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SUMMARY:Use of mesoporous materials to overcome reactant incompatibility a
 nd for homogeneous and heterogeneous catalysis - Prof. Krister Holmberg\, 
 Department of Chemical and Biological Engineering\, Chalmers University of
  Technology\, Gothenburg\, Sweden
DTSTART:20080425T140000Z
DTEND:20080425T150000Z
UID:TALK11051@talks.cam.ac.uk
CONTACT:Dr Jonathan Barnard
DESCRIPTION:Microemulsions and other microheterogeneous media can be used 
 to overcome  incompatibility problems in organic synthesis. Reactant incom
 patibility is a well-known problem in preparative organic chemistry and a 
 common approach to the problem is to use a two-phase system with added pha
 se transfer catalyst. We have shown that the microemulsion concept can be 
 seen not only as an alternative but also as a complement to phase transfer
  catalysis. Very high reaction rates were obtained when the reaction was p
 erformed in a microemulsion with added phase transfer catalyst. We have al
 so shown that the microemulsion-based reaction medium need not be a one-ph
 ase system. Also Winsor systems\, i.e.\, a microemulsion coexisting with a
 n excess oil phase\, an excess water phase or two excess phases\, work wel
 l.\n\nLiquid crystalline phases and dispersions of mesoporous materials ar
 e other types of microheterogeneous media useful for overcoming reactant i
 ncompatibility. Mesoporous materials can also be used as host for homogene
 ous catalysts. Such a catalyst\, which may be a synthetic metal-organic co
 mpound or an enzyme\, can be immersed into the aqueous pores of the mesopo
 rous material. Catalyst-loaded fine particles of the mesoporous material a
 re subsequently dispersed in an apolar phase that contains lipophilic reac
 tants. The reaction occurs at the interface\, i.e.\, the pore openings. Th
 e approach can also be reversed. Instead of using hydrophilic mesoporous o
 xide\, such as silica\, alumina or titania\, a mesoporous material that is
  hydrophobic in character is used. It may be either mesoporous carbon or a
  mesoporous oxide that has been hydrophobized by a silanization procedure.
  A hydrophobic homogeneous catalyst is immersed in the pores and the catal
 yst-filled material is subsequently dispersed in an aqueous solution of hy
 drophilic reactants. Again the reaction occurs at the pore openings. \n\nT
 he approach of incorporating a homogeneous catalyst in the pores of a meso
 porous material (“heterogenization”) combines the benefits of homogene
 ous catalysis with those of heterogeneous catalysis. The reaction process 
 is that of homogeneous catalysis\; yet\, the work-up is as simple as for h
 eterogeneous catalysis: the catalyst-loaded particles are simply filtered 
 off and reused. We have also demonstrated that a column procedure can be u
 sed. The reactants are added to a column packed with the catalyst-containi
 ng particles and the products are recovered from the effluent.  
LOCATION:T001 [Tower Seminar Room]\, Materials Science and Metallurgy\, De
 partment of
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