KR20230054174A - Manufacturing method of 2 dimensional mww type zeolite catalyst for conversion reaction of glucose and 2 dimensional mww type zeolite catalyst manufactured by the method - Google Patents

Abstract

A two-dimensional (2D) molecular sieve with highly dispersed active centers has great potential as a catalyst for the conversion of bulky biomass derivatives due to the ease of molecular diffusion and resistance to deactivation by coke deposition. The present invention relates to a single-step preparation method of 2D Lewis acid zincosilicate delaminated MWW layer (Zn-DML) and Lewis-Brønsted acid ZnAl-DML catalyst by using simple hydrothermal treatment of a borosilicate MWW precursor using Zn and/or Al precursor solutions. While both framework Zn and ultra-small Zn clusters are highly distributed in the Zn-DML, framework Al species dominates Zn in the ZnAl-DML catalyst. The Zn-DML catalyst exfoliates more than the ZnAl-DML catalyst. Density functional theory calculations show that heteroatom-substituted 2D MWW layers are stabler than 3D analogues thereof and the Al-containing system is stabler than Zn. While the Lewis acid Zn-DML was selective to fructose, the Lewis-Brønsted acid ZnAl-DML catalyst was selective to 5-hydroxymethylfurfural (5-HMF) in the conversion of glucose as a catalyst.

Description

Manufacturing method of two-dimensional MWW-based zeolite catalyst for glucose conversion reaction and catalyst prepared thereby

The present invention provides a method for preparing a two-dimensional MWW-based zeolite catalyst for glucose conversion reaction prepared from a 3D borosilicate MWW precursor through a simple single-step hydrothermal synthesis method using only a M(NO ₃ ) _x (M = Zn and/or Al) precursor solution, and It relates to a catalyst prepared accordingly.

Utilizing biomass-derived resources as chemical feedstocks is essential for humankind for sustainable development because of their renewable nature and carbon neutrality. Carbohydrates are the most abundant, accounting for about 75% of the total amount of biomass, and are produced from carbon dioxide and water through photosynthesis.

The U.S. Department of Energy (DOE) lists ethanol, furfural, 5-hydroxymethylfurfural (HMF), 2,5-furandicarboxylic acid (FDCA), glycerol, isoprene, succinic acid, 3-hydroxypropionic acid/aldehyde, We designated the most plausible platform chemicals from the biorefining of carbohydrates, including levulinic acid, lactic acid, sorbitol and xylitol.

Among them, 2,5-furandicarboxylic acid (FDCA) is used as a raw material for biomass-based polyethylene furandicarboxylic acid (PEF), which is a potential substitute for mass-produced petroleum-derived polyethylene terephthalate (PET). This is especially important. Generally, FDCA is produced by oxidation of HMF, and HMF production cost is the most expensive process among all processes.

Therefore, various catalytic approaches have been attempted to selectively produce HMF from carbohydrates such as glucose and fructose. Because of its natural abundance and low cost, glucose is more advantageous than fructose as a raw material for HMF production.

The production of HMF from glucose proceeds through a two-step cascade reaction, each involving the isomerization of glucose to fructose and a series of dehydrations of fructose to HMF via Lewis and Bronsted acids, respectively. Thus, the balance of Lewis and Bronsted acidity in the catalyst is a critical factor determining the selectivity of fructose and/or HMF. Many types of catalysts, such as metal oxides, zeolites, mesoporous silica, and heteropolyacids, have been studied for the conversion of glucose.

Zhang et al. reported an HMF yield of about 40% for a balanced ZrO ₂ catalyst of Lewis and Bronsted acid sites obtained by optimizing the calcination temperature. Yan et al. also reported an HMF yield of about 48% by introducing SO ₄ ^2- ions into ZrO ₂ -Al ₂ O ₃ . Chung et al showed a high yield (50%) of HMF by introducing a bi-functional Cu-Cr/ZSM-5 zeolite catalyst (framework type MFI), and Hu et al. reported H-beta zeolite (*BEA) with excellent HMF yield (about 50%) compared to other zeolite catalysts (FAU, MOR and MFI). Mesoporous silica (Sn-MCM-41) containing framework Sn atoms was synthesized as a bifunctional heterogeneous catalyst for glucose conversion and yields of up to 70% HMF were obtained at 110 °C.

Zeolites are an attractive class of catalysts because of their excellent hydrothermal stability, unique texture and acidic properties, and diverse framework structures. By controlling the acidic nature of zeolites, such as Bronsted and Lewis acidity, these materials can be used as catalysts in a variety of ways.

In general, this can be achieved by controlling the framework/additional framework Al species by dealumination and successive heterotypic substitutions of heteroatoms (eg Sn, Ti and Zn) at tetrahedral framework positions. However, the use of zeolites for the conversion of bulky biomass molecules is limited due to their inherent microporosity. Exfoliation of a three-dimensional (3D) layer of zeolite precursors to a 2D zeolite layer with a large external surface area is one of the efficient ways to alleviate the limitations of use due to steric hindrance.

A representative 2D MWW layered ITQ-2 can be readily prepared from a 3D precursor (i.e., MCM-22(P)) following well-established procedures reported in the literature. However, this process is difficult to apply in practice because it involves complex synthesis steps, namely expansion of the MWW layer by surfactant, layer destruction by sonication, and surface hydroxyl stabilization by hydrochloric acid treatment.

Korean Patent Registration No. 10-2035397

In order to solve the above problems, the present invention provides a glucose conversion reaction prepared through a simple single-step hydrothermal synthesis method using only a M(NO ₃ ) _x (M = Zn and/or Al) precursor solution from a 3D borosilicate MWW precursor. It relates to a method for preparing a two-dimensional MWW-based zeolite catalyst and a catalyst prepared thereby.

In the present invention, Lewis acidic zincosilicate (Zn-DML), Bronsted acidic aluminosilicate (Al-DML), and Lewis-Brønsted acidic zincoaluminosilicate exfoliated MWW layer (ZnAl-DML) are 3D borosilicate It was prepared from the MWW precursor through a simple one-step hydrothermal synthesis using only the M(NO ₃ ) _x (M = Zn and/or Al) precursor solution (B-MWW(P)).

The existence of the framework Zn and Al species was confirmed through various analytical tools such as UV diffuse reflectance spectroscopy (DRS), structural IR and ²⁹ Si MAS NMR spectroscopy.

The relative amounts of Lewis and Bronsted acid sites in the catalyst were characterized by IR spectroscopy with pyridine adsorption.

The preferential replacement of framework B by Al over Zn and the easier formation of 2D MWW layers rather than 3D structures was demonstrated by density functional theory (DFT) calculations.

Then, Zn-DML, Al-DML and ZnAl-DML catalysts were used to convert glucose to fructose and HMF.

Specifically, preparing a borosilicate MWW-based zeolite precursor according to an embodiment of the present invention; and contacting the borosilicate MWW-based zeolite precursor with a M(NO ₃ ) _x (M = Zn and Al) precursor solution and subjecting the precursor to hydrothermal treatment; Including, characterized in that the borosilicate MWW-based zeolite precursor is exfoliated by the hydrothermal treatment, and the exfoliated borosilicate MWW-based zeolite is Zn _y Al _z -DML-x (where y + z = 1.00, 0.25≤z<1.0, 100 ℃≤x≤160 ℃) provides a method for producing a two-dimensional MWW-based zeolite catalyst for glucose conversion reaction, characterized in that.

The exfoliated borosilicate MWW-based zeolite is characterized in that Zn _y Al _z -DML-x (where y + z = 1.00, 0.50≤z < 1.0, 100 ° C ≤ x ≤ 160 ° C).

The exfoliated borosilicate MWW series zeolite Zn _y Al _z -DML-x (where y + z = 1.00, 0.50 ≤ z < 1.0, 100 ° C ≤ x ≤ 160 ° C) has a Si / Al ratio of 8.4 to 11.8 characterized by

The exfoliated borosilicate MWW series zeolite Zn _y Al _z -DML-x (where y + z = 1.00, 0.50≤z < 1.0, 100 ° C ≤ x ≤ 160 ° C) is 5-hydroxy than fructose It is characterized by being more selective for methyl furfural (5-Hydroxymethylfurfural, 5-HMF).

The exfoliated borosilicate MWW series zeolite Zn _y Al _z -DML-x (where y + z = 1.00, 0.25 ≤ z < 1.0, 100 ° C ≤ x ≤ 160 ° C) has a Si / B ratio of 1100 to 6800 characterized by

The exfoliated borosilicate MWW-based zeolite Zn _y Al _z -DML-x (where y + z = 1.00, 0.25 ≤ z < 1.0, 100 ° C ≤ x ≤ 160 ° C) is a Lewis and Bronsted acid site ) is characterized by the appearance of pyridine adsorption bands in all of them.

The borosilicate MWW-based zeolite precursor is characterized in that it is a three-dimensional (3D) layered zeolite precursor.

According to one embodiment of the present invention, the Zn-DML catalyst is suitable for glucose conversion due to the high concentration of Lewis acid sites and the high external surface area due to framework B substitution by Zn and exfoliation of layered precursors, respectively. showed high selectivity for

In contrast, the ZnAl-DML catalyst was selective for HMF in the multistage conversion of glucose because of the balanced concentration of Bronsted and Lewis acid sites achieved by the controlled substitution of B by Zn and Al.

Also, unlike ZnAl-DML, Zn-DML catalysts could be recycled for glucose conversion due to their exfoliating properties that prevent pore blockage by organic or inorganic residues.

The overall results of the present invention point toward the development of active and stable supported metal and oxide catalysts as well as acid/base catalysts using heteroatom-substituted exfoliated MWW layers.

The effects of the present invention are not limited to the effects mentioned above. It should be understood that the effects of the present invention include all effects that can be inferred from the following description.

1 shows (a) powder XRD patterns of synthesized B-MWW(P) and Zn-DML-x samples, (b) BET surface area of calcined B-MWW and Zn-DML-x catalysts, and (c) ICP elemental composition. , (d) STEM HAADF and EDS elemental mapping images.
Figure 2 shows (a) powder XRD pattern of the synthesized Zn _y Al _z -DML-x sample, (b) BET surface area of the calcined Zn _y Al _z -DML-x, (c) ICP elemental composition, (d) STEM HAADF and an EDS elemental mapping image.
3 is a diagram showing the DFT-optimized structures of 3D and 2D MWW frameworks with substituted Al ³⁺ and Zn ²⁺ atoms (the last symbol in the model identification (i.e., O1 and/or O2) indicates the position of an acidic proton; , the reaction energies for heteroatom substitution are specified in parentheses: Si, yellow; O, red; Al, pink; Zn, purple; H, white. During optimization, the relaxed and fixed regions are ball and stick and presented using the line style).
4 shows UV-DRS spectra of calcined (a) B-MWW and Zn-DML-x and (b) Zn _y Al _z -DML-160, calcined (c) B-MWW and Zn-DML-x, (d) IR spectra in the structural regions of Zn _y Al _z -DML-160 and Zn 2p XPS of calcined (e) B-MWW and Zn-DML-x and (f) Zn _y Al _z -DML-160 catalysts It is a diagram showing the spectrum.
5 shows (a) ²⁹ Si MAS NMR spectra of B-MWW, Zn-DML-100, Zn-DML-160, Zn _0.50 Al _0.50 -DML-160, Al-DML-160 catalysts, and (b) B- MWW, (c) exfoliated B-MWW, (d) decomposition spectra of Zn-DML-160: a diagram showing experimental values (top), simulated values (middle), and decomposition components (bottom).
Figure 6 shows the IR spectra in the 3200-2900 region of calcined (a) B-MWW and Zn-DML-x and (b) Zn _y Al _z -DML-160 and calcined (c) B-MWW and Zn-DML -x and (d) Pyridine adsorption IR spectra of Zn _y Al _z -DML-160 catalyst (IR bands not identified due to background spectrum after pretreatment at 450 °C are marked with asterisks).
Figure 7 shows (a, d) glucose conversion of (b, e) fructose and (c, f) HMF for Zn-DML-x (top) and Zn _y Al _z -DML-160 (bottom) catalysts at 160 ° C. and yield (catalyst data for SnAl-BEA added for comparison).
Figure 8 shows (a) Zn-DML-160 and (b) Al-DML-160 catalysts for 3 hours and 12 hours, respectively, glucose conversion and yield to fructose and HMF, respectively, continuous at 160 ℃ for 3 hours and 12 hours. (c) Powder XRD patterns, (d) IR spectra of structured regions, and (e) TEM-EDS images of the Zn-DML-160 and Al-DML-160 catalysts used after three runs.
Figure 9 shows powder XRD patterns of (a) exfoliated B-MWW and (b) SnAl-BEA.
10 shows the initial structures of (a) 3D and (b) 2D MWW silicates for DFT calculations (Si, yellow; O, red; H, white; Si1 atoms of the 3D MWW structure connected to O1 and O2 atoms are colored green). shown).
Figure 11 is the TGA/DTA curves for synthesized B-MWW(P), Zn-DML-x and Zn _y Al _z -DML-160 samples.
12 is powder XRD patterns of calcined (a) B-MWW and Zn-DML-x and (b) Zn _y Al _z -DML-160 catalysts.
13 is N ₂ adsorption isotherms of calcined B-MWW, Zn-DML-x, Zn _y Al _z -DML-160 and SnAl-BEA catalysts.
Figure 14 is the powder XRD patterns of synthesized Al-DML-180 and Al-DML-200 samples.
15 shows (a) an IR spectrum in the 3400-3900 region and (b) a pyridine adsorption IR spectrum of SnAl-BEA.
Figure 16 shows the yields for (a) glucose conversion and (b) fructose, (c) HMF and (d) LA + FA in the absence of catalyst at 160 °C.
Figure 17 shows the LA + FA yields of (a) Zn-DML-x and SnAl-BEA and (b) Zn _y Al _z -DML-160 catalysts at 160 °C.

The above objects, other objects, features and advantages of the present invention will be easily understood through the following preferred embodiments in connection with the accompanying materials. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed content will be thorough and complete and the spirit of the present invention will be sufficiently conveyed to those skilled in the art.

In this specification, terms such as "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that it does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Unless otherwise specified, all numbers, values and/or expressions expressing components and reaction conditions used herein are approximations, reflecting various uncertainties in measurements that such numbers may inherently arise in obtaining such values among others. Since they are, it should be understood that all cases are modified by the term "about". Also, when numerical ranges are disclosed herein, such ranges are contiguous and include all values from the minimum value of such range to the maximum value inclusive, unless otherwise indicated. Furthermore, where such ranges refer to integers, all integers from the minimum value to the maximum value inclusive are included unless otherwise indicated.

[Experiment]

catalyst manufacturing

B-MWW(P) with a Si/B ratio of 9.5 was synthesized using hexamethyleneimine (99%, Sigma Aldrich) as an organic structure-directing agent (SDA). In a typical formulation, hexamethyleneimine and sodium hydroxide (99%, Sigma-Aldrich) were dissolved in deionized (DI) water and then boric acid (99.5%, Junsei) was added at 50 °C. After boric acid was completely dissolved, fumed silica (Evonik) was gradually added to homogenize the solution. The final solution was transferred to a Teflon-lined stainless steel autoclave and heated at 175° C. for 7 days. The white solid was recovered by filtration with deionized (DI) water and dried at room temperature (RT). The exfoliated B-MWW was prepared through a well-known three-step process (interlayer expansion→ultrasound→acidification) reported in the literature.

Zn-DML-x and Al-DML-x were prepared in 1.00M zinc(II) nitrate hexahydrate (98%, Samchun Pure Chemical) and aluminum nitrate nonahydrate (98%, Samchun Pure Chemical) was synthesized by one-step hydrothermal treatment of B-MWW(P) with an aqueous solution. The Zn _y Al _z -DML-x catalyst was synthesized using y + z = 1.00 M zinc (y) and aluminum (z) precursor solutions, other things being the same as mentioned above. After hydrothermal treatment, the solid product was recovered by filtration with DI water and dried at RT. All synthesized M-DML (M = Zn and/or Al) samples were calcined at 550 °C for 8 h to remove the closed organic SDA prior to characterization and catalysis.

For comparison, a Sn-substituted beta zeolite (SnAl-BEA) was also prepared by successive acid dealumination and isomorphic replacement of Sn. In general, 1.0 g of commercial NH ₄ -beta (Zeolyst CP 814E, Si/Al = 12.5) powder was dealuminized by acid leaching by refluxing in aqueous nitric acid solution (7.0 M) at 100 °C for 24 hours. The treated samples were recovered by filtration with DI water until the pH of the filtrate reached ~7.0 and calcined in flowing air at 550 °C for 4 hours. Exfoliated beta zeolite (1.0 g) was immersed in 100 mL isopropyl alcohol containing 27 mmol SnCl ₄ .5H ₂ O (Sigma-Aldrich, 98%) and then refluxed at 80° C. for 6 hours in N ₂ atmosphere. The treated sample was collected by filtration of excess isopropyl alcohol, and finally calcined at 200°C for 6 hours and at 550°C for 6 hours in flowing air.

characteristic

Powder X-ray diffraction (XRD) patterns were measured on a Rigaku SmartLab X-ray diffractometer with Cu-Kα radiation (scan rate=4° min ^-1 ) in the 2θ range of 3-50°. Thermogravimetric analysis (TGA) was performed in air using a Hitachi STA7200 thermal analyzer, and the weight loss associated with combustion of organic SDA was further confirmed by differential thermal analysis (DTA) using the same analyzer. N ₂ adsorption experiments were performed using a Micromeritics Tristar II analyzer. Elemental analysis was performed using a PerkinElmer OPTIMA 7300DV inductively coupled plasma (ICP) spectrometer. Transmission electron microscopy (TEM) and STEM-EDS high angle annular dark field (HAADF) images were obtained using a FEI TALOS F200X operating at 200 kV.

UV-DRS was performed using a Shimadzu UV-2600 UV-Vis spectrophotometer. UV absorption spectra were plotted using the Kubelka-Munk function. IR spectra of the structure region were collected using a Shimadzu IR Tracer-100 FT-IR spectrometer in ATR mode. X-ray photoelectron spectroscopy (XPS) was performed using a PHI 5000 Versa Probe II with Al-Kα radiation (hυ = 1,486.6 eV), and the spectrum showed the binding energy of adventitious carbon (C 1s, 284.6 eV). corrected on the basis of XPS samples were prepared using about 20 mg self-supporting zeolite wafers with a diameter of 1.3 cm in dry conditions. ²⁹ Si MAS NMR spectra were obtained using a 500 MHz Avance III HD Bruker solid-state NMR spectrometer at 5 kHz rotation rate, 99.36 MHz ²⁹ Si frequency with π/2 rad pulse length of 4 μs, recycle delay 60 s, and approximately 300 transient pulse acquisitions. it was recorded A chemical change of ²⁹ Si has been reported with respect to TMS.

The acidic properties of the solid samples were measured using the same IR spectroscopy method using pyridine as the probe molecule as mentioned above. Pyridine adsorption-desorption measurements were performed on self-supporting solid wafers with a diameter of 1.3 cm and weighing approximately 20 mg that were activated under flowing He at 100 mL min ^-1 for 2 h at 450 °C inside a domestic IR cell. Before pyridine adsorption, the IR spectrum of the hydroxy region was recorded at 450 °C. The sample was then cooled to 100 °C, saturated with a dry He flow containing pyridine for 10 minutes, and then washed with excess He at the same temperature for 30 minutes to remove physically adsorbed pyridine. After desorption at 200 °C, the concentrations of the Bronsted and Lewis acid sites were determined using the Emeis equation with IR band intensities of about 1550 and 1450 cm ^-1 , respectively. All spectral decomposition and simulation calculations were performed using the Origin 9.0 curve-fitting program.

DFT calculation

Perdew-Burke of generalized gradient approximation implemented in Materials Studio 7.0 to calculate heteroatomic (Al ³⁺ and Zn ²⁺ ) substitution reaction energies for 3D MWW silicate frameworks and defects in corresponding 2D layers. -Ernzerhof performed DFT calculations in periodic boundary conditions using DMol3. Although only the gamma k point and version 4.4 of the DNP criterion set were applied, the SCF tolerance and maximum angular momentum function were set to 1.0 Х 10 ^-6 and hexadecapoles, respectively. When including heteroatoms, a thermal smearing of 0.01 Ha was applied for shape optimization. For the model without heteroatoms (i.e., the model with only Si and O atoms), single-point energy calculations with the same thermal smearing were performed after geometrical optimization of the Fermi occupation. The convergence tolerances for geometry optimization are: energy, 1.0 Х 10 ^-5 Ha; peak force, 0.002 Ha Å ^-1 ; Maximum displacement, 0.005 Å. The refined structure of ITQ-1 was used as an initial model for the 3D MWW silicate (designated 3D-MWW[Si]; Si ₇₂ O ₁₄₄ per unit cell).

In order to construct the 2D MWW layered silicate model (2D-MWW[Si]; Si ₇₂ O ₁₄₆ H ₄ per unit cell), in the present invention, each O1 atom connected to two Si1 atoms is c- The bond with the Si1 atom on one side was removed by capping with an H atom at a distance of 1.11 Å along the axis, resulting in a terminal O atom (FIG. 10).

One Si1 atom is surrounded by one O1 atom and three O2 atoms. 3D and 2D MWW silicate models were symmetrically optimized with full relaxation of all atomic positions. Al and Zn atoms were replaced with Si1 sites in the silicate model optimized for DFT. Then, acidic protons and terminal OH groups were added and removed, respectively, to render the framework neutral.

Consequently, 3D and 2D MWW models with Al and Zn (designated as aD-MWW[b]-c; where a is the dimension of the framework (2 or 3) and b is the type of heteroatom (Al or Zn ), where c is the position of the acidic proton (O1 or O2)) is a unit cell such as AlSi ₇₁ O ₁₄₄ H, ZnSi ₇₁ O ₁₄₄ H ₂ , AlSi ₇₁ O ₁₄₅ H ₃ , and ZnSi ₇₁ O ₁₄₄ H ₄ , respectively. have a composition During geometry optimization, regions near heterogeneous elements (3D-MWW[Al], 3D-MWW[Zn], 2D-MWW[Al] and 2D-MWW[Zn], respectively, AlSi ₅ O ₁₆ H, ZnSi ₅ O ₁₆ H ₂ , AlSi ₄ O ₁₂ and ZnSi ₄ O ₁₂ H) are relaxed and other elements are fixed. The reaction formula for heteroatomic substitution is:

3D-MWW[Si] + Al(OH) ₃ → SiO(OH) ₂

3D-MWW[Si] + Zn(OH) ₂ → SiO ₂

2D-MWW[Si] + Al(OH) ₃ → Si(OH) ₄

2D-MWW[Si] + Zn(OH) ₂ → SiO(OH) ₂

For example, the reaction energy (E _rx ) for Al substitution in 3D MWW silicate is E _rx = E(3D-MWW[Al]) + E(SiO(OH) ₂ ) - E(3D-MWW[Si]) - E(Al(OH) ₃ ), (where E(3D-MWW[Al]), E(SiO(OH) ₂ ), E(3D-MWW[Si]), and E(Al(OH) ₃ are the respective energies of 3D-MWW[Al], SiO(OH) ₂ , 3D-MWW[Si], and Al(OH) ₃ with optimized geometries). was calculated in the same way.

catalyst

Glucose conversion was performed under autogenous pressure in a 23 mL Teflon-lined stainless autoclave reactor containing 1 g glucose, 10 g solvent ((DMSO, Samchun, 99%):DI water = 2:1) and 0.1 g catalyst. at 160° C. and 100 rpm for 1-24 h under After a certain reaction time, the autoclave was washed, the reaction product was recovered using a syringe filter, and a high-performance liquid chromatograph (Youngin Chromass YL9100 plus) equipped with a refractive index and UV (280 nm) detector and an Agilent H column (300 Х 7.7 mm ) was used to dilute with DI water for analysis. The mobile phase was a 5 mM H ₂ SO ₄ aqueous solution, and the flow rate was 0.6 mL min ^-1 at a column temperature of 65 °C. All reactions were repeated more than once to confirm the reproducibility of the reactions. For comparison, a blank test without catalyst was also performed under the same reaction conditions. In addition, the catalyst used after 3 or 12 hours of reaction was recovered by filtration, washed repeatedly at 550 ° C. for 6 hours, and then used for a reusability test. Glucose conversion and production selectivity were determined as follows:

Glucose conversion (%) = (moles of reacted glucose/moles of initial glucose) Х 100

Production selectivity (%) = (moles of product produced/moles of glucose reacted) Х 100.

Results and discussion

Synthesis and characterization of M-DML (M = Zn and/or Al)

Figure 1a shows the powder XRD patterns of samples of B-MWW(P) and as-synthesized Zn-DML-x (x = 100-160 °C). The low-angle X-ray diffraction peaks of B-MWW(P) appearing at about 6.6°, 7.4°, 8.1°, and 9.9° correspond to the (002), (100), (101), and (102) reflections of the MWW structure, respectively. . The interlayer reflection (00 l ) represents the thin-plate structure of the MWW-type material occurring in the far-field order along the c-direction, and the (100) reflection is a characteristic of the intralayer reflection ( hk 0). The reflection intensity (002) of the Zn-DML-x sample continuously decreased as the hydrothermal treatment temperature increased due to the disordered nature of the exfoliated material. In particular, the low intensity of (101) and (102) reflections in Zn-DML-140 indicate a lack of order in the stacking direction. The XRD pattern of Zn-DML-160 was amorphous due to severe exfoliation and partial structural collapse. However, weak and broad humps in the range of 33°-36°, which is the main X-ray diffraction peak region of ZnO nanoparticles, were also observed in Zn-DML-140 and Zn-DML-160. It also shows that small amounts of ZnO nanoparticles were formed on the exfoliated surfaces of these materials. The gradual decrease of the organic content of the as-synthesized Zn-DML-x sample from about 20 wt.% to 5 wt.% with increasing hydrothermal temperature indicates the exfoliation of the MWW structure (Fig. 11). On the other hand, in the XRD patterns of calcined B-MWW and Zn-DML-x, the (002) reflection was completely eliminated and the intralayer reflection was restored because there was no far-field order along the C-direction (Fig. 12a).

Figure 1b shows the BET surface area of calcined B-MWW and Zn-DML-x catalysts. As the hydrothermal temperature x increased from 100 °C to 160 °C, the total surface area of Zn-DML-x decreased from 480 to 170 m ² g ^-1 , but the external surface area increased continuously from 30 to 170 m ² g ^-1 . In addition, the N ₂ adsorption isotherm of Zn-DML-160 is IV-type adsorption-desorption with H3-type hysteresis (FIG. 13), which corresponds to the typical interparticle void volume between parallel plates. This provides clear evidence for the delamination of the MWW layer precursor. On the other hand, the low BET surface area (170 m ² g ^-1 ) of Zn-DML-160, which is only 35% of the B-MWW value, can be attributed to micropore blocking by Zn derivative nanoclusters (see below).

As shown in Fig. 1c, the amount of Zn in the Zn-DML-x sample was proportional to the heat treatment temperature, and Zn species (about 25 wt.%) were the highest in Zn-DML-160. The Zn-DML-x samples with x = 100-140 °C still had significant amounts of B (Si/B = 21-49 in Table 1), indicating that the B atoms of the B-MWW(P) framework are attached to the Zn atoms. indicates that it is not completely substituted by When the framework configuration of Zn-DML-x is calculated assuming 72 tetrahedral atoms of the MWW unit cell, the Si/Ni framework ratio of Zn-DML-160(10) is the Si/B ratio of B-MWW ( 9.5). This indicates that the optimum hydrothermal temperature for heterogeneous element substitution is 160°C. On the other hand, the total Si/Zn ratios of Zn-DML-140 and 160 samples (4.6 and 3.5, respectively) were lower than those of B-MWW, and some Zn species were also added to the framework as bovine Zn clusters and ZnO particles. appeared to exist. As discussed above, these small-scale clusters have the potential to contribute to the micropore blockage of Zn-DML-x.

^a Calculated for 8 hours at 550 °C. ^b Calculated from _N2 adsorption isotherms. ^c Si/Sn molar ratio. ^d Calculation assuming that the number of framework tetrahedral atoms is 72, including 65.2 Si atoms, equal to the concentration of B-MWW. ^e Concentrations of Bronsted and Lewis acid sites determined from the intensities of the pyridine adsorption IR bands at about 1550 cm ⁻¹ and 1450 cm ⁻¹ respectively ( FIGS. 6 and 14 ). nd means cannot be determined due to the background spectrum.

Figure 1d shows STEM HAADF and EDS elemental mapping images of calcined B-MWW and Zn-DML-x catalysts. The HAADF image of the Zn-DML-x sample clearly shows the delamination of the MWW layer. As the hydrothermal treatment temperature increased, the rigid and horny plate-shaped crystals of B-MWW were converted into flexible and thin layers. In addition, according to the elemental analysis results (Fig. 1c), the atomic content of Zn-DML-160 measured by EDS analysis increased to about 33 wt.% with high dispersion. However, the tiny Zn clusters and ZnO nanoparticles could not be distinguished by STEM resolution.

Figure 2a shows the XRD pattern of the synthesized Zn _y Al _z -DML-160 sample. Unlike the case of Zn-DML-x described above, as the proportion of Al increased in Zn _y Al _z -DML-160, the (101) and (102) reflection intensities were concentrated at 8.1° and 9.9°, respectively. These X-ray diffraction peaks originate from mixed reflection between layers of disordered layered materials. As shown in Fig. 12b, the XRD pattern of the calcined Zn _y Al _z -DML-160 sample with z = 0.25–1.00 was similar to 3D B-MWW. This also made the outer surface area of Al-DML-160 (66 m ² g ^-1 ) much smaller than that of Zn-DML. Also, the N ₂ adsorption isotherms of Zn _y Al _z -DML-160 with z = 0.25–1.00 were close to those of type I microporous solids (FIG. 13). This indicates that when B is substituted by Al, the layered precursor is not exfoliated and instead the 3D MWW structure is stabilized.

As shown in FIG. 2c, the Al element content (about 4.1 to 5.4 wt.%) of the Zn _y Al _z -DML-160 sample did not change even when the concentration of Al in the precursor solution increased. Therefore, the Si/Al ratios of the Zn _y Al _z -DML-160 samples with z = 0.50–1.00 (ca. 8.4–11.8) were close to the Si/B values (9.5) of the B-MWW (Table 1). This indicates that the substitution of B by Al is easier than that of Zn, and that all introduced Al atoms are mainly present in skeletal tetrahedral sites. Therefore, the Si/B ratio (1100-6800) of the Zn _y Al _z -DML-160 sample with z = 0.25–1.00 is much higher than that of the Zn-DML-x sample (21-240). Since the atomic radius of Al (118 pm) is smaller than that of Zn (142 pm), and the Al-O bond length (1.71 Å) is smaller than that of Zn-O (1.95 Å), the ratio of Al to Zn in the tetrahedral structure of the MWW structure is Stabilization is better. Figure 2d shows STEM HAADF and EDS elemental mapping images of the calcined Zn _y Al _z -DML-160 catalyst. Rigid and angular plate-shaped crystals of B-MWW were preserved after hydrothermal treatment at 160 °C using Zn and/or Al precursors. EDS analysis also measured about 4–7 wt.% of Al species and a negligible amount of Zn (< 0.4 wt.%).

3 shows the DFT optimized structures of 3D and 2D MWW frameworks in which Al ³⁺ and Zn ²⁺ are substituted at the Si1 site. It should be noted that, unlike the 3D and 2D MWW silicate models (FIG. 10), acidic protons and terminal OH groups were introduced and removed respectively in the model with heteroatoms, rendering the framework neutral. In the 3D MWW structure, the Zn atom associated with the two acidic protons was more displaced from the original position of the Si1 site than the Al atom, regardless of the location of the acidic protons. On the other hand, in the case of 2D, the degree of movement of Zn atoms associated with one acidic proton was not significantly different compared to Al atoms without acidic protons. Regarding the reaction energy for heteroatom substitution, the dimensions of the framework (3D Al, 105-127 kJ mol ^-1 versus 3D Zn, 539-544 kJ mol ^-1 , 2D Al, -82 kJ mol ^-1 versus 2D Zn , 232 kJ mol ⁻¹ , Fig. 3), the energy for Al is lower than that for Zn.

This means that Al is more easily substituted into the MWW structure than Zn. In terms of dimensional effects, 2D frameworks are preferred over 3D frameworks for Al and Zn substitution (3D Al, 105–127 kJ mol ^vs. 2D Al, -82 kJ ^mol ; 3D Zn, 539–544 kJ mol ⁻¹ versus 2D Zn, 232 KJ mol ⁻¹ , Fig. 3). Although both Zn and Al atoms are more stable in 2D structure than in 3D, in the case of Al, the 3D MWW structure was still maintained during the heteroatom substitution process under hydrothermal conditions at 180 °C (Fig. 14). Since the stabilization energy is a thermodynamic state function, the kinetic path function should be considered for the heteroatom substitution and exfoliation process by hydrothermal treatment. Interestingly, when the hydrothermal temperature was raised to 200 °C, the powder XRD pattern of Al-DML-200 became similar to that of 2D MWW (Fig. 14). Therefore, it can be inferred that a higher activation energy is required to form the most stable 2D aluminosilicate MWW structure.

Figure 4a shows the UV-DRS spectra of the calcined B-MWW and Zn-DML-x catalysts. B-MWW showed only a very weak absorption band around 250–350 nm, but the Zn-DML-x sample showed a dominant and intense UV absorption band below 230 nm. The intensity of these bands increases proportionally with increasing hydrothermal treatment temperature. These can be assigned to heterogeneously substituted Zn atoms in the zeolite framework. Zn-DML-100 and Zn-DML-120 samples also showed very weak peaks at about 258 nm and 300 nm, respectively. This is due to the effect of the O ^2- → Zn ²⁺ ligand on the conversion of metal charge transfer from ZnO.

In addition, Zn-DML-140 and Zn-DML-160 showed a fairly wide absorption band in the range of 250–800 nm, which may be due to the influence of various coordination environments between the Zn species in the framework and the ZnO nanoclusters. However, as shown in Fig. 4b, the Zn _y Al _z -DML-160 with z = 0.25–1.00 sample has a four-coordinated framework Al and an Al–O charge transfer transition of the additional framework Al species. This resulted in a fairly weak UV absorption band centered around 250–280 nm.

Framework Zn formation in calcined Zn-DML-x was further investigated by IR spectroscopy of the structural regions (Fig. 4c).

B-MWW exhibits IR absorption bands at 445, 569, 611, 809, 1183, 1243 and 1398 cm ⁻¹ , which are typical characteristics of skeletal vibration in the MWW structure. Interestingly, when Zn substitution proceeded at elevated hydrothermal temperatures of 100 to 160 °C, it was clearly observed at about 1014 cm ^-1 , and the intensity gradually increased, indicating that within the framework of Zn-DML-x, Zn- At the same time as O bonds are formed, an additional band of 658 cm ^-1 corresponding to Zn-O bonds of ZnO nanoclusters can be formed, especially in Zn-DML-140 and Zn-DML-160 samples.

In addition, the central band at 1390 cm ⁻¹ decreases as the hydrothermal temperature increases, corresponding to the vibration of Si-OB, which almost disappeared in the case of Zn-DML-160. On the other hand, as shown in Figure 4d, the IR spectrum of the Zn _y Al _z -DML-160 sample with z = 0.25 ~ 1.00 was similar to the B-MWW spectrum except for the case where there was no Si-OB vibration. This indicates that there are no framework Zn species in this material.

The chemical state of the Zn species located on the outer surface of Zn-DML-x and Zn _y Al _z -DML-160 samples was characterized by Zn 2p core level XPS. As shown in Fig. 4e, all Zn-DML-x samples have peaks of 1022.0–1022.7 eV (Zn 2p _3/2 ) and 1045.11–1045.8 eV (Zn 2p _1/2 ) due to spin-orbit splitting due to the double peak energy separation of 23.1 eV. It showed two peaks in the range. As the Zn content increased (Fig. 1c), the intensity of the two Zn 2p peaks also increased. When the Zn 2p _3/2 peak of Zn-DML-x was decomposed into two species centered on 1022 and 1023 eV corresponding to ZnO and framework Zn, respectively, the ZnO ratio increased as the hydrothermal temperature increased from 100 to 160 °C. increased (Table 2). This indicates that the content of framework Zn in Zn-DML-x increased with increasing hydrothermal temperature (Table 1), and some excess Zn species were present in the form of ZnO on the outer surface of the MWW 2D layer. This correlates well with the powder XRD results (Fig. 1a).

On the other hand, among the Zn _y Al _z -DML-160 samples (Fig. 4f), only Zn-DML-160 and Zn _0.75 Al _0.25 -DML-160 showed Zn 2p peaks, and the other two samples did not show Zn species. Interestingly, Zn _0.75 Al _0.25 -DML-160 had much less Zn content than Zn-DML-160 (Fig. 2c), but the Zn 2p peak intensity of Zn _0.75 Al _0.25 -DML-160 was not significantly different from Zn-DML-160. did not This indicates that most of the Zn species in Zn _0.75 Al _0.25 -DML-160 were present as Zn and ZnO nanoparticles on the outer surface.

5A shows ^{the 29} Si MAS NMR spectra of the calcined B-MWW, Zn-DML-100, Zn-DML-160, Zn _0.50 Al _0.50 -DML-160 and Al-DML-160 samples. As shown in FIG. 5b, the decomposition spectrum of B-MWW is about -92 ppm (Q ² ), -98 ppm (Q ³ ), -105 ppm (Q ⁴ ), -111 ppm (Q ⁴ ), -116 ppm (Q ⁴ ) and -120 ppm (Q ⁴ ) showed six distinct bands, which are similar to the values reported by Quang et al. The spectrum of Zn-DML-100 was similar to that of B-MWW, and the intensity of the remaining three samples synthesized at 160 °C increased markedly at -98 ppm.

This is most likely due to the formation of external silanol Q ³ (SiOH) sites in the 2D MWW layered structure. In particular, Zn-DML-160 showed a much stronger band at -98 ppm, and the intensity also increased significantly at -92 ppm. This can be reasonably inferred from the chemical shifts by framework Zn of Zn-DML-160 (ie, Q ⁴ (1Zn) and Q ⁴ (2Zn)).

Figure 5c shows the resolved ²⁹ Si MAS NMR spectrum of 2D exfoliated B-MWW. Comparing with the decomposed spectrum of 3D B-MWW (Fig. 5b), the relative intensity of the band at -111 ppm corresponding to Q ⁴ (nB) was reduced by deboration, while the Q ³ (at -98 and -92 ppm) The relative intensities of the sub-bands containing SiOH) and Q ² (Si(OH) ₂ ) increased, respectively. The resolved spectrum of Zn-DML-160 clearly compares the strong bands of -98 ppm and -92 ppm (Fig. 5d), of which the relative increase is the result of Q ⁴ (1Zn) and Q ⁴ (2Zn), respectively. Based on this, the Si/Zn ratio of Zn-DML-160 can be calculated to be up to 15, which is quite similar to the Si/Zn _Framework ~10 determined by ICP analysis (Table 1). This suggests that the Zn species are well integrated into the framework of Zn-DML-160.

Figure 6a shows the IR spectra of the hydroxyl regions of B-MWW and Zn-DML-x catalysts. The OH-IR spectrum of B-MWW showed two absorption bands concentrated at 3738 and 3684 cm ^-1 that can be assigned to terminal silanol (Si-OH) and OB(OH) ₂ groups, respectively. As the temperature of the hydrothermal treatment increased, the relative strength of the terminal silanol groups of Zn-DML-x increased due to exfoliation of the layered precursor. Interestingly, a new IR band at 3635 cm ⁻¹ was generated in Zn-DML-x, which became much stronger with increasing hydrothermal temperature. It is likely that it originates from the hydroxyl of the Si-O-Zn moiety. Meanwhile, as shown in FIG. 6b, the IR spectrum of Zn _y Al _z -DML-160 with z = 0.25-1.00 had two dominant bands concentrated at 3734 and 3600 cm ^-1 , respectively. Also, as described above, a slight peak was observed at 3635 cm ^-1 in the IR spectrum of Zn _y Al _z -DML-160 due to the small amount of framework Zn species.

6C shows the pyridine adsorption IR spectra of B-MWW and Zn-DML-x catalysts, and the Bronsted and Lewis acid concentrations of B-MWW and Zn-DML-x catalysts are summarized in Table 1.

In particular, since pyridine was not adsorbed at both 1540 and 1450 cm ⁻¹ of B-MWW, no Brønsted acid site and Lewis acid site were observed. However, as the annealing temperature increased, Lewis acid sites were mainly generated in the Zn-DML-x sample. The concentration of Lewis acid in Zn-DML-x was higher than SnAl-BEA (FIG. 15), which is the most typical Lewis acidic zeolite catalyst. This is consistent with the SiOH-Zn formation of the Zn-DML-x sample shown in Fig. 6a. Du. reported that the ZnOH ⁺ species play a central role as an active Lewis acid in the dehydrogenation of butane and cyclohexane. Zn-DML-160 had a higher Zn content than Zn-DML-140 (Fig. 1c), but the Lewis acid concentration was higher in Zn-DML-140. This may be due to the large external surface area of Zn-DML-140. On the other hand, Zn _y Al _z -DML-160 with z = 0.25-1.00 showed pyridine adsorption bands at both Lewis and Bronsted acid sites (Fig. 6d).

Although the relative amounts of the two acid sites were not systematically controlled by the concentrations of Zn and Al used in the synthesis, much higher Lewis acid concentrations were observed regardless of the low Zn. This can be rationalized by atomically dispersed Zn in the high surface area Zn _y Al _z -DML framework.

Multi-step glucose conversion for M-DML (M = Zn and/or Al)

The multi-step conversion of glucose to fructose and HMF was investigated using Zn-DML-x and Zn _y Al _z -DML-160 catalysts. 7a-7c show the glucose conversion and yield of fructose and HMF for Zn-DML-x and SnAl-BEA catalysts. All catalysts had higher glucose conversion than the reaction without catalyst (FIG. 16). Compared to the best performing catalyst, the glucose conversion at 24 hours of reaction time was about 2.4 times higher. In addition, all Zn-DML-x catalysts showed higher glucose conversion than SnAl-BEA, a reactive Bronsted-Lewis acidic zeolite catalyst. As shown in FIG. 7a, glucose conversion increased in the order of Zn-DML-100 < Zn-DML-120 < Zn-DML-160 < Zn-DML-140. Clearly, these catalytic performance trends correspond to the order of external surface area (Fig. 1b and Table 1). The concentration of acid sites and catalytic performance depend on the total surface area of the catalyst as well as the amount of heteroatoms substituted. As described above, Zn-DML-140 (20 wt.%, Fig. 1c) has a lower Zn content than Zn-DML-160 (25 wt.%), but the former catalyst (165 m ² g ^-1 ) The external surface area is higher than the latter (165 m ² g ^-1 ), which can compensate for the concentration of acid sites (191 vs. 84 μmol g ^-1 ) as well as the catalytic activity.

Thus, for the conversion of bulky molecules such as glucose, the zeolitic outer structure serves as the main active site compared to the microporous structure.

As shown in Figs. 7b and 7c, all Zn-DML-x catalysts are selective for fructose rather than HMF, whereas SnAl-BEA mainly catalyzes glucose isomerization only for fructose compared to the Lewis acidity of Zn-DML-x. It was more selective for HMF (FIG. 6c). Zn-DML-160 catalyst showed a slightly lower glucose conversion than Zn-DML-140 (FIG. 7a), but showed a high yield of fructose in 3 hours. On the other hand, the yield of fructose for the Zn-DML-x catalyst decreased, whereas the yield of HMF increased as a function of reaction time.

Regarding the thermodynamics of the reaction steps, the isomerization of glucose to fructose is weakly endothermic (μHr = 8.4 kJ mol ^-1 ) and the dehydration of fructose to HMF is highly endothermic (∼92 kJ mol ^-1 ). On the other hand, the hydration of HMF to levulinic acid (LA) + formic acid (FA) is exothermic (-16.7 to -133.9 kJ mol ^-1 ). Therefore, the dehydration step is thermodynamically favorable at elevated temperatures, and the conversion of fructose to HMF proceeds without a catalyst at 160 °C, as shown in Fig. S8.

Hydration of HMF to LA + FA is the most favorable thermodynamically, but the yield of LA + FA after 24 h in Zn-DML-x is poor due to the lack of Bronsted acidity of the catalyst and the use of a polar aprotic DMSO solvent ( 17a) could be neglected. Indeed, DMSO binds more strongly than water, and solvation of HMF by DMSO increases the LUMO energy and reduces susceptibility to nucleophilic attack, minimizing undesirable hydration and humin formation.

7d shows glucose conversion through the Zn _y Al _z -DML-160 catalyst. Clearly, all values were higher than SnAl-BEA, and the performance of Zn _y Al _z -DML-160 catalysts was comparable to each other due to similar levels of element content, acidity concentration and exfoliation properties (Fig. 2). The Zn _y Al _z -DML-160 catalyst has an MWW structure with smaller 10-ring pores than the 12-ring pores of SnAl-BEA and a smaller BET surface area (Table 1), but a higher acid site for the former catalyst. The easy control of the concentration of β and the Bronsted and Lewis acidity led to high catalytic performance for glucose conversion. Also shown in Figs. 7e, 7f, the Zn _y Al _z -DML-160 catalyst with z = 0.50–1.00 is more selective for HMF than fructose, whereas the Zn _0.75 Al _0.25 -DML-160 is more selective for other Zn _y Al _z - Compared to the DML-160 catalyst, the production of HMF was low due to the lower concentration of Bronsted acid. In addition, the LA + FA yield of Zn _y Al _z -DML-160 with z = 0.25–1.00 was higher than that of the Zn-DML-x catalyst due to the influence of Bronsted acid that catalyzes the hydration of HMF (FIG. 17).

Reusability tests of Zn-DML-160 and Al-DML-160 catalysts for glucose conversion were tested at 160°C for 3 hours and 12 hours, respectively. As shown in Fig. 8a, after the first recycling, the glucose conversion slightly decreased (52% → 47%), but after 3 h, the yield of fructose relative to Zn-DML-160 increased for three consecutive times (32% → 32% → 30%). ) was almost maintained. Also, the formation of HMF during the reusability test was significantly low (<1%), consistent with the results shown in Fig. 7c. This can be explained by the exfoliation property of Zn-DML-160, which is resistant to pore blocking by coke species formed during the reaction.

On the other hand, the conversion of glucose (89% → 52% → 45%) and the yield of HMF (40% → 22% → 17%) after 12 h for Al-DML-160 decreased continuously during three consecutive tests ( Figure 8b).

As shown in Fig. 8c, the XRD patterns of the Zn-DML-160 and Al-DML-160 catalysts were almost unchanged, showing that the crystal structures were not damaged even after three consecutive reactions and regeneration. However, unlike the IR spectrum of Zn-DML-160, which is almost identical to the original IR spectrum (Fig. 4c), the IR spectrum of Al-DML-160 is greatly changed. This is due to the reduced content of Bronsted acidic framework Al (Fig. 8d). Treatment with Al-DML-160 causes irreversible deactivation due to loss of Bronsted acidity of the catalyst. However, extraction of Zn from the zeolite framework of Zn-DML-160 does not affect the catalytic activity because the extracted ZnO is also Lewis acidic. In addition, the Zn content (24 wt.%) of Zn-DML-160 measured by STEM-EDS analysis was lower than the value of the unrecycled catalyst (33 wt.%), and the Al content of Al-DML-160 was measured for three recycling runs. (4 wt.%) did not change.

The difference in these deviations may have originated from the location of the metal. The Al species extracted from the zeolite framework are trapped and protected by the 3D structure of Al-DML-160, and the total content of Al-DML-160 is maintained after the reaction. However, the Zn species extracted from Zn-DML-160 cannot be protected by the zeolite framework because of the 2D morphology of the crystals and are abraded by agitation during the catalytic reaction.

conclusion

A 2D Lewis acidic Zn-DML catalyst and a Lewis-Brønsted acidic ZnAl-DML catalyst were prepared by a single-step hydrothermal treatment of B-MWW(P) using Zn and Zn + Al precursor solutions, respectively. The external surface area and Zn content of the Zn-DML-x (x = 100–160 °C) catalyst increased proportionally with increasing hydrothermal treatment temperature due to the sequential process of heteroatom substitution and exfoliation of the MWW layer.

The Zn content of Zn-DML-160 was about 25 wt% and both framework and additional framework Zn species were present together. In contrast, in ZnAl-DML, the incorporation of Al atoms (1.6–5.4 wt.%) was more dominant than the incorporation of Zn atoms (~0.5 wt.%) and exfoliation was delayed.

The stabilization energies of the 2D and 3D MWW frameworks by the addition of Zn and Al were calculated using DFT. The stability of the framework decreased in the following order: Al in 2D structure > Al in 3D structure > Zn in 2D structure > Zn in 3D structure.

The Zn-DML catalyst showed high selectivity for fructose for glucose conversion due to the high concentration of Lewis acid sites and the high external surface area due to framework B substitution by Zn and exfoliation of layered precursors, respectively.

In contrast, the ZnAl-DML catalyst was selective for HMF in the multistage conversion of glucose because of the balanced concentration of Bronsted and Lewis acid sites achieved by the controlled substitution of B by Zn and Al.

Also, unlike ZnAl-DML, Zn-DML catalysts can be recycled for glucose conversion because of their exfoliating properties that prevent pore blockage by organic or inorganic residues.

The overall results of the present invention point toward the development of active and stable supported metal and oxide catalysts as well as acid/base catalysts using heteroatom-substituted exfoliated MWW layers.

The present invention described above is not limited to the above-described embodiments, since various substitutions and changes can be made to those skilled in the art within the scope of the technical idea of the present invention. .

Claims (7)

Preparing a borosilicate MWW-based zeolite precursor; and
Contacting the borosilicate MWW-based zeolite precursor with a M(NO ₃ ) _x (M = Zn and Al) precursor solution and subjecting the precursor to hydrothermal treatment; Including,
It is characterized in that the borosilicate MWW-based zeolite precursor is exfoliated by the hydrothermal treatment, and the exfoliated borosilicate MWW-based zeolite is Zn _y Al _z -DML-x (where y + z = 1.00, 0.25 ≤ z < 1.0, 100 ℃ ≤ x ≤ 160 ℃) characterized in that
Method for preparing a two-dimensional MWW-based zeolite catalyst for glucose conversion reaction. According to claim 1,
The exfoliated borosilicate MWW-based zeolite is Zn _y Al _z -DML-x (where y + z = 1.00, 0.50≤z < 1.0, 100 ° C ≤ x ≤ 160 ° C), characterized in that
Method for preparing a two-dimensional MWW-based zeolite catalyst for glucose conversion reaction. According to claim 2,
The exfoliated borosilicate MWW series zeolite Zn _y Al _z -DML-x (where y + z = 1.00, 0.50 ≤ z < 1.0, 100 ° C ≤ x ≤ 160 ° C) has a Si / Al ratio of 8.4 to 11.8 characterized by
Method for preparing a two-dimensional MWW-based zeolite catalyst for glucose conversion reaction. According to claim 2,
The exfoliated borosilicate MWW series zeolite Zn _y Al _z -DML-x (where y + z = 1.00, 0.50≤z < 1.0, 100 ° C ≤ x ≤ 160 ° C) is 5-hydroxy than fructose Characterized in that it is more selective for methyl furfural (5-Hydroxymethylfurfural, 5-HMF)
Method for preparing a two-dimensional MWW-based zeolite catalyst for glucose conversion reaction. According to claim 1,
The exfoliated borosilicate MWW series zeolite Zn _y Al _z -DML-x (where y + z = 1.00, 0.25 ≤ z < 1.0, 100 ° C ≤ x ≤ 160 ° C) has a Si / B ratio of 1100 to 6800 characterized by
Method for preparing a two-dimensional MWW-based zeolite catalyst for glucose conversion reaction. According to claim 1,
The exfoliated borosilicate MWW-based zeolite Zn _y Al _z -DML-x (where y + z = 1.00, 0.25 ≤ z < 1.0, 100 ° C ≤ x ≤ 160 ° C) is a Lewis and Bronsted acid site ), characterized in that all pyridine adsorption bands appear
Method for preparing a two-dimensional MWW-based zeolite catalyst for glucose conversion reaction. According to claim 1,
Characterized in that the borosilicate MWW-based zeolite precursor is a three-dimensional (3D) layered zeolite precursor
Method for preparing a two-dimensional MWW-based zeolite catalyst for glucose conversion reaction.

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