Radical reactivity of mesoporous sulfonic polydivinylbenzene as the catalytic support in the direct synthesis of hydrogen peroxide and its role in the formation of palladium hydrides

Abstract

The direct synthesis of H2O2 is nowadays a hotspot in heterogeneous catalysis. The reaction is promoted by Pd nanoparticles supported on a porous material, strongly affecting the catalytic performance. Nanostructured Pd supported on ion-exchange resins shows remarkable catalytic activity, as compared to catalysts supported on inorganic materials. Novel catalysts supported by a highly accessible cross-linked polymer have been developed, by using a mesoporous form of polydivinylbenzene (pDVB). Different sulfonation procedures lead to different morphology and reactivity of the supports, hence to different performances of palladium catalysts supported thereby. XRD suggests the formation of palladium hydride during the metal precursor reduction with H2. This phase is stable under laboratory conditions for several weeks, but its catalytic role, if any, also depends on other conditions, such as the presence of sulfonic groups. EPR of the spent catalysts points out radical species, suggesting the participation of pDVB in the formation of H2O2.