Preparation method of binder-free Beta molecular sieve catalyst
The one-step dry gel crystallization method for preparing binder-free Beta molecular sieve catalysts solves the problems of complex processes, high costs, and large amounts of waste liquid in existing technologies. It realizes the preparation of efficient and low-cost binder-free Beta molecular sieve catalysts with significantly improved catalytic performance and compressive strength, making them suitable for industrial applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHENGDU ORGANIC CHEM CO LTD CHINESE ACAD OF SCI
- Filing Date
- 2026-03-16
- Publication Date
- 2026-06-30
AI Technical Summary
Existing technologies require secondary crystallization or the use of large amounts of template agents when preparing binder-free Beta molecular sieve catalysts, resulting in complex processes, high costs, large amounts of waste liquid, significant environmental pressure, and insufficient number of catalyst active centers.
A binder-free Beta molecular sieve catalyst was prepared by a dry gel method. The binder-free Beta molecular sieve was directly prepared through one-step crystallization and ion exchange. TEABr was used as a template agent to reduce the amount of template agent and water used. By combining pore-forming agents and binders, the silicon-aluminum ratio and crystallization conditions were optimized, and the process steps were simplified.
We have achieved the preparation of a high-efficiency, low-cost, and environmentally friendly binder-free Beta molecular sieve catalyst. The catalyst has high crystallinity, good compressive strength, and excellent catalytic performance, making it suitable for industrial applications. It also exhibits high conversion rate of paraformaldehyde and high product selectivity, as well as extended service life.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of catalytic chemistry, and more particularly to a method for preparing a binder-free Beta molecular sieve catalyst. Background Technology
[0002] Beta zeolite was first successfully synthesized by Mobil in 1967. It is a highly stacked defect chiral zeolite composed of both tetragonal and monoclinic crystal systems, exhibiting a three-dimensional interlocked twelve-membered ring channel structure, a stacking fault structure formed by the accumulation of two or three ordered structures, and numerous channel dislocations and structural vacancies. Due to its strong acidity and unique pore structure, Beta zeolite offers many advantages as a catalytic material in petrochemicals and has been widely used in various petroleum refining and petrochemical engineering processes. Its applications in alkylation, catalytic cracking, esterification, isomerization, disproportionation, reforming, and many other catalytic fields are extensive. Catalysts prepared using Beta zeolite as the active component have been successfully applied to the catalytic synthesis of PODE from paraformaldehyde and methyl acetal. n The process.
[0003] To meet the requirements of industrial applications, the conventional preparation method for Beta molecular sieves currently requires mixing the molecular sieve with additives such as binders to form a catalyst with a certain size, shape, and strength. However, the addition of binders further obscures the active sites of the molecular sieve and limits the content of the molecular sieve as the active component in the catalyst, generally below 80 wt%. Therefore, the number of active sites in commercially available, pre-formed Beta molecular sieve catalysts is far lower than that in unformed Beta molecular sieves.
[0004] Binder-free zeolite molecular sieves refer to zeolite particles that contain no inert binder or only a small amount of binder. They rely on the chemical bonds between zeolite crystals to form a self-supporting structure, have specific macroscopic shapes and sizes, rich pore structures, high zeolite content, and are free from the influence of binders, thus having broad application prospects in industrial catalysis.
[0005] Chinese patent application CN114433191A discloses a method for preparing a binder-free ZSM-5 type molecular sieve catalyst. The method involves mixing molecular sieve powder with sodium aluminate, silica sol, and sodium silicate to form a catalyst precursor. This precursor is then contacted with a solution containing an electrolyte, undergoing secondary crystallization, drying, and calcination, followed by ammonium exchange treatment to obtain a binder-free molecular sieve catalyst with high mechanical strength. The method requires 20%–80% molecular sieve powder and 80%–20% binder, necessitating the use of a large amount of molecular sieve seed crystals and secondary crystallization.
[0006] Chinese patent application CN105439164A discloses a method for preparing binder-free Beta molecular sieve catalysts. First, Beta molecular sieve powder is prepared. Then, 20-80% molecular sieve is used as seed crystals. Precursor molding materials containing sodium, silicon, and aluminum sources are hydrothermally crystallized in tetraethylammonium ion aqueous solution to convert them into binder-free Beta molding zeolite. The binder-free molecular sieve is prepared by a secondary crystallization method. However, the preparation process also requires secondary crystallization.
[0007] To address the aforementioned issue of requiring secondary crystallization, numerous improvements have been made in this field. For example, Chinese patent application CN107511171A, while eliminating the need for secondary crystallization, requires the prior synthesis of a "synthetic Beta molecular sieve." The Beta molecular sieve catalyst precursor contains 40-90% by weight of Beta molecular sieve, essentially a "high-proportion seed crystal + binder" system, resulting in high raw material costs. Furthermore, this report removes the binder (amorphous SiO2) using acidic or alkaline solutions (such as NaOH) (generating sodium silicate which dissolves in the waste liquid), only removing the binder without conversion, leading to low raw material utilization. Moreover, this report requires solid-liquid separation, generating saline industrial waste liquid, resulting in high subsequent treatment costs.
[0008] For example, Chinese patent application CN107512726A still requires the preparation of synthetic Beta molecular sieves first. This step involves crystallization at 150°C for 3 days, followed by the addition of a binder and a second silicon or aluminum source. The synthetic Beta molecular sieve content is 40-80% by weight, requiring crystallization at 150°C for 28 hours. It relies on the "synthetic Beta molecular sieve" as a basic raw material (40-80 wt% in the precursor), and requires the addition of a second silicon / aluminum source to adjust the silicon-aluminum ratio (20-100). This makes the raw material system complex and increases the difficulty of process control; in essence, it still requires secondary crystallization. Furthermore, this report describes liquid-phase crystallization, requiring filtration to separate the solid product, generating waste liquid containing template agents. The water consumption is 6-30 times that of SiO2, resulting in high pressure inside the reactor and a high risk of leakage. In addition, this report requires filtration and washing to separate the solid product after crystallization, which is time-consuming and results in product loss.
[0009] For example, Chinese patent application CN114471685A requires a template agent, silicon source, first aluminum source, amorphous SiO2, second aluminum source, and reinforcing agent. This results in a wide variety of raw materials, high costs, and poor industrial applicability. Furthermore, the application involves a six-step core process (preparation of mixture A → preparation of mixture B → molding → gas-solid phase conversion → washing → calcination → ammonium exchange). Preparation of mixture A requires pre-activation by stirring at 100-130℃ for 2-10 hours, crystal conversion requires 24-72 hours, and calcination at 500-600℃ for 4-8 hours, leading to high total energy consumption. In addition, the application adds a template agent before molding, and template agent vapor is still required for crystallization. After gas-solid phase conversion, washing to pH 7-8 is necessary, generating a large amount of waste liquid. Subsequent treatment requires neutralization and filtration, resulting in high environmental costs.
[0010] Therefore, how to provide a method for preparing binder-free Beta molecular sieve catalysts that is simple in process steps, low in cost, high in yield and with significant environmental benefits is a technical problem that urgently needs to be solved in this field. Summary of the Invention
[0011] The purpose of this invention is to provide a novel method for preparing binder-free Beta molecular sieve catalysts to solve the above-mentioned problems.
[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0013] A method for preparing a binderless Beta molecular sieve catalyst, comprising the following steps in sequence:
[0014] (1) Dry adhesive preparation: Add alkali source, silicon source and water to a container and stir, then add aluminum source, template agent and / or Beta molecular sieve seed crystals, stir evenly, and then dry to obtain precursor dry adhesive;
[0015] (2) Granulation: Grind the dry adhesive obtained in step (1), sieve it to obtain powder, then add pore-forming agent and binder, stir well and shape it, then cut it into granules and dry it;
[0016] (3) Molecular sieve crystallization: Weigh the dried particles from step (2), place them on a support, add water to the bottom of the hydrothermal crystallization kettle, place the support into the inner liner of the hydrothermal crystallization kettle, and crystallize; then wash with water, dry, and calcine to obtain binder-free Beta molecular sieve;
[0017] (4) Ion exchange: Weigh the binder-free Beta molecular sieve obtained in step (3) and put it into a container. Add hydrogen ion exchange solution to carry out ion exchange, and the product is obtained.
[0018] As a preferred technical solution, in step (1), the alkali source is selected from at least one of NaOH, KOH, and LiOH. The basic composition of the Beta molecular sieve used in this invention is (M).2 / n O·Al₂O₃·xSiO₂·pH₂O, where M represents a metal ion (e.g., Na₂O). + K + Ca 2+ Li + (e.g., the most basic structure of a molecular sieve framework is the SiO4 and AlO4 tetrahedron. Using other base sources, such as KOH, will only change the cations bonded to the framework. Considering factors such as raw material cost and the solubility product of the base, NaOH is generally the most commonly used base in the artificial synthesis of molecular sieves.)
[0019] The silicon source is selected from at least one of silica gel, silicic acid, silica sol, tetraethyl orthosilicate, and sodium silicate; the aluminum source is selected from at least one of sodium aluminate, boehmite, aluminum chloride, aluminum nitrate, and aluminum sulfate; the template agent is selected from one of TEAOH and TEABr; the added silicon source is calculated as SiO2, and the aluminum source is calculated as Al2O3, with a molar ratio of SiO2 to Al2O3 of 15–100; the molar ratio of template agent to SiO2 is 0.05–0.4; and the molar ratio of water to SiO2 is 4–20. When the molar ratio of SiO2 to Al2O3 is too low, the excessive Al content leads to numerous framework defects, decreased catalyst stability, and the inability of the molecular sieve to form an effective Beta molecular sieve crystal structure. When the ratio is too high, there are insufficient acidic sites, resulting in decreased catalytic performance of the molecular sieve catalyst and a significant reduction in TOX conversion. When the molar ratio of template agent to SiO2 is too low, the template guiding effect is insufficient, the molecular sieve crystal form is incomplete, and crystallinity may be reduced or impurities may appear. If the ratio is too high, excessive template agent will cause pore blockage and increase costs; if the water-to-SiO2 molar ratio is too low, the dry adhesive will lack moisture, resulting in incomplete crystallization. If the ratio is too high, it will resemble hydrothermal crystallization, leading to increased pressure inside the reactor and increased waste liquid volume.
[0020] As a further preferred technical solution, the alkali source is NaOH, the silicon source is silica gel, the aluminum source is sodium aluminate, and the template agent is TEABr.
[0021] Compared to the traditional TEAOH (tetraethylammonium hydroxide) template agent, the present invention preferably uses TEABr (tetraethylammonium bromide) as the template agent, which has advantages including at least the following: the amount of template agent itself can be reduced by 20% to 30%; the amount of water used at the bottom of the reactor can be reduced by 40% to 80%, thereby effectively reducing production costs and significantly reducing safety risks; therefore, the present invention prefers TEABr.
[0022] Compared with existing technologies, such as Example 13 of CN107511171A, where TEABr / SiO2 = 0.06 (molar ratio), and with SiO2 = 25g, the mass of TEABr is approximately 315g, which is 35 to 46 times that of the present invention.
[0023] For example, in Example 6 of CN107512726A, 2g of TEABr (99wt%) was added, corresponding to a total SiO2 content of ≈50g, and TEABr / SiO2 ≈4wt%, which is 2 to 3 times that of the present invention.
[0024] As a preferred technical solution, in step (1), the amount of Beta molecular sieve seed crystals added is calculated based on the proportion of Beta molecular sieve to the total mass of solid material during the molding process in step (2), and the proportion range is 0 to 5%; the amount of template agent added is calculated based on the TEAOH / SiO2 molar ratio, and the ratio range is 0.05 to 0.5:1.
[0025] It should be noted that this invention can be completely without seed crystals (i.e., 0% concentration). The reason is that the strong guiding effect of the vapor permeation of the template agent (such as TEABr) in the dry adhesive method, combined with an optimized silicon-aluminum source ratio, allows for the spontaneous formation of the Beta crystal form without seed induction. However, without seed crystals, the amount of template agent increases, resulting in a longer crystallization time.
[0026] As a preferred technical solution, in step (2), the pore-forming agent is selected from at least one of hydroxypropyl methylcellulose, methylcellulose, guar gum, polyethylene glycol, starch, and ammonium bicarbonate, more preferably hydroxypropyl methylcellulose; the binder is selected from at least one of silica sol, silane coupling agent, and boehmite.
[0027] In this invention, hydroxypropyl methylcellulose acts not only as a pore-forming agent but also as a plasticizer, aiding in catalyst extrusion molding. The aforementioned pore-forming agent decomposes and volatilizes during high-temperature calcination, leaving behind channels with uniform pore size, without affecting the molecular sieve framework structure. Among the optional binders, silane coupling agents can chemically connect dry adhesive particles, enhancing molding strength. Phobospore partially transforms into molecular sieve framework components during crystallization, acting as both a binder and reducing the overall silicon-to-aluminum ratio.
[0028] As a preferred technical solution, in step (2), the molding method is extrusion molding.
[0029] As a preferred technical solution, in step (3), the crystallization temperature is 130-170℃, preferably 150℃, the crystallization time is 1-5d, preferably 4d; the drying temperature is 40-100℃, the calcination temperature is 450-550℃, and the calcination time is 4h.
[0030] As a preferred technical solution, in step (4), the hydrogen ion exchange solution is selected from one of NH4NO3 solution, NH4Cl solution, and (NH4)2SO4 solution. All of the above solutions can provide NH4... +Among the various methods for achieving ion exchange, NH4Cl has the lowest cost (but chloride ions are not easily washed away), while (NH4)2SO4 has a higher exchange efficiency.
[0031] As a preferred technical solution, in step (4), the ion exchange temperature is 70-90℃, the time is 2-4h, and the process is carried out at a rotation speed of 60-100 r / min.
[0032] As a preferred technical solution, the water in steps (1) and (3) is deionized water.
[0033] Compared with the prior art, the advantages of the present invention are as follows:
[0034] (1) Compared with existing technologies (such as CN114433191A, CN107512726A, etc.), which require first synthesizing molecular sieve powder (more than 20% of seed crystals), then adding binder to form, and then secondary crystallization to obtain binder-free Beta molecular sieve catalyst, this invention directly uses silicon source and aluminum source as basic raw materials, without the need for the synthesis step of powder molecular sieve, and realizes the whole binder-free Beta molecular sieve catalyst from the raw material silicon source and aluminum source in one crystallization. It only requires dry glue preparation, forming, one-time crystallization, and ion exchange to complete the process. There is no pre-activation step, no need for precise temperature control and stirring, the process steps are significantly shortened, the crystallization time is short, the production efficiency is high, it is more conducive to industrial production, and the raw material cost is reduced by more than 50%.
[0035] (2) Compared with the existing technology (such as CN107511171A), which requires the removal of binder (amorphous SiO2) through acid and alkali solutions (such as NaOH) (generating sodium silicate dissolved in waste liquid), which only removes but does not transform, the present invention transforms binder (silica sol) into molecular sieve framework through dry glue method, with 100% raw material utilization and no waste;
[0036] (3) Compared with existing technologies (such as CN107511171A, CN107512726A, etc.), which require solid-liquid separation and washing, resulting in a large amount of waste liquid, high treatment costs, high environmental pressure and low product yield, the present invention directly dries and roasts after crystallization, without solid-liquid separation, only a small amount of water washing is required, the amount of waste liquid discharge is reduced by more than 80%, there is basically no environmental treatment cost, and the yield is increased to more than 95%;
[0037] (4) Traditional methods for preparing binder-free Beta molecular sieve catalysts generally use hydrothermal methods, which require a large amount of water to crystallize, resulting in high pressure inside the reactor and a large amount of organic template agent used. This invention uses a dry gel method, which reduces the amount of organic template agent used, eliminates the complicated steps of separating the product from the bottom liquid of the reactor, does not generate a large amount of waste liquid, is environmentally friendly, and has high operational safety.
[0038] (5) The catalyst prepared by this invention has a compressive strength of over 8.6 N / mm, which meets the requirements for catalysts in the synthesis of polyoxymethylene dimethyl ether from methyl acetal and trioxymethylene, and is suitable for large-scale industrial production; the obtained catalyst is used for the continuous fixed-bed catalytic synthesis of PODE. n The reaction yields a conversion rate of over 95% for trioxymethylene (TOX), producing PODE. 3-8 Selectivity can reach over 75%, and the product PODE 2-8 It has a selectivity of over 95%, with a selectivity of less than 5% for the byproduct methyl formate (MF), demonstrating excellent catalytic performance.
[0039] (6) Compared with the catalysts prepared by secondary crystallization and catalysts containing inert binders in the prior art, the molecular sieve catalyst prepared by the present invention has higher crystallinity, better compressive strength, and significantly improved strong acid content and weak acid content. The strong acid content can reach 0.46 mmol / g and the weak acid content can reach 0.26 mmol / g, which provides sufficient and efficient active sites for catalytic reaction and fundamentally improves the conversion efficiency of catalytic reaction.
[0040] (7) The binder-free Beta molecular sieve catalyst prepared by the present invention eliminates the surface defects introduced by the inert binder, significantly reduces the silanol groups on the surface of the molecular sieve, and significantly optimizes the surface hydrophobicity. The static contact angle can reach 35.79°, effectively reducing the negative impact of water on the catalytic reaction. It avoids water competing with reactants for adsorption acid active sites and can significantly inhibit the occurrence of water-mediated methyl formate (MF) side reaction, greatly improving the water tolerance of the catalyst. Even if the water content in the raw material increases from 0.05wt% to 3.20wt%, the conversion rate of paraformaldehyde only decreases by 10.3%, which is far better than the 39.4% decrease of traditional binder-containing catalysts. It has extremely strong adaptability in industrial water-containing raw material systems.
[0041] (8) This invention achieves synergistic optimization of acid site density, hydrophobicity and catalytic performance. High acid content provides sufficient active centers for the reaction, and excellent hydrophobicity ensures high conversion and high selectivity of the reaction under aqueous conditions. At the same time, combined with the structural advantages of high crystallinity and high compressive strength, the service life of the catalyst is extended to 1200h, which is much higher than the 800h of traditional binder-containing catalysts, further reducing the overall cost of industrial applications. Attached Figure Description
[0042] Figure 1 The XRD patterns of the catalysts prepared in Example 1, Comparative Examples 1 and 2 are shown below.
[0043] Figure 2 The NH3-TPD spectra of the catalysts prepared in Example 1, Comparative Examples 1 and 2 are shown.
[0044] Figure 3 Static contact angle photographs of the catalysts prepared in Example 1, Comparative Examples 1 and 2. Detailed Implementation
[0045] To explain the technical content, objectives, and effects of the present invention in detail, the following specific embodiments are provided to further illustrate the content of the present invention. However, the content of the present invention is far more than the following examples.
[0046] It should be noted that, unless otherwise specified, all raw materials and reagents used in the following examples are commercially available.
[0047] The "Beta molecular sieve seed crystal" mentioned in this invention refers to the finished molecular sieve powder synthesized by the hydrothermal crystallization method well known in the art, with a particle size range of 1 to 10 μm, which serves as a nucleus for crystal growth.
[0048] The compressive strength test method of the following embodiments: referring to GB / T 44750-2024 "Measurement of compressive strength of particles", the radial compressive strength of 2mm×1mm cylindrical particles was measured using a ZQJ-Ⅲ intelligent particle strength testing machine (Dalian Intelligent Testing Machine Factory), and the average value of 10 tests was taken.
[0049] The catalysts prepared in the following examples are used for catalytic reactions, as detailed below:
[0050] The catalytic reaction in a fixed-bed reactor employs a trickle-bed reaction mode. The reactor has an inner diameter of 20 mm, a isothermal zone length of 80 mm, and a volume of 25 mL. The catalyst is loaded within the isothermal zone, with 15 mL of catalyst and a bed height of 50 mm. Quartz sand is packed both above and below the catalyst bed. The molar ratio of the reactants, dimethyl acetal (DMM), trioxymethylene (TOX), and water, is 1:1.2:0.06. Before the reaction begins, the reactor is purged with N2 six times, followed by the injection of N2 into the fixed bed at a pressure of 1 MPa and a space velocity (h⁻¹). -1 The temperature was increased to 75℃, and after the temperature stabilized, the reaction solution was pumped in at a rate of 1.25 mL / min. The reaction was carried out at this constant temperature for 8 hours. The moisture content of the raw materials and products was determined by the Karl Fischer method using a ZDY-504 moisture analyzer from Leici Co., Ltd.
[0051] Formaldehyde content was determined using the method specified in the national standard for industrial formaldehyde solution (GB / T 9009-2011). The analytical procedure is as follows: Formaldehyde analysis was performed using the sodium sulfite titration method. Using thymolphthalein as an indicator, a certain amount of formaldehyde reacted with excess sodium sulfite solution (1.0 mol / L), and titrated with sulfuric acid of known concentration (0.5 mol / L). The mass fraction of formaldehyde was calculated based on the amount of sulfuric acid consumed.
[0052] TOX, DMM, MeOH, MF, HF n (n≤2) and all PODEs n (2≤n≤10) The determination was performed using an Agilent GC-7890B gas chromatograph (GC). The chromatogram was equipped with a flame ionization detector (FID), an HP-1 quartz capillary column (30 mm × 0.32 mm × 0.25 μm), and nitrogen as the carrier gas. The detector temperature was 300 °C, the injection port temperature was 280 °C, and the column temperature program was as follows: initial temperature 40 °C, hold for 5.8 min, then at 30 °C / min. -1 The temperature was increased to 250°C at a rate of 100°C and held for 5.8 minutes.
[0053] TOX conversion rate X TOX The calculation formula is as follows:
[0054]
[0055] Product PODE 2-10 The selectivity calculation formula for MF is as follows:
[0056]
[0057]
[0058]
[0059] Example 1
[0060] A binder-free Beta molecular sieve catalyst is prepared by the following steps:
[0061] (1) Preparation of dry gel: 1.35g of solid NaOH, 25.0g of 100-200 mesh silica gel and 47.16g of deionized water were added to a 250mL beaker and stirred for 0.5h. Then, 6.0g of NaAlO2 solution (of which Na2O accounts for 18.59wt.% and Al2O3 accounts for 15.68wt.%), 1.91g of Beta molecular sieve seed crystals and 39.13g of 25%wt.TEAOH solution were added and stirred for 4h. The solution was poured onto a watch glass and dried at 60℃ for 24h to obtain the precursor dry gel.
[0062] (2) Granulation: The precursor dry gel obtained in step (1) is ground and sieved through a 100-mesh sieve to obtain 44.88g of powder. It is then transferred to a kneader, 1.91g of hydroxypropyl methylcellulose is added, and 27.27g of 30wt.% silica sol is added dropwise. After stirring, it is extruded into shape using an extruder. After drying slightly, it is cut into cylindrical granules of about 2mm. It is then dried at 40℃ for 12h.
[0063] (3) Molecular sieve crystallization: Weigh 10.0g of the cylindrical particles dried in step (2), place them on a stainless steel support, add 20.0g of deionized water to the bottom of the hydrothermal crystallization kettle, place the stainless steel support into the inner liner of the crystallization kettle, and crystallize at 150℃ for 4d; after washing the particles with water, dry them at 110℃ for 12h, and calcine them at 550℃ for 4h; obtain binder-free Beta molecular sieve;
[0064] (4) Ion exchange: Weigh 5.0 g of the binderless Beta molecular sieve obtained in step (3) into a three-necked flask, add 50 g of 1 mol / L NH4NO3 solution, and exchange at 80℃ and 80 r / min for 3 h to obtain H-type molecular sieve particles, i.e., binderless Beta molecular sieve catalyst A. It should be noted that H-type here refers to free cations such as Na in the molecular sieve. + K + After ion exchange with ammonia solution, it is calcined to form H + Therefore, it is called H-type or hydrogen type.
[0065] The total solid mass of the raw materials used in this embodiment is as follows: 44.88g of powder after grinding and sieving the dry glue in step (1), minus 39.13g × 25% = 9.78g of TEAOH template agent in the dry glue, the effective solid mass of the powder after sieving the dry glue is 35.10g; the solid content of the added binder (30wt% silica sol) is 27.27g × 30% = 8.18g; the total is 35.10g + 8.18g = 43.28g. The final mass of the molecular sieve catalyst is 39.14g. The overall yield is (39.14g ÷ 43.2785g) × 100% ≈ 90.44% (wherein the template agent and pore-forming agent are removed by calcination at 550℃ to become H2O and CO2, respectively, and are not included in the effective solid mass, most of which are lost during kneading and extrusion).
[0066] The XRD pattern of the obtained catalyst A is as follows: Figure 1 As shown, from Figure 1 As can be seen, characteristic diffraction peaks belonging to Beta zeolite are present without other impurity peaks, indicating that the prepared Beta zeolite catalyst has a pure phase structure. The characteristic diffraction peaks of pure phase Beta zeolite (2θ=7.8°, 13.5°, 22.5°, 25.7°, 27.8°) are clear, without impurity peaks (such as the broad peak of amorphous SiO2). The NH3-TPD spectrum is shown below. Figure 2 As shown, the weak acid has a capacitance of 0.46 mmol / g, and the strong acid has a capacitance of 0.26 mmol / g. Static contact angle photographs are shown below. Figure 3 As shown, the contact angle is 35.79°.
[0067] The compressive strength test result of catalyst A obtained in this embodiment is 8.61 N / mm.
[0068] It should be noted that the catalyst of this invention is used in fixed-bed PODE. n The synthesized catalyst (reaction pressure 1 MPa) has a strength of 8.61 N / mm (i.e., 86.1 N / cm), which meets the requirements for industrial use. The strength is mainly determined by the amount of binder used during molding (silica sol accounting for 15-20 wt%) and the calcination temperature (550℃). Existing technologies (such as CN114471685A) for catalysts used in high-pressure applications such as heavy oil catalysis require even higher strength.
[0069] The unbound Beta molecular sieve catalyst A obtained in this embodiment was used for the aforementioned continuous fixed-bed catalytic synthesis of PODE. n The reaction and results showed that the conversion rate of trioxymethylene (TOX) was 94.90%, and the product PODE was obtained. 2-8 The selectivity reached 97.11%, and the selectivity of the byproduct methyl formate (MF) was 0.52%.
[0070] Example 2
[0071] A binder-free Beta molecular sieve catalyst is prepared by the following steps:
[0072] (1) Preparation of dry adhesive: Weigh 4.03g of solid NaOH and 1.85g of boehmite, add 139g of deionized water and stir for 30min; add 160.4g of 30wt.% silica sol and stir for 1h; add 65wt.% HNO3 solution dropwise until the solution pH=9.89, age in a water bath at 80℃ for 8h, and dry at 120℃ for 12h to obtain silica-alumina dry adhesive;
[0073] (2) Granule molding: Grind the above-mentioned dry adhesive and sieve it through a 100-mesh sieve to obtain 64.86g of powder. Transfer it to a kneader, add 3.24g of hydroxypropyl methylcellulose, 3.24g of Beta molecular sieve seed crystals, and 25.35g of TEABr. After stirring, add 42.81g of water and extrude it into shape using an extruder. After slightly drying, cut it into cylindrical granules of about 2mm. Dry it at 50℃ for 12h.
[0074] It should be noted that the template agent (TEAOH / TEABr) and seed crystals can be added during the dry adhesive preparation or particle molding stage, both of which can achieve crystallization guidance. In Example 1, TEAOH (solution) was added during dry adhesive preparation to ensure uniform dispersion; in Example 2, TEABr (solid powder) was added during molding and could still exert its effect through vapor permeation. Neither method affected the performance of the final product.
[0075] (3) Molecular sieve crystallization: Weigh 7.08g of the above particles, place them on a stainless steel support, add 19.66g of deionized water to the bottom of the hydrothermal crystallization kettle, put the support into the inner liner of the crystallization kettle, and crystallize at 150℃ for 3d; after washing the particles with water, dry them at 110℃ for 2h, and calcine them at 550℃ for 4h to obtain binder-free Beta molecular sieve.
[0076] (4) Ion exchange: Weigh 14.85g of the molecular sieve obtained in step (3) into a three-necked flask, add 148.50g of 1mol / L NH4NO3 solution, exchange at 80℃ and 80r / min for 3h, dry at 110℃ for 2h, and calcine at 550℃ for 2h to obtain binder-free Beta molecular sieve catalyst B.
[0077] The overall yield of catalyst B in this embodiment is 91.51%, and the compressive strength test result of catalyst B obtained in this embodiment is 7.49 N / mm.
[0078] The binderless Beta molecular sieve catalyst B obtained in this embodiment was used for the continuous fixed-bed catalytic synthesis of PODE. n The reaction and results showed that the conversion rate of trioxymethylene (TOX) was 93.51%, and the product was PODE. 2-8 The selectivity reached 93.43%, while the selectivity of the byproduct methyl formate (MF) was 0.47%.
[0079] Examples 3 to 12 below are all based on Example 2, with only a single variable (crystallization temperature, time, molar ratio, etc.) changed.
[0080] Example 3
[0081] Compared with Example 2, this embodiment only changes the crystallization temperature of step (3) to 130°C, while keeping other conditions unchanged, to obtain the unbonded Beta molecular sieve catalyst C;
[0082] The overall yield of catalyst C in this embodiment is 88.16%, and the compressive strength test result of catalyst C obtained in this embodiment is 6.23 N / mm.
[0083] The resulting unbound Beta molecular sieve catalyst C underwent the same catalytic reaction as in Example 2, with the following results: TOX conversion of 92.59% and PODE... 2-8 Selectivity was 96.82%, and MF selectivity was 1.57%.
[0084] Example 4
[0085] Compared with Example 2, this embodiment only changes the crystallization temperature of step (3) to 170°C, while keeping other conditions unchanged, to obtain the unbonded Beta molecular sieve catalyst D;
[0086] The overall yield of catalyst D in this embodiment is 88.47%, and the compressive strength test result of catalyst D obtained in this embodiment is 7.85 N / mm.
[0087] The resulting unbound Beta molecular sieve catalyst D was subjected to the same catalytic reaction as in Example 2, with the following results: TOX conversion of 95.53% and PODE... 2-8 Selectivity was 93.19%, and MF selectivity was 5.29%.
[0088] Example 5
[0089] Compared with Example 2, this embodiment only differs in that the crystallization time in step (3) is 1 day, while other conditions remain unchanged, resulting in a non-bonded Beta molecular sieve catalyst E.
[0090] The overall yield of catalyst E in this embodiment is 91.94%, and the compressive strength test result of catalyst E obtained in this embodiment is 4.13 N / mm.
[0091] The resulting unbound Beta molecular sieve catalyst E was subjected to the same catalytic reaction as in Example 2, with the following results: TOX conversion of 85.45% and PODE... 2-8 Selectivity was 97.53%, and MF selectivity was 1.36%.
[0092] Example 6
[0093] Compared with Example 2, this embodiment only differs in that the crystallization time in step (3) is 5 days, while other conditions remain unchanged, resulting in a non-binding Beta molecular sieve catalyst F;
[0094] The overall yield of catalyst F in this embodiment is 90.62%, and the compressive strength test result of catalyst F obtained in this embodiment is 8.53 N / mm.
[0095] The resulting unbound Beta molecular sieve catalyst F was subjected to the same catalytic reaction as in Example 2, with the following results: TOX conversion of 93.18% and PODE... 2-8 Selectivity was 97.16%, and MF selectivity was 1.26%.
[0096] Example 7
[0097] Compared with Example 2, this embodiment only differs in that the SiO2 / Al2O3 ratio in step (1) is 15 by molar ratio, while other conditions remain unchanged, resulting in a non-bonded Beta molecular sieve catalyst G.
[0098] The overall yield of catalyst G in this embodiment is 91.48%, and the compressive strength test result of catalyst G obtained in this embodiment is 6.85 N / mm.
[0099] The resulting unbound Beta molecular sieve catalyst G was subjected to the same catalytic reaction as in Example 2, with the following results: TOX conversion of 94.15% and PODE... 2-8 Selectivity was 95.42%, and MF selectivity was 3.14%.
[0100] Example 8
[0101] Compared with Example 2, this embodiment only differs in that SiO2 / Al2O3 = 100 in step (1) using a molar ratio, while other conditions remain unchanged, resulting in a non-bonded Beta molecular sieve catalyst H.
[0102] The overall yield of catalyst H in this embodiment is 91.10%, and the compressive strength test result of catalyst H obtained in this embodiment is 8.47 N / mm.
[0103] The obtained unbound Beta molecular sieve catalyst H was subjected to the same catalytic reaction as in Example 2, and the results showed a TOX conversion of 84.41% and a PODE conversion of [missing information]. 2-8 Selectivity was 89.52%, and MF selectivity was 0.84%.
[0104] Example 9
[0105] Compared with Example 2, this embodiment only differs in that the TEAOH / SiO2 ratio in step (2) is 0.05 using a molar ratio meter, while other conditions remain unchanged, resulting in a non-binding Beta molecular sieve catalyst I.
[0106] The overall yield of catalyst I in this embodiment is 85.13%, and the compressive strength test result of catalyst I obtained in this embodiment is 3.21 N / mm.
[0107] The resulting unbound Beta molecular sieve catalyst I was subjected to the same catalytic reaction as in Example 2, and the results showed a TOX conversion of 90.3% and a PODE conversion of 100%. 2-8 Selectivity was 96.2%, and MF selectivity was 1.89%.
[0108] Example 10
[0109] Compared with Example 2, this embodiment only differs in that the TEAOH / SiO2 ratio in step (2) is 0.4 using a molar ratio meter, while other conditions remain unchanged, resulting in a non-binding Beta molecular sieve catalyst J.
[0110] The overall yield of catalyst J in this embodiment is 87.51%, and the compressive strength test result of catalyst J obtained in this embodiment is 9.15 N / mm.
[0111] The resulting unbound Beta molecular sieve catalyst J underwent the same catalytic reaction as in Example 2, with the following results: TOX conversion of 94.7% and PODE... 2-8 Selectivity was 92.8%, and MF selectivity was 4.95%.
[0112] Example 11
[0113] Compared with Example 2, this embodiment only differs in that the H2O / SiO2 ratio in step (1) is 4 using a molar ratio meter, while other conditions remain unchanged, resulting in a non-bonded Beta molecular sieve catalyst K.
[0114] The overall yield of catalyst K in this embodiment is 88.82%, and the compressive strength test result of catalyst K obtained in this embodiment is 6.73 N / mm.
[0115] The resulting unbound Beta molecular sieve catalyst K was subjected to the same catalytic reaction as in Example 2, with the following results: TOX conversion of 91.2% and PODE... 2-8 Selectivity was 97.0%, and MF selectivity was 1.43%.
[0116] Example 12
[0117] Compared with Example 2, this embodiment only differs in that the H2O / SiO2 ratio in step (1) is 20 using a molar ratio meter, while other conditions remain unchanged, resulting in a non-bonded Beta molecular sieve catalyst L.
[0118] The overall yield of catalyst L in this embodiment is 92.59%, and the compressive strength test result of catalyst L obtained in this embodiment is 7.22 N / mm.
[0119] The resulting unbound Beta molecular sieve catalyst L was subjected to the same catalytic reaction as in Example 2, and the results showed a TOX conversion of 93.5% and a PODE conversion of 100%. 2-8 Selectivity was 94.6%, and MF selectivity was 2.78%.
[0120] Comparative Example 1
[0121] This comparative example demonstrates the preparation of binder-free Beta molecular sieve catalysts via a binder conversion method. Traditional Beta molecular sieve moldings containing inert binders are used as precursors, and hydrothermal crystallization is employed to convert the binder into the molecular sieve framework. This serves as a comparative sample for the binder-free catalyst of this invention. The specific preparation method includes the following steps:
[0122] (1) Particle molding: Weigh 25.0g of Beta molecular sieve powder (SiO2 / Al2O3=60) and 1.91g of hydroxypropyl methylcellulose, transfer them to a kneader, add 27.27g of 30wt.% silica sol, add an appropriate amount of deionized water until the mixture is in a uniform plastic state, stir well and then extrude it into shape using an extruder; after slightly drying, cut it into cylindrical particles of about 2mm, and dry them at 40℃ for 12h to obtain the Beta molecular sieve molding precursor containing an inert binder;
[0123] (2) Hydrothermal crystallization: Weigh 10.0g of the precursor particles dried in step (1), place them on a stainless steel support, add 20.0g of deionized water to the bottom of the hydrothermal crystallization kettle, place the stainless steel support into the inner liner of the crystallization kettle, and crystallize at 150℃ for 4d; after washing the particles with water, dry them at 110℃ for 12h, and calcine them at 550℃ for 4h to realize the conversion of silica sol binder to Beta molecular sieve framework, and obtain binder-converted binder-free Beta molecular sieve;
[0124] (3) Ion exchange: Weigh 5.0g of the binderless Beta molecular sieve obtained in step (2) into a three-necked flask, add 50g of 1mol / L NH4NO3 solution, and stir at 80℃ and 80r / min for 3h to obtain H-type molecular sieve particles, namely binder-converted binderless Beta molecular sieve catalyst M.
[0125] The XRD pattern of the obtained catalyst M is as follows: Figure 1 As shown, from Figure 1 As can be seen, characteristic diffraction peaks belonging to Beta zeolite were observed without any other impurity peaks, indicating that the prepared Beta zeolite catalyst has a pure phase structure. The NH3-TPD spectrum is shown below. Figure 2 As shown, the weak acid has a concentration of 0.34 mmol / g, and the strong acid has a concentration of 0.16 mmol / g. Static contact angle photographs are shown below. Figure 3 As shown, the contact angle is 20.07°.
[0126] The compressive strength test result of catalyst M obtained in this comparative example is 7.43 N / mm.
[0127] The obtained unbound Beta molecular sieve catalyst M was subjected to the same catalytic reaction as in Example 1, and the results showed that the conversion rate of trioxymethylene (TOX) was 89.21%, and the product PODE... 2-8 The selectivity reached 95.80%, and the selectivity of the byproduct methyl formate (MF) was 1.39%.
[0128] Comparative Example 2
[0129] This comparative example is a conventional method for preparing Beta molecular sieve catalysts using an inert binder. It eliminates the crystallization / binder conversion step, directly using molecular sieve powder as raw material and adding a binder for molding. It serves as a comparison sample for the binder-free catalyst of this invention. The specific preparation method includes the following steps:
[0130] (1) Granule molding: Weigh 25.0g of Beta molecular sieve powder (SiO2 / Al2O3=60) and 1.91g of hydroxypropyl methylcellulose, and transfer them together into a kneader. Add 27.27g of 30wt.% silica sol dropwise while adding deionized water and kneading until the mixture forms a uniform plastic paste. After stirring, extrude it into shape using an extruder. After drying slightly, cut it into cylindrical granules of about 2mm and dry them at 40℃ for 12h.
[0131] (2) Calcination and impurity removal: The cylindrical particles dried in step (1) are placed directly in a muffle furnace and calcined at 550°C for 4 hours to remove the pore-forming agent hydroxypropyl methylcellulose, thereby obtaining Beta molecular sieve shaped particles containing inert silica sol binder.
[0132] (3) Ion exchange: Weigh 5.0g of the molecular sieve shaped particles obtained in step (2) into a three-necked flask, add 50g of 1mol / L NH4NO3 solution, and perform ion exchange for 3h at 80℃ and magnetic stirring speed of 80r / min. After the exchange is completed, filter and dry to obtain H-type molecular sieve particles, namely the traditional molecular sieve catalyst N containing inert binder Beta.
[0133] The XRD pattern of the obtained catalyst N is as follows: Figure 1 As shown, from Figure 1 As can be seen, characteristic diffraction peaks belonging to Beta zeolite were observed without any other impurity peaks, indicating that the prepared Beta zeolite catalyst has a pure phase structure. The NH3-TPD spectrum is shown below. Figure 2 As shown, the weak acid has a concentration of 0.15 mmol / g, and the strong acid has a concentration of 0.07 mmol / g. Static contact angle photographs are shown below. Figure 3 As shown, the contact angle is 13.87°.
[0134] The compressive strength test result of catalyst N obtained in this comparative example is 5.18 N / mm.
[0135] The obtained unbound Beta molecular sieve catalyst N was subjected to the same catalytic reaction as in Example 1, and the results showed that the conversion rate of trioxymethylene (TOX) was 76.951%, and the product PODE... 2-8 The selectivity reached 96.17%, and the selectivity of the byproduct methyl formate (MF) was 1.83%.
[0136] Compared with traditional catalytic PODE n Compared to Beta molecular sieve catalysts (containing inert binders and secondary crystallization): the catalyst of this invention improves TOX conversion by 5-8% and PODE... 2-8 The selectivity is improved by 8-12%, the selectivity of byproduct MF is reduced by 50%, and the service life is extended to 1200h (compared to 800h for traditional catalysts).
[0137] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing a binder-free Beta molecular sieve catalyst, characterized in that, The steps are as follows: (1) Dry adhesive preparation: Add alkali source, silicon source and water to a container and stir, then add aluminum source, template agent and / or Beta molecular sieve seed crystals, stir evenly, and then dry to obtain precursor dry adhesive; (2) Granulation: Grind the dry adhesive obtained in step (1), sieve it to obtain powder, then add pore-forming agent and binder, stir well and shape it, then cut it into granules and dry it; (3) Molecular sieve crystallization: Weigh the dried particles from step (2), place them on a support, add water to the bottom of the hydrothermal crystallization kettle, place the support into the inner liner of the hydrothermal crystallization kettle, and crystallize; then wash with water, dry, and calcine to obtain binder-free Beta molecular sieve; (4) Ion exchange: Weigh the binder-free Beta molecular sieve obtained in step (3) and put it into a container. Add hydrogen ion exchange solution to carry out ion exchange, and the product is obtained.
2. The method for preparing the binderless Beta molecular sieve catalyst according to claim 1, characterized in that, In step (1), the alkali source is selected from at least one of NaOH, KOH, and LiOH; the silicon source is selected from at least one of silica gel, silicic acid, silica sol, tetraethyl orthosilicate, and sodium silicate; the aluminum source is selected from at least one of sodium aluminate, boehmite, aluminum chloride, aluminum nitrate, and aluminum sulfate; the template agent is selected from one of TEAOH and TEABr; the added silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, the molar ratio of SiO2 to Al2O3 is 15 to 100; the molar ratio of template agent to SiO2 is 0.05 to 0.4; and the molar ratio of water to SiO2 is 4 to 20.
3. The method for preparing the binderless Beta molecular sieve catalyst according to claim 2, characterized in that, The alkali source is NaOH, the silicon source is silica gel, the aluminum source is sodium aluminate, and the template agent is TEABr.
4. The method for preparing the binderless Beta molecular sieve catalyst according to claim 1, characterized in that, In step (1), the amount of Beta molecular sieve seed crystals added is calculated based on the proportion of Beta molecular sieve to the total mass of solid material during the molding process in step (2), and the proportion range is 0 to 5%; the amount of template agent added is calculated based on the TEAOH / SiO2 molar ratio, and the ratio range is 0.05 to 0.5:
1.
5. The method for preparing the binderless Beta molecular sieve catalyst according to claim 1, characterized in that, In step (2), the pore-forming agent is selected from at least one of hydroxypropyl methylcellulose, methylcellulose, guar gum, polyethylene glycol, starch, and ammonium bicarbonate, more preferably hydroxypropyl methylcellulose; the binder is selected from at least one of silica sol, silane coupling agent, and boehmite.
6. The method for preparing the binderless Beta molecular sieve catalyst according to claim 1, characterized in that, In step (2), the molding method is extrusion molding.
7. The method for preparing the binderless Beta molecular sieve catalyst according to claim 1, characterized in that, In step (3), the crystallization temperature is 130-170℃, preferably 150℃, and the crystallization time is 1-5 days, preferably 4 days; the drying temperature is 40-100℃, the calcination temperature is 450-550℃, and the calcination time is 4 hours.
8. The method for preparing the binderless Beta molecular sieve catalyst according to claim 1, characterized in that, In step (4), the hydrogen ion exchange solution is selected from one of NH4NO3 solution, NH4Cl solution, and (NH4)2SO4 solution.
9. The method for preparing the binderless Beta molecular sieve catalyst according to claim 1, characterized in that, In step (4), the ion exchange temperature is 70-90℃, the time is 2-4h, and the rotation speed is 60-100 r / min.
10. The method for preparing the binderless Beta molecular sieve catalyst according to claim 1, characterized in that, The water used in steps (1) and (3) is deionized water.