Detail drawing of glacial acetic acid

Acetic acid, also known as acetic acid, is an organic compound with the chemical formula CH3COOH. It is an organic monobasic acid and the main component of vinegar. Pure anhydrous acetic acid (glacial acetic acid) is a colorless hygroscopic liquid with a freezing point of 16.6 ℃ (62 ℉). After solidification, it becomes a colorless crystal. Its aqueous solution is weakly acidic and highly corrosive, with strong corrosiveness to metals. Steam has a stimulating effect on the eyes and nose.
Acetic acid is widely distributed in nature, such as in fruits or vegetable oils, where it mainly exists in the form of esters. Acetic acid exists in the form of free acid in animal tissues, excreta, and blood. Many microorganisms can convert different organic compounds into acetic acid through fermentation.
Chinese name: Acetic acid
Foreign name: Academic Acid
Nickname: acetic acid, glacial acetic acid
Chemical formula: CH3COOH
Molecular weight: 60.052
CAS login number: 64-19-7
EINECS login number: 231-791-2
Melting point: 16.6 ℃
Boiling point: 117.9 ℃
Water solubility: soluble
Density: 1.05 g/cm ³
Appearance: Colorless transparent liquid with a pungent odor
Flash point: 39 ℃ (CC)
Acetic acid fermenting bacteria (Acetobacillus) can be found in every corner of the world, and every ethnic group inevitably discovers vinegar - it is a natural product of these alcoholic beverages exposed to the air. There is a saying in China that Du Kang's son Heita obtained vinegar due to prolonged brewing time.
The people of ancient Rome boiled sour wine in lead containers to obtain a high sweetness syrup called "sapa". Sapa is rich in a sweet lead sugar called lead acetate. In the 8th century AD, Persian alchemist Jabir concentrated acetic acid in vinegar by distillation.
During the Renaissance, people prepared acetic acid by dry distillation of metal acetate. In the 16th century, German alchemist Andreas Libafius compared the acetic acid produced by this method with the acid extracted from vinegar. Due to the presence of water, the properties of acetic acid have undergone significant changes, to the extent that chemists have believed for centuries that these are two completely different substances. Until French chemist Pierre Adet proved that the main components of these two substances were the same.
In 1847, German scientist Adolf Wilhelm Hermann Kolbe synthesized acetic acid for the first time using inorganic materials. The reaction process is as follows: first, carbon disulfide is converted into carbon tetrachloride through chlorination, followed by the high-temperature decomposition of carbon tetrachloride, which is hydrolyzed and chlorinated to produce trichloroacetic acid. Finally, acetic acid is produced through electrolytic reduction.
In 1910, most of the glacial acetic acid was extracted from coal tar obtained from dry distilled wood. The process first involves treating coal tar with calcium hydroxide, and then acidification of the formed calcium acetate with sulfuric acid to obtain acetic acid.
In 1911, the world's first industrial facility for the oxidation of acetaldehyde to acetic acid was built in Germany, followed by the development of a low-carbon alkane oxidation method for producing acetic acid. In 1925, the British company Seranis developed the first pilot device for methyl carbonylation to produce acetic acid. However, the application of this method has been limited due to the lack of containers that can withstand high pressure (200atm or higher) and corrosion.
In 1963, BASF Chemical Company of Germany developed the first process suitable for industrial production of acetic acid using cobalt as a catalyst.
In 1968, the use of rhodium catalysts greatly reduced the difficulty of the reaction. A catalyst system composed of rhodium carbonyl compounds and iodides is used to react methanol and carbon monoxide in a water acetic acid medium at 175 ℃ and below 3 megapascals to obtain acetic acid product. Due to the high activity and selectivity of the catalyst, there are very few by-products of the reaction. The low-pressure carbonylation of methanol to produce acetic acid has advantages such as low raw material cost, mild operating conditions, high acetic acid yield, good product quality, and simple process flow. However, the reaction medium has serious corrosiveness and requires the use of corrosion-resistant special materials.
In 1970, Monsanto Corporation in the United States built a facility using this process, making rhodium catalyzed methyl carbonylation to acetic acid gradually the dominant Monsanto method.
In the late 1990s, BP successfully commercialized the Cativa catalytic process, which used iridium catalysts and (Ir (CO) ₂ I ₂), making it greener and more efficient than the Monsanto process.
The crystal structure of acetic acid shows that molecules combine through hydrogen bonds to form dimers (also known as dimers), which also exist in a vapor state at 120 ℃. The dimer has high stability, and it has been proven through the determination of molecular weight by freezing point reduction and X-ray diffraction that carboxylic acids with smaller molecular weights, such as formic acid and acetic acid, exist in the form of dimers in solid, liquid, and even gas states. When acetic acid dissolves with water, the hydrogen bonds between the dimers will quickly break. Other carboxylic acids also exhibit similar dimerization phenomena.