A Critical Review on Hemicellulose Pyrolysis

Abstract

Fast pyrolysis is a promising thermochemical technology that breaks down renewable and abundant lignocellulosic biomass into a primary liquid product (bio‐oil) in seconds. The bio‐oil can then be potentially catalytically upgraded into transportation fuels and multiple commodity chemicals. Hemicellulose is one of the three major components of lignocellulosic biomass and is characterized as a group of cell wall polysaccharides that are neither cellulose nor pectin. The composition and structural features of hemicellulose (mixture of different heterogeneous polysaccharides) and different specific hemicellulose polysaccharides are reviewed. Particular focus is then given to reviewing the status of hemicellulose pyrolysis in terms of experimental investigations, reaction mechanisms, and kinetic modeling. For each aspect, recent results, challenges, and future prospects are addressed.

Measuring biomass fast pyrolysis kinetics: State of the art

“…However, the typical heating rates do not correspond to fast pyrolysis conditions and are prone to transport effects (Mettler, Vlachos, & Dauenhauer, 2012; Paulsen, Mettler, & Dauenhauer, ). To make it easier to understand biomass pyrolysis kinetics, pyrolysis of individual biomass components, namely, cellulose, hemicellulose, and lignin have been performed (Bahng et al, ; Bridgwater & Peacocke, ; Burnham, Zhou, & Broadbelt, ; Butler et al, ; Pandey & Kim, ; Shen et al, ; Shen, Jin, Hu, Xiao, & Luo, ; Wang et al, ; Zhou, Li, Mabon, & Broadbelt, ). The resulting simplified global kinetics corresponding to these components have been combined with computational fluid dynamics to derive product distributions in various reactor configurations and for process optimization (Gentile, Cuoci, Frassoldati, Faravelli, & Ranzi, ; Kersten, Wang, Prins, & van Swaaij, ; Papadikis, Gu, & Bridgwater, ; Simone, Biagini, Galletti, & Tognotti, ; Xue, Dalluge, Heindel, Fox, & Brown, ; Xue, Heindel, & Fox, ).…”

“…For example, hardwood is known to have a higher number of syringyl units while guaiacyl units dominate in softwood derived lignins (Kotake, Kawamoto, & Saka, 2014;Wang et al, 2015). To simply understand cellulose thermal decomposition, feedstocks such as α-cellulose, cotton, and commercially available Sigmacell, Avicel, and Whatmann filter papers have been used (Shen, Jin, et al, 2015) Glucan, galactans, mannans, xylans, and xyloglucans are used as surrogates to illustrate the pyrolytic behavior of naturally occurring hemicellulose (Patwardhan, Brown, & Shanks, 2011a;Wang, Ru, Lin, & Luo, 2013;Wang, Zhou, Liang, & Guo, 2013;Zhang et al, 2015;Zhou, Li, et al, 2017). A variety of technical lignins such as Kraft, Organosolv, Etek, and Haak, have been derived through chemical extraction and precipitation processes to investigate lignin fast pyrolysis kinetics (Bentivenga, Bonini, D'Auria, & De Bona, 2003;Constant et al, 2016;Dorrestijn, Laarhoven, Arends, & Mulder, 2000;Nowakowski, Bridgwater, Elliott, Meier, & de Wild, 2010;Pandey & Kim, 2011;Windt, Meier, Marsman, Heeres, & de Koning, 2009;Zakzeski, Bruijnincx, Jongerius, & Weckhuysen, 2010;Zhou, Brown, & Bai, 2015).…”

Future prospects of delignification pretreatments for the lignocellulosic materials to produce second generation bioethanol

“…Search for new catalysts or new techniques to increase the conversion to the highest amount of aromatic hydrocarbons due to pyrolysis . Pyrolysis chemistry is still poorly understood . An increase of the catalyst‐to‐biomass C/B ratio enhances the conversion to pyrolysis vapors, but this technique is not suitable for bioethanol production .…”

“…[27][28][29][30][31][32] Pyrolysis chemistry is still poorly understood. [33][34][35] An increase of the catalyst-to-biomass C/B ratio enhances the conversion to pyrolysis vapors, but this technique is not suitable for bioethanol production. 36,37 The claims that the C/B ratio is a factor that optimizes the catalytic fast pyrolysis process are needed to be confirmed.…”

Wärmeinduzierte Vorbehandlung lignocellulosehaltiger Biomassen – Prozesse, Verfahren und deren Einordnung

“…Durch eine Abspaltung von Wasser (H 2 O) aus diesen Produkten bilden sich Teere und Koks [15]. Diese müssen jedoch noch durch kinetische Modellierung validiert oder durch quantenchemische Berechnungen gestützt werden [17]. Verschiedene Autoren stellten Reaktionsschemen für den thermischen Hemicelluloseabbau auf, die ebenfalls Decarbonylierungs-und Decarboxylierungsreaktionen sowie Dehydrations-und Depolymerisierungsreaktionen enthalten.…”