Fast real time and quantitative gas analysis method for the investigation of the CO2 reduction reaction mechanism

Abstract

We present a new fast real time and quantitative gas analysis method by means of mass spectrometry (MS), which has approximately an order of magnitude faster sampling rate in comparison with a traditional gas chromatography. The method is presented and discussed on the example of the CO 2 reduction reaction. The advantages of the method are the possibility to analyze the reaction kinetics, where the kinetically determined reaction range is often only tens of degrees wide. Furthermore, due to the fast sampling rate, the experiments are much shorter and effects due to possible aging of the catalyst are significantly reduced. The quantification of the gas partial pressures is achieved by calibrating the Faraday detector in the quadrupole MS for the expected reactants and products. One major challenge to achieve a quantitative measurement with the MS is to correct for the pressure fluctuations over the probing capillary over the course of the experiment. This fluctuation is compensated in the analysis by normalizing the sum of all calculated partial pressures to the measured reaction pressure for every measured spectrum. With that, a precise, fast, and quantitative gas analysis is achieved. This is the fundament for, e.g., the kinetic reaction analysis where a high data point density is required. The method is discussed on the example of the CO 2 hydrogenation reaction to CH 4 on a commercial Ru/Al 2 O 3 catalyst. Additionally, the key features of the gas controlling and analysis setup built for the CO 2 hydrogenation reaction are described.

Modelling the CO2 hydrogenation reaction over Co, Ni and Ru/Al2O3

“…120s per spectra) achieved with the MS, which enables a quasi in situ measurement of the reaction products. We followed the calibration procedure and partial pressure determination as described in depth in our previous work on the quantitative gas analysis by means of mass spectrometry [25]. The MS was calibrated for H2, CO2, CO and CH4.…”

Infrared Thermography as an Operando Tool for the Analysis of Catalytic Processes: How to Use It?

“…The absence of other species in the product stream was verified in preliminary experiments. The procedure for quantitative analysis of the MS spectra through the Faraday detector follows our previously developed methodology [37].…”

CO2 Hydrogenation over Unsupported Fe-Co Nanoalloy Catalysts

“…The CO 2 hydrogenation experiments were carried out in a dedicated gas control and analysis system with a highly isothermal packed bed [19]. The reactor was loaded with 10 mg of catalyst in the glovebox and the reactor tubing was pumped out and flushed with He three times before the valves that connect the reactor to the tubing were opened.…”

“…For the analysis of the products of the catalytic reaction, we applied a semi-quantitative method by means of mass spectrometry (MS), which allowed for the comparison of the activity and selectivity among the catalysts. This method is a variation of the quantitative analysis method we developed and described in detail in our previous work [19,20]. In comparison to that method, we accounted for the pressure fluctuations over the MS capillary by normalizing the intensity of the signal to a reference pressure, which was defined and the same for all experiments.…”