Preparation method of solid acid catalyst and application thereof in caprolactam preparation

Abstract

The application relates to the technical field of catalysts, and discloses a preparation method of a solid acid catalyst and application of the solid acid catalyst in preparation of caprolactam. The preparation of the catalyst comprises the following steps: S1, mixing, slurry mixing and slurry conditioning of a molecular sieve, an additive and a binder, and then spray drying and forming to obtain a granular composite carrier; S2, immersing and treating the composite carrier in acid liquor, and then filtering and drying to obtain a catalyst after acidification; S3, immersing the catalyst after acidification in a precursor solution of an active component, and then filtering and drying, and finally roasting to obtain a solid acid catalyst with acid centers. When the catalyst is used for preparing caprolactam, the problems of easy deactivation and short service life of existing catalysts can be solved, and the catalyst has the advantages of high selectivity, high stability and easy regeneration.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of caprolactam and catalyst, in particular to a preparation method of solid acid catalyst and its application in caprolactam preparation. BACKGROUND

[0002] Caprolactam is an important chemical product, mainly used in textile, automobile, electronics, construction and other fields. Among them, caprolactam as the monomer of nylon 6, is used for the preparation of poly caprolactam fiber, poly caprolactam resin and artificial leather, etc., and plays an important role in economic development.

[0003] At present, the main production routes of caprolactam are phenol hydrogenation method, cyclohexane oxidation method, toluene oxidation method, etc. Most of the production processes need to pass through the Beckmann rearrangement reaction of cyclohexanone oxime to obtain caprolactam. There are two kinds of process methods for preparing caprolactam from cyclohexanone oxime, namely liquid phase Beckmann rearrangement and gas phase Beckmann rearrangement. The liquid phase Beckmann rearrangement process is that cyclohexanone oxime undergoes rearrangement reaction under the catalysis of fuming sulfuric acid, and the excess sulfuric acid is neutralized by ammonia to obtain ammonium sulfate. This process method is mature, and is the most widely used Beckmann rearrangement process. However, this process not only easily corrodes the equipment, but also produces a large amount of ammonium sulfate, causing environmental pollution. The gas phase Beckmann rearrangement process is that the vaporized cyclohexanone oxime undergoes Beckmann rearrangement reaction on the active center of the catalyst. This method has no by-product ammonium sulfate, and avoids the problems of equipment corrosion and environmental pollution.

[0004] The gas phase Beckmann rearrangement reaction needs high temperature condition, has more by-products, and the catalyst is easy to deactivate. The research of catalyst is the key direction of the current Beckmann rearrangement reaction. At present, the catalysts for the gas phase Beckmann rearrangement reaction of cyclohexanone oxime mainly include oxides, molecular sieves, ionic liquids, etc. CN1256967A discloses a preparation method of a molecular sieve catalyst containing MFI structure for the reaction of converting cyclohexanone oxime into caprolactam. The patent application uses acidic silica gel as a binder, and gel microspheres are prepared by mixing, emulsifying, curing, washing and calcining. The results show that most of the catalysts have certain activity, but the common disadvantage is that the catalyst is easy to deactivate, the catalyst has short service life, and cannot meet the requirements of industrialization. SUMMARY

[0005] The present application provides a preparation method of solid acid catalyst and its application in caprolactam preparation, which solves the problems of easy deactivation and short service life of the existing catalyst, and has the advantages of high selectivity, high stability and easy regeneration.

[0006] The technical scheme of the present application is to provide a preparation method of solid acid catalyst, which comprises the following steps:

[0007] S1, mixing and sizing the molecular sieve, the auxiliary agent and the binder, and then performing spray drying to form a granular composite carrier; the auxiliary agent is a metal oxide with an alkali center;

[0008] S2, immersing the composite carrier in an acidic solution, and then filtering and drying to obtain an acidified catalyst;

[0009] S3, immersing the acidified catalyst in a precursor solution of an active component, and then filtering and drying, and finally calcining to obtain a solid acid catalyst with an acid center.

[0010] Optionally, the molecular sieve is one of ZSM-5, S-1, TS-1, [B]-MFI, MCM-41, Y type, NaHY type; and / or the auxiliary agent is one of MgO, CaO, ZnO, BaO, Cr2O3, Cs2O, Rb2O, SrO; and / or the binder is one of silica sol, aluminum sol, silica-aluminum sol, sesbania powder.

[0011] Optionally, the use amount ratio of the molecular sieve, the auxiliary agent and the binder is (30-50 wt%):(10-40 wt%):(10-60 wt%).

[0012] Optionally, water is added for mixing and sizing in S1, the slurry pH is controlled to be 5-9, the stirring temperature is controlled to be 20-80℃, the stirring time is controlled to be 10-48h, and then spray drying is performed.

[0013] Optionally, the acidic solution in S2 is an aqueous solution of hydrochloric acid, nitric acid, perchloric acid, acetic acid, formic acid, benzoic acid, sulfuric acid, selenic acid, hydrogen sulfide, carbonic acid, metasilicic acid, oxalic acid, glutamic acid or aspartic acid.

[0014] Optionally, in the immersion treatment in S2, reflux stirring immersion is performed at 30-50℃ for 12-36h.

[0015] Optionally, the active component in S3 is one of aluminum oxide, zirconium oxide, molybdenum oxide, tungsten oxide or titanium oxide; and the precursor solution of the active component is an aqueous solution or an alcoholic solution of one of aluminum nitrate, aluminum carbonate, zirconium nitrate, zirconium carbonate, phosphotungstic acid, phosphomolybdic acid, isopropyl titanate or tetrabutyl titanate.

[0016] Optionally, in the immersion in S3, reflux stirring immersion is performed at 30-80℃ for 6-24h; the volume ratio of the acidified catalyst to the precursor solution of the active component is 1:(1-1.5), the concentration of the precursor solution is 50-80 wt%; the calcination temperature is 320-600℃, and the calcination time is 1-10h.

[0017] The application also relates to the solid acid catalyst prepared by the preparation method.

[0018] The application also relates to application of the solid acid catalyst prepared by the preparation method to gas phase rearrangement of cyclohexanone oxime to prepare caprolactam.

[0019] The application has the following advantages:

[0020] 1. The cyclohexanone oxime rearrangement reaction needs to be carried out under the condition of an acid catalyst, and the acid sites of the catalyst are the active centers for catalyzing the rearrangement reaction, and the main active centers are more inclined to the weakly acidic, moderately acidic and silicon hydroxyl sites of the catalyst. Increasing the activity of the catalyst is to increase the weakly acidic sites, moderately acidic sites and silicon hydroxyl sites on the surface of the catalyst. The catalyst provided by the application is granular composite carrier prepared by mixing and granulating a molecular sieve, an additive and a binder. The surface and pore structure of the molecular sieve contain part of the weakly acidic sites and the strongly acidic sites. The application can reduce the strongly acidic sites of the molecular sieve carrier and increase the weakly acidic sites by adding metal oxides with alkali centers as the additive, so as to achieve the purposes of reducing the carbon deposition, prolonging the service life of the catalyst, promoting the main reaction and inhibiting the side reaction. Meanwhile, the metal oxides contain not only the alkali centers but also the weakly acidic centers, and the addition of the metal oxides to the molecular sieve carrier can further increase the weakly acidic centers, and avoids further treatment of the carrier by using an alkali solution, thereby simplifying the steps.

[0021] 2. The active silicon hydroxyl sites of the molecular sieve are silicon hydroxyl pits, and the terminal silicon hydroxyl and bridged hydroxyl can cause the deactivation of the catalyst. The application can reduce the formation of the terminal silicon hydroxyl and bridged hydroxyl by adding the additive metal oxides to interact with the silicon hydroxyl on the surface of the molecular sieve to form stable (metal-O-Si) bonds, thereby increasing the content of the hydroxyl pits of the catalyst, forming new active sites, further improving the pore structure to form mesopores, increasing the specific surface area, facilitating the diffusion of the reactants and the discharge of the products, and thereby avoiding the deactivation of the catalyst caused by the carbon deposition.

[0022] 3. The application mixes the molecular sieve, the additive and the binder, and adopts the spray drying forming mode, thereby shortening the drying and forming time, making the size of the catalyst uniform, and obtaining the granular composite carrier which is successively immersed in an acid solution and a precursor solution of the active component, and the solid acid catalyst is prepared by the competitive adsorption mode. The application adopts the high specific surface area molecular sieve as the carrier, and the porous structure of the carrier can improve the dispersity of the active component and increase the activity of the catalyst. In addition, the active component is impregnated in the form of the precursor, which can control the uniform distribution of the active component on the surface of the carrier, further improve the dispersity of the active component, and obtain the catalyst which can increase the dispersity of the active component and improve the stability of the catalyst. The preparation method is simple in operation, safe and environmentally friendly, the catalyst is easy to recycle in the application process, and can be used for industrial production. DETAILED DESCRIPTION

[0023] The experimental methods in the following examples are all conventional methods unless otherwise specified. The materials used in the following examples are all commercially available products unless otherwise specified.

[0024] The present application provides a preparation method of a solid acid catalyst, comprising the following steps:

[0025] S1, mixing and slurrying the molecular sieve, the additive and the binder, and then spray drying and forming to obtain a granular composite carrier; the additive is a metal oxide with an alkali center;

[0026] S2, immersing the composite carrier in an acidic solution for treatment, and then filtering and drying to obtain a catalyst after acidification;

[0027] S3, immersing the catalyst after acidification in a precursor solution of an active component, and then filtering and drying, and finally calcining to obtain a solid acid catalyst with an acid center.

[0028] Among them, the molecular sieve is one of ZSM-5, S-1, TS-1, [B]-MFI, MCM-41, Y type, NaHY type. The additive is one of MgO, CaO, ZnO, BaO, Cr2O3, Cs2O, Rb2O, SrO. The binder is one of silica sol, aluminum sol, silica-aluminum sol, and sesbania.

[0029] In some embodiments, the amount ratio of the molecular sieve, the additive and the binder is 30-50wt%:10-40wt%:10-60wt%. Preferably, it is 40-50wt%:30-40wt%:10-30wt%.

[0030] In preferred embodiments, when water is added for mixing and slurring in S1, the slurry pH is controlled to be 5-9, the stirring temperature is 20-80℃, and the stirring time is 10-48h, and then spray drying and forming. The amount of water added during slurring is 1-1.2 times the total amount of solids, preferably the stirring temperature is 30-60℃, preferably the stirring time is 12-24h, the spray drying and forming catalyst particle size is controlled to be 100-500um.

[0031] In preferred embodiments, the acidic solution in S2 is an aqueous solution of hydrochloric acid, nitric acid, perchloric acid, acetic acid, formic acid, benzoic acid, sulfuric acid, selenic acid, hydrogen sulfide acid, carbonic acid, metasilicic acid, oxalic acid, glutamic acid or aspartic acid. More preferably, it is hydrochloric acid, nitric acid, acetic acid, formic acid, benzoic acid, carbonic acid or oxalic acid.

[0032] In preferred embodiments, during the immersion in S2, reflux stirring immersion is carried out at 30-50℃ for 12-36h; the mass ratio of the composite carrier to the acidic solution is 1:0.1-1.

[0033] In a preferred embodiment, the active component in S3 is alumina, zirconia, molybdenum oxide, tungsten oxide or titanium oxide; more preferably zirconia or titanium oxide. The precursor solution of the active component is an aqueous or alcoholic solution of one of the following: aluminum nitrate, aluminum carbonate, zirconium nitrate, zirconium carbonate, phosphotungstic acid, phosphomolybdic acid, isopropyl titanate, tetrabutyl titanate.

[0034] In a preferred embodiment, the impregnation in S3 is carried out at 30-80°C under reflux and stirring for 6-24h; the volume ratio of the acidified catalyst to the precursor solution of the active component is 1:1-1.5, the concentration of the precursor solution is 50-80wt%, the calcination temperature is 320-600°C, and the calcination time is 1-10h.

[0035] The embodiments of the present application will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only for illustration of the present application and should not be regarded as limiting the scope of the present application.

[0036] Example 1

[0037] 5g of S-1 molecular sieve powder was mixed with 4g of MgO and 1g of silica sol in 10ml of water to form a slurry, the pH of the slurry was kept at 8, the stirring temperature was 30°C, and the stirring time was 24h. The mixed slurry was then spray-dried to form a 100um granular composite carrier. The composite carrier was then immersed in a 10wt% nitric acid solution, and impregnated at 50°C under reflux and stirring for 24h. After filtration and drying, the acidified catalyst was immersed in 1.2 times the volume of a 50wt% zirconium nitrate aqueous solution, and impregnated at 60°C under reflux and stirring for 6h. After filtration and drying at 50°C for 10h, the catalyst was finally calcined at 480°C for 5h. Catalyst 1 was obtained.

[0038] The 5g of catalyst obtained in Example 1 was used in the experiment of preparing caprolactam by gas phase rearrangement of cyclohexanone oxime: 10% cyclohexanone oxime solution, nitrogen as the carrier gas, space velocity 0.1h-1, and reaction temperature 300°C. The results are shown in Table 1.

[0039] Example 2:

[0040] 5g of MCM-41 molecular sieve powder was mixed with 4g of ZnO and 1g of sesbania powder in 11ml of water to form a slurry, the pH of the slurry was kept at 7, the stirring temperature was 40°C, and the stirring time was 12h. The mixed slurry was then spray-dried to form a 150um granular composite carrier. The composite carrier was then immersed in a 10wt% acetic acid solution, and impregnated at 50°C under reflux and stirring for 24h. After filtration and drying, the acidified catalyst was immersed in 1.2 times the volume of a 50wt% isopropyl titanate alcoholic solution, and impregnated at 80°C under reflux and stirring for 10h. After filtration and drying at 50°C for 12h, the catalyst was finally calcined at 540°C for 4h. Catalyst 2 was obtained.

[0041] The catalyst obtained in Example 2 was used in the experiment of preparing caprolactam by gas phase rearrangement of cyclohexanone oxime, and the experimental conditions were the same as in Example 1. The results are shown in Table 1.

[0042] Example 3

[0043] 5 g of Y-type molecular sieve powder was mixed with 4 g of Cr2O3 and 1 g of silica-alumina sol to form a slurry with 11 ml of water, and the slurry was kept at a pH of 8 and stirred at a temperature of 50°C for 32 h. The mixed slurry was spray-dried to form a 300 um granular composite carrier. The composite carrier was then immersed in a 20 wt% acetic acid solution and refluxed and stirred at 30°C for 36 h. After filtration and drying, the acidified catalyst was immersed in 1.2 times the volume of a 60 wt% phosphotungstic acid aqueous solution and refluxed and stirred at 70°C for 10 h. After filtration and drying at 100°C for 12 h, the catalyst was finally calcined at 500°C for 5 h. Catalyst 3 was obtained.

[0044] The catalyst obtained in Example 3 was used in the experiment of preparing caprolactam by gas phase rearrangement of cyclohexanone oxime, and the experimental conditions were the same as in Example 1. The results are shown in Table 1.

[0045] Example 4

[0046] 5 g of ZSM-5 molecular sieve powder was mixed with 4 g of BaO and 1 g of aluminum sol to form a slurry with 12 ml of water, and the slurry was kept at a pH of 8 and stirred at a temperature of 30°C for 12 h. The mixed slurry was spray-dried to form a 200 um granular composite carrier. The composite carrier was then immersed in a 10 wt% carbonic acid solution and refluxed and stirred at 60°C for 24 h. After filtration and drying, the acidified catalyst was immersed in 1.2 times the volume of a 60 wt% aluminum carbonate aqueous solution and refluxed and stirred at 60°C for 8 h. After filtration and drying at 50°C for 14 h, the catalyst was finally calcined at 480°C for 6 h. Catalyst 4 was obtained.

[0047] The catalyst obtained in Example 4 was used in the experiment of preparing caprolactam by gas phase rearrangement of cyclohexanone oxime, and the experimental conditions were the same as in Example 1. The results are shown in Table 1.

[0048] Table 1

[0049]

[0050] From the results of Table 1, it can be seen that the activities of the catalysts obtained by using S-1, MCM-41, Y and ZSM-5 molecular sieves as the carrier, MgO, ZnO, Cr203 and BaO as the additive, and zirconium nitrate, isopropyl titanate, phosphotungstic acid and aluminum carbonate as the active component are different. The catalyst with S-1 as the carrier, MgO as the additive and zirconium nitrate as the active component has higher activity, and the conversion rate and selectivity of cyclohexanone oxime are both above 99.5%. This is mainly because the full-silicon zeolite S-1 has only weak acid sites and contains more hydroxyl active sites, and zirconium nitrate has high catalytic activity for gas phase rearrangement, so the catalyst with S-1 as the carrier has higher activity. The other three carriers contain part of strong acid sites, and weak acid sites are obtained by alkalization with the additive, and the activity of the treated catalyst can also maintain high catalytic activity.

[0051] Comparative Example 1

[0052] The same as Example 1, but without adding MgO.

[0053] 5 g of S-1 molecular sieve powder was mixed with 1 g of silica sol and 6 ml of water to prepare a slurry, and the slurry was stirred at 30°C for 24 h. The mixed slurry was spray-dried to form a 100 um granular composite carrier. The composite carrier was immersed in a 10 wt% nitric acid solution, and refluxed and stirred at 50°C for 24 h. After filtration and drying, the acid-treated catalyst was immersed in 1.2 times the volume of a 50 wt% zirconium nitrate aqueous solution, and refluxed and stirred at 60°C for 6 h. After filtration and drying at 50°C for 10 h, the catalyst was calcined at 480°C for 5 h to obtain Comparative Catalyst 1.

[0054] The catalyst obtained in Comparative Example 1 was used in the experiment of preparing caprolactam by gas phase rearrangement of cyclohexanone oxime, and the experimental conditions were the same as in Example 1. The results are shown in Table 2.

[0055] Comparative Example 2

[0056] The same as Example 1, but the acid immersion step was omitted.

[0057] 5 g of S-1 molecular sieve powder was mixed with 4 g of MgO and 1 g of silica sol and 10 ml of water to prepare a slurry, and the slurry was stirred at 30°C for 24 h. The mixed slurry was spray-dried to form a 100 um granular composite carrier. The composite carrier was immersed in 1.2 times the volume of a 50 wt% zirconium nitrate aqueous solution, and refluxed and stirred at 60°C for 6 h. After filtration and drying at 50°C for 10 h, the catalyst was calcined at 480°C for 5 h to obtain Comparative Catalyst 2.

[0058] The catalyst obtained in Comparative Example 2 was used in the experiment of preparing caprolactam by gas phase rearrangement of cyclohexanone oxime, and the experimental conditions were the same as in Example 1. The results are shown in Table 2.

[0059] Comparative Example 3:

[0060] The same as Example 1, but without adding MgO and omitting the acid impregnation step.

[0061] 5 g of S-1 molecular sieve powder was mixed with 1 g of silica sol and 6 ml of water to form a slurry, which was adjusted to a pH of 8 with ammonia water and stirred at 30°C for 24 h. The slurry was then spray-dried to form a 100 um granular composite carrier. The composite carrier was then immersed in 1.2 times its volume of a 50 wt% aqueous zirconium nitrate solution, and refluxed and stirred at 60°C for 6 h. The catalyst was then filtered, dried at 50°C for 10 h, and calcined at 480°C for 5 h to obtain Comparative Catalyst 3.

[0062] The catalyst obtained in Comparative Example 3 was used in a test for the vapor phase rearrangement of cyclohexanone oxime to prepare caprolactam, under the same conditions as in Example 1. The results are shown in Table 2.

[0063] Comparative Example 4:

[0064] The same as Example 1, but without adding MgO and adding magnesium nitrate in the final impregnation step.

[0065] 5 g of S-1 molecular sieve powder was mixed with 1 g of silica sol and 6 ml of water to form a slurry, which was adjusted to a pH of 8 with ammonia water and stirred at 30°C for 24 h. The slurry was then spray-dried to form a 100 um granular composite carrier. The composite carrier was then immersed in 10 wt% nitric acid, and refluxed and stirred at 50°C for 24 h. The acid-treated catalyst was then immersed in 1.2 times its volume of a 70 wt% magnesium nitrate and 50 wt% zirconium nitrate aqueous solution, and refluxed and stirred at 60°C for 6 h. The catalyst was then filtered, dried at 50°C for 10 h, and calcined at 480°C for 5 h to obtain Comparative Catalyst 4.

[0066] The catalyst obtained in Comparative Example 4 was used in a test for the vapor phase rearrangement of cyclohexanone oxime to prepare caprolactam, under the same conditions as in Example 1. The results are shown in Table 2.

[0067] Table 2

[0068]

[0069] From the data results of the above table, the catalyst of Comparative Example 1 is not added with the additive for alkalization, but is alkalized with ammonia water. The catalyst activity is reduced, and the conversion rate of cyclohexanone oxime and the selectivity of caprolactam are reduced to 92.5% and 95.4%, respectively. It is shown that the ammonia water alkalization cannot improve the active sites of the catalyst. The catalyst of Comparative Example 2 is not impregnated in the acid solution after the alkalization of the composite carrier, which leads to the reduction of the catalyst activity. Compared with the catalyst of Comparative Example 1 without acidification, the selectivity of caprolactam is greatly affected. The catalyst of Comparative Example 3 is alkalized with ammonia water and is not acidified, which leads to the low weak acid sites of the catalyst and the uneven distribution of the active components, thereby further reducing the conversion rate of cyclohexanone oxime and the selectivity of caprolactam. The catalyst 4 is the carrier which is alkalized with ammonia water and is impregnated in the metal salt solution of the active components and the additive at the same time. The conversion rate of cyclohexanone oxime and the selectivity of caprolactam are reduced at the same time. The active sites of the molecular sieve carrier are low, and the metal salt of the additive and the precursor solution of the active components form competitive adsorption, which leads to the low loading amount of the active components, and thus the activity of the catalyst is low. From the above data, the alkalization of the metal oxide can change the acid sites to improve the activity, and the acid solution acidification can promote the dispersion of the active components, so as to obtain the catalyst through competitive adsorption, and further strengthen the activity of the catalyst.

[0070] Example 5:

[0071] The used catalyst 1 was taken out and separated, and was calcined at 480°C for 2h in a nitrogen atmosphere. The regenerated catalyst 1 was obtained.

[0072] The regenerated catalyst 1 was used for the experiment of preparing caprolactam by the gas phase rearrangement of cyclohexanone oxime. The reaction conditions were the same as those of Example 1, and the results are shown in Table 3.

[0073] The used regenerated catalyst 1 was taken out and separated, and was calcined at 480°C for 2h in a nitrogen atmosphere. The regenerated catalyst 2 was obtained.

[0074] The regenerated catalyst 2 was used for the experiment of preparing caprolactam by the gas phase rearrangement of cyclohexanone oxime. The reaction conditions were the same as those of Example 1, and the results are shown in Table 3.

[0075] The used catalyst 2 was taken out and separated, and was calcined at 480°C for 2h in a nitrogen atmosphere. The regenerated catalyst 3 was obtained.

[0076] The regenerated catalyst 3 was used for the experiment of preparing caprolactam by the gas phase rearrangement of cyclohexanone oxime. The reaction conditions were the same as those of Example 1, and the results are shown in Table 3.

[0077] Table 3

[0078]

[0079] From Table 3, it can be seen that after the catalyst 1 is reused for 3 times, the cyclohexanone oxime conversion rate and the caprolactam selectivity do not show obvious decreasing trend, thus indicating that the catalyst prepared by the method can still maintain high catalytic activity after being reused, and the activity of the regenerated catalyst and the fresh catalyst is not much different, the stability of the catalyst is good, and the catalyst can be reused and industrialized production can be realized.

[0080] The above examples describe the preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other manner, and these simple modifications and combinations should also be considered as the disclosed content of the present application and belong to the protection scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A method for preparing a solid acid catalyst, characterized in that, Includes the following steps: S1. Molecular sieves, additives, and binders are mixed and slurried, then spray-dried to form a granular composite carrier; the additives are metal oxides with alkali centers. S2. The composite support is impregnated in an acidic solution, then filtered and dried to obtain the acidified catalyst. S3. The acidified catalyst is impregnated in the precursor solution of the active component, then filtered and dried, and finally calcined to obtain a solid acid catalyst with acidic centers. The molecular sieve is one of ZSM-5, S-1, TS-1, [B]-MFI, MCM-41, Y-type, and NaHY-type; and / or the auxiliaries are one of MgO, CaO, ZnO, BaO, Cr2O3, Cs2O, Rb2O, and SrO; and / or the binder is one of silica sol, alumina sol, aluminosilicate sol, and guar gum powder; the ratio of molecular sieve, auxiliaries, and binder is (30~50wt%):(10~40wt%):(10... (~60wt%); the acidic solution in S2 is an aqueous solution of hydrochloric acid, nitric acid, perchloric acid, acetic acid, formic acid, benzoic acid, sulfuric acid, selenic acid, hydrosulfuric acid, carbonic acid, metasilicic acid, oxalic acid, glutamic acid, or aspartic acid; the active component in S3 is one of aluminum oxide, zirconium oxide, molybdenum oxide, tungsten oxide, or titanium oxide; the precursor solution of the active component is an aqueous solution or alcoholic solution of one of aluminum nitrate, aluminum carbonate, zirconium nitrate, zirconium carbonate, phosphotungstic acid, phosphomolybdic acid, isopropyl titanate, or tetrabutyl titanate.

2. The preparation method according to claim 1, characterized in that: Water is added to S1 for mixing and slurry preparation. The pH of the slurry is controlled at 5-9, the stirring temperature is 20-80℃, and the stirring time is 10-48h. Then, it is spray-dried and molded.

3. The preparation method according to claim 1, characterized in that: During the S2 impregnation treatment, reflux and stir at 30-50℃ for 12-36 hours.

4. The preparation method according to claim 1, characterized in that: When impregnating in S3, reflux and stir at 30-80℃ for 6-24h; the volume ratio of the acidified catalyst to the precursor solution of the active component is 1:(1~1.5), and the concentration of the precursor solution is 50~80wt%; the calcination temperature is 320-600℃, and the calcination time is 1-10h.

5. The solid acid catalyst obtained by the preparation method according to any one of claims 1 to 4.

6. The application of the solid acid catalyst obtained by the preparation method according to any one of claims 1 to 4 or the catalyst according to claim 5 in the gas-phase rearrangement of cyclohexanone oxime to prepare caprolactam.

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