ORIGINAL PAPER

Aqueous-Phase Processing of Bio-oil Model CompoundsOver Pt–Re Supported on Carbon

Jie Fu • Sikander H. Hakim • Brent H. Shanks

Published online: 28 March 2012

� Springer Science+Business Media, LLC 2012

Abstract The aqueous-phase processing (APP) of bio-

mass-derived bio-oil model compounds such as ethanol,

acetaldehyde, formic acid and acetic acid over Pt–Re/C

was examined. For the APP of ethanol at 250 �C, the

product distribution was determined and quantified. H2,

CO2, CH4, C2H6, acetaldehyde, ethyl ether, ethyl acetate,

acetic acid were found to be primary products and C3H8,

methanol, butanol and acetal were found to be minor

products. By also exploring the product distributions of

acetaldehyde, acetic acid and formic acid under APP

conditions with the Pt–Re/C, the reaction network associ-

ated with the APP conversion of ethanol was determined.

Using this reaction network, flux analysis was performed

on the ethanol reaction system to determine the reaction

pathway and relative rates (v1–v8) for each step. From this

analysis, it was found that the dehydrogenation of the

ethanol was the most active reaction in the reaction system.

Keywords Aqueous-phase processing � Biomass �Ethanol � Pt–Re/C � Flux analysis

1 Introduction

Diminishing petroleum resources combined with environ-

mental concerns related to fossil fuels are making it increas-

ingly important to explore the potential of renewable fuels

from biomass. Lignocellulosic biomass, including trees,

grasses, energy crops and agricultural wastes, is in principle

a low-cost and abundant form of biomass [1] and bio-oil

derived from lignocellulosic biomass is a relatively inex-

pensive liquid fuel [2]. However, the bio-oil has limited

viability in its as-produced form due to its high content of

oxygenated species, which includes various acids, alcohols,

aldehydes, ketones, sugars, guaiacols, syringols furans, and

furfurals [3, 4]. These species can be divided into water

soluble and insoluble compounds, with the water soluble

species coming primarily from the carbohydrate portion of

the biomass. The soluble portion typically accounts for

about 60 wt% of bio-oil and has higher oxygen content [1],

so processing this fraction is a critical issue for upgrading

bio-oil to higher quality fuels.

The utilization of aqueous-phase processing (APP) was

first reported by Dumesic and co-workers [5, 6] for the

conversion of sugars and polyols to targeted hydrogen and

alkanes. An advantage of this approach was that targeted

products could be selectively produced by carefully con-

trolling the chemistry occurring in the aqueous phase. The

initial work in APP, which was termed aqueous phase

reforming, focused on the generation of hydrogen from

carbohydrates and their derivatives. This reaction was

generally catalyzed by Group VIII metals catalyst [5–18],

since these metals generally have higher activities for

breaking C–C bonds [19, 20]. In particular, Pt, Ni and Ru

exhibited high activities for the reforming reaction with Pt

and Pd yielding relatively high selectivity for the produc-

tion of H2. However, the activity of a Pt catalyst was low

when reaction temperatures were decreased below 570 K

[21]. Subsequently, a carbon-supported Pt–Re catalyst was

found to give high activity, stability, and selectivity to H2/

CO at relatively low temperatures [22], which was utilized

to convert glycerol into synthesis gas [21, 23, 24].

Recently, Dumesic and co-workers [25] applied the Pt–Re/

J. Fu � S. H. Hakim � B. H. Shanks (&)

Department of Chemical and Biological Engineering, Iowa State

University, 2114 Sweeney Hall, Ames, IA 50010, USA

e-mail: bshanks@iastate.edu

123

Top Catal (2012) 55:140–147

DOI 10.1007/s11244-012-9784-4

C to the conversion of sorbitol resulting in the production

of mono-functional hydrocarbons such as alcohols,

ketones, carboxylic acids, and heterocycles, which could be

used as reactive intermediates for fine chemicals and

polymers. They also proposed several approaches to

upgrade the monofunctional hydrocarbons to longer-chain

alkanes via ketonization, aldol condensation, hydrogena-

tion, and dehydration.

The soluble portion of bio-oil is known to contain var-

ious carbohydrates and their derivatives (Table 1 [1])

containing multiple oxygen-containing functional groups.

As such, the Pt–Re/C catalyst could be a good candidate

for converting the soluble portion of bio-oil to mono-

functional hydrocarbons that could be further upgraded.

However, the chemical complexity of this soluble portion

will result in a myriad of reactions when APP is applied.

Additionally, it would be desirable for the mono-functional

molecules present in the soluble bio-oil fraction to be less

reactive than those with multiple functional groups, so that

these molecules would not be converted. To determine

whether conversion of the soluble bio-oil fraction could be

accomplished with selective production of mono-functional

molecules there is a need to perform model compound

studies to understand the relative rates of the reactions that

could occur during the application of APP. Due to the large

number of species present in the soluble portion of bio-oil,

model compound studies in which simple to progressively

more complex molecules are examined create a systematic

basis for understanding the efficacy of applying APP to

bio-oil.

In the current study, ethanol, acetaldehyde, formic acid

and acetic acid were selected as the initial model com-

pounds. Although they represent some of the mono-func-

tional compound targets, the testing of them will provide

the necessary reactivity basis information needed to

advance to the more complicated multi-functional

compounds such as hydroxyacetaldehyde, hydroxyacetone,

furfural, and levoglucosan.

2 Experimental Section

2.1 Materials

Ethanol was obtained from Decon Labs Inc. Acetaldehyde

and acetal were obtained from Acros Organics and formic

acid, acetic acid, ethyl ether, ethyl acetate and butanol from

Fisher Chemical. The chemicals used to synthesize the

catalyst, H2PtCl6�6H2O and HReO4 and carbon black

(Vulcan, CV-XC72R) were obtained from Strem Chemi-

cals and Clean Fuel Energy, LLC, respectively. All of the

chemicals were used as received. Deionized water was

prepared in house.

2.2 Preparation and Characterization of Catalyst

5 % Pt–Re/C was prepared by incipient wetness impreg-

nation of carbon black with equimolar aqueous solutions of

H2PtCl6�6H2O and HReO4. The support was dried in air for

12 h at 110 �C before impregnation, and 4.5 g of solution

was used for each gram of the carbon support. The catalyst

was dried at 110 �C for 12 h in air after impregnation. The

ratio of Pt versus Re used was 1:1 [23].

Surface area, pore volume and the pore size distribution

of the catalyst were determined by N2 physisorption at

77 K with a Micromeritics ASAP 2020 instrument. A 0.1 g

catalyst sample was degassed at 100 �C for 5 h prior to

analysis. Table 2 shows the textural properties for the

catalyst as synthesized, after reduction and after use in the

reaction. The total number of surface metal atoms and

concomitant metal dispersion were determined from H2

chemisorption using a Micromeritics AutoChem II 2920. A

0.03 g catalyst sample was placed into a U-tube and

reduced at 450 �C in a hydrogen flow of 50 cm3/min for

2 h prior to analysis. The stoichiometric ratios used for

H/Pt and H/Re was both 1. The measured surface metal

atoms and metal dispersion were found to be 11 lmol/g

and 2.1 %, respectively.

Table 1 Composition of bio-oil

aqueous portion [1]Component Range

(wt%)

Formic acid 4–8

Acetic acid 8–12

Hydroxyacetaldehyde 5–10

Hydroxyacetone 8–12

Furfural 2–5

2-Furanone 2–5

Glucose 15–20

Levoglucosan 15–20

Guaiacol 4–8

Water 15–20

Table 2 Textural properties for the Pt–Re catalyst as synthesized and

after reduction and reaction

Catalyst BET SA

(m2/g)

BJH PV

(cc/g)

Pore

size (nm)

As synthesized 110 0.39 32–65

After reduction 140 0.38 37–60

After reaction 102 0.29 30–64

Top Catal (2012) 55:140–147 141

123

2.3 Experimental Procedure

APP was performed at 250 �C in a stainless steel, high pres-

sure batch reactor with a volume of 114 mL (Autoclave

Engineers), equipped with an electrical heating jacket, a gas

inlet, a thermocouple, a gas sample outlet, a liquid sample

outlet and a mechanical stirrer. Prior to reaction, in situ

reduction of catalyst within the reactor was carried out at

450 �C for 3 h in a hydrogen flow of 300 cm3/min. After the

reduction process, nitrogen was flowed through the reactor at

800 cm3/min for 20 min to remove any residual hydrogen.

The reactant solution of 59 mL was placed in the injector and

degassed using high-purity nitrogen from a cylinder. After

injecting the reactant solution into the reactor, the system

pressure was increased to 2 MPa using high-pressure nitrogen

from a cylinder. After the temperature inside the reactor had

reached the desired reaction temperature, the mechanical

stirrer was turned on which corresponded to t = 0. Samples

were collected at specific batch reaction times.

2.4 Sampling and Analysis

For a liquid sample, 2–3 mL samples were collected after

1 mL of solution had first been vented to purge the sample

line. The sample was filtered to remove particulate and

then diluted to a suitable concentration for analysis. The

sample was analyzed quantitatively using a GC-FID (Ag-

ilent 7890A) with a FID detector employing the external

reference method. The column used was Agilent DB824

(30 m 9 320 lm 9 1.8 lm). 0.2 lL of the sample was

injected onto the column using a split ratio of 30:1. Both

the injector and detector temperatures were set at 300 �C.

The oven temperature was held at 40 �C for 5 min and then

ramped to 120 �C (10 �C/min). Peaks were identified by

comparison of their retention times with those of standard

solutions of the pure compounds, and identities were con-

firmed using a GC/MS (Agilent 7890A/5975C).

Total organic carbon (TOC) in the liquid phase was

determined using a TOC/TN Analyzer (FormacsHT/TN). For

the analysis, a 2.5 mL sample was diluted in a 25 mL

volumetric flask by deionized water. The following oper-

ating conditions were used, a TC temperature of 680 �C,

injection volume of 25 lL and an air flow of 150 mL/min.

For gas samples, an amount of gas, which corresponded to

about a 3 bar drop in reaction pressure, was vented to purge

the sample line. Then, the same amount of gas was collected

using an airbag. The gas sample in the airbag was quantita-

tively analyzed using a SRI GC8610C equipped with TCD

and FID detectors. The detector temperatures for the TCD and

FID were set at 150 and 380 �C, respectively. The oven

temperature was held at 30 �C for 5 min and then ramped to

150 �C (15 �C/min). Peaks were identified by comparison of

their retention times with pure gases.

3 Results and Discussion

3.1 Distribution and Carbon Balance of Products

Given in Table 3 is the product distribution found for the

APP of ethanol using the standard reaction conditions with

and without the presence of the catalyst. The standard

deviations were determined from two replicate experi-

ments. The reactions were carried out with an ethanol

concentration of 25 wt%, a catalyst loading of 0.1 g, a

reaction temperature of 250 �C, a stirring rate of 750 rpm,

and a reaction time of 6 h. The results showed that H2,

CO2, CH4, C2H6, acetaldehyde, ethyl ether, ethyl acetate,

acetic acid were the main products from the reaction with

C3H8, methanol, butanol and acetal also observed but as

minor products. The yields of nearly all of the products

were quite low in the experiments without the catalyst with

the primary exception of acetaldehyde, which was found at

higher yield than was observed in the presence of the

catalyst. The blank experiments had carbon balances of

95 % and the experiments with the catalyst had carbon

balances of about 90 %. For further confirmation of the

carbon balance determined from quantifying the individual

species, the TOC in the liquid phase was determined. The

calculated carbon percent in the liquid phase by TOC plus

the calculated carbon percent in the gases as determined by

SRI GC was 88 %, which was quite similar to the carbon

Table 3 The product distribution (carbon mol%) resulting from APP

of ethanol

Blank (6 h) Pt–Re/C (6 h)

Gas products

H2a 1.0 ± 0.2 13.3 ± 1.9

CO – 0.09 ± 0.03

CO2 0.014 ± 0.002 1.6 ± 0.6

CH4 0.002 ± 0.0001 2.2 ± 0.6

C2H6 0.001 ± 0.0007 0.38 ± 0.09

C3H8 0.0004 ± 0.00004 0.02 ± 0.01

Liquid products

Acetaldehyde 1.32 ± 0.06 0.37 ± 0.07

Methanol 0.05 ± 0.01 0.08 ± 0.04

Ethyl ether 1.05 ± 1.09 2.1 ± 0.3

Ethyl acetate 0.08 ± 0.02 1.8 ± 0.3

Acetic acid 0.03 ± 0.01 3.5 ± 0.6

Butanol 0.02 ± 0.001 0.06 ± 0.02

Acetal 0.03 ± 0.003 0.03 ± 0.01

Reactant

Ethanol 92.1 ± 0.7 77.1 ± 1.8

Total 94.7 ± 0.9 89.4 ± 1.0

a The molar yield of H2 is calculated as the number of the moles of

H2 divided by the initial number of the moles of ethanol loaded into

the reactor

142 Top Catal (2012) 55:140–147

123

balance via the GC characterization. Therefore, about 10 %

of the carbon was not identified in the liquid and gas. One

source of this carbon lost could be coking or absorption of

compounds onto the supported carbon. The re-usability of

Pt–Re/C for a second cycle was investigated. The con-

version of ethanol over the recovered catalyst was 26 %,

which was very close to the conversion over the fresh

catalyst (22.9 ± 1.8 %) indicating good activity mainte-

nance for the catalyst.

3.2 Effect of Stirring Rate on the Reaction

Figure 1 shows the effect of stirring rate on the APP of

ethanol. The error bars in Fig. 1 represent standard devia-

tions as determined from two replicate experiments. The

reactions were carried out at a temperature of 250 �C, an

initial ethanol concentration of 25 wt%, an initial pressure

of 20 bar, and a reaction time of 6 h. The ethanol con-

version and the yields of most products are similar at 600,

750, 900 rpm, which indicated that the catalyst, solvent and

reactants were mixed well at stirring rates above 600 rpm.

3.3 Effect of Initial Pressure on the Reaction

Figure 2 shows the effect of the initial reaction pressure on

ethanol APP. The error bars in Fig. 2 represent standard

deviations as determined from two replicate experiments. The

reactions were performed at a temperature of 250 �C, an initial

ethanol concentration of 25 wt%, a catalyst loading of 0.1 g, a

stirring rate of 750 rpm, and a reaction time of 6 h. As with

stirring rate, the effect of initial pressure on ethanol conversion

and the product yields was not seen to be significant. This

result suggested that the presence of N2 did not affect the gas–

liquid chemical equilibrium between the species in the gas and

liquid phase.

3.4 Effect of Catalyst Loading on the Reaction

Figure 3 shows the effect of catalyst loading on the APP of

ethanol with the error bars representing the standard devia-

tions as determined from two replicate experiments. The

reactions were carried out at a temperature of 250 �C, an

initial ethanol concentration of 25 wt%, an initial pressure of

20 bar, a stirring rate of 750 rpm, and a reaction time of 6 h.

Neither the conversion of ethanol nor the product yields were

found to increase proportionally with the increase of catalyst

loading. However, the yields of CH4 and C2H6 were found to

significantly increase with catalyst loading.

3.5 Effect of Ethanol Concentration on the Reaction

Figure 4 shows the effect of initial ethanol concentration

on the APP reactions. The reactions were carried out at the

same base conditions as discussed above with only the

initial ethanol concentration being varied and the catalyst

loading being held at 0.2 g. The ethanol conversion and H2

yield were found to decrease significantly with increasing

ethanol concentration with the yields of CH4, CO2, CO and

(a)

(b)

(c)

Fig. 1 Effect of stirring rate on ethanol APP at 250 �C. a Ethanol

conversion and H2 molar yield: (filled diamond) H2 molar yield; (opensquare) ethanol conversion. b Major product yields: (filled diamond)

ethyl ether; (open square) ethyl acetate; (filled triangle) acetic acid;

(open triangle) CO2; (filled square) CH4. c Minor product yields:

(filled diamond) acetaldehyde; (open square) methanol; (filledtriangle) butanol; (open triangle) acetal; (filled square) C2H6; (opendiamond) C3H8; (times) CO

Top Catal (2012) 55:140–147 143

123

methanol also decreasing. In contrast, the yields of most of

the liquid products were not significantly affected by the

initial ethanol concentration.

3.6 Reaction Pathway and Flux Analysis

To establish a reaction network for ethanol conversion

under APP conditions, experiments were performed with

acetaldehyde, acetic acid and formic acid as the reactants.

The product distributions resulting from these experiments

(a)

(b)

(c)

Fig. 2 Effect of initial pressure on ethanol APP at 250 �C. a Ethanol

conversion and H2 molar yield: (filled diamond) H2 molar yield; (opensquare) ethanol conversion. b Major product yields: (filled diamond)

ethyl ether; (open square) ethyl acetate; (filled triangle) acetic acid;

(open triangle) CO2; (filled square) CH4. c Minor product yields:

(filled diamond) acetaldehyde; (open square) methanol; (filledtriangle) butanol; (open triangle) acetal; (filled square) C2H6; (opendiamond) C3H8; (times) CO

0

10

20

30

40

0 0.1 0.2 0.3 0.4

catalyst loading/g

conv

ersi

on o

r mol

ar y

ield

/%

0

1

2

3

4

5

6

0 0.1 0.2 0.3 0.4

catalyst loading/g

carb

on y

ield

/%

0

0.1

0.2

0.3

0.4

0.5

0 0.1 0.2 0.3 0.4

catalyst loading/g

carb

on y

ield

/%

(a)

(b)

(c)

Fig. 3 Effect of catalyst loading on ethanol APP at 250 �C. a Ethanol

conversion and H2 molar yield: (filled diamond) H2 molar yield; (opensquare) ethanol conversion. b Major product yields: (filled diamond)

ethyl ether; (open square) ethyl acetate; (filled triangle) acetic acid;

(open triangle) CO2; (filled square) CH4; (open diamond) C2H6.

c Minor product yields: (filled diamond) acetaldehyde; (open square)

methanol; (filled triangle) butanol; (open triangle) acetal; (filledsquare) C3H8; (open diamond) CO

144 Top Catal (2012) 55:140–147

123

are shown in Table 4. The acetaldehyde was performed at

250 �C for 4 h with a 10 wt% acetaldehyde initial con-

centration and 0.1 g of catalyst. The shorted reaction time

was used as acetaldehyde was nearly completely consumed

within 4 h demonstrating its much higher reactivity than

ethanol over the Pt–Re/C catalyst. The main products were

very similar with those from ethanol: H2, CO2, CH4, C2H6,

acetaldehyde, ethyl ether, ethyl acetate, and acetic acid.

The abundance of acetic acid suggested that it was directly

formed from acetaldehyde. Shabaker et al. [16] reported

that acetic acid was produced from ethanol. The current

results were consistent with this report and further dem-

onstrated that acetaldehyde was a highly reactive inter-

mediate between ethanol and acetic acid.

As formic acid was even more reactive than acetalde-

hyde, the formic acid APP reaction was only run for 3 h at

250 �C with a 10 wt% of initial concentration and 0.1 g of

catalyst. Even for this shorted period, the formic acid was

almost completely consumed. A large amount of H2 and

CO2 was produced, but very little CH4 was observed. A

number of reports have stated that alkanes (especially CH4)

can be formed from the gas phase reaction of H2 and CO/

CO2 via methanation and Fischer–Tropsch reactions as the

reaction of H2 with CO/CO2 to form alkanes is highly

favorable at low temperature. The equilibrium constant at

500 K for the conversion of CO2 and H2 to methane is of

the order of 1010 per mole of CO2 [10, 26–28]. However,

the current work suggested that neither methanation nor

Fischer–Tropsch reactions involving CO/CO2 and H2

appeared to be important reactions over Pt–Re/C under the

conditions in this study.

In contrast to the reactivity of acetaldehyde and formic

acid, acetic acid was fairly nonreactive at the APP

(a)

(b)

(c)

Fig. 4 Effect of ethanol concentration on ethanol APP at 250 �C.

a Ethanol conversion and H2 molar yield: (filled diamond) H2 molar

yield; (open square) ethanol conversion. b Major product yields:

(filled diamond) ethyl ether; (open square) ethyl acetate; (filledtriangle) acetic acid; (open triangle) CO2; (filled square) CH4; (opendiamond) C2H6. c Minor product yields: (filled diamond) acetalde-

hyde; (open square) methanol; (filled triangle) butanol; (opentriangle) acetal; (filled square) C3H8; (open diamond) CO

Table 4 Product distributions (carbon mol%) resulting from the APP

of acetaldehyde, acetic acid and formic acid

Product Acetaldehyde Acetic acid Formic acid

H2a 10.8 5.7 79

CO 0.4 – 2.6

CO2 5.4 1.35 20.9

CH4 7.2 2 0.17

C2H6 0.2 0.04 0.03

C3H8 8.9 0.004 0.02

Ethanol 13.7 – –

Ethyl ether 0.5 – –

Ethyl acetate 0.3 – –

Acetic acid 17.0 – –

Butanol 0.5 – –

Acetal 0.2 – –

Conversion 99.8 2.4 99.3

C-balance 54.5 101 24.5

a The molar yield of H2 is calculated as the number of the moles of

H2 divided by the initial number of the moles of ethanol loaded into

the reactor

Top Catal (2012) 55:140–147 145

123

conditions of 250 �C for 5 h with 10 wt% of initial con-

centration and 0.1 g of catalyst. Only a small amount of H2,

CO2, and CH4 were produced and the conversion of acetic

acid was less than 3 % even after 5 h of reaction time. As

such, acetic acid was very stable at 250 �C in the presence

of the Pt–Re/C catalyst.

Based on the experiments performed in this work and

prior APP results from the literature [10, 16], a possible

reaction pathway that can be proposed for this reaction

system is shown in Fig. 5. Using the reaction data obtained

at 250 �C, 25 wt% initial ethanol concentration and 0.2 g

of catalyst, the stoichiometry predicted by the reaction

pathway was compared with the experimental results. The

moles of carbon contained in all of the reaction products,

including the end products (ethyl acetate, ethyl ether, CO,

CH4, C2H6) and the intermediate products (acetic acid,

acetaldehyde, CO2), were used in conjunction with the

reaction stoichiometry from the network in Fig. 5 to cal-

culate the number of ethanol moles consumed and the H2

molar yield. These calculated values of the ethanol moles

consumed and the molar yield H2 were 77.4 and

58.8 mmol, respectively, which was very close to the

experiment values (ethanol consumed: 78.1 mmol and H2

yield: 60.1 mmol). The close agreement between these

values demonstrated that the proposed reaction network

was a reasonable representation of the reaction system. The

model could then be used to evaluate the relative rates of

carbon flux (v1–v8) through the reaction network as shown

in Table 5.

3.7 Discussion

Several key points can be determined from comparing the

relative rates obtained from the flux analysis. First, the

activity for dehydrogenation/oxidation (v1, v6) was much

higher than activities for C–C cleavage (v2), dehydration/

hydrogenation (v3, v7), water–gas shift (v8) or other types

of reactions (v4, v5). The model could also be used in

conjunction with the parametric studies presented earlier.

In the effect of catalyst loading (Sect. 3.4), the yields of

CH4 and C2H6 were found to increase with higher catalyst

levels. From the reaction pathway analysis, CH4 and C2H6

would be expected to result from the C–O bond cleavage of

ethanol, followed by dehydration/hydrogenation, which

would suggest that the catalyst loading might have a

stronger influence on the dehydration/hydrogenation reac-

tion pathway. From the reactant concentration results (Sect.

3.5), ethanol conversion and H2 yield decreased with the

increase of ethanol concentration. While the yields of CH4,

CO2, CO and methanol also decreased, the yields of most

of the liquid products did not appear to be significantly

affected by the ethanol concentration ethanol. The amount

of ethanol present tended to impact the dehydrogenation,

C–C cleavage and dehydration/hydrogenation reaction

pathways, but did not seem to affect the other types of

reactions in the network.

4 Conclusion

Under the standard APP reaction conditions used in the

study, acetaldehyde and formic acid are rapidly converted

over the Pt–Re/C catalyst. While ethanol was also reactive,

it was less reactive. In contrast, acetic acid was quite stable

under the reaction conditions, so it was effectively a ter-

minal molecule. The conversion of ethanol led to H2, CO2,

CH4, C2H6, acetaldehyde, ethyl ether, ethyl acetate, acetic

acid as the primary products and C3H8, methanol, butanol

and acetal as minor products. A reaction network model

was generated for the APP of ethanol and fluxes through

the network calculated. From this work, it was determined

that the ethanol dehydrogenation was the most active

reaction for ethanol conversion. The amount of catalyst

present in the reaction system appeared to affect the

dehydration/hydrogenation reaction within the network,

whereas the initial concentration has stronger effect on the

Fig. 5 The reaction pathway for APP of ethanol over Pt–Re/C

Table 5 Relative rates of the carbon flux for each step in the ethanol

APP network

Relative rate Reaction mmol/h

v1 CH3CH2OH ? CH3CHO ? H2 17.1

v2 CH3CH2OH ? 3H2O ? 2CO2 ? 6H2 0.82

v3 C2H6O ? H2 � C2H6 ? H2O 0.82

v4 2CH3CH2OH ? C2H5OC2H5 ? H2O 2.3

v5 CH3COOH ? CH3CH2OH �

CH3COOCH2CH3 ? H2O

1.12

v6 CH3CHO ? H2O ? CH3COOH ? H2 5.98

v7 C2H6O ? 2H2 � 2CH4 ? H2O 2.66

v8 CO2 ? H2 � CO ? H2O 0.14

146 Top Catal (2012) 55:140–147

123

dehydrogenation, C–C cleavage and dehydration/hydro-

genation reaction cascade within the network. Under the

conditions explored in the study, the reaction of H2 and

CO/CO2 via methanation or Fischer–Tropsch reactions was

not active. With the knowledge gained on the reaction

network and fluxes related to ethanol APP, it will now be

possible to explore bio-oil molecules possessing higher

levels of functionality to determine the efficacy of utilizing

the APP reaction to upgrade the water soluble portion of

biomass-derived bio-oil.

Acknowledgments We acknowledge the financial support from

Department of Energy through the National Advanced Biofuels

Consortium (NABC).

References

1. Tushar PV, Huber GW (2009) Green Chem 11:1433

2. Wright MM, Brown RC (2007) Biofuel Bioprod Bior 1:49

3. Mohan D, Pittman CU, Steele PH (2006) Energy Fuel 20:848

4. Milne TA, Agblevor F, Davis M, Deutch S, Johnson D (1997) In:

Bridgwater AV, Boocock DGB (eds) Developments in thermo-

chemical biomass conversion. Blackie Academic and Profes-

sional, London

5. Cortright RD, Davda RR, Dumesic JA (2002) Nature 418:964

6. Huber GW, Cortright RD, Dumesic JA (2004) Angew Chem Int

Ed 43:1549

7. Shabaker JW, Davda RR, Huber GW, Cortright RD, Dumesic JA

(2003) J Catal 215:344

8. Davda RR, Dumesic JA (2003) Angew Chem Int Ed 42:4068

9. Davda RR, Dumesic JA (2004) Chem Commun 36

10. Davda RR, Shabaker JW, Huber GW, Cortright RD, Dumesic JA

(2005) Appl Catal B Environ 56:171

11. Huber GW, Dumesic JA (2006) Catal Today 111:119

12. Huber GW, Shabaker JW, Evans ST, Dumesic JA (2006) Appl

Catal B Environ 62:226

13. Luo N, Fu X, Cao F, Xiao T, Edwards PP (2008) Fuel 87:3483

14. Tang Z, Monroe J, Dong J, Nenoff T, Weinkauf D (2009) Ind Eng

Chem Res 48:2728

15. Davda RR, Shabaker JW, Huber GW, Cortright RD, Dumesic JA

(2003) Appl Catal B Environ 43:13

16. Shabaker JW, Huber GW, Davda RR, Cortright RD, Dumesic JA

(2003) Catal Lett 88:1

17. Cruz IO, Ribeiro NFP, Aranda DAG, Souza MMVM (2008)

Catal Commun 9:2606

18. Valenzuela MB, Jones CW, Agrawal PK (2006) Energy Fuel

20:1744

19. Sinfelt JH, Yates DJC (1967) J Catal 8:82

20. Somorjai GA (1994) Introduction to surface chemistry and

catalysis. Wiley, New York

21. Simonetti DA, Kunkes EL, Dumesic JA (2007) J Catal 247:298

22. Soares RR, Simonetti DA, Dumesic JA (2006) Angew Chem Int

Ed 45:3982

23. Kunkes EL, Simonetti DA, Dumesic JA, Pyrz WD, Murillo LE,

Chen JG, Buttrey DJ (2008) J Catal 260:164

24. King DL, Zhang L, Xia G, Karim AM, Heldebrant DJ, Wang X,

Peterson T, Wang Y (2010) Appl Catal B Environ 99:206

25. Kunkes EL, Simonetti DA, West RM, Serrano-Ruiz JC, Gartner

CA, Dumesic JA (2008) Science 322:417

26. Iglesia E, Soled SL, Fiato RA (1992) J Catal 137:212

27. Kellner CS, Bell AT (1981) J Catal 70:418

28. Vannice MA (1977) J Catal 50:228

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