Pd, Pt, Ti incorporated ZSM-5 and promotional role of Ni for oxidation of methane in presence of molecular oxygen: Partial oxidation vs total oxidation

Methane is considered one of the most potent greenhouse gases, with a significant contribution to climate change. The tremendous heat-trapping capacity of methane and its growing emissions make global warming more alarming. In this study, Pd, Pt, and Ti incorporated ZSM-5 (PdPtTiZSM-5), and the promotional addition of Ni are investigated for the partial oxidation of methane (POM). The catalysts are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, surface area analysis, temperature-programmed reduction/oxidation/desorption techniques, FT-infrared-Raman spectroscopy, and transmission electron microscopy. According to the results of the present study, Pd–Pt nanoalloy assisted by Ptx + -Ti4+ acts as an active catalyst for the POM, producing primarily desired products, with total oxidation of methane (TOM) occurring as a minor side reaction. Moreover, the addition of 0.1 wt% Ni promotes the formation of Pd–Pt alloy phase exclusively upon reduction. Such a catalyst (0.1Ni/PdPtTiZSM-5) is enriched with active sites and achieves ∼55 % H2 yield with a 2.8H2/CO ratio at 600 °C and ∼70 % H2-yield with a 2.15H2/CO ratio at 650 °C during 240 min time on stream. This catalyst also occupies a minimum CO2 yield (∼32 %) at 600 °C, which indicates the presence of TOM to a minimum extent over 0.1Ni/PdPtTiZSM-5 than other investigated catalysts. The production of hydrogen-rich syngas with good H2 yield over the current catalyst system sets a high ambition for achieving hydrogen energy goals.