Hydrolysis and glycosidation of sugars during the esterification of fast pyrolysis bio-oil

Acid-catalysed esterification converts organic acids in bio-oil into useful esters. However, the conditions to carry out esterification also promote the hydrolysis of anhydro-sugars in bio-oil. This paper reports the hydrolysis and glycosidation of sugars during the esterification of bio-oil using Amberlyst-70 solid acid catalyst at 70–170 °C. The bio-oil was prepared from the fast pyrolysis of mallee biomass in a fluidised-bed reactor. Our results show that sugar oligomers and levoglucosan in bio-oil can be hydrolysed to form d-glucose, which further reacts with methanol to form methyl-α-d-glucopyranoside, concurrently with the esterification of acids (e.g. formic, acetic and propionic acids) in bio-oil. The effects of other important parameters such as catalyst loading and methanol to bio-oil ratio on the hydrolysis-glycosidation of sugar compounds present in bio-oil are also reported.