JP2006290757A - Method for separating and retrieving aromatic compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for separating efficiently and retrieving an aromatic compound from a mixed gas comprising it and hydrogen chloride. <P>SOLUTION: The method for separating and retrieving the aromatic compound from a mixed gas comprising it and hydrogen chloride is provided, being characterized by involving making the separation under a pressure of 0.3-1.0 MPa to condense the aromatic compound. In this method, the aromatic compound is e.g. benzene, toluene, xylenes; from an industrial point of view, use of benzene is especially important, and the mixing molar ratio of the aromatic compound to hydrogen chloride in the mixed gas is normally (0.1:1) to (3:1). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for separating and recovering hydrogen chloride. More particularly, the present invention relates to a method for separating and recovering hydrogen chloride from a mixed gas containing an aromatic compound and hydrogen chloride, and relates to a method for separating and recovering an aromatic compound that is excellent in aromatic compound separation efficiency. It is.

  For example, a method for producing a chlorinated aromatic compound such as chlorobenzene (monochlorobenzene means the same hereinafter) by chlorinating an aromatic compound such as benzene with chlorine is known (for example, patents). Reference 1). Here, a mixed gas containing an aromatic compound and hydrogen chloride is obtained. The aromatic compound in the mixed gas is preferably used effectively by a method such as separation from hydrogen chloride and recycling to chlorination. On the other hand, the separated hydrogen chloride can be used as a raw material for the production of hydrochloric acid, the production of chlorine by oxygen oxidation or electrolysis, the production of a chlorinated hydrocarbon compound by oxychlorination, etc. It is required from the standpoints of ensuring product purity and preventing the formation of harmful polychlorinated aromatic compounds.

US Pat. No. 2,653,904

  In such a situation, the problem to be solved by the present invention is a method for separating and recovering an aromatic compound from a mixed gas containing an aromatic compound and hydrogen chloride, and the aromatic compound having excellent separation efficiency of the aromatic compound Is to provide a separation and recovery method.

  That is, the present invention is a method for separating and recovering an aromatic compound from a mixed gas containing an aromatic compound and hydrogen chloride, and the aromatic compound is obtained by performing the separation operation at a pressure of 0.3 to 1.0 MPa. The present invention relates to a method for separating and recovering aromatic compounds that are condensed and separated and recovered.

  According to the present invention, a method for separating and recovering hydrogen chloride from a mixed gas containing an aromatic compound and hydrogen chloride, which is excellent in the separation efficiency of the aromatic compound, can be provided.

  As the aromatic compound, benzene, toluene, xylene and the like can be raised, and it is particularly important to use benzene from an industrial viewpoint.

As the mixed gas, those obtained in the following chlorination step can be used.
Chlorination step: A step of reacting an aromatic compound and chlorine to obtain a chlorinated aromatic compound and hydrogen chloride

  The mixing ratio of the aromatic compound and hydrogen chloride in the mixed gas containing the aromatic compound and hydrogen chloride is usually 0.1 / 1 to 3/1 (molar ratio of aromatic compound / hydrogen chloride).

  In the chlorination step, a chlorinated aromatic compound obtained by chlorinating the aromatic compound is obtained, and a mixed gas containing the aromatic compound and hydrogen chloride is obtained.

There is no restriction | limiting in particular about the method of making an aromatic compound and chlorine react, A well-known method can be used. An example of a specific method is as follows. The molar ratio of aromatic compound to chlorine (aromatic compound / chlorine) is 3 or more, the reaction temperature is 25 to 140 ° C., and the reaction pressure is 0.02 to 1.0 MPa. As the reactor, for example, a tank reactor can be used. For the reaction, FeCl ₂ can be used as a catalyst.

  In the present invention, when the aromatic compound is separated and recovered from the mixed gas containing the aromatic compound and hydrogen chloride, the separation operation is performed at a pressure of 0.3 to 1.0 MPa. A more preferable pressure for the separation operation is 0.35 to 0.8 MPa. If the separation operation pressure is too low, it is difficult to sufficiently condense and remove aromatic compounds in hydrogen chloride. On the other hand, if the separation operation pressure is too high, the energy and equipment costs required to increase the mixed gas to the operation pressure are increased. It becomes large and disadvantageous economically. Here, the pressure of the separation operation refers to the pressure of hydrogen chloride recovered as a gas without finally condensing.

  A specific example of the method for separating and recovering the aromatic compound by cooling the mixed gas and condensing the aromatic compound is as follows.

  The mixed gas containing the aromatic compound and hydrogen chloride may be cooled as it is to condense the aromatic compound, but if the pressure is low, the aromatic compound may be condensed after being compressed to a preferred pressure. When cooling is performed, a single heat exchanger may be used, or a plurality of heat exchangers may be installed in series or in parallel. The refrigerant used for cooling the mixed gas is not particularly limited, but when the mixed gas is cooled to a temperature lower than the atmospheric temperature, first, it is cooled with normal cooling water, and then the uncondensed gas is cooled with a lower temperature refrigerant. In some cases, energy required for cooling can be saved.

  The aromatic compound separated and recovered by the present invention can be used as a raw material for the chlorination reaction.

Next, the present invention will be described with reference to examples.
Example 1
Benzene was reacted with chlorine to obtain monochlorobenzene and hydrogen chloride. Here, the reaction temperature was 116 ° C. and the reaction pressure was 0.6 MPa. The raw material chlorine flow rate was 421 kg-mol / hr, and the molar ratio of benzene / chlorine supplied from the outside was 8/1. By the reaction, 624 kg-mol / hr of mixed gas containing benzene and hydrogen chloride at a molar ratio of 0.7 / 1 was generated. This was first cooled to 40 ° C. with ordinary cooling water, and the uncondensed gas was further cooled to 5 ° C. using a low-temperature refrigerant to condense and separate benzene. As a result, 99% of the benzene in the mixed gas was recovered, and the mole fraction of benzene in the separated hydrogen chloride was reduced to 0.008. The condensed liquid consisting mainly of benzene was recycled to the chlorination reaction.

It is an example of the flow which implements this invention.

Explanation of symbols

A Reactor B, C Heat exchanger D Tank E Pump

Claims (3)

A method for separating and recovering an aromatic compound from a mixed gas containing an aromatic compound and hydrogen chloride, wherein the aromatic compound is condensed and separated and recovered by performing a separation operation at a pressure of 0.3 to 1.0 MPa. A method for separating and recovering aromatic compounds. The method according to claim 1, wherein a mixed gas containing an aromatic compound and hydrogen chloride is obtained in the following chlorination step.
Chlorination step: A step of reacting an aromatic compound with chlorine to obtain a chlorinated aromatic compound and hydrogen chloride. The process according to claim 1, wherein the aromatic compound is benzene.

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