Infrared Spectra of Some Nonreduced Methanation Catalysts

Abstract

The infrared spectra (4000 to 400 cm⁻¹) of two commercial nonreduced methanation catalysts have been recorded and interpreted. The catalysts are prepared as mixtures of (a) nickel in a silica support and (b) nickel in an alumina support. Graphite is added to these mixtures as a binder to facilitate pressing of catalyst pellets for commercial use. It is revealed in the spectra of the catalysts that although (a) is prepared to have a simple NiO/SiO₂ composition the silica support is not of the form SiO₂; rather the spectral characteristics are similar to those found for linear chain silicates. In (b) the Al—O vibrations are characteristic of amorphous Al₂O₃, and H₂O is tightly bound in the pellet. The CO₃⁼ ion is present in both (a) and (b). It is not bound to Ni in either (a) or (b), but it is bound in the silicate structure of (a) and associated with Al in (b). The presence of the ion cannot be explained by only in situ generation from atmospheric CO₂ and H₂O, but its presence must be due to residual CO₃⁼ from the catalyst preparation.