Manganese cerium aerogel multifunctional catalytic material and preparation method and application thereof

Abstract

The application discloses a manganese-cerium aerogel multifunctional catalytic material and a preparation method and application thereof. Tetraethyl orthosilicate, ethanol and water are uniformly stirred to obtain a silica sol; manganese acetate and cerium nitrate are dissolved in water, and the silica sol is added and stirred to obtain a gel; an aging solution is poured into the gel for aging, then hexane is used for replacement, then gradient drying is carried out, and finally, calcination and heat preservation are carried out to obtain a metal-loaded silicon aerogel; the above gel is immersed in an acetic acid solution to etch metal oxides on the surface of the aerogel, and the obtained sample is washed by deionized water and dried; tetrapropylammonium hydroxide and urea are dissolved in water, and aluminum isopropoxide is added and stirred at room temperature; the obtained solution is sprayed on aerogel powder, and the mixture is placed in a polytetrafluoroethylene inner liner of a reaction kettle, and then the reaction kettle is placed in an oven for hydrothermal crystallization; subsequent washing, suction filtration, drying and calcination are carried out to obtain a manganese-cerium-loaded aerogel molecular sieve composite multifunctional catalytic material.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of waste liquid treatment, in particular to a manganese cerium aerogel multifunctional catalytic material, a preparation method and application thereof, and is applied to the cracking and oxidation of organic matters contained in waste liquid in a gas-solid fluidization system. BACKGROUND

[0002] In today's rapid industrialization process, the treatment of chemical waste liquid has become an important issue that cannot be avoided in environmental protection and sustainable industrial development. Chemical waste liquid, especially waste from pharmaceutical, textile, petroleum chemical industry and other fields, due to its complex composition, high chemical oxygen demand (COD) and biochemical oxygen demand (BOD), rich in organic matter, and at the same time has flammable and explosive, corrosive and reactive characteristics, which brings great challenge to the treatment. If these waste liquids are not properly treated and directly discharged, not only will it cause serious damage to the aquatic ecosystem, but also may accumulate through the food chain, ultimately affecting human health.

[0003] For the treatment of such high concentration of organic waste liquid, the traditional methods such as physical precipitation, chemical oxidation, biological degradation, etc. often due to low efficiency, high cost or secondary pollution and other problems limit its wide application. In recent years, with the increasingly stringent environmental regulations and the continuous progress of environmental protection technology, it is particularly important to explore efficient, economical and environmentally friendly waste liquid treatment technology. Among them, the use of fluidized bed reaction system for waste liquid cracking oxidation treatment, because it can realize the efficient conversion of organic matter, has gradually become a research hotspot. The fluidized bed reaction system is a kind of reactor that can enhance the mass and heat transfer efficiency by making the solid particles in a fluidized state. In this system, the waste liquid is atomized and fully contacted with the catalyst in a fluidized state, which can promote the cracking oxidation reaction of organic matter under normal pressure conditions, and finally convert into harmless inorganic small molecules such as carbon dioxide and water. This treatment method not only can effectively reduce the organic matter content in the waste liquid, but also can reduce the emission of harmful substances, has high environmental benefits and potential economic value. However, the conventional catalysts face many challenges when applied to the gas-solid fluidization system for waste liquid treatment. First of all, due to the large specific gravity of the catalyst, its gas-solid fluidization performance in the fluidized bed is poor, and it is difficult to maintain a stable fluidized state, which affects the catalytic efficiency. Secondly, the catalyst has poor moisture resistance, and its activity is easily reduced or even deactivated in a high humidity environment, resulting in a significant reduction in treatment effect. In addition, the mass and heat transfer performance of conventional catalysts in the reaction process is difficult to effectively control, and the reaction often shows a disordered state, which not only affects the conversion efficiency of organic matter, but also may cause side reactions and produce new pollutants. Therefore, the development of a new type of catalytic material to overcome the above problems of conventional catalysts in the gas-solid fluidization system for waste liquid treatment has become a key technical problem to be solved in the field of waste liquid treatment. In particular, how to optimize the specific gravity, moisture resistance and mass and heat transfer performance of the catalyst through material design, and how to improve the stability and catalytic activity of the catalyst, are the core directions of the research and development of new catalytic materials. Under this background, the proposal of manganese-cerium aerogel molecular sieve composite multifunctional catalyst material provides a new idea and possibility for efficient treatment of chemical waste liquid. SUMMARY

[0004] The technical problem solved by the present application is to provide a manganese-cerium aerogel multifunctional catalyst material, its preparation method and application, which has a wide application environment and few self-restrictions.

[0005] Technical solution: A preparation method of manganese cerium aerogel multifunctional catalytic material, the preparation steps comprising: (a) stirring uniformly tetraethyl orthosilicate, ethanol and water, the molar ratio of the tetraethyl orthosilicate, ethanol and water is n (TEOS) : n (EtOH) : n (H2O) = 1: (3-12) : (3-8), the pH is adjusted to 2-3, and then hydrolysis is carried out to obtain a silica sol; (b) dissolving manganese acetate and cerium nitrate two metal salts in water, the corresponding oxides formed after calcination of the metal salts account for 2wt.%-30wt.% of the mass of the aerogel carrier, after mixing, the mixture is added to the silica sol and stirred, the pH is adjusted to 6-8, and the gel is obtained by standing at room temperature; (c) preparing an aging liquid by mixing tetraethyl orthosilicate and ethanol, the volume ratio is V (ETOH) / V (TEOS) = (4-10) : 1, pouring the aging liquid into the gel for aging, then replacing with n-hexane, then gradient drying, and finally calcining and heat preservation to obtain a metal-loaded silicon aerogel; (d) immersing the aerogel in an acetic acid solution for stirring to etch the metal oxides on the surface of the aerogel, washing the obtained sample with deionized water until the filtrate is neutral, and drying in an oven; (e) dissolving tetrapropylammonium hydroxide and urea in water, then adding aluminum isopropoxide, stirring at room temperature, the molar ratio of the aluminum isopropoxide, tetrapropylammonium hydroxide, water and urea is n (AIP) : n (TPAOH) : n (H2O) : n (urea) = 1: (5-20) : (800-3000) : (20-80), spraying the obtained solution on the aerogel powder, standing at room temperature, then transferring the mixture to a polytetrafluoroethylene reaction kettle inner liner, placing the reaction kettle in an oven for hydrothermal crystallization, and then washing, suction filtering, drying and calcining to obtain a manganese cerium-loaded aerogel molecular sieve composite multifunctional catalytic material.

[0006] Preferably, in the step (a), the molar ratio of the tetraethyl orthosilicate, anhydrous ethanol and deionized water is (TEOS) : n (EtOH) : n (H2O) = 1:4:4; the pH adjusting agent is 0.1-1 mol / L dilute hydrochloric acid; the hydrolysis temperature is 25-60℃, and the hydrolysis time is 0.5-5h.

[0007] Preferably, in the step (b), the pH adjusting agent is 0.1-2.5 mol / L dilute ammonia water.

[0008] Preferably, in the step (c), the volume ratio of the aging liquid is V (ETOH) / V (TEOS) = 4:1; the aging temperature is 25-70℃, the aging time is 24-72h; the replacement temperature is 25-60℃, the time is 9-24h; the gradient drying temperature is 2-4 points within 50-200℃, and the drying time at each temperature point is 1-4h; the calcination temperature is 400-700℃, and the heat preservation time is 4-6h.

[0009] Preferably, the stirring time in step (d) is 20-120 min; the drying temperature is 60-120 DEG C, and the time is 8-12 h.

[0010] Preferably, the molar ratio of aluminum isopropoxide, tetrapropylammonium hydroxide, ionized water and urea in step (e) is n(AIP):n(TPAOH):n(H2O):n(urea) = 1:10:1500:40; the stirring time is 1-24 h; the room temperature standing time is 3-15 h; the hydrothermal temperature is 80-180 DEG C, and the hydrothermal time is 9-72 h; the drying temperature is 80-120 DEG C, and the drying time is 8-12 h; the calcination temperature is 400-600 DEG C, and the calcination time is 3-6 h.

[0011] The manganese cerium aerogel multifunctional catalytic material obtained by the preparation method.

[0012] The application of the manganese cerium aerogel multifunctional catalytic material in cracking and oxidizing organic matters in chemical waste liquid in a fluidized system.

[0013] Beneficial effects: 1. The inner layer of the catalytic material is an aerogel main body loaded with metal active sites, the inner pores are developed, the density is lower than that of ordinary catalysts, and the catalytic material is easy to fluidize. 2. The outer layer of the catalytic material is a molecular sieve film, so that the material has good hydrophobicity and is not easy to be deactivated in an environment rich in water molecules. 3. The double-layer structure of the catalytic material weakens the interference of the external environment on the inner active metal sites, and effectively protects the core oxidation area. 4. The catalytic material makes the reaction cracking and oxidation process orderly controllable, the heat released by the organic matters is transferred from the inside to the outside, the outer layer cracking process is strengthened, and the energy is fully utilized. 5. The catalytic material realizes the catalytic cracking and catalytic oxidation of organic matter under high humidity environment and gas-solid fluidization state, greatly reduces the reaction energy consumption and macro pyrolysis temperature through heat complementation, and provides support for efficient and low-energy pyrolysis of waste liquid. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 It is the effect comparison chart of the examples and the comparative examples of the application for removing COD of waste liquid.

[0015] Figure 2 It is the expansion ratio chart of the examples and the comparative examples of the application under different gas flow rates.

[0016] Figure 3 It is a scanning electron microscope graph of example 1 of the application.

[0017] Figure 4 It is a scanning electron microscope graph of the comparative example. DETAILED DESCRIPTION

[0018] The application designs a manganese cerium aerogel multifunctional catalytic material. The inner layer of the catalyst is an aerogel main body loaded with metal active sites, the inner pores of which are developed, the density of which is controllable, the catalyst is lower than ordinary catalysts, and the catalyst is easy to fluidize. The outer layer is a molecular sieve film, so that the material has good hydrophobicity and is not easy to be deactivated in an environment rich in water molecules. At the same time, the double-layer structure weakens the interference of the external environment on the inner active metal sites, effectively protecting the core oxidation area. The macromolecules of the organic matter are cracked into small organic molecules at the acid sites of the outer layer of the catalyst, and continue to migrate inward through the pores to the inner layer, and are subjected to severe oxidation combustion and release a large amount of heat under the active oxygen environment of the active sites in the inner layer. The heat is transferred from the inside to the outside, strengthening the cracking process of the outer layer, so that the energy can be fully utilized. The multifunctional catalyst realizes the coupling of catalytic cracking and catalytic oxidation of organic matter in a high-humidity environment and a gas-solid fluidized state, greatly reduces the reaction energy consumption and the macro pyrolysis temperature through heat complementation, and provides support for efficient and low-energy pyrolysis of waste liquid.

[0019] Example 1

[0020] (1) Add 17.38 g of tetraethyl orthosilicate (TEOS), 19.16 g of anhydrous ethanol and 7.48 g of deionized water into a beaker, magnetically stir for 30 min to mix uniformly, then drop 1 mol / L dilute hydrochloric acid, adjust pH to 2-3, hydrolyze for 2 h under 40℃ water bath, to obtain silica sol. (2) Dissolve 0.35 g of manganese acetate tetrahydrate and 0.32 g of cerium nitrate hexahydrate in 5 mL of deionized water, mix uniformly, then add to the above silica sol, continue to stir for 30 min, add 2.5 mol / L dilute ammonia water to adjust pH to 6-8, and stand at room temperature to obtain a gel. (3) Stir 10 mL of tetraethyl orthosilicate and 40 mL of anhydrous ethanol uniformly for 15 min to prepare an aging solution, pour into the above gel, and age at 50℃ water bath for 24 h. After the end, replace with n-hexane at 40℃ for 10 h, then dry at 60℃, 80℃, 100℃, 120℃ and 150℃ under normal pressure for 2 h respectively. Place in a muffle furnace at 550℃ for 5 h to obtain a silica aerogel loaded with metal, which is ground into powder for use. (4) Disperse the above aerogel powder into acetic acid solution, stir at room temperature for 30 min to etch the metal oxide on the surface of the aerogel. Wash the obtained sample with deionized water until the filtrate is neutral, and finally dry in a 100℃ oven for 12 h. (5) Dissolve 6.79 g of tetrapropylammonium hydroxide (TPAOH) and 4 g of urea in 90.10 g of deionized water, then add 0.69 g of aluminum isopropoxide (AIP) and stir at room temperature for 2 h. Spray the aerogel powder with the solution, stand at room temperature for 12 h, then transfer the mixture to a polytetrafluoroethylene reaction kettle liner, place in an oven at 180℃ for hydrothermal crystallization for 48 h. Subsequently, wash, suction filter and dry in a 100℃ oven for 8 h, and finally obtain the catalyst material after removing the template agent at 500℃ in a muffle furnace for 5 h.

[0021] Example 2

[0022] (1) Add 17.38 g of tetraethyl orthosilicate (TEOS), 19.16 g of anhydrous ethanol and 7.48 g of deionized water into a beaker, stir magnetically for 30 min to mix evenly, then drop 1 mol / L dilute hydrochloric acid to adjust the pH to 2-3, hydrolyze for 2 h under 40 °C water bath, and obtain a silica sol. (2) Dissolve 0.35 g of manganese acetate tetrahydrate and 0.32 g of cerium nitrate hexahydrate in 5 mL of deionized water, mix evenly, then add to the silica sol prepared in the above step (1), continue to stir for 30 min, add 2.5 mol / L dilute ammonia water to adjust the pH value to 6-8, and stand at room temperature to obtain a gel. (3) Stir 10 mL of tetraethyl orthosilicate and 40 mL of anhydrous ethanol for 15 min to prepare an aging solution, pour into the gel prepared in step (2), and age at 50 °C water bath for 24 h. After the aging is completed, replace with n-hexane at 40 °C for 10 h, then dry at 60 °C, 80 °C, 100 °C, 120 °C and 150 °C under normal pressure for 2 h respectively. Place in a muffle furnace at 550 °C for 5 h to obtain a metal-loaded silicon aerogel, which is ground into powder for use. (4) Disperse the above aerogel powder into an acetic acid solution, stir at room temperature for 30 min to etch the metal oxide on the surface of the aerogel. Wash the obtained sample with deionized water until the filtrate is neutral, and finally dry in an oven at 100 °C for 12 h. (5) Dissolve 6.79 g of tetrapropylammonium hydroxide (TPAOH) and 4 g of urea in 90.10 g of deionized water, then add 0.69 g of aluminum isopropoxide (AIP), stir at room temperature for 2 h, use the solution to spray the aerogel powder, stand at room temperature for 12 h, then transfer the mixture to a polytetrafluoroethylene inner liner of a reaction kettle, place in an oven at 150 °C for hydrothermal crystallization for 72 h. After subsequent washing, suction filtration and drying in an oven at 100 °C for 8 h, finally remove the template agent at 500 °C in a muffle furnace for 5 h to obtain a catalyst material.

[0023] Example 3

[0024] (1) Into a beaker, 17.38 g of tetraethyl orthosilicate (TEOS), 19.16 g of anhydrous ethanol and 7.48 g of deionized water were added, and the mixture was stirred magnetically for 30 min to be uniformly mixed, then 1 mol / L dilute hydrochloric acid was added dropwise to adjust the pH to 2-3, and hydrolysis was carried out at 40°C water bath for 2 h to obtain a silica sol. (2) 0.35 g of manganese acetate tetrahydrate and 0.32 g of cerium nitrate hexahydrate were dissolved in 5 mL of deionized water, and then added to the silica sol prepared in the above step (1), and stirred for 30 min, then 2.5 mol / L dilute ammonia water was added to adjust the pH to 6-8, and the gel was obtained by standing at room temperature. (3) 10 mL of tetraethyl orthosilicate and 40 mL of anhydrous ethanol were stirred uniformly for 15 min to prepare an aging solution, which was poured into the gel prepared in step (2), and then aged at 50°C water bath for 24 h, after which the aging solution was replaced with n-hexane at 40°C for 10 h, and then dried at 60°C, 80°C, 100°C, 120°C and 150°C for 2 h respectively under normal pressure. Then, the sample was placed in a muffle furnace and heated at 550°C for 5 h to obtain a metal-loaded silicon aerogel, which was ground into powder for use. (4) The silicon aerogel powder was dispersed in an acetic acid solution, and the metal oxide on the surface of the aerogel was etched by stirring at room temperature for 30 min. The obtained sample was washed with deionized water until the filtrate was neutral, and finally dried in an oven at 100°C for 12 h. (5) 6.79 g of tetrapropylammonium hydroxide (TPAOH) and 4 g of urea were dissolved in 90.10 g of deionized water, and then 0.69 g of aluminum isopropoxide (AIP) was added, and the mixture was stirred at room temperature for 2 h. The obtained solution was used to spray the aerogel powder, and the mixture was left to stand at room temperature for 12 h, and then transferred to a polytetrafluoroethylene inner liner of a reaction kettle, and placed in an oven at 120°C for hydrothermal crystallization for 36 h. Subsequently, the sample was washed, suction-filtered and dried in an oven at 100°C for 8 h, and finally calcined at 500°C in a muffle furnace for 5 h to remove the template agent to obtain the catalyst material.

[0025] Comparative Example

[0026] 0.8 g of manganese acetate tetrahydrate and 0.72 g of cerium nitrate hexahydrate were weighed into a beaker, and then 40 mL of deionized water was added to the beaker, and the mixture was stirred magnetically for 30 min until the salt was completely dissolved. Then, 11.4 g of ZSM-5 molecular sieve with a silicon-aluminum ratio of 50 was added to the solution, and the mixture was stirred for 12 h, and then ultrasonicated for 15 min. Then, the mixture was transferred to an oven and dried at 80°C for 12 h, and finally the sample was placed in a muffle furnace and heated at 500°C for 3 h to obtain a conventional molecular sieve supported catalyst, which was ground into powder for use.

[0027] Performance test of the example and the comparative example

[0028] (liquid waste COD removal rate test) with self-prepared high concentration phenol-containing simulated liquid waste as target pollutants, the initial COD was tested by potassium dichromate method, then the materials prepared in examples 1, 2, 3 and the comparative example were used as catalysts, which were filled into the reaction tube, the temperature program was started, the temperature was set to 350℃, after the reaction temperature reached, air was introduced into the reaction tube from the bottom at a speed of 500mL / min, and the phenolic waste liquid was input into the reaction tube by a micro-injection pump at a speed of 10mL / h, at the same time, the end condensing device of the reaction system was opened, the condensate was collected and its COD was tested, compared with the initial COD and the COD removal rate was calculated. In addition, the program was set to 350℃, 360℃, 370℃, 380℃, 390℃, 400℃ respectively, and other steps were the same as above, the test was carried out and the COD was tested. The COD removal effect of the four materials at different temperatures is shown in Figure 1 As can be seen from the figure, in this reaction system, the COD removal effect of examples 1, 2 and 3 at different temperatures is better than that of the comparative example, in addition, the COD removal rate of the comparative example at 400℃ just reaches the level of examples at 350℃, which shows that the energy released by the inner layer oxidation of organic molecules is transferred to the outer layer, which supplements the energy for the outer layer cracking process, so that the energy is more fully utilized, thereby reducing the reaction energy consumption and macroscopic pyrolysis temperature, which reflects the advantages of high efficiency and low energy of the catalyst of examples.

[0029] (expansion ratio) 20g of the materials prepared in examples 1, 2, 3 and the comparative example were taken respectively and put into the reaction tube, then air was introduced from the bottom of the reaction tube at a flow rate of 200mL / min, 400mL / min and 600mL / min respectively, and the expansion was recorded (as shown in Figure 2 As can be seen from the figure, under different air flow rates, the expansion ratio of examples is much larger than that of the comparative example, so examples are more easily fluidized than the comparative example.

[0030] The embodiments of the present application are described in detail above in combination with the drawings, but the present application is not limited to the above-described embodiments, and for those skilled in the art, after learning the contents described in the present application, without departing from the principles of the present application, a number of equivalent transformations and substitutions can be made, which should be regarded as belonging to the protection scope of the present application.

Claims

1. A method for preparing a manganese cerium aerogel multifunctional catalytic material, characterized in that, The preparation steps comprise: (a) stirring tetraethyl orthosilicate, ethanol and water uniformly, the molar ratio of the tetraethyl orthosilicate, ethanol and water being n (TEOS): n (EtOH): n (H2O) = 1: (3-12): (3-8), adjusting pH to 2-3, and then hydrolyzing to obtain a silica sol; (b) dissolving manganese acetate and cerium nitrate in water, the corresponding oxides formed after calcination of the two metal salts accounting for 2wt.%-30wt.% of the mass of the aerogel carrier, stirring uniformly, adding to the silica sol, adjusting pH to 6-8, and standing at room temperature to obtain a gel; (c) preparing an aging solution of tetraethyl orthosilicate and ethanol, the volume ratio being V (ETOH) / V (TEOS) = (4-10): 1, pouring into the gel for aging, then replacing with n-hexane, and then gradient drying, and finally calcining and keeping warm to obtain a metal-loaded silica aerogel; (d) stirring the aerogel in an acetic acid solution to etch the metal oxides on the surface of the aerogel, washing the obtained sample with deionized water until the filtrate is neutral, and drying in an oven; (e) dissolving tetrapropylammonium hydroxide and urea in water, adding aluminum isopropoxide, stirring at room temperature, the molar ratio of the aluminum isopropoxide, tetrapropylammonium hydroxide, water and urea being n (AIP): n (TPAOH): n (H2O): n (urea) = 1: (5-20): (800-3000): (20-80), spraying the obtained solution on the aerogel powder, standing at room temperature, then transferring the mixture to a polytetrafluoroethylene inner liner of a reaction kettle, placing the reaction kettle in an oven for hydrothermal crystallization, and finally washing, suction filtering, drying and calcining to obtain a manganese-cerium-loaded aerogel molecular sieve composite multifunctional catalytic material.

2. The method for preparing the manganese cerium aerogel multifunctional catalytic material according to claim 1, characterized in that, In step (a), the molar ratio of the tetraethyl orthosilicate, anhydrous ethanol and deionized water is (TEOS): n (EtOH): n (H2O) = 1:4:4; the pH adjusting agent is 0.1-1mol / L dilute hydrochloric acid; and the hydrolysis temperature is 25-60℃ and the hydrolysis time is 0.5-5h.

3. The method for preparing the manganese cerium aerogel multifunctional catalytic material according to claim 1, characterized in that, In step (b), the pH adjusting agent is 0.1-2.5mol / L dilute ammonia water.

4. The method for preparing the manganese cerium aerogel multifunctional catalytic material according to claim 1, characterized in that, In step (c), the volume ratio of the aging solution is V (ETOH) / V (TEOS) = 4:1; the aging temperature is 25-70℃ and the aging time is 24-72h; the replacement temperature is 25-60℃ and the time is 9-24h; the gradient drying temperature is 50-200℃ and the drying time at each temperature point is 1-4h; and the calcination temperature is 400-700℃ and the keeping warm time is 4-6h.

5. The method for preparing the manganese cerium aerogel multifunctional catalytic material according to claim 1, characterized in that, In step (d), the stirring time is 20-120min; and the drying temperature is 60-120℃ and the time is 8-12h.

6. The method for preparing the manganese cerium aerogel multifunctional catalytic material according to claim 1, characterized in that, The molar ratio of aluminum isopropyl alcohol, tetrapropyl ammonium hydroxide, ionized water and urea in step (e) is n (AIP) : n (TPAOH) : n (H2O) : n (urea) = 1:10:1500:40; the stirring time is 1-24 h; the standing time at room temperature is 3-15 h; the hydrothermal temperature is 80-180 ℃, the hydrothermal time is 9-72 h; the drying temperature is 80-120 ℃, the drying time is 8-12 h; the calcination temperature is 400-600 ℃, and the calcination time is 3-6 h.

7. The manganese cerium aerogel multifunctional catalytic material obtained by the preparation method of any one of claims 1-6.

8. The use of the manganese cerium aerogel multifunctional catalytic material in claim 7 in the pyrolysis oxidation fluidized system for organic matters contained in chemical waste liquid.

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