CN101811067A - Novel CO2 cycloaddion ionic liquid catalyst and preparation method thereof - Google Patents

Abstract

The invention provides a novel high-efficiency _CO2 cycloaddition reaction ionic liquid catalyst with high selectivity and high conversion rate, which is composed of N-methylimidazole and allyl chloride mixed in a certain molar ratio and heated to 55-70 ℃, under the protection of nitrogen, react for 8-12 hours to obtain 1-allyl-3-methylimidazolium chloride ionic liquid; then it is prepared by copolymerization of 1-allyl-3-methylimidazolium chloride ionic liquid and acrylic acid . The ionic liquid catalyst prepared by the present invention has good thermal stability, has high selectivity and conversion rate for the reaction of carbon dioxide and epoxy compounds to generate five-membered ring compounds, and its preparation method is simple, low in cost and can be reused. It is suitable for large-scale production and has broad application prospects in the field of industrial catalysis.

Description

A novel CO2 cycloaddition reaction ionic liquid catalyst and preparation method thereof

technical field

The invention belongs to the technical field of industrial catalysis, and relates to a _CO2 cycloaddition reaction catalyst, in particular to a novel high-efficiency _CO2 cycloaddition reaction catalyst with high selectivity and high conversion rate.

Background technique

With the acceleration of industrialization and the increasing population of countries all over the world, the demand for resources such as coal, oil and natural gas is increasing. These limited and non-renewable resources on the earth are being consumed in large quantities. Moreover, it also causes regional air pollution and "greenhouse effect" due to combustion emissions. According to statistics, in the past 100 years, the surface temperature has increased by 0.6°C, which means that for every 10% increase in CO ₂ in the atmosphere, the surface temperature will rise by 0.43°C. According to relevant information, every time the concentration of CO ₂ in the atmosphere doubles, the temperature will increase by 2.8-5.2°C. Climate warming will also cause great changes in the earth's climate, posing a serious threat to human existence. Therefore, corresponding countermeasures must be taken to reduce _CO2 emissions to the atmosphere. In addition to limiting CO ₂ emissions, another effective measure is to recycle the generated CO ₂ and convert it into chemicals, fuels, or other useful products. Among them, the reaction of _CO2 and epoxy compound to generate cyclocarbonate through catalytic coupling is an effective method. This is because cyclic carbonates are widely used as monomers for polymer synthesis, polar aprotic solvents, pharmaceutical intermediates, and other biochemical applications. Moreover, CO ₂ is directly coupled with epoxy compounds to form carbonates, and no other by-products are produced, which is in line with the views of green chemistry and atom economy.

Since Karl first discovered that sodium hydroxide supported on activated carbon can effectively catalyze the cycloaddition reaction with epoxy compounds in 1943, so far, people have successively developed new catalysts such as metal oxides, alkali metal halides, and ionic liquids. . As a catalyst for the cycloaddition reaction with epoxides, the environmental friendliness of ionic liquids makes the reaction conditions milder than traditional quaternary ammonium salt catalysts, the catalytic reaction activity and product selectivity are higher, and the reaction does not require solvents, etc. , as a new type of reaction catalyst. However, after the ionic liquid is used as a catalyst to catalyze the reaction, vacuum distillation is required to separate the product from the ionic liquid, which is not suitable for industrial production from the perspective of energy consumption. From the point of view of practical application, the catalyst activity is still not satisfactory. Therefore, the development of simple, easy-to-separate, industrializable, and highly efficient catalysts is the top priority of current research.

Contents of the invention

The object of the present invention is to provide a novel high-efficiency _CO2 cycloaddition reaction ionic liquid catalyst with high selectivity and high conversion.

Another object of the present invention is to provide a preparation method of the novel high-efficiency CO _{cycloaddition} reaction ionic liquid catalyst.

1. Novel _CO2 cycloaddition reaction catalyst

Novel CO of the present invention _{cycloaddition} reaction ionic liquid catalyst, its structural formula is as follows:

2. Preparation of novel _CO2 cycloaddition reaction catalysts

Novel CO of the present invention The preparation method of _{cycloaddition} reaction catalyst comprises the following processing steps:

(1) Synthesis of chlorinated 1-allyl-3-methylimidazolium ionic liquid: N-methylimidazole and allyl chloride are mixed in a molar ratio of 1:1.10 to 1:1.11 and heated to 55 to 70 °C, react for 8-12 hours under the protection of nitrogen to obtain 1-allyl-3-methylimidazolium chloride ionic liquid;

(2) Preparation of ionic liquid catalyst: mix 1-allyl-3-methylimidazolium chloride ionic liquid with acrylic acid at a molar ratio of 1:5 to 1:10, and then add 2 to 5 moles of acrylic acid to it. Double N,N-dimethylformamide and azobisisobutyronitrile with 1-2% molar weight of acrylic acid, react at 60-70°C for 24-36h under the protection of nitrogen; then precipitate with chloroform, filter and dry to obtain Light yellow target polymer.

Its synthetic route is as follows:

3. Characterization of polymers

The polymer (new CO ₂ cycloaddition reaction catalyst) prepared by the present invention is characterized by infrared, thermogravimetric, elemental analysis, and light scattering through specific experiments below.

1. Experimental raw materials

Allyl chloride and chloroform were of analytical grade, purchased from Sinopharm Chemical Reagent Co., Ltd., and used directly without treatment. N,N-Dimethylformamide (DMF), acrylic acid were redistilled before use. Azobisisobutyronitrile is technical grade.

2 Characterization of polymers

(1) Infrared Spectrum

After the samples were compressed with KBr, they were tested with a 360 FT-IR spectrometer produced by Nigoni Company, USA.

Fig. 1 is the infrared spectrogram of catalyst. As can be seen from Fig. 1, the absorption peak at 1553cm ^-1 is the spectrum peak of C=N above the methylimidazole, while the standard spectrum peak of polyacrylic acid does not have the spectrum peak of C=N at 1553cm ^-1 place, thus can It can be seen that we successfully copolymerized acrylic acid and ionic liquid together.

(2) Thermogravimetric analysis:

Thermogravimetric analysis (TG-DTA) was measured by TG-DTA 2000S, with a scanning range of 30-500°C, a heating rate of 10°C·min ^-1 , and a nitrogen flow rate of 100mL·min ^-1 .

Figure 2 is the thermogravimetric curve of the novel _CO2 cycloaddition reaction catalyst. It can be seen from Figure 2 that before 150°C, the weight loss of 1% is due to the water absorption of the polymer. It shows that the catalyst prepared by the present invention is stable before 150°C, and the thermogravimetric analysis shows that the novel catalyst prepared by the present invention has good thermal stability and can be successfully applied to the CO ₂ cycloaddition reaction.

(3) Elemental analysis

Elemental analysis results: N: 3.80%, C: 48.29%, H: 5.67%, Cl: 13.91%, O: 28.33%. It was shown that 3.9 mmol of ionic liquid was loaded on each gram of polymer.

(4) Light scattering analysis

Using a light scattering instrument (model Wyatt Technology DAWN EOS), with acetic acid solution as the mobile phase, the weight average molecular weight was measured.

Light scattering analysis results: the weight average molecular weight of the novel CO ₂ cycloaddition reaction catalyst prepared by the present invention is _Mw =2645, D=1.27. It can be known from the D value that the dispersion coefficient of the polymer is close to 1, indicating that the dispersion of the polymer is good.

4. Application of Catalysts in _CO2 Cycloaddition Reaction

The following specific experiments illustrate the catalytic effect of the new catalyst of the present invention on the reaction of carbon dioxide and epoxy compounds to form five-membered ring compounds.

Test method: Add 10ml of epichlorohydrin, magneton, and 0.1g of the catalyst prepared by the present invention into a 50mL stainless steel high-pressure reaction kettle. After replacing the air, first heat up to the set temperature, and then pass carbon dioxide to adjust the pressure. to react for a certain period of time. After the reaction was completed, it was cooled with an ice-salt bath, and then deflated, and the obtained mixture was filtered to obtain the corresponding cyclocarbonate.

The reaction formula is as follows:

The curves of the conversion rate and selectivity of the catalyst of the present invention in the _CO2 cycloaddition reaction with reaction time and temperature are shown in Fig. 3 and Fig. 4 . It can be seen from Figure 3 and Figure 4 that as the temperature increases, the conversion increases first, and reaches the maximum conversion rate of 90% at 120°C, with a selectivity of 99%. With the prolongation of time, the conversion first increased and then decreased. When the reaction time was 2h, the conversion reached the maximum value: 90%, and the selectivity was 99%. The above experiments prove that the catalyst prepared by the present invention is a catalyst for the _CO2 cycloaddition reaction, has high selectivity and conversion rate for the reaction of carbon dioxide and epoxy compounds to form five-membered ring compounds, and can be reused.

Through a lot of research, it is found that the cycloaddition reaction between epoxy compound and CO ₂ has the best effect under the condition of the presence of the catalyst, at 1.25Mpa, the temperature is 115°C, and the reaction time is 1h.

Compared with the prior art, the present invention has the following advantages:

1. The catalyst prepared by the present invention has good thermal stability, and reacts with epoxy compounds to form five-membered ring compounds with high selectivity and conversion rate.

2. The preparation method of the high-efficiency catalyst of the present invention is simple, low in cost, reusable, suitable for large-scale production, and has broad application prospects in the field of industrial catalysis.

Description of drawings

Fig. 1 is the infrared spectrogram of CO of the present invention _{Cycloaddition} reaction catalyst

Fig. 2 is the thermogravity curve of _CO cycloaddition reaction catalyst of the present invention

Fig. 3 is the change curve of conversion rate and selectivity with reaction time in CO _{cycloaddition} reaction of catalyst of the present invention

Fig. 4 is the change curve of conversion rate and selectivity with reaction temperature in CO _{cycloaddition} reaction of catalyst of the present invention

Detailed ways

Embodiment 1, novel CO The preparation of _{cycloaddition} reaction catalyst

1. Synthesis of chlorinated 1-allyl-3-methylimidazolium ionic liquid: mix N-methylimidazole and allyl chloride at a molar ratio of 1:1.11, heat to 55°C, and react under nitrogen protection 8h, 1-allyl-3-methylimidazolium chloride ionic liquid was obtained, yield: 78%.

2. Preparation of ionic liquid by copolymerization of 1-allyl-3-methylimidazolium chloride ionic liquid and acrylic acid: mixing 1-allyl-3-methylimidazolium chloride ionic liquid with acrylic acid in a molar ratio of 1:8 , then add N,N-dimethylformamide (DMF) with 2 times the molar weight of acrylic acid and azobisisobutyronitrile with 1% molar weight of acrylic acid, react at 70°C for 24h under the protection of nitrogen, and then precipitate with chloroform, Filter to obtain a light yellow polymer, and dry it in a vacuum oven at 100°C for 24 hours. Yield: 51%.

Embodiment 2, catalytic CO _{Cycloaddition} reaction

Add 10ml of epichlorohydrin, magneton, and 0.1g of the catalyst of the present invention into a 50mL stainless steel autoclave. After replacing the air, first raise the temperature to 150° C., then pass carbon dioxide, adjust the pressure of the reactor to 1.25Mpa, and stir. When reacting for 1h. After the reaction was completed, it was cooled with an ice-salt bath, and then deflated, and the obtained mixture was filtered to obtain the corresponding cyclocarbonate. The conversion rate was 92%.

Claims (2)

1. A novel CO _{cycloaddition} reaction ionic liquid catalyst, its structural formula is as follows:

2. novel CO as claimed in claim 1 The preparation method of _{cycloaddition} reaction ionic liquid catalyst comprises the following processing steps: (1) Synthesis of chlorinated 1-allyl-3-methylimidazolium ionic liquid: N-methylimidazole and allyl chloride are mixed in a molar ratio of 1:1.10 to 1:1.11 and heated to 55 to 70 °C, react for 8-12 hours under the protection of nitrogen to obtain 1-allyl-3-methylimidazolium chloride ionic liquid; (2) Preparation of ionic liquid catalyst: mix 1-allyl-3-methylimidazolium chloride ionic liquid with acrylic acid at a molar ratio of 1:5 to 1:10, and then add 2 to 5 moles of acrylic acid to it. Double N,N-dimethylformamide and azobisisobutyronitrile with 1-2% molar weight of acrylic acid, react at 60-70°C for 24-36h under the protection of nitrogen; then precipitate with chloroform, filter and dry to obtain Light yellow target polymer.

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