Analyzing CO with Hiden’s CO-A

CO oxidation is a widely studied catalysis reaction that is central to a number of industrial processes, including the abatement of gaseous waste in petrochemical industries, fuel production, vehicle pollution reduction and pure H₂ production for proton-exchange membrane fuel cells.

Hiden Analytical CO-A. Image Credit: Hiden Analytical

It can be challenging to accurately measure CO and CO₂ in N₂ using a mass spectrometer (MS) because of overlapping spectral fragments resulting from gases at m/z 28.

While other fragments are available and the m/z 12 signals for CO + CO₂ can be deconvoluted in combination with m/z 44 for CO₂, it should be noted that m/z 12 is a relatively low-intensity fragment. Therefore, overlap removal can lead to additional noise and errors in the resulting signal.

One potential means of addressing this limitation lies in the use of a discrete CO analyzer such as the Hiden CO-A (carbon monoxide analyzer). Such an instrument can be used to unambiguously measure the CO component of the mixture alone,  combining this with analysis from the mass spectrometer.

This article outlines a study into the CO oxidation reaction using a Pt/Al₂O₃ catalyst with 1% CO + 1 % O2 gas mix in an N₂ carrier gas.

Experimental

First, a single 0.05 g pellet of 1% Pt/Al₂O₃ was inserted into a CATLAB microreactor from Hiden. A gas flow of 1% CO + 1% O₂ + 98% N₂ was passed over the sample. This was done at a total flow rate of 100 ml per minute.

Next, the CATLAB reactor’s exhaust was connected to the Hiden CO-A and HPR-20 gas analyzer. This was done using 1/8” stainless steel tubing. Once the gas flows had stabilized, the temperature was increased to 250 °C at a rate of 15 °C per minute.

Results - MS Only

The results below illustrate the result of analyzing the m/z 44 signal for CO₂ (red) and the m/z 12 signal for CO + CO₂ (green) using only the HPR-20.

The increases in CO₂ signal on m/z 44 are clearly visible when CO oxidation occurs. The m/z 12 signal also increases, however, due to the combination of the CO + CO₂ fragments present at this m/z value.

Image Credit: Hiden Analytical

Results - MS + CO-A

The results shown below were obtained by employing the MS in combination with the Hiden CO-A. The data plainly demonstrates the reaction of CO (blue) to form CO₂ (red) with the complete conversion of CO with zero interference from the CO₂ signal.

Spectral deconvolution represents a viable solution for specific applications, but the CO analyzer is able to eliminate uncertainty in the CO measurement – a key consideration in cases where there may be spectral interference that cannot be accounted for in deconvolution methods or for applications that involve higher amounts of CO₂ and nitrogen than anticipated.

Image Credit: Hiden Analytical

Conclusion

Leveraging a combination of the Hiden CO-A and the HPR-20 affords users a means of unambiguously detecting CO in environments where standalone MS analysis may struggle, for example, CO oxidation reactions within an N₂ atmosphere.

The CO-A unit is suitable for integration with any Hiden atmospheric gas analysis system, such as the ExQ, QGA, HPR-20 R&D, HPR-20 EGA and the HPR-20 TMS. It is ideally suited to applications that necessitate accurate CO measurement in the presence of overlapping species such as N₂ and CO₂.

This information has been sourced, reviewed and adapted from materials provided by Hiden Analytical.

For more information on this source, please visit Hiden Analytical.