Abstract
Catalytic properties of ruthenium phosphide (Ru2P) supported on silica for hydrodenitrogenation (HDN) of pyrrole were compared with those of Ru/SiO2 catalyst to clarify the effect of phosphidation. At higher W/F (652 g h mol−1), pyrrole conversion over Ru/SiO2 catalyst remarkably decreased with increasing reduction temperature. In contrast, pyrrole conversion over P-added Ru (Ru–P/SiO2) catalyst at the same W/F was enhanced with increasing reduction temperature due to Ru2P formation. This activity was higher than that of sulfided NiMoP/Al2O3 catalyst but lower than that of Ru/SiO2 catalyst at the same W/F. At lower W/F (130-391 g h mol−1), Ru–P/SiO2 catalyst showed higher activity and stability for pyrrole HDN than Ru/SiO2 catalyst. The cracking products (almost all CH4) were formed over Ru/SiO2 catalysts and butanes were formed over Ru–P/SiO2 catalysts. The results of CO adsorption and TEM images revealed that the particle size of Ru–P/SiO2 catalyst was smaller than that of Ru/SiO2 catalyst. The TOF of Ru–P/SiO2 catalyst increased with reduction temperature, and this TOF was lower than that of Ru/SiO2 catalyst. After HDN reaction, the peak of particle size distribution for Ru/SiO2 catalyst shifted to larger diameter, whereas that of Ru–P/SiO2 catalyst remained the same. Therefore, the stable activity of Ru–P/SiO2 catalyst can be explained by excess phosphorus species acting to stabilize Ru2P particles.
