## 2 Results and Discussion
### Reactivities of Model Bio-Oil Components  
In order to prove the feasibility of this upgrading process, more clearly outline the complicated reaction mechanism and probe the causes for catalyst deactivation, additional model reactions were investigated. Figure 1 shows the phenol conversions of phenol/1-octene reactions at 120 \({}^{\circ}\)C for 3 h over all five catalysts both with and without water present. All the catalysts exhibit high activities in neat phenol/1-octene reactions based on the high phenol conversions (\(>\)80%). Water significantly lowered the phenol conversions of phenol/1-octene reactions over DX2 (42.1%), A36 (38.3%), A15 (15.8%) and Cs\({}_{2.5}\)/K10 (19.9%). However, a good phenol conversion (74.5%) was still obtained over SSA. This further illustrated the high activity of SSA under hydrothermal conditions. Phenolic compounds are present in bio- oils, primarily derived from lignin species. These acidic phenolic fractions are prone to oligomerization reactions with other bio-oil components [25]. Friedel-Crafts-type alkylations of phenol with 1-octene over solid catalysts leads to a mixture of _O_- and _C_-alkylated phenols (Table 4). Isomeric octyl phenyl ethers (_O_-alkylates) and octyl phenols (_ortho/para-C_-alkylates) were formed (Scheme 1), indicating that the 2-octyl carbocation undergoes 1, 2-hydride shifts to generate the 3- and 4-octyl cations in competition with _O_- and _C_-alkylation. _O_-Alkylation is faster than _C_-alkylation but _O_-alkylation is reversible and the initially generated _O_-alkylated products can be increasingly converted to _C_-alkylated (thermodynamic) products as a function of reaction conditions. All catalyst used gave high phenol conversions (Figure 1). Water is the most abundant compound in raw bio-oil. It is difficult to remove due to its miscibility with hydrophilic thermolysis products present from cellulose and hemicellulose [5,6]. Phenol conversions from the reactions of 1-octene with water/phenol over solid acid catalysts were summarized in Figure 1. The lower phenol consumption with all catalysts when water was present is most likely due to water solvation of the sulfonic acid sites which lowers the Bronsted acidity or to mass transport effects due to phase separation. The sulfonic acid resins showed higher phenol conversions than Cs\({}_{2.5}\)/K10. This could be due to swelling of resins. This swelling allows a distribution of all reactants to access a larger fraction of the internal acid sites of this macroreticular resin. Figure 1: Comparison of phenol conversions by 1-octene with and without water present at 120 \({}^{\circ}\)C over Amberlyst15, Cs\({}_{2.5}\)/K10, Amberlyst36, Dowex50 WX2 and SSA (cataly, 0.15 g; time: 3 h; 1-octene: phenol: water (mmol) = 10:10:10). However, partial Amberlyst15 decomposition occurred. Product distributions of these reactions are shown in Table 5. Obviously, competition between water and phenol for 1-octene occurred because 1-octanol and its isomers were formed by water uptake. Intermolecular reaction of these octanols further formed ethers (Scheme 2). Meanwhile, the significant increase in the concentration of octanols with increasing water concentration affirmed the water consumption by olefin hydration [18]. Olefin acid-catalyzed hydration removes water. This is the key reason for the success of this upgrading process. **Scheme 1. ** Acid-catalyzed reactions of phenol as a model phenolic compound with 1-octene. Carboxylic acids, like acetic and propanoic acids, make bio-oil corrosive, especially at an elevated temperature [7]. 1-Octene was reacted with phenol/water/acetic acid solutions and their phenol conversions and octyl acetates yields were shown in Table 6. Along with the 1-octene hydration and phenol alkylation, simultaneous conversion of acetic acid to octyl acetates occurred by addition across