Sustainable Gel-Less Synthesis of Sub-1-μm-Thick All-Silica CHA Zeolite Membranes for Efficient CO<sub>2</sub> Capture
Nana Wang, Siwei Yan, Wenhan Wang, Junjing Zhou, Bin Wang, Bo Liu, Rongfei Zhou
Abstract
Carbon capture and storage are extensively recognized as promising technologies for relieving climate change. All-silica CHA (Si-CHA) zeolite membranes have an extremely attractive CO 2 separation performance and high resistance to humidity and CO 2 partial pressures. However, it remains an environmental issue for synthesizing Si-CHA zeolite and zeolite membranes by the conventional route because a large amount of gel containing toxic fluorite is used. Herein, we have reported a sustainable gel-less synthesis approach to fabricate uniform and sub-1-micron Si-CHA zeolite membranes. The sustainability and economy of membrane synthesis by the current approach can be improved since the amount of gel is saved by up to 95% and no fluoride is used compared with the conventional approach. Moreover, a formation mechanism of Si-CHA zeolite membranes is proposed. The effects of synthesis temperature, time, seeding layer, and gel composition on membrane formation are investigated. Thin Si-CHA membrane prepared under optimized conditions shows a notable CO 2 permeance of 1.3 × 10 –6 mol/(m 2 s Pa) and a CO 2 /N 2 selectivity of 31 in an equimolar CO 2 /N 2 mixture. Such a separation performance of the current membrane surpasses that of the reported membranes. The membrane also displays excellent separation performance in CO 2 /CH 4 mixtures. The environmentally friendly gel-less synthesis approach is promising to produce Si-CHA zeolite membranes on a large scale for practical applications of the CO 2 capture from flue gas, natural gas, and biogas.