An indium oxide catalyst for carbon dioxide conversion, its preparation method and application

Abstract

The present invention belongs to the technical field of catalysts and their applications, and relates to an indium oxide catalyst for carbon dioxide conversion, its preparation method and application. The preparation method includes the following steps: S1. Preparation of indium oxide precursor: Using indium nitrate as a raw material, an indium oxide precursor is prepared by a precipitation method; S2. Preparation of catalyst: The obtained indium oxide precursor is placed in a dielectric barrier discharge system and treated at a power of 50W - 60W for 15min - 20min to obtain an indium oxide catalyst. The present invention prepares an indium oxide catalyst through dielectric barrier discharge technology, which has high catalytic activity and can improve the conversion rate of carbon dioxide in the conversion of carbon dioxide to carbon monoxide.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts and their applications, and relates to an indium oxide catalyst for carbon dioxide conversion, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of human society, people's dependence on fossil energy has become increasingly urgent. However, a large amount of greenhouse gases are generated during the consumption of fossil energy, which has an impact on the environment. In particular, carbon dioxide greenhouse gas has led to a series of environmental problems such as global warming and sea-level rise. Therefore, carbon dioxide emission reduction is a current research hotspot.

[0003] At present, the methods for carbon dioxide emission reduction are mainly divided into two categories: namely, carbon capture and storage (CCS), and carbon capture and utilization (CCU). Compared with CCS, CCU can convert carbon dioxide into value-added chemicals. Among the existing methods for converting CO2 into value-added chemicals, since carbon monoxide is an important chemical raw material for synthesizing various products, directly converting carbon dioxide into carbon monoxide is one of the most promising methods.

[0004] The traditional methods for converting carbon dioxide into carbon monoxide mainly include pyrolysis. This method reduces carbon dioxide to carbon monoxide through a high-temperature environment. However, since pyrolysis is a process of decomposing organic substances into gaseous, liquid, and solid substances under high temperature and oxygen-deficient conditions, in this process, the chemical bonds in carbon dioxide molecules are broken to form carbon monoxide and oxygen, and high temperature and a suitable catalyst are required to improve the reaction rate and selectivity. Therefore, there are problems such as harsh conversion conditions, complex processes, and high costs. So, it is necessary to find a better conversion method.

[0005] At present, researchers have proposed electrocatalytic methods and photocatalytic methods, etc. The electrocatalytic method is that in an electrochemical device, carbon dioxide dissolves in water and carbon monoxide is generated through the action of an electrocatalyst. The photocatalytic method is a method of using solar energy and a photocatalyst to convert carbon dioxide into high-value-added chemicals or fuels. Although both of these methods can convert carbon dioxide into carbon monoxide, since the catalysts used are mainly CeO2, C3N4, TiO2, etc., the activity of the catalysts is poor and the stability is poor, resulting in low conversion efficiency and poor selectivity for carbon monoxide.

[0006] Based on this, how to develop a catalyst with good activity and a conversion method to improve the conversion rate is an important issue currently faced. Summary of the Invention

[0007] Aiming at the technical problems of poor catalyst activity and low conversion efficiency existing in the existing carbon dioxide catalytic conversion, the present invention provides an indium oxide catalyst for carbon dioxide conversion, a preparation method thereof, and an application thereof.

[0008] The present invention prepares an indium oxide catalyst for carbon dioxide conversion through a precipitation method in cooperation with a dielectric barrier discharge technology, which has high catalytic activity and can improve the conversion rate of carbon dioxide in the conversion of carbon dioxide to carbon monoxide.

[0009] The present invention also constructs a dielectric barrier discharge system, and under the action of the catalyst, converts carbon dioxide into carbon monoxide, improves the conversion rate of carbon dioxide, and also improves the selectivity of the catalyst to carbon monoxide.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] A preparation method of an indium oxide catalyst for carbon dioxide conversion, comprising the following steps:

[0012] S1. Preparation of indium oxide precursor

[0013] Using indium nitrate as a raw material, an indium oxide precursor is prepared by a precipitation method;

[0014] S2. Preparation of indium oxide catalyst

[0015] The obtained indium oxide precursor is placed in a dielectric barrier discharge system and treated at a power of 50W - 60W for 15min - 20min to obtain an indium oxide catalyst for carbon dioxide conversion.

[0016] Further defined, in the step S1, the specific process of preparing the indium oxide precursor is:

[0017] S1.1. Dissolve indium nitrate in water to prepare a precursor solution;

[0018] S1.2. Under the conditions of heating and stirring, dropwise add sodium carbonate solution to the precursor solution until the pH of the precursor solution is 9.5 - 10, and then through aging, washing and drying, obtain an intermediate product;

[0019] S1.3. Calcinate the intermediate product to obtain an indium oxide precursor.

[0020] Further defined, in the step S1, the specific process of preparing the indium oxide precursor is:

[0021] S1.1. Dissolve indium nitrate in water to prepare a precursor solution;

[0022] S1.2. Under the conditions of heating and stirring, dropwise add sodium carbonate solution to the precursor solution until the pH of the precursor solution is 9.5 - 10, and then through aging, washing and drying, obtain an intermediate product;

[0023] S1.3. Calcine the intermediate product to obtain an indium oxide precursor.

[0024] It is further defined that in step S1.2, the conditions for heating and stirring are: temperature of 75°C-85°C, speed of 750r / min-800r / min; dropwise addition rate of 100mL / min-120mL / min; aging conditions of 3h-5h at 70°C-90°C; and drying conditions of 12h-16h at 75°C-95°C.

[0025] It is further defined that in step S1.3, the calcination conditions are: heating rate 5°C / min-10°C / min, calcination temperature 400°C-450°C, and holding time 3h-5h.

[0026] The indium oxide catalyst for carbon dioxide conversion is prepared by the method for preparing the indium oxide catalyst for carbon dioxide conversion.

[0027] It is further defined that the indium oxide catalyst for carbon dioxide conversion has an average crystal size of 17 nm and a maximum specific surface area of ​​50.154 m 2 / g, the maximum cumulative pore volume is 0.013cc / g, and the maximum oxygen vacancy is 1.254×10 13 spins / g.

[0028] The indium oxide catalyst for carbon dioxide conversion is used to improve the conversion rate of carbon dioxide to carbon monoxide.

[0029] A method for converting carbon dioxide into carbon monoxide comprises the following steps:

[0030] A1. 0.2 g to 0.8 g of a catalyst is loaded into a dielectric barrier discharge reactor, wherein the catalyst is an indium oxide catalyst prepared by the method for preparing an indium oxide catalyst for carbon dioxide conversion;

[0031] A2, applying an AC power supply to the dielectric barrier discharge reactor to form a discharge region inside the dielectric barrier discharge reactor; simultaneously, introducing carbon dioxide gas into the dielectric barrier discharge from one end of the dielectric barrier discharge reactor; the introduction amount of the carbon dioxide gas is 20mL / min-80mL / min; AC power supply: voltage 90V-220V, power 35W-80W;

[0032] A3. Carbon dioxide gas flows through the discharge area and is converted into carbon monoxide under the action of the catalyst and discharged from the other end of the dielectric barrier discharge reactor and collected.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present invention prepares an indium oxide catalyst for carbon dioxide conversion by using a precipitation method and a dielectric barrier discharge system. The specific surface area of this indium oxide catalyst is up to 50.154 m 2 / g, the cumulative pore volume is up to 0.013 cc / g, and the oxygen vacancies are up to 1.254×10 13 spins / g. Compared with commercial indium oxide, it has high oxygen vacancies, specific surface area and pore volume, and exhibits higher catalytic activity.

[0035] 2. The indium oxide catalyst for carbon dioxide conversion prepared by the present invention has high energy efficiency in a dielectric barrier discharge system (DBD system), and thus generates more high-energy electrons. CO2 molecules are captured by a large number of oxygen vacancies on the catalyst surface and adsorbed on the catalyst surface. The high-energy electrons generated by dielectric barrier discharge (DBD) bombard CO2 molecules, causing the double bond to break, generating CO and O radicals. Among them, CO desorbs from the catalyst surface, and the generated O radicals fill the oxygen vacancies of the catalyst to reduce the catalyst. Finally, the oxygen atoms in the plasma generated by the dielectric barrier discharge system can recombine with the oxygen on the catalyst to form O2 and desorb from the catalyst, reforming oxygen vacancies, thereby promoting the carbon dioxide conversion process.

[0036] 3. The indium oxide catalyst for carbon dioxide conversion prepared by the present invention, as a catalyst, catalyzes the conversion of carbon dioxide to carbon monoxide in the environment of a dielectric barrier discharge reactor (DBD reactor), which is beneficial to the conversion of carbon dioxide. At the same time, due to the higher specific surface area and oxygen vacancies of this catalyst, CO2 molecules are adsorbed at the oxygen vacancy positions on the catalyst, endowing the catalyst with more excellent carbon dioxide adsorption ability and further enhancing the carbon dioxide conversion rate.

[0037] 4. The present invention adopts the dielectric barrier discharge (DBD) technology. In addition to enhancing the catalytic activity of this catalyst, when the catalyst is deactivated during the conversion process, its catalytic activity can be restored by DBD reprocessing, realizing the regeneration of the catalyst. This not only shows that this catalyst has regenerability, but also the regeneration method is simple. Description of the Drawings

[0038] Figure 1 is the XRD pattern of different indium oxide catalysts;

[0039] Figure 2 is the SEM scan of commercial indium oxide at a magnification of 10K;

[0040] Figure 3 is the SEM scan of commercial indium oxide at a magnification of 20K;

[0041] Figure 4SEM scanning image of commercial indium oxide at a magnification of 60K;

[0042] Figure 5 SEM scanning image of indium oxide catalyst for carbon dioxide conversion at a magnification of 10K;

[0043] Figure 6 SEM scanning image of indium oxide catalyst for carbon dioxide conversion at a magnification of 20K;

[0044] Figure 7 SEM scanning image of indium oxide catalyst for carbon dioxide conversion at a magnification of 60K;

[0045] Figure 8 EPR diagrams of different indium oxide catalysts;

[0046] Figure 9 Pore size distribution diagrams of different indium oxide catalysts;

[0047] Figure 10 Cumulative pore volume diagrams of different indium oxide catalysts;

[0048] Figure 11 Isothermal adsorption and desorption results of commercial indium oxide catalyst;

[0049] Figure 12 Isothermal adsorption and desorption results of indium oxide catalyst for carbon dioxide conversion;

[0050] Figure 13 Carbon dioxide conversion rate results of different indium oxide catalysts at different SIEs;

[0051] Figure 14 CO yield results of different indium oxide catalysts at different SIEs;

[0052] Figure 15 Energy efficiency results of different indium oxide catalysts at different SIEs;

[0053] Figure 16 Carbon dioxide conversion results of indium oxide catalyst for carbon dioxide conversion at different flow rates;

[0054] Figure 17 Carbon dioxide conversion rate of indium oxide catalyst for carbon dioxide conversion at different dosages;

[0055] Figure 18 CO yield of indium oxide catalyst for carbon dioxide conversion at different dosages;

[0056] Figure 19 Energy efficiency of indium oxide catalyst for carbon dioxide conversion at different dosages;

[0057] Figure 20 Regeneration performance results of indium oxide catalyst for carbon dioxide conversion;

[0058] Figure 21 Mechanism for catalytic conversion of carbon dioxide in the present invention. Detailed implementation manners

[0059] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0060] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention pertains.

[0061] For technologies, methods, and devices known to those of ordinary skill in the relevant fields, they may not be discussed in detail, but where appropriate, the said technologies, methods, and devices shall be regarded as part of the specification.

[0062] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. These other embodiments are also covered by the protection scope of the present invention.

[0063] The present invention uses a combination of precipitation method and dielectric barrier discharge (DBD) to prepare an indium oxide catalyst for carbon dioxide conversion. Specifically, an indium oxide precursor is first obtained by the precipitation method, and then the indium oxide precursor is treated by dielectric barrier discharge. Under the plasma discharge field generated by the dielectric barrier discharge, indium oxide has high oxygen vacancies, specific surface area, and pore volume, so that when used as a catalyst, it exhibits higher catalytic activity.

[0064] The present invention provides a method for preparing an indium oxide catalyst for carbon dioxide conversion, comprising the following steps:

[0065] S1. Preparation of indium oxide precursor

[0066] An indium oxide precursor is prepared by the precipitation method using indium nitrate as a raw material.

[0067] In step S1 of the present invention, the specific process of preparing the indium oxide precursor is as follows:

[0068] S1.1. Dissolve indium nitrate in water to prepare a precursor solution.

[0069] S1.2. Under the conditions of heating and stirring, drop sodium carbonate solution into the precursor solution until the pH of the precursor solution reaches 9.5 - 10, and then obtain the intermediate product through aging, washing, and drying.

[0070] Preferably, the conditions of heating and stirring are: temperature 75°C - 85°C, speed 750 r / min - 800 r / min; the dropping speed is 100 ml / min - 120 ml / min; the conditions of aging are: aging at 70°C - 90°C for 3 h - 5 h; the conditions of drying are: drying at 75°C - 95°C for 12 h - 16 h.

[0071] S1.3. Calcinate the intermediate product to obtain the indium oxide precursor.

[0072] Preferably, the conditions of calcination are: heating rate 5°C / min - 10°C / min, calcination temperature 400°C - 450°C, holding time 3 h - 5 h.

[0073] S2. Preparation of indium oxide catalyst

[0074] Place the obtained indium oxide precursor in a dielectric barrier discharge system and process it at a power of 50 W - 60 W for 15 min - 20 min to finally obtain the indium oxide catalyst.

[0075] The indium oxide catalyst prepared by the present invention for carbon dioxide conversion has an average grain size of 17 nm, and has a large specific surface area, oxygen vacancies, and pore volume, and can be used as a catalyst for the conversion of carbon dioxide to carbon monoxide.

[0076] The present invention also provides a method for converting carbon dioxide to carbon monoxide, including the following steps:

[0077] A1. Load 0.2 g - 0.8 g of the catalyst into the internal part of the dielectric barrier discharge reactor, and the catalyst is the indium oxide catalyst for carbon dioxide conversion prepared by the above - mentioned preparation method of the indium oxide catalyst for carbon dioxide conversion;

[0078] A2. Apply an alternating current power supply to the dielectric barrier discharge reactor to form a discharge region inside the DBD reactor (dielectric barrier discharge reactor); at the same time, introduce carbon dioxide gas into the DBD reactor from one end of the dielectric barrier discharge reactor; the introduction amount of the carbon dioxide gas is 20 mL / min - 80 mL / min; alternating current power supply: voltage 90 V - 220 V, power 35 W - 80 W;

[0079] A3. The carbon dioxide gas flows through the discharge region and is converted into carbon monoxide under the action of the catalyst and discharged from the other end of the dielectric barrier discharge reactor and collected.

[0080] The present invention utilizes the prepared indium oxide catalyst for carbon dioxide conversion in combination with a dielectric barrier discharge reactor (DBD reactor). When carbon dioxide gas is introduced into the DBD reactor, under the synergistic action of this oxidant and the plasma discharge field generated by dielectric barrier discharge, the conversion rate of carbon dioxide is greatly improved.

[0081] The present invention uses dielectric barrier discharge to achieve the conversion of carbon dioxide under normal temperature and pressure conditions, and at the same time has a relatively fast reaction rate and high reaction activity, providing a new method for the conversion of carbon dioxide to carbon monoxide.

[0082] The following uses several specific examples to explain in detail the treatment and performance of the catalyst of the present invention.

[0083] It should be noted that the operations adopted in the following examples are all conventional operations in the art without special instructions. The pharmaceutical reagents and the like adopted in the following examples are all purchased from the market.

[0084] Example 1

[0085] This example uses the precipitation method and dielectric barrier discharge (DBD) to jointly prepare an indium oxide catalyst for carbon dioxide conversion.

[0086] This example provides a preparation method for an indium oxide catalyst for carbon dioxide conversion, including the following steps:

[0087] S1. Dissolve indium nitrate in 50 mL of deionized water to prepare a precursor solution, and then dissolve sodium carbonate in deionized water to prepare a 0.2 mol / L sodium carbonate solution; subsequently, under the stirring conditions of 80 °C and 800 r / min, use an injection pump to slowly drop the sodium carbonate solution into the precursor solution at a speed of 120 mL / min, and stop dropping when the pH = 10. After aging for 3 h at 80 °C, filter by suction and wash with hot deionized water. Dry the obtained sample at 80 °C for 12 h, and then calcine it in a muffle furnace with a heating rate of 5 °C / min, a calcination temperature of 450 °C, and a holding time of 3 h to obtain an indium oxide precursor.

[0088] S2. Place the obtained indium oxide precursor in the DBD system and treat it at a power of 60 W for 20 min to finally obtain a light yellow powdery solid, that is, an indium oxide catalyst for carbon dioxide conversion.

[0089] Example 2

[0090] This example uses the precipitation method and dielectric barrier discharge (DBD) to jointly prepare an indium oxide catalyst for carbon dioxide conversion.

[0091] This embodiment provides a method for preparing an indium oxide catalyst for carbon dioxide conversion, comprising the following steps:

[0092] S1. Dissolve indium nitrate in 50 mL of deionized water to prepare a precursor solution, and dissolve sodium carbonate in deionized water to prepare a 0.2 mol / L sodium carbonate solution. Subsequently, under the stirring conditions of 75 °C and 750 r / min, use an injection pump to slowly drop the sodium carbonate solution into the precursor solution at a rate of 100 mL / min. Stop dropping when the pH reaches 10. Age for 5 h at 70 °C, then perform suction filtration and wash with hot deionized water. Dry the obtained sample at 75 °C for 14 h, then calcine it in a muffle furnace at a heating rate of 10 °C / min, a calcination temperature of 400 °C, and a holding time of 3 h to obtain an indium oxide precursor.

[0093] S2. Place the obtained indium oxide precursor in a DBD system and treat it at a power of 50 W for 15 min to finally obtain a pale yellow powdery solid, which is the indium oxide catalyst for carbon dioxide conversion.

[0094] Example 3

[0095] This embodiment uses a combination of precipitation method and dielectric barrier discharge (DBD) to prepare an indium oxide catalyst for carbon dioxide conversion.

[0096] This embodiment provides a method for preparing an indium oxide catalyst for carbon dioxide conversion, comprising the following steps:

[0097] S1. Dissolve indium nitrate in 50 mL of deionized water to prepare a precursor solution, and dissolve sodium carbonate in deionized water to prepare a 0.2 mol / L sodium carbonate solution. Subsequently, under the stirring conditions of 85 °C and 780 r / min, use an injection pump to slowly drop the sodium carbonate solution into the precursor solution at a rate of 110 mL / min. Stop dropping when the pH reaches 10. Age for 4 h at 90 °C, then perform suction filtration and wash with hot deionized water. Dry the obtained sample at 95 °C for 16 h, then calcine it in a muffle furnace at a heating rate of 8 °C / min, a calcination temperature of 420 °C, and a holding time of 5 h to obtain an indium oxide precursor.

[0098] S2. Place the obtained indium oxide precursor in a DBD system and treat it at a power of 55 W for 20 min to finally obtain a pale yellow powdery solid, which is the indium oxide catalyst for carbon dioxide conversion.

[0099] Example 4

[0100] The method for carbon dioxide conversion to carbon monoxide provided in this embodiment comprises the following steps:

[0101] A1. Load 0.2 g of the catalyst inside the dielectric barrier discharge reactor. The catalyst is the indium oxide catalyst for carbon dioxide conversion prepared in Example 1.

[0102] A2. Apply an alternating current power supply to the dielectric barrier discharge reactor to form a discharge region inside the DBD reactor; at the same time, introduce carbon dioxide gas into the DBD reactor from one end of the dielectric barrier discharge reactor; the flow rate of the carbon dioxide gas is 20 mL / min; the voltage of the alternating current power supply is 100 V and the power is 35 W.

[0103] A3. The carbon dioxide gas flows through the discharge region and is converted into carbon monoxide under the action of the catalyst, which is discharged from the other end of the dielectric barrier discharge reactor and collected.

[0104] Example 5

[0105] The method for converting carbon dioxide into carbon monoxide provided in this example includes the following steps:

[0106] A1. Load 0.4 g of the catalyst inside the dielectric barrier discharge reactor. The catalyst is the indium oxide catalyst for carbon dioxide conversion prepared in Example 1.

[0107] A2. Apply an alternating current power supply to the dielectric barrier discharge reactor to form a discharge region inside the DBD reactor; at the same time, introduce carbon dioxide gas into the DBD reactor from one end of the dielectric barrier discharge reactor; the flow rate of the carbon dioxide gas is 20 mL / min; the voltage of the alternating current power supply is 220 V and the power is 80 W.

[0108] A3. The carbon dioxide gas flows through the discharge region and is converted into carbon monoxide under the action of the catalyst, which is discharged from the other end of the dielectric barrier discharge reactor and collected.

[0109] Next, the performance of the indium oxide catalyst for CO2 conversion prepared in the above examples and the effect of carbon dioxide conversion into carbon monoxide are verified through experiments.

[0110] Experiment 1: XRD

[0111] Samples: The indium oxide catalyst for carbon dioxide conversion in Example 1 and commercial indium oxide.

[0112] Testing process: The testing instrument is Rigaku Smartlab SE from Japan. The testing conditions are to place 20 mg - 50 mg of the catalyst sample on the sample stage, set the scanning range to 10° - 80°, and set the scanning speed to 10° / min. The results are as Figure 1 shown.

[0113] See Figure 1, An indium oxide catalyst for carbon dioxide conversion. The characteristic diffraction peaks at 2θ diffraction angles of 21.5°, 30.6°, 35.5°, 51.0° and 60.7° respectively correspond to the (211), (222), (400), (440) and (622) crystal planes of c-In2O3 (cubic indium oxide). Its diffraction peaks match well with the standard card PDF#87-018-7791 of In2O3, indicating that the prepared indium oxide is cubic indium oxide.

[0114] The grain size calculated by the following formula D :

[0115]

[0116] Where: D is the grain size; 0.943 is a calculation constant, which is actually a function of crystal morphology and reticular plane index. Since indium oxide is a cubic crystal, it is defined as 0.943; where λ, β, and θ are the x-ray radiation wavelength (Cu / Kα1 = 0.154059 nm) used in the test, the full width at half maximum (FWHM) of the diffraction peak, and the Bragg diffraction angle respectively.

[0117] It can be calculated that the average grain size of the indium oxide catalyst for carbon dioxide conversion prepared in Example 1 is 17 nm; while the average grain size of commercial indium oxide is 45.3 nm. It can be seen that the indium oxide catalyst for carbon dioxide conversion prepared in Example 1 has a smaller grain size and thus a higher specific surface area.

[0118] Experiment 2: SEM

[0119] Samples: The indium oxide catalyst for carbon dioxide conversion in Example 1 and commercial indium oxide.

[0120] Test process: The test instrument is a field emission scanning electron microscope Zeiss sigma300. The test conditions are to take 20 mg - 50 mg of the catalyst sample and stick it on the sample stage with conductive adhesive, evacuate, set the test mode to secondary electron InLens mode, set the acceleration voltage to 5 KV, and set the working distance to 7.3 mm - 7.6 mm. The SEM scanning images of commercial indium oxide at different magnifications are shown in Figure 2 、 Figure 3 and Figure 4 shown. The SEM scanning images of the indium oxide catalyst for carbon dioxide conversion prepared in Example 1 at different magnifications are shown in Figure 5 、 Figure 6 and Figure 7 shown.

[0121] See Figures 2 to 4 It can be seen that commercial indium oxide presents a crystalline state; at the same time, inFigure 5 It was observed that the indium oxide catalyst for carbon dioxide conversion prepared in Example 1 had more uniformly distributed micropores than commercial indium oxide.

[0122] Experiment 3: EPR

[0123] In order to test whether there are oxygen vacancies in the indium oxide catalyst for carbon dioxide conversion, electron paramagnetic resonance spectroscopy (EPR) was used for detection under dark conditions, room temperature and atmospheric environment.

[0124] Samples: The indium oxide catalyst for carbon dioxide conversion of Example 1, and commercial indium oxide.

[0125] Test process: The test instrument was Bruker A300. The test conditions were to weigh 10 mg - 25 mg, place it on the sample stage, set the scanning frequency to 100 HZ, the scanning time to 61.44 s, and the number of scans to 1 time. The results are as Figure 8 and Table 1 show.

[0126] See Figure 8 , it can be observed that at g = 2.003, although both catalysts showed characteristic signals related to oxygen vacancies, indicating the presence of bulk oxygen vacancies in both catalysts; however, it can be seen that for the indium oxide catalyst for carbon dioxide conversion prepared in Example 1, the intensity of the characteristic signal related to oxygen vacancies was much higher than that of commercial indium oxide. At the same time, combining the quantitative data of oxygen vacancies in Table 1, the oxygen vacancy content of the indium oxide catalyst for carbon dioxide conversion prepared in Example 1 was approximately 3.2 times that of commercial indium oxide. It indicates that there are more oxygen vacancies in the catalyst prepared in Example 1.

[0127] Experiment 4: Pore size distribution

[0128] Samples: The indium oxide catalyst for carbon dioxide conversion of Example 1, and commercial indium oxide.

[0129] Test process: The test instrument was Quantachrome Autosorb-iQ. The test conditions were to weigh 50 mg - 70 mg of the catalyst sample and place it on the sample stage, set the degassing temperature to 120 °C, and the degassing time to 7 h. The results are as Figure 9 , Figure 10 and Table 1 show.

[0130] Table 1 Comparison of the performance of two catalysts

[0131]

[0132] Figure 9 are the pore size distribution diagrams of the two catalysts; Figure 10It is the cumulative pore volume diagram of two catalysts. Combining with Table 1, it can be seen that the pore diameters of the two catalysts are mainly distributed between 0.6 nm and 0.9 nm, and the average pore diameter is 0.627 nm, belonging to the micropore range. And from the right figure and the table, it can be seen that the cumulative pore volume of the indium oxide catalyst used for carbon dioxide conversion can reach 0.013 cc / g, which is much higher than 0.002 cc / g of commercial indium oxide. At the same time, the surface areas of the two catalysts are calculated by the BET (Brunauer - Emmett - Teller) method. The specific surface area of the indium oxide catalyst used for carbon dioxide conversion reaches 50.154 m 2 / g, which is much higher than 7.523 m 2 / g of commercial indium oxide.

[0133] Experiment 5: Adsorption and desorption

[0134] Samples: The indium oxide catalyst for carbon dioxide conversion in Example 1, and commercial indium oxide.

[0135] Testing process: The testing instrument is Quantachrome Autosorb - iQ. The testing conditions are to weigh 50 mg - 70 mg of the catalyst sample and place it on the sample stage, set the degassing temperature to 120 °C, and the degassing time to 7 h. The results are as Figure 11 and Figure 12 shown. Figure 11 is the CO2 isothermal adsorption and desorption of commercial indium oxide, Figure 12 is the isothermal adsorption and desorption of the indium oxide catalyst for carbon dioxide conversion.

[0136] Referring to Figure 11 and Figure 12 it can be seen that: the maximum adsorption of commercial indium oxide for carbon dioxide is 0.83 cc / g, while the maximum adsorption of the indium oxide for carbon dioxide conversion prepared in the present invention is 5.68 cc / g, which is much higher than that of commercial indium oxide. This shows that the indium oxide catalyst for carbon dioxide conversion prepared in the present invention has a better adsorption capacity for carbon dioxide, which is beneficial to the catalytic conversion of carbon dioxide.

[0137] Experiment 6: Catalytic activities of different catalysts

[0138] Testing samples: Commercial indium oxide, the indium oxide catalyst for carbon dioxide conversion prepared in Example 1.

[0139] Test procedure: The test instrument is a coaxial dielectric barrier discharge (DBD) reactor. The main structure of the DBD reactor device is a quartz tube with a length of 300 mm, an inner diameter of 15 mm, and an outer diameter of 18 mm. Inside it, a stainless-steel electrode rod with a length of 150 mm and a diameter of 13 mm is placed along the axis of the quartz tube and applied to a high-voltage power supply. The outside of the quartz tube is wound with a stainless-steel mesh with a size of 100 mm × 120 mm as the grounding electrode, with a discharge gap of 1 mm and a discharge length of 120 mm. The reaction gas during the test is high-purity carbon dioxide gas, which enters from one side of the reactor after the flow rate is controlled by a pressure regulator valve and a mass flow meter, flows through the discharge area to participate in the reaction, and is collected at the outlet. The experiment uses a high-frequency alternating current power supply as the power source, uses a TM10 oscilloscope to measure the plasma power, and the reaction gas passes through a GC9790Ⅱ gas chromatograph equipped with a thermal conductivity detector (TCD) to determine the gas products after the reaction. Respectively weigh 0.2 g of commercial indium oxide and the indium oxide catalyst for carbon dioxide conversion prepared in Example 1, and place them in the DBD reactor by the IPC method respectively. Control the flow rate at 20 ml / min, and regulate the specific input energy (SIE) at 105 KJ / L, 145 KJ / L, 190 KJ / L, and 230 KJ / L respectively by changing the input power (35 W - 80 W). And compare with the conversion results of an empty DBD reactor without a catalyst. The results are as Figure 13 and Figure 14 shown.

[0140]

[0141] Wherein: SIE is the specific input energy, unit KJ / L; Input power is the input power, unit W; F CO2in is the CO2 inlet gas flow rate, unit mL / min.

[0142] See Figure 13 and Figure 14, after increasing the specific energy input of the DBD system, the conversion rate of carbon dioxide and the yield of carbon monoxide will increase accordingly. This is because increasing the input voltage of the DBD system fills the system with more high-energy electrons, increasing the collision probability between carbon dioxide and high-energy electrons, thus improving the conversion efficiency of carbon dioxide. The carbon dioxide conversion rate and carbon monoxide yield of the DBD filled with catalyst are both higher than those of the empty DBD, which is due to the synergistic effect of indium oxide and plasma discharge on CO2 conversion. The CO2 conversion rate and CO yield of the DBD device filled with indium oxide catalyst for CO2 conversion at the highest SIE are significantly higher than those of the DBD filled with commercial indium oxide and the empty DBD, reaching 29.7% and 24.5% respectively. Compared with the empty DBD without catalyst, its catalytic effect is increased by about 50.7%. This is because the indium oxide catalyst for carbon dioxide conversion has a higher specific surface area, more bulk oxygen vacancies and better carbon dioxide adsorption ability, all of which are beneficial to its catalytic conversion of carbon dioxide.

[0143] The measured energy efficiency is as Figure 15 shown. As the SIE increases, the energy efficiency of the reaction system generally shows a trend of increasing first and then decreasing, and reaches the maximum value at an SIE of 145 KJ / L. At low power, as the input power increases, the electric field strength in the discharge region increases, and the density of activated particles and high-energy electrons in the system also increases. The probability of CO2 molecules being bombarded by high-energy electrons in the plasma region will also increase, thus increasing the conversion rate of CO2 and further improving the energy efficiency of the system.

[0144] Experiment 7. Influence of flow rate

[0145] Sample: Indium oxide catalyst for carbon dioxide conversion prepared in Example 1.

[0146] Test procedure: The test instrument is a coaxial dielectric barrier discharge (DBD) reactor. The main structure of the DBD reactor device is a quartz tube with a length of 300 mm, an inner diameter of 15 mm, and an outer diameter of 18 mm. Inside it, a stainless-steel electrode rod with a length of 150 mm and a diameter of 13 mm is placed along the axis of the quartz tube and applied to a high-voltage power supply. The outside of the quartz tube is wound with a stainless-steel mesh with a length of 100 mm × 120 mm as the grounding electrode. The discharge gap is 1 mm and the discharge length is 120 mm. The reaction gas in the experimental process is high-purity carbon dioxide gas. After the flow rate is controlled by a pressure regulator valve and a mass flowmeter, it enters from one side of the reactor, flows through the discharge area to participate in the reaction, and is collected at the outlet. The experiment uses a high-frequency alternating current power supply as the power source, and a TM10 oscilloscope is used to measure the plasma power. The reaction gas passes through a GC9790Ⅱ gas chromatograph equipped with a thermal conductivity detector (TCD) to determine the gas products after the reaction. Weigh 0.4 g of the indium oxide catalyst prepared in Example 1 for carbon dioxide conversion, and place it in the DBD reactor using the IPC method. The input power is set to 35 W, and the flow rates are set to 20 mL / min, 40 mL / min, 60 mL / min, and 80 mL / min respectively. The results are as Figure 16 shown.

[0147] It can be observed from Figure 16 that as the flow rate of carbon dioxide decreases and the residence time of carbon dioxide in the DBD system increases, the corresponding CO2 conversion rate also increases. This shows that as the residence time of CO2 in the DBD increases, carbon dioxide molecules are more likely to collide with high-energy electrons in the DBD, thus improving the degradation efficiency; however, when the flow rate decreases, the reaction time will increase. Therefore, considering comprehensively, the preferred carbon dioxide flow rate is 20 mL / min.

[0148] Test 8. Catalyst dosage

[0149] Sample: The indium oxide catalyst prepared in Example 1 for carbon dioxide conversion.

[0150] Test process: The test instrument is a coaxial dielectric barrier discharge (DBD) reactor. The main structure of the DBD reactor device is a quartz tube with a length of 300 mm, an inner diameter of 15 mm, and an outer diameter of 18 mm. Inside it, a stainless-steel electrode rod with a length of 150 mm and a diameter of 13 mm is placed along the axis of the quartz tube and applied to a high-voltage power supply. The outside of the quartz tube is wound with a stainless-steel mesh with a length of 100 mm × 120 mm as the grounding electrode. The discharge gap is 1 mm, and the discharge length is 120 mm. The reaction gas in the test process is high-purity carbon dioxide gas. After the flow rate is controlled by a pressure regulator valve and a mass flowmeter, it enters from one side of the reactor, flows through the discharge area to participate in the reaction, and is collected at the outlet. The experiment uses a high-frequency AC power supply as the power source, and a TM10 oscilloscope is used to measure the plasma power. The reaction gas passes through a GC9790Ⅱ gas chromatograph equipped with a thermal conductivity detector (TCD) to measure the gas products after the reaction. Respectively, 0.2 g, 0.4 g, 0.6 g, and 0.8 g of the indium oxide catalyst prepared in Example 1 for carbon dioxide conversion are placed in the DBD reactor by the IPC method. The flow rate is controlled at 20 mL / min, and the energy density SIE is adjusted to 102 KJ / L, 145 KJ / L, 190 KJ / L, and 230 KJ / L respectively by changing the input power (35 W - 80 W). The results are as Figure 17 , Figure 18 and Figure 19 shown.

[0151]

[0152] Where: SIE is the energy density, unit KJ / L; Input power is the input power, unit W; F CO2in is the CO2 inlet flow rate, unit mL / min.

[0153] From Figure 17 , Figure 18 and Figure 19 it can be seen that with the decrease in the catalyst dosage, the carbon dioxide conversion rate and CO yield of the DBD system increase under each SIE. The maximum value appears when the catalyst dosage is 0.2 g. At the highest SIE, its carbon dioxide conversion rate can reach 29.7%, and at the same time, the CO yield can reach 24.5%. Compared with the empty DBD without filling the catalyst in Experiment 6, its catalytic effect is relatively improved by 50.7%, and the catalytic effect far exceeds that of the empty DBD under the same conditions. It shows that the combination of the indium oxide catalyst prepared in the present invention for carbon dioxide conversion and the DBD reactor can greatly improve the conversion rate of carbon dioxide and the selectivity of carbon monoxide.

[0154] Test 9. Regenerability

[0155] Experimental apparatus and procedures: The test instrument is a self-made coaxial dielectric barrier discharge (DBD) reactor. The main structure of the DBD reactor is a quartz tube with a length of 300 mm, an inner diameter of 15 mm, and an outer diameter of 18 mm. Inside it, a stainless-steel electrode rod with a length of 150 mm and a diameter of 13 mm is placed along the axis of the quartz tube and applied to a high-voltage power supply. The outside of the quartz tube is wound with a stainless-steel mesh with a length of 100 mm × 120 mm as the grounding electrode, with a discharge gap of 1 mm and a discharge length of 120 mm. The reaction gas in the test process is high-purity carbon dioxide gas, which enters from one side of the reactor after the flow rate is controlled by a pressure regulator valve and a mass flow meter, flows through the discharge area to participate in the reaction, and is collected at the outlet. Weigh 0.4 g of the indium oxide catalyst prepared in Example 1 for carbon dioxide conversion and place it in the DBD reactor by the internal method. Set the input power to 35 W and the gas flow rate to 20 mL / min, and record the change of CO2 conversion rate over time. The results are as Figure 20 shown.

[0156] Figure 20 shown. As the reaction time prolongs, the conversion rate of carbon dioxide gradually increases, indicating that there is a catalyst activation process in the reaction. When the catalyst is in the activation stage, a large number of high-energy electrons bombard indium oxide, resulting in an increase in the number of oxygen vacancies, an increase in specific surface area, and an improvement in carbon dioxide capture ability. All these enhance the ability to capture carbon dioxide, thus improving the catalytic conversion ability. At the same time, it can be observed that the conversion rate of carbon dioxide tends to be stable after 1 h and remains stable after 2 h. Subsequently, the indium oxide catalyst for carbon dioxide conversion is re-treated at 160 V voltage in an air atmosphere for 20 min.

[0157] Then, the regenerated catalyst is re-tested for CO2 conversion at a constant CO2 flow rate of 35 W and 20 mL / min. It can be seen that the catalyst can be regenerated in the DBD plasma reactor. However, as the number of catalyst regeneration operations increases, the carbon dioxide conversion rate also decreases. Since the bond energy of the In-O bond in indium oxide is 9.3 eV, the DBD dielectric barrier discharge reactor generates high-energy electrons with an average electron energy of 1 eV - 10 eV. These electrons can bombard the In-O bond in the catalyst, resulting in the reappearance of oxygen vacancies. This shows that the indium oxide catalyst prepared in the present invention for carbon dioxide conversion can be regenerated under DBD treatment, not only indicating that this indium oxide catalyst itself has regenerability, but also that the regeneration can be completed in the conversion system, and the regeneration method is simpler.

[0158] To sum up, the schematic diagram of CO2 conversion in the low-temperature plasma reactor is as Figure 21As shown in the figure. After being bombarded by high-energy electrons in the DBD system, carbon dioxide splits into CO and O free radicals, and then the unstable oxygen free radicals combine in pairs to form O2. The DBD filled with the alkali metal oxide In2O3 shows more excellent CO2 conversion performance than the unfilled DBD, which indicates that there is a synergistic effect between the DBD and the catalyst. Therefore, the catalyst plays a crucial role in the conversion of CO2 in the DBD plasma because the CO2 conversion process in the DBD plasma reactor filled with the catalyst is largely affected by the discharge characteristics and surface reactions of the catalyst. Therefore, in the DBD system filled with indium oxide prepared by the present invention for carbon dioxide conversion, the energy efficiency is higher than that of the empty DBD under the same SIE, which shows that the plasma with the catalyst generates more high-energy electrons, thus promoting the CO2 conversion process. At the same time, In2O3 with a high specific surface area and a large number of oxygen vacancies can capture CO2 molecules. The CO2 molecules are adsorbed at the oxygen vacancy positions on the catalyst, and the high-energy electrons generated by the DBD bombard the CO2 molecules, causing their double bonds to break, generating CO and O free radicals. Among them, CO desorbs from the catalyst surface, and the generated O free radicals fill the oxygen vacancies of the catalyst, reducing the catalyst. Finally, the oxygen atoms in the DBD plasma can recombine with the oxygen on the catalyst to form O2, which desorbs from the catalyst and forms oxygen vacancies again.

[0159] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. Application of an indium oxide catalyst for carbon dioxide conversion to improve the conversion rate of carbon dioxide to carbon monoxide, characterized in that: The preparation method of the indium oxide catalyst for carbon dioxide conversion comprises the following steps: S1. Preparation of indium oxide precursor An indium oxide precursor is prepared by a precipitation method using indium nitrate as a raw material; In step S1, the specific process of preparing the indium oxide precursor is: S1.1, dissolving indium nitrate in water to prepare a precursor solution; S1.2, under heating and stirring conditions, adding sodium carbonate solution to the precursor solution until the pH of the precursor solution is 9.5-10, and then aging, washing and drying to obtain an intermediate product; S1.3, calcining the intermediate product to obtain an indium oxide precursor; S2. Preparation of indium oxide catalyst The indium oxide precursor obtained above is placed in a dielectric barrier discharge system and treated at a power of 50W-60W for 15min-20min to obtain an indium oxide catalyst for carbon dioxide conversion; The indium oxide catalyst for carbon dioxide conversion was prepared by using a precipitation method and a dielectric barrier discharge system, with a maximum specific surface area of ​​50.154 m 2 / g, the maximum cumulative pore volume is 0.013cc / g, and the maximum oxygen vacancy is 1.254×10 13 spins / g.

2. The use according to claim 1, characterized in that: In the step S1.2, the heating and stirring conditions are: temperature of 75°C-85°C, speed of 750r / min-800r / min; dropwise addition speed of 100mL / min-120mL / min; aging conditions of 3h-5h at 70°C-90°C; and drying conditions of 12h-16h at 75°C-95°C.

3. The use according to claim 1, characterized in that: In the step S1.3, the calcination conditions are: heating rate 5°C / min-10°C / min, calcination temperature 400°C-450°C, and holding time 3h-5h.

4. A method for converting carbon dioxide into carbon monoxide, characterized in that: The following steps are involved: A1. 0.2 g to 0.8 g of a catalyst is loaded into a dielectric barrier discharge reactor. The catalyst is an indium oxide catalyst for carbon dioxide conversion. The preparation method comprises the following steps: S1. Preparation of indium oxide precursor An indium oxide precursor is prepared by a precipitation method using indium nitrate as a raw material; In step S1, the specific process of preparing the indium oxide precursor is: S1.1, dissolving indium nitrate in water to prepare a precursor solution; S1.2, under heating and stirring conditions, adding sodium carbonate solution to the precursor solution until the pH of the precursor solution is 9.5-10, and then aging, washing and drying to obtain an intermediate product; S1.3, calcining the intermediate product to obtain an indium oxide precursor; S2. Preparation of indium oxide catalyst The indium oxide precursor obtained above is placed in a dielectric barrier discharge system and treated at a power of 50W-60W for 15min-20min to obtain an indium oxide catalyst for carbon dioxide conversion; The indium oxide catalyst for carbon dioxide conversion was prepared by using a precipitation method and a dielectric barrier discharge system, with a maximum specific surface area of ​​50.154 m 2 / g, the maximum cumulative pore volume is 0.013cc / g, and the maximum oxygen vacancy is 1.254×10 13 spins / g; A2, applying an AC power supply to the dielectric barrier discharge reactor to form a discharge region inside the dielectric barrier discharge reactor; simultaneously, introducing carbon dioxide gas into the dielectric barrier discharge from one end of the dielectric barrier discharge reactor; the introduction amount of the carbon dioxide gas is 20mL / min-80mL / min; AC power supply: voltage 90V-220V, power 35W-80W; A3. Carbon dioxide gas flows through the discharge area and is converted into carbon monoxide under the action of the catalyst and discharged from the other end of the dielectric barrier discharge reactor and collected.

5. The method for converting carbon dioxide to carbon monoxide according to claim 4, characterized in that: In the step S1.2, the heating and stirring conditions are: temperature of 75°C-85°C, speed of 750r / min-800r / min; dropwise addition speed of 100mL / min-120mL / min; aging conditions of 3h-5h at 70°C-90°C; and drying conditions of 12h-16h at 75°C-95°C.

6. The method for converting carbon dioxide to carbon monoxide according to claim 4, characterized in that: In the step S1.3, the calcination conditions are: heating rate 5°C / min-10°C / min, calcination temperature 400°C-450°C, and holding time 3h-5h.

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