In situ measurement of gas adsorption processes using Flux Response Technology

摘要

Flux Response Technology (FRT) is being developed as a powerful in situ perturbation technique to facilitate detailed characterisation of heterogeneous catalysts. FRT works by measuring minuscule changes in flowrate between two gas streams for potentially any gaseous process involving a change in volume (dV/dt). FRT functions analogous to an electrical Wheatstone bridge assembly whereby gas molecules represent electrons and flow capillaries represent resistors. A perturbation of pressure, temperature, but particularly of concentration causes an imbalance in the system, which is measured directly by a very sensitive differential pressure transducer (DPT). It is demonstrated how FRT can provide a simple, inexpensive, highly accurate means of quantifying the acidic sites of zeolites using ammonia ad/desorption as well as determining the dynamically available surface areas of catalysts using nitrogen adsorption at liquid nitrogen temperature. Temperature programmed experiments (temperature perturbations) can also be employed with FRT to rapidly compare catalyst activity directly (for catalyst development but also for quality control) without the need for much calibration.