Amorphous alumina aerogel was activated by hydrogen or oxygen spillover and also by successive H 2 -O 2 or O 2 -H 2 spillovers at 430°C and was tested in the hydrogenation of ethylene at 180°C. Depending on the type of the spillover treatment the catalytic behaviour of alumina differs by the presence or the absence of an induction period (related to the presence or the absence of the spilt over hydrogen), by the trend in the deactivation for several consecutive catalytic runs, by the behaviour towards H 2 O, NH 3 , NO present in the reactants.