Two-step continuous upgrading of sawdust pyrolysis oil to deoxygenated hydrocarbons using hydrotreating and hydrodeoxygenating catalysts

Accepted Manuscript Title: Two-step continuous upgrading of sawdust pyrolysis oil to deoxygenated hydrocarbons using hydrotreating and hydrodeoxygenating catalysts Authors: Gayoung Kim, Jangwoo Seo, Jae-Wook Choi, Jungho Jae, Jeong-Myeong Ha, Dong Jin Suh, Kwan-Young Lee, Jong-Ki Jeon, Jae-Kon Kim PII: DOI: Reference:

S0920-5861(17)30634-X http://dx.doi.org/10.1016/j.cattod.2017.09.027 CATTOD 11032

To appear in:

Catalysis Today

Received date: Revised date: Accepted date:

31-5-2017 26-8-2017 15-9-2017

Please cite this article as: Gayoung Kim, Jangwoo Seo, Jae-Wook Choi, Jungho Jae, Jeong-Myeong Ha, Dong Jin Suh, Kwan-Young Lee, Jong-Ki Jeon, Jae-Kon Kim, Two-step continuous upgrading of sawdust pyrolysis oil to deoxygenated hydrocarbons using hydrotreating and hydrodeoxygenating catalysts, Catalysis Todayhttp://dx.doi.org/10.1016/j.cattod.2017.09.027 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Two-step continuous upgrading of sawdust pyrolysis oil to deoxygenated hydrocarbons using hydrotreating and hydrodeoxygenating catalysts

Gayoung Kima,b, Jangwoo Seoa,c, Jae-Wook Choia, Jungho Jaea, Jeong-Myeong Ha*,a,c,d, Dong Jin Suh*,a,d, Kwan-Young Leea,b,d, Jong-Ki Jeone, Jae-Kon Kimf

a

Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 02792,

Republic of Korea b

Department of Chemical and Biological Engineering, Korea University, Seoul 02841, Republic

of Korea c

Division of Energy & Environment Technology, KIST School, Korea University of Science and

Technology, Seoul 02792, Republic of Korea d

Green School (Graduate School of Energy and Environment), Korea University, Seoul 02841,

Republic of Korea e

Department of Chemical Engineering, Kongju National University, Chenan , Republic of Korea

f

Research Institute of Petroleum Technology, Korea Petroleum Quality & Distribution Authority,

Chungcheongbuk-do 28115, Republic of Korea

*Corresponding authors at: Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea. E-mail address: [email protected] (J.-M. Ha), [email protected] (D. J. Suh)

1

Graphical abstarct

Highlights 

Two-step upgrading using Pd/C then Ru/W-ZrO2 was performed.



Hydrotreating catalysts hydrogenate aldehyde and saturate furans.



The removal of aldehydes and furans suppresses the coking on the Ru catalsysts.

Abstract The two-step hydrodeoxygenation of pine sawdust pyrolysis oil, or bio-oil, is performed using pairs of first-step hydrotreating and second-step hydrodeoxygenating catalysts. The reaction results demonstrate that the combination of hydrotreating carbon-supported 5 wt% Pd (5 wt% Pd/C) and hydrodeoxygenating tungstate-zirconia-supported 3 wt% Ru (3 wt% Ru/WZr) catalysts produced the highest yield of oil products and the lowest yield of cokes and tars. The 2

hydrodeoxygenated liquid products are further analyzed using FT-IR, which indicates the removal of carbonyls and hydroxyls along with an increase of methyls. The roles of hydrotreating Pd/C are further studied using GC/MS results of the hydrotreated liquid products; these results indicate that the hydrogenation of carbonyls to alcohols and the saturation of furans occur during the first step of the hydrotreating process. The removal of carbonyls and unsaturated furans may suppress their strong adsorption to noble metal surfaces and then their carbonization to cokes.

Keywords: hydrotreating; hydrodeoxygenation; ruthenium; tungstate-zirconia; palladium.

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1. Introduction

The pyrolysis of biomass has been interesting because it can fully convert all parts of biomass into useful feedstocks, including gas, liquids, and solids [1-6]. Although solid and gas products can be used in numerous applications [7-9], the liquid products, or bio-oils, can be converted into transportation and heating fuels, replacing or co-combusting with currently used petroleum fuels [3,10]. The use of bio-oil in current petroleum-using applications is attractive, but the direct use of bio-oil for such applications is frequently limited because of its low heating values, high acidity, and high viscosity, all of which are attributable to its high oxygen content [1,11,12]. The upgrading of bio-oil to deoxygenated liquid fuels via hydrodeoxygenation [13-18], decarboxylation [19], and ketonization [20] has been attempted. Among these processes, the hydrodeoxygenation of bio-oil is promising because it can fully remove oxygen functionalities and minimize the loss of carbon atoms [11,21]. Numerous catalysts have been suggested for the hydrodeoxygenation of bio-oil and its model compounds. Noble metals including Pt, Pd, Ru, and Rh are frequently used to hydrodeoxygenate catalysts [13-15,22-24]. Transition metals Ni and Fe are also used to reduce the costs of catalysts [25,26]. Metal phosphides have been developed to achieve good deoxygenation activity [27,28]. Metal sulfides including Mo sulfides, Ni-Mo sulfides, and Co-Mo sulfides, although they require a continuous supply of additional sulfur compounds to suppress the formation of inactive Mo oxides, exhibit good deoxygenation activity [29,30]. Among these catalysts, we have focused on noble metal catalysts given their strong hydrogenation ability and sulfur-free reaction conditions [13-15,22-24].

4

In practical bench-, pilot-, or industry-scale processes, the continuously stable operation of reaction systems is critical to determine the feasibility of the chemical processes. Significant deactivation of catalysts must be suppressed for long-term stability of these processes. Along with developing deactivation-resistant catalysts, pretreating crude bio-oil has been suggested for the stable operation of ensuing hydrodeoxygenation processes [31,32]. Among the potential pretreatment

methods

at

present,

the

in-situ

stabilization

of

bio-oil

before

the

hydrodeoxygenation step has been suggested for continuous flow reaction systems, though multistep processes have also been attempted [32,33]. After several years of efforts to develop stable upgrading processes, feasible reaction systems are still under investigation and more efforts will be required to understand hydrodeoxygenation systems and the deactivation of catalysts. A lowtemperature hydrotreating step has been found to be successful in converting aldehydes, ketones, and sugars to their corresponding alcohols [34-36].

In this study, the catalytic hydrodeoxygenation of bio-oil prepared by the fast pyrolysis of pine sawdust is performed by means of two-step hydrodeoxygenation. A tungstate-zirconia-supported Ru (Ru/WZr) catalyst is selected for hydrodeoxygenation (HDO) process based on our previous works [18,37]. Although HDO using Ru/WZr was successful, the lightly colored upgraded oil was easily degraded, becoming a brown solution which indicated incomplete deoxygenation (Fig. S1). For better deoxygenation and less formation of coke, a low-temperature hydrotreating (HYT) at ~150 °C followed by high-temperature hydrodeoxygenation (HDO) at ~350 °C is used in sequence to suppress plugging in the continuous flow reaction system. Based on the reaction results, the roles of the HYT catalysts are investigated, as is the quality of the reaction products.

5

Optimum pairs of HYT and HDO catalysts are selected based on the yields of the hydrodeoxygenated products and cokes.

2. Experimental

2.1. Materials

Carbon-supported 5 wt% Pd (5 wt% Pd/C), carbon-supported 5 wt% Pt (5wt% Pt/C), carbonsupported 5 wt% Ru (5 wt% Ru/C), alumina-supported 5 wt% Ru (5 wt% Ru/Al2O3), ruthenium chloride hydrate (RuCl3xH2O, 99.99 wt%), nickel(II) nitrate hexahydrate (Ni(NO3)2·6H2O, 99.999 wt%), titanium(IV) oxide (TiO2 , 99.5 wt%), activated carbon (Darco, 60 - 100 mesh), zirconium(IV) hydroxide (Zr(OH)4, 97 wt%) and ammonium metatungstate hydrate ((NH4)6H2W12O40·xH2O, 99.99 wt%) were purchased from Aldrich (Milwaukee, Wisconsin, USA). Cobalt(II) nitrate hexahydrate (Co(NO3)2 ·6H2O, 97.0 wt%) and diethyl ether (99 wt%) were purchased from Junsei (Tokyo, Japan). Ethyl acetate (99 wt%) was purchased from Daejung (Seoul, Korea). Deuterated dimethyl sulfoxide (DMSO, 99.9%) was purchased from Cambridge Isotope Laboratories (Tewksbury, MA, USA).

2.2. Catalyst preparation

The hydrothermal impregnation method was used to prepare the tungstate-zirconia (WZr) support. Ammonium metatungstate hydrate (0.5 g) and zirconium hydroxide (4 g) were dissolved in DI water (50 mL) and stirred for 3 h under ambient conditions. The slurry mixture was loaded 6

into an autoclave and heated to 180 °C for 12 h. Using a rotary evaporator, the resulting mixture was dried at 70 °C; it was then calcined at 800 °C for 2 h. 20 wt% Ni/C, 20 wt% Co/C, 5 wt% Ru/TiO2 and Ru/WZr were prepared by an impregnation method using the corresponding precursors. An aqueous mixture of a metal precursor and a support was stirred for 12 h under ambient conditions. Using a rotary evaporator, the mixture was dried at 70 °C and then dried at 105 °C under a vacuum. Prior to the reaction, the prepared catalysts were reduced for 2 h at 350 °C (for Co and Ru) or 550 °C (for Ni) using H2/Ar (5% v/v). The reduced catalysts were passivated for 30 min using O2/N2 (5% v/v).

2.3. Upgrading of ether-extracted bio-oil

Crude bio-oil obtained by the pyrolysis of pine sawdust was supplied by Daekyung Esco Co., Ltd. (Incheon, Korea). The crude bio-oil was extracted using diethyl ether to remove tiny biochar particles that nucleate the formation of cokes. The crude bio-oil was then mixed with diethyl ether at a ratio of 2:1 (v/v) to form a biphasic mixture composed of an upper-layer ether phase and a lower-layer aqueous phase. Using a rotary evaporator, the upper layer was carefully collected and dried to obtain the ether-extracted bio-oil. After the ether extraction step, using a continuous-flow fixed-bed reaction system, the bio-oil was hydrodeoxygenated via the addition of hydrogen gas (Figs. S2 and S3). The fixed-bed reactor was made of stainless steel 316. The hydrogen gas flow was controlled using a mass flow controller (MFC). When the two-step reaction was performed, the hydrotreating catalyst powder in the first step was charged using a catalyst basket (inner diameter = 14 mm). The temperature of the first-step catalyst bed was maintained in a range of 100 – 190 °C, and the furnace temperature was fixed at 115 °C. The 7

hydrodeoxygenating catalyst was charged in the second-step catalyst basket (inner diameter = 18 mm). The temperature of the second-step catalyst bed was maintained in a range of 300 – 390 °C while the furnace temperature was fixed at 440 °C. After the reaction, the upgraded bio-oil was cooled using a chiller and the liquid products were collected. Using back-pressure regulators, the pressure of the reaction system was fixed at 100 bar. Prior to the reaction, the catalysts were reduced at 350 °C for 2 h using a pure hydrogen flow at 1 bar. After the reaction, the coke and solid residue which formed in the catalyst beds were weighed. Yields of liquid product, oil, and solid residue were calculated based on the following equations: Yield of liquid product (g/g feed) = (Mass of liquid product)/(Mass of bio-oil entering to the reactors) Yield of oil (g/g feed) = (Mass of oil product in the oil phase)/(Mass of bio-oil entering to the reactors) Yield of soild residue (g/g feed) = [(Mass of catalyst bed after the reaction) – (Mass of catalyst bed before the reaction)]/(Mass of bio-oil entering to the reactors)

2.4. Characterization of reactants and products

The bio-oil reactants and the hydrodeoxygenated products were dissolved in ethyl acetate and identified using an Agilent 7890A/5975C inert MS XLD gas chromatograph-mass spectrometer combined (GC/MS) with an HP-5MS capillary column (60 m×0.25 mm×250 μm). The moisture in the oil was quantified using a Karl Fischer Moisture Titrator (model MKV-710) with HYDRANAL-Composite 5 and a solvent mixture of methanol (75 vol%) and chloroform (25 vol%). Elemental analyses of the reactants and products performed at the K-Petro Advanced 8

Analysis Center (Korea Petroleum Quality & Distribution Authority, Cheongju, Korea) using a Flash 2000 series CHNS organic elemental analyzer (Thermo Scientific, USA) while oxygen contents were measured using a Fisons Instruments EA 1108 element analyzer (Thermo Scientific, USA). Fourier-transform infrared spectroscopy (FTIR) of the bio-oil reactants and hydrodeoxygenated products was performed using a Nicolet IS 10 spectrometer (Thermo Scientific, USA) with the Smart Miracle accessory. 1H-NMR of the bio-oil reactants and upgraded liquid products (0.15 g/L) dissolved in deuterated dimethyl sulfoxide was performed using a 600 MHz Agilent spectrometer at the KIST Advanced Characterization Center (Seoul, Korea). The Dulong equation was used to calculate the higher heating values (HHVs) of the oils [38]: HHV (MJ/kg) = 33.742 × [C] + 143.905 × ([H] × [O]/8) + 9.396 × [S], where [C], [H], [O], and [S] are the mass fractions as determined through an elemental analysis.

2.5. Characterization of catalysts

CO-chemisorption measurements was performed using a pulsed injection of 10% CO/He with a BELCAT-M catalyst analyzer (BEL Japan, Osaka, Japan) equipped with a thermal conductivity detector (TCD). NH3-temperature-programmed desorption (NH3-TPD) analyses were performed using a BELCAT-B catalyst analyzer (BEL Japan, Osaka, Japan) equipped with a thermal conductivity detector (TCD). N2-physisorption was performed using a Micromeritics ASAP 2020.

3. Results and discussion

3.1. Incomplete deoxygenation of bio-oil using one-step upgrading process 9

Based on our previous works [18,37], tungstate-zirconia-supported Ru (Ru/WZr) was selected for the hydrodeoxygenation (HDO) of the sawdust bio-oil. Although the deoxygenation of bio-oil has successfully been demonstrated at 310 - 390 °C [18] with almost complete deoxygenation, achieving a ratio of O/C = 0.01 (atom/atom) from the ratio of O/C = 0.42 (atom/atom) of the biooil reactant which was extracted with diethyl ether to remove tiny biochar particles, incomplete deoxygenation was frequently observed, as evidenced by the degradation of the HDO products, which changed from colorless to brown (Fig. S1). The change of color indicates that the HDO products contain functionalities of oxygenates or unsaturated carbon bonds. Oligomerization may occur because of these functionalities and reduce the quality of the liquid fuels [22,39]. The FT-IR results of the one-step upgraded bio-oil, however, did not show hydroxyl or carbonyl functionalities (Fig. S1), suggesting that a tiny amount of oxygen functionality remained after the one-step upgrading using Ru/WZr. The pretreatment of bio-oil may improve the efficiency of the hydrodeoxygenation process. The hydrotreating (HYT) step was used for the pretreatment of biooil to reduce the burden during the HDO step, facilitate the operation of the continuous flow reaction, and improve the quality of the liquid fuel products. As a combination of HYT and HDO was used in this study, multiple reaction steps are frequently used in chemical reaction processes to produce the desired products selectively and to maintain mild reaction conditions, thus avoiding significantly exothermic reactions [33,40].

3.2. Screening combination of hydrotreating and hydrodeoxygenation catalysts

10

In order to remove the functionalities containing oxygen atoms and unsaturated bonds completely, the hydrotreating (HYT) step was performed before the hydrodeoxygenation (HDO) step. These reaction results are listed in Tables 1 and 2. In the reactor, the volumes of the HYT and HDO catalyst beds were fixed at 5 and 10 mL, respectively, and the thickness of the HYT and HDO catalyst beds were correspondingly fixed at 3.2 and 3.9 cm. Because thick catalyst beds were used for the typical lab-scale differential reactors instead of thin catalyst beds, the temperatures of the first- and second-step catalyst beds ranged from 110 to 190 °C and 310 to 390 °C along the thickness of the beds, respectively; these values were determined by the catalyst-dependent reaction behavior. The continuous-flow reaction using WZr as a catalyst without the supported metals at 310 - 390 °C did not proceed because of the plugging of the reactor caused by the significant coking.

(Table 1)

Among the pairs of catalysts, large yields of liquid products and oils were observed when using 5 wt% Pd/C (HYT) then 5 wt% Pd/C (HDO), 5 wt% Ru/C (HYT) then 5 wt% Pd/C (HDO), 5 wt% Pd/C (HYT) then 3 wt% Ru/WZr (HDO), 5 wt% Pd/C (HYT) then 5 wt% Pt/C (HDO), and 5 wt% Pd/C (HYT) then 20 wt% Ni/C, which exhibited liquid yields larger than 0.6 g/g and oil yields larger than 0.4 g/g. Although the pairs which exhibited larger yields of liquid products, significant coking was also observed, which suppressed the continuous operation by plugging the catalyst beds. The formation of cokes and tars was observed for both the HYT and HDO beds. In this study, the lowest amount of coking was observed for the pair of 5 wt% Pd/C (HYT) and 3 wt% Ru/WZr (HDO). The elemental analysis indicates that the pair of 5 wt% Pd/C and 3 wt% 11

Ru/WZr produced the lowest oxygen content of 0.7 wt%, exhibiting a ratio of O/C = 0.01 (atom/atom); the calculated HHV was 46.5 MJ/kg (Table 2). Other pairs of HYT catalysts and 3 wt% Ru/WZr exhibited the high deoxygenation activity although they exhibited the higher yields of solid residue on the spent catalyst beds. When Ru/WZr was not used for the HDO step, the worse deoxygenation activity was observed. The liquid products obtained using poor catalysts turned brown, indicating incomplete deoxygenation (Table S1). The formation of cokes and tars causes the loss of carbon atoms and the formation of water by the significant dehydration of reactant to carbons and oligomers during the reaction. Smaller yields of liquid and oil phase products are observed when the yields of cokes and tars are larger. Only aqueous-phase products were produced when 5 wt% Pd/C then 5 wt% Ru/C, 5 wt% Pd/C then 5 wt% Ru/TiO2 and 5 wt% PdC then 5 wt% Ru/Al2O3 were used. Because the carbon contents in the aqueous-phase products existed at less than 1 wt% for both the biphasic and aqueous-phase-only products, we did not analyze the aqueous products.

(Table 2)

FT-IR measurements of the reactants and products were taken to understand the results of the two-step reaction (Fig. 1). The strong peaks of hydroxyl (–OH, ~3400 cm-1) and carbonyl (-C=O, ~1700 cm-1) functionalities were observed for the ether-extracted bio-oil reactants [41]. The FTIR spectra of the representative phenolic compounds are similar to the FT-IR spectrum of the bio-oil reactant (Fig. S4). The observed hydroxyl groups indicate the existence of phenolic compounds, alcohols, and carboxylic acids, which are frequently observed in biomass-derived pyrolysis oils. Weak peaks of methyl (-C-H, 2800 – 3000, ~1450 and ~1370 cm-1) bonds were 12

also observed, indicating the formation of organic compounds. Complex multi-peak outcomes were observed in a range lower than ~1550 cm-1; these were similar to the peaks observed for guaiacol and 2-methyl furan, indicating the complex nature of bio-oil. A significant change in the FT-IR results was observed for the hydrodeoxygenated liquid products. The peaks of –OH and – C=O became negligible or weaker and those of –C-H became stronger. When 5 wt% Pd/C then 3 wt% Ru/WZr and 20 wt% Ni/C and then 3 wt% Ru/WZr were used, nearly complete removal of –OH and –C=O peaks was observed, indicating complete deoxygenation. The triplets of –C-H of the hydrodeoxygenated oil at 2800 – 3000 cm-1 were identical to those of cyclohexane; this indicated the formation of saturated cycloalkanes in the hydrodeoxygenated liquid products. The complex peaks in the range lower than ~1550 cm-1 almost disappear for the completely deoxygenated products, except for the peaks of –C-H at ~1450 and ~1370 cm-1 (Figs. 1 and S4), indicating the complete removal of phenolic and other oxygen functionalities. From the above observations, the FT-IR spectra of hydrodeoxygenated products, in general, can be said to have become simple compared to those of the bio-oil reactants. The removal of complex functionalities, aromaticity, and unsaturated carbon bonds is clearly demonstrated.

(Fig. 1)

When the peaks of the bio-oil reactant were compared to those of the deoxygenated products, we note that a weak shoulder at 3030 - 2960 cm-1 exists for the bio-oil reactant and the incompletely deoxygenated products (Figs. 1 and S4). These must be the peaks of aromatic -C-H, which are commonly observed for aromatic or phenolic model compounds.

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1

H-NMR measurements of the ether-extracted bio-oil and upgraded bio-oil using 5 wt% Pd/C

then 3 wt% Ru/WZr confirmed complete deoxygenation (Figs. 2, S5, and Table S2) [42]. The carboxylic and aldehyde Hs (8 - 11 ppm) were almost completely removed after the HYT step confirming the removal of carboxylic and aldehyde groups improved the HDO activity of the second step. The alkoxy Hs (3 - 4.2 ppm) were completely removed after the two-step upgrading process. The aromatic, furanyl, and alkenyl Hs were not completely removed, as small remaining amounts of aromatic and alkenyl Hs were noted.

(Fig. 2)

The surface areas and the metal nanoparticle dispersions of the catalysts were measured (Table 3). The best hydrotreating catalyst in this study, Pd/C, exhibited the largest [CO]/[Metal] (mol/mol) ratio, which may indicate that the hydrotreating activity depends on the quantity of surface-metal active sites: however, based on the characterization results of other catalysts, this trend is not clear. When Pd/C was used as the hydrotreating catalyst, Ru/WZr exhibited the largest yields of liquid and oil products (Table 1), but the surface area and the Ru dispersion were not greater than those obtained using the other HDO catalysts. These observations confirm that the HDO activity is dependent on the acidity of the catalysts, as discussed for the Ru and WZr catalysts in our previous works [24,37].

(Table 3)

3.3. Roles of hydrotreating catalysts 14

It appears that the addition of the HYT step before the HDO step improved the reaction performance; the roles of the HYT step were observed via GC/MS measurements of the liquid products obtained after the HYT step using 5 wt% Pd/C (Fig. 3). Ketones and unsaturated furans were observed for the bio-oil reactant. The HYT products, however, did not contain these ketones of unsaturated furans but instead contained ethers and alcohols, indicating that the HYT step hydrogenated the –C=O functionalities and unsaturated furans [34-36]. In our previous study, the existence of carbonyls and unsaturated furans was attributed to the formation of cokes on the noble metal catalyst surface [14]. The strong adsorption of furans containing carbonyls and aldehydes on the noble metal surface poisoned the surfaces of the Ru particles supported on tungstate-zirconia. The strongly adsorbed compounds appear to be converted to cokes and tars during the reaction, which must have deactivated the catalysts, leading to the poor deoxygenation performance. The upgraded liquid products after the HDO step did not contain alcohols, ethers, ketones, or furans indicating complete deoxygenation.

(Fig. 3)

4. Conclusion

In this study, the optimum pair of hydrotreating Pd/C and hydrodeoxygenating Ru/WZr is observed to produce completely deoxygenated products with the least formation of cokes and tars. The reaction results and the FT-IR spectra indicate that the hydrotreating Pd/C hydrogenates the carbonyl functionalities, including aldehydes, to alcohols and unsaturated carbon bonds. The 15

removal of carbonyls and unsaturated carbon bonds may suppress the poisoning of the noble metal surface and maintain the catalytic hydrodeoxygenation activity, as was suggested in our previous report [14].

Acknowledgement This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of Republic of Korea (No. 20163010092210). The authors thank Daekyung ESCO Co., Ltd. (Incheon, Korea) for the supply of the sawdust pyrolysis oil.

Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/

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List of Figures Fig. 1. FT-IR results of ether-extracted and upgraded bio-oil. Fig. 2. 1H-NMR results of (a) ether-extracted bio-oil and (b) upgraded bio-oil using 5 wt% Pd/C then 3 wt% Ru/WZr. The sharp peaks at 2.5 and 3.2 ppm are DMSO and water, respectively. Fig. 3. GC/MS results of bio-oil hydrotreated using 5 wt% Pd/C: (a) ether-extracted bio-oil, (b) hydrotreated bio-oil using 5 wt% Pd/C, and (c) upgraded bio-oil using 5 wt% Pd/C then 3 wt% Ru/WZr. The peak of the ethyl acetate solvent is also observed.

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Fig. 1. FT-IR results of ether-extracted and upgraded bio-oil. (a) -OH peak at 3800 - 3000 cm-1. (b) -C-H peak at 3100 - 2700 cm-1. (c) -C=O and -C-H peaks at 1900 - 1300 cm-1.

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Fig. 2. 1H-NMR results of (a) ether-extracted bio-oil and (b) upgraded bio-oil using 5 wt% Pd/C then 3 wt% Ru/WZr. The sharp peaks at 2.5 and 3.2 ppm are DMSO and water, respectively.

21

Fig. 3. GC/MS results of bio-oil hydrotreated using 5 wt% Pd/C: (a) ether-extracted bio-oil, (b) hydrotreated bio-oil using 5 wt% Pd/C, and (c) upgraded bio-oil using 5 wt% Pd/C then 3 wt% Ru/WZr. The peak of the ethyl acetate solvent is also observed.

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List of Tables Table 1. Two-step upgrading Results Table 2. Compositions of the Selected Two-step Upgrading Products Table 3. N2-physisorption and CO-chemisorption Results of Catalysts

23

Table 1. Two-step upgrading results.a Catalyst HYT

HDO

None 5 wt% Pd/C 5 wt% Pt/C 5 wt% Ru/C 20 wt% Ni/C 3 wt% Ru/WZr 5 wt% Pd/C 5 wt% Ru/C 20 wt% Ni/C 10 wt% Co/C 5 wt% Ru/TiO2

3 wt% Ru/WZrb

5 wt% Pd/C

3 wt% Ru/WZr

5 wt% Pt/C

117 - 158 115 - 160 153 - 188

336 – 385 339 – 384 310 – 364

5 wt% Ru/C

153 - 188

310 – 364

20 wt% Ni/C 10 wt% Co/C

112 - 161 110 - 167

312 – 371 349 – 370

5 wt% Ru/TiO2

117 - 167

341 – 388

5 wt% Ru/Al2O3

108 - 162

312 – 379

5 wt% Ru/Al2O3 3 wt% Ru/WZr

5 wt% Pd/C

a

Catalyst bed temperature Liquid Yield of coke and tar (°C) product yield Oil yield (g/g (g/g of feed oil) (g/g of feed of feed oil) HYT HDO HYT HDO oil) n. a. 350 - 355 0.60 0.30 n. a. 0.07 146 - 198 335 – 364 0.65 0.48 0.03 0.09 112 - 170 323 – 378 0.45 0.27 0.17 0.23 119 - 173 323 – 372 0.69 0.49 0.08 0.01 114 - 165 331 – 381 0.53 0.33 0.03 0.04 111 - 151 337 – 398 0.57 0.41 0.31 0.20 108 - 162 312 – 385 0.74 0.42 0.01 0.03 119 - 165 309 – 385 0.56 0.24 0.02 0.05 114 - 157 328 – 380 0.62 0.24 0.02 0.02 121 - 176 337 – 386 0.43 0.11 0.03 0.03 121 - 166 348 – 387 0.48 0.14 0.02 0.10 0.55 0.52 0.73 0.32 (Aqueous phase only) 0.65 0.61 0.33 (Aqueous phase only) 0.29 (Aqueous phase only)

0.24 0.14 0.44

0.04 0.12 0.02

0.06 0.03 0.03

~0

0.04

0.06

0.40 0.29

0.03 0.08

0.06 0.13

~0

0.10

0.04

~0

0.05

0.06

LHSV, (reactant flow rate)/(combined volume of HYT and HDO catalyst beds), was set to ~0.4

h-1. b

LHSV, (reactant flow rate)/(volume of HDO catalyst bed), was set to ~0.7 h-1. The feed flow

rate and the quantity of HDO catalysts are the same as those of two-step catalysis, but the HYT catalyst was removed.

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Table 2. Compositions of selected two-step upgrading products. Catalyst

O/C H/C Moisture in N S O HHV (atom/ (atom/ an oil phase (wt%) (wt%) (wt%)a (MJ/kg) atom) atom) (wt%) b 0.9 ~0 34.9 0.475 1.57 7.00 22.7 1.1 ~0b 31.7 0.42 1.53 6.2 23.8 b 0.2 ~0 0.88 0.01 1.79 0.2 46.8 1.28 ~0b 11.2 0.12 1.88 2.6 38.4 b 0.19 ~0 18.0 0.20 2.00 0.3 35.9 0.44 ~0b 10.2 0.10 1.95 3.6 41.0 0.27 ~0b 6.4 0.07 1.88 2.6 42.1 0.38 ~0b 5.0 0.09 1.92 1.6 41.1 0.07 ~0b 0.7 0.01 1.82 0.1 46.5 1.37 ~0b 2.3 0.02 1.73 0.4 45.4 0.28 ~0b 1.2 0.01 1.83 0.2 47.1 1.31 ~0b 1.3 0.01 1.88 0.3 47.2 b 1.43 ~0 1.0 0.01 1.88 0.3 47.9

C (wt%)

H (wt%)

Crude bio-oil Ether extracted bio-oil None 3 wt% Ru/WZrb 5 wt% Pd/C 5 wt% Pt/C 5 wt% Pd/C 5 wt% Ru/C 20 wt% Ni/C 3 wt% Ru/WZr 5 wt% Pd/C 5 wt% Ru/C 20 wt% Ni/C 10 wt% Co/C 3 wt% Ru/WZr 5 wt% Ru/TiO2

55.2 56.6 85.0 72.0 67.7 75.0 76.7 75.4 83.9 84.1 85.0 84.4 84.9

7.2 7.2 12.7 11.2 11.3 12.2 12.0 12.1 12.7 12.1 13.0 13.2 13.5

5 wt% Ru/Al2O3

83.9 83.8 78.0

12.6 14.0 11.7

1.38 1.26 0.08

79.3 81.9

12.4 12.4

0.54 0.32

HYT

HDO

3 wt% Ru/WZr

5 wt% Pd/C

5 wt% Pt/C 5 wt% Ru/C 20 wt% Ni/C 10 wt% Co/C 5 wt% Ru/TiO2 5 wt% Ru/Al2O3

a

Aqueous phase only

Measured using an oxygen detector.

b

~0b 1.3 0.01 1.80 b ~0 0.8 0.01 1.99 ~0b 6.9 0.07 1.80 Aqueous phase only ~0b 7.1 0.07 1.87 ~0b 5.0 0.05 1.81 Aqueous phase only

Smaller than its detection limit.

25

0.5 0.3 0.9

46.1 48.2 41.8

2.7 0.5

43.3 44.6

Table 3. N2-physisorption and CO-chemisorption results of catalysts. N2-Physisorption

CO-chemisorption

Catalyst BET surface area (m2/g) 5 wt% Pd/C 930 5 wt% Pt/C 1340 5 wt% Ru/C 656 20 wt% Ni/C 679 10 wt% Co/C 853 5 wt% Ru/TiO2 53 5 wt% Ru/Al2O3 80 3 wt% Ru/WZr 62 a Calculated by a t-plot analysis.

Micropore surface area (m2/g)a 598 847 437 497 619 10 ~0 4

26

[CO]/[Metal] (mol/mol) 0.303 0.218 0.091 0.028 0.052 0.148 0.167 0.139