Ind. Eng. Chem. Prod. Res. Dev. 1902, 21 566-570
566
~
Catalytic Oxidation of Hydroquinone to Quinone Using Molecular Oxygen Robert J. Radel,' Jack M. Sullivan, and John. D. Hatfleld Division of Chemical Development, National Fertilizer Development Center, Tennessee Valley Authority, Muscle Shoals, Alabama 35660
The use of the hydroquinone-quinone oxidant system on an industrial scale requires the development of a process for the ready regeneration of the quinone oxidant from recycled hydroquinone. This paper describes procedures for the oxidation of both substituted and unsubstituted hydroquinones using metal salts and supported metal catalysts and molecular oxygen. The effects of the solvent, temperature, and oxygen pressure were studied.
Introduction One method for preparing dialkyl oxalates by oxidative carbonylation of alcohols uses an organic oxidant, p benzoquinone (2,5-cyclohexadiene-1,4-dione) (Radel et al., 1982;Zehner, 1977;Fenton and Steinwand, 1974). The use of this oxidant serves two purposes. Primarily, it increases catalyst activity and selectivity toward oxalate esters, and secondly, it eliminates the explosion hazard presented by the use of oxygen. Upon completion of the reaction, hydroquinone is formed along with the desired oxalate. The use of the hydroquinone-quinone oxidant system on an industrial scale requires the easy regeneration of the quinone oxidant with a minimum loss of recyclable material. This investigation was carried out to examine the various methods available for quinone regeneration and to develop a simple process to carry out such an oxidation. The oxidation of hydroquinone to quinone has received considerable attention in the literature (Patai, 1974; Buehler and Pearson, 1970). A great number of these oxidations use inorganic oxidants in stoichiometric quantities. The major drawback to the use of these methods is that the oxidants used are expensive, corrosive, and often toxic. There are, however, reports in the literature which indicate that the oxidation may be carried out catalytically. James et al. (1938)published a study of the autoxidation of hydroquinone and its mono-, di-, and trimethyl derivatives. Their findings indicate that the first step in the autoxidation of hydroquinones is accompanied by the formation of hydrogen peroxide.
0H
c
If at least one of the R s is a hydrogen, the peroxide reacts with the quinone to give the hydroxy compound.
'humic acids"
(2)
If more than one R is a hydrogen, then polymerization of the hydroxy quinone produces a humic acid-like substance. It is therefore necessary to develop a catalytic system which hinders the formation of these humic acid-like substances.
Several French patents issued to Rhijne-Poulenc (1963, 1964, 1965) describe the oxidation of hydroquinone to p-benzoquinone using rhodium or ruthenium catalysts in acetic acid solution. ?H
0
OH
0
The reaction which proceeds in almost quantitative yield is carried out at 80 "C and with 35-40 mm oxygen pressure. In this procedure, however, the quinone is not separated from the acetic acid but rather it is used in situ. The separation of quinone from acetic acid may prove difficult due to the relatively high boiling point of acetic acid. Two reports in the literature show the use of cobalt as a catalyst, one in the form of a dioxygen complex (McKillop and Ray, 1977)and the other in the form of an electrochemically sulfonated cobalt phthalocyanine (Meshitsuka et al., 1975). In both cases the formation of hydrogen peroxide is evidenced both by the formation of polymeric materials and by low yields of quinones. Here we report the results of our investigation of the catalytic conversion of hydroquinones to quinones using various metal salt and metal catalyst systems, reaction solvents, and molecular oxygen as the oxidant. Experimental Section To confirm the identity of the quinone, hydroquinone, and quinhydrone products, the following instruments were employed. A Digilab 14 FT-IR spectrometer was used to measure infrared (IR) spectra of the samples, which were ground and compressed into KBr pellets. The nuclear magnetic resonance spectra were determined using a Varian EM-360 NMR spectrometer. Elemental analyses were obtained using a Perkin-Elmer 240B elemental analyzer, and melting points were taken on an Electrothermal melting point apparatus. Oxidation of Hydroquinone to Quinone with Oxygen at Atmospheric pressure. The appropriate amounts (Table I) of catalyst, solvent, and hydroquinone were added to a round-bottom flask equipped with a magnetic stirrer and a gas dispersion tube for oxygen introduction. The reaction mixture was heated to the appropriate temperature and oxygen was introduced. The oxygen flow was maintained throughout the reaction. Thin-layer chromatography was used to measure the extent of reaction. The reaction solution then was cooled to room temperature, the catalyst was filtered, and the solvent was removed via
This article not subject to U.S. Copyright. Published 1982 by the American Chemical Society
Ind. Eng. Chem. Prod. Res. Dev., Vol. 21, No. 4, 1982 567
Table I. Oxidation of Hydroquinone to Quinone with Oxygen a t Atmospheric Pressure
expt no. 1 2 3 4 5 6 7
8 9 10 11 12
hydroauinone iharged time, g h
cat., g
solvent, mL
1%Ru/G (0.4) 1%Ru/G (0.4) 5% Pd/C (1.0) FeC1, (0.294) FeC1, (0.294) CuCl(0.3) CuCl/Cu(CH,CO,), (0.3U0.3) V,O, (0.5) Cu(CH,CO,), (0.3) Cu(CH,CO,), (0.63) CuCl(O.3) CuCl(1.5)
CH,CO,H (45) H,O (50) CH,CO,H(250) 2 N HCl(50) 2 N HCl(65) 2 N HCl(65) CH,CO,H (75)
1 1 10
CH,CO,H (55) CH,CN (7 5) CH,CN (200) CH,CN ( 7 5) CH,CN (300)
2 2 10 2 10
2 5 5 2
products, g temp, "C
48 48 24 1.5 16 16 48
80-85 80-85 80-90 57-60 60-70 60 80-90
2 72 98 48 72
80-90 25 25 25 25
quinone
polymer
quinhydrone
0.582 0.1 0.115 2.00 4.0 1.6 0.152 1.06 0.04 4.0
0.6 0.242 8.27 1.45 2.75
Table 11. Oxidation of Hydroquinone to Quinone with Oxygen under Pressure
expt no.
cat., g
1 2 3
1%Ru/G (0.4) 1%Ru/G (0.4) 1%Ru/G (0.4)
4 5 6 7 8 9
CuCl(4 .94)"' CuSO, (8.0) a Cu(CH,CO,), (2.61) 5% Rh/A1,0, (5.0) 5% Ru/C (4.0) Cu(CH,CO,), (10.45)
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
CuCl (4.94) CuCl(4.94) c u s o , (2.0) Cu(CH,CO,), (10.45) Cu(CH,CO,), (10.45) 5% Rh/A1,0, (5.0) 5% Ru/C (4.0) CuCl (1.25) c u s o , (2.00) Cu(CH,CO,), (2.61) 5% Rh/A1,0, (5.0) 5% Rh/A120, (5.0) 5% Ru/C (4.00) 5% Ru/C (4.00) 5% Ru/C (4.00) CuCl (1.25)
26
c u s o , (2.00)
27
Cu(CH,CO,), (2.61)
28
5% Rh/A1,0, (5.0)
29
5% Ru/C (4.0)
hydroauinone 0, charged, press., g psig
products, g temp, "C
time, h
quinone
Oxidations Using a Shaker Reactor 1 25 80 CH,CO,H (20) CH,CO,H (20) 1 30 80 CH,CO,H (20) 1 35 80
0.5 20 40
0.22 0.12
solvent, mL
Oxidations Using a Parr Stirred Reactor 2-C,H70H (500) 55 125 25 55 130 25 2-C,H70H (500) 13.75 125 25 2-C,H70H(500) 2-C,H70H (500) 13.75 125 25 2-C,H70H(500) 13.75 125 25 CH, CN/H,O 55 100 25 (400/100) CH,CN 55 125 25 CH,CN 55 200 25 CH,CN (500) 13.75 125 25 CH,CN (500) 55 125 25 55 125 25 CH,CN (500) CH,CN (500) 13.75 125 25 CH,CN (500) 13.75 125 25 CH,CO,H(500) 13.75 125 25 CH,CO,H (500) 13.75 125 25 CH,CO,H (500) 1375 125 25 27.50 125 80-85 CH,CO,H (500) CH,CO,H (500) 13.75 125 80-85 CH,CO,H (500) 55 125 25 55 125 80-85 CH,CO,H (500) CH,CO,H (500) 13.75 125 80-85 CH,CN/B-C,H,OH 13.75 125 25 (230/230) CH,CN/P-C,H,OH 13.75 125 25 (230/230) CH,CN/%-C,H,OH 13.75 125 25 ( 2 50/ 250) CH3CN/2-C,H,OH 13.75 125 25 (250/250) CH,CN/S-C,H,OH 13.75 125 25 (250/250)
48 48 24 16 24 1
9 3.5 24 1.5 1.5 20 24 24 24 22 4 4 96 6c 6 29
4.00 29.67 49.31 49.33 40.08 40.36
0.31 0.46
13.00 6.87 16.00 trace trace no reaction trace trace 13.00 11.00
1.60
4.30 8.00
no reaction no reaction no reaction 7.57
10.00 44.6 37.00
10.63 12.30
trace no reaction
11.23
20 22
quinhydrone
no reaction no reaction no reaction
24 16
polymer
12.73 0.66
12.3
'
a Triethylamine was added after 24 h. There was approximately 5 g of starting material unaccounted for. This is probably due to the loss of the volatile quinone during the evaporation of solvent. Thus, this yield could easily approach 100%. The temperature was maintained at 80 to 8 5 "C for 6 h, after which time the reactor was allowed to stir overnight at room temperature. Absence of polymer or quinhydrone formation indicates quantitative conversion.
rotary evaporation. The solid residue was extracted with benzene and was filtered, leaving brown, polymeric material. The benzene extract then was evaporated and the ensuing solid was extracted continuously with hexane, leaving a dark-green solid (hydroquinone). The hexane extract was evaporated to give quinone. Oxidation of Hydroquinone to Quinone Using Oxygen Under Pressure. (A) Utilizing Shaking Reactor.
A 150-cm3Whitney sample cylinder was charged with 0.4 g of 1% ruthenium on graphite, 20 mL of acetic acid, and 1 g of hydroquinone (Table 11). The cylinder was sealed, purged with oxygen, and pressurized to the desired pressure. The cylinder was placed in a Burrell wrist-action shaker and shaken in an oil bath at 78-80 "C overnight. Upon termination of the reaction the vessel was cooled, the gases were vented, and the reactor contents were fil-
568
Ind. Eng.
Chem. Prod. Res. Dev..
Vol. 21, No. 4, 1982
Table 111. Oxidation of Tetrachlorohydroquinone with Oxygen a t Elevated Pressures - - __ __ - - - - - - - -- - --. -. .- - - - - ____ TCHQa press., 0, rxpt charged, temp,
-.
--
-nu. I
2
:> i 7
b ?i
9 10
solvent,__ mL
cat.. g
CUCl (0.08) CuSO, (0.126) Cu(CH,C02), (0.16) 5% Rh/AI,O, (1.641 5% Ru/C (1.6 CuCl(O.08) cuso, (0.126) Cu(CH,CO,), (0.16) 5% Rh/Al.O, (1.64) 6% IlUiC iI .6 1)
"C
Oxidations Using a Mechanically Shaken Reactor 2-C3H,0H ( 5 0 ) 2.0 125 25 2-C3H,0H (50) 2.0 125 25 2-C,H70H (50) 2.0 125 25 2-C,H70H ( 5 0 ) 2.0 125 25 2-C,H70H (50) 2.0 125 25 CH,CN (50) 2.0 125 25 CH,CN ( 5 0 ) 2.0 125 25 CH ,CN ( 5 0 ) 2.0 125 25 CH,CN (50) 2.0 125 25 CH CN (50) 2.0 125 25 'rCQ
=
g
%
22 22 20 24 24 23 23 23 23 24
1.27 0.68 1.58 1.66 1.90 1.83 0.95 0.90 1.30 1.62
64 32 79 83 95 91 46 45 65 81
tetrachloroquinone
tered. The solid was washed with methanol, leaving a black powder (recovered catalyst). The filtrate was evaporated and the solid residue was washed with cold benzene, leaving a dark solid (quinhydrone). The benzene filtrate was chromatographed on silica gel (grade 111) using benzene as the solvent to give light yellow crystals of quinone upon evaporation of the solvent. (B) Oxidation Using a 2-L Parr Stirred Reactor. An appropriate amount of hydroquinone, catalyst, and solvent (Table 111) was added to a 2-L Parr stirred reactor. The reactor was closed, purged twice, and then pressurized with oxygen. In some experiments, heating was maintained by an external furnace. Upon completion of the reaction, the reactor was cooled and the gases were vented. The reactor contents were filtered to remove the catalyst. The reaction mixture was evaporated to dryness and the solid residue taken up in 2 L of anhydrous ether. The solid was filtered and washed with 300 mL of benzene, leaving the solid, polymeric material as residue. The combined filtrate was evaporated to dryness and the yellow-green solid was extracted continuously with hexane, leaving the dark green quinhydrone. The hexane extract was evaporated to give the yellow quinone. Oxidation of Tetrachlorohydroquinone (TCHQ) with Oxygen at Elevated Pressures. A slurry of 2 g of tetrachlorohydroquinone and the appropriate catalyst in 50 mL of solvent (Table 11) was added to a 150-cm3 Whitney sample cylinder. The cylinder was closed, purged twice, and pressurized with 125 psig oxygen. The cylinder was shaken at room temperature using a Burrell wristaction shaker. After an appropriate time, the reactor was vented and the contents were filtered and rinsed with acetone, leaving a yellow solid whose identity was determined to be tetrachloroquinone (TCQ). The washings and filtrate were evaporated to give a residue, which was extracted with benzene. The benzene-insoluble material was identified as additional TCQ. The benzene was evaporated to yield recovered TCHQ. Results Catalytic Oxidation of Hydroquinone to Quinone via Molecular Oxygen. A series of experiments was run in which the oxidation of hydroquinone to quinone was investigated using oxygen a t atmospheric pressure and a metal salt or supported metal catalyst according to eq. 4.
'L
Psig
yield of TCQ
_ _ I _ _ _ _ _ _ _ _ - I _
TCHQ = tetrachlorohvdroquinone
?
g
time, h
ap IO 0 c u CI
CuSOq
C U I C ~ H ~ O ~ )Rh(Al203) ~
RU(C )
CATALYST E M P L O Y E D
CUCl
CuSO4
CuICzH3021~
R h IA I z O3l
Ru IC1
CATALYST EMPLOYED
Figure 1. Comparison of catalyst-solvent effectiveness in the oxidation of hydroquinone to p-benzoquinone with molecular oxygen at elevated pressures.
Figure 2. Comparison of catalyst-solvent effectiveness in the oxidation of hydroquinone to quinhydrone with molecular oxygen at elevated pressures.
catalysts are ineffective in the formation of quinhydrone. Copper(I1) sulfate was not active for either quinone (Figure 1) or quinhydrone (Figure 2) formation. Rhodium- and ruthenium-supported catalysts gave very good yields of quinhydrone. From these experimental results, it appears that copper(1) chloride and copper(I1) acetate in nitrile solvents or nitrile-containing solvent mixtures are the most promising catalyst-solvent systems for the formation of quinone. The rhodium- and ruthenium-supported catalysts gave excellent yields of quinhydrone. Further experiments using copper(1) iodide and copper(1) bromide were carried out. The results of these experiments (Table IV) indicate that neither copper(1) bromide nor copper(1) iodide are
effective catalysts in the oxidation of hydroquinone to quinone. However, copper(1) bromide does give good yields of quinhydrone. Catalytic Oxidation of Tetrasubstituted Hydroquinone to Tetrasubstituted Quinones via Molecular Oxygen. There are several problems associated with the industrial use of the hydroquinone-quinone oxidant system. One of these is the formation of polymeric material associated with the oxidation of quinone by hydrogen peroxide, resulting in a loss of recyclable material. A second problem ariseO from the high volatility of quinone itself. Both these problems can be overcome through the use of much less volatile tetrasubstituted derivatives which are incapable of forming polymers and exhibit lower vapor pressures.
Ind. Enp. Chem. Prd. Res. Dev. 1982, 21, 570-575
570
The results of these experiments are given in Table III and are shown in Figure 3. The catalysts ranked in decreasing order of activity were ruthenium on carbon > copper(1) chloride > rhodium on alumina > copper(I1) acetate > copper(I1) sulfate. In addition, a comparison of the available copper(1) halides also was made, of which copper(1) chloride gave the best results (Table V). In general, the oxidation of tetraehlorohydrcquinone proceeded in greater yield than in the case of hydroquinone itself, with a maximum yield of 95%. No polymeric materials were isolated in any of the experiments. In those experiments with lower yields, a portion of the starting material was recovered. Literature Cited CAThLIST EUPLO"E0
Figure 3. Comparison of catdystaolvent effectiveness in the oxidation of tetrachlorohydroquinoine with molecular oxygen at elevated pressures.
To investigate the use of these substituted derivatives, several experiments were run in which tetrachlorohydroquinone (IV) was oxidized catalytically at elevated pressures (eq 6). OH
n
OH
0
BuBhltK. C. A.; Pearson. D. E. "Survey of m n l c Synlhases": Wlley-Inlersclence: New Ywk. 1970;VOl. 1. p 730. Fenton. D. M.: Stalnwand.P. J. J . Ckg. Chem. 1974. 39. 701. James. T. H.: Snell. J. M.; Welsaberger. A. J . Am. Chem. SOC. 1998. BO.
2084. MCKillop. A.: Ray. S. J. Synfhesk 1977.847. MeshRsuka.S.: Ichlkawa.M.: Tamaru. K. J . Chem. SOC. Chem. Commwr. 1975,0, 360. Patai. S.. Ed. "The Chemistry 04 oulnom Gomwnds. Parts 1 and 2"; Wlley: New Voh, 1974. Radel. R. J.: Sullivan. J. M.: Hallleeld. J. D. Ind. Eng. Chem. Rod. Res. B v . 1982,I" press. Rhone-Poubnc, S. A. French Patonl 1388462. 1983. Rhone-Podenc. S. A. French Patent 83 108. 1964. Rhone-Podenc, S.A. French Patent 1388869. 1965. Zehner. L. R. US. Palem 4005 130. 1977.
Received for review February 16, 1982 Accepted May 21, 1982
Wet Oxidation of Acetic Acid Catalyzed by Co-Bi Complex Oxides Sei-lchlro Imamura,' Aklhlro Hlrano, and Narlyoohl Kawabata oepamnent of C.%mb!sfry, Kyoto InsfflMeof Technology.Matswsaki, Sakyo-ku. Kyoto 80s. Japan
Wet oxidation of acetic acid was carried out in the presence of various heterogeneous catalysts. Bismuhcontainlng catalysts were found to be active, of which cobalt-bismuth complex oxide with a molar ratio of Co to Bi of 5 (Co/Bi(S/l))exhibited the highest activity. Calcination temperature in the preparation of Co/Bi(S/l) affected its
surface area: however, specific activity of Co/Bi(5/1) was indifferent to calcination temperature. Co/Bi(5/1) apparently had basic sites where acetic acid was preferentially adsorbed by an acid-base interaction in the first step of the reaction. Co/BYS/l) also exhibited a remarkable activity in the decomposition of hydrogen peroxide, and, therefore, it was assumed that the redox property of Co/Bi(S/l)contributed to its high actvity in the oxidation of acetic acid.
Introduction Wet-air oxidation, k e d out in air under high pressure and at elevated temperature, is particularly effective for the treatment of wastewaters containing organic chemicals which are resistant to biological treatment. It has been applied successfully to the treatment of wastewaters discharged from petroleum and petrochemical industries (Tagashira et al., 1976) and to the treatment Bfpttlp and paper mill wastes (Teletzke, 1964). Organic pollutants can be removed completely under appropriate conditions of 019&4321/82/1221-0570$01.25/0
treatment. Recovery of mechanical energy is also possible when the process is applied to a highly contaminated wastewater such as that discharged from coal gasification process (Chou and Verhoff, 1981). Therefore, the importance of the wet-oxidation process will increase in the future. However, the severe reaction conditions require high operating and installation costs and practical applications of this process are limited. The development of various catalysts has been attempted in order to mitigate the severe reaction conditions (Katzer et al., 1976; Levec 0 1982 American Chemical Soclely
