Application of a poisoning titration method for measuring support effects in new AlPO4-supported nickel catalysts

Abstract

With the help of a poisoning titration method, using n-butanethiol as the poison, we have determined the number of active sites responsible for the liquid-phase catalytic hydrogenation of hex-1-ene over a series of nickel catalysts supported on AlPO₄, SiO₂ and AlPO₄–SiO₂, for a wide range of dispersions and nickel loadings.

These results, taken in conjunction with the metal surface area of the catalysts, obtained by X-ray diffraction, have allowed us to obtain the fraction of catalytically active surface nickel atoms. This value, a measure of the metal–support interaction, is independent of particle size for catalysts with the same support and nickel loading, whereas it decreases as the nickel loading is reduced with regard to the support; the fraction of active sites decreases in the sequence: Ni/SiO₂≈ Ni/AlPO₄–SiO₂ > Ni/AlPO₄. This behaviour is associated with a strong metal–support interaction, which may be explained by electronic effects.