Extraction of hydroperoxides

A hydroperoxide containing reaction mixture also containing a corresponding unreacted hydrocarbon is treated with an aqueous alcoholic solvent, e.g., aqueous methanolic solvent, to provide in a first step an extract containing a high percentage of hydroperoxide and an appreciable amount of original or unreacted hydrocarbon whereupon the extract is treated with water under recited conditions to obtain two desired phases, one of which is primarily hydrocarbon rejected from the extract by the addition of water and the other an aqueous methanolic solution of the desired hydroperoxide suitable for use in the acid-catalyzed decomposition for the production of carbonyl compounds and hydroxy compounds.

This invention relates to the extraction of hydroperoxides from mixtures 
containing them. More specifically, it relates to the recovery of 
hydroperoxides from a reaction mixture in which the hydroperoxide is 
present together with a corresponding hydrocarbon. 
According to a concept of the invention, there is provided a process 
wherein in a first step aqueous alcoholic solvent, e.g., an aqueous 
methanolic solvent, is employed to produce two phases; an aqueous phase or 
extract phase which contains the hydroperoxide which it is desired to 
recover and an appreciable amount of the original unreacted hydrocarbon 
and solvent and a second step wherein a limited amount of water is added 
to said extract to displace therefrom an oily layer which contains only a 
minor proportion of peroxide and a major proportion of hydrocarbon. A more 
specific concept of the invention provides a process in which the said 
limited amount of water added to the extract is an amount broadly between 
2 and 50 wt. %, preferably from 5 to 30 wt. % based on the weight of the 
extract. 
Thus, we have discovered that by limiting, as herein described, the amount 
of water added to the extract we can obtain contrary to the teachings of 
the art, an oily layer containing only a minor proportion of peroxide 
while containing a major proportion of hydrocarbon which, of course, means 
that there will remain in the extract, desirably so, more peroxide to be 
recovered therefrom after separation of the oily layer. 
In U.S. Pat. No. 2,430,864, issued Nov. 18, 1947 to Adalbert Farkas and 
Arthur F. Stribley, Jr., there is a disclosure which teaches that after 
separating the aqueous alcohol phase from the hydrocarbon phase in 
separating a peroxide concentrate, the alcohol phase is subsequently 
diluted with water to reject an oily layer comprising a major proportion 
of peroxide and minor proportion of other partial oxidation products and 
hydrocarbon. The disclosure of the patent is incorporated herein by 
reference. 
An object of this invention is to provide a process for the recovery of 
hydroperoxides from reaction mixtures containing the same. Another object 
of the invention is to provide a process for the improved recovery of a 
hydroperoxide from a reaction mixture in which it has been produced by so 
operating a two-step extraction process that there will be rejected in a 
second step an oily layer comprising only a minor proportion of peroxides 
and a major proportion of hydrocarbon. 
Other aspects, concepts, objects and the several advantages of the 
invention are apparent from a study of this disclosure and the appended 
claims. 
According to the present invention there is provided a process for the 
recovery of hydroperoxide from a reaction mixture containing the same and 
unreacted corresponding hydrocarbon from which it has been produced which 
comprises, in a first step extracting said mixture with an aqueous 
alcoholic solvent to obtain an extract containing a high percentage of 
hydroperoxide and, in a second step, adding to said extract an amount of 
water only sufficient to reject an oily layer containing a minor 
proportion of hydroperoxide and a major proportion of the hydrocarbon. 
In its now preferred form the amount of water added to the extract in the 
second step, broadly described, will be between from about 2 to about 50 
wt. % but preferably will be from about 5 to about 30 wt. % based on the 
weight of the extract. 
The now preferred alcohol is methanol. 
The invention will now be further described with reference to the preferred 
alcohol, namely methanol. 
For the first step of the invention we have found that a concentration for 
the aqueous methanol of about 80-95 wt. % should be employed. Preferably 
this concentration should be from about 83 to about 92 wt. %. Above the 
high end of this range the system approaches total miscibility and below 
the low end of the range the density of the solvent approaches the density 
of the feed so closely that economical extraction rates cannot be obtained 
in continuous commercial equipment. The importance of density difference 
in liquid-liquid extraction is shown by Treybal, "Mass Transfer 
Operations," McGraw-Hill, pages 375-380. The limiting practical specific 
gravity difference between the feed and solvent phases is about 0.15-0.20. 
This density difference is further reduced within the extraction column by 
partial miscibility of the phases. The specific gravity difference between 
the feed and 80% methanol is about 0.15 at 20.degree. C.; for 90% methanol 
the difference is about 0.18. 
The invention is concerned with treatment of a hydroperoxide containing 
reaction mixture in which the principal impurity is the corresponding 
unreacted hydrocarbon. Such reaction mixtures are conventionally obtained 
in the preparation of hydroperoxides by the oxidation of hydrocarbons in 
the presence of an oxygen containing gas with or without added initiators 
or oxidation catalysts. Such oxidation processes are well known in the art 
for example, the preparation of cumene hydroperoxide from cumene. From one 
viewpoint, the process of the invention provides a hydroperoxide 
containing mixture which is of considerably higher purity on a 
solvent-free basis than the original crude oxidation reaction mixture. 
From another viewpoint, the process of the invention provides a 
hydroperoxide containing mixture suitable for treatment with aqueous 
mineral acids, e.g., H.sub.2 SO.sub.4, to provide an acid-catalyzed 
decomposition of the hydroperoxide to form carbonyl compounds and hydroxy 
compounds. With regard to the latter viewpoint, the invention provides a 
significant advantage over the practice of the prior art in that the 
amount of unreacted hydrocarbon originally present in the crude reaction 
mixture is greatly reduced in the hydroperoxide mixture taken to the acid 
catalyzed decomposition reaction zone thereby effecting considerable 
economy in energy and equipment by said reduced amount of hydrocarbon. 
The invention is applicable to the treatment of oxidation reaction mixtures 
obtained from hydrocarbons, i.e., to organic hydroperoxide containing 
mixtures in which the hydroperoxide contained therein is represented by 
the following general formula: 
##STR1## 
in which R can be hydrogen, or an alkyl radical of 1 to 4 carbon atoms or 
taken together the R groups can form a cycloalkyl ring of from 4 to 7 
carbon atoms, R' can be R or an aryl radical of from 6 to 10 carbon atoms 
or an alkyl substituted aryl radical of from 7 to about 22 carbon atoms 
and said hydroperoxides contain from 4 to about 30 carbon atoms per 
molecule. Preferably the hydroperoxides will have from about 7 to about 24 
carbon atoms per molecule. 
Examples of specific hydroperoxides which when in admixture with unreacted 
corresponding hydrocarbon, can be treated according to the process of the 
instant invention include cyclohexylbenzene hydroperoxide tertiary butyl 
hydroperoxide, 2-ethyl-2-hexyl hydroperoxide, 2-methyl-2-butyl 
hydroperoxide, 2,4,4-trimethyl-2-pentyl hydroperoxide, 1-methylcyclohexyl 
hydroperoxide, cycloheptyl hydroperoxide, .alpha.-methyl-benzyl 
hydroperoxide, .alpha.,.alpha.-dimethylbenzyl hydroperoxide, 
1-phenylcyclohexyl hydroperoxide, benzyl hydroperoxide, 
1-phenyl-2-methylcyclopentyl hydroperoxide, and the like. 
The crude oxidation reaction mixtures treated according to the instant 
invention can contain broadly from about 3 to about 80% by weight of the 
hydroperoxide and preferably from about 10 to about 50 wt. % of the 
hydroperoxide. 
The remainder of the oxidation reaction mixture is essentially the 
unreacted corresponding hydrocarbon from which the hydroperoxide is 
derived. Small amounts of other materials or by-products of the oxidation 
may be present in the crude oxidation mixture. 
According to the process to which the invention is applied, the crude 
hydroperoxide containing mixture described above is treated in a first 
step with an aqueous methanolic solvent to provide a solvent extract of 
the hydroperoxide. Said aqueous methanol solvent broadly contains from 
80-95 wt. % methanol and preferably from 83-92 wt. % methanol based on the 
total solvent composition. 
The total amount of extraction solvent that is employed to treat the crude 
hydrocarbon oxidation reaction mixture which contains the hydroperoxide is 
broadly from 0.5/1 to 20/1 and preferably from 1/1 to 5/1 wherein the 
above ratios express the weight ratio of extraction solvent to the crude 
oxidation reaction mixture (feed). 
The first step with the solvent with ratios of solvent to feed described 
above, can be carried out in any manner which is known in the art. The 
solvent extraction step provides an extract which contains a high 
percentage of the original hydroperoxide in addition to an appreciable 
amount of the original unreacted hydrocarbon and the extraction solvent. 
The material which does not appear in the extract is primarily the 
unreacted hydrocarbon with small amounts of the hydroperoxide and 
extraction solvent. It is often convenient to return this material to the 
oxidation reaction zone. 
According to the process of the invention in the second step, the extract 
of hydroperoxide obtained by using aqueous methanol, as described herein, 
is further treated with a limited additional amount of water. The total 
amount of water added to the extract is limited broadly to between 2 and 
50 wt. % and preferably is limited to be from about 5 to about 30 wt. % 
based on the weight of the extract. 
The mixing of water with the extract in this step of the instant invention 
can be conducted in a variety of ways. For example, a single stage 
contacting zone can be utilized or a plurality of trays in a column can be 
utilized to obtain the desired mixing of water with the extract. 
According to the invention, the addition of water, within the ranges 
specified above, to the extract will provide two phases, one of which is 
primarily hydrocarbon which has been rejected from the extract by the 
addition of water and the other of which is an aqueous methanolic solution 
of the hydroperoxide suitable for use in the acid-catalyzed decomposition 
for the production of carbonyl compounds and hydroxy compounds. The latter 
phase which can be termed a final extract or treated extract contains the 
hydroproxide in a much higher purity on a solvent free basis than the 
original extract. Also more of the originally formed hydroperoxide has 
been recovered. Thus, the process of the instant invention provides for a 
recovery of 70 to 95% of the original hydroperoxide in the crude 
hydrocarbon oxidation reaction mixture while at the same time it increases 
the concentration of the hydroperoxide in the extract up to from 50 to 
90%. Compared to the prior teaching of aqueous methanolic extraction of 
hydroperoxides, the invention provides a further improvement in that the 
hydrocarbon in the original crude oxidation reaction mixture is separated 
in a more convenient and economical manner from the hydroperoxide. 
Specifically, the invention, in the steps provided as described above, 
avoids the need to distill large amounts of the hydrocarbon from the 
mixture either before or after the acid-catalyzed decomposition (cleavage) 
step has been conducted. This feature alone provides a significant 
economic advantage in the employment of smaller equipment for the cleavage 
zone and subsequent distillation of the reaction mixture.

EXAMPLE I 
Twenty grams of a hydrocarbon (cyclohexylbenzene) oxidation reaction 
mixture which contained by analysis 16.1 weight percent cyclohexylbenzene 
hydroperoxide (also named 1-phenylcyclohexyl hydroperoxide) was extracted 
with 30 grams of an aqueous methanol solvent (10/90 H.sub.2 O/CH.sub.3 OH) 
at 25.degree. C. from which there was obtained an extract phase weighing 
36.95 grams and the residue phase weighing 12.66 grams. Said residue phase 
contained 0.59 grams of the hydroperoxide by analysis and an estimated 
0.38 grams of the solvent which amount was estimated from the phase 
diagram behavior for this mixture with aqueous methanol of the composition 
described. This then indicated that 11.69 grams of the residue phase was 
cyclohexylbenzene and a negligible amount of impurities. The composition 
of the extract phase was then calculated by difference to indicate 5.09 
grams of cyclohexylbenzene and a negligible amount of impurities, 2.63 
grams of hydroperoxide and 29.62 grams of the solvent. It can be noted 
that a loss of 0.39 grams of material occurred during the transfer in the 
extraction. For purposes of this example, it is assumed that the loss 
occurred from the extract phase and each component of the extract phase 
can then be multiplied by the ratio 36.95/37.34 to obtain a normalized 
composition which is as follows: cyclohexylbenzene 5.04 grams, 
cyclohexylbenzene hydroperoxide 2.60 grams, and extraction solvent 29.31 
grams. It is seen that the purity of the cyclohexylbenzene hydroperoxide 
extract on a solvent free basis is then 2.60/7.64.times.100 or 34%. 
According to the instant invention, 4.88 grams of water was added to the 
extract phase and there was obtained a separation into two phases. The 
lesser phase being essentially the cyclohexylbenzene rejected from the 
extract phase by the addition of water according to this invention. This 
phase weighed 4.23 grams and was comprised of 3.74 grams of 
cyclohexylbenzene, 0.36 grams of cyclohexylbenzene hydroperoxide by 
analysis, and an estimated 0.13 grams of solvent. The final extract phase 
or treated extract weighed 37.02 grams and was comprised of 1.30 grams of 
cyclohexylbenzene, 2.29 grams of cyclohexylbenzene hydroperoxide and 33.43 
grams of aqueous methanol. Again, the cyclohexylbenzene hydroperoxide 
content was determined by analysis. It can be noted that the sum of the 
hydroproxide contents of the two phases is 2.65 grams which is reasonably 
close to the original 2.60 grams calculated for the normalized extract. It 
can be seen that the treated extract or final extract is greatly reduced 
in cyclohexylbenzene content and the calculated weight percent 
hydroperoxide on a solvent free basis is 2.29/3.59.times.100 or 64%. It 
can also be calculated that 71% of the original cyclohexylbenzene 
hydroperoxide is now present in the treated extract phase which can be 
readily utilized in a mineral acid catalyzed decomposition reaction to 
provide a mixture of cyclohexanone and phenol. 
EXAMPLE II 
In a manner similar to that carried out in Example I above, 20 grams of 
crude cyclohexylbenzene oxidation reaction mixture which was the same as 
that utilized in Example I was treated with 20 grams of a 10/90 
water/methanol extraction solvent at 35.degree. C. The initial residue 
from extraction weighed 14.61 grams and was comprised of 13.21 grams of 
cyclohexylbenzene, 0.96 grams of cyclohexylbenzene hydroperoxide as 
determined by analysis, and 0.44 grams of solvent estimated from phase 
diagram relations. The extract phase was comprised of 3.57 grams of 
cyclohexylbenzene, 2.26 grams of cyclohexylbenzene hydroperoxide and 19.56 
grams of solvent to give a total weight of 25.39 grams. On a solvent free 
basis, the hydroperoxide content of the extract phase was 
2.26/5.83.times.100 or 39%. Now according to the instant invention, 5 
grams of water was added to the extract phase and there was obtained two 
phases as before in Example I. The rejected phase or residue phase weighed 
3.61 grams and was composed of 2.95 grams of cyclohexylbenzene, 0.55 grams 
of cyclohexylbenze hydroperoxide and an estimated 0.11 grams of extraction 
solvent. The hydroperoxide content was again determined by analysis. The 
treated or final extract phase now contained 23.33 grams of extraction 
solvent (aqueous methanol), 1.75 grams of cyclohexylbenzene hydroperoxide 
determined by analysis and 0.62 grams of cyclohexylbenzene. However, it 
can be noted that the sum of weights of the treated extract phase and the 
rejected phase equals 29.31 grams which differs from the expected weight 
obtained by adding 5.0 grams to the original extract phase of 25.39 grams 
or 30.39 grams. This difference of 1.08 grams probably reflects losses in 
handling and evaporation of solvent. Said hydroperoxide concentration in 
the treated extract phase is 1.75/2.37.times.100 or 74% on a solvent free 
basis. It can be seen then that the hydroperoxide purity (on a solvent 
free basis) was improved from 39% in the original extract phase to about 
74% in the treated extract phase by the addition of water to the original 
extract phase according to this invention. 
Reasonable variation and modification are possible within the scope of the 
foregoing disclosure and the appended claims to the invention the essence 
of which is that in a two step process as described for the recovery of 
hydroperoxide from a reaction mixture containing the same and a 
hydrocarbon from which the hydroperoxide has been produced there is 
employed in the second step of the process a limited amount of water as 
herein described to obtain a oily layer containing only a minor proportion 
of peroxide and a major proportion of hydrocarbon.