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/SiO2@TiO2 catalyst was designed and prepared. With the precise architecture of this core-shell structured catalyst, n-pentanal can be firstly in contact with TiO2 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/SiO2 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/TiO2 catalyst. Furthermore, the reaction kinetics of one-step synthesis of 2-PH from n-pentanal catalyzed by Ni/SiO2@TiO2 was studied and its kinetic model was established which is useful for reactor design and scale-up.