Highly dispersed platinum supported on oxygen-deficient zinc oxide photocatalyst, method of preparation and use thereof in the photocatalytic dehydrogenation of propane to propylene

Abstract

High-dispersed platinum loaded oxygen-deficient zinc oxide photocatalyst, preparation method and application thereof in photocatalytic preparation of propylene from propane dehydrogenation belong to the field of photocatalysis technology. A zinc salt solution is stirred under alkaline condition to generate white precipitate, which is then added into hydrogen peroxide and stirred in oil bath, and dried to obtain zinc peroxide powder; the zinc peroxide powder is ground and calcined at high temperature to obtain an oxygen-deficient zinc oxide carrier, which is then immersed in a platinum precursor solution, dried and calcined at high temperature to obtain the photocatalyst. The photocatalyst takes oxygen-deficient zinc oxide as carrier and trace amount of noble metal platinum as active component, wherein the mass percentage of the noble metal platinum is 0.2% to 1.0%. The catalyst exhibits high reaction activity far beyond the thermodynamic limit under low temperature and visible light irradiation, and the selectivity of propylene can reach more than 99%, the catalyst has good stability, and no obvious deactivation is observed after 100 hours of continuous work, the catalyst has high carbon deposition resistance and high noble metal atom utilization rate.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, specifically relating to a highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalyst, its preparation method, and its application in the low-temperature photocatalytic direct dehydrogenation of propane to propylene. Background Technology

[0002] Propylene is one of the most important raw materials for producing many industrial products, including acrolein, polypropylene, acetone, polyacrylonitrile, and propylene oxide. Traditional industrial processes for propylene production involve fluidized bed catalytic cracking and steam cracking of naphtha, light diesel oil, and other petroleum byproducts. With the rapid depletion of fossil fuels, traditional propylene production methods can no longer meet the growing demand. Therefore, developing an efficient and economical propylene production method is crucial. Over the past few decades, many efficient propylene production methods have been developed, such as direct propane dehydrogenation (PDH), methanol-olefins processes, and the Fischer-Tropsch olefins process. Among these methods, due to the development of shale gas extraction methods in recent years, which produce large quantities of low-chain alkanes, and PDH being a direct propylene production method, PDH technology is considered one of the most promising propylene production methods.

[0003] The direct dehydrogenation of propane to produce propylene is a reversible reaction, and the chemical reaction formula is as follows: △H 298K =124.3 kJ / mol. It can be seen that this reaction is thermodynamically balanced and highly endothermic. Therefore, according to the Le Chatelier principle, higher reaction temperatures and / or lower alkane partial pressures are required to achieve high conversion rates. In actual production, the dehydrogenation process of C2–C4 low-chain alkanes typically requires temperatures of 550℃–750℃ to achieve an alkane conversion rate of ≥50% at 1 bar. Currently, the Lummus Catofin and UOP Oleflex processes are mainly used in industrial production to prepare propylene (Chem. Rev. 2014, 114, 10613-10653). The Lummus Catofin process uses a chromium / aluminum-based photocatalyst, exhibiting good performance and stability, and a high propylene yield with a selectivity exceeding 87%. However, the frequent switching to high-temperature conditions leads to low process efficiency; furthermore, the toxicity of chromium makes chromium-based photocatalysts not environmentally friendly. The UOP Oleflex process uses platinum / aluminum-based photocatalysts, which have higher propylene selectivity and catalytic activity. Moreover, platinum-based photocatalysts are more environmentally friendly than chromium-based photocatalysts.

[0004] Platinum, a noble metal, exhibits excellent activity for the direct dehydrogenation of propane due to its affinity for the CH bonds of alkanes. The active components of platinum-based photocatalysts are platinum clusters or platinum nanoparticles. Xing Gui Zhou and colleagues used density functional theory (DFT) to show that the dehydrogenation and desorption barriers of propylene on Pt(111) are similar, while the dehydrogenation barrier on Pt(211) (0.29 eV) is much lower than the desorption barrier of propylene (1.43 eV). Therefore, the main problem with platinum nanoparticles is the formation of coke due to carbon-carbon bond cleavage and deep dehydrogenation. Simultaneously, due to the Ostwald ripening mechanism, the high temperatures required for direct propane dehydrogenation and photocatalyst regeneration can lead to severe sintering of platinum nanoparticles (the Tammann temperature of platinum is 750 °C, Chem. Soc. Rev., 2021, 50, 3315–3354). Therefore, in order to obtain higher direct propane dehydrogenation activity, it is often necessary to increase the reaction temperature to above 500℃. However, under high temperature conditions, photocatalysts are prone to deactivation and can easily lead to side reactions such as propane thermal cracking, hydrogenolysis, or carbon deposition. Such constraints limit the development of direct propane dehydrogenation in industrial catalysis. Summary of the Invention

[0005] The purpose of this invention is to provide a highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalyst, its preparation method, and its application in the low-temperature photocatalytic direct dehydrogenation of propane to propylene.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The preparation method of a highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalyst according to the present invention comprises the following steps:

[0008] (1) The zinc salt solution was stirred under alkaline conditions to form a white precipitate, and then washed and filtered repeatedly to remove excess alkali metal ions.

[0009] (2) The white precipitate obtained in step (1) was added to hydrogen peroxide and stirred in an oil bath. Then it was washed and filtered multiple times. After drying at 60℃~120℃, zinc peroxide powder was obtained.

[0010] (3) The zinc peroxide powder obtained in step (2) is ground and then calcined at high temperature to obtain an oxygen-deficient zinc oxide carrier.

[0011] (4) The oxygen-deficient zinc oxide support obtained in step (3) is immersed in a platinum precursor solution, taken out, dried and calcined at high temperature to obtain a highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalyst.

[0012] Unless otherwise specified, the solvent used in the solutions of this invention is deionized water.

[0013] Further, in step (1), the zinc salt is zinc chloride, zinc nitrate, zinc sulfate or zinc acetate, and the zinc ion concentration in the zinc salt solution is 0.01 to 10 mol / L; the alkaline conditions are ammonia water, lithium hydroxide solution, sodium hydroxide solution, potassium hydroxide solution, cesium hydroxide solution or urea solution, with a concentration of 0.01 to 10 mol / L.

[0014] Furthermore, in step (1), the water is washed 3 to 5 times with deionized water, and after each wash, the water is used for filtration.

[0015] Further, in step (2), the concentration of hydrogen peroxide is 0.1 mol / L to 10 mol / L, the treatment temperature is 20℃ to 90℃, and the treatment time is 0.1 h to 20 h; the mixture is filtered by a water pump and washed with deionized water 3 to 5 times.

[0016] Furthermore, the high-temperature calcination in step (3) specifically refers to calcining at 200℃ to 800℃ for 0.1h to 20h in a vacuum, argon, nitrogen, oxygen or air atmosphere at a heating rate of 1℃ to 10℃.

[0017] Further, the platinum precursor solution in step (4) is a chloroplatinic acid solution, a sodium chloroplatinate solution, or a tetraammine nitrate platinum solution, with a platinum ion mass concentration of 0.1 mg / mL to 10 mg / mL; based on the mass of the oxygen-deficient zinc oxide support, the mass percentage of platinum impregnated is 0.2% to 1.0%.

[0018] Furthermore, the high-temperature calcination in step (4) specifically refers to calcining at a temperature of 200℃ to 600℃ (lower than the calcination temperature in step (3)) for 0.1h to 20h in a vacuum, argon, nitrogen, hydrogen, oxygen or air atmosphere at a heating rate of 1℃ to 10℃; the platinum precursor decomposes under heat to form platinum single atoms / single atom clusters, platinum sub-nanoclusters with a particle size of 0.8nm to 2nm, or platinum nanoparticles with a particle size of 2nm to 5nm.

[0019] The present invention also relates to a highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalyst, which is prepared by the above method.

[0020] This invention also relates to the application of the above-mentioned highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalyst in the low-temperature photocatalytic direct dehydrogenation of propane to propylene.

[0021] The aforementioned low temperature range is 0℃~300℃.

[0022] The light source for the above photocatalysis is ultraviolet light, visible light or near-infrared light, with a wavelength range of 180nm to 2500nm.

[0023] The above-mentioned photocatalytic direct dehydrogenation of propane to propylene reaction process is as follows: the reaction temperature is precisely controlled using a constant temperature reaction bath device; high-purity propane gas is introduced into a quartz reactor; the illumination time is 0–12 h; and the types of reactants are detected by gas chromatography. Further, the stability of the photocatalyst is tested using a propane gas mobile phase reaction device for 0–100 h; online gas chromatography is used for detection, and the conversion rate of propane and the selectivity for propylene production are quantitatively calculated.

[0024] The advantages of this invention compared to the prior art are:

[0025] (1) The photocatalyst of the present invention has a simple synthesis step and a short process time; deionized water is mostly used as a solvent in the preparation process, resulting in less pollution; the equipment requirements are not high and the reaction conditions are easy to achieve.

[0026] (2) The present invention uses an oxygen-deficient zinc oxide as a support, which can effectively anchor platinum atoms, thereby achieving the stability and recyclability of the photocatalyst. Furthermore, the preparation method uses an impregnation method to load the active component platinum, and the component content is easy to control and has high repeatability.

[0027] (3) The photocatalyst of the present invention is used for the first time in the photocatalytic direct dehydrogenation of propane to prepare propylene. Under the conditions of room temperature (20°C) and visible light (λ≥400nm) irradiation, propane can undergo dehydrogenation reaction with a high conversion rate, which greatly breaks through the thermodynamic limitations of the reaction.

[0028] (4) This invention achieves the first low-temperature photocatalytic direct dehydrogenation of propane to propylene, effectively avoiding side reactions such as propane thermal cracking and hydrogenolysis caused by high temperature (≥500℃) in thermal catalysis. Therefore, the selectivity of propylene is good, reaching more than 99%, and the photocatalyst has no obvious deactivation after working continuously for 100 hours. Attached Figure Description

[0029] Figure 1 These are XRD patterns comparing the zinc peroxide synthesized in Example 1 of this invention, the oxygen-deficient zinc oxide support, and commercial zinc oxide. Zinc peroxide corresponds to the ZnO2 curve marked in the figure, and the oxygen-deficient zinc oxide support corresponds to the ZnO2 curve marked in the figure. 1-x The curve corresponds to the ZnO curve marked in the figure for commercial zinc oxide.

[0030] Figure 2 This is a transmission electron microscope image of the oxygen-deficient zinc oxide support synthesized in Example 1 of this invention, with a bar chart of the particle size distribution of the oxygen-deficient zinc oxide support attached to the blank space of the image.

[0031] Figure 3 This is the electron paramagnetic resonance spectrum of the oxygen-deficient zinc oxide photocatalyst synthesized in Example 1 of this invention.

[0032] Figure 4 This is a high-angle annular dark-field scanning transmission image (HAADF-STEM) of the highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalyst prepared in Example 1 of this invention (based on the mass of the oxygen-deficient zinc oxide photocatalyst, the mass percentage of platinum is 0.5%).

[0033] Figure 5 The standard curves (left) and (right) for different amounts of propane and propylene were determined by gas chromatography (GC). The vertical axis represents the peak area of ​​different amounts of propane (left) and propylene (right) in GC, which can quantitatively describe the conversion rate of propane and the selectivity of propylene.

[0034] Figure 6 The images show XRD patterns (left) of oxygen-deficient zinc oxide photocatalysts synthesized using different alkaline solutions in Examples 1 to 5 of this invention, and bar graphs (right) of propylene yield in direct propane dehydrogenation of highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalysts synthesized using different alkaline solutions.

[0035] Figure 7 This is a photocatalytic performance graph of the photocatalysts loaded with different platinum contents in Examples 6 to 9 of this invention. The bar chart represents the propylene yield of the oxygen-deficient zinc oxide photocatalysts loaded with different platinum contents, and the dotted line graph represents the conversion frequency (TOF) of the oxygen-deficient zinc oxide photocatalysts loaded with different platinum contents, i.e., the number of propane molecules converted per platinum atom per minute. The calculation formula is: TOF = (n(C3H8)) in -n(C3H8)] out ) / n(Pt) / t(min), it can be calculated that when the mass percentage of impregnated platinum is 0.5%, the utilization rate of platinum atoms is the highest.

[0036] Figure 8 This is a mobile phase catalytic stability diagram of the direct propane dehydrogenation reaction catalyzed by the highly dispersed platinum-supported 4-oxygen-deficient zinc oxide photocatalyst (platinum mass percentage of 0.5%) in Example 10 of this invention. The diagram illustrates that the highly dispersed platinum-supported photocatalyst on the oxygen-deficient zinc oxide photocatalyst exhibits excellent stability, maintaining a high propane conversion rate and over 99% propylene selectivity even after 100 hours of stability testing.

[0037] Figure 9 This figure represents the final conversion rate of propane after 12 hours of continuous reaction of highly dispersed platinum supported on an oxygen-deficient zinc oxide photocatalyst in Example 11 of this invention. The curve represents the equilibrium conversion rate of propane at different temperatures, and the pentagram represents the conversion rate of propane after 12 hours of visible light irradiation at room temperature (20°C) using the above photocatalyst. This figure illustrates that the photocatalyst of this invention breaks the thermodynamic limitations of the reaction in the low-temperature photocatalytic direct dehydrogenation of propane to propylene. Detailed Implementation

[0038] The following specific embodiments provide a more detailed description of the present invention. The specific operational processes in these embodiments will enable those skilled in the art to gain a more comprehensive understanding of the present invention. The embodiments described below are merely some, not all, of the present invention; therefore, the scope of protection of the present invention is not limited to the following embodiments.

[0039] Example 1:

[0040] (1) Prepare a 100mL round-bottom flask, add 25mL of deionized water to the round-bottom flask, place the flask on a magnetic stirrer, weigh 1.36g of anhydrous zinc chloride, slowly add it to the deionized water and stir to dissolve it, so as to obtain a zinc chloride aqueous solution; weigh 0.40g of sodium hydroxide and dissolve it in a beaker containing 25mL of deionized water, and then slowly add the prepared sodium hydroxide solution to the zinc chloride aqueous solution while stirring, and continue stirring at 1000 rpm for 2 hours to generate a white precipitate; wash with deionized water 4 times, and after each wash, use a water pump to filter to remove residual alkali metal ions.

[0041] (2) Transfer the white precipitate obtained in step (1) to a 250 mL round-bottom flask, then add 100 mL of 1 mol / L hydrogen peroxide that has been prepared in advance, place the round-bottom flask in an oil bath at 75 °C, and stir continuously at 1000 rpm for 2 h; after the stirring is finished, cool the suspension in the round-bottom flask to room temperature and wash it 4 times with deionized water. After each washing, filter it with a water pump. The obtained product is vacuum dried overnight to obtain zinc peroxide powder.

[0042] (3) Grind the zinc peroxide powder obtained in step (2) and put it into a quartz boat, then transfer it into a vacuum tube furnace and calcine it at 400℃ for 2 hours at a heating rate of 4℃ / min to obtain oxygen-deficient zinc oxide photocatalyst.

[0043] like Figure 1 As shown, X-ray diffraction was tested, and XRD spectra of zinc peroxide, oxygen-deficient zinc oxide, and commercial zinc oxide were obtained. The peak positions of the synthesized zinc peroxide were consistent with the standard card PDF#13-0311 for zinc peroxide, and the peak positions of the synthesized oxygen-deficient zinc oxide and commercial zinc oxide were consistent with the standard card PDF#36-1451 for zinc oxide, indicating that the corresponding crystal forms of zinc peroxide and zinc oxide were successfully synthesized.

[0044] like Figure 2 As shown, a transmission electron microscope was used to obtain a TEM image of the oxygen-deficient zinc oxide photocatalyst. The average particle size of the oxygen-deficient zinc oxide synthesized by the above method was measured to be 10 nm to 15 nm.

[0045] like Figure 3 As shown, the electron paramagnetic resonance spectrum of the oxygen-deficient zinc oxide photocatalyst synthesized by the above method was obtained. The position marked g = 1.960 is the metal cation defect position and the position marked g = 2.003 is the surface oxygen defect position, which proves that oxygen-deficient zinc oxide was synthesized.

[0046] (4) Using deionized water as solvent, prepare a chloroplatinic acid solution with a platinum ion mass concentration of 2 mg / mL. Use a pipette to transfer 50 μL of the chloroplatinic acid aqueous solution and impregnate it onto the surface of 20 mg of the oxygen-deficient zinc oxide photocatalyst obtained in step (3). Dry it with an infrared lamp and transfer it to a quartz reactor. Under vacuum, calcine it at a heating rate of 5 °C / min to 250 °C for 0.5 h to obtain a highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalyst. The platinum impregnation mass percentage is 0.5% based on the mass of the oxygen-deficient zinc oxide photocatalyst.

[0047] like Figure 4 As shown, the scanning transmission high-angle annular dark field pattern (HAADF-STEM) of the highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalyst prepared by the above method was tested. It can be seen from the figure that platinum is highly dispersed on the oxygen-deficient zinc oxide.

[0048] (5) After the quartz reactor cools to room temperature, 100 μmol of high-purity propane gas is introduced into it. Then the reactor is transferred to a constant temperature reaction device at 20°C. Photocatalytic direct dehydrogenation of propane to propylene is carried out using a xenon lamp light source with a 400 nm filter. The illumination time is 5 min. The reaction products are quantitatively analyzed by gas chromatography. Combined with the standard curves of the molar amounts of propane and propylene in gas chromatography, the conversion rate of propane and the selectivity of propylene production can be calculated.

[0049] like Figure 5 As shown, standard curves for propane and propylene were plotted by recording the peak area and molarity of the gases obtained from gas chromatography (GC). The conversion rate of propane and the selectivity of propylene can be calculated using the following formulas:

[0050] Selectivity: Sel(%) = ([n(C3H6)] out / ([n(C3H8)] in -[n(C3H8)] out ))x100

[0051] Conversion rate: Con(%) = (([n(C3H8)]) in -n(C3H8)] out ) / [n(C3H8)] in )x100

[0052] Wherein, [n(C3H8)] inand [n(C3H8)] out These represent the amount of propane introduced before the reaction and the amount of propane remaining after the reaction, respectively. [n(C3H6)] out This represents the amount of propylene produced after the reaction.

[0053] Example 2:

[0054] The preparation and reaction were carried out using the method of Example 1, the only difference being that 0.56g of potassium hydroxide was weighed in step (1).

[0055] Example 3:

[0056] The preparation and reaction were carried out using the method of Example 1, the only difference being that 1.50g of cesium hydroxide was weighed in step (1).

[0057] Example 4:

[0058] The preparation and reaction were carried out using the method of Example 1, the only difference being that 1.71g of barium hydroxide was weighed in step (1).

[0059] Example 5:

[0060] The preparation and reaction were carried out using the method of Example 1, the only difference being that in step (1), concentrated ammonia with a concentration of 10 mol / L was measured and the pH was adjusted to 9-10.

[0061] The results and data from the above embodiments were analyzed, such as... Figure 6 As shown, the left figure shows the XRD patterns of oxygen-deficient zinc oxide photocatalysts synthesized using different alkaline solutions. The peak shapes of the XRD patterns of the oxygen-deficient zinc oxide photocatalysts synthesized using sodium hydroxide, potassium hydroxide, cesium hydroxide, and ammonia are basically consistent, while the peak shape of the oxygen-deficient zinc oxide photocatalyst synthesized using barium hydroxide is weaker. The right figure shows the propylene yield of highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalysts synthesized using different alkaline solutions in the direct dehydrogenation of propane. The propylene yield of the oxygen-deficient zinc oxide photocatalysts synthesized using sodium hydroxide, potassium hydroxide, cesium hydroxide, and ammonia is basically consistent, while the propylene yield of the oxygen-deficient zinc oxide photocatalyst synthesized using barium hydroxide is weaker, which corresponds to the pattern in the left figure.

[0062] Example 6:

[0063] The preparation and reaction were carried out using the method of Example 1, the only difference being that in step (4), 20 μL of chloroplatinic acid aqueous solution was transferred by pipette, and the mass percentage of platinum impregnation was 0.2% based on the mass of the oxygen-deficient zinc oxide photocatalyst.

[0064] Example 7:

[0065] The preparation and reaction were carried out using the method of Example 1, the only difference being that in step (4), 30 μL of chloroplatinic acid aqueous solution was transferred by pipette, and the mass percentage of platinum impregnation was 0.3% based on the mass of the oxygen-deficient zinc oxide photocatalyst.

[0066] Example 8:

[0067] The preparation and reaction were carried out using the method of Example 1, the only difference being that in step (4), 80 μL of chloroplatinic acid aqueous solution was transferred by pipette, and the mass percentage of platinum impregnation was 0.8% based on the mass of the oxygen-deficient zinc oxide photocatalyst.

[0068] Example 9:

[0069] The preparation and reaction were carried out using the method of Example 1, the only difference being that in step (4), 100 μL of chloroplatinic acid aqueous solution was transferred by pipette, and the mass percentage of platinum impregnation was 1.0% based on the mass of the oxygen-deficient zinc oxide photocatalyst.

[0070] The results and data from the above embodiments were analyzed, such as... Figure 7 As shown, the bar chart represents the propylene yield of oxygen-deficient zinc oxide photocatalysts with different platinum contents, and the dotted line graph represents the conversion frequency of oxygen-deficient zinc oxide photocatalysts with different platinum contents, i.e., the number of propane molecules converted per platinum atom per minute. It can be seen from the graph that as the platinum content increases, the propylene yield also increases, while the conversion frequency first increases and then decreases with the increase of platinum content. Therefore, it can be concluded that when the mass percentage of impregnated platinum is 0.5%, the utilization rate of platinum atoms is the highest.

[0071] Example 10:

[0072] The preparation and reaction were carried out using the method of Example 1, the only difference being that in step (5), a mobile phase photoreactor was used, 100% high-purity propane was introduced, the propane flow rate was 20 mL / min, WHSV = 106.5, and a xenon lamp light source with a 400 nm filter was used to carry out the photocatalytic direct dehydrogenation of propane to propylene reaction. The reaction products were quantitatively analyzed online using gas chromatography. Combined with the standard curves of the molar amounts of propane and propylene in gas chromatography, the conversion rate of propane and the selectivity of propylene production could be calculated.

[0073] The results and data from the above embodiments were analyzed, such as... Figure 8As shown in the figure, the triangle represents the propane conversion rate in the direct dehydrogenation of propane to propylene reaction, and the circle represents the propylene selectivity in the direct dehydrogenation of propane to propylene reaction. As can be seen from the figure, the photocatalyst stability test of the highly dispersed platinum supported on oxygen-deficient zinc oxide photocatalyst is very good. After continuous operation for 100 hours, it can still maintain a high propane conversion rate, and the propylene selectivity is still as high as 99% or more.

[0074] Example 11:

[0075] The preparation and reaction were carried out using the method of Example 1, the only difference being that the light irradiation time in step (5) was 12h.

[0076] The results and data from the above embodiments were analyzed, such as... Figure 9 As shown, the curves represent the equilibrium conversion rates of propane at different temperatures, and the pentagrams represent the propane conversion rates of the aforementioned photocatalyst after 12 hours of visible light irradiation at room temperature (20°C). This indicates that the highly dispersed platinum-supported zinc oxide photocatalyst significantly breaks the thermodynamic equilibrium of the reaction in the low-temperature photocatalytic direct dehydrogenation of propane to propylene.

Claims

1. A method for preparing a highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalyst, comprising the following steps: (1) The zinc salt solution was stirred under alkaline conditions to form a white precipitate, and then washed and filtered repeatedly to remove excess alkali metal ions; (2) The white precipitate obtained in step (1) was added to hydrogen peroxide and stirred in an oil bath. Then it was washed and filtered multiple times. After drying at 60℃~120℃, zinc peroxide powder was obtained. (3) The zinc peroxide powder obtained in step (2) is ground and then calcined at high temperature to obtain an oxygen-deficient zinc oxide carrier; (4) The oxygen-deficient zinc oxide support obtained in step (3) is immersed in a platinum precursor solution, taken out, dried and calcined at high temperature to obtain a highly dispersed platinum-loaded oxygen-deficient zinc oxide photocatalyst; the platinum precursor solution is a chloroplatinic acid solution, sodium chloroplatinate solution or tetraammine nitrate platinum solution, and the platinum ion mass concentration is 0.1 mg / mL~10 mg / mL; based on the mass of the oxygen-deficient zinc oxide support, the mass percentage of platinum impregnated is 0.2%~1.0%; the calcination temperature in this step is lower than the calcination temperature in step (3), and the platinum precursor is decomposed by heat to form platinum single atoms / single atom clusters, platinum sub-nano clusters with a particle size of 0.8 nm~2 nm or platinum nanoparticles with a particle size of 2 nm~5 nm.

2. The method for preparing a highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalyst as described in claim 1, characterized in that: In step (1), the zinc salt is zinc chloride, zinc nitrate, zinc sulfate, or zinc acetate, and the zinc ion concentration in the zinc salt solution is 0.01~10 mol / L; the alkaline conditions are ammonia water, lithium hydroxide solution, sodium hydroxide solution, potassium hydroxide solution, cesium hydroxide solution, or urea solution, with a concentration of 0.01~10 mol / L; the solution is filtered by water pump and washed with deionized water 3~5 times.

3. The method for preparing a highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalyst as described in claim 1, characterized in that: In step (2), the hydrogen peroxide concentration is 0.1 mol / L to 10 mol / L, the treatment temperature is 20℃ to 90℃, and the treatment time is 0.1 h to 20 h; the process involves filtration with a water pump and washing with deionized water 3 to 5 times.

4. The method for preparing a highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalyst as described in claim 1, characterized in that: The high-temperature calcination in step (3) refers to calcining at 200℃~800℃ for 0.1h~20h in a vacuum, argon, nitrogen, oxygen or air atmosphere at a heating rate of 1℃ / min~10℃ / min.

5. The method for preparing a highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalyst as described in claim 1, characterized in that: The high-temperature calcination in step (4) refers to calcining at 200℃~600℃ for 0.1h~20h in a vacuum, argon, nitrogen, hydrogen, oxygen or air atmosphere at a heating rate of 1℃ / min~10℃ / min.

6. A highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalyst, characterized in that: It is prepared by the method described in any one of claims 1 to 5.

7. The application of the highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalyst of claim 6 in the photocatalytic direct dehydrogenation of propane to propylene in a low temperature range of 0℃ to 300℃.

8. The application of the highly dispersed platinum-supported oxygen-deficient zinc oxide photocatalyst as described in claim 7 in the photocatalytic direct dehydrogenation of propane to propylene in a low-temperature range of 0℃ to 300℃, characterized in that: The light source for photocatalysis is ultraviolet light, visible light, or near-infrared light, with a wavelength range of 180nm~2500nm.

Images