A study on the deactivation and reactivation of a Ni/Al2O3 aldehyde hydrogenation catalyst: Effects of regeneration on the activity and properties of the catalyst

The effectiveness of different experiments for the regeneration of a phosphorus poisoned 15 wt.% Ni/Al2O3 catalyst was investigated during the time on stream hydrogenation of octanal to octanol. The catalyst was deactivated after being exposed to feed contaminated with 500 ppm of triphenylphosphine. Regeneration of the catalyst was attempted by either treating the poisoned catalyst with hydrogen, washing the catalyst with octanol or conducting a combined octanol wash-hydrogen treatment experiment, all at elevated temperatures and at atmospheric pressure. The combined regeneration experiment was the most effective, since the conversion and octanol selectivity were recovered to a significant extent. Characterisation of the regenerated catalysts by ICP-OES, XRD, magnetic measurements and TEM showed that sintering also contributed to the deactivation of the catalysts, and that regeneration did not remove phosphorus from the catalyst, due to phosphorus having reacted with nickel. It was also established that some phosphorus was incorporated into the alumina support to generate strongly acidic sites.