Hydrogen peroxide anthraquinone process

The above method has now been largely replaced by a newer process, in which the substance 2-ethylanthraquinone is reduced by hydrogen in presence of a catalyst to 2-ethylanthraquinol when this substance is oxidised by air, hydrogen peroxide is formed and the original anthraquinone is recovered ... 

Although considered an active participant in the process cycle, the tetrahydroaLkylanthraquinone (10) may not be a significant part of the catalytic hydrogenation because, dependent on the concentration in the working solution, these could all be converted to the hydroquinone by the labile shift per equation 17 and not be available to participate. None of the other first- or second-generation anthraquinone derivatives produce hydrogen peroxide, but most are susceptible to further reaction by oxidative or reductive mechanisms. 

The chemical yield of hydrogen peroxide and the anthraquinone per process cycle is very high, but other secondary reactions necessitate regeneration of the working solution and hydrogenation catalyst, and the removal of organic material from the extracted hydrogen peroxide. 

Interest has continued in on-site manufacture of hydrogen peroxide from the elements, particularly for remote sites located considerable distances from wodd-scale anthraquinone processes. However, no commercial-scale direct combination plants have been constmcted as of this writing. 

High pressure Hquid chromatography (qv) (138) and coulometry can be used to detect and quantify anthraquinones and thek derivatives in a hydrogen peroxide process working solution. 

A + RCH2OH - AH. + RCHOH At low concentrations of photoexcited dye and in competition with radiationless deactivation processes the radicals can react with oxygen to form additional radicals and/or hydrogen peroxide. At higher concentrations electron transfer reactions to semi-reduced (A ) and semi-oxidized (A +) anthraquinone compounds can occur which in turn undergo secondary reactions. 

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... 

The advantage of the above two methods are high yields of epoxides, and the titanium silicalite catalyst is not deactivated or poisoned by the contaminants in the crude oxidation mixture. Hence, the processes are commercially attractive. The in situ hydrogen peroxide generation based on the AO process from either the anthraquinone/anthrahydroquinone or ketone/alcohol redox couples has also been used for the following synthetic reactions ... 

In principle, process integration applies even more to direct synthesis of hydrogen peroxide, further improving the advantages over the anthraquinone route. Methanol can be used to replace water as the solvent and the dilute methanol solution obtained fed into the epoxidation reactor. Minimal purification may be required, for example for the removal of hydrogen bromide and other additives that may have been needed to increase the selectivity. 

Of these processes, the first has only historical interest the plants which produced 15 000 t/a of hydrogen peroxide and 30 000 t/a of acetone were shut down in 1980. Only in the former States of the USSR are such plants still in use. The electrochemical oxidation process is also of limited importance. Over 95% of the hydrogen peroxide is produced with the anthraquinone process. Electrochemical... 

J. M. Campos-Martin, G. Blanco-Brieva, J. L. G. Fierro, Hydrogen peroxide syntliesis, an outlook beyond the anthraquinone process, Angew. Chem. Int. Ed. 45, 6962-6984 (2006). 

The direct oxidation of benzene into phenol constitutes one of the challenges in chemistry to substitute the cumene process at the industrial level. Such oxidation has also been achieved with several TpfCu complexes as catalysts, leading to moderate yields and high selectivity toward phenol, in a transformation using hydrogen peroxide as the oxidant and at moderate temperatures. The same catalytic system has been employed for the selective oxidation of anthracenes into anthraquinones (Scheme 24). 

On an industrial scale, the predominant manufacturing process for hydrogen peroxide is by the auto-oxidation of anthraquinone. The North American hydrogen peroxide production was estimated to be 445-520 million lbs in 1989 [20]. Electrochemical processes can compete with this process for small scale operations. At hydrogen peroxide production rates below 3-4 tons/day, electrochemical processes have a cost advantage [23]. 

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