Year: 1899

page_text: I, PAUL BOESSNECK, Doctor of Philosophy, of Glauchau, in the Kingdom of
Saxony, do hereby declare the nature of this invention to be as follows:-
This invention relates to the distillation of acetic acid from mixtures con-
taining the same in a free condition.
Commercial acetic acid is usually obtained by distilling pyrolignate of lime
or other acetates with sulphuric or hydrochloric acid in retorts of iron or copper.
The process is always carried out intermittently, in as much as after the acetic
acid contained in a charge has been driven out, and when the apparatus is being
charged afresh, the distillation of the acetic acid is interrupted.
As far as I have been able to ascertain, the distillation of acetic acid from
acetates is not carried out continuously anywhere, nor has such a process been
described in the technical literature.
I have found, however, that the continuous manufacture of commercial acetic
acid by distilling acetates with acid, constitutes important progress by enhancing
the capacity of production of the manufacturing plant.
The most suitable raw material for the manufacture of acetic acid from
acetates and a mineral acid is a mixture of acetate of lime and hydrochloric
acid, because the residue resulting from the distillation of such a mixture is a
concentrated calcium chloride solution, which can be easily kept liquid.
Various systems of apparatus may be employed for the continuous distillation
of acetic acid, for instance.
1. Apparatus commonly used for the concentration of sulphuric acid, in which
the mixture of hydrochloric acid and acetate or pyrolignate of lime contained in
closed receptacles gradually approaches the source of heat, and after the acetic
acid has been driven off, the residue consisting of a calcium chloride solution
leaves the apparatus, while the acetic acid escaping from the liquid takes the
opposite way to the cooler.
2. A battery of distilling vessels, in which the distillate of the last vessel passes
first through all other vessels and thereby becomes richer in acetic acid.
3. The most suitable appliances are those constructed on the principle of
column stills, the mixture of acid and calcium acetate or pyroligmate being
charged in the top ring, while the residue relieved of acetic acid escapes at the
bottom. The source of heat in this case may be steam (either saturated or super-
heated) hot air or heating gases. The columns may, however, be heated
indirectly. Or gaseous hydrochloric acid may be conducted through a system of
tubes which are charged with pyrolignate of lime.
Dated this 18th day of December 1899.
FAIRFAX & WETTER,
Agents for the Applicant.

page_text: I, PAUL BOESSNECK, Doctor of Philosophy, of Glauchau, in the Kingdom of
Saxony, 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:-
Commercial acetic acid is usually obtained by distilling pyrolignate of lime
or other acetates with a strong mineral acid, such as sulphuric or hydrochloric,
acid in retorts, of iron or copper. The process is always carried out inter-
mittently, that is to say, after the acetic acid contained in the charge has
been driven out by the hydrochloric or sulphuric acid, and when the apparatus is
being charged afresh, the distillation of the acetic acid is interrupted.
As far as I have been able to ascertain, the distillation of acetic acid from
acetates is not carried out uninterruptedly anywehere, nor has such a process
been described in the technical literature.
I have found, however, that the continuous manufacture of commercial acetic
acid by distilling acetate with acid in such a manner that the acetate under
treatment and the acetic acid given off by the same travel through the apparatus
in opposite directions, and that the acetate mixture gradually approaches the
source of heat, constitutes an important progress, in as much as it enhances
the capacity of production of the manufacturing plant, and reduces the cost of
manufacture.
The most suitable raw material for the manufacture of acetic acid from acetates
and a strong mineral acid is a mixture of acetate of lime and hydrochloric acid,
because the residue resulting from the distillation of such a mixture is a con-
centrated calcium chloride solution, which can be easily kept in a liquid condition.
Various systems of apparatus may be employed for the continuous distillation
of acetic acid according to my invention, but the most suitable appliances are
continuous column stills, as illustrated by the accompanying drawings, of which
Fig. 1 is a vertical section, Fig. 2 a horizontal section alone line A-B of Fig. 1
and Fig. 3 a horizontal section along line C-D of Fig. 1.
The apparatus chiefly comprises a series of evaporating dishes or shallow
vessels a placed one above the other and communicating with each other through
tubes 6 placed alternately on diametrically opposite sides, as indicated by Fig. 2,
and also through openings h formed in the floor of each vessel, each opening
extending through a conical elevation and being covered by a conical hood g.
The floor of each vessel a has also a pair of upright ribs or deflecting plates c,
which force the liquid poured into the said vessels to take a zig-zag course in
flowing from one side of the vessel to the other.
The stack of evaporating vessels a is mounted on a box or hollow stand d,
having an outlet f for steam and an outlet e for liquid, and which is provided
with a water gauge.
The mixture of pyroligmate of lime and hydrochloric acid to be treated in
the apparatus is caused to flow into the uppermost of the dishes a, through
which it is guided by the ribs c, and in which it rises to the upper edge of the
down-pipe b situated below the mouth of the conical openings h. Through the
pipe the liquid flows into the second dish a, thence into the third and so on,
until it reaches the hollow stand d, from which it escapes through the outlet e.
At the same time superheated steam admitted through the opening f to the
hollow stand d, rises into the lowest of the evaporating vessels through the
conical openings h situated in the bottom of the same, and passes through the

page_text: layer of liquid lying on the bottom of the said vessel, whereby the steam is
charged with acetic acid. Subsequently the steam rises into the next higher
evaporating vessel through the conical openings in the bottom of the same, and
is further enriched with acetic acid vapours by its contact with the liquid
situated in the said vessel. In this manner the steam rises from one vessel to
another, until it reaches the topmost vessel a, after it has been gradually enriched
with acetic acid. From the topmost vessel the mixture of acetic acid and steam
is led off to a condenser, where the acetic acid is recovered in the known manner.
In this manner acetic acid is produced continuously, while the calcium
chloride solution running off contains only traces of acetic acid.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is;-
1. The process for obtaining acetic acid from a mixture of an acetate and a
strong mineral acid, which consists in continuously supplying the said mixture
to a receptacle or series of receptacles, causing it to pass through the same, and
heating it by means of a hot elastic fluid passing in the opposite direction, so
as to gradually drive out the acetic acid from the mixture, substantially as
described.
2. The process for obtaining acetic acid from a mixture of an acetate and
a strong mineral acid, which consists in causing a continuous supply of the
said mixture to flow through a receptacle or a series of receptacles, and at the
same time causing steam or other suitable heating fluid to flow through the
same in the opposite direction, in order to heat the said mixture and gradually
absorb the acetic acid vapours given off by the same, and then treating the
heating fluid discharged from the receptacle in the known manner for recovering
the acetic acid absorbed by the same, substantially as described.
3. The process for obtaining acetic acid from a mixture of calcium pyrolignate
and hydrochloric acid, which consists in causing a continuous supply of the said
mixture to flow through the receptacle or series of receptacles in one direction,
and at the same time causing steam or other suitable heating fluid to flow
through the same in the opposite direction, in order to heat the said mixture
and gradually absorb the acetic acid vapours given off by the same, and then
treating the steam or other heating fluid discharged from the receptacle, in the
known manner for recovering the acetic acid absorbed by the same, substantially
as described.
4. The methods described above for the continuous manufacture of acetic acid
from an acetate or pyrolignate.
FAIRFAX & WETTER,
Agents, 37 and 39, Essex Street, Strand, London.