Inverse gas chromatography (IGC) was used to study the interactions of reactants and products with styrene divinylbenzene copolymer (SDB) and Pd supported on SDB catalysts for the propylene partial oxidation to acrylic acid. The adsorption heat, free energies, and specific interaction of propylene, oxygen, water, acrolein, and acrylic acid with the solid surface were measured and compared with n-alkane probe molecules. It was found that adsorption of oxygen on Pd/SDB catalysts is very weak, even weaker than methane. Water does not adsorb on the support or the catalyst, but strong adsorption of reaction products, acrolein, and acrylic acid was observed. Based on these results, a mechanism for propylene oxidation over Pd/SDB is proposed.