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The experiments in Lagow's lab produce mixtures of carbon chains, which haven't yet been separated. To gain a better understanding of the molecules, the researchers used conventional solution-phase methods to prepare model compounds that contain acetylenic chains of eight, 16, 24, and 28 carbon atoms. These chains, they find, are stable to at least 130 °C. An X-ray crystal structure of the C8 compound shows the chain is slightly curved. Lagow believes much longer chains, present as diradicals in vaporization experiments, could form spiral structures that would undergo a series of
"zipperlike" cross-linking reactions, similar to Diels-Alder reactions, to give fullerenes or fullerene-like materials. However, cautions another chemist familiar with the work, this "spiral zipper hypothesis" hasn't been substantiated by experiment. Lagow says his linear carbon material should be considered a new elemental form of carbon—in the same realm as graphite, diamond, and fullerenes/ nanotubes. Not everyone agrees. "This is the best chemistry ever done in my laboratory," he says. But he admits "not everyone is going to believe [our results]." Ron Dagani
Process change boosts polyethylene production BP Chemicals has unveiled a simple modification in its gas-phase process for making polyethylene that promises, for a modest investment, to more than double a reactor's capacity, slashing unit production costs. Introduction of the "high-productivity technology" by the London-based chemicals arm of British Petroleum follows several years of development. The work included X-ray imaging at the company's corporate research center in Sunbury, near London, and process runs at its 110 million-lb-per-year polyethylene test plant at Lavera on the French Mediterranean coast. A key problem with gas-phase fluidbed polyethylene polymerization has
Modified polyethylene process reactor throughput
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JANUARY 23,1995 C&EN
been removal of heat from the reactor, where reaction temperatures commonly run from 75 to 105 °C. This forms an intrinsic reactor bottleneck, limiting production capacity. BP Chemicals tackled this problem by turning to vaporization. Its new design enhances heat-exchange capacity so gases given off during polymerization are cooled and liquefied. The resulting liquids are separated and fed by a special injection nozzle back into the reactor, where they vaporize, absorbing heat from the system. Enough heat is removed to eliminate the bottleneck, the company says, enabling reactor output to more than double. The process works with any currently used catalysts and will accommodate metallocene catalysts being deincreases veloped throughout the industry. The company has applied for patents on the gas-phase technology in all major countries. The application, WO94/28032, was published in early December under the international Patent Cooperation Treaty. The firm plans to license the technology to other producers. BP Chemicals will install the technology in a retrofit of its 275 millionlb-per-year polyethylene plant at Grangemouth, Scotland, boosting capacity to 353 million lb by the end of 1995 and to 440 million lb in 1997, says
Michael Buzzacott, chief executive officer of the polymers and olefins division. Buzzacott says BP is sensitive to the issue of expanding capacity, noting the chemical industry has "just been through three terrible years" of low or nonexistent profitability. "But our customers at Grangemouth are now on allocation, and polyethylene markets, particularly in Europe, are growing quickly," he adds. There is a high probability the firm also will install the new process during expansion of a joint venture in Indonesia. Licensing General Manager Martin Howard claims the new technology will make obsolete all polyethylene processes except gas-phase polymerization. Whether it will or not, it offers polymer makers a new option in deciding whether to enlarge current facilities or build new ones. BP Chemicals is the second-largest licensor worldwide of gas-phase technology for making polyethylene, behind Union Carbide. Howard calculates BP's technology has been used in 27% of new plants built in the past decade, versus 38% for Carbide's. BP expects gas-phase technology to take an even larger share of new plants in the next investment cycle. "Our goal is to overtake Union Carbide to become number one," he says. Patricia Layman
FDA drug approval rate still draws industry fire The Food & Drug Administration made major improvements last year in its review speed for new drug applications. But the pharmaceutical industry still expresses concern about FDA's performance. FDA's just-issued annual summary of drug approval statistics shows significant improvement in review times in 1994 for approval of 85 new drugs and biological products. The median review time for 23 approved vaccines and biological products was 12.2 months, about half that in 1993. But of the 23, only one—ReoPro, a monoclonal antibody marketed by Centocor for use in angioplasty—was a new molecular entity (a product containing an active substance never marketed in any form in the U.S.). The agency's median time for approval of 52 new drugs (those not in
