Scope
This test method covers the determination of the total pore volume of catalysts and catalyst carriers, that is, the volume of pores having pore diameter between approximately 14 μm and 0.4 nm.
Summary of Test Method
The total pore volume of a catalyst or catalyst carrier is determined as the difference between the particle volume and the true volume, measured by mercury intrusion and helium pycnometry, respectively. The particle volume is determined by mercury intrusion at ambient pressure and the true volume is determined by helium displacement at pressures above ambient.
Significance and Use
This test method provides for the measurement of volume of pores that are in the range of catalytic importance and possibly for adsorption processes. This test method requires the use of mercury in order to perform the measurements.
Apparatus
For Helium Pycnometry—A schematic diagram of the pycnometer apparatus is shown in Fig. 2. It should be constructed from metal and have the following features:
6.3.1 Sample Cell, having a volume suitable for the desired sample size and calibrated to the nearest 0.1 cm3. This volume is indicated in Fig. 2.
6.3.2 Reference Volume (VR), a precisely calibrated volume known to the nearest 0.02 cm3.
6.3.3 Pressure Transducer, (0 to 25 psig or 0 to 172.3 kPa) with minimum volume displacement and linear within 0.1 %.
6.3.4 Pressure Relief Valve, set to 25 psig (172.3 kPa), to avoid overpressurization of the transducer.
6.3.5 Filter, to prevent powder from contaminating the pressure transducer.
6.3.6 Input Flow Control Valves, to control pressurization.
6.3.7 Output Flow Control Valves, to vent the gas.
6.3.8 Valve, to connect the reference volume to the sample cell.
6.3.9 Non-Porous Calibration Standard, (preferably stainless steel) of known volume which fills 1⁄4 to 2⁄3 of the sample cup.
6.3.10 Digital Meter, for reading the pressure to 0.001 psig (6.89 Pa) from the transducer.
6.3.11 Sample Cell Cover, with O-ring seal.
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