A supported transition metal single-atom catalyst, its preparation method and application
By using a supported transition metal single-atom catalyst to catalyze the dehydrogenation reaction of vinyl carbonate in a fixed bed reactor, the dangers of using chlorine in the prior art and environmental pollution problems are solved, and an efficient and environmentally friendly vinyl carbonate preparation process is achieved.
Patent Information
- Application Number
- CN202211489014.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-11-25
- Publication Date
- 2025-04-29
- Estimated Expiration
- 2042-11-25
AI Technical Summary
Prior Art In the preparation of vinyl carbonate, the use of chlorine gas causes danger, environmental pollution and complex processes, low yields and difficulty in purification.
The catalyst is prepared by microwave thermal reaction and calcination reduction steps, and is used in the fixed bed reactor for dehydrogenation of vinyl carbonate in a fixed bed reactor.
It achieves high conversion and selectivity of vinylene carbonate, has a simple process and is environmentally friendly, is suitable for industrial production, and reduces production costs.
Smart Images
Figure BDA0003964089520000011 
Figure BDA0003964089520000091
Abstract
Description
Technical Field
[0001] The invention relates to a loaded transition metal single atom catalyst and its preparation and application, in particular to its application in the reaction of preparing vinylene carbonate by dehydrogenation of ethylene carbonate. Background Art
[0002] Vinylene carbonate is an important additive in lithium battery electrolyte, which can greatly improve the safety performance of lithium battery. At present, there are many patents for vinylene carbonate. The synthesis method is basically to use vinylene carbonate as raw material, react with chlorine to obtain monochloroethylene carbonate, and then remove chlorine under alkaline conditions to form double bonds to obtain vinylene carbonate. The specific route is as follows:
[0003]
[0004] This route has the following disadvantages: First, chlorine is a highly toxic gas and is very dangerous. Currently, chlorine needs to be used under extremely good experimental environment conditions, and most manufacturers cannot produce it normally; second, the chlorinated products generated during the reaction will cause environmental pollution, and the generated HC1 will corrode the pipeline; then, this route has many operating steps and complex processes, which ultimately results in a low yield of vinylene carbonate. In addition, the vinylene carbonate synthesized by this route contains a large amount of by-products and chlorides, making subsequent separation and purification more difficult.
[0005] Based on the existing technology, how to develop a method for preparing vinylene carbonate with simple preparation process, low cost, high yield, and easy purification and separation is the key to solving the above problems. Summary of the invention
[0006] The purpose of the present invention is to provide a supported transition metal single atom catalyst in order to improve the deficiencies of the prior art. Another purpose of the present invention is to provide a method for preparing the above catalyst. Another purpose of the present invention is to provide the application of the above catalyst in catalyzing the dehydrogenation of ethylene carbonate to synthesize vinylene carbonate.
[0007] The technical solution of the present invention is: a loaded transition metal single atom catalyst, characterized in that the catalyst uses a hollow Cr2O3-ZnO composite metal oxide as a carrier and a transition metal M as an active component; the morphology of the catalyst is a hollow porous sphere, wherein the molar ratio of Cr2O3 to ZnO in the carrier is (0.5-1):1, and the mass ratio of the active component to Cr2O3-ZnO is (0.01-0.02):1.
[0008] Preferably, the transition metal M is one of Ir, Ru, Pt, Pd or Rh.
[0009] The present invention provides a method for preparing the above-mentioned supported transition metal single atom catalyst M / Cr2O3-ZnO, the specific steps of which are:
[0010] (1) Preparation of SiO2@Cr2O3-ZnO: Weigh chromium and zinc metal salts to prepare aqueous solution A, add silica nanospheres to aqueous solution A, then add ammonia water to adjust the pH value, stir, wash, dry and calcine to obtain SiO2@Cr2O3-ZnO;
[0011] (2) Preparation of hollow Cr2O3-ZnO: SiO2@Cr2O3-ZnO was added to an alkaline solution, and then heated, stirred, etched, washed, and vacuum dried to obtain hollow Cr2O3-ZnO;
[0012] (3) Preparation of M / Cr2O3-ZnO catalyst: Weigh transition metal M salt and dispersant to prepare aqueous solution B, add hollow Cr2O3-ZnO into aqueous solution B, and then subject to microwave thermal reaction, washing, drying, calcination and reduction to obtain the loaded transition metal single atom catalyst M / Cr2O3-ZnO.
[0013] Preferably, the molar ratio of chromium to zinc in the aqueous solution A in step (1) is (1-2):1, and the concentration is C(Zn 2+ )+C(Cr 3+ )=0.3~0.5mol / L; the mass ratio of chromium salt to silica nanospheres is (2~5):1, and the diameter of silica nanospheres is 60~200nm; the stirring pH is 9~10, and the time is 12~24h; the calcination temperature is 500-700℃, and the calcination time is 2-4h.
[0014] Preferably, the chromium metal salt in step (1) is any one of chromium chloride, chromium nitrate or chromium sulfate; and the zinc metal salt is any one of zinc chloride, zinc nitrate or zinc sulfate.
[0015] Preferably, in step (2), the alkaline solution is either NaOH or KOH, with a concentration of 1-3 mol / L; the heating etching temperature is 80-120° C., and the etching time is 6-12 h.
[0016] Preferably, in step (3), the transition metal M salt is one of H2IrCl6·nH2O, H2PtCl6·6H2O, PdCl2·nH2O, RuCl3·nH2O or RhCl3·nH2O, and the mass ratio of the transition metal M salt to the hollow Cr2O3-ZnO is 1:(50-100); the dispersant is one of PVP or polyethylene glycol, and the mass ratio of the hollow Cr2O3-ZnO to the dispersant is 1:(0.25-0.5); the temperature of the microwave reaction is 60-80°C, and the reaction time is 6-12h; the roasting reduction gas is a hydrogen-nitrogen mixed atmosphere, the hydrogen gas volume fraction is 10-20%, and the flow rate is 60-100mL / min; the roasting reduction temperature is 400-600°C, the heating rate is 2-5°C / min, and the roasting reduction time is 2-4h.
[0017] The present invention provides an application of the above-mentioned supported transition metal single atom catalyst in catalyzing the dehydrogenation of ethylene carbonate to synthesize vinylene carbonate. The catalyst is added into a fixed bed reactor, a carrier gas is introduced, the reaction pressure is controlled, ethylene carbonate is introduced into the micro fixed bed reactor by a micro injection pump, and the temperature is raised to react.
[0018] The preferred mass space velocity of ethylene carbonate is 20 to 50 g / h·g cat ; The flow rate of the carrier gas is 50-80 mL / min, and the carrier gas pressure is 0.5-3 MPa; the reaction temperature is 200-400°C, and the reaction time is 18-36 h; the carrier gas is one of nitrogen, argon or hydrogen.
[0019] Beneficial effects:
[0020] (1) The M / Cr2O3-ZnO catalyst synthesis method provided by the present invention has simple equipment, convenient operation, and mild conditions. Compared with the existing process technology using chlorine, the process is environmentally friendly and conducive to large-scale production.
[0021] (2) The M / Cr2O3-ZnO catalyst provided by the present invention is used to catalyze the dehydrogenation of ethylene carbonate to produce vinylene carbonate, has a high conversion rate and selectivity, and the reaction process is simple, which is more conducive to industrial production. DETAILED DESCRIPTION
[0022] The present invention is described in more detail below with examples. These examples are only descriptions of the best mode of implementation of the present invention and do not limit the protection scope of the present invention in any way.
[0023] Example 1
[0024] Step 1: Add Zn(NO3)2·6H2O and Cr(NO3)3·9H2O salts into 50mL deionized water at a Zn / Cr molar ratio of 1:1.5 to dissolve the mixture into a concentration of C(Zn 2+ )+C(Cr 3+ )=0.5mol / L aqueous solution A, ultrasonic for 30min. Then, silica nanospheres with a diameter of 100-150nm were added to solution A at a mass ratio of Cr(NO3)3·9H2O / SiO2 of 3:1, and stirred for 30min. Ammonia water was added dropwise to make the solution pH 10, and stirred for 12h. The solution was filtered and washed with deionized water until the filtrate was neutral, dried for 12h, and calcined at 600℃ for 3h in air atmosphere to obtain SiO2@Cr2O3-ZnO.
[0025] Step 2: Pipette 150 mL of 2 mol / L NaOH solution into a beaker, add 2 g of the SiO2@Cr2O3-ZnO catalyst prepared in step 1, and continue etching at 90 °C for 10 h to allow the SiO2 to react completely. Then filter and wash with deionized water until the filtrate is neutral, and vacuum dry at 80 °C for 12 h to obtain a hollow Cr2O3-ZnO catalyst.
[0026] Step 3: Pipette 10 g L -1 5 mL of H2IrCl6·nH2O was placed in a flask, and 20 mL of deionized water was added to form solution B according to the mass ratio of PVP to hollow Cr2O3-ZnO being 0.4:1, and ultrasonicated for 30 min. Subsequently, the hollow Cr2O3-ZnO catalyst in step 2 was added to solution B at a mass ratio of Ir to hollow Cr2O3-ZnO of 1:50, and the mixture was placed in a microwave reactor after continuous stirring for 30 min, heated at 80°C, stirred for 8 h under 600 W microwave radiation, filtered and washed with deionized water until the filtrate was neutral, dried for 12 h, and calcined and reduced at 400°C for 3 h in a hydrogen-nitrogen mixed atmosphere with a hydrogen gas volume fraction of 10%, a flow rate of 80 mL / min, and a heating rate of 3°C / min to obtain Ir / Cr2O3-ZnO, wherein the molar ratio of Cr2O3 to ZnO was 0.75:1, and the mass ratio of the active component Ir to Cr2O3-ZnO was 0.02:1.
[0027] Example 2
[0028] Step 1: Add ZnCl2·6H2O and Cr(NO3)3·9H2O into 50mL of deionized water at a Zn / Cr molar ratio of 1:1 to dissolve the two salts to prepare a concentration of C(Zn 2+ )+C(Cr 3+)=0.4mol / L aqueous solution A, ultrasonic for 30min. Then, silica nanospheres with a diameter of 60-100nm were added to solution A at a mass ratio of Cr(NO3)3·9H2O / SiO2 of 2:1, and stirred for 30min. Ammonia water was added dropwise to make the solution pH 9, and stirred for 16h. The solution was filtered and washed with deionized water until the filtrate was neutral, dried for 12h, and calcined at 500℃ for 4h in air atmosphere to obtain SiO2@Cr2O3-ZnO.
[0029] Step 2: Pipette 150 mL of 3 mol / L NaOH solution into a beaker, add 2 g of the SiO2@Cr2O3-ZnO catalyst prepared in step 1, and continue etching at 80°C for 8 h to allow the SiO2 to react completely. Then filter and wash with deionized water until the filtrate is neutral, and vacuum dry at 80°C for 12 h to obtain a hollow Cr2O3-ZnO catalyst.
[0030] Step 3: Pipette 10 g L -1 5 mL of H2PtCl6·6H2O was placed in a flask, and 20 mL of deionized water was added to prepare solution B according to the mass ratio of polyethylene glycol to hollow Cr2O3-ZnO of 0.25:1, and ultrasonicated for 30 min. Subsequently, the hollow Cr2O3-ZnO catalyst in step 2 was added to solution B at a mass ratio of Pt to hollow Cr2O3-ZnO of 1:100, and after continuous stirring for 30 minutes, it was placed in a microwave reactor, heated at 60°C, stirred for 12 hours under 600W microwave radiation, filtered and washed with deionized water until the filtrate was neutral, dried for 12 hours, and calcined and reduced at 600°C for 2 hours in a hydrogen-nitrogen mixed atmosphere with a hydrogen gas volume fraction of 20%, a flow rate of 60mL / min, and a heating rate of 5°C / min to obtain Pt / Cr2O3-ZnO, wherein the molar ratio of Cr2O3 to ZnO was 0.5:1, and the mass ratio of the active component Pt to Cr2O3-ZnO was 0.01:1.
[0031] Example 3
[0032] Step 1: Add ZnCl2·6H2O and Cr2(SO4)3·9H2O salts into 50mL deionized water at a Zn / Cr molar ratio of 1:2 to dissolve them into a concentration of C(Zn 2+ )+C(Cr 3+)=0.3mol / L aqueous solution A, ultrasonic for 30min. Then, silica nanospheres with a diameter of 80-120nm were added to solution A at a mass ratio of Cr2(SO4)3·9H2O / SiO2 of 4:1. After continuous stirring for 30min, ammonia water was added dropwise to make the solution pH 9, and stirring was continued for 24h. The solution was filtered and washed with deionized water until the filtrate was neutral, dried for 12h, and calcined at 700℃ in air atmosphere for 2h to obtain SiO2@Cr2O3-ZnO.
[0033] Step 2: Pipette 150mL of 1mol / L KOH solution into a beaker, add 2g of SiO2@Cr2O3-ZnO catalyst prepared in step 1, and continue etching for 12h at 100℃ to complete the reaction of SiO2. Then filter and wash with deionized water until the filtrate is neutral, and vacuum dry at 80℃ for 12h to obtain a hollow Cr2O3-ZnO catalyst.
[0034] Step 2: Pipette 10 g L -1 5 mL of PdCl2·nH2O was placed in a flask, and 20 mL of deionized water was added to make solution B according to the mass ratio of PVP to hollow Cr2O3-ZnO being 0.5:1, and ultrasonicated for 30 min. Subsequently, the hollow Cr2O3-ZnO catalyst in step 2 was added to solution B at a mass ratio of Pd to hollow Cr2O3-ZnO of 1:75, and after continuous stirring for 30 minutes, it was placed in a microwave reactor, heated at 70°C, stirred for 10 hours under 600W microwave radiation, filtered and washed with deionized water until the filtrate was neutral, dried for 12 hours, and calcined and reduced at 500°C for 4 hours in a hydrogen and nitrogen mixed atmosphere with a hydrogen gas volume fraction of 15%, a flow rate of 100mL / min, and a heating rate of 2°C / min to obtain Pd / Cr2O3-ZnO, wherein the molar ratio of Cr2O3 to ZnO is 1:1, and the mass ratio of the active component Pd to Cr2O3-ZnO is 0.0133:1.
[0035] Example 4
[0036] Step 1: Add ZnSO4·6H2O and Cr2(Cl2)3·9H2O salts into 50mL deionized water at a Zn / Cr molar ratio of 1:2 to dissolve them into a concentration of C(Zn 2+ )+C(Cr 3+)=0.4mol / L aqueous solution A, ultrasonic for 30min. Then, silica nanospheres with a diameter of 160-200nm were added to solution A at a Cr2(Cl2)3 / SiO2 mass ratio of 5:1, and stirred for 30min. Ammonia water was added dropwise to make the solution pH 10, and stirred for 16h. The solution was filtered and washed with deionized water until the filtrate was neutral, dried for 12h, and calcined at 600℃ for 3h in air atmosphere to obtain SiO2@Cr2O3-ZnO.
[0037] Step 2: Pipette 150 mL of 2 mol / L KOH solution into a beaker, add 2 g of the SiO2@Cr2O3-ZnO catalyst prepared in step 1, and continue etching at 120°C for 6 h to allow the SiO2 to react completely. Then filter and wash with deionized water until the filtrate is neutral, and vacuum dry at 80°C for 12 h to obtain a hollow Cr2O3-ZnO catalyst.
[0038] Step 3: Pipette 10 g L -1 5 mL of RuCl3·nH2O was added to a flask, and 20 mL of deionized water was added to prepare solution B according to the mass ratio of polyethylene glycol to hollow Cr2O3-ZnO of 0.4:1, and ultrasonicated for 30 minutes. Subsequently, the hollow Cr2O3-ZnO catalyst in step 2 was added to solution B according to the mass ratio of Ru to hollow Cr2O3-ZnO of 1:80, and was placed in a microwave reactor after continuous stirring for 30 minutes, heated at 80°C, stirred for 6 hours under 600W microwave radiation, filtered and washed with deionized water until the filtrate was neutral, dried for 12 hours, and calcined and reduced at 500°C for 4 hours in a hydrogen-nitrogen mixed atmosphere with a hydrogen gas volume fraction of 20%, a flow rate of 100 mL / min, and a heating rate of 3°C / min to obtain Ru / Cr2O3-ZnO, wherein the molar ratio of Cr2O3 to ZnO was 1:1, and the molar ratio of active components Ru to Cr2O3 was 0.0125:1.
[0039] Example 5
[0040] Step 1: Add ZnSO4·6H2O and Cr(NO3)3·9H2O salts into 50mL deionized water at a Zn / Cr molar ratio of 1:1 to dissolve them into a concentration of C(Zn 2+ )+C(Cr 3+)=0.3mol / L aqueous solution A, ultrasonic for 30min. Then, silica nanospheres with a diameter of 120-160nm were added to solution A at a mass ratio of Cr(NO3)3·9H2O / SiO2 of 3:1, and stirred for 30min. Ammonia water was added dropwise to make the solution pH 10, and stirred for 16h. The solution was filtered and washed with deionized water until the filtrate was neutral, dried for 12h, and calcined at 500℃ for 3h in air atmosphere to obtain SiO2@Cr2O3-ZnO.
[0041] Step 2: Pipette 150 mL of 2 mol / L NaOH solution into a beaker, add 2 g of the SiO2@Cr2O3-ZnO catalyst prepared in step 1, and continue etching at 100 °C for 8 h to allow the SiO2 to react completely. Then filter and wash with deionized water until the filtrate is neutral, and vacuum dry at 80 °C for 12 h to obtain a hollow Cr2O3-ZnO catalyst.
[0042] Step 3: Pipette 10 g L -1 5 mL of RhCl3·nH2O was placed in a flask, and 20 mL of deionized water was added to make solution B according to the mass ratio of PVP to hollow Cr2O3-ZnO being 0.4:1, and ultrasonicated for 30 min. Subsequently, the hollow Cr2O3-ZnO catalyst in step 2 was added to solution B at a mass ratio of Rh to hollow Cr2O3-ZnO of 1:100, and after continuous stirring for 30 minutes, it was placed in a microwave reactor, heated at 70°C, stirred for 10 hours under 600W microwave radiation, filtered and washed with deionized water until the filtrate was neutral, dried for 12 hours, and calcined and reduced at 500°C for 3 hours in a hydrogen-nitrogen mixed atmosphere with a hydrogen gas volume fraction of 10%, a flow rate of 80 mL / min, and a heating rate of 3°C / min to obtain Rh / Cr2O3-ZnO, wherein the molar ratio of Cr2O3 to ZnO is 0.5:1, and the molar ratio of the active component Rh to Cr2O3 is 0.01:1.
[0043] Using M@Cr2O3-ZnO as catalyst, ethylene carbonate is dehydrogenated to vinylene carbonate:
[0044] Application Example 1
[0045] 1g Ir / Cr2O3-ZnO catalyst was loaded into a fixed bed reaction tube, and quartz sand was used to fill the top and bottom. The carrier gas was introduced to control the reaction pressure. Ethylene carbonate was introduced into the micro fixed bed reactor by a micro-injection pump. The reaction started after the temperature was raised to the reaction temperature. The reaction product was collected by a condensation device and analyzed by gas chromatography. The carrier gas was N2, and the mass space velocity of ethylene carbonate was 30g / h·g cat, the flow rate of the protective gas is 80 mL / min, the reaction temperature is 400° C., the protective gas pressure is 1.5 MPa, and the reaction time is 18 h. The chromatographic data are analyzed to obtain a yield of vinylene carbonate of 86.36%.
[0046] Application Example 2
[0047] 1g of Pt / Cr2O3-ZnO catalyst was loaded into a fixed bed reaction tube, and quartz sand was used to fill the top and bottom. The carrier gas was introduced to control the reaction pressure. Ethylene carbonate was introduced into the micro fixed bed reactor by a micro-injection pump. The reaction started after the temperature was raised to the reaction temperature. The reaction product was collected by a condensation device and analyzed by gas chromatography. The carrier gas was Ar, and the mass space velocity of ethylene carbonate was 20g / h·g cat , the flow rate of the protective gas is 50 mL / min, the reaction temperature is 200° C., the protective gas pressure is 3 MPa, and the reaction time is 18 h. The chromatographic data are analyzed to obtain a yield of vinylene carbonate of 82.53%.
[0048] Application Example 3
[0049] 1g of Pd / Cr2O3-ZnO catalyst was placed in a fixed bed reaction tube, and quartz sand was used to fill the top and bottom. A carrier gas was introduced to control the reaction pressure. Ethylene carbonate was introduced into the micro fixed bed reactor using a micro-injection pump. The reaction started after the temperature was raised to the reaction temperature. The reaction product was collected by a condensation device and analyzed by gas chromatography. The carrier gas was N2, and the mass space velocity of ethylene carbonate was 30g / h·g cat , the flow rate of the protective gas is 50 mL / min, the reaction temperature is 300° C., the protective gas pressure is 1.5 MPa, and the reaction time is 36 h. The chromatographic data are analyzed to obtain a yield of vinylene carbonate of 88.32%.
[0050] Application Example 4
[0051] 1g of Ru / Cr2O3-ZnO catalyst was placed in a fixed bed reaction tube, and quartz sand was used to fill the top and bottom. A carrier gas was introduced to control the reaction pressure. Ethylene carbonate was introduced into the micro fixed bed reactor using a micro-injection pump. The reaction started after the temperature was raised to the reaction temperature. The reaction product was collected by a condensation device and analyzed by gas chromatography. The carrier gas was H2, and the mass space velocity of ethylene carbonate was 40g / h·g cat , the flow rate of the protective gas is 70 mL / min, the reaction temperature is 400° C., the protective gas pressure is 0.5 MPa, and the reaction time is 36 h. The chromatographic data are analyzed to obtain a yield of vinylene carbonate of 85.12%.
[0052] Application Example 5
[0053] 1g Rh / Cr2O3-ZnO catalyst was loaded into a fixed bed reaction tube, and quartz sand was used to fill the top and bottom. The carrier gas was introduced to control the reaction pressure. Ethylene carbonate was introduced into the micro fixed bed reactor by a micro-injection pump. The reaction started after the temperature was raised to the reaction temperature. The reaction product was collected by a condensation device and analyzed by gas chromatography. The carrier gas was Ar, and the mass space velocity of ethylene carbonate was 50g / h·g cat , the flow rate of the protective gas is 60 mL / min, the reaction temperature is 300° C., the protective gas pressure is 2 MPa, and the reaction time is 24 h. The chromatographic data are analyzed to obtain a yield of vinylene carbonate of 84.52%.
[0054] The experimental results of the application example are shown in Table 1
[0055] Table 1 Application example experimental results
[0056]
Claims
1. A supported transition metal single atom catalyst, characterized in that The catalyst uses a hollow Cr2O3-ZnO composite metal oxide as a carrier and a transition metal as an active component; the catalyst has a hollow porous spherical shape, wherein the molar ratio of Cr2O3 to ZnO in the carrier is (0.5-1):1, and the mass ratio of the active component to Cr2O3-ZnO is (0.01-0.02):
1. The catalyst is prepared by the following method, the specific steps of which are: (1) Preparation of SiO2@Cr2O3-ZnO: Weigh chromium and zinc metal salts to prepare aqueous solution A, add silica nanospheres to aqueous solution A, then add ammonia water to adjust the pH value, stir, wash, dry and calcine to obtain SiO2@Cr2O3-ZnO; (2) Preparation of hollow Cr2O3-ZnO: SiO2@Cr2O3-ZnO was added to an alkaline solution, and then heated, stirred, etched, washed, and vacuum dried to obtain hollow Cr2O3-ZnO; (3) Preparation of M / Cr2O3-ZnO catalyst: Weigh transition metal M salt and dispersant to form aqueous solution B, add hollow Cr2O3-ZnO to aqueous solution B, and then subject to microwave thermal reaction, washing, drying, and calcination reduction to obtain a loaded transition metal single atom catalyst M / Cr2O3-ZnO; the calcination reduction gas is a hydrogen and nitrogen mixed atmosphere, the hydrogen gas volume fraction is 10-20%, and the flow rate is 60-100 mL / min; the calcination reduction temperature is 400-600°C, and the calcination reduction time is 2-4 h.
2. The supported transition metal single atom catalyst according to claim 1, characterized in that The transition metal is one of Ir, Ru, Pt, Pd or Rh.
3. The supported transition metal single atom catalyst according to claim 2, characterized in that The molar ratio of chromium to zinc in the aqueous solution A described in step (1) is (1-2):1, and the concentration is C(Zn 2+ )+C(Cr 3+ )=0.3~0.5mol / L; the mass ratio of chromium salt to silica nanospheres is (2~5):1, and the diameter of silica nanospheres is 60~200nm; the stirring pH is 9~10, and the time is 12~24h; the calcination temperature is 500-700℃, and the calcination time is 2-4h.
4. The supported transition metal single atom catalyst according to claim 2, characterized in that The chromium metal salt described in step (1) is any one of chromium chloride, chromium nitrate or chromium sulfate; the zinc metal salt is any one of zinc chloride, zinc nitrate or zinc sulfate.
5. The supported transition metal single atom catalyst according to claim 2, characterized in that In step (2), the alkaline solution is any one of NaOH or KOH, and the concentration is 1-3 mol / L; the heating etching temperature is 80-120° C., and the etching time is 6-12 h.
6. The supported transition metal single atom catalyst according to claim 2, characterized in that In step (3), the transition metal M salt is one of H2IrCl6·nH2O, H2PtCl6·6H2O, PdCl2·nH2O, RuCl3·nH2O or RhCl3·nH2O, and the mass ratio of the transition metal M salt to the hollow Cr2O3-ZnO is 1:(50-100); the dispersant is one of PVP or polyethylene glycol, and the mass ratio of the hollow Cr2O3-ZnO to the dispersant is 1:(0.25-0.5); the temperature of the microwave reaction is 60-80°C, and the reaction time is 6-12h; the heating rate of the calcination reduction is 2-5°C / min.
7. Use of the supported transition metal single atom catalyst as claimed in claim 1 in catalyzing the dehydrogenation of ethylene carbonate to synthesize vinylene carbonate.
8. The use according to claim 7, characterized in that The catalyst is added into the fixed bed reactor, the carrier gas is introduced, the reaction pressure is controlled, ethylene carbonate is introduced into the micro fixed bed reactor by a micro injection pump, and the temperature is raised to react.
9. The use according to claim 7, characterized in that: The mass space velocity of ethylene carbonate is 20-50 g / h·g cat ; The flow rate of the carrier gas is 50-80 mL / min, and the carrier gas pressure is 0.5-3 MPa; the reaction temperature is 200-400°C, and the reaction time is 18-36 h; the carrier gas is one of nitrogen, argon or hydrogen.