We propose and demonstrate an integrated electrified plasma-assisted chemical looping (PACL) process that yields supra-equilibrium CO 2 conversions unattainable with conventional catalysis at temperatures ≪3000 K. CO 2 is first dissociated inside plasma into CO/O at supra-equilibrium conversions (up to 60%) at a bulk gas temperature of 773 K and a 403 kJ/mol energy cost. Supra-equilibrium CO 2 conversions (29% on average) are achieved at the reactor outlet by placing a nanostructured CeO 2 /Fe 2 O 3 oxygen scavenger, prereduced by H 2 plasma, downstream of the plasma zone, to capture produced oxygen species and suppress CO/O recombination. Without plasma-material synergy, such an average CO 2 conversion can only be attained at temperatures ≥ 2775 K, according to chemical equilibrium calculations. This concept of plasma-assisted chemical looping allows reaching 3-fold higher conversions than state-of-the-art plasma technologies.
The plasma dry reforming reaction of methane with carbon dioxide is investigated in a nanosecond repetitively pulsed discharge, a type of plasma that offers some of the highest performance and non-equilibrium characteristics. The experiment's purpose was to examine the effect of varying the sequence of high-voltage pulses. We find that when successive pulses are closer than 500 μs, a memory-dominated regime gradually develops, which influences subsequent breakdown events. While reactant conversions increase with the plasma energy, both energy efficiency and conversions increase by shortening the inter-pulse time at the same plasma energy. This finding suggests that plasma power is not the only thing that matters to achieve better performance. How it is delivered can make a significant difference, in particular for CO2, whose conversion doubles at the maximum energy for molecule investigated, 1.6 eV molecule -1 .
Power-to-chemical
technologies with CO2 as feedstock
recycle CO2 and store energy into value-added compounds.
Plasma discharges fed by renewable electricity are a promising approach
to CO2 conversion. However, controlling the mechanisms
of plasma dissociation is crucial to improving the efficiency of the
technology. We have investigated pulsed nanosecond discharges, showing
that while most of the energy is deposited in the breakdown phase,
CO2 dissociation only occurs after an order of microsecond
delay, leaving the system in a quasi-metastable condition in the intervening
time. These findings indicate the presence of delayed dissociation
mechanisms mediated by CO2 excited states rather than direct
electron impact. This “metastable” condition, favorable
for an efficient CO2 dissociation, can be prolonged by
depositing more energy in the form of additional pulses and critically
depends on a sufficiently short interpulse time.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.