In this work, the conversion of CO2into O2-free CO has been investigated in an atmospheric plasmatron via the reaction with biochar. The effects of the biochar source, pyrolysis temperature for biochar preparation, and gas-solid reaction patterns (fixed bed and fluidized bed) on the reaction performance were evaluated under different feed flow rates. The underlying mechanisms were explored using in situ optical emission spectroscopy focusing on understanding the role of plasma chemistry and thermochemistry in CO2conversion. The results revealed that the presence of both biochar and plasma significantly facilitate CO2conversion. In comparison to thermal CO2splitting, the plasmatron CO2+ C process dramatically enhanced the CO2conversion from 0 to 27.1%. Walnut shell biochar prepared at relatively high pyrolysis temperatures favored CO2conversion due to a high carbon content. A fixed bed surprisingly provided remarkably better performance than a fluidized bed for the CO2+ C reaction, benefiting from a prompt consumption of the generated O2by biochar. The high electron density achieved in the plasmatron (1015cm-3) allows for a high processing capacity, and the moderate electron temperature (1.1-1.5 eV) with enhanced vibrational energy (6300-8200 K) obtained stimulates the most efficient CO2activation routes through vibrational excitation. The relatively high rotational (gas) temperatures in the core plasma area (2100-2400 K) and in the gas-solid reaction region (<1573 K) detrimentally drive the reverse reactions of CO2splitting and advantageously boost the biochar-involved reactions, respectively, by thermochemistry. The synergy of plasma-chemistry-dominated CO2dissociation and the thermochemistry-dominated CO2+ C and O2+ C reactions accounts for the high CO2conversion obtained in the plasmatron CO2+ C process. The immediate study provides a novel route for efficient CO2conversion by coupling plasma chemistry and thermochemistry.
|Number of pages||14|
|Journal||ACS Sustainable Chemistry and Engineering|
|Early online date||26 May 2022|
|Publication status||Published - 13 Jun 2022|
Bibliographical noteFunding Information:
This work was supported by the National Key Technologies R&D Program of China (no. 2018YFE0117300) and the National Natural Science Foundation of China (nos. 52076190 and 51976191). C.W. and X.T. acknowledge the funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement no. 823745.
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- plasma chemistry
ASJC Scopus subject areas
- Environmental Chemistry
- Chemical Engineering(all)
- Renewable Energy, Sustainability and the Environment