Acetic acid, CAS 64-19-7

Acetic acid, CH3COOH, is a colorless, volatile liquid at ambient temperatures. The pure compound, glacial acetic acid, owes its name to its ice-like crystalline appearance at 15.6°C. As generally supplied, acetic acid is a 6 N aqueous solution (about 36%) or a 1 N solution (about 6%). These or other dilutions are used in adding appropriate amounts of acetic acid to foods. Acetic acid is the characteristic acid of vinegar, its concentration ranging from 3.5 to 5.6%. Acetic acid and acetates are

Acetic Acid is a common chemical reagent used in a multitude of organic reactions. It is the primary constituent of vinegar, contributing to its distinct taste and odor. It is used in the synthesis of dye-sensitized solar cells.

Acetic acid Use and Manufacturing

Methods of Manufacturing

1. Acetic acid is widely distributed in nature. For example in fruit or vegetable oils, mainly in the form of esters; in the tissues of animals, excretions and blood are present in the form of free acids. Many microorganisms can convert different organisms into acetic acid by fermentation. In ancient China there is a record on the vinegar, as early as BC, humans have been able to use alcohol by a variety of acetic acid oxidation of fermentation vinegar, the late 19th century, found that wood distillation can get acetic acid. In 1911, in Germany, the world's first set of acetaldehyde oxidation of acetic acid production plant. And soon the development of low carbon hydrocarbon oxidation of acetic acid production methods. In 1960 the former Federal Republic of Germany using methanol at high pressure (20MPa) by carbonylation of acetic acid method. Subsequently, the United States Monsanto rhodium complex catalyst (to iodide as a catalyst), the carbonylation of methanol to acetic acid pressure drop to 0.3-3.0MPa, and in 1970 the production capacity of 135kt acetic acid methanol low-pressure carbonylation industry Device. As the method of advanced technology and economy, from the mid-seventies of the new manufacturers to use more low-pressure methanol carbonylation method. In 1984 the world's annual production capacity of acetic acid has reached 6Mt, of which low-pressure carbonylation of about 40%. 1. Fermentation of starch fermentation using light liquor (containing 3-6% ethanol), the role of vinegar in the mother of bacteria, at about 35 ℃ for fermentation, light wine is air oxidation to vinegar. In addition to vinegar containing 3-6% acetic acid, it still contains other organic acids, esters and proteins. Fermentation is mainly used to make food vinegar. 2. Synthesis method It is the main method of industrial production of acetic acid. (1) oxidation of acetaldehyde. Liquid-phase oxidation was carried out in a bubble column reactor using acetaldehyde as the raw material, using oxygen or air as an oxidant, at 50-80 ° C, 0.6-1.0 MPa and manganese acetate catalyst, in the presence of the catalyst (see Industrial Example). (2) methanol low-pressure carbonylation method. Also known as Monsanto law. Methanol and carbon monoxide in aqueous acetic acid medium at about 175 ℃ and below the conditions of 3.0MPa reaction, the formation of acetic acid, the use of carbonyl compounds of rhodium and iodide catalyst system. As the catalyst activity and selectivity are very high, so little side effects. The reaction product is first treated with a stripping column and a dehydration column. The separated components and aqueous acetic acid can be recycled to the reactor. The gas leaving the reactor is first washed with cold methanol to recover the extracted methyl iodide (intermediate product ), And then sent to the carbon monoxide recovery unit. The crude product is purified by distillation to obtain the finished acetic acid. The methanol yield was & gt; 99%. Methanol low-pressure carbonylation of acetic acid, with low cost of raw materials, operating conditions ease, high yield of acetic acid, product quality and the advantages of simple process, the current technical and economic production of acetic acid the most advanced method. However, the reaction medium is severely corrosive and requires the use of expensive special steels. (3) methanol high-pressure carbonyl synthesis method. Methanol and carbon monoxide in aqueous acetic acid reaction, carbonyl cobalt as catalyst, methyl iodide as co-catalyst, the reaction conditions for 250 ℃ and 70MPa. After the reaction of the product separated by the separation system, you can get the finished product. With methanol, the yield of up to 90%. (4) low-alkane liquid-phase oxidation. N-butane as raw material, acetic acid as solvent, 170-180 ° C, 5.5MPa and cobalt acetate catalyst in the presence of air as oxidant liquid-phase oxidation. You can also use liquefied petroleum gas or light oil as raw material. This side of the use of raw materials cheaper, but the process longer, serious corrosion, and acetic acid yield is not high, it is limited to cheap butane or liquefied petroleum gas supply in the regional use. For example, the United States Celance company with butane oxidation, yield 76%, by-product formic acid 6%. Such as refinery 30-100 ℃ light oil as raw material, oxidation temperature 165-167 ℃, pressure 3.92-4.90MPa, the amount of cobalt naphthenate catalyst is about oil into the 0.1 millionths. The mixed acid obtained by air-liquid phase oxidation was separated into acetic acid through six columns, and the yield was about 40% of the light oil. For every 1t of acetic acid, 0.1t of propionic acid, 0.02t of succinic acid, 0.12t of formic acid and 0.4t of neutral acid are produced, which consume about 2.4t of light oil and 0.2kg of catalyst. Acetaldehyde oxidation of acetic acid to the industrial example: Acetaldehyde and acetic acid from the bottom of the tower to join the oxidation tower, oxygen, the reaction temperature is controlled at 70-75 ℃, the top gas pressure maintained at 9.81 × 104Pa, Appropriate amount of nitrogen to prevent gas phase explosion. Continuous discharge. The solidification point of the crude acetic acid produced by the reaction should be between 8.5 ℃ and 9 ℃, flow into the concentration refining process, the exhaust gas is cooled by the low temperature, the condensate is refluxed to the oxidation tower and the gas is vented. Crude acetic acid into the concentrated tower, the top temperature is controlled at 95-103 ℃, the condenser condensed dilute acetic acid in the recovery of acetic acid in dilute acid recovery tower, can not condense into the low-temperature gas condensed into dilute acetaldehyde recovery. To remove the low boiling point of acetic acid acetic acid evaporation pot, the top temperature maintained at around 120 ℃, acetic acid distillation is finished. The bottom of the high boiling point and catalyst can be burned to remove the organic matter recovery catalyst. Food sour agent with acetic acid by GB1903-80, content ≥ 98.0%, impurity indicators should meet the requirements. Reagent Acetic acid purification method: in industrial grade acetic acid by adding potassium permanganate powder (acetic acid weight of 1-2%), stir to dissolve.Content should be maintained within 1h potassium permanganate does not fade. Finally, the lower part of the insoluble part. The acetic acid was distilled off in a distillation column, and an appropriate amount of powdered chromic anhydride was added to the newly distilled acetic acid. So that the dissolution of the supernatant for sub-distillation. Take the middle distillate is finished. Dehydration method In addition to using acetic anhydride, but also can use ethyl acetate, butyl acetate, benzene, diisopropyl ether and water composition of the azeotropic mixture for azeotropic distillation dehydration. 2. Acetaldehyde oxidation method: Acetaldehyde and acetic acid from the bottom of the tower to join the oxidation tower, oxygen into the sub-paragraph, the reaction temperature controlled at 70 ~ 75 ℃, the top gas pressure maintained at 0.098MPa, the top of the tower through the appropriate amount of nitrogen To prevent gas phase explosion. The solidification point of crude acetic acid should be between 8.5 ℃ and 9.0 ℃, and continuously enter the refining process. The exhaust gas is cooled by the low temperature, the condensate is refluxed to the oxidation tower, and the gas is vented. Crude acetic acid into the concentrated tower, the top temperature is controlled at 95 ~ 103 ℃, the condenser condensed dilute acetic acid in the recovery of acetic acid in dilute acid recovery tower, can not condense into the low-temperature condensed condensate into acetaldehyde recovery. To remove the low boiling point of acetic acid acetic acid evaporation pot, the top temperature maintained at around 120 ℃, distillation of acetic acid is finished. 3. Low-alkane liquid-phase oxidation method: often with butane as raw material, acetic acid as solvent, cobalt acetate as a catalyst to air as oxidant, 170 ~ 180 ℃: and 5.5MPa under the conditions of liquid catalytic oxidation. Can also be 30 ~ 100 ℃ light oil as raw material. The resulting mixed acid was separated by 6 columns of acetic acid. Refining method: acetic acid contains water, acetaldehyde, acetone, formic acid, propionic acid, esters, sulfates, sulfites, chloride, acetate and other impurities. The purification is carried out by adding equimolar anhydride to acetic acid in water, reacting with the water present, adding chromic anhydride (2 g of chromic anhydride per 100 mL of acetic acid), heating at a temperature close to the boiling point for 1 hour, and then fractionating. Can also add 2% to 5% potassium permanganate instead of chromic anhydride, refluxing 2 to 6 hours after fractionation. Further purification can be carried out by fractional crystallization. Absolute acetic acid (glacial acetic acid) easily absorbs water. Dehydration method In addition to acetic anhydride, can also be used desiccant such as magnesium perchlorate, anhydrous copper sulfate, boron triacetate, chromium triacetate. In addition, the azeotropic mixture of water, such as ethyl acetate, butyl acetate, benzene, diisopropyl ether, etc., can be used for dehydration by azeotropic distillation. 4. Industrial production of methanol by carbonylation of acetic acid; and then potassium permanganate oxidation, filtration and distillation of acetic acid can be fine. At a temperature of less than 15 ° C under constant temperature crystallization of acetic acid, and then vacuum filtration or centrifugal separation of the crystallization of its part, that is pure glacial acetic acid products. 5. Acetylene method: the acetylene and water in the presence of the catalyst directly hydrated to acetaldehyde, and then in the acetic acid manganese catalyst acetic acid solution, with the oxidation of acetaldehyde derived. 6. Ethylene: the ethylene and oxygen in the presence of catalyst, one-step direct oxidation of acetaldehyde synthesis, and then oxidation in acetic acid. Light oil liquid phase oxidation: the light oil in the presence of cobalt catalyst, liquid-phase oxidation of acetic acid, formic acid, propionic acid, butyric acid and other mixtures, and then distillation, derived from two distillation. 7. Ethylene oxidation

Uses

Acetic acid occurs in vinegar. It is producedin the destructive distillation of wood. Itfinds extensive application in the chemicalindustry. It is used in the manufacture ofcellulose acetate, acetate rayon, and variousacetate and acetyl compounds; as a solventfor gums, oils, and resins; as a food preservative in printing and dyeing; and in organicsynthesis. Glacial Acetic Acid is an acidulant that is a clear, colorless liquid which has an acid taste when diluted with water. It is 99.5% or higher in purity and crystallizes at 17°c. It is used in salad dressings in a diluted form to provide the required acetic acid. It is used as a preservative, acidulant, and flavoring agent. It is also termed acetic acid, glacial. Acetic acid is used as table vinegar, as preservative and as an intermediate in the chemical industry, e.g. acetate fibers, acetates, acetonitrile, pharmaceuticals, fragrances, softening agents, dyes (indigo) etc. Product Data Sheet It is used in aqueous and non-aqueous acid-base titrations. manufacture of various acetates, acetyl compounds, cellulose acetate, acetate rayon, plastics and rubber in tanning; as laundry sour; printing calico and dyeing silk; as acidulant and preservative in foods; solvent for gums, resins, volatile oils and many other substances. Widely used in commercial organic syntheses. Pharmaceutic aid (acidifier). Acetic acid is an important industrial chemical. The reaction of acetic acid with hydroxyl containing compounds, especially alcohols, results in the formation of acetate esters. The largest use of acetic acid is in the production of vinyl acetate . Vinyl acetate can be produced through the reaction of acetylene and acetic acid. It is also produced from ethylene and acetic acid. Vinyl acetate is polymerized into polyvinyl acetate (PVA), which is used in the production of fibers, films, adhesives, and latex paints. Cellulose acetate, which is used in textiles and photographic film, is produced by reacting cellulose with acetic acid and acetic anhydride in the presence of sulfuric acid. Other esters of acetic acid, such as ethyl acetate and propyl acetate, are used in a variety of applications. Acetic acid is used to produce the plastic polyethylene terephthalate (PET) . Acetic acid is used to produce pharmaceuticals.