Cobalt-doped calcium lanthanum ferrite perovskite-type photo-thermal catalyst, and preparation method and application thereof

Abstract

The application discloses a cobalt-doped lanthanum ferrite perovskite type photo-thermal catalyst and a preparation method and application thereof, and relates to the technical field of photo-thermal catalysis. The preparation method of the cobalt-doped lanthanum ferrite perovskite type photo-thermal catalyst comprises the following steps: mixing metal salts and water until uniform to obtain a metal salt solution, wherein the metal salts are a mixture of a lanthanum source, an iron source and a cobalt source; mixing all the metal salt solution and a metal chelating agent until uniform to obtain a precursor solution; stirring the precursor solution at 70-80 DEG C until the precursor solution is in a gel state, drying, calcining at 800-850 DEG C, and cooling to room temperature to obtain the cobalt-doped lanthanum ferrite perovskite type photo-thermal catalyst. The cobalt-doped lanthanum ferrite perovskite type photo-thermal catalyst has a toluene removal rate of more than 95% under photo-thermal catalysis at 250 DEG C, has water resistance and thermal stability, and has the ability to resist the influence of impurity gases under complex working conditions.

Description

Technical Field

[0001] This invention belongs to the field of perovskite metal oxide catalyst technology, specifically relating to a cobalt-doped lanthanum ferrite perovskite photothermal catalyst, its preparation method, and its application. Background Technology

[0002] With the strengthening of green and environmental protection policies and the increasing public awareness of improving air quality, air pollution and its prevention and control measures have attracted widespread attention worldwide. Volatile organic compounds (VOCs) in the environment are easily volatilized at room temperature and are characterized by their diversity, high toxicity, and wide diffusion range. In particular, they pose a direct threat to human health by causing cancer, birth defects, and mutations. Toluene, as a typical VOC, is prone to forming secondary pollutants due to its unusually stable aromatic ring structure. It exhibits significant carcinogenicity and neurotoxicity and has always been a focus of attention in the field of VOCs treatment. Therefore, controlling toluene emissions has a profound impact on regional air quality, climate change, and even the stability of the entire ecosystem.

[0003] Currently, there are numerous methods for eliminating toluene, among which thermocatalysis and photocatalysis are widely used. However, thermocatalysis alone still faces problems such as high operating costs and poor resistance to water and sulfur. Traditional photocatalysis requires high-energy ultraviolet light to drive catalysis, but ultraviolet light only accounts for a small portion of the solar spectrum, resulting in low light energy utilization. Furthermore, most current catalysts are susceptible to the influence of complex waste gas components under actual operating conditions, making it crucial to improve the catalyst's resistance to high humidity environments and other toxic gases. Therefore, designing a photothermal catalyst with a wider spectral response range, while simultaneously promoting the adsorption and activation of toluene on the catalyst surface, is particularly important for improving catalytic performance under complex operating conditions. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing a cobalt-doped lanthanum ferrite perovskite-type photothermal catalyst.

[0005] Another object of the present invention is to provide a cobalt-doped lanthanum ferrite perovskite photothermal catalyst (LaCo) obtained by the above preparation method. x Fe 1-x O3).

[0006] Another object of the present invention is to provide the application of the above-mentioned cobalt-doped lanthanum ferrite perovskite photothermal catalyst in the removal of toluene.

[0007] The objective of this invention is achieved through the following technical solution.

[0008] A method for preparing a cobalt-doped lanthanum ferrite perovskite-type photothermal catalyst includes the following steps:

[0009] Step 1: Mix the metal salt and water until homogeneous to obtain a metal salt solution, wherein the metal salt is a mixture of lanthanum source, iron source and cobalt source;

[0010] In step 1, the lanthanum source is lanthanum nitrate hexahydrate, the iron source is ferric nitrate nonahydrate, and the cobalt source is cobalt nitrate hexahydrate.

[0011] In step 1, the ratio of the molar amount of lanthanum to the volume amount of water in the lanthanum source is 5: (80~100), with the molar amount in mmol and the volume amount in mL.

[0012] Step 2: Mix all the metal salt solutions and metal chelating agents until homogeneous to obtain a precursor solution. Stir the precursor solution at 70~80℃ until it becomes a gel state, dry it, calcine it at 800~850℃ for 3~3.5h, and cool it to room temperature to obtain a cobalt-doped lanthanum ferrite perovskite type photothermal catalyst.

[0013] Based on the molar amounts of substances, the ratio of lanthanum in the lanthanum source, cobalt in the cobalt source, iron in the iron source, and metal chelating agent is 1:x:(1-x):2.5, where x = 0.1~0.5.

[0014] In step 2, the metal chelating agent is citric acid monohydrate.

[0015] In step 2, the precursor solution is stirred at 70-80°C for 7-8 hours until it reaches a gel state.

[0016] In step 2, the drying temperature is 110~120℃ and the drying time is 10~12h.

[0017] The cobalt-doped lanthanum ferrite perovskite photothermal catalyst obtained by the above preparation method.

[0018] The application of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst in the removal of toluene.

[0019] In the above technical solution, a cobalt-doped lanthanum ferrite perovskite photothermal catalyst is used to catalyze the oxidation of toluene and its degradation into carbon dioxide.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. Compared with lanthanum ferrite perovskite catalysts, the cobalt-doped lanthanum ferrite perovskite photothermal catalyst of the present invention has stronger catalytic reduction and photoresponsiveness, which is beneficial to the adsorption and activation of toluene.

[0022] 2. The cobalt-doped lanthanum ferrite perovskite photothermal catalyst of the present invention achieves a toluene removal rate of over 95% under photothermal catalysis at 250°C.

[0023] 3. The cobalt-doped lanthanum ferrite perovskite photothermal catalyst of the present invention has water resistance and thermal stability, as well as the ability to resist the influence of impurity gases under complex working conditions. Attached Figure Description

[0024] Figure 1 XRD patterns of the cobalt-doped lanthanum ferrite perovskite photothermal catalysts prepared in Examples 1-4 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1;

[0025] Figure 2 The TEMs are as follows: (a) is the TEM of the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1, and (b) is the TEM of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3.

[0026] Figure 3 EDS elemental mapping diagram of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3, where (i) is the La elemental distribution, (ii) is the Fe elemental distribution, (iii) is the Co elemental distribution, and (iv) is the O elemental distribution;

[0027] Figure 4 The X-ray photoelectron spectra of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 are shown, where (a) is a high-resolution La 3d spectrum, (b) is a high-resolution O 1s spectrum, (c) is a high-resolution Fe 2p spectrum, and (d) is a high-resolution Co 2p spectrum.

[0028] Figure 5 H2-TPR spectra of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1.

[0029] Figure 6 O2-TPD spectra of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1.

[0030] Figure 7 The photocurrent response spectra of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 are shown.

[0031] Figure 8 The toluene temperature-programmed desorption curves are shown for the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1.

[0032] Figure 9The toluene removal rates of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 are shown. (a) represents the toluene removal rate under thermal catalysis and photothermal catalysis at T℃ = 225℃, and (b) represents the toluene removal rate under thermal catalysis and photothermal catalysis at T℃ = 250℃.

[0033] Figure 10 Toluene removal rates under different temperatures were measured for the cobalt-doped lanthanum ferrite perovskite photothermal catalysts prepared in Examples 1-4 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1.

[0034] Figure 11 The toluene removal rates of the cobalt-doped lanthanum ferrite perovskite photothermal catalysts prepared in Examples 1-4 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 under photothermal catalysis at different temperatures are shown.

[0035] Figure 12 The carbon dioxide generation rates of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 at different temperatures were compared.

[0036] Figure 13 The result of the loop test;

[0037] Figure 14 This is the result of the water resistance stability test. Detailed Implementation

[0038] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0039] The information on the pharmaceuticals involved in the following examples and comparative examples is as follows: Lanthanum nitrate hexahydrate (La(NO3)3·6H2O, analytical grade), ferric nitrate nonahydrate (Fe(NO3)3·9H2O, analytical grade), cobalt nitrate hexahydrate (Co(NO3)2·6H2O, analytical grade), and citric acid monohydrate (C6H8O7·H2O, analytical grade) were all purchased from Shanghai E. En Chemical Technology Co., Ltd.

[0040] The following information pertains to the gases used in the examples and comparative examples: toluene (C7H8) concentration was 1000 ppm, oxygen (O2) purity was 99.999%, and nitrogen (N2) purity was 99.999%. Toluene, oxygen, and nitrogen were all purchased from Shijiazhuang Xisanjiao Practical Gas Co., Ltd.

[0041] The simplified atmospheric pressure photothermal synergistic fixed-bed reactor was purchased from Hunan Huasi Instrument Co., Ltd., model number PDF-500.

[0042] In the following examples and comparative examples, the water used is deionized water.

[0043] Examples 1-4

[0044] A method for preparing a cobalt-doped lanthanum ferrite perovskite-type photothermal catalyst includes the following steps:

[0045] Step 1: Mix the metal salt and water until homogeneous to obtain a metal salt solution. The metal salt is a mixture of lanthanum source, iron source and cobalt source. The molar ratio of lanthanum to water in the lanthanum source is 5:100. The molar ratio is in mmol and the volume ratio is in mL. The lanthanum source is lanthanum nitrate hexahydrate, the iron source is ferric nitrate nonahydrate, and the cobalt source is cobalt nitrate hexahydrate. The process of mixing the metal salt and water until homogeneous includes: mixing the lanthanum source and water, stirring at 400 r / min at room temperature until homogeneous, then adding the cobalt source and iron source sequentially, and stirring at 400 r / min at room temperature until homogeneous to obtain the metal salt solution.

[0046] Step 2: Mix all the metal salt solutions and metal chelating agent (citric acid monohydrate) from Step 1 until homogeneous (add citric acid monohydrate to the metal salt solutions while stirring at 400 rpm) to obtain a precursor solution. Stir the precursor solution at 70°C for 8 hours until it reaches a gel state. Dry it in a 120°C electric thermostatic drying oven for 10 hours. Then, place it in a muffle furnace and dry it at 5°C for 1 minute. -1 The temperature was increased to 800℃ and calcined at 800℃ for 3 hours, then cooled to room temperature to obtain a cobalt-doped lanthanum ferrite perovskite photothermal catalyst.

[0047] The ratio of lanthanum in the lanthanum source, cobalt in the cobalt source, iron in the iron source, and metal chelating agent, based on molar amounts, is 1:x:(1-x):2.5. The value of x is shown in Table 1.

[0048] Table 1

[0049]

[0050] Comparative Example 1

[0051] A method for preparing a lanthanum ferrite perovskite catalyst (LaFeO3) is basically the same as that in Example 4, except that no cobalt source is added, and in Comparative Example 1, the ratio of lanthanum in the lanthanum source, iron in the iron source, and metal chelating agent by molar amount is 1:1:2.5.

[0052] The XRD patterns of the cobalt-doped lanthanum ferrite perovskite photothermal catalysts prepared in Examples 1-4 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 are as follows: Figure 1 As shown, by Figure 1It can be seen that the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 has different exposed crystal planes and is consistent with the standard card 37-1493 of LaFeO3, and the phase structure is a Pnma orthorhombic crystal system. When Co is doped, the XRD patterns of the cobalt-doped lanthanum ferrite perovskite photothermal catalysts prepared in Examples 1-4 do not show obvious phase changes. The (121) crystal plane peak at the 32-33° diffraction angle shifts to a higher angle, which indicates that the Co species are successfully doped into the lattice without changing the phase structure of the lanthanum ferrite perovskite.

[0053] TEM images of the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 are shown below. Figure 2 As shown in (a), the TEM image of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 is as follows. Figure 2 As shown in (b). By Figure 2 As shown in (a), the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 exhibits a sharply defined, irregular polyhedral structure, reflecting typical perovskite oxide crystal growth characteristics. Figure 2 As can be seen from (b), the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 has a more rounded profile than that of Comparative Example 1, with no obvious sharp edges, confirming that cobalt doping changes the growth direction of the crystal and causes lattice distortion.

[0054] The EDS elemental mapping diagram of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 is shown below. Figure 3 As shown, Figure 3 In Example 3, elements (i) to (iv) correspond to La, Fe, Co, and O, respectively. The results confirm that La, Fe, Co, and O are uniformly distributed in Example 3. The EDS elemental mapping of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 is shown below. Figure 1 The results were consistent, confirming that the cobalt species were successfully doped and that all elements were evenly distributed.

[0055] The X-ray photoelectron spectra of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 are as follows: Figure 4 As shown, by Figure 4 As shown in (a), the high-resolution La3d spectra of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 are not significantly different from those of the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1, both exhibiting clearly separated spin-orbit splitting peaks in La3d. 3 / 2 and La 3d 5 / 2 ;Depend on Figure 4As shown in (b), the high-resolution O 1s spectra of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 were both deconvolved into two characteristic peaks. The peaks at 531.8 eV and 529.5 eV were attributed to adsorbed oxygen and lattice oxygen, respectively. Furthermore, the integral area ratio of the lattice oxygen peak in the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 was smaller than that in Comparative Example 1, indicating that the exchange of electrons between cobalt and iron is balanced by the generation of oxygen vacancies. Figure 4 As can be seen from (c), in the high-resolution Fe 2p spectra of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1, the Fe 2p peak at the spin orbital splitting peak is... 1 / 2 and Fe 2p 3 / 2 Satellite peaks appeared in both directions. Figure 4 In (c) "Satellite", and the satellite peak of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 is wider; by Figure 4 As can be seen from (d), in the high-resolution Co 2p spectra of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1, the spin orbital splitting peak Co 2p is present. 1 / 2 and Co 2p 3 / 2 Satellite peaks appeared in both directions. Figure 4 The satellite peak of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 is wider than that of the satellite peak, indicating that there is an interaction between cobalt atoms and iron atoms.

[0056] The effect of cobalt doping on the reducibility of cobalt-doped lanthanum ferrite perovskite photothermal catalyst was further evaluated using hydrogen temperature-programmed reduction (H2-TPR) testing (lanthanum atoms are hardly reduced below 1000℃, so only the reduction processes of iron and cobalt ions are discussed). Specifically, 80 mg of sample was weighed and placed in a U-shaped quartz tube, dried by heating from room temperature to 200℃ at a rate of 10℃ / min, then helium gas (50 mL / min) was introduced at 200℃ and purged for 1 h, cooled to 50℃, and then a first mixed gas was introduced at 50℃ at a rate of 50 mL / min for 0.5 h (without purging) until the baseline stabilized. The first mixed gas was then introduced at a rate of 50 mL / min (without purging), and the temperature was increased from 50℃ to 700℃ at a rate of 10℃ / min for hydrogen temperature-programmed reduction testing. The entire hydrogen temperature-programmed reduction test was conducted using an AutoChem II thermocouple equipped with a thermal conductivity detector (TCD). The intensity of the TCD response signal corresponding to the reducing gas (hydrogen) in the exhaust gas was detected using a 2920 chemisorption analyzer (Micromeritics). The intensity of the TCD response signal reflects the degree of hydrogen consumption during the reduction process. The test results are as follows: Figure 5 As shown. The first mixed gas is a mixture of hydrogen and argon, with a volume ratio of hydrogen to argon of 10:90. The sample is one of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1.

[0057] Depend on Figure 5 It can be seen that the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 exhibits a significant H2 consumption peak at around 392℃, while the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 exhibits an H2 consumption peak at around 442℃. This indicates that Example 3 has a lower reduction temperature compared to Comparative Example 1. It can be considered that moderate Co doping effectively improves the reduction performance of the catalyst and increases the lattice oxygen (O2) content. latt The cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 has a much larger peak area in the 100~500℃ range than Comparative Example 1, meaning that the H2 consumption is much greater than that of Comparative Example 1. This indicates that the cobalt-doped lanthanum ferrite perovskite photothermal catalyst has more active sites and stronger catalytic reduction ability.

[0058] The oxygen release capability of the crystal lattice was further evaluated by oxygen-programmed temperature desorption (O2-TPD) testing. Specifically, 80 mg of sample was placed in a U-shaped quartz tube and dried by heating from room temperature to 200 °C at a rate of 10 °C / min. Helium gas was then introduced at 200 °C at a rate of 50 mL / min and purged for 1 hour. The sample was then cooled to 50 °C, and a second mixed gas was introduced at 50 °C at a rate of 50 mL / min for 1 hour (without purging) to allow the sample to adsorb oxygen to saturation. The He gas flow was then switched, and helium gas was introduced again at 50 °C (50 mL / min) and purged for 1 hour to remove weakly adsorbed physical oxygen. Finally, helium gas was introduced again at a rate of 50 mL / min and purged, and the temperature was increased to 700 °C at a rate of 10 °C / min for oxygen-programmed temperature desorption testing. The entire oxygen-programmed temperature desorption test was conducted in an AutoChem II crystal oscillator equipped with a TCD. The intensity of the TCD response signal corresponding to the desorbed oxygen was detected on a 2920 chemisorption analyzer (Micromeritics). The intensity of the TCD response signal reflects the degree of oxygen desorption. The test results are as follows: Figure 6 As shown. The second mixed gas is a mixture of oxygen and helium, with a volume ratio of oxygen to helium of 10:90. The sample is one of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1.

[0059] Depend on Figure 6 It can be seen that both the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 exhibit two characteristic desorption ranges: 100~200℃ corresponds to adsorbed oxygen desorption, and 300~500℃ corresponds to lattice oxygen desorption. The initial desorption temperature of adsorbed oxygen in the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 (87℃) is lower than that in Comparative Example 1 (137℃), and the initial desorption temperature of lattice oxygen in the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 (346℃) is also lower than that in Comparative Example 1 (363℃). This indicates that cobalt doping lowers the desorption temperature of adsorbed oxygen and lattice oxygen, making oxygen species easier to activate and migrate. The above results are consistent with... Figure 5 The results were consistent: cobalt doping is beneficial to the adsorption and activation of oxygen molecules.

[0060] Photocurrent response testing is an important means of evaluating the photoelectric properties and charge separation efficiency of materials. Using a DH7003 electrochemical workstation, photocurrent response testing was performed using a three-electrode system, which included a working electrode, a counter electrode (platinum sheet), and a reference electrode (Ag / AgCl electrode). The method for preparing the working electrode included: weighing 2 mg of sample and dissolving it in 1 mL of dispersion (1 mL of dispersion was obtained by mixing 0.68 mL of ultrapure water, 0.3 mL of anhydrous ethanol, and 0.02 mL of 5 wt% Nafion perfluorinated resin solution (Shanghai Xushuo Biotechnology Co., Ltd.)) to obtain a slurry. 16 μL of the slurry was coated onto a fluorine-doped tin oxide transparent glass conductive substrate (2.5 cm long and 1 cm wide) to form the working electrode. The sample was one of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1. The three-electrode system was placed in an electrolyte solution, using a sodium sulfate aqueous solution (Na₂SO₄ concentration of 0.5M). The sodium sulfate aqueous solution was added enough to submerge the three-electrode system. The photocurrent response test employed a cyclical pattern of "lamp off for 30 seconds - lamp on for 30 seconds," repeated five times. At the end of the test, the lamp was turned off and reset. The lamp used was a xenon lamp equipped with an ultraviolet filter (luminous intensity of 800 mW / cm²). 2 A xenon lamp was used to simulate sunlight irradiation of the working electrode, with a distance of 20 cm between the lamp and the electrode. Changes in current density were observed, and the results are as follows: Figure 7 As shown.

[0061] Depend on Figure 7 It can be seen that, compared with Comparative Example 1, Example 3 exhibits a higher and more stable instantaneous current response, indicating that the free electrons generated in Example 3 after being exposed to light can act on the catalyst surface, resulting in higher charge separation efficiency and electron mobility.

[0062] The toluene adsorption capacity of a catalyst is another important factor affecting its catalytic performance. Toluene adsorption capacity was characterized by a temperature-programmed desorption (TPD) test. The specific steps included: weighing 80 mg of sample and placing it in a U-shaped quartz tube; drying the sample by heating it from room temperature to 200 °C at a rate of 10 °C / min; purging with helium at 30 mL / min for 1 h at 200 °C; cooling to 50 °C; and then purging with a third mixed gas at 30 mL / min for 1 h at 50 °C (without purging) to saturate the sample with toluene adsorption. The He gas flow was then switched, and helium was again purged at 50 °C (30 mL / min) for 1 h to remove weakly adsorbed physical toluene. Finally, helium was continuously purged at 50 mL / min, and the temperature was increased to 800 °C at a rate of 10 °C / min for the TPD desorption test. The entire TPD desorption test was performed using an AutoChem II thermocouple equipped with a TCD. The intensity of the TCD response signal corresponding to the desorbed toluene was detected using a 2920 chemisorption analyzer (Micromeritics). The results are as follows: Figure 8 As shown. The third mixed gas is a mixture of toluene and helium, with a volume ratio of toluene to helium of 10:90. The sample is one of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1.

[0063] Depend on Figure 8 It can be seen that both the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 exhibit two significant characteristic peaks near 100℃ and 450℃, corresponding to the physical adsorption-desorption peak and the chemical adsorption-desorption peak, respectively. The intensities of both the physical adsorption-desorption peak and the chemical adsorption-desorption peak of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 are significantly higher than those in Comparative Example 1. Figure 8 The toluene temperature-programmed desorption curve was integrated to quantitatively analyze the physical and chemical adsorption amounts of toluene on the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1. The physical adsorption amount of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 was 0.021 mmol g. -1 The chemisorption capacity was 0.129 mmol g. -1 The physical adsorption capacity of the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 was 0.01 mmol g. -1 The chemisorption capacity was 0.058 mmol g. -1 This indicates that the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 greatly promoted the adsorption and activation of toluene.

[0064] Performance testing of thermocatalytic oxidation of toluene: 50 mg of sample was placed in a photothermal quartz tube with a 13 mm × 13 mm square window. The photothermal quartz tube was placed in a simple atmospheric pressure photothermal synergistic fixed-bed reactor. Reaction gas was introduced into the simple atmospheric pressure photothermal synergistic fixed-bed reactor, and the heating program was started to raise the temperature of the simple atmospheric pressure photothermal synergistic fixed-bed reactor to T℃ (heating rate of 10℃ / min). The reaction gas was allowed to react with the sample, and the reaction tail gas was directly connected to the gas chromatograph injection port for detection. The concentrations of toluene and carbon dioxide in the reaction tail gas were collected after 30 min of reaction gas introduction. The toluene removal rate (toluene removal rate under thermocatalysis) and carbon dioxide generation rate were then obtained, and the reaction temperature (T℃) at which the toluene removal rate reached 90% was recorded. 90% (°C)

[0065] Performance test of photothermal catalytic oxidation of toluene: 50 mg of sample was placed in a photothermal quartz tube with a square window of 13 mm × 13 mm. The photothermal quartz tube was placed in a simple atmospheric pressure photothermal synergistic fixed-bed reactor. Reactive gas was introduced into the simple atmospheric pressure photothermal synergistic fixed-bed reactor, and the heating program was started to heat the simple atmospheric pressure photothermal synergistic fixed-bed reactor to T℃ (heating rate of 10℃ / min). At the same time as heating, light was applied to the sample through the square window (the light was provided by a xenon lamp equipped with an ultraviolet filter (cutoff wavelength of 380 nm) to filter out ultraviolet light, retaining only visible and infrared light to simulate sunlight, with a light intensity of 800 mW / cm²). 2 The reaction gas was passed through the sample to react, and the reaction tail gas was directly connected to the gas chromatograph inlet for detection. The concentrations of toluene and carbon dioxide in the reaction tail gas were collected after 30 minutes of reaction gas introduction. The toluene removal rate (toluene removal rate under photothermal catalysis) and carbon dioxide generation rate were then obtained, and the reaction temperature (T) at which the toluene removal rate reached 90% was recorded. 90% (°C)

[0066] In the performance tests of thermocatalytic oxidation of toluene and photocatalytic oxidation of toluene, the method for obtaining samples included: placing the catalyst (powder) in a tablet press, holding it at 5 MPa for 30 s, crushing it, and sieving it to obtain particles of 40-60 mesh size as samples. The catalyst was one of the cobalt-doped lanthanum ferrite perovskite photothermal catalysts prepared in Examples 1-4 and the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1. The reaction gas was a mixture of toluene, oxygen, and nitrogen (used as a balance gas), with an oxygen volume fraction of 20%, a toluene concentration of 1000 ppm, a total flow rate of 40 mL / min, and a controlled reaction space velocity (GHSV) of 48,000 mL g. -1 h -1In the thermocatalytic oxidation of toluene performance test, when the catalyst was the lanthanum ferrite perovskite type catalyst prepared in Comparative Example 1, T℃ = 100℃, 150℃, 200℃, 225℃, 250℃, 275℃, 300℃, 325℃, or 350℃; when the catalyst was the cobalt-doped lanthanum ferrite perovskite type photothermal catalyst prepared in Example 1, T℃ = 100℃, 150℃, 200℃, 225℃, 250℃, 275℃, 300℃, or 325℃; when the catalyst was the cobalt-doped lanthanum ferrite perovskite type photothermal catalyst prepared in Examples 2-4, T℃ = 100℃, 150℃, 200℃, 225℃, 250℃, 275℃, or 300℃. In the performance test of photothermal catalytic oxidation of toluene, when the catalyst is the lanthanum ferrite perovskite type catalyst prepared in Comparative Example 1 or the cobalt-doped lanthanum ferrite perovskite type photothermal catalyst prepared in Example 1, T℃ = 100℃, 150℃, 200℃, 225℃, 250℃, 275℃, 300℃, or 325℃; when the catalyst is the cobalt-doped lanthanum ferrite perovskite type photothermal catalyst prepared in Examples 2-4, T℃ = 100℃, 150℃, 200℃, 225℃, 250℃, or 275℃.

[0067] The formula for calculating the toluene removal rate is: Toluene removal rate (%) = The toluene concentration at the inlet is the same as the toluene concentration in the reaction gas (ppm), and the toluene concentration at the outlet is the same as the toluene concentration in the reaction tail gas (ppm).

[0068] The formula for calculating the carbon dioxide formation rate is: Carbon dioxide formation rate (%) = The carbon dioxide concentration at the outlet is the same as the carbon dioxide concentration in the reaction tail gas (ppm), and the toluene concentration at the inlet is the same as the toluene concentration in the reaction gas (ppm).

[0069] The temperatures at which the toluene removal rate under thermal catalysis reaches 90% are shown in Table 2.

[0070] Table 2

[0071]

[0072] The temperatures at which the toluene removal rate under photothermal catalysis reaches 90% are shown in Table 3.

[0073] Table 3

[0074]

[0075] When T℃ = 225℃, the toluene removal rate under thermocatalysis corresponding to the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 is ( Figure 9(a) “Example 3 Thermal Catalysis” and toluene removal rate under photothermal catalysis ( Figure 9 (a) “Example 3 Photothermal Catalysis” and the toluene removal rate under thermal catalysis corresponding to the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 ( Figure 9 (a) "Comparative Example 1 Thermocatalysis") and toluene removal rates under photothermal catalysis ( Figure 9 (a) “Comparative Example 1 Photothermal Catalysis” was drawn in Figure 9 (a). When T℃ = 250℃, the toluene removal rate under thermocatalysis corresponding to the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 ( Figure 9 (b) “Example 3 Thermal Catalysis” and toluene removal rate under photothermal catalysis ( Figure 9 (b) "Example 3 Photothermal Catalysis" and the toluene removal rate under thermal catalysis corresponding to the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 ( Figure 9 (b) "Comparative Example 1 Thermocatalysis" and photothermal catalysis toluene removal rate ( Figure 9 (b) “Comparative Example 1 Photothermal Catalysis” was drawn in Figure 9 (b). For example Figure 9 As shown in (a), at 225°C, the toluene removal rate under photothermal catalysis of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 was 57% higher than that under thermal catalysis. In contrast, the toluene removal rate under photothermal catalysis of the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 was only 9% higher than that under thermal catalysis. This indicates that the cobalt-doped lanthanum ferrite perovskite photothermal catalyst exhibits strong photoresponse characteristics at low temperatures. Figure 9 As shown in (b), at 250°C, the toluene removal rate under photothermal catalysis of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 was 72% higher than that under thermal catalysis. The toluene removal rate under photothermal catalysis of the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 was 50% higher than that under thermal catalysis. Although the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 also had a certain photoresponse at 250°C, the toluene removal rate under photothermal catalysis of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 at 250°C was still much higher than that under photothermal catalysis of Comparative Example 1.

[0076] Based on the thermocatalytic oxidation performance test of toluene, the toluene removal rates of the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 at 100, 150, 200, 225, 250, 275, 300, 325, and 350 °C, the toluene removal rates of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 1 at 100, 150, 200, 225, 250, 275, 300, and 325 °C, and the toluene removal rates of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Examples 2-4 at 100, 150, 200, 225, 250, 275, and 300 °C are plotted on the graph. Figure 10 ( Figure 10 The vertical axis "Toluene Removal Rate" represents the toluene removal rate under thermocatalysis. (For example...) Figure 10 As shown, at 275°C, the toluene removal rate of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 exceeded 90%. Compared to Comparative Example 1, the introduction of cobalt significantly promoted the conversion of toluene. Furthermore, Example 3 exhibited superior catalytic performance compared to Comparative Example 1 across the entire temperature range, demonstrating that the introduction of cobalt promoted the catalytic process and improved catalytic efficiency.

[0077] Based on the performance test of photothermal catalytic oxidation of toluene, the toluene removal rates of the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 and the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 1 at photothermal catalysis temperatures of 100, 150, 200, 225, 250, 275, 300, and 325 °C, and the toluene removal rates of the cobalt-doped lanthanum ferrite perovskite photothermal catalysts prepared in Examples 2-4 at photothermal catalysis temperatures of 100, 150, 200, 225, 250, and 275 °C are plotted on [the graph]. Figure 11 ( Figure 11 The vertical axis "Toluene Removal Rate" represents the toluene removal rate under photothermal catalysis. (For example...) Figure 11 As shown, at 250°C, the toluene removal rate of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 exceeded 95%. Furthermore, Example 3 exhibited superior catalytic performance compared to Comparative Example 1 throughout the entire temperature range, demonstrating that the introduction of cobalt promoted the photothermal catalytic process, improved the light response capability of Comparative Example 1, and thus enhanced the catalytic efficiency.

[0078] Based on the performance test of thermocatalytic oxidation of toluene, the carbon dioxide generation rates of the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 at 100, 150, 200, 225, 250, 275, 300, 325, and 350 °C, and the carbon dioxide generation rates of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 at 100, 150, 200, 225, 250, 275, and 300 °C are plotted on [the graph]. Figure 12Based on the performance test of photothermal catalytic oxidation of toluene, the carbon dioxide generation rates of the lanthanum ferrite perovskite catalyst prepared in Comparative Example 1 at 100, 150, 200, 225, 250, 275, 300, and 325 °C, and the carbon dioxide generation rates of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 at 100, 150, 200, 225, 250, and 275 °C are plotted on [the graph]. Figure 12 ,like Figure 12 As shown, Example 3 exhibited superior catalytic performance compared to Comparative Example 1 across the entire temperature range, further demonstrating that the introduction of cobalt promoted the catalytic process, improved the electronic structure and photoresponse capability of LaFeO3, and thus enhanced catalytic efficiency.

[0079] In practical applications, the catalytic oxidation removal of toluene is often affected by competing components such as water vapor and carbon dioxide. These competing components compete with the reactant gases for adsorption on the catalyst surface, leading to a decrease in the toluene removal rate. Therefore, the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 was subjected to five cycles of testing according to the aforementioned "Photothermal Catalytic Oxidation of Toluene Performance Test" to evaluate its stability. The test results are as follows: Figure 13 As shown ( Figure 13 The vertical axis "Toluene Removal Rate" represents the toluene removal rate under photothermal catalysis. No significant decreasing trend in the toluene removal rate was observed, indicating that the cobalt-doped lanthanum ferrite perovskite photothermal catalyst has good catalytic stability.

[0080] The water stability of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 was tested at 250°C.

[0081] Test 1: Basically the same as the "Performance Test of Thermal Catalytic Oxidation of Toluene", with the only difference being: During the first 4 hours, a reaction gas (the same as the reaction gas in the aforementioned "Performance Test of Thermal Catalytic Oxidation of Toluene") is introduced; at the 4th hour, the steam valve is opened; during the 4th to 12th hours, a first reaction gas containing water vapor is introduced (the first reaction gas containing water vapor is a mixture of toluene, oxygen, nitrogen, and water vapor, with an oxygen volume fraction of 20%, a toluene concentration of 1000 ppm, and a water vapor volume fraction of 5%); during the 12th to 20th hours, a second reaction gas containing water vapor is introduced (the second reaction gas containing water vapor is a mixture of toluene, oxygen, nitrogen, and water vapor, with an oxygen volume fraction of 20%, a toluene concentration of 1000 ppm, and a water vapor volume fraction of 10%); at the 20th hour, the steam valve is closed; and during the 20th to 24th hours, a reaction gas (the same as the reaction gas in the aforementioned "Performance Test of Thermal Catalytic Oxidation of Toluene") is introduced.

[0082] Test 2: Basically the same as the "Performance Test of Photothermal Catalytic Oxidation of Toluene", with the only difference being: During the first 4 hours, a reaction gas (the same as the reaction gas in the aforementioned "Performance Test of Photothermal Catalytic Oxidation of Toluene") is introduced; at the 4th hour, the steam valve is opened; during the 4th to 12th hours, a first reaction gas containing water vapor is introduced (the first reaction gas containing water vapor is a mixture of toluene, oxygen, nitrogen, and water vapor, with an oxygen volume fraction of 20%, a toluene concentration of 1000 ppm, and a water vapor volume fraction of 5%); during the 12th to 20th hours, a second reaction gas containing water vapor is introduced (the second reaction gas containing water vapor is a mixture of toluene, oxygen, nitrogen, and water vapor, with an oxygen volume fraction of 20%, a toluene concentration of 1000 ppm, and a water vapor volume fraction of 10%); at the 20th hour, the steam valve is closed; and during the 20th to 24th hours, a reaction gas (the same as the reaction gas in the aforementioned "Performance Test of Photothermal Catalytic Oxidation of Toluene") is introduced.

[0083] Test 1 ( Figure 14 "Example 3 Thermocatalysis" and Test 2 ( Figure 14 The results of "Example 3 Photothermal Catalysis" are as follows: Figure 14 As shown, in Test 2, the average toluene removal rate (toluene removal rate under photothermal catalysis) was 98% in the 0-4 hour range, 90% in the 4-12 hour range, 84% in the 12-20 hour range, and 98% in the 20-24 hour range. In Test 1, the average toluene removal rate (toluene removal rate under thermal catalysis) was 64% in the 0-4 hour range, 45% in the 4-12 hour range, 35% in the 12-20 hour range, and 58% in the 20-24 hour range. The results show that the cobalt-doped lanthanum ferrite perovskite photothermal catalyst prepared in Example 3 can still retain a relatively high catalytic activity under photothermal catalytic conditions in a water vapor competing atmosphere, and has excellent thermal stability and water vapor resistance, and can adapt to complex working environments.

[0084] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. The application of cobalt-doped lanthanum ferrite perovskite-type photothermal catalyst in the removal of toluene from water vapor under photothermal catalytic conditions, characterized in that, The cobalt-doped lanthanum ferrite perovskite photothermal catalyst exhibits a toluene removal rate exceeding 95% under photothermal catalysis at 250℃. The preparation method of the cobalt-doped lanthanum ferrite perovskite photothermal catalyst includes the following steps: Step 1: Mix the metal salt and water until homogeneous to obtain a metal salt solution, wherein the metal salt is a mixture of lanthanum source, iron source and cobalt source; Step 2: Mix all the metal salt solutions and metal chelating agents until homogeneous to obtain a precursor solution. Stir the precursor solution at 70~80℃ until it becomes a gel state, dry it, calcine it at 800~850℃ for 3~3.5h, and cool it to room temperature to obtain a cobalt-doped lanthanum ferrite perovskite type photothermal catalyst. Based on the molar amounts of substances, the ratio of lanthanum in the lanthanum source, cobalt in the cobalt source, iron in the iron source, and metal chelating agent is 1:x:(1-x):2.5, where x=0.

4.

2. The application according to claim 1, characterized in that, In step 1, the ratio of the molar amount of lanthanum to the volume amount of water in the lanthanum source is 5: (80~100), with the molar amount in mmol and the volume amount in mL.

3. The application according to claim 1, characterized in that, In step 1, the lanthanum source is lanthanum nitrate hexahydrate, the iron source is ferric nitrate nonahydrate, and the cobalt source is cobalt nitrate hexahydrate.

4. The application according to claim 1, characterized in that, In step 2, the precursor solution is stirred at 70-80°C for 7-8 hours until it reaches a gel state.

5. The application according to claim 1, characterized in that, In step 2, the metal chelating agent is citric acid monohydrate.

6. The application according to claim 1, characterized in that, Cobalt-doped lanthanum ferrite perovskite photothermal catalysts are used to catalyze the oxidation of toluene and its degradation into carbon dioxide.

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