Precious Metal Doped Ni–Mg/Ceria–Zirconia Catalysts for Methane Conversion to Syngas by Low Temperature Bi-reforming

Abstract: Low temperature (450–600 °C) bi-reforming of methane was studied over platinum (0.16 wt%) or palladium (0.13 wt%) along with nickel (1.4 wt%) and magnesium (1.0 wt%) immobilized onto a ceria–zirconia support (termed 0.16Pt and 0.13Pd). Bi-reforming studies using a feed ratio of 3:1:2 for CH₄:CO₂:H₂O, respectively, showed that the H₂:CO ratio neared the desired ratio of 2 between 500 and 600 °C for the 0.16Pt catalyst and consistent with bi-reforming at more traditional conditions. This H₂:CO ratio was desirable (near 2) compared to dry or steam reforming alone, as well as to other CH₄:CO₂:H₂O ratios. Reaction studies showed that CH₄ conversion decreased with increasing GHSV (68,000–272,000 h⁻¹) at 500 °C and increased with increasing temperature at a GHSV of 136,000 h⁻¹ for both catalyst systems. However, the Pt-based catalyst had more consistent H₂:CO ratios between 1.9 and 2.2 (T ≥ 500 °C) compared to its Pd counterpart (H₂:CO ratios of 1.6–3.0), which was linked to the increased rWGS activity and stronger CO₂ adsorption. This study indicates reasonable CH₄ conversions and H₂:CO ratio near 2 can be achieved despite operating in this low temperature regime and may enable intensified processes for the conversion of methane to value-added products. Graphical Abstract: [Figure not available: see fulltext.].