Pyrolysis is a promising method for converting biomass to biofuels. However, some of pyrolysis oil's physiochemical properties still limit its commercial applications. Here, the autohydrolysis pretreatment at 175 � 3 �C for 40 min was conducted to improve the resulting pine pyrolysis oil?s properties as a fuel. During autohydrolysis, deacetylation and decomposition of hemicellulose was observed by ion-exchange chromatography and Fourier transform infrared spectroscopy (FT-IR). Additionally, the cleavage of lignin ether bonds was clearly determined by <
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C cross-polarization/magic angle spinning (CP/MAS) nuclear magnetic resonance (NMR). Phosphitylation followed by <
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P NMR analysis of the heavy oils gave detailed structural information of the hydroxyl groups
the results revealed that autohydrolysis pretreatment led to a reduction of carboxyl acids in the heavy oils generated at all three pyrolysis temperatures (400, 500, and 600 �C). The <
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P NMR analysis also revealed that autohydrolysis pretreatment led to a reduction of condensed phenolic hydroxyl groups in the heavy oils produced at 600 �C. <
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C heteronuclear single-quantum correlation (HSQC) NMR analysis showed that at a pyrolysis temperature of 600 �C, the pretreated pine produced lower methoxy group constituents. In both <
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P and HSQC NMR results indicated that autohydrolysis pretreatment increased levoglucosan yields in the bio-oils.