Issue Date: September 3, 2007
Mapping The Future Of Catalysis R&D
CATALYSTS, in one form or another, lie at the heart of the great majority of industrial and natural chemical transformations. Worldwide, more than $3 trillion worth of chemicals and materials are manufactured annually through catalytic chemistry. With catalysts mediating nearly every chemical process associated with production of today's fuels, the energy sector is particularly tied to these reaction-enabling agents. That connection is expected to grow even stronger in the coming years as investigators develop new catalysts and catalytic processes to meet growing energy demands by tapping alternative fuels and energy sources.
"There is a tremendous opportunity for catalysis to make an impact on the nation's—and the world's—future energy needs, and we're here to help realize that opportunity." That's the way Douglas Ray described the role of attendees at a Department of Energy catalysis workshop that was held last month near Washington, D.C. Ray, associate director at Pacific Northwest National Laboratory, was one of the organizers of the gathering, which was sponsored by DOE's Office of Basic Energy Sciences (BES).
The meeting was the 10th and final event in a series of workshops aimed at prioritizing areas of research that need to be addressed to make significant advances in a number of scientific fields. Previous workshops in the series focused on such topics as basic research needs for effective utilization of solar energy and the development of advanced nuclear energy systems.
As with the earlier workshops, the goal of the latest gathering was to draft a report that enumerates priority research directions that are judged to be essential, in this case, to meet the grand challenges in catalytic chemistry that underpin energy conversion and utilization. BES Associate Director Patricia M. Dehmer noted that reports from previous workshops in the series have been well-received by the scientific community, Congress, and the Bush Administration. Dehmer claimed that the reports have made an impact on decision- and policymakers in DOE and other departments and have influenced the structure of government research budgets.
"You have an opportunity now to define the future of your discipline," Dehmer declared at the opening of the meeting. Noting that catalysis has a long history and well-established methodologies, Dehmer cautioned the workshop's roughly 125 invited participants not to be confined by conventional boundaries and traditional ways of thinking in catalysis. Rather, she urged, think broadly and outside the box to identify the underlying scientific limitations and key challenges in catalysis that cannot be met with current technology.
To Ray and fellow organizers Alexis T. Bell, professor of chemical engineering at the University of California, Berkeley, and Bruce C. Gates, professor of chemical engineering at UC Davis, it came as no surprise that the final workshop in this series focused specifically on catalysis. "Catalysis is the enabling technology in the arena of chemical transformations," Bell said. That theme came up repeatedly in earlier workshops—for example, 1n discussions about the hydrogen economy, solar energy, and clean transportation fuels. "If we want to control chemical conversions—how fast and to what products, it's a matter of finding the right catalyst," Gates emphasized. He added that molecular-scale control of chemical transformations is at the heart of fuel and energy issues.
TO JUMP-START the workshop activities, a few scientists were called upon to review the state of affairs in a couple of key areas related to catalysis. For example, Dow Chemical's chief technical officer, William F. Banholzer, articulated the importance of diversifying the supply of chemical feedstocks. He pointed out that, in the U.S., soaring costs of traditional feedstocks such as natural gas have driven manufacturers to build chemical plants in the Middle East and other parts of the world, where supplies are far less expensive.
Accordingly, Banholzer made the case for exploiting biomass, alcohols, and other alternative starting materials. He also emphasized the need to develop energy-efficient processes, likely based on novel catalysts, for converting methane (the major constituent of natural gas) to more valuable chemicals, such as ethylene, propylene, and olefin precursors. To hasten that discovery process, Dow recently announced plans to fund public research proposals in methane-conversion chemistry (C&EN, March 19, page 12).
Converting biomass—various types of grasses, trees, and agricultural by-products—into liquid fuels or hydrogen is on the research agenda in many laboratories nowadays. UC Berkeley's Harvey W. Blanch, professor of chemical engineering, gave an overview describing the composition of biomass and several methods for converting the material into useful products.
Plant cell walls, which are composed in large part of cellulose and lignin, are the principal components of biomass under investigation for production of fuels, Blanch explained. Cellulose is a polysaccharide that forms microcrystalline fibrous structures, and lignin is a large biopolymer made from p-coumaryl alcohol and related alcohol monomers. A number of methods for converting biomass to fuels have been studied for years. These include gasification to produce a mixture of carbon monoxide and hydrogen (syngas), and acid- or enzyme-catalyzed hydrolysis to form ethanol or other fuels.
In general, though, those methods are inefficient and costly, Blanch noted. One approach being studied for lowering the cost of the enzymes is cultivating biomass crops that abundantly produce cellulose- and lignin-decomposing enzymes.
For the better part of two days, researchers from industry, academia, and national labs spent their time in topical discussion groups prioritizing catalysis research needs and then presented their preliminary findings to the entire group. Johannes A. Lercher of Technical University of Munich noted that the panel he led, which focused on fossil energy feedstocks, recognized from the outset that despite broad efforts to develop alternative energy sources, fossil fuels are likely to be a key component of the energy mix for years to come. For that reason, it is imperative, he said, to come up with creative ways to use those resources in nonpolluting processes that are more efficient than today's methods.
THE FOSSIL FUEL feedstocks panel identified a number of key areas for research, including developing novel methods for functionalizing light alkanes—for example, through selective partial oxidation or catalytic methane coupling chemistry—and discovering new techniques for ridding raw materials of heteroatoms such as sulfur, nitrogen, and oxygen. The group stipulated that those purification procedures should not affect olefinic bonds and not depend on the costly hydrotreating technology used today.
The group also stressed the need to design advanced catalytic procedures that will enable complex fuels to be synthesized directly in single-pot reactions from multiple starting materials. Success in that area requires broadening current understanding of cooperative effects among multiple neighboring functional groups.
One of the other panels, which focused on opportunities in photo- and electro-catalytic chemistry, identified water splitting and CO2 reduction as important topics in need of concentrated research. In addition to articulating the importance of pursuing the primary goal of producing hydrogen inexpensively from noncarbon sources, the panel emphasized the need to uncover the mechanisms of water oxidation to O2 and to develop efficient, robust, and low-cost (noble-metal-free) catalysts to mediate water splitting.
Similarly, the group called for developing catalytic routes to convert CO2 to liquid fuels, a process with the potential to make a positive impact on the CO2 emissions problem. The researchers noted that, in general, CO2- and water-conversion technologies provide methods for harvesting and storing solar energy in the form of chemical bonds.
The team that focused on biomass conversions acknowledged that that field is, more or less, in its scientific infancy. Little is known at the molecular scale about catalyst design, reaction mechanisms, thermodynamics, kinetics, and other factors that control the conversion processes, they said. Tapping the energy stored in plant matter in an efficient way requires a battery of fundamental chemical studies.
Many other scientific goals and research priorities were enumerated at the workshop's preliminary reporting session. For example, several groups identified the need to develop advanced computational tools and new types of analytical techniques that provide multipronged probes of catalytic processes. The organizers and a handful of panelists are now combing through the workshop's findings and plan to submit a final report to DOE in October. The document will be available to the public shortly thereafter.
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