(275c) Flux Response Technology: A Novel and Robust Method for Dynamic Gas Sorption Measurements

Characterisation techniques play an invaluable role in understanding materials and processes used in chemical engineering and chemistry. A new in-situ perturbation technique, termed Flux Response Technology (FRT), has been developed to help measure and analyse dynamic gas sorption processes. FRT can be used to measure minuscule changes in transient flows of the order of 10-2 ìl/min. FRT functions analogous to an electrical Wheatstone bridge assembly, where electrons are replaced by gas molecules and tubes function as conductors/resistors. Perturbations of pressure, temperature and especially concentration cause an imbalance in the system, which is measured directly by a differential pressure transducer (DPT). FRT has been applied to measure adsorption processes and heterogeneous catalytic reactions. For example, ammonia ad-/desorption cycles are being used to directly quantify the number of acid sites on zeolites, isothermally. A strong correlation between the number of acid sites and the Si/Al ratios can be observed (Figure 1). Due to the dynamic nature of FRT, repeated exposure to sorbates can be facilitated in a short period of time. The resulting sorption data may be used to discriminate between physisorbed and chemisorbed quantities. This might be useful for the development of pressure swing processes, where the dynamic, reversible loading of the sorbent is an important parameter in the design of such systems. Without the need for cumbersome calibration, FRT offers an opportunity for precise and rapid measurement of a number of sorption phenomena. Figure 1: Effect of temperature on the number of acid sites for zeolites with varying Si/Al ratios