Catalytic combustion of volatile organic compounds on Indian Ocean manganese nodules

Catalytic combustion of acetone, methanol and 2-propanol as model volatile organic compounds (VOCs) has been measured over several manganese nodules o f Indian Ocean origin in the temperature range 180-280 degrees C. The catal ytic activity of the nodules for the decomposition of these species is corr elated with their chemical composition/surface properties (e.g. surface oxy gen). CO2 and H2O are detected as the only combustion products of acetone a nd methanol at all reaction temperatures. In the case of 2-propanol, aceton e and a small amount of propene are detected as byproducts. The formation o f acetone and propene is correlated with the redox properties and silica co ntent, respectively. These toxic effluents are further transformed to CO2 a nd H2O by passing over another catalytic reactor containing manganese nodul es at 230 degrees C. The catalytic activity of this naturally occurring mat erial is also compared with synthetic delta-MnO2 and gamma-FeOOH, which are the major components of manganese nodules. The iron-bearing phase, gamma-F eOOH, has no contribution, while delta-MnO2 plays the major role (at the op erating experimental conditions). It is observed that manganese nodules are effective enough for the destruction of VOCs and can be considered as low temperature oxidation catalysts. (C) 1999 Elsevier Science B.V. All rights reserved.