Zeolites have long been valued for their combination of shape-selective character combined with their robust temperature and hydrothermal stability in their successful commercial catalyst implementation. In recent years, the focus on the internal transition-state selectivity which certain zeolite structures may afford has led to the development of yet newer shape-selective catalysts. The discovery of side-pocket use in Mordenite to impart control in carbonylation was one of the great demonstrations of this capability [1]. More recently our lab program had shown that a certain region in the novel zeolite SSZ-57 could be electively utilized for catalysis [ 2]. A different approach to creating novel sites was demonstrated by the primary delamination of layered zeolite precursors, containing crystalline structure details built into the layers, followed by site modification once the surfaces were exposed [3]. In recent years one of the growth areas for zeolite utilization has been the recognition that small pore zeolites make attractive co-catalysts with copper or iron exchanged into them for the removal of NOx in diesel exhaust systems [4]. This has led to increased activity in (a) looking at a larger variety of small pore zeolites as potential candidates in this service,(b) attempts to understand in greater chemical detail how the catalysts function and (c) efforts to extend the range of useful catalytic behavior to increase the yields in DeNOx behavior and lifetimes for the catalysts. In parallel, it is recognized that the same zeolites used in this application are also amongst the best in converting methanol, derived from coal, to small olefins like ethylene and propylene. This has seen a successful commercialization in recent years in China with several plants running. In our presentation we will explore the synthesis issues which led to the discovery of several new small pore zeolites which could then be considered for use in both of the above applications. We will discuss how the selection of reagents and reaction conditions can bias the type of zeolite product to be made and why a focus on ABC-6 type zeolite products is particularly timely in attempts to create new candidates for the catalysts mentioned. Then we will also consider the challenges to expand the composition fields ( needed for greater catalyst stability ) and some novel approaches to reducing the cost of the synthesis of zeolites which emerge as attractive in these uses.

Importance of site-selectivity in zeolite catalysts: A resurgence in interest in small pore zeolites

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.