A composite catalyst, a preparation method and application thereof, and a method for preparing aldehyde through alcohol catalytic oxidation

Abstract

This invention provides a composite catalyst, its preparation method, and its application, as well as a method for the catalytic oxidation of alcohols to aldehydes, belonging to the field of organic synthesis technology. In the composite catalyst provided by this invention, elemental chromium improves the dispersibility of elemental silver on modified γ-Al₂O₃, thereby enhancing the oxidation activity of the composite catalyst for ethanol, reducing side reactions (further oxidation of aldehydes to acids or decomposition) during the catalytic oxidation of alcohols to aldehydes, and improving the selectivity, yield, and purity of aldehydes. The modified γ-Al₂O₃ has a more developed pore structure than uncalcined γ-Al₂O₃, and when used as a support, it improves the mechanical strength of the composite catalyst. Moreover, the composite catalyst provided by this invention reduces the reaction temperature and energy consumption for the catalytic oxidation of alcohols to aldehydes without affecting the alcohol conversion rate and aldehyde selectivity, thus reducing the cost of aldehyde preparation and making it more suitable for industrial use in the catalytic oxidation of alcohols to aldehydes.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a composite catalyst, its preparation method and application, and a method for preparing aldehydes by catalytic oxidation of alcohols. Background Technology

[0002] Acetaldehyde is an important aliphatic compound widely used in agriculture, industry, and daily life, possessing high application value. Currently, the most common method for synthesizing acetaldehyde is the ethanol oxidation process. The catalysts used in the ethanol oxidation process mainly include silver-manganese dioxide catalysts, copper chromate, or calcium salt oxides. However, the reaction temperature for preparing acetaldehyde using the above catalysts via ethanol oxidation is as high as 300–450℃. Excessively high reaction temperatures can lead to further oxidation of acetaldehyde to acetic acid or decomposition into carbon dioxide and water, significantly reducing the selectivity of acetaldehyde. Therefore, providing a catalyst that can lower the reaction temperature for preparing acetaldehyde via ethanol oxidation, thereby improving the selectivity of acetaldehyde, is of great significance. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a composite catalyst, its preparation method and application, and a method for the catalytic oxidation of alcohol to prepare aldehydes. The composite catalyst provided by this invention is used to catalyze the oxidation of ethanol to prepare acetaldehyde, which has high selectivity and high yield.

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

[0005] The present invention provides a composite catalyst comprising a support and an active component supported on the support; the active component comprises elemental silver and elemental chromium; the support comprises modified γ-Al2O3; the modified γ-Al2O3 is γ-Al2O3 that has undergone calcination treatment.

[0006] Preferably, the loading of elemental silver is 17.6–24.5 wt%, and the loading of elemental chromium is 35.5–42.4 wt%.

[0007] This invention provides a method for preparing the composite catalyst described in the above technical solution, comprising the following steps:

[0008] A composite catalyst is obtained by mixing water-soluble silver salt, water-soluble chromium salt, modified γ-Al2O3, reducing agent and water and carrying out a reduction reaction.

[0009] Preferably, the water-soluble silver salt includes silver nitrate and / or silver fluoride;

[0010] The water-soluble chromium salt includes chromium nitrate;

[0011] The molar ratio of the water-soluble silver salt to the water-soluble chromium salt is 1:3 to 5;

[0012] The molar ratio of the water-soluble silver salt to the modified γ-Al2O3 is 0.5 to 0.8:1.

[0013] Preferably, the reducing agent includes sodium borohydride;

[0014] The molar ratio of the water-soluble silver salt to the reducing agent is 1:20 to 50.

[0015] Preferably, the reduction reaction is carried out at a temperature of 20–28°C for 1.5–3 hours.

[0016] This invention provides the application of the composite catalyst described in the above technical solution or the composite catalyst prepared by the preparation method described in the above technical solution in the catalytic oxidation of alcohols to aldehydes.

[0017] This invention provides a method for the catalytic oxidation of alcohols to prepare aldehydes, comprising the following steps:

[0018] In an oxygen-containing gas atmosphere, an alcohol and a catalyst are mixed and subjected to a catalytic oxidation reaction to obtain an aldehyde; the temperature of the catalytic oxidation reaction is <300℃.

[0019] The catalyst is the composite catalyst described in the above technical solution or the composite catalyst prepared by the preparation method described in the above technical solution.

[0020] Preferably, the mass ratio of the alcohol to the catalyst is 1:0.03 to 0.04;

[0021] The ratio of the mass of the alcohol to the flow rate of the oxygen-containing gas is 1 g: 128-135 L / min.

[0022] Preferably, the oxygen-containing gas includes air or oxygen.

[0023] This invention provides a composite catalyst comprising a support and an active component loaded on the support; the active component comprises elemental silver and elemental chromium; the support comprises modified γ-Al₂O₃; the modified γ-Al₂O₃ is calcined γ-Al₂O₃. In the composite catalyst provided by this invention, elemental chromium improves the dispersibility of elemental silver on the modified γ-Al₂O₃, thereby improving the oxidation activity of the composite catalyst for ethanol, reducing the occurrence of side reactions (further oxidation of aldehydes to acids or decomposition) during the catalytic oxidation of alcohols to aldehydes (especially the catalytic oxidation of ethanol to acetaldehyde), and improving the selectivity, yield, and purity of aldehydes; the pore structure of modified γ-Al₂O₃ is more developed than that of uncalcined γ-Al₂O₃, and its use as a support improves the mechanical strength of the composite catalyst. Moreover, the composite catalyst provided by this invention reduces the reaction temperature and energy consumption for the catalytic oxidation of alcohols to aldehydes without affecting the alcohol conversion rate and aldehyde selectivity, reducing the preparation cost of aldehydes, and is more suitable for industrial use in the catalytic oxidation of alcohols to aldehydes.

[0024] This invention provides a method for preparing the composite catalyst described in the above technical solution. The preparation method provided by this invention requires only one reduction reaction in the liquid phase to load elemental silver and chromium onto modified γ-Al₂O₃. It is simple to operate, low in cost, and suitable for industrial production. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a scanning electron microscope image of the modified γ-Al2O3.

[0027] Figure 2 This is a scanning electron microscope image of Ag-Cr-modified γ-Al2O3. Detailed Implementation

[0028] The present invention provides a composite catalyst comprising a support and an active component supported on the support; the active component comprises elemental silver and elemental chromium; the support comprises modified γ-Al2O3; the modified γ-Al2O3 is γ-Al2O3 that has undergone calcination treatment.

[0029] In this invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art.

[0030] In this invention, the loading amount of elemental silver (i.e., the ratio of the mass of elemental silver to the mass of the carrier) is preferably 17.6 to 24.5 wt%, more preferably 20 to 24 wt%, and most preferably 22 to 23 wt%.

[0031] In this invention, the loading of elemental chromium is preferably 35.5–42.4 wt%, more preferably 37–41 wt%, and most preferably 38–40 wt%. Cr improves the dispersibility of Ag on modified γ-Al₂O₃, thereby improving the catalyst's oxidation activity for ethanol, lowering the reaction temperature, reducing acetic acid formation, and improving the selectivity for acetaldehyde.

[0032] In this invention, the particle size of the modified γ-Al2O3 is preferably <150 μm, more preferably 90–120 μm, and most preferably 100–110 μm.

[0033] In this invention, the preparation method of the modified γ-Al2O3 preferably includes the following steps: grinding γ-Al2O3 to <150μm and then calcining it. In this invention, the calcination preferably includes sequentially performing a first heating, a first holding, a second heating, and a second holding; the heating rate of the first heating is preferably 2-3℃ / min, more preferably 2.2-2.8℃ / min, and most preferably 2.4-2.6℃ / min; the temperature of the first holding is preferably 116-125℃, more preferably 118-123℃, and most preferably 120-121℃, and the holding time is preferably 2-3h, more preferably 2.2-2.8h, and most preferably 2.4-2.6h; the heating rate of the second heating is preferably 5-8℃ / min, more preferably 5.5-7.5℃ / min, and most preferably 6-7℃ / min; the holding temperature of the second holding is preferably 530-560℃, more preferably 535-555℃, and most preferably 540-550℃, and the holding time is preferably 4-5h, more preferably 4.2-4.8h, and most preferably 4.4-4.6h. This invention uses calcined modified γ-Al2O3, whose pore structure is more developed than that of uncalcined γ-Al2O3, which improves the mechanical strength of the composite catalyst when used as a support.

[0034] After calcination, the present invention preferably further includes cooling the obtained calcined product to room temperature. The present invention does not have any particular limitation on the cooling process; any cooling method well known to those skilled in the art can be used, such as natural cooling.

[0035] This invention provides a method for preparing the composite catalyst described in the above technical solution, comprising the following steps:

[0036] A composite catalyst is obtained by mixing water-soluble silver salt, water-soluble chromium salt, modified γ-Al2O3, reducing agent and water and carrying out a reduction reaction.

[0037] In this invention, the water-soluble silver salt preferably includes silver nitrate and / or silver fluoride, more preferably silver nitrate; the water-soluble chromium salt preferably includes chromium nitrate. In this invention, the molar ratio of the water-soluble silver salt to the water-soluble chromium salt is preferably 1:3 to 5; more preferably 1:3.5 to 4.5, and most preferably 1:3.8 to 4.2; the molar ratio of the water-soluble silver salt to γ-Al₂O₃ is preferably 0.5 to 0.8:1, more preferably 0.6 to 0.7:1.

[0038] In this invention, the reducing agent preferably comprises sodium borohydride. In this invention, the molar ratio of the water-soluble silver salt to the reducing agent is preferably 1:20–50, more preferably 1:25–45, and most preferably 1:30–40.

[0039] In this invention, the preparation method of the modified γ-Al2O3 is preferably the same as that described above, and will not be repeated here.

[0040] In this invention, the mixing temperature is preferably room temperature. The mixing process preferably includes: first stirring and mixing γ-Al₂O₃, a water-soluble silver salt aqueous solution, and a water-soluble chromium salt aqueous solution, followed by second stirring and mixing the resulting mixture with a reducing agent. The first stirring and mixing time is preferably 60–90 min, more preferably 60–80 min, and most preferably 60–70 min; the stirring speed is preferably 300–500 rpm, more preferably 350–450 rpm, and most preferably 380–400 rpm. The second stirring and mixing speed is preferably 300–500 rpm, more preferably 350–450 rpm, and most preferably 380–400 rpm. This invention does not have a specific limitation on the second stirring and mixing time, as long as the raw materials are mixed evenly.

[0041] In this invention, the temperature of the reduction reaction is preferably 20–28°C, more preferably 22–26°C, and most preferably 23–25°C; the time of the reduction reaction is preferably 1.5–3 h, more preferably 1.8–2.5 h, and most preferably 2–2.3 h. In this invention, the reduction reaction is preferably carried out under stirring conditions; this invention does not have a specific limitation on the stirring speed, as long as it ensures the smooth progress of the reduction reaction.

[0042] Following the reduction reaction, the present invention preferably further includes washing and drying the solid product obtained from the reduction reaction to obtain a composite catalyst. In the present invention, the washing preferably includes sequential alcohol washing and water washing. In the present invention, the alcohol used for alcohol washing preferably includes ethanol, more preferably anhydrous ethanol; the number of alcohol washings is preferably 3-5 times, more preferably 3-4 times. The present invention does not have a special limitation on the mass of the alcohol used for alcohol washing, as long as it is sufficient to submerge the solid product. In the present invention, the number of water washings is preferably 3-5 times, more preferably 3-4 times. The present invention does not have a special limitation on the mass of the water used for water washing, as long as it is sufficient to submerge the solid product. In the present invention, the drying temperature is preferably 78-85℃, more preferably 80-84℃, and most preferably 80-82℃; the drying time is preferably 10-14 hours, more preferably 11-13 hours, and most preferably 12-12.5 hours.

[0043] This invention provides the application of the composite catalyst described in the above technical solution or the composite catalyst prepared by the preparation method described in the above technical solution in the catalytic oxidation of alcohols to aldehydes.

[0044] In this invention, the alcohol preferably includes ethanol or methanol.

[0045] This invention provides a method for the catalytic oxidation of alcohols to prepare aldehydes, comprising the following steps:

[0046] In an oxygen-containing gas atmosphere, an alcohol and a catalyst are mixed and subjected to a catalytic oxidation reaction to obtain an aldehyde; the temperature of the catalytic oxidation reaction is <300℃.

[0047] The catalyst is the composite catalyst described in the above technical solution or the composite catalyst prepared by the preparation method described in the above technical solution.

[0048] In this invention, the alcohol preferably includes ethanol or methanol. In this invention, the mass ratio of the alcohol to the catalyst is preferably 1:0.03–0.04, more preferably 1:0.032–0.038, and most preferably 1:0.034–0.036. In this invention, the oxygen-containing gas preferably includes air or oxygen, more preferably air. In this invention, the air is preferably purified air. In this invention, the flow rate of the oxygen-containing gas is preferably 128–135 L / min, more preferably 130–133 L / min, and most preferably 131–132 L / min. In this invention, the mass ratio of the alcohol to the flow rate of the oxygen-containing gas is preferably 1 g:128–135 L / min, more preferably 1 g:130–133 L / min, and most preferably 1 g:131–132 L / min. This invention uses purified air as the atmosphere for the catalytic oxidation reaction, which avoids the accumulation of dirt in the ethanol vaporizer due to prolonged use, thus preventing it from affecting the heat transfer effect. At the same time, it avoids suspended solids from entering the reactor and affecting the performance of the composite catalyst (for example, suspended solids covering the catalyst surface can cause accelerated carbonization and deactivation of the composite catalyst).

[0049] In this invention, the temperature of the catalytic oxidation reaction is <300℃, preferably 170-220℃, more preferably 180-210℃, and most preferably 190-200℃; the space velocity of the catalytic oxidation reaction is preferably 240-360 h⁻¹. -1 More preferably 260-320h -1 The optimal time is 280-300 hours. -1 The pressure for the catalytic oxidation reaction is preferably atmospheric pressure.

[0050] Following the catalytic oxidation reaction, the present invention preferably further includes cooling and then distilling the reactants obtained from the catalytic oxidation reaction. In the present invention, the final cooling temperature is preferably 70–80°C, more preferably 72–78°C, and most preferably 74–76°C. In the present invention, the distillation is preferably carried out in an aldehyde distillation column. In the present invention, the top temperature of the aldehyde distillation column is preferably 30–35°C, more preferably 31–34°C, and most preferably 32–33°C; the bottom temperature of the aldehyde distillation column is preferably 60–65°C, more preferably 61–64°C, and most preferably 62–63°C. In the present invention, the bottom liquid level of the aldehyde distillation column is preferably 25–35% of the column height, more preferably 26–32%, and most preferably 28–30%; in a specific embodiment of the present invention, the bottom liquid level of the aldehyde distillation column is preferably 30–40 cm, more preferably 32–38 cm, and most preferably 34–36 cm.

[0051] To further illustrate the present invention, the following detailed descriptions, in conjunction with embodiments, illustrate the composite catalysts provided by the present invention, their preparation methods and applications, and the method for preparing aldehydes by catalytic oxidation of alcohols. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0052] Example 1

[0053] γ-Al2O3 was ground to <100 mesh and calcined in a muffle furnace, then naturally cooled to room temperature to obtain calcined γ-Al2O3. The calcination conditions were as follows: at room temperature, the temperature was increased to 120℃ at a heating rate of 2℃ / min and held for 2 hours, then increased to 550℃ at a heating rate of 5℃ / min and held for 5 hours.

[0054] 0.1 g of the calcined γ-Al₂O₃ was weighed and dispersed in 40 mL of water. 10 mL of 0.05 mol / L AgNO₃ solution and 10 mL of 0.2 mol / L Cr(NO₃)₃ solution were added, and the mixture was magnetically stirred for 1 h until completely homogeneous. Then, 25 mL of 0.5 mol / L NaBH₄ solution was added, and the reaction was continued for 2 h. The resulting solid product was washed three times by centrifugation with anhydrous ethanol and distilled water, and dried in a vacuum drying oven at 80 °C for 12 h to obtain the composite catalyst (Ag-Cr-modified γ-Al₂O₃).

[0055] Figure 1 This is a scanning electron microscope image of modified γ-Al2O3. Figure 2 This is a scanning electron microscope (SEM) image of Ag-Cr-modified γ-Al₂O₃. (Source: [Insert image here]) Figure 1-Figure 2 It can be seen that in the Ag-Cr-modified γ-Al2O3 composite catalyst prepared by the present invention, Ag and Cr are loaded onto the modified γ-Al2O3.

[0056] Example 2

[0057] 4600g of ethanol and purified air were fed into an ethanol evaporator (air flow rate of 131L / min). The temperature of the ethanol evaporator was set to 120℃. The mixed gas (ethanol vapor and air mixture) from the ethanol evaporator entered a fixed-bed reactor containing 150g of the composite catalyst prepared in Example 1. The reaction was carried out at 200℃ and atmospheric pressure with a space velocity of 300h⁻¹. -1 The reaction liquid enters the condenser for condensation, and the condensed liquid enters the acetaldehyde distillation column for distillation (the top temperature of the column is controlled at 33℃, the bottom temperature is controlled at 62℃, and the bottom liquid level is controlled at 34cm). The material at the top of the column is condensed to obtain acetaldehyde, and the liquid at the bottom of the column enters the ethanol recovery column, and the recovered ethanol is recycled.

[0058] The acetaldehyde distillation column yielded 4218g of acetaldehyde by condensation at the top, with a yield of 94.9%, a purity of 95.3%, and an acetaldehyde selectivity of 95.9%.

[0059] Example 3

[0060] 4600g of ethanol and purified air were fed into an ethanol evaporator (air flow rate of 131L / min). The temperature of the ethanol evaporator was set to 120℃. The mixed gas (ethanol vapor and air mixture) from the ethanol evaporator entered a fixed-bed reactor containing 150g of the composite catalyst prepared in Example 1. The reaction was carried out at 220℃ and atmospheric pressure with a space velocity of 300h⁻¹. -1 The reaction liquid enters the condenser for condensation, and the condensed liquid enters the acetaldehyde distillation column for distillation (the top temperature of the column is controlled at 33℃, the bottom temperature is controlled at 62℃, and the bottom liquid level is controlled at 34cm). The material at the top of the column is condensed to obtain acetaldehyde, and the liquid at the bottom of the column enters the ethanol recovery column, and the recovered ethanol is recycled.

[0061] The acetaldehyde distillation column yielded 4083g of acetaldehyde by condensation at the top, with a yield of 91.9%, a purity of 94.2%, and an acetaldehyde selectivity of 92.8%.

[0062] Example 4

[0063] 4600g of ethanol and purified air were fed into an ethanol evaporator (air flow rate of 131L / min). The temperature of the ethanol evaporator was set to 120℃. The mixed gas (ethanol vapor and air mixture) from the ethanol evaporator entered a fixed-bed reactor containing 150g of the composite catalyst prepared in Example 1. The reaction was carried out at 180℃ and atmospheric pressure with a space velocity of 300h⁻¹. -1The reaction liquid enters the condenser for condensation, and the condensed liquid enters the acetaldehyde distillation column for distillation (the top temperature of the column is controlled at 33℃, the bottom temperature is controlled at 62℃, and the bottom liquid level is controlled at 34cm). The material at the top of the column is condensed to obtain acetaldehyde, and the liquid at the bottom of the column enters the ethanol recovery column, and the recovered ethanol is recycled.

[0064] The acetaldehyde distillation column yielded 3983g of acetaldehyde by condensation at the top, with a yield of 90.1%, a purity of 92.5%, and an acetaldehyde selectivity of 90.5%. Lower temperatures in the catalytic oxidation of ethanol lead to increased impurities and reduced purity in the acetaldehyde product.

[0065] Comparative Example 1

[0066] 4600g of ethanol and purified air were fed into an ethanol evaporator (air flow rate of 131L / min). The temperature of the ethanol evaporator was set to 120℃. The mixed gas (ethanol vapor and air mixture) from the ethanol evaporator entered a fixed-bed reactor containing 150g of the composite catalyst prepared in Example 1. The reaction was carried out at 320℃ and atmospheric pressure with a space velocity of 300h⁻¹. -1 The reaction liquid enters the condenser for condensation, and the condensed liquid enters the acetaldehyde distillation column for distillation (the top temperature of the column is controlled at 33℃, the bottom temperature is controlled at 62℃, and the bottom liquid level is controlled at 34cm). The material at the top of the column is condensed to obtain acetaldehyde, and the liquid at the bottom of the column enters the ethanol recovery column, and the recovered ethanol is recycled.

[0067] The acetaldehyde distillation column yielded 2653g of acetaldehyde by condensation at the top, with a yield of 59.7%, a purity of 95.2%, and an acetaldehyde selectivity of 60.3%. The yield and selectivity of acetaldehyde were significantly reduced.

[0068] Comparative Example 2

[0069] 4600g of ethanol and purified air were fed into an ethanol evaporator (air flow rate of 131L / min). The temperature of the ethanol evaporator was set to 120℃. The mixed gas (ethanol vapor and air mixture) from the ethanol evaporator entered a fixed-bed reactor containing 150g of the composite catalyst prepared in Example 1. The reaction was carried out at 365℃ and atmospheric pressure with a space velocity of 300h⁻¹. -1 The reaction liquid enters the condenser for condensation, and the condensed liquid enters the acetaldehyde distillation column for distillation (the top temperature of the column is controlled at 33℃, the bottom temperature is controlled at 62℃, and the bottom liquid level is controlled at 34cm). The material at the top of the column is condensed to obtain acetaldehyde, and the liquid at the bottom of the column enters the ethanol recovery column, and the recovered ethanol is recycled.

[0070] The acetaldehyde distillation column yielded 3726g of acetaldehyde by condensation at the top, with a yield of 83.8%, a purity of 94.8%, and an acetaldehyde selectivity of 84.7%. The yield and selectivity of acetaldehyde were significantly reduced.

[0071] Comparative Example 3

[0072] The Ag-MnO2 catalyst was prepared as follows: 0.1 g of MnO2 support was dissolved in 40 mL of water, and 10 mL of 0.05 mol / L AgNO3 solution was added. The mixture was magnetically stirred for 1 h until completely homogeneous. Then, 25 mL of 0.5 mol / L NaBH4 solution was added, and stirring was continued for 2 h. The mixture was washed three times by centrifugation with anhydrous ethanol and distilled water, and dried overnight in a vacuum drying oven at 80 °C. The Ag / MnO2 catalyst was obtained.

[0073] 4600g of ethanol and purified air were fed into an ethanol evaporator (air flow rate of 131L / min). The temperature of the ethanol evaporator was set to 120℃. The mixed gas (ethanol vapor and air mixture) from the ethanol evaporator entered a fixed-bed reactor containing 150g of Ag-MnO2 catalyst. The reaction was carried out at 330℃ and atmospheric pressure with a space velocity of 300h⁻¹. -1 The reaction liquid enters the condenser for condensation, and the condensed liquid enters the acetaldehyde distillation column for distillation (the top temperature of the column is controlled at 33℃, the bottom temperature is controlled at 62℃, and the bottom liquid level is controlled at 34cm). The material at the top of the column is condensed to obtain acetaldehyde, and the liquid at the bottom of the column enters the ethanol recovery column, and the recovered ethanol is recycled.

[0074] The acetaldehyde distillation column yielded 4156g of acetaldehyde by condensation at the top, with a yield of 84.7%, a purity of 93.4%, and an acetaldehyde selectivity of 88.2%, indicating a significant decrease in acetaldehyde selectivity.

[0075] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A composite catalyst for the catalytic oxidation of an alcohol to produce an aldehyde, characterized in that, The composite catalyst comprises a carrier and an active component supported on the carrier; the active component comprises silver and chromium; the carrier comprises modified γ-Al2O3; the modified γ-Al2O3 is γ-Al2O3 treated by calcination; The loading amount of the silver is 17.6-24.5 wt%, and the loading amount of the chromium is 35.5-42.4 wt%. The alcohol is catalytically oxidized to prepare aldehyde, specifically, alcohol and a catalyst are mixed in an oxygen-containing gas atmosphere, and catalytic oxidation reaction is carried out to obtain aldehyde. The preparation method of the composite catalyst comprises the following steps: water-soluble silver salt, water-soluble chromium salt, modified γ-Al2O3, reducing agent and water are mixed, and reduction reaction is carried out to obtain the composite catalyst.

2. A process for the preparation of the composite catalyst of claim 1, characterized in that, The preparation method of the composite catalyst comprises the following steps: Water-soluble silver salt, water-soluble chromium salt, modified γ-Al2O3, reducing agent and water are mixed, and reduction reaction is carried out to obtain the composite catalyst.

3. The production method according to claim 2, characterized by, The water-soluble silver salt comprises silver nitrate and / or silver fluoride; The water-soluble chromium salt comprises chromium nitrate; The molar ratio of the water-soluble silver salt to the water-soluble chromium salt is 1:3-5; The molar ratio of the water-soluble silver salt to the modified γ-Al2O3 is 0.5-0.8:

1.

4. The production method according to claim 2, characterized by, The reducing agent comprises sodium borohydride; The molar ratio of the water-soluble silver salt to the reducing agent is 1:20-50.

5. The production method according to claim 2, 3 or 4, characterized in that, The temperature of the reduction reaction is 20-28℃, and the time is 1.5-3h.

6. The application of the composite catalyst of claim 1 or the composite catalyst prepared by the preparation method of any one of claims 2-5 in catalyzing alcohol oxidation to prepare aldehyde.

7. A method for the catalytic oxidation of an alcohol to an aldehyde, characterized in that The preparation method of the composite catalyst comprises the following steps: Alcohol and a catalyst are mixed in an oxygen-containing gas atmosphere, and catalytic oxidation reaction is carried out to obtain aldehyde; the temperature of the catalytic oxidation reaction is <300℃; The catalyst is the composite catalyst of claim 1 or the composite catalyst prepared by the preparation method of any one of claims 2-5.

8. The method of claim 7, wherein, The mass ratio of the alcohol to the catalyst is 1:0.03-0.04; The ratio of the mass of the alcohol to the flow rate of the oxygen-containing gas is 1g:128-135L / min.

9. The method according to claim 7 or 8, characterized in that, The oxygen-containing gas comprises air or oxygen.

Images