Boosting the conversion of CO2 with biochar to clean CO in an atmospheric plasmatron: a synergy of plasma chemistry and thermochemistry

Hao Zhang*, Qinhuai Tan, Qunxing Huang, Kaiyi Wang, Xin Tu, Xiaotong Zhao, Chunfei Wu, Jianhua Yan, Xiaodong Li

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)

Abstract

In this work, the conversion of CO2 into 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 CO2 conversion. The results revealed that the presence of both biochar and plasma significantly facilitate CO2 conversion. In comparison to thermal CO2 splitting, the plasmatron CO2+ C process dramatically enhanced the CO2 conversion from 0 to 27.1%. Walnut shell biochar prepared at relatively high pyrolysis temperatures favored CO2 conversion 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 O2 by biochar. The high electron density achieved in the plasmatron (1015 cm-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 CO2 activation 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 CO2 splitting and advantageously boost the biochar-involved reactions, respectively, by thermochemistry. The synergy of plasma-chemistry-dominated CO2 dissociation and the thermochemistry-dominated CO2+ C and O2+ C reactions accounts for the high CO2 conversion obtained in the plasmatron CO2+ C process. The immediate study provides a novel route for efficient CO2 conversion by coupling plasma chemistry and thermochemistry.

Original languageEnglish
Pages (from-to)7712-7725
Number of pages14
JournalACS Sustainable Chemistry and Engineering
Volume10
Issue number23
Early online date26 May 2022
DOIs
Publication statusPublished - 13 Jun 2022

Keywords

  • biochar
  • COconversion
  • plasma chemistry
  • plasmatron
  • thermochemistry

ASJC Scopus subject areas

  • General Chemistry
  • Environmental Chemistry
  • General Chemical Engineering
  • Renewable Energy, Sustainability and the Environment

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