Synthesis and characterization of high-silica LTA produced by direct synthesis using a combination of organic SDAs

Abstract

Recent years have seen resurgence in 8-ring, large cage microporous materials for NO_x conversion, sepns., methanol-to-olefins reactions, and biomass applications. Systems that are currently being investigated include AFX, CHA, LEV and other 8-ring systems. Another promising framework for these applications could be LTA, which has 8-ring pores and LTA cages (are 11.4 Å in diam.). Zeolite A is unsuitable for these applications as conventional LTA synthesis results in a material with Si/Al=1. Tetramethylammonium cations can be used to obtain LTA with ca. Si/Al=3, but these materials are not suitable for the aforementioned applications due to poor hydrothermal stability and pore blockage due to cations. Corma and co-workers first reported the synthesis of germanosilicate, pure-silica and aluminosilicate LTA using a supramol. self-assembling org. SDA in 2004, denoted ITQ-29. This material showed great promise for applications in sepns., catalysis and low dielec. const. membranes. We have recently discovered a facile route to produce LTA using a combination of org. SDAs that do not require a supramol. assembly of the orgs. We will describe the synthetic procedure and the properties of materials formed.