Chemical Engineering December 2010 - 13

ChementatoR
Story Name
(Continued from p. 15)
Fructose from fruit
(Continued from p. 15)
Commercialization may be in the works
for a 'cleaner' gold-recovery process
A
" green " hydrometallurgical process for
recovering gold from ore, developed by
Haber, Inc. (Arlington, Mass.; www.habercorp.com),
may make its commercial debut
in Suriname. Albert Conti, Haber's CEO,
says the Republic of Suriname has made a
commitment to develop a strategic partnership
with the company for the use of the process.
The elimination of mercury pollution is
a goal of the government in Suriname, where
small-scale gold miners use the metal to absorb
gold from gold concentrates, recovering
the Au as a gold-mercury amalgam. Excess
Hg is driven off as a vapor by heating. In
contrast, Haber's process doesn't use Hg and
avoids the use of cyanide, commonly used in
large-scale mining to leach gold from ore.
The commitment follows recent government-sponsored
tests of Haber's process in
Paramaribo, Suriname's capital. A number of
sulfide ores were processed and gold recovery
ranged from 96.1-99.7%, says Conti. This
compares with recoveries of about 35% for
current small-scale commercial operations
in Suriname, he says, noting that Suriname
has more than 25,000 small-scale miners and
about 100 larger gold-mining entities.
Conti declines to give specific details on
the process, except to say that it involves a
sequence of proprietary steps. Sulfide ore
is crushed to 20-120 mesh and pretreated
to liberate gold from sulfur-bearing compounds.
The Au is leached from the ore by a
lixiviant in an aqueous solution and recovered
as a fine powder by adding a proprietary
formulation that converts the dissolved
Au from the ionic to the metallic form. Conti
says the process is faster and cheaper than
roasting or treating the ore with bacteria,
the current, popular liberation methods.
Nanoclusters that selectively catalyze oxidation reactions
P
rofessor Shu Kobayashi, University of
Tokyo (Tokyo, Japan; www.s.u-tokyo.
ac.jp), has discovered that bimetallic nanoclusters
can catalyze the oxidation of
alcohols. Kobayashi's group has demonstrated
the ability to control the reaction
pathways of alcohol oxidation to aldehydes,
carboxylic acids or esters using nanoclusters
composed of a few to several-tens of
atoms of gold, platinum and palladium.
These carbon-stabilized, polymer-incarcerated,
bimetallic nanocluster catalysts
exhibit selective oxidation of alcohols. The
reactivity and selectivity are strongly dependent
on the metal pairs in the cluster
and the solvent system used. For example,
nutritis (Toulouse; www.nutritis.com),
in cooperation with
novasep Process (Pompey,
both France; www.novasep.
com), plans to scale up a new
process for producing fructose
from apple juice. Details
about the process were not
disclosed, but the companies
say the patented technology
enables production of fructose
that can be labeled as 100%
fruit, making it suitable for fruitbased
preparations such as
dairy products and jams. Conventional
industrial processes
make fructose by the hydrolysis
of sucrose from sugar cane,
sugar beets and corn starch.
nutritis plans to produce fructose
from substandard fruit
that cannot otherwise be sold.
1-octylalcohol reacting over a Au/Pt cluster
(room temperature, 1 atm of O2 and a
benzotrifluoride-water solvent) yields the
corresponding aldehyde (C7H15-CHO) with
92% selectivity after 9 h, whereas a Au/Pd
cluster (methanol-H2O solvent) yields the
corresponding ester (C7H15-COOCH3) with
78% selectivity after 24 h.
Electron microscopy shows that the average
diameter of the two clusters are about
the same (2 nm), but the ratio of the metal
atoms are different (1:1 for Au/Pt and 4:1
to 3:1 for Au/Pd). The research is said to be
the first example of controlling the reaction
pathway of gold-catalyzed reactions by introducing
a second metal.
Miniature ESR spectrometer facilitates study of free radicals
A
Nanoscrolls split water
Kazuhiko maeda, assistant
professor at The University of
Tokyo (Tokyo; www.domen.t.utokyo.ac.jp)
and professor
Thomas e. mallouk at Penn
State University, have developed
a highly efficient photocatalyst
for splitting water with
visible light. The catalyst - a
nano-scale " scroll " of niobate
- has a quantum yield of 25%
with 450-nm radiation, which
is about 20 times more active
than layered niobate systems,
and ten times more than
titanate-based photocatalysts,
says maeda.
To make the catalyst, an
miniaturized electron spin resonance
(ESR) spectrometer developed by Active
Spectrum Inc. (Foster City, Calif.; www.activespectrum.com)
can facilitate studies of
chemical species with unpaired electrons,
such as organic free radicals and transition
metal complexes. Available in both online
and benchtop models, the Micro-ESR spectrometer
greatly reduces the size, cost and
complexity of ESR measurements, allowing
the technique to be widely accessible to nonspecialist
users in chemical processing and
industrial research.
ESR spectroscopy is valuable for studying
the composition and concentration of shortlived
free radicals in oils, food products and
biological materials. A key advantage of
ESR over optical spectroscopy techniques
is its ability to scan dirty, mixed or opaque
samples without any sample preparation.
It is also highly specific - most substrates
have no unpaired electrons and therefore do
not interfere with ESR.
Traditional ESR equipment uses large
and expensive 1970s-era microwave technology
and magnets adapted from nuclear
magnetic resonance (NMR) spectroscopy.
(Continues on p. 14)
exfoliation process removes
single layers from a niobate
compound to give cylindrical
scrolls. by combining the
scrolls with a ruthenium-based
dye, the catalyst becomes active
with visible light. The h2
production rate (3.5 mol/h) is
also about 20 times faster than
alternative catalysts. These
improvements are believed
to be due to the high specific
area of the scrolls, which is
about 200 times more than
layered niobate.
Fluorinated graphene
This year's physics nobel Prize
laureates, professors andre
geim and Kostya novoselov,
and colleagues at The University
of manchester (U.K.;
www.manchester.ac.uk), have
successfully fluorinated each
carbon atom of graphene to
(Continues on p. 19)
ChemiCal engineering www.Che.Com DeCember 2010
13
(Continues on p. 14)
http://www.nutri http://www.tis.com http://www.novasep http://www.haber http://www.corp.com http://www.domen.t.u http://tokyo.ac.jp http://www.s.u-tokyo http://www.ac.jp http://www.ac http://www.tivespectrum.com http://www.manchester.ac.uk http://www.Che.Com
Chemical Engineering December 2010

Table of Contents for the Digital Edition of Chemical Engineering December 2010
