Pyrochlore (A2B2O7) Based Catalysts for Hydrogen Production By Hydrocarbon Reforming

Pyrochlores are a class of ternary metal oxides with general formula (A₂B₂O₇) where the A-site is occupied by the large rare-earth metal cation and the B-site is occupied by the smaller transition metal. By proper choice of the A and B-site metals, a very thermally stable crystal lattice can be obtained which can be very strong contenders as catalytic materials for high temperature applications like fuel reforming reactions. These catalysts allow isomorphic substitution of the catalytic active metals binding them to the A and B-site which results in atomic dispersion of the active metals, thus improving their resistance towards sintering at high temperatures unlike the supported commercial catalysts. The inherent lattice oxygen reactivity of pyrochlore crystal helps in increasing the pool of oxygen on the catalyst which helps in limiting deactivation due to carbon deposition. These materials have been tested for reforming of commercial diesel fuel with high sulfur and aromatic content at temperatures is excess of 900°C. Pyrochlore catalysts showed uninterrupted hydrogen production by diesel fuel reforming for a period of over 1000 hrs. Apart from aromatic and sulfur containing commercial diesel fuel reforming; these materials have also shown long lasting stable activity towards Jet-Propellant 8 (JP-8) fuel, biodiesel, and natural gas reforming for hydrogen or syngas production. Our customers have tested pyrochlore based catalysts for diesel fuel reforming in solid oxide fuel cell application and observed stable performance for about 2000 hrs. These catalysts would be of great value in high temperature reactions where other conventional catalysts would fail due to thermal instability or due to contamination of feed stream.