Vapor Phase Separation of Water/Acetic Acid Mixtures through Mordenite Type Zeolite Membrane

The aqueous solution of acetic acid (AcOH) is by-produced in many chemical processes and reuse of AcOH requires de-watering of the AcOH aqueous solution. However, separation of water/AcOH mixtures by distillation consumes a large amount of energy due to the low relative volatility of water and AcOH. Combination of a membrane separation unit with distillation one can drastically reduce energy demand for the dehydration of acetic acid. While this system requires vapor phase separation of water/acetic acid mixture, there have so far been few studies on membrane separation under these conditions.

Mordenite is a kind of zeolites with both high stability and hydrophilic nature. In this communication, we report vapor phase separation properties of water/AcOH mixture through a mordenite type zeolite membrane.

A mordenite membranes was prepared on the outer surface of tubular porous a alumina support by a secondary-growth method, following the procedure described elsewhere [1]. Vapor permeation and separation measurements were performed using a stainless steel tube module cell. The effective membrane area was 6.28 cm².

The mordenite membrane highly separated steam from water/AcOH mixtures. In the case of an equimolar mixture of water/AcOH (10/10 kPa), the permeances of water was 1.4 x 10^-7 mol m^-2 s^-1 Pa^-1 and the separation factor of water/AcOH exceeded 1000 at steady state at 448 K. The separation mechanism will be discussed.

[1] K. Sawamura et al., J. Chem. Eng. Jpn., 41 (2008) 870-877. >