Fischer–Tropsch Synthesis on the Al2O3-Modified Ordered

7/26/2019 FischerTropsch Synthesis on the Al2O3-Modified Ordered

1/9

Catalysis Today 265 (2016) 2735

Contents lists available at ScienceDirect

Catalysis Today

j ournal homepage : www.elsevier .com/ locate /cattod

FischerTropsch synthesis on the Al2O3-modified ordered

mesoporous Co3O4with an enhanced catalytic activity and stability

Chang-Il Ahn,Jong Wook Bae

School of Chemical Engineering, Sungkyunkwan University (SKKU), Suwon, Gyeonggi-do440-746, Republic of Korea

a r t i c l e i n f o

Article history:

Received 26 June 2015

Received in revised form 19 August 2015

Accepted 10 September 2015

Keywords:

FischerTropsch synthesis

Ordered mesoporous Co3 O4Al2O3 modification

Structural stability

Deactivation

a b s t r a c t

Ordered mesoporous Co3O4 metal oxide synthesized by nano-casting method using a hard template of

KIT-6 was subsequently modified with Al component to increase catalytic activity and structural sta-

bilities even under H2-rich FischerTropsch synthesis (FTS) conditions. While using a highly ordered

mesoporous Co3O4 for FTS reaction, a significant structural change by forming larger cobalt aggregates

and encapsulated cokes accelerated a catalyst deactivation. By introducing an irreducible Al species on

the inner surfaces or in the main frameworks ofmesoporous Co3O4, the ordered mesoporous structures

ofCo3O4 were successfully maintained even after FTS reaction. These modifications ofthe mesoporous

Co3O4 structures were carried out by adding a pillaring material of aluminum oxide or by preparing

mesoporous mixed binary metal oxides with the partial formation of a spinel CoAl2O4 phase, and a

higher structural stability and activity were observed due to the suppressed collapses ofthe mesopore

structures of Co3O4 . The improved stability of the Co3O4 mesopores seems to be related with a lower

mobility ofan irreducible Al2O3pillar by strongly interacting with the inner surfaces ofthe mesoporous

Co3O4or by enhancing the interactions ofCo3O4with Al2O3in a main framework ofmixed binary metal

oxides. 2015 Elsevier B.V. All rights reserved.

1. Introduction

FischerTropsch synthesis (FTS) reaction has been well known

to be an efficient chemical conversion process using the synthe-

sis gases, which can be synthesized from the reforming of natural

gas or coal (or biomass) gasification, to produce some clean fuels

or petrochemicals [13]. The cobalt-based FTS catalysts have the

advantages such as a higheryieldfor linearhydrocarbons at a lower

operating temperature with a suppressed water gas shift activity

compared to the iron-based FTS catalysts [4]. The supported FTS

catalysts can be prepared by supporting cobalt nanoparticles on

the highly porous irreducible metal oxides with a high dispersion

of them, however, significant aggregations of the cobalt nanopar-

ticles with the reoxidation to form an inactive cobalt species and

the possible deposition of heavy waxes (or coke precursors) during

the FTS reaction haven been known for the main reasons for cat-

alyst deactivations [4]. To overcome these general disadvantages

of supported catalysts, ordered mesoporous supports such as the

ordered mesoporous silica, carbons or transition metal oxides have

been widely investigated in the field of heterogeneous catalysis due

Corresponding author.

E-mail address: [email protected] (J.W. Bae).

to their well-developed regular mesopore structures with a higher

surface area [2,3] through well-known nano-casting methods for

some applications of battery technologies and oxidation catalytic

reactions and so on [5,6]. However, the direct applications of the

transition metal oxides for some catalytic reactions have been lim-

ited dueto their structureinstabilityunder H2-richconditions [7,8].

Thephasetransformationfrom metal oxidesto metallic species can

cause a severeaggregationand a structural collapse of thereducible

mesoporous transition metal oxide frameworks resulted in accel-

erating catalyst deactivation. As far as we know, these deactivation

mechanisms may be main reasons for the small research reports

concerning practical applications of mesoporous transition metal

oxides for the FTS reaction till now.

In the present study, we investigated two possible methodolo-

gies to suppress the structural collapses of the mesoporous Co3O4even under the reductive CO hydrogenation conditions by intro-

ducing an irreducible aluminum oxide in the mesoporous surfaces

[10] or by preparing mixed binary metal oxides of CoAlOx in the

main frameworks of Co3O4 to elucidate the roles of aluminum

oxide on the surfaces or mainframes of mesoporous Co3O4. These

modifications of the mesoporous Co3O4 with irreducible Al2O3species showed a stable activity by maintaining regular meso-

porous structures during the FTS reaction. The improved catalytic

activity and structural stability of the mesoporous Co3O4 were

http://dx.doi.org/10.1016/j.cattod.2015.09.047

0920-5861/ 2015 Elsevier B.V. All rights reserved.
http://localhost/var/www/apps/conversion/tmp/scratch_6/dx.doi.org/10.1016/j.cattod.2015.09.047http://www.sciencedirect.com/science/journal/09205861http://www.elsevier.com/locate/cattodmailto:[email protected]://localhost/var/www/apps/conversion/tmp/scratch_6/dx.doi.org/10.1016/j.cattod.2015.09.047http://localhost/var/www/apps/conversion/tmp/scratch_6/dx.doi.org/10.1016/j.cattod.2015.09.047mailto:[email protected]://crossmark.crossref.org/dialog/?doi=10.1016/j.cattod.2015.09.047&domain=pdfhttp://www.elsevier.com/locate/cattodhttp://www.sciencedirect.com/science/journal/09205861http://localhost/var/www/apps/conversion/tmp/scratch_6/dx.doi.org/10.1016/j.cattod.2015.09.047


2/9


3/9

C.-I. Ahn, J.W. Bae / Catalysis Today 265 (2016) 2735 29

calculated to compare the surface composition changes before and

after FTS reaction. Transmission electron microscopy (TEM) anal-

ysis was also carried out to verify the changes of the local surface

morphologies on the fresh and used mesoporous Co3O4 catalysts

using TECNAI G2 operated at an accelerating voltage of 200 kV.

Catalytic activity test of the as-prepared mesoporous Co3O4catalysts were carried out in a stainless steel fixed-bed tubular

reactor having an outer diameter of 12.7 m m using 100 m g of

the catalyst after mixing with 1.0 g of gamma-Al2

O3

as a diluent

with the a granule size of 60100m. Prior to the FTS reac-

tion, the mesoporous Co3O4 catalysts were reduced in situ at

400 C under a flow of 5%H2 balanced with N2 for 12 h. After

the reduction, the reactor temperature was cooled down to room

temperature and the reactant of syngas having a feed gas com-

position of H2/N2/CO = 62.84/5.60/31.56 was introduced. The FTS

reaction was performed for around 2060h under the following

reaction conditions; T= 2 30 and 240 C, P=2.0MPa, and weight

hourly space velocity (WHSV)= 24000 L (mixed gas)/(kgcat h). The

effluent productsfrom thereactorwereanalyzedby using an online

gas chromatograph (YoungLin Acme 6500, GC) equipped with GS-

GASPRO capillary column connected to flame ionization detector

(FID) for the analysis of hydrocarbons, and Carboxen 1000 packed

columnconnectedto TCDfor theanalysis ofCO, CO2, CH4 andH2. CO

conversion was calculated using the variations of CO moles before

and after FTS reaction corrected by using the area changes of inter-

nalstandardgas andthe product distributions were also calculated

based on the total carbon balances. In addition, the reaction rate

wasdefinedas thereactedCOmol/(gcat s)andtheTOFwasdefined

as the reacted CO molecules/(surface cobaltatoms), where the rate

and TOF were calculated using the results of FTS reaction at around

20h on stream.

3. Results and discussion

3.1. Physicochemical properties of the Al-modified mesoporous

Co3O4

The surface area, pore volume and average pore diameter of the

mesoporousCo3O4catalystswith theirpore size distributions were

measured by N2sorption method, and the results are summarized

in Table 1 and Fig. 1. As shown in Fig. 1, the presence of the meso-

pore structures was clearly observed with a type IV isotherm and

H1 hysteresis on the mesoporous Co3O4 catalysts. In addition, the

hysteresis pattern on the comparative bulk-Co3O4suggests a typi-

cal non-porous material structure. The sharp peak intensities with

a pore size around 4 nm were observed on the Al-modified meso-

porous Co3O4 catalysts such as the meso-Co3O4, Al/meso-Co3O4,

and Al/meso-CoAlOx, however the bulk-Co3O4 showeda broadpore

size distribution between 10 and 100nm in pore size as shown

in an inset of Fig. 1. The broad pore size distribution on the bulk-

Co3O4 seems to be attributed to the inter-particular pores of Co3O4nanoparticles byshowing a lower surface area of 32m2/g andlarger

pore diameter of 20.3nm. The surface areas of the mesoporous

Co3O4 catalysts were significantly decreased after Al modification

from 104m2/g on the meso-Co3O4 by showing a bimodal pore

size distribution to 98m2/g on the Al/meso-Co3O4and 47m2/g on

the Al/meso-CoAl0.25Ox by showing an unimodal size distribution

with a sharp peak intensity at around 4nm in size. The observa-

tion strongly suggests that Al2O3pillar was highlydispersed on the

inner surfaces of the meso-Co3O4 and the meso-CoAlOx without

significant aggregation of Al2O3 pillar or a possible structural col-

lapse during the preparation steps [8,10,11]. The pore volume and

average pore diameter were also observed with a similar trend by

showing the respective values of 0.070.19 cm3/g and 4.76.1 nm

except for the bulk-Co3O4 as summarized in Table 1. The slightly

Fig. 1. N2

adsorptiondesorption patterns and pore size distributions of the fresh

mesoporous Co3O4catalysts.

increased average pore diameter of 6.1 nm on the Al/meos-Co3O4from that of 5.0 nm on the meos-Co3O4can be possibly attributed

to the formation of inter-particular pores originated from the par-

tially collapsed Co3O4 and Al2O3 pillar at around 50nm (an inset

of Fig. 1). Interestingly, the ordered mesoporous structures were

well developedon the Al/meso-CoAl0.25Ox and Al/meso-CoAl0.13Ox,

which seems to have a positive effect for a superior catalytic activ-

ity and stability through a facile transport of heavy hydrocarbons

formed during FTS reaction [10].

Wide angel powder XRD patterns of the fresh mesoporous

Co3O4catalysts are displayed in Fig. 2(A), and the calculated aver-

age particle sizes of Co3O4 were also summarized in Table 1. Thespinel structures of Co3O4crystalline phases were clearly observed

atthe2valuesof 19.0,31.2, 38.5,44.8,59.3and 65.2,whichcanbe

corresponding to the characteristic crystalline Co3O4 diffractions

of (1 1 1), (2 2 0), (3 1 1), (4 0 0), (5 1 1) and (4 4 0) planes [12]. The

particle sizes of Co3O4were further calculated by DebyeScherrer

equation using the most intense characteristic diffraction peak at

2=36.8. The particle sizes of the mesoporous Co3O4 catalysts

even after Al modification were found to be around 15.916.9 nm,

which could be a grain size of main framework of cobalt oxides,

except for the bulk-Co3O4with a particle size of 27.9nm. The par-

ticle sizes of metallic cobalt were calculated by using the equation

of d(Co0)=0.75d(Co3O4) [13], and the calculated particle sizes of

metallic cobaltwerefoundto beabove12 nmon allthe mesoporous

Co3O4 catalysts, which has been generally known to be a trivialeffect to the intrinsic activity for the FTS reaction due to its charac-

ter of structure insensitivity above 8 nm in size [4]. Therefore, the

different intrinsic catalytic activity of the turnover frequency (TOF)

on the mesoporous Co3O4catalysts seems to be mainly attributed

to the other characteristics such as the mesoporosity with its sta-

bility and the mass transport of products of heavy hydrocarbons

and so on. Even though the spinel structure of the cobalt aluminate

of CoAl2O4was not clearly observed by the XRD analysis due to an

identical diffraction peak position with Co3O4 [14,15], a possible

formation of cobalt aluminate on the Al/meso-Co3O4, Al/meso-

CoAl0.25Ox and Al/meso-CoAl0.13Ox seems to be a main reason for

an enhanced structural stability and activity by forming a particle

size of around 16nm, which corresponds to a main frameworks

granule size of Co3O4. As shown in Fig. 2(B), the characteristic 2D


4/9

30 C.-I. Ahn, J.W. Bae / Catalysis Today 265 (2016) 2735

Table 1

Characteristics of the Al-modified ordered mesoporous Co3 O4catalysts.

Catalysts BET XRD H2-Chem. TPR XPS

Surface

area

(m2/g)

Pore

volume

(cm3 /g)

Pore

diameter

(nm)

Particle

size of

Co3O4 (nm)

Surface area

of cobalt

(m2/gCo)

Degree of

reduction

(%)a

BE (eV)of

Co2p3/2

BE(eV) ofAl2p IAl /ICob (103)

Fresh/used Fresh/used Fresh/used

Bulk-Co3O4c 32 0.22 20.3 27.9 12.1 98.2

Meso-Co3O4c 104 0.19 5.0 15.5 22.8 62.9 780.2/780.0 / /

Al/meso-Co3O4c 98 0.21 6.1 16.9 31.0 44.0 780.5/780.3 75.8/75.0 1.28/1.14

Al/meso-CoAl 0.13 Ox 68 0.10 4.7 15.9 8.4 50.4 781.0/780.9 74.4/74.2 2.12/2.15

Al/meso-CoAl 0.25 Ox 47 0.07 5.5 16.4 10.9 50.3 778.8/778.7 74.2/73.8 4.36/4.31

a The degrees of reduction of catalysts were calculated using TPR data with an amount of H2 consumption below 450C divide d by t ot al H2 consumption in the full

temperature ranges.b Thevalues of theintensity ratio ofIAl /ICo were calculated using theintegrated area of each peak by correcting thearea usingthe atomicsensitivityfactors (ASF) with the

values ofSCo=4.5 and SAl= 0.11.c The characterization results of the bulk-Co3O4 , meso-Co3O4 and Al/meso-Co3O4was partly reported in ourpreviousworks [8,10].

Fig. 2. (A)Wide-angle XRD patterns and (B)small angle X-ray scattering (SAXS)patternsof the fresh mesoporous Co3O4 catalysts.

hexagonal ordered mesostructures assigned to planes of (10 0),

(11 0), and (20 0) reflections [16,17] were clearly observed on the

ordered mesoporous Co3O4 before and after Al modification. The

peak intensity of (10 0) plane was observed much larger on the Al-

incorporated meso-Co3O4such as on the Al/meso-CoAl0.25Ox, and

it suggests the facile formation of well-ordered mesoporous struc-

tures on the mesoporous mixed oxides which is in line with the

results of N2sorption analysis.

3.2. Reducibility and structural stability of the Al-modified

mesoporous Co3O4

The reduction patterns of Co3O4 crystallites are known to fol-

low two-step reductions such as Co3O4CoOCo0. From TPR

analysis of the mesoporous Co3O4catalysts as shown in Fig. 3, the

stepwise reductions with two distinctive reduction peaks can be

assigned as the first reduction of Co3O4 to CoO at around 300C

and the second reduction of CoO to metallic cobalt above 400 C

[18,19]. In the case of the unmodified Co3O4, two H2 absorption

peaks of Co3O4were clearly observed at much lower temperatures

of 303 and 374 C on the bulk-Co3O4, and at the temperatures of

280 C and 493 C on the meso-Co3O4, which are also responsi-

ble for the typical two step reductions of Co3O4. Interestingly, a

higherreduction temperature shift of thesecond peak on themeso-

Co3O4 can be possibly attributed to the suppressed H2 transport Fig. 3. TPR profiles of thefresh mesoporous Co3O4 catalysts.


5/9


Fig. 4. TEM imagesof thefresh(A) bulk-Co3O4 , (B)meso-Co3O4 , (C) Al/meso-Co3O4 , (D) Al/meso-CoAl0.25 Ox catalysts.

rate by the trapped water generated during the reduction step in

the mesopores of the meso-Co3O4[2,8,20]. On the Al/meso-Co3O4,

two characteristic reduction peaksappearedat 371and 446Cwith

a medium reduction temperature of 402 C, which are also in line

with the typical stepwise reduction steps of Co3O4, and a shoulder

peak at 402 C may be originated from the aggregated cobalt parti-

cles during the synthesis steps through partial structural collapses

[8,10]. The shifts of reduction peaks to higher temperatures on the

Al/meso-Co3O4 compared to the meso-Co3O4 were attributed to

the dispersed Al2O3 pillar on the inner framework surfaces of the

mesoporous Co3O4 by forming a strong metal-support interaction.In addition,a reductionpeak at 724C on theAl/meso-Co3O4seems

to be originatedfrom a possibleformation of spinel structuralcobalt

aluminate [4]. Generally, it has been known that irreducible metal

oxides such as Al2O3, SiO2 and TiO2 can lead to the formation of

strong metal-support interactions on the supportedmetal catalysts

[4,21]. Even though these phenomena can show negative effects

in terms of catalytic activity due to the difficult reduction behav-

ior of the strongly interacted cobalt particles on the supports, the

enhanced structural stability can be originated from a strongly

interacted Al2O3 pillar on the meso-Co3O4and meso-CoAlOxeven

under H2-rich reaction conditions.

The reduction patterns on the Al2O3 incorporated Al/meso-

CoAlOx were similar with the Al/meso-Co3O4 by shifting to lower

temperatures, especially on the Al/meso-CoAl0.25Ox. The two stepreductions of Co3O4 particles were observed at around 330 and

490 C, and the medium temperature of 383C on the Al/meso-

CoAl0.13Ox seems to be originated from the aggregated cobalt

particles through a partial structural collapses [8,10]. Interest-

ingly, the higher temperature reduction peaks at a respective

654 and 611 C on the Al/meso-CoAl0.13Oxand Al/meso-CoAl0.25Oxcan generate a strong interaction between Co3O4 and impreg-

nated (or incorporated) Al2O3 species. This can be beneficial for

an enhanced structural stabilityof the mesoporous Co3O4catalysts

by forming spinel CoAl2O4phases possibly. The reduction degrees

ofCo3O4 particleswere foundto be lower on theAl-modifiedmeso-

porous Co3O4catalysts with the values of 44.0, 50.4, and 50.3% on

the respective Al/meso-Co3O4, Al/meso-CoAl0.13Ox and Al/meso-

CoAl0.25

Ox

compared to the meso-Co3

O4

with a value of 62.9%,

which strongly suggests the formation of new strong interactions

between Co3O4andAl2O3particles.In addition,the observed lower

reduction temperatures on the Al/meso-CoAl0.25Oxthan thatof the

Al/meso-CoAl0.13Ox seemsto be attributed to smaller total amounts

of Al2O3content n in the mesoporous Co3O4main frameworks.

To further verify the structural stability after Al modification on

the mesoporous Co3O4catalysts, TEM analyses were carried outon

the as-prepared catalysts as shown in Fig. 4 with magnified inset

figures. The bulk-Co3O4 showed the bundles of spheres with the

particle sizes of 2030 nm, and the ordered mesopore structures

on the meso-Co3O4 were clearly observed with an average porediameter around 5 nm. In addition, the observed different parti-

cle sizes of Co3O4 on the Al-modified meso-Co3O4 between XRD

and TEM analysis seems to be mainly attributed to a formation

of larger cobalt clusters in the frameworks of mesoporous Co3O4which could be the aggregates of the separate Co3O4grains mainly

measured by XRD analysis.The regularity of the mesoporous struc-

tures on the meso-Co3O4seems to be responsible for the observed

higher specific surface area of metallic cobalt compared to that of

the bulk-Co3O4. In addition, the typical ordered mesoporous struc-

tures with a pore diameter of 68 nm were clearly observed on the

Al/meso-Co3O4 which was also sustainedeven after the addition of

Al2O3 pillaring material. This observation suggests that the Al2O3pillar is well dispersed inside the mesopores of the meso-Co3O4. It

also suggests that Al2O3 particles can be strongly interacted withthe mesoporous Co3O4 surfaces by forming a strong metal-support

interaction (confirmedby TPR), which canplay an importantrole in

stabilizing the mesopore structures of Co3O4 under the reductive

FTS conditions. In addition, TEM images of the fresh Al/meso-

CoAl0.25Ox also support that the mesoporous frameworks of Co-Al

mixed oxides originated from vacant pores of the KIT-6 mesopores

are well developed with similar pore sizes of the Al/meso-Co3O4.

H2 chemisorption analysis was carried out on the mesoporous

Co3O4 catalysts to verify the active metallic surface area of cobalt

species, andthe results aresummarized in Table1. The larger metal-

lic cobalt surface areas of 22.8 and 31.0m2/gCo were observed on

the meso-Co3O4 and the Al/meso-Co3O4, respectively, compared

to that of bulk-Co3O4 with a value of 12.1m2/gCo. However, with

an incorporation of Al2

O3

particles on the Al/meso-CoAl0.13

Ox

and


6/9


Fig. 5. Catalytic activities on the mesoporous Co3O4 catalysts with time on stream

(h).

Al/meso-CoAl0.25Oxmixed oxides, the metallic cobalt surface areas

were decreased to 8.4 and 10.9m2/gCo due to a smaller content

of cobalt species. In addition, from our previous study [10], thedecreased metallic surface area after the reduction treatment was

mainly attributed to the partial structure collapses of the meso-

Co3O4. Although the Al2O3 modified meso-Co3O4 has a smaller

metallic surface area than that of the meso-Co3O4 due to the

well-developed mesoporous structures, the structural collapse of

the ordered mesoporous structures without Al modification can

increase the structural instability during the reductionstep through

a intrinsicvolume contraction from Co3O4to metallic cobalt, which

resulted in showing a lower catalytic activity and stability. The

observed higher metallic cobalt surface area of the Al-modified

meso-Co3O4 suggests that the ordered mesoporous structures are

well preservedthrougha higherdispersionof theAl2O3 pillar inside

the pores of the meso-Co3O4 and meso-CoAlOx. Generally, it has

been also known that the irreducible metal oxide having a lowermelting point and smaller particle size can have a higher mobility

onthe surfacesat a much lowermeting temperature ofmetaloxides

during thermal treatment [21,22]. Based on the above phenomena,

a pillaring oxide of Al2O3 can be evenly dispersed on the inside

of the meso-Co3O4 or meso-CoAlOx surfaces which are verified

by the variations of specific surface areas after the Al impregna-

tion. The higher metallic cobalt surface area of the Al/meso-Co3O4suggests theformation of thestrongerinteractionbetween thesur-

faces of mesoporous Co3O4 with thermally stable Al2O3 particles

under a higher temperature reductive condition. In addition, with

the increase of the amount of Al2O3 in the main frameworks of

the meso-CoAlOx, the amount of active metallic cobalt sites can be

diminished by showing a lower metallic cobaltsurface area around

8.410.9m

2

/gCocompared to the Al/meso-Co3O4.

3.3. Activity and stability of the Al modified meso-Co3O4under

reductive conditions

The catalytic activities on the mesoporous Co3O4catalysts were

carried out at T=230 and 240 C, P=2.0MPa, and WHSV= 24000L

(mixed gas)/(kgcat h). As shown in Fig. 5 with the summarized

results in Table 2, the superior catalytic activity at 230 C was

observedonthemeso-Co3O4 compared to the bulk-Co3O4 by show-

ing CO conversions of 6.1 and 11.7% with a similar trend of reaction

rates at steady-state, which can be induced from regular meso-

porous structures and suppressed paraffin wax deposition on the

activecobalt sites resulted in theenhancementof mass transportof

the heavier hydrocarbons formed as reported in our previous work

[8]. The TOFs (defined as number of reacted CO molecules/(surface

cobalt atom s )) were found to be similar values of 0.055 and

0.035 s1 on the bulk-Co3O4 and the meso-Co3O4 because of the

structure insensitive characters of the cobalt nanoparticles above

8nm in size [4,23,24]. A higher CH4 and a lower C5+ selectivity on

the meso-Co3O4 (i.e., 6.9% for CH4 and 81.8% for C5+) compared

to those on the bulk-Co3O4 (i.e., 3.1% for CH4 a nd 94.0% for C5+)

were attributed to the presence of the partially reduced cobalt

particles with a higher mesoporosity on the meso-Co3

O4

d ue to

a lower intrinsic activity for the secondary reactions of light olefins

to the heavy hydrocarbons [4,23,2527]. Based on our previous

work [20], the catalyst deactivation was mainly originated form

the structural collapses of the meso-Co3O4and the wax encapsula-

tion and filamentous carbon formation on the bulk-Co3O4surfaces

verified by thecharacterizationsof FT-IR,Raman andTEM analyses.

In addition, the possible catalyst deactivation by the deposition of

heavy wax components in the mesopores of meso-Co3O4 cannot

be overlooked [4], however, a collapse of regular mesopore struc-

tures seems to be more dominant deactivation mechanism of the

meso-Co3O4.

As shown in Fig. 6(A) and (B), the particle sizes of cobalt after

the FTS reaction were increased up to 50100 nm on the used

meso-Co3O4 with the complete structural collapse of mesoporous

Co3O4, and the particle size of cobalt on the used bulk-Co3O4was more significantly increased from 30nm to above 100nm

[8,10]. The morphologies of deposited carbons were significantly

different by showing an encapsulation of the aggregated cobalt

particles with amorphous carbons on the bulk-Co3O4 which can

disrupt the transport of reactants to the active cobalt sites, and a

growth of filamentous whisker carbons on the meso-Co3O4which

is likely to form on the surfaces of metallic crystallites having a

weak metal-support interaction with a small cobalt particle size

[28,29].

To stabilize the ordered mesoporous Co3O4 structures with

lower carbon depositions, the modification with irreducible metal

oxide of Al2O3 was further applied to the meso-Co3O4 by pillar-

ing Al2O3 into the mesopores or by preparing mixed-metal oxide

frameworks such as CoAlOx. As shown in Fig. 5 and summarizedin Table 2, a significant increase of activity and stability on the

Al/meso-Co3O4 was observed at T=230C with CO conversion

above 83%during 40h on streamwithouta significant deactivation.

The reaction rate and TOF were also dramatically increased on the

Al/meso-Co3O4 with values of 82.8 [reacted COmol/(gcat s)] and

0.153 [reacted CO molecules/(surface cobalt atom s)] compared to

the unmodified meso-Co3O4. A slight increase of CH4selectivity of

11.6%and decrease ofC5+ selectivity of 77.3% on the Al/meso-Co3O4can be attributed to the formation of the strongly interacted Al2O3pillaringoxide withthe surfaces of meso-Co3O4 whichalso resulted

in forming a largely oxidized electronic states of cobalt particles

by decreasing the adsorption properties of H2 and increasing CH4selectivity possibly due to a known relatively fast formation rate of

light hydrocarbons [4,10,3032]. However, the strong interactionsbetween the metallic cobalt surfaces of the meso-Co3O4 frame-

works and the Al2O3 pillar can stabilize the mesopore structures

even under FTS reaction condition by maintaining stable catalytic

activity. As shown in Fig. 6(C) with the magnified inset TEM image,

the ordered mesoporous structures with a pore size of around6 nm

on the used Al/meso-Co3O4 were well maintained after the FTS

reaction for 40h with local aggregations of the mesoporous Co3O4and without filamentous carbon formations. The structural stability

on the Al/meso-Co3O4 was improved because of an even distri-

bution of the thermal stable Al2O3 pillar inside the meso-Co3O4pores, which resulted in showing a higher catalytic activity and

stability. Since the collapses of the mesopore structures of the

Al/meso-Co3O4 were also insignificant under H2 reduction pre-

treatment as confirmed by our previous study through N2sorption


7/9


Table 2

Catalytic performances on the Al-modified ordered mesoporous Co3O4 catalysts.

Catalysts Reaction Temp. (C) Reaction duration (h) Activitya Product distribution (C-mol%)

CO conv. (C-mol%) Rateb TOFb C1/C2C4/C5+ Olefins in C2C4(%)

Bulk-Co3O4 230 20 6.1 5.8 0.055 3.1/2.9/94.0 43.4

Meso-Co3O4 230 20 11.7 10.9 0.035 6.9/11.3/81.8 61.1

Al/meso-

Co3O4c 230

20 88.2 82.8 0.153 11.6/11.1/77.3 11.6

40 83.6 9.7/11.9/78.4 16.5

Al/meso-

CoAl0.13 Ox 240 20 93.9 88.2 0.406 8.3/6.1/85.6 7.5

60 91.3 6.4/5.4/88.2 16.5

Al/meso-

CoAl0.25 Ox240

20 95.8 90.0 0.234 13.4/7.5/79.1 4.2

60 85.9 12.1/8.8/79.1 25.2

a The FTS reaction was car ried out at t he f ollo wing con ditions ; T= 230 and 240 C, P=2.0MPa, WHSV=24000L/(kgcath), and a feed gas composition of

H2/N2/CO= 62.84/5.60/31.56.b Thereactionrate was definedas thereacted COmol/(gcats) andthe TOFwas definedas thereacted CO molecules/(surface cobalt atom s),where therate andTOF were

calculated using thereactiondate at around20 h on stream.c The results of theAl/meso-Co3O4 was reported in our previous work [10].

and TEM analysis [10], the highlyorderedmesoporous structuresof

the Al/meso-Co3O4seems to be maintained through the formation

of thestrong interaction between thereducible cobaltparticles and

the irreducible Al2O3pillaring metal oxide.

To further improve a structural stability of mesoporous metal

oxide catalysts, the Al2

O3

incorporated mixed metal oxides of

the Al/meso-CoAl0.13Ox and Al/meso-CoAl0.25Ox were prepared

by nano-casting method and the representative catalytic activi-

ties are summarized in Table 2 with the activity with time on

stream at T=240 C in Fig. 5. A higher catalytic activity and sta-

bility without significant deactivation (i.e., CO conversion of 93.9%

at 20 h and 91.3% after 60 h on stream) were observed on the

Al/meso-CoAl0.13Ox, and the activity was slightly decreased with

an increase of Al2O3 content in the mixed metal oxide structures

such as the Al/meso-CoAl0.25 Ox (i.e., Co conversion of 95.8% at

20h and 85.9% after 60h on stream). The reaction rates and TOFs

were also found to be higher on the Al/meso-CoAl0.13Ox with the

values of 88.2 [reacted CO mol/(gcat s)] and 0.406 [reacted CO

molecules/(surface cobalt atoms)] with a lower CH4 selectivity

of 8.3% and a higher C5+ selectivity of 85.6% than those on the

Al/meso-CoAl0.25Ox. Thesehigher catalyticactivityand stabilitycanbe mainly attributed to the stable maintenance of the mesoporous

frameworks by using Al2O3modifier through the formation of the

strongly interacted Al2O3 and a possible formation of the inac-

tive CoAl2O4 species on the Al/meso-Co3O4 and Al/meso-CoAlOx.

As shown in Fig. 6(D) with the magnified inset TEM image, there

were no large differences in the ordered mesoporous structures

between the fresh and used Al/meso-CoAl0.25Ox, which strongly

suggests thatthe structural collapse can be successfullysuppressed

by using the Al2O3 modifier to the mesoporous Co3O4 struc-

tures through pillaring method of irreducible Al2O3 or preparing

mixed metal oxide structures of meso-CoAlOx. In addition, the

increased C5+ selectivity with an increase of reaction time on all

the Al-modified mesoporous Co3O4can be attributed to thesurface

changes through the reconstruction andaggregation of cobalt parti-

cles or thecarbon depositions andso on [4,18,25,32]. The decreased

olefin selectivity on the Al-modified meso-Co3O4 compared to the

meso-Co3O4 seems to be attributed to the higher oxidation states

of cobalt particles or the increased surface acidity [4,16] dueto the

formation of the strong new interactions of Al2O3species with the

outer surfaces or the frameworks of the mesoporous Co3O4. It was

also supported from the measured isoparaffin percentage based

on the total paraffin in the range of C2C4 hydrocarbons with the

values of 3.73, 3.59, 2.29, 1.97 and 0% on the Al/meso-CoAl0.25Ox,Al/meso-CoAl0.13Ox, Al/meso-Co3O4, meso-Co3O4and bulk-Co3O4,

respectively.

Fig. 6. TEM imagesof theused (A)bulk-Co3O4 , (B)meso-Co3O4 , (C) Al/meso-Co3O4 , (D) Al/meso-CoAl0.25 Oxcatalysts.


8/9


Fig. 7. XPS spectra ofCo2pon the mesoporous(A) fresh and (B) usedCo3O4 catalysts.

To further verify the possible reasons for the enhanced struc-

tural stability after the Al2O3 modification on the mesoporous

Co3O4, XPS analysis was also carried out on the fresh and used

FTS catalysts and the results are summarized Table 1 with the

XPS peaks of Co2p in Fig. 7. The values of BEs on the fresh meso-

porous Co3O4 were found to be in the ranges of 778.8781.0eV

and 778.7780.9eV on the used mesoporous Co3O4. In general,

the core level BEs of Co2p3/2 on the supported Co3O4 catalysts

have been reported to slightly increase compared to those of pure

Co3O4 nanoparticles due to the strong metal-support interaction

due to different surface properties of the supports such as acid-

ity or hydrophilicity and so on [33,34]. Therefore, the observed

slight increases of BEs after Al2O3modification on the mesoporousCo3O4 compared to the pure meso-Co3O4 may suggest the forma-

tion a new strong interactions between the Al2O3 pillar (or the

mixed metal oxides of CoAlOx) and the mesoporous Co3O4 sur-

faces. Due to the possible superposition of Co2p3/2 peak assigned

to the cobalt oxides with various oxidation states such as Co3O4,

CoO and CoAl2O4with the reference metallic cobalt BE of 780.0 eV

[35,36], the formation of spinel cobalt aluminate species cannot be

overlooked dueto a observed newreductionpeak ata higherreduc-

tion temperature above 600 C from TPR results after the Al2O3modification on the meso-Co3O4. In addition, a main aluminum

phase seems to be the stable gamma-Al2O3from the observed BEs

of Al at around 75 eV on the fresh and used mesoporous Co3O4catalysts without significant variations. The modification with a

thermally stable Al2O3 on the Al/meso-Co3O4 and Al/CoAlOx maybe related with an enhanced stability of mesopore structures by

partially forming CoAl2O4 spinel structures in the interfaces of

Al2O3and Co3O4particles possibly. This hypothesis was supported

by comparing the intensity ratio of Co2p3/2peak with that of Al2p

peak on the fresh and used catalysts as summarized in Table 1.

The calculated values of IAl/ICo were found to be 1.28, 2.12 and

4.36 on thefreshAl/meso-Co3O4, Al/meso-CoAl0.13Ox and Al/meso-

CoAl0.25Oxrespectively, and the observed higher ratios ofIAl/ICoon

the fresh Al/meso-CoAlOx were attributed to a higher content of

Al2O3 species. In addition,a smallshoulderpeak intensityat around

785.0 eV on the fresh Al/meso-CoAlOx and Al/meso-Co3O4 can be

assigned to a shake-up process of a high spin Co2+ species, which

can be correlated with the formation of non-reducible inactive

cobalt aluminate species as well [37]. Therefore, the XPS spectra

of the Al2O3-modified mesoporous Co3O4 catalysts after FTS reac-

tion further revealedthatthe shake-up processof thehighspin Co2+

increased due to the additionally generated spinelcobalt aluminate

species during FTS reaction possibly, which can be mainly respon-

sible for the structural stability with a lower deactivation rate on

the Al/meso-Co3O4 and Al/meso-CoAlOx. Interestingly, the calcu-

lated values ofIAl/ICo were found to be 1.14, 2.15 and 4.31 on the

used Al/meso-Co3O4, Al/meso-CoAl0.13Oxand Al/meso-CoAl0.25 Ox,

respectively without significant variations compared to those of

the fresh catalysts. These observations also support that the Al2O3species as a pillaring material or as a mixed metal oxide forma-

tion seems to be thermally stable even under the FTS reaction by

not being segregated and by forming strong interactions with themesoporous Co3O4 surfaces and the framework structures of the

Al/meso-Co3O4and Al/meso-CoAlOxsufficiently.

In summary, the irreducible Al2O3 modification of the meso-

porous Co3O4 catalysts through the pillaring method or the

formation of mixed metal oxide of mesoporous CoAlOx can suc-

cessfully enhance the catalytic activity and stabilityby maintaining

stable ordered mesopore structures even under the reductive FTS

reaction conditions at a higher space velocity with a simultaneous

suppression of coke or wax deposition on the active cobalt metal

surfaces. The newlyformed strong interactions between Co3O4and

Al2O3particles by partially forming spinel structure of the inactive

CoAl2O4 species were the main reasons for the enhanced struc-

turalstability of the mesoporesof Al-modified Co3O4. Theimproved

structural stability of mesoporous Co3O4 was attributed to thelower mobility and thermal stability of the irreducible Al2O3 pil-

lar by strongly interacting with the inner surfaces of the ordered

mesoporous Co3O4 which were well verified by the surface char-

acterizations such as TEM, XPS and TPR analysis.

4. Conclusions

The FTS activity of the mesoporous Co3O4synthesized through

a well-known nano-casting methodusing the mesoporous KIT-6 as

a hard template was investigated. The mesoporous structures and

the enhanced structural stability of the mesopores after the mod-

ification with an irreducible and thermally stable metal oxide of

Al2O3showed an enhanced catalytic activity with less coke or wax


9/9


deposition on the active sites. These improved activity and struc-

tural stability were mainly attributed to a lower mobility of the

Al2O3modifier by strongly interacting with cobalt particles on the

surfaces of themesoporous Co3O4or in themain frameworks of the

mixed metal oxide of CoAlOx. The formation of an inactive CoAl2O4spinel structure on the Al/meso-Co3O4and Al/meso-CoAlOxseems

to be responsible for maintaining the stable ordered mesoporous

structures even under the reductive FTS reaction conditions. The

irreducible Al2

O3

modification of the mesoporous structures of

Co3O4by pillaringAl2O3on thesurfacesof activecobalt particlesor

byforming mixed metal oxide of mesoporous CoAlOx canbe further

applied forthe FTS reaction working at a higher space velocity with

a lower coke or wax deposition on the active cobalt metal surfaces

due to its ordered mesoporosity and structural stability.

Acknowledgments

This work was also supported by the R&D Center for Valuable

Recycling (Global-Top R&D Program) of the Ministry of Environ-

ment with a project number of GT-14-C-01-038-0. The authors

acknowledge the financial support from the National Research

Foundation of Korea (NRF) grant funded by the Korea government

(NRF-2014R1A1A2A16055557). This work was supported by the

NationalResearchCouncil of Science and Technology(NST) through

Degree and Research Center (DRC) Program (2014). This work was

also supported by the Korea Institute of Energy Technology Evalu-

ation and Planning (KETEP) under Energy Efficiency and Resources

Programs with Project numbers of 20142010102790.

References

[1] T. Tsoncheva, L. Ivanova, J. Rosenholm, M. Linden, Appl. Catal. B: Environ. 89(2009) 365374.

[2] G. Prieto, A. Martizez, R. Murciano, M.A. Arribas, Appl. Catal. A: Gen. 367(2009) 146156.

[3] J.S. Jung, S.W. Kim, D.J. Moon, Catal. Today 185 (2012) 168174.[4] A.Y. Khodakov, W. Chu, P. Fongarland, Chem. Rev. 107 (2007) 16921744.[5] H. Tuysuz, Y. Liu, C. Weidenthaler, F. Schuth, J. Am. Chem. Soc. 130 (2008)

1410814110.

[6] M.Jin, J.N. Park, J.K. Shon, J.H. Kim, Z. Li, Y.K. Park, J.M. Kim, Catal. Today 185(2012) 183190.

[7] D. Zhao, Y. Wan,W. Zhou, Ordered Mesoporous Materials, Wiley-VCH, 2012.

[8] C.I.Ahn, H.M. Koo, M.Jin, J.M. Kim, T. Kim, Y. Suh, K.J. Yoon, J.W. Bae,Microporous Mesoporous Mater. 188 (2014) 196202.

[9] T.W. Kim,F. Kleitz, B.Paul, R. Ryoo, J. Am. Chem. Soc. 127 (2005) 76017610.[10] C.I.Ahn, H.M. Koo, J.M. Jo, H.S. Roh, J.B. Lee, Y.J. Lee, E.J. Jang, J.W. Bae, Appl.

Catal. B: Environ. 180 (2016) 139149.[11] J.W. Bae, S.M. Kim, Y.J. Lee, M.J. Lee, K.W. Jun, Catal. Commun. 10 (2009)

13581362.[12] H. Zhu, R. Razzaq, L. Jiang,C. Li, Catal. Commun. 23 (2012) 4347.[13] D. Schanke, S. Vada, E.A. Blekkan, A.M. Hilmen, A. Hoff, A. Holmen, J. Catal. 156

(1995) 8595.[14] H. Xiong,Y. Zhang, K. Liew, J. Li, J. Mol. Catal. A: Chem. 231 (2005) 145151.

[15] D. Song, J. Li, J. Mol. Catal. A: Chem. 247 (2006) 206212.[16] D.Y. Zhao, Q.S. Huo, J.L. Feng, B.F. Chmelka, N. Melosh, G.H. Fredrikson, G.D.

Stucky, Science 279 (1998) 548552.[17] D.J. Kim, B.C. Dunn, P. Cole, G. Turpin, R.D. Ernst,R.J. Pugmire, M. Kang, J.M.

Kim, E.M. Eyring, Chem. Commun. (2005) 14621464.[18] R.J. Madon,E. Iglesia, J. Catal. 139 (1993) 576590.[19] B.A. Sexton, A.E. Hughes, T.W. Turney, J. Catal. 97 (1986) 390406.[20] J.Y. Luo, M. Meng, X. Li, X.G. Li, Y.Q. Zha, T.D. Hu, Y.N. Xie, J. Zhang, J. Catal. 254

(2008) 310324.[21] G. Melaet, W.T. Ralston, C. Li, S. Alayoglu, K. An, N. Musselwhite,B. Kalkan,

G.A. Somorjai, J. Am. Chem. Soc. 136 (2014) 22602263.[22] K.S. Smith,The Geological Society of America Reviews in Engineering

Geology, vol. XVII, 2007.[23] G.L. Bezemer, J.H. Bitter, H.P.C.E. Kuipers, H. Oosterbeek, J.E. Holewijn, X. Xu,F.

Kapteijn, A. Jos van Dillen, K.P. de Jong, J. Am. Chem. Soc. 128 (2006)39563964.

[24] E. Iglesia, S.L. Soled,R.A. Fiato, J. Catal. 137 (1992) 212224.[25] J.W. Bae, S.J. Park, M.H. Woo, J.Y. Cheon, K.S. Ha, K.W. Jun, D.H. Lee, H.M. Jung,

ChemCatChem3 (2011) 13421347.

[26] I.H. Jang, S.H.Um, B. Lim, M.H.Woo,K.W. Jun, J.B. Lee, J.W. Bae,Appl. Catal. A:Gen. 450 (2013) 8895.

[27] E. Iglesia, Appl. Catal. A: Gen. 161 (1997) 5978.[28] B.S.Lee,H.M.Koo, M.J. Park, B. Lim, D.J. Moon, K.J. Yoon, J.W.Bae,Catal. Lett.

143(2013) 1822.[29] T.V. Reshetenko, L.B. Avdeeva, Z.R. Ismagilov, V.V. Pushkarev, S.V.

Cherepanova, A.L. Chuvilin, V.A. Likholobov, Carbon 41 (2003) 16051615.[30] J.P. den Breejen, P.B. Radstake, G.L. Bezemer, J.H. Bitter, V. Froseth, A. Holmen,

K.P. deJong, J. Am. Chem. Soc. 131 (2009) 71977203.[31] A. Tuxen,S. Carenco, M. Chintapalli, C.H. Chuang, C. Escudero, E. Pach, P. Jiang,

F. Borondics, B. Beberwyck, A.P. Alivisatos, G. Thornton,W.F. Pong, J. Guo, R.Perez, F. Besenbacher, M. Salmeron,J. Am. Chem. Soc. 135 (2013) 22732278.

[32] T. Koh, H.M. Koo, T. Yu, B. Lim, J.W. Bae, ACS Catal. 4 (2014) 10541060.[33] L. Ji, J. Lin, H.C. Zeng, J. Phys. Chem. B 104 (2000) 17831790.[34] J.M. Cho, C.I. Ahn, C. Pang, J.W. Bae, Catal. Sci. Technol. 5 (2015) 35253535.[35] G. Prieto, P. Concepcion, R. Murciano,A. Martinez,J. Catal. 302 (2013)

3748.[36] B. Lee,I.H.Jang, J.W.Bae,S.H. Um, P.J. Yoo, M.J. Park, Y.C.Lee,K.W. Jun, Catal.

Surv. Asia 16 (2012) 121137.[37] Y. Yang, L. Jia, B. Hou, D. Li, J. Wang, Y. Sun,Catal. Sci. Technol. 4 (2014)717728.
http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0190http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0190http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0190http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0190http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0195http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0195http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0195http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0200http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0200http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0205http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0205http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0205http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0220http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0220http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0230http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0230http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0245http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0245http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0260http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0260http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0275http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0275http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0280http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0280http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0295http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0295http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0305http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0305http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0320http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0320http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0345http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0345http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0350http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0350http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0355http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0355http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0360http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0360http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0360http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0370http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0365http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0360http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0360http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0360http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0360http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0360http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0360http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0360http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0360http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0360http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0360http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0360http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0360http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0360http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0360http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0360http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0355http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0355http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0355http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0355http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0355http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0355http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0355http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0355http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0355http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0355http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0355http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0355http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0355http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0355http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0355http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0355http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0350http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0350http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0350http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0350http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0350http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0350http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0350http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0350http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0350http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0350http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0350http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0350http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0350http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0350http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0345http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0345http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0345http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0345http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0345http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0345http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0345http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0345http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0345http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0345http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0345http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0345http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0345http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0345http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0345http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0345http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0340http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0335http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0330http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0325http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0320http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0320http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0320http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0320http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0320http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0320http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0320http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0320http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0320http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0320http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0320http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0315http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0310http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0305http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0305http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0305http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0305http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0305http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0305http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0305http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0305http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0305http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0305http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0305http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0305http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0300http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0295http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0295http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0295http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0295http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0295http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0295http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0295http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0295http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0295http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0295http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0295http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0295http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0295http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0295http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0290http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0285http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0280http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0280http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0280http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0280http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0280http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0280http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0280http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0280http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0280http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0280http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0280http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0280http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0280http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0275http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0275http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0275http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0275http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0275http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0275http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0275http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0275http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0275http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0275http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0270http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0265http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0260http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0260http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0260http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0260http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0260http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0260http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0260http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0260http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0260http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0260http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0260http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0260http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0260http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0260http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0255http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0250http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0245http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0245http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0245http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0245http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0245http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0245http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0245http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0245http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0245http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0245http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0245http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0245http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0245http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0245http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0245http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0240http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0235http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0230http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0230http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0230http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0230http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0230http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0230http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0230http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0230http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0230http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0230http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0230http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0230http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0230http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0230http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0230http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0230http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0225http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0220http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0220http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0220http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0220http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0220http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0220http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0220http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0220http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0220http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0220http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0220http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0215http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0210http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0205http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0205http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0205http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0205http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0205http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0205http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0205http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0205http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0205http://refhub.elsevier.com/S0920-5861(15)00660-4/sbref0

Fischer–Tropsch Synthesis on the Al2O3-Modified Ordered

Documents

Transcript of Fischer–Tropsch Synthesis on the Al2O3-Modified Ordered