Enhanced process for the purification of anhydrous hydrogen chloride gas

Abstract

The present invention relates to a process for purifying anhydrous hydrogen chloride gas (“aHCl”), and preferably the anhydrous hydrogen chloride gas recovered from an isocyanate production process. In the process of the present invention, the content of chlorinated organics may be reduced from up to 1000 ppm by volume to below 10 ppb by volume levels. Generally, the process of the invention allows for chlorinated organic levels to be reduced to from 1 to 100 ppb, rendering the treated hydrogen chloride gas usable in a catalytic oxychlorination process or a Deacon process. The treated gas is also suitable for absorption in water or dilute hydrochloric acid.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to a process for purifying anhydrous hydrogen chloride gas (“aHCl”), and preferably the anhydrous hydrogen chloride gas recovered from an isocyanate production process. In the process of the present invention, the content of chlorinated organics may be reduced from up to 1000 ppm by volume to below 10 ppb by volume levels. Generally, the process of the invention allows for chlorinated organic levels to be reduced to from 1 to 100 ppb, rendering the treated hydrogen chloride gas usable in a catalytic oxychlorination process or a Deacon process. The treated gas is also suitable for absorption in water or dilute hydrochloric acid. [0002] A number of important chemical processes generate aHCl as a byproduct. Examples of such processes include chlorination processes, silane production processes and phosgenation processes. Because large amounts of aHCl can not be disposed of, one of the challenges encountered with each of th...

AI Technical Summary

Benefits of technology

"The present invention is a process for purifying anhydrous hydrogen chloride gas, which involves compressing the gas, cooling it with a heat exchanger, and then using a distillation column to separate the gas from contaminants. The process can reduce the concentration of chloro-aromatic compounds in the gas to below 10 ppb, making it suitable for use in various chemical processes. The invention also provides a method for separating small quantities of high boiling material from large volumes of anhydrous HCl gas."

Problems solved by technology

Because large amounts of aHCl can not be disposed of, one of the challenges encountered with each of these processes is purification of the aHCl generated to obtain a usable technical product or raw material for other processes.

The processes disclosed in these patents require high amounts of energy and expensive equipment.

The process disclosed in the '957 patent results in contaminant levels occasionally unacceptable for use in vinyl chloride production.

The contaminant level achieved is always unacceptable for use in Deacon processes.

However, the volume of HCl byproduct produced often exceeds the market demand.

This process is very sensitive to traces of some contaminants, such as sulfur and some organic compounds, which over time can lead to catalyst deactivation and / or plugging of reactors, which in turn can lead to unwanted by-product formation.

), which limits the usefulness of this approach.

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