Reactions of Phenol, Water, Acetic Acid, Methanol, and 2

Ind. Eng. Chem. Res. 2010, 49, 2003–2013

2003

Reactions of Phenol, Water, Acetic Acid, Methanol, and 2-Hydroxymethylfuran with Olefins as Models for Bio-oil Upgrading Xulai Yang,†,‡ Sabornie Chatterjee,‡ Zhijun Zhang,‡,§ Xifeng Zhu,*,† and Charles U. Pittman, Jr.*,‡ Key Laboratory for Biomass Clean Energy of Anhui ProVince, UniVersity of Science and Technology of China, Hefei, 230026, P. R. China, Department of Chemistry, Mississippi State UniVersity, Mississippi State, Mississippi, 39762, and Key Laboratory of Bio-based Material Science and Technology of Ministry of Education, Northeast Forest UniVersity, Harbin, 150040, P.R. China

Model liquid phase reactions of 1-octene with phenol in the presence of water, acetic acid, methanol, and 2-hydroxymethylfuran, respectively, were carried out over acid catalysts for bio-oil upgrading, including 30 wt % acidic salt Cs2.5H0.5PW12O40 supported on K-10 clay (30%Cs2.5/K-10), Nafion (NR50) and Amberlyst 15. Temperatures from 40 to 120 °C were examined. Both catalysts had a high activity and selectivity for O-alkylation of phenol with 1-octene but not with 2,4,4-trimethylpentene. The presence of water, acetic acid, and methanol lowered the yield of alkylated phenols by the competitive formation of octanols and dioctyl ethers, octyl acetates, and methyl ethers, respectively. Higher O-alkylation selectivity was obtained at the expense of lower phenol conversion in the presence of water, methanol, or acetic acid. 30%Cs2.5/K-10 is an excellent water-tolerant catalyst while Amberlyst 15 decomposed at higher temperatures and higher water concentrations. 2-Hydroxymethylfuran deactivated catalysts significantly, indicating furan derivatives in biooil may require modification before upgrading with olefins. 1. Introduction Biomass is a renewable energy resource. Lignocellulosic biomass from plants is the most abundant form of biomass and does not directly compete with the human food chain. Fast pyrolysis liquids from lignocellulosic biomass can be stored for later use or shipped as a more energy dense liquid to other locations for use as fuel or as chemical feedstock.1 However, these liquids react further to undergo chemical and phase changes, and they are chemically corrosive.2 The thermal processes involved in the formation of the liquid bio-oil result in a diverse collection of chemical fragments, including the low pH carboxylic acids, highly reactive phenols and catechols, hydroxyaldehydes, hydroxyketones, substituted furans, anhydrosugars, other carboxyl compounds, and oligomeric fragments from both cellulose and lignin, and water.1–5 Therefore, bio-oil refining is needed before its use in engines for a transportation fuel is possible. Bio-oil upgrading by hydrodeoxygenation or cracking has proved to be difficult, due to extensive coking of most catalyst systems tried to date.6–9 These reactions require temperatures from 275 to 500 °C where coke formation is fast and the catalysts are rapidly inactivated. Hydrodeoxygenation of biooil to pure hydrocarbons requires too much hydrogen to be economically competitive. Petroleum refineries will not currently accept feeds containing even 5% by weight oxygen but biooils contain from 30 to 45% oxygen, even after some pretreatments. Importantly, bio-oil contains substantial dissolved water, typically 15-30 wt %, which decreases heating value and causes bio-oil to be immiscible with petroleum-derived fuel. An alternative to refining bio-oil to hydrocarbons is the partial conversion to a less acidic, less hydrophilic, and higher heating

value fuel mixture which retains substantial oxygen. Therefore, we have investigated the modification of bio-oil using acid catalyzed reactions of olefins and olefin mixtures with bio-oil. The addition of water, alcohols, and organic acids across olefin double bonds can generate alcohols, ethers, and esters, respectively, as shown in Scheme 1. Phenolic molecules can be either O- or C-alkylated. Water content and acidity would be reduced and heating value enhanced. The product ethers and esters are less corrosive, and these products would enhance the modified bio-oil’s miscibility with petroleum-derived fuels. These reactions are all acid-catalyzed and occur at low temperatures, far below those of hydrodeoxygenation or cracking.10–17 Thus, catalyst coking and bio-oil polymerization might be avoided. However, solid acid catalysts are generally less active in water and can be poisoned, but a few have been found to be water-tolerant.18,19 Heteropoly acids (HPA) and their salts are known to be active green catalysts for many homogeneous and heterogeneous acid catalyzed reactions.20–24 HPAs behave as very strong Bro¨nsted acids, approaching superacid strengths with fairly high stability, high proton mobility, high catalytic activity, and homogeneous examples have high solubility in polar solvents. Solid heteropoly acids exhibit pseudoliquid phase behavior and behave like Scheme 1. Hydroxyl and Carboxyl Additions Across Olefins

* To whom correspondence should be addressed. Phone: +1-6623257616. Fax: +1-662-3257611. E-mail: [email protected]. edu (C.U.P.). Phone: +86-551-3600040. Fax: +86-551-3606689. E-mail: [email protected] (X.Z.). † University of Science and Technology of China. ‡ Mississippi State University. § Northeast Forest University of China. 10.1021/ie900998d  2010 American Chemical Society Published on Web 01/26/2010

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Ind. Eng. Chem. Res., Vol. 49, No. 5, 2010

concentrated acid solutions toward polar substances. Reactions proceed on both the surface and in the bulk of crystalline heteropoly acids. The insoluble acidic salt Cs2.5H0.5PW12O40 (hereafter designated Cs2.5) exhibits very high catalytic activities for various reactions in which water participates, including ester hydrolyses, hydrations, alkene acetoxylation, and esterification, in excess water.15,16,18 Most bio-oil upgrading methods are developed by studying model compounds and their mixtures.25–29 In this research, olefination of model bio-oil componentsswater, methanol, phenol, acetic acid and furfural alcohol and various mixtures of these were studied. They represent key functional groups present in the bio-oil in high concentrations. Phenol is acidic, and its fuel content in current engines must be limited to avoid elastomer compatibility problems.30 This paper also reports the synthesis of 30% Cs2.5 supported on K-10 clay with intact Keggin anions. Cs2.5/K-10 clay, Amberlyst 15, and Nafion are employed as heterogeneous catalysts. The applicability of these catalysts for hydroxyl and carboxyl additions across olefins (Scheme 1) was investigated as a prelude to developing bio-oil modification processes. H3PW12O40 supported on SiO2 was not chosen because it leaches on exposure to higher polar solvent concentrations.31 1-Octene and 2,4,4-trimethylpentene were selected as model alkylating olefins, because the C8 chain length is representative of the naphtha range olefins targeted for phenol alkylation,30 and they are convenient to work with in laboratory glassware unlike C3 and C4 olefins. Fuel production by partial upgrading of fast pyrolysis oil with olefins is our goal. C8 alcohols from water addition to C8 olefins are excellent fuels, as are ethers from hydroxyl group additions across olefins by hydroxyl components of bio-oil. Thus, we used C8 olefins in this initial study. Phenyl ethers are high cetane number diesel fuel components, and alkylated phenols have high heating values, with ortho isomers providing antioxidant properties. Acetate esters are excellent fuels, and their formation from acetic acid removes acidity and lowers hydrophilicity. Specific attention was also given to the effects of water, acetic acid, methanol, and 2-hydroxymethylfuran on the other reactions. 2. Experimental Section 2.1. Chemicals. Phenol (99%), glacial acetic acid, 1-octene (98%), Nafion (NR50), and Montmorillonite K-10 were procured from Sigma Aldrich Company. Amberlyst 15, 2-hydroxymethylfuran (95%), and 12-tungstophosphoric acid hydrate were purchased from Alfa Aesar Company. All chemicals were used without further purification. 2.2. Catalyst Preparation. K-10 clay was dried at 120 °C for 3 h in air prior to its use. The following supported catalysts were prepared by well-developed procedures.32 Cs2.5/K-10 systems were prepared by the incipient wetness impregnation technique and calcined in air at 300 °C for 3 h. K-10 clay was first impregnated with an aqueous solution of Cs2CO3, dried at 120 °C overnight, and calcined at 300 °C for 3 h. Next, H3PW12O40 was impregnated into K-10 clay using an aqueous solution, followed by drying at 120 °C overnight and calcining in air at 300 °C for 3 h. Bulk Cs2.5 was prepared by adding an aqueous Cs2CO3 (2.5 mmol) solution dropwise to H3PW12O40 (2 mmol) solution while stirring. The resulting precipitate was dried at 120 °C overnight and calcined at 300 °C for 3 h in air. All catalyst samples were powdered and dried at 120 °C for 3 h prior to use. FTIR spectra were recorded to analyze the Keggin structure on a Thermo Scientific Nicolet 6700 spectrophotometer.

2.3. Catalytic Reactions. 1-Octene or 2,4,4-trimethylpentene was added to the catalyst and model compound mixture in a two-necked glass flask, equipped with a reflux condenser and a magnetic stirrer. Phenol, phenol/acetic acid, phenol/water, phenol/2-hydroxymethylfuran and phenol/methanol, phenol/ water/acetic acid, phenol/water/acetic acid/methanol, and phenol/ water/acetic acid/methanol/2-hydroxymethylfuran were used as feedstocks. Since the O-alkylate content from phenol was reported to be highest when the phenol/1-octene mole ratio is 1,33 this ratio was used in all phenol alkylation experiments with 1-octene. For example, phenol (0.94 g, 0.01 mol), 1-octene (1.12 g, 0.01 mol), and catalyst (0.2 g) were reacted at 80 °C, with vigorous stirring for 3 h (no solvent). The reaction was monitored by TLC. Similar reactions were conducted with varying amounts of the catalyst and different reaction times and temperatures. The liquid products were identified using a Shimadzu QP2010S GC-MS with helium as the carrier gas. A SHRXI5MS 30 m × 0.25 mm i.d. × 0.25 µm film capillary column was used with a 50:1 split ratio. The temperature program used was: 30 °C for 5 min, ramping from 30 to 300 °C at 10 °C/ min, and then holding at 300 °C for 10 min. 1-Octene alkylatedphenols were identified by their mass-to-charge ratio (m/z), and the fragmentation patterns which were matched with compound libraries. The peaks at 94 m/z for phenyl ethers,30,34 107 m/z for ortho-alkylated phenols, and 121 m/z for meta- and paraalkylated phenols30,35 were especially valuable. Quantitative analyses were carried out using dodecane as the internal standard, and all response factors were predetermined relative to dodecane over a range of mole ratios. There were three octyl phenyl ether isomers and three ortho- and three para/metaoctylphenols (C-alkylates) and several small dialkylated phenols in the products. It was assumed that the response factors for each of the octyl phenyl ether isomers had the same value, and this same assumption was used for the C-alkylates. Thus, a weighed amount of the mixture of these three isomers was used to get an averaged octyl phenol ether response factor. Then, when analyzing each product mixture, the sum of the octyl phenyl ether areas was added and this sum was employed to compare to dodecane’s (the internal standard) area using this averaged response factor. The same method was applied to the C-alkylated phenols. These response factors were determined via previous calibrations as 3.51, 3.18, 2.13, 1.52, 1.54, 1.01, and 1.82 for 1-octene, phenol, phenyl acetate, O-alkylates, C-akylates, 1-octyl acetate, and 1-octanol, respectively. The standard compounds required for the quantitative analysis were synthesized in the laboratory following established organic synthesis methods. 3. Results and Discussion 3.1. Catalyst FTIR Spectral Analysis. Typical Fourier transform infrared (FTIR) spectra of bulk H3PW12O40 powder and supported catalysts are shown in Figure 1, respectively. The fingerprint absorption bands in the range from 700 to 1100 cm-1 are ascribed to the Keggin structure.36 The characteristic peaks present in bulk H3PW12O40 and supported Cs2.5 are observed. Bulk K-10 clay showed a strong broad absorption band in the range of 900-1200 cm-1, which partially overlapped the PsO stretching vibration in the central tetrahedron (1075 cm-1) and the terminal W d O (954 cm-1) in H3PW12O40. Supported Cs2.5 showed the characteristic IR bands at ca. 1075 cm-1 (PsO in the central tetrahedron), 981 cm-1 (terminal W d O), and 886 and 797 cm-1 (asymmetric WsOsW vibrations) associated with the Keggin polyanion. As the Cs2.5 loading increased to


Figure 1. FTIR spectra of the catalysts and their precursors.

40 wt %, the characteristic peaks are obvious and become sharper. Once the protons in bulk PW are partly substituted by Cs+ ions, the vibrational frequency of the W d O bonds shifts from 954 to 981 cm-1 and asymmetric WsOsW vibration from 896 to 886 cm-1 for the supported Cs2.5 catalyst. However, the positions of the other two bonds remain intact. These results imply that exchanging Cs+ ions with protons has little influence on the Keggin structure. 3.2. Alkylation of Phenol with 1-Octene. Phenol alkylation with a 1 mol equiv of 1-octene over 30%Cs2.5/K-10 at 40-100 °C produced mostly monoalkylated products. In the absence of a catalyst, the reaction did not proceed even after 5 h at 100 °C. Both O- and C-alkylated products formed in parallel over the catalyst. Isomeric octyl phenyl ethers (O-alkylates) and octyl phenols (ortho/para-C-alkylates) were produced (see Scheme 2), showing 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. 3.2.1. Effect of Clay Catalyst Loading. To investigate the change in alkylation selectivity and phenol conversion versus heteropolyanion catalyst loading onto the clay substrate, 20-40% Cs2.5 on K-10 and bulk Cs2.5 were tested at 60 °C. Using bulk Cs2.5 gave 68% phenol conversions (Figure 2). The effect of changing catalyst loadings on clay was quite interesting. Phenol conversion after 3 h over both 20%Cs2.5/K-10 and 30%Cs2.5/ K10 was essentially the same (58%). O-Alkylation selectivity over 20%Cs2.5/K-10 (70-71%) was close to that over 30%Cs2.5/ K-10 (72-74%), observed in three trials of each (Figure 2). With an increase in Cs2.5 loading from 30 to 40 wt % of K-10 clay, the phenol conversion decreased to 38% and O-alkylation selectivity was 71%. Though highest phenol conversion was obtained when bulk Cs2.5 was employed, lower O-alkylation selectivity and higher dialkylation content were observed. Therefore, 30%Cs2.5/K-10 was used for further experiments. 3.2.2. Effect of Catalyst Quantity. The phenol conversion versus the amount of catalyst used in 1-octene alkylation reactions at 80 °C over 30%Cs2.5/K-10 is presented in Figure 3. The phenol/ 1-octene mole ratio was 1. A modest increase in conversion occurred on increasing the quantity of 30%Cs2.5/K-10 5-fold, and no further increase occurred after a 4-fold increase. Therefore, 0.2 g catalyst per 0.94 g (0.01 mol) phenol was used in further experiments. However, O-alkylation selectivity decreased with an increase in conversion (e.g., more catalyst). After reaching the lowest value of selectivity (58%) with 0.2 g catalyst, the selectivity increased slightly with more catalyst. 3.2.3. Effect of Reaction Temperature and Time. The effect of temperature on conversion and selectivity was studied between 40 and 100 °C (Table 1). Phenol conversions increased substantially with increasing temperature over both Amberlyst

2005

15 and 30%Cs2.5/K-10, implying kinetic control. Phenyl octyl ether selectivity decreased slightly with increased conversion at 40-50 °C. O-alkylation selectivity dropped progressively as temperature increased from 60 to 100 °C as equilibrium control increasingly dominates. At higher temperatures, O-alkylated product formation is reversible as previously observed,37 and the more stable C-alkylated products formed with higher activation energies are favored. No 1-octene oligomerization occurred at a 1:1 phenol/1-octene mole ratio between 40 and 100 °C unless it was preceded by skeletal isomerization. Higher temperatures favor more C-alkylation in all cases. To maximize ether formation, the temperature should be below 60 °C when alkylating with 1-octene. In most reactions, para/meta-Calkylated phenols dominated over ortho-C-alkylated products. This is likely due to continuous, low activation energy, acidcatalyzed ortho- to para/meta-rearrangements, a thermodynamically driven process.37 In general, 30%Cs2.5/K-10 and Amberlyst 15 catalysts gave similar results. The O-alkylation selectivity over 30%Cs2.5/K-10 was slightly higher than that over Amberlyst 15, especially at 80 °C or higher, but phenol conversions were a little lower than those over Amberlyst 15. 3.3. Effect of Carbocation Stability and Catalyst Type on the Selectivity of O-Alkylation to C-Alkylation. Reactivity differences of 1-octene, 2,4,4-trimethylpentene, and cyclohexene with phenol have been studied over Amberlyst 15 and 30%Cs2.5/ K-10 at 80 °C, in 3 h (Table 2). Amberlyst 15 and 30%Cs2.5/ K-10 exhibited similar activities and selectivities. Phenol conversion with the three olefins followed the order: 1-octene ≈ cyclohexene > 2,4,4-trimethylpentene. Thus, the olefins generating more reactive secondary carbocations reacted faster than 2,4,4-trimethylpentene, which forms a tertiary carbocation upon protonation. 1-Octene and cyclohexene also gave higher O-alkylation selectivities than 2,4,4-trimethylpentene, which only gave C-alkylated phenols. Almost all of these C-alkylated phenols were para isomers. The results agree well with a previous report.38 Tertiary and secondary carbocations react most rapidly by O-alkylation. However, phenyl t-alkyl ethers isomerize far more rapidly to C-alkylated products than phenyl sec-alkyl ethers. Thus, 1-octene and cyclohexene give more O-alkylation products under these reaction conditions because these ethers are more stable at the reaction conditions. The isomerization of phenyl-1,1,3,3-tetramethylbutyl ether to orthoand para-C-alkylated products is faster because ether cleavage to the tertiary dimethyl neopentyl carbenium ion proceeds at a lower activation energy than the corresponding cleavage of 2-phenyoxyoctane, thereby rapidly producing the para-Calkylation products. No 1-octene oligomerization to C16 or higher oligomers occurred unless it was preceded by skeletal isomerization at 80 °C. However, 2,4,4-trimethylpentene readily oligomerized at this temperature (Scheme 3). This difference might be due to the formation and higher stability of the secondary phosphoric ester intermediates at the catalyst surface and the time periods involved in their reactions with water, alcohols, carboxylic acids, and phenols versus secondary to tertiary carbocation rearrangements.39 12-Tungstophosphoric acid catalyst seems to have more in common with phosphoric acid catalyst than with typical Brønsted acid catalysts. Phosphoric acid catalysis proceeds through an ester formation mechanism with olefins. 2,4,4Trimethylpentene oligomerization was also accompanied by cracking. Selective cracking of C8 and C16 olefins produced isobutene and other fragments. Reoligomerization of isobutene yielded C8, C12, and C16 olefins. Almost all the unreacted olefins in the products were oligomers of 2,4,4-trimethylpentene

2006


Scheme 2. Major Reactions in Alkylation of Phenol with Neat 1-Octene

after the reaction. This may be related to the lower phenol conversion. When phenol alkylation with 2,4,4-trimethylpentene was carried out over Nafion with 1:6 olefin/phenol mole ratio at 80 °C, 3% para-t-butylphenol was found with the major product 4-(2,4,4-trimethylpentan-2-yl)-phenol. At 55 °C, 4% para-t-butylphenol and 5% para-t-amylphenol were found. This demonstrates that fragmentation to C4 and C5 olefins occurred during the alkylations. Acid-catalyzed olefin oligomerization to larger olefins and fragmentations to smaller olefins compete to some degree and increase the product complexity when 2,4,4-

Figure 2. Effect of Cs2.5 loading on K-10 in phenol alkylation with 1-octene (phenol:1-octene 0.01:0.01 mol, catalyst based on 0.06 g Cs2.5, temperature 60 °C, reaction time 3 h, in air).

Figure 3. Response of phenol conversion and O-alkylation selectivity to the amount of 30%Cs2.5/K-10 used in alkylation reactions at 80 °C. Three replicates were performed for those experiments shown. The conversion range is shown by the error bars.

trimethylpentene was used. Cyclohexene dimer was found in a small amount (1%) after the reaction. Thus, the reactivities and the product selectivities in phenol alkylation depend on the nature of both catalysts and olefins. 3.4. Alkylation of Phenol with 1-Octene in the Presence of Water. Water is the most abundant compound in bio-oil obtained by fast pyrolysis technology. It has significant influence on bio-oil’s properties and upgrading. The effect of different amounts of water (1-20 wt % in phenol) on acidcatalyzed phenol alkylation with 1-octene was investigated. Water reacts with 1-octene to form octanols which can react further to form dioctyl ethers, as shown in Scheme 4, in competition with O- and C-alkylation of phenol. 1-Octene hydration and phenol alkylation occur in a two phase system composed of 1-octene/H2O-phenol, due to the very low 1-octene solubility in water. Water lowered the alkylation reaction rate significantly. Olefin hydration competes with phenol alkylation. Phenol conversion in the presence of 5 wt % water increased with temperature, especially between 100 and 120 °C (Figure 4). The yield of hydration to C8 alcohols increased as temperature increased from 60 to 100 °C, then dropped after 100 °C (Figure 5). A few dioctyl ethers were observed only at 80 and 100 °C over 30%Cs2.5/K-10. These ethers are due to further octanol addition to 1-octene or acidcatalyzed nucleophilic substitution of octanol hydroxyl groups by another octanol. A competition exists between phenol and water adsorption on the catalysts. The catalyst activity may be lowered due to water adsorption on these hydrophilic sites, or the rate decrease may simply reflect the presence of two liquid phases reacting at the third solid catalyst phase. Conversions over Amberlyst 15 and 30%Cs2.5/K-10 were similar below 100 °C, but 30%Cs2.5/K-10 is better above 100 °C, where Amberlyst 15 will desulfonate and loose activity more rapidly. Since these are three-phase reactions, specific interpretations are difficult. Liquid phase compositions vary with temperature, stirring, and mass transfer rates. Similar difficulties will be encountered in olefin/bio-oil reactions. Phenol conversion in the presence of 5 wt % water at 80 °C increased with time. When reaction time increased from 3 to 10 h, the conversion increased from 6% to 46% over Amberlyst 15 and from 2% to 30% over 30%Cs2.5/ K-10. The cost of bio-oil upgrading will increase with reaction time. Therefore, 3 h at 100 °C were chosen to investigate the influence of water on phenol alkylation in model reactions. The effect of water content on phenol conversion and O-alkylation selectivity at 100 °C is shown in Figure 6 for Amberlyst 15 and 30%Cs2.5/K-10. Phenol conversion decreased


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Table 1. Comparison of Amberlyst 15 and 30%Cs2.5/K-10 Activities at Different Temperatures and Times in Phenol Alkylation with 1-Octenea selectivity (%) catalyst Amberlyst 15

30%Cs2.5/K-10

temperature (°C)

time (h)

phenol conversion (%)

O-alkylate

ortho-C-alkylate

para/meta-C-alkylateb

dialkylate

40 40 50 60 80 100 40 40 50 60 60 80 100

10 3 3 5 5 3 10 3 3 3 5 3 3

41 35 75 76 82 87 55 31 55 58 62 73 79

79 76 73 54 49 0 74 78 74 72 71 58 7

5 6 8 16 17 46 4 10 4 4 3 6 33

16 19 20 24 24 48 15 13 15 17 16 19 44

0 0 0 6 11 6 7 0 6 8 10 18 22

a

Reaction conditions: catalyst 0.2 g. Phenol/1-octene moles used: 0.01/0.01 mol/mol. together but almost all the product was para based on other experiments.

b

In these reactions, the para- and meta-isomers were summed

Table 2. Differences in Olefin Reactivities in Phenol Alkylation over Amberlyst 15 or 30%Cs2.5/K-10 at 80 °Ca selectivity (%) catalyst Amberlyst 15 30%Cs2.5/K-10

a

olefin

conversion of phenol (%)

O-alkylate

ortho-C-alkylate


dialkylate

cyclohexene 2,4,4-trimethyl-pentene 1-octene cyclohexene 2,4,4-trimethyl-pentene 1-octene

82 74 81 67 53 73

48 0 49 64 0 58

30 0 17 27 0 6

17 91 24 8 98 19

5 9 10 1 2 17

Reaction conditions: temperature 80 °C; catalyst, 0.2 g; the phenol/1-octene moles used: 0.01/0.01 mol/mol. b See footnote b, Table 1.

Scheme 3. Oligomerization and Fragmentation Compete with Direct Phenol Alkylation

Scheme 4. Acid-Catalyzed 1-Octene Hydration

dramatically with increasing water content with both catalysts. Partial decomposition of Amberlyst 15 occurred, especially at 5 wt % or more water content. Clearly, 30%Cs2.5/K-10 is more water-tolerant than Amberlyst 15 at high water content. The presence of water in the reaction mixture had a very favorable effect on process selectivity with respect to octyl phenyl ethers. As water content increased, O-alkylation selectivity increased significantly, with a maximum selectivity approaching 90% at 15 wt % water. This selectivity exceeds that obtained at 60 °C with neat phenol/1-octene. O/C-Alkylated phenols (the O/C-alkylation ratio determined by GC/MS was 78%/22%) were isolated. Then they were used to investigate the effect of water on O-alkylation selectivity. The isomerization of O-alkylated products to C-alkylated species was inhibited in the presence of water at 80 and 100 °C (Table

3). Water did not intercept carbocation intermediates during this isomerization as demonstrated by the absence of octanol

Figure 4. Phenol conversion versus temperature during 1-octene alkylations catalyzed by heterogeneous acid catalysts in the presence of 5 wt % water in phenol feedstock. Three repetitions of the experiments were conducted in the examples shown where the conversion range is indicated by the error bars.

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Figure 5. Octanol yields (%) versus temperature during phenol alkylations catalyzed by heterogeneous acid catalysts in the presence of 5 wt % water in phenol feedstock. Three repetitions of specific experiments are shown in the examples where the yield range is represented by the error bars.

Figure 6. Phenol conversion and O-alkylation selectivity for phenol alkylations with 1-octene at 100 °C in the presence of different water contents (1-20 wt %): (2) conversion over Amberlyst 15; (9) selectivity over Amberlyst 15; (•) conversion over 30%Cs2.5/K-10; (1) selectivity over 30%Cs2.5/K-10. Table 3. Isomerizations of O-Alkylated Phenol Products over 30%Cs2.5/K-10 reactiona feedstock (O-alkylation content) 100 °C without water or phenol 100 °C in the presence of 0.04 mol water 100 °C in the presence of 0.01 mol water and 0.001 mol phenol 100 °C in the presence of 0.001 mol phenol 80 °C in the presence of 0.01 mol water and 0.001 mol phenol 80 °C in the presence of 0.001 mol phenol

product O-alkylation content (%) 78 66 69 67 67 74 73

a

Reaction conditions: feedstock (O/C-alkylated products), 0.5 g; 30%Cs2.5/K-10 catalyst, 0.05 g; time, 3 h.

formation. O-Alkylated products were converted to C-alkylates. The rate of rearrangement of O-alkylated products slows with increasing water content. For example, the selectivity to O-alkylated products was 69% after reaction at 100 °C in the presence of 0.04 mol water versus 67% in the presence of 0.01 mol water. The phenol concentration had little effect on this rearrangement. These results agree with a reaction network description where O-alkylation is faster, forming the primary alkylation product. C-Alkylation subsequently occurs by inter-

Figure 7. Yield of octanols produced in 1-octene alkylations of phenol with different water feed contents at 100 °C. Three replicates of each reaction were run and the yield range is represented by the error bars.

molecular isomerization of the O-alkylate where secondary octyl cations, if formed, C-alkylate phenol without being intercepted by water. Water also influences the catalytic acid sites. Amberlyst 15 swells in the reactant mixture, increasing accessibility to active sites inside the resin. A 50% volume swelling of the micrograins was reported in the presence of water.40 Water effects the energies of the reagents, transition states, and products. Apparently, some combination of all these influences reduces the rate of ether isomerization to C-alkylation products. Capture of the octyl cations, generated upon 1-octene protonation, is a competition between water and phenol. With increasing water concentration from 2 to 10 wt %, the concentration of octanols increased significantly, then dramatically decreased from 10 to 20 wt % at 100 °C (Figure 7). This trend was similar to the change in O-alkylation selectivity. The phenol conversion dropped (Figure 6) because water increasingly captures the C8 cation relative to phenol as water concentration increases. Water concentration at the catalytically active sites increases with swelling. Amberlyst 15 swells more with water than 30%Cs2.5/K-10, consistent with the higher yields of octanols over Amberlyst 15 at a water level of 10-15 wt %. A small amount of dioctyl ethers were observed over 30%Cs2.5/ K-10, and this content increased from 0.6 to 1.5% when water content increased from 2 to 15 wt %. In contrast, no dioctyl ethers were found at 1 and 20 wt % water content over 30%Cs2.5/K-10. Also dioctyl ethers were not observed in any of the reactions over Amberlyst 15. The conversion of water to octanols and dioctyl ethers was higher over 30%Cs2.5/K-10 than over Amberlyst 15 (Figure 8). At 10 wt % water content, water conversion was greater over Amberlyst 15. This could be due to swelling of Amberlyst 15. Swelling allows a distribution of all reactants to access a larger fraction of the internal acid sites of this macroreticular resin, where much of the conversion occurs. However, the reagent mole ratios within the swollen resin will be different than that of bulk reaction phase or that at the 30% Cs2.5/K-10 catalyst surface. 3.5. Alkylation of Phenol with 1-Octene in the Presence of Acetic Acid. Bio-oil is highly acidic. The most abundant acid in crude bio-oil is acetic acid.1,4 Therefore, the influence of 10 wt % acetic acid in phenol was investigated from 60 to 120 °C in 3 h reactions with 1-octene. The phenol/ acetic acid/olefin composition was one phase liquid. Acetic acid easily added to C8 cations generated from 1-octene, yielding


Figure 8. Water conversions in phenol alkylations with 1-octene over Amberlyst 15 and 30% Cs2.5/K-10 in the presence of different water feed contents. Three replicates of each reaction were performed.

Scheme 5. Reactions in Acetoxylation of 1-Octene

three isomeric octyl acetates (Scheme 5). More acetic acid was converted into acetates over 30%Cs2.5/K-10 than over Amberlyst 15. A small quantity of phenyl acetate formed by phenol esterification was also observed. Table 4 shows representative phenol conversions and product selectivities from 60 to 120 °C. Phenol conversions dropped when acetic acid was present due to competition by these two reagents for the intermediate carbocations. O-Alkylation selectivity quickly decreased over Amberlyst 15 with increasing phenol conversion as the temperature rose from 60 to 120 °C. O-Alkylation selectivity was much lower over Amberlyst 15 at 80-120 °C. Phenol conversions were higher at 80-120 °C using Amberlyst 15 than when 30%Cs2.5/K-10 was employed. The formation of octyl acetates over 30%Cs2.5/K-10 was higher than that over Amberlyst 15. Phenol O-alkylation selectivity over 30%Cs2.5/K-10 was still 62% and 42% even at 100 and 120 °C, respectively. Orthoand para/meta-mono-C-alkylated phenols were observed, and dialkylated phenols were present in small amounts at 80-120 °C. 3.6. Alkylation of Phenol with 1-Octene in the Presence of 2-Hydroxymethylfuran. Furan derivatives are obtained during fast pyrolysis of cellulosic materials and represent an important class of bio-oil components. Therefore, phenol alkylation was conducted in the presence of 10 wt % 2-hydroxymethylfuran in phenol. This alcohol readily polymerizes under acidic conditions and can form coke on catalysts. 2-Hydroxymethylfuran deactivated 30%Cs2.5/K-10, greatly reducing phenol conversion (see Table 5). The initially white 30%Cs2.5/K-10 catalyst became black during the reaction, even at 60 °C. A small amount of difuran-2-ylmethane was found in the liquid reaction products (GC/MS). The 30%Cs2.5/K-10 surfaces were coked which prevented further effective catalysis. The activity of Amberlyst 15 was also lower in the presence of 2-hydroxymethylfuran. This is readily seen by comparing data in Table 5 with that in Table 1 at equivalent temperatures and times. However, Amberlyst 15 still has catalytic activity, most likely due to swelling that allows reactants to access internal active sites inside which continue to function. More rapid coking

2009

of 30%Cs2.5/K-10 surface retards phenol/1-octene alkylation. It remains to be seen if furan derivatives will seriously degrade these catalysts when bio-oil is used and water is present. If this does occur, then the reactive furans would need to be removed or modified before upgrading via olefination. 3.7. Alkylation of Phenol with 1-Octene in the Presence of Methanol. Methanol is not present or only present in traces in bio-oil. Here methanol was used to simulate the reaction of primary aliphatic alcohols. Table 6 shows representative phenol conversions and product selectivities from 60 to 120 °C in the presence of 10 wt % methanol in phenol (0.31/1 mol ratio). The phenol/methanol/olefin composition was one liquid phase before reactions. Methanol inhibited the phenol alkylation by the competitive formation of methyl octyl ethers. Also, traces of anisole were observed to form at 120 °C over Amberlyst 15. A competition exists between phenol and methanol for absorption on the catalysts and for capture of octyl cations. Catalyst activity may be lowered due to methanol solvation. Phenol conversions increased with temperature and O-alkylation selectivities were very high at 100 °C (Table 6). Even at 120 °C, O-alkylation selectivities were 58%. Thus, methanol raises O-alkylation selectivity similar to water. Yields of methyl octyl ether formation increased with an increase of reaction temperature. More methyl octyl ether formation occurred with Amberlyst 15 than with 30%Cs2.5/K-10. 3.8. Rate Comparison of Hydration, Etherification (Methanolic), and Acetoxylation. Phenol conversion was also investigated when 0.27 equiv of water, methanol, or acetic acid to 1 equiv of phenol was present (Table 7). A 1:1:0.27 mol ratio of phenol/1-octene/additive was used at 100 °C in 3 h. The phenol/water/1-octene mixture was a two phase liquid and phenol/1-octene/acetic acid or methanol reactions were one phase before heating at 100 °C. When heated at 100 °C, phenol/ water/1-octene mixture was still a two-phase liquid. Phenol conversion was higher in the presence of 5 wt % water than when the equivalent mole ratio of methanol (8.4 wt %) or acetic acid (15 wt %) was present. However, 23% of the acetic acid was converted into octyl acetates and phenyl acetate at these conditions, and 12% of the water was converted into the corresponding octanols or dioctyl ethers. Only 3% of the methanol formed methyl octyl ethers. Therefore, 1-octene acetoxylation was more efficient than hydration or etherification in the presence of the same molar amounts of water or methanol in phenol over 30%Cs2.5/K-10. Etherification 1-octene with methanol was the slowest reaction at these conditions. Phase equilibrium factors and solvation of catalyst acid sites complicate interpretations of these results. 2,4,4-Trimethylpentene/methanol (1:6 mol ratio) and 2,4,4trimethylpentene/water (1:6 mol ratio) reactions were also examined over Amberlyst 15. The former was a one phase liquid, and the latter was a two phase liquid. Table 8 shows representative 2,4,4-trimethylpentene conversions and product distributions. 2,4,4-Trimethylpentene oligomerized readily, even at 55 °C. Methanol inhibited the oligomerization of the olefin more effectively than water. The yield of 2-methoxy-2,4,4trimethylpentane (ether) was higher than that of 2,4,4-trimethylpentan-2-ol (tertiary alcohol) at the same reaction conditions. More methanol should be in the olefin phase than water. Thus methanol captures more of the initially protonated olefin to form 2-methoxy-2,4,4-trimethylpentane. 3.9. Reactions between Bio-oil Simulants and 1-Octene. Model reactions of three-component and four-component biooil simulants with 1-octene were carried out over 30%Cs2.5/ K-10. This is one step toward bio-oil in feed component

2010


Table 4. Product Distribution and Phenol Conversion in Acid-Catalyzed Alkylations with 1-Octene in the Presence of 10 wt % Acetic Acida catalyst Amberlyst 15

30%Cs2.5/K-10

alkylated phenol selectivity (%)

temperature (°C)


O-alkylate

C-alkylate

dialkylate

60 80 100 120 60 80 100 120

34 67 72 86 27 44 54 60

81 36 14 1 81 81 62 42

19 58 80 92 21 18 31 48

0 6 6 7 0 1 7 10

content of esters (%)b

acetic acid conversion (%)

octyl acetates

phenyl acetate

35 49 38

4 7 6

2 1 1

59 56 68 61

10 9 11 9

2 2 1 1

a Reaction conditions: the phenol/1-octene/acetic acid moles in feed: 0.01:0.01:0.0017; catalyst: 0.2 g; time: 3 h. b Compared to the sum of alkylated phenols and unreacted phenol.

Table 5. Effect of 2-Hydroxymethylfuran on Activity and Selectivity during Phenol Alkylation by 1-Octene over Amberlyst 15 and 30%Cs2.5/K-10a catalyst Amberlyst 15

30%Cs2.5/K-10

temperature (°C)


selectivity for O-alkylates (%)

60 80 100 120 60 80 100 120

4 11 39 38 3 3 3 3

72 81 55 50 75 79 73 77

a Reaction conditions: the phenol/1-octene/2-hydroxymethylfuran moles used in the feed: 0.01:0.01:0.0011; catalyst: 0.2 g; time: 3 h.

complexity. Table 9 shows the conversions of phenol/water/ acetic acid with 1-octene over 30%Cs2.5/K-10 at 100 °C. The phenol/water/acetic acid/1-octene mixture was a two phase liquid before heating. When heated at 100 °C, the mixture was still two phases. However, the mixtures had became a one phase liquid after reactions at the mole ratios used. The conversions after 3 h of each reagent decreased with an increase of water content. Phenyl octyl ether selectivities were 73-74%. Two other systems were examined. The four-component solution, phenol (0.5 g)/2-hydroxymethylfuran (0.05 g)/methanol (0.16 g)/acetic acid (0.3 g) (abbreviated PHMA) was reacted with 1-octene (1.12 g). Also the three-component system, phenol (0.5 g)/methanol (0.16 g)/acetic acid (0.3 g) (abbreviated PMA) was reacted with 1-octene (1.12 g). Both systems were one phase liquids. Tables 10 and 11 summarize representative reactions. After 3 h at 100 or 120 °C over 0.2 g 30%Cs2.5/K-10 catalyst, the PHMA/1-octene reaction became a two phase liquid. The upper layer was yellow, and the lower layer was black. The PMA/1-octene reaction remained one phase throughout the reaction period, yielding a light yellow liquid. The reaction progress was followed by phenol conversion. At 100 °C, phenol conversion was 1.4% in the absence of 2-hydroxymethylfuran (PMA reactions) but only 0.05% in the presence of 2-hydroxymethylfuran (PHMA reactions). At 120 °C, phenol conversion after 3 h was 5.5% in the absence of 2-hydroxymethylfuran and 0.5% in the presence of 2-hydroxymethylfuran. Therefore, higher temperatures were favorable. The presence of 2-hydroxymethylfuran seriously degraded the catalyst 30%Cs2.5/K-10. Table 10 shows the product composition after reactions. Methyl acetate, formed by esterification of acetic acid, was one of the main products. Octanol formed from 1-octene and water produced during esterification. The water also caused the PHMA reaction to be a two phase liquid after 3 h although additional olefin and reaction time would eventually convert all the water to octanol. The addition of 0.1 g water to PMA or PHMA gave a two phase liquid. There were still two phases present after reactions

at 120 °C, 3 h over 0.2 g 30%Cs2.5/K-10 catalyst. The phenol conversion was low (0.9% in the absence of 2-hydroxymethylfuran and only 0.1% in the presence of 2-hydroxymethylfuran). The product distributions from reactions of PMA and PHMA in the presence of 0.1 g water over 30%Cs2.5/K-10 are shown in Table 11. 1-Octene hydration and esterification of acetic acid by methanol were the two main reactions in the 3 h period. Amberlyst 15 was also used at 120 °C with PMA and PHMA. Without added water, the phenol conversion was 5% in the absence of 2-hydroxymethylfuran and 3% in the presence of 2-hydroxymethylfuran. Methyl acetate was the main product. No octanol formed from 1-octene hydration by the water of esterification at 120 °C over Amberlyst 15. Amberlyst 15 was decomposed after reaction when 0.1 g water was added to the feed at 120 °C. 3.10. Fate of 2-Hydroxymethylfuran over 30%Cs2.5/ K-10. The 30%Cs2.5/K-10 surfaces coked when 2-hydroxymethylfuran was a reactant. This greatly decreased catalytic activity. To study this issue, neat 2-hydroxymethylfuran (2 g) was heated at 100 °C over 0.2 g of 30%Cs2.5/K-10 catalyst. After 1 h, the catalyst and the liquid phase became black. The product composition was determined by GC/MS (Table 12). 2-Hydroxymethylfuran polymerized rapidly to form difuran-2ylmethane, difurfuryl ether, 5-furfuryl-furfuryl alcohol, etc. as shown in Table 12. Higher molecular weight, unidentified compounds and coke formed which covered on the surface of catalyst. The product structures showed that acid-catalyzed loss of formaldehyde occurred jointly with electrophilic condensation. Therefore, the reactive furans may need to be removed or modified before upgrading raw bio-oil via olefination. 4. Conclusions Acid-catalyzed refining of bio-oil will be an extremely complex system. This model study enhanced our understanding of the using olefins to react individually and simultaneously with carboxylic acids, water, phenol, and alcohols (2-hydroxymethylfuran and methanol) for potential bio-oil upgrading process development. Phenol alkylation alone and in the presence of these other components illustrated that hydration, acetoxylation, phenol esterification, or etherification could simultaneously occur with the O- and C-alkylation of phenol. All of these reactions constitute bio-oil upgrading possibilities. The competition of various reactants with olefins is a complex function of temperature and phase separation. Water, acetic acid, and methanol can slow the rate of phenol O/C-alkylation. These model compound studies are now being used to design catalysts for bio-oil upgrading and select conditions to use in exploring a process design for refining bio-oil. A preliminary report of our bio-oil/olefin studies at low olefins stoichiometries has appeared.41


2011

a

Table 6. Product Distribution and Phenol Conversion in Acid-Catalyzed Reactions with 1-Octene in the Presence of 10 wt % Methanol catalyst Amberlyst 15

30%Cs2.5/K10

c

selectivity of alkylated phenols (%)

temperature (°C)


O-alkylate

ortho-C-alkylate


dialkylate

yield of methyl octyl ethers (%)c

60 80 100 120 60 80 100 120

3 16 33 45 2 7 33 38

79 83 84 58 83 79 81 58

8 6 5 14 0 3 7 9

13 12 12 23 17 18 13 25

0 0 0 5 0 0 0 9

0.5 0.7 0.8 1.7 0.2 0.3 0.6 0.9

a Reaction conditions: the phenol/1-octene/methanol moles used in the feed: 0.01:0.01:0.0031; catalyst: 0.2 g; time: 3 h. Compared to the sum of alkylated phenols and unreacted phenol.

b

See footnote b in Table 1

Table 7. Effects of 0.27 equiv Water, Methanol, or Acetic Acid on Phenol Alkylation Reactions at 100 °Ca alkylated phenol selectivity (%) additives

temperature (°C)


O-alkylate

C-alkylate

dialkylate

additives conversion (%)b

water methanol acetic acid

100 100 100

62 36 31

57 72 79

30 23 19

12 5 3

12 3 23

a Reaction conditions: moles of phenol/additive fed to reaction: 0.01:0.0027; catalyst 30%Cs2.5/K-10: 0.2 g. b Methanol conversion was just based on the yield of methyl octyl ethers.

Table 8. Comparison of 2,4,4-Trimethylpentene Etherification with Methanol and Hydration with Water over Amberlyst 15a water addition

methanol addition

temperature (°C)

olefin conversion (%)

tertiary alcohol yield (%)

yield of olefin oligomers (%)

olefin conversion (%)

ether yield (%)

yield of olefin oligomers (%)

80 55

100 100

9 4

91 96

71 60

12 13

59 47

a

Reaction conditions: the moles of olefin/water or methanol fed for reaction: 0.01:0.06; catalyst Amberlyst 15: 0.2 g; time: 6 h.

Table 9. Conversions of Phenol/Water/Acetic Acid Reacted with 1-Octene over 30%Cs2.5/K-10a reagent mole ratio (mol/mol)b 0.01:0.0027:0.0027:0.0154 0.01:0.0027:0.0054:0.0181

phenol acetic acid octanol phenyl ether conversion conversion yield selectivity (%) (%)c (%)d (%) 30 18

15 10

1.8 0.6

74 73

a Reaction conditions: catalyst 30%Cs2.5/K-10:0.2 g; time: 3 h; temperature: 100 °C. b Reagents ) phenol:acetic acid:water:1-octene. Note, 1 equiv 1-octene was used per the sum of phenol, acetic acid, and water in both reactions. c Acetic acid conversion was based on the yield of octyl acetate and phenyl acetate. d Compared to the sum of alkylated phenols and unreacted phenol. The total of all water that could be present in the system should be the sum of water in feed and water from esterification of acetic acid.

Liquid phase alkylation of phenol with 1-octene at a 1:1 mol ratio over 30%Cs2.5/K-10 or Amberlyst 15 produced mainly monoalkylates. O-Alkylation with 1-octene is favored over C-alkylation at low temperatures. Phenol conversions increased with increasing temperature over both catalysts. O-Alkylation selectivity decreased with an increase in temperature and conversion. Both catalysts had similar activity and selectivity for O-alkylated phenols in the absence of other reagents. Reactivity and the product selectivity are also a function of olefin structure. For example, O-alkylation selectivity with 1-octene was much higher than that with 2,4,4-trimethylpentene which forms tertiary cations on protonation. The latter also underwent oligomerization and fragmentation more readily than 1-octene. Fragmentation led to the observation of such C-alkylated phenols as p-t-butylphenol and p-t-amylphenol. All these trends give us a glimpse of the complexity that will be faced in a biorefinery employing mixed olefin feeds. Water, acetic acid, and methanol lowered the yield of alkylated phenols by the competitive formation of octanols and

Table 10. Product Distributions from PMA and PHMA Reactions at 120 °C for 3 h over 30%Cs2.5/K-10a product distribution in PMA reaction (%)

product distribution in PHMA reaction (%)

compound name

100 °C

120 °C

100 °C

120 °C

methyl acetate acetic acid methyl octyl ether phenol octanol phenyl acetate octyl acetate phenyl octyl ether C-alkylated phenol othersb

2.4 3.6 0.1 90.2 0.7 nd 0.3 2.7 nd nd

1.3 0.5 0.2 82.6 1.1 0.3 2.0 9.5 2.4 nd

1.9 3.7 nd 93.1 0.5 nd nd 0.1 nd 0.5

1.6 0.7 nd 94.8 0.7 nd nd 1.1 nd 1.1

a Methanol was used as the solvent for GC/MS analysis. Product distributions were given in area percent determined by GC/MS analyses using an ion current detector. nd ) not detected. PMA ) phenol (5 mmol)/methanol (5 mmol)/acetic acid (5 mmol). PHMA ) phenol (5 mmol)/2-hydroxymethylfuran (0.5 mmol)/methanol (5 mmol)/acetic acid (5 mmol). b Compounds derived from 2-hydroxymethylfuran.

dioctyl ethers, octyl acetates, and methyl ethers, respectively, in 1-octene reactions. Thus, sufficient olefin feed stoichiometries will be required in bio-oil upgrading processes if a large decrease in phenolic hydroxyls is required in the fuel product. Olefin acetoxylation is faster than hydration or methanolic etherification over 30%Cs2.5/K-10, suggesting that olefin treatment is a viable route to reduce acidity. O-Alkylation selectivity was enhanced in the presence of water, acetic acid, methanol, and 2-hydroxymethylfuran when compared at similar reaction conditions. Optimum O-alkylation occurred at 60 °C with high phenol conversion when only phenol and 1-octene were reacted. However, substantial O-alkylation occurs at 100 °C in the presence of water, acetic acid, or methanol. This suggests that

2012


Table 11. Product Distributions from PMA and PHMA Reactions in the Presence of Water at 120 °C for 3 h over 30%Cs2.5/K-10a

compound name

product distribution from PMA reactions (%)

product distribution from PHMA reactions (%)

methyl acetate acetic acid phenol octanol phenyl octyl ether C-alkylated phenol othersb

2.1 3.1 92.1 1.0 1.8 nd nd

0.54 3.8 94.3 0.6 0.2 nd 0.5

a Methanol was used as the solvent for GC/MS analysis. Product distributions were given in area percent determined by GC/MS analyses using an ion current detector. nd ) not detected. PMA ) phenol (5 mmol)/methanol (5 mmol)/acetic acid (5 mmol). PHMA ) phenol (5 mmol)/2-hydroxymethylfuran (0.5 mmol)/methanol (5 mmol)/acetic acid (5 mmol). b Compounds derived from 2-hydroxymethylfuran.

Table 12. Products Formed from 2-Hydroxymethylfuran on Heating at 100 °C over 30%Cs2.5/K-10 for 1 ha

or diesel fuel is replaced by lignocellulosic-derived fuels, more petroleum could be converted to olefins feeds. Disclaimer This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Acknowledgment This material is based upon work performed through the Sustainable Energy Research Center at Mississippi State University (MSU) and is supported by the Department of Energy under Award Number DE-FG3606GO86025. X.Y. and Z.Z. thank the China Scholarship Council (CSC) for financial support. Mr. Brandon Doss at the Department of Chemistry of MSU is thanked for helpful discussions and assistance with sample characterizations. Literature Cited

a Products were analyzed by GC/MS. Each product was identified by excellent matches of their MS fragmentation patterns. These patterns were unique, and -CH2OH group were clearly observed in the molecular ions of 1, 5, and 6.

phenyl ether production, rather than C-alkylation, can be made to dominate in bio-oil upgrading with olefins. 30%Cs2.5/K-10 was an excellent water-tolerant catalyst. It is superior to Amberlyst 15 in the presence of 5 wt % or more water in feedstock. Amberlyst 15 increasingly desulfonated at higher water contents, especially above 100 °C. The effect of the presence of some furan derivatives remains a concern. 2-Hydroxymethylfuran deactivated the catalysts, especially 30%Cs2.5/K-10 (as did levoglucosan in preliminary studies). Hydroxymethylfuran was studied here because it easily polymerizes and gives tar in the presence of acid. Hydroxymethylfurfural is more prevalent in bio-oil but less reactive to the acidcatalyzed polymerization. Model compound studies with levoglucosan, hydroxyacetone, hydroxyacetaldehyde, and methoxyphenols are being conducted now to supplement process development on refining bio-oil with olefins. Unlike exhaustive hydrodeoxygenation, upgrading bio-oil with olefins can preserve in the final fuel all the caloric content originally present in the bio-oil. Of course, the olefin added supplements the heating values further. This olefin feed must currently be derived from petroleum. To the degree that gasoline

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ReceiVed for reView June 19, 2009 ReVised manuscript receiVed December 29, 2009 Accepted December 29, 2009 IE900998D

Reactions of Phenol, Water, Acetic Acid, Methanol, and 2

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