A rotating sample cell for in situ measurements of adsorption with x-rays

A novel device for in situ study of gas adsorption under rotation

The effect of rotation on adsorption kinetics of CO₂ on activated carbon (AC) is studied using a novel rotation device. The device consists of a rotating cylindrical cell with inner dimensions of 4.5 cm radius and 1 mm height, while it operates at 5000 and 8000 rpm. Various cases of the CO₂/AC system are examined under a rotation field: in particular, (a) solid at vacuum, (b) gas without solid, (c) gas/solid at a non-equilibrium state of the adsorption process, and (d) gas/solid near an equilibrium state of the adsorption process. Micro-fragmentation of solid particles is observed at 8000 rpm but not at 5000 rpm; the latter is then chosen as the preferable speed for the rest of the experiments. During rotation of the gas, a well is noticed at the pressure curve, the size of which is in accordance with theoretical predictions of the behavior of a spinning gas. Rotation at an early stage of the adsorption process can suppress the filling time of a rotating storage reservoir to half of its value. Rotation near the equilibrium point reveals an enhanced adsorption capacity of the solid. The physics behind these phenomena are discussed with the aid of N₂-adsorption porosimetry and scanning electron microscopy measurements.