Abstract: A reactor, for example, for adsorption processes, is described which is designed essentially cylindrically and is symmetrical with respect to an essentially vertical axis. The reactor is bounded by a shell. A circular bed filled with free-flowing material (e.g., an adsorbent or catalyst) is positioned inside the shell. The free-flowing material is contained within an inner basket and an outer basket and supported by a bottom support member from below. Both baskets are rigidly connected in the radial direction and rigidly connected at their lower end to the shell. At least one of the two baskets is both expandable in the axial direction and rigidly connected at its upper end to the shell.