Don't believe in all marketing crap you hear. There are cars designed to run on E85 (85% ethanol, 15% gasoline). If you believe that the ethanol would not produce practically any emissions, the emissions of E85 would be 15% (or perhaps a tiny bit more) of the emissions of pure gasoline. This is so low that the catalytic converter could probably be made much, much smaller or perhaps even eliminated completely.
Look at what kind of catalytic converters such cars actually have. Yes, they have catalytic converters equivalent to the ones in gasoline cars.
According to a book Vehicular Air Pollution I found from Google Books, ethanol fuel actually has some emissions worse than gasoline: ethanol emits more aldehydes. Also, if cold start enrichment is required for ethanol engines, then it does definitely emit VOCs, as all of the ethanol in a rich mixture cannot burn. The only thing that ethanol definitely does not emit is SO2.
The real reason for the existence of ethanol fuel is that it is somewhat easier to produce ethanol from agricultural products than it is to produce biogasoline. However, technology is quickly advancing and we may see biogasoline in the future. At least in Finland, I have read that there are plans to build biogasoline plants. The purpose of ethanol fuel is not to reduce harmful emissions (except carbon dioxide, obviously, if the ethanol is produced from biological sources and not from fossil fuels).