Method for preparing hydrogen peroxide by photocatalysis at ultra-low temperature

Abstract

This invention discloses a method for preparing hydrogen peroxide using ultra-low temperature photocatalysis. The method includes: adding a photocatalytic material to water or a solution and dispersing it completely, adjusting the pH to obtain a reaction solution; adding O2 to the reaction solution until saturation, and turning on a light source to initiate the photocatalytic reaction; after the reaction, detecting the concentration of H2O2 using potassium iodide-ammonium molybdate spectrophotometry; the photocatalytic material is a semiconductor metal oxide; and the temperature of the photocatalytic reaction is -5 to -60°C. This method significantly increases the reactant concentration by concentrating the catalyst and oxygen in micron-sized intercrystalline water at ultra-low temperatures. Furthermore, the ultra-low temperature allows for rapid desorption of the catalytically generated hydrogen peroxide, inhibiting its decomposition reaction, thereby significantly improving the production of hydrogen peroxide per unit mass and per unit time.

Description

Technical Field

[0001] This invention relates to a method for preparing hydrogen peroxide, specifically a method for preparing hydrogen peroxide by ultra-low temperature photocatalysis, belonging to the field of photocatalytic reaction technology. Background Technology

[0002] Hydrogen peroxide (H2O2) is an environmentally friendly, high-energy, multifunctional chemical widely used in chemical synthesis, environmental remediation, bleaching, and disinfection, and has been listed as one of the world's 100 most important chemicals. Currently, over 95% of H2O2 is produced using the anthraquinone process (OA), which is the main method for industrial production. However, large-scale applications require high energy input for multi-step hydrogenation and oxidation reactions, making the process complex, including subsequent separation and concentration steps, costly, and generating large amounts of wastewater, waste gas, and waste residue. Furthermore, the hydrogenation catalytic method uses H2 and O2 as feedstocks to directly synthesize H2O2 under the action of a noble metal catalyst, providing an effective route for in-situ H2O2 production. However, noble metal catalysts are too expensive and difficult to reuse, and the mixing of H2 and O2 can easily lead to explosions, resulting in low safety and hindering industrial application.

[0003] Solar-driven O2 reduction to 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, suffer from poor light absorption, making it difficult for O2 to effectively utilize the photogenerated electrons, resulting in poor photocatalytic performance at room temperature. Current research on H2O2 photocatalysis mainly focuses on improving catalyst efficiency. This involves modifying existing photocatalysts like TiO2, CuO, and ZnO through methods such as complexing cations and anions, loading with nano-noble metal particles, graphene heterogeneity, and quantum dot modification. It also involves designing and developing new photocatalysts, such as g-C3N4, metal-organic frameworks, and organic polymers. However, these techniques are complex, and the designed photocatalysts exhibit uncertainties and instabilities, making it difficult to achieve efficient and stable H2O2 production. This inevitably increases the cost of H2O2 photocatalytic production. Furthermore, the efficiency improvement of modified catalysts is limited, and the reaction process easily pollutes the environment, which is inconsistent with current green energy production concepts.

[0004] Therefore, existing technologies continue to seek an efficient and safe method for preparing hydrogen peroxide to address or alleviate the current reliance on modified catalysts or the development of new catalysts to improve the production efficiency of H2O2, thereby enabling the industrial-scale photocatalytic production of hydrogen peroxide. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for preparing hydrogen peroxide using ultra-low temperature photocatalysis. This method significantly increases the reactant concentration by concentrating the catalyst and oxygen in micron-sized intercrystalline water at ultra-low temperatures. Furthermore, the ultra-low temperature allows for rapid desorption of the catalytically generated hydrogen peroxide, inhibiting its decomposition reaction, thereby significantly improving the production yield of hydrogen peroxide per unit mass of catalyst and per unit time.

[0006] To achieve the above-mentioned technical objectives, the present invention aims to provide a method for preparing hydrogen peroxide via ultra-low temperature photocatalysis, characterized in that it comprises:

[0007] Step S1: After adding the photocatalytic material to water or solution and dispersing it completely, adjust the pH to obtain a reaction solution;

[0008] Step S2: Add O2 to the reaction solution until saturated, and turn on the light source to carry out the photocatalytic reaction;

[0009] Step S3: After the reaction is complete, the concentration of H2O2 is determined by potassium iodide-ammonium molybdate spectrophotometry.

[0010] The photocatalytic material is a semiconductor metal oxide; the temperature of the photocatalytic reaction is -5 to -60°C.

[0011] The method provided by this invention mainly transforms most of the liquid 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, thus significantly increasing the reactant concentration and the effective contact area with the catalyst, and thus effectively improving the photocatalytic activity and reaction rate.

[0012] As a preferred embodiment, the concentration of the photocatalytic material in the reaction solution is 0.005~0.05 g / L.

[0013] As a preferred embodiment, the pH of the reaction solution is 4 to 8.

[0014] As a preferred embodiment, the semiconductor metal oxide is at least one of TiO2, CuO, ZnO, MgO, Co3O4, and CeO2.

[0015] It should be noted that since the main innovation of this invention lies in confining the solute oxygen space to the intercrystalline water on the surface of the micron-sized catalyst through freezing, the photocatalytic performance of any material with photoelectric effect is significantly improved. This improvement effect is universal, that is, it can be applied to any combination, reconstruction and modification of hydrogen peroxide photocatalysts.

[0016] As a preferred embodiment, the particle size of the photocatalytic material is 20~60nm.

[0017] As a preferred embodiment, the solution is an inorganic salt solution and / or an organic ligand solution.

[0018] As a preferred embodiment, when the solution is an organic ligand solution, its concentration is 5-20%.

[0019] As a preferred embodiment, the organic ligand is at least one of isopropanol, ethanol, methanol, and formic acid.

[0020] As a preferred embodiment, the O2 flow rate is 100~200mL / min, and the infusion time is 8~15min.

[0021] As a preferred embodiment, the photocatalytic reaction process is as follows: under sealed conditions, a mercury lamp is turned on, the system temperature is maintained at -20~-60℃, and the reaction time is 5~10h.

[0022] As a preferred embodiment, the mercury lamp has a power of 200~300W.

[0023] As a preferred method, pretreatment, including thawing and filtration, is required before detecting the concentration of H2O2.

[0024] As a preferred embodiment, the thawing process is as follows: the system after the photocatalytic reaction is completed is heated in a water bath at 30~38℃ until the system is completely thawed.

[0025] As a preferred embodiment, the filtration process is as follows: the completely thawed system is filtered using a filter head with a diameter of 0.22 μm or less to obtain a test solution free of catalyst particles.

[0026] As a preferred embodiment, the ionic reaction formula for detecting hydrogen peroxide concentration in the potassium iodide-ammonium molybdate spectrophotometric method is: Formula 1: H₂O₂ + 3I₂ - +2H+=I3 - +2H2O.

[0027] In this invention, the method for generating hydrogen peroxide employs freezing technology, which concentrates the catalyst and oxygen within micron-sized intercrystalline water. Compared to liquid solutions, this increases the solute concentration by several orders of magnitude, enhancing the interfacial electron transport capacity. Consequently, more O2 adsorbed on the catalyst surface can be reduced by photogenerated electrons to produce superoxide radicals (•O2). - Singlet oxygen () 1The photocatalytic generation of hydrogen peroxide (H₂O) and other reactive species (ROS) further generate hydrogen peroxide. Furthermore, under freezing conditions, the generated hydrogen peroxide can rapidly desorb from the catalyst surface and release into the solution, inhibiting its decomposition and increasing the accumulation of hydrogen peroxide under freezing conditions. Therefore, freezing conditions can promote the photocatalytic generation of hydrogen peroxide while inhibiting its decomposition, achieving efficient hydrogen peroxide generation from conventional photocatalysts at low concentrations.

[0028] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are as follows:

[0029] 1) The method provided by the present invention significantly increases the reactant concentration by concentrating the catalyst and oxygen in micron-sized intercrystalline water at ultra-low temperature. Furthermore, the hydrogen peroxide generated by the catalyst can be rapidly desorbed and its decomposition reaction can be inhibited at ultra-low temperature, thereby significantly increasing the production of hydrogen peroxide per unit mass and per unit time.

[0030] 2) The method provided by this invention does not have strict requirements for the catalyst. It significantly improves the photocatalytic performance of any material with photoelectric effect. This improvement effect is universal, that is, it can be applied to any combination, reconstruction and modification of hydrogen peroxide photocatalyst. Taking semiconductor metal oxide as an example, the production efficiency of hydrogen peroxide by this method is 4 to 17 times that of conventional liquid phase reaction system. In addition, this method also has the advantages of simple operation, low equipment cost and environmental friendliness.

[0031] 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. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some example drawings of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0033] Figure 1 These are transmission electron microscopy (TEM) images showing the enrichment trends of low-concentration nano-TiO2 under room temperature and frozen conditions in Example 1 and Comparative Example 1 of this invention; wherein, Figure 1 (a) is a TEM image of nano-TiO2 at room temperature. Figure 1 (b) is a TEM image of nano-TiO2 under freezing conditions;

[0034] in, Figure 1 (a) is a TEM image of nano-TiO2 at room temperature. Figure 1 (b) is a TEM image of nano-TiO2 under freezing conditions;

[0035] Figure 2 The graph shows the efficiency results of low-concentration nano-TiO2 photocatalytic production of hydrogen peroxide under ambient temperature and freezing conditions in Examples 1 and 2 and Comparative Examples 1 and 2 of the present invention.

[0036] Figure 3 The graph shows the efficiency results of low-concentration nano-TiO2 photocatalytic production of hydrogen peroxide under ambient temperature conditions and different freezing conditions in Example 3 and Comparative Example 3 of the present invention.

[0037] Figure 4 The graph shows the efficiency results of photocatalytic production of hydrogen peroxide by different low concentrations of nano-TiO2 under room temperature and different freezing conditions in Example 4 and Comparative Example 4 of the present invention.

[0038] Figure 5 The graph shows the efficiency results of low-concentration nano-photocatalyst semiconductors for producing hydrogen peroxide under normal temperature and freezing conditions in Examples 5-9 and Comparative Examples 5-9 of this invention. Detailed Implementation

[0039] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0041] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0042] Unless otherwise defined, all technical and scientific terms used in this invention are consistent with the prior art known to those skilled in the art and the description of this invention. This invention may also be implemented using any prior art methods, devices and materials similar to or equivalent to those described, used or made by means of methods, devices and materials in the embodiments of this invention.

[0043] To address or alleviate the current situation where improving the photocatalytic production of H2O2 relies solely on modified catalysts or the development of new catalysts, this invention provides a method for the efficient photocatalytic production of H2O2 without any modification measures, comprising the following steps:

[0044] Step S1: Add the photocatalyst material to the aqueous solution or organic ligand solution, sonicate it to disperse it evenly, adjust the pH, and obtain the reaction solution;

[0045] The reaction solution comprises two systems: an aqueous solution or an organic ligand solution. The organic ligand solution is one of isopropanol, ethanol, methanol, and formic acid, with a volume fraction of 5-30% vol. As a sacrificial agent, the organic ligand effectively scavenges holes, inhibits electron-hole binding, enhances the transport capacity of photogenerated electrons, and significantly increases the yield of hydrogen peroxide.

[0046] The photocatalyst material is one of the most widely used semiconductor photocatalyst materials, including but not limited to nano-TiO2, nano-CuO, nano-ZnO, nano-MgO, nano-Co3O4, and nano-CeO2. No modification is performed on these catalysts; the particle size is 20-30 nm, and the concentration is 0.005-0.05 g / L.

[0047] The ultrasonic treatment power is 200W, and the treatment time is 10 minutes, so that the catalyst is uniformly dispersed in the solution and the pH of the solution is adjusted to 4~8.

[0048] Step S2: O2 is continuously introduced into the above reaction solution until it reaches saturation.

[0049] The introduced O2 is 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 reaches a saturated state.

[0050] Step S3: Adjust the temperature of the low-temperature constant temperature reaction bath, place the reaction solution in a quartz test tube and put it into the reaction bath, and irradiate it with a light source at the same time.

[0051] The solution used in the low-temperature constant-temperature reaction bath is water and ethylene glycol (volume ratio 1:1) to control the reaction temperature. Specifically, the reaction temperatures are set at room temperature (25℃) and freezing conditions (-5 to -40℃). Of course, to ensure a constant reaction temperature, the ethylene glycol solution in the reaction bath must be replaced regularly to ensure temperature variations are within ±1℃.

[0052] 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, labeled and sealed, and immediately placed in a reaction bath while the light source is turned on for irradiation. This moment is defined as the reaction start point.

[0053] Step S4: After the reaction is complete, remove the quartz test tube and place it in a water bath for thawing. After the solution is completely thawed, the concentration of H2O2 is detected by potassium iodide-ammonium molybdate spectrophotometry.

[0054] The reaction time was set to 0-6 hours, and a sample was taken out every 1 hour for thawing and analysis; the temperature of the water bath was 35±1℃, and the reaction solution was allowed to thaw completely.

[0055] The detection method for hydrogen peroxide is the potassium iodide-ammonium molybdate spectrophotometric method. Specifically, the thawed solution is filtered through a 0.22 μm filter to obtain a test solution free of catalyst particles. The concentration of hydrogen peroxide in the test solution is detected using a colorimetric method of potassium iodide (KI) and ammonium molybdate ((NH4)2MoO4), and I3 is measured at 350 nm using a UV-Vis spectrophotometer. - The absorbance was used to determine the hydrogen peroxide content. H₂O₂ and I₂ - The reaction is as follows: H2O2 + 3I - +2H+=I3 - +2H2O.

[0056] Example 1

[0057] This embodiment provides a method for preparing hydrogen peroxide by ultra-low temperature photocatalysis, the process of which is as follows:

[0058] 1. Weigh 10 mg of nano titanium dioxide sample with a particle size of approximately 25 nm, place it in 1000 mL of deionized water, and sonicate it with 200 W for 10 minutes to disperse it evenly. Adjust the pH to 6 to obtain a reaction solution with a nano titanium dioxide (TiO2) concentration of 0.01 g / L.

[0059] 2. Measure 200 mL of the reaction solution from step 1 into a 500 mL beaker, and introduce O2 at a flow rate of 150 mL / min for 10 minutes to saturate the reaction solution with O2.

[0060] 3. Adjust the temperature of the low-temperature constant-temperature reaction bath, place the reaction solution in a quartz test tube and put it into the reaction bath, and irradiate it with a light source at the same time; adjust the temperature of the low-temperature constant-temperature reaction bath to -20℃, measure 10mL of the reaction solution from step 2 and put it into 12 25mL quartz test tubes, stopper them and seal them with sealing film, put them into the low-temperature constant-temperature reaction bath, and irradiate them with a 250W mercury lamp at the same time. Set this moment as the reaction start point, and the reaction time is 6 hours.

[0061] 4. After the reaction is complete, the quartz test tubes under both freezing and room temperature conditions are removed at the same time intervals. The frozen samples are then thawed in a water bath at 35±1℃. After the solution is completely thawed, the thawed / reacted samples are immediately filtered through a 0.22µm filter membrane to remove catalyst particles. The concentration of H₂O₂ is determined using the potassium iodide-ammonium molybdate spectrophotometric method. Specifically, 1mL of the filtrate is mixed with 2mL of 0.1M KI solution and 0.05mL of 0.01M (NH₄)₂MoO₄, and reacted in the dark for 30min. The I₃ concentration is then measured at 350nm using a UV-Vis spectrophotometer. - The absorbance was used to determine the hydrogen peroxide content.

[0062] Comparative Example 1

[0063] 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 from step 2 is measured and placed into 12 25 mL quartz test tubes, the tubes are capped and sealed with sealing film, and placed in the low-temperature constant temperature reaction bath. At the same time, a 250W mercury lamp is used for illumination. This moment is defined as the reaction start point, and the reaction time is 6 hours.

[0064] The results of Example 1 and Comparative Example 1 are as follows: Figure 2 As shown in (a), in aqueous solution, nano-TiO2 exhibits higher photocatalytic H2O2 production efficiency under frozen conditions compared to room temperature conditions. Specifically, the H2O2 production efficiency under frozen conditions is 2.68 mmol / g, while the H2O2 production efficiency under room temperature conditions is 0.24 mmol / g. In aqueous solution (without organic ligands), the H2O2 production efficiency of nano-TiO2 under frozen conditions is increased by 11.11 times.

[0065] Example 2

[0066] This embodiment is exactly the same as Example 1, except that: 1. Weigh 10mg of nano titanium dioxide sample with a particle size of about 25nm and place it in 500mL of deionized water. Measure 100mL of the above solution into a 250mL beaker, add 20mL of isopropanol solution and 80mL of deionized water, and sonicate at 200W for 10 minutes to disperse it evenly. Adjust the pH to 6 to obtain the reaction solution. The concentration of nano titanium dioxide (TiO2) is 0.01g / L and the concentration of isopropanol organic ligand is 10% vol.

[0067] Comparative Example 2

[0068] 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 from step 2 is measured and placed into 12 25 mL quartz test tubes, the tubes are capped and sealed with sealing film, and placed in the low-temperature constant temperature reaction bath. At the same time, a 250W mercury lamp is used for illumination. This moment is defined as the reaction start point, and the reaction time is 6 hours.

[0069] 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 exhibits higher photocatalytic H2O2 production efficiency under frozen conditions compared to room temperature conditions. The H2O2 production efficiency under frozen conditions is 16.8 mmol / g, while the H2O2 production efficiency under room temperature conditions is 1.06 mmol / g. In the isopropanol organic ligand solution, the H2O2 production efficiency of nano-TiO2 under frozen conditions is increased by approximately 15 times. Compared with Example 1, the organic ligand can significantly improve the H2O2 production efficiency of nano-TiO2 under both frozen and room temperature conditions, with the improvement under frozen conditions being much greater than that under room temperature conditions.

[0070] Example 3

[0071] This embodiment is exactly the same as Embodiment 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 from step 2 is measured and placed into 12 25 mL quartz test tubes, the tubes are capped and sealed with sealing film, and placed in the low-temperature constant temperature reaction bath. At the same time, a 250W mercury lamp is used for illumination. This moment is defined as the reaction start point, and the reaction time is 6 hours.

[0072] Comparative Example 3

[0073] 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 from step 2 is measured and placed into 12 25 mL quartz test tubes, the tubes are capped and sealed with sealing film, and placed in the low-temperature constant temperature reaction bath. At the same time, a 250W mercury lamp is used for illumination. This moment is defined as the reaction start point, and the reaction time is 6 hours.

[0074] The results of Example 3 and Comparative Example 3 are as follows Figure 3 As shown, in isopropanol organic ligand solution, nano-TiO2 exhibits higher photocatalytic H2O2 production efficiency under freezing conditions of -20℃ compared to room temperature conditions. Different freezing temperatures affect the aggregation of nano-TiO2 and O2 in the intercrystalline water, thereby affecting the photocatalytic generation of H2O2.

[0075] Example 4

[0076] This embodiment is exactly the same as Example 2, except that: 10 mg of nano titanium dioxide sample (particle size of about 25 nm) was weighed and placed in deionized water. 100 mL of the above solution was measured into a 250 mL beaker, 20 mL of isopropanol solution and 80 mL of deionized water were added, and the mixture was ultrasonically treated at 200 W for 10 minutes to disperse it evenly. The pH was adjusted to 6 to obtain the reaction solution. The reaction concentration of nano titanium dioxide (TiO2) was set to 0.005, 0.01, 0.02 and 0.05 g / L, respectively, and the concentration of isopropanol organic ligand was 10% vol.

[0077] Comparative Example 4

[0078] 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 from step 2 is measured and placed into 12 25 mL quartz test tubes, the tubes are capped and sealed with sealing film, and placed in the low-temperature constant temperature reaction bath. At the same time, a 250W mercury lamp is used for illumination. This moment is defined as the reaction start point, and the reaction time is 6 hours.

[0079] The results of Example 4 and Comparative Example 4 are as follows Figure 4 As shown, in the isopropanol organic ligand solution, the photocatalytic production efficiency of H2O2 by nano-TiO2 under both freezing and room temperature conditions exhibits a trend of first increasing and then decreasing, with the efficiency increase under freezing conditions being significantly greater than that under room temperature conditions. Specifically, the photocatalytic production efficiency of H2O2 is highest under freezing conditions when the concentration of nano-TiO2 is 0.01 g / L.

[0080] Example 5

[0081] This embodiment is exactly the same as Example 2, except that: 10 mg of nano zinc oxide sample (particle size of about 50 nm) was weighed and placed in 500 mL of deionized water. 100 mL of the above solution was measured into a 250 mL beaker, and 20 mL of isopropanol solution and 80 mL of deionized water were added. The mixture was ultrasonically treated at 200 W for 10 minutes to disperse it evenly. The pH was adjusted to 6 to obtain the reaction solution. The concentration of nano zinc oxide (ZnO) was 0.01 g / L, and the concentration of isopropanol organic ligand was 10% vol.

[0082] Comparative Example 5

[0083] 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 from step 2 is measured and placed into 12 25 mL quartz test tubes, the tubes are capped and sealed with sealing film, and placed in the low-temperature constant temperature reaction bath. At the same time, a 250W mercury lamp is used for illumination. This moment is defined as the reaction start point, and the reaction time is 6 hours.

[0084] The results of Example 5 and Comparative Example 5 are as follows: Figure 5 As shown, nano-ZnO exhibits higher photocatalytic H2O2 production efficiency under frozen conditions compared to room temperature conditions. Specifically, the H2O2 production efficiency under frozen conditions is 10.12 mmol / g, while the efficiency under room temperature conditions is only 1.67 mmol / g.

[0085] Example 6

[0086] This embodiment is exactly the same as Example 2, except that: 10 mg of nano copper oxide sample (particle size of about 40~60 nm) was weighed and placed in 500 mL of deionized water. 100 mL of the above solution was measured into a 250 mL beaker, 20 mL of isopropanol solution and 80 mL of deionized water were added, and the mixture was ultrasonically treated at 200 W for 10 minutes to disperse it evenly. The pH was adjusted to 6 to obtain the reaction solution. The concentration of nano copper oxide (CuO) was 0.01 g / L, and the concentration of isopropanol organic ligand was 10% vol.

[0087] Comparative Example 6

[0088] 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 from step 2 is measured and placed into 12 25 mL quartz test tubes, the tubes are capped and sealed with sealing film, and placed in the low-temperature constant temperature reaction bath. At the same time, a 250W mercury lamp is used for illumination. This moment is defined as the reaction start point, and the reaction time is 6 hours.

[0089] The results of Example 6 and Comparative Example 6 are as follows Figure 5As shown, nano-CuO exhibits higher photocatalytic H2O2 production efficiency under frozen conditions compared to room temperature conditions. Specifically, the H2O2 production efficiency under frozen conditions is 7.50 mmol / g, while the H2O2 production efficiency under room temperature conditions is only 1.15 mmol / g.

[0090] Example 7

[0091] This embodiment is exactly the same as Example 2, except that: 10 mg of nano copper oxide sample (particle size of about 40~60 nm) was weighed and placed in 500 mL of deionized water. 100 mL of the above solution was measured into a 250 mL beaker, 20 mL of isopropanol solution and 80 mL of deionized water were added, and the mixture was ultrasonically treated at 200 W for 10 minutes to disperse it evenly. The pH was adjusted to 6 to obtain the reaction solution. The concentration of nano copper oxide (CuO) was 0.01 g / L, and the concentration of isopropanol organic ligand was 10% vol.

[0092] Comparative Example 7

[0093] 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 from step 2 is measured and placed into 12 25 mL quartz test tubes, the tubes are capped and sealed with sealing film, and placed in the low-temperature constant temperature reaction bath. At the same time, a 250W mercury lamp is used for illumination. This moment is defined as the reaction start point, and the reaction time is 6 hours.

[0094] The results of Example 7 and Comparative Example 7 are as follows Figure 5 As shown, nano-MgO exhibits higher photocatalytic H2O2 production efficiency under frozen conditions compared to room temperature conditions. Specifically, the H2O2 production efficiency under frozen conditions is 1.57 mmol / g, while the H2O2 production efficiency under room temperature conditions is only 0.42 mmol / g.

[0095] Example 8

[0096] This embodiment is exactly the same as Example 2, except that: 10 mg of nano cobalt oxide sample (particle size of about 50 nm) was weighed and placed in 500 mL of deionized water. 100 mL of the above solution was measured into a 250 mL beaker, and 20 mL of isopropanol solution and 80 mL of deionized water were added. The mixture was ultrasonically treated at 200 W for 10 minutes to disperse it evenly. The pH was adjusted to 6 to obtain the reaction solution. The concentration of nano cobalt oxide (Co3O4) was 0.01 g / L, and the concentration of isopropanol organic ligand was 10% vol.

[0097] Comparative Example 8

[0098] 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 from step 2 is measured and placed into 12 25 mL quartz test tubes, the tubes are capped and sealed with sealing film, and placed in the low-temperature constant temperature reaction bath. At the same time, a 250W mercury lamp is used for illumination. This moment is defined as the reaction start point, and the reaction time is 6 hours.

[0099] The results of Example 8 and Comparative Example 8 are as follows Figure 5 As shown, nano-Co3O4 exhibits higher photocatalytic H2O2 production efficiency under frozen conditions compared to room temperature conditions. Specifically, the H2O2 production efficiency under frozen conditions is 2.75 mmol / g, while the H2O2 production efficiency under room temperature conditions is only 0.60 mmol / g.

[0100] Example 9

[0101] This embodiment is exactly the same as Example 2, except that: 10 mg of nano-cerium oxide sample (particle size of about 20~30 nm) was weighed and placed in 500 mL of deionized water. 100 mL of the above solution was measured into a 250 mL beaker, and 20 mL of isopropanol solution and 80 mL of deionized water were added. The mixture was ultrasonically treated at 200 W for 10 minutes to disperse it evenly. The pH was adjusted to 6 to obtain the reaction solution. The concentration of nano-cerium oxide (CeO2) was 0.01 g / L, and the concentration of isopropanol organic ligand was 10% vol.

[0102] Comparative Example 9

[0103] 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 from step 2 is measured and placed into 12 25 mL quartz test tubes, the tubes are capped and sealed with sealing film, and placed in the low-temperature constant temperature reaction bath. At the same time, a 250W mercury lamp is used for illumination. This moment is defined as the reaction start point, and the reaction time is 6 hours.

[0104] The results of Example 9 and Comparative Example 9 are as follows Figure 5 As shown, nano-CeO2 exhibits higher photocatalytic H2O2 production efficiency under frozen conditions compared to room temperature conditions. Specifically, the H2O2 production efficiency under frozen conditions is 1.83 mmol / g, while the H2O2 production efficiency under room temperature conditions is only 0.50 mmol / g.

[0105] Therefore, the described method for generating hydrogen peroxide achieves highly efficient generation of hydrogen peroxide using traditional photocatalysts at low concentrations. Specifically, the production efficiency of hydrogen peroxide is significantly improved by using freezing conditions; the method is simple to operate, inexpensive, environmentally friendly, safe, reliable, and widely applicable.

[0106] In summary, the above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications 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: After adding the photocatalytic material to water or solution and dispersing it completely, adjust the pH to obtain a reaction solution; Step S2: Add O2 to the reaction solution until saturated, and turn on the light source to carry out the photocatalytic reaction; Step S3: After the reaction is complete, the concentration of H2O2 is determined 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. The solution is an organic ligand solution; the organic ligand solution is one of isopropanol, ethanol, methanol and formic acid, and its concentration is 5-20%.

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; the particle size of the photocatalytic material is 20~60nm.

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

5. The method for preparing hydrogen peroxide by ultra-low temperature photocatalysis according to claim 1, characterized in that: The photocatalytic reaction process is as follows: under sealed conditions, a mercury lamp is turned on, the system temperature is maintained at -20~-60℃, and the reaction time is 5~10h.

6. The method for preparing hydrogen peroxide by ultra-low temperature photocatalysis according to claim 5, characterized in that: The mercury lamp has a power of 200~300W; the H2O2 concentration needs to be detected by pretreatment, including thawing and filtration.

7. The method for preparing hydrogen peroxide by ultra-low temperature photocatalysis according to claim 6, characterized in that: The thawing process is as follows: the system after the photocatalytic reaction is completed is heated in a water bath at 30~38℃ until the system is completely thawed.

8. The method for preparing hydrogen peroxide by ultra-low temperature photocatalysis according to claim 6, characterized in that: The filtration process is as follows: the completely thawed system is filtered using a filter head with a diameter of 0.22 μm or less to obtain a test solution free of catalyst particles.

9. The method for preparing hydrogen peroxide by ultra-low temperature photocatalysis according to claim 1, characterized in that: The ionic reaction formula for detecting hydrogen peroxide concentration in the potassium iodide-ammonium molybdate spectrophotometric method is as follows: Equation 1: H2O2 + 3I - + 2H+ = I3 - + 2H2O.

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