A system for treatment of one or more flowing materials includes a support bed (32) comprising a plurality of support elements (34). The support bed may have a void fraction of at least 45%. An active bed (36), such as a bed of catalytic elements, may be supported by the support bed. The void fraction of the support bed may be larger than that of an equivalent bed of conventional, spherical elements, enabling significant improvements in the flow rate of reactants through the bed and/or a reduced pressure drop across the support bed.