Ammonium functionalization of mesopore walls

초록

Supported transition-metals (e.g., Co, Ni, Cu) have attracted much attention owing to their low costs and potential to replace expensive noble-metal nanoparticles.1,2 However, supported transition metals exhibited low catalytic activities than those of noble-metal catalysts.3 Therefore, the loading amount of non-noble metals has to be higher (typically, 10-30wt%) to achieve competent activities, considering to the size of industrial reactors.4 For such high amounts of metal loading, dispersion becomes poor.4 In my presentation, I introduced a simple route to circumvent this poor dispersion problem at high levels of metal loading (~ 30 wt. %). The key point is a functionalization of mesopore walls with basic ?C3H6?N+(Me)3(OH)- groups. When metal salts (nitrate or chloride) approach into their close environment, the basic functional groups induce their spontaneous precipitation as metal hydroxides. After the calcination, we obtained highly dispersed metal oxide nanoparticles. This new approach was demonstrated for NiO, CuO, and SnO2 nanoparticles supported on MFI zeolite nanosponge, MCM-48 mesoporous silica, and porous alumina with 30 wt. % loading amount. The metal nanoparticles can be finally obtained by reduction in the flow of hydrogen. As a result of high dispersion, the supported non-noble metal catalysts obtained in the present work showed potential to replace Pt-based catalysts in CO oxidation reaction.