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Патент USA US2136187

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Patented Nov. 8, 1938
2,136,187
UNITED STATES PATENT OFFICE
2,136,187
NITRATION OF PARA C'RESOL
Robert Frye and Grady M. O’Neal, Chicago, Ill.,
assignors to The Sherwin-Williams Company,
Cleveland, Ohio, a corporation of Ohio
No Drawing. Application April 5, 1937,
Serial No. 135,107
11 Claims. (Cl. 260-622)
Our present invention relates to the nitration
of para cresol to form meta nitro para cresol,
expressed as 4-methyl~2-nitro-l-hydroxy-ben
zene.
Some compounds are readily nitrated by well
known procedures, while others are not subject
to such procedures owing to numerous undesired
results, such as isomeric nitration, di-nitration,
oxidation, resinification, or owing to the effect
of the procedure upon impurities or isomers ac
companying the desired raw material.
Para cresol as such is a fairly expensive raw
material, but when mixed with its meta isomer
roughly in the proportion of 60 parts meta to
40 parts para, it is a much less expensive ma
terial. At considerable cost for treatment, the
content of the meta isomer may be reduced.
Considering costs, yields, purities, kinds of ni
tration processes, and commercial supplies, speci
20 ?cations, and demands, there is still a place for
a low-cost nitrating process operable upon either
a pure para cresol or upon an impure para cresol,
such as one containing its isomeric forms, par
ticularly the meta cresol, to yield an acceptable
25 grade of meta nitro para cresol.
Para cresol has heretofore offered practical
and economic di?iculties for low-cost nitration
processes.
So far as we have been able to as
certain, a complicated procedure has been em
30 ployed heretofore, involving use of solvents, such
as ether, and a necessary cooling. The nitra
tion of cresol offers di?iculties not encountered
in nitrating phenol. While there is but one form
of phenol, there are three isomeric forms of
35 cresol. These may or may not react differently
to some selected nitration procedure. A pro
cedure which nitrates one isomer may not ni
trate another; and where mixed isomers are pres
ent, one isomer may interfere with nitration of
40 another isomer.
The present invention aims to provide a simple
practical and economic process for the nitration
of para cresol, which may be practiced upon a
pure para cresol, and also upon mixed cresol
isomers to nitrate the para cresol content, and
to give in both cases a useful grade of meta nitro
para cresol.
A particular object of the invention is the
aqueous nitration of cresol containing para cresol
by the action of an aqueous solution of nitric
acid to secure the desired nitration of the para
cresol content.
A further object of the invention is the aque
ous nitration of cresol containing para cresol
by the action of a nitration mixture derived from
sulphuric acid and a nitrate salt, and used with
considerable water.
Various other and ancillary objects and ad
vantages will hereinafter become apparent.
We have discovered that our process is selec
tive in that it effects nitration of para cresol,
but does not likewise nitrate isomeric cresols.
When our invention is practiced upon pure para
cresol, it gives a clean product and a suitably
high yield. However, when mixed isomers are if)
used, such as one containing 85% para cresol
and 15% meta cresol, the reaction mass ex
hibits considerable oxidation and formation of
tar or resin, without seriously altering the ex
pected yield of meta nitro para cresol based on
the actual content of para cresol initially em
ployed. Further, we have found that the proc
ess does not nitrate pure ortho cresol or pure
meta cresol in any smooth manner comparable
to its nitration of pure para cresol.
Therefore,
we may use our process for nitrating either a
pure para cresol or a mixture of cresol isomers,
to obtain nitration of the para cresol isomer
without similar or interfering nitration of the
other isomers. Although products of oxidized
or resini?ed character may be produced by the
process from meta or ortho isomers, or from
minor reaction on the para isomer, these only
create mechanical difficulties having to do largely
with the recovery and puri?cation of the de 30
sired meta nitrated para cresol. The extent of
these difficulties will therefore in part deter
mine how much impurity may attend the para
cresol in the original cresol, and also deter
mine to what extent the preferred process may
be varied within the permissible limits set forth.
We have found it very practicable to nitrate
either pure para cresol, or an impure para cresol
containing as much as 15% of the meta isomer,
without materially changing the yield or effi
ciency of the procedure based upon the chemical
conversion of the actual content of pure para
cresol.
Puri?cation of commercial “60-40”
mixed isomers to a point where composition is
roughly 85% or more of para cresol and 15%
or less of meta cresol is feasible and economi
cally practicable for the present procedure. And
likewise the present procedure is practicable for
such an impure para cresol.
The process is distinctive in being carried out
as an aqueous nitration and by contact in a
two-phase mixture with the cresol employed,
para cresol being not completely if at all soluble
in the aqueous nitrating solution. As practi
cally carried out, a dilute sulphuric acid solu 55
2
‘2,136,187
tion containing nitric acid is formed. This may
be done in various ways as by adding nitric acid
to dilute sulphuric acid, or adding a nitrate salt
to a strong or dilute sulphuric acid, and diluting
if required. Practically, an excess of a strong
sulphuric acid and sodium nitrate are mixed.
This forms nitric acid, sodium acid sulphate,
and a weaker sulphuric acid.
This mixture is
then poured into water, or into mixed ice and
10 water, to give quickly and directly a sufficiently
cool nitrating liquid for the process. Then with
heavy agitation, the pure or impure cresol is
slowly added in small stream, dropwise, or like
manner over an extended period to assure good
15 mixing, such as an hour’s time more or less,
dependent upon the character of apparatus and
the agitation. The time is not a critical factor,
The two-phase mixture resulting, is further
agitated to assure completion of the reaction,
20 and a period of two hours agitation after com
pletion of the mixture is suitable. This time
period is not critical with a su?icient agitation
to assure good nitrating contact to complete the
reaction. A heavy oil layer is then allowed to
having practically no effect. Below 25° C. the
nitration proceeds very slowly. Above 60” C.
certain ingredients of the mass “burn up” or are
destroyed. The best results are obtained by fol
lowing the procedure as given above, within the
preferred temperature limits of 30° C. to 40° C.
and with 1400 to 1600 parts of Water, which is
from 78 to 89 mols of water. Considering the
added water above mentioned the preferred ni
trating acid solution contains roughly from 80 10
to 90 mols of water for at least 1 mol of nitric
acid, and a small amount of free sulphuric acid.
A yield of 80% to 85% of meta nitro para cresol
is thus obtained based upon the actual para
cresol originally present in the raw material.
15
However, it is to be understood that variations
are permissible as will be shown from the fol
lowing tabulated examples, using a ?xed quantity
of 480 parts of 92% sulphuric acid, 125 parts of
sodium nitrate, 108 parts of cresol, and the vari 20
ations as follows:
Example
N o.
y
“ at"
Cresol
- Tempera-
purity
ture, °C.
-
Ymld'
25 settle to the bottom, which layer is separated
25
from the upper layer, washed, and puri?ed, pref
erably through a vapor phase as a distillate by
steam distillation. This is the desired meta
nitro para cresol.
30
The temperature of the reaction may be from
0° C. to 60° C. Preferably it is lower at the
beginning so that any increase by heat gen
erated may keep it below the prescribed limit.
It is further preferred to keep the temperature
35 between 30° C. and 40° C. Lower temperature
seems to extend the time of nitration reaction,
permitting side reactions to proceed too far, and
this is more noticeable as the acid concentra
tion is greater.
The following speci?c example gives a range
of proportions of materials which may be
employed.
Example 1
Parts by weight
Sodium nitrate (or equivalent po
tassium nitrate) ______________ __ 120 to 125
92% sulphuric acid _____________ __ 450 to 480
Water (600 parts ice) * __________ __ 400 to 4000
Pure or crude para cresol ______ __ 108
"l‘m-l'l-riw ll 01m- where water is 1400 to 1000 parts.
The foregoing formula is based upon 108 parts
of the para cresol being a molecular quantity,
or 1 mol of cresol. It may contain, for example
15% of admixed meta isomer, and the 108 parts
or” the formula may be calculated upon the mixed
isomers or upon the content of the para isomer.
The amount of sodium nitrate or equivalent
nitric acid set forth is about 1.4 to 1.5 mols for
the 1 mol of cresol to be nitrated and therefore
there is an excess of nitric acid available for
loss and for side reactions not desired. The
amount of sulphuric acid is roughly 4.2 to 4.5
mols, and only about 1.4 mols of this is lost as
, free acid in generating 1.4 to 1.5 mols of nitric
acid from the nitrate salt. Excess sulphuric
acid no doubt serves at this low dilution as the
usual nitration catalyst. The large amount of
water is necessary to minimize resini?cation and
oxidation arising from any undesired side reac
tions which may occur. The water item of the
formula is from about 20 to about 220 mols to
which about 2 mols are added by the sulphuric
acid item of the formula, and another mol of
75 water is created in the nitration, such additions
Percent
300
98 para
0-5
Excessive oxidation
and
400
600
1500
4000
08
98
98
98
para
para
para
para
1500 { @5153‘; }
0-5
2-19
30-40
40-60
resinl?cation
36. 6%
72. 3%
80. 7%
55. 0%
30-40
80. 8%
30
‘Based on content of para cresol.
The process is of great practical merit because
it is applicable to both pure para cresol, and to 35
mixed isomers containing para cresol, without
change of procedure. Its selective action, in ni
trating the para isomer and in not similarly ni
trating the ortho and meta isomers, makes it a
valuable procedure in that the product of using 40
mixed cresols is relatively free from mixed ni
trated isomers resulting from simultaneous nitra
tion of the mixed cresol isomers. For the eco
nomic use of the process, the practical limits of
para cresol in mixed cresol isomers may be fixed
by many conditions entirely independent of the
invention. It will thus appear to those skilled
in the art, that the invention may be used in
various ways with great chemical advantage as
an isolation procedure for para isomeric com
pounds within the scope of materials involved,
and with great economic advantage according to
raw materials available, and other economic fac
tors.
55
We claim:
1. A process for the nitration of para cresol to
form meta nitro para cresol, which comprises
subjecting‘ up to 1 mol of such cresol to the ac
tion of an aqueous nitrating acid solution having
at least 1 mol of nitric acid, free sulphuric acid, 60
and from 20 to 220 mols of water, said action
being conducted at a temperature from 0° C.
to 60° C.
‘2. A process for the nitration of the para
cresol content of mixed cresol isomers to form 65
meta 'nitro para cresol, which comprises sub
jecting up to 1 mol of such mixed cresol isomers
to the action of an aqueous nitrating acid solu
tion having at least 1 mol of nitric acid, free sul
70
phuric acid, and from 20 to 220 mols of water,
said action being conducted at a temperature
from 0° C. to 60° C.
3. A process for the nitration of para cresol to
form meta nitro para cresol, which comprises 75
2,136,187
subjecting up to 1 mol of such cresol to the action
of an aqueous nitrating acid solution having at
least 1 mol of nitric acid, free sulphuric acid,
and from 20 to 220 mols of water, said action
being conducted at a temperature from 30° C.
to 40° C.
4. A process for the nitration of the para
cresol content of mixed cresol isomers to form
meta nitro para cresol, which comprises subject
10 ing up to 1 mol of such mixed cresol isomers to
the action of an aqueous nitrating acid solution
3
nitro para cresol, which comprises subjecting up
to 1 mol of such mixed cresol isomers to the ac
tion of an aqueous nitrating acid solution con
sisting of the reaction products of at least 1 mol
of a nitrate salt, at least about 4 mols of sul
phuric acid calculated as 100%, and from 80 to
90 mols of water, said nitration being conducted
at a temperature from 30° C. to 40° C.
9. A process for nitrating para cresol to form
meta nitro para cresol which comprises mixing
para cresol with an aqueous nitrating acid solu
having at least 1 mol of nitric acid, free sulphuric
acid, and from 20 to 220 mols of water, said ac
tion being conducted at a temperature from 30°
tion containing sulphuric acid at from 0° C. to
60° C. whereby para cresol is converted to meta
C. to 40° C.
acid solution, separating said oil from the said 15
spent acid solution, and purifying the separated
oil through its vapor phase.
'
5. A process for the nitration of para cresol to
form meta nitro para cresol, which comprises
subjecting up to 1 mol of such cresol to the ac
tion of an aqueous nitrating acid solution hav
ing at least 1 mol of nitric acid, free sulphuric
acid, and from 80 to 90 mols of water, said action
being conducted at a temperature from 30° C.
to 40° C.
6. A process for the nitration of the para cresol
content of mixed cresol isomers to form meta
nitro para cresol, which comprises subjecting up
to 1 mol of such mixed cresol isomers to the
action of an aqueous nitrating acid solution hav
ing at least 1 mol of nitric acid, free sulphuric
acid, and from 80 to 90 mols of water, said action
being conducted at a temperature from 30° C.
to 40° C.
7. A process for the nitration of para cresol to
form meta nitro para cresol, which comprises
subjecting up to 1 mol of such cresol to the action
of an aqueous nitrating acid solution consisting
of the reaction products of at least 1 mol of a
nitrate salt, at least about 4 mols of sulphuric
acid calculated as 100%, and from 20 to 220 mols
40 of water, said nitration being conducted at a tem
perature from 0° C. to 60° C.
8. A process for the nitration of the para cresol
content of mixed cresol isomers to form meta
nitro para cresol as an oil in the spent nitrating
10. The method of making a separation of a
para compound from accompanying isomeric
compounds which consists in subjecting a mix 20
ture of isomeric cresols containing a substantial
amount of para cresol to the action of an aqueous
nitrating acid solution containing sulphuric acid
at from 0“ C. to 60° C. whereby para cresol is
converted to meta nitro cresol as an oil in. the 25
spent nitrating acid solution and the isomeric
cresol is largely converted to tar or resinous mat
ter, and separating‘ the tar and resinous matter
from the meta nitro para cresol.
11. The method of selectively treating para 30
cresol in the presence of an isomeric cresol to
form meta nitro para cresol substantially free
from isomers, which consists of subjecting the
isomeric cresols to the action at from 0° C. to
60° C. of an aqueous nitrating solution contain 35
ing sulphuric acid, the action of the nitrating
solution being selective to nitrate the para cresol
isomer, and to convert the isomeric cresol into
waste matter separable from the resulting meta
nitro para cresol.
40
ROBERT FRYE.
GRADY M. O’NEAL.
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