Synthesis, reproducibility, characterization, pervaporation and technical feasibility of preferentially b-oriented mordenite membranes for dehydration of acetic acid solution

Abstract

This paper describes the development of mordenite membranes for industrial purpose to apply in dehydration processes of acetic acid (AAc) aqueous solution under high-temperature and high-pressure conditions. The membrane formation process is clarified as a function of synthesis time by investigation of the properties of permselective, crystalline state and surface morphology in the synthesized polycrystalline thin film. The crystallographic development from the random orientation to the preferred orientation of b-axis was observed in the synthesized membranes with increasing of crystallization times. The membrane performance in pervaporation was measured in a feed mixture of water (50 wt.%)/AAc (50 wt.%) to be 10.9 kg m −2 h −1 for permeate flux and to be 0.77 × 10 −6 mol m −2 s −1 Pa −1 for water permeance with separation factor ( α) of 500 at 130 °C. A technical feasibility study was undertaken for a hybrid pervaporation–distillation system to produce acetic acid with 1 wt.% of water content from a feed flow with water (55 wt.%)/AAc (45 wt.%) for 1000 kg h −1. It was a case in which dehydration from 55 wt.% to 40 wt.% water content was processed in a feed flow before distillation by pervaporation at 110 °C. Two values of (1) the energy saving ratio compared with a case of distillation alone and (2) the required membrane area were calculated to be 34% and 55 m 2, respectively, using the experimentally determined values of membrane performance. This size of the membrane module for the 55 m 2 membrane area could be a realistic scale for industrial utilizations. Therefore, the present fabrication method for mordenite membrane deserves to further technological developments of large-scale membranes and mass-production.