Preparation method and application of zeolite molecular sieve for industrial coating exhaust gas

Abstract

The application belongs to the technical field of atmospheric pollution treatment and adsorption materials, and provides a preparation method and application of a zeolite molecular sieve for industrial coating waste gas. The preparation method of the zeolite molecular sieve for industrial coating waste gas comprises the following steps: mixing a silicon source, an aluminum source, an alkali source and water to form a synthesis gel; subjecting the synthesis gel to a first-stage hydrothermal crystallization reaction at a first temperature of 80 DEG C to 120 DEG C, and then subjecting the synthesis gel to a second-stage hydrothermal crystallization reaction at a second temperature of 120 DEG C to 180 DEG C to form an intermediate product; the second temperature is greater than the first temperature, and the temperature difference between the second temperature and the first temperature is greater than or equal to 40 DEG C; and calcining the intermediate product at a temperature of 500 DEG C to 600 DEG C to form the zeolite molecular sieve for industrial coating waste gas. The preparation method realizes in-situ synergistic generation of micropores and mesopores of the zeolite molecular sieve for industrial coating waste gas in the same hydrothermal system, and directionally synthesizes the zeolite molecular sieve suitable for VOCs adsorption of industrial coating waste gas.

Description

Technical Field

[0001] This application belongs to the field of atmospheric pollution control and adsorption materials technology, and in particular relates to a method for preparing zeolite molecular sieves for industrial coating waste gas and their application. Background Technology

[0002] Volatile organic compounds (VOCs) are among the main air pollutants generated during industrial coating, painting, and surface treatment processes. They are complex in composition, fluctuate greatly in emission conditions, and are often accompanied by high humidity, significantly impacting regional air quality and human health. Currently, VOCs treatment technologies mainly include adsorption, condensation, membrane separation, and catalytic oxidation. Among these, adsorption is widely used in industrial coating waste gas treatment due to its relatively mature technology, low energy consumption, and wide applicable concentration range.

[0003] In adsorption methods, molecular sieves are considered an important development direction for VOCs adsorbents due to their regular pore structure, good thermal stability, and renewability. Existing research and engineering practice show that by controlling the silica-alumina ratio, pore structure, or surface properties of molecular sieves, their adsorption performance for specific VOCs can be improved to a certain extent. Therefore, the compositional design and preparation process optimization of molecular sieves have become important research directions for VOCs treatment.

[0004] However, industrial coating exhaust gases are typically characterized by high humidity, a wide variety of VOCs, and a large range of concentration variations. Existing molecular sieves still face many challenges in practical applications. On the one hand, some molecular sieves rely primarily on a single microporous structure, which limits their adaptability to VOCs with large differences in molecular size, leading to problems such as decreased adsorption capacity and limited mass transfer under complex operating conditions. On the other hand, methods used to improve adsorption performance, such as metal ion impregnation, surface organic modification, and the introduction of pore-forming agents, often result in complex preparation processes, increased costs, and insufficient structural stability and repeatability during scale-up preparation and long-term operation.

[0005] Furthermore, the research and optimization of existing molecular sieve materials often rely on extensive experimental screening. Different raw material ratios, hydrothermal conditions, and post-processing methods require repeated experimental verification, resulting in a long research and development cycle and making it difficult to balance the controllability of material structure with industrial feasibility. Although some studies have attempted to design and screen molecular sieve structures using methods such as molecular simulation, these methods are mostly used in the material selection stage and cannot directly address the problem of insufficient controllability of pore structure evolution and crystallization processes during the large-scale preparation of molecular sieves.

[0006] Therefore, there is still a lack of a synthetic route that is relatively simple, has a controllable crystallization process, requires no complex post-modification treatment, and can form stable micropores. Molecular sieves with mesoporous composite pore structures and their preparation methods are proposed to better meet the adsorption application requirements of VOCs in industrial coating waste gas under high humidity and complex working conditions. Summary of the Invention

[0007] In view of this, embodiments of this application provide a method for preparing zeolite molecular sieves for industrial coating waste gas and their application. The method for preparing zeolite molecular sieves for industrial coating waste gas has a simple synthesis path, a controllable crystallization process, requires no additional treatment, and can form a stable pore structure. In addition, it can effectively adsorb volatile organic compounds in industrial coating waste gas under high humidity and complex working conditions.

[0008] The first aspect of this application provides a method for preparing zeolite molecular sieves for industrial coating waste gas, comprising the following steps: A synthetic gel is formed by mixing silicon source, aluminum source, alkali source and water; The synthesized gel is first subjected to a first stage of hydrothermal crystallization reaction at a first temperature of 80℃-120℃, and then subjected to a second stage of hydrothermal crystallization reaction at a second temperature of 120℃-180℃ to form an intermediate product; wherein, the second temperature is greater than the first temperature, and the temperature difference between the second temperature and the first temperature is greater than or equal to 40℃. The intermediate product is calcined at a temperature of 500℃-600℃ to form the zeolite molecular sieve for industrial coating waste gas.

[0009] In some embodiments, in the synthetic gel, the molar ratio of the silicon source, the aluminum source, the alkali source, and the water is 1:(0.008-0.05):(0.1-0.5):(10-50).

[0010] In some embodiments, mixing the silicon source, aluminum source, alkali source, and water to form a synthetic gel includes: The silicon source, the aluminum source, the alkali source and the water are mixed, the pH is adjusted to 9-13, and the initial molar ratio of silicon source to aluminum source is set to 20-120 to form the synthetic gel.

[0011] In some embodiments, mixing the silicon source, aluminum source, alkali source, and water to form a synthetic gel includes: The silicon source, the aluminum source, the alkali source and the water are mixed, the pH is adjusted to 9-13, the initial molar ratio of silicon source to aluminum source is set to 20-120, and the target zeolite seed crystals are added to form the synthetic gel. The target zeolite seed crystals account for 0.1%-5% of the dry mass of the synthesized gel.

[0012] In some embodiments, the process of first subjecting the synthesized gel to a first-stage hydrothermal crystallization reaction at a first temperature of 80°C-120°C, and then subjecting it to a second-stage hydrothermal crystallization reaction at a second temperature of 120°C-180°C to form an intermediate product includes: The synthesized gel was placed in a sealed hydrothermal reaction vessel and subjected to hydrothermal crystallization treatment in two stages. The first stage of hydrothermal crystallization treatment was carried out at a first temperature of 80℃-120℃ for 6h-24h, and the second stage of hydrothermal crystallization treatment was carried out at a second temperature of 120℃-180℃ for 12h-48h, forming the intermediate product.

[0013] In some embodiments, calcining the intermediate product at a temperature of 500°C-600°C to form the zeolite molecular sieve for industrial coating waste gas includes: The intermediate product is filtered and washed until the pH of the filtrate is 7-8. Then it is dried at 80℃-120℃ for 6h-12h, and then heated to 500℃-600℃ at a heating rate of 1℃ / min-5℃ / min. Finally, it is calcined at 500℃-600℃ for 3h-8h to form the zeolite molecular sieve for industrial coating waste gas.

[0014] In some embodiments, prior to mixing the silicon source, aluminum source, alkali source, and water to form a synthetic gel, the method for preparing the zeolite molecular sieve for industrial coating waste gas further includes: Provides clay minerals and alkali sources; The clay mineral and the alkali source are mixed at a mass ratio of 0.5-2:1 and calcined at 300℃-900℃ for 1h-10h. After calcination, the product is cooled to room temperature and dissolved in water, with the solid-liquid ratio controlled at 1g: (5-20)mL. The mixture is then stirred and dissolved for 0.5h-4h. After solid-liquid separation, the resulting solution is used as the silicon source and / or the aluminum source.

[0015] In some embodiments, prior to providing the clay minerals and alkali source, the method for preparing the zeolite molecular sieve for industrial coating waste gas further includes: pretreating the clay minerals with at least one of the following: (1). Acid washing pretreatment: The clay minerals are soaked in an inorganic acid solution with a molar concentration of 1mol / L-8mol / L for 1h-8h; (2). Alkali washing pretreatment: The clay minerals are soaked in an alkaline solution with a molar concentration of 1mol / L-8mol / L for 1h-8h; (3) Heat pretreatment: The clay minerals are roasted at 300℃-700℃ for 1h-8h.

[0016] A second aspect of this application provides a zeolite molecular sieve for industrial coating exhaust gas prepared according to the above-described method for preparing zeolite molecular sieves for industrial coating exhaust gas. The zeolite molecular sieve for industrial coating exhaust gas has a micropore-mesopore composite pore structure, which includes micropores and mesopores, and at least one of the micropores is in communication with at least one of the mesopores. The pore size of the micropores is less than 2 nm, and the pore size of the mesopores is 2 nm-10 nm. And / or, the total pore volume of the zeolite molecular sieve used for industrial coating waste gas is 0.2 cm³. 3 / g-0.6cm 3 / g; And / or, the specific surface area of ​​the zeolite molecular sieve for industrial coating waste gas is 300 m². 2 / g-800m 2 / g.

[0017] In some embodiments, the industrial coating waste gas is made into any one of molecular sieve paper, adsorption rotor, or honeycomb adsorbent using zeolite molecular sieves.

[0018] Compared with the prior art, this application has the following technical effects: This application provides a method for preparing zeolite molecular sieves for industrial coating waste gas and their application. By controlling the crystallization path and structural evolution during the synthesis process, a stable crystal structure with a reasonable pore distribution can be formed, improving its adaptability under industrial coating waste gas conditions. At the same time, the preparation method is simple, controllable, and reproducible, and is applicable under high humidity and complex conditions. It has industrial scale-up feasibility, reduces the cost and engineering difficulty caused by existing methods that rely on a large number of experimental screenings and complex modification steps, improves the practicality of zeolite molecular sieves for industrial coating waste gas in the adsorption and treatment of volatile organic compounds, and is conducive to large-scale industrial production and application. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments or related technologies of this application will be briefly introduced below. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0020] Figure 1 This is a process flow diagram of the preparation process of the first type of zeolite molecular sieve for industrial coating waste gas provided in the embodiments of this application; Figure 2 This is a process flow diagram of the preparation process of the second type of zeolite molecular sieve for industrial coating waste gas provided in the embodiments of this application; Figure 3This is a process flow diagram of the preparation process of the third type of zeolite molecular sieve for industrial coating waste gas provided in the embodiments of this application; Figure 4 This is a process flow diagram of the preparation process of the fourth type of zeolite molecular sieve for industrial coating waste gas provided in the embodiments of this application; Figure 5 This is a process flow diagram of the fifth type of zeolite molecular sieve for industrial coating waste gas provided in the embodiments of this application; Figure 6 This is a process flow diagram of the sixth type of zeolite molecular sieve for industrial coating waste gas provided in the embodiments of this application; Figure 7 This is a process flow diagram of the preparation process of the seventh type of zeolite molecular sieve for industrial coating waste gas provided in the embodiments of this application. Detailed Implementation

[0021] To enable those skilled in the art to better understand the solutions of this application, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0022] The term "comprising" and any variations thereof in the specification, claims, and accompanying drawings are intended to cover a non-exclusive inclusion. For example, a process, method, system, product, or apparatus that comprises a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such processes, methods, products, or apparatus.

[0023] Furthermore, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order.

[0024] The term "at least one" means "one or more"; the term "multiple" means "two or more".

[0025] Industrial coating refers to the spraying / baking / coating process in industrial production. It involves applying paint to the surface of a workpiece to form a protective or decorative layer, achieving aesthetic enhancement. Specifically, in factories, mechanized, automated, and large-scale methods are used to spray, electrophoretically coat, or dip-coat the surfaces of products such as metal, plastic, and wood to form a protective film or decorative layer. This is a commonly used surface treatment process in industries such as machinery manufacturing, furniture production, automobile manufacturing, and hardware processing. Throughout the production process, raw and auxiliary materials such as paints, varnishes, thinners, cleaning agents, and curing agents are the core production materials. These chemical materials generally contain a large amount of volatile organic compounds (VOCs) that are easily volatilized at room temperature. VOCs typically continue to evaporate and dissipate throughout the entire process, including spraying, brushing, curtain coating, drying and curing, as well as paint mixing, gun washing, and material storage and transportation in the workshop.

[0026] In actual production, as coating operations continue, large amounts of VOCs are constantly released into the air, and then discharged through fugitive emissions and waste gas collection systems, becoming the most significant air pollutant in industrial coating. Moreover, VOCs have a complex composition, and their emission concentration fluctuates significantly with airflow conditions, influenced by coating processes, paint types, and workload. Furthermore, operations such as washing and humidifying paint in coating workshops lead to high humidity in the exhaust gas, directly polluting the factory area and surrounding air. Long-term exposure can also harm the respiratory system and health of workers, and is a major contributing factor to regional ozone and smog pollution.

[0027] Currently, VOCs treatment technologies mainly include adsorption, condensation, membrane separation, and catalytic oxidation. Among these, adsorption has been widely used in the treatment of waste gas from industrial coating processes due to its relatively mature technology, low energy consumption, and wide applicable concentration range. In adsorption, the performance of the adsorbent is a key factor determining the treatment effect. Molecular sieves, with their regular and ordered pore structure, excellent thermal stability, and good regeneration and recycling capabilities, have become highly promising and efficient adsorbents for treating VOCs waste gas from coating processes.

[0028] However, the exhaust gas generated by industrial coating is usually high in humidity, and the VOCs are diverse, complex in composition, and vary greatly in concentration. This leads to numerous problems for existing molecular sieves in practical applications. For example, some molecular sieves mainly rely on a single pore structure, which has limited adsorption effect on VOCs with large differences in molecular size, resulting in problems such as decreased adsorption capacity and limited mass transfer under complex working conditions. Alternatively, to improve the adsorption performance of molecular sieves, pore-forming agents such as mesoporous silica (SiO2) / organic substances (e.g., glucose) / surfactants, hard templates, and soft templates are introduced, or post-treatment modifications such as metal ion impregnation, ion exchange, and surface silanization are used, which leads to complex preparation processes and increased costs. Furthermore, molecular sieves often suffer from insufficient structural stability, limited adaptability to complex operating conditions, and poor reproducibility during large-scale preparation and long-term operation. Alternatively, the development and optimization of existing molecular sieves often rely on extensive experimental screening. Different raw material ratios, hydrothermal conditions, and post-treatment methods require repeated experimental verification, resulting in long development cycles and difficulty in balancing material structure controllability and industrial feasibility. Although some studies have attempted to design and screen molecular sieve structures through molecular simulation and other means, most existing methods are still in the material screening stage and cannot directly improve the problems of insufficient pore structure and crystallization controllability in the large-scale preparation process of molecular sieves. This makes it difficult to simultaneously consider adsorption, regeneration, and engineering application feasibility.

[0029] In summary, there is still a lack of molecular sieves and their preparation methods that have relatively simple synthesis routes, controllable crystallization processes, do not require complex post-modification treatments, and can form stable pore structures, so as to make them well applicable to the adsorption application of VOCs in industrial coating waste gas under high humidity and complex working conditions.

[0030] Based on the above, in a first aspect, embodiments of this application provide a method for preparing zeolite molecular sieves for industrial coating waste gas. For example... Figure 1 As shown in the embodiments of this application, the preparation method of zeolite molecular sieve for industrial coating waste gas may include the following steps: S1. Mix the silicon source, aluminum source, alkali source and water, stir evenly to form a synthetic gel.

[0031] S2. The synthesized gel is placed under hydrothermal reaction conditions. First, a first stage of hydrothermal crystallization reaction is carried out at a first temperature of 80℃-120℃ for a period of time, and then a second stage of hydrothermal crystallization reaction is carried out at a second temperature of 120℃-180℃ for a period of time to form an intermediate product.

[0032] The second temperature is greater than the first temperature, and the temperature difference between the second temperature and the first temperature is greater than or equal to 40℃.

[0033] S3. Dry the intermediate product and calcine it at 500℃-600℃ for a period of time to form zeolite molecular sieve for industrial coating waste gas.

[0034] The method for preparing zeolite molecular sieves for industrial coating exhaust gas provided in this application starts from the crystallization process regulation and pore structure synergistic evolution mechanism, and moves the structural design to the synthesis stage. Specifically, it involves raw material pretreatment, preparation of alkali-activated silicon-aluminum source, construction of synthetic gel, staged hydrothermal crystallization, regulation of framework silicon-aluminum structure and post-treatment, forming an overall directional synthesis route. This enables the in-situ synergistic generation of microporous structure and secondary mesoporous structure of zeolite molecular sieves for industrial coating exhaust gas in the same hydrothermal system, thereby directionally synthesizing zeolite molecular sieves suitable for VOCs adsorption in industrial coating exhaust gas.

[0035] Therefore, compared with related technologies that typically introduce pore-forming agents such as mesoporous SiO2 / organic (e.g., glucose) / surfactants, hard templates, and soft templates into molecular sieves with hierarchical pores, or employ post-treatment modifications such as metal ion impregnation, ion exchange, and surface silanization, this method can achieve in-situ construction of hierarchical pore structures without introducing pore-forming agents such as mesoporous SiO2 / organic / surfactants, hard templates, and soft templates during the preparation process. Instead, it uses two-stage hydrothermal crystallization to regulate crystal nucleation and crystal growth kinetics. Simultaneously, it allows for the control of the silicon-aluminum ratio and aluminum distribution in the framework without post-treatment modifications such as metal ion impregnation, ion exchange, or surface silanization, thereby obtaining the intrinsic moisture resistance of the material. Furthermore, by designing the synthesis parameters specifically based on the molecular size, polarity, and boiling point distribution characteristics of VOCs in industrial coating exhaust gases, the matching optimization between the pore structure of the zeolite molecular sieve for industrial coating exhaust gases and the target pollutant molecules can be achieved. In addition, this preparation method is simple and easy to implement, which is beneficial for large-scale industrial production and application.

[0036] The steps in the embodiments of this application are described in detail below.

[0037] [Step S1] like Figure 2 As shown, step S1 above, mixing the silicon source, aluminum source, alkali source, and water, and stirring until homogeneous to form a synthetic gel, may include: S11. Mix silicon source, aluminum source, alkali source and water, adjust the pH of the system to 9-13, and set the initial molar ratio of silicon source to aluminum source to 20-120, and form a uniform synthetic gel under stirring conditions.

[0038] In applications, silicon sources can include artificial silicon sources, natural silicon mineral raw materials, etc. Aluminum sources can include artificial aluminum sources, natural aluminum mineral raw materials, etc.

[0039] For example, the pH value of the system can be 9, 10, 11, 12, or 13, etc. This can effectively promote the dissolution of silicon and aluminum sources (hereinafter referred to as silicon-aluminum sources) in water, accelerate the condensation reaction of functional groups in silicon-aluminum sources, and facilitate the uniform formation of synthesized gels; at the same time, it can induce the formation of crystal nuclei and crystal growth of zeolite molecular sieves for industrial coating waste gas, improve crystallinity, and thus significantly reduce the formation of amorphous impurities.

[0040] For example, the initial molar ratio of silicon source to aluminum source can be 20, 40, 60, 80, 100, or 120, etc. Among them, when the initial molar ratio of silicon source to aluminum source is 60-120, the resulting zeolite molecular sieve for industrial coating exhaust gas has high hydrophobicity and moisture resistance; while when the initial molar ratio of silicon source to aluminum source is 20-60, the resulting zeolite molecular sieve for industrial coating exhaust gas has more acidic sites. Thus, even without pore-forming agents such as mesoporous SiO2 / organic / surfactants, hard templates, soft templates, or post-treatment modifications such as metal ion impregnation, ion exchange, or surface silanization modification, the zeolite molecular sieve for industrial coating exhaust gas can still exhibit preferential adsorption characteristics for VOCs under high humidity conditions. It should be noted that if the Si source is not pure SiO2, but contains other substances such as silica sol, or if the Al source is not pure Al2O3, but contains other substances such as sodium aluminate, the direct use of the raw material molar ratio may result in deviation. Therefore, the embodiments of this application set the initial molar ratio of the silicon source to the aluminum source. This initial molar ratio of the silicon source to the aluminum source means that when feeding materials, all Si is calculated as SiO2 and all Al is calculated as Al2O3, and the molar ratio (SiO2 / Al2O3) is 20-120.

[0041] Based on the above, in the synthesized gel, the molar ratio of silicon source, aluminum source, alkali source, and water is 1:(0.008-0.05):(0.1-0.5):(10-50). For example, the molar ratio of silicon source, aluminum source, alkali source, and water can be 1:0.008:0.1:10, 1:0.01:0.2:15, 1:0.02:0.3:20, 1:0.03:0.4:30, 1:0.04:0.4:40, or 1:0.05:0.5:50, etc. This allows the zeolite molecular sieve for industrial coating exhaust gas to exhibit preferential and excellent adsorption of VOCs under high humidity conditions, without the need for the introduction of pore-forming agents such as mesoporous SiO2 / organic / surfactants, hard templates, soft templates, or post-treatment modification methods such as metal ion impregnation, ion exchange, or surface silanization modification as in related technologies. It should be noted that the molar ratio of silicon source, aluminum source, alkali source, and water here is also the molar ratio at the time of feeding.

[0042] Furthermore, such as Figure 3As shown, step S11 above, mixing the silicon source, aluminum source, alkali source, and water, adjusting the pH of the system to 9-13, and setting the initial molar ratio of silicon source to aluminum source to 20-120, and forming a uniform synthetic gel under stirring conditions may include: S111. Mix silicon source, aluminum source, alkali source and water, adjust the pH of the system to 9-13, control the initial molar ratio of silicon source to aluminum source to 20-120, add target zeolite seed crystals, and stir to form a uniform synthetic gel.

[0043] In applications, the target zeolite seed crystals account for 0.1%-5% of the dry mass of the synthesized gel. For example, the target zeolite seed crystals account for 0.1%, 0.5%, 1%, 2%, 3%, 4%, or 5% of the dry mass of the synthesized gel. This promotes the formation of the target crystalline phase of the target zeolite.

[0044] It should be noted that the target zeolite seed crystals are usually made from fine powder of the same type of zeolite, mainly used to guide crystallization, accelerate crystallization, and directionally grow into the target zeolite.

[0045] [Step S2] like Figure 4 As shown, in step S2 above, the synthesized gel is placed under hydrothermal reaction conditions. First, a first-stage hydrothermal crystallization reaction is carried out at a first temperature of 80℃-120℃ for a period of time, followed by a second-stage hydrothermal crystallization reaction at a second temperature of 120℃-180℃ for a period of time. The intermediate product formed may include: S21. The synthesized gel is transferred and placed in a sealed hydrothermal reaction vessel, and hydrothermal crystallization is carried out in two stages. The conditions for the first stage of hydrothermal crystallization are: reacting at a first temperature of 80℃-120℃ for 6h-24h, and the conditions for the second stage of hydrothermal crystallization are: reacting at a second temperature of 120℃-180℃ for 12h-48h, to form an intermediate product.

[0046] In applications, the sealed hydrothermal reaction vessel can be a sealed stainless steel reactor with a polytetrafluoroethylene (PTFE) liner, etc.

[0047] The first stage of hydrothermal crystallization is the nucleation induction stage, which induces the formation of crystal nuclei in the synthesized gel at a relatively low initial temperature and establishes the initial crystal structure, i.e., nucleation and preliminary structural rearrangement. For example, the first temperature can be 80℃, 90℃, 100℃, 110℃, or 120℃, etc., and the duration of the first stage of hydrothermal crystallization can be 6h, 10h, 15h, 20h, or 24h, etc.

[0048] The second stage of hydrothermal crystallization is a phase of co-evolution of crystal growth and pore structure: the second temperature is increased to 120℃-180℃, and the reaction time is 12h-48h. For example, the second temperature can be 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, or 180℃, and the duration of the second stage of hydrothermal crystallization can be 12h, 15h, 20h, 25h, 30h, 35h, 40h, or 48h, etc. This allows for the orderly evolution of crystal growth and pore structure, enabling the synergistic completion of micropores, mesopores, and composite pore structures with interconnected micropores and mesopores within the same hydrothermal system.

[0049] Furthermore, the second temperature of the second stage of hydrothermal crystallization treatment is greater than the first temperature of the first stage of hydrothermal crystallization treatment, and the temperature difference between the second temperature and the first temperature is greater than or equal to 40°C. For example, the temperature difference between the second temperature and the first temperature can be 40°C, 45°C, 50°C, 55°C, 60°C, or 65°C, etc.

[0050] Therefore, through the above two-stage crystallization process, the in-situ synergistic evolution and construction of micropores (pore size ≤ 2 nm) and secondary mesopores (pore size 2 nm-10 nm) in the micropore-mesopore composite pore structure can be achieved without introducing additional pore-forming agents such as mesoporous SiO2 / organic / surfactants, hard templates, soft templates, or post-treatment modification methods such as metal ion impregnation, ion exchange, or surface silanization modification.

[0051] It should be noted that the number of stages, temperature, and sequence of hydrothermal crystallization treatment in the embodiments of this application can be adjusted according to the required crystal, pore structure, etc., and no specific limitation is made here.

[0052] Furthermore, by combining steps S1 and S2, and by controlling the kinetic conditions such as the ratio of silicon-aluminum source, system alkalinity, temperature of hydrothermal crystallization treatment, and time of hydrothermal crystallization treatment, the distribution state of aluminum in the zeolite molecular sieve framework for industrial coating exhaust gas can be adjusted, thereby regulating the ratio of Brønsted acid sites to Lewis acid sites.

[0053] [Step S3] like Figure 5 As shown, step S3 above, drying the intermediate product and calcining it at 500℃-600℃ for a period of time to form a zeolite molecular sieve for industrial coating waste gas, may include: S31. The intermediate product is filtered and washed sequentially until the pH of the filtrate is 7-8. Then, it is dried at 80℃-120℃ for 6-12 hours, and then heated to 500℃-600℃ at a heating rate of 1℃ / min-5℃ / min. Finally, it is calcined at 500℃-600℃ for 3-8 hours to form a zeolite molecular sieve for industrial coating waste gas.

[0054] In applications, the washing step in the post-treatment process can be water washing, etc. Specifically, the crystallized product can be filtered and washed with deionized water until the pH of the filtrate is 7-8.

[0055] For example, the filtrate can be washed with deionized water until the pH value is 7 or 8, etc.

[0056] For example, the drying temperature can be 80℃, 90℃, 100℃, 110℃ or 120℃, etc., and the drying time can be 6h, 7h, 8h, 9h, 10h, 11h or 12h, etc.

[0057] For example, the heating rate from the drying temperature to the calcination temperature can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, or 5℃ / min, etc.

[0058] For example, the calcination temperature can be 500℃, 520℃, 540℃, 560℃, 580℃ or 600℃, etc., and the calcination time can be 3h, 4h, 5h, 6h, 7h or 8h, etc.

[0059] This allows for further removal of impurities, stabilization of the microporous-mesoporous composite pore structure, and improvement of thermal stability, moisture resistance, and adsorption-regeneration performance.

[0060] In some embodiments, the silicon source provided in this application may include one or more combinations of silica sol (colloidal SiO2, dispersed in water), silica (precipitated SiO2•nH2O), tetraethyl orthosilicate (tetraethoxysilane, Si(OC2H5)4), fumed silica, alkali-activated clay mineral solution, or industrial by-product silicon source.

[0061] The aluminum source may include one or a combination of alumina (Al2O3), sodium aluminate (NaAlO2), boehmite (AlO(OH) or Al2O3•H2O), aluminum nitrate (Al(NO3)3), aluminum sulfate (Al2(SO4)3), or aluminum trichloride (AlCl3).

[0062] The alkaline source may include one or more combinations of sodium oxide (Na2O), sodium hydroxide (NaOH), potassium hydroxide (KOH), sodium carbonate (Na2CO3), or potassium carbonate (K2CO3).

[0063] Furthermore, the silicon source can be SiO2, the aluminum source can be Al2O3, and the alkali source can be Na2O. Specifically, the molar ratio of SiO2:Al2O3:Na2O:H2O can be 1:(0.008-0.05):(0.1-0.5):(10-50).

[0064] The method for preparing zeolite molecular sieves for industrial coating exhaust gas provided in this application embodiment uses simple and readily available raw materials, has low cost, and can produce zeolite molecular sieves with preferential and excellent adsorption characteristics for VOCs under high humidity conditions without the need for additional pore-forming agents such as mesoporous SiO2 / organic / surfactants, hard templates, soft templates, or post-treatment modification methods such as metal ion impregnation, ion exchange, or surface silanization modification in related technologies.

[0065] In some embodiments, such as Figure 6 As shown, before step S1 above, where silicon source, aluminum source, alkali source and water are mixed and stirred evenly to form a synthetic gel, the preparation method of zeolite molecular sieve for industrial coating waste gas provided in this application embodiment may further include the following steps: Step S01: Provide clay minerals and alkali source.

[0066] Step S02: Mix clay minerals and alkali source at a mass ratio of 0.5-2:1 and calcine at 300℃-900℃ for 1-10 hours. After calcination, cool the product to room temperature (20℃-40℃) and then dissolve it in water, controlling the solid-liquid ratio to 1g:(5-20)mL. Stir and dissolve for 0.5-4 hours. After solid-liquid separation, the resulting solution is used as a silicon source and / or aluminum source.

[0067] In applications, the aforementioned water can specifically be deionized water, etc.

[0068] Solid-liquid separation can be achieved through filtration or centrifugation.

[0069] The clay minerals may include one or more combinations of kaolin, montmorillonite, diatomite, attapulgite, or metakaolin.

[0070] Therefore, the silicon-aluminum source can be pretreated by activating it with an alkali.

[0071] In some embodiments, before step S01 above, providing clay minerals and alkali source, the preparation method of zeolite molecular sieve for industrial coating waste gas provided in this application embodiment may further include the following steps: S001. The clay minerals are subjected to at least one of the following pretreatments: (1) Acid washing pretreatment: the clay minerals are soaked in an inorganic acid solution with a molar concentration of 1mol / L-8mol / L for 1h-8h; (2) Alkali washing pretreatment: the clay minerals are soaked in an alkaline solution with a molar concentration of 1mol / L-8mol / L for 1h-8h; (3) Heat pretreatment: the clay minerals are calcined at a temperature of 300℃-700℃ for 1h-8h.

[0072] The above pretreatment can improve the reactivity of clay minerals.

[0073] In applications, inorganic acid solutions can include one or more combinations of hydrochloric acid, sulfuric acid, or nitric acid. Inorganic acid solutions can remove soluble impurities and some skeletal aluminum from clay minerals, thereby improving the activity and solubility of the clay minerals.

[0074] The alkaline solution can include one or more combinations of NaOH or KOH. Therefore, the alkaline solution can further activate the clay mineral structure and enhance the dissolution efficiency of the silica-alumina components, thereby improving the reactivity of the subsequent gel synthesis.

[0075] The heat treatment described above can disrupt the crystal structure of clay minerals and enhance their reactivity.

[0076] A specific preparation method of zeolite molecular sieve for industrial coating waste gas in this application embodiment is provided, including: 1. Raw material pretreatment step: Selecting clay minerals as auxiliary silicon-aluminum source, and subjecting the clay minerals to at least one of acid washing, alkali washing or heat treatment to obtain pretreated clay minerals.

[0077] II. Preparation steps of alkali-activated silicon-aluminum source: Mix the pretreated clay minerals with the alkali source at a mass ratio of 0.5-2:1, calcine at 300℃-900℃ for 1-10h, cool the product to room temperature after calcination, and then dissolve it in deionized water, controlling the solid-liquid ratio to 1g:(5-20)mL, and dissolve it under stirring for 0.5h-4h. After filtration or centrifugation, obtain an alkaline solution containing silicon and aluminum as the silicon-aluminum source (i.e., silicon source and aluminum source).

[0078] III. Gel synthesis steps: Mix silicon source, aluminum source, alkali source and water, adjust the pH of the system to 9-13, control the initial silicon-aluminum molar ratio to 20-120, add the target zeolite seed crystals, and form a uniform synthetic gel under stirring conditions.

[0079] The molar ratio of silicon source, aluminum source, alkali source and water is: 1:(0.008-0.05):(0.1-0.5):(10-50).

[0080] IV. Staged hydrothermal crystallization step: The synthesized gel is transferred to a closed stainless steel reactor with a polytetrafluoroethylene liner for staged hydrothermal crystallization treatment: (1). Crystal nucleus induction stage: react at a first temperature of 80℃-120℃ for 6h-24h.

[0081] (2). Co-evolution stage of crystal growth and pore structure: Increase the temperature to 120℃-180℃ and react for 12h-48h.

[0082] The temperature difference between the two hydrothermal crystallization processes is no less than 40℃.

[0083] V. Steps for regulating the silicon-aluminum structure in the framework: By controlling the kinetic conditions such as the silicon-aluminum ratio, system alkalinity, crystallization temperature, and crystallization time during the hydrothermal crystallization process, the distribution state of aluminum in the framework is adjusted, thereby regulating the ratio of Brønsted acid sites to Lewis acid sites.

[0084] VI. Post-processing steps: The crystallized product is treated as follows: (1). Filtration and washing: Filter the crystallized product and wash with deionized water until the pH of the filtrate is 7-8.

[0085] (2). Drying: Dry at 80℃-120℃ for 6h-12h.

[0086] (3) Calcination: Calcine at 500℃-600℃ for 3h-8h, with a heating rate of 1℃ / min-5℃ / min, to obtain zeolite molecular sieve for industrial coating waste gas.

[0087] Therefore, by regulating the crystallization path and pore structure evolution during the synthesis process, specifically by adopting a staged crystallization method, without introducing additional pore-forming agents such as mesoporous SiO2 / organic / surfactants, hard templates, or soft templates, or by performing post-treatment modifications such as metal ion impregnation, ion exchange, or surface silanization, a stable crystal structure with a reasonable pore distribution can be formed. This achieves the in-situ synergistic evolution of micropores (pore size <2nm) and mesopores (pore size 2nm-10nm), and improves its adaptability under industrial coating exhaust gas conditions. In addition, this preparation method has good reproducibility and industrial scale-up feasibility, which can effectively reduce the R&D costs and engineering application difficulties caused by relying on a large number of experimental screenings and complex modification steps in related technologies, thereby improving the practicality of zeolite molecular sieves for VOCs adsorption and treatment in industrial coating exhaust gas from the source.

[0088] Secondly, this application provides a zeolite molecular sieve for industrial coating exhaust gas, which is prepared by the method described in the above embodiments.

[0089] The zeolite molecular sieve for industrial coating waste gas provided in this application has good crystallinity and adjustable pore structure. It can effectively adsorb VOCs in industrial coating waste gas, especially under various conditions such as high humidity and significant fluctuations in the emission of VOCs, which have many molecular types, large differences in molecular size, and high humidity. It overcomes the limitations of traditional molecular sieves as adsorbent materials, such as easy water competition for adsorption under high humidity conditions. It can effectively adsorb VOCs in industrial coating waste gas, especially under various conditions such as high humidity and multiple components, and can maintain good adsorption stability and regeneration performance, thus meeting the long-term and stable treatment needs of industrial coating waste gas.

[0090] In some embodiments, the zeolite molecular sieve for industrial coating exhaust gas provided in this application has a micropore-mesopore composite pore structure, which includes micropores and mesopores, with at least one micropore communicating with at least one mesopore.

[0091] In applications, micropores and mesopores can be optionally interconnected throughout their entirety to form a multi-level interconnected pore network structure.

[0092] Among them, micropores are the inherent framework channels of the zeolite molecular sieve crystals used in industrial coating exhaust gas treatment. They exist inside each crystal grain and are regularly arranged, with uniform channels and strong sealing. The well-developed and interconnected micropores can ensure a large specific surface area and total pore volume, enabling precise adsorption of a large amount of VOCs. Here, the pore size of the micropores is less than or equal to 2nm. For example, the pore size of the micropores can be 0.1nm, 0.5nm, 1nm, 1.5nm, or 2nm, etc. Mesopores are mainly distributed between the crystal grains and are interstitial pores formed by the accumulation and bonding of countless tiny crystals. The large channels of mesopores are not easily blocked by paint mist, macromolecular resins, etc., which can extend the service life of the zeolite molecular sieve used in industrial coating exhaust gas treatment. Here, the pore size of the mesopores is 2nm-10nm. For example, the pore size of the mesopores can be 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, or 10nm, etc.

[0093] The total pore volume of zeolite molecular sieves used for industrial coating waste gas is 0.2 cm³. 3 / g-0.6cm 3 / g, for example, the total pore volume of zeolite molecular sieves used for industrial coating waste gas can be 0.2 cm³. 3 / g, 0.3cm 3 / g, 0.4cm 3 / g, 0.5cm 3 / g or 0.6cm 3 / g etc. Therefore, the zeolite molecular sieve for industrial coating exhaust gas has sufficient capacity to efficiently adsorb VOCs and stably meet standards; at the same time, the reasonable combination of micropores and mesopores makes it resistant to clogging and has fast mass transfer, making the structure of the zeolite molecular sieve for industrial coating exhaust gas more stable; moreover, the zeolite molecular sieve for industrial coating exhaust gas has gentle desorption, long service life, safety and energy saving, and good regenerability; in addition, the zeolite molecular sieve for industrial coating exhaust gas is highly adaptable to the working conditions of large air volume, low concentration, and high humidity coating exhaust gas.

[0094] The specific surface area of ​​zeolite molecular sieves used in industrial coating waste gas is 300 m². 2 / g-800m 2 / g, for example, the specific surface area of ​​zeolite molecular sieves for industrial coating waste gas can be 300m². 2 / g、400m 2 / g、500m 2 / g、600m 2 / g、700m 2 / g or 800m 2 / g etc. Therefore, zeolite molecular sieves for industrial coating waste gas have multiple adsorption sites, high VOCs removal rate, good resistance to high humidity and water vapor interference, easy desorption, low regeneration energy consumption, long service life, good structural strength, reasonable wind resistance, strong industrial applicability, and are safe and reliable.

[0095] In some embodiments, the zeolite molecular sieve for industrial coating waste gas provided in this application can be made into any one of molecular sieve paper, adsorption rotor, honeycomb adsorbent, etc.

[0096] In applications, molecular sieve paper can be made from zeolite molecular sieves used in industrial coating waste gas, along with inorganic fiber carriers, binders, etc.

[0097] An adsorption rotor can be made by impregnating and coating industrial coating waste gas with zeolite molecular sieves using honeycomb ceramic fiber paper or inorganic fiber substrate as a carrier.

[0098] Honeycomb adsorbents can be made by mixing zeolite molecular sieves with inorganic binders, etc., using industrial coating waste gas, extruding, and sintering at high temperature.

[0099] Based on the above, molecular sieve paper, adsorption rotor, honeycomb adsorbent, etc. can be arranged in the adsorption unit of the organic waste gas treatment system in the painting workshop to selectively adsorb benzene, ketone, ester and alcohol VOCs in the waste gas under normal temperature or medium temperature (80℃-150℃) conditions, and regenerate and reuse them through hot air or inert gas.

[0100] The zeolite molecular sieve for industrial coating waste gas provided in this application embodiment can be used to prepare molecular sieve paper, adsorption rotors, and honeycomb adsorbents without the need for additional pore-forming agents such as mesoporous SiO2 / organic / surfactants, hard templates, soft templates, or post-treatment modifications such as metal ion impregnation, ion exchange, or surface silanization. Because its adsorption mechanism, operating temperature range, and regeneration method are consistent with existing molecular sieve adsorption systems, it can be directly applied to existing fixed-bed, honeycomb, and rotor adsorption devices. Furthermore, its application enables the prepared molecular sieve paper, adsorption rotors, and honeycomb adsorbents to effectively adsorb and treat VOCs in industrial coating waste gas. It maintains good adsorption stability and regeneration performance even under high humidity and multi-component conditions, and has a long service life, thus meeting the long-term, stable operation requirements for industrial coating waste gas treatment. It also has good engineering compatibility with existing industrial VOCs adsorption treatment devices, which is beneficial for large-scale industrial production and application.

[0101] Example The following embodiments describe the disclosure of this application in more detail. These embodiments are for illustrative purposes only, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0102] I. Preparation method of zeolite molecular sieve for industrial coating waste gas in the embodiments of this application: Example 1 1. Preparation of synthetic gel: Silica sol was selected as the silicon source, NaAlO2 as the aluminum source, and NaOH as the alkali source. They were mixed with deionized water in the following molar ratio: SiO2:Al2O3:Na2O:H2O=1:0.02:0.30:30. The mixture was stirred at 25°C to form a uniform synthetic gel. The pH of the synthetic gel was adjusted to 10-12. The initial silicon-aluminum molar ratio (SiO2 / Al2O3) of the resulting synthetic gel was 50.

[0103] 2. Staged hydrothermal crystallization treatment: The resulting synthetic gel was transferred to a closed stainless steel hydrothermal reactor with a polytetrafluoroethylene liner. The first stage of hydrothermal crystallization was carried out at 100°C for 12 hours to induce the formation of molecular sieve crystal nuclei. The second stage of hydrothermal crystallization was carried out at 150°C for 24 hours to promote crystal growth and achieve the synergistic evolution of pore structure.

[0104] It should be noted that this staged crystallization method has been proven to be beneficial for controlling crystal growth kinetics and pore structure characteristics. During this staged crystallization process, the synthesized gel mainly undergoes nucleation and preliminary structural rearrangement under the first-stage crystallization conditions. Under the higher temperature conditions of the second stage, crystal growth and the ordered evolution of the pore structure are further promoted, which is conducive to the formation of a pore structure feature with a synergistic distribution of micropores and mesopores.

[0105] 3. Post-processing: The product after hydrothermal crystallization was taken out and filtered and washed with water in sequence until the pH value of the filtrate was close to neutral. Then it was dried at 100℃ for 8 hours and finally calcined at 550℃ for 5 hours in air atmosphere, with the heating rate controlled at 2℃ / min, to obtain zeolite molecular sieve for industrial coating waste gas.

[0106] The zeolite molecular sieve for industrial coating exhaust gas prepared in Example 1 has a silicon-to-aluminum molar ratio in the range of 20-120 and a composite pore structure with both micropores and mesopores. The micropores have a diameter of less than 2 nm, while the mesopores are mainly distributed in the range of 2 nm-10 nm. This micropore-mesopore composite structure is beneficial to the selective adsorption capacity of the zeolite molecular sieve for small molecule VOCs and the mass transfer performance for medium molecular size VOCs, giving it good application potential under the high humidity conditions commonly encountered in industrial coating exhaust gas.

[0107] The zeolite molecular sieve for industrial coating waste gas prepared in Example 1 can be combined with an inorganic fiber carrier to prepare a molecular sieve paper; or, the zeolite molecular sieve for industrial coating waste gas prepared in Example 1 can be combined with a honeycomb ceramic carrier to prepare an adsorption rotor. Both can be well applied to the adsorption and treatment of VOCs in industrial coating waste gas.

[0108] Example 2 The only difference between Example 2 and Example 1 is that the initial silicon-aluminum molar ratio (SiO2 / Al2O3) of the resulting synthetic gel is 20, while all other aspects are the same.

[0109] When the initial silicon-aluminum molar ratio of the synthesized gel obtained in Example 2 is at a low value, the aluminum content in the framework is relatively high, which is beneficial to enhancing the interaction ability of zeolite molecular sieves for industrial coating exhaust gas with polar VOCs molecules.

[0110] Example 3 The only difference between Example 3 and Example 1 is that the initial silicon-aluminum molar ratio (SiO2 / Al2O3) of the resulting synthetic gel is 120, while all other aspects are the same.

[0111] When the initial silicon-aluminum molar ratio of the synthesized gel obtained in Example 3 is at a high value, the zeolite molecular sieve for industrial coating exhaust gas exhibits strong hydrophobicity and is more suitable for the adsorption of hydrophobic VOCs under high humidity conditions.

[0112] Comparing Examples 1, 2, and 3, it was found that by adjusting the initial silicon-aluminum molar ratio of the synthesized gel, the adsorption characteristics of zeolite molecular sieves for industrial coating waste gas can be controlled without changing the overall process route.

[0113] Example 4 The only difference between Example 4 and Example 1 is that the synthetic gel was directly constructed using artificial silicon and artificial aluminum sources; all other aspects are the same.

[0114] Example 4 does not rely on natural silicon-aluminum mineral raw materials, omits the pretreatment steps of mineral raw materials, and simplifies the process flow. It is suitable for application scenarios that are less sensitive to raw material costs but have high requirements for process stability.

[0115] Example 5 The only difference between Example 5 and Example 1 is that the target zeolite seed crystals are introduced during the preparation of the synthetic gel; everything else is the same.

[0116] Example 5 introduces a small amount of zeolite molecular sieve seed crystals of the target crystal form into the synthesized gel, which helps to shorten the crystallization induction period, achieve rapid crystallization, and also improve the formation rate of the target crystal phase. In addition, the use of staged hydrothermal crystallization conditions combined with the addition of zeolite molecular sieve seed crystals of the target crystal form can improve the overall crystallization efficiency while ensuring the pore structure control effect.

[0117] II. Preparation method of zeolite molecular sieve in the comparative example: Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that a single hydrothermal crystallization condition was used; everything else was the same.

[0118] Comparative Example 1 does not employ a staged hydrothermal crystallization strategy, but instead performs hydrothermal treatment on the synthesized gel under a single temperature condition. This results in lower flexibility in pore structure control, and the development of mesopores (secondary pores) in the obtained zeolite molecular sieve is relatively limited. This verifies the role of the staged hydrothermal crystallization strategy provided in the embodiments of this application in pore structure control.

[0119] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that a mesoporous pore-forming agent or an organic pore-forming agent is introduced into the synthetic gel; otherwise, they are the same.

[0120] Although Comparative Example 2 can form a mesoporous structure to a certain extent, the process steps are relatively complex and require additional raw materials and post-processing, which does not have any advantages from the perspective of process simplification and engineering applicability.

[0121] By comparing Examples 1-5 with Comparative Examples 1-2, it was found that without introducing mesoporous pore-forming agents and without post-modification treatment, Examples 1-5 can effectively control the pore structure of zeolite molecular sieves for industrial coating waste gas by optimizing the composition of the synthesized gel through reasonable design and adopting a staged hydrothermal crystallization strategy.

[0122] Therefore, compared with the comparative example, the embodiments of this application have the following beneficial effects: First, the process is simplified, avoiding complex post-processing steps: The embodiments of this application introduce a staged hydrothermal crystallization process in the synthesis stage, which can realize the in-situ synergistic evolution of the micropore and secondary mesoporous structure of the zeolite molecular sieve for industrial coating exhaust gas. It eliminates the need for complex processes such as acid washing, alkali washing, addition of pore-forming agents such as mesoporous SiO2 / organic / surfactant, hard template / soft template treatment, or metal ion impregnation treatment, ion exchange treatment, and surface silanization modification treatment after synthesis. This fundamentally simplifies the preparation process of multi-level porous molecular sieves and overcomes the problems of long process and high cost in existing processes.

[0123] Secondly, the zeolite molecular sieve for industrial coating exhaust gas exhibits excellent intrinsic moisture resistance, making it suitable for high-humidity VOCs conditions. This application embodiment modifies the silicon-aluminum structure in the framework of the zeolite molecular sieve for industrial coating exhaust gas, enabling it to maintain preferential adsorption of VOCs molecules even in high-humidity environments. This effectively alleviates the competitive adsorption problem between water molecules and VOCs. Compared to existing solutions that rely on surface hydrophobic layers or organosilicon alkylation modification, the moisture resistance of this application embodiment stems from the intrinsic characteristics of the zeolite molecular sieve framework for industrial coating exhaust gas, making it more conducive to long-term stable operation in industrial VOCs treatment.

[0124] Third, no metal ion impregnation or surface modification is required, reducing costs and complexity: Unlike the commonly used multi-step treatment methods such as nickel impregnation, cerium ion exchange, or silanization surface modification, the zeolite molecular sieve for industrial coating exhaust gas in this application embodiment can obtain materials suitable for VOCs adsorption without introducing metal ion impregnation or organic surface modification, avoiding the increased costs and process complexity caused by precious metals or multiple modification treatments.

[0125] Fourth, it has strong engineering adaptability and is easy to integrate with existing treatment equipment: The zeolite molecular sieve for industrial coating waste gas prepared in the embodiments of this application has good molding adaptability and can be directly used for the preparation of engineered carriers such as molecular sieve paper, adsorption rotor and honeycomb adsorbent. It has good compatibility with existing industrial VOCs adsorption concentration and subsequent treatment systems, which is convenient for engineering scale-up and practical use.

[0126] Fifth, the raw materials are widely available and suitable for industrial promotion: the embodiments of this application can use natural clay minerals such as kaolin and montmorillonite as silicon and aluminum sources, and can also use industrial by-product silicon sources as supplementary raw materials. The raw materials are widely available and the cost is low, which is conducive to reducing the preparation cost of zeolite molecular sieves for industrial coating waste gas, and is in line with the development direction of resource recycling and green manufacturing.

[0127] Sixth, good stability during recycling and regeneration, suitable for high-temperature regeneration conditions: The zeolite molecular sieve for industrial coating waste gas prepared in the embodiments of this application has a complete skeleton structure. At the same time, because no easily decomposable organic modification groups or unstable surface layers are introduced, it can still maintain good structural stability and service life under thermal regeneration conditions, and is suitable for the high-temperature recycling operation mode commonly used in industrial VOCs treatment.

[0128] Seventh, adaptable to the adsorption and removal of various typical industrial coating VOCs: For common VOCs such as benzene series compounds, esters and ketones in industrial coating exhaust gas, the zeolite molecular sieve for industrial coating exhaust gas prepared in this application can effectively adsorb various VOCs through the synergistic regulation of pore structure and framework characteristics. It has good applicability and promotion potential, which is conducive to large-scale industrial production and application.

[0129] This section only introduces the content related to the invention point; other content can be obtained by referring to relevant technologies, and will not be explained in detail here.

[0130] Finally, it should be noted that the above descriptions are merely preferred embodiments of this application and are not intended to limit the application. Although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Therefore, any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing zeolite molecular sieves for industrial coating waste gas, characterized in that, Includes the following steps: A synthetic gel is formed by mixing silicon source, aluminum source, alkali source and water; The synthesized gel is first subjected to a first stage of hydrothermal crystallization reaction at a first temperature of 80℃-120℃, and then subjected to a second stage of hydrothermal crystallization reaction at a second temperature of 120℃-180℃ to form an intermediate product; wherein, the second temperature is greater than the first temperature, and the temperature difference between the second temperature and the first temperature is greater than or equal to 40℃. The intermediate product is calcined at a temperature of 500℃-600℃ to form the zeolite molecular sieve for industrial coating waste gas.

2. The method for preparing zeolite molecular sieves for industrial coating waste gas according to claim 1, characterized in that, In the synthetic gel, the molar ratio of the silicon source, the aluminum source, the alkali source, and the water is 1:(0.008-0.05):(0.1-0.5):(10-50).

3. The method for preparing zeolite molecular sieves for industrial coating waste gas according to claim 1 or 2, characterized in that, The process of mixing silicon source, aluminum source, alkali source and water to form a synthetic gel includes: The silicon source, the aluminum source, the alkali source and the water are mixed, the pH is adjusted to 9-13, and the initial molar ratio of silicon source to aluminum source is set to 20-120 to form the synthetic gel.

4. The method for preparing zeolite molecular sieves for industrial coating waste gas according to claim 1 or 2, characterized in that, The process of mixing silicon source, aluminum source, alkali source and water to form a synthetic gel includes: The silicon source, the aluminum source, the alkali source and the water are mixed, the pH is adjusted to 9-13, the initial molar ratio of silicon source to aluminum source is set to 20-120, and the target zeolite seed crystals are added to form the synthetic gel. The target zeolite seed crystals account for 0.1%-5% of the dry mass of the synthesized gel.

5. The method for preparing zeolite molecular sieves for industrial coating waste gas according to claim 1 or 2, characterized in that, The process involves first performing a first-stage hydrothermal crystallization reaction on the synthesized gel at a first temperature of 80℃-120℃, followed by a second-stage hydrothermal crystallization reaction at a second temperature of 120℃-180℃ to form intermediate products, including: The synthesized gel was placed in a sealed hydrothermal reaction vessel and subjected to hydrothermal crystallization treatment in two stages. The first stage of hydrothermal crystallization treatment was carried out at a first temperature of 80℃-120℃ for 6h-24h, and the second stage of hydrothermal crystallization treatment was carried out at a second temperature of 120℃-180℃ for 12h-48h, forming the intermediate product.

6. The method for preparing zeolite molecular sieves for industrial coating waste gas according to claim 1 or 2, characterized in that, The intermediate product is calcined at a temperature of 500℃-600℃ to form the zeolite molecular sieve for industrial coating waste gas, comprising: The intermediate product is filtered and washed until the pH of the filtrate is 7-8. Then it is dried at 80℃-120℃ for 6h-12h, and then heated to 500℃-600℃ at a heating rate of 1℃ / min-5℃ / min. Finally, it is calcined at 500℃-600℃ for 3h-8h to form the zeolite molecular sieve for industrial coating waste gas.

7. The method for preparing zeolite molecular sieves for industrial coating waste gas according to claim 1 or 2, characterized in that, Before mixing the silicon source, aluminum source, alkali source, and water to form a synthetic gel, the preparation method of the zeolite molecular sieve for industrial coating waste gas further includes: Provides clay minerals and alkali sources; The clay mineral and the alkali source are mixed at a mass ratio of 0.5-2:1 and calcined at 300℃-900℃ for 1h-10h. After calcination, the product is cooled to room temperature and dissolved in water, with the solid-liquid ratio controlled at 1g: (5-20)mL. The mixture is then stirred and dissolved for 0.5h-4h. After solid-liquid separation, the resulting solution is used as the silicon source and / or the aluminum source.

8. The method for preparing zeolite molecular sieves for industrial coating waste gas according to claim 7, characterized in that, Before providing the clay minerals and alkali source, the method for preparing the zeolite molecular sieve for industrial coating waste gas further includes: pretreating the clay minerals with at least one of the following: (1). Acid washing pretreatment: The clay minerals are soaked in an inorganic acid solution with a molar concentration of 1mol / L-8mol / L for 1h-8h; (2). Alkali washing pretreatment: The clay minerals are soaked in an alkaline solution with a molar concentration of 1mol / L-8mol / L for 1h-8h; (3) Heat pretreatment: The clay minerals are roasted at 300℃-700℃ for 1h-8h.

9. A zeolite molecular sieve for industrial coating waste gas prepared by the method according to any one of claims 1-8, characterized in that, The zeolite molecular sieve for industrial coating waste gas has a microporous-mesoporous composite pore structure, which includes micropores and mesopores, and at least one of the micropores is connected to at least one of the mesopores. The pore size of the micropores is less than 2 nm, and the pore size of the mesopores is 2 nm-10 nm. And / or, the total pore volume of the zeolite molecular sieve used for industrial coating waste gas is 0.2 cm³. 3 / g-0.6cm 3 / g; And / or, the specific surface area of ​​the zeolite molecular sieve for industrial coating waste gas is 300 m². 2 / g-800m 2 / g.

10. The zeolite molecular sieve for industrial coating waste gas according to claim 9, characterized in that, The industrial coating waste gas is made into any one of the following: molecular sieve paper, adsorption rotor, or honeycomb adsorbent using zeolite molecular sieves.

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