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Renewable Energy xxx (2014) 1e5

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Renewable Energy

journal homepage: www.elsevier .com/locate/renene

Catalytic conversion of waste particle board and polypropylene overH-beta and HY zeolites

Hyung Won Lee a, Suek Joo Choi a, Jong-Ki Jeon b, Sung Hoon Park c, Sang-Chul Jung c,Young-Kwon Park a, d, *

a Graduate School of Energy and Environmental System Engineering, University of Seoul, Seoul 130-743, South Koreab Department of Chemical Engineering, Kongju National University, Cheonan 330-717, South Koreac Department of Environmental Engineering, Sunchon National University, Suncheon 540-950, South Koread School of Environmental Engineering, University of Seoul, Seoul 130-743, South Korea

a r t i c l e i n f o

Article history:Received 17 March 2014Accepted 22 July 2014Available online xxx

Keywords:Waste particle boardPolypropyleneCatalytic copyrolysisBio-oilH-betaHY

* Corresponding author. School of EnvironmentaSeoul, Seoul 130-743, South Korea. Tel.: þ82 2 6490 2

E-mail address: catalica@uos.ac.kr (Y.-K. Park).

http://dx.doi.org/10.1016/j.renene.2014.07.0400960-1481/© 2014 Elsevier Ltd. All rights reserved.

Please cite this article in press as: Lee HW, eRenewable Energy (2014), http://dx.doi.org/

a b s t r a c t

The catalytic copyrolysis of waste particle board (WPB) and polypropylene (PP) was investigated for thefirst time over HY (5.1), HY (30), H-Beta and Ga/H-Beta catalysts. The catalysts were characterized by BETand NH3-TPD analyses. The catalytic pyrolysis of the WPB increased the production of gas products (CO,CO2, C1eC4) compared to non-catalytic pyrolysis. Acids and levoglucosan, which are the main compo-nents of bio-oil produced from non-catalytic pyrolysis, were converted to more valuable aromatics,phenolics, and furans through dehydration, deoxygenation and aromatization. The most abundantproducts from the copyrolysis of WPB and PP were large-molecular-mass hydrocarbons (�C10). However,catalytic copyrolysis increased the yields of small-molecular-mass hydrocarbons in the gasoline range,aromatics and phenolics. The water content in bio-oil was reduced significantly by copyrolysis with PP,contributing to the improvement in oil quality. HY (5.1) with the largest number of acid sites showedhigher catalytic activity than HY (30) and H-Beta because the decomposition and reforming reactionsduring catalytic copyrolysis occurred on the acid sites of the catalysts. Ga/H-Beta showed even higherselectivity toward the aromatics than H-Beta despite the smaller quantity of acid sites, suggesting that Gapromoted the dehydrocyclization of the reaction intermediates.

© 2014 Elsevier Ltd. All rights reserved.

1. Introduction

The production of bio-fuel from biomass, which is aimed atreplacing conventional petroleum-derived fuels, has attractedconsiderable attention. Among these bio-fuels, bio-oil is producedfrom the pyrolysis of biomass [1,2]. In general, the bio-oil producedfrom biomass pyrolysis has the following characteristics: heatingvalue of 16e19MJ/kg, carbon content of 54e58%, oxygen content of35e40%, andmoisture content of 15e30%, which are quite differentfrom those of petroleum-derived fuels [3]. Bio-oil has a low heatingvalue and poor miscibility in petroleum-derived fuels of bio-oilowing to its high oxygen and moisture content [3], which stemsfrom its low carbon content (47e51 wt%) and high oxygen content(42e46 wt%) of the feedstock biomass. Therefore, pyrolyzing

l Engineering, University of780; fax: þ82 2 6490 2859.

t al., Catalytic conversion of w10.1016/j.renene.2014.07.040

biomass together with another material with a high carbon andhydrogen content can be an effective method for improving thebio-oil quality and its miscibility in petroleum-derived fuels.

Although biomass is a natural polymer, plastic materials, such aspolyethylene and polypropylene (PP) are synthetic polymerscomposed only of carbon and hydrogen. These synthetic polymerscan be used as auxiliary materials that can provide carbon andhydrogen to biomass upon copyrolysis. Copyrolysis of a variety ofdifferent biomass materials and synthetic polymers has beenexamined [4e16]. These studies reported that the interaction be-tween the biomass material and synthetic polymer affected thequality and yield of product bio-oil [4,5,17]. On the other hand, thebio-oil produced from copyrolysis consisted mostly of large-molecular-mass species, resulting in relatively low oil quality.Therefore, the oil quality needs to be improved by additionalupgrading processes, such as catalytic cracking.

Although the catalytic pyrolysis of biomass and the catalyticpyrolysis of plastic materials have been carried out, there are fewreports of the catalytic copyrolysis of a mixture of biomass and

aste particle board and polypropylene over H-beta and HY zeolites,

Fig. 1. Gas, oil and char yields obtained from the pyrolysis of WPB.

H.W. Lee et al. / Renewable Energy xxx (2014) 1e52

plastic materials. Liu et al. [18] reported the copyrolysis of pubes-cens and LDPE over catalysts based on a mesoporous material, Al-MCM-41. Nevertheless, there are no reports of the catalytic copy-rolysis over HY and H-Beta, which are microporous zeolite mate-rials. The copyrolysis of biomass and plastic materials is importantin terms of the waste fuel quality improvement because they arethe main components of municipal solid waste.

The catalytic copyrolysis of waste particle board (WPB), arepresentative waste wood material contained in municipal solidwaste, and PP, a model compound of waste plastic, was carried outin this study. HY, H-Beta, and Ga/H-Beta were used as the catalysts.The pyrolysis of WPB only over HY, H-Beta, and Ga/H-Beta was alsoperformed for comparison. The goal of this study was to obtainupgraded bio-oil with low moisture content and high contents ofhydrocarbon and mono-aromatics using catalytic co pyrolysis.

2. Materials and methods

2.1. Biomass and plastic samples

Proximate analysis and ultimate analysis of WPB and PP wereperformed using the method reported in Ref. [19]. Table S1 (Sup-plementary Information) lists the characteristics of WPB and PP.WPB was composed of moisture (2.6 wt%), volatiles (79.4 wt%),fixed carbon (15.9 wt%), and ash (2.1 wt%). PP exhibited a compo-sition of volatiles (99.8 wt%) and ash (0.2 wt%). From elementalanalysis, WPB showed the following: C: 44.42 wt%, H: 5.14 wt%, O:48.85 wt%, and N: 1.29 wt%, whereas PP contained only C: 85.4 wt%and H:14.6 wt%.

2.2. Synthesis and characterization of catalyst

Commercial zeolites, H-Beta, HY (5.1) and HY (30), were pur-chased from Zeolyst. Ga/H-Beta was synthesized by impregnating1wt% Ga onto H-Beta using Ga(NO3)3 as the precursor. The catalystswere characterized using BET and temperature programmeddesorption of NH3 (NH3-TPD). The detailed procedures of theseanalysis methods are described in Ref. [19].

2.3. Catalytic pyrolysis using a fixed bed reactor

A U-type quartz reactor, whose inlet/outlet diameter, height,and volume were 1.5 cm, 16 cm, and 50 cc, respectively, was used.The reactorwas purgedwith N2 gas with a flow rate of 50 cc/min for30 min prior to each experiment to create O2-free conditions. Twocondensers connected in series were used to collect the bio-oil. Thecondensers were maintained at �20 �C to allow the condensationof low volatility species. The gaseous products that passed throughthe condensers were collected in a Teflon gas bag. The experimentswere carried out under a gas flow with a flow rate of 50 cc/min at500 �C. Each experiment was performed for 1 h with a 5 g sample.Catalytic upgrading was performed using a fixed bed reactor sys-tem. The reaction temperature of the catalytic bed was set to500 �C. The ratio of catalyst/wood was 1/10. In the case of copy-rolysis, 2.5 g of biomass and 2.5 g of PP weremixed and used for thereaction. The detailed experimental procedures are described inRef. [17]. All the experiments were repeated 3 times and averagevalues were used for comparison.

2.4. Catalytic copyrolysis using Py-GC/MS

The same experimental instruments, a single-shot pyrolyzer(Frontier-Lab Co., Py-2020iD) and a GC/MS system, as those used ina previous study [19] were used in the present study for thecopyrolysis of WPB and PP. The procedure of pyrolysis and GC/MS

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analysis was also identical to that used in the previous study [19]except that a mixture of 1 mg each of the WPB and PP samplewas used in each experiment. For catalytic copyrolysis, catalyst(2 mg) was laid over the reactants (mixture of WPB and PP). Theexperiments repeated 3 times and average value was used.

3. Results and discussion

3.1. Characterization of the catalysts

Table S2 (Supplementary Information) lists the characteristics ofthe catalysts. Two different SiO2/Al2O3 ratios of HY zeolite, 5.1 and30, were used. The specific surface areas corresponding to theseSiO2/Al2O3 ratios were 730 and 623 m2/g, respectively. Also, thespecific surface area of H-Beta (SiO2/Al2O3 ¼ 25) was a 680 m2/g.The impregnation of Ga onto H-Beta reduced the specific surfacearea slightly to 648 m2/g due to partial blocking of the pores byadded Ga. HY showed a larger pore size (7.4 Å) than H-Beta (ca.6.6 Å).

Fig. S1 (Supplementary Information) shows the acid character-istics of the catalysts analyzed by NH3-TPD. All catalysts exhibited apeak at approximately 210 �C representing theweak acid sites and apeak at approximately 350 �C representing medium-strength acidsites, which indicates that the acidities of the catalysts were allsimilar. The quantity of acid sites decreased with increasing SiO2/Al2O3 ratio. Ga/H-Beta had fewer acid sites than H-Beta, probablybecause of the added Ga replaced acid sites. The order of the acidsite quantity was HY (5.1) > H-Beta > HY (30) z Ga/H-Beta.

3.2. Catalytic pyrolysis of WPB

Fig. 1 presents the yields of the solid, liquid and gaseous prod-ucts obtained from the pyrolysis of WPB under different catalyticconditions. In all catalytic pyrolysis experiments, the oil yield was5e7% lower than that of the non-catalytic pyrolysis, whereas thegas yield was 5e7% larger. These changes in the oil and gas yieldswere attributed to the improved cracking and deoxygenation of thereaction intermediates on the acid sites of the catalysts. Park et al.[20] reported that the oil yield was reduced and the gas yield wasincreased by the catalyst in the pyrolysis of a range of biomassmaterials, such as radiata pine, and attributed these changes to thereactions occurring on the acid sites of the catalysts.

The water content of bio-oil was increased by ca. 20 wt% usingthe catalyst (Table 1). This was attributed to the removal of oxygen

aste particle board and polypropylene over H-beta and HY zeolites,

Table 1Gaseous product yields and water content in bio-oil obtained from the pyrolysis ofWPB under different conditions.

Catalyst Non-catalyst HY(5.1) H-beta Ga/H-beta HY(30)

Yield (wt%) CO 4.71 8.36 7.97 7.44 7.15CO2 13.62 15.92 15.23 15.19 15.14C1 ~ C4 1.53 3.14 2.86 2.70 2.44

Water contents inbio-oil (wt%)

35.50 58.59 56.40 55.52 54.93

FuransFuranones

Cyclopentanones

Levoglucosan

Other-oxygenates

Dis

trib

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n(ar

ea%

)

0

5

10

15

20Non-CatalystH-BetaGa/H-BetaHY(5.1)HY(30)

Fig. 3. Oxygenate species distributions obtained from the pyrolysis of WPB.

H.W. Lee et al. / Renewable Energy xxx (2014) 1e5 3

in the biomass by dehydration on the catalyst's acid sites. The maincomponents of the product gas were CO, CO2 and hydrocarbons.The fractions of these species were also affected by the catalysts.Although their yields were increased by the catalysts, as mentionedabove, the increases in the yields of CO and hydrocarbons wereparticularly large. CO, CO2 and CH4 are produced from the decar-bonylation, decarboxylation, and demethylation of biomass,respectively [21]. Therefore, the data shown in Table 1 suggests thatthese reactions (particularly decarbonylation) were promoted bythe catalysts. Overall, a large number of acid sites are advantageousto catalytic pyrolysis because deoxygenation (dehydration, decar-bonylation, and decarboxylation) and demethylation are enhancedin the presence of acid sites. In this study, the gas yield and watercontent of bio-oil increased with increasing number of acid sites:HY (5.1) > H-Beta > Ga/H-Beta z HY (30).

Fig. 2 shows the product distributions obtained from the py-rolysis of WPB determined using Py-GC/MS. The main products ofnon-catalytic pyrolysis were oxygenates, acids, large-molecular-mass hydrocarbons, and phenolics. Considerable amounts of oxy-genates and acids were removed by the catalysis, whereas thefraction of phenolics increased. The production of aromatics andPAHs, which were produced in small quantities from non-catalyticpyrolysis, were also enhanced to a large extent. As shown in Fig. 3,the main component of the oxygenates was levoglucosan, whichwas removed completely by catalysis. The removed levoglucosan isbelieved to have been converted to other species, such as furans,furanones and cyclopentanones. For example, furans are producedfrom the dehydration of levoglucosan. Therefore, the increase in thefraction of furans observed in this study (Fig. 3) was attributed tothe conversion of levoglucosan to furans by the acidic catalysts.Because furans are used as basic petrochemical feedstockmaterials,their production contributes to the increase in the economic valueof bio-oil. In general, HY (5.1), which has the largest number of acid

Acids

Oxygenates

High-hydrocarbonsAromatics

PAHsPhenolics

Dis

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)

0

10

20

30

40

50Non-CatalystH-BetaGa/H-BetaHY(5.1)HY(30)

Fig. 2. Pyrolysis product distributions of WPB obtained over different catalysts.

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sites, showed the best deoxygenation performance, whereas HY(30), with the fewest acid sites, showed the lowest deoxygenationefficiency. Acids such as acetic acid showed a similar trend.

The order of the aromatics production capability of the catalystswas Ga/H-Beta > HY (5.1) > H-Beta > HY (30). It is known that suf-ficient Br€onsted acid sites are effective for the production of aro-matics. This is why HY (5.1) produced a large quantity of aromatics.Ga/H-Beta, which had a smaller number of acid sites than HY (5.1)and H-Beta, produced more aromatics because Ga enhanced thearomatization of the reaction intermediates. Park et al. [20] reportedthat the addition of Ga increased the yield of aromatics in the cat-alytic pyrolysis of radiata pine, which is in agreement with thisstudy. In particular, BTEX (benzene, toluene, ethylbenzene, andxylene), which are basic petrochemical feedstock materials,accounted for 77.9% of the total aromatics (Fig. 4), suggesting thatthe economic value of the bio-oil can be increased by catalysis.

The production of phenolics is also welcomed because they canbe used as feedstock to produce phenolic resins. As shown in Fig. 2,the productivity of phenolics increased with increasing number ofacid sites, HY (5.1) produced the largest quantity of phenolics. Inaddition, the phenolics produced consisted of hydroxyl phenyl,guaiacyl phenyl, and syringyl phenyl (Fig. 5). Previous studies

BenzeneToluene

EthylbenzeneXylene

C9 mono-aromatics

C10 mono-aromatics

Dis

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0.0

0.5

1.0

1.5

2.0

2.5

3.0

Non-CatalystH-BetaGa/H-BetaHY(5.1)HY(30)

Fig. 4. Aromatic species distributions obtained from the pyrolysis of WPB.

aste particle board and polypropylene over H-beta and HY zeolites,

Light-phenolics

Guaiacyl-phenolics

Syringyl-phenolics

Other-phenolics

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2

4

6

8

10

12

14

16

18

Non-CatalystH-BetaGa/H-BetaHY(5.1)HY(30)

Fig. 5. Phenolic species distributions obtained from the pyrolysis of WPB.

Table 2Gaseous product yields and water content in bio-oil obtained from the copyrolysis ofWPB and PP under different conditions.

Catalyst Non-catalyst HY(5.1) H-beta Ga/H-beta HY(30)

Yield (wt%) CO 3.42 5.54 5.27 4.89 4.46CO2 10.07 12.12 12.03 11.68 11.94C1 ~ C4 4.55 8.68 8.53 8.52 8.61

Water contents inbio-oil (wt%)

2.08 9.82 9.36 9.04 8.58

H.W. Lee et al. / Renewable Energy xxx (2014) 1e54

[21,22] on the catalytic pyrolysis of lignin, fromwhich phenolics areproduced, reported that lignin was converted to phenolics bydeoxygenation (decarbonylation, decarboxylation, and dehydra-tion), demethoxylation, and cracking on the acid sites, leading to anincrease in the yield of phenolics, which is in good agreement withthe present study.

The pore size of the catalyst might also affect the catalytic ac-tivity. For example, HY and H-Beta have different pore sizes. In thisstudy, however, the effect of the pore size was negligible. The ac-tivity of HY (30), which has larger pores than H-Beta, was lowerthan that of H-Beta, suggesting that the acidity is a much moreimportant factor in determining the catalytic activity than the poresize.

3.3. Catalytic copyrolysis of WPB and PP

Fig. 6 shows the results of the catalytic copyrolysis of WPB andPP in a fixed bed reactor. As in the pyrolysis of WPB only, the gasyield was increased and the oil yield was decreased by the catalysis.HY (5.1) with the largest number of acid sites produced the largestamount of gas, whereas HY (30), with the fewest acid sites pro-duced the smallest amount of gas. The increase in the yields of CO,CO2, and hydrocarbons by the catalysis (Table 2) were attributed to

Fig. 6. Gas, oil and char yields obtained from the copyrolysis of WPB and PP.

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decarbonylation, decarboxylation, and cracking promoted by cata-lysts, as mentioned in Section 3.2. In particular, the yield of hy-drocarbons increased to a large extent, suggesting that PP haddecomposed to hydrocarbons in the presence of acidic catalysts. Aprevious study reported that PP was decomposed to C3eC9 hy-drocarbons over HY, which is in good agreement with the presentstudy [23].

The water content of bio-oil produced from non-catalyticcopyrolysis was 2.08%, which is much smaller than that obtainedfrom the non-catalytic pyrolysis of WPB only (35.50%). This mightbe due to the supply of sufficient C and H by PP. Catalytic copy-rolysis resulted in a larger water content (ca. 9%) in the bio-oil thannon-catalytic copyrolysis, which was attributed to the enhanceddehydration by the catalysts. On the other hand, the water contentof ca. 9% was much smaller than that of the catalytic pyrolysis ofWPB only (ca. 55e60%).

Fig. 7 shows the product distributions obtained from copyrolysisdetermined by Py-GC/MS. Although the oxygenates were the mostabundant products in the non-catalytic pyrolysis of WPB only(Fig. 2), hydrocarbons derived from PP were the most abundantproducts in the non-catalytic copyrolysis of WPB and PP. The hy-drocarbon fraction decreased, whereas those of aromatics andphenolics were increased by catalysis. This can be attributed to theconversion of hydrocarbons, oxygenates, and acids into aromaticsand phenolics by cracking, oligomerization, deoxygenation, andaromatization occurring on the acid sites of catalysts as in Section3.2. Ga/H-Beta showed the highest selectivity toward aromatics,whereas HY (30) with the lowest number of acid sites led to thelowest yield of aromatics. This suggests that aromatization occur-ring on the acid sites was promoted by Ga-induced dehydrocycli-zation. The yield of aromatics obtained from catalytic copyrolysiswas slightly larger than that obtained from the catalytic pyrolysis ofWPB only. On the other hand, the yield of PAHs obtained from

Acids

Oxygenates

HydrocarbonsAromatics

PAHsPhenolics

Dis

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n(ar

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)

0

10

20

30

40

50

60

70

Non-CatalystH-BetaGa/H-BetaHY(5.1)HY(30)

Fig. 7. Product distributions obtained from the copyrolysis of WPB and PP.

aste particle board and polypropylene over H-beta and HY zeolites,

C1~C4C5~C9

C10~C17Over C17

Dis

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40

Non-CatalystH-BetaGa/H-BetaHY(5.1)HY(30)

Fig. 8. Product carbon number distributions obtained from the copyrolysis of WPB andPP over different catalysts.

H.W. Lee et al. / Renewable Energy xxx (2014) 1e5 5

copyrolysis was smaller than that from the pyrolysis of WPB only.Because PAHs are carcinogenic and can deactivate the catalyst, thesuppression of their production by the catalysis in this study isencouraging.

In terms of the carbon number distribution of the oil species(Fig. 8), the main products of non-catalytic copyrolysis were waxspecies (�C17) and large-molecular-mass compounds (�C10). Onthe other hand, catalytic copyrolysis produced small-molecular-mass compounds, mainly in the gasoline range (C5eC9).

4. Conclusions

The catalytic pyrolysis of WPB was carried out over the HY andH-Beta catalysts. HY (5.1) with the largest amounts of acid sites wasmost favorable to cracking and deoxygenation reactions. The maincompounds obtained from the catalytic pyrolysis of WPB only werephenolics, furans and aromatics. On the other hand, the mainproducts of the catalytic copyrolysis of WPB with PP were hydro-carbons, aromatics and phenolics. The water content in bio-oil wasdecreased significantly by copyrolysis with PP, contributing to theimprovement in oil quality. Catalytic copyrolysis suppressed theformation of PAHs, which are carcinogenic and cause coke forma-tion. C5eC9 hydrocarbons were mostly generated from the copy-rolysis. The addition of Ga led to enhanced aromatics production(particularly BTEX) for both the catalytic pyrolysis of WPB only andthe catalytic copyrolysis of WPB and PP.

Acknowledgment

This research was supported by Basic Science Research Programthrough the National Research Foundation of Korea (NRF) fundedby the Ministry of Education (2012R1A1B3003394).

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Appendix A. Supplementary data

Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.renene.2014.07.040.

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