Methanizer question

[chemguy]

Hi everyone. Newbie to the forum.

My application involves permanent gas separation and due to the low levels of CO & CO2, I use a methanizer to convert them to Methane. My sample also contains some hydrocarbons. Can these deactivate the nickel catalyst in the methanizer?

Thanks in advance for any replies.

[GasMan]

Chemguy,

You need to read what your supplier of the methanizer quotes as the max concentration of hydrocarbons. What can happen is that the hydrocarbons carbonize and leave a thin film of carbon on the catalyst which will eventually kill the methanizer. However, you will start to see that the system becomes sensitive to oxygen. The oxygen in your sample will react with the carbon to form CO2. This in turn is converted to methane and is then detected by the flame detector. I believe I have seen a UOP method where it suggests injecting large volumes of air until you see no response for oxygen.

The methanizer that I am familiar with suggests that above 100 ppm one should think about bypassing the nickel catalyst when the hydrocarbons elute from your column. This can be done with an automated valve.

Gasman

[arie2044]

Hi
I'm using methanizer for very low (15-200ppb) CO & CO2 analysis, and another one for 50 - 2000 ppm CO & CO2 analysis, in presence of 20%Vol of CH4 that elutes between the CO & CO2 peaks,and then backflush of the remain hydrocarbons, for years with no problems. I believe your problem is the Oxygen that oxydes the catalyst. Try to increase the flow of H2 to the catalyst.

[chromatographer1]

different catalysts can react or degrade by different means. Not everyone uses nickel based catalysts. Palladium platinum rhodium are also used.

Certainly it is recommended that hydrocarbons not pass through a methanizer if possible. But if you have to have one hydrocarbon pass through, methane is the best choice.

Another reason of a methanizer giving a variable response is the poisoning of the catalyst from sulfur compounds. Sometimes that can be reversed partially, and sometimes it cannot.

Since H2S COS and others elute with the higher hydrocarbons it is another reason not to pass higher hydrocarbons through a methanizer.

best wishes,

Rod