Chemical Engineering August 2015 - 16

been developed by a team of researchers from
the Technical University of Munich (TUM; Germany;
www.tum.de), Eindhoven University of
Technology (www.tue.nl) and University of Amsterdam
(both the Netherlands; www.uva.nl).
This copper-exchanged zeolite with mordenite
structure mimicks the reactivity of methane
monooxygenase (MMO) - an enzyme known
to efficiently and selectively oxidize methane
to methanol.
In a recent issue of Nature Communications,
the researchers show that the micropores of the
zeolite provide a perfect confined environment
for the highly selective stabilization of an intermediate
copper-containing trimer molecule.
Trinuclear copper-oxo clusters were identified
that exhibit a high reactivity towards activation
of carbon-hydrogen bonds in methane and its
subsequent transformation to methanol. " The
developed zeolite is one of the few examples of
a catalyst with well-defined active sites evenly
distributed in the zeolite framework - a truly
single-site heterogeneous catalyst, " says TUM
professor Johannes Lercher. " This allows for
much higher efficiencies in conversion of methane
to methanol than with zeolite catalysts previously
reported. "
The achievement has promising implications
for small-scale, gas-to-liquids technologies for
utilizing stranded natural gas.
Making hydrogen from methanol
T
he research group of professor
Ken-ichi Fujita at
Kyoto University (Kyoto,
www.h.kyoto-u.ac.jp) has
developed an efficient catalytic
system for the production of hydrogen
from an aqueous methanol
solution. The process uses a new,
anionic iridium complex bearing a
functional bipyridonate ligand as a
catalyst. This system operates in a
weakly basic solution (0.046 mol/L
of NaOH) and mild temperatures
(below 100°C), which is far below
the high temperatures (more than
700°C) needed to steam reform hydrocarbons
into H2, as well as the
200°C needed to generate H2 from
methanol by other catalytic processes,
says Fujita. Also, the process
does not require an additional
organic solvent, which makes it
simpler and safer than the recently
developed homogeneous transition-metal-complex
catalyst system,
which uses organic solvents
such as tetrahydrofuran, toluene
and 2,5,8,11-tetraoxadodecane
(triglyme) at rather strong basic
conditions (8.0 mol/L of KOH).
The new, water-soluble iridiumcomplex
catalyst is highly active
for generating H2 by dehydrogenation
of methanol. In laboratory trials,
an 80% yield for H2 and CO2
was observed with 0.5 mol% of the
catalyst using a 1-to-4 mixture of
methanol in water after refluxing for
20 h at 88°C. The chemists speculate
(and experimentally confirmed)
that this catalytic reaction is composed
of four steps: (1) formation
of formaldehyde by the dehydrogenation
of methanol; (2) formation
of methanediol by the hydration of
formaldehyde; (3) formation of formic
acid by the dehydrogenation of
methanediol; and (4) formation of
H2 and CO2 by the decomposition
of formic acid.
The researchers have also
achieved long-term (150 h), continuous
H2 production with a turnover
number (TON) of 10,000.
n
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Chemical Engineering August 2015

Table of Contents for the Digital Edition of Chemical Engineering August 2015
