Temperature-Dependent Selectivity of Hydrogenation/Hydrogenolysis during Phenol Conversion over Ni Catalysts

Abstract

It is challenging to selectively upgrade phenolic compounds to aromatics because of much weaker adsorption of hydroxyl compared to that of phenyl upon Ni catalysts. With 10% Ni loading in theory, three Ni catalysts with different Ni nanoparticle sizes were prepared with the wet impregnation method on SiO2 and Silicalite-1 and with the in situ encapsulation method (Silicalite-1). On the basis of the results, we proposed a general rule concerning temperature-dependent selectivity control on phenol hydroconversion over Ni catalysts. As well as benzene saturation in consecutive mode, hydrogenation of phenyl ring was more dramatically inhibited at elevated temperature via decreased adsorption of benzene rings than that of hydroxyl to selectively favor hydrogenolysis over hydrogenation in parallel mode. Among three Ni catalysts, Ni@Silicalite-1 with 3–5 nm Ni nanoparticle sizes encapsulated imposed the restricted adsorption conformation of phenol via end-up mode within channels of Silicalite-1 zeolite to furthe...