STUDY ON THE CATALYTIC OXIDATION WITH AIR OF FURANE DERIVATIVES SUBSTITUTED IN THE
Cl:POSITION
By
Z. CSUROS, R. SOOS, E. FOGASSY and G. T. SZABO
Department of Organic Chemical Technology, Technical University Budapest (Received September 18, 1973)
In our earlier communications [1-3] "we reported that we succeeded to prepare catalysts with favourable properties for the catalytic oxidation with air of carbohydrates, and that these catalysts were suited for the oxidation of di-O-iso-propylidene hexoses 'lnd O-iso-propylidene hexoses, yielding the corre- sponding monocarbonic acid. In the oxidation of the latter compounds, ho"wever, by-products are also formed under certain conditions. Among these, the for- mation of oxalic acid can readily be followed.
Since all investigated sugar derivatives "were compounds containing the furanose or pyranose ring, a further simplification of these models could be achieved by studying the catalytic oxidation "ith air of furane deriva- tives.
In the present paper we shall discuss catalytic oxidation with air of the model compounds tetrahydrofurfuryl alcohol (THFA), furfuryl alcohol (FA), furfural (F) and iX-methylfurane (}IF). The aim of oxidation "was in all cases to prepare the corresponding furane-iX-carbonic acid. The experimental pro- cedure was the same as developed in our previous work on di-O-iso-propylidene hexoses.
Oxidation in acid solution does not lead to the formation of furane-iX- carbonic acids [4
J.
BROWN [5] oxidized furfuraL furfuryl alcohol and 2-methylfurane "with potassium iron(III)cyanide in a solution containing KOH. The furane-·iX-carbon- ic acid yields were 22
%,
21%
and 5 o~, resp.HIDEO ARITA and co-"workers [6] obtained furane-iX-carbonic acid with a yield of 98% by oxidizing furfural with sodium hypochlorite. This path is also applicable for the oxidation of sugars.
SALKHINKE\" and LUKOVA [7] carried out oxidation "with sodium hypo- bromite and achieved a yield of 64%.
Ko and HIDEO [8] oxidized furfural with hydrogen peroxide to furane- iX-carbonic acid with a yield of 96%.
Oxidations using solid catalysts in aqueous alkaline solution and a chemi- cal oxidant or oxygen are also known.
250 Z. CSCRtJS et al.
KIYOKO TAKAHAI [9] oxidized furfural to furane-iZ-carbonic acid with chlorates in the presence of Mn203' Al20 3 or Fe20 3 catalyst.
DUNLOP [10] introduced oxygen into an aqueous alkaline solution of furfural at 50 to 60 cC. The catalyst contained Ca, Ni, Fe, Ag, Pt and Au (main- ly oxides).
CADIGLONA and PIACE~ZA [11] used an Mn0 2 catalyst actiYated with Ag20 for this purpose.
ADRISANO [12] oxidized a 5
%
by weight aqueous alkaline solution of furfural to furane-iZ-carhonic acid 'with a yield of 91%,
using oxygen and an Ag20 catalyst.Other authors, namelyDINELLI [13], OKADA and co-workers [14] and
MO~TEGNA and MCQUILLO~ [15] found that copper oxide containing traces of silYer ,,'as also suitable as catalyst.
RYUICHI and co-workers [16] observed that yield depended on the condi- tions of catalyst preparation. Optimum temperature was 30 cC and yield was directly proportional to the quantity of catalyst.
OKADO and KUTAyIURA [17], using a mixture of Ag20 and CuO on pumice support, stated the rate of reaction to be proportional to the concentration of furfural, but was not affected by the mass flow between gas -liquid and liquid -.: solid phases.
The first compound whose oxidation we investigated was tetrahydro- furfuryl alcohol, yielding, as expected, tetrahydrofurane-iZ-carbonic acid:
H 0 CH·,OH
X /"·.
"''' 1 -'""
H H Hi H
'L.Jj
I .
I \
H H
--
Yield was good (92 %), no by-products formed.
Oxidations were carried out at different temperatures (Fig. 1), indicating that the rate of reaction was maximum at 50 to 60°C (Fig. 2). The Arrhenius plot (Fig. 3) gave an apparent activation energy of 3.2 kcaljmol (between 45 and 55 cC). Oxidations in solutions "ith different initial concentrations (Fig. 4) indicated that the rate of oxidation vs. concentration pasl"ed through a mild maximum (Fig. 5). These findings indicate great similarity to the oxida- tion of MAG and D-glucose.
The next simple model compound differing from THFA only in the aro- matic character of the ring was furfuryl alcohol, yielding furane-iZ-carbonic acid with a yield of 83
%:
CATALlTIC OXIDATIOS OF Fl"RASE DERIVATIVES 231
; - ,
H H
Oxidation was studied at various temperatures (Figs 6 and 7). The rate of oxidation is maximum at 40 to 50 cC (Fig. 8). Apparent activation energy calculated from the Arrhenius plot (Fig. 9) is 3.7 kcal/mol.
10-3 mol/litre 3. 4.
160
11;0
120
100
80 60 40 20
0 20 40 60 80 100 min
Fig. 1. Oxidation of tetrahydrofuriuryl alcohol L·S. time at different temperatures. 1 - 40°C 2 - 56 QC; 3 - 66 QC: 4 - 76 QC
W70-3 moljlitre/hr 760
740 720
100
80
40 50 60 70 80°C
Fig. 2. Rate of tetrahydrofurfuryl alcohol oxidation vs. temperature
252
IgW+2 0,21
0,19
0,17 0,15
Z. CSuROS ct al.
0,13 '---'---'---'---'---'---'- 3,06 3,08 3,10 3,72 3,14 3,16 70-3/
Fig. 3. Logarithm of the rate of tetrahydrofurfuryl alcohol oxidation vs. liT (45-55 0c)
10-Cimol/iitre 160 140 120
100 80 60 40
zo
o
20 40 60 80 100 minFig. 4. Oxidation of tetrahydrofurfuryl alcohol vs. time at different initial concentrations.
1 -- 190.0 . 10 -3 mol/litre; 2 - 264.0 . 10 -3 mol/litre; 3 - 362.0 . 10 -3 mol/litre W· fO-3mol/lilre/hr
170
100
90
80L-_~ __ -'-_~_--'-_____ ---' ____ ~
5 10 15 20 25 30 35 40
9 le Ira hydro furfuryl alcohol per litre Fig. 5. Rate of tetrahydrofurfuryl alcohol oxidation vs. concentration
CATALYTIC OXIDATIO.Y OF FCRASE DERIT-ATIFES 253
10-:3 mol/litre
140 1_
720
100
80
60
40 20
o
20 60 80 100 120 minFig. 6. Oxidation of furfuryl alcohol vs. time at different temperatures. 1 - 33°C; 2 - 42 cC;
3 - 52°C
10-3 mol/litre
140
120
80
6.
60 o
o 1;0
20
o
20 40 60 80 100 minFig. 7. Oxidation of furfuryl alcohol vs. time at different temperatures. -1. - 52°C; 5 - 76 °C;
6 93°C
254
W.!0-3 mol/lilre/hr
700
80 60 40
Z. CSCROS et al.
o
20~ __ ~ __ ~ __ ~ __ ~ ____ ~ __ ~ __ ~ __ ~ __ _
10 20 30 40 50 60 70 80 gO °C
Fig. 8. Rate of furfuryl alcohol oxidation vs. temperature
7,06 IgW+7
1,04
7,02 0
7,00
0
0,98
0,96
3.18 J,20 3,22 3,24 3,26 3,28 J,30 3,32 10-3
t
Fig. 9. Logarithm of the rate of furfuryl alcohol oxidation vs. IjT (30-42 QC)
Rate of reaction vs. concentration vields a curve 'with a maximum III
this case too (Figs 10 and 11).
The results are similar to those obtained with THF A. Chemical differences appeared not to affect the rate of oxidation. However, to decide this question, the oxidation of other substrates was also investigated.
Studies on the oxidation of THF A and FA necessarily led to the study of the oxidation of furfural, a compound of remarkable interest also from the industrial vie·w. The oxidizable group of furfural is the carbonyl group:
H~ o ~COOH
H
H H
CATAL YTIC OXIDATIOS OF FCRASE DERHATIVES 255
The reaction product, VIZ. furane-a-carhonic acid "was ohtained 'wirh yields exceeding 90%. No hy-products "were formed in the oxidation.
",Ve studied the oxidation of furfural at various temperatures (Figs 12 and 13). The rate of reaction has a maximum at 40 to 50 QC (Fig. 14). Apparent actiYation energy calculated from the Arrhenius plot hetween 28 and 40 cC (Fig. 15) is 3.3 kcal/mol.
Oxidation was also studied in solutions with different concentrations (Fig. 16). Concentration dependence of the rate of reaction, similarly to the previous cases, gave a maximum curve (Fig. 17).
10-3 mol/litre 140
120
100
80 60
40 20
o
3.
20 40 60 80 100 min
Fig. 10. Oxidation of furfuryl alcohol vs. time at different initial concentrations 1 - 191.0 . . 10-3 mol/litre: 2 - 261.0 . 10-3 mol/litre; 3 - 349.0 . 10-3 mol/litre
W.l0-3 moljlilre/hr 80
70 60
50
40~ ____ ~ ____ ~ ____ ~ ____ ~ ___
G 10 20 30 40
9 furfuryl-alcohol per litre
Fig. 11. Rate of furfuryl alcohol oxidation vs. concentration
256 Z. CSuRDS et crI.
70-3 mol/lilre
160
140
720
100
80 60 40 20
0 20 'to 60 80 700 120 min
Fig. 12. Oxidation of furfural vs. time at different temperatures 1 - 20°C; 2 30 °C;
3 40°C
10-3 mol/litre 4.
160 5.
140
120
100
80 60 40 20
t:. _ _ _ *-8.
,.. ~*
o
20 40 60 80 100 minFig. 13. Oxidation of furfural vs. time at different temperatures 4 - 50°C: 5 60°C;
5 60°C; 6 - 70 DC; 7 - 80 °C; 8 - 90 cC
CA TAL YTIC OXIDATIO."Y OF FFRA."YE DERIVATIVES 257
The following model compound investigated was cr.-methylfurane. This was of interest, because it allowed to decide whether our process suited the oxidation of the methyl group to the carboxyl group:
---
H~ (J ~COOH
~I
H H
)J:CH'
H H
The oxidation of MF yielded furane-:x-carbonic acid without any by- product. Yield was close to 60%. The lower yield can be explained by the poor
·water solubility of MF under the conditions of oxidation, so that the reaction mixture ,dll consist of four phases.
Wl0-3 mol/litre/hr o
250
o o
230
210 o
190
170~ __ ~ __ ~ __ ~ __ ~ __ ~ __ ~ ____ ~ __ ~_
o
10 20 3D 40 50 60 70 80 DCFig. 14. Rate of furfural oxidation vs. temperature
IgWf2 0,43
0,41
0,39 0,37
0,35 o
Q33~~--~--~--~ ________________ ~ 1 3,19 3,21 3,23 3,25 3,27 3,29 3,31 3,33 10-3 T
Fig. 15. Logarithm of the rate of furfural oxidation vs. liT (28-.1,0 DC)
258 Z. CSUROS et al.
Oxidation experiments at various temperatures (Fig. 18) showed the rate of oxidation to have a maximum around 40 QC in this case too (Fig. 19).
The Arrhenius plot (Fig. 20) yields a value of 10.0 kcaljmol for apparent acti- vation energy. This value significantly differs from the values found for other furane derivatives.
10-3 mol/litre 4.
200 I
180 160
140 3.
120 100
80 + q. 2.
60
0 7.
40 20
o 20 40 60 80 100 120 140 min
Fig. 16. Oxidation of furfural vs. time at different initial concentrations. 1 - 52.0 . 10-3 m~ljlitre; 2 - 10·1.0 . 10-3 mol/litre; 3 191.0 . 10-3 mol/litre; 4 - 261.0 . 10-3 moUitre;
5 - 364,.0 . 10 -3 mol/litre
kl. 10-3 moljlitre/hr 90
80 70
60~ __ ~ __ ~ __ ~ __ ~ __________ ~ __
o
5 10 15 20 25 30 35 9 furfural per litreFig. 1 i. Rate of furfural oxidation vs. concentration
CATALYTIC OXIDATIO,," OF FL"RASE DERIJ"ATII"ES 259 10-3 mol/litre
120 1
100
80 60
1;0
20
o
20 1,0 60 80 100 120 1£;0 160 minFig. 18. Oxidation of 2-methylfurane vs. time at different temperatures. 1 - 40 °C; 2 - 43 °C;
3 - 47°C W10-3 mol/fitre/hr
120
100
80 60 40
20~ __ ~ __ ~~ __ ~ ______ ~ ______ __
20 25 30 35 1,0 45 50°C
Fig. 19. Rate of 2-methylfurane oxidation vs. temperature /g/./
0.10 o 0.08
0,06
o
~
0,04
0.02
3,22 3,23 3,24 3,25 3,26 10-3
+
Fig. 20. Logarithm of the rate of oxidation of 2-methylfuralle vs. liT (35-38 QC)
260 Z. CSUROS cl al.
Also, the relationship between rate of reaction and concentration (Figs 21 and 22) differs from the results obtained 'with the other furane derivatives:
in the case of o:-methylfurane, the rate of reaction decreases with increasing concentration.
10-3 mol/liire 1.
50
40 30
20 10
o
10 20 30 40 50 60 70 80 mir.Fig. 21. Oxidation of 2-methylfurane t"S. time at different initial concentrations. 1 - 131.0 . . 10-3 mol/litre; 2 - 192.0 . 10-3 mol/litre; 3 267.0' 10-3 mol/litre
Summing up, the results allow to state that furane derivatives substituted in the 0: position are readily oxidized with our catalysts and procedure. No differen~e was found between the oxidation of the -CHzOH group, whether attached to tetrahydrofurane or to furane. The situation was similar 'when the -CHO group was attached to furane. A difference was found only in the case of the -CH3 group, this, however, being explainable hy the four-phase reaction mixture with 7.-methylfurane.
W.10-3 mol/litre/hr 40
30
20
70
o
5m
0 ~ ~ M9 2-melhylfurane per litre
Fig. 22. Rate of 2-methylfurane oxidation vs. temperature
CATAL YTIC OXIDATIOS OF FUR.·LYE DERHATIT-eS 261
Maxima of the rate of oxidation are found around 60 cC and at concen- trations of about 200 mmolflitre. The yalues of apparent activation energy are hetween 3.2 and 3.7 kcaljmol. All these yalues are much similar to the yalues found 'with O-iso-propylidene hexoses and hexoses.
Summary
The palladium catalysts on bone black support developed by us and well suited for catalytic oxidation with air, in aqueous alkaline solution, of di-O-iso-propylidene hexoses, O-iso-propylidene hexoses and hexoses, have now been tested for their suitability in the catalytic oxidation with air of tetrahydrofurfuryl alcohol, furfuryl alcohol. furfural and a-methylfurane. The corresponding monocarbonic acids were found to form in the reaction.
Yields were around 90%, in the case of a-methylfurane only 60~~. The rate of oxidation plotted against temperature and concentration yields curves pa.ssing through a maximum.
References
1. CSUROS, Z.-PETRO, J.-FOGASSY, E.-LEXGYEL, A.: Periodica Polytechn. Chem. Eng.
2. CS-GROS, Z.-PETRO, J.-FOGASSY~ E.-LE~GYEL, _.\..: Periodica Polytechn. Cheln. Eng.
3. CSfROS, Z.-Soos, R.-FOGASSY, E.-SZABO, G. T.-~IoL],;"\R, V.: Periodica Polytechn.
Chem. Eng.
4. BOEsEKEx, 1.-VER::lIY, C.-Bu?;GE, ::\I.-van ~IEEuwE],;, C.: Chim. 50, 1023 (1931) 5. BRow?;, E. Y.: Iowa State ColI. J. Sci. 11, 227 (1927)
6. Japanese Patent Ko. 1130
7. SALKHI~KIiX, A. P.-LAPKOVA~ L. B.-A_RESTE~KO~ A .. P.: Zh. prikl. khim. 28~ 216 (1955) 8. Japanese Patent 2'\0. 6113
9. Japanese Patent 2'\0. 137 755 10. U.S.A. Patent 2'\0. 2 407 066 11. Italian Patent 2'\0. 4399·1.7
12. ADRISA],;O, R.: BoIl. Sci. Facolt:i Chim. lnd. Bologna, 7, 88 (1949) 13. DI],;ELLI, 0.: Ann. Chim. Applicate 29, 4-18 (1939)
H. OK.mA, L.-~IORITA, S.-]\LI.TSUDA, 1.: Yakugaku Zasshi 86, 932 (1966) 15. British Patent 2'\0. 782 430
16. RYUICHI, K.- YUTAKA, M.: Bull. Chelll. Res. Kyoto Univ. 34, 250 (1956) 17. OK_,\.DO, 1.-KITA2IIURA, K.: Yakagaku Zasshi 87, 1273 (1967)
Prof. Dr. Zoltall Cs tROS Dr. Rudolf S06s
Dr. Elemer FOGASSY
Dr. Gabor Tamas SZAB6
6 Periodica Polytechnika CH. 18/3
) H·!52! Budap'"
