Impact of Macroporosity on Catalytic Upgrading of Fast Pyrolysis Bio-Oil by Esterification over Silica Sulfonic Acids

Article abstract of DOI:10.1002/cssc.201700959

Fast pyrolysis bio-oils possess unfavorable physicochemical properties and poor stability, in large part, owing to the presence of carboxylic acids, which hinders their use as biofuels. Catalytic esterification offers an atom- and energy-efficient route to upgrade pyrolysis bio-oils. Propyl sulfonic acid (PrSO₃H) silicas are active for carboxylic acid esterification but suffer mass-transport limitations for bulky substrates. The incorporation of macropores (200 nm) enhances the activity of mesoporous SBA-15 architectures (post-functionalized by hydrothermal saline-promoted grafting) for the esterification of linear carboxylic acids, with the magnitude of the turnover frequency (TOF) enhancement increasing with carboxylic acid chain length from 5 % (C₃) to 110 % (C₁₂). Macroporous–mesoporous PrSO₃H/SBA-15 also provides a two-fold TOF enhancement over its mesoporous analogue for the esterification of a real, thermal fast-pyrolysis bio-oil derived from woodchips. The total acid number was reduced by 57 %, as determined by GC×GC–time-of-flight mass spectrometry (GC×GC–ToFMS), which indicated ester and ether formation accompanying the loss of acid, phenolic, aldehyde, and ketone components.

Full text of DOI:10.1002/cssc.201700959

Accepted Article
Title: Impact of macroporosity on catalytic upgrading of fast pyrolysis
bio-oil by esterification over silica sulfonic acids
Authors: Jinesh Manayil, Amin Osatiashtiani, Alvaro Mendoza,
Christopher Parlett, Lee Durndell, Mark Isaacs, Chrysoula
Michailof, Eleni Heracleous, Angelos Lappas, Adam Lee, and
Karen Wilson
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: ChemSusChem 10.1002/cssc.201700959
Link to VoR: http://dx.doi.org/10.1002/cssc.201700959
A Journal of
www.chemsuschem.org

ChemSusChem
10.1002/cssc.201700959
Communication
Impact of macroporosity on catalytic upgrading of fast pyrolysis
bio-oil by esterification over silica sulfonic acids
a
a
a,b
a
Jinesh C. Manayil , Amin Osatiashtiani , Alvaro Mendoza , Christopher M.A. Parlett , Mark A. Isaacs
a
a
c
c
c
a
,
Lee J. Durndell , Chrysoula Michailof , Eleni Heracleous , Angelos Lappas , Adam F. Lee , Karen
a
Wilson *
Abstract:
Fast
pyrolysis
bio-oils
possess
unfavourable
Pyrolysis is a widespread approach for bio-oil[4] synthesis,
in which biomass is thermally decomposed in an oxygen-free or
oxygen-limited environment.[5] The resulting crude bio-oil is a
complex mixture of acids, alcohols, furans, aldehydes, esters,
ketones, sugars and multifunctional compounds such as
hydroxyacetic acid, hydroxyl-acetaldehyde and hydroxyacetone
(derived from cellulose and hemicellulose), together with 3-
hydroxy-3-methoxy benzaldehyde, phenols, guaiacols and
syringols derived from the lignin component.[1b, 6] Pyrolysis bio-oils
thus require ‘upgrading’ through deoxygenation and neutralisation
to enhance their energy density, stability and physical
properties.[6a, 7] A range of catalytic upgrading methods are
known,[8] at least at laboratory scale, including esterification,
physicochemical properties and poor stability, due in large part to the
presence of carboxylic acids, which hinders their use as biofuels.
Catalytic esterification offers an atom and energy efficient route to
upgrade pyrolysis bio-oils. Propyl sulfonic acid silicas are active for
carboxylic acid esterification but suffer mass-transport limitations for
bulky substrates. Macropore (200 nm) incorporation enhances the
activity of mesoporous SBA-15 architectures (post-functionalised by
hydrothermal saline promoted grafting) for the esterification of linear
carboxylic acids, with the magnitude of turnover frequency (TOF)
enhancement increasing with chain length from 5 % (C
3
) to 110 %
(C12). Macroporous-mesoporous PrSO H/SBA-15 also offers a two-
3
[9]
fold TOF enhancement over its mesoporous analogue for the
esterification of a real, thermal fast pyrolysis bio-oil derived from
woodchips. The total acid number was reduced by 57 %, with
GCxGC-ToFMS evidencing ester and ether formation accompanying
loss of acid, phenolic, aldehyde and ketone components.
ketonisation,[ hydrodeoxygenation, and condensation.
10]
[11]
[12]
Carboxylic acids comprise 5-10 wt% of pyrolysis bio-oils,[9,
and are largely responsible for their poor chemical stability,
1
3]
hence esterification (particularly employing bio-derived alcohols
such as methanol, ethanol or phenols[ ) offers an energy efficient
and atom-economical route to upgrading.[8b, 15] Homogeneous
mineral acid catalysts are historically employed for esterification,
however their process disadvantages and poor (environmental)
E-factors are well-documented, hence strong drivers remain for
the development of heterogeneous solid acid counterparts.[
Note that while base catalysts are widely used for the
transesterification of vegetable oils (triacylglycerides) to yield
biodiesel, they are unsuitable for catalytic esterification due to
neutralisation/saponification.[1d]
14]
Introduction
Biofuels have an important role to play in mitigating
anthropogenic climate change arising from the combustion of
fossil fuels.[1] In the context of energy, despite significant growth
in fossil fuel reserves, great uncertainties remain in the
economics/environmental impact of exploitation, and crucially
11]
~65-80 % of such carbon resources cannot be burned without
Diverse solid acids have been explored for esterification,
breaching the UNFCC targets for a 2 °C increase in mean global
temperature. Biofuels will prove critical in helping many countries
meet their renewable energy commitments, which for the UK are
including zeolites,[16]
,
heteropolyacids, [17], sulfated metal
oxides[ , carbon-based acid catalysts
18]
[19]
and functionalized
mesoporous silicas[20]. Research on the latter indicates that
mesoporous SBA-15[21], KIT-6[22], and PMO[23] sulfonic acids, and
a macro-mesoporous SBA-15 (MM-SBA-15)[20g] analogue, are
among the most promising due to their tunable pore architecture
strong Brønsted acidity and hydrophobicity.[2a, 14a, 20g, 23-24] 3-
15 % by 2020, alongside greenhouse gas (GHG) emission
reductions of 34 % by 2020 and 80 % by 2050 (cf. 1990 levels).
They also represent drop-in fuels able to utilise existing pipeline
and filling station distribution networks.[2] Thermochemical
processing of waste biomass such as lignocellulosic materials
sourced from agriculture or municipal waste offers a promising
route to biofuels through pyrolysis.[3]
3
Propylsulfonic acid (PrSO H)/SBA-15 is reported an efficient
[
2a, 25]
catalyst for acetic acid esterification with methanol
and other
alcohols in simulated bio-oils,[
26]
and the most widely used
sulfonic acid in solid acid catalysed esterification.[27] Such
catalysts exhibit improved water tolerance during esterification
[
a]
Dr Jinesh C. Manayil, Dr Amin Osatiashtiani, Mr. Alvaro Mendoza, Dr
Christopher M.A. Parlett, Dr. Mark A. Isaacs, Dr Lee J. Durndell, Prof
Adam F. Lee, Prof Karen Wilson. European Bioenergy Research
Institute, Aston University, Birmingham, B4 7ET, UK.
when the sulfonated silica surface is co-functionalised with alkyl
chains.[
2a, 5, 25b]
We recently reported a post-modification
E-mail: k.wilson@aston.ac.uk
[
[
b]
c]
Mr. Alvaro Mendoza, Department of Chemical and Energy Technology,
Universidad Rey Juan Carlos, C/Tulipꢀn s/n, E-28933 Mꢁstoles, Madrid,
Spain.
Dr Chrysoula Michailof, Dr Eleni Heracleous, Dr Angelos Lappas,
Chemical Process & Energy Resources Institute Centre for Research
and Technology-Hellas (CPERI/CERTH) 6th km Harilaou-Thermi Road,
Hydrothermal Saline Promoted Grafting (HSPG) route to
introduce higher sulfonic acid loadings into mesoporous silicas
than achievable by conventional grafting methods,[24a] and confer
stability towards leaching during the esterification of model
acids.[24b, 28] Hydrophobicity, and catalytic reactivity, can also be
enhanced through incorporating organic groups into the silica
framework.[24b] Mesopore interconnectivity also plays a role in
controlling esterification activity, with interconnectivity between
57001, Thessaloniki, Greece.
Supporting information for this article is given via a link at the end of the
document.
These authors contributed equally to this work.
[]
3
the hexagonal cylindrical mesopores of PrSO H/KIT-6 offering
This article is protected by copyright. All rights reserved.

ChemSusChem
10.1002/cssc.201700959
Communication
superior mass transport and active site accessibility to non-
DRIFT spectra of the parent silicas showed bands at 700-
1400 cm-1 and 3000-3800 cm-1 indicative of framework Si-O-Si
and surface silanols respectively (Fig. S5).[15] Additional bands
appeared after sulfonation of both materials around 2960-2830
interconnected PrSO
5 to 14 nm),[14a] and macropore incorporation[23] offer alternative
approaches to enhance the esterification activity of PrSO H/SBA-
5 for long chain fatty acid esterification.
With respect to bio-oil upgrading through catalytic
H/SBA-15.[20g] Mesopore expansion (from
3
~
3
-1
1
cm , attributable to CH
new CH -Si band centred at 1360 cm . CHNS elemental analysis
of the sulfonated silicas revealed that both contained ~6 wt%
sulfur (Table 1) representing five-fold increase over
in good agreement with our
2
vibrations of the propyl backbone, and a
-1
2
esterification, most studies have employed only model
compounds due to the complex nature of real pyrolysis bio-oils[7a]
and associated analytical challenge. We previously reported the
a
conventional toluene grafting,[
14a, 23]
application of PrSO
model bio-oils.[26, 28] Here, we report the synthesis and application
of HSPG-derived mesoporous PrSO H/SBA-15, and
macroporous counterpart, for the esterification of simple
carboxylic acids (C , C and C12), and the upgrading of thermal
fast pyrolysis bio-oil derived from woodchips.
Results and discussion
Catalyst characterisation
3
H/SBA-15 for acetic acid esterification of
preliminary discovery of the HSPG method.[24a] Sulfur 2p XP
spectra of both sulfonic acid-functionalised materials in Fig S6
reveal two distinct S chemical environments; a low binding energy
centred at 164.5 eV associated with unoxidised thiol, and a higher
energy doublet arising from sulfonic acid groups centred at 168.9
eV.[30] Quantitative XPS analysis (Table S4) shows that ~85 % of
S was incorporated as sulfonic acid groups. Thermogravimetric
analysis (Fig S7b) highlighted two major weight losses; one below
3
a
3
6
1
2
00 °C attributed to physisorbed water; and the second between
50-650 °C due to propylsulfonic acid decomposition.[31] The bulk
S content estimated from this second loss feature was ~5 wt% in
accordance with elemental analysis. Acid properties of both
sulfonated silica were subsequently probed through pyridine and
propylamine adsorption. DRIFT spectra of pyridine titrated
materials (Fig S8) evidenced only Brønsted acid sites.[26]
Temperature-programmed analysis of reactively-formed propene
Successful synthesis of an ordered mesoporous and macro-
mesoporous (MM) skeleton for the SBA-15 and MM-SBA-15
supports was confirmed by TEM. An ordered, two dimensional
hexagonal mesopore channel network was observed for the
former (Fig. S1), and a well-defined interconnecting macro-
mesopore network for the latter (with a mean macropore diameter
from chemisorbed propylamine confirmed that PrSO
3
H/SBA-15
and PrSO H/MM-SBA-15 possessed similar acid strengths and
3
loadings (Fig S9 and Fig S10). We can thus conclude that the
incorporation of macropores into the SBA-15 architecture had
minimal impact on silica functionalisation; the propylsulfonic acid
~200nm, close to that of the polystyrene colloidal hard template,
Fig. S2). Formation of the desired p6mm pore architecture for
both SBA-15 and MM-SBA-15 was confirmed by low angle X-ray
diffraction (Fig S3) which revealed reflections characteristic of
hexagonally ordered mesostructures. Both supports retained
hexagonal close packed pore architectures following
functions grafted over silica surfaces in PrSO
3
H/SBA-15 and
PrSO H/MM-SBA-15 catalysts were chemically identical. Any
3
differences in TOFs between the two catalysts must therefore
arise solely from diffusion phenomena. However, despite their
similar acid site loadings, the surface coverage of acid sites was
higher over the macroporous material (which possessed a lower
surface area). Note that the higher S loadings accessible through
2
functionalisation by propylsulfonic acid in a H O/NaCl mixture (the
HSPG method). However, a shift in diffraction peaks to higher
angle is observed post-functionalisation due to mesopore
contraction.[23] Mesopore generation (and retention after
-1
the HSPG method offer acid loadings around 1.5 mmol g ,
-1
approximately twice those (0.6-0.8 mmol g ) obtained through
sulfonic acid grafting in toluene.[2a] Molecular dynamics
simulations and adsorption calorimetry reveal that cooperative
effects between silanol and sulfonic acid functions can weaken
sulfonation) was further evidenced by N
showed type IV isotherms with H1 hysteresis loops for all
materials (Fig S4). Textural properties of PrSO H/SBA-15 and
PrSO H/MM-SBA-15 are summarised in Table 1. BET surface
2
porosimetry which
3
3
their acidity in PrSO
3
H/MCM-41 due to hydrogen bonding and
areas decreased after sulfonic acid grafting over both silicas due
to micropore blockage, apparent as a dramatic drop in micropore
area and pore volume. These changes are accompanied by a
decrease in pore diameter and increase in wall thickness,
suggesting the uniform grafting of sulfonic acid groups throughout
both pore networks without distortion of their unit cells. Previous
studies have shown the macropores in such hierarchical
frameworks are open and interconnected by bottleneck pore
openings.[23] [29]
associate sulfonate reorientation.[ However, such effects only
operate for low sulfonic acid loadings, and are absent on crowded
surfaces such as those employed in this work, hence cooperative
effects are not expected to influence catalytic performance.
32]
Esterification of model carboxylic acids
The catalytic performance of mesoporous and
macroporous-mesoporous sulfonic acid silicas was evaluated in
3 6
the esterification of propanoic (C ), hexanoic (C ) and lauric acids
Table 1. Physicochemical properties of mesoporous SBA-15 and macroporous-mesoporous SBA-15 and their sulfonic acid analogues.
Unit cell
parameter
Surface area a
d
b
V
V
c
Wall thickness
S loading d
Acid loadinge
p
total
-1
micropore
Sample
2
-1
-1
-1
/
nm
5.5
3.8
4.5
3.4
/ nm
5.5
7.3
5.9
7.2
/ nm
/ wt%
/
m .g
/ cc.g
1.17
0.49
0.55
0.24
/ cc.g
0.08
0.01
0.02
0.00
/ mmol.g
SBA15
879
379
357
186
11.0
11.1
9.0
-
-
PrSO
MM-SBA-15
PrSO H/MM-SBA-15
3
H/SBA15
5.8
-
1.5
-
3
9.2
5.5
1.6
a
BET, b BJH, c t-plot, d CHNS, e propylamine adsorption/TGA-MS.
This article is protected by copyright. All rights reserved.

ChemSusChem
10.1002/cssc.201700959
Communication
(
C
12) with methanol to explore the influence of macropores on
50
[2a]
reactivity under previously optimised conditions.
Since both
Propanoic acid
catalysts possess similar acid loadings and strength, any
differences in activity must arise from their pore architecture. Both
sulfonic acid catalysts were active for methylic esterification of the
Hexanoic acid
Lauric acid
3
SO H
40
30
20
10
0
HO
3
S
SO
3
H
3
SO H
SO
3
H
HO S
3
C
3
, C
6
and C12 acids (Fig S11) which were 100 % selective to their
3
HO S
HO
3
S
SO3
H
HO
3
S
HO
3
S
SO
3
H
OH
corresponding methyl esters. The rate of esterification
decreasedwith increasing alkyl chain length due to polar and
steric effects.[
HO
3
S
SO
3
H
HO3
S
HO3
S
HO
3
S
OH
SO
OH
SO
3
H
HO
3
S
3
SO H
SO
3
H
HO
3
S
SO
3
H
SO3
H
HO
3
S
OH
3
OH
SO
SO3
H
S
SO H
SO
3
H
SO
3
H
HO3
SO
3
H
HO
3
S
SO3
H
3
H
3
H
33]
OH
SO H
3
SO3H
OH
The associated turnover frequencies (TOFs) for carboxylic
acid esterification were similar over the both catalysts for the C
and C acids (Fig 1), whereas the TOF for lauric acid over the
hierarchical PrSO H/MM-SBA-15 was twice that observed for the
purely mesoporous PrSO H/SBA-15 (Fig S12). This rate
3
6
3
3
enhancement for the bulky lauric acid esterification is readily
explicable in terms of improved sulfonic acid accessibility through:
(
i) faster in-pore diffusion of the reactant/ester product; (ii) shorter
mesopore channel lengths due to truncation by macropores; and
(
iii) an increased number of mesopore openings which may boost
the sulfonic acid density at mesopore entrances.[23]
MM-SBA-15
SBA-15
Fig 1. TOF for esterification of various carboxylic acids over PrSO
and PrSO
mmol acid, acid:MeOH molar ratio= 1:30, 60 °C)
3
H/SBA-15
3
H/MM-SBA-15 catalysts. (Reaction conditions: 25 mg catalyst, 5
Esterification of thermal pyrolysis bio-oil
The performance of both sulfonic acid silicas was also
assessed for the upgrading of a bio-oil produced via thermal fast
pyrolysis of oak woodchips in a bench-scale, continuous fluidised
bed reactor at 500 °C. Some physicochemical properties of the
parent biomass feedstock are presented in Table S1, and of the
crude bio-oil in Table S2. Note that while the bio-oil possessed a
similar calorific value to the woodchips, the volumetric energy
density of the former is significantly higher than the original
50
40
30
20
10
0
6
4
0
0
-3
20
0
biomass whose density was only 600-900 kg.m . The bio-oil
contained 23 wt% water, typical of fast pyrolysis bio-oil.[6b, 34],
although the total acid number (TAN) measured by the Modified
[
35]
-1
D664A acid number titration method
relatively low.[34]
of 61.6 mg KOH g was
0
2
4
6
Reaction time / h
Fig. 2 compares TOFs for total acid removal (as determined
by KOH titration) via catalytic esterification with methanol, and the
corresponding reaction profiles for total acid conversion (Fig. 2
inset). The PrSO
more active in terms of TOF, and converted twice the amount of
acid after 6 h, than the PrSO H/SBA-15. Since the pyrolysis oil
contains numerous bulky compounds as described in Tables 2-3
and Table S3) we attribute the superior performance of the
3
H/MM-SBA-15 catalyst was almost three times
3
(
hierarchical catalyst to improved active site accessibility akin to
that for lauric acid esterification. Note that carboxylic acid
constituents of fast pyrolysis bio-oils may drive low level (<5 %)
autocatalytic esterification.[36] This was consistent with a control
experiment in the absence of any sulfonic acid catalyst which
revealed <8 % total acid conversion of the pyrolysis bio-oil, and
hence autocatalysis exerted minimal impact on our results.
The chemical composition of the crude and upgraded bio-
MM-SBA-15
SBA-15
Fig 2. Effect of support architecture on the TOFs of sulfonic acid catalysed bio-
oil esterification. Inset: acid conversion profiles for bio-oil esterification using
sulfonic acid catalysts. (Reaction conditions: 9.2 g bio-oil ≈ 10 mmol acid, 12.1
ml MeOH (Acid:MeOH molar ratio= 1:30), 100 mg catalyst, 85 °C)
as ‘unidentified’. A more detailed classification of each molecular
group and their relative chromatographic area is presented in
Table 2. Almost complete loss of organic acids (from 19.7 to
0.9 %) and a significant decrease in phenolics, ketones,
aldehydes and sugars was observed following catalytic upgrading,
accompanied by a significant increase in ester and alcohol
components, consistent with esterification. Additional detail on the
removal/formation of specific phenolics, ethers and carbonyls is
presented in Table S3. Acetic acid was the major organic acid in
both crude and upgraded bio-oils. Esters with relative areas >0.1
in the crude and upgraded bio-oils are presented in Table 3.
3
oil following catalytic treatment by PrSO H/MM-SBA-15 were
analysed in detail by GCxGC-ToFMS, with resulting 2D
chromatograms shown in Fig. 3. For both crude and upgraded
bio-oils the chromatographic space was divided into six discreet
molecular groups: acids and esters; aldehydes and ketones
(
(
including furanoics and cyclic carbonyls); hydrocarbons
saturated and unsaturated non-aromatic); aromatic
hydrocarbons; phenolic compounds; and sugars. Compounds
that could not be identified by the library and/or did not meet the
required identification criteria (as detailed in ESI) were classified
This article is protected by copyright. All rights reserved.

ChemSusChem
10.1002/cssc.201700959
Communication
Table 3. Esters present in crude and upgraded thermal fast pyrolysis bio-oils
following treatment with PrSO
3
H/MM-SBA-15 catalyst.
Aldehydes & Levoglucosan
Crude bio-oil
Esterified bio-oil
ketones
Sugars
Phenolic
derivatives
Acetic acid, methyl ester
Acetic acid, methyl ester
Butanedioic acid, dimethyl ester
Hexanoic acid, methyl ester
9-Octadecenoic acid (Z)-, methyl ester
Butanedioic acid, methyl-, dimethyl ester
Methyl propionate
Formic acid, 2-propenyl ester
Ethanedioic acid, diethyl ester
Propanoic acid, ethenyl ester
Ethyl homovanillate
Octanoic acid, methyl ester
Benzene derivatives
Levulinic acid, methyl ester
Nonanoic acid, methyl ester
Hydrocarbons
Acids
Methyl acetate accounts for 10.8 % of the total chromatographic
area of the esterified bio-oil, as compared to only 1.4 % of the
crude bio-oil, alongside a range of methyl and dimethyl esters
Acetic acid
(a)
from C
methoxy-compounds,
3
-C11 compounds. Identifiable ethers were mainly C
3 6
-C
0
2000
4000
6000
1st dimension / s
with 1,1,2,2-tetramethoxyethane
predominant. Considering phenolics, upgrading principally
removed methoxy-phenols, whereas cresol and catechol
derivatives were recalcitrant. The increase in alcohols appears to
arise from glycolaldehyde dimethyl acetal (GDA) formation from
levoglucosan.[37] Previous studies reveal that levoglucosan can be
transformed in alcohol media by acid catalysts to methyl levulinate,
through intermediate glycolaldehyde (GA) formation[ (which
may itself form glycolaldehyde dimethyl acetal). GA and GDA
were detected in the upgraded bio-oil, supporting this proposed
reaction pathway. Future work will address the recyclability of
Aldehydes &
ketones
Levoglucosan
Sugars
Phenolic
derivatives
38]
Benzene derivatives
Hydrocarbons
3
PrSO H/MM-SBA-15 for the esterification of real bio-oils, wherein
we expect strong adsorption of organics that will require the
development of low temperature regeneration protocols that avoid
decomposition of the grafted sulfonate.
Acids
In summary, GCxGC-ToFMS analysis confirmed that
PrSO H/MM-SBA-15 was an effective catalyst for the
3
Methyl acetate Acetic acid
(b)
esterification of a real thermal pyrolysis bio-oil, significantly
reducing the bio-oil acidity through esterification of organic acids
under mild reaction conditions.
0
2000
4000
6000
1st dimension / s
Figure 3. GCxGC-ToFMS chromatogram of a) crude thermal fast pyrolysis bio-
oil and b) bio-oil after esterification over PrSO H/MM-SBA-15.
3
Conclusions
Table 2. Compositions of crude and upgraded bio-oils following treatment with
PrSO H/MM-SBA-15 catalyst.
3
Mesoporous and hierarchical macroporous-mesoporous propyl
sulfonic acid silicas were synthesised by hydrothermal saline
promoted grafting of the pre-formed architectures. Textural
properties of the parent silicas were unperturbed by sulfonation,
which resulted in similar sulfonic acid loadings and strengths for
both pore networks. Turnover frequencies for catalytic
Crude bio-oil
Upgraded bio-oil
/ Area%
Group
/
Area%
Aromatic hydrocarbons
Aliphatic hydrocarbons
Phenolic compounds
Furanic compounds
Organic acids
Esters
1.8
0.4
1.9
2.1
25.8
0.6
7.8
3
esterification of model C -C12 carboxylic acids with methanol
1.4
decreased with alkyl chain length over both materials, however
the introduction of 200 nm macropores into the SBA-15
framework doubled the activity per acid site for the bulkiest lauric
acid, attributed to enhanced mass transport and active site access,
19.7
1.9
0.9
11.8
26.1
6.5
Alcohols
1.1
3
and a higher -PrSO H surface density. Macropore incorporation
Ethers
1.0
also enhanced esterification activity for the upgrading of a real
bio-oil derived from thermal fast pyrolysis of oak woodchips; the
TOF for total organic acid removal increased three-fold relative to
the mesoporous sulfonic acid silica, again attributed to superior
in-pore mass transport and active site accessibility. The total acid
number was reduced by 57 % over 6 h reaction at 85 °C using the
Aldehydes
5.2
0.4
Ketones
10.8
26.6
5.3
2.9
Sugars and anhydro sugars
Unidentified
13.5
24.7
3
hierarchical PrSO H/MM-SBA-15 catalyst. GCxGC-ToFMS
confirmed that catalytic upgrading removed almost all organic
This article is protected by copyright. All rights reserved.

ChemSusChem
10.1002/cssc.201700959
Communication
acids, and significantly lowered the concentration of reactive,
phenolic, aldehyde and ketone components, accompanied by the
formation of carboxylic acids methyl esters and ethers.
[11] K. Wilson, A. F. Lee, Catalysis Science & Technology 2012, 2, 884-897.
[
12] a) T. C. Keller, E. G. Rodrigues, J. Pérez-Ramírez, ChemSusChem 2014,
, 1729-1738; b) E. G. Rodrigues, T. C. Keller, S. Mitchell, J. Perez-
7
Ramirez, Green Chemistry 2014, 16, 4870-4874.
[13] C. A. Mullen, A. A. Boateng, N. M. Goldberg, I. M. Lima, D. A. Laird, K.
B. Hicks, Biomass and Bioenergy 2010, 34, 67-74.
Experimental
[14] a) J. P. Dacquin, A. F. Lee, C. Pirez, K. Wilson, Chemical
Communications 2012, 48, 212-214; b) L. Ciddor, J. A. Bennett, J. A.
Hunns, K. Wilson, A. F. Lee, Journal of Chemical Technology and
Biotechnology 2015, 90, 780-795.
Full details of the catalyst synthesis, bulk and surface characterisation
(TEM, XRD,
N
2
porosimetry, DRIFTS, XPS, TGA, pyridine
[
[
15] C. Pirez, K. Wilson, A. F. Lee, Green Chemistry 2014, 16, 197-202.
16] a) A. Corma, H. Garcia, S. Iborra, J. Primo, Journal of Catalysis 1989,
adsorption/DRIFTS, propylamine adsorption/TGA-MS), and catalytic
esterification and bio-oil analysis protocols are provided in the ESI.
120, 78-87; b) J. Bedard, H. Chiang, A. Bhan, Journal of Catalysis 2012,
90, 210-219; c) M. Milina, S. Mitchell, J. Pérez-Ramírez, Catalysis
2
Today 2014, 235, 176-183; d) J. Peng, P. Chen, H. Lou, X. Zheng,
Bioresource Technology 2009, 100, 3415-3418; e) B. M. Chandra
Shekara, C. Ravindra Reddy, C. R. Madhuranthakam, B. S. Jai Prakash,
Y. S. Bhat, Industrial & Engineering Chemistry Research 2011, 50, 3829-
Acknowledgement
We thank the EPSRC for financial support (EP/K000616/2, EP/G007594/4,
EP/K036548/2 and EP/N009924/1) and the award of a Leadership
Fellowship to AFL. KW thanks the Royal Society for an Industry Fellowship.
The British Council is also acknowledged for funding through the Newton
Institutional Links scheme. Support from the European Union Seventh
Framework Programme (FP7/2007–2013) under grant agreement no.
3
835; f) K. Y. Nandiwale, S. K. Sonar, P. S. Niphadkar, P. N. Joshi, S. S.
Deshpande, V. S. Patil, V. V. Bokade, Applied Catalysis A: General 2013,
60–461, 90-98.
4
[17] a) K. Srilatha, T. Issariyakul, N. Lingaiah, P. S. Sai Prasad, J. Kozinski,
A. K. Dalai, Energy & Fuels 2010, 24, 4748-4755; b) X. Duan, Y. Liu, Q.
Zhao, X. Wang, S. Li, Rsc Advances 2013, 3, 13748-13755; c) S. Singh,
A. Patel, Journal of Cleaner Production 2014, 72, 46-56.
6
04307 is also greatly acknowledged. Underpinning data can be found at
0.17036/researchdata.aston.ac.uk.
[
18] a) K. Arata, Green Chemistry 2009, 11, 1719-1728; b) B. M. Reddy, M.
K. Patil, Chemical Reviews 2009, 109, 2185-2208; c) X.-R. Chen, Y.-H.
Ju, C.-Y. Mou, The Journal of Physical Chemistry C 2007, 111, 18731-
1
1
8737; d) D. Rattanaphra, A. P. Harvey, A. Thanapimmetha, P.
Keywords: mesoporous silica • sulfonic acid • esterification •
bio-oil • acidity • pore architecture
Srinophakun, Renewable Energy 2011, 36, 2679-2686.
[
19] a) F. Liu, J. Sun, L. Zhu, X. Meng, C. Qi, F.-S. Xiao, Journal of Materials
Chemistry 2012, 22, 5495-5502; b) R. P. Rocha, M. F. R. Pereira, J. L.
Figueiredo, Catalysis Today 2013, 218–219, 51-56; c) H. Yu, Y. Jin, Z.
Li, F. Peng, H. Wang, Journal of Solid State Chemistry 2008, 181, 432-
Reference
4
38; d) M. Hara, T. Yoshida, A. Takagaki, T. Takata, J. N. Kondo, S.
Hayashi, K. Domen, Angewandte Chemie International Edition 2004, 43,
955-2958.
[
1]
a) T. F. Stocker, D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung,
A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.), Cambridge, United
Kingdom and New York, NY, USA; b) C. A. Mullen, A. A. Boateng, Energy
2
[
20] a) I. K. Mbaraka, B. H. Shanks, Journal of Catalysis 2005, 229, 365-373;
b) J. A. Melero, L. F. Bautista, G. Morales, J. Iglesias, D. Briones, Energy
&
Fuels 2008, 22, 2104-2109; c) J. N. Chheda, G. W. Huber, J. A.
Dumesic, Angewandte Chemie International Edition 2007, 46, 7164-
183; d) A. F. Lee, J. A. Bennett, J. C. Manayil, K. Wilson, Chemical
&
Fuels 2008, 23, 539-547; c) I. K. Mbaraka, D. R. Radu, V. S. Y. Lin, B.
H. Shanks, Journal of Catalysis 2003, 219, 329-336; d) J. J. Woodford,
J.-P. Dacquin, K. Wilson, A. F. Lee, Energy & Environmental Science
7
Society Reviews 2014, 43, 7887-7916.
2
012, 5, 6145-6150; e) A. Martin, G. Morales, F. Martinez, R. van
Grieken, L. Cao, M. Kruk, Journal of Materials Chemistry 2010, 20, 8026-
035; f) A. Vinu, N. Gokulakrishnan, V. V. Balasubramanian, S. Alam, M.
P. Kapoor, K. Ariga, T. Mori, Chemistry – A European Journal 2008, 14,
1529-11538; g) C. Pirez, J.-M. Caderon, J.-P. Dacquin, A. F. Lee, K.
[
[
2]
3]
a) K. Wilson, A. F. Lee, Phil. Trans. R. Soc. A 2016, 374, 20150081; b)
A. F. Lee, K. Wilson, Catalysis Today 2015, 242, Part A, 3-18; c) G. W.
Huber, A. Corma, Angewandte Chemie International Edition 2007, 46,
8
7
184-7201; d) G. W. Huber, S. Iborra, A. Corma, Chemical Reviews 2006,
06, 4044-4098.
1
1
Wilson, Acs Catalysis 2012, 2, 1607-1614.
a) M. Stöcker, Angewandte Chemie International Edition 2008, 47, 9200-
211; b) D. Carpenter, T. L. Westover, S. Czernik, W. Jablonski, Green
[
[
21] A. Alcala, A. V. Bridgwater, Fuel 2013, 109, 417-426.
22] S. Xiu, A. Shahbazi, Renewable and Sustainable Energy Reviews 2012,
9
Chemistry 2014, 16, 384-406.
1
6, 4406-4414.
23] J. Dhainaut, J.-P. Dacquin, A. F. Lee, K. Wilson, Green Chemistry 2010,
2, 296-303.
[
[
4]
5]
S. Czernik, A. V. Bridgwater, Energy & Fuels 2004, 18, 590-598.
A. Alcala, A. V. Bridgwater, A. Alcala, A. V. Bridgwater, blends of
biodiesel and pyrolysis oil 2014, 109, 417-426.
[
[
1
24] a) C. Pirez, A. F. Lee, J. C. Manayil, C. M. A. Parlett, K. Wilson, Green
Chemistry 2014, 16, 4506-4509; b) C. Pirez, M. T. Reche, A. F. Lee, J.
C. Manayil, V. C. dos-Santos, K. Wilson, Catalysis Letters 2015, 145,
[
[
6]
7]
a) Q. Zhang, J. Chang, T. Wang, Y. Xu, Energy Conversion and
Management 2007, 48, 87-92; b) D. Mohan, C. U. Pittman, P. H. Steele,
Energy & Fuels 2006, 20, 848-889.
1483-1490.
a) P. M. Mortensen, J. D. Grunwaldt, P. A. Jensen, K. G. Knudsen, A. D.
Jensen, Applied Catalysis A: General 2011, 407, 1-19; b) I. Graça, J. M.
Lopes, H. S. Cerqueira, M. F. Ribeiro, Industrial & Engineering Chemistry
Research 2013, 52, 275-287.
[
25] a) S. Miao, B. H. Shanks, Journal of Catalysis 2011, 279, 136-143; b) M.
V. Opanasenko, W. J. Roth, J. Cejka, Catalysis Science & Technology
2
016, 6, 2467-2484.
26] J. C. Manayil, C. V. M. Inocencio, A. F. Lee, K. Wilson, Green Chemistry
016, 18, 1387-1394.
[
[
[
[
[
8]
9]
a) S. Zhang, Y. Yan, T. Li, Z. Ren, Bioresource Technology 2005, 96,
2
545-550; b) A. H. Zacher, M. V. Olarte, D. M. Santosa, D. C. Elliott, S. B.
27] A. F. Lee, K. Wilson, in Handbook of Green Chemistry, Wiley-VCH
Verlag GmbH & Co. KGaA, 2010.
Jones, Green Chemistry 2014, 16, 491-515.
[
[
L. Ciddor, J. A. Bennett, J. A. Hunns, K. Wilson, A. F. Lee, Journal of
Chemical Technology and Biotechnology 2015, 90, 780-795.
28] J. C. Manayil, V. C. dos Santos, F. C. Jentoft, M. Granollers Mesa, A. F.
Lee, K. Wilson, ChemCatChem 2017, n/a-n/a.
10] a) C. M. A. Parlett, K. Wilson, A. F. Lee, Chemical Society Reviews 2013,
2, 3876-3893; b) C. A. Gärtner, J. C. Serrano-Ruiz, D. J. Braden, J. A.
Dumesic, ChemSusChem 2009, 2, 1121-1124.
29] a) Z.-Y. Yuan, B.-L. Su, Journal of Materials Chemistry 2006, 16, 663-
4
677; b) C. M. A. Parlett, M. A. Isaacs, S. K. Beaumont, L. M. Bingham,
N. S. Hondow, K. Wilson, A. F. Lee, Nat Mater 2016, 15, 178-182.
This article is protected by copyright. All rights reserved.

ChemSusChem
10.1002/cssc.201700959
Communication
[
[
[
[
[
[
[
30] P. F. Siril, N. R. Shiju, D. R. Brown, K. Wilson, Applied Catalysis A:
General 2009, 364, 95-100.
31] X. Wang, S. Cheng, J. C. C. Chan, The Journal of Physical Chemistry C
2007, 111, 2156-2164.
32] J.-P. Dacquin, H. E. Cross, D. R. Brown, T. Duren, J. J. Williams, A. F.
Lee, K. Wilson, Green Chemistry 2010, 12, 1383-1391.
33] A. Osatiashtiani, L. J. Durndell, J. C. Manayil, A. F. Lee, K. Wilson, Green
Chemistry 2016, 18, 5529-5535.
34] A. Oasmaa, B. van de Beld, P. Saari, D. C. Elliott, Y. Solantausta, Energy
&
Fuels 2015, 29, 2471-2484.
35] S. H. Roby, M. Dutta, Y. Zhu, A. Pathiparampil, Energy & Fuels 2015, 29,
58-862.
8
36] X. Li, R. Gunawan, C. Lievens, Y. Wang, D. Mourant, S. Wang, H. Wu,
M. Garcia-Perez, C.-Z. Li, Fuel 2011, 90, 2530-2537.
[
[
37] R. Hilten, J. Weber, J. R. Kastner, Energy & Fuels 2016, 30, 8357-8368.
38] a) M. S. Holm, Y. J. Pagan-Torres, S. Saravanamurugan, A. Riisager, J.
A. Dumesic, E. Taarning, Green Chemistry 2012, 14, 702-706; b) X. Hu,
L. Wu, Y. Wang, D. Mourant, C. Lievens, R. Gunawan, C.-Z. Li, Green
Chemistry 2012, 14, 3087-3098.
This article is protected by copyright. All rights reserved.

ChemSusChem
10.1002/cssc.201700959
Communication
Entry for the Table of Contents (Please choose one layout)
Layout 1:
COMMUNICATION
SO
3
H
OH
SO
Text for Table of Contents
OH
3
H
SLOW
Jinesh C. Manayil, Amin
Osatiashtiani, Alvaro Mendoza,
OH
SO
OH
SO
OH
SO
3
H
H
H
3
3
OH
SO
3
H
SO
3
H
OH
Christopher M.A. Parlett, Mark A.
Isaacs, Lee J. Durndell, Chrysoula
Michailof, Eleni Heracleous, Angelos
Lappas, Adam F. Lee, Karen Wilson*
Catalytic
Bio-oil Upgrade
esterification
Page No. – Page No.
HO
SO
3
S
3
SO H
3
H
SO
3
H
SO
3
H
3
HO S
HO
3
S
Impact of macroporosity on
catalytic upgrading of fast
pyrolysis bio-oil by esterification
over silica sulfonic acids
HO
3
S
SO3
H
HO
3
S
HO
S
3
S
HO
3
S
SO
H
HO3
3
HO S
3
3
HO S
HO
SO
3
S
SO
3
H
3
HO S
H
FAST
H
HO
3
S
SO
3
H
3
SO3
SO
3
H
SO
3
H
SO
3
H
HO3
S
SO
3
H
HO
3
S
SO3H
This article is protected by copyright. All rights reserved.