RU2046654C1 - Method for obtaining organic compound and carbonic oxide oxidation catalyst - Google Patents

Abstract

FIELD: chemical industry. SUBSTANCE: method involves impregnating aluminum oxide used as carrier with palladium salt solution; drying and recycling. Palladium tri/diacetate used as palladium salt is preliminarily solved in aqueous solution of sodium acetate taken in an amount of 1-31% by weight. Carrier is impregnated with 0.1-0.5%-solution of palladium tri/diacetate. EFFECT: increased efficiency and high quality of catalyst. 1 tbl

Description

 The invention relates to the production of catalysts based on platinoids and may find application in the chemical and oil refining industries.

A known method of producing a catalyst by impregnating alumina with an aqueous solution of sodium hydroxochloropalladates, followed by drying and activation with hydrogen [1]
The disadvantage of this method is to obtain a catalyst with low specific activity.

 Closest to the invention in technical essence is a method of producing a catalyst ShPK-0.5 [2] The preparation of the catalyst is carried out by impregnating the alumina carrier with an acidic aqueous solution of palladium chloride, followed by drying and reduction with hydrogen or sodium formate.

 The disadvantage of this method is the low specific activity of the catalyst.

 The objective of the invention is to increase the activity of the catalyst while reducing the content of precious metal in it.

 For this, in the method for producing an oxidation catalyst for organic compounds and carbon monoxide, which includes impregnating a γ-alumina support with a palladium salt solution, drying and reduction, palladium tris (diacetate) palladium is used, which is previously dissolved in a 1-31% aqueous solution sodium acetate and impregnation of the carrier are 0.1-0.5% solution of tris (diacetate) palladium.

Pd(OH)OAc+HOAc, которое однако тормозится присутствием в растворе большого количества НОАс, образующихся по реакции:
NaOAc+H-OH

Na⁺ + OH^- + HOAc.The essence of the invention lies in the fact that by the proposed technology it is possible to obtain catalysts with a higher specific activity. Sodium acetate is a salt of weak acetic acid and a strong base. The dissolution of sodium acetate in water leads to a slight increase in the pH of the medium in the range from 6.0 to 7.0 if a solution with 31 wt. concentration. Upon dissolution of [Pd (OAc) ₂ ] ₃ in aqueous solutions of sodium acetate, the trimer acetate bridges break and some hydrolytic cleavage of the terminal acetate groups occurs: Pd (OAc) + H-OH

Pd (OH) OAc + HOAc, which, however, is inhibited by the presence in solution of a large amount of HOAc formed by the reaction:
NaOAc + H-OH

Na ⁺ + OH ^- + HOAc.

 This is confirmed by the fact that the impregnating solutions are stable in time, including at the boiling point. Acetic acid, released as a result of partial hydrolysis of palladium acetate, leads to a certain decrease in the pH of the impregnating solution and provides the formation of a buffer system: a weak acid salt is a weak acid. The presence of a buffer system prevents the impregnation solution from abrupt changes in pH during the impregnation of the support, which could lead to a change in the structure of the catalyst precursor and even to the precipitation of palladium hydroxide.

The lower the concentration of [Pd (OAc) ₂ ] ₃ , the more hydrolyzed and the more HOAc enters the solution, the greater the buffer capacity of the system and the less likely the pH will change during the carrier impregnation.

 The pH of the solutions was measured using an EV-74 ionometer. The palladium content in the obtained samples is determined by the colorimetric method.

The obtained catalysts were tested for activity in the oxidation reaction of carbon monoxide according to the standard method described in TU6-09-5531-85 (industrial catalyst ShPK-1), as well as in the oxidation reaction of organic compounds of benzene in a flow-through unit, volumetric speed 15000 h ^-1 , the initial concentration of benzene in the air is 350-400 mg / m ³ .

Example 1. 989 g of distilled water was placed in a flat-bottomed flask and 10 g of NaOAc was added to the resulting solution, while stirring, 1.05 g of [Pd (OAc) ₂ ] _{3 was} added. The mixture was heated to 90 ^{° C} and stirred until complete dissolution of palladium salts (approximately 2 hours). pH of NaOAc solution 6.90 pH of solution [Pd (OAC) ₂ ] ₃ 6.90
To the impregnating solution, add 1000 g of the carrier γ-Al ₂ O ₃ , previously dried at 200 ^about C for 2 hours

After impregnation, the end of which is determined by the complete discoloration of the impregnating solution (6-8 hours), the catalyst is separated from the solution by decantation. The catalyst was dried at ¹⁸⁰ ° C for 2 hours, then reduced with sodium formate at 60-80 ^{° C} until complete reduction of palladium (about 2 hours). The reduced catalyst was washed until neutral wash water and dried at ¹⁸⁰ ° C for 2-3 h. The pH after impregnation solution 6.90. The palladium content in the catalyst sample is 0.05 wt. The degree of conversion of benzene 99.5 is achieved at 327 ^about C. The degree of conversion of carbon monoxide 75 wt. achieved at 175 ^about C.

PRI me R 2. 838 g of H ₂ About placed in a flat-bottomed flask and add 160 g of NaOAc. 2.1 g of [Pd (OAc) ₂ ] ₃ are added to the resulting solution with stirring. The mixture was heated to 90 ^{° C} and stirred until complete dissolution of palladium salt. pH of NaOAc solution 6.90 pH of solution [Pd (OAc) ₂ ] ₃ 6.90
To the resulting solution, add 1000 g of the carrier (γ-Al ₂ O ₃ ) and prepare the catalyst, as described in example 1. The pH of the solution after impregnation of 6.90. The palladium content in the sample is 0.10 wt. The degree of conversion of benzene 99.5 is achieved at 330 ^about C, the degree of conversion of carbon monoxide 75 wt. achieved at 155 ^about C.

PRI me R 3. 686 ml of N ₂ About placed in a flat-bottomed flask and add 310 g of NaOAc. 4.2 g of [Pd (OAc) ₂ ] ₃ are added to the resulting solution with stirring. The mixture was heated to 90 ^{° C} and stirred until complete dissolution of palladium salt. pH of NaOAc solution 7.0 pH of solution [Pd (OAc) ₂ ] ₃ 6.93
To the resulting solution add 1000 g of carrier and prepare the catalyst, as in example 1. The pH of the solution after impregnation of 7.00. The palladium content in the sample is 0.20 wt.

The degree of conversion of benzene 99.5 is achieved at 310 ^about C, the degree of conversion of carbon monoxide 75 wt. achieved at 115 ^about C.

 Comparative data on the activity in the processes of carbon monoxide oxidation of catalyst samples obtained in examples 1-3 and an industrial analogue (prototype) are given in the table.

 The table shows that the samples synthesized by the proposed method are superior in activity to the industrial analog of ShPK-0.5 and contain 2.5 times less active component of palladium.

 Thus, the proposed method allows to obtain catalysts with increased activity in the oxidation reactions of organic substances and carbon monoxide. The method of preparation of the catalyst is simple due to the fact that concentrated acids are not used in the preparation of the impregnating solutions, as well as the absence of toxic emissions into the atmosphere.

Claims (1)

 METHOD FOR PRODUCING AN ORGANIC COMPOUNDS OXIDATION CATALYST AND CARBON OXIDE, comprising impregnating γ-alumina support with a palladium salt solution, drying and reducing, characterized in that palladium tris (diacetate) palladium is used, which is previously dissolved in 1 31% aqueous a solution of sodium acetate, and the carrier is impregnated with a 0.1 - 0.5% solution of tris (diacetate) palladium.

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