Perovskite Adsorbents for Warm-Gas Arsenic and Phosphorus Removal

Integrated Gasification Combined Cycle (IGCC) electric power plants equipped with solid-oxide fuel cells offer great potential for increasing the efficiency of next generation power plants. However, synthesis gas produced by gasification of coal is contaminated with arsenic and phosphorus that will poison the nickel catalysts in solid-oxide fuel cells unless the concentrations of these contaminants are lowered to below 20 parts per billion by volume (ppbv). Standard sorbents based upon zinc are limited by reactions with steam, which release arsenic and phosphorus to ppmv levels. This project will develop solid sorbents with a perovskite crystal structure that will very strongly bind arsenic, phosphorus, and other catalyst poisons originating from coal. The sorbents will contain (1) manganese, which forms one of the most thermally stable arsenides, Mn2As, with a melting point of 1400°C; (2) cobalt, which forms a very thermally stable phosphide, Co2P, with a melting point of 1386°C; (3) lanthanum and cerium, which form extremely stable phosphates as well as sulfides stable to above 2100°C; and (4) iron and nickel as general-purpose getters for other catalyst poisons released from coal. Commercial Applications and other Benefits as described by the awardee: Removal of arsenic, phosphorus, and other catalyst poisons from synthesis gas would enable coal to be utilized in non-polluting IGCC power plants equipped with solid-oxide fuel cells or membranes for sequestration of CO2. Other applications for the sorbents would include the protection of nickel catalysts used in the production of substitute natural gas, protection of catalysts used in the production of syngas-derived ethano and Fischer-Tropsch liquids for diesel fuel, and protection of palladium-based membranes used to purify hydrogen derived from coal.