SBA-15 molecular sieve loaded defective manganese-based catalyst as well as preparation method and application thereof

Abstract

The invention provides an SBA-15 molecular sieve loaded defective manganese-based catalyst, the SBA-15 molecular sieve is prepared by using silicon-containing solid waste as a raw material, the phase composition of active components of the defective manganese-based catalyst comprises beta-MnO2, Mn2O3 and Mn5O8, and the molar ratio of Mn < 3 + > to Mn < 4 + > is (8-12): 1. The invention also provides a preparation method and application of the SBA-15 molecular sieve loaded defective manganese-based catalyst. The supported defective manganese-based catalyst provided by the invention has very excellent catalytic activity, does not need to use noble metal as an active component, and has an excellent effect in the aspect of catalytic oxidation of volatile organic compounds such as ethylene. The preparation method provided by the invention is simple and convenient in process, low in cost, high in operability and high in safety, so that the preparation method has good industrial practicability and is suitable for large-scale production and application.

Description

Technical Field

[0001] The invention relates to the field of environmental governance, and in particular to a defective manganese-based catalyst supported by an SBA-15 molecular sieve, and also to a preparation method of the defective manganese-based catalyst supported by an SBA-15 molecular sieve and application of the catalyst in catalytic oxidation of ethylene. Background Art

[0002] Volatile Organic Compounds (VOC) refer to organic compounds with a saturated vapor pressure of more than 70Pa and a boiling point of 50-260°C at room temperature. The concentration of VOCs in the atmospheric environment is relatively low, but their hazards are very large. Once the safety threshold is exceeded, they will have serious toxic effects on humans, animals and plants, and endanger the human nervous system and respiration. Most VOCs are toxic and have strong irritating odors. Long-term contact with these gases can cause chronic poisoning in people, and even have serious consequences such as carcinogenicity, teratogenicity and mutagenicity. Therefore, increasing environmental governance efforts, strictly controlling emissions from pollution sources, and developing technologies that effectively control VOC pollution have become current research hotspots.

[0003] Catalytic oxidation is an important method for controlling VOC. This method enables VOC to be completely oxidized and decomposed at a lower temperature (50-300°C) under the action of a catalyst. This reaction temperature is lower than the temperature required for thermal combustion. Most volatile organic compounds can be completely oxidized at a lower temperature. As the core of the catalytic oxidation method, the catalyst has a great influence on the process operation cost, oxidation temperature and removal efficiency. Therefore, it is very necessary to select a catalyst with high catalytic activity, high stability and good selectivity.

[0004] At present, the most widely used type of catalyst in catalytic oxidation is precious metal catalyst, which has the advantages of high activity and good selectivity. It mainly includes platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), gold (Au), etc., which are usually loaded on carriers such as Al2O3, SiO2, TiO2, etc. Due to the high cost of precious metals and the disadvantages of active components being volatile and easy to be poisoned, researchers have begun to focus on transition metal catalytic materials with lower prices and wider sources. At present, metal oxides of some transition metal elements (such as Cr, Mn, Co, Fe, Cu, etc.) are mainly used as the main active components of the catalyst. However, single metal oxides have the disadvantages of low low-temperature catalytic activity and unstable structure, which cannot meet the needs of catalytic oxidation technology. Therefore, researchers currently improve the low-temperature catalytic performance of transition metal catalysts by regulating the preparation process, doping with other elements, loading, etc.

[0005] Manganese-based catalysts exhibit excellent redox properties due to their variable valence states, unique crystal structure, and strong electron and oxygen transfer capabilities. They are also environmentally friendly and inexpensive, so they are widely used in the field of environmental catalysis, such as NH3 selective catalytic reduction of nitrogen oxides (NH3-SCR), ozone oxidation, and VOC catalytic oxidation.

[0006] Chinese patent CN 112156778A discloses a manganese oxide-supported noble metal single atom formaldehyde oxidation catalyst, which supports noble metal single atoms on the surface of manganese oxide, and utilizes the characteristics of manganese species with multiple valence states, rich pore structure, and more defect sites to achieve uniform and stable placement of noble metal single atoms, thereby obtaining better catalytic activity and stability. Chinese patent CN 112108147A discloses a platinum-manganese-based bimetallic catalyst for low-temperature catalytic oxidation of ethylene, which uses an oil phase reduction method to prepare Pt2Mn nanocrystals, and then uses an impregnation method to load the Pt2Mn nanocrystals onto a commercial TiO2 carrier, which is then calcined to form Pt-MnOx / TiO2.

[0007] Commonly used catalyst carriers include oxides, activated carbon, molecular sieves, etc. Mesoporous molecular sieves have a highly ordered pore structure, uniform pore size and adjustable size, and also have the characteristics of high specific surface area, large pore volume and adsorption capacity, good thermal stability, and easy-to-modify silanol groups on the pore surface. Therefore, mesoporous molecular sieves have great application value in adsorption and catalysis. In the field of organic catalysis, mesoporous molecular sieves can be used as carriers to load active components and improve the catalytic rate. SBA-15 mesoporous molecular sieve has become a research hotspot for many researchers and enterprises in recent years because of its larger pore size and specific surface area than MCM-41 molecular sieve and higher hydrothermal stability than MCM-41 molecular sieve. Traditional SBA-15 molecular sieve is prepared with sodium silicate or ethyl orthosilicate as silicon source, which is expensive and toxic and not suitable for large-scale industrial production. Summary of the invention

[0008] In order to make up for the deficiencies of the catalysts used in the catalytic oxidation of VOCs in the prior art, an object of the present invention is to provide a defective manganese-based catalyst supported by an SBA-15 molecular sieve, which has excellent catalytic performance and can be effectively used in the catalytic oxidation of ethylene.

[0009] Another object of the present invention is to provide a method for preparing the SBA-15 molecular sieve-supported defective manganese-based catalyst.

[0010] Another object of the present invention is to provide the application of the defective manganese-based catalyst supported by the SBA-15 molecular sieve.

[0011] The first aspect of the present invention provides a defective manganese-based catalyst supported by an SBA-15 molecular sieve, wherein the SBA-15 molecular sieve is prepared using silicon-containing solid waste as a raw material, and the phase composition of the active component of the defective manganese-based catalyst includes β-MnO2, Mn2O3 and Mn5O8, wherein Mn 3+ / Mn 4+ The molar ratio is 8 to 12:1.

[0012] The catalytic oxidation reaction of volatile organic compounds usually occurs on the surface of the catalyst. The internal utilization rate of the catalyst is not high, which easily leads to waste of the catalyst. Therefore, reducing the size of the particles of the active components of the catalyst and avoiding agglomeration between the particles (i.e., improving the dispersion of the active components) can increase the probability of the volatile organic compounds reacting with the active components of the catalyst, thereby improving the catalytic activity.

[0013] The defective manganese-based catalyst loaded with the SBA-15 molecular sieve provided by the present invention can effectively utilize the larger specific surface area of ​​the mesoporous SBA-15 molecular sieve, which is conducive to the mass transfer and diffusion of reaction substrates (such as volatile organic compounds, such as ethylene) and oxygen. The SBA-15 molecular sieve has a uniform pore structure, which can limit the active ingredient manganese oxide, prevent the aggregation of the active ingredient, reduce the size of the manganese oxide, increase the unit specific surface activity, and then reduce the amount of the active ingredient, reducing the use cost of the catalyst. In addition, the SBA-15 molecular sieve carrier can not only disperse the active ingredient, but also provide certain mechanical strength and support, and can prevent the sintering of the catalyst under high temperature conditions, thereby extending its service life.

[0014] The active components of the defective manganese-based catalyst supported by the SBA-15 molecular sieve provided by the present invention have a specific phase composition, forming more defect sites, and the manganese-containing active components have excellent dispersibility and a smaller size through the confinement effect of the molecular sieve, thereby significantly improving the catalytic performance of the catalyst, thereby achieving the purpose of being able to catalyze ethylene degradation alone without introducing precious metal elements as active components. In addition, the high specific surface area of ​​the molecular sieve carrier is also conducive to the adsorption, activation and oxidation of ethylene gas, further improving the catalytic performance and increasing the catalytic efficiency.

[0015] In some preferred embodiments, in the phase composition of the active component of the defective manganese-based catalyst, Mn 3+ / Mn 4+ The molar ratio is 10-12:1.

[0016] In some preferred embodiments, the phase composition of the active component of the defective manganese-based catalyst may include, by mole, 2-10% β-MnO2, 45-90% Mn2O3, and 2-50% Mn5O8. In some more preferred embodiments, the phase composition of the active component of the defective manganese-based catalyst may include, by mole, 5-10% β-MnO2, 50-90% Mn2O3, and 3-45% Mn5O8.

[0017] In some preferred embodiments, the specific surface area of ​​the defective manganese-based catalyst supported by the SBA-15 molecular sieve provided by the present invention can be 300 to 400 m 2 / g (for example, about 300 m 2 / g, about 310m 2 / g, about 320m 2 / g, about 330m 2 / g, about 340m 2 / g, about 350m 2 / g, about 360m 2 / g, about 370m 2 / g, about 380m 2 / g, about 390m 2 / g, about 400m 2 In some more preferred embodiments, the specific surface area of ​​the defective manganese-based catalyst supported by the SBA-15 molecular sieve provided by the present invention can be 300 to 360 m 2 / g.

[0018] In some preferred embodiments, the average pore size of the defective manganese-based catalyst supported by the SBA-15 molecular sieve provided by the present invention can be 5 to 20 nm (for example, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, about 10 nm, about 11 nm, about 12 nm, about 15 nm, about 18 nm, about 20 nm or any combination of pore size intervals). In some more preferred embodiments, the average pore size of the defective manganese-based catalyst can be 5 to 10 nm.

[0019] In some preferred embodiments, the microscopic morphology of the defective manganese-based catalyst supported by the SBA-15 molecular sieve provided by the present invention is rod-shaped, such as Figure 5 shown.

[0020] In some preferred embodiments, the silicon-containing solid waste can be selected from common silicon-containing solid wastes in industry, including but not limited to fly ash, coal gangue, red mud (industrial solid waste discharged when alumina is extracted in the aluminum industry), waste SCR catalysts, waste MTO catalysts, and one or more of waste VOC catalysts.

[0021] In some preferred embodiments, the chemical composition of the SBA-15 molecular sieve may include 0.5-5% (e.g., about 0.5%, about 1%, about 1.5%, about 2%, about 2.5%, about 3%, about 3.5%, about 4%, about 4.5%, about 5%, or any combination of mass percentage intervals) of Al2O3 and the balance of SiO2. In some more preferred embodiments, the chemical composition of the SBA-15 molecular sieve may include 2.5-5% of Al2O3 and the balance of SiO2 by mass percentage.

[0022] The second aspect of the present invention provides a method for preparing a defective manganese-based catalyst supported by an SBA-15 molecular sieve as described in any one of the above technical solutions, which comprises the following steps:

[0023] S1: placing silicon-containing solid waste in an alkaline solution for desiliconization, and filtering to obtain a desiliconized filtrate;

[0024] S2: adding a template to the desiliconized filtrate and adjusting the pH value to 3-5, performing hydrothermal crystallization, separating the obtained colloid, washing, drying and calcining to obtain SBA-15 molecular sieve;

[0025] S3: dissolving potassium permanganate and a divalent manganese salt in water to obtain a manganese-containing solution, wherein the molar ratio of the potassium permanganate to the divalent manganese salt is 1:1.5-3; mixing the manganese-containing solution and the SBA-15 molecular sieve and performing a hydrothermal reaction to obtain a hydrothermal material; and

[0026] S4: separating the solid matter from the hydrothermal material, washing, drying and calcining to obtain the SBA-15 molecular sieve supported defective manganese-based catalyst.

[0027] The preparation method provided by the present invention first uses silicon-containing industrial solid waste as a silicon source to prepare a mesoporous SBA-15 molecular sieve with a large specific surface area, and then uses a manganese-containing solution to load a manganese oxide with defect sites on the surface of the molecular sieve through a hydrothermal method, thereby obtaining the SBA-15 molecular sieve-loaded defective manganese-based catalyst. Figure 3 As shown, the defective manganese-based catalyst loaded with the SBA-15 molecular sieve prepared by the present invention still has the typical pore structure of the SBA-15 molecular sieve, indicating that the hydrothermal loading process does not change the pore structure of the SBA-15.

[0028] In addition, the preparation method provided by the present invention controls the Mn in the hydrothermal system. 2+ and Mn 7+The ratio of 2:1 to 4:1 makes the manganese species in the obtained manganese oxide active component mixed with various valence states, with more defect sites and special micromorphology, which can further improve the catalytic performance of the catalyst, thereby achieving the purpose of catalyzing ethylene degradation alone without introducing precious metal elements as active components.

[0029] In the preparation method provided by the present invention, in the step S1, the alkali solution can be an aqueous solution of sodium hydroxide or potassium hydroxide, and the concentration can be 10 to 16 mol / L. In some preferred embodiments, the mass ratio of the silicon-containing solid waste to the sodium hydroxide or potassium hydroxide can be 1:0.5 to 1. In some more preferred embodiments, the mass ratio of the silicon-containing solid waste to the sodium hydroxide or potassium hydroxide can be 1:0.5 to 0.7.

[0030] In the preparation method provided by the present invention, in step S1, the desiliconization can be carried out in a hydrothermal reactor, the desiliconization temperature can be 90-120° C., and the desiliconization time can be 2-8 hours. In some preferred embodiments, the desiliconization temperature can be 110-120° C., and the desiliconization time can be 3-6 hours.

[0031] In the preparation method provided by the present invention, the desiliconization filtrate obtained in step S1 is mainly a sodium silicate solution or a potassium silicate solution, which usually contains 45-55 g / L of SiO2, 60-80 g / L of Na2O or K2O, and 180-500 mg / L of Al2O3.

[0032] In the preparation method provided by the present invention, in the step S2, the template may be a triblock copolymer P123 (full name: polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, molecular formula: PEO-PPO-PEO).

[0033] In the preparation method provided by the present invention, in the step S2, the amount of the template used can be 2 to 5 times the amount of the silicon-containing solid waste used by mass.

[0034] In the preparation method provided by the present invention, in step S2, a hydrochloric acid solution with a concentration of 1 to 3 mol / L (eg, 2 mol / L) can be used to adjust the pH value.

[0035] In the preparation method provided by the present invention, in step S2, the temperature of the hydrothermal crystallization can be 100-160° C., and the crystallization time can be 40-70 hours. In some preferred embodiments, the temperature of the hydrothermal crystallization can be 100-120° C., and the crystallization time can be 48-60 hours.

[0036] In the preparation method provided by the present invention, in step S2, the obtained mixture can be stirred at 20-40° C. for 1-10 hours before hydrothermal crystallization and after adjusting the pH value.

[0037] In the preparation method provided by the present invention, in step S2, the separated colloid can be washed with deionized water until it becomes neutral, for example, washed 2 to 4 times, and the washing temperature can be room temperature (ie, 25° C.).

[0038] In the preparation method provided by the present invention, in step S2, the drying temperature can be 80-150° C., and the drying time can be 3-15 hours. In some preferred embodiments, the drying temperature can be 90-120° C., and the drying time can be 8-12 hours.

[0039] In the preparation method provided by the present invention, in step S2, the calcination temperature can be 450-700°C, and the calcination time can be 3-10 hours. In some preferred embodiments, the calcination temperature can be 550-650°C, and the calcination time can be 5-8 hours.

[0040] In the preparation method provided by the present invention, in step S2, the pore volume of the SBA-15 molecular sieve can be 0.7 to 1 cm 3 / g, and the specific surface area can be 700~950m 2 / g, the average pore size can be 5-10 nm, and the average particle size can be 10-25 nm. In some preferred embodiments, the pore volume of the SBA-15 molecular sieve can be 0.75-0.85 cm 3 / g, the specific surface area can be 720~900m 2 / g, the average pore diameter can be 6-10nm, and the average particle size can be 15-22nm.

[0041] In the preparation method provided by the present invention, in step S3, the divalent manganese salt may be a common divalent manganese water-soluble salt or a hydrate thereof in the art. In some preferred embodiments, the divalent manganese salt may be selected from one or more of manganese sulfate, manganese nitrate, manganese acetate or a hydrate thereof, wherein the hydrate of the divalent manganese salt may be a hydrate containing any amount of crystal water.

[0042] In the preparation method provided by the present invention, in the step S3, the temperature of the hydrothermal reaction can be 120 to 180° C., and the reaction time can be 12 to 18 hours.

[0043] In the preparation method provided by the present invention, in the step S3, the amount of the SBA-15 molecular sieve used is 0.5 to 12.5 times the amount of the potassium permanganate used by mass (for example, it can be about 0.5 times, about 0.8 times, about 1 times, about 1.5 times, about 2 times, about 2.5 times, about 3 times, about 3.5 times, about 4 times, about 4.5 times, about 5 times, about 6 times, about 7 times, about 8 times, about 9 times, about 10 times, about 11 times, about 12 times, or can be any combination of multiple intervals).

[0044] In the preparation method provided by the present invention, the preparation process of the manganese-containing solution may further include the following steps:

[0045] S301: dissolving the potassium permanganate in water at 30-50° C. to obtain a potassium permanganate aqueous solution; and

[0046] S302: adding the divalent manganese salt to the potassium permanganate aqueous solution, stirring at 80-100° C. for 1-5 hours to obtain the manganese-containing solution.

[0047] In the preparation method provided by the present invention, in step S4, the drying temperature can be 80-120° C., and the drying time can be 10-20 hours. In some preferred embodiments, the drying temperature can be 90-110° C., and the drying time can be 10-15 hours.

[0048] In the preparation method provided by the present invention, in step S4, the calcination temperature can be 400-650°C, and the calcination time can be 3-8 hours. In some preferred embodiments, the calcination temperature can be 500-600°C, and the calcination time can be 5-8 hours.

[0049] In the preparation method provided by the present invention, in step S4, the separated solid matter can be washed 2 to 4 times with deionized water, and the washing temperature can be room temperature (ie, 25° C.).

[0050] In the preparation method provided by the present invention, the heating rate during calcination can be 3-8°C / min, for example, 5°C / min.

[0051] In the preparation method provided by the present invention, the desired material can be obtained through a separation step, such as separating solid matter from a hydrothermal material, and the separation method can be a common method in the art, including but not limited to natural sedimentation, (normal pressure or vacuum) filtration, centrifugation, etc.

[0052] The third aspect of the present invention provides the use of the defective manganese-based catalyst supported by the SBA-15 molecular sieve described in any one of the above technical solutions or the defective manganese-based catalyst supported by the SBA-15 molecular sieve prepared by the preparation method described in any one of the above technical solutions in the catalytic oxidation of ethylene.

[0053] The supported defective manganese-based catalyst provided by the present invention has excellent catalytic activity. In the absence of any precious metal as an active component, a high ethylene catalytic oxidation activity can be achieved, and the ethylene conversion rate can reach 90% at 160-200°C (e.g. Figure 6 As shown), and the CO2 selectivity can reach more than 99%.

[0054] The technical solution provided by the present invention has the following advantages:

[0055] (1) The supported defective manganese-based catalyst provided by the present invention uses the mesoporous SBA-15 molecular sieve as a carrier, which can not only fully recycle industrial solid waste to achieve the purpose of waste utilization, but also make full use of the high specific surface area and uniform pore structure of the SBA-15 molecular sieve, thereby greatly improving the catalytic activity of the manganese-based catalyst, thereby improving the utilization efficiency of the catalyst and reducing the use cost of the catalyst.

[0056] (2) The supported defective manganese-based catalyst provided by the present invention has the characteristics of diverse manganese oxide species, mixed valence states, controllable morphology, and a large number of defect sites, so it has excellent catalytic activity and does not require the use of precious metals as active components, further reducing the catalyst cost.

[0057] (3) The supported defective manganese-based catalyst provided by the present invention has an excellent effect in the catalytic oxidation of ethylene, and can therefore be used as a new and efficient ethylene degradation catalyst, which is beneficial to the degradation and removal of ethylene and other volatile organic compounds, and provides a new idea for the prevention and control of volatile organic compound pollution. It is green and environmentally friendly and has very important economic value and social significance.

[0058] (4) The preparation method provided by the present invention can effectively realize the reuse of solid waste, thereby reducing the storage of waste and reducing its impact on the environment, which is green and environmentally friendly. The preparation of defective manganese oxide can also use cheap and easily available potassium permanganate and divalent manganese salt as raw materials, and the overall process has high economic efficiency. Moreover, the preparation method provided by the present invention also has the advantages of simple process, strong operability, high safety, etc., and thus has good industrial applicability and is very suitable for large-scale production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 A transmission electron microscope (TEM) image of the SBA-15 mesoporous molecular sieve prepared in Example 3;

[0060] Figure 2 The wide-angle X-ray powder diffraction pattern of the catalyst prepared in Example 3;

[0061] Figure 3The small angle X-ray powder diffraction pattern of the catalyst prepared in Example 3;

[0062] Figure 4 The nitrogen adsorption-desorption isotherm diagram of the catalyst prepared in Example 3;

[0063] Figure 5 This is a SEM image of the catalyst prepared in Example 3;

[0064] Figure 6 This is a graph showing the relationship between temperature and ethylene conversion when the catalyst prepared in Example 3 catalyzes ethylene oxidation. DETAILED DESCRIPTION

[0065] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments.

[0066] Unless otherwise specified, the raw materials or reagents used in the examples and comparative examples of the present invention are commercially available products.

[0067] The percentages used in the embodiments and comparative examples of the present invention are all mass percentages unless otherwise specified.

[0068] Example 1

[0069] Mix 10g fly ash and 7g sodium hydroxide, add 17.5mL water to a concentration of 10mol / L NaOH, and desiliconize the resulting mixture in a hydrothermal reactor at 120°C for 3h. Filter after desiliconization, and take the filtrate (mainly sodium silicate solution) for standby use. According to the mass ratio of fly ash and P123 of 1:3, take 30mL sodium silicate solution, add 30g P123 to dissolve it, and then add 100mL of 2mol / L HCl to adjust the pH value of the system to 4. After continuous mechanical stirring at 35°C for 3h, pour it into a stainless steel reactor with a polytetrafluoroethylene liner and crystallize at 110°C for 48h. Filter the mixture obtained after crystallization, wash the colloid obtained after filtration with deionized water until neutral, and dry it at 100°C for 8h. The dried material was calcined at 550°C for 6 h with a heating rate of 5°C / min, and then cooled to obtain a powdered SBA-15 mesoporous molecular sieve. The pore volume of the SBA-15 mesoporous molecular sieve is 0.80 cm 3 / g, specific surface area is 895m 2 / g, an average pore diameter of 8.16nm, and an average particle size of 18.67nm. According to XRF testing, the chemical composition of the prepared SBA-15 molecular sieve includes 0.5% Al2O3 by mass percentage, and the rest is SiO2.

[0070] 0.5 g potassium permanganate powder was dissolved in 100 mL of deionized water at 30°C. Then 1.27 g manganese nitrate was added to the above solution, and the molar ratio of manganese nitrate to potassium permanganate was 3.2:2, and stirred at 80°C for 1 hour. The above obtained mixture and 0.4 g of the prepared SBA-15 mesoporous molecular sieve were placed in a polytetrafluoroethylene hydrothermal reactor for hydrothermal reaction, the hydrothermal reaction temperature was 160°C, and the reaction time was 12 hours.

[0071] The mixture obtained after the hydrothermal reaction was centrifuged, and the solid obtained after separation was washed with deionized water, washed at room temperature, and washed three times. Finally, the solid was dried at 100°C for 12 hours, and calcined at 550°C for 6 hours at a heating rate of 5°C / min to obtain a defective manganese-based catalyst supported by an SBA-15 mesoporous molecular sieve.

[0072] The main phase composition of the active components of the catalyst is: β-MnO2, Mn2O3 and Mn5O8. The phase composition obtained by semi-quantitative XRD includes (by mole): β-MnO2 about 5.8%, Mn2O3 about 52.67% and Mn5O8 about 41.53%. 3+ / Mn 4+ The molar ratio of the catalyst is 10. The specific surface area of ​​the catalyst is 325m 2 / g, and the average pore size is 5.32nm.

[0073] Example 2

[0074] Mix 10g of coal gangue and 5g of potassium hydroxide, add 6.4mL of water to a KOH concentration of 14mol / L, and desiliconize the resulting mixture in a hydrothermal reactor at a temperature of 110°C for 6h. Filter after desiliconization, and take the filtrate (mainly sodium silicate solution) for standby use. According to the mass ratio of coal gangue to P123 of 1:2, take 30mL of sodium silicate solution, add 20g of P123 to dissolve it, and then add 100mL of 2mol / L HCl to adjust the pH value of the system to 5. After continuous mechanical stirring at 35°C for 5h, pour it into a stainless steel reactor with a polytetrafluoroethylene liner and crystallize at 100°C for 50h. Filter the mixture obtained after crystallization, wash the colloid obtained after filtration with deionized water until neutral, and dry it at 90°C for 10h. The dried material was calcined at 600°C for 5 h with a heating rate of 5°C / min, and then cooled to obtain a powdered SBA-15 mesoporous molecular sieve. The pore volume of the SBA-15 mesoporous molecular sieve is 0.75 cm 3 / g, specific surface area is 749m 2 / g, an average pore diameter of 9.16nm, and an average particle size of 20.37nm. According to XRF testing, the chemical composition of the prepared SBA-15 molecular sieve includes 2.8% Al2O3 by mass percentage, and the rest is SiO2.

[0075] 0.55g potassium permanganate powder was dissolved in 100mL deionized water at 40°C. Then 1.41g manganese acetate was added to the above solution, and the molar ratio of manganese acetate to potassium permanganate was 5.1:2, and stirred at 100°C for 3h. The above-obtained mixture and 2.25g of the prepared SBA-15 mesoporous molecular sieve were placed in a polytetrafluoroethylene hydrothermal reactor for hydrothermal reaction, and the hydrothermal reaction temperature was 180°C and the reaction time was 16h.

[0076] The mixture obtained after the hydrothermal reaction was centrifuged, and the solid obtained after separation was washed with deionized water, washed at room temperature, and washed three times. Finally, the solid was dried at 100°C for 12 hours, and calcined at 500°C for 5 hours at a heating rate of 5°C / min to obtain a defective manganese-based catalyst supported by an SBA-15 mesoporous molecular sieve.

[0077] The main phase composition of the active components of the catalyst is: β-MnO2, Mn2O3 and Mn5O8. The phase composition obtained by semi-quantitative XRD includes (by mole): β-MnO2 about 6.4%, Mn2O3 about 69.74% and Mn5O8 about 23.86%. The XPS peak fitting results show that Mn 3+ / Mn 4+ The molar ratio is 12. The specific surface area of ​​the catalyst is 308m 2 / g, and the average pore size is 10.49nm.

[0078] Example 3

[0079] 10g of waste SCR catalyst and 10g of sodium hydroxide were mixed, and 15.6mL of water was added to the concentration of NaOH to 16mol / L. The resulting mixture was desiliconized in a hydrothermal reactor at a temperature of 120°C for 6h. After desiliconization, the mixture was filtered and the filtrate (mainly sodium silicate solution) was taken for standby use. According to the mass ratio of waste SCR catalyst and P123 of 1:5, 30mL of sodium silicate solution was taken, 50g of P123 was added to it to dissolve, and then 100mL of 2mol / L HCl was added to adjust the pH value of the system to 5. After continuous mechanical stirring at 35°C for 10h, it was poured into a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 120°C for 60h. The mixture obtained after crystallization was filtered, and the colloid obtained after filtration was washed with deionized water until neutral, and dried at 120°C for 8h. The dried material was calcined at 650°C for 5 h with a heating rate of 5°C / min, and then cooled to obtain powdered SBA-15 mesoporous molecular sieve. The pore volume of SBA-15 mesoporous molecular sieve is 0.82 cm 3 / g, specific surface area is 788m 2 / g, the average pore size is 6.11nm, and the average particle size is 12.16nm. According to XRF testing, the chemical composition of the prepared SBA-15 molecular sieve includes 5% Al2O3 by mass percentage, and the rest is SiO2. The TEM image of SBA-15 molecular sieve is shown in Figure 1 shown.

[0080] 0.04 g potassium permanganate powder was dissolved in 100 mL of deionized water at 50°C. Then 0.076 g manganese sulfate was added to the above solution, and the molar ratio of manganese sulfate to potassium permanganate was 2:1, and stirred at 90°C for 2 h. The above obtained mixture and 0.5 g of the prepared SBA-15 mesoporous molecular sieve were placed in a polytetrafluoroethylene hydrothermal reactor for hydrothermal reaction, the hydrothermal reaction temperature was 120°C, and the reaction time was 18 h.

[0081] The mixture obtained after the hydrothermal reaction was centrifuged, and the solid obtained after separation was washed with deionized water, washed at room temperature, and washed three times. Finally, the solid was dried at 100°C for 12 hours, and calcined at 600°C for 8 hours at a heating rate of 5°C / min to obtain a defective manganese-based catalyst supported by an SBA-15 mesoporous molecular sieve.

[0082] like Figure 2 As shown, the main phase composition of the catalyst active component is: β-MnO2, Mn2O3 and Mn5O8. The phase composition obtained by semi-quantitative XRD includes (by mole): β-MnO2 about 8.7%, Mn2O3 about 86.9% and Mn5O8 about 4.4%. 3+ / Mn4+ The molar ratio of the catalyst is 11. The specific surface area of ​​the catalyst is 354m 2 / g, and the average pore size is 7.86nm.

[0083] Comparative Example 1

[0084] The preparation process of SBA-15 mesoporous molecular sieve is the same as that in Example 1.

[0085] 2.9g of manganese nitrate was mixed with 1g of the SBA-15 mesoporous molecular sieve prepared above at a mass ratio of MnO2 to SBA-15 molecular sieve of 1:10, 100mL of deionized water was added, and stirred at 80°C for 8h. Mn was loaded onto the SBA-15 mesoporous molecular sieve by impregnation. After that, the mixture obtained above was dried at 90°C for 12h and calcined at 550°C for 5h with a heating rate of 5°C / min to obtain a manganese-based catalyst loaded with SBA-15 mesoporous molecular sieve. The main phase composition of the active component of the catalyst is: β-MnO2. The specific surface area of ​​the catalyst is 278m 2 / g, and the average pore size is 5.02nm.

[0086] Comparative Example 2

[0087] Except that the amount of manganese nitrate added was in a molar ratio of manganese nitrate to potassium permanganate of 1:1, the other preparation processes were the same as in Example 1, and a manganese-based catalyst supported by an SBA-15 mesoporous molecular sieve was obtained. The main phase composition of the catalyst active component was: β-MnO2. The specific surface area of ​​the catalyst was 328 m 2 / g, and the average pore size is 5.66nm.

[0088] Comparative Example 3

[0089] Commercially available Mn2O3 (Sigma-Aldrich, CAS 1317-34-6) was used as the catalyst.

[0090] Test Case

[0091] The SBA-15 mesoporous molecular sieve supported catalysts prepared in Examples 1-3 and Comparative Examples 1-3 were pelletized (40-60 mesh) and tested for their catalytic activity in catalyzing ethylene oxidation. -1 , ethylene concentration is 700ppm, carrier gas is N2, the ethylene conversion rate is calculated by the inlet and outlet ethylene concentration of the test device (American MKS MultiGas 6030 Fourier transform infrared gas analyzer), and the temperature is programmed at a rate of 5°C / min to test the temperature T90 corresponding to the ethylene conversion rate reaching 90%. The test results are shown in Table 1.

[0092] Table 1 Activity test results of catalysts for ethylene oxidation

[0093]

[0094]

[0095] From the results in Table 1, it can be seen that the defective manganese-based catalyst supported by the SBA-15 mesoporous molecular sieve provided by the present invention has excellent catalytic activity in the catalytic oxidation of ethylene, and does not require the use of precious metals as active ingredients, so it can be used as a new and efficient ethylene degradation catalyst with strong industrial applicability. The catalysts of Comparative Examples 1-3 are manganese oxides composed of a single phase, so it is difficult to achieve a good catalytic effect.

[0096] Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0097] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Those skilled in the art may make various other substitutions, changes and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above embodiments, but is only limited by the claims.

Claims

1. A defective manganese-based catalyst supported by SBA-15 molecular sieve, characterized in that: The SBA-15 molecular sieve is prepared using silicon-containing solid waste as raw material. The active component of the defective manganese-based catalyst comprises β-MnO2, Mn2O3 and Mn5O8. 3+ / Mn 4+ The molar ratio is 8 to 12:

1.

2. The defective manganese-based catalyst according to claim 1, characterized in that The phase composition of the active component of the defective manganese-based catalyst comprises, by mole, 2 to 10% of β-MnO2, 45 to 90% of Mn2O3 and 2 to 50% of Mn5O8; and / or The specific surface area of ​​the defective manganese-based catalyst is 300 to 400 m 2 / g; and / or The average pore diameter of the defective manganese-based catalyst is 5 to 20 nm.

3. The defective manganese-based catalyst according to claim 1 or 2, characterized in that The silicon-containing solid waste is selected from one or more of fly ash, coal gangue, red mud, waste SCR catalyst, waste MTO catalyst, and waste VOC catalyst; and / or The chemical composition of the SBA-15 molecular sieve includes 0.5-5% Al2O3 and the balance SiO2 by mass percentage.

4. The method for preparing the defective manganese-based catalyst supported by the SBA-15 molecular sieve according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1: placing the silicon-containing solid waste in an alkaline solution for desiliconization, and filtering to obtain a desiliconized filtrate; S2: adding a template to the desiliconization filtrate and adjusting the pH value to 3-5, performing hydrothermal crystallization, separating the obtained colloid, washing, drying and calcining to obtain SBA-15 molecular sieve; S3: dissolving potassium permanganate and a divalent manganese salt in water to obtain a manganese-containing solution, wherein the molar ratio of the potassium permanganate to the divalent manganese salt is 1:1.5-3; mixing the manganese-containing solution and the SBA-15 molecular sieve and performing a hydrothermal reaction to obtain a hydrothermal material; and S4: separating the solid matter from the hydrothermal material, washing, drying and calcining to obtain the SBA-15 molecular sieve supported defective manganese-based catalyst.

5. The preparation method according to claim 4, characterized in that: In step S1, the alkali solution is an aqueous solution of sodium hydroxide or potassium hydroxide, and the concentration is 10-16 mol / L; preferably, the mass ratio of the silicon-containing solid waste to the sodium hydroxide or potassium hydroxide is 1:0.5-1; and / or The desiliconization is carried out in a hydrothermal reaction kettle, the desiliconization temperature is 90-120° C., and the desiliconization time is 2-8 hours.

6. The preparation method according to claim 4 or 5, characterized in that: In the step S2, the template is selected from the triblock copolymer P123; and / or The amount of the template used is 2 to 5 times the amount of the silicon-containing solid waste by mass; and / or The pH value was adjusted using a hydrochloric acid solution with a concentration of 1 to 3 mol / L.

7. The preparation method according to any one of claims 4 to 6, characterized in that: In the step S2, the hydrothermal crystallization temperature is 100-160° C., and the crystallization time is 40-70 hours; and / or The drying temperature is 80-150° C. and the drying time is 3-15 hours; and / or The calcination temperature is 450-700° C., and the calcination time is 3-10 hours.

8. The preparation method according to any one of claims 4 to 7, characterized in that: In step S3, the divalent manganese salt is selected from one or more of manganese sulfate, manganese nitrate, manganese acetate or hydrates thereof; and / or The temperature of the hydrothermal reaction is 120-180° C. and the reaction time is 12-18 hours; and / or The amount of the SBA-15 molecular sieve used is 0.5 to 12.5 times the amount of the potassium permanganate used by mass.

9. The preparation method according to any one of claims 4 to 8, characterized in that: In step S4, the drying temperature is 80-120° C. and the drying time is 10-20 hours; and / or The calcination temperature is 400-650° C., and the calcination time is 3-8 hours.

10. Use of the defective manganese-based catalyst supported on SBA-15 molecular sieve according to any one of claims 1 to 3 or the defective manganese-based catalyst supported on SBA-15 molecular sieve prepared by the preparation method according to any one of claims 4 to 9 in catalytic oxidation of ethylene.

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