Bio-oil is a mixture of many compounds with different functions groups. Acids, alcohols, aldehydes, esters, ketones, sugars, phenols, gicaols, syringols, furans, lignin derived phenols and extractible terpene with multiple functional groups comprise most of the bio-oil (Mohan et al. 2006; Lee et al. 2008; Guo et al. 2011).

Bio-oil Upgrading

Many of the undesirable properties of bio-oil are due to its high oxygen content. Hence primary purpose of bio-oil upgrading is to reduce oxygen contents so that upgraded bio-oil can be converted into power, fuels and chemicals. The primary techniques used to upgrade bio-oil are: (i) hydrodeoxygenation, (ii) catalytic vapor upgrading, (iii) aqueous reforming, and (iv) steam reforming.