Spherical all-silica molecular sieve catalyst and preparation method thereof, and method for gas-phase beckmann rearrangement of cyclohexanone oxime

Abstract

The application relates to the technical field of catalysts, and discloses a spherical full-silicon molecular sieve catalyst, a preparation method thereof, and a method for gas-phase Beckmann rearrangement of cyclohexanone oxime, which comprises the following steps: (1) mixing a silicon source, an organic alkali and water, performing hydrolysis, and obtaining a colloidal mixture; (2) performing crystallization on the colloidal mixture, and then performing drying to obtain a molecular sieve raw powder; (3) optionally mixing the molecular sieve raw powder with a binder, and then performing rotary molding to obtain spherical particles; and (4) performing calcination on the spherical particles, and then contacting the spherical particles with an alkaline buffer solution containing an ammonium salt, ammonia water, a magnesium salt and a bromine salt; the content of the magnesium salt, calculated according to Mg elements, is 1-500 ppm based on the total amount of the alkaline buffer solution, and the content of the bromine salt, calculated according to Br elements, is 1-500 ppm. In a moving bed or fixed bed reaction system, the spherical ZSM-5 structure full-silicon molecular sieve catalyst has a high conversion rate of cyclohexanone oxime.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a spherical all-silica molecular sieve catalyst and its preparation method, and a method for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime. Background Technology

[0002] The ZSM-5 type all-silica molecular sieve was first successfully synthesized in 1978 by EMFlanigen et al. of UCC, and belongs to the last member of the "Pentasil" family. All-silica molecular sieves are aluminum-free molecular sieves and are the simplest type in the ZSM-5 molecular sieve family, with a framework containing only silicon and oxygen atoms, and the basic structural unit being the SiO4 tetrahedron. The synthesis of ZSM-5 type all-silica molecular sieves generally employs the traditional hydrothermal method using organic raw materials. For example, JP59164617 discloses the preparation of all-silica-1 molecular sieves using tetraethyl orthosilicate (TEOS) as the silicon source and tetrapropylammonium hydroxide as the template agent. CN1338427A discloses an all-silica-1 molecular sieve including two synthesis methods, both using tetraethyl orthosilicate and tetrapropylammonium hydroxide as synthetic raw materials.

[0003] Caprolactam is a key raw material for the production of three major product series: nylon, industrial tire cord, and nylon engineering plastics. Demand for it remains consistently high, and it is generally prepared via the Beckmann rearrangement reaction of cyclohexanone oxime. To develop solid acid catalysts suitable for gas-phase Beckmann rearrangement reactions, researchers both domestically and internationally have conducted extensive studies on catalysts such as oxides (composite oxides) and zeolite molecular sieves. CN102050464A discloses a method for synthesizing a ZSM-5 type all-silica molecular sieve. This all-silica molecular sieve is prepared by crystallizing ethyl silicate as the silicon source, tetrapropylammonium hydroxide as the base source and template agent at 80-120℃ for 1-3 days. The molecular sieve obtained by this method exhibits high cyclohexanone oxime conversion and caprolactam selectivity when used in the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime to prepare caprolactam.

[0004] However, ZSM-5 type all-silica molecular sieves face significant difficulties in extrusion, tableting, and even roll forming. Even after forming, the crushing strength of the catalyst is far from ideal (<60 N / cm or <1 kg / particle), making industrial application impossible. Currently, industrial production primarily utilizes liquid-phase rearrangement processes using concentrated sulfuric acid or fuming sulfuric acid as catalysts. This process produces approximately 90% of the world's caprolactam, but it consumes large amounts of sulfuric acid and ammonia. Typically, producing 1.3-1.8 tons of ammonium sulfate as a byproduct for every ton of caprolactam produced, resulting in high production costs. The use of sulfuric acid also causes equipment corrosion and environmental pollution. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of poor strength, unsatisfactory conversion rate and selectivity of existing spherical all-silica molecular sieve catalysts, and to provide a spherical all-silica molecular sieve catalyst and its preparation method, as well as a method for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime. The spherical all-silica molecular sieve catalyst prepared by this method has the characteristics of high crushing strength, good conversion rate and selectivity.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a spherical all-silica molecular sieve catalyst, comprising the following steps:

[0007] (1) Mix silicon source, organic base and water, and hydrolyze to obtain colloidal mixture;

[0008] The silicon source is an organosilicone ester, and the molar ratio of silicon source, organic base and water, calculated as SiO2, is 1:(0.04-0.25):(15-45).

[0009] (2) The colloidal mixture is crystallized and then dried to obtain molecular sieve powder;

[0010] The crystallization temperature is 95-150℃, and the time is 0.5-5 days;

[0011] (3) The molecular sieve powder is optionally mixed with a binder, and then rotated to form spherical particles;

[0012] (4) The spherical particles are calcined and then contacted with an alkaline buffer solution containing ammonium salt, ammonia water, magnesium salt and bromide salt;

[0013] 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.

[0014] The second aspect of the present invention provides a spherical all-silica molecular sieve catalyst prepared by the above preparation method.

[0015] The 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 spherical all-silica molecular sieve catalyst described in the second aspect.

[0016] Preferably, the contact takes place in a fixed-bed or moving-bed reactor.

[0017] The preparation method provided by this invention can obtain a highly crystalline, fine-particle, and nearly neutral ZSM-5 type all-silica molecular sieve. After rolling molding, it is post-treated with an alkaline buffer solution containing ammonium salt, magnesium salt, and bromide salt. Under the overall effect of molecular sieve synthesis and post-treatment conditions, the resulting spherical catalyst has good crushing strength. In a moving bed or fixed bed reaction system, the method of preparing caprolactam by gas-phase Beckmann rearrangement of cyclohexanone oxime using this spherical ZSM-5 type all-silica molecular sieve as a catalyst can achieve long-cycle, continuous production of caprolactam. While maintaining the selectivity of caprolactam essentially unchanged, it can improve the conversion rate of cyclohexanone oxime, extend the catalyst life, and improve the economics of the new gas-phase rearrangement process technology. Attached Figure Description

[0018] Figure 1 This is a TEM image of the spherical all-silica molecular sieve catalyst prepared in Example 1 of this invention. Detailed Implementation

[0019] 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.

[0020] The first aspect of this invention provides a method for preparing a spherical all-silica molecular sieve catalyst, comprising the following steps:

[0021] (1) Mix silicon source, organic base and water, and hydrolyze to obtain colloidal mixture;

[0022] The silicon source is an organosilicone ester, and the molar ratio of silicon source, organic base and water, calculated as SiO2, is 1:(0.04-0.25):(15-45).

[0023] (2) The colloidal mixture is crystallized and then dried to obtain molecular sieve powder;

[0024] The crystallization temperature is 95-150℃, and the time is 0.5-5 days;

[0025] (3) The molecular sieve powder is optionally mixed with a binder, and then rotated to form spherical particles;

[0026] (4) The spherical particles are calcined and then contacted with an alkaline buffer solution containing ammonium salt, ammonia water, magnesium salt and bromide salt;

[0027] 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.

[0028] Using the above-mentioned preferred preparation method, and employing an alkaline buffer solution containing ammonium, magnesium, and bromide salts for post-treatment, the resulting spherical catalyst exhibits good crushing strength under the combined effect of molecular sieve synthesis and post-treatment conditions. In a moving bed or fixed bed reaction system, using this spherical ZSM-5 type all-silica molecular sieve as a catalyst for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime to prepare caprolactam enables long-cycle, continuous production of caprolactam. While maintaining the selectivity of caprolactam essentially unchanged, it can improve the conversion rate of cyclohexanone oxime and extend the catalyst lifetime.

[0029] According to the present invention, preferably, the silicon source is methyl orthosilicate and / or ethyl orthosilicate, more preferably ethyl orthosilicate.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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 compounds are preferably alkyl quaternary ammonium base compounds containing 1-4 carbon atoms, and more preferably tetraethylammonium hydroxide and / or tetrapropylammonium hydroxide.

[0034] According to the present invention, the mixing in step (1) further includes the addition of KOH; preferably, 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), more preferably 1:(0.03-0.05):(0.08-0.2):(20-30).

[0035] 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 the alkyl quaternary ammonium bases are quite strict, usually requiring 5-10 ppm. In this invention, by introducing KOH, the requirement for sodium ion content in the alkyl quaternary ammonium bases can be relaxed. Even with a sodium ion content exceeding 10 ppm, high-quality all-silica-1 molecular sieve raw powder can still be synthesized without affecting the catalytic performance of the catalysts further prepared.

[0036] 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.

[0037] Preferably, the organic base contains less than 500 ppm sodium ions, no more than 10 ppm iron ions, no 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.

[0038] 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.

[0039] According to some preferred embodiments of the present invention, the mixing further includes the addition of a low-carbon alcohol, which may be, for example, methanol and / or ethanol.

[0040] Preferably, the molar ratio of the low-carbon alcohol to the silicon source (calculated as SiO2) is 3.5-15:1.

[0041] 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.

[0042] 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.

[0043] According to the present invention, before the drying in step (2), the crystallized product is further washed and separated into solid and liquid phases. The present invention does not have any particular limitation on this, and conventional methods can be used to obtain a solid product.

[0044] Preferably, the drying temperature in step (2) is 90-120℃ and the time is 12-36h.

[0045] According to some preferred embodiments of the present invention, the BET specific surface area of ​​the molecular sieve powder after calcination at 550°C for 6 hours is 380-460 m². 2 / g, with an external specific surface area of ​​10-60m² 2 / g.

[0046] In this invention, the BET specific surface area and external specific surface area data of the molecular sieve raw powder were measured by a Micromeritics ASAP-2400 automatic adsorption instrument from the United States. The test conditions were: N2 as adsorbate, adsorption temperature of -196.15℃ (liquid nitrogen temperature), and constant temperature degassing at 1.3 Pa and 300℃ for 6 hours.

[0047] In this invention, preferably, the binder is a precursor of water or silicon dioxide. The silicon dioxide precursor can be selected from any substance that can be converted into silicon dioxide by calcination, and this invention does not have any particular limitation. Preferably, the silicon dioxide precursor is silica sol and / or silica fume, more preferably silica sol. The SiO2 content in the silica sol is 20-45% by weight.

[0048] In this invention, the rotational molding in step (2) can be performed using conventional methods in the art, with the aim of obtaining spherical particles. Preferably, the particle size of the spherical particles is 0.1-3 mm, more preferably 0.2-2.5 mm. Preferably, the rotational molding is performed in a rotary molding machine.

[0049] According to some preferred embodiments of the present invention, the conditions for rotary forming include: a turntable inclination angle of 40-55 degrees, preferably 45-50 degrees; to maintain a good ratio between the material and spherical particles of different sizes, it is generally desirable that the relationship between the turntable diameter D and the turntable depth H is H = (0.1-0.5)D, preferably H = (0.1-0.4)D; a turntable rotation speed of 10-50 rpm, preferably 20-40 rpm; a residence time (referring to the average time from the addition of the molecular sieve raw material to the formation of the target spherical particles and their departure from the turntable forming machine) of 10-600 minutes, preferably 30-180 minutes; a processing capacity of the turntable forming machine, based on the amount of catalyst produced per hour, of 20-100 kg / h, preferably 60 kg / h; and a material storage amount in the turntable, referring to the amount of micro- or small spherical catalyst particles in the turntable that have not reached the qualified diameter, preferably controlled at 1 / 10-1 / 4 of the processing capacity.

[0050] According to some preferred embodiments of the present invention, step (3) of rotational forming includes:

[0051] (3-1) Select a first powder sample with a particle size of 200-500 mesh from the solid material obtained by crushing, mix the first powder sample with a portion of the binder, and perform a first rotational molding to obtain a first spherical particle with a particle size of 0.1-0.8 mm, wherein the mass ratio of the first powder sample to the first binder is 1:(0.2-1);

[0052] (3-2) Select a second powder sample with a particle size of 100-1000 mesh from the solid material obtained by crushing. Mix the second powder sample, the remaining binder and the first spherical particles, and perform a second rotation molding to obtain a second spherical particle with a particle size of 1.3-2.5 mm. The mass ratio of the second powder sample to the remaining binder is 1:(0.001-0.5).

[0053] (3-3) Dry the second spherical particles obtained in step (3-2).

[0054] In this invention, the second powder sample and the remaining binder in step (3-2) can be added to the rotary molding machine separately or added after being pre-mixed evenly. More preferably, the second powder sample and the remaining binder are mixed and then re-pulverized to below 30 mesh before being added to the rotary molding machine having the first spherical particles described in step (1).

[0055] In this invention, the weight ratio of the first powder sample to the second powder sample can be any ratio as needed, and can be adjusted at any time according to the spheroidization of the molecular sieve; this invention does not impose any particular limitations. Preferably, the weight ratio of the first powder sample to the second powder sample is 1:20-100.

[0056] The terms "first" and "second" in "first rotational forming" and "second rotational forming" are only used to distinguish rotational forming operations in different steps, and both can be performed according to the aforementioned rotational forming conditions.

[0057] To further improve the performance of the catalyst product, preferably, an additive is introduced during the rotational molding process in step (3). The additive is selected from at least one of the following: guar gum powder, graphite, activated carbon, paraffin wax, glycerol, citric acid, starch, polyethylene glycol, polyvinyl alcohol, nitric acid, hydrochloric acid, acetic acid, formic acid, ammonia, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrapropylammonium hydroxide.

[0058] Preferably, the amount of additive introduced is 1-5 wt%, based on the dry weight of the molecular sieve powder.

[0059] According to some preferred embodiments of the present invention, the preparation method further includes drying the product obtained by rotational molding. The present invention does not particularly limit the drying method, as long as moisture is removed. The drying method includes, but is not limited to, natural drying, heat drying, and forced-air drying. The drying temperature can be 80-200℃, and the drying time can be 2-24 hours.

[0060] According to some preferred embodiments of the present invention, after the rotational molding in step (3) (preferably before the drying), the preparation method further includes: polishing the product obtained by rotational molding. The polishing process can be carried out in a manner conventional in the art. Specifically, for example, the product obtained by rotational molding is blown at 20-50°C, and water is added multiple times (e.g., 3-10 times) during the blowing process, and then tightened.

[0061] According to some preferred embodiments of the present invention, the calcination conditions in step (4) include: a temperature of 200-600℃, preferably 250-550℃, and a time of 1-20h.

[0062] 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.

[0063] 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.

[0064] 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 10-300 ppm; and 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 obtained catalyst, exhibiting higher total selectivity and total yield of caprolactam compared to all-silica molecular sieve catalysts obtained through existing post-processing methods.

[0065] The present invention has a wide range of choices for the ammonium salt, magnesium salt and bromide salt, and can use conventional soluble salts in the art that can provide nitrogen, magnesium and bromine elements.

[0066] Preferably, the ammonium salt is selected from ammonium nitrate and / or ammonium acetate.

[0067] Preferably, the magnesium salt is selected from at least one of magnesium nitrate hexahydrate, magnesium acetate, magnesium chloride, magnesium sulfate, and magnesium hydrogen phosphate.

[0068] Preferably, the bromide salt is tetrapropylammonium bromide.

[0069] The present invention has a wide range of solvent options for the alkaline buffer solution, with water being the preferred solvent.

[0070] Preferably, the alkaline buffer solution includes ammonia, an aqueous solution of ammonium salt, magnesium salt, and bromide salt.

[0071] Preferably, the weight ratio of ammonia water to ammonium salt aqueous solution is 1-3:1.

[0072] Preferably, the concentration of the ammonia solution is 5-30 wt%, more preferably 20-30 wt%.

[0073] Preferably, the concentration of the ammonium salt aqueous solution is 0.5-10 wt%.

[0074] 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 calcined spherical particles.

[0075] 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.

[0076] 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.

[0077] Preferably, step (4) may further include: solid-liquid separation, washing and drying of the contacted product.

[0078] 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.

[0079] According to some particularly preferred embodiments of the present invention, the preparation method of the spherical all-silica molecular sieve catalyst includes:

[0080] (1) Mix silicon source, KOH, organic base and water, and hydrolyze to obtain colloidal mixture;

[0081] 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);

[0082] (2) The colloidal mixture is crystallized and then dried to obtain molecular sieve powder;

[0083] The crystallization temperature is 95-150℃, and the time is 0.5-5 days;

[0084] (3) The molecular sieve powder is optionally mixed with a binder, and then rotated to form spherical particles;

[0085] (4) The spherical particles are calcined and then contacted with an alkaline buffer solution containing ammonium salt, ammonia water, magnesium salt and bromide salt;

[0086] Based on the total amount of the alkaline buffer solution, the content of ammonium salt is 0.5-10 wt%, the content of ammonia water is 5-30 wt%, the content of magnesium salt (calculated as Mg) is 1-500 ppm, and the content of bromide salt (calculated as Br) is 1-500 ppm.

[0087] To ensure the formation of ZSM-5 type all-silica-1 molecular sieves, existing technologies typically employ a hydrothermal method using organic raw materials to synthesize molecular sieves with a high silica-to-alumina ratio (greater than 5000). 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 during the synthesis process, resulting in highly crystalline, fine-particle, and nearly neutral ZSM-5 type all-silica molecular sieves. After rolling molding, post-treatment with an alkaline buffer solution containing ammonium salts, ammonia, magnesium salts, and bromide salts further enhances the catalytic activity and stability of the prepared catalyst.

[0088] The second aspect of the present invention provides a spherical all-silica molecular sieve catalyst prepared by the above preparation method.

[0089] 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.

[0090] 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.

[0091] In this invention, the metal ion content of the sample is determined using a Baird PS-4 type ICP-AES plasma inductively coupled atomic emission spectrometer. The test conditions are as follows: the solid molecular sieve or catalyst is dissolved in HF acid or aqua regia to make the silica in the sample volatile, and the determination is performed in an aqueous solution.

[0092] Preferably, the particle size of the catalyst is 0.1-3 mm, more preferably 0.2-2.5 mm; the particle size of the catalyst is measured by taking pictures with a common camera.

[0093] Preferably, the crushing strength of the catalyst is not less than 2 kg / particle, and more preferably 2-3.5 kg / particle.

[0094] In this invention, the crushing strength (σ) of the catalyst was measured using the RIPP25-90 method in "Analytical Methods for Petrochemicals" (Yang Cuiding et al., Science Press, 1990) on a particle strength tester of type QCY-602 (produced by the former Alkali Industry Research Institute of the Ministry of Chemical Industry).

[0095] 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 spherical all-silica molecular sieve catalyst described in the second aspect.

[0096] Preferably, the contact takes place in a fixed-bed or moving-bed reactor.

[0097] Preferably, the solvent is a C1-C6 fatty alcohol, preferably methanol and / or ethanol.

[0098] Preferably, the molar ratio of the solvent to cyclohexanone oxime is (2-10):1.

[0099] 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.

[0100] According to the present invention, preferably, the molar ratio of the inert gas to cyclohexanone oxime is 10-80:1, more preferably 40-60:1.

[0101] 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 0.1-15 h⁻¹ for cyclohexanone oxime. -1 Preferably 0.5-2h -1 The reaction temperature is 300-500℃, preferably 350-400℃, and more preferably 360-390℃; 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.

[0102] 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).

[0103] The present invention will be described in detail below through embodiments.

[0104] 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.

[0105] 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.

[0106] Potassium hydroxide: purchased from Sinopharm Group.

[0107] Example 1

[0108] 208 kg of tetraethyl orthosilicate, 135 kg of 22.5% tetrapropylammonium hydroxide, 1.96 kg of KOH, and 255 kg of water were mixed and stirred at room temperature for 4 hours to form a colloidal mixture. The molar ratio of the mixture was SiO2:TPAOH:KOH:H2O = 1:0.15:0.035:20. The mixture was then transferred to a 1M... 3 In a stainless steel reactor, the mixture is hydrothermally crystallized at 120°C for 2 days, washed, filtered, dried at 120°C for 24 hours, and then pulverized on a pulverizer to the required mesh size for rolling molding, thus obtaining the raw powder of all-silicon molecular sieve.

[0109] The BET specific surface area was 422 m² after calcining the all-silicon molecular sieve powder at 550℃ for 6 hours. 2 / gram, with an external specific surface area of ​​45 meters. 2 / gram.

[0110] Two kilograms of 200-500 mesh all-silica molecular sieve were placed in a rotary molding machine. The rotary molding machine had a disc diameter of 1.2 m, a disc depth of 450 mm, a disc inclination angle of 50°, and a disc rotation speed of 30 rpm. Approximately 1.5 kg of deionized water was sprayed into the machine, resulting in first spherical particles with a diameter of approximately 0.2-0.8 mm.

[0111] Separately, 220 kg of 200-800 mesh all-silica molecular sieve and 100 kg of alkaline silica sol with a SiO2 content of 30% by weight were mixed evenly at a weight ratio of 2.2:1 and then re-pulverized. 300 kg of particles smaller than 30 mesh were then uniformly added to the rotary forming machine containing the first spherical particles, with the addition completed within 240 minutes. The mixture was then sieved through 12-mesh and 9-mesh sieves to obtain approximately 160 kg of the second spherical particles with a diameter of 1.7-2.2 mm.

[0112] The 90 kg of the second spherical particles obtained above were blown with air at 45°C, with trace amounts of water added to the rolling mill several times during the process. The mixture was then tightened for 2 hours, dried at 120°C for 24 hours, and finally calcined at 550°C for 10 hours. This yielded a spherical all-silica molecular sieve with a molecular sieve content of 86 wt%.

[0113] 100 kg of the above-mentioned spherical all-silica molecular sieve and 1000 kg of alkaline buffer solution (the alkaline buffer solution includes ammonia, ammonium nitrate aqueous solution, 130 g tetrapropylammonium bromide and 26.6 g magnesium nitrate hexahydrate, wherein the concentration of ammonia is 26 wt%, the content of ammonium nitrate in the ammonium nitrate aqueous solution is 7.5 wt%, the weight ratio of ammonia to ammonium nitrate aqueous solution is 3:2, and the pH value of the alkaline buffer solution is 11.35) were added to a 2M solution. 3 In a pressurized reactor, at 85℃ and 2.7 kg / cm²... 2 The catalyst was stirred under pressure for 3 hours, then washed, filtered, and dried to obtain spherical catalysts containing Mg. 2+ The concentration was 85 ppm, designated A1. The catalyst crushing strength σ = 2.7 kg / particle. The TEM morphology of the catalyst is as follows. Figure 1 As shown.

[0114] Example 2

[0115] 208 kg of tetraethyl orthosilicate, 135 kg of 22.5% tetrapropylammonium hydroxide, 1.96 kg of KOH, and 255 kg of water were mixed and stirred at room temperature for 3 hours to form a colloidal mixture. The molar ratio of the mixture was SiO2:TPAOH:KOH:H2O = 1:0.15:0.035:20. The mixture was then transferred to a 1M... 3 In a stainless steel reactor, the mixture is hydrothermally crystallized at 110℃ for 3 days, washed, filtered, dried at 120℃ for 24 hours, and then pulverized on a pulverizer to the required mesh size for rolling molding, thus obtaining the raw powder of all-silicon molecular sieve.

[0116] The BET specific surface area was 426 m² after calcining the all-silicon molecular sieve powder at 550℃ for 6 hours. 2 / gram, with an external specific surface area of ​​44 meters. 2 / gram.

[0117] Two kilograms of 200-500 mesh all-silica molecular sieve were placed in a rotary molding machine. The rotary molding machine had a disc diameter of 1.2 m, a disc depth of 450 mm, a disc inclination angle of 50°, and a disc rotation speed of 30 rpm. Approximately 1.4 kg of deionized water was sprayed into the machine, resulting in first spherical particles with a diameter of approximately 0.2-0.8 mm.

[0118] Separately, 200 kg of 200-800 mesh all-silica molecular sieve and 40 kg of alkaline silica sol with a SiO2 content of 30% by weight were mixed at a weight ratio of 5:1. Then, 55 kg of water was added, and the mixture was thoroughly mixed and re-crushed. Particles smaller than 30 mesh were then added at a uniform rate of 280 kg to the rotary forming machine containing the first spherical particles, to be added within 300 minutes. The mixture was then sieved through 12-mesh and 9-mesh sieves to obtain approximately 150 kg of the second spherical particles with a diameter of 1.7-2.2 mm.

[0119] The 100 kg of the second spherical particles obtained above were blown with air at 45°C, with trace amounts of water added to the rolling mill several times during the process. The mixture was then tightened for 2 hours, dried at 120°C for 24 hours, and finally calcined at 550°C for 10 hours. This yielded a spherical all-silica molecular sieve with a molecular sieve content of 93%.

[0120] 100 kg of the above-mentioned spherical all-silica molecular sieve and 1000 kg of alkaline buffer solution (the alkaline buffer solution includes ammonia, ammonium nitrate aqueous solution, 130 g tetrapropylammonium bromide, and 53 g magnesium nitrate hexahydrate, wherein the concentration of ammonia is 26 wt%, the content of ammonium nitrate in the ammonium nitrate aqueous solution is 7.5 wt%, the weight ratio of ammonia to ammonium nitrate aqueous solution is 3:2, and the pH value of the alkaline buffer solution is 11.35) were added to a 2M solution. 3 In a pressurized reactor, at 90℃ and 3.2 kg / cm²... 2 The catalyst was stirred under pressure for 2 hours, then washed, filtered, and dried to obtain spherical catalysts containing Mg. 2+ The concentration was 168 ppm, designated A2. The catalyst crushing strength σ = 2.8 kg / particle. The catalyst TEM morphology is similar to... Figure 1 similar.

[0121] Example 3

[0122] 208 kg of tetraethyl orthosilicate, 90 kg of 22.5 wt% tetrapropylammonium hydroxide, 2.24 kg of KOH, and 470 kg of water were mixed and stirred at room temperature for 4 hours to form a colloidal mixture. The molar ratio of the mixture was SiO2:TPAOH:KOH:H2O = 1:0.10:0.04:30. The mixture was then transferred to a 1M... 3 In a stainless steel reactor, the mixture is hydrothermally crystallized at 120°C for 2 days, washed, filtered, dried at 120°C for 24 hours, and then pulverized on a pulverizer to the required mesh size for rolling molding, thus obtaining the raw powder of all-silicon molecular sieve.

[0123] The BET specific surface area was 426 m² after calcining the all-silicon molecular sieve powder at 550℃ for 6 hours. 2 / gram, with an external specific surface area of ​​45 meters. 2 / gram.

[0124] Two kilograms of 200-500 mesh all-silica molecular sieve were placed in a rotary molding machine. The rotary molding machine had a disc diameter of 1.2 m, a disc depth of 450 mm, a disc inclination angle of 50°, and a disc rotation speed of 30 rpm. Approximately 1.5 kg of alkaline silica sol with a SiO2 content of 30% by weight was added to the mixture, resulting in first spherical particles with a diameter of approximately 0.2-0.8 mm.

[0125] Separately, 200 kg of 200-800 mesh all-silica molecular sieve and 50 kg of alkaline silica sol with a SiO2 content of 40% by weight were mixed evenly at a weight ratio of 4:1. Then, 45 kg of water was added and mixed evenly, and the mixture was re-crushed. 280 kg of particles smaller than 30 mesh were then added at a uniform speed to the rotary forming machine containing the first spherical particles, and the addition was completed within 300 minutes. The mixture was then sieved through 12-mesh and 9-mesh sieves to obtain approximately 150 kg of the second spherical particles with a diameter of 1.7-2.2 mm.

[0126] The 100 kg of the second spherical particles obtained above were blown with air at 45°C, with trace amounts of water added to the rolling mill several times during the process. The mixture was then tightened for 2 hours, dried at 120°C for 24 hours, and finally calcined at 550°C for 10 hours. This yielded spherical all-silica molecular sieves with a molecular sieve content of 89.5%.

[0127] 100 kg of the above-mentioned spherical all-silica molecular sieve and 1000 kg of alkaline buffer solution (the alkaline buffer solution includes ammonia water, ammonium nitrate aqueous solution, 130 g tetrapropylammonium bromide, and 26.6 g magnesium nitrate hexahydrate, 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, and the pH value of the alkaline buffer solution is 11.35) were added to a 2M solution. 3 In a pressurized reactor, at 82℃ and 2.4 kg / cm²... 2 The catalyst was stirred under pressure for 3 hours, then washed, filtered, and dried to obtain spherical catalysts containing Mg. 2+ The concentration was 87 ppm, designated A3. The catalyst crushing strength σ = 2.5 kg / particle. The catalyst TEM morphology is similar to... Figure 1 similar.

[0128] Example 4

[0129] The method is the same as in Example 1, except that 100 kg of spherical all-silica molecular sieve and 1000 kg of alkaline buffer solution (the alkaline buffer solution includes ammonia, ammonium nitrate aqueous solution, 130 g tetrapropylammonium bromide, and 1235 g magnesium nitrate hexahydrate, wherein the concentration of ammonia is 26 wt%, the content of ammonium nitrate in the ammonium nitrate aqueous solution is 7.5 wt%, the weight ratio of ammonia to ammonium nitrate aqueous solution is 3:2, and the pH value of the alkaline buffer solution is 11.35) are added to a 2M solution. 3In a pressurized reactor, at 90℃ and 3.2 kg / cm²... 2 The mixture was stirred under pressure for 1 hour, then washed, filtered, and dried to obtain spherical catalysts containing Mg. 2+ The concentration was 3962 ppm, designated A4. The catalyst crushing strength σ = 2.6 kg / particle. The catalyst TEM morphology is similar to... Figure 1 similar.

[0130] Example 5

[0131] 208 kg of tetraethyl orthosilicate, 180 kg of 22.5% tetrapropylammonium hydroxide, 275 kg of ethanol, and 130 kg of water were mixed and stirred at room temperature for 6 hours to form a colloidal mixture. The molar ratio of the mixture was SiO2:TPAOH:H2O = 1:0.2:15, and the ethanol / SiO2 ratio was 10. The mixture was then transferred to a 1M... 3 In a stainless steel reactor, hydrothermal crystallization was carried out at 120℃ for 2 days. After washing and filtration, the mixture was dried at 120℃ for 24 hours and then pulverized to the required mesh size for rolling molding to obtain the raw silicon molecular sieve powder. The raw silicon molecular sieve powder was then calcined at 550℃ for 6 hours, resulting in a BET specific surface area of ​​435 m². 2 / gram, with an external specific surface area of ​​46 meters. 2 / gram.

[0132] Following the method of Example 1, molding and post-processing were performed to obtain spherical catalysts, wherein Mg 2+ The concentration was 83 ppm, designated A5. The catalyst crushing strength σ = 2.6 kg / particle. The catalyst TEM morphology is similar to... Figure 1 similar.

[0133] Example 6

[0134] 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 ethyl orthosilicate (calculated as SiO2): TPAOH: KOH: H2O = 1:0.15:0.15:20.

[0135] A spherical all-silica molecular sieve catalyst A6 was obtained.

[0136] Example 7

[0137] The method was followed in Example 1, except that the tetraethyl orthosilicate used was 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 a formic acid and propionic acid content of 26 ppm.

[0138] A spherical all-silica molecular sieve catalyst A7 was obtained.

[0139] Comparative Example 1

[0140] All-silica molecular sieve catalysts were synthesized according to Method 2 disclosed in CN1338427A.

[0141] 139 kg of tetraethyl orthosilicate was poured into a 1M solution at room temperature. 3 In the reaction vessel, after stirring for 30 minutes, 120 kg of 22.5% tetrapropylammonium hydroxide (TPAOH) aqueous solution was added to tetraethyl orthosilicate. The mixture was stirred and hydrolyzed at room temperature for 5 hours. Then, 147 kg of water and 267 kg of ethanol were added and stirred until a sol was formed. At this point, the chemical composition of the mixed sol was H2O / SiO2 = 20, EtOH / SiO2 = 12.7, and TPAOH / SiO2 = 0.20. The mixture was crystallized at 110°C for 3 days, washed, filtered, and dried at 120°C for 24 hours to obtain the all-silicon molecular sieve required for rolling molding in this embodiment. The sieve was then pulverized in a pulverizer to the mesh size required for rolling molding.

[0142] The prepared all-silica molecular sieve sample, calcined at 550℃ for 6 hours, had a BET specific surface area of ​​432 m². 2 / gram, with an external specific surface area of ​​52 meters. 2 / gram.

[0143] 220 kg of the prepared all-silica molecular sieve and 100 kg of alkaline silica sol with a SiO2 content of 30% by weight were placed in a rotary molding machine for rolling molding. The rotary molding machine had a disc diameter of 1.2 m, a disc depth of 450 mm, a disc inclination angle of 50°, and a disc rotation speed of 30 rpm. Spherical particles with a diameter of approximately 1.7-2.2 mm were then dried at 120°C for 24 hours and calcined at 550°C for 10 hours. Finally, spherical all-silica molecular sieves with a molecular sieve content of 86% were obtained.

[0144] 100 kg of the above-mentioned spherical all-silica molecular sieve and 1000 kg of alkaline buffer solution (the alkaline buffer solution is a mixture of 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, and the pH value of the alkaline buffer solution is 11.35) were added to a 2M solution. 3 In a pressurized reactor, at 82℃ and 2.4 kg / cm²... 2 The catalyst was stirred under pressure for 1 hour, then washed, filtered, and dried to obtain catalyst number DA1. The catalyst crushing strength σ = 2.1 kg / particle.

[0145] Comparative Example 2

[0146] All-silica molecular sieve catalysts were synthesized according to the method disclosed in CN102050464A.

[0147] 208 kg of tetraethyl orthosilicate was poured into a 1M solution at room temperature. 3 In the reaction vessel, stir for 30 minutes. Add 180 kg of 22.5% tetrapropylammonium hydroxide (TPAOH) solution to tetraethyl orthosilicate. Hydrolyze at room temperature for 3-5 hours. Add 220 kg of water to form a sol. Stir until homogeneous. The molar concentrations are TPAOH / SiO2 = 0.2 and H2O / SiO2 = 20. Transfer the mixture to a 1M... 3 In a stainless steel reactor, the material is crystallized at 100°C for 3 days, washed, filtered, and dried at 120°C for 24 hours to obtain the all-silicon molecular sieve required for rolling molding in this embodiment. The sieve is then pulverized in a pulverizer to the mesh size required for rolling molding.

[0148] The prepared all-silica molecular sieve sample, calcined at 550℃ for 6 hours, had a BET specific surface area of ​​438 m². 2 / gram, external specific surface area is 61 meters 2 / gram.

[0149] 220 kg of the prepared all-silica molecular sieve and 100 kg of alkaline silica sol with a SiO2 content of 30% by weight were placed in a rotary molding machine for rolling molding. The rotary molding machine had a disc diameter of 1.2 m, a disc depth of 450 mm, a disc inclination angle of 50°, and a disc rotation speed of 30 rpm. Spherical particles with a diameter of approximately 1.7-2.2 mm were then dried at 120°C for 24 hours and calcined at 550°C for 10 hours. Finally, spherical all-silica molecular sieves with a molecular sieve content of 86% were obtained.

[0150] 100 kg of the above-mentioned spherical all-silica molecular sieve and 1000 kg of alkaline buffer solution (the alkaline buffer solution is a mixture of 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, and the pH value of the alkaline buffer solution is 11.35) were added to a 2M solution. 3 In a pressurized reactor, at 82℃ and 2.4 kg / cm²... 2 The catalyst was stirred under pressure for 1 hour, then washed, filtered, and dried to obtain catalyst number DA3. The catalyst crushing strength σ = 2.2 kg / particle.

[0151] Comparative Example 3

[0152] All-silica molecular sieve catalysts were synthesized according to the method of Example 1 of US4061724A1.

[0153] NaOH solution, a hydrosol with a SiO2 content of 30% by weight, and tetrapropylammonium bromide (TPABr) solution were mixed to obtain a mixture with a molar ratio of 4.1Na2O:50SiO2:691H2O:1TPABr. The mixture was crystallized at 200°C for 3 days, washed, filtered, and dried at 110°C for 24 hours to obtain the all-silicon molecular sieve required for roll forming in this embodiment. The sieve was then pulverized in a pulverizer to the mesh size required for roll forming.

[0154] The prepared all-silica molecular sieve sample, calcined at 600℃ for 4 hours, had a BET specific surface area of ​​417 m². 2 / gram, external specific surface area is 36 meters 2 / gram.

[0155] 220 kg of the prepared all-silica molecular sieve and 100 kg of alkaline silica sol with a SiO2 content of 30% by weight were placed in a rotary molding machine for rolling molding. The rotary molding machine had a disc diameter of 1.2 m, a disc depth of 450 mm, a disc inclination angle of 50°, and a disc rotation speed of 30 rpm. Spherical particles with a diameter of approximately 1.7-2.2 mm were then dried at 120°C for 24 hours and calcined at 560°C for 10 hours. Finally, spherical all-silica molecular sieves with a molecular sieve content of 86% were obtained.

[0156] 100 kg of the above-mentioned spherical all-silica molecular sieve and 1000 kg of alkaline buffer solution (the alkaline buffer solution is a mixture of 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, and the pH value of the alkaline buffer solution is 11.35) were added to a 2M solution. 3 In a pressurized reactor, at 82℃ and 2.4 kg / cm²... 2The catalyst was stirred under pressure for 1 hour, then washed, filtered, and dried to obtain catalyst number DA3. The crushing strength of the catalyst σ = 2.1 kg / particle.

[0157] Test Implementation Examples

[0158] The catalysts prepared in the above examples and comparative examples were used to carry out the gas-phase Beckmann rearrangement of cyclohexanone oxime under experimental conditions 1 and 2, respectively.

[0159] Experimental Condition 1: The reaction apparatus was a continuous flow fixed bed reactor at atmospheric pressure with an inner diameter of 5 mm. The catalyst loading was 0.469 g. The catalyst bed was topped with approximately 30 mm high, 30-mesh coarse quartz sand, and the bottom was filled with 50-mesh fine quartz sand. The catalyst particle size was 20-60 mesh. After being loaded into the reaction tube, the catalyst was pretreated for 1 hour at atmospheric pressure and 350°C under a nitrogen atmosphere. The concentration of the feedstock cyclohexanone oxime was 35%, and the weight hourly space velocity (WHSV) was 16 h⁻¹. -1 The solvent was ethanol, the reaction temperature was 380℃, the nitrogen flow rate was 45mL / min (the molar ratio of nitrogen to cyclohexanone oxime was 2.27:1), the reaction product was cooled by an ice-water mixture and then entered a collection bottle for gas-liquid separation. The reaction time was 6 hours, and the product composition was analyzed.

[0160] Experimental conditions 2: The reaction apparatus was a continuous flow fixed bed reactor with an inner diameter of 28 mm; reaction pressure: 0.1 MPa; N2:oxime = 12:1 (molar ratio); water / oxime mass percentage: 1.2%m; vaporizer temperature control: 175℃; pipeline insulation: 185℃; industrially prepared catalyst: 30 g; bed height: 15.0 cm; concentration of cyclohexanone oxime feedstock: 35%; weight hourly space velocity (WHSV): 0.5 h⁻¹ -1 The solvent was ethanol, the reaction temperature was 380℃, and the reaction time was 600 hours for product composition analysis.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] Cyclohexanone oxime conversion (mol%) = (100 - cyclohexanone oxime molar percentage in reaction product) / 100 × 100%;

[0165] Caprolactam selectivity (mol%) = (mol percentage of caprolactam in the reaction product) / (100 - mol percentage of cyclohexanone oxime in the reaction product) × 100%.

[0166] Table 1

[0167]

[0168]

[0169] As can be seen from the comparison of the above examples and comparative examples, the spherical all-silica molecular sieve catalyst prepared by the method of the present invention has high crushing strength, which can reach more than 2.8 kg / particle, and is particularly suitable for fixed bed or moving bed processes for the preparation of caprolactam from cyclohexanone oxime by the gas-phase Beckmann rearrangement.

[0170] As can be seen from the results in Table 1, the catalyst prepared in this invention has a high conversion rate of cyclohexanone oxime. Under the same experimental conditions, the all-silica molecular sieves of proportions 1-3 were used as catalysts for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime, and the catalysts were deactivated after 600 hours, with a conversion rate of less than 99%. However, the spherical all-silica molecular sieves prepared in the examples still achieved a conversion rate of over 99.70% after 600 hours of reaction, indicating a longer catalyst life.

[0171] 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 spherical all-silica molecular sieve catalyst, characterized in that, Includes the following steps: (1) Mix silicon source, organic base and water, and hydrolyze to obtain colloidal mixture; The silicon source is an organosilicone ester, and the molar ratio of silicon source, organic base and water, calculated as SiO2, is 1:(0.04-0.25):(15-45). (2) The colloidal mixture is crystallized and then dried to obtain molecular sieve powder; The crystallization temperature is 95-150℃, and the time is 0.5-5 days; (3) The molecular sieve powder is optionally mixed with a binder, and then rotated to form spherical particles; (4) The spherical particles are calcined and then contacted with an alkaline buffer solution containing ammonium salt, ammonia water, magnesium salt and bromide salt; 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.

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 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, Step (1) of the mixing process also includes the addition of KOH; Preferably, 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), and more preferably 1:(0.03-0.05):(0.08-0.2):(20-30); Preferably, the mixing in step (1) further includes the addition of a low-carbon alcohol, preferably methanol and / or ethanol; Preferably, the molar ratio of the low-carbon alcohol to the silicon source (based on SiO2) is 3.5-15:1; 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 (3), the binder is a precursor of water or silicon dioxide, and the precursor of silicon dioxide is silica sol and / or silica, preferably silica sol; Preferably, the weight ratio of molecular sieve powder (dry basis) to binder (SiO2) is 1:(0.05-1), more preferably 1:(0.1-0.8).

6. The preparation method according to any one of claims 1-5, characterized in that, The spherical particles have a particle size of 0.1-3 mm, preferably 0.2-2.5 mm; Preferably, the rotational forming is performed in a rotary forming machine; Preferably, the conditions for the rotational forming include: the turntable tilt angle is 40-55 degrees, preferably 45-50 degrees; the relationship between the turntable diameter D and the turntable depth H is H = (0.1-0.5)D, preferably H = (0.1-0.4)D; and the turntable rotation speed is 10-50 rpm, preferably 20-40 rpm. Preferably, the rotational forming in step (3) includes: (3-1) Select a first powder sample with a particle size of 200-500 mesh from the solid material obtained by crushing, mix the first powder sample with the first binder, and perform the first rotation molding to obtain a first spherical particle with a particle size of 0.1-0.8 mm, wherein the mass ratio of the first powder sample to the first binder is 1:(0.2-1); (3-2) Select a second powder sample with a particle size of 100-1000 mesh from the solid material obtained by crushing. Mix the second powder sample, the second binder and the first spherical particles and perform a second rotation molding to obtain a second spherical particle with a particle size of 1.3-2.5 mm. The mass ratio of the second powder sample to the second binder is 1:(0.001-0.5). (3-3) Dry the second spherical particles obtained in step (3-2).

7. The preparation method according to any one of claims 1-6, characterized in that, In step (3), an additive is introduced during the rotational molding 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 powder.

8. The preparation method according to any one of claims 1-7, characterized in that, The roasting conditions in step (4) include: a temperature of 200-600℃, preferably 250-550℃, and a time of 1-20h; Preferably, the pH of the alkaline buffer solution is 8.5-13.5; 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 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 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 calcined spherical particles. 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. The spherical all-silica molecular sieve catalyst 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 catalyst has a particle size of 0.1-3 mm, more preferably 0.2-2.5 mm; Preferably, the crushing strength of the catalyst is not less than 2 kg / particle.

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 spherical all-silica molecular sieve catalyst as described in claim 9. Preferably, the contact takes place in a fixed-bed or moving-bed reactor.

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