CN101024183A - Copper-carried crystallization silver catalyst for gas-phase oxidation synthesization of biformyl and its preparing method - Google Patents

Abstract

The invention belongs to the technical field of chemistry and chemical engineering, and specifically relates to a copper-loaded crystalline silver catalyst for gas-phase oxidation synthesis of glyoxal, a preparation method and application thereof. The catalyst is obtained by electroless plating and depositing a modified amount of copper on crystalline silver particles, and the copper loading is 1-100mg/g. The plating solution of the electroless plating is composed of copper ammonium ions, ammonia water and a reducing agent. The crystalline silver particles are put into the plating solution for chemical plating, and then filtered and roasted to obtain the catalyst. The catalyst can be used for gas-phase catalytic oxidation of ethylene glycol to synthesize glyoxal. The yield of glyoxal is high, and the service life of the catalyst is long.

Description

Copper-loaded crystalline silver catalyst for gas-phase oxidation synthesis of glyoxal and preparation method thereof

technical field

The invention belongs to the technical field of chemistry and chemical engineering, and in particular relates to a catalyst for gas-phase catalytic oxidation of ethylene glycol to synthesize glyoxal and a preparation method thereof.

Background technique

Glyoxal can be synthesized from ethylene glycol by gas-phase catalytic oxidation. British Patent GB1,272,592 describes the synthesis of glyoxal by gas-phase oxidation of ethylene glycol on a copper-silver alloy catalyst, and the yield of glyoxal can reach 55%-72%, but its raw material ethylene glycol is The conversion rate is low, and the space velocity of the raw material is also relatively small. German patent DE1,967,147 describes the synthesis of glyoxal by silver catalysis, and the yield can reach 70%, but the same conversion rate and raw material space velocity are not satisfactory. U.S. Patent No. 4,258,216 has obtained a glyoxal yield up to 80.5% by using a copper-silver catalyst, but the bromine added in the raw material has a strong corrosion effect in the presence of oxygen, and the aging of the catalyst based on copper is relatively high quick. British Patent GB1,361,190 describes the method of treating the catalyst with excess oxygen to regenerate it to increase the service life of the copper-silver catalyst. The disadvantage of this method is that the production must be stopped during regeneration, and the excess oxygen used for regeneration must be completely driven away. Failure to do so creates the risk of an explosion. U.S. Patent No. 4,242,282 uses crystalline silver with a particle size of 0.1-2.5mm as a catalyst, the residence time of the reaction gas on the catalyst is greatly shortened, the space velocity of the raw material is several times that of the above catalyst, and the catalytic efficiency is greatly improved. Aldehyde yield is only 55%. U.S. Patent No. 4,511,739 improves the method of U.S. Pat. No. 4,242,282. Water or glyoxal aqueous solution absorbs the product gas of heat, and the yield of glyoxal is increased to 62% from 55%, and the conversion rate of ethylene glycol is 98%. This method can directly obtain 40% commercial glyoxal aqueous solution, and the chromaticity of the product is also much lower than that of the aforementioned method. The shortcoming of this method is that the content of glycolaldehyde in the product is relatively high, and there is no suitable method at present Removal of glycolaldehyde in aqueous glyoxal solution. U.S. Patent No. 4,503,261 paves copper catalysts and crystalline silver catalysts in layers, and the catalyst bed contains one or more layers of copper catalysts and one or more layers of crystalline silver catalysts. The copper and silver catalysts are particles of 0.1-2.5 mm. The method can directly obtain 40% commercial glyoxal aqueous solution, the highest conversion rate of ethylene glycol can reach 99.9%, the yield of glyoxal can reach 76%, and the content of glycolaldehyde is 1%. The life of the catalyst reaches 90 days, and the catalytic activity of using zero-valent metal copper and metal silver is obviously better than that of the copper catalyst and the silver catalyst. .

Contents of the invention

The object of the present invention is to provide a copper-supported crystalline silver catalyst for gas-phase oxidation synthesis of glyoxal and a preparation method thereof. The catalyst has a long service life and is used for synthesizing glyoxal with high product yield.

The copper-loaded crystallization catalyst for gas-phase oxidation synthesis of glyoxal proposed by the present invention is obtained by depositing a modified amount of copper on crystalline silver particles by electroless plating, and the copper loading is 1-100 mg/g. Electroless plating is a method in which oxidation-reduction occurs in the same solution with the help of a reducing agent in the absence of current, so that metal ions are reduced and deposited on the surface of the carrier. The composition of the electroless plating solution and its corresponding working conditions make the reaction only It is limited to the surface of the carrier with catalytic effect, and the reaction does not proceed spontaneously in the solution body and on the container wall. The invention reduces and deposits the copper ions on the crystalline silver particles, thereby preparing a stable copper-loaded crystalline silver catalyst.

The electroless plating bath is generally composed of copper ammonium ions, ammonia water, and a reducing agent. The speed of electroless copper plating increases with the content of copper ions, but the concentration of copper ions is high and the solution is unstable. Generally, the concentration of 0.05 to 0.5 mol/L is used. Ammonia in the plating solution is beneficial to the stability of copper ammonium ions, increasing the concentration of ammonia water will increase the stability of copper ammonium ions, but if it is too high, it will slow down the copper plating speed. Generally, the molar ratio of free ammonia to copper ammonium ions is 1 to 10 .

In the above-mentioned plating solution, the reducing agent generally includes formaldehyde, glucose, tartrate or hydrazine sulfate, and the reduction rate is formaldehyde > glucose > tartrate > hydrazine sulfate. For the same reducing agent, the concentration is low, and the electroless plating speed is slow. The rapid increase of the speed will easily cause the plating solution to self-decompose, and metal copper will be precipitated in the plating liquid phase. Generally, the molar ratio of the reducing agent to the copper ammonium ion is 1-10.

Sodium hydroxide can also be added to the above-mentioned plating solution. Sodium hydroxide is a speed regulator. With the increase of alkalinity, the reduction speed will be accelerated.

In the catalyst proposed by the present invention, the copper loading is 1-100 mg/g, more preferably 5-50 mg/g.

The crystalline silver of electroless copper plating is washed, dried, and calcined at 400-700° C. for 1-6 hours to obtain a copper-loaded crystalline silver catalyst.

Preparation method of the present invention is further described as follows:

(1) Copper nitrate is dissolved in distilled water, and after being completely dissolved, ammoniacal liquor is slowly added while stirring, and copper hydroxide precipitation is first formed, and a blue copper ammonia complex solution is formed after adding excessive ammoniacal liquor;

(2) Add reducing agent into distilled water, sodium hydroxide can be added when necessary, stir and dissolve;

(3) the above two solutions are mixed to obtain the electroless plating solution;

(4) putting the crystalline silver particles into the electroless plating solution for electroless plating;

(5) After filtering and drying, calcining at 400-700° C. for 1-6 hours to obtain a copper-loaded crystalline silver catalyst.

The copper-loaded crystalline silver catalyst proposed by the invention can be used for gas-phase synthesis of glyoxal. The specific method is as follows:

Copper-loaded crystalline silver is used as a catalyst, and ethylene glycol, oxygen, water and inert gases such as nitrogen are oxidized on the catalyst at 400°C-800°C to form glyoxal, and the particle size of the catalyst is 0.1-2.5mm.

In the present invention, ethylene glycol is oxidized in the presence of an inert gas such as nitrogen, and the molar ratio of the inert gas to oxygen is not lower than 4.4:1, generally 4.4:1-10:1. A suitable molar ratio of oxygen to ethylene glycol is between 0.7:1 and 1.4:1. The liquid hourly space velocity of ethylene glycol on the catalyst is 5-50h-1.

In the present invention, the catalyst is paved in two or more layers according to the particle size, preferably 3 to 6 layers. Taking 4 layers of paving as an example, the particle size of each layer of catalyst from top to bottom can be 0.2-0.4mm, 0.4 -0.75mm, 0.75-1.0mm, 1.0-2.5mm. The thickness of each catalyst layer is the same, and the total thickness of the catalyst is 10-100 mm, preferably 20 to 60 mm.

The catalyst provided by the invention has a long service life, is used for synthesizing glyoxal, and has a high product yield.

Detailed ways

The present invention is further described below by way of examples.

Embodiment 1. Copper nitrate is dissolved in distilled water and is mixed with the solution of 0.05mol/L, then slowly adds ammoniacal liquor while stirring, first generates copper hydroxide precipitation, forms colorless transparent silver-ammonia complex solution after adding excessive ammoniacal liquor Dark blue copper ammonium complex solution, the molar ratio of excess ammonia to copper ammonium ions is 1. Add reducing agent formaldehyde in another distilled aqueous solution, the molar ratio of formaldehyde and copper ammine ion is 2, adjust alkalinity with NaOH, make NaOH concentration be 0.4mol/L. After the above two solutions are mixed evenly, the electroless plating solution is obtained. The crystalline silver is put into the electroless plating solution for electroless plating, and the deposition amount of copper is controlled to be 5 mg/g catalyst. After plating, filter, dry and bake at 650°C for 5 hours to obtain a copper-loaded crystalline silver-silver catalyst.

5 grams of catalyst are divided into 4 layers and loaded into a stainless steel reactor with a diameter of 14mm. The particle size and weight percentage are (from top to bottom): the first layer is 0.2-0.4mm, 20%; the second layer is 0.4-0.75mm , 20%; the third layer 0.7-1.0mm, 40%; the fourth layer 1.0-2.5mm, 20%. Put the ethylene glycol aqueous solution into the gasifier with a metering pump, mix it with preheated air and nitrogen, and then enter the catalytic bed for reaction after heating. The liquid hourly space velocity of ethylene glycol is 50hr ^-1 , and oxygen and ethylene glycol The molar ratio of alcohol is 1.35, the molar ratio of nitrogen and oxygen is 25, the molar ratio of water and oxygen is 5, the reaction temperature is 600 ° C, the product is quenched and absorbed by spraying, and the supplementary water amount of spraying is controlled to obtain 40% ethylene glycol Aldehyde product, the conversion rate of ethylene glycol is 99.9%, the selectivity of methylglyoxal is 80.6%, and the service life of the catalyst is 150 days.

Embodiment 2. Copper nitrate is dissolved in distilled water and is mixed with the solution of 0.5mol/L, then slowly adds ammoniacal liquor while stirring, first generates copper hydroxide precipitation, forms dark blue copper ammonium complex solution after adding excessive ammoniacal liquor , the molar ratio of excess ammonia to copper ammonium ions is 1. Add reducing agent tartrate in another distilled aqueous solution, its molar ratio to copper ammonium complex ion is 2, adjust alkalinity with NaOH, make NaOH concentration be 0.4mol/L. The electroless plating solution is obtained after the above two solutions are mixed evenly, and the crystalline silver is put into the electroless plating solution for electroless plating, and the deposition amount of copper is controlled to be 50 mg/g catalyst. After plating, filter, dry and bake at 550°C for 5 hours to obtain a copper-loaded crystalline silver catalyst.

5 grams of catalyst are loaded into a stainless steel reactor with a diameter of 14mm in three layers, and its particle size and weight percentage are (from top to bottom): the first layer 0.2-0.4mm, 20%; the second layer 0.4-1.0mm , 60%; the third layer 1.0-2.5mm, 20%. Put the ethylene glycol aqueous solution into the vaporizer with a metering pump, mix it with the preheated air, and then enter the catalytic bed for reaction after being heated. The liquid hourly space velocity of ethylene glycol is 10hr ^-1 , and the oxygen and ethylene glycol The molar ratio is 0.8, the molar ratio of nitrogen to oxygen is 5, the molar ratio of water to oxygen is 5, the reaction temperature is 450°C, the product is quenched and absorbed by spraying, and the supplementary water amount of spraying is controlled to obtain 40% glyoxal product , the conversion rate of ethylene glycol is 96.2%, the selectivity of methylglyoxal is 73.5%, and the service life of the catalyst is 90 days.

Embodiment 3. Copper nitrate is dissolved in distilled water and is mixed with the solution of 0.1mol/L, then slowly adds ammoniacal liquor while stirring, first generates copper hydroxide precipitation, forms dark blue copper ammonium complex solution after adding excessive ammoniacal liquor , the molar ratio of excess ammonia to copper ammonium ions is 10. Add reducing agent glucose to the above solution, the molar ratio of glucose to silver ammine ions is 9, and mix well to obtain the electroless plating solution. Put the crystalline silver into the electroless plating solution for electroless plating, control the deposition amount of copper to 10mg/g catalyst, filter the catalyst after plating, dry it and bake it at 450°C for 4 hours to obtain the copper-loaded crystalline silver catalyst.

5 grams of catalyst are loaded into a stainless steel reactor with a diameter of 14mm in 5 layers, and its particle size and weight percentage are (from top to bottom): the first layer of 0.2-0.4mm, 20%; the second layer of 0.4-0.6mm , 20%; the third layer 0.6-0.8mm, 20%; the fourth layer 0.8-1.0mm, 20%; the fifth layer 1.0-2.5mm, 20%. Put ethylene glycol into the gasifier with a metering pump, mix with preheated air and water vapor, and then enter the catalytic bed for reaction. The liquid hourly space velocity of ethylene glycol is 30hr ^-1 , and the molar ratio of oxygen to ethylene glycol 1.1, the molar ratio of nitrogen to oxygen is 15, the molar ratio of water to oxygen is 5, the reaction temperature is 550°C, the conversion rate of ethylene glycol is 99.9%, the selectivity of glyoxal is 81.5%, and the service life of the catalyst is 100 days.

Embodiment 4. Copper nitrate is dissolved in distilled water and is mixed with the solution of 0.3mol/L, then slowly adds ammoniacal liquor while stirring, first generates copper hydroxide precipitation, forms dark blue copper ammonium complex solution after adding excessive ammoniacal liquor , the molar ratio of excess ammonia to copper ammonium ions is 5. Add reducing agent hydrazine sulfate to the above solution, its molar ratio to copper ammonium ions is 5, and mix well to obtain an electroless plating solution. Put the crystalline silver into the electroless plating solution for electroless plating, control the copper deposition amount to 20 mg/g, filter the catalyst after plating, dry it, and bake it at 500°C for 3 hours to obtain the copper-loaded crystalline silver catalyst.

Put 5 grams of catalyst into a stainless steel reactor with a diameter of 14mm, inject ethylene glycol into the gasifier with a metering pump, mix with preheated air and water vapor, and then enter the catalytic bed for reaction. The hourly space velocity is 10hr ^-1 , the molar ratio of oxygen to ethylene glycol is 0.9, the molar ratio of nitrogen to oxygen is 10, the molar ratio of water to oxygen is 5, the reaction temperature is 420°C, and the conversion rate of ethylene glycol is 99.8%. The selectivity of glyoxal is 74.3%, and the service life of the catalyst is 80 days.

Claims (8)

1. A copper-supported crystalline silver catalyst for the synthesis of glyoxal by gas phase oxidation, characterized in that it is obtained by depositing a modified amount of copper by electroless plating on the crystalline silver particles, and the copper loading is 1-100mg/g . 2. A method for preparing a copper-supported crystalline silver catalyst as claimed in claim 1, characterized in that the specific steps are as follows: (1) Copper nitrate is dissolved in distilled water, and after being completely dissolved, ammoniacal liquor is added while stirring, and copper hydroxide precipitation is first formed, and blue copper ammonia complex solution is formed after adding excessive ammoniacal liquor; (2) adding reducing agent into distilled water, stirring and dissolving; (3) the above two solutions are mixed to obtain the electroless plating solution; (4) putting the crystalline silver particles into the electroless plating solution for electroless plating; (5) filtering, drying, and then roasting at 400-700° C. for 1-6 hours to obtain a copper-loaded crystalline silver catalyst; In electroless copper plating, the concentration of copper ions is controlled to be 0.05-0.5 mol/L, the molar ratio of free ammonia to copper ammonium ions is 1-10, and the molar ratio of reducing agent to copper ammonium ions is 1-10. 3. The preparation method of copper-supported crystalline silver catalyst according to claim 2, characterized in that sodium hydroxide is added to the electroless plating solution at a concentration of 0-0.5 mol/L. 4. The preparation method of copper-supported crystalline silver catalyst according to claim 2, characterized in that the reducing agent used is formaldehyde or tartrate or hydrazine sulfate or glucose. 5. The application of a copper-supported crystalline silver catalyst as claimed in claim 1 in the synthesis of glyoxal by gas phase oxidation. 6. The application according to claim 5, characterized in that the specific steps are as follows: oxidize ethylene glycol, oxygen, water and inert gas on the catalyst at 400°C-800°C to generate glyoxal, wherein the catalyst The particle size is 0.1-2.5mm; the molar ratio of inert gas to oxygen is not less than 4.4:1, the molar ratio of oxygen to ethylene glycol is 0.7:1 to 1.4:1, and the liquid hourly space velocity of ethylene glycol on the catalyst is 5 -50h ^-1 . 7. The application according to claim 6, characterized in that the silver catalyst is paved in two or more layers according to the particle size, each layer has the same thickness, and the total thickness of the catalyst layer is 10-100 mm. 8. The application according to claim 7, characterized in that the number of catalyst layers is 4, and the particle sizes of the catalyst layers from top to bottom are: 0.2-0.4mm, 0.4-0.75mm, 0.75-1.0mm, 1.0 -2.5mm.