Preparation method of adsorption material for catalytic combustion of VOCs (Volatile Organic Compounds)

Abstract

The invention discloses a preparation method of an adsorption material for catalytic combustion of VOCs, and belongs to the technical field of environment-friendly catalytic materials. The method comprises the following steps: mixing silica sol, kaolin and an HZSM-5 molecular sieve according to a mass ratio of 1: (0.6-0.8): (0.4-0.5), and pulping to form slurry with the solid content of 25%-40%; adding polyethylene glycol (the molecular weight is 300-600) which accounts for 1-5% of the mass of the slurry, and uniformly dispersing; dripping into an oil phase at the temperature of more than or equal to 70 DEG C through a 0.5-1 mm dropper to form a 1-2 mm gel bead; pre-drying for 2-4 hours at the temperature of 80-120 DEG C, heating to 600-750 DEG C at the speed of 3-5 DEG C / min, and roasting for 2-5 hours; and the roasted pellets, sodium metaaluminate, a guiding agent and water are subjected to dynamic crystallization according to the mass ratio of 1: (0.1-0.3): (0.05-0.15): (5-10), and finally metal is loaded. The sphericity of the carrier is gt under the synergistic effect of oil column forming and polyethylene glycol; the compressive strength is not less than 40 N; the kaolin enhances the mechanical performance, and the HZSM-5 constructs hierarchical pore channels (the pore volume is 0.3-0.5 cm / g, and the specific surface area is gt and 300 m / g), so that the VOCs adsorption capacity is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental protection catalytic materials, and particularly to a preparation method for a catalytic combustion adsorption material for VOCs. Background Art

[0002] Volatile Organic Compounds (VOCs) refer to organic compounds with a saturated vapor pressure greater than 70 Pa at normal temperature and a boiling point between 50 - 260 °C under normal pressure, or all organic compounds with a vapor pressure ≥ 10 Pa at 20 °C and being volatile. Such substances can be classified into categories such as non-methane hydrocarbons, oxygen-containing organic compounds, halogenated hydrocarbons, nitrogen-containing organic compounds, and sulfur-containing organic compounds according to their chemical structures. VOCs are mainly generated in industrial processes such as petrochemical industry, coal chemical industry, organic synthesis, pharmaceuticals, printing, coating manufacturing, and solvent use. Their compositions are complex and variable, often containing multiple isomers and derivatives, and may contain flammable and explosive components (such as benzene series, low molecular weight olefins) as well as substances with peculiar smells or odors (such as thiols, amines).

[0003] In recent years, the governance of VOCs at home and abroad has become increasingly strict. As an important part of the Convention on Long-Range Transboundary Air Pollution, the Gothenburg Protocol has imposed legally binding restrictions on VOCs emissions. According to the latest revised terms of this protocol, EU countries are required to reduce the total VOCs emissions to 50% of the 2006 level by 2020. This strict goal has promoted the in-depth treatment of industrial emission sources in European countries, including the mandatory installation of Best Available Techniques (BAT) equipment, the implementation of Leak Detection and Repair (LDAR) procedures, and the promotion of clean production processes as alternatives. Non-compliant enterprises will face huge fines and production license restrictions, prompting the relevant industries to accelerate the upgrading of pollution control facilities. The supervision of VOCs emissions from industrial stationary sources in China has also been strengthened year by year.

[0004] Current treatment methods include direct combustion method, catalytic decomposition method, biodegradation method, plasma technology, adsorption concentration, etc. Among them, the direct combustion method is applicable to high-concentration waste gas (> 3000 ppm), and realizes efficient treatment (> 98%) by oxidizing VOCs into CO2 and H2O at a high temperature above 760 °C. However, its fuel consumption is huge, the operating cost is high, and it is prone to generate x secondary pollution. The catalytic combustion method can significantly reduce the reaction temperature to 300 - 400 °C under the action of a catalyst, and is applicable to the medium-concentration range (1000 - 300 ppm), with the advantages of low energy consumption and less x NO generation, but faces bottlenecks such as high costs of noble metal (Pt, Pd, etc.) catalysts, easy deactivation due to sulfur / halogen poisoning, and weak resistance to complex components.

[0005] CN108862311A reports a method for preparing a high-silicon ZSM-5 molecular sieve adsorbent material. Using alkylammonium compounds as template agents, a silicon source, an alkali source, and ZSM-5 seed crystals are mixed for preparation. Aluminum in the molecular sieve is introduced as a silicon source impurity. The molecular sieve requires subsequent treatment with acids such as hydrochloric acid and nitric acid, followed by ammonium exchange, to obtain the high-silicon HZSM-5 molecular sieve. However, this method suffers from long crystallization time, low yield, complex preparation process, and high cost. Summary of the Invention

[0006] The main objective of this invention is to provide a method for preparing volatile organic compounds (VOCs) catalytic combustion adsorption materials to solve the problems of poor sphericity, simple pore structure, and poor adsorption capacity of existing VOCs adsorption materials. This method optimizes the carrier molding and surface modification process to prepare spherical adsorption materials with good sphericity, strong adsorption capacity, and high stability.

[0007] To achieve the above objectives, the present invention provides a method for preparing adsorbent materials for VOCs catalytic combustion, comprising the following steps:

[0008] Step (1): Mix a certain amount of silica sol, kaolin, and HZSM-5 molecular sieve to form a slurry with a solid content of 25%–40%.

[0009] Step (2): Add a certain amount of polyethylene glycol to the slurry from step (1) and stir until homogeneous;

[0010] Step (3): The mixed solution is dripped into kerosene or diesel oil at ≥ 70 ℃ through a dispersing dropper, and formed into gel microspheres with excellent sphericity by the oil column.

[0011] Step (4): Transfer the gel microspheres to an oven tray for preliminary drying and calcination.

[0012] Step (5): Transfer the calcined microspheres to a pressure reactor, add water, sodium aluminate and a directing agent, stir at a speed of >50 r / min and complete the crystallization reaction. After washing and drying, the crystallization product is used to obtain adsorbent material microspheres.

[0013] Step (6) involves exchanging the adsorbent microspheres with noble metal / non-noble metal compounds to obtain the adsorbent material for VOCs catalytic combustion.

[0014] In the preparation method of the adsorbent material for VOCs catalytic combustion described in this invention, preferably, the mass ratio of a certain amount of silica sol, kaolin, and HZSM-5 molecular sieve in step (1) is 1:(0.6–0.8):(0.4–0.5).

[0015] In the preparation method of the adsorbent material for VOCs catalytic combustion described in this invention, preferably, the amount of polyethylene glycol added in step (2) is 1%-5% of the total mass of the slurry, and the molecular weight of polyethylene glycol is 300-600.

[0016] In the preparation method of the adsorbent material for VOCs catalytic combustion described in this invention, preferably, the pore size of the dispersing dropper in step (3) is 0.5-1 mm, and the particle size of the gel microspheres is 1-2 mm.

[0017] In the preparation method of the adsorbent material for VOCs catalytic combustion described in this invention, preferably, the initial drying temperature in step (4) is 80-120 °C and the time is 2-4 h.

[0018] The method for preparing adsorbent material for VOCs catalytic combustion according to the present invention preferably includes the following calcination conditions in step (4): heating to 600-750 ℃ ​​at a rate of 3-5 ℃ / min in a tube furnace and calcining at a constant temperature for 2-5 h.

[0019] The preparation method of the adsorbent material for VOCs catalytic combustion according to the present invention preferably involves the following material mass ratio in step (5): small spheres: sodium aluminate: directing agent: water = 1:(0.1–0.3):(0.05–0.15):(5–10), where m in the directing agent... Na2O : m Al2O3 : m SiO2 : m H2O = 16 : 1 : 15 : 320.

[0020] The preparation method of the adsorbent material for VOCs catalytic combustion according to the present invention preferably includes the following crystallization reaction conditions in step (5): crystallization at 120-180 °C for 12-36 h.

[0021] In the preparation method of VOCs catalytic combustion adsorption material of the present invention, preferably, the noble metal compound in step (6) is one or more of H2PtCl6 and PdCl2, with a content between 0.1% and 1% (based on the percentage of metal mass to adsorption material mass).

[0022] In the preparation method of VOCs catalytic combustion adsorption material of the present invention, preferably, the non-precious metal compound in step (6) is one or more of SnCl4, FeCl3, and (NH4)2MoO4, with a content between 2% and 20% (based on the percentage of metal mass to adsorption material mass).

[0023] Advantages of this invention:

[0024] (1) Through the synergistic effect of oil column molding and polyethylene glycol shaping, a carrier with high sphericity and high strength is obtained, with an average crushing strength of not less than 40 N;

[0025] (2) Combining the mechanical properties of kaolin with the pore structure regulation of ZSM-5 molecular sieve to enhance adsorption capacity;

[0026] (3) Crystallization modification optimizes the acidic sites on the surface, promotes the dispersion of active components, and significantly improves the low-temperature catalytic activity and stability of VOCs. Detailed Implementation

[0027] The following provides a detailed description of specific implementations of the present invention. It should be understood that the content described herein is illustrative and not restrictive of the invention.

[0028] The silica sol, HZSM-5, kaolin, and sodium aluminate used were all industrial grade and sourced from Qingdao Huicheng Environmental Protection Technology Group Co., Ltd.

[0029] Silica sol, mass concentration 40%.

[0030] HZSM-5 zeolite, loss on ignition 8.4% by weight, silica-alumina ratio 38.

[0031] Kaolin, loss on ignition 27.1% by weight.

[0032] Sodium aluminate, containing 169.8 g / L of aluminum oxide and a specific gravity of 1.366.

[0033] Polyethylene glycol, purchased from Sinopharm Group, analytical grade.

[0034] Example 1

[0035] (1) Weigh 151.0 g of silica sol, 145.4 g of kaolin, and 74.2 g of HZSM-5 molecular sieve, add 629.4 g of deionized water, and stir at 500 r / min for 1 h to form a homogeneous slurry with a solid content of 32.5% (total mass 1000.0 g).

[0036] (2) Add 30.0 g of polyethylene glycol 400 (PEG-400) (3% of the slurry mass) to the slurry and continue stirring for 30 minutes until completely dissolved.

[0037] (3) Transfer the mixed slurry to a dispersion device and drip it into kerosene at 75℃ at a rate of 5 mL / min through a dropper with a 0.8 mm orifice. The oil column height is 50 cm, forming gel spheres with a particle size of 1.5 ± 0.2 mm. After removal, wash three times with petroleum ether.

[0038] (4) The gel microspheres were laid flat on a tray and dried in an oven at 105℃ for 3 h. After taking them out, the dried microspheres were transferred to a tube furnace and heated to 680℃ at 4℃ / min. They were then calcined at a constant temperature for 4 h and allowed to cool naturally to room temperature.

[0039] (5) Take 100.0 g of calcined small balls, 20.0 g of sodium aluminate, 10.0 g of directing agent and 750.0 g of deionized water and add them to the high pressure reactor. Stir at 60 r / min and heat to 150℃ for 24 h to crystallize.

[0040] (6) After washing and drying the crystallized product, PdCl2 0.84 g (containing Pd 0.5 g) was dissolved in 50 mL of deionized water, 100.0 g of modified microspheres were added, and the mixture was stirred and exchanged at 80 °C for 4 h. After filtration, the product was washed with water 3 times.

[0041] Example 2

[0042] (1) Weigh 140.0 g of silica sol, 153.6 g of kaolin, and 61.1 g of HZSM-5 molecular sieve, add 653.2 g of deionized water, and stir at 600 r / min for 1.5 h to form a slurry with a solid content of 30.8% (total mass 1000.0 g).

[0043] (2) Add 20.0 g of polyethylene glycol 600 (PEG-600) (2% of the slurry mass) to the slurry and stir for 40 minutes;

[0044] (3) The gel beads with a particle size of 1.8 ± 0.2 mm were dropped into diesel oil at a rate of 8 mL / min using a 1.0 mm dropper and washed twice with petroleum ether.

[0045] (4) The gel microspheres were laid flat on a tray and dried in an oven at 105 ℃ for 3 h. After taking them out, the dried microspheres were transferred to a tube furnace and heated to 750 ℃ ​​at 5 ℃ / min. They were then calcined at a constant temperature for 3 h and allowed to cool naturally to room temperature.

[0046] (5) Take 100.0 g of calcined small balls, 30.0 g of sodium aluminate, 15.0 g of directing agent and 1000.0 g of water, add them to the high-pressure reactor, stir at 60 r / min and crystallize at 180 ℃ for 18 h;

[0047] (6) After washing and drying the crystallized product, 38.2 g of (NH4)2MoO4 (containing 20.0 g of Mo) was dissolved in 50 mL of ethanol solution, 100.0 g of modified microspheres were added, and the mixture was stirred and exchanged at 80 °C for 4 h. After filtration, the mixture was washed with water 3 times.

[0048] Example 3

[0049] (1) Weigh 160 g of silica sol, 131.38 g of kaolin, and 78.3 g of HZSM-5 molecular sieve, add 630.2 g of deionized water, and stir at 600 r / min for 1.5 h to form a slurry with a solid content of 32.8% (total mass 1000.0 g).

[0050] (2) Add 50.0 g of polyethylene glycol 300 (PEG-300) (5% of the slurry mass) to the slurry and stir for 40 minutes;

[0051] (3) The gel beads with a particle size of 1.2 ± 0.1 mm were dropped into diesel oil at a rate of 8 mL / min using a 0.5 mm dropper and washed twice with petroleum ether.

[0052] (4) The gel microspheres were laid flat on a tray and dried in an oven at 80 ℃ for 4 h. After taking them out, the dried microspheres were transferred to a tube furnace and heated to 600 ℃ at 3 ℃ / min. They were then calcined at a constant temperature for 5 h and allowed to cool naturally to room temperature.

[0053] (5) Take 100.0 g of calcined small balls, 10.0 g of sodium aluminate, 5.0 g of directing agent and 500.0 g of water, add them to the high-pressure reactor, stir at 60 r / min and crystallize at 120 ℃ for 36 h;

[0054] (6) After washing and drying the crystallized product, 38.2 g of H2PtCl6 (containing 3% Pt) was dissolved in 50 mL of ethanol solution, 100.0 g of modified microspheres were added, and the mixture was stirred and exchanged at 80 °C for 4 h. After filtration, the product was washed with water 3 times.

[0055] Example 4

[0056] (1) Weigh 155.0 g of silica sol, 148.1 g of kaolin, and 67.5 g of HZSM-5 molecular sieve, and add 629.4 g of deionized water. Stir mechanically at 450 r / min for 1.5 h to form a homogeneous slurry with a solid content of 32.5% (total mass 1000.0 g).

[0057] (2) Add 10.0 g of polyethylene glycol 400 (PEG-400, analytical grade) (1% of the total mass of the slurry) to the slurry and continue stirring for 40 minutes until the solution is clear and free of particles.

[0058] (3) The gel beads with a particle size of 1.9 ± 0.3 mm were dropped into diesel oil at a rate of 6 mL / min using a 0.9 mm dropper and washed twice with petroleum ether.

[0059] (4) The gel microspheres were evenly spread on an alumina tray and treated in a 95 ℃ forced-air drying oven for 2.5 h; the dried microspheres were placed in a tube furnace and heated to 650 ℃ at 3.8 ℃ / min and calcined at a constant temperature for 4.5 h.

[0060] (5) Take 100.0 g of calcined small balls, 15.0 g of sodium aluminate, 8.0 g of directing agent and 600.0 g of deionized water and add them to a 50 mL high-pressure reactor. Stir at 70 r / min and heat to 130 ℃ for crystallization for 28 h.

[0061] (6) After washing and drying the crystallized product, PdCl2 0.168 g (containing Pd 0.1 g) was dissolved in 50 mL of aqueous solution, 100.0 g of modified microspheres were added, and the mixture was stirred and exchanged at 80 °C for 4 h. After filtration, the product was washed with water 3 times.

[0062] Saturated adsorption capacity test: 2.0 g of adsorbent material with a particle size of 1.0 – 2.0 mm was packed into a quartz fixed-bed reactor with an inner diameter of 10 mm and pretreated for 2 h under dry nitrogen (100 mL / min, 25 ℃). A mixed gas containing 1500 ppm toluene, 20% oxygen, and balancing nitrogen (relative humidity 50% ± 3%) was introduced, with a space velocity controlled at 10,000 h⁻¹ and a temperature of 30 ℃ ± 1 ℃. The outlet gas concentration was monitored using an online PID detector, and data was recorded every 5 min until the ratio of outlet concentration to inlet concentration was ≥0.95 (saturation breakthrough point). The saturated adsorption capacity was calculated using an integral breakthrough curve.

[0063] The final product was subjected to nitrogen adsorption-desorption (BET method), crushing strength, and performance tests. The test results are shown in Table 1 below.

[0064] serial number Specific surface area / m² / g Total pore volume / cm³ / g Compressive strength / N Saturated adsorption capacity (mg / g) Example 1 412 0.38 40 720.8 Example 2 378 0.42 35 658.6 Example 3 453 0.35 40 758.1 Example 4 487 0.41 38 876.2

[0065] Under simulated industrial conditions (1500 ppm toluene, 50% RH, space velocity 10000 h⁻¹, 30°C), the material in Example 4 exhibited the best adsorption performance: its breakthrough time reached 180 minutes, and its saturated adsorption capacity was 876.2 mg / g, significantly higher than other examples (Example 1: 720.8 mg / g; Example 3: 758.1 mg / g; Example 2: 658.6 mg / g). This is mainly attributed to the synergistic effect of its high specific surface area (487 m² / g) and reasonable pore volume (0.41 cm³ / g), which effectively mitigated the influence of water vapor competitive adsorption. After three cycles of 250°C hot nitrogen desorption, the adsorption capacity retention rate of Example 4 was >95%, confirming its excellent regeneration stability and suitability for continuous VOCs treatment processes.

Claims

1. A method for preparing adsorbent materials for VOCs catalytic combustion, characterized in that, Includes the following steps: (1) Mix a certain amount of silica sol, kaolin, and HZSM-5 molecular sieve to form a slurry with a solid content of 25%-40%; (2) Add a certain amount of polyethylene glycol to the slurry from step (1) and stir until homogeneous; (3) The mixed solution is dropped into kerosene or diesel at ≥ 70 ℃ through a dispersing dropper, and the mixture is formed into gel microspheres with excellent sphericity by the oil column. (4) Transfer the gel microspheres to an oven tray for preliminary drying and calcination; (5) After calcination, the microspheres are transferred to a pressure reactor, water, sodium aluminate and a directing agent are added, and the mixture is stirred at a speed of >50 r / min to complete the crystallization reaction. After washing and drying, the crystallization product is used to obtain adsorbent material microspheres. (6) Exchange the adsorbent material microspheres with noble metal / non-noble metal compounds to obtain adsorbent material for VOCs catalytic combustion.

2. The method according to claim 1, characterized in that: The mass ratio of a certain amount of silica sol, kaolin, and HZSM-5 molecular sieve mentioned in step (1) is 1 : (0.6 – 0.8) : (0.4 – 0.5).

3. The method according to claim 1, characterized in that: In step (2), the amount of polyethylene glycol added is 1% – 5% of the total mass of the slurry, and the molecular weight of polyethylene glycol is 300-600.

4. The method according to claim 1, characterized in that: In step (3), the pore size of the dispersing dropper is 0.5-1 mm, and the particle size of the gel microspheres is 1-2 mm.

5. The method according to claim 1, characterized in that: The initial drying temperature in step (4) is 80 – 120 ℃, and the time is 2 – 4 h.

6. The method according to claim 1, characterized in that: The calcination conditions in step (4) are as follows: in a tube furnace, the temperature is increased to 600-750 ℃ ​​at a rate of 3-5 ℃ / min, and calcined at a constant temperature for 2-5 h.

7. The method according to claim 1, characterized in that: In step (5), the mass ratio of the modified materials is: small balls: sodium aluminate: directing agent: water = 1 : (0.1 – 0.3) : (0.05 – 0.15) : (5 – 10), where m in the directing agent... Na2O : m Al2O3 : m SiO2 : m H2O = 16 : 1 : 15 :

320.

8. The method according to claim 1, characterized in that: The crystallization reaction conditions for step (5) are: crystallization at 120 – 180 ℃ for 12 – 36 h.

9. The method according to claim 1, characterized in that: The noble metal compound in step (6) is one or more of H2PtCl6 and PdCl2, with a content between 0.1% and 1% (based on the percentage of metal mass to adsorbent mass).

10. The method according to claim 1, characterized in that: The non-precious metal compound in step (6) is one or more of SnCl4, FeCl3, and (NH4)2MoO4, with a content between 2% and 20% (based on the percentage of metal mass to adsorbent mass).