CN101328264B - Process for producing polycarbonate using ion liquid supported catalysts - Google Patents

Abstract

The invention discloses a method for preparing polycarbonate by a Salen metal catalyst supported by an ionic liquid. Carbon dioxide and an epoxy compound are taken as raw materials, Salen metal supported by the ionic liquid is taken as a catalyst, and a copolymerization reaction is performed at a carbon dioxide pressure of between 0.1 and 5.5MPa and a reaction temperature of between 20 and 150 DEG C to prepare the polycarbonate. The catalyst used by the method has good thermal stability to the temperature of air and water, simple operation and higher catalytic activity. The prepared polycarbonate has the characteristics of higher molecular weight, narrow molecular weight distribution and so on.

Description

Method for preparing polycarbonate with ionic liquid supported catalyst

technical field

The invention relates to a method for preparing polycarbonate by copolymerization of carbon dioxide and epoxy compound by using ionic liquid supported Salen metal as a catalyst.

Background technique

Copolymerization of carbon dioxide and epoxy compounds to produce degradable polycarbonate materials is one of the research hotspots in the field of environmentally friendly materials. The research reports on the catalytic system of the copolymerization of carbon dioxide and epoxy compounds mainly include: diethyl zinc-promoter catalyst (J.Polym.Sci.Part B: Polym.Let., 1969, 7, 287-292), ZnEt2- Although the multiprotic compound catalytic system was developed earlier, the system is very sensitive to water and air, and it is difficult to operate in practice. Zinc carboxylate (J.Polym.Sci.: Polym.Chem., 1999,37 (12): 1863-1876) is another class of catalyst system that can catalyze CO2 and epoxy compound copolymerization, and its catalytic efficiency is higher than ZnEt2 system Well, it is relatively stable to water and air, and it is relatively simple to operate, but its catalytic efficiency is still low, making it difficult to realize industrial applications. Inspired by the structure of chlorophyll, in 1978 Inoue et al. (Makromol.Chem., 1978, 179(5): 1377-1381) found that α, β, γ, δ-tetraphenylmethoxyporphyrin aluminum (TPP) AlX is A new catalyst for the copolymerization of CO2 and propylene oxide. The polycarbonate synthesized from porphyrin-aluminum system has monodisperse characteristics, but the content of carbonate bonds in the copolymer is low. The preparation process of the porphyrin aluminum system is complicated, the polymerization time is long (12-40d), the content of carbonate bonds in the copolymer is low, and the molecular weight is not high. Later research on this system was limited to the exploration of the catalytic mechanism, but the high selectivity brought about by the high steric hindrance of porphyrin aluminum has a good reference for the development of future catalysts. Shen Zhiquan et al. (CN 85104956) used the ternary rare earth metal catalyst Y(P204)3-Al(i-Bu)3-glycerol to realize the copolymerization reaction of CO2 and epoxy compounds. This catalyst gives high molecular weight polycarbonates, but the molecular weight distribution of the polycarbonates is broad. Salen metal catalyst (Acc.Chem.Res., 2004, 37, 836-844; J.Am.Chem.Soc., 2005, 127, 14026-14038) has high catalytic efficiency to water and air temperature, and the prepared Polycarbonate has a narrow molecular weight distribution and is a catalyst with relatively promising industrial applications. At present, the main problem of the traditional Salen metal catalyst is that the polycarbonate obtained by catalysis has a low molecular weight, the catalytic efficiency needs to be further improved, and some reaction cycles are also long. Therefore, the development of new high-efficiency, easy-to-operate, cheap and easy-to-obtain Salen metal catalysts is the current research direction of carbon dioxide copolymerization catalysts.

Contents of the invention

The purpose of the present invention is to provide a new method for preparing polycarbonate, using the Salen metal complex supported by ionic liquid as a catalyst, and preparing polycarbonate by copolymerization of carbon dioxide and epoxy compound.

The method for preparing polycarbonate with ionic liquid-supported Salen catalyst provided by the present invention uses carbon dioxide and epoxy compounds as raw materials, uses ionic liquid-supported Salen metal as catalyst, and the pressure of carbon dioxide is 0.1-5.5MPa, and the temperature is 20°C. At a reaction temperature of ~150°C, the copolymerization reaction produces polycarbonate.

The structural formula of the Salen metal catalyst supported by the ionic liquid used in the present invention is as follows:

In the formula: R ₁ , R ₂ , R ₃ , R ₄ , R ₅ are H, Me, Et, Pr or Bu; metal ion M is Co ³⁺ or Cr ³⁺ , anion Y ^- is BF ₄ ^- , PF ₆ ^- , Cl ^- , Br ^- , F ^- , NO ₃ ^- or CH ₃ COO ^- .

In the present invention, the molar ratio of the epoxy compound and the Salen metal catalyst supported by the ionic liquid can be within a wide range, usually between 10000: 1 and 100: 1, and preferably between 5000: 1 and 1000: 1 between.

The reaction temperature of the present invention is between 20°C and 150°C, and preferably between 50°C and 100°C.

The carbon dioxide pressure in the present invention is controlled at 0.1-5.5Mpa, and preferably between 3-4MPa.

Compared with traditional methods, the catalyst used in the present invention is very novel, and the Salen catalyst supported by this ionic liquid has the following characteristics: 1) good thermal stability, very stable to water and air; 2) relatively stable in water Good solubility; 3) High catalytic activity (TOF>1000); 4) The prepared polycarbonate has a higher molecular weight (>20,000); 5) The prepared polycarbonate has a narrow molecular weight distribution (1.1～ 1.3).

Detailed ways

The following implementation will describe the present invention more fully.

Example 1

80 g of cyclohexene oxide (CHO), 0.5 g of SalenCrCl catalyst supported by ionic liquid and 1.5 g of cocatalyst (methylimidazole) were added into a 200 ml autoclave. After being airtight, replace it with nitrogen for 2-3 times, raise the temperature rapidly and fill it with CO ₂ to a pressure of 2.5MPa. After reacting for a period of time (5h), quickly cool down and release the pressure. The obtained copolymer was dried under vacuum at 60°C, and the molecular weight and distribution of the polymer were measured by Water150-C gel permeation chromatography, tetrahydrofuran was used as the solvent, the mass fraction was about 5‰, 35°C, flow rate 0.8ml/mim, 12 Calibration with a polystyrene standard. The selectivity of the reacted polycarbonate was 98%, the TOF was 1020, the molecular weight of the polymer was 31200, and the molecular weight distribution was 1.15.

Example 2-5

Similar to Example 1, the polymerization reaction temperature is 60°C, the carbon dioxide pressure is 3.5MPa, and the reaction time is 5h; the ratio of the ionic liquid supported catalyst and cyclohexene oxide is changed, and the following results are obtained after the reaction (Table one):

Table 1 The effect of the amount of ionic liquid supported catalyst on the catalytic effect of CHO

Example 6

50 g (1 mol) of propylene oxide (PO), 0.5 g of ionic liquid supported SalenCoCl catalyst and 1.5 g of cocatalyst (methylimidazole) were added. After being airtight, replace it with nitrogen for 2-3 times, raise the temperature quickly and fill it with CO ₂ to a pressure of 4MPa. After reacting for a period of time (5h), quickly cool down and release the pressure. The obtained copolymer was dried under vacuum at 60°C. The selectivity of the reacted polycarbonate was 97%, the TOF was 1300, the molecular weight of the polymer was 31300, and the molecular weight distribution was 1.15.

Example 7-10

Similar to Example 6, the polymerization reaction temperature was 80°C, the carbon dioxide pressure was 4MPa, and the reaction time was 5h; the ratio of the ionic liquid supported catalyst to propylene oxide was changed, and the following results were obtained after the reaction (Table 2) :

Table 2 Effect of the amount of ionic liquid supported catalyst on the catalytic effect of PO

Claims (2)

1. a kind of method that prepares polycarbonate with ionic liquid supported Salen metal catalyst, it is characterized in that with carbon dioxide and epoxy compound as raw material, carry out copolymerization reaction and prepare polycarbonate with ionic liquid supported Salen metal as catalyzer, described The molar ratio of the epoxy compound to the Salen metal catalyst supported by the ionic liquid is between 10000:1 and 100:1, the carbon dioxide pressure is 3 to 4 MPa, and the reaction temperature is 50°C to 100°C; the ionic liquid supports the Salen metal The structural formula of the catalyst is as follows:

In the formula: R ₁ , R ₂ , R ₃ , R ₄ , R ₅ are H, Me, Et, Pr or Bu; metal ion M is Co ³⁺ or Cr ³⁺ , anion Y ^- is BF ₄ ^- , PF ₆ ^- , Cl ^- , Br ^- , F ^- , NO ₃ ^- or CH ₃ COO ^- . 2. the method for preparing polycarbonate with ionic liquid supported Salen metal catalyst according to claim 1, it is characterized in that the epoxy compound that copolymerization reaction occurs with carbon dioxide is cyclohexene oxide, propylene oxide or oxyethylene .