Particulate Systems’ HPVA II Series of adsorption analyzers utilizes the static volumetric technique in order to achieve high-pressure desorption and adsorption isotherms.
With the volumetric method, a known amount of gas (adsorptive) is introduced into the chamber that contains the sample to be characterized. As soon as the sample reaches equilibrium with the adsorbate gas, the last equilibrium pressure is recorded. These data are utilized to determine the amount of gas adsorbed by the sample.
The procedure is repeated at specified pressure intervals until the maximum preselected pressure is reached. The pressure can then be reduced to provide a desorption isotherm. Finally, each of the equilibrium points, i.e. equilibrium pressure and volume adsorbed, are plotted to provide an isotherm.
Using separate transducers for monitoring high and low pressures provides excellent precision and reproducibility. For extensive hydrogen storage studies at high pressures and low temperatures, the HPVA II can also be interfaced with a cryostat to control temperatures down to 30 K.
The main features of the HPVA II high pressure volumetric analyzer include:
- Wide temperature capability from cryogenic to 500 °C
- Wide operating pressure range from high vacuum to 100 or 200 bar
- Excellent control of sample temperature with a cryogen dewar, recirculating temperature bath, or furnace
- Manifold temperature is controlled with heater for precision and stability
- Handles adsorbates such as nitrogen, hydrogen, oxygen, methane, carbon dioxide, and argon
- Fully automated analysis using interactive software
- Software includes NIST REFPROP
- Excellent data reproducibility
- Data analysis package using Microsoft Excel macros for data processing and graphing
The HPVA II high pressure volumetric analyzer offers the following benefits:
- Isotherm and weight percentage plots generated automatically
- Dual free-space measurement for accurate isotherm data
- Free space can be measured or entered
- Reports provided as interactive spreadsheets
- Real-time charts for Temperature vs. Time and Pressure vs. Time
- Kinetic data provided for rate of adsorpotion calculations
- Gas mixtures with up to three components can be utilized
- Langmuir equation utilized to model Type I isotherms
- System can achieve a maximum pressure of 200 bar
- High-pressure transducer offers a reading precision of ±0.04% full scale with a stability of ±0.1%
- Langmuir surface area, BET surface area, and total pore volume calculations included
- Hydrogen gas sensor automatically shuts down system in event of hydrogen leaks