CN109772426B - Microspheric MFI topological structure all-silicon-1 molecular sieve catalyst containing trace rare earth ions and spray forming preparation method thereof - Google Patents
Microspheric MFI topological structure all-silicon-1 molecular sieve catalyst containing trace rare earth ions and spray forming preparation method thereof Download PDFInfo
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Abstract
The invention relates to the field of all-silicon-1 molecular sieves, and discloses a microspheric MFI topological structure all-silicon-1 molecular sieve catalyst containing trace rare earth ions and a spray forming preparation method thereof, wherein the catalyst comprises 70-95 wt% of all-silicon-1 molecular sieve containing trace rare earth ions and 5-30wt% of a binder, which are calculated by dry weight; the particle size of the catalyst is 20-400 (m, the abrasion index K is less than 5; the BET specific surface area of the all-silicon-1 molecular sieve is 400-2(10)/g, the weight ratio of the silicon oxide to the rare earth ions is (10000-) -200000): 1. the catalyst has low abrasion index, and can effectively improve the technical economy of a new process when being used for carrying out the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime in a fluidized bed process.
Description
Technical Field
The invention relates to the field of all-silicon-1 molecular sieves, in particular to a microspherical MFI topological structure all-silicon-1 molecular sieve catalyst containing trace rare earth ions and a spray forming preparation method thereof.
Background
Silicalite-1 molecular sieves (abbreviated as all-silica-1 molecular sieves) were successfully synthesized in 1978 by E.M. Flanigen et al of UCC corporation for the first time, and were the last of the "Pentasil" familyAnd (4) each member. The all-silicon-1 molecular sieve is an aluminum-free all-silicon-1 molecular sieve with MFI topological structure, is a simplest molecular sieve in a ZSM-5 type structure molecular sieve family, and has a framework only containing silicon atoms and oxygen atoms and a basic structural unit of SiO4A tetrahedron. The all-silicon-1 molecular sieve has rich microporous structure and regular and uniform three-dimensional fine pore channels, has a determined crystal structure of the ZSM-5 type molecular sieve, and has the performances of higher internal specific surface area, good thermal stability, adsorption and desorption capacity and the like. The all-silicon-1 molecular sieve can be used as an application material of a chemical sensor, a photoelectric sound wave device and a membrane reactor. In particular, the molecular sieve membrane is applied to gas permeable membranes, pervaporation membranes, sensing material membranes, optical material membranes and the like. Therefore, the development and application of the all-silicon-1 molecular sieve in the fields of membrane adsorption separation, purification, catalytic materials and the like are receiving increasing attention.
The synthesis method of the all-silicon-1 molecular sieve generally adopts a traditional organic raw material hydrothermal method, a silicon source can be selected from solid silicon oxide, silica sol, white carbon black, Tetraethoxysilane (TEOS) and the like, a template agent mostly adopts tetrapropylammonium hydroxide (TPAOH), low-carbon hydrocarbon quaternary ammonium salt or a mixture of the tetrapropylammonium hydroxide and the lower-carbon hydrocarbon quaternary ammonium salt, an amine compound and the like, and the crystallization is carried out for three days at the temperature of 170 ℃. Research groups such as united states carbide corporation (UCC), sweden Stety, and india p. They mainly apply the all-silicon-1 molecular sieve to the research field of inorganic microporous materials.
The all-silica-1 molecular sieve of MFI structure disclosed in Japanese patent JP59164617 is prepared by using tetraethyl orthosilicate (TEOS) as a silicon source and tetrapropylammonium hydroxide as a template agent. Researches in CATAL.REV. -SCI.ENG, 39(4), 395-424 (1997) show that the all-silicon-1 molecular sieve synthesized by using tetraethoxysilane as a silicon source has higher BET total specific surface area and external surface area which can reach 400 m respectively2Per gram and 15-30 m2In grams, and the conversion of cyclohexanone oxime and the selectivity of caprolactam are directly proportional to the increase of the external surface area.
The all-silicon-1 molecular sieve disclosed in Chinese patents CN00123576.1 and ZL00123577.x comprises two synthesis methods, one of which is as follows: reacting ethyl orthosilicate with tetrapropyl hydroxideAmmonium is mixed, stirred and hydrolyzed at room temperature, the temperature is raised to 70-75 ℃, water is added, the mixture is hydrothermally crystallized, and then the mixture is mixed with organic alkali and sealed, and alcohol is removed by raising the temperature in the synthesis process. The second method is that the tetraethoxysilane and the tetrapropylammonium hydroxide are mixed and stirred at room temperature, after hydrolysis, water and ethanol are added to form the mixture with the molar concentration of TPAOH/SiO2＝0.05-0.5，EtOH/SiO2＝4-30，H2O/SiO22-100 in admixture; carrying out hydrothermal crystallization on the mixture; the roasted product and the organic alkali are mixed uniformly and then are subjected to closed treatment, a large amount of ethanol is added in the synthesis process, the raw material cost is high, the COD discharge amount is large, and the solid content of the molecular sieve in the synthesis kettle is low.
The synthetic process of the all-silicon-1 molecular sieve disclosed in Chinese patent CN 102050464A comprises the following steps: (1) mixing ethyl orthosilicate and tetrapropylammonium hydroxide at room temperature, stirring, fully hydrolyzing for 3-5 hours, and adding water to form TPAOH/SiO with molar concentration2＝0.05-0.5，EtOH/SiO2＝4，H2O/SiO2A mixture of 5 to 100; (2) the mixture is crystallized for 0.5 to 10 days at the autogenous pressure of 80 to 120 ℃ in a closed reaction kettle, and then is washed, filtered and dried, and is roasted for 1 to 10 hours at the temperature of 400 ℃ and 600 ℃.
ZL200910210326.6 discloses a method for synthesizing an all-silicon-1 molecular sieve, wherein the all-silicon-1 molecular sieve takes ethyl silicate as a silicon source and tetrapropylammonium hydroxide as an alkali source and a template agent, and the gel mixture before the molecular sieve is crystallized comprises the following molar compositions: SiO 22∶0.05～0.5TPAOH∶4EtOH∶5～100H2And O, crystallizing at the temperature of 80-120 ℃ for 1-3 days. When the molecular sieve obtained by the method is used for preparing caprolactam through cyclohexanone-oxime gas-phase Beckmann rearrangement reaction, the cyclohexanone-oxime conversion rate and caprolactam selectivity are high.
Because the all-silicon-1 molecular sieve has great difficulty in extrusion molding, tabletting molding, even rolling molding and the like, even after molding, the crushing strength of the catalyst is not ideal (less than 60N/cm or less than 1 kg/particle), and industrial application cannot be realized at all.
Caprolactam is a main raw material for producing three series products of nylon, industrial cord and nylon engineering plastics, and the demand is always more vigorous. The caprolactam is generally obtained by Beckmann rearrangement of cyclohexanone oxime. At present, the liquid phase rearrangement process using concentrated sulfuric acid or fuming sulfuric acid as a catalyst is generally adopted in industry. The caprolactam produced by the process accounts for about 90% of the total caprolactam production in the world, but the process needs to consume a large amount of sulfuric acid and ammonia water, and the production cost is high because a byproduct of 1.3-1.8 tons of ammonium sulfate is generated every 1 ton of caprolactam is produced. In addition, the use of sulfuric acid causes problems of equipment corrosion, environmental pollution and the like.
The gas phase Beckmann rearrangement reaction of cyclohexanone oxime on a solid acid catalyst is a new process for realizing the sulfur-free ammonification of caprolactam, has the problems of no equipment corrosion, no environmental pollution and the like, and greatly simplifies the separation and purification of products, so the gas phase Beckmann rearrangement reaction process of the sulfur-free ammonification is greatly concerned by the persons in the industry.
In order to develop a solid acid catalyst suitable for gas phase Beckmann rearrangement reaction, researchers at home and abroad have carried out a great deal of research on catalysts such as oxides (composite oxides), zeolite molecular sieves and the like, and the results show that most of the catalysts have certain activity, but the common defects are that the catalysts are easy to deactivate, the service life of the catalysts is short, and the industrial requirements cannot be met.
The process which makes the production more economical and meets the requirement of greenization is a gas phase Beckmann rearrangement method. The method for preparing caprolactam by carrying out gas-phase Beckmann rearrangement on cyclohexanone oxime does not use sulfuric acid and ammonia water, and has the advantages of no equipment corrosion, no environmental pollution, no byproduct ammonium sulfate and the like. There are various solid acids as catalysts in the vapor phase beckmann rearrangement reaction, such as: silica-alumina catalysts used in british patent GB881,927; solid phosphoric acid catalysts as used in british patent GB881,956; catalysts containing boric acid as used in british patent GB1,178,057; the MFI structure molecular sieve catalyst with high silicon/aluminum ratio adopted in the Chinese patent CN1269360A, and the like. So far, the fluidized bed process is suitable for gas phase Beckmann rearrangement reaction, and the microspheres are suitable for serving as a catalyst of the process.
Spray forming is the most common method for preparing microspherical catalysts, is simple and practical, and is widely used in the field of petrochemical industry. Spray forming belongs to a combined technological process of spraying and drying. The raw material slurry is sprayed into extremely fine fog-like liquid drops under the action of an atomizer, then the extremely fine fog-like liquid drops are uniformly mixed with hot air, and then heat exchange and mass exchange are rapidly carried out to evaporate water, so that the granular product is obtained. Such as microspheres.
The spray forming is divided into three types, namely a pressure type, a centrifugal disc type and an air flow type, and has the characteristics of simple process flow, convenient production, strong production capacity, easy adjustment and control of the diameter, the particle size distribution, the moisture content and the like of catalyst particles. However, the thermal efficiency of spray forming is low, the pump delivery is difficult for sticky paste materials, spray forming is carried out after dilution, and meanwhile, the requirement on gas-solid separation is high, and the equipment is huge. The microspheres are of a moderate strength due to the spraying action of the catalyst.
In EP576295 it is proposed to prepare microspheres of a molecular sieve by spray drying without adding any binder and then to heat treat them in water to increase the mechanical strength of the microspheres, so that the microspherical catalyst can be used in a fluidized bed reactor for the conversion of cyclohexanone oxime to caprolactam. Obviously, such strength is not satisfactory for industrial applications.
Chinese patent CN1256967A discloses a method for preparing a molecular sieve catalyst containing MFI structure for use in the reaction of converting cyclohexanone oxime into caprolactam. The basic starting point of the method is to use acid silica gel as a binder, and the method comprises the following specific steps: the silica oligomer prepared by acid hydrolysis of alkoxy silicon is mixed with water or alcohol-water dispersion of submicron particles of MFI structure molecular sieve with the pH value less than or equal to 5, and the mixture is emulsified, solidified, washed and roasted to prepare the gel microsphere. The catalyst is suitable for fluidized bed reactors.
U.S. Pat. No. 4,485985 discloses a method for preparing titanium-containing silicon molecular sieve catalyst by using basic silica gel as binder. The alkaline silica gel is prepared by hydrolyzing tetraalkyl silicate, preferably tetraalkyl orthosilicate in tetraalkyl ammonium hydroxide aqueous solution at room temperature to 200 ℃ for 0.2-10 hours, wherein the pH of the alkaline silica gel is more than or equal to 10. The prepared catalyst is a microsphere catalyst suitable for a fluidized bed reactor.
The cyclohexanone oxime gas phase Beckmann rearrangement reaction fixed bed or moving bed process has the defects of short service life of a catalyst, difficulty in long-period continuous operation, high nitrogen oxime molar ratio, difficulty in heat transfer, poor technical economy and the like. The fluidized bed process is relatively suitable for cyclohexanone oxime gas phase Beckmann rearrangement reaction.
So far, no relevant documents and patents exist for applying the all-silicon-1 molecular sieve containing extremely trace rare earth ions to cyclohexanone oxime gas phase Beckmann rearrangement reaction by spray forming to be microspherical.
Disclosure of Invention
In order to solve the technical problems, the invention provides a microspheric MFI topological structure all-silicon-1 molecular sieve catalyst containing trace rare earth ions and a spray forming preparation method thereof.
The specific technical scheme of the invention is as follows: a microspheric MFI topological structure all-silicon-1 molecular sieve catalyst containing trace rare earth ions comprises 70-95 wt% of MFI topological structure all-silicon-1 molecular sieve containing trace rare earth ions and 5-30wt% of a binder, wherein the weight of the catalyst on a dry basis is taken as a reference; the particle size of the catalyst is 20-400 mu m, and the abrasion index K is less than 5.
The lower the attrition index K, the higher the attrition resistance of the catalyst is demonstrated.
The BET specific surface area of the MFI topological structure all-silicon-1 molecular sieve is 400-500m2The weight ratio of silicon dioxide to rare earth ions in the MFI topological structure all-silicon-1 molecular sieve is (10000-.
Preferably, the catalyst comprises 80-90 wt% of MFI topological structure all-silicon-1 molecular sieve containing trace rare earth ions and 10-20 wt% of binder, based on the dry weight of the catalyst; the particle size of the catalyst is 40-200 mu m.
Preferably, the binder is silica sol, and the silica solThe sodium ion content of the glue is 10-500ppm, SiO2The content is 20-45 wt%.
The invention also discloses a spray forming preparation method of the catalyst, which comprises the following steps:
a. mixing a silicon source, a rare earth ion source, an organic template agent and water to obtain a colloid mixture; wherein SiO in the colloid mixture2The mol ratio of the organic template agent to the water is 1 to (0.05-0.50) to (5-100); the mass ratio of the silicon source to the rare earth ions is (10000-) -200000: 1; and (3) performing hydrothermal crystallization on the colloid mixture at 50-60 ℃ for 0.5-3 days, performing hydrothermal crystallization at 80-120 ℃ for 0.5-3 days, performing membrane filtration on the obtained crystallized product, and washing until the pH value is 7.5-10 to obtain molecular sieve slurry with the solid content of 25-35 wt%.
b. And mixing the molecular sieve slurry with a binder, and pulping to obtain the molecular sieve-binder mixed slurry with the solid content of 10-35 wt%.
c. And (3) carrying out spray forming on the molecular sieve-binder mixed slurry, and then roasting to obtain the microspheric MFI topological structure all-silicon-1 molecular sieve.
d. And (3) contacting the microspheric MFI topological structure all-silicon-1 molecular sieve with an alkaline buffer solution containing a nitrogen compound, and then washing, filtering and drying to obtain a finished product.
Different cations have different degrees of difficulty in entering the molecular sieve framework, for example, Si, Al and the like can easily enter the molecular sieve framework, transition metals can hardly enter the molecular sieve framework, and the difficulty of noble metals is higher. And the rare earth elements have larger atomic and ionic radii than the noble metals, which means that the rare earth elements are more difficult to enter the molecular sieve framework than the noble metals. The invention adopts a specific technical means of segmentation and temperature-changing crystallization, solves the problem that rare earth ions are difficult to enter the framework, and enables extremely trace rare earth ions to enter the all-silicon-1 molecular sieve framework. The invention successfully prepares the MFI topological structure all-silicon-1 molecular sieve containing trace rare earth ions for the first time in the world. Compared with other elements such as noble metals, the rare earth has lower cost, and particularly has more obvious cost advantage under the condition of high rare earth reserves in China.
AsPreferably, in step b, the molecular sieve slurry contains SiO and molecular sieve dry basis2The weight ratio of the adhesive is 1 to (0.05-0.5).
Preferably, in step c, the spray forming conditions are as follows: the inlet temperature of the sprayer is 180-240 ℃; the outlet temperature is 80-120 ℃.
Further preferably, the inlet temperature of the sprayer is 200-220 ℃; the outlet temperature is 90-100 ℃.
Preferably, in step c, the roasting conditions are as follows: the temperature is 200 ℃ and 600 ℃ and the time is 1-20 hours.
Preferably, in step d, the alkaline buffer solution containing the nitrogen-containing compound contains ammonium salt and alkali, the content of the ammonium salt is 0.5-20wt%, the content of the alkali is 5-30wt%, and the pH value of the alkaline buffer solution containing the nitrogen-containing compound is 8.5-13.5.
Preferably, in the step d, the weight ratio of the microspheric MFI topological structure all-silicon-1 molecular sieve to the alkaline buffer solution of the nitrogen-containing compound is 1 to (5-15) on a dry basis, the contact temperature is 50-120 ℃, and the contact pressure is 0.5-5kg/cm2The contact time is 10 to 300 minutes, and the performance of the catalyst determines whether or not the alkaline buffer solution post-treatment of the nitrogen-containing compound is repeated several times.
Preferably, in step a, the rare earth ion is selected from Ce3+、Ce4+、La3+At least one of; the rare earth ion source is selected from La (NO)3)3·6H2O、La(OAc)3·5H2O、LaCl3·7H2O、La2(CO3)3·xH2O、Ce(NO3)3·6H2O、Ce(NO3)4·7H2O、Ce(OAc)3·5H2O、Ce(SO4)2·2H2O、CeCl3·7H2At least one of O.
Preferably, in the step a, the silicon source is at least one selected from the group consisting of silica gel, silica sol and organosilicate; preferably of the formula (OR)1)4Organosilicates of SiWherein R is1Is an alkyl group of 1 to 4 carbon atoms; more preferably, tetraethoxysilane.
Preferably, the organic template is at least one selected from the group consisting of fatty amine compounds, alcohol amine compounds and quaternary ammonium base compounds; preferably alkyl quaternary ammonium base compounds having 1 to 4 carbon atoms; more preferably tetraethylammonium hydroxide and/or tetrapropylammonium hydroxide.
Preferably, in step a, the colloidal mixture further comprises a lower alcohol, and the lower alcohol is mixed with SiO2The molar ratio of the low carbon alcohol to the alcohol is 1 to (4-15), and the low carbon alcohol is methanol and/or ethanol.
Preferably, the spray forming in step c may be performed with the addition of additives to further improve the performance of the catalyst product. The additive may be added to the molecular sieve-binder mixed slurry, followed by the spray forming. The additive may be at least one selected from sesbania powder, graphite, activated carbon, paraffin, stearic acid, glycerin, oxalic acid, tartaric acid, citric acid, starch, polyethylene glycol, polyvinyl alcohol, polyethylene oxide, polyallylamine, cellulose methyl ether, cellulose, polymeric alcohol, nitric acid, hydrochloric acid, acetic acid, formic acid, ammonia water, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrapropylammonium hydroxide, and the amount thereof may be adjusted according to actual needs, and generally, the amount of the additive is 1 to 5wt% based on the dry weight of the molecular sieve. It will be appreciated by those skilled in the art that the additive may have a modifying or pore-expanding effect or may facilitate molding, but it may be completely volatilized during the subsequent calcination process and may not remain on the catalyst, so that the finally prepared catalyst does not contain additive components, depending on the requirements.
The invention also discloses a preparation method of caprolactam, which comprises the following steps: the cyclohexanone oxime is contacted with the catalyst in the presence of a solvent to carry out a gas phase Beckmann rearrangement reaction.
When the microsphere all-silicon-1 molecular sieve catalyst containing extremely trace rare earth ions is applied to cyclohexanone-oxime gas-phase Beckmann rearrangement reaction, the cyclohexanone-oxime conversion rate and caprolactam selectivity are high, long-period and continuous production of caprolactam can be realized, and the total caprolactam selectivity and the total caprolactam yield are higher than those of the existing all-silicon-1 molecular sieve catalyst. And the total amount of the by-products is reduced, so that the energy consumption for separating the products is reduced, and the technical economy is effectively improved.
Preferably, the molar ratio of the solvent to the cyclohexanone oxime is (2-10) to 1.
Preferably, the solvent is selected from fatty alcohols of C1-C6.
Preferably, the gas phase Beckmann rearrangement reaction is carried out in the presence of nitrogen gas, and the molar ratio of the nitrogen gas to the cyclohexanone oxime is (10-80): 1. Preferably (20-40) to 1. In addition, a certain amount of NH was bubbled into the nitrogen3、(CH3)3N and other nitrogen-containing basic gases are beneficial to improving the rearrangement performance of the catalyst.
Preferably, the conditions under which the gas phase beckmann rearrangement reaction is carried out are: the weight space velocity of the cyclohexanone-oxime is 0.1-20 hours-1Preferably 0.5 to 10 hours-1(ii) a The reaction temperature is 300-500 ℃, preferably 350-400 ℃, and the reaction pressure is 0.1-0.5 MPa.
Preferably, the method further comprises mixing the cyclohexanone oxime and water in a molar ratio of 1 to (0.01-2.5), and then contacting the mixture with the catalyst in the presence of the solvent to perform a gas-phase Beckmann rearrangement reaction.
Compared with the prior art, the invention has the beneficial effects that: according to the invention, a trace amount of rare earth ions are added in the synthesis process of the all-silicon-1 molecular sieve, so that the performance of the all-silicon-1 molecular sieve can be effectively changed, and then the microspheric all-silicon-1 molecular sieve catalyst with higher strength and wear resistance is obtained through spray forming. In a fluidized bed reaction system, the microsphere all-silicon-1 molecular sieve catalyst is adopted to carry out cyclohexanone-oxime gas-phase Beckmann rearrangement reaction to prepare caprolactam, long-period and continuous production of caprolactam can be realized, the caprolactam has higher total selectivity and total yield than the existing all-silicon-1 molecular sieve catalyst, the energy consumption for separating the product is reduced due to the reduction of the total amount of byproducts, and the technical economy is effectively improved.
Drawings
Figure 1 is a photograph of a product of the invention.
Detailed Description
The present invention will be further described with reference to the following examples. The BET specific surface and external specific surface data of the samples of the all-silicon-1 molecular sieve in the examples are measured by an automatic adsorption apparatus, model ASAP-2400, Micromeritics, USA, under the following test conditions: n is a radical of2As adsorbate, the adsorption temperature is-196.15 deg.C (liquid nitrogen temperature), and degassing is carried out at constant temperature of 1.3Pa and 300 deg.C for 6 h. The content of the rare earth ions of the sample is measured by using a Baird PS-4 type ICP-AES plasma inductively coupled atomic emission spectrometer, and the test conditions are as follows: dissolving the solid molecular sieve or catalyst with HF acid or aqua regia to make the silicon oxide in the sample volatile, and measuring in water solution. The particle size distribution of the catalyst is measured by a BT-9300S type laser particle size distribution instrument of Baite instruments Limited, Dong, the test method is a wet test, water is used as a medium, and the sample concentration is as follows: 0.5-2% and the scanning speed is 2000 times/second. The catalyst attrition index K was measured on an attrition index analyzer according to the RIPP29-90 method in the petrochemical analysis method (Yankeeding et al, scientific Press, 1990).
The microspheric MFI topological structure all-silicon-1 molecular sieve catalyst containing trace rare earth ions comprises 70-95 wt% of MFI topological structure all-silicon-1 molecular sieve containing trace rare earth ions and 5-30wt% of binder, wherein the weight of the catalyst on a dry basis is taken as a reference; the particle size of the catalyst is 20-400 mu m, and the abrasion index K is less than 5.
The BET specific surface area of the MFI topological structure all-silicon-1 molecular sieve is 400-500m2The weight ratio of silicon dioxide to rare earth ions in the MFI topological structure all-silicon-1 molecular sieve is (10000-.
Preferably, the catalyst comprises 80-90 wt% of MFI topological structure all-silicon-1 molecular sieve containing trace rare earth ions and 10-20 wt% of binder, based on the dry weight of the catalyst; the particle size of the catalyst is 40-200 mu m.
Preferably, the binder is silica solThe content of sodium ions in the silica sol is 10-500ppm, SiO2The content is 20-45 wt%.
The invention also discloses a spray forming preparation method of the catalyst, which comprises the following steps:
a. mixing a silicon source, a rare earth ion source, an organic template agent and water to obtain a colloid mixture; wherein SiO in the colloid mixture2The mol ratio of the organic template agent to the water is 1 to (0.05-0.50) to (5-100); the mass ratio of the silicon source to the rare earth ions is (10000-) -200000: 1; and (3) performing hydrothermal crystallization on the colloid mixture at 50-60 ℃ for 0.5-3 days, performing hydrothermal crystallization at 80-120 ℃ for 0.5-3 days, performing membrane filtration on the obtained crystallized product, and washing until the pH value is 7.5-10 to obtain molecular sieve slurry with the solid content of 25-35 wt%.
b. And mixing the molecular sieve slurry with a binder, and pulping to obtain the molecular sieve-binder mixed slurry with the solid content of 10-35 wt%.
c. And (3) carrying out spray forming on the molecular sieve-binder mixed slurry, and then roasting to obtain the microspheric MFI topological structure all-silicon-1 molecular sieve.
d. And (3) contacting the microspheric MFI topological structure all-silicon-1 molecular sieve with an alkaline buffer solution containing a nitrogen compound, and then washing, filtering and drying to obtain a finished product.
Preferably, in step b, the molecular sieve slurry contains SiO as a dry basis of molecular sieve2The weight ratio of the adhesive is 1 to (0.05-0.5).
Preferably, in step c, the spray forming conditions are as follows: the inlet temperature of the sprayer is 180-240 ℃; the outlet temperature is 80-120 ℃.
Further preferably, the inlet temperature of the sprayer is 200-220 ℃; the outlet temperature is 90-100 ℃.
Preferably, in step c, the roasting conditions are as follows: the temperature is 200 ℃ and 600 ℃ and the time is 1-20 hours. Roasting to obtain SiO2Preferably 100-250m2/g。
Preferably, in step d, the alkaline buffer solution containing the nitrogen-containing compound contains ammonium salt and alkali, the content of the ammonium salt is 0.5-20wt%, the content of the alkali is 5-30wt%, and the pH value of the alkaline buffer solution containing the nitrogen-containing compound is 8.5-13.5.
Preferably, in the step d, the weight ratio of the microspheric MFI topological structure all-silicon-1 molecular sieve to the alkaline buffer solution of the nitrogen-containing compound is 1 to (5-15) on a dry basis, the contact temperature is 50-120 ℃, and the contact pressure is 0.5-5kg/cm2The contact time is 10 to 300 minutes, and the performance of the catalyst determines whether or not the alkaline buffer solution post-treatment of the nitrogen-containing compound is repeated several times.
Preferably, in step a, the rare earth ion is selected from Ce3+、Ce4+、La3+At least one of; the rare earth ion source is selected from La (NO)3)3·6H2O、La(OAc)3·5H2O、LaCl3·7H2O、La2(CO3)3·xH2O、Ce(NO3)3·6H2O、Ce(NO3)4·7H2O、Ce(OAc)3·5H2O、Ce(SO4)2·2H2O、CeCl3·7H2At least one of O.
Preferably, in the step a, the silicon source is at least one selected from the group consisting of silica gel, silica sol and organosilicate; preferably of the formula (OR)1)4Organosilicates of Si wherein R1Is an alkyl group of 1 to 4 carbon atoms; more preferably, tetraethoxysilane.
Preferably, the organic templating agent may be conventionally selected in the art, and may be, for example, at least one selected from the group consisting of fatty amine-based compounds, alcohol amine-based compounds, and quaternary amine-based compounds. Wherein the general formula of the aliphatic amine compound is R2(NH2)n，R2Is an alkyl group having 1 to 6 carbon atoms, n is an integer of 1 to 3, and the aliphatic amine compound is preferably at least one selected from the group consisting of ethylamine, n-butylamine, n-propylamine, ethylenediamine, and hexamethylenediamine. Wherein the general formula of the alcohol amine compound is (HOR)3)mN，R3Is an alkyl group having 1 to 4 carbon atoms, m is an integer of 1 to 3, and the alcohol amine compound is preferably at least one selected from the group consisting of monoethanolamine, diethanolamine and triethanolamine. The quaternary ammonium base compound is preferably an alkyl quaternary ammonium base compound having 1 to 4 carbon atoms, and more preferably tetraethylammonium hydroxide and/or tetrapropylammonium hydroxide.
Preferably, in step a, the colloidal mixture further comprises a lower alcohol, and the lower alcohol is mixed with SiO2The molar ratio of the low carbon alcohol to the alcohol is 1 to (4-15), and the low carbon alcohol is methanol and/or ethanol.
Preferably, the spray forming in step c may be performed with the addition of additives to further improve the performance of the catalyst product. The additive may be added to the molecular sieve-binder mixed slurry, followed by the spray forming. The additive may be at least one selected from sesbania powder, graphite, activated carbon, paraffin, stearic acid, glycerin, oxalic acid, tartaric acid, citric acid, starch, polyethylene glycol, polyvinyl alcohol, polyethylene oxide, polyallylamine, cellulose methyl ether, cellulose, polymeric alcohol, nitric acid, hydrochloric acid, acetic acid, formic acid, ammonia water, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrapropylammonium hydroxide, and the amount thereof may be adjusted according to actual needs, and generally, the amount of the additive is 1 to 5wt% based on the dry weight of the molecular sieve. It will be appreciated by those skilled in the art that the additive may have a modifying or pore-expanding effect or may facilitate molding, but it may be completely volatilized during the subsequent calcination process and may not remain on the catalyst, so that the finally prepared catalyst does not contain additive components, depending on the requirements.
A process for producing caprolactam, comprising: the cyclohexanone oxime is contacted with the catalyst in the presence of a solvent to carry out a gas phase Beckmann rearrangement reaction.
Preferably, the molar ratio of the solvent to the cyclohexanone oxime is (2-10) to 1.
Preferably, the solvent is selected from fatty alcohols of C1-C6.
Preferably, the gas phase Beckmann rearrangement reaction is carried out in the presence of nitrogen gas, and the molar ratio of the nitrogen gas to the cyclohexanone oxime is (10-80): 1. Preferably (20-40) to 1.
Preferably, the conditions under which the gas phase beckmann rearrangement reaction is carried out are: the weight space velocity of the cyclohexanone-oxime is 0.1-20 hours-1Preferably 0.5 to 10 hours-1(ii) a The reaction temperature is 300-500 ℃, preferably 350-400 ℃, and the reaction pressure is 0.1-0.5 MPa.
Preferably, the method further comprises mixing the cyclohexanone oxime and water in a molar ratio of 1 to (0.01-2.5), and then contacting the mixture with the catalyst in the presence of the solvent to perform a gas-phase Beckmann rearrangement reaction.
The service life of the catalyst can be prolonged by adding a small amount of water into the cyclohexanone oxime.
Preferably, after the baked microspherical molecular sieve is contacted with the alkaline buffer solution containing the nitrogen compound, the material after the contact with the deionized water can be washed to remove the nitrogen compound on the surface of the microspherical molecular sieve catalyst, and then the filtration and the drying are carried out. The drying is carried out as long as the moisture is sufficiently removed, and the drying method can be heating drying, air-blast drying or natural drying, wherein the drying temperature can be 100-120 ℃, and the drying time can be 10-24 hours. When the catalyst obtained by washing and drying the contacted materials is used for preparing caprolactam from cyclohexanone oxime, the catalyst is favorable for improving the conversion rate of cyclohexanone oxime and the selectivity of caprolactam.
Example 1
416kg of ethyl orthosilicate, 360kg of 22.5% by weight tetrapropylammonium hydroxide, 14.6gCe (NO)3)4·7H2O and 440kg of water are mixed and stirred for 5 hours at normal temperature to form a colloidal mixture with the pH value of 12.45, and the molar ratio of the mixture is SiO2∶TPAOH∶H2O＝1∶0.2∶20，SiO2And Ce3+Is 30300: 1, transferring the mixture to 2m3In a stainless steel reaction kettle, firstly carrying out hydrothermal crystallization at 50 ℃ for 1 day, then carrying out hydrothermal crystallization at 100 ℃ for 2 days, wherein the pH value of a crystallization product is 13.55, then carrying out membrane filtration by adopting a 50nm six-tube membrane and adoptingWashing with water at 40-60 deg.C, the amount of washing water is 7.0m3The pH of the washing water of the crystallized product reached 9.1. Concentrating the slurry obtained after washing: 395kg of molecular sieve slurry with a solids content of 26.8 wt.%.
Drying a small amount of the molecular sieve slurry at 120 ℃ for 20 hours to obtain the all-silicon-1 molecular sieve raw powder containing extremely trace rare earth ions. The all-silicon-1 molecular sieve is calcined at 550 ℃ for 6 hours, and the content of cerium ions is 33ppm, and the BET specific surface area is 441 m2Per gram, external specific surface 59 m2The grain size is 0.15-0.25 mu m.
The above molecular sieve slurry was mixed with 86.5kg of 30% alkaline silica sol (pH 9.5, sodium ion content 324ppm, SiO)2The content is 40 weight percent, and SiO is obtained after roasting2Has a surface area of 225m2Per g), mixing, molecular sieve dry basis in molecular sieve slurry and mixing with SiO2The weight ratio of the alkaline silica sol is 1: 0.22, the mixture is stirred evenly and pulped to obtain the molecular sieve-binder mixed slurry with the solid content of 27.5 weight percent. The mixture was fed into a spray forming apparatus (model LPG-5, manufactured by Henmei drying equipment Co., Ltd., Changzhou city) to spray form at inlet and outlet temperatures of 200 ℃ and 95 ℃ respectively. Then feeding into a 3m3In a heating shuttle furnace (manufactured by Huaxia electro-thermal engineering equipment Co., Ltd., Huanggang, Hubei), the materials are respectively roasted at 280 ℃, 400 ℃ and 480 ℃ for 2h, and finally roasted at 550 ℃ for 12h to obtain 130kg of microsphere molecular sieve, wherein the content of the all-silicon-1 molecular sieve containing trace rare earth ions is 80 wt%, and the content of the adhesive silica sol is 20 wt%.
Adding 100g of the microsphere molecular sieve and 1000g of a nitrogen-containing compound alkaline buffer solution (the nitrogen-containing compound alkaline buffer solution is a mixed solution of ammonia water and an ammonium nitrate aqueous solution, wherein the content of the ammonia water is 26 wt%, the content of the ammonium nitrate in the ammonium nitrate aqueous solution is 7.5 wt%, the weight ratio of the ammonia water to the ammonium nitrate aqueous solution is 3: 2, and the pH value is 11.35) to 2m3In a stainless steel reaction kettle (KCF-2 type magnetic stirring autoclave, Nicoti Hi-Chu-Kogyo research institute), 2.3kg/cm at 82 deg.C2Stirred under pressure for 1.5 hours, then filtered and washed until the pH of the filtered supernatant is9, and then dried at 120 ℃ for 24 hours to obtain the microspherical molecular sieve catalyst with the code A1.
The particle size of the microspherical molecular sieve catalyst A1 is measured to be concentrated in 70-150 mu m, and the abrasion index K is 2.8.
TABLE 1
Example 2
416kg of ethyl orthosilicate, 360kg of 22.5% by weight tetrapropylammonium hydroxide, 28gCe (NO)3)3·6H2O and 440kg of water are mixed and stirred for 5 hours at normal temperature to form a colloidal mixture with the pH value of 12.47, and the molar ratio of the mixture is SiO2∶TPAOH∶H2O＝1∶0.2∶20，SiO2And Ce3+In a mass ratio of 13500: 1, the mixture was transferred to 2m3In a stainless steel reaction kettle, firstly carrying out hydrothermal crystallization at 50 ℃ for 1.5 days, then carrying out hydrothermal crystallization at 100 ℃ for 1.5 days, wherein the pH value of a crystallization product is 13.73, then carrying out membrane filtration by adopting a 50nm six-tube membrane and washing by adopting water at 40-60 ℃, and the dosage of washing water is 6.7m3The pH value of the washing water of the crystallized product reaches 9.0. Concentrating the slurry obtained after washing: 436kg of a molecular sieve slurry having a solids content of 24.5% by weight.
Drying a small amount of the molecular sieve slurry at 120 ℃ for 20 hours to obtain the all-silicon-1 molecular sieve raw powder containing extremely trace rare earth ions. The all-silicon-1 molecular sieve is calcined for 6 hours at 550 ℃, and the content of cerium ions is measured to be 72ppm, the BET specific surface area is 437 meters2Per gram, external specific surface 55 m2The grain size is 0.15-0.25 mu m.
The above molecular sieve slurry was mixed with 60kg of 30% alkaline silica sol (pH 9.5, sodium ion content 324ppm, SiO)2The content is 40 weight percent, and SiO is obtained after roasting2Has a surface area of 225m2Per gram) mixed, molecular sieve slurryMolecular sieve dry basis in liquid and with SiO2The weight ratio of the alkaline silica sol is 1: 0.15, 70kg of water is added, the mixture is stirred evenly and pulped, and the molecular sieve-binder mixed slurry with the solid content of 22 weight percent is obtained. The mixture is sent into a spray forming device for spray forming, and the inlet temperature and the outlet temperature are 205 ℃ and 100 ℃ respectively. Then feeding into a 3m3Respectively roasting in a heating shuttle furnace at 280 ℃, 400 ℃ and 480 ℃ for 2h, and finally roasting at 550 ℃ for 12h to obtain 120kg of microsphere molecular sieve, wherein the content of the all-silicon-1 molecular sieve containing extremely trace rare earth ions is 85 wt%, and the content of the adhesive silica sol is 15 wt%.
Adding 95g of the microsphere molecular sieve and 950g of a basic buffer solution of a nitrogen-containing compound (the basic buffer solution of the nitrogen-containing compound is a mixed solution of ammonia water and an ammonium acetate water solution, wherein the ammonia water content is 26 wt%, the ammonium acetate content in the ammonium acetate water solution is 7.5 wt%, the weight ratio of the ammonia water to the ammonium acetate water solution is 3: 2, and the pH value is 11.39) to 2m3In a stainless steel reaction kettle at 85 deg.C and 2.5kg/cm2Stirring for 1.5 hours under pressure, then filtering, washing until the pH of the filtered clear solution is 9, and then drying for 24 hours at 120 ℃ to obtain the microsphere molecular sieve catalyst with the code A2.
The particle size of the microspherical molecular sieve catalyst A2 is measured to be concentrated in 70-150 mu m, and the abrasion index K is 3.0.
Example 3
416kg of ethyl orthosilicate, 360kg of 22.5% by weight tetrapropylammonium hydroxide, 7.4 g of Ce (OAc)3·5H2O and 440kg of water, and stirring the mixture at normal temperature for 5 hours to form a colloidal mixture, wherein the colloidal mixture has a pH value of 12.46 and the molar ratio of the mixture is SiO2∶TPAOH∶H2O＝1∶0.2∶20，SiO2And Ce3+Is 48000: 1, the mixture is transferred to 2m3In a stainless steel reaction kettle, firstly carrying out hydrothermal crystallization at 60 ℃ for 1 day, then carrying out hydrothermal crystallization at 100 ℃ for 2 days, wherein the pH value of a crystallization product is 13.42, then carrying out membrane filtration by adopting a 50nm six-tube membrane, and washing by adopting water at 40-60 ℃, wherein the dosage of washing water is 6.7m3The pH of the washing water of the crystallized product reached 9.1. Obtained after washingConcentrating the slurry: 380kg of a molecular sieve slurry having a solids content of 28.4% by weight.
Drying a small amount of the molecular sieve slurry at 120 ℃ for 20 hours to obtain the all-silicon-1 molecular sieve raw powder containing extremely trace rare earth ions. The all-silicon-1 molecular sieve is calcined at 550 ℃ for 6 hours, and the content of cerium ion is measured to be 22ppm, and the BET specific surface area is 443 m2Per gram, external specific surface 60 m2The grain size is 0.1-0.25 mu m.
The above molecular sieve slurry was mixed with 110kg of 30% alkaline silica sol (pH 9.5, sodium ion content 324ppm, SiO)2The content is 40 weight percent, and SiO is obtained after roasting2Has a surface area of 225m2Per g), mixing, molecular sieve dry basis in molecular sieve slurry and mixing with SiO2The weight ratio of the alkaline silica sol is 1: 0.275, 450kg of water is added, the mixture is stirred evenly and pulped, and the molecular sieve-binder mixed slurry with the solid content of 15 weight percent is obtained. The mixture is sent into a spray forming device for spray forming, and the inlet temperature and the outlet temperature are 210 ℃ and 105 ℃ respectively. Then feeding into a 3m3And (3) respectively roasting in a heating shuttle furnace at 280 ℃, 400 ℃ and 480 ℃ for 2h, and finally roasting at 550 ℃ for 12h to obtain 140kg of the microsphere molecular sieve, wherein the content of the all-silica-1 molecular sieve containing extremely trace rare earth ions is 76 wt%, and the content of the adhesive silica sol is 24 wt%.
Adding 100g of the microsphere molecular sieve and 1000g of a nitrogen-containing compound alkaline buffer solution (the nitrogen-containing compound alkaline buffer solution is a mixed solution of ammonia water and an ammonium nitrate aqueous solution, wherein the content of the ammonia water is 26 wt%, the content of the ammonium nitrate in the ammonium nitrate aqueous solution is 7.5 wt%, the weight ratio of the ammonia water to the ammonium nitrate aqueous solution is 3: 2, and the pH value is 11.35) to 2m3In a stainless steel reaction kettle at 100 deg.C and 3kg/cm2Stirring for 1.5 hours under pressure, filtering, drying for 24 hours at 120 ℃, repeating the contact operation of the basic buffer solution containing the nitrogen compound once again under the same conditions, filtering again, washing until the pH of the filtered clear solution is 9, and drying for 24 hours at 120 ℃ to obtain the microsphere molecular sieve catalyst with the code of A3.
The particle size of the microspherical molecular sieve catalyst A3 is measured to be concentrated in 70-150 mu m, and the abrasion index K is 2.2.
Example 4
416kg of ethyl orthosilicate, 720kg of 22.5 wt% tetrapropylammonium hydroxide, 370kg of ethanol, 40.4 g of Ce (NO)3)4·7H2Mixing O with 880kg of water, stirring at room temperature for 5 hours to form a colloidal mixture with a pH of 12.58, the molar ratio of the mixture being SiO2∶TPAOH∶H2O＝1∶0.4∶40，SiO2And Ce4+The mass ratio of (1) to (2) is 10900: 1, ethanol/SiO2Transferring the mixture to 5m3In a stainless steel reaction kettle, firstly carrying out hydrothermal crystallization at 50 ℃ for 1 day, then carrying out hydrothermal crystallization at 100 ℃ for 2 days, wherein the pH value of a crystallization product is 13.80, then carrying out membrane filtration by adopting a 50nm six-tube membrane and washing by adopting water at 40-60 ℃, and the dosage of washing water is 7.5m3The pH value of the washing water of the crystallized product reaches 9.0. The slurry obtained after washing was concentrated to obtain 520kg of a molecular sieve slurry having a solid content of 20.7% by weight.
Drying a small amount of the molecular sieve slurry at 120 ℃ for 20 hours to obtain the all-silicon-1 molecular sieve raw powder containing extremely trace rare earth ions. The all-silicon-1 molecular sieve is calcined for 6 hours at 550 ℃, and the content of cerium ions is measured to be 90ppm, the BET specific surface area is 433 meters2Per gram, external specific surface 52 m2The grain size is 0.15-0.25 mu m.
The above molecular sieve slurry was mixed with 90kg of 30% alkaline silica sol (pH 9.5, sodium ion content 324ppm, SiO)2The content is 40 weight percent, and SiO is obtained after roasting2Has a surface area of 225m2Per g), mixing, molecular sieve dry basis in molecular sieve slurry and mixing with SiO2The weight ratio of the alkaline silica sol is 1: 0.225, the mixture is evenly stirred and pulped to obtain the molecular sieve-binder mixed slurry with the solid content of 22 weight percent. The mixture is sent into a spray forming device for spray forming, and the inlet temperature and the outlet temperature are respectively 200 ℃ and 100 ℃. Then feeding into a 3m3Respectively roasting at 280 deg.C, 400 deg.C and 480 deg.C for 2 hr, and finally roasting at 550 deg.C for 12 hr to obtain 134kg microsphere molecular sieve, wherein the content of all-silicon-1 molecular sieve containing trace rare earth ions is 80 wt%, and the content of binder silica sol is 20wt%％。
Adding 100g of the microsphere molecular sieve and 1000g of a nitrogen-containing compound alkaline buffer solution (the nitrogen-containing compound alkaline buffer solution is a mixed solution of ammonia water and an ammonium nitrate aqueous solution, wherein the content of the ammonia water is 26 wt%, the content of the ammonium nitrate in the ammonium nitrate aqueous solution is 7.5 wt%, the weight ratio of the ammonia water to the ammonium nitrate aqueous solution is 3: 2, and the pH value is 11.35) to 2m3In a stainless steel reaction kettle at 85 deg.C and 2.6kg/cm2Stirring for 1.5 hours under pressure, filtering, drying for 24 hours at 120 ℃, repeating the contact operation of the basic buffer solution containing the nitrogen compound once again under the same conditions, filtering again, washing until the pH of the filtered clear solution is 9, and drying for 24 hours at 120 ℃ to obtain the microsphere molecular sieve catalyst with the code of A4.
The particle size of the microspherical molecular sieve catalyst A4 is measured to be concentrated in 70-150 mu m, and the abrasion index K is 3.2.
Example 5
208kg of ethyl orthosilicate, 90kg of 22.5 wt% tetrapropylammonium hydroxide, 276kg of ethanol and 24 g of La (NO)3)3·6H2Mixing O with 110kg of water, stirring at normal temperature for 5 hours to form a colloidal mixture with a pH value of 12.91, wherein the molar ratio of the mixture is SiO2∶TPAOH∶H2O＝1∶0.1∶10，SiO2And La3+The mass ratio of (1) to (2) is 15300: 1, ethanol/SiO2Transferring the mixture to 1m ═ 103In a stainless steel reaction kettle, firstly carrying out hydrothermal crystallization for 2 days at 50 ℃, then carrying out hydrothermal crystallization for 2 days at 100 ℃, wherein the pH value of a crystallization product is 13.48, then carrying out membrane filtration by adopting a 50nm six-tube membrane and washing by adopting water at 40-60 ℃, and the dosage of washing water is 6.5m3The pH value of the washing water of the crystallized product reaches 9. Concentrating the slurry obtained after washing: 160kg of a molecular sieve slurry having a solids content of 34.1% by weight. The above procedure was repeated once, to give a total of 320kg of a molecular sieve slurry having a solids content of 34.1% by weight.
Drying a small amount of the molecular sieve slurry at 120 ℃ for 20 hours to obtain the all-silicon-1 molecular sieve raw powder containing extremely trace rare earth ions. The all-silicon-1 molecular sieve is calcined at 550 ℃ for 6 hours, and the lanthanum ion content is measured to be 64ppm, the BET specific surface area is 451Rice and its production process2G, external specific surface area of 69 m2The grain size is 0.15-0.35 mu m.
The above molecular sieve slurry was mixed with 40kg of 30% alkaline silica sol (pH 9.5, sodium ion content 324ppm, SiO)2The content is 40 weight percent, and SiO is obtained after roasting2Has a surface area of 225m2Per g), mixing, molecular sieve dry basis in molecular sieve slurry and mixing with SiO2The weight ratio of the alkaline silica sol is 1: 0.11, the mixture is stirred evenly and pulped to obtain the molecular sieve-binder mixed slurry with the solid content of 33.5 percent by weight. The mixture is sent into a spray forming device for spray forming, and the inlet temperature and the outlet temperature are respectively 200 ℃ and 100 ℃. Then feeding into a 3m3Respectively roasting in a heating shuttle furnace at 280 ℃, 400 ℃ and 480 ℃ for 2h, and finally roasting at 550 ℃ for 12h to obtain 120kg of microsphere molecular sieve, wherein the content of the all-silicon-1 molecular sieve containing extremely trace rare earth ions is 90wt%, and the content of the adhesive silica sol is 10 wt%.
Adding 100g of the microsphere molecular sieve and 1000g of a nitrogen-containing compound alkaline buffer solution (the nitrogen-containing compound alkaline buffer solution is a mixed solution of ammonia water and an ammonium nitrate aqueous solution, wherein the content of the ammonia water is 26 wt%, the content of the ammonium nitrate in the ammonium nitrate aqueous solution is 7.5 wt%, the weight ratio of the ammonia water to the ammonium nitrate aqueous solution is 3: 2, and the pH value is 11.35) to 2m3In a stainless steel reaction kettle at 80 deg.C and 2.1kg/cm2Stirring for 1.5 hours under pressure, filtering, drying for 24 hours at 120 ℃, repeating the contact operation of the basic buffer solution containing the nitrogen compound once again under the same conditions, filtering again, washing until the pH of the filtered clear solution is 9, and drying for 24 hours at 120 ℃ to obtain the microsphere molecular sieve catalyst with the code of A5.
The particle size of the microspherical molecular sieve catalyst A5 is measured to be concentrated in 70-150 mu m, and the abrasion index K is 4.3.
Example 6
416kg of ethyl orthosilicate, 360kg of 22.5% by weight tetrapropylammonium hydroxide, 550kg of ethanol, 2.6 g of La (OAc)3·5H2O and 260kg of water, and stirring at normal temperature for 6 hours to form a colloidal mixture with a pH of 12.85, the molar ratio of the mixtureRatio of SiO2∶TPAOH∶H2O＝1∶0.2∶15，SiO2And La3+With a mass ratio of 140000: 1, ethanol/SiO2Transfer the mixture to 3m3In a stainless steel reaction kettle, firstly carrying out hydrothermal crystallization at 60 ℃ for 1 day, then carrying out hydrothermal crystallization at 100 ℃ for 2 days, wherein the pH value of a crystallization product is 13.55, then carrying out membrane filtration by adopting a 50nm six-tube membrane, and washing by adopting water at 40-60 ℃, wherein the dosage of washing water is 6.8m3The pH of the washing water of the crystallized product reached 9.1. Concentrating the slurry obtained after washing: 390kg of a molecular sieve slurry having a solids content of 26.9% by weight.
Drying a small amount of the molecular sieve slurry at 120 ℃ for 20 hours to obtain the all-silicon-1 molecular sieve raw powder containing extremely trace rare earth ions. The all-silicon-1 molecular sieve is calcined at 550 ℃ for 6 hours, and the lanthanum ion content is measured to be 7ppm, the BET specific surface area is 443 m2Per gram, external specific surface 67 m2The grain size is 0.15-0.25 mu m.
The above molecular sieve slurry was mixed with 86.5kg of 30% alkaline silica sol (pH 9.5, sodium ion content 324ppm, SiO)2The content is 40 weight percent, and SiO is obtained after roasting2Has a surface area of 225m2Per g), mixing, molecular sieve dry basis in molecular sieve slurry and mixing with SiO2The weight ratio of the alkaline silica sol is 1: 0.22, the mixture is stirred evenly and pulped to obtain the molecular sieve-binder mixed slurry with the solid content of 27.5 weight percent. The mixture is sent into a spray forming device for spray forming, and the inlet temperature and the outlet temperature are respectively 200 ℃ and 95 ℃. Then feeding into a 3m3Respectively roasting in a heating shuttle furnace at 280 ℃, 400 ℃ and 480 ℃ for 2h, and finally roasting at 550 ℃ for 12h to obtain 130kg of microsphere molecular sieve, wherein the content of the all-silicon-1 molecular sieve containing trace rare earth ions is 80 wt%, and the content of the adhesive silica sol is 20 wt%.
Mixing 100g of the microsphere molecular sieve and 1000g of a nitrogen-containing compound alkaline buffer solution (the nitrogen-containing compound alkaline buffer solution is a mixed solution of ammonia water and an ammonium nitrate aqueous solution, wherein the content of the ammonia water is 26 wt%, the content of the ammonium nitrate in the ammonium nitrate aqueous solution is 7.5 wt%, the weight ratio of the ammonia water to the ammonium nitrate aqueous solution is 3: 2, and the pH value is 311.35) to 2m3In a stainless steel reaction kettle at 82 deg.C and 2.3kg/cm2Stirring for 1.5 hours under pressure, filtering, drying for 24 hours at 120 ℃, repeating the contact operation of the basic buffer solution containing the nitrogen compound once again under the same conditions, filtering again, washing until the pH of the filtered clear solution is 9, and drying for 24 hours at 120 ℃ to obtain the microsphere molecular sieve catalyst with the code of A6.
The particle size of the microsphere molecular sieve catalyst A6 is concentrated in 70-150 mu m, and the abrasion index K is 4.6.
From the results of examples 1-6, it can be seen that the microspherical all-silica-1 molecular sieve catalyst containing extremely small amount of rare earth ions disclosed by the invention has low abrasion index, and thus can be used in the fluidized bed process for preparing caprolactam by gas phase Beckmann rearrangement of cyclohexanone oxime.
Test examples photographs of the catalysts obtained according to the present invention are shown in fig. 1, and the test examples are provided to illustrate the catalytic reaction results of the all-silicon-1 molecular sieve catalysts prepared in examples 1 to 6 in the gas phase beckmann rearrangement reaction.
The cyclohexanone oxime gas phase Beckmann rearrangement reaction is carried out by using catalysts A1-A6 respectively under the following conditions:
performing cyclohexanone-oxime gas-phase Beckmann rearrangement reaction in a stainless steel fixed bed reactor, wherein the inner diameter of the reactor is 5mm, 0.469 g of catalyst with 40-60 meshes is filled in the reactor, coarse quartz sand with the height of about 30mm and the size of 30 meshes is filled on the upper surface of a catalyst bed layer, and fine quartz sand with the size of 50 meshes is filled below the catalyst bed layer. The rearrangement reaction conditions are as follows: normal pressure; the reaction temperature is 380 ℃; the weight space velocity (WHSV, cyclohexanone oxime flow in feeding/catalyst weight in bed) of the cyclohexanone oxime is 16h-1(ii) a The reaction solvent is methanol, and the weight of the methanol is 65 percent of that of the reaction raw materials; carrier gas (N)2) The flow rate is 45ml/min, the reaction product enters a collecting bottle for gas-liquid separation after being cooled by an ice-water mixture, and the composition analysis of the product is carried out after the reaction is carried out for 6 hours.
The reaction product was quantitatively analyzed by Agilent 6890 gas chromatography (hydrogen flame ion detector, PEG20M capillary chromatographic column, column length 50m), the vaporization chamber temperature was 250 deg.C, the detection chamber temperature was 240 deg.C, the column temperature was programmed to increase, the temperature was maintained at 110 deg.C for 8 minutes, 15 deg.C/min was increased to 230 deg.C, and the temperature was maintained for 14 minutes.
The content of rearrangement products of caprolactam and cyclohexenone after the reaction is calculated by adopting an area normalization method, and the solvent does not participate in the integral.
The molar percentage content of cyclohexanone oxime in the reaction product and the molar percentage content of caprolactam in the reaction product are obtained through the analysis, and the conversion rate of cyclohexanone oxime and the selectivity of caprolactam are calculated according to the following formula. The results are shown in Table 1.
Cyclohexanone oxime conversion (mol%) (100-cyclohexanone oxime mol% in reaction product)/100 × 100%
Total caprolactam selectivity (mol%) × 100% for caprolactam mol% (caprolactam mol%) in the reaction product/(100-cyclohexanone oxime mol% in the reaction product)
In the byproduct of the cyclohexanone oxime gas phase Beckmann rearrangement reaction, methyl-epsilon-caprolactam accounts for about 40 percent of the total amount of all the byproducts, and the byproducts are generated by the alcoholysis reaction of methanol and enol structure tautomer of caprolactam. Under the action of water, methyl-epsilon-caprolactam is continuously generated by hydrolysis reaction of methyl-epsilon-caprolactam. Thus, the amount of methyl-epsilon-caprolactam hydrolysis to caprolactam is included in the calculation of the total caprolactam selectivity.
TABLE 2
| Catalyst numbering | Cyclohexanone oxime conversion (mol%) | Caprolactam Total Selectivity (mol%) |
| A1 | 99.26 | 95.98 |
| A2 | 99.31 | 95.75 |
| A3 | 99.03 | 96.68 |
| A4 | 99.15 | 96.43 |
| A5 | 98.73 | 96.47 |
| A6 | 98.52 | 96.36 |
As can be seen from Table 2, the microsphere all-silicon-1 molecular sieve catalyst containing extremely trace rare earth ions prepared by the invention has extremely high cyclohexanone oxime conversion rate, and when the weight space velocity (WHSV) of cyclohexanone oxime is 16h-1Then, the reaction time can reach 99.31 percent at most after 6 hours, and the selectivity to caprolactam is high and can reach 96.68 percent at most.
The raw materials and equipment used in the invention are common raw materials and equipment in the field if not specified; the methods used in the present invention are conventional in the art unless otherwise specified.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, alterations and equivalents of the above embodiments according to the technical spirit of the present invention are still within the protection scope of the technical solution of the present invention.
Claims (11)
1. The application of a microspheric MFI topological structure all-silicon-1 molecular sieve containing trace rare earth ions as a gas phase Beckmann rearrangement reaction catalyst in caprolactam production is characterized in that: based on the dry weight of the catalyst, the catalyst comprises 70-95 wt% of MFI topological structure all-silicon-1 molecular sieve containing trace rare earth ions and 5-30wt% of binder, wherein the MFI topological structure all-silicon-1 molecular sieve contains trace rare earth ions; the particle size of the catalyst is 20-400 mu m, and the abrasion index K is less than 5; the rare earth ion is selected from Ce3+、Ce4+、La3+At least one of;
the BET specific surface area of the MFI topological structure all-silicon-1 molecular sieve is 400-500m2The weight ratio of silicon dioxide to rare earth ions in the MFI topological structure all-silicon-1 molecular sieve is (10000-200000): 1;
the catalyst is prepared by a spray forming method, and comprises the following steps:
a. mixing a silicon source, a rare earth ion source, an organic template agent and water to obtain a colloid mixture; wherein SiO in the colloid mixture2The mol ratio of the organic template agent to the water is 1 (0.05-0.50) to (5-100); the mass ratio of the silicon source to the rare earth ions is (10000- & lt 200000- & gt) 1; carrying out hydrothermal crystallization on the colloid mixture at 50-60 ℃ for 0.5-3 days, then carrying out hydrothermal crystallization at 80-120 ℃ for 0.5-3 days, carrying out membrane filtration on the obtained crystallized product, and washing until the pH value is 7.5-10 to obtain molecular sieve slurry with the solid content of 25-35 wt%;
b. mixing the molecular sieve slurry with a binder, and pulping to obtain a molecular sieve-binder mixed slurry with a solid content of 10-35 wt%;
c. spray forming the molecular sieve-binder mixed slurry, and then roasting to obtain a microspherical MFI topological structure all-silicon-1 molecular sieve;
d. and (3) contacting the microspheric MFI topological structure all-silicon-1 molecular sieve with an alkaline buffer solution containing a nitrogen compound, and then washing, filtering and drying to obtain a finished product.
2. The use according to claim 1, wherein the catalyst comprises 80 to 90wt% of MFI topological structure all-silicon-1 molecular sieve containing trace rare earth ions and 10 to 20wt% of binder, based on the dry weight of the catalyst; the particle size of the catalyst is 40-200 mu m.
3. Use according to claim 1, wherein the binder is a silica sol having a sodium ion content of 10-500ppm, SiO2The content is 20-45 wt%.
4. The use of claim 1, wherein in step b, the molecular sieve slurry comprises SiO as the dry basis of molecular sieve2The weight ratio of the calculated binder is 1: (0.05-0.5).
5. The use according to claim 1, wherein in step c, the spray forming conditions are: the inlet temperature of the sprayer is 180-240 ℃; the outlet temperature is 80-120 ℃.
6. The use according to claim 5, wherein the inlet temperature of the nebulizer is 200 to 220 ℃; the outlet temperature is 90-100 ℃.
7. The use of claim 1, wherein in step c, the firing conditions are: the temperature is 200 ℃ and 600 ℃ and the time is 1-20 hours.
8. The use according to claim 1, wherein in step d, the nitrogen-containing compound alkaline buffer solution contains ammonium salt and alkali, the ammonium salt content is 0.5-20wt%, the alkali content is 5-30wt%, and the nitrogen-containing compound alkaline buffer solution has a pH value of 8.5-13.5.
9. The use of claim 8, wherein in step d, the weight ratio of the microspherical MFI topological structure all-silicon-1 molecular sieve to the basic buffer solution of nitrogen-containing compound on a dry basis is 1:(5-15), the contact temperature is 50-120 ℃, and the contact pressure is 0.5-5kg/cm2The contact time is 10 to 300 minutes, and the performance of the catalyst determines whether or not the alkaline buffer solution post-treatment of the nitrogen-containing compound is repeated several times.
10. The use according to claim 1, wherein in step a, the silicon source is at least one selected from the group consisting of silica gel, silica sol and organosilicate; the organic template agent is selected from at least one of fatty amine compounds, alcohol amine compounds and quaternary ammonium base compounds.
11. The use of claim 1, wherein in step a, the colloidal mixture further comprises a lower alcohol, the lower alcohol being in contact with the SiO2In a molar ratio of 1: (4-15).
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| CN111790434A (en) * | 2020-07-03 | 2020-10-20 | 浙江恒澜科技有限公司 | Catalyst containing silicon molecular sieve with MFI topological structure, preparation method and application thereof, and gas phase Beckmann rearrangement reaction method |
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