(704c) The Synthesis of Hierarchical SAPO-34 Zeolite and Potential Adsorption Applications

Zeolites are among the most mature adsorbents and catalysts. The uniform pore sizes defined the crystalline structure are advantageous for achieving molecular sieving effects for enhanced performance. On the other hand, the small sub-nanometer sized pores are also adding high transport resistance for the molecules to reach internal pores, particularly for molecules approaching the pore size. To reduce the transport resistance, the zeolite crystals could be made as either nanosized or hierarchical with larger non-zeolitic pores. However, there are typically high cost associated with the specially designed synthesis precursor or the mesopore generating structure directing agents (SDAs). In this work, we will discuss the synthesis of hierarchical SAPO-34 zeolite using a cheap secondary SDA by a dual-SDA strategy. The influence of different secondary SDAs on resultant zeolite structure and pore size distribution will be discussed. The hierarchical zeolite will be further investigated for adsorption isotherms and dynamic uptake of a few hydrocarbon molecules and compared with conventional SAPO-34 zeolite. This work will help reveal the potential applications enabled by reduced transport resistance and possible limitations of the hierarchical SAPO-34 zeolite.