Amines are important platform molecules in the chemical industry,can be used as the intermediates for medicine,pesticides,dyes and detergents.Now,direct amination of alcohols with ammonia becomes a research hotspot,and has been regarded as the most impressing method to obtain amines.In this work,we prepared two kinds of Ru catalysts:nonsupported Ruthenium nanoparticles Ru-NPs and core/shell Ruthenium nanoreactor catalyst Ru@SiO2.Then,the catalytic performance was investigated in direct amination of octanol and other alcohols in the presence of ammonia.Ru nanoparticles with sizes from 2 to 9 nm were prepared by microemulsion method.The 90%selectivity to octylamine was obtained over small Ru-NP-2nm even at 92%conversion,whereas for larger Ru nanoparticles,the octylamine selectivity dropped as the octanol conversion approached 70-80%.At low ratio of ammonia/alcohol,small size Ru nanoparticles still provide high selectivity of primary amine.Besides,similar reactions involved in alcohol amination were observed for different substrates.And we prepared a silica-confined Ruthenium nanoreactor catalyst Ru@SiO2 besed on Ru-NPs.The core/shell structure with suitable shell thickness gives excellent conversion and selectivity in alcohol catalytic amination.The experimental results show that the selectivity of Ru@SiO2-5nm to octylamine is always higher than Ru@SiO2-10nm when the same conversion is reached.Local condensation of ammonia inside silica shell was confirmed,thereby guaranteeing the high selectivity to primary amines even at low ratio of ammonia/alcohol. |