CN115106082A - Composite oxide loaded gold-based alloy catalyst and preparation method and application thereof - Google Patents

Abstract

The invention discloses a composite oxide supported gold-based alloy catalyst and a preparation method and application thereof, belonging to the technical field of catalysts. Firstly, a composite oxide is obtained through a coprecipitation method, a precursor of the oxide is added while loading the gold-based alloy, and then a layer of oxide is modified on the surface, so that the gold-based alloy catalyst loaded by the composite oxide and wrapped by the oxide is obtained. The gold-based alloy catalyst disclosed by the invention keeps higher conversion rate and selectivity, the stability of the gold-based alloy catalyst is obviously improved, the gold-based alloy catalyst is applied to long-term operation of a slurry bed, the loss of metal in the catalyst is not obvious, the activity is better kept, and compared with the reaction of an intermittent reaction kettle, the reaction of the slurry bed is easier to industrially amplify, and the promotion of industrialization is facilitated.

Description

A kind of complex oxide supported gold-based alloy catalyst and its preparation method and application

technical field

The invention belongs to the technical field of catalysts, and in particular relates to a gold-based alloy catalyst supported by a composite oxide, a preparation method thereof, and its application in slurry bed preparation of methyl glycolate.

Background technique

Methyl glycolate is a very important intermediate in drug synthesis and organic synthesis, and an excellent solvent for cellulose, resin and rubber. Known processes for the large-scale production of methyl glycolate include: addition of formaldehyde to hydrocyanic acid, free radical addition of methylal to formaldehyde, carbonyl esterification of formaldehyde, and coupling reactions of methyl formate and formaldehyde. However, due to the high price of raw materials, serious corrosiveness in the production process, and difficulty in separating the products, it was gradually eliminated. Therefore, there is an urgent need to develop a method for preparing methyl glycolate with cheap raw materials, wide sources, simple process and environmental protection. Currently. Using ethylene glycol and methanol as starting materials, the synthesis of methyl glycolate through one-step oxidative esterification has become the focus of research. In the process, the separation and purification process of the product is simple, the product purity is high, and the cost is low, and it is a green chemical process route with development prospects.

In the prior art, by the method of co-deposition, the supported catalyst is modified with oxides, and the reaction is carried out in an intermittent reaction kettle, which effectively improves the conversion rate and selectivity of ethylene glycol to methyl glycolate. Stability issues need to be addressed urgently.

SUMMARY OF THE INVENTION

In view of this, the purpose of the present invention is to provide a complex oxide supported gold-based alloy catalyst and its preparation method and application. The gold-based alloy catalyst of the present invention maintains high conversion rate and selectivity, and its stability is significantly improved. When applied to the long-term operation of the slurry bed, the loss of metal in the catalyst is not obvious, and the activity is well maintained. , the method is significantly better than the results obtained in batch reactors.

The object of the present invention is to realize in the following ways:

The invention provides a preparation method of a composite oxide supported gold-based alloy catalyst, the preparation method mainly comprises the following steps:

(1) Dissolve the precursors of the two oxides in water. The precursors of the oxides include sodium salts, potassium salts, calcium salts, barium salts, chromium salts, magnesium salts, aluminum salts, lanthanum salts, praseodymium salts, and neodymium salts. , samarium salt, cerium salt, and the mass ratio of the precursors of the two oxides is 1:10-10:1, the pH value of the system is adjusted to 7.5-10 with an alkaline aqueous solution, dried after aging, and dried in oxygen and inert calcining in a gas mixture at a calcination temperature of 400-800°C to obtain a composite oxide carrier;

(2) Dispersing the composite oxide carrier obtained in step (1) into an aqueous solution in which the gold salt and the second metal salt are dissolved, then adding the precursor of the coating oxide, drying after aging, and drying in oxygen and an inert gas calcined in the mixed gas, and then reduced in hydrogen to obtain a gold-based alloy catalyst supported by composite oxides.

Based on the above technical solutions, preferably, the specific process of drying after aging described in step (1) is to heat the obtained solution to 50-70° C., stir for 1-5h, evaporate the water to dryness, and then heat the obtained precipitate at 100-70° C. Dry at 150°C.

Based on the above technical solution, preferably, at least one of the precursors of the two oxides in step (1) is a precursor of an alkaline oxide, and the other is a precursor of sodium, potassium, zinc, barium, chromium, magnesium , iron, calcium, copper, cobalt, nickel, aluminum, lanthanum, praseodymium, neodymium, samarium, cerium chloride, nitrate, sulfate, acetate, a kind of aluminum isopropoxide.

Based on the above technical solutions, preferably, the alkaline aqueous solution described in step (1) is one of the aqueous solutions of ammonia, potassium hydroxide, sodium hydroxide, potassium bicarbonate and sodium bicarbonate.

Based on the above technical scheme, preferably, the volume percentage of oxygen in the mixture of oxygen and inert gas described in step (1) is 10-50%, the inert gas includes argon and nitrogen, and the heating temperature rise rate is 1-10°C/ minutes, the roasting time is 2-10h.

Based on the above technical scheme, preferably, the gold salt described in step (2) is one of tetrachloroauric acid, gold chloride, Au(en) ₂ Cl ₃ , and the second metal salt is platinum, ruthenium, rhodium , one of the water-soluble salts of palladium, osmium, iridium, iron, cobalt, nickel, copper and zinc.

Based on the above technical solutions, preferably, the gold loading in the gold-based alloy catalyst in step (2) is 0.1-10 wt %, and the loading of the second metal in the gold-based alloy catalyst is 0.1-5 wt %.

Based on the above technical solutions, preferably, the precursor of the coating oxide in step (2) is sodium, potassium, zinc, barium, chromium, magnesium, iron, calcium, copper, cobalt, nickel, aluminum, lanthanum, praseodymium , one of neodymium, samarium, cerium chloride, nitrate, sulfate, acetate, ethyl orthosilicate, aluminum isopropoxide, and the loading of the coating oxide is 1-20wt%.

Based on the above technical solutions, preferably, the aging condition in step (2) is to treat at 50-80° C. for 1-5 hours.

Based on the above technical scheme, preferably, the volume percentage of oxygen in the mixture of oxygen and inert gas described in step (2) is 10-50%, the inert gas includes argon and nitrogen, the roasting temperature is 400-600 ° C, and the roasting temperature is 400-600 ° C. The time is 2-10h, the reduction temperature is 200-400°C, and the reduction time is 1-4h.

Another aspect of the present invention provides the composite oxide-supported gold-based alloy catalyst prepared by the above preparation method.

The present invention also provides a method for preparing methyl glycolate by using the above-mentioned composite oxide-supported gold-based alloy catalyst, wherein the composite oxide-supported gold-based alloy catalyst is placed in a slurry bed reactor, and methanol is pumped into it. And ethylene glycol, pass air, and react at 60-150 to obtain methyl glycolate.

Based on the above technical solutions, preferably, the mass ratio of methanol and ethylene glycol is 0.1-50, the reaction temperature is 110-130° C., and the pressure is 0.1-5 MPa.

The beneficial effects that the present invention has with respect to the prior art are as follows:

The composite oxide used in the present invention enhances the strong interaction between the metal and the carrier. After adding the second metal, the electronic effect of gold is obviously affected, and a high conversion rate and selectivity are maintained. After that, the interface effect between the metal and the oxide is greatly exerted, so that its stability is significantly improved. Under the long-term operation of the slurry bed, the loss of metal in the catalyst is not obvious, and the activity is well maintained. , the method is significantly better than the results obtained in batch reactors.

Description of drawings

In order to describe the embodiments of the present invention more clearly, the accompanying drawings related to the embodiments will be briefly introduced below.

Figure 1 is a comparison chart of the stability test of different catalysts in slurry bed catalyzing ethylene glycol to prepare methyl glycolate.

Detailed ways

The present invention will be described in detail below in conjunction with the examples, but the embodiments of the present invention are not limited thereto. Obviously, the examples in the following description are only part of the examples of the present invention. Under the premise of creative work, obtaining other similar embodiments all fall within the protection scope of the present invention.

Preparation of Comparative Example 1 Catalyst 1%Au/MgAlOx

Preparation of composite oxide: Add aluminum nitrate and magnesium nitrate with a mass ratio of 1:1 into water, adjust the pH of the solution to about 8 by adding ammonia water, then heat the solution to 60 ° C, continue stirring for 2 hours, and then the temperature rises to 80 The water was evaporated to dryness at ℃, and then the obtained precipitate was dried at 120 ℃ and then calcined at 650 ℃ to obtain the composite oxide MgAlOx.

Preparation of supported catalyst: take the prepared chloroauric acid solution in a 250mL beaker, add ultrapure water and stir, add composite oxide MgAlOx to make the theoretical loading of gold on the composite oxide 1%, adjust the concentration of the solution by ammonia water. The pH was about 7, and after aging for 3 hours, it was washed with deionized water and filtered with suction. The samples were placed in an 80°C oven to dry for 3 hours. The catalyst was subsequently calcined at 500° C. for 4 hours in an air atmosphere, and the resulting catalyst was denoted as 1% Au/MgAlOx.

Get 200g catalyst and place it in the slurry bed reactor, pump the mixed solution (10:1) of methanol and ethylene glycol into the slurry bed reactor at a speed of 5ml/min, keep the system pressure at 0.5MPa during the reaction, and the air The flow rate was 5 L/min, and the reaction temperature was 120 °C. The product was condensed and stored in a liquid storage tank. Samples were taken at regular intervals for analysis. The results are shown in Table 1.

Preparation of Comparative Example 2 Catalyst (1%Au/MgAlOx)@ _SiO2

Preparation of composite oxide: Add aluminum nitrate and magnesium nitrate with a mass ratio of 1:1 into water, adjust the pH of the solution to about 8 by adding ammonia water, then heat the solution to 60 ° C, continue stirring for 2 hours, and then the temperature rises to 80 ℃ evaporate the water to dryness. Subsequently, the obtained precipitate was dried at 120° C. and then calcined at 650° C. to obtain the composite oxide MgAlOx.

Preparation of supported catalyst: take the prepared chloroauric acid solution in a 250mL beaker, add ultrapure water and stir, add composite oxide MgAlOx to make the theoretical loading of gold on the composite oxide 1%, adjust the concentration of the solution by ammonia water. When the pH is about 7, the solution is heated to 70°C, and then 1 ml of ethyl orthosilicate is added dropwise. After aging for 3 hours, the solution is washed with deionized water and filtered with suction. The samples were placed in an 80°C oven to dry for 3 hours. The catalyst was subsequently calcined at 500° C. for 4 hours in an air atmosphere, and the resulting catalyst was denoted as (1%Au/MgAlOx)@SiO ₂ .

Get 200g catalyst and place it in the slurry bed reactor, pump the mixed solution (10:1) of methanol and ethylene glycol into the slurry bed reactor at a speed of 5ml/min, keep the system pressure at 0.5MPa during the reaction, and the air The flow rate was 5 L/min, and the reaction temperature was 120 °C. The product was condensed and stored in a liquid storage tank. Samples were taken at regular intervals for analysis. The results are shown in Table 1.

Example 1 Preparation of catalyst (1%Au0.1%Pd/MgAlOx)@ _SiO2

Preparation of composite oxide carrier: Add aluminum nitrate and magnesium nitrate with a mass ratio of 1:1 into water, adjust the pH of the solution to about 8 by adding ammonia water, then heat the solution to 60 ° C, continue stirring for 2 hours, and then the temperature rises The water was evaporated to dryness at 80° C., and then the obtained precipitate was dried at 120° C. and then calcined at 650° C. to obtain the composite oxide MgAlOx.

Preparation of supported catalyst: take the prepared solution of chloroauric acid and chloropalladium acid in a 250 mL beaker, add ultrapure water and stir, add composite oxide MgAlOx to make the theoretical loading of gold on composite oxide 1%, palladium The theoretical loading amount on the composite oxide is 0.1%, the pH of the solution is adjusted to about 7 by ammonia water, then the solution is heated to 70 ° C, and then 1 ml of ethyl orthosilicate is added dropwise, aged for 3 hours, and washed with deionized water , Suction filtration. The samples were placed in an 80°C oven to dry for 3 hours. Subsequently, the catalyst was calcined at 500° C. for 4 hours in an air atmosphere, and then reduced under a 300° C. hydrogen atmosphere for 2 hours, and the obtained catalyst was marked as (1%Au0.1%Pd/MgAlOx)@SiO ₂ .

Get 200g catalyst and place it in the slurry bed reactor, pump the mixed solution (10:1) of methanol and ethylene glycol into the slurry bed reactor at a speed of 5ml/min, keep the system pressure at 0.5MPa during the reaction, and the air The flow rate was 5 L/min, and the reaction temperature was 120 °C. The product was condensed and stored in a liquid storage tank. Samples were taken at regular intervals for analysis. The results are shown in Table 1.

Example 2 Preparation of catalyst (1%Au0.1%Pt/MgAlOx)@ _SiO2

Preparation of composite oxide carrier: Add aluminum nitrate and magnesium nitrate with a mass ratio of 1:1 into water, adjust the pH of the solution to about 8 by adding ammonia water, then heat the solution to 60 ° C, continue stirring for 2 hours, and then the temperature rises The water was evaporated to dryness at 80° C., and then the obtained precipitate was dried at 120° C. and then calcined at 650° C. to obtain the composite oxide MgAlOx.

Preparation of supported catalyst: take the prepared chloroauric acid and chloroplatinic acid solution in a 250mL beaker, add ultrapure water and stir, add composite oxide MgAlOx to make the theoretical loading of gold on composite oxide 1%, platinum The theoretical loading amount on the composite oxide is 0.1%, the pH of the solution is adjusted to about 7 by ammonia water, then the solution is heated to 70 ° C, and then 1 ml of ethyl orthosilicate is added dropwise, aged for 3 hours, and washed with deionized water , Suction filtration. The sample was placed in an oven at 80°C to dry for 3 hours, then the catalyst was calcined at 500°C for 4 hours in an air atmosphere, and then reduced in a hydrogen atmosphere at 300°C for 2 hours, and the obtained catalyst was marked as (1%Au0.1%Pt /MgAlOx)@SiO ₂ .

Get 200g catalyst and place it in the slurry bed reactor, pump the mixed solution (10:1) of methanol and ethylene glycol into the slurry bed reactor at a speed of 5ml/min, keep the system pressure at 0.5MPa during the reaction, and the air The flow rate was 5 L/min, and the reaction temperature was 120 °C. The product was condensed and stored in a liquid storage tank. Samples were taken at regular intervals for analysis. The results are shown in Table 1.

Example 3 Preparation of catalyst (1%Au0.3%Ni/MgAlOx)@ _SiO2

Preparation of composite oxide carrier: Add aluminum nitrate and magnesium nitrate with a mass ratio of 1:1 into water, adjust the pH of the solution to about 8 by adding ammonia water, then heat the solution to 60 ° C, continue stirring for 2 hours, and then the temperature rises The water is evaporated to dryness at 80°C, and then the obtained precipitate is dried at 120°C and then calcined at 650°C to obtain a composite oxide MgAlOx.

Preparation of supported catalyst: take the prepared chloroauric acid and nickel nitrate solution in a 250mL beaker, add ultrapure water and stir, add composite oxide MgAlOx to make the theoretical loading of gold on the composite oxide 1%, and nickel in the composite oxide. The theoretical loading on the composite oxide is 0.3%, the pH of the solution is adjusted to about 7 by ammonia water, then the solution is heated to 70 ° C, and then 1 ml of ethyl orthosilicate is added dropwise, and after aging for 3 hours, it is washed with deionized water, Suction filtration. The sample was dried in an oven at 80°C for 3 hours, then the catalyst was calcined at 500°C for 4 hours in an air atmosphere, and then reduced under a hydrogen atmosphere at 450°C for 2 hours, and the obtained catalyst was marked as (1%Au0.3%Ni /MgAlOx)@SiO ₂ .

Get 200g catalyst and place it in the slurry bed reactor, pump the mixed solution (10:1) of methanol and ethylene glycol into the slurry bed reactor at a speed of 5ml/min, keep the system pressure at 0.5MPa during the reaction, and the air The flow rate was 5 L/min, and the reaction temperature was 120 °C. The product was condensed and stored in a liquid storage tank. Samples were taken at regular intervals for analysis. The results of ethylene glycol conversion, methyl glycolate selectivity and catalyst stability are shown in Table 1 and Figure 1.

Table 1. Ethylene glycol conversion and product selectivity for different catalysts reacted in slurry bed for 3 hours

It can be seen from the data in Figure 1 and Table 1 that, compared with Comparative Examples 1-2, the catalysts prepared in Examples 1-3 not only have higher conversion rate of ethylene glycol and selectivity of methyl glycolate, but also have very high ethylene glycol conversion. Excellent catalytic stability.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features thereof can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention. scope.

Claims (10)

1. The preparation method of the composite oxide supported gold-based alloy catalyst is characterized by mainly comprising the following steps of:

(1) dissolving precursors of two oxides in water, wherein the precursors of the oxides comprise sodium salt, potassium salt, calcium salt, barium salt, chromium salt, magnesium salt, aluminum salt, lanthanum salt, praseodymium salt, neodymium salt, samarium salt and cerium salt, the mass ratio of the precursors of the two oxides is 1:10-10:1, adjusting the pH value of a system to 7.5-10 by using an alkaline aqueous solution, aging, drying, roasting in a mixed gas of oxygen and inert gas at the roasting temperature of 400-800 ℃, and preparing a composite oxide carrier;

(2) and (2) dispersing the composite oxide carrier obtained in the step (1) into an aqueous solution in which a gold salt and a second metal salt are dissolved, adding a precursor of a coating oxide, aging, drying, roasting in a mixed gas of oxygen and an inert gas, and reducing in hydrogen to obtain the composite oxide-loaded gold-based alloy catalyst.

2. The method according to claim 1, wherein at least one of the precursors of the two oxides in step (1) is a precursor of an alkaline oxide, and the other is one of chlorides, nitrates, sulfates, acetates, and aluminum isopropoxide of sodium, potassium, zinc, barium, chromium, magnesium, iron, calcium, copper, cobalt, nickel, aluminum, lanthanum, praseodymium, neodymium, samarium, and cerium.

3. The preparation method according to claim 1, wherein the volume percentage of oxygen in the mixed gas of oxygen and inert gas in the step (1) is 10-50%, the inert gas comprises argon and nitrogen, the roasting temperature rise rate is 1-10 ℃/min, and the roasting time is 2-10 h.

4. The method according to claim 1, wherein the gold salt in the step (2) is tetrachloroauric acid, gold chloride, Au (en) ₂ Cl ₃ The second metal salt is one of water-soluble salts of platinum, ruthenium, rhodium, palladium, osmium, iridium, iron, cobalt, nickel, copper and zinc.

5. The method of claim 1, wherein the gold loading in the gold-based alloy catalyst in step (2) is 0.1 to 10 wt% and the second metal loading in the gold-based alloy catalyst is 0.1 to 5 wt%.

6. The preparation method according to claim 1, wherein the precursor of the coating oxide in the step (2) is one of chlorides, nitrates, sulfates, acetates, ethyl orthosilicate and aluminum isopropoxide of sodium, potassium, zinc, barium, chromium, magnesium, iron, calcium, copper, cobalt, nickel, aluminum, lanthanum, praseodymium, neodymium, samarium and cerium, and the loading of the coating oxide is 1-20 wt%.

7. The method according to claim 1, wherein the volume percentage of oxygen in the mixed gas of oxygen and inert gas in step (2) is 10-50%, the inert gas comprises argon and nitrogen, the calcination temperature is 400-.

8. A complex oxide-supported gold-based alloy catalyst produced by the production method described in any one of claims 1 to 7.

9. A method for preparing methyl glycolate by using the composite oxide supported gold-based alloy catalyst of claim 8, wherein the composite oxide supported gold-based alloy catalyst is placed in a slurry bed reactor, methanol and ethylene glycol are pumped, air is introduced, and the reaction is carried out at 60-150 ℃ to obtain the methyl glycolate.

10. The method as claimed in claim 9, wherein the mass ratio of methanol to ethylene glycol is 0.1-50, the reaction temperature is 110-130 ℃, and the pressure is 0.1-5 MPa.

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