Catalytic productivity

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The catalytic productivity  P (Eng. Turnover Number , abbreviation  TON ) is a dimensionless quantity in catalysis . It indicates the amount of product per amount of catalyst under certain reaction conditions .

In organometallic homogeneous catalysis

In organometallic homogeneous catalysis , the catalytic productivity is usually given on a molecular basis as the amount of substance (in moles ) of the substrate that one mole of the catalyst can convert before it becomes irreversibly inactive:

In polymerizations such as the Ziegler-Natta polymerization , the unit

used. It can be determined by determining the catalyst concentration in the end product using analytical methods such as X-ray fluorescence spectroscopy or elemental analysis . In the case of metallocene- catalyzed olefin polymerizations, a catalytic productivity of 60,000,000 g PE / g metal was demonstrated.

In heterogeneous catalysis

In heterogeneous catalysis , the volume of reactants converted per bulk volume of the catalyst is chosen as a reference value:

Other reference values ​​are the BET surface area , the number of catalytically active sites, for example determined by chemisorption / desorption of hydrogen or carbon monoxide for metal catalysts or of ammonia for acidic sites.

In enzyme catalysis

In enzyme catalysis , the turnover number is defined differently, namely as turnover per catalytically active center and per unit of time . This value is otherwise defined in catalysis as the turnover number , turnover rate or turnover frequency .

literature

  • D. Steinborn: Fundamentals of organometallic complex catalysis , 346 pages, Verlag Teubner BG GmbH (2007), ISBN 3-8351-0088-2

Individual evidence

  1. Bernd Peifer, M. Bruce Welch, Helmut G. Alt: Synthesis and characterization of C1- and C2-bridged bis (fluorenyl) complexes of zirconium and hafnium and their application in catalytic olefin polymerization. In: Journal of Organometallic Chemistry. 544, 1997, pp. 115-119, doi : 10.1016 / S0022-328X (97) 00338-0 .
  2. M. Boudart: Turnover Rates in Heterogeneous Catalysis. In: Chemical Reviews. 95, 1995, pp. 661-666, doi : 10.1021 / cr00035a009 .
  3. Entry on turnover frequency . In: IUPAC Compendium of Chemical Terminology (the “Gold Book”) . doi : 10.1351 / goldbook.T06534 .

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