Separation of high added-value chemical compositions derived from biomass pyrolysis liquid via sequential multi-step pH adjustment

Abstract

The complexity of the components in pyrolysis liquid causes serious problems for its downstream utilization. In order to increase the added value and commercialization of pyrolysis liquid, a novel method was developed by combining the sequential multi-step pH adjustment and organic solvent extraction methods to separate the chemical components of crude pyrolysis liquid. The chemical composition of crude pyrolysis liquid was determined by fourier transform infrared spectrometry and gas chromatography–mass spectrometry. The results showed that acids (17.54%) and phenolics (57.44%) were the major constituents. The neutral compounds (e.g. ketones) (38.57%) were enriched at pH 14. Methoxyphenols (e.g., 2,6-dimethoxyphenol) were separated at pH 11, accounting for 63.4%. Phenol and maltol were mainly found at pH 9 and 7, with relative contents of 11.30% and 10.09%, respectively. At pH 6 and 4, acetic acid was the most abundant compound, with contents of 17.23% and 20.72%, respectively. The main compound at pH 2 was 2-methyl-propanoic acid anhydride (35.05%). Principal component analysis (PCA) results showed that the PC1 and PC2 components explained 38.8% and 26.2% of the chemical variance, respectively. The DPPH free radical scavenging rate showed positive correlation with the phenolic component, and was negatively correlated with the acid component. The highest DPPH free radical scavenging rate (88%) was obtained at pH 11. This study provided a theoretical reference for the separation of target components in pyrolysis liquid.