Acetic acid industrial preparation

When we prepare a compound industrially or even study a reaction in the laboratory, we deal with tremendous numbers of molecules or ions. Suppose you wish to prepare acetic acid, starting from 10.0 g of ethanol. This small sample (less than 3 tea-spoonsful) contains 1.31 X 10 molecules, a truly staggering number. Imagine a device that counts molecules at the rate of one million per second. It wonld take more than four billion years—nearly the age of the earth—for this device to count that many molecules Chemists have adopted the mole concept as a convenient way to deal with the enormons numbers of molecules or ions in the samples they work with. 

Although these humble origins make interesting historical notes m most cases the large scale preparation of carboxylic acids relies on chemical synthesis Virtually none of the 3 X 10 lb of acetic acid produced m the United States each year is obtained from vinegar Instead most industrial acetic acid comes from the reaction of methanol with carbon monoxide... 

Iron(III) acetate [1834-30-6], Ee(C2H202)3, is prepared industrially by treatment of scrap iron with acetic acid followed by air oxidation. Iron(III) acetate is used as a catalyst in organic oxidation reactions, as a mordant, and as a starting material for the preparation of other iron-containing compounds. 

Uranium tetrachloride [10026-10-5], UCl, has been prepared by several methods. The first method, which is probably the best, involves the reduction/chlorination of UO [1344-58-7] with boiling hexachloropropene. The second consists of heating UO2 [1344-57-6] under flowing CCl or SOCI2. The stmcture of the dark green tetrachloride is identical to that of Th, Pa, and Np, which all show a dodecahedral geometry of the chlorine atoms about a central actinide metal atom. The tetrachloride is soluble in H2O, alcohol, and acetic acid, but insoluble in ether, and chloroform. Industrially the tetrachloride has been used as a charge for calutrons. 

The hydrolysis of ethyl acetate, prepared by the reaction of ethylene with acetic acid under pressure (154), and the hydrolysis of the ethyl ester of chlorosulfonic acid (155) have been considered and found to be of Httie industrial importance. 

Vinyl acetate was originally prepared industrially by the reaction of acetylene with acetic acid or by oxidation of ethylene. 

An alkyne is a hydrocarbon that contains a carbon-carbon triple bond. Acetylene.. H—C= C—H, the simplest alkyne, was once widely used in industry as the starting material for the preparation of acetaldehyde, acetic acid, vinyl chloride, and other high-volume chemicals, but more efficient routes to these substances using ethylene as starting material are now available. Acetylene is still used in the preparation of acrylic polymers but is probably best known as the gas burned in high-temperature oxy-acetylene welding torches. 

Approximately 2.5 million tons of acetic acid is produced each year in the United States for a variety of purposes, including preparation of the vinyl acetate polymer used in paints and adhesives. About 20% of the acetic acid synthesized industrially is obtained by oxidation of acetaldehyde. Much of the remaining 80% is prepared by the rhodium-catalyzed reaction of methanol with carbon monoxide. 

An alternative to extraction crystallization is used to obtain a desired enantiomer after asymmetric hydrolysis by Evonik Industries. In such a way, L-amino acids for infusion solutions or as intermediates for pharmaceuticals are prepared [35,36]. For example, non-proteinogenic amino acids like L-norvaline or L-norleucine are possible products. The racemic A-acteyl-amino acid is converted by acylase 1 from Aspergillus oryzae to yield the enantiopure L-amino acid, acetic acid and the unconverted substrate (Figure 4.7). The product recovery is achieved by crystallization, benefiting from the low solubility of the product. The product mixture is filtrated by an ultrafiltration membrane and the unconverted acetyl-amino acid is reracemized in a subsequent step. The product yield is 80% and the enantiomeric excess 99.5%. 

Enol esters are distinct from other esters not because of a particular stability or lability toward hydrolases, but due to their hydrolysis releasing a ghost alcohol (an enol), which may immediately tautomerize to the corresponding aldehyde or ketone. A well-studied example is that of vinyl acetate (CH3-C0-0-CH=CH2), a xenobiotic of great industrial importance that, upon hydrolysis, liberates acetic acid (CH3-CO-OH) and acetaldehyde (CH3-CHO), the stable tautomer of vinyl alcohol [25], The results of two studies are compiled in Table 7.1, and demonstrate that vinyl acetate is a very good substrate of carboxylesterase (EC 3.1.1.1) but not of acetylcholinesterase (EC 3.1.1.7) or cholinesterase (EC 3.1.1.8). The presence of carboxylesterase in rat plasma but not in human plasma explains the difference between these two preparations, although the different experimental conditions in the two studies make further interpretation difficult. 

We have discussed these reactions previously in connection with equilibrium limitations on reactions, and we will discuss them again in Chapter 7, because both use catalysts. These reactions are very important in petrochemicals, because they are used to prepare industrial H2 and CO as well as methanol, formaldehyde, and acetic acid. As noted previously, these processes can be written as... 

Preparation of acid anhydrides Acid anhydrides are prepared from carboxylic acids by the loss of water. For example, acetic anhydride is prepared industrially by heating acetic acid to 800 °C. Other anhydrides are difficult to prepare directly from the corresponding carboxylic acids. Usually they are prepared from acid chloride and sodium carboxylate salt (see below). 

The preparation of acetic acid represents a special case. Olah and coworkers as well as Hogeveen and coworkers have demonstrated that CO can react with methane under superacidic conditions, giving the acetyl cation and by subsequent quenching acetic acid or its derivatives (see Section 7.2.3). Monosubstituted methanes, such as methyl alcohol (or dimethyl ether), can be carbonylated to acetic acid.115 Similarly, methyl halides undergo acid-catalyzed carbonylation.115,116 Whereas the acid-catalyzed reactions can be considered as analogs of the Koch reaction, an efficient Rh-catalyzed carbonylation of methyl alcohol in the presence of iodine (thus in situ forming methyl iodide) was developed by Monsanto and became the dominant industrial process (see Section 7.2.4). 

Whatever the source of synthesis gas, it is the starting point for many industrial chemicals. Some examples to be discussed are the hydroformylation process for converting alkenes to aldehydes and alcohols, the Monsanto process for the production of acetic acid from methanol, the synthesis of methanol from methane, and the preparation of gasoline by the Mobil and Fischer-Tropsch methods. 

Ethanol (industrial solvent Acetaldehyde (used in used in preparation of ethyl preparation of acetic acid) acetate unleaded gasoline additive)... 

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