**2. Properties of alcohol fuels**

Alcohols and ethers can replace gasoline and oil. **Table 1** exhibits properties of n-butanol, ethanol, and gasoline for comparison. In **Table 1**, RON, MON, and RVP values for butanol and ethanol are meant for gasoline blend fuels.

**Table 2** contains a more wide range of properties of alcohols and ethers compared to gasoline and fusel oil. Fusel oil or fusel alcohol is defined as a mixture of several alcohols produced as a by-product of alcoholic fermentation.

In general, alcohols contain higher values than gasoline in oxygen content, octane number, and autoignition/flash point temperatures, while freezing point temperature is lower.

Tetraethyllead has been banned for use as an additive to improve octane number of gasoline fuel. Methyl tertiary-butyl ether (MTBE) and alcohols are thus used as alternative additives to gasoline, but MTBE has also been banned after the 2000s, and alcohols have become useful additives to increase octane number of gasoline.

Water solubility of alcohols is an important property when alcohols are being used as fuel. Gasoline has a water solubility value of less than 0.01, whereas ethanol exhibits a full miscibility as 100. When alcohols contain a high solubility in water, spill or leakage of the mixed alcohol fuels can cause polluting the underground water.


#### **Table 1.**

*Properties of n-butanol and ethanol with gasoline [4].*


#### **Table 2.**

*Detailed properties of alcohols, ethers, and related fuels [3].*

Methanol, ethanol, and propanol are completely miscible in water, which means that they dissolve in water in any amount. Both methanol and ethanol dissolve readily in water, are fortunately biodegradable, and do not bioaccumulate. They are not rated as toxic to aquatic organisms [5].

Starting with the four-carbon alcohol (butanol), solubility is starting to decrease, and from the seven-carbon length heptanol, alcohols are practically immiscible in water (**Table 3**) [6]. This is one of the backgrounds for the development of butanol as another alcohol fuel.

Other important properties of alcohol fuels reside in its inherent swelling of plastics and corroding power for metals. These properties ask modification in the existing infrastructure of automobiles and other appliances.

*Alcohol Fuels: Current Status and Future Direction DOI: http://dx.doi.org/10.5772/intechopen.89788*


**Table 3.**

*Alcohol solubility in water in mol/100 g of H2O (1 bar, 25°C) [6].*
