fermentation method
Agricultural products rich in starch, such as grains and potatoes. Or wild plant fruit, washing and crushing, pressure cooking to gelatinize the starch, then adding a proper amount of water, cooling to about 60 DEG C, and adding amylase to hydrolyze the starch into maltose and glucose in turn. Then zymogen is added for fermentation to obtain ethanol.
Hydration method
It is prepared by addition reaction of ethylene and water. Hydration is divided into indirect hydration and direct hydration. Indirect hydration method is also called sulfate method, and the reaction is carried out in two steps. Firstly, 95 ~ 98% sulfuric acid and 50 ~ 60% ethylene are absorbed and reacted in a tower reactor according to the weight ratio of 2: 1, and sulfate is generated at 60 ~ 80℃ and 0.78 ~ 1.96 MPa. The second step is to hydrolyze sulfate in a hydrolysis tower at 80 ~ 100℃ and 0.2~0.29MPa to obtain ethanol, and at the same time generate by-product diethyl ether. Olefins react directly with water to produce ethanol. Direct hydration is a one-step process. It is prepared by hydration of ethylene and water in the presence of phosphoric acid catalyst at high temperature and high pressure. This method has the advantages of simple process, low corrosiveness, no need for special steel and less by-product ether, but it requires high purity of ethylene and high power consumption. Whether it is fermentation or ethylene hydration, the ethanol produced is usually the boiling point of ethanol and water, that is, industrial ethanol with a concentration of 95%.
method of purification
Generally, the purity of anhydrous ethanol on the market can only reach 99.5%. Many reactions need anhydrous ethanol with higher purity, and they often need to be prepared by themselves. Generally, 95.5% ethanol for industrial use cannot be directly distilled to produce anhydrous ethanol, because 95.5% ethanol and 4.5% water form a constant boiling point mixture. In order to remove water, the first step is to add calcium oxide (quicklime) to boil and reflux, so that the water in ethanol reacts with quicklime to generate calcium hydroxide, and then distilled anhydrous ethanol. The anhydrous ethanol thus obtained has the highest purity of about 99.5%. Anhydrous ethanol with high purity can be treated with metallic magnesium or metallic sodium.
Colorless transparent liquid. It smells of burning. It is easy to flow and absorb water from the air, and can be mutually dissolved with organic solvents such as water, chloroform and ether in any proportion. It can form a * * * boiling mixture with water (water content is 4.43%), and the * * * boiling point is 78. 15℃. Relative density (d204)0.789. Melting point-1 14. 1℃. The boiling point is 78.5℃. Refractive index (N20d) 1.438+0. Flash point when the cup is closed (flammable gas is heated and volatilized in a container with a specified structure, mixed with air near the liquid level, and can be ignited by Mars when it reaches a certain concentration) 13℃. Flammable. Steam and air can form explosive mixture, and the explosion limit is 3.5% ~ 18.0% (volume).