From Table 2, it was found that the water content of upgraded bio-oil decreased drastically to less than 16% after upgrading process. Generally, H
O molecules tend to combine with hydrophilic compounds (such as organic acid) via intermolecular hydrogen bond to form bound water. This is why water contained in the bio-oil is difficult to be removed. Fortunately, hydrophilicity of bio-oil decreased since that the hydrophilic compounds were removed in the upgrading process, which led to the break of the intermolecular hydrogen bond. So, most of the bound water was converted into free water [8]. And the free water can be efficiently removed by anhydrous MgSO
2
. Interestingly, decreased water content can give rise to an evident increase for the high heating value of upgraded bio-oil. As shown in Table 2, the high heating value of bio-oil drastically increased from 13.1 MJ kg
4
1
to above 23 MJ kg
1
. Based on the results presented in Table 2, it can be concluded that the upgraded bio-oil is more suitable to be used as low quality fuel than that of crude bio-oil.