The scent source of the new Baijiu is mainly flavors and fragrances. Esters are the main components of Baijiu's aroma. The main esters in Baijiu include ethyl caproate, ethyl lactate, ethyl acetate, ethyl butyrate, and ethyl valerate. Ethyl acetate is also known as ethyl acetate. Pure ethyl acetate is a colorless, transparent and aromatic liquid. Today's ethyl acetate production routes are divided into four methods: esterification, acetaldehyde condensation, ethylene addition, and ethanol dehydrogenation.
The esterification method is the main process route for the industrial production of ethyl acetate in China. It is a relatively traditional method. Acetic acid and ethanol are used as raw materials, and sulfuric acid is used as a catalyst to directly esterify ethyl acetate, and then dehydrated and fractionated to obtain the finished product. The chemical reaction equation is as follows:
In our country, most of the raw ethanol used in this process is produced by grain fermentation, and a small amount is legally produced by ethylene water. This process has problems such as high production cost, serious equipment corrosion, difficult treatment of reaction waste liquid and large consumption of grain.
The traditional process must go through three stages: oxidative dehydrogenation of ethanol to acetaldehyde, oxidation of acetaldehyde to acetic acid, and esterification of acetic acid and ethanol to complete.
The new process does not use acetic acid, but directly oxidizes ethanol under the action of catalyst to synthesize ethyl acetate in one step. Its chemical reaction formula is:
The reaction characteristics are: low production cost, in areas where there is no methanol method to produce acetic acid, the price advantage is great. The process is simple and easy to operate. Basically no corrosion and three waste emissions. But the product quality is not as good as the esterification method. Although it can reach the national standard, if the impurities such as butanone produced are difficult to completely separate, it is not suitable for food and wine flavoring and other industries.
Ethyl acetate is synthesized from acetaldehyde under the catalysis of aluminum ethyl alcohol. Acetaldehyde and aluminum ethyl alcohol are continuously added to two reactors in series, and the reaction is carried out at 0-20 ℃. After the reaction, ethyl acetate is distilled. The reaction formula is:
The advantage of this process is that the reaction is carried out at atmospheric pressure and low temperature, and the process conditions are relatively mild. The disadvantage is that the aluminum-based catalyst cannot be recovered, and the residual ethanol aluminum in the distilled waste liquid is added to water to generate aluminum hydroxide emissions, resulting in environmental pollution. Most foreign countries use this method to produce ethyl acetate. Some people in China are also conducting research and development.
In the presence of water vapor, ethylene will hydrate to form ethanol, which will then continue to esterify with acetic acid to form ethyl acetate products.
The process relies on ethylene resources and can only be produced economically in regions where ethylene and acetic acid are abundant and inexpensive.
