Upgrading bio-heavy oil via esterification of fatty acids and glycerol

Bio-heavy oil (BHO), a crude mixture of fatty acids (FAs) and mono-, di-, and triglycerides unavoidably generated as waste during biodiesel production processes, is an alternative replacement of petro-heavy oil as a fuel for power generation. It is reported for the first time that upgrading the quality of raw BHO (lowering the acid value (AV) of BHO) can be achieved via a low-pressure non-catalytic esterification process. Esterification of the FAs contained in raw BHO on solid acid catalysts (tungsten trioxide and niobium pentoxide) were investigated by comparison with the non-catalytic method. The AV of raw BHO can be successfully reduced from 116 to ∼38 in 2 h under a low pressure (0.1 bar) via the non-catalytic esterification process. Catalytic esterification with Nb₂O₅ or WO₃ showed similar performance to the non-catalytic esterification. It can be suggested a possibility to make a high-quality renewable fuel (e.g., BHO with a low acid value) for power generation from inexpensive feedstock. Copyright © 2019 Elsevier Ltd. All rights reserved.