N-alkylation of ammonia and amines with alcohols catalyzed by Ni-loaded CaSiO3

Nickel nanoparticles loaded onto calcium silicate (Ni/CaSiO3) have been prepared by ion-exchange method followed by in situ H2-reduction of the calcined precursor. Ni/CaSiO3 was found to be effective for the catalytic direct synthesis of primary amines from alcohols and NH3 under relatively mild conditions. Various aliphatic alcohols are tolerated, and the turnover number (TON) was higher than those of Ru-based homogeneous catalysts. The catalyst was recoverable and was reused. Effects of the surface oxidation states and particle size of Ni on the catalytic activity were studied by infrared (IR) investigation of the states of adsorbed CO and transmission electron microscopy (TEM). It is clarified that the surface Ni sites on small (3 nm) sized Ni nanoparticles are the catalytically active species. Ni/CaSiO3 was also effective for the alkylation of anilines and aliphatic amines with various alcohols (benzyl and aliphatic alcohols) under additive free conditions; primary amines were converted into secondary amines and secondary amines into tertiary amines. C) 2013 Elsevier B.V. All rights reserved.