Do. Uner et al., OPTIMIZATION OF THE VOLUMETRIC HYDROGEN CHEMISORPTION TECHNIQUE FOR DISPERSIONS OF RU SIO2 CATALYSTS/, Journal of catalysis, 156(1), 1995, pp. 60-64
Metal dispersions of silica-supported ruthenium catalysts determined b
y the standard volumetric chemisorption technique were found to be ina
ccurate due to irreversible spillover of hydrogen to the support. Dire
ct evidence was obtained via in situ H-1 NMR for an irreversibly bound
component of the hydrogen that migrated from the metal to the support
on a time scale of tens of minutes or longer at room temperature. It
was also shown in this work that hydrogen saturated the surface of the
metal particles on a shorter time scale, on the order of minutes. Bas
ed on H-1 NMR, optimum conditions for the volumetric chemisorption met
hod were determined in order to alleviate the interference of spillove
r with measurements of hydrogen uptake on the metal. Ruthenium dispers
ions obtained from the optimized volumetric chemisorption technique we
re more accurate and agreed well with the results of the H-1 NMR metho
d. (C) 1995 Academic Press, Inc.