Abstract:
Biomass fast pyrolysis oil is a potential renewable alternative to fossil fuels, but its viability
is constrained by its corrosiveness, low higher heating value and instability, caused by high oxygenate
concentrations. A few studies have outlined layered double hydroxides (LDHs) as possible catalysts
for the improvement of biomass pyrolysis oil characteristics. In this study, the goal was to reduce
the concentration of oxygen-rich compounds in E. grandis fast pyrolysis oils using CaAl- and MgAl-
LDHs. The LDHs were supported by mesoporous silica, synthesised at different pHs to obtain
different pore sizes (3.3 to 4.8 nm) and surface areas (up to 600 m2/g). The effects of the support
pore sizes and use of LDHs were investigated. GC/MS results revealed that MgAl-LDH significantly
reduced the concentrations of ketones and oxygenated aromatics in the electrostatic precipitator
oils and increased the concentration of aliphatics. CaAl-LDH had the opposite effect. There was
little effect on the oxygenate concentrations of the heat exchanger oils, suggesting that there was a
greater extent of conversion of the lighter oil compounds. Bomb calorimetry also showed a marked
increase in higher heating values (16.2 to 22.5 MJ/kg) in the electrostatic precipitator oils when using
MgAl-LDH. It was also found that the mesoporous silica support synthesised at a pH of 7 was the
most effective, likely due to the intermediate average pore width (4 nm).
