NiO/κ-CeZrO4 functional oxygen carriers with Niδ+ and oxygen vacancy synergy for chemical looping partial oxidation reforming of methane

Abstract

Chemical looping partial oxidation reforming (CLPOR) technology is an economically attractive, sustainable, and environmental-friendly process strategy of CH4 conversion. In this study, NiO-promoted κ-CeZrO4 functional oxygen carriers (OCs) were designed and synthesized for the CLPOR of methane, with excellent lattice oxygen (LO) transmission performance and structural stability, aiming to reduce the energy penalty and temperature required for methane conversion. The crystalline phase, reaction performance, surface properties and reaction mechanism of the OC were systematically analyzed. In-situ CH4-XPS analysis was further carried out to reveal the internal mechanism with NiO/κ-CeZrO4 and the reason for higher CO selectivity at a low temperature. The methane conversion rate (≥ 80%) and syngas selectivity (≥ 93%) can be obtained under the most of reported reaction conditions (over 850 °C). More importantly, a higher methane conversion rate (52–72%) with syngas selectivity (88–92%) was even able to be achieved at a relative low temperature range 700–800 °C. The excellent performance was attributed to the reducing transmission temperature of the LO and a synergetic effect of Niδ+ and the oxygen vacancies (existed on the surface), thereby inhibiting carbon deposition caused by the excessively fast methane cracking rate under high temperature atmosphere.