Waste Acids, and of the Bye-products Resulting therefrom.
Year: 1885

page_text: Treatment of the Waste Acids Resulting from the Purification
of the Light Oils of Coal Tar for the Utilization of the said
. Waste Acids, and of the Bye-products Resulting therefrom.
I, ANDREAS ALEXANDER VALE, of 34 Mildmay Chambers, Bishopsgate Street in
the City of London, Merchant, do hereby declare the nature of my invention for
"TREATMENT OF THE WASTE ACIDS RESULTING FROM THE PURIFICATION OF THE
LIGHT OILS OF COAL TAR FOR THE UTILIZATION OF THE SAID WASTE ACIDS, AND OF"
THE BYE-PRODUCTS RESULTING THEREFROM to be as follows:-
"
The light oils of coal tar are purified by agitating them with concentrated
sulphuric acid. When allowed to rest, the acid settles at bottom in the form of a
blackish brown thickish liquid, which is termed waste acid, and which, up to the
present time, has met with no application, and consequently forms a troublesome
product of the tar distilleries, tar factories, and similar works, that is with difficulty
disposed of.
The manner in which the sulphuric acid acts upon the impurities of the tar oils
has not up to the present time been ascertained with certainty.
My correspondents have discovered that the sulphuric acid, independently of its
property of dissolving the bases contained in the raw light oils, in the first instance
only polymerises or renders resinous the turpentine-like and other substances
contained therein and only oxydises them under separation of carbon after
lengthened contact. A portion of the product resulting from this action of the
acid, in particular the polymerised compounds, remains dissolved in light oils, while
the remainder, in particular the resinous compounds, passes into the sulphuric acid.
On the basis of this fact, my correspondents have invented a process for utilising
this waste acid in all its constituents, by converting the sulphuric acid contained
therein into marketable sulphate of ammonia, and rendering the resin like
substances separated from the waste acid available as impregnating liquids or
paints in the form of solutions in tar oil, carbolic acid and the like. At the same
time my correspondents combine herewith the costless production of the organic
bases contained in the raw light oils,

page_text: For these purposes, in order to prevent decomposition or oxidation, the waste
acid is preferably diluted to such an extent with water immediately after it is
drawn off from the oils that the greater part of the tarry substances dissolved in
the acid separate out and that the sulphuric acid still very impure and of a reddish
brown color, situated beneath them has a specific gravity of from 12 to 1.25. For
obtaining a better separation, my correspondents add to this liquid tar oils (light
oil anthracite oil, raw carbolic acid) and they then separate the supernatant tarry
substances, which have now become more liquid, from the acid below. In order to
remove any remaining quantity of acid from the upper layer this is treated with
gaseous ammonia or with aqueous ammonia, and is separated from the preci-
pitated ammonium sulphate; it can then, after filtration, be used for purposes of
impregnation, as paint and the like.
The above mentioned acid of 1-2 to 1.25 specific gravity separated from the tarry
substances can be rendered perfectly colorless by again agitating it together with
tar oils, carbolic acid and the like, and may then be employed for the production
of other sulphates, but my correspondents employ it for the extraction of the
organic bases contained in the raw light oils, before they are washed with
concentrated sulphuric acid.
About double the quantity of the said acid is added as is necessary to bind the
bases present; the acid solution of the bases is then separated from the light oils,
and is saturated with gaseous or aqueous ammonia. The solution of ammonium
sulphate separates clear and colorless, while the impurities of the acid remain
dissolved in the supernatant free tar bases. The solution of ammonium sulphate
is evaporated and is separated by. crystallisation from the small quantitios of
foreign salts contained therein such as sulphites thiophensulphates, benzosulphates,
while the tar bases are separated from the resins by distillation, and are either
again used for the purification of waste acids or otherwise utilised.
It will be readily understood that with this process, when other sulphates are
to be produced, the ammonia must be replaced by other stronger bases; also the acid
can be used directly for saturating these bases and the impurities be extracted by
agitation with tar bases or carbolic acid.
In tar distilleries, the process is best combined with the simultaneous treatment
of the gas and tar liquor, by distilling the liquor in the usual apparatus under
addition with lime and using the free ammonia for neutralising the acid or for
liberating the organic bases. By this means it is easily possible to arrange the
entire process which admits of certain variations in the proportions in such manner
that in treating a given quantity of raw tar, almost the entire quantity of sulphuric
acid required for the purification of the light oils is regained free of cost as
commercial sulphate of ammonia, while at the same time both the tar bases as also
the tarry substances formed by the washing with concentrated sulphuric acid are
obtained without further addition of reagents.
BOOK

page_text: Treatment of the Waste Acids Resulting from the Purification
of the Light Oils of Coal Tar for the Utilization of the said
Waste Acids, and of the Bye-products Resulting therefrom.
I, ANDREAS ALEXANDER VALE, of 34 Mildmay Chambers, Bishopsgate Street in
the City of London, Merchant, 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 :—
The light oils of coal tar and other light oils of a similar nature are purified by
agitating them with concentrated sulphuric acid. When allowed to rest, a blackish
brown thickish liquid settles at bottom, which is termed "waste-acid," and which,
up to the present time, has met with no practical application, and consequently
forms a troublesome product of the tar distilleries, tar factories and similar works,
that is with difficulty disposed of.
For the purpose of purifying and utilising this waste acid, it is, according to this
invention, diluted with water immediately upon its removal from the purifying
vessel. The extent of the dilution is variable within certain limits, according to
the nature of the waste acid, but, as a rule, the proportion of water added should
be about equal to the volume of concentrated sulphuric acid contained in the waste
acid. On allowing this mixture to settle, two strata of liquid are formed; the
lower stratum, if it is to be used to furnish free acid, is freed from resinous
impurities still dissolved therein by washing with substances of the phenole class,
such as creosote or carbolic acid, yielding a nearly colourless liquid that may be
used directly for decomposing the alkaline compounds of phenol and creosol; but
it is employed with greater advantage for the production of ammonium sulphate.
For this purpose, there is first added a small quantity of tar bases (aniline, pyridine
and chinoline bases) of which 5 per cent are sufficient, and the mixture is then
neutralised with ammonia obtained in any known manner, such as by distilling
gas liquor. The result is a clear solution from which commercially pure ammonium
sulphate may be obtained without difficulty the tar bases together with the resinous
impurities originally dissolved in the acid floating over the solution.
In the light oils of coal tar such bases as are required for the process exist in
sufficient quantity, so that instead of using the separated bases for washing the
sulphuric acid, a suitable quantity of raw light oils may be employed, these yielding
to the acid only the required tar bases.
In tar distilleries therefore it would be advantageous to combine with this
process the simultaneous utilisation of the gas and tar liquors, thus obtaining the
tar bases as bye products.
The upper stratum obtained by the above mentioned dilution of the waste acids
with water, consists mostly of sulpho-acids and hydrocarbons. This is again
diluted with larger quantities of water and from the ammonia salts of the sulpho
acids contained in the diluted mixture, the carbon compounds contained therein can
be regained, while the remaining resinous and oily hydrocarbons similar to tar oils
of high boiling point, can be utilised like these oils for known purposes.

page_text: Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
1. The herein described process for obtaining dilute sulphuric acid, separate from
sulpho-acids, and hydrocarbons, from the waste-acid resulting from the refining of
light oils, by diluting the waste acid with water, and washing the sulphuric acid
which separates by gravity with phenol substances, such as creosote and carbolic
acid.
2. The herein described process for obtaining ammonium sulphate from the waste-
acid resulting from the refining of light oils, by diluting the waste acid with water
and after treating with tar bases the sulphuric acid which separatos by gravity,
neutralising the acid with ammonia.