Phenol, water, acetic acid, acetaldehyde, hydroxyacetone, D-glucose and 2-hydroxymethylfuran were mixed together and used as a model bio-oil to react with 1-octene/1-butanol at 120 °C for 3 h over each of the five catalysts: Cs25/K10, A15, A36, DX2 and SSA. Table 3 shows the 1-octene, 1-butanol and phenol conversions as well as the 1-octene isomerization and O-alkylation selectivities of these reactions [22]. 1-Octene conver­sions differed significantly over these catalysts and followed the order: SSA («60%) > DX2 (40-50%) > A15 (27%) > A36 (14%) > Cs25/K10 (10%). Similar differences occurred for both phenol conversion and 1-oc — tene isomerization. The phenol conversion was higher with SSA (64.1%) verses DX2 (37.3%), A15 (27.6%), A36 (6.1%) and Cs25/K10 (1.2%). The 1-octene isomerization activities of these five catalysts are 87.9% (SSA), 55.5% (DX2), 54.1% (A15), 13.5% (A36) and 1.9% (Cs25/K10). These follow the same order and show the higher activity of the SSA catalyst. Higher phenol conversion was accompanied by higher 1-octene isomeri­zation activity and higher 1-octene conversions. SSA is the most active catalyst. This is because it is a stronger acid than the three resin sulfonic acids. Compared with the resin sulfonic acids (P-C6H4-SO3H), where the S atom has 3 O atoms attached, the S atom in SSA (SiO2-OSO3H) has 4 O atoms attached. This causes the weaker basicity of — O-SO3- verses that of Ph-SO3-. Thus, SSA is the strongest acid. The stronger the acid, the more 1-octene protonation is favored. Hence, more octyl cations are generated. With the increase in octyl cation concentration, both phenol alkylation
(phenolic oxygen attack on the carbocation) and 1-octene isomerization reaction (loss of proton from the carbocation) would speed up accompa­nied with faster consumption of 1-octene. This is consistent with higher phenol conversion and both 1-octene isomerization activity and conver­sion to other products with SSA.

aMaterial ratio: 1-octene: 1-butanol: phenol: water: acetic acid: acetaldehyde: hydroxyacetone: D-glucose: 2-hydroxymethylfuran (g) = 1.35: 0.15: 0.94: 0.15: 0.15: 0.12: 0.12: 0.15: 0.15, catalyst: 0.15g; b1-Octene conversion = 100% x (1- GC area% of unreacted octenes versus the sum of the GC area% of alkylated phenols, octanols, dioctyl ethers, oligomers and octyl acetates); cPhenol conversions = 100% x GC area% of phenol alkylates versus the sum of the GC area% of unreacted phenol and phenol alkylates; dPercent of 1-octene isomerization = 100% x (1- GC area% of 1-octene versus the sum of the GC area% of 1-octene and 1-octene isomers); ‘1-Butanol conversion = 100% x (1- GC area% of unreacted 1-butanol versus the sum of the GC area% of butyl acetate, dibutyl ether, 1,1-dibutoxyethane and butyl levulinate); fO-Alkylates selectivity = 100% x GC area% of O-alkylates versus the sum of the GC area% of all phenol alkylates.

Stronger acids also promote both esterification and acetal formation rates. This can be observed from the higher 1-butanol conversion (97.4%) with SSA catalyst. Except for the modest 1-butanol conversion (68%) formed over Cs2.5/K10, 1-butanol conversions with the three resin sulfonic acids catalysts all exceeded 90%. Carboxylic acid esterifications and alde­hyde/ketone acetal formation with 1-butanol are reversible or equilibrium reactions. The desirable forward reaction products like esters and acetals were produced accompanied by formation of water. That water and the original water present in bio-oil would inhibit the forward reactions, limit­ing further formation of more esters and acetals. Water removal by acid catalyzed hydration of 1-octene helped to shift these equilibria forming esters and acetals toward completion.

Phenol alkylates (C — and O-) are desired because of their high octane number and high heating values [15]. The O-alkylated products are espe­cially desirable because the acidic phenolic hydroxyl group is converted to an ether lowering product acidity and decreasing hydrophilicity. Moreover,

O-alkylated phenol ethers are readily combusted. Except for Cs25/K10, all the catalysts gave high O-alkylation selectivity (>60%). Compared with the three resin sulfonic acids, SSA gives more C-alkylates because that stronger acid promotes conversion of O-alkylates into the thermodynamic phenol C-alkylates by enhancing O-alkylate protonation.

SSA exhibited a higher water-tolerance than other catalysts based on the model systems shown in Table 3. Desulfonation of the three resin sulfonic acids catalyst occurred progressively at 120 °C over time, leading to partial deactivation of these catalysts. Cs25/K10 lost almost all catalytic activity.