N-Hexadecane hydroisomerization over Pt-HBEA catalysts. Quantification and effect of the intimacy between metal and protonic sites

摘要

n-Hexadecane (n-C_(16)) transformation was carried out at 220 C and 30 bar over bifunctional catalysts with Pt and HBEA as hydro-dehydrogenating and acid components. Three series of catalysts were prepared, with different levels of proximity between Pt and acid sites: in series 1, Pt was essentially located on the outer surface of HBEA crystal agglomerates of ～12.5 μm, series 2 and 3 resulted from combination of Pt-Al_2O_3 and HBEA particles of ～70 μm and from mechanical mixture of Pt-Al _2O_3 and HBEA particles of ～300 μm, respectively. The rate and selectivity of n-C16 hydroisomerization was shown to be determined by only two parameters, the balance between the metal and acid functions and their degree of intimacy. Both of them were easy to be quantified: the first one by the C_(Pt)/C_(H+) ratio between the concentrations of accessible Pt and protonic sites, the second one by n _(as), the number of acid steps undergone by olefinic intermediates during their diffusion between two Pt sites which can be drawn from the initial product distribution.