Catalyst for bayer-villiger oxidation reaction comprising hierarchically nanoporous zeolite and method for preparing the same

Abstract

The present invention relates to a catalyst for a Baeyer-Villiger oxidation reaction, and more specifically, to a catalyst for a Baeyer-Villiger oxidation reaction comprising a zeolite carrier having a hierarchical nanoporous structure including micropores and mesopores; and tin (Sn) supported on the zeolite carrier, wherein the diameter of the micropores is 1 nm or less, the diameter of the mesopores is 2 nm to 10 nm, and the Si / Sn ratio is 20 to 120.

Description

Technology Field

[0001] The following various embodiments relate to a catalyst that can be used in a Bayer-Villiger oxidation reaction and a method for preparing the same. Background Technology

[0003] Zeolite is a crystalline aluminosilicate material in which micropores with a diameter of less than 2 nm are arranged very regularly. Basically, silicon or aluminum is connected to oxygen atoms in a tetrahedral structure, and depending on the connection method, various types of pore sizes, structures, and frameworks can be formed.

[0004] As such, zeolites have a uniform microporous structure that allows them to function as molecular sieves, and they also possess excellent mechanical and thermal stability, as well as strong acid sites and ion exchange capabilities derived from aluminum atoms within their framework. Therefore, they are widely used as acid catalysts in fields such as petrochemicals on their own. Furthermore, by using the zeolite as a support and supporting or doping metals such as platinum, nickel, and cobalt onto the surface of the zeolite or within the micropores, they are also widely used to produce various types of heterogeneous catalysts that have high activity in specific organic reactions.

[0005] Among these heterogeneous catalysts, zeolite catalysts containing tin (Sn) metal are used as catalysts for various organic reactions requiring Lewis acids, such as the Baeyer-Villiger oxidation reaction, the Meerwein-Ponndorf-Verley reduction reaction, and the hydrocarbon isomerization reaction, and the catalyst is known to have high activity, high selectivity, and high stability characteristics due to the advantages of the zeolite described above.

[0006] However, conventional zeolites contain only a large number of micropores with very small diameters. This leads to a problem where the conversion rate drops sharply due to reduced diffusion of reactant and product molecules as chemical reactions proceed. Furthermore, organic compounds larger than a certain size cannot pass through the micropores and thus fail to meet active sites, resulting in limited reactivity. To address this, researchers synthesized a so-called hierarchical nanoporous zeolite that includes mesopores with larger diameters alongside micropores, with the micropores and mesopores organically interconnected to form a network. This new structural zeolite has been shown to possess advantages over conventional zeolites in terms of the diffusion of reactants or products larger than a certain size.

[0007] Recently, Román and his colleagues succeeded in synthesizing a tin-doped hierarchical nanoporous zeolite catalyst by including a tin precursor in the hydrothermal synthesis process of such a hierarchical nanoporous zeolite, but they had difficulty introducing more than a certain amount of tin, so they could not synthesize a catalyst with a Si / Sn ratio of 125 or less, and there was a problem in that a large amount of tin oxide (SnO2), which is not reactive in the above reactions, was found in the catalyst due to the instability of the tin precursor, etc. in the liquid environment.

[0008] Therefore, in order to improve the efficiency of processes such as the Bayer-Billiger oxidation reaction for organic compounds of a certain size or larger, there is a need to develop a new catalyst manufacturing method and a catalyst based thereon that can introduce a certain amount of tin into a hierarchical nanoporous zeolite, while simultaneously ensuring that the tin is evenly dispersed on the zeolite and preventing the generation of byproducts such as tin oxide within the catalyst. Prior art literature

[0010] H. Y. Luo, L. Bui, W. R. Gunther, E. Min, Y. Romαn-Leshkov, Synthesis and catalytic activity of Sn-MFI nanosheets for the Baeyer-Villiger oxidation of cyclic ketones, ACS Catal. 2 (2012) 2695-2699. The problem to be solved

[0011] To solve the above-mentioned problems, we aim to provide a hierarchical nanoporous zeolite-based catalyst in which tin (Sn) particles are evenly dispersed while the Si / Sn ratio is controlled to be below a specific value by introducing a special post-synthetic method in which a zeolite carrier having a hierarchical nanoporous structure is synthesized and tin (Sn) metal atoms are supported on the zeolite carrier.

[0012] However, the problems intended to be solved in this specification are not limited to those mentioned above, and other unmentioned problems will be clearly understood by a person skilled in the art from the description below. means of solving the problem

[0014] A catalyst for a Baeyer-Villiger oxidation reaction according to one embodiment comprises a zeolite carrier having a hierarchical nanoporous structure including micropores and mesopores; and tin (Sn), wherein the average diameter of the micropores is less than 2 nm, the average diameter of the mesopores is 2 nm to 10 nm, and the Si / Sn ratio may be 20 to 120.

[0015] The above zeolite carrier may have one or more crystal structures among MFI, BEA, MRE, and MTW.

[0016] The above tin (Sn) may include those having a size of 1 nm or less.

[0017] The above-mentioned catalyst for the Beyer-Willigger oxidation reaction has a BET specific surface area of ​​400 m² 2 / g to 800 m 2 / g, and the external specific surface area is 200 m² 2 / g to 600 m 2 It can be / g.

[0018] The above-mentioned catalyst for the Bayer-Williger oxidation reaction has a total pore volume of 0.1 cm² 3 / g to 1.0 cm 3 It can be / g.

[0019] The above-mentioned catalyst for the Bayer-Billiger oxidation reaction has a Lewis acid site content of tin (Sn) of 20 μmol / g to 150 μmol / g, and the Lewis acid site content of tin (Sn) is due to trimethylphosphine (TMPO) adsorption. 31 P-solid state nuclear magnetic resonance spectroscopy ( 31 It may be measured by P-Solid state nuclear magnetic resonance spectroscopy.

[0020] A method for preparing a catalyst for a Bayer-Billiger oxidation reaction according to one embodiment may include the steps of: synthesizing a borosilicate zeolite having a hierarchical nanoporous structure; synthesizing a zeolite carrier by removing boron (B) from the borosilicate zeolite; and supporting a tin (Sn) metal on the zeolite carrier.

[0021] The step of synthesizing a borosilicate zeolite having the above-mentioned hierarchical nanoporous structure may include: mixing a solution containing a structure directing surfactant (SDS), a silicon (Si) precursor, and a boron (B) precursor; synthesizing a borosilicate zeolite by carrying out hydrothermal synthesis with the solution; and calcining the synthesized borosilicate zeolite at a temperature of 450 ℃ to 650 ℃ under an oxygen (O2) atmosphere.

[0022] The above structure-directing surfactant (SDS) may have the structure of Chemical Formula 1 below:

[0023] [Chemical Formula 1]

[0024]

[0025] (In the above Chemical Formula 1, R1 and R3 are each an alkyl group having 3 to 25 carbon atoms, R2 is an alkylene group having 2 to 10 carbon atoms or an arylene group having 6 to 10 carbon atoms, and n is one of an integer from 1 to 10.)

[0026] The step of synthesizing a zeolite carrier by removing boron (B) from the borosilicate zeolite may include the step of mixing the borosilicate zeolite and a nitric acid solution; the step of heating the mixed solution to remove boron from the borosilicate zeolite; and the step of obtaining a zeolite carrier from which boron has been removed.

[0027] The step of supporting tin (Sn) metal on the zeolite carrier may include: a step of dehydrating the zeolite carrier by heating it under vacuum conditions; a step of synthesizing a tin-supported zeolite by introducing a tin (Sn) precursor into the dehydrated zeolite carrier; and a step of calcining the tin (Sn)-supported zeolite at a temperature of 450 ℃ to 650 ℃ under an oxygen (O2) atmosphere.

[0028] The step of synthesizing a tin-supported zeolite by introducing a tin (Sn) precursor into the dehydrated zeolite carrier may include introducing the tin precursor into the dehydrated zeolite carrier by chemical vapor deposition (CVD).

[0029] The above tin (Sn) precursor may include one or more of dimethyltin dichloride, trimethyltin chloride, tetramethyltin, butyltin trichloride, butyltin chloride dihydroxide, tributyltin chloride, tetrabutyltin, diphenyltin dichloride, tin dichloride, tin tetrachloride, and tin oxalate. Effects of the invention

[0031] A catalyst for a Bayer-Billiger oxidation reaction according to one embodiment comprises a zeolite carrier having a hierarchical nanoporous structure including micropores and mesopores; and tin (Sn) supported on the zeolite carrier, wherein the Si / Sn ratio is controlled to be below a specific value, thereby possessing a large number of Lewis acid sites on the catalyst surface and mesopores, and is characterized by having high catalytic activity and selectivity even for the oxidation reaction of organic matter of a certain size or larger, as well as excellent thermal stability.

[0032] The effects according to one embodiment in this specification are not limited to the effects described above, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description of the invention or the claims in this specification. Brief explanation of the drawing

[0034] FIG. 1 is a diagram showing the X-ray diffraction (XRD) pattern of a catalyst for a Bayer-Billiger oxidation reaction according to one embodiment. Figure 2 is a diagram showing the X-ray diffraction (XRD) patterns for the Beyer-Williger oxidation reaction catalysts of comparative examples. FIG. 3 is a diagram showing scanning electron microscope (SEM), scanning transmission electron microscope (STEM) images, and energy dispersive X-ray analysis (EDS) results for a catalyst for a Bayer-Billiger oxidation reaction according to one embodiment. FIG. 4 is a diagram showing the pore size distribution (PSD) obtained from the nitrogen gas adsorption method for a catalyst for a Bayer-Billiger oxidation reaction according to one embodiment. FIG. 5 relates to a borosilicate zeolite and a boron-removed zeolite carrier according to one embodiment, 11 B-solid state nuclear magnetic resonance spectroscopy ( 11 This is a diagram showing the B-Solid state NMR spectrum. FIG. 6 illustrates a catalyst for a Bayer-Billiger oxidation reaction according to one embodiment, 29 Si-solid state nuclear magnetic resonance spectroscopy ( 29 This is a diagram showing the Si-Solid State NMR spectrum. FIG. 7 illustrates the adsorption of trimethylphosphine oxide (TMPO) on a catalyst for a Bayer-Billiger oxidation reaction according to one embodiment. 31 P-solid state nuclear magnetic resonance spectroscopy ( 31 This is a diagram showing the P-Solid state NMR spectrum. Figure 8 is a graph showing the conversion rate of the Bayer-Billiger oxidation reaction over time for the catalysts for the Bayer-Billiger oxidation reaction of the examples and comparative examples. Figure 9 is a graph showing the conversion rate of the Bayer-Billiger oxidation reaction for the catalysts of the examples and comparative examples at different temperatures. Specific details for implementing the invention

[0035] Embodiments are described in detail below. However, various modifications may be made to the embodiments, and thus the scope of the patent application is not limited or restricted by these embodiments. It should be understood that all modifications, equivalents, and substitutions to the embodiments are included within the scope of the rights.

[0036] To those skilled in the art, the scope of the present invention is not limited by these embodiments according to the gist of the invention.

[0037] The terms used in the embodiments are for illustrative purposes only and should not be interpreted as intended to be limiting. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprising" or "having" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0038] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the embodiments pertain. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0039] In addition, when describing the embodiments, if it is determined that a detailed description of related prior art could unnecessarily obscure the essence of the embodiments, such detailed description is omitted.

[0040] In addition, terms such as first, second, A, B, (a), (b), etc. may be used when describing the components of the embodiments. These terms are used only to distinguish the components from other components, and the essence, order, or sequence of the components is not limited by the terms.

[0041] Components included in any one embodiment and components having common functions shall be described using the same names in other embodiments. Unless otherwise stated, the descriptions given in any one embodiment may also apply to other embodiments, and specific descriptions shall be omitted to the extent of overlap.

[0042] Throughout the specification, when a part is described as "including" a certain component, this means that it does not exclude other components but may include additional components.

[0044] A catalyst for a Baeyer-Villiger oxidation reaction according to one embodiment comprises a zeolite support having a hierarchical nanoporous structure including micropores and mesopores; and tin (Sn), wherein the average diameter of the micropores is less than 2 nm, the average diameter of the mesopores is 2 nm to 10 nm, and the Si / Sn ratio may be 20 to 120. As the catalyst according to one embodiment satisfies all of the above conditions, it may possess the characteristics of exhibiting high catalytic activity and selectivity even in oxidation reactions of organic matter of a certain size or larger, as well as excellent thermal stability.

[0045] The above zeolite carrier may be a concept including zeolite or silicon-containing pseudo-zeolite. The silicon-containing pseudo-zeolite is a material having the same or similar crystal structure as zeolite, and may include a pure silicate composed solely of silicon without aluminum in the aluminosilicate composition of the zeolite, or a metallosilicate in which the aluminum is substituted with other metal atoms such as titanium, zirconium, vanadium, iron, lithium, calcium, strontium, germanium, magnesium, and manganese. Additionally, the pure silicate may be manufactured as silicate from the beginning, or it may be manufactured by removing metal atoms other than silicon from the metallosilicate.

[0046] As described above, the above-mentioned hierarchical nanoporous structure may represent a structure in which micropores and mesopores contained in a catalyst or carrier are organically connected to form a network, thereby enabling a compound entering the micropores to move directly to the mesopores or vice versa, and may be referred to as a 'nanosponge structure'.

[0047] In addition, the above hierarchical nanoporous structure may include a crystalline framework (or crystal) having an ultrafine thickness corresponding to one to ten or fewer single unit cells that includes micropores, wherein the micropores and mesopores are formed by the organic connection of the crystalline framework to form mesopores of very uniform size, which have a regular hexagonal structure, a cubic structure, or a third irregular structure. Meanwhile, the thickness of the crystalline framework may be proportional to the number of single unit cells included in the framework and may be 1 nm to 10 nm.

[0048] The diameters of the micropores and mesopores may be calculated from an adsorption isotherm measured from gas adsorption, and specifically, may be calculated from the maximum point of the pore size distribution (PSD) obtained from the adsorption isotherm based on the Barrett-Joyner-Halenda (BJH) algorithm.

[0049] The form in which the tin (Sn) is included in the zeolite carrier may include being supported on the outer surface of the zeolite carrier or being supported on the inner wall surface of pores such as micropores or mesopores of the zeolite carrier, and the 'support' may include a form in which a portion of the surface of the tin nanoparticle is in contact with the surface of the zeolite carrier or a form of doping in which atomic-level tin is included in the surface framework of the zeolite carrier while one surface of the tin is simultaneously exposed to the outside.

[0050] The above Si / Sn ratio can be interpreted as an indicator representing the amount of tin relative to the total mass of the catalyst, and a smaller value indicates an increase in the amount of tin relative to the total mass of the catalyst. Additionally, the Si / Sn ratio may be a value measured by analyzing the prepared catalyst using inductively coupled plasma atomic emission spectroscopy (ICP-AES).

[0051] The above Si / Sn ratio may be 20 to 120, preferably 20 to 70, more preferably 20 to 50, and most preferably 20 to 40. If the Si / Sn ratio exceeds the upper limit of the above range, the amount of tin in the catalyst may be too low to achieve the target conversion rate or the reaction may not proceed at all; if it is below the lower limit of the above range, tin may not be evenly distributed within the catalyst, the size of the tin particles may become very large, causing the conversion rate per metal mass to decrease sharply, and some micropores may be blocked, so the diffusion of reactants / products may not occur properly.

[0052] The above-mentioned Baeyer-Villiger oxidation reaction is an organic reaction that adds an oxygen atom to a ketone or aldehyde compound at a position immediately adjacent to the alpha carbon of a carbonyl (C=O) group. Depending on the type of acid site acting as a catalyst, the reaction can proceed as a main reaction (see Reaction Scheme 1 below) or a side reaction (see Chemical Formula 2 below). It is known that the main reaction is usually carried out by Lewis acid sites, while the side reaction is carried out by Brønsted acid sites. Therefore, to obtain the product from the main reaction, it is advantageous to have a sufficient number of Lewis acid sites within the catalyst and to have as few Brønsted acid sites as possible.

[0053] [Reaction Equation 1]: Main reaction

[0054]

[0055] [Reaction Equation 2]: Side reaction (decomposition reaction)

[0056]

[0058] According to one embodiment, the zeolite carrier may have one or more crystal structures among MFI, BEA, MRE, and MTW. The crystal structure may be derived from the nomenclature established by the International Zeolite Association (IZA). Additionally, the zeolite carrier may have a single crystal structure or may have multiple crystal structures such as a primary phase and a secondary phase.

[0060] According to one embodiment, the tin (Sn) may include having a size of 1 nm or less.

[0061] A catalyst according to one embodiment may include tin present in a state of being atomically dispersed or having a size of 1 nm or less on a zeolite carrier by being manufactured by the manufacturing method according to one embodiment below. That is, through this, even if the amount of tin included in the catalyst is increased beyond a certain level, by-products such as excessively large tin particles or tin oxide may not be generated, and as the size of the tin particles decreases, the effect of increasing the activity of tin acting as Lewis acid sites may also be maintained. Meanwhile, the size of the tin may be measured through images obtained from a high-resolution scanning transmission electron microscope (High-resolution STEM) and energy dispersive X-ray spectroscopy (EDS).

[0063] According to one embodiment, the catalyst for the Bayer-Billiger oxidation reaction has a BET specific surface area of ​​400 m² 2 / g to 800 m 2 It can be / g, or 500 m 2 / g to 800 m 2 / g, or 500 m 2 / g to 700 m 2 / g, or 600 m 2 / g to 700 m 2 It may be / g. In addition, the catalyst for the Bayer-Billiger oxidation reaction has an external specific surface area of ​​200 m² 2 / g to 600 m 2 It can be / g, or 300 m 2 / g to 600 m 2 / g, or 300 m 2 / g to 500 m 2 / g, or 400 m 2 / g to 500 m 2 It can be / g.

[0064] According to one embodiment, the catalyst for the Bayer-Billiger oxidation reaction has a total pore volume of 0.1 cm² 3 / g to 1.0 cm 3 It can be / g, or 0.3 cm 3 / g to 1.0 cm 3 / g, or 0.5 cm 3 / g to 1.0 cm 3 / g, or 0.5 cm 3 / g to 0.8 cm 3 It can be / g.

[0065] A catalyst according to one embodiment includes a zeolite support having a hierarchical nanoporous structure, and possesses the characteristics of having a significantly large BET specific surface area and external specific surface area, as well as a very large pore volume, thereby securing a large space for reactants to be located within the catalyst, while also having the characteristic that Lewis acid sites present on the surface of the zeolite crystal can easily come into contact with the reactants.

[0066] The above BET specific surface area, external specific surface area, and total pore volume may be calculated from an adsorption isotherm according to the gas adsorption method. Specifically, the BET specific surface area may be calculated from the amount of adsorption in the range where the relative pressure (P / P0) in the adsorption isotherm is 0.05 to 0.20, the external specific surface area may be calculated from the adsorption isotherm using the t-plot method, and the total pore volume may be calculated based on the amount of adsorption at the point where the relative pressure in the adsorption isotherm is 0.95.

[0068] According to one embodiment, the catalyst for the Bayer-Billiger oxidation reaction may have a Lewis acid site content of tin (Sn) of 20 μmol / g to 150 μmol / g, preferably 45 μmol / g to 150 μmol / g, more preferably 60 μmol / g to 150 μmol / g, even more preferably 90 μmol / g to 150 μmol / g, and most preferably 120 μmol / g to 150 μmol / g.

[0069] A catalyst according to one embodiment not only contains a large amount of tin acting as a Lewis acid site within the catalyst, but also has tin particles evenly distributed on the zeolite or within the zeolite framework, thereby possessing optimal catalytic activity conditions for reactions with organic compounds. Therefore, the Lewis acid site content can serve as a primary indicator of the catalyst's performance.

[0070] Meanwhile, the Lewis acid site content due to the above tin (Sn) is due to the adsorption of trimethylphosphine (TMPO). 31 P-solid state nuclear magnetic resonance spectroscopy ( 31It may be measured by P-Solid-state nuclear magnetic resonance spectroscopy. Specifically, after adsorbing a TMPO probe molecule onto the target catalyst material, regarding the adsorbed catalyst material 31 After obtaining a spectrum showing one or more peaks through P-solid-state nuclear magnetic resonance spectroscopy, the Lewis acid site content due to tin (Sn) can be calculated from the measured values ​​by quantitatively analyzing the peaks corresponding to Lewis acid sites.

[0072] A method for preparing a catalyst for a Bayer-Billiger oxidation reaction according to one embodiment may include the steps of: synthesizing a borosilicate zeolite having a hierarchical nanoporous structure; synthesizing a zeolite carrier by removing boron (B) from the borosilicate zeolite; and supporting a tin (Sn) metal on the zeolite carrier. Thus, a catalyst prepared by introducing a post-synthetic method of performing post-treatment on the synthesized borosilicate zeolite can possess characteristics such as a Si / Sn ratio of 120 or less, unlike a catalyst prepared from a conventional single-step hydrothermal synthesis method, and can also possess characteristics such as having tin with a size of 1 nm or less evenly dispersed without containing by-products such as tin oxide.

[0074] According to one embodiment, the step of synthesizing a borosilicate zeolite having a hierarchical nanoporous structure may include: mixing a solution comprising a structure directing surfactant (SDS), a silicon (Si) precursor, and a boron (B) precursor; synthesizing a borosilicate zeolite by carrying out hydrothermal synthesis with the solution; and calcining the synthesized borosilicate zeolite at a temperature of 450°C to 650°C under an oxygen (O2) atmosphere.

[0075] In the step of mixing a solution containing the above-mentioned structure-directing surfactant (SDS), silicon (Si) precursor, and boron (B) precursor, the hydrophilic portion of the surfactant interacts with the inorganic precursor to induce the formation of a gel, and the hydrophobic portion interacts with each other through non-covalent bonds (van der Waals forces, etc.) so that the gel forms a specific structure. Meanwhile, the solution may further include alkali metal precursors such as sodium (Na) and potassium (K), and the zeolite crystal structure produced may change depending on the composition of the components included in the solution.

[0076] According to one embodiment, the structure-directing surfactant (SDS) may have the structure of the following chemical formula 1:

[0077] [Chemical Formula 1]

[0078]

[0079] (In the above Chemical Formula 1, R1 and R3 are each an alkyl group having 3 to 25 carbon atoms, R2 is an alkylene group having 2 to 10 carbon atoms or an arylene group having 6 to 10 carbon atoms, and n is one of an integer from 1 to 10.)

[0080] The above-mentioned structure-inducing surfactant is the most critical component for synthesizing zeolites having a hierarchical nanoporous structure, unlike conventional zeolites, and must possess at least two ammonium functional groups within its structure; depending on the number of these groups, the thickness of the resulting zeolite crystalline framework can be increased. Furthermore, by varying the number of ammonium functional groups of the surfactant, the type and length of the hydrocarbon chain, etc., micropores and mesopores having various structures and arrangements can be generated.

[0081] In the step of synthesizing borosilicate zeolite by proceeding with hydrothermal synthesis using the above solution, the organic-inorganic composite gel produced in the previous step is converted into borosilicate zeolite through a crystallization process induced by high temperature and high pressure steam, and the synthesized borosilicate zeolite can be obtained by filtration or centrifugation.

[0082] In the step of calcining the synthesized borosilicate zeolite at a temperature of 450°C to 650°C under an oxygen (O2) atmosphere, organic substances such as structure-inducing surfactants may be removed, and covalent bonds within the zeolite framework may be formed and rearranged, thereby increasing the density of the structure.

[0084] According to one embodiment, the step of synthesizing a zeolite carrier by removing boron (B) from the borosilicate zeolite may include the step of mixing the borosilicate zeolite and a nitric acid solution; the step of heating the mixed solution to remove boron from the borosilicate zeolite; and the step of obtaining a zeolite carrier from which boron has been removed.

[0085] In the step of mixing the borosilicate zeolite and the nitric acid solution, the nitric acid solution may be an aqueous solution having a concentration of 0.5 M to 0.2 M, and may be used in an amount of 20 to 100 ml relative to 1 g of borosilicate zeolite, and may be appropriately selected and used within the temperature and volume ranges to remove all boron from the borosilicate zeolite.

[0086] In the step of removing boron from the borosilicate zeolite by heating the mixed solution, the solution may be heated at a temperature range of 40 to 80°C for 3 to 12 hours, and similarly, a value within the temperature and time range that can remove all the boron from the borosilicate zeolite may be appropriately selected and used. The zeolite carrier prepared by removing boron as described above may be a silicate containing silanol groups (Si-OH) at the sites where boron was removed.

[0088] According to one embodiment, the step of supporting tin (Sn) metal on the zeolite carrier may include: a step of dehydrating the zeolite carrier by heating it under vacuum conditions; a step of synthesizing a tin-supported zeolite by introducing a tin (Sn) precursor into the dehydrated zeolite carrier; and a step of calcining the tin (Sn)-supported zeolite at a temperature of 450°C to 650°C under an oxygen (O2) atmosphere.

[0089] In the step of dehydrating the boron-removed zeolite carrier by heating it under vacuum conditions, the zeolite carrier may be heated under vacuum conditions at a temperature range of 300 to 500 ℃ for 3 to 12 hours, and in this process, water molecules physically adsorbed in the micropores and mesopores of the zeolite carrier may be removed.

[0090] According to one embodiment, the step of synthesizing a tin-supported zeolite by introducing a tin (Sn) precursor into the dehydrated zeolite carrier may include introducing the tin precursor into the dehydrated zeolite carrier by chemical vapor deposition (CVD). Specifically, the tin precursor may have any phase, such as solid, liquid, or gas; however, if the tin precursor is solid, the zeolite carrier and the tin precursor are first sufficiently and evenly mixed in a solid state to prepare a mixture, and then the mixture is heated under vacuum conditions at a temperature of 300°C to 500°C to bring the tin precursor, which has been converted into a gaseous phase, into contact with the silanol groups of the zeolite carrier, thereby synthesizing a tin (Sn)-supported zeolite.

[0091] According to one embodiment, the tin (Sn) precursor may include one or more of dimethyltin dichloride, trimethyltin chloride, tetramethyltin, butyltin trichloride, butyltin chloride dihydroxide, tributyltin chloride, tetrabutyltin, diphenyltin dichloride, tin dichloride, tin tetrachloride, and tin oxalate, and preferably may include dimethyltin dichloride.

[0093] The present invention will be explained in more detail below through examples. The following examples are described for the purpose of illustrating the present invention and do not limit the scope of the present invention.

[0095] - Preparation Example: Preparation of a catalyst for the Bayer-Williger oxidation reaction

[0096] <Example 1>

[0097] (1) Preparation of hierarchical nanoporous borosilicate zeolite (B-MFI-ns)

[0098] [C 18 H 37 -N + (CH3)2-C6H 12 -N + (CH3)2-C 6 H 13 ][Br - ]2 was added, tetraorthosilicate as a Si source, boric acid as a B source, and sodium hydroxide as a Na source, and then sulfuric acid and water were added and mixed to form a gel having a composition of '100 SiO2 / 3.3 B(OH)3 / 7.5 SDS / 30 Na2O / 18 H2SO4 / 5000 H2O (molar ratio)'. The formed gel was placed in an autoclave and hydrothermal synthesis was carried out at 150 °C for 46 hours, and the synthesized borosilicate zeolite was obtained in the form of powder through a series of processes including 'washing with distilled water - filtering - drying'. Finally, the obtained borosilicate zeolite was calcined at a temperature of 550 °C under an oxygen (O2) atmosphere to produce and obtain a final borosilicate zeolite (crystal structure: MFI), which was named 'B-MFI-ns'.

[0099] (2) Preparation of boron-removed hierarchical nanoporous silicate (deB-MFI-ns)

[0100] The borosilicate zeolite (B-MFI-ns) prepared above was added to a 0.1 M nitric acid (HNO3) aqueous solution and mixed at 60°C for 6 hours. The sample, after nitric acid treatment was completed, was obtained in the form of a powder through a series of processes including 'washing with distilled water - filtering - drying'. The process of nitric acid treatment and drying was repeated two more times to prepare and obtain a hierarchical nanoporous zeolite carrier (silicate) from which boron had been removed, and this was named 'deB-MFI-ns'.

[0101] (3) Preparation of a catalyst for the Bayer-Billiger oxidation reaction containing tin (Sn)

[0102] The above boron-removed hierarchical nanoporous zeolite carrier (deB-MFI-ns) was subjected to a dehydration process at 400 °C for 6 hours under vacuum conditions. The dehydrated sample was then mixed with dimethyltin dichloride in a solid state to achieve a Si / Sn ratio of 200. The mixture was placed in a reactor and heat-treated at 550 °C for 6 hours under vacuum conditions. The heat-treated sample was calcined at 550 °C under an oxygen (O2) atmosphere to finally prepare and obtain a catalyst for the Bayer-Williger oxidation reaction, which was named 'Sn-MFI-ns-200'. (Note: The number following Sn-MFI-ns was named based on the Si / Sn ratio derived from the ICP-AES results of Experimental Example 1 below.)

[0104] <Example 2>

[0105] of Example 1 above '(3) Preparation of a catalyst for the Bayer-Billiger oxidation reaction containing tin (Sn)' In this example, a catalyst for the Bayer-Billiger oxidation reaction was prepared and obtained in the same manner as in Example 1, except that the dehydrated sample and dimethyltin dichloride were mixed in a solid state so that the Si / Sn ratio was 120, and this was named 'Sn-MFI-ns-120'.

[0107] <Example 3>

[0108] of Example 1 above '(3) Preparation of a catalyst for the Bayer-Billiger oxidation reaction containing tin (Sn)' In this example, a catalyst for the Bayer-Billiger oxidation reaction was prepared and obtained in the same manner as in Example 1, except that the dehydrated sample and dimethyltin dichloride were mixed in a solid state so that the Si / Sn ratio was 70, and this was named 'Sn-MFI-ns-60'.

[0110] <Example 4>

[0111] of Example 1 above '(3) Preparation of a catalyst for the Bayer-Billiger oxidation reaction containing tin (Sn)' In this example, a catalyst for the Bayer-Billiger oxidation reaction was prepared and obtained in the same manner as in Example 1, except that the dehydrated sample and dimethyltin dichloride were mixed in a solid state so that the Si / Sn ratio was 30, and this was named 'Sn-MFI-ns-30'.

[0113] <Comparative Example 1>

[0114] SnCl4·5H2O was added as a Sn source and tetraethyl orthosilicate as a Si source, and tetra-n-propyl ammonium hydroxide (TPAOH) and distilled water were added and mixed to form a gel having a composition of '0.03 SnO2 / 1 SiO2 / 0.45 TPAOH / 35 H2O'. The formed gel was placed in an autoclave and hydrothermal synthesis was carried out at 150 °C for 48 hours to synthesize a microporous zeolite, and the synthesized zeolite was obtained in the form of powder through a series of processes including 'washing with distilled water - filtering - drying'. The obtained zeolite was calcined at a temperature of 480 °C for 10 hours under an oxygen (O2) atmosphere to finally produce and obtain a tin (Sn) containing microporous zeolite (crystal structure: MFI), which was named 'Sn-bulk-MFI'.

[0116] <Comparative Example 2>

[0117] Fumed silica was added as a Si source and tetramethylammonium hydroxide (TMAOH) was added and mixed, then SnCl4·5H2O was added as a Sn source, and distilled water and hexadecyltrimethylammonium bromide (CTABR) were added and mixed to form a gel having a composition of '1 SiO2 / 0.01 SnCl4 / 0.24 CTABR / 0.3 TMAOH / 25 H2O'. The formed gel was placed in an autoclave and hydrothermal synthesis was carried out at 90°C for 72 hours, and subsequently, the synthesized mesoporous silica was obtained in the form of powder through a series of processes including 'washing with distilled water - filtering - drying'. The obtained sample was calcined at a temperature of 480°C for 10 hours under an oxygen (O2) atmosphere to finally produce and obtain a tin (Sn) containing mesoporous silica (MCM-41 structure), which was named 'Sn-MCM-41'.

[0119] - Experimental Example 1: Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) Analysis

[0120] For the catalyst samples of the examples and comparative examples according to the above manufacturing example, ICP-AES analysis was performed to measure the Si / Sn ratio, and the results are shown in Table 1 below.

[0121] Sample name Si / Sn ratio Example 1 Sn-MFI-ns-200 200 Example 2 Sn-MFI-ns-120 120 Example 3 Sn-MFI-ns-60 63 Example 4 Sn-MFI-ns-30 27 Comparative Example 1 Sn-bulk-MFI 33 Comparative Example 2 Sn-MCM-41 55

[0123] Looking at Table 1 above, it was confirmed that tin (Sn) was included in all catalysts of the examples and comparative examples, and in particular, for the catalysts of Examples 1 to 4, it was confirmed that as the Si / Sn ratio of the material added during the manufacturing process decreased, the Si / Sn ratio of the manufactured catalyst also decreased in proportion.

[0125] - Experimental Example 2: X-ray diffraction (XRD) analysis

[0126] XRD patterns were collected for the catalysts of the Examples and Comparative Examples, along with the 'B-MFI-ns' and 'deB-MFI-ns' materials generated during the catalyst synthesis of the Examples among the above preparation examples, using a Rigaku Multiflex diffractometer in the range of 2θ = 5° to 40° under Cu-Kα line conditions. Among these, the XRD patterns for the 'B-MFI-ns' and 'deB-MFI-ns' materials and the catalysts of Examples 1 to 4 are shown as in FIG. 1, and the XRD patterns for Comparative Examples 1 and 2 are shown as in FIG. 2.

[0128] First, since all XRD patterns in Fig. 1 contain peaks corresponding to the MFI crystal structure, it was confirmed that a zeolite material having an overall MFI structure was successfully synthesized. Additionally, the absence of a broad peak in the 2θ = 20°–30° range confirmed that amorphous silica was not synthesized separately. Furthermore, the lack of significant changes in the XRD pattern peaks before and after boron removal or tin loading confirmed that the crystal structure remained intact and well-maintained despite high-temperature treatment during the synthesis process.

[0129] And looking at Fig. 2(a), the XRD pattern of Comparative Example 1 has a peak corresponding to the MFI crystal structure, so it was confirmed that Comparative Example 1 is also a material having an MFI zeolite structure. Meanwhile, judging from the fact that the XRD peak of Fig. 1 is much broader (i.e., has a larger full width at half maximum) than the XRD peak of Fig. 2(a), it was found that while the catalysts of Examples 1 to 4 consist of very small zeolite crystals, Comparative Example 1 consists of relatively much larger bulk zeolite.

[0130] Finally, looking at Fig. 2(b), the XRD pattern for Comparative Example 2 contains not only peaks in the 2θ < 5° range derived from the regular arrangement of mesopores according to the MCM-41 structure, but also broad peaks in the 2θ = 20° to 30° range appearing from the amorphous silica walls of the mesopores, indicating that the MCM-41 material was successfully synthesized.

[0132] - Experimental Example 3: Shape observation using electron microscopy and Energy dispersive X-ray spectroscopy (EDS) analysis

[0133] Scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) images were taken and observed for the catalyst samples (Sn-MFI-ns-200 and 30) of Examples 1 and 4, along with the 'B-MFI-ns' and 'deB-MFI-ns' samples generated during the catalyst synthesis of the above manufacturing examples. For the catalyst samples (Sn-MFI-ns-200 and 30) of Examples 1 and 4, EDS analysis was performed on the regions in the STEM images where tin (Sn) particles were presumed to be present. The results of the SEM, STEM images, and EDS analysis are shown in Figure 3.

[0135] First, looking at the SEM and STEM images ((a) to (h)) of each sample in Fig. 3, it can be seen that zeolite crystals with a thickness of about 10 nm or less are randomly arranged to form mesopores, and from this, it was directly confirmed that zeolite having a hierarchical nanoporous structure (or nanosponge structure) was successfully synthesized. In addition, as with the XRD pattern analysis results of Experimental Example 2 above, it was also confirmed that the zeolite crystals did not collapse throughout the synthesis process and the hierarchical nanoporous structure was well maintained.

[0136] In addition, when examining the STEM images ((g) and (h)) of the catalysts of Examples 1 and 4, unlike the STEM images ((e) and (f)) of the 'B-MFI-ns' and 'deB-MFI-ns' samples, it can be seen that bright spots smaller than 1 nm are evenly dispersed, and through EDS analysis of the corresponding region, it was found that these bright spots correspond to tin (Sn). That is, from the STEM and EDS analyses, it was confirmed that not only the catalyst of Example 1 (Sn-MFI-ns-200), but also the catalyst of Example 4 (Sn-MFI-ns-30), which has the highest Sn content relative to Si, contains very fine tin particles smaller than 1 nm or at the atomic level evenly.

[0138] - Experimental Example 4: Nitrogen gas adsorption method (Nitrogen(N 2 ) gas adsorption) analysis

[0139] Along with the 'B-MFI-ns' and 'deB-MFI-ns' samples generated during the catalyst synthesis of the example among the above preparation examples, nitrogen gas adsorption was performed on the catalyst materials of the examples and comparative examples using a Micromeritics TriStar 3000 volumetric adsorption analyzer at a temperature of 77 K to obtain adsorption isotherms, and from this, the BET specific surface area (S BET ), external specific surface area (S ext ) and total pore volume (V tot The value was calculated.

[0140] Specifically, the BET specific surface area was calculated from the adsorption amount in the range where the relative pressure (P / P0) of the adsorption isotherm was 0.05 to 0.20, the external specific surface area was calculated from the adsorption isotherm using the t-plot method, and the total pore volume was calculated based on the adsorption amount at the point where the relative pressure of the adsorption isotherm was 0.95, and the results are shown in Table 2 below.

[0141] In addition, for 'B-MFI-ns (Reference Example 1 below)', 'deB-MFI-ns (Reference Example 2 below)', and the catalyst materials of Examples 1 to 4, a pore size distribution (PSD) calculated based on the Barrett-Joyner-Halenda (BJH) algorithm from the adsorption isotherms was obtained and shown as in Figure 4.

[0142] Sample name S BET (m 2 / g) S ext (m 2 / g) V tot (cm 3 / g) Reference Example 1 B-MFI-ns 670 480 0.65 Reference Example 2 deB-MFI-ns 640 450 0.65 Example 1 Sn-MFI-ns-200 640 470 0.72 Example 2 Sn-MFI-ns-120 630 460 0.70 Example 3 Sn-MFI-ns-60 630 450 0.66 Example 4 Sn-MFI-ns-30 630 470 0.65 Comparative Example 1 Sn-bulk-MFI 300 20 0.14 Comparative Example 2 Sn-MCM-41 1,435 1,015 1.04

[0144] Looking at Table 2 above, it was confirmed that the catalyst materials from Reference Example 1 (B-MFI-ns) and Reference Example 2 (deB-MFI-ns) to Examples 1 to 4 (Sn-MFI-ns series) not only have a large BET specific surface area and external specific surface area derived from zeolite nanocrystals and their micropores, but also have a large pore volume derived from the micropores and mesopores. In addition, from the pore size distribution in Figure 4, the reference and example materials all possess mesopores of 2 nm to 10 nm, and as confirmed by the SEM and STEM images of Experimental Example 3, they all appear to have a hierarchical nanoporous structure.

[0145] In addition, as the reference example and example materials maintained the specific surface area and pore volume of Table 1 as well as the shape of the pore size distribution in Figure 4 almost consistently, it was confirmed once again that the unique hierarchical nanoporous structure of the material was hardly destroyed throughout the synthesis process.

[0147] - Experimental Example 5: Solid-state nuclear magnetic resonance (NMR) spectroscopy analysis

[0148] (1) 11 B-Solid state NMR analysis

[0149] With respect to the 'B-MFI-ns' and 'deB-MFI-ns' materials generated during the catalyst synthesis of the examples among the above manufacturing examples,11 B-Solid state NMR analysis was performed, and the spectra of the results are shown in Figure 5.

[0151] Looking at Figure 5, it was observed that in the B-MFI-ns material, a single peak (Chemical shift = -3.3 ppm) corresponding to boron connected in a tetrahedral structure was observed, whereas in the deB-MFI-ns material that underwent a boron removal step, the corresponding peak was hardly observed. Therefore, it was found that the boron in the borosilicate zeolite could be almost completely removed from the boron removal step according to the above preparation example.

[0153] (2) 29 Si-Solid State NMR Analysis

[0154] With respect to the catalyst materials of Examples 1 to 4, together with the 'B-MFI-ns' and 'deB-MFI-ns' materials generated during the catalyst synthesis of the examples among the above manufacturing examples, 29 Si-Solid state NMR analysis was performed, and the spectra of the results are shown in Figure 6. For reference, in the spectra above, Q3 (Chemical shift = -107 ppm) is the peak for the central Si of the Si(OSi)3OH unit, and Q4 (Chemical shift = -117 ppm) is the peak for the central Si of the Si(OSi)4 unit.

[0156] Looking at Figure 6, first of all, it can be seen that the 'ratio of Q3 peak intensity to Q4 peak intensity' of the deB-MFI-ns material increased significantly compared to the B-MFI-ns material. From this, it was found that through the boron removal process of the above preparation example, boron was removed and at the same time, a large number of silanol (Si-OH) groups were generated.

[0157] In addition, considering that the 'ratio of Q3 peak intensity to Q4 peak intensity' of the Sn-MFI-ns series materials of Examples 1 to 4 decreased again compared to the deB-MFI-ns material, it could be inferred that the silanol group was reduced as tin (Sn) particles were introduced into the silanol group portion while the silanol group interacted with the tin precursor. Furthermore, considering that the 'ratio of Q3 peak intensity to Q4 peak intensity' of Examples 1 to 3, which have relatively less tin than Example 4, was similar to that of Example 4, it could also be inferred that the silanol group not used for the introduction of tin particles was converted back into an oxygen linkage (Si-O-Si) during the heat treatment process.

[0158] When these analysis results are combined with the STEM and EDS analysis results of Experimental Example 3 above, it can be inferred that tin particles of 1 nm or smaller or atomic level could be evenly distributed throughout the zeolite carrier due to the generation of silanol groups according to the post-synthetic method of 'boron removal and Sn introduction' of the above preparation example, and through this, a catalyst with a lower Si / Sn ratio than conventional catalysts could be synthesized.

[0160] (3) Due to the adsorption of trimethylphosphine oxide (TMPO) 31 P-Solid state NMR analysis

[0161] Dehydration was performed on the catalyst materials of Examples 1 to 4, along with the 'B-MFI-ns' and 'deB-MFI-ns' substances generated during the catalyst synthesis of the examples among the above preparation examples, at a temperature of 550 °C for 6 hours under vacuum conditions. After dehydration, the materials were mixed with TMPO in a glove box to proceed with TMPO adsorption, and heat-treated at a temperature of 150 °C for 2 hours to induce uniform adsorption of TMPO. Regarding the materials adsorbed with TMPO 31 P-Solid state NMR analysis was performed, and the spectra of the results are shown in Figure 7.

[0163] First, looking at the spectrum for B-MFI-ns in Fig. 7, it can be seen that peaks corresponding to TMPO adsorbed on strong Brønsted acid sites (Chemical shift = 84 ppm, 71 ppm) and peaks corresponding to TMPO adsorbed on weak Brønsted acid sites and Lewis acid sites (Chemical shift = 60 ppm) are observed (Note: The peak with a Chemical shift of 48 ppm corresponds to physically adsorbed TMPO), which can be seen as originating from the boron of the material.

[0164] On the other hand, examining the spectrum for deB-MFI-ns, it can be observed that the peaks corresponding to Brønsted and Lewis acid sites originating from boron decreased sharply as the boron removal step was performed.

[0165] Meanwhile, examining the spectra for the Sn-MFI-ns series (Examples 1 to 4), it can be observed that the peak corresponding to the Lewis acid site (Chemical shift = 60 ppm) increased again with the introduction of tin, and the 'Lewis acid site content due to tin per unit mass of catalyst (LA)' calculated from the corresponding peak tot )' was summarized and presented as shown in Table 3 below.

[0166] Sample name LA tot (μmol / g) Example 1 Sn-MFI-ns-200 13 Example 2 Sn-MFI-ns-120 41 Example 3 Sn-MFI-ns-60 86 Example 4 Sn-MFI-ns-30 130

[0168] From the results of Table 3 above, it was confirmed that as the Si / Sn ratio of the raw material input during the manufacture of the Sn-MFI-ns series decreased, the Lewis acid site content due to tin also increased proportionally, and it was found that this corresponded to the result derived from the ICP-EAS analysis of Experimental Example 1 above.

[0170] - Experimental Example 6: Evaluation of Catalytic Activity of 2-Adamatanone for the Baeyer-Villiger Oxidation Reaction

[0171] For 50 mg of the catalyst of the example and comparative example according to the above preparation example, 2 mmol of 2-adamantanone, 2 mmol of hydrogen peroxide (H2O2), and 6 ml of 1,4-dioxane solvent were introduced into a reactor, and a Bayer-Billiger oxidation reaction was carried out at 80 °C. Then, a portion of the reaction solution was collected at regular intervals, and the components of the reaction solution were analyzed by gas chromatography.

[0172] The conversion rate and selectivity after 3 hours, along with the turnover frequency per unit mass of catalysts after 1 hour, were calculated and presented as shown in Table 4 below, and the conversion rate graph over time was shown as shown in Figure 8.

[0173] Sample name Conversion rate (%) Selectivity (%) Conversion frequency (mmol / g cat ·h) Example 1 Sn-MFI-ns-200 10.0 >99 2 Example 2 Sn-MFI-ns-120 12.5 >99 2.4 Example 3 Sn-MFI-ns-60 15.0 >99 3.2 Example 4 Sn-MFI-ns-30 33.0 >99 6.8 Comparative Example 1 Sn-bulk-MFI 0.0 - - Comparative Example 2 Sn-MCM-41 39.0 >99 8.2

[0175] 2-adamanthanone, used as a reactant in the above oxidation reaction, has the molecular structure of Chemical Formula 2 below and is known to have a volume that is difficult to pass through the micropores of typical MFI zeolites:

[0176] [Chemical Formula 2]

[0177]

[0178] Accordingly, the conversion rate of the catalyst in Comparative Example 1 (Sn-bulk-MFI), in which a significant amount of tin particles are distributed in the micropores, was found to be 0% after 3 hours, and as shown in the graph of Fig. 8(b), the conversion rate did not exceed 10% even after approximately 48 hours had elapsed. In other words, this can be interpreted to mean that general microporous zeolite-based catalysts are unsuitable for the oxidation reaction of bulky organic materials.

[0179] On the other hand, the catalysts of Examples 1 to 4 (Sn-MFI-ns series), which have a hierarchical nanoporous structure, were found to exhibit a relatively higher conversion rate compared to Comparative Example 1, as shown in the results of Table 4, due to tin particles distributed on the surface of numerous nano-sized zeolite crystals or on the walls of mesopores. It was also confirmed that the conversion rate increases proportionally as the Si / Sn ratio decreases (i.e., as the Sn content relative to Si increases), and this fact was also confirmed in the conversion rate graph over time in Figure 8(a). In particular, Example 4 (Sn-MFI-ns-30), which has the lowest Si / Sn ratio among the catalysts of Examples 1 to 4, reached a conversion rate of 100% most quickly in about 24 hours, exhibiting the best catalytic performance among the examples, thereby directly confirming the effect of the amount of acid sites on catalytic performance. In addition, since the tin particles act as Lewis acid sites rather than Brønsted acid sites, almost no side reactions occur in the Bayer-Williger oxidation reaction, and it was confirmed from the results in Table 4 that the catalysts of Examples 1 to 4 all exhibit a selectivity of 99% or higher.

[0180] Meanwhile, according to the graph in Table 4 and Figure 8(b) above, it can be confirmed that the catalyst of Example 4 (Sn-MFI-ns-30) exhibits performance that is nearly comparable to, but slightly inferior to, the catalytic performance of Comparative Example 2 (Sn-MCM-41). In this regard, according to the ICP-AES results of Experimental Example 1 above, the Si / Sn ratio of Example 4 is 27, whereas the Si / Sn ratio of Comparative Example 2 is 55, indicating that the 'Sn content relative to Si' of Example 4 is higher than that of Comparative Example 2. However, while Comparative Example 2 consists of mesoporous silica with amorphous silica walls and almost no micropores, Example 4 has a hierarchical nanoporous structure containing a significantly high proportion of micropores; thus, it is presumed that the tin contained within the micropores could not come into contact with the 2-adamanthanone, and accordingly, it is interpreted that the catalytic performance of Example 4 is slightly inferior to that of Comparative Example 2. Therefore, if an oxidation reaction is carried out on organic matter capable of passing through micropores, it can be inferred that, unlike the above results, the performance of the hierarchical nanoporous zeolite-based catalyst may be higher than that of the mesoporous silica-based catalyst.

[0182] - Experimental Example 7: Evaluation of Thermal Stability of Catalyst

[0183] For the catalysts of Example 4 (Sn-MFI-ns-30) and Comparative Example 2 (Sn-MCM-41), Bayer-Billiger oxidation reactions were carried out for 20 hours at temperatures of 600 °C, 800 °C, and 1000 °C, respectively, under conditions identical to the reactant composition of Experimental Example 8. Subsequently, the reaction solution was collected and analyzed by gas chromatography to measure the conversion rate, and the resulting graph is shown in Fig. 9.

[0185] Looking at the graph in Fig. 9, it was found that at 600 ℃, the catalyst of Comparative Example 2 (Sn-MCM-41) had a higher conversion rate than the catalyst of Example 4 (Sn-MFI-ns-30), but as the temperature increased to 800 ℃ and 1,000 ℃, it was confirmed that the decrease in conversion rate of the catalyst of Example 4 with respect to temperature was much smaller compared to the catalyst of Comparative Example 2.

[0186] This can be seen as a result of the superior thermal stability compared to the amorphous silica, as the zeolite constituting the mesopores of the catalyst in Example 4 has crystallinity, whereas the walls constituting the mesopores of the catalyst in Comparative Example 2 are amorphous silica. Therefore, it can be seen that the catalyst based on a hierarchical nanoporous zeolite support, such as in Example 4, is superior to the mesoporous silica-based catalyst in Comparative Example 2 in terms of long-term durability, especially in actual catalyst processes conducted under high-temperature environments for extended periods.

[0188] Although the embodiments have been described above with reference to limited drawings, those skilled in the art can apply various technical modifications and variations based on the above. For example, suitable results can be achieved even if the described techniques are performed in a different order than the described method, and / or the described components are combined or assembled in a form different from the described method, or are replaced or substituted by other components or equivalents.

[0189] Therefore, other implementations, other embodiments, and equivalents to the claims also fall within the scope of the claims set forth below.

Claims

Claim 1 A catalyst for a Baeyer-Villiger oxidation reaction comprising: a zeolite carrier having a hierarchical nanoporous structure including micropores and mesopores; and tin (Sn), wherein the average diameter of the micropores is less than 2 nm, the average diameter of the mesopores is 2 nm to 10 nm, and the Si / Sn ratio is 20 to 120. Claim 2 In claim 1, the zeolite carrier is a catalyst for a Bayer-Billiger oxidation reaction having one or more crystal structures of MFI, BEA, MRE, and MTW. Claim 3 A catalyst for a Bayer-Billiger oxidation reaction according to claim 1, wherein the tin (Sn) comprises having a size of 1 nm or less. Claim 4 In claim 1, the catalyst for the Bayer-Billiger oxidation reaction has a BET specific surface area of ​​400 m² 2 / g to 800 m 2 / g, and the external specific surface area is 200 m² 2 / g to 600 m 2 / g phosphorus, catalyst for Bayer-Billiger oxidation reaction. Claim 5 In claim 1, the catalyst for the Bayer-Williger oxidation reaction has a total pore volume of 0.1 cm² 3 / g to 1.0 cm 3 / g phosphorus, catalyst for Bayer-Billiger oxidation reaction. Claim 6 In claim 1, the catalyst for the Bayer-Billiger oxidation reaction has a Lewis acid site content of tin (Sn) of 20 μmol / g to 150 μmol / g, and the Lewis acid site content of tin (Sn) is due to trimethylphosphine (TMPO) adsorption. 31 P-solid state nuclear magnetic resonance spectroscopy ( 31 Catalyst for Bayer-Billiger oxidation reaction, measured by p-solid-state nuclear magnetic resonance spectroscopy. Claim 7 A method for preparing a catalyst for a Bayer-Williger oxidation reaction, comprising the steps of: synthesizing a borosilicate zeolite having a hierarchical nanoporous structure; synthesizing a zeolite carrier by removing boron (B) from the borosilicate zeolite; and supporting a tin (Sn) metal on the zeolite carrier. Claim 8 A method for preparing a catalyst for a Bayer-Billiger oxidation reaction according to claim 7, wherein the step of synthesizing a borosilicate zeolite having a hierarchical nanoporous structure comprises: mixing a solution containing a structure directing surfactant (SDS), a silicon (Si) precursor, and a boron (B) precursor; synthesizing a borosilicate zeolite by carrying out hydrothermal synthesis with the solution; and calcining the synthesized borosilicate zeolite at a temperature of 450 ℃ to 650 ℃ under an oxygen (O2) atmosphere. Claim 9 In claim 8, the structure-directing surfactant (SDS) is a method for preparing a catalyst for a Bayer-Billiger oxidation reaction having the structure of the following chemical formula 1: [Chemical Formula 1] (In the above Chemical Formula 1, R1 and R3 are each an alkyl group having 3 to 25 carbon atoms, R2 is an alkylene group having 2 to 10 carbon atoms or an arylene group having 6 to 10 carbon atoms, and n is one of an integer from 1 to 10.) Claim 10 A method for preparing a catalyst for a Bayer-Billiger oxidation reaction, wherein, in claim 7, the step of synthesizing a zeolite carrier by removing boron (B) from the borosilicate zeolite comprises: mixing the borosilicate zeolite and a nitric acid solution; heating the mixed solution to remove boron from the borosilicate zeolite; and obtaining a zeolite carrier from which boron has been removed. Claim 11 A method for manufacturing a catalyst for a Bayer-Williger oxidation reaction according to claim 7, wherein the step of supporting tin (Sn) metal on the zeolite carrier comprises: a step of dehydrating the zeolite carrier by heating it under vacuum conditions; a step of synthesizing a tin-supported zeolite by introducing a tin (Sn) precursor into the dehydrated zeolite carrier; and a step of calcining the tin (Sn)-supported zeolite at a temperature of 450 ℃ to 650 ℃ under an oxygen (O2) atmosphere. Claim 12 A method for manufacturing a catalyst for a Bayer-Billiger oxidation reaction, wherein, in claim 11, the step of synthesizing a tin-supported zeolite by introducing a tin (Sn) precursor into the dehydrated zeolite carrier comprises introducing the tin precursor into the dehydrated zeolite carrier by chemical vapor deposition (CVD). Claim 13 A method for preparing a catalyst for a Bayer-Billiger oxidation reaction according to claim 12, wherein the tin (Sn) precursor comprises one or more of dimethyltin dichloride, trimethyltin chloride, tetramethyltin, butyltin trichloride, butyltin chloride dihydroxide, tributyltin chloride, tetrabutyltin, diphenyltin dichloride, tin dichloride, tin tetrachloride, and tin oxalate.

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