Correlation between microstructure and hydrogenolysis activity and selectivity of noble metal catalyst particles

摘要: Abstract Transmission electron microscopy (TEM) gives direct observation of the shapes, phases, and locations catalyst particles down to atomic dimensions. We have used TEM correlate particle microstructure with reactivity selectivity in alkane hydrogenolysis on Rh, Pt, Ir, Ru, Ni supported SiO2 by determining microreactor kinetics following either heating strongly H2 at 600°C (annealed) or oxidation O2 followed low temperature reduction reform metal (oxidized). In these experiments we examine same repeatedly after treatments, thus effects due loading treatment differences are excluded. Ethane activities found vary up 104 depending annealing pretreatment, changes reversible that catalysts can be cycled many times between pretreatments. Selectivities activation energies also significantly showing alters structure surface, not just surface area. shows high transforms all from single crystal metals (typically 100A diameter) into tiny clusters 10A microstructures stable indefinitely under reaction conditions, 180–260°C. Similar results reported for Rh-Ce/SiO2 catalysts, but large change observed causes only a slight enhancement activity.