An Investigation into the use of Coated Vanadium Alloys for the Purpose of Hydrogen Separation

A need for a new energy vector is highlighted, as carbon-based transport fuels are identified as producing sub-micron particulate causing both environmental and health issues. It is suggested that this energy vector should be hydrogen, however current commercial hydrogen production relies on the use of expensive hydrogen separation technologies such as amine separation and pressure swing adsorption. It is suggested in this work that a focus be put on the development of hydrogen separation membranes, and in particular a focus on metallic membranes due to their potential for delivering a large hydrogen flux at a high purity and low operating cost. The major barrier to utilisation is identified as cost and thus motivation is provided for the need to develop a new generation of membrane. The problem is identified as having two parts: identifying suitable surface catalysts and bulk membrane materials. Theoretical modelling was used to investigate the design of idealised membranes before tests were conducted. A number of membranes were tested in a bespoke enclosure under conditions designed to mimic real-life operation, with tests undertaken under non-dilute hydrogen conditions and with a mixed CO2/H2 feed. Tests on a non-palladium containing surface catalyst, oxidised silver, proved to show no positive results. Pd-Ag Coated V-Ni and V-Ni-Al membranes are shown to have a maximum apparent permeability of 3.3 x10-8 mol m-1 s-1 Pa-0.5 and 4.1 x10-8 mol m-1 s-1 Pa-0.5 when tested at 300 °C with a binary feed mixture of CO2 and H2. In both instances the purity of the permeate was found to be 99.9% hydrogen. The permeability of both membranes under these conditions warrants further study.