Cu2O-loaded ZnAl-LDH catalyst for catalyzing CO2 and substituted alkynol to synthesize cyclic carbonate as well as preparation method and application of Cu2O-loaded ZnAl-LDH catalyst

Abstract

The invention relates to a Cu2O loaded ZnAl-LDH catalyst for catalyzing synthesis of cyclic carbonate from CO2 and substituted alkynol and a preparation method and application thereof, the preparation method comprises the following steps: S1, dissolving Zn salt, Al salt and Cu salt in deionized water, adjusting the pH value to be alkaline, and heating for reaction to obtain CuO loaded ZnAl-LDH; and S2, the CuO loaded ZnAl-LDH prepared in the step S1 is subjected to heating reduction, and the Cu2O loaded ZnAl-LDH catalyst is obtained. Compared with the prior art, the catalyst prepared by the method has abundant Cu (I) catalytic sites, CO2 and alkynol compounds can be subjected to cycloaddition reaction under mild conditions to synthesize cyclic carbonate, and the reaction has high activity, high conversion rate and high selectivity.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a Cu2O-loaded ZnAl-LDH catalyst for catalyzing CO2 and substituted alkynol to synthesize cyclic carbonate, and a preparation method and application thereof. Background Art

[0002] Due to the massive consumption of fossil raw materials, the emission of greenhouse gases such as carbon dioxide in the atmosphere has increased significantly. The substantial increase in the CO2 content in the environment has broken the original carbon balance, thus causing a serious greenhouse effect, further aggravating global extreme climate, glacier melting, permafrost melting and other phenomena. On the other hand, CO2 is also considered to be a non-toxic, renewable and abundant C1 resource. Making full use of this important C1 resource is of great significance for future sustainable development. In this case, carbon capture, storage and utilization (CCUS) aims to capture carbon dioxide in waste gas or the atmosphere and convert it into chemicals with high added value, which is currently recognized as the most effective "carbon reduction, negative carbon" technical means.

[0003] The atomic utilization rate of the reaction of CO2 and alkynol compounds to generate substituted cyclic carbonates is as high as 100%. The existence of cyclic carbonates can directly promote the development of many industries. The reaction has high selectivity and few by-products, which meets the requirements of green chemistry and atom economy. Cyclic carbonates, which have the characteristics of high boiling point, stable properties, good solubility, non-corrosiveness, safety and non-toxicity, are a very important class of chemicals with a wide range of uses: they can be used as reaction intermediates or inert polar aprotic solvents in organic synthesis, as electrolytes in lithium batteries, as fuel additives and raw materials for synthetic engineering plastics in industry, and as additives and fixatives for synthetic fibers, spinning solvents and water-soluble dye dispersants in the textile industry. Therefore, the preparation of substituted cyclic carbonates from carbon dioxide and alkynol compounds has important research significance and application value in both the environmental and energy fields.

[0004] At present, many methods for preparing cyclic carbonates have been reported, which has improved researchers' understanding of this conversion. Among them, the reaction of CO2 with geminal diols has been replaced because of its low atomic utilization rate; and the route of synthesizing carbonates with halogenated alcohols has been abandoned because of the large amount of halogenated salts produced as byproducts and low economic value.

[0005] The synthetic route of preparing α-alkylene cyclic carbonates through the carboxyl cyclization reaction of CO2 and alkynols has become an important method for preparing cyclic carbonates. This method has become the most valuable method for the synthesis of cyclic carbonates with the advantages of 100% atomic utilization, no by-products and more environmental protection. However, CO2 molecules have great stability, and it is difficult to carry out the carboxyl cyclization reaction under certain reaction conditions. Therefore, the development of highly active catalysts is particularly important and has become a difficulty in the catalytic conversion of CO2.

[0006] The surface of metal oxides is usually distributed with acid and base centers, and the preparation method is simple, cheap, stable and easy to recycle, so oxide catalysts are widely used in the catalytic industry. Early catalysts used for carbon dioxide cyclocarbonation reactions include cuprous oxide, zinc oxide, aluminum oxide, silver oxide, etc. Among them, copper, as a cheap non-precious metal element, has the ability to activate the carbon-carbon triple bond of propargyl alcohol, and has become a research hotspot for catalytic carboxyl cyclization reactions. On the other hand, it is generally believed that Cu(I) contributes significantly to the absorption and activation of CO2. However, metal oxides may agglomerate during use, thereby reducing the catalytic efficiency. Therefore, they are usually combined with some carriers. After loading, the dispersion (the ratio of the number of metal atoms exposed on the particle surface to the total number of metal atoms) can be increased. MOF-derived metal oxides usually retain the unique porosity of MOF and abundant unsaturated metal sites. This structure provides a special environment for gas adsorption and desorption. Among the many MOFs, ZnO derived from ZIF-8 can retain the porous hollow structure of ZIF-8 and have the characteristics of ZnO crystals. The pore structure can be effectively regulated by bimetallic loading, and bimetallic doping can combine the different energy band structures of the two metal elements, promote the transfer of electrons by forming a pn junction, and thus promote its catalytic activity. The pore structure and exposed alkaline sites of MOFs themselves are conducive to the effective adsorption of CO2. Through the migration of electron pairs, CO2 is stably bound to the surface of the adsorbent or catalyst, which is conducive to subsequent activation and conversion, which has attracted widespread attention.

[0007] However, the development of efficient, highly stable and sustainable non-precious metal-based catalysts to achieve the carboxylation cyclization reaction of alkynols with carbon dioxide under mild conditions is still a huge challenge in the current resource utilization of CO2. In summary, in order to achieve the resource utilization of CO2, the present invention constructs a Cu2O-loaded ZnAl-LDH multifunctional catalytic system for catalyzing the carboxylation cyclization reaction of carbon dioxide and alkynols. Summary of the invention

[0008] The purpose of the present invention is to provide a Cu2O-supported ZnAl-LDH catalyst for catalyzing the synthesis of cyclic carbonates from CO2 and substituted alkynols, and a preparation method and application thereof, in order to overcome the defects of the above-mentioned prior art. The catalyst prepared has high activity and high yield; and the reaction conditions of the catalytic CO2 and substituted alkynols are mild, the selectivity is good, the substrate is widely applicable, and a good catalytic effect can be achieved for most substituted alkynols.

[0009] The purpose of the present invention can be achieved by the following technical solutions:

[0010] One of the technical solutions of the present invention is to provide a method for preparing a Cu2O-loaded ZnAl-LDH catalyst, comprising the following steps:

[0011] S1, dissolving Zn salt, Al salt and Cu salt in deionized water, adjusting the pH to alkaline, and heating the reaction to obtain CuO-loaded ZnAl-LDH;

[0012] S2. The CuO-loaded ZnAl-LDH prepared in step S1 is heated and reduced to obtain a Cu2O-loaded ZnAl-LDH catalyst.

[0013] In some specific embodiments, in step S1, the anion in the Zn salt is selected from any one of nitrate, sulfate, and chloride;

[0014] The anion in the Al salt is selected from any one of nitrate, sulfate and chloride;

[0015] The anion in the Cu salt is selected from any one of nitrate, sulfate and chloride.

[0016] In some specific embodiments, in step S1, the molar ratio of the Zn salt to the Al salt is 3:1, and the molar ratio of the Cu salt to the Al salt is 1:5 to 1:20.

[0017] In some specific embodiments, in step S1, the pH value is adjusted to 10-14.

[0018] In some specific embodiments, in step S1, a mixed solution of NaOH and Na2CO3 is used to adjust the pH value, the mass ratio of NaOH and Na2CO3 is 1:9 to 9:1, and the concentration is 10wt% to 30wt%.

[0019] In some specific embodiments, in step S1, the heating reaction temperature is 80-160° C. and the time is 1-12 hours.

[0020] In some specific embodiments, in step S2, a mixed gas of nitrogen and hydrogen is used to heat and reduce the CuO-supported ZnAl-LDH, and the volume content of hydrogen in the mixed gas is not less than 5%.

[0021] In some specific embodiments, in step S2, the temperature of heating reduction is 200-300° C., and the time is 1-4 hours.

[0022] The second technical solution of the present invention is to provide a Cu2O-loaded ZnAl-LDH catalyst, which is obtained based on the preparation method described in one of the above technical solutions.

[0023] The third technical solution of the present invention is to provide an application of the Cu2O-loaded ZnAl-LDH catalyst as described in the above technical solution 2 in catalyzing the reaction of CO2 and alkynol compounds to synthesize cyclic carbonates.

[0024] The present invention also provides a Cu2O-supported ZnAl-LDH catalyst for catalyzing the reaction of CO2 and alkynol compounds to synthesize cyclic carbonates, comprising the following steps:

[0025] A1. Put the Cu2O-loaded ZnAl-LDH catalyst, the co-catalyst, the alkynol compound substrate and the solvent into a pressure-resistant reactor and mix them;

[0026] A2. Pass CO2 into a pressure-resistant reactor to react and obtain a cyclic carbonate.

[0027] As preferably, the method comprises the following steps:

[0028] A1. Place the Cu2O-loaded ZnAl-LDH catalyst, co-catalyst, alkynol compound substrate, and solvent into a pressure-resistant reactor, add a magnetic stirrer or mechanical stirrer, and tighten the pressure-resistant reactor;

[0029] A2, connect the CO2 cylinder to the liquid phase inlet of the pressure-resistant reactor through a pressure reducing valve and a back pressure valve, and adjust the pressure of the pressure reducing valve and the back pressure valve; start stirring, start heating, and react to obtain a cyclic carbonate;

[0030] After the reaction was completed, the reactor was cooled to room temperature and the back pressure valve was closed; the reaction yield was quantitatively calculated by gas chromatography.

[0031] As a more preferred embodiment, the alkynol compound substrate is selected from any one of 2-methyl-3-butyn-2-ol, 2-methyl-4-phenyl-3-butyn-2-ol, 3-methyl-1-pentyn-3-ol, 1-ethynyl-1-cyclohexanol, 3-methyl-1-heptyn-3-ol, 3-ethyl-1-pentyn-3-ol, 3,4,4-trimethyl-1-pentyn-3-ol, 3-ethyl-1-pentyn-3-ol, dimethyl (vinyl) ethynyl methanol, 2-methyl-3-pentyn-2-ol, 2,5-dimethyl-3-hexyn-2,5-diol, and 2-methyl-3-hexyn-2-ol;

[0032] The co-catalyst is selected from any one of 4-dimethylaminopyridine, DBU, N,N-dimethylaniline, diisopropylethylamine, 2-methylimidazole, and N-methylmorpholine;

[0033] The solvent is selected from any one of DMF, toluene, N,N-dimethylacetamide, N-methylpyrrolidone, ethylene glycol dimethyl ether and DMSO.

[0034] As a more preferred embodiment, in step A1, the mass ratio of the Cu2O-supported ZnAl-LDH catalyst to the alkynol compound substrate is 1:5 to 1:200; the molar ratio of the co-catalyst to the alkynol compound substrate is 1:5 to 1:300.

[0035] As a more preferred embodiment, in step A2, the CO2 pressure is controlled to be 0-4 MPa (not 0), the temperature is 20-60°C, and the time is 1-12 h.

[0036] The reaction formula for the synthesis of cyclic carbonates by CO2 and alkynol compounds catalyzed by Cu2O-supported ZnAl-LDH catalyst is as follows:

[0037]

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The supported catalyst of the present invention contains Cu2O catalytically active species and LDH supported substrate. Through the adsorption and activation of CO2 gas by LDH substrate and the activation of alkynol compounds by metal active centers, the catalyst has high catalytic activity under synergistic effect, thereby effectively ensuring the stability of the reaction and improving production efficiency. At the same time, the pressure requirement for carbon dioxide in the reaction process is low and the reaction temperature is as low as room temperature. Therefore, the production cost can be effectively reduced, and the production safety can be improved, which has good industrial application prospects.

[0040] (2) The raw materials for preparing the Cu2O-supported ZnAl-LDH catalyst of the present invention are readily available, the synthesis steps are few and the yield is high, the operation method is safe and simple, environmentally friendly, and easy to recycle. The catalyst has abundant Cu(I) catalytic sites, and can cause CO2 to react with alkynol compounds to synthesize cyclic carbonates under mild conditions, and the reaction has high activity, high conversion rate, and high selectivity. Under preferred reaction conditions, the yield of the target product of the cycloaddition reaction is not less than 88%, which has good catalytic effect and good industrial application value.

[0041] 3. The Cu2O-loaded ZnAl-LDH catalyst of the present invention is used to catalyze the cycloaddition reaction of CO2 and alkynol compounds, and its substrate universality is wide. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram of the preparation process (a) and morphology (b-d) of the Cu2O-loaded ZnAl-LDH catalyst prepared in Example 1.

[0043] Figure 2 This is the XRD comparison diagram of the Cu2O-supported ZnAl-LDH catalyst prepared in Example 1 before and after use.

[0044] Figure 3 This is a comparison chart of infrared spectra of the Cu2O-loaded ZnAl-LDH catalyst prepared in Example 1 before and after use.

[0045] Figure 4 Schematic diagram of the online infrared reaction of the synthesis of cyclic carbonates from CO2 and substituted alkynols catalyzed by the Cu2O-supported ZnAl-LDH catalyst prepared in Example 1. DETAILED DESCRIPTION

[0046] The present invention is to achieve catalysis under mild conditions CO2 and substituted alkynols are used to synthesize cyclic carbonates, and a Cu2O-supported ZnAl-LDH catalyst is improved. The catalyst has high activity, high catalytic yield, good selectivity, and wide substrate universality.

[0047] The present invention also provides a method for preparing a Cu2O-supported ZnAl-LDH catalyst, such as Figure 1 (a) is a schematic diagram of the preparation process, and the reaction conditions shown in the figure are only a preferred scheme.

[0048] The steps include:

[0049] S1, dissolving Zn salt, Al salt and Cu salt in deionized water, adjusting the pH to alkaline, and heating the reaction to obtain CuO-loaded ZnAl-LDH;

[0050] S2. The CuO-loaded ZnAl-LDH prepared in step S1 is heated and reduced to obtain a Cu2O-loaded ZnAl-LDH catalyst.

[0051] Preferably, in step S1, the anion in the Zn salt is selected from any one of nitrate, sulfate and chloride;

[0052] The anion in the Al salt is selected from any one of nitrate, sulfate and chloride;

[0053] The anion in the Cu salt is selected from any one of nitrate, sulfate and chloride.

[0054] Preferably, in step S1, the molar ratio of the Zn salt to the Al salt is (3-6):1, and the molar ratio of the Cu salt to the Al salt is 1:5-1:20.

[0055] Preferably, in step S1, the pH value is adjusted to 10-14.

[0056] Preferably, in step S1, a mixed solution of NaOH and Na2CO3 is used to adjust the pH value, wherein the mass ratio of NaOH to Na2CO3 is 1:9 to 9:1, and the concentration is 10wt% to 30wt%.

[0057] Preferably, in step S1, the heating reaction temperature is 80-160° C. and the time is 1-12 hours.

[0058] Preferably, in step S2, a mixed gas of nitrogen and hydrogen is used to heat and reduce the CuO-supported ZnAl-LDH, and the content of hydrogen in the mixed gas is not less than 5%.

[0059] Preferably, in step S2, the temperature of the heating reduction is 200-300°C and the time is 1-4 hours.

[0060] The present invention also provides an application of a Cu2O-supported ZnAl-LDH catalyst, that is, the Cu2O-supported ZnAl-LDH catalyst catalyzes CO2 and an alkynol compound to synthesize a cyclic carbonate, comprising the following steps:

[0061] A1. Place the Cu2O-loaded ZnAl-LDH catalyst, co-catalyst, alkynol compound substrate, and solvent into a pressure-resistant reactor, add a magnetic stirrer or mechanical stirrer, and tighten the pressure-resistant reactor;

[0062] A2, connect the CO2 cylinder to the liquid phase inlet of the pressure-resistant reactor through a pressure reducing valve and a back pressure valve, and adjust the pressure of the pressure reducing valve and the back pressure valve; start stirring, start heating, and react to obtain a cyclic carbonate;

[0063] After the reaction was completed, the reactor was cooled to room temperature and the back pressure valve was closed; the reaction yield was quantitatively calculated by gas chromatography.

[0064] Preferably, the alkynol compound substrate is selected from any one of 2-methyl-3-butyn-2-ol, 2-methyl-4-phenyl-3-butyn-2-ol, 3-methyl-1-pentyn-3-ol, 1-ethynyl-1-cyclohexanol, 3-methyl-1-heptyn-3-ol, 3-ethyl-1-pentyn-3-ol, 3,4,4-trimethyl-1-pentyn-3-ol, 3-ethyl-1-pentyn-3-ol, dimethyl (vinyl) ethynyl methanol, 2-methyl-3-pentyn-2-ol, 2,5-dimethyl-3-hexyn-2,5-diol, and 2-methyl-3-hexyn-2-ol;

[0065] The co-catalyst is selected from any one of 4-dimethylaminopyridine, DBU, N,N-dimethylaniline, diisopropylethylamine, 2-methylimidazole, and N-methylmorpholine;

[0066] The solvent is selected from any one of DMF, toluene, N,N-dimethylacetamide, N-methylpyrrolidone, ethylene glycol dimethyl ether and DMSO.

[0067] Preferably, in step A1, the mass ratio of the Cu2O-supported ZnAl-LDH catalyst to the alkynol compound substrate is 1:5 to 1:200; and the molar ratio of the co-catalyst to the alkynol compound substrate is 1:5 to 1:300.

[0068] Preferably, in step A2, the CO2 pressure is controlled to be 0-4 MPa (not 0), the temperature is 20-60°C, and the time is 1-12 h.

[0069] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0070] In the following examples, unless otherwise specified, raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0071] Embodiment 1:

[0072] This embodiment 1 provides a method for preparing a Cu2O-supported ZnAl-LDH catalyst having a Zn / Al molar ratio of 3:1 and a Cu / Al molar ratio of 1:10, comprising the following steps:

[0073] (1) 14.256 g (0.048 mol) of Zn(NO3)2·6H2O, 6.002 g (0.016 mol) of Al(NO3)3·9H2O and 0.386 g (0.0016 mol) of Cu(NO3)2·3H2O were dissolved in deionized water, and then a 30 wt% aqueous solution of NaOH and Na2CO3 (mass ratio of 4:1) was added to a pH value of 12. After stirring for 10 min, the mixed solution was heated at 120 °C in a sealed autoclave for 8 h. The obtained precipitate was washed with deionized water to a pH value of 7, and then dried in an oven at 80 °C overnight to obtain Cu(OH)2-loaded ZnAl-LDH.

[0074] (2) The Cu(OH)2-loaded ZnAl-LDH was transferred to a crucible and placed in a tubular furnace. The air in the furnace was first purged with a mixed gas containing 90% nitrogen and 10% hydrogen at a flow rate of 100 mL / min for half an hour, and then heated to 250°C at 5°C / min and maintained for 2 hours to obtain Cu2O-loaded ZnAl-LDH, which was recorded as 0.1Cu2O@ZnAl-LDH.

[0075] Figure 1 (a) Schematic diagram of the preparation process and SEM image of the prepared 0.1Cu2O@ZnAl-LDH catalyst Figure 1 (b-d) As shown in the figure, the ZnAl-LDH has a flake structure of about 100nm, and Cu2O particles are loaded on the surface of the flake-loaded ZnAl-LDH, with a size of about 30-50nm.

[0076] Embodiment 2:

[0077] This embodiment 2 provides a method for preparing a Cu2O-supported ZnAl-LDH catalyst having a Zn / Al molar ratio of 3:1 and a Cu / Al molar ratio of about 1:6.67, comprising the following steps:

[0078] (1) 14.256 g (0.048 mol) of Zn(NO3)2·6H2O, 6.002 g (0.016 mol) of Al(NO3)3·9H2O, and 0.564 g (0.0024 mol) of Cu(NO3)2·3H2O were dissolved in deionized water, and then a 20 wt% aqueous solution of NaOH and Na2CO3 (mass ratio of 9:1) was added to a pH value of 14. After stirring for 10 min, the mixed solution was heated at 100 °C for 10 h in a sealed autoclave. The obtained precipitate was washed with deionized water to a pH value of 7, and then dried in an oven at 60 °C overnight to obtain Cu(OH)2-loaded ZnAl-LDH.

[0079] (2) The Cu(OH)2-loaded ZnAl-LDH was transferred to a crucible and placed in a tubular furnace. The air in the furnace was first purged with a mixed gas containing 80% nitrogen and 20% hydrogen at a flow rate of 70 mL / min for half an hour, and then heated to 200°C at 3°C / min and maintained for 2 hours to obtain Cu2O-loaded ZnAl-LDH, recorded as 0.15Cu2O@ZnAl-LDH.

[0080] Embodiment 3:

[0081] This embodiment 3 provides a method for preparing a Cu2O-supported ZnAl-LDH catalyst having a Zn / Al molar ratio of 3:1 and a Cu / Al molar ratio of about 1:20, comprising the following steps:

[0082] (1) 13.80 g (0.048 mol) of ZnSO4·7H2O, 10.66 g (0.016 mol) of Al2(SO4)3·18H2O and 0.20 g (0.0008 mol) of CuSO4·5H2O were dissolved in deionized water, and then a 30 wt% aqueous solution of NaOH and Na2CO3 (mass ratio of 1:9) was added to a pH value of 10. After stirring for 30 min, the mixed solution was heated at 120 °C in a sealed autoclave for 8 h. The obtained precipitate was washed with deionized water to a pH value of 7, and then dried in an oven at 80 °C overnight to obtain Cu(OH)2-loaded ZnAl-LDH.

[0083] (2) The Cu(OH)2-loaded ZnAl-LDH was transferred to a crucible and placed in a tubular furnace. The air in the furnace was first purged with a mixed gas containing 90% nitrogen and 10% hydrogen at a flow rate of 80 mL / min for half an hour, and then heated to 250°C at 5°C / min and maintained for 2 hours to obtain Cu2O-loaded ZnAl-LDH, which was recorded as 0.05Cu2O@ZnAl-LDH.

[0084] Embodiment 4:

[0085] This embodiment 3 provides a method for preparing a Cu2O-supported ZnAl-LDH catalyst having a Zn / Al molar ratio of 3:1 and a Cu / Al molar ratio of about 1:5, comprising the following steps:

[0086] (1) 6.528 g (0.048 mol) of ZnCl2, 10.66 g (0.016 mol) of AlCl3·6H2O and 0.54 g (0.0032 mol) of CuSO4·5H2O were dissolved in deionized water, and then a 10 wt% aqueous solution of NaOH and Na2CO3 (mass ratio of 1:4) was added to a pH value of 13. After stirring for 30 min, the mixed solution was heated at 140 °C for 4 h in a sealed autoclave. The obtained precipitate was washed with deionized water to a pH value of 7, and then dried in an oven at 70 °C overnight to obtain Cu(OH)2-loaded ZnAl-LDH.

[0087] (2) The Cu(OH)2-loaded ZnAl-LDH was transferred to a crucible and placed in a tubular furnace. The air in the furnace was first purged with a mixed gas containing 75% nitrogen and 25% hydrogen at a flow rate of 60 mL / min for half an hour, and then heated to 300°C at 2°C / min and maintained for 4 hours to obtain Cu2O-loaded ZnAl-LDH, which was recorded as 0.2Cu2O@ZnAl-LDH.

[0088] Test Example 1:

[0089] This test example 1 provides a catalytic reaction of catalyzing the conversion reaction of CO2 and alkynol compounds to generate cyclic carbonates by the 0.2Cu2O@ZnAl-LDH catalyst prepared by Example 4, which specifically includes the following steps:

[0090] (1) The solvent DMF (20 mL), the catalyst 0.2Cu2O@ZnAl-LDH (0.1 g), the co-catalyst DBU (0.05 g, 0.00032 mol) and the reaction substrate 3-methyl-1-pentyn-3-ol (2 g, 0.02 mol) were placed in a pressure reactor, a magnetic stirrer was added, and the pressure reactor was tightened.

[0091] (2) Connect the carbon dioxide cylinder to the liquid phase inlet of the pressure-resistant reactor through a pressure reducing valve and a back pressure valve, and adjust the pressure of the pressure reducing valve and the back pressure valve to control the pressure in the reactor to be no higher than 2 MPa.

[0092] (3) Start stirring, start heating, control the reaction at 50°C, and after 3 hours of reaction, obtain the target product. Cool the reactor to room temperature and close the back pressure valve.

[0093] The reaction yield was 98% as determined by gas chromatography.

[0094] The structure of the reaction substrate 3-methyl-1-pentyn-3-ol is:

[0095]

[0096] After identification, the structure of the target product is:

[0097]

[0098] Test Example 2:

[0099] This test example 2 provides a catalytic reaction of catalyzing the conversion reaction of CO2 and alkynol compounds to generate cyclic carbonates by the 0.1Cu2O@ZnAl-LDH catalyst prepared by Example 1, which specifically includes the following steps:

[0100] (1) Place solvent N-methylpyrrolidone (40 mL), catalyst 0.1Cu2O@ZnAl-LDH (0.4 g), co-catalyst diisopropylethylamine (0.2 g, 0.0015 mol) and reaction substrate 2-methyl-3-butyn-2-ol (8 g, 0.095 mol) into a pressure reactor with mechanical stirring, and tighten the pressure reactor.

[0101] (2) Connect the carbon dioxide cylinder to the liquid phase inlet of the pressure-resistant reactor through a pressure reducing valve and a back pressure valve, and adjust the pressure of the pressure reducing valve and the back pressure valve to control the pressure in the reactor to no more than 0.1 MPa.

[0102] (3) Stirring was started and the reaction was carried out at 30° C. After 9 hours of reaction, the target product was obtained. The reactor was cooled to room temperature and the back pressure valve was closed.

[0103] The reaction yield was 95% as determined by gas chromatography.

[0104] The structure of the reaction substrate 2-methyl-3-butyn-2-ol is:

[0105]

[0106] After identification, the structure of the target product is:

[0107]

[0108] Figure 2 and Figure 3 By analyzing the XRD and infrared images of the recovered catalyst and the newly prepared catalyst after filtration, it can be seen that the catalyst maintained good stability before and after use.

[0109] Figure 4 Schematic diagram of the online infrared reaction of CO2 and substituted alkynols catalyzed by the catalyst to synthesize cyclic carbonates.

[0110] Test Example 3:

[0111] This test example 3 provides a catalytic reaction of catalyzing the conversion reaction of CO2 and alkynol compounds to generate cyclic carbonates by the 0.05Cu2O@ZnAl-LDH catalyst prepared by Example 3, which specifically includes the following steps:

[0112] (1) The solvent ethylene glycol dimethyl ether (30 mL), the catalyst 0.05Cu2O@ZnAl-LDH (0.5 g), the co-catalyst N,N-dimethylaniline (0.3 g, 0.0025 mol) and the reaction substrate 3-methyl-1-heptyn-3-ol (3 g, 0.02 mol) were placed in a pressure reactor with mechanical stirring, and the pressure reactor was tightened.

[0113] (2) Connect the carbon dioxide cylinder to the liquid phase inlet of the pressure-resistant reactor through a pressure reducing valve and a back pressure valve, and adjust the pressure of the pressure reducing valve and the back pressure valve to control the pressure in the reactor to be no higher than 1 MPa.

[0114] (3) Stirring was started and the reaction was carried out at 60° C. After 4 hours of reaction, the target product was obtained. The reactor was cooled to room temperature and the back pressure valve was closed.

[0115] The reaction yield was 93% as determined by gas chromatography.

[0116] The structure of the reaction substrate 3-methyl-1-heptyn-3-ol is:

[0117]

[0118] After identification, the structure of the target product is:

[0119]

[0120] Test Example 4:

[0121] This test example 4 provides a catalytic reaction of catalyzing the conversion reaction of CO2 and alkynol compounds to generate cyclic carbonates by the 0.2Cu2O@ZnAl-LDH catalyst prepared by Example 4, which specifically includes the following steps:

[0122] (1) The solvent DMSO (20 mL), the catalyst 0.2Cu2O@ZnAl-LDH (0.5 g), the co-catalyst N-methylmorpholine (0.2 g, 0.00198 mol) and the reaction substrate 2-methyl-3-hexyn-2-ol (3 g, 0.027 mol) were placed in a pressure reactor equipped with a magnetic stirrer and the pressure reactor was tightened.

[0123] (2) Connect the carbon dioxide cylinder to the liquid phase inlet of the pressure-resistant reactor through a pressure reducing valve and a back pressure valve, and adjust the pressure of the pressure reducing valve and the back pressure valve to control the pressure in the reactor to be no higher than 1 MPa.

[0124] (3) Stirring was started and the reaction was carried out at 40° C. After 12 hours of reaction, the target product was obtained. The reactor was cooled to room temperature and the back pressure valve was closed.

[0125] The reaction yield was 91% as determined by gas chromatography.

[0126] The structure of the reaction substrate 2-methyl-3-hexyn-2-ol is:

[0127]

[0128] After identification, the structure of the target product is:

[0129]

[0130] Test Example 5:

[0131] This test example 5 provides a catalytic reaction of catalyzing the conversion reaction of CO2 and alkynol compounds to generate cyclic carbonates by the 0.15Cu2O@ZnAl-LDH catalyst prepared by Example 2, which specifically includes the following steps:

[0132] (1) The solvent toluene (20 mL), the catalyst 0.15Cu2O@ZnAl-LDH (0.4 g), the co-catalyst N-methylmorpholine (0.1 g, 0.00099 mol) and the reaction substrate dimethyl(vinyl)ethynylmethanol (2 g, 0.018 mol) were placed in a pressure reactor equipped with a magnetic stirrer, and the pressure reactor was tightened.

[0133] (2) Connect the carbon dioxide cylinder to the liquid phase inlet of the pressure-resistant reactor through a pressure reducing valve and a back pressure valve, and adjust the pressure of the pressure reducing valve and the back pressure valve to control the pressure in the reactor to be no higher than 4 MPa.

[0134] (3) Start stirring and control the reaction at 20° C. After 12 hours of reaction, the target product is obtained. The reactor is cooled to room temperature and the back pressure valve is closed.

[0135] The reaction yield was 88% as determined by gas chromatography.

[0136] The structure of the reaction substrate dimethyl (vinyl) ethynyl methanol is:

[0137]

[0138] After identification, the structure of the target product is:

[0139]

[0140] Test Example 6:

[0141] This test example 6 provides a catalytic reaction of catalyzing the conversion reaction of CO2 and alkynol compounds to generate cyclic carbonates by the 0.1Cu2O@ZnAl-LDH catalyst prepared by Example 1, which specifically includes the following steps:

[0142] (1) The solvent DMF (100 mL), the catalyst 0.1Cu2O@ZnAl-LDH (0.1 g), the co-catalyst DBU (0.1 g, 0.00066 mol) and the reaction substrate 3-ethyl-1-pentyn-3-ol (20 g, 0.178 mol) were placed in a pressure reactor with mechanical stirring, and the pressure reactor was tightened.

[0143] (2) Connect the carbon dioxide cylinder to the liquid phase inlet of the pressure-resistant reactor through a pressure reducing valve and a back pressure valve, and adjust the pressure of the pressure reducing valve and the back pressure valve to control the pressure in the reactor to be no higher than 2 MPa.

[0144] (3) Start stirring and control the reaction at 25°C. After reacting for 12 hours, the target product is obtained, and the reactor is cooled to room temperature, and the back pressure valve is closed.

[0145] The reaction yield was 89% as determined by gas chromatography.

[0146] The structure of the reaction substrate 3-ethyl-1-pentyn-3-ol is:

[0147]

[0148] After identification, the structure of the target product is:

[0149]

[0150] Test Example 7:

[0151] This test example 7 provides a catalytic reaction of catalyzing the conversion reaction of CO2 and alkynol compounds to generate cyclic carbonates by the 0.1Cu2O@ZnAl-LDH catalyst prepared by Example 1, which specifically includes the following steps:

[0152] (1) The solvent N,N-dimethylacetamide (30 mL), the catalyst 0.1Cu2O@ZnAl-LDH (0.8 g), the co-catalyst 4-dimethylaminopyridine (0.2 g, 0.0016 mol) and the reaction substrate 2-methyl-3-pentyn-2-ol (4 g, 0.04 mol) were placed in a pressure reactor equipped with a magnetic stirrer and the pressure reactor was tightened.

[0153] (2) Connect the carbon dioxide cylinder to the liquid phase inlet of the pressure-resistant reactor through a pressure reducing valve and a back pressure valve, and adjust the pressure of the pressure reducing valve and the back pressure valve to control the pressure in the reactor to be no higher than 3 MPa.

[0154] (3) Start stirring and control the reaction at 40°C. After 6 hours of reaction, the target product is obtained. The reactor is cooled to room temperature and the back pressure valve is closed.

[0155] The reaction yield was 95% as determined by gas chromatography.

[0156] The structure of the reaction substrate 2-methyl-3-pentyn-2-ol is:

[0157]

[0158] After identification, the structure of the target product is:

[0159]

[0160] Table 1

[0161]

[0162] In summary, the structures of the reaction substrates and their corresponding target products in Test Examples 1 to 7 are shown in Table 1.

[0163] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing a Cu2O-supported ZnAl-LDH catalyst, characterized in that: The steps include: S1, dissolving Zn salt, Al salt and Cu salt in deionized water, adjusting the pH to alkaline, and heating the reaction to obtain CuO-loaded ZnAl-LDH; S2. The CuO-loaded ZnAl-LDH prepared in step S1 is heated and reduced to obtain a Cu2O-loaded ZnAl-LDH catalyst.

2. The preparation method according to claim 1, characterized in that: In step S1, the anion in the Zn salt is selected from any one of nitrate, sulfate and chloride; The anion in the Al salt is selected from any one of nitrate, sulfate and chloride; The anion in the Cu salt is selected from any one of nitrate, sulfate and chloride.

3. The preparation method according to claim 2, characterized in that: In step S1, the molar ratio of the Zn salt to the Al salt is 3:1, and the molar ratio of the Cu salt to the Al salt is 1:5 to 1:

20.

4. The preparation method according to claim 1, characterized in that: In step S1, the pH value is adjusted to 10-14.

5. The preparation method according to claim 4, characterized in that: In step S1, a mixed solution of NaOH and Na2CO3 is used to adjust the pH value, wherein the mass ratio of NaOH to Na2CO3 is 1:9 to 9:1, and the concentration is 10 wt% to 30 wt%.

6. The preparation method according to claim 1, characterized in that: In step S1, the heating reaction temperature is 80-160° C. and the time is 1-12 hours.

7. The preparation method according to claim 1, characterized in that: In step S2, a mixed gas of nitrogen and hydrogen is used to heat and reduce the CuO-supported ZnAl-LDH, wherein the volume content of hydrogen in the mixed gas is not less than 5%.

8. The preparation method according to claim 1, characterized in that: In step S2, the temperature of heating reduction is 200-300°C and the time is 1-4 hours.

9. A Cu2O-supported ZnAl-LDH catalyst, characterized in that: The method is based on any one of claims 1 to 8.

10. Use of the Cu2O-supported ZnAl-LDH catalyst as claimed in claim 9 in catalyzing the reaction of CO2 and alkynol compounds to synthesize cyclic carbonates.

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