de - Beste verfügbare Techniken (BVT) - Umweltbundesamt
Teilen Einbetten Melden
ePaper herunterladen

de - Beste verfügbare Techniken (BVT) - Umweltbundesamt

de - Beste verfügbare Techniken (BVT) - Umweltbundesamt de - Beste verfügbare Techniken (BVT) - Umweltbundesamt

bvt.umweltbundesamt.de
von bvt.umweltbundesamt.de Mehr von diesem Publisher
05.01.2013 Aufrufe

Chapter 2 Clarifying may be necessary on completion of the reaction (by filtration over SiO2, Al2O3 or charcoal) to remove unreacted amine and salty, resin-like or oily by-products, followed by precipitation of the product (usually by salting out or pH change), filtration, washing, dissolving and, e.g. spray drying to yield the standardised dyestuff. Alternatively, the reaction mixture is immediately passed through a pressure permeation (see also Section 4.2.26), followed by, e.g. belt, spin flash, spray or oven drying. Coupling component Alkali, H 2O Primary amine NaNO 2, HCl, H 2 O, Ice Alkali, buffer Ice Salt H 2 O H 2O Diazotisation Dissolving Filtration Filtration Precipitation Filtration Washing Dissolving Azo Coupling Drying Spray drying Product Permeation Mother liquor Permeate Wash-water Figure 2.13: Typical sequence of operations for diazotisation and azo coupling Possible input materials (on the left) and the associated waste streams (grey background) 44 Dezember 2005 OFC_BREF HCl

2.5.5 Esterification [6, Ullmann, 2001] Chapter 2 Organic esters are of considerable economic importance. Because of their highly lipophilic and hydrophobic nature and low polarity, esters are widely used as solvents, extractants, and diluents. Ethyl acetate is the most common technical solvent. Large quantities of esters, especially phthalates, adipates, and fatty acid esters, are used as plasticisers. Esters with a pleasant odour are used in fragrances, flavours, cosmetics, and soaps. Esters can be converted into various derivatives and are useful intermediates in the synthesis, e.g. of vitamins or pharmaceuticals. Chemical reaction A great variety of production methods for carboxylic acid esters are known, but the simplest and most common method of esterification is the reaction of an alcohol with a carboxylic acid with the elimination of water: R 1 C O OH Figure 2.14: Common esterification H + + R 2 OH R 1 C OFC_BREF Dezember 2005 45 O OR 2 + H 2O Esterification is the reverse of hydrolysis and leads to an equilibrium reaction, which is the reason that quantitative esterification is possible only by continuous removal of one of the products, i.e. ester or water. In the case of transesterification, an alcohol is released instead of water. Suitable catalysts are sulphuric acid, hydrogen chloride, arylsulphonic acids such as p-toluenesulphonic acid, and chlorosulphuric acid. Phosphoric acid, polyphosphoric acids, and mixtures of acids are also recommended. If the acids are adsorbed on a solid support, esterification can be carried out as a continuous process. Removal of water usually involves the addition of entrainers, which form azeotropes with relatively low boiling points and high water contents (usually toluene, xylene, cyclohexane, seldom also benzene or CCl4). Operations The reaction is generally carried out by refluxing the reaction mixture until all the water has been split off. The water or the ester is removed from the equilibrium by distillation. Water is usually removed by distillation of the azeotrope with the alcohol or an entrainer. After condensation, the azeotrope separates into an aqueous phase and an organic phase, and the entrainer or alcohol is recycled into the reaction mixture. In particular cases, a co-solvent such as benzene or toluene is added to the condensate to achieve separation of the organic phase. Many esters are produced continuously in pipes, distillation columns or plate columns. Ionexchange resins are especially suitable as catalysts in continuous processes. The reactants pass through or over the solid catalyst, and no separation or neutralisation of the catalyst is necessary.

Chapter 2<br />

Clarifying may be necessary on completion of the reaction (by filtration over SiO2, Al2O3 or<br />

charcoal) to remove unreacted amine and salty, resin-like or oily by-products, followed by<br />

precipitation of the product (usually by salting out or pH change), filtration, washing, dissolving<br />

and, e.g. spray drying to yield the standardised dyestuff. Alternatively, the reaction mixture is<br />

immediately passed through a pressure permeation (see also Section 4.2.26), followed by, e.g.<br />

belt, spin flash, spray or oven drying.<br />

Coupling component<br />

Alkali, H 2O<br />

Primary amine<br />

NaNO 2,<br />

HCl, H 2 O,<br />

Ice<br />

Alkali, buffer<br />

Ice<br />

Salt<br />

H 2 O<br />

H 2O<br />

Diazotisation<br />

Dissolving<br />

Filtration Filtration<br />

Precipitation<br />

Filtration<br />

Washing<br />

Dissolving<br />

Azo<br />

Coupling<br />

Drying Spray drying<br />

Product<br />

Permeation<br />

Mother liquor<br />

Permeate<br />

Wash-water<br />

Figure 2.13: Typical sequence of operations for diazotisation and azo coupling<br />

Possible input materials (on the left) and the associated waste streams (grey background)<br />

44 Dezember 2005 OFC_BREF<br />

HCl

logo

Produkte

Ressourcen

Unternehmen

AGB
Datenschutzerklärung
Cookie-Richtlinien
Cookie-Einstellungen
Impressum
Change language
Made with love in Switzerland
© 2024 Yumpu.com all rights reserved

Hurra! Ihre Datei wurde hochgeladen und ist bereit für die Veröffentlichung.

Erfolgreich gespeichert!

Leider ist etwas schief gelaufen!