Process for producing .alpha.-anthraquinonesulfonic acids and recovering the catalyst used therein

The present invention concern a process for producing .alpha.-anthraquinonesulfonic acids in the presence of a metal catalyst in oleum and recovering the metal catalyst which is solubilized in the resulting sulfonation mixture. A porous carrier is introduced into the resulting sulfonation mixture which is subsequently treated with a reducing agent thereby depositing the metal catalyst on the porous carrier.

TECHNICAL FIELD OF THE INVENTION 
The present invention relates to a process for producing 
.alpha.-anthraquinonesulfonic acids by sulfonating anthraquinone in oleum 
and recovering the catalyst which is solubilized in the resulting 
sultonating mixture. 
BACKGROUND OF THE INVENTION 
In the process for the production of .alpha.-anthraquinonesulfonic acids by 
sulfonating anthraquinone in solvent, a metal type catalyst is required. 
Different catalysts and solvents have been disclosed in the past in order 
to accomplish the sulfonation reaction with a high conversion ratio and 
.alpha.-selectivity, and methods for recovering the catalyst also have 
been discussed. However, a process which has a high conversion ratio, 
.alpha.-selectivity, and in which the catalyst recovered therefrom retains 
the same activity has not been disclosed heretofore. 
A well known process for producing 1-anthraquinonesulfonic acid, as is 
taught in Kirk-Othmer, "Encyclopedia of Chemical Technology", 3rd edition 
(1978), vol. 2, P.729, wherein anthraquinone is sulfonated in oleum in the 
presence of mercury salt, requires that the sulfonation reaction is 
interrupted as soon as about 45% of the starting anthraquinone have been 
converted, since otherwise disulfonation will be predominant. 
U.S. Pat. No. 3,763,191 teaches a process for producing 
.alpha.-anthraquinonesulfonic acids in substantially higher yield and 
higher selectivity, especially if palladium or compounds containing the 
same are used. However, the degree of sulfonation and .alpha.-selectivity 
shown in the examples of said U.S. patent are still less than desired and 
furthermore, a process for recovering the catalyst solubilized in the 
reaction mixture is not disclosed therein. 
U.S. Pat. No. 3,792,065 discloses a process for the production of 
.alpha.-anthraquinonesulfonic acids which are substantially devoid of 
mercury, in which mercury introduced in the form of the sulfate as the 
catalyst is seperated from the sulfonation mixture as metal by the 
addition of a reducing agent. 
New catalysts which promote selectively the .alpha.-sulfonation of 
anthraquinone in liquid sulfur dioxide as a solvent are taught addressed 
in, "Palladium-Catalyzed .alpha.-Monosulfonation of Anthraquinone by 
Sulfur Trioxide in Liquid Sulfur Dioxide" by Yasuziro Kawabata, et al., 
appearing in Journal of the Chemical Society of Japan, 1980, (3), p. 
322-326, wherein the use of liquid sulfur dioxide and palladium containing 
compounds in the sulfonation reaction resulted in about 100% conversion of 
anthraquinone and 76% yield of 1-anthraquinonesulfonic acid with 99% 
.alpha.-selectivity. Further, Kawabata, et al. disclose a process of 
reprecipitation of the solubilized palladium on carbon by hydrogen 
treating, in which the pH value of the reaction mixture was adjusted to 
&gt;7, and then 20 atm hydrogen was introduced to deposit the solubilized Pd 
on carbon. However, the conversion of anthraquinone was found to have 
decreased to 70% as the recovered Pd-carbon was recycled. Additionally, 
air or oxygen was introduced into the mixture after the Pd-carbon had been 
removed in order to precipitate a salt of the monoanthraquinonesulfonic 
acid. 
SUMMARY OF THE INVENTION 
The present invention is a process for producing 
.alpha.-anthraquinonesulfonic acids, which comprises sulfonating 
anthraquinone in oleum in the presence of a metal catalyst which is 
deposited on a porous carrier; treating the resulting sulfonation mixture 
with a reducing agent such that the solubilized metal catalyst is 
redeposited on the porous carrier; and filtering out the catalyst and 
subsequently isolating .alpha.-anthraquinonesulfonic acid product from the 
mixture. 
The high conversion ratio and high .alpha.-selectivity of the above 
sulfonation reaction together with the catalyst recovered retaining 
substantially the same activity afford a process for producing 
.alpha.-anthraquinonesulfonic acids more economical than any known process 
.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention provides a process for producing 
.alpha.-anthraquinonesulfonic acid products, especially 
1-anthraquinonesulfonic acid, and for recovering the solubilized catalyst 
from the sulfonation mixture. The process involves sulfonating 
anthraquinone in oleum in the presence of a metal catalyst and 
reprecipitating the solubilized metal catalyst on an added porous carrier 
with a reducing agent. 
In general, the metal catalysts which are disclosed in U.S. Pat. No. 
3,763,191 the disclosure of which is incorporated herein by reference are 
suitable for use in the process. A group of suitable catalysts include 
ruthenium, rhodium, palladium, osmium, iridium, platinum, silver, gold, 
cobalt, nickel, mercury, thallium, and compounds containing the same. The 
preferred catalysts of the present invention are palladium, ruthenium, and 
compounds containing these metals, especially palladium and compound 
containing palladium, such as Pd, PdO, Pd(OAc).sub.2 et al. In the most 
preferred embodiment, sponge Pd particles having a mesh number greater 
than 60 are utilized as a starting catalyst. 
Suitable materials for the porous carrier in the process are, for example, 
SiO.sub.2, TiO.sub.2, BaSO.sub.4, anthraquinone, and carbon, wherein 
carbon is most preferable. 
Oleum which has a SO.sub.3 concentration higher than 20% may be used in the 
present process to decrease the amount of sulfuric acid in the resulting 
sulfonation mixture. Preferable SO.sub.3 concentration of the oleum ranges 
from 35-45wt %. Further, the preferred mole ratio or SO.sub.3 to 
anthraquinone is about 4:1. 
As it is well known to those skilled in the art, the variables affecting 
the sulfonation reaction, such as reaction temperature, catalyst 
concentration, reaction time, will generally be controlled in accordance 
with the desired product. In one of the preferred embodiments of present 
invention, wherein palladium is used as catalyst and 
1-anthraquinonesulfonic acid product is desired, the sulfonation reaction 
is accomplished at a temperature ranging from room temperature to 
120.degree. C., preferably ranging from 80.degree. to 110.degree. C., and 
a concentration of palladium catalyst ranging from 0.3-2.0wt %, based on 
anthraquinone, preferably ranging from 0.35-1.5wt %, and the reaction is 
stopped when at about 97% of the starting anthraquinone which has been 
converted to optimize the yield of the 1-anthraquinonesulfonic acid 
product The interruption of sulfonation reaction is effected by the 
addition of ice water or water, which also causes the reaction mixture to 
be diluted as well. 
In general, reducing agents disclosed in U.S. Pat. No. 3,792,065 are 
suitable for use in the present process, and details thereof are 
incorporated by reference. The reducing agents, for example, include 
formaldehyde, glucose, sodium sulfite, potassium sulfite, sodium hydrogen 
sulfite, potassium hydrogen sulfite, sulfur dioxide, formic acid, sodium 
formate, potassium formate, oxalic acid, and neutral or alkali metal salts 
of oxalic acid, wherein formaldehyde is preferred. 
The reducing reaction of solubilized metal catalyst according to the 
present invention may be carried out at atmospheric pressure with stirring 
at a temperature ranging from room temperature to 115.degree. C., 
preferably ranging from 80.degree. to 110.degree. C. Particularly, 
adjusting the pH value of sulfonation mixture before reprecipitating the 
solubilized metal catalyst as taught by Kawabata et al. is not necessary 
for the present process The precipitated metal-carrier which is filtered 
out from the reaction mixture is washed with water until free from acid, 
and then dried to yield a catalyst which is ready to be used in the next 
sulfonation reaction. The 1-anthraquinonsulfonic acid product is obtained 
from the filtrate by the conventional salting out method. 
The invention will be further illustrated by the following examples in 
which parts and precentages are by weight unless otherwise indicated. 
EXAMPLE 1 
The objectives of this example are to produce 1-anthraquinonesulfonic acid 
using sponge Pd particles as catalyst and to recover the sponge Pd 
catalyst as a deposited form. 
0.83 g., mesh number 325, sponge Pd particles is introduced with stirring 
into 95 ml. of 25% oleum in a 500 ml. three-neck flask equipped with a 
mechanical agitator, a thermometer, and a heating jacket, the mixture is 
heated, and antraquinone whose weight is 125.5 times that of the Pd is 
added at 70.degree. C., i.e. 104.2 g. anthraquinone is added, and 90 ml. 
of 65% oleum is dripped in slowly at 90.degree. C. The temperature of the 
mixture reaches about 98.degree. C. within 5-10 minutes and is maintained 
for 5 hours after the dripping began, and then a sample is taken from the 
mixture to find about 3.4% of the starting anthraquinone unreacted. The 
mixture heating is stopped and the mixture is left to cool to room 
temperture, and then it is introduced into 1100 ml. ice water, the flask 
reactor is washed with 100 ml water; and the washing water is combined 
with the diluted mixture. 17 g. active carbon and 75 g. of 37% formalin 
are added to the diluted aqueous solution and, the solution is heated and 
kept at about 110.degree. C. for 45 minutes. When the solution is still 
hot, it is filtered to yield a cake of Pd-carbon. The cake is washed with 
100 ml hot water to dissolve the undesired soluble material, filtered 
again, and dried to product the Pd-carbon catalyst which is used in the 
next sulfonation reaction in the following example. A sample taken from 
the mixture of the filtrate and the washing water is analyzed by AA method 
to measure the concentration of solubilized Pd. 
The mixture of the filtrate and the washing water is heated to about 
85.degree. C., and saturated KCl aqueous solution is added. A total of KCl 
added is about and the mixture is kept at 85.degree. C. with stirring for 
about 1 hour, and then heating is stopped and the mixture left to stand 
overnight. The potassium salt of 1-anthraquinonesulfonic acid is filtered 
out from above said mixture, the resulting cake is washed with 200 ml. of 
3% KCl aqueous solution and dried. The potassium salt of 1-anthraquinone 
acid obtained from above process is 133.5 g., which is 85% based on 
converted anthraquinone. 
The analytic data of the composition of the sulfonated product, and the 
loss of Pd are given in the following Table 1. 
EXAMPLE 2 
The objective of this example is to illustrate that the catalyst which is 
recovered according to the process of present invention will have 
substantially the same activity as the original catalyst. 
The process of example 1 is repeated except that the sponge Pd particles 
are replaced by the Pd-carbon recovered from above example 1, designated 
as Pd-C(I), and the active carbon is not added into the reaction mixture 
before the reducing reaction 
The process is repeated for another two cycles using the Pd-carbon which is 
recovered from the previous process, designated as Pd-C(II) and Pd-C(III), 
respectively. 
The analytic data of the composition of the sulfonated product, and the 
loss of Pd are given in the following Table 1. 
TABLE 1 
______________________________________ 
Composition of Sulfonated Product (%).sup.(b) 
Uniden- 
Percentages.sup.(c) 
tified of Re- 
Catalyst 
1-AQ-SO.sub. 3 H 
1.5- 1.8- Material 
covered Pd 
______________________________________ 
Pd..sup.(a) 
85 2.3 3.6 9.1 100 
Pd-C(I) 85 3.8 3.7 7.5 97.2 
Pd-C(II) 
85.4 3.8 3.5 7.3 94.2 
Pd-C(III) 
84.8 3.6 3.6 8.0 92.4 
______________________________________ 
.sup.(a) Example 1. 
.sup.(b) Data of the composition of sulfonated products obtained by HPLC 
method. 
.sup.(c) Percentages of recovered Pd = [(weight of the starting Pd) - 
(weight of the solubilized Pd)]/(weight of the starting Pd) .times. 100% 
As it can be seen from Table 1 the Pd-carbon recovered from each cycle has 
substantially the same activity as the starting sponge Pd particles, and 
further the loss of solubilized Pd is minimized to significant extent 
compared to the method taught Kawabata et al. In fact, the process of 
example 2 has been carried out as far as to the eleventh cycle, wherein 
the Pd-carbon recovered therefrom retains substantially the same activity 
as fresh sponge Pd particles.