MICROPOROUS POLY-(N,N-DIMETHYL-ACRYLAMIDE)-(1-METHACRYLOYL-ETHYLENE-2-SULFONATE)-(N, N'-METHYLENE-BIS-ACRYLAMIDE) RESINS AS HYDROPHILIC SUPPORTS FOR METAL-CATALYSTS

The synthesis of poly-(N,N-dimethyl-acrylamide)-(1-methacryloyl-ethylene-2-sulphonate) (M4K) with 4 mol. % of N,N'-methylene-bis-acrylamide (MBAA) as crosslinker, and of poly-(N,N-dimethyl-acrylamide)-(1-methacryloyl-ethylene-2-sulphonic acid) (M4A) with 4 mol. % MBAA is described. Polymerization was performed under gamma rays irradiation of a water solution of monomers (M4K), or of the monomer mixture (M4A), at room temperature. High affinity to protonic solvents was observed for both materials. Palladium catalysts were prepared from M4K through ion-exchange with [Pd(NH3)4]2+ and from M4A through ion-exchange with palladium acetate; the subsequent Pd(II) reduction with sodium borohydride in ethanol yielded the final catalysts with a uniform distribution of metal throughout the resin particles. The average size of metal crystallites obtained by X-ray diffraction was about 4 nm and did not show any dependence on metal content in the polymer in the range from 0.5 to 8.8 w/w % of metal. The rate of hydrogenation of p-nitrotoluene and cyclohexene in catalytic tests with 1 and 0.5 w/w % Pd catalysts was proportional to the metal content in catalysts, which confirmed a very good accessibility of these supports. Catalysts with low metal content also exhibit a significant deactivation in the course of the hydrogenation of p-nitrotoluene to p-toluidine in methanol under ambient conditions.