CHEMCATCHEM
COMMUNICATIONS
DOI: 10.1002/cctc.201402390
The Effect of Water on Furan Conversion over ZSM-5
Christopher J. Gilbert,[a] Juliana S. Espindola,[b] William C. Conner, Jr.,[c] Jorge O. Trierweiler,[b]
and George W. Huber*[a]
Catalytic fast pyrolysis is a method for converting lignocellulo-
sic biomass into renewable aromatics and olefins. Water is a by-
product of this reaction and is also present in the biomass
feed. As the water partial pressure is increased from 0 to
212 Torr (0 to 28 kPa), there is an increase in furan conversion
from 43.8 to 84.8% over ZSM-5. The CO2 and propylene yields
also increase from 0.7 to 16.4% and 2.9 to 44.9%, respectively,
as the water partial pressure increases. Water partial pressures
in an industrial catalytic fast pyrolysis reactor should be within
the range of water partial pressures used in this study. These
results demonstrate that the presence of water promotes hy-
drolysis reactions in the gas-phase conversion of furanic pyrol-
ysis vapors over zeolite catalysts.
water [at a partial pressure of 74 Torr (1 Torr=0.13 kPa)] with
biomass during pyrolysis, and then upgrading the pyrolytic
vapors over a bed of ZSM-5. The water was found to double
the yields of all gaseous product species (CO, CO2, H2, meth-
ane, and C2 and C3 alkanes and olefins) at all temperatures in-
vestigated (400–5508C). The addition of steam to the catalytic
pyrolysis of lipids produced by the algae Chlorella pyrenoidosa
(the main fatty acids contained in this algae are oleic acid, lino-
leic acid, and palmitic acid) over ZSM-5 has been shown to
shift product selectivity towards CO, CO2, and C2–C4 olefins, as
well as decreasing selectivity towards alkanes and coke.[6]
Table 1 and Figure 1a–c show the effect of increasing the
water partial pressure for furan conversion over ZSM-5 at
6008C. These experiments were done by co-feeding water and
furan over a ZSM-5 catalyst (H-form, obtained from Zeolyst,
Inc.; SiO2/Al2O3 =30). As shown in Figure 1a the furan conver-
sion increased with increasing water partial pressure. The CO2
and propylene yields also increased with increasing water par-
tial pressure, as shown in Figure 1b and c. These results show
that increasing the water partial pressure increases the overall
furan conversion, and that water catalyzes the hydrolysis of
furan into CO2 and propylene. Therefore, water has an impor-
tant role in CFP.
Lignocellulosic biomass is an inexpensive and renewable feed-
stock that can be used to produce renewable fuels and chemi-
cals.[1] Several processes for biomass conversion are currently
under development.[1a] One approach is catalytic fast pyrolysis
(CFP), which converts lignocellulosic biomass into aromatics in
a single-step reaction that uses zeolite catalysts[2] and a fluid-
ized bed reactor.[2c,e,f] Previously, it has been reported[2a,b,3] that
during CFP the biomass first undergoes pyrolysis reactions to
produce anhydrosugars (such as levoglucosan), followed by
dehydration, decarbonylation, and decarboxylation reactions,
which produce furanic intermediate species that are further
converted into aromatic species through acid-catalyzed reac-
tions. The conversion of furans over HZSM-5 has been used as
a model reaction for the CFP of real biomass[2c,4] in an attempt
to elucidate the reaction chemistry. Water is a byproduct of
the CFP process produced in the dehydration reactions. In ad-
dition, water is present with the biomass and therefore fed
into the process with the biomass. The objective of this paper
is to study the effect of water on the CFP chemistry.
The product yields and selectivities for individual species are
shown in Table 1. The results obtained in the absence of
a water co-feed are comparable to those that have been re-
ported previously under similar reaction conditions.[4b,c] The
overall aromatic yield decreased with increasing water partial
pressure. The yield of CO did not change with increasing water
partial pressure. Coke yield did not change appreciably until
the water partial pressure was increased to 212 Torr; a decrease
in the coke yield was observed at that pressure relative to
lower pressures. The increase in olefin yield is almost entirely
due to the increase in propylene. The toluene and xylene se-
lectivity increases with water partial pressure. Cheng and
Huber have previously shown that toluene can be produced
from a reaction of furan with propylene by Diels–Alder con-
densation in the vapor phase over ZSM-5.[4c] These authors
also showed a decrease in the selectivity towards heavier aro-
matics (e.g., styrene, ethylbenzene, indene, naphthalene) upon
co-feeding propylene with furan at a propylene/furan molar
ratio of 2.4:1. The increase in the toluene and xylene selectivity
is probably related to an increase in the propylene concentra-
tion that is produced by the hydrolysis of furan with water.
The yield of the polycyclic aromatics decreased with increasing
water content, which again, is probably related to the increase
in propylene yield. The yield of oxygenates did not show
a major change with water content. However, among oxygen-
ates, there is a shift in selectivity towards acetone and acetal-
There are a few studies in the literature that have reported
on the role of water in conversion of pyrolysis vapors over zeo-
lite catalysts. Horne et al.[5] examined the effect of co-feeding
[a] C. J. Gilbert, Prof. G. W. Huber
Department of Chemical and Biological Engineering
University of Wisconsin-Madison
1415 Engineering Drive, Madison, WI 53706 (USA)
[b] J. S. Espindola, Prof. J. O. Trierweiler
Department of Chemical Engineering
Federal University of Rio Grande do Sul
Rua Luiz Englert s/n, 90040-040-Porto Alegre (Brazil)
[c] Prof. W. C. Conner, Jr.
Department of Chemical Engineering
University of Massachusetts-Amherst
686 North Pleasant Street, Amherst, MA 01003 (USA)
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemCatChem 2014, 6, 2497 – 2500 2497