Abstract

The infrared spectrum of a sulfur-resistant NiO/Cr₂O₃/MgAl₂O₄ methanation catalyst is presented and compared to the spectra of the catalyst after it was reduced, sulfided, and tested for methanation activity. The molecular structure of the catalyst is shown to be represented by NiO and MgO dispersed in a quasitridimensional Cr—O—Al network. Reduction and sulfiding reorders this network and alters the AlO_n coordination while reducing Cr⁶⁺ to Cr³⁺ or Cr²⁺. The sulfided and methanation-tested catalyst has intense sulfate absorption indicative of sulfur which is coordinated with NiCr and/or NiMg sites.

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