New experimental method for the determination of single-component isotherms: an application of the flow-rate retention time

In this paper, we investigate adsorption of a single component (refrigerant) from the variation in the flow rate leaving the column. This requires evaluation of the flow-rate retention time-a measure of the net change in the amount adsorbed in the column, which can be positive or negative. The arrangement includes a system to deliver a fixed flow (30 mL/min) of helium through a column packed with 0.05 g of adsorbent. An experiment is initiated by adding a flow of refrigerant to the helium, and monitoring the outlet flow rate from the column. There are two main advantages of this approach: the experimental times are short (the order of 10 minutes) and the sensitivity is very high so that it can be used with very small as well as large amounts of adsorbent. Indeed, a sensitivity analysis suggests that the resolution is of the order of 10(-5) g. The first results section considers the corrections required to the measured flow-rate retention time-these are small and determined by empty volume in the system. The second results section involves a determination of the adsorption isotherm of HFC-134A on an activated carbon at 35 degrees C up to a partial pressure of 0.25 bar.