A catalyst with both oxidation-reduction sites and acid sites, a preparation method and application in catalysis of chlorine-containing mixed vocs
By preparing catalysts with both redox sites and acid sites, the problem of catalyst poisoning was solved, and efficient degradation of chlorine-containing VOCs was achieved, especially in the treatment of VOCs in the pharmaceutical industry, where it showed excellent stability and efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JILIN UNIVERSITY
- Filing Date
- 2026-04-20
- Publication Date
- 2026-06-16
Smart Images
Figure CN122209448A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalytic material preparation, specifically relating to a catalyst with both redox sites and acid sites for use in the pharmaceutical industry, its preparation method, and its application in the catalysis of chlorine-containing mixed VOCs. Background Technology
[0002] As one of the six major industrial emission sources, the pharmaceutical industry emits volatile organic compounds (VOCs) with a complex composition, including oxygenated VOCs (OVOCs), chlorinated VOCs (CVOCs), and aromatic hydrocarbons. These VOCs undergo a series of chemical reactions in the atmosphere, causing air pollution such as smog and ozone, which seriously harms the environment and human health.
[0003] In recent years, catalytic combustion technology (catalytic oxidation) has attracted widespread attention from researchers. This technology can achieve efficient VOCs removal with the help of catalysts, operates at low temperatures (below 500 °C), and produces minimal secondary pollution, significantly improving VOCs treatment efficiency and reducing energy consumption. The core of catalytic oxidation technology is a high-performance catalyst. Research has found that redox sites in the catalyst weaken the conjugation between C–Cl bonds through electron-withdrawing impacts, thus breaking the C–Cl bonds. However, due to the electronegativity of chlorine species, they are easily adsorbed onto redox sites. If they cannot be rapidly transferred and removed from the catalyst surface, they will combine with metals to form metal chlorides, thereby poisoning and deactivating the catalyst. Therefore, in the oxidation of chlorine-containing mixed VOCs, it is necessary to introduce dechlorination sites and maintain an appropriate distance from the redox sites to overcome the problem of chlorine species not being able to migrate and transform rapidly, leading to catalyst poisoning. Recent studies have shown that acid sites in the catalyst play a crucial role in C–Cl bond breaking and chlorine species migration and transformation. The breaking of the C–Cl bond is mainly related to Lewis acids, while the catalyst's ability to migrate and transform chlorine species is closely related to Brønsted acid sites (Brønsted acids). Therefore, it is necessary to regulate the acid sites and oxygen vacancies in the catalyst to enable the two active sites to cooperate efficiently and improve the catalyst's degradation efficiency for chlorine-containing mixed VOCs. Summary of the Invention
[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a catalyst with both redox sites and acid sites for use in the pharmaceutical industry, a preparation method, and its application in the catalysis of chlorine-containing mixed VOCs.
[0005] A method for preparing a catalyst possessing both redox sites and acid sites, comprising the following steps:
[0006] (1) Prepare a precursor solution with redox sites in the catalyst by mixing metal salt solution with citric acid;
[0007] (2) Select HZSM-5 molecular sieve to provide acidic sites in the catalyst, and use in-situ assembly method to disperse it in a certain proportion in the precursor solution obtained in step (1), and stir evenly;
[0008] (3) The mixed components obtained in step (2) are heated and evaporated into a paste, dried and calcined to obtain a catalyst with both redox sites and acid sites.
[0009] Furthermore, the metal salt solution mentioned in step (1) is one or more of cobalt salt, cerium salt, manganese salt, and nickel salt; the preferred metal salt is cobalt salt.
[0010] The molar ratio of the metal salt to citric acid is 1:0.5~5, preferably 1:1;
[0011] The silicon-aluminum atomic ratio of the HZSM-5 molecular sieve is 18~500:1, and the preferred silicon-aluminum atomic ratio is 50:1;
[0012] The mass ratio of the HZSM-5 molecular sieve to the metal salt is 1:0.5~10, and the preferred mass ratio is 1:2;
[0013] The calcination temperature is 300~800 ℃ and the calcination time is 2~5 h; the preferred calcination temperature is 450 ℃ and the calcination time is 3 h.
[0014] The catalyst described in this invention, which possesses both redox sites and acid sites, is prepared by the above-described preparation method.
[0015] This invention also provides the application of the above-mentioned catalyst, which has both redox sites and acid sites, in the catalysis of chlorine-containing mixed VOCs.
[0016] Compared with the prior art, the beneficial effects of the present invention are:
[0017] This invention addresses the treatment of chlorine-containing mixed VOCs in the pharmaceutical industry, creatively proposing the construction of "balanced adjacent" oxygen vacancy-acid sites (such as... Figure 1 The catalyst (shown) achieves C–Cl bond cleavage at relatively balanced oxygen vacancies and rapidly removes chlorine species at adjacent acid sites, realizing a 90% conversion rate of dichloromethane and acetone mixed components in chlorine-containing mixed VOCs at 300℃, and the catalyst maintains a stable conversion efficiency within 100 h. Attached Figure Description
[0018] Figure 1 Transmission electron microscope images and elemental distribution images of Example 1;
[0019] Figure 2 Comparative Example 3: Transmission electron microscope image and elemental distribution image;
[0020] Figure 3 (a) ~ Figure 3 (b): Catalytic oxidation activity curves of the catalysts prepared in Example 1 and the comparative example for dichloromethane and acetone; Figure 3 (c)~ Figure 3 (d): Catalytic oxidation stability test curves of the catalysts prepared in Example 1 and the comparative example for dichloromethane and acetone. Detailed Implementation
[0021] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments.
[0022] Example 1
[0023] A method for preparing a catalyst possessing both redox sites and acid sites, comprising the following steps:
[0024] (1) Prepare a precursor solution with redox sites in the catalyst by mixing 80 mL of cobalt nitrate aqueous solution (concentration of 0.25 mmol / mL) with 20 mL of citric acid aqueous solution (concentration of 1.00 mmol / mL);
[0025] (2) Weigh out HZSM-5 molecular sieve with a mass ratio of 1:2 to cobalt nitrate and a silicon-aluminum atomic ratio of 50:1 and disperse it in the precursor solution obtained in step (1), and stir until homogeneous;
[0026] (3) The mixed components obtained in step (2) are heated and evaporated at 80 °C for 6 h to form a paste, then dried at 110 °C for 3 h, and then calcined at 450 °C for 3 h to obtain 5 g of catalyst A which has both redox sites and acid sites.
[0027] 0.10 g of the prepared catalyst A was weighed and subjected to a fixed-bed reaction. The mixed gas contained 1000 ppm of dichloromethane standard gas (nitrogen as the balance gas), 1000 ppm of acetone standard gas (nitrogen as the balance gas), and 20% O2 by volume. The space velocity was 15000 mL / (g·h), and the activity was tested at 100–400 °C. The concentrations of reactants and products were determined by gas chromatography, and the VOCs conversion rate was calculated as [(VOCs concentration at reactor inlet - VOCs concentration at reactor outlet) / (VOCs concentration at reactor inlet)] × 100%.
[0028] Figure 1 The transmission electron microscope (TEM) image and elemental distribution image of catalyst A show that the metal oxides providing redox sites are in close contact and uniformly dispersed with the HZSM-5 molecular sieve providing acid sites, which will facilitate the migration and transformation of dechlorination species. Figure 2 In Comparative Example 3, the redox sites and acid sites are randomly distributed, which is not conducive to their synergistic effect. Figure 3 The catalytic oxidation activity and stability of catalyst A and the catalysts prepared in the comparative example for dichloromethane and acetone were tested. Figure 3 (a) ~ Figure 3 (b) On catalyst A, the temperatures required for 90% degradation of dichloromethane and acetone are 292 °C and 281 °C, respectively, which are lower than the temperatures required in the comparative example; furthermore, Figure 3 (c)~ Figure 3 (d) shows that catalyst A can maintain 90% degradation efficiency of dichloromethane and acetone for at least 100 h at 300 °C, while the control catalyst is severely deactivated after 20 h.
[0029] Example 2
[0030] The only difference between Example 2 and Example 1 is that in step (2), the mass ratio of HZSM-5 to cobalt nitrate is 1:3 (the mass of HZSM-5 is 1.94 g), and the mass of the catalyst B prepared is 5 g. 0.10 g of the prepared catalyst B is weighed and subjected to a fixed-bed reaction to test its catalytic performance on the mixed components of dichloromethane and acetone.
[0031] Example 3
[0032] The only difference between Example 3 and Example 1 is that in step (2), the mass ratio of HZSM-5 to cobalt nitrate is 1:4 (the mass of HZSM-5 is 1.46 g), and the mass of the catalyst C prepared is 5 g. 0.10 g of the prepared catalyst C is weighed and subjected to a fixed-bed reaction to test its catalytic performance on the mixed components of dichloromethane and acetone.
[0033] Example 4
[0034] The only difference between Example 4 and Example 1 is that in step (2), the mass ratio of HZSM-5 to cobalt nitrate is 1:5 (the mass of HZSM-5 is 1.16 g), and the mass of the catalyst D obtained is 5 g. 0.10 g of the obtained catalyst D is weighed and subjected to a fixed-bed reaction to test its catalytic performance on the mixed components of dichloromethane and acetone.
[0035] Example 5
[0036] The only difference between Example 5 and Example 4 is that the silicon-aluminum atomic ratio of HZSM-5 in step (2) is 21:1. The mass of the prepared catalyst E is 5g; 0.10g of the prepared catalyst E is weighed and subjected to a fixed-bed reaction to test its catalytic performance on the mixed components of dichloromethane and acetone.
[0037] Example 6
[0038] The only difference between Example 6 and Example 5 is that the calcination temperature used in step (3) is 800 °C. The mass of the catalyst F obtained is 5 g; 0.10 g of the obtained catalyst F is weighed and subjected to fixed-bed reaction to test its catalytic performance on the mixed components of dichloromethane and acetone.
[0039] Example 7
[0040] The only difference between Example 7 and Example 1 is that the silicon-aluminum atomic ratio of HZSM-5 in step (2) is 200:1. The mass of the catalyst G prepared is 5g; 0.10g of the prepared catalyst G is weighed and subjected to a fixed-bed reaction to test its catalytic performance on the mixed components of dichloromethane and acetone.
[0041] Example 8
[0042] The only difference between Example 8 and Example 7 is that the calcination temperature used in step (3) is 600 °C. The mass of the catalyst H prepared is 5 g; 0.10 g of the prepared catalyst H is weighed and subjected to a fixed-bed reaction to test its catalytic performance on the mixed components of dichloromethane and acetone.
[0043] Example 9
[0044] The only difference between Example 9 and Example 7 is that the calcination temperature used in step (3) is 300 °C. The mass of the catalyst I prepared is 5 g; 0.10 g of the prepared catalyst I was weighed and subjected to a fixed-bed reaction to test its catalytic performance on the mixed components of dichloromethane and acetone.
[0045] Example 10
[0046] The only difference between Example 10 and Example 1 is that the metal salt solution used in step (1) is an aqueous solution of cerium nitrate, and the mass of the catalyst J prepared is 5g; 0.10g of the prepared catalyst J is weighed and subjected to a fixed-bed reaction to test its catalytic performance on the mixed components of dichloromethane and acetone.
[0047] Example 11
[0048] The only difference between Example 11 and Example 1 is that the metal salt solution used in step (1) is an aqueous solution of manganese nitrate, and the mass of the catalyst K prepared is 5g; 0.10g of the prepared catalyst K is weighed and subjected to a fixed-bed reaction to test its catalytic performance on the mixed components of dichloromethane and acetone.
[0049] Example 12
[0050] The only difference between Example 11 and Example 1 is that the metal salt solution used in step (1) is an aqueous solution of cobalt nitrate and manganese nitrate (the molar ratio of the two is 1:1), and the mass of the catalyst L prepared is 5g; 0.10g of the prepared catalyst L is weighed and subjected to a fixed-bed reaction to test its catalytic performance on the mixed components of dichloromethane and acetone.
[0051] Comparative Example 1
[0052] The difference between Comparative Example 1 and Example 1 is that step (2) is omitted, that is, HZSM-5 is not added. The mass of the catalyst obtained is 5g. 0.10g of the prepared catalyst is weighed and subjected to fixed-bed reaction to test its catalytic performance on the mixed components of dichloromethane and acetone.
[0053] Comparative Example 2
[0054] Comparative Example 2 used HZSM-5 with a silicon-to-aluminum atomic ratio of 50:1 as a catalyst. 0.10 g of HZSM-5 was weighed and subjected to a fixed-bed reaction to test its catalytic performance on a mixture of dichloromethane and acetone.
[0055] Comparative Example 3
[0056] Comparative Example 3 involved physically mixing the products obtained from Comparative Example 1 and Comparative Example 2 at a mass ratio of 1:2 to obtain a catalyst with a mass of 15g. 0.10g of the prepared catalyst was weighed and subjected to a fixed-bed reaction to test its catalytic performance on a mixture of dichloromethane and acetone.
[0057] Table 1: Oxidation efficiency data of catalysts for dichloromethane and acetone obtained in the examples and comparative examples
[0058] Example Metal salts Molecular sieve-metal salt mass ratio The silicon-to-aluminum atomic ratio of molecular sieves Calcination temperature (°C) Temperature (°C) required for 90% conversion of dichloromethane Temperature (°C) required for 90% acetone conversion Comparative Example 1 Cobalt nitrate / / 450 322 294 Comparative Example 2 Cobalt nitrate / 50：1 / 345 Greater than 400 Comparative Example 3 Cobalt nitrate 1:2 50：1 450 349 347 Example 1 Cobalt nitrate 1:2 50：1 450 292 281 Example 2 Cobalt nitrate 1:3 50：1 450 285 300 Example 3 Cobalt nitrate 1:4 50：1 450 270 315 Example 4 Cobalt nitrate 1:5 50：1 450 280 303 Example 5 Cobalt nitrate 1:5 21：1 450 275 325 Example 6 Cobalt nitrate 1:5 21：1 800 353 340 Example 7 Cobalt nitrate 1:2 200：1 450 345 324 Example 8 Cobalt nitrate 1:2 200：1 600 342 330 Example 9 Cobalt nitrate 1:2 200：1 300 335 321 Example 10 Cerium nitrate 1:2 50：1 450 312 296 Example 11 manganese nitrate 1:2 50：1 450 324 283 Example 12 The molar ratio of cobalt nitrate to manganese nitrate is 1:1. 1:2 50：1 450 307 298
[0059] As shown in the table, the conversion rates of the catalyst for dichloromethane and acetone are related to the type of metal salt, the mass ratio of the molecular sieve to the metal salt, the silicon-to-aluminum atomic ratio of the molecular sieve, and the calcination temperature. When the metal salt is cobalt nitrate, the mass ratio of the molecular sieve to the metal salt is 1:2, the silicon-to-aluminum atomic ratio of the molecular sieve is 50:1, and the calcination temperature is 450 ℃, the catalyst requires a lower temperature to oxidize the mixed components of dichloromethane and acetone. Therefore, by adjusting the appropriate acidic and redox site strengths and distances between the molecular sieve and the metal oxide, and ensuring their efficient "coordination," the efficient removal of chlorine-containing mixed VOCs can be achieved, providing a significant possibility for the treatment of VOCs emitted from the pharmaceutical industry.
[0060] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a catalyst possessing both redox sites and acid sites, comprising the following steps: (1) Prepare a precursor solution with redox sites in the catalyst by mixing metal salt solution with citric acid; (2) Select HZSM-5 molecular sieve to provide acidic sites in the catalyst, and use in-situ assembly method to disperse it in a certain proportion in the precursor solution obtained in step (1), and stir evenly; (3) The mixed components obtained in step (2) are heated and evaporated into a paste, dried and calcined to obtain a catalyst with both redox sites and acid sites.
2. The method for preparing a catalyst possessing both redox sites and acid sites as described in claim 1, characterized in that: In step (1), the metal salt solution is one or more of cobalt salt, cerium salt, manganese salt, and nickel salt.
3. The method for preparing a catalyst possessing both redox sites and acid sites as described in claim 1, characterized in that: In step (1), the molar ratio of metal salt to citric acid is 1:0.5~5.
4. The method for preparing a catalyst possessing both redox sites and acid sites as described in claim 1, characterized in that: In step (2), the silicon-aluminum atomic ratio of HZSM-5 molecular sieve is 18~500:
1.
5. The method for preparing a catalyst possessing both redox sites and acid sites as described in claim 1, characterized in that: In step (2), the mass ratio of HZSM-5 molecular sieve to metal salt is 1:0.5~10.
6. The method for preparing a catalyst possessing both redox sites and acid sites as described in claim 1, characterized in that: In step (3), the calcination temperature is 300~800 ℃ and the calcination time is 2~5 h.
7. A catalyst possessing both redox sites and acid sites, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 6.
8. The application of the catalyst with both redox sites and acid sites as described in claim 7 in the catalysis of chlorine-containing mixed VOCs.