A kind of Al 3+ Modified K-OMS-2 photocatalyst, its preparation method and application

Abstract

This invention discloses an Al 3+ This invention relates to a modified K-OMS-2 photocatalyst, its preparation method, and its applications, belonging to the field of environmental catalysis technology. The method involves mixing MnSO4·H2O, KMnO4, Al(NO3)3·9H2O, concentrated nitric acid, and deionized water, followed by a hydrothermal reaction. After the reaction, the mixture is cooled, centrifuged, washed, dried, calcined, and ground to obtain the Al-KM photocatalyst. This invention achieves deep oxidation of toluene by promoting the adsorption and activation of toluene and the rapid conversion of intermediate species, ultimately converting toluene into non-toxic CO2. The raw materials used in this invention are low-toxicity, low-cost, and the manufacturing process is simple. The resulting catalyst is highly practical and has excellent application prospects and environmental benefits.

Description

Technical Field

[0001] This invention belongs to the field of environmental catalysis technology, specifically relating to an Al 3+ Modified K-OMS-2 photocatalyst, its preparation method and application. Background Technology

[0002] Volatile organic compounds (VOCs) are a collective term for a class of volatile organic compounds that have polluting effects on human health and the environment. Toluene is a typical VOC, possessing properties that can cause cancer, birth defects, and mutations. Excessive indoor toluene concentrations can seriously affect human health. Therefore, ensuring human health urgently requires the development of economical and efficient toluene removal technologies. Photocatalytic oxidation technology can achieve the complete degradation of pollutants under mild conditions, offering advantages such as being green, efficient, and free of secondary pollution. It has attracted widespread attention in recent years. K-OMS-2, as a common transition metal semiconductor catalyst, has advantages such as being economical, efficient, inexpensive, and low in toxicity, and shows promising application prospects in the field of photocatalysis.

[0003] K-OMS-2 is a common type of manganese dioxide (MnO2), abundant in quantity and widely used. Its narrow band gap and excellent light absorption properties make it a potential photocatalytic material. However, it has the following drawbacks: (i) Due to the narrow band gap, photogenerated electron-hole pairs easily recombine within the catalyst, resulting in a shorter lifetime and fewer photogenerated electron-hole pairs participating in the reaction, leading to lower photocatalytic efficiency; (ii) K + The presence of K-OMS-2 is beneficial for enhancing the adsorption of toluene, but it is not conducive to the desorption of reaction intermediates on the catalyst surface, which covers the reaction sites, reduces the reaction rate, and thus poisons the catalyst.

[0004] Ion doping is a simple and effective modification method that can effectively improve the properties of semiconductor materials and optimize their intrinsic photoelectric properties, carrier concentration, charge transfer efficiency, and reactive oxygen species concentration. Currently, K-OMS-2 ion doping modification mainly focuses on transition metal ions or alkali (earth) metal ions, while less attention has been paid to aluminum (Al), an element that is less expensive and abundant in the Earth's crust. This invention is the first to discover Al... 3+ Modified K-OMS-2 nanorod photocatalysts can improve the photocatalytic oxidation performance of toluene. Summary of the Invention

[0005] In view of the above-mentioned problems existing in the prior art, the first technical problem to be solved by the present invention is to provide an Al 3+ A method for preparing modified K-OMS-2 photocatalysts, involving a one-step synthesis of Al via a simple hydrothermal reaction. 3+The modified K-OMS-2 photocatalyst has a simple process and is convenient for mass production. The second technical problem this invention aims to solve is to provide an Al... 3+ The modified K-OMS-2 photocatalyst exhibits good light absorption and redox capabilities. The third technical problem this invention aims to solve is to provide an Al... 3+ The application of modified K-OMS-2 photocatalyst in the catalytic oxidation of VOCs can convert toluene into non-toxic CO2, reducing environmental pollution.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] A kind of Al 3+ The modified K-OMS-2 photocatalyst is prepared by mixing MnSO4·H2O, KMnO4, Al(NO3)3·9H2O, concentrated nitric acid and deionized water, and carrying out a hydrothermal reaction. After the reaction is completed, the mixture is cooled, centrifuged, washed, dried, calcined and ground to obtain the Al-KM photocatalyst.

[0008] Furthermore, the hydrothermal reaction temperature is 160°C and the reaction time is 4 hours.

[0009] Furthermore, the drying temperature is 110°C and the drying time is 12 hours.

[0010] Furthermore, the atomic ratio of Al to Mn in the mixed solution is 1:9.

[0011] Furthermore, the mass ratio of MnSO4·H2O to KMnO4 is 2.48:1.66.

[0012] Furthermore, the calcination temperature is 300℃ and the calcination time is 6h.

[0013] Furthermore, the amount of concentrated nitric acid added is 3 ml.

[0014] Furthermore, the Al prepared by the method 3+ Modified K-OMS-2 photocatalyst.

[0015] Furthermore, the Al mentioned above 3+ Application of modified K-OMS-2 photocatalyst in the catalytic oxidation of VOCs.

[0016] Furthermore, the VOCs are toluene.

[0017] Beneficial effects: Compared with the prior art, the advantages of this invention are:

[0018] (1) The Al-KM photocatalyst prepared by the present invention has a simple preparation process, low toxicity, green and clean, and has the prospect of industrial application. Furthermore, the catalytic material exhibits excellent performance in removing low concentrations of toluene and has certain application value in treating low concentrations of volatile organic pollutants indoors.

[0019] (2) The Al-KM photocatalyst prepared in this invention, Al 3+ Incorporation into the K-OMS-2 framework alters, to some extent, the valence ratio of manganese ions and the content of reactive oxygen species in the K-OMS-2 host. The Al incorporated into the framework... 3+ This process creates more oxygen vacancies within the catalyst framework, enhancing its ability to deeply oxidize toluene. Simultaneously, it strengthens the catalyst's light absorption capacity and optimizes its redox potential, which helps extend the lifetime of photogenerated electron-hole pairs, thereby enhancing the catalyst's photocatalytic degradation ability for toluene.

[0020] (3) The Al-KM photocatalyst prepared in this invention can be used as a high-performance photocatalyst, doped with Al in the framework. 3+ With its abundant oxygen vacancies, Al-KM achieves a dual enhancement in adsorption and oxidation capabilities, which is beneficial for enhancing the adsorption of toluene and subsequent deep oxidation processes, thereby effectively improving the photocatalytic performance of the catalytic material. Therefore, Al-KM has broad application prospects in the photocatalytic purification of volatile organic compounds in indoor environments.

[0021] (4) This invention introduces Al 3+ Subsequently, the photoelectric properties of K-OMS-2 are enhanced, the recombination efficiency of photogenerated electron-hole pairs is reduced, which is conducive to the generation of active free radicals, thereby enhancing the catalyst's ability to oxidize toluene in many ways.

[0022] (5) This invention utilizes the abundant Al element in the Earth's crust to dope K-OMS-2 catalyst in a one-step process to prepare Al-KM photocatalyst. Under the condition of using only light, it can achieve efficient and green degradation of indoor volatile pollutant toluene. The technology is simple to operate and has a wide range of applications. It can be used to eliminate pollutants in indoor environments. Attached Figure Description

[0023] Figure 1 The XRD pattern of the sample prepared in this embodiment;

[0024] Figure 2 The H2-TPR and O2-TPD spectra of the sample prepared in this embodiment are shown below.

[0025] Figure 3 This is the SEM image of the sample prepared in this embodiment;

[0026] Figure 4 The photoelectric property spectrum of the sample prepared in this embodiment;

[0027] Figure 5 This is a graph showing the oxidation performance of the sample prepared in this embodiment on toluene under full-spectrum irradiation. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments.

[0029] Example 1

[0030] Preparation of K-OMS-2 nanorods: 2.48 g of hydrated manganese sulfate (MnSO4·H2O) and 1.66 g of potassium permanganate (KMnO4) were placed in a 150 mL stainless steel autoclave with a polytetrafluoroethylene liner, and 75 mL of deionized water was added. The reaction was carried out at a constant temperature of 160 °C for 4 h. After the reaction was completed, the mixture was naturally cooled to room temperature and washed three times by centrifugation with ultrapure water. The obtained sample was dried at 110 °C for 12 h. The dried sample was then placed in a muffle furnace and calcined at 300 °C for 6 h. After the calcination was completed, the product was naturally cooled to room temperature and then ground to obtain K-OMS-2 powder.

[0031] Example 2

[0032] Preparation of Al-KM nanorods: 2.48 g of hydrated manganese sulfate (MnSO4·H2O), 1.66 g of potassium permanganate (KMnO4), and 0.95 g of aluminum nitrate nonahydrate (Al(NO3)3·9H2O) were placed in a 150 mL stainless steel autoclave with a polytetrafluoroethylene liner. 75 mL of deionized water and 3 mL of concentrated nitric acid were added, and the reaction was carried out at a constant temperature of 160 °C for 4 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, and the sample was washed three times by centrifugation with ultrapure water. The obtained sample was dried at 110 °C for 12 h. The dried sample was placed in a muffle furnace and calcined at 300 °C for 6 h. After the calcination was completed, the sample was allowed to cool naturally to room temperature, and the product was ground to obtain Al-KM powder.

[0033] Figure 1 The figure shows the XRD pattern of the sample prepared in this embodiment. As can be seen from the figure, the diffraction peaks of the composite sample after metal ion doping did not shift significantly, indicating that the doping of foreign metal ions did not have a significant impact on the texture properties of OMS-2. However, the diffraction peaks of Al-KM at 60° to 61° showed a slight shift, which may be due to the Al... 3+ This is caused by incorporation into the K-OMS-2 backbone.

[0034] Figure 2 The above are the H2-TPR and O2-TPD spectra of the sample prepared in this embodiment. Figure 2 (a) is the H2-TPR spectrum of the prepared sample. Figure 2 (b) shows the O2-TPD spectrum of the prepared sample; Figure 2(a) It can be seen that after ion doping, the reduction peak at low or high temperatures shifts to lower temperatures. Compared with the pure K-OMS-2 sample, Al-KM exhibits a lower reduction temperature. Figure 2 (b) It can be seen that Al-KM has the lowest surface oxygen temperature, indicating that it has more active oxygen species in room temperature or low temperature catalysis and has a strong advantage in activating oxygen.

[0035] Figure 3 The image shows the SEM spectra of the sample prepared in this embodiment. As can be seen from the figure, the Al-doped sample retains the original slender nanorod structure, but the average length and dispersion of the nanorods are reduced. After doping, the specific surface area of ​​Al-KM is 65.64 m². 2 / g, while the specific surface area of ​​K-OMS-2 before doping is only 51.52m². 2 / g. It can be seen that Al doping can effectively increase the specific surface area and the adsorption capacity for toluene, which is conducive to the subsequent deep oxidation of toluene.

[0036] Figure 4 This is the photoelectric property spectrum of the sample prepared in this embodiment. Figure 4 (a) is the solid-state UV-vis DRS spectrum of the prepared sample. Figure 4 (b) PL spectrum of the prepared sample Figure 4 (c) shows the impedance spectrum (EISNyquist) of the prepared sample; from Figure 4 (a) It can be seen that Al 3+ The modified catalyst exhibits significantly enhanced light absorption. This superior light absorption facilitates the generation of photogenerated electron-hole pairs, thereby further promoting the formation of free radicals. Figure 4 (b) It can be seen that Al-KM exhibits the weakest PL emission peak intensity, indicating that it can effectively suppress the recombination of photogenerated electron-hole pairs and promote the effective separation of photogenerated charges. Figure 4 (c) It can be seen that Al-KM clearly has the smallest quister radius, which can be proven by Al. 3+ After modification, the internal resistance of the catalyst material is reduced, which is conducive to the rapid migration of photogenerated carriers, prolongs the lifetime of photogenerated charges, and thus improves the catalytic reaction activity.

[0037] Example 3

[0038] Catalytic oxidation performance test of Al-KM nanorods on toluene: The toluene oxidation reaction was carried out under full-spectrum irradiation, with a toluene concentration of 50 ppm in the flowing gas phase and a relative humidity of 20%.

[0039] The photocatalytic oxidation of toluene was carried out in a cylindrical reactor with a volume of 1.5 L, using a 300W xenon lamp as the simulated light source. 50 mg of catalyst was evenly spread on a 304 stainless steel mesh. A reaction gas with a stable relative humidity was continuously introduced during the catalytic oxidation process. The reacted gas was then analyzed by a gas chromatograph. The toluene conversion rate was calculated using the following formula:

[0040]

[0041] In the formula, [C7H8] in and [C7H8] out These represent the inlet and outlet concentrations (ppm) of gaseous toluene in the reactor.

[0042] Figure 5 The graph shows the toluene oxidation performance of the sample prepared in this embodiment under full-spectrum irradiation. As can be seen from the graph, K-OMS-2 initially exhibits high toluene removal performance, but its stability is insufficient. When Al is introduced... 3+ Subsequently, the stability of the photocatalytic oxidation of toluene was enhanced, and the CO2 concentration curve also indicated that the addition of Al... 3 Subsequently, CO2 production significantly increased, and even increased in the middle of the reaction, indicating its strong ability to mineralize toluene and effectively enhance the catalyst's resistance to poisoning. Compared to doping with transition metals Ni and Cu ions, the performance of Al-KM was significantly improved after Al doping. Therefore, by incorporating Al... 3+ Incorporating the K-OMS-2 framework can help improve the toluene conversion rate and activity stability of K-OMS-2, and promote the deep oxidation of toluene. This is mainly due to the Al... 3+ Modification can increase the content of reactive oxygen species in K-OMS-2, thereby optimizing the redox potential of the catalyst. At the same time, Al-KM exhibits the best light absorption capacity and the longest photogenerated electron-hole pair lifetime, which further contributes to the generation of free radicals in subsequent reactions.

[0043] Example 4

[0044] Application of Al-KM nanorods in toluene adsorption

[0045] Toluene adsorption was conducted in the dark with a toluene concentration of 50 ppm in the flowing gas phase and a relative humidity of 20%. During the dark adsorption process, Al-KM exhibited strong adsorption for various species. Peaks centered at 1376, 1402, and 1456 cm⁻¹ were observed. -1 The toluene adsorption peak at [value] cm⁻¹ appears at 1645, 1650–1652, 1662, and 1699 cm⁻¹. -1The signal peak belongs to benzaldehyde. The characteristic peaks of the further oxidation product benzoic acid are mainly distributed at 1538–1540 and 1558 cm⁻¹. -1 Near the same location, Al-KM exhibits a more prominent peak intensity compared to K-OMS-2. This is particularly evident in the 3300–3550 cm⁻¹ range. -1 Al-KM exhibits a relatively regular hydroxyl peak signal on the surface of the metal oxide, with the strongest intensity. Al-KM demonstrates a strong adsorption signal for hydroxyl groups, which are important active species in the toluene oxidation reaction. Furthermore, Al-KM exhibits the most sustained adsorption capacity and possesses more adsorption active sites. Comparing Al before and after doping... 3+ The introduction of Al-KM effectively enhanced the adsorption of reactants and intermediate species on the catalyst surface. Compared to other catalysts, we observed that K-OMS-2 and Zn-KM gradually approached adsorption saturation, while Al-KM maintained continuous adsorption capacity, indicating that Al-KM may possess more adsorption active sites. Further comparison of spectral scales revealed that the overall adsorption intensity followed the order Al-KM > Zn-KM > KM, demonstrating that ion doping effectively enhances the adsorption of reactants and intermediate species on the catalyst surface. Moreover, based on characterization results, Al-KM doped into the framework... 3+ It has a stronger effect on enhancing adsorption and activation capabilities.

Claims

1. An Al 3+ A method for preparing modified K-OMS-2 photocatalyst, characterized in that, MnSO4·H2O, KMnO4, Al(NO3)3·9H2O, concentrated nitric acid, and deionized water were mixed and subjected to a hydrothermal reaction. After the reaction, the mixture was cooled, centrifuged, washed, dried, calcined, and ground to obtain an Al-KM photocatalyst. The hydrothermal reaction was carried out at 160℃ for 4 hours. The drying temperature was 110℃ for 12 hours. The atomic ratio of Al to Mn in the mixed solution was 1:

9. The mass ratio of MnSO4·H2O to KMnO4 was 2.48:1.

66. The calcination temperature was 300℃ for 6 hours. The amount of concentrated nitric acid added was 3 ml.

2. The Al prepared by the method of claim 1 3+ Modified K-OMS-2 photocatalyst.

3. The Al as described in claim 2 3+ Application of modified K-OMS-2 photocatalyst in the catalytic oxidation of VOCs.

4. The Al according to claim 3 3+ The application of modified K-OMS-2 photocatalyst in the catalytic oxidation of VOCs is characterized by, The VOCs are toluene.

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