A method for preparing and applying a high-strength sheet-like S-1 molecular sieve microsphere catalyst
By using a silica sol-zirconia composite binder and boron-pretreated sheet-like S-1 molecular sieve, the problems of catalyst mechanical strength and selectivity were solved, and a high-strength and high-selectivity catalyst suitable for industrial fluidized bed reactions was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG HENGYI PETROCHEMICAL RES INST CO LTD
- Filing Date
- 2026-02-13
- Publication Date
- 2026-07-31
AI Technical Summary
Existing layered S-1 molecular sieve catalysts have insufficient mechanical strength in gas-phase Beckmann rearrangement reactions, which cannot meet the requirements of long-term, high-intensity industrial fluidized bed operation. Furthermore, traditional silica sol binders lead to a decrease in the concentration of silanol clusters at active centers, resulting in reduced catalytic selectivity.
A layered S-1 molecular sieve was prepared by hydrothermal crystallization using a silica sol-zirconia composite binder. Combined with boron-containing additive pretreatment and spray drying molding, the content of terminal silanol groups was reduced, thereby improving mechanical strength and catalytic selectivity.
It significantly improves the mechanical strength and catalytic selectivity of the catalyst, reduces the wear index to below 1.0%, maintains caprolactam selectivity of 95.0% or higher, and is suitable for long-term, high-intensity industrial fluidized bed operation.
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Figure CN122479792A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the technical field of molecular sieve preparation, and in particular to a method for preparing and applying a high-strength sheet-like S-1 molecular sieve microsphere catalyst. Background Technology
[0002] In the synthesis of caprolactam, the Beckmann rearrangement of cyclohexanone oxime is an indispensable core step. Currently, the liquid-phase Beckmann rearrangement process is the most widely used in industrial production. This process uses concentrated sulfuric acid as both a catalyst and a reaction medium. While it offers advantages such as mild reaction conditions and high product yields, it also has several significant problems: it produces large amounts of ammonium sulfate as a byproduct, causes severe equipment corrosion, and carries potential environmental pollution risks. In contrast, the gas-phase Beckmann rearrangement process uses a solid acid as a catalyst, directly converting gaseous cyclohexanone oxime into caprolactam. This process boasts significant advantages such as high atom economy, no equipment corrosion risks, and no ammonium sulfate byproduct, thus it is widely recognized as a green alternative to the traditional liquid-phase process. Among various solid acid catalysts, the high-silica MFI molecular sieve Silicalite-1 (S-1) is considered the catalyst with the greatest potential for industrial application due to its superior catalytic performance.
[0003] The layered S-1 molecular sieve disclosed in patent CN117380249A exhibits excellent mass transfer performance and abundant silanol nests due to its unique nanosheet structure, demonstrating good catalytic performance. However, to achieve industrial applications of gas-phase Beckmann rearrangement, the molecular sieve catalyst must undergo shaping to meet the mechanical strength and hydrodynamic performance requirements of fluidized bed or fixed bed reactors. Traditional silica sol bonding molding introduces a large number of terminal silanol groups, leading to a decrease in the concentration of active center silanol nests, which in turn causes a reduction in catalyst selectivity, while also resulting in insufficient mechanical strength. To address these issues, various technologies have been explored in this field. For example, patent EP576295 prepares molecular sieve microspheres through binderless spray drying combined with hydrothermal treatment, but the resulting product has insufficient mechanical strength and is not suitable for long-term operation in fluidized bed reactors.
[0004] Therefore, it is necessary to develop a new molding technology that, while retaining the high selectivity of the S-1 molecular sieve, significantly enhances the mechanical strength of the catalyst by improving the binder system, thereby obtaining a catalyst with superior overall performance and more suitable for long-term operation in industrial fluidized beds. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention provides a method for preparing and applying a high-strength sheet-like S-1 molecular sieve microsphere catalyst. By employing a silica sol-zirconia composite binder, not only can a relatively low content of terminal silanol groups be ensured and high caprolactam selectivity be maintained, but the mechanical strength of the sheet-like S-1 molecular sieve catalyst can also be significantly improved, thus enabling it to better adapt to long-cycle, high-intensity industrial fluidized bed operation.
[0006] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for preparing a high-strength sheet-like S-1 molecular sieve microsphere catalyst, comprising the following steps: S1. Layered S-1 molecular sieves were prepared by hydrothermal crystallization to obtain crystallized molecular sieve slurry. S2. The boron-containing additive is mixed with the molecular sieve slurry, dried, and then calcined for the first time to obtain the pretreated molecular sieve raw powder. S3. Mix the pretreated molecular sieve powder, silica sol-zirconia composite binder and water, grind and adjust the pH to 3-6 to obtain a slurry; S4. After spray drying and second calcination, the slurry is washed with an acidic solution and then dried to obtain the layered S-1 molecular sieve microsphere catalyst.
[0007] This invention improves the catalytic selectivity of the S-1 molecular sieve catalyst in the gas-phase Beckmann rearrangement of cyclohexanone oxime by pretreating the molecular sieve powder with boron-containing additives, thereby reducing the content of terminal hydroxyl groups. However, its mechanical properties (wear index of approximately 1.5%-2.0%) still have room for further improvement under long-term, high-intensity industrial fluidized bed operation. Therefore, this invention employs a silica sol-zirconia composite binder, which not only ensures a low relative content of terminal silanol groups and maintains high caprolactam selectivity, but also significantly enhances the mechanical strength of the catalyst, thus making it better suited for long-term, high-intensity industrial fluidized bed operation.
[0008] Preferably, in S1, the hydrothermal crystallization method includes the following steps: mixing a silicon source, an amide compound, an organic template agent, and water to obtain a colloidal mixture; and subjecting the colloidal mixture to hydrothermal crystallization to obtain a crystallized molecular sieve slurry.
[0009] Preferably, in S2, the boron-containing additive is at least one selected from boron oxide, boric acid, metaboric acid, ammonium borate, phenylboronic acid, trimethyl borate, and triethyl borate; the amount of the boron-containing additive added is calculated based on the mass of boron oxide accounting for 1.6-12.8% of the dry molecular sieve mass in the molecular sieve slurry.
[0010] Preferably, in S2, the temperature of the first calcination is 400-600℃ and the time is 6-10 h.
[0011] Preferably, in S3, the mass ratio of the silica sol-zirconia composite binder, based on oxides, is SiO2:ZrO2 = 1:(0.05-0.2), more preferably, SiO2:ZrO2 = 1:(0.08-0.15).
[0012] The choice of components in composite binders has a significant impact on reaction selectivity, and the ratio of SiO2 to ZrO2 also affects reaction selectivity. The addition of zirconium oxide to composite binders can improve reaction selectivity and mechanical properties, but excessive addition can also have an adverse effect on reaction selectivity.
[0013] Preferably, in S3, the silica sol-zirconia composite binder is a mixture of silica sol and zirconia source, wherein the silica sol is alkaline, neutral or acidic silica sol, and the zirconia source is at least one of nano zirconia sol and ammonium zirconium carbonate.
[0014] Preferably, in step S3, the pH is adjusted to 3-4; the solution used for adjusting the pH is a solution of nitric acid, acetic acid, oxalic acid, or citric acid.
[0015] Preferably, in S3, the solid particle size D50 in the slurry is not greater than 50 µm; and the viscosity of the slurry is 100-600 mPa•s.
[0016] Preferably, in S4, the atomizing disc of the spray dryer rotates at a speed of 100-300 r / min, has an inlet temperature of 200-400℃, and an outlet temperature of 100-250℃. More preferably, the atomizing disc rotates at a speed of 150-200 r / min, has an inlet temperature of 250-300℃, and an outlet temperature of 120-180℃.
[0017] Preferably, in step S4, the temperature of the second roasting is 430-550℃ and the time is 3-12 h; more preferably, the temperature of the second roasting is 450-500℃ and the time is 4-8 h.
[0018] Preferably, in step S4, the liquid-to-solid mass ratio used for washing is 5:1-20:1, the washing temperature is 25-80℃, the washing time for a single wash is 4-10 h, and the number of washes is 3-5 times; the washing solution used for washing is an acid solution with a concentration of no more than 3.0 mol / L, more preferably, the washing solution is an acid solution with a concentration of no more than 1.0 mol / L; the acid solution includes nitric acid, acetic acid, hydrochloric acid, or citric acid solution.
[0019] Preferably, in step S4, the washing is performed until the residual boron content in the catalyst is 100-1000 ppm; more preferably, the washing is performed until the residual boron content in the catalyst is 100-400 ppm.
[0020] Preferably, in step S4, the drying temperature is 100-130°C and the time is 12-24 h.
[0021] Preferably, in S4, the content of pretreated molecular sieve powder in the layered S-1 molecular sieve microsphere catalyst is 30-75% based on the dry weight of the catalyst, and the content of SiO2 and ZrO2 is 25-70%; more preferably, the content of pretreated molecular sieve powder is 70-50%, and the content of SiO2 and ZrO2 is 30-50%.
[0022] Preferably, in S4, the bulk density of the layered S-1 molecular sieve microsphere catalyst is 0.5-0.7 g / cm³. 3 The particle size D50 is 60-90 µm, and the wear index is less than 1.0%.
[0023] Secondly, the present invention provides an application of the sheet-like S-1 molecular sieve microsphere catalyst in the preparation of caprolactam, the application comprising: cyclohexanone oxime and the sheet-like S-1 molecular sieve microsphere catalyst undergoing a gas-phase Beckmann rearrangement reaction in a fluidized bed reactor to prepare caprolactam.
[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) Significantly improved mechanical strength: By adopting a silica sol-zirconia composite binder system, while maintaining the high selectivity of the catalyst, its wear index is reduced from 1.5%-2.0% in the prior art to below 1.0%, which significantly improves the mechanical strength and durability of the catalyst; (2) Good catalytic performance: On the basis of improving mechanical strength, the obtained catalyst can still maintain caprolactam selectivity of 95.0% or more (2h reaction) in the gas phase Beckmann rearrangement of cyclohexanone oxime, achieving a good balance between strength and selectivity. Attached Figure Description
[0025] Figure 1 The image shows the 1H MAS NMR spectrum of the sheet-like S-1 molecular sieve catalyst prepared in Example 1.
[0026] Figure 2 This is a SEM image of the sheet-like S-1 molecular sieve catalyst prepared in Example 1. Detailed Implementation
[0027] The technical solution of the present invention will be illustrated below with specific embodiments, but the scope of protection of the present invention is not limited thereto.
[0028] The layered S-1 molecular sieves in Examples 1-3 of this invention were prepared according to the method disclosed in Example 1 of CN117380249A, specifically including the following steps: Tetraethyl orthosilicate, 25 wt.% tetrapropylammonium hydroxide (TPAOH) aqueous solution, carbamide (urea), and water were mixed and stirred at room temperature for 12 hours to form a colloidal mixture. The molar ratio of the colloidal mixture was SiO2:TPAOH:H2O:urea = 1:0.35:35:0.81. The mixture was then transferred to a stainless steel reactor lined with polytetrafluoroethylene and crystallized at 180℃ for 3 days to obtain a crystallized molecular sieve slurry. The BET specific surface area of the layered S-1 molecular sieve was 367 m². 2 / g, b-axis is 80nm.
[0029] Example 1 S1. Add H3BO3 equivalent to 5.72% of the dry molecular sieve mass to the crystallized molecular sieve slurry, stir at room temperature for 6 h, and then dry at 110℃ for 12 h; crush the dried sample to below 100 mesh, and then calcine it for the first time at 500℃ in air atmosphere for 8 h to remove the template agent and obtain the pretreated molecular sieve raw powder.
[0030] S2. Alkaline silica sol (pH=9.5, SiO2 content 40 wt.%) and nano-zirconia sol (pH=3.0-4.0, ZrO2 content 20 wt.%) are mixed, with the amounts of silica sol and zirconium sol calculated according to a molar ratio of SiO2:ZrO2=1:0.1 to obtain a silica sol-zirconia composite binder. The pretreated molecular sieve powder and silica sol-zirconia composite binder are mixed at a dry basis mass ratio of 65:35. Deionized water is added to adjust the solid content of the system to 40 wt.%. The pH value of the slurry is adjusted to 3.5 using a 30 wt.% dilute nitric acid solution. After being mechanically stirred evenly, the mixture is transferred to a colloid mill for grinding until the particle size D50 of the slurry is less than 50 µm. At this point, the viscosity of the slurry is measured to be 168 mPa•s.
[0031] S3. The obtained homogeneous slurry is centrifugally spray-dried and shaped. The process conditions are: atomizing wheel speed 150 r / min, inlet temperature 280℃, and outlet temperature 140℃. The collected shaped catalyst is calcined a second time in an air atmosphere at 480℃ for 6 h.
[0032] S4. The calcined sample was washed with 1.0 mol / L nitric acid solution in a stainless steel reactor at a liquid-to-solid ratio of 10:1 for 4 h at 80 °C. This acid washing process was repeated twice. The sample was then repeatedly washed and filtered with sufficient deionized water until the filtrate was neutral. Finally, the solid product was dried at 120 °C for 12 h to obtain the layered S-1 molecular sieve catalyst. The residual boron content of the washed sample was 221 ppm as determined by ICP.
[0033] Example 2 S1. Add H3BO3 equivalent to 5.72% of the dry molecular sieve mass to the crystallized molecular sieve slurry, stir at room temperature for 6 h, and then dry at 110℃ for 12 h; crush the dried sample to below 100 mesh, and then calcine it for the first time at 500℃ in air atmosphere for 8 h to remove the template agent and obtain the pretreated molecular sieve raw powder.
[0034] S2. Alkaline silica sol (pH=9.5, SiO2 content 40 wt.%) and ammonium zirconium carbonate (CAS:22829-17-0, 99 wt.%) are mixed, with the amounts of silica sol and ammonium zirconium carbonate calculated according to a molar ratio of SiO2:ZrO2=1:0.1 to obtain a silica sol-zirconia composite binder. The pretreated molecular sieve powder and silica sol-zirconia composite binder are mixed at a dry basis mass ratio of 65:35. Deionized water is added to adjust the solid content of the system to 40 wt.%, and the pH value of the slurry is adjusted to 3.5 using a 30 wt.% dilute nitric acid solution. After being mechanically stirred evenly, the mixture is transferred to a colloid mill for grinding until the particle size D50 of the slurry is less than 50µm. At this point, the viscosity of the slurry is measured to be 150 mPa•s.
[0035] S3. The obtained homogeneous slurry is centrifugally spray-dried and shaped. The process conditions are: atomizing wheel speed 145 r / min, inlet temperature 280℃, and outlet temperature 140℃. The collected shaped catalyst is calcined a second time in an air atmosphere at 480℃ for 6 h.
[0036] S4. The calcined sample was washed with 1.0 mol / L nitric acid solution in a stainless steel reactor at a liquid-to-solid ratio of 10:1 for 4 h at 80 °C. This acid washing process was repeated twice. The sample was then repeatedly washed and filtered with sufficient deionized water until the filtrate was neutral. Finally, the solid product was dried at 120 °C for 12 h to obtain the layered S-1 molecular sieve catalyst. The residual boron content of the washed sample was 189 ppm as determined by ICP.
[0037] Example 3 S1. Add H3BO3 equivalent to 2.86% of the dry molecular sieve mass to the crystallized molecular sieve slurry, stir at room temperature for 6 h, and then dry at 110℃ for 12 h; crush the dried sample to below 100 mesh, and then calcine it for the first time at 500℃ in air atmosphere for 8 h to remove the template agent and obtain the pretreated molecular sieve powder.
[0038] S2. Alkaline silica sol (pH=9.5, SiO2 content 40 wt.%) and nano-zirconia sol (pH=3.0-4.0, ZrO2 content 20 wt.%) are mixed, with the amounts of silica sol and zirconium sol calculated according to a molar ratio of SiO2:ZrO2=1:0.15 to obtain a silica sol-zirconia composite binder. The pretreated molecular sieve powder and silica sol-zirconia composite binder are mixed at a dry basis mass ratio of 65:35. Deionized water is added to adjust the solid content of the system to 40 wt.%. The pH value of the slurry is adjusted to 3.5 using a 30 wt.% dilute nitric acid solution. After being mechanically stirred evenly, the mixture is transferred to a colloid mill for grinding until the particle size D50 of the slurry is less than 50 µm. At this point, the viscosity of the slurry is measured to be approximately 210 mPa•s.
[0039] S3. The obtained homogeneous slurry is centrifugally spray-dried and shaped. The process conditions are: atomizing wheel speed 145 r / min, inlet temperature 280℃, and outlet temperature 140℃. The collected shaped catalyst is calcined a second time in an air atmosphere at 480℃ for 6 h.
[0040] S4. The calcined sample was washed with 1.0 mol / L nitric acid solution in a stainless steel reactor at a liquid-to-solid ratio of 10:1 for 4 h at 80 °C. This acid washing process was repeated twice. The sample was then repeatedly washed and filtered with sufficient deionized water until the filtrate was neutral. Finally, the solid product was dried at 120 °C for 12 h to obtain the layered S-1 molecular sieve catalyst. The residual boron content of the washed sample was 292 ppm, as determined by ICP.
[0041] Example 4 S1. Add H3BO3 equivalent to 5.72% of the dry molecular sieve mass to the crystallized molecular sieve slurry, stir at room temperature for 6 h, and then dry at 110℃ for 12 h; crush the dried sample to below 100 mesh, and then calcine it for the first time at 500℃ in air atmosphere for 8 h to remove the template agent and obtain the pretreated molecular sieve raw powder.
[0042] S2. Alkaline silica sol (pH=9.5, SiO2 content 40 wt.%) and nano-zirconia sol (pH=3.0-4.0, ZrO2 content 20 wt.%) are mixed, with the amounts of silica sol and zirconium sol calculated according to a molar ratio of SiO2:ZrO2=1:0.1 to obtain a silica sol-zirconia composite binder. The pretreated molecular sieve powder and silica sol-zirconia composite binder are mixed at a dry weight ratio of 60:40. Deionized water is added to adjust the solid content of the system to 40 wt.%. The pH value of the slurry is adjusted to 3.5 using a 30 wt.% dilute nitric acid solution. After being mechanically stirred evenly, the mixture is transferred to a colloid mill for grinding until the particle size D50 of the slurry is less than 50 µm. At this point, the viscosity of the slurry is measured to be 306 mPa•s.
[0043] S3. The obtained homogeneous slurry is centrifugally spray-dried and shaped. The process conditions are: atomizing wheel speed 150 r / min, inlet temperature 280℃, and outlet temperature 140℃. The collected shaped catalyst is calcined a second time in an air atmosphere at 480℃ for 6 h.
[0044] S4. The calcined sample was washed with 1.0 mol / L nitric acid solution in a stainless steel reactor at a liquid-to-solid ratio of 10:1 for 4 h at 80 °C. This acid washing process was repeated twice. The sample was then repeatedly washed and filtered with sufficient deionized water until the filtrate was neutral. Finally, the solid product was dried at 120 °C for 12 h to obtain the layered S-1 molecular sieve catalyst. The residual boron content of the washed sample was 287 ppm as determined by ICP.
[0045] Example 5 S1. Add H3BO3 equivalent to 5.72% of the dry molecular sieve mass to the crystallized molecular sieve slurry, stir at room temperature for 6 h, and then dry at 110℃ for 12 h; crush the dried sample to below 100 mesh, and then calcine it for the first time at 500℃ in air atmosphere for 8 h to remove the template agent and obtain the pretreated molecular sieve raw powder.
[0046] S2. Alkaline silica sol (pH=9.5, SiO2 content 40 wt.%) and nano-zirconia sol (pH=3.0-4.0, ZrO2 content 20 wt.%) are mixed, with the amounts of silica sol and zirconium sol calculated according to a molar ratio of SiO2:ZrO2=1:0.2 to obtain a silica sol-zirconia composite binder. The pretreated molecular sieve powder and silica sol-zirconia composite binder are mixed at a dry basis mass ratio of 35:65. Deionized water is added to adjust the solid content of the system to 40 wt.%. The pH value of the slurry is adjusted to 3.5 using a 30 wt.% dilute nitric acid solution. After being mechanically stirred evenly, the mixture is transferred to a colloid mill for grinding until the particle size D50 of the slurry is less than 50 µm. At this point, the viscosity of the slurry is measured to be 253 mPa•s.
[0047] S3. The obtained homogeneous slurry is centrifugally spray-dried and shaped. The process conditions are: atomizing wheel speed 150 r / min, inlet temperature 280℃, and outlet temperature 140℃. The collected shaped catalyst is calcined a second time in an air atmosphere at 480℃ for 6 h.
[0048] S4. The calcined sample was washed with 1.0 mol / L nitric acid solution in a stainless steel reactor at a liquid-to-solid ratio of 10:1 for 4 h at 80 °C. This acid washing process was repeated twice. The sample was then repeatedly washed and filtered with sufficient deionized water until the filtrate was neutral. Finally, the solid product was dried at 120 °C for 12 h to obtain the layered S-1 molecular sieve catalyst. The residual boron content of the washed sample was 264 ppm, as determined by ICP.
[0049] Comparative Example 1 The crystallized molecular sieve slurry was washed and filtered. The solid product was dried at 100℃ for 24 hours and then calcined at 550℃ for 4 hours to obtain the layered S-1 molecular sieve with a BET specific surface area of 367 m². 2 / g, b-axis is 80 nm.
[0050] Comparative Example 2 (no boron-containing additives added and only silica sol used as binder) S1. The crystallized molecular sieve slurry is dried at 110℃ for 12 h; the dried sample is crushed to below 100 mesh, and then calcined for the first time at 500℃ in air atmosphere for 8 h to remove the template agent and obtain the molecular sieve raw powder.
[0051] S2. Molecular sieve powder and alkaline silica sol (pH=9.5, SiO2 content 40 wt.%) are mixed at a dry basis mass ratio of 65:35. Deionized water is added to adjust the solid content of the system to 40 wt.%. The pH value of the slurry is adjusted to 3.0 using 30 wt.% dilute nitric acid solution. After being mechanically stirred evenly, the mixture is transferred to a colloid mill for grinding until the particle size D50 of the slurry is less than 50 µm. At this point, the viscosity of the slurry is measured to be 130 mPa•s.
[0052] S3. The obtained homogeneous slurry is centrifugally spray-dried and shaped. The process conditions are: atomizing wheel speed 160 r / min, inlet temperature 260℃, and outlet temperature 130℃. The collected shaped catalyst is calcined a second time in an air atmosphere at 500℃ for 8 hours to obtain the sheet S-1 molecular sieve shaped catalyst.
[0053] Comparative Example 3 (using only silica sol as the adhesive) S1. Add H3BO3 equivalent to 5.72% of the dry molecular sieve mass to the crystallized molecular sieve slurry, stir at room temperature for 6 h, and then dry at 110℃ for 12 h; crush the dried sample to below 100 mesh, and then calcine it for the first time at 500℃ in air atmosphere for 8 h to remove the template agent and obtain the pretreated molecular sieve raw powder.
[0054] S2. The pretreated molecular sieve powder and alkaline silica sol (pH=9.5, SiO2 content 40 wt.%) were mixed at a dry basis mass ratio of 65:35. Deionized water was added to adjust the solid content of the system to 40 wt.%. The pH value of the slurry was adjusted to 4.0 using 30 wt.% dilute nitric acid solution. After being mechanically stirred evenly, the mixture was transferred to a colloid mill for grinding until the particle size D50 of the slurry was less than 50µm. At this point, the viscosity of the slurry was measured to be 235 mPa•s.
[0055] S3. The obtained homogeneous slurry is centrifugally spray-dried and shaped. The process conditions are: atomizing wheel speed 160 r / min, inlet temperature 260℃, and outlet temperature 130℃. The collected shaped catalyst is then calcined a second time in air at 480℃ for 6 h.
[0056] S4. The calcined sample was washed with 1.0 mol / L nitric acid solution in a stainless steel reactor at a liquid-to-solid ratio of 10:1 for 4 h at 80 °C. This acid washing process was repeated twice. The sample was then repeatedly washed and filtered with sufficient deionized water until the filtrate was neutral. Finally, the solid product was dried at 120 °C for 12 h to obtain the layered S-1 molecular sieve catalyst. The residual boron content of the washed sample was 267 ppm as determined by ICP.
[0057] Comparative Example 4 (Preparation of composite binder using alumina instead of zirconium oxide) S1. Add H3BO3 equivalent to 5.72% of the dry molecular sieve mass to the crystallized molecular sieve slurry, stir at room temperature for 6 h, and then dry at 110℃ for 12 h; crush the dried sample to below 100 mesh, and then calcine it for the first time at 500℃ in air atmosphere for 8 h to remove the template agent and obtain the pretreated molecular sieve raw powder.
[0058] S2. Alkaline silica sol (pH=9.5, SiO2 content 40 wt.%) and nano alumina sol (pH=3.0-4.0, Al2O3 content 20 wt.%) are mixed, with the amounts of silica sol and alumina sol calculated according to a molar ratio of SiO2:Al2O3=1:0.1 to obtain a silica sol-alumina composite binder. The pretreated molecular sieve powder and silica sol-alumina composite binder are mixed at a dry basis mass ratio of 65:35. Deionized water is added to adjust the solid content of the system to 40 wt.%. The pH value of the slurry is adjusted to 3.5 using a 30 wt.% dilute nitric acid solution. After being mechanically stirred evenly, the mixture is transferred to a colloid mill for grinding until the particle size D50 of the slurry is less than 50 µm. At this point, the viscosity of the slurry is measured to be 480 mPa•s.
[0059] S3. The obtained homogeneous slurry is centrifugally spray-dried and shaped. The process conditions are: atomizing wheel speed 150 r / min, inlet temperature 280℃, and outlet temperature 140℃. The collected shaped catalyst is calcined a second time in an air atmosphere at 480℃ for 6 h.
[0060] S4. The calcined sample was washed with 1.0 mol / L nitric acid solution in a stainless steel reactor at a liquid-to-solid ratio of 10:1 for 4 h at 80 °C. This acid washing process was repeated twice. The sample was then repeatedly washed and filtered with sufficient deionized water until the filtrate was neutral. Finally, the solid product was dried at 120 °C for 12 h to obtain the layered S-1 molecular sieve catalyst. The residual boron content of the washed sample was 486 ppm as determined by ICP.
[0061] Comparative Example 5 (excessive proportion of zirconium oxide in the composite binder) S1. Add H3BO3 equivalent to 5.72% of the dry molecular sieve mass to the crystallized molecular sieve slurry, stir at room temperature for 6 h, and then dry at 110℃ for 12 h; crush the dried sample to below 100 mesh, and then calcine it for the first time at 500℃ in air atmosphere for 8 h to remove the template agent and obtain the pretreated molecular sieve raw powder.
[0062] S2. Alkaline silica sol (pH=9.5, SiO2 content 40 wt.%) and nano-zirconia sol (pH=3.0-4.0, ZrO2 content 20 wt.%) are mixed, with the amounts of silica sol and zirconium sol calculated according to a molar ratio of SiO2:ZrO2=1:0.3 to obtain a silica sol-zirconia composite binder. The pretreated molecular sieve powder and silica sol-zirconia composite binder are mixed at a dry basis mass ratio of 65:35. Deionized water is added to adjust the solid content of the system to 40 wt.%. The pH value of the slurry is adjusted to 3.5 using a 30 wt.% dilute nitric acid solution. After being mechanically stirred evenly, the mixture is transferred to a colloid mill for grinding until the particle size D50 of the slurry is less than 50 µm. At this point, the viscosity of the slurry is measured to be 380 mPa•s.
[0063] S3. The obtained homogeneous slurry is centrifugally spray-dried and shaped. The process conditions are: atomizing wheel speed 150 r / min, inlet temperature 280℃, and outlet temperature 140℃. The collected shaped catalyst is calcined a second time in an air atmosphere at 480℃ for 6 h.
[0064] S4. The calcined sample was washed with 1.0 mol / L nitric acid solution in a stainless steel reactor at a liquid-to-solid ratio of 10:1, and stirred at 80℃ for 4 h. This acid washing process was repeated twice. The sample was then repeatedly washed and filtered with sufficient deionized water until the filtrate was neutral. Finally, the solid product was dried at 120℃ for 12 h to obtain the layered S-1 molecular sieve catalyst. The residual boron content of the washed sample was 348 ppm as determined by ICP.
[0065] Performance testing: (1) H magic angular spin (MAS) nuclear magnetic resonance (NMR) spectrum: acquired on a Brook AVANCE III HD spectrometer.
[0066] (2) Catalyst bulk density: The free packing method was used to determine the density of the catalyst powder by letting it fall freely into a 100 mL graduated cylinder through a funnel. After being compacted by vibration until the volume is constant, the density was calculated by the mass-to-volume ratio.
[0067] (3) Catalyst particle size and distribution: The particle size was determined using a Dandong Baite 2000E laser particle size analyzer. The test conditions were: wet measurement in water medium, shading rate 5%-20%, ultrasonic degassing, sample mass concentration 0.5%-2%, and scanning rate 2000 times / second.
[0068] (4) Catalyst wear index: Measured on a dedicated wear index analyzer according to the RIPP 29-90 method in Petrochemical Analysis Methods (Yang Cuiding et al., Science Press, 1990).
[0069] (5) Catalytic performance of the catalyst: The catalyst was evaluated in a micro fluidized bed reactor. The specific reaction conditions were as follows: reaction temperature 390℃, catalyst loading 25 g, feed ethanol solution of cyclohexanone oxime (cyclohexanone oxime concentration 40 wt.%, water content 0.7 wt.%), reaction pressure 0.03-0.5 MPa, and cyclohexanone oxime mass hourly space velocity 4 h⁻¹. -1 The carrier gas flow rate was 4000 mL / min. The reaction products were condensed and then subjected to gas-liquid separation. Liquid phase products were collected every 2 h for compositional analysis. Since the catalyst in Comparative Example 1 was molecular sieve powder, it could not be evaluated in a micro fluidized bed reactor. Therefore, it was evaluated in a micro fixed-bed reactor under the following conditions: reaction temperature 390℃, catalyst loading 1 g, feed was an ethanol solution of cyclohexanone oxime (cyclohexanone oxime concentration 40 wt.%, water content 0.7 wt.%), reaction pressure 0.03-0.5 MPa, and cyclohexanone oxime mass hourly space velocity 8 h⁻¹. -1 Carrier gas flow rate: 400 mL / min.
[0070] Product analysis was performed using a Shimadzu GC-2010 Pro gas chromatograph equipped with an FID detector and an S19170 S1 capillary column (30.0 m × 0.50 µm × 0.02 mm). Temperature programming was employed, and quantification was performed using area normalization (solvent peaks were not included in the calculation). Cyclohexanone oxime conversion = (Amount of cyclohexanone oxime in feed - Amount of cyclohexanone oxime in product) / (Amount of cyclohexanone oxime in feed) × 100%; caprolactam selectivity = Amount of caprolactam in product / (100 - Amount of cyclohexanone oxime in product) × 100%.
[0071] Table 1 Performance test results of the S-1 molecular sieve shaped catalyst Table 2. Terminal silanol content of layered S-1 molecular sieve catalysts like Figure 2 The image shown is an SEM image of the sheet-like S-1 molecular sieve shaped catalyst prepared in Example 1. As shown in the figure, the shaped catalyst has an elliptical microsphere morphology, and its bulk density was measured to be 0.64 g / cm³. 3 The wear index K is 0.85% / h, and the D50 is 72 µm.
[0072] like Figure 1The image shows the 1H MAS NMR spectrum of the layered S-1 molecular sieve catalyst prepared in Example 1, where the peak with a chemical shift of 1.8 ppm is attributed to terminal silanol groups. Studies have shown that the content of these silanol groups is negatively correlated with the selectivity of the catalyst in the cyclohexanone oxime gas-phase Beckmann rearrangement reaction; that is, the lower the relative content, the higher the selectivity for caprolactam. As shown in Table 2, Comparative Example 2, using only silica sol as a binder, introduces a large number of terminal silanol groups into the catalyst, resulting in a significantly higher signal intensity of terminal silanol groups in the molecular sieve powder compared to Comparative Example 1. In Comparative Example 3, by improving the layered molecular sieve forming process and adding boron for pretreatment of the slurry, the resulting layered S-1 molecular sieve catalyst has a lower signal intensity of terminal silanol groups, thus exhibiting higher selectivity. Example 1, using a silica sol-zirconia composite binder, yielded a layered S-1 molecular sieve catalyst with a signal intensity of terminal silanol groups comparable to that of Comparative Example 3. Meanwhile, as shown in Table 1, the catalyst in Example 1 also has a lower wear index, which indicates that the use of composite binder can not only ensure a lower relative content of terminal silanol groups, but also significantly improve the mechanical strength of the catalyst, thus making it better suited for long-cycle, high-intensity industrial fluidized bed operation.
[0073] Furthermore, although Comparative Examples 4 and 5 also used composite binders, the silica sol-alumina composite binder used in Comparative Example 4 had a significant negative impact on catalytic selectivity, and the mechanical strength of the molecular sieve was not significantly improved. The high ZrO2 proportion in the silica sol-zirconia composite binder used in Comparative Example 5 also led to poor caprolactam selectivity. This indicates that the components and their proportions in the composite binder affect reaction selectivity and mechanical strength.
[0074] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.
Claims
1. A method for preparing high-strength sheet S-1 molecular sieve microsphere catalyst, characterized in that, Includes the following steps: S1. Layered S-1 molecular sieves were prepared by hydrothermal crystallization to obtain crystallized molecular sieve slurry. S2. The boron-containing additive is mixed with the molecular sieve slurry, dried, and then calcined for the first time to obtain the pretreated molecular sieve raw powder. S3. Mix the pretreated molecular sieve powder, silica sol-zirconia composite binder and water, grind and adjust the pH to 3-6 to obtain a slurry; S4. After spray drying and second calcination, the slurry is washed with an acidic solution and then dried to obtain the layered S-1 molecular sieve microsphere catalyst.
2. The method for preparing high-strength sheet S-1 molecular sieve microsphere catalyst according to claim 1, characterized in that, In S2, the boron-containing additive is at least one of boron oxide, boric acid, metaboric acid, ammonium borate, phenylboronic acid, trimethyl borate, and triethyl borate; the amount of the boron-containing additive added is calculated based on the mass of boron oxide being 1.6-12.8% of the dry molecular sieve mass in the molecular sieve slurry.
3. The method for preparing high-strength sheet S-1 molecular sieve microsphere catalyst according to claim 1 or 2, characterized in that, In S2, the temperature of the first roasting is 400-600℃ and the time is 6-10 h.
4. The method for preparing high-strength sheet S-1 molecular sieve microsphere catalyst according to claim 1, characterized in that, In S3, the mass ratio of the silica sol-zirconia composite binder, based on oxides, is SiO2:ZrO2 = 1:(0.05-0.2); the silica sol-zirconia composite binder is a mixture of silica sol and zirconia source, wherein the silica sol is alkaline, neutral or acidic silica sol, and the zirconia source is at least one of nano zirconia sol and ammonium zirconium carbonate.
5. The method for preparing high-strength sheet S-1 molecular sieve microsphere catalyst according to claim 1 or 4, characterized in that, In S3, the solid particle size D50 in the slurry is no greater than 50 µm; the viscosity of the slurry is 100-600 mPa•s.
6. The method for preparing the high-strength sheet-like S-1 molecular sieve microsphere catalyst according to claim 1, characterized in that, In S4, the atomizing disc of the spray dryer rotates at 100-300 r / min, the inlet temperature is 200-400℃, and the outlet temperature is 100-250℃; the temperature of the second calcination is 430-550℃, and the time is 3-12 h.
7. The method for preparing the high-strength sheet-like S-1 molecular sieve microsphere catalyst according to claim 1 or 6, characterized in that, In S4, the washing is performed until the residual boron content in the catalyst is 100-1000 ppm; the washing solution used is an acid solution with a concentration of no more than 3.0 mol / L; the acid solution includes nitric acid, acetic acid, hydrochloric acid or citric acid solution.
8. The method for preparing the high-strength sheet-like S-1 molecular sieve microsphere catalyst according to claim 1 or 6, characterized in that, In S4, the drying temperature is 100-130℃ and the time is 12-24 h; in the sheet S-1 molecular sieve microsphere catalyst, the content of pretreated molecular sieve powder is 50-70% and the content of SiO2 and ZrO2 is 30-50% based on the dry mass of the catalyst.
9. The method for preparing high-strength sheet S-1 molecular sieve microsphere catalyst according to claim 1, characterized in that, In S1, the hydrothermal crystallization method includes the following steps: mixing a silicon source, an amide compound, an organic template agent, and water to obtain a colloidal mixture; and hydrothermally crystallizing the colloidal mixture to obtain a crystallized molecular sieve slurry.
10. Use of the sheet S-1 molecular sieve microsphere catalyst prepared by the preparation method of any one of claims 1-9 in the preparation of caprolactam, characterized in that, Caprolactam was prepared by gas-phase Beckmann rearrangement reaction of cyclohexanone oxime and sheet-like S-1 molecular sieve microsphere catalyst in a fluidized bed reactor.