Process for preparing 1,5-dinitroanthraquinone

A mixture of various dinitroanthraquinone isomers prepared from anthraquinone by mixed acid nitration is subjected to a suspension treatment at a temperature above 50.degree. C. with a mixed acid of a content satisfying the following three equations and then the crystals of 1,5-dinitroanthraquinone are separated: EQU y.ltoreq.-2x+230, EQU 50.ltoreq.y.ltoreq.75 and EQU y.ltoreq.-2x+110, wherein ##EQU1## 1,5-DINITROANTHRAQUINONE OF A HIGH PURITY CAN BE OBTAINED WITH EASE.

BACKGROUND OF THE INVENTION 
This invention relates to a process for producing 1,5-dinitroanthraquinone 
and, in particular, to a process for separating 1,5-dinitroanthraquinone 
of a high purity from a mixture containing various dinitroanthraquinone 
isomers prepared from anthraqinone by nitrating the same with a mixed acid 
(a mixture of nitric acid and sulfuric acid). 
Dinitroanthraquinones have been used widely, in general, as an 
intermediates for the production of dyes or the like and, among all, 
1,5-dinitroanthraquinone is important as an intermediate for blue color 
dyes of a high fastness to sublimation. 1,5-dinitroanthraquinone is 
generally produced by nitrating anthraquinone with a mixed acid but the 
1,5-dinitroanthraquinone thus prepared contains, in most cases, 
1,8-dinitroanthraquinone, 1,6-dinitroanthraquinone, 
2,6-dinitroanthraquinone and the like, that is, it is obtained as a 
mixture of various isomers. 
Isolation of pure 1,5-dinitroanthraquinone from the above isomer mixture 
has heretofore required a complicated process, for example, heating the 
mixture together with 100% by weight sulfuric acid to isolate less soluble 
1,5-dinitroanthraquinone from other isomers and then further 
recrystallizing the same from an appropriate solvent. 
SUMMARY OF THE INVENTION 
In view of the foregoing, we have made a study on a process for separating 
1,5-dinitroanthraquinone from a mixture of various dinitroanthraquinone 
isomers and, as a result, accomplished this invention based on the finding 
that 1,5-dinitroanthraquinone can be prepared with ease by subjecting the 
above isomer mixture to a suspension treatment in a specified suspending 
medium at a specified temperature. Accordingly, the object of this 
invention is to provide an industrially advantageous process for preparing 
1,5-dinitroanthraquinone of a high purity by separating it from a mixture 
of various dinitroanthraquinone isomers prepared through nitration of 
anthraquinone with a mixed acid, and the object can be attained with ease 
by subjecting a mixture of various dinitroanthraquinone isomers obtained 
from anthraquinone by the nitration reaction with nitric acid in the 
presence of a mixed acid consisting sulfuric acid and nitric acid to a 
suspension treatment at a temperature from 50.degree. to 90.degree. C. in 
a mixed acid consisting of sulfuric acid and nitric acid in a proportion 
satisfying the following three equations (1) to (3): 
EQU y.ltoreq.-2x+230 (1), 
EQU 50.ltoreq.y.ltoreq.75 (2) and 
EQU y.gtoreq.-2x+110 (3), 
wherein 
##EQU2## 
and then isolating the crystals of 1,5-dinitroanthraquinone therefrom.

This invention will now be described more specifically by way of examples 
thereof but it should be understood that this invention is no way limited 
to such examples. In the examples, all "%" means % by weight. 
EXAMPLES 1-7 
These examples were conducted for demonstrating the production of 
1,5-dinitroanthraquinone of a high purity by the suspension treatment with 
heating using, in each run, a specified amount of mixed acid in a 
once-through manner. The conditions and the results thereof are shown in 
Table 1. 
Anthraquinone was added at a specified temperature and over a specified 
period of time to a mixed acid consisting of specified amounts of 98% 
nitric acid and 98% sulfuric acid with stirring, and stirring is further 
continued for a specified period of time. The resultant slurry was heated 
to a specified temperature and suspended over a specified period of time 
while stirring. The slurry was then cooled to a specified temperature to 
crystallize 1,5-dinitro isomer, which was thereafter filtered out and 
washed with 70% nitric acid to remove the mixed acid mother liquor. Then, 
1,5-dinitro isomer cake was obtained after water washing and drying. 
Analysis of the cake composition was performed by means of high speed 
liquid chromatography. 
EXAMPLE 8 
In this example, an additional amount of the mixed acid was supplemented to 
the slurry resulting from the nitration of anthraquinone to prepare a 
slurry containing a specified amount of mixed acid, which was subjected to 
the suspension treatment with heating. 
208 g of anthraquinone was added to a mixed acid consisting of 984 g of 98% 
nitric acid and 1400 g of 98% sulfuric acid at 20.degree. C. over one hour 
and then further stirred for an additional two hours. 3090 g of 98% nitric 
acid and 660 g of 98% sulfuric acid were further added to the resultant 
slurry to adjust the slurry composition to x=64.3 and y=60 in the 
foregoing equations. Then, the adjusted slurry was suspended with heating 
at 90.degree. C. for five hours and filtered at 40.degree. C. to obtain a 
cake weighing 93.0 g (31.2% yield). The cake composition was as follows: 
1,5-dinitroanthraquinone: 95.2% 
1,8-dinitroanthraquinone: 4.3% 
others: 0.5% 
COMISON EXAMPLE 1 
The same procedures as in Example 1 were repeated except that the slurry 
resulting from the anthraquinone by the dinitration reaction was treated 
without subjecting to the heating suspension. The conditions and the 
results are as shown in Table 1, where 1,5-isomer cake of a low purity is 
obtained. 
COMISON EXAMPLES 2-4 
In these examples, heating suspension was conducted under the conditions 
out side of the range specified above. As can be seen from the results 
shown in Table 1, none of the examples can provide 1,5-dinitro isomer cake 
of a high purity. 
COMISON EXAMPLES 5-6 
The same procedures as in Example 6 were repeated except that anthraquinone 
was added over longer periods of time. The results show that the purity of 
the resulting 1,5-isomer cake is below 90% and high purity can not be 
attained even if the time for the heating suspension is increased. The 
conditions and the results of the experiments are also shown in Table 1. 
Table 1 
__________________________________________________________________________ 
Nitration condition 
Heat Filtra- 
Charging weight anthra- 
hold- 
suspension condition 
tion 
1,5-isomer cake 
Exam- 98% 
98% tempera- 
quinone 
ing 
tempera- tempe- composition (%) 
ple anthra- 
nitric 
sulfuric 
ture add, time 
time 
ture time rature 
yield 
1,5- 
1,8- 
beta- 
No. quinone 
acid 
acid 
(.degree. C.) 
(hr) (hr) 
(.degree. C.) 
(hr) 
x y (.degree. C.) 
(%) 
isomer 
isomer 
isomers 
__________________________________________________________________________ 
1 208 g 2894 
1551 g 
40 1 2 80 6 44.8 
65 40 32.8 
95.2 
4.7 0.4 
g 
2 208 4107 
2773 
20 1 2 90 5 64.7 
60 40 30.4 
95.9 
3.7 0.4 
3 208 2627 
2017 
40 1 2 80 2 40.4 
55 60 31.9 
91.5 
7.7 0.8 
4 208 2792 
2974 
40 2 -- 80 2 59.7 
55 60 29.2 
94.2 
5.3 0.5 
5 208 4948 
4337 
40 2 1 90 3 78.5 
52.5 
60 30.7 
93.8 
5.6 0.6 
6 20.8 kg 
366.4 
297.8 
40 0.5 -- 80 0.5 
57.5 
54.1 
60 36.2 
94.3 
5.1 0.5 
kg kg 
7 20.8 kg/hr 
385.0 
300.5 
40 0.5 -- 80 0.6 
60.2 
55.2 
60 36.5 
93.6 
5.6 0.7 
kg/hr 
kg/hr 
contin- 
uous 
__________________________________________________________________________ 
Comparison Example 
1 208 g 2894 
1551 g 
40 1 2 (without heating 
40 44.8 
74.8 
22.3 
2.9 
g suspension) 
2 208 1509 
1006 
20 1 2 80 4 22.3 
60 40 38.8 
85.8 
12.9 
1.3 
3 208 2676 
2958 
20 1 2 90 4 41.5 
47.5 
60 34.3 
84.4 
13.2 
1.4 
4 208 4135 
5013 
20 1 2 90 4 65.5 
45.2 
60 36.8 
82.5 
15.9 
1.6 
5 20.8 kg 
366.3 
296.8 
40 5.0 -- 80 0.5 
57.5 
54.1 
60 40.8 
87.2 
11.5 
1.3 
kg kg 
6 20.8 kg 
366.3 
296.8 
40 5.0 -- 80 2.0 
57.5 
54.1 
60 40.3 
88.0 
10.7 
1.4 
__________________________________________________________________________ 
EXAMPLES 9-13 
These example were conducted for demonstrating the effect of a recycling 
system (recycling system A) wherein grain size of 1,5-dinitroanthraquinone 
can be increased and the amount of waste acid be decreased, by suspending 
with heating the isomer mixture in a specified amount of mixed acid to 
isolate highly pure 1,5-dinitroanthraquinone and 1,8-dinitroanthraquinone 
therefrom and reusing the mother liquor again for the reaction. The 
conditions and the results are shown in Table 2. 
A continuous type experimental apparatus for each of the steps in the 
recycling system A shown in FIG. 2 was employed in these examples, and 
substantially the same procedures as in Examples 1-7 were repeated to 
isolate 1,5-dinitroanthraquinone using nitric acid, sulfuric acid and a 
mother liquor for reuse shown in Table 2 (make up at the starting). 
The resultant filtrate was charged in an evaporation vessel and nitric acid 
was evaporated to 30-42 mol per mol anthraquinone charged at 
50.degree.-60.degree. C. for 1-1.5 hours of residence time to cause 
crystallization. Then, 1,8-dinitroanthraquinone cake was obtained after 
filtration, washed and dried. 
A 200 hour's continuous operation in which the above filtrate was reused, 
showed no substantial changes in the results. 
EXAMPLES 14-18 
These examples were conducted for demonstrating the effect of another 
recycling system (recycling system B) wherein the amount of waste acid can 
further be reduced by reusing a mother liquor for the reaction. In this 
example 1,8-dinitroanthraquinone cake was separated from the filtrate in 
the same manner as in Examples 9-13 and then isolated from the 
.beta.-isomer through crystallization. The conditions and the results are 
also shown in Table 2. 
Employing the continuous type experimental equipment for each of the steps 
in the recycling system B shown in FIG. 2 and in substantially the same 
procedures as in Examples 9-13, 1,5- and 1,8-dinitroanthraquinone cakes 
were separated and then the mother liquor was subjected to evaporation 
until the nitric acid content therein settled to about 40-50%, based on 
the amoung of the nitric acid at the separation of the 1,5-isomer, to 
isolate the .beta.-isomer through crystallization. 
A 200 hour's continuous operation in which the above filtrate was reused 
showed no substantial changes in the results. 
EXAMPLE 19 
This example was conducted in the same procedure as in Examples 14-18 
except that the recycling system was not used. The conditions and the 
results are also shown in Table 2. 
Table 2 
__________________________________________________________________________ 
Charging amount (kg/hr) Reuse 
reused mother liquor of Nitration condition 
dinitro- 99% 100% 
mother 
tempera- 
residence 
Example 
Recycle 
anthra- anthra- nitric 
sulfuric 
liquor 
ture time 
No. system 
quinone 
HNO.sub.3 
H.sub.2 SO.sub.4 
H.sub.2 O 
quinone 
others 
total 
acid acid 
(%) (.degree. 
(hr) 
__________________________________________________________________________ 
9 A 20.8 141.8 
268.0 
20.4 
15.6 4.9 450.6 
313.2 
89.3 
75 40 0.6 
10 A 20.8 237.6 
361.1 
37.2 
28.8 9.3 674.0 
299.8 
63.8 
85 40 0.6 
11 A 20.8 58.8 
156.0 
7.7 
13.4 4.4 240.3 
341.8 
156.0 
50 30 0.5 
12 A 20.8 269.2 
364.3 
52.4 
37.9 14.2 
738.0 
242.6 
40.5 
90 40 0.5 
13 A 20.8 238.2 
193.3 
31.7 
29.7 10.0 
502.6 
201.0 
34.1 
85 20 0.7 
14 B 20.8 72.6 
198.1 
24.9 
7.4 9.1 312.1 
384.1 
106.6 
65 40 0.6 
15 B 20.8 104.0 
283.5 
59.4 
9.2 12.0 
468.1 
299.5 
31.5 
90 40 0.6 
16 B 20.8 40.8 
222.6 
24.7 
8.4 11.0 
307.5 
340.6 
74.2 
75 20 0.6 
17 B 20.8 29.1 
158.8 
8.5 
5.9 6.3 208.6 
377.8 
158.8 
50 30 0.5 
18 B 20.8 34.7 
124.5 
25.2 
19.3 12.3 
216.1 
272.3 
31.1 
80 20 0.7 
19 -- 20.8 (mother liquor not reused) 
404.5 
315.0 
0 40 0.6 
__________________________________________________________________________ 
Filtra- 
1,5-isomer cake 1,8-isomer 
H.sub.2 SO.sub.4 not 
reused 
Heat suspension condition 
tion average beta- 
in mother liquor 
tempera- tempera- 
composition (%) 
grain isomer ratio 
Example 
ture ture yield 
1,5- 1,8- 
beta- 
diameter 
yield 
content 
amount 
to 1,5- 
No. (.degree. C.) 
x y (.degree. C.) 
(%) 
isomer 
isomer 
isomers 
(.mu.) 
(%) (%) (kg/hr) 
cake 
__________________________________________________________________________ 
9 80 69.0 55 60 33.8 
95.0 4.6 0.4 32.3 40.3 
10.2 
89.3 8.8 
10 80 82.2 55 60 32.8 
95.0 4.6 0.4 39.5 41.3 
10.0 
63.8 6.5 
11 80 60.3 55 60 34.5 
94.9 4.7 0.4 38.7 39.9 
9.3 156.0 
15.1 
12 80 78.5 55 60 35.0 
90.0 9.4 0.6 39.5 41.9 
15.1 
40.5 3.9 
13 60 67.0 65 45 32.5 
94.4 5.0 0.6 37.5 38.9 
6.3 34.1 3.5 
14 80 59.0 55 60 36.6 
93.1 6.2 0.7 34.5 34.2 
4.5 106.6 
9.8 
15 80 60.8 55 60 35.9 
93.8 5.6 0.6 37.0 34.1 
3.9 31.5 2.9 
16 80 57.6 55 60 37.0 
92.0 7.2 0.8 35.5 36.8 
7.5 74.2 6.7 
17 80 61.5 55 60 35.1 
95.5 4.0 0.5 31.5 34.5 
3.5 158.8 
15.2 
18 60 45.8 65 45 34.5 
92.2 7.2 0.6 32.0 36.3 
5.6 31.1 3.0 
19 80 61.0 55 60 36.3 
94.6 4.9 0.5 24.0 36.0 
8.0 315.0 
29.4 
__________________________________________________________________________