Catalyst containing ZSM-5 type structure all-silicon molecular sieve and preparation method thereof, and cyclohexanone-oxime gas phase Beckmann rearrangement reaction method
By preparing a ZSM-5 type structured all-silica molecular sieve catalyst, the problems of unsatisfactory catalytic activity and insufficient selectivity in the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime were solved, achieving efficient cyclohexanone oxime conversion and caprolactam selectivity, reducing raw material costs and improving the economics of fluidized bed reaction process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING RISUN TECH CO LTD
- Filing Date
- 2024-12-09
- Publication Date
- 2026-05-22
Smart Images
Figure CN122071010A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of catalyst technology, specifically to a catalyst containing a ZSM-5 type all-silica molecular sieve and its preparation method, as well as a method for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime. Background Technology
[0002] In 1978, EMFlanigen et al. of UCC successfully synthesized Silicalite-1 molecular sieve (abbreviated as all-silica-1 molecular sieve). All-silica-1 molecular sieve belongs to the last member of the "Pentasil" family. It is an aluminum-free all-silica-1 molecular sieve with a ZSM-5 structure and is the simplest molecular sieve in the ZSM-5 molecular sieve family. Its framework contains only silicon and oxygen atoms, and its basic structural unit is the SiO4 tetrahedron. The synthesis method of all-silica-1 molecular sieve generally adopts the traditional organic raw material hydrothermal method. Silicon sources can be solid silica, silica sol, silica fume, tetraethyl orthosilicate (TEOS), etc. Template agents often include tetrapropylammonium hydroxide (TPAOH), low-carbon hydrocarbon quaternary ammonium salts or mixtures of both, amine compounds, etc., and crystallization is carried out at 170°C for three days. For example, JP59164617 discloses the preparation of all-silica-1 molecular sieve using tetraethyl orthosilicate (TEOS) as the silicon source and tetrapropylammonium hydroxide as the template agent. CN1338427A discloses an all-silica-1 molecular sieve, which includes two synthesis methods, both using tetraethyl orthosilicate and tetrapropylammonium hydroxide as raw materials. CN112239212A discloses the addition of an alcohol and a metal source during the molecular sieve synthesis process, the use of organic amines and organic template agents, and the use of a two-stage variable-temperature alcohol-hydrothermal system for crystallization.
[0003] Caprolactam is a major raw material for the production of three major series of products: nylon, industrial tire cord, and nylon engineering plastics. It is generally obtained through the Beckmann rearrangement reaction of cyclohexanone oxime. Various solid acids can be used as catalysts in the gas-phase Beckmann rearrangement reaction, such as the silica-alumina catalyst used in GB881,927; the solid phosphoric acid catalyst used in GB881,956; the boric acid-containing catalyst used in British Patent GB1,178,057; and the high silica / alumina ratio MFI structure molecular sieve catalyst used in CN1269360A. CN1256967A discloses a method for preparing an MFI structure molecular sieve catalyst for the conversion of cyclohexanone oxime to caprolactam. The basic premise of this method is to use acidic silica gel as a binder. The specific method is to mix the silica oligomer obtained by acidic hydrolysis of alkoxysilane with an aqueous or alcohol-water dispersion of MFI structure molecular sieve submicron particles with pH≤5, and then emulsify, solidify, wash and calcine the mixture to obtain gel microspheres.
[0004] The fixed-bed process for the gas-phase Beckmann rearrangement of cyclohexanone oxime has disadvantages such as short catalyst lifetime, difficulty in long-term continuous operation, high nitrogen-oxime molar ratio, difficulty in heat transfer, and poor technical and economic efficiency. Summary of the Invention
[0005] The purpose of this invention is to overcome the problems of unsatisfactory catalytic activity and insufficient selectivity of existing catalysts for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime. This invention provides a catalyst containing a ZSM-5 type all-silica molecular sieve, its preparation method, and a method for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime. The catalyst prepared by this method has a high cyclohexanone oxime conversion rate and caprolactam selectivity.
[0006] To achieve the above objectives, the present invention provides a method for preparing a catalyst containing a ZSM-5 type all-silica molecular sieve, comprising the following steps:
[0007] (1) Mix silicon source, KOH, organic base and water, and hydrolyze to obtain colloidal mixture;
[0008] Wherein, the silicon source is an organosilicate, and the molar ratio of silicon source, KOH, organic base and water, calculated as SiO2, is 1:(0.01-0.1):(0.04-0.25):(15-45);
[0009] (2) The colloidal mixture is crystallized, and the resulting crystallization mother liquor is optionally concentrated to obtain a molecular sieve slurry;
[0010] The crystallization temperature is 95-150℃, and the time is 0.5-5 days.
[0011] (3) The molecular sieve slurry is mixed with the binder and then pulped to obtain a molecular sieve-binder slurry; the molecular sieve-binder slurry is spray-molded and then calcined;
[0012] (4) The product obtained by roasting in step (3) is contacted with an alkaline buffer solution containing ammonium salt, ammonia water, magnesium salt and bromide salt, and then dried.
[0013] The second aspect of the present invention provides a catalyst containing a ZSM-5 type structured all-silica molecular sieve prepared by the above preparation method.
[0014] A third aspect of the present invention provides a method for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime, the method comprising: reacting cyclohexanone oxime with a catalyst in the presence of a solvent under the conditions of the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime, wherein the catalyst is the catalyst containing a ZSM-5 type structure all-silica molecular sieve as described in the second aspect.
[0015] Preferably, the contact takes place in a fluidized bed reactor.
[0016] Through the above technical solutions, the microspherical all-silica-1 molecular sieve catalyst prepared by the preparation method provided by the present invention has a high cyclohexanone oxime conversion rate and caprolactam selectivity, and is particularly suitable for the fluidized bed reaction process of cyclohexanone oxime gas-phase Beckmann rearrangement reaction. Attached Figure Description
[0017] Figure 1 This is the X-ray diffraction pattern of the all-silica-1 molecular sieve raw powder prepared in Example 1. Detailed Implementation
[0018] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0019] The first aspect of this invention provides a method for preparing a catalyst containing a ZSM-5 type all-silica molecular sieve, comprising the following steps:
[0020] (1) Mix silicon source, KOH, organic base and water, and hydrolyze to obtain colloidal mixture;
[0021] Wherein, the silicon source is an organosilicate, and the molar ratio of silicon source, KOH, organic base and water, calculated as SiO2, is 1:(0.01-0.1):(0.04-0.25):(15-45);
[0022] (2) The colloidal mixture is crystallized, and the resulting crystallization mother liquor is optionally concentrated to obtain a molecular sieve slurry;
[0023] The crystallization temperature is 95-150℃, and the time is 0.5-5 days.
[0024] (3) The molecular sieve slurry is mixed with the binder and then pulped to obtain a molecular sieve-binder slurry; the molecular sieve-binder slurry is spray-molded and then calcined;
[0025] (4) The product obtained by roasting in step (3) is contacted with an alkaline buffer solution containing ammonium salt, ammonia water, magnesium salt and bromide salt, and then dried.
[0026] To ensure the formation of ZSM-5 type all-silica-1 molecular sieves, existing technologies typically employ hydrothermal synthesis of high silica-to-alumina ratio (greater than 5000) molecular sieves using organic raw materials. To date, there have been no reports of using inorganic alkalis as a base source for the synthesis of all-silica-1 molecular sieves, thus keeping the synthesis cost consistently high. The preparation method provided by this invention breaks through the technical biases in conventional all-silica-1 molecular sieve synthesis. It creatively introduces an appropriate amount of KOH into the synthesis process, combined with suitable crystallization conditions. Furthermore, post-treatment using an alkaline buffer solution containing ammonium salts, ammonia, magnesium salts, and bromide salts, combined with the synergistic effect of the molecular sieve slurry synthesis and post-treatment conditions, improves the conversion rate and selectivity of the prepared catalyst in the gas-phase Beckmann rearrangement reaction. Simultaneously, the catalyst preparation process effectively reduces the amount of TPAOH used, lowering the raw material cost of molecular sieve synthesis and improving the economics of the gas-phase rearrangement process.
[0027] According to the present invention, preferably, the silicon source is methyl orthosilicate and / or ethyl orthosilicate, more preferably ethyl orthosilicate.
[0028] In this invention, the silicon source can be obtained commercially. In commercially available organosilicone esters, in addition to the effective components, impurities such as alcohols may also be present. The inventors of this invention have found in experiments that selecting a silicon source with a purity of not less than 98wt%, a platinum-cobalt color of not more than 20mg / L, and a Cl ion concentration of not more than 50ppm as a raw material is beneficial to improving the selectivity of the catalyst.
[0029] In this invention, the purity of the silicon source refers to the content of the effective component in the silicon source. For example, when the effective component of the silicon source is tetraethyl orthosilicate, its purity refers to the mass fraction of tetraethyl orthosilicate in the silicon source.
[0030] The platinum-cobalt colorimetric method uses the color exhibited in 1 L of water containing 1 mg of Pt(Ⅳ) and 2 mg of cobalt chloride hexahydrate(Ⅱ) as a standard unit of colorimetry, generally referred to as 1 degree. In this invention, following the platinum-cobalt colorimetric method, a set of standard colors of 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 degrees are prepared, and then compared to determine the colorimetry of the silicon source.
[0031] According to the present invention, preferably, the organic base is selected from at least one of aliphatic amine compounds, alkanolamine compounds, and quaternary ammonium base compounds. The quaternary ammonium base compound is preferably an alkyl quaternary ammonium base compound containing 1-4 carbon atoms, and more preferably tetrapropylammonium hydroxide.
[0032] As is known to those skilled in the art, commercially available organic bases, especially alkyl quaternary ammonium bases, typically contain small amounts of sodium ions. In the prior art, when using organic bases alone as the base source and template agent to synthesize all-silica-1 molecular sieves, the requirements for sodium ions in alkyl quaternary ammonium bases are quite strict, usually requiring 5-10 ppm. In this invention, by introducing KOH, the requirements for sodium ion content in alkyl quaternary ammonium bases can be relaxed, and high-quality all-silica-1 molecular sieves can still be synthesized even when the sodium ion content exceeds 10 ppm.
[0033] According to the present invention, preferably, the bromide ion content in the organic base is less than 1.5 wt%, more preferably 0.5-1.5 wt%. The inventors of the present invention have discovered that using an organic base containing a certain amount of bromide ions as a synthetic raw material, such as tetrapropylammonium hydroxide containing a certain amount of tetrapropylammonium bromide, is beneficial to further improve the selectivity of caprolactam. The reason for this may be that the bromide present in the organic amine is conducive to the formation of ethyl-ε-caprolactamimide, which can be further converted into caprolactam through hydrolysis, ultimately resulting in improved catalyst selectivity.
[0034] Preferably, the iron ion content in the organic base is not greater than 10 ppm.
[0035] Preferably, the organic base contains less than 500 ppm sodium ions, not more than 550 ppm free acid, less than 0.2 wt% carbonate ions, and an APHA color value not exceeding 100. The free acid includes, for example, any one or more of formic acid, acetic acid, and propionic acid.
[0036] According to some particularly preferred embodiments of the present invention, step (1) includes: mixing tetraethyl orthosilicate, KOH, tetrapropylammonium hydroxide and water, and hydrolyzing to obtain a colloidal mixture. Using the above preferred embodiments is beneficial for improving the stability of the catalyst.
[0037] According to the present invention, preferably, the molar ratio of silicon source, KOH, organic base and water, calculated as SiO2, is 1:(0.02-0.08):(0.08-0.20):(20-40), more preferably 1:(0.03-0.05):(0.08-0.2):(20-30).
[0038] According to the present invention, preferably, the hydrolysis is carried out under stirring conditions. The present invention does not have any particular limitation on the conditions of the hydrolysis. Preferably, the hydrolysis temperature is 10-50°C and the time is 0.5-10h.
[0039] According to the present invention, a higher crystallization temperature and a shorter crystallization time are preferably used for the crystallization in step (2). Preferably, in step (2), the crystallization temperature is 110-140°C and the time is 1-3 days. By adopting the above-mentioned preferred embodiment, with the introduction of appropriate KOH and combined with high-temperature rapid crystallization, it is beneficial to improve the crystallinity of the molecular sieve, thereby further improving the stability of the catalyst.
[0040] According to the present invention, preferably, before the concentration, the preparation method further includes: washing the crystallization mother liquor until the pH of the washing water is below 9.4, preferably below 9.2, for example, a pH value of 8.5-9.2. The present invention does not particularly limit the washing process and can use various washing methods already used in the art. The present invention also does not particularly limit the washing agent used in the washing process, for example, it can be water. The water can be purified water, deionized water, ion-exchanged water, chemically treated water, or other water without anions or cations. In the present invention, the washing can be repeated, and the present invention does not particularly limit the number of repetitions, for example, it can be repeated 1-10 times. Preferably, the temperature of the washing water is 20-80°C.
[0041] According to the present invention, those skilled in the art may choose to perform or not perform the concentration in step (2). The present invention has a wide range of choices for the concentration method in step (2), as long as it can meet the solid content range of the molecular sieve slurry.
[0042] According to a preferred embodiment of the present invention, the washing and concentration of molecular sieves are achieved by membrane filtration, for example, using a six-tube membrane. Specific operations are well known to those skilled in the art and will not be described in detail here.
[0043] Preferably, in step (2), the solid content of the molecular sieve slurry is 20-50% by weight, more preferably 25-45% by weight. Under this preferred condition, it is more beneficial to improve the performance of the obtained catalyst.
[0044] According to the present invention, in step (3), the solid content of the molecular sieve-binder slurry is 20-60% by weight, preferably 30-50% by weight. In this preferred case, it is more conducive to the spray molding process, resulting in a lower catalyst attrition index.
[0045] According to the present invention, preferably, in the molecular sieve-binder slurry, the weight ratio of the dry molecular sieve basis to the binder based on the dry basis is 1:(0.05-1), more preferably 1:(0.1-0.7).
[0046] In this invention, preferably, the binder is a precursor of silicon oxide, which can be selected from any substance that can be converted into silicon oxide through calcination; this invention does not have any particular limitation on this. Preferably, the precursor of silicon oxide is silica sol and / or fumed silica, and more preferably silica sol.
[0047] In this invention, the spray molding can be performed using conventional methods. Preferably, the spray molding conditions result in particles with a diameter of 20-400 μm, more preferably 40-250 μm.
[0048] According to some preferred embodiments of the present invention, the spray molding conditions include: an inlet temperature of 180-240°C, preferably 200-220°C; and an outlet temperature of 80-120°C, preferably 90-105°C. Under these preferred embodiments, the resulting catalyst exhibits better performance, thereby more effectively improving the conversion rate of cyclohexanone oxime and the selectivity of caprolactam.
[0049] According to the present invention, preferably, the calcination conditions include: a temperature of 200-600℃, more preferably 250-550℃, and a time of 1-20h.
[0050] According to the present invention, preferably, the roasting can be carried out in stages. Specifically, for example, the roasting can include stage 1) and stage 2); the conditions of stage 1) include: temperature of 200-400℃ and time of 2-10h; the conditions of stage 2) include: temperature of 400-600℃ and time of 2-15h. More preferably, stage 1) includes stage 1-1) and stage 1-2), the conditions of stage 1-1) include: temperature of 200-300℃ and time of 2-5h, the conditions of stage 1-2) include: temperature of 300-400℃ and time of 2-5h; stage 2) includes stage 2-1) and stage 2-2), the conditions of stage 2-1) include: temperature of 400-500℃ and time of 2-5h, the conditions of stage 2-2) include: temperature of 500-600℃ and time of 8-13h.
[0051] To further improve the performance of the catalyst product, preferably, the spray molding in step (3) can be carried out with the addition of additives. The additives can be added to the molecular sieve-binder mixture slurry and then the spray molding can be carried out.
[0052] According to some preferred embodiments of the present invention, an additive is also introduced in the pulping process of step (3), the additive being selected from at least one of guar gum powder, graphite, activated carbon, paraffin wax, glycerin, citric acid, starch, polyethylene glycol, polyvinyl alcohol, nitric acid, hydrochloric acid, acetic acid, formic acid, ammonia, tetramethylammonium hydroxide, tetraethylammonium hydroxide and tetrapropylammonium hydroxide.
[0053] Preferably, the amount of additive introduced is 1-5 wt%, based on the dry weight of the molecular sieve in the molecular sieve slurry.
[0054] The inventors of this invention discovered in their research that post-treatment of the calcined product with an alkaline buffer solution containing ammonium salt, ammonia water, magnesium salt, and bromide salt can further improve the catalytic performance of the catalyst, resulting in higher total selectivity and total yield of caprolactam.
[0055] According to the present invention, preferably, the pH of the alkaline buffer solution is 8.5-13.5, more preferably 10-12, and even more preferably 11-11.5.
[0056] Preferably, based on the total amount of the alkaline buffer solution, the content of magnesium salts (calculated as Mg) is 1-500 ppm, more preferably 2-300 ppm, and even more preferably 2-100 ppm; the content of bromide salts (calculated as Br) is 1-500 ppm, more preferably 5-300 ppm. Using the above-mentioned preferred embodiments is beneficial for further improving the catalytic performance of the prepared catalyst, exhibiting higher total selectivity and total yield of caprolactam compared to existing all-silica-1 molecular sieve catalysts.
[0057] The present invention has a wide range of choices for the ammonium salt, ammonia water, magnesium salt and bromide salt, and can use conventional soluble salts in the art that can provide nitrogen, magnesium and bromine elements.
[0058] Preferably, the ammonium salt is selected from ammonium nitrate and / or ammonium acetate.
[0059] Preferably, the magnesium salt is selected from at least one of magnesium nitrate hexahydrate, magnesium acetate, magnesium chloride, magnesium sulfate, and magnesium hydrogen phosphate.
[0060] Preferably, the bromide salt is tetrapropylammonium bromide.
[0061] The present invention has a wide range of solvent options for the alkaline buffer solution, with water being the preferred solvent.
[0062] Preferably, the alkaline buffer solution includes ammonia, an aqueous solution of ammonium salt, magnesium salt, and bromide salt.
[0063] Preferably, the weight ratio of ammonia water to ammonium salt aqueous solution is 1-3:1.
[0064] Preferably, the concentration of the ammonia solution is 5-30 wt%, more preferably 20-30 wt%.
[0065] Preferably, the concentration of the ammonium salt aqueous solution is 0.5-10 wt%.
[0066] According to the present invention, preferably, the amount of alkaline buffer solution used is 500-1500 parts by weight, more preferably 700-1200 parts by weight, relative to 100 parts by weight of the product obtained by calcination on a dry basis.
[0067] Preferably, the contact conditions include: a temperature of 50-120°C, more preferably 70-100°C; and a pressure of 0.5-10 kg / cm². 2 The preferred value is 1.5-4 kg / cm². 2 The time is 0.1-5 hours, preferably 1-3 hours.
[0068] According to the present invention, the contact process can be repeated. The present invention does not particularly limit the number of repetitions, but can determine them based on the effectiveness of the contact, with the aim of improving the performance of the catalyst; for example, it can be repeated 1-3 times.
[0069] Preferably, step (4) may further include: solid-liquid separation, washing and drying of the contacted product.
[0070] The present invention does not particularly limit the washing agent used in the washing process; for example, it can be water. Specifically, the washing process may include washing until the pH of the filtrate is 9-10.5. The drying method can be carried out according to any existing technology in the art, such as heating drying, forced air drying, or natural drying. The drying temperature can be 100-120°C, and the drying time can be 10-24 hours. The catalyst obtained by washing and drying the contacted material is beneficial for improving the conversion rate of cyclohexanone oxime and the selectivity of caprolactam when used in the preparation of caprolactam from cyclohexanone oxime.
[0071] The second aspect of the present invention provides a catalyst containing a ZSM-5 type structured all-silica molecular sieve prepared by the above preparation method.
[0072] Preferably, the catalyst comprises a molecular sieve and a binder; the content of the molecular sieve, based on the dry weight of the catalyst, is 50-95% by weight, preferably 55-80% by weight; and the content of the binder, based on oxides, is 5-50% by weight, preferably 20-45% by weight.
[0073] Preferably, the catalyst further contains Mg and Br elements, which are introduced at least partially by the alkaline buffer solution contact process in step (4). Preferably, based on the total amount of the catalyst, the content of Mg is 20-1000 ppm, more preferably 20-500 ppm; and the content of Br is 10-1000 ppm, more preferably 10-500 ppm.
[0074] In this invention, the metal ion content of the sample was determined using a Baird PS-4 ICP-AES inductively coupled plasma atomic emission spectrometer. The test conditions were as follows: the solid molecular sieve or catalyst was dissolved in HF acid or aqua regia to make the silica in the sample volatile, and the sample was measured in an aqueous solution. The Br ion content was determined by ion chromatography.
[0075] Preferably, the particle size of the catalyst is 20-400 μm, and more preferably 40-250 μm.
[0076] The particle size and particle size distribution of the catalyst were determined using a Malvern 3000 laser particle size analyzer. The test method was a wet test, with water as the medium, a sample mass concentration of 0.5%-2%, and a scanning speed of 2000 times / second.
[0077] Preferably, the wear index K of the catalyst is less than 3, more preferably less than 2.5, and even more preferably 1.5-2.5.
[0078] In this invention, the catalyst attrition index K is determined on an attrition index analyzer according to the RIPP29-90 method in "Analytical Methods for Petrochemical Products" (Yang Cuiding et al., Science Press, 1990).
[0079] A third aspect of the present invention provides a method for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime, the method comprising: reacting cyclohexanone oxime with a catalyst in the presence of a solvent under the conditions of the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime, wherein the catalyst is the catalyst containing a ZSM-5 type structure all-silica molecular sieve as described in the second aspect.
[0080] Preferably, the contact takes place in a fluidized bed reactor.
[0081] Preferably, the solvent is a C1-C6 fatty alcohol, preferably methanol and / or ethanol.
[0082] Preferably, the molar ratio of the solvent to cyclohexanone oxime is (2-10):1.
[0083] According to the present invention, preferably, the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime is carried out under an inert atmosphere. In the present invention, the inert atmosphere is provided by an inert gas, preferably selected from at least one of nitrogen, helium, argon and neon, and more preferably nitrogen.
[0084] According to the present invention, preferably, the molar ratio of the inert gas to cyclohexanone oxime is 1-10:1, more preferably 0.5-10:1, and more preferably 0.5-5:1.
[0085] According to some preferred embodiments of the present invention, the gas-phase Beckmann rearrangement reaction conditions for cyclohexanone oxime include: a weight hourly space velocity (WHSV) of cyclohexanone oxime of 0.5-20 h⁻¹. -1 Preferably 1-10h -1 The reaction temperature is 300-500℃, preferably 350-400℃, and the reaction pressure is 0.05-0.8MPa, preferably 0.1-0.5MPa. Unless otherwise specified, all pressures mentioned in this invention are gauge pressures.
[0086] According to the present invention, preferably, the method further includes mixing cyclohexanone oxime with water, and then contacting the catalyst in the presence of the solvent to carry out a gas-phase Beckmann rearrangement reaction. This preferred embodiment is more advantageous in improving the stability of the catalyst. Preferably, the molar ratio of cyclohexanone oxime to water is 1:(0.01-2.5).
[0087] The present invention will be described in detail below through embodiments.
[0088] Unless otherwise specified, the raw materials used in the following examples are from the following sources:
[0089] Tetraethyl orthosilicate: purchased from Zhejiang Kaihua Synthetic Materials Co., Ltd., with a purity of 99 wt%, ethanol content not exceeding 1 wt%, platinum-cobalt color not exceeding 20 mg Pt-Co / L, and Cl ion content not exceeding 50 ppm.
[0090] Tetrapropylammonium hydroxide: Purchased from Guangzhou Dayou Fine Chemical Co., Ltd., with a tetrapropylammonium hydroxide content of 22.5 wt%, sodium ion content not exceeding 500 ppm, bromide ion content not exceeding 1.5 wt%, carbonate ion content not exceeding 0.2 wt%, APHA color not exceeding 100, potassium ion content not exceeding 1.5% wt%, iron ion content not exceeding 10 ppm, acetic acid content not exceeding 500 ppm, and formic acid and propionic acid content not exceeding 50 ppm.
[0091] Potassium hydroxide: purchased from Sinopharm Group.
[0092] Example 1
[0093] 416 kg of tetraethyl orthosilicate, 271 kg of 22.5% tetrapropylammonium hydroxide, 3.92 kg of potassium hydroxide, and 870 kg of water were mixed and stirred at room temperature for 4 hours to form a colloidal mixture with a pH of 12.41. The molar ratio of the mixture was SiO2:TPAOH:KOH:H2O = 1:0.15:0.035:30. The mixture was then transferred to a 2m... 3In a stainless steel reactor, crystallization was carried out at 120℃ for 2 days. The pH value of the crystallization product was 13.60. Then, it was filtered using a 50nm six-tube membrane (Beijing Zhongtianyuan Environmental Engineering Co., Ltd.) and washed with water at 40-60℃, with a washing water volume of 7.5m³. 3 The pH value of the washing water for the crystallized product reached 9.0. The slurry obtained after washing was concentrated to produce 315 kg of molecular sieve slurry with a solid content of 33.5% by weight.
[0094] A small amount of the molecular sieve slurry was dried at 120℃ for 20 hours to obtain raw powder containing all-silica-1 molecular sieve. The all-silica-1 molecular sieve was calcined at 550℃ for 6 hours, and its BET specific surface area was 422 m². 2 / gram, with an external specific surface area of 45 meters. 2 / g, particle size 0.1-0.2μm. The X-ray diffraction pattern of the raw silicon-1 molecular sieve powder is shown below. Figure 1 As shown, its X-ray diffraction (XRD) pattern is consistent with the standard XRD pattern characteristics of the MFI structure described in Microporous Materials, Vol 22, p637, 1998, indicating that the molecular sieve has an MFI crystal structure.
[0095] The above molecular sieve slurry was mixed with 65 kg of 40% alkaline silica sol (pH 9.5, sodium ion content 324 ppm, SiO2 content 40% by weight), and after calcination, the surface area of the resulting SiO2 was 225 m². 2 The molecular sieve dry base and alkaline silica sol (calculated as SiO2) in the molecular sieve slurry were mixed at a weight ratio of 1:0.2. The mixture was stirred until homogeneous and then pulped to obtain a molecular sieve-binder mixed slurry with a solid content of 34% by weight. This slurry was then fed into a spray forming device (manufactured by Wuxi Tianyang Spray Drying Equipment Co., Ltd., model LT-300) for spray forming, with inlet and outlet temperatures of 200℃ and 95℃, respectively. Then it was fed into a 3m... 3 In a heating shuttle furnace (manufactured by Hubei Huanggang Huaxia Electromechanical Thermal Equipment Co., Ltd.), the microspheres were calcined at 280℃, 400℃, and 480℃ for 2 hours each, and finally calcined at 550℃ for 12 hours to obtain 130 kg of microsphere molecular sieves, of which the content of all-silica-1 molecular sieve was 80% by weight and the content of binder was 20% by weight.
[0096] 100 kg of the above-mentioned microsphere molecular sieve and 1000 kg of an alkaline buffer solution containing nitrogen compounds (wherein, the concentration of ammonia water is 26 wt%, the content of ammonium nitrate in the ammonium nitrate aqueous solution is 7.5 wt%, the weight ratio of ammonia water to ammonium nitrate aqueous solution is 3:2, the pH value is 11.35, 130 g of tetrapropylammonium bromide, and 26.6 g of magnesium nitrate hexahydrate) were added to a 2m... 3 In a stainless steel reactor, at 88℃ and 3.2 kg / cm²... 2The mixture was stirred under pressure for 1.5 hours, then filtered. This process was repeated once more, followed by washing until the pH of the filtrate reached 9.1. The filtrate was then dried at 120°C for 24 hours to obtain the microsphere molecular sieve catalyst, containing Mg. 2+ It is 85 ppm, designated A1.
[0097] The particle size of the microsphere molecular sieve catalyst A1 was found to be concentrated in the range of 40-180 μm, and the wear index K = 1.6.
[0098] Example 2
[0099] 416 kg of tetraethyl orthosilicate, 216.5 kg of 22.5% tetrapropylammonium hydroxide, 3.92 kg of potassium hydroxide, and 552 kg of water were mixed and stirred at room temperature for 4 hours to form a colloidal mixture with a pH of 12.44. The molar ratio of the mixture was SiO2:TPAOH:KOH:H2O = 1:0.12:0.035:20. The mixture was then transferred to a 2m... 3 In a stainless steel reactor, crystallization was carried out at 120℃ for 2 days. The pH value of the crystallization product was 13.60. The product was then filtered through a 50nm six-tube membrane and washed with water at 40–60℃, using 7.5 ml of washing water. 3 The pH value of the washing water for the crystallized product reached 9.0. The slurry obtained after washing was concentrated to produce 315 kg of molecular sieve slurry with a solid content of 33.5% by weight.
[0100] A small amount of the molecular sieve slurry was dried at 120℃ for 20 hours to obtain the raw powder of all-silica-1 molecular sieve. The all-silica-1 molecular sieve was calcined at 550℃ for 6 hours, and its BET specific surface area was 427 m². 2 / gram, with an external specific surface area of 46 meters. 2 / gram, with a particle size of 0.1-0.2 μm.
[0101] Molecular sieve slurry was mixed with 51.5 kg of 35% alkaline silica sol (pH 9.5, sodium ion content 324 ppm, SiO2 content 40% by weight). After calcination, the surface area of the resulting SiO2 was 225 m². 2 The molecular sieve dry base and alkaline silica sol (calculated as SiO2) in the molecular sieve slurry were mixed in a weight ratio of 1:0.15. The mixture was stirred thoroughly and then pulped to obtain a molecular sieve-binder mixed slurry with a solid content of 22% by weight. This slurry was then fed into a spray molding device for spray molding, with inlet and outlet temperatures of 205℃ and 100℃, respectively. Then it was fed into a 3m... 3 In a heated shuttle furnace, the microspheres were calcined at 280℃, 400℃, and 480℃ for 2 hours each, and finally calcined at 550℃ for 12 hours to obtain 121 kg of microsphere molecular sieves, of which the content of all-silica-1 molecular sieve was 85% by weight and the content of binder was 15% by weight.
[0102] 100 kg of the above-mentioned microsphere molecular sieve and 1000 kg of alkaline buffer solution (the alkaline buffer solution includes ammonia water and ammonium acetate aqueous solution, wherein the ammonia water content is 26 wt%, the ammonium acetate content in the ammonium acetate aqueous solution is 7.5 wt%, the weight ratio of ammonia water to ammonium acetate aqueous solution is 3:2, the pH value is 11.39, and 130 g of tetrapropylammonium bromide and 53 g of magnesium nitrate hexahydrate) were added to a 2m... 3 In a stainless steel reactor, at 85℃ and 2.8 kg / cm²... 2 The mixture was stirred under pressure for 3 hours, then filtered, washed until the pH of the filtrate reached 9, and then dried at 120°C for 24 hours to obtain the microsphere molecular sieve catalyst, in which Mg... 2+ It is 168 ppm, designated A2.
[0103] The particle size of the microsphere molecular sieve catalyst A2 was found to be concentrated in the range of 40-180 μm, and the wear index K = 2.0.
[0104] Example 3
[0105] Molecular sieves were synthesized according to the method in Example 1. After washing, the resulting slurry was concentrated to obtain 373 kg of molecular sieve slurry with a solid content of 28.4% by weight.
[0106] The above molecular sieve slurry was mixed with 110 kg of 30% alkaline silica sol (pH 9.5, sodium ion content 324 ppm, SiO2 content 40% by weight). After calcination, the surface area of the resulting SiO2 was 225 m². 2 The molecular sieve dry base and alkaline silica sol (calculated as SiO2) in the molecular sieve slurry were mixed in a weight ratio of 1:0.312. The mixture was stirred until homogeneous and then pulped to obtain a molecular sieve-binder mixed slurry with a solid content of 28.8% by weight. This slurry was then fed into a spray molding device for spray molding, with inlet and outlet temperatures of 210℃ and 105℃, respectively. It was then fed into a 3m... 3 In a heated shuttle furnace, the microspheres were calcined at 280℃, 400℃, and 480℃ for 2 hours each, and finally calcined at 550℃ for 12 hours to obtain 138 kg of microsphere molecular sieves, of which the content of all-silica-1 molecular sieve was 76% by weight and the content of binder was 24% by weight.
[0107] 100 kg of the above-mentioned microsphere molecular sieve and 1000 kg of alkaline buffer solution (the alkaline buffer solution includes ammonia water and ammonium nitrate aqueous solution, wherein the ammonia water content is 26 wt%, the ammonium nitrate content in the ammonium nitrate aqueous solution is 7.5 wt%, the weight ratio of ammonia water to ammonium nitrate aqueous solution is 3:2, the pH value is 11.35, and 130 g of tetrapropylammonium bromide and 26.5 g of magnesium nitrate hexahydrate) were added to a 2m... 3 In a stainless steel reactor, at 90℃ and 3.6 kg / cm³... 2The mixture was stirred under pressure for 1.5 hours, then filtered, dried at 120°C for 24 hours, and then the contact operation with the alkaline buffer solution containing nitrogen compounds was repeated once under the same conditions. The mixture was then filtered again, washed until the pH of the filtrate was 9, and then dried at 120°C for 24 hours to obtain the microsphere molecular sieve catalyst, in which Mg... 2+ It was 81 ppm, designated A3.
[0108] The particle size of the microsphere molecular sieve catalyst A3 was found to be concentrated in the range of 40-180 μm, and the wear index K = 1.8.
[0109] Example 4
[0110] Molecular sieves were synthesized according to the method in Example 1. After washing, the resulting slurry was concentrated to obtain 346 kg of molecular sieve slurry with a solid content of 30.6% by weight.
[0111] The above molecular sieve slurry was mixed with 235 kg of 30% alkaline silica sol (pH 9.5, sodium ion content 324 ppm, SiO2 content 40% by weight). After calcination, the surface area of the resulting SiO2 was 225 m². 2 The molecular sieve dry base and alkaline silica sol (calculated as SiO2) in the molecular sieve slurry were mixed in a weight ratio of 1:0.666. The mixture was stirred thoroughly and then pulped to obtain a molecular sieve-binder mixed slurry with a solid content of 30.3% by weight. This slurry was then fed into a spray molding device for spray molding, with inlet and outlet temperatures of 200℃ and 100℃, respectively. It was then fed into a 3m... 3 In a heated shuttle furnace, the microspheres were calcined at 280℃, 400℃, and 480℃ for 2 hours each, and finally calcined at 550℃ for 12 hours to obtain 134 kg of microsphere molecular sieves, of which the content of all-silica-1 molecular sieve was 60% by weight and the content of binder silica sol was 40% by weight.
[0112] 100 kg of the above-mentioned microsphere molecular sieve and 1000 kg of alkaline buffer solution (the alkaline buffer solution includes ammonia water and ammonium nitrate aqueous solution, wherein the ammonia water content is 26 wt%, the ammonium nitrate content in the ammonium nitrate aqueous solution is 7.5 wt%, the weight ratio of ammonia water to ammonium nitrate aqueous solution is 3:2, the pH value is 11.35, 130 g of tetrapropylammonium bromide, and 2.6 g of magnesium nitrate hexahydrate) were added to a 2m... 3 In a stainless steel reactor, at 85℃ and 2.8 kg / cm²... 2 The mixture was stirred under pressure for 1.5 hours, then filtered, dried at 120°C for 24 hours, and then the contact operation with the alkaline buffer solution containing nitrogen compounds was repeated once under the same conditions. The mixture was then filtered again, washed until the pH of the filtrate was 9, and then dried at 120°C for 24 hours to obtain the microsphere molecular sieve catalyst, in which Mg... 2+ It is 8 ppm, designated A4.
[0113] The particle size of the microsphere molecular sieve catalyst A4 was found to be concentrated in the range of 40-180 μm, and the wear index K = 2.5.
[0114] Example 5
[0115] Molecular sieves were synthesized according to the method in Example 2. After washing, the resulting slurry was concentrated to obtain 346 kg of molecular sieve slurry with a solid content of 30.6% by weight.
[0116] The above molecular sieve slurry was mixed with 40 kg of 30% alkaline silica sol (pH 9.5, sodium ion content 324 ppm, SiO2 content 40% by weight). After calcination, the surface area of the resulting SiO2 was 225 m². 2 The molecular sieve dry base and alkaline silica sol (calculated as SiO2) in the molecular sieve slurry were mixed in a weight ratio of 1:0.11. The mixture was stirred until homogeneous and then pulped to obtain a molecular sieve-binder mixed slurry with a solid content of 30.45% by weight. This slurry was then fed into a spray molding device for spray molding, with inlet and outlet temperatures of 200℃ and 100℃, respectively. It was then fed into a 3m... 3 In a heated shuttle furnace, the microspheres were calcined at 280℃, 400℃, and 480℃ for 2 hours each, and finally calcined at 550℃ for 12 hours to obtain 120 kg of microsphere molecular sieves, of which the content of all-silica-1 molecular sieve was 90% by weight and the content of binder was 10% by weight.
[0117] 100 kg of the above-mentioned microsphere molecular sieve and 1000 kg of alkaline buffer solution (the alkaline buffer solution includes ammonia water and ammonium nitrate aqueous solution, wherein the ammonia water content is 26 wt%, the ammonium nitrate content in the ammonium nitrate aqueous solution is 7.5 wt%, the weight ratio of ammonia water to ammonium nitrate aqueous solution is 3:2, the pH value is 11.35, 130 g of tetrapropylammonium bromide, and 1233 g of magnesium nitrate hexahydrate) were added to a 2m... 3 In a stainless steel reactor, at 80℃ and 2.1 kg / cm³... 2 The mixture was stirred under pressure for 1.5 hours, then filtered, dried at 120°C for 24 hours, and then the contact operation with the alkaline buffer solution containing nitrogen compounds was repeated once under the same conditions. The mixture was then filtered again, washed until the pH of the filtrate was 9, and then dried at 120°C for 24 hours to obtain the microsphere molecular sieve catalyst, in which Mg... 2+ It was 3992 ppm, designated A5.
[0118] The particle size of the microsphere molecular sieve catalyst A5 was found to be concentrated in the range of 40-180 μm, and the wear index K = 2.6.
[0119] Example 6
[0120] Molecular sieves were synthesized according to the method in Example 2. The slurry obtained after washing was dried at 120°C for 20 hours to obtain 126.6 kg of all-silica-1 molecular sieve raw powder.
[0121] The 126 kg of molecular sieve powder was pulverized to approximately 100 mesh and mixed with 86.5 kg of 30% alkaline silica sol (pH 9.5, sodium ion content 324 ppm, SiO2 content 40% by weight). After calcination, the resulting SiO2 had a surface area of 225 m². 2 The molecular sieve dry base and alkaline silica sol (calculated as SiO2) in the molecular sieve slurry were mixed in a weight ratio of 1:0.246. 45 kg of water was added, and the mixture was stirred until homogeneous and then slurried to obtain a molecular sieve-binder mixed slurry with a solid content of 52% by weight. This slurry was then fed into a spray molding device for spray molding, with inlet and outlet temperatures of 200℃ and 95℃, respectively. Then it was fed into a 3m... 3 In a heated shuttle furnace, the microspheres were calcined at 280℃, 400℃, and 480℃ for 2 hours each, and finally calcined at 550℃ for 12 hours to obtain 130 kg of microsphere molecular sieves, of which the content of all-silica-1 molecular sieve was 80% by weight and the content of binder was 20% by weight.
[0122] 100 kg of the above-mentioned microsphere molecular sieve and 1000 kg of alkaline buffer solution (the alkaline buffer solution includes ammonia water and ammonium nitrate aqueous solution, wherein the ammonia water content is 26 wt%, the ammonium nitrate content in the ammonium nitrate aqueous solution is 7.5 wt%, the weight ratio of ammonia water to ammonium nitrate aqueous solution is 3:2, the pH value is 11.35, and 65 g of tetrapropylammonium bromide and 26.6 g of magnesium nitrate hexahydrate) were added to a 2m... 3 In a stainless steel reactor, at 82℃ and 2.3 kg / cm²... 2 The mixture was stirred under pressure for 1.5 hours, then filtered, dried at 120°C for 24 hours, and then the contact operation with the alkaline buffer solution containing nitrogen compounds was repeated once under the same conditions. The mixture was then filtered again, washed until the pH of the filtrate was 9, and then dried at 120°C for 24 hours to obtain the microsphere molecular sieve catalyst, in which Mg... 2+ It is 83 ppm, item number A6.
[0123] The particle size of microsphere molecular sieve catalyst A6 is concentrated in the range of 40-180 μm, and the wear index K = 2.6.
[0124] Example 7
[0125] Following the method of Example 1, except that the tetraethyl orthosilicate was obtained from Jiangxi Chenguang New Material Co., Ltd., with a purity of 99.4 wt%, an ethanol content of 0.4 wt%, a platinum-cobalt color of 12 mg Pt-Co / L, and a Cl ion content of 65 ppm. The tetrapropylammonium hydroxide used was purchased from Tokyo Chemical Reagents, with a tetrapropylammonium hydroxide content of 25 wt%, a sodium ion content of 28.5 ppm, a bromide ion content of 1.2 wt%, a carbonate ion content of 0.2 wt%, an APHA color of 30, a potassium ion content of 1.1 wt%, an iron ion content of 38 ppm, an acetic acid content of 214 ppm, and formic acid and propionic acid contents of 26 ppm. Microsphere molecular sieve catalyst A7 was obtained.
[0126] Example 8
[0127] The method is the same as in Example 1, except that the amount of KOH used is such that the molar ratio of the colloidal mixture is tetraethyl orthosilicate (calculated as SiO2): TPAOH: KOH: H2O = 1:0.10:0.05:20, and the rest is the same as in Example 1.
[0128] Microsphere molecular sieve catalyst A8 was obtained.
[0129] Comparative Example 1
[0130] The method was followed in Example 1, except that KOH was not added during the molecular sieve synthesis process, and the molar ratio of the colloidal mixture was ethyl orthosilicate (based on SiO2): TPAOH: H2O = 1:0.10:30. The nitrogen-containing compound post-treatment did not include the addition of tetrapropylammonium bromide and magnesium nitrate hexahydrate. Everything else was the same as in Example 1. The resulting microsphere molecular sieve catalyst was designated DA1.
[0131] Test Implementation Examples
[0132] The cyclohexanone oxime gas-phase Beckmann rearrangement reaction was carried out using the catalysts prepared in the above examples and comparative examples respectively:
[0133] The gas-phase Beckmann rearrangement reaction of cyclohexanone oxime was carried out in a fixed fluidized bed reactor. The vertical 316L stainless steel fluidized bed reactor had an upper diameter of 20 cm and a lower diameter of 10 cm, with upper and lower section lengths of 60 cm and 80 cm respectively. The microsphere molecular sieve catalyst loading in the fixed fluidized bed reactor was 250 g. The reaction conditions in the fluidized bed reactor included: reaction pressure 0.1 MPa, fluidized bed reaction temperature 385 °C, gas atomization spray feeding, vaporization chamber temperature control 190 °C, minimum vaporizer temperature 160 °C, outlet pipeline insulation 200 °C, and a WHSV of 4.2 h⁻¹. -1 Cyclohexanone oxime accounts for 35% by weight of the total amount of cyclohexanone oxime and ethanol, water accounts for 0.8% by weight of the total amount of water, ethanol and cyclohexanone oxime, and the molar ratio of nitrogen to cyclohexanone oxime is 2.
[0134] After 10 hours of reaction, the conversion rate of cyclohexanone oxime and the selectivity of caprolactam were analyzed. The feed of cyclohexanone oxime, ethanol and water was stopped, and nitrogen was continuously introduced into the fluidized bed reactor at a rate of 450 L / h for 30 minutes. Then, the nitrogen was switched to air at a rate of 180 L / h, and the temperature of the fluidized bed reactor was raised from 385 °C to 450 °C. The catalyst was then regenerated at this temperature for 14 hours.
[0135] The reaction products were quantitatively analyzed using an Agilent 6890 gas chromatograph (flame ionization detector, PEG20M capillary column, 50m column length). The vaporization chamber temperature was 250℃, the detection chamber temperature was 240℃, and the column temperature was programmed: 110℃ for 8 minutes, then increased to 230℃ at a rate of 15℃ / min and held for 14 minutes.
[0136] The contents of the rearranged products of caprolactam and cyclohexenone after the reaction were calculated using the area normalization method, and the solvent was not included in the integration.
[0137] The above analysis yielded the molar percentages of cyclohexanone oxime and caprolactam in the reaction products. The conversion rate of cyclohexanone oxime and the selectivity of caprolactam were then calculated using the following formulas. The results are shown in Table 1.
[0138] Cyclohexanone oxime conversion (mol%) = (100 - cyclohexanone oxime molar percentage in reaction product) / 100 × 100%;
[0139] Total selectivity of caprolactam (mol%) = molar percentage of caprolactam in the reaction product / (100 - molar percentage of cyclohexanone oxime in the reaction product) × 100%;
[0140] In the cyclohexanone oxime gas-phase Beckmann rearrangement reaction, ethyl-ε-caprolactam accounts for approximately 40% of all byproducts. This byproduct is generated by the alcoholysis of ethanol and the enol tautomer of caprolactam. Ethyl-ε-caprolactam further undergoes hydrolysis in the presence of water to regenerate caprolactam. Therefore, the amount of caprolactam generated from the hydrolysis of ethyl-ε-caprolactam is included in the calculation of the overall caprolactam selectivity.
[0141] Table 1
[0142]
[0143]
[0144] As can be seen from Table 1, the cyclohexanone oxime conversion rate of the microsphere all-silica-1 molecular sieve catalyst prepared by the present invention is extremely high, reaching up to 99.95% after 10 hours of reaction, and the selectivity for caprolactam is also very high, reaching up to 96.68%.
[0145] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A method for preparing a catalyst containing a ZSM-5 type all-silica molecular sieve, characterized in that, Includes the following steps: (1) Mix silicon source, KOH, organic base and water, and hydrolyze to obtain colloidal mixture; Wherein, the silicon source is an organosilicate, and the molar ratio of silicon source, KOH, organic base and water, calculated as SiO2, is 1:(0.01-0.1):(0.04-0.25):(15-45); (2) The colloidal mixture is crystallized, and the resulting crystallization mother liquor is optionally concentrated to obtain a molecular sieve slurry; The crystallization temperature is 95-150℃, and the time is 0.5-5 days; (3) The molecular sieve slurry is mixed with the binder and then pulped to obtain a molecular sieve-binder slurry; the molecular sieve-binder slurry is spray-molded and then calcined; (4) The product obtained by roasting in step (3) is contacted with an alkaline buffer solution containing ammonium salt, ammonia water, magnesium salt and bromide salt, and then dried.
2. The preparation method according to claim 1, characterized in that, The silicon source is methyl orthosilicate and / or ethyl orthosilicate; Preferably, the Cl ion content in the organosilicon ester is not greater than 50 ppm; Preferably, the platinum-cobalt color of the organosilicon ester is not greater than 20 mg / L; Preferably, the purity of the organosilicon ester is not less than 98 wt%.
3. The preparation method according to claim 1 or 2, characterized in that, The organic base is selected from at least one of aliphatic amine compounds, alcoholic amine compounds, and quaternary ammonium base compounds; The quaternary ammonium base compound is preferably an alkyl quaternary ammonium base compound containing 1-4 carbon atoms, and more preferably tetraethylammonium hydroxide and / or tetrapropylammonium hydroxide; Preferably, the organic base contains less than 1.5 wt% bromide ions, and more preferably 0.5-1.5 wt%. Preferably, the iron ion content in the organic base is not greater than 10 ppm; Preferably, the organic base contains less than 500 ppm sodium ions, not more than 550 ppm free acid, less than 0.2 wt% carbonate ions, and an APHA color of no more than 100.
4. The preparation method according to any one of claims 1-3, characterized in that, In step (1), the molar ratio of silicon source, KOH, organic base and water, calculated as SiO2, is 1:(0.02-0.08):(0.08-0.2):(20-40), preferably 1:(0.03-0.05):(0.08-0.2):(20-30); Preferably, in step (1), the hydrolysis is carried out under stirring conditions, the hydrolysis temperature is 10-50℃, and the time is 0.5-10h.
5. The preparation method according to any one of claims 1-4, characterized in that, In step (2), the crystallization temperature is 110-140℃ and the time is 1-3 days; Preferably, in step (2), the solid content of the molecular sieve slurry is 20-50% by weight, and more preferably 25-45% by weight.
6. The preparation method according to any one of claims 1-5, characterized in that, In step (3), the solid content of the molecular sieve-binder slurry is 20-60% by weight, preferably 30-50% by weight; Preferably, the weight ratio of the dry molecular sieve basis to the binder basis in the molecular sieve-binder slurry is 1:(0.05-1); Preferably, the binder is a precursor of silicon oxide, which is silica sol and / or silica, preferably silica sol; Preferably, the spray forming conditions include: an inlet temperature of 180-240℃, more preferably 200-220℃; and an outlet temperature of 80-120℃, more preferably 90-105℃. Preferably, the calcination conditions include: a temperature of 200-600℃, more preferably 250-550℃, and a time of 1-20h.
7. The preparation method according to any one of claims 1-6, characterized in that, In step (3), an additive is introduced during the pulping process. The additive is selected from at least one of the following: guar gum powder, graphite, activated carbon, paraffin wax, glycerin, citric acid, starch, polyethylene glycol, polyvinyl alcohol, nitric acid, hydrochloric acid, acetic acid, formic acid, ammonia, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrapropylammonium hydroxide. Preferably, the amount of additive introduced is 1-5 wt%, based on the dry weight of the molecular sieve in the molecular sieve slurry.
8. The preparation method according to any one of claims 1-7, characterized in that, The pH of the alkaline buffer solution is 8.5-13.5; Preferably, based on the total amount of the alkaline buffer solution, the content of magnesium salts (calculated as Mg) is 1-500 ppm, and the content of bromide salts (calculated as Br) is 1-500 ppm. Preferably, the ammonium salt is selected from ammonium nitrate and / or ammonium acetate; Preferably, the magnesium salt is selected from at least one of magnesium nitrate hexahydrate, magnesium acetate, magnesium chloride, magnesium sulfate, and magnesium hydrogen phosphate; Preferably, the bromide salt is tetrapropylammonium bromide; Preferably, the alkaline buffer solution comprises ammonia, an ammonium salt aqueous solution, a magnesium salt, and a bromide salt; Preferably, the weight ratio of ammonia water to ammonium salt aqueous solution is 1-3:1; Preferably, the concentration of the ammonia solution is 5-30 wt%. Preferably, the concentration of the ammonium salt aqueous solution is 0.5-10 wt%. Preferably, the amount of alkaline buffer solution used is 500-1500 parts by weight, more preferably 700-1200 parts by weight, relative to 100 parts by weight of the product obtained by calcination on a dry basis. Preferably, the contact conditions include: a temperature of 50-120°C, more preferably 70-100°C; and a pressure of 0.5-10 kg / cm². 2 The preferred value is 1.5-4 kg / cm². 2 The time is 0.1-5 hours, preferably 1-3 hours.
9. A catalyst containing a ZSM-5 type structured all-silica molecular sieve prepared by the preparation method according to any one of claims 1-8; Preferably, the catalyst comprises a molecular sieve and a binder; based on the dry weight of the catalyst, the content of the molecular sieve, on a dry weight basis, is 50-95% by weight, preferably 55-80% by weight; the content of the binder, based on oxides, is 5-50% by weight, preferably 20-45% by weight. Preferably, the catalyst further contains Mg and Br elements, wherein the content of Mg element is 20-1000 ppm, preferably 20-500 ppm; and the content of Br element is 10-1000 ppm, preferably 10-500 ppm. Preferably, the particle size of the catalyst is 20-400 μm, more preferably 40-250 μm; Preferably, the wear index K of the catalyst is less than 3.
10. A method for the gas-phase Beckmann rearrangement of cyclohexanone oxime, the method comprising: Under the conditions of the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime, in the presence of a solvent, cyclohexanone oxime is reacted with a catalyst, wherein the catalyst is the all-silica molecular sieve containing the ZSM-5 type structure as described in claim 9. Preferably, the contact takes place in a fluidized bed reactor.