CN115739168A - Composite molecular sieve and preparation method and application thereof - Google Patents
Composite molecular sieve and preparation method and application thereof Download PDFInfo
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- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 title claims abstract description 209
- 239000002808 molecular sieve Substances 0.000 title claims abstract description 182
- 239000002131 composite material Substances 0.000 title claims abstract description 133
- 238000002360 preparation method Methods 0.000 title abstract description 19
- VEZUQRBDRNJBJY-UHFFFAOYSA-N cyclohexanone oxime Chemical compound ON=C1CCCCC1 VEZUQRBDRNJBJY-UHFFFAOYSA-N 0.000 claims abstract description 50
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 48
- 239000010703 silicon Substances 0.000 claims abstract description 48
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 47
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 37
- 229910021389 graphene Inorganic materials 0.000 claims abstract description 36
- 239000003054 catalyst Substances 0.000 claims description 42
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- JBKVHLHDHHXQEQ-UHFFFAOYSA-N epsilon-caprolactam Chemical compound O=C1CCCCCN1 JBKVHLHDHHXQEQ-UHFFFAOYSA-N 0.000 claims description 26
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 25
- 238000000034 method Methods 0.000 claims description 25
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
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- 238000000465 moulding Methods 0.000 claims description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 239000011148 porous material Substances 0.000 claims description 6
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- 239000011248 coating agent Substances 0.000 claims description 5
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- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 4
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- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 claims description 3
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- 239000004677 Nylon Substances 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
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- ZBCBWPMODOFKDW-UHFFFAOYSA-N diethanolamine Chemical compound OCCNCCO ZBCBWPMODOFKDW-UHFFFAOYSA-N 0.000 description 1
- 125000003700 epoxy group Chemical group 0.000 description 1
- SYECJBOWSGTPLU-UHFFFAOYSA-N hexane-1,1-diamine Chemical compound CCCCCC(N)N SYECJBOWSGTPLU-UHFFFAOYSA-N 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
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Abstract
The invention provides a composite molecular sieve and a preparation method and application thereof, wherein the composite molecular sieve comprises the following components: a silicon-based molecular sieve core body having a porous structure, and the surface of the silicon-based molecular sieve core body being divided into an interior surface and an exterior surface; the silicon-based molecular sieve nucleus is selected from one or more of MFI type molecular sieve, Y type molecular sieve, beta type molecular sieve, MOR type molecular sieve or MWW type molecular sieve; and the graphene oxide shell layer is coated on the outer surface of the silicon-based molecular sieve core body. The composite molecular sieve prepared by the invention is easy to form, has higher axial strength and radial strength, has higher selectivity and conversion rate when being applied to the reaction of catalyzing the gas phase rearrangement of cyclohexanone oxime, shows excellent stability and longer service life, can avoid using other forming auxiliaries, and has the advantages of cost reduction and environmental friendliness.
Description
Technical Field
The invention relates to the technical field of petrochemical industry, and particularly relates to a composite molecular sieve and a preparation method and application thereof.
Background
Caprolactam is used as an important intermediate in industrial production of nylon, and has important significance for the comprehensive popularization and application of nylon. The Beckmann rearrangement of cyclohexanone oxime also plays a significant role as a key step in the caprolactam production process. At present, the prior liquid phase rearrangement process which takes concentrated sulfuric acid as a catalyst is mainly adopted for industrially producing caprolactam. Although the reaction conditions of the process are mild, and the conversion rate and the selectivity are ideal, a large amount of ammonium sulfate is produced as a byproduct in the process, which easily causes equipment corrosion and environmental pollution. In view of this, in recent years, more and more technicians have focused on solid acid catalysts such as molecular sieves and the like, and have used them as catalysts instead of conventional concentrated sulfuric acid catalysts. For example, the prior patents USP4061724, JP59164617, CN1338427 and CN104307556, etc. successively report the synthesis methods of a series of silicon-based molecular sieves and disclose that they can be applied to the synthesis of caprolactam.
However, the reaction temperature required by the gas-phase Beckmann rearrangement process is high, and the above-mentioned molecular sieve catalysts have the disadvantages of low activity, low selectivity and poor stability when catalyzing the gas-phase rearrangement of cyclohexanone oxime, so that the industrial requirements are difficult to meet. In order to solve the problem, researchers further propose that the composition and the number of acid sites can be adjusted by alkali modification, the hydrophilicity and hydrophobicity of the surface of the molecular sieve can be adjusted, and the morphological structure of the molecular sieve can be optimized, so that the performance of the molecular sieve for catalyzing cyclohexanone oxime gas-phase Beckmann rearrangement can be improved. For example, related patents CN1164576 and CN104307556 both modify MFI molecular sieve with aliphatic amine and quaternary ammonium base, resulting in cyclohexanone oxime conversion of greater than 99% and caprolactam selectivity of greater than 95%. However, such modified molecular sieves are difficult to mold, and even if they can be molded, the mechanical strength of the catalysts is low, and thus they are not satisfactory for industrial use.
Therefore, in the prior art, when the molecular sieve catalyzes the gas phase rearrangement reaction of cyclohexanone oxime, the catalytic performance is poor due to the difficulty in forming the molecular sieve, or even if the molecular sieve is formed under the condition of adding a large amount of forming auxiliary agent, the catalytic effect of the catalyst is poor due to the increase of impurities, the environmental pollution is caused, and the like.
Disclosure of Invention
The invention mainly aims to provide a composite molecular sieve and a preparation method and application thereof, and aims to solve the problems that the molecular sieve in the prior art is difficult to form or has poor catalytic performance or is not environment-friendly due to the addition of a large amount of forming auxiliary agents when catalyzing the gas-phase rearrangement reaction of cyclohexanone-oxime.
In order to achieve the above object, according to one aspect of the present invention, there is provided a composite molecular sieve comprising: a silicon-based molecular sieve core having a porous structure, wherein the surface of the silicon-based molecular sieve core is divided into an inner surface and an outer surface; the silicon-based molecular sieve nucleus is selected from one or more of MFI type molecular sieve, Y type molecular sieve, beta type molecular sieve, MOR type molecular sieve or MWW type molecular sieve; and the graphene oxide shell layer is coated on the outer surface of the silicon-based molecular sieve core body.
Further, in the composite molecular sieve, the weight ratio of the silicon-based molecular sieve core body to the graphene oxide shell layer is (40-200): 1; preferably, the MFI-type molecular sieve is selected from one or more of the group consisting of Silicate-1 molecular sieve, ZSM-5 molecular sieve and TS-1 molecular sieve.
Furthermore, the shape of the composite molecular sieve is columnar, and the length-diameter ratio of the composite molecular sieve is preferably 1 (0.5-1.5); the optimized composite molecular sieve has a porous structure, the porosity of the composite molecular sieve is 25-40%, the pore size of a mesoporous is 5-50 nm, and the specific surface area is 200-450 m 2 (ii)/g; preferably, the silicon-based molecular sieve core is spherical or spheroidal in shape and has an average radius of 50 to 500nm.
In order to achieve the above objects, according to one aspect of the present invention, there is provided a method for preparing a composite molecular sieve, the method comprising: providing a silicon-based molecular sieve core; and coating a graphene oxide shell layer on the outer surface of the silicon-based molecular sieve to obtain the composite molecular sieve.
Further, the preparation method of the composite molecular sieve comprises the following steps: step S1, mixing a silicon-based molecular sieve, graphene oxide, a composite auxiliary agent and a solvent, and then sequentially carrying out self-assembly and drying to obtain a composite molecular sieve precursor; and S2, sequentially molding and calcining the composite molecular sieve precursor to obtain the composite molecular sieve.
Further, the weight ratio of the silicon-based molecular sieve, the graphene oxide, the composite auxiliary agent and the solvent is 1 (0.01-0.2) to (0.2-8) to (2-20), and further preferably 1 (0.01-0.05) to (0.2-2) to (5-20); the silicon-based molecular sieve is preferably in the form of particles, and the average particle size of the silicon-based molecular sieve is 50 to 500nm, more preferably 100 to 300nm.
Further, the solvent is selected from one or more of water, methanol, ethanol, isopropanol, n-butanol, acetonitrile, formamide or acetone; preferably assembled in an autoclave, the treatment temperature is 120-180 ℃, and the treatment time is 6-72 h.
Further, the structural form of the graphene oxide is a layered structure, and the number of layers of the graphene oxide is more preferably 1 to 10; preferably, the composite auxiliary agent is an organic polybasic primary amine compound; more preferably, the structural formula of the composite auxiliary agent is
Wherein n is 1 to 6.
Further, the drying treatment temperature is 50-160 ℃, and the treatment time is 1-180 h; preferably, the drying treatment temperature is 80-120 ℃, and the treatment time is 6-48 h; preferably, the molding is carried out by any one of extrusion, tabletting or compression; preferably, the calcination is carried out under an inert atmosphere comprising one or more of nitrogen, helium, neon or argon; preferably, the calcining treatment temperature is 300-500 ℃, and the treatment time is 1-96 h; the treatment temperature is further preferably 360 to 420 ℃ and the treatment time is preferably 2 to 8 hours.
According to another aspect of the invention, a catalyst for preparing caprolactam from cyclohexanone oxime is provided, and the catalyst comprises the composite molecular sieve or the composite molecular sieve prepared by the preparation method of the composite molecular sieve.
The composite molecular sieve prepared by the invention is easy to form, has higher axial strength and radial strength, has higher selectivity and conversion rate when being applied to the reaction of catalyzing the gas phase rearrangement of cyclohexanone-oxime, shows excellent stability and longer service life, can avoid using other forming aids, and has the advantages of cost reduction and environmental friendliness.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
fig. 1 shows an SEM image (magnification 30000 times) of the composite molecular sieve obtained according to the preparation method of example 1 of the present invention.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
As described in the background of the invention section, the molecular sieves in the prior art have the problems of difficult molding or poor catalytic performance of the catalyst or environmental unfriendliness due to the addition of a large amount of molding aids when catalyzing the gas phase rearrangement reaction of cyclohexanone oxime. To solve this problem, the present invention provides a composite molecular sieve comprising: a silicon-based molecular sieve core body having a porous structure, and the surface of the silicon-based molecular sieve core body being divided into an interior surface and an exterior surface; the silicon-based molecular sieve core body is selected from one or more of MFI type molecular sieve, Y type molecular sieve, beta type molecular sieve, MOR type molecular sieve or MWW type molecular sieve; and the graphene oxide shell layer is coated on the outer surface of the silicon-based molecular sieve core body.
Therefore, when the molecular sieve is used as a catalyst for cyclohexanone oxime gas phase rearrangement reaction, the catalyst is easy to form, has excellent catalytic activity and stability, and can promote the reaction to have higher selectivity. Particularly, the graphene oxide shell layer is coated on the outer surface of the silicon-based molecular sieve with the rigid structure, so that the composite molecular sieve has a lubricating effect on one hand, and the flowability of the composite molecular sieve in the molding processing process is obviously enhanced. Therefore, the invention can complete the forming process of the composite molecular sieve on the premise of not using other forming aids, and avoids the problems of catalyst selectivity reduction, service life shortening, higher cost, environmental unfriendliness and the like caused by metal residues of conventional forming aids. On the other hand, the graphene oxide shell layer contains many oxygen-containing functional groups (for example, hydroxyl group, carbonyl group, carboxyl group, epoxy group, and the like). In the subsequent catalytic application process, the oxygen-containing functional group with larger polarity and organic poly-primary amine are subjected to reduction reaction to form the nitrogen-doped graphene. The nitrogen-doped sites in the nitrogen-doped graphene are weakly alkaline, and the surface binding force of the nitrogen-doped sites and a strongly acidic substance is stronger than that of a weakly acidic substance, so that the weakly acidic substance (product caprolactam) is easily exposed, the desorption capacity of the product on the surface of the catalyst is effectively improved, the stability and the operation life of the catalyst are further improved, and the conversion rate and the product selectivity of cyclohexanone oxime can be further improved. In addition, the composite molecular sieve also has the advantages of good mechanical property, long service life and easy realization of industrialization.
In a preferred embodiment, in the composite molecular sieve, the weight ratio of the silicon-based molecular sieve core body to the graphene oxide shell layer is (40-200): 1, so that the flowability of catalyst particles can be further improved, the catalyst reaction activity is improved, and the stability of the catalyst and the selectivity of a product are further improved. In order to further improve the mechanical strength of the composite molecular sieve and make the catalytic performance thereof more excellent, it is preferable that the MFI type molecular sieve is one or more selected from the group consisting of a Silicate-1 molecular sieve, a ZSM-5 molecular sieve or a TS-1 molecular sieve.
In a preferred embodiment, the composite molecular sieve is in a columnar shape, so that the pressure resistance of the catalyst can be further improved, the mechanical strength of the catalyst is enhanced, the stability and the service life of the catalyst are improved, the selectivity of a product is further improved, and the length-diameter ratio of the composite molecular sieve is further preferably (0.5-1.5).
In order to further improve the adsorption performance of the composite molecular sieve and improve the adsorption rate of the composite molecular sieve in the catalysis process, the composite molecular sieve is preferably provided with a porous structure, the porosity of the composite molecular sieve is 25-40%, the pore size of a mesoporous is 5-50 nm, and the specific surface area is 200-450 m 2 (iv) g. In order to further promote the coating uniformity of the graphene oxide shell layer on the silicon-based molecular sieve core body and ensure that the catalytic performance of the graphene oxide shell layer is better, the silicon-based molecular sieve core body is preferably spherical or quasi-spherical, and the average radius of the silicon-based molecular sieve core body is 50-500 nm.
In another aspect of the present invention, a method for preparing a composite molecular sieve is provided, the method comprising: providing a silicon-based molecular sieve core; and coating a graphene oxide shell layer on the outer surface of the silicon-based molecular sieve to obtain the composite molecular sieve. One skilled in the art can first take a silicon-based molecular sieve core body and then coat a graphene oxide shell layer on the outer surface of the silicon-based molecular sieve to obtain the composite molecular sieve. The composite molecular sieve prepared by the preparation method is used as a catalyst in the reaction of synthesizing caprolactam by cyclohexanone-oxime gas phase rearrangement catalysis, and has the advantages of strong activity, high selectivity, good stability, high mechanical strength, long service life, simple preparation method and easy industrialization.
In a preferred embodiment, the method for preparing the composite molecular sieve comprises the following steps: step S1, mixing a silicon-based molecular sieve, graphene oxide, a composite auxiliary agent and a solvent, and then sequentially carrying out self-assembly and drying to obtain a composite molecular sieve precursor; and S2, sequentially molding and calcining the composite molecular sieve precursor to obtain the composite molecular sieve.
A person skilled in the art can firstly mix the silicon-based molecular sieve, the graphene oxide, the composite auxiliary agent and the solvent, and then sequentially carry out self-assembly and drying to obtain a composite molecular sieve precursor; and then sequentially molding and calcining the composite molecular sieve precursor to finally obtain the composite molecular sieve. The preparation method has simple preparation process and convenient operation, thereby being easy to realize industrialized large-scale preparation and having wide industrialized application prospect. As mentioned above, when the composite molecular sieve prepared by the method is applied to the catalysis of the gas phase rearrangement reaction of cyclohexanone-oxime, the composite molecular sieve has the advantages of higher selectivity, excellent stability and long operation life, can avoid using other forming aids, and has the advantages of cost reduction and environmental friendliness.
In order to further promote self-assembly to obtain a more ordered and stable structure, and prepare for subsequent molding and calcining of the composite molecular sieve, the weight ratio of the silicon-based molecular sieve, the graphene oxide, the composite auxiliary agent and the solvent is preferably 1 (0.01-0.2): (0.2-8): 2-20), and more preferably 1 (0.01-0.05): 0.2-2): 5-20. In order to further improve the mechanical strength of the composite molecular sieve, better promote uniform coating of the graphene oxide shell layer, improve the fluidity of catalyst particles, improve the reaction activity of the catalyst, and further improve the stability of the catalyst and the selectivity of the product, it is preferable that the silicon-based molecular sieve is in the form of particles, and the average particle size of the silicon-based molecular sieve is 50 to 500nm, and more preferably 100 to 300nm.
In a preferred embodiment, in order to further promote the stability of the self-assembled structure, so that the self-assembly process is orderly carried out, and a more stable ordered structure is obtained, the solvent is preferably selected from one or more of water, methanol, ethanol, isopropanol, n-butanol, acetonitrile, formamide or acetone. The method is preferably carried out by assembling in an autoclave, the treatment temperature is 120-180 ℃, and the treatment time is 6-72 hours, so that the raw material can obtain the composite molecular sieve precursor with excellent performance under the preferable conditions, and the preparation is provided for the subsequent molding and calcination of the composite molecular sieve, so that the composite molecular sieve with more excellent performance can be obtained.
In a preferred embodiment, after self-assembly, a filtering and washing treatment is required, so that the self-assembled product is filtered out and the solvent and the composite auxiliary agent on the product are washed, thereby avoiding affecting the performance of the composite molecular sieve. Preferably, the filtration is one or more of gravity filtration, reduced pressure filtration, pressure filtration or centrifugal filtration, and the detergent used is one or more selected from water, methanol, ethanol or isopropanol.
In order to further enhance the fluidity of the catalyst particles and the desorption capability of the catalyst, thereby improving the stability and operating life of the catalyst, the structural form of the graphene oxide is preferably a layered structure, and the number of layers of the graphene oxide is more preferably 1 to 10. In order to promote the composite auxiliary agent to better play a role in structure guidance in the composite molecular sieve, the graphene oxide and the silicon-based molecular sieve are effectively compounded to obtain the composite molecular sieve, so that the composite molecular sieve has higher activity and stability when being used as a catalyst, the composite auxiliary agent is preferably an organic multi-primary amine compound, and the structural formula of the composite auxiliary agent is further preferably shown as
Wherein n is 1 to 6. The composite auxiliary with the structure can obtain a stable composite structure, and can be better removed in a subsequent calcining stage, so that the phenomenon that the pore passages of the composite molecular sieve are blocked to influence the catalytic performance of the composite molecular sieve is avoided.
In order to further dry and remove impurities such as solvent and composite auxiliary agent contained in the self-assembly product and reduce the influence on the catalytic performance of the composite molecular sieve as a catalyst, the drying treatment temperature is preferably 50-160 ℃, the treatment time is preferably 1-180 hours, more preferably 80-120 ℃, and the treatment time is preferably 6-48 hours. In order to further obtain the formed molecular sieve, the forming is preferably performed by any one of extrusion, tabletting or compression. Preferably, the calcination is carried out in an inert atmosphere, wherein the inert atmosphere comprises one or more of nitrogen, helium, neon or argon, so that the composite auxiliary can be removed better in the process, the pore channel blockage of the composite molecular sieve is avoided, the structure of the composite molecular sieve is more stable, the composite molecular sieve has better selectivity and higher conversion rate when being used as a catalyst to catalyze cyclohexanone oxime to prepare caprolactam, and simultaneously the stability and the service life of the catalyst are improved, the calcination treatment temperature is preferably 300-500 ℃, the treatment time is 1-96 hours, the calcination treatment temperature is further preferably 360-420 ℃, and the treatment time is 2-8 hours.
The invention also provides a catalyst for preparing caprolactam from cyclohexanone oxime, which comprises the composite molecular sieve or the composite molecular sieve prepared by the preparation method of the composite molecular sieve. As mentioned above, the composite molecular sieve has high selectivity when being applied to the catalysis of the gas phase rearrangement reaction of cyclohexanone-oxime, and the catalyst shows excellent stability and long service life, can avoid the use of other forming aids, and has the advantages of cost reduction and environmental friendliness.
The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.
Example 1
100g of Silicate-1 molecular sieve (average particle size 100 nm), 2g of technical graphene oxide monolayer (purchased from Cifeng technology, suzhou), 20g of ethylenediamine, 200g of water and 300g of ethanol were self-assembled in an autoclave at a treatment temperature of 120 ℃ for 72 hours. And then filtering by adopting a decompression filtering mode, washing by using ultrapure water, and drying the washed wet filter cake at the drying temperature of 160 ℃ for 1h to obtain the composite molecular sieve precursor. And (3) forming the composite molecular sieve precursor into a cylinder in a tabletting mode, and calcining at 400 ℃ in a nitrogen atmosphere for 4 hours to obtain the composite molecular sieve.
Fig. 1 shows an SEM image (magnification 30000 times) of the composite molecular sieve obtained according to the preparation method of example 1 of the present invention.
Example 2
100g of beta-type molecular sieve (average particle size 300 nm), 1g of multilayer graphene oxide (8-10 layers, available from Cifeng technology, suzhou), 200g of dodecadiamine, 300g of water and 700g of methanol were self-assembled in an autoclave at a treatment temperature of 180 ℃ for 6 hours. And then filtering by adopting a pressure filtration mode, washing by using ultrapure water, and drying the washed wet filter cake at the drying temperature of 160 ℃ for 1h to obtain the composite molecular sieve precursor. And (3) forming the composite molecular sieve precursor into a cylinder in a tabletting mode, and calcining at 500 ℃ in a nitrogen atmosphere for 1h to obtain the composite molecular sieve.
Example 3
100g of ZSM-5 type molecular sieve (average particle size 500 nm), 5g of few-layer graphene oxide (3-5 layers, purchased from Suzhou carbon technology), 80g of hexamethylenediamine, 500g of water and 1500g of acetonitrile are taken for self-assembly in an autoclave, the treatment temperature is 150 ℃, and the reaction time is 24h. And then filtering by adopting a gravity filtration mode, washing by using ultrapure water, and drying the washed wet filter cake at the drying temperature of 100 ℃ for 72 hours to obtain the composite molecular sieve precursor. And (3) forming the composite molecular sieve precursor into a cylinder by adopting a tabletting mode, and calcining at 300 ℃ in a helium atmosphere for 96 hours to obtain the composite molecular sieve.
Example 4
The only difference from example 1 is that the solvent was 200g of water and 300g of acetonitrile.
Example 5
The only difference from example 1 is that the solvent was 300g of water and 200g of isopropanol.
Example 6
The only difference from example 1 is that the solvents were 250g of acetonitrile and 250g of ethanol.
Example 7
The only difference from example 1 is that the solvent was 400g of water and 100g of n-butanol.
Example 8
The only difference from example 1 is that the solvent was 400g of water and 800g of formamide.
Example 9
The only difference from example 1 is that the solvent was 400g of water and 800g of acetone.
Example 10
The only difference from example 1 is that the solvent was 400g of acetonitrile and 800g of acetone.
Example 11
The only difference from example 1 is that the solvent was 400g of ethanol and 800g of acetone.
Example 12
The only difference from example 1 is that the solvent was 400g of water and 800g of methanol.
Example 13
The only difference from example 1 is that the solvent was 400g of methanol and 800g of acetonitrile.
Comparative example 1
Only the difference from example 1 is the absence of graphene oxide.
Comparative example 2
The only difference from example 1 is the absence of organic poly-primary amines.
And (3) performance testing:
(1) And (3) testing the tensile property:
taking the composite molecular sieve prepared in the above examples and comparative examples, the size specification of the composite molecular sieve
And (3) performing a tension test on a GH-5613 type servo stripping tension instrument at a tension speed of 8.5mm/min to obtain the axial strength and the radial strength of the composite molecular sieve.
(2) And (3) testing the catalytic performance:
taking the composite molecular sieve prepared in the above examples and comparative examples as a catalyst, adding the catalyst into an ethanol solution with 20% cyclohexanone oxime, taking nitrogen as a carrier gas and the space velocity of 0.2h -1 The cyclohexanone oxime/ethanol solution is mixed with ammonia and then passes through a bed layer at 320 ℃ to generate heavy reactionDischarging the reaction and synthesizing caprolactam. And calculating the cyclohexanone oxime conversion rate, the caprolactam selectivity and the stable operation time of the catalyst.
Table 1 shows the characteristic data of the composite molecular sieves prepared in the examples and comparative examples.
Table 2 shows the performance results of the composite molecular sieves prepared in the examples and comparative examples.
TABLE 1
TABLE 2
From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:
from the test results of examples 1, 2 and 3 and comparative example 1, it can be found that when the composite molecular sieve of the present invention is used for catalyzing the gas phase rearrangement reaction of cyclohexanone oxime, the selectivity and the conversion rate are high, the catalyst shows excellent stability and long operation life, and simultaneously, other forming aids can be avoided, so that the composite molecular sieve has the advantages of cost reduction and environmental friendliness.
From the test results of examples 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, it can be found that when the preparation method of the present invention is employed, in which the solvent is selected from one or more of water, methanol, ethanol, isopropanol, n-butanol, acetonitrile, formamide or acetone, the prepared composite molecular sieve exhibits excellent stability and long operating life, and also the product selectivity and the conversion rate of the reactant are high.
From the test results of examples 1, 2 and 3, it can be found that when the preparation method of the present invention is adopted and self-assembly is carried out in an autoclave, the treatment temperature is 120-180 ℃, and the treatment time is 6-72 h (120 ℃,72h for example 1, 180 ℃,6h for example 2 and 150 ℃,24h for example 3), the prepared composite molecular sieve has high conversion rate and selectivity when being used as a catalyst for catalyzing the gas phase rearrangement reaction of cyclohexanone oxime, and the catalyst has excellent stability and long service life.
From the test results of examples 1, 2 and 3 and comparative example 2, it can be seen that when the molecular sieve of the present invention is used and the composite assistant is an organic poly-primary amine compound (ethylenediamine in example 1, dodecadiamine in example 2, and hexanediamine in example 3) during the preparation process, the prepared composite molecular sieve has high selectivity, long service life and high axial and radial strength when applied to the catalysis of the gas phase rearrangement reaction of cyclohexanone oxime, and particularly when the structural formula of the composite assistant is represented as
Wherein, when n is 1-6 (the ethylenediamine in the embodiment 1 and the hexamethylenediamine in the embodiment 3), the composite molecular sieve is easier to form, and the catalytic performance is better.
In conclusion, the composite molecular sieve prepared by the method is easy to form, has higher axial strength and radial strength, has higher selectivity and conversion rate when being applied to the reaction of catalyzing the gas phase rearrangement of cyclohexanone-oxime, shows excellent stability and longer service life, can avoid using other forming aids, and has the advantages of cost reduction and environmental friendliness.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A composite molecular sieve, wherein the composite molecular sieve comprises:
a silicon-based molecular sieve core body having a porous structure, and a surface of the silicon-based molecular sieve core body being divided into an interior surface and an exterior surface of a pore; the silicon-based molecular sieve nucleus is selected from one or more of MFI type molecular sieve, Y type molecular sieve, beta type molecular sieve, MOR type molecular sieve or MWW type molecular sieve;
and the graphene oxide shell layer is coated on the outer surface of the silicon-based molecular sieve core body.
2. The composite molecular sieve of claim 1, wherein the weight ratio of the silicon-based molecular sieve core to the graphene oxide shell in the composite molecular sieve is (40-200): 1;
preferably, the MFI-type molecular sieve is selected from one or more of a Silicate-1 molecular sieve, a ZSM-5 molecular sieve or a TS-1 molecular sieve.
3. The composite molecular sieve of claim 1 or 2, wherein the composite molecular sieve is columnar, and preferably has an aspect ratio of 1 (0.5-1.5);
preferably, the composite molecular sieve has a porous structure, the porosity of the composite molecular sieve is 25-40%, the pore size of a mesoporous is 5-50 nm, and the specific surface area is 200-450 m 2 /g；
Preferably, the silicon-based molecular sieve nuclei are spherical or spheroidal in shape and have an average radius of from 50 to 500nm.
4. A method of making the composite molecular sieve of any one of claims 1 to 3, comprising:
providing a silicon-based molecular sieve core;
and coating a graphene oxide shell layer on the outer surface of the silicon-based molecular sieve to obtain the composite molecular sieve.
5. The method of preparing the composite molecular sieve of claim 4, wherein the method comprises the steps of:
step S1, mixing a silicon-based molecular sieve, graphene oxide, a composite auxiliary agent and a solvent, and then sequentially carrying out self-assembly and drying to obtain a composite molecular sieve precursor;
and S2, sequentially molding and calcining the composite molecular sieve precursor to obtain the composite molecular sieve.
6. The method for preparing the composite molecular sieve of claim 5, wherein the weight ratio of the silicon-based molecular sieve, the graphene oxide, the composite auxiliary agent and the solvent is 1 (0.01-0.2): 2-20, and more preferably 1 (0.01-0.05): 0.2-2): 5-20;
preferably, the silicon-based molecular sieve is in a granular form, and the average particle size of the silicon-based molecular sieve is 50 to 500nm, and more preferably 100 to 300nm.
7. The method of claim 5 or 6, wherein the solvent is selected from one or more of water, methanol, ethanol, isopropanol, n-butanol, acetonitrile, formamide or acetone;
preferably, the self-assembly is carried out in an autoclave, the treatment temperature is 120-180 ℃ and the treatment time is 6-72 h.
8. The method for preparing the composite molecular sieve according to any one of claims 5 to 7, wherein the structural morphology of the graphene oxide is a layered structure, and more preferably the number of layers of the graphene oxide is 1 to 10;
preferably, the composite auxiliary agent is an organic poly primary amine compound;
more preferably, the structural formula of the composite auxiliary agent is
Wherein n is 1 to 6.
9. The method for preparing the composite molecular sieve according to any one of claims 5 to 8, wherein the drying treatment temperature is 50 to 160 ℃ and the treatment time is 1 to 180 hours; preferably, the drying treatment temperature is 80-120 ℃, and the treatment time is 6-48 h;
preferably, the shaping is performed by any one of extrusion, tabletting or compression;
preferably, the calcination is carried out under an inert atmosphere comprising one or more of nitrogen, helium, neon or argon;
preferably, the calcining treatment temperature is 300-500 ℃, and the treatment time is 1-96 h; the treatment temperature is further preferably 360 to 420 ℃ and the treatment time is preferably 2 to 8 hours.
10. A catalyst for preparing caprolactam from cyclohexanone oxime, wherein the catalyst comprises the composite molecular sieve of any one of claims 1 to 3 or the composite molecular sieve prepared by the method for preparing the composite molecular sieve of any one of claims 4 to 9.
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