Chlorine-containing organic waste gas low-temperature combustion catalyst and preparation method thereof

Abstract

The invention discloses a chlorine-containing organic waste gas low-temperature combustion catalyst and a preparation method thereof, the low-temperature combustion catalyst is obtained by compression molding of metal waste and calcium hydroxide and calcination, and the specific surface area of the low-temperature combustion catalyst can reach 3000-5000 m < 2 > / m < 3 >; and low-temperature (less than 300 DEG C) catalysis of chlorine-containing organic waste gas combustion is realized. A large number of metal elements in the metal waste and calcium hydroxide are calcined and oxidized into corresponding oxides in the air atmosphere, cracks and pore channels are formed at the same time, the filler-shaped catalyst in the corresponding shape is obtained, chlorine-containing compounds such as (chlorobenzene) on the surface of a CaO phase can be promoted to be dechlorinated to form HCl, and the catalyst has the advantages of being environmentally friendly and low in cost. And dechlorination sites are transferred from the surface of the metal oxide to the surface of CaO, so that active sites on the surface of the metal oxide are prevented from being covered by chlorine and poisoned. The catalyst has excellent catalytic activity and regeneration reusability, and in addition, a new way for resource utilization of metal waste gas materials is opened up.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst material preparation, and particularly relates to a catalyst for low-temperature combustion of chlorinated organic waste gas and a preparation method thereof. Background Art

[0002] Organic waste gas generally has the characteristics of being flammable, explosive, toxic, harmful, insoluble in water, soluble in organic solvents, and difficult to treat. In the treatment of organic waste gas, various principles such as activated carbon adsorption treatment method, catalytic combustion method, catalytic oxidation method, acid-base neutralization method, and plasma method are generally adopted. A relatively good organic waste gas treatment method is the catalytic oxidation purification system, which has a well-designed waste gas treatment and filters the waste gas layer by layer, with good effects. The catalytic combustion method is a common treatment method, but it cannot be used to treat chlorinated organic waste gas. Because chlorinated waste gas generally produces toxic and harmful by-products such as chlorinated aromatic hydrocarbons during high-temperature combustion, which causes harm to the environment and human health, restricting the application of catalytic combustion technology in this regard.

[0003] Research shows that high temperature is prone to produce chlorinated toxic by-products, and controlling the combustion temperature and burning at low temperature (<300 °C) is relatively safe without the generation of chlorinated toxic by-products. However, there will be a problem that Cl species are difficult to desorb from the catalyst surface, ultimately leading to rapid deactivation of the catalyst and failure of the entire equipment. If the catalyst needs to be replaced, production must be stopped and a new catalyst needs to be purchased and replaced, which is time-consuming, laborious, and extremely costly. Therefore, it is urgent to solve the problem of catalytic combustion treatment of chlorinated organic compounds. Summary of the Invention

[0004] In view of the problems existing in the existing catalysts for combustion of chlorinated organic waste gas pointed out in the background art, the present invention aims to provide a catalyst for low-temperature combustion of chlorinated organic waste gas and a preparation method thereof.

[0005] In the first aspect of the present invention, a catalyst for low-temperature combustion of chlorinated organic waste gas is provided. The specific surface area of this catalytic material can reach 3000 - 5000 m 2 / m 3 , which is much higher than the specific surface area of general honeycomb ceramic materials (500 - 1200 m 2 / m 3 ). The gas-solid phase contact condition is good, and it can realize the catalytic combustion of chlorinated organic waste gas at low temperature (<300 °C). This catalytic material includes metal oxides and calcium oxide, and is obtained by high-temperature oxidation after pressing metal waste and calcium hydroxide into a mold. Among them, the metal waste includes metal shavings and metal powders.

[0006] In the second aspect of the present invention, a preparation method of a catalyst for low-temperature combustion of chlorinated organic waste gas is provided, including the following steps: (1) Surface treatment of metal shavings and metal powders; The metal shavings and metal powders are sourced from the scraps generated during machining, and can be made of iron, steel, copper, aluminum, or stainless steel, or can be shavings or powders composed of a mixture of multiple metal materials.

[0007] The surface treatment process includes acid water washing, soaking in 0.1 - 0.2 mol / L hydrochloric acid for 5 - 20 minutes to remove the oxide layer on the surface, and then rinsing with clean water 2 - 3 times.

[0008] (2) After surface treatment of the metal powder (particle size ranging from 10 mesh to 100 mesh), it is mixed evenly with calcium hydroxide powder (particle size ranging from 30 mesh to 100 mesh) in a ratio of calcium hydroxide powder: metal powder = 1:1 - 2 (by mass). After thorough mixing, an aqueous solution of polyacrylate is added. For every 1 kg of the mixed powder, 0.2 - 0.5 L of an aqueous solution of polyacrylate with a mass concentration of 20% - 50% is added, and then stirred evenly to form a thin paste - like mixture.

[0009] (3) The surface - treated metal shavings are added to the thin paste - like mixture, mixed and taken out, so that a layer of the thin paste - like mixture adheres to the surface of the shavings. Then it is added to a mold, compacted and shaped. The metal shavings are pressed into the required shapes, such as round cake - like, cube - like or cone - shaped tube, which can be freely stacked. At this time, the thin paste - like mixture fills the gaps between the formed metal shavings.

[0010] (4) The pressed metal shavings are placed in a muffle furnace and calcined at 600 - 700 °C in an air atmosphere for 30 - 60 minutes. Calcium hydroxide is calcined into calcium oxide, and at the same time, the added polyacrylate is burned and removed, and cracks and pores are formed. Meanwhile, the metal shavings and metal powders are oxidized into corresponding oxides, completing the production of the catalyst and forming a filler - shaped catalyst of the corresponding shape.

[0011] In the third aspect of the present invention, an application of the above - mentioned low - temperature combustion catalyst in the catalytic combustion of chlorinated organic waste gas is provided.

[0012] The chlorinated organic waste gas described in the present invention includes at least one of chlorobenzene, dichloromethane, vinyl chloride, trichloroethylene, and carbon tetrachloride.

[0013] The specific application method: Place the filler - shaped catalyst in a furnace to form a catalytic channel, maintain a certain temperature in the furnace, introduce the chlorinated organic waste gas to be treated, and the waste gas can be processed into harmless substances. At the same time, absorb hydrogen chloride with an alkaline substance at the furnace outlet and then the burned air can be discharged.

[0014] Among them, the catalytic combustion reaction temperature T of the low-temperature combustion catalyst prepared in the present invention ranges from 100 °C ≤ T < 300 °C, preferably 200 °C ≤ T < 300 °C, and most preferably 200 °C. In the specific embodiments of the present invention, taking chlorobenzene and dichloromethane as examples, the low-temperature combustion catalyst prepared in the present invention can catalyze their combustion reaction at 100 °C and achieve complete combustion at 200 °C.

[0015] Technical principle of the present invention: The main components of metal shavings not only contain iron, but also manganese, nickel, chromium, etc., forming rich metal oxides, such as iron oxide, nickel oxide, manganese oxide, etc.; the combination of metal oxides and CaO can promote the dechlorination of chlorine-containing compounds (such as chlorobenzene) on the surface of the CaO phase to form HCl, and transfer the dechlorination site from the surface of the metal oxide to the surface of CaO, thereby preventing the active sites on the surface of the metal oxide from being poisoned by chlorine coverage.

[0016] The beneficial effects of the present invention are as follows: 1. The catalytic material prepared in the present invention can catalyze the combustion of chlorine-containing organic compounds at low temperature (<300 °C), avoid the generation of toxic by-products, and reduce environmental risks. During the catalytic combustion of chlorine-containing organic waste gas, the Cl species on the active sites can be desorbed at a lower temperature, avoiding the poisoning of active sites.

[0017] 2. The specific surface area of the catalytic material prepared in the present invention can reach 3000 - 5000 m 2 / m 3 , which is much larger than the specific surface area of general honeycomb ceramic materials (500 - 1200 m 2 / m 3 ). The gas-solid phase contact conditions are good, and it is not easy to break, has good strength, and can be recycled.

[0018] 3. The preparation method of the combustion catalyst provided in the present invention makes full use of waste materials, improves the utilization rate of waste resources, and the preparation method is simple. The catalyst prepared from metal shavings has the characteristics of good air permeability, high catalytic efficiency, and low-temperature catalytic combustion. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below in conjunction with the drawings and embodiments.

[0020] Figure 1 It is the removal rate of chlorobenzene by the packed catalyst prepared in the present invention at different temperatures.

[0021] Figure 2 It is the stability of the packed catalyst and iron shaving catalyst prepared in Example 1 of the present invention for catalytic removal of chlorobenzene at a temperature of 270 °C.

[0022] Figure 3Removal rates of the packed catalyst prepared in Example 2 of the present invention for chlorobenzene / dichloromethane at different temperatures. Detailed implementation manners

[0023] To make the above objects, features and advantages of the present invention more obvious and understandable, the following describes the detailed implementation manners of the present invention in conjunction with the embodiments of the specification.

[0024] Many specific details are set forth in the following description in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar promotions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below. Example 1

[0025] A preparation method of a catalyst for burning chlorinated organic waste gas includes the following steps: (1) Surface treatment of metal shavings and metal powders; The metal shavings and metal powders are derived from the scraps of machining, and can be iron, steel, copper, aluminum or stainless steel, or shavings or powders of a mixture of multiple metal materials; The surface treatment process includes acid water washing, soaking in 0.1 mol / L hydrochloric acid for 20 min to remove the oxide layer on the surface, and then rinsing with clean water 3 times; (2) After the surface treatment of the metal powder (particle size of 100 mesh), it is mixed evenly with calcium hydroxide powder (particle size of 100 mesh), and mixed according to the ratio of calcium hydroxide powder: metal powder = 1:1 (mass ratio). After mixing evenly, an aqueous solution of polyacrylate is added. For every 1 kg of the mixed powder, 0.2 L of an aqueous solution of polyacrylate with a mass concentration of 50% is added, and stirred evenly to form a thin paste-like mixture; (3) Add the surface-treated metal shavings to the thin paste-like mixture, mix and take out, so that a layer of thin paste-like mixture adheres to the surface of the shavings, and then add it to the mold, press and shape it, and press the metal shavings into the required shape, such as round cake shape, cube shape or cone tube shape, which can be freely stacked. At this time, the thin paste-like mixture fills the gaps of the formed metal shavings; (4) Place the pressed metal shavings in a muffle furnace, calcine at 700 °C in an air atmosphere for 30 min, calcine calcium hydroxide into calcium oxide, and at the same time burn and remove the added polyacrylate, and form cracks and pores. At the same time, the metal shavings and metal powders are oxidized into corresponding oxides to complete the production of the catalyst and form a packed catalyst of the corresponding shape. Example 2

[0026] The difference between this example and Example 1 is that the mass ratio of the metal powder to the calcium hydroxide powder is: The surface treatment process includes acid washing with water, soaking in 0.2 mol / L hydrochloric acid for 5 min to remove the oxide layer on the surface, and then rinsing twice with clean water; After the surface treatment of the metal powder (particle size of 10 mesh), it is mixed evenly with calcium hydroxide powder (particle size of 30 mesh), and mixed according to the ratio of calcium hydroxide powder: metal powder = 1:2 (mass ratio). After mixing evenly, an aqueous solution of polyacrylate is added. For every 1 kg of the mixed powder, 0.5 L of an aqueous solution of polyacrylate with a mass concentration of 20% is added, and stirred evenly to form a thin slurry-like mixture; The surface-treated metal shavings are added to the thin slurry-like mixture, mixed and taken out, so that a layer of thin slurry-like mixture adheres to the surface of the shavings, and then added to a mold and pressed into shape; The pressed metal shavings are placed in a muffle furnace and calcined at 600 °C for 60 min in an air atmosphere to prepare a filler-like catalyst. Example 3

[0027] The difference between this example and Example 1 is that no metal powder is added to the thin slurry-like mixture; a filler-like catalyst is prepared.

[0028] Comparative Example 1: In this example, the iron shavings are directly pressed into shape after being pickled in the same way as in Example 1, and then calcined under the same conditions in an air atmosphere to become an iron shaving catalyst.

[0029] Comparative Example 2: Calcium hydroxide is calcined at the same temperature as in Example 1 to obtain calcium oxide particles.

[0030] Catalytic combustion of chlorobenzene The filler-like catalysts prepared in Example 1, 3 and Comparative Examples 1 and 2 are filled in a furnace tube with a diameter of 10 cm, and the filling height is 20 cm. The reaction temperature range is set to 75 - 475 °C. The initial concentration of the gas to be treated: chlorobenzene is 100 ppm, the volume concentration of oxygen is 10%, nitrogen is used as the carrier gas, and the mass space velocity is 30 L / (g·h). The chlorobenzene removal rate is tested. The results are as Figure 1 shown.

[0031] As Figure 1 shown, when the reaction temperature of the filler-like catalyst is less than 200 °C, chlorobenzene can be oxidized and removed by 100%. However, the catalytic ability of iron shavings is weak, and a higher temperature, about 400 °C, is required to remove nearly 100%. Calcium oxide has little or very weak removal ability.

[0032] Stability test The packing catalyst prepared in Example 1 was filled in the furnace tube, and the temperature was maintained at 270 °C. The ability of the catalyst to catalytically degrade chlorobenzene was continuously tested, and the removal rate of iron filings was used as a comparison under the same conditions. The results are as follows Figure 2 shown. It can be seen from the figure that at this temperature, the packing catalyst can continuously maintain 100% removal of chlorobenzene for more than 100 hours. At this temperature, the removal rate of iron filings is only about 90%, and at this temperature, the removal efficiency gradually decreases, resulting in slow catalyst poisoning.

[0033] The specific surface areas of the packing catalysts prepared in Examples 1 and 2 were measured by the adsorption-desorption method, and their specific surface areas were 4505 m 2 / m 3 , 5012 m 2 / m 3 .

[0034] The present invention also investigated the catalytic combustion temperatures of the packing catalyst prepared in Example 2 for chlorobenzene and dichloromethane. The results are shown in Figure 3 , and it can be seen that chlorobenzene and dichloromethane can be completely combusted and removed at 225-250 °C.

[0035] Based on the ideal embodiments of the present invention as inspiration, through the above description, relevant workers can make various changes and modifications without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A catalyst for low-temperature combustion of chlorine-containing organic waste gas, characterized in that, The described low-temperature combustion catalyst includes metal oxides and calcium oxide, and is obtained by high-temperature oxidation after pressing metal waste and calcium hydroxide into a mold; the specific surface area of the low-temperature combustion catalyst is 3000-5000 m 2 / m 3 ; the temperature at which the low-temperature combustion catalyst catalyzes the combustion of chlorine-containing organic waste gas is <300 °C.

2. The preparation method of the chlorine-containing organic waste gas low-temperature combustion catalyst according to claim 1, characterized in that, It includes the following steps: (1) Provide pretreated metal shavings and pretreated metal powder respectively; (2) Mix the pretreated metal powder evenly with calcium hydroxide powder to obtain a mixed powder; add an aqueous solution of polyacrylate and stir evenly to obtain a thin paste-like mixture; (3) Immerse the pretreated metal shavings in the thin paste-like mixture to make the surface of the shavings adhere to the thin paste-like mixture; then put them into a mold, press and shape to obtain a catalyst blank; (4) Subject the catalyst blank to high-temperature oxidation treatment to obtain the combustion catalyst described.

3. The preparation method of the low-temperature combustion catalyst for chlorine-containing organic waste gas according to claim 2, characterized in that, The metal shavings and metal powder are derived from the scraps of machining.

4. The preparation method of the low-temperature combustion catalyst for chlorine-containing organic waste gas according to claim 2, wherein, The pretreatment includes acid washing with water, and the acid washing method is to soak in 0.1 - 0.2 mol / L hydrochloric acid for 5 - 20 min and then rinse with clean water.

5. The preparation method of the chlorine-containing organic waste gas low-temperature combustion catalyst according to claim 2, characterized in that, The particle size of the metal powder is 10 mesh - 100 mesh, the particle size of the calcium hydroxide powder is 30 mesh - 100 mesh, and the mass ratio of the calcium hydroxide powder to the metal powder is 1:1 - 2.

6. The preparation method of the low-temperature combustion catalyst for chlorine-containing organic waste gas according to claim 2, characterized in that, Add 0.2 - 0.5 L of an aqueous solution of polyacrylate with a mass concentration of 20% - 50% to every 1 kg of the mixed powder.

7. The preparation method of the chlorine-containing organic waste gas low-temperature combustion catalyst according to claim 2, characterized in that, The high-temperature oxidation is calcination at 600 - 700 °C for 30 - 60 min in an air atmosphere.

8. Application of the low-temperature combustion catalyst described in Claim 1 or the low-temperature combustion catalyst prepared by the preparation method described in any one of Claims 2 - 7 in the catalytic combustion of chlorinated organic waste gas.

9. The application according to claim 8, wherein The chlorinated organic waste gas described includes at least one of chlorobenzene, dichloromethane, vinyl chloride, trichloroethylene, and carbon tetrachloride.

10. The application according to claim 8, characterized in that, The temperature T range of the catalytic combustion of the chlorinated organic waste gas is: 100 °C ≤ T < 300 °C.

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