Cerium oxide supported catalyst for synergistically removing various malodorous VOCs (Volatile Organic Compounds) in papermaking industry as well as preparation method and application of cerium oxide supported catalyst

Abstract

The invention belongs to the technical field of catalysts, and particularly relates to a cerium oxide supported catalyst for synergistically removing various malodorous VOCs in the papermaking industry as well as a preparation method and application of the cerium oxide supported catalyst. The catalyst comprises a cerium oxide carrier and an active component uniformly loaded on the cerium oxide carrier; the cerium oxide carrier is nano rod-shaped cerium oxide; the active components are niobium and copper. The catalyst disclosed by the invention can be used for simultaneously removing various stink VOCs (Volatile Organic Compounds) such as sulfur-containing organic matters, alkanes, oxygen-containing organic matters and chlorine-containing organic matters generated in the papermaking industry, especially for hydrogen sulfide, acetone and dichloromethane, and has the advantages of high removal efficiency, no catalyst poisoning, excellent low-temperature activity, low cost and the like. The excellent purification efficiency can be shown under the multi-component complex working condition.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and specifically relates to a cerium oxide-supported catalyst for collaboratively removing various types of malodorous VOCs in the papermaking industry, and a preparation method and application thereof. Background Art

[0002] The malodorous waste gas caused by the papermaking industry mainly includes hydrogen sulfide, acetone, dichloromethane, etc. Among them, hydrogen sulfide, as a peculiar substance with a high threshold dilution factor produced in the wastewater treatment and pulping links of the papermaking industry, is extremely harmful to the human body and has paralytic and irritating effects. Even long-term exposure to chronic poisoning can cause symptoms such as dermatitis or coma in the human body.

[0003] At present, the main methods for treating malodorous VOCs are: biological method, chemical adsorption method, activated carbon adsorption method and catalytic combustion method. The catalytic combustion method has the characteristics of low conversion temperature and not easy to produce secondary pollution. It is one of the most effective methods for controlling VOCs emissions. Among them, the development of catalysts is the key. Cerium-based catalysts have good redox ability due to their special crystalline structure, high oxygen storage capacity and oxygen release capacity. They are a good catalyst carrier and have been widely studied in the field of catalytic oxidation of VOCs. In the Chinese patent document with publication number 110280235A, a cerium oxide catalyst was prepared by impregnation method. It was found that the catalyst has the characteristics of high activity, strong stability and long life. The conditions for catalytic decomposition of odorous substances are mild and no secondary pollutants are generated after catalytic decomposition. Yuan Saisai (Yuan Saisai. Synthesis and modification of cerium dioxide photocatalyst and its mechanism research [D]. Yangzhou University, 2018.) used cerium dioxide-based nanomaterials prepared by solvothermal method as photocatalysts, and used bubbling to bubble a large amount of carbon dioxide gas into the precursor solution. Since the cerium dioxide crystals themselves contain a large number of alkaline active sites, and carbon dioxide is an acidic gas, carbon dioxide is easily adsorbed on the surface of the cerium dioxide crystals, which is conducive to the formation of hollow cerium dioxide structures and can increase the height of its valence band, thereby improving the photocatalytic activity to accelerate the degradation of odors. However, photocatalysts are only suitable for treating VOCs with relatively low concentrations, and the preparation process is complicated and prone to secondary pollution; for sulfur-containing organic matter, stable sulfides will be produced during the degradation process, which will cover the active sites and easily lead to catalyst poisoning and deactivation; and chlorine-containing organic matter is prone to catalyst chlorine poisoning. In the actual emission process of enterprises, multiple components of VOCs are often produced, so there is a lack of synergistic removal of VOCs. Summary of the invention

[0004] In order to solve the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a cerium oxide-supported catalyst for the synergistic removal of multiple types of malodorous VOCs in the papermaking industry. The catalyst can significantly improve the catalytic activity in the reaction of synergistically removing multiple types of malodorous VOCs generated in the papermaking industry.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned cerium oxide supported catalyst.

[0006] Another object of the present invention is to provide an application of the above-mentioned cerium oxide supported catalyst.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A cerium oxide supported catalyst for collaboratively removing multiple types of malodorous VOCs in the papermaking industry comprises a cerium oxide support and active components uniformly supported on the cerium oxide support; the active components are niobium and copper.

[0009] The mass ratio of niobium to copper in the active component is 1:(3-10), preferably 1:4.8.

[0010] The mass ratio of the cerium oxide carrier to the active component is 1:(0.01-0.5), preferably 1:(0.05-0.5), and more preferably 1:(0.05-0.3).

[0011] The cerium oxide carrier is nanorod-shaped cerium oxide or nanoparticle-shaped cerium oxide.

[0012] The present invention discloses a novel cerium oxide supported catalyst, which uses cerium oxide as a carrier. The unique CeO 2 The (110) crystal plane has abundant oxygen vacancies and acidic sites, which are beneficial to enhance the redox performance of the catalyst and the adsorption performance of odorous substances; CeO 2 The (110) crystal plane is also conducive to the stable existence of active components Nb and Cu, and strengthens the synergistic effect of the carrier and the active components. When dichloromethane and acetone coexist, the catalytic degradation of the two can promote each other. Acetone with a higher hydrogen content produces more hydroxyl groups, which is helpful for the removal of chlorine species; acetone is oxidized to formic acid and acetic acid, providing more acid sites for the catalyst, which is conducive to the adsorption and degradation of dichloromethane; in addition, the intermediate products chloroacetone and dichloroacetone are chemically active and promote the reaction. At the same time, the special nanorod morphology and rich pore structure of the catalyst induce the formation of abundant catalytic active sites, which provide active sites for the catalytic degradation of different types of odorous VOCs. In addition, SO generated by sulfur-containing organic matter during the reaction 2The sulfate produced by the active components will enhance the Bronstrd acid sites on the catalyst surface, which is beneficial to the stability of catalytic oxidation and can improve the catalyst's ability to synergistically remove. When the catalyst is purged at high temperature, the unstable sulfate on the catalyst surface is converted into SO 2 , which escapes through the unique pore structure on the catalyst surface, making the catalyst regenerative. Therefore, the supported catalyst not only has good low-temperature activity, but also has good synergistic removal ability for malodorous VOCs such as sulfur-containing organic matter, alkanes, oxygen-containing organic matter, and chlorine-containing organic matter in the papermaking industry. The catalytic oxidation of CVOCs is completed under the joint action of acidic centers and redox centers. The acidic sites on the catalyst are mainly doped with Nb. The C-Cl bond is mainly broken at the L acidic site on the catalyst surface, and the chlorine species avoid chlorine poisoning under the action of B acid; due to the large number of oxygen vacancies and Cu 2+ It has high redox performance, so it can convert chlorine-containing byproducts; dichloromethane in CeO 2 The (110) crystal surface has a better dechlorination effect, making it easier to transfer chlorine species; and copper oxide with good low-temperature redox performance can further oxidize and degrade byproducts. Sulfur species in sulfur-containing organic matter are more inclined to combine with Cu sites with stronger oxidative properties to form copper sulfate. After the influence of sulfur species, the surface components of cerium oxide carrier are transformed into trivalent Ce 2 (SO 4 ) 3 After adding Cu, some tetravalent Ce still exists on the catalyst surface after being affected by sulfur species. This shows that the presence of Cu can effectively protect Ce. 4+ , Ce 4+ The presence of can effectively ensure the good redox performance of the catalyst, making the catalyst have better resistance to sulfur poisoning.

[0013] In the present invention, the malodorous VOCs mainly include one or more of sulfur-containing organic matter, alkanes, oxygen-containing organic matter, and chlorine-containing organic matter, preferably hydrogen sulfide, acetone, and dichloromethane.

[0014] It is found through experiments that the cerium oxide supported catalyst prepared by the present invention can remove hydrogen sulfide, acetone and dichloromethane simultaneously, and has good synergistic removal effect and anti-poisoning performance.

[0015] The present invention also discloses a method for preparing a cerium oxide supported catalyst for collaboratively removing multiple types of malodorous VOCs in the papermaking industry, comprising the following steps:

[0016] (1) dissolving a cerium source precursor and a strong base in water respectively, then slowly adding the strong base solution to the cerium source precursor solution, and stirring to obtain a mixed solution; transferring the mixed solution to a hydrothermal kettle for hydrothermal reaction, filtering and washing the reaction product, adjusting the pH value to neutral, and finally calcining at high temperature to obtain a carrier; or directly drying the mixed solution and calcining at high temperature to obtain the carrier;

[0017] (2) dissolving niobium oxalate and copper nitrate in water, then adding the carrier prepared in step (1), stirring evenly and calcining to obtain the cerium oxide supported catalyst.

[0018] In step (1), the temperature of the hydrothermal reaction is 100 to 200° C., and the time is 1 to 36 hours;

[0019] The high temperature calcination temperature is 400-600° C. and the time is 1-10 hours.

[0020] In step (1), the temperature of the hydrothermal reaction is preferably 120° C., and the time is preferably 12 to 24 hours;

[0021] The temperature of the high temperature calcination is preferably 400-500° C., and the time is preferably 4-6 hours.

[0022] In step (1), the cerium source precursor is selected from at least one of cerium nitrate, cerium acetate, and cerium acetate;

[0023] The strong base is selected from at least one of sodium hydroxide and potassium hydroxide;

[0024] The mass ratio of the cerium source precursor to the strong base is 1:(5-10).

[0025] In step (2), the mass ratio of niobium oxalate to copper nitrate is 1:(3-10), preferably 1:4.8.

[0026] In step (2), the mass ratio of the carrier to the sum of niobium oxalate and copper nitrate is 1:(0.01-0.5), preferably 1:(0.05-0.5), and more preferably 1:(0.05-0.3).

[0027] In step (2), the calcination refers to calcination at 400-500° C. for 4-6 hours.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] The present invention discloses a cerium oxide-supported catalyst for collaboratively removing various types of malodorous VOCs in the papermaking industry. The catalyst can simultaneously remove various malodorous VOCs such as sulfur-containing organic matter, alkanes, oxygen-containing organic matter, chlorine-containing organic matter, etc. generated in the papermaking industry, especially hydrogen sulfide, acetone and dichloromethane. The catalyst has high removal efficiency, will not cause catalyst poisoning and has excellent low-temperature activity. The catalyst can exhibit excellent purification efficiency under multi-component complex working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 From left to right are the nanorods (Cu-Nb / CeO 2 nanorod) catalyst, the granular (Cu-Nb / CeO 2 nanoparticle) catalyst, cubic (Cu-Nb / CeO 2 TEM image of the catalyst.

[0031] Figure 2 The nanorod-shaped (Cu-Nb / CeO 2 nanorod) catalyst, the granular (Cu-Nb / CeO 2 nanoparticle) catalyst, cubic (Cu-Nb / CeO 2 The activity test diagram of nanocube catalyst for dichloromethane. From the figure, we can find that the nanorod-shaped (Cu-Nb / CeO 2 nanorod) catalyst has the highest catalytic activity for dichloromethane, and the granular (Cu-Nb / CeO 2 nanoparticle) followed by cubic (Cu-Nb / CeO 2 nanocube) is the worst.

[0032] Figure 3 The nanorod-shaped (Nb / CeO 2 nanorod) catalyst, the granular (Nb / CeO 2 nanoparticle) catalyst, cubic (Nb / CeO 2 Activity test diagram of nanocube) catalyst towards dichloromethane. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below in conjunction with the examples and drawings, but the embodiments of the present invention are not limited thereto. The raw materials involved in the present invention can be purchased directly from the market. For process parameters not particularly noted, conventional techniques can be used.

[0034] Example 1

[0035] 3.48g of cerium nitrate and 32g of sodium hydroxide were dissolved in 70mL and 60mL of water respectively to prepare sodium hydroxide solution and cerium nitrate solution, and then the sodium hydroxide solution was slowly added dropwise to the cerium nitrate solution and stirred to prepare a turbid solution. The turbid solution was added to a 200mL stainless steel high-pressure hydrothermal autoclave and hydrothermally reacted at 120°C for 24h. After cooling to room temperature, the precipitate was collected by vacuum filtration and washed with anhydrous ethanol until neutral. It was then dried in air at 60°C and calcined at 450°C for 5h to obtain a carrier. Then niobium oxalate and copper nitrate (niobium oxalate: copper nitrate = 1:4.8, mass ratio) were dissolved in 50mL of water, and the carrier was added (carrier: niobium oxalate: copper nitrate = 1:0.05:0.24, mass ratio), stirred for 3h and placed in an oven to dry, and finally calcined at 450°C in a muffle furnace for 6h to obtain a catalyst. The TEM image of the catalyst is shown in the figure Figure 1 As shown, its morphology is nanorod-like.

[0036] Example 2

[0037] Dissolve 3.48g of cerium nitrate and 32g of sodium hydroxide in 70mL and 60mL of water respectively to prepare sodium hydroxide solution and cerium nitrate solution, then slowly add the sodium hydroxide solution to the cerium nitrate solution and stir to make a turbid solution. Then dry it in air at 60℃ and calcine it at 450℃ for 5h to obtain a carrier. Then dissolve niobium oxalate and copper nitrate (niobium oxalate: copper nitrate = 1:4.8, mass ratio) in 50mL of water, add the carrier (carrier: niobium oxalate: copper nitrate = 1:0.05:0.24, mass ratio), stir for 3h and place in an oven to dry, finally calcine in a muffle furnace at 450℃ for 6h to obtain a catalyst. The TEM image of the catalyst is as follows Figure 2 As shown, its morphology is nanoparticle-like.

[0038] Example 3

[0039] 3.48g of cerium nitrate and 32g of sodium hydroxide were dissolved in 70mL and 60mL of water respectively to prepare sodium hydroxide solution and cerium nitrate solution, and then the sodium hydroxide solution was slowly added dropwise to the cerium nitrate solution and stirred to prepare a turbid solution. The turbid solution was added to a 200mL stainless steel high-pressure hydrothermal autoclave and hydrothermally reacted at 180°C for 24h. After cooling to room temperature, the precipitate was collected by vacuum filtration and washed with anhydrous ethanol until neutral. It was then dried in air at 60°C and calcined at 450°C for 5h to obtain a carrier. Then niobium oxalate and copper nitrate (niobium oxalate: copper nitrate = 1:4.8, mass ratio) were dissolved in 50mL of water, and the carrier was added (carrier: niobium oxalate: copper nitrate = 1:0.05:0.24, mass ratio), stirred for 3h and placed in an oven to dry, and finally calcined at 450°C in a muffle furnace for 6h to obtain a catalyst. The TEM image of the catalyst is shown in the figure Figure 3 As shown, its shape is cubic.

[0040] Comparative Example 1

[0041] 3.48g of cerium nitrate and 32g of sodium hydroxide were dissolved in 70mL and 60mL of water respectively to prepare sodium hydroxide solution and cerium nitrate solution, and then the sodium hydroxide solution was slowly added to the cerium nitrate solution and stirred to prepare a turbid solution. The turbid solution was added to a 200mL stainless steel high-pressure hydrothermal autoclave and hydrothermally reacted at 120℃ for 24h. After cooling to room temperature, the precipitate was collected by vacuum filtration and washed with anhydrous ethanol until neutral. It was then dried in air at 60℃ and calcined at 450℃ for 5h to obtain a carrier. Then 1.07g of niobium oxalate was dissolved in 50mL of water, and the carrier was added (carrier: niobium oxalate = 1:0.05, mass ratio), stirred for 3h, and then placed in an oven to dry, and finally calcined at 450℃ in a muffle furnace for 6h to obtain a catalyst. The morphology of the catalyst is nanorod-like.

[0042] Comparative Example 2

[0043] 3.48g of cerium nitrate and 32g of sodium hydroxide were dissolved in 70mL and 60mL of water respectively to prepare sodium hydroxide solution and cerium nitrate solution, and then the sodium hydroxide solution was slowly added to the cerium nitrate solution and stirred to make a turbid solution. It was then dried in air at 60°C and calcined at 450°C for 5h to obtain a carrier. 1.07g of niobium oxalate was dissolved in 50mL of water, and the carrier was added (carrier: niobium oxalate = 1:0.05, mass ratio), stirred for 3h, and then placed in an oven to dry, and finally calcined at 450°C in a muffle furnace for 6h to obtain a catalyst. The morphology of the catalyst is granular.

[0044] Comparative Example 3

[0045] 3.48g of cerium nitrate and 32g of sodium hydroxide were dissolved in 70mL and 60mL of water respectively to prepare sodium hydroxide solution and cerium nitrate solution, and then the sodium hydroxide solution was slowly added to the cerium nitrate solution and stirred to prepare a turbid solution. The turbid solution was added to a 200mL stainless steel high-pressure hydrothermal autoclave and hydrothermally reacted at 180℃ for 24h. After cooling to room temperature, the precipitate was collected by vacuum filtration and washed with anhydrous ethanol until neutral. It was then dried in air at 60℃ and calcined at 450℃ for 5h to obtain a carrier. Then 1.07g of niobium oxalate was dissolved in 50mL of water, and the carrier was added (carrier: niobium oxalate = 1:0.05, mass ratio), stirred for 3h, and then placed in an oven to dry, and finally calcined at 450℃ in a muffle furnace for 6h to obtain a catalyst. The morphology of the catalyst is cubic.

[0046] The catalytic activity of the catalysts prepared in the above Examples 1-3 and Comparative Examples 1-3 on dichloromethane was evaluated: the catalyst test device was divided into three parts: the gas distribution system, the VOCs catalytic combustion reaction system, and the sampling and measurement system. First, dichloromethane, oxygen and nitrogen were fully mixed in the buffer tank through the mass flow meter, and then converted through the catalytic bed. Finally, the dichloromethane concentration at the reaction inlet and outlet was measured by gas chromatography. The experimental results are shown in Table 1.

[0047] Table 1

[0048]

[0049]

[0050] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A cerium oxide-supported catalyst for synergistically removing multiple types of malodorous VOCs in the papermaking industry. It is characterized in that The invention comprises a cerium oxide carrier and active components uniformly loaded on the cerium oxide carrier; the cerium oxide carrier is nanorod-shaped cerium oxide or nanoparticle-shaped cerium oxide; and the active components are niobium and copper.

2. The catalyst according to claim 1, It is characterized in that The mass ratio of niobium to copper in the active component is 1:(3-10), preferably 1:4.

8.

3. The catalyst according to claim 1, It is characterized in that The mass ratio of the cerium oxide carrier to the active component is 1:(0.01-0.5), preferably 1:(0.05-0.5), and more preferably 1:(0.05-0.3).

4. A method for preparing a cerium oxide-supported catalyst for synergistically removing multiple types of malodorous VOCs in the papermaking industry. It is characterized in that The following steps are involved: (1) dissolving a cerium source precursor and a strong base in water respectively, and then slowly adding the strong base solution to the cerium source precursor solution to form a mixed solution; transferring the mixed solution to a hydrothermal kettle for hydrothermal reaction, filtering and washing the reaction product, adjusting the pH value to neutral, and finally calcining at high temperature to obtain a carrier; Alternatively, the mixed solution is directly dried and then calcined at high temperature to obtain the carrier; (2) dissolving niobium oxalate and copper nitrate in water, then adding the carrier prepared in step (1), stirring evenly and calcining to obtain the cerium oxide supported catalyst.

5. The preparation method according to claim 4, It is characterized in that In step (1), the temperature of the hydrothermal reaction is 100 to 200° C., and the time is 1 to 36 hours; The high temperature calcination temperature is 400-600° C. and the time is 1-10 hours.

6. The preparation method according to claim 4, It is characterized in that In step (1), the cerium source precursor is selected from at least one of cerium nitrate, cerium acetate, and cerium acetate; The strong base is selected from at least one of sodium hydroxide and potassium hydroxide; The mass ratio of the cerium source precursor to the strong base is 1:(5-10).

7. The preparation method according to claim 4, It is characterized in that In step (2), the mass ratio of niobium oxalate to copper nitrate is 1:(3-10), preferably 1:4.

8.

8. The preparation method according to claim 4, It is characterized in that In step (2), the mass ratio of the carrier to the sum of niobium oxalate and copper nitrate is 1:(0.01-0.5), preferably 1:(0.05-0.5), and more preferably 1:(0.05-0.3).

9. The preparation method according to claim 4, It is characterized in that In step (2), the calcination refers to calcination at 400-500° C. for 4-6 hours.

10. Use of the cerium oxide-supported catalyst for synergistically removing multiple types of malodorous VOCs in the papermaking industry as claimed in any one of claims 1 to 3 in treating multiple types of malodorous VOCs in the papermaking industry.

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