Affiliation: Honeywell UOP
Seminar title, “Synthesis and Characterization of Novel Small-Pore (Silico)Aluminophosphates”
Host: Dr. Josh Goldberger
Microporous materials are at the heart of many commercial processes, particularly in the fields of catalysis, adsorbents, and separations. In industry, these materials, also called molecular sieves, have traditionally been synthetic aluminosilicates (i.e., synthetic zeolites) as well as their phosphate-based analogues, the aluminophosphates (AlPOs) and silicoaluminophosphates (SAPOs). Small-pore molecular sieves in particular are widely employed in a variety of industrial areas. For example, the 8-ring LTA zeotype is found in numerous adsorbent and separation applications, such as air separation by pressure swing adsorption. In catalysis, SAPO-34 is the material of choice for the conversion of methanol to light olefins (MTO reaction), while copper-containing CHA zeolites can be found in many selective catalytic reduction (SCR) catalysts for the conversion of nitrogen oxides to ammonia.
Many of these small-pore molecular sieves are members of the ABC-6 family of zeotypes. This class of porous materials is composed of 6-membered rings of tetrahedral atoms (linked by bridging oxygens), which are stacked along the c-axis of a hexagonal unit cell. The 6-rings can assume one of three positions in the unit cell, commonly designated as A, B, and C. The connectivity and ordering of the A, B, and C positions determines the proportions of double-6-ring (d6r) and single-6-ring (s6r) subunits in the material, which in turn affect the secondary/composite building units and ultimately the overall porosity.
The ABC-6 family is a very fertile ground for the discovery of new materials. High-throughput computational methods have recently been developed that allow for the enumeration of hundreds of potential novel and interesting structures. In recent years, some of these hypothetical structures have been synthetically realized in either zeolitic or SAPO/MeAPSO form. We present here several new examples of this family of materials, along with a brief discussion of potential applications.
