Hydrophilic modified molecular sieve based catalyst as well as preparation method and application thereof

Abstract

The invention provides a hydrophilic modified molecular sieve-based catalyst as well as a preparation method and application thereof, and the method comprises the following steps: mixing a molecular sieve carrier, a titanium-containing compound and a solvent, carrying out dipping treatment, and then drying and calcining to obtain a titanium-loaded molecular sieve; mixing the titanium-loaded molecular sieve with a sulfydryl silanization reagent and an organic solvent, carrying out a modification reaction, and carrying out separation treatment to obtain a sulfydryl modified intermediate; mixing the sulfydryl modified intermediate with an oxidizing agent solution for reaction, and separating and drying to obtain the hydrophilic modified molecular sieve based catalyst. The catalyst is used for catalytically converting a biomass-derived phenolic compound into a polyphenol antioxidant, and the density of water molecules in an active site adjacent region can be enhanced under the synergism of a-SO3H group and TiO2, so that the contact between a hydrated hydrogen ion cluster and the phenolic compound is enhanced to improve the yield of the polyphenol compound.

Description

Technical Field

[0001] The present disclosure relates to the field of catalysis technology, and in particular to a hydrophilic modified molecular sieve-based catalyst and a preparation method and application thereof. Background Art

[0002] In the materials and food industries, synthetic antioxidants are widely used due to their excellent antioxidant properties. However, their raw materials are mostly derived from petroleum, which poses toxic risks and is non-renewable, limiting their long-term development. Lignin in biomass is an aromatic polymer composed of three phenylpropane units: p-hydroxyphenyl, guaiacyl, and syringyl, cross-linked by CO and CC bonds. Due to its high oxygen content, some oxygen is retained in the product as oxygen-containing compounds during its depolymerization process (thermal decomposition, hydrolysis, oxidative degradation, or reductive fractionation), forming a variety of phenolic compounds (such as phenol, guaiacol, and 4-propylguaiacol). Phenolic compounds extracted or enriched from biomass and its by-products can be used as antioxidants, providing a green alternative source of antioxidants. However, their antioxidant effect is generally lower than that of synthetic antioxidants.

[0003] Studies have shown that converting monophenols into polyphenols through catalytic means can significantly enhance their antioxidant activity. However, the current catalytic process mostly uses homogeneous catalysts, which have problems such as difficult product separation and complex processes, seriously restricting the industrial application of biomass-derived polyphenol antioxidants. Summary of the Invention

[0004] The present disclosure provides a hydrophilic modified molecular sieve-based catalyst and a preparation method and application thereof, in order to at least solve the above technical problems existing in the prior art.

[0005] According to a first aspect of the present disclosure, there is provided a method for preparing a hydrophilically modified molecular sieve-based catalyst, the method comprising:

[0006] The molecular sieve carrier, the titanium-containing compound and the solvent are mixed, impregnated, dried and calcined to obtain the titanium-loaded molecular sieve;

[0007] The titanium-loaded molecular sieve is mixed with a mercaptosilylating agent and an organic solvent to carry out a modification reaction, and a mercapto-modified intermediate is obtained after separation treatment;

[0008] The thiol-modified intermediate is mixed with an oxidant solution for reaction, and then separated and dried to obtain a hydrophilic modified molecular sieve-based catalyst.

[0009] In one embodiment, the molecular sieve carrier is an aluminosilicate molecular sieve having a porous structure.

[0010] In one embodiment, based on the mass of the molecular sieve carrier, the mass fraction of the titanium-containing compound relative to the molecular sieve carrier is 0.5-10%.

[0011] In one embodiment, the calcination atmosphere is air, the calcination temperature is 400-600° C., and the calcination time is 2-4 hours.

[0012] In one embodiment, the mass ratio of the mercaptosilylating agent to the molecular sieve carrier is 0.5-6:1.

[0013] In one embodiment, the mass volume ratio of the molecular sieve carrier to the solvent is 1 g:2.5-20 mL.

[0014] In one embodiment, the titanium-loaded molecular sieve is mixed with a mercaptosilylating agent and an organic solvent, and condensed and refluxed at 70° C. for 24 to 48 hours to perform a modification reaction.

[0015] In one embodiment, the mass volume ratio of the thiol-modified intermediate to the oxidant solution is 1 g: 10-30 mL.

[0016] According to a second aspect of the present disclosure, a hydrophilic modified molecular sieve-based catalyst is provided, which is prepared according to the above preparation method.

[0017] According to a third aspect of the present disclosure, there is provided an application of a hydrophilic modified molecular sieve-based catalyst in the preparation of a biomass-derived polyphenol antioxidant, wherein the biomass-derived phenolic compound is converted into a polyphenolic substance through a catalytic reaction under the action of the hydrophilic modified molecular sieve-based catalyst.

[0018] The present disclosure provides a method for preparing a hydrophilic modified molecular sieve-based catalyst, which comprises mixing a molecular sieve carrier, a titanium-containing compound and a solvent, performing an impregnation treatment, and then drying and calcining to obtain a titanium-loaded molecular sieve; then mixing the titanium-loaded molecular sieve with a mercaptosilane reagent and an organic solvent, performing a modification reaction, and obtaining a mercapto-modified intermediate after separation treatment; then mixing the mercapto-modified intermediate with an oxidant solution for reaction, separating and drying to obtain a hydrophilic modified molecular sieve-based catalyst. This scheme adopts a step-by-step impregnation loading method to introduce the titanium-containing compound and the mercaptosilane reagent into the molecular sieve carrier, thereby realizing the insertion of -SO3H groups and TiO2 particles into the active sites of the molecular sieve carrier. The -SO3H group is a strongly polar group that can form hydrogen bonds with water molecules, significantly improving the surface wettability of the catalyst and enhancing the hydronium ions (H3O +) concentration, the TiO2 particle surface readily combines with water to form surface hydroxyl groups (-OH), which tend to enrich water molecules near the active sites. Water molecules act as nucleophiles to promote methyl shedding. This catalyst is used to catalyze the conversion of biomass-derived phenolic compounds into polyphenol antioxidants. The -SO3H groups and TiO2 synergistically enhance the density of water molecules near the active sites, thereby strengthening the contact between hydronium ion clusters and phenolic compounds, thereby increasing the yield of polyphenolic compounds.

[0019] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other objects, features and advantages of the exemplary embodiments of the present disclosure will become readily understood by reading the detailed description below with reference to the accompanying drawings, in which several embodiments of the present disclosure are shown by way of example and not limitation, wherein:

[0021] In the drawings, the same or corresponding reference numerals denote the same or corresponding parts.

[0022] Figure 1 A schematic flow chart of a method for preparing a hydrophilically modified molecular sieve-based catalyst according to an embodiment of the present disclosure is shown;

[0023] Figure 2 TEM images and HAADF-STEM images of the catalyst prepared in Example 1 of the present disclosure are shown;

[0024] Figure 3 The XRD patterns of the catalysts prepared in Example 1, Comparative Example 1, Comparative Example 3 and Comparative Example 4 of the present disclosure are shown;

[0025] Figure 4 NH3-TPD diagrams of the catalysts prepared in Example 1 and Comparative Example 1 of the present disclosure are shown;

[0026] Figure 5 The XPS spectrum of the catalyst prepared in Example 1 of the present disclosure is shown. DETAILED DESCRIPTION

[0027] To make the purposes, features, and advantages of the present disclosure more apparent and understandable, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present disclosure without creative work shall fall within the scope of protection of the present disclosure.

[0028] Phenolic compounds extracted or enriched from biomass and its byproducts can be used as antioxidants. While this approach offers the advantage of being green and sustainable, its antioxidant activity is generally weaker than that of synthetic antioxidants. Multiple phenolic hydroxyl groups form intramolecular hydrogen bonds and intermolecular hydrogen bonds with adjacent methoxy groups, which contribute to enhanced antioxidant activity. Saturated alkyl substituents on the benzene ring help lower the bond dissociation enthalpy of phenolic compounds, increasing the stability of the central hydroxyl group and free radicals, further enhancing their antioxidant activity. Therefore, catalytic conversion of monophenols into polyphenols can be used to enhance the antioxidant activity of biomass-derived phenolic compounds.

[0029] In related technologies, phenolic compounds are reacted with terminal olefins in the presence of a catalyst to introduce alkyl chains into the phenolic molecules, thereby improving the molecular weight, thermal stability, and material compatibility of the antioxidant. The products obtained by this method have excellent antioxidant properties, but the catalyst used is a homogeneous catalyst, which makes product separation difficult. Based on this, the present disclosure proposes a new catalyst designed to be used in the preparation of polyphenol antioxidants from biomass-derived phenolic compounds, thereby solving the existing catalyst separation problem, further improving antioxidant performance, and providing an innovative path for the green and efficient production of antioxidants.

[0030] The present disclosure provides a method for preparing a hydrophilic modified molecular sieve-based catalyst, such as Figure 1 Schematic diagram of the process of the method, the method comprises the following steps:

[0031] Step 1: Mix a molecular sieve carrier, a titanium-containing compound and a solvent, perform an impregnation treatment, and then dry and calcine to obtain a titanium-loaded molecular sieve.

[0032] Molecular sieves are selected as carriers because they have a regular pore structure and a large specific surface area, which can provide good dispersion space for the active components. In a preferred embodiment, the molecular sieve carrier is a porous aluminosilicate molecular sieve with a silicon-aluminum ratio of 25-40. The molecular sieve carrier is preferably Hβ25 or Hβ40.

[0033] The titanium-containing compound is preferably a soluble titanium salt, such as titanium isopropoxide, titanium chloride, etc. The solvent, as a dissolving medium for the titanium salt, may be methanol, ethanol, or isopropanol.

[0034] In one example, the mass fraction of the titanium-containing compound relative to the molecular sieve carrier is 0.5-10%, and the mass volume ratio of the molecular sieve carrier to the solvent is 1 g: 2.5-20 mL.

[0035] The molecular sieve carrier, titanium salt and solvent are placed in a beaker and stirred and impregnated at room temperature for 6-48 hours. During this process, the titanium salt gradually adheres to the surface and pores of the molecular sieve through physical adsorption and chemical action. Stirring can make the titanium salt evenly distributed in the system, ensuring that the loading process is sufficient and uniform. After the impregnation is completed, it is dried overnight to remove the solvent and then calcined in a tube furnace. The specific calcination conditions are: the calcination atmosphere is air, the gas flow rate is 80mL / min, the heating rate is 1-5℃ / min, the calcination temperature is 400-600℃, and the calcination time is 2-4h. During the calcination process, the titanium salt undergoes a decomposition reaction. The calcination process can promote the decomposition of the titanium salt, convert it into a stable titanium oxide, and chemically bond with the surface of the molecular sieve, thereby enhancing the binding force between the active component and the carrier, and obtaining the loaded molecular sieve powder, that is, the titanium-loaded molecular sieve.

[0036] Step 2: Mixing the titanium-loaded molecular sieve with a mercaptosilylating agent and an organic solvent to carry out a modification reaction, and obtaining a mercapto-modified intermediate after separation treatment.

[0037] The mercaptosilylating agent is (3-mercaptopropyl)trimethoxysilane, whose molecular structure contains a mercapto group (-SH) and a trimethoxysilane group (-Si(OCH3)3). The trimethoxysilane group is highly reactive and can undergo a condensation reaction with the hydroxyl groups (-OH) on the surface of the molecular sieve, removing the methanol molecules and forming Si-O-Si chemical bonds on the surface of the molecular sieve, thereby grafting the mercaptopropyl group onto the molecular sieve surface. The introduction of the mercapto group provides a unique chemically active site for the catalyst. The mercapto group has strong nucleophilicity and can undergo specific interactions with electrophilic groups in reactants or reaction intermediates, such as binding to certain active sites in phenolic compounds, thereby affecting the selectivity and reaction rate of the reaction.

[0038] An organic solvent, toluene in this example, is used to dissolve (3-mercaptopropyl)trimethoxysilane. The mass ratio of the mercaptosilanization agent to the molecular sieve support is 0.5-5:1, and the mass-to-volume ratio of the molecular sieve support to toluene is 1 g:5-15 mL. The titanium-loaded molecular sieve powder, (3-mercaptopropyl)trimethoxysilane, and toluene are mixed and stirred according to the appropriate ratios, then refluxed at 70°C for 24-48 hours. Stirring ensures full contact between the reactants, promoting the condensation reaction between (3-mercaptopropyl)trimethoxysilane and the hydroxyl groups on the molecular sieve surface. A reflux unit condenses and refluxes volatilized toluene and reactant-generated methanol back into the reaction system, minimizing the loss of reactants and solvent and ensuring complete reaction. After the reaction, the resulting mixture is thoroughly washed to remove unreacted (3-mercaptopropyl)trimethoxysilane and reaction byproducts, and then dried overnight to yield the mercapto-modified intermediate.

[0039] Step 3: mixing the thiol-modified intermediate with an oxidant solution for reaction, separating and drying to obtain a hydrophilic modified molecular sieve-based catalyst.

[0040] The oxidant solution is 30% hydrogen peroxide (H2O2). H2O2 is a strong oxidant. The peroxide bond (-OO-) in its molecule has a high oxidation potential, which can oxidize sulfhydryl groups (-SH) to sulfonic acid groups (-SO3H). Sulfonic acid groups are highly hydrophilic and can significantly change the wettability and polarity of the catalyst surface, improving its dispersibility and compatibility in aqueous solutions or reaction systems containing water. Furthermore, the H2O2 oxidation reaction is relatively mild and can proceed at room temperature. The reaction products are primarily water and oxygen, which does not introduce new impurities and helps maintain the purity and performance of the catalyst.

[0041] The thiol-modified intermediate is placed in a 30% H₂O₂ solution at a mass-to-volume ratio of 1 g of thiol-modified intermediate to 10-30 mL of H₂O₂ solution and stirred at room temperature for 12-24 hours. Agitation promotes full contact between H₂O₂ molecules and the thiol groups on the surface of the thiol-modified intermediate, accelerating the oxidation reaction and ensuring complete hydrophilic modification. After the reaction, the product is washed to remove residual H₂O₂ and reaction byproducts, and then dried to obtain the final hydrophilic-modified catalyst. In the reaction system for preparing polyphenol antioxidants from biomass-derived phenolic compounds, the hydrophilic-modified catalyst allows for better contact with the reactants, promoting mass transfer and improving catalytic reaction efficiency.

[0042] In the above scheme, a molecular sieve carrier, a titanium-containing compound and a solvent are mixed, impregnated, and then dried and calcined to obtain a titanium-loaded molecular sieve; the titanium-loaded molecular sieve is then mixed with a mercaptosilane reagent and an organic solvent for modification reaction, and a mercapto-modified intermediate is obtained after separation treatment; the mercapto-modified intermediate is then mixed with an oxidant solution for reaction, and separated and dried to obtain a hydrophilic modified molecular sieve-based catalyst. This scheme adopts a step-by-step impregnation loading method to introduce the titanium-containing compound and the mercaptosilane reagent into the molecular sieve carrier, so that the -SO3H group and TiO2 particles are inserted into the active site of the molecular sieve carrier. The -SO3H group is a strongly polar group that can form hydrogen bonds with water molecules, significantly improving the surface wettability of the catalyst and enhancing the hydronium ions (H3O + ) concentration, the TiO2 particle surface readily combines with water to form surface hydroxyl groups (-OH), which tend to enrich water molecules near the active sites. Water molecules act as nucleophiles to promote methyl shedding. This catalyst is used to catalyze the conversion of biomass-derived phenolic compounds into polyphenol antioxidants. The -SO3H groups and TiO2 synergistically enhance the density of water molecules near the active sites, thereby strengthening the contact between hydronium ion clusters and phenolic compounds, thereby increasing the yield of polyphenolic compounds.

[0043] The present disclosure also provides an application of a hydrophilically modified molecular sieve-based catalyst in the preparation of a biomass-derived polyphenol antioxidant. Under the action of the hydrophilically modified molecular sieve-based catalyst, the biomass-derived phenolic compounds are converted into polyphenols through a catalytic reaction.

[0044] The hydrophilic modification improves the catalyst's dispersibility and wettability in the reaction system, particularly in water-based or water-containing reaction systems. This effectively improves the mass transfer between reactants and products on the catalyst surface. Reactants diffuse more quickly to the catalyst's active sites, and products detach promptly, preventing catalyst deactivation caused by product accumulation at the active sites. This allows for sustained and efficient catalytic reactions, resulting in the production of more polyphenolic products with excellent antioxidant properties. Furthermore, the phenolic hydroxyl group in the resulting polyphenolic products is a key group in exerting antioxidant activity. The catalyst's unique structure and active sites may help stabilize free radical intermediates during polyphenol formation, reduce side reactions, and promote the retention and effective combination of phenolic hydroxyl groups, thereby enhancing the antioxidant properties of the final product.

[0045] The present solution will be described in detail below with reference to specific embodiments.

[0046] Example 1

[0047] A method for preparing a hydrophilic modified molecular sieve-based catalyst comprises the following steps:

[0048] Step S11, place 2 g of Hβ25 molecular sieve, 0.59 g of titanium isopropoxide, and 20 mL of anhydrous ethanol in a beaker, stir and immerse at room temperature for 12 hours, then dry at 65°C overnight, put the dried powder into a porcelain boat and place it in a tube furnace for calcination, set the heating rate to 1°C / min, the target temperature to 400°C, and the holding time to 4 hours. After cooling to room temperature, take out the porcelain boat to obtain 5 wt.% Ti-loaded Hβ25 molecular sieve.

[0049] Step S12: 2 g of 5 wt.% Ti-loaded Hβ25 molecular sieve, 6 g of (3-mercaptopropyl)trimethoxysilane, and 20 mL of toluene were placed in a conical flask, stirred, and condensed and refluxed at 70°C for 24 h. The resulting mixture was thoroughly washed and dried in an oven at 80°C overnight to obtain a thiol-modified intermediate.

[0050] Step S13: 2 g of the thiol-modified intermediate and 20 mL of a 30% H2O2 solution were placed in a beaker, sealed, stirred at room temperature for 24 h, washed thoroughly with deionized water, and then dried in an oven at 80°C to obtain a hydrophilic modified molecular sieve-based catalyst, which was designated as 5Ti / Hβ25-SO3H(3).

[0051] Example 2

[0052] A method for preparing a hydrophilic modified molecular sieve-based catalyst comprises the following steps:

[0053] Step S21, place 2 g of Hβ25 molecular sieve, 0.04 g of titanium tetrachloride, and 20 mL of anhydrous ethanol in a beaker, stir and immerse at room temperature for 12 hours, then dry at 65°C overnight, put the dried powder into a porcelain boat and place it in a tube furnace for calcination, set the heating rate to 1°C / min, the target temperature to 400°C, and the insulation time to 4 hours. After cooling to room temperature, take out the porcelain boat to obtain 0.5 wt.% Ti-loaded Hβ25 molecular sieve.

[0054] Step S22: 2 g of 0.5 wt.% Ti-loaded Hβ25 molecular sieve, 6 g of (3-mercaptopropyl)trimethoxysilane, and 20 mL of toluene were placed in a conical flask, stirred, and condensed and refluxed at 70°C for 24 h. The resulting mixture was thoroughly washed and placed in an oven at 80°C for drying overnight to obtain a thiol-modified intermediate.

[0055] Step S23: 2 g of the thiol-modified intermediate and 20 mL of a 30% H2O2 solution were placed in a beaker, sealed, stirred at room temperature for 24 h, washed thoroughly with deionized water, and dried in an oven at 80°C to obtain a hydrophilic modified catalyst, which was designated as 0.5Ti / Hβ25-SO3H(3).

[0056] Example 3

[0057] A method for preparing a hydrophilic modified molecular sieve-based catalyst comprises the following steps:

[0058] Step S31, place 2g of Hβ25 molecular sieve, 0.79g of titanium tetrachloride, and 20mL of anhydrous ethanol in a beaker, stir and immerse at room temperature for 12h, then dry at 65℃ overnight, put the dried powder into a porcelain boat and place it in a tube furnace for calcination, set the heating rate to 1℃ / min, the target temperature to 400℃, and the insulation time to 4h. After cooling to room temperature, take out the porcelain boat to obtain 10wt.% Ti-loaded Hβ25 molecular sieve.

[0059] Step S32: 2 g of 10 wt.% Ti-loaded Hβ25 molecular sieve, 6 g of (3-mercaptopropyl)trimethoxysilane, and 20 mL of toluene were placed in a conical flask, stirred, and condensed and refluxed at 70°C for 24 h. The resulting mixture was thoroughly washed and dried in an oven at 80°C overnight to obtain a thiol-modified intermediate.

[0060] Step S33: 2 g of the thiol-modified intermediate and 20 mL of a 30% H2O2 solution were placed in a beaker, sealed, stirred at room temperature for 24 h, washed thoroughly with deionized water, and dried in an oven at 80°C to obtain a hydrophilic modified catalyst, which was designated as 10Ti / Hβ25-SO3H(3).

[0061] Example 4

[0062] A method for preparing a hydrophilic modified molecular sieve-based catalyst comprises the following steps:

[0063] Step S41, place 2g of Hβ40 (silicon-aluminum ratio of 40) molecular sieve, 0.59g of titanium isopropoxide, and 20mL of anhydrous ethanol in a beaker, stir and immerse at room temperature for 12h, then dry at 65℃ overnight, put the dried powder into a porcelain boat and place it in a tube furnace for calcination, set the heating rate to 1℃ / min, the target temperature to 400℃, and the insulation time to 4h. After cooling to room temperature, take out the porcelain boat to obtain 5wt.% Ti-loaded Hβ40 molecular sieve.

[0064] Step S42: 2 g of 5 wt.% Ti-loaded Hβ40 molecular sieve, 6 g of (3-mercaptopropyl)trimethoxysilane, and 20 mL of toluene were placed in a conical flask, stirred, and condensed and refluxed at 70°C for 24 h. The resulting mixture was thoroughly washed and dried in an oven at 80°C overnight to obtain a thiol-modified intermediate.

[0065] Step S43: 2 g of the thiol-modified intermediate and 20 mL of a 30% H2O2 solution were placed in a beaker, sealed, stirred at room temperature for 24 h, washed thoroughly with deionized water, and dried in an oven at 80°C to obtain a hydrophilic modified catalyst, which was designated as 5Ti / Hβ40-SO3H(3).

[0066] Example 5

[0067] A method for preparing a hydrophilic modified molecular sieve-based catalyst comprises the following steps:

[0068] Step S51, place 2g of Hβ25 molecular sieve, 0.59g of titanium isopropoxide, and 20mL of anhydrous ethanol in a beaker, stir and immerse at room temperature for 12h, then dry at 65℃ overnight, put the dried powder into a porcelain boat and place it in a tube furnace for calcination, set the heating rate to 1℃ / min, the target temperature to 400℃, and the holding time to 4h. After cooling to room temperature, take out the porcelain boat to obtain 5wt.% Ti-loaded Hβ25 molecular sieve.

[0069] Step S52: 2 g of 5 wt.% Ti-loaded Hβ25 molecular sieve, 1 g of (3-mercaptopropyl)trimethoxysilane, and 20 mL of toluene were placed in a conical flask, stirred, and condensed and refluxed at 70°C for 24 h. The resulting mixture was thoroughly washed and dried in an oven at 80°C overnight to obtain a thiol-modified intermediate.

[0070] Step S53: Take 2 g of the thiol-modified intermediate and 20 mL of 30% H2O2 solution and place them in a beaker, seal and stir at room temperature for 24 hours, wash them thoroughly with deionized water, and then place them in an oven and dry them at 80°C to obtain a hydrophilic modified catalyst, which is recorded as 5Ti / Hβ25-SO3H(0.5).

[0071] Comparative Example 1

[0072] A molecular sieve catalyst. This comparative example provides an unmodified Hβ25 molecular sieve catalyst. The difference between this comparative example and Example 1 is that Ti loading and -SO3H group introduction are not performed.

[0073] Comparative Example 2

[0074] A molecular sieve catalyst, this comparative example provides an unmodified Hβ40 molecular sieve catalyst. The difference between this comparative example and Example 1 is that the silicon-aluminum ratio of the Hβ molecular sieve is 40 and Ti loading and -SO3H group introduction are not performed.

[0075] Comparative Example 3

[0076] A molecular sieve catalyst, this comparative example provides a 5Ti / Hβ25 catalyst. The difference between this comparative example and Example 1 is that no -SO3H group is introduced; the other parameters are consistent with Example 1. The preparation method includes the following steps:

[0077] 2 g of Hβ25 molecular sieve, 0.59 g of titanium isopropoxide, and 20 mL of anhydrous ethanol were placed in a beaker, stirred and immersed at room temperature for 12 h, and then dried at 65 ° C overnight. The dried powder was loaded into a porcelain boat and placed in a tube furnace for calcination. The heating rate was set to 1 ° C / min, the target temperature was 400 ° C, and the holding time was 4 h. After cooling to room temperature, the porcelain boat was taken out to obtain a 5Ti / Hβ25 catalyst.

[0078] Comparative Example 4

[0079] A molecular sieve catalyst, this comparative example provides a Hβ25-SO3H(3) catalyst, which differs from Example 1 in that Ti is not loaded; the other parameters are consistent with Example 1. The preparation method comprises the following steps:

[0080] 2 g of Hβ25 molecular sieve, 6 g of (3-mercaptopropyl)trimethoxysilane and 20 mL of toluene were placed in a conical flask, stirred, and condensed and refluxed at 70°C for 24 h. The resulting mixture was thoroughly washed and placed in an oven at 80°C for drying overnight to obtain a modified intermediate; 2 g of the modified intermediate and 20 mL of 30% H2O2 solution were placed in a beaker, sealed and stirred at room temperature for 24 h, thoroughly washed with deionized water, and placed in an oven at 80°C for drying to obtain Hβ25-SO3H(3) catalyst.

[0081] Comparative Example 5

[0082] A method for preparing a hydrophilic modified molecular sieve-based catalyst comprises the following steps:

[0083] Step D51, place 2 g of Hβ40 molecular sieve, 1.19 g of titanium isopropoxide, and 20 mL of anhydrous ethanol in a beaker, stir and immerse at room temperature for 12 hours, then dry at 65°C overnight, put the dried powder into a porcelain boat and place it in a tube furnace for calcination, set the heating rate to 1°C / min, the target temperature to 400°C, and the insulation time to 4 hours. After cooling to room temperature, take out the porcelain boat to obtain 10 wt.% Ti-loaded Hβ40 molecular sieve.

[0084] Step D52: 2 g of 10 wt.% Ti-loaded Hβ40 molecular sieve, 12 g of (3-mercaptopropyl)trimethoxysilane, and 20 mL of toluene were placed in a conical flask, stirred, and condensed and refluxed at 70°C for 24 h. The resulting mixture was thoroughly washed and dried in an oven at 80°C overnight to obtain a thiol-modified intermediate.

[0085] Step D53: 2 g of the thiol-modified intermediate and 20 mL of a 30% H2O2 solution were placed in a beaker, sealed, and stirred at room temperature for 24 h. After being thoroughly washed with deionized water, the mixture was dried in an oven at 80°C to obtain a hydrophilic modified catalyst, which was designated as 10Ti / Hβ40-SO3H(6).

[0086] Comparative Example 6

[0087] A method for preparing a hydrophilic modified molecular sieve-based catalyst comprises the following steps:

[0088] Step D61, place 2 g of HZSM-5 (silicon-aluminum ratio of 25) molecular sieve, 0.59 g of titanium isopropoxide, and 20 mL of anhydrous ethanol in a beaker, stir and soak at room temperature for 12 hours, then dry at 65°C overnight, put the dried powder into a porcelain boat and place it in a tube furnace for calcination, set the heating rate to 1°C / min, the target temperature to 400°C, and the holding time to 4 hours. After cooling to room temperature, take out the porcelain boat to obtain 5 wt.% Ti-loaded HZSM-5 molecular sieve.

[0089] Step D62: 2 g of 5 wt.% Ti-loaded HZSM-5 molecular sieve, 6 g of (3-mercaptopropyl)trimethoxysilane, and 20 mL of toluene were placed in a conical flask, stirred, and condensed and refluxed at 70°C for 24 h. The resulting mixture was thoroughly washed and dried in an oven at 80°C overnight to obtain a thiol-modified intermediate.

[0090] Step D63: 2 g of the thiol-modified intermediate and 20 mL of a 30% H2O2 solution were placed in a beaker, sealed, and stirred at room temperature for 24 h. The mixture was thoroughly washed with deionized water and then dried in an oven at 80°C to obtain a hydrophilic modified catalyst, which was designated as 5Ti / HZSM5-SO3H(3).

[0091] Comparative Example 7

[0092] A method for preparing a hydrophilic modified molecular sieve-based catalyst comprises the following steps:

[0093] Step D71, place 2 g of HY (silicon-aluminum ratio of 40) molecular sieve, 0.59 g of titanium isopropoxide, and 20 mL of anhydrous ethanol in a beaker, stir and soak at room temperature for 12 hours, then dry at 65°C overnight, put the dried powder into a porcelain boat and place it in a tube furnace for calcination, set the heating rate to 1°C / min, the target temperature to 400°C, and the holding time to 4 hours. After cooling to room temperature, take out the porcelain boat to obtain 5 wt.% Ti-loaded HY molecular sieve.

[0094] Step D72: Take 2 g of 5 wt.% Ti-loaded HY molecular sieve, 12 g of (3-mercaptopropyl)trimethoxysilane, and 20 mL of toluene, place them in a conical flask, stir, and condense and reflux at 70°C for 24 hours. After washing the resulting mixture thoroughly, place it in an oven at 80°C and dry it overnight to obtain a thiol-modified intermediate.

[0095] Step D73: Take 2 g of the thiol-modified intermediate and 20 mL of 30% H2O2 solution and place them in a beaker, seal and stir at room temperature for 24 h, wash them thoroughly with deionized water, and then place them in an oven and dry them at 80°C to obtain a hydrophilic modified catalyst, which is recorded as 5Ti / HY-SO3H(3).

[0096] Catalyst characterization

[0097] 1. TEM characterization of the 5Ti / Hβ25-SO3H(3) catalyst prepared in Example 1 was performed. Figure 2 As shown in Figure (a); High angle annular dark field scanning transmission electron microscopy (HAADF-STEM) Figure 2 As shown in Figure (b).

[0098] The TEM image shows that the catalyst is in the form of irregular particles. This irregular shape increases the specific surface area of ​​the catalyst and can provide more active sites. For example, the loaded titanium species can be dispersed on the surface and inside the particles, which is conducive to the adsorption of reactant molecules. Biomass-derived phenolic compounds can more easily contact active sites to react and promote the production of antioxidants. The lattice fringes in the image indicate the presence of a crystalline phase. Taking the loaded titanium oxide as an example, its crystalline phase determines the electron transfer ability and adsorption-desorption performance of the reactants. This crystalline phase can accelerate electron transfer in the reaction and improve catalytic efficiency.

[0099] According to the HAADF-STEM image, the bright areas show the distribution of elements such as titanium. The uniform dispersion of the active components allows the reactant molecules to react evenly on the catalyst surface, avoiding local overreaction or side reactions, ensuring that the reaction proceeds in the direction of producing polyphenol antioxidants, and improving catalytic selectivity. Secondly, the interface between the active components and the molecular sieve support can be observed. There is a synergistic effect between the two. The pore structure of the molecular sieve can limit the diffusion path of reactants and products, cooperate with the active components, and optimize the reaction path.

[0100] 2. XRD patterns of 5Ti / Hβ25-SO3H(3) prepared in Example 1, Hβ25 molecular sieve catalyst provided in Comparative Example 1, 5Ti / Hβ25 catalyst prepared in Comparative Example 3, and Hβ25-SO3H(3) catalyst prepared in Comparative Example 4 were characterized. Figure 3 shown.

[0101] Comparing the XRD patterns of the 5Ti / Hβ25-SO3H(3) catalyst prepared in Example 1 and the Hβ25 molecular sieve provided in Comparative Example 1, it can be seen from the XRD pattern that the lattice has a certain distortion, as the Ti and sulfonic acid groups exist in the lattice of the molecular sieve skeleton in an amorphous manner. Specifically, the signals of some peaks are shifted to the right as a whole and the peak width increases, indicating that titanium and sulfonic acid groups have been successfully introduced. At the same time, the main characteristic peaks of the Hβ25 molecular sieve still exist, indicating that the main structure of the molecular sieve has not undergone fundamental changes. Titanium dioxide can provide redox active sites, which is beneficial to the electron transfer in the catalytic reaction and promotes the activation of the reactants; while the introduction of sulfonic acid groups increases the acidity of the catalyst surface, strengthens the adsorption of reactants, and reduces the activation energy of the reaction. The two work together to enable the 5Ti / Hβ25-SO3H(3) catalyst to catalyze the reaction more efficiently in the preparation of antioxidants from biomass-derived phenols.

[0102] 3. NH3-TPD test was performed on 5Ti / Hβ25-SO3H (3) prepared in Example 1 and Hβ25 molecular sieve catalyst provided in Comparative Example 1. Figure 4 shown.

[0103] The peak area of ​​the curve corresponding to 5Ti / Hβ25-SO3H(3) is larger, indicating that the number of acidic sites in the 5Ti / Hβ25-SO3H(3) catalyst increases after titanium loading and sulfonic acid group modification. This is because the sulfonic acid group is a strong acidic functional group, and the introduction of the acidic sites increases; titanium also participates in changing the electronic structure of the catalyst surface, promoting the production of more acid. In the preparation of antioxidants from biomass-derived phenols, acidic sites are crucial. The large number of acidic sites and unique acid strength distribution of the 5Ti / Hβ25-SO3H(3) catalyst make it more capable of adsorbing phenolic reactants. For example, weak acidic sites can enrich phenolic molecules on the catalyst surface through physical adsorption; strong acidic sites can cause phenolic molecules to undergo protonation and other reactions through chemical adsorption, activate functional groups such as phenolic hydroxyl groups, reduce the reaction activation energy, and promote condensation and oxidation reactions between phenolic molecules, thereby efficiently generating polyphenolic antioxidants.

[0104] 4. XPS analysis was performed on 5Ti / Hβ25-SO3H(3) prepared in Example 1. Figure 5 shown.

[0105] The obvious peak in the figure is Ti 2p, indicating the presence of titanium in the catalyst 5Ti / Hβ25-SO3H(3). The appearance of the Ti 2p peak directly proves that titanium was successfully loaded onto the molecular sieve during the preparation process. The binding energy values ​​on the abscissa correspond to specific titanium oxidation states. The binding energy of the Ti 2p peak is in the range of approximately 458-464 eV, indicating that titanium exists primarily in the form of TiO2.

[0106] Catalytic performance test

[0107] The catalysts prepared in Examples 1-5 and Comparative Examples 1-7 were ground and sieved to 60-80 mesh, and then the catalyst activity was evaluated.

[0108] In the evaluation of catalyst activity, the preparation of polyphenol antioxidants from biomass-derived phenolic compounds was carried out in a high-pressure reactor. 6 mmol of biomass-derived phenolic compounds, 0.3 g of catalyst, and 7 mL of deionized water were added to the reactor in sequence. The reactor was sealed and high-purity nitrogen was introduced for 15 minutes to expel the air. The reaction conditions were as follows: reaction pressure of 1 MPa, reaction atmosphere of nitrogen, reaction temperature of 280°C, reaction time of 150 minutes, and rotation speed of 800 rpm. Specific data are shown in Table 1.

[0109] Table 1

[0110]

[0111]

[0112] Substrate type, G is guaiacol, 4-MG is 4-methylguaiacol, 4-EG is 4-ethylguaiacol, 4-PG is 4-propylguaiacol, and DP is 2,6-dimethoxyphenol.

[0113] According to the experimental results in Table 1, the catalysts prepared in Examples 1-5 are applied to the preparation of polyphenol antioxidants from biomass-derived phenolic compounds, and have a high polyphenol yield under various substrate types. Comparative Examples 1 and 2 both use unloaded molecular sieves directly as catalysts, while Comparative Examples 3 and 4 load either Ti or -SO3H, respectively, and the polyphenol yield is relatively low. The high loading of -SO3H in Comparative Example 5 will lead to a decrease in the polyphenol yield; the molecular sieve supports used in Comparative Examples 6 and 7 are HZSM and HY, and the polyphenol yield is significantly lower than that of Hβ25 and Hβ40. It should be understood that the various forms of the process shown above can be used to reorder, add or delete steps. For example, the steps recorded in the present disclosure can be performed in parallel, sequentially, or in different orders, as long as the desired results of the technical solution disclosed in the present disclosure can be achieved, and this document does not limit them here.

[0114] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. Throughout the present disclosure, "plurality" means two or more, unless otherwise specifically defined.

[0115] The above description is merely a specific embodiment of the present disclosure, but the scope of protection of the present disclosure is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this disclosure should be included in the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on the scope of protection of the claims.

Claims

1. A method for preparing a hydrophilic modified molecular sieve-based catalyst, characterized in that: The method comprises: The molecular sieve carrier, the titanium-containing compound and the solvent are mixed, impregnated, dried and calcined to obtain the titanium-loaded molecular sieve; The titanium-loaded molecular sieve is mixed with a mercaptosilylating agent and an organic solvent to carry out a modification reaction, and a mercapto-modified intermediate is obtained after separation treatment; The thiol-modified intermediate is mixed with an oxidant solution for reaction, and then separated and dried to obtain a hydrophilic modified molecular sieve-based catalyst.

2. The method for preparing a hydrophilic modified molecular sieve-based catalyst according to claim 1, wherein: The molecular sieve carrier is an aluminosilicate molecular sieve with a porous structure.

3. The method for preparing a hydrophilic modified molecular sieve-based catalyst according to claim 1, wherein: Based on the mass of the molecular sieve carrier, the mass fraction of titanium in the titanium-containing compound relative to the mass fraction of the molecular sieve carrier is 0.5-10%.

4. The method for preparing a hydrophilic modified molecular sieve-based catalyst according to claim 1, wherein: The calcination atmosphere is air, the calcination temperature is 400-600° C., and the calcination time is 2-4 hours.

5. The method for preparing a hydrophilic modified molecular sieve-based catalyst according to claim 1, wherein: The mass ratio of the mercaptosilylating agent to the molecular sieve carrier is 0.5-6:

1.

6. The method for preparing a hydrophilic modified molecular sieve-based catalyst according to claim 1, wherein: The mass volume ratio of the molecular sieve carrier to the solvent is 1 g:2.5-20 mL.

7. The method for preparing a hydrophilic modified molecular sieve-based catalyst according to claim 1, wherein: The titanium-loaded molecular sieve is mixed with a mercaptosilylating agent and an organic solvent, and condensed and refluxed at 70° C. for 24 to 48 hours to perform a modification reaction.

8. The method for preparing a hydrophilic modified molecular sieve-based catalyst according to claim 1, wherein: The mass volume ratio of the thiol-modified intermediate to the oxidant solution is 1 g:10-30 mL.

9. A hydrophilic modified molecular sieve-based catalyst, characterized in that: The hydrophilic modified molecular sieve-based catalyst is prepared according to the preparation method of any one of claims 1 to 8.

10. Use of a hydrophilic modified molecular sieve-based catalyst in the preparation of a biomass-derived polyphenol antioxidant, characterized in that: The hydrophilic modified molecular sieve-based catalyst is prepared according to the preparation method of the hydrophilic modified molecular sieve-based catalyst according to any one of claims 1 to 8; the biomass-derived phenolic compound is converted into a monophenol into a polyphenol substance through a catalytic reaction under the action of the hydrophilic modified molecular sieve-based catalyst.

Images