Kinetics of non‐isothermal sorption in molecular sieve crystals

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Abstract
A mathematical model is developed to describe non‐isothermal sorption kinetics and used to interpret experimental uptake curves for CO2 in 4A zeolite and for CO2 and in C5H12 in 5A zeolite. The model assumes that the dominant mass transfer resistance is intracrystalline diffusion while the major resistance to heat transfer is the external heat transfer between the adsorbent sample and the surroundings. It gives a good representation of the kinetic behavior over a wide range of conditions. Both the extreme cases of isothermal diffusion and complete heat transfer control are demonstrated experimentally. Intermediate situations, in which the uptake rate is controlled by the combined effects of diffusion and heat transfer, are demonstrated as well. The parameters derived from the model are consistent, reproducible, and agree well with a priori estimates. The model provides a useful theoretical basis for the analysis of rapid sorption processes for which the non‐isothermal approximation is invalid.

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