Preparation method of nitrogen-doped titanium dioxide nanosheet-supported Pt selective hydrogenation catalyst

Abstract

The present invention discloses a method for preparing a nitrogen-doped titanium dioxide nanosheet-supported Pt selective hydrogenation catalyst, the method comprising the following steps: (i) preparing a titanium dioxide precursor solution; (ii) preparing an amino acid and titanium dioxide mixed gel; (iii) preparing a nitrogen-doped TiO 2 Nanosheet composites; (IV) Preparation of nitrogen-doped TiO 2 Nanosheet-supported Pt selective hydrogenation catalyst; The advantages of the present invention are: (i) the above preparation method is used to achieve nitrogen-doped TiO 2 Synthesis of Pt selective hydrogenation catalyst supported on nanosheets; (ii) Nitrogen-doped TiO prepared by the present invention 2 Compared with existing precious metal catalysts, the nanosheet-supported Pt selective hydrogenation catalyst has better stability and high-efficiency selective hydrogenation catalytic activity; (iii) the preparation process is simple, the process conditions are mild and easy to operate; (iv) the present invention realizes the control of the precious metal particle size, improves its utilization rate, reduces the production cost, and expands new ideas for the preparation of selective hydrogenation catalysts.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst preparation, and in particular to a method for preparing a nitrogen-doped titanium dioxide nanosheet-supported Pt selective hydrogenation catalyst. Background Art

[0002] The active components of hydrogenation catalysts usually include precious metals (Pt, Pd, Ru, and Ir) and group VIII transition metals (Fe, Co, and Cu). Among them, precious metals have high catalytic activity and good selectivity, but precious metal reserves are low, the price is relatively expensive, and they are easy to agglomerate to form larger particles, resulting in a reduction in exposed active sites, thereby reducing catalytic activity, which limits their practical application in the field of catalytic hydrogenation. Therefore, researchers have been exploring methods to avoid precious metal agglomeration and reduce the amount of precious metals used. The carrier morphology and structure of supported precious metal catalysts can affect the size and dispersion of precious metal particles, produce electronic effects and spatial effects through the interaction between metals and carriers, improve the activity and selectivity of the catalyst, and reduce the amount of precious metals used. Usually, the carrier of supported precious metal catalysts is carbon, molecular sieves or metal oxides. Compared with other carriers, titanium dioxide has attracted attention due to its non-toxicity, good thermodynamic properties, and interaction with precious metal nanoparticles, and is conducive to exposing more active sites. Therefore, it is of great significance to rationally design and prepare titanium dioxide carriers with special morphology and structure and effectively control the size of precious metal particles.

[0003] At present, with the development of my country's green industry and the continuous acceleration of the industrialization process, the excessive consumption of fossil energy will inevitably cause energy crisis and environmental pollution problems, prompting people to actively develop chemical synthesis routes based on green renewable energy. The C=O and C=C hydrogenation of unsaturated aldehydes and ketones are common types of catalytic hydrogenation reactions. For example, the selective hydrogenation of furfural and cinnamaldehyde can produce high-value-added fine chemicals. These reactions can not only produce important intermediate organic matter, but also remove impurities in the product. In view of the sustainable development theme in the field of environment and energy, the development of cheap, efficient and high-performance catalysts is the key to achieving green synthesis of products, which can not only improve the yield, but also generate huge economic benefits. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a nitrogen-doped titanium dioxide nanosheet-supported Pt selective hydrogenation catalyst, so as to solve the problems of low stability and catalytic activity of the existing selective hydrogenation catalyst and reduce the cost. 2 Nanosheet-supported Pt selective hydrogenation catalysts have problems such as large particle size, uncontrollable reaction ratio and harsh process conditions.

[0005] To achieve the above object, the technical solution of the present invention is a method for preparing a nitrogen-doped titanium dioxide nanosheet-supported Pt selective hydrogenation catalyst, comprising the following steps:

[0006] 1. Preparation of titanium dioxide precursor solution: Take block polymer Bri-35, add a certain amount of tetrahydrofuran, use tetrabutyl titanate as titanium source, continue stirring for 30 minutes, control the stirring rate to 800r / min, add 2.5 mL of concentrated hydrochloric acid, then drop hydrofluoric acid, ultrasonicate for a period of time to form a transparent solution for standby use;

[0007] 2. Preparation of amino acid and titanium dioxide mixed sol: Add amino acid to the sample obtained in step (1), stir at a constant speed for 5 to 12 hours, and age at room temperature to obtain amino acid and titanium dioxide mixed sol;

[0008] 3. Preparation of Nitrogen-doped TiO 2 Nanosheet composite: The sample obtained in step (ii) was transferred to a 50 mL high pressure hydrothermal reactor and heated at a controlled temperature for 24 hours. After the hydrothermal reaction, the brown powder was separated by centrifugation, washed three times with distilled water and anhydrous ethanol respectively, and dried at 60 °C overnight. The prepared sample was calcined at a gradient temperature for 3 hours to obtain nitrogen-doped TiO 2 Nanosheet composites;

[0009] 4. Preparation of Nitrogen-doped TiO 2 Nanosheet-supported Pt selective hydrogenation catalyst: The nitrogen-doped TiO 2 The nanosheet composite was added to 30 mL of ethylene glycol, stirred at a constant speed for 1 to 2 hours, and 1% chloroplatinic acid solution was added dropwise. After ultrasonic treatment at a certain frequency for 5 to 20 minutes, the composite was transferred to a hydrothermal reactor, hydrothermalized at 180°C, filtered, washed with distilled water and ethanol respectively, and dried in a vacuum at 60°C. Nitrogen-doped TiO 2 Nanosheet-supported Pt selective hydrogenation catalyst.

[0010] In the step (i), 20 to 40 mL of tetrahydrofuran is added to the block polymer Bri-35, 0.3 to 0.6 mL of hydrofluoric acid is added dropwise, and the ultrasonic time is 2 to 5 minutes;

[0011] In step (ii), the mass ratio of tetrabutyl titanate to amino acid is controlled to be 10:1 to 10:3, and the aging time is 2 to 4 hours;

[0012] The temperature of step (iii) is controlled at 150-180°C, wherein the gradient temperature increase is calcining at 300°C for 1 hour, and then increasing the temperature to 450°C for 2 hours;

[0013] In step (iv), the ultrasonic frequency is 50-70 kHz, the temperature-controlled hydrothermal time is 12-24 hours, and the nitrogen-doped TiO2 The mass ratio of nanosheets to chloroplatinic acid solution is 1:1 to 1:5;

[0014] The amino acid is one or more of lysine, alanine and glutamic acid.

[0015] Advantages of the present invention: 1. The above preparation method is used to achieve nitrogen-doped TiO 2 Synthesis of Pt selective hydrogenation catalyst on nanosheets; II. Nitrogen-doped TiO prepared by the present invention 2 Compared with existing precious metal catalysts, the nanosheet-supported Pt selective hydrogenation catalyst has better stability and high-efficiency selective hydrogenation catalytic activity; third, the preparation process is simple, the process conditions are mild and easy to operate; the present invention realizes the control of the precious metal particle size, improves its utilization rate, reduces the production cost, and expands new ideas for the preparation of selective hydrogenation catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 , Figure 2 , Figure 3 The nitrogen-doped TiO obtained in Example 1, Example 2 and Example 3 are 2 Transmission electron microscopy image of nanosheet-supported Pt selective hydrogenation catalyst. Implementation

[0017] In order to better understand the present invention, the technical solution of the present invention is described below through specific embodiments.

[0018] Example 1: A method for preparing a nitrogen-doped titanium dioxide nanosheet-supported Pt selective hydrogenation catalyst is specifically completed by the following steps:

[0019] 1. Preparation of titanium dioxide precursor solution: Take block polymer Bri-35, add 20 mL of tetrahydrofuran, use tetrabutyl titanate as titanium source, continue stirring for 30 minutes, control the stirring rate to 800r / min, add 2.5 mL of concentrated hydrochloric acid, then add 0.3 mL of hydrofluoric acid, ultrasonicate for 2 minutes to form a transparent solution for standby use;

[0020] 2. Preparation of amino acid and titanium dioxide mixed sol: Add amino acid to the sample obtained in step (1), stir at a constant speed for 5 to 12 hours, and age at room temperature to obtain amino acid and titanium dioxide mixed sol;

[0021] 3. Preparation of Nitrogen-doped TiO 2 Nanosheet composite: The sample obtained in step (ii) was transferred to a 50 mL high pressure hydrothermal reactor and heated at 150 °C for 24 hours. After the hydrothermal reaction, the brown powder was separated by centrifugation, washed three times with distilled water and anhydrous ethanol respectively, and dried at 60 °C overnight. The prepared sample was calcined at a gradient temperature for 3 hours to obtain nitrogen-doped TiO2 Nanosheet composites;

[0022] 4. Preparation of Nitrogen-doped TiO 2 Nanosheet-supported Pt selective hydrogenation catalyst: The nitrogen-doped TiO 2 The nanosheet composite was added to 30 mL of ethylene glycol, stirred at a constant speed for 1 to 2 hours, and 1% chloroplatinic acid solution was added dropwise. After ultrasonic treatment at 50 Hz for 5 to 20 minutes, the composite was transferred to a hydrothermal reactor and hydrothermalized at 180°C for 12 hours. The composite was filtered, washed with distilled water and ethanol, and dried under vacuum at 60°C. 2 Nanosheet-supported Pt selective hydrogenation catalyst.

[0023] In this example, 1.5 g of block polymer Bri-35 was added.

[0024] In this embodiment, the gradient temperature increase is calcining at 300°C for 1 hour, and then increasing the temperature to 450°C for 2 hours;

[0025] In this embodiment, nitrogen-doped TiO 2 The mass ratio of nanosheets to chloroplatinic acid solution was 1:1;

[0026] The nitrogen-doped TiO 2 The nanosheet-supported Pt selective hydrogenation catalyst was tested by transmission electron microscopy, and the transmission electron microscopy photos were obtained as follows Figure 1 As shown, the particle size is about 2.8 nm and is evenly distributed.

[0027] Example 2: A method for preparing a nitrogen-doped titanium dioxide nanosheet-supported Pt selective hydrogenation catalyst is specifically completed by the following steps:

[0028] 1. Preparation of titanium dioxide precursor solution: Take block polymer Bri-35, add 30 mL of tetrahydrofuran, use tetrabutyl titanate as titanium source, stir continuously for 30 minutes, control the stirring rate to 800r / min, add 2.5 mL of concentrated hydrochloric acid, then drop 0.4 mL of hydrofluoric acid, ultrasonicate for 3 minutes to form a transparent solution for standby use;

[0029] 2. Preparation of amino acid and titanium dioxide mixed sol: Add amino acid to the sample obtained in step (1), stir at a constant speed for 5 to 12 hours, and age at room temperature to obtain amino acid and titanium dioxide mixed sol;

[0030] 3. Preparation of Nitrogen-doped TiO 2Nanosheet composite: The sample obtained in step (ii) was transferred to a 50 mL high pressure hydrothermal reactor and heated at 160°C for 24 hours. After the hydrothermal reaction, the brown powder was separated by centrifugation, washed three times with distilled water and anhydrous ethanol respectively, and dried at 60°C overnight. The prepared sample was calcined at a gradient temperature for 3 hours to obtain nitrogen-doped TiO 2 Nanosheet composites;

[0031] 4. Preparation of Nitrogen-doped TiO 2 Nanosheet-supported Pt selective hydrogenation catalyst: The nitrogen-doped TiO 2 The nanosheet composite was added to 30 mL of ethylene glycol, stirred at a constant speed for 1 to 2 hours, and 1% chloroplatinic acid solution was added dropwise. After ultrasonication at 60 Hz for 5 to 20 minutes, the composite was transferred to a hydrothermal reactor and hydrothermalized at 180°C for 18 hours. The composite was filtered, washed with distilled water and ethanol, and dried under vacuum at 60°C. 2 Nanosheet-supported Pt selective hydrogenation catalyst.

[0032] In this example, 1.7 g of block polymer Bri-35 was added;

[0033] In this embodiment, the hydrothermal temperature is controlled at 160°C, and the gradient temperature increase is calcining at 300°C for 1 hour, and then increasing the temperature to 450°C for 2 hours;

[0034] In this embodiment, the ultrasonic frequency is 60kHz, the temperature control hydrothermal time is 18 hours, and the nitrogen-doped TiO 2 The mass ratio of nanosheets to chloroplatinic acid solution was 1:2;

[0035] The nitrogen-doped TiO 2 The nanosheet-supported Pt selective hydrogenation catalyst was tested by transmission electron microscopy, and the transmission electron microscopy photos were obtained as follows Figure 1 As shown, the particle size is about 3.0 nm and is evenly distributed.

[0036] Example 3: A method for preparing a nitrogen-doped titanium dioxide nanosheet-supported Pt selective hydrogenation catalyst is specifically completed by the following steps:

[0037] 1. Preparation of titanium dioxide precursor solution: Take block polymer Bri-35, add 40 mL of tetrahydrofuran, use tetrabutyl titanate as titanium source, continue stirring for 30 minutes, control the stirring rate to 800r / min, add 2.5 mL of concentrated hydrochloric acid, then drop 0.6 mL of hydrofluoric acid, ultrasonicate for 5 minutes to form a transparent solution for standby use;

[0038] 2. Preparation of amino acid and titanium dioxide mixed sol: Add amino acid to the sample obtained in step (1), stir at a constant speed for 5 to 12 hours, and age at room temperature to obtain amino acid and titanium dioxide mixed sol;

[0039] 3. Preparation of Nitrogen-doped TiO 2 Nanosheet composite: The sample obtained in step (ii) was transferred to a 50 mL high pressure hydrothermal reactor and heated at 180°C for 24 hours. After the hydrothermal reaction, the brown powder was separated by centrifugation, washed three times with distilled water and anhydrous ethanol respectively, and dried at 60°C overnight. The prepared sample was calcined at a gradient temperature for 3 hours to obtain nitrogen-doped TiO 2 Nanosheet composites;

[0040] 4. Preparation of Nitrogen-doped TiO 2 Nanosheet-supported Pt selective hydrogenation catalyst: The nitrogen-doped TiO 2 The nanosheet composite was added to 30 mL of ethylene glycol, stirred at a constant speed for 1 to 2 hours, and 1% chloroplatinic acid solution was added dropwise. After ultrasonication at 70 Hz for 5 to 20 minutes, the composite was transferred to a hydrothermal reactor and hydrothermalized at 180°C for 24 hours. The composite was filtered, washed with distilled water and ethanol, and dried under vacuum at 60°C. Nitrogen-doped TiO 2 Nanosheet-supported Pt selective hydrogenation catalyst.

[0041] In this example, 1.8 g of block polymer Bri-35 was added;

[0042] In this embodiment, the hydrothermal temperature is controlled at 180°C, and the gradient temperature increase is calcination at 300°C for 1 hour, and then the temperature is increased to 450°C for 2 hours;

[0043] In this embodiment, the temperature-controlled hydrothermal time is 24 hours, and the nitrogen-doped TiO 2 The mass ratio of nanosheets to chloroplatinic acid solution was 1:5;

[0044] The nitrogen-doped TiO 2 The nanosheet-supported Pt selective hydrogenation catalyst was tested by transmission electron microscopy, and the transmission electron microscopy photos were obtained as follows Figure 1 As shown, the particle size is about 3.1 nm and is evenly distributed.

Claims

1. A method for preparing a nitrogen-doped titanium dioxide nanosheet-supported Pt selective hydrogenation catalyst, Features: The preparation method comprises the following steps: (i) Preparation of titanium dioxide precursor solution: Take block polymer Bri-35, add 20-40 mL of tetrahydrofuran, use tetrabutyl titanate as titanium source, continue stirring for 30 minutes, control the stirring rate to 800 r / min, add 2.5 mL of concentrated hydrochloric acid, then drop 0.3-0.6 mL of hydrofluoric acid, ultrasonicate for 2-5 minutes to form a transparent solution for standby use; (ii) preparing a mixed sol of amino acid and titanium dioxide: adding amino acid to the sample obtained in step (i), stirring at a constant speed for 5 to 12 hours, and aging at room temperature to obtain a mixed sol of amino acid and titanium dioxide; controlling the mass ratio of tetrabutyl titanate to amino acid to be 10:1 to 10:3; (III) Preparation of nitrogen-doped TiO 2 Nanosheet composite: The sample obtained in step (ii) was transferred to a 50 mL high pressure hydrothermal reactor and heated at a controlled temperature for 24 hours. After the hydrothermal reaction, the brown powder was separated by centrifugation, washed three times with distilled water and anhydrous ethanol respectively, dried at 60 °C overnight, and the prepared sample was calcined at a gradient temperature for 3 hours to obtain nitrogen-doped TiO 2 Nanosheet composite; gradient heating is calcined at 300°C for 1 hour, then heated to 450°C for 2 hours; (4). Preparation of nitrogen-doped TiO 2 nanosheet-supported Pt selective hydrogenation catalyst: Add the nitrogen-doped TiO 2 nanosheet composite obtained in step (3) to 30 mL of ethylene glycol, stir uniformly for 1 - 2 hours, dropwise add 1% chloroplatinic acid solution, after ultrasonic treatment at a frequency of 50 - 70 kHz for 5 - 20 minutes, transfer it to a hydrothermal autoclave, hydrothermal react at 180 °C, filter by suction, wash with distilled water and ethanol respectively, and dry in vacuum at 60 °C to obtain the nitrogen-doped TiO 2 nanosheet-supported Pt selective hydrogenation catalyst.

2. The method for preparing a nitrogen-doped titanium dioxide nanosheet-supported Pt selective hydrogenation catalyst according to claim 1, Features: In the step (i), 0.3-0.6 mL of hydrofluoric acid is added dropwise.

3. The method for preparing a nitrogen-doped titanium dioxide nanosheet-supported Pt selective hydrogenation catalyst according to claim 1, Features: The aging time in step (ii) is 2 to 4 hours.

4. The method for preparing a nitrogen-doped titanium dioxide nanosheet-supported Pt selective hydrogenation catalyst according to claim 1, Features: The temperature of step (iii) is controlled at 150-180°C.

5. The method for preparing a nitrogen-doped titanium dioxide nanosheet-supported Pt selective hydrogenation catalyst according to claim 1, Features: The temperature-controlled hydrothermal time in step (iv) is 12 to 24 hours, and the nitrogen-doped TiO 2 The mass ratio of the nanosheets to the chloroplatinic acid solution is 1:1 to 1:

5.

6. The method for preparing a nitrogen-doped titanium dioxide nanosheet-supported Pt selective hydrogenation catalyst according to claim 1, Features: The amino acid is one or more of lysine, alanine and glutamic acid.

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