Two-Dimensional Perturbation Correlation Infrared Spectroscopy for Probing Pyrolysis of Biomass: Fundamentals, Applications, and Mechanistic Understanding

Abstract

Pyrolysis is a promising technology that can efficiently convert biomass into gas, liquid, and solid fuels. Elucidating the biomass pyrolysis reaction mechanism is essential for the effective biomass utilization. However, the biomass components and structure are very complex, which complicates the investigation of biomass pyrolysis using traditional approaches. Two-dimensional perturbation correlation infrared spectroscopy (2D-PCIS) represents a new analytical method for visualizing the raw Fourier transform infrared spectroscopy data. When volatile compound release properties are studied, the biomass pyrolysis mechanism can be determined. In this paper, the theoretical concept, developments, and applications of 2D-PCIS are described in detail with the emphasis on probing biomass pyrolysis reactions via the analysis of the functional group evolution and bond breakage processes.

Dynamic Evolution and Covariant Response Mechanism of Volatile Organic Compounds and Residual Functional Groups during the Online Pyrolysis of Coal and Biomass Fuels

“…61 Previous studies also reported that the functional group chemistry of biomass was dominated by bonded OH and R−CH n to be dominated by free −OH and RCH n groups at approximately 300−350 °C. 31,34 Additionally, the depolymerization/cracking reactions of unstable compounds in cellulose and the ether-bridge structures in lignin could result in the formation of large aromatic rings in residues and small-chain VOCs of aldehydes, ketones, and cyclopentanones. 32,61 Kibet et al also found that the gaseous acetones released from lignin achieved a maximum concentration at ∼350 °C.…”

“…61,76 This result was in good agreement with the heterosynchronous gas−solid correlations and the reported gaseous chain/cyclic oxygen-containing molecules released from hemicellulose dehydration at 200−300 °C. 34 Subsequently, through ring opening and fragmentation, the oxygen bridge bond, pyran ring C−O, aliphatic −CH, and −COOH groups on the residual aromatic branches could result in the formation of gaseous alcohols/phenols/esters. Previous studies supported this result and reported that the rupture of aromatic methoxy and aliphatic −CH 2 OH groups in alkyl side chains in lignin provoked the release of gaseous phenolic/alcohols (e.g., methanol) below 300 °C.…”

“…The large oxygen-containing molecules previously released from hemicellulose degradation could undergo secondary cracking reactions to produce smaller gaseous aldehydes/ketones. 34,61 Intermediates from cellulose decomposition could form aromatic rings through molecular reconstruction/fragmentation of −CH 3 /−CH 2 −/−CH groups, accompanied by the release of gaseous phenols and unsaturated carbonyl compounds. 61 Previous studies also reported that the functional group chemistry of biomass was dominated by bonded OH and R−CH n to be dominated by free −OH and RCH n groups at approximately 300−350 °C.…”

“…Moreover, driven by oxygen reactions, −CH 3 /−CH 2 −/−CH and free hydroxyl groups in SBC residues with the most prioritized responses were initially oxidized to form residual acids/aldehydes/ketones, while intra/inter-molecular hydroxyl groups with higher thermal stability remained intact as the temperature increased (Figure S12). 31,34,77 Environment Implications. Our study provides novel insights into a covariant evolution mechanism to interpret the dynamically evolved relationships between gas and solid products during online CBF pyrolysis.…”

“…34−37 Yang's and Wang's groups systematically summarized the fundamentals, applications, and processes understanding of 2D-FTIR-COS in solid char formation, providing deep insights into practical 2D-FTIR-COS applications in biomass pyrolysis reactions. 19,23,34 They carried out innovative 2D-FTIR-COS work to probe the thermal reactions, functional group evolution, and pyrolysis/ torrefaction mechanisms of various materials, such as xylan, 32 cellulose, 38,39 hemicellulose, 40 stalks, 41 and bamboo. 31,42 Yang and Wang et al found that a high 2D-FTIR-COS resolution could allow identification of more fingerprint functional groups in biomass char structures and elucidation of the pyrolysis mechanism in more detail by combining data sets of detected volatile compounds.…”