Highly Efficient Mesoporous Core-Shell Structured Ag@SiO 2 Nanosphere as an Environmentally Friendly Catalyst for Hydrogenation of Nitrobenzene.

The size-uniformed mesoporous Ag@SiO2 nanospheres' catalysts were prepared in one-pot step via reducing AgNO3 by different types of aldehyde, which could control the size of Ag@SiO2 NPs and exhibit excellent catalytic activity for the hydrogenation of nitrobenzene. The results showed that the Ag core size, monitored by different aldehydes with different reducing abilities, together with the ideal monodisperse core-shell mesoporous structure, was quite important to affect its superior catalytic performances. Moreover, the stability of Ag fixed in the core during reaction for 6 h under 2.0 MPa, 140 degrees C made this type of Ag@SiO2 catalyst separable and environmentally friendly compared with those conventional homogeneous catalysts and metal NPs catalysts. The best catalyst with smaller Ag cores was prepared by strong reducing agents such as CH2O. The conversion of nitrobenzene can reach 99.9%, the selectivity was 100% and the catalyst maintained its activity after several cycles, and thus, it is a useful novel candidate for the production of aniline.