Chemical looping steam reforming of glycerol for hydrogen production over NiO–Fe₂O₃/Al₂O₃ oxygen carriers

Abstract

Fe-based oxygen carriers (OCs) are widely used in chemical looping steam reforming (CLSR) due to excellent resistance to carbon buildup, low toxicity, and high activity. In this study, a type of nano NiO-Fe₂O₃/Al₂O₃ Fe-based OC that can easily be reduced by fuels and re-oxidized by air was developed for use in glycerol CLSR. It was synthesized by co-precipitation and impregnation. Based on the quadratic regression orthogonal model, a quadratic polynomial function was established to investigate the effects of temperature (<i>T</i>), water/carbon ratio (<i>S</i>/<i>C</i>), and loading (<i>M</i>) on hydrogen content (HL) and hydrogen selectivity (<i>S</i>). The OCs were characterized by XRD, XPS, SEM/EDX-mapping, TEM, and H₂-TPR to determine their physicochemical properties. XPS shows the Fe phase highly interacted with the Al₂O₃ supporting matrix by forming Fe aluminates in NiO-Fe₂O₃/Al₂O₃. The <i>S</i> (85.33%) and HL (78.41%) were obtained under the optimal conditions <i>T</i> = 600 °C, <i>S</i>/<i>C</i> = 1.0 mol mol^-1 and <i>M</i> = 0. A hydrogen content fluctuation within 4% was obtained under <i>T</i> = 700 °C, <i>S</i>/<i>C</i> = 1.0 mol mol^-1, and <i>M</i> = 2.5%, which means the cycle stability is perfect because of the addition of Ni. This study provides a basis for the development of efficient oxygen carriers in the CLSR system.