SU1255200A1 - Method of recovery of silver catalyst - Google Patents

Description

The invention relates to methods for regenerating a silver catalyst for the oxidation of ethylene to ethylene oxide.

A known method for regenerating a catalyst for the oxidation of ethylene by treating a spent silver catalyst with aqueous-alcoholic solutions of cesium and rubidium salts. After removal of the solvent, the regenerated catalyst contains 0.02 wt.% Cesium (German patent No. 2611856, class B 01 J 23/96, published 1977).

The known method of regeneration of silver25

thirty

A catalyst for the oxidation of these 15-ethylene to ethylene oxide is leached by washing it with water followed by treatment with alkali metal salts — cesium, potassium, and sodium — in an organic solvent so that the amount of alkali metal ions reaches A 8 -10 g g-eq / kg of catalyst (German application No. 2746976, class B 01 J 23/50, published in 1978).

The method of catalyst regeneration for the oxidation of ethylene is known by moistening the catalyst with water and drying it at 100-300 ° C (German Application No. 2709306, class B 01 J 23/96, published 1977).

A known method of regenerating a catalyst for the oxidation of ethylene by treating it with oxygen at 200-400 ° C and a pressure of 0.1-100 bar in the presence of an inert gas (British Patent No. 1544081, class B 01 J 23/96, published in: liquor 1979) .

These methods are effective for some types of catalyst passivation, mainly for carrying out regeneration on a laboratory scale.

However, the presence of large amounts of oxygen in industrial reactors, mainly at high non-adsorbed amounts of organic substances, not only does not increase the activity and selectivity of the catalyst, but can even lead to irreversible deactivation or change the reversible passivation of the catalyst to irreversible. Moisturizing the catalyst is practically ineffective and can contribute to its more rapid mechanical wear.

The aim of the invention is to increase the efficiency of the method.

high efficiency, mainly the elimination of catalyst poisoning with hydrocarbons C and higher sulfur compounds, and

20 degrees, irreversible changes in the catalyst are prevented. In addition, there is the possibility of carrying out catalyst regeneration directly in the catalytic beds of industrial reactors, and this concerns a short regeneration time and the safety of such regeneration. Moreover, the method makes it possible to reduce the irreversible poisoning of the catalyst, as well as after carrying out regeneration, to produce with a higher effect the activation of the catalyst by treatment with alkali metal salts and other compounds, which in other cases

35 could be practically ineffective.

The catalyst is regenerated in a relatively wide pressure range, and in most cases it is more convenient to operate at pressures lower than those used in the synthesis of ethylene oxide. Thus, you must first work with a low total pressure, and then gradually increase it. Investigator40

45

however, the total pressure can be from 0 kPa to 1.5 MPa.

The temperature of the catalyst during regeneration should be within 200-.

Regeneration can be carried out even under high vacuum, but the most suitable from the technical and economic point of view 55 is the range of easy attainment of pressure. Atmosphere can create a synthesis gas that does not contain oxygen, but in this case it is necessary as

This goal is achieved by a silver catalyst regeneration method for the oxidation of ethylene to ethylene oxide, which consists in heat treating the catalyst at 200-315 s and a pressure of 0 kPa to 1.5 MPa in a synthesis gas atmosphere or a synthesis gas atmosphere with the addition of a corrosive substance - molecular chlorine or oxide and nitrogen dioxide in the amount of 1-10 - by weight of the catalyst.

The advantage of the method of regeneration of the silver catalyst for the oxide

neither ethylene to ethylene oxide is

high efficiency, mainly the elimination of catalyst poisoning with hydrocarbons C and higher sulfur compounds, and

irreversible changes in the catalyst are prevented. In addition, there is the possibility of carrying out catalyst regeneration directly in the catalytic beds of industrial reactors, and this concerns a short regeneration time and the safety of such regeneration. Moreover, the method makes it possible to reduce the irreversible poisoning of the catalyst, as well as after carrying out regeneration, to produce with a higher effect the activation of the catalyst by treatment with alkali metal salts and other compounds, which in other cases

could be practically ineffective.

The catalyst is regenerated in a relatively wide pressure range, and in most cases it is more convenient to operate at pressures lower than those used in the synthesis of ethylene oxide. Thus, you must first work with a low total pressure, and then gradually increase it. Investigator

however, the total pressure can be from 0 kPa to 1.5 MPa.

The temperature of the catalyst during regeneration should be within 200-.

Regeneration can be carried out even under high vacuum, but the most suitable from a technical and economic point of view is the range of ease of pressure. Atmosphere can create a synthesis gas that does not contain oxygen, but in this case it is necessary as

a lower pressure can be applied in order to prevent oxidation other than the oxidation of ethylene to ethylene oxide, also organic components adsorbed on the catalyst, and thereby catalyst overheating and agglomeration of silver particles. Therefore, it is necessary to work with synthesis gas, which is almost free of oxygen, containing ethylene, nitrogen, argon, carbon dioxide, methane, ethane, and controlled chemicals of organochlorine compounds or other inhibitors. Such organochlorine compounds can be tetrachloroethane, dichloroethane, vinyl chloride, trichlorethylene. By the inert gas of the best-known inert gases is also meant the gases which, under the specified reaction conditions, behave as inert, therefore methane and ethane are also included. Corrosive substance is a separate gas or mixture of gases,

- a mixture of gases and vapors is possible, which, at a regeneration or reactivation temperature, can attack not only the catalyst or its silver and other active components, but also help to remove other metals that are an undesirable component of the poisoned catalyst and that have fallen on it with raw materials or as a result equipment corrosion. Thus, the corrosive substance allows

It is possible to rid the catalyst of catalyst poisons or to raise the surface of silver particles as much as possible.

Such corrosive substances are oxides of nitrogen - oxide or dioxide.

The amount of corrosive substance must be controlled, since an excessive amount may temporarily reduce the activity of the catalyst. In addition, a corrosive substance can be used in controlled amounts not only in the reactivation or regeneration of the catalyst, but in much smaller amounts as an impurity in the feedstock or otherwise directly into the reactor with the catalyst in the manufacture of ethylene oxide.

Example 1. Into the laboratory test apparatus, 0.5 g (0.4 cm) of silver catalyst with a content of 9.2 wt.% Silver per al; 0

50

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fa-aluminum as a carrier. The size of the catalyst is O, 5–0; 63 mm, and it is a question of a catalyst prepared by crushing a poisoned catalyst, the activity of which has decreased by approximately one fifth during two years of use. This catalyst, heated to the desired reaction temperature, is first supplied with a reaction gas containing,% by volume: oxygen 7, ethylene 39, carbon dioxide 4, nitrogen with argon 50, at a space velocity of 900 h. Then, at a pressure almost close to atmospheric (100 kPa), the temperature gradually increases, and at the same time the conversion and selectivity of ethylene to ethylene oxide are determined with one pass of the catalyst.

The results of the effect of heating on the conversion of ethylene and selectivity to ethylene oxide as a function of temperature are shown in FIGS. 1 and 2 (curve 1).

After completing these measurements, the reaction gas, freed from oxygen (below 1 vol.%), Is supplied to the catalyst at 220 ° C for 20 hours at a volumetric rate of 900. Then, after rinsing with nitrogen, the reaction gas of the specified composition (7 vol.% 0, 39 vol.%, 4 vol.% COg, the residue is nitrogen) is added, while the conversion of ethylene and the selectivity to oxide increases. ethylene, as can be seen from the results of the influence of temperature on Figures 1 and 2 (curve 4).

Example 2, the regeneration of the catalyst specified in Example 1 is carried out in a stream of nitrogen containing 0.1% by volume of carbon dioxide and 0.15% by volume of oxygen at 220 s and a pressure of 100 kPa for 20 hours at a space velocity of 1000 . After this time, the temperature is reduced. activity test The results obtained (using the reaction gas specified in Example 1) of the conversion of ethylene in one pass through the catalyst and the selectivity to ethylene oxide are graphically depicted in Figures 1 and 2 (cr 2).

Example 3: Regeneration of a silver catalyst on alpha-aluminum as the carrier specified in Example 1 is carried out in current.

a reaction gas, also specified in example 1, at a pressure of 100 kPa for 2 hours and a space velocity of 900. The reactor flow with the catalyst is cooled to 220 ° C and using a reaction gas consisting,% by volume: oxygen 7-, ethylene 39, carbon dioxide 4, nitrogen mixed with argon 50, a temperature test of its activity is carried out.

The results obtained, depending on the temperature, are graphically shown in figures 1 and 2 (curve 5). Obviously, there is a significant increase in the activity of the catashiser, as evidenced by a significant increase in the conversion of ethylene and the selectivity of the transition of ethylene to ethylene oxide.

Example 4. The catalyst specified in example 1, first, at 2 ° C, the temperature is gradually reduced to

   ethyl oxide production temperature

they are heated to the current of the reaction gas specified in Example 1. At this temperature and a space velocity of 900, conversion of ethylene and selectivity to ethylene oxide 25, shown in Figures 1 and 2 (curve 1), is achieved. Then, gaseous molecular chlorine is added to the reaction gas stream directly in front of the reactor by a single injection in a quantity of 0.0020 mass% (calculated on the weight of the silver catalyst). After that, the catalyst still remains in the flow of the reaction gas released from

At 215 G, while at the time of decreasing the temperature, the pressure in the circulation area is adjusted to 1.7 MPa and the concentration of ethylene is adjusted to 30 mol%. After reaching a temperature of 215 ° C and a gradual addition of oxygen, the synthesis of ethylene oxide begins, depending on the oxygen concentration at the outlet of the reactor, at 4.5 mol%.

On the catalyst regenerated in this way, a 97% yield of ethylene oxide, achieved on a new catalyst, reaches a selectivity with respect to ethylene oxide of 75.6%.

oxygen, at a space velocity of 900 for 20 hours. After this time, the activity of the catalyst is measured. .

The results obtained are graphically depicted in FIGS. 3 and 4 (curves 3, 1 represent the reference results on the catalyst without regeneration).

Example 5. The regeneration of the poisoned silver catalyst, 45 specified in Example 1, is carried out in the same manner as in Example 4, but a mixture of oxide and nitrogen dioxide in an amount of 0.002% by weight is used instead of chlorine. on the mass of the catalyst. 50 The activity of the catalyst is greatly enhanced, as can be seen from the graphical

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5 shows the results in FIGS. 3 and 4 (curve 6),

 Example In a semi-production reactor producing ethylene oxide by directly oxidizing ethylene and using the catalyst specified in Example 1, the catalyst is regenerated so that the pressure of the tubular reactor with catalyst is maintained at 0.7-1.5 MPa. synthesis gas whose oxygen was reacted. The composition of the gas, mol.%: Ethylene 30, carbon dioxide 5, methane with ethane 44, argon 4, nitrogen residue, and this gas contains traces of organochlorine compounds in the amount of total t, chlorine retention 5-10 wt.%. The reaction temperature for 4 h is maintained at a value of 240-260 C. Then

-ABOUT,

At 215 G, while at the time of decreasing the temperature, the pressure in the circulation area is adjusted to 1.7 MPa and the concentration of ethylene is adjusted to 30 mol%. After reaching a temperature of 215 ° C and a gradual addition of oxygen, the synthesis of ethylene oxide begins, depending on the oxygen concentration at the outlet of the reactor, at 4.5 mol%.

On the catalyst regenerated in this way, a 97% yield of ethylene oxide, achieved on a new catalyst, reaches a selectivity with respect to ethylene oxide of 75.6%.

PRI me R 7. The catalyst specified in Example 1 was first heated to 200 ° C in a stream of reaction gas specified in Example 1 at a pressure of 0.1 kPa. Then, gaseous molecules were added to the current of the reaction gas directly in front of the reactor. In a semi-continuous 110 wt.% chlorine (calculated on the weight of the silver catalyst), the activity of the catalyst was measured for 16 hours. At 280 ° C and a space velocity of 900 pg, ethylene conversion is achieved — at one pass through the catalyst, 5.5%, and selectivity with respect to ethylene oxide is 60%.,

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Editor G. Volkova

Compiled by N.Putov

Tehred A. Kravchuk Proofreader S. Cherni

Order 4743/7 Circulation 527 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Project, 4

Claims (1)

METHOD FOR REGENERATING SILVER CATALYST FOR oxidizing ethylene to ethylene oxide by heat treatment at 200-315 ° С and increased pressure in a gaseous medium, which is necessary in order to increase the efficiency of the method, heat treatment is carried out at pressure from 0.1 kPa to 1.5 MPa in the atmosphere of synthesis gas or in the atmosphere of synthesis gas with the addition of a corrosive substance -. molecular chlorine or oxide and dioxide in the amount of 1Ί0 ' ⁵ 2Ί0 ³ % by weight of the catalyst. 1255200 2