PTR-MS was used to provide compositional information about the VOCs in the reactor off-gas.
Fig. 4 PTR-MS spectrum for experiment 3 (119 h) where background VOCs, reactor off-gas air sampled through the catalyst, have been subtracted from the reactor off-gas spectrum.
The platinum catalyst, CO2 detector and PTR-MS sampled approximately 200 mL/min of the diluted reactor off-gas stream.
The reason for the appearance of unconverted combustible gases in the fuel reactor off-gas needs further investigation.
An LI-840 CO2/H2O non-dispersive infrared gas analyzer (Li-cor Biosciences; Lincoln, NE, USA), quantified CO2 in the reactor off-gas continuously without impacting it.
Additionally, no breakthrough was detected by the PTR-MS when the reactor off-gas was passed through the platinum catalyst, beyond decreasing system memory effects.
The two-stage fuel reactor performed well and CO2-concentrations in the dry fuel reactor off-gas of above 90 vol.% were achieved.
Additional reactor off-gas VOC ions are present in the spectra, but they represented less than three percent of the ion intensity before death phase and were not quantified.
Reactor off-gas was then diluted with 900 mL/min of dry medical grade air to keep water from condensing in the system and to keep concentrations within the linear range of the CO2 detector and PTR-MS.
Reactor off-gas was sampled from the top of the reactor, diluted and sent to a CO2 detector to measure respiratory CO2 and then to the PTR-MS for quantification of major VOC species.
With real-time gas phase measurement capability, the PTR-MS readily ties VOC data to experimental conditions and temporal changes, and can non-invasively utilize reactor off-gas for measurements (Luchner et al. 2012; Romano et al. 2015).
