The objective of this project is to develop a new research technique for studying zeolite mass transport. Sorption rate measurements are conducted on a single zeolite crystal suspended in a flowing carrier gas by an electrodynamic containment device. An electronic feedback control circuit senses particle displacement due to weight increase and automatically adjusts the electrostatic field to keep the particle at the null position. The sorption uptake curve is then computed from a knowledge of the levitation voltage as a function of time. Mass transport phenomena are directly responsible for the unique molecular sieve and shape selective properties of zeolite. However, the characterization of intracrystalline diffusion in zeolite is complicated by extracrystalline mass transport resistance, crystalline size distribution, sorption heat effects, and finite instrumentation response time. Consequently, large discrepancies are often observed between diffusivities obtained by the various conventional methods and between diffusivities reported by different investigators using the same techniques of measurement. This new technique has the potential for eliminating all of these problems. By studying single crystallites, extracrystalline resistance are eliminated and so is the need to contend with a distribution of particle sizes. Sorption heat effects can be probed in an independent fashion by varying carrier gas flowrate. The new apparatus contains no moving parts, hence, instrumentation response times should be dramatically improved.
