CN109589977B - Preparation method of silver-based catalyst for degrading VOCs (volatile organic compounds) - Google Patents

Abstract

The invention discloses a preparation method of a silver-based catalyst for degrading VOCs (volatile organic compounds), which comprises the following steps: soaking the activated carbon fiber sheet in a methanol solution, washing, drying, soaking in a NaOH solution, and drying. Putting the obtained activated carbon fiber sheet into (NH)₄)₂C₂O₄·H₂O and KMnO₄Adding hydrochloric acid into the mixed solution to adjust the pH value of the mixed system, then placing the mixed system in a constant-temperature oil bath kettle to be stirred and reacted, taking out the activated carbon fiber sheet after the reaction is finished, washing and drying. Adding aqueous ammonia solution to AgNO₃To the solution and stirred until the solution became clear. Soaking the obtained activated carbon fiber sheet in transparent solution and adding H₂O₂And (4) stirring the solution. Finally, the activated carbon fiber is taken out, washed, dried and calcined to obtain Ag/MnO₂-an ACF catalyst. The method greatly improves the degradation rate and mineralization rate of the VOCs and enhances the stability while realizing stronger adsorption of the VOCs.

Description

Preparation method of silver-based catalyst for degrading VOCs (volatile organic compounds)

Technical Field

The invention belongs to the technical field of catalysts, and particularly relates to a silver-based catalyst for degrading VOCs (volatile organic compounds) and a preparation method thereof.

Background

With the increasing serious pollution of the atmospheric environment, people are more aware of the threat of the air environment to human health, and the VOCs (volatile organic compounds), namely the volatile organic pollutants, are extremely harmful pollutants in the atmosphere, so that the human respiratory mucosa can be directly damaged, surface skin allergy can be caused, and photochemical smog and ozone which are formed by secondary reaction in the atmosphere further cause greater harm to the human health are further caused. The national departments have incorporated the discharge of VOCs into control targets, and therefore the development of efficient VOCs degradation technology is becoming more important. By using Ag/MnO₂The catalytic degradation of VOCs by the ACF catalyst is one of the most efficient methods, and the VOCs content is reduced by the efficient degradation and is converted into CO₂And H₂And the harmless emission of O is realized.

Most of the existing high-efficiency catalysts are mainly nano-scale crystal catalysts, the reaction temperature is generally higher (above 110 ℃), the noble metal catalysts are used more in the supported catalysts, the noble metals are expensive, the industrial application is difficult, the utilization rate of the noble metals is improved, and the catalytic reaction is carried out at normal temperature to realize the catalysisThe economic and safety of degrading VOCs has become an important research direction. In Ag/MnO₂In the ACF catalyst, the size of the Ag active site is reduced to realize atomic-scale loading, so that the Ag active site is highly dispersed, the catalytic activity is improved, the utilization rate of noble metal Ag is improved, and MnO is simultaneously used₂The carrier with stronger adsorption function formed by the carrier and the ACF carrier not only enhances the load stability of Ag single atoms, but also exerts the synergistic effect of adsorption and catalysis and greatly improves the catalytic activity.

Ag/MnO₂The stable dispersion of the monoatomic Ag in the ACF catalyst is closely related to the vacancy of the catalyst surface, and the realization of the monoatomic stable load is facilitated according to the vacancy of the carrier surface. In the course of research on silver nanoparticle catalysts, the tang happy topic group, etc. found that the catalytic reaction occurred mainly at the surrounding atoms where the carrier and the metal were in contact, and it is very desirable to reduce the particle size of the noble metal to improve the metal atom utilization. NiO/AL was used separately for longlisan et AL₂O₃、CoO/AL₂O₃、MnO₂/AL₂O₃、Fe₂O₃/AL₂O₃And CuO/AL₂O₃The performance of the catalyst for catalyzing ozone to oxidize toluene is researched, and the toluene degradation rate of the catalyst with the best catalytic performance under the normal temperature condition is only 40%. Cu-Mn-Ce-O/gamma-AL is used for simaclet and the like₂O₃The catalyst degrades toluene at the temperature of 110-130 ℃ under certain ozone concentration, and the conversion rate of toluene reaches 83.9 percent. The nanometer catalyst still has the defect of low catalytic performance at normal and low temperature. The size of the active site is reduced, the utilization rate of the noble metal can be improved, and the catalytic activity is also improved to a certain extent. TiO supported by MinLi or the like₂On the activated carbon fiber, the efficient degradation of toluene is realized under the condition of ultraviolet light. However, no relevant report is found in the article of stably loading the monoatomic atom on the Activated Carbon Fiber (ACF).

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a preparation method of a catalyst for VOCs degradation, which can realize efficient degradation of VOCs at normal temperature, can also give full play to the utilization rate of noble metals to realize monatomic loading, and enhances the possibility of industrial application of the catalyst.

The technical scheme adopted by the invention for solving the technical problem is as follows:

the invention relates to a preparation method of a catalyst for VOCs degradation, which comprises the following steps:

(1) soaking the activated carbon fiber sheet in a methanol solution with the concentration of 0.1-0.2mol/L for 3-5min, then washing with deionized water for 3-5min to remove possible residues on the surface, taking out and placing the activated carbon fiber sheet into a beaker, placing the beaker in an oven with the temperature of 55-65 ℃ for 20-30min, taking out and placing the beaker into a NaOH solution with the concentration of 0.5-1mol/L for 2-3min, placing the activated carbon fiber sheet stained with the NaOH solution into the beaker, placing the beaker into an oven with the temperature of 100 ℃ and 120 ℃ and heating for 30-40min to promote the hydrolysis of the surface of the activated carbon fiber;

(2) taking (NH) with the mass ratio of (1-1.5) to 4₄)₂C₂O₄·H₂O and KMnO₄Dissolving the KMnO in deionized water to form a mixed solution, wherein the KMnO is a non-ionic surfactant₄The solid-to-liquid ratio of the deionized water to the deionized water is (0.015g-0.020g) 1 ml;

putting the activated carbon fiber sheet obtained in the step (1) into the mixed solution, adding 0.2-0.5mol/L hydrochloric acid to adjust the pH value of the mixed system to 7-7.3, then putting the mixed system into a constant-temperature oil bath kettle at 90-110 ℃, stirring at the stirring speed of 140-160rpm for reaction for 9-11h, taking out the activated carbon fiber sheet after the reaction is finished, washing the activated carbon fiber sheet with deionized water for 3-5 times, and putting the activated carbon fiber sheet into an oven at 60-80 ℃ for drying for 40-60 min; the activated carbon fiber sheet and KMnO₄The mass ratio of (1) to (0.3-0.6);

(3) slowly adding ammonia water solution with the mass fraction of 25% -30% into AgNO₃Stirring the solution until the solution becomes transparent; the AgNO₃AgNO in solution₃The mass ratio of the activated carbon fiber sheet taken in the step (1) to the activated carbon fiber sheet taken in the step (1) is (0.005-0.010) to 1;

(4) mixing 30-35% of H₂O₂Adding the solution into the transparent solution obtained in the step (3), soaking the activated carbon fiber sheet obtained in the step (2), stirring at 0-10 ℃ for 30-40min, finally filtering the mixture in the beaker, and washing the filtrate with deionized water for 3-5 times, wherein H is₂O₂H in solution₂O₂With AgNO₃The mass ratio of (1.5-2) is 1;

(5) drying the washed filtrate at 60-80 deg.C for 10-12h, calcining at 300-400 deg.C for 3-5h to obtain Ag/MnO₂-ACF。

The invention has the beneficial effects that: in Ag/MnO₂In the ACF catalyst, the size of the Ag active site is reduced to realize atomic-scale loading, so that the Ag active site is highly dispersed, the catalytic activity is improved, the utilization rate of noble metal Ag is improved, and MnO is simultaneously used₂The carrier with stronger adsorption function formed by the carrier and the ACF carrier not only enhances the load stability of Ag single atoms, but also exerts the synergistic effect of adsorption and catalysis and greatly improves the catalytic activity.

Drawings

FIG. 1 shows the preparation of Ag/MnO in accordance with the present invention₂-ACF catalyst process schematic.

Detailed Description

The present invention will be described in detail with reference to specific examples.

The invention relates to a preparation reaction formula of an Ag/Mn2-ACF monatomic catalyst, which comprises the following steps:

KMnO₄+(NH₄)₂C₂O₄·H₂O+-OH→MnO₂-

NH₃·H₂O+AgNO₃→Ag(NH₃)₂OH+H₂O

Ag(NH₃)₂OH+H₂O₂+MnO₂-→AgMnO₂-

the Activated Carbon Fiber (ACF) also has abundant hydroxyl groups, which can be oxidized by potassium permanganate to form MnO chemically bonded with the ACF₂And further with MnO₂MnO formed by reaction of potassium permanganate and ammonium oxalate in liquid phase as minor crystals₂Form MnO with more holes on the surface of the ACF stably₂ACF carrier, in turn loading Ag monatomic into MnO by the inverse Ostwald method₂On an ACF carrier, thereby obtaining a monoatomic Ag/MnO₂-an ACF catalyst.

Based on the above principle, the preparation method of the catalyst for the adsorption and degradation of VOCs of the invention comprises the following steps:

(1) soaking the activated carbon fiber sheet in a methanol solution with the concentration of 0.1-0.2mol/L for 3-5min, then washing with deionized water for 3-5min to remove possible residues on the surface, taking out and placing the activated carbon fiber sheet into a beaker, placing the beaker in an oven with the temperature of 55-65 ℃ for 20-30min, taking out and placing the beaker into a NaOH solution with the concentration of 0.5-1mol/L for 2-3min, placing the activated carbon fiber sheet stained with the NaOH solution into the beaker, and placing the beaker into an oven with the temperature of 100-120 ℃ for heating for 30-40min to promote the hydrolysis of the surface of the activated carbon fiber.

(2) Taking (NH) with the mass ratio of (1-1.5) to 4₄)₂C₂O₄·H₂O and KMnO₄Dissolving the KMnO in deionized water to form a mixed solution, wherein the KMnO is a non-ionic surfactant₄The solid-liquid ratio of the deionized water to the deionized water is (0.015g-0.020g) and 1 ml. And (2) putting the activated carbon fiber sheet obtained in the step (1) into the mixed solution, adding 0.2-0.5mol/L hydrochloric acid to adjust the pH value of the mixed system to 7-7.3, then putting the mixed system into a constant-temperature oil bath kettle at 90-110 ℃, stirring at the stirring speed of 140-160rpm for reaction for 9-11h, taking out the activated carbon fiber sheet after the reaction is finished, washing with deionized water for 3-5 times, and putting into an oven at 60-80 ℃ for drying for 40-60 min. The activated carbon fiber sheet and KMnO₄The mass ratio of (1) to (0.3-0.6).

(3) Slowly adding ammonia water solution with the mass fraction of 25% -30% into AgNO₃To the solution and stirred until the solution became clear. The AgNO₃AgNO in solution₃The mass ratio of the activated carbon fiber sheet taken in the step (1) to the activated carbon fiber sheet taken in the step (1) is (0.005-0.010): 1.

(4) Mixing 30-35% of H₂O₂Adding the solution into the transparent solution obtained in the step (3), soaking the activated carbon fiber sheet obtained in the step (2), stirring at 0-10 ℃ for 30-40min, finally filtering the mixture in the beaker, and washing the filtrate with deionized water for 3-5 times, wherein H is₂O₂H in solution₂O₂With AgNO₃The mass ratio of (1.5-2) to (1).

(5) Drying the washed filtrate at 60-80 deg.C for 10-12h, calcining at 300-400 deg.C for 3-5h to obtain Ag/MnO₂-ACF。

Example 1

(1) Soaking 0.1g of activated carbon fiber sheet in a methanol solution with the concentration of 0.1mol/L for 3min, then washing the activated carbon fiber sheet with deionized water for 3min to remove possible residues on the surface, taking out the activated carbon fiber sheet, placing the activated carbon fiber sheet in a beaker, placing the beaker in an oven with the temperature of 55 ℃ for 20min, taking out the beaker, placing the beaker in a NaOH solution with the concentration of 0.5mol/L for 2min, placing the activated carbon fiber sheet dipped with the NaOH solution in the beaker, and placing the beaker in the oven with the temperature of 100 ℃ for heating for 30min to promote the hydrolysis of the surface of the activated.

(2) Taking (NH) with the mass ratio of 1:4₄)₂C₂O₄·H₂O and KMnO₄Dissolving the KMnO in deionized water to form a mixed solution, wherein the KMnO is a non-ionic surfactant₄The solid-to-liquid ratio of the deionized water is 0.015g to 1 ml. And (2) putting the activated carbon fiber sheet obtained in the step (1) into the mixed solution, adding 0.2mol/L hydrochloric acid to adjust the pH value of the mixed system to 7, then putting the mixed system into a 90-DEG C constant-temperature oil bath kettle, stirring at a stirring speed of 140rpm for reaction for 9 hours, taking out the activated carbon fiber sheet after the reaction is finished, washing with deionized water for 3 times, and putting the activated carbon fiber sheet into a 60-DEG C oven for drying for 40 minutes. The activated carbon fiber sheet and KMnO₄The mass ratio of (A) to (B) is 1: 0.3.

(3) Slowly adding ammonia water solution with the mass fraction of 25% into AgNO₃To the solution and stirred until the solution became clear. The AgNO₃AgNO in solution₃The mass ratio of the active carbon fiber tablets to the active carbon fiber tablets obtained in the step (1) is 0.005: 1.

(4) Mixing 30% of H₂O₂Adding the solution into the transparent solution obtained in the step (3), soaking the activated carbon fiber sheet obtained in the step (2), stirring at 0 ℃ for 30min, finally filtering the mixture in a beaker, and washing the filtrate with deionized water for 3 times, wherein H is₂O₂H in solution₂O₂With AgNO₃In a mass ratio of 1.5: 1.

(5) Drying the washed filtrate at 60 deg.C for 10h, and calcining at 300 deg.C for 3h to obtain Ag/MnO₂ACF, noted A.

Example 2

(1) Soaking 0.1g of activated carbon fiber sheet in a methanol solution with the concentration of 0.15mol/L for 4min, then washing with deionized water for 4min to remove possible residues on the surface, taking out and placing the activated carbon fiber sheet into a beaker, placing the beaker in a 60 ℃ oven for 25min, taking out and placing the beaker into a NaOH solution with the concentration of 0.8mol/L for 2.5min, then placing the activated carbon fiber sheet stained with the NaOH solution into the beaker, and placing the beaker in an oven with the temperature of 110 ℃ for heating for 35min to promote hydrolysis of the surface of the activated carbon fiber.

(2) Taking (NH) with the mass ratio of 1.2:4₄)₂C₂O₄·H₂O and KMnO₄Dissolving the KMnO in deionized water to form a mixed solution, wherein the KMnO is a non-ionic surfactant₄The solid-to-liquid ratio of the deionized water is 0.018:1 ml. And (2) putting the activated carbon fiber sheet obtained in the step (1) into the mixed solution, adding 0.3mol/L hydrochloric acid to adjust the pH value of the mixed system to 7.2, then putting the mixed system into a 100 ℃ constant-temperature oil bath kettle, stirring and reacting for 10 hours at a stirring speed of 150rpm, taking out the activated carbon fiber sheet after the reaction is finished, washing with deionized water for 4 times, and putting the activated carbon fiber sheet into a 70 ℃ oven for drying for 50 minutes. The activated carbon fiber sheet and KMnO₄The mass ratio of (A) to (B) is 1: 0.4.

(3) Slowly adding an ammonia water solution with the mass fraction of 28% into AgNO₃To the solution and stirred until the solution became clear. The AgNO₃AgNO in solution₃The mass ratio of the active carbon fiber tablets to the active carbon fiber tablets obtained in the step (1) is 0.008: 1.

(4) Mixing 33% of H₂O₂Adding the solution into the transparent solution obtained in the step (3), soaking the activated carbon fiber sheet obtained in the step (2), stirring at 5 ℃ for 35min, finally filtering the mixture in a beaker, and washing the filtrate with deionized water for 4 times, wherein H is₂O₂H in solution₂O₂With AgNO₃In a mass ratio of 1.8: 1.

(5) Drying the washed filtrate at 70 deg.C for 11h, and calcining at 350 deg.C for 4h to obtain Ag/MnO₂ACF, noted B.

Example 3

(1) Soaking 0.1g of activated carbon fiber sheet in a methanol solution with the concentration of 0.2mol/L for 5min, then washing with deionized water for 5min to remove possible residues on the surface, taking out and placing the activated carbon fiber sheet into a beaker, placing the beaker into a 65 ℃ oven for 30min, taking out and placing the beaker into a NaOH solution with the concentration of 1mol/L for 3min, placing the activated carbon fiber sheet stained with the NaOH solution into the beaker, and placing the beaker into a 120 ℃ oven to heat for 40min to promote the hydrolysis of the surface of the activated carbon fiber.

(2) Taking (NH) with the mass ratio of 1.5:4₄)₂C₂O₄·H₂O and KMnO₄Dissolving the KMnO in deionized water to form a mixed solution, wherein the KMnO is a non-ionic surfactant₄The solid-liquid ratio of the deionized water to the deionized water is 0.020g to 1 ml. And (2) putting the activated carbon fiber sheet obtained in the step (1) into the mixed solution, adding 0.5mol/L hydrochloric acid to adjust the pH value of the mixed system to 7.3, then putting the mixed system into a 110-DEG C constant-temperature oil bath kettle, stirring at a stirring speed of 160rpm for reaction for 11 hours, taking out the activated carbon fiber sheet after the reaction is finished, washing with deionized water for 5 times, and putting the activated carbon fiber sheet into an oven at 80 ℃ for drying for 60 minutes. The activated carbon fiber sheet and KMnO₄The mass ratio of (A) to (B) is 1: 0.6.

(3) Slowly adding ammonia water solution with the mass fraction of 30% into AgNO₃To the solution and stirred until the solution became clear. The AgNO₃AgNO in solution₃The mass ratio of the activated carbon fiber sheet obtained in the step (1) to the activated carbon fiber sheet is 0.010: 1.

(4) Mixing 35% of H₂O₂Adding the solution into the transparent solution obtained in the step (3), soaking the activated carbon fiber sheet obtained in the step (2), stirring at 10 ℃ for 40min, finally filtering the mixture in the beaker, washing the filtrate with deionized water for 5 times, wherein H is₂O₂H in solution₂O₂With AgNO₃In a mass ratio of 2: 1.

(5) Drying the washed filtrate at 80 deg.C for 12h, and calcining at 400 deg.C for 5h to obtain Ag/MnO₂ACF, noted C.

The catalysts of examples 1, 2 and 3 were loaded into a catalytic evaluation apparatus and used for adsorption catalytic degradation of toluene at a reaction temperature of 65 ℃ and a reaction space velocity of 8000h under a reaction condition of 500ppm for toluene^-1. The catalytic activity is shown in Table 1.

TABLE 1

As can be seen from Table 1, Ag/MnO prepared according to the present invention₂The ACF catalyst has higher toluene degradation rate and mineralization rate.

Although embodiments of the present invention have been shown and described, the present invention is not limited to the above-described embodiments, which are only illustrative and not restrictive, and it should be apparent to those skilled in the art that several simple deductions or substitutions can be made without departing from the spirit of the present invention and all such changes and modifications should be considered as falling within the scope of the present invention as determined by the appended claims.

Claims (1)

1. A preparation method of a silver-based catalyst for degrading VOCs is characterized by comprising the following steps:

(1) soaking the activated carbon fiber sheet in a methanol solution with the concentration of 0.1-0.2mol/L for 3-5min, then washing with deionized water for 3-5min to remove possible residues on the surface, taking out and placing the activated carbon fiber sheet into a beaker, placing the beaker in an oven with the temperature of 55-65 ℃ for 20-30min, taking out and placing the beaker into a NaOH solution with the concentration of 0.5-1mol/L for 2-3min, placing the activated carbon fiber sheet stained with the NaOH solution into the beaker, placing the beaker into an oven with the temperature of 100 ℃ and 120 ℃ and heating for 30-40min to promote the hydrolysis of the surface of the activated carbon fiber;

(2) taking (NH) with the mass ratio of (1-1.5) to 4₄)₂C₂O₄·H₂O and KMnO₄Dissolving the KMnO in deionized water to form a mixed solution, wherein the KMnO is a non-ionic surfactant₄The solid-to-liquid ratio of the deionized water to the deionized water is (0.015g-0.020g) 1 ml; putting the activated carbon fiber sheet obtained in the step (1) into the mixed solution, adding 0.2-0.5mol/L hydrochloric acid to adjust the pH value of the mixed system to 7-7.3, then putting the mixed system into a constant-temperature oil bath kettle at 90-110 ℃, stirring at the stirring speed of 140-160rpm for reaction for 9-11h, taking out the activated carbon fiber sheet after the reaction is finished, washing the activated carbon fiber sheet with deionized water for 3-5 times, and putting the activated carbon fiber sheet into an oven at 60-80 ℃ for drying for 40-60 min; the activated carbon fiber sheet and KMnO₄The mass ratio of (1) to (0.3-0.6);

(3) slowly adding ammonia water solution with the mass fraction of 25% -30% into AgNO₃Stirring the solution until the solution becomes transparent; the AgNO₃AgNO in solution₃The mass ratio of the activated carbon fiber sheet taken in the step (1) to the activated carbon fiber sheet taken in the step (1) is (0.005-0.010) to 1;

(4) mixing 30-35% of H₂O₂Adding the solution into the transparent solution obtained in the step (3), soaking the activated carbon fiber sheet obtained in the step (2), stirring at 0-10 ℃ for 30-40min, finally filtering the mixture in the beaker, and washing the filtrate with deionized water for 3-5 times, wherein H is₂O₂H in solution₂O₂With AgNO₃The mass ratio of (1.5-2) is 1;

(5) drying the washed filtrate at 60-80 deg.C for 10-12h, calcining at 300-400 deg.C for 3-5h to obtain Ag/MnO₂-ACF。

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