Differential pressure-jump method for routine measurement of sorption kinetics

A sensitive pressure-jump method has been developed for the measurement and characterization of material transport in porous solids. The apparatus is automatically operated and the data evaluation is performed by means of numerical methods based on the Crank-Nicholson procedure. As an example, the sorption ofn-butane and ethene in spherical mesoporous silica gel pellets has been studied. In this way, it is possible to obtain uptake curves and in case of known particle shape to derive values for effective diffusion coefficients. From the pressure and temperature dependence ofD_e, information on the transport mechanism by means of Knudsen and surface diffusion can be obtained as well as the tortuosity factor characterizing the pore network.