Influence of methanol additive on bio-oil stability

Methanol at different mass concentrations (1, 6, 11, 16, 21 wt %) was added into crude bio-oil to upgrade oil properties. Indexes including pH value, water content and viscosity were measured regularly during a storage period of 91 days. GC-MS analysis was conducted before and after storage. An addition of 21 wt % methanol was found to improve the pH value from 2.97 to 3.88, and decrease the water content and viscosity after storage by 35.02% and 81.35%, respectively. The GC-MS analysis result convincingly showed that methanol could inhibit aging reactions such as polymerization and esterification which created new compounds in the oil. The FTIR and NMR analysis showed that methanol caused some structural changes in bio-oil.