A method for preparing ZSM-5 catalyst by using paint residue and application of ZSM-5 catalyst

Abstract

The present application belongs to the technical field of resource recycling, and particularly relates to a method for preparing ZSM-5 catalyst by using paint slag and application thereof. The method for preparing ZSM-5 catalyst by using paint slag provided by the present application uses paint slag as raw material to prepare ZSM-5 catalyst, and sequentially carries out washing and drying, high-temperature calcination, alkali fusion activation and dissolution aging treatment on the paint slag, and uses tetrapropylammonium bromide as a template agent to prepare ZSM-5 catalyst. In addition, ZSM-5 catalyst can also be prepared by using segmented crystallization treatment without a template agent. In the present application, the organic matter and impurities in the paint slag are removed after pretreatment, and the catalyst has high reaction activity. The use of tetrapropylammonium bromide as a template agent or the non-use of a template agent can reduce the cost and meet the environmental protection requirements.

Description

Technical Field

[0001] This invention belongs to the technical field of resource recycling, specifically relating to a method for preparing ZSM-5 catalyst using paint residue and the application of ZSM-5 catalyst. Background Technology

[0002] The preparation of ZSM-5 catalysts typically relies on chemically pure reagents as silicon and aluminum sources, such as water glass, silica sol, and tetraethyl orthosilicate as silicon sources, and aluminum sulfate and sodium aluminate as aluminum sources. A typical preparation process includes the following steps: First, the silicon source, aluminum source, template agent (such as tetrapropylammonium hydroxide), and deionized water are mixed in a certain proportion and stirred until a uniform initial gel is formed. Then, the gel is transferred to a high-pressure reactor with a polytetrafluoroethylene liner and subjected to a crystallization reaction under autogenous pressure for a period of time. After crystallization, the catalyst is filtered, washed, dried, and finally calcined at high temperature to remove the organic template agent, thereby obtaining the ZSM-5 catalyst product.

[0003] In the catalytic cracking of polystyrene, existing technologies generally use commercially available ZSM-5 catalysts, either purchased directly or prepared using the aforementioned traditional methods. A typical application process involves physically mixing waste polystyrene (such as foamed plastic) with the ZSM-5 catalyst, placing it in a fixed-bed or fluidized-bed reactor, and heating the reaction system to a specific temperature under an inert atmosphere (such as nitrogen) to carry out the catalytic cracking reaction. The volatile products produced are condensed and collected to obtain liquid oil, with the target product being styrene monomer. Summary of the Invention

[0004] This invention is based on the inventor's discoveries and understanding of the following facts and problems: Firstly, the preparation of the ZSM-5 catalyst relies entirely on high-purity chemical reagents as silicon and aluminum sources, and requires expensive organic template agents to guide the crystal structure, resulting in high overall production costs. This limits its large-scale application in cost-sensitive fields such as bulk solid waste treatment. Furthermore, this preparation process fails to achieve resource utilization of industrial solid waste, which is inconsistent with the development concept of green chemistry.

[0005] Secondly, in the application of catalytic cracking of polystyrene, the commercial ZSM-5 catalyst used in existing technologies is not specifically designed and optimized for the polystyrene cracking reaction. Its pore structure and acidic site characteristics may not be optimal, leading to rapid deactivation of the catalyst due to carbon deposition during the reaction, and the selectivity of the target product, styrene monomer, needs further improvement. In addition, the initial mixing and contact efficiency between the catalyst and polystyrene materials (especially low-density foam plastics) is often low, resulting in mass transfer limitations and affecting the initial reaction rate and overall conversion efficiency.

[0006] This invention aims to at least partially address one of the technical problems in related technologies. To this end, embodiments of this invention propose a method for preparing ZSM-5 catalyst using paint slag.

[0007] The method for preparing ZSM-5 catalyst using paint residue according to embodiments of the present invention includes the following steps: (1) The paint residue is washed, dried and then calcined to obtain inorganic powder; (2) After the inorganic powder obtained in step (1) is activated by alkali fusion, an alkali fusion product is obtained. After the alkali fusion product is dissolved and aged, a paint slag-based silicon-aluminum source precursor liquid is obtained. After filtration and drying, paint slag powder is obtained. (3) The paint residue powder, silicon source, template agent, alkali source and water obtained in step (2) are mixed evenly and stirred vigorously to form a synthetic gel. The synthetic gel is transferred to a reaction vessel for crystallization reaction to obtain crystallization slurry. (4) The crystallized slurry obtained in step (3) is subjected to filtration, washing and drying treatment and then calcined for the first time. Then, it is subjected to ion exchange with acid solution and then calcined for the second time to obtain the catalyst.

[0008] The advantages and technical effects of the method for preparing ZSM-5 catalyst using paint slag in this embodiment of the invention are as follows: 1. The method of this embodiment of the invention uses paint slag, which typically contains inorganic fillers such as aluminum hydroxide, aluminum phosphate, and aluminum sulfate, as well as some aluminum-containing pigments. These substances can be converted into active aluminum species during high-temperature alkali fusion or acid treatment, serving as the aluminum source for synthesizing ZSM-5 catalyst, thus realizing the resource utilization of solid waste; 2. The method of this embodiment of the invention uses washing and drying treatments to remove water-soluble salts and some free organic matter from the paint slag; calcination treatment can completely remove organic resin components, while converting inorganic substances (such as SiO2 and Al2O3) in the paint slag into more reactive active states; alkali fusion activation can destroy inert crystalline SiO2 and aluminum-containing minerals, converting them into soluble sodium silicate and sodium aluminate, greatly improving the reaction activity of the catalyst; 3. The method of this embodiment of the invention produces a catalyst with excellent cycle stability, which can be recycled multiple times.

[0009] In some embodiments, in step (1), the detergent used in the washing process includes at least one of deionized water and / or ethanol; the temperature of the drying process is 100~150°C; And / or, in step (1), the calcination temperature is 550~650℃ and the calcination time is 2~4h.

[0010] In some embodiments, in step (2), the alkaline fusion activation includes: mixing inorganic powder and solid sodium hydroxide at a mass ratio of 1:(1.2 to 1.5) until homogeneous, and then melting and reacting them at 500 to 550°C for 1 to 2 hours.

[0011] In some embodiments, in step (2), the dissolution and aging process includes: dissolving the alkali fusion product in deionized water, stirring to form an aluminosilicate solution, and allowing it to stand for aging for 12-24 hours; And / or, in step (2), the drying temperature is 100~150℃ and the drying time is 20~25h.

[0012] In some embodiments, in step (3), the silicon source includes at least one of industrial-grade water glass or silica. And / or, the template agent is tetrapropylammonium bromide; And / or, the alkali source is Na2O.

[0013] In some embodiments, in step (3), the molar ratio of the paint residue powder, silicon source, template agent, alkali source and water is SiO2:Al2O3:Na2O:TPABr:H2O=1:(0.01~0.05):(0.2~0.6):(0.1~0.3):(20~50); And / or, in step (3), the speed of the vigorous stirring is 300~500 rpm; And / or, in step (3), the temperature of the crystallization reaction is 150~180℃, and the time of the crystallization reaction is 24~72h; And / or, in step (3), the reactor is a stainless steel reactor with a polytetrafluoroethylene liner.

[0014] In some embodiments, in step (4), the temperature of the first calcination treatment is 500~600℃, and the time of the first calcination treatment is 3~8 h; And / or, in step (4), the acid solution is an ammonium nitrate solution with a concentration of 0.5~2 mol / L; And / or, in step (4), the temperature of the second roasting treatment is 500~600℃, and the time of the second roasting treatment is 3~8h.

[0015] In some embodiments, step (3) is as follows: the paint residue powder, silicon source, alkali source and water obtained in step (2) are mixed and stirred at room temperature for 2-6 hours to form a silica-alumina gel. The silica-alumina gel is then transferred to a reaction vessel for segmented crystallization treatment to obtain a crystallization slurry. The ratio of the amount of paint residue powder, silicon source, alkali source and water is SiO2:Al2O3:Na2O:H2O = 1:(0.01~0.03):(0.3~0.7):(20~40). The step (4) is as follows: the crystallized slurry obtained in step (3) is filtered, washed and dried, and then ion exchanged with an acid solution and calcined to obtain a catalyst.

[0016] In some embodiments, in step (3), the silicon source includes at least one of industrial-grade water glass or white carbon black, and the alkali source is Na2O; And / or, in step (3), the segmented crystallization treatment includes: a first-stage hydrothermal pre-crystallization: placing the reactor in an oven at 120~160℃ for 12~24h for pre-crystallization, forming a highly active nucleation precursor in the gel; a second-stage hydrothermal crystallization: after cooling the pre-crystallized slurry, a trace amount of ZSM-5 seed crystals can be selectively added, and the mixture is placed again in an oven at 160~190℃ for secondary crystallization for 24~48h, and crystallized after stirring evenly; the amount of ZSM-5 seed crystals added is 0.1~2wt% of the total mass of the gel; And / or, in step (4), the acid solution is an ammonium nitrate solution with a concentration of 0.5~2 mol / L, the calcination temperature is 500~600℃, and the calcination time is 3~8h.

[0017] The present invention also provides the application of the ZSM-5 catalyst prepared by the above method in the catalytic cracking of polystyrene, including: crushing waste polystyrene foam and mixing it with the catalyst, and carrying out the catalytic cracking reaction under an inert atmosphere; Preferably, the mass ratio of polystyrene to catalyst is (1~5):1, the temperature of the catalytic cracking reaction is 300~500℃, the heating rate is 8~15℃ / min, and the catalytic cracking reaction is carried out in a fixed bed or microreactor.

[0018] The slag-based ZSM-5 catalyst prepared in this embodiment of the invention, due to its suitable acidity and regular microporous channels, can efficiently catalyze the chain scission and isomerization reactions of PS macromolecules. Compared with traditional thermal cracking or non-catalytic cracking, the selectivity of styrene monomer in its liquid products is significantly improved (reaching more than 60 wt%), while the yield of by-products (such as heavy tar and wax) and gases (such as C1-C4 alkanes) is greatly reduced. Using the ZSM-5 catalyst prepared from paint slag for catalytic cracking of polystyrene realizes the transformation of hazardous waste (paint slag) and "white pollution" (polystyrene) into high-value-added chemical raw materials (styrene monomer), which has significant environmental and economic benefits. Attached Figure Description

[0019] Figure 1 This is an SEM image of the catalyst prepared in Example 1; Figure 2 This is the XRD pattern of the catalyst prepared in Example 1; Figure 3 This is the NH3-TPD curve of the catalyst prepared in Example 1; Figure 4 Bar chart showing the catalytic cracking effect of catalysts on polystyrene at different reaction times; Figure 5 Bar chart showing the catalytic cracking effect of catalysts on polystyrene at different reaction temperatures; Figure 6 Bar chart showing the catalytic cracking effect of catalyst on polystyrene at different dosage ratios; Figure 7 Bar chart showing the catalytic cracking effect of the catalyst on polystyrene at different cycle numbers. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] The method for preparing ZSM-5 catalyst using paint residue according to embodiments of the present invention includes the following steps: (1) The paint residue is washed, dried and then calcined to obtain inorganic powder; (2) After the inorganic powder obtained in step (1) is activated by alkali fusion, an alkali fusion product is obtained. After the alkali fusion product is dissolved and aged, a paint slag-based silicon-aluminum source precursor liquid is obtained. After filtration and drying, paint slag powder is obtained. (3) The paint residue powder, silicon source, template agent, alkali source and water obtained in step (2) are mixed evenly and stirred vigorously to form a synthetic gel. The synthetic gel is transferred to a reaction vessel for crystallization reaction to obtain crystallization slurry. (4) The crystallized slurry obtained in step (3) is subjected to filtration, washing and drying treatment and then calcined for the first time. Then, it is subjected to ion exchange with acid solution and then calcined for the second time to obtain the catalyst.

[0022] The method for preparing ZSM-5 catalyst using paint sludge in this embodiment of the invention utilizes paint sludge, which typically contains inorganic fillers such as aluminum hydroxide, aluminum phosphate, and aluminum sulfate, as well as some aluminum-containing pigments. These substances can be converted into active aluminum species during high-temperature alkali fusion or acid treatment, serving as the aluminum source for synthesizing ZSM-5 catalyst, thus realizing the resource utilization of solid waste. The method of this embodiment removes water-soluble salts and some free organic matter by washing and drying the paint sludge; calcination completely removes organic resin components and converts inorganic substances (such as SiO2 and Al2O3) in the paint sludge into more reactive active states; alkali fusion activation destroys inert crystalline SiO2 and aluminum-containing minerals, converting them into soluble sodium silicate and sodium aluminate, greatly improving the catalyst's reactivity. The catalyst prepared by the method of this embodiment exhibits excellent cycle stability and can be recycled multiple times.

[0023] In some embodiments, preferably, in step (1), the detergent used in the washing process includes at least one of deionized water and / or ethanol; the temperature of the drying process is 100~150°C; And / or, in step (1), the calcination temperature is 550~650℃ and the calcination time is 2~4h.

[0024] In some embodiments, preferably, in step (2), the alkaline fusion activation includes: mixing inorganic powder and solid sodium hydroxide at a mass ratio of 1:(1.2~1.5) until uniform, and then melting and reacting at 500~550°C for 1~2 hours.

[0025] In some embodiments, preferably, in step (2), the dissolution and aging process includes: dissolving the alkali fusion product in deionized water, stirring to form an aluminosilicate solution, and allowing it to stand for aging for 12-24 hours; And / or, in step (2), the drying temperature is 100~150℃ and the drying time is 20~25h.

[0026] In some embodiments, preferably, in step (3), the silicon source includes at least one of industrial-grade water glass or silica; And / or, the template agent is tetrapropylammonium bromide (TPABr); And / or, the alkali source is Na2O.

[0027] In this embodiment of the invention, tetrapropylammonium bromide (TPABr) is used as a template agent. TPABr has a similar structure-directing function to tetrapropylammonium hydroxide (TPAOH), but it is cheaper, less toxic, and can also effectively guide the formation of the ZSM-5 skeleton.

[0028] In some embodiments, preferably, in step (3), the molar ratio of the paint residue powder, silicon source, template agent, alkali source and water is SiO2:Al2O3:Na2O:TPABr:H2O=1:(0.01~0.05):(0.2~0.6):(0.1~0.3):(20~50); And / or, in step (3), the speed of the vigorous stirring is 300~500 rpm.

[0029] In this embodiment of the invention, the SiO2 / Al2O3 ratio (silicon-aluminum ratio) is controlled between 20 and 100, precisely regulated by supplementing with external silicon or aluminum sources. A higher silicon-aluminum ratio is beneficial for forming strong acid centers and hydrophobic surfaces, making it more suitable for polystyrene pyrolysis. The Na2O / SiO2 ratio (basicity) is controlled between 0.2 and 0.6 to ensure sufficient basicity in the synthesis system to dissolve silicon and aluminum species and promote crystallization, but without generating impurity crystals. The H2O / SiO2 ratio (water-silicon ratio) is controlled between 20 and 50, within the range commonly used in hydrothermal synthesis, ensuring gel fluidity and mass transfer. The TPABr / SiO2 ratio (template agent ratio) is controlled between 0.1 and 0.3; if a template agent route is used, this ratio is crucial in affecting crystallinity and grain size.

[0030] In some embodiments, preferably, in step (3), the temperature of the crystallization reaction is 150~180℃ and the time of the crystallization reaction is 24~72h; And / or, in step (3), the reactor is a stainless steel reactor with a polytetrafluoroethylene liner.

[0031] In some embodiments, preferably, in step (4), the temperature of the first calcination treatment is 500~600℃, and the time of the first calcination treatment is 3~8h; And / or, in step (4), the acid solution is an ammonium nitrate solution with a concentration of 0.5~2 mol / L; And / or, in step (4), the temperature of the second roasting treatment is 500~600℃, and the time of the second roasting treatment is 3~8h.

[0032] In some embodiments, preferably, step (3) is: mixing the paint residue powder, silicon source, alkali source and water obtained in step (2) and stirring at room temperature for 2-6 hours to form a silica-alumina gel, transferring the silica-alumina gel to a reaction vessel for segmented crystallization treatment to obtain a crystallization slurry, wherein the ratio of the paint residue powder, silicon source, alkali source and water is SiO2:Al2O3:Na2O:H2O = 1:(0.01~0.03):(0.3~0.7):(20~40); The step (4) is as follows: the crystallized slurry obtained in step (3) is filtered, washed and dried, and then ion exchanged with an acid solution and calcined to obtain a catalyst.

[0033] In this embodiment of the invention, a template-free and segmented crystallization process is adopted. The template-free process can reduce costs, improve environmental friendliness, simplify the processing procedure, reduce energy consumption and protect the crystal structure. The segmented crystallization process can achieve precise control of crystal growth.

[0034] In some embodiments, preferably, in step (3), the silicon source includes at least one of industrial-grade water glass or white carbon black, and the alkali source is Na2O; And / or, in step (3), the segmented crystallization treatment includes: a first-stage hydrothermal pre-crystallization: placing the reactor in an oven at 120~160℃ for 12~24h of pre-crystallization, forming a highly active nucleation precursor in the gel; a second-stage hydrothermal crystallization: cooling the pre-crystallized slurry, selectively adding a trace amount of ZSM-5 seed crystals, and placing it again in an oven at 160~190℃ for secondary crystallization for 24~48h, stirring evenly and then crystallizing to generate crystals; the amount of ZSM-5 seed crystals added is 0.1~2wt% of the total mass of the gel.

[0035] In some embodiments, preferably, in step (4), the acid solution is an ammonium nitrate solution with a concentration of 0.5~2 mol / L, the calcination temperature is 500~600℃, and the calcination time is 3~8h.

[0036] The present invention also provides the application of the ZSM-5 catalyst prepared by the above method in the catalytic cracking of polystyrene, including: crushing waste polystyrene foam and mixing it with the catalyst, and carrying out the catalytic cracking reaction under an inert atmosphere; Preferably, the mass ratio of polystyrene to catalyst is (1~5):1, the temperature of the catalytic cracking reaction is 300~500℃, the heating rate is 8~15℃ / min, and the catalytic cracking reaction is carried out in a fixed bed or microreactor.

[0037] The slag-based ZSM-5 catalyst prepared in this embodiment of the invention, due to its suitable acidity and regular microporous channels, can efficiently catalyze the chain scission and isomerization reactions of PS macromolecules. Compared with traditional thermal cracking or non-catalytic cracking, the selectivity of styrene monomer in its liquid products is significantly improved (reaching more than 60 wt%), while the yield of by-products (such as heavy tar and wax) and gases (such as C1-C4 alkanes) is greatly reduced. Using the ZSM-5 catalyst prepared from paint slag for catalytic cracking of polystyrene realizes the transformation of hazardous waste (paint slag) and "white pollution" (polystyrene) into high-value-added chemical raw materials (styrene monomer), which has significant environmental and economic benefits.

[0038] The lacquer residue-based ZSM-5 catalyst in this application is specifically designed to address the molecular structure and pyrolysis reaction pathway of polystyrene. By utilizing specific transition metals (such as Fe and Zn) and carbonaceous components in lacquer residue, the acidic sites of the catalyst are simultaneously controlled during synthesis (enhancing the interaction with moderately strong acids and Lewis acids to break C-C bonds and promote aromatization) and a hierarchical pore structure is constructed (to accommodate macromolecular diffusion). As a result, compared to the general-purpose ZSM-5 catalyst, it significantly improves the selectivity of target aromatic products and effectively inhibits carbon deposition in the polystyrene pyrolysis reaction, achieving specific optimization from raw materials to functional design.

[0039] The technical solution of the present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0040] Example 1 (1) After washing the paint residue with deionized water to remove water-soluble salts and some free organic matter, it is dried at 105°C. Then, the dried paint residue is calcined in a muffle furnace at 600°C for 3 hours. The calcined paint residue becomes grayish-white inorganic powder. (2) The calcined inorganic powder and solid sodium hydroxide were mixed uniformly at a mass ratio of 1:1.3 and melted at 520°C for 1.5 h. The alkaline fusion product was dissolved in deionized water and stirred to form a silicate solution. After standing and aging for 20 h, the paint residue-based silicate precursor liquid for catalyst synthesis was obtained. After filtration, it was dried at 105°C for 24 h to obtain pretreated paint residue powder. (3) The pretreated paint residue powder, industrial grade water glass, tetrapropylammonium bromide (TPABr), Na2O and water are mixed evenly in the ratio of SiO2:Al2O3:Na2O:TPABr:H2O=1:0.03:0.4:0.1:30. The mixture is stirred vigorously at 400 rpm to form a uniform synthetic gel. The synthetic gel is transferred to a stainless steel reactor lined with polytetrafluoroethylene and crystallized at 160℃ for 50 h to obtain a crystallized slurry. (4) After the crystallized slurry is filtered, washed and dried, it is first calcined at 550°C for 5 hours to remove the template agent. Then, it is ion exchanged with 1 mol / L ammonium nitrate solution to convert it into the hydrogen form. Then, it is calcined at 550°C for 5 hours to obtain the catalyst.

[0041] The SEM image of the catalyst prepared in this embodiment is shown below. Figure 1 As shown, from Figure 1 As can be seen from the above, the catalyst prepared in Example 1 is a micron-sized irregular aggregate with a rough surface and abundant pores, which is conducive to reactant diffusion and exposure of active sites.

[0042] The XRD pattern of the catalyst prepared in this embodiment is as follows. Figure 2 As shown, from Figure 2 As can be seen, the prepared catalyst exhibits the MFI characteristic peak, maintains the ZSM-5 crystal structure, has good crystallinity, and is suitable for catalytic applications.

[0043] The NH3-TPD curve of the catalyst prepared in this embodiment is shown in the figure below. Figure 3 As shown, from Figure 3 It can be seen that the prepared catalyst has a moderate amount of acid, which balances activation ability and anti-carbon deposition performance.

[0044] Example 2 The preparation method of this embodiment is the same as that of embodiment 1, except that: in step (4), the pretreated paint residue powder, industrial grade water glass, Na2O and water are mixed evenly in the ratio of SiO2:Al2O3:Na2O:H2O=1:0.03:0.4:30 and stirred at room temperature for 5h to form a silica-alumina gel. The silica-alumina gel is then transferred to a reactor for segmented crystallization treatment, which includes: the first stage of hydrothermal precrystallization: the reactor is placed in an oven at 150°C and precrystallized for 20h, forming a highly active nucleation precursor in the gel; the second stage of hydrothermal crystallization: after cooling the precrystallized slurry, 0.5% of the total mass of ZSM-5 seed crystals are added, and the slurry is placed in an oven at 180°C for secondary crystallization for 30h. After stirring evenly, crystals are generated to obtain a crystallized slurry. In step (5), after the crystallized slurry is filtered, washed and dried, it is ion-exchanged with a 1 mol / L ammonium nitrate solution to convert it into the hydrogen form, and then calcined at 550°C for 5 h to obtain the catalyst.

[0045] Example 3 The preparation method of this embodiment is the same as that of Example 1, except that in step (3), the pretreated paint residue powder, industrial grade water glass, tetrapropylammonium bromide (TPABr), Na2O and water are mixed evenly in the ratio of SiO2:Al2O3:Na2O:TPABr:H2O=1:0.04:0.5:0.2:40.

[0046] Example 4 The preparation method of this embodiment is the same as that of Example 2, except that the pretreated paint residue powder, industrial-grade water glass, Na2O and water are mixed evenly in the ratio of SiO2:Al2O3:Na2O:H2O=1:0.02:0.5:30.

[0047] Comparative Example 1 The preparation method of this comparative example is the same as that of Example 1, except that steps (1) to (3) are omitted, and paint residue is directly added in step (4).

[0048] Comparative Example 2 The preparation method of this comparative example is the same as that of Example 1, except that in step (2), no melting reaction is carried out.

[0049] Comparative Example 3 (1) The silicon source is silica sol, the aluminum source is aluminum sulfate (Al2(SO4)3·18H2O), the alkali source is sodium hydroxide (NaOH), the template agent is tetrapropylammonium hydroxide (TPAOH), and the solvent is deionized water.

[0050] (2) Weigh each raw material according to the molar ratio SiO2:Al2O3:Na2O:TPAOH:H2O=1:0.02:0.2:0.15:40. First, dissolve aluminum sulfate in part of deionized water, add sodium hydroxide and stir until completely dissolved; then slowly add silica sol and continue stirring; finally add TPAOH solution and stir vigorously for 2 seconds. After 3 hours, a uniform synthetic gel is formed; (3) Transfer the gel to a stainless steel reactor lined with polytetrafluoroethylene, seal it and place it in an oven to crystallize at 170°C for 48 hours.

[0051] (4) After crystallization, the product was cooled, filtered, and washed with deionized water until the pH of the filtrate was ≈9; it was then dried at 110℃ for 12 h to obtain ZSM. 5. Raw powder. The dried powder was calcined at 550℃ for 6 hours to remove the template agent, then ion-exchanged three times with 0.5 mol / L ammonium nitrate solution at 80℃, followed by washing, drying, and calcination at 50℃ for 4 hours to obtain ZSM. 5. Catalysts.

[0052] Performance testing (1) The catalysts prepared in Examples 1-4 and Comparative Examples 1-3, as well as the commercially available ZSM-5 catalyst (Qingdao Yuanke Catalyst Co., Ltd.), were used for the catalytic cracking of polystyrene: 300 mg of polystyrene was added to a reactor, followed by 150 mg of ZSM-5 catalyst. The mixture was heated to 400 °C under a nitrogen atmosphere and reacted for 5 h to obtain a liquid product containing styrene. The conversion rate and selectivity of polystyrene were tested, and the results are shown in Table 1. Table 1

[0053] As can be seen from Table 1, the catalysts prepared in Examples 1-4 have better catalytic cracking effects on polystyrene.

[0054] (2) Effect of different reaction times on catalytic performance 300 mg of polystyrene was added to a reactor, followed by 150 mg of the ZSM-5 catalyst prepared in Example 1. The reactor was heated to 400 °C under a nitrogen atmosphere and reacted for 1 h, 2 h, 3 h, 4 h, 5 h, 10 h, 15 h, and 20 h to obtain a liquid product containing styrene. The conversion rate of polystyrene and the selectivity of styrene were tested, and the results are as follows: Figure 4 As shown.

[0055] from Figure 4 As can be seen, the conversion rate of polystyrene gradually increases with the extension of reaction time. When the reaction time is 1–5 hours, the selectivity of styrene is around 80%. However, as the reaction time continues to increase, the selectivity decreases. This is because, with prolonged reaction time, the generated styrene monomer undergoes further secondary reactions at the acidic and metal sites of the catalyst, transforming into other aromatic hydrocarbons or carbon precursors, leading to a decrease in selectivity. Considering all factors, a reaction time of 3–5 hours yields better technical results.

[0056] (3) Effect of different reaction temperatures on catalytic performance 300 mg of polystyrene was added to a reactor, followed by 150 mg of the catalyst prepared using ZSM-5 as described in Example 1. The mixture was heated to 300°C, 350°C, 400°C, 450°C, and 500°C under a nitrogen atmosphere for 5 hours to obtain a liquid product containing styrene. The conversion rate and selectivity of the polystyrene were tested, and the results are as follows: Figure 5 As shown.

[0057] from Figure 5 As can be seen, the conversion rate of polystyrene gradually increases with the increase of reaction temperature, but the selectivity of styrene remains at around 80%, and it is not sensitive to temperature changes.

[0058] (4) Effect of different addition ratios on catalytic performance 300 mg of polystyrene was added to a reactor, followed by 60 mg, 75 mg, 100 mg, 150 mg, and 300 mg of the ZSM-5 catalyst prepared in Example 1, respectively. The mixture was heated to 400 °C and reacted for 5 hours under a nitrogen atmosphere to obtain a liquid product containing styrene. The conversion rate of polystyrene and the selectivity of styrene were tested, and the results are as follows: Figure 6 As shown.

[0059] from Figure 6 As can be seen, the conversion rate of polystyrene is not strongly correlated with the amount of catalyst used, while the selectivity of styrene increases slightly with the increase of catalyst amount and then tends to stabilize.

[0060] (5) Cyclic stability of the catalyst 300 mg of polystyrene was added to a reactor, followed by 150 mg of the ZSM-5 catalyst prepared in Example 1. The mixture was heated to 400°C and reacted for 5 hours under a nitrogen atmosphere to obtain a liquid product containing styrene. After the reaction, the catalyst was centrifuged and calcined in a muffle furnace at 500°C for 5 hours under an air atmosphere, followed by calcination at 400°C for 5 hours under a hydrogen atmosphere to regenerate the catalyst, which was then used again for the catalytic cracking of polystyrene. The above experiment was repeated, and the conversion rate of polystyrene and the selectivity of styrene were tested in each cycle. The results are shown below. Figure 7 As shown.

[0061] from Figure 5 As can be seen, after five cycles of use, the conversion rate of polystyrene and the selectivity of styrene remain at a high level, indicating that the catalyst prepared in this invention has good cycle stability.

[0062] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0063] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A method for preparing ZSM-5 catalyst using paint slag, characterized in that, Includes the following steps: (1) The paint residue is washed, dried and then calcined to obtain inorganic powder; (2) After the inorganic powder obtained in step (1) is activated by alkali fusion, an alkali fusion product is obtained. After the alkali fusion product is dissolved and aged, a paint slag-based silicon-aluminum source precursor liquid is obtained. After filtration and drying, paint slag powder is obtained. (3) The paint residue powder, silicon source, template agent, alkali source and water obtained in step (2) are mixed evenly and stirred vigorously to form a synthetic gel. The synthetic gel is transferred to a reaction vessel for crystallization reaction to obtain crystallization slurry. (4) The crystallized slurry obtained in step (3) is subjected to filtration, washing and drying treatment and then calcined for the first time. Then, it is subjected to ion exchange with acid solution and then calcined for the second time to obtain the catalyst.

2. The method for preparing ZSM-5 catalyst using paint slag according to claim 1, characterized in that, In step (1), the detergent used in the washing process includes at least one of deionized water and / or ethanol; the temperature of the drying process is 100~150℃. And / or, in step (1), the calcination temperature is 550~650℃ and the calcination time is 2~4h.

3. The method for preparing ZSM-5 catalyst using paint slag according to claim 1, characterized in that, In step (2), the alkaline fusion activation includes: mixing inorganic powder and solid sodium hydroxide at a mass ratio of 1:(1.2~1.5) until uniform, and then melting and reacting at 500~550℃ for 1~2h.

4. The method for preparing ZSM-5 catalyst using paint slag according to claim 1 or 3, characterized in that, In step (2), the dissolution and aging process includes: dissolving the alkali fusion product in deionized water, stirring to form an aluminosilicate solution, and allowing it to stand for aging for 12-24 hours; And / or, in step (2), the drying temperature is 100~150℃ and the drying time is 20~25h.

5. The method for preparing ZSM-5 catalyst using paint slag according to claim 1, characterized in that, In step (3), the silicon source includes at least one of industrial-grade water glass or silica. And / or, the template agent is tetrapropylammonium bromide; And / or, the alkali source is Na2O.

6. The method for preparing ZSM-5 catalyst using paint slag according to claim 1 or 5, characterized in that, In step (3), the molar ratio of the paint residue powder, silicon source, template agent, alkali source and water is SiO2:Al2O3:Na2O:TPABr:H2O=1:(0.01~0.05):(0.2~0.6):(0.1~0.3):(20~50); And / or, in step (3), the speed of the vigorous stirring is 300~500 rpm; And / or, in step (3), the temperature of the crystallization reaction is 150~180℃, and the time of the crystallization reaction is 24~72h; And / or, in step (3), the reactor is a stainless steel reactor with a polytetrafluoroethylene liner.

7. The method for preparing ZSM-5 catalyst using paint slag according to claim 1, characterized in that, In step (4), the temperature of the first roasting treatment is 500~600℃, and the time of the first roasting treatment is 3~8h; And / or, in step (4), the acid solution is an ammonium nitrate solution with a concentration of 0.5~2 mol / L; And / or, in step (4), the temperature of the second roasting treatment is 500~600℃, and the time of the second roasting treatment is 3~8h.

8. The method for preparing ZSM-5 catalyst using paint slag according to claim 1, characterized in that, Step (3) is as follows: the paint residue powder, silicon source, alkali source and water obtained in step (2) are mixed and stirred at room temperature for 2-6 hours to form a silica-alumina gel. The silica-alumina gel is transferred to a reaction vessel for segmented crystallization treatment to obtain a crystallization slurry. The ratio of the amount of paint residue powder, silicon source, alkali source and water is SiO2:Al2O3:Na2O:H2O = 1:(0.01~0.03):(0.3~0.7):(20~40). The step (4) is as follows: the crystallized slurry obtained in step (3) is filtered, washed and dried, and then ion exchanged with an acid solution and calcined to obtain a catalyst.

9. The method for preparing ZSM-5 catalyst using paint slag according to claim 8, characterized in that, In step (3), the silicon source includes at least one of industrial-grade water glass or white carbon black, and the alkali source is Na2O; And / or, in step (3), the segmented crystallization treatment includes: a first-stage hydrothermal pre-crystallization: placing the reactor in an oven at 120~160℃ for 12~24h for pre-crystallization, forming a highly active nucleation precursor in the gel; a second-stage hydrothermal crystallization: after cooling the pre-crystallized slurry, a trace amount of ZSM-5 seed crystals can be selectively added, and the mixture is placed again in an oven at 160~190℃ for secondary crystallization for 24~48h, and crystallized after stirring evenly; the amount of ZSM-5 seed crystals added is 0.1~2wt% of the total mass of the gel; And / or, in step (4), the acid solution is an ammonium nitrate solution with a concentration of 0.5~2 mol / L, the calcination temperature is 500~600℃, and the calcination time is 3~8h.

10. The application of the ZSM-5 catalyst prepared by the method for preparing ZSM-5 catalyst using paint slag according to any one of claims 1 to 9 in the catalytic cracking of polystyrene, characterized in that, include: Waste polystyrene foam was crushed and mixed with a catalyst, and then subjected to a catalytic cracking reaction under an inert atmosphere. Preferably, the mass ratio of polystyrene to catalyst is (1~5):1, the temperature of the catalytic cracking reaction is 300~500℃, the heating rate is 8~15℃ / min, and the catalytic cracking reaction is carried out in a fixed bed or microreactor.

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