Hi all,
In our labs, we perform standard N2 ad/des-sorption isotherm measurements with our Micromeritics Tristar II.
The research is slowly expanding from oxide materials to microporous carbons so I would like to implement CO2 ad/des-sorption as well.
I understand that CO2 ad/des-sorption is performed at 0°C.
So practically, could I simply fill the dewar with a suitable cooling liquid? The latter I will circulate through an external thermostat to keep it at 0°C during the measurement.
Micromeritics sells so-called "chiller dewars" (https://www.micromeritics.com/Product-Showcase/Sub-Ambient-Temperature-Control-Devices.aspx#Chiller%20Dewar) but if we can use the cheap DIY route, why not.
Additionally, the saturation pressure of CO2 at 0°C is around 25000 mmHg.
Hence the P/P0 range set in the program should be lowered to 0-0.03 (~760 mmHg) right?
Otherwise, the measurement tubes might burst off due to the high pressure compared to the atmosphere.
Is this possibility or am I thinking of this too simply?
Any advice would be greatly appreciated!
Thanks!
You are correct on both points:
-you can even use a standard dewar (without recirculation bath) and fill it with a water/ice mixture (you will only need to check that the ice is present during the whole measurement
-you can only measure your isotherm up to 1 atm of CO2. Actually, this is the whole set-up (not only the glass cell) that is not suitable for high pressure measurement: measurement of CO2 adsorption isotherm at high pressure (often used for the characterization of MOF) requires a specific set-up