In organic chemistry, the Ziegler process (also called the Ziegler-Alfol synthesis) is a method for producing fatty alcohols from ethylene using an organoaluminium compound. The reaction produces linear primary alcohols with an even numbered carbon chain. The process uses an aluminum compound to oligomerize ethylene and allow the resulting alkyl group to be oxygenated. The usually targeted products are fatty alcohols, which are otherwise derived from natural fats and oils. Fatty alcohols are used in food and chemical processing. They are useful due to their amphipathic nature. The synthesis route is named after Karl Ziegler, who described the process in 1955.[1][2]
Process details
The Ziegler alcohol synthesis involves oligomerization of ethylene using triethylaluminium followed by oxidation.[2] The triethylaluminium is produced by action of aluminium, ethylene, and hydrogen gas. In the production process, two-thirds of the triethylaluminium produced is recycled back into the reactor, and only one-third is used to produce the fatty alcohols. The recycling step is used to produce triethylaluminium at a higher yield and with less time. Triethylaluminium reacts with ethylene to form higher molecular weight trialkylaluminium. The number of equivalents of ethylene n equals the total number of monomer units being grown on the initial ethylene chains, where (n = x + y + z), and x, y, and z are the number of ethylene units per chain. Trialkylaluminium is oxidized with air to form aluminum alkoxides, and finally hydrolyzed to aluminum hydroxide and the desired alcohols.[1]
- Al+3ethylene+1.5H2 → Al(C2H5)3
- Al(C2H5)3 n-ethylene → Al((CH2CH2)nCH2CH3)3
- Al((CH2CH2)nCH2CH3)3+ O2 → Al(O(CH2CH2)nCH2CH3)3
- Al(O(CH2CH2)nCH2CH3)3+3H2O → Al(OH)3 + CH3CH2(CH2CH2)nOH
The temperature of the reaction influences the molecular weight of alcohol growth. Temperatures in the range of 60-120°C form higher molecular weight trialkylaluminium while higher temperatures (e.g., 120-150 °C) cause thermal displacement reactions that afford α-olefin chains. Above 150 °C, dimerization of the α-olefins occurs.
Applications
Aluminum hydroxide, the byproduct of the synthesis, can be dehydrated to give aluminium oxide, which, at high purities, has a high commercial value. One modification of the Ziegler process is called the EPAL process. In this process, chain growth is optimized to produce alcohols with narrow molecular weight distribution. Synthesis of other alcohols use Ziegler and the updated EPAL process, such as the transalkylation of styrene to form 2-phenylethanol. Diethylaluminum hydride can be employed in place of triethylaluminium.[1]
References
- 1 2 3 Klaus Noweck, Wolfgang Grafahrend (2006). "Fatty Alcohols". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a10_277.pub2. ISBN 978-3-527-30673-2.
- 1 2 Zerong Wang "Ziegler Alcohol Synthesis (Ziegler Higher Alcohol Synthesis, Alfol Process, Ziegler-Alfol Process, Ziegler-Alfol Synthesis)" in Comprehensive Organic Name Reactions and Reagents, 2010, John Wiley & Sons, Inc. Online ISBN 9780470638859
|
---|
By consumption | Alcohols found in alcoholic drinks |
- 1-Propanol
- 2-Methyl-1-butanol
- Ethanol
- Isoamyl alcohol
- Isobutanol
- Phenethyl alcohol
- tert-Amyl alcohol
- tert-Butyl alcohol
- Tryptophol
|
---|
Medical alcohol |
- Ethchlorvynol
- Methylpentynol
- Methanol poisoning
|
---|
Toxic alcohols |
- Isopropyl alcohol
- Methanol
|
---|
|
---|
Primary alcohols (1°) | Methanol |
- 4-Methylcyclohexanemethanol
- Aminomethanol
- Cyclohexylmethanol
- Methoxymethanol
- Methylazoxymethanol
- Trifluoromethanol
|
---|
Ethanol |
- 1-Aminoethanol
- 2,2,2-Trichloroethanol
- 2,2,2-Trifluoroethanol
- 2-(2-Ethoxyethoxy)ethanol
- 2-(2-Methoxyethoxy)ethanol
- 2-(2-Methoxyethoxy)ethanol
- 2-Butoxyethanol
- 2-Chloroethanol
- 2-Ethoxyethanol
- 2-Fluoroethanol
- 2-Mercaptoethanol
- 2-Methoxyethanol
- Aminoethylethanolamine
- Diethylethanolamine
- Dimethylethanolamine
- Ethanol
- Ethanolamine
- N,N-Diisopropylaminoethanol
- N-Methylethanolamine
- Phenoxyethanol
- Tribromoethanol
|
---|
Butanol |
- 2-Methyl-1-butanol
- Isobutanol
- n-Butanol
|
---|
Straight-chain saturated C1 — C9 |
- Methanol
- Ethanol
- 1-Propanol
- 1-Butanol
- 1-Pentanol
- 1-Hexanol
- 1-Heptanol
- 1-Octanol (capryl)
- 1-Nonanol (pelargonic)
|
---|
Straight-chain saturated C10 — C19 |
- 1-Decanol (capric)
- 1-Undecanol (hendecyl)
- 1-Dodecanol (lauryl)
- 1-Tridecanol
- 1-Tetradecanol (myristyl)
- 1-Pentadecanol
- 1-Hexadecanol (cetyl / palmityl)
- 1-Heptadecanol
- 1-Octadecanol (stearyl)
- 1-Nonadecanol
|
---|
Straight-chain saturated C20 — C29 |
- 1-Icosanol (arachidyl)
- 1-Heneicosanol
- 1-Docosanol (behenyl)
- 1-Tricosanol
- 1-Tetracosanol (lignoceryl)
- 1-Pentacosanol
- 1-Hexacosanol (ceryl)
- 1-Heptacosanol
- 1-Octacosanol (cluytyl / montanyl)
- 1-Nonacosanol
|
---|
Straight-chain saturated C30 — C39 |
- 1-Triacontanol (melissyl / myricyl)
- 1-Hentriacontanol
- 1-Dotriacontanol (lacceryl)
- 1-Tritriacontanol
- 1-Tetratriacontanol (geddyl)
- 1-Pentatriacontanol
- 1-Hexatriacontanol
- 1-Heptatriacontanol
- 1-Octatriacontanol
- 1-Nonatriacontanol
|
---|
Straight-chain saturated C40 — C49 |
- 1-Tetracontanol
- 1-Hentetracontanol
- 1-Dotetracontanol
- 1-Tritetracontanol
- 1-Tetratetracontanol
- 1-Pentatetracontanol
- 1-Hexatetracontanol
- 1-Heptatetracontanol
- 1-Octatetracontanol
- 1-Nonatetracontanol
|
---|
- 2-Ethylhexanol
- Allyl alcohol
- Anisyl alcohol
- Benzyl alcohol
- Cinnamyl alcohol
- Crotyl alcohol
- Furfuryl alcohol
- Isoamyl alcohol
- Neopentyl alcohol
- Nicotinyl alcohol
- Perillyl alcohol
- Phenethyl alcohol
- Prenol
- Propargyl alcohol
- Salicyl alcohol
- Tryptophol
- Vanillyl alcohol
- Veratrole alcohol
|
---|
Secondary alcohols (2°) |
- 1-Phenylethanol
- 2-Butanol
- 2-Deoxyerythritol
- 2-Heptanol
- 3-Heptanol
- 2-Hexanol
- 3-Hexanol
- 3-Methyl-2-butanol
- 2-Nonanol
- 2-Octanol
- 2-Pentanol
- 3-Pentanol
- Cyclohexanol
- Cyclopentanol
- Cyclopropanol
- Diphenylmethanol
- Isopropanol
- Pinacolyl alcohol
- Pirkle's alcohol
- Propylene glycol methyl ether
|
---|
Tertiary alcohols (3°) |
- 2-Methyl-2-pentanol
- 2-Methylheptan-2-ol
- 2-Methylhexan-2-ol
- 3-Methyl-3-pentanol
- 3-Methyloctan-3-ol
- Diacetone alcohol
- Ethchlorvynol
- Methylpentynol
- Nonafluoro-tert-butyl alcohol
- tert-Amyl alcohol
- tert-Butyl alcohol
- Triphenylethanol
- Triphenylmethanol
|
---|
Hydric alcohols | Monohydric alcohols |
- Methanol (C1)
- Ethanol (C2)
- Isopropanol (C3)
- 1-Butanol (C4)
- 1-Pentanol (C5)
- Cetyl alcohol (C16)
|
---|
Dihydric alcohols |
- Ethylene glycol
- Propylene glycol
|
---|
Trihydric alcohols | |
---|
Polyhydric alcohols (sugar alcohols) |
- Pentaerythritol
- Ethylene glycol (C2)
- Glycerol, Propylene glycol (C3)
- Erythritol, Threitol (C4)
- Xylitol (C5)
- Mannitol, Sorbitol (C6)
- Volemitol (C7)
|
---|
|
---|
Amyl alcohols |
- 2,2-Dimethylpropan-1-ol
- 2-Methylbutan-1-ol
- 2-Methylbutan-2-ol
- 3-Methylbutan-1-ol
- 3-Methylbutan-2-ol
- Pentan-1-ol
- Pentan-2-ol
- Pentan-3-ol
|
---|
Aromatic alcohols |
- Benzyl alcohol
- 2,4-Dichlorobenzyl alcohol
- 3-Nitrobenzyl alcohol
|
---|
Saturated fatty alcohols |
- Cetostearyl alcohol
- Decanol
- Lauryl alcohol
- Myristyl alcohol
- Nonanol
- Octanol
- Tridecanol
- Undecanol
|
---|
Branched and unsaturated fatty alcohols |
- 3-Methyl-3-pentanol
- Erucyl alcohol
- Linolenyl alcohol
- Linoleyl alcohol
- Oleyl alcohol
- Palmitoleyl alcohol
- tert-Amyl alcohol
- tert-Butyl alcohol
|
---|
Sugar alcohols | C1 — C7 |
- Methylene glycol (C1)
- Ethylene glycol (C2)
- Glycerol (C3)
- Erythritol (C4)
- Threitol (C4)
- Arabitol (C5)
- Ribitol (C5)
- Xylitol (C5)
- Mannitol (C6)
- Sorbitol (C6)
- Galactitol (C6)
- Iditol (C6)
- Volemitol (C7)
|
---|
Deoxy sugar alcohols | |
---|
Cyclic sugar alcohols | |
---|
Glycylglycitols |
- Maltitol
- Lactitol
- Isomalt
- Maltotriitol
- Maltotetraitol
- Polyglycitol
|
---|
|
---|
Terpene alcohols | Monoterpene alcohols |
- Borneol
- Citronellol
- Geraniol
- Linalool
- Menthol
- Nerol
- Rhodinol
- Terpineol
|
---|
Sesquiterpene alcohols |
- Bisabolol
- Farnesol
- Nerolidol
- Patchoulol
|
---|
Diterpene alcohols | |
---|
|
---|
Dialcohols |
- 1,4-Butanediol
- 1,5-Pentanediol
- 2-Methyl-2-propyl-1,3-propanediol
- Diethylpropanediol
- Ethylene glycol
|
---|
Trialcohols | |
---|
Sterols |
- Cholesterol
- Ergosterol
- Lanosterol
- β-Sitosterol
- Stigmasterol
|
---|
Fluoroalcohols |
- 1,3-Difluoro-2-propanol
- 2,2,2-Trifluoroethanol
- 2-Fluoroethanol
- Nonafluoro-tert-butyl alcohol
- Trifluoromethanol
|
---|
Preparations | |
---|
Reactions | |
---|
|