The Manufacturing Of Acetone
Labels:
#manufakturing
Acetone (dimethyl ketone, 2-propanone, CH3COCH3, melting point: –94.6oC, boiling point: 56.3oC, density: 0.783) is the simplest ketone and is a colorless liquid that is miscible in all proportions with water, alcohol, or ether. There are two major processes for the production of acetone (2-propanone). The feedstock for these is either iso-propyl alcohol [(CH3)2CHOH] or cumene [iso-propyl benzene, C6H5CH(CH3)2]. In the last few years there has been a steady trend away from iso-propyl alcohol and toward cumene, but iso-propyl alcohol should continue as a precursor since manufacture of acetone from only cumene would require a balancing of the market with the coproduct phenol from this process. Acetone is made from iso-propyl alcohol by either dehydrogenation (preferred) or air oxidation. These are catalytic processes at 500oC and 40 to 50 psi. The acetone is purified by distillation, boiling point 56oC and the conversion per pass is 70 to 85 percent, with the overall yield being in excess of 90 percent.
CH3CH(OH)CH3 → CH3C(=O)CH3 + H2 .2CH3CH(OH)
CH3 + O2 → CH3C(=O)CH3 + 2H2O
Cumene is also used as a feedstock for the production of acetone. In this process, cumene first is oxidized to cumene hydroperoxide followed by the decomposition of the cumene hydroperoxide into acetone and phenol. The hydroperoxide is made by reaction of cumene with oxygen at 110 to 115oC until 20 to 25 percent of the hydroperoxide is formed. Concentration of the hydroperoxide to 80% is followed by catalyzed rearrangement under moderate pressure at 70 to 100oC. During the reaction, the palladium chloride (PdCl2) catalyst is reduced to elemental palladium to produce hydrogen chloride that catalyzes the rearrangement, and reoxidation of the palladium is brought about by use of cupric chloride (CuCl2) that is converted to cuprous chloride (CuCl). The cuprous chloride is reoxidized during the catalyst regeneration cycle.The overall yield is 90 to 92 percent. By-products are acetophenone, 2-phenylpropan-2-ol, and α-methylstyrene. Acetone is distilled first at boiling point 56oC.
Vacuum distillation recovers the unreacted cumene and yields α−methylstyrene, which can be hydrogenated back to cumene and recycled. Further distillation separates phenol, boiling point 181oC, and acetophenone, boiling point 202oC.
In older industrial processes, acetone is prepared (1) by passing the vapors of acetic acid over heated lime. Calcium acetate is produced in the first step followed by a breakdown of the acetate into acetone and calcium carbonate:
CH3CO2H + CaO → (CH3CO2)2Ca + H2O (CH3CO2)2
Ca → CH3COCH3 + CaCO3
and (2) by fermentation of starches, such as maize, which produce acetone along with butyl alcohol. Acetone is a very important solvent and is widely used in the manufacture of plastics and lacquers. For storage purposes, acetone may be used as a solvent for acetylene. Acetone is the starting ingredient or intermediate for numerous organic syntheses. Closely related, industrially important compounds are diacetone alcohol [CH3COCH2COH(CH3)2], which is used as a solvent for cellulose acetate and nitrocellulose, as well as for various resins and gums, and as a thinner for lacquers and inking materials. Acetone is used for the production of methyl methacrylate, solvents, bisphenol A, aldol chemicals, and pharmaceuticals. Methyl methacrylate is manufactured and then polymerized to poly(methyl methacrylate), an important plastic known for its clarity and used as a glass substitute.
Aldol chemicals refer to a variety of substances desired from acetone involving an aldol condensation in a portion of their synthesis. The most important of these chemicals is methyl iso-butyl ketone (MIBK), a common solvent for many plastics, pesticides, adhesives, and pharmaceuticals. Bisphenol A is manufactured by a reaction between phenol and acetone, the two products from the cumene hydroperoxide rearrangement. Bisphenol A is an important diol monomer used in the synthesis of polycarbonates and epoxy resins. A product known as synthetic methyl acetone is prepared by mixing acetone (50%), methyl acetate (30%), and methyl alcohol (20%) and is used widely for coagulating latex and in paint removers and lacquers.
CH3CH(OH)CH3 → CH3C(=O)CH3 + H2 .2CH3CH(OH)
CH3 + O2 → CH3C(=O)CH3 + 2H2O
Cumene is also used as a feedstock for the production of acetone. In this process, cumene first is oxidized to cumene hydroperoxide followed by the decomposition of the cumene hydroperoxide into acetone and phenol. The hydroperoxide is made by reaction of cumene with oxygen at 110 to 115oC until 20 to 25 percent of the hydroperoxide is formed. Concentration of the hydroperoxide to 80% is followed by catalyzed rearrangement under moderate pressure at 70 to 100oC. During the reaction, the palladium chloride (PdCl2) catalyst is reduced to elemental palladium to produce hydrogen chloride that catalyzes the rearrangement, and reoxidation of the palladium is brought about by use of cupric chloride (CuCl2) that is converted to cuprous chloride (CuCl). The cuprous chloride is reoxidized during the catalyst regeneration cycle.The overall yield is 90 to 92 percent. By-products are acetophenone, 2-phenylpropan-2-ol, and α-methylstyrene. Acetone is distilled first at boiling point 56oC.
Vacuum distillation recovers the unreacted cumene and yields α−methylstyrene, which can be hydrogenated back to cumene and recycled. Further distillation separates phenol, boiling point 181oC, and acetophenone, boiling point 202oC.
In older industrial processes, acetone is prepared (1) by passing the vapors of acetic acid over heated lime. Calcium acetate is produced in the first step followed by a breakdown of the acetate into acetone and calcium carbonate:
CH3CO2H + CaO → (CH3CO2)2Ca + H2O (CH3CO2)2
Ca → CH3COCH3 + CaCO3
and (2) by fermentation of starches, such as maize, which produce acetone along with butyl alcohol. Acetone is a very important solvent and is widely used in the manufacture of plastics and lacquers. For storage purposes, acetone may be used as a solvent for acetylene. Acetone is the starting ingredient or intermediate for numerous organic syntheses. Closely related, industrially important compounds are diacetone alcohol [CH3COCH2COH(CH3)2], which is used as a solvent for cellulose acetate and nitrocellulose, as well as for various resins and gums, and as a thinner for lacquers and inking materials. Acetone is used for the production of methyl methacrylate, solvents, bisphenol A, aldol chemicals, and pharmaceuticals. Methyl methacrylate is manufactured and then polymerized to poly(methyl methacrylate), an important plastic known for its clarity and used as a glass substitute.
Aldol chemicals refer to a variety of substances desired from acetone involving an aldol condensation in a portion of their synthesis. The most important of these chemicals is methyl iso-butyl ketone (MIBK), a common solvent for many plastics, pesticides, adhesives, and pharmaceuticals. Bisphenol A is manufactured by a reaction between phenol and acetone, the two products from the cumene hydroperoxide rearrangement. Bisphenol A is an important diol monomer used in the synthesis of polycarbonates and epoxy resins. A product known as synthetic methyl acetone is prepared by mixing acetone (50%), methyl acetate (30%), and methyl alcohol (20%) and is used widely for coagulating latex and in paint removers and lacquers.
