A new research tool has been developed that allows in-situ measurement of the transient adsorption and coke deposition that occurs on zeolitic catalysts during short contact time interactions with reactants. The tool is a microbalance pulse reactor (MPR), whose central feature is a new kind of microbalance that can accurately weigh a catalyst bed without regard to high velocities of vapor passing through. This TEOM microbalance measures mass by inertia instead of weight. In the MPR, zeolitic catalysts are exposed to short pulses of vapor-phase adsorbate carried through the catalyst bed on helium carrier gas. Substituting nonporous quartz for the catalyst allows quantitation of the vapor pulse shape. Adsorption responses to pulses of n-decane, isopropylbenzene and triisopropylbenzene on La3+Y zeolite are reported. The MPR has application to understanding the mechanisms of catalytic cracking, which include a complex interaction of adsorption, shape-selective diffusion, and rapid deactivation by coke.
