SU540554A3 - Silver catalyst for the oxidation of organic compounds - Google Patents

Description

one

This invention relates to silver catalysts for the oxidation of organic compounds, in particular for the production of ethylene oxide.

A known catalyst for the oxidation of organic compounds containing 19.5%. silver on a porous material, such as alumina.

A disadvantage of the known catalyst is the high operating temperature and low selectivity, in particular in the oxidation of ethylene to ethylene oxide due to the large size of the sebrum particles (2-4 microns) and their unevenness in shape.

In order to eliminate these drawbacks, namely, to reduce the working temperature and increase the activity, a catalyst has been proposed with a content of 2-15% by weight of silver in the form of uniformly arranged semi-pyramidal particles with a diameter of 0.1-1 μm, preferably 0.3 μm, on a porous carrier, preferably a-oxide

aluminum with the following characteristics: specific surface area 0.03-1.0 mg / g, preferably 0.15-0.6 mg / g, apparent porosity 42-56%, preferably 46-52%, average pore diameter 1-12 μm, of which not less than 70% of the size of 1.5-15 μm, the specific pore volume of 0.2-0.3 cm / g, preferably 0.22-0.28.

The proposed catalyst has a working temperature of 210-240 ° C and a degree of oxygen conversion of 73-78% in the oxidation of ethylene to ethylene oxide.

Example. Preparation and properties of catalysts.

Four types of cylindrical rings with a height and an outer diameter of 8.0 mm and an inner diameter of 3.0 mm with the following properties are used as carriers.

Media materials

Specified surface area

Specific pore volume, cm / g

Average pore diameter, μm Percentage of pores having a diameter of 1.5–15 μm Percent Number of pores with a diameter of 2–40 μm Apparently with porosity,% Content, wt.%: A-alumina, silicon dioxide (oxides of other metals

 Including 0.27 wt.% Barium oxide.

The required amount of a carrier consisting of such rings is pierced with a solution of silver salt, and the rings are wholly filled with the solution. A more complete filling of the pores is possible due to the use of vacuum. The impregnated material is heated in a furnace using a stream of hot air. In this case, the solvent is first removed, then a reduction reaction occurs, towards the end of which only silver remains on the surface of the carrier, as well as on the inner surface of the pores.

Special conditions in the manufacture of various catalysts are given in Table. 2. For the limits of temperature change, the initial and final values are given, in between which constant heating is carried out.

The solutions listed in the table are prepared as follows.

Solution 1. Silver oxalate, ammonia, eganolamine.

2A-5556

SA.-101

2 A-956

ZAr4n8

0.35

0.6

0.24 0.17-0.24

0.31

0.25

0.19 4.4

: 25 2.5

5.7

81

47

90

48-49

0-44

38-47

99.3

99.3

93.5

93.4 0.4 0.4 5.3 8.5 1.1 1.2 0.3 0.3

Silver oxalate is precipitated from an aqueous solution of silver nitrate by means of potassium oxalate (pure analytical grade), diluted five times with deionized water and dissolved in an aqueous ammonia solution of 80% concentration. The resulting solution of Ag (NH,) j, Cjb, j, 48 mol%) is mixed with ethanolamine in such a way that the ethanolamine concentration is 10 vol.%, I, which corresponds approximately to 0.5 mol of ethanolamine per 1 mol of silver .

Explanation 2. Silver oxalate, ammonia, ethanolamine.

Prepared as indicated for the preparation of solution I, with the difference that the molar ratio between cejpe6poM and ethanolamine is 1: 1.

Solution 3. Silver oxalate, ammonia, ethanolamine.

Prepared as indicated in the preparation of solution 1, with the difference that the molar ratio between silver and ethanolamine is 1: 1.5.

Table 2

Proposed

ZA-956 ZA-5556 ZA-101

ZA-5556 ZA-5556 Z A-555 6

ZA-55.6

6.1

0.2-0.4

4 4 4 4 4 4 4

7.3 0.1-0.3 7.2

0.2-0.5 3.1

2 3 4 0.1-0.5 3.0 0.1-0.5 3.6 O, -0.5 3.6 0.1-0.5

Ra with TV op4. Silver oxalate, ammonia, ethanolamia.

Prepared as indicated when preparing solution 1

with the difference that the molar ratio between silver and ethanolamine is 1: 2.

Explanation 5. Silver oxalate, ethylenediamine, ethanolamine.

A pure solution of silver oxalate, prepared as for solution 1, is dissolved in an aqueous solution containing 14.2 mol / l of ethylenediamine (ED) by means of calculation to obtain a solution containing 2.05 mol / l. Continuously with this solution, as in solution 1, ethanolamine is added in an amount of 10% by volume.

Solution 6. Silver carbonate, ethylenediamine, ethanolamine.

Silver carbonate is dissolved in ethylene diamine water solution so as to obtain a solution containing 4.5 mol / l of silver, and the molar ratio between ethylene diamine and

silver, should range from 1.2 to 1.1. Then 0.4 mol of ethanolamine per mole of silver is added. The finished solution has a concentration of 0.4 mol / l of silver.

Solution - silver lactate, ethylenediamine, ethanolamine;

 PacTBOpS - silver acetate, etipenediamine ethanolamine;

Mortar9 - silver gluconate, ethylenediamine, ethanolamine;

Solution - citrate; silver, ethylene diamine, ethanolamine.

Solutions -10 are prepared analogously to solution 6, only changing the silver salt.

Solution 11- Silver oxalate, ammonia, ethylene diamine.

The method of preparation is the same as for solution I, with the difference that instead of 10% by volume of ethanolamine, 10% by weight of ethylenediamine is added.

Solution 12. Comparative catalyst: silver nitrate.

Silver nitrate is dissolved in water so as to obtain a 53% solution.

Solution 13. Comparative catalyst: silver oxalate and ammonia.

The method of preparation is the same as for solution 1, with the difference that no ethanolamine is added. The prepared solution contains silver oxalate 2.24 mol / l and ammonia 5 mol / l.

Listed in table. 2, after the silver is diluted with silver, catalysts Chi and X are dried at 110 ° C, then reduced by heating at 220 ° C in a stream of hydrogen gas.

All catalysts are examined with an electron microscope. In the proposed catalysts, silver is evenly spaced along the surface of the carrier in the form of semicircular particles that are firmly attached to the surface, and the pore diameter of the carrier is within narrow limits. In contrast, catalysts of types X and X are characterized by the presence of large, rather uneven silver bands with an average diameter of about 2-3 microns. The strength of adhesion of silver with the carrier in this case is worse. The average particle diameter of silver exceeds 1 micron.

These catalysts can be characterized by the ratio of the average pore diameter to the average diameter of the silver particles. For catalyst B, this ratio is 17.6.

Example 2 Comparison of catalysts in the production of ethylene oxide in their presence.

The catalysts described in example 1 are tested in the reaction of synthesis of ethylene oxide.

The reaction is carried out by passing the reactive substances through a different 12.5 cm tube with an inner diameter of 0.5 cm, ir || 1, the permeable gas mixture contains ethylene, air and a small amount of mo &

deratora (Arohlor). Rings of mm (5/16 in.) To which the catalyst was applied are crushed to a size of 30-40 mesh. The amount of catalyst in the tube is 3.5 tons. 6Conditions of the reaction.

Pressure abs. atm.15

Productivity, hour 2360

Ethylene co)

feed mixture, mol.% 30

The ratio between ethylene

and oxygen in the feed mixture of 3.75: 1

Chlorine content (due to

presence, - Arochlora in composition

feed mixture), million units, Z

In assessing the applicability of catalysts, the selectivity of the formation of ethylene oxide as a target, a product from ethylene or oxygen reacted, referred to as S (Et) or SCOj and the percentage of conversion per pass, hereinafter referred to as C (Et ) or C (0j).

When conducting experiments corresponding to this example, the degree of conversion is taken as an independent variable, and the reaction temperature (T) and selectivity serve as dependent variables. The standard degree of conversion (%) of C (02) 40 and then the values of T. S S (02) corresponding to it are determined. The experiments are carried out in such a way that T rises until C / 02 reaches 40. The T value is considered as a criterion for evaluating the activity of the catalyst (the lower the temperature, the higher the activity will be). Value 8 (02) is a measure of the effectiveness of a catalyst.

The results of experiments conducted with various catalysts are compared in Table. 3

Table3