Co-free La0.9Ca0.1Fe1-xCuxO3-δ (x = 0.05, 0.1) hollow fiber membranes for H2/N2 and H2/CO co-production by coupling water splitting and partial oxidation of methane

Mixed ionic-electronic conducting oxygen transport membranes have demonstrated high oxygen permeability, which can be coupled with other oxidation reactions. The membrane reactor coupling water splitting with partial oxidation of methane reaction has great practical potential as it produces valuable feedstocks such as ammonia syngas and liquid fuel syngas. However, the existing membrane materials often exhibit structural stability issue and/or unsatisfactory oxygen permeability. In this work, copper-doped LCF_1-xCu_xO_3-δ (x = 0.05–0.1) hollow fiber membranes were used for hydrogen production by coupling the oxygen separation with water splitting and partial oxidation of methane. A small amount of copper doping could effectively reduce the sintering temperature of the membrane and increase the conductivity of the material, where a maximum oxygen flux of 0.55 mL min⁻¹ cm⁻² was achieved on LCFCu_0.05 membrane under the experimental conditions. In the water splitting test, a maximum hydrogen production rate of 3.7 mL min⁻¹ cm⁻² was achieved by using steam as the raw gas (driven by nitrogen) at the shell side and hydrogen/helium mixture as the sweep gas at the lumen side of the LCFCu_0.05 hollow fiber membrane with 10 wt.% Ni/SDC catalyst coated on the shell side. As pure methane gas was introduced at the lumen side coated with Ni/LaNiO₃/γ-Al₂O₃ catalyst, the H₂ production rate was further increased to its highest of 4.4 mL min⁻¹ cm⁻². In addition, the membrane reactor could be stably operated for 300 h under three different flow conditions without performance degradation. These results paves the development of robust membrane reactor for integrated water splitting and partial oxidation of methane.