Design of one-component ceramic membrane-reactor for natural gas conversion

One-component ceramic membrane-reactor, constituting of the same type of Ca0.8Sr0.2Ti1-xFexO3-alpha perovskite-type oxide for the catalyst involving support oxides, i.e., Ni/Ca0.8Sr0.2Ti0.9Fe0.1O3-alpha and the oxide ionic and electronic mixed conductor, i.e., Ca0.8Sr0.2Ti0.7Fe0.3O3-alpha, has been investigated for the partial oxidation of methane into synthesis gas in natural gas conversion process. Unique point of the membrane reactor is that the products formed between catalyst and membrane material should have no influence as a blocking layer against the oxygen pumping since catalyst and membrane material are consisted of same component, leading long time operation at the process of natural gas. Ni/Ca0.8Sr0.2Ti0.9Fe0.1O3-alpha, used as a catalyst for partial oxidation of methane into synthesis gas shows the excellent activity for the anti-coking performance by the insertion of mixed conduction into the perovskite support. From the relationship between the amount of carbon deposited on the catalyst and the mixed conduction property in the support, it is suggested that a self-migration of lattice oxygen inside the support regulated the balance of the conductivities of oxide ion and electron plays an important role to prevent accumulation of carbon deposition. Ca0.8Sr0.2Ti1-xFexO3-alpha performed as an oxygen separator from air chamber to reaction chamber, and its oxygen pumping property enhanced with increase in the Fe partial substitution. In addition, we demonstrated the one-component ceramic membrane-reactor for the methane conversion into synthesis gas at 1173 K. Methane conversion was drastically accelerated by the electrochemical oxygen pumping with one component membrane reactor. An addition of cathodic catalyst brought about further acceleration of methane conversion, and highly level of methane conversion (50%) and CO selectivity (95%) was reached. It is suggested that oxygen permeation was dependent on the cathodic process when the Ca0.8Sr0.2Ti0.7Fe0.3O3-alpha. was used as a mixed conducting oxide in the membrane system. (C) 2006 Elsevier B.V. All rights reserved.