MOLECULAR ENGINEERING OF HETEROGENEOUS CATALYSTS - AN EFFICIENT CATALYST FOR THE PRODUCTION OF HYDROGEN-PEROXIDE

A goal of chemists for many years has been to control the structure of solid-state compounds to induce desired chemical properties. A porous metal phosphonate compound with chemically active pillaring groups, w hich allow for the direct production of hydrogen peroxide from hydroge n and oxygen, has been designed. The porous compound, Z(2)(PO4)(O3PCH2 CH2-bipyridinium-CH2CH2PO3)X(3) . 3H(2)O (X = halide) was prepared by low-temperature hydrothermal reaction. The organic groups of this mate rial act as pillars for the inorganic layers, leading to large pores ( ca. 8 x 9 Angstrom) in the solid. Platinum and palladium colloids can be incorporated into the structure by ion-exchanging the free halide w ith a solution of K(2)MCI(4) (M = Pd or Pt) followed by hydrogen reduc tion. In these materials, the Pt and Pd colloids act as microelectrode s for the reduction of viologen by hydrogen, which selectively reduces oxygen to hydrogen peroxide. Treatment of aqueous suspensions of thes e porous catalysts with H-2 and O-2 gases at atmospheric pressure lead s to H2O2 solutions with concentrations as high as 0.21 M. Reactions c arried out at higher pressures lead to significantly higher concentrat ions of H2O2 The yield of H2O2 based on H-2 consumed was estimated at 40%. (C) 1996 Academic Press, Inc.