A composite material for photo-thermal synergistic catalysis of CO2 cycloaddition reaction and a preparation method and application thereof

Abstract

The application belongs to the technical field of inorganic semiconductor heterogeneous catalysis, and relates to a composite material for photo-thermal synergistic catalysis of CO2 cycloaddition reaction and preparation and application thereof, and comprises the following steps: taking two different alkali metal chlorides, then taking urea with a mass ratio of 3:5 to the alkali metal chlorides to obtain a precursor of alkali metal high-crystalline carbon nitride; taking zinc nitrate hexahydrate and grinding and uniformly mixing the zinc nitrate hexahydrate and the precursor of alkali metal high-crystalline carbon nitride according to a mass ratio of 1:(1-20), and then heating the obtained precursor to 550 DEG C under a nitrogen atmosphere, reacting for 2-5 h to obtain the composite material. The alkali metal high-crystalline carbon nitride and the cyanamide metal compound hetero-composite material prepared by the one-step method have good catalytic performance in photo-thermal synergistic catalysis of CO2 cycloaddition reaction under relatively mild conditions, the performance of the composite material does not obviously decrease after being recycled for multiple times, the stability is good, the recovery is simple, and the performance is still relatively excellent under industrial simulation gas experiment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of inorganic semiconductor heterogeneous catalysis, and particularly relates to a composite material for photocatalytic and thermocatalytic CO2 cycloaddition reaction and preparation and application thereof. BACKGROUND

[0002] With the combustion of fossil fuels, the emission of CO2 is increasing year by year, which has caused a series of environmental problems such as seawater acidification, glacier melting, sea level rise and greenhouse effect, and therefore how to reduce the emission of CO2 as much as possible while catalytically converting it is a problem that the world is closely concerned about. Although CO2 is difficult to activate, it is a non-toxic, abundant and renewable C1 resource, which can be used to prepare high-value-added formic acid, cyclic carbonate and methanol and other products by means of reduction, cycloaddition, hydrogenation and other means. Among them, CO2 cycloaddition reaction has attracted widespread attention due to its 100% atom economy. Since 1958, its product cyclic carbonate has begun to be commercialized and applied to battery electrolyte, pharmaceutical intermediates and other important organic chemical products.

[0003] For catalytic CO2 cycloaddition reaction, if pure thermal catalysis is used, high temperature and high pressure reaction conditions are needed, which is easy to scale up, but the reaction cost is too high; and if pure light catalysis is used, the quantum efficiency is too low, which is difficult to realize industrial scale, therefore, the combination of light and heat is used to promote the progress of CO2 cycloaddition reaction by using light and heat synergy, which is helpful to realize high reaction efficiency under relatively mild reaction conditions and gradually used for industrial scale.

[0004] At present, people have explored a variety of catalysts for CO2 cycloaddition reaction, such as homogeneous catalysts (imidazole salt Angew. Chem., 2020, 59, 18446-18451, quaternary ammonium salt ACS Sustainable Chem. Eng., 2019, 7, 5940-5945, pyridine salt New J. Chem., 2019, 43, 18525-18533) and heterogeneous catalysts (Salen complex, carbon nitride-based catalyst, metal-organic framework Applied Catalysis B: Environmental 296 (2021) 120329, supported ionic liquid, etc.). However, the homogeneous catalysts in the current CO2 cycloaddition reaction are difficult to separate and recover, and generally need to be carried out under high temperature and high pressure reaction conditions, and therefore the preparation of heterogeneous catalysts with high efficiency and high repeatability under mild conditions is the prerequisite for realizing large-scale industrialization of CO2 cycloaddition reaction.

[0005] Heterogeneous catalysts have many advantages in product separation, catalyst recovery, and can exhibit higher catalytic activity than homogeneous catalysts. Carbon nitride-based materials have attracted attention as a heterogeneous catalyst. However, ordinary carbon nitride materials have high recombination rates of photo-generated carriers and lack Lewis acid sites. The addition of alkali metal salts such as sodium and potassium significantly reduces the recombination rate of photo-generated carriers, but still lacks Lewis acid sites. Therefore, cyanamide metal compounds can act as Lewis acid sites. For ZnNCN / NaK-CN composite materials, the advantages of the two components can be integrated to efficiently convert CO2 and epoxide into industrially valuable cyclic carbonates under relatively mild conditions. SUMMARY

[0006] The present application aims to solve the above problems in the prior art and proposes a composite material for photocatalytic and thermal catalytic CO2 cycloaddition reaction and a preparation method and application thereof. Unlike the prior art, which first prepares crystalline carbon nitride (NaK-CN), then prepares zinc cyanamide (ZnNCN), and then prepares a heterogeneous composite catalyst, the present application uses a one-step method to prepare a heterogeneous composite catalyst (ZnNCN / NaK-CN). The alkali metal high-crystalline carbon nitride and cyanamide metal compound heterogeneous composite material prepared by the one-step method has good photocatalytic and thermal catalytic CO2 cycloaddition reaction performance under relatively mild conditions, and the composite material has good stability and does not significantly decrease in performance after multiple cycles. The recovery is simple, and the performance is still relatively excellent under industrial simulation gas experiments.

[0007] The technical solution of the present application is:

[0008] A preparation method of a composite material for photocatalytic and thermal catalytic CO2 cycloaddition reaction, characterized in that it comprises the following steps: first, weigh two different alkali metal chlorides, and the molar ratio of the two alkali metal chlorides is 1:9-2:3; then weigh urea with a mass ratio of 3:5 to the alkali metal chloride to obtain a precursor of alkali metal high-crystalline carbon nitride; weigh zinc nitrate hexahydrate and mix the zinc nitrate hexahydrate with the precursor of alkali metal high-crystalline carbon nitride at a mass ratio of 1:(1-20) to obtain a mixture, and then heat the mixture to 550℃ at a rate of 5℃ / min under a nitrogen atmosphere, react for 2-5h, cool, wash, and vacuum dry to obtain the composite material.

[0009] Further, the alkali metal chlorides include sodium chloride, lithium chloride, potassium chloride, and calcium chloride.

[0010] Preferably, the mass ratio of the zinc nitrate hexahydrate to the precursor of alkali metal high-crystalline carbon nitride is 1:(4-8), and more preferably, the mass ratio is 1:(5-7); further, the mass ratio of the zinc nitrate hexahydrate to the precursor of alkali metal high-crystalline carbon nitride is 1:6.

[0011] Further, first, sodium chloride and potassium chloride with a molar ratio of 1:9-2:3 are weighed, then urea with a mass ratio of 3:5 to the total mass of sodium chloride and potassium chloride is weighed, to obtain a precursor of NaK-CN, and then the precursor of NaK-CN and zinc nitrate hexahydrate with a mass ratio of 1:(1-20) are ground and mixed uniformly and then transferred to a porcelain boat, and then the porcelain boat is heated to 550 DEG C at a rate of 5 DEG C / min under a nitrogen atmosphere, and then the reaction is carried out for 3 h, and then the obtained material is washed with deionized water to remove metal salts, and then the material is dried in a vacuum drying oven overnight, to obtain a ZnNCN / NaK-CN composite material.

[0012] The application provides a composite material for synergistically catalyzing a CO2 cycloaddition reaction by light and heat, which is prepared by the preparation method according to any one of the above.

[0013] The application also provides application of the composite material prepared by the preparation method according to any one of the above in synergistically catalyzing a CO2 cycloaddition reaction by light and heat.

[0014] Further, the composite material is used as a catalyst in a cycloaddition reaction of an epoxide and CO2, and the method comprises the following steps:

[0015] The catalyst, the cocatalyst and propylene oxide are sequentially added to a reactor and sealed, and then the reactor is purged with CO2 to ensure that there is no other gas in the reactor, and then the pressure of the reactor is set to 1 Mpa, and the temperature of the reactor is set to 80 DEG C, and then the reactor is irradiated by a full-spectrum xenon lamp, and the reaction is continuously stirred during the reaction, and the reaction time is 4 h. 2 The reaction is continuously stirred during the reaction, and the reaction time is 4 h.

[0016] The mass ratio of the catalyst, the cocatalyst and propylene oxide is 3:9:88, and the cocatalyst is tetrabutylammonium bromide.

[0017] Further, after the reaction, the reactor is cooled in an ice bath, the obtained product is taken out by using acetonitrile as a solvent, calibration is performed by using diphenyl as an internal standard, the suspension is filtered by using a 0.22 mu m syringe, and the yield is calculated.

[0018] Further, the epoxide comprises propylene oxide, styrene oxide, epichlorohydrin, epibromohydrin, styrene oxide, allyl glycidyl ether and epoxycyclohexane.

[0019] The application also provides application of the composite material prepared by the preparation method according to any one of the above in a simulated industrial waste gas, and the ZnNCN-6 / NaK-CN composite material is also used in a simulated industrial waste gas V(N2):V(CO2)=85:15, and the reaction yield can reach 67.49% within 4 h, which indicates that the ZnNCN / NaK-CN composite material has good industrial applicability.

[0020] The beneficial effects of this invention are:

[0021] (1) The one-step synthesis of alkali metal highly crystalline carbon nitride and cyanamide metal compounds such as sodium potassium bimetallic carbon nitride (NaK-CN) and zinc cyanamide (ZnNCN) heterocomposite material is simple to prepare, has low production cost, and is easy to scale up. As a catalyst, this composite material can catalyze the CO2 cycloaddition reaction under relatively mild conditions with photothermal synergistic effect, thus reducing energy consumption.

[0022] (2) The catalyst synthesized in this invention has Lewis acid-base properties, is a heterogeneous catalyst, is easy to separate, and has good stability. The catalyst can significantly accelerate the ring-opening rate of epoxides in the CO2 cycloaddition reaction, which is the rate-determining step of the reaction.

[0023] (3) The addition of light allows the reaction to proceed under relatively mild conditions, reducing reaction energy consumption; light excites the catalyst to generate hot electrons, thereby accelerating the ring-opening rate and increasing the reaction rate.

[0024] (4) No solvent is involved in the reaction process, and the catalyst is relatively easy to separate. Attached Figure Description

[0025] Figure 1 A schematic diagram of the preparation process of the composite material provided by the present invention;

[0026] Figure 2 Cyclic graph of composite material properties provided by the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] To further understand the present invention, it will be further described in conjunction with the accompanying drawings and embodiments.

[0029] Example 1

[0030] like Figure 1 As shown, this embodiment provides a method for preparing a composite material for photothermal synergistic catalytic CO2 cycloaddition reaction, comprising the following steps:

[0031] First, sodium chloride and potassium chloride were weighed according to a molar ratio of 1:9, and the total mass of sodium chloride and potassium chloride was controlled at 6 g, then 10 g of urea was weighed to obtain a precursor of NaK-CN, zinc nitrate hexahydrate and the precursor of NaK-CN were weighed according to a mass ratio of 1:6, and after grinding and mixing uniformly, they were transferred to a porcelain boat, which was placed in a tube furnace, and heated to 550 ℃ at a rate of 5 ℃ per minute under a nitrogen atmosphere, reacted for 2 h, and then the obtained material was washed with deionized water to remove metal salts and dried in a vacuum drying oven overnight to obtain ZnNCN-6 / NaK-CN.

[0032] Example 2

[0033] The preparation method of the present embodiment comprises the following steps:

[0034] First, sodium chloride and potassium chloride were weighed according to a molar ratio of 2:3, and the total mass of sodium chloride and potassium chloride was controlled at 6 g, then 10 g of urea was weighed to obtain a precursor of NaK-CN, zinc nitrate hexahydrate and the precursor of NaK-CN were weighed according to a mass ratio of 1:6, and after grinding and mixing uniformly, they were transferred to a porcelain boat, which was placed in a tube furnace, and heated to 550 ℃ at a rate of 5 ℃ per minute under a nitrogen atmosphere, reacted for 3 h, and then the obtained material was washed with deionized water to remove metal salts and dried in a vacuum drying oven overnight to obtain ZnNCN-6 / NaK-CN.

[0035] Example 3

[0036] The preparation method of the present embodiment comprises the following steps:

[0037] First, sodium chloride and potassium chloride were weighed according to a molar ratio of 1:5, and the total mass of sodium chloride and potassium chloride was controlled at 6 g, then 10 g of urea was weighed to obtain a precursor of NaK-CN, zinc nitrate hexahydrate and the precursor of NaK-CN were weighed according to a mass ratio of 1:7, and after grinding and mixing uniformly, they were transferred to a porcelain boat, which was placed in a tube furnace, and heated to 550 ℃ at a rate of 5 ℃ per minute under a nitrogen atmosphere, reacted for 4 h, and then the obtained material was washed with deionized water to remove metal salts and dried in a vacuum drying oven overnight to obtain ZnNCN-7 / NaK-CN.

[0038] Example 4

[0039] In the preparation method of the present embodiment, the mass ratio of zinc nitrate hexahydrate to the precursor of NaK-CN is 1:1, and the remaining steps are the same as those of Example 2.

[0040] ZnNCN-1 / NaK-CN composite material was prepared.

[0041] Example 5

[0042] In the preparation method of this example, the mass ratio of zinc nitrate hexahydrate to the precursor of NaK-CN was 1:10, and the remaining steps were the same as those in Example 2.

[0043] ZnNCN-10 / NaK-CN composite material was prepared.

[0044] Example 6

[0045] In the preparation method of this example, the mass ratio of zinc nitrate hexahydrate to the precursor of NaK-CN was 1:20, and the remaining steps were the same as those in Example 2.

[0046] ZnNCN-20 / NaK-CN composite material was prepared.

[0047] Example 7

[0048] In the preparation method of this example, the two metal chlorides weighed were lithium chloride and potassium chloride, and the remaining steps were the same as those in Example 2.

[0049] ZnNCN-6 / LiK-CN composite material was prepared.

[0050] Example 8

[0051] In the preparation method of this example, the two metal chlorides weighed were lithium chloride and sodium chloride, and the remaining steps were the same as those in Example 2.

[0052] ZnNCN-6 / LiNa-CN composite material was prepared.

[0053] Application Example 1

[0054] The ZnNCN-6 / NaK-CN composite material prepared in Example 1 was used as a catalyst, and tetrabutylammonium bromide (TBAB) was used as a cocatalyst to catalyze the cycloaddition reaction of CO2 ring and propylene oxide (PO), and the process was as follows:

[0055] The photo-thermal CO2 cycloaddition reaction was carried out in a special reactor with a light-transmitting quartz plate at the top. The catalyst, TBAB and PO were added to the reactor in a mass ratio of 3:9:88 and sealed, and then the reactor was purged with CO2 to ensure that there was no other gas in the reactor, and the pressure of the reactor was increased to 1Mpa to achieve the set reaction conditions. The CO2 cycloaddition reaction was carried out at 80℃, the heat source was provided by an oil bath, and the light source was provided by a full-spectrum xenon lamp with a light intensity of 300mW / cm 2The reaction was carried out with continuous stirring. The reaction time was 4 hours. After the reaction, the reactor was cooled in an ice bath. Acetonitrile was used as a solvent to remove the product, and biphenyl was used as an internal standard for calibration. The suspension was filtered with a 0.22 μm syringe. The conversion rate was calculated to be 99.4%.

[0056] Application Example 2

[0057] The substrate in Application Example 1 was replaced with oxidized styrene, epoxy bromopropane, epoxy chloropropane, oxidized styrene, allyl glycidyl ether, or epoxy cyclohexane, and catalytic reactions were respectively carried out.

[0058] Reaction conditions: [b]: propylene oxide (20 mmol), catalyst (30 mg), 80°C, reaction pressure 1 Mpa CO2, reaction time 4h.

[0059] [c]: propylene oxide (20 mmol), catalyst (30 mg), 80°C, reaction pressure 1 Mpa CO2, reaction time 6h.

[0060] After the reaction was completed, the conversion rate was calculated as shown in Table 1 below:

[0061] Table 1: Conditions and conversion rates of catalytic reactions with different substrates

[0062]

[0063] As shown in Table 1, other POs with -CH2Br, -CH2Cl, -CH2OCH2CH2, -Ph, and -CH2(CH2)2CH3 instead of -CH3 all showed high catalytic performance under the reaction conditions (80°C, full spectrum illumination, 30 mg catalyst, co-catalyst TBAB (0.3 mmol), PO (20 mmol), 1 MPa, 6h).

[0064] Test Example 1: recyclability test of the catalyst

[0065] Recyclability is an important indicator for measuring the potential of industrial application of a catalyst.

[0066] The used catalyst in Application Example 1 was washed and dried and then applied again, and the results are shown in Figure 2 As can be seen from the yield on the graph, after five uses, the yield of ZnNCN-6 / NaK-CN was still as high as 92.9%, with no great loss, which indicates that the catalyst has great potential for industrial application.

[0067] Test Example 2: reaction condition exploration experiment

[0068] As shown in Table 2, under standard reaction conditions (80 °C, full spectrum illumination, catalyst: co-catalyst: propylene oxide mass ratio of 3:9:88, 1 MPa, 4 hours), the effect of the amount of zinc precursor on catalytic activity was studied, and it was observed that the yield of propylene carbonate increased with the amount of zinc nitrate hexahydrate. The optimal combination of ZnNCN-x / NaK-CN was ZnNCN-6 / NaK-CN (i.e., a mass ratio of 1:6), and the highest yield was as high as 88.4% (higher than any component, 1.5 times that of ZnNCN).

[0069] To clarify the role of the ZnNCN-6 / NaK-CN catalyst, a control experiment was performed. As shown in Table 2, in the absence of the co-catalyst TBAB, the cycloaddition reaction was almost impossible to occur, which highlights the necessity of the Br anion nucleophilic attack. In the absence of heat and full spectrum light, the yield was only 24.5% and 55.9%, respectively, which means the dual necessity of external heat and photocatalysis. In contrast, the role of the catalyst can be observed obviously, because in the absence of Zn, the yield was only 35.7%.

[0070]

[0071] Table 2 Experimental data of reaction conditions and corresponding yields

[0072]

[0073]

[0074] [a] The target product cyclic propylene carbonate was quantitatively analyzed by GC-FID.

[0075] The above description is merely preferred embodiments of the present application, and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, the technical solutions recorded in the foregoing embodiments can be modified or equivalent replaced by those skilled in the art. Any modification, equivalent replacement, modification, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a composite material for photo-thermal co-catalysis of CO2 cycloaddition reaction, characterized in that, The method comprises the following steps: firstly, taking two different alkali metal chlorides, and the molar ratio of the two alkali metal chlorides is 1:9-2:3; then taking urea with a mass ratio of 3:5 to the alkali metal chlorides to obtain a precursor of high-crystalline carbon nitride of alkali metal; taking zinc nitrate hexahydrate, and grinding and uniformly mixing the zinc nitrate hexahydrate and the precursor of high-crystalline carbon nitride of alkali metal at a mass ratio of 1:(1-20), and then heating the obtained precursor to 550 DEG C at a rate of 5 DEG C / min under a nitrogen atmosphere, reacting for 2-5 h, cooling, washing and vacuum drying to obtain a composite material.

2. The production method according to claim 1, characterized by, The alkali metal chlorides include sodium chloride, lithium chloride, potassium chloride and calcium chloride.

3. The production method according to claim 1, characterized by, The mass ratio of the zinc nitrate hexahydrate to the precursor of high-crystalline carbon nitride of alkali metal is 1:

6.

4. The production method according to claim 2, characterized by, Firstly, sodium chloride and potassium chloride are taken at a molar ratio of 1:9-2:3, and then urea is taken with a mass ratio of 3:5 to the total mass of the sodium chloride and the potassium chloride to obtain a precursor of NaK-CN, the zinc nitrate hexahydrate and the precursor of NaK-CN are ground and uniformly mixed at a mass ratio of 1:(1-20), and then transferred to a porcelain boat, heated to 550 DEG C at a rate of 5 DEG C / min under a nitrogen atmosphere, reacted for 3 h, and then cooled, washed with deionized water to remove metal salts, and dried in a vacuum drying oven overnight to obtain a ZnNCN / NaK-CN composite material.

5. A composite material for the photo-thermal co-catalysis of the CO2 cycloaddition reaction, characterized by, The method is prepared according to any one of claims 1-4.

6. Application of the composite material prepared according to any one of claims 1-4 in a photo-thermal synergistic catalytic CO2 cycloaddition reaction.

7. Use according to claim 6, characterized in that, The composite material is used as a catalyst in a cycloaddition reaction of an epoxide and CO2, and the method comprises the following steps: The catalyst, the cocatalyst and the propylene oxide were sequentially added into the reactor and sealed, and then the reactor was purged with CO2 to ensure that there was no other gas in the reactor, the pressure of the reactor was set to 1 Mpa, the temperature was set to 80℃, and the power was set to 300 mW / cm2. 2 The whole spectrum xenon lamp irradiation, the reaction process was continuously stirred, the reaction time was 4 hours; The mass ratio of the catalyst, the cocatalyst and the propylene oxide is 3:9:88, and the cocatalyst is tetrabutylammonium bromide.

8. Use according to claim 7, characterized in that, After the reaction, the reactor is cooled in an ice bath, the obtained product is taken out using acetonitrile as a solvent, calibrated using biphenyl as an internal standard, and the suspension is filtered using a 0.22 mu m syringe.

9. Use according to claim 7, characterized in that, The epoxide includes propylene oxide, styrene oxide, epoxy bromopropane, epoxy chloropropane, styrene oxide, allyl glycidyl ether and epoxy cyclohexane.

10. Use of the composite material prepared according to the process of any one of claims 1-4 in the simulation of industrial exhaust gases, characterized by the fact that, The ZnNCN / NaK-CN composite material is used for simulating industrial waste gas with a volume ratio of nitrogen to carbon dioxide of 85:15.

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