From octahedral open structures to octahedral tetrahedral open structures: Synthesis, characterization and catalysis of manganese oxides and manganese (oxo- and/or hydroxo-) phosphates

Date of Completion

January 2001

Keywords

Chemistry, Inorganic

Degree

Ph.D.

Abstract

Novel preparation methods were employed to explore the richness of the synthetic chemistry of manganese oxide. Surfactant cations, tetradecyl-trimethyl-ammonium (TTA+), were directly intercalated into sodium birnessite to expand the microporous layered structure into a meso-structural one. Organization of the surfactant cations of the intercalated product is similar to that of the pure surfactant. Manjiroite was prepared as a single product for the first time. Very uniquely, this Na-OMS-2 has a meso and micro dual porosity. The morphology is comprised of multiple threads of tiny Na-OMS-2 crystals that form a knotted 3-dimensional network. ^ Synthetic strategies have been designed to introduce phosphate groups into the octahedral framework of manganese oxides. A few new materials with octahedral tetrahedral open structures have been synthesized. MPOS-3, Na 2Mn2O(PO4)2H2O has a rigid layered structure. MPOS-4, Na2Mn(HPO4)(PO4) is a chiral molecular sieve. MPOS-5, Na0.437MnO1.764(PO 4)0.236·xH2O is a mixed valent microporous material. ^ Various instrumentation methods were used to characterize the above materials. MPOS-3 demonstrated fair catalytic activity in the gas phase partial oxidation reaction of 2-propanol to acetone with carbon dioxide as the only by-product. The mixed valent manganese oxide and phosphate materials can be used as efficient catalysts in the partial oxidation of benzylic alcohols to aldehydes by air. ^

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