Reference product: hydroquinone [kg]
Location: RER - Europe
The process “hydroquinone, at plant, RER” is modelled for the production of hydroquinone from phenol in Europe. Raw materials are modelled with a stoechiometric calculation. Emissions are estimated. Energy consumptions, infrastructure and transports are calculated with standard values.
Hydroquinone (C6H6O2; CAS 123-31-9, 1,4-benzenediol, 1,4-dihydroxybenzene, p-dihydroxy benzene, hydroquinol, quinol) is a colourless crystalline solid when pure. Three processes are used for the industrial production of hydroquinone: hydroperoxidation of p-diisopropylbenzene, hydroxylation of phenol and oxidation of aniline. Although other processes are known, they are not industrially important.
Hydroperoxidation of p-Diisopropylbenzene
p-Diisopropylbenzene (p-DIPB) is produced by Friedel–Crafts alkylation of benzene with propene ( Acylation and Alkylation). Purified p-DIPB (13) is subsequently converted to the dihydroperoxide (DHP) by air oxidation under slightly alkaline conditions at 80 – 90 °C. The DHP (14) is separated from the reaction mixture either by extraction or by crystallization, and is then cleaved to hydroquinone (1) and acetone by an acid-catalyzed Hock rearrangement; the DHP solution is treated with sulfuric acid catalyst (0.2 – 1.0 %) at 60 – 80 °C. The hydroquinone is crystallized and isolated. The overall yield of (1) (based on p-DIPB) is ca. 80 %.
Hydroxylation of Phenol
The catalyzed hydroxylation of phenol at ca. 80 °C with 70 % aqueous hydrogen peroxide produces a mixture of hydroquinone and catechol. The catalyst may be a strong mineral acid, iron(II), or a cobalt(II) salt. Depending on catalyst selection, the ratio of catechol to hydroquinone can be varied from 3 : 1 to 0.1 : 1; in practice, the ratio is typically 1.5 : 1, i.e., catechol is the major product. The reaction proceeds by an ionic mechanism in which hydrogen peroxide is polarized by the strong acid catalyst and phenol is subsequently hydroxylated the resulting isomers are separated by a series of extractions and solvent-stripping operations.
The ratio of the products hydroquinone and catechol may be influenced by the presence of superacids or shape-selective zeolites. Thus, use of a vanadium–modified Nafion perfluorosulfonate polymer for the oxidation of phenol gave a hydroquinone–catechol ratio of 12.5 : 1. The use of a shape–selective zeolite in the hydroxylation of phenol has yielded hydroquinone with 99 % selectivity.
Oxidation of Aniline
Oxidation of aniline is the oldest process used for the production of hydroquinone. Aniline is oxidized with manganese dioxide (15 – 20 % excess) in aqueous sulfuric acid at 0 – 5 °C to produce p-benzoquinone. This intermediate is removed from the reaction mixture by steam stripping and collected. A byproduct, manganese sulfate, may be retrieved from the depleted reaction mixture and sold for agricultural applications.
Hydroquinone is obtained from the intermediate p-benzoquinone by reduction with iron at 55 – 65 °C or by catalytic hydrogenation. The product (usually technical grade) is crystallized, isolated from the typically aqueous stream by centrifugation, and dried in a vacuum dryer. The overall yield of hydroquinone from aniline is ca. 85 %.
Aniline oxidation is a batchwise process and, therefore, relatively labor intensive. The use of ground manganese ore and finely divided iron leads to extremely abrasive processing conditions; a great deal of maintenance is usually required. Disposal of the inorganic coproducts (amounting to ca. 85 % of the total weight of products) is of environmental concern.
Carboxylate esters of aromatic diols can be prepared by Baeyer–Villiger oxidation of a 4-hydroxy-substituted aromatic ketone with 97 % conversion and 97 % efficience. Microbiological oxidation of either benzene or phenol produces hydroquinone with very high selectivity. Copper-catalyzed air oxidation of phenol provides p-benzoquinone in greater than 90 % selectivity. Benzene has been oxidized to hydroquinone in the presence of copper(I) chloride or titanium. Oxidation of benzene in aqueous solution with ozone gives p-benzoquinone and hydroquinone.
Other preparative methods include the reaction of p-isopropenylphenol with 30 % aqueous hydrogen peroxide under acidic conditions; p-isopropenylphenol may be obtained from bisphenol A by alkaline cracking. Hydroquinone can also be produced by the carbonylation of acetylene; catalytic hydrogenation of nitrobenzene in acidic solution; acid hydrolysis of nitrobenzene or p-nitrosophenol; and electrochemical oxidation of benzene or phenol in dilute sulfuric acid, followed by reduction.
Hydroquinone and its derivatives are used in photographic applications, the rubber industry, monomer inhibitors, dyes and pigments, antioxidants, agricultural chemicals, and other diverse and special applications.
The largest demand for hydroquinone is as a photographic developer, principally for black-and-white film, lithography, photochemical machining, microfilm, and X-ray film. Many derivatives of hydroquinone are used in photographic applications, e.g., the sulfate salt of p-N-methylaminophenol and potassium 2,5-dihydroxybenzenesulfonate.
The second largest consumer of hydroquinone is the rubber industry, which requires hydroquinone for the production of antioxidants and antiozonants. Hydroquinone derivatives used in this area include N,N′-diaryl-p-phenylenediamines, dialkylated hydroquinones, N-alkyl-p-aminophenols, dialkyl-p-phenylenediamines, and aralkyl-p-phenylenediamines.
Hydroquinone, hydroquinone monomethyl ether, and p-benzoquinone are used extensively in the vinyl monomer industry to inhibit free-radical polymerization during both processing and storage. Hydroquinone, p-benzoquinone, 2-methylhydroquinone, 2-tert-butylhydroquinone, and 2,5-di-tert-butylhydroquinone are used as stabilizers for unsaturated polyester resins. Food-grade antioxidants include 2-tert-butylhydroquinone and 2-tert-butyl-4-methoxyphenol.
Hydroquinone and several derivatives are used in topical formulations as skin bleaching and depigmenting agents.
Several new applications for hydroquinone and its derivatives are emerging. The oxygen-scavenging properties of hydroquinone are being exploited for use in boiler water treatment. Hydroquinone and certain C-alkylated or Carylated derivatives are useful monomers for the preparation of a variety of polymers, including liquid crystal polyesters for high-performance plastics, composites, and fibers. In addition to high tensile and impact strengths, these materials exhibit good weatherability, solvent resistance, flame retardance, transparency to microwave radiation, and retention of strength at elevated temperature.
Frischknecht R., Jungbluth N., Althaus H.-J., Doka G., Dones R., Heck T., Hellweg S., Hischier R., Nemecek T., Rebitzer G. and Spielmann M. (2007) Overview and Methodology. Final report ecoinvent v2.0 No. 1. Swiss Centre for Life Cycle Inventories, Dübendorf, CH, retrieved from: www.ecoinvent.org.
Gendorf (2000) Umwelterklärung 2000, Werk Gendorf. Werk Gendorf, Burgkirchen as pdf-File under: http://www.gendorf.de/pdf/umwelterklaerung2000.pdf
Phillip M. Hudnall: Hydroquinone. Published online: 2000. In: Ullmann's Encyclopedia of Industrial Chemistry, Seventh Edition, 2004 Electronic Release (ed. Fiedler E., Grossmann G., Kerse-bohm D., Weiss G. and Witte C.). 7 th Electronic Release Edition. Wiley InterS-cience, New York, Online-Version under: DOI: 10.1002/14356007.a13_499
[This dataset has been generated using the system model “Allocation at the point of substitution" (APOS). A system model describes how activity datasets are linked to form product systems. The APOS model subdivides multi-output activities by physical properties, economic, mass or other properties allocation. By-products of treatment processes are considered to be part of the waste-producing system and are allocated together. Markets in this model include all activities in proportion to their current production volume.
Version 3 of the ecoinvent database offers three system models to choose from. For more information, please visit: https://www.ecoinvent.org/database/system-models-in-ecoinvent-3/system-models-in-ecoinvent-3.html)]
hydroxylation of phenol