Nanodiamond / graphene composite material loaded with iridium copper catalyst and its preparation method and application

Abstract

The present invention discloses a nanodiamond / graphene composite material-supported iridium-copper catalyst, its preparation method, and application, and belongs to the technical field of catalysts for the direct dehydrogenation of n-butane. The present invention first prepares a nanodiamond / graphene composite material as a carrier, and iridium and copper are dispersed and fixed in the graphene shell in the form of diatoms. The catalyst efficiently dehydrogenates butane to produce butenes (1-butene and 2-butene) in a mixed feed gas, and the operating temperature of the catalyst is 380-600°C. Compared with traditional platinum-tin bimetallic catalysts and chromium oxide catalysts, the graphitized nanodiamond-supported iridium-copper catalyst of the present invention can achieve efficient conversion of butane to butenes under low temperature conditions and is pollution-free to the environment.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts for the direct dehydrogenation reaction of n-butane, and in particular to a nano-diamond / graphene composite material-supported iridium-copper catalyst, a preparation method thereof, and applications thereof. Background Art

[0002] Alkane dehydrogenation is an important route to produce high-value-added olefins. One of the industrial routes for producing propylene is direct dehydrogenation of propane. The key steps in alkane dehydrogenation are C-H bond activation and olefin desorption. Commonly used industrial catalysts (such as platinum-based catalysts) all have a certain C-H activation ability. However, due to the limited activation ability of C-H, the reaction temperature needs to be increased to improve the alkane conversion rate. Therefore, the reaction temperature for direct propane dehydrogenation is generally above 550°C, and in basic research, the reaction temperature for direct butane dehydrogenation exceeds 500°C. However, high temperature conditions not only increase energy consumption but also cause changes in the catalyst structure during the reaction, reducing the catalyst's activity and lifespan. Therefore, it is very important to develop catalysts that are highly active at lower temperatures.

[0003] In recent years, single-atom catalysts have demonstrated promising catalytic activity in numerous reactions. In supported noble metal catalysts, noble metal atoms are dispersed as single atoms on the support surface, achieving 100% noble metal atom utilization and saving catalyst preparation costs in industrial production. For alkane dehydrogenation, several single-atom metal catalysts have demonstrated excellent activity and selectivity, such as Al2O3-supported Ni single atoms, molecular sieve-confined Fe and Co single atoms, and N-doped carbon materials-supported Ru single atoms. However, the application of single-atom catalysts in alkane dehydrogenation remains limited. This is due to the high surface free energy of single atoms, which can lead to aggregation at high temperatures, resulting in decreased activity. Furthermore, due to near-saturation coordination between single atoms and surrounding atoms, their adsorption capacity for reactants and intermediates is weak, and their CH activation capacity needs to be improved.

[0004] Metal promoters are a common strategy for improving catalyst performance in alkane dehydrogenation reactions. Introducing a second metal as a promoter significantly improves catalyst stability and inhibits high-temperature aggregation through metal-metal interactions. It also modulates the metal surface electronic structure and enhances the catalyst's ability to activate C-H bonds. Introducing a second metal as a promoter on a single-atom catalyst to create atom-pair active sites can not only mitigate the limited C-H bond activation ability of single atoms but also improve catalyst stability. However, the application of atom-pair catalysts in alkane dehydrogenation reactions remains underdeveloped. Summary of the Invention

[0005] The present invention provides a nanodiamond / graphene composite-supported iridium-copper catalyst, its preparation method, and application. The prepared nanodiamond / graphene composite-supported iridium-copper catalyst, when used in the direct dehydrogenation of n-butane to butene, can effectively catalyze the dehydrogenation of n-butane to butene at relatively low temperatures.

[0006] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0007] A nanodiamond / graphene composite material-supported iridium-copper catalyst uses iridium-copper diatoms as active materials and a nanodiamond / graphene composite material as a carrier. Iridium and copper are uniformly dispersed on the surface of the nanodiamond / graphene composite material carrier in the form of diatomic pairs and form bonds with carbon atoms on graphene defects.

[0008] The nanodiamond / graphene composite material has a core-shell structure, with nanodiamond as the core and graphene as the shell; iridium and copper are uniformly dispersed on the surface of the graphene shell in the form of diatomic pairs. At the same time, iridium and copper are both atomically dispersed and bonded to carbon atoms on graphene defects.

[0009] In the catalyst, the content of iridium is 0.001-1 wt%, and the content of copper is 0.001-1 wt%.

[0010] The preparation method of the nanodiamond / graphene composite material loaded with iridium copper catalyst comprises the following steps:

[0011] (1) Using nanodiamond as raw material, preparing nanodiamond / graphene composite materials;

[0012] (2) loading iridium species and copper species on the nanodiamond / graphene composite material by an impregnation method to obtain an iridium-copper-based nanodiamond / graphene composite material catalyst precursor;

[0013] (3) placing an iridium-copper-based nanodiamond / graphene composite catalyst precursor in a quartz tube, performing an oxidation treatment in an oxygen-containing mixed gas, and then performing a calcination treatment in an inert gas. After cooling to room temperature, the nanodiamond / graphene composite material-loaded iridium-copper catalyst is obtained.

[0014] The preparation process of the nano-diamond / graphene composite material carrier in step (1) is as follows: the nano-diamond raw material is subjected to high-temperature calcination treatment to obtain graphitized nano-diamond, which is the nano-diamond / graphene composite material carrier; the high-temperature calcination treatment process is as follows: the nano-diamond raw material is placed in an inert atmosphere at 900-1100° C. and 80-150 ml / min for treatment for 3-8 hours, and the nano-diamond / graphene composite material is obtained after the calcination treatment.

[0015] In step (2), the process of the impregnation method is as follows: 2-5 ml of ethanol is added to a 25 ml beaker, an aqueous solution of chloroiridic acid and an aqueous solution of cuprous chloride are taken in proportion in the beaker, the nano-diamond / graphene composite material obtained after the roasting treatment in step (1) is placed in a small beaker, ultrasonically dispersed for 2-10 minutes, stirred for 12-24 hours under an open condition with a magnetic stirrer, and then kept warm for 10-24 hours under vacuum conditions at a holding temperature of 60-150° C. After cooling to room temperature, iridium species and copper species are loaded on the nano-diamond / graphene composite material, thereby obtaining an iridium-copper-based nano-diamond / graphene composite material catalyst precursor.

[0016] During the oxidation treatment in step (3), the oxygen-containing mixed gas is a mixture of oxygen and an inert gas, wherein the volume fraction of oxygen is 2-50%, the flow rate of the oxygen-containing mixed gas is 30-100 mL / min, the treatment temperature is 200-400° C., and the treatment time is 1-3 h; during the calcination treatment in step (3), the flow rate of the inert gas is 30-100 mL / min, the calcination treatment temperature is 400-600° C., and the calcination treatment time is 1-5 h; after the calcination treatment, the mixture is cooled to room temperature in an inert gas with a flow rate of 7-100 mL / min, and the nano-diamond / graphene composite material loaded with iridium copper catalyst is obtained after being taken out and collected; the type of the inert gas is nitrogen, argon or helium.

[0017] The nanodiamond / graphene composite material-supported iridium-copper catalyst is used as a catalyst for the direct dehydrogenation of n-butane. The catalyst is used at a temperature of 380-600°C. The catalytic reaction conditions are: a space velocity of 1000-90000 mL / g·h, an n-butane molar concentration of 1-5%, and a n-butane to hydrogen molar ratio of 1:(0.5-5). The butene is 1-butene and / or 2-butene. The catalyst exhibits good activity and stability during use.

[0018] The present invention has the following advantages and beneficial effects:

[0019] 1. This invention is the first to prepare an iridium-copper atom pair catalyst on a nanodiamond / graphene composite material, and it is also the first time that a diatomic pair catalyst has been used in an alkane dehydrogenation reaction.

[0020] 2. The nanocarbon-supported noble metal catalyst used in the present invention can obtain higher n-butane direct dehydrogenation reaction activity at a relatively low temperature (380-450°C), which is much lower than the operating temperature of traditional industrial devices (500-650°C), and can significantly reduce reaction energy consumption.

[0021] 3. The catalyst of the present invention is environmentally friendly and highly efficient without causing any pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1HAADF-STEM images of 0.2IrCu / ND@G; among them: (a) HAADF-STEM image at low magnification; (b)-(e) HAADF-STEM images at high magnification.

[0023] Figure 2 HAADF-STEM image of 0.1IrCu / ND@G.

[0024] Figure 3 HAADF-STEM image of 0.1Ir / ND@G.

[0025] Figure 4 It is a comparison chart of the reaction results of Example 3 and Comparative Example 1.

[0026] Figure 5 The figure is a comparison chart of the apparent activation energy test results of Example 4 and Comparative Example 2.

[0027] Figure 6 The figure is a comparison chart of the butane reaction rate measurement results of Example 5 and Comparative Example 3.

[0028] Figure 7 These are HAADF-STEM images of Comparative Example 4; wherein: (a) HAADF-STEM image at low magnification; (b) HAADF-STEM image at high magnification.

[0029] Figure 8 The TOF comparison of Example 4, Comparative Example 2 and Comparative Example 4 is shown. DETAILED DESCRIPTION

[0030] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0031] Example 1:

[0032] The preparation process of the catalyst in this embodiment is as follows:

[0033] The nanodiamond raw material was subjected to high-temperature calcination to obtain functionalized nanodiamonds, which served as the nanodiamond support. The high-temperature calcination process involved treating the nanodiamond raw material at 1100°C in argon at 80 ml / min for 4 hours. After calcination, the nanodiamond / graphene composite support was obtained. 200 mg of the support was placed in a 25 ml beaker and 2 ml of ethanol was added. The amount of iridic acid chlorohydrate solution was calculated based on a 0.2 wt% loading, weighed, and added to the beaker. The amount of cuprous chloride solution was calculated based on a 0.4 wt% loading, weighed, and added to the beaker. Ultrasonication was performed for 2 minutes to achieve uniform dispersion. The mixture was stirred with a magnetic stirrer in an open atmosphere for 24 hours, then maintained at 60°C under vacuum for 24 hours. The mixture was then cooled to room temperature to obtain the iridium-copper-based nanodiamond / graphene composite catalyst precursor. The precursor was then placed in a quartz tube and oxidized in a mixture of oxygen and helium at a flow rate of 30 ml / min for 1.5 hours. The volume fraction of oxygen in the mixed gas is 20%, and the oxidation treatment temperature is 300°C. The gas is then switched to helium, the gas flow rate is 30 mL / min, the calcination temperature is 500°C, and the calcination time is 2 h. After the calcination is completed, the nanodiamond / graphene composite material loaded with iridium copper atom pair catalyst is obtained after cooling to room temperature in a 30 mL / min helium atmosphere, which is recorded as 0.2IrCu / ND@G. Using a spherical aberration corrected high-angle annular dark field-scanning transmission electron microscope (HAADF-STEM) to observe Preparation Example 1, Ir and Cu are both atomically dispersed and distributed in pairs on the surface of the nanodiamond / graphene composite material ( Figure 1 ).

[0034] Example 2:

[0035] The preparation process of the catalyst in this embodiment is as follows:

[0036] The nanodiamond raw material was subjected to high-temperature calcination to obtain functionalized nanodiamonds, which served as nanodiamond supports. The high-temperature calcination process involved treating the nanodiamond raw material at 1100°C in an argon atmosphere at 80 ml / min for 4 hours. After calcination, a nanodiamond / graphene composite support was obtained. 200 mg of the nanodiamond / graphene composite support was placed in a 25 ml beaker and 2 ml of ethanol was added. The amount of iridic acid solution was calculated based on a 0.1 wt% loading and weighed, then added to the beaker. The amount of cuprous chloride solution was calculated based on a 0.4 wt% loading and weighed, then added to the beaker. Ultrasonication was performed for 2 minutes to achieve uniform dispersion. The mixture was stirred under an open magnetic stirrer for 24 hours, then incubated at 60°C under vacuum for 24 hours before cooling to room temperature to obtain an iridium-copper-based nanodiamond / graphene composite catalyst precursor. The precursor was then placed in a quartz tube and oxidized in a mixture of oxygen and helium at a flow rate of 30 ml / min for 1.5 hours. The volume fraction of oxygen in the mixed gas is 20%, and the oxidation treatment temperature is 300°C. The gas is then switched to helium, the gas flow rate is 30 mL / min, the calcination temperature is 500°C, and the calcination time is 2 h. After the calcination, the nanodiamond / graphene composite material is cooled to room temperature in a 30 mL / min helium atmosphere to obtain the iridium-copper atomic pair catalyst, which is recorded as 0.1IrCu / ND@G. Using HAADF-STEM to observe the preparation example 1, Ir and Cu are both atomically dispersed and distributed in pairs on the surface of the nanodiamond / graphene composite material ( Figure 2 ).

[0037] Example 3:

[0038] This example uses the catalyst prepared in Example 2 to test the catalytic performance of n-butane dehydrogenation:

[0039] The catalyst performance test was conducted using a fixed bed reactor. Quartz wool was placed in a quartz glass reactor, 20 mg of catalyst was weighed and placed in the middle of the quartz wool, the reactor was placed in the reactor, and the catalyst bed was heated using a three-stage heating method. He was first introduced for 30 minutes, and then the temperature was raised to 450°C. At a space velocity of 45000 mL / g cat The reaction gas was introduced under the condition of 1:1 ratio of H, nC4:H2 and He balance for 10 h. The composition of the reaction product was analyzed by gas chromatography during the reaction.

[0040] Comparative Example 1:

[0041] The difference between this example and Example 2 is that no cuprous chloride solution is added during the catalyst preparation process, and the iridium atom loading is 0.1 wt%, denoted as 0.1Ir / ND@G. Using HAADF-STEM to observe Comparative Example 1, Ir is distributed in the form of single atoms on the surface of the nanodiamond / graphene composite material ( Figure 3 The catalyst performance test was conducted using a fixed bed reactor. The operation was the same as in Example 1. During the reaction, the composition of the reaction product was analyzed online by gas chromatography.

[0042] Example 4:

[0043] This example uses the catalyst prepared in Example 1 to test the apparent activation energy of n-butane dehydrogenation:

[0044] The catalyst performance test was carried out using a fixed bed reaction device. Quartz wool was placed in a quartz glass reactor, 1 mg of catalyst was weighed, and 0.5 g of quartz sand was mixed in. After mixing evenly, it was placed in the middle of the quartz wool. The reactor was placed in the reaction device, and the catalyst bed was heated by three-stage heating. He was first introduced for 30 minutes, and then the temperature was raised to 410°C, 420°C, 430°C, 440°C, 450°C and 460°C respectively. In order to ensure that the conversion rate was within the kinetic range (<5%), the reaction gas was introduced under the conditions of butane flow rate nC4:H2=1:1 and He balance, and the composition of the reaction product was analyzed online by gas chromatography. The TOF at each temperature (T) was calculated using the formula (TOF=(amount of substance input into butane per second) / (amount of substance at the metal active site × metal dispersion), and an XY image of 1000 / T-Ln(TOF) was plotted. The test results are shown in the figure. Figure 5 shown.

[0045] Comparative Example 2:

[0046] This example uses the catalyst prepared in Comparative Example 1 to test the apparent activation energy of n-butane dehydrogenation:

[0047] The catalyst performance test was carried out using a fixed bed reaction device. Quartz wool was placed in a quartz glass reactor, 10 mg of catalyst was weighed, and 0.5 g of quartz sand was mixed in. After mixing evenly, it was placed in the middle of the quartz wool. The reactor was placed in the reaction device, and the catalyst bed was heated by three-stage heating. He was first passed in for 30 minutes, and then the temperature was raised to 410°C, 420°C, 430°C, 440°C, 450°C and 460°C respectively. In order to ensure that the conversion rate is within the kinetic range (<5%), the reaction gas was passed in under the conditions of butane flow rate nC4:H2=1:1 and He balance, and the composition of the reaction products was analyzed online by gas chromatography. The TOF at each temperature (T) was calculated using the formula, and the XY image of 1000 / T-Ln(TOF) was plotted. The test results are shown in the figure. Figure 5 shown.

[0048] Example 5:

[0049] This example is a determination of the butane reaction rate of low-temperature n-butane dehydrogenation using the catalyst prepared in Example 1:

[0050] The catalyst performance test was conducted using a fixed bed reactor. Quartz wool was placed in a quartz glass reactor, 20 mg of catalyst was weighed and placed in the middle of the quartz wool, the reactor was placed in the reactor, and the catalyst bed was heated using a three-stage heating method. He was first introduced for 30 minutes, and then the temperature was raised to 400°C. At a space velocity of 45000 mL / g cat The reaction gas was introduced under the conditions of 1:1, nC4:H2, and He balance for 10 hours. During the reaction, the composition of the reaction product was analyzed online by gas chromatography. The butane reaction rate was calculated by the formula (butane reaction rate = (input butane flow rate × butane conversion × 60) / (Ir mass × 22.4)). The measurement results are shown in Figure 2. Figure 6 shown.

[0051] Comparative Example 3:

[0052] This example is the determination of the butane reaction rate of low-temperature n-butane dehydrogenation using the catalyst prepared in Comparative Example 1:

[0053] The catalyst performance test was conducted using a fixed bed reactor. Quartz wool was placed in a quartz glass reactor, 20 mg of catalyst was weighed and placed in the middle of the quartz wool, the reactor was placed in the reactor, and the catalyst bed was heated using a three-stage heating method. He was first introduced for 30 minutes, and then the temperature was raised to 400°C. At a space velocity of 45000 mL / g cat The reaction gas was introduced under the conditions of 1:1, He balance and the reaction was continued for 10 hours. The composition of the reaction products was analyzed by gas chromatography during the reaction. The butane reaction rate was calculated by the formula. The results are shown in the figure. Figure 6 shown.

[0054] Comparative Example 4:

[0055] 200 mg of the nanodiamond-graphene composite material carrier prepared in Example 1 was placed in a flask, ultrasonically dispersed for 30 minutes, and the pH value in the flask was adjusted to 9 with sodium formate. Based on the iridium loading of 1.3wt%, the amount of chloroiridic acid solution was calculated, and the required amount of chloroiridic acid solution was then adjusted to pH 4 with ammonia solution. The chloroiridic acid solution was then added to the carrier solution, incubated in an oil bath at 100°C for 1 hour, and then cooled to room temperature. After suction filtration and washing, the sample was incubated under vacuum for 24 hours at 60°C, cooled to room temperature, and a nanodiamond-supported atomically dispersed iridium cluster catalyst precursor was obtained. The resulting nanodiamond-supported atomically dispersed iridium cluster catalyst was then placed in a quartz tube and reduced in a mixture of hydrogen and nitrogen at a flow rate of 30mL / min for 2 hours. The hydrogen volume fraction in the mixture was 10%, and the reduction treatment temperature was 450°C. After the reduction treatment, the mixture was cooled to room temperature in a 30 mL / min helium atmosphere to obtain the nanodiamond-supported atomically dispersed iridium cluster catalyst, denoted as 1.3Ir / ND@G. The HAADF-STEM results are shown in FIG. Figure 7 As shown. The catalyst performance test was carried out using a fixed bed reaction device. Quartz wool was placed in a quartz glass reactor, 5 mg of catalyst was weighed, and 0.5 g of quartz sand was mixed in. After mixing evenly, it was placed in the middle of the quartz wool. The reactor was placed in the reaction device, and the catalyst bed was heated by three-stage heating. He was first passed in for 30 minutes, and then the temperature was raised to 450°C. In order to ensure that the conversion rate was within the kinetic range (<5%), the reaction gas was passed in under the conditions of butane flow rate nC4:H2=1:1 and He balance, and the composition of the reaction product was analyzed online by gas chromatography. The TOF was calculated using the formula and compared with the TOF of Example 2 and Comparative Example 2 at 450°C. The results are shown as follows. Figure 8 shown.

[0056] like Figure 4 As shown in Figure 3, by comparing the reaction results of Example 3 and Comparative Example 1, it is found that the IrCu atomic pair catalyst synthesized by the present invention has a higher butane conversion rate than the Ir single atom catalyst. At the same time, through the determination of the reaction activation energy, the activation energy of the IrCu atomic pair catalyst is much lower than that of the Ir single atom catalyst, indicating that the introduction of the paired atomic Cu can reduce the energy of the dehydrogenation process and is conducive to the dehydrogenation reaction ( Figure 5 At the same time, when the reaction temperature is 400℃, the IrCu atoms still have a high butane reaction rate on the catalyst, showing high activity under harsh reaction conditions. Ir clusters ( Figure 7 ) and Ir single atoms are common catalysts in Ir dehydrogenation systems, such as Figure 8As shown, the TOF of the IrCu atom-pair catalyst is much greater than that of single Ir atoms and Ir clusters, indicating that the introduction of a single Cu atom significantly improves the alkane dehydrogenation performance of the Ir site. Therefore, the dehydrogenation catalyst of the present invention can achieve high catalytic activity at low noble metal loadings and low temperatures, which also helps improve catalyst stability, reduce energy consumption, and lower unit production costs, showing promising application prospects. Furthermore, the present invention applies atom-pair catalysts to the field of alkane dehydrogenation, providing new ideas for the design of high-performance alkane dehydrogenation catalysts.

[0057] The above examples are for reference only. Technical solutions that are similar to the present invention or extended from the concept of this patent are all within the scope of protection of the present invention.

Claims

1. A nanodiamond / graphene composite material-supported iridium-copper catalyst for direct dehydrogenation of n-butane to butene, characterized in that: The catalyst uses iridium-copper diatoms as active sites and a nanodiamond / graphene composite material as a carrier. Iridium and copper are evenly dispersed on the carrier surface in the form of diatomic pairs.

2. The nanodiamond / graphene composite material supported on iridium copper catalyst according to claim 1, characterized in that: The nanodiamond / graphene composite material has a core-shell structure, with nanodiamond as the core and graphene as the shell; iridium and copper are uniformly dispersed on the surface of the graphene shell in the form of diatomic pairs. At the same time, iridium and copper are both atomically dispersed and bonded to carbon atoms on graphene defects.

3. The nanodiamond / graphene composite material supported on iridium copper catalyst according to claim 1, characterized in that: The iridium content in the catalyst is 0.001-1 wt%, and the copper content is 0.001-1 wt%.

4. The method for preparing the nanodiamond / graphene composite material supported on iridium copper catalyst according to claim 1, wherein: The method comprises the following steps: (1) First, nanodiamond is used as raw material to prepare nanodiamond / graphene composite materials; (2) loading iridium species and copper species onto the nanodiamond / graphene composite material by an impregnation method to obtain an iridium-copper-based nanodiamond / graphene composite catalyst precursor; (3) placing an iridium-copper-based nanodiamond / graphene composite catalyst precursor in a quartz tube, first performing an oxidation treatment in an oxygen-containing mixed gas, and then performing a calcination treatment in an inert gas, and obtaining the nanodiamond / graphene composite supported iridium-copper catalyst after cooling to room temperature.

5. The method for preparing the nanodiamond / graphene composite material supported on iridium copper catalyst according to claim 4, wherein: The preparation process of the nano-diamond / graphene composite material carrier in step (1) is as follows: the nano-diamond raw material is subjected to high-temperature calcination treatment to obtain graphitized nano-diamond, which is the nano-diamond / graphene composite material carrier; the high-temperature calcination treatment process is as follows: the nano-diamond raw material is placed in an inert atmosphere at 900-1100 ° C and 80-150 ml / min for treatment for 3-8 hours, and the nano-diamond / graphene composite material is obtained after calcination.

6. The method for preparing the iridium-copper-based nanodiamond / graphene composite catalyst precursor according to claim 5, characterized in that: In step (2), the impregnation process is as follows: adding 2-5 ml of ethanol to a 25 ml beaker, taking a chloroiridic acid aqueous solution and a cuprous chloride aqueous solution in proportion in the beaker, placing the nanodiamond / graphene composite material obtained after the calcination treatment in step (1) into a small beaker, ultrasonically dispersing it evenly for 2-10 min, stirring it with a magnetic stirrer under open conditions for 12-24 h, and then keeping it warm under vacuum conditions for 10-24 h at a holding temperature of 60-150 ° C. After cooling to room temperature, iridium species and copper species are loaded on the nanodiamond / graphene composite material, and an iridium-copper-based nanodiamond / graphene composite material catalyst precursor is obtained.

7. The method for preparing the nanodiamond / graphene composite material supported on iridium copper catalyst according to claim 4, characterized in that: During the oxidation treatment in step (3), the oxygen-containing mixed gas is a mixture of oxygen and an inert gas, wherein the volume fraction of oxygen is 2-50%, the flow rate of the oxygen-containing mixed gas is 30-200 mL / min, the oxidation treatment temperature is 200-400°C, and the oxidation treatment time is 1-3 h; during the calcination treatment in step (3), the flow rate of the inert gas is 30-200 mL / min, the calcination treatment temperature is 400-600°C, and the calcination treatment time is 1-5 h; after the calcination treatment, the mixture is cooled to room temperature in an inert gas at a flow rate of 7-200 mL / min, and the nanodiamond / graphene composite material loaded with iridium copper catalyst is obtained after being taken out and collected; the type of the inert gas is argon or helium.

8. Use of the nanodiamond / graphene composite material supported iridium copper catalyst in direct dehydrogenation of n-butane according to claim 1, characterized in that: The catalyst is used for direct dehydrogenation of n-butane to produce butene.

9. Use of the nanodiamond / graphene composite material supported iridium copper catalyst in direct dehydrogenation of n-butane according to claim 8, characterized in that: During the direct dehydrogenation reaction of n-butane, the catalyst is used at a temperature of 380-600°C; the catalytic reaction conditions are: a space velocity of 1000-90000 ml / g·h, a n-butane molar concentration of 1-5%, and a molar ratio of n-butane to hydrogen of 1:(0.5-5).

10. Use of the nanodiamond / graphene composite material supported iridium copper catalyst in direct dehydrogenation of n-butane according to claim 8, characterized in that: The butene is 1-butene and / or 2-butene.

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