Ultrasound-Assisted\nSequential Extraction for Lignocellulose\nPyrolysis Bio-oil Fractionation. Part II: Comparative Application

Building upon the novel ultrasound-assisted sequential\nextraction\n(UASE) method introduced in Part I, the second paper delves deeper\ninto the fractionation and analysis of bio-oils produced from lignocellulosic\npyrolysis. The current study exploits advanced analytical techniques\nsuch as GPC-UV-DAD and negative-ion Electrospray Ionization (ESI)\ncoupled with ultrahigh-resolution mass spectrometry, 21 T FT-ICR MS,\nto facilitate a detailed comparative analysis of various bio-oil samples\nproduced from lignocellulosic pyrolysis. The results highlight significant\ndifferences in composition, molecular weight distribution, and oxygen\ncontent as a function of process conditions, which demonstrate the\nefficacy of the UASE method to distinguish different types of bio-oils.\nA sample generated by reactive catalytic fast pyrolysis (RCFP) reveals\na composition that has potential for fuel production, evident by its\nlow oxygen-to-carbon ratio and high concentration of non- to moderately\npolar fractions. Interestingly, the most polar fraction obtained by\nthe UASE method has a GPC elution behavior consistent with lignin\nstandards, indicating that the method unravels “undesired”\npyrolysis byproducts and recalcitrant species. The characterization\nworkflow presented confirms the potential of the RCFP process for\nfuel production and advances our understanding of bio-oil molecular\ncomposition. The insights gained are pivotal for advancing bio-oil\nprocessing techniques and standardizing quality assessment, especially\nfor industrial applications, thereby continuing the advancement of\nbio-oil research established in the first paper of this two-part paper\nseries.