Methanizer

Discussions about sample preparation: extraction, cleanup, derivatization, etc.

8 posts Page 1 of 1
Greetings,

I am analyzing CO and CO2 on a Haysep Q (Pre-column & backflushed) and Haysep R column (separation column). The samples goes thru the methanizer and is detected by FID.

Its a new GC and i have only try it out with calibration gas, 20ppm CO&CO2 each (Helium as balance gas). Its been Day 5 and I notice that the area of CO2 keep falling everyday. But the are of CO is very consistent since Day 1.

Does anyone have any suggested possibly in this kind of problem?

Thank you

First, delay your backflush 20 seconds and see if your CO2 peak increases.

That means due to a change in column flow the CO2 peak is eluting slightly later and you were backflushing part of the CO2 peak.

The change in flow can result from a change in your carrier supply system or a leak or column aging. A change in column temperature could also delay the CO2 peak.

Second, the methanizer itself may be losing its efficiency due to choking (contamination of the catalyst). It is also possible that the temperature of the catalyst heater has changed causing a loss of conversion of CO2 to methane.

Good luck,

Rodney George
consultant

CO2

Hi Rodney,

Thanks for your reply.
I have try increasing the backflush time without any success. If there is a leak in the system, wouldnt the CO peak drop as well?

The method is using isothermal throughout the run, so there is no change in column temperature. Currently I have not run any hydrocarbon or sulfur samples so contaminants should not be a issue.

Could moisture in the carrier gas cause a drop in CO2? Is CO2 more sensitive to moisture than CO?
Other than the causes for drop in CO2, could it be the CO2 have not stabilize in the system causing a spike in CO2 and now it is trying to stabilize?

Thank you very much.

You wrote:

Thanks for your reply.
I have try increasing the backflush time without any success. If there is a leak in the system, wouldnt the CO peak drop as well?

Not necessarily, if the leak was in the sample valve. I am focused on the retention time of the peaks.

The method is using isothermal throughout the run, so there is no change in column temperature.

Just because the instrument says the temperature is the same doesn't mean it is.

Currently I have not run any hydrocarbon or sulfur samples so contaminants should not be a issue.

Could moisture in the carrier gas cause a drop in CO2? Is CO2 more sensitive to moisture than CO?

The CO2 is more difficult for the catalyst to convert than CO. A loss of efficiency of catalyst conversion could be the problem. CO2 can react with amines forming the carbonate.

Other than the causes for drop in CO2, could it be the CO2 have not stabilize in the system causing a spike in CO2 and now it is trying to stabilize?

Yes, it could be a sample homogeneity issue.

Good luck,

Rodney George

CO2

Hi Rodney,

Thanks for your Input.

The method that my vendor set for me is based on constant pressure, does it affect my CO2 peak area?
The CO2 peak eluted around 4min from 2nd column but the back flush time is at 6 mins so it seem ample time for the CO2 to go thru without being backflush.

Its a new GC and methanizer, so seem seem doesnt make sense to be malfunction. What is the normal temperature for conditioning the methanizer?

Thank you very much

The quick and correct answer is :

You should ask your vendor for their temperature and other conditions for their recommendation for conditioning the methanizer.


If the catalyst was not prepared properly you may find it fails rather quickly. It is prepared at conditions you will not be able to reproduce (it is beyond the temperature limits of GC ovens) unless you have special equipment, and of course, the conditioning gas is HYDROGEN. So you can replace the bad catalyst or ask them how to regenerate the catalyst. Different catalysts (Ni, Pt, etc) require different conditions.

You should be using hydrogen carrier gas of course, and I assume it does not contain moisture (or oxygen) as through (possibly) from a hydrogen generator or a air leak.

Talk to the company to whom you gave your money. They should help you.

best wishes,

Rodney George

Hi Rodney,

Yes the carrier gas im using is hydrogen.

The air leak u are refering is it to the gas line from hydrogen generator to GC? If there is minor leaking in the gas line , is it possible for air and moisture to enter the gasline?

You mention about mositure and oxygen. Can it affect the methanizer efficiency in converting CO2? What kind of impurity is methanizer (nickel catalyst) is sensitive to?

Thank you very much

Regards

If you have a leak to the atmosphere anywhere in your system, you can have moisture and oxygen enter the carrier gas flow.

Nickel catalyst can be deactivated by carbon containing compounds, oxygen, and/or moisture.

If you have carbonized the catalyst then you may have to purge the catalyst with air or oxygen to remove the carbon.

If the catalyst was made properly you may be able to restore its activity by passing hydrogen through the methanizer while heating the catalyst at a high temperature.

Discuss these procedures with your catalyst supplier BEFORE YOU DO ANYTHING.

Discuss these procedures with your catalyst supplier BEFORE YOU DO ANYTHING.

Discuss these procedures with your catalyst supplier BEFORE YOU DO ANYTHING.

Did I forget to mention:

Discuss these procedures with your catalyst supplier BEFORE YOU DO ANYTHING.

best wishes,

Rodney George
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