JP2001048871A - Reactor for producing ethylene oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject reactor capable of improving the selectivity when carrying out a vapor-phase oxidation of ethylene by treating a part of the surface of the reactor contacting with a reactant gas with a solution of a nitrite. SOLUTION: This reactor is a carbon-steel shell-and-tube type reactor for producing ethylene oxide by oxidizing ethylene in the presence of a silver- carrying catalyst, and has at least a part of the surface of the reactor, contacting with the reactant gas (e.g. the inner surface of each reaction tube and the inner surface of a tube plate face), and treated with a solution of a nitrite. The solution of the nitrite is preferably an aqueous solution of 0.1-10 wt.% sodium nitrite. The formation of an aldehyde or the like is thought to be suppressed because an iron oxide coating membrane is formed by the surface treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor for producing ethylene oxide, and more particularly to a carbon steel shell and tube reactor suitable for producing high quality ethylene oxide.

[0002]

2. Description of the Related Art The production of ethylene oxide by vapor-phase oxidation of ethylene in the presence of a silver-supported catalyst is widely practiced industrially. Usually, a shell and tube reactor is used for this reaction, and each reaction tube is filled with a silver-supported catalyst,
A raw material gas is introduced into the catalyst layer to perform a gas phase oxidation reaction.

[0003] This shell-and-tube type reactor is conventionally made of stainless steel, but in recent years, an inexpensive carbon steel reactor has been used.

[0004]

Although the technology for producing ethylene oxide has already reached a high level, it still has to be 1-2.
% Selectivity is also industrially desirable given the ethylene oxide production scale. It is also industrially desirable to produce high quality ethylene oxide by reducing the content of impurities which are difficult to separate and remove by distillation of aldehyde and the like.

[0005] The inventors of the present invention have repeatedly studied for the purpose of producing high quality ethylene oxide, and found that the reaction gas in a carbon steel shell-and-tube type reactor used for producing ethylene oxide was used. Impurities such as aldehydes are generated on the surface that comes into contact with ethylene oxide, and the quality of ethylene oxide is degraded. It has been found that filling a tube with a catalyst can effectively prevent it, and based on this finding, the present invention has been completed.

That is, the present invention relates to a carbon steel shell and tube reactor for producing ethylene oxide by subjecting ethylene to gas phase oxidation in the presence of a silver-supported catalyst, which is in contact with a reaction gas of the reactor. A reactor for producing ethylene oxide, wherein at least a part of the surface is treated with a nitrite solution.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The shell-and-tube reactor used in the present invention is not particularly limited, and carbon dioxide generally used for producing ethylene oxide by gas-phase oxidation of ethylene in the presence of a silver-supported catalyst is used. Steel shell and tube reactors can be used. The present invention is characterized in that at least a part of the surface of the shell-and-tube reactor that comes into contact with the reaction gas is treated with a nitrite solution. The surface of the reactor that comes into contact with the reaction gas includes, specifically, the inner surface of each reaction tube, the inner surface of the tube plate surface (particularly, the tube plate surface on the reaction gas outlet side), the inner surface of the channel cover, and gas piping ( In particular, the inner surface of the outlet gas pipe) can be mentioned. Preferably, substantially all of these inner surfaces, at least the inner surfaces of each reaction tube, are treated with the solution.

It is believed that by treating the above-mentioned surface of the reactor with a nitrite solution, an iron oxide film is formed to suppress generation of impurities such as aldehyde. Therefore, the type of nitrite solution, treatment method, treatment condition, and the like may be appropriately selected so that an effective amount of iron oxide film is formed.

Representative examples of the nitrite solution include aqueous solutions of alkali metal salts such as sodium nitrite and ammonium salts. The concentration of this aqueous solution is not particularly limited, but it is generally preferable to use it at a concentration of 0.1 to 10% by weight.

[0010]

According to the reactor of the present invention, generation of impurities and, consequently, deterioration of the quality of ethylene oxide can be effectively prevented. That is, high quality ethylene oxide can be produced by using the reactor of the present invention.

[0011]

Example 1 A pilot monotubular reactor made of carbon steel having an inner diameter of 35 mm and an outer diameter of 14,000 mm was used. After a 2% by weight aqueous solution of sodium nitrite (NaNO ₂ ) was passed through the reaction tube for 10 minutes, air at 80 ° C. was blown and dried to perform pretreatment of the inner surface of the reaction tube.

Next, the catalyst was charged. That is,
As an inlet preheating zone of 700 mm from the source gas inlet side,
Fill with 10mmφ inert filler, and on the downstream side, about 1
The reaction was performed for a year, and a ring-shaped silver catalyst having a stable activity was filled.

An ethylene-containing gas is introduced into the reaction tube,
Gas phase oxidation was performed for 3 days. The reaction conditions were as follows.

Space velocity (l / hr): 4,880 Inlet gas temperature (° C.): 100 Pressure (kg / cm ² G): 25.0 Ethylene (vol%): 23.1 Oxygen (vol%): 7 5.5 CO ₂ (vol%): 6.5 Others (argon, nitrogen, methane, etc.) (vol%): 62.9 Outlet gas temperature (° C): 230 Ethylene oxide (vol%): 2.0 3 days after the above reaction Aldehyde concentration in outlet gas of
ppm.

Comparative Example 1 Gas-phase oxidation was performed in the same manner as in Example 1 except that the pretreatment of the inner surface of the reaction tube was not performed.

The aldehyde concentration in the outlet gas after 3 days from the reaction was 4.3 ppm, which was inferior to the ethylene oxide obtained in Example 1.

Claims (2)

[Claims] 1. A carbon steel shell-and-tube reactor for producing ethylene oxide by subjecting ethylene to gas phase oxidation in the presence of a silver-supported catalyst, wherein at least one of the surfaces of the reactor is in contact with a reaction gas. A reactor for producing ethylene oxide, wherein a part of the reactor is treated with a nitrite solution. 2. The reactor according to claim 1, wherein the nitrite solution is a 0.1 to 10% by weight aqueous sodium nitrite solution.