Conversion of 2-octanol over nickel-alumina, cobalt-alumina, and alumina catalysts

Structural characterization of Co-Al and Ni-Al coprecipitated catalysts has been accomplished using techniques such as X-ray diffraction, DTA, TGA, TG-MS, BET surface area and pore volume. The catalyst samples were prepared by coprecipitation of cobalt (or nickel) and aluminum from their aqueous salt solutions. The interaction of Co (or Ni) with aluminum has been investigated by X-ray diffraction as a function of calcination temperature. The results indicate that the interaction between Co and Al can lead to the formation of a normal spinel of CoAl2O4 at a very low temperature such as 473 K. On the other hand the interaction between Ni and Al is not sufficient to form well crystallized NiAl2O4 species at low temperatures but nickel-aluminate formation was seen above 973 K. The activity and selectivity of these catalysts for 2-octanol conversion are dependent on the reaction temperature, liquid hour space velocity (LHSV) as well as on the calcination temperature. The dehydrogenation activity of nickel based catalysts is attributed to the presence of nickel oxide whereas the dehydration activity is due to the spinel phase. The differences in the dehydration activity between alumina and nickel-alumina is mostly because of the incomplete formation of spinel phase (i.e., low temperature calcined samples). Catalytic activity of cobalt-alumina catalysts is comparable with that of alumina catalysts towards 2-octanol conversion.