Understanding the Impact of Hydrogen Activation by SrCe 0.8Zr0.2O 3−δ Perovskite Membrane Material on Direct Non-Oxidative Methane Conversion

Abstract

Understanding the Impact of Hydrogen Activation by SrCe 0.8Zr0.2O 3−δ Perovskite Membrane Material on Direct Non-Oxidative Methane Conversion Sichao Cheng 1†, Su Cheun Oh 1†, Mann Sakbodin 1 , Limei Qiu 2 , Yuxia Diao 2 and Dongxia Liu 1 * 1 Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, MD, United States, 2 Research Institute of Petroleum Processing, SINOPEC, Beijing, China Direct non-oxidative methane conversion (DNMC) converts methane (CH 4 ) in one step to olefin and aromatic hydrocarbons and hydrogen (H 2) co-product. Membrane reactors comprising methane activation catalysts and H 2 -permeable membranes can enhance methane conversion by in situ H 2 removal via Le Chatelier’s principle. Rigorous description of H 2 kinetic effects on both membrane and catalyst materials in the membrane reactor, however, has been rarely studied. In this work, we report the impact of hydrogen activation by hydrogen-permeable SrCe 0.8Zr 0.2O 3−δ (SCZO) perovskite oxide material on DNMC over an iron/silica catalyst. The SCZO oxide has mixed ionic and electronic conductivity and is capable of H2 activation into protons and electrons for H 2 permeation. In the fixed- bed reactor packed with a mixture of SCZO oxide and iron/silica catalyst, stable and high methane conversion and low coke selectivity in DNMC was achieved by co-feeding of H 2 in methane stream. The characterizations show that SCZO activates H 2 to favor “soft coke” formation on the catalyst. The SCZO could absorb H 2 in situ to lower its local concentration to mitigate the reverse reaction of DNMC in the tested conditions. The co-existence of H 2 co-feed, SCZO oxide, and DNMC catalyst in the present study mimics the conditions of DNMC in the H2 -permeable SCZO membrane reactor. The findings in this work offer the mechanistic understanding of and guidance for the design of H2 -permeable membrane reactors for DNMC and other alkane dehydrogenation reactions.