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INNOVATIVE RESEARCH FOR A SUSTAINABLE FUTURE
Sustainable Chemistry, the Spinning Tube-in-Tube (STTŪ) Reactor and GREENSCOPE:
Innovation and Industrial Partnerships
Introduction
The chemical industry faces
environmental, social and health
challenges that are common across
all economic sectors. From worker
exposure to toxic substances, to
product design and use, to the cost
and handling of waste disposal, the
industry must overcome numerous
complex hurdles to secure a more
sustainable future.
To help address these hurdles, EPA
researchers are generating new
strategies and approaches to
developing cleaner technologies for
synthesizing commodity and
specialty chemicals. An
interdisciplinary group of EPA
researchers and their industrial
partners are exploring innovative,
reactor technologies and benign
substitutes for harsh chemicals,
catalysts and solvents. Their
research applies green chemistry
principles and philosophies to the
design of new chemical processes.
Furthermore, they apply green
engineering principles to process
intensification, which strives for
better efficiency and safety, and for
developing faster and more accurate
processes and optimization. They
use sustainability indicators to
measure their improvements to the
processes and to gauge their
progress.
Process Design, Intensification
and Optimization Using Green
Chemistry and Engineering
Through industrial partnerships,
EPA scientists and engineers are
facilitating the development and
wider adoption of green approaches
that can produce thousands of
different chemicals. This EPA
research influences process design
by applying principles of green
chemistry and engineering, such as
using increased mixing to replace
toxic solvents. EPA researchers and
their industrial collaborators are
working at the interface of chemistry
and chemical engineering for faster
implementation of new reaction
strategies in the marketplace. One
resulting strategy is the application
of the Spinning Tube-in-Tube
(STTŪ) reactor (4 Rivers Biofuels,
Calvert City, KY).
Research to date has demonstrated
the STTŪ reactor can perform
reactions without the need for any
chemical inputs other than the
reactants. One reactor, with a reactor
zone volume of 1.2mL, can fit on a
six-foot table, and is capabable of
producing up to 12 tons of product
per year, depending on the residence
time of the reaction. This feature is a
demonstration of green engineering
since the size of a plant using STTŪ
reactors is orders of magnitude
smaller than that needed for
conventional chemical
manufacturing with room-sized
reactor vessels, separation towers,
filtering systems and pipelines.
The increased mixing in the STTŪ
reactor, which is based on a two-
dimensional fluid film that flows
longitudinally, allows for enhanced
mixing. This allows for increased
mass transfer, resulting in reaction
rates up to three orders of magnitude
greater than a conventional reactor.
With this increased mass transfer,
the reactor also allows for increased
conversions, product selectivity and
yields, and decreased energy usage,
costs, and exposure risks to workers.
For faster process optimization, EPA
researchers are utilizing real-time
monitoring to identify product
distributions as a result of altering
reaction conditions. The real-time
analytical data allow EPA
researchers to optimize reaction
conditions to yield maximum results
in hours as opposed to days.
As an example, the STTŪ reactor has
demonstrated the solvent-free
preparation of a number of high
purity, commercially relevant
epoxides with excellent conversions
and throughput. Additionally, the
reactor has accomplished the high
throughput production of high purity
imines from a wide variety of
starting aldehyde/ketones and
amines in quantities and purities that
are impractical or impossible via
standard batch reaction techniques.
Using this reactor and a wide variety
of starting materials, researchers
have also completed the high
throughput production of high purity
imidazole derivatives, which may be
used as ligands in organometallic
chemistry.
Below, EPA researcher and branch
chief Michael Gonzalez works with
the STTŪ Magellan Reactor with
Mettler-Toledo IC-45 React IR.
U.S. Environmental Protection Agency
Office of Research and Development
EPA 600-F11025
August 2011
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In conjunction with industrial
partners, EPA researchers using the
STTŪ reactor have developed
oxidation, hydrogenation and
esterification reaction chemistries.
The reactor has the potential to be
applied to the pharmaceutical,
industrial chemical, food additive,
and fragrance sectors. As a result of
these collaborations, the reactor
technology and its application have
been licensed by two companies that
aim to build commercial-scale
operations to produce their
consumer products.
Reactor Modeling
With the advances in understanding
the influence of reaction conditions
in this novel reactor, efforts are on-
going to model the STTŪ to fully
understand the benefits observed,
including increased reaction rates,
yields and conversion. This
modeling could lead to faster
process optimization, will allow
reaction conditions to be predicted,
and will quantify results.
Sustainability Indicators
The GREENSCOPE or Gauging
Reaction Effectiveness for the
ENvironmental Sustainability of
Chemistries with a multi-Objective
Process Evaluator research project
team is creating a methodology that
they will develop into a software
tool that can assist researchers from
academia, industry, and government
agencies in designing more
sustainable chemical processes. The
Sustainability of a chemical process
can be evaluated in terms of four
indicator areas: Environment,
Efficiency, Energy and Economics,
or the 4 E's. Within the 4 E's are
147 indicators that are representative
of a chemical process. Each
indicator is placed on a Sustainability
scale and provides a snapshot of the
Sustainability of the chemical
process. To evaluate the
environmental aspects of alternative
chemistries or technologies,
GREENSCOPE employs the Waste
Reduction algorithm (Young and
Cabezas, 1999). Efficiencies for
chemical reactions are also reflected
in indicators such as conversion and
selectivity. GREENSCOPE has the
ability to evaluate a new or existing
process, perhaps one employing
green chemistry principles on the
laboratory scale, and to assess if it
has a beneficial or negative effect
on the overall Sustainability of a
chemical process or of a process that
has been scaled up for industrial
production.
Below, the indicators for a
hypothetical process show measures
(in blue) that fall between 0 and
100% of Sustainability.
Industrial Partnerships
To address and tackle real-life
challenges, apply sustainable
solutions to these challenges, and
partner with industry to infuse these
technological solutions into the
marketplace, EPA researchers have
collaborated with many partners.
The Spinning Tube-in-Tube (STTŪ)
reactor research has led the EPA to
collaborate with over 20 chemical
companies, including two companies
that took the results and research
further. The work produced a
potential patent application and
spurred other chemical companies to
collaborate with the EPA.
Since 2003, EPA researchers have
collaborated with Kreido
Laboratories (Camarillo, CA)
through a Cooperative Research and
Development Agreement involving
the STTŪ reactor. Since 2009, the
EPA has also been collaborating
with the Four Rivers Energy
Company to co-develop and advance
the spinning tube-in-tube technology
for chemical synthesis applications.
Companies that are interested and
want to test the STTŪ technology
for potential application can contact
EPA researchers to arrange to use
the needed facilities, staff and
analytical equipment.
References
Smith, R. L. and Gonzalez, M. A.
Methods for evaluating the
Sustainability of green processes.
Comp. Aided Chem. Eng., 2004,
Vol. 18, 1135-1140.
Young, D.M. and Cabezas, H.
Designing Sustainable Processes
with Simulation: The Waste
Reduction (WAR) Algorithm.
Comput. Chem. Eng., 1999, Vol. 23,
1477-1491.
Contact
Michael Gonzalez, Ph.D., Office of
Research & Development, 513-569-
7998, gonzalez.michael@epa.gov
Recycled/ recyclable
Printed with vegetable-based ink on
paper that consists of a minimum of
50% post-consumer fiber content
processed chlorine free
U.S. Environmental Protection Agency
Office of Research and Development
EPA 600-F11025
August 2011
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