Published on Web 10/30/2009
High Yield of Liquid Range Olefins Obtained by Converting
i-Propanol over Zeolite H-ZSM-5
Uffe V. Mentzel,*,†,‡ Saravanamurugan Shunmugavel,† Sarah L. Hruby,§
Claus H. Christensen,‡ and Martin S. Holm*,†,‡
Department of Chemistry, Technical UniVersity of Denmark, DK-2800 Kgs. Lyngby, Haldor
Topsøe A/S, 2800 Kgs. Lyngby, and Department of Chemical and Biological Engineering, Iowa
State UniVersity, Ames, Iowa 50011
Received September 10, 2009; E-mail: uvm@kemi.dtu.dk; msh@kemi.dtu.dk
Abstract: Methanol, ethanol, and i-propanol were converted under methanol-to-gasoline (MTH)-like
conditions (400 °C, 1-20 bar) over zeolite H-ZSM-5. For methanol and ethanol, the catalyst lifetimes and
conversion capacities are comparable, but when i-propanol is used as the reactant, the catalyst lifetime is
increased dramatically. In fact, the total conversion capacity (calculated as the total amount of alcohol
converted before deactivation in galcohol/gzeolite) is more than 25 times higher for i-propanol compared to the
lower alcohols. Furthermore, when i-propanol is used as the reactant, the selectivity toward alkanes and
aromatics declines rapidly over time on stream, and at 20 bar of pressure the liquid product mixture consists
almost exclusively of C4-C12 alkenes after approximately a third of the full reaction time. This discovery
could open a new route to hydrocarbons via i-propanol from syn-gas or biobased feedstocks.
Introduction
system has become generally accepted. This idea was originally
suggested by Mole11 and Langner,12 and a decade later Kolboe
The methanol-to-hydrocarbons (MTH) reaction was discov-
ered and commercialized more than two decades ago. However,
due to the situation on the global oil market, the gasoline
synthesis was discontinued.1,2 Currently, the MTH reaction is
receiving renewed attention due to the focus on renewable fuel
sources.3 The level to which this reaction can contribute to a
sustainable nonfossil-based energy sector naturally depends on
the origin of the methanol.4 Methanol is traditionally produced
from coal or natural gas via syn-gas, but many interesting
nonfossil routes for the production of methanol as well as higher
alcohols are investigated today.5 Methods for production of
higher alcohols from syn-gas are also under development6,7 as
is the gasification of biomass to syn-gas.8
et al.13,14 introduced a more general mechanism. Through
isotopic labeling experiments Bjørgen et al.15 uncovered further
mechanistic details about the hydrocarbon pool and suggested
“the dual cycle mechanism”. Recently, mechanistic modeling
has also been used to gain insight into the mechanistic
details.16,17
In the MTH reaction, the zeolite catalyst suffers from
deactivation due to coking and frequent regeneration by
combustion of the deposited coke is required. It is thus a key
research area to improve the catalyst lifetime between regenera-
tions. Another important objective is to suppress the formation
of aromatic compounds and shift the selectivity toward the
production of olefins (the MTO reaction).18,19 Numerous ap-
proaches have been tried to obtain these goals, most of them
dealing with optimization of the catalyst or modifying the
reaction conditions.20-24
Since the MTH reaction was discovered in the early 1970s
and published in 1977,9 the reaction mechanism has been widely
debated.10 The “hydrocarbon pool mechanism” in which car-
bonaceous species in the zeolitic pores are part of the catalytic
† Technical University of Denmark.
‡ Haldor Topsøe A/S.
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§ Iowa State University.
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10.1021/ja907692t CCC: $40.75 2009 American Chemical Society
J. AM. CHEM. SOC. 2009, 131, 17009–17013 17009