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 °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 Cs25/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.

FIGURE 1: Comparison of phenol conversions by 1-octene with and without water present at 120 °C over Amberlyst15, Cs25/K10, Amberlyst36, Dowex50WX2 and SSA (catalyst, 0.15 g; time: 3 h; 1-octene: phenol: water (mmol) = 10:10:10).

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-al — kylates) 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-alkyla — tion. 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 Cs25/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. 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.

TABLE 4: Product distributions of 1-octene reaction with neat phenol over different catalysts at 120 °Ca. Catalyst Selectivity (%) O-alkylates C-alkylates Di-C-alkylates Amberlyst 15 5.5 86.0 8.5 Cs25/K10 3.2 65.9 30.9 Amberlyst 36 8.0 86.3 5.7 Dowex50WX2 33.5 63.2 3.3 SSA 37.2 34.4 28.4 “Reaction conditions: (solid catalyst, 0.15 g; time: 3 h; 1-octene: phenol (mmol) = 10:10.

SCHEME 1: Acid-catalyzed reactions of phenol as a model phenolic compound with 1-octene.

TABLE 5: Product distributions from 1-octene reactions in phenol/water at 120 °C a. Catalyst Selectivity (%)b Yield (%) O-alkylates C-alkylates Di-C-alkylates Octanols Dioctyl ethers Amberlyst 15 82.5 16.0 1.5 5.4 0.2 Cs25/K10 75.9 20.8 3.3 6.7 0.4 Amberlyst 36 73.7 25.0 1.4 0.7 0.2 Dowex50WX2 84.5 12.5 3.0 4.7 1.7 SSA 75.1 19.5 5.4 3.4 1.7 “Reaction conditions: (solid catalyst, 0.15 g; time: 3 h; 1-octene: phenol: water (mmol) = 10:10:10. bGC area% of involved compounds versus the sum of the GC area% of all products that remained after the reaction.

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 1-octene (Scheme 3), generat­ing three groups of improved fuel components in one operation without water generation. Trace amount of phenyl acetate were formed. The phe­nyl acetate yield decreased with increasing temperatures from 60 to 100 °C [17]. Both SSA and DX2 show higher catalytic activity than other three catalysts based on related phenol conversions and octyl acetates yields.

Table 6. Phenol conversions and octyl acetates yield of 1-octene reactions with phenol/ water/acetic acid over different catalysts at 120 °Ca. Catalyst Phenol Conversion (%) bYield (%) Octyl acetates Amberlyst 15 5.6 0.6 Cs25/K10 2.3 0.4 Amberlyst 36 6.5 1.0 Dowex50WX2 63.1 4.3 SSA 67.2 9.4

“Reaction conditions: (solid catalyst, 0.15 g; time: 3 h; 1-octene: phenol: water: acetic acid (mmol) = 10:10:10:3.0; bGC area% of involved compounds versus the sum of the GC area% of all products remained after the reaction.

SCHEME 3: Acid-catalyzed reactions of acetic acid as a model carboxylic acid with 1-octene.

Bio-oil contains a large number of primary and secondary aliphatic hydroxyl groups from cellulose and hemicellulose pyrolysis. Table 7 pro­vides the phenol conversions and butyl octyl ethers yields of 1-octene re­actions with phenol/water/1-butanol mixtures over Dowex50WX2, SSA, Amberlyst15 and Cs2.5/K10, respectively. Except for the reactions men­tioned above, butyl octyl ethers were generated by either 1-butanol etheri­fication with octanols or 1-butanol addition across octenes (Scheme 4). SSA gave the highest phenol conversion (69.2%), illustrating it had the highest catalytic activity. Cs25/K10, which gave a phenol conversion of only 6.9%, lost almost all its activity during the reaction.

Multifunctional compounds such as hydroxyacetone or hydroxyetha — nal in bio-oil can oligomerize and polymerize. Aldol condensation reac­tions accelerate bio-oil aging [7]. Table 8 summarizes the effect of the presence of hydroxyacetone upon 1-octene reactions with phenol/water over Cs25/K10 and SSA catalysts. A good phenol conversion (64.0%) was obtained over SSA. Cs25/K10 was deactivated by hydroxyacetone based on the greatly reduced phenol conversion (2.2%). No hydroxyac­etone was detected after reaction. However, small amounts of 3-methyl — 2-hydroxycyclopent — 2-enone were detected. To further study this issue, neat 1-hydroxyacetone was heated at 100 °C for 1h over 30% Cs25/K10 and the products were identified by GC-MS (Table 9) [22]. Propionic acid (43.7%), hydroxyacetone dimers (24.8%) and 2-hydroxy-3-methylcyclo- pent-2-enone (9.7%) formed, together with about 1.8% of an unknown species. Three carbon a-hydroxycarbonyl species such as 1-hydroxyac- etone (acetol) can undergo enolization and dimerization to yield the struc­tures illustrated in Scheme 5. The keto form of 1-hydroxyacetone exists in equilibrium with its enol, enediol and aldehydo forms. In both neat and concentrated solutions, 1-hydroxyacetone can dimerize generating the cy­clic structures (a) and (b). Decomposition of (b) produces propionic acid. Meanwhile, intermolecular aldol condensation reactions of 1-hydroxyac — etone and subsequent serial of dehydration reactions occurred generat­ing 3-methyl-2-hydroxycyclopent-2-enone (c) and its isomers. As a con­sequence of dimerization and aldol condensation, the 1-hydroxyacetone monomers are expected to diminish with time during upgrading.

TABLE 7: Yields of butyl octyl ethers and phenol conversions in acid-catalyzed 1-octene reactions with phenol/water/1-butanol over different catalysts at 120 °Ca. Catalyst Phenol Conversion (%) bYield (%) Butyl octyl ethers Amberlyst 15 40.7 0.17 Cs25/K10 6.9 nd Dowex50WX2 40.6 0.69 SSA 69.2 0.24 a Reaction conditions: (solid catalyst, 0.15 g; time: 3 h; 1-octene: phenol: water: 1-butanol (mmol) = 10:10:11.6:3.4; b GC area% of involved compounds versus the sum of the GC area% of all products remained after the reaction.

SCHEME 4: Acid-catalyzed reactions of 1-butanol as a model alcohol with 1-octene.

TABLE 8: Phenol conversions and yields of new products derived from the added reagent (2-hydroxymethylfuran or hydroxyacetone or D-glucose) in 1-octene reactions with water/ phenola. Added Reagent Catalyst Phenol conversion (%) dProducts yield (%) Hydroxyacetone SSA 64.0 Methyl cyclopentenolone (0.12) Cs25/K10 2.2 Methyl cyclopentenolone, (0.21) 2-Hydroxymeth- ylfuran SSA 65.0 UNb (0.18) Cs25/K10 4.5 UNb (0.87) D-glucose SSA 64.7 Anhydrosugarc (0.14) Cs25/K10 3.5 Anhydrosugarc (0.20) A15 40.5 octyl formates, 0.28 DX2 41.3 octyl formates, 0.36

“Reaction conditions: (120 °C,3h, catalyst, 0.15 g; 1-octene (10 mmol); phenol (10 mmol); water (10mmol); hydroxyacetone (1.4 mmol) or 2-hydroxymethylfuran (1.0 mmol) or D-glucose (0.6mmol)); bUnkown compound; cAnhydrosugar: 1,6-Anhydro-3,4-dideoxy-fi — D-manno-hexapyranose; d GC area% of involved compounds versus the sum of the GC area% of all products remained after the reaction.

Furan derivatives such as 2-hydroxymethylfuran and hydroxymethyl- furfural present in bio-oil can polymerize easily and give tar in the pres­ence of acid [26]. Table 8 shows the effect of 2-hydroxymethylfuran ad­dition on the 1-octene reaction with phenol/water over Cs25/K10 and SSA catalysts. SSA shows a good catalytic activity giving a phenol conversion of 64.7%. However, the Cs25/K10 surfaces coked seriously, which greatly decreased its catalytic activity and reduced phenol conversion (4.5%). Po­lymerization of 2-hydroxymethylfuran occurred under acidic conditions forming coke or tar on the catalysts [27]. This has been further confirmed by the reaction products identified from GC-MS analysis (Table 8) of the reaction where neat 2-hydroxymethylfuran (2 g) was heated at 100 °C for or 1h over 30% Cs25/K10. In addition to the unreacted 2-hydroxymethyl — furan, difurffuryl ether (9.4%), 5-furffuryl-furfuryl alcohol (4.9%) and difu — ran-2-ylmethane (4.8%), together with about 2.6% other compounds were detected in the products [22]. Rapid polymerization of 2-hydroxymeth — ylfuran occurred at 120 °C via acid-catalyzed electrophilic condensation with the accompanying loss of formaldehyde [18], generating difurfuryl ether, 5-furfuryl-furfuryl alcohol, difuran-2-ylmethane, etc. (Scheme 6).

TABLE 9: Products formed from hydroxyacetone or 2-hydroxymethylfuran on heating at 100 °C over 30% Cs2.5/K10 for 1 ha. 2 — Hydro xymethy lfuran Hydroxyacetone Compounds Peak area (%) Compounds Peak area (%) 2-hydroxymethylfuran 78.3 Propionic acid 63.4 Difurfuryl ether 9.4 Hydroxyacetone dimers 24.8 5-Furfuryl-furfuryl alcohol 4.9 Methyl cyclopentenolone 9.7 Difuran-2-ylmethane 4.8 Unkown species 1.8 Others 2.6 aProducts were analyzed by GC/MS. Each product was identified by excellent matches of their MS fragmentation patterns.

A large number of compounds with hydroxyl groups, particularly, an- hydro monosaccharides such as levoglucosan, were derived from pyrolysis of cellulose and hemicellulose components of the pine wood feed during bio-oil production [5]. Anhydro monosaccharides readily hydrate back to monosaccharides when heated with acid and water. Therefore, the effects

of D-glucose addition on 1-octene reactions with phenol/water over Cs25/ K10, DX2, A15 and SSA catalysts were studied at 120 °C for 3 h (Table 8). SSA gives a higher activity than DX2, A15 and Cs25/K10. Trace amounts of octyl formates were formed over A15 and DX2 by esterification of for­mic acid by octanols. The formic acid was generated by the known acid — catalyzed conversions pathways of D-glucose (Scheme 7) [2,27]. 5-Hy — droxymethylfurfural (HMF) was formed by D-glucose dehydration. Then, subsequent HMF hydration to its hemiacetal occurred in acidic media, followed by rehydration, ring-opening, loss of both water and formic acid to form levulinic acid. Also, small amounts of 1,6-anhydro-3,4-dideoxy — P-D-mannohexapyranose, generated by dehydration of D-glucose, were detected over SSA and Cs25/K10.

SCHEME 6: Acid-catalyzed reactions of 2-hydroxymethylfuran.

SCHEME 7: Acid-catalyzed reactions of D-glucose as model monosaccharide [27].

In addition to the reactions discussed above occurring between 1-oc- tene with model bio-oil components, some additional olefin reactions took place. Table 10 shows the product distributions of individual olefin re­actions conducted using equimolar amounts of olefin (1,7-octadiene, cy­clohexene, 1-octene, or 2,4,4-trimethylpentene)/phenol/water over SSA at 120 °C for 3 h. Skeletal isomerization reactions of all olefins occurred except with cyclohexene. Intramolecular diene cyclizations occurred for 1,7-octadiene, individually.

No oligomerization or cracking of either 1-octene or 1,7-octadiene oc­curred. However, 1-octene isomers were detected in the reactions where neat phenol and 1-octene operated at 100 °C over Cs25/K10 or A15 cata­lysts. 2,4,4-Trimethylpentene oligomerized to C16 olefins and cracked into C4 olefins readily at these conditions. Cracking of 2,4,4-trimethylpen — tene mainly produced isobutene. Cyclohexene’s dimer 1-cyclohexyl-1-cy­clohexene was found. Reoligomerization of isobutene gave C8, C12, and C16 olefins. Hydration reactions to form alcohols occurred for all olefins, followed by etherification of these resulting alcohols generating ethers and water (Scheme 8). Thus, the choice of olefin structure will play a role in the product distribution observed, but all the olefins help drive the upgrad­ing process to remove water and promote esterification, acetal formation, generate ethers and both O — and C-alkylate phenols.

TABLE 10: Product distributions and phenol conversions in addition reactions by different olefins in phenol/water at 120 °C in 3h over the SSA catalysta. Olefins PC (%)b Product distributions (GC area %)c 1,7-Octadiene 52.4 Skeletal isomers (4.5%): 1,6-octadiene, 3,5-octadiene, 2-meth — yl-1,5-heptadiene, 2,4-dimethyl-1,5-hexadiene, 3-methyl-1,5- heptadiene, etc. Cycloolefins (14.2%): bicyclo[4.1.0]heptane, 2-methylbicy — clo[2.2.1]heptane, 4-ethyl-1-cyclohexene, cyclooctene,1-ethyl — 2-methylcyclopen-tene, 1,6-dimethyl-cyclohexene, ethylidenecycloh exane, 1,2-dimethyl-1-cyclohexene, etc. Alcohols and ethers (8.8%): 1,7-octanediol, 4-ethylcyclohexanol, 1-ethylcyclohexanol, 2- propyl-tetrahydropyran, 2,5-diethyltetrahydrofur-an, 2-propyltet — rahydropyran, 2-butyl-3-ethyloxirane, etc. O-Alkylates (33.4%); Mono-C-alkylates (4.1%); Di-C-alkylates (10.1%) Cyclohexene 62.0 Oligomers (0.2%):1-cyclohexyl-1-cyclohexene, etc. Alcohols and ethers(1.4%):cyclohexanol, di-cyclohexyl ether O-Alkylates (2.9%): cyclohexyl phenyl ether Mono-C-alkylates (33.4%): o-cyclohexylphenol, p-cyclohexylphe — nol 1-Octene Di-C-alkylates (26.8%); Tri-C-alkylates (8.3%):2,4,6-tricyclohexyl — phenol 74.5 Skeletal isomers (12.1%):2-octene, 3-octene, 4-ocene, 1-octene. Alcohols and ethers (5.1%):2-octanol, 3-octanol dioctyl ethers, etc. O-Alkylates (48.6%):2-Octyl phenyl ether, 3-Octyl phenyl ether, etc. 2,4,4-Trimethyl- pentene Mono-C-alkylates (14.5%): o-octylphenol, p-octylphenols, etc. Di-C-alkylates (11.5%): 2,4-di-octylphenols, 2,6-dioctylphenols, 89.9 Skeletal isomers (4.7%): 2,4,4-trimethyl-1-pentene, 3,4,4-trimethyl- 2-pentene, etc. Fragments and oligomers (3.8%): 4,4-dimethyl-2-neopentyl-1-pen — tene, 2,2,4,6,6-pentamethyl-3-heptene, 2,2,4,4,6,8,8-heptamethyl — nonane, 2,4,4,6,6,8,8-heptamethyl-1-nonene, 2,2,4,6,6- pentameth — yl-3-heptene, etc. Alcohols and ethers (1.8%): 2,5,5-trimethyl-2-pentanol Mono-C-alkylates (64.2%): p-(1,1,3,3-tetramethylbutyl)phenol, o-t — butylphenol, p-t-butylphenol, etc. Di-C-alkylates (12.1%): 2,4-di-t-butylphenol, 2,5-di-t-butylphenol, 2,6-di-t-butylphenol, 2-t-butyl-4-(1,1,3,3-tetramethylbutyl)phenol, etc. Tri-C-alkylates (6.7%): 2,4,6-tri-t-butylphenol

“Reaction conditions: (SSA, 0.15 g; olefin: phenol: water (mmol) = 10:10:10; bPhenol conversions; cGC area% of involved compounds versus the sum of the GC area% of all products remained after the reaction.

TABLE 11: Product distributions and 1-butanol conversions in acid-catalyzed 1-octene/ 1-butanol reactions with phenol/water at 120 °Ca. Catalyst 1-Buta­nol Conv. (%) Selectivity (%) Yield (%)b Mono-O- octylates Mono-C- octylates Di-octy- lates Octa- nols Dioctyl ethers Dibutyl ether O-Bu- tylate A15 60.9 84.2 14.5 1.2 6.3 2.0 11.9 0.14 DX2 58.7 84.8 14.1 1.0 6.9 2.1 11.9 0.61 SSA 74.8 82.3 13.8 3.9 4.8 1.9 12.4 0.1 Cs25/K10 8.2 53.4 46.6 0 0.1 Nd 0.1 Nd

“Reaction conditions: (solid catalyst, 0.15 g; time: 3 h; 1-octene: phenol: water: 1-butanol (mmol) = 10:10:11.6:3.4; b GC area% of involved compounds versus the sum of the GC area% of all products remained after the reaction.

In addition, intermolecular dehydration of 1-butanol occurred produc­ing dibutyl ether with both Dowex50WX2 and SSA (Table 11). Also, trac­es of butyl phenyl ether were formed. Small amounts of t-butyl phenols

(0.9%) were detected when 2-butanol was used as replacement of 1-buta­nol over SSA. Under acid catalyzed conditions, 2-butanol was protonated, and then dehydrated generating secondary carbocations. Some isomeriza­tion to tertiary carbocations must then occur. Phenol added to these C4 cations generating O-t-butylated phenol, followed by isomerization of the t-butyl phenyl ether to the thermodynamic C-t-butylated phenol products along with some bis-alkylated phenols formation (Scheme 9). Also, both acetic acid esterification and acetaldehyde acetalation reactions with 1-bu­tanol occurred, generating butyl acetate and 1,1-dibutoxyethane (acetal), respectively, when acetic acid and acetaldehyde were present.

Table 12 summarizes the product compositions of the model bio-oil (phenol/water/acetic acid/acetaldehyde/hydroxyacetone/D-glucose/2-hy- droxymethylfuran mixtures) reactions with 1-octene/1-butanol over all five acid catalysts at 120 °C for 3 h [22].

In addition to alkylated phenols (both O-octylated and C-octylated), octanols, dibutyl ether and dioctyl ether, butyl acetate and various octyl acetates, 1-octene oligomers and isomers mentioned above, 1,1-dibutoxy­ethane and butyl levulinate were formed over all the catalysts. 1,1-Dib — utoxyethane was formed by acetal formation between acetaldehyde and

1- butanol (Scheme 9). Levulinic acid reacted with 1-butanol forming bu­tyl levulinate. Levulinic acid was derived from the acid-catalyzed conver­sions of both D-glucose (Scheme 7) and 2-hydroxymethylfuran (Scheme 10), which are both known pathways. Levulinic acid has been obtained by dehydration of hexoses to 5-hydroxymethylfurfural (HMF) and its sub­sequent hydration in acidic media [2,28]. Acid-catalyzed conversion of 2-hydroxymethylfuran to levulinic acid in aqueous solutions also has been recently reported [29].

TABLE 12: Product compositions of model bio-oil reactions with 1-octene/1-butanol over Cs25/K10, A15, A36, DX2 and SSA catalysts at 120 °C in 3 ha. Peak area (%) Products Cs25/K10 A3 6 A15 DX2 SSA Unreacted 1-octene 48.4 54.1 26.4 20.3 4.0 1-butanol 1.0 0.2 0.1 0.3 0.2 phenol 40.4 21.9 15.7 15.3 9.6 1-Dodecane (Internal standard) 1.4 1.4 1.5 1.8 3.0 In common 1-Octene isomers 1.0 8.5 31.1 25.3 28.9 Phenol octylates 0.8 2.9 12.4 18.8 35.3 Octanols 0.1 2.3 2.6 3.8 1.5 Dioctyl ethers 0.1 Nd 0.1 0.3 1.3 b1-Octene oligmers and their hydrates 3.8 4.2 4.7 5.0 6.1 Octyl acetates 0.8 0.9 1.6 6.7 4.8 1,1-Dibutoxyethane 0.3 0.1 0.1 0.1 0.1 Dibutyl ether 1.4 0.1 0.3 0.4 2.7 Butyl acetate 0.3 2.9 3.0 1.7 2.3 Butyl levulinate 0.1 0.6 0.3 0.2 0.4 Independent 2-Hydroxy-3-methylcyclopent-2-enone 0.1 Nd 0.1 0.1 Nd 2-(2-Furylmethyl)furan 0.1 Nd Nd Nd Nd

“Reaction conditions: (catalyst, 0.15 g; 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; time: 3 h; nd: not detected); these results were first noted in the preliminary communication of this work found in reference 23; bC8, C16 and C24 olefins and their hydrates.

SCHEME 10: Acid-catalyzed conversion of 2-hydroxymethylfuran to levulinic acid in aqueous solution [29].

Butyl levulinate shows the extent of levulinic acid formation. Table 13 demonstrates that it originates from both D-glucose and 2-hydroxy — methylfuran. Increasing butyl levulinate formation was observed when the amount of 2-hydroxymethylfuran and D-glucose were increased in the model bio-oil [22]. Trace amounts of 3-methyl-2-hydroxycyclopent — 2-enone were generated from hydroxyacetone over Cs25/K10, A15 and DX2 catalysts. Among the new products formed, 1-octene oligomers were the most abundant components over Cs25/K10 or A36. However, phenol alkylates became the most abundant products for the other three catalysts. Trace amount of 2-(2-furylmethyl) furan, formed by furfuryl alcohol po­lymerization, was detected over the Cs25/K10 catalyst. No 2-(2-furylmeth — yl) furan was detected over other catalysts, because all the reactive furan products were consumed by these more acidic catalysts.