A comprehensive review on how ionic liquids enhance the pyrolysis of cellulose, lignin, and lignocellulose toward a circular economy

Abstract

The sustainable use of plant biomass (PB) to produce new valuable compounds helps alleviate the world's excessive reliance on fossil fuels. Among the different processes available, pyrolysis has drawn significant attention for its efficiency in converting PB (including lignin, hemicellulose, and cellulose) into solid, liquid, and gas products by thermal degradation. Moreover, the participation of ionic liquids (ILs) in the pyrolysis process can further facilitate this process, improve the quality of pyrolysis products, and enhance the operational parameters. This review article presents an in‐depth examination of how ILs enhance the pyrolysis of lignin, cellulose, and lignocellulose toward sustainability and circular economy (CE). The structural chemistry of the components of PB, namely cellulose, lignin, and hemicellulose, is first discussed. Furthermore, the role of ILs in the pyrolysis of cellulose, lignin, and lignocellulose is thoroughly investigated. These roles include pre‐treating agent before pyrolysis, catalyst after or during pyrolysis, template during pyrolysis, and extractant after pyrolysis. In the following, the sustainability of PB pyrolysis with the participation of ILs is examined from three aspects: environmental, social, and economical. Finally, the PB pyrolysis was investigated from the CE aspect. There is no doubt that the participation of ILs in the pyrolysis process positively affects the operating conditions and product quality, so the whole process is only one step away from complete sustainability. This article is categorized under: Sustainable Development > Sustainable Development Goals Sustainable Energy > Bioenergy Climate and Environment > Circular Economy

Coke Formation and Zeolite Catalyst Effects on Products from Co‐pyrolysis of Waste Tyre and Poplar Wood in a Semi‐Batch Reactor under N2 Atmosphere

“…The broad peak observed at 3400–3900 cm −1 is mainly dedicated to –OH stretching. [ 30,33,35 ] The intensity of this peak is higher in char obtained from pyrolysis without catalyst. This functional group is related to alcohols and its high intensity indicates the high amount of oxygen in it.…”

“…Aromatic compounds originated from the thermal degradation of lignin in the poplar wood structure and aromatic chain in waste tyre. [ 33 ] Additionally, acids and alcohols were mainly derived from the cracking of cellulose and hemicellulose in the wood structure, as well as the cracking of functional group chains in the waste tyre. The comparison of the results showed that aromatics were more intense than other groups.…”

“…[ 35,39 ] The peaks in the range of 500–750 cm −1 also suggest aromatics, the intensity of which was greater for bio‐oil obtained from catalytic pyrolysis. [ 33,40,41 ]…”

“…This bond is related to aromatic C–H‐functional groups and symmetric and asymmetric mode of aliphatic‐functional groups. [ 33–36 ] This peak is more intense for char resulting from the catalytic process. This peak usually signifies the existence of aromatics in the char, which suggests that the catalyst enhances the speed of the reaction that produces aromatics.…”

Product low‐carbon design, manufacturing, logistics, and recycling: An overview

“…Low-carbon recycling is the practice of recycling and reusing refuse to lessen resource loss and environmental damage. Circular economies (Eqbalpour et al, 2023), sustainable resource management, and refuse recycling (Porshnov, 2022) are just a few examples of low-carbon recycling methods that are now commonly used. For trash management to be more effective and viable, low-carbon recycling needs to put more emphasis on resource integration and sharing.…”