Following gradual shift of primary resources from fossil towards renewable ones in chemical industry, biomass based ethanol has been attracting growing interests as a fuel to replace gasoline and as a chemical feed stock to replace ethylene. This paper reviews major work reported in the last 10 years for the production of acetaldehyde, acetic acid, and other related compounds from ethanol. At present acetic acid can be industrially produced more economically from methanol than from ethylene, the production of acetic acid from ethanol is not profitable. Acetaldehyde, which is more expensive than ethanol, can be selectively produced in gas phase by dehydrogenation over supported Cu catalysts and by oxidation with O 2 over V and Mo based oxides. It is noteworthy that gold nanoparticles deposited on basic and acidic metal oxides are highly selective to acetaldehyde by oxidation with O 2 . Acetic acid can be produced in water solvent over Au catalysts supported on MgAl 2 O 4 or on Cu doped NiO, while in gas phase over Mo-V-Nb mixed oxides combined with TiO 2 colloids.

Twenty three kinds of metal oxides were screened as supports for Au nanoparticles (Au NPs) in the gas phase oxidation of ethanol. Mild oxidation to acetaldehyde, which is economically preferable, is catalyzed by Au NPs deposited on catalytically inert metal oxides, in particular, strongly acidic MoO 3 or weakly basic La 2 O 3 . Deep oxidation to acetic acid takes place over Au NPs deposited on n-type semiconductive metal oxides such as ZnO and V 2 O 5 , which exhibit a little catalytic activity for ethanol oxidation at 200 1C. Complete oxidation to CO 2 and H 2 O preferentially takes place over p-type semiconductive metal oxides such as MnO 2 and Co 3 O 4 , and CeO 2 which has oxygen-storage and discharge capability. These metal oxides show catalytic activity for ethanol oxidation even at 100 1C producing mainly acetaldehyde, and their catalytic activity is noticeably enhanced in the conversion of ethanol and the selectivity to CO 2 by the deposition of Au NPs. The wide range of product tunability can be explained by the adsorption structures of ethanol and by the reactivities of oxygen species on the metal oxide supports.