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.

The importance of accurately measuring gas diffusivity in porous materials has led to a number of methods being developed. In this study the Temporal Analysis of Products ( To be submitted to Chem. Eng. Sci.

Flux Response Technology (FRT) has been successfully adapted as an in situ perturbation technique in dynamic gas sorption measurements to extract hydrocarbon diffusion coefficients in alumina/CeZrO x washcoats of cordierite monoliths. FRT works by measuring minuscule changes in flowrate between two gas streams for any gaseous process involving a change in volume (δV /δt). Adand desorption transients, which can be collected during the same experimental run have been analysed using the zero length column (ZLC) method to study propane diffusivity within an alumina/CeZrO x washcoat as a function of temperature. Extracted diffusivities and activation energies compare favourably with literature data.

The adaptation of flux response technology (FRT) as a novel in situ perturbation technique in gas sorption measurements continues to yield consistent results with literature values. Earlier studies have successfully reported on the FRT-zero length column method of studying propane diffusivity within an alumina/CeZrOx washcoat as a function of temperature (Maguire et al. in Chem Eng Sci 87:224-233, 2013; Sasegbon and Hellgardt in Adsorption, 2012). This study details FRT's ability in quantifying and analysing the dynamic process of carbon dioxide (CO 2 ) adsorption on zeolites with varying Si/Al ratios as well as measurements of CO 2 diffusion coefficients without the need for running separate experiments. This is made possible because FRT measures miniscule changes in transient flows in the order of 10 −2 µl/min for gaseous processes involving a change in volume (dV /dt). These changes are measured directly by a very sensitive differential pressure transducer in a pneumatic system analogous to an electrical Wheatstone bridge assembly, whereby gas molecules replace electrons and capillaries function as resistors.

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