Alkylanthraquinones

The derivatives of l-methyl-9,10-anthraquinone exhibit photochromism in an ethanol matrix at 77 K. The recovery of the initial structure was found to occur at ambient temperature.16,18,26 

One can see from Table 7.1 that a compound in which two hydrogen atoms in the methyl group are replaced by two phenyl groups showed no photochromism.26 

Compounds with substituted methyl groups were characterized by complex kinetics of thermal relaxation from the photoinduced form to the initial form because of the production of two photoinduced isomers with different (by an order of magnitude) lifetimes.26,30 

The study of photochromic transformations of 1-methylanthraquinone and its deuterium analog by means of laser photolysis over a wide temperature range30 

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Hydrogenated vegetable oil, in cosmetic molded sticks, 7 840t Hydrogenation(s), 13 769 acetylene, 1 180 10 613-614 alkylanthraquinone, 14 47 asymmetric, 5 210—212 butadiene, 4 370 carbon monoxide, 5 3 carbon dioxide, 26 881 catalytic, 10 504 catalytic aerogels for, l 763t chlorocarbons, 6 235 conditions of, 10 810 cyclopentadiene and dicyclopentadiene, 8 224-225... 

The alkylated anthraquinone process accounts for over 95% of the world production of H202, mainly because the it operates under mild conditions and direct contact of 02 and H2 is avoided. In this process, 2-alkylanthraquinone (the alkyl group is typically an ethyl, terf-butyl or amyl group) is dissolved in a mixture of a non-polar solvent (C9-Cn alkylbenzene) and a polar solvent [Trioctyl phosphate (TOP), or tetrabutyl urea (TBU) or diisobutyl carbinol (DIBC)] and then hydrogenated over a precious metal (Pd or Ni) catalyst in a three-phase reactor (trickle bed or slurry bubble column) under mild reaction conditions (<5bar, <80 °C) to generate 2-alkylanthrahydroquinone [1-3, 5], The latter is then auto-oxidized with air in a... 

As in the case of 5-methyl-1,4-naphthoquinone, photochromic transformations of 1-alkylanthraquinone derivatives represent a thermally reversible photoenolization which was first demonstrated for l-methyl-9,10-anthraquinone (II, R1= CH3, R2 = R3 = H) (Scheme 11).16... 

Quantum yields of photoproduction of ana-quinones of acetoxy-substituted anthraquinones with amino substituents in the anthraquinone ring as well as with an acetyl group proved to be the lowest (Table 7.2) As in the case of photochromic alkylanthraquinones, the reverse photoreaction, from ana-quinone to para-quinone for derivatives of acetoxyanthraquinone, proved to be impossible.21 The transition from ana-quinone to para-quinone occurred during freezing out of a sample owing to thermal bleaching. 

Photochromism of 1-alkylanthraquinones (which is different from 1-methylan-thraquinone) in ethanol at 77 K was complicated by secondary photochemical reactions that generated a new product.26 This product was formed very inefficiently at room temperature owing to the short lifetime of the photoinduced form of this... 

Arco have developed an integrated process for the production of industrially important epoxides via an adapted AO process (Figure 1.13).33 34 A sulfonic acid substituted alkylhydroanthraquinone alkylammonium salt is reacted with molecular oxygen to form the alkylanthraquinone and hydrogen peroxide. The hydrogen peroxide is then reacted with an alkene in the presence of a titanium zeolite catalyst (TS-1 see Chapter 4). The epoxide product is then separated, and the anthraquinone salt recycled to a hydrogenator for reaction with... 

Large-scale production of hydrogen peroxide has been put on stream using monoliths for hydrogenation of alkylanthraquinones [37,38,5]. Irandoust et al. [5] studied the process... 

The monolith reactors have found broad applications in gas-phase processes and are at the development stage for catalytic gas-liquid processes. Currently, there is only one process, hydrogenation of alkylanthraquinones in production of hydrogen peroxide, operating on a commercial scale. 

Since the early 1980s, EniChem has been a pioneer in the development of the process, holding a portfolio of patents [10c,dj. The integration of HP synthesis by means of alkylanthraquinone/alkylanthrahydroquinone (RAQ/RAHQ) cycle technology, with PO production, by means of propene epoxidation with H P, is possible because of the peculiar properties of the TS-1 catalyst (Scheme 6.5). TS-1 can selectively epoxidize propene using diluted HP [12]. A water- methanol mixture is the solvent for the epoxidation the alcohol is necessary to obtain a sufficient reaction rate. Therefore, a cost-saving feature in this process is the fact that the crude H P produced can be used directly in the epoxidation of propene. Moreover, integration of the two processes is also allowed by the easily accomplished separation of propene and PO from the water-methanol mixture. Methanol, after separation and purification, can be recycled to the epoxidation step. 

The first reaction, hydrogenation of the alkylanthraquinone, is catalyzed by Pd. The second, the epoxidation of propene by the HP generated by air oxidation of the RAHQ, is catalyzed by TS-1. This is possible because TS-1 activity is not affected by the polynuclear compounds forming the redox couple, since they do not enter the zeolite cages due to steric hindrance (the average diameter of the channel system of TS-1 and TS-2, with ME I and MEL type structures, respectively, is 0.55 nm the cross... 

A mixture of solvents is used 2-methylnaphthalene (22vol.%) to dissolve the alkylanthraquinone, a polar compound, preferably methylisobutylcarbynol (68vol.%) to dissolve the alkylanthrahydroquinone, and methanol (10 vol.%). Methanol is also a co-catalyst, since the rate of reaction is much accelerated in the presence of this solvent. The best yield to PO, based on starting ethylanthraquinone, was 78%, at 30 °C, with 3 atm propene, 2 atm air and 0.31 wt% TS-1 as the catalyst, in a 1.5 h reaction time. For this to happen, autoxidation and epoxidation must occur at the same temperature, that is to say, a moderate temperature, to prevent the degradation of anthraquinone. The disadvantage of the process is that the optimal conditions for the generation of H P are not the same as for the epoxidation reaction. 

Cetyltrimethylammonium bromide, SDS, and Tween 20 micelles have been used to solubilize alkylanthraquinones in the photoreduction of electron acceptors such as (8) and ferricyanide in an aqueous medium. Irradiation of... 

As noted previously, even if they did form the Diels-Alder adducts, they would not yield alkylanthraquinones because of the absence of hydrogen atoms at the 1- and/or 4-positions. Figure I.B-1 also summarizes the various anthraquinonecarboxylic acids which could arise from the phytadienes depicted. 

FIGURE I.B-1 Phytadienes with potential to yield Diels-Alder adducts and subsequently alkylanthraquinones and anthraquinonecarboxylic acids. 

Industrially, hydrogen peroxide is almost universally produced by the alternate hydrogenation and oxidation with air of an alkylanthraquinone [2], Although the process is efficient from a yield standpoint, it is quite complex and is carried out in two separate steps, using a stoichiometric amount of expensive high molecular weight quinones e.g. 2-ethylanthraquinone). 

In the autoxidation step of the AO process, the 2H /2e reduction of O2 to HjOj is coupled to the uncatalyzed oxidation of anthrahydroquinone to anthraquinone. A variety of 2-alkylanthraquinones have been reported, but 2-ethylanthraquinone... 

Hydrogen peroxide is an oxidant used in many markets, including the pulp and paper industry. Almost all of the world capacity is based on alternately hydrogenating and oxidizing an expensive alkylanthraquinone. 

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