A nano-oxygen carrier particle, a photo-reactor and a chemical looping system

Abstract

The application belongs to the technical field of chemical looping combustion, and discloses a nano oxygen carrier particle, a photo reactor and a chemical looping system. The nano oxygen carrier particle comprises a metal oxide, a noble metal / rare earth metal and a semiconductor material. The metal oxide has oxidizing property. The semiconductor material generates photo-generated holes and photo-generated electrons under light irradiation. The photo-generated holes have oxidizing property, and the photo-generated electrons have reducing property. The noble metal serves as a catalytic site and forms a Schottky barrier with the semiconductor. The Schottky barrier continuously captures the photo-generated electrons to improve the separation efficiency of the photo-generated electron-photo-generated hole pair. The application further discloses a photo reactor and a chemical reaction chain using the nano oxygen carrier. Through the application, the multifunctional nano oxygen carrier particle with lattice oxygen transfer, photocatalysis and thermal catalysis is synthesized, the operation temperature of the chemical looping system is below 200 DEG C, the low-temperature chemical looping combustion process is realized, and the sintering and agglomeration of the oxygen carrier material are avoided.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field related to chemical looping combustion, and more particularly relates to a nano oxygen carrier particle, a photo reactor and a chemical looping system. BACKGROUND

[0002] Chemical looping combustion (CLC) is a new energy utilization method, which can avoid the direct contact between fossil fuels and air by transferring lattice oxygen between the fuel reactor and the air reactor, thereby realizing the internal separation and enrichment of CO2, and avoiding the generation of pollutants such as nitrogen oxides. In addition, the traditional "one-step" combustion process is divided into two relatively independent oxidation-reduction reaction processes, which realizes the cascade utilization of energy and improves the energy conversion efficiency. Therefore, CLC technology is considered to be one of the most promising carbon capture technologies, with the advantages of high energy conversion efficiency, low CO2 capture cost and pollution control.

[0003] In order to maintain a high reaction rate and conversion rate, the traditional CLC process typically operates at a high temperature range of 800-1000℃, and the solid oxygen carrier material is easily sintered and deactivated, thereby seriously affecting the cycle stability and system economy. CLC operating in a medium-low temperature range has obtained due attention, which can avoid the sintering and agglomeration of oxygen carrier materials on the one hand, and can reduce the system energy loss on the other hand. However, lower temperatures usually lead to the deterioration of reaction kinetics, so it is necessary to study the reaction characteristics and activity enhancement strategies of low-temperature CLC oxygen carriers, and to develop oxygen carrier materials and chemical looping systems suitable for low-temperature operation. SUMMARY

[0004] In view of the above defects or improvement needs of the prior art, the present application provides a nano oxygen carrier particle, a photo reactor and a chemical looping system, which solves the problems of high reaction temperature and sintering and agglomeration of oxygen carrier materials in the chemical looping combustion process.

[0005] To achieve the above-mentioned purpose, according to the present application, a nano oxygen carrier particle is provided, which comprises nano oxygen, noble metal and semiconductor material, and the nano oxygen carrier particle comprises metal oxide, noble metal / rare earth metal and semiconductor material, wherein: the metal oxide has oxidizing property, the semiconductor material generates photo-generated holes and photo-generated electrons under light irradiation, the photo-generated holes have oxidizing property, the photo-generated electrons have reducing property, and the noble metal forms a Schottky barrier with the semiconductor as a catalytic site, which continuously traps photo-generated electrons to improve the separation efficiency of photo-generated electron-photo-generated hole pairs.

[0006] Further preferably, the particle size of the nano oxygen carrier particle is in the range of 1nm-100nm.

[0007] Further preferably, the metal oxide is one or a combination of CuO / Cu2O, Ag2O, NiO, FeO / Fe3O4 / Fe2O3, CoO / Co3O4 / Co2O3, MnO / Mn3O4 / Mn2O3, CuFe2O4, LaFeO3, LaCoO3, LaMnO3, and CaFeO3.

[0008] Further preferably, the noble / rare metal is one or a combination of Pt, Pd, Rh, Ir, Os, Ru, Re, Au, Ag, Nb, La, and Ce.

[0009] Further preferably, the semiconductor material is one or a combination of CuO / Cu2O, Ag2O, NiO, FeO / Fe3O4 / Fe2O3, CoO, MnO, In2O3, Bi2O3, SnO2, TiO2, ZnO, WO3, V2O5, SrTiO3, NiTiO3, BiMoO6, BiOBr, ZnS, CdS, and Ag3PO4.

[0010] According to yet another aspect of the present application, there is provided a photo-reactor for manufacturing the nano-oxygen carrier particles as described above, the photo-reactor comprising a light-transmitting plate and a substrate, wherein:

[0011] The light-transmitting plate and the substrate are arranged in parallel, and a reaction cavity is formed between the two, the reaction cavity being open at both ends as an inlet and an outlet for gas, fuel or air being introduced into the reaction cavity, and the upper surface of the substrate being uniformly coated with the nano-oxygen carrier particles to form a nano-oxygen carrier coating layer, the nano-oxygen carrier coating layer being used as a reaction interface for receiving light, and the nano-oxygen carrier particles being oxidized or reduced in reaction with the fuel or air in the reaction cavity when the light is transmitted through the light-transmitting plate and irradiated onto the nano-oxygen carrier coating layer.

[0012] Further preferably, the thickness of the nano-oxygen carrier coating layer is 10 μm to 200 μm.

[0013] Further preferably, the distance between the nano-oxygen carrier coating layer and the light-transmitting plate is 10 to 100 times the thickness of the nano-oxygen carrier coating layer.

[0014] Further preferably, a heat exchanger is arranged below the substrate for reducing the temperature in the reaction cavity.

[0015] According to yet another aspect of the present application, there is provided a chemical looping system formed by the photo-reactor as described above, the system comprising two photo-reactors connected in parallel, and the oxidation and reduction reactions being alternately performed between the two photo-reactors, and the reaction temperature in the photo-reactor being lower than 200 °C.

[0016] Overall, compared with the prior art, the above technical solutions conceived by the present application have the following beneficial effects:

[0017] 1. The nano oxygen carrier particles provided by the present application mainly include the following functions: chemical chain lattice oxygen transfer function, photocatalytic function under sunlight, and thermal catalytic function; the chemical chain lattice oxygen transfer function refers to that the nano oxygen carrier particles lose lattice oxygen (reduction process) by reacting with fuel, and restore lattice oxygen (oxidation process) by reacting with oxygen in the air, and the reduction process and the oxidation process can be alternately and cyclically performed; the photocatalytic function refers to that the nano oxygen carrier particles directly utilize sunlight to generate photo-generated carriers (holes and electrons) to participate in the oxidation-reduction reaction of the oxygen carrier, thereby reducing the required temperature and increasing the reaction rate; the thermal catalytic function refers to that high-activity catalytic sites (including single atoms, quantum dots, clusters, etc.) are modified on the surface of the nano oxygen carrier particles, so as to enhance the oxidation-reduction reaction activity of the oxygen carrier, further reduce the required temperature, and make the operation temperature of the chemical chain process lower than 200 DEG C.

[0018] 2. The photo reactor provided by the present application utilizes clean and renewable solar energy, establishes a complementary coupling low-carbon energy system of clean and renewable energy and fossil energy, and improves comprehensive benefits.

[0019] 3. The present application couples the photo / thermal catalytic principle with the chemical chain combustion reaction, improves the reaction activity of the oxygen carrier material through the photo / thermal catalytic technology, realizes the chemical chain combustion process at a lower temperature, and avoids the sintering and agglomeration of the oxygen carrier material. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a structural schematic diagram of a photo reactor constructed according to the preferred embodiment of the present application;

[0021] Figure 2 is a structural schematic diagram of a photocatalytic low-temperature chemical chain system constructed according to the preferred embodiment of the present application;

[0022] Figure 3 is a spherical aberration electron microscope photo of Pt / CuO nano oxygen carrier synthesized by flame spray pyrolysis according to the preferred embodiment of the present application;

[0023] Figure 4 is the H2-TPR test result of the Pt / CuO sample under light irradiation / non-light irradiation conditions according to the preferred embodiment of the present application;

[0024] Figure 5 is the CO-TPR test result of the 0.5Pt / CuO sample under light irradiation / non-light irradiation conditions according to the preferred embodiment of the present application;

[0025] Figure 6The results of 100 oxidation-reduction cycle tests of the 0.5Pt / CuO sample constructed according to the preferred embodiment of the present application for photocatalytic CO chemical looping combustion.

[0026] In all the drawings, the same reference numerals are used to represent the same elements or structures, wherein:

[0027] 1-gas / air inlet, 2-flue gas / lean oxygen air outlet, 3-heat exchange medium inlet, 4-heat exchange medium outlet, 5-light transmission plate, 6-reaction cavity, 7-nano oxygen carrier coating, 8-substrate, 9-heat exchanger, 10-gas / air switching valve, 11-flue gas / lean oxygen air switching valve, 12-flue gas outlet, 13-lean oxygen air outlet, 14-gas pipeline, 15-air pipeline. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application is further described in detail below with reference to the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0029] A multifunctional nano oxygen carrier particle has a particle size of 1-100 nm, can fully contact with reactants (fuel, oxygen), and improves the reaction effect. The multifunctional nano oxygen carrier particle generally comprises two or more components, wherein the component for realizing the chemical chain lattice oxygen transfer function is a metal oxide, which is one or a combination of CuO / Cu2O, Ag2O, NiO, FeO / Fe3O4 / Fe2O3, CoO / Co3O4 / Co2O3, MnO / Mn3O4 / Mn2O3, CuFe2O4, LaFeO3, LaCoO3, LaMnO3, CaFeO3, CuO / Cu2O, Ag2O, NiO, FeO / Fe3O4 / Fe2O3, CoO, MnO, In2O3, Bi2O3, SnO2, TiO2, ZnO, WO3, V2O5, SrTiO3, NiTiO3, BiMoO6, BiOBr, ZnS, CdS, Ag3PO4. The component for realizing the thermal catalysis function is a noble metal or a rare earth metal, which is one or a combination of Pt, Pd, Rh, Ir, Os, Ru, Re, Au, Ag, Nb, La, Ce.

[0030] Various oxygen carrier material preparation techniques are used to synthesize multifunctional nano oxygen carrier particles meeting the desired target, such as sol-gel method, coprecipitation method, impregnation method, mechanical mixing method, high-energy ball milling method, flame spray pyrolysis method, etc. Different synthesis methods need to be able to accurately and effectively regulate the size of nano oxygen carrier particles, the degree of component mixing, the single atom dispersion, etc.

[0031] Pt / CuO multifunctional nano oxygen carriers are synthesized by flame spray pyrolysis, in which CuO assumes the function of lattice oxygen transfer and photocatalysis, and Pt assumes the function of thermal catalysis. The molar ratio of Pt to Cu ranges from 0.025 mol% to 1 mol%. The preferred molar ratio of Pt to Cu is 0.5 mol%, and Pt is dispersed in the form of single atoms on the surface of CuO crystals, reducing the initial reaction temperature of H2 and CO chemical looping combustion to 142℃ and 89℃, respectively.

[0032] The light reactor includes a light-transmitting plate 5, a reaction cavity 6, a nano oxygen carrier coating 7, a substrate 8, a heat exchanger 9, a support frame, etc. The multifunctional nano oxygen carrier particles are uniformly coated on the upper surface of the substrate 8 to form a coating (thickness 10μm-200μm) for receiving solar irradiation and providing a reaction interface; the substrate 8 and the light-transmitting plate 5 are fixed and packaged by the support frame, so that the nano oxygen carrier coating 7 maintains a certain parallel spacing (10 times-100 times the coating thickness) with the light-transmitting plate 5, forming a gas film reaction cavity 6; the upper and lower edges of the reaction cavity 6 are perforated to connect the fuel gas / air inlet and the flue gas / lean oxygen air outlet 2. The heat exchanger 9 is closely connected to the lower surface of the substrate 8 to carry away the heat generated in the reaction cavity 6. In this embodiment, the light-transmitting plate 5 is made of light-transmitting quartz glass plate.

[0033] In order to realize the alternating cycle of the reduction process and the oxidation process of the multifunctional nano oxygen carrier particles at low temperature, the present application proposes a light-coupled chemical looping reaction system, which adopts a parallel plate type light reactor, as shown in Figure 1 The light-coupled chemical looping reaction system includes a first reaction chamber and a second reaction chamber, which are respectively configured with a fuel gas / air inlet and a flue gas / lean oxygen air outlet 2. The fuel gas / air switching valve 10 controls the alternating input of fuel gas and air into the two reaction chambers, and correspondingly, the flue gas / lean oxygen air switching valve 11 controls the discharge of the gas. The heat generated by the light reactor is utilized through the heat exchanger 9.

[0034] The first reaction chamber and the second reaction chamber of the parallel flat-plate photo-reactor are identical in structure and alternately realize reduction process and oxidation process. Before operation, nitrogen is introduced into the two reaction chambers through the fuel gas pipeline 14 and the air pipeline 15 to perform purging and remove the air in the reactor. Then a certain flow of fuel gas or air is introduced into the first reaction chamber and the second reaction chamber respectively through the fuel gas / air switching valve 10. Correspondingly, the flue gas / lean oxygen air switching valve 11 is adjusted to make the first reaction chamber communicate with the flue gas outlet 12 and the second reaction chamber communicate with the lean oxygen air outlet 13, and the first reaction chamber and the second reaction chamber are respectively in the reduction stage and the oxidation stage. After a period of time, the reaction is completed, and nitrogen is introduced into the two reaction chambers through the fuel gas pipeline 14 and the air pipeline 15 to perform purging. After the purging is completed, the two switching valves are adjusted to make the first reaction chamber communicate with the air pipeline 15 and the lean oxygen air outlet 13 and the second reaction chamber communicate with the fuel gas pipeline 14 and the flue gas outlet 12, and the first reaction chamber and the second reaction chamber are respectively in the oxidation stage and the reduction stage. The chemical chain process is realized by alternating circulation.

[0035] In the reduction stage, the semiconductor material in the multifunctional nano oxygen carrier coating 7 is excited to generate photo-generated holes and photo-generated electrons under sunlight, wherein the photo-generated holes have strong oxidizing property and promote the oxidation process of the fuel; the photo-generated electrons have strong reducing property and promote the reduction process of the oxygen carrier. The noble metal catalytic sites (including single atoms, quantum dots, clusters, etc.) on the surface of the nano oxygen carrier particles form a Schottky barrier with the semiconductor, and the Schottky barrier acts as an electron trap to continuously capture photo-generated electrons, thereby improving the separation efficiency of the electron-hole pairs. Under light irradiation, the noble metal has a localized surface plasmon resonance effect (LSPR) to generate hot electrons, thereby rapidly heating the surface of the nano oxygen carrier particles and improving the activity of the surface adsorbed species.

[0036] In the oxidation stage, the excitation and separation process of the photo-generated holes and the photo-generated electrons are similar to those in the reduction stage, and the difference lies in that the photo-generated holes promote the oxidation of the reduced oxygen carrier and the photo-generated electrons promote the reduction of oxygen.

[0037] The fuel can be a gaseous fuel, including a gas rich in hydrocarbons (H2, CO, CH4, C2H6, C2H4, C2H2, C3H8) and the like, a solid fuel or a liquid fuel, which can be gasified in advance before entering the reaction chamber. This process is not limited to chemical chain combustion, and when used for chemical chain partial oxidation, chemical chain reforming and the like, the fuel can also be partially oxidized, such as preparation of synthesis gas, ethane dehydrogenation to prepare ethylene / aromatics, etc.

[0038] The application will be further described below in conjunction with specific examples.

[0039] Example 1: Pt / CuO nano oxygen carrier photocatalytic H2 chemical chain combustion

[0040] The method for preparing the Pt / CuO nano-oxygen carrier particles comprises the following steps:

[0041] Copper nitrate trihydrate (Cu(NO3)2-3H2O) is used as the copper precursor and platinum acetylacetonate (Pt(C 10 H 14 O4Pt) is used as the platinum precursor. Both are dissolved in anhydrous ethanol (C2H6O) to prepare a precursor solution. The Cu(NO3)2 concentration of the precursor solution is 0.5 mol / L, and the amount of Pt(C 10 H 14 O4Pt) added can be adjusted, with the concentration ranging from 1.25×10 -4 mol / L to 5.0×10 -3 mol / L, i.e., the molar ratio of Pt to Cu is 0.025 mol% to 1 mol%.

[0042] The precursor solution is used to synthesize a series of Pt / CuO nano-oxygen carriers by a flame spray pyrolysis device. The precursor solution is injected into the spray system at a feeding flow rate of 5 mL / min and is atomized and ignited under the action of dispersion gas. The precursor is rapidly pyrolyzed in the high-temperature flame, and the organic metal components in the nanoparticles are combusted violently to form fine Pt-doped CuO particles. The synthesized powder is collected by a glass fiber filter device above the flame reactor. Figure 3 is a representative sample spherical aberration electron microscope photo of the Pt / CuO nano-oxygen carrier synthesized by flame spray pyrolysis, in which the molar ratio of Pt to Cu is 0.05 mol%, and Pt is dispersed on the surface of the CuO crystal in the form of single atoms.

[0043] The series of Pt / CuO nano-oxygen carriers synthesized above are used for photocatalytic low-temperature chemical chain tests. First, in order to test the low-temperature reduction performance of the Pt / CuO nano-oxygen carrier, a hydrogen temperature programmed experiment (H2-TPR) is performed. In the experiment, 40 mg of the sample is weighed and placed in a transparent quartz glass reaction chamber 6, and a xenon lamp is used as the light source to simulate sunlight. The sample is heated from room temperature to 300°C under an atmosphere of 10 vol.% H2 (Ar gas as the balancing gas) at a heating rate of 10°C / min, and the hydrogen signal is determined by a mass spectrometer detector.

[0044] As Figure 4As shown, the reaction activity of Pt / CuO samples under light conditions is obviously better than that without light. Among them, the 0.5Pt / CuO material (the molar ratio of Pt to Cu is 0.5 mol%) achieves the best performance, and the starting reduction temperature of the sample in the H2-TPR experiment under light conditions is as low as 142°C, which is 16°C lower than that in the dark condition, and is significantly lower than 152°C of the 0.2Pt / CuO sample and 161°C of the 0.1Pt / CuO sample. In addition, the reaction peak temperature under light conditions is greater than that without light, indicating that light improves the reaction activity of the oxygen carrier.

[0045] Example 2: Photocatalytic CO chemical looping combustion of 0.5Pt / CuO nano-oxygen carriers

[0046] The preferred 0.5Pt / CuO nano-oxygen carrier of Example 1 was used to conduct CO temperature programmed experiments (CO-TPR). In the experiment, 40 mg of the sample was weighed and placed in a transparent quartz glass reaction chamber, and a xenon lamp was used as the light source to simulate sunlight. The sample was heated from room temperature to 300°C under a 10 vol.% CO (Ar gas as the balance gas) atmosphere, and the heating rate was 5°C / min. The gas signal was determined by a mass spectrometer detector. As shown in Figure 5 As shown, the starting reaction temperature of the 0.5Pt / CuO oxygen carrier with CO under light conditions is as low as 89°C, which is 25°C lower than that without light.

[0047] In order to further test the stability of the photocatalytic CO chemical looping combustion of the 0.5Pt / CuO nano-oxygen carrier, the 0.5Pt / CuO nano-oxygen carrier was tested for 100 cycles of oxidation-reduction at 110°C using a photocatalytic low-temperature chemical looping combustion experimental device. Figure 6 is the 100-cycle test result of the photocatalytic CO chemical looping combustion of the 0.5Pt / CuO oxygen carrier material. In the first 20 chemical looping cycles, the oxygen loss rate and CO conversion rate of the oxygen carrier decreased, but after 20 cycles, the conversion rate and oxygen loss rate remained basically stable, indicating that the oxygen carrier has good stability in the photocatalytic low-temperature chemical looping combustion cycle.

[0048] Those skilled in the art will readily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. Use of nano-oxygen carrier particles in photocatalytic hydrogen or carbon monoxide chemical looping combustion, characterized in that, The application discloses a photo-reactor using nano-oxygen carrier particles, wherein the nano-oxygen carrier is a Pt / CuO nano-oxygen carrier synthesized by flame spray pyrolysis, and Pt is dispersed on the surface of CuO crystals in the form of single atoms; the photo-reactor comprises a light-transmitting plate (5) and a base plate (8), wherein: the light-transmitting plate (5) and the base plate (8) are arranged in parallel, and a reaction cavity (6) is arranged between the light-transmitting plate (5) and the base plate (8); the reaction cavity (6) is open at both ends to serve as a gas inlet and a gas outlet; fuel or air is introduced into the reaction cavity (6); the upper surface of the base plate (8) is uniformly coated with the nano-oxygen carrier particles to form a nano-oxygen carrier coating (7); the nano-oxygen carrier coating (7) is used as a reaction interface and is irradiated by light transmitted by the light-transmitting plate (5); and the nano-oxygen carrier particles are oxidized or reduced in the reaction cavity (6) when the light is irradiated on the nano-oxygen carrier coating (7). The thickness of the nano-oxygen carrier coating (7) is 10-200 microns.

2. Use according to claim 1, characterized in that, The distance between the nano-oxygen carrier coating (7) and the light-transmitting plate (5) is 10-100 times the thickness of the nano-oxygen carrier coating (7).

3. Use according to claim 1 or 2, characterized in that, A heat exchanger (9) is arranged below the base plate (8) to reduce the temperature in the reaction cavity (6).

4. The use according to claim 1, wherein The photo-reactor forms a chemical chain system, and the system comprises two photo-reactors connected in parallel; oxidation and reduction reactions are alternately performed between the two photo-reactors; and the reaction temperature in the photo-reactor is lower than 200 DEG C.

5. The use according to claim 1, wherein ​

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