Structural Changes in a Sulfur-Resistant Methanation Catalyst as Determined from Infrared Spectra

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 quasi-tridimensional Cr—O—Al network. Reduction and sulfiding reorders this network and alters the AlOn 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.