A vessel packed with a microfibrous media made of micron-sized highly conductive fibers, which are able (and may be used) to immobilize various reactive materials including catalysts, sorbents, electrocatalysts, and other chemically reactive solids. The vessel enables fine temperature control and a uniform temperature profile for a range of highly endothermic or exothermic chemical reactions, sorptions, separation processes, mixing operations, and heat transfer applications.