Method for synergistically producing hydrogen by utilizing all-component hydrothermal gasification coupled photo-thermal of municipal sludge

Abstract

The invention discloses a method for synergistically producing hydrogen by utilizing all-component hydrothermal gasification coupled photo-thermal of municipal sludge, which comprises the following steps: firstly, gasifying the municipal sludge by a hydrothermal conversion method to produce hydrogen, and simultaneously obtaining liquid-phase and solid-phase byproducts; and secondly, extracting copper ions in the solid-phase by-product, preparing a Cu / TiO2 catalyst by taking TiO2 as a carrier, and applying the catalyst to a photo-thermal catalytic hydrogen production reaction process of the liquid-phase by-product. According to the method, energy and resource utilization of all components of the municipal sludge is achieved, clean energy mainly containing hydrogen is obtained, and a new thought is provided for clean and efficient conversion of the municipal sludge.

Description

Technical Field

[0001] The invention discloses a technical field related to environmental protection and new energy, and in particular to a method for producing hydrogen by coupling hydrothermal gasification of all components of municipal sludge with photothermal synergy. Background Art

[0002] Hydrothermal gasification of sludge to produce hydrogen has broad development prospects in terms of sludge reduction, harmlessness and resource utilization. However, hydrothermal treatment will produce aqueous by-products rich in organic matter, nitrogen, phosphorus, etc. The treatment and resource utilization of aqueous by-products are related to the promotion and application of hydrothermal technology. At present, there are relatively few studies on the utilization of aqueous by-products. Photothermal catalytic conversion of aqueous by-products through photocatalytic technology is an important way to achieve high-value utilization of such wastes, which has attracted widespread attention from scholars at home and abroad. By 2025, the hydrogen production of renewable energy is expected to reach 10×10 4 t, can reduce CO2 emissions by 100×10 4 t or more. Photocatalytic hydrogen production has become a key technology for green hydrogen production due to its low energy consumption and low carbon emissions. In addition, the solid residue after hydrothermal gasification of sludge also contains a large amount of Cu element, which can be used to make raw materials for loading catalysts for photocatalytic hydrogen production reactions of aqueous byproducts. In summary, the energy and resource utilization of organic matter and inorganic components in sludge can be achieved through thermochemical conversion coupled with photothermal catalytic conversion, thereby improving the efficiency of sludge energy utilization.

[0003] Therefore, it is very meaningful to use hydrogen as the main clean energy, efficiently and cleanly utilize municipal sludge, and realize the energy and resource utilization of organic and inorganic components of municipal sludge. Summary of the invention

[0004] In view of this, the present invention provides a method for synergistic hydrogen production by coupling hydrothermal gasification of all components of municipal sludge with photothermal energy, which improves the energy utilization efficiency of municipal sludge and the overall hydrogen production yield by converting organic components in the sludge into energy and inorganic components into resources.

[0005] The present invention provides a method for producing hydrogen by coupling hydrothermal gasification of all components of municipal sludge with photothermal synergy, comprising the following steps:

[0006] Step 1: gasifying municipal sludge to produce hydrogen by hydrothermal conversion, and obtaining liquid by-products and solid by-products;

[0007] Step 2: extracting copper ions from the solid phase product and using TiO2 as a carrier to prepare a Cu / TiO2 catalyst;

[0008] Step 3: Using the Cu / TiO2 catalyst to perform photothermal catalytic conversion on the liquid by-product to produce hydrogen.

[0009] Preferably, the step 1: gasifying municipal sludge to produce hydrogen by hydrothermal conversion comprises:

[0010] a: Mix municipal sludge and solvent and pour into a stainless steel high-pressure reactor;

[0011] b: Introduce N2 into the reactor to replace the air in the reactor, and seal the reactor;

[0012] c: Set the reaction temperature and agitator speed in the kettle to carry out hydrothermal reaction;

[0013] d: After the reaction is completed and the temperature drops to room temperature, the reactor is purged with N2 and the gas phase product is collected until it fills a 500 mL gas bag;

[0014] e: After pouring out the product, vacuum filter; the filtrate is fixed to 100 mL with deionized water, which is the liquid by-product; the filter residue is the solid by-product.

[0015] Preferably, the solvent is a mixture of ethanol and deionized water.

[0016] Preferably, the step 2: extracting copper ions from the solid phase product and preparing a Cu / TiO2 catalyst using TiO2 as a carrier comprises:

[0017] a: Dissolve the filter residue with dilute H2SO4 to obtain a solid-liquid mixture, wherein the concentration of dilute H2SO4 is 1-5 mol / L;

[0018] b: After the obtained solid-liquid mixture is solid-liquid separated, the filtrate is retained, 0.5 mol / L NaOH is added to the filtrate to adjust the pH to 6, and the Cu-rich mixture is obtained by suction filtration, and then dilute sulfuric acid is added to the Cu-rich mixture to dissolve it, and suction filtration is performed to obtain a filter residue and a filtrate respectively;

[0019] c: Add sufficient amount of 0.5 mol / L NaOH, TiO2 and 100 mL of 0.25 mol / L Na2SO3 solution to the residue obtained in b, shake and stir, and obtain a solid precipitate after centrifugation;

[0020] d: repeatedly add deionized water to the precipitate, wash the precipitate three times, centrifuge to remove excess Na2SO4, and dry the final solid phase in a vacuum drying oven;

[0021] e: Grind the dried solid block into powder and sieve;

[0022] f: Collect the powder into a sealed bag to obtain the Cu / TiO2 photocatalyst;

[0023] Preferably, the step 3: using the Cu / TiO2 catalyst to perform photothermal catalytic conversion on the liquid phase byproduct to produce hydrogen comprises:

[0024] a: The liquid by-product and methanol were added into the photothermal reactor in a volume ratio of 3:2, and 50 mg of Cu / TiO2 catalyst was added;

[0025] b: He is introduced into the reactor to replace the air in the reactor, and the initial pressure is 0.5 MPa;

[0026] c: Set the temperature in the kettle to 30-150℃, the agitator speed to 250r / min, and stay for 6 hours after reaching the target temperature;

[0027] d: After the reaction is completed and the temperature drops to room temperature, open the exhaust valve and purge the reactor with He until the 500mL air bag is filled.

[0028] Preferably, the light source wavelength of the photothermal reactor is 350-780nm, and the light intensity is 300W.

[0029] The present invention provides a method for producing hydrogen by coupling hydrothermal gasification of all components of municipal sludge with photothermal synergy. In the method, a Cu / TiO2 photocatalyst is first prepared by recycling solid by-products in the process of thermochemical conversion of municipal sludge. The catalyst exhibits good catalytic performance in photothermal catalysis.

[0030] By the method of the present invention, the amount of hydrogen produced by hydrothermal gasification of municipal sludge reaches 6.35 mmol, and the amount of hydrogen produced in the photothermal catalytic reaction of the liquid byproduct of hydrothermal gasification reaches 70.5 μmol; using municipal sludge as raw material, through the hydrothermal gasification-photothermal catalytic reaction process, the amount of hydrogen produced per unit mass of municipal sludge (water content 70%) reaches 6.24 mmol / g; the process effectively utilizes the solid and liquid organic wastes of municipal sludge, and improves the efficiency of energy conversion and utilization.

[0031] The present invention improves the comprehensive utilization efficiency of organic and inorganic components of municipal sludge, and provides a new idea for realizing the high-value transformation of municipal sludge.

[0032] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0034] 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, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 XRD spectrum of Cu / TiO2 provided for the disclosed embodiment of the present invention;

[0036] Figure 2 A flow chart of a method for synergistic hydrogen production using municipal sludge hydrothermal gasification coupled with photothermal catalysis provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples of devices and methods consistent with some aspects of the present invention as detailed in the appended claims.

[0038] Traditional photocatalyst TiO2 can only capture and utilize ultraviolet and near-ultraviolet light. Through research, it is found that loading metal atoms in the gaps of TiO2 can effectively change the wavelength of absorbed light. The effect of Cu on TiO2 is more obvious than that of other metals. By anchoring Cu single atoms in the vacancies on the TiO2 surface, the system can be transformed into a photocatalyst by Cu. 2+ / Cu + The reversible reaction realizes the separation and transfer of photogenerated carriers.

[0039] Patent CN118359334A discloses a solar-assisted shale oil wastewater biochemical-microbial electrolysis hydrogen production complementary system. The system makes full use of solar energy, bioenergy, and microbial energy to purify shale oil wastewater to produce hydrogen, achieve multi-energy complementarity, reduce treatment costs, and save energy and protect the environment.

[0040] Patent CN117985906A discloses a hydrogen production, hydrogen storage and cogeneration system and process for a sewage treatment plant. The carbon dioxide absorption device is connected to the biogas steam reforming hydrogen production device to absorb the carbon dioxide produced by the biogas steam reforming hydrogen production device. The water source heat pump absorbs heat from the waste heat recovery pipeline and generates water vapor. The water vapor is used for anaerobic digestion in the anaerobic digestion device. This application solves the problem of the single waste heat application scenario and carbon emissions in biogas power generation in the existing system.

[0041] Patent CN118344905A discloses a solar thermal-driven waste plastic supercritical H2O-CO2 co-gasification hydrogen production system and method. Through the coupling design of a solar molten salt heat storage system and a supercritical H2O-CO2 co-gasification power generation system, the application of solar molten salt heat storage technology in the treatment of organic waste solid waste is realized.

[0042] The above technologies report methods for producing hydrogen from organic solid wastes such as plastics and wastewater, mainly water electrolysis, steam reforming and gasification. The present invention discloses a method for producing hydrogen by coupling photothermal synergy of all components of municipal sludge with hydrothermal gasification. Compared with the prior art, the present invention can improve the comprehensive conversion efficiency of thermochemical hydrogen production from municipal sludge organic solid waste.

[0043] The present invention firstly gasifies municipal sludge to produce hydrogen through a hydrothermal conversion method. The organic matter in the municipal sludge produces hydrogen through a series of reactions such as pyrolysis, hydrolysis, steam reforming and water-gas conversion under hydrothermal conditions, and simultaneously obtains liquid and solid by-products; secondly, the copper element in the solid by-product is extracted by an alkaline precipitation method, and a Cu / TiO2 catalyst is prepared by an impregnation method using TiO2 as a carrier; finally, the catalyst is used in the photothermal catalytic hydrogen production process of liquid by-products. This method realizes the energy and resource utilization of organic and inorganic components of municipal sludge, obtains clean energy mainly based on hydrogen, and provides a new idea for the efficient and clean utilization of municipal sludge.

[0044] Preferably, the process of gasifying municipal sludge to produce hydrogen by hydrothermal conversion to obtain liquid by-products and solid by-products comprises the following steps:

[0045] a: Take a certain mass of municipal sludge and a mixed solvent of ethanol and deionized water (volume ratio of ethanol / water is 1:1), mix them according to 1.0g (dry sludge) / 30mL, and pour them into a stainless steel high-pressure reactor;

[0046] b: Check the air tightness of the reactor, whether the circuits and pipelines are unobstructed. After confirming that the above conditions are good, introduce N2 into the reactor and keep it for 2 minutes to replace the air in the reactor, then seal the reactor and open the cooling water valve;

[0047] c: Open the computer program that controls the reactor, set the temperature in the reactor to 280-340°C, the speed of the agitator to 150r / min, and keep it at the reaction temperature for a certain period of time;

[0048] d: After the reaction is finished, the temperature in the reactor is lowered to room temperature with a fan, the exhaust valve is opened, the reactor is purged with N2, and the gas phase product is collected until the 500mL air bag is filled;

[0049] e: After pouring out the product, clean the inner wall of the reactor three times; the cleaning liquid and the product are vacuum filtered together; the filtrate is made up to 100 mL with deionized water, and the filter residue is used for the subsequent preparation of the catalyst.

[0050] Preferably, the copper ions in the solid phase byproduct are extracted and TiO2 is used as a carrier to prepare a Cu / TiO2 catalyst, comprising:

[0051] a: Dissolve the filter residue with dilute H2SO4 to obtain a solid-liquid mixture, wherein the concentration of dilute H2SO4 is 1-5 mol / L;

[0052] b: After the solid-liquid separation of the obtained solid-liquid mixture, the filtrate is retained, 0.5 mol / L NaOH is added to the filtrate to adjust the pH to 6, and the Cu-rich mixture is obtained by suction filtration, and then dilute sulfuric acid is added to the Cu-rich mixture.

[0053] dissolving it, and filtering to obtain filter residue and filtrate respectively;

[0054] c: Add sufficient amount of 0.5 mol / L NaOH, TiO2 and 100 mL of 0.25 mol / L Na2SO3 solution to the residue obtained in b, shake and stir, and obtain a solid precipitate after centrifugation;

[0055] d: repeatedly add deionized water to the precipitate, wash the precipitate three times, centrifuge to remove excess Na2SO4, and dry the final solid phase in a vacuum drying oven;

[0056] e: Grind the dried solid block into powder and sieve;

[0057] f: Collect the powder into a sealed bag to obtain the Cu / TiO2 photocatalyst;

[0058] Preferably, the Cu / TiO2 photocatalyst is applied to the sludge hydrothermal liquid phase photocatalytic reaction, comprising: adding the collected liquid phase and methanol in a volume ratio of 3:2 to a photothermal reactor, and adding 50 mg of Cu / TiO2 catalyst;

[0059] a: Check the air tightness of the device, whether the circuit and pipeline are unobstructed. After confirming that the above conditions are good, introduce He into the reactor and keep it for 2 minutes to replace the air in the reactor. The initial pressure is 0.5MPa;

[0060] b: Open the computer program that controls the reactor, set the temperature in the reactor to 30-150°C, the agitator speed to 250r / min, and stay at the target temperature for 6 hours;

[0061] c: After the reaction is completed, use a fan to lower the temperature in the autoclave to room temperature, open the exhaust valve, and purge the reactor with He until the 500mL air bag is filled.

[0062] The present invention is further explained below in conjunction with specific embodiments.

[0063] Example 1

[0064] Weigh 6g of sludge (water content 70%) and measure 30mL of ethanol and 30mL of deionized water respectively and add them to the high-temperature reactor. Purge the reactor with N2 for 2min to replace the air in the reactor. The reactor temperature is set to 280°C, the agitator speed is 150rpm, and the residence time is 180min. After the reaction is completed, cool the reactor to room temperature with a fan, open the exhaust valve, and purge the reactor with N2 until it is filled with a 500mL air bag. Open the reactor, pour out the product in the reactor, wash the inner wall of the reactor with deionized water three times, and vacuum filter the collected products to obtain liquid products and solid products respectively. After the solid product was dried in an oven at 105°C for 12h, diluted H2SO4 was added to dissolve it, and magnetic stirring was carried out at room temperature for 3h (250r / min), and then solid-liquid separation was performed, and 1.25g TiO2 was added to the obtained filter residue, ultrasonic oscillation was carried out at room temperature for 30min, and then sufficient NaOH (0.5mol / L) and 100mL Na2SO3 (0.25mol / L) solution were added, and oscillated and stirred at 80°C for 1h, centrifuged and deionized water was repeatedly added to the precipitate to remove excess Na2SO4, and the final precipitate product was placed in a vacuum drying oven and dried for 12h to finally obtain Cu / TiO2 catalyst. The collected liquid product and methanol (sacrificial agent) were added to the photothermal reactor in a volume ratio of 3:2 (a total of 100mL), and then 50mg Cu / TiO2 catalyst was added to carry out photothermal catalytic reaction. Check the air tightness of the device, whether the circuit and pipeline are unobstructed. After confirming that the above conditions are good, introduce He into the reactor and keep it for 2 minutes to replace the air in the reactor, and set the initial pressure to 0.5MPa. Turn on the computer program that controls the reactor, set different temperatures in the reactor, set the agitator speed to 250r / min, and react for 6 hours after rising to 40°C. After the reaction is completed, use a fan to reduce the temperature in the reactor to room temperature, open the exhaust valve, and purge the reactor with He until it is filled with a 500mL air bag. The H2 content in the gas product was detected by gas chromatography, of which the H2 production in the hydrothermal gasification process was 6.35mmol, and the H2 production in the photothermal catalytic process was 70.5μmol.

[0065] Embodiment 2:

[0066] Weigh 6g of sludge (water content 70%) and measure 30mL of ethanol and 30mL of deionized water respectively and add them to the high-temperature reactor. Purge the reactor with N2 for 2min to replace the air in the reactor. The reactor temperature is set to 300℃, the agitator speed is 150rpm, and the residence time is 180min. After the reaction is completed, cool the reactor to room temperature with a fan, open the exhaust valve, and purge the reactor with N2 until it is filled with a 500mL air bag. Open the reactor, pour out the product in the reactor, wash the inner wall of the reactor with deionized water three times, and vacuum filter the collected products to obtain liquid products and solid products respectively. After the solid product was dried in an oven at 105°C for 12h, diluted H2SO4 was added to dissolve it, and magnetic stirring was carried out at room temperature for 3h (250r / min), and then solid-liquid separation was performed, and 1.25g TiO2 was added to the obtained filter residue, ultrasonic oscillation was carried out at room temperature for 30min, and then sufficient NaOH (0.5mol / L) and 100mL Na2SO3 (0.25mol / L) solution were added, and oscillated and stirred at 80°C for 1h, centrifuged and deionized water was repeatedly added to the precipitate to remove excess Na2SO4, and the final precipitate product was placed in a vacuum drying oven and dried for 12h to finally obtain Cu / TiO2 catalyst. The collected liquid product and methanol (sacrificial agent) were added to the photothermal reactor in a volume ratio of 3:2 (a total of 100mL), and then 50mg Cu / TiO2 catalyst was added to carry out photothermal catalytic reaction. Check the air tightness of the device, whether the circuit and pipeline are unobstructed. After confirming that the above conditions are good, introduce He into the reactor and keep it for 2 minutes to replace the air in the reactor, and set the initial pressure to 0.5MPa. Turn on the computer program that controls the reactor, set different temperatures in the reactor, set the agitator speed to 250r / min, and react for 6 hours after rising to 40°C. After the reaction is completed, use a fan to reduce the temperature in the reactor to room temperature, open the exhaust valve, and purge the reactor with He until it is filled with a 500mL air bag. The H2 content in the gas product was detected by gas chromatography, of which the H2 production in the hydrothermal gasification process was 6.28mmol, and the H2 production in the photothermal catalytic process was 57.5μmol.

[0067] Embodiment 3:

[0068] Weigh 6g of sludge (water content 70%) and measure 30mL of ethanol and 30mL of deionized water respectively and add them to the high-temperature reactor. Purge the reactor with N2 for 2min to replace the air in the reactor. The reactor temperature is set to 320℃, the agitator speed is 150rpm, and the residence time is 180min. After the reaction is completed, cool the reactor to room temperature with a fan, open the exhaust valve, and purge the reactor with N2 until it is filled with a 500mL air bag. Open the reactor, pour out the product in the reactor, wash the inner wall of the reactor with deionized water three times, and vacuum filter the collected products to obtain liquid products and solid products respectively. After the solid product was dried in an oven at 105°C for 12h, diluted H2SO4 was added to dissolve it, and magnetic stirring was carried out at room temperature for 3h (250r / min), and then solid-liquid separation was performed, and 1.25g TiO2 was added to the obtained filter residue, ultrasonic oscillation was carried out at room temperature for 30min, and then sufficient NaOH (0.5mol / L) and 100mL Na2SO3 (0.25mol / L) solution were added, and oscillated and stirred at 80°C for 1h, centrifuged and deionized water was repeatedly added to the precipitate to remove excess Na2SO4, and the final precipitate product was placed in a vacuum drying oven and dried for 12h to finally obtain Cu / TiO2 catalyst. The collected liquid product and methanol (sacrificial agent) were added to the photothermal reactor in a volume ratio of 3:2 (a total of 100mL), and then 50mg Cu / TiO2 catalyst was added to carry out photothermal catalytic reaction. Check the air tightness of the device, whether the circuit and pipeline are unobstructed. After confirming that the above conditions are good, introduce He into the reactor and keep it for 2 minutes to replace the air in the reactor, and set the initial pressure to 0.5MPa. Open the computer program that controls the reactor, set different temperatures in the reactor, set the agitator speed to 250r / min, and react for 6 hours after rising to 40°C. After the reaction is completed, use a fan to reduce the temperature in the reactor to room temperature, open the exhaust valve, and purge the reactor with He until it is filled with a 500mL air bag. The H2 content in the gas product was detected by gas chromatography, of which the H2 production in the hydrothermal gasification process was 6.29mmol, and the H2 production in the photothermal catalytic process was 51.1μmol.

[0069] Embodiment 4:

[0070] Weigh 6g of sludge (water content 70%) and measure 30mL of ethanol and 30mL of deionized water respectively and add them to the high-temperature reactor. Purge the reactor with N2 for 2min to replace the air in the reactor. The reactor temperature is set to 340°C, the agitator speed is 150rpm, and the residence time is 180min. After the reaction is completed, cool the reactor to room temperature with a fan, open the exhaust valve, and purge the reactor with N2 until it is filled with a 500mL air bag. Open the reactor, pour out the product in the reactor, wash the inner wall of the reactor with deionized water three times, and vacuum filter the collected products to obtain liquid products and solid products respectively. After the solid product was dried in an oven at 105°C for 12h, diluted H2SO4 was added to dissolve it, and magnetic stirring was carried out at room temperature for 3h (250r / min), and then solid-liquid separation was performed, and 1.25g TiO2 was added to the obtained filter residue, ultrasonic oscillation was carried out at room temperature for 30min, and then sufficient NaOH (0.5mol / L) and 100mL Na2SO3 (0.25mol / L) solution were added, and oscillated and stirred at 80°C for 1h, centrifuged and deionized water was repeatedly added to the precipitate to remove excess Na2SO4, and the final precipitate product was placed in a vacuum drying oven and dried for 12h to finally obtain Cu / TiO2 catalyst. The collected liquid product and methanol (sacrificial agent) were added to the photothermal reactor in a volume ratio of 3:2 (a total of 100mL), and then 50mg Cu / TiO2 catalyst was added to carry out photothermal catalytic reaction. Check the air tightness of the device, whether the circuit and pipeline are unobstructed. After confirming that the above conditions are good, introduce He into the reactor and keep it for 2 minutes to replace the air in the reactor, and set the initial pressure to 0.5MPa. Turn on the computer program that controls the reactor, set different temperatures in the reactor, set the agitator speed to 250r / min, and react for 6 hours after rising to 40°C. After the reaction is completed, use a fan to reduce the temperature in the reactor to room temperature, open the exhaust valve, and purge the reactor with He until it is filled with a 500mL air bag. The H2 content in the gas product was detected by gas chromatography, of which the H2 production in the hydrothermal gasification process was 5.77mmol, and the H2 production in the photothermal catalytic process was 70.5μmol.

[0071] In summary, it can be seen that the hydrogen production of sludge hydrothermal gasification reaction is relatively high; secondly, the supported Cu / TiO2 catalyst prepared using the solid phase product of the hydrothermal gasification process also shows a good catalytic effect on the photothermal catalytic hydrogen production of wastewater.

[0072] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

[0073] It should be understood that the present invention is not limited to what has been described above and that various modifications and changes may be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for producing hydrogen by coupling hydrothermal gasification of all components of municipal sludge with photothermal synergy, characterized in that: The steps include: Step 1: gasifying municipal sludge to produce hydrogen by hydrothermal conversion, and obtaining liquid by-products and solid by-products; Step 2: extracting copper ions from the solid phase product and using TiO2 as a carrier to prepare a Cu / TiO2 catalyst; Step 3: Using the Cu / TiO2 catalyst to perform photothermal catalytic conversion on the liquid by-product to produce hydrogen.

2. According to claim 1, a method for producing hydrogen by coupling hydrothermal gasification of all components of municipal sludge with photothermal synergy is characterized in that: The step 1: gasifying municipal sludge to produce hydrogen by hydrothermal conversion method, comprising: a: Mix municipal sludge and solvent and pour into a stainless steel high-pressure reactor; b: Introduce N2 into the reactor to replace the air in the reactor, and seal the reactor; c: Set the reaction temperature and agitator speed in the kettle to carry out hydrothermal reaction; d: After the reaction is completed and the temperature drops to room temperature, the reactor is purged with N2 and the gas phase product is collected until it fills a 500 mL gas bag; e: After pouring out the product, vacuum filter; the filtrate is fixed to 100 mL with deionized water, which is the liquid by-product; the filter residue is the solid by-product.

3. The method for producing hydrogen by coupling hydrothermal gasification of all components of municipal sludge with photothermal synergy according to claim 2, characterized in that: The solvent is a mixture of ethanol and deionized water.

4. The method for producing hydrogen by coupling hydrothermal gasification of all components of municipal sludge with photothermal synergy according to claim 1, characterized in that: The step 2: extracting copper ions from the solid phase product and using TiO2 as a carrier to prepare a Cu / TiO2 catalyst comprises: a: Dissolve the filter residue with dilute H2SO4 to obtain a solid-liquid mixture, wherein the concentration of dilute H2SO4 is 1-5 mol / L; b: After the obtained solid-liquid mixture is solid-liquid separated, the filtrate is retained, 0.5 mol / L NaOH is added to the filtrate to adjust the pH to 6, and the Cu-rich mixture is obtained by suction filtration, and then dilute sulfuric acid is added to the Cu-rich mixture to dissolve it, and suction filtration is performed to obtain a filter residue and a filtrate respectively; c: Add sufficient amount of 0.5 mol / L NaOH, TiO2 and 100 mL of 0.25 mol / L Na2SO3 solution to the residue obtained in b, shake and stir, and obtain a solid precipitate after centrifugation; d: repeatedly add deionized water to the precipitate, wash the precipitate three times, centrifuge to remove excess Na2SO4, and dry the final solid phase in a vacuum drying oven; e: Grind the dried solid block into powder and sieve; f: Collect the powder into a sealed bag to obtain the Cu / TiO2 photocatalyst.

5. The method for producing hydrogen by coupling hydrothermal gasification of all components of municipal sludge with photothermal synergy according to claim 1, characterized in that: The step 3: using the Cu / TiO2 catalyst to perform photothermal catalytic conversion on the liquid phase byproduct to produce hydrogen, comprises: a: The liquid by-product and methanol were added into the photothermal reactor in a volume ratio of 3:2, and 50 mg of Cu / TiO2 catalyst was added; b: He is introduced into the reactor to replace the air in the reactor, and the initial pressure is 0.5 MPa; c: Set the temperature in the kettle to 30-150℃, the agitator speed to 250r / min, and stay for 6 hours after reaching the target temperature; d: After the reaction is completed and the temperature drops to room temperature, open the exhaust valve and purge the reactor with He until the 500mL air bag is filled.

6. The method for producing hydrogen by coupling hydrothermal gasification of all components of municipal sludge with photothermal synergy according to claim 1, characterized in that: The light source wavelength of the photothermal reactor is 350-780nm, and the light intensity is 300W.

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