CN110026196B - Supported heterogeneous catalyst and preparation method and application thereof - Google Patents
Supported heterogeneous catalyst and preparation method and application thereof Download PDFInfo
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- C07D301/03—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds
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Abstract
The invention belongs to the technical field of catalytic materials, and particularly relates to a supported heterogeneous catalyst, and a preparation method and application thereof. The supported heterogeneous catalyst provided by the invention comprises an alumina nanotube and cobalt oxide deposited on the outer surface of the alumina nanotube, wherein the alumina nanotube is used as a carrier, and the cobalt oxide as an active component is deposited on the outer surface of the carrier, so that the active component can be uniformly dispersed, and further the catalyst with higher activity is obtained. The results of the examples show that when the catalyst provided by the invention is used in the styrene epoxidation reaction, the selectivity reaches 74.3-94.8%, and the conversion rate reaches 77.2-91.4%.
Description
Technical Field
The invention belongs to the technical field of catalytic materials, and particularly relates to a supported heterogeneous catalyst, and a preparation method and application thereof.
Background
The epoxy phenylethane is an important organic intermediate, is mainly used for synthesizing spices, medicines, preparing high-grade coatings and the like, and can also be used as an epoxy resin diluent, a UV-absorbing agent, a flavoring agent, a stabilizing agent and the like. Traditionally, styrene oxide is produced by the reaction of styrene and a peracid (peroxyacid) catalyzed by a homogeneous catalyst, such as a transition metal compound, in a stoichiometric ratio; although the catalyst has higher catalytic activity, the cost of the peroxy acid used in the reaction is high, the performance stability is poor, and the recycling cost of the homogeneous catalyst is high. Therefore, the development of a novel catalyst to reduce the production cost of styrene oxide is currently a major task.
Disclosure of Invention
The invention aims to provide a supported heterogeneous catalyst which has higher selectivity and conversion rate when used in the epoxidation reaction of styrene.
In order to achieve the above purpose, the invention provides the following technical scheme:
the invention provides a supported heterogeneous catalyst, which comprises alumina nanotubes and cobalt oxide deposited on the outer surface of the alumina nanotubes.
Preferably, the particle size of the cobalt oxide is 1-2 nm, and the deposition thickness is 4-5 nm.
Preferably, the thickness of the wall of the alumina nanotube is 5-41 nm.
Preferably, the supported heterogeneous catalyst further comprises an auxiliary active component deposited on the inner surface of the alumina nanotube.
Preferably, the co-active component comprises platinum.
Preferably, the mass content of the auxiliary active component is 3.5-5%; the particle size of the auxiliary active component is 2-6 nm.
The invention provides a preparation method of a supported heterogeneous catalyst, which comprises the following steps:
(1) coating the carbon nanofiber dispersion liquid on a substrate, and removing a dispersing agent to obtain a template;
(2) depositing alumina on the template obtained in the step (1), and removing the template through calcination to obtain an alumina nanotube;
(3) depositing cobalt oxide on the outer surface of the alumina nano-tube obtained in the step (2) to obtain the supported heterogeneous catalyst.
Preferably, the method further comprises the steps of depositing an auxiliary active component on the template obtained in the step (1), and then performing the operations of the step (2) and the step (3) on the template on which the auxiliary active component is deposited.
Preferably, the deposition is atomic layer deposition.
The invention provides the application of the supported heterogeneous catalyst in the technical scheme or the supported heterogeneous catalyst prepared by the preparation method in the technical scheme in catalyzing styrene epoxidation.
The supported heterogeneous catalyst provided by the invention comprises an alumina nanotube and cobalt oxide deposited on the outer surface of the alumina nanotube, wherein the alumina nanotube is used as a carrier, and the cobalt oxide as an active component is deposited on the outer surface of the carrier, so that the active component can be uniformly dispersed, and further the catalyst with higher activity is obtained. The embodiment result shows that when the catalyst provided by the invention is used in the styrene epoxidation reaction, and styrene, acetonitrile and tert-butyl hydroperoxide are used as reactants, the selectivity of generating styrene oxide reaches 74.3-94.8%, and the conversion rate reaches 77.2-91.4%; peroxy acid is not needed in the reaction, and the reaction cost is reduced.
Drawings
FIG. 1 is a TEM image of a supported heterogeneous catalyst obtained in example 1 of the present invention;
FIG. 2 is a TEM image of a supported heterogeneous catalyst obtained in example 3 of the present invention;
FIG. 3 is a TEM image of the supported heterogeneous catalyst obtained in example 6 of the present invention.
Detailed Description
The invention provides a supported heterogeneous catalyst, which comprises alumina nanotubes and cobalt oxide deposited on the outer surface of the alumina nanotubes.
The supported heterogeneous catalyst provided by the invention comprises an alumina nanotube, wherein the wall thickness of the alumina nanotube is preferably 5-41 nm, more preferably 5-35 nm, and further preferably 5-9 nm. The invention has no special requirements on the inner diameter and the length of the alumina nanotube, and is determined by the diameter and the length of the template agent; the diameter and length of the templating agent are described in the methods of preparation. The invention takes the alumina nanotube as a carrier, can uniformly disperse the active components on the outer surface of the nanotube, enlarges the contact surface of the active components and a reaction substrate, and promotes the catalytic reaction.
The supported heterogeneous catalyst provided by the invention comprises cobalt oxide deposited on the outer surface of the alumina nanotube. In the present invention, the cobalt oxide is CoOxWherein x is 4/3-2, which represents the mixed valence state of cobalt. In the invention, the cobalt oxide is granular, and the particle size of the cobalt oxide is preferably 1-2 nm; the thickness of the cobalt oxide deposition is preferably 2-5 nm, and more preferably 3-4 nm. In the present invention, the mass of the cobalt oxide is preferably 3 to 4.5%, more preferably 3.5 to 4% of the mass of the supported heterogeneous catalyst.
In the present invention, the supported heterogeneous catalyst preferably further comprises an auxiliary active component deposited preferably on the inner surface of the alumina nanotubes. In the present invention, the auxiliary active component preferably includes platinum; the deposition amount of the auxiliary active component is preferably 3.5-5% of the mass of the supported heterogeneous catalyst, and more preferably 4%; the auxiliary active component is preferably granular, and the particle size is preferably 2-6 nm, and more preferably 2-3 nm.
The invention provides a preparation method of a supported heterogeneous catalyst, which comprises the following steps:
(1) coating the carbon nanofiber dispersion liquid on a substrate, and removing a dispersing agent to obtain a template;
(2) depositing alumina on the template obtained in the step (1), and removing the template through calcination to obtain an alumina nanotube;
(3) depositing cobalt oxide on the alumina nano-tube obtained in the step (2) to obtain the supported heterogeneous catalyst.
The method comprises the steps of coating a carbon nanofiber dispersion liquid on a substrate, and removing a dispersing agent to obtain a template, wherein the carbon nanofiber dispersion liquid preferably comprises carbon nanofibers and ethanol, the diameter of the carbon nanofibers is preferably 100-120 nm, more preferably 100nm, the length of the carbon nanofibers is preferably in a nanometer or micrometer level, and the carbon nanofibers are commercially available products with conventional sizes well known to the skilled person.
The invention has no special requirement on the substrate, and the substrate is made of a high-temperature-resistant and flat-surface material, and can be a quartz plate. The invention has no special requirement on the coating mode of the carbon nanofiber dispersion liquid and can adopt a conventional mode. After coating, the carbon nanofiber dispersion liquid coating layer is subjected to dispersant removal treatment, and the removal method can adopt a drying-by-distillation mode. After the solvent is removed, the invention obtains a template having a uniform helical structure. The invention preferably takes the carbon nano-fiber as a template and provides a basis for preparing the alumina nano-tube.
According to the method, the atomic layer deposition (A L D) is preferably carried out in an atomic layer deposition vacuum reaction cavity, the temperature of the cavity is preferably 120-130 ℃, more preferably 122-128 ℃, further preferably 125 ℃, the pressure of the cavity is preferably 40-60 Pa, more preferably 45-55 Pa, further preferably 50Pa, the deposition speed is preferably 1-2 nm/cycle, more preferably 1.4nm/cycle, the deposition time is preferably expressed by the deposition cycle number, the deposition cycle number is preferably 30-300, and particularly 30, 35, 40, 45, 50, 55, 60, 65, 70, 80, 100, 120, 150, 180, 200 or 300.
After depositing the alumina, the invention calcines the material obtained after deposition to remove the carbon nano-fiber (template) and obtain the alumina nano-tube. In the invention, the calcination temperature is preferably 450-650 ℃, more preferably 475-625 ℃, and further preferably 500-600 ℃; the calcination time is preferably 1-3 h, more preferably 1-2.5 h, and further preferably 1.5-2 h, and specifically can be 1h, 1.5h, 2h, 2.5h or 3 h; the calcination is preferably carried out under an air atmosphere.
After calcination, cobalt oxide is deposited on the outer surface of the alumina nanotube to obtain the supported heterogeneous catalyst. In the invention, the cobalt oxide is obtained by depositing cobaltocene and ozone which are used as precursors; the amount of cobaltocene and ozone used may be any amount known to those skilled in the art. In the invention, the deposition is preferably atomic layer deposition, and the atomic layer deposition is preferably carried out in an atomic layer deposition vacuum reaction cavity; during deposition, the temperature of the cavity is preferably 230-280 ℃, more preferably 240-270 ℃, and further preferably 250 ℃; the pressure of the cavity is preferably 40-60 Pa, more preferably 45-55 Pa, and further preferably 50 Pa; the deposition time is preferably expressed by the number of deposition cycles, and the number of deposition cycles is preferably 20-50, and more preferably 30-40.
The supported heterogeneous catalyst prepared by the preparation method comprises the components of alumina nanotubes and cobalt oxide deposited on the outer surfaces of the alumina nanotubes, and is prepared by CoOx/Al2O3This is shown to be a supported cobalt catalyst.
In the present invention, when the supported heterogeneous catalyst further comprises an auxiliary active component, the preparation method according to the above technical solution further comprises depositing the auxiliary active component on the obtained template, and then sequentially performing the operations of the step (2) and the step (3) on the template on which the auxiliary active component is deposited. In the present invention, when the auxiliary active component is platinum, it is preferably obtained by deposition using (trimethyl) methylcyclopentadienyl platinum and ozone as precursors. In the present invention, the ratio of the (trimethyl) methylcyclopentadienyl platinum to the ozone is well known to those skilled in the art; the deposition is preferably atomic layer deposition, and more preferably is performed in an atomic layer deposition vacuum reaction chamber. During deposition, the temperature of the cavity is preferably 230-280 ℃, and more preferably 240-270 ℃; the pressure of the cavity is preferably 40-60 Pa, and more preferably 45-55 Pa; the deposition time is expressed by the number of deposition cycles, and the number of deposition cycles is preferably 15-20. In the present invention, the carrier gas for deposition is preferably contained in a bagHigh-purity nitrogen is included; the volume ratio of the carrier gas to the vacuum reaction cavity is preferably 1/10-1/5 min-1。
In the present invention, when the deposition step of the auxiliary active component is included, the composition of the resulting supported heterogeneous catalyst preferably includes alumina nanotubes, cobalt oxide deposited on the outer surface of the alumina nanotubes and the auxiliary active component deposited on the inner surface of the alumina nanotubes; if the auxiliary active component is represented by R, the supported heterogeneous catalyst can be CoOx/Al2O3the/R is represented by the formula, wherein x is 4/3-2, and CoO can be used as the supported heterogeneous catalyst when the auxiliary active component is platinumx/Al2O3the/Pt is expressed, wherein x is 4/3-2, and the catalyst can be regarded as a Co and Pt space separation catalyst.
The invention further provides an application of the supported heterogeneous catalyst in the technical scheme or the supported heterogeneous catalyst prepared by the preparation method in the technical scheme in the catalytic styrene epoxidation reaction, in the invention, a system of the styrene epoxidation reaction preferably comprises styrene, tert-butyl hydroperoxide, acetonitrile and a catalyst, the mass ratio of the styrene to the tert-butyl hydroperoxide is preferably 1 (1-4), more preferably 1 (1-3), and further preferably 1:2, and the mass ratio of the acetonitrile to the styrene is preferably (15-30) m L: 3.5mmol, more preferably (18-25) m L: 3.5mmol, and further preferably 20m L: 3.5 mmol.
In the invention, in the styrene epoxidation reaction, the amount of the catalyst is preferably 1.2-7.5 mg/mmol, more preferably 1.4-7.2 mg/mmol, and still more preferably 1.5-7.0 mg/mmol based on 3.5mmol of styrene.
In the invention, the styrene epoxidation reaction is preferably carried out in a hydrogen or air atmosphere, and the reaction temperature is preferably 78-85 ℃, and more preferably 80 ℃; the reaction time is preferably 7-10 h, and more preferably 8 h; the reaction is preferably carried out under stirring conditions; the stirring speed is preferably 650-800 r/min, and more preferably 700 r/min.
In the present invention, the catalytic activity of the catalyst is evaluated by the conversion and the selectivity, which is the mass (or molar) ratio of the styrene consumed by the reaction to produce styrene oxide to the total styrene raw material consumed; the selectivity is 74.3-94.8%;
the conversion rate refers to the ratio of the consumption (mass or amount of substance) of a component to produce a product by reaction to the total amount (mass or amount of substance) of the component before reaction under certain conditions; the conversion rate of the supported heterogeneous catalyst is preferably 77.2-91.4%.
In order to further illustrate the present invention, the following detailed description of the supported heterogeneous catalyst and the preparation method and application thereof provided by the present invention are given with reference to the accompanying drawings and examples, which should not be construed as limiting the scope of the present invention.
Example 1
Load type CoOxPreparation of the catalyst
Dispersing carbon nano fiber in ethanol to form carbon nano fiber ethanol dispersion liquid with the concentration of 0.03g/m L, and depositing Al by taking trimethyl aluminum and water as precursors2O3(ii) a CoO deposition by using cobaltocene and ozone as precursorsxNanoparticles.
(1) Uniformly coating the carbon nanofiber ethanol dispersion liquid on the surface of a glass sheet, evaporating to dryness, and placing the glass sheet into an atomic layer deposition vacuum reaction cavity;
(2) taking the carbon nano-fiber prepared in the step (1) as a template, controlling the temperature of a cavity to be 125 ℃ when depositing the alumina, controlling the pressure of the cavity to be 50 Pa., and firstly depositing Al for 50 cycles by using A L D2O3Oxide nanotubes are formed.
(3) Calcining the sample obtained in the step (2) in air at 500 ℃ to remove the template of the carbon nanofiber, and then depositing CoOxNano particles to obtain alumina nano tube loaded CoOxCatalyst (x is 4/3-2) marked as CoOx/50Al2O3. Deposition of CoOxWhen nano particles are used, the temperature of the cavity is controlled to be 250 ℃, and the pressure of the cavity is controlled to be 50 Pa.
The morphology of the obtained product was characterized by transmission scanning electron microscopy, and the results are shown in fig. 1. As can be seen from the TEM of FIG. 1, the CoOxNano meterThe particles are uniformly loaded on the outer wall of the alumina nanotube, and the thickness of the alumina nanotube wall is 7 nm.
Evaluation of catalyst Activity was carried out in a three-necked flask of 50m L, to which was added 20m L acetonitrile, 3.5mmol of styrene, 7mmol of t-butyl hydroperoxide, and 8mg of this catalyst sample, followed by stirring reaction at a reaction temperature of 80 ℃ under an air atmosphere, and after 8 hours of reaction, the conversion of styrene was 91.0%, and the selectivity of epoxy product was 74.3%.
And adding acetonitrile, styrene, tert-butyl hydroperoxide and a catalyst according to the above dosage, and stirring and reacting for 8 hours at the reaction temperature of 80 ℃ in a hydrogen atmosphere, wherein the conversion rate of the styrene is 87.8 percent, and the selectivity of the epoxy product is 75.9 percent.
Example 2
Pt and CoOxPreparation of spatially separated catalysts
Dissolving carbon nano fiber in ethanol to form carbon nano fiber ethanol dispersion liquid with concentration of 0.03g/m L, depositing Al by taking trimethyl aluminum and water as precursors2O3(ii) a Depositing Pt nano particles by using (trimethyl) methyl cyclopentadienyl platinum and ozone as precursors; CoO deposition by using cobaltocene and ozone as precursorsxNanoparticles.
(1) Coating carbon nano-fibers on a glass sheet, evaporating to dryness, placing the glass sheet into an atomic layer deposition vacuum reaction cavity, and depositing 20 cycles of Pt nano-particles firstly, wherein the deposition conditions are as follows: the temperature of the cavity is 250 ℃, the pressure of the cavity is 50Pa, and the volume ratio of the carrier gas to the vacuum reaction cavity is 1/8min in the deposition process-1Introducing carrier gas into the cavity;
(2) then depositing Al on the Pt nanoparticle layer of the step (1) for 30 cycles2O3Forming oxide nanotubes, and depositing conditions: the temperature of the cavity is 125 ℃, and the pressure of the cavity is 50 Pa;
(3) calcining the sample obtained in the step (2) in air at 500 ℃ to remove the template of the carbon nanofiber, and finally depositing 35 cycles of CoOxThe deposition conditions of the nano particles are the same as those of the Pt nano particles; obtaining Pt and CoOxSpatially separated catalysts, labelled CoOx/30Al2O3Pt (x is 4/3-2).
The obtained catalyst is characterized by a transmission electron microscope, wherein the thickness of the aluminum oxide is 5nm, Pt nano particles are confined in oxide nano tubes, and CoOxThe nano particles are uniformly dispersed on the outer surface of the oxide nano tube.
The catalyst activity evaluation was carried out in a three-necked flask of 50m L, to which was added 20m L acetonitrile, 3.5mmol styrene, 7mmol t-butyl hydroperoxide, and 5mg of a catalyst sample, followed by stirring at a reaction temperature of 80 ℃ under a hydrogen atmosphere to react for 8 hours, the conversion of styrene was 78.2%, and the selectivity of epoxy product was 93.9%.
Example 3
Pt and CoOxPreparation of spatially separated catalysts
A catalyst was prepared according to the method of example 2, except that 50 cycles of Al were deposited2O3Oxide nanotubes are formed. The structure of the obtained catalyst was characterized by transmission electron microscopy, and the results are shown in FIG. 2, in which Pt nanoparticles are confined in oxide nanotubes, the average diameter of the Pt nanoparticles was 2.5nm, the thickness of the alumina tube wall was 7nm, and CoO was presentx(x is 4/3-2) nano particles are uniformly dispersed on the outer surface of the oxide nano tube to obtain a catalyst sample with the composition of CoOx/50Al2O3/Pt。
The catalytic activity of the catalyst was tested by adding 20m L acetonitrile, 3.5mmol styrene, 7mmol t-butyl hydroperoxide, 8mg of this catalyst sample to a three-necked flask, and then after stirring and reacting for 8 hours at a reaction temperature of 80 ℃ under a hydrogen atmosphere, the conversion of styrene was 77.2% and the selectivity of epoxy product was 94.8%.
The amount, reaction temperature and time were the same as above, and the reaction was carried out in an air atmosphere, with a styrene conversion of 91.4% and an epoxy product selectivity of 76.2%.
Example 4
A catalyst was prepared in the same manner as in example 3, except that 65 cycles of alumina were deposited, and the sample thus prepared was designated as CoOx/65Al2O3Pt, reacting the obtained catalyst sample in a hydrogen atmosphere, and testing the catalytic performance of the catalyst, wherein the conversion rate of styrene is 80.3%, and the selectivity of epoxy products is 86.5%.
Example 5
Pt and CoOxPreparation of spatially separated catalysts
A catalyst was prepared according to the method of example 2, except that 80 cycles of Al were deposited2O3Oxide nanotubes are formed. The structure of the obtained catalyst was characterized by transmission electron microscopy, and the results were similar to those in example 3, in which the Pt nanoparticles were confined in the oxide nanotubes, the average diameter of the Pt nanoparticles was 2.5nm, the thickness of the alumina tube wall was 10nm, and CoO was presentxThe nano particles are uniformly dispersed on the outer surface of the oxide nano tube, and the composition mark is CoOx/80Al2O3Pt (x is 4/3-2).
20m of L acetonitrile, 3.5mmol of styrene, 7mmol of tert-butyl hydroperoxide and 12mg of the catalyst sample are added into a three-neck flask, and then the mixture is stirred and reacted at the reaction temperature of 80 ℃ under a hydrogen atmosphere, after 8 hours of reaction, the conversion rate of the styrene is 83.7 percent, and the selectivity of an epoxy product is 77.1 percent.
Example 6
Pt and CoOxPreparation of spatially separated catalysts
A catalyst was prepared according to the method of example 2, except that 100 cycles of Al were deposited2O3Oxide nanotubes are formed. The structure of the obtained catalyst was characterized by transmission electron microscopy, as shown in fig. 3, and the results showed that: the Pt nano particles are confined in the oxide nano tube, the average diameter of the Pt nano particles is 2.5nm, the thickness of the wall of the alumina tube is 14nm, and CoOx(x is 4/3-2) nano particles are uniformly dispersed on the outer surface of the oxide nano tube, and the composition mark is CoOx/100Al2O3/Pt。
20m of L acetonitrile, 3.5mmol of styrene, 7mmol of tert-butyl hydroperoxide and 15mg of the catalyst sample are added into a three-neck flask, and then the mixture is stirred and reacted at the reaction temperature of 80 ℃ under a hydrogen atmosphere, after 8 hours of reaction, the conversion rate of the styrene is 84.9 percent, and the selectivity of an epoxy product is 76.8 percent.
Example 7
Pt and CoOxPreparation of spatially separated catalysts
A catalyst was prepared according to the method of example 2, except that step (2) deposited 300 cycles of Al2O3Forming oxide nanotubes, wherein the calcining temperature in the step (3) is 600 ℃. The structure of the obtained catalyst was characterized by transmission electron microscopy, and the results were similar to those of example 2: pt nanoparticles confined in oxide nanotubes, CoOxThe nano particles are uniformly dispersed on the outer surface of the oxide nano tube, and the chemical composition mark is CoOx/300Al2O3/Pt。
20m of L acetonitrile, 3.5mmol of styrene, 7mmol of tert-butyl hydroperoxide and 35mg of the catalyst sample are added into a three-neck flask, and then the mixture is stirred and reacted at the reaction temperature of 80 ℃ under a hydrogen atmosphere, after 8 hours of reaction, the conversion rate of the styrene is 86.6 percent, and the selectivity of the epoxy product is 75.1 percent.
Comparative example 1
Preparation of supported Pt-based catalyst
A catalyst was prepared according to the method of example 2, except that step (2) deposited Al for 50 cycles2O3Forming oxide nanotubes without depositing CoO in step (3)xNanoparticles. Marked Al2O3and/Pt is a limited Pt-based catalyst.
The catalyst activity evaluation was performed in a 50m L three-necked flask, to which 20m L of acetonitrile, 3.5mmol of styrene, 7mmol of t-butyl hydroperoxide, and 8mg of this catalyst sample were added, followed by stirring at a reaction temperature of 80 ℃ under an air atmosphere, and after 8 hours of reaction, the conversion of styrene was 17.7%, and the selectivity of epoxy product was 72.4%.
The catalytic performance of the catalysts obtained in examples 1 to 7 and comparative example 1 is shown in table 1.
TABLE 1 Supported heterogeneous catalyst structures and catalytic Performance test results of examples 1-7 and comparative example 1
As shown in the test results in Table 3, when the supported heterogeneous catalyst provided by the invention is used for catalyzing the epoxidation catalytic reaction of styrene, CoO is generatedxIs the main active site when CoO is absentxWhen the catalyst is used, the conversion rate of styrene is obviously influenced, and the selectivity is relatively low; and containing CoOxDuring the catalytic reaction, the conversion rate and the selectivity of the styrene are both at a higher level; the existence of Pt has a certain promotion effect on the conversion rate and the selectivity of styrene.
Alternatively, Pt and CoO under hydrogen conditionsxThe wall thickness of the alumina nano-tube in the space separation catalyst also has certain influence on the catalytic performance of the catalyst, when Al2O3When the wall thickness of the nano tube is about 7nm (50 cycles), the selectivity of styrene in the catalytic reaction can reach 94.8%.
From the above examples, it can be seen that the supported heterogeneous catalyst provided by the present invention uses the alumina nanotubes as the carrier, and after the active component cobalt oxide is supported, the conversion rate and selectivity of the styrene catalytic reaction can be improved, which is advantageous for large-scale production of styrene oxide.
The invention also provides a preparation method of the supported heterogeneous catalyst, which has the advantages of simple preparation, easy control and high repeatability, and can realize the control of the thickness of the alumina nanotube by adjusting the deposition parameters.
Although the present invention has been described in detail with reference to the above embodiments, it is only a part of the embodiments of the present invention, not all of the embodiments, and other embodiments can be obtained without inventive step according to the embodiments, and the embodiments are within the scope of the present invention.
Claims (6)
1. A supported heterogeneous catalyst comprising alumina nanotubes and cobalt oxide deposited on the outer surface of the alumina nanotubes; the auxiliary active component is deposited on the inner surface of the alumina nanotube; the auxiliary active component comprises platinum; the wall thickness of the aluminum oxide nanotube is 5-9 nm; the supported heterogeneous catalyst is used for catalyzing styrene epoxidation reaction.
2. The supported heterogeneous catalyst according to claim 1, wherein the cobalt oxide has a particle size of 1 to 2nm and a thickness of 4 to 5 nm.
3. The supported heterogeneous catalyst according to claim 1, wherein the mass content of the auxiliary active component is 3.5-5%; the particle size of the auxiliary active component is 2-6 nm.
4. A method for preparing a supported heterogeneous catalyst comprising the steps of:
(1) coating the carbon nanofiber dispersion liquid on a substrate, and removing a dispersing agent to obtain a template;
(2) depositing alumina on the template obtained in the step (1), and removing the template through calcination to obtain an alumina nanotube;
(3) depositing cobalt oxide on the outer surface of the alumina nanotube obtained in the step (2) to obtain a supported heterogeneous catalyst;
and (2) depositing an auxiliary active component on the template obtained in the step (1), and then performing the operations of the step (2) and the step (3) on the template deposited with the auxiliary active component.
5. The method of claim 4, wherein the deposition is atomic layer deposition.
6. Use of the supported heterogeneous catalyst according to any one of claims 1 to 3 or the supported heterogeneous catalyst prepared by the preparation method according to any one of claims 4 to 5 in the catalysis of styrene epoxidation.
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