Synthesis, characterization, and applications of palladium membranes

A membrane is a permeable phase, often in the form of a thin film, made of a variety of materials ranging from inorganic solids to different types of polymers. The main role of the membrane film is to control the exchange of materials between the two adjacent fluid phases. A membrane is able to act as a selective barrier, which separates different species either by sieving or by controlling their relative rate of transport through itself. Transport processes across the membrane are the result of a driving force, which is generally associated with a gradient of concentration, pressure, temperature, electric potential, etc. According to the IUPAC definition, a membrane reactor is a device that combines the separation properties of membranes with the typical characteristics of catalytic reaction steps in only one unit. In particular, the membrane does not only play the role as a separator but also as a part of the reactor itself. In other words, a membrane reactor is an engineering device that selectively removes a product from the reaction system, giving the possibility of achieving higher conversion than a traditional process under the same operation conditions.