] 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 indeno(1,2,3-cd)pyrene and indeno(1,2,3-cd)pyrene 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 a first co-catalyst and a second co-catalyst; the first co-catalyst includes an alkyl aluminum catalyst; the second co-catalyst includes at least one of a borate catalyst and a phenyl catalyst.

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 co-catalyst is 1:(1-150).

4. The composite catalyst according to claim 1, characterized in that The molar ratio of the first co-catalyst to the second co-catalyst is (1-50):

1.

5. The composite catalyst according to claim 1, characterized in that The alkyl aluminum catalyst is selected from 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 Include at least one of the following: A. The borate catalyst is selected from at least one of trityl-tetrakis(pentafluorophenyl)borate, N,N-dimethylaniline-tetrakis(pentafluorophenyl)borate, and N,N-dimethylaniline-tetraphenylborate; B. The phenyl-based catalyst includes at least one of diphenylzinc and phenylsilane.

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

8. A method for preparing syndiotactic polystyrene, characterized in that: The steps include: Styrene, a solvent and the composite catalyst according to any one of claims 1 to 6 are added into a reactor to carry out a polymerization reaction to obtain the syndiotactic polystyrene; the polymerization reaction temperature is 130 to 170° C., and the solvent is a halogenated benzene or a halogenated hydrocarbon with a boiling point greater than 130° C.

9. The method for preparing syndiotactic polystyrene according to claim 8, characterized in that: The dosage of the main catalyst is 0.004-0.03 mmol / 1 mol of styrene.

10. The method for preparing syndiotactic polystyrene according to claim 8, characterized in that: Include at least one of the following: Ⅰ. The solvent is selected from at least one of o-dichlorobenzene, trichlorobenzene and tetrachloroethane; II. The mass ratio of styrene to solvent is 1:(0.1-0.5); III. The number average molecular weight of the syndiotactic polystyrene is 2×10 5 ~3×10 5 g / mol.

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