Mild Detemplation of Sub-Micron Silicalite-1 Membranes for Xylene and Butane Isomer Separation

Conventional thermal detemplation of zeolite membranes with high temperatures at ~500 °C usually leads to defects or cracks due to the mismatched thermal expansions between zeolite membrane and substrate. Also, high temperature detemplation methods preclude the application of temperature-sensitive substrates such as polymer supports. In addition, the energy cost of thermal detemplation can limit industrial application. Here, we fabricated sub-micron silicalite-1 membranes supported on porous silica and used them as model membranes to evaluate two mild detemplation methods: (i) low temperature thermal and (ii) UV/ozone treatment. The silicalite-1 membranes were fabricated with exfoliated nanosheets as the seed layer followed by gel-free secondary growth, which led to sub-micron b-oriented silicalite-1 membranes on the porous silica supports made by quartz fibers. Xylene and butane isomer permeation tests demonstrated that thermal treatment at a nominal oven temperature as low as 280 °C for 8 hours or UV/ozone treatment for 6 hours is sufficient to establish high selectivity. The highest temperature during the UV/ozone treatment was around 80 °C. The implications of these findings to membranes supported on flat porous polymer sheets or polymer hollow fibers will be discussed.