Two Pt(0.3 %)-Ge/Al2O3 catalysts containing 0.15 and 0.45 % Ge have been characterized by CO chemisorption and FTIR spectra of adsorbed CO after series of oxidation/reduction and oxychlorination/reduction cycles and have also been used for the catalytic hydroreforming of heptane. Catalysts after oxychlorination contained chloro- and oxychloro-Pt complexes which were responsible for the efficient spreading of Pt over the support surface and hence for the maintenance of a good Pt dispersion after reduction. XRD study of a more highly loaded catalyst gave no evidence for Pt-Ge alloy formation or for Ge-0 species. Reduced Cl-containing catalysts contained small clustered arrays of Pt atoms dispersed possibly as mats rather than particles over the GeOx-modified alumina such that all the exposed Pt atoms were influenced by an electron withdrawing effect of both Ge2+ ions and Cl ions. Germanium did not block low-coordination Pt sites but may have partially decorated arrays of high coordination sites. Germanium partially stabilized Pt/Al2O3 against loss of activity through coking. The dominant mutual effect of Ge and Cl in catalysts was a significant loss in hydrogenolysis selectivity, but gains in the selectivities of aromatization, isomerization, and cyclization reactions. The addition of Ge to Pt/Al2O3 did not compromise the availability of Pt adsorption sites and only reduced by a small amount the turnover frequencies for heptane reforming reactions. Good activities were therefore maintained in the absence of GeO or alloy formation during catalyst reduction, (C) 2000 Academic Press.