Anthracene liquid phase oxidation

Anthracene and 2,6-dinitrophenol terminate chains in oxidizing PP reacting with alkyl as well as with peroxyl radicals [50]. It is important to note that the last two inhibitors retard the liquid phase oxidation of hydrocarbons and aldehydes only by the reaction with peroxyl... 

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) ... 

For the liquid-phase oxidation of anthracene (AN) described in problem 5-17, Rodriguez and Tijero (1989) obtained the following values for the rate constants at 95°C in the two-step series reaction network ... 

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."... 

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. 

It is recovered by redistillation of the fluorene oil fraction, which boils between 290 and 305 °C (or from the distillation fore-runnings in anthracene production), followed by recrystallization, for example, from solvent naphtha. Technical fluorene, 95% pure, is commonly used to produce fluorenone by liquid-phase oxidation with air/oxygen at around 100 °C. Fluorenone can principally be used as a mild oxidant for Oppenauer oxidation, particularly in steroid chemistry. 

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. 

Anthracene-benzene biplanemers (119) were prepared through the electrolytic oxidative decarboxylation of (4 + 4) photocycloadducts between substituted anthracenes and 1,2-dihydrophthalic anhydrides [165,166] (Scheme 36). Chemiluminescence was observed for 119 only in the solid state at > 120°C, but not in a liquid phase, whereas 119 (X = F or Cl, Y = Z = H) were not chemiluminescent [167], Efficient chemiluminescence was observed in the photocycloreversion of all biplanemers tested in both phases. 

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. 

Solvent or fractional condensation methods, however, do not give complete separation from the anthracene of such substances as acridine, Ruorantln-enc, flnorene, pyrene, methyl-anthracene, chrysene, acenaphthene, high molecular weight paraffin hydrocarbons, etc., which are present in the crude anthracene press cake. During the subsequent oxidation of anthracene by the liquid phase method these substances result in the formation of impurities difficult to separate from the anthraquinoue and detracting considerably from its quality as a dye intermediate. 

Electrolytic oxidation of anthracene in 20 per cent sulfuric acid solution with 1 per cent of vanadium pentoxide present is carried out at 80° C. with lead electrodes and a current density of 300 amperes per square meter at 1.6 volts. Good yields have been claimed 10 for this process. Air under pressure has been used for the oxidation of anthracene in the form of dispersions in aqueous ferric sulfate solutions,20 or as a solution iu pyridine or dispersion in aqueous alkaline solutions preferably in the presence of catalysts 21 of copper, cobalt, nickel or lead compounds. Vanadium compounds have been found more active than chromium compounds for use as oxidation catalysts in the form of suspensions in the liquid phase, as in the preparation of aniline black.22 Anthracene suspended in water or dilute sulfuric arid or dissolved in a solvent as acetone is oxidized with ozone, or ozonized oxygen at ordinary temperatures.28... 

Table 7.3 Oxidative dehydrogenation of 9,10-dihydroanthracene ito anthracene in the liquid phase over carbon-based catalysts.

In this experiment the metal-free carbon nanotubes acted directly as a support and active phase for the liquid-phase ODH of dihydroanthracene to anthracene at low temperature. The results are compared with those obtained on other catalysts. Oxidative dehydrogenation of dihydroanthracene in the liquid-phase was carried out over different CNT-based materials. The results are presented in Table 7.3. The test was also performed on an exfoliated graphite material for comparison. The results clearly showed that the reaction was chemically selective whatever... 

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