DE2237188C3 - Continuous process for the production of ethylene oxide - Google Patents

Description

20th

JO

The ethylene oxide has a high reactivity and is therefore a valuable raw material for Production of various polymeric materials, biological and physiological agents, various Aggregates, additives, surface-active substances and a valuable monomer for the production of Intermediate products (semi-products) of organic and petrochemical synthesis.

It is a process for the production of ethylene oxide by direct oxidation of ethylene by air or known pure oxygen in the stationary layer of a silver catalyst on a support. It will be in Apparatus of the tube type carried out (see the book "Äthylenoxid", Verlag "Chimija", Moscow, 1967, Pages 227 - 234, in Russian).

The process is carried out in tubes filled with the catalyst, while the heat dissipation medium circulates in the space between the tubes. The yield of ethylene oxide in one pass is 25 to 30% by volume, based on the ethylene passed through, and 55 to 60% by volume, based on the ethylene converted. The concentration of ethylene oxide exceeds 1 vol .-% and the volume of ethylene oxide per liter of catalytic converters _b 5 tor per hour 80 to 120 g not.

The main disadvantage of this process is that it is not isothermal and the oxidation of Ethylene is difficult to control and monitor. The uneven distribution of the raw material in the numerous tubes and the low coefficient of heat transfer of the immovable layer bothers the course of the desired reaction under optimal conditions, thereby reducing the yield of ethylene oxide sinks

Another disadvantage of the known process is the poor utilization of catalyst and raw material, whereby the performance of the existing systems is restricted (the performance of the individual aggregates of the tube type does not exceed 10 to 15 thousand tons of ethylene oxide per year). That known method requires a structurally complex, metal-intensive reaction apparatus, the Number of tubes reached 10,000

The process described in DE-PS 10 68 684 consists in the pneumatic application of a huge amount of powdered catalyst with the reaction gas in the reaction zone, the ratio of gas mixture: catalyst = 1:20 to 1: 400. For example, the amount of catalyst participating in the reaction in Example 1 is 720,000 kg at an output, based on the reaction mixture, of 2490 nm ³ / h, the ethylene concentration in the mixture being 4% by volume (the mixture consists of 100 nm ³ ethylene and 2390 nm ³ air).

The yield of ethylene oxide is 70% of theory per 4% by volume of ethylene.

Because of the two simultaneous reactions

C ₂ H ₄ + 1 / 2O ₂

C ₂ H ₄ + 2O ₂

C ₂ H ₄ O

2H ₂ O + 2CO ₂

arise from 56 gramol ethylene and 48 gramol O ₂ , ie from 104 gramol reactants theoretically 44 gramol ethylene oxide. The 70% ethylene oxide given in the PS thus constitutes 30.8 gram mol. For every 104 grams of reactants consumed, 30.8 grams of ethylene oxide are produced, which makes up a total of 29.5% and, based on ethylene, 55%.

In the process proposed according to the invention, with an ethylene concentration of the mixture of 3.1 to 3.3% by volume (Examples 1 and 2), the ethylene oxide concentration reaches 1.95 to 2.15%, based on ethylene 62 to 65.7%. The reactor is charged at an output of 3000 nm ³ / h reaction mixture (compared to 2500 nm ³ ) with 0.4501 catalyst (compared to 720 t), which is 1600 times below the value of the German patent.

If one therefore proceeds from the one-time charging of 720 t of expensive Ag catalysts listed in the DE-PS from, the operating expenses are around one compared to the method proposed according to the invention Many times higher, which has a very negative effect on the economy of the entire process.

The process of US Pat. No. 2,600,444 is a fluid process that operates at a rate of the gas catalyst stream from 0.3 to 0.7 m / sec, a convact time of 3 to 4 seconds and a temperature of 220 to 260 ° C is carried out. The volume ratio of ethylene: oxygen = 1: 0.7 must be strictly adhered to.

(1 part by volume of 0.4 to ₁ J O by volume) specified: in fact is a large ratio range O2 ethylene in the reaction mixture.

However, if one assumes the ethylene: O2 volume ratio in the reaction mixture = 1: 0.7 and an ethylene content in the ethylene fraction of 80% and O ₂ with 98% purity, the theoretical concentration of ethylene, O ₂ and Methane-ethane-H ₂ mixture in each case 50.8% by volume, 35.7% by volume and 13.5% by volume - ⁰ zo. Such a composition of the reaction mixture corresponds to all known reaction areas of explosive ethylene-O ₂ mixtures.

In mixtures containing high ethylene _{concentrations, the O 2} concentration should be adjusted so that the ratio to ethylene is 1: 7 (see Okis etilena, Chimija, M, 1967, pp. 235-236).

According to other literature, the O ₂ content in a system of ethylene, O ₂ , H ₂ , methane and ethane fluctuates, depending on the process conditions, in a range from 5 to 8% by volume (see Chimija i technologija organitscheskich proizvodstv, p. 803-805).

As for the yield of ethylene oxide (78%), even assuming that a _{mixture containing 50.8% ethylene and 35.7% O 2} is real, it is practically impossible to obtain such a yield because of the equation

C ₂ H ₄ + 1 / 2O ₂

C ₂ H ₄ O

WC ₂ H ₄ O = K,

WCO ₂ = K ₂

C-OAS ^ C ₂ II ₄

. C.

.0.5

ι, ι

10

15th

25th

by the oxidation of this mixture at 100% conversion and 100% selectivity, the amount of the Ethylene oxide obtained from the contact gas is 68% compared to the US Pat.

Based on what has been said, the ethylene concentration and oxygen concentration in the total mixture 15 and 10.5% by volume, respectively. The remaining 74.5% is an inert gas containing methane, ethane, H and others. The from many researchers (Tweeg, Margolis, Roginski, Maksted, Schwab and Ashmor) performed kinetic Investigations into the direct oxidation of ethylene on an Ag catalyst have led to the following Equations led:

30th

35

45

50

On the basis of these equations it can be determined that the order of magnitude of the oxidation of ethylene to ethylene oxide and to CO _{2 has a} partial character. In the case of oxidation of ethylene to oxide, the order of magnitude, based on ethylene, is 0.45 and on O ₂ 0.5 mol, corresponding to the formation of CO ₂ 0.3 and 1.1.

A complete conversion of the ethylene to ethylene oxide is therefore not possible. With 100% conversion of the ethylene under harsh conditions, ie at a temperature of 400 ° C. and above, the reaction shifts in the direction of CO ₂ , since the activation energy of this reaction is considerably higher than the activation energy of the final reaction. In addition, under the conditions mentioned, practically not only all of the ethylene but also the ethylene oxide formed converts to CO ₂ .

On the basis of what has been said and numerous publications, it can thus be clearly stated that the incomplete oxidation of ethylene and other hydrocarbons, practically no more than 70 to 80% hydrocarbons take part. In addition, the O content of the mixture with HC substances severely restricted by the explosiveness of these mixtures

Based on the equations given, the ethylene content in the starting mixture is 15% by volume and the O content 10.5%. Under these conditions it is practically impossible to do the things stated in US-PS 78% Ethylenoid to be obtained.

Apparently this is the total conversion of ethylene.

The following should also be noted regarding the implementation conditions of the process in US Pat. No. 2,600,444:

The control of the temperature in the reaction zone by supplying cold catalyst is very ineffective, because due to the fluid process with the defects adhering to it and the mixing of the Gas catalyst mixture in the longitudinal and transverse directions does not have a uniform temperature in the layer can be achieved, which inevitably leads to temperature gradients, Nfcbenreaktionen and reduction of Ethylene oxide yields leads. This considerable deficiency of the fluid processes is also addressed in the DEPS 10 68 684 pointed out.

The heat exchanger surfaces, lines for the transport of the catalyst (8,24) for the circulation of the cold Catalyst from zones (4,21) into zones (3,20), the narrowing of the apparatus (22) and the change in direction of the currents, etc. lead to a Disturbance of the gas dynamics of the layer and mean considerable catalyst and metal wear.

The permissible flow velocities inherent in the fluid processes are 0.2 to 0.7 m / sec depending on the catalyst.

In the method proposed according to the invention, the flow velocity reaches 10 m / sec. the The performance of a single unit exceeds the corresponding values of the known many times over Process, which means a considerable increase in economic efficiency.

On the other hand, the performance of the catalyst in the fluid process is 120 to 200 g / l catalyst. In the invention proposed method, however, this value is due to the improvement of the mass exchange between the catalyst and the gas and carrying out the reaction in the two with each other combined reactors 800 g / l h, d. H. it is 4 to 6.5 times higher.

The purpose of the present invention is to eliminate the disadvantages mentioned.

The invention was based on the object, the principle of contact of the ethylene / air mixture with the catalyst in the process of producing ethylene oxide to change that in direct Oxidation of ethylene by atmospheric oxygen in the presence of a silver catalyst on a support consists.

As can be seen from the preceding claims, the set object has been achieved.

By changing the contact principle of the phases, one achieves uninterrupted contact of the ethylene / air mixture with the entire surface of the catalyst, resulting in a high degree of Conversion of ethylene in the target direction leads.

Since the speed of the ethylene / air mixture in the ascending stream is the speed of the Catalyst by 2 to 2.5 times and in that

descending stream of the catalyst its falling speed the speed of the ethylene / air mixture, that is fed in countercurrent to the catalyst by twice as much is the Catalyst in a unit of time in constant contact with fresh raw material, which increases the The speed of the target reaction causes the oxidation of ethylene is an exothermic reaction. the high speeds of the ethylene / air mixture and the catalyst cause a momentary Heat transfer between phases, eliminating the possibility of hot spots forming, which is the Carrying out the reaction under isothermal conditions enables this, in turn, also leads to an increase in the speed of the main reaction. Thus it makes the method of the invention possible to increase the yield of ethylene oxide more than twice compared to known processes, while by using the ethylene / air mixture at the same time as a means of transport ζίγπ lifting the Catalyst eliminates the need to use a special means of transport.

In addition, the method according to the invention is simple in terms of its technological design.

It is done as follows:

The ethylene is mixed with the air heated to 300 ° C up to a total concentration in the ethylene / air mixture of 3.15 to 3.30% by volume. The mixture obtained is fed to the mixer for mixing with microspherical catalyst on a support and its concentration in the mixture is brought to 130 to 160 kg / m ³ , after which the ethylene / air mixture at a speed of 10 to 12 m / s together the catalyst, the speed of which is 4 to 6 m / s, is fed in an ascending flow for the oxidation of the ethylene to the first reactor, which is an ascending flow reactor.

The reaction takes place at a temperature of 290 to 300 ° C and a contact time of the ethylene / air mixture with the catalyst of 1.26 to 1.42 seconds. The reaction products are passed together with the catalyst into a separator in which the reaction products are separated from the catalyst. The reaction products mentioned, the ethylene oxide, unreacted ethylene and carbon ^ dioxide contained are led out from the system and directed to separation, while the catalyst passes under the action of its own gravity into the second reactor is a reactor with descending catalyst stream. A mixture of the unreacted ethylene separated from the reaction products of the first reactor and the air heated to a temperature of 300 ° C. is fed to this reactor in countercurrent to the catalyst at a speed of 5 m / s, which is preferably used to increase the yield of the end product Adding ethylene until it reaches its concentration in the ethylene / air mixture of 2.00 to 3.50% by volume.

In said second reactor the oxidation at 260 to 280 ° C, a contact time of the _b o ethylene / air mixture with the catalyst of 1 second and a concentration of the catalyst in said mixture from 70 to 80 kg / m ³ is performed.

The reaction products are led out of this reactor _h <- and passed to the separation.

The catalyst is poured into the mixer, mixed again with the ether / air mixture and the mixture obtained is fed back to the first reactor, whereby the circulation of the catalyst, d. H. the continuity of the process is achieved.

In order to better understand the present invention, the following specific examples are given in which the conditions for carrying out the process are indicated for each of the reactors.

example 1

Ethylene is mixed with the air heated to a temperature of 300 ° C until its total concentration in the ethylene / air mixture of 3.15% by volume is achieved and it is passed along with the silver catalyst on the support, the concentration of which is 135 kg / m ³ , in an ascending stream into the first reactor, the speed of the ethylene / air mixture being 12 m / s. The speed of the catalyst is 6 m / s, the contact time of the ethylene / air mixture with the catalyst 1.26 seconds, the reaction temperature 290 ° C. Oxidation occurs, through which a reaction mixture is obtained which contains ethylene oxide, carbon dioxide and unreacted ethylene contains. The mixture obtained is separated from the catalyst and discharged from the separation system, while the catalyst enters the second reactor. Separation of the reaction products gave 1.30% by volume of ethylene oxide; 1.25% by volume carbon dioxide; 1.22% by volume of unreacted ethylene. The yield of ethylene oxide, based on the ethylene passed through, is 41.20 vol .- ^u / o. the yield of ethylene oxide, based on the converted ethylene, 67.30% by volume.

The unreacted ethylene is mixed with the air heated to 300 ° C and fed to the second reactor for further oxidation, where the maximum conversion of the ethylene is achieved through the recycle. Said mixture is passed in countercurrent to the catalyst at a speed of 5 m / s. The concentration of the catalyst is 70 kg / m ³ , the contact time of the ethylene / air mixture with the catalyst is 1 second, the reaction temperature is 260 ° C.

The reaction gives a reaction mixture, which ethylene oxide, carbon dioxide and unreacted Contains ethylene. The mixture is passed out of the separation system. By separating the Products are obtained with 0.60% by volume of ethylene oxide, 0.60% by volume of carbon dioxide and 0.27% by volume of unreacted Ethylene.

The yield of ethylene oxide, based on the ethylene passed through, is 49.20% by volume Yield of ethylene oxide based on the converted ethylene, 67.00% by volume.

Through the gradual oxidation in two reactors of the ethylene / air mixture containing 3.15% by volume of ethylene 1.90% by volume of ethylene oxide, 1.85% by volume of carbon dioxide and 0.27% by volume of unreacted are obtained Ethylene.

The yield of ethylene oxide, based on the ethylene passed through, is 62.00% by volume Yield of ethylene oxide based on the converted ethylene, 68.00% by volume.

Example 2

The oxidation of ethylene to ethylene oxide is analogous to Example 1 except for the technological Parameters carried out.

First reactor

Technological parameters: speed of the ethylene / air mixture 10 m / s; Speed of the catalyst 4 m / s; Concentration of the catalyst 160 kg / m ³ ; Contact time 1.42 seconds; Reaction temperature ^{300 0 C}

There were used in the reaction, vol .-%: ethylene 3.30; Air 96.70.

The reaction gave,% by volume: ethylene oxide ι ο 1.45; Carbon dioxide 1.30; (unreacted) ethylene 1.20.

The yield of ethylene oxide, based on the ethylene passed through, is 44.00% by volume, the Yield of ethylene oxide, based on the converted ethylene, 69.00% by volume.

Second reactor

Technological parameter: speed of the ethylene / air mixture 5 m / s; Concentration of the catalyst 80 kg / m ³ ; Contact duration 1 second; Reaction temperature 280 ⁰ C.

There were used in the reaction, vol .-% ethylene 1.20; Air 98.80.

The reaction gave,% by volume: ethylene oxide 0.68; Carbon dioxide 0.70; (unreacted) ethylene 0.17.

The yield of ethylene oxide, based on the ethylene passed through, is 56.70% by volume, the Yield of ethylene oxide based on the converted ethylene, 65.80% by volume.

The stepwise oxidation of the mixture containing 3.3% ethylene in 2 reactors gave % By volume: ethylene oxide 2.13; Carbon dioxide 2.00; (unreacted) ethylene 0.17.

The yield of ethylene oxide, based on the ethylene passed through, is 65.70, the yield on Ethylene oxide, based on the converted ethylene, 68.20% by volume.

Example 3

The oxidation of ethylene to ethylene oxide is carried out under the conditions described in Example 1 carried out

The composition of the ethylene / air / catalyst system fed to the first reactor corresponds the system of example 1.

The unreacted ethylene separated from the reaction products after the first reactor is with a fresh portion of ethylene until it has reached its total concentration in the ethylene / air mixture of 3.02% by volume supplemented. 3.02% by volume of ethylene and 96.98% by volume of air were fed to the second reactor for the reaction.

The reaction in the second reactor gave,% by volume: ethylene oxide 1.05; Carbon dioxide 1.00; (unimplemented) Ethylene 1.47.

The yield of ethylene oxide, based on the ethylene passed through, is 34.70% by volume, the Yield of ethylene oxide based on the converted ethylene, 67.20% by volume.

Through the gradual oxidation of the ethylene / air mixture containing 4.95% by volume of ethylene into two Reactors were obtained,% by volume: ethylene oxide 2.35; Carbon dioxide 2.25 and (unreacted) ethylene 1.47.

The yield of ethylene oxide, based on the ethylene passed through, is 47.50% by volume Yield of ethylene oxide, based on the converted ethylene, 67.50% by volume.

Example 4

The oxidation of ethylene to ethylene oxide is carried out under the conditions described in Example 2 carried out.

The composition of the ethylene / air / catalyst system fed to the first reactor corresponds the system of example 2.

The unreacted ethylene separated from the reaction products after the first reactor is with a fresh portion of ethylene until it has reached its total concentration in the ethylene-air mixture supplemented by 3.20% by volume.

3.20% by volume of ethylene and 96.80% by volume of air were fed to the reactor for the reaction.

The reaction in the second reactor gave,% by volume: ethylene oxide 1.20; Carbon dioxide 1.00 and (unreacted) ethylene 1.50.

The yield of ethylene oxide, based on the ethylene passed through, is 37.80% by volume, the Yield of ethylene oxide based on the converted ethylene, 70.50% by volume.

By the gradual oxidation of the 5.30 vol .-% ethylene containing ethylene / air mixture in two Reactors were obtained,% by volume: ethylene oxide 2.65; Carbon dioxide 230 and (unreacted) ethylene 1.50.

The yield of ethylene oxide, based on the passed ethylene is 50.00 vol .-%, the yield of ethylene oxide, based on the converted Ethylene, 69.80% by volume.

Claims (2)

Patent claims: 1. Continuous process for the production of ethylene oxide by direct oxidation of ethylene with atmospheric oxygen ar a flowing silver catalyst on support at elevated temperature, characterized in that ethylene is heated with air heated to 300 ° C up to a total concentration in the ethylene / air mixture of 3 , Mixes 15 to 330 vol%, mixes the ethylene / air mixture in a mixer with a microspherical silver catalyst on a carrier and ^{brings its concentration in the mixture to 135-160 kg / m 3} , then the ethylene / air mixture at a rate of 10 to 12 m / s together with the catalyst, the speed of which is 4 to 6 m / s, in an ascending stream to a first reactor with an ascending current and the oxidation at a temperature of 290 to 300 ⁰ C and a contact time of J, 26 to 1.42 seconds, then the reaction products are separated off from the catalyst in a separator and passed for separation, while the catalyst is fed to a second reactor is performed in which in countercurrent to the descending catalyst the separated from the reaction product of the first reactor, unreacted and mixed with 300 ° C hot air is postoxidized at a temperature of 260 to 280 ° C and a contact time of 1 sec, the The speed of the ethylene / air mixture is 5 m / sec, with the catalyst rotating continuously in the system. 2. The method according to claim 1, characterized in that the unreacted ethylene Ethylene up to a total concentration of the same in the ethylene / air mixture of 2.00 to 3.50 Vol.% Admits. 10