High-temperature-resistant sulfur-resistant VOCs catalyst suitable for RTO and preparation method and application thereof

Abstract

The invention 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.The high-temperature-resistant sulfur-resistant VOCs catalyst comprises a carrier and an active layer on the carrier, and the active layer comprises modified macroporous aluminum oxide and metal oxide on the surface of the modified macroporous aluminum oxide; the modified macroporous alumina is obtained by modifying transition metal, and the transition metal is selected from one or more of cobalt, manganese, lanthanum and iron; the metal in the metal oxide is selected from at least three of lanthanum, manganese, cerium, cobalt, copper and tin. The catalyst can bear the working temperature as high as 1000 DEG C in a short time and over 700 DEG C for a long time, the catalyst can keep high activity even if the environment contains a sulfur component, and VOCs gas can be stably and efficiently treated.

Description

Technical Field

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

[0002] Volatile organic compounds (VOCs) are the general term for organic compounds generated in industries, pharmaceuticals and other productions; at the same time, a large amount of VOCs gases are also generated in industries such as petrochemical, pharmaceutical, painting, printing, etc. VOCs are the key precursors for the formation of photochemical smog and secondary organic aerosols, and direct contact will cause various 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 method (RCO). Among them, precious metal catalysts are often added to the combustion chamber in RCO to improve the purification efficiency of VOCs. However, the applicable temperature of this precious metal catalyst is 200°C - 500°C, and high temperature will cause its sintering and permanent inactivation; at the same time, due to the sulfur component in natural gas, the sulfur resistance of this precious metal catalyst is poor, making it difficult to meet the actual treatment requirements. The regenerative thermal oxidation technology (RTO) uses ceramic regenerators (700 - 1200°C) to store the heat generated during the decomposition of organic waste gas, and uses the thermal energy stored in the ceramic regenerators to preheat and decompose the untreated organic waste gas, so that the VOCs in the waste gas are oxidized and decomposed into carbon dioxide and water. Therefore, it has the advantages of high purification efficiency, wide applicability and high heat recovery efficiency. However, it is often used to treat medium and low concentration (100 - 3500mg / m 3 ) waste gas. When the working conditions are discontinuous or the concentration of VOCs gas is low, a large amount of natural gas needs to be consumed to maintain the furnace temperature to ensure that the purification efficiency meets the standard. How to ensure the high purification efficiency of VOCs in RTO while reducing energy consumption is an urgent problem to be solved at present. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-temperature resistant and sulfur-resistant VOCs catalyst applicable to RTO, and a preparation method and application thereof, so as to overcome the deficiencies of the prior art. This catalyst is arranged in the RTO regenerator and can withstand a working temperature of up to 1000°C in a short time and above 700°C for a long 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 purpose, the technical solution of the present invention is as follows:

[0006] In the first aspect, the present invention provides a high-temperature resistant and sulfur-resistant VOCs catalyst applicable to RTO, including a carrier and an active layer on the carrier, and the active layer includes modified macroporous alumina and metal oxides on its surface;

[0007] The modified macroporous alumina is obtained by modification with transition metals 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, for the modified macroporous alumina, the pores with a pore diameter of 20 - 100 nm account for 70 - 75% of the total volume, the pores with a pore diameter above 100 nm account for 15 - 20% of the total pore volume, and the pores with a pore diameter 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 。

[0012] Second, the present invention provides a method for preparing the high-temperature resistant and sulfur-resistant VOCs catalyst for RTO described in the first aspect, comprising the following steps:

[0013] (1) Mix pseudo-boehmite powder, pore-forming agent, and the first binder as solid raw materials with water, and obtain macroporous alumina through extrusion molding, drying, and calcination;

[0014] (2) Immerse the macroporous alumina in the first transition metal salt solution, dry, and calcine to obtain modified macroporous alumina;

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

[0016] (4) Vacuum coat the mixed solution on the surface of the cordierite ceramic carrier, and obtain the high-temperature resistant and sulfur-resistant catalyst after drying and calcination.

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

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

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

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

[0021] The pore former 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-liquid ratio of the macroporous alumina to the first transition metal salt solution is 1 g:(5 - 10) mL;

[0026] The temperature of the impregnation is 60 - 80 °C, and the time is 2 - 24 h;

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

[0028] The calcination is first at 450 - 650 °C, with a holding time of 1 - 3 h and a heating rate of 3 - 5 °C / min; then it is heated to 750 - 950 °C, with a holding time of 2 - 4 h and a 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] Or, 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] In the solid composition of the mixed solution, by mass percentage of each raw material, it includes 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 at least three water-soluble salts of lanthanum, manganese, cerium, cobalt, copper, and tin;

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

[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] More preferably, the molar ratio of cations in 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] Or, 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 heat preservation time is 1-3 h;

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

[0050] Thirdly, the present invention provides an application of the high-temperature resistant sulfur-resistant VOCs catalyst applicable to RTO described in the first aspect in the treatment of VOCs.

[0051] Fourthly, the present invention provides a method for treating VOCs, which is to install the high-temperature resistant sulfur-resistant VOCs catalyst applicable to RTO described in the first aspect in the heat storage chamber of RTO.

[0052] The beneficial effects of the present invention:

[0053] (1) The present invention reduces the set temperature of the RTO by installing a catalyst on the RTO regenerator, thereby reducing fuel consumption and the carbon emissions and fuel consumption caused by natural gas combustion.

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

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

[0056] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0057] Figure 1 It is the change of the p-xylene removal rate with time of the high-temperature and sulfur-resistant catalyst in Examples 1-10 of the present invention under Test Condition 1;

[0058] Figure 2 It is the change of the p-xylene removal rate with time of the high-temperature and sulfur-resistant catalyst in Example 5 and Comparative Examples 1-3 under Test Condition 2;

[0059] Figure 3 It is the surface XRD spectrum of the high-temperature and sulfur-resistant catalyst of Example 2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0060] Those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention. Specific conditions are not indicated in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. Components not indicated by the manufacturer are all conventional products available commercially.

[0061] The carrier used in the present invention is a cordierite honeycomb ceramic carrier, the number of openings per cross-section is 100 mesh - 600 mesh, and the structure of the cordierite honeycomb ceramic carrier is a cuboid, with a length, width, and height of 100 mm, 100 mm, and 50 mm respectively.

[0062] The cordierite ceramic honeycomb carrier has significant advantages in VOCs catalysts. It has a high specific surface area and low gas resistance, which is conducive to catalytic reactions; it has strong thermal stability and a small expansion coefficient, and can adapt to temperature changes; it has high mechanical strength and corrosion resistance, and can improve the dispersion and compatibility of active components, effectively improving the VOCs treatment efficiency and the catalyst life.

[0063] I. Preparation of High-Temperature and Sulfur-Resistant Catalyst for RTO

[0064] Example 1

[0065] A preparation method of a high-temperature and sulfur-resistant catalyst for RTO includes 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 into a stainless steel stirring kettle equipped with a powerful stirrer, stir at a speed of 350 - 650 rpm for 1 - 5 h to form a uniform paste; extrude the paste through an extruder to form cylindrical bars with a diameter of 2 - 4 mm, and then cut them into particles with a length of 3 - 5 mm using a granulator; place them in an oven, dry at 100 °C for 2 h, transfer to a muffle furnace, calcine at 600 °C for 2 h, and after cooling to room temperature, obtain macroporous alumina.

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

[0068] Step 3: Take 2000 g of lanthanum nitrate, manganese nitrate, stannous chloride (the molar ratio of their cations is 1:0.7:0.3), 2500 g of modified macroporous alumina and 100 g of aluminum sol, dissolve them in 3400 g of deionized water, stir well and then grind twice at 500 rpm / min using a grinder, add 4% of the total mass of the slurry of carboxymethyl cellulose, and continue to stir for 2 h.

[0069] Step 4: Coating the slurry obtained in Step 3 on a cordierite honeycomb ceramic carrier through a bottom-feed vacuum coating device. After coating, dry at 95 °C for 2 h and calcine at 1000 °C for 3 h to prepare a high-temperature and sulfur-resistant catalyst.

[0070] Example 2

[0071] A preparation method of a high-temperature and sulfur-resistant catalyst for RTO, which is different from Example 1 in that in Step 2, the impregnation solution is manganese acetate solution to obtain manganese-modified macroporous alumina, and the remaining steps are the same as those in Example 1.

[0072] Example 3

[0073] A method for preparing a high temperature resistant and sulfur resistant catalyst suitable for RTO, which differs 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, which differs 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, which differs from Example 1 in that, in step 3, 2000 grams 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 grams of modified macroporous alumina, and 100 grams of aluminum sol are dissolved in 3400 grams of deionized water, and after sufficient stirring, the mixture is ground twice at 500 rpm / min in a grinder, and 4% of the total mass of the slurry is added to the hydroxymethyl cellulose, and stirring is continued for 2 hours; the remaining steps are consistent with those of 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 preparation method of a high-temperature resistant and sulfur-resistant catalyst applicable to RTO, which is different from Example 5 in that in Step 3, among the transition metal salts (lanthanum nitrate, cerium nitrate, copper sulfate, tin acetate) added, the cation ratio is 0.7:0.8:0.2:0.3, and the remaining steps are the same as those in Example 5. 4wer

[0086] Example 10

[0087] A preparation method of a high-temperature resistant and sulfur-resistant catalyst applicable to RTO, which is different from Example 5 in that in Step 3, among the transition metal salts (lanthanum nitrate, cerium nitrate, copper sulfate, tin acetate) added, the cation ratio is 0.8:0.7:0.2:0.3, and the remaining steps are the same as those in Example 5.

[0088] Comparative Example 1

[0089] A preparation method of a high-temperature resistant and sulfur-resistant catalyst applicable to RTO, using 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 diameter: 18.84 nm (standard value, ±0.64)) to replace the manganese-modified macroporous alumina in Example 5, specifically including the following steps:

[0090] Step 1: Take 2000 g of lanthanum nitrate, cerium nitrate, copper sulfate, and tin acetate (the molar ratio of their cations is 0.7:0.8:0.3:0.2), 2500 g of alumina, and 100 g of aluminum sol, dissolve them in 3400 g of deionized water, stir well, grind twice with a grinder at 500 rpm / min, add 4% of the total mass of the slurry of hydroxymethyl cellulose, and continue to stir for 2 h.

[0091] Step 2: Coat the slurry obtained in Step 1 on a cordierite honeycomb ceramic carrier through a bottom-feed vacuum coating device. After coating, dry at 95°C for 2 h and calcine at 1000°C for 3 h to prepare a high-temperature resistant and sulfur-resistant catalyst.

[0092] Comparative Example 2

[0093] A preparation method of a high-temperature resistant and sulfur-resistant catalyst applicable to RTO, using macroporous alumina to replace the manganese-modified macroporous alumina in Example 5, specifically including 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, put it into an oven, dry at 100°C for 2 h, transfer it to a muffle furnace, calcine at 600°C for 2 h, and after cooling to room temperature, 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, dissolve them in 3400 grams of deionized water, stir them thoroughly, grind them twice at 500 rpm / min in a grinder, add 4% of the total mass of the slurry, 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 hours and calcined at 1000° C. for 3 hours 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 manganese 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, fully stir, filter and wash three times, spread the filter cake on a tray in a vacuum drying oven, and dry until the water is completely evaporated. After transferring to a muffle furnace, calcine at 550°C for 2h, 850°C for 3h, and cool to room temperature to obtain manganese-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, dissolve in 3400 grams of deionized water, stir thoroughly, grind twice at 500 rpm / min in a grinder, add 4% of the total mass of the slurry, and continue stirring for 2 hours.

[0101] Step 3: The slurry obtained in step 2 is coated on the cordierite honeycomb ceramic carrier by a bottom feeding vacuum coating device. After coating, it is dried at 95° C. for 2 hours and calcined at 1000° C. for 3 hours 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 in Example 1.

[0104] Comparative Example 5

[0105] 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 transition metal salt added is only manganese nitrate, and the remaining steps are consistent with Example 5.

[0106] Comparative Example 6

[0107] A preparation method of a high-temperature sulfur-resistant catalyst applicable to RTO, different from Example 5 in that in Step 3, two transition metal salts, lanthanum nitrate and copper nitrate, are added, and the cation ratio is 1:1, and the remaining steps are the same as those in Example 5.

[0108] II. Performance Verification

[0109] The high-temperature sulfur-resistant catalysts prepared in the examples and comparative examples were tested. The change in the xylene removal rate over time in a sulfur-containing atmosphere and the change in the xylene removal rate under high-temperature conditions at 1000°C for a long time were investigated.

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

[0111] Test Condition 2: Temperature 1000°C, xylene: 1000 ppm, water: 3%, volumetric space velocity: 30000 h -1 .

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

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

[0114]

[0115] It can be seen from Table 1 that the change in the Bet data of the modified macroporous alumina after aging at 1000°C for 30 h is small. This is because the proportion of mesopores in the modified macroporous alumina after aging is 65%, significantly higher than 45% of the unmodified one, and the anti-sintering ability 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 number of active sites after modification increases.

[0116] The set temperature of the existing RTO reactor is often set at 850°C. When the catalyst prepared by the present invention is installed, the set temperature of the RTO can be reduced to 700°C without affecting the VOC removal effect, thereby reducing fuel consumption and carbon emissions caused by natural gas combustion. After calculation, when the set temperature of an RTO reactor is reduced from 850°C to 700°C, the fuel consumption will be reduced by more than 30%, and the carbon emissions reduced due to fuel consumption are close to one-third. The specific calculation process is as follows:

[0117] 1. Comparison of theoretical heat requirements

[0118] The heat calculation formula required for RTO to maintain the combustion temperature:

[0119]

[0120] Parameter setting:

[0121] · Exhaust gas flow rate V = 10,000 Nm 3 / h (typical industrial scale)

[0122] · Exhaust gas density ρ = 1.293 kg / Nm 3 , specific heat capacity c = 1.005 kJ / (kg·K)

[0123] · Inlet temperature t i = 25°C, original operating condition thermal efficiency η 1 = 95%, thermal efficiency η after temperature reduction 2 = 97% (after temperature reduction optimization)

[0124] Calculation steps:

[0125] · Original operating condition (850°C):

[0126]

[0127] · New operating condition (700°C):

[0128]

[0129] 2. Additional optimization factors for actual fuel consumption reduction

[0130] · Thermal efficiency improvement: After the temperature reduction, the heat recovery efficiency of the ceramic regenerator increases from 95% to 97%, further reducing the fuel demand.

[0131] · Reduction of heat dissipation loss: For every 100°C reduction in the combustion chamber temperature, the surface heat dissipation loss is reduced by approximately 15%. After a 150°C temperature reduction, the heat dissipation loss is reduced by approximately 22.5%, corresponding to a further reduction in fuel consumption of approximately 5%.

[0132] · Enhancement of waste gas self-heating: When the concentration of organic matter in the waste gas is high (such as toluene), the heat released by its oxidation can replace part of the external fuel demand. For example, the calorific value of toluene combustion is 41,120 kJ / kg. If the inlet concentration is 1,000 mg / m 3 , approximately 411,200 kJ of heat can be released per hour, reducing the fuel demand by approximately 4.6%.

[0133] Comprehensive actual reduction ratio:

[0134] 21% (theoretical) + 5% (heat dissipation optimization) + 4.6% (self-heating optimization) ≈ 30.6%

[0135] Figure 1The variation of the p-xylene removal rate with time for the high-temperature sulfur-resistant catalyst in Examples 1-10 under Test Condition 1. From 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 the catalytic application of high-temperature sulfur-resistant VOCs. After macroporous alumina is impregnated with lanthanum nitrate solution, LaAlO is formed with alumina during the calcination process 3 , effectively inhibiting γ-Al 2 O 3 from transforming into α-Al with a low specific surface area above 800 °C 2 O 3 . Secondly, due to the weak metal-support interaction, the specific surface area of the manganese and cobalt-modified systems decays significantly; secondly, La 3+ forms strong basic sites (pH>9.5) on the alumina surface, preferentially combining with sulfur-containing pollutants (such as SO 2 ) to form thermodynamically stable La 2 (SO 4 ) 3 , avoiding the poisoning of active components by sulfur species; while sulfates of transition metals such as manganese and iron (such as MnSO 4 , FeSO 4 ) are easily decomposed at high temperatures, resulting in secondary release of sulfur and blockage of pores. In addition, the LaO x nanoclusters (particle size 3-5 nm) formed after lanthanum nitrate impregnation can serve as anchor points to promote the uniform dispersion of subsequent platinum, while the manganese and cobalt-modified supports have a low surface hydroxyl density, which easily leads to agglomeration of active metals and reduces the density of effective reaction sites.

[0136] The test results of Examples 5-10 show that when different components and different molar ratios of the second transition metal salts are added to the modified macroporous alumina, due to the interaction between multiple metals, different effects on the sulfur resistance and high-temperature resistance of the catalyst will be produced. The high content of lanthanum (0.7) improves the thermal stability of alumina and inhibits high-temperature phase transformation; the oxygen storage capacity of cerium (0.3) complements that of lanthanum, promoting the deep oxidation of VOCs through the Ce 3+ / Ce 4+ redox cycle at high temperatures; manganese dominates the active sites, and the high loading of manganese (0.8) significantly improves the catalytic activity. The multivalent state of MnO x (Mn 2+ / Mn 3+ / Mn 4+ ) maintains a high oxygen migration rate at high temperatures, promoting the activation and cleavage of C-H bonds in VOCs molecules. Compared with Example 6 (Mn = 0.8 but Ce = 0.2), the higher Ce content in Example 5 compensates for the activity decay of Mn after sulfur poisoning; a low Sn ratio (0.2) passes through SnO 2Strong interaction with the active component (SMSI effect), inhibiting the sintering of the active component, and avoiding the coverage of active sites caused by excessive Sn (e.g., Sn = 0.3 in Example 9), which affects the mass transfer efficiency.

[0137] Figure 2 This is for Example 5 and Comparative Examples 1 - 3 of the high-temperature and sulfur-resistant catalyst. Under the test conditions of 2, the change of p-xylene removal rate with time. From 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 relatively 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 fast diffusion channel for reactant and product molecules, enabling molecules to quickly enter and exit inside the carrier, reducing the diffusion resistance, and improving the efficiency of the catalytic reaction; the macroporous structure can also relieve the thermal stress generated during the temperature change process. When macroporous alumina is heated, due to the pores existing 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 extend into the pore space, thereby reducing the internal stress concentration caused by thermal expansion. The dispersion of this stress helps prevent the material from cracking or breaking due to excessive thermal stress, further enhancing the stability of macroporous alumina in a high-temperature environment. The macroporous alumina modified by transition metals has better performance. The addition of transition metals can effectively inhibit the phase transformation of alumina during the heating process, enabling alumina to maintain a relatively stable structure in a high-temperature environment, thereby maintaining a relatively high specific surface area and pore volume, and reducing the sintering and agglomeration phenomena at high temperatures.

[0138] In Comparative Example 4, the method in Example 1 of CN114950573B was used to prepare a macroporous alumina support to replace the lanthanum-modified macroporous alumina in Example 5. Its p-xylene removal rate is relatively low. Firstly, in terms of the crystal structure stability, the lanthanum-modified macroporous alumina forms LaAlO 3 , inhibiting the phase transformation of γ-Al 2 O 3 to α-Al 2 O 3 , and can maintain a stable structure and a large specific surface area to provide more active sites. However, the macroporous alumina in Comparative Example 4 has poor structural stability at high temperatures, its specific surface area is easily attenuated, and the number of active sites decreases; secondly, the dispersion degree of the active metal is different. The LaO x nanoclusters formed by impregnation with lanthanum nitrate in the original literature can promote the uniform dispersion of the active metal, increasing the number of effective reaction sites. The macroporous alumina in Comparative Example 4 lacks this mechanism, with a low dispersion degree of the active metal and few effective reaction sites, ultimately resulting in low activity for p-xylene.

[0139] In Comparative Example 5, only manganese nitrate, a transition metal salt, was added, lacking the synergistic effect of other metals and unable to fully utilize the advantages of each metal, resulting in insufficient sulfur resistance and high-temperature resistance of the catalyst, thereby affecting the removal rate of p-xylene. In Comparative Example 6, although two transition metal salts, lanthanum nitrate and copper nitrate, were added, compared with Example 5, the types of metals were fewer, and the cation ratio was 1:1, rather than the optimized ratio in Example 5. This combination and ratio were not conducive to the formation of an efficient catalytic active center and could not achieve the synergistic enhancement among multiple metals, making the catalyst performance lower than that of Example 5 and the p-xylene removal rate lower.

[0140] Figure 3 XRD spectrum of the surface of the high-temperature resistant and sulfur resistant catalyst in Example 2. Through Figure 3 It can be seen that lanthanum and manganese in the catalyst form a perovskite structure, and the lanthanum-manganese perovskite framework can still maintain the crystal structure above 800 °C, resisting high-temperature phase change through strong metal-oxygen bonds; the main role of tin is still sulfur resistance.

[0141] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high temperature resistant and sulfur resistant VOCs catalyst suitable for RTO, characterized in that: It includes a carrier and an active layer on the carrier, wherein the active layer includes modified macroporous alumina and metal oxide on its surface; 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; The metal in the metal oxide is selected from at least three of lanthanum, manganese, cerium, cobalt, copper and tin.

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: The pores with a pore diameter of 20-100 nm in the modified macroporous alumina account for 70-75% of the total 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 .

4. A method for preparing a high temperature resistant and sulfur resistant VOCs catalyst suitable for RTO according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) mixing pseudo-boehmite powder, a pore-forming agent and a first binder as solid raw materials with water, extruding, drying and calcining to obtain macroporous alumina; (2) adding macroporous alumina into a first transition metal salt solution, impregnating, drying, and calcining to obtain modified macroporous alumina; (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; (4) The mixed solution is vacuum coated on the surface of a cordierite ceramic carrier, and after drying and calcining, a high temperature resistant and sulfur resistant catalyst is obtained.

5. The method for preparing a high temperature resistant and sulfur resistant VOCs catalyst suitable for RTO according to claim 4, 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 insulation 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.

6. The method for preparing a high temperature resistant and sulfur resistant VOCs catalyst suitable for RTO according to claim 4, characterized in that: In step (2), the concentration of the first transition metal salt solution is 0.1-0.5 mol / L; The first transition metal salt is one or more of cobalt, manganese, lanthanum and iron salts; 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 2-24h; The drying temperature is 95-120°C and the drying time is 5-12h; The calcination is first carried out at 450-650°C, with a holding time of 1-3 hours and a heating rate of 3-5°C / min; then the temperature is raised to 750-950°C, with a holding time of 2-4 hours and a heating rate of 2-4°C / min.

7. The method for preparing a high temperature resistant and sulfur resistant VOCs catalyst suitable for RTO according to claim 4, characterized in that: In step (3), the solid content of the mixed solution is 40-45wt%; The solid composition of the mixed solution includes, 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 transition metal salt is at least three water-soluble salts of lanthanum, manganese, cerium, cobalt, copper and tin; The second binder is one of aluminum sol and silica sol; the concentration of the second binder is 10-40wt%; The modifier is one or more of hydroxymethyl cellulose, hydroxypropyl methyl cellulose, ethylene glycol, polyethylene glycol, polyvinyl alcohol, polyethylene oxide, and polyacrylamide; 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; Preferably, the molar ratio of cations in the three salts of lanthanum, manganese and tin is 1:0.7:0.3; 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); 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.

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

9. Use of the high temperature resistant and sulfur resistant VOCs catalyst suitable for RTO according to any one of claims 1 to 3 in VOCs treatment.

10. A method for treating VOCs, characterized in that: The high temperature resistant and sulfur resistant VOCs catalyst suitable for RTO as described in any one of claims 1 to 3 is installed in the RTO heat storage chamber.

Images