CN114405505A - Platinum modified indium-based oxide catalyst and preparation method and application thereof - Google Patents

Abstract

The invention relates to a platinum-modified indium-based oxide catalyst, a preparation method and application thereof. The catalyst is mainly composed of noble metal active component Pt and oxide carrier In ₂ O ₃ . The use of Pt/In ₂ O ₃ composite catalyst is beneficial to improve the activity of carbon dioxide hydrogenation reaction. It can be used in the reaction of carbon dioxide hydrogenation to synthesize methanol under high pressure, and can achieve a carbon dioxide conversion rate of more than 15% and a methanol selection of more than 80%. sex. The process route of the present invention is simple and convenient, and has the characteristics of high selectivity, high conversion rate and high yield, and the reaction conditions are relatively mild, and the raw materials are easily available and have good application prospects.

Description

A platinum-modified indium-based oxide catalyst and its preparation method and application

technical field

The invention relates to the field of catalyst technology and energy chemical industry, in particular to a platinum-modified indium-based oxide catalyst and a preparation method and application thereof.

Background technique

In the past 60 years, the rapid growth of global energy demand and the continuous increase of man-made carbon dioxide emissions have led to serious environmental problems such as climate deterioration and global warming. _CO2 hydrogenation to synthesize methanol is one of the important ways to rationally utilize _CO2 and has broad application prospects. Methanol is a clean and efficient fuel and can be used as a gasoline additive; in addition, methanol is not only a raw material for the preparation of C ₂ -C ₄ advanced olefins, but also an important raw material for the preparation of pharmaceuticals, cosmetics, polyesters and many other fine chemicals, so carbon dioxide Catalytic conversion to methanol has received a lot of attention.

Due to the stable chemical properties and difficult activation of CO ₂ , the conversion rate of this reaction is generally low, and the formation of methanol is an exothermic reaction, and low temperature is thermodynamically favorable for methanol production. However, low temperature is not conducive to the activation of carbon dioxide, so it is necessary to select an appropriate reaction temperature and design a more efficient catalyst.

On the other hand, carbon monoxide and methanol are two concomitant products in the hydrogenation of carbon dioxide, which have similar intermediates and occur at the same catalytic site, resulting in low selectivity for both; therefore How to promote the _CO2 activation conversion and adjust the product selectivity, and then can efficiently obtain methanol is an urgent problem to be solved.

At present, the widely studied catalysts for methanol synthesis are copper-zinc-aluminum catalysts. For example, the copper-based catalysts reported in patent CN 103272607 A have higher carbon dioxide conversion rates, but the methanol selectivity is only about 60%, and it is easy to sinter and deactivate under high temperature reaction conditions. . In recent years, indium-based catalysts with high methanol selectivity under certain reaction conditions have received extensive attention. However, the reaction conditions of indium-based catalysts are relatively harsh. For example, a hexagonal phase indium oxide reported in CN 110479235 A patent of Shanghai Institute of Advanced Studies requires a higher reaction temperature (360°C) and a higher proportion of hydrogen [n(H ₂ )/n(CO ₂ )=6] can have good catalytic performance. In addition, indium-based catalysts have poor catalytic activity and stability and are prone to high temperature deactivation. According to reports (DOI: 10.1039/d0gc01597k), although the metal Pt supported on In ₂ O ₃ by the deposition precipitation method in the article improves the stability of the catalyst, the selectivity at its optimum reaction temperature (300 °C) is only At 54%, the catalytic activity is not ideal.

Therefore, how to reduce the reaction temperature while improving the catalytic activity and stability of the catalyst still faces great challenges.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a platinum-modified indium-based oxide catalyst and its preparation method and application which can improve the yield of methanol and reduce the reaction temperature and hydrogen partial pressure in order to overcome the above-mentioned defects of the prior art.

The object of the present invention can be realized through the following technical solutions:

The catalyst of the invention adopts Pt/In ₂ O ₃ composite material, and the In ₂ O ₃ carrier has a special plate-like shape, has a large specific surface area, and is easy to contact the reaction gas and the catalyst, and the In ₂ with special shape is modified by Pt. O ₃ increases the active sites at the metal/oxide interface, on the one hand, the yield of the product methanol is significantly improved, and on the other hand, the reaction temperature and hydrogen partial pressure are effectively reduced;

On the other hand, a platinum-modified indium-based oxide catalyst and a preparation method thereof are provided. Plate-shaped indium oxide is synthesized by a hydrothermal method, and platinum is supported on an indium oxide carrier for modification by a deposition precipitation method, thereby realizing At about 290 °C, the conversion rate of carbon dioxide is greater than 15% and the methanol selectivity is about 80%. At the same time, the catalyst can achieve a stability of more than 15h. Its excellent activity performance mainly comes from Pt nanoparticles and specific morphology In ₂ The strong interaction of O ₃ , the specific scheme is as follows:

A platinum-modified indium-based oxide catalyst, the catalyst is a metal/oxide composite catalyst, that is, metal active components are supported on an oxide carrier, including carrier plate-shaped In ₂ O ₃ , and active component Pt particles, the catalyst Its chemical composition is xPt/In ₂ O ₃ , where x is the mass percentage of Pt in the catalyst; where x=0.5-10.0, preferably 1-2, more preferably 1.5.

Further, the particle size of the Pt particles is less than 1 nm, the long side of the plate-shaped In ₂ O ₃ is 400-450 nm, the short side is 300-400 nm, and the thickness is 20-30 nm.

The size of the supported metal particles can be observed by high magnification electron microscope, but no obvious aggregation of Pt metal is found in the catalyst in the present application. It can also be observed that the particle size of Pt is obviously less than 1 nm by the element distribution test, as shown in Figure 8.

_The catalytic synergy and strong interaction of Pt and _In2O3 are beneficial to increase the number of oxygen vacancies and reactive oxygen species at the metal-oxide interface, which are crucial for the catalytic performance, can greatly improve the yield of the product methanol, and make the The optimum reaction temperature was lowered to 290°C. By comparing the activities of the catalysts, it can be known that the platinum-modified plate-shaped indium oxide catalyst prepared by the present invention has more excellent catalytic activities than the corresponding platinum-modified conventional indium oxide and alumina catalysts.

A preparation method of platinum-modified indium-based oxide catalyst as described above, the method comprises the following steps:

(1) Preparation of plate-like In ₂ O ₃ carrier:

After mixing water and alcohol, solution 1 is obtained, and indium salt is dissolved in solution 1 to obtain solution 2;

In addition, after mixing water and alcohol, solution 3 is obtained, and then the precipitant is dissolved in solution 3 to obtain solution 4;

Under stirring, solution 4 was added to solution 2, and after stirring, a hydrothermal reaction was carried out;

After the reaction, the obtained precipitate is centrifuged, washed, dried and calcined to obtain a plate-shaped In ₂ O ₃ carrier;

(2) Pt modified In ₂ O ₃ :

Dissolve the platinum precursor in deionized water to prepare an aqueous solution;

The plate-shaped In ₂ O ₃ carrier is added to the aqueous solution, after stirring, a precipitant is added, and then heated and stirred;

After cooling to room temperature, the precipitate was centrifuged and washed, then vacuum-dried, and calcined at high temperature to obtain catalyst xPt/In ₂ O ₃ .

Further, the indium salt is indium nitrate tetrahydrate, the precipitating agent is urea, and the platinum precursor is chloroplatinic acid.

Further, in step (1), during hydrothermal reaction, the mass ratio of described indium salt and precipitant is (4-5):4; The volume ratio of described ethanol and water is (2-6): 1;

The temperature of the hydrothermal reaction is 115-125°C, and the time is 16-18h; the temperature of the calcination is 290-310°C, and the time is 4-6h.

Further, in step (2), the temperature of the heating and stirring is 75-85°C; the temperature of the high-temperature calcination is 440-460°C, and the time is 2-4h.

An application of the platinum-modified indium-based oxide catalyst as described above, which is used in the reaction of carbon dioxide hydrogenation to methanol.

Further, the conditions for hydrogenating carbon dioxide to synthesize methanol are: the reaction pressure is 1-7MPa, the reaction temperature is 210-330°C, the space velocity is 9000-40000mL (h ^-1 g _cat ^-1 ), n(H ₂ ):n( CO ₂ ) molar ratio = 2-7.

Further, the reaction pressure is 4-6MPa, the reaction temperature is 270-310°C, the space velocity is 15000-24000mL (h ^{- 1} g _cat ^-1 ), and the molar ratio of n(H ₂ ):n(CO ₂ )=3-5 .

Further, the reaction pressure is 5MPa, the reaction temperature is 290°C, and the space velocity is 9000-21000mL (h ^-1 g _cat ^-1 ), preferably 12000-18000mL (h ^-1 g _cat ^-1 ), n(H ₂ ):n (CO ₂ ) molar ratio=3.

Compared with the prior art, the present invention has the following advantages:

(1) The present invention adopts Pt/In ₂ O ₃ composite catalyst, which greatly improves the catalytic activity of carbon dioxide hydrogenation reaction, can reduce the reaction temperature to 290°C, and enhance the stability of the catalyst. The process route of the invention is simple and convenient, and has the characteristics of high selectivity, high conversion rate and high yield, and the reaction conditions are relatively low, and the raw materials are easily available and have good application prospects;

(2) The catalyst of the present invention can effectively improve the selectivity of carbon dioxide hydrogenation to methanol, the optimum operating temperature is 290° C., and the sintering resistance and stability are good. Under the conditions of 5MPa, 290℃, 18000mL (h ^-1 g _cat ^-1 ), the methanol selectivity can exceed 80%, and the single-pass conversion rate can be maintained above 15%;

(3) The present invention successfully prepared metal platinum-modified plate In ₂ O ₃ composite catalysts by an easy-to-operate hydrothermal method, and evaluated their performance in the reaction of carbon dioxide hydrogenation to methanol, and found that plate xPt The /In ₂ O ₃ composite catalyst exhibits excellent catalytic performance, which is mainly derived from the strong interaction between Pt nanoparticles and In ₂ O ₃ with specific morphology.

Description of drawings

Fig. 1 is the _CO conversion rate and CH ₃ OH selectivity diagram of catalyst in Example 5;

Fig. 2 is the methanol yield figure of catalyst among the embodiment 5;

Fig. 3 is the stability test chart of catalyst in embodiment 5;

Fig. 4 is the transmission electron microscope picture of catalyst in embodiment 5;

Fig. 5 is the transmission electron microscope picture of catalyst in embodiment 5;

Fig. 6 is the hydrogen temperature programmed reduction diagram of catalyst in embodiment 1 and 5;

Fig. 7 is the O1S energy spectrum of catalyst in embodiment 1 and 5;

FIG. 8 is a Pt element distribution diagram of the catalyst in Example 5. FIG.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and provides a detailed implementation manner and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

A method for preparing a platinum-modified indium-based oxide catalyst. The indium salt is indium nitrate tetrahydrate, the precipitant is urea, and the platinum precursor is chloroplatinic acid. The method includes the following steps:

(1) Preparation of plate-like In ₂ O ₃ carrier:

After mixing water and alcohol, solution 1 is obtained, and indium salt is dissolved in solution 1 to obtain solution 2;

In addition, after mixing water and alcohol, solution 3 is obtained, and then the precipitant is dissolved in solution 3 to obtain solution 4;

Under stirring, add solution 4 to solution 2, and after stirring, carry out hydrothermal reaction; during hydrothermal reaction, the mass ratio of indium salt to precipitant is (4-5):4; the volume ratio of ethanol to water is (2-6): 1; the temperature of the hydrothermal reaction is 115-125°C, and the time is 16-18h;

After the reaction, the obtained precipitate is centrifuged, washed, dried and calcined to obtain a plate-shaped In ₂ O ₃ carrier; the calcination temperature is 290-310° C., and the time is 4-6h;

(2) Pt modified In ₂ O ₃ :

Dissolve the platinum precursor in deionized water to prepare an aqueous solution;

The plate-shaped In ₂ O ₃ carrier is added to the aqueous solution, after stirring, a precipitant is added, and then heated and stirred; the temperature of heating and stirring is 75-85° C.;

After cooling to room temperature, the precipitate was centrifuged and washed, then vacuum dried, and calcined at high temperature to obtain catalyst xPt/In ₂ O ₃ ; the temperature of high temperature calcination was 440-460° C., and the time was 2-4 h.

The catalyst is a metal/oxide composite catalyst, that is, metal active components are supported on an oxide carrier, including carrier plate-like In ₂ O ₃ , and active component Pt particles. Its chemical composition is xPt/In ₂ O ₃ , where x is the mass percentage of Pt in the catalyst; wherein x=0.5-10.0, preferably 1-2, more preferably 1.5. The Pt _x /In ₂ O ₃ catalyst has oxygen vacancies and surface active oxygen at the metal-oxide interface. The particle size of the Pt particles is less than 1 nm, the long side of the plate-like In ₂ O ₃ is 400-450 nm, the short side is 300-400 nm, and the thickness is 20-30 nm.

The catalyst is used in the reaction of carbon dioxide hydrogenation to methanol. The activity evaluation of the catalyst for the hydrogenation of carbon dioxide to methanol was carried out on a pressurized fixed-bed continuous flow reactor-GC combined system. Before the reaction, nitrogen was purged at 200 °C for 0.5 h, and then switched to hydrogen for reduction for 1.0 h. The conditions for hydrogenating carbon dioxide to synthesize methanol are: reaction pressure 1-6MPa, reaction temperature 210-310℃, space velocity 9000-40000mL(h ^-1 g _cat ^-1 ), n(H ₂ ):n(CO ₂ ) Molar ratio = 2-4.

Example 1

Hydrothermal preparation of indium oxide: take 32 mL of ethanol and 5 mL of deionized water to prepare solution 1. Solution 2 was prepared by dissolving 4.07 g of indium nitrate tetrahydrate into the above solution 1. Another 20 mL of ethanol and 5 mL of deionized water were taken to prepare solution 3. Solution 4 was prepared by dissolving 4.0 g of urea into the above solution 3. With vigorous stirring, solution 4 was added to solution 2 and stirring was continued at room temperature for 2 hours. The solution was then taken out and placed in a reaction kettle, which was kept at 120°C for 17 hours. After the reaction, the sample was taken out and washed with deionized water for several times, dried at 60° C. for 12 hours, and calcined at 300° C. for 5 hours to obtain plate-shaped indium oxide.

Example 2

5 g of indium nitrate tetrahydrate was calcined at 300° C. for 5 hours to obtain amorphous indium oxide nanoparticles.

It can be seen that the adjustment of the morphology of indium oxide requires special reaction conditions. In this application, indium nitrate is used as the precursor, and by adjusting the ratio of water and alcohol in the solvent, a hydrothermal method is used to obtain a specific morphology under high temperature and high pressure. Indium oxide is often used in the preparation of traditional catalysts to adjust the morphology, that is, in a sealed pressure vessel, using water or alcohol as a solvent, the powder is dissolved and recrystallized. The method of preparing the material.

For excellent catalytic activity, the oxygen vacancies on the catalyst surface act as basic sites in traditional _CO2 activation, that is, the active sites of _CO2 , the increase of oxygen vacancies will facilitate the adsorption and activation of _CO2 , and the introduction of metals will It is favorable for the dissociation of _H2 , and the metal platinum with small particle size in this application makes the dissociation of _H2 more efficient with excellent dispersion. The interaction of Pt and In ₂ O ₃ in this application, the Metal Support Strong Interaction (SMSI), is crucial in the generation of methanol.

Example 3

Preparation of 0.5Pt/In ₂ O ₃ nanoplates by deposition and precipitation: take a certain amount of chloroplatinic acid aqueous solution (containing 2.512 mg of platinum) and dissolve it in 50 ml of deionized water, and stir at room temperature for 0.5 h. The prepared plate-like indium oxide was added to the solution and stirred for 1.0 h. Add 0.2 g of urea to the solution and continue stirring for 3.0 h at 80 °C. After cooling to room temperature, centrifuged and washed 3 times (35ml of water each time), vacuum dried at 60°C for 12h, and calcined at 450°C for 3.0h to obtain 0.5Pt/ln ₂ O ₃ nanoplates.

Example 4

Preparation of 1.0Pt/In ₂ O ₃ nanoplates by deposition precipitation method: take a certain amount of chloroplatinic acid aqueous solution (containing 5.025 mg of platinum) and dissolve it in 50 ml of deionized water, and stir at room temperature for 0.5 h, take 0.495 g of Example 1 The prepared plate-like indium oxide was added to the solution and stirred for 1.0 h. Add 0.2 g of urea to the solution and continue stirring for 3.0 h at 80 °C. After cooling to room temperature, centrifuged and washed 3 times (35ml of water each time), vacuum dried at 60°C for 12h, and calcined at 450°C for 3.0h to obtain 1.0Pt/In ₂ O ₃ nanoplates.

Example 5

Preparation of 1.5Pt/In ₂ O ₃ nanoplates by deposition precipitation method: take a certain amount of chloroplatinic acid aqueous solution (platinum content 7.538mg) and dissolve it in 50ml deionized water, and stir at room temperature for 0.5h, take 0.495g of Example 1 The prepared plate-like indium oxide was added to the solution and stirred for 1.0 h. Add 0.2 g of urea to the solution and continue stirring for 3.0 h at 80 °C. After cooling to room temperature, centrifuged and washed 3 times (35ml of water each time), vacuum dried at 60°C for 12h, and calcined at 450°C for 3.0h to obtain 1.5Pt/In ₂ O ₃ nanoplates.

Fig. 4 is the TEM image of 1.5Pt/plate In ₂ O ₃ , Fig. 5 is the TEM image of 1.5Pt/plate In ₂ O ₃ ; Fig. 7 is the plate In ₂ O ₃ in Example 1 and the present embodiment Example 1. O1S energy spectrum of 5Pt/plate In ₂ O ₃ ; the oxygen vacancy concentration of plate In ₂ O ₃ is 34.23%, and the oxygen vacancy concentration of 1.5Pt/plate In ₂ O ₃ is 47.32%.

Figure 1 is a graph of 1.5Pt/plate In ₂ O ₃ CO ₂ conversion and CH ₃ OH selectivity; Figure 2 is a graph of 1.5Pt/plate In ₂ O ₃ methanol yield; Figure 3 is 1.5Pt/plate In ₂ O ₃ stability test chart, standard test conditions: 0.1g catalyst; reaction pressure: 5MPa; space velocity: 18000ml g _cat ^-1 h ^-1 ; reaction gas composition: H ₂ :CO ₂ :N ₂ =73:24: 3.

Example 6

Preparation of 2.0Pt/In ₂ O ₃ nanoplates by deposition precipitation method: Dissolve a certain amount of chloroplatinic acid aqueous solution (containing 10.051 mg of platinum) in 50 ml of deionized water, and stir at room temperature for 0.5 h, take 0.495 g of Example 1 The prepared plate-like indium oxide was added to the solution and stirred for 1.0 h. Add 0.2 g of urea to the solution and continue stirring for 3.0 h at 80 °C. After cooling to room temperature, centrifuged and washed 3 times (35ml of water each time), vacuum dried at 60°C for 12h, and calcined at 450°C for 3.0h to obtain 2.0Pt/In ₂ O ₃ nanoplates.

Example 7

Preparation of 5.0Pt/In ₂ O ₃ nanoplates by deposition and precipitation method: take a certain amount of chloroplatinic acid aqueous solution (containing 26.05 mg of platinum) and dissolve it in 50 ml of deionized water, and stir at room temperature for 0.5 h, take 0.495 g of Example 1 The prepared plate-like indium oxide was added to the solution and stirred for 1.0 h. Add 0.2 g of urea to the solution and continue stirring for 3.0 h at 80 °C. After cooling to room temperature, centrifuged and washed 3 times (35ml of water each time), vacuum dried at 60°C for 12h, and calcined at 450°C for 3.0h to obtain 5.0Pt/In ₂ O ₃ nanoplates.

Example 8

Preparation of 10.0Pt/In ₂ O ₃ nanoplates by deposition precipitation method: take a certain amount of chloroplatinic acid aqueous solution (containing 55.00 mg of platinum) and dissolve it in 50 ml of deionized water, and stir at room temperature for 0.5 h. The prepared plate-like indium oxide was added to the solution and stirred for 1.0 h. Add 0.2 g of urea to the solution and continue stirring for 3.0 h at 80 °C. After cooling to room temperature, centrifugal washing 3 times (35ml water each time), vacuum drying at 60°C for 12h, and calcination at 450°C for 3.0h to obtain 10.0Pt/In ₂ O ₃ nanoplates.

Example 9

Preparation of 1.5Pt/In ₂ O ₃ nanoparticles by deposition precipitation method: take a certain amount of chloroplatinic acid aqueous solution (containing 7.538 mg of platinum) and dissolve it in 50 ml of deionized water, and stir at room temperature for 0.5 h, take 0.495 g of Example 2 The prepared amorphous indium oxide nanoparticles were added to the solution and stirred for 1.0 h. Add 0.2 g of urea to the solution and continue stirring for 3.0 h at 80 °C. After cooling to room temperature, centrifugal washing 3 times (35ml water each time), vacuum drying at 60°C for 12h, and calcination at 450°C for 3.0h to obtain 1.5Pt/In ₂ O ₃ nanoparticles.

Example 10

Preparation of 1.5Pt/Al ₂ O ₃ by deposition precipitation method: Dissolve a certain amount of chloroplatinic acid aqueous solution (platinum content 7.538 mg) in 50 ml of deionized water, stir at room temperature for 0.5 h, and add 0.495 g of commercial alumina to the solution and stirred for 1.0 h. Add 0.2 g of urea to the solution and continue stirring for 3.0 h at 80 °C. After cooling to room temperature, centrifugal washing 3 times (35ml water each time), vacuum drying at 60°C for 12h, and calcination at 450°C for 3.0h to obtain 1.5Pt/Al ₂ O ₃ .

Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the specific embodiments described above.

Table 1

It can be seen from Table 1 that the indium oxide supported noble metal platinum catalyst provided by the present invention is used in the reaction of carbon dioxide hydrogenation to prepare methanol with high selectivity, and under appropriate conditions, the selectivity of the target product can be improved, and the selectivity of carbon monoxide can be reduced.

Table 2

Table 3 1.5Pt/In ₂ O ₃ nanoplate catalyst activity and space velocity relationship

Combined with Tables 1-3, the catalysts obtained in the examples are under the conditions of P=5.0MPa, T=210-310°C, GHSV=18000mLh ^-1 g _cat ^-1 and n(H ₂ )/n(CO ₂ )=3 The target product has high reactivity and high selectivity, among which the carbon dioxide conversion rate is as high as 15.21%, the methanol selectivity is as high as 80.31%, and the space-time yield is as high as 0.7538g _CH3OH g _cat ^-1 h ^-1 .

The calculation process of the space-time yield of methanol is as follows:

In the formula: F _CO2 is the molar flow rate of _CO2 entering the reactor; X _CO2 is the conversion rate of _CO2 ; S _CH3OH is the selectivity of methanol; M is the molecular mass of methanol 106.4g mol ^-1 ; W is the quality of the catalyst.

By adjusting the space velocity, it is found that the catalyst has the best catalytic activity under the condition of 18000mL h ^-1 g _cat ^-1 .

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention in other forms. Any person skilled in the art may use the technical content disclosed above to make changes or modifications to equivalent changes. Example. However, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solutions of the present invention still belong to the protection scope of the technical solutions of the present invention.

Claims (10)

What is claimed is: 1. A platinum-modified indium-based oxide catalyst, characterized in that the catalyst is a metal/oxide composite catalyst, comprising a carrier plate-shaped In ₂ O ₃ , and active component Pt particles. 2 . The platinum-modified indium-based oxide catalyst according to claim 1 , wherein the chemical composition of the catalyst is xPt/In ₂ O ₃ , and x is the mass percentage of Pt in the catalyst; wherein x=0.5- 10.0 (preferably 1 to 2). 3 . The platinum-modified indium-based oxide catalyst according to claim 1 , wherein the particle size of the Pt particles is less than 1 nm, the long side of the plate-shaped In ₂ O ₃ is 400-450 nm, and the short side is 400-450 nm. 4 . The sides are 300-400nm and the thickness is 20-30nm. 4. A method for preparing a platinum-modified indium-based oxide catalyst according to any one of claims 1-3, wherein the method comprises the following steps: (1) Preparation of plate-like In ₂ O ₃ carrier: After mixing water and alcohol, solution 1 is obtained, and indium salt is dissolved in solution 1 to obtain solution 2; In addition, after mixing water and alcohol, solution 3 is obtained, and then the precipitant is dissolved in solution 3 to obtain solution 4; Under stirring, solution 4 was added to solution 2, and after stirring, a hydrothermal reaction was carried out; After the reaction, the obtained precipitate is centrifuged, washed, dried and calcined to obtain a plate-shaped In ₂ O ₃ carrier; (2) Pt modified In ₂ O ₃ : Dissolve the platinum precursor in deionized water to prepare an aqueous solution; The plate-shaped In ₂ O ₃ carrier is added to the aqueous solution, after stirring, a precipitant is added, and then heated and stirred; After cooling to room temperature, the precipitate was centrifuged and washed, then vacuum-dried, and calcined at high temperature to obtain a platinum-modified indium-based oxide catalyst xPt/In ₂ O ₃ . The method for preparing a platinum-modified indium-based oxide catalyst according to claim 4, wherein the indium salt is indium nitrate tetrahydrate, the precipitating agent is urea, and the platinum precursor is The body is chloroplatinic acid. 6. The preparation method of a platinum-modified indium-based oxide catalyst according to claim 4 or 5, wherein in step (1), during the hydrothermal reaction, the mass ratio of the indium salt to the precipitating agent It is (4-5): 4; The volume ratio of described ethanol and water is (2-6): 1. The temperature of the hydrothermal reaction is 115-125°C, and the time is 16-18h; the temperature of the calcination is 290-310°C, and the time is 4-6h. The method for preparing a platinum-modified indium-based oxide catalyst according to claim 4 or 5, wherein in step (2), the temperature of the heating and stirring is 75-85°C; the high-temperature calcination The temperature is 440-460 ℃, and the time is 2-4h. 8. An application of the platinum-modified indium-based oxide catalyst according to any one of claims 1-3, wherein the catalyst is used in the reaction of carbon dioxide hydrogenation to methanol. 9 . The application of a platinum-modified indium-based oxide catalyst according to claim 8 , wherein the conditions for hydrogenating carbon dioxide to synthesize methanol are: reaction pressure 1-7 MPa, reaction temperature 210-330° C., space velocity 9000-40000 mL (h ^{- 1} g _cat ^-1 ), n(H ₂ ):n(CO ₂ ) molar ratio=2-7. 10. The application of a platinum-modified indium-based oxide catalyst according to claim 9, wherein the reaction pressure is 4-6MPa, the reaction temperature is 270-310°C, and the space velocity is 15000-24000mL (h ^-1 g _cat ^-1 ), n(H ₂ ):n(CO ₂ ) molar ratio=3-5.

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