Separation of Permanent Gases and Heavy Hydrocarbons

[BerkeleyPhD]

Hello Everyone,

I need to separate and quantify C1-C12 hydrocarbons, as well as the gases H2, CO2, CO, O2, and (ideally) Ar. The O2/Ar separation is quite difficult and is not as essential, however. It would be very helpful so that I can use Ar as an internal standard, but I may be able to get around that another way.

I have a ten-port sampling valve and two columns, each of which is connected to a detector (a Porapak Q column connected to a TCD and a HP-1 capillary column connected to an FID). I use He as a carrier gas and I have hooked up liquid N2 to my system so that I can bring the oven temperature down to -60C.

The capillary column does just find with separating the heavy hydrocarbons.
It seems as though there are a lot of micropacked columns that can separate the light gases nicely, but the problem is that all of them that I have found say that they become very quickly clogged by heavy hydrocarbons. I unfortunately cannot implement a switching/backflushing system, so I need to find a column that will perform the light gases separation but will not be damaged quickly by my heavy hydrocarbons. I don't mind replacing the column every couple of months if that's what it takes.

Thank you in advance for your help! Any input is greatly appreciated.

[Peter Apps]

Welcome to the forum.

While we wait for an expert on permanent gasses to come along, have you thought of passing the sample through a charcoal filter on its way to the sampling valve - the charcoal will remove the hydrocarbons from ethane upwards, leaving the gasses and methane. You would need to replace the charcoal very frequently, but charcoal is cheap and readily available.

Peter

[BerkeleyPhD]

Thank you very much Peter! That is an excellent idea. Do you have any recommendations for charcoal filters that may work well for this purpose?

[Peter Apps]

You can get single use charcoal tubes for air sampling - the ones that you break the ends off. Some charcoal between glass wool plugs in a glass Pasteur pipette would probably also do the job for less money.

Peter