High-selectivity partial oxidation of methane into synthesis gas: the role of the red-ox transformations of rare earth — alkali earth cobaltate-based catalyst components

Abstract

La1+xSr1−xCoO4 (x=0; 0.25) and NdCaCoO3.96 compounds with a layered perovskite-like structure synthesized by the solid state method and characterized by XRD, XPS, EDAX and H2-TPR were used as catalyst precursors for the partial oxidation of methane to synthesis gas. Catalytic tests were carried out in a quartz flow reactor using a CH4/O2 mixture without dilution with inert gases. The higher activity of the NdCaCoO4±δ-based catalyst in comparison with La1+xSr1−xCoO4 is associated with the easier formation of Nd and Ca oxides and metallic cobalt in the course of NdCaCoO4±δ reduction in the POM environment. Preliminary reduction of the catalysts with hydrogen leads to a significant increase in synthesis gas production at 800–850°С. Different activity and selectivity of NdCaCoO4±δ and La1+xSr1−xCoO4-based catalysts can also be related to the different morphologies of metal-oxide nanocomposites that appear in the course of the reductive decomposition of cobaltates.