Preparation method and application of highly cross-linked polymer / SiO2 aerogel composite material

Abstract

The invention relates to the technical field of preparation of catalysts, and particularly discloses a preparation method and application of a highly crosslinked polymer / SiO2 aerogel composite material. The aluminum-doped silicon dioxide aerogel is synthesized by selecting solid waste coal gangue as a silicon source and adopting a sol-gel method. Furthermore, in the presence of SiO2 aerogel, a highly-crosslinked polymer is loaded in situ through a Friedel-Crafts alkylation reaction, and the highly-crosslinked polymer / SiO2 aerogel composite material is obtained. The prepared HCPs coated SiO2 composite material has the characteristics of no halogen, large specific surface area, wide pore size distribution and the like. As a halogen-free catalyst, the composite material shows excellent catalytic activity and cycling stability in the cycloaddition reaction of CO2 and epoxide, the toxicity residue and corrosion risk of a traditional halogen-containing system is avoided due to the environment-friendly characteristic of the composite material, meanwhile, the post-treatment process of a product is simplified, and the composite material shows remarkable potential in industrial large-scale application.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, specifically to a method for preparing a highly cross-linked polymer / SiO2 aerogel composite material and its application. Background Technology

[0002] According to relevant statistics, my country has a large historical stockpile of coal gangue, a solid waste generated during coal mining and processing. The main component of coal gangue is silicon-aluminum oxide, which is considered a potential raw material for preparing silicon-aluminum aerogels. SiO2 aerogels, due to their high specific surface area, low density, and excellent thermal stability, have wide applications in catalysis, adsorption, and insulation. However, the cost of preparing silicon-aluminum aerogels using traditional inorganic salts is relatively high. Using coal gangue as a raw material can significantly reduce production costs and promote the high-value utilization of solid waste resources.

[0003] In recent years, the excessive use of fossil fuels has led to a sharp rise in atmospheric CO2 concentration, causing environmental problems such as global warming and ocean acidification that seriously threaten the ecological balance. How to effectively reduce atmospheric CO2 concentration and realize its resource utilization has become a major challenge in the environmental and energy fields. Although CO2 is one of the major greenhouse gases, it is also an abundant, inexpensive, non-toxic, and non-flammable renewable C1 resource. Capturing and converting it into high-value-added products through chemical conversion technologies is of great practical significance and ecological value.

[0004] CO2, as a C1 resource, can be converted into various high-value-added chemical products, such as methanol, urea, formic acid, carbonates, oxazolidinones, and quinazolinones, through the development of advanced catalytic technologies. Among these, the cycloaddition reaction of CO2 with epoxides to synthesize cyclic carbonates has attracted widespread attention. On the one hand, this reaction is 100% atom-economical and can replace the traditional phosgene process for producing cyclic carbonates; on the other hand, cyclic carbonates are a very important class of chemical products, widely used in lithium-ion battery solvents, polymer monomers, and pharmaceutical intermediates.

[0005] Therefore, developing efficient catalytic systems is crucial for the efficient synthesis of cyclic carbonates from the cycloaddition reaction of CO2 with epoxides. Currently, while homogeneous catalysts exhibit excellent catalytic activity, the challenges in their separation and recovery processes severely limit their application. To address this issue, polyionic liquids (PILs), as heterogeneous catalysts combining the properties of polymer matrices and ionic liquids (ILs), have attracted considerable attention. However, this system still faces challenges in practical applications: active sites (halogen ions) are easily lost during the reaction, and residual halide ions may corrode metal equipment and adversely affect building materials. Summary of the Invention

[0006] To address the environmental pollution caused by coal gangue and the problems existing in the practical application of current polyionic liquids, this invention aims to provide a method for preparing a highly cross-linked polymer / SiO2 aerogel composite material and its application. This invention uses solid waste coal gangue as the silicon source and synthesizes aluminum-doped SiO2 aerogel under normal pressure using a sol-gel method. Based on the characteristics of aluminum-doped SiO2 aerogel, such as high specific surface area, rich micropores, mesopores, and macropores, low density, excellent thermal stability, and adsorption performance, a highly cross-linked polymer is in-situ loaded into its pores via Friedel-Crafts alkylation reaction to obtain the highly cross-linked polymer / SiO2 aerogel composite material. This preparation strategy can efficiently integrate halogen-free highly cross-linked polymers into low-density, high-porosity, and high-specific-surface-area aluminum-doped SiO2 aerogel, resulting in a halogen-free, high-specific-surface-area, and wide-pore-distribution highly cross-linked polymer / SiO2 aerogel composite material. Its environmentally friendly properties avoid the toxic residues and corrosion risks of traditional halogen-containing systems, while simplifying the post-processing of the product, demonstrating significant potential for large-scale industrial applications.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a highly cross-linked polymer / SiO2 aerogel composite material includes the following steps:

[0009] An N-containing aromatic monomer, alkylating agent, acidic catalyst, and organic solvent were mixed and stirred until homogeneous. Aluminum-doped SiO2 aerogel was then added to the mixture, and a Friedel-Crafts alkylation reaction was carried out at 40℃-100℃ for 18-36 h. After the reaction, the resulting solid was washed with methanol by centrifugation and dried to obtain a highly cross-linked polymer / SiO2 aerogel composite material.

[0010] The N-containing aromatic monomer is one of 4,5-dibenzimidazole, 1,3-diphenylguanidine, and 1-benzylimidazole, preferably 1,3-diphenylguanidine;

[0011] The alkylating agent is a combination of one of dimethoxymethane, trimethyl orthoformate or trimethyl orthoacetate and benzene, or is 1,4-dimethoxybenzene, wherein the alkylating agent is preferably dimethoxymethane and benzene;

[0012] The acidic catalyst is one of anhydrous ferric chloride, anhydrous aluminum chloride, titanium tetrachloride, and zinc chloride, preferably anhydrous ferric chloride;

[0013] The organic solvent is one of 1,2-dichloroethane and dichloromethane, preferably 1,2-dichloroethane;

[0014] The aluminum-doped SiO2 aerogel was prepared using coal gangue as the silicon source via a sol-gel method.

[0015] The ratio of the total mass of the N-containing aromatic monomer and the alkylating agent to the mass of the aluminum-doped SiO2 aerogel is 1:0.5-3, preferably 1:1-2, and more preferably 1:2;

[0016] The molar ratio of the N-containing aromatic monomer to the alkylating agent is 1:3-5, preferably 1:3-4;

[0017] The molar ratio of N-containing aromatic monomers to benzene in the alkylating reagent is 3:1;

[0018] The molar ratio of the acid catalyst to the alkylating agent, specifically dimethoxymethane, trimethyl orthoformate, or trimethyl orthoacetate, is 1:1.

[0019] The ratio of the mass of the organic solvent to the sum of the masses of other substances in the reaction system is 10-15 mL: 1-2.2 g.

[0020] Preferably, a method for preparing a highly cross-linked polymer / SiO2 aerogel composite material includes the following steps:

[0021] 1,3-Diphenylguanidine, dimethoxymethane, benzene, an acidic catalyst, and 1,2-dichloroethane were mixed and stirred until homogeneous. Aluminum-doped SiO2 aerogel was then added to the mixture, wherein the mass ratio of the sum of the masses of 1,3-diphenylguanidine, dimethoxymethane, and benzene to the mass of the aluminum-doped SiO2 aerogel was 1:2. A Friedel-Crafts alkylation reaction was carried out at 40℃-100℃ for 18-36 h. After the reaction, the resulting solid was washed with methanol by centrifugation and dried to obtain a highly crosslinked polymer / SiO2 aerogel composite material.

[0022] Preferably, the conditions for carrying out the Friedel-Crafts alkylation reaction are: first reacting at 40-60℃ for 3-12h, and then reacting at 80℃-100℃ for 15-24h.

[0023] Furthermore, the aluminum-doped SiO2 aerogel prepared using coal gangue as the silicon source via the sol-gel method includes the following steps:

[0024] S1 involves crushing, grinding, and sieving coal gangue, followed by calcination to obtain activated coal gangue powder; preferably, the calcination is carried out at 350℃ for 2 hours.

[0025] S2. The activated coal gangue powder is soaked in acid, centrifuged, and the acid-soaked filter residue is washed with water until neutral and dried to obtain coal gangue filter residue; preferably, it is soaked in 0.5 mol / L sulfuric acid solution at 50℃ for 2 hours;

[0026] S3 mixes coal gangue filter residue with an alkaline solid and calcines it to obtain alkali-fused coal gangue powder; preferably, the coal gangue filter residue is mixed with one of sodium hydroxide, sodium carbonate, potassium hydroxide, and potassium carbonate in a mass ratio of 1:0.2-1, preferably 1:0.5, and calcined at 850°C for 2 hours.

[0027] S4 reacts alkali-fused coal gangue powder with hydrochloric acid, filters, and obtains aluminum-doped SiO2 sol; preferably, alkali-fused coal gangue powder is mixed with 3 mol / L hydrochloric acid and heated to 90℃ for 15 min.

[0028] S5. After gelling and aging the aluminum-doped SiO2 sol in a 60°C oven for 3 hours, the aged gel is then placed in a mixed solution of anhydrous ethanol, n-hexane, and silane coupling agent for hydrophobic modification, filtered, and a hydrophobic gel is obtained. Preferably, the silane coupling agent is one of hexamethyldisilazane (HMDZ), trimethylchlorosilane (TMCS), methyltrimethoxysilane (MTMS), trimethylethoxysilane (MTES), and phenyltriethoxysilane (PTES), preferably trimethylchlorosilane; the volume ratio of anhydrous ethanol, n-hexane, and silane coupling agent is 5:6:1.

[0029] S6. The hydrophobic gel is dried at 100-180℃ to obtain precursor aerogel powder, and then calcined at 400-800℃ for 2h to obtain aluminum-doped SiO2 aerogel. Preferably, it is calcined at 600℃ for 2h.

[0030] Applications of the highly cross-linked polymer / SiO2 aerogel composite materials prepared by the above method in the catalytic cycloaddition reaction of epoxides with CO2 to synthesize cyclic carbonates. Specific applications include:

[0031] Add epoxide and highly cross-linked polymer / SiO2 aerogel composite material to a high-pressure reactor, seal the reactor, replace the air in the reactor with CO2, and after filling with 0.2-3MPa CO2, heat the reactor to 25-150℃ and react for 1-36 hours.

[0032] The epoxide is at least one of propylene oxide, cyclohexene oxide, and styrene oxide.

[0033] Furthermore, the reaction temperature is 80-150℃, preferably 100-140℃, and most preferably 120℃.

[0034] Furthermore, the reaction pressure is 0.5 MPa.

[0035] Furthermore, the reaction time is 4-8 hours.

[0036] The preferred reaction conditions are: a reaction temperature of 120°C and a reaction pressure of 0.5 MPa.

[0037] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0038] (1) In the presence of aluminum-doped SiO2 aerogel, a Friedel-Crafts alkylation reaction is carried out in one step between N-containing aromatic monomers and alkylating agents to obtain a highly cross-linked polymer / SiO2 aerogel composite material. The preparation method of this composite material is simple and efficient.

[0039] (2) The HCPs@SiO2 composite material prepared by the present invention has the characteristics of large specific surface area, wide pore size distribution, good thermal stability, no halogen, and rich in Lewis acid. In the cycloaddition reaction of CO2 and epoxide, it exhibits excellent catalytic performance and recycling performance, and is expected to be used in actual industrial production.

[0040] (3) As a halogen-free catalyst, this composite material avoids the toxic residues and corrosion risks of traditional halogen-containing systems, while simplifying the post-processing of products, and shows significant potential for industrial-scale application. Attached Figure Description

[0041] Figure 1 The nitrogen adsorption-desorption isotherm curve of HCPs@SiO2-1 prepared in Example 1 is shown.

[0042] Figure 2 The image shows the XRD pattern of HCPs@SiO2-1 prepared in Example 1.

[0043] Figure 3 This is a TEM image of HCPs@SiO2-1 prepared in Example 1.

[0044] Figure 4 The image shows a SEM image of HCPs@SiO2-1 prepared in Example 1.

[0045] Figure 5 The image shows the FT-IR spectrum of HCPs@SiO2-1 prepared in Example 1.

[0046] Figure 6 The HCPs@SiO2-1 prepared in Example 1 13 C-NMR spectrum.

[0047] Figure 7 This is a TEM image of aluminum-doped SiO2 aerogel based on coal gangue.

[0048] Figure 8 This is a SEM image of aluminum-doped SiO2 aerogel based on coal gangue.

[0049] Figure 9 The image shows the XRD pattern of aluminum-doped SiO2 aerogel based on coal gangue. Detailed Implementation

[0050] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, so as to further illustrate the technical content of the present invention.

[0051] In the following embodiments, the aluminum-doped SiO2 aerogel is prepared by the following steps:

[0052] Coal gangue (from Shuozhou, Shanxi Province, with alumina, silica, and iron oxide contents of 43.10%, 53.80%, and 0.74%, respectively, and other substances accounting for 2.36%) was crushed, ground, and passed through a 200-mesh sieve. After calcination at 350℃ for 2 hours, activated coal gangue powder was obtained. The activated coal gangue powder was placed in a 0.5 mol / L sulfuric acid solution at a solid-liquid volume ratio of 1:2, stirred evenly, and then soaked at 50℃ for 2 hours for acid leaching to remove impurities. After centrifugation, the acid leaching residue was washed with deionized water until neutral and dried to obtain coal gangue filter residue. The coal gangue filter residue was mixed with solid sodium hydroxide at a mass ratio of 1:0.5 and calcined at 850℃ for 2 hours to obtain alkali-fused coal gangue powder. Subsequently, alkali-fused coal gangue powder was mixed with 3 mol / L hydrochloric acid at a solid-liquid mass ratio of 1:7, and the mixture was heated to 90℃ for 15 min while stirring. After filtration, aluminum-doped SiO2 sol was obtained. The aluminum-doped SiO2 sol was gelled and aged in a 60℃ oven for 3 h. Then, the aged gel was placed in a mixed solution of anhydrous ethanol / n-hexane / trimethylchlorosilane with a volume ratio of 5:6:1 under stirring at a solid-liquid volume ratio of 1:2 for one-step solvent displacement-hydrophobic modification at 40℃ for 6 h. After modification, the mixture was filtered to obtain a hydrophobic gel filter cake. The hydrophobic gel filter cake was dried in a forced-air drying oven at 100℃ for 1 h, 120℃ for 1 h, and 180℃ for 2 h to obtain precursor aerogel powder. The precursor aerogel powder was then placed in a muffle furnace and calcined at 600℃ for 2 h to obtain aluminum-doped SiO2 aerogel.

[0053] Nitrogen adsorption-desorption isotherm analysis of aluminum-doped SiO2 aerogels showed that the specific surface area of ​​the SiO2 aerogels was 975 m² / g. 2 / g, the material is rich in micropores, mesopores and macropores, with an average pore size of 32.58nm. TEM analysis shows that the prepared SiO2 aerogel is an amorphous three-dimensional network structure composed of nanoparticles.

[0054] Example 1: Highly cross-linked polymer / SiO2 aerogel composite catalytic material (HCPs@SiO2-1)

[0055] In a 100 ml pressure-resistant bottle, 0.42 g (2 mmol) of 1,3-diphenylguanidine, 0.05 g (0.67 mmol) of benzene, 0.46 g (6 mmol) of dimethoxymethane, 0.97 g (6 mmol) of anhydrous ferric chloride, and 20 ml of 1,2-dichloroethane were added sequentially and stirred until homogeneous. Then, 1.86 g of aluminum-doped SiO2 aerogel was added to the mixture, and stirring was continued for 30 min. After purging with nitrogen three times, the bottle was sealed. The pressure-resistant bottle was transferred to a 45 °C oil bath and reacted for 5 h. Subsequently, it was heated at 80 °C for 20 h to complete the condensation reaction. After the reaction was completed, it was naturally cooled to room temperature. The obtained solid was washed three times with methanol by centrifugation and then dried in a 60 °C vacuum drying oven for 24 h to obtain a highly cross-linked polymer / SiO2 aerogel composite catalyst material, denoted as HCPs@SiO2-1, with an actual yield of 2.33 g.

[0056] Nitrogen adsorption-desorption isotherm analysis of HCPs@SiO2-1 showed that the specific surface area of ​​HCPs@SiO2-1 was 750 m² / g. 2 / g, the material is rich in micropores, mesopores and macropores, with an average pore size of 27.58nm; Figure 3 TEM analysis showed that the prepared HCPs@SiO2-1 was an amorphous three-dimensional network structure composed of nanoparticles; XRD results showed that ( Figure 2 The crystal structure of SiO2 aerogel did not change significantly during the composite process with highly cross-linked polymers; the chemical structure of the highly cross-linked polymers in HCPs@SiO2-1 was determined by... 13 C-NMR determination ( Figure 6 The signals at 40 and 53 ppm (labeled as 8) are attributed to carbon atoms in -CH2-, and the peaks at chemical shifts of approximately 122 ppm and 135 ppm correspond to carbon atoms in unsubstituted benzene ring carbon and substituted benzene ring carbon, respectively. In addition, the signals detected at 156 ppm (labeled as 4, 5) can be attributed to carbon atoms in C=N groups, which confirms the successful synthesis of highly crosslinked polymers. Figure 5 The FT-IR spectrum shows that at 3000 cm⁻¹ -1 The stretching vibration peaks of the methylene CH bond are observed at 1650 and 1579 cm⁻¹. -1 The peak at that location corresponds to the characteristic peaks of C=N and C=C stretching vibrations in the benzene ring skeleton, indicating that the highly cross-linked polymer has been successfully loaded onto SiO2 aerogel.

[0057] Example 2: Highly cross-linked polymer / SiO2 aerogel composite catalytic material (HCPs@SiO2-2)

[0058] In a 100 ml pressure-resistant bottle, 0.42 g (2 mmol) of 1,3-diphenylguanidine, 0.05 g (0.67 mmol) of benzene, 0.46 g (6 mmol) of dimethoxymethane, 0.97 g (6 mmol) of anhydrous ferric chloride, and 15 ml of 1,2-dichloroethane were added sequentially and stirred until homogeneous. Then, 0.93 g of aluminum-doped SiO2 aerogel was added to the mixture, and stirring was continued for 30 min. Nitrogen gas was then purged three times before sealing. The pressure-resistant bottle was transferred to a 45 °C oil bath and reacted for 5 h. Subsequently, the mixture was heated at 80 °C for 20 h to complete the condensation reaction. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The resulting solid was washed three times by centrifugation with methanol and then dried in a 60 °C vacuum drying oven for 24 h to obtain a highly cross-linked polymer / SiO2 aerogel composite catalyst, denoted as HCPs@SiO2-2, with an actual yield of 1.41 g.

[0059] Nitrogen adsorption-desorption isotherm analysis of HCPs@SiO2-2 showed that the specific surface area of ​​HCPs@SiO2-2 was 610 m² / g. 2 / g, the material is rich in micropores, mesopores and macropores, with an average pore size of 18.35nm; TEM analysis shows that the prepared HCPs@SiO2-2 is an amorphous three-dimensional network structure composed of nanoparticles; XRD results show that the crystal structure of SiO2 aerogel does not change significantly during the composite process with highly cross-linked polymers; FT-IR spectra show that highly cross-linked polymers have been successfully loaded onto SiO2 aerogels.

[0060] Example 3: Highly cross-linked polymer / SiO2 aerogel composite catalytic material (HCPs@SiO2-3)

[0061] In a 100 ml pressure-resistant bottle, 0.42 g (2 mmol) of 1,3-diphenylguanidine, 0.05 g (0.67 mmol) of benzene, 0.46 g (6 mmol) of dimethoxymethane, 0.97 g (6 mmol) of anhydrous ferric chloride, and 15 ml of 1,2-dichloroethane were added sequentially and stirred until homogeneous. Then, 0.47 g of aluminum-doped SiO2 aerogel was added to the mixture, and stirring was continued for 30 min. After purging with nitrogen three times, the bottle was sealed. The pressure-resistant bottle was transferred to a 45 °C oil bath and reacted for 5 h. Subsequently, it was heated at 80 °C for 20 h to complete the condensation reaction. After the reaction was completed, it was naturally cooled to room temperature. The obtained solid was washed three times with methanol by centrifugation and then dried in a vacuum drying oven at 60 °C for 24 h to obtain a highly cross-linked polymer / SiO2 aerogel composite catalyst, denoted as HCPs@SiO2-3, with an actual yield of 0.95 g.

[0062] Nitrogen adsorption-desorption isotherm analysis of HCPs@SiO2-3 showed that the specific surface area of ​​HCPs@SiO2-3 was 458 m². 2 / g, the material is rich in micropores, mesopores and macropores, with an average pore size of 15.35nm; TEM analysis shows that the prepared HCPs@SiO2-3 is an amorphous three-dimensional network structure composed of nanoparticles; XRD results show that the crystal structure of SiO2 aerogel does not change significantly during the composite process with highly cross-linked polymers; FT-IR spectra show that highly cross-linked polymers have been successfully loaded onto SiO2 aerogels.

[0063] Example 4: Highly cross-linked polymer / SiO2 aerogel composite catalytic material (HCPs@SiO2-4)

[0064] In a 100 ml pressure-resistant bottle, 0.44 g (2 mmol) of 4,5-dibenzimidazole, 0.05 g (0.67 mmol) of benzene, 0.46 g (6 mmol) of dimethoxymethane, 0.97 g (6 mmol) of anhydrous ferric chloride, and 20 ml of 1,2-dichloroethane were added sequentially and stirred until homogeneous. Then, 1.9 g of aluminum-doped SiO2 aerogel was added to the mixture, and stirring was continued for 30 min. After purging with nitrogen three times, the bottle was sealed. The pressure-resistant bottle was transferred to a 45 °C oil bath and reacted for 5 h. Subsequently, it was heated at 80 °C for 20 h to complete the condensation reaction. After the reaction was completed, it was naturally cooled to room temperature. The obtained solid was washed three times with methanol by centrifugation and then dried in a vacuum drying oven at 60 °C for 24 h to obtain a highly cross-linked polymer / SiO2 aerogel composite catalyst, denoted as HCPs@SiO2-4, with an actual yield of 2.41 g.

[0065] Nitrogen adsorption-desorption isotherm analysis of HCPs@SiO2-4 showed that the specific surface area of ​​HCPs@SiO2-4 was 695 m² / g. 2 / g, the material is rich in micropores, mesopores and macropores, with an average pore size of 25.95nm; TEM analysis shows that the prepared HCPs@SiO2-4 is an amorphous three-dimensional network structure composed of nanoparticles; XRD results show that the crystal structure of SiO2 aerogel does not change significantly during the composite process with highly cross-linked polymers; FT-IR spectra show that highly cross-linked polymers have been successfully loaded onto SiO2 aerogels.

[0066] Example 5: Highly cross-linked polymer / SiO2 aerogel composite catalytic material (HCPs@SiO2-5)

[0067] In a 100 ml pressure-resistant bottle, 0.32 g (2 mmol) of 1-benzylimidazole, 0.05 g (0.67 mmol) of benzene, 0.46 g (6 mmol) of dimethoxymethane, 0.97 g (6 mmol) of anhydrous ferric chloride, and 20 ml of 1,2-dichloroethane were added sequentially and stirred until homogeneous. Then, 1.66 g of aluminum-doped SiO2 aerogel was added to the mixture, and stirring was continued for 30 min. Nitrogen gas was then purged three times before sealing. The pressure-resistant bottle was transferred to a 45 °C oil bath and reacted for 5 h. Subsequently, the mixture was heated at 80 °C for 20 h to complete the condensation reaction. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The resulting solid was washed three times by centrifugation with methanol and then dried in a 60 °C vacuum drying oven for 24 h to obtain a highly cross-linked polymer / SiO2 aerogel composite catalyst, denoted as HCPs@SiO2-5, with an actual yield of 2.01 g.

[0068] Nitrogen adsorption-desorption isotherm analysis of HCPs@SiO2-5 showed that the specific surface area of ​​HCPs@SiO2-5 was 684 m². 2 / g, the material is rich in micropores, mesopores and macropores, with an average pore size of 26.6nm; TEM analysis shows that the prepared HCPs@SiO2-5 is an amorphous three-dimensional network structure composed of nanoparticles; XRD results show that the crystal structure of SiO2 aerogel does not change significantly during the composite process with highly cross-linked polymers; FT-IR spectra show that highly cross-linked polymers have been successfully loaded onto SiO2 aerogels.

[0069] Example 6: Highly cross-linked polymer / SiO2 aerogel composite catalytic material (HCPs@SiO2-6)

[0070] In a 100 ml pressure-resistant bottle, 0.42 g (2 mmol) of 1,3-diphenylguanidine, 0.83 g (6 mmol) of 1,4-dimethoxybenzene, 0.97 g (6 mmol) of anhydrous ferric chloride, and 25 ml of 1,2-dichloroethane were added sequentially and stirred until homogeneous. Then, 2.5 g of aluminum-doped SiO2 aerogel was added to the mixture, and stirring was continued for 30 min. After purging with nitrogen three times, the bottle was sealed. The pressure-resistant bottle was transferred to a 45 °C oil bath and reacted for 5 h. Subsequently, it was heated at 80 °C for 20 h to complete the condensation reaction. After the reaction was completed, it was naturally cooled to room temperature. The obtained solid was washed three times with methanol by centrifugation and then dried in a vacuum drying oven at 60 °C for 24 h to obtain a highly cross-linked polymer / SiO2 aerogel composite catalyst material, denoted as HCPs@SiO2-6, with an actual yield of 2.96 g.

[0071] Nitrogen adsorption-desorption isotherm analysis of HCPs@SiO2-6 showed that the specific surface area of ​​HCPs@SiO2-6 was 690 m² / g. 2 / g, the material is rich in micropores, mesopores and macropores, with an average pore size of 24.13nm; TEM analysis shows that the prepared HCPs@SiO2-6 is an amorphous three-dimensional network structure composed of nanoparticles; XRD results show that the crystal structure of SiO2 aerogel does not change significantly during the composite process with highly cross-linked polymers; FT-IR spectra show that highly cross-linked polymers have been successfully loaded onto SiO2 aerogels.

[0072] Example 7: Highly cross-linked polymer / SiO2 aerogel composite catalytic material (HCPs@SiO2-7)

[0073] In a 100 ml pressure-resistant bottle, 0.42 g (2 mmol) of 1,3-diphenylguanidine, 0.05 g (0.67 mmol) of benzene, 0.64 g (6 mmol) of trimethyl orthoformate, 0.97 g (6 mmol) of anhydrous ferric chloride, and 20 ml of 1,2-dichloroethane were added sequentially and stirred until homogeneous. Then, 2.22 g of aluminum-doped SiO2 aerogel was added to the mixture, and stirring was continued for 30 min. After purging with nitrogen three times, the bottle was sealed. The pressure-resistant bottle was transferred to a 45 °C oil bath and reacted for 5 h. Subsequently, it was heated at 80 °C for 20 h to complete the condensation reaction. After the reaction was completed, it was naturally cooled to room temperature. The obtained solid was washed three times by centrifugation with methanol and then dried in a vacuum drying oven at 60 °C for 24 h to obtain a highly cross-linked polymer / SiO2 aerogel composite catalyst material, denoted as HCPs@SiO2-7, with an actual yield of 2.63 g.

[0074] Nitrogen adsorption-desorption isotherm analysis of HCPs@SiO2-7 showed that the specific surface area of ​​HCPs@SiO2-7 was 679 m². 2 / g, the material is rich in micropores, mesopores and macropores, with an average pore size of 22.6nm; TEM analysis shows that the prepared HCPs@SiO2-7 is an amorphous three-dimensional network structure composed of nanoparticles; XRD results show that the crystal structure of SiO2 aerogel does not change significantly during the composite process with highly cross-linked polymers; FT-IR spectra show that highly cross-linked polymers have been successfully loaded onto SiO2 aerogels.

[0075] Example 8: Highly cross-linked polymer / SiO2 aerogel composite catalytic material (HCPs@SiO2-8)

[0076] 0.42 g (2 mmol) of 1,3-diphenylguanidine, 0.05 g (0.67 mmol) of benzene, 0.46 g (6 mmol) of dimethoxymethane, 0.97 g (6 mmol) of anhydrous ferric chloride, and 20 ml of dichloromethane were added sequentially to a 100 ml pressure-resistant bottle and stirred until homogeneous. Then, 1.86 g of aluminum-doped SiO2 aerogel was added to the mixture, and stirring was continued for 30 min. Nitrogen gas was then purged three times before sealing. The pressure-resistant bottle was transferred to a 45 °C oil bath and reacted for 5 h. Subsequently, the mixture was heated at 80 °C for 20 h to complete the condensation reaction. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The resulting solid was washed three times by centrifugation with methanol and then dried in a vacuum drying oven at 60 °C for 24 h to obtain a highly cross-linked polymer / SiO2 aerogel composite catalyst, denoted as HCPs@SiO2-8, with an actual yield of 2.32 g.

[0077] Nitrogen adsorption-desorption isotherm analysis of HCPs@SiO2-8 showed that the specific surface area of ​​HCPs@SiO2-8 was 732 m². 2 / g, the material is rich in micropores, mesopores and macropores, with an average pore size of 24.77nm; TEM analysis shows that the prepared HCPs@SiO2-8 is an amorphous three-dimensional network structure composed of nanoparticles; XRD results show that the crystal structure of SiO2 aerogel does not change significantly during the composite process with highly cross-linked polymers; FT-IR spectra show that highly cross-linked polymers have been successfully loaded onto SiO2 aerogels.

[0078] Example 9: Highly cross-linked polymer / SiO2 aerogel composite catalytic material (HCPs@SiO2-9)

[0079] In a 100 ml pressure-resistant bottle, 0.42 g (2 mmol) of 1,3-diphenylguanidine, 0.05 g (0.67 mmol) of benzene, 0.46 g (6 mmol) of dimethoxymethane, 0.97 g (6 mmol) of anhydrous ferric chloride, and 20 ml of chloroform were added sequentially and stirred until homogeneous. Then, 1.86 g of aluminum-doped SiO2 aerogel was added to the mixture, and stirring was continued for 30 min. Nitrogen gas was then purged three times before sealing. The pressure-resistant bottle was transferred to a 45 °C oil bath and reacted for 5 h. Subsequently, the mixture was heated at 80 °C for 20 h to complete the condensation reaction. After the reaction, the mixture was allowed to cool naturally to room temperature. The resulting solid was washed three times by centrifugation with methanol and then dried in a 60 °C vacuum drying oven for 24 h to obtain a highly cross-linked polymer / SiO2 aerogel composite catalyst, denoted as HCPs@SiO2-9. The actual yield was 2.19 g, with a large mass loss, indicating poor cross-linking effect.

[0080] Nitrogen adsorption-desorption isotherm analysis of HCPs@SiO2-9 showed that the specific surface area of ​​HCPs@SiO2-9 was 702 m². 2 / g, the material is rich in micropores, mesopores and macropores, with an average pore size of 21.5nm; TEM analysis shows that the prepared HCPs@SiO2-9 is an amorphous three-dimensional network structure composed of nanoparticles; XRD results show that the crystal structure of SiO2 aerogel does not change significantly during the composite process with highly cross-linked polymers; FT-IR spectra show that highly cross-linked polymers have been successfully loaded onto SiO2 aerogels.

[0081] Example 10: Cycloaddition reaction of propylene oxide and CO2 catalyzed by HCPs

[0082] 29.04 g (0.5 mol) of propylene oxide and 0.19 g (0.25 mmol) of HCP catalyst were added to a high-pressure reactor. The reactor was sealed, and the air inside was replaced with CO2. This process was repeated three times, followed by purging with 0.5 MPa of CO2. The reactor was then heated to 120 °C and reacted for 4 hours. After the reaction was complete, the product was qualitatively and quantitatively analyzed by gas chromatography. The yield of propylene carbonate was 30%, with a selectivity of 99.7%.

[0083] The preparation method of the HCPs catalyst includes the following steps:

[0084] In a 100 ml pressure-resistant bottle, 0.42 g (2 mmol) of 1,3-diphenylguanidine, 0.05 g (0.67 mmol) of benzene, 0.46 g (6 mmol) of dimethoxymethane, 0.97 g (6 mmol) of anhydrous ferric chloride, and 15 ml of 1,2-dichloroethane were added sequentially and stirred until homogeneous. The mixture was then purged with nitrogen three times and sealed. The pressure-resistant bottle was transferred to a 45 °C oil bath and reacted for 5 h. Subsequently, the mixture was heated at 80 °C for 20 h to complete the condensation reaction. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The resulting solid was washed three times by centrifugation with methanol and then dried in a vacuum drying oven at 60 °C for 24 h to obtain the highly crosslinked polymer, denoted as HCPs.

[0085] Example 11: Cycloaddition reaction of propylene oxide with CO2 catalyzed by HCPs@SiO2-1

[0086] 29.04 g (0.5 mol) of propylene oxide and 0.87 g of HCPs@SiO2-1 catalyst (n(HCPs) = 0.25 mmol) were added to a high-pressure reactor. The reactor was sealed, and the air inside was replaced with CO2, with the mixture being purged and vented three times. Then, 0.5 MPa of CO2 was introduced, and the reactor was heated to 120 °C and reacted for 4 hours. After the reaction was complete, the product was qualitatively and quantitatively analyzed by gas chromatography. The yield of propylene carbonate was 92%, and the selectivity was 99.4%.

[0087] Example 12: Cycloaddition reaction of propylene oxide with CO2 catalyzed by HCPs@SiO2-1

[0088] The reaction temperature was changed from 120°C to room temperature, and the remaining conditions and parameters were the same as in Example 11. The yield of propylene carbonate was 0.2% and the selectivity was 99.6%.

[0089] The reaction temperature was changed from 120°C to 80°C, and the other conditions and parameters were the same as in Example 11. The yield of propylene carbonate was 72% and the selectivity was 99.8%.

[0090] The reaction temperature was changed from 120°C to 100°C, and the other conditions and parameters were the same as in Example 11. The yield of propylene carbonate was 86% and the selectivity was 99.6%.

[0091] The reaction temperature was changed from 120°C to 140°C, and the other conditions and parameters were the same as in Example 11. The yield of propylene carbonate was 95% and the selectivity was 99.2%.

[0092] The reaction pressure was changed from 0.5 MPa to 3 MPa, and the remaining conditions and parameters were the same as in Example 11. The yield of propylene carbonate was 94% and the selectivity was 99.3%.

[0093] Example 13: Cycloaddition reaction of propylene oxide with CO2 catalyzed by other catalysts

[0094] Replacing 0.87 g of HCPs@SiO2-1 catalyst with 0.87 g of HCPs@SiO2-2 catalyst (n(HCPs) = 0.41 mmol), with all other conditions and parameters unchanged, yielded propylene carbonate with a yield of 84.1% and a selectivity of 99.5%.

[0095] Replacing 0.87 g of HCPs@SiO2-1 catalyst with 0.87 g of HCPs@SiO2-3 catalyst (n(HCPs) = 0.61 mmol), with all other conditions and parameters unchanged, yielded propylene carbonate with a yield of 79.4% and a selectivity of 99.6%.

[0096] Replacing 0.87 g of HCPs@SiO2-1 catalyst with 0.9 g of HCPs@SiO2-4 catalyst (n(HCPs) = 0.25 mmol), with all other conditions and parameters unchanged, yielded propylene carbonate with 87% yield and 99.4% selectivity.

[0097] Replacing 0.87 g of HCPs@SiO2-1 catalyst with 0.75 g of HCPs@SiO2-5 catalyst (n(HCPs) = 0.25 mmol), with all other conditions and parameters unchanged, yielded propylene carbonate with a yield of 71.5% and a selectivity of 99.4%.

[0098] Replacing 0.87 g of HCPs@SiO2-1 catalyst with 0.74 g of HCPs@SiO2-6 catalyst (n(HCPs) = 0.25 mmol), with all other conditions and parameters unchanged, yielded propylene carbonate with 88% yield and 99.5% selectivity.

[0099] Replacing 0.87 g of HCPs@SiO2-1 catalyst with 0.98 g of HCPs@SiO2-7 catalyst (n(HCPs) = 0.25 mmol), with all other conditions and parameters unchanged, yielded propylene carbonate with a yield of 82.8% and a selectivity of 99.3%.

[0100] Replacing 0.87 g of HCPs@SiO2-1 catalyst with 0.87 g of HCPs@SiO2-8 catalyst (n(HCPs) = 0.23 mmol), with all other conditions and parameters unchanged, yielded propylene carbonate at 90.3% and selectivity at 99.5%.

[0101] Replacing 0.87 g of HCPs@SiO2-1 catalyst with 0.87 g of HCPs@SiO2-9 catalyst (n(HCPs) = 0.13 mmol), with all other conditions and parameters unchanged, yielded propylene carbonate with a yield of 49.7% and a selectivity of 99.4%.

[0102] Example 14: Cycloaddition reaction of cyclohexene oxide with CO2 catalyzed by HCPs@SiO2-1

[0103] Referring to Example 11, 29.04 g (0.5 mol) of propylene oxide was replaced with 49.07 g (0.5 mol) of cyclohexene oxide, and the reaction time was changed from 4 hours to 8 hours. All other conditions and parameters remained unchanged. The yield of cyclohexene carbonate was 36.26%, and the selectivity was 95.2%.

[0104] Example 15: Cycloaddition reaction of styrene with CO2 catalyzed by HCPs@SiO2-1

[0105] Referring to Example 11, 29.04 g (0.5 mol) of propylene oxide was replaced with 60.1 g (0.5 mol) of styrene oxide, the reaction time was changed from 4 hours to 8 hours, and all other conditions and parameters remained unchanged. The yield of styrene carbonate was 60.86%, and the selectivity was 91.6%.

[0106] Example 16: Catalyst Recycling

[0107] 29.04 g (0.5 mol) of propylene oxide and 0.87 g of HCPs@SiO2-1 catalyst (n(HCPs) = 0.25 mmol) were added to a high-pressure reactor. The reactor was sealed, and the air inside was replaced with CO2. The reactor was purged and vented three times, followed by purging with 0.5 MPa CO2. The reactor was then heated to 120 °C and reacted for 4 hours. After the reaction, the products were qualitatively and quantitatively analyzed by gas chromatography. The yield of propylene carbonate was 92%, and the selectivity was 99.4%. After the reaction, the centrifuged catalyst was washed 3-5 times with anhydrous ethanol, dried under vacuum at 60 °C for 24 hours, and the catalytic reaction was repeated. The catalyst was reused 20 times to examine its recycling performance. The catalytic activity results are shown in Table 1 below.

[0108] Table 1

[0109]

Claims

1. A method for preparing a high cross-linked polymer / SiO2 aerogel composite material, characterized in that, The method comprises the following steps: The N-containing aromatic monomer, the alkylating agent, the acid catalyst and the organic solvent are mixed and stirred uniformly, then the aluminum-doped SiO2 aerogel is added into the mixture, and a Friedel-Crafts alkylation reaction is carried out at 40-100 DEG C for 18-36 hours; after the reaction is completed, the obtained solid is washed by centrifugation with methanol and dried to obtain the high-crosslinking polymer / SiO2 aerogel composite material.

2. The production method according to claim 1, characterized by, The N-containing aromatic monomer is one of 4,5-dibenzimidazole, 1,3-diphenyl guanidine and 1-benzyl imidazole; The alkylating agent is one of dimethoxymethane, trimethyl orthoformate or trimethyl orthoacetate in combination with benzene or 1,4-dimethoxybenzene; The acid catalyst is one of anhydrous ferric chloride, anhydrous aluminum chloride, titanium tetrachloride and zinc chloride; The organic solvent is one of 1,2-dichloroethane and dichloromethane; The aluminum-doped SiO2 aerogel is prepared by using coal gangue as a silicon source and a sol-gel method; The mass ratio of the sum of the N-containing aromatic monomer and the alkylating agent to the aluminum-doped SiO2 aerogel is 1:0.5-3.

3. The preparation method according to claim 2, characterized in that, The mass ratio of the sum of the N-containing aromatic monomer and the alkylating agent to the aluminum-doped SiO2 aerogel is 1:1-2.

4. The production method according to claim 3, characterized by, The method comprises the following steps: the 1,3-diphenyl guanidine, dimethoxymethane, benzene, the acid catalyst and 1,2-dichloroethane are mixed and stirred uniformly, then the aluminum-doped SiO2 aerogel is added into the mixture, the mass ratio of the sum of the 1,3-diphenyl guanidine, dimethoxymethane and benzene to the aluminum-doped SiO2 aerogel is 1:2, and a Friedel-Crafts alkylation reaction is carried out at 40-100 DEG C for 18-36 hours; after the reaction is completed, the obtained solid is washed by centrifugation with methanol and dried to obtain the high-crosslinking polymer / SiO2 aerogel composite material.

5. The preparation method according to claim 4, characterized in that, The Friedel-Crafts alkylation reaction is carried out under the following conditions: first, at 40-60 DEG C for 3-12 hours, and then, at 80-100 DEG C for 15-24 hours.

6. The preparation method according to claim 2, characterized in that, The molar ratio of the N-containing aromatic monomer to the alkylating agent is 1:3-5, preferably 1:3-4; The molar ratio of benzene in the N-containing aromatic monomer and the alkylating agent is 3:1; The molar ratio of the acid catalyst to dimethoxymethane, trimethyl orthoformate or trimethyl orthoacetate in the alkylating agent is 1:1; The ratio of the organic solvent in the reaction system to the sum of the mass of other substances in the system is 10-15 mL:1-2.2 g.

7. The preparation method according to claim 2, characterized in that, The aluminum-doped SiO2 aerogel is prepared by using coal gangue as a silicon source and a sol-gel method, and the preparation process comprises the following steps: S1: the coal gangue is crushed, ground, sieved, calcined and activated to obtain activated coal gangue powder; S2: the activated coal gangue powder is soaked with acid, centrifuged, and the acid-soaked residue is washed with water until neutral, and then dried to obtain coal gangue residue; S3: the coal gangue residue is mixed with an alkaline solid, calcined and fused to obtain alkali-fused coal gangue powder; S4: the alkali-fused coal gangue powder is reacted with hydrochloric acid, filtered and dried to obtain aluminum-doped SiO2 sol; S5 put the aluminum-doped SiO2 sol into a 60℃ oven to gelate and age for 3h, then put the aged gel into a mixed solution of anhydrous ethanol, n-hexane and silane coupling agent for hydrophobic modification, filter to obtain hydrophobic gel; S6 dry the hydrophobic gel at 100-180℃ to obtain precursor aerogel powder, then calcine at 400-800℃ for 2h to obtain aluminum-doped SiO2 aerogel.

8. The preparation method according to claim 7, characterized in that, In step S1, calcine at 350℃ for 2h; In step S2, use 0.5mol / L sulfuric acid solution to soak at 50℃ for 2h; In step S3, mix the coal gangue filter residue with one of sodium hydroxide, sodium carbonate, potassium hydroxide and potassium carbonate at a mass ratio of 1:0.2-1, and calcine at 850℃ for 2h; In step S4, mix the alkali-fused coal gangue powder with 3mol / L hydrochloric acid, and heat to 90℃ for 15min; In step S5, the silane coupling agent is one of hexamethyldisilazane, trimethylchlorosilane, methyltrimethoxysilane, trimethylethoxysilane and phenyltriethoxysilane, and the volume ratio of anhydrous ethanol, n-hexane and silane coupling agent is 5:6:1; In step S6, calcine at 600℃ for 2h.

9. The use of the high cross-linked polymer / SiO2 aerogel composite material prepared by the method of any one of claims 1-8 in the catalytic reaction of epoxide with CO2 for the synthesis of cyclic carbonate; preferably, the epoxide is at least one of propylene oxide, cyclohexene oxide and styrene oxide.

10. Use according to claim 9, characterized in that, Comprising: adding epoxide and high cross-linked polymer / SiO2 aerogel composite material into a high-pressure reaction kettle, sealing the kettle, replacing the air in the kettle with CO2, charging 0.2-3MPa CO2, heating the reaction kettle to 25-150℃, and reacting for 1-36h; preferably, the reaction temperature is 80-150℃, preferably 100-140℃, and most preferably 120℃; and / or the reaction pressure is 0.5MPa; and / or the reaction time is 4-8h.

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