Cobalt-cerium composite oxide, preparation method and application in degradation of volatile organic compounds

Abstract

The invention provides a cobalt-cerium composite oxide, a preparation method and an application in degrading volatile organic compounds, and relates to the technical field of material synthesis. The cobalt-cerium composite oxide contains a cerium and oxygen double vacancy structure, provides an effective space for the adsorption of molecular oxygen and toluene, and can transfer more charges to the adsorbed molecular oxygen.

Description

Technical Field

[0001] The invention relates to the technical field of material synthesis, and in particular to a cobalt-cerium composite oxide, a preparation method and photoactivation pretreatment thereof, and application thereof in degrading volatile organic matter. Background Art

[0002] Volatile organic compounds (VOCs), mainly toluene, are considered to be a large class of chemicals that are toxic to human health in terms of mutagenesis and carcinogenesis, seriously threatening the natural environment and human health. Eliminating these volatile organic compounds has become a research hotspot in recent years. At present, the removal of VOCs is mainly based on terminal treatment technologies such as adsorption, thermal catalysis, and photocatalysis. Photothermal catalysis synergy is a new type of catalytic technology that can effectively combine thermal catalysis with photocatalysis to accelerate the degradation of pollutants.

[0003] Generally speaking, catalysts used for VOCs degradation can be divided into precious metal and transition metal oxide catalysts. Compared with precious metal catalysts, transition metal oxides (such as Co 3 O 4 , Fe 2 O 3 、MnO 2 、CeO 2 , CuO, etc.) catalysts have attracted wide attention due to their high reactivity and low cost. 2 Due to its excellent oxygen storage and release capacity and good redox behavior, it is often used as a catalyst carrier or component for air pollution oxidation control. 3 O 4 It has the advantages of low cost and good stability. Its relatively weak Co-O bond and wide range of light absorption intensity are also suitable for the adsorption and oxidation of VOCs. 2 、Co 3 O 4 The research on photothermal catalytic oxidation of toluene is mainly focused on 150-300°C. The reaction temperature is relatively high. At lower temperatures, it is impossible to achieve efficient treatment and prevention of high-concentration and high-space-velocity VOCs. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the existing CeO 2 、Co 3 O 4 The reaction temperature of photothermal catalytic oxidation of VOCs is relatively high, and at lower temperatures, efficient catalytic degradation of VOCs at high concentrations and high space velocities cannot be achieved. Thus, a cobalt-cerium composite oxide containing cerium-oxygen divacancy is provided.

[0005] The invention also provides a method for preparing the cobalt-cerium composite oxide.

[0006] The invention also provides an application of a light irradiation activation pretreatment technology for cobalt-cerium composite oxide in the degradation of volatile organic matter.

[0007] The technical solution of the present invention has the following advantages:

[0008] 1. The cobalt-cerium composite oxide provided by the present invention has a cerium-oxygen double vacancy structure, which provides effective space for the adsorption of molecular oxygen and toluene. Compared with the common materials containing only oxygen vacancies, more charges can be transferred to the adsorbed molecular oxygen;

[0009] 2. The cobalt-cerium composite oxide provided by the present invention can generate a large amount of active oxygen species such as peroxide, monatomic oxygen and superoxide anion on the surface of the material after photoactivation. In the process of degrading toluene, the formation of the key intermediate benzoic acid can be regulated. The formation of benzoic acid is an important process for the complete degradation of toluene. Toluene can be completely oxidized to carbon dioxide within seconds at a bed temperature of about 50°C, which provides a new technology design strategy for the development of low-temperature and efficient VOCs removal in industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0011] Figure 1 The XRD diagrams and partial enlarged diagrams of Examples 1 to 5, Comparative Examples 1 and 2 of the present invention;

[0012] Figure 2 is a high-magnification transmission electron microscopy image of a 10% CoCe sample prepared in Example 4 of the present invention;

[0013] Figure 3 This is a high-angle annular dark field scanning transmission spherical aberration electron microscope spectrum of a 10% CoCe sample prepared in Example 4 of the present invention;

[0014] Figure 4 is the XPS spectrum of O1s of the 10% CoCe sample prepared in Example 4 of the present invention;

[0015] Figure 5 The 10% CoCe prepared in Example 4 of the present invention and the CeO prepared in Comparative Example 1 are 2 Sample and purchase CeO 2 L of Ce of the sample 3 -ege near edge absorption spectroscopy (XANES) diagram;

[0016] Figure 6 is the in-situ ESR curve of 10% CoCe prepared in Example 4 of the present invention under different conditions;

[0017] Figure 7 The CeO prepared in Comparative Example 1 of the present invention 2 , Co prepared in Comparative Example 2 3 O 4 and the 10% CoCe O prepared in Example 4 2 -TPD-mass result diagram;

[0018] Figure 8 The conventional XPS spectrum and the light-added XPS spectrum of the 10% CoCe sample prepared in Example 4;

[0019] Fig. 9 is the catalyst bed temperature after toluene is introduced in Experimental Examples 1 to 5 of the present invention;

[0020] Fig.10 The toluene conversion rate data diagram of Experimental Examples 1 to 5;

[0021] Fig.11 The data diagram of the selectivity of Experimental Examples 1 to 5 to carbon monoxide and carbon dioxide;

[0022] Fig.12 is the conversion rate of toluene in Experimental Example 4, Experimental Example 6 and Experimental Example 7;

[0023] Fig.13 is the degradation rate of toluene in Experimental Example 8, Experimental Example 9 and Experimental Example 10;

[0024] Fig.14 -a is the infrared spectrum of Experimental Example 11; Fig.14 -b is the infrared spectrum of Experimental Example 12. DETAILED DESCRIPTION

[0025] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0026] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0027] Example 1

[0028] Weigh 4.34 g of cerium nitrate hexahydrate and 0.99 g of glucose monohydrate in a beaker, mix them, add 0.157 g of cobalt nitrate hexahydrate, place them on a heating furnace for heating, stir them evenly after they become a solution, heat them to catalytic combustion until a solid product is obtained, and stop heating;

[0029] After the solid product is fully ground, it is placed in a muffle furnace for calcination at a temperature of 600° C. for 4 hours to obtain a cobalt-cerium composite oxide;

[0030] The cobalt-cerium composite oxide was placed in a quartz tube and irradiated with a 1.5 W visible light source for 30 minutes in an atmosphere of helium to obtain a cobalt-cerium composite oxide containing cerium oxygen divacancies, which was recorded as 2.5% CoCe.

[0031] Example 2

[0032] Weigh 4.34 g of cerium nitrate hexahydrate and 0.99 g of glucose monohydrate in a beaker, mix them, add 0.330 g of cobalt nitrate hexahydrate, place them on a heating furnace for heating, stir them evenly after they become a solution, heat them to catalytic combustion until a solid product is obtained, and stop heating;

[0033] After the solid product is fully ground, it is placed in a muffle furnace for calcination at a temperature of 500° C. for 5 hours to obtain a cobalt-cerium composite oxide;

[0034] The cobalt-cerium composite oxide was placed in a quartz tube, helium was introduced first, the air in the quartz tube was removed, and the tube was directly irradiated with a 1.5 W visible light source for 60 minutes to obtain a cobalt-cerium composite oxide containing cerium oxygen divacancy, which was recorded as 5% CoCe.

[0035] Example 3

[0036] Weigh 4.34 g of cerium nitrate hexahydrate and 0.99 g of glucose monohydrate in a beaker, mix them, add 0.507 g of cobalt nitrate hexahydrate, place them on a heating furnace for heating, stir them evenly after they become a solution, heat them to catalytic combustion until a solid product is obtained, and stop heating;

[0037] After the solid product is fully ground, it is placed in a muffle furnace for calcination at a temperature of 600° C. for 4 hours to obtain a cobalt-cerium composite oxide;

[0038] The cobalt-cerium composite oxide was placed in a quartz tube, helium was introduced first, the air in the quartz tube was removed, and hydrogen was continuously introduced. It was irradiated with a 1.5W visible light source for 90 minutes to obtain a cobalt-cerium composite oxide containing cerium oxygen divacancy, recorded as 7.5% CoCe.

[0039] Example 4

[0040] Weigh 4.34 g of cerium nitrate hexahydrate and 0.99 g of glucose monohydrate in a beaker, mix them, add 0.698 g of cobalt nitrate hexahydrate, place them on a heating furnace for heating, stir them evenly after they become a solution, heat them to catalytic combustion until a solid product is obtained, and stop heating;

[0041] After the solid product is fully ground, it is placed in a muffle furnace for calcination at a temperature of 500° C. for 5 hours to obtain a cobalt-cerium composite oxide;

[0042] The cobalt-cerium composite oxide was placed in a quartz tube, helium was introduced first, the air in the quartz tube was removed, and hydrogen was continuously introduced. It was irradiated with a 1.5W visible light source for 120 minutes to obtain a cobalt-cerium composite oxide containing cerium oxygen divacancy, recorded as 10% CoCe.

[0043] Example 5

[0044] Weigh 4.34 g of cerium nitrate hexahydrate and 0.99 g of glucose monohydrate in a beaker, mix them, add 0.894 g of cobalt nitrate hexahydrate, place them on a heating furnace for heating, stir them evenly after they become a solution, heat them to catalytic combustion until a solid product is obtained, and stop heating;

[0045] After the solid product is fully ground, it is placed in a muffle furnace for calcination at a temperature of 480° C. for 5.5 hours to obtain a cobalt-cerium composite oxide;

[0046] The cobalt-cerium composite oxide was placed in a quartz tube, helium was introduced first, the air in the quartz tube was removed, and then hydrogen was continuously introduced. It was irradiated with a 1.5 W visible light source for 100 minutes to obtain a cobalt-cerium composite oxide containing cerium oxygen divacancy, recorded as 12.5% ​​CoCe.

[0047] Comparative Example 1

[0048] Weigh 4.34 g of cerium nitrate hexahydrate and 0.99 g of glucose monohydrate in a beaker, mix them, place them on a heating furnace for heating, stir them evenly after they become a solution, heat them to catalytic combustion until a solid product is obtained, and stop heating;

[0049] After the solid product is fully ground, it is placed in a muffle furnace for calcination at a temperature of 500° C. for 5 hours to obtain cerium oxide;

[0050] The cerium oxide was placed in a quartz tube, helium was introduced first, the air in the quartz tube was removed, and hydrogen was continuously introduced. The cerium oxide was irradiated with a 1.5W visible light source for 120 minutes to obtain cerium oxide, which was recorded as CeO 2 .

[0051] Comparative Example 2

[0052] Weigh 0.99 g of glucose monohydrate and 0.698 g of cobalt nitrate hexahydrate, stir evenly, place on a heating furnace for heating, stir evenly after it becomes a solution, heat to catalytic combustion until a solid product is obtained, and stop heating;

[0053] After the solid product is fully ground, it is placed in a muffle furnace for calcination at a temperature of 500° C. for 5 hours to obtain cobalt oxide;

[0054] The cobalt oxide was placed in a quartz tube, helium was introduced first, the air in the quartz tube was removed, and hydrogen was continuously introduced. The tube was irradiated with a 1.5W visible light source for 120 minutes to obtain cobalt oxide, which was recorded as Co 3 O 4 .

[0055] Comparative Example 3

[0056] Weigh 4.34 g of cerium nitrate hexahydrate and 0.99 g of glucose monohydrate in a beaker, mix them, add 1.396 g of cobalt nitrate hexahydrate, place them on a heating furnace for heating, stir them evenly after they become a solution, heat them to catalytic combustion until a solid product is obtained, and stop heating;

[0057] After the solid product is fully ground, it is placed in a muffle furnace for calcination at a temperature of 500° C. for 5 hours to obtain a cobalt-cerium composite oxide;

[0058] The cobalt-cerium composite oxide was placed in a quartz tube, helium was introduced first, the air in the quartz tube was removed, and hydrogen was continuously introduced. It was irradiated with a 1.5W visible light source for 120 minutes to obtain a cobalt-cerium composite oxide containing cerium oxygen divacancy, recorded as 20% CoCe.

[0059] Figure 1 -a is the XRD pattern of the samples prepared in Example 1 to Example 5, Comparative Example 1 and Comparative Example 2, Figure 1 -b is Figure 1 -A partial enlarged view at 32°-40°, from Figure 1 -a As can be seen in Figure 1, pure CeO 2 The diffraction peak intensity and peak shape of the prepared CeO 2 The sample is of high purity and free of impurities. The characteristic diffraction peaks at 28.55°, 33.08°, 47.48°, and 56.34° are (111), (200), (220), and (311) crystal planes, respectively. 3 O4 The sample has clear characteristic diffraction peaks and peak intensities, corresponding to the standard card (PDF#42-1467), where the main characteristic peaks at 19.00, 31.27, 36.85 and 44.80° are attributed to (111), (220), (311) and (400) diffraction crystal planes. 2 Surface loading of different contents of Co 3 O 4 When the characteristic diffraction peaks of samples with different CoCe contents are 2 The diffraction peaks of the samples are the same, and with the increase of Co 3 O 4 With the increase of content, Co at 2θ = 36.8° 3 O 4 The peak intensity of the characteristic diffraction peak continues to increase, proving that the catalyst is composed of CeO 2 and Co 3 O 4 Composite composition.

[0060] In order to accurately study the microstructure of the cobalt-cerium composite oxide, the following characterization analysis was performed.

[0061] Figure 2 This is a high-magnification transmission electron microscopy image of the 10% CoCe sample prepared in Example 4.

[0062] pass Figure 2 -a shows that the 10% CoCe sample contains abundant porous flaky structures. Figure 2 -b indicates that the main exposed crystal surface is CeO 2 (200) and Co 3 O 4 (400) crystal plane. Figure 2 Figure -c confirms that the three elements of cobalt, cerium and oxygen are evenly distributed, further proving that the catalyst is composed of CeO 2 and Co 3 O 4 Composite composition.

[0063] Figure 3 Figure 3-e is a high-angle annular dark field scanning transmission spherical aberration electron microscopy spectrum of the 10% CoCe sample prepared in Example 4. Figure 3-e is a density diagram of the atomic intensity of cerium, oxygen and cobalt along X1Y1, X2Y2 and X3Y3 in 3-d relative to the spatial position. It can be seen that along the dotted line direction, the density of cerium and oxygen elements gradually decreases, indicating that in CeO 2 and Co 3 O 4 Cerium vacancies and oxygen vacancies appeared at the heterojunction interface.

[0064] Figure 4This is the XPS spectrum of O1s of the 10% CoCe sample prepared in Example 4. Figure 4 It can be seen that an XPS signal peak attributed to surface oxygen vacancies appears near 531.2 eV, further confirming the existence of surface oxygen vacancies.

[0065] Figure 5 The 10% CoCe prepared in Example 4 and the CeO prepared in Comparative Example 1 2 L of Ce of the sample 3 -ege near edge absorption spectrum (XANES) diagram. As can be seen from the figure, compared with the standard CeO 2 Compared with the CeO prepared in Comparative Example 1, 2 The energy of Ce L3-edge of 10% CoCe prepared in Example 4 all shifts to lower binding energy, which may be related to the appearance of oxygen vacancies. At the same time, it also shows that the valence state of cerium in these three samples is between +3 and +4.

[0066] Figure 6 The in-situ ESR curves of 10% CoCe prepared in Example 4 under different conditions. The conditions in the figure are oxygen + light irradiation for 5 minutes, oxygen + dark conditions, and nitrogen + dark conditions from top to bottom;

[0067] From the in-situ ESR results, it can be seen that compared with the nitrogen atmosphere, the sample in the oxygen atmosphere exhibits a lower oxygen vacancy (g = 1.999) intensity and can generate O - species (g = 2.023), it can be inferred that the active sites for oxygen adsorption and photoactivation on the 10% CoCe surface are oxygen vacancies rather than Ce 3+ site (g=1.968).

[0068] Figure 7 The CeO prepared in Comparative Example 1 2 , Co prepared in Comparative Example 2 3 O 4 and the 10% CoCe O prepared in Example 4 2 -TPD-mass result diagram. In order to further explore O - The formation mechanism of O species on 10% CoCe was investigated by online quadrupole mass spectrometry. 2 The programmed temperature desorption products were analyzed. As shown in the figure, monatomic oxygen (m / z = 16) is present in CeO 2 、Co 3 O 4 The first desorption peaks on 10% CoCe and 10% CoCe are 182.8° C., 850.9° C. and 62.0° C., respectively. This indicates that among the three samples, the oxygen dissociation temperature of the 10% CoCe sample is the lowest, that is, it is easiest to dissociate.

[0069] Figure 8 The conventional XPS spectrum and the light-added XPS spectrum of the 10% CoCe sample prepared in Example 4. In order to determine the electron transfer direction between components in the 10% CoCe sample under illumination, conventional XPS and light-added XPS characterization were performed, such as Figure 8 -a, when light is irradiated to the 10% CoCe surface, the binding energy of the 3d electrons of the Ce element moves significantly to the lower binding energy. 3+ The intensity of the XPS signal is significantly stronger than that under no illumination conditions, which may be related to the CeO 2 Acceptance of foreign electrons. Figure 8 -b indicates that the electron binding energy of Co2p moves slightly toward lower binding energy, and the corresponding XPS signal intensity increases. 3+ The 2p electron binding energy of Co 2+ Therefore, it is speculated that this phenomenon may be related to the loss of electrons leading to the 3 + At the same time, cerium vacancies are generated after electron transfer.

[0070] The divacancy structure based on the material can directly activate molecular oxygen to dissociate into O 2 - and O - , in order to enhance O 2 - and O - The ability to pre-activate the material is to generate more O 2 - and O - , in the process of toluene degradation, it is used to regulate the production of benzoic acid with the lowest ring-opening ability.

[0071] Experimental Example 1

[0072] 0.1 g of the cobalt-cerium composite oxide prepared in Example 4 was placed in a quartz tube (inner diameter 0.6 cm, length 50 cm), and air was introduced into the quartz tube, followed by irradiation with a xenon lamp for 10 minutes for activation.

[0073] After activation, toluene was bubbled into the quartz tube at 45 mL / min of argon, 40 mL / min of air flow was used to provide oxygen source for the reactants, and 15 mL / min of argon was used as the balance gas. Toluene was bubbled into circulating water at 3°C ​​to produce a toluene concentration of 100 ppm. The total flow rate through the catalyst bed was fixed at 100 mL / min, and the gas weight hourly space velocity (GHSV) was 60,000 mL·g - 1 h -1,During the experiment, samples were taken and the concentration data of toluene, carbon monoxide and carbon dioxide were detected by gas chromatograph.

[0074] Experimental Example 2

[0075] 0.1 g of the cobalt-cerium composite oxide prepared in Example 4 was placed in a quartz tube (inner diameter 0.6 cm, length 50 cm), and after air was passed through the quartz tube, it was irradiated with a xenon lamp for 20 min for activation.

[0076] After activation, toluene was introduced, and toluene was bubbled into the quartz tube at 45 mL / min of argon, with 40 mL / min of air flow providing an oxygen source for the reactants, and 15 mL / min of argon as the balance gas. Toluene was bubbled into circulating water at 3°C ​​to produce a toluene concentration of 500 ppm, and the total flow rate through the catalyst bed was fixed at 100 mL / min, and the gas weight hourly space velocity (GHSV) was 60,000 mL·g -1 h -1 ,During the experiment, samples were taken and the concentration data of toluene, carbon monoxide and carbon dioxide were detected by gas chromatograph.

[0077] Experimental Example 3

[0078] 0.1 g of the cobalt-cerium composite oxide prepared in Example 4 was placed in a quartz tube (inner diameter 0.6 cm, length 50 cm), and after air was passed through the quartz tube, it was irradiated with a xenon lamp for 30 min for activation.

[0079] After activation, toluene was introduced, and toluene was bubbled into the quartz tube at 45 mL / min of argon, with 40 mL / min of air flow providing an oxygen source for the reactants, and 15 mL / min of argon as the balance gas. Toluene was bubbled into circulating water at 3°C ​​to produce a toluene concentration of 1500 ppm. The total flow rate through the catalyst bed was fixed at 100 mL / min, and the gas weight hourly space velocity (GHSV) was 60,000 mL·g -1 h -1 ,During the experiment, samples were taken and the concentration data of toluene, carbon monoxide and carbon dioxide were detected by gas chromatograph.

[0080] Experimental Example 4

[0081] 0.1 g of the cobalt-cerium composite oxide prepared in Example 4 was placed in a quartz tube (inner diameter 0.6 cm, length 50 cm), and after air was passed through the quartz tube, it was irradiated with a xenon lamp for 40 min for activation.

[0082] After activation, toluene was introduced, and toluene was bubbled into the quartz tube at 45 mL / min of argon, with 40 mL / min of air flow providing an oxygen source for the reactants, and 15 mL / min of argon as the balance gas. Toluene was bubbled into circulating water at 3°C ​​to produce a toluene concentration of 2500 ppm. The total flow rate through the catalyst bed was fixed at 100 mL / min, and the gas weight hourly space velocity (GHSV) was 60,000 mL·g -1 h -1 ,During the experiment, samples were taken and the concentration data of toluene, carbon monoxide and carbon dioxide were detected by gas chromatograph.

[0083] Experimental Example 5

[0084] 0.1 g of the cobalt-cerium composite oxide prepared in Example 4 was placed in a quartz tube (inner diameter 0.6 cm, length 50 cm), and after air was passed through the quartz tube, it was irradiated with a xenon lamp for 60 min / min for activation.

[0085] After activation, toluene was introduced, and toluene was bubbled into the quartz tube at 45 mL / min of argon, with 40 mL / min of air flow providing an oxygen source for the reactants, and 15 mL / min of argon as the balance gas. Toluene was bubbled into circulating water at 3°C ​​to produce a toluene concentration of 3500 ppm. The total flow rate through the catalyst bed was fixed at 100 mL / min, and the gas weight hourly space velocity (GHSV) was 60,000 mL·g -1 h -1 ,During the experiment, samples were taken and the concentration data of toluene, carbon monoxide and carbon dioxide were detected by gas chromatograph.

[0086] Experimental Example 6

[0087] 0.1 g of the cerium oxide prepared in Comparative Example 1 was placed in a quartz tube (inner diameter 0.6 cm, length 50 cm), and after air was passed through the quartz tube, it was irradiated with a xenon lamp for 40 min for activation.

[0088] After activation, toluene was introduced, and toluene was bubbled into the quartz tube at 45 mL / min of argon, with 40 mL / min of air flow providing an oxygen source for the reactants, and 15 mL / min of argon as the balance gas. Toluene was bubbled into circulating water at 3°C ​​to produce a toluene concentration of 2500 ppm. The total flow rate through the catalyst bed was fixed at 100 mL / min, and the gas weight hourly space velocity (GHSV) was 60,000 mL·g -1 h -1 ,During the experiment, samples were taken and the concentration data of toluene, carbon monoxide and carbon dioxide were detected by gas chromatograph.

[0089] Experimental Example 7

[0090] 0.1 g of the cobalt oxide prepared in Comparative Example 2 was placed in a quartz tube (inner diameter 0.6 cm, length 50 cm), and after air was passed through the quartz tube, it was irradiated with a xenon lamp for 40 min / min for activation.

[0091] After activation, toluene was introduced, and toluene was bubbled into the quartz tube at 45 mL / min of argon, with 40 mL / min of air flow providing an oxygen source for the reactants, and 15 mL / min of argon as the balance gas. Toluene was bubbled into circulating water at 3°C ​​to produce a toluene concentration of 2500 ppm. The total flow rate through the catalyst bed was fixed at 100 mL / min, and the gas weight hourly space velocity (GHSV) was 60,000 mL·g -1 h -1 ,During the experiment, samples were taken and the concentration data of toluene, carbon monoxide and carbon dioxide were detected by gas chromatograph.

[0092] Experimental Example 8

[0093] 0.1 g of the cobalt-cerium composite oxide prepared in Examples 1-5 and Comparative Example 3 was placed in a quartz tube (inner diameter 0.6 cm, length 50 cm), and after air was passed through the quartz tube, it was irradiated with a xenon lamp for 40 min / min for activation.

[0094] After activation, toluene was introduced, and toluene was bubbled into the quartz tube at 45 mL / min of argon, with 40 mL / min of air flow providing an oxygen source for the reactants, and 15 mL / min of argon as the balance gas. Toluene was bubbled into circulating water at 3°C ​​to produce a toluene concentration of 2500 ppm. The total flow rate through the catalyst bed was fixed at 100 mL / min, and the gas weight hourly space velocity (GHSV) was 60,000 mL·g -1 h -1 ,During the experiment, samples were taken and the concentration data of toluene, carbon monoxide and carbon dioxide were detected by gas chromatograph.

[0095] As shown in Table 1, the degradation rate of toluene by cobalt-cerium composite oxide at different ratios.

[0096] Table 1 Toluene degradation rate

[0097] sample 2.5% CoCe 5% CoCe 7.5% CoCe 10% CoCe 12.5% ​​CoCe 20% CoCe Toluene degradation rate 90％ 93％ 98％ 99％ 96％ 90％

[0098] Fig. 9 The catalyst bed temperature of Experimental Examples 1 to 5 after the introduction of toluene. It can be seen from the figure that the bed temperature was lower than 50°C during the processes of Experimental Examples 1 to 5.

[0099] Fig.10 The toluene conversion rate data of Experimental Examples 1 to 5 are shown in FIG. Fig.10It can be seen that when the concentration of toluene is between 100ppm and 2500ppm, the conversion rate of toluene on the 10% CoCe surface is above 95%.

[0100] Fig.11 The data graphs of the selectivity of carbon monoxide and carbon dioxide for Experimental Examples 1 to 5 are shown. The peak areas of carbon monoxide and carbon dioxide in the gas chromatograph are read. The selectivity of carbon dioxide is the peak area of ​​carbon dioxide / (peak area of ​​carbon dioxide + peak area of ​​carbon monoxide)*100; the selectivity of carbon monoxide is the peak area of ​​carbon monoxide / (peak area of ​​carbon dioxide + peak area of ​​carbon monoxide)*100. It can be seen from the graph that when the concentration of toluene is between 100ppm and 2500ppm, the selectivity of 10% CoCe to carbon dioxide reaches 100%.

[0101] Fig.12 is the conversion rate of toluene in Experimental Examples 4, 6 and 7. It can be seen from the figure that when the average temperature of the bed is between 40-50°C, pure CeO 2 It is about 5%, indicating that it has almost no oxidation removal ability for high concentration toluene. 3 O 4 The degradation rate of 2500ppm toluene is only 60%, which is comparable to that of pure CeO 2 and pure Co 3 O 4 In contrast, when the catalyst bed temperature was only 50°C, the conversion rate of 10% CoCe to 2500 ppm toluene was close to 100%.

[0102] Experimental Example 8

[0103] 0.1 g of the cobalt-cerium composite oxide prepared in Example 4 was placed in a quartz tube (inner diameter 0.6 cm, length 50 cm), and after air was passed through the quartz tube, it was irradiated with a xenon lamp for 20 min for activation.

[0104] After activation, toluene was introduced, and toluene was bubbled into the quartz tube with 45 mL / min of argon, and an air flow of 40 mL / min provided an oxygen source for the reactants, and 15 mL / min of argon was used as a balance gas. Toluene was bubbled in circulating water at 3°C ​​to produce a toluene concentration of 2500 ppm. The total flow rate through the catalyst bed was fixed at 100 mL / min. The gas weight hourly space velocity was the ratio of the total flow rate of the catalyst bed to the mass of the composite oxide, that is, the gas weight hourly space velocity (GHSV) in this experimental example was 6000 mL·g -1 h -1 ,At the same time, during the experiment, the toluene concentration was measured by gas phase.

[0105] Experimental Example 9

[0106] 0.05 g of the cobalt-cerium composite oxide prepared in Example 4 was placed in a quartz tube (inner diameter 0.6 cm, length 50 cm), and after air was passed through the quartz tube, it was irradiated with a xenon lamp for 20 min for activation.

[0107] After activation, toluene was introduced, and toluene was bubbled into the quartz tube at 45 mL / min of argon, and an air flow of 40 mL / min provided an oxygen source for the reactants, with 15 mL / min of argon as the balance gas. Toluene was bubbled in circulating water at 3°C ​​to produce a toluene concentration of 2500 ppm. The total flow through the catalyst bed was fixed at 100 mL / min. The gas weight hourly space velocity (GHSV) was 120,000 mL·g based on the ratio of the total flow of the catalyst bed to the mass of the composite oxide. -1 h -1 ,During the experiment, the toluene concentration was determined by gas phase.

[0108] Experimental Example 10

[0109] 0.025 g of the cobalt-cerium composite oxide prepared in Example 4 was placed in a quartz tube (inner diameter 0.6 cm, length 50 cm), and after air was passed through the quartz tube, it was irradiated with a xenon lamp for 20 min for activation.

[0110] After activation, toluene was introduced, and toluene was bubbled into the quartz tube at 45 mL / min of argon, and an air flow of 40 mL / min provided an oxygen source for the reactants, with 15 mL / min of argon as the balance gas. Toluene was bubbled in circulating water at 3°C ​​to produce a toluene concentration of 2500 ppm. The total flow through the catalyst bed was fixed at 100 mL / min. The gas weight hourly space velocity (GHSV) was 2400,000 mL·g based on the ratio of the total flow of the catalyst bed to the mass of the composite oxide. -1 h -1 ,At the same time, during the experiment, the toluene concentration was measured by gas phase.

[0111] Fig.13 ] is the degradation rate of toluene in Experimental Example 8, Experimental Example 9 and Experimental Example 10. It can be seen from the figure that the greater the gas weight hourly space velocity, the higher the degradation rate of toluene.

[0112] Experimental Example 11

[0113] The Bruker INVENIO in-situ infrared device is equipped with an infrared spectrometer, an in-situ diffuse reflection cell, a heating device, a low-temperature cooling circulation pump, and a 1-meter-long optical fiber light guide connected to a 300W xenon lamp light source.

[0114] 0.1 g of the cobalt-cerium composite oxide prepared in Example 4 was placed in the in-situ cell of the Bruker INVENIO in-situ infrared device. Ar gas was first introduced into the in-situ cell, the heating device was stabilized to 300° C., and heat treated for 180 min to remove the substances adsorbed on the surface, and then samples were taken for infrared measurement.

[0115] After the temperature of the in-situ cell dropped to room temperature, the heating device was stabilized at 50°C, and oxygen was introduced at 100 mL / min for 60 min to achieve adsorption-desorption equilibrium, and samples were taken for infrared measurement.

[0116] The surface of the cobalt-cerium composite oxide was purged with argon gas at a rate of 50 ml / min for 15 minutes. Then, a xenon lamp was introduced through an optical fiber light guide to irradiate the surface of the cobalt-cerium composite oxide for 20 minutes, and samples were taken for infrared measurement.

[0117] Turn off the light source, introduce toluene with a toluene concentration of 350ppm, conduct a degradation experiment, and take samples to measure infrared.

[0118] After a period of time, turn on the light source and continue the degradation experiment. Take samples and measure infrared light 10s, 20s, and 30s after turning on the light.

[0119] Experimental Example 12

[0120] The Bruker INVENIO in-situ infrared device is equipped with an infrared spectrometer, an in-situ diffuse reflection cell, a heating device, a low-temperature cooling circulation pump, and a 1-meter-long optical fiber light guide connected to a 300W xenon lamp light source.

[0121] 0.1 g of the cobalt-cerium composite oxide prepared in Example 4 was put into the in-situ cell of the Bruker INVENIO in-situ infrared device. Ar gas was first introduced into the in-situ cell, the heating device was stabilized to 300° C., and heat treated for 180 min to remove the substances adsorbed on the surface.

[0122] After the temperature of the in-situ pool drops to room temperature, the heating device is stabilized at 50°C, and 100mL / min of oxygen is introduced for 60 minutes to achieve adsorption-desorption equilibrium. The sample is purged with 50ml / min of argon for 15 minutes. After that, toluene is introduced, and a xenon light source is introduced through an optical fiber light guide to irradiate the cobalt-cerium composite oxide. The toluene concentration is 350ppm, and a degradation experiment is carried out. Samples are taken and infrared measurements are measured at 0s, 10s, 20s, and 30s after the light is turned on.

[0123] Fig.14 -a is the infrared spectrum of Experimental Example 11; Fig.14 -b is the infrared spectrum of Experimental Example 12. Fig.14-b shows that before activation, the surface of the cobalt-cerium composite oxide has a large amount of superoxide anions. After toluene and oxygen are introduced and light is added, the superoxide anions are gradually converted into peroxide anions. -1 The CH vibration of toluene appears at the same time, benzyl alcohol, benzaldehyde, benzoic acid, maleic anhydride, acetic acid, formic acid and CO can be observed. 2 The characteristic peak of 1300cm -1 The peak at the center is the characteristic peak of benzyl alcohol. It can be seen that the peak height of the characteristic peak of benzyl alcohol is the largest among the intermediates, indicating that within 30 seconds of light addition, due to the relatively small content of peroxide anions, the main intermediate of toluene oxidation is benzyl alcohol.

[0124] from Fig.14 -a, it can be seen that after photoactivation, a large number of peroxide anions exist on the surface of the cobalt-cerium composite oxide. After toluene is introduced, carbon dioxide can be produced in the dark to achieve oxidation of toluene. At the same time, the characteristic peaks of intermediates such as toluene and benzyl alcohol can be found. However, after adding light for 20 seconds, the characteristic peak of benzyl alcohol gradually decreases, while the characteristic peak of benzoic acid gradually increases. It is speculated that after photoactivation, due to the presence of a large number of peroxide anions on the catalyst surface, the introduction of toluene promotes the conversion of benzyl alcohol and benzaldehyde to benzoic acid. After adding light for 30 seconds, the peaks of benzoic acid, anhydride, acetic acid and formic acid decrease, and the peak of carbon dioxide increases, indicating that deep oxidation of toluene can be achieved after adding light for 30 seconds.

[0125] In summary, the present invention also provides a photoactivation treatment technology for photoenhancing active species to regulate the generation of key intermediates, which can reduce the light source intensity and surface temperature for achieving the same toluene concentration conversion rate compared with those without photoactivation treatment.

[0126] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A cobalt-cerium composite oxide, characterized in that: The cobalt-cerium composite oxide contains a cerium and oxygen double vacancy structure.

2. The method for preparing the cobalt-cerium composite oxide according to claim 1, characterized in that: The following steps are involved: S1, weighing cerium nitrate hexahydrate, glucose monohydrate and cobalt nitrate hexahydrate, putting them into a container, placing them on a heating device for heating, stirring them evenly after they become a solution, heating them until they become a solution and then burning them until a solid product is obtained, and stopping heating; S2, grinding the solid product into powder and placing it in a muffle furnace for calcination to obtain a cobalt-cerium composite oxide; S3, placing the cobalt-cerium composite oxide in a quartz tube, irradiating it with a light source under a hydrogen and / or inert gas atmosphere, and photo-reducing the cobalt-cerium composite oxide to obtain a cobalt-cerium composite oxide containing cerium oxygen divacancy.

3. The method for preparing a cobalt-cerium composite oxide according to claim 2, characterized in that: In step S2, the calcination temperature is 400-600°C, and the calcination time is 4-6 hours.

4. The method for preparing a cobalt-cerium composite oxide according to claim 2, characterized in that: In step S3, an inert gas is first introduced to remove oxygen in the quartz tube.

5. The method for preparing a cobalt-cerium composite oxide according to claim 2, characterized in that: In step S3, the light source is a visible light source, and the illumination time is 30-120 minutes.

6. The method for preparing a cobalt-cerium composite oxide according to claim 2, characterized in that: In step S1, the mass ratio of the cerium nitrate hexahydrate to the cobalt nitrate hexahydrate is 1:(0.035-0.210).

7. Use of the cobalt-cerium composite oxide prepared by the method according to any one of claims 1 to 6 in the degradation of volatile organic compounds, characterized in that: The following steps are involved: Weighing cobalt-cerium composite oxide and putting it into a reactor; The reactor is irradiated with a light source, and the cobalt-cerium composite oxide is pre-treated by photoactivation in an atmosphere of oxygen or air; After activation, VOCs gas is introduced for catalytic oxidation degradation.

8. The use of the cobalt-cerium composite oxide in degrading volatile organic compounds as claimed in claim 7, characterized in that: The light source used is a xenon lamp; the light pre-activation time is 10-60 minutes.

9. The use of the cobalt-cerium composite oxide in degrading volatile organic compounds as claimed in claim 7, characterized in that: During the catalytic oxidation degradation process, the bed temperature of the cobalt-cerium composite oxide is 40-50°C.

10. The use of the cobalt-cerium composite oxide in degrading volatile organic compounds according to claim 7, characterized in that: The VOCs gas contains toluene, and the reaction space velocity is 60,000-240,000 mL·g -1 ·h -1 .

11. The use of the cobalt-cerium composite oxide in degrading volatile organic compounds according to claim 7, characterized in that: The VOCs gas contains toluene, and the concentration of toluene is 100-3500ppm.

Images