Numerous techniques have been proposed for measuring mass transfer rates in microporous adsorbents. The most popular techniques include analyzing the results from gravimetric uptake and release experiments, breakthrough and elution curves tests, zero length column experiments, and pressure, concentration and volumetric frequency response methods. The latter frequency response methods appear to be unique in that they seem to be the only technique that has the ability to discriminate between the different mass transfer mechanisms that may be controlling the transport of a gas into and out of a microporous adsorbent. In fact, with the frequency response technique it is possible to observe different controlling mechanisms in different frequency ranges.Professor Ritter and his team recently commissioned a unique volumetric frequency response apparatus (VFRA) in his laboratory. The small change in volume, which causes a concomitant change in pressure, is carried out in a closed, isothermal system using a bellows connected to a reciprocating shaft. This VFRA is capable of measuring the transport of a gas into and out of a microporous adsorbent at frequencies ranging from 5x10-5 to 10 Hz, at temperatures ranging from 25 to 75 oC, and at pressures ranging from 0.1 to 1 atm. The sample chamber can handle up to about 100 g of adsorbent in beaded, pelleted, granular or structured forms, with regeneration capability at vacuums as low as 10-5 torr and temperatures up to 350 oC.During this presentation the VFRA apparatus will be described in detail, along with its operation. The methodology for determining the experimental in and out of phase responses will also be discussed. Experimental results obtained at several pressures and temperatures with O2, Ar, N2 and CO2 as probe gases in CMS 172K and with CO2 as a probe gas in zeolite 13X will be presented.

Adsorption and diffusion of gases in microporous adsorbents using volumetric frequency response

246th National Meeting (2013)

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