The amazingly efficient lungs of birds and the swim bladders of fish have become the inspiration for a new filtering system to remove carbon dioxide from electric power station smokestacks before the main greenhouse gas can billow into the atmosphere and contribute to global climate change.
A report on the new technology, more efficient than some alternatives, is on the agenda today at the 246th National Meeting & Exposition of the American Chemical Society (ACS), the world’s largest scientific society. The meeting, which features almost 7,000 presentations on new advances in science and other topics, continues here through Thursday in the Indiana Convention Center and downtown hotels.
With climate change now a major concern, many power plants rely on CO2 capture and sequestration methods to reduce their greenhouse gas emissions. Speaking at a symposium, “CO2 Separation and Capture,” Aaron P. Esser-Kahn, Ph.D., said he envisions new CO2-capture units with arrays of tubes made from porous membranes fitted side-by-side, much like blood vessels in a natural lung. Once fabricated to be highly efficient and scalable to various sizes by repeating units, these units can then be “plugged” into power plants and vehicles, not unlike catalytic converters, he explained.
To capture the most CO2, the Esser-Kahn group from the University of California, Irvine, first had to figure out the best pattern to pack two sets of different-sized tubes –– one for waste emissions and the other a CO2-absorbing liquid –– into the unit. “The goal is to cram as much surface area into the smallest space possible,” said Esser-Kahn.
They studied the way blood vessels are packed in the avian lung and the fish swim bladder. Birds need to exchange CO2 for oxygen rapidly, as they burn a lot of energy in flight, while fish need to control the amount of gas in their swim bladder effectively to move up and down in the water. “We’re trying to learn from nature,” said Esser-Kahn, adding that the avian lung and fish swim bladder are biologically well-suited systems for exchanging gases.
But the blood vessels in the avian lung and fish swim bladder are packed in different patterns. The avian lung consists of a hexagonal pattern where three large tubes form the vertices of a triangle and a small tube sits in the gap, while the fish swim bladder has a squarer pattern where a large and small tube alternate between vertices of a square. It turned out that this tube-packing challenge is a well-studied mathematical problem with nine unique solutions, or patterns, Esser-Kahn said.
The team used computer simulations to predict how efficient gas exchange would be for each pattern. Four were predicted to be highly efficient, including the avian lung’s hexagonal pattern and the fish swim bladder’s squarer pattern. However, the most efficient pattern was actually one not found in nature: the double-squarer pattern, similar to the squarer one in the fish swim bladder, but with two small tubes alternating with a large tube. Esser-Kahn’s team then synthesized miniature units up to a centimeter long and confirmed experimentally that the double-squarer pattern was the most efficient, outperforming the avian lung and fish swim bladder by almost 50 percent.
Now, scientists can conduct further research to improve CO2-capture units’ efficiencies by adjusting the sizes of the tubes, thicknesses of the tube walls and membrane materials that make up the tube walls. “Biological systems spent an incredible amount of time and effort moving towards optimization,” said Esser-Kahn. “What we have is the first step in a longer process.”
Other presentations at the symposium included:
- Novel carbon capture and sequestration: Biomimetic solid sorbents and gas shale analysis
- Process and thermodynamics considerations of CO2 capture from post-combustion flue gases
- Improving the regeneration of CO2-binding organic liquids with a polarity change
Abstracts for the symposium appear below.
A press conference on this topic will be held Monday, Sept. 9, at 3 p.m. in the ACS Press Center, Room 211, in the Indiana Convention Center. Reporters can attend in person or access live audio and video of the event and ask questions at http://www.ustream.tv/channel/acslive.
The American Chemical Society is a nonprofit organization chartered by the U.S. Congress. With more than 163,000 members, ACS is the world’s largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.
To automatically receive news releases from the American Chemical Society, contact [email protected].
Note to journalists: Please report that this research was presented at a meeting of the American Chemical Society.
Microvascular materials for mass and energy transport
Aaron P. Esser-Kahn, [email protected], Department of Chemistry, University of California, Irvine, Irvine, California 92697, United States
Work into synthesizing microvascular materials has recently taken a step forward in the form of a new synthetic process VaSC (Vaporization of a Sacrificial Component) that enables the formation of 3D microstructures that are meters in length. We report on our recent advances in using VaSC to create three-dimensional gas exchange units modeled on the design of avian lungs and vascular systems for heat distribution. We are focused on mass transfer applications for the capture of CO2. We will report on recent research into creating high surface area micro-structures and the use of two phase flow systems to release gas from capture solutions.
New directions in the synthesis of oxacalixarenes and related oxacyclophanes
Jay Wm. Wackerly, [email protected], Department of Chemistry, Central College, Pella, IA 50219, United States
Our research has focused on two areas of oxacyclophane synthesis which are discussed in this talk. The first area involves a new approach towards the synthesis of oxacalixarenes. Traditionally, halogens are utilized as leaving groups in the nucleophilic aromatic substitution reaction to make oxacalixarenes; however our approach utilizes a two-step process of activation followed by substitution to allow for the use of hydroxyl groups (i.e., phenols) as leaving groups. Our other area of focus is in the synthesis of a new class of redox active oxacyclophanes that contain p-benzoquinones.
Developments in the synthesis of small and large molecules using olefin metathesis catalysts
Robert H. Grubbs, [email protected], Division of Chemisttry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91106, United States
Olefin metathesis is an established technique for making and breaking carbon-carbon double bonds, and has been adapted in applications that range from total synthesis to high performance plastics. Over the past several decades, efforts have been directed toward the development of catalysts that display enhanced functional group tolerance or increased selectivity as compared to their precursors, or facilitate access to small and macromolecules with unique structures and functions. In this presentation, we will describe previous and recent efforts aimed at designing and accessing new classes of olefin metathesis catalysts as well as our efforts toward using catalysts in hand in various applications.
Self-healing polymer design via noncovalent and dynamic covalent interactions
Zhibin Guan, [email protected], Yulin Chen, Aaron Kushner, Yixuan Lu. Department of Chemistry, University of California, Irvine, Irvine, CA 92697, United States
The development of polymers that can spontaneously repair themselves after mechanical damage would significantly improve the safety, lifetime, energy efficiency, and environmental impact of manmade materials. Our laboratory has recently succeeded in developing self-healing polymers via either noncovalent or dynamic covalent bonding interactions. For noncovalent mechanism, we developed multiphase supramolecular thermoplastic elastomers that combine high modulus and toughness with spontaneous healing capability (Nature Chemistry 2012, 4, 467; Angew. Chem., Int. Ed. 2012, 51, 10561). In contrast to previous self-healing polymers, our systems spontaneously self-heals as a single-component solid material at ambient conditions without the need of any external stimulus, healing agent, plasticizer, or solvent.
Oxidative de-polymerization and the flex fuel generator: An ideal context based learning tool
Larry J. Markoski, [email protected], INI Power Systems, Inc., Morrisville, NC 27560, United States
The basic concepts within math and science are best learned and retained when the joy of connecting the dots between cause and effect relationships can be drawn within the context of iterative hands-on experimentation. The foundational concepts of reaction kinetics, catalysis, thermodynamics, ideal gas laws, stoichiometry, viscosity, radical reactions, and chain length dependent material properties are topics usually first encountered in the classroom in the absence of an experiential context. To best prepare the next generation of creative problem solvers and innovators we must reintroduce i) useful context and ii) the joy of real time hands-on discovery into the learning process. An inexpensive method and apparatus (Flex Fuel Generator) capable of achieving both of these goals will be introduced and discussed.
Controlled catalyst transfer polycondensation of a p-phenyleneethynylene-based monomer: Surface-initiated polymerizations and other applications
Songsu Kang, Robert J. Ono, Christopher Bielawski, [email protected]. Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, United States
Conjugated polymers, such as the poly(p-phenyleneethylene)s (PPEs), hold promise for use in organic light-emitting diodes, molecular wires, and many other applications. The aforementioned polymers are typically synthesized from A2+ B2 or A-B type monomers using Sonogashira-type cross coupling chemistry or alkyne metathesis. Since these methodologies grow polymer in a step-growth fashion, it can be difficult to access high molecular weight materials with low polydispersity or prepare relatively sophisticated materials, such as block copolymers or surface-grafted polymer brushes. We envisioned that the drawbacks intrinsic to the step-growth polymerization of phenyleneethynylene-based monomers may be overcome through the development of a chain-growth catalyst transfer polycondensation (CTP) method. While CTPs have been successfully utilized to prepare various conjugated homo- and copolymers, including poly(thiophene)s, poly(fluorene)s, and poly(phenylenes), the first synthesis of a PPE via chain-growth CTP will be described in this presentation. Ongoing and future efforts involing the use of CTP based methods to prepare well-defined macromolecular structures containing PPEs, such as block copolymers, surface-grafted polymers, and other materials capable of self-assembling into well-ordered structures on the nanoscale will also be discussed.
Development of chain-growth condensation polymerization since coming back from Jeff’s group
Tsutomu Yokozawa, [email protected], Department of Material and Life Chemistry, Kanagawa University, Yokohama, Kanagawa 221-8686, Japan
I stayed Jeff’s group for a year in 1997-98 as a visiting scientist. Before that we had set up research on chain-growth condensation polymerization (CGCP), but our landmark JACS paper about CGCP in solid-liquid phase was published in 1999 when I came back to Japan. In this paper, I would like to talk about development of CGCP.
Conventional condensation polymerization proceeds in step-growth polymerization mechanism, but the mechanism can be converted to chain-growth by enhancement of the reactivity of the polymer end group; the monomer reacts only with the initiator and the polymer end group. The approaches we have adopted are (1) change of substituent effect induced by bond formation of the monomer with the polymer end group, and (2) selective transfer of catalysts to the polymer end group in coupling polymerization with a transition metal catalyst.
In the first case, we have attained CGCP for the synthesis of well-defined poly(p-benzamide)s, poly(m-benzamide)s, aromatic polyethers, poly(ether sulfone), and aromatic polyesters. Taking advantage of the living polymerization nature, we synthesized a variety of condensation polymer-containing architectures such as block copolymers, star polymers, graft copolymers, and hyperbranched polymers.
The second case of CGCP with a metal catalyst has been independently found by us and McCullough et al. in the synthesis of poly(hexylthiophene). We have developed this polymerization to the precision synthesis of poly(p-phenylene), polyfluorene, poly(N-alkylpyrrole), and poly(pyridine-3,5-diyl). Block copolymers of different π-conjugated polymers were also synthesized by successive catalyst-transfer condensation polymerization in one pot.
Brief discussion on water treatment solutions of GE waters and process technologies
Ashok Shetty, [email protected], GE Water and Process Technologies, Trevose, Pennsylvania, United States
Dr. Ashok Shetty has lead the Chemical Synthesis team at GE Water & Process Technologies (GEWPT). GEWPT, a part of GE Power and Water, provides water treatment, wastewater treatment and process systems solutions. Its goal is to help solve complex challenges related to water availability and quality, to increase productivity, reduce costs and help our customers meet environmental regulations. This presentation will be focused on GE’s Water Treatment Solutions that include Cooling water, Boiler and Waste Water Treatments.
Synthesis and analysis of redox shuttles for overcharge protection in lithium-ion batteries
Susan A. Odom, [email protected], Selin E. Ergun, Pramod P. Poudel, Corrine N. F. Elliott, Nelson Ng. Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055, United States
Hundreds of compounds have been tested as redox shuttle additives for overcharge protection in lithium-ion batteries, a condition that shortens battery lifetimes, yet only a few compounds have proven effective for ³100 overcharge cycles. Identifying new redox shuttles with improved solubilities, oxidation potentials that match specific battery cathodes, and retaining or increasing shuttle lifetimes has been a challenge for this field.Determining the efficacy of redox shuttles can be a slow process, especially if shuttles are successful at overcharge protection; each cycle takes ~20 hours, so researchers may wait months or longer for their batteries to fail. Driven by the desire to obtain faster experimental results, we developed a new screening method to identify promising redox shuttle candidates. We compared reported battery cycling results to those from our own laboratory using cyclic voltammetry of neutral molecules and UV-vis and EPR analysis of radical cations generated by chemical oxidation. We found that UV-vis and EPR spectroscopies were both more effective at predicting overcharge performance, and testing requires only a few hours. Using this method, we can weed out poor candidates and focus on further testing of redox shuttles whose radical cations slow rates of decay. Our method requires no battery electrolyte – just the redox shuttle candidate, chemical oxidant, dry solvent, and a UV-vis or EPR instrument to record the intensity of the radical cation spectra vs time. This presentation will focus on results concerning commercially available redox shuttles and those synthesized in our laboratory, including derivatives of 1,4-dimethoxybenzene and phenothiazine.
Hybrid functional materials by surface modification: Applications in catalysis and adsorption
Justin M. Notestein, [email protected], Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208, United States
Research in the Notestein group focuses on the development of novel hybrid or inorganic materials and understanding how extended surfaces alter the properties of reactive sites for applications primarily in catalysis and adsorption. This talk will emphasize our work on hybrid materials, including grafted inorganic catalysts and novel materials derived from oligomeric aromatic structures grafted onto and grown from oxide surfaces. The latter work was strongly influenced by time spent under Professor Jeffrey Moore’s direction.
Development and applications of 3D covalent organic polyhedrons (COPs) and porous polymer frameworks (PPFs) through dynamic covalent chemistry
Wei Zhang, [email protected],