The number of motor vehicles in the world is constantly growing, along with the consumption of fuel. This causes the growing harmful emissions. One of the ways to tackle this problem is to replace the traditional fossil fuel with gasoline containing various additives.
Using ethanol to produce fuel increases octane number and reduces the amount of harmful emissions by 30-50%.
Regular refined alcohol has 5-7% water by weight and its solubility in gasoline is limited. Therefore, to make ethanol gasoline, ethanol is dehydrated by one of the two methods: azeotropic rectification or adsorption with zeolite. Several factors influence the homogeneity of the solution, of which the residual water content in ethanol after dehydration is the most important. This factor influences the cost of the dehydration process.
When such fuel is made, to homogeneous phases are created, in which the ratio of aromatic hydrocarbons to paraffin-naphthene hydrocarbons does not change, but the ratio of water to ethanol changes sharply. The hydrocarbon phase takes only some ethanol from the initial mix, in which the content of water drops sharply. The other phase is the ethanol phase, which contains ethanol with much higher water content, and some hydrocarbons, saturated with aromatic hydrocarbons as compared to the initial mix. In other words, the heterogeneous mixture of ethanol and gasoline is separated into two phases, the quantity and composition of which is defined by the percentage of ethanol in the initial mix.
The lower phase is ethanol, where most of the water from the original mix with gasoline is concentrated, and some gasoline, which can solve ethanol with increased water content at subzero temperature. This phase is sent to refining, where ethanol with 5% water is obtained.