A peroxide-supported mn-based oxide catalyst, its preparation method and use

Abstract

The application discloses a kind of peroxide load Mn base oxide catalyst and its preparation method and application, it is with H2O, CH2Cl2 stratification as interface, KMnO4, Zr (NO3) 4 is dissolved to upper H2O, n-butylamine is slowly injected into lower CH2Cl2, n-butylamine enters aqueous phase reaction from organic phase in the reaction process, δ-MnO2 is generated on interface, and is adsorbed on δ-MnO2 surface, further agglomeration of product is hindered, and mesoporous δ-MnO2 is formed.In addition, n-butylamine is alkaline, in the process of slowly diffusing to upper solution, Zr 4+ In the application, the obtained MnZr catalyst is immersed in (NH) 3PO4 solution, and a phosphate load MnZr oxide catalyst is obtained by centrifugal drying and calcination.The raw materials used in the method are cheap and easy to obtain, and the method is simple and easy to popularize.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of preparation methods of high-efficiency CVOCs catalysts, in particular to a Mn-based oxide catalyst loaded with acid radical salt, a preparation method thereof and application thereof in the removal of CVOCs in fixed sources (chlor-alkali industry, pharmaceutical and chemical industry, pesticide and chemical industry, etc.). BACKGROUND

[0002] With the development of industry, various pollution problems have become increasingly serious, and air pollution is one of them. Chlorine-containing volatile organic compounds (CVOCs) are major air pollutants, mainly derived from the use and emission of CVOCs-containing products. Low-temperature catalytic oxidation technology is a promising CVOCs control technology due to its low reaction temperature, low energy consumption, high safety, etc.

[0003] Generally, the catalytic oxidation process of CVOCs includes four steps: adsorption, activation, Cl dissociation and deep oxidation. The resistance to chlorine poisoning depends on the adsorption and dissociation of Cl on the acid sites. In addition, the form of Cl dissociation plays a crucial role in the production of polychlorinated by-products. The introduction of B acid sites to promote the dechlorination of HCl is an effective strategy to inhibit the chlorination of organic compounds and the formation of polychlorinated by-products. Based on the Marse van Krevelen (MvK) mechanism, the catalytic oxidation of VOCs largely depends on the recycling of oxygen species through the oxygen vacancies on the transition metal oxide catalyst. Therefore, by simultaneously increasing the oxygen vacancies and acid sites, the oxidation and acidity of the transition metal oxide are synergistically improved, which is an effective strategy to improve the catalytic activity of CB oxidation, resist chlorine poisoning and inhibit by-products.

[0004] Manganese-based catalysts have been widely studied as a catalyst for low-temperature CVOC catalytic oxidation. Mn, as a transition element with multiple valence states, not only promotes electron transfer, but also generates oxygen vacancies, promoting the migration of oxygen species in the conversion of Zr, as a cheap and non-toxic transition metal element, has been widely used in various catalyst formulations. The doping of Zr can increase the oxygen vacancy content in Mn oxides, and the coordination between Mn and Zr is conducive to the formation of acid sites; in addition to bulk doping, the surface loading of phosphate can induce the formation of surface oxygen vacancies of the catalyst, and the hydroxyl groups introduced by phosphate provide abundant acid sites. Therefore, the design and synthesis of Mn-based oxide catalysts with abundant oxygen vacancies and acid sites are of great significance for the efficient removal of CVOCs in chlor-alkali industry, pharmaceutical and chemical industry, pesticide and chemical industry, etc. SUMMARY

[0005] The application provides a peroxo salt loaded Mn-based oxide catalyst, a preparation method thereof and application thereof in removing CVOCs in chlor-alkali industry, pharmaceutical chemical industry, pesticide chemical industry and the like.

[0006] The prepared catalyst has high specific surface area, rich oxygen vacancies and acid sites, which exhibit excellent low-temperature catalytic performance in catalytic oxidation of CVOCs (90% removal efficiency can be reached at 181 DEG C under a space velocity of 50000 h-1 and a load of 500 ppm chlorobenzene). -1 Meanwhile, raw materials used in the catalyst are cheap and easy to obtain, and the preparation method is simple and fast, so the catalyst has a potential application prospect in the field of catalytic oxidation of CVOCs.

[0007] A preparation method of a peroxo salt loaded Mn-based oxide catalyst, comprising the following steps:

[0008] 1) KMnO4 and metal salt are weighed and dissolved in water to form solution A;

[0009] dichloromethane is taken as solution B;

[0010] solution A is poured into a reactor containing solution B, and layering is waited to form an interface, and the reactor is placed in a 20-30 DEG C water bath;

[0011] n-butylamine is injected into the lower dichloromethane in the reactor, and a yellow-brown precipitate is generated at the interface, the precipitate is centrifuged, dried and moved to a muffle furnace, and is calcined at 300-400 DEG C in an air atmosphere for 2-4 hours to obtain a MnZr oxide catalyst;

[0012] 2) the MnZr oxide catalyst is dissolved in water, stirred and ultrasonically dispersed, and peroxo salt is added and stirred, and after stirring, centrifugation, water washing and drying, the peroxo salt loaded Mn-based oxide catalyst is moved to a muffle furnace and is calcined at 300-400 DEG C in an air atmosphere for 2-4 hours.

[0013] The application uses KMnO4 and n-butylamine as raw materials, and prepares a mesoporous catalyst with rich pores and high specific surface area by using an interface oxidation-reduction method; the application uses the alkalinity of n-butylamine to slowly precipitate metal cations in the upper layer while generating delta-MnO2 by oxidation-reduction, so that a manganese-based composite oxide catalyst with uniform element doping is prepared, and the formation of oxygen vacancies is promoted; the application loads peroxo salt on the manganese-based composite oxide catalyst to prepare a peroxo salt loaded Mn-based oxide catalyst, and the synergistic promotion of oxygen vacancies and acid sites is promoted.

[0014] In step 1), the metal salt is at least one of Zr(NO3)3, Zr(NO3)4, Fe(NO3)3, Sn(NO3)4, Ni(NO3)2.

[0015] In step 1), the molar ratio of the metal salt to KMnO4 is 1:1-7.

[0016] In step 1), the molar ratio of n-butylamine to KMnO4 is 3-7:1.

[0017] In step 1), the standing time is 10-30h.

[0018] In step 2), the acid salt is one of (NH)3PO4·2H2O, (NH4)2SO4, (NH4)6W7O 24 ·6H2O, (NH4)2MoO4.

[0019] In step 2), the mass ratio of the acid salt to the MnZr oxide catalyst is 0.5-2.0:1.

[0020] In step 2), the acid salt is added and stirred for 1-20h using a sealing film.

[0021] Further, the specific technical solutions of the present application are as follows:

[0022] Take 3.16g (0.02mol) KMnO4, dissolve an appropriate amount of Zr(NO3)4 in 100ml deionized water, continuously stir for 30min, form solution A; measure 50ml CH2Cl2, mark as solution B. First slowly pour B solution into a 250ml beaker, then slowly pour A solution into it, stand for 5min, wait for layering, form the interface, place the beaker in a 25℃ water bath. Take 7.314g (0.1mol) n-butylamine, introduce it into a syringe, slowly inject the n-butylamine into the lower CH2Cl2, stand for 24h, generate yellow-brown precipitate at the interface, centrifuge and wash with water 6 times, dry at 80℃ for 8h, then move to a muffle furnace, calcine at 350℃ in an air atmosphere for 3h, obtain Mn-based composite oxide catalyst Zr1Mn x , 1 / x represents the molar ratio of Zr(NO3)4 to KMnO4 of different samples. Dissolve 1g Zr1Mn x oxide catalyst in 40ml deionized water, stir for 30min, then ultrasonic disperse for 30min, take an appropriate amount of (NH)3PO4·2H2O and dissolve it in the above solution, stir for 10h, then centrifuge and wash with water 3 times, dry at 80℃ for 8h, then move to a muffle furnace, calcine at 350℃ in an air atmosphere for 3h, obtain phosphoric acid group loaded Mn-based composite oxide catalyst nP-Zr1Mn xn% represents the P in (NH4)3PO4·2H2O feed and Zr1Mn x The mass ratio of the catalyst.

[0023] The preparation method of the high-performance Mn-based composite oxide low-temperature CVOCs removal catalyst described above, the preferred nitrate is Zr(NO3)4, and there is better mutual synergy between Mn and Zr.

[0024] The preferred molar ratio of Zr(NO3)4 to KMnO4 is 1 / 5.

[0025] The preferred standing time after slow injection of n-butylamine is 24h, and the reaction is not complete if the time is too short, and the product particle size is too large if the time is too long.

[0026] The preferred acid salt is (NH4)3PO4·2H2O, and the phosphate has better electron control ability on the surface of the Mn oxide.

[0027] The preferred amount of (NH4)3PO4·2H2O feed is 0.98g, and the loading amount of phosphate is too small if the amount is too small, and the loading amount is too much if the amount is too much.

[0028] The preferred stirring time after dissolving (NH4)3PO4·2H2O is 10h, and the loading amount is too small if the time is too short, and the loading amount is too much if the time is too long.

[0029] A high-performance Mn-based composite oxide low-temperature CVOCs removal catalyst prepared by the above preparation method.

[0030] The high-performance phosphate-loaded Mn-based composite oxide low-temperature CVOCs removal catalyst described above is applied to CVOCs in tail gas in chlor-alkali industry, pharmaceutical chemical industry, and pesticide chemical industry.

[0031] Compared with the prior art, the present application has the following advantages:

[0032] 1. The raw materials used are cheap and easy to obtain, the preparation method is simple, the equipment is simple, and it is easy to popularize and can be produced on a large scale.

[0033] 2. It is a universal preparation method of acid salt-loaded Mn-based composite oxides.

[0034] 3. The manganese-based composite oxide catalyst prepared by the method has the advantages of rich mesoporous structure, high specific surface area, rich oxygen vacancies, acidic sites, uniform dispersion of loaded elements, etc., thereby showing excellent low-temperature CVOCs catalytic oxidation activity and stability. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The XRD results of the manganese-based composite oxide catalyst.

[0036] Figure 2 SEM results of the Mn-based composite oxide catalysts.

[0037] Figure 3 N2-adsorption-desorption results of the Mn-based composite oxide catalysts.

[0038] Figure 4 EDS results of the Mn-based composite oxide catalysts.

[0039] Figure 5 TEM results of the Mn-based composite oxide catalysts.

[0040] Figure 6 NH3-TPD results of the Mn-based composite oxide catalysts.

[0041] Figure 7 Activity results (removal efficiency) of the Mn-based catalysts in catalyzing the oxidation of chlorobenzene.

[0042] Figure 8 Stability test results of the Mn-based catalysts in catalyzing the oxidation of chlorobenzene.

[0043] Figure 9 Activity results of the 15P-Zr1Mn5 catalyst in catalyzing the oxidation of dichloromethane, chloroethylene and dichloroethane. DETAILED DESCRIPTION

[0044] Example 1, Preparation of Zr1Mn3 Mn-based catalyst

[0045] Accurately weighed 3.16 g (0.02 mol) of KMnO4, 2.87 g of Zr(NO3)4·5H2O was dissolved in 100 ml of deionized water, continuously stirred for 30 min to form solution A; 50 ml of CH2Cl2 was measured and recorded as solution B. First, slowly pour the B solution into a 250 ml beaker, then slowly pour the A solution, stand for 5 min, wait for the layering, form the interface, place the beaker in a 25°C water bath. Weigh 7.314 g (0.1 mol) of n-butylamine, introduce it into a syringe, slowly inject the n-butylamine into the lower layer of CH2Cl2, stand for 24 hours, a yellow-brown precipitate is generated at the interface, centrifuge and wash the precipitate with water for 6 times, dry at 80°C for 8 hours, then move to a muffle furnace, calcine at 350°C for 3 hours in air atmosphere, to obtain the Mn-based composite oxide catalyst Zr1Mn3. The BET test results show that the specific surface area of the Zr1Mn3 Mn-based composite oxide catalyst prepared with a molar ratio of Zr(NO3)4 to KMnO4 of 1 / 3 reaches 127.7 m 2 / g, the average pore size is 10.48 nm, and the pore volume reaches 0.314 cm 3 / g (as shown in Table 1).

[0046] Example 2, Preparation of Zr1Mn5 Manganese-based catalyst

[0047] The mass of Zr(NO3)4·5H2O taken in Example 1 was changed to 1.72 g, and the rest of the conditions were unchanged to obtain the Mn-based catalyst Zr1Mn5 sample. The BET test results showed that the specific surface area of the Zr1Mn5 manganese-based composite oxide catalyst prepared with a molar ratio of Zr(NO3)4 to KMnO4 of 1 / 5 reached 193.8 m2 / g, the average pore size was 5.47 nm, and the pore volume reached 0.474 cm3 / g (as shown in Table 1). 2 3

[0048] Example 3, Preparation of Zr1Mn7 manganese-based catalyst

[0049] The mass of Zr(NO3)4·5H2O taken in Example 1 was changed to 1.23 g, and the rest of the conditions were unchanged to obtain the Mn-based catalyst Zr1Mn7 sample. The BET test results showed that the specific surface area of the Zr1Mn7 manganese-based composite oxide catalyst prepared with a molar ratio of Zr(NO3)4 to KMnO4 of 1 / 7 reached 131.2 m2 / g, the average pore size was 16.58 nm, and the pore volume reached 0.291 cm3 / g (as shown in Table 1). 2 3

[0050] Example 4, Preparation of 10P-Zr1Mn5 manganese-based catalyst

[0051] 1 g of the Zr1Mn5 catalyst obtained in Example 2 was weighed, dissolved in 40 ml of deionized water, and stirred for 30 min before being ultrasonically dispersed for 30 min. 0.65 g of (NH)3PO4·2H2O was weighed and dissolved in the above solution, and stirred for 10 h before being centrifuged and washed with water three times. After drying at 80°C for 8 hours, it was moved to a muffle furnace and calcined at 350°C for 3 hours in an air atmosphere to obtain 10P-Zr1Mn5 with a P loading of 10%. The BET test results showed that the specific surface area of the prepared 10P-Zr1Mn5 catalyst reached 189.27 m2 / g, the average pore size was 6.63 nm, and the pore volume reached 0.375 cm3 / g (as shown in Table 1). 2 3

[0052] Example 5, Preparation of 15P-Zr1Mn5 manganese-based catalyst

[0053] The mass of (NH)3PO4·2H2O taken in Example 4 was changed to 0.98 g, and the rest of the conditions were unchanged to obtain 15P-Zr1Mn5 with a P loading of 15%. The BET test results showed that the specific surface area of the prepared 15P-Zr1Mn5 catalyst reached 182.9 m2 / g.​​​​​​2 / g, the average pore size was 6.89 nm, and the pore volume reached 0.347 cm 3 / g (as shown in Table 1).

[0054] Example 6, Preparation of 20P-Zr1Mn5 Manganese-based catalyst

[0055] The mass of (NH)3PO4·2H2O taken in Example 4 was changed to 1.30 g, and the rest of the conditions were unchanged, to obtain 20P-Zr1Mn5 with a P loading of 20%. The BET test results showed that the specific surface area of the prepared 15P-Zr1Mn5 catalyst reached 173.2 m 2 / g, the average pore size was 7.74 nm, and the pore volume reached 0.335 cm 3 / g (as shown in Table 1).

[0056] The XRD results of the manganese-based composite oxide catalysts are shown in Figure 1 From the figure, it can be seen that the obtained catalysts present a δ-MnO2 crystal phase, and as the molar ratio of Zr(NO3)4 to KMnO4 increases, the XRD peak intensity decreases, and as the phosphate loading increases, the structure gradually tends to be amorphous.

[0057] The SEM results of the manganese-based composite oxide catalysts are shown in Figure 2 From the figure, it can be seen that the catalysts have a large number of pore structures.

[0058] The N2-adsorption / desorption results of the manganese-based composite oxide catalysts are shown in Figure 3 From the figure, it can be seen that the catalysts have abundant mesopores, and Zr doping improves the specific surface area of Mn oxides.

[0059] The EDS results of the manganese-based composite oxide catalysts are shown in Figure 4 From the figure, it can be seen that the Zr, Mn, and P elements of the 15P-Zr1Mn5 catalyst prepared with a molar ratio of Zr(NO3)3 to KMnO4 of 1 / 5 and a phosphate loading of 15% are uniformly dispersed, which is due to the fact that the interface preparation method is conducive to the full mixing of Zr and Mn, and the doping of Zr improves the specific surface area of Mn oxides, which is conducive to the uniform loading of phosphates and helps to form a stronger synergistic effect between elements.

[0060] The TEM results of the manganese-based composite oxide catalysts are shown in Figure 5 From the figure, it can be seen that the yellow T represents lattice distortion, and the green oval frame represents lattice defects, indicating that the 15P-Zr1Mn5 catalyst prepared with a molar ratio of Zr(NO3)3 to KMnO4 of 1 / 5 and a phosphate loading of 15% has a large number of lattice defects, indicating that abundant oxygen vacancies are formed.

[0061] NH3-TPD results of Mn-based composite oxide catalysts are shown in Figure 6 The doping of Zr increases the weak acid amount of δ-MnO2, and the loading of phosphate increases the strong acid amount of δ-MnO2.

[0062] Chlorobenzene oxidation activity results (removal efficiency) of Mn-based catalysts are shown in Figure 7 Chlorobenzene oxidation stability test results of Mn-based catalysts are shown in Figure 8 Dichloromethane, chloroethylene, dichloroethane oxidation activity results of 15P-Zr1Mn5 catalyst are shown in Figure 9 From Figure 7 , 8, 9, it can be seen that the phosphate-loaded Mn-based composite oxide series catalysts have good low-temperature catalytic oxidation activity and stability when catalyzing the oxidation of CVOCs.

[0063] Table 1

[0064]

[0065] The catalysts prepared in Examples 1, 2, 3, 4, 5, and 6 were applied to CVOCs catalytic oxidation reactions, and all showed good catalytic activity. The removal efficiency of the catalysts prepared in Examples 1, 2, 3, 4, 5, and 6 is shown in Figure 6 The reaction was carried out on a CVOCs catalytic oxidation evaluation device, which mainly consisted of four parts: gas pipeline, fixed bed reactor, flow control system, and gas detection system. During the experiment, mass flow meters were used to accurately control the flow of each gas. A quartz tube with an outer diameter of 10 mm and an inner diameter of 6 mm was used as the catalytic reactor, which was heated by a resistance furnace and the temperature inside the reactor was monitored by a K-type thermocouple. The total flow of the mixed gas was 50 mL·min -1 , of which the volume fraction of O2 was 20%, and the chlorobenzene was controlled at 1000 mL·min -3 by adjusting the flow ratio of the two standard air flows. During the experiment, the loading of the catalyst was 300 mg, the particle size was 40-60 mesh, and the corresponding mass space velocity (WHSV) was 10000 mL·(g·h) -1 .

Claims

1. A method for preparing an acid salt-supported Mn-based oxide catalyst, characterized in that: The following steps are involved: 1) Weigh KMnO4 and metal salt Zr(NO3)4, dissolve them in water, and stir to form solution A; Take dichloromethane and record it as solution B; Pour solution A into the reactor containing solution B, wait for the layers to separate and form an interface, and place the reactor in a water bath at 20-30°C; Inject n-butylamine into the lower layer of dichloromethane in the reactor and let it stand. A yellow-brown precipitate is generated at the interface. The precipitate is centrifuged, dried, and transferred to a muffle furnace. It is calcined at 300-400°C in an air atmosphere for 2-4 hours to obtain a MnZr oxide catalyst showing a δ-MnO2 crystal phase. 2) The MnZr oxide catalyst was dissolved in water, stirred, and then ultrasonically dispersed. The acid salt (NH4)3PO4·2H2O was added and stirred. After stirring, the mixture was centrifuged and washed with water and dried. The mixture was then transferred to a muffle furnace and calcined at 300-400°C in an air atmosphere for 2-4 hours to obtain an acid salt-supported Mn-based oxide catalyst.

2. The method for preparing the acid salt-supported Mn-based oxide catalyst according to claim 1, wherein: In step 1), the molar ratio of the metal salt to KMnO4 is 1:1-7.

3. The method for preparing the acid salt-supported Mn-based oxide catalyst according to claim 1, wherein: In step 1), the molar ratio of n-butylamine to KMnO4 is 3-7:

1.

4. The method for preparing the acid salt-supported Mn-based oxide catalyst according to claim 1, wherein: In step 1), the standing time is 10-30 h.

5. The method for preparing the acid salt-supported Mn-based oxide catalyst according to claim 1, wherein: In step 2), the mass ratio of the acid radical salt to the MnZr oxide catalyst is 0.5-2.0:

1.

6. The method for preparing an acid salt-supported Mn-based oxide catalyst according to claim 1, wherein: In step 2), add acid salt and stir with sealing film for 1-20 h.

7. An acid salt-supported Mn-based oxide catalyst prepared according to the preparation method according to any one of claims 1 to 6.

8. Use of the acid salt-supported Mn-based oxide catalyst according to claim 7 in the removal of CVOCs at low temperature.

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