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CHEMISTRY
Design of a "green" one-step catalytic production of -caprolactam (precursor of nylon-6)

John Meurig Thomas ^*, , , and Robert Raja 

^*Department of Materials Science, University of Cambridge, Cambridge CB2 3QZ, United Kingdom; Davy Faraday Research Laboratory, Royal Institution of Great Britain, 21 Albemarle Street, London W1S 4BS, United Kingdom; and Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom

Communicated by John D. Roberts, California Institute of Technology, Pasadena, CA, August 11, 2005 (received for review June 1, 2005)

The ever-increasing industrial demand for nylon-6 (polycaprolactam) necessitates the development of environmentally benign methods of producing its precursor, -caprolactam, from cyclohexanone. It is currently manufactured in two popular double-step processes, each of which uses highly aggressive reagents, and each generates substantial quantities of largely unwanted ammonium sulfate as by-product. Here we describe a viable laboratory-scale, single-step, solvent-free process of producing -caprolactam using a family of designed bifunctional, heterogeneous, nanoporous catalysts containing isolated acidic and redox sites, which smoothly convert cyclohexanone to -caprolactam with selectivities in the range 65–78% in air and ammonia at 80°C. The catalysts are microporous (pore diameter 7.3 Å) aluminophosphates in which small fractions of the and tetrahedra constituting the 4-connected open framework are replaced by and tetrahedra, which become the loci of the redox and acidic centers, respectively. The catalysts may be further optimized, and already may be so designed as to generate selectivities of 80% for the intermediate oxime, formed from NH₂OH, which is produced in situ within the pore system. The advantages of such designed heterogeneous catalysts, and their application to a range of other chemical conversions, are also adumbrated.

hydroxylamine | single-site heterogeneous catalysts (SSHC) | ammoximation

Abbreviations: SSHC, single-site heterogeneous catalyst; AlPO, aluminophosphate.

To whom correspondence should be addressed: E-mail: jmt2{at}cam.ac.uk.

© 2005 by The National Academy of Sciences of the USA

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