10.1 Manufacture of Ethanol

10.1 Manufacture of Ethanol

1. Making ethanol by fermentation

When aqueous glucose is mixed with yeast and left for several days at $25 - 35^{\circ}C$ in the absence of oxygen. Enzymes present in yeast convert the glucose into ethanol and carbon dioxide. This process is called fermentation.

The fermentation process produces $10 - 15\%$ ethanol. The yeast is killed beyond this concentration. The ethanol is separated from the mixture by fractional distillation, which gives $96\%$ pure alcohol also called rectified spirit. The remaining $4\%$ of water cannot be removed by fractional distillation. Rectified spirit is converted into $100\%$ pure ethanol by using a dehydrating agent such as concentrated ${\mathrm{H}}_2{\mathrm{S}\mathrm{O}}_4$$\mathrm{H}_{2}\mathrm{SO}_{4}$. This method uses renewable resources and low energy levels.