Chemical Engineering June 2010 - 12

ChementatoR
(Continued from p. 11)
CNTs show promise as a filter
and a catalyst support
C
arbon nanotube (CNT) membranes developed
by researchers at Rice University
(Houston; www.rice.edu) could have applications
as nanoparticulate filters, and as nanoscale
scaffolds for catalysts. The devices are
silicon dioxide wafers with laser-bored holes
(~500-µm dia.). The holed wafers are subjected
to a chemical-vapor-deposition (CVD)
process, during which a " forest " of CNTs
grows inside the holes (photo).
The CNTs inside the holes create a matrix
through which only nanoscale particles
can pass. In testing, the research team, led
by Rice engineer Robert Vajtai, was able to
remove greater than 99% of sub-micron particles
from air. The filters' permeability is affected
strongly by the duration of nanotube
growth, Vajtai explains.
components in rechargeable
lithium-ion batteries.
The grant - awarded as
part of the american recovery
and reinvestment act of 2009
- is intended to help honeywell
become the first domestic
supplier of liPF6. honeywell
has developed a process that
produces less waste and a
more consistently pure liPF6
than alternative processes,
says the firm.
In a recent paper in the journal ACS
Nano, the researchers reported functionalizing
the nanotubes with catalytic palladium
metal to achieve gas-phase heterogeneous
catalysis. Using the dehydrogenation reaction
of propene to propane as a test system,
the activated membranes showed " excellent
and durable activity " as a catalytic support,
enabling a low activation energy for the propene
dehydrogenation reaction of ~27.8 kJ/
mol and a turnover rate of 1.1 molecules per
Pd site per second.
An enhanced photocatalyst for making H2 from water
K
azuhiro Sayama and colleagues at the
Solar Light Energy Conversion Group
at Energy Technology Research Institute,
National Institute of Advanced Industrial
Science and Technology (AIST; Tsukuba,
Japan; unit.aist.go.jp/energy), have developed
a cesium-treated tungsten oxide photocatalyst
that shows a 19% quantum efficiency
at 420 nm, which is 48 times higher
compared to existing photocatalysts. The
Cs-WO3 photocatalyst is expected to boost
the commercial potential for making hydrogen
from water in a low-voltage electrolysis
process developed at AIST.
The enhanced catalyst is made by surface
treatment of WO3 photocatalyst, either by
adding a cesium salt to a solution for hydrothermal
treatment, or by impregnating the
WO3 particles with Cs2CO3 and sintering at
500°C. Subsequent washing with a strong
acid or FeSO4 solution removes excess Cs
ions from the WO3 surface, forming ion exchange
sites. The catalyst is used as an ionexchange
membrane of an electrolysis cell
operating with an aqueous Fe2(SO4)3 solution
as electrolyte. When the cell is irradiated
by light, the Fe+2 is oxidized to Fe+3 at
the catalyst site. This enables the electrolysis
of water into H2 to proceed at about half
the voltage of a conventional electrolyzer.
Combined CO2 mitigation and H2S removal
L
ast month at the Global Refining
Summit (Rotterdam, the Netherlands;
May 17-19), Swapsol Corp.
(Monmouth Junction, N.J.; www.swapsol.com)
introduced a completely new
sour-gas-cleanup process that reduces
hydrogen sulfide levels below detectable
levels (under 4 ppb) while reacting
with carbon dioxide to form water, sulfur
and a polymer of sulfur and carbon
(carsul). Although still in the laboratory
stage of development, the process
promises to have application in cleaning
up landfill gas, sour-gas, fluegas
and Claus tailgas, as well as serving
Biotech milestone
last month, DSm Biologics
(www.dsmbiologics.com),
a business unit of DSm
Pharmaceutical Products
(Parsippany, n.J.), successfully
scaled up its proprietary
XD technology from 2 l to
50 l using a Cho (Chinese
hamster ovary) line. XD technology
dramatically increases
the cell density and optimizes
the conditions for protein
production of a biological
culture. The scaleup runs at
DSm demonstrated a record
level of viable cell densities
of up to 170 million cells/ml,
and record titer improvements
of 5-10 fold over standard
fed-batch and perfusion
processes have been consistently
achieved in multiple
mammalian cell systems,
including Cho and Per.C6,
says the company.
" Companies can now substantially
shrink their bioreactor
size requirements by 5-10
fold, reducing Capex [capital
expenses] required for building
a new plant and ultimately reducing
overall cost of goods, "
says Jeremy Caudill, vice
president, sales and business
development.
as an alternative to Claus technology,
says COO Wolf Koch. Swapsol has applied
for U.S. and international patents
on all aspects of its technology.
Named after its discoverers,
the
Stenger-Wasas Process (SWAP) involves
the reaction of H2S and CO2 at temperatures
of 70-200°C and ambient to moderate
pressures. The exothermic reaction
is carried out in a catalyst-packed tubular
reactor and produces sulfur, water
and carsuls. The catalyst is a naturally
occurring mineral ore that is pretreated
in a manner analogous to common hydrotreating
catalysts, says Koch. Sulfur
12 ChemiCal engineering www.Che.Com June 2010
can be recovered from carsul by simply
heating it, leaving behind a polymer of
carbon that may have applications as a
construction material.
Thus far the company has performed
the reaction in 1- and 2-in.-dia. tubular
reactors, and believes scaleup to a commercial
process with a large shell containing
multiple tubes is not a problem.
Swapsol is now planning to start testing
its applications in a pilot plant during
the 3rdQ of 2010, and move to the first
commercial application - most probably
a landfill-gas-cleanup operation -
during 2011, says Koch.
http://www.rice.edu http://www.dsmbiologics.com http://unit.aist.go.jp/energy http://www.swap http://www.sol.com http://www.Che.Com
Chemical Engineering June 2010

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