Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates to a process for the mono-
nitration of anthraquinone with sulphuric acid/nitric acid mix-
tures, it being possible to obtain l-ni-troanthraquinone in high
yields.
A number of processes for the mononitration of anthra-
quinone are known in which the n:itration of anthraquinone is
carried out either with nitric acid alone or with mixtures of
nitric acid and other substances (see, for example, U.S Patent
Specification 2,874,168, DT-OS's (German Published Specifica-
tions) 2,103,360, 2,232,464 and 2,241,627 and Polish Patent
Speci~ication 46,428). These processes are disadvan-tage~
ous since they require long reaction times and/or the use of
relatively large amounts of mineral acids. Very aggressive
reagents are also used in some of these processes, so that
particularly corrosion-resistant materials must be used for the
manufacture ~ the required equipment. .
Processes for the mononitration o~ anthraquinone with
sulphuric acid/nitric acid mixtures have also already been known
for a long time, see, for example, Liebermann, Berichte 16, page
54 (1883). In this process, when the nitration is carried
out to such an extent that less than 5% of unreacted anthra-
quinone remains in the reaction product, l-nitroanthraquinone is
obtained in yields of only about 60%. The poor yields are
caused by the fact that the anthraquinone formed cannot be
sufficiently protectedagainst being further nitrated to dinitro-
anthraquinones. This situation has been re~erred to in
various instances, for example in DT-AS (Ge~man Published
Specification) 2,039,822.
A process for the preparation o~ l-nitroanthraquinone
by nitrating anthraquinone in sulphuric acid is also described
in DT-AS (German Published Speci~ication) 2,039,822, in which
Le A 17 494 - 2 -
the nitration of the anthraquinone is carried ou-t in a he-tero
geneous phase in 75 -to 82% strength sulphuric acid in the temp~
erature range from approximately 20 to approximately 60C, until
approximately 75% by weight of l-nitroanthraquinone are formed
According to Example 1 o~ this DT-AS (German Published Speci~ic-
ation), 51 parts of 98% strength nitric acid are employed per
160 parts of 78% strength sulphuric ac~d, that ls to say a sub-
stantially smaller amount of nitric acid -than sulphuric acid.
The disadvantages of this process are the long reaction times re-
quired (according to Example 1, 12 to 15 hours) and the sensiti-
vity of the course of the reaction towards variations in the
temperature and the concentration of the nitra-ting acid, which
is expressly referred to in DT-OS (German Published Specification)
2,204,516. A further serious disadvantage of the process in
DT-AS (German Published Specification) 2,039,822 is that large
amounts of sulphuric acid are required, relative to anthraquin-
one, which either must be worked up, with high costs, a~ter the
reaction has ended or lead to severe pollution of the effluent.
These disadvantages are already pointed out in DT-OS (German
Published Specification) 2,233,185.
Even the processes according to DT-OS's (German Publish-
ed Specifications) 2,204,516 and 2,233,185 do not completely
remove the disadvantages of the process according to DT-AS (Ger-
man Published Specification) 2,039,822, since according to DT-
OS (German Published Specification) 2,204,516 the reaction is
likewise carried out with relatively high amounts of acid, rela-
tive to anthraquinone, and according to DT-OS (German Published
Speci~ication) 2,233,185, although a substantially smaller
amount of acid is employed, relative to anthraquinone, in addi-
tion, the reaction must be carried out in the presence of an
i~ert organic solvent.
e A 17 494 - 3 -
3 6 ~
A process has now been ~ound for the mononitration of
anthraquinone wlth nitric acid/sulphuric acid mixtures, which i~
characterised in that anthraquinone is nitrated in a nitric acid/
sulphuric acid mixture, in which the weight ratio o~ nitric acid
to sulphuric acid is about 1:1 to about 2:1, in which the weight
ratio of sulphuric acid to anthraquinone is about 0.5:1 to about
1:1 and in which the weight ratio of sulphuric acid to water is
about 2.5:1 to about 5.5:1, the weigh-t ratios relating -to the sum
of the materials employed, at temperatures in the range from 45
to 70C until the anthraquinone content is less than 3% by weight,
relative to the sum of the anthraquinone compounds.
The process according -to the invention can be carried
out at temperatures from 45 -to 70C, advantageously at temperatures
in the range ~rom 48 to 60C,
15Furthermore, it is advantageous to carry out the initial
I phase of the nitration at relatively low tempera-tures within the
ranges indicated and to raise the reaction temperature to rela-
tively higher temperatures within the ranges indicated with the
progressive formation of mononitroanthraquinone. It is
particularly preferable to carry out the initial phase of the
nitration at low temperatures in the range from 45 to 55C,
preferably in the range ~rom 48 to 53C, and, after over 50% of
the anthraquinone employed has been mononitrated, to raise the
temperature -to 55 to 70, preferably to about 60C. When
the anthraquinone content in the nitration mixture has reached
a value of about 3% by weight, relative to the sum of all the
anthraquinone compounds, it is advantageous to maintain a maxi-
mum reaction temperature o~ 60C for no longer than one hour,
otherwise ther0 is the possibility that the mononitroanthra-
quinones, above all l-nitroanthraquinone, react further to an
appreciable extent to give dinitroanthraquinones.
Le A 17 494 ~ 4 ~
~ 3 6~
The process according to the invention can be carried
out in various ways. For example, it is possible initially
to introduce the entire nitric acid/sulphuric acid mixture
and to introduce the anthraquinone into this. The intro~
; 5 duction o~ the anthraquinone can take place all at once or in
the course o~ up to 3 hours. The procedure can also be to
meter the nitric acid/sulphuric acid mixture and -the anthra-
quinone, separately but synchronously, into a mixture in which
the reactionhas~eto co~ple~on,~l~y or partially. Furthermore,
the procedure can be to carry out the process in a multi-stage
reaction cascade, for example a kettle cascade, and to carry
out the metering of the nitric acid/sulphuric acid mix-ture and
of the an-thraquinone into the first element of the reaction cas-
cade synchronously in a continuous process~ The process
according to the invention can also be carried out in a reac-
tion tube and the nitric acid/sulphuric acid mixture and the
anthraquinon~ ~n ~ metered into a reaction tube synchronously in
a continuous process. The procedure can also be to stir all
or part of the anthraquinone into a portion o~ the nitric acid/
sulphuric acid mixture, the water content of which is, for
example, above 22% by weight, and to meter in the remainder o~
the nitric acid/sulphuric acid mixture, with a water content of,
for example, below 5% by weight, and if appropriate the remain-
ing anthra~uinone 0.5 to 3 hours later. In the latter case,
the nitration takes place only slowly in the mixed acid con-
taining a relatively high proportion of water (water content,
for example, over 22% by weight) and starts at an appreciable
rate only when the nitric acid/sulphuric acid mixture which is
anhydrous or contains little water (water content, for example,
below 5% by weight) is added. This procedure is advantage-
; ous when9 for example ~or reasons of hea-t removal, the
Le A 17 494 _ 5 _
. . .
6~3~i8
anthraquinone must be added slowly in the initial phase, tha-t
is to say the ~03/anthraquinone ratio is ~2~ Over-
nitration is -then avoided, which would be obtained if a mixed
acid were employed, the water content of which corresponds to
that of the total mixed acid (= average value of all mixed
acid portions added).
In the process according to the invention it is essen-
-tial that a liquid phase, consisting predominantly of organic
constituents, forms during the nitration reaction. In the ~ollow-
ing text, this phase is described as a "liquid organic phase".
It forms under the weight ratios and temperatures indicated
above and leads to the formation of an emulsion of the liquid
organic phase of lower specific gravity, which is composed pre-
; dominantly of anthraquinones and mixed acids, and an inorganic; 15 phase, which is also liquid and contains the remaining portions
of nitric and sulphuric acid. In general, the liquid org-
anic phase consists to the extent of more than 50% of
anthraquinones and contains nitric acid and sulphuric acid in
a weight ratio of over 3:1, preferably of over 4:1~ The
liquid inorganic phase contains the remaining portions of nit-
ric and sulphuric acid (the proportion by weight of sulphuric
acid exceeding that of nitric acid) and small amounts of org-
anic substance in the dissolved form. The formation of a
liquid organic phase is of decisive importance for the feasi-
bility of the process according to the invention. On the
one hand, it ensures that the further nitration of the l-nitro-
anthraquinone formed and present in the liquid organic phase
is retarded, and on the other hand it is thereby possible to
carry out the nitration in very concentrated mixtures, that is
to say with relatively low amounts of acid, relative to the
anthraquinone employed. Thus 9 for example 9 the nitration
Le A 17 494 - 6 -
, . . _
3~
mixture can still be industrially handled without problems
with a content of over 50% by weight o~ an-thraquinones; that
is to say it remains stirrable and can be pumped without par-
ticular difficulties. The formation of a liquid organic
phase has not hitherto been observed during the nitration of
an-thraquinone with nitric acid o.r nitric acid/sulphuric acid
mixtures. In known processes for the nitration of anthra-
quinone in a heterogeneous phase, for example in the process
of DT-AS (German Published Specification) 2,039,822, a liquid
organic phase of this type does not occur, bu-t a solid phase
which contains virtually only anthraquinones. ~ven when
the temperature is raised during or after the addition of the
nitric acid in Example 1, no liquid organic phase forms. If
an attempt is made to carry ou-t the procedure of DT-AS (German
Published Specification) 2,039,822 in the temperature range
claimed according to the invention with similar concentrations
of anthraquinones as in the process according to the inven-
tion, the mixtures are no longer stirrable during the reaction
because no liquid organic phase appears (see Example 13).
On the other hand, with the process according to the inven-
tion it is possible to introduce a large proportion of the
anthraquinone only when a liquid organic phase has already
formed. Stirring in larger amounts of anthraquinone then
presents no difficulty ~rom the point of view of consistency
since it is taken up in the liquid organic phase, the fluidity
of the reaction mixture being maintained completely.
The nitration in accordance with the process according
to the invention is possibly an interfacial reaction. I~
the inorganic liquid phase is separated off by suitable opera-
tions, for example by centrifuging, the reaction soon stops,
although the organic phase contains relatively large amounts
Le A 1? 494 - 7 -
~ 3 ~ ~
of ni-tric acid. After adding the inorganic phase which has
been separated off or ~resh sulphuric acid, the reaction starts
again. Thus good, thorough mixing of the two phases by
vigorous stirring or other suitable measures should be pro
vided for during the reaction
The cause of the formation of the liquid organic
phase is probably the formation of an anthraquinone/nitric
acid adduct, and in particular an adduct in the molar ratio of
anthraquinone to nitric acid of 2:1 or 3:1. The composi-
tion of the phases during -the reactiongives indications of
this. In the stage of maximum de-mixing, which is the stage
at which the organic liquid phase has an optimum liquid con-
sistency, a marked concentration of nitric acid is observed in
the organic liquid phase with a corresponding dilution in the in-
organic liquid phase. The nitric acid in the inorganic
phase becomes markedly more concentrated again at the rate at
which the liquid organic phase decomposes, with the separation
of solid nitroanthraquinone (see Example 12). During the
decomposition of the liquid organic phase, the l-nitroan-thra-
quinone is obtained in a particularly compact form, so tha-t in
spite of their high an-thraquinone proportion, the reaction mix-
tures remain readily stirrable even in the final phase of the
nitration. However, the indications found for explaining
the course of the reaction according to the invention and the
formation and decomposition of the liquid organic phase do not
limit the process according to the invention to any theory of
the course of the reaction and of the formation and decomposi-
tion of the liquid organic phase. The above explanations
serve only to illustrate the process according to the inven-
tion, no claim to thecorrectness of the explanations with
regard to the course of the reaction and the formation and
Le A 17 494 - 8 -
decomposition of the liquid organic phase being made.
In order to obtain a liquid organic phase during the
nitration according to the invention it is necessary to main-
tain cer-tain nitrating conditions. Thus, the proportion of
anthraqu:inone in the ni-tra-tion mixture should initially be
at least 20% by weight, preferably at least 30% b~ weight.
The weight ratio of nitric acid to sulphuric acid in the pro-
cess according to the invention is initially about 1:1 to
about 2:1, for example 1:1 to 2:1, preferably 1.2:1 to 1.5:1.
The weight ratio of sulphuric acid to anthraquinone in the pro-
cess according to the invention is ini-tially about 0.5:1 to
l:l, for example 0.5:1 to 1:1, preferably 0.6:1 to 0.8:1.
The weight ratio of sulphuric acid to water in the process
according -to the invention is initially about 2.5:1 to about
5.5:1, for example 2.5:1 to 5.5:1, preferably 3. 5:1 to 5.3:1.
The weight ratios indicated relate to the sum of all the mat-
erials employed. The process according to the invention is
carried out at temperatures in the range from 45 to 70C, pre-
ferably at temperatures in the range from 48 to 60C. In
general, the sulphuric acid employed in the process according
to the invention has a concentration in the range from 70 to
85% by weight, preferably in the range ~rom 74 to 84% by weight,
the total amount of water in the mixed acid being attributed
to the sulphuric acid, and the nitric acid is employed in a
concentration of 90 to 100% by weight, pre~erably 97 to 99% by
weight. These data, above all for the concentrations and
weight ratios, relate to the total amount of material employed;
partial amounts employed can certainly be outside these ranges
indicated, for example when mixed acid, which contains little
water or is anhydrous, is subsequently metered into a nit-
ration mixture which initially contains a high proportion o~
Le A 17 494 ~ 9 -
~ 8
water, as described in Example 10 and ll, or when anthra-
quinone is slowly introduced into large amounts of H2S04
and/or nitric acid at the start of the reaction, as described,
for example, in Example 5.
In order to obtain high yields of l-nitroanthra-
quinone in accordance with the process according to the
invention, it is advantageous to match the measures to be
taken with one another so that a further nitration of the
l-nitroanthraquinone is largely avoided. Although
the appearance of the liquid organic phase makes the reac-
tion more insensitive towards further nitra-tion, in principle
it does not prevent a further nitration of mononitroanthra-
quinonesto dinitroanthraquinones. Thus, for example, the
higher the water content of the sulphuric acid and the
higher the anthraquinone proportion in the nitration mixture,
the more the weight ratio of nitric acid to sulphuric acid
can be shifted in favour of the nitric acid. Furthermore,
it is advantageous, for example, to carry out the reaction
a) with a particular weight ratio of sulphuric acid to water
and with a high weight ratio of sulphuric acid to anthra-
quinone at a high weight ratio of nitric acid to sulphuric
acid,
b) with a particular weight ratio of sulphuric acid to
anthraquinone and with a high weight ratio of nitric acid to
sulphuric acid at a low weight ratio of sulphuric acid to
water and
c) with a high weight ratio of nitric acid to sulphuric acid
and with a high weight ratio of sulphuric acid to anthraquin-
one at a low weight ratio of sulphuric acid to water, and
3 vice versa.
The terms "high weight ratio" and "low weight ratio"
Le A 17 494 - lO -
.
6~68
denote, in each case, high ox~ respecti~ely, low weight
ratios within the limits indicated.
The -temperature should not fall below 45C in the
process according to the invention, since otherwise the
liquid organic phase begins to solidify and as the reaction
progresses there is the danger that the mixture no longer
remains stirrable. (Compare Example lb), On the
other hand, temperatures of 70C, preferably of 60C, should
not be exceeded, since a-t higher temperatures dinitroanthra-
quinone forms to an increasing extent and/or anthraquinone
and nitroanthraquinones are degraded by oxidation. Since
considerable amounts of heat are released during the nitra-
tion reaction according to the invention it is necessary, in
general, to remove some or all of the heat of thereaction
and thus to avoid toohigh an increase in the temperature in
the reaction mixture. The heat can be removed in any
desired manner, for example by cooling the walls with water,
brine or vaporising ammonia, by evaporative cooling by
allowing excess nitric acid to distil under reflux, prefer-
20 ~ ably under reduced pressure, or by external cooling surfaces
outside the reactor, for example using a loop reactor.
The reaction time should be chosen so that after an
anthraquinone content in the nitration mixture of less than
3% by weight, preferably of about 2 to 3% by weight ~in each
case relative to the sum of the anthraquinone compounds) is
reached, the reaction mixture is after-treated for no longer
than 2 hours, preferably no longer than l hour, at maximum
temperatures o:E 60C. Dinitroanthraquinones can otherwise
form to an appreciable extent~ so that in spite of a decrease
in the anthraquinone content, no further increase in the
yield of l-nitroanthraquinone takes place. In general,
Le A 17 494 - 11 -
3~a3
the reac-tion time is between 2 and 7 hours, pre~erably
between ~ and 5 hours, in general the time required being a
little greater for -the continuous procedure than ~or the dis-
continuous procedure.
At least 2 mols of nitric acid per mol o~ anthra-
quinone employed are required for the process according to
the invention. However, it is advantageous when 2.5 to 4
mols, preferably 2.7 to 3.5 mols, of nitric acid are used
per mol of anthraquinone employed.
The particle size of the anthraquinone to be
employed in the process according to the invention is no-t
critical, since on the one hand relatively large anthraquin-
one particles are thoroughly nitrated in the liquid organic
phase and on the other hand very fine anthraquinone particles
lead to no particular thickening of the reaction mixtures.
The process according to the invention is not as sen-
sitive towards variations in the sulphuric acid concentration
as other processes, for example the process according to DT-
AS (German Published Specification) 2,039,822. As a result
of running the process according to the invention at very
high concentrations, a lowering of the sulphuric acid
concentration of up to 10% by weight is achieved during the
reaction by the water of reaction liberated. Towards the
end of the reaction9acid concentration ranges are thereby
automatically obtained in which nitric acid possesses no more than
sligh-t nitrating action. For this reason, variations in
the amount of nitric acid are also not as critical as in
other processes.
The process according to the inven-tion can be carried
out in various advantageous varian-ts. The following vari-
ants may be mentioned as examples:
Le A 17 494 - 12 -
~ 6
Variant 1:
100 par-ts by weight o~ anthraquinone are introduced
into a mixed acid, which contains 60 to 80 par-ts by weigh-t o~
sulphuric acid (100% strength by weight), 100 to 85 parts by
weight of nitric acid (100% strength by weight) ~nd 15 to 18
parts by weigh-t of water, at 48 to 52C. The nitration is
carried out at temperatures ~rom 50 to 60C un-til less than
3% by weight of anthraquinone (relative to the sum of -the
anthraquinone compounds) can be detected in the nitration mix-
ture, which in general takes about 2 to 5 hours. In this
procedure, numeri~llyrelatively small amoun-ts of H2S04 and
water are preferably combined with numerically higher values of
HN03, within the ranges indicated, and vice versa.
Variant 2:
80 to 100 parts by weight of an-thraquinone are intro-
duced into 100 to 150 parts by weight o~ a 72 to 78% strength
by weight sulphuric acid at 20 to 50C, 80 to 110 parts by
weight of nitric acid (98% strength by weight) are added, and
then a further 100 to 120 parts by weight of anthraquinone and
120 to 150 parts by weight of a mi~ed acid consisting of 35 to
45% by weight o~ sulphuric acid (100% strength by weight), 63
; to 52% by weight of nitric acid (100% strength by weight) and
2 to 3% by weight of water are added simultaneously. The
nitration is carried out at temperatures from 50 to 60C until
less than 3% by weight o~ anthraquinone (relative to the sum
of the an-thraquinone compounds) can be detected in the nitra-
tion mixture, which in general takes 2 to 5 hours. In this
procedure, in each case numerical values close to the
numbers first mentioned or numerical values close to the
numbers last mentioned are preferably combined with one
another, withi:n th0 ranges indicated.
Le A 17 494 - 13 -
3~ 51
Variant 3:
10 to 20% of a preceding mixture, in which the reac~
tion has ended, having the composi-tion of 42 to 46% of crude
l-nitroanthraquinone (l-nitroanthraquinone content about 75%)
and 54 to 58~o Of a mixed acid consisting of 38 to 40% of
nitric acid (100% strength), 46 to 44% of sulphuric acid (100%
strength) and lL~ to 16% of water are retained. The 9-fold
to 4-fold amount of anthra~uinone and mixed acid are intro-
duced simultaneously into this retained portion of a preceding
mixture in the course of 1 to 5 hours, 160 to 210 parts by
weight of mixed acid being introduced per 100 parts by weight
of anthraquinone, the mixed acid containing 40 to 35% by
weight of sulphuric acid (100% strength), 52 to 5~% by weight
of nitric acid (100% ~trength) and 8 to 11% of water. The
nitration is carried out at temperatures in the range from 48
to 60C until only less than 3% by weight of anthraquinone
(relative to the sum of the anthraquinone compounds) can be
; detected in the nitration mixture, which in general takes about2 to 5 hours. In this procedure, in each case numerical
values close to the numbers first mentioned or numerical values
close to the numbers last mentioned are preferably combined
with one another, within the ranges indicated.
The process according to the invention can be carried
out both discontinuously and continuously; a continuous
procedure in which, for ex~mple, the process is carried out in
a reaction tube or a kettle cascade, is particularly advan-
tageous. In order to obtain a high a-nitration rate, it is
advisable to begin the nitration close to the lower tempera-
ture limit, for example at 45 to 50C, and only to proceed to
higher temperatures, for example to 55 to 65C 9 when at least
75% of the anthraquinone are nitrated.
Le A 17 494 - 14 -
~ ~ 6 ~ ~
The reaction mixture can be worked up in a manner which
is in itself known, for example by metering the nitration mix-
ture into water or metering water into the nitration mixture,
whereupon a product mixture precipi-tates. This is approp-
riately filtered off or centrifuged~ washed with water untilneutral and then dried. If the nitration mixture is
diluted with an amount of water such that the acid content of
the mixture is below 50/0, the nitroanthraquinones present and
unreacted anthraquinone precipitate almost completely.
After these compounds have been separated off, a mixture of
sulphuric acid and nitric acid containing a high proportion of
water remains, which is virtually free from organic constitu-
ents and salts.
This mixture is advantageously separated into its con-
stituents by distillation and used again for further nitra-
tions. In this procedure, it is possible either to
initially distil off nitric acid and water until an abou-t 70%
strength sulphuric acid which is virtually free from nitric
acid remains, in the sump 9 which is then processed to concen-
trated sulphuric acid, water being distilled off, for examplein a Plinke ins-tallation. It is also possible initially to
add an amount of concentrated sulphuric acid such thatat
least 70% strength acid is present, relative to sulphuric acid
and water, from which nitric acid is then distilled off as
highly concentrated nitric acid, whilst the sump which remains,
containing sulphuric a¢id, is concentrated, for example in a
Plinke installation. Organic substances, which may be
contained in the filtrate or centri~ugate obtained b~
separating off the reaction products, are broken down by
oxidation during an ~cid regeneration of this type. I~ a
working-up of the acid is carried out in accordance with the
Le A 17 494 - 15 -
?~3~B
above procedure an~ the nitric acid and sulphuric acid -thus
obtained are re-used and the wash water is used for diluting
the nitration melts, as described in Example 3~ no effluent at
all is obtained in the process according to the invention.
As already indicated above, the nitration according to
the invention is carried out until the anthraquinone content
in the nitration mix-ture (relative to the sum of the anthra-
quinone compounds) has fallen to less than 3% by weight, pre-
ferably to - 2, The determination of the anthraquinone
conten-t in the nitration mixture required ~or thi~ can be
carried out in a manner which is in itself known. For
example, an analysis by means of quantita-tive thin layer
chromatography or high pressure liquid chromatography gives
results which can be easily~ro~uced, so that the reaction
time established once for given apparatus conditions and other
condi-tions nolonger have to be checked continuously.
After the nitration mixture has been worked up, in
particular the nitration mixtures obtained in accordance with
Variants 1 to 3, a product mixture is obtained which contains
over 73% of l-nitroanthraquinone, less than 3 - 4% of anthra-
quinone and, in total, less than 10%, preferably less than 7%,
of 1,5- and 1,8-dinitroanthraquinone. In general, the yield
: : of l-nitroanthraquinone is 74 to 80%, relative to anthraquinone
employed, of the theoretical yield calculated ~rom the reaction
equation.
The process.accQrding to the invention has a.number of
advantages. Thus, in comparison with known processes 9 the
nitration can be carried.out.with only small amounts of
mineral acid, it being.possible for the anthraquinone propor-
tions in the nitration mixture to be over 50%. . Therefore,
the space/time yields can be several times greater, for example
Le A 17 494 - 16 -
i3~E~
in comparison with -the process according to DT-AS (German
Published Specifica- tion) 2,039,822, which also additionally
requires a considerably longer reaction time, The process
according to the invention is no-t particularly sensitive
towards variations in -the nitric acid and/or sulphuric acid
concentration. As a result ofnux~ngthe p~cessetvery h~h concen-
tratiors,a reduction in the sulphuric acid concentration of up
to 10% is achieved during the process by the liberation of the
water of reac~tion, so that towards the end of the reaction
acid concentration ranges in which the nitric acid has no rnore
~n a sli~ht nitrating action are automatically obtained. In
contrast with this, for example, the sulphuric acid concen-
tration in the process according to DT-AS (German Published
Specification) 2,039,822 must be kept to exactly, since the
water of reac-tion liberated does not have such a marked effect
on the concen-tration of -the acids there because of the large
excesses of acids to be used. From Example l in DT-AS
(German Published Specification) 2,039,822, for example, a
sulphuric acid concentration of 77.6% is calculated in the
initial state, and one of 76.9% in the final state. From
this it is evident that in the process in DT-AS (German Pub-
; lished Specification) 2,039,822, variations in the concen-
tration of the sulphuric acid employed have a much greater
effect on the course of the reaction than in the process
according to the invention. The amount and concentration
of HN03 are also to be rated more critical. A further
advantage of the process according to the invention is that
the individual parameters can be matched with one another so
that the nitration rate over long stretches o~ the nitration
can be kept constant, so that the heat of reaction liberated
per unit of time remains almost constant and can be removed in
Le A 17 494 - 17 -
' ' ' ' ~ '
.
6~
a relatively simple manner Finally, i-t is -to be pointed
out that in -the process according to the invention it is no-t
necessary to employ anthraquinone in a particular form, ~or
example finely sieved, The yields and purities o~ the 1-
nitroanthraquinone which is accessible according to the inven-
tion are -the same or better than in o-ther processes. In
general, no more than 20 to 23% of by-products arise, in
particular no more than a total of 10% of 1,5- and 1,8-
dinitroanthraquinone, in general even less than 8%,
As is known, l-ni-troanthraquinone is an importan-t
industrial intermediate product, which can be used, for
example, for the preparation of l-aminoanthraquinone, from
which many anthraquinone dyestuffs can be prepared. The 1-
nitroanthraquinone prepared according to the invention can be
reduced directly to l-aminoanthraquinone in a known manner,
for example by treatment with an aqueous solution of sodium
sulphide. However, if a still purer product is desired, it
can also be further purified by known processes, for example
by treatment with aqueous solutions of sodium sulphite (see
U.S. Patent Specification 2,302,729) or by treatment with acid
amides (see DT-AS (German Published Specification) 2,039,822~.
The percentage data in the examples which follow
relate to the weight, unless otherwise indicated. I~ the
content data for mineral acids or mineral acid mixtures are
~ 25 given in per cent, the deficit to make up -to 100% is water.
; Examples:
Example 1
a) 150 g of a nitration mixture, in which the reaction has
ended, which contains 68 g of crude l-nitroanthraquinone
(composition, see table on page 21) are initially
introduced into a cylindrical reaction vessel (1.5 1 capacity,
Le A 17 494 - 18 -
.
diameter 10 cm, height 20 cm) which has a lid fitted with 4
-tubes and is provided with an anchor stirrer (diameter 9 crn,
height 12 cm), thermometer, cooler and dropping funnel.
500 g of technical an-thraquinone (99% pure) and ~90 g of m:Lxed
acid of the following composition: 351 g of H2S04 (100%
streng-th), 464 g of HN03 (100% strength) and 76.5 g of H20 are
introduced into this mix-ture uniformly and separately, but
with synchronous metering, at 48 to 50C in the course of 3
hours at a stirring speed of 200 revolutions/minute.
During this procedure, the -temperature is adjusted to 49 to
51C After 10 to 20% of the materials employed have been
introduced, a two phase system forms which exhibits a great
de-mixing tendency. It consists of a liquid, clear,
inorganic phase of higher specific gravity which consists of
mixed acid, in which small portions of anthraquinone or
nitrated anthraquinone are dissolved, and an organic phase 3
which is also completely or predominantly liquid, of lower
specific gravity consisting of anthraquinone, nitroanthraquin-
one, nitric acid and small proportions of sulphuric acid.
This two-phase system remains during the entire metering-in
time.
After the metering-in has ended, the mixture is
stirred for a further one hour at 50C and finally for a
further 3 hours at 60C. During this procedure, the liquid
organic phase gradually passes into a solid phase with an
; increasing degree of nitration of the anthraquinone, whereupon
a continuous thickening of the mixture can be observed, but it
remains easily stirrable until the end of the reaction.
During the reaction, representative average samples (about 5 g)
are removed9 whilst stirring, and stirred into water and the
precipitate is ~iltered off, washed with hot water until
Le A 17 494 - 19 -
neu-tral and dried. The dried sample,s are analysed by the
method of high pressure liquid chroma-tography, The reslllts
in the table on page 21 are obtained:
b) The procedure followed is as described in a), but the
process is carried out a-t ~8-40. No liquid organic phase
forms and the reaction mixture becomes very thick; after about
half has been metered in, the mixture is no longer stirrable
and a regulated temperature control is no longer possible.
If the temperature is now increased to 45, the mass
can be set in motion with some difficulty; -the mixture becomes
stirrable again only when the temperature is further raised to
48-50, and when the metering-in is continued a liquid organic
phase forms.
Le A 17 494 - 20 -
.
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Le A 17 494 - 21 -
~ -
.
3 6
Exam~ 2
The procedure ~ollowed :Ls as in Example 1, but the
taking of samples is dispensed with and the entire mixture is
wor~ed up as follows: the mixture is stirred into 5 1 o~ cold
water, stirred for a ~urther ~ hour at 60C and the precipitate
is filtered o~f, washed with hot water until neutral and dried
in vacuo at 120C. The yield of product thus obtained is
685 g. Composition: 1.9% of anthraquinone, 73.9% o~ 1-
nitroanthraquinone, 8,0% of 2-ni-troanthraquinone, 3.2% of' 1,6-
dinitroanthraquinone, 3.4% o~ 1,7-dinitroanthraquinone, 3.6%
of 1,5-dinitroan-thraquinone, 3.4~ of 1,8-dinitroanthraquinone
and 0.2% of 2,6- + 2,7-dinitroanthraquinoneO
The yield o~ l-nitroanthraquinone is 75% o~ theory.
Example 3
10,000 g of anthraquinone (99% pure) and 16,100 g of
mixed acid (composition: 52,1% of HN03 (100% strength), 39.3%
o~ H2S04 (100% strength) and 8.6% of H20) per hour are metered
synchronously at 48 to 50C into the first element of a four-
stage cascade (three-stage reaction cascade + dilution cascade)
with a capacity of 35 1 in each element and is provided with a
charging screw and mixed acid metering pump on cascade 1, a
water metering pump on cascade 4 and water jackets, which can
be heated and cooled, on cascades 1 to 4, whilst stirring
vigorously. The washing 1 from the filtration of the 1-
nitroanthraquinone obtained (about 18,900 g/hour) is metered
; synchronously into cascade 4 at the same time.
The temperatures in the individual elements of the
cascade are adjusted as ~ollows: cascade 1 48-50C, cascade 2
54-56C, cascacLe 3 59-61C and cascade 4 58-62C 7
The working-up is carried out by filtering continuously
the overflow from cascade 4 on a rotary filter and washing the
Le A 17 494 - 22 -
.
,, . . -. . .
material on the filter with wa-ter at 60~ in two di~ferent
zones. In the ~irst zone, 17,900 g of water per hour are
added and the ~iltrate obtainable in this procedure (washing 13 9
which is obtained in an amount o~ about 18,900 g/hour, is used
for the dilution in cascade 4 12,400 g of water per hour
are fed into the second zone. The filtrate obtainable in
this procedure (washing 2) can be fed to the biological
processing of the effluent.
The material on the filter, washed until neutral, is
thoroughly dried in vacuo. 12,550 g o~ product of the
following composition are obtained per hour: 3~0% of anthra-
quinone, 6.7% of 2-nitroan-thraquinone, 73.6% o~ l-nitroanthra-
quinone, 4.0% of 1,6-dinitroanthraquinone, 3.8% o~ 1,7 di-
nitroanthraquinone, 3.8% of 1,5-dinitroanthraquinone, 3.4% o~
1,8-dinitroanthraquinone, 0.6% of 2,7- + 2,6-dinitroanthraquin-
one and 1.1% of other substances.
The yield of l-nitroanthraquinone is 75.9% of theory.
The working-up o~ the mother liquor from the filtration
on the rotary pressure filter was carried out in 2 variants.
a) By the methodwhich is in itself known and which is
named "Schott variant", the nitric acid was distilled off as
water-containing nitric acid.
b) By the method which is in itself known and which is
named "extractive distillation", an amount o~ anhydrous or 96%
strength sulphuric acidwas added initially such that, relating
the water content to sulphuric acid, a 70% strength acid was
present9 and the nitric acid was distilled o~f as highly con-
centrated nitric acid.
The approximately 70% strength sulphuric acid remaining
as the distillation residue after a) or b) was concentrated to
96% strength sulphuric acid in a manner ~hich is in itsel~
Le A 17 494 - 23 -
~ ~ . ~;
361~
known in a so-called Plinke installa-tion, with water being
distilled of~, The acids -thus obtained were ~ed again -to
the ni-tration process.
Example 4
650 g of a mixed acid consisting of 320 g of ~03
(98% strength) and 250 g of H2S04 (78% strength) are initially
introduced into a reaction vessel as described in Example 1 an~
500 g of anthraquinone are introduced in the course of 5
minutes, starting at 25C and stopping the rise in temperature
at 52 to 54C, whilst stirring vigorously. The mix-ture is
stirred for a further hour at 50C and for a further 30 minutes
at 60C. 270 g of a mixed acid which consists of 150 g of
HN03 (98% strength) and 120 g of H2S04 (96% strength) are
metered in at this temperature in -the course of 30 minutes and
the mixture is again stirred for a further 2 to 3 hours at 60C.
About 10 to 15 minutes after the anthraquinone has been
introduced, a two-phase system forms consisting of mixed acid
and a completely or partially liquid organic phase, which
gradually decomposes after -the mixed acid has been added at
60C, solid nitrated anthraquinone separating out,
The reaction mixture is worked up by stirring into
4,000 ml of water, stirring for ~ hour at 80C, filtering the
precipitate, washing the precipitate wi-th water at 70C until
neutral and drying the precipitate. 625 g of dry product
are obtained which has the following composition: 2.4% of
anthraquinone, 9.5% of 2-nitroanthraquinone, 74.9% of l-nitro-
anthraquinone, 2.4% of 19 6-dinitroanthraquinone, 1.8% of 1 J 7-
dinitroanthraquinone, 3.1% of 1,5-dinitroanthraquinone, 2.9% of
1,8-dinitroanthraquinone, 0.4% of 2,6- ~ 2,7-dinitroanthraquin-
one and 2.6% of other substancesO
The yield of l-nitroanthraquinone is 77% of theor~.
Le A 17 494 - 24 -
- '
368
The procedure followed is as in Example 4, but the
an-thraquinone is introduced at a uniform rate in the course of
1 to 2 hours The metering-in of the mixed acid, the
after-treatment and the working-up are carried out as described
in E~ample 4O 622 g of dry product are obtained wi-th a 1-
nitroanthraquinone content of 73,5%. The yield of l-nitro-
anthraquinone is 74,9% of theory.
Example 6
The procedure ~ollowed is as described in Example 1,
but 500 g of anthraquinone are metered into a mixed acid which
consists of 315 g of H2S04 (100% strength), 400 g of HN03 (100%
strength) and 65,5 g of H20. The mix-ture is stirred for a
further 1 hour at 50C and for a further 5 hours at 60C.
After working up analogously to Example 2, 621 g of a 1-nitro-
anthraquinone mixture of the following composition are obtained:
2,0% of anthraquinone, 8.7~o of 2-nitroanthraquinone, 73,5% of
1-nitroanthraquinone, 3.4% of 1,6-dinitroanthraquinone~ 3.3% of
1,7-dinitroanthraquinone, 3.4% of 1,5-dinitroanthraquinone, 3.0%
of 1,8-dinitroanthraquinone, 0.6% of 2,6- ~ 2,7-dinitroanthra-
quinone and 2,1% of other substances.
The yield of l-nitroanthraquinone is 74.9% of theory.
Example 7
300 g of anthraquinone are stirred into 375 g o~
H2S04 (82% strength) and 420 g of HN03 (98% strength) are added
dropwise at 50 to 55C in the course of 2 hours. During
this procedure, the initially thick mixture becomes more fluid
after about 3/4 to 1 hour, and after 1 1/4 hours a liquid
organic phase :~orms which, however, still contains solid con-
stituents. At this point in time, a further 200 g of
anthraquinone are added. After the dropwise addition of the
! Le A 17 494 - 25 -
.
;36iE3
nitric acid has ended, the mixture is stirred ~or a further 1
hour at 50C, warmed -to 60C and a mixture of 43 g of mono--
hydrate (= 100% strength sulphuric acid) and 53 g of HN03
(98% strength) is added at this temperature in the course of
15 minutes. The mixture is finally stirred for a further
2 hours at 60C
After stirring the reaction mixture into 3,000 ml of
water, filtering off the precipitate, washing until neutral
and drying,627 gof a l-nitroanthraquinone mixture of the
following composition are obtained: 1.2% of anthraquinone 9
7,5% of 2-nitroanthraquinone, 75.4% of l-nitroan-thraquinone,
3.4% of 1,6-dinitroanthraquinone, 3.2% of 1,7-dinitroanthra-
quinone, 3.2% of 1,5-dinitroanthraquinone, 3 2% of 1,8-di-
nitroanthraquinone and 0.5% of 2,6- + 2,7-dinitroanthraquinone.
The yield of l-nitroanthraquinone is 77.5% of theory.
Example 8
a) The procedure followed is as described in Example 4,
but after the anthraquinone has been introduced the process is
carried out in vacuo (about 70 to 100 mm Hg), so that the e~cess
HN03 distils and condenses in an intensive condenser, mounted
on the reaction vessel and fed with brine at -20C as the
cooling liquid, and runs back into the reaction mixture.
A constant nitric acid distillation is ensured during the entire
reaction. The heat of the nitration reaction i~ initially
sufficient for this; towards the end of the reaction it is
necessary -to hea-t the reaction vessel.
After working up, 620 g of a l-nitroanthraquinone
mixture are obtained. The l-nitroanthraquinone content is
; 73.8% and the an-thraquinone content is 3.0%. The yield of
l-nitroanthraquinone is 75.2% of theory.
b) The procedure followed is as described in a)~ but the
Le A 17 494 - 26 -
'6 ~ 6~
hea-ting of -the reaction vessel is dispensed with. As soon
as the temperature in the reaction mixture falls below the
desired temperature, the vacuum is removed and the reaction is
comple-ted as described in Example 4.
Exam~le 9
a) The procedure followed is as described in Example 4,
but during the reaction the nitration mixture is circulated
via a water-cooled Liebig condenser installed outside the
reaction vessel. In this case also, the reaction vessel
must be hea-ted towards -the end o~ the reaction so that the
reaction tempera-ture can be maintained, Af-ter working up,
620 g of a l-nitroan-thraquinone mixture are obtained, The
l-nitroan-thraquinone content is 73. 8% and the anthraquinone
content is 2.9%. The yield of l-nitroanthraquinone is 75.2%
of theory.
b) When the desired temperature in the reaction vessel
can no longer be maintained by the heat of reaction alone, it
is also possible to dispense with the circulation and tocomplete
the reaction as described in Example L~.
Example 10
230 g of H2S04 (74% strength) are initially introduced
into a cylindrical reaction vessel, 150 g of anthraquinone are
stirred into this and 235 g o~ HN03 (98% strength) are added
dropwise in the course of 1 hour. During this procedure,
the temperature rises to about 40C, 430 g of a mixed acid
consisting of 235 g of HN03 (9~% strength) and 195 g of H2S04
(96% strength) are now added at a uni~orm rate in the course of
2 hours. During this procedure the temperature rises to 50
to 52C. This temperature is maintained during the further
30 course of the reac-tion. When about 25% of the mi~ed acid
have been added, an emulsion is obtained, into which a further
Le A 17 49~ - 27 -
$~3~
350 g of anthraquinone are stirred in the course of 10 minutes.
After the addition o~ the mixed acid has ended, the mi~-ture is
stirred for a further half hour at 50C and then for a further
3 hours at 60C. The r~action mixture is then stirred into
4 1 of water, the precipitate is ~iltered off and -the material
on the filter is washed with hot water until neutral and dried,
618 g of a l-nitroanthraquinone mixture of the following com-
position are thus obtained: 2.5% of anthraquinone~ 6.8% of 2-
nitroanthraquinone, 75,9% of l-nitroanthraquinone, 3.0% of 1,6-
dinitroanthraquinonel 3,3% of 1,7-dinitroanthraquinone, 3.7% of
1,5-dinitroanthraquinone and 3.2% of 1,8-dinitroanthraquinone.
The yield of l-nitroanthraquinone is 77.2% of theory,
Example 11
280 g of H2S04 (78% strength) are initially introduced
into a cylindrical reaction vessel, 200 g of anthraquinone are
stirred into this and 235 g of HN03 (98% strength) are added
dropwise in the course of 30 minutes, whilst stirring.
During this procedure the temperature rises to 47C. A
mixture of 137 g of H2S04 (96% strength) and 235 g o~ HN03
(98% strength) is then added at a uniform rate in the course o~
~e ~ur, and during the addition of the last 75% o~ the mixed
acid, 300 g of anthraquinone are added at a uniform rate.
During this procedure a temperature of 50 to 52C is maintained.
The mixture is stirred for a further hour at 50C and for a
further 2 hours at 60C. After working up analogously to
Example 10, 619 g of a l-nitroanthraquinone mixture of the
following composition are obtained: 1.5% of anthraquinone,
8.2% of 2-nitroanthraquinone, 75.1% of l-nitroanthraquinone,
3.0% of 1,6-dinitroanthraquinone, 2.9% o~ 1,7-dinitroanthra-
quinone, 3.7% of 1,5-dinitroanthraquinone and 2~9% of 1,8-di-
nitroanthraquinone.
Le A 17 494 - 28 -
~ 636~3
The yield of l-nitroanthraquinone is 76.6% of theor~,
Example_12
A) 305 g f a mixture, in which the reaction has ended,
are initially in-troduced into a cylindrical reaction ~essel of
2 1 capacity, which is provided with a bottom ou-tlet.
600 g of anthraquinone and a mixed acid consisting of 501 g of
sulphuric acid (84% strength) ancl 595 g of HN03 (98% strength)
are introduced synchronously in the course o~ 2 hours at 50 to
52C, whilst stirring vigorously~, The mixture is stirred
for a further 20 minutes and stirring is then interrupted,
Two layers form. The lower inorganic layer (894 g), which
is as clear as water, is separated ~`rom the upper organic
yellow liquid layer through the bottom outlet. After remov-
ing an intermediate phase, in order to eliminate false values
due to interfacial effects, 1007 gof organicphase remain. About
1/10 of eachofthetwophasesisdilutedwith anamountofwatersuch
thatall theanthraquinone compoundsprecipitate. Themixture isthen
filtered, the residue is washed until neutral and dried and the
filtrate is analysed. The following compositions o~ the
said phases can be calculated from the dry weights of the
residues and the analytical data:
inorganic phase: 455 g of H2S04, 232 g of HN03, 31 g of
anthraquinones and 176 g of water; and
organic phase: 61.3 g of H2S04, 224 g of HN03, 681 g of
anthraquinonesand 41 g of water.
The weight ratio of sulphuric acid to nitric acid is
1.98:1 in the inorganic phase and 0.27:1 in the organic phase.
B) The procedure followed is as described under A), but
after the introduction has ended, the mixture is stirred for a
~urther hour at 50C and for a further 3 hours at 60C.
The melt is diluted with an amount o~ water such that all the
Le A 17 494 - 29 -
~L~q~;3~
anthraquinone compounds precipitate~ the mixture is filtered
and the weight ratio o~ sulphuric acid to nitric acid is deter-
mined analytically in the filtrate. It is 1.33:1, and has
thus shifted significantly in favour of the nitric acid, com-
pared with the inorganic phase from A). 1,990 g of reactionmixture contain 419 g of HN03, 558 g of H2S04 and 751 g of
anthraquinones,
Example 13
a) 500 g of anthraquinone are stirred into 420 g of H2S04
(84~ strength) in the course o~ 5 minutes and 120 g of HN03
(98% strength) are added at 25C in the course of 10 minutes.
During this procedure, the temperature rises to 55C and the
mixture becomes so viscous that it is scarcely still stirrable;
on attempting to add a further 120 g of HN03 at 50-55C, the
melt thickens so severely that it is no longer stirrable.
In spite of intensive cooling, the internal temperature of the
melt rises to values above 55. The reaction can no longer
be controlled.
b) The procedure followed is as described in a), but an
81.5% strength H2S04 is employed. In this case also, such a
severe thickening begins by addlng the nitric acid that the
reaction mixture does not remain stirrable.
c) The procedure followed is as in a), but the amount of
H2S04 employed is increased by 25%; in this case also, the
melt can no longer be stirred after adding about 160 g of HN03,
In all the experiments a) to c), no liquid organic
phase appears during the reaction,
Le A 17 494 - 30 -
