Process for isolating and recovering meta- and para-cresols from crude cresol-containing compositions composed of cresol components, unreacted cymene components and high-boiling by-products

A improvement in the process for isolating and recovering meta- and para-cresols from crude cresol-containing compositions composed of cresol components, unreacted cymene components and high-boiling by-products, by distillation in a distillation zone, the characteristic features residing in that: (i) the unreacted cymene components content in the crude cresol-containing composition is adjusted to 5-25% by weight of said composition after the adjustment, and the water content of said composition is adjusted to become 0.17-1.5 times by weight of the total cresol-components present in the composition, before the crude cresol-containing composition is supplied to the distillation zone, and also in that (ii) in said distillation zone, the cresol component containing ortho-cresol at a higher concentration than that in the supplied crude cresol-containing composition is distilled off as an azeotropic mixture with the unreacted cymene components and water, whereby the cresol component composed of more condensed meta- and para-cresols being isolated and recovered.

This invention relates to an improvement in the process comprising 
subjecting a crude cresol-containing composition composed of cresol 
components, unreacted cymene components and high-boiling by-products 
having boiling points higher than that of para-cresol, to distillation 
under addition of water, to distil off the unreacted cymene components as 
an azeotropic mixture with water, whereby isolating and recovering the 
cresol component. 
More particularly, the invention relates to an improved process for 
isolating and recovering meta- and para-cresols of high purity with a high 
recovery ratio, with an easy operation and high separating efficiency, 
from a crude cresol-containing composition, by distilling off ortho-cresol 
and unreacted cymene components as an azeotropic mixture with water. 
The method of producing cresol by oxidizing cymene with a molecular 
oxygen-containing gas and acid cleaving the resulting cymene hydroperoxide 
has been recently practiced on industrial scales. The cymene to be used as 
the starting material is normally produced by isopropylation of toluene 
and which is an isomeric mixture of meta-cymene, para-cymene and a minor 
amount of ortho-cymene. When such an isomeric mixture of cymene is used as 
the starting material, the reaction product is also obtained as an 
isomeric mixture of meta-cresol, para-cresol and a minor amount of 
ortho-cresol. Ortho-cresol, however, shows a higher neural toxicity 
compared with other cresol isomers, and hence a cresol product 
substantially free of orthocresol is required for certain usages. 
In the past various methods for separating ortho-cresol from cresol 
isomeric mixtures have been proposed, including distillation, 
crystallization, extraction, absorption and combination of the foregoing. 
With the crude cresol-containing composition to which the present 
invention is to be applied, i.e., the crude cresol-containing composition 
composed of cresol components, unreacted cymene components and 
high-boiling by-products having the boiling points higher than that of 
para-cresol, which is obtained through the process comprising oxidizing a 
cymene isomeric mixture with a molecular oxygen-containing gas, acid 
cleaving the oxidation product containing cymene hydroperoxide and 
removing acetone from the acid cleavage product by distillation, however, 
it is difficult to selectively remove ortho-cresol from its cresol 
components. Such attempts have been invariably accompanied with 
disadvantageous addition of extra operations, apparatuses or steps, or by 
a significant drop in the yields of object meta- and para-cresols. For 
example, ortho-cresol can be separated by rectification alone from a 
mixture composed entirely of ortho-cresol, meta-cresol and para-cresol. 
The crude cresol-containing composition to which the present invention is 
to be applied, however, is a complex mixed system containing the cresol 
components, unreacted cymene components, high-boiling byproducts, a minor 
amount of water, i.e., normally up to 0.15 weight times the total cresol 
components and other minor components. An attempt to selectively remove 
orthocresol from such a composition by rectification alone, therefore, can 
hardly achieve the purpose because the water and cymene components form an 
azeotropic mixture with ortho-, meta- and para-cresols to be together 
distilled off. Furthermore, the object meta- and para-cresols are lost in 
the distilled off azeotropic mixture at a substantial ratio, considerably 
lowering their yields and consequently, raising their production cost. 
In the art of separating a mixture of aromatic isopropyl compound and 
corresponding phenols into the individual components by distillation, it 
has been proposed to add water to the mixture before the distillation, 
whereby to completely distil off the aromatic isopropyl compound as an 
azeotropic mixture with water and recover the phenols remaining as the 
bottom, thus improving the separation efficiency of the two components. 
(see Japanese Official Patent Gazette, Publication No. 5170/55 and its 
U.S. Pat. No. 2,862,855, British Pat. No. 768,941). 
The above literatures furthermore disclose that a mixture of 75 Kg of a 
cresol isomeric mixture composed of ortho-, meta, and para-cresols boiling 
at 192.degree.-210.degree. C., with 225 Kg of para-cymene and 225 Kg of 
water (the water content being 3 weight times the total cresol components) 
was distilled at 97.degree. C. to distil off the para-cymene-water 
mixture, and that the cresol content in the para-cymene in said distillate 
was 0.04-0.08% (Example 3). In all other working examples given in the 
literatures, similarly three weight times the total cresol component of 
water was used in every run. Furthermore, the literatures are entirely 
silent on the technical idea of selectively distilling ortho-cresol off 
from the cresol isomeric mixture. As to the amount of water to be used, 
based on the total weight of the cresol components, again the only 
disclosure found in the literatures in the "three weight times" in said 
Example, no other descriptions being given on the optimum range of said 
amount. Furthermore, the literatures in nowhere refer to the mixed system 
containing the cresol isomeric mixture, unreacted cymene isomeric mixture, 
high-boiling by-products, etc., i.e., the system to which the subject 
invention is to be applied, but their object is to separate and recover 
the aromatic isopropyl compound such as cymene, in the state substantially 
free of phenols such as cresol which shows an inhibiting action to the 
liquid phase-oxidation of aromatic isopropyl compound. Hence, the 
literatures give no disclosure on the technical idea or means for 
selectively removing ortho-cresol from the cresol isomeric mixture in the 
specified mixed system. 
We have engaged in extensive studies in search for an improved process for 
selectively removing ortho-cresol from a crude cresol-containing 
composition composed of cresol components, unreacted cymene components and 
high-boiling by-products having the boiling point higher than that of 
para-cresol, said composition having been obtained through the procedures 
of oxidizing a cymene isomeric mixture with a molecular oxygen-containing 
gas, acid cleaving the oxidation product containing cymene hydroperoxide 
and distilling acetone off from the acid cleavage product, by such a 
simple means as distillation, and separating and recovering from the 
system the cresol components composed mainly of meta- and para-cresols 
with a conspicuously reduced ortho-cresol content. 
As a result we discovered that, by adjusting the amounts of the unreacted 
cymene components and of water in said crude cresol-containing composition 
to be supplied to the distillation zone to specific ranges, the loss of 
meta- and para-cresols at the distillation can be reduced to the minimum 
while selectively distilling ortho-cresol off, and hence, the bottom 
residue containing high purity meta- and para-cresols at high yields can 
be obtained. Furthermore, we discovered that meta- and para-cresols of 
extremely low ortho-cresol content can be easily obtained upon, for 
example, subjecting the bottom to distillation. 
Accordingly, the object of the present invention is to provide an improved 
method for isolating and recovering, from the crude cresol-containing 
composition composed of cresol components, unreacted cymene components and 
high-boiling by-products, high purity meta- and para-cresols with 
industrial advantage, by selectively removing ortho-cresol in the 
aforesaid cresol components. 
The above and many other objects and advantages of this invention will 
become more apparent from the following descriptions. 
According to the present invention, an improvement of the process 
comprising distilling a crude cresol-containing composition composed of 
cresol components, unreacted cymene components and high-boiling 
by-products having the boiling points higher than that of para-cresol, 
under addition of water, said composition having been obtained through the 
procedures of oxidizing a cymene isomeric mixture with a molecular 
oxygen-containing gas, acid cleaving the oxidation product containing 
cymene hydroperoxide, and distilling acetone off from the acid cleavage 
product, to distil off the unreacted cymene components as an azeotropic 
mixture with water, and whereby separating and recovering the cresol 
component is provided, the characteristic features residing in that said 
distillation is practiced under the conditions meeting the following 
requirements (i) and (ii): 
(i) before the crude cresol-containing composition is supplied to the 
distillation zone, its unreacted cymene components content is adjusted to 
5-25% by weight of said composition after the adjustment, and the water 
content is adjusted to become 0.17-1.5 times by weight of the total cresol 
components also after the adjustment; and 
(ii) in said distillation zone, the cresol component containing 
ortho-cresol at a higher concentration than that in the supplied 
composition is distilled off from the system as an azeotropic mixture with 
the unreacted cymene components and water, whereby isolating and 
recovering from the system the cresol component composed of more condensed 
meta- and para-cresols. 
The crude cresol-containing composition, to which the subject process is to 
be applied, is that obtained from the procedures comprising oxidizing a 
cymene isomeric mixture with a molecular oxygen-containing gas by the 
means known per se, acid cleaving the resulting oxidation product 
containing cymene hydroperoxide, and distilling acetone off from the acid 
cleavage product. As the cymene isomeric mixture, for example, that 
obtained by isopropylation reaction of toluene, e.g., by the reaction of 
toluene with propylene in the presence of a Friedel-Crafts type catalyst, 
is useful. Such a mixture is an isomeric mixture containing meta- and 
para-cymenes as the chief components, and also a minor amount of 
ortho-cymene. 
The cymene isomeric mixture as above can be converted to the oxidation 
product containing the cymene hydroperoxides corresponding to said cymene 
isomers by the process known per se, for example, by contacting the 
mixture in liquid phase with a molecular oxygen-containing gas such as 
air, under heating at the temperatures ranging from normal temperature to 
approx. 200.degree. C. The liquid phase oxidation reaction with a 
molecular oxygen-containing gas may also be effected by the practices 
known per se, for example, by stirring the system in the presence of a 
basic aqueous solution, i.e., an aqueous solution of an alkali 
metal-containing base such as lithium hydroxide, sodium hydroxide, 
potassium hydroxide, sodium acetate, potassium acetate, sodium propionate, 
potassium propionate, sodium benzoate, potassium toluate and sodium 
p-isopropylbenzoate; or of an alkaline earth metal-containing base such as 
magnesium hydroxide and barium hydroxide. Or, still other known methods 
using a known radical initiator or a catalyst composed of various heavy 
metal compounds may be employed for the liquid phase oxidation if 
required. 
In the first mentioned embodiment, the temperature may range from, for 
example, approx. 60.degree. to approx. 200.degree. C., and in the latter 
case, those of normal to 200.degree. C. can be employed. Specific examples 
of the radical initiator or catalyst to be used in the latter embodiment 
include the various compounds such as inorganic salts, organic salts and 
chelated complexes of various heavy metals such as copper, manganese, 
cobalt, nickel and iron, or hydroperoxides including cymene hydroperoxide 
itself. 
Normally the liquid phase oxidation is effected, using a large excess of 
cymene. Or, the cymene may be diluted with an inert solvent such as 
benzene, chlorobenzene or trifluoromethylbenzene. It is recommended that 
the oxidation should be carried out until the cymene conversion reaches 
approx. 5-50%. If the oxidation is effected as a two-liquid phase system 
in the presence of a basic aqueous solution, first the aqueous phase is 
separated and removed and if necessary, the oil phase is washed with 
water, before it is subjected to a distillation to be freed from the 
solvent and the unreacted cymene, and also to be given a higher 
concentration level of the formed cymene hydroperoxide. The concentration 
level in that case is conveniently controlled so that the crude 
cresol-containing composition composed of cresol components, unreacted 
cymene components and high-boiling by-products, which is obtained upon 
distilling acetone off from the oxidation product containing cymene 
hydroperoxide and which is to be supplied to the distillation zone, would 
contain, based on the weight of supplied composition, 5-25%, preferably 
8-20%, of the unreacted cymene components, to meet the requirement (i) of 
this invention. For this purpose, the distillation of the oxidation 
product is recommended to be continued until the solvent and unreacted 
cymene are distilled off and the cymene hydroperoxide content reaches 
approx. 3-20%, preferably approx. 6-16% by weight, of the remaining 
condensed oxidation product. 
Thereafter the oxidation product is subjected to acid cleavage by the means 
known per se, for example, heating to normal temperature to approx. 
100.degree. C. in the presence of a suitable acidic catalyst such as a 
protonic acid, e.g., hydrochloric, sulfuric, nitric, perchloric, 
phosphoric or para-toluenesulfonic acid; or a solid acid, e.g., 
silica-alumina or silica. 
The so formed acid cleavage product contains the cresol components derived 
from the cymene hydroperoxides corresponding to the starting cymene 
isomeric mixture, such as cresol isomeric mixture, and acetone. The 
product furthermore contains minor amounts of by-products, such as the 
isomers of methylacetophenone, dimethyltolylcarbinol, isopropylbenzyl 
alcohol, cuminaldehyde and isopropenyl toluene. Upon neutralizing thus 
formed acid cleavage product with an alkali such as sodium hydroxide, 
potassium hydroxide, sodium carbonate or potassium carbonate, and 
distilling the same by the means known per se to remove acetone therefrom, 
the crude cresol-containing composition composed of cresol components, 
unreacted cymene components and high-boiling by-products having the 
boiling points higher than that of para-cresol is obtained. 
More specifically, the composition contains, for example, meta-cresol, 
para-cresol, a minor amount of ortho-cresol, unreacted cymene components, 
traces of aromatic hydrocarbons such as isopropenyl toluene, tar-like 
high-boiling by-products and a minor amount of water soluble in the crude 
cresol-containing composition. 
According to the process of this invention, water is added to the crude 
cresol-containing composition, which is then distilled in the distillation 
zone. 
The distillation is effected under the conditions fulfilling the 
requirements (i) and (ii) of the present invention. As specified in said 
requirement (i), it is essential for achieving the purpose of this 
invention to adjust the amount of the unreacted cymene components in the 
composition to 5-25% by weight, based on the weight of said composition 
after the adjustment, as well as to adjust the amount of water to 0.17-1.5 
weight times that of the total cresol components, before supplying the 
composition to the distillation zone. 
The controlling of the unreacted cymene components content is recommendably 
effected at the concentration step of aforesaid oxidation product 
containing cymene hydroperoxide, to the operational advantage, taking into 
consideration in advance the expected rise in their concentration to be 
brought about by the acid cleavage step and acetone-removing step. 
Also the controlling of water content of the composition can be effected by 
either adding water to the composition after the acetone-distilling off 
step or supplying water into the distillation zone together with the 
composition. 
If the content of unreacted cymene components in the composition exceeds 
the upper limit specified in the requirement (i) of this invention, during 
the distilation the unreacted cymene components and other aromatic 
hydrocarbons such as isopropenyl toluene remain as the bottom in the 
distillation column, degrading the quality of object meta- and 
para-cresols. Whereas, when it is lower than 5% by weight, the separation 
efficiency of ortho-cresol in the distillation is impaired. 
According to the invention, the water content in the composition to be 
supplied to the distillation zone should be 0.17-1.5 weight times, 
preferably 0.2-1 times by weight, more preferably 0.2-0.7 times by weight, 
the total cresol components in the composition. When the water content is 
less than the above-specified lower limit, the separation efficiency of 
ortho-cresol is impaired. Whereas, use of water exceeding the above upper 
limit invites no further improvement in the separation efficiency, 
uselessly increasing the calorific consumption for distilling off the 
large amount of water as an azeotropic mixture. Furthermore, because the 
cresol components are dissolved in the distilled water to the saturation 
point, the increase in the amount of distilled water results in the 
increased loss of the cresol components, as demonstrated in the later 
given Control 5 by way of example. The increase again causes the need of 
troublesome waste water treatment. 
The "separation efficiency of ortho-cresol" mentioned herein signifies the 
value obtained by, separating the distillate into oil phase and aqueous 
phase, determining the contents of each cresol isomer in the oil phase, 
and calculating the mol ratio of meta- and para-cresols to ortho-cresol. 
According to the invention, "the water content in the crude 
cresol-containing composition to be supplied to the distillation zone" 
signifies the total sum of the water contained in the crude 
cresol-containing composition obtained by distilling acetone off from the 
acid cleavage product, and the water added to the composition from an 
exterior source. The water contained in the composition as aforesaid is 
within the range of approx. 3 to 4.5% by weight of the composition, which 
corresponds to approx. 0.04-0.15 weight times of the total cresol 
components. 
The ratio of water to the cymene components in the crude cresol-containing 
composition, of which unreacted cymene components content and the water 
content have been adjusted as specified in the requirement (i), preferably 
ranges from approx. 0.5-5, more preferably, from approx. 0.6-3. 
According to the subject process, as specified in the requirement (ii), 
from the crude cresol-containing composition meeting the requirement (i), 
the cresol component containing ortho-cresol at a higher concentration 
than that in the crude cresol-containing composition is distilled off as 
an azeotropic mixture with the unreacted cymene components and water, and 
the cresol component composed of more condensed meta- and para-cresols is 
isolated and recovered. 
The azeotropic mixture distilled off from the top of the distillation zone 
is separated into two phases upon cooling, one being the oil phase 
composed of the cresol components of increased ortho-cresol content as 
aforesaid and the unreacted cymene components, and the other being an 
aqueous phase. The distillation column for practicing the azeotropic 
distillation is normally operated under a suitable reflux ratio in order 
for improving the separation efficiency. Thus both the oil phase and 
aqueous phase are partly refluxed to the top of the distillation column, 
and the remainders, are separately withdrawn as the distillates. A part or 
the whole of the withdrawn aqueous phase can be recycled into the 
distillation column for the azeotropic distillation. 
The bottoms in the distillation zone of said azeotropic distillation 
contain the cresol component composed substantially of meta- and 
para-cresol and high-boiling by-products. The bottoms can be treated by 
means known per se such as rectification, extraction or crystallization, 
allowing the isolation and recovery of a mixture composed substantially of 
high purity meta- and para-cresols with a high yield. Most commonly the 
bottoms are rectified to advantageously separate the mixture composed 
substantially of meta- and para-cresols. 
Hereinafter the process of this invention will be explained more 
specifically, with reference to the working examples. 
EXAMPLE 1 
(1) A mixture composed of a cymene isomeric mixture containing 
ortho-cymene, meta-cymene and para-cymene, which had been obtained through 
an isopropylation of toluene, and a basic aqueous solution, was contacted 
with air under heating and stirring, to effect a liquid phase oxidation. 
The mixture after the oxidation reaction was separated into an oil phase 
and aqueous phase. Distilling the oil phase under a reduced pressure, the 
cymene hydroperoxide therein was condensed, and a mixture containing 8% by 
weight of cymene and 70% by weight of cymene hydroperoxide was obtained. 
The oxidation product was subjected to an acid cleavage in the presence of 
an acidic catalyst. Upon neutralizing the acid cleavage product and 
distilling acetone off therefrom, a crude cresol-containing composition 
containing 12% of cymene isomeric mixture, 1% of cresol, 35% of meta- and 
para-cresol mixture and 4% of water, the percentages being by weight, was 
obtained, the balance being composed mostly of high-boiling by-products.

(2) Into a distillation apparatus as illustrated in the attached FIG. 1, 
which was equipped with a distillation column 1, reboiler 12, condenser 5, 
oil-water separation tank 6 and refluxing devices 7, 8 and 9, the crude 
cresol-containing composition obtained in (1) above was supplied through a 
conduit 2 at a rate of 900 g per hour, and water was supplied through a 
conduit 3 at a rate of 30 g per hour, to effect a continuous distillation. 
The ratio of the total water entering into the distillation column 
including the water contained in the composition, to the total cresol 
components was 0.204 by weight. The distillate from the column top was 
cooled, separated into the oil phase and aqueous phase in the oil-water 
separation tank 6, and separately refluxed through the conduits 7, 8 and 
9, respectively. The reflux ratios of the aqueous phase and oil phase were 
0.4 and 1.8, respectively, and the temperature at the column top was 
113.degree. C. 
The oil phase thus obtained from the conduit 11 contained cymene, a trace 
amount of by-product hydrocarbons and the cresol isomeric mixture, in 
which the mol ratio of the mixture of meta- and para-cresols to 
ortho-cresol was 1.40. 
The ortho-cresol content of the bottoms residue obtained through the 
conduit 13 of the distillation column was 0.02-0.04% by weight, and no 
cymene was detected. By rectifying the bottoms continuously in another 
distillation column, a mixture of meta- and para-cresols (containing 
0.03-0.06% by weight of ortho-cresol and no cymene) was obtained from the 
column top, and from the bottom of the column high-boiling by-products 
were obtained. 
EXAMPLE 2 
Example 1 was repeated except that the feed rate of water through the 
conduit 3 in the step (2) was made 190 g per hour (the weight ratio of 
water entering into the distillation column inclusive of the water 
contained in the crude cresol-containing composition, to the total cresol 
component was 0.70), the temperature at the column top was made 
103.degree. C., and the reflux ratios of the aqueous phase and oil phase 
were made 0.1 and 18, respectively. 
The mol ratio of the mixture of meta- and para-cresols to ortho-cresol in 
the oil phase obtained from the conduit 11 (which contained cymene, 
by-produced aromatic hydrocarbons and the cresol isomeric mixture) was 
1.35. The bottom residue contained 0.02-0.03% by weight of ortho-cresol 
and no cymene. By a continuous distillation of this bottom residue similar 
to Example 1, a mixture of meta- and para-cresols (containing 0.03-0.05% 
by weight of ortho-cresol and no cymene) was obtained from the column top, 
and from the bottom the high-boiling by-products were obtained. 
EXAMPLE 3 
Example 1 was repeated except that the feed rate of water through the 
conduit 3 in step (2) was made 290 g/hour (the weight ratio of water 
entering into the distillation column, inclusive of the water contained in 
the crude cresol-containing composition, to the total cresol component was 
1.0), the temperature at the column top was made 100.degree. C., and the 
reflux ratios of the aqueous phase and oil phase were made 0.1 and 1.8, 
respectively. 
The mol ratio of the mixture of meta- and para-cresols to ortho-cresol in 
the oil phase obtained from the conduit 11 (which contained cymenes 
by-produced aromatic hydrocarbon by-products and the cresol isomeric 
mixture) was 1.34. The bottoms residue contained 0.02-0.03% by weight of 
ortho-cresol and no cymene. By a continuous distillation of the bottoms 
similar to Example 1, a mixture of meta- and para-cresol (containing 
0.03-0.05% by weight of ortho-cresol and no cymene) was obtained from the 
column top, and high-boiling by-products were obtained as bottoms. 
CONTROL 1 
Example 1 was repeated except that no water was fed through the conduit 3 
in step (2) (the weight ratio of the water entering the distillation 
column to the total cresol component in the composition was 0.11), the 
temperature at the column top was made 118.degree. C., and the reflux 
ratios of the aqueous phase and oil phase were made 0.7 and 1.8, 
respectively. 
The mol ratio of the mixture of meta- and para-cresols to ortho-cresol in 
the oil phase obtained from the conduit 11 (which contained cymene, 
aromatic hydrocarbon by-products, and the cresol isomeric mixture) was 
4.2. The ortho-cresol content of the bottoms residue increased to 0.12% by 
weight, but the bottoms residue contained no cymene. By a continuous 
distillation of the bottoms similar to Example 1, a mixture of meta- and 
para-cresols (containing 0.18% by weight of ortho-cresol and no cymene) 
was obtained from the column top and high-boiling by-products were 
obtained as bottoms. 
CONTROL 2 
The step (1) of Example 1 was repeated except that the concentration level 
of cymene hydroperoxide, in the occasion of removing cymene from the oil 
phase in the oxidation reaction mixture by distillation, was controlled. 
Thus obtained crude cresol-containing composition contained 3% of a cymene 
isomeric mixture, 1.1% of ortho-cresol, 39% of a mixture of meta- and 
para-cresols and 4.4% of water, the percentages being by weight and the 
balance being mostly the high-boiling by-products. 
The subsequent step (2) was practiced similar to Example 1, except that the 
crude cresol-containing composition as above-obtained was used, the feed 
rate of water through the conduit 3 was made 30 g/hour, the temperature at 
the column top was made 112.degree. C. and the reflux ratios of the 
aqueous phase and oil phase were made 0.4 and 3.0, respectively. 
The mol ratio of the mixture of meta- and para-cresols to the ortho-cresol 
in the oil phase obtained from the conduit 11 (which contained cymene, 
aromatic hydrocarbon by-products and the cresol isomeric mixture) was 
2.70. The ortho-cresol content in the bottom residue was 0.08% by weight, 
but the bottoms contained no cymene. By a continuous distillation of the 
bottoms, a mixture of meta- and para-cresols (which contained 0.12% by 
weight of ortho-cresol and no cymene) was obtained from the column top, 
and high-boiling by-products were obtained as bottoms. 
CONTROL 3 
The step (1) of Example 1 was repeated except that the concentration level 
of cymene hydroperoxide, in the occasion of removing cymene from the oil 
phase of the oxidation reaction mixture by distillation, was controlled. 
Thus obtained crude cresol-containing composition contained 30% of the 
cymene isomeric mixture, 0.8% of ortho-cresol, 28% of a mixture of meta- 
and para-cresols, and 3.4% of water, the percentages being by weight and 
the balance being mostly the high-boiling by-products. 
The subsequent step (2) was practiced as in Example 1, except that the 
above-obtained crude cresol-containing composition was used, the feed rate 
of water through the conduit 3 was made 30 g/hour, the temperature at the 
column top was made 114.degree. C., and the reflux ratios of the aqueous 
phase and oil phase were made 0.4 and 0.8, respectively. 
The mol ratio of the mixture of meta- and para-cresols to the ortho-cresol 
in the oil phase obtained from the conduit 11 (which contained cymene, 
by-produced aromatic hydrocarbons and the cresol isomeric mixture) was 
1.45. The bottom residue contained only 0.02% by weight of ortho-cresol, 
but its contents of cymene and aromatic hydrocarbon by-products increased 
to 0.10% by weight. By a continuous distillation of the bottoms similar to 
Example 1, a mixture of meta- and para-cresols (which contained 0.03% of 
ortho-cresol, and 0.15% of cymene and the aromatic hydrocarbons) was 
obtained from the column top, and high-boiling by-products were obtained 
as bottoms. The product contained a large amount of neutral component, and 
was not a high quality product. 
EXAMPLE 4 
The step (1) of Example 1 was repeated except that the concentration level 
of cymene hydroperoxide, in the occasion of removing cymene from the oil 
phase in the oxidation reaction mixture by distillation, was controlled. 
Thus obtained crude cresol-containing composition contained 18% of a 
cymene isomeric mixture, 0.9% of ortho-cresol, 33% of a mixture of meta- 
and para-cresols, and 3.8% of water, the percentages being by weight and 
the balance being the high-boiling by-products. 
The subsequent step (2) was repeated as in Example 1, except that the 
above-obtained crude cresol-containing composition was used, the feed rate 
of water through the conduit 3 was made 30 g/hour (the weight ratio of the 
water entering into the distillation column inclusive of the water 
contained in the composition, to the total cresol component was 0.2), the 
temperature at the column top was made 113.degree. C., and the reflux 
ratios of the aqueous phase and oil phase were made 0.4 and 1.5, 
respectively. 
The azeotropic mixture distilled off from the azeotropic distillation 
system was separated into two phases. The mol ratio of the mixture of 
meta- and para-cresols to the ortho-cresol in the oil phase obtained from 
the conduit 11 (which contained cymene, aromatic hydrocarbon by-products 
and the cresol isomeric mixture) was 1.42. The bottom residue contained 
0.02-0.03% by weight of ortho-cresol and a trace of cymene. 
By a continuous distillation of the bottoms similar to Example 1, a mixture 
of meta- and para-cresols (which contained 0.03-0.05% by weight of 
ortho-cresol and trace of cymene) was obtained from the column top, and 
high-boiling by-products were obtained as bottoms. 
CONTROL 4 
Example 1 was repeated except that in step (2), the water feed rate through 
the conduit 3 was made 12.6 g/hour (the weight ratio of the water entering 
into the distillation column inclusive of the water contained in the 
starting composition, to the total cresol component was 0.15), the 
temperature at the column top was made 116.degree. C., and the reflux 
ratios of the aqueous phase and the oil phase were made 0.5 and 1.8, 
respectively. 
The azeotropic mixture distilled off from the azeotropic distillation 
system was separated into two phases. The mol ratio of the mixture of 
meta- and para-cresols to the ortho-cresol in the oil phase obtained from 
the conduit 11 (which contained cymene, aromatic hydrocarbon by-products 
and the cresol isomeric mixture) was 2.7. The bottom residue contained 
0.06-0.08% by weight of ortho-cresol and no cymene. 
By a continuous distillation of this bottom similar to Example 1, a mixture 
of meta- and para-cresols containing 0.09-0.12% by weight of ortho-cresol 
and no cymene was obtained from the top of the column. 
From the results of Controls 1 and 4, it can be understood that when the 
weight ratio of water supplied into the azeotropic distillation column 
inclusive of the water contained in the crude cresol-containing 
composition to the total cresol component in said composition becomes less 
than 0.17, the meta- and para-cresols contents in the azeotropic mixture 
distilled off from the top of the column increases, conspicuously lowering 
the separation efficiency of ortho-cresol. 
CONTROL 5 
Example 1 was repeated except that in step (2), the feed rate of water 
through the conduit 3 was made 612 g/hour (the weight ratio of the water 
entering into the distillation column inclusive of the water contained in 
the composition, to the total cresol component was 2), the temperature at 
the column top was made 100.degree. C., and the reflux ratios of the 
aqueous phase and oil phase were made 0.5 and 1.8, respectively. 
The azeotropic mixture distilled off from the azeotropic distillation 
system was separated into two phases. The mol ratio of the mixture of 
meta- and para-cresols to the ortho-cresol in the oil phase obtained 
through the conduit 11 (which contained cymene, by-produced aromatic 
hydrocarbons and the cresol isomeric mixture) was 1.34. The bottom residue 
contained 0.02% by weight of ortho-cresol, and no cymene. 
By a continuous distillation of the bottoms similar to Example 1, a mixture 
of meta- and para-cresols containing 0.03% by weight of ortho-cresol but 
no cymene was obtained top of the column, and from the high-boiling 
by-products were obtained as bottoms. 
In this Control, the weight ratio of water inclusive of the water contained 
in the crude cresol-containing composition to be supplied to the 
azeotropic distillation column, to the total cresol component in said 
composition was made greater than 1.5, but the mol ratio of the meta- and 
para-cresols mixture to the ortho phenol in the oil phase distilled off 
from the top of the azeotropic distillation column as an azeotropic 
mixture was not decreased, i.e., the separation efficiency of ortho-cresol 
was not improved. On the contrary, large quantities of water were 
distilled off as the azeotropic mixture (as large as ten times that of 
Example 1), containing the cresol component to the saturation point as 
dissolved therein. Hence, the loss of cresol component was markedly 
increased (approximately ten times that of Example 1). Furthermore, the 
large amount of distilled water containing traces of the cresol component 
must be treated to make it harmless as waste water. This Control also 
proved an additional disadvantage that a large amount of calories 
(approximately 4.5 times that required in Example 1, as the calories 
required for the entire azeotropic distillation) was consumed for 
distilling off the large amount of water (approx. 10 times that distilled 
off in Example 1).