Method for preparing hydrogen peroxide through ultralow-temperature photocatalysis

Abstract

The invention discloses a method for preparing hydrogen peroxide through ultralow-temperature photocatalysis. The method comprises the following steps: adding a photocatalytic material into water or a solution, completely dispersing, and adjusting the pH value to obtain a reaction solution; o2 is added into the reaction solution until saturation, and a light source is turned on for a photocatalytic reaction; after the reaction is finished, detecting the concentration of H2O2 by adopting a potassium iodide-ammonium molybdate spectrophotometric method; the photocatalytic material is a semiconductor metal oxide; the temperature of the photocatalytic reaction is-5 to-60 DEG C. According to the method, the catalyst and oxygen are concentrated in micron-sized intergranular water in an ultralow-temperature state, so that the reactant concentration is greatly improved, and hydrogen peroxide generated by catalysis can be quickly desorbed in the ultralow-temperature state, and the decomposition reaction of the hydrogen peroxide can be inhibited, so that the unit mass of the catalyst and the production quantity of the hydrogen peroxide in unit time are remarkably improved.

Description

Technical Field

[0001] The invention relates to a method for preparing hydrogen peroxide, in particular to a method for preparing hydrogen peroxide by ultra-low temperature photocatalysis, and belongs to the technical field of photocatalytic reactions. Background Art

[0002] Hydrogen peroxide (H2O2) is an environmentally friendly, high-energy, multifunctional chemical widely used in chemical synthesis, environmental governance, bleaching, disinfection and other fields. It has been listed as one of the 100 most important chemicals in the world. Currently, more than 95% of H2O2 is produced by the anthraquinone method (OA), which is the main method for industrial production. In large-scale applications, multi-step hydrogenation and oxidation reactions require high energy input, and the process is complex, including subsequent separation and concentration steps. It is costly and produces a large amount of wastewater, waste gas and waste residue. In addition, the hydrogenation catalytic method uses H2 and O2 as raw materials to directly synthesize H2O2 under the action of precious metal catalysts, which provides an effective way to produce H2O2 in situ. However, the cost of precious metal catalysts is too high and difficult to reuse. The mixture of H2 and O2 is prone to explosion, and the safety is low, making it difficult to achieve industrial application.

[0003] Solar-driven reduction of O2 to generate H2O2 has become a green, safe, environmentally friendly and sustainable method for producing H2O2. Traditional photocatalysts such as nano-TiO2, nano-CuO, and nano-ZnO have poor light absorption performance, and the photogenerated electrons generated are difficult to be effectively utilized by O2, and the photocatalytic performance is poor at room temperature. At present, the photocatalytic research on H2O2 is mainly focused on improving the catalytic efficiency of catalysts. On the one hand, the existing photocatalysts TiO2, CuO, and ZnO are modified, such as complexing anions and cations, loading nano-precious metal particles, graphene heterogeneity, quantum dot modification, etc. On the other hand, new photocatalysts are designed and developed, such as g-C3N4, metal-organic frameworks, and organic polymers. These technical procedures are complicated, and the designed photocatalysts have uncertainty and instability, making it difficult to achieve efficient and stable production of H2O2, which inevitably increases the cost of photocatalytic generation of H2O2. The efficiency improvement of H2O2 produced by the modified catalyst is also very limited, and it is easy to cause environmental pollution during the reaction process, which does not conform to the current concept of green energy production.

[0004] Therefore, the prior art continues to provide an efficient and safe method for preparing hydrogen peroxide to solve or alleviate the current reliance on modified catalysts or development of new catalysts to improve the production efficiency of H2O2 to achieve industrialized photocatalytic production of hydrogen peroxide. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a method for preparing hydrogen peroxide by ultra-low temperature photocatalysis. The method greatly increases the concentration of reactants by concentrating the catalyst and oxygen in micron-sized intercrystalline water under ultra-low temperature conditions, and can achieve rapid desorption of catalytically generated hydrogen peroxide under ultra-low temperature conditions, inhibiting its decomposition reaction, thereby significantly increasing the production of hydrogen peroxide per unit mass of the catalyst and per unit time.

[0006] In order to achieve the above technical objectives, the object of the present invention is to provide a method for preparing hydrogen peroxide by ultra-low temperature photocatalysis, a method for preparing hydrogen peroxide by ultra-low temperature photocatalysis, characterized in that it comprises: Step S1, adding a photocatalytic material to water or a solution, dispersing the material completely, and adjusting the pH to obtain a reaction solution; Step S2, adding O2 to the reaction solution until saturated, and turning on the light source to carry out a photocatalytic reaction; Step S3, after the reaction is completed, the concentration of H2O2 is detected by potassium iodide-ammonium molybdate spectrophotometry; The photocatalytic material is a semiconductor metal oxide; the temperature of the photocatalytic reaction is -5 to -60°C.

[0007] The method provided by the present invention mainly converts most of the liquid phase solution into a solid phase under low temperature conditions, thereby confining the solute oxygen space to the intercrystalline water on the surface of the micron-sized catalyst, thereby greatly increasing the reactant concentration and the effective contact area with the catalyst, thereby effectively improving the reaction activity and reaction rate of the photocatalysis.

[0008] As a preferred solution, the concentration of the photocatalytic material in the reaction solution is 0.005-0.05 g / L.

[0009] As a preferred solution, the pH of the reaction solution is 4-8.

[0010] As a preferred embodiment, the semiconductor metal oxide is at least one of TiO2, CuO, ZnO, MgO, Co3O4 and CeO2.

[0011] It should be noted that since the main innovation of the present invention is to confine the solute oxygen space to the intercrystalline water on the surface of the micron-sized catalyst by freezing, the photocatalytic performance of any substance with photoelectric effect is significantly improved. This improvement effect is universal, that is, it is applicable to any combination, reconstruction and modification of hydrogen peroxide photocatalysts.

[0012] As a preferred solution, the particle size of the photocatalytic material is 20-60 nm.

[0013] As a preferred solution, the solution is an inorganic salt solution and / or an organic ligand solution.

[0014] As a preferred solution, when the solution is an organic ligand solution, its concentration is 5-20%.

[0015] As a preferred solution, the organic ligand is at least one of isopropanol, ethanol, methanol and formic acid.

[0016] As a preferred solution, the flow rate of O2 introduction is 100-200 mL / min, and the introduction time is 8-15 min.

[0017] As a preferred solution, the process of the photocatalytic reaction is: under closed conditions, start the mercury lamp, maintain the system temperature at -20~-60°C, and the reaction time is 5~10h.

[0018] As a preferred solution, the power of the mercury lamp is 200-300W.

[0019] As a preferred solution, the detection of H2O2 concentration requires pretreatment, including thawing and filtering.

[0020] As a preferred solution, the thawing process is: heating the system after the photocatalytic reaction is completed in a water bath at 30-38° C. until the system is completely thawed.

[0021] As a preferred solution, the filtration treatment process is: using a filter head with a diameter of less than or equal to 0.22 μm to filter the completely thawed system to obtain a test solution that does not contain catalyst particles.

[0022] As a preferred solution, the ion reaction formula for detecting the concentration of hydrogen peroxide in the potassium iodide-ammonium molybdate spectrophotometry is: Formula 1: H2O2+3I - +2H+=I3 - +2H2O.

[0023] In the present invention, the method for generating hydrogen peroxide adopts freezing technology, which can concentrate the catalyst and oxygen in micron-sized intercrystalline water. Compared with the liquid phase solution, the solute concentration can be increased by several orders of magnitude, the transmission capacity of the interface electrons is enhanced, and the O2 adsorbed on the catalyst surface can be reduced by more photogenerated electrons to produce superoxide free radicals (•O2 - )、Singlet oxygen( 1 O2) and other reactive species (ROS), further generating hydrogen peroxide. In addition, under freezing conditions, the generated hydrogen peroxide can be quickly desorbed from the catalyst surface and released into the solution, which inhibits its decomposition and increases the accumulation of hydrogen peroxide under freezing conditions. Therefore, under freezing conditions, the photocatalytic generation of hydrogen peroxide can be promoted and its decomposition can be inhibited, achieving efficient generation of hydrogen peroxide by conventional photocatalysts at low concentrations.

[0024] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are: 1) The method provided by the present invention greatly increases the concentration of reactants by concentrating the catalyst and oxygen in micron-sized intercrystalline water under ultra-low temperature conditions, and can achieve rapid desorption of catalytically generated hydrogen peroxide under ultra-low temperature conditions, inhibiting its decomposition reaction, thereby significantly increasing the production of hydrogen peroxide per unit mass of the catalyst and per unit time.

[0025] 2) In the method provided by the present invention, there are no strict requirements for the catalyst, and the photocatalytic performance of any substance with photoelectric effect is significantly improved. This improvement effect is universal, that is, it is applicable to any combination, reconstruction and modification of hydrogen peroxide photocatalysts. Taking semiconductor metal oxides as an example, the production efficiency of hydrogen peroxide in this method is 4 to 17 times that of conventional liquid phase reaction systems. This method also has the advantages of simple operation, low equipment cost and environmental friendliness.

[0026] 3) In the technical solution provided by the present invention, due to the spatial confinement effect under freezing conditions, a large amount of reactants are enriched on the catalyst surface, which effectively increases the contact area between the catalyst and the reactants, and realizes the efficient generation of hydrogen peroxide by the photocatalyst at low concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some example drawings of the present invention. For ordinary personnel in this field, other drawings can be obtained according to the structures shown in these drawings without paying creative work.

[0028] Figure 1 The transmission electron microscope (TEM) images of the enrichment trend of low-concentration nano-TiO2 under normal temperature and freezing conditions in Example 1 of the present invention and Comparative Example 1 are shown; wherein, Figure 1 (a) is the TEM image of nano-TiO2 at room temperature. Figure 1 (b) TEM image of nano-TiO2 under freezing conditions; in, Figure 1 (a) is the TEM image of nano-TiO2 at room temperature. Figure 1 (b) TEM image of nano-TiO2 under freezing conditions; Figure 2 The efficiency result diagram of the photocatalytic production of hydrogen peroxide by low-concentration nano-TiO2 under normal temperature and freezing conditions in Examples 1 and 2 of the present invention and Comparative Examples 1 and 2; Figure 3The efficiency result diagram of the photocatalytic production of hydrogen peroxide by low-concentration nano-TiO2 under normal temperature conditions and different freezing conditions in Example 3 of the present invention and Comparative Example 3; Figure 4 The efficiency result diagram of photocatalytic production of hydrogen peroxide by nano-TiO2 at different low concentrations under normal temperature conditions and different freezing conditions in Example 4 of the present invention and Comparative Example 4; Figure 5 This is a graph showing the efficiency of producing hydrogen peroxide using low-concentration nano-photocatalyst semiconductors under normal temperature and freezing conditions in Examples 5 to 9 of the present invention and Comparative Examples 5 to 9. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be described clearly and completely below in conjunction with the drawings of the specification. Obviously, the described implementation is only a part of the implementation of the present invention, not all of the implementation. Based on the implementation of the present invention, all other implementations obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Furthermore, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in the field. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0031] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or the conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased on the market.

[0032] Unless otherwise defined, all technical and scientific terms used in the present invention are consistent with the prior art knowledge of those skilled in the art and the description of the present invention. The present invention can also be implemented using any methods, devices and materials in the prior art that are similar or equivalent to the methods, devices and materials described in the embodiments of the present invention.

[0033] In order to solve or alleviate the current situation of improving the photocatalytic production of H2O2 by only relying on modified catalysts or developing new catalysts, a method for efficiently producing H2O2 by photocatalysis without any modification measures is established. The present invention provides a method for generating hydrogen peroxide, comprising the following steps: Step S1, adding a photocatalyst material to an aqueous solution or an organic ligand solution, subjecting the solution to ultrasonic treatment to make it uniformly dispersed, and adjusting the pH to obtain a reaction solution; The reaction solution is an aqueous solution or an organic ligand solution, wherein the organic ligand solution is one of isopropanol, ethanol, methanol and formic acid, and the volume fraction is 5-30% vol. As a sacrificial agent, the organic ligand can effectively remove holes, inhibit the combination of electrons and holes, enhance the transmission capacity of photogenerated electrons, and effectively increase the yield of hydrogen peroxide.

[0034] The photocatalyst material is the most widely used semiconductor photocatalyst material, including but not limited to nano-TiO2, nano-CuO, nano-ZnO, nano-MgO, nano-Co3O4, and nano-CeO2. These catalysts are not modified in any way, and the particle size of the catalyst is 20-30 nm, and the concentration is 0.005-0.05 g / L.

[0035] The ultrasonic treatment power is 200 W, the treatment time is 10 minutes, the catalyst is evenly dispersed in the solution, and the pH of the solution is adjusted to 4-8.

[0036] Step S2, continuously introducing O2 into the reaction solution to make it reach a saturated state; The O2 introduced was high-purity oxygen with a flow rate of 150 mL / min and an introduction time of 10 minutes, so that the O2 in the reaction solution reached a saturated state.

[0037] Step S3, adjusting the temperature of the low-temperature constant-temperature reaction bath, placing the reaction solution in a quartz test tube, and placing it in the reaction bath, while irradiating with a light source; The solution used in the low-temperature constant temperature reaction bath is water and ethylene glycol (volume ratio is 1:1) to achieve the purpose of controlling the reaction temperature. The specific reaction temperature is set to 25°C at room temperature and -5~-40°C at freezing conditions. Of course, in order to ensure the constant reaction temperature, the ethylene glycol aqueous solution in the reaction bath should be replaced in time to ensure that the temperature change is within ±1°C.

[0038] The light source is a 250W mercury lamp with a main wavelength of 365nm ultraviolet light. Specifically, a certain volume of reaction solution is placed in a quartz test tube, marked and sealed, and immediately placed in a reaction bath, and the light source is turned on for irradiation, and this moment is defined as the reaction starting point.

[0039] Step S4, after the reaction is completed, the quartz test tube is taken out and placed in a water bath for thawing. After the solution is completely thawed, the concentration of H2O2 is detected by potassium iodide-ammonium molybdate spectrophotometry.

[0040] The reaction time was set to 0-6 h, and a sample was taken out every 1 h for thawing analysis; the temperature of the water bath was 35±1° C., and the reaction solution was completely thawed.

[0041] The detection method of hydrogen peroxide is potassium iodide-ammonium molybdate spectrophotometry. Specifically, the thawed solution is filtered with a 0.22um filter to obtain a test solution free of catalyst particles. The concentration of hydrogen peroxide in the test solution is detected by a colorimetric method using potassium iodide (KI) and ammonium molybdate ((NH4)2MoO4), and I3 is measured at 350nm using a UV-visible spectrophotometer. - The absorbance of H2O2 is used to obtain the content of hydrogen peroxide. - The reaction is as follows: H2O2+3I - +2H+=I3 - +2H2O.

[0042] Example 1 This embodiment provides a method for preparing hydrogen peroxide by ultra-low temperature photocatalysis, the process of which is as follows: 1. Weigh 10 mg of nano titanium dioxide sample with a particle size of about 25 nm, put it in 1000 mL of deionized water solution, and use 200W ultrasonic treatment for 10 minutes to make it evenly dispersed. Adjust the pH to 6 to obtain a reaction solution with a nano titanium dioxide (TiO2) concentration of 0.01 g / L. 2. Take 200 mL of the reaction solution in step 1 and put it into a 500 mL beaker. Pass O2 at a flow rate of 150 mL / min for 10 minutes to saturate the reaction solution with O2.

[0043] 3. Adjust the temperature of the low-temperature constant-temperature reaction bath, place the reaction solution in a quartz test tube, and place it in the reaction bath, and irradiate with a light source at the same time; adjust the temperature of the low-temperature constant-temperature reaction bath to -20°C, measure 10mL of the reaction solution in step 2 and place them in 12 25mL quartz test tubes, cover them with stoppers and seal them with sealing film, place them in a low-temperature constant-temperature reaction bath, and irradiate with a 250W mercury lamp at the same time. This moment is defined as the starting point of the reaction, and the reaction time is 6 hours.

[0044] 4. After the reaction is completed, the quartz test tubes under the frozen condition and the room temperature condition are taken out at the same time interval, and the frozen samples are placed in a water bath at 35±1°C for thawing. After the solution is completely thawed, the thawed / reacted samples are immediately filtered with a 0.22um filter membrane to remove the catalyst particles, and the concentration of H2O2 is detected by potassium iodide-ammonium molybdate spectrophotometry. Specifically, 1mL of the filtrate is mixed with 2mL of 0.1M KI solution and 0.05mL of 0.01M (NH4)2MoO4, reacted in the dark for 30min, and I3 was measured at 350nm using a UV-visible spectrophotometer. - The absorbance was used to obtain the content of hydrogen peroxide.

[0045] Comparative Example 1 This comparative example is exactly the same as Example 1, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to 25°C, 10 mL of the reaction solution in step 2 is measured and placed in 12 25 mL quartz test tubes, the tubes are covered with stoppers and sealed with sealing films, and the tubes are placed in a low-temperature constant-temperature reaction bath. At the same time, a 250 W mercury lamp is used for illumination. This moment is defined as the reaction starting point, and the reaction time is 6 hours.

[0046] The results of Example 1 and Comparative Example 1 are as follows Figure 2 As shown in (a), in aqueous solution, nano-TiO2 has a higher photocatalytic H2O2 production efficiency under freezing conditions than under normal temperature conditions. The production efficiency of H2O2 under freezing conditions is 2.68mmol / g, while the production efficiency of H2O2 under normal temperature conditions is 0.24mmol / g. In aqueous solution (without organic ligands), the production efficiency of H2O2 of nano-TiO2 under freezing conditions is increased by 11.11 times.

[0047] Example 2 This embodiment is exactly the same as Example 1, except that: 1. Weigh 10 mg of nano titanium dioxide sample with a particle size of about 25 nm, put it in 500 mL of deionized water solution, measure 100 mL of the above solution in a 250 mL beaker, add 20 mL of isopropanol solution and 80 mL of deionized water, and treat it with 200 W ultrasound for 10 minutes to make it evenly dispersed, adjust the pH to 6, and prepare a reaction solution, the concentration of nano titanium dioxide (TiO2) is 0.01 g / L, and the concentration of isopropanol organic ligand is 10% vol.

[0048] Comparative Example 2 This comparative example is exactly the same as Example 2, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to 25°C, 10 mL of the reaction solution of step 2 is measured and placed in 12 25 mL quartz test tubes, the tubes are covered with stoppers and sealed with sealing films, and the tubes are placed in a low-temperature constant-temperature reaction bath. At the same time, a 250 W mercury lamp is used for illumination. This moment is defined as the reaction starting point, and the reaction time is 6 hours.

[0049] The results of Example 2 and Comparative Example 2 are as follows Figure 2 As shown in (b), in the isopropanol organic ligand solution, nano-TiO2 has a higher photocatalytic H2O2 production efficiency under freezing conditions compared to room temperature conditions. The production efficiency of H2O2 under freezing conditions is 16.8mmol / g, while the production efficiency of H2O2 under room temperature conditions is 1.06mmol / g. In the isopropanol organic ligand solution, the production efficiency of H2O2 of nano-TiO2 under freezing conditions is increased by about 15 times. Compared with Example 1, organic ligands can significantly improve the production efficiency of H2O2 of nano-TiO2 under freezing and room temperature conditions, and the improvement efficiency under freezing conditions is much greater than that under room temperature conditions.

[0050] Example 3 This example is exactly the same as Example 2, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to -5, -10, -20, -40, and -60°C, respectively; 10 mL of the reaction solution of step 2 is measured and placed in 12 25 mL quartz test tubes, respectively; the tubes are covered with stoppers and sealed with sealing films; the tubes are placed in a low-temperature constant-temperature reaction bath; and a 250 W mercury lamp is used for illumination. This moment is defined as the reaction starting point, and the reaction time is 6 hours.

[0051] Comparative Example 3 This comparative example is exactly the same as Example 3, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to 25°C, 10 mL of the reaction solution in step 2 is measured and placed in 12 25 mL quartz test tubes, the tubes are covered with stoppers and sealed with sealing films, and the tubes are placed in a low-temperature constant-temperature reaction bath. At the same time, a 250 W mercury lamp is used for illumination. This moment is defined as the reaction starting point, and the reaction time is 6 hours.

[0052] The results of Example 3 and Comparative Example 3 are as follows Figure 3 As shown, in the isopropanol organic ligand solution, compared with room temperature conditions, nano-TiO2 has a higher photocatalytic H2O2 production efficiency under -20°C freezing conditions. Different freezing temperatures affect the aggregation of nano-TiO2 and O2 in intercrystalline water, thereby affecting the photocatalytic generation of H2O2.

[0053] Example 4 This embodiment is exactly the same as Example 2, except that: 10 mg of nano titanium dioxide sample (particle size is about 25 nm) is weighed and placed in a deionized water solution, 100 mL of the above solution is measured in a 250 mL beaker, 20 mL of isopropanol solution and 80 mL of deionized water are added, and the mixture is treated with 200 W ultrasound for 10 minutes to make it evenly dispersed, the pH is adjusted to 6, and a reaction solution is prepared, and the reaction concentrations of nano titanium dioxide (TiO2) are set to 0.005, 0.01, 0.02, and 0.05 g / L, respectively, and the concentration of the isopropanol organic ligand is 10% vol.

[0054] Comparative Example 4 This comparative example is exactly the same as Example 4, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to 25°C, 10 mL of the reaction solution of step 2 is measured and placed in 12 25 mL quartz test tubes, the tubes are covered with stoppers and sealed with sealing film, and the tubes are placed in a low-temperature constant-temperature reaction bath. At the same time, a 250 W mercury lamp is used for illumination. This moment is defined as the reaction starting point, and the reaction time is 6 hours.

[0055] The results of Example 4 and Comparative Example 4 are as follows Figure 4As shown in the graph, in the isopropanol organic ligand solution, the photocatalytic H2O2 production efficiency of nano-TiO2 under both freezing and room temperature conditions showed a trend of first increasing and then decreasing, and the efficiency under freezing conditions was significantly greater than that under room temperature. Specifically, when the concentration of nano-TiO2 was 0.01g / L, the photocatalytic production efficiency of H2O2 under freezing conditions was the highest.

[0056] Example 5 This example is exactly the same as Example 2, except that: 10 mg of nano zinc oxide sample (particle size is about 50 nm) is weighed and placed in 500 mL of deionized water solution, 100 mL of the above solution is measured and placed in a 250 mL beaker, 20 mL of isopropanol solution and 80 mL of deionized water are added, and the mixture is ultrasonically treated at 200 W for 10 minutes to make it evenly dispersed, and the pH is adjusted to 6 to obtain a reaction solution, wherein the concentration of nano zinc oxide (ZnO) is 0.01 g / L, and the concentration of the isopropanol organic ligand is 10% vol.

[0057] Comparative Example 5 This comparative example is exactly the same as Example 5, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to 25°C, 10 mL of the reaction solution in step 2 is measured and placed in 12 25 mL quartz test tubes, the tubes are covered with stoppers and sealed with sealing films, and the tubes are placed in a low-temperature constant-temperature reaction bath. At the same time, a 250 W mercury lamp is used for illumination. This moment is defined as the reaction starting point, and the reaction time is 6 hours.

[0058] The results of Example 5 and Comparative Example 5 are as follows Figure 5 As shown in the figure, compared with room temperature conditions, nano ZnO has a higher photocatalytic H2O2 production efficiency under freezing conditions. The H2O2 production efficiency under freezing conditions is 10.12mmol / g, while the H2O2 production efficiency under room temperature conditions is only 1.67mmol / g.

[0059] Example 6 This embodiment is exactly the same as embodiment 2, except that: 10 mg of nano copper oxide sample (particle size is about 40-60 nm) is weighed and placed in 500 mL of deionized water solution, 100 mL of the above solution is measured and placed in a 250 mL beaker, 20 mL of isopropanol solution and 80 mL of deionized water are added, and the mixture is evenly dispersed by ultrasonic treatment at 200 W for 10 minutes, and the pH is adjusted to 6 to obtain a reaction solution, wherein the concentration of nano copper oxide (CuO) is 0.01 g / L, and the concentration of the isopropanol organic ligand is 10% vol.

[0060] Comparative Example 6 This comparative example is exactly the same as Example 6, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to 25°C, 10 mL of the reaction solution of step 2 is measured and placed in 12 25 mL quartz test tubes, the tubes are covered with stoppers and sealed with sealing films, and the tubes are placed in a low-temperature constant-temperature reaction bath. At the same time, a 250 W mercury lamp is used for illumination. This moment is defined as the reaction starting point, and the reaction time is 6 hours.

[0061] The results of Example 6 and Comparative Example 6 are as follows Figure 5 As shown in the figure, compared with room temperature conditions, nano-CuO has a higher photocatalytic H2O2 production efficiency under freezing conditions. The H2O2 production efficiency under freezing conditions is 7.50mmol / g, while the H2O2 production efficiency under room temperature conditions is only 1.15mmol / g.

[0062] Example 7 This embodiment is exactly the same as embodiment 2, except that: 10 mg of nano copper oxide sample (particle size is about 40-60 nm) is weighed and placed in 500 mL of deionized water solution, 100 mL of the above solution is measured and placed in a 250 mL beaker, 20 mL of isopropanol solution and 80 mL of deionized water are added, and the mixture is evenly dispersed by ultrasonic treatment at 200 W for 10 minutes, and the pH is adjusted to 6 to obtain a reaction solution, wherein the concentration of nano copper oxide (CuO) is 0.01 g / L, and the concentration of the isopropanol organic ligand is 10% vol.

[0063] Comparative Example 7 This comparative example is exactly the same as Example 7, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to 25°C, 10 mL of the reaction solution of step 2 is measured and placed in 12 25 mL quartz test tubes, the tubes are covered with stoppers and sealed with sealing film, and the tubes are placed in a low-temperature constant-temperature reaction bath. At the same time, a 250 W mercury lamp is used for illumination. This moment is defined as the reaction starting point, and the reaction time is 6 hours.

[0064] The results of Example 7 and Comparative Example 7 are as follows Figure 5 As shown in the figure, compared with room temperature conditions, nano-MgO has a higher photocatalytic H2O2 production efficiency under freezing conditions. The H2O2 production efficiency under freezing conditions is 1.57mmol / g, while the H2O2 production efficiency under room temperature conditions is only 0.42mmol / g.

[0065] Example 8 This example is exactly the same as Example 2, except that: 10 mg of nano cobalt oxide sample (particle size is about 50 nm) is weighed and placed in 500 mL of deionized water solution, 100 mL of the above solution is measured and placed in a 250 mL beaker, 20 mL of isopropanol solution and 80 mL of deionized water are added, and the mixture is ultrasonically treated at 200 W for 10 minutes to make it evenly dispersed, and the pH is adjusted to 6 to obtain a reaction solution, wherein the concentration of nano cobalt oxide (Co3O4) is 0.01 g / L, and the concentration of the isopropanol organic ligand is 10% vol.

[0066] Comparative Example 8 This comparative example is exactly the same as Example 8, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to 25°C, 10 mL of the reaction solution of step 2 is measured and placed in 12 25 mL quartz test tubes, the tubes are covered with stoppers and sealed with sealing film, and the tubes are placed in a low-temperature constant-temperature reaction bath. At the same time, a 250 W mercury lamp is used for illumination. This moment is defined as the reaction starting point, and the reaction time is 6 hours.

[0067] The results of Example 8 and Comparative Example 8 are as follows Figure 5 As shown in the figure, compared with room temperature conditions, nano Co3O4 has a higher photocatalytic H2O2 production efficiency under freezing conditions. The H2O2 production efficiency under freezing conditions is 2.75mmol / g, while the H2O2 production efficiency under room temperature conditions is only 0.60mmol / g.

[0068] Example 9 This embodiment is exactly the same as Example 2, except that: 10 mg of nano cerium oxide sample (particle size is about 20-30 nm) is weighed and placed in 500 mL of deionized water solution, 100 mL of the above solution is measured in a 250 mL beaker, 20 mL of isopropanol solution and 80 mL of deionized water are added, and the mixture is evenly dispersed by ultrasonic treatment at 200 W for 10 minutes, and the pH is adjusted to 6 to obtain a reaction solution, wherein the concentration of nano cerium oxide (CeO2) is 0.01 g / L, and the concentration of the isopropanol organic ligand is 10% vol.

[0069] Comparative Example 9 This comparative example is exactly the same as Example 9, except that: the temperature of the low-temperature constant-temperature reaction bath is adjusted to 25°C, 10 mL of the reaction solution of step 2 is measured and placed in 12 25 mL quartz test tubes, the stoppers are covered and sealed with sealing film, and the tubes are placed in a low-temperature constant-temperature reaction bath. At the same time, a 250 W mercury lamp is used for illumination. This moment is defined as the reaction starting point, and the reaction time is 6 hours.

[0070] The results of Example 9 and Comparative Example 9 are as follows Figure 5As shown in the figure, compared with room temperature conditions, nano CeO2 has a higher photocatalytic H2O2 production efficiency under freezing conditions. The H2O2 production efficiency under freezing conditions is 1.83mmol / g, while the H2O2 production efficiency under room temperature conditions is only 0.50mmol / g.

[0071] It can be seen that the method for generating hydrogen peroxide achieves efficient generation of hydrogen peroxide by conventional photocatalysts at low concentrations. Specifically, the production efficiency of hydrogen peroxide is significantly improved through freezing conditions; the operation is simple, the price is low, and the process is green and environmentally friendly; it is safe, reliable, and has strong applicability.

[0072] In summary, the above technical solutions of the present invention are only preferred embodiments of the present invention, and do not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly used in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing hydrogen peroxide by ultra-low temperature photocatalysis, characterized in that: include: Step S1, adding a photocatalytic material to water or a solution, dispersing the material completely, and adjusting the pH to obtain a reaction solution; Step S2, adding O2 to the reaction solution until saturated, and turning on the light source to carry out a photocatalytic reaction; Step S3, after the reaction is completed, the concentration of H2O2 is detected by potassium iodide-ammonium molybdate spectrophotometry; The photocatalytic material is a semiconductor metal oxide; the temperature of the photocatalytic reaction is -5 to -60°C.

2. The method for preparing hydrogen peroxide by ultra-low temperature photocatalysis according to claim 1, characterized in that: The concentration of the photocatalytic material in the reaction solution is 0.005-0.05 g / L; the pH of the reaction solution is 4-8.

3. The method for preparing hydrogen peroxide by ultra-low temperature photocatalysis according to claim 1, characterized in that: The semiconductor metal oxide is at least one of TiO2, CuO, ZnO, MgO, Co3O4 and CeO2; and the particle size of the photocatalytic material is 20-60 nm.

4. The method for preparing hydrogen peroxide by ultra-low temperature photocatalysis according to claim 1, characterized in that: The solution is an inorganic salt solution and / or an organic ligand solution; when the solution is an organic ligand solution, its concentration is 5-20%.

5. The method for preparing hydrogen peroxide by ultra-low temperature photocatalysis according to claim 1, characterized in that: The flow rate of O2 introduction is 100-200 mL / min, and the time of introduction is 8-15 min.

6. The method for preparing hydrogen peroxide by ultra-low temperature photocatalysis according to claim 1, characterized in that: The process of the photocatalytic reaction is: under closed conditions, start the mercury lamp, maintain the system temperature at -20 to -60°C, and the reaction time is 5 to 10 hours.

7. The method for preparing hydrogen peroxide by ultra-low temperature photocatalysis according to claim 1, characterized in that: The power of the mercury lamp is 200-300W; and before detecting the concentration of H2O2, pre-treatment is required, including thawing and filtering.

8. The method for preparing hydrogen peroxide by ultra-low temperature photocatalysis according to claim 7, characterized in that: The thawing process is: heating the system after the photocatalytic reaction is completed in a water bath at 30-38° C. until the system is completely thawed.

9. The method for preparing hydrogen peroxide by ultra-low temperature photocatalysis according to claim 7, characterized in that: The filtration treatment process is: using a filter head with a diameter of less than or equal to 0.22 μm to filter the completely thawed system to obtain a test solution that does not contain catalyst particles.

10. The method for preparing hydrogen peroxide by ultra-low temperature photocatalysis according to claim 1, characterized in that: The ion reaction formula for detecting the concentration of hydrogen peroxide in the potassium iodide-ammonium molybdate spectrophotometry is: Formula 1: H2O2 + 3I - + 2H+ = I3 - + 2H2O。

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