Unravelling the complexity of hemicellulose pyrolysis: Quantitative and detailed product speciation for xylan and glucomannan in TGA and fixed bed reactor

作者：Veronica Piazza, Roberto Batista da Silva, Alessio Frassoldati, Luca Lietti, Chiara Gambaro, Kishore Rajendran, De Chen, Tiziano Faravelli, Alessandra Beretta · 发表于：Chemical Engineering Journal · 年份：2024 · DOI：10.1016/j.cej.2024.154579 · 被引用次数：34 · 研究领域：Lignin and Wood Chemistry、Thermochemical Biomass Conversion Processes、Biofuel production and bioconversion

For the first time, the complete characterization of the pyrolysis of key biomass components – xylan (representative of pentose-based hardwood hemicellulose) and glucomannan (representative of hexose-based softwood hemicellulose) – is herein obtained by applying a novel methodology based on TGA (thermogravimetric analysis), previously developed for cellulose. Data on devolatilization rates, onset temperatures and detailed quantification of the mass yield of ∼ 50 products in the gas, liquid, solid phase were achieved simultaneously, with closure of mass balance, thus providing unique kinetic information. Pyrolysis tests were also carried out in a fixed bed reactor to explore larger scales and validate the TGA-based approach. At both scales, combinations of different analytical techniques (online MS, offline GC-FID/MS, Karl Fischer titration) and sampling protocols (cold condenser, sorbent traps, vapour syringes, gas bags) were tuned to achieve closure of mass balances and rigorous product speciation. While the pyrolysis of cellulose – chosen as reference system − maximized the bio-oil production (mostly levoglucosan), the pyrolysis of xylan resulted into an even distribution among solid, liquid and gas phases, with condensable oxygenates spanning homogeneously in the C1-C9 range. Interestingly, glucomannan showed an intermediate behaviour between cellulose and xylan, mirroring its intermediate chemical structure. Raman and oxidation analyses on the collected char samples showe...