A high-temperature-resistant sulfur-resistant VOCs catalyst suitable for RTO, and a preparation method and application thereof

Abstract

The application belongs to the technical field of VOCs catalysts, and particularly relates to a high-temperature-resistant sulfur-resistant VOCs catalyst suitable for RTO and a preparation method and application thereof, which comprises a carrier and an active layer on the carrier, the active layer comprises modified macroporous alumina and metal oxides on the surface of the modified macroporous alumina; the modified macroporous alumina is obtained by modification of a transition metal, and the transition metal is selected from one or more of cobalt, manganese, lanthanum and iron; and the metal in the metal oxides is selected from at least three of lanthanum, manganese, cerium, cobalt, copper and tin. The catalyst can withstand a working temperature of up to 1000 DEG C in a short time and a working temperature of above 700 DEG C for a long time, and can maintain high activity even if the catalyst is in an environment containing sulfur components, and can stably and efficiently treat VOCs gas.

Description

Technical Field

[0001] The present invention belongs to the technical field of VOCs catalysts, and specifically relates to a high-temperature resistant and sulfur-resistant VOCs catalyst suitable for RTO, and a preparation method and application thereof. Background Art

[0002] Volatile organic compounds (VOCs) are a general term for organic compounds produced in industrial and pharmaceutical production. At the same time, petrochemical, pharmaceutical, coating, printing and other industries also produce a large amount of VOCs gas. VOCs are key precursors to the formation of photochemical smog and secondary organic aerosols, and direct contact can cause multiple toxic effects on the human body.

[0003] There are two common treatment modes for removing VOCs, namely regenerative thermal oxidation technology (RTO) and regenerative catalytic combustion (RCO). In RCO, precious metal catalysts are often added into the combustion chamber to improve the purification efficiency of VOCs. However, the applicable temperature of the precious metal catalyst is 200℃-500℃, and high temperature will cause it to sinter and permanently deactivate. At the same time, since natural gas contains sulfur components, the precious metal catalyst has poor sulfur resistance and is difficult to meet actual treatment requirements. Regenerative thermal oxidation technology (RTO) uses ceramic thermal storage bodies (700-1200℃) to store the heat generated during the decomposition of organic waste gas, and uses the heat energy stored in the ceramic thermal storage body to preheat and decompose the untreated organic waste gas, so that the VOC in the waste gas is oxidized and decomposed into carbon dioxide and water. Therefore, it has the advantages of high purification efficiency, wide applicability and high heat recovery efficiency, but it is often used to treat medium and low concentrations (100-3500mg / m 3 When operating conditions are intermittent or VOC concentrations are low, large amounts of natural gas are consumed to maintain furnace temperatures and ensure acceptable purification efficiency. Maintaining high VOC purification efficiency in RTO while reducing energy consumption is a pressing challenge. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-temperature resistant and sulfur-resistant VOCs catalyst suitable for RTO, as well as its preparation method and application, so as to overcome the shortcomings of the existing technology. The catalyst is arranged in the RTO heat storage chamber and can withstand operating temperatures as high as 1000°C for a short period of time and above 700°C for a long period of time. Even if the environment contains sulfur components, the catalyst can maintain high activity and can stably and efficiently treat VOCs gas.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] In a first aspect, the present invention provides a high-temperature resistant and sulfur-resistant VOCs catalyst suitable for RTO, comprising a carrier and an active layer on the carrier, wherein the active layer comprises modified macroporous alumina and a metal oxide on its surface;

[0007] The modified macroporous alumina is obtained by modification with a transition metal, wherein the transition metal is selected from one or more of cobalt, manganese, lanthanum and iron;

[0008] The metal in the metal oxide is selected from at least three of lanthanum, manganese, cerium, cobalt, copper and tin.

[0009] In some other embodiments, the metal oxide is a perovskite-type metal oxide;

[0010] The carrier is a cordierite honeycomb ceramic carrier.

[0011] In some other embodiments, the modified macroporous alumina has pores with a diameter of 20-100 nm accounting for 70-75% of the total volume, pores with a pore diameter of more than 100 nm accounting for 15-20% of the total pore volume, and pores with a pore diameter of less than 20 nm accounting for less than 8% of the total pore volume; the BET specific surface area is 215-230 m 2 ·g -1 .

[0012] In a second aspect, the present invention provides a method for preparing the high-temperature resistant and sulfur-resistant VOCs catalyst suitable for RTO according to the first aspect, comprising the following steps:

[0013] (1) Pseudo-boehmite powder, a pore-forming agent, and a first binder are mixed as solid raw materials with water, and the mixture is extruded, dried, and calcined to obtain macroporous alumina;

[0014] (2) adding the macroporous alumina into a first transition metal salt solution, impregnating, drying, and calcining to obtain modified macroporous alumina;

[0015] (3) mixing the second transition metal salt, the second binder, and the modified macroporous alumina with water, and then adding the modifier to obtain a mixed solution;

[0016] (4) The mixed solution is vacuum coated on the surface of the cordierite ceramic carrier, and after drying and calcination, a high-temperature resistant and sulfur-resistant catalyst is obtained.

[0017] In some other embodiments, in step (1), the mass ratio of water to solid raw material is controlled at (1.5-3.5):1;

[0018] The mass ratio of the pseudo-boehmite powder, the pore-forming agent and the first binder is 1: (1-20%): (1-20%);

[0019] The drying temperature is 120°C and the holding time is 1-20h;

[0020] The calcination temperature is 400-800°C, the holding time is 2-6h, and the heating rate is 1-5°C / min;

[0021] The pore-forming agent is one or more of sesbania powder, starch, and carbon black;

[0022] The first binder is one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, ethylene glycol, polyethylene glycol, polyvinyl alcohol, polyethylene oxide, and polyacrylamide.

[0023] In some other embodiments, in step (2), the concentration of the first transition metal salt solution is 0.1-0.5 mol / L;

[0024] The first transition metal salt is one or more of cobalt, manganese, lanthanum and iron salts;

[0025] The solid-to-liquid ratio of the macroporous alumina and the first transition metal salt solution is 1 g: (5-10) mL;

[0026] The immersion temperature is 60-80°C and the time is 2-24 hours;

[0027] The drying temperature is 95-120°C and the drying time is 5-12 hours;

[0028] The calcination is first carried out at 450-650°C, holding time for 1-3 hours, and heating rate of 3-5°C / min; then heating to 750-950°C, holding time for 2-4 hours, and heating rate of 2-4°C / min;

[0029] Preferably, the cobalt salt is one or more of cobalt nitrate and cobalt sulfate;

[0030] Or, the manganese salt is one or more of manganese acetate, manganese sulfate and manganese nitrate;

[0031] Or, the lanthanum salt is one or more of lanthanum carbonate, lanthanum sulfate and lanthanum nitrate;

[0032] Alternatively, the iron salt is one or more of iron oxalate, iron sulfate and iron nitrate.

[0033] In some other embodiments, in step (3), the solid content in the mixed solution is 40-45 wt %;

[0034] The solid composition of the mixed solution comprises, by weight percentage of each raw material, 35-45% of the second transition metal salt, 2-5% of the second binder, 45-55% of the modified macroporous alumina, and 5-10% of the modifier;

[0035] The second transition metal salt is a water-soluble salt of at least three of lanthanum, manganese, cerium, cobalt, copper and tin;

[0036] The second binder is one of aluminum sol and silica sol; the concentration of the second binder is 10-40wt%;

[0037] The modifier is one or more of hydroxymethyl cellulose, hydroxypropyl methyl cellulose, ethylene glycol, polyethylene glycol, polyvinyl alcohol, polyethylene oxide, and polyacrylamide;

[0038] Preferably, the second transition metal salt is composed of three salts of lanthanum, manganese and tin or four salts of lanthanum, cerium, copper and tin;

[0039] Preferably, the molar ratio of cations in the three salts of lanthanum, manganese and tin is 1:0.7:0.3;

[0040] The molar ratio of cations in the four salts of lanthanum, cerium, copper and tin is (0.7-0.8): (0.7-0.8): (0.2-0.3): (0.2-0.3);

[0041] Further preferably, the molar ratio of the cations of the four salts of lanthanum, cerium, copper and tin is 0.7:0.8:0.3:0.2;

[0042] Preferably, the lanthanum salt is one or more of lanthanum carbonate and lanthanum nitrate;

[0043] Or, the manganese salt is one or more of manganese acetate and manganese nitrate;

[0044] Or, the cerium salt is one or more of cerium nitrate and cerium sulfate;

[0045] Or, the cobalt salt is one or more of cobalt nitrate and cobalt hydroxide;

[0046] Or, the copper salt is one or more of copper sulfate and copper nitrate;

[0047] Alternatively, the tin salt is one or more of stannous chloride and tin acetate.

[0048] In some other embodiments, in step (4), the drying temperature is 95-120° C. and the holding time is 1-3 h;

[0049] The calcination temperature is 900-1100° C., the holding time is 1-3 hours, and the heating rate is 3-5° C. / min.

[0050] In a third aspect, the present invention provides use of the high-temperature resistant and sulfur-resistant VOCs catalyst suitable for RTO described in the first aspect in VOCs treatment.

[0051] In a fourth aspect, the present invention provides a method for treating VOCs, wherein the high-temperature-resistant and sulfur-resistant VOCs catalyst suitable for RTO described in the first aspect is installed in the RTO heat storage chamber.

[0052] Beneficial effects of the present invention:

[0053] (1) The present invention reduces the set temperature of RTO by adding a catalyst to the RTO heat storage body, thereby reducing fuel consumption and reducing carbon emissions and fuel consumption caused by natural gas combustion.

[0054] (2) The high-temperature resistant and sulfur-resistant catalyst prepared by the present invention has a simple production process, does not contain precious metals, and has a low production cost; while retaining the high heat recovery efficiency of RTO, it ensures high purification efficiency.

[0055] (3) The high-temperature resistant and sulfur-resistant catalyst prepared by the present invention uses modified macroporous alumina as a carrier, has extremely high heat resistance and stability, and is added with sulfur-resistant components, so it can still maintain high activity in a sulfur-containing environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0057] Figure 1 The change of the p-xylene removal rate over time under test condition 1 is the high temperature resistant and sulfur resistant catalyst in Examples 1-10 of the present invention;

[0058] Figure 2 The change of the p-xylene removal rate over time under test condition 2 for the high temperature resistant and sulfur resistant catalysts in Example 5 and Comparative Examples 1-3;

[0059] Figure 3 This is the surface XRD spectrum of the high temperature resistant and sulfur resistant catalyst of Example 2. DETAILED DESCRIPTION

[0060] Those skilled in the art will appreciate that the following examples are intended to illustrate the present invention only and should not be construed as limiting the scope of the invention. Unless otherwise specified, the examples were performed under conventional conditions or manufacturer's recommended conditions. Components used without manufacturer's indication are commercially available conventional products.

[0061] The carrier used in the present invention is a cordierite honeycomb ceramic carrier with a cross-sectional opening number of 100-600 meshes. The cordierite honeycomb ceramic carrier structure is a rectangular parallelepiped with a length, width and height of 100 mm, 100 mm and 50 mm respectively.

[0062] Cordierite ceramic honeycomb carriers have significant advantages in VOCs catalysts. They have a high specific surface area and low air resistance, which are conducive to catalytic reactions; they have strong thermal stability and a small expansion coefficient, and can adapt to temperature changes; they have high mechanical strength and corrosion resistance, and can improve the dispersion and compatibility of active components, effectively improving VOCs treatment efficiency and catalyst life.

[0063] 1. Preparation of high temperature resistant and sulfur resistant catalyst suitable for RTO

[0064] Example 1

[0065] A method for preparing a high-temperature resistant and sulfur-resistant catalyst suitable for RTO comprises the following steps:

[0066] Step 1: Weigh 1 kg of pseudo-boehmite powder, 20 g of sesbania powder, and 50 g of carboxymethyl cellulose, add 2 kg of deionized water, and place in a stainless steel stirring kettle equipped with a powerful stirrer. Stir at 350-650 rpm for 1-5 hours to form a uniform paste. Extrude the paste through an extruder to form cylindrical strips with a diameter of 2-4 mm, and then cut into 3-5 mm long pellets using a pelletizer. Place in an oven and dry at 100°C for 2 hours. Transfer to a muffle furnace and calcine at 600°C for 2 hours. After cooling to room temperature, macroporous alumina is obtained.

[0067] Step 2: Prepare a 0.2 mol / L lanthanum nitrate solution, add the macroporous alumina prepared in step 1 to the solution (solid-liquid ratio of 1 g:10 mL), stir thoroughly, filter and wash three times, spread the filter cake on a tray in a vacuum drying oven with a thickness of about 1-3 cm, dry (100°C, 12 h) until the water is completely evaporated, transfer to a muffle furnace, calcined at 550°C for 2 h, calcined at 850°C for 3 h, and cooled to room temperature to obtain lanthanum-modified macroporous alumina.

[0068] Step 3: Take 2000 grams of lanthanum nitrate, manganese nitrate, and stannous chloride (the cation molar ratio is 1:0.7:0.3), 2500 grams of modified macroporous alumina, and 100 grams of aluminum sol, and dissolve them in 3400 grams of deionized water. After thorough stirring, grind them twice in a grinder at 500 rpm / min. Add 4% of the total mass of the slurry to hydroxymethyl cellulose, and continue stirring for 2 hours.

[0069] Step 4: The slurry obtained in step 3 is coated on the cordierite honeycomb ceramic carrier through a bottom feeding vacuum coating device. After coating, it is dried at 95° C. for 2 h and calcined at 1000° C. for 3 h to prepare a high temperature resistant and sulfur resistant catalyst.

[0070] Example 2

[0071] A method for preparing a high-temperature resistant and sulfur-resistant catalyst suitable for RTO is different from Example 1 in that, in step 2, the impregnation solution is a manganese acetate solution to obtain manganese-modified macroporous alumina, and the remaining steps are consistent with Example 1.

[0072] Example 3

[0073] A method for preparing a high-temperature resistant and sulfur-resistant catalyst suitable for RTO is different from Example 1 in that, in step 2, the impregnation solution is a ferric oxalate solution to obtain iron-modified macroporous alumina, and the remaining steps are consistent with Example 1.

[0074] Example 4

[0075] A method for preparing a high-temperature resistant and sulfur-resistant catalyst suitable for RTO is different from Example 1 in that, in step 2, the impregnation solution is a cobalt nitrate solution to obtain cobalt-modified macroporous alumina, and the remaining steps are consistent with Example 1.

[0076] Example 5

[0077] A method for preparing a high-temperature resistant and sulfur-resistant catalyst suitable for RTO is disclosed, which differs from Example 1 in that, in step 3, 2000 g of lanthanum nitrate, cerium nitrate, copper sulfate, and tin acetate (the cation molar ratio of which is 0.7:0.8:0.3:0.2), 2500 g of modified macroporous alumina, and 100 g of aluminum sol are dissolved in 3400 g of deionized water, and after sufficient stirring, the mixture is ground twice in a grinder at 500 rpm / min, and 4% of the total mass of the slurry is added to hydroxymethyl cellulose, and stirring is continued for 2 hours; the remaining steps are consistent with Example 1.

[0078] Example 6

[0079] A method for preparing a high-temperature resistant and sulfur-resistant catalyst suitable for RTO, which differs from Example 5 in that, in step 3, the cation ratio of the added transition metal salt (lanthanum nitrate, cerium nitrate, copper sulfate, tin acetate) is 0.8:0.8:0.2:0.2, and the remaining steps are consistent with Example 5.

[0080] Example 7

[0081] A method for preparing a high-temperature resistant and sulfur-resistant catalyst suitable for RTO, which differs from Example 5 in that, in step 3, the cation ratio of the added transition metal salt (lanthanum nitrate, cerium nitrate, copper sulfate, tin acetate) is 0.7:0.7:0.3:0.3, and the remaining steps are consistent with Example 5.

[0082] Example 8

[0083] A method for preparing a high-temperature resistant and sulfur-resistant catalyst suitable for RTO, which differs from Example 5 in that, in step 3, the cation ratio of the added transition metal salt (lanthanum nitrate, cerium nitrate, copper sulfate, tin acetate) is 0.8:0.7:0.3:0.2, and the remaining steps are consistent with Example 5.

[0084] Example 9

[0085] A method for preparing a high-temperature resistant and sulfur-resistant catalyst suitable for RTO, which differs from Example 5 in that, in step 3, the cation ratio of the added transition metal salt (lanthanum nitrate, cerium nitrate, copper sulfate, tin acetate) is 0.7:0.8:0.2:0.3, and the remaining steps are consistent with Example 5.

[0086] Example 10

[0087] A method for preparing a high-temperature resistant and sulfur-resistant catalyst suitable for RTO, which differs from Example 5 in that, in step 3, the cation ratio of the added transition metal salt (lanthanum nitrate, cerium nitrate, copper sulfate, tin acetate) is 0.8:0.7:0.2:0.3, and the remaining steps are consistent with Example 5.

[0088] Comparative Example 1

[0089] A method for preparing a high-temperature resistant and sulfur-resistant catalyst suitable for RTO is provided, wherein commercially available alumina (specific surface area: 59.3 m 2 / g (standard value, ±2.3), pore volume: 0.279 cm 3 / g (standard value, ±0.009), pore size: 18.84 nm (standard value, ±0.64)) to replace the lanthanum-modified macroporous alumina in Example 5, specifically comprising the following steps:

[0090] Step 1: Take 2000 grams of lanthanum nitrate, cerium nitrate, copper sulfate, and tin acetate (the cation molar ratio is 0.7:0.8:0.3:0.2), 2500 grams of aluminum oxide, and 100 grams of aluminum sol and dissolve them in 3400 grams of deionized water. After thorough stirring, grind them twice in a grinder at 500 rpm / min. Add 4% of the total mass of the slurry to hydroxymethyl cellulose and continue stirring for 2 hours.

[0091] Step 2: The slurry obtained in step 1 is coated on a cordierite honeycomb ceramic carrier by a bottom-feed vacuum coating device. After coating, it is dried at 95° C. for 2 h and calcined at 1000° C. for 3 h to prepare a high-temperature resistant and sulfur-resistant catalyst.

[0092] Comparative Example 2

[0093] A method for preparing a high-temperature resistant and sulfur-resistant catalyst suitable for RTO, wherein the lanthanum-modified macroporous alumina in Example 5 is replaced by macroporous alumina, specifically comprising the following steps:

[0094] Step 1: Weigh 1 kg of pseudo-boehmite powder, 20 g of sesbania powder and 50 g of carboxymethyl cellulose, add 2 kg of deionized water, stir evenly and put into an oven, dry at 100 ° C for 2 h, transfer to a muffle furnace, calcine at 600 ° C for 2 h, and cool to room temperature to obtain macroporous alumina.

[0095] Step 2: Take 2000 grams of lanthanum nitrate, cerium nitrate, copper sulfate, and tin acetate (the cation molar ratio is 0.7:0.8:0.3:0.2), 2500 grams of macroporous alumina, and 100 grams of aluminum sol and dissolve them in 3400 grams of deionized water. After thorough stirring, grind them twice in a grinder at 500 rpm / min. Add 4% of the total mass of the slurry to hydroxymethyl cellulose and continue stirring for 2 hours.

[0096] Step 3: The slurry obtained in step 2 is coated on the cordierite honeycomb ceramic carrier through a bottom feeding vacuum coating device. After coating, it is dried at 95° C. for 2 h and calcined at 1000° C. for 3 h to prepare a high temperature resistant and sulfur resistant catalyst.

[0097] Comparative Example 3

[0098] A method for preparing a high-temperature resistant and sulfur-resistant catalyst suitable for RTO, wherein the alumina used in Comparative Example 1 is modified with a lanthanum nitrate solution to obtain lanthanum-modified macroporous alumina, specifically comprising the following steps:

[0099] Step 1: Prepare a 0.2 mol / L lanthanum nitrate solution. Add alumina to the solution, stir thoroughly, and then filter and wash three times. Spread the filter cake flat on a tray in a vacuum drying oven and dry until the water is completely evaporated. Transfer to a muffle furnace and calcine at 550°C for 2 hours and then 850°C for 3 hours. Cool to room temperature to obtain lanthanum-modified macroporous alumina.

[0100] Step 2: Take 2000 grams of lanthanum nitrate, cerium nitrate, copper sulfate, and tin acetate (the cation molar ratio is 0.7:0.8:0.3:0.2), 2500 grams of modified alumina, and 100 grams of aluminum sol and dissolve them in 3400 grams of deionized water. After thorough stirring, grind them twice in a grinder at 500 rpm / min. Add 4% of the total mass of the slurry to hydroxymethyl cellulose and continue stirring for 2 hours.

[0101] Step 3: The slurry obtained in step 2 is coated on the cordierite honeycomb ceramic carrier through a bottom feeding vacuum coating device. After coating, it is dried at 95° C. for 2 h and calcined at 1000° C. for 3 h to prepare a high temperature resistant and sulfur resistant catalyst.

[0102] Comparative Example 4

[0103] The macroporous alumina carrier was prepared by the method of Example 1 in CN114950573B to replace the lanthanum-modified macroporous alumina in Example 5, and the remaining steps were consistent with those of Example 1.

[0104] Comparative Example 5

[0105] A method for preparing a high-temperature resistant and sulfur-resistant catalyst suitable for RTO is different from Example 5 in that in step 3, the transition metal salt added is only manganese nitrate, and the remaining steps are consistent with Example 5.

[0106] Comparative Example 6

[0107] A method for preparing a high-temperature resistant and sulfur-resistant catalyst suitable for RTO, which differs from Example 5 in that, in step 3, two transition metal salts, lanthanum nitrate and copper nitrate, are added with a cation ratio of 1:1, and the remaining steps are consistent with Example 5.

[0108] 2. Performance Verification

[0109] The high-temperature sulfur-resistant catalysts prepared in the examples and comparative examples were tested to examine the changes in their p-xylene removal rates over time in a sulfur-containing atmosphere and under long-term high-temperature conditions of 1000°C.

[0110] Test condition 1: temperature 700°C, xylene: 1000ppm, sulfur dioxide: 50ppm, water: 3%, volume space velocity: 30000 h -1 .

[0111] Test condition 2: temperature 1000°C, xylene: 1000 ppm, water: 3%, volume space velocity: 30,000 h -1 .

[0112] Table 1 shows the Bet data of macroporous alumina and modified macroporous alumina.

[0113] Table 1 shows the Bet data of macroporous alumina and modified macroporous alumina in Example 2

[0114]

[0115] As can be seen from Table 1, the Bet data of the modified macroporous alumina after aging at 1000℃ for 30h changes little. This is because the mesopores of the modified macroporous alumina account for 65% after aging, which is significantly higher than the 45% of the unmodified one, and the sintering resistance is enhanced; the specific surface area retention rate of the modified material after aging is 61.4%, while that of the unmodified one is only 31.4%, and the active sites after modification increase.

[0116] The set temperature of existing RTO reactors is often set at 850°C. When the catalyst prepared in this invention is added, the set temperature can be lowered to 700°C without affecting VOC removal efficiency, thereby reducing fuel consumption and lowering carbon emissions caused by natural gas combustion. Calculations show that lowering the set temperature of an RTO reactor from 850°C to 700°C reduces fuel consumption by over 30%, and the reduction in carbon emissions due to fuel consumption is close to one-third. The specific calculation process is as follows:

[0117]

[0118]

[0119] Figure 1 The high temperature resistant and sulfur resistant catalyst in Example 1-10, under test condition 1, changes in the removal rate of p-xylene over time. Figure 1 It can be seen that the test results of Examples 1-4 show that lanthanum-modified macroporous alumina is significantly superior to manganese, iron, and cobalt-modified systems in high-temperature sulfur-resistant VOCs catalytic applications. After the macroporous alumina is impregnated with lanthanum nitrate solution, it forms LaAlO3 with alumina during the calcination process, effectively inhibiting the phase transition of γ-Al2O3 to α-Al2O3 with low specific surface area above 800°C. However, the manganese and cobalt-modified systems have a larger specific surface area attenuation due to the weak metal-support interaction; secondly, La 3+ Strong alkaline sites (pH>9.5) are formed on the surface of alumina, which preferentially combine with sulfur-containing pollutants (such as SO2) to generate thermodynamically stable La2(SO4)3, thus avoiding the poisoning of active components by sulfur species; while sulfates of transition metals such as manganese and iron (such as MnSO4, FeSO4) are easily decomposed at high temperatures, resulting in the secondary release of sulfur and blocking the pores. In addition, the LaO formed after lanthanum nitrate impregnation x Nanoclusters (particle size 3-5nm) can serve as anchoring points to promote the subsequent uniform dispersion of platinum, while manganese and cobalt modified supports have low surface hydroxyl density, which easily leads to active metal agglomeration and reduces the density of effective reaction sites.

[0120] The test results of Examples 5-10 show that when modified macroporous alumina is added with different components and different molar ratios of second transition metal salts, the interaction between the multiple metals will have different effects on the sulfur resistance and high temperature resistance of the catalyst. The high content of lanthanum (0.7) improves the thermal stability of alumina and inhibits high temperature phase transition; the oxygen storage capacity of cerium (0.3) complements that of lanthanum, and at high temperature, Ce 3+ / Ce 4+ The redox cycle promotes the deep oxidation of VOCs; manganese dominates the active sites, and the high manganese loading (0.8) significantly improves the catalytic activity. X The multivalent states (Mn 2+ / Mn 3+ / Mn 4+ ) maintains a high oxygen mobility at high temperature, promotes the activation and breaking of C-H bonds in VOCs molecules. Compared with Example 6 (Mn=0.8 but Ce=0.2), Example 5 has a higher Ce content, which makes up for the activity attenuation of Mn after sulfur poisoning; the low Sn ratio (0.2) inhibits the sintering of active components through the strong interaction between SnO2 and active components (SMSI effect), and avoids excessive Sn (such as Sn=0.3 in Example 9) causing the active sites to be covered, thereby affecting the mass transfer efficiency.

[0121] Figure 2The change of the p-xylene removal rate over time in the high temperature resistant and sulfur resistant catalysts in Example 5 and Comparative Examples 1-3 under test condition 2. Figure 2 It can be seen that the test results of Example 5 and Comparative Examples 1-3 show that the catalyst prepared from ordinary alumina has the worst high temperature resistance, the modified alumina has poor high temperature resistance, the macroporous alumina has better high temperature resistance, and the modified macroporous alumina has the best high temperature resistance. This is consistent with the test data results in Table 1. Although the macroporous structure of macroporous alumina provides a channel for rapid diffusion of reactant and product molecules, allowing molecules to quickly enter and exit the carrier, reducing diffusion resistance and improving the efficiency of the catalytic reaction; the macroporous structure can also alleviate the thermal stress generated by the material during temperature changes. When the macroporous alumina is heated, due to the presence of pores inside the material, these pores can provide a certain space for the expansion of the material. When the temperature rises, the expanded part of the material can stretch into the pore space, thereby reducing the internal stress concentration caused by thermal expansion. This stress dispersion helps prevent the material from cracking or breaking due to excessive thermal stress, further enhancing the stability of the macroporous alumina in a high temperature environment. Transition metal-modified macroporous alumina has better performance. The addition of transition metals can effectively inhibit the phase change of alumina during the heating process, so that alumina maintains a relatively stable structure in a high-temperature environment, thereby maintaining a higher specific surface area and pore volume, and reducing sintering and agglomeration at high temperatures.

[0122] Comparative Example 4 uses the method of Example 1 in CN114950573B to prepare a macroporous alumina carrier to replace the lanthanum-modified macroporous alumina in Example 5. Its removal rate of xylene is low. First, in terms of crystal structure stability, the lanthanum-modified macroporous alumina forms LaAlO3 during calcination, inhibiting the phase transition from γ-Al2O3 to α-Al2O3, maintaining a stable structure and a large specific surface area to provide more active sites. The macroporous alumina in Comparative Example 4 has poor structural stability at high temperatures, easy attenuation of specific surface area, and reduced active sites; second, the dispersion of active metals is different. The LaO formed by lanthanum nitrate impregnation in the original document is not as good as the original document. x Nanoclusters can promote the uniform dispersion of active metals and increase effective reaction sites. The macroporous alumina in Comparative Example 4 lacks this mechanism, resulting in low dispersion of active metals and few effective reaction sites, which ultimately leads to low activity of xylene.

[0123] Comparative Example 5, in which only manganese nitrate was added as a transition metal salt, lacked the synergistic effects of the other metals, failing to fully utilize the advantages of each metal. This resulted in insufficient sulfur resistance and high-temperature resistance in the catalyst, which in turn affected the p-xylene removal rate. Comparative Example 6, while incorporating lanthanum nitrate and copper nitrate as transition metal salts, contained fewer metals than in Example 5, and the cation ratio was 1:1, not the optimized ratio used in Example 5. This combination and ratio was not conducive to the formation of efficient catalytic active centers and failed to achieve synergistic enhancement among the multiple metals, resulting in lower catalyst performance than in Example 5 and a lower p-xylene removal rate.

[0124] Figure 3 The surface XRD spectrum of the high temperature resistant and sulfur resistant catalyst of Example 2 is shown in FIG. Figure 3 It can be seen that lanthanum manganese in the catalyst forms a perovskite structure, and the lanthanum manganese perovskite skeleton can still maintain its crystal structure above 800°C, resisting high-temperature phase change through strong metal-oxygen bonds; the main function of tin is to resist sulfur.

[0125] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A high temperature resistant and sulfur resistant VOCs catalyst suitable for RTO, characterized in that: The invention comprises a carrier and an active layer on the carrier, wherein the active layer comprises modified macroporous alumina and metal oxide on its surface; The modified macroporous alumina is obtained by modification with a transition metal, and the transition metal is selected from lanthanum; The metal in the metal oxide is selected from at least three of lanthanum, manganese, cerium, cobalt, copper and tin; The preparation method of the high-temperature resistant and sulfur-resistant VOCs catalyst suitable for RTO comprises the following steps: (1) Pseudo-boehmite powder, a pore-forming agent, and a first binder are mixed as solid raw materials with water, and the mixture is extruded, dried, and calcined to obtain macroporous alumina; (2) Adding macroporous alumina to a first transition metal salt solution, impregnating, drying, and calcining to obtain modified macroporous alumina; the first transition metal salt is a lanthanum salt; wherein the pores with a pore diameter of 20-100 nm in the modified macroporous alumina account for 70-75% of the total pore volume, the pores with a pore diameter of more than 100 nm account for 15-20% of the total pore volume, and the pores with a pore diameter of less than 20 nm account for less than 8% of the total pore volume; the BET specific surface area is 215-230 m 2 ·g -1 ; (3) mixing a second transition metal salt, a second binder, and modified macroporous alumina with water, and then adding a modifier to obtain a mixed solution; the second transition metal salt is at least three water-soluble salts of lanthanum, manganese, cerium, cobalt, copper, and tin, and the modifier is one or more of hydroxymethyl cellulose, hydroxypropyl methyl cellulose, ethylene glycol, polyethylene glycol, polyvinyl alcohol, polyethylene oxide, and polyacrylamide; (4) The mixed solution is vacuum coated on the surface of the cordierite ceramic carrier, and after drying and calcination, a high-temperature resistant and sulfur-resistant VOCs catalyst is obtained.

2. The high temperature resistant and sulfur resistant VOCs catalyst suitable for RTO according to claim 1, characterized in that: The metal oxide is a perovskite-type metal oxide; The carrier is a cordierite honeycomb ceramic carrier.

3. The high temperature resistant and sulfur resistant VOCs catalyst suitable for RTO according to claim 1, characterized in that: In step (1), the mass ratio of water to solid raw material is controlled at (1.5-3.5):1; The mass ratio of the pseudo-boehmite powder, the pore-forming agent and the first binder is 1: (1%-20%): (1%-20%); The drying temperature is 120°C and the holding time is 1-20h; The calcination temperature is 400-800°C, the holding time is 2-6h, and the heating rate is 1-5°C / min; The pore-forming agent is one or more of sesbania powder, starch, and carbon black; The first binder is one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, ethylene glycol, polyethylene glycol, polyvinyl alcohol, polyethylene oxide, and polyacrylamide.

4. The high temperature resistant and sulfur resistant VOCs catalyst suitable for RTO according to claim 1, characterized in that: In step (2), the concentration of the first transition metal salt solution is 0.1-0.5 mol / L; The solid-to-liquid ratio of the macroporous alumina and the first transition metal salt solution is 1 g: (5-10) mL; The immersion temperature is 60-80°C and the time is 2-24 hours; The drying temperature is 95-120°C and the drying time is 5-12 hours; The calcination is first carried out at 450-650° C., keeping the temperature for 1-3 hours, and heating at a rate of 3-5° C. / min; then heating the temperature to 750-950° C., keeping the temperature for 2-4 hours, and heating at a rate of 2-4° C. / min.

5. The high temperature resistant and sulfur resistant VOCs catalyst suitable for RTO according to claim 1, characterized in that: In step (3), the solid content of the mixed solution is 40-45 wt%; The solid composition of the mixed solution comprises, by weight percentage of each raw material, 35-45% of the second transition metal salt, 2-5% of the second binder, 45-55% of the modified macroporous alumina, and 5-10% of the modifier; The second binder is one of aluminum sol and silica sol; the concentration of the second binder is 10-40 wt%.

6. The high temperature resistant and sulfur resistant VOCs catalyst suitable for RTO according to claim 1, characterized in that: In step (3), the second transition metal salt is composed of three salts of lanthanum, manganese and tin or four salts of lanthanum, cerium, copper and tin.

7. The high temperature resistant and sulfur resistant VOCs catalyst suitable for RTO according to claim 6, characterized in that: In step (3), the molar ratio of the cations of the four salts of lanthanum, cerium, copper and tin is (0.7-0.8): (0.7-0.8): (0.2-0.3): (0.2-0.3).

8. The high temperature resistant and sulfur resistant VOCs catalyst suitable for RTO according to claim 6, characterized in that: In step (3), the molar ratio of cations in the three salts of lanthanum, manganese and tin is 1:0.7:0.

3.

9. The high temperature resistant and sulfur resistant VOCs catalyst suitable for RTO according to claim 6, characterized in that: In step (3), the molar ratio of the cations of the four salts of lanthanum, cerium, copper and tin is 0.7:0.8:0.3:0.

2.

10. The high temperature resistant and sulfur resistant VOCs catalyst suitable for RTO according to claim 1, characterized in that: In step (4), the drying temperature is 95-120°C and the holding time is 1-3h; The calcination temperature is 900-1100° C., the holding time is 1-3 hours, and the heating rate is 3-5° C. / min.

11. Use of the high-temperature resistant and sulfur-resistant VOCs catalyst suitable for RTO according to any one of claims 1 to 10 in VOCs treatment.

12. A method for treating VOCs, characterized in that: The high-temperature resistant and sulfur-resistant VOCs catalyst suitable for RTO according to any one of claims 1 to 10 is installed in the RTO heat storage chamber.

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