Rapid synthesis of AlPO-18 molecular sieve for gas separation with dual-template agent

Abstract

A rapid and facile strategy for AEI type AlPO-18 molecular sieves preparation was hydrothermally processed by dual templates of TEAOH (tetraethyl ammonium hydroxide) and low-cost DIPEA (N, N-diisopropylethylamine). Pure and high crystallinity AlPO-18 molecular sieve with the crystal size of 2 μm and the aspect ratio about 20 were obtained in a short period of 1 h under the dual-template strategy. The effect of single and binary templates on the growth process of AlPO-18 molecular sieve was compared in detail. TEAOH is conducive to the pure phase AEI formation since a long synthesis time is needed. DIPEA favors to the rapid formation of AEI structure, however the sole DIPEA template promotes to form the AFI type AlPO-5 impurities. The combined templates TEAOH/DIPEA work synergistically, and the 13C MAS NMR results showed that both the TEAOH and DIPEA templates were occluded in micropore space of AlPO-18 molecular sieves. In addition, the adsorption isotherms of CO2, CH4 and N2 on the samples synthesized by dual-template for 1 h were tested and compared with other AlPO-18 molecular sieves reported in the literature. The results showed that the current AlPO-18 molecular sieve is expected to be used as adsorbent for light gas separation.