Synthesis gas generation by chemical-looping selective oxidation of methane using Pr1−xZrxO2−δ oxygen carriers

The Pr1−xZrxO2−δ complex oxides (x = 0, 0.1, 0.3, 0.5, 0.7, and 0.9) prepared by precipitation method were characterized by X-ray diffraction (XRD), H2 temperature programmed reduction (H2-TPR), O2 temperature programmed desorption (O2-TPD) and X-ray photoelectron spectroscopy (XPS) technologies. Chemical-looping selective oxidation of methane (CLSOM) process using a gas-solid reaction between methane and Pr-Zr complex oxides was investigated at 850 °C for the synthesis gas generation. Pr-Zr-O solid solution could be formed by incorporation of Zr4+ to Pr6O11 at a large proportion range (0.1-0.9). Oxygen mobility and thermal stability of Pr-Zr samples was obviously enhanced by the formation of Pr-Zr-O solid solution. Pr-rich Pr-Zr oxygen carriers showed high selectivity towards CO and H2 and high methane conversion. Synthesis gas with a suitable H2/CO ratio of 2.0 could be obtained over those samples. Pr0.7Zr0.3O2−δ performed satisfactory performance for the successive generation of synthesis gas in CLSOM process.