Stable diesel and bio-oil emulsion through solvent extraction and ultrasonic aided emulsification

Abstract

Fast pyrolysis bio-oil is considered a highly preferable supplement to conventional fossil fuels. However, the direct application of pyrolysis bio-oil is limited due to poor fuel properties. Emulsification of bio-oil with diesel using a solvent is considered a relatively straightforward technique for utilizing bio-oil directly with diesel. In this study, new solvents were studied with the aid of sonication to produce a stable emulsion of diesel and bio-oil. 2-Octanol, 2-Heptanol and 2-Octanone were selected as solvents based on computer-aided molecular design (CAMD) method. Bio-oil was blended with 5, 10, 15 and 20 wt% of 2-Octanol using sonication. The solvent-oil blends with different solvents (2-Heptanol and 2-Octanone) at 20 wt% were also investigated for extracting organics from bio-oil. Subsequently, sonication-assisted emulsification of the solvent-extracted bio-oil with diesel was conducted with the aid of a composite surfactant with a hydrophilic-lipophilic balance (HLB) value of 7. Extraction of bio-oil with 20 wt% of 2-Octanol provided a maximum organic yield of 37.9 ± 1.3 % with a Higher Heating Value (HHV) of 31.9 MJ/kg. The desired ratio for emulsification was found to be 80: 15: 5 (diesel: surfactant: solvent-extracted bio-oil). The emulsion samples showed promising quality with an HHV of 44.0 MJ/kg and a pH of 8.0 ± 0.1. Moreover, no phase separation was observed even after the accelerated ageing process at 80 ºC for 24 hours. The results showed that all three solvents had an overall positive effect on the extraction of organics from bio-oil and aided in emulsification with diesel in which 2-Octanol was the most effective solvent for achieving a stable diesel – bio-oil emulsion.