Montmorillonite-metal composite catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of catalysts, in particular to a montmorillonite-metal composite catalyst and a preparation method and application thereof, and the montmorillonite-metal composite catalyst comprises M1, M2, M3 and M4, wherein M1 is a first metal element, M2 is a second metal element, M3 is a functional body, M4 is a composite clay material, the mass ratio of M1 to M2 to M3 to M4 is (1-20): (1-3): (10-30): (4-15), and the mass of M4 accounts for 1-10% of the total mass of the catalyst. M1 is Fe < 3 + >, M2 is Al < 3 + >, and M3 is at least one of phthalic acid, oxalic acid, citric acid, maleic acid and malonic acid. The prepared montmorillonite-metal composite catalyst shows good catalytic activity and stability in the plastic pyrolysis process, can effectively promote the pyrolysis reaction of plastics, and improves the reaction yield and quality.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and more specifically, to a montmorillonite-metal composite catalyst, its preparation method, and its application. Background Technology

[0002] With the increasing severity of global plastic pollution, plastic recycling and reuse have become an important environmental task. Plastic pyrolysis technology is an effective method for converting waste plastics into valuable chemicals and energy. During plastic pyrolysis, catalysts play a crucial role in promoting the depolymerization and transformation of plastic molecules.

[0003] However, traditional plastic pyrolysis catalysts have some problems. Some commonly used catalysts, such as metal oxides and acid oxides, suffer from low activity, short lifespan, and easy deactivation. Therefore, finding a highly efficient and stable technology for preparing plastic pyrolysis catalysts has become a research hotspot.

[0004] In recent years, clay-based catalysts have attracted widespread attention due to their unique structure and excellent catalytic performance. Montmorillonite, a layered silicate mineral, possesses a large number of pores and tunable surface properties, providing good catalytic activity and selectivity. Metal-organic frameworks (MOFs), on the other hand, are crystalline materials composed of metal ions and organic ligands, exhibiting highly tunable structure and chemical properties. Combining montmorillonite with MOFs to prepare montmorillonite-based metal catalysts has become a promising technique for preparing plastic pyrolysis catalysts. These catalysts not only possess high activity and selectivity but also long catalytic lifetime and stability.

[0005] In the prior art, patent CN101024776A describes a catalyst for catalytic cracking of waste plastics to produce fuel oil. The resulting catalyst is an alumina catalyst, primarily used for the pyrolysis of a single type of plastic. Due to its specificity, it may not be effective in treating multiple types of plastic waste, limiting its widespread application in practice. Furthermore, the alumina catalyst may experience a decline in activity over long-term reactions, requiring frequent replacement or regeneration, increasing operating costs and complexity. Patent CN116328854B describes a method for preparing a catalyst for pyrolysis of waste plastics to produce oil and its application. This technology uses coal gangue as a raw material to prepare the catalyst. Although the raw material source is wide-ranging, the oil yield is less than 50%, meaning its energy conversion efficiency is low and may not meet the economic efficiency requirements of industrial production. In addition, the low oil yield may lead to problems in the treatment of byproducts such as gaseous and solid waste, increasing the difficulty and cost of subsequent treatment. CN118105980A discloses a multi-supported composite-supported transition metal pyrolysis catalyst, its preparation method, and its application. This patent uses at least one of CaO and Al2O3 to prepare a porous support via an impregnation method. While this method can produce a porous catalyst, the pyrolysis oil yield is less than 20%, and the pyrolysis carbon content is as high as 40%, indicating low catalyst efficiency and potentially generating significant solid waste, increasing the burden on subsequent treatment and environmental protection. CN202111318632.9 discloses a method for preparing an alkaline catalyst for the pyrolysis of waste plastics. This patented technology limits the use of alkaline catalysts for PP plastics, with the products primarily being gaseous. This limitation restricts its application scope, as the types of plastic waste requiring treatment are diverse. Furthermore, the predominance of gaseous products may imply lower liquid fuel yields, potentially hindering energy recovery and economic efficiency. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a montmorillonite-metal composite catalyst, its preparation method, and its application.

[0007] In a first aspect, the present invention provides a montmorillonite-metal composite catalyst, comprising M1, M2, M3 and M4; wherein M1 is a first metal element, M2 is a second metal element, M3 is a functional component, and M4 is a composite clay material, wherein the mass ratio of M1, M2, M3 and M4 is (1-20):(1-3):(10-30):(4-15), and the mass of M4 accounts for 1-10% of the total mass of the catalyst.

[0008] Preferably, M1 is Fe 3+ M2 is Al 3+ M3 is at least one of phthalic acid, oxalic acid, citric acid, maleic acid, and malonic acid.

[0009] Preferably, the composite clay material includes modified montmorillonite, kaolin, and modified attapulgite, and the mass ratio of the modified montmorillonite, kaolin, and modified attapulgite is (3-8):(1-5):(1-2).

[0010] Preferably, the modified montmorillonite is prepared by modifying montmorillonite with TiO2, and the mass ratio of TiO2 to montmorillonite is (1-2):(3-5).

[0011] Preferably, the modified attapulgite is obtained by functionalizing natural attapulgite by loading lanthanum.

[0012] Secondly, the present invention provides a method for preparing a montmorillonite-metal composite catalyst, comprising the following steps:

[0013] (1) Dissolve salts M1, M2 and M3 in DMF and mix them evenly by magnetic stirring to obtain a precursor solution;

[0014] (2) Add M4 to the precursor solution, transfer it to a polytetrafluoroethylene-lined reactor, react at 120-160℃ for 24-48 hours, and then cool to room temperature to obtain the preform.

[0015] (3) The preform was filtered and washed with methanol. The filtered product was suspended in methanol and stirred. Then it was filtered and calcined in static air, and then sieved into powder to obtain montmorillonite-metal composite catalyst.

[0016] Preferably, in step (1), the M1 salt is at least one of the chloride, nitrate, sulfate, carbonate, and acetate of element M1; and the M2 salt is at least one of the chloride, nitrate, sulfate, carbonate, and acetate of element M2.

[0017] Preferably, in step (4), the calcination temperature is 500-800℃ and the time is 5-8h.

[0018] Thirdly, the present invention provides an application of a montmorillonite-metal composite catalyst in the pyrolysis of plastics.

[0019] Preferably, the application of montmorillonite-metal composite catalysts includes the following steps:

[0020] S1: Place the mixed plastic at the bottom of the horizontal fixed-bed reactor;

[0021] S2: Add a layer of glass wool between the plastic and the catalyst for isolation;

[0022] S3: When the temperature reaches the preset reaction parameters, put the plastic and the catalyst into the reactor; the mass ratio of the plastic to the montmorillonite-metal composite catalyst is (10-20):1; the reaction parameters are 450-550℃;

[0023] S4: Liquid products are collected through a two-stage intermediate water cooler, and non-condensable gases are collected or analyzed through a gas bag or an online GC system.

[0024] In summary, the present invention has the following beneficial effects:

[0025] 1. In this invention, a homogeneous solution is prepared by dissolving a metal salt and phthalic acid or other organic acid ligands in dimethylformamide, then adding a composite clay material, and reacting under high temperature conditions to synthesize the catalyst. The catalyst exhibits good catalytic activity and stability during the pyrolysis of plastics, effectively promoting the pyrolysis reaction of plastics and improving the reaction yield and quality.

[0026] 2. The composite clay materials added to the metal composite catalyst in this invention include modified montmorillonite, kaolin, and modified attapulgite. The modified montmorillonite surface forms strong Lewis acid sites, which can efficiently activate functional groups such as carbonyl groups. Its catalytic activity even exceeds that of homogeneous superacids. Through intercalation and pillaring, the interlayer spacing can be expanded to form a mesoporous structure, which is beneficial for reactant diffusion and product desorption, thereby increasing the reaction rate. Pillared montmorillonite maintains structural stability at high temperatures and has strong tolerance to impurities (such as heavy metals), extending catalyst lifetime. The layered structure can effectively fix metal nanoparticles (such as Pd, Ru, Fe), preventing aggregation and improving catalytic efficiency. Kaolin imparts a lower attrition index to the catalyst, and the modified attapulgite introduces functional groups such as -NH2 and -SH, firmly immobilizing metal ions or complexes and improving catalytic stability. After modification, these three types of clay minerals can significantly improve the activity, selectivity, and stability of metal catalysts by regulating acidity, expanding specific surface area and pores, improving metal dispersion, and enhancing resistance to poisoning and mechanical strength, while reducing catalyst costs.

[0027] 3. The montmorillonite-metal composite catalyst and pyrolysis technology prepared by this invention can be used for the pyrolysis of mixed plastics, and the products can be controlled. By adjusting the proportion of catalyst components, an oil yield of over 70% or a gas yield of over 70% can be achieved. Waste plastic pyrolysis products can be flexibly produced according to actual market demand.

[0028] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the scope of protection of the present invention. Attached Figure Description

[0029] Figure 1This is a schematic diagram of the pyrolysis process of plastics using the montmorillonite-metal composite catalyst prepared according to the present invention. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are carried out according to conventional conditions or the conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments can be obtained from commercially available sources.

[0031] Example

[0032] Example 1

[0033] A method for preparing a montmorillonite-metal composite catalyst includes the following steps:

[0034] (1) Dissolve 60 mmol / L of M1 salt and M2 salt and 30 mmol / L of M3 in 60 mL of DMF and mix them evenly by magnetic stirring to obtain a precursor solution; M1 salt is ferric chloride, M2 salt is aluminum sulfate, the mass ratio of ferric chloride to aluminum sulfate is 3:1, and M3 is phthalic acid;

[0035] (2) Add M4 to the precursor solution, transfer it to a polytetrafluoroethylene-lined reactor, react at 120°C for 24 h-h, and then cool to room temperature to obtain the preform; M4 is a composite clay material, and the mass of M4 accounts for 5% of the total mass of the catalyst, including modified montmorillonite, kaolin and modified attapulgite, with a mass ratio of 3:1:1; the modified montmorillonite is obtained by modifying montmorillonite with TiO2 with a mass ratio of 1:3; the modified attapulgite is obtained by functionalizing natural attapulgite by loading lanthanum, and the mass of the loaded lanthanum is 10%.

[0036] (3) The preform was filtered and washed with methanol. The filtered product was suspended in methanol and stirred. Then it was filtered and calcined in static air at a temperature of 500°C for 5 hours. The product was then sieved into powder to obtain the montmorillonite-metal composite catalyst.

[0037] The pyrolysis reaction of the plastic was carried out at 500°C. The catalyst significantly increased the yield of the oil product to 64 wt%, indicating that the synergistic catalytic effect of iron and aluminum significantly promoted the formation of liquid products. The carbon yield decreased sharply to 2 wt%, while the yield of the gaseous product was 34 wt%, a reduction compared to Example 1, which may be because the catalyst promoted the formation of more liquid oil.

[0038] Example 2

[0039] A method for preparing a montmorillonite-metal composite catalyst includes the following steps:

[0040] (1) Dissolve 65 mmol / L of M1 salt and M2 salt, and 35 mmol / L of M3 in 60 mL of DMF, and mix them evenly by magnetic stirring to obtain a precursor solution; M1 salt is ferric chloride, M2 salt is aluminum sulfate, the mass ratio of ferric chloride to aluminum sulfate is 1:3, and M3 is phthalic acid;

[0041] (2) Add M4 to the precursor solution, transfer it to a polytetrafluoroethylene-lined reactor, react at 120°C for 24 hours, and then cool to room temperature to obtain the preform. M4 is a composite clay material, and the mass of M4 accounts for 5% of the total mass of the catalyst. It includes modified montmorillonite, kaolin and modified attapulgite, with a mass ratio of 3:1:1. Modified montmorillonite is obtained by modifying montmorillonite with TiO2 at a mass ratio of 1:3. Modified attapulgite is obtained by functionalizing natural attapulgite by loading lanthanum, and the mass of the lanthanum loading is 10%.

[0042] (3) The preform was filtered and washed with methanol. The filtered product was suspended in methanol and stirred. Then it was filtered and calcined in static air at a temperature of 500°C for 5 hours. The product was then sieved into powder to obtain the montmorillonite-metal composite catalyst.

[0043] Plastic pyrolysis was carried out at 500°C. The yield of oil products further increased to 67 wt%, which may be due to the more significant catalytic effect of the increased aluminum content on the pyrolysis reaction, promoting the formation of oil products. At the same time, the carbon yield further decreased to 1 wt%, and the yield of gaseous products was 32 wt%, which further demonstrates the influence of the iron-aluminum ratio on the distribution of plastic pyrolysis products.

[0044] Example 3

[0045] A method for preparing a montmorillonite-metal composite catalyst includes the following steps:

[0046] (1) Dissolve 70 mmol / L of M1 salt and M2 salt, and 40 mmol / L of M3 in 60 mL of DMF and mix them evenly by magnetic stirring to obtain a precursor solution; M1 salt is ferric chloride, M2 salt is aluminum sulfate, the mass ratio of ferric chloride to aluminum sulfate is 1:1, and M3 is phthalic acid;

[0047] (2) Add M4 to the precursor solution, transfer it to a polytetrafluoroethylene-lined reactor, react at 120°C for 24 hours, and then cool to room temperature to obtain the preform. M4 is a composite clay material, and the mass of M4 accounts for 5% of the total mass of the catalyst. It includes modified montmorillonite, kaolin and modified attapulgite, with a mass ratio of 3:1:1. Modified montmorillonite is obtained by modifying montmorillonite with TiO2 at a mass ratio of 1:3. Modified attapulgite is obtained by functionalizing natural attapulgite by loading lanthanum, and the mass of the lanthanum loading is 10%.

[0048] (3) The preform was filtered and washed with methanol. The filtered product was suspended in methanol and stirred. Then it was filtered and calcined in static air at a temperature of 500°C for 5 hours. The product was then sieved into powder to obtain the montmorillonite-metal composite catalyst.

[0049] The process was carried out under pyrolysis conditions at 500°C. The oil product yield reached 73 wt%, a very significant improvement, indicating that an equal ratio of iron and aluminum may provide optimal catalytic effect for the pyrolysis reaction. The carbon yield remained at a low level of 1 wt%, while the gaseous product yield decreased to 26 wt%, a change likely due to more pyrolysis products being converted into liquid oil.

[0050] Example 4

[0051] A method for preparing a montmorillonite-metal composite catalyst includes the following steps:

[0052] (1) Dissolve 40 mmol / L of M1 salt and M2 salt, and 50 mmol / L of M3 in 60 mL of DMF and mix them evenly by magnetic stirring to obtain a precursor solution; M1 salt is ferric chloride, M2 salt is aluminum sulfate, the mass ratio of ferric chloride to aluminum sulfate is 2:3, and M3 is phthalic acid;

[0053] (2) Add M4 to the precursor solution, transfer it to a polytetrafluoroethylene-lined reactor, react at 120°C for 24 hours, and then cool to room temperature to obtain the preform. M4 is a composite clay material, and the mass of M4 accounts for 5% of the total mass of the catalyst. It includes modified montmorillonite, kaolin and modified attapulgite, with a mass ratio of 3:1:1. Modified montmorillonite is obtained by modifying montmorillonite with TiO2 at a mass ratio of 1:3. Modified attapulgite is obtained by functionalizing natural attapulgite by loading lanthanum, and the mass of the lanthanum loading is 10%.

[0054] (3) The preform was filtered and washed with methanol. The filtered product was suspended in methanol and stirred. Then it was filtered and calcined in static air at a temperature of 500°C for 5 hours. The product was then sieved into powder to obtain the montmorillonite-metal composite catalyst.

[0055] The plastic pyrolysis at 500°C yielded an oil product yield of 73 wt%, the same as in Example 4. This indicates that under certain conditions, different iron-aluminum ratios can achieve similar optimization results. The carbon yield increased slightly to 3 wt%, while the gaseous product yield decreased to 24 wt%, possibly due to different pyrolysis dynamic equilibria resulting from fine-tuning of the catalyst composition.

[0056] Example 5

[0057] A method for preparing a montmorillonite-metal composite catalyst includes the following steps:

[0058] (1) Dissolve 80 mmol / L of M1 salt and M2 salt, and 40 mmol / L of M3 in 60 mL of DMF and mix them evenly by magnetic stirring to obtain a precursor solution; M1 salt is ferric chloride, M2 salt is aluminum sulfate, the mass ratio of ferric chloride to aluminum sulfate is 3:2, and M3 is phthalic acid;

[0059] (2) Add M4 to the precursor solution, transfer it to a polytetrafluoroethylene-lined reactor, react at 120°C for 24 hours, and then cool to room temperature to obtain the preform. M4 is a composite clay material, and the mass of M4 accounts for 5% of the total mass of the catalyst. It includes modified montmorillonite, kaolin and modified attapulgite, with a mass ratio of 3:1:1. Modified montmorillonite is obtained by modifying montmorillonite with TiO2 at a mass ratio of 1:3. Modified attapulgite is obtained by functionalizing natural attapulgite by loading lanthanum, and the mass of the lanthanum loading is 10%.

[0060] (3) The preform was filtered and washed with methanol. The filtered product was suspended in methanol and stirred. Then it was filtered and calcined in static air at a temperature of 500°C for 5 hours. The product was then sieved into powder to obtain the montmorillonite-metal composite catalyst.

[0061] At 500°C, the pyrolysis of plastics yielded the highest oil product yield in this series of experiments, reaching 78 wt%. This result highlights the potential advantage of catalysts with relatively high iron content in oil product formation. The carbon yield remained low at 1 wt%, while the gaseous product yield further decreased to 21 wt%, demonstrating the potential for optimizing oil product yields.

[0062] Example 6

[0063] A method for preparing a montmorillonite-metal composite catalyst includes the following steps:

[0064] (1) Dissolve 70 mmol / L of M1 salt and M2 salt, and 50 mmol / L of M3 in 60 mL of DMF and mix them evenly by magnetic stirring to obtain a precursor solution; M1 salt is ferric chloride, M2 salt is aluminum sulfate, the mass ratio of ferric chloride to aluminum sulfate is 3:1, and M3 is phthalic acid;

[0065] (2) Add M4 to the precursor solution, transfer it to a polytetrafluoroethylene-lined reactor, react at 120°C for 24 hours, and then cool to room temperature to obtain the preform. M4 is a composite clay material, and the mass of M4 accounts for 5% of the total mass of the catalyst. It includes modified montmorillonite, kaolin and modified attapulgite, with a mass ratio of 3:1:1. Modified montmorillonite is obtained by modifying montmorillonite with TiO2 at a mass ratio of 1:3. Modified attapulgite is obtained by functionalizing natural attapulgite by loading lanthanum, and the mass of the lanthanum loading is 10%.

[0066] (3) The preform was filtered and washed with methanol. The filtered product was suspended in methanol and stirred. Then it was filtered and calcined in static air at a temperature of 500°C for 5 hours. The product was then sieved into powder to obtain the montmorillonite-metal composite catalyst.

[0067] In the pyrolysis of plastics at 600°C, the oil product yield decreased to 27 wt%, which may be because at higher temperatures, the catalyst promoted the formation of more gaseous products rather than oil products. The carbon yield was 2 wt%, and the gaseous product yield increased significantly to 71 wt%, which may indicate that under these conditions, the catalyst had a more significant catalytic effect on the formation of gaseous products.

[0068] Example 7

[0069] A method for preparing a montmorillonite-metal composite catalyst includes the following steps:

[0070] (1) Dissolve 90 mmol / L of M1 salt and M2 salt, and 20 mmol / L of M3 in 60 mL of DMF and mix them evenly by magnetic stirring to obtain a precursor solution; M1 salt is ferric chloride, M2 salt is aluminum sulfate, the mass ratio of ferric chloride to aluminum sulfate is 1:3, and M3 is phthalic acid;

[0071] (2) Add M4 to the precursor solution, transfer it to a polytetrafluoroethylene-lined reactor, react at 120°C for 24 hours, and then cool to room temperature to obtain the preform. M4 is a composite clay material, and the mass of M4 accounts for 5% of the total mass of the catalyst. It includes modified montmorillonite, kaolin and modified attapulgite, with a mass ratio of 3:1:1. Modified montmorillonite is obtained by modifying montmorillonite with TiO2 at a mass ratio of 1:3. Modified attapulgite is obtained by functionalizing natural attapulgite by loading lanthanum, and the mass of the lanthanum loading is 10%.

[0072] (3) The preform was filtered and washed with methanol. The filtered product was suspended in methanol and stirred. Then it was filtered and calcined in static air at a temperature of 500°C for 5 hours. The product was then sieved into powder to obtain the montmorillonite-metal composite catalyst.

[0073] Plastic pyrolysis was performed at 600°C, yielding an oil product yield of 39 wt%, a carbon yield of 1 wt%, and a gaseous product yield of 60 wt%. Compared to Example 8, the oil product yield was improved, which may be due to the higher aluminum content catalyst having a better catalytic effect on the formation of oil products at this temperature.

[0074] Example 8

[0075] A method for preparing a montmorillonite-metal composite catalyst includes the following steps:

[0076] (1) Dissolve 80 mmol / L of M1 salt and M2 salt, and 30 mmol / L of M3 in 60 mL of DMF and mix them evenly by magnetic stirring to obtain a precursor solution; M1 salt is ferric chloride, M2 salt is aluminum sulfate, the mass ratio of ferric chloride to aluminum sulfate is 1:1, and M3 is phthalic acid;

[0077] (2) Add M4 to the precursor solution, transfer it to a polytetrafluoroethylene-lined reactor, react at 120°C for 24 hours, and then cool to room temperature to obtain the preform. M4 is a composite clay material, and the mass of M4 accounts for 5% of the total mass of the catalyst. It includes modified montmorillonite, kaolin and modified attapulgite, with a mass ratio of 3:1:1. Modified montmorillonite is obtained by modifying montmorillonite with TiO2 at a mass ratio of 1:3. Modified attapulgite is obtained by functionalizing natural attapulgite by loading lanthanum, and the mass of the lanthanum loading is 10%.

[0078] (3) The preform was filtered and washed with methanol. The filtered product was suspended in methanol and stirred. Then it was filtered and calcined in static air at a temperature of 500°C for 5 hours. The product was then sieved into powder to obtain the montmorillonite-metal composite catalyst.

[0079] Pyrolysis of plastics at 600℃ yielded an oil product yield of 54 wt%. This significant improvement is likely due to the catalyst's ability to effectively promote oil product formation even at high temperatures, despite its balanced iron-aluminum ratio. The carbon yield was 4 wt%, while the gaseous product yield was 42 wt%, indicating that under these conditions, the catalyst helps balance the distribution of different pyrolysis products.

[0080] Example 9

[0081] A method for preparing a montmorillonite-metal composite catalyst includes the following steps:

[0082] (1) Dissolve 50 mmol / L of M1 salt and M2 salt and 60 mmol / L of M3 in 60 mL of DMF and mix them evenly by magnetic stirring to obtain a precursor solution; M1 salt is ferric chloride, M2 salt is aluminum sulfate, the mass ratio of ferric chloride to aluminum sulfate is 2:3, and M3 is phthalic acid;

[0083] (2) Add M4 to the precursor solution, transfer it to a polytetrafluoroethylene-lined reactor, react at 120°C for 24 hours, and then cool to room temperature to obtain the preform. M4 is a composite clay material, and the mass of M4 accounts for 5% of the total mass of the catalyst. It includes modified montmorillonite, kaolin and modified attapulgite, with a mass ratio of 3:1:1. Modified montmorillonite is obtained by modifying montmorillonite with TiO2 at a mass ratio of 1:3. Modified attapulgite is obtained by functionalizing natural attapulgite by loading lanthanum, and the mass of the lanthanum loading is 10%.

[0084] (3) The preform was filtered and washed with methanol. The filtered product was suspended in methanol and stirred. Then it was filtered and calcined in static air at a temperature of 500°C for 5 hours. The product was then sieved into powder to obtain the montmorillonite-metal composite catalyst.

[0085] The pyrolysis of plastics at 600℃ yielded an oil product yield of 53 wt%, a carbon yield of 3 wt%, and a gaseous product yield of 44 wt%. This result indicates that even with a high aluminum content, the catalyst can still maintain a high oil product yield while also promoting the formation of gaseous products.

[0086] Example 10

[0087] A method for preparing a montmorillonite-metal composite catalyst includes the following steps:

[0088] (1) Dissolve 40 mmol / L of M1 salt and M2 salt and 10 mmol / L of M3 in 60 mL of DMF and mix them evenly by magnetic stirring to obtain a precursor solution; M1 salt is ferric chloride, M2 salt is aluminum sulfate, the mass ratio of ferric chloride to aluminum sulfate is 3:2, and M3 is phthalic acid;

[0089] (2) Add M4 to the precursor solution, transfer it to a polytetrafluoroethylene-lined reactor, react at 120°C for 24 h-h, and then cool to room temperature to obtain the preform; M4 is a composite clay material, and the mass of M4 accounts for 5% of the total mass of the catalyst, including modified montmorillonite, kaolin and modified attapulgite, with a mass ratio of 3:1:1; the modified montmorillonite is obtained by modifying montmorillonite with TiO2 with a mass ratio of 1:3; the modified attapulgite is obtained by functionalizing natural attapulgite by loading lanthanum, and the mass of the loaded lanthanum is 10%.

[0090] (3) The preform was filtered and washed with methanol. The filtered product was suspended in methanol and stirred. Then it was filtered and calcined in static air at a temperature of 500°C for 5 hours. The product was then sieved into powder to obtain the montmorillonite-metal composite catalyst.

[0091] In the high-temperature pyrolysis reaction at 600℃, the oil product yield was 72 wt%, the carbon yield was 4 wt%, and the gaseous product yield decreased significantly to 24 wt%. This result may indicate that at higher temperatures, the iron content has a significant effect on increasing the oil product yield, while relatively reducing the formation of gaseous products.

[0092] Example 11

[0093] The difference from Example 1 is that the mass ratio of ferric chloride to aluminum sulfate is 3:1, and the pyrolysis temperature of the plastic is 700°C.

[0094] Example 12

[0095] The difference from Example 1 is that the mass ratio of ferric chloride to aluminum sulfate is 1:3, and the pyrolysis temperature of the plastic is 700°C.

[0096] Example 13

[0097] The difference from Example 1 is that the mass ratio of ferric chloride to aluminum sulfate is 1:1, and the pyrolysis temperature of the plastic is 700°C.

[0098] Example 14

[0099] The difference from Example 1 is that the mass ratio of ferric chloride to aluminum sulfate is 2:3, and the pyrolysis temperature of the plastic is 700°C.

[0100] Example 15

[0101] The difference from Example 1 is that the mass ratio of ferric chloride to aluminum sulfate is 3:2, and the pyrolysis temperature of the plastic is 700°C.

[0102] Comparative Example 1

[0103] Plastics were processed in a pyrolysis environment at 500°C without the addition of any catalyst. The results showed that the oil product yield was 30 wt%, indicating that only a relatively low amount of oil product can be obtained from plastic pyrolysis without a catalyst. Meanwhile, the yield of solid carbon products was 19 wt%, while the yield of gaseous products was relatively high at 51 wt%, likely due to the generation of more non-condensable gases during pyrolysis.

[0104] Comparative Example 2

[0105] The plastic was treated in a pyrolysis environment at 600°C without the use of a catalyst. At this higher temperature, the yield of oil products was 32 wt%, slightly higher than the blank experiment at 500°C. The carbon yield was 8 wt%, and the gaseous product yield was as high as 60 wt%, demonstrating the promoting effect of increased temperature on the gaseous product yield.

[0106] Comparative Example 3

[0107] The difference from Example 1 is that the plastic was treated in a pyrolysis environment at 700°C without the use of a catalyst.

[0108] Table 1. Results of test on the effect of catalyst and reaction temperature on the performance of plastic pyrolysis

[0109] iron-aluminum ratio Reaction temperature / ℃ Oil yield wt / % Carbon yield wt / % Gas product yield wt / % Comparative Example 1 blank 500 30 19 51 Example 1 3:1 500 64 2 34 Example 2 1:3 500 67 1 32 Example 3 1:1 500 73 1 26 Example 4 2:3 500 73 3 24 Example 5 3:2 500 78 1 21 Comparative Example 2 blank 600 32 8 60 Example 6 3:1 600 27 2 71 Example 7 1:3 600 39 1 60 Example 8 1:1 600 54 4 42 Example 9 2:3 600 53 3 44 Example 10 3:2 600 72 4 24 Comparative Example 3 blank 700 26 20 54 Example 11 3:1 700 7 3 90 Example 12 1:3 700 4 2 94 Example 13 1:1 700 29 1 70 Example 14 2:3 700 35 2 63 Example 15 3:2 700 26 1 73

[0110] The above description is merely an exemplary embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A montmorillonite-metal composite catalyst, characterized in that, It includes M1, M2, M3 and M4; wherein M1 is the first metallic element, M2 is the second metallic element, M3 is the functional component, and M4 is the composite clay material. The mass ratio of M1, M2, M3 and M4 is (1-20):(1-3):(10-30):(4-15), and the mass of M4 accounts for 1-10% of the total mass of the catalyst.

2. The montmorillonite-metal composite catalyst according to claim 1, characterized in that, M1 is Fe 3+ M2 is Al 3+ M3 is at least one of phthalic acid, oxalic acid, citric acid, maleic acid, and malonic acid.

3. The montmorillonite-metal composite catalyst according to claim 1, characterized in that, The composite clay material includes modified montmorillonite, kaolin, and modified attapulgite, and the mass ratio of the modified montmorillonite, kaolin, and modified attapulgite is (3-8):(1-5):(1-2).

4. The montmorillonite-metal composite catalyst according to claim 1, characterized in that, The modified montmorillonite is prepared by modifying montmorillonite with TiO2, and the mass ratio of TiO2 to montmorillonite is (1-2):(3-5).

5. The montmorillonite-metal composite catalyst according to claim 1, characterized in that, The modified attapulgite is prepared by functionalizing natural attapulgite by loading lanthanum.

6. The method for preparing the montmorillonite-metal composite catalyst according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Dissolve salts M1, M2 and M3 in DMF and mix them evenly by magnetic stirring to obtain a precursor solution; (2) Add M4 to the precursor solution, transfer it to a polytetrafluoroethylene-lined reactor, react at 120-160℃ for 24-48 hours, and then cool to room temperature to obtain the preform. (3) The preform was filtered and washed with methanol. The filtered product was suspended in methanol and stirred. Then it was filtered and calcined in static air, and then sieved into powder to obtain montmorillonite-metal composite catalyst.

7. The method for preparing the montmorillonite-metal composite catalyst according to claim 6, characterized in that, In step (1), the M1 salt is at least one of the chloride, nitrate, sulfate, carbonate, and acetate of element M1; the M2 salt is at least one of the chloride, nitrate, sulfate, carbonate, and acetate of element M2.

8. The method for preparing the montmorillonite-metal composite catalyst according to claim 6, characterized in that, In step (4), the calcination temperature is 500-800℃ and the time is 5-8h.

9. The application of the montmorillonite-metal composite catalyst according to any one of claims 1-5 or the montmorillonite-metal composite catalyst prepared by the preparation method according to claims 6-8 in the pyrolysis of plastics.

10. The application of the montmorillonite-metal composite catalyst according to claim 9, characterized in that, Includes the following steps: S1: Place the mixed plastic at the bottom of the horizontal fixed-bed reactor; S2: Add a layer of glass wool between the plastic and the catalyst for isolation; S3: When the temperature reaches the preset reaction parameters, put the plastic and the catalyst into the reactor; the mass ratio of the plastic to the montmorillonite-metal composite catalyst is (10-20):1; the reaction parameters are 450-550℃; S4: Liquid products are collected through a two-stage intermediate water cooler, and non-condensable gases are collected or analyzed through a gas bag or an online GC system.

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