2012 Edition, May 1, 2012
Standard Practice for Calculation of Pore Size Distributions of Catalysts and Catalyst Carriers from Nitrogen Desorption Isotherms
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Description / Abstract:
This practice covers the calculation of pore size distributions
for catalysts and catalyst carriers from nitrogen desorption
isotherms. The computational procedure is particularly useful for
determining how the pore volume is distributed in catalyst samples
containing pores whose sizes range from approximately 1.5 to 100 nm
(15 to 1000 Å) in radius. It should be used with caution when
applied to isotherms for samples containing pores both within this
size range and pores larger than 100 nm (1000 Å) in radius. In such
instances the isotherms rise steeply near P/Po = 1 and the
total pore volume cannot be well defined. The calculations should
be begun at a point on the isotherm near saturation preferably in a
region near P/Po = 0.99, establishing an upper limit on
the pore size distribution range to be studied. Simplifications are
necessary regarding pore shape.Acylindrical pore model is assumed,
and the method treats the pores as non-intersecting, open-ended
capillaries which are assumed to function independently of each
other during the adsorption or desorption of nitrogen.