Preparation, characterization and activity of novel silica-pillared layered titanoniobate supported copper catalysts for the direct decomposition of NO

A series of silica-pillared layered titanoniobate supported copper catalysts (Cu/Si-TiNbO5) were prepared for the direct decomposition of NO. It was found that Cu/Si-TiNbO5 catalysts were highly active for the reaction of NO (0.1 vol.% in He) decomposition in the space velocity range of 3000–30,000 cm3 g−1 h−1. The 3.5 wt.% Cu/Si-TiNbO5 catalyst showed the highest conversion into N2 for NO decomposition. While 2.0 wt.% Cu/Si-TiNbO5 had the highest specific activity at low temperature (≤550°C) and 1.0 wt.% Cu/Si-TiNbO5 showed the highest specific activity at high temperature (>550°C). XRD and temperature-programmed reduction (TPR) results indicated that there existed well-dispersed copper oxide species and large copper oxide particles in the catalysts. Well-dispersed copper oxide species were reduced more easily than large copper oxide particles by H2. X-ray photoelectron spectra (XPS) and Auger electron spectra (AES) results revealed that Cu+ species existed in Cu/Si-TiNbO5 catalysts and that the copper oxide species in Cu/Si-TiNbO5 catalysts after used for NO decomposition were different from those before the reaction. Well-dispersed copper oxide species were active for NO decomposition and the most active sites might be the dimeric copper oxide species over the support.