Preparation of phthalimide-based ionic liquid and method for catalyzing synthesis of α-alkyl unsaturated cyclic carbonate using the same

Abstract

The present invention relates to a type of phthalimide-based ionic liquid having any of the following structural formulas: #imgabs0#. The present invention also provides a method for catalyzing the synthesis of α-alkyl unsaturated cyclic carbonates using the ionic liquid. The present invention solves the problems of low catalyst performance, harsh reaction conditions, and the use of organic solvents in the existing method of synthesizing α-alkyl unsaturated cyclic carbonates using carbon dioxide (CO2) and propargyl alcohol. The novel phthalimide-based ionic liquid is used as a main catalyst to catalyze propargyl alcohol and CO2 to undergo a cycloaddition reaction at 0.1-1 MPa and 30°C to generate α-alkyl unsaturated cyclic carbonates, and the maximum yield can reach 98.7%.

Description

Technical Field

[0001] The invention belongs to the technical field of environmentally friendly catalysis, and specifically relates to a novel phthalimide-based ionic liquid, a preparation method, and a method for synthesizing alpha-alkyl unsaturated cyclic carbonate by catalyzing the reaction of carbon dioxide (CO2) and propynyl alcohol using the ionic liquid. Background Art

[0002] With the increase of CO2 content in the atmosphere and the greenhouse effect it causes, large-scale carbon capture and storage are the main methods to achieve carbon emission reduction and respond to global warming. CO2 is a cheap, non-toxic and renewable C1 resource. Lewis alkaline alkanolamine aqueous solutions such as 2-hydroxyethylamine, N-methyldiethanolamine, 1,1,3,3-tetramethylguanidine, phthalimide, etc. are usually used as CO2 capture agents. Since CO2 has the characteristics of thermodynamic stability and kinetic inertness, this type of reaction generally needs to be catalyzed under high temperature and high pressure conditions, and the reaction conditions are relatively harsh. CO2 can be converted into a variety of high value-added compounds, such as methanol, urea, quinazoline dione, cyclic carbonates and α-alkyl unsaturated cyclic carbonates. At the same time, this also meets the requirements of green and sustainable development.

[0003] The most effective and widely used method is to use ionic liquids to catalyze the cycloaddition reaction of CO2 and propargyl alcohol. However, most ionic liquids have one or more shortcomings, such as low catalytic activity, poor reusability, and harsh reaction conditions. Therefore, it is necessary to explore an ionic liquid that can be used under mild conditions, has high catalytic activity, and is reusable. Summary of the invention

[0004] In order to solve the technical defects of the existing method for synthesizing α-alkyl unsaturated cyclic carbonates, such as low catalytic activity, poor reuse effect, and harsh reaction conditions, the present invention aims to provide a novel phthalimide-based ionic liquid, which can be used to catalyze the synthesis of α-alkyl unsaturated cyclic carbonates at room temperature and pressure, has high catalytic activity and good reuse effect.

[0005] The present invention also provides a method for preparing the novel phthalimide-based ionic liquid and a method for catalyzing and synthesizing α-alkyl unsaturated cyclic carbonate using the phthalimide-based ionic liquid.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A novel phthalimide-based ionic liquid having any of the following structural formulas:

[0008]

[0009] The present invention provides a method for preparing the novel phthalimide-based ionic liquid, which comprises the following steps:

[0010] Phthalimide is reacted with 1,1,3,3-tetramethylguanidine, 1,8-diazabicyclo[5.4.0]undec-7-ene, benzyltrimethylammonium hydroxide or choline hydroxide in the presence of a solvent at room temperature for 6 to 18 hours. After the reaction is completed, the product is subjected to rotary evaporation, washing and drying.

[0011] The synthesis route of the novel phthalimide-based ionic liquid is as follows:

[0012]

[0013] The preparation method of the novel phthalimide-based ionic liquid is as follows: specifically, the molar ratio of phthalimide to 1,1,3,3-tetramethylguanidine, 1,8-diazabicyclo[5.4.0]undec-7-ene, benzyltrimethylammonium hydroxide or choline hydroxide is 1:1-1.2; and the solvent is methanol or ethanol.

[0014] The present invention also provides a method for synthesizing α-alkyl unsaturated cyclic carbonate esters by catalyzing the above-mentioned phthalimide-based ionic liquid, which specifically comprises: adding the phthalimide-based ionic liquid and propargyl alcohol into a reactor in a certain molar ratio, sealing the reactor and introducing CO2, and carrying out a cycloaddition reaction under certain reaction pressure and certain reaction temperature conditions to synthesize the α-alkyl unsaturated cyclic carbonate esters.

[0015] In the above method for synthesizing α-alkyl unsaturated cyclic carbonate esters using phthalimide-based ionic liquid as catalyst, the propargyl alcohol may be a compound of any of the following structures:

[0016] In order to obtain a higher yield, the above method of synthesizing α-alkyl unsaturated cyclic carbonate esters using phthalimide-based ionic liquid as catalyst, further preferably, the molar ratio of phthalimide-based ionic liquid to propargyl alcohol is 0.5-7:100, further preferably 1-7:100, and most preferably 2-5:100. The reaction pressure of the cycloaddition reaction is 0.1-1MPa. The reaction temperature of the cycloaddition reaction is 30±5°C. The reaction time of the cycloaddition reaction is 3-11h, preferably 7-11h. Under this condition, the yield of the product α-alkyl unsaturated cyclic carbonate ester is about 98.7%, and the selectivity is >99%.

[0017] Furthermore, in the above method of synthesizing α-alkyl unsaturated cyclic carbonate using phthalimide-based ionic liquid as catalyst, a co-catalyst (such as AgOAc, Ag2CO3, AgBr or AgI, etc.) can be added during the cycloaddition reaction, and the molar ratio of the co-catalyst to propargyl alcohol is 0.5 to 5:100, preferably 0.7 to 1:100.

[0018] The present invention provides a method for preparing α-alkyl unsaturated cyclic carbonate by catalyzing CO2 and propargyl alcohol using a novel phthalimide-based ionic liquid, that is, using the novel phthalimide-based ionic liquid as a catalyst, under mild conditions, without using a solvent, CO2 and propargyl alcohol are reacted through a cycloaddition reaction to synthesize the α-alkyl unsaturated cyclic carbonate. The reaction equation for preparing the α-alkyl unsaturated cyclic carbonate by the cycloaddition reaction of CO2 and propargyl alcohol is as follows:

[0019]

[0020] Wherein R and R' form the substrate of the following structure:

[0021]

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1) The four novel phthalimide-based ionic liquids [Pth][TMGH], [Pth][DBUH], [Pth][BTMA] and [Pth][Ch] provided by the present invention can efficiently catalyze CO2 and propargyl alcohol to generate α-alkyl unsaturated cyclic carbonates under mild, organic solvent-free conditions. The catalyst can catalyze the cycloaddition reaction of different propargyl alcohols with CO2 and exhibits excellent universality;

[0024] 2) The present invention solves the problems of low catalyst performance, harsh reaction conditions, and the use of organic solvents in the existing method of synthesizing α-alkyl unsaturated cyclic carbonates using CO2 and propargyl alcohol. The present invention uses a novel phthalimide-based ionic liquid as a catalyst to catalyze the cycloaddition reaction of propargyl alcohol and CO2 at 0.1-1MPa and 30±5°C to generate α-alkyl unsaturated cyclic carbonates, with a maximum yield of 98.7%;

[0025] 3) The novel phthalimide-based ionic liquid of the present invention can be recycled for multiple times to catalyze CO2 and propargyl alcohol. After catalytic generation of α-alkyl unsaturated cyclic carbonate, it can be easily separated under the condition of adding n-hexane. After simple washing and drying, the solid ionic liquid can be obtained again, and the recycling performance is good, and the cost is reduced. The catalyst has high activity in the cycloaddition reaction of CO2 and propargyl alcohol, mild reaction conditions, no solvent, high operating safety, and very good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 and Figure 2 They are respectively the hydrogen and carbon nuclear magnetic resonance spectra of the [Pth][TMGH] catalyst prepared in Example 1;

[0027] Figure 3 and Figure 4 They are respectively the hydrogen and carbon nuclear magnetic resonance spectra of the [Pth][DBUH] catalyst prepared in Example 1;

[0028] Figure 5 and Figure 6 They are respectively the hydrogen and carbon nuclear magnetic resonance spectra of the [Pth][BTMA] catalyst prepared in Example 1;

[0029] Figure 7 and Figure 8 They are respectively the hydrogen and carbon nuclear magnetic resonance spectra of the [Pth][Ch] catalyst prepared in Example 1. DETAILED DESCRIPTION

[0030] The present invention will be further described in detail in conjunction with specific implementation methods. The following examples are only used to illustrate the present invention and are not intended to limit the present invention.

[0031] In the following examples, unless otherwise specified, all the raw materials used are common commercial products that can be directly purchased in the art. The room temperature refers to 25±5°C.

[0032] Example 1

[0033] The structural formula of the novel phthalimide-based ionic liquid catalyst prepared in this example is as follows:

[0034]

[0035] The ionic liquid [Pth][TMGH] was synthesized by the following steps:

[0036] In a 100ml single-mouth bottle, 0.03mol (4.4g) of phthalimide and 0.03mol (3.5g) of 1,1,3,3-tetramethylguanidine (TMG) were dissolved in 30ml of methanol solvent and stirred at room temperature for 12h. After the reaction, methanol was removed by rotary evaporation, then washed with ethyl acetate and dried at 50℃ for 12h to obtain a white solid [Pth][TMGH]. Its H NMR and C NMR spectra are shown in Table 1. Figure 1 and 2 .

[0037] Referring to the above method, the raw material TMG in the first step reaction was replaced by 1,8-diazabicyclo[5.4.0]undec-7-ene, benzyltrimethylammonium hydroxide and choline hydroxide, respectively, to finally obtain novel phthalimide-based ionic liquids [Pth][DBUH], [Pth][BTMA] and [Pth][Ch], respectively; their H NMR and C NMR spectra were shown in Table 1. Figure 3 , 4 , Figure 5 , 6 ,and Figure 7 , 8 .

[0038] Figure 1 and 2 The data is as follows: [Pth][TMGH]: 1 H NMR (300MHz, Deuterium Oxide) δ7.63–7.37 (m, 4H), 2.88 (d, J = 0.7Hz, 12H). 13 C NMR (101MHz, DMSO) δ179.71, 163.05, 137.22, 131.86, 120.86.

[0039] Figure 3 and 4 The data is as follows: [Pth][DBUH]: 1 H NMR(300MHz,Deuterium Oxide)δ7.64–7.43(m,4H),3.61–3.46(m,4H),3.31(t,J=5.9Hz,2H),2.61(dd,J=7.3,3.1Hz,2H),2.08–1.93(m,2H),1.70(dt,J=12.9,4.5Hz,6H). 13 C NMR (101MHz, DMSO) δ181.19,164.63,137.93,131.80,120.84,53.32,48.21,39.08,32.65,28.96,26.96,24.51,20.18.

[0040] Figure 5 and 6 The data are as follows: [Pth][BTMA]: 1 H NMR (400MHz, DMSO-d6) δ7.62–7.46(m,5H),7.46–7.28(m,4H),4.62(s,2H),3.08(s,9H). 13C NMR (101MHz, DMSO) δ185.46,139.90,133.33,130.70,130.57,129.34,128. 94,119.80,68.11,52.15,40.63,40.43,40.22,40.01,39.80,39.59,39.38.

[0041] Figure 7 and 8 The data are as follows: [Pth][Ch]: 1 H NMR (400MHz, DMSO-d6) δ7.72–7.63(m,1H),7.37–7.26(m,2H),7.21(ddd,J=7.8 ,6.5,2.2Hz,1H),3.84(dt,J=5.4,2.6Hz,2H),3.44–3.38(m,2H),3.11(s,9H). 13 C NMR (101MHz, DMSO) δ172.61,169.38,143.67,130.99,129.56,128.76,127.94,125.84,67.00,55.05,53.12,39.93,39.72,39.51,39.30,39.09.

[0042] from Figures 1 to 8 From the analysis of the hydrogen nuclear magnetic resonance spectrum, carbon nuclear magnetic resonance spectrum and the corresponding nuclear magnetic resonance data, it can be seen that the synthesized catalyst is the target catalyst.

[0043] Example 2

[0044] In a 50mL stainless steel reactor with a digital pressure gauge, 0.15mmol [Pth] [TMGH] main catalyst prepared in Example 1, 0.05mmol AgOAc and 5mmol propargyl alcohol (3-methylbutyn-3-ol) were added, the molar content of the main catalyst and the co-catalyst AgOAc in propargyl alcohol was 3mol% and 1mol%, respectively. CO2 was slowly introduced to remove residual air in the reactor. The reactor was closed and the temperature was controlled to 30°C. CO2 gas was continuously introduced to maintain the pressure at 0.1MPa. The cycloaddition reaction was carried out for 9h. After the reaction was completed, the product was analyzed by gas chromatography, and the yield of the product α-alkyl unsaturated cyclic carbonate was measured to be 93.2%, and the selectivity was >99%.

[0045] Example 3

[0046] The specific experimental process and detection method are the same as those in Example 2, except that the main catalyst used is [Pth][DBUH]. The product yield is measured to be 93.6% and the selectivity is >99%.

[0047] Example 4

[0048] The specific experimental process and detection method are the same as those in Example 2, except that the main catalyst used is [Pth][BTMA]. The measured product yield is 98.7% and the selectivity is >99%.

[0049] Example 5

[0050] The specific experimental process and detection method are the same as those in Example 2, except that the main catalyst used is [Pth][Ch]. The measured product yield is 1.8%, and the selectivity is >99%.

[0051] Example 6

[0052] The specific experimental process and detection method are the same as those in Example 4, except that the co-catalyst AgOAc is not used. The measured product yield is 2.2% and the selectivity is >99%.

[0053] Example 7

[0054] The specific experimental process and detection method are the same as those in Example 4, except that the main catalyst is not used, and the measured product yield is 0% and the selectivity is 0%.

[0055] Example 8

[0056] The specific experimental process and detection method are the same as those in Example 4, except that the co-catalyst used is Ag2CO3. The measured product yield is 97.2% and the selectivity is >99%.

[0057] Example 9

[0058] The specific experimental process and detection method are the same as those in Example 4, except that the co-catalyst used is AgBr. The measured product yield is 59.7%, and the selectivity is >99%.

[0059] Example 10

[0060] The specific experimental process and detection method are the same as those in Example 4, except that the co-catalyst used is AgI. The measured product yield is 26.6%, and the selectivity is >99%.

[0061] Embodiment 11

[0062] The specific experimental process and detection method are the same as those in Example 4, except that the molar content of the co-catalyst used in propynyl alcohol is 0.5 mol%. The measured product yield is 83.4% and the selectivity is >99%.

[0063] Example 12

[0064] The specific experimental process and detection method are the same as those in Example 4, except that the molar content of the co-catalyst used in propynyl alcohol is 0.7 mol %. The measured product yield is 90.5%, and the selectivity is >99%.

[0065] Example 13

[0066] The specific experimental process and detection method are the same as those in Example 4, except that the molar content of the co-catalyst used in propargyl alcohol is 3 mol %. The measured product yield is 73.7% and the selectivity is >99%.

[0067] Embodiment 14

[0068] The specific experimental process and detection method are the same as those in Example 4, except that the molar content of the co-catalyst used in propargyl alcohol is 5 mol %. The measured product yield is 13.1% and the selectivity is >99%.

[0069] Embodiment 15

[0070] The specific experimental process and detection method are the same as those in Example 4, except that the molar content of the main catalyst in propargyl alcohol is 1 mol %. The measured product yield is 45.7% and the selectivity is >99%.

[0071] Example 16

[0072] The specific experimental process and detection method are the same as those in Example 4, except that the molar content of the main catalyst in propargyl alcohol is 2 mol%, and the measured product yield is 94.3%, and the selectivity is >99%.

[0073] Embodiment 17

[0074] The specific experimental process and detection method are the same as those in Example 4, except that the molar content of the main catalyst in propargyl alcohol is 5 mol%, and the measured product yield is 92.5%, and the selectivity is >99%.

[0075] Embodiment 18

[0076] The specific experimental process and detection method are the same as those in Example 4, except that the molar content of the main catalyst in propargyl alcohol is 7 mol%, and the measured product yield is 85.6%, and the selectivity is >99%.

[0077] Embodiment 19

[0078] The specific experimental process and detection method are the same as those in Example 4, except that the reaction time is 3 h. The measured product yield is 83.7% and the selectivity is >99%.

[0079] Embodiment 20

[0080] The specific experimental process and detection method are the same as those in Example 4, except that the reaction time is 5 h. The measured product yield is 88.7% and the selectivity is >99%.

[0081] Embodiment 21

[0082] The specific experimental process and detection method are the same as those in Example 4, except that the reaction time is 7 h. The measured product yield is 93.9% and the selectivity is >99%.

[0083] Embodiment 22

[0084] The specific experimental process and detection method are the same as those in Example 4, except that the reaction time is 11 h. The measured product yield is 98.7% and the selectivity is >99%.

[0085] Embodiment 23

[0086] The specific experimental process and detection method are the same as those in Example 4, except that the propargyl alcohol used is 3-methyl-1-pentene-4-yn-3-ol. The measured product yield is 95.3% and the selectivity is >98%.

[0087] The reaction equation for this experiment is:

[0088]

[0089] Embodiment 24

[0090] The specific experimental process and detection method are the same as those in Example 4, except that the propargyl alcohol used is 3,5-dimethyl-1-hexyn-3-ol. The measured product yield is 94.4% and the selectivity is >99%.

[0091] The reaction equation for this experiment is:

[0092]

[0093] Embodiment 25

[0094] The specific experimental process and detection method are the same as those in Example 4, except that the propargyl alcohol used is 3-methyl-1-pentyn-3-ol. The measured product yield is 87.6% and the selectivity is >99%.

[0095] The reaction equation for this experiment is:

[0096]

[0097] Embodiment 26

[0098] The specific experimental process and detection method are the same as those in Example 4, except that the propargyl alcohol used is 1-ethynyl-1-cyclopentanol. The measured product yield is 99.2% and the selectivity is >99%.

[0099] The reaction equation for this experiment is:

[0100]

[0101] Embodiment 27

[0102] The specific experimental process and detection method are the same as those in Example 4, except that the propargyl alcohol used is 1-ethynylcyclohexanol. The measured product yield is 66.5%, and the selectivity is >99%.

[0103] The reaction equation for this experiment is:

[0104]

[0105] Embodiment 28

[0106] The specific experimental process and detection method are the same as those in Example 4, except that the propargyl alcohol used is 3-phenyl-2-propyn-1-ol. The measured product yield is 0% and the selectivity is 0%.

[0107] The reaction equation for this experiment is:

[0108]

[0109] Embodiment 29

[0110] The specific experimental process and detection method are the same as those in Example 4, except that the propargyl alcohol used is ethyl ethynyl methanol, the reaction pressure is 1 MPa, and the measured product yield is 46.2%, and the selectivity is >99%.

[0111] The reaction equation for this experiment is:

[0112]

[0113] Examples 30-37

[0114] The specific experimental process and detection method are the same as those in Example 4, except that the catalyst used is the [Pth][BTMA] catalyst recovered in Example 4, and 8 cycles of recovery experiments were carried out under the same conditions, and the results are shown in Table 1. The specific recovery method is as follows: After the reaction is completed, the reaction mixture is extracted with n-hexane (4×15 mL); the solvent is removed from the upper layer to obtain the product, and the lower layer is composed of silver acetate and [Pth][BTMA], which is vacuum dried at 60° C. for 12 h to obtain the recovered [Pth][BTMA].

[0115] Table 1 Catalytic results of catalyst recovery and use of Examples 30-37

[0116]

[0117] It can be seen from Table 1 that after 8 cycles of recovery, the catalyst still has good activity, the product yield is 96.2%, the selectivity is 99.6%, and the catalytic performance is good.

Claims

1. A method for synthesizing α-alkyl unsaturated cyclic carbonate esters using phthalimide-based ionic liquid as catalyst, characterized in that: The main catalyst phthalimide-based ionic liquid and propargyl alcohol are added into a reaction kettle, the reaction kettle is closed and CO2 is introduced, and a cycloaddition reaction is carried out under certain reaction pressure and certain reaction temperature conditions to obtain; The phthalimide-based ionic liquid has any of the following structural formulas: 。 2. The method for synthesizing α-alkyl unsaturated cyclic carbonate esters using phthalimide-based ionic liquid as catalyst according to claim 1, characterized in that: The propynyl alcohol is a compound of any of the following structures: , .

3. The method for synthesizing α-alkyl unsaturated cyclic carbonate esters using phthalimide-based ionic liquid as catalyst according to claim 1, characterized in that: The molar ratio of the phthalimide-based ionic liquid to the propargyl alcohol is 0.5-7:

100.

4. The method for synthesizing α-alkyl unsaturated cyclic carbonate esters using phthalimide-based ionic liquid as catalyst according to claim 1, characterized in that: The reaction pressure of the cycloaddition reaction is 0.1~1 MPa.

5. The method for synthesizing α-alkyl unsaturated cyclic carbonate esters using phthalimide-based ionic liquid as catalyst according to claim 1, characterized in that: The reaction temperature of the cycloaddition reaction is 30±5°C.

6. The method for synthesizing α-alkyl unsaturated cyclic carbonate esters using phthalimide-based ionic liquid as catalyst according to claim 1, characterized in that: The reaction time of the cycloaddition reaction is 3~11h.

7. The method for synthesizing α-alkyl unsaturated cyclic carbonate esters using phthalimide-based ionic liquid as catalyst according to claim 1, characterized in that: During the cycloaddition reaction, a co-catalyst such as AgOAc, Ag2CO3, AgBr or AgI is added, and the molar ratio of the co-catalyst to propynyl alcohol is 0.5-5:100.

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