Journal of Analytical and Applied Pyrolysis ( IF 6 ) Pub Date : 2021-01-21 , DOI: 10.1016/j.jaap.2021.105019 Héctor Hernando , Gema Gómez-Pozuelo , Juan A. Botas , David P. Serrano
Fractional pyrolysis of lignocellulosic biomass, by staged thermal treatment, has been assessed as an in-situ speciation method of the bio-oil components that could be highly beneficial for extracting valuable compounds or for their subsequent catalytic upgrading. Wheat straw and pine woodchips were used as representative biomasses. Based on the results of TG analyses in an inert atmosphere, 350 and 700 °C were selected, respectively, as operational temperatures for the fractional pyrolysis. Compared to single-step pyrolysis, fractional thermal treatment of both biomasses led to some reduction of the bio-oil yield but with improved properties due to their lower oxygen content. Sharp differences were observed in the bio-oil composition obtained at the two steps of fractional pyrolysis. GC-MS analyses revealed that most of the compounds detected in the bio-oil obtained at 350 °C were products formed by the decomposition of polysaccharides, such as carboxylic acids, furans, sugars, and light oxygenates. In contrast, the organic liquid phase obtained during the subsequent treatment at 700 °C was rich in aromatic oxygenated compounds, coming from the lignin conversion. The content of oligomeric and heavy species, not detected by GC-MS, was much higher in the bio-oils obtained in the high-temperature step of fractional pyrolysis, denoting that they are largely formed from lignin. Significant changes were also observed in the relative contribution of the deoxygenation pathways during the two steps of fractional pyrolysis. Thus, dehydration was the predominant deoxygenation route during the degradation of the holocellulose biopolymers at the low-temperature step, whereas the decomposition of the lignin-rich solid at the high-temperature treatment proceeded with a significant contribution of decarbonylation and decarboxylation. These results evidence the great potential of lignocellulose fractional pyrolysis to generate bio-oil streams with high speciation of the components, facilitating sharply their further processing and upgrading.
中文翻译:
评估分馏热解的生物油形态,使其转化为全纤维素和木质素衍生化合物
通过分阶段热处理,木质纤维素生物质的部分热解已被评估为生物油成分的原位形成方法,可能对提取有价值的化合物或随后的催化提纯非常有利。小麦秸秆和松木碎片被用作代表生物量。根据惰性气氛中TG的分析结果,分别选择350和700°C作为分馏热解的操作温度。与单步热解相比,两种生物质的分步热处理均导致生物油收率的降低,但由于其较低的氧含量而具有改善的性能。在分步热解的两个步骤中获得的生物油组成中观察到了明显的差异。GC-MS分析表明,在350°C下获得的生物油中检测到的大多数化合物都是通过多糖(例如羧酸,呋喃,糖和轻质含氧化合物)分解形成的产物。相反,在随后的700°C处理过程中获得的有机液相富含木质素转化产生的芳香族氧化化合物。在分馏热解的高温步骤中获得的生物油中,GC-MS未检测到的低聚和重物质的含量要高得多,表明它们主要是由木质素形成的。在分馏热解的两个步骤中,还观察到了脱氧途径的相对贡献的显着变化。从而,脱水是全纤维素生物聚合物在低温步骤降解过程中的主要脱氧途径,而富含木质素的固体在高温处理过程中的分解过程则对脱羰和脱羧有重要贡献。这些结果证明了木质纤维素分级热解具有产生具有高形态组分的生物油流的巨大潜力,从而极大地促进了它们的进一步加工和升级。