A method for preparing CeO2@P2O5@SBA15 catalyst and its application

Abstract

The application belongs to the technical field of supported catalyst preparation, and relates to a preparation method and application of a CeO2@P2O5@SBA15 catalyst. The CeO2@P2O5@SBA15 catalyst is obtained by loading CeO2 and P2O5 in SBA15 as a carrier in situ through a tartaric acid sol-gel method, and is used for preparing o-hydroxybenzyl anisole by single etherification of o-diphenol and methyl alcohol. The catalyst has the characteristics of high reaction activity, few by-products, low selectivity to by-products and high stability.

Description

Technical Field

[0001] This invention belongs to the field of supported catalyst preparation technology, and more specifically relates to a method for preparing CeO2@P2O5@SBA15 catalyst and its application. Background Technology

[0002] Guaiacin (o-hydroxyanisole) is a chemically synthesized organic compound with significant applications in pharmaceuticals and food processing. Various methods have been employed to synthesize guaiacin, with diazotization hydrolysis being a common approach in the initial industrial stages; however, this generates substantial amounts of diazotization wastewater. Alternatively, a continuous catalytic method using alkyl reagents for catechol methylation, facilitated by a solid catalyst in a fixed-bed reactor, offers greater advantages. Currently, researchers primarily focus on catalysts based on POx and Al2O3, such as Al-PO, modified M-Al-PO (M = Ti, Zr, K), modified γ-Al2O3, and sulfate-modified zirconium. However, the catechol conversion rate and stability of these catalysts require further improvement. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing CeO2@P2O5@SBA15 catalyst and its application. By incorporating cerium oxide from tartaric acid sol-gel into the SBA15-supported P2O5 catalyst, the problem of the prior art can be solved, and high conversion rate of catechol and high stability of the catalyst can be achieved.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] One of the technical solutions of the present invention is to provide a method for preparing a CeO2@P2O5@SBA15 catalyst, wherein SBA15 is used as a support, and CeO2 and P2O5 are loaded in situ in the support by tartaric acid sol-gel method.

[0006] Furthermore, the CeO2 loading in the CeO2@P2O5@SBA15 catalyst is 5–15 wt%.

[0007] Furthermore, the step of in-situ loading CeO2 and P2O5 includes:

[0008] The cerium-containing compound was dissolved in a mixed solvent, and tartaric acid was added and stirred to obtain a mixed solution;

[0009] SBA15 was added to the mixed solution under stirring conditions, followed by the addition of a phosphorus-containing compound and potassium carbonate. After stirring until a sol was formed, the mixture was heated to prepare a semi-dry gel.

[0010] The semi-dry gel was dried and calcined to obtain the CeO2@P2O5@SBA15 catalyst.

[0011] Preferably, the cerium-containing compound is at least one selected from cerium nitrate hexahydrate, cerium carbonate, basic cerium carbonate, and cerium hydroxide.

[0012] Preferably, the phosphorus-containing compound is at least one of phosphoric acid, diammonium hydrogen phosphate, and diammonium dihydrogen phosphate.

[0013] Preferably, the molar ratio of cerium in the cerium-containing compound to phosphorus in the phosphorus-containing compound is 1:1.

[0014] Preferably, the mixed solvent is obtained by mixing water and ethanol in an equal volume ratio.

[0015] Preferably, the mass / volume ratio of the cerium-containing compound, the mixed solvent, and SBA15 is 0.81–2.88 g: 50 mL: 6 g.

[0016] Preferably, the mass ratio of the phosphorus-containing compound to potassium carbonate is 4:1.

[0017] Preferably, the temperature is increased to 80°C.

[0018] Preferably, the drying is performed in an oven at 100°C for 8 hours.

[0019] Preferably, the calcination is carried out by heating to 500°C at a heating rate of 10°C / min and calcining for 4 hours.

[0020] In this invention, the CeO2 formed by the sol-gel process provides the addition of CeO2 during the incorporation of SBA15, while the phosphorus-containing compound provides the addition of P2O5. As a uniform sol forms, the solvent evaporates and the chemical reaction proceeds, the sol gradually transforms into a gel. The mesoporous channels of SBA15 contain uniformly dispersed Ce and P-containing substances. The calcination temperature promotes the diffusion and chemical reaction between reactants without damaging the structure of SBA15.

[0021] The second technical solution of the present invention provides a CeO2@P2O5@SBA15 catalyst prepared by the above method.

[0022] The third technical solution of the present invention provides an application of the above-mentioned CeO2@P2O5@SBA15 catalyst in the preparation of o-hydroxyanisole by monoetherification of catechol and methanol.

[0023] The present invention discloses the following technical effects:

[0024] The present invention utilizes a CeO2@P2O5@SBA15 catalyst prepared by incorporating cerium oxide into tartaric acid sol-gel with SBA15-supported P2O5. This catalyst is used for the monoetherification of catechol with methanol to prepare o-hydroxyanisole, exhibiting good conversion rate and stability.

[0025] The CeO2@P2O5@SBA15 catalyst prepared by this invention has the characteristics of high reactivity, few byproducts, low selectivity for byproducts, and high stability. Attached Figure Description

[0026] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0027] Figure 1 The nitrogen adsorption-desorption isotherms of the catalysts prepared in Examples 1-3 and Comparative Example 1 are shown below.

[0028] Figure 2 The pore size distribution diagrams are shown for the catalysts prepared in Examples 1-3 and Comparative Example 1.

[0029] Figure 3 The nitrogen adsorption-desorption isotherms of the catalysts prepared in Example 1 and Comparative Examples 2-3 are shown below.

[0030] Figure 4 The pore size distribution diagrams are shown for the catalysts prepared in Example 1 and Comparative Examples 2-3.

[0031] Figure 5 The image shows a SEM image of the catalyst prepared in Comparative Example 1.

[0032] Figure 6 The image shows a SEM image of the catalyst prepared in Example 2.

[0033] Figure 7 The image shows a SEM image of the catalyst prepared in Example 1.

[0034] Figure 8 The image shows a SEM image of the catalyst prepared in Example 3.

[0035] Figure 9 The image shows a SEM image of the catalyst prepared in Comparative Example 3.

[0036] Figure 10 The image shows a SEM image of the catalyst prepared in Comparative Example 2.

[0037] Figure 11 The image shows the stability of the catalyst prepared in Example 1. Detailed Implementation

[0038] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0039] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0040] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0041] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0042] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0043] Unless otherwise specified, in the specific embodiments of the present invention, "overnight" refers to 12 hours, and "room temperature" and "normal temperature" both refer to 25±5℃.

[0044] The preparation steps of SBA15 molecular sieve used in the specific embodiment of the present invention are as follows: 20g P123 is added to 600mL HCl (2mol / L), and stirred at 40℃ for 3-4h until clear. 42.5g TEOS is slowly added dropwise, and stirred at 40℃ for 24h. The mixture is then placed in a bottle, dried at 90℃ for 24h, removed and cooled to room temperature, filtered, and dried overnight at 100℃ to obtain a solid product. The solid product is heated to 600℃ at a heating rate of 2℃ / min and calcined for 8h to obtain SBA15.

[0045] In a specific embodiment of the present invention, the volume ratio of water to ethanol in the mixed solvent of water and ethanol is 1:1.

[0046] In a specific embodiment of the present invention, cerium in the cerium-containing compound and phosphorus in the phosphorus-containing compound can be substituted for each other while ensuring that the molar ratio of cerium to phosphorus in the phosphorus-containing compound is 1:1. The cerium-containing compound can be selected from at least one of cerium nitrate hexahydrate, cerium carbonate, basic cerium carbonate and cerium hydroxide, and the phosphorus-containing compound can be selected from at least one of phosphoric acid, diammonium hydrogen phosphate and diammonium dihydrogen phosphate.

[0047] In this invention, potassium carbonate is used as an auxiliary agent to provide stability to the catalyst. Therefore, in the comparative example, the activity of the prepared product is not affected even without the addition of potassium carbonate.

[0048] Example 1

[0049] Preparation of CeO2-P2O5 / SBA15:

[0050] S1. Dissolve 1.74g of cerium-containing compound (cerium nitrate hexahydrate) in a mixed solvent of 50mL deionized water and ethanol, then add 10g of tartaric acid and stir rapidly for 4h until a pale yellow mixed solution is formed.

[0051] S2. Under stirring at 65℃, 6g of SBA-15 was added to the mixed solution, followed by the slow addition of a total of 0.4g of phosphoric acid and 0.1g of potassium carbonate. The mixture was stirred until a yellow sol appeared, and the temperature was raised to 80℃ and stirring was stopped to prepare a semi-dry gel.

[0052] S3. The semi-dry gel was dried in an oven at 100°C for 8 hours, then transferred to a muffle furnace and calcined at 500°C at a rate of 10°C / min for 4 hours to obtain the CeO2-P2O5 / SBA15 catalyst, denoted as 10wt% CeO2-P2O5 / SBA15 (CeO2 loading is 10wt%).

[0053] Example 2

[0054] Preparation of CeO2-P2O5 / SBA15:

[0055] S1. Dissolve 0.81g of cerium-containing compound (cerium nitrate hexahydrate) in a mixed solvent of 50mL deionized water and ethanol, then add 10g of tartaric acid and stir rapidly for 4h until a pale yellow mixed solution is formed.

[0056] S2. Under stirring at 65℃, 6g of SBA-15 was added to the mixed solution, followed by the slow addition of a total of 0.18g of phosphoric acid and 0.045g of potassium carbonate. The mixture was stirred until a yellow sol appeared, and the temperature was raised to 80℃ and stirring was stopped to prepare a semi-dry gel.

[0057] S3. The semi-dry gel was dried in an oven at 100°C for 8 hours, then transferred to a muffle furnace and calcined at 500°C at a rate of 10°C / min for 4 hours to obtain the CeO2-P2O5 / SBA15 catalyst, denoted as 5wt% CeO2-P2O5 / SBA15 (CeO2 loading is 5wt%).

[0058] Example 3

[0059] Preparation of CeO2-P2O5 / SBA15:

[0060] S1. Dissolve 2.88g of cerium-containing compound (cerium nitrate hexahydrate) in a mixed solvent of 50mL deionized water and ethanol, then add 10g of tartaric acid and stir rapidly for 4h until a pale yellow mixed solution is formed.

[0061] S2. Under stirring at 65℃, 6g of SBA-15 was added to the mixed solution, followed by the slow addition of a total of 0.65g of phosphoric acid and 0.1625g of potassium carbonate. The mixture was stirred until a yellow sol appeared, and the temperature was raised to 80℃ and stirring was stopped to prepare a semi-dry gel.

[0062] S3. The semi-dry gel was dried in an oven at 100°C for 8 hours, then transferred to a muffle furnace and calcined at 500°C at a rate of 10°C / min for 4 hours to obtain the CeO2-P2O5 / SBA15 catalyst, denoted as 15wt% CeO2-P2O5 / SBA15 (CeO2 loading is 15%).

[0063] Comparative Example 1

[0064] SBA15, used in Example 1, was used as the catalyst.

[0065] Comparative Example 2

[0066] Preparation of CeO2 / SBA15:

[0067] S1. Dissolve 1.68g of cerium-containing compound (cerium nitrate hexahydrate) in a mixed solvent of 50mL deionized water and ethanol, then add 10g of tartaric acid and stir rapidly for 4h until a pale yellow mixed solution is formed.

[0068] S2. Add 6g of SBA-15 to the mixed solution under stirring at 65℃, stir until a yellow sol appears, and then heat to 80℃ and stop stirring to prepare a semi-dry gel.

[0069] S3. The semi-dry gel was dried in an oven at 100°C for 8 hours, then transferred to a muffle furnace and calcined at 500°C at a rate of 10°C / min for 4 hours to obtain the CeO2 / SBA15 catalyst, denoted as CeO2 / SBA15 (CeO2 loading is 10wt%).

[0070] Comparative Example 3

[0071] Preparation of P2O5 / SBA15:

[0072] S1. Dissolve 0.92g of phosphoric acid in a mixed solvent of 50mL deionized water and ethanol, then add 10g of tartaric acid and stir rapidly for 4h to form a mixed solution.

[0073] S2. Add 6g of SBA-15 to the mixed solution under stirring at 65℃, stir until a sol appears, and then heat to 80℃ and stop stirring to prepare a semi-dry gel.

[0074] S3. The semi-dry gel was dried in an oven at 100°C for 8 hours, then transferred to a muffle furnace and calcined at 500°C at a rate of 10°C / min for 4 hours to obtain the P2O5 / SBA15 catalyst, denoted as P2O5 / SBA15 (P2O5 loading is 10wt%).

[0075] Test case

[0076] The catalysts prepared in Examples 1-3 and Comparative Examples 1-3 were used in the gas-solid phase monoetherification of catechol with methanol to prepare o-hydroxyanisole. The reaction was carried out in a fixed-bed apparatus under the following conditions: catechol to methanol molar ratio of 1:6, reaction temperature of 280°C, and reaction space velocity of 1.2 mL g / L. -1 h -1 .

[0077] The conversion rate of catechol, the selectivity of o-hydroxyanisole, the selectivity of o-phenylene diether, and the selectivity of other byproducts were calculated, and the results are shown in Table 1.

[0078] Table 1

[0079]

[0080]

[0081] As shown in Table 1, the P2O5 / SBA15 catalyst prepared in Comparative Example 3 had a conversion rate of only 35.3% for catechol, while the CeO2 / SBA15 catalyst prepared in Comparative Example 2 showed almost no activity. The data from Comparative Example 1 also shows that pure SBA15 had almost no conversion, indicating that pure SBA15 lacks active sites. However, the catalysts prepared in Examples 1-3 of this invention show that the addition of CeO2 and P2O5 during the preparation process significantly improved the conversion rate and selectivity. This is because the combined addition of CeO2 and P2O5 improved the surface area and surface acidity, increasing the number of active sites and thus exhibiting a stronger adsorption effect on catechol, rapidly converting it to guaiacol. With increasing CeO2 loading, the conversion rate initially increased and then decreased. As the CeO2 loading gradually increased, it contained more active sites. However, when the CeO2 loading was excessive, the excessive loading caused blockage of the SBA15 pores, resulting in fewer active sites and consequently a decrease in conversion rate.

[0082] BET characterization results are as follows Figures 1-4 As shown in Table 2.

[0083] Table 2

[0084]

[0085] Figure 1 The nitrogen adsorption-desorption isotherms of the catalysts prepared in Examples 1-3 and Comparative Example 1 are shown below. Figure 2 The pore size distribution diagrams are shown for the catalysts prepared in Examples 1-3 and Comparative Example 1. Figure 3 The nitrogen adsorption-desorption isotherms of the catalysts prepared in Example 1 and Comparative Examples 2-3 are shown below. Figure 4 The images show the pore size distribution of the catalysts prepared in Examples 1 and Comparative Examples 2-3. Figures 1-4 It can be seen that the isotherms of SBA15 exhibit type IV isotherm curves with H1 type hysteresis loops. This is a typical cylindrical channel mesoporous structure. Furthermore, when CeO2 and P2O5 are introduced into the mesoporous SBA-15, the shape of the type IV isotherm remains unchanged, indicating that the mesoporous structure of SBA15 is still preserved.

[0086] Table 2 analyzes the effects of different CeO2 doping amounts and SBA15 catalysts on specific surface area, pore volume, and pore size. It was found that Comparative Example 3 showed a significant decrease in specific surface area (SBET) and pore volume (Vp) compared to Example 1. This was attributed to the formation of non-porous P2O5 on the pore surface, leading to blockage of some pores. In Examples 1-3, the specific surface area decreased somewhat with increasing doping amount, but the pore size did not change significantly from a 5% to 10% loading. This is because although the content of the loaded material increased after calcination, it was uniformly dispersed and occupied the pore positions of the SBA15 support, without blockage. Therefore, the BET analysis results show that the CeO2-P2O5 / SBA15 catalyst maintains a complete mesoporous structure with a relatively stable internal pore structure that is not easily collapsed.

[0087] SEM characterization results

[0088] SEM images of Examples 1-3 and Comparative Examples 1-3 are shown below. Figures 5-10 As shown, where, Figure 5 The image shows a SEM image of the catalyst prepared in Comparative Example 1. Figure 6 The image shows a SEM image of the catalyst prepared in Example 2.

[0089] Figure 7 The image shows a SEM image of the catalyst prepared in Example 1. Figure 8 The image shows a SEM image of the catalyst prepared in Example 3. Figure 9 The image shows a SEM image of the catalyst prepared in Comparative Example 3. Figure 10 The image shows a SEM image of the catalyst prepared in Comparative Example 2. Figures 5-10 It can be seen that the mesoporous silica material exhibits a uniform fibrous cylindrical morphology, which is consistent with the typical SBA-15 morphology. With the addition of CeO2 and P2O5, small round protrusions appear on the surface of SBA-15 particles, indicating that CeO2 and P2O5 are uniformly dispersed on the carrier surface in the form of small particles without damaging the mesoporous structure of SBA-15. With the increase of doping amount, more small particles can be seen on the surface of SBA-15, and the protrusions gradually become larger and more numerous. When the doping amount increases to a certain level, pore blockage may occur, thus causing a change in performance. This is consistent with the decrease in conversion rate with the increase of doping amount in Table 1.

[0090] Stability test

[0091] Test method: The catalyst prepared in Example 1 was applied to the gas-solid phase monoetherification of catechol and methanol to prepare o-hydroxyanisole. The reaction was carried out in a fixed-bed apparatus under the following conditions: catechol to methanol molar ratio 1:6, reaction temperature 280℃, and reaction space velocity 1.2 mL g / L. -1 h -1The reaction time is 120 hours.

[0092] Figure 11 The stability graph of the catalyst prepared in Example 1 is shown below. Figure 11 As can be seen, with the reaction time extended to 120 hours, the catalyst maintained more than half of its activity (approximately 40% catechol conversion) throughout the entire reaction process, while maintaining approximately 90% selectivity for guaiacol. This is because the high specific surface area and large pore size of SBA15 itself allow the active sites to be uniformly dispersed on SBA15, reducing the possibility of carbon deposition. Furthermore, because the tartaric acid sol-gel forms more dispersed cerium oxide, CeO2 is more easily distributed throughout the pores of SBA15 and undergoes a stable reaction with P2O5, thereby increasing the stability of the catalyst and making it suitable for long-term use in flow systems with high catalytic activity and guaiacol selectivity.

[0093] It is evident that the CeO2-P2O5 / SBA15 catalyst prepared by the tartaric acid sol-gel method exhibits high conversion rate, high selectivity, and excellent stability in the monoetherification of catechol and methanol to guaiacol. This method maintains the original highly ordered hexagonal structure, narrow pore size distribution, and uniform tubular channel structure of SBA15. Characterization by BET and SEM revealed that 10% CeO2-P2O5 / SBA15 is a material with a high specific surface area and an ordered large-pore structure. Furthermore, comparative examples 1-3 demonstrate that the addition of CeO2 and P2O5 introduces stronger active sites within the SBA15 channels. However, example 3 shows that the increasing amount of CeO2 leads to agglomeration, causing pore blockage and resulting in a decrease in conversion rate. In addition to its high conversion rate and selectivity, 10wt% CeO2-P2O5 / SBA15 also exhibits relatively excellent stability, thus showing broad application prospects in the preparation of o-hydroxyanisole by the monoetherification of catechol and methanol.

[0094] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0095] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a CeO2@P2O5@SBA15 catalyst, characterized in that, Using SBA15 as a carrier, CeO2 and P2O5 were in situ loaded in the carrier via the tartaric acid sol-gel method.

2. The preparation method according to claim 1, characterized in that, The in-situ loading of CeO2 and P2O5 includes: The cerium-containing compound was dissolved in a mixed solvent, and tartaric acid was added and stirred to obtain a mixed solution; SBA15 was added to the mixed solution under stirring conditions, followed by the addition of a phosphorus-containing compound and potassium carbonate. After stirring until a sol was formed, the mixture was heated to prepare a semi-dry gel. The semi-dry gel was dried and calcined to obtain the CeO2@P2O5@SBA15 catalyst.

3. The preparation method according to claim 2, characterized in that, The cerium-containing compound is at least one of cerium nitrate hexahydrate, cerium carbonate, basic cerium carbonate, and cerium hydroxide; the phosphorus-containing compound is at least one of phosphoric acid, diammonium hydrogen phosphate, and diammonium dihydrogen phosphate; the mixed solvent is obtained by mixing water and ethanol in equal volume ratios.

4. The preparation method according to claim 2, characterized in that, The molar ratio of cerium in the cerium-containing compound to phosphorus in the phosphorus-containing compound is 1:1; the mass / volume ratio of the cerium-containing compound, the mixed solvent, and SBA15 is 0.81–2.88 g: 50 mL: 6 g.

5. The preparation method according to claim 2, characterized in that, The mass ratio of the phosphorus-containing compound to potassium carbonate is 4:

1.

6. The preparation method according to claim 2, characterized in that, The heating is to raise the temperature to 80°C; the drying is to dry in an oven at 100°C for 8 hours; the calcination is to raise the temperature to 500°C at a heating rate of 10°C / min and calcinate for 4 hours.

7. The preparation method according to claim 1, characterized in that, The CeO2 loading in the CeO2@P2O5@SBA15 catalyst is 5–15 wt%.

8. A CeO2@P2O5@SBA15 catalyst prepared by the method according to any one of claims 1 to 7.

9. The application of the CeO2@P2O5@SBA15 catalyst as described in claim 8 in the preparation of o-hydroxyanisole by monoetherification of catechol and methanol.

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