A composite silicon molecular sieve catalyst, preparation method and application thereof

Abstract

The present invention provides a composite silicon molecular sieve catalyst, a preparation method and application thereof. The preparation method comprises the following steps: S1, mixing an organosilicon compound, a quaternary ammonium template and water, and then sequentially performing a hydrolysis reaction, a distillation and a crystallization reaction to obtain a solid-liquid mixture; S2, adjusting the solid-liquid mixture to neutral or alkaline, and then filtering to obtain a filter cake and a filtrate; S3, performing a first roasting of the filter cake to obtain a roasted solid material; S4, mixing the roasted solid material with graphene oxide, an organic amine and a solvent, performing a composite modification treatment, and then performing solid-liquid separation to obtain a modified solid material and a liquid phase; S5, performing a second roasting of the modified solid material to obtain a composite silicon molecular sieve catalyst. The composite silicon molecular sieve catalyst prepared by the present invention can take into account high selectivity, long service life, low energy consumption and easy industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon molecular sieves, and in particular to a composite silicon molecular sieve catalyst, a preparation method and application thereof. Background Art

[0002] Caprolactam is an important intermediate in the industrial production of nylon, and the Beckmann rearrangement of cyclohexanone oxime is one of the key steps in the production process of caprolactam. At present, the traditional liquid phase rearrangement process using concentrated sulfuric acid as a catalyst is mainly used in industry. Although the reaction conditions of this process are relatively mild, the conversion rate and selectivity are also relatively ideal, a large amount of ammonium sulfate is produced as a by-product, and it is easy to cause equipment corrosion and environmental pollution. In order to overcome the above shortcomings, the gas phase Beckmann rearrangement process of cyclohexanone oxime catalyzed by solid acids such as molecular sieves has attracted attention in recent years. However, the reaction temperature required for the gas phase Beckmann rearrangement process is high, the stability of the catalyst is poor, the deactivation is fast, and the selectivity of the catalyst is also relatively low.

[0003] USP4061724, JP59164617 and CN1338427 etc. all report the synthesis method of MFI type silicon molecular sieve, which can be used for the synthesis of caprolactam.But all the above molecular sieve catalysts have the disadvantages of low catalyst activity, low selectivity and poor stability during the gas phase rearrangement of cyclohexanone oxime, which is difficult to industrial application.In order to solve the above problems, the composition and quantity of acid sites can be adjusted by alkali modification, and the morphology structure of MFI type silicon molecular sieve can be optimized to improve the performance of its catalytic cyclohexanone oxime gas phase Beckmann rearrangement.Although CN1164576 and CN104307556 all use aliphatic amine and quaternary ammonium base to modify MFI molecular sieve, so that cyclohexanone oxime conversion is greater than 99%, and caprolactam selectivity is greater than 95%, but it is difficult to shape, and still can not meet the needs of industrialization. In the above-mentioned molecular sieve-catalyzed cyclohexanone oxime gas-phase rearrangement process, since the product has a high boiling point and high polarity, it is difficult to desorb on the molecular sieve surface, so it is necessary to maintain a high temperature in the reaction system to promote product desorption, which not only increases energy consumption, but also easily produces more by-products, reduces product selectivity, and shortens catalyst life.

[0004] Therefore, it is necessary to invent a silicon molecular sieve catalyst for caprolactam which has high selectivity, long operating life, low energy consumption and is easy to realize industrial production. Summary of the invention

[0005] The main purpose of the present invention is to provide a composite silicon molecular sieve catalyst, its preparation method and application, so as to solve the problem that silicon molecular sieve catalysts in the prior art are difficult to achieve high selectivity, long operating life, low energy consumption and easy industrial production.

[0006] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a method for preparing a composite silicon molecular sieve catalyst is provided, and the preparation method comprises the following steps: S1, mixing an organosilicon compound, a quaternary ammonium template and water, and then sequentially performing a hydrolysis reaction, a distillation reaction and a crystallization reaction to obtain a solid-liquid mixture; S2, adjusting the solid-liquid mixture to neutral or alkaline, and then filtering to obtain a filter cake and a filtrate; S3, performing a first calcination on the filter cake to obtain a calcined solid material; S4, mixing the calcined solid material with graphene oxide, an organic amine and a solvent, performing a composite modification treatment, and then performing solid-liquid separation to obtain a modified solid material and a liquid phase; S5, performing a second calcination on the modified solid material to obtain a composite silicon molecular sieve catalyst.

[0007] Furthermore, the molar ratio of the organosilicon compound, the quaternary ammonium template and water is 1:(0.05-2.0):(10-50); preferably, in step S1, an aluminum source and / or a titanium source are simultaneously mixed in the mixing step, and then a hydrolysis reaction is carried out; more preferably, the molar ratio of the organosilicon compound and the aluminum source is 1:(0.001-0.005); more preferably, the molar ratio of the organosilicon compound and the titanium source is 1:(0.001-0.01).

[0008] Further, the aluminum source is sodium aluminate and / or potassium aluminate; preferably, the titanium source is one or more of tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate or tetrabutyl titanate; preferably, the organosilicon compound is one or more of ethyl orthosilicate, propyl orthosilicate and butyl orthosilicate; preferably, the quaternary ammonium template is one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium bromide, tetraethylammonium chloride and tetrapropylammonium chloride.

[0009] Furthermore, the hydrolysis reaction temperature is 20-40°C and the time is 2-4h.

[0010] Furthermore, the crystallization reaction temperature is 150-200° C., and the time is 48-96 hours.

[0011] Further, in step S2, an organic acid is used to adjust the pH; preferably, the organic acid is one or more of formic acid, acetic acid, propionic acid, oxalic acid, 1,3-propanedioic acid, benzoic acid, terephthalic acid, phthalic acid, isophthalic acid and trimesic acid; more preferably, the organic acid is one or more of formic acid, acetic acid and oxalic acid; most preferably, the molar ratio of the organic acid to the quaternary ammonium template is (0.2-2):1.

[0012] Furthermore, the first calcination temperature is 400-600° C., and the time is 1-72 hours.

[0013] Furthermore, the weight ratio of the solid material after calcination to graphene oxide is 1:(0.01-0.2); preferably, the weight ratio of the solid material after calcination to the organic amine is 1:(0.2-8), more preferably 1:(1-4); more preferably, the weight ratio of the solid material after calcination to the solvent is 1:(2-20).

[0014] Furthermore, the number of layers of graphene oxide is 1 to 10; preferably, the organic amine comprises Wherein n=1-6; preferably, the solvent is one or more of water, methanol, ethanol, isopropanol, n-butanol, acetonitrile, formamide, and acetone.

[0015] Furthermore, the temperature of the composite modification treatment is 140-180° C., and the time is 6-24 hours.

[0016] Furthermore, the composite modification process includes a first stage and a second stage performed sequentially; wherein,

[0017] In the first stage, the temperature is raised to 80-100°C at a heating rate of 0.5-2°C / min, and then kept warm for 4-12 hours; in the second stage, the temperature is raised to 140-180°C at a heating rate of 0.5-2°C / min to carry out composite modification treatment.

[0018] Furthermore, the second calcination is carried out under an inert atmosphere, the temperature of the second calcination is 300-500° C., and the time is 1-96 hours; preferably, the inert atmosphere is one or more of nitrogen, helium, neon, and argon.

[0019] In order to achieve the above object, according to one aspect of the present invention, a composite silicon molecular sieve catalyst prepared by the above preparation method is provided.

[0020] According to another aspect of the present invention, there is provided a use of a composite silicon molecular sieve catalyst in catalyzing the preparation of caprolactam from cyclohexanone oxime.

[0021] By applying the technical solution of the present invention, a composite silicon molecular sieve catalyst is obtained by using alkaline organic amine and graphene oxide to modify silicon molecular sieve. Organic amine modification removes the terminal silanol sites with strong polarity, reduces the surface polarity of the silicon molecular sieve, and is conducive to the desorption of caprolactam, the Beckmann rearrangement product of cyclohexanone oxime, reduces the optimal reaction temperature of the silicon molecular sieve catalytic process, and inhibits the by-products formed at high temperatures. The molecular sieve prepared by the preparation method of the present application can be used as an efficient catalyst for the synthesis of caprolactam by gas-phase rearrangement of cyclohexanone oxime, and the catalyst has the advantages of good catalytic activity, high selectivity, low optimal operating temperature, and long service life. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0023] In order to solve the problems in the prior art as described above, according to one aspect of the present invention, a method for preparing a composite silicon molecular sieve catalyst is provided, the preparation method comprising the following steps:

[0024] S1, mixing an organosilicon compound, a quaternary ammonium template and water, and then sequentially performing hydrolysis reaction, distillation and crystallization reaction to obtain a solid-liquid mixture;

[0025] S2, adjusting the solid-liquid mixture to neutral or alkaline, and then filtering to obtain a filter cake and a filtrate;

[0026] S3, performing a first calcination on the filter cake to obtain a calcined solid material;

[0027] S4, mixing the calcined solid material with graphene oxide, organic amine and solvent, performing composite modification treatment, and then performing solid-liquid separation to obtain a modified solid material and a liquid phase;

[0028] S5, performing a second calcination on the modified solid material to obtain a composite silicon molecular sieve catalyst.

[0029] By applying the technical solution of the present invention, a composite silicon molecular sieve catalyst is obtained by using reduced graphene oxide to composite modified silicon molecular sieve. Since the composite of reduced graphene oxide and modified silicon molecular sieve covers the terminal silanol sites with strong polarity, the surface polarity of the silicon molecular sieve is reduced, which is beneficial to the desorption of caprolactam, the Beckmann rearrangement product of cyclohexanone oxime, reduces the optimal reaction temperature of the silicon molecular sieve catalytic process, and inhibits the by-products formed at high temperature. The molecular sieve prepared by the preparation method of the present application can be used as an efficient catalyst for the synthesis of caprolactam by gas-phase rearrangement of cyclohexanone oxime, and the catalyst has the advantages of good catalytic activity, high selectivity, low optimal operating temperature, and long service life.

[0030] In the preparation method of the present invention, a precursor sol of a crystallized synthetic molecular sieve is obtained by hydrolysis reaction; the molecular sieve is then crystallized to obtain the molecular sieve; the pH value is adjusted to allow the molecular sieve to be separated into solid and liquid; and an organic base is added to wash away amorphous silicon on the one hand and reduce graphene oxide on the other hand and link graphene sheets.

[0031] In order to better modify the silicon molecular sieve, in a preferred embodiment, the molar ratio of the organosilicon compound, the quaternary ammonium template and water is 1:(0.5-5.0):(10-150); preferably, in step S1, an aluminum source and / or a titanium source are simultaneously mixed in the mixing step, and then a hydrolysis reaction is carried out; more preferably, the molar ratio of the organosilicon compound and the aluminum source is 1:(0.001-0.005); more preferably, the molar ratio of the organosilicon compound and the titanium source is 1:(0.001-0.01).

[0032] When no aluminum source or titanium source is mixed, the all-silicon molecular sieve Silicalite-1 is synthesized and prepared; when an aluminum source is added, the silicon-aluminum molecular sieve ZSM-5 is synthesized and prepared; when a titanium source is added, the titanium silicon molecular sieve TS-1 is synthesized and prepared.

[0033] In a preferred embodiment, the aluminum source is sodium metaaluminate and / or potassium metaaluminate; preferably, the titanium source is one or more of tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate or tetrabutyl titanate; preferably, the organosilicon compound is one or more of ethyl orthosilicate, propyl orthosilicate and butyl orthosilicate; preferably, the quaternary ammonium template is one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium bromide, tetraethylammonium chloride and tetrapropylammonium chloride. The above raw materials are preferred, which is more conducive to obtaining a composite silicon molecular sieve catalyst with excellent comprehensive performance.

[0034] In order to make the hydrolysis reaction occur more fully, in a preferred embodiment, the hydrolysis reaction temperature is 20-40° C. and the time is 2-4 hours.

[0035] In actual operation, the preferred distillation temperature is 70-100° C., and the preferred distillation time is 1-6 hours. Selecting the above preferred conditions in this step can better remove alcohol and provide a basis for the subsequent crystallization reaction.

[0036] In order to make the crystallization reaction occur more fully, in a preferred embodiment, the temperature of the crystallization reaction is 150-200° C. and the time is 48-96 hours.

[0037] In order to make the pH adjustment process more controllable, in a preferred embodiment, in step S2, an organic acid is used to adjust the pH; preferably, the organic acid is one or more of formic acid, acetic acid, propionic acid, oxalic acid, 1,3-propanedioic acid, benzoic acid, terephthalic acid, phthalic acid, isophthalic acid and trimesic acid; more preferably, the organic acid is one or more of formic acid, acetic acid and oxalic acid.

[0038] In actual operation, preferably, the pH is adjusted to 7.0-10.0 in this step.

[0039] In the present invention, the technician should adjust the amount of acid according to the pH value. In the process of adjusting the pH value, the amine substance after the decomposition of the quaternary ammonium template reacts with the acid to generate a salt, and then the salt is separated from the system.

[0040] In actual operation, the filter cake obtained after pH adjustment still has a certain humidity, and is preferably washed and dried, which steps should be well known to those skilled in the art. In order to further improve the drying effect, in a preferred embodiment, the drying temperature is 40 to 120° C., and the drying time is preferably 4 to 120 hours.

[0041] In order to make the calcination more complete, in a preferred embodiment, the temperature of the first calcination is 400-600° C. and the time is 1-72 hours.

[0042] In order to make the composite modification of graphene oxide more complete, in a preferred embodiment, the weight ratio of the solid material and graphene oxide after calcination is 1:(0.01-0.2); preferably, the weight ratio of the solid material and organic amine after calcination is 1:(0.2-8), more preferably 1:(1-4); more preferably, the weight ratio of the solid material and solvent after calcination is 1:(2-20).

[0043] In order to further improve the effect of composite modification, in a preferred embodiment, the number of graphene oxide layers is 1 to 10 layers; preferably, the organic amine includes Wherein n=1-6; preferably, the solvent is one or more of water, methanol, ethanol, isopropanol, n-butanol, acetonitrile, formamide, and acetone.

[0044] In order to further improve the effect of the composite modification, in a preferred embodiment, the temperature of the composite modification treatment is 140-180° C., and the time is 6-24 hours.

[0045] In order to further improve the effect of the composite modification, in a preferred embodiment, the composite modification treatment includes a first stage and a second stage carried out in sequence; wherein, in the first stage, the temperature is increased to 80-100°C at a heating rate of 0.5-2°C / min, and then kept warm for 4-12h; in the second stage, the temperature is increased to 140-180°C at a heating rate of 0.5-2°C / min to carry out the composite modification treatment.

[0046] In the first stage of heating and heat preservation, amorphous silicon oxide on the surface of the molecular sieve is removed, and the organic amine initially reacts and combines with the carboxyl, carbonyl and hydroxyl groups of graphene oxide to form a composite unit, which promotes the effective composite of the molecular sieve and graphene; and the second stage of heating makes the modification process of the acidic sites on the surface of the molecular sieve by the organic amine and the graphene assembly unit combined with the organic amine be composited on the surface of the molecular sieve. This process is a synergistic process with a good composite effect, thereby reducing the acidity and hydrophilicity of the molecular sieve, facilitating the desorption of the substrate, reducing the production of N-alkyl caprolactam during the reaction, improving selectivity, and reducing the difficulty of separation.

[0047] Preferably, the modified solid material obtained after solid-liquid separation is washed and dried, and the drying temperature is preferably 50 to 160° C., and the drying time is 1 to 180 hours.

[0048] In order to make the calcination more complete, in a preferred embodiment, the second calcination is carried out under an inert atmosphere, the temperature of the second calcination is 300-500° C., and the time is 1-96 hours; preferably, the inert atmosphere is one or more of nitrogen, helium, neon, and argon.

[0049] According to another aspect of the present invention, a composite silicon molecular sieve catalyst prepared by the above method is provided. The molecular sieve prepared by the preparation method of the present application can be used as a high-efficiency catalyst for the gas-phase rearrangement of cyclohexanone oxime to synthesize caprolactam, and the catalyst has the advantages of good catalytic activity, high selectivity, low optimal operating temperature and long life.

[0050] According to another aspect of the present invention, there is provided a use of the composite silicon molecular sieve catalyst in catalyzing the preparation of caprolactam from cyclohexanone oxime. The catalyst has the advantages of good catalytic activity, high selectivity, low optimal operating temperature and long service life.

[0051] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0052] Example 1

[0053] 416 g of tetraethyl orthosilicate, 200 g of 40% tetrapropylammonium hydroxide aqueous solution and 160 g of ultrapure water were mixed and hydrolyzed at room temperature for 3 h, then heated to 80 ° C and kept at a constant temperature for 3 hours to remove alcohol, and the alcohol removal rate reached more than 70%, and then the colloid was transferred to an autoclave and heated to 150 ° C for crystallization for 96 h; 48.1 g of acetic acid was added dropwise to the mixture under mechanical stirring conditions, the pH was adjusted to 7.04, and filtered, the wet filter cake was washed with ultrapure water, and then dried at 40 ° C for 120 h; then calcined at 400 ° C for 72 h to obtain 118.5 g of solid; the obtained solid and 11.8 g of multilayer graphene oxide were added. (3-10 layers), 952g hexamethylenediamine, 117.1g water and 117.6g acetonitrile were reacted in an autoclave, first heated to 100°C at 0.5°C / min and maintained for 4h, then continued to heat at 0.5°C / min, controlled the reaction temperature at 180°C, and the reaction time was 6h; after the modification reaction, filtered and washed with ultrapure water; the washed wet filter cake was dried at 100°C for 72h; then calcined at 500°C in a nitrogen atmosphere for 1h to obtain a composite silicon molecular sieve.

[0054] Prepared with 20% cyclohexanone oxime ethanol solution, nitrogen was used as carrier gas, and the space velocity was 0.2h -1 The cyclohexanone oxime / ethanol solution was mixed with ammonia and passed through a 300°C bed to undergo a rearrangement reaction to generate caprolactam. The cyclohexanone oxime conversion rate was 99.8%, the caprolactam selectivity was 98.7%, and the stable operation lasted for 2550 hours.

[0055] Example 2

[0056] 416g of tetraethyl orthosilicate, 0.82g of potassium aluminate, 200g of 40% tetrapropylammonium hydroxide aqueous solution and 160g of ultrapure water were mixed and hydrolyzed at 20°C for 4h, then heated to 100°C and kept constant for 1 hour to remove alcohol, and the alcohol removal rate reached more than 70%, then the colloid was transferred to an autoclave and heated to 200°C for crystallization for 48h; 15.7g of acetic acid was added dropwise to the mixture under mechanical stirring conditions, the pH was adjusted to 10.00, and filtered, the wet filter cake was washed with ultrapure water, and then dried at 120°C for 24h; then roasted at 500°C for 8h to obtain 114.8g of solid; The obtained solid, 1.2g of single-layer graphene oxide, 23.4g of ethylenediamine, 572.6g of water and 572.9g of ethanol were reacted in an autoclave, firstly heated to 80°C at 2°C / min and maintained for 12h, then continued to heat at 2°C / min, controlled the reaction temperature at 140°C, and the reaction time was 24h; after the modification reaction, filtered and washed with ultrapure water; the washed wet filter cake was dried at 160°C for 1h; and then calcined at 300°C in a mixed gas atmosphere of helium and neon for 96h to obtain a composite silicon molecular sieve.

[0057] Prepared with 20% cyclohexanone oxime ethanol solution, nitrogen was used as carrier gas, and the space velocity was 0.2h -1 The cyclohexanone oxime / ethanol solution was mixed with ammonia and passed through a 300°C bed to undergo a rearrangement reaction to generate caprolactam. The cyclohexanone oxime conversion rate was 99.8%, the caprolactam selectivity was 98.9%, and the stable operation lasted for 2750 hours.

[0058] Example 3

[0059] 416 g of tetraethyl orthosilicate, 5.68 g of tetrapropyl titanate, 200 g of 40% tetrapropyl ammonium hydroxide aqueous solution and 160 g of ultrapure water were mixed and hydrolyzed at room temperature for 3 h, then heated to 70 ° C and kept constant for 6 hours to remove alcohol, and the alcohol removal rate reached more than 70%, and then the colloid was transferred to an autoclave and heated to 170 ° C for crystallization for 72 h; 38.8 g of acetic acid was added dropwise to the mixture under mechanical stirring conditions, the pH was adjusted to 8.17, and filtered, the wet filter cake was washed with ultrapure water, and then dried at 120 ° C for 24 h; roasted at 600 ° C for 1 h to obtain 119.3 g of solid; the obtained solid , 23.9g of multilayer graphene oxide (3 to 10 layers), 24.6g of dodecanediamine, 119.2g of water and 119.7g of methanol are reacted in an autoclave, firstly heated to 100°C at 1°C / min and maintained for 6h, then continued to heat at 2°C / min, the reaction temperature is controlled at 150°C, and the reaction time is 18h; after the modification reaction, filtering and washing with ultrapure water are carried out; the washed wet filter cake is dried at 50°C for 180h; and then calcined at 400°C in an argon atmosphere for 48h to obtain a composite silicon molecular sieve.

[0060] Prepared with 20% cyclohexanone oxime ethanol solution, nitrogen was used as carrier gas, and the space velocity was 0.2h -1 The cyclohexanone oxime / ethanol solution was mixed with ammonia and passed through a 300°C bed to undergo a rearrangement reaction to generate caprolactam. The cyclohexanone oxime conversion rate was 99.8%, the caprolactam selectivity was 97.9%, and the system ran stably for 2450 hours.

[0061] Embodiments 4 to 13

[0062] The types of acid and solvent were changed on the basis of Example 1, and the performance evaluation of the catalyst is shown in Table 1:

[0063] Embodiment 14

[0064] The difference from Example 1 is that the amount of multilayer graphene oxide used is 1.185 g. The performance evaluation of the catalyst is shown in Table 1.

[0065] Embodiment 15

[0066] The difference from Example 1 is that the amount of multilayer graphene oxide used is 23.7 g. The performance evaluation of the catalyst is shown in Table 1.

[0067] In the above-mentioned embodiments, the conversion rate of cyclohexanone oxime and the selectivity of caprolactam are calculated based on the average values ​​of the catalyst running for 50 to 100 hours.

[0068] Comparative Example 1

[0069] The only difference from Example 1 is that there is no graphene oxide.

[0070] Comparative Example 2

[0071] The only difference from Example 1 is that there is no organic amine.

[0072] Comparative Example 3

[0073] The only difference from Example 1 is that during the composite modification, the temperature is directly increased to 180° C. at 0.5° C. / min without a gradient heating process.

[0074] Table 1

[0075]

[0076]

[0077] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0078] The composite silicon molecular sieve catalyst prepared according to the present invention has good catalytic activity, high selectivity, low optimal operating temperature and long service life.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a composite silicon molecular sieve catalyst, characterized in that: The preparation method comprises the following steps: S1, mixing an organosilicon compound, a quaternary ammonium template and water, and then sequentially performing hydrolysis reaction, distillation and crystallization reaction to obtain a solid-liquid mixture; S2, adjusting the solid-liquid mixture to neutral or alkaline, and then filtering to obtain a filter cake and a filtrate; S3, performing a first calcination on the filter cake to obtain a calcined solid material; S4, mixing the calcined solid material with graphene oxide, organic amine and solvent, performing composite modification treatment, and then performing solid-liquid separation to obtain a modified solid material and a liquid phase; the weight ratio of the calcined solid material to the graphene oxide is 1:(0.01-0.2); the composite modification treatment includes a first stage and a second stage performed in sequence; wherein, the first stage increases the temperature to 80-100°C at a heating rate of 0.5-2°C / min, and then keeps the temperature for 4-12h; the second stage increases the temperature to 140-180°C at a heating rate of 0.5-2°C / min to perform the composite modification treatment; S5, performing a second calcination on the modified solid material to obtain the composite silicon molecular sieve catalyst; the second calcination is performed under an inert atmosphere.

2. The preparation method according to claim 1, characterized in that: The molar ratio of the organosilicon compound, the quaternary ammonium template and the water is 1:(0.05-2.0):(10-50).

3. The preparation method according to claim 2, characterized in that: In the step S1, an aluminum source and / or a titanium source are simultaneously mixed in the mixing step, and then the hydrolysis reaction is performed.

4. The preparation method according to claim 3, characterized in that: The molar ratio of the organosilicon compound to the aluminum source is 1:(0.001-0.005); the molar ratio of the organosilicon compound to the titanium source is 1:(0.001-0.01).

5. The preparation method according to claim 3, characterized in that: The aluminum source is sodium aluminate and / or potassium aluminate; the titanium source is one or more of tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate or tetrabutyl titanate.

6. The preparation method according to claim 2, characterized in that: The organosilicon compound is one or more of ethyl orthosilicate, propyl orthosilicate and butyl orthosilicate; the quaternary ammonium template is one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium bromide, tetraethylammonium chloride and tetrapropylammonium chloride.

7. The preparation method according to any one of claims 1 to 6, characterized in that The temperature of the hydrolysis reaction is 20-40° C. and the time is 2-4 hours.

8. The preparation method according to any one of claims 1 to 6, characterized in that The crystallization reaction temperature is 150-200° C. and the time is 48-96 hours.

9. The preparation method according to any one of claims 1 to 6, characterized in that: In the step S2, an organic acid is used to adjust the pH.

10. The preparation method according to claim 9, characterized in that: The organic acid is one or more of formic acid, acetic acid, propionic acid, oxalic acid, 1,3-propanedioic acid, benzoic acid, terephthalic acid, phthalic acid, isophthalic acid and trimesic acid.

11. The preparation method according to claim 9, characterized in that: The organic acid is one or more of formic acid, acetic acid and oxalic acid.

12. The preparation method according to claim 9, characterized in that: The molar ratio of the organic acid to the quaternary ammonium template is (0.2-2):

1.

13. The preparation method according to any one of claims 1 to 6, characterized in that: The first calcination is carried out at a temperature of 400-600° C. and for a time of 1-72 hours.

14. The preparation method according to any one of claims 1 to 6, characterized in that: The weight ratio of the calcined solid material to the organic amine is 1:(0.2-8).

15. The preparation method according to claim 14, characterized in that: The weight ratio of the calcined solid material to the organic amine is 1:(1-4).

16. The preparation method according to claim 14, characterized in that: The weight ratio of the calcined solid to the solvent is 1:(2-20).

17. The preparation method according to any one of claims 1 to 6, characterized in that: The number of layers of the graphene oxide is 1 to 10.

18. The preparation method according to any one of claims 1 to 6, characterized in that: The organic amines include , where n=1~6.

19. The preparation method according to any one of claims 1 to 6, characterized in that: The solvent is one or more of water, methanol, ethanol, isopropanol, n-butanol, acetonitrile, formamide, and acetone.

20. The preparation method according to any one of claims 1 to 6, characterized in that: The temperature of the composite modification treatment is 140-180° C. and the time is 6-24 hours.

21. The preparation method according to any one of claims 1 to 6, characterized in that: The second calcination is carried out at a temperature of 300-500° C. and for a time of 1-96 hours.

22. The preparation method according to any one of claims 1 to 6, characterized in that: The inert atmosphere is one or more of nitrogen, helium, neon and argon.

23. A composite silicon molecular sieve catalyst prepared by the preparation method according to any one of claims 1 to 22.

24. Use of the composite silicon molecular sieve catalyst according to claim 23 in catalyzing the preparation of caprolactam from cyclohexanone oxime.

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