5.1 MANUFACTURING PROCESSES:
Acetone is produced directly or indirectly by propylene. Early processes for the manufacture of acetone were based on the thermal decomposition of calcium acetate or the carbohydrate fermentation of corn starch or molasses. The ready availability of propylene in the 1960s led to routes based on the dehydrogenation of isopropyl alcohol or cumene peroxidation.
(1) By Cumene Oxidation (Hock Process).
Propene is added to benzene [71-43-2] to form cumene [98-82-8], which is then oxidized by air to cumene hydroperoxide, and cleaved in the presence of an acid catalyst like zeolite. Phenol [108-95-2] and acetone [67-64-1] produced in the process are recovered by distillation. Ratio of phenol to acetone is 1:0.6.
(2) By Dehydrogenation of 2-proponal
The hydration of propene [115-07-1] gives 2-propanol [67-63-0], which is then dehydrogenated to acetone. In the United States a C3 stream containing 40 – 60 % propene is used for the manufacture of 2-propanol. A large number of catalysts for 2-propanol dehydrogenation have been studied, including copper, zinc, and lead metals, as well as metal oxides, e.g., zinc oxide, copper oxide, chromium-activated copper oxide, manganese oxide, and magnesium oxide. Inert supports, such as pumice, may be used.
CH3CH=CH2 CH3CH(OH)CH3 CH3COCH3 +H2
(3) By catalytic oxidation of Propene (Wacker-Hoechst).
The process is analogous to the oxidation of ethylene to acetaldehyde by theWacker process. The catalyst solution typically contains 0.045M Palladium (II) chloride, 1.8M Copper (II) Chloride, and acetic acid. The reaction usually is carried out in two alternating stages. In the first stage, air is used to oxidize the metal ions to the +2 oxidation state. In the second, air is removed and propene added. Palladium (II) oxidizes propene, and the resulting Palladium (I) is reoxidized by the pool of copper (II). Besides propionaldehyde, chlorinated carbonyl compounds and carbon dioxide also are formed. Acetone and the byproducts are removed from the catalyst solution by flash evaporation with steam and separated by fractional distillation. A mixture of acetone (92 % selectivity) and propionaldehyde (2 – 4 % selectivity) is produced.
CH3CH=CH2 + ½ O2 CH3COCH3 + CH3CH2CHO
(4) By oxidation of p-Disisopropyl Benzene (Goodyear Process). Acetone is coproduced with hydroquinone [123-31-9] from p-diisopropylbenzene [100-18-5] in a process analogous to the phenol – acetone production from cumene. In the Goodyear process p-diisopropylbenzene is oxidized by oxygen in the presence of caustic. The p-diisopropylbenzene dihydroperoxide [3159-98-6] formed is crystallized and washed with benzene. It is then dissolved in acetone and cleaved to hydroquinone and acetone in the presence of sulfuric acid. Next the acid is neutralized with ammonia and the ammonium sulfate formed is filtered. Acetone is recovered by distillation from the reaction mixture.
(5) By distillation of Calcium Acetate.
Manufacture of Acetone from Acetate of Lime, etc. - Acetone is produced commercially by the dry distillation of various acetates, calcium acetate (commercial grey acetate of lime) or barium acetate being generally used. The single acetate is usually employed, although mixtures of two acetates have been recommended. Grey calcium acetate usually contains about 80 per cent calcium acetate, the remaining 20 per cent consisting of water and various impurities, including small quantities of calcium formate and propionate as well as salts of other organic acids. Calcium acetate when heated at a temperature of about 380° C. decomposes, giving acetone and a residue of calcium carbonate, but at the same time the accompanying calcium salts present as impurities also react and acetaldehyde and various higher ketones are formed together with the condensation products. In addition other impurities (such as dumasin) and tar-like bodies are...
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