A method for preparing liquid fuel using waste plastics

Abstract

The application discloses a method for preparing liquid fuel from waste plastics, which comprises the following steps: mixing waste plastics with a catalyst, sealing, forming a reaction system, making the reaction system react, separating the catalyst, and obtaining liquid fuel; the catalyst is a layered molecular sieve with mesoporous micropores and acid sites on the outer surface, specifically a layered self-supporting MFI / MEL topological structure molecular sieve. The application has the advantages of mild reaction conditions, no additional hydrogen source, high-quality gasoline mainly composed of isomeric alkanes obtained through a self-hydrogen supply strategy, no solvent, no noble metal, inexpensive and stable molecular sieve as a catalyst, almost complete conversion of waste plastics into gasoline, only a small amount of C1-C3 gas (<2%) as by-products, the liquid product obtained through conventional filtration can be directly used as gasoline, the obtained gasoline is high-quality gasoline, mainly composed of a large amount of branched alkanes (C4-C12), a small amount of straight-chain alkanes, naphthenes and aromatic hydrocarbons, and no olefins, and the reaction process is simple and environment-friendly.

Description

Technical Field

[0001] This invention relates to the field of catalytic conversion and utilization of waste plastics, and more particularly to a method for preparing liquid fuels by catalytic degradation of waste plastics using solid acidic molecular sieves. Background Technology

[0002] Plastics play an indispensable role in people's production and daily lives. As of 2015, the global cumulative amount of plastics was approximately 8.3 billion tons, and it is projected to reach 52 billion tons by 2050. Of these, 12 billion tons will be incinerated, and 12 billion tons will be discarded or landfilled. This causes serious environmental pollution and resource waste. In recent years, people have begun to develop new recycling concepts, clean incineration methods, and rapidly biodegradable plastics in an effort to address the environmental pollution caused by plastics. The application of chemical methods will play a central role in providing solutions. If waste plastics can be degraded and converted into liquid fuels, it is possible to solve environmental pollution while simultaneously turning waste into treasure.

[0003] Currently, polyethylene (PE, 29%), polypropylene (PP, 19%), polyvinyl chloride (PVC, 10%), and polystyrene (PS, 7%), which are widely used, account for approximately 65% ​​of plastics. Their common characteristic is that their skeleton is composed of saturated carbon-carbon bonds. These saturated carbon-carbon bonds are chemically stable and difficult to break, generally requiring harsh conditions such as high temperature or high pressure with hydrogenation to achieve rupture. Existing patents (CN1141331A, CN1236016C, CN1084546A, CN1077479A, CN1059454C, CN102977909A, CN101117585A, CN105536818A, WO2005 / 017069A1) have reported methods for producing gasoline, kerosene, and diesel fuels from waste plastics. However, the reaction temperature generally needs to be raised to above 300℃ for effective degradation of the plastics, and the degradation products generally contain a large amount of unsaturated hydrocarbons, requiring further processing before they can be used as liquid fuels. Patent WO2021257783A1 reports a method for converting waste plastics into gasoline and diesel fuel using a physical mixture of Pt / WO3 / ZrO2 and HY molecular sieves as a catalyst at 200-250℃ and 30 bar hydrogen conditions. However, the use of precious metals and high-pressure hydrogen increases production costs and reduces operational safety. Chinese patent (CN1141359C) reports a method for converting waste plastics into gasoline and diesel fuel under milder conditions (50-320℃); however, its process is complex, requiring plastic thermal cracking, aluminum silicate catalytic thermal cracking, distillation, and rare earth / ferric oxide catalytic cracking to produce gasoline and diesel fuel.

[0004] In summary, existing technologies for producing liquid fuels from waste plastics have not yet reached the level of producing high-quality liquid fuels efficiently, selectively, and at low cost under mild conditions. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for preparing liquid fuel from waste plastics through the catalytic degradation of layered self-supporting solid acidic molecular sieves. This method utilizes the open framework of the molecular sieve material with three-coordinated aluminum as strong Lewis acid sites to efficiently activate saturated alkane CH bonds and catalyze hydrogen transfer reactions. Through a self-supplying hydrogen mode, the method achieves efficient and selective conversion of waste plastics into high-quality liquid fuels under mild conditions (240°C) without precious metals, external hydrogen sources, or solvents.

[0006] To achieve the above objectives, the technical solution adopted in this invention is as follows: a layered acidic molecular sieve catalyst and waste plastic are mixed evenly and added to a closed reactor, reacted at a certain temperature for a certain time, and the catalyst and product are separated by conventional filtration methods to obtain high-quality liquid fuel.

[0007] The method for preparing liquid fuel from waste plastics provided by this invention includes the following steps:

[0008] 1) Mix the waste plastic with the catalyst, seal the mixture, and form a reaction system.

[0009] 2) The reaction system is made to react, the catalyst is separated, and liquid fuel is obtained;

[0010] In step 1) of the above method, the waste plastic is a polymer whose backbone is composed of carbon-carbon saturated bonds, including but not limited to polyethylene, polypropylene, polystyrene, and polyvinyl chloride;

[0011] The catalyst is a layered molecular sieve with mesoporous micropores and acidic sites on its outer surface;

[0012] The outer surface of the layered molecular sieve has abundant acidic sites, which can effectively contact plastic macromolecules. Furthermore, the super-strong Lewis acidic sites on the outer surface can efficiently activate the CH bonds of waste plastics. The primary products obtained from activation and pyrolysis can enter the micropores in the layer for further shape-selective reactions, thus preparing liquid fuels with high selectivity.

[0013] The layered molecular sieve can specifically be a layered self-supporting MFI / MEL topology molecular sieve (named LSP-Z), and its Si:Al molar ratio is 25 to 300, specifically 49 or 57.

[0014] The layered molecular sieve was prepared by the following method:

[0015] Taking the synthesis of a molecular sieve (LSP-Z57) with an MFI / MEL topology and a Si / Al ratio of 57 as an example, the synthesis process is as follows: Aluminum isopropoxide is added to tetraethyl orthosilicate, and then tetrabutylammonium hydroxide (TBAOH) is added dropwise to the mixture while stirring. Then, an aqueous solution of sodium hydroxide is added to the mixture. The composition of the above mixture is 60SiO2:0.30Al2O3:18TBAOH:0.75NaOH:600H2O:240EtOH (the initial Si / Al ratio of the reaction feed is 100, and the Si / Al ratio of the synthesized molecular sieve becomes 57). After stirring for 12 hours, the mixture was sealed in a high-pressure hydrothermal reactor and heated at 120°C for 88 hours. The product was centrifuged and washed several times with water until the pH value was below 9. The product was then dried at 70°C for 12 hours and calcined at 550°C for 16 hours. The molecular sieve was then washed with deionized water at 70°C for 12 hours. The suspension was centrifuged, and the solid was collected. Ion exchange was then performed using a 1 mol / L ammonium chloride aqueous solution at 80°C. This process was repeated three times. The solid was washed, dried at 70°C, and calcined at 550°C for 4 hours to convert the sodium-form molecular sieve into a hydrogen-form molecular sieve. High-resolution transmission electron microscopy and X-ray powder diffraction results showed that the synthesized molecular sieve had a layered self-supporting structure. Figure 1 It has MFI and MEL topologies. Figure 2 ).

[0016] The weight ratio of waste plastic to catalyst can be 20:1 to 0.1:1, specifically 5:1;

[0017] Before mixing, the process also includes crushing, rinsing, and drying the waste plastics.

[0018] In step 2) of the above method, the reaction temperature can be 150-280℃, specifically 200-240℃; the reaction time can be 0.5-24 hours, preferably 1.5-15.5 hours, more preferably 4 hours;

[0019] The reaction process generates pressure, and the catalyst is separated using conventional filtration methods to obtain liquid fuel.

[0020] The liquid fuel is primarily gasoline, which is mainly composed of branched alkanes.

[0021] Compared with the prior art, the present invention has the following significant advantages:

[0022] (1) The reaction conditions are mild (200-240℃), no external hydrogen source is required, no solvent is needed, no precious metals are required, and cheap and stable molecular sieves are used as catalysts;

[0023] In this process, no external hydrogen source is required, and the system obtains high-quality gasoline, primarily composed of isoalkanes, through a self-supplying hydrogen strategy. Figure 3 )——PE undergoes β-cracking under the activation of a catalyst to produce unsaturated long carbon chains and olefins. The unsaturated long carbon chains are dehydrogenated to provide hydrogen for the olefins, which are then further converted into alkanes to obtain stable (olefin content <2%) and high-quality gasoline with low environmental pollution (aromatic content <15%).

[0024] (2) This strategy can efficiently convert polyethylene into gasoline under mild conditions, thanks to the unique acidic properties of LSP molecular sieves. Figure 4 The infrared spectrum of pyridine adsorbed by LSP molecular sieve indicates the Lewis acid of LSP molecular sieve (1454 cm⁻¹). -1 The Lewis acid in the LSP molecular sieve is abundant and strong; even at 450℃, pyridine cannot be completely desorbed from the pyridine, while the Lewis acid in the infrared spectrum of HZSM-5 is less abundant and almost completely desorbed at 450℃. The infrared spectrum of 2,6-di-tert-butylpyridine adsorbed by the LSP molecular sieve shows that almost all of the LSP molecular sieve adsorbs Lewis acid. The acid sites can be approached and protonated by the larger diameter 2,6-di-tert-butylpyridine molecule (3610 cm⁻¹). -1 , Acid hydroxyl vibration peaks: 3370, 1616, 1530 cm⁻¹ -1 (Protonated 2,6-di-tert-butylpyridine vibrational peak), while HZSM-5's Most of the acid sites are inaccessible to the probe molecule.

[0025] The super-strong Lewis acid sites of LSP-zeolites originate from the unique active sites of layered self-supporting zeolites (LSP zeolites)—open framework three-coordinate aluminum sites that can efficiently activate the CH bonds of saturated alkanes. Organophosphorus probe molecules were adsorbed onto the zeolite, and the open framework three-coordinate aluminum sites of the LSP zeolite were characterized. These sites, acting as super-strong Lewis acid sites, can activate the CH bonds of deuterated n-hexane and isopentane, achieving hydrogen transfer reactions. Mass spectra and chromatograms of the products show that some isopentane activated by LSP undergoes deuteration by deuterated n-hexane-donated atoms. Figure 5 In the middle (E, m / z = 73-83), deuterated n-hexane loses some deuterium atoms and transfers an equal amount of hydrogen atoms ( Figure 5 (F, m / z = 95-99). The illustrated model reaction demonstrates the LSP molecular sieve's superior ability to activate saturated alkane CH bonds, enabling it to activate polyethylene under mild conditions and convert it into high-quality gasoline.

[0026] (3) Waste plastics are almost completely converted into gasoline, with only a small amount of C1-C3 gas (<2%) as a byproduct. The liquid product obtained by conventional filtration does not require further distillation and can be used directly as gasoline.

[0027] (4) The obtained gasoline is high-quality gasoline, with a large amount of branched alkanes (C4-C12) as the main component, and a small amount of straight-chain alkanes, cycloalkanes and aromatics, and no olefins;

[0028] (5) The catalyst is resistant to carbon deposits (<0.6%), and can continuously complete four rounds of catalytic reactions without regenerating the catalyst. The gasoline yield does not decrease significantly, and the atom economy is higher than 90%.

[0029] (6) The reaction process is simple and environmentally friendly. Attached Figure Description

[0030] Figure 1 This is a high-resolution transmission electron microscope image of the LSP-Z57 molecular sieve prepared in this invention.

[0031] Figure 2 The X-ray powder diffraction patterns of the LSP-Z57 and LSP-Z49 molecular sieves prepared in this invention are compared with those of HZSM-5 (MFI topology) and HZSM-11 (MEL topology).

[0032] Figure 3 This is a diagram illustrating the self-supplying hydrogen mechanism of the present invention.

[0033] Figure 4 Infrared spectra of LSP-Z57(A) and HZSM-5(B) before and after adsorption of pyridine; infrared spectra of LSP-Z57(C) and HZSM-5(D) after adsorption of 2,6-di-tert-butylpyridine.

[0034] Figure 5 Solid-state phosphorus NMR spectra and their corresponding structures (A, B) are used to characterize the framework three-coordinate aluminum sites of the molecular sieve as organophosphorus probes; schematic diagram (C), product chromatogram (D), and product mass spectrum (E, F) of the reaction between molecular sieve-activated deuterated n-hexane and isopentane hydrogen transfer.

[0035] Figure 6 This is a chromatogram of the product obtained in Example 1 of the present invention.

[0036] Figure 7 This is a graph showing the trend of yield of each product as a function of reaction time. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0038] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0039] This invention provides a method for preparing liquid fuel from waste plastics, namely, uniformly mixing layered acidic molecular sieve catalyst and waste plastics and adding them into a closed reactor, reacting them at a certain temperature for a certain time, and separating the catalyst and products using conventional filtration methods to obtain high-quality liquid fuel.

[0040] The liquid fuel is primarily gasoline, which is mainly composed of branched alkanes.

[0041] Comparative Example 1

[0042] This demonstrates the effectiveness of conventional molecular sieve catalysts in catalyzing the degradation of waste plastics.

[0043] The first step involves mixing the catalyst HZSM-5 (Si / Al = 60) and the reactant high-density polyethylene. The two are then thoroughly mixed (by grinding), sealed, and a reaction system is formed. The weight ratio of reactant to catalyst is 5:1.

[0044] In the second step, the reaction system from the first step is reacted at 240°C for 4 hours. The catalyst and unreacted polyethylene are separated by conventional filtration methods, and the remaining liquid is the product liquid fuel.

[0045] The analysis results show that the polyethylene conversion rate is 35.1% and the gasoline yield is 34.5%.

[0046] Comparative Examples 2-13

[0047] Except for the following differences, everything else is the same as Comparative Example 1:

[0048] In the first step, the catalyst is:

[0049] Comparative Example 2HY (Si / Al = 5) Molecular Sieves

[0050] Comparative Example 3: Ultrastable HY (Si / Al = 5.5) mesoporous molecular sieve

[0051] Comparative Example 4HY (Si / Al = 5) mesoporous molecular sieve

[0052] Comparative Example 5SBA-15 (hydrogen form, Si / Al = 20) mesoporous molecular sieve

[0053] Comparative Example 6MCM-41 (hydrogen form, Si / Al = 12.5) mesoporous molecular sieve

[0054] Comparative Example 7: Fresh FCC Cracking Catalyst

[0055] Comparative Example 8: Equilibrium FCC Crack Catalyst

[0056] Comparative Example 9: Short b-axis ZSM-5 catalyst

[0057] Comparative Example 10: [C4Py]Cl-AlCl3 Butylpyridine aluminochlorochloride ionic liquid

[0058] Comparative Example 11Ru / C

[0059] Comparative Example 12Pt / γ-Al2O3

[0060] Comparative Example 13Pt / WO3 / ZrO2+HY(30)

[0061] The analysis results show that

[0062] Comparative Example 2 showed a polyethylene conversion rate of 3.8% and a gasoline yield of 3.7%.

[0063] Comparative Example 3 showed a polyethylene conversion rate of 9.1% and a gasoline yield of 9.0%.

[0064] Comparative Example 4 showed a polyethylene conversion rate of 19.0% and a gasoline yield of 18.7%.

[0065] Comparative Example 5: Polyethylene conversion rate <1%, gasoline yield 0%.

[0066] Comparative Example 6 showed a polyethylene conversion rate of 9.6% and a gasoline yield of 9.3%.

[0067] Comparative Example 7 showed a polyethylene conversion rate of 5.8% and a gasoline yield of 5.6%.

[0068] Comparative Example 8: Polyethylene conversion rate <1%, gasoline yield <1%.

[0069] Comparative Example 9 showed a polyethylene conversion rate of 12.0% and a gasoline yield of 11.8%.

[0070] Comparative Example 10: Polyethylene conversion rate <1%, gasoline yield <1%.

[0071] Comparative Example 11: Polyethylene conversion rate <1%, gasoline yield <1%.

[0072] Comparative Example 12: Polyethylene conversion rate <1%, gasoline yield <1%.

[0073] Comparative Example 13 showed a polyethylene conversion rate of 12.5% ​​and a gasoline yield of 12.2%.

[0074] The above comparative examples show that, in a system without hydrogen and solvent, and after a reaction at 240°C for 4 hours, conventional catalysts have poor effects on the conversion of waste plastics.

[0075] Example 1

[0076] The first step involves mixing LSP-Z57 (Si / Al = 57) as the catalyst and high-density polyethylene as the reactant. The two are mixed evenly, and the weight ratio of reactant to catalyst is 5:1.

[0077] In the second step, the reaction system from the first step is reacted at 240°C for 4 hours. The catalyst and unreacted polyethylene are separated by conventional filtration methods, and the remaining liquid is the product liquid fuel.

[0078] The analysis results show that the polyethylene conversion rate is 81.7% and the gasoline yield is 81.1%. The specific composition of the products under these conditions is shown in Table 1 and... Figure 6 As shown:

[0079] Table 1: Composition of the product in this example

[0080]

[0081]

[0082]

[0083]

[0084] Example 2

[0085] Except for the following differences, everything else is the same as in Example 1:

[0086] In the first step, the reaction time is changed from 4 hours to 24 hours.

[0087] The analysis results show that the polyethylene conversion rate is 90.3% and the gasoline yield is 87.2%. The detailed product composition is shown in the table below:

[0088] Table 2: Composition of the product in this example

[0089]

[0090]

[0091]

[0092] In this example, the yields of each product were monitored as the reaction time increased. It was found that after 4 hours of reaction, the yield of the C7-C12 product decreased with increasing reaction time, while the yield of the C4-C6 product increased. This is because the C7-C12 product underwent secondary cleavage. Figure 7 (As shown). Therefore, to obtain high-quality gasoline (with C8 alkanes having the highest value), it is necessary to avoid secondary cracking of C7 and higher alkanes due to excessively long reaction times.

[0093] Table 3: Yield of each product over reaction time

[0094]

[0095]

[0096] Example 3

[0097] Except for the following differences, everything else is the same as in Example 1:

[0098] In the first step, the catalyst is: LSP-Z49 (Si / Al = 49) molecular sieve.

[0099] The analysis results show that the polyethylene conversion rate was 78.8% and the gasoline yield was 77.2%. The detailed product composition is shown in the table below:

[0100] Table 4: Composition of the product in this example

[0101]

[0102]

[0103] Compared to Example 1, Example 3 uses a different catalyst with a different Si / Al ratio and different pore structure, resulting in different gasoline yields.

[0104] Table 5: The composition of the gasoline obtained in Example 1 is compared with that of commercial gasoline.

[0105]

[0106] As can be seen from the results of the above embodiments, compared with the comparative examples, the effect of the present invention is that, under mild conditions, the gasoline yield can be increased from <15% to >90%, and the prepared gasoline can be used directly without post-processing or distillation.

[0107] Example 4

[0108] Except for the following differences, everything else is the same as in Example 1:

[0109] In the first step, the reaction temperature is 220 degrees Celsius, and the catalyst / substrate ratio is 1:3.

[0110] The analysis results show that the polyethylene conversion rate is 90.0% and the gasoline yield is 87.9%. The detailed product composition is shown in the table below:

[0111] Table 6: Composition of the product in this example

[0112]

[0113]

[0114]

[0115] Example 5

[0116] Except for the following differences, everything else is the same as in Example 1:

[0117] In the first step, the reaction temperature was 260℃, and the reactants were high-density polyethylene, low-density polyethylene, and their recycled materials. The analytical results are shown in the table below:

[0118] Table 7: Gasoline Yields with Different Plastic Substrates

[0119] High-density polyethylene 85.1 High-density polyethylene recycled material 78.3 Low-density polyethylene 65.1 Low-density polyethylene recycled material 64.9

[0120] Taking the conversion of recycled high-density polyethylene at 260℃ as an example, the composition of the products obtained from the conversion reaction is shown in the table below. The product compositions of the other three groups are similar to those in the table below:

[0121] Table 8: Composition of the product in this example

[0122]

[0123]

[0124]

[0125] Example 6

[0126] Except for the following differences, everything else is the same as in Example 1:

[0127] In the second step, the solids after each reaction (including the catalyst and unbroken long-chain polyethylene) are collected, mixed with newly added polyethylene, and the next round of reaction is carried out directly (heated to 240°C and maintained for 4 hours).

[0128] The analysis results show that the gasoline yield did not decrease significantly after four cycles. The reaction feed details and detailed product composition are shown in the table below:

[0129] Table 9: Reactor Feeding Status in Four Cycles

[0130]

[0131] Table 10: Gasoline Production and Composition in the Four-Wheel Cycle

[0132]

[0133] The present invention has been described in detail above. Those skilled in the art will recognize that the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. While specific embodiments have been provided, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein.

[0134] The present invention has been described in detail above. Those skilled in the art will recognize that the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. While specific embodiments have been provided, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein.

Claims

1. A method for preparing liquid fuel from waste plastics, comprising the following steps: 1) Mix the waste plastic with the catalyst, seal it, and form a reaction system; 2) The reaction system is subjected to reaction at 200–240 °C without an external hydrogen source to separate the catalyst and obtain liquid fuel; Its features are, The catalyst is a layered molecular sieve with mesoporous micropores and acidic sites on its outer surface; The catalyst is a layered, self-supporting molecular sieve with an MFI / MEL topology. The molecular sieve has open three-coordinate aluminum sites and Brønsted acid sites. The open three-coordinate aluminum sites are Lewis acid sites. The Brønsted acid sites can be approached by 2,6-di-tert-butylpyridine molecules and protonated. The liquid fuel is mainly gasoline composed of branched alkanes.

2. The method according to claim 1, characterized in that, The molar ratio of Si to Al in the layered self-supporting molecular sieve is 25–300.

3. The method according to claim 2, characterized in that, The molar ratio of Si to Al in the layered self-supporting molecular sieve is 49 or 57.

4. The method according to claim 1, characterized in that, The infrared spectrum of the molecular sieve after adsorption of 2,6-di-tert-butylpyridine is at 3370 cm⁻¹. -1 1616 cm -1 and 1530 cm -1 It exhibits a vibrational peak at the point where protonated 2,6-di-tert-butylpyridine is present.

5. The method according to claim 1, characterized in that, The waste plastic is a polymer whose backbone is composed of carbon-carbon saturated bonds.

6. The method according to claim 5, characterized in that, The polymer is polyethylene.

7. The method according to claim 1, characterized in that, The weight ratio of the waste plastic to the catalyst is 20:1 to 0.1:

1.

8. The method according to claim 1, characterized in that, The reaction time is 1.5 to 15.5 hours.

9. The method according to claim 1, characterized in that, The waste plastic is high-density polyethylene, the molar ratio of Si to Al in the catalyst is 57, the weight ratio of the waste plastic to the catalyst is 5:1, and the reaction is carried out at 240 °C for 4 hours.

10. The method according to claim 1, characterized in that, The waste plastic is high-density polyethylene, the molar ratio of Si to Al in the catalyst is 57, the weight ratio of the waste plastic to the catalyst is 3:1, and the reaction is carried out at 220 °C for 4 hours.

11. The method according to claim 9, characterized in that, The molecular sieve with a Si:Al molar ratio of 57 was prepared by the following method: aluminum isopropoxide was added to tetraethyl orthosilicate, and tetrabutylammonium hydroxide was added dropwise to the resulting mixture while stirring. Then, an aqueous sodium hydroxide solution was added to make the molar composition of the mixture 60 SiO2 : 0.30 Al2O3 : 18 TBAOH : 0.75 NaOH : 600 H2O : 240 EtOH. After stirring for 12 hours, the mixture was sealed in a high-pressure hydrothermal reactor and heated at 120 °C for 88 hours. The resulting product was centrifuged and washed with water until the pH value was below 9. It was then dried at 70 °C for 12 hours and calcined at 550 °C for 16 hours. Subsequently, it was washed with deionized water at 70 °C for 12 hours, and the solid was collected by centrifugation. Ion exchange was performed with a 1 mol / L ammonium chloride aqueous solution at 80 °C, and the ion exchange was repeated three times. The solid was washed, dried at 70 °C, and calcined at 550 °C for 4 hours to obtain a hydrogen-form layered self-supporting molecular sieve.

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