A vessel that is filled with a solid packing material for the purpose of enhancing a chemical reaction or a separation by improving the contact area available for the reaction or separation. The packing material is usually inert and resistant to the process materials and is typically made of ceramic, plastic, glass, or metal. Structured packing consists of corrugated sheets that allow the two phases such as a liquid and a gas to intimately contact one another through complicated channels. Unstructured or random packing consists of small objects that have been designed to provide a high contact area for a minimum volume. Raschig rings, Lessing rings, and Berl saddles are some of the most commonly encountered types of packing material and are loaded into vessels such as distillation columns, adsorption and absorption towers. Catalytic particles also form packed beds to promote chemical reactions and are loaded into vessels or tubes depending on the design. Adsorption materials such as zeolites are loaded into vessels to form packed beds.