A core–shell Ni/SiO2@TiO2 catalyst for highly selective one-step synthesis of 2-propylheptanol from n-pentanal

Abstract

One-step synthesis of 2-propylheptanol (2-PH) from n -pentanal via a reaction integration of n -pentanal self-condensation and successive hydrogenation is of great significance for it can simplify process flow and reduce energy consumption. The key to promotion of 2-PH selectivity is to enhance the competitiveness of n -pentanal self-condensation with respect to its direct hydrogenation. For this purpose, a core–shell structured Ni/SiO 2 @TiO 2 catalyst was designed and prepared. With the precise architecture of this core–shell structured catalyst, n -pentanal can be firstly in contact with TiO 2 to 2-propyl-2-heptenal (2-PHEA) while the direct hydrogenation to n -pentanol can be effectively inhibited, and then 2-PHEA diffuses into the core of Ni/SiO 2 and is hydrogenated to 2-PH. The spatial threshold of the core–shell catalyst significantly enhanced its catalytic performance; a 2-PH selectivity of 77.9% was reached with a 100% n -pentanal conversion. The 2-PH selectivity is much higher than that obtained by employing Ni/TiO 2 catalyst. Furthermore, the reaction kinetics of one-step synthesis of 2-PH from n -pentanal catalyzed by Ni/SiO 2 @TiO 2 was studied and its kinetic model was established which is useful for reactor design and scale-up.