A method for preparing Ti-MWW zeolite from waste TS-1 catalyst

Abstract

This invention discloses a method for preparing Ti-MWW zeolite from waste TS-1 catalyst, belonging to the field of molecular sieve catalyst preparation technology. The method uses waste TS-1 molecular sieve as the sole silicon-titanium source. After grinding and pretreatment, it is mixed with an alkali source, a boron source, a template agent, and deionized water to prepare a transcrystalline gel. The pH of the system is adjusted to >13, and a hydrothermal crystallization reaction is used to achieve directional transcrystalline transformation from the MFI topology to the MWW topology. After washing, acid leaching to remove impurities, and calcination activation, a highly crystalline and highly catalytically active Ti-MWW zeolite product is obtained. This invention eliminates the need for additional silicon and titanium sources, significantly reducing raw material costs, realizing the resource utilization of waste TS-1, solving the problem of solid waste treatment, and demonstrating significant environmental benefits and industrial application prospects. The prepared Ti-MWW zeolite exhibits excellent catalytic performance in selective oxidation reactions.

Description

Technical Field

[0001] This invention relates to a method for preparing Ti-MWW zeolite from waste TS-1 catalyst, belonging to the field of molecular sieve catalyst preparation technology. Background Technology

[0002] Ti-MWW titanium silicate zeolite possesses a layered MWW topology with a complex pore system of ten- and twelve-membered rings, exhibiting excellent catalytic selectivity and stability in reactions such as cyclohexane oxidation, olefin epoxidation, phenol hydroxylation, and ketone ammonium oximeation. Current methods for preparing Ti-MWW mainly involve the traditional two-step method and a one-step hydrothermal method. Both methods use chemical raw materials such as tetrabutyl orthosilicate and tetrabutyl titanate as silicon and titanium sources, respectively, and require the addition of boric acid as a structural aid and piperidine as a template agent. These methods suffer from high raw material costs, cumbersome synthesis steps, and large amounts of template agents required.

[0003] CN201811502475.5 discloses a method for preparing mordenite zeolite from waste MTP catalyst and its application. Waste MTP molecular sieve catalyst (SiO2 / Al2O3=4-14) is used as raw material, and carbon deposits are removed by calcination before its application in the preparation of mordenite zeolite. CN202410391426.8 discloses a method for preparing ZSM-35 molecular sieve from waste ZSM-5 molecular sieve. Related studies have shown that industrial waste zeolite catalysts can be reused through zeolite crystallization. Therefore, this study investigates a method for efficiently converting waste Y catalyst (SiO2 / Al2O3=20-200) into mordenite zeolite, avoiding the calcination of the waste catalyst, thereby reducing the economic cost of mordenite zeolite and preventing the generation of large amounts of polluting gases. TS-1 molecular sieve has an MFI topology and unique shape-selective catalytic properties. It is widely used in selective oxidation reactions such as olefin epoxidation, ketone ammoxidation, and aromatic hydrocarbon hydroxylation, and is one of the core catalysts in the fine chemical and petrochemical fields. However, during use, TS-1 is prone to losing its catalytic performance due to factors such as deactivation of active sites, carbon buildup in pores, and partial collapse of the framework structure, resulting in a large amount of waste TS-1 catalyst. Direct disposal not only wastes titanium and silicon resources but also causes solid waste pollution problems. Therefore, it is urgent to develop resource utilization technologies for waste TS-1.

[0004] This invention uses waste TS-1 as a silicon-titanium source and achieves directional crystal transformation from MFI topology to MWW topology through alkali source regulation and template agent guidance, directly preparing Ti-MWW zeolite without the need for additional silicon or titanium sources, significantly reducing the preparation cost of Ti-MWW, while solving the problem of waste TS-1 disposal, thus possessing both economic value and environmental significance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing Ti-MWW zeolite from waste TS-1 catalyst. This method uses waste TS-1 as the sole silicon-titanium source and achieves directional transformation of the topological structure through a hydrothermal crystallization process to prepare Ti-MWW zeolite with high crystallinity and high catalytic activity. The process is simple, the raw material cost is low, and it is environmentally friendly, realizing the resource utilization of waste.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing Ti-MWW zeolite from waste TS-1 catalyst includes the following steps: (a) Pretreatment of waste TS-1 catalyst: The waste TS-1 catalyst was ground to control the crystal particle size after grinding to <10 μm, and the pretreated waste TS-1 powder was obtained, which was directly used as the silicon-titanium source for the preparation of Ti-MWW zeolite. (b) Gel preparation: Take pretreated TS-1 powder (calculated as SiO2), alkali source, boron source, template agent and deionized water. First, mix the alkali source, boron source and deionized water and stir until completely dissolved. Add the pretreated waste TS-1 powder and stir for 1-3 h. Then add the template agent and stir at 40-60℃ for 2-4 h. Adjust the pH of the system to >13 to obtain a homogeneous transcrystalline gel. (c) Preparation of Na-type Ti-MWW zeolite: The crystallization gel was transferred to a pressure-resistant sealed container lined with polytetrafluoroethylene and subjected to hydrothermal crystallization reaction at 150-200℃ for 72-168 h. After crystallization, the mixture was cooled to room temperature and the solid product was obtained by solid-liquid separation, which is the crude Na-type Ti-MWW zeolite. (d) Preparation of Ti-MWW zeolite product: The crude Na-type Ti-MWW zeolite was washed with deionized water until neutral, dried at 80-100℃ for 10-14 h, and then acid-washed to remove boron and impurities, and calcined and activated to obtain the Ti-MWW zeolite product.

[0007] Preferably, the waste TS-1 catalyst in step (a) has a silicon-titanium molar ratio of SiO2 / TiO2 of 20-80.

[0008] Preferably, the alkali source is one or a mixture of sodium hydroxide and potassium hydroxide.

[0009] Preferably, the boron source is boric acid.

[0010] Preferably, the template agent is one or a mixture of two of piperidine, cycloheximine, and N,N,N-trimethyl-1-adamantylammonium hydroxide.

[0011] Preferably, in step (b), the pretreatment of waste TS-1 powder is based on SiO2, the boron source is based on B2O3, and the molar ratio of SiO2:B2O3:template agent is 1:(0.1-0.4):(0.5-1.5).

[0012] Preferably, the specific operation of acid washing for boron removal and impurity removal in step (d) is as follows: the dried solid product is added to a 2-3 mol / L nitric acid solution with a liquid-to-solid ratio of 30:1 (mL / g), refluxed at 100℃ for 6-12 h, and after solid-liquid separation, washed with deionized water until neutral, and dried at 80-100℃ for 8-10 h.

[0013] Preferably, the specific operation of calcination activation in step (d) is as follows: the acid-washed and dried product is placed in a muffle furnace, heated to 550°C in an air atmosphere at a heating rate of 2°C / min, calcined for 4-6 h, and then naturally cooled to room temperature to obtain the Ti-MWW zeolite product.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention uses waste TS-1 as the only silicon-titanium source and directly prepares Ti-MWW zeolite through hydrothermal crystallization. There is no need to add additional silicon-titanium raw materials such as tetrabutyl tetrasilicate and tetrabutyl titanate, which greatly reduces the preparation cost of Ti-MWW. At the same time, it solves the problem of waste TS-1 solid waste disposal, realizes the recycling of titanium and silicon resources, and has significant environmental benefits.

[0015] (2) This invention achieves directional crystallization from MFI topology to MWW topology by precisely controlling the concentration of alkali source, type and ratio of template agent, pH value, crystallization temperature and time, effectively retaining the skeletal titanium species in waste TS-1, and ensuring high crystallinity and high catalytic activity of Ti-MWW zeolite by boric acid-assisted crystallization and acid elution to remove boron; the preparation process of this invention is simple, no complicated pretreatment equipment is required, the ground waste TS-1 can be used directly, and the crystallization and post-treatment steps are easy to operate and easy to scale up, making it suitable for industrial production.

[0016] (3) The Ti-MWW zeolite product prepared by this invention is free of impurities, has uniform dispersion of titanium species and rich pore structure. It exhibits excellent catalytic performance in selective oxidation reactions such as the oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-dicarboxyfuran (DFF) and has good prospects for industrial application. Attached Figure Description

[0017] Figure 1 The XRD pattern of the Ti-MWW zeolite molecular sieve prepared in Example 1; Figure 2 The XRD pattern of the Ti-MWW zeolite molecular sieve prepared in Example 2; Figure 3The attached figure shows the nitrogen adsorption-desorption process of the Ti-MWW zeolite molecular sieve prepared in Example 2; Figure 4 The reaction performance of different catalysts for the selective oxidation of HMF to DFF; Figure 5 The image shows the GC diagram of the sample after the Ti-MWW zeolite molecular sieve catalytic reaction prepared in Example 1. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to specific embodiments, but it is not limited thereto.

[0019] Example 1 A method for preparing Ti-MWW zeolite from waste TS-1 catalyst, the specific steps of which are as follows: (1) The waste TS-1 catalyst was ground and the crystal particle size after grinding was controlled to be <10 μm to obtain pretreated waste TS-1 powder, which was directly used as the silicon-titanium source for preparing Ti-MWW zeolite. (2) Weigh 2 g of pretreated waste TS-1, 0.60 g of sodium hydroxide, 0.49 g of boric acid, 1.65 g of piperidine, and 21 g of deionized water. First, mix sodium hydroxide, boric acid, and deionized water and stir until completely dissolved. Then add the pretreated waste TS-1 powder and stir at room temperature for 2 h. Next, add piperidine and stir at 50°C for 3 h to obtain a gel solution.

[0020] (3) The gel was transferred to a high-pressure reactor with a polytetrafluoroethylene liner and crystallized at 180°C for 144 h to obtain crude Na-type Ti-MWW zeolite; (4) The crude Na-type Ti-MWW zeolite was washed with deionized water until neutral and dried at 90°C for 12 h. The dried product was added to 2 mol / L nitric acid solution at a liquid-to-solid ratio of 30:1 (mL / g) and refluxed at 100°C for 10 h. The product was then filtered, washed with water until neutral, and dried at 90°C for 9 h. The acid-washed and dried product was placed in a muffle furnace and heated to 550°C at 2°C / min in air atmosphere and calcined for 5 h to obtain the Ti-MWW zeolite product, which was labeled as Ti-MWW-S.

[0021] Example 2 A method for preparing Ti-MWW zeolite from waste TS-1 catalyst, the specific steps of which are as follows: (1) The waste TS-1 catalyst was ground and the crystal particle size after grinding was controlled to be <10 μm to obtain pretreated waste TS-1 powder, which was directly used as the silicon-titanium source for preparing Ti-MWW zeolite. (2) Weigh 2 g of pretreated waste TS-1, 0.5 g of sodium hydroxide, 1.0 g of boric acid, 0.5 g of piperidine, 0.85 g of hexamethylimine, and 20 g of deionized water. First, mix sodium hydroxide, boric acid, and deionized water and stir until completely dissolved. Then add the pretreated waste TS-1 powder and stir at room temperature for 2 h. Next, add the template agent and stir at 50°C for 3 h to obtain a transcrystalline gel.

[0022] (3) The crystallization gel was transferred to a high-pressure reactor with a polytetrafluoroethylene liner and crystallized at 160°C for 120 h to obtain crude Na-type Ti-MWW zeolite. (4) Wash the crude zeolite until neutral and dry it; add the dried product to 2 mol / L nitric acid solution, with a liquid-to-solid ratio of 30:1 (mL / g), reflux at 100℃ for 10 h, filter, wash with water until neutral, and dry at 90℃ for 9 h; place the product in a muffle furnace, heat it to 550℃ at 2℃ / min in air atmosphere, calcine for 5 h, and cool naturally to obtain Ti-MWW zeolite product.

[0023] Example 3 A method for preparing Ti-MWW zeolite from waste TS-1 catalyst, the specific steps of which are as follows: (1) The waste TS-1 catalyst was ground and the crystal particle size after grinding was controlled to be <10 μm to obtain pretreated waste TS-1 powder, which was directly used as the silicon-titanium source for preparing Ti-MWW zeolite. (2) Weigh 2 g of pretreated waste TS-1, 0.7 g of sodium hydroxide, 1.2 g of boric acid, 0.80 g of hexamethylimine, 0.6 g of N,N,N-trimethyl-1-adamantyl ammonium hydroxide, and 25 g of deionized water. First, mix sodium hydroxide, boric acid, and deionized water and stir until completely dissolved. Then add the pretreated waste TS-1 powder and stir at room temperature for 2 h. Next, add the template agent and stir at 60°C for 3 h to obtain a transcrystalline gel.

[0024] (3) The crystallization gel was transferred to a high-pressure reactor with a polytetrafluoroethylene liner and crystallized at 200°C for 100 h to obtain crude Na-type Ti-MWW zeolite. (4) Wash the crude zeolite until neutral and dry it; add the dried product to 2 mol / L nitric acid solution, with a liquid-to-solid ratio of 30:1 (mL / g), reflux at 100℃ for 10 h, filter, wash with water until neutral, and dry at 90℃ for 9 h; place the product in a muffle furnace, heat it to 550℃ at 2℃ / min in air atmosphere, calcine for 5 h, and cool naturally to obtain Ti-MWW zeolite product.

[0025] Comparative Example 1 A conventional hydrothermal method for preparing Ti-MWW zeolite includes the following steps: Ti-MWW was prepared according to this method: Piperidine (PI) was used as a structure-directing agent (SDA), and Ti-MWW was synthesized via a hydrothermal method with the assistance of boric acid. A gel with a molar ratio of 1.0 SiO2:0.025 TiO2:1.4 PI:0.67 B2O3:22 H2O was crystallized at 175℃ for 72 h under stirring (200 rpm). The resulting solid was then washed with deionized water, filtered, and dried overnight at 100℃. The obtained Ti-MWW was added to a 2 mol / L nitric acid solution at a liquid-to-solid ratio of 30:1 (mL / g), refluxed at 100℃ for 10 h, filtered, washed with water until neutral, and dried at 90℃ for 9 h. The product was then placed in a muffle furnace, heated to 550℃ at 2℃ / min under air atmosphere, calcined for 5 h, and naturally cooled to obtain the Ti-MWW zeolite product, denoted as Ti-MWW-B.

[0026] Test Example 1 Structural characterization tests (XRD and nitrogen adsorption-desorption) Test method: X-ray diffraction (XRD) test: The samples prepared in Example 1 and Example 2 were scanned in the range of 5° to 35° (2θ) using an X-ray powder diffractometer (e.g., Cu Kα radiation, tube voltage 40 kV, tube current 40 mA) at a scanning rate of 2° / min.

[0027] Nitrogen adsorption-desorption test: The samples prepared in Example 2 were tested using a fully automated specific surface area and porosity analyzer at a liquid nitrogen temperature of -196℃ (77 K). Before the test, the samples needed to be pretreated in a vacuum at 300℃ for more than 4 hours to remove moisture and impurities from the pores.

[0028] XRD test characterization results are as follows: Figure 1-2 As shown, both samples prepared in Examples 1 and 2 exhibited typical characteristic peaks of Ti-MWW, indicating good crystallinity. No characteristic peaks of titanium oxide (TiO2) or other heterocrystalline phases were observed in the spectra. This demonstrates that pure-phase Ti-MWW molecular sieves can be successfully prepared using waste TS-1 as raw material through the synthesis method of this invention.

[0029] The results of nitrogen adsorption-desorption characterization are as follows: Figure 3As shown, the sample exhibits a classic type IV isotherm with a distinct hysteresis loop. In the region of low relative pressure (P / P0) (<0.1), the adsorption capacity increases sharply, indicating that the material possesses a rich microporous structure. A distinct H3-type hysteresis loop appears in the relative pressure range of P / P0 = 0.45–0.95, indicating the simultaneous presence of numerous mesoporous structures in the sample. This result demonstrates that the Ti-MWW zeolite prepared in this invention successfully introduces a hierarchical (mesoporous) structure. This structure can effectively improve the mass transfer resistance of macromolecular substrates within the microporous channels, facilitating the diffusion of reactant and product molecules.

[0030] Test Example 2 Selective oxidation performance test of 5-hydroxymethylfurfural (HMF) The selective oxidation of 5-hydroxymethylfurfural (HMF) to prepare 2,5-dicarboxyfuran (DFF) was used as a model reaction to investigate the catalytic performance of different catalysts.

[0031] A 25 mL round-bottom flask equipped with a reflux condenser and magnetic stirrer was used. 50 mg of waste TS-1 catalyst (TS-1), 50 mg of sample catalyst from Comparative Example 1 (Ti-MWW-B), and 50 mg of sample catalyst from Example 1 (Ti-MWW-S) were accurately weighed into the round-bottom flask, along with 10 mL of acetonitrile (solvent). 10 mmol of 5-hydroxymethylfurfural (HMF) was added, followed by the slow addition of 30 mmol of 30 wt% hydrogen peroxide (H2O2) as an oxidant. The mixture was heated in a 90°C oil bath with stirring for 2 hours. After the reaction, the reaction solution was quantitatively analyzed by gas chromatography (GC) to calculate the conversion rate of HMF and the yield of DFF. Specific results are shown in [link to results]. Figure 4 As shown.

[0032] from Figure 4 As can be seen, the Ti-MWW-B catalyst prepared by this invention exhibits optimal catalytic activity, with an HMF conversion rate as high as 90% and a DFF yield of 86%. Ti-MWW-S prepared by conventional methods has an HMF conversion rate of 70% and a DFF yield of approximately 67%, showing significantly lower catalytic activity than the Ti-MWW-B of this invention. TS-1 molecular sieves, limited by the diffusion constraints of the microporous channel structure, make it difficult for macromolecular reactants to enter the active center, resulting in an HMF conversion rate of only 40% and a DFF yield of approximately 45%. The reason why the Ti-MWW-B prepared in this application has the best catalytic activity is mainly due to the introduction of a hierarchical mesoporous structure that effectively eliminates the mass transfer limitations of the microporous channels on macromolecular reactants (HMF) and products (DFF), making it easier for reactants to access the titanium active center; at the same time, the abundant pore structure also improves the utilization rate of active sites. Therefore, the Ti-MWW titanium silicate zeolite provided by this invention has significant industrial application potential in the selective oxidation reaction of biomass platform molecules.

[0033] Figure 5 This is the GC chromatogram of the sample after the Ti-MWW-S zeolite molecular sieve catalytic reaction prepared in Example 1. Gas chromatography analysis shows that after the reaction, the chromatographic peak of the raw material HMF almost completely disappeared, while the target product DFF showed a significant strong response peak. This chromatogram clearly demonstrates that under the action of this catalyst, the reaction not only has an extremely high HMF conversion rate but also excellent DFF selectivity. Quantitative calculations using the internal standard method (or external standard method) show that the HMF conversion rate can reach 90%, the DFF yield is approximately 86%, and no obvious byproduct impurity peaks are observed in the chromatogram, indicating that the catalyst system prepared in this invention is highly efficient and clean.

[0034] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A method for preparing a Ti-MWW zeolite from a spent TS-1 catalyst, characterized in that, It includes the following steps: (a) Pretreatment of waste TS-1 catalyst: The waste TS-1 catalyst was ground to control the crystal particle size after grinding to <10μm, and the pretreated waste TS-1 powder was obtained. (b) Gel preparation: Take pretreated waste TS-1 powder, alkali source, boron source, template agent and deionized water. First, mix the alkali source, boron source and deionized water and stir until completely dissolved. Add the pretreated waste TS-1 powder and stir at room temperature for 1-3 h. Then add the template agent and stir at 40-60℃ for 2-4 h. Adjust the pH of the system to >13 to obtain a homogeneous transcrystalline gel. (c) Preparation of Na-type Ti-MWW zeolite: The crystallization gel was transferred to a pressure-resistant sealed container lined with polytetrafluoroethylene and subjected to hydrothermal crystallization reaction at 150-200℃ for 72-168 h. After crystallization, the mixture was cooled to room temperature and the solid product was obtained by solid-liquid separation, which is the crude Na-type Ti-MWW zeolite. (d) Preparation of Ti-MWW zeolite finished product: The crude Na-type Ti-MWW zeolite was washed with deionized water, dried, and then acid-washed to remove boron and impurities, and then calcined and activated to obtain the Ti-MWW zeolite finished product.

2. The method for preparing Ti-MWW zeolite from waste TS-1 catalyst according to claim 1, characterized by, The discarded TS-1 catalyst in step (a) has a silicon-titanium molar ratio of 20-80 (SiO2 / TiO2).

3. The method for preparing Ti-MWW zeolite from waste TS-1 catalyst according to claim 1, characterized by, The alkali source is one or a mixture of sodium hydroxide and potassium hydroxide.

4. The method for preparing Ti-MWW zeolite from waste TS-1 catalyst according to claim 1, characterized by, The boron source is boric acid.

5. The method for preparing Ti-MWW zeolite from waste TS-1 catalyst according to claim 1, characterized by, The template agent is one or a mixture of two of piperidine, cycloheximine, and N,N,N-trimethyl-1-adamantylammonium hydroxide.

6. The method of preparing Ti-MWW zeolite from waste TS-1 catalyst according to claim 1, characterized by, In step (b), the waste TS-1 powder is pretreated with SiO2 and the boron source is B2O3. The molar ratio of SiO2:B2O3:template agent is 1:(0.1-0.4):(0.5-1.5).

7. The method of preparing Ti-MWW zeolite from waste TS-1 catalyst according to claim 1, characterized by, The specific operation of acid washing to remove boron and impurities in step (d) is as follows: the dried solid product is added to a 2-3 mol / L nitric acid solution with a liquid-to-solid ratio of 30:1 (mL / g), refluxed at 100℃ for 6-12 h, and after solid-liquid separation, washed with deionized water until neutral, and dried at 80-100℃ for 8-10 h.

8. The method for preparing Ti-MWW zeolite from waste TS-1 catalyst according to claim 1, characterized in that, The specific operation of calcination activation in step (d) is as follows: the acid-washed and dried product is placed in a muffle furnace, heated to 550℃ in an air atmosphere at a heating rate of 2℃ / min, calcined for 4-6 h, and then naturally cooled to room temperature to obtain the Ti-MWW zeolite product.

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