Effect of Structure-Directing Agents on FAU–CHA Interzeolite Conversion and Preparation of High Pervaporation Performance CHA Zeolite Membranes for the Dehydration of Acetic Acid Solution

Abstract

Abstract FAU–CHA interzeolite conversions were investigated in the presence of benzyltrimethylammonium hydroxide (BTMAOH) and 1-adamantyltrimethylammonium hydroxide (AdaTMOH) as organic structure-directing agents (OSDAs). AdaTMOH was well able to both decompose/dissolve the starting FAU-type zeolites into locally ordered aluminosilicate species (nanoparts) and transform them into CHA-type zeolites. In contrast, although BTMAOH did not show such high performance in the decomposition and transformation as compared to AdaTMOH, the obtained CHA-type zeolites exhibited higher acid stability. Next, the application of the highly acid-resistant CHA-type zeolites to membranes was investigated. The CHA zeolite membrane prepared on the outer surface of a porous α-alumina tube by FAU–CHA interzeolite conversion demonstrated excellent pervaporation performance in the dehydration of acetic acid aqueous solution. A high permeate flux of ca. 8 kg m−2 h−1 with a high separation factor of ca. 2500 was maintained during long-term (1700 h) testing.