Control of zeolite framework flexibility for ultra-selective carbon dioxide separation
Peng Du, Yuting Zhang, Xuerui Wang, Stefano Canossa, Zhou Hong, Gwilherm Nénert, Wanqin Jin, Xuehong Gu
Abstract
Abstract Molecular sieving membranes with uniform pore size are highly desired for carbon dioxide separation. All-silica zeolite membranes feature well-defined micropores, but the size-exclusion effect is significantly compromised by the non-selective macro-pores generated during detemplation. Here we propose a template modulated crystal transition (TMCT) approach to tune the flexibility of Decadodecasil 3 R (DD3R) zeolite to prepare ultra-selective membranes for CO 2 /CH 4 separation. An instantaneous overheating is applied to synchronize the template decomposition with the structure relaxation. The organic template molecules are transitionally converted to tight carbon species by the one-minute overheating at 700 °C, which are facilely burnt out by a following moderate thermal treatment. The resulting membranes exhibit CO 2 /CH 4 selectivity of 157~1,172 and CO 2 permeance of (890~1,540) × 10 −10 mol m −2 s −1 Pa −1 . The CO 2 flux and CO 2 /CH 4 mixture selectivity reach 3.6 Nm 3 m −2 h −1 and 43 even at feed pressure up to 31 bar. Such strategy could pave the way of all-silica zeolite membranes to practical applications.