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Science 23 April 1993:
Vol. 260. no. 5107, pp. 511 - 515
DOI: 10.1126/science.260.5107.511
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Articles

Manganese Oxide Octahedral Molecular Sieves: Preparation, Characterization, and Applications

Y. F. Shen 1, R. P. Zerger 1, R. N. DeGuzman 1, S. L. Suib 2, L. McCurdy 3, D. I. Potter 3, and C. L. O'Young 4

1 Department of Chemistry, U-60, University of Connecticut, Storrs, CT 06269
2 Departments of Chemistry and Chemical Engineering and Institute of Materials Science, U-60, University of Connecticut, Storrs, CT 06269
3 Department of Metallurgy and Institute of Materials Science, University of Connecticut, Storrs, CT 06269
4 Texaco Research Center, Texaco, Inc., P.O. Box 509, Beacon, NY 12508

A thermally stable 3 x 3 octahedral molecular sieve corresponding to natural todorokite (OMS-1) has been synthesized by autoclaving layer-structure manganese oxides, which are prepared by reactions of MnO4- and Mn2+ under markedly alkaline conditions. The nature and thermal stability of products depend strongly on preparation parameters, such as the MnO4-/Mn2+ ratio, pH, aging, and autoclave conditions. The purest and the most thermally stable todorokite is obtained at a ratio of 0.30 to 0.40. Autoclave treatments at about 150° to 180°C for more than 2 days yield OMS-1, which is as thermally stable (500°C) as natural todorokite minerals. Adsorption data give a tunnel size of 6.9 angstroms and an increase of cyclohexane or carbon tetrachloride uptake with dehydration temperature up to 500°C. At 600°C, the tunnel structure collapses. Both Lewis and Brönsted acid sites have been observed in OMS-1. Particular applications of these materials include adsorption, electrochemical sensors, and oxidation catalysis.

Submitted on October 6, 1992
Accepted on January 21, 1993


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