Anchoring sulfonic acid on silica surface through Si[sbnd]C bond for immobilization of catalyst for polyketone synthesis

Abstract

Sulfonic acid groups were anchored on a silica surface through robust SiC bonds. The successive treatment of dehydroxylated silica with benzylmagnesium chloride and H2SO4 resulted in the surface tethering of CH2C6H4SO3H groups at a high coverage rate (0.50-CH2C6H4SO3H/nm2). The pore structure of the silica remained unchanged during this surface-modification process. Next, the CH2C6H4SO3H groups on the surface were successfully used for preparing a supported catalyst for CO/ethylene copolymerization; the ≡SiCH2C6H4SO3H groups on the surface were reacted with [1,3-bis(di(2-methoxyphenyl)phosphino)propane]Pd(OAc)2 to generate dicationic palladium species, which were anchored on the silica surface through ionic interactions with the sulfonate anions generated on the surface. The supported catalyst prepared in this way exhibited a high activity (up to 43kg/g-Pd or 0.61kg/g-cat) with respect to CO/ethylene copolymerization. The morphology of the obtained polymer particles replicated that of the silica particles. Thus, a polymer powder that exhibited a high bulk density (0.30g/mL) could be obtained while causing minimal reactor fouling.