Bio-oil catalytic esterification and its stability with storage

The model reaction catalyzed by cation exchange resin between methanol and acetic acid was designed by the three factors Box-Behnken method to achieve optimized reaction conditions. The esterification between bio-oil and methanol was carried out under the optimized reaction conditions and the properties of the bio-oils during storage were studied. Typical properties of blank (crude bio-oil), group M (bio-oil with 10% methanol without esterification) and group E (bio-oil with 10% methanol after esterification) were measured. Results showed that after storage, the ash content and density of group E were the lowest ones among the three groups, which were 0.1128% and 1.1349 g/mL, respectively. Its heating value was 16.412 MJ/kg, which is the highest one. In addition, after storage, the pH value, water content and viscosity (40℃) of group E were 2.61, 28.14% and 11.29 mmVs, respectively, which were the lowest ones. The FTIR and GC-MS analysis also convinced that the content of ester was increased while the content of the organic acid was decreased in group E. The quality of bio-oil has been improved after catalytic esterification.