The Catalyst Review (July 2016) - 6

PROCESS NEWS
Selective Conversion of
Plastics to Waxes...

High Temperatures Turn Nanoparticles into SingleAtom Catalysts...

A proprietary technology and patented
process from GreenMantra Technologies
(Canada) that produces synthetic waxes
from underutilized plastic recycling
streams, including films and bags, has
reached commercialization. The company's
first industrial-scale manufacturing
plant started up in May, and can process
5,000 metric tons per year (m.t./yr) of
polyolefin waste into wax products. The
cornerstone of the process is a family
of proprietary heterogeneous catalysts
that enables extremely selective thermocatalytic depolymerization reactions to
occur, with high yields of the final product.
The catalyst allows for control over the
molecular weight, structural and thermal
properties of resulting polymers, creating
a variety of specialty waxes. Tailored for
longterm use with contaminated recycling
streams, the catalyst's aluminum oxide
support can be regenerated back to its
virgin form as needed and re-impregnated
with active metals. When compared
with other chemical recycling processes,
GreenMantra's process not only operates
at a much lower temperature (the lower
threshold of the thermal degradation
point), but also avoids the randomness
of the depolymerizations experienced
in processes based on pyrolysis or
gasification. According to technical
director Domenic Di Mondo, the yield
is also quite high, with conversion rates
of up to 97%. Currently, the process is
run on a semi-continuous basis, where
re-processed polyolefin is melted and fed
into a series of parallel batch reactors. The
residence time, temperature and pressure
of the polymer in the reactor vessels can
be adjusted based on the specific wax
that is being produced. At this point, the
product is cooled, purified and solidified
into prills. The company hopes to move
to a fully continuous basis using fixed-bed
reactors, and add an additional 5,000 mt/
yr of capacity by 2017, says Di Mondo.
Going forward, GreenMantra is also
further developing its product portfolio
to include novel polymers for use in inks,
coatings and other applications. Source:
Chemical Engineering, 7/2016, p. 11.

A team of researchers, led by University of New Mexico chemical engineer Abhaya
K. Datye, have exploited a process that normally destroys supported metal catalysts
to make stable ones consisting of isolated platinum atoms on a solid support. From
earlier work, Datye and coworkers knew that hot oxidizing conditions turn platinum
nanoparticle catalysts into larger, less active platinum clumps by converting the metal to
PtO2, which is volatile and desorbs from nanoparticle surfaces. Datye reasoned that this
supply of mobile atoms could allow his team to produce single-atom catalysts. The team
wondered if ceria might serve as this atom trap because other researchers had shown
that small amounts of the oxide prevented nanoparticle sintering or fusing. They mixed
an alumina-supported platinum-lanthanum catalyst with various forms of ceria and
heated the mixtures to 800 °C in air for a week. After the treatment, X-ray diffraction
and other methods showed the complete absence of platinum nanoparticles. Electron
microscopy revealed that platinum had migrated from the alumina and become trapped
as isolated atoms on ceria nanorods and octahdera along lattice features known as step
edges. In the absence of ceria, the harsh treatment formed large platinum crystals on
alumina. The team showed that the single-atom catalysts were effective at CO oxidation
and that the platinum atoms remained isolated during the reaction. Source: Chemical &
Engineering News, 7/11/2016, p. 6.

Catalyst Combo Could Oxidize Biomass Alcohols...
A pair of catalysts can oxidize alcohols electrochemically in a relatively efficient and
speedy manner. Such a catalyst system could find use in fuel cells powered by biomass.
Organic alcohols are abundant in biomass derived from trees and other plants, and fuel
cells could generate electricity by oxidizing such alcohols electrochemically. TEMPO
(2,2,6,6-tetramethyl-1-piperidine N-oxyl) is an effective catalyst for such oxidations, but
it requires running fuel cells at high electrode potentials, which is not energy efficient.
Shannon S. Stahl and Artavazd Badalyan at the University of Wisconsin, Madison, have
now developed a dual electrocatalyst system that overcomes this problem. They show
that (2,2′-bipyridine)Cu(II) and TEMPO work cooperatively as catalytic redox partners in
a two-electron oxidation of alcohols. The two-catalyst oxidations run at a more-efficient
electrode potential-a reduction of a half-volt-and are nearly fivefold faster, compared
with TEMPO-only reactions. Electrocatalysis expert Shelley D. Minteer of the University
of Utah says that the next steps toward incorporating the cocatalysts in a fuel cell are
demonstrating their long-term stability and that they can be immobilized on surfaces.
Source: Chemical & Engineering News, 7/4/2016.

KTH Team Develops New Cost-Effective Water-Splitting
Electrocatalyst for H2 Production...
Researchers at KTH Royal Institute of Technology in Stockholm have developed
a new cost-effective electrocatalyst for water-splitting to produce hydrogen. The
monolayer of nickel-vanadium-layered double hydroxide shows a current density of
27 mA cm−2 (57 mA cm−2 after ohmic-drop correction) at an overpotential of 350 mV
for water oxidation. This performance is comparable to those of the best-performing
electrocatalysts that are composed of non-precious materials-nickel-iron-layered
double hydroxides for water oxidation in alkaline media-the researchers report
in an open access paper in Nature Communications. The new catalyst also offers a
competitive, cheap alternative to catalysts that rely on more expensive, precious
materials, such as iridium oxide (IrO2) or ruthenium oxide (RuO2). The research team,
led by KTH Professor Licheng Sun, had earlier developed molecular catalysts for water
oxidation with an efficiency approaching that of natural photosynthesis. Source: Green
Car Congress, 6/27/2016.

The Catalyst Review

July 2016

The Catalyst Review (July 2016)

Table of Contents for the Digital Edition of The Catalyst Review (July 2016)