Crystal face regulated titanium dioxide solid superacid as well as preparation method and application thereof

Abstract

The invention discloses crystal face regulated titanium dioxide solid superacid as well as a preparation method and application thereof. The preparation method comprises the following steps: uniformly stirring ascorbic acid, tetrabutyl titanate and absolute ethyl alcohol in a hydrothermal kettle; adding hydrofluoric acid into the hydrothermal kettle, stirring to obtain a precursor, reacting at a set temperature for 12-36 hours to obtain a product, washing the product, filtering and drying to obtain a dried product; placing the dried product in a tubular furnace under the protection of inert gas, and calcining at the constant temperature of 400-600 DEG C for set time to obtain titanium dioxide carbon compounds with different crystal face proportions {001} and {101}; mixing the product with sulfuric acid, uniformly stirring, washing, precipitating, filtering and drying; and transferring the dried product into a tubular furnace under the protection of inert gas, calcining at the constant temperature of 400-600 DEG C for 2-5 hours, and cooling to room temperature to obtain the titanium dioxide carbon compound solid superacid of which the crystal face ratio of {101} to {001} is (1: 9)-(9: 1).

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and particularly relates to a crystal plane-regulated titanium dioxide solid superacid, a preparation method thereof, and an application thereof. Background Art

[0002] Silicone oil and its modified products, with excellent electrical insulation properties, outstanding antioxidant capacity, high flash point, and low dielectric loss, show extensive application value in the electrical industry. They are often used as insulation media and cooling impregnation materials for various transformers and capacitors, and are also widely used in the insulation treatment of electronic devices, electrical components and devices, as well as the insulation protection and cooling dip coating of cables. These properties make silicone oil and modified silicone oil important materials for ensuring the stable operation of electrical equipment and extending its service life.

[0003] However, traditional methods for producing silicone oil mostly use acid methods or alkali methods, and there are problems such as equipment corrosion, inability to recycle the catalyst, and environmental pollution in traditional production methods.

[0004] Solid superacids have the advantages of being easy to separate from reactants, reusable, non-corrosive to reactors, and reducing catalyst pollution, and are widely used in petroleum refining and petrochemical processes, such as hydrocarbon cracking, reforming, isomerization, as well as olefin hydration, olefin polymerization, and aromatic alkylation. Titanium dioxide solid superacid (SO4 2- / TiO2) has been widely studied.

[0005] Chem.Commun., 2015, 51, 14219 - 14222 synthesized 5,7-dihydroxy-4-methylcoumarin by preparing TiO2 solid superacids dominated by different crystal planes, and proved that the TiO2 solid superacid dominated by the {001} crystal plane has better catalytic activity than that dominated by the {101} crystal plane; Catalysts 2019, 9, 126 prepared a titanium dioxide-carbon solid acid catalyst by microwave-assisted method, and this catalyst has high stability and heterogeneity in the synthesis of 5-hydroxymethylfurfural; Applied Chemistry, 2015, 14(32): 140326, proved that the catalytic activity of titanium dioxide solid superacid is better than that of the sulfuric acid catalytic system when preparing linear dimethylsiloxane, and the catalytic activity of the solid superacid remains basically unchanged after recycling more than three times.

[0006] In summary, titanium dioxide solid superacid has excellent catalytic activity, recyclability and other advantages. Preparing carbon composite titanium dioxide solid superacids (SO4 2- / TiO2@C) dominated by different crystal planes has important significance in the application of preparing dimethyl silicone oil. Summary of the Invention

[0007] In view of the deficiencies in the prior art, the present invention provides a crystal plane-regulated titanium dioxide solid superacid, its preparation method and application. Through the crystal plane regulation and carbon composite technology, the present invention prepares an efficient and reusable solid superacid catalyst, and the raw materials for preparation are cheap and easy to obtain and will not corrode pipelines.

[0008] The first object of the present invention is to provide a preparation method of a crystal plane-regulated titanium dioxide solid superacid, including:

[0009] S1. Stir ascorbic acid, tetrabutyl titanate, and absolute ethanol evenly in a hydrothermal reactor. The material ratio of ascorbic acid, tetrabutyl titanate, and absolute ethanol is (0.3 - 1.2 g): 5 mL: (14 - 15 mL);

[0010] S2. Add hydrofluoric acid to the hydrothermal reactor, stir to obtain a precursor, and react at a set temperature for 12 - 36 hours to obtain a primary hydrothermal product. The dosage of hydrofluoric acid is 0 - 1.2 mL;

[0011] S3. Wash the primary hydrothermal product, filter, and dry to obtain a dried product;

[0012] S4. Place the dried product obtained in S3 in a tube furnace under inert gas protection and calcine at a constant temperature for a set time to obtain a titanium dioxide-carbon composite TiO2@C with different ratios of {001} and {101} crystal planes. The temperature of the constant-temperature calcination is 400 - 600 °C;

[0013] S5. Mix the titanium dioxide-carbon composite TiO2@C with different ratios of {001} and {101} crystal planes with sulfuric acid and stir evenly; wherein, the concentration of sulfuric acid is 0.5 - 1.5 mol / L, and the material ratio of the titanium dioxide-carbon composite TiO2@C with different ratios of {001} and {101} crystal planes to sulfuric acid is 1 g: (15 - 30) mL;

[0014] S6. Wash and precipitate the product obtained in S5, filter, and dry to obtain a dried product;

[0015] S7. Transfer the dried product obtained in S6 to a tube furnace under inert gas protection, calcine at a constant temperature for 2 - 5 hours, and then cool to room temperature to obtain a titanium dioxide-carbon composite solid superacid SO4 2- / TiO2@C; wherein, the temperature of the constant-temperature calcination is 400 - 600 °C, and the ratio of the {101} crystal plane to the {001} crystal plane is (1:9) - (9:1).

[0016] As a further improvement of the present invention, in S2, the set temperature is 180 °C.

[0017] As a further improvement of the present invention, in S3, the hydrothermal product is washed 3 to 5 times with deionized water and absolute ethanol and then filtered and dried.

[0018] As a further improvement of the present invention, in S6, the product obtained in S5 is washed with absolute ethanol for precipitation 3 to 5 times and then vacuum filtered and dried to obtain a dried product.

[0019] As a further improvement of the present invention, in S3 and S6, the drying conditions are both: drying in an oven at 80 °C for 12 hours.

[0020] As a further improvement of the present invention, the stirring speed in S1, S2, and S5 is 800 r / min.

[0021] As a further improvement of the present invention, the stirring time in S1, S2, and S5 is 30 min.

[0022] As a further improvement of the present invention, when the amount of hydrofluoric acid used in S2 is 0 mL, the ratio of the {001} crystal plane to the {101} crystal plane of the titanium dioxide-carbon composite TiO2@C obtained in S4 is 9:1; when the amount of hydrofluoric acid used in S2 is 1.2 mL, the ratio of the {001} crystal plane to the {101} crystal plane of the titanium dioxide-carbon composite TiO2@C obtained in S4 is 0.2:9.8.

[0023] The second object of the present invention is to provide a crystal plane-regulated titanium dioxide solid superacid, which is prepared according to the above preparation method, and the ratio of the {101} crystal plane to the {001} crystal plane of the crystal plane-regulated titanium dioxide solid superacid is (1 to 9):(9 to 1).

[0024] The third object of the present invention is to provide an application of a crystal plane-regulated titanium dioxide solid superacid, which is prepared according to the above preparation method, and the crystal plane-regulated titanium dioxide solid superacid is used as a catalyst in the synthesis of dimethyl silicone oil.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. The preparation raw materials are cheap and easily available and will not corrode the pipeline.

[0027] 2. The prepared titanium dioxide-carbon composite solid superacids dominated by different crystal planes have excellent catalytic performance, and the catalyst can be reused. Description of the Drawings

[0028] Figure 1 is a flow chart of the preparation method;

[0029] Figure 2 is the XRD spectrum of Examples 1, 5, and 9;

[0030] Figure 3 The HRTEM spectrum of Example 5. Detailed implementation manners

[0031] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0032] The present invention will be further described in detail below with reference to the accompanying drawings:

[0033] This embodiment provides a preparation method of a crystal plane-regulated titanium dioxide solid superacid, and the method flow is as Figure 1 shown, including:

[0034] S1. Stir ascorbic acid, tetrabutyl titanate, and absolute ethanol in a hydrothermal autoclave for 30 min at a stirring speed of 800 r / min; wherein, the material ratio of ascorbic acid, tetrabutyl titanate, and absolute ethanol is (0.3 - 1.2 g): 5 mL: (14 - 15 mL);

[0035] S2. Add hydrofluoric acid to the hydrothermal autoclave, stir for 30 min at 800 r / min to obtain a precursor, and react at 180 °C for 12 - 36 hours to obtain a hydrothermal primary product, and the dosage of the hydrofluoric acid is 0 - 1.2 mL;

[0036] S3. Wash the hydrothermal primary product with deionized water and absolute ethanol 3 - 5 times and then filter and dry to obtain a dried product, and the drying conditions are drying in an oven at 80 °C for 12 hours;

[0037] S4. Place the dried product obtained in S3 in a tubular furnace under the protection of an inert gas (argon or nitrogen) and calcine it at a constant temperature for 2 hours to obtain a titanium dioxide-carbon composite TiO2@C with different proportions of {001} and {101} crystal planes, and the temperature of the constant-temperature calcination is 400 - 600 °C;

[0038] S5. Mix the titanium dioxide-carbon composite TiO2@C with different proportions of {001} and {101} crystal planes with sulfuric acid and stir for 30 min at 800 r / min; wherein, the concentration of the sulfuric acid is 0.5 - 1.5 mol / L, and the material ratio of the titanium dioxide-carbon composite TiO2@C with different proportions of {001} and {101} crystal planes to sulfuric acid is 1 g: 15 mL;

[0039] S6. Wash the product obtained in S5 with absolute ethanol for precipitation 3 - 5 times, then filter and dry to obtain a dried product.

[0040] S7. Transfer the dried product obtained in S6 to a tube furnace under the protection of an inert gas (argon or nitrogen), calcine it at a constant temperature for 2 - 5 hours, and then cool it to room temperature to obtain a solid superacid SO4 of titanium dioxide carbon composite with different proportions of {001} and {101} crystal planes 2- / TiO2@C; wherein, the temperature of the constant - temperature calcination is 400 - 600 °C, and the ratio of the {101} crystal plane to the {001} crystal plane is (1:9) - (9:1).

[0041] Among them, the proportions of the {101} and {001} crystal planes of the titanium dioxide carbon composite TiO2@C obtained in S4 are jointly affected by hydrofluoric acid and ascorbic acid. When the material ratio of ascorbic acid, tetrabutyl titanate, and absolute ethanol remains unchanged, changing the dosage of hydrofluoric acid can change the proportions of the {101} and {001} crystal planes of the titanium dioxide carbon composite TiO2@C obtained in S5. Specifically:

[0042] When the dosage of hydrofluoric acid in S2 is 0 mL, the ratio of the {001} crystal plane to the {101} crystal plane of the titanium dioxide carbon composite TiO2@C obtained in S4 is 9:1; when the dosage of hydrofluoric acid in S2 is 1.2 mL, the ratio of the {001} crystal plane to the {101} crystal plane of the titanium dioxide carbon composite TiO2@C obtained in S4 is 0.2:9.8.

[0043] This embodiment provides an application of a crystal - plane - regulated titanium dioxide solid superacid. The crystal - plane - regulated titanium dioxide solid superacid is prepared according to the above - mentioned preparation method, and the crystal - plane - regulated titanium dioxide solid superacid is used as a catalyst in the synthesis of dimethyl silicone oil;

[0044] The dimethyl silicone oil is synthesized from intermediates (dimethylsiloxane mixed cyclic bodies, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane) and a capping agent hexamethyldisiloxane under the action of a solid superacid catalyst. The mass ratio of the intermediate to the capping agent is 60:1, the mass ratio of the catalyst, the intermediate, and the capping agent mixture is 3:100, the synthesis reaction temperature is 110 °C, and the reaction time is 4 hours.

[0045] The preparation method provided by the present invention has inexpensive and easily available raw materials and will not corrode pipelines. At the same time, the obtained titanium dioxide carbon composite solid superacid dominated by different crystal planes as a catalyst has excellent catalytic performance and can be reused in the synthesis of dimethyl silicone oil.

[0046] The following through specific examples and comparative examples show that the solid superacid of titanium dioxide carbon composite dominated by different crystal planes prepared by the preparation method provided by the present invention SO42- The effect of SO4

[0047] Example 1:

[0048] (1) 0.3 g of ascorbic acid, 5 mL of tetrabutyl titanate, and 15 mL of absolute ethanol were stirred in a hydrothermal reactor at a stirring speed of 800 r / min for 30 min to obtain a red liquid;

[0049] (2) The red liquid was transferred to an oven and reacted at 180 °C for 12 h to obtain a hydrothermal product;

[0050] (3) After the hydrothermal product was washed 3 - 5 times with deionized water and absolute ethanol, it was dried in an oven at 80 °C for 12 h and carefully ground into powder;

[0051] (4) The powder was transferred to a tubular furnace and calcined at a constant temperature of 400 °C for 2 h under nitrogen protection and then cooled to room temperature to obtain an off-white product;

[0052] (5) 3 g of the off-white product was added to 45 mL of 0.5 mol / L sulfuric acid and stirred at 800 r / min for 30 min. After the precipitate was washed 3 - 5 times with absolute ethanol, it was vacuum filtered to obtain a product;

[0053] (6) The product was dried in an oven at 80 °C for 12 h and carefully ground into powder;

[0054] (7) The powder was transferred to a tubular furnace and calcined at a constant temperature of 400 °C for 2 h under nitrogen protection and then cooled to room temperature to obtain an SO4 2- / TiO2@C catalyst with a ratio of {101} crystal plane to {001} crystal plane of 1:9.

[0055] Example 2:

[0056] (1) 0.3 g of ascorbic acid, 5 mL of tetrabutyl titanate, and 14.6 mL of absolute ethanol were stirred in a hydrothermal reactor at a stirring speed of 800 r / min for 30 min to obtain a red liquid;

[0057] (2) 0.4 mL of hydrofluoric acid was added to the red liquid and stirred at 800 r / min for 30 min;

[0058] (3) The solution was transferred to an oven and reacted at 180 °C for 24 h to obtain a hydrothermal product;

[0059] (4) After the hydrothermal product was washed 3 - 5 times with deionized water and absolute ethanol, it was dried in an oven at 80 °C for 12 h and carefully ground into powder;

[0060] (5) Transfer the powder into a tubular furnace. Under nitrogen protection, calcine it at a constant temperature of 500 °C for 2 hours and then cool it to room temperature to obtain a grayish-white product;

[0061] (6) Add 3 g of the grayish-white product to 45 mL of 1 mol / L sulfuric acid. Stir at 800 r / min for 30 min, wash the precipitate with absolute ethanol 3 - 5 times, and then perform vacuum filtration to obtain the product;

[0062] (7) Dry the product in an oven at 80 °C for 12 hours and carefully grind it into powder;

[0063] (8) Transfer the powder into a tubular furnace. Under nitrogen protection, calcine it at a constant temperature of 500 °C for 2 hours and then cool it to room temperature to obtain an SO4 2- / TiO2@C catalyst with the ratio of {101} crystal plane to {001} crystal plane being 4:6.

[0064] Example 3:

[0065] (1) Stir 0.3 g of ascorbic acid, 5 mL of tetrabutyl titanate, and 14.2 mL of absolute ethanol in a hydrothermal autoclave at a stirring speed of 800 r / min for 30 min to obtain a red liquid;

[0066] (2) Add 0.8 mL of hydrofluoric acid to the red liquid and stir at 800 r / min for 30 min;

[0067] (3) Transfer the solution to an oven and react at 180 °C for 36 hours to obtain a hydrothermal product;

[0068] (4) After washing the hydrothermal product with deionized water and absolute ethanol 3 - 5 times, dry it in an oven at 80 °C for 12 hours and carefully grind it into powder;

[0069] (5) Transfer the powder into a tubular furnace. Under nitrogen protection, calcine it at a constant temperature of 600 °C for 2 hours and then cool it to room temperature to obtain a grayish-white product;

[0070] (6) Add 3 g of the grayish-white product to 45 mL of 0.5 mol / L sulfuric acid. Stir at 800 r / min for 30 min, wash the precipitate with absolute ethanol 3 - 5 times, and then perform vacuum filtration to obtain the product;

[0071] (7) Dry the product in an oven at 80 °C for 12 hours and carefully grind it into powder;

[0072] (8) Transfer the powder into a tubular furnace. Under nitrogen protection, calcine it at a constant temperature of 600 °C for 2 hours and then cool it to room temperature to obtain an SO4 2- / TiO2@C catalyst with the ratio of {101} crystal plane to {001} crystal plane being 2:8.

[0073] Example 4:

[0074] (1) 0.6 g of ascorbic acid, 5 mL of tetrabutyl titanate, and 15 mL of absolute ethanol were stirred in a hydrothermal autoclave at a stirring speed of 800 r / min for 30 min to obtain a red liquid;

[0075] (2) The red liquid was transferred to an oven and reacted at 180 °C for 24 hours to obtain a hydrothermal product;

[0076] (3) After the hydrothermal product was washed 3 - 5 times with deionized water and absolute ethanol, it was dried in an oven at 80 °C for 12 hours and carefully ground into a powder;

[0077] (4) The powder was transferred to a tube furnace and calcined at a constant temperature of 500 °C for 2 hours under nitrogen protection and then cooled to room temperature to obtain an off-white product;

[0078] (5) 3 g of the off-white product was added to 45 mL of 1.5 mol / L sulfuric acid and stirred at 800 r / min for 30 min. After the precipitate was washed 3 - 5 times with absolute ethanol, it was vacuum filtered to obtain a product;

[0079] (6) The product was dried in an oven at 80 °C for 12 hours and carefully ground into a powder;

[0080] (7) The powder was transferred to a tube furnace and calcined at a constant temperature of 500 °C for 2 hours under nitrogen protection and then cooled to room temperature to obtain an SO4 2- / TiO2@C catalyst with a ratio of {101} crystal plane to {001} crystal plane of 1:9.

[0081] Example 5:

[0082] (1) 0.6 g of ascorbic acid, 5 mL of tetrabutyl titanate, and 14.6 mL of absolute ethanol were stirred in a hydrothermal autoclave at a stirring speed of 800 r / min for 30 min to obtain a red liquid;

[0083] (2) 0.4 mL of hydrofluoric acid was added to the red liquid and stirred at 800 r / min for 30 min;

[0084] (3) The solution was transferred to an oven and reacted at 180 °C for 24 hours to obtain a hydrothermal product;

[0085] (4) After the hydrothermal product was washed 3 - 5 times with deionized water and absolute ethanol, it was dried in an oven at 80 °C for 12 hours and carefully ground into a powder;

[0086] (5) The powder was transferred to a tube furnace and calcined at a constant temperature of 400 °C for 2 hours under nitrogen protection and then cooled to room temperature to obtain an off-white product;

[0087] (6) Add 3 g of the off-white product to 45 mL of 1 mol / L sulfuric acid, stir at 800 r / min for 30 min, wash the precipitate with absolute ethanol 3 - 5 times, and then perform vacuum filtration to obtain the product;

[0088] (7) Dry the product in an oven at 80 °C for 12 hours and carefully grind it into a powder;

[0089] (8) Transfer the powder to a tubular furnace, under nitrogen protection, calcine it at a constant temperature of 500 °C for 2 hours, and then cool it to room temperature to obtain an SO4 2- / TiO2@C catalyst with a ratio of {101} crystal plane to {001} crystal plane of 4:6. The HRTEM spectrum of the catalyst is as Figure 3 shown.

[0090] Example 6:

[0091] (1) Stir 0.6 g of ascorbic acid, 5 mL of tetrabutyl titanate, and 14.6 mL of absolute ethanol in a hydrothermal reactor at a stirring speed of 800 r / min for 30 min to obtain a red liquid;

[0092] (2) Add 0.4 mL of hydrofluoric acid to the red liquid and stir at 800 r / min for 30 min;

[0093] (3) Transfer the solution to an oven and react at 180 °C for 36 hours to obtain a hydrothermal product;

[0094] (4) After washing the hydrothermal product with deionized water and absolute ethanol 3 - 5 times, dry it in an oven at 80 °C for 12 hours and carefully grind it into a powder;

[0095] (5) Transfer the powder to a tubular furnace, under nitrogen protection, calcine it at a constant temperature of 400 °C for 2 hours, and then cool it to room temperature to obtain an off-white product;

[0096] (6) Add 3 g of the off-white product to 45 mL of 0.5 mol / L sulfuric acid, stir at 800 r / min for 30 min, wash the precipitate with absolute ethanol 3 - 5 times, and then perform vacuum filtration to obtain the product;

[0097] (7) Dry the product in an oven at 80 °C for 12 hours and carefully grind it into a powder;

[0098] (8) Transfer the powder to a tubular furnace, under nitrogen protection, calcine it at a constant temperature of 600 °C for 2 hours, and then cool it to room temperature to obtain an SO4 2- / TiO2@C catalyst.

[0099] Example 7:

[0100] (1) 0.6 g of ascorbic acid, 5 mL of tetrabutyl titanate, and 14.2 mL of absolute ethanol were stirred in a hydrothermal reactor at a stirring speed of 800 r / min for 30 min to obtain a red liquid;

[0101] (2) 0.8 mL of hydrofluoric acid was added to the red liquid and stirred at 800 r / min for 30 min;

[0102] (3) The solution was transferred to an oven and reacted at 180 °C for 12 h to obtain a hydrothermal product;

[0103] (4) After the hydrothermal product was washed 3 - 5 times with deionized water and absolute ethanol, it was dried in an oven at 80 °C for 12 h and carefully ground into a powder;

[0104] (5) The powder was transferred to a tubular furnace and calcined at a constant temperature of 500 °C for 2 h under nitrogen protection and then cooled to room temperature to obtain an off - white product;

[0105] (6) 3 g of the off - white product was added to 45 mL of 1 mol / L sulfuric acid and stirred at 800 r / min for 30 min. After the precipitate was washed 3 - 5 times with absolute ethanol, it was vacuum - filtered to obtain a product;

[0106] (7) The product was dried in an oven at 80 °C for 12 h and carefully ground into a powder;

[0107] (8) The powder was transferred to a tubular furnace and calcined at a constant temperature of 400 °C for 2 h under nitrogen protection and then cooled to room temperature to obtain an SO4 2- / TiO2@C catalyst with a ratio of {101} crystal plane to {001} crystal plane of 2:8.

[0108] Example 8:

[0109] (1) 1.2 g of ascorbic acid, 5 mL of tetrabutyl titanate, and 15 mL of absolute ethanol were stirred in a hydrothermal reactor at a stirring speed of 800 r / min for 30 min to obtain a red liquid;

[0110] (2) The red liquid was transferred to an oven and reacted at 180 °C for 24 h to obtain a hydrothermal product;

[0111] (3) After the hydrothermal product was washed 3 - 5 times with deionized water and absolute ethanol, it was dried in an oven at 80 °C for 12 h and carefully ground into a powder;

[0112] (4) The powder was transferred to a tubular furnace and calcined at a constant temperature of 500 °C for 2 h under nitrogen protection and then cooled to room temperature to obtain an off - white product;

[0113] (5) Add 3 g of the off-white product to 45 mL of 1 mol / L sulfuric acid, stir at 800 r / min for 30 min, wash the precipitate with absolute ethanol 3 - 5 times, and then perform vacuum filtration to obtain the product;

[0114] (6) Dry the product in an oven at 80 °C for 12 hours and carefully grind it into powder;

[0115] (7) Transfer the powder to a tubular furnace, under nitrogen protection, calcine at 500 °C for 2 hours and then cool to room temperature to obtain an SO4 2- / TiO2@C catalyst with a ratio of {101} crystal plane to {001} crystal plane of 1:9.

[0116] Example 9:

[0117] (1) Stir 1.2 g of ascorbic acid, 5 mL of tetrabutyl titanate, and 14.6 mL of absolute ethanol in a hydrothermal autoclave at a stirring speed of 800 r / min for 30 min to obtain a red liquid;

[0118] (2) Add 0.4 mL of hydrofluoric acid to the red liquid and stir at 800 r / min for 30 min;

[0119] (3) Transfer the solution to an oven and react at 180 °C for 36 hours to obtain a hydrothermal product;

[0120] (4) After washing the hydrothermal product with deionized water and absolute ethanol 3 - 5 times, dry it in an oven at 80 °C for 12 hours and carefully grind it into powder;

[0121] (5) Transfer the powder to a tubular furnace, under nitrogen protection, calcine at 400 °C for 2 hours and then cool to room temperature to obtain an off-white product;

[0122] (6) Add 3 g of the off-white product to 45 mL of 1.5 mol / L sulfuric acid, stir at 800 r / min for 30 min, wash the precipitate with absolute ethanol 3 - 5 times, and then perform vacuum filtration to obtain the product;

[0123] (7) Dry the product in an oven at 80 °C for 12 hours and carefully grind it into powder;

[0124] (8) Transfer the powder to a tubular furnace, under nitrogen protection, calcine at 600 °C for 2 hours and then cool to room temperature to obtain an SO4 2- / TiO2@C catalyst with a ratio of {101} crystal plane to {001} crystal plane of 4:6.

[0125] Example 10:

[0126] (1) 1.2 g of ascorbic acid, 5 mL of tetrabutyl titanate, and 14.2 mL of absolute ethanol were stirred in a hydrothermal reactor at a stirring speed of 800 r / min for 30 min to obtain a red liquid;

[0127] (2) 0.8 mL of hydrofluoric acid was added to the red liquid and stirred at 800 r / min for 30 min;

[0128] (3) The solution was transferred to an oven and reacted at 180 °C for 24 h to obtain a hydrothermal product;

[0129] (4) After the hydrothermal product was washed 3 - 5 times with deionized water and absolute ethanol, it was dried in an oven at 80 °C for 12 h and carefully ground into a powder;

[0130] (5) The powder was transferred to a tubular furnace and calcined at a constant temperature of 400 °C for 2 h under nitrogen protection and then cooled to room temperature to obtain an off - white product;

[0131] (6) 3 g of the off - white product was added to 45 mL of 0.5 mol / L sulfuric acid and stirred at 800 r / min for 30 min. After the precipitate was washed 3 - 5 times with absolute ethanol, it was vacuum - filtered to obtain a product;

[0132] (7) The product was dried in an oven at 80 °C for 12 h and carefully ground into a powder;

[0133] (8) The powder was transferred to a tubular furnace and calcined at a constant temperature of 500 °C for 2 h under nitrogen protection and then cooled to room temperature to obtain an SO4 2- / TiO2@C catalyst with a ratio of {101} crystal plane to {001} crystal plane of 2:8.

[0134] Example 11:

[0135] (1) 1.2 g of ascorbic acid, 5 mL of tetrabutyl titanate, and 14.2 mL of absolute ethanol were stirred in a hydrothermal reactor at a stirring speed of 800 r / min for 30 min to obtain a red liquid;

[0136] (2) 0.8 mL of hydrofluoric acid was added to the red liquid and stirred at 800 r / min for 30 min;

[0137] (3) The solution was transferred to an oven and reacted at 180 °C for 24 h to obtain a hydrothermal product;

[0138] (4) After the hydrothermal product was washed 3 - 5 times with deionized water and absolute ethanol, it was dried in an oven at 80 °C for 12 h and carefully ground into a powder;

[0139] (5) Transfer the powder into a tubular furnace. Under nitrogen protection, calcine it at a constant temperature of 500 °C for 2 hours and then cool it to room temperature to obtain an off-white product;

[0140] (6) Add 3 g of the off-white product to 45 mL of 1 mol / L sulfuric acid. Stir it at 800 r / min for 30 min. Wash the precipitate with anhydrous ethanol 3 - 5 times and then perform vacuum filtration to obtain the product;

[0141] (7) Dry the product in an oven at 80 °C for 12 hours and carefully grind it into powder;

[0142] (8) Transfer the powder into a tubular furnace. Under nitrogen protection, calcine it at a constant temperature of 500 °C for 2 hours and then cool it to room temperature to obtain an SO4 2- / TiO2@C catalyst with a ratio of {101} crystal plane to {001} crystal plane of 2:8.

[0143] The XRD patterns of Examples 1, 5, and 9 are as Figure 2 shown, Figure 2 where the diffraction peaks are located at 2θ = 25.3°, 38.7°, 48.2°, 53.9°, 55.1°, and 62.3°, corresponding to the {101}, {112}, {200}, {105}, {213}, and {200} crystal planes of anatase TiO2, respectively. The change in the diffraction intensity of the crystal plane indicates that TiO2 with different proportions of the {001} crystal plane has a similar crystal phase, confirming that the sulfation treatment does not significantly change the properties of the crystal phase, and the difference in the full width at half maximum confirms that carbon is introduced in an amorphous form.

[0144] Comparative Example 1:

[0145] (1) Add 3 g of commercial anatase titanium dioxide (dominated by the {101} crystal plane) to 45 mL of 1 mol / L sulfuric acid. Stir it at 800 r / min for 30 min. Wash the precipitate with anhydrous ethanol 3 - 5 times and then perform vacuum filtration to obtain the product;

[0146] (2) Dry the product in an oven at 80 °C for 12 hours and carefully grind it into powder;

[0147] (3) Transfer the powder into a tubular furnace. Under nitrogen protection, calcine it at a constant temperature of 500 °C for 2 hours and then cool it to room temperature to obtain an SO4 2- / TiO2@C catalyst dominated by the {101} crystal plane.

[0148] Application Example 1:

[0149] The catalysts prepared in Examples 1 - 11 and Comparative Example were respectively used for the synthesis of dimethyl silicone oil. By testing the kinematic viscosity of dimethyl silicone oil, the catalytic performance of the catalysts prepared in Examples 1 - 11 and Comparative Example 1 was detected.

[0150] The viscosity of silicone oil is affected by the molecular weight. The larger the molecular weight, the higher the viscosity of silicone oil. Therefore, in Application Example 1, the greater the viscosity of the product, the more complete the catalytic reaction, and the higher the molecular weight of silicone oil.

[0151] The specific process for synthesizing dimethyl silicone oil is as follows:

[0152] (1) Add 60 g of decamethylcyclopentasiloxane and 1 g of hexamethyldisiloxane into a three-necked flask, and stir at 800 r / min for 10 min;

[0153] (2) Add 1.8 g of the catalysts prepared in Examples 1 to 11 and Comparative Example 1 into the three-necked flask respectively, heat up to 110 °C at 800 r / min, and react for 4 hours to obtain the product;

[0154] (3) Perform vacuum filtration on the product to separate the catalyst, and obtain a mixed liquid of dimethyl silicone oil and endblocker;

[0155] (4) Perform vacuum distillation on the mixed liquid to obtain dimethyl silicone oil, and test the kinematic viscosity of dimethyl silicone oil. The test results of the kinematic viscosity are shown in Table 1.

[0156] Table 1

[0157]

[0158] Only in Examples 1, 4, and 8, hydrofluoric acid was not used in the preparation of the catalyst. According to Table 1, only the catalysts prepared in Examples 4 and 8 had a catalytic effect inferior to that of the commercial anatase titanium dioxide used in Comparative Example 1. The catalytic effect of the catalyst prepared in Example 1 was similar to that of the commercial anatase titanium dioxide used in Comparative Example 1. The effects of the catalysts prepared in the remaining examples were significantly better than that of the commercial anatase titanium dioxide used in Comparative Example 1;

[0159] At the same time, when the ratio of the {001} crystal plane to the {101} crystal plane reaches a suitable value, the catalytic effect is the best. For example, for the catalyst prepared in Example 5, its HRTEM spectrum is as Figure 3 shown.

[0160] Application Example 2:

[0161] Application Example 2 explores the reusability of the solid superacid catalyst prepared in Example 5. The specific process is as follows:

[0162] (1) Wash the catalyst separated in step (3) of Application Example 1 (prepared in Example 5) with petroleum ether, deionized water, and absolute ethanol in sequence, and dry it in an oven at 80 °C for 12 hours;

[0163] (2) Transfer the catalyst to a tubular furnace. Under nitrogen protection, calcine it at a constant temperature of 500 °C for 2 hours to obtain the recovered solid superacid catalyst;

[0164] (3) Repeat the catalytic synthesis of dimethyl silicone oil reaction with the recovered catalyst for 5 times. The reaction steps are the same as those in Application Example 1. The performance of the catalyst obtained from the 5-cycle test is shown in Table 2.

[0165] Table 2

[0166]

[0167] Application Example 2 is only to prove the reusability of the catalyst. Therefore, the product with the best catalytic performance is selected for the reuse test, that is, the catalyst prepared in Example 5 is used for the test. According to Table 2, after 5 repetitions, the performance of the catalyst does not decrease significantly, and the catalyst can be reused.

[0168] As can be seen from the above application examples, the titanium dioxide-carbon composite solid superacid dominated by different crystal planes prepared by the preparation method provided by the present invention has excellent catalytic performance, and the catalyst can be reused.

[0169] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a titanium dioxide solid superacid with crystal surface regulation, characterized in that: include: S1. Stir ascorbic acid, tetrabutyl titanate and anhydrous ethanol in a hydrothermal kettle, wherein the material ratio of ascorbic acid, tetrabutyl titanate and anhydrous ethanol is (0.3-1.2 g): 5 mL: (14-15 mL); S2, adding hydrofluoric acid to the hydrothermal kettle, stirring to obtain a precursor, and reacting at a set temperature for 12 to 36 hours to obtain a hydrothermal initial product, wherein the amount of hydrofluoric acid used is 0 to 1.2 mL; S3, washing the initial hydrothermal product, filtering and drying to obtain a dry product; S4, placing the dried product obtained in S3 in a tubular furnace under inert gas protection and calcining at a constant temperature for a set time to obtain titanium dioxide carbon composites TiO2@C with different {001} and {101} crystal plane proportions, wherein the constant temperature calcination temperature is 400-600°C; S5, mixing the titanium dioxide carbon composite TiO2@C with different {001} and {101} crystal plane ratios with sulfuric acid and stirring evenly; wherein the concentration of the sulfuric acid is 0.5-1.5 mol / L, and the material ratio of the titanium dioxide carbon composite TiO2@C with different {001} and {101} crystal plane ratios to sulfuric acid is 1 g: (15-30) mL; S6, washing and precipitating the product obtained in S5, filtering and drying to obtain a dry product; S7, the dried product obtained in S6 is transferred to a tube furnace under the protection of inert gas and calcined at a constant temperature for 2 to 5 hours, and then cooled to room temperature to obtain a titanium dioxide carbon composite solid superacid SO4 with different {001} and {101} crystal plane ratios. 2- / TiO2@C; wherein the constant temperature calcination temperature is 400-600°C, and the ratio of the {101} crystal plane to the {001} crystal plane is (1:9)-(9:1).

2. The preparation method according to claim 1, characterized in that: In S2, the set temperature is 180°C.

3. The preparation method according to claim 1, characterized in that: In S3, the hydrothermal product is washed with deionized water and anhydrous ethanol for 3 to 5 times and then filtered and dried.

4. The preparation method according to claim 1, characterized in that: In S6, the product obtained in S5 is washed with anhydrous ethanol for 3 to 5 times, precipitated, vacuum filtered and dried to obtain a dry product.

5. The preparation method according to claim 1, characterized in that: In S3 and S6, the drying conditions are both: drying in an oven at 80° C. for 12 hours.

6. The preparation method according to claim 1, characterized in that: The stirring speed in S1, S2 and S5 is 800 r / min.

7. The preparation method according to claim 1 or 6, characterized in that: The stirring time in S1, S2 and S5 is 30 min.

8. The preparation method according to claim 1, characterized in that: When the amount of hydrofluoric acid in S2 is 0 mL, the ratio of the {001} crystal plane to the {101} crystal plane of the titanium dioxide carbon composite TiO2@C obtained by S4 is 9:1; when the amount of hydrofluoric acid in S2 is 1.2 mL, the ratio of the {001} crystal plane to the {101} crystal plane of the titanium dioxide carbon composite TiO2@C obtained by S4 is 0.2:9.

8.

9. A crystal face-regulated titanium dioxide solid superacid, prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The crystal plane regulates the ratio of the {101} crystal plane to the {001} crystal plane of the titanium dioxide solid superacid to be (1-9):(9-1).

10. An application of a crystal face-regulated titanium dioxide solid superacid, wherein the crystal face-regulated titanium dioxide solid superacid is prepared according to the preparation method according to any one of claims 1 to 8, characterized in that: The crystal surface regulated titanium dioxide solid superacid is used as a catalyst for synthesizing dimethyl silicone oil.

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