Plasma and plasma catalysis are gaining increasing interest for CO2 conversion into value-added chemicals and renewable fuels. Gliding arc plasmas are quite energy efficient for converting CO2 into CO and O2, but the overall conversion is limited, among others by recombination of CO with O/O2 after the plasma. In this talk, I will show how a carbon bed after a gliding arc plasma reactor can help to increase the CO2 conversion and CO yield, by trapping the O/O2 on the carbon bed (to avoid these recombination reactions), and (if the temperature is high enough) by the reverse Boudouard reaction (CO2(g) + C(s) -&gt; 2 CO(g)). In addition, the carbon bed allows to remove O2 and obtain a (more or less) pure CO2/CO stream. Our experimental results show that the CO2 conversion is enhanced by almost a factor two (from 7.6 % to 12.6 %), while the energy efficiency rises from 28 % to 45 %, corresponding to a drop in energy cost from 42 kJ.L-1 (without) to 25 kJ.L-1 (with carbon bed). In addition, the CO concentration even increases by a factor three, and O2 is completely removed from the exhaust mixture. We also measured the temperature as a function of distance from the reactor outlet, as well as the CO2, CO and O2 concentrations and the temperature in the carbon bed as a function of time, which is important for understanding the underlying mechanisms. Indeed, these time-resolved measurements reveal that the initial enhancements in CO2 conversion and in CO concentration are not maintained in our current setup. Therefore, we present a model to study the gasification of carbon with different feed gases (i.e., O2, CO and CO2 separately), from which we can conclude that the oxygen coverage at the surface plays a key role in determining the product composition and the rate of carbon consumption. Indeed, our model insights indicate that the drop in CO2 conversion and in CO concentration after a few minutes is attributed to deactivation of the carbon bed, due to rapid formation of oxygen complexes at the surface.

Post-plasma carbon bed to enhance the CO2 conversion and remove O2 from the product mix

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.