Partial oxidation of methane to syngas over the catalyst derived from double perovskite (La_(0.5)Sr_(0.5))2FeNiO_(6-δ)

摘要

Double perovskite-type oxide (La_(0.5)Sr_(0.5))2FeNiO_(6-δ) (LSFN) was invented as the precursor of a catalyst for the partial oxidation of methane (POM). The catalyst derived from LSFN is the K2NiF4-supported Ni(0) system, where K2NiF4 denotes the oxide (La_(0.5)Sr_(0.5))_2Ni_(1-x)FeO_(4+δ), a chemically stable structure with mixed ionic and electronic conducting properties. Among the four catalysts derived from LSFN, the best catalyst showed a high CH4 conversion (X_(ch4)>99%). high syngas selectivity (>98%) and, most importantly, nil coke formation at 900 °C. Detailed structural characterizations revealed that the presence of a small amount of SrCO3, left initially by incomplete formation of LSFN, and of nano-Ni(O) domains (or clusters <5 nm on average) on the K2NiF4 support is vital to this extraordinary catalytic performance. Furthermore, the decrease of H2/CO molar ratio with the increase in methane conversion happening in the course of activation was simulated using a group of the proposed key reaction steps of POM.