Egg-like magnetically immobilized nanospheres: A long-lived catalyst model for the hydrogen transfer reaction in a continuous-flow reactor

A novel egg-like nanosphere was designed as a long-lived catalyst and is described as Fe3O4@nSiO(2)-NH2-Fe2O3.xBi(2)O(3)@mSiO(2). The catalyst was prepared using a modified Stober method with template-free surface-protected etching. The catalyst particle consists of a magnetic Fe3O4 core as the yolk, an inner silica shell bearing active Fe2O3.xBi(2)O(3) species as the egg white, and outer mesoporous silica as the egg shell. It exhibits an excellent performance in the catalytic reduction of nitro aromatics to corresponding anilines in a fixed-bed continuous-flow reactor. The reaction could be performed at 80 degrees C and could reach complete conversion in less than 1 min with only a 7% excess of hydrazine hydrate. The catalyst bed could be easily shifted between different substrates without cross-contamination because of the uniformity of the catalyst particles. This catalyst exhibited very good stability in the continuous-flow protocol. In the long-term reduction of p-nitrophenol with 0.5 mmol.min(-1) productivity, it worked for more than 1,500 cycles without any catalytic activity loss.