A process for preparing impregnated substantially spherical alumina-containing particles comprises the steps of impregnating specific starting material with (NH.sub.4).sub.2 SO.sub.4 and then heating the thus impregnated material at about 500.degree.-900.degree. C. for improved crush strength retention. In a preferred embodiment a fixed catalyst bed comprises at least one layer of the alumina-containing particles and at least one layer of catalyst particles comprising a refractory inorganic carrier and at least one hydrogenation promoter.