Surface and bulk analysis of a deactivated Raney nickel methanation catalyst

In a joint PETC-NBS experiment, a Raney nickel methanation catalyst in a hot gas recycle (HGR) bench-scale reactor (used for catalyst lifetime testing) has been examined with a wide range of modern analytical techniques sensitive to both surface and bulk chemical properties of the catalyst. The reactor was designed to use a catalyst essentially identical to that used in previous lifetime testing and to allow both the sampling at various positions along the catalyst bed and the introduction of the samples into the various analytical instruments under inert atmospheric conditions (i.e., without exposure to oxygen, water, etc.). The purpose of this work was to explore the reasons for the premature failure of the catalyst in pilot plant lifetime tests. The results indicate that in spite of significant catalyst deactivation only low levels of carbon (a small fraction of a surface monolayer) are formed on the catalyst surface. The primary cause of catalyst deactivation in this lifetime test was determined to be the growth of the nickel crystallites and subsequent decrease in active catalyst surface area.