CN103041826A - Bimetal nanometer catalyst as well as preparation and application method thereof - Google Patents

Abstract

The invention discloses a bimetallic nano-catalyst for producing dimethyl oxalate through gas-phase oxidation coupling of CO and a preparation and application method thereof, belonging to the technical field of dimethyl oxalate preparation. The catalyst carrier is α-alumina, the active component is Pd-Cu nanoparticles, and the average particle size is 2-3nm; based on the mass of the catalyst carrier, the active component Pd content is 0.01-2%, and the Cu content is 0.01- 0.04%. The catalyst is prepared by an in-situ loading method at room temperature, the preparation method is simple, the energy consumption is low, and the catalyst is suitable for industrial production. The active component Pd-Cu nanoparticles in the catalyst have high dispersion, large specific surface area, small size and uniform distribution. The catalyst of the present invention adopts Pd-Cu bimetallic nanoparticles as the active component, and under the premise of maintaining the high activity and stability of the catalyst, the content of the noble metal Pd is reduced to 0.1% by utilizing the synergistic effect and the nano effect of the bimetallic component, which is greatly improved. The cost of the catalyst is reduced, and partial substitution of noble metals is realized.

Description

A kind of bimetallic nano catalyst and its preparation and application method

Technical field:

The invention belongs to the technical field of dimethyl oxalate preparation, and relates to a bimetallic nano-catalyst used for preparing dimethyl oxalate through gas-phase oxidation coupling of CO in coal-based ethylene glycol and a preparation and application method thereof.

technical background:

Dimethyl oxalate is an important organic chemical raw material, which can be used to prepare oxalic acid, oxalyl chloride, oxalic acid ammonium, and can also be used in fine chemical industry to produce various dyes, medicines, important solvents, extractants and various intermediates. In addition, the hydrogenation of dimethyl oxalate can produce ethylene glycol, an extremely important chemical basic raw material. Ethylene glycol is widely used and is widely used in the production of polyester and antifreeze. In 2011, the global demand for ethylene glycol exceeded 25 million tons, of which 40% was in China. However, my country's production capacity is 3.1 million tons, and imports exceed 7 million tons. Usually, the production of ethylene glycol adopts the technical route of petroleum ethylene, and my country is a country rich in coal and low in oil. Therefore, the development of coal-based ethylene glycol can not only effectively alleviate the contradiction between supply and demand of ethylene glycol, but also make up for the shortage of my country's petroleum resources. Insufficient, has important strategic significance.

Coal-to-ethylene glycol technology includes three main steps. They are: 1) dehydrogenation and purification of carbon monoxide; 2) gas-phase oxidative coupling of carbon monoxide to produce dimethyl oxalate; 3) hydrogenation of dimethyl oxalate to produce ethylene glycol. Among them, the gas-phase oxidative coupling of carbon monoxide to dimethyl oxalate is a key step in the conversion of inorganic carbon monoxide to organic chemical dimethyl oxalate in coal-to-ethylene glycol. Although coal-to-ethylene glycol technology has fully entered the stage of industrialization and achieved good economic benefits, the first two steps of coal-to-ethylene glycol use precious metal palladium catalysts, and the content of palladium is relatively high (>1%) . Since the 1980s, new progress in the research of CO gas-phase oxidation coupling to oxalate has been reported at home and abroad. The Patent JP8242.656 Patent Publication reports a process flow for synthesizing dimethyl oxalate at atmospheric pressure using CO and methyl nitrite using platinum group metal-supported catalysts. The space-time yield of the catalyst reported in this patent is 432g∙L ^-1 ∙h ^-1 , and the yield does not decrease after 480 hours of continuous reaction. Subsequently, many patents have successively reported that catalysts such as Zr, Ce, Ti, Fe, La, Re, Ga and other additives are added to the catalyst, which are applied in the process of gas-phase synthesis of oxalate from CO and nitrite, but it has been reported that The loading amount of catalyst noble metal Pd in the patent is generally on the high side. For example, the Pd-Zr/Al ₂ O ₃ catalyst reported by Chinese patent CN95116136.9 and the Pd-La-Re/Al ₂ O ₃ catalyst reported by CN101791555A contain about 1.5% of Pd; the Pd-Ce reported by Chinese patent CN1381310A /Al ₂ O ₃ catalyst, Pd-Ga/Al ₂ O ₃ catalyst reported by CN1055492A, Pd-Ti-Ce/Al ₂ O ₃ reported by CN101138722A and Pd-La/Al ₂ O ₃ content of Pd in the catalyst reported by CN101596455A Both are around 1%. Pd is a noble metal with high price and limited reserves. The high loading of Pd leads to high catalyst cost and affects its use in industry.

Chinese patent CN101612580A discloses that a Pd-Cu/Al ₂ O ₃ catalyst is used in the gas-phase catalytic coupling of carbon monoxide to synthesize diethyl oxalate. Although the catalyst of the present invention is similar to the previous patent in composition, there are obvious differences in the structure and content of the components. The catalyst active component Pd-Cu of the present invention is that the average size is 2-3nm highly dispersed nanometer particle on the support, and the content of Cu is lower than 0.05%, and the target product prepared by the catalyst of the present invention is also different, is It is used for gas-phase oxidative coupling of carbon monoxide and methyl nitrite to prepare dimethyl oxalate. The catalyst of the present invention utilizes the small size effect of nanoparticles to significantly improve the catalytic performance. Many supported nanocatalysts show better catalytic performance in various catalytic reactions because of the small size effect of nanoparticles. For example, in the literature CATTECH, 2002, 6: 102-115, the author Haruta. M. found that bulk gold is chemically inert and has no catalytic activity, but when the gold particle size is as small as 10nm or less, it exhibits in many reactions. amazing catalytic performance. Therefore, the research and development of a series of new high-efficiency and low-loaded noble metal nanocatalysts can save a lot of precious metals, which is of great significance to solve the excessive consumption of precious metal resources and implement sustainable development strategies.

Invention content:

The main purpose of the present invention is: to provide a kind of noble metal loading capacity low, high performance for the catalyst noble metal Pd loading capacity is higher in CO gas-phase oxidation coupling process of producing dimethyl oxalate in the coal-to-ethylene glycol technology, catalyst cost is high, etc. A bimetallic nano-catalyst with high stability and high stability used for CO gas-phase oxidation coupling to prepare dimethyl oxalate and a preparation method thereof.

Another object of the present invention is to provide the application of above-mentioned nano catalyst in the preparation of dimethyl oxalate.

In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

A bimetallic nanocatalyst for producing dimethyl oxalate by CO gas-phase oxidation coupling, the carrier of the catalyst is α-alumina, and the active component is Pd-Cu nanoparticles; the composition of the catalyst is based on the mass of the carrier, and the active component is The Pd content is 0.01–2%, and the Cu content is 0.01–0.04%.

The specific surface area of the α-alumina carrier is 1-20m ² /g, the specific pore volume is 0.01-0.1cm ³ /g, and the average pore diameter is 10-50nm; the size distribution of the Pd-Cu nanoparticles is in 1-20nm, preferably 1-5nm; the dispersion of the Pd-Cu nanoparticles is 15-60%, and the specific surface area is 50-400m ² /g

The preparation method of the nano-catalyst of the present invention is prepared by adopting room temperature in-situ loading method, comprising the following steps:

(1) Precious metal palladium salt, copper salt, organic complexing agent and surfactant are formulated into a mixed aqueous solution;

The palladium salt is selected from any one of palladium nitrate, palladium chloride, potassium chloropalladate, potassium chloropalladate or ammonium chloropalladate; the copper salt is selected from copper chloride, copper acetate, nitric acid Any one in copper or copper sulfate; Described organic complexing agent is selected from any one in citric acid, sodium citrate, potassium citrate or ammonium citrate; Described surfactant is selected from polyvinylpyrrolidone , polyvinyl alcohol, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, or cetyltrimethylammonium bromide.

(2) Adding the α-alumina carrier to the mixed aqueous solution in step (1) and stirring for 0.5-2 hours;

(3) Add the reducing agent into a solution to the suspension in the above step (2), and stir and reduce at room temperature for 10-48 hours;

The reducing agent is selected from any one of ascorbic acid, glucose, formic acid or sodium formate, preferably ascorbic acid.

(4) Filter and separate the product of step (3) to obtain filtrate and solid matter, then wash the solid matter with water, absolute ethanol, and acetone several times, and dry in vacuum at 60-80°C for 5-20 hours;

(5) Activate the dried solid in step (4) for 3-6 hours in a pure hydrogen atmosphere, the hydrogen flow rate is 10-60 ml/min, the activation temperature is 250-450°C, and then cool down to room temperature in a pure hydrogen atmosphere , to obtain the nanocatalyst.

The soluble copper salt added in step (1) of the preparation method is excessive, Cu ²⁺ ions play a significant role in the reaction process, and the introduction of Cu ²⁺ ions will affect the nucleation and growth of Pd nanoparticles, It can effectively improve the dispersion of Pd nanoparticles, while Cu ²⁺ ions themselves are difficult to be reduced by weaker reducing agents at room temperature, and only trace amounts of Cu ²⁺ ions are reduced to Cu due to the underpotential deposition on the Pd surface Nanoparticles, constituting one of the active components of the catalyst.

The unreacted palladium salt in the filtrate of step (4) of the preparation method can be used again.

The application method of the bimetallic nano-catalyst for producing dimethyl oxalate through gas-phase oxidation coupling of CO provided by the present invention comprises the following steps: using a fixed-bed reactor, the amount of catalyst is 0.2-2mL, and the flow ratio of raw gas CO and methyl nitrite is controlled Between 1.2-1.6, the gas phase space velocity is 2000-5000h ^-1 , the raw material gas is contacted with the nano-catalyst under the condition of normal pressure and 90-150°C to obtain the dimethyl oxalate product. Feed gas and products are monitored and analyzed online by gas chromatography.

Compared with the prior art, the present invention has the following remarkable effects:

1. The bimetallic nano-catalyst of the present invention adopts Pd-Cu bimetallic nano-particles as active components, and the Pd-Cu nano-particles have high dispersion, large specific surface area, small size and uniform distribution.

2. The bimetallic nanocatalyst of the present invention reduces the content of the noble metal Pd in the catalyst to 0.1% by utilizing the synergistic effect of the bimetallic component and the nanometer effect, which can save a large amount of noble metal, greatly reduce the cost of the catalyst, and realize partial substitution of the noble metal.

3. The bimetallic nanocatalyst of the present invention has good catalytic activity at a low noble metal loading (about 0.1%) and a reaction temperature of 130°C, the single-pass conversion rate of CO is as high as 62%, the selectivity of dimethyl oxalate is 97%, and the selectivity of dimethyl oxalate is 97%. The space-time yield of ester is greater than 1300 g∙L ^-1 ∙h ^-1 ; while the loading of noble metal Pd on industrial catalysts is relatively high (about 2%), and the single-pass conversion rate of CO is only 35% at the reaction temperature of 130°C, and dimethyl oxalate The space-time yield of ester is 750 g∙L ^-1 ∙h ^-1 .

4. The bimetallic nanocatalyst of the present invention has higher catalytic activity at a lower reaction temperature of 100°C, the single-pass conversion rate of CO reaches 42%, the selectivity of dimethyl oxalate reaches 98%, and the space-time yield of dimethyl oxalate reaches 911 g ∙L ^-1 ∙h ^-1 , which will greatly reduce industrial energy consumption.

5. The preparation process of the bimetallic nano-catalyst of the invention is simple and easy to operate, low in energy consumption and low in cost.

Description of drawings

Fig. 1 is the chromatogram of the nano catalyst prepared in Example 1 collected at a reaction temperature of 130°C.

Fig. 2 is the chromatographic analysis graph collected at the reaction temperature of 130° C. for the nano-catalyst prepared in Comparative Example 1.

FIG. 3 is an XPS spectrum of the nanocatalyst Pd _3d element prepared in Example 1.

Fig. 4 is the nano-catalyst Cu _2p element XPS spectrogram prepared in embodiment 1.

FIG. 5 is an XPS spectrum of the nanocatalyst Pd _3d element prepared in Comparative Example 1.

FIG. 6 is a transmission electron micrograph of the nano-catalyst prepared in Example 1.

FIG. 7 is a transmission electron micrograph of the nano-catalyst prepared in Comparative Example 1.

FIG. 8 is a transmission electron micrograph of the nano-catalyst prepared in Example 2.

FIG. 9 is a transmission electron micrograph of the nano-catalyst prepared in Example 3.

FIG. 10 is a transmission electron micrograph of the nano-catalyst prepared in Example 4.

FIG. 11 is a transmission electron micrograph of the nano-catalyst prepared in Example 5.

FIG. 12 is a transmission electron micrograph of the nano-catalyst prepared in Example 6.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Example 1:

Weigh 1g of α-alumina and add it to 15ml aqueous solution containing 0.0163g potassium chloropalladate, 0.0170g copper chloride, 0.2220g polyvinylpyrrolidone (PVP), 0.2100g citric acid, stir at room temperature for 0.5 hours, then add A 5ml aqueous solution of 0.0700g ascorbic acid was stirred and reduced at room temperature for 16 hours, and the product was separated by filtration to obtain a filtrate and a solid, and then the solid was washed 6 times with water, absolute ethanol, and acetone, and dried in vacuum at 60°C for 8 hours. The dried solid was activated at 400°C for 3 hours in an atmosphere of pure hydrogen (flow rate 40ml/min), and then cooled to room temperature in an atmosphere of pure hydrogen to prepare the catalyst. The XPS spectra of the catalyst are shown in Figures 3 and 4. From the electronic binding energies of Pd3d and Cu2P, it can be known that the valence states of Pd and Cu elements in the catalyst are both zero valence. The electron microscope photo of the catalyst is shown in Figure 6. The electron microscope photo shows that the Pd-Cu nanoparticles on the catalyst are highly dispersed on the surface of the carrier, the size of the nanoparticles is distributed in the range of 1-5nm, and the average size is 2.7nm. The actual loading of Pd is 0.13%, and the actual loading of Cu is 0.014%.

Catalyst evaluation: The catalyst in the example of the present invention was applied to the CO gas-phase oxidative coupling reaction to produce dimethyl oxalate, the catalyst dosage was 1 mL, the flow ratio of feed gas CO and methyl nitrite was 1.4, and the gas-phase space velocity was 3000 h ^{- 1.} The reaction temperature is 90-150°C, and the reaction pressure is 0.1Mpa. The raw material gas and products are monitored and analyzed by gas chromatography on-line. The chromatographic analysis is shown in Figure 1, and the reaction results are shown in Table 1.

Table 1: Catalytic performance of the catalyst of Example 1 in CO gas-phase oxidative coupling reaction to produce dimethyl oxalate

As can be seen from the data in Table 1: the catalyst of the present invention can efficiently catalyze CO gas-phase oxidative coupling to synthesize oxalate at low noble metal loads and lower temperatures, and the catalyst has good stability. After 100 hours of continuous reaction at 130°C, the catalyst activity and selectivity did not decrease.

Comparative example 1:

Weigh 1g of α-alumina and add it to 15ml aqueous solution containing 0.0163g potassium chloropalladate, 0.2220g polyvinylpyrrolidone (PVP), 0.2100g citric acid, stir at room temperature for 0.5 hours, then add 5ml aqueous solution containing 0.0700g ascorbic acid , stirred and reduced at room temperature for 16 hours, the product was separated by filtration to obtain a filtrate and a solid, and then the solid was washed 6 times with water, absolute ethanol, and acetone, and dried in vacuum at 60°C for 8 hours. The dried solid was activated at 400°C for 3 hours in an atmosphere of pure hydrogen (flow rate 40ml/min), and then cooled to room temperature in an atmosphere of pure hydrogen to prepare the catalyst. The XPS spectrum of the catalyst is shown in Figure 5. From the Pd3d electron binding energy, it can be known that the valence state of the Pd element in the catalyst is zero. The electron microscope photo of the catalyst is shown in Figure 7. The electron microscope photo shows that the Pd nanoparticles on the catalyst are large in size and unevenly distributed, a little agglomerated, and the average size of the nanoparticles is 11.6nm. The actual loading of Pd in the catalyst was determined to be 0.37% by plasma emission spectroscopy (ICP).

The catalyst of Comparative Example 1 was evaluated in the same manner as in Example 1, wherein the reaction temperature was 130° C., the chromatographic analysis is shown in FIG. 2 , and the reaction results are shown in Table 2.

Table 2: Catalytic performance of the catalysts of Example 1 and Comparative Example 1 in CO gas-phase oxidative coupling reaction to produce dimethyl oxalate

Table 3: Different physical properties of the catalysts of Example 1 and Comparative Example 1

From the data in Table 2, it can be found that although the loading amount of noble metal Pd in the catalyst of Example 1 is one-third of the loading amount of Pd in the catalyst of Comparative Example 1, the catalytic activity of the catalyst of Example 1 is twice that of the catalyst of Comparative Example 1. It can be shown from the data in Table 3 that the main reason for the difference in catalytic activity is that the active component Pd-Cu nanoparticles in the catalyst of Example 1 have smaller particle size, higher dispersion and larger specific surface area.

Example 2:

Take by weighing 1g α-alumina and join in the filtrate among the embodiment 1, stir at room temperature 0.5 hour, then add the 5ml aqueous solution that contains 0.0700g ascorbic acid, stir and reduce at room temperature for 24 hours, product filtration separation obtains filtrate and solid, then The solid was washed 6 times with water, absolute ethanol and acetone, and dried under vacuum at 60°C for 8 hours. The dried solid was activated at 400°C for 3 hours in an atmosphere of pure hydrogen (flow rate 40ml/min), and then cooled to room temperature in an atmosphere of pure hydrogen to prepare the catalyst. The transmission electron microscope photo of the catalyst is shown in Figure 8. The electron microscope photo shows that the Pd-Cu nanoparticles on the catalyst are highly dispersed on the surface of the carrier, the size of the nanoparticles is distributed in the range of 1-5nm, and the average size is 2.7nm. The actual loading of Pd in the catalyst was 0.121% and the actual loading of Cu was 0.019% as measured by plasma emission spectroscopy (ICP).

Example 3:

Weigh 1g of α-alumina and add it to 15ml aqueous solution containing 0.0163g potassium chloropalladate, 0.0200g copper acetate, 0.2220g polyvinylpyrrolidone (PVP), 0.2100g citric acid, stir at room temperature for 0.5 hours, then add 0.0700 5ml of aqueous solution of ascorbic acid was stirred and reduced at room temperature for 16 hours, and the product was filtered and separated to obtain a filtrate and a solid, and then the solid was washed 6 times with water, absolute ethanol, and acetone, and dried at 60° C. in vacuum for 8 hours. The dried solid was activated at 400°C for 3 hours in an atmosphere of pure hydrogen (flow rate 40ml/min), and then cooled to room temperature in an atmosphere of pure hydrogen to prepare the catalyst. The transmission electron microscope photo of the catalyst is shown in Figure 9. The electron microscope photo shows that the Pd-Cu nanoparticles on the catalyst are highly dispersed on the surface of the carrier, the size of the nanoparticles is distributed in the range of 1-4nm, and the average size is 2.0nm. The actual loading of Pd in the catalyst was 0.087% and the actual loading of Cu was 0.026% as measured by plasma emission spectroscopy (ICP).

Example 4:

Take by weighing 1g α-alumina and join in the filtrate among the embodiment 3, stir at room temperature 0.5 hour, then add the 5ml aqueous solution that contains 0.0700g ascorbic acid, stir and reduce at room temperature for 24 hours, product filtration separation obtains filtrate and solid, then The solid was washed 6 times with water, absolute ethanol and acetone, and dried under vacuum at 60°C for 8 hours. The dried solid was activated at 400°C for 3 hours in an atmosphere of pure hydrogen (flow rate 40ml/min), and then cooled to room temperature in an atmosphere of pure hydrogen to prepare the catalyst. The transmission electron microscope photo of the catalyst is shown in Figure 10. The electron microscope photo shows that the Pd-Cu nanoparticles on the catalyst are highly dispersed on the surface of the carrier, the size of the nanoparticles is distributed in the range of 1-4nm, and the average size is 2.0nm. The actual loading of Pd in the catalyst was 0.119%, and the actual loading of Cu was 0.015% measured by plasma emission spectroscopy (ICP).

Example 5:

Weigh 1g of α-alumina and add it to 15ml aqueous solution containing 0.0163g potassium chloropalladate, 0.0242g copper nitrate, 0.2220g polyvinylpyrrolidone (PVP), 0.2100g citric acid, stir at room temperature for 0.5 hours, then add 0.0700 5ml of aqueous solution of ascorbic acid was stirred and reduced at room temperature for 16 hours, and the product was filtered and separated to obtain a filtrate and a solid, and then the solid was washed 6 times with water, absolute ethanol, and acetone, and dried at 60° C. in vacuum for 8 hours. The dried solid was activated at 400°C for 3 hours in an atmosphere of pure hydrogen (flow rate 40ml/min), and then cooled to room temperature in an atmosphere of pure hydrogen to prepare the catalyst. The transmission electron microscope photos of the catalyst are shown in Figure 11. The electron microscope photos show that the Pd-Cu nanoparticles on the catalyst are highly dispersed on the surface of the carrier, the size of the nanoparticles is distributed in the range of 1-5nm, and the average size is 2.9nm. The actual loading of Pd in the catalyst was 0.118%, and the actual loading of Cu was 0.027% measured by plasma emission spectroscopy (ICP).

Embodiment 6:

Take by weighing 1g α-alumina and join in the filtrate among the embodiment 5, stir at room temperature 0.5 hour, then add the 5ml aqueous solution that contains 0.0700g ascorbic acid, stir and reduce at room temperature for 24 hours, product filtration separation obtains filtrate and solid, then The solid was washed 6 times with water, absolute ethanol and acetone, and dried under vacuum at 60°C for 8 hours. The dried solid was activated at 400°C for 3 hours in an atmosphere of pure hydrogen (flow rate 40ml/min), and then cooled to room temperature in an atmosphere of pure hydrogen to prepare the catalyst. The transmission electron microscope photo of the catalyst is shown in Figure 12. The electron microscope photo shows that the Pd-Cu nanoparticles on the catalyst are highly dispersed on the surface of the carrier, the size of the nanoparticles is distributed in the range of 1-5nm, and the average size is 2.7nm. The actual loading of Pd in the catalyst was 0.106% and the actual loading of Cu was 0.019% as measured by plasma emission spectroscopy (ICP).

The catalysts of Examples 2-6 were evaluated in the same manner as in Example 1, wherein the reaction temperature was 130° C., and the reaction results are shown in Table 4.

Table 4: Catalytic performance of the example catalysts in CO gas-phase oxidative coupling reaction to produce dimethyl oxalate

It can be seen from the data in Table 4 that the catalyst of the present invention can efficiently catalyze CO gas-phase oxidation coupling into dimethyl oxalate at a low noble metal loading (about 0.1%), and the CO conversion rate, dimethyl oxalate selectivity and The space-time yield is relatively high. This shows that the active component Pd-Cu nanoparticles in the bimetallic nanocatalyst of the present invention have high dispersion, large specific surface area, small size and uniform distribution. This point can be verified by transmission electron microscope photos and size distribution histograms.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (7)

1. a CO gaseous oxidation coupling dimethyl oxalate processed bimetal nano catalyst is characterized in that this catalyst is take Alpha-alumina as carrier, take the Pd-Cu nano particle as active component; The composition of catalyst is in the quality of carrier, and active component Pd content is 0.01 – 2%, and Cu content is 0.01-0.04%.

2. nanocatalyst according to claim 1 is characterized in that, the specific area of described alpha-alumina supports is 1 – 20m ²/ g, specific pore volume are 0.01-0.1cm ³/ g, average pore size is 10-50nm.

3. nanocatalyst according to claim 1 is characterized in that, the distribution of sizes of described Pd-Cu nano particle is preferably 1-5nm at 1 – 20nm.

4. nanocatalyst according to claim 1 is characterized in that, the decentralization of described Pd-Cu nano particle is 15-60%, and specific area is 50-400m ²/ g.

5. the preparation method of a CO gaseous oxidation coupling dimethyl oxalate usefulness processed bimetal nano catalyst is characterized in that, this catalyst employing room temperature original position load method preparation may further comprise the steps:

(1) precious metal palladium salt, mantoquita, organic complexing agent and surfactant are made into mixed aqueous solution;

(2) alpha-alumina supports is joined in the mixed aqueous solution of step (1) and stirred 0.5-2 hour;

(3) the reducing agent wiring solution-forming is joined in the suspension of above-mentioned steps (2), and stir reduction 10-48 hour under the room temperature;

Described reducing agent is selected from any one in ascorbic acid, glucose, formic acid or the sodium formate, preferred ascorbic acid;

(4) the product isolated by filtration with step (3) obtains filtrate and solids, and then solids water, absolute ethyl alcohol, acetone wash repeatedly, vacuum 60-80 ℃ of drying 5 – 20 hours;

(5) with the dried solids of step (4) under pure hydrogen atmosphere activation process 3-6 hour, hydrogen flow rate 10-60 ml/min, activation temperature 250-450 ℃, then in pure hydrogen atmosphere, be cooled to room temperature, namely make described nanocatalyst.

6. CO gaseous oxidation coupling as claimed in claim 5 dimethyl oxalate processed is characterized in that with the preparation method of bimetal nano catalyst, and precious metal palladium salt, mantoquita, organic complexing agent and surfactant are made into mixed aqueous solution;

Described palladium salt is selected from any one in palladium nitrate, palladium bichloride, potassium chloropalladite, potassium chloropalladate or the ammonium chloropalladate;

Described mantoquita is selected from any one in copper chloride, Schweinfurt green, copper nitrate or the copper sulphate;

Described organic complexing agent is selected from any one in citric acid, natrium citricum, potassium citrate or the ammonium citrate;

Described surfactant is selected from any one in polyvinylpyrrolidone, polyvinyl alcohol, lauryl sodium sulfate, neopelex or the softex kw.

7. the application of the catalyst of claim 5 preparation in CO gaseous oxidation coupling dimethyl oxalate reaction processed, it is characterized in that, adopt fixed bed reactors, catalyst amount is 0.2 – 2mL, unstripped gas CO and methyl nitrite flow-ratio control are between 1.2-1.6, and the gas phase air speed is 2000 – 5000h ^-1, unstripped gas contacts with described nanocatalyst under the condition of 150 ℃ of normal pressures, 90 –, obtains the dimethyl oxalate product.

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