Indium oxide catalyst for carbon dioxide conversion and preparation method and application thereof

Abstract

The invention belongs to the technical field of catalysts and application thereof, and relates to an indium oxide catalyst for carbon dioxide conversion and a preparation method and application thereof.The preparation method comprises the following steps that S1, an indium oxide precursor is prepared, specifically, indium nitrate serves as a raw material, and the indium oxide precursor is prepared through a precipitation method; and S2, catalyst preparation: placing the obtained indium oxide precursor in a dielectric barrier discharge system, and treating at the power of 50-60W for 15-20 minutes to obtain the indium oxide catalyst. The indium oxide catalyst is prepared through a dielectric barrier discharge technology, has very high catalytic activity, and can improve the conversion rate of carbon dioxide in the process of converting carbon dioxide into carbon monoxide.

Description

Technical Field

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

[0002] With the rapid development of human society, people's dependence on fossil energy is becoming more and more urgent. However, fossil energy will produce a large amount of greenhouse gases in the process of consumption, which will have an impact on the environment, especially carbon dioxide greenhouse gases, which will lead to a series of environmental problems such as global warming and sea level rise. Therefore, the reduction of carbon dioxide emissions is a hot topic in current research.

[0003] At present, there are two main ways to reduce carbon dioxide emissions: 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 of converting CO2 into value-added chemicals, since carbon monoxide is an important chemical raw material for synthesizing a variety of products, directly converting carbon dioxide into carbon monoxide is one of the most promising methods.

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

[0005] At present, researchers have proposed electrocatalytic and photocatalytic methods. In the electrocatalytic method, carbon dioxide is dissolved in water in an electrochemical device and carbon monoxide is generated through the action of an electrocatalyst. The photocatalytic method uses solar energy and photocatalysts to convert carbon dioxide into high-value-added chemicals or fuels. Although both methods can convert carbon dioxide into carbon monoxide, the catalysts used are mainly CeO2, C3N4 and TiO2, and the catalysts have poor activity and stability, 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] In view of the technical problems of poor catalyst activity and low conversion efficiency in the existing catalytic conversion of carbon dioxide, the present invention provides an indium oxide catalyst for carbon dioxide conversion and a preparation method and application thereof.

[0008] The present invention prepares an indium oxide catalyst for carbon dioxide conversion by a precipitation method in conjunction with a dielectric barrier discharge technology. The indium oxide catalyst has high catalytic activity and can improve the conversion rate of carbon dioxide when used for converting carbon dioxide to generate carbon monoxide.

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

[0010] In order to achieve the above object, the technical solution adopted by the present invention is: A method for preparing an 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; 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.

[0011] It is further defined that 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. Calcine the intermediate product to obtain an indium oxide precursor.

[0012] It is further defined that 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. Calcine the intermediate product to obtain an indium oxide precursor.

[0013] 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.

[0014] 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.

[0015] The indium oxide catalyst for carbon dioxide conversion is prepared by the method for preparing the indium oxide catalyst for carbon dioxide conversion.

[0016] 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.

[0017] The indium oxide catalyst for carbon dioxide conversion is used to improve the conversion rate of carbon dioxide to carbon monoxide.

[0018] A method for converting carbon dioxide into carbon monoxide comprises the following steps: 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; 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.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 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 indium oxide catalyst has 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, which has high oxygen vacancies, specific surface area and pore volume, and exhibits higher catalytic activity relative to commercial indium oxide.

[0020] 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), thereby generating 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 the dielectric barrier discharge (DBD) bombard the CO2 molecules, thereby breaking their double bonds to generate CO and O free radicals, wherein CO desorbs on the catalyst surface, and the generated O free 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, which is desorbed from the catalyst and reforms the oxygen vacancies, thereby promoting the CO2 conversion process.

[0021] 3. The indium oxide catalyst for carbon dioxide conversion prepared by the present invention is used as a catalyst to catalyze the conversion of carbon dioxide to generate carbon monoxide in a dielectric barrier discharge reactor (DBD reactor) environment, which is beneficial to the conversion of carbon dioxide. At the same time, since this catalyst has a higher specific surface area and oxygen vacancies, CO2 molecules are adsorbed at the oxygen vacancy positions on the catalyst, so that the catalyst has a better carbon dioxide adsorption capacity, further enhancing the conversion rate of carbon dioxide.

[0022] 4. The present invention adopts dielectric barrier discharge (DBD) technology. In addition to enhancing the catalytic activity of the catalyst, when the catalyst is deactivated during the conversion process, the catalytic activity can be restored through DBD reprocessing to achieve catalyst regeneration. This not only shows that the catalyst is regenerative, but also the regeneration method is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 XRD patterns of different indium oxide catalysts; Figure 2 This is a SEM scan of commercial indium oxide at 10K magnification; Figure 3 This is a SEM scan of commercial indium oxide at 20K magnification; Figure 4 This is a SEM scan of commercial indium oxide at 60K magnification; Figure 5 This is a SEM scan of an indium oxide catalyst for carbon dioxide conversion at 10K magnification; Figure 6This is a SEM scan of an indium oxide catalyst for carbon dioxide conversion at 20K magnification; Figure 7 This is a SEM scan of an indium oxide catalyst for carbon dioxide conversion at a magnification of 60K; Figure 8 EPR graphs of different indium oxide catalysts; Fig. 9 is the pore size distribution diagram of different indium oxide catalysts; Fig.10 is the cumulative pore volume diagram of different indium oxide catalysts; Fig.11 Isothermal adsorption and desorption results of commercial indium oxide catalyst; Fig.12 The isothermal adsorption and desorption results of indium oxide catalyst for carbon dioxide conversion; Fig.13 The carbon dioxide conversion results of different indium oxide catalysts under different SIE; Fig.14 CO yield results of different indium oxide catalysts at different SIEs; Fig.15 The energy efficiency results of different indium oxide catalysts under different SIE; Fig.16 The results of carbon dioxide conversion at different flow rates using indium oxide catalyst for carbon dioxide conversion; Fig.17 The carbon dioxide conversion rate of indium oxide catalyst used for carbon dioxide conversion at different dosages; Fig.18 CO yield at different dosages of indium oxide catalyst used for carbon dioxide conversion; Fig.19 The energy efficiency of indium oxide catalyst for carbon dioxide conversion at different dosages; Fig. 20 The regeneration performance results of indium oxide catalysts for carbon dioxide conversion are shown; Fig.21 This is the mechanism of catalytic conversion of carbon dioxide in the present invention. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0025] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0026] Technologies, methods, and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

[0027] In addition, it should be understood that although this specification is described according to the implementation modes, not every implementation mode includes only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. These other implementation modes are also covered within the protection scope of the present invention.

[0028] The present invention adopts a precipitation method and a dielectric barrier discharge (DBD) to jointly prepare an indium oxide catalyst for carbon dioxide conversion. Specifically, an indium oxide precursor is first obtained by a precipitation method, and then the indium oxide precursor is treated by a dielectric barrier discharge. Under the plasma discharge field generated by the dielectric barrier discharge, the indium oxide has high oxygen vacancies, specific surface area and pore volume, so that when used as a catalyst, it exhibits higher catalytic activity.

[0029] The present invention provides a method for preparing an indium oxide catalyst for carbon dioxide conversion, comprising the following steps: S1. Preparation of indium oxide precursor The indium oxide precursor is prepared by a precipitation method using indium nitrate as a raw material.

[0030] In step S1 of the present invention, the specific process of preparing the indium oxide precursor is: S1.1. Dissolve indium nitrate in water to prepare a precursor solution.

[0031] S1.2. Under heating and stirring conditions, sodium carbonate solution is added dropwise to the precursor solution until the pH of the precursor solution is 9.5-10, and then the precursor solution is aged, washed and dried to obtain an intermediate product.

[0032] Preferably, the heating and stirring conditions 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.

[0033] S1.3. Calcine the intermediate product to obtain an indium oxide precursor.

[0034] Preferably, the calcination conditions are: heating rate 5°C / min-10°C / min, calcination temperature 400°C-450°C, and holding time 3h-5h.

[0035] 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 finally obtain an indium oxide catalyst.

[0036] The indium oxide catalyst for carbon dioxide conversion prepared by the present invention has an average crystal particle size of 17nm and has a large specific surface area, oxygen vacancies and pore volume, and can be used as a catalyst for converting carbon dioxide to generate carbon monoxide.

[0037] The present invention also provides a method for converting carbon dioxide into carbon monoxide, comprising the following steps: 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 for carbon dioxide conversion prepared by the above-mentioned method for preparing an indium oxide catalyst for carbon dioxide conversion; A2, applying an AC 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, introducing 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 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.

[0038] 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, the conversion rate of carbon dioxide is greatly improved under the synergistic effect of the oxidant and the plasma discharge field generated by the dielectric barrier discharge.

[0039] The present invention adopts dielectric barrier discharge to realize the conversion of carbon dioxide under normal temperature and pressure conditions, and has a faster reaction rate and higher reaction activity, thereby providing a new method for converting carbon dioxide into carbon monoxide.

[0040] The following is a detailed explanation of the processing and performance of the catalyst of the present invention with reference to several groups of specific examples.

[0041] It should be noted that the operations used in the following examples are all conventional operations in the art unless otherwise specified. The pharmaceutical reagents used in the following examples are all purchased from the market.

[0042] Example 1 In this embodiment, a precipitation method and a dielectric barrier discharge (DBD) are combined to prepare an indium oxide catalyst for carbon dioxide conversion.

[0043] This embodiment provides a method for preparing an indium oxide catalyst for carbon dioxide conversion, comprising the following steps: S1. Dissolve indium nitrate in 50mL deionized water to prepare a precursor solution, and then dissolve sodium carbonate in deionized water to prepare a 0.2mol / L sodium carbonate solution; then, under stirring conditions of 80°C and 800 r / min, use a syringe pump to slowly add the sodium carbonate solution to the precursor solution at a rate of 120mL / min, and stop adding after the pH reaches 10. After aging at 80°C for 3h, filter and wash with hot deionized water. The obtained sample was dried at 80°C for 12h, and then calcined in a muffle furnace with a heating rate of 5°C / min, a calcination temperature of 450°C, and a holding time of 3h to obtain an indium oxide precursor.

[0044] S2. The indium oxide precursor obtained above is placed in a DBD system and treated at a power of 60 W for 20 min to finally obtain a light yellow powdery solid, i.e., an indium oxide catalyst for carbon dioxide conversion.

[0045] Example 2 In this embodiment, a precipitation method and a dielectric barrier discharge (DBD) are combined to prepare an indium oxide catalyst for carbon dioxide conversion.

[0046] This embodiment provides a method for preparing an indium oxide catalyst for carbon dioxide conversion, comprising the following steps: S1. Dissolve indium nitrate in 50mL deionized water to prepare a precursor solution, and then dissolve sodium carbonate in deionized water to prepare a 0.2mol / L sodium carbonate solution; then, under stirring conditions of 75°C and 750 r / min, use a syringe pump to slowly add the sodium carbonate solution to the precursor solution at a rate of 100mL / min, and stop adding after the pH reaches 10. After aging at 70°C for 5h, filter and wash with hot deionized water. The obtained sample was dried at 75°C for 14h, and then calcined in a muffle furnace with a heating rate of 10°C / min, a calcination temperature of 400°C, and a holding time of 3h to obtain an indium oxide precursor.

[0047] S2. The indium oxide precursor obtained above is placed in a DBD system and treated at a power of 50 W for 15 min to finally obtain a light yellow powdery solid, i.e., an indium oxide catalyst for carbon dioxide conversion.

[0048] Example 3 In this embodiment, a precipitation method and a dielectric barrier discharge (DBD) are combined to prepare an indium oxide catalyst for carbon dioxide conversion.

[0049] This embodiment provides a method for preparing an indium oxide catalyst for carbon dioxide conversion, comprising the following steps: S1. Dissolve indium nitrate in 50mL deionized water to prepare a precursor solution, and then dissolve sodium carbonate in deionized water to prepare a 0.2mol / L sodium carbonate solution; then, under stirring conditions of 85°C and 780r / min, use a syringe pump to slowly add the sodium carbonate solution to the precursor solution at a rate of 110mL / min, and stop adding after the pH reaches 10. After aging at 90°C for 4h, filter and wash with hot deionized water. The obtained sample was dried at 95°C for 16h, and then calcined in a muffle furnace with a heating rate of 8°C / min, a calcination temperature of 420°C, and a holding time of 5h to obtain an indium oxide precursor.

[0050] S2. The indium oxide precursor obtained above is placed in a DBD system and treated at a power of 55 W for 20 min to finally obtain a light yellow powdery solid, i.e., an indium oxide catalyst for carbon dioxide conversion.

[0051] Example 4 The method for converting carbon dioxide to carbon monoxide provided in this embodiment comprises the following steps: A1. 0.2 g of catalyst was loaded into a dielectric barrier discharge reactor. The catalyst was the indium oxide catalyst for carbon dioxide conversion prepared in Example 1.

[0052] A2. Apply an AC 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 introduction amount of the carbon dioxide gas is 20 mL / min; the voltage of the AC power supply is 100 V and the power is 35 W.

[0053] 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.

[0054] Example 5 The method for converting carbon dioxide to carbon monoxide provided in this embodiment comprises the following steps: A1. 0.4 g of catalyst was loaded into a dielectric barrier discharge reactor. The catalyst was the indium oxide catalyst for carbon dioxide conversion prepared in Example 1.

[0055] A2. Apply an AC 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 introduction amount of the carbon dioxide gas is 20 mL / min; the voltage of the AC power supply is 220 V and the power is 80 W.

[0056] 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.

[0057] The performance of the indium oxide catalyst for CO2 conversion prepared in the above example and its effect on the conversion of carbon dioxide to carbon monoxide are verified by experiments.

[0058] Test 1: XRD Samples: the indium oxide catalyst for carbon dioxide conversion of Example 1, and commercial indium oxide.

[0059] Test process: The test instrument is Japan Rigaku Smartlab SE, and the test conditions are to take 20mg-50mg of catalyst sample and place it on the sample table, set the scanning range to 10°-80°, and set the scanning speed to 10° / min. The results are as follows Figure 1 shown.

[0060] See also Figure 1 , 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° correspond to the (211), (222), (400), (440) and (622) crystal planes of c-In2O3 (cubic phase In2O3), respectively, and 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.

[0061] The grain size is calculated by the following formula D : in: D is the grain size; 0.943 is a calculation constant, which is actually a function of the crystal morphology and mesh index. Since indium oxide is a cubic phase crystal, it is defined as 0.943; where λ, β, and θ are the X-ray radiation wavelength (Cu / Kα1=0.154059 nm), the half-maximum width (FWHM) of the diffraction peak, and the Bragg diffraction angle used in the test, respectively.

[0062] Through calculation, it can be known that the indium oxide catalyst for carbon dioxide conversion prepared in Example 1 has an average grain size of 17nm, while the average grain size of commercial indium oxide is 45.3nm. It can be seen that the indium oxide catalyst for carbon dioxide conversion prepared in Example 1 has a smaller grain size and thus has a higher specific surface area.

[0063] Experiment 2: SEM Samples: the indium oxide catalyst for carbon dioxide conversion of Example 1, and commercial indium oxide.

[0064] Test process: The test instrument is a field emission scanning electron microscope Zeiss sigma300. The test conditions are to take 20mg-50mg of catalyst sample and stick it on the sample stage with conductive glue, evacuate the sample, set the test mode to secondary electron InLens mode, set the acceleration voltage to 5KV, and set the working distance to 7.3mm-7.6mm. SEM scans of commercial indium oxide at different magnifications are shown below. Figure 2 , Figure 3 and Figure 4 As shown, the SEM scans of the indium oxide catalyst for carbon dioxide conversion prepared in Example 1 at different magnifications are as follows Figure 5 , Figure 6 and Figure 7 shown.

[0065] See also Figure 2~Figure 4 It can be seen that commercial indium oxide is crystalline; Figure 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.

[0066] Experiment 3: EPR To test the presence of oxygen vacancies in the indium oxide catalyst for CO2 conversion, electron paramagnetic resonance spectroscopy (EPR) was performed under dark conditions, room temperature, and atmospheric conditions.

[0067] Samples: the indium oxide catalyst for carbon dioxide conversion of Example 1, and commercial indium oxide.

[0068] Test process: The test instrument is Bruker A300, the test conditions are to weigh 10mg-25mg, place it on the sample stage, set the scanning frequency to 100HZ, the scanning time to 61.44s, and the scanning number to 1. The results are as follows Figure 8 And as shown in Table 1.

[0069] See also Figure 8It can be observed that when g=2.003, although both catalysts show characteristic signals related to oxygen vacancies, indicating that there are oxygen vacancies in the two catalysts, it can be seen that the intensity of the characteristic signal related to oxygen vacancies in the indium oxide catalyst for carbon dioxide conversion prepared in Example 1 is much higher than that in commercial indium oxide. Combined with 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 is about 3.2 times that of commercial indium oxide. This shows that there are more oxygen vacancies in the catalyst prepared in Example 1.

[0070] Test 4: Pore size distribution Samples: the indium oxide catalyst for carbon dioxide conversion of Example 1, and commercial indium oxide.

[0071] Test process: The test instrument is Quantachrome Autosorb-iQ, and the test conditions are to weigh 50mg-70mg of catalyst sample and place it on the sample table, set the degassing temperature to 120℃, and the degassing time to 7h. Fig. 9 , Fig.10 And as shown in Table 1.

[0072] Table 1 Comparison of performance of two catalysts Fig. 9 is the pore size distribution diagram of the two catalysts; Fig.10 The cumulative pore volume diagram of the two catalysts, combined with Table 1, shows that the pore sizes of the two catalysts are mainly distributed between 0.6nm-0.9nm, with an average pore size of 0.627nm, which belongs to the micropore range. From the right figure and table, it can be seen that the cumulative pore volume of the indium oxide catalyst used for carbon dioxide conversion can reach 0.013cc / g, which is much higher than the 0.002cc / g of commercial indium oxide. At the same time, the surface area of ​​the two catalysts was calculated by the BET (Brunauer-Emmetttteller) method. The specific surface area of ​​the indium oxide catalyst used for carbon dioxide conversion reached 50.154m 2 / g, much higher than the 7.523m / g of commercial indium oxide 2 / g.

[0073] Test 5: Adsorption and desorption Samples: the indium oxide catalyst for carbon dioxide conversion of Example 1, and commercial indium oxide.

[0074] Test process: The test instrument is Quantachrome Autosorb-iQ, and the test conditions are to weigh 50mg-70mg of catalyst sample and place it on the sample table, set the degassing temperature to 120℃, and the degassing time to 7h. Fig.11 and Fig.12 As shown, Fig.11The CO2 isothermal adsorption and desorption of commercial indium oxide. Fig.12 Isothermal adsorption and desorption of indium oxide catalyst used for carbon dioxide conversion.

[0075] See also Fig.11 and Fig.12 It can be seen that the maximum adsorption of carbon dioxide by commercial indium oxide is 0.83cc / g, while the maximum adsorption of carbon dioxide by the indium oxide for carbon dioxide conversion prepared by the present invention is 5.68cc / g, which is much higher than that of commercial indium oxide. This shows that the indium oxide catalyst for carbon dioxide conversion prepared by the present invention has a better adsorption capacity for carbon dioxide, which is beneficial to the catalytic conversion of carbon dioxide.

[0076] Experiment 6: Catalytic activity of different catalysts Test samples: commercial indium oxide, and the indium oxide catalyst for carbon dioxide conversion prepared in Example 1.

[0077] 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 300mm, an inner diameter of 15mm, and an outer diameter of 18mm. A stainless steel electrode rod with a length of 150mm and a diameter of 13mm is placed inside the quartz tube along the axis of the quartz tube, and it is applied to a high-voltage power supply. A stainless steel mesh with a length of 100mm×120mm is wrapped around the outside of the quartz tube as a grounding electrode. Its discharge gap is 1mm and the discharge length is 120mm. The reaction gas in the test process is high-purity carbon dioxide gas. After the flow rate is controlled by a pressure regulating 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 supply, and a TM10 oscilloscope is used to measure the plasma power. The reaction gas passes through a GC9790Ⅱ gas chromatograph, and a thermal conductivity detector (TCD) is used to determine the gas products after the reaction. Weigh 0.2g of commercial indium oxide and the indium oxide catalyst for carbon dioxide conversion prepared in Example 1, respectively, and place them in the DBD reactor by IPC method, control the flow rate to 20ml / min, and adjust the energy density SIE to 105KJ / L, 145KJ / L, 190KJ / L and 230KJ / L by changing the input power (35W-80W). The conversion results are compared with those of an empty DBD reactor without a catalyst. The results are as follows: Fig.13 and Fig.14 shown.

[0078] in: SIE is the energy density, unit is KJ / L; Input power is the input power, in W; F CO2in is the CO2 inlet flow rate, in mL / min.

[0079] See also Fig.13 and Fig.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 the input voltage of the DBD system is increased, so that the system is filled with more high-energy electrons, which increases the collision probability between carbon dioxide and high-energy electrons, thereby improving the conversion efficiency of carbon dioxide. The carbon dioxide conversion rate and carbon monoxide yield of the catalyst-filled DBD are 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, which can reach 29.7% and 24.5%, respectively. Compared with the empty DBD without catalyst, its catalyst effect is relatively improved by about 50.7%. This is because the indium oxide catalyst for carbon dioxide conversion has a higher specific surface area, more volume oxygen vacancies and better carbon dioxide adsorption capacity, which are all conducive to its catalytic conversion of carbon dioxide.

[0080] The energy efficiency was measured as Fig.15 As shown in the figure, with the increase of SIE, the energy efficiency of the reaction system shows a trend of first increasing and then decreasing, and reaches the maximum value when SIE is 145KJ / L. At low power, with the increase of input power, the electric field intensity in the discharge area increases, the density of activated particles and high-energy electrons in the system also increases, and the probability of CO2 molecules being bombarded by high-energy electrons in the plasma area also increases, thereby increasing the conversion rate of CO2 and the energy efficiency of the system.

[0081] Test 7: Traffic Impact Sample: Indium oxide catalyst for carbon dioxide conversion prepared in Example 1.

[0082] 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 300mm, an inner diameter of 15mm, and an outer diameter of 18mm. A stainless steel electrode rod with a length of 150mm and a diameter of 13mm is placed inside the quartz tube along the axis of the quartz tube, and it is applied to a high-voltage power supply. A stainless steel mesh with a length of 100mm×120mm is wrapped around the outside of the quartz tube as a grounding electrode. Its discharge gap is 1mm and the discharge length is 120mm. The reaction gas in the experimental process is high-purity carbon dioxide gas. After the flow rate is controlled by a pressure regulating 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 supply, and a TM10 oscilloscope is used to measure the plasma power. The reaction gas passes through a GC9790Ⅱ gas chromatograph, and a thermal conductivity detector (TCD) is used to determine the gas products after the reaction. 0.4 g of the indium oxide catalyst prepared in Example 1 for conversion with carbon dioxide was weighed and placed in a DBD reactor using the IPC method. The input power was set to 35 W, and the flow rates were set to 20 mL / min, 40 mL / min, 60 mL / min, and 80 mL / min, respectively. Fig.16 shown.

[0083] from Fig.16 It can be observed that as the flow rate of carbon dioxide decreases, the residence time of carbon dioxide in the DBD system increases, and 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, thereby improving the degradation efficiency; however, the reaction time will increase as the flow rate decreases. Therefore, considering all factors, the optimal carbon dioxide inlet flow rate is 20mL / min.

[0084] Test 8, Catalyst dosage Sample: Indium oxide catalyst for carbon dioxide conversion prepared in Example 1.

[0085] 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 300mm, an inner diameter of 15mm, and an outer diameter of 18mm. A stainless steel electrode rod with a length of 150mm and a diameter of 13mm is placed inside the quartz tube along the axis of the quartz tube, and it is applied to a high-voltage power supply. A stainless steel mesh with a length of 100mm×120mm is wrapped around the outside of the quartz tube as a grounding electrode. Its discharge gap is 1mm and the discharge length is 120mm. The reaction gas in the test process is high-purity carbon dioxide gas. After the flow rate is controlled by a pressure regulating 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 supply, and a TM10 oscilloscope is used to measure the plasma power. The reaction gas passes through a GC9790Ⅱ gas chromatograph, and a thermal conductivity detector (TCD) is used to determine the gas products after the reaction. 0.2 g, 0.4 g, 0.6 g and 0.8 g of the indium oxide catalyst for carbon dioxide conversion prepared in Example 1 were respectively weighed and placed in the DBD reactor by the IPC method. The flow rate was controlled to be 20 mL / min. The energy density SIE was adjusted to 102 KJ / L, 145 KJ / L, 190 KJ / L and 230 KJ / L by changing the input power (35 W-80 W). The results are as follows: Fig.17 , Fig.18 and Fig.19 shown.

[0086] in: SIE is the energy density, unit is KJ / L; Input power is the input power, in W; F CO2in is the CO2 inlet flow rate, in mL / min.

[0087] from Fig.17 , Fig.18 and Fig.19 It can be seen that with the decrease in the amount of catalyst, the carbon dioxide conversion rate and CO yield of the DBD system are improved at each SIE, and the maximum value appears when the catalyst dosage is 0.2g. At the highest SIE, the carbon dioxide conversion rate can reach 29.7%, and the CO yield can reach 24.5%. Compared with the empty DBD without catalyst in test 6, its catalytic effect is relatively improved by 50.7%, which is much better than the empty DBD under the same conditions. It shows that the combination of the indium oxide catalyst for carbon dioxide conversion prepared by the present invention and the DBD reactor can greatly improve the conversion rate of carbon dioxide and the selectivity of carbon monoxide.

[0088] Test 9: Regeneration Experimental instruments and steps: The test instrument is a homemade 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. A stainless steel electrode rod with a length of 150 mm and a diameter of 13 mm is placed inside the quartz tube along the axis of the quartz tube, and it is applied to a high-voltage power supply. A stainless steel mesh with a length of 100 mm × 120 mm is wrapped around the outside of the quartz tube as a grounding electrode. Its 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 regulating 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. Weigh 0.4 g of the indium oxide catalyst for carbon dioxide conversion prepared in Example 1 and place it in the DBD reactor by the built-in method. Set the input power to 35 W and the gas flow rate to 20 mL / min. Record the change in CO2 conversion rate over time. The results are as follows: Fig. 20 shown.

[0089] Fig. 20 It shows that the conversion rate of carbon dioxide gradually increases with the extension of reaction time, which indicates 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, and an increase in the specific surface area and carbon dioxide capture capacity. This enhances the ability to capture carbon dioxide, thereby improving the catalytic conversion capacity. At the same time, it can be observed that the conversion rate of carbon dioxide tends to stabilize after 1 hour and remains stable after 2 hours. Subsequently, the indium oxide catalyst for carbon dioxide conversion was re-treated at a voltage of 160V and in an air atmosphere for 20 minutes.

[0090] The regenerated catalyst was then retested for CO2 conversion at a constant CO2 flow rate of 35W and 20mL / 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 of indium oxide is 9.3eV, the DBD dielectric barrier discharge reactor produces high-energy electrons with an average electron energy of 1eV-10eV. These electrons can bombard the In-O bonds in the catalyst, resulting in the reappearance of oxygen vacancies. This shows that the indium oxide catalyst for carbon dioxide conversion prepared by the present invention can be regenerated under DBD treatment, which not only shows that the indium oxide catalyst itself is regenerable, but also that the regeneration can be completed in the conversion system, and the regeneration method is simpler.

[0091] In summary, the schematic diagram of CO2 conversion in a low-temperature plasma reactor is as follows: Fig.21As shown. Carbon dioxide is split into CO and O radicals after being bombarded by high-energy electrons in the DBD system, and then the unstable oxygen radicals combine in pairs to generate O2. The DBD filled with alkali metal oxide In2O3 shows better CO2 conversion performance than the unfilled DBD, which shows that there is a synergistic effect between DBD and the catalyst. Therefore, the catalyst plays a vital role in the conversion of CO2 in DBD plasma. This is because the CO2 conversion process in the DBD plasma reactor filled with catalyst is greatly affected by the discharge characteristics and surface reactions of the catalyst. Therefore, in the DBD system filled with indium oxide for carbon dioxide conversion prepared by the present invention, its energy efficiency is higher than that of the empty DBD under the same SIE, which shows that the plasma with catalyst produces more high-energy electrons, thereby promoting the CO2 conversion process. In2O3, which has a high specific surface area and a large number of oxygen vacancies, can capture CO2 molecules. CO2 molecules are adsorbed at the oxygen vacancies on the catalyst. The high-energy electrons generated by DBD bombard the CO2 molecules, breaking their double bonds and generating CO and O free radicals. CO is desorbed on the catalyst surface, and the generated O free radicals fill the oxygen vacancies of the catalyst to reduce the catalyst. Finally, the oxygen atoms in the DBD plasma can recombine with the oxygen on the catalyst to form O2, which is desorbed from the catalyst and reforms the oxygen vacancies.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention is described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing an indium oxide catalyst for carbon dioxide conversion, characterized in that: The following steps are involved: S1. Preparation of indium oxide precursor An indium oxide precursor is prepared by a precipitation method using indium nitrate as a raw material; 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.

2. The method for preparing an indium oxide catalyst for carbon dioxide conversion according to claim 1, characterized in that: 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. Calcine the intermediate product to obtain an indium oxide precursor.

3. The method for preparing an indium oxide catalyst for carbon dioxide conversion according to claim 2, 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.

4. The method for preparing an indium oxide catalyst for carbon dioxide conversion according to claim 2, 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.

5. An indium oxide catalyst for carbon dioxide conversion prepared by the method for preparing an indium oxide catalyst for carbon dioxide conversion according to claim 1.

6. The indium oxide catalyst for carbon dioxide conversion according to claim 5, characterized in that: The average crystal size of the indium oxide catalyst is 17 nm, and the maximum specific surface area is 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.

7. Use of the indium oxide catalyst for carbon dioxide conversion as claimed in claim 5 in improving the conversion rate of carbon dioxide to carbon monoxide.

8. 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, wherein the catalyst is an indium oxide catalyst prepared by the method for preparing an indium oxide catalyst for carbon dioxide conversion according to claim 1; 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.

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