Synthesis, characterization and catalytic properties of sulfonic acid functionalized magnetic-poly(divinylbenzene-4-vinylpyridine) for esterification of propionic acid with methanol

The magnetic-poly(divinylbenzene-4-vinylpyridine) [m-poly(DVB-4VP)] microbeads (average diameter: 180-212 mu m) were synthesized by copolymerizing of divinylbenzene (DVB) with 4-vinylpyridine (4VP) and by mixing this copolymer with Fe3O4 nanoparticles. The resultant material was characterized by N-2 adsorption/desorption, ESR, elemental analysis, scanning electron microscope (SEM) and swelling studies. After functionalized with sulfonic acid, m-poly(DVB-4VP-SO3H) was characterized by FT-IR and TGA analysis. The results showed that both of Fe3O4 and -SO3H are bonded to the polymer successfully. N-2 adsorption/desorption isotherms of synthesized samples had the hysteresis behaviour associated with mesoporous materials (pore diameter: 3.73 nm). Sulfonic acid functionalized mesoporous m-poly(DVB-4VP-SO3H) has been demonstrated to have higher reactivity than commercially available solid acid catalysts for the conversion of propionic acid to methyl ester. The apparent activation energy was found to be 38.5 kJ mol(-1) for m-poly(DVB-4VP-20%SO3H). The catalyst showed negligible loss of activity after four repetitive cycles. Published by Elsevier B.V.