Magnetic study of CO and C/sub 2/ hydrocarbons adsorption on Pd/SiO/sub 2/ catalyst

The adsorption of H/sub 2/, CO, C/sub 2/H/sub 2/, C/sub 2/H/sub 4/, and C/sub 2/H/sub 6/ on a Pd/SiO/sub 2/ catalyst has been studied by measuring the variation of the paramagnetic susceptibility of the metal in relation to the adsorbate and its coverage. For H/sub 2/, it is assumed that each adsorbed atom cancels out the magnetization of one surface palladium atom (Pd/sub s/). For CO, only one state of chemisorption is detected which involves 1.5 Pd/sub s//CO. For C/sub 2/H/sub 6/, complete breaking may occur since 16 Pd/sub s/ are concerned by the chemisorption of one molecule of C/sub 2/H/sub 6/. With C/sub 2/H/sub 4/, two species are observed. The first, at low coverage is probably dehydrogenated, the other, at high coverage, is linked with 3 or 4 Pd/sub s/. With C/sub 2/H/sub 2/, only one species is detected, over the full range of coverage, which involves 2 Pd/sub s/. A bi-..pi.. coordinated model, in good agreement with recent work done by electronic spectroscopies, has been proposed. 17 references, 4 figures, 2 tables.