that consists of a chaotic assemblage of fullerene shards bonded together. The material contains pores with a narrow size distribution around 5 A. In terms of its pore structure, the mem brane material "is basically like a zeolite," even though it is noncrystalline. "It's a fascinating material," Foley comments. Previous attempts to create tubular nanoporous carbon membranes usually were thwarted by cracks that spread through the material, rendering it use less. The Delaware researchers careful-
Carbon membrane eyed for gas separation Researchers have ultrasonically pre pared a robust, nanoporous carbon membrane that allows oxygen mole cules to pass through its pores 30 times faster than nitrogen molecules—an im pressively high selectivity, according to one membrane expert. The researchers—chemical engineer ing professor Henry C. Foley of the Uni versity of Delaware, Newark, and re search engineer Mark B. Shiflett of DuPont Central R&D in Wilmington, D e l believe that such ceramic membranes, if developed further, could have potential for industrial gas separations and enrich ment of protein broths. The membrane material might also have catalytic and fuel cell applications, according to Foley. In a paper published last week [Sci ence, 2 8 5 , 1902 (1999)], Shiflett and Foley report that air passed through the carbon membrane was enriched by about 100%—changing from 21% oxy gen to 44%. The enrichment would have been considerably greater if the mem brane had performed ideally—that is, true to its ideal 0 2 /N 2 selectivity of 30— but that hasn't yet been achieved. Nevertheless, Foley believes that nan oporous carbon membranes could be come a more economical way to separate nitrogen and oxygen from air than existing methods such as cryogenic distillation. Nitrogen, the most widely used gas in the world, and oxygen are crucial to many processes in the chemical, petroleum, and metals industries, among others. According to Shiflett, who is pursu ing a Ph.D. in chemical engineering un der Foley, the new carbon membrane's selectivity is comparable to, or better than, the selectivity of conventional polymer membranes used for oxygennitrogen separations from air. 'There's a strong interest," though, in moving to ceramic membranes like the carbon material because they can tolerate hotter, harsher environments than polymer membranes, Foley notes. Ceramic membranes also last longer, and they may be less expensive than polymer membranes. Foley and Shiflett prepare their car bon membranes by ultrasonically dis persing polyfurfuryl alcohol into tiny droplets, which are deposited in thin films on a porous stainless steel tube. The coated tube is then pyrolyzed at 450 °C, creating a 15- to 20-um-thick film
ly control the membrane thickness to avoid cracking. Foley would like to make the mem brane thinner to increase its throughput capacity 10-fold while preserving its se lectivity. Achieving that would put the material on the fast track to commercial ization, he says. The most important hur dle, though, is finding a way to make the membrane manufacturable on a large scale. Toward this goal, "we couldn't have a finer partner than DuPont," Foley says. Ron Dagani
NRC study will scrutinize chemical sciences of the chemical sciences in a historical context, in part by referring to previous assessments. These include NRC's 1965 report on chemistry headed by Frank H. Westheimer, professor of chemistry emeritus at Harvard University, and its 1985 successor led by the late George C. Pimentel, who was professor of chemis try at the University of California, Berke ley; a 1988 NRC report on | chemical engineering | headed by NealRAmund1 son, professor of chemical £ engineering and math at | the University of Houston; PΕ and 'Technology Vision Le 2020: The U.S. Chemical F Industry," which was pro -α ο duced in 1996 by a coali ο tion of professional and trade organizations. Beyond this, Raber says, the survey will "iden tify new areas of opportunity, scientific and techni d Brown (left) and cal obstacles, and other Breslow challenges that chemical sciences and technology will face in the ucation and careers, research strate next decade." gies, and policy and funding matters. Study results will be published in a se Ronald Breslow, professor of chemis try at Columbia University, and Robert ries of reports, beginning with an over A. Brown, provost and professor ol view. Breslow says this first section will chemical engineering at Massachusetts identify major advances in the past sever Institute of Technology, will cochair the al decades and evaluate their impact; ex study. The study committee will be amine the interfaces with other fields rounded out by about 10 other experts such as biology, environmental science, materials science, medicine, and physics; in the chemical sciences. Breslow believes that "chemistry is identify today's "grand challenges"; and not sufficiently appreciated by the public determine what infrastructure is needed and its elected representatives or the me to move the field ahead. dia." He hopes the report will improve Reports in the second stage of the this attitude by describing the significant project will be based on workshops that contributions that chemistry and chemi "address the linkages between basic re cal engineering have already made and search and areas of societal need," can be expected to make in the future. Breslow says. Sophie Wilkinson The team will place the current status The National Research Council's (NRC) Board on Chemical Sciences & Tech nology (BCST) has initiated a wideranging study of the current status, fu ture opportunities, and challenges for the chemical sciences. BCST Director Douglas J. Raber says the two-year study will assist students, researchers, science and technology managers, and government agencies in making decisions on ed-
CO
SEPTEMBER 20,1999 C&EN
11
