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What optical methods can be used to measure the concentration of reacting gases in a packed bed reactor during an exothermic and fast reaction? I need to monitor and measure the local concentration of gases used to produce methane (i.e. methane, carbon monoxide, carbon dioxide, water, and hydrogen) along the length of the reactor bed in order to be able to clarify the kinetics of this reaction.

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  • $\begingroup$ So @Toulousain has suggested some spectroscopic methods for gas monitoring, and from the stoichiometry of the reaction you can infer the concentration of all the species if you track one. I'm not sure what specifications you are unclear about, you will tell the vendor or whoever will make the monitoring setup what you are trying to track, to what degree of accuracy, and the operating conditions. $\endgroup$ – J. Ari Aug 4 '17 at 13:01
  • $\begingroup$ Depending on the reaction you might in theory be able to track all the species if monitoring one. However, this is often not possible as measurement noise leads to unacceptable uncertainties on the rest of the species. Tracking several species and performing any kind of data reconciliation is more sensible $\endgroup$ – Toulousain Aug 7 '17 at 8:43
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Would some form of spectroscopy work? I.e. measuring the absorption of particular wavelengths that the gasses you're concerned about absorb and using the resultant data to infer concentrations?

This company (http://www.vertilas.com/content/spectroscopy-gas-sensing) seems to have a product available.

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  • $\begingroup$ Thank u for your answer. yes I am looking for some sort of spectroscopy, but exactly which method with which specifications is my problem. $\endgroup$ – SarvF Aug 4 '17 at 7:10
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You need to tell us much more about which species or functional groups you want to follow, concentration range, sampling rate, temperatures, etc.

Infrared can be useful for some molecules (water, CO2, N2O), fluorescence for O2 or nitric oxide...

Edit after comment:

From your comment I can say that methane, CO, CO2 and water are all infrared active with specific bands well apart from each other so you could measure all those with an infrared probe that can read (simultaneously or sequentially) different wavenumbers. I would say that the sampling time should not be shorter than 1 minute for each species. I cannot tell you much about the temperature requirements. I think it should be fine but you need to check with a provider

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  • $\begingroup$ species include: methane, carbon mono oxide, carbon dioxide, water, hydrogen. the flow rate about: 1-2 lpm. the T of this catalytic reaction is: 280-400 degree Celsius. The reaction would be in a packed bed reactor. $\endgroup$ – SarvF Aug 4 '17 at 12:25

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