In
chemical gas adsorption a reactive gas as hydrogen or carbon monoxide
is used to obtain information on the active properties of the metal
phase of a (supported) metal catalyst. The sample is first reduced
in hydrogen and then evacuated to retrieve the active metal phase.
In the volumetric method, known amounts of hydrogen (Pt, Ni, Rh,
Ru) or CO (Pd, Pt) are dosed and subsequently adsorbed at different
partial pressures, resulting in a chemisorption isotherm. This isotherm
measurement is repeated after applying an evacuation step at the
analysis temperature, to remove weakly adsorbed species (back-sorption
method). The difference between the two isotherms represents the
chemically bonded reactive gas and is used in the calculations.
The measurements
are performed on a Quantachrome Autosorb-1C and the
report consists of a graphical representation of the chemisorption isotherms
and a table providing information
on specific metal surface area, metal dispersion, and average crystallite
size.
In
chemical gas adsorption a reactive gas as hydrogen or carbon monoxide
is used to obtain information on the active properties of the metal
phase of a (supported) metal catalyst. The sample is first reduced
in hydrogen and then evacuated to retrieve the active metal phase.
In the volumetric method, known amounts of hydrogen (Pt, Ni, Rh,
Ru) or CO (Pd, Pt) are dosed and subsequently adsorbed at different
partial pressures, resulting in a chemisorption isotherm. This isotherm
measurement is repeated after applying an evacuation step at the
analysis temperature, to remove weakly adsorbed species (back-sorption
method). The difference between the two isotherms represents the
chemically bonded reactive gas and is used in the calculations.
