Platinum Catalysts on Activated Carbon Supports Prepared from Mononuclear and Polynuclear Precursors: Influence of Porous Structure of the Support (pp.393-408)
Authors: (L.B. Okhlopkova, S.Yu. Troitskii, Boreskov Institute of Catalysis, Novosibirsk, Russia)
Abstract: A number of catalysts have been prepared by adsorption of platinum precursors on
activated carbons of different origin followed by reduction in flowing hydrogen. They were
characterized by CO chemisorption, TEM and liquid-phase hydrogenation of cyclohexene.
Porous structure of the support and the nature of platinum precursor proved to have a
profound influence on the properties of catalysts.
The metal dispersion of catalysts prepared from platinum (IV) chloride can be controlled
in the range from 10 to 90%. Activity of the catalysts reached a maximum in the range of
intermediate metal dispersion, with the limit being dependent on the support used. It has been
suggested that a part of the supported metal became inaccessible to the organic substrate due
to localization of metal particles in narrow pores of the support.
The extent of blocking proved to be higher for highly dispersed Pt particles and on the
supports with smaller pores. An alternative route to preparing supported Pt catalysts is the
synthesis of polynuclear hydroxochloride complexes from Pt(II) chloride that is followed by
their deposition on carbon.
The catalysts prepared from polynuclear precursor showed high activity even in the range
of high metal dispersion and for microporous carbons. Structure of product of Pt(II) chloride
hydrolysis was established by means of NMR 195Pt, 17O.