A method for preparing benzyl alcohol by hydrogenating benzaldehyde using an Au@Pt / C catalyst

Abstract

The present invention provides a method for preparing benzyl alcohol by hydrogenating benzaldehyde using an Au@Pt / C catalyst. In this reaction, benzaldehyde is used as the raw material, and a supported Au-core-Pt-shell nanostructure catalyst is used to catalyze the conversion of benzaldehyde. Among them, the 1 wt% Au@Pt / C (mAu:mPt = 1:1.22) catalyst, under the conditions of 1 MPa hydrogen and 60 °C, hydrogenates benzaldehyde in one pot in isopropanol solvent. The conversion rate of benzaldehyde is 99.9%, the selectivity of benzyl alcohol is 96.9%, and the yield of benzyl alcohol has an increase of more than 45% compared with the Pt-based catalyst, which is superior to most of the catalysts reported at present. The preparation process of the catalyst of the present invention is simple, the catalyst has high activity and stability, the reaction conditions are milder, the energy consumption is reduced to a certain extent, and it is more environmentally friendly. Therefore, the present invention has broad application prospects in the industry.

Description

Technical Field

[0001] The present invention belongs to the field of biomass energy catalysis, and relates to a method for catalytic hydrogenation of biomass-derived benzaldehyde to prepare fine chemical benzyl alcohol, and particularly relates to a catalyst with an Au core-Pt shell nanostructure, which can effectively catalyze the selective hydrogenation of benzaldehyde to prepare benzyl alcohol. Background Art

[0002] In the energy and chemical industries, fossil carbon sources are increasingly being replaced by renewable carbonaceous materials to reduce greenhouse gas carbon dioxide emissions and thus slow down global warming. Lignocellulosic biomass lignin is an abundant and renewable carbon resource and is expected to replace traditional non-renewable fossil resources in chemical and fuel production. Lignin is derived from lignocellulosic biomass, which can be depolymerized into various platform compounds, and these platform compounds can be further upgraded into high-value chemicals and fuels.

[0003] Benzaldehyde is an important biomass-based platform compound and an important chemical intermediate, usually used as a solvent for inks, paints and varnishes. It is also an indispensable fixative in the formulation of cosmetics and some fine chemical products (such as fragrances). It was initially commercially synthesized by the hydrolysis of benzyl chloride and sodium hydroxide, but the hydrolysis process leaves excessive chlorine residues in the product, causing serious environmental toxicity. In addition, it can also be prepared by methods such as electrocatalytic hydrogenation of benzaldehyde, electrocatalytic oxidation of toluene and liquid-phase catalytic hydrogenation of benzaldehyde. Among these methods, liquid-phase catalytic hydrogenation of benzaldehyde is a better choice because of its advantages such as low energy consumption and simple process, and thus has received extensive attention from researchers. Pt-based catalysts have received relatively more research in the catalytic hydrogenation of benzaldehyde due to their high catalytic activity. Catalysts mainly composed of Pt nanoparticles tend to produce more deeply hydrogenated products such as toluene during the hydrogenation of benzaldehyde. One of the effective means to solve this problem is to dope and modify Pt-based catalysts to make them have higher benzyl alcohol selectivity. In view of the above problems, it is imperative to develop new strategies and methods for preparing catalysts to improve the conversion efficiency and the selectivity of target products. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a method for using an Au@Pt catalyst for the hydrogenation of benzaldehyde to prepare benzyl alcohol. The preparation process of the present invention is simple, the catalyst has high activity and stability, the reaction conditions are milder, the energy consumption is reduced to a certain extent, and it is more environmentally friendly. The present invention has broad application prospects in industry.

[0005] The 1wt% Au@Pt / C obtained by using this preparation method (m Au :m Pt=1:1.22) The catalyst can achieve high conversion of benzaldehyde and high selectivity of benzyl alcohol under mild conditions.

[0006] To solve the technical problems of the present invention, the technical solution proposed is: A method for preparing benzyl alcohol by hydrogenating benzaldehyde using an Au@Pt catalyst, comprising the following steps:

[0007] (1) Mix the chloroauric acid solution with the sodium citrate aqueous solution and then reduce it with the sodium borohydride aqueous solution to obtain Au nanoparticles;

[0008] (2) Mix the chloroplatinic acid solution with the Au nanoparticles in step (1), and then reduce it with ascorbic acid to obtain Au@Pt nanoparticles; the mass ratio of the two metals Au:Pt is 1:1.22;

[0009] (3) Add activated carbon to deionized water, disperse it by stirring, and then obtain an activated carbon slurry through ultrasonic treatment;

[0010] (4) Use activated carbon as the carrier, mix the activated carbon slurry in step (3) with the Au@Pt nanoparticles in step (2), and filter and dry the obtained suspension to prepare the Au@Pt / C catalyst; the total mass fraction of Au and Pt metals accounts for 1 wt% of the catalyst;

[0011] (5) Add the reaction raw materials benzaldehyde, solvent and the Au@Pt / C catalyst in step (4) to a high-pressure reactor equipped with a thermal conductivity detector, and carry out the hydrogenation of benzaldehyde to prepare benzyl alcohol under stirring; the initial pressure of hydrogen is 1 - 2 MPa; the reaction temperature is 40 - 100 °C; the reaction time is ≥2 h; the solvent is isopropanol; after the reaction, the catalyst and the reaction solution are separated by centrifugation.

[0012] Preferably, in step (5), the catalyst dosage is based on the molar ratio of Pt to benzaldehyde of 1:1000.

[0013] Preferably, (1) Preparation of Au nanoparticles: Measure 150 mL of deionized water and place it in a beaker, add a certain amount of the Au precursor salt chloroauric acid to the beaker, weigh an appropriate amount of sodium citrate and add it to the beaker, and stir at a speed of 1200 rpm for 1 min; weigh a certain amount of sodium borohydride and dissolve it in 10 mL of ice-cold deionized water, and quickly add the freshly prepared sodium borohydride solution to the vigorously stirred Au precursor with a 5 mL plastic dropper. The solution quickly changes from light yellow to wine red. After stirring at 1200 rpm for 5 minutes, turn off the stirring and let it stand at room temperature for 1 h. The prepared Au nanoparticles are stored in a refrigerator at 4 °C;

[0014] (2)Preparation of Au@Pt nanoparticles: Stir the aqueous solution of Au nanoparticles prepared in step (1) at a speed of 1200 rpm; add a certain amount of the precursor salt of Pt, chloroplatinic acid, and stir for 1 min; weigh a certain amount of ascorbic acid and dissolve it in 10 mL of deionized water. Use a 5 mL plastic dropper to add the freshly prepared ascorbic acid solution to the beaker and stir at a speed of 1200 rpm for 45 min to obtain an aqueous solution of Au@Pt nanoparticles. Store the prepared Au@Pt nanoparticles in a refrigerator at 4 °C;

[0015] (3)Take a certain amount of activated carbon in a beaker, add 300 mL of deionized water, stir at a speed of 1000 rpm for 1 min, and then sonicate for 10 min to obtain an activated carbon slurry;

[0016] (4)Load Au@Pt onto the activated carbon: Stir the activated carbon slurry prepared in step (3) at 1200 rpm. Use a 5 mL plastic dropper to gradually add the Au@Pt nanoparticle solution prepared in step (2) to the activated carbon slurry and stir for 1 h;

[0017] (5)Filter the catalyst slurry collected in step (4) by suction filtration, and wash it with deionized water until the conductivity is 0. Place the solid obtained after suction filtration in a petri dish and dry it in a vacuum drying oven at 80 °C for 12 h, and then store it sealed after drying;

[0018] (6)Add reaction raw materials, solvents, and catalysts to a high-pressure reactor equipped with a thermal conductivity detector, and carry out catalytic hydrogenolysis reaction under stirring; before the reaction, purge the reactor with hydrogen several times to remove the air in the reactor.

[0019] Preferably, the preparation steps of the catalyst are as follows:

[0020] (1)Preparation of Au nanoparticles: Measure 150 mL of deionized water and place it in a beaker. Take 1 g of HAuCl4 and dissolve it in 25 mL of deionized water to prepare an Au precursor solution, with Au: 18.335 mg / mL for standby; take 491 μL of the Au precursor solution and add it to the beaker. Measure an appropriate amount of sodium citrate and add it to the beaker at a mass ratio of Au to sodium citrate of 1:5. Stir at a speed of 1200 rpm for 1 min; weigh 7.5 mg of sodium borohydride and dissolve it in 10 mL of ice-cold deionized water. Use a 5 mL plastic dropper to quickly add the freshly prepared sodium borohydride solution to the vigorously stirred Au precursor. The solution quickly changes from light yellow to wine red. After stirring at 1200 rpm for 5 minutes, turn off the stirring and let it stand at room temperature for 1 h. Store the prepared Au nanoparticles in a refrigerator at 4 °C;

[0021] (2)Preparation of Au@Pt nanoparticles: Stir the aqueous solution of Au nanoparticles prepared in step (1) at a speed of 1200 rpm. Dissolve 1 g of H2PtCl6 in 50 mL of deionized water to prepare a Pt precursor solution with Pt: 7.61 mg / mL for standby. Take 1445 μL of the Pt precursor solution and add it to the aqueous solution of Au nanoparticles, and stir for 1 min. Weigh 20 mg of ascorbic acid and dissolve it in 10 mL of deionized water. Use a 5 mL plastic dropper to add the freshly prepared ascorbic acid solution to the beaker and stir at a speed of 1200 rpm for 45 min to obtain an aqueous solution of Au@Pt nanoparticles. The prepared Au@Pt nanoparticles are stored in a refrigerator at 4 °C.

[0022] (3)Take 1980 mg of activated carbon in a beaker, add 300 mL of deionized water, stir at a speed of 1000 rpm for 1 min, and then ultrasonicate for 10 min to obtain an activated carbon slurry.

[0023] (4)Load Au@Pt onto activated carbon: Stir the activated carbon slurry prepared in step (3) at 1200 rpm. Use a 5 mL plastic dropper to gradually add the Au@Pt nanoparticle solution prepared in step (2) to the activated carbon slurry and stir for 1 h.

[0024] (5)Filter the catalyst slurry collected in step (4) by suction filtration, and wash it with deionized water until the conductivity is 0. Place the solid obtained after suction filtration in a petri dish and dry it in a vacuum drying oven at 80 °C for 12 h. After drying, seal and store it. The catalyst is 1wt% Au@Pt / C m Au :m Pt = 1:1.22.

[0025] Preferably, the reaction conditions in step (5) are an initial hydrogen pressure of 1 MPa, a reaction temperature of 60 °C, and a reaction time of 2 h.

[0026] Preferably, in step (5), the mass of the catalyst added to the reaction kettle is based on a molar ratio of Pt to benzaldehyde of 1:1000, 1 mmol of benzaldehyde and 10 mL of isopropanol.

[0027] Preferably, use 1wt% Au@Pt / C m Au :m Pt = 1:1.22 to catalyze the hydrogenation of benzaldehyde to prepare benzyl alcohol. At a hydrogen pressure of 1 MPa and a reaction temperature of 60 °C for 120 min, the conversion rate of benzaldehyde is 99.9%, and the selectivity of benzyl alcohol is 96.9%.

[0028] Beneficial effects:

[0029] The present invention provides a method for preparing an Au core-Pt shell nanostructured catalyst. The 1 wt% Au@Pt / C (m Au :m Pt =1:1.22) catalyst obtained by using this preparation method can achieve high conversion of benzaldehyde and high selectivity of benzyl alcohol under mild conditions. Under the conditions of 1 MPa hydrogen and 60 °C, benzaldehyde is hydrogenated in one pot in isopropanol solvent. The conversion of benzaldehyde is 99.9%, the selectivity of benzyl alcohol is 96.9%, and the yield of benzyl alcohol is more than 45% higher than that of the Pt-based catalyst, which is better than most of the currently reported catalysts.

[0030] For the catalyst 1 wt% Au@Pt / C (m Au :m Pt =1:0.54) prepared in Example 1, the conversion of benzaldehyde is 89.9% and the selectivity of benzyl alcohol is 94.1%; for the catalyst Au@Pt / C (m Au :m Pt =1:2.07) prepared in Example 3, the conversion of benzaldehyde is 97.4% and the selectivity of benzyl alcohol is 96.2%; for the catalyst Au@Pt / C (m Au :m Pt =1:3) prepared in Example 4, the conversion of benzaldehyde is 98.7% and the selectivity of benzyl alcohol is 87.6%; for the catalyst Au@Pt / C (m Au :m Pt =1:1.22) prepared in Example 2, the conversion of benzaldehyde is 99.9% and the selectivity of benzyl alcohol is 96.9%. It has the best catalytic performance among the catalysts prepared in Examples 1-4, and the yield of benzyl alcohol is more than 45% higher than that of Pt / C prepared by the impregnation method. In addition, the activity and selectivity of the catalyst with an Au core-Pt shell structure are both better than those of the Pt / C catalyst and the Au-Pt / C catalyst with an alloy structure.

[0031] As can be seen from Table 2, the catalyst with activated carbon as the carrier has a benzaldehyde conversion of 99.9% and a benzyl alcohol selectivity of 96.9%, which is the best.

[0032] The present invention prepared a series of supported Au core-Pt shell nanostructured catalysts and applied them to the reaction of hydrogenating benzaldehyde to prepare benzyl alcohol. Through the optimization of the reaction conditions, it was found that under the optimized 1 wt% Au@Pt / C (m Au :m Pt= 1:1.22), isopropanol as the solvent, under the reaction conditions of 1 MPa hydrogen pressure and 60 °C, with a reaction time of 120 min, a conversion rate of benzaldehyde of 99.9% and a selectivity of benzyl alcohol of 96.9% can be achieved. For the results of the catalyst recycling reaction, after 5 consecutive cycles, the conversion rate of benzaldehyde decreased slightly, from 99.9% to 94.4%, while the yield of benzyl alcohol was still 90.0%. It indicates that the 1wt% Au@Pt / C (m Au :m Pt = 1:1.22) catalyst has good reusability. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 TEM and EDS diagrams of the Au@Pt / C catalyst prepared in Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention will be further described in detail below with reference to specific examples. These examples are only for illustrative purposes of the present invention, but the present invention is not limited to the following examples.

[0035] Example 1

[0036] (1) Preparation of Au nanoparticles. Measure 150 mL of deionized water and place it in a beaker. The Au precursor can be its metal precursor salt solution. Taking chloroauric acid as an example, take 1 g of HAuCl4 and dissolve it in 25 mL of deionized water to prepare an Au precursor solution (Au: 18.335 mg / mL) for standby. Take 709 μL of the Au precursor solution and add it to the beaker. Measure an appropriate amount of sodium citrate (the mass ratio of Au to sodium citrate is 1:5) and add it to the beaker. Stir at a speed of 1200 rpm for 1 min. Weigh 10.8 mg of sodium borohydride and dissolve it in 10 mL of ice-cold deionized water. Quickly add the freshly prepared sodium borohydride solution to the vigorously stirred Au precursor with a 5 mL plastic dropper. The solution quickly changes from light yellow to wine red. After stirring at 1200 rpm for 5 minutes, turn off the stirring and let it stand at room temperature for 1 h. The prepared Au nanoparticles can be stored in a refrigerator at 4 °C.

[0037] (2)Preparation of Au@Pt nanoparticles. Stir the aqueous solution of Au nanoparticles prepared in step (1) at a speed of 1200 rpm. The precursor of Pt can be its metal precursor salt solution. Taking chloroplatinic acid as an example, dissolve 1 g of H2PtCl6 in 50 mL of deionized water to prepare a Pt precursor solution (Pt: 7.61 mg / mL) for standby. Add 920 μL of the Pt precursor solution to the aqueous solution of Au nanoparticles and stir for 1 min. Weigh 12.8 mg of ascorbic acid and dissolve it in 10 mL of deionized water. Use a 5 mL plastic dropper to add the freshly prepared ascorbic acid solution to the beaker and stir at a speed of 1200 rpm for 45 min to obtain an aqueous solution of Au@Pt nanoparticles. The prepared Au@Pt nanoparticles can be stored in a refrigerator at 4°C.

[0038] (3)Take 1980 mg of activated carbon in a beaker, add 300 mL of deionized water, stir at a speed of 1000 rpm for 1 min, and then ultrasonicate for 10 min to obtain an activated carbon slurry.

[0039] (4)Load Au@Pt onto the activated carbon. Stir the activated carbon slurry prepared in step (3) at 1200 rpm, and use a 5 mL plastic dropper to gradually add the Au@Pt nanoparticle solution prepared in step (2) to the activated carbon slurry and stir for 1 h.

[0040] (5)Filter the catalyst slurry collected in step (4) by suction filtration, and wash it with deionized water until the conductivity is 0. Place the solid obtained after suction filtration in a petri dish and dry it in a vacuum drying oven at 80°C for 12 h, and then seal and store it after completion.

[0041] The catalyst is named 1wt% Au@Pt / C (m Au :m Pt =1:0.54).

[0042] Example 2

[0043] (1)Preparation of Au nanoparticles. Measure 150 mL of deionized water and place it in a beaker. The Au precursor can be its metal precursor salt solution. Taking chloroauric acid as an example, dissolve 1 g of HAuCl4 in 25 mL of deionized water to prepare an Au precursor solution (Au: 18.335 mg / mL) for standby. Add 491 μL of the Au precursor solution into the beaker, measure an appropriate amount of sodium citrate (the mass ratio of Au to sodium citrate is 1:5) and add it into the beaker, and stir at a speed of 1200 rpm for 1 min. Weigh 7.5 mg of sodium borohydride and dissolve it in 10 mL of ice-cold deionized water. Quickly add the freshly prepared sodium borohydride solution into the vigorously stirred Au precursor with a 5 mL plastic dropper. The solution quickly changes from light yellow to wine red. After stirring at 1200 rpm for 5 minutes, turn off the stirring and let it stand at room temperature for 1 h. The prepared Au nanoparticles can be stored in a refrigerator at 4 °C.

[0044] (2)Preparation of Au@Pt nanoparticles. Stir the aqueous solution of Au nanoparticles prepared in step (1) at a speed of 1200 rpm. The Pt precursor can be its metal precursor salt solution. Taking chloroplatinic acid as an example, dissolve 1 g of H2PtCl6 in 50 mL of deionized water to prepare a Pt precursor solution (Pt: 7.61 mg / mL) for standby. Add 1445 μL of the Pt precursor solution into the aqueous solution of Au nanoparticles and stir for 1 min. Weigh 20 mg of ascorbic acid and dissolve it in 10 mL of deionized water. Add the freshly prepared ascorbic acid solution into the beaker with a 5 mL plastic dropper and stir at a speed of 1200 rpm for 45 min to obtain an aqueous solution of Au@Pt nanoparticles. The prepared Au@Pt nanoparticles can be stored in a refrigerator at 4 °C.

[0045] (3)Take 1980 mg of activated carbon and place it in a beaker, add 300 mL of deionized water, stir at a speed of 1000 rpm for 1 min, and then sonicate for 10 min to obtain an activated carbon slurry.

[0046] (4)Load Au@Pt onto the activated carbon. Stir the activated carbon slurry prepared in step (3) at 1200 rpm, and slowly add the Au@Pt nanoparticle solution prepared in step (2) drop by drop into the activated carbon slurry with a 5 mL plastic dropper, and stir for 1 h.

[0047] (5)Filter the catalyst slurry collected in step (4) by suction filtration, and wash it with deionized water until the conductivity is 0. Place the solid obtained after suction filtration in a petri dish and dry it in a vacuum drying oven at 80 °C for 12 h, and then seal and store it after completion.

[0048] The catalyst is named 1wt% Au@Pt / C (m Au :m Pt = 1:1.22).

[0049] Example 3

[0050] (1)Preparation of Au nanoparticles. Measure 150 mL of deionized water and place it in a beaker. The Au precursor can be its metal precursor salt solution. Taking chloroauric acid as an example, dissolve 1 g of HAuCl4 in 25 mL of deionized water to prepare an Au precursor solution (Au: 18.335 mg / mL) for standby. Take 355 μL of the Au precursor solution and add it to the beaker. Measure an appropriate amount of sodium citrate (the mass ratio of Au to sodium citrate is 1:5) and add it to the beaker. Stir at a speed of 1200 rpm for 1 min. Weigh 5.5 mg of sodium borohydride and dissolve it in 10 mL of ice-cold deionized water. Quickly add the freshly prepared sodium borohydride solution to the vigorously stirred Au precursor with a 5 mL plastic dropper. The solution quickly changes from light yellow to wine red. After stirring at 1200 rpm for 5 minutes, turn off the stirring and let it stand at room temperature for 1 h. The prepared Au nanoparticles can be stored in a refrigerator at 4°C.

[0051] (2)Preparation of Au@Pt nanoparticles. Stir the aqueous solution of Au nanoparticles prepared in step (1) at a speed of 1200 rpm. The Pt precursor can be its metal precursor salt solution. Taking chloroplatinic acid as an example, dissolve 1 g of H2PtCl6 in 50 mL of deionized water to prepare Pt for standby. Take 1774 μL of the Pt precursor solution and add it to the aqueous solution of Au nanoparticles, and stir for 1 min. Weigh 24.5 mg of ascorbic acid and dissolve it in 10 mL of deionized water. Add the freshly prepared ascorbic acid solution to the beaker with a 5 mL plastic dropper and stir at a speed of 1200 rpm for 45 min to obtain an aqueous solution of Au@Pt nanoparticles. The prepared Au@Pt nanoparticles can be stored in a refrigerator at 4°C.

[0052] (3)Take 1980 mg of activated carbon and place it in a beaker. Add 300 mL of deionized water, stir at a speed of 1000 rpm for 1 min, and then sonicate for 10 min to obtain an activated carbon slurry.

[0053] (4)Load Au@Pt onto the activated carbon. Stir the activated carbon slurry prepared in step (3) at 1200 rpm. Dropwise add the Au@Pt nanoparticle solution prepared in step (2) to the activated carbon slurry with a 5 mL plastic dropper and stir for 1 h.

[0054] (5)Filter the catalyst slurry collected in step (4) by suction filtration, and wash it with deionized water until the conductivity is 0. Place the solid obtained after suction filtration in a petri dish and dry it in a vacuum drying oven at 80°C for 12 h, and then seal and store it after completion.

[0055] The catalyst is named 1wt% Au@Pt / C (mAu :m Pt = 1:2.07).

[0056] Example 4

[0057] (1) Preparation of Au nanoparticles. Measure 150 mL of deionized water and place it in a beaker. The Au precursor can be its metal precursor salt solution. Taking chloroauric acid as an example, dissolve 1 g of HAuCl4 in 25 mL of deionized water to prepare an Au precursor solution (Au: 18.335 mg / mL) for standby. Take 273 μL of the Au precursor solution and add it to the beaker. Measure an appropriate amount of sodium citrate (the mass ratio of Au to sodium citrate is 1:5) and add it to the beaker. Stir at 1200 rpm for 1 min. Weigh 4.2 mg of sodium borohydride and dissolve it in 10 mL of ice-cold deionized water. Quickly add the freshly prepared sodium borohydride solution to the vigorously stirred Au precursor with a 5 mL plastic dropper. The solution quickly changes from light yellow to wine red. After stirring at 1200 rpm for 5 minutes, turn off the stirring and let it stand at room temperature for 1 h. The prepared Au nanoparticles can be stored in a refrigerator at 4 °C.

[0058] (2) Preparation of Au@Pt nanoparticles. Stir the aqueous solution of Au nanoparticles prepared in step (1) at 1200 rpm. The Pt precursor can be its metal precursor salt solution. Taking chloroplatinic acid as an example, dissolve 1 g of H2PtCl6 in 50 mL of deionized water to prepare Pt for standby. Take 1971 μL of the Pt precursor solution and add it to the aqueous solution of Au nanoparticles, and stir for 1 min. Weigh 27.2 mg of ascorbic acid and dissolve it in 10 mL of deionized water. Add the freshly prepared ascorbic acid solution to the beaker with a 5 mL plastic dropper and stir at 1200 rpm for 45 min to obtain an aqueous solution of Au@Pt nanoparticles. The prepared Au@Pt nanoparticles can be stored in a refrigerator at 4 °C.

[0059] (3) Take 1980 mg of activated carbon in a beaker, add 300 mL of deionized water, stir at 1000 rpm for 1 min, and then sonicate for 10 min to obtain an activated carbon slurry.

[0060] (4) Load Au@Pt onto the activated carbon. Stir the activated carbon slurry prepared in step (3) at 1200 rpm. Slowly add the Au@Pt nanoparticle solution prepared in step (2) drop by drop to the activated carbon slurry with a 5 mL plastic dropper and stir for 1 h.

[0061] (5) Filter the catalyst slurry collected in step (4) by suction filtration, and wash it with deionized water until the conductivity is 0. Place the solid obtained after suction filtration in a petri dish and dry it in a vacuum drying oven at 80 °C for 12 h, and then seal and store it after completion.

[0062] The catalyst is named 1wt% Au@4 ML-Pt / C (m Au :m Pt = 1:3).

[0063] Example 5

[0064] (1) The reaction for the hydrogenation of benzaldehyde to benzyl alcohol was carried out in a high-pressure reactor equipped with a thermal conductivity detector. First, an appropriate amount of the 1wt% Au@Pt / C (m Au :m Pt = 1:1.22) catalyst prepared in Example 2 (the molar ratio of Pt to benzaldehyde in the catalyst was 1:1000), 1 mmol of benzaldehyde, and 10 mL of isopropanol were added to the reactor. Before the reaction, the reactor was purged with hydrogen at 1 MPa three times to remove the air in the reactor, and then filled with hydrogen at a pressure of 1 MPa. The temperature was maintained at 60 °C, and the reaction time was 2 h;

[0065] (2) After the reaction was completed, the reactor was quickly cooled to room temperature in an ice bath, and the catalyst and the reaction solution were separated by centrifugation. The catalyst powder was filtered out, continuously rinsed with ethanol, and then recycled. The filtrate was analyzed using a flame ionization detector (FID) of a gas chromatograph (GC) equipped with an HP-5 capillary column.

[0066] Example 6

[0067] The difference between this example and Example 5 is that the reaction time was 10 min, and the others were the same as in Example 5.

[0068] Example 7

[0069] The difference between this example and Example 5 is that the reaction time was 20 min, and the others were the same as in Example 5.

[0070] Example 8

[0071] The difference between this example and Example 5 is that the reaction time was 30 min, and the others were the same as in Example 5.

[0072] Example 9

[0073] The difference between this example and Example 5 is that the reaction time was 60 min, and the others were the same as in Example 5.

[0074] Example 10

[0075] The difference between this example and Example 5 is that the reaction time was 150 min, and the others were the same as in Example 5.

[0076] Example 11

[0077] The difference between this example and Example 5 is that the reaction pressure is 0.5 MPa, and the others are the same as in Example 5.

[0078] Example 12

[0079] The difference between this example and Example 5 is that the reaction pressure is 2 MPa, and the others are the same as in Example 5.

[0080] Example 13

[0081] The difference between this example and Example 5 is that the reaction temperature is 20 °C, and the others are the same as in Example 5.

[0082] Example 14

[0083] The difference between this example and Example 5 is that the reaction temperature is 40 °C, and the others are the same as in Example 5.

[0084] Example 15

[0085] The difference between this example and Example 5 is that the reaction temperature is 80 °C, and the others are the same as in Example 5.

[0086] Example 16

[0087] The difference between this example and Example 5 is that the reaction temperature is 100 °C, and the others are the same as in Example 5.

[0088] Example 17

[0089] The operation steps of this example are the same as those of Example 5. The centrifuged catalyst was washed with ethanol, then placed in a vacuum oven at 80 °C for drying for 12 h, and a recycling experiment was carried out under the same conditions. The catalyst was recycled for the second time to obtain the yield of benzyl alcohol product.

[0090] Example 18

[0091] The operation steps of this example are the same as those of Example 5, but the catalyst was recycled for the third time to obtain the yield of benzyl alcohol product.

[0092] Example 19

[0093] The operation steps of this example are the same as those of Example 5, but the catalyst was recycled for the fourth time to obtain the yield of benzyl alcohol product.

[0094] Example 20

[0095] The operation steps of this example are the same as those of Example 5, but the catalyst was recycled for the fifth time to obtain the yield of benzyl alcohol product.

[0096] Comparative Example 1-1

[0097] (1)Preparation of Au nanoparticles. Measure 150 mL of deionized water and place it in a beaker. The Au precursor can be its metal precursor salt solution. Taking chloroauric acid as an example, dissolve 1 g of HAuCl4 in 25 mL of deionized water to prepare an Au precursor solution (Au: 18.335 mg / mL) for standby. Add 491 μL of the Au precursor solution into the beaker, measure an appropriate amount of sodium citrate (the mass ratio of Au to sodium citrate is 1:5) and add it into the beaker, and stir at a speed of 1200 rpm for 1 min. Weigh 7.5 mg of sodium borohydride and dissolve it in 10 mL of ice-cold deionized water. Quickly add the freshly prepared sodium borohydride solution into the vigorously stirred Au precursor with a 5 mL plastic dropper. The solution quickly changes from light yellow to wine red. After stirring at 1200 rpm for 5 minutes, turn off the stirring and let it stand at room temperature for 1 h. The prepared Au nanoparticles can be stored in a refrigerator at 4°C.

[0098] (2)Preparation of Au@Pt nanoparticles. Stir the aqueous solution of Au nanoparticles prepared in step (1) at a speed of 1200 rpm. The Pt precursor can be its metal precursor salt solution. Taking chloroplatinic acid as an example, dissolve 1 g of H2PtCl6 in 50 mL of deionized water to prepare Pt for standby. Add 1445 μL of the Pt precursor solution into the aqueous solution of Au nanoparticles and stir for 1 min. Weigh 20 mg of ascorbic acid and dissolve it in 10 mL of deionized water. Add the freshly prepared ascorbic acid solution into the beaker with a 5 mL plastic dropper and stir at a speed of 1200 rpm for 45 min to obtain an aqueous solution of Au@Pt nanoparticles. The prepared Au@Pt nanoparticles can be stored in a refrigerator at 4°C.

[0099] (3)Take 1980 mg of ZnO in a beaker, add 300 mL of deionized water, stir at a speed of 1000 rpm for 1 min, and then sonicate for 10 min to obtain a carrier slurry.

[0100] (4)Load Au@Pt onto ZnO. Stir the ZnO slurry prepared in step (3) at 1200 rpm. Slowly add the Au@Pt nanoparticle solution prepared in step (2) into the ZnO slurry drop by drop with a 5 mL plastic dropper and stir for 1 h.

[0101] (5)Filter the catalyst slurry collected in step (4) by suction filtration, and wash it with deionized water until the conductivity is 0. Place the solid obtained after suction filtration in a petri dish and dry it in a vacuum drying oven at 80°C for 12 h. After that, seal and store it.

[0102] The catalyst is named 1wt%Au@Pt / ZnO (m Au :m Pt =1:1.22)

[0103] Comparative Example 1-2

[0104] (1)Preparation of Au nanoparticles. Measure 150 mL of deionized water and place it in a beaker. The Au precursor can be its metal precursor salt solution. Taking chloroauric acid as an example, dissolve 1 g of HAuCl4 in 25 mL of deionized water to prepare an Au precursor solution (Au: 18.335 mg / mL) for later use. Take 491 μL of the Au precursor solution and add it to the beaker. Measure an appropriate amount of sodium citrate (the mass ratio of Au to sodium citrate is 1:5) and add it to the beaker, and stir at a speed of 1200 rpm for 1 min. Weigh 7.5 mg of sodium borohydride and dissolve it in 10 mL of ice-cold deionized water. Quickly add the freshly prepared sodium borohydride solution to the vigorously stirred Au precursor with a 5 mL plastic dropper. The solution quickly changes from light yellow to wine red. After stirring at 1200 rpm for 5 minutes, turn off the stirring and let it stand at room temperature for 1 h. The prepared Au nanoparticles can be stored in a refrigerator at 4°C.

[0105] (2)Preparation of Au@Pt nanoparticles. Stir the aqueous solution of Au nanoparticles prepared in step (1) at a speed of 1200 rpm. The Pt precursor can be its metal precursor salt solution. Taking chloroplatinic acid as an example, dissolve 1 g of H2PtCl6 in 50 mL of deionized water to prepare Pt for later use. Take 1445 μL of the Pt precursor solution and add it to the aqueous solution of Au nanoparticles, and stir for 1 min. Weigh 20 mg of ascorbic acid and dissolve it in 10 mL of deionized water. Add the freshly prepared ascorbic acid solution to the beaker with a 5 mL plastic dropper, and stir at a speed of 1200 rpm for 45 min to obtain an aqueous solution of Au@Pt nanoparticles. The prepared Au@Pt nanoparticles can be stored in a refrigerator at 4°C.

[0106] (3)Take 1980 mg of MgO in a beaker, add 300 mL of deionized water, stir at a speed of 1000 rpm for 1 min, and then ultrasonicate for 10 min to obtain a carrier slurry.

[0107] (4)Load Au@Pt onto MgO. Stir the MgO slurry prepared in step (3) at 1200 rpm. Use a 5 mL plastic dropper to gradually add the Au@Pt nanoparticle solution prepared in step (2) to the MgO slurry, and stir for 1 h.

[0108] (5)Filter the catalyst slurry collected in step (4) by suction filtration, and wash it with deionized water until the conductivity is 0. Place the solid obtained after suction filtration in a petri dish and dry it in a vacuum drying oven at 80°C for 12 h, and then seal and store it after completion.

[0109] The catalyst is named 1wt% Au@Pt / MgO (m Au:m Pt = 1:1.22)

[0110] Comparative Examples 1 - 3

[0111] (1)Preparation of Au nanoparticles. Measure 150 mL of deionized water and place it in a beaker. The Au precursor can be its metal precursor salt solution. Taking chloroauric acid as an example, dissolve 1 g of HAuCl4 in 25 mL of deionized water to prepare an Au precursor solution (Au: 18.335 mg / mL) for standby. Take 491 μL of the Au precursor solution and add it to the beaker. Measure an appropriate amount of sodium citrate (the mass ratio of Au to sodium citrate is 1:5) and add it to the beaker. Stir at a speed of 1200 rpm for 1 min. Weigh 7.5 mg of sodium borohydride and dissolve it in 10 mL of ice-cold deionized water. Quickly add the freshly prepared sodium borohydride solution to the vigorously stirred Au precursor with a 5 mL plastic dropper. The solution quickly changes from light yellow to wine red. Stir at 1200 rpm for 5 min and then turn off the stirrer. Let it stand at room temperature for 1 h. The prepared Au nanoparticles can be stored in a refrigerator at 4°C.

[0112] (2)Preparation of Au@Pt nanoparticles. Stir the aqueous solution of Au nanoparticles prepared in step (1) at a speed of 1200 rpm. The Pt precursor can be its metal precursor salt solution. Taking chloroplatinic acid as an example, dissolve 1 g of H2PtCl6 in 50 mL of deionized water to prepare Pt for standby. Take 1445 μL of the Pt precursor solution and add it to the aqueous solution of Au nanoparticles, and stir for 1 min. Weigh 20 mg of ascorbic acid and dissolve it in 10 mL of deionized water. Add the freshly prepared ascorbic acid solution to the beaker with a 5 mL plastic dropper and stir at a speed of 1200 rpm for 45 min to obtain an aqueous solution of Au@Pt nanoparticles. The prepared Au@Pt nanoparticles can be stored in a refrigerator at 4°C.

[0113] (3)Take 1980 mg of Al2O3 in a beaker, add 300 mL of deionized water, stir at a speed of 1000 rpm for 1 min, and then ultrasonicate for 10 min to obtain a carrier slurry.

[0114] (4)Load Au@Pt onto Al2O3. Stir the Al2O3 slurry prepared in step (3) at 1200 rpm. Use a 5 mL plastic dropper to gradually add the Au@Pt nanoparticle solution prepared in step (2) to the Al2O3 slurry and stir for 1 h.

[0115] (5)Filter the catalyst slurry collected in step (4) by suction filtration, and wash it with deionized water until the conductivity is 0. Place the solid obtained after suction filtration in a petri dish and dry it in a vacuum drying oven at 80°C for 12 h, and then seal and store it after completion.

[0116] The catalyst is named 1wt%Au@Pt / Al2O3 (m Au :m Pt =1:1.22)

[0117] Comparative Examples 1 - 4

[0118] (1) The precursor of Au can be its metal precursor salt solution. Taking chloroauric acid as an example, 1 g of HAuCl4 is dissolved in 25 mL of deionized water to prepare an Au precursor solution (Au: 18.335 mg / mL) for standby. The precursor of Pt can be its metal precursor salt solution. Taking chloroplatinic acid as an example, 1 g of H2PtCl6 is dissolved in 50 mL of deionized water to prepare Pt for standby.

[0119] (2) Weigh 495 mg of activated carbon and spread it evenly on a mortar. Take 361 μL of the Pt precursor solution, shake and ultrasonicate it before taking, then add 123 μL of the Au precursor solution and an appropriate amount of deionized water, and ultrasonicate for 5 min to make it mix evenly. Drop the mixed solution evenly onto the carrier, grind until the catalyst is fully impregnated, and place it in a 70°C drying oven to dry for 12 h;

[0120] (3) Take out the impregnated and dried catalyst, grind it into uniform fine particles, and load it into a vertical tubular furnace. Quartz wool is installed above and below the catalyst bed. At a heating rate of 5°C / min, heat from room temperature to 400°C, calcine at 400°C for 4 h with nitrogen at 60 mL / min, then cool down to 250°C, and reduce it with hydrogen at 40 mL / min for 1 h. After cooling down to room temperature, change to nitrogen to purge the pipeline, take out, and obtain 1wt% Au - Pt / C catalyst

[0121] The catalyst is named impregnation method 1wt% Au - Pt / C (m Au :m Pt =1:1.22)

[0122] Comparative Example 2 - 1

[0123] The difference between this comparative example and Example 5 is that the reaction solvent is 10 mL of ethanol, and the others are the same as Example 5.

[0124] Comparative Example 2 - 2

[0125] The difference between this comparative example and Example 5 is that the reaction solvent is 10 mL of methanol, and the others are the same as Example 5.

[0126] Comparative Example 2 - 3

[0127] The difference between this comparative example and Example 5 is that the reaction solvent is 10 mL of 1,4 - dioxane, and the others are the same as Example 5.

[0128] Table 1 Activity test of Au@Pt / C catalysts with different mass ratios of Au and Pt for the hydrogenation of benzaldehyde to benzyl alcohol

[0129]

[0130] a For the specific preparation method of the impregnation method Pt / C catalyst, refer to Patent CN113999088B

[0131] According to the experimental results in Table 1, the conversion rate of benzaldehyde of the Pt / C catalyst is 65.8%, and the selectivity of benzyl alcohol is 80.4%. For the Au-Pt / C catalyst with an alloy structure, the conversion rate of benzaldehyde is 81.2%, and the selectivity of benzyl alcohol is 72.1%. The incorporation of Au makes the catalyst show better activity. Compared with the Pt / C catalyst, the conversion rate of benzaldehyde is increased by 15.4%, while the selectivity of benzyl alcohol decreases by 8.3%. The catalyst 1wt%Au@Pt / C (m Au :m Pt =1:0.54) prepared in Example 1 has a benzaldehyde conversion rate of 89.9% and a benzyl alcohol selectivity of 94.1%; the catalyst Au@Pt / C (m Au :m Pt =1:2.07) prepared in Example 3 has a benzaldehyde conversion rate of 97.4% and a benzyl alcohol selectivity of 96.2%; the catalyst Au@Pt / C (m Au :m Pt =1:3) prepared in Example 4 has a benzaldehyde conversion rate of 98.7% and a benzyl alcohol selectivity of 87.6%; the catalyst Au@Pt / C (m Au :m Pt =1:1.22) prepared in Example 2 has a benzaldehyde conversion rate of 99.9% and a benzyl alcohol selectivity of 96.9%, showing the best catalytic performance among the catalysts prepared in Examples 1-4. In addition, compared with the Pt / C prepared by the impregnation method, the yield of benzyl alcohol has increased by more than 45%. Moreover, the catalysts with Au core-Pt shell structure have better activity and selectivity than the Pt / C catalyst and the Au-Pt / C catalyst with alloy structure.

[0132] Table 2 Influence of different supports on the hydrogenation of benzaldehyde to benzyl alcohol

[0133]

[0134] According to Table 2, we investigated the influence of different supports. Since the surface of the support has abundant acid / base active sites, and the ratio of acid / base active sites has a certain influence on the reaction selectivity, we selected several supports with different ratios of acid / base active sites to prepare catalysts. Basic oxide: ZnO; amphoteric oxide: MgO, Al2O3。 When ZnO, MgO, and Al2O3 are used as supports respectively, the conversion of benzaldehyde and the selectivity of benzyl alcohol do not exceed 90%, and the catalytic performance is inferior to that of the catalyst with activated carbon as the support. This may be due to the decline in catalytic performance caused by the metal-support synergy effect. The catalyst with activated carbon as the support has a benzaldehyde conversion of 99.9% and a benzyl alcohol selectivity of 96.9%, which is the best.

[0135] Through the above optimization of different bimetallic ratios and supports, we selected the 1wt% Au@Pt catalyst of Example 2 as the catalyst for the hydrogenation of benzaldehyde to prepare benzyl alcohol, and investigated the effects on catalytic activity and selectivity under different conditions.

[0136] Table 3 Effects of reaction temperature on the hydrogenation of benzaldehyde to prepare benzyl alcohol

[0137]

[0138] Table 3 shows the effects of reaction temperature on the conversion and selectivity of the hydrogenation of benzaldehyde to prepare benzyl alcohol. As the reaction temperature increases (20 - 100 °C), the catalytic activity first increases and then stabilizes. The conversion of benzaldehyde increases from 88.8% to 99.9%. And the selectivity of the target product benzyl alcohol first increases and then decreases, and the highest selectivity of benzyl alcohol (96.9%) is obtained at 60 °C. When the reaction temperature is increased from 60 °C to 100 °C, the conversion of benzaldehyde has only a slight change, indicating that benzaldehyde can be converted relatively stably under this temperature gradient. However, the selectivity of the target product benzyl alcohol decreases by 3.6%, and the selectivity of the by-product toluene increases by 2.9%. This may be due to the hydrogenation and deoxygenation of the carbon-oxygen bond on benzaldehyde or benzyl alcohol at too high reaction temperature, resulting in the formation of more toluene. Therefore, the reaction temperature of 60 °C is the best, and the hydrogenation of benzaldehyde to prepare benzyl alcohol has the highest conversion and selectivity.

[0139] Table 4 Effects of different reaction solvents on the hydrogenation of benzaldehyde to prepare benzyl alcohol

[0140]

[0141] Table 4 shows the effects of different reaction solvents on the conversion rate and selectivity of benzaldehyde. It can be seen from Table 4 that when the solvent is isopropanol, the highest conversion rate (99.9%) and selectivity (96.9%) are obtained. Followed by ethanol, with a conversion rate of 69.5% and a selectivity of 72.7%. While when methanol is used as the solvent, both the conversion rate (25.4%) and selectivity (26.6%) are relatively low. This may be because when the solvent is an alcohol, the solubility of hydrogen in the alcohol increases with the increase of the relative molecular mass of the alcohol. At the same time, with the increase of the alcohol chain length, the electron density of the hydroxyl oxygen in the alcohol will have a stronger interaction with the catalyst surface. When the solvent is 1,4-dioxane, the reaction conversion rate is 54.2% and the selectivity is 69.9%, and the catalytic effect is not as good as that with isopropanol as the solvent. Therefore, the optimal reaction solvent for the hydrogenation of benzaldehyde to benzyl alcohol over 1wt% Au@Pt / C catalyst is isopropanol.

[0142] Table 5 Effects of Different Hydrogen Pressures on the Hydrogenation of Benzaldehyde to Benzyl Alcohol

[0143]

[0144] According to the results in Table 5, when the reaction is carried out under 0.5 MPa hydrogen, the conversion rate of benzaldehyde is 89.5% and the selectivity of benzyl alcohol is 90.4%. As the hydrogen pressure increases to 1 MPa, the conversion rate (99.9%) and selectivity (96.9%) of benzaldehyde reach the highest. As the hydrogen pressure further increases to 2 MPa, the conversion rate of benzaldehyde remains unchanged, and the selectivity of benzyl alcohol (92.1%) decreases slightly. Therefore, it can be concluded that an effective catalytic conversion of benzaldehyde to benzyl alcohol can be achieved when the initial hydrogen pressure is 1 MPa.

[0145] Table 6 Effects of Reaction Time on the Hydrogenation of Benzaldehyde to Benzyl Alcohol

[0146]

[0147] According to Table 6, as the reaction time increases from 10 min to 150 min, the conversion rate of benzaldehyde gradually increases from 39.9% to 99.9% and then tends to be stable. The selectivity of benzyl alcohol gradually increases from 82.5% to 96.9% to reach the maximum value, and then decreases slightly. This may be because the long reaction time leads to the hydrogenation and deoxygenation of the carbon-oxygen bond on benzyl alcohol, generating more toluene. Therefore, the optimal reaction time for the hydrogenation of benzaldehyde to benzyl alcohol is 120 min.

[0148] Table 7 Recycling Experiment of 1wt% Au@Pt / C (m Au :m Pt = 1:1.22) Catalyst

[0149]

[0150] According to the results of the catalytic cycle reaction in Table 7, after 5 consecutive cycles, the conversion rate of benzaldehyde decreased slightly, from 99.9% to 94.4%, while the yield of benzyl alcohol remained at 90.0%. It shows that the 1wt% Au@Pt / C (m Au :m Pt = 1:1.22) catalyst has good reusability.

[0151] The nanostructure and elemental distribution of the 1wt% Au@Pt / C (m Au :m Pt = 1:1.22) catalyst were analyzed by HAADF-STEM. Figure 1 The HAADF-STEM image of the 1wt% Au@Pt / C (m Au :m Pt = 1:1.22) catalyst and the EDS elemental mappings of Au (red) and Pt (green) are shown. From the HAADF-STEM image, the nanoparticle sizes are uniform and well-dispersed. From the EDS elemental mapping, the nanoparticles have an obvious Au core-Pt shell structure, confirming the formation of the Au@Pt core-shell structure.

[0152] Based on the reaction results and related characterizations, it can be concluded that a series of supported Au core-Pt shell nanostructure catalysts were prepared in the present invention and applied to the reaction of hydrogenating benzaldehyde to prepare benzyl alcohol. Through the optimization of reaction conditions, it was found that under the optimized 1wt% Au@Pt / C (m Au :m Pt = 1:1.22), with isopropanol as the solvent, at a hydrogen pressure of 1 MPa and a reaction temperature of 60 °C, a conversion rate of benzaldehyde of 99.9% and a yield of benzyl alcohol of 96.9% can be achieved. The catalyst has high activity and stability, the reaction conditions are milder, the energy consumption is reduced to a certain extent, and it is more environmentally friendly. Therefore, the present invention has broad application prospects in industry.

[0153] The present invention is not limited to the specific technical solutions described in the above embodiments. Any technical solutions formed by equivalent substitution are within the scope of protection required by the present invention.

Claims

1. A method for preparing benzyl alcohol by hydrogenating benzaldehyde using an Au@Pt / C catalyst, characterized in that: The preparation steps of the catalyst are as follows: (1)Preparation of Au nanoparticles: Measure 150 mL of deionized water and place it in a beaker. Dissolve 1 g of HAuCl4 in 25 mL of deionized water to prepare an Au precursor solution for later use. Take 491 μL of the Au precursor solution and add it to the beaker. Measure an appropriate amount of sodium citrate and add it to the beaker at a mass ratio of Au to sodium citrate of 1:

5. Stir at a speed of 1200 rpm for 1 min. Weigh 7.5 mg of sodium borohydride and dissolve it in 10 mL of ice-cold deionized water. Quickly add the freshly prepared sodium borohydride solution to the vigorously stirred Au precursor using a 5 mL plastic dropper. The solution quickly changes from light yellow to wine red. Stir at 1200 rpm for 5 minutes and then turn off the stirrer. Let it stand at room temperature for 1 h. Store the prepared Au nanoparticles in a refrigerator at 4°C. (2)Preparation of Au@Pt nanoparticles: Stir the aqueous solution of Au nanoparticles prepared in step (1) at a speed of 1200 rpm. Dissolve 1 g of H2PtCl6 in 50 mL of deionized water to prepare a Pt precursor solution for later use. Take 1445 μL of the Pt precursor solution and add it to the aqueous solution of Au nanoparticles, and stir for 1 min. Weigh 20 mg of ascorbic acid and dissolve it in 10 mL of deionized water. Add the freshly prepared ascorbic acid solution to the beaker using a 5 mL plastic dropper and stir at a speed of 1200 rpm for 45 min to obtain an aqueous solution of Au@Pt nanoparticles. Store the prepared Au@Pt nanoparticles in a refrigerator at 4°C. (3)Take 1980 mg of activated carbon and place it in a beaker. Add 300 mL of deionized water and stir at a speed of 1000 rpm for 1 min, then sonicate for 10 min to obtain an activated carbon slurry. (4)Load Au@Pt onto activated carbon: Stir the activated carbon slurry prepared in step (3) at 1200 rpm. Dropwise add the Au@Pt nanoparticle solution prepared in step (2) to the activated carbon slurry using a 5 mL plastic dropper and stir for 1 h. (5) Filter the slurry collected in step (4) by suction filtration, and wash it with deionized water until the conductivity is 0. Place the solid obtained after suction filtration in a petri dish and dry it in a vacuum drying oven at 80 °C for 12 h. After completion, seal and store it. The catalyst is Au@Pt / C, m Au :m Pt = 1:1.22, where the total mass fraction of Au and Pt metals accounts for 1 wt% of the catalyst.

2. The method for preparing benzyl alcohol by hydrogenating benzaldehyde using the Au@Pt / C catalyst according to claim 1, wherein: The reaction conditions for the hydrogenation of benzaldehyde to benzyl alcohol are an initial hydrogen pressure of 1 MPa, a reaction temperature of 60°C, and a reaction time of 2 h.

3. The method for preparing benzyl alcohol by hydrogenating benzaldehyde using the Au@Pt / C catalyst according to claim 2, characterized in that: In the hydrogenation of benzaldehyde to benzyl alcohol, add the catalyst to the reaction kettle at a molar ratio of Pt to benzaldehyde of 1:1000, 1 mmoL of benzaldehyde and 10 mL of isopropanol.

4. The method for preparing benzyl alcohol by hydrogenating benzaldehyde using the Au@Pt / C catalyst according to claim 3, characterized in that: Using Au@Pt / C to catalyze the hydrogenation of benzaldehyde to benzyl alcohol, at a hydrogen pressure of 1 MPa and a reaction temperature of 60°C for 120 min, the conversion rate of benzaldehyde is 99.9% and the selectivity of benzyl alcohol is 96.9%.

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