Experimental and Comprehensive Evaluation of Vegetable Oils for Biomass Tar Absorption

Biomass tar is the bottleneck of biomass gasification, which not only is adverse to energy production but also brings severe environmental issues. A scrubber with vegetable oil is considered as a low-cost but efficient approach for tar removal, but the effects of oil's properties on different tar absorptions were rarely reported. In this study, canola oil, palm oil, and pure oleic acid and linoleic acid, which are the main compounds of vegetable oils, were employed for absorptive removal of benzene, toluene, and phenol. The degree of unsaturation, average molecular weight, and average chain length of solvents were quantitatively characterized. A series of time and temperature-dependent absorption experiments were conducted, and the relationship between oils' properties and absorption performances was built. Results showed that pure oleic acid had the biggest absorption capacity for benzene and toluene due to the mono-unsaturated structure. Increasing the average molecular weight and chain length also enhanced tar absorption. Moreover, Grey relative analysis was employed to investigate the influence of each factor on tar absorption. The average molecular weight exerted the most significant influence on tar absorption in the tested temperature range whose comprehensive relevance coefficients reached the highest at 0.9810, 0.7669, and 0.7739 for benzene, toluene, and phenol, respectively. This study puts more attention on the nature of vegetable oils, and we hope to provide useful information for modulating a better oil-based scrubber medium and further enhancing tar absorptive removal.