Synthesis gas production to desired hydrogen to carbon monoxide ratios by tri-reforming of methane using Ni–MgO–(Ce,Zr)O2 catalysts

This paper highlights the performance of Ni–MgO–(Ce,Zr)O2 tri-reforming catalysts under various reaction conditions and explains results using catalyst characterization. Testing under controlled reaction conditions and the use of several catalyst characterization techniques (BET, XRD, TPR, SEM-EDS, and XPS) were employed to better explain the effects of the synthesis parameters on the reaction performances. The support Ce:Zr ratio, metal loading techniques, metal wt%, and Ni:Mg ratios all had a pronounced influence on the catalyst performance. An even ratio of Ce:Zr for the support and an even ratio of Ni:Mg gave the best performance. The wet impregnation method consistently showed more resistance to coke formation when compared to the deposition precipitation method, but the difference was attributed to a better ability to load Mg by wet impregnation. Lower than previously reported H2O concentrations in the feed gas composition also led to desired H2:CO ratios needed for FT synthesis while maintaining high conversions of CO2 and resistance to coke formation. High GHSV (61,000 h−1) yielded significantly higher H2:CO ratios when compared to reactions run at lower GHSV (25,000 h−1). These results suggest that steam reforming reactions are kept further from equilibrium at higher GHSV and result in higher H2 production. The tested tri-reforming catalyst produced desired H2:CO ratios with minimal deactivation, high reactant conversions, and extended catalyst lifetime.

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► Ni–MgO–(Ce,Zr)O2 catalysts optimized for tri-reforming.
► Ni:Mg and Ce:Zr ratios important to limit coking.
► Ideal formulation was Ce0.6Zr0.4O2–8Ni8Mg prepared by wet impregnation.
► Optimized gas feed ratios were CH4:CO2:H2O:O2 = 1:0.7:0.5:0.2.
► Hydrogen-to-carbon monoxide ratio increased with space velocity.