Collect. Czech. Chem. Commun. 1979, 44, 3183-3193

Asymmetric distribution of a metal in a heterogenized homogeneous catalyst

Roman Řeřichaa, Antonín Vítekb, Dana Kolihovác, Václav Sychrac, Zdeněk Šíra and Jiří Hetflejša

a Institute of Chemical Process Fundamentals, Czechoslovak Academy of Sciences, 165 02 Prague - Suchdol
b Institute of Organic Chemistry and Biochemistry, Czechoslovak Academy of Sciences, 166 10 Prague
c Laboratory of Atomic Absorption Spectrometry, Prague Institute of Chemical Technology, 166 28 Prague


Beads of a styrene-divinylbenzene copolymer modified by dimethylaminomethyl groups (an analogue of the Amberlyst A-21 anex), were used as a support for H2PtCl6 in the form of its trialkylammonium salt (about 12 wt.% of Pt). A distribution of the metal in individual beads was estimated analyzing traces of Pd in 107 single beads by flameless atomic absorption spectrometry (ratio Pd : Pt = 1 : 104). The distribution curve is assymetric and fits a three-parameter, log-normal curve (Johnson SL family of empirical distributions). The correlation coefficient between the weight of one bead and its absolute content of Pd was rather low (0.56). So, it is obvious that any biased sampling of such catalysts may cause misleading results, both in the elemental analysis and in catalytic data, especially in experiments carried out on millimole scale. A working procedure for an unbiased sampling of bead catalysts is proposed.