Control of Ni metal particle size in Ni/SiO2 catalysts by calcination and reduction temperatures

It has been found that the particle size of Ni in Ni/SiO2 catalysts prepared by the alkoxide technique can be controlled by the calcination and reduction temperatures as well as by the extent of Ni loading in the catalyst. The mechanisms of sintering of the Ni metal and of redispersion of NiO particles during reduction and calcination respectively, are discussed. The sintering occurs by a particle-migration mechanism and the redispersion may occur by direct splitting to small particles. The catalytic property of Ni particles whose sizes were controlled either by their Ni loading or by their calcination and reduction temperatures was examined by using the catalyst for the Boudouard reaction.