Alcohol Fuels and Blends with Gasoline

Methanol is expected to oxidize to formaldehyde, both during combustion and after emission to the atmosphere. As discussed in Chapter 6.H, OH reacts with methanol primarily at the methyl group  

Both CH2OH and CH30 then react with 02 to give HCHO (and H02). However, as discussed in detail in 

An additional problem with alcohol-gasoline blends is the increase in vapor pressure of gasoline in the mixture (e.g., see National Research Council, 1991 Calvert et al., 1993 and Timpe and Wu, 1995). This can contribute to much higher Reid vapor pressures, increasing the relative importance of evaporative emissions. 

Overall, the use of ethanol blends is believed not to be effective in reducing ozone, but may actually increase it (Calvert et al., 1993 Dunker et al., 1996). 

Since the oxidation of H2 produces water, it should be one of the cleanest possible fuels, and this indeed appears to be the case, with emissions consisting primarily of NO, and very small amounts of VOC and CO from the combustion of some oil in the system. While it is being used in some buses, for example, it has not yet found widespread use due to technical and safety problems encountered on the passenger vehicle scale. 

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