Process for separating liquid mixture

Details Process for separating liquid mixture Process for separating liquid mixture

1988-09-19

1990-08-28

Sever, Frank

Liquid purification or separation

Processes

Liquid/liquid solvent or colloidal extraction or diffusing...

210654, B01D 6136

Patent

active

049523198

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
The present invention relates to a separation process of removing the water from a liquid mixture by pervaporation using highly hydrophilic polymeric material.
2. Background Art
Removal of the water from water-soluble liquid is often necessary in the industrial field and separation methods such as vaporization, freezing, extraction, dialysis and reverse osmosis have been employed selectively depending on the conditions upon use.
As the water soluble liquid, there can be mentioned oxygen-containing organic compounds such as alcohols, phenols, esters, ketones, ethers, aldehydes and organic acids, nitrogen-containing organic compounds such as nitriles, inorganic compounds such as inorganic acids, as well as mixtures thereof.
Although the methods as described above can be mentioned for the removal of the water from the liquid mixture, it can not always be said that they are suitable to the separation of those forming azeotropic mixtures or the separation of materials having similar boiling points from each other, and research and development for the separation by pervaporation have become vigorous in recent years by the demand also in view of the energy. Further, since heat resistance, chemical resistance and mechanical strength are also important as well as the separating performance upon actual use, it has been demanded for the development of such material as having high separation performance while taking consideration with the properties.
For the above purpose, there are remarkable problems how to provide a membrane with the characteristic affinity with a compound to be separated, how to form an extremely thin membrane efficiently, often with no pinholes, for obtaining a practical separation performance and, further, how to keep the endurance against the compounds in a liquid mixture intended to carry out the separation.
The present inventors, taking notice of the foregoings, have made development and study on polymeric material excellent in the heat resistance, chemical resistance and mechanical strength and having high separating performance and, as a result, have attained the present invention on the finding that an aromatic copolyimide or copolyamide-imide of a specific structure is excellent in view of the membrane-formation, durability and also in view of the separating performance.


DISCLOSURE OF THE INVENTION

The feature of the present invention lies in a separation process for a liquid mixture of removing the water from a liquid mixture by a pervaporation method in which the main constituent material for a membrane is a copoly-imide comprising the constitutional repeating unit represented by the following general formula (I): ##STR6## wherein R represents ##STR7## in 10 to 30 mol % of said constitutional repeating units, while R represents ##STR8## in 90 to 70 mol % of said constitutional repeating unit, or
a coplyamide-imide comprising from 90 to 10 mol % of the constitutional repeating unit having the structure represented by the formula (II): ##STR9## and from 10 to 90 mol % of the constitutional repeating unit having the structure represented by the formula (III): ##STR10##
The present invention is to be described more specifically. The pervaporation referred to in the present invention is a method of separating a specific ingredient from a liquid mixture by using a polymeric membrane or a ceramic membrane. Among many separation methods, this method is effective for the separation of those forming azeotropic mixtures, for the separation of those ingredients having similar boiling points or for the separation of mixtures containing ingredients with low thermal stability, and research and development have been made vigorously in recent years.
In the present invention, water is selected as an object to be separated, and it is an object thereof to remove water from the following substantially homogenous liquid mixtures. That is, the liquid mixture means a mixture of various kinds of liquid and water with no particular restrictions for the ratio so long as it is ho

REFERENCES:
patent: 3789079 (1974-01-01), Perry et al.
patent: 4307135 (1981-12-01), Fox
patent: 4532041 (1985-07-01), Shuey
patent: 4755299 (1988-07-01), Bruschke
Chem. Abstracts 107:63 No. 155658X (Nov. 1987).
Chemabs (ESA) No. 107(18)155658.

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