GB908193A - Improvements in processes for the manufacture of hydrogen peroxide - Google Patents

Abstract

In a cyclic process for producing hydrogen peroxide by the alternate reduction and oxidation of an anthraquinone derivative, the derivative used is an ester of an anthraquinone mono-or di-carboxylic acid, or a tetrahydro derivative thereof. The alcohol esterified may be a primary monohydric alcohol, preferably with 5 to 11 carbon atoms, a secondary monohydric alcohol which may be either aliphatic or cycloaliphatic, a tertiary monohydric alcohol, or a polyhydric, preferably dihydric, alcohol. In the last-mentioned case, the ester may be a mono- or di-ester. Aliphatic chains may be substituted with alkoxy, aromatic or cyclo-aliphatic groups. The esters have good solubility in conventional solvents, and in the case of the tetrahydro derivatives increased solubility is shown by both the quinone and the reduced form. Greater solubility is obtained if the alcohol esterified is a component of the solvent mixture. Various solvents and solvent-mixtures for the esters when in use are specified. Numerous esters are specified, including the n-dodecyl, 2-phenylethyl, 2:6-dimethylheptyl-4, and g -hydroxybutyl esters of 2-anthraquinonecarboxylic acid, bis-2-anthraquinonecarboxylic pentamethylene diester, anthraquinone-2:6-dicarboxylic bis-2-ethylhexyl ester, and the ethyl and 2-ethylhexyl esters of tetrahydroanthraquinone-2-carboxylic acid. The preferred esters are the low melting-point esters 2-anthraquinone carboxylic 2-octyl ester, 2-anthraquinone carboxylic 2-ethylhexyl ester, and 2:3-anthraquionedicarboxylic bis-(2-ethylhexyl) diester (liquid). A comparison is drawn between the production of H2O2 using 2-ethylanthraquinone in a 30:70 methylnaphthalene/octyl alcohol solvent mixture and its production using anthraquinone-2-carboxylic 2-ethylhexyl ester in a 30:70 alpha-methylnaphthalene/2-ethylhexanol mixture. Specifications 669,274, 671,524 and 803,121 are referred to. Reference has been directed by the Comptroller to Specification 777,138.ALSO:Esters of anthraquinone mono- and dicarboxylic acids are prepared by reacting the acid with straight or branched chain, p-, sec-or t-aliphatic or cyclo-aliphatic monohydric alcohols which may be substituted with hydroxy or alkoxy groups, or with polyhydric alcohols. The reaction may be performed in a solvent such as toluene in the presence of p-toluene sulphonic acid. Examples describe the preparation of esters of 2-anthraquinone carboxylic acid with methyl to dodecyl alcohols, isobutyl, 2-methyl butyl, 2-ethyl hexyl, 2-6-dimethyl heptyl, 2-methoxy ethyl, 2-ethoxy ethyl, 2-phenyl ethyl alcohols, propanol-2, butanol-2, pentanol-2, octanol-2, nonanol-2, decanol-2, 2,6-dimethyl heptanol-4, cyclohexanol, t-butanol, ethylene glycol, butanediol-1,4, pentanediol-1,5, hexanediol-1,6, nonanediol-1,9, decanediol-1,10, 2,2-dimethyl-, 2,2 - diethyl-, 2 - methyl - 2 - propyl-, 2-ethyl-2-butyl-propanediols-1,3, and esters of anthraquinone dicarboxylic-2,3 acid with methanol and 2-ethyl hexanol and anthraquinone dicarboxylic-2,6 acid with 2-ethyl hexanol. 2-anthraquinone carboxylic chloride is prepared by the reaction of thionyl chloride on the acid. 5,6,7,8-tetrahydro anthraquinone carboxylic esters are prepared by hydrogenating the ester e.g. ethyl and 2-ethyl hexyl ester in the presence of Raney nickel. Specifications 669,274, 671,524 and 803,121 are referred to. Reference has been directed by the Comptroller to Specification 777,183.