Process for the Manufacture of Picric Acid by Crude Phenols.
Year: 1889

page_text: Date of Application, 25th Nov., 1889
Complete Specification Left, 22nd Aug., 1890-Accepted. 27th Sept.. 1890
PROVISIONAL SPECIFICATION.
Process for the Manufacture of Picric Acid by Crude Phenols.
A communication from abroad by EMILE DE LOM DE BERG, of Brussels, in the
Kingdom of Belgium.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for Foreign
Patent Solicitors, 6 Lord Street, Liverpool, and 6 Bank Street, Manchester both in
the County of Lancaster, and 323 High Holborn, in the County of Middlesex, Civil
Engineer, do hereby declare the nature of this invention to be as follows:-
:-
Many industries depend largely for their success upon the preparation of pure
picric acid. This has hitherto necessitated the employment of pure phenols as raw
material, and as the price of these phenols is very high, it follows that hitherto it has
only been possible to supply picric acid at a price relatively somewhat dear. This
acid plays a large part in the manufacture of explosive substances; it is therefore of
great importance to be able to produce it under less onerous conditions than those
under which the manufacturers supply it at present. Experiments have led to the
discovery of conditions under which the preparation of these products may be attained
much more cheaply than heretofore.
In place of using pure and crystallised phenol, crude phenols, which only contain
a certain proportion of crystallisable phenol, have been utilised by the process of this
invention, and even great advantages are obtained from the use of it.
Hitherto the various methods attempted of nitrifying crude phenols have only ended
in failure; a mixture of nitro-phenol, nitro-cresol, and hydro-carburet was produced,
the nitrification was then very complex, the separation extremely costly, difficult, and
almost always uncertain.
This process is based on the following observations :-
1. Nitrification of phenol is more easily brought about in the sulphonic combinations
(sulfo-conjugué) than in the product itself.
2. The crystallisable sulphonic combination of phenol is made easier than the
sulphonic combination of cresol or of the other products contained in the crude
phenol.
3. In effecting the nitrification either by means of a quantity of acid not sufficient
for complete nitrification or by regulating the temperature, the impure products have
been successfully nitrified in the first place, whilst the phenols are only transformed
later on, the group NO² connects itself preferably to the non-crystallisable phenols.
Taking these observations into consideration, the manufacture of pieric acid has
been carried out to great advantage, starting with crude phenol and employing two
different methods.
1st Process. To crude phenol is added a quantity of sulphuric acid corresponding
to the amount of crystallisable phenol contained in it. With a view to produce the
sulphonic combination of phenol, the latter, in an oily state, is plunged into water,
the sulphonic combination is dissolved, and the other products are separated in an
bily condition, they are then separated by decantation. The acid liquor is then
reated with a quantity of nitric acid (or a suitable nitrate and sulphuric acid)
ecessary for transforming the sulphonic combinations into trinitric picric acid
products.
During this treatment, the portion of cresol which was not previously removed by
he decantation is scarcely attacked by the nitric acid. When the reaction is
completed, the whole is concentrated to the consistency of syrup, concentrated
ulphuric acid is then added with the object of forming the sulphonic combination
of cresol with the cresol which may be remaining; the whole is then plunged in
Prine S1
、

page_text: water, and, by this means, the picric acid, but slightly soluble in water, is separated,
the sulpho-cresol being very soluble remains in the solution, the picric acid obtained
is redissolved in water and recrystallised.
2nd Method. Crude phenol is treated with a great excess of sulphuric acid in
order to obtain the sulphonic combinations, these are dissolved in water, and treated
by one of the methods described in observation 3. In the cooled liquor, after the
first stage of nitrification, an oily layer is formed, composed of nitro-cresol, they are
separated by decantation, and by nitrifying them separately, trinitric cresol is obtained.
The liquor is treated by the nitric acid remaining (or by nitrate and sulphuric acid)
just as if a solution of pure phenol had been employed, and there is obtained, as final
product, pure picric acid free from any foreign matter.
Dated this 11th day of January 1890.
WM. P. THOMPSON & Co.,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Process for the Manufacture of Picric Acid by Crude Phenols.
A communication from abroad by EMILE DE OM DE BERG, of Brussels, in the
Kingdom of Belgium.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for Foreign
Patent Solicitors, 6 Lord Street Liverpool and 6 Bank Street Manchester both in
the County of Lancaster and 323 High Holborn in the County of Middlesex, Civil
Engineer, do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by the
following statement :-
Many industries depend largely for their success upon the preparation of pure
picric acid. This has hitherto necessitated the employment of pure phenols as raw
material, and as the price of these phenols is very high, it follows that bitherto it has
only been possible to supply picric acid at a price relatively somewhat dear. This
acid plays a large part in the manufacture of explosive substances; it is therefore of
great importance to be able to produce it under less onerous conditions than those
under which the manufacturers supply it at present. Experiments have led to the
discovery of conditions under which the preparation of these products may be attained
much more cheaply than heretofore.
In place of using pure and crystallised phenol, crude phenols, which only contain a
certain proportion of crystallisable phenol, have been utilised by the process of this
invention, and even great advantages are obtained from the use of it.
Hitherto the various methods attempted of nitrifying crude phenols have only
ended in failure; a mixture of nitro-phenol, nitro-cresol, and hydro-carburet was
produced, the nitrification was then very complex, the separation extremely costly,
difficult, and almost always uncertain.
This process is based on the following observations:
1. Nitrification of phenol is more easily brought about in the sulphonic combinations
(sulfo-conjugué) than in the product itself.
2. The crystallisable sulphonic combination of phenol is made easier than the
sulphonic combination of cresol or of the other products contained in the crude
phenol.
3. In effecting the nitrification either by means of a quantity of acid not sufficient
for complete nitrification or by regulating the temperature, the impure products have
been successfully nitrified in the first place, whilst the phenols are only transformed
later on, the group NO³ connects itself preferably to the non-crystallisable
phenols.
Taking these observations into consideration, the manufacture of picric acid bas
been carried out to great advantage, starting with crude phenol and employing two
different methods.

page_text: 1st Process. To crude phenol is added a quantity of sulphuric acid corresponding
to the amount of crystallisable phenol contained in it. With a view to produce the
sulphonic combination of phenol, the latter, in an oily state, is plunged into water, the
sulphonic combination is dissolved, and the other products are separated in an oily
condition, they are then separated by decantation. The acid liquor is then treated
with a quantity of nitric acid (or a suitable nitrate and sulphuric acid) necessary for
transforming the sulphonic combinations into trinitric picric acid products.
During this treatment, the portion of cresol which was not previously removed by
the decantation is scarcely attacked by the nitric acid. When the reaction is
completed, the whole is concentrated to the consistency of syrup, concentrated
sulphuric acid is then added with the object of formning the sulphonic combination of
cresol with the cresol which may be remaining; the whole is then plunged in water,
and, by this means, the picric acid, but slightly soluble in water, is separated, the
sulpho-cresol being very soluble remains in the solution, the picric acid obtained is
redissolved in water and recrystallised.
2nd Method. Crude phenol is treated with a great excess of sulphuric acid in order
to obtain the sulphonic combinations, these are dissolved in water, and treated by one
of the methods described in observation 3. In the cooled liquor, after the first stage
of nitrification, an oily layer is formed, composed of nitro-cresol. This is separated by
decantation. Each of the liquors are nitrified separately, and trinitro-cresol is obtained
from the nitro-cresol. The other liquor is treated with sufficient nitric acid (or with
nitrate and sulphuric acid) to form the trinitro compound just as if a solution of pure
phenol had been employed, and there is obtained, as final product, pure picric acid
free from any foreign matter.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me
by my foreign correspondent, I declare that what I claim is :-
In the preparation of pure picric acid by means of crude phenol-
1. The use of sulphuric acid at two distinct periods substantially as described.
2. The carrying out of the nitrification at two distinct periods and the separation of
the nitro-cresol after the first period, substantially as described.
3. The obtaining of trinitro-cresol as bye-product in the manufacture of pure picric
acid by means of crude phenol, substantially as described.
Dated this 21st day of August 1890.
WM. P. THOMPSON & Co.,
Agents for the Applicant.