Method for producing hydrogen by photocatalysis using waste crab shell and method for producing hydrogen by photocatalysis using chitin

Abstract

The application discloses a method for photocatalytic hydrogen production by using waste crab shell and a method for photocatalytic hydrogen production by using chitin, and belongs to the technical field of photocatalytic hydrogen production. The method comprises the following steps: (1) ball milling the crab shell powder or chitin powder to obtain a leaching object; (2) placing the leaching object in 10-50 times of water, stirring and leaching, collecting the filtrate through solid-liquid separation, and obtaining a depolymerization solution; (3) adding a TiO2 photocatalyst into the depolymerization solution to obtain a suspension, placing the suspension in a reaction system for vacuum treatment, and performing photocatalysis under the irradiation of a xenon lamp or an ultraviolet lamp for 1-6 hours to obtain a reaction gas. The method uses waste crab shell or chitin as raw material, obtains a depolymerization solution with high N-acetylglucosamine content through ball milling treatment, and then catalyzes hydrogen production through a TiO2 photocatalyst, and the method has the advantages of convenient operation, environmental protection, greenness, low cost and high hydrogen production efficiency.

Description

TECHNICAL FIELD

[0001] The application relates to a method for producing hydrogen by photocatalysis of waste crab shells and a method for producing hydrogen by photocatalysis of chitin, and belongs to the technical field of photocatalytic hydrogen production. BACKGROUND

[0002] In the seafood processing industry and daily life in coastal areas, a large amount of waste crab shells will be produced. These seemingly useless wastes actually contain valuable resources, the most eye-catching of which is the rich chitin. Scientific tests and analysis show that the content of chitin in waste crab shells is quite high, so waste crab shells have become one of the ideal raw materials for obtaining chitin.

[0003] As a new technology, photocatalytic biomass reforming has unique advantages in relieving environmental pressure and optimizing resource utilization. However, as a high polymer, chitin has a highly organized hydrogen bond network structure, which makes its chemical properties stable and its solubility in water extremely low. At present, it is difficult to directly apply chitin in waste crab shells to photocatalytic reactions. Therefore, it is urgent to develop an environmentally friendly and efficient method for photocatalytic hydrogen production from waste crab shells or chitin at low cost. SUMMARY

[0004] In order to solve the above problems, a method for producing hydrogen by photocatalysis of waste crab shells and a method for producing hydrogen by photocatalysis of chitin are provided. The method uses waste crab shells or chitin as raw materials, obtains a depolymerization solution with high N-acetylglucosamine content by processing, and then produces hydrogen by TiO2 photocatalyst catalysis. The method has the advantages of convenient operation, environmental protection, low cost and high hydrogen production efficiency.

[0005] According to one aspect of the application, a method for producing hydrogen by photocatalysis of waste crab shells is provided, comprising the following steps:

[0006] (1) crushing waste crab shells to obtain crab shell powder, and ball milling the crab shell powder to obtain a leachable substance;

[0007] (2) placing the leachable substance in 10-50 times water, stirring and leaching, and collecting the filtrate by solid-liquid separation to obtain a depolymerization solution;

[0008] (3) adding TiO2 photocatalyst to the depolymerization solution to obtain a suspension, the mass-volume ratio of the TiO2 photocatalyst to the depolymerization solution is 0.5-2, and the suspension is placed in a reaction system for vacuum treatment under the irradiation of an ultraviolet lamp or a xenon lamp for 1-6 hours to obtain a reaction gas.

[0009] The step (1) of the above preparation method crushes the crab shell, which lays a foundation for subsequent ball milling treatment and improves the ball milling effect; the ball milling of step (1) not only refines the crab shell powder, increases the specific surface area, and increases the contact area with water in the stirring leaching, thereby facilitating the dissolution of the effective components; but also effectively reduces the crystallinity of chitin in the crab shell, destroys the hydrogen bond network structure, and increases the solubility of chitin structural monomer N-acetylglucosamine (NAG) in water, so as to increase the content of N-acetylglucosamine in the depolymerization solution, and then improve the yield of formic acid, acetic acid, acetamide and hydrogen.

[0010] The stirring leaching step of step (2) is beneficial to the dissolution of N-acetylglucosamine in the leaching object, and increases the content of N-acetylglucosamine in the depolymerization solution, but the depolymerization solution also contains metal cations such as magnesium ions and calcium ions, which can inhibit the evolution of H2.

[0011] Step (3) photocatalyzes the depolymerization solution, which can efficiently catalyze the conversion of N-acetylglucosamine in the depolymerization solution to hydrogen under the above conditions, and produce value-added organic matters such as formic acid, acetic acid and acetamide, thereby improving the utilization rate of raw materials. The evolution rate of H2 in step (3) is as high as 89.7 μmol.g -1 .h -1 , which has extremely high application value.

[0012] Optionally, the stirring leaching liquid of step (2) is subjected to solid-liquid separation by a reverse osmosis membrane to retain the calcium ions and magnesium ions therein, which is beneficial to enhancing the photocatalytic hydrogen evolution performance.

[0013] Optionally, the temperature of the photocatalysis of step (3) is 5-25℃, and the power of the lamp is 100-300 W.

[0014] The temperature of the above photocatalysis is normal temperature catalysis, which is beneficial to the evolution of H2 and ensures economic benefits. If the temperature is lower than the range, the activity of H2 evolution is reduced, and if the temperature is higher than the range, the energy consumption is increased. The power of the lamp is beneficial to the catalytic reaction, if the power is lower than the range, the catalytic reaction cannot occur, and if the power is higher than the range, the stability of the catalyst is reduced and the energy consumption is increased.

[0015] Optionally, the lamp of step (3) is a xenon lamp, which has a light range covering ultraviolet-visible-infrared region, simulates natural sunlight, and can effectively excite the TiO2 photocatalyst.

[0016] Optionally, the particle size of the crab shell powder obtained by crushing in step (1) is less than 50 μm.

[0017] The particle size of the pulverized powder is conducive to subsequent ball milling. If the particle size is greater than the particle size, the uniformity of subsequent ball milling is poor, which leads to poor stirring leaching effect in step (2), thereby reducing the overall photocatalytic hydrogen production.

[0018] Optionally, in step (1), kaolin and grinding balls are used to ball mill the crab shell powder, the ball milling time is 1-12 h, and the ball milling speed is 120-480 rpm.

[0019] In the ball milling of the crab shell powder, not only grinding balls are used, but also kaolin is added for ball milling, which can improve the flowability and dispersibility of the material, reduce the caking and agglomeration phenomenon in the ball milling process, thereby improving the ball milling efficiency and shortening the ball milling time.

[0020] Specifically, the ball milling time can be 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, or any time therebetween, and is preferably 12 h; the ball milling speed can be 120 rpm, 240 rpm, 360 rpm, 480 rpm, or any speed therebetween, and is preferably 480 rpm.

[0021] Optionally, the weight ratio of kaolin to crab shell powder is (1-10):1, and the particle size of kaolin is 2-5 μm.

[0022] The weight of kaolin is greater than the weight of crab shell powder in the above ball milling, because kaolin can improve the flowability and dispersibility of the material, and under the above weight ratio, the caking and agglomeration phenomenon in the ball milling process can be reduced, thereby improving the ball milling efficiency and shortening the ball milling time. The particle size of kaolin can reduce the particle size and further reduce the crystallinity.

[0023] Specifically, the weight ratio of kaolin to crab shell powder can be 10:1, 5:1, 2:1, 1:1, or any ratio therebetween, and is preferably 2:1.

[0024] Optionally, the grinding balls include large-diameter grinding balls and small-diameter grinding balls, the particle size of the large-diameter grinding balls is 10-20 mm, and the particle size of the small-diameter grinding balls is 3-10 mm.

[0025] The grinding balls used in the ball milling are divided into two diameters, which can synergistically improve the ball milling efficiency.

[0026] Optionally, the number ratio of large-diameter grinding balls to small-diameter grinding balls is 1:(1-10), and the mass ratio of crab shell powder to grinding balls is 1:(100-300).

[0027] The number ratio of the large-diameter grinding balls and the small-diameter grinding balls can significantly shorten the ball milling time, improve the ball milling efficiency, and ensure uniform particle size distribution after ball milling.

[0028] Specifically, the number ratio of the large-diameter grinding balls and the small-diameter grinding balls can be 1:1, 1:2, 1:5, 1:10, or any ratio therebetween, and is preferably 1:5.

[0029] Optionally, the material of the grinding balls is selected from at least one of Al2O3, ZrO2, and ZrSiO4.

[0030] Optionally, the stirring speed in the step (2) is 500-900 rpm, the temperature is 15-25℃, and the time is 0.3-2 h.

[0031] The above settings in the step (2) can increase the content of N-acetylglucosamine in the depolymerization solution, and can also retain calcium ions and magnesium ions in the solution by using a reverse osmosis membrane, which is beneficial to enhancing the photocatalytic hydrogen evolution performance.

[0032] Optionally, the content of N-acetylglucosamine in the depolymerization solution in the step (2) is 1.5-6.8 g / L.

[0033] Optionally, the TiO2 photocatalyst is TiO2-001.

[0034] The catalyst refers to TiO2 with a {001} crystal plane, which has excellent hydroxyl radical (•OH) generation ability. The catalyst has a hydrogen evolution rate of 89.7 μmol.g -1 .h -1 in the hydrogen production by the above method, which is 58.9 times and 6.3 times that of TiO2-101 and TiO2-100, respectively. The high-exposure {001} crystal plane promotes the separation of photo-generated carriers, enhances the adsorption and activation of H2O, and accelerates the generation of •OH, thus showing excellent light reforming performance and further improving the hydrogen production efficiency.

[0035] According to another aspect of the present application, a method for photocatalytic hydrogen production from chitin is provided, which is characterized by comprising the following steps:

[0036] (1) ball milling chitin to obtain a leaching object;

[0037] (2) placing the leaching object in 10-50 times water, stirring and leaching, collecting the filtrate by solid-liquid separation, and obtaining a depolymerization solution;

[0038] (3) adding TiO2 photocatalyst into the depolymerization solution to obtain a suspension, the mass-volume ratio of the TiO2 photocatalyst to the depolymerization solution is 0.5-2, mg / mL, and the suspension is placed in a reaction system for vacuum treatment and photocatalysis under the irradiation of a xenon lamp or an ultraviolet lamp for 1-6 h to obtain a reaction gas.

[0039] The ball milling of step (1) in the above preparation method can effectively reduce the crystallinity of chitin, destroy the hydrogen bond network structure, increase the solubility of chitin structural monomer N-acetylglucosamine in water, and thus increase the content of N-acetylglucosamine in the depolymerization solution, thereby improving the yield of formic acid, acetic acid, acetamide and hydrogen.

[0040] The stirring leaching step of step (2) is conducive to the dissolution of N-acetylglucosamine in the leaching material, and increases the content of N-acetylglucosamine in the depolymerization solution.

[0041] Step (3) is photocatalysis of the depolymerization solution, which can efficiently catalyze the conversion of N-acetylglucosamine in the depolymerization solution into hydrogen under the above conditions, and produce value-added organic substances such as formic acid, acetic acid and acetamide, thereby improving the utilization rate of raw materials, and the hydrogen evolution rate of step (3) is as high as 262.8 μmol.g -1 .h -1 , which has extremely high application value.

[0042] Optionally, the stirring leaching solution of step (2) is subjected to solid-liquid separation by a reverse osmosis membrane to retain calcium ions and magnesium ions therein, which is conducive to enhancing the photocatalytic hydrogen evolution performance.

[0043] Optionally, the temperature of the photocatalysis of step (3) is 5-25℃, and the power of the lamp is 100-300 W.

[0044] The temperature of the above photocatalysis is normal temperature catalysis, which is conducive to H2 evolution and ensures economic benefits. If the temperature is lower than the range, the H2 evolution activity decreases, and if the temperature is higher than the range, the energy consumption increases and the economic benefits decrease. The power of the lamp is conducive to the catalytic reaction. If the power is lower than the range, the catalytic reaction cannot occur, and if the power is higher than the range, the stability of the catalyst decreases.

[0045] Optionally, the lamp of step (3) is a xenon lamp, and the light range thereof covers ultraviolet-visible-infrared region, simulates natural sunlight, and can effectively excite the TiO2 photocatalyst.

[0046] Optionally, kaolin and grinding balls are used for ball milling of the chitin powder in step (1), the ball milling time is 1-12 h, and the ball milling rotation speed is 120-480 rpm.

[0047] The chitin powder ball milling not only uses grinding balls, but also adds kaolin for ball milling, which can improve the fluidity and dispersibility of the material, reduce the caking and agglomeration phenomenon in the ball milling process, thereby improving the ball milling efficiency and shortening the ball milling time.

[0048] Specifically, the ball milling time can be 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h and any time therebetween, preferably 12h; the ball milling speed can be 120 rpm, 240 rpm, 360 rpm, 480 rpm and any speed therebetween, preferably 480 rpm.

[0049] Optionally, the weight ratio of kaolin to chitin powder is (1-10):1, and the particle size of kaolin is 2-5 μm.

[0050] The weight of kaolin in the above ball milling is greater than the weight of chitin powder, because kaolin can improve the fluidity and dispersibility of the material, and under the above weight ratio, the caking and agglomeration phenomenon in the ball milling process can be reduced, thereby improving the ball milling efficiency and shortening the ball milling time, and the particle size of kaolin can reduce the particle size and further reduce the crystallinity.

[0051] Specifically, the weight ratio of kaolin to chitin powder can be 10:1, 5:1, 2:1, 1:1 and any ratio therebetween, preferably 2:1.

[0052] Optionally, the grinding balls include large-diameter grinding balls and small-diameter grinding balls, the particle size of the large-diameter grinding balls is 10-20 mm, and the particle size of the small-diameter grinding balls is 3-10 mm.

[0053] The grinding balls used in the ball milling of the application are divided into two diameters, which can synergistically improve the ball milling efficiency.

[0054] Optionally, the number ratio of the large-diameter grinding balls to the small-diameter grinding balls is 1:(1-10).

[0055] The number ratio of the large-diameter grinding balls to the small-diameter grinding balls can significantly shorten the ball milling time, improve the ball milling efficiency, and ensure uniform particle size distribution after ball milling.

[0056] Specifically, the number ratio of the large-diameter grinding balls to the small-diameter grinding balls can be 1:1, 1:2, 1:5, 1:10 and any ratio therebetween, preferably 1:5.

[0057] Optionally, the material of the grinding balls is selected from at least one of Al2O3, ZrO2 and ZrSiO4.

[0058] Optionally, the stirring speed of step (2) is 500-900 rpm, the temperature is 15-25 ℃, and the time is 0.3-2 h.

[0059] Optionally, the content of N-acetylglucosamine in the depolymerization solution of step (2) is 3.2-18.9 g / L.

[0060] Optionally, the TiO2 photocatalyst is TiO2-001.

[0061] The catalyst refers to TiO2 with {001} crystal plane, which has excellent hydroxyl radical (•OH) generation ability. The H2 release rate in the above method for hydrogen production is as high as 262.8 μmol.g -1 .h -1 -1.h-1, which is 67.4 times and 5.7 times of TiO2-101 and TiO2-100, respectively. The high-exposed {001} crystal plane promotes the separation of photo-generated carriers, enhances the adsorption and activation of H2O, and accelerates the generation of •OH, thus showing excellent light reforming performance and further improving the hydrogen production efficiency.

[0062] The beneficial effects of the present application include but are not limited to:

[0063] 1. The method for photocatalytic hydrogen production from waste crab shells according to the present application, which processes waste crab shells to obtain a depolymerization solution, and uses a TiO2 photocatalyst to catalyze the depolymerization solution to convert chitin structural monomer N-acetylglucosamine in the depolymerization solution into formic acid, acetic acid, acetamide and hydrogen (H2), providing an innovative solution for biomass resource utilization and green hydrogen energy development.

[0064] 2. The method for photocatalytic hydrogen production from waste crab shells according to the present application, which recycles waste crab shells, not only produces hydrogen, but also obtains usable chemicals, promoting the recycling of waste resources and sustainable development.

[0065] 3. The method for photocatalytic hydrogen production from waste crab shells and the method for photocatalytic hydrogen production from chitin according to the present application, which ball-mills crab shell powder or chitin, can effectively reduce the crystallinity of chitin, destroy its hydrogen bond network structure, increase the solubility of chitin structural monomer N-acetylglucosamine in water, increase the content of N-acetylglucosamine in the depolymerization solution, and further improve the yield of photocatalytic products.

[0066] 4. The method for photocatalytic hydrogen production from waste crab shells and the method for photocatalytic hydrogen production from chitin according to the present application, which has the advantages of convenient operation, environmental protection, low cost, high efficiency of hydrogen production, and high utilization rate of raw materials, has great guiding significance in practical application, and has great commercial value.

[0067] 5. The application and the method for photocatalytic hydrogen production using chitin can catalyze the depolymerization solution of chitin with TiO2 photocatalyst to obtain hydrogen, which widens the application prospect of chitin, and also obtains additional chemicals such as formic acid, acetic acid and acetamide, and provides an innovative solution for the resource utilization of chitin and the development of green hydrogen energy. BRIEF DESCRIPTION OF DRAWINGS

[0068] The drawings described herein are intended to provide further understanding of the present application, and constitute a part of the present application. The illustrative embodiments of the present application and their description serve to explain the present application, and do not constitute an improper limitation of the present application. In the drawings:

[0069] Figure 1 The color comparison chart of the depolymerization solution of chitin obtained at different ball milling times according to Example 1 of the present application.

[0070] Figure 2 The hydrogen production activity comparison chart of the depolymerization solution of chitin obtained at different ball milling times according to Example 1 of the present application.

[0071] Figure 3 The hydrogen production activity comparison chart of the depolymerization solution of TiO2 photocatalyst with different crystal faces according to Example 2 of the present application.

[0072] Figure 4 The ESR chart of •OH of the TiO2 photocatalyst with different crystal faces according to Example 2 of the present application.

[0073] Figure 5 The appearance and hydrogen production activity comparison chart of the depolymerization solution of water and waste crab shell according to Example 3 of the present application.

[0074] Figure 6 The preparation flow chart of the photocatalytic hydrogen production using waste crab shell according to Examples 3 and 4 of the present application. DETAILED DESCRIPTION

[0075] The present application will be described in detail below in combination with examples, but the present application is not limited to these examples.

[0076] Unless otherwise specified, the raw materials in the examples and comparative examples of the present application are purchased through commercial channels.

[0077] Unless otherwise specified, the methods used in the examples and comparative examples of the present application are conventional methods in the prior art.

[0078] Example 1

[0079] The present example relates to a method for photocatalytic hydrogen production using chitin, which comprises the following steps:

[0080] (1) Mix 2.0g of chitin powder with 4.0g of kaolin with a particle size of 2μm evenly and place it in a 50 mL corundum ball mill jar. Then, add 4 Al2O3 grinding balls with a diameter of 15 mm and 20 Al2O3 grinding balls with a diameter of 10 mm to the corundum ball mill jar. Place the resulting mixture in a ball mill and mill at a speed of 480 rpm for a certain period of time to obtain the extract to be leached.

[0081] (2) Place the substance to be leached in 50 times its volume of water, stir at 600 rpm and 25°C for 1 h, separate the solid and liquid, collect the filtrate, and obtain the depolymerization solution;

[0082] (3) 50 mg of TiO2-001 photocatalyst was added to 100 mL of depolymerization solution to obtain a suspension. The suspension was then transferred to a test system equipped with a closed gas circulation system. Before the test, the reaction system was evacuated to completely remove dissolved air. A 300 W xenon lamp was then used as the test light source, and the reaction temperature was controlled at 15 °C by cooling circulating water. After 4 h of photocatalytic reaction, the reaction gas was obtained.

[0083] In this embodiment, the ball milling times were set to 0 h (no ball milling), 1 h, 3 h, 6 h, and 12 h, respectively named 1-0#, 1-1#, 1-3#, 1-6#, and 1-12#. The colors of the depolymerization solutions obtained at the different ball milling times were compared, and the test results are shown below. Figure 1 Meanwhile, hydrogen production activity was compared according to step (3), and the test results are shown in [see figure]. Figure 2 .

[0084] like Figure 1 As shown, the color of the depolymerization solution gradually changes from colorless to deep yellow as the ball milling time increases. This indicates that mechanical ball milling can reduce the crystallinity of chitin and increase its depolymerization degree and water solubility, and this process is enhanced with increasing ball milling time.

[0085] Figure 2 As shown, the H2 generation rate of the TiO2-001 photocatalyst in the unmilled depolymerization solution is only 74.4 μmol·g. -1 .h -1 This is due to the highly organized structure and low water solubility of chitin, making unprocessed chitin unsuitable for photocatalytic hydrogen production. With increasing ball milling time, the H2 generation rate gradually increased. The H2 generation rates of the TiO2-001 photocatalyst in the solution after 1 h, 3 h, and 6 h of ball milling were 102.2 μmol / g, respectively. -1 .h -1 145.7 μmol·g -1 .h -1and 255.7 μmol.g -1 .h -1 When the ball-milling time was prolonged to 12 h, the H2 generation rate tended to be balanced, reaching 262.8 μmol.g -1 .h -1 The results show that the ball-milling treatment of chitin can effectively realize the depolymerization of chitin and increase the concentration of monomer N-acetylglucosamine in water, thereby obtaining a higher photocatalytic hydrogen production rate to improve the utilization of raw materials.

[0086] Example 2

[0087] In this example, different crystal plane TiO2-101, TiO2-100, TiO2-001 photocatalysts were used for catalytic hydrogen production compared with the example of 12 h ball-milling time in Example 1, and the hydrogen production activity comparison chart is shown in Figure 3 According to Figure 3 , the H2 release rate shows obvious crystal plane-dependent activity. When TiO2-101 is used as a photocatalyst, the hydrogen generation rate is only 3.9 μmol.g -1 .h -1 The hydrogen generation rate of TiO2-100 is higher than that of TiO2-101, reaching 46.3 μmol.g -1 .h -1 When TiO2-001 is used as a photocatalyst, the hydrogen generation rate is as high as 262.8 μmol.g -1 .h -1 , which is 67.4 times and 5.7 times that of TiO2-101 and TiO2-100, respectively.

[0088] The ESR test of •OH on different crystal plane dominant TiO2 is as follows: 5 mg of photocatalytic material is uniformly dispersed in 1 mL of water, which contains 10 mM of 5, 5-dimethyl-1-pyrroline-N-oxide (DMPO) as a hydroxyl radical trapping agent. A 300 W xenon lamp is used as a test light source, and after 10 min of full light irradiation, the intensity of DMPO-•OH adduct is measured using an electron spin resonance spectrometer.

[0089] The ESR graph of •OH on different crystal plane dominant TiO2 is shown in Figure 4 The production capacity of •OH on TiO2-101, TiO2-100, and TiO2-001 is compared by ESR test. Figure 4In the present application, •OH can bind with spin trapping agent DMPO to produce characteristic signal peaks. Under the same test conditions, the characteristic signal peak intensity of TiO2-001 is higher, indicating that TiO2-001 has stronger •OH generation capacity compared with TiO2-101 and TiO2-100, and therefore TiO2-001 exhibits more excellent catalytic performance in photocatalytic chitin reforming.

[0090] Example 3

[0091] This example relates to a method for photocatalytic hydrogen production using waste crab shells, and the preparation flow chart is shown in Figure 6 , which comprises the following steps:

[0092] (1) The waste crab shells are crushed to obtain crab shell powder with a particle size of less than 50 μm. 2.0 g of crab shell powder is uniformly mixed with 2.0 g of kaolin with a particle size of 5 μm, and then placed in a 50 mL corundum ball mill tank. Subsequently, 2 Al2O3 grinding balls with a diameter of 20 mm and 20 Al2O3 grinding balls with a diameter of 10 mm are added to the corundum ball mill tank. The obtained mixture is placed in a ball mill, and ball milling is carried out for 12 h to obtain a leaching material;

[0093] (2) The leaching material is placed in 50 times water, stirred at a speed of 900 rpm and a temperature of 25 ℃ for 2 h, and the filtrate is collected by solid-liquid separation to obtain a depolymerization solution;

[0094] (3) 50 mg of TiO2-001 photocatalyst is added to 100 mL of the depolymerization solution to obtain a suspension. Subsequently, the suspension is transferred to a test system equipped with a closed gas circulation system, and the reaction system is vacuumized before testing to completely remove dissolved air. Then, a 300 W xenon lamp is used as a test light source, and the reaction temperature is controlled at 15 ℃ by cooling circulating water. After 4 h of photocatalytic reaction, a reaction gas is obtained.

[0095] The ball milling speed of this example is set to 120 rpm, 240 rpm, 360 rpm and 480 rpm, respectively, and is named as 3-1#, 3-2#, 3-3# and 3-4#.

[0096] The water and the ball milling time of 12 h and the speed of 480 rpm of Example 1 are used for hydrogen production performance comparison, and the test results are shown in Figure 5 , Figure 5 In the present application, •OH can bind with spin trapping agent DMPO to produce characteristic signal peaks. Under the same test conditions, the characteristic signal peak intensity of TiO2-001 is higher, indicating that TiO2-001 has stronger •OH generation capacity compared with TiO2-101 and TiO2-100, and therefore TiO2-001 exhibits more excellent catalytic performance in photocatalytic chitin reforming. Figure 5 In the present application, •OH can bind with spin trapping agent DMPO to produce characteristic signal peaks. Under the same test conditions, the characteristic signal peak intensity of TiO2-001 is higher, indicating that TiO2-001 has stronger •OH generation capacity compared with TiO2-101 and TiO2-100, and therefore TiO2-001 exhibits more excellent catalytic performance in photocatalytic chitin reforming. -1 .h -1and the hydrogen evolution rate in the depolymerization solution is as high as 89.7 μmol.g -1 .h -1 , which is 9.3 times of that of pure water. It is proved that the depolymerization solution obtained by the method has excellent hydrogen production effect and can be popularized and used in industry.

[0097] Example 4

[0098] This example relates to a method for photocatalytic hydrogen production by using waste crab shell, and the preparation flow chart is shown in Figure 6 , which comprises the following steps:

[0099] (1) The waste crab shell is crushed to obtain crab shell powder with a particle size of less than 50 μm, 2.0 g of the crab shell powder is uniformly mixed with 20.0 g of kaolin with a particle size of 2 μm, and then the mixture is placed in a 50 mL corundum ball mill tank. Then, 20 Al2O3 grinding balls with a diameter of 10 mm and 20 Al2O3 grinding balls with a diameter of 3 mm are added to the corundum ball mill tank. The obtained mixture is placed in a ball mill, the ball milling speed is 480 rpm, and the ball milling time is 12 h to obtain a leaching material;

[0100] (2) The leaching material is placed in 50 times of water, stirred and leached at a speed of 500 rpm and a temperature of 15℃, the filtrate is collected by solid-liquid separation to obtain a depolymerization solution;

[0101] (3) 50 mg of TiO2-001 photocatalyst is added to 100 mL of the depolymerization solution to obtain a suspension, and then the suspension is transferred to a test system equipped with a closed gas circulation system. The reaction system is vacuumized before testing to completely remove the dissolved air. Then, a 300 W xenon lamp is used as a test light source, and the reaction temperature is controlled at 15℃ by cooling circulating water. After 4 h of photocatalytic reaction, a reaction gas is obtained.

[0102] In this example, the leaching time of step (2) is set to 0.3 h, 0.6 h and 1.0 h, respectively, and is named as 4-1#, 4-2# and 4-3#.

[0103] Example 5

[0104] In this example, the photocatalytic temperature is 5℃ and 25℃, respectively, compared with the example of 3-4# in Example 3, and is named as 5-1# and 5-2#.

[0105] Example 6

[0106] In this example, the power of the photocatalytic lamp is 100 W, compared with the example of 3-4# in Example 3, and is named as 6#.

[0107] Example 7

[0108] This example is compared with the example of ball milling time of 12 h in Example 3, without adding kaolin in the ball milling, named as 7#.

[0109] Example 8

[0110] This example is compared with the example of ball milling time of 12 h in Example 3, only using Al2O3 grinding balls with a diameter of 10 mm for ball milling in the ball milling, named as 8#.

[0111] Comparative Example 1

[0112] This example is compared with the example of ball milling time of 12 h in Example 3, without performing the ball milling step of step (1), only performing step (2) on the crab shell powder of step (1), named as D1#.

[0113] Test Example

[0114] The reaction gas prepared by the above examples and comparative examples is tested to obtain the total hydrogen production, and the content of formic acid, acetic acid and acetamide in the depolymerization solution is tested to obtain the total formic acid production, the total acetic acid production and the total acetamide production, and the test results are shown in the following table.

[0115] Table 1

[0116]

[0117] According to the above test results, under the conditions of ball milling time of 12 h, ball milling speed of 480 rpm, depolymerization stirring time of 1 h, photocatalytic test temperature of 15 ℃, xenon lamp light power of 300 W, and adding kaolin and different size ratio of grinding balls in the ball milling process, the production of hydrogen, formic acid, acetic acid and acetamide is the highest.

[0118] Based on the comparison of the above Examples 3, 4-8, it is known that when the photocatalytic temperature, photocatalytic lamp power, whether kaolin is added in the ball milling and the diameter of corundum balls are adjusted, different hydrogen production effects will be shown, which is consistent for both the crab shell photocatalytic hydrogen production method and the chitin hydrogen production method, so the present application does not set a single comparison example for chitin.

[0119] The above is only an embodiment of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. The present application can have various changes and variations for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the technical thought and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for photocatalytic hydrogen production using waste crab shells, characterized in that, Includes the following steps: (1) The waste crab shells are crushed to obtain crab shell powder, and the crab shell powder is ball-milled to obtain the extract to be extracted; (2) Place the substance to be leached in 10-50 times its volume of water, stir to leach, separate the solid and liquid, collect the filtrate, and obtain a depolymerization solution with high N-acetylglucosamine content; (3) Add TiO2 photocatalyst to the depolymerization solution to obtain a suspension. The mass-volume ratio of TiO2 photocatalyst to depolymerization solution is 0.5-2, and the unit is mg / mL. Place the suspension in the reaction system and vacuum it. Photocatalyze it for 1-6 h under ultraviolet or xenon lamp irradiation. The lamp power is 100-300 W to obtain the reaction gas.

2. The method for photocatalytic hydrogen production using waste crab shells according to claim 1, characterized in that, Step (3) The photocatalytic temperature is 5-25℃; and / or The TiO2 photocatalyst is a TiO2 nanosheet that mainly exposes the {001} crystal plane, namely TiO2-001.

3. The method for photocatalytic hydrogen production using waste crab shells according to claim 1, characterized in that, The particle size of the crab shell powder obtained by crushing in step (1) is less than 50 μm; In step (1), the crab shell powder is ball-milled using kaolin and grinding balls for 1-12 h, at a speed of 120-480 rpm, with a weight ratio of kaolin to crab shell powder of (1-10):1, and the particle size of the kaolin is 2-5 μm.

4. The method for photocatalytic hydrogen production using waste crab shells according to claim 3, characterized in that, The grinding balls include large-diameter grinding balls and small-diameter grinding balls. The particle size of the large-diameter grinding balls is 10-20 mm, and the particle size of the small-diameter grinding balls is 3-10 mm.

5. The method for photocatalytic hydrogen production using waste crab shells according to claim 4, characterized in that, The ratio of the number of large-diameter grinding balls to small-diameter grinding balls is 1:(1-10).

6. The method for photocatalytic hydrogen production using waste crab shells according to claim 1, characterized in that, Step (2) The stirring speed for leaching is 500-900 rpm, the temperature is 15-25℃, and the time is 0.3-2 h; In step (2), the N-acetylglucosamine content in the depolymerization solution is 1.5-6.8 g / L.

7. A method for hydrogen production via photocatalysis using chitin, characterized in that, Includes the following steps: (1) Chitin was ball-milled to obtain the extract to be extracted; (2) Place the substance to be leached in 10-50 times its volume of water, stir to leach, separate the solid and liquid, collect the filtrate, and obtain a depolymerization solution; (3) Add TiO2 photocatalyst to the depolymerization solution to obtain a suspension. The mass-volume ratio of TiO2 photocatalyst to depolymerization solution is 0.5-2, and the unit is mg / mL. Place the suspension in the reaction system and vacuum it. Photocatalyze it under a xenon lamp or ultraviolet lamp for 1-6 hours. The power of the lamp is 100-300 W. The reaction gas is obtained.

8. The method for hydrogen production using chitin photocatalysis according to claim 7, characterized in that, Step (3) The photocatalytic temperature is 5-25 ℃; and / or The TiO2 photocatalyst is TiO2-001.

9. The method for hydrogen production using chitin photocatalysis according to claim 7, characterized in that, In step (1), kaolin and grinding balls are used to ball mill the chitin for 1-12 h, with a ball milling speed of 120-480 rpm. The weight ratio of kaolin to chitin is (1-10):1, and the particle size of kaolin is 2-5 μm.

10. The method for hydrogen production using chitin photocatalysis according to claim 7, characterized in that, Step (2) The stirring speed for leaching is 500-900 rpm, the temperature is 15-25 ℃, and the time is 0.3-2 h; In step (2), the content of N-acetylglucosamine in the depolymerization solution is 3.2-18.9 g / L.

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