Synthesis and characterization of thermally stable acidic forms of zeolite A

• Main Author: Sawada, James Alexander
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/11168

Zeolite A has several attributes which make it attractive as a solid acid catalyst. The framework has pores on the order of 4-5 Å which show a strong selectivity toward small molecules by excluding species with larger diameters than linear hydrocarbons. The pores intersect to form a 3-dimensional channel network which is advantageous as it allows for free diffusion throughout the entire structure. Furthermore, zeolite A is already commercially available and is inexpensive to produce. Acidic forms of zeolite A , however, have long been considered unachievable as a result of the reduced stability of the zeolite A framework compared to those of more siliceous zeolites. This thesis describes the preparation and characterization of a series of zeolite A materials which demonstrate both thermal stability and Bronsted acidity. Zeolite A materials were prepared whose frameworks contained both C a ²⁺ and NH₄⁺ ions. The three materials studied had Ca ²⁺: NH₄⁺ ratios of 70:30, 60:40, and 50:50. The materials were systematically examined using powder X-ray diffraction, electron microscopy, solid-state NMR, and gas physisorption to establish their homogeneities and thermal stabilities. Finally, catalytic testing of the materials for the conversion of methanol to olefins was carried out to establish their activity in a model acid-catalyzed reaction.