Synthesis of manganese oxide octahedral molecular sieves containing cobalt, nickel, or magnesium, and the catalytic properties for hydration of acrylonitrile

An octahedral molecular sieve known as OMS-1 has todorokite structure composed of magnesium and manganese oxides, which was named as Mg-todorokite here. Octahedral molecular sieves containing cobalt (Co-todorokite) or nickel (Ni-todorokite) without magnesium were prepared by a sequential method under optimum conditions and compared with the Mg-todorokite by powder XRD, ICP, FESEM, and catalytic reactions. The compositions of Co-todorokite, Ni-todorokite, and Mg-todorokite are Co0.37MnO2.3(H2O)2.1, Ni0.24MnO2.0(H2O)2.1, and Mg0.22MnO2.0(H2O)2.2, respectively. The Co-todorokite and Ni-todorokite are comparable in crystallinity with the highly crystalline Mg-todorokite. The catalytic properties were examined for the hydration of acrylonitrile. The apparent activation energies depend on the foreign metals. The order is Co-todorokite < Ni-todorokite < Mg-todorokite. The four products of the Mg-todorokite catalysis are 3-hydroxy-propionitrile, and bis-2-cyano-ethylether, succinonitrile, and acrylamide. The acid treatments for Mg-todorokite suppress the formations of 3-hydroxy-propionitrile and bis-2-cyano-ethylether, which would be due to the weakening of the basicity with the removal of magnesium ions. The only product of the Co-todorokite and the Ni-todorokite catalysis is acrylamide because of not containing magnesium.

The highly crystalline octahedral molecular sieves containing cobalt (Co-todorokite), nickel (Ni-todorokite), and magnesium (Mg-todorokite) were prepared by the sequential method under optimum conditions. For the acrylonitrile hydration, the apparent activation energies of todorokite catalysts depend on the foreign metals. Some products were formed over Mg-todorokite. The only product formed over Co-todorokite and the Ni-todorokite was acrylamide. Figure optionsDownload as PowerPoint slide