Anthraquinone liquid phase

Various organic molecules are used as photosensitizers in liquid-phase reactions, for example, anthraquinones, aryl ketones, polycyclic aromatic hydrocarbons, dyes, etc. The following mechanism, as the most probable, was suggested for the initiation by the organic photosensitizer Q with the aromatic ring [204-208] ... 

In pulp and paper processing, anthraquinone (AQ) accelerates the delignification of wood and improves liquor selectivity. The kinetics of the liquid-phase oxidation of anthracene (AN) to AQ with NO2 in acetic acid as solvent has been studied by Rodriguez and Tijero (1989) in a semibatch reactor (batch with respect to the liquid phase), under conditions such that the kinetics of the overall gas-liquid process is controlled by the rate of the liquid-phase reaction. This reaction proceeds through the formation of the intermediate compound anthrone (ANT) ... 

Anthraquinone. Anthraquinone an important intermediate used extensively in the dye industry can be manufactured through the oxidation of anthracene.1041,1042 Almost all anthraquinone is currently produced by oxidation with Cr03 in the liquid phase (50-100°C) with selectivity better than 90% at complete conversion. 

Organic Adsorbents. (a) Organic crystal compounds (e.g., benzophenone on firebrick, anthraquinone on graphitized carbon black, phthalic anhydride and/or phthalic acid isomers on Chromo-sorb G). (b) Liquid phases below their melting point (e.g.,... 

The direct synthesis of anthraquinone from phthalic anhydride and benzene has been reported to proceed over zeolite Beta [50] in a shape selective manner. In a conventional anthraquinone synthesis, anthracene is used as a feedstock for oxidation. Once there is a shortage of it in the market, additional anthracene could be produced by isomerization of its isomer, viz. phenanthrene. This, however, is not possible by direct isomerization of the trinuclear aromatic system but involves the partially (symmetrically) hydrogenated species. Consequently, isomerization of symmetrical octahydrophenanthrene to symmetrical octahydro-anthracene was studied by Song and Moffatt [51]. As sketched in Figure 3, a high yield of symmetrical octahydroanthracene can be obtained over zeolite H-mordenite (ngj/nyy = 8) at 250 °C (liquid phase, decalin as solvent). These examples show that (shape selective) catalysis on zeolites is more and more expanding into the conversion of polycyclic aromatics, and we foresee continued interest and success in this field of zeolite catalysis. 

Liquid phase oxidation. In spite of the difficulties attending the purification of anthracene by the solvent extraction method, the first vat colors made in this country were from anthraquinone obtained by the oxidation of anthracene.10 Anthracene crystallized from pyridine is distilled with superheated steam or sublimed to render it in a finely divided form suitable for oxidation. Oxidation with chromic acid is simple and almost quantitatively to anthraquinone. However, disposition of the chromic sulfate resulting from the process presents serious difficulties."... 

Weighed amounts of ether and anthraquinone were placed in glass tubes which were then sealed. The temperature noted at which the anthraquinone disappeared and also at which the liquid phase disappeared (critical temp.). The two curves cross at 195° and again at 241°. Between these two temperatures the critical curve lies below the solubility curve, hence for this range of temperature no solubility curve is shown. The following figures were read from the curves, and are therefore only approximately correct. 

Oxidative dehydrogenation of tetrahydroanthraquinone to anthraquinone takes place in the liquid phase with a conversion of almost 100% selectivity is also practically quantitative. The crude anthraquinone is removed from the base of the oxidation reactor and further purified by distillation. 

Apart from gas-phase oxidation, liquid-phase oxidation with dichromate is an expedient process if the chromium-(III)-sulfate by-product can be used as a tanning agent. The largest anthraquinone plant Bayer/ Qsi Germany) with a capacity of 11,000 tpa applies this process. Batch oxidation is carried out with pulverized 94-95% anthracene in a stirred tank reactor with the addition of sodium dichromate and sulfuric add at 60 to 105 °C. The reaction takes between 25 and 30 hours. The yield of anthraquinone, which is produced in purities of around 95%, is over 90%. The purity can be increased to over 99% by recrystallization from nitrobenzene or cyclohexanol/cyclohexanone. 

Hydrogen peroxide is mostly produced on a large scale using the anthraquinone (AQ) autoxidation process. The key step is the selective liquid-phase hydrogenation of the AQs to their corresponding hydroquinones (Scheme 9.8). An industrial process has been designed at Chalmers University and developed and used by Akzo-Nobel on the pilot scale. It involves a three-phase monolith reactor but very few details... 

The linking groups of the ALS molecules, cholesteryl 4-(2-anthryloxy)buta-noate (CAB) and cholesteryl anthraquinone-2-carboxyIate (CAQ), allow them to adopt an overall rodlike shape. (See Structure 4.) CAB forms gels with hydrocarbons, alcohols, aldehydes, esters, amines, etc. (Table l) [76[, and both CAB and CAQ gel more complex fluids, like silicone oils [77[. Many CAB gels are luminescent and some are metastable, exhibiting a gel-to-liquid/solid phase separation after various periods of time. 

Until now there has only been one report on the use of reversed-phase liquid chromatography (LC) for the isolation of anthraquinones from rubiaceous plants. Demagos and co-workers (44) used reversed-phase liquid chromatography for the separation of anthraquinone glycosides from Morinda lucida heartwood. For the separation of anthraquinone glycosides reversed-phase high performance (HP) LC seems... 

In this chapter we describe the synthesis and the phase behaviour of liquid crystalline anthraquinone copolymers with different mesogenic units and azo dye-containing copolymers of the general structure ... 

The phenylbenzoate copolymers with the anthraquinone dye form nematic phases which decrease with increasing content of the dye monomer as shown in Fig. 2. The copolymer with an anthraquinone monomer content of about 39 % by weight is no longer liquid crystalline. 

Dye Contents and Phase Behaviour of Anthraquinone-Containing Liquid... 

---