(323g) Water Splitting and Partial Oxidation of Methane Using an Oxygen Permeable Membrane with Ni Catalyst

In this presentation, we will discuss hydrogen production from water thermolysis and partial oxidation of methane (POM) in an oxygen permeable MIEC (mixed ionic-electronic conducting) membrane reactor. Water thermolysis on the feed side is the oxygen source, and oxygen diffuses through the membrane to react with methane on the sweep side. Conventional nickel catalysts for POM suffer from carbon deposition due to the insufficient supplies of oxygen. Besides, due to the exothermic reaction of POM, the catalysts experience high temperature spots, which lead to melting or agglomeration. These two problems can be solved in an oxygen permeable membrane reactor with water thermolysis.

Oxygen permeable La_0.9Ca_0.1FeO_3-δ (LCF-91) membrane is used [1] [2]. The overall reaction is endothermic, so hot spots on nickel catalysts can be avoided. Moreover, carbon deposition from methane decomposition is suppressed by increasing the oxygen flux through the application of nickel catalysts. Experimental results show that optimum syngas composition for gas-to-liquid pathway i.e., H₂/CO = 2 is achieved on the sweep side. Local measurements on the membrane surface reveal that the methane oxidation mechanism depends on the availability of surface oxygen. The catalytic porous layer on the sweep side also enhances the water thermolysis by two orders of magnitude. Long term study shows that the catalytic layer maintains high performances for 54 hours.

Additionally, a novel approach is adapted to synthesis nickel nanoparticles on perovskite supports on the sweep side. Because of thermodynamic equilibrium, nickel atoms exsolve from perovskite lattices and form nanoparticles on the perovskite grains with good distribution under reducing conditions. These nickel nanoparticles are expected to have high catalytic performances and good stability; and hydrogen production from water and methane in the oxygen permeable membrane can be enhanced.

Reference:

[1] Wu, X. Y., Chang, L., Uddi, M., Kirchen, P., and Ghoniem, A. F., 2015, "Toward enhanced hydrogen generation from water using oxygen permeating LCF membranes," PCCP, 17(15), pp. 10093-10107.

[2] Wu, X. Y., Uddi, M., and Ghoniem, A. F., 2016, "Enhancing co-production of H2 and syngas via water splitting and POM on surface-modified oxygen permeable membranes," invited to submit to AIChE Journal, under review.