Process for the production of hydroxy-aromatic substances

The process for the production of hydroxy aromatic substances by means of catalytic oxidation of isoalkyl aromatic substance with oxygen, and decomposition of the hydroperoxide thus formed, is based on the concept that isoalkylaromatic substances are emulsified with an aqueous catalyst solution and brought to a temperature ranging from 50.degree. C. up to the boiling temperature of the emulsion; thereupon the oxygen is allowed to act for 2 to 20 hours and the hydroperoxide formed decomposed, in the presence of an inorganic acid as catalyst, into an hydroxyaromatic substance and a ketone.

The invention relates to a process for the production of hydroxyaromatic 
substances, in particular B-naphthol, cumene, p-cresol and resorcin by 
catalytic oxidation of isopropylated or isobutylated aromatic substances, 
and decomposition of the resulting hydroperoxide. A corresponding process 
is represented in the following reaction equation by way of example, for 
the production .beta.-naphthol 
##STR1## 
This process, which is described in H. G. Franck, J. W. Stadelhofer, 
Industrielle Aromatenchemie, Springer publishing house, 1987, cannot be 
carried out on an industrial scale, however, since in the oxidation of 
2-isopropyl naphthalene (2-IPN) only a very low conversion is achieved, so 
that ultimately the maximally attained hydroperoxide content does not 
exceed 30%. A further hindrance in performing this process is providing of 
a technical raw material as starting material which is free from, or 
contains only little, 1-isopropyl naphthalene. This impairs the conversion 
of 2-isopropyl naphthalene to the hydroperoxide of the 2-isopropyl 
naphthalene. If the staring material contains, for example, 10% 1-IPN, the 
maximal hydroperoxide-2-IPN concentration in the product amounts even to 
only 20%. 
The problem underlying the invention, therefore, is the provision of a 
process for using process streams containing 1- and 2-isopropylnaphthalene 
without pre-purification of the same for the production of compounds of 
the general formula ArOH, such as .beta.-naphthol. 
This problem is solved by a process for the production of hydroxyaromatic 
substances by catalytic oxidation of 2-isoalkyl aromatic substances with 
oxygen and decomposition of the formed hydroperoxides, in which the 
starting substance mixture containing the isoalkyl-aromatic substance is 
agitated with an aqueous catalyst solution up to the formation of an 
emulsion, warmed to a temperature ranging from 50.degree. C. up to the 
boiling temperature of the emulsion, exposed for 2 to 20 hours to the 
action of oxygen, and the resulting hydroperoxide is split in the presence 
of an inorganic acid into a hydroxyaromatic substance and a ketone. 
Isoalkylaromatic substances to be used according to the invention are 
isopropyl- and isobutyl-aromatic substances which have a tertiary hydrogen 
in alpha position to the aromatic ring and are represented by the general 
formula Ar--CHRR' in which R and R' are the same or different and 
represent methyl, ethyl, and propyl. Ar represents phenyl and its 
homologues as well as naphthyl and its homologues. Homologues of phenyl 
are, for example, toluyl, benzyl or xylyl as well as phenyl substituted by 
one or more methyl or ethyl groups, homologues of naphthyl are the methyl 
and ethyl derivatives thereof. To be mentioned by way of example are 
2-isopropyl naphthalene, p-cymene, m-diisopropyl benzene. 
It has proved, surprisingly, that by the process of the invention, for 
example, a conversion of 2-isopropyl naphthalene to the hydroperoxide of 
more than 50% is possible in one reaction stage, even if the technical raw 
material contains 8 to 11% of 1-isopropyl naphthalene. After the 
disintegration of the hydroperoxide the B-naphthol yield, for example, 
amounts to 86%. 
As catalyst there are used preferably inorganic or organic copper 
compounds, inorganic cyanides or organic nitriles that activate the 
oxidation. Especially preferred copper compounds are the chlorides, 
stearates, acetates, carbonates, acetylacetones, bromides and copper(I)- 
and copper(II)-oxides. These copper compounds are introduced preferably in 
an amount of 0.000001 to 0.01 mole per mole of 2-isopropyl naphthalene. 
The inorganic cyanides and the organic nitriles to be especially 
preferably introduced are sodium-, potassium- and ammonium-cyanide, 
acetonitrile, chloroacetonitrile, benzonitrile, azo-bis-cyanocyclohexane, 
azo-bis-butyronitrile and tetracyanoethylene. 
These are preferably used in a quantity ranging from 0.00001 to 0.2 mol per 
mol of 2-isopropyl naphthalene. 
According to an embodiment preferred according to the invention, 
alkalihydroxides of alkalimetal carbonates can be used in an amount of 
0.001 to 1 mass %, with respect to the mass of the catalyst solution. 
Preferably the hydrocarbon phase stands in a volume ratio of 1:5 to 3:1 to 
the aqueous catalyst solution; according to an especially preferred form 
of execution, however, the emulsification occurs in the ratio of 1:1. 
After oxidation is completed, the organic phase is separated from the 
aqueous phase, diluted with acetone, for example 10 to 200 parts by weight 
of acetone, and the 2-isopropyl naphthalene hydroperoxide contained in it 
is decomposed by warming to a temperature of 20 to 70.degree. C. in the 
presence of an inorganic acid, for example sulfuric acid. This reaction is 
preferably carried out at the boiling temperature of acetone, as the 
organic phase is introduced into the acetone solution of the inorganic 
acid. The .beta.-naphthol thus formed can be easily separated out by means 
of extraction with alkaline solutions or by means of crystallization or 
distillation, and the hydrocarbon layer after the extraction is 
additionally oxidized with hydrogen peroxide in the presence of an 
inorganic acid as catalyst, after which the additionally obtained 
hydroperoxides are again decomposed. 
The production of .beta.-naphthol according to the process of the invention 
has, in comparison to the already known processes, many advantages. The 
process procedure according to the invention makes possible in particular 
a 50 % conversion of the 2-isopropyl naphthalene contained in the starting 
material to the hydroperoxide in one passage, and by the additional 
treatment of the mixture after the separating-out of the .beta.-naphthol 
with hydrogen peroxide, this conversion can be increased in one passage to 
60 to 70%. 
This process can also be used for the production of phenol from cumene, 
p-cresol from p-cymene, and resorcin from m-diisopropylbenzene, thus, the 
products of the process of the invention are within the general formula 
ArOH, in which Ar has the same meaning as defined before. The following 
examples explain the invention.

EXAMPLE I 
Into a thermostatic glass reactor with a magnetic agitating mechanism, 
there are introduced 3 g of technical 2-isopropyl naphthalene (Rutgers 
Kureha Solvents GmbH, Duisburg, Germany), purity 90.2%; 1-isopropyl 
naphthalene content 9.0%; 3 cm.sup.3 of 0.3-percent aqueous NaOH solution, 
0.001 g of palmitic acid and 0.0005 g of copper cyanate; all this is mixed 
for 15 minutes at room temperature to emulsion formation and then warmed 
to 90.degree. C. 
Technical oxygen is then supplied and the emulsion is heated for 13 hours 
at this temperature. After the separating-off of the aqueous layer by 
means of a centrifuge, the organic layer contains 54.3% of 2-isopropyl 
naphthalene hydroperoxide and 9.3% of 2-isopropyl naphthyl alcohol. 
This layer is then instilled into boiling one-percent sulfuric acid 
solution in acetone, with simultaneous separating-off of the acetone that 
has formed during the decomposition of the hydroperoxide. After the 
extraction of the distillation residue with 15% sodium hydroxide solution 
and the saturation of the extract with 20% sulfuric acid solution there is 
obtained 1.18 g of .beta.-naphthol which, after single recrystallization 
from diluted ethanol, melts at a temperature of 121.9.degree. C. Into the 
organic layer there are then added, after the extraction, 3 cm3 of 30% 
hydrogen peroxide solution and sulfuric acid, whereby there is obtained 
further 2-isopropyl naphthalene hydroperoxide, which yields after its 
decomposition (as above) additionally 0.16 g of B-naphthol. 
EXAMPLES II TO IX 
In the same manner as in example I and with use of the catalysts, 
activators and process conditions presented in Table 1, there are achieved 
the conversions, mentioned in Table 1, of the 2-isopropyl naphthalene into 
the hydroperoxide of technical 2-isopropyl naphthalene, the characteristic 
of which is to be seen from example I. 
In all these cases there are obtained 1.03 to 1.16 g of .beta.-naphthol and 
in addition about 0.13 to 0.17 g of .beta.-naphthol after decomposition of 
the hydroperoxide that has arisen during the oxidation of the 2-isopropyl 
naphthol alcohol with hydrogen peroxide. 
TABLE 1 
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reaction- 
conversion of 
water phase reaction 
temperature 
2-isopropyl naphthaline 
example 
(3 cm.sup.3) 
catalyst + activator 
surfactant 
time (h) 
(.degree. C.) 
to hydroperoxide % 
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II 0.3% NaOH 
CuCl.sub.2.2H.sub.2 O NaCN 
palmitic acid 
12 90 50.9 
III 0.3% NaOH 
copper(II)stearate 
-- 12 92 49.9 
azobicyclohexylnitrile 
IV 1% NaOH 
copper(II)stearate 
-- 13 92 50.3 
benzonitrile 
V 1% NaOH 
copper(II)stearate 
-- 13 92 50.1 
chloracetonitrile 
VI 1% KOH 
CuCl.sub.2.2H.sub.2 O KCN 
stearinic acid 
12 90 50.7 
VII 1% KOH 
copper(II)nitrate 
stearinic acid 
12 90 50.9 
tetracyanoethylene 
VIII 
1% KOH 
Cu.sub.2 O azobisiso- 
palmitic acid 
10 92 51.3 
butyronitrile 
IX 1% Na.sub.2 CO.sub.3 
copper(II)stearate 
palmitic acid 
12 90 45.0 
azobicyclohexylnitrile 
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