(2021) Environmental Pollution_CO₂-assisted catalytic pyrolysis of cellulose acetate using Ni-based catalysts

Cho S.H., Jung S., Rinklebe J., Kwon E.E.

(Elsevier Ltd) Environmental Pollution ISSN: 2697491 Vol.275 Issue. Article No.116667 DOI: 10.1016/j.envpol.2021.116667

Cellulose acetate (CA) is one of widely used polymers for chemical and medical applications due to its versatile physico-chemical functionalities. Although its recycle is available after a deacetylation process, the recycle process releases a huge amount of wastewater. Thus, this study investigated a direct disposal process of CA with its valorization to syngas (H₂ and CO) through pyrolysis. To construct more environmentally benign process, CO₂ was used as a co-feedstock with CA to simultaneously convert them into syngas. Pyrolysis of CA in N₂ was performed as a reference study to examine the effectiveness of CO₂ on valorization of CA. Acetic acid and methyl acetate were main volatile pyrolysates (VPs) from CA pyrolysis, and the further thermal cracking of VPs resulted in syngas and CH₄ formations under both N2 and CO₂ conditions. To expedite syngas formations, multi-stage pyrolysis (two-stage pyrolysis) and catalytic pyrolysis were employed. With the increased thermal energy through two-stage pyrolysis, four times more production of syngas was shown, comparing to the result of a single-stage pyrolysis. With Ni catalysts, the syngas formation was the two orders of magnitude higher than the single-stage pyrolysis, and the significant enhancement of CO formation was shown in the presence of CO₂ due to combined effects of CO₂ and the Ni-based catalysts. This CO enhancement resulted from catalytically expedited gas phase reactions between CO₂ and VPs evolved from CA. In addition, the CO₂ contributed to the suppression of coke deposition on the catalyst, thereby suggesting more technical and environmental benefits of CO₂ as a reactive co-feedstock of pyrolysis in reference to N₂. Therefore, this study proved the direct and versatile technical platform to convert CA and CO₂ into syngas. © 2021 Elsevier Ltd

This study was supported by the National Research Foundation of Korea ( NRF ) grant funded by the Korea Government ( MSIT ) (No. NRF-2019R1A4A1027795 ). Seong-Heon Cho also acknowledges financial support from Hyundai Motor Chung Mong-Koo Foundation .