Chromatography Forum

Hi everybody,

I am trying to find the which column can be used for analyzing the following mixture of gases: CO, CO2, C3H8, C3H6, N2, and O2.

The problem is how to use only one column to separate the above mixture of gases.

Thanks in advance for your guides.

Best Regards,

Vu Bao Khanh

It is possible with some of the special Capillary Gas columns (GS-GasPro 113-4632) but only if you can cryogenically cool the GC down below ambient. It runs all the gases from Hydrogen to C8 from -80C to 260C om a 60m 0.32mm id Column This also assumes low levels of Oxygen Nitrogen which really require a Molsieve to separate but if one of thse is used I doubt you will get the higher Hydrocarbons off. Two column method really. What is the balance gas ?

I'd look at the Carboxen 1010 PLOT from Supelco. No cryo required. The literature shows it out through ethane, could probably do propane/propylene. We use it as an alternative to dual column Poraplot Q/5A mol sieve for the permanent gases and then backflush the HC's off the column.

That component list is about an 18-20 minute run on a 2 meter ShinCarbon column with a temperature program. I have a customer doing just such an analysis. Watch out for water!

Best regards.

As AICMM mentioned, the ShinCarbon column performs just as mentioned. Our analysis consits of H2, O2, N2, CH4, CO2 and C2H6. We use Ar as carrier and a TCD, utilizing ethane as our ISTD and thus our run time is approx 6min with ethane the final compound to elute.

We use an external air conditioning apparatus to cool the oven rapidly back to the intial +75C (temp gradient of 75-160C) and with a oven equil. time of 1min, the run takes from ready to ready only 7min 30sec.

Thanks very much for your supported information, however, I cannot find the right column for my purpose.

For ShinCarbon column, It can be used to separate the permanent gases to C1+C2 on one column configuration (2 meter x 1mm ID micropacked (cat.# 19808) and from C1-C6 on another configuration (1 meter x 1mm ID Silcosteel®micropacked column (cat.# 19809). In fact, this column cannot be used, only one column, to separate all gases ranging from permanent to C3 as I mentioned. The following link contains the specifications of ShinCarbon column: http://www.chromspec.com/pdf/e/rk99.pdf ... c7902a7650

For Carboxen-1010 PLOT, It has also the same theme as ShinCarbon, so It can be used for separating the permanent gases to C1+C2 as column supplier mentions in its specification: http://www.sigma-aldrich.co.jp/supelco/ ... en1010.pdf

Can anybody help me to find out which column being used for my bug? thanks a lot.

vbk,

Said customer of earlier post just sent me a chromatogram (yesterday) of separation of propane/propylene at about 25 minutes on ShinCarb column. The chromatogram (a standard) had ethylene so I should find out today what kind of separations between ethane and ethylene today when they run the ethane standard. I do not believe it will be an issue. Required that they take the column up to 225 and hold for a while but well resolved. They are now looking to see what it would take to get to the butanes on that column. They are using HID to measure the fixed gases and the hydrocarbons on the same column.

Best regards

Dear AICMM,

Thanks for your reply,

Could you send me the chromatogram? I really wonder if the column you mentioned can separate the mixture of gases I want,

Thanks in advance and Best Regards,

vbk,

VBK

There are many factors to consider when an analytical method is chosen.

The use of a single column is one such factor.

Doing the analysis accurately (good resolution, linearity, and reproducibility) over a range of measurement is another factor.

Only a few columns will separate O2 and N2 at ambient or higher temperatures. Similarly, the separation of olefin and paraffin in C2 and C3 hydrocarbon gases are achieved by only a few columns at temperatures conveniently found in the lab.

Molecular sieve aluminum silicates, carbon sieves, and porous glass sieves will separate the former. Some porous polymers or porous glass sieves will separate the latter.

Unfortunately, there is no simple solution using only one column.

It is possible to perform the analysis very accurately, and very quickly when a method using two columns is chosen. There are many vendors who can supply you with a solution for this easy turn-key application.

How much value does this analysis have for you to do it well? Or are you only looking for a approximation or trend analysis?

There are many ways to do it poorly and a few ways to do it well.

Decide which you think is best.

Rodney George
consultant

CHROMATOGRAPHER1,

Thanks a lot for your supported information,

I have contacted with the instrumental vendor, and I required them to install two column; one capillary column coupled with FID for analyzing the hydrocarbon and one packed column coupled with TCD for detecting permanent gases as I mentioned,

I am doing my research about oxidative dehydrogenation of propane over noble catalysts at high temperature, and the outlet gases containing several gases should be quantitative in terms of conversion and selectivity,

Thanks and Best Regards,

VBK,

Vbk.

I will ask my customer for permission to send you chromatogram. I don’t expect any issue. Post your e-mail address and I can send you a standard chromatogram from the Shincarbon in conjunction with a Hayesep D. Customer is using the D with an FID for just hydrocarbons and using the ShinCarb with my HID to measure up to propane/propylene. Customer is working at percent levels from pyrolysis but I have used ShinCarb for hydrogen down to ppm levels. I have heard some comments about issues at very low levels for some compounds but if you are dealing with high levels then this column should work well. Single injection valve to a T to both columns so a single valve injection will inject on both columns.

I am curious, do you expect anything heavier than propane in your mix? While you could keep the ShinCarb hot for a long time to get heaviers off it is not the greatest way to do this. Also, if you are expecting heavies then you might want to think about alumina at that point since it will give very good speciation of C4's and C5's.

Best regards.

AICMM,

My email address is vubaokhanh@yahoo.com,

In the products, there are maybe several heavy gases such as C4, C5 and C6 (very low level),

Thanks a lot for your useful explanations, and please send the chromatogram to me if it is permitted from your clients,

Best Regards,

VBK,