Hello!
I need to measure the rate of ethylene removal by a certain material placed in a closed system.
So far, I'm thinking of using a vacuum desiccator cabinet or gas bag. Keeping an initial concentration of 10% ethylene and inert synthetic gas (O2, N2, CO2) with the adsorbent material and timely measurements using gas chromatography.
If someone has done similar procedure or suggestions on the setup, gas sampling, making of calibration gas mixtures are highly appreciated. Thank you
Howdy,
Typically, you require a measurement technique based on an OPEN flow measuring system. Feed your measuring vessel with constant flow rates (and mass flow rates) of a gas mixture with different ethylene concentrations. The difference between your ingoing ethylene flux (your known ingoing ethylene mass flow) and the outgoing ethylene flux (your measured outgoing ethylene mass flow - which may be variable) equals the ethylene adsorption rate by your adsorption agent in the measuring vessel.
With a CLOSED measuring system your measurements will be biased because you will not keep all gas mixing ratio's constant! Do not use a closed system to perform this experiment. Pay attention as well to the detection system used to measure ethylene. You need a continuous system (laser induced ultrasound detector) or semi-continuous system (FID gas-chromatography of small organic hydrocarbons up to propane).
Also have a look at the following papers, which describe the basics of open flow measurement systems.
Article Can ethylene, a simple gaseous hydrocarbon, be considered as...
Article Importance of Time Constants in an Open Flow System: Mathema...
Have fun (und erfolg),
Frank
Dear Prof. Frank Veroustraete ,
Thank you very much for the detailed answer. However, the resources available are limited.
If I go for a closed system, keeping a constant gas mix in a gas bag and drawing equal volumes from there for separate analysis would give a constant gas ratio right?
Could work if no other gas species in the mixture interferes with the adsorption process. This means that your adsorbent is inert for all gases except ethylene.
Unfortunately this can only be corroborated with an open flow system. With a closed measurement system you end up in a vicious circle in regard to your hypothesis.
I fear that only with an open flow system you will be able to corroborate the physicochemical background of the adsorption process. Sorry to say.
Best regards,
Frank
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