714
Ind. Eng. Chem. Prod. Res.
(46) Schott, H. J. Pherm. Sci. 1969, 58, 1443. (47) SMnOde, K. "Colloidal Surfactants"; Academic: New York, 1963; Chapters 1 and 2. (48) . . Shinoda, K. "Solvent Properties of Surfactant Solutions"; M. Dekker: New York, 1967; Chapter 2. (49) Shbmda, K. J . Co/bU Interface Sci. 1967, 2 4 , IO. (50) Shinoda, K. h. 5th Int. Congr. Surface Active Substances, Barcebna. 1968, 2, 275. (51) Shinoda, K.; Takeda, H. J . Colbkj Interface Sci. 1970, 32, 642.
Dev. 1981, 20, 714-719 (52) Sunderland, V. B.; Enever, R. P. J. Pharm. phSrmaco1. 1972, 2 4 , 808. (53) Tanford, C. J . Phys. Chem. 1979, 78, 2469. (54) Weiden. M. H. J.; Norton, L. B. J . Co//oklScj. 1953. 8. 606.
Received for review October 30, 1980 Revised manuscript received June 1, 1981 Accepted June 23, 1981
Smokeless Fuel from Carbonized Sawdust Snehalatha K. Chembukulam, Arunkumar S. Dandge, Narasknhan L. Kovllur, Rao K. Seshaglri, and R. Valdyeswaran Regional Research Laboratory, Hyderabad 500009 (CSIR), India
Sawdust from five types of wood was carbonized at 600 'C. Carbonization of teak wood sawdust was studied in detail and the temperature required for producing char suitable for use as smokeless domestic fuel was arrived at. The tar, pyroligneous liquor, and gas emanating from carbonization were subjected to thermal cracking on firebrick pieces, before condensation. Effect of temperature of cracking on the yield and quality of gas was studied. Cracking over semicoke/charcoal at 950 OC resulted in almost complete decomposition of tar and pyroligneous liquor into gas of low calorific value. From the enthalpy balance for the cracking process the endothermicity of the process was evaluated. Conceptual schemes for the cracking of tar and pyroligneous liquor are presented.
Introduction It is estimated that about two million tons of sawdust less than 1mm in size is produced in India as a byproduct in the timber industry. Though a part of it is used in particle board industry, and some directly as fuel, a major portion still remains unutilized and its disposal is a serious problem faced by the timber mills. Briquetting of sawdust to make logs (Sadakichi, 1969) for use as domestic fuel is not a solution as it leads to atmospheric pollution during combustion. Carbonization of sawdust followed by briquetting of residual char ( S t a " and Harris, 1954) to get a smokeless fuel appears to be attractive. The char can also be used for the preparation of activated carbon (Hassler, 1951). In the context of the present energy crisis, production of smokeless fuel for domestic use from waste of a renewable source such as wood deserves serious consideration in a country like India. The volatile products obtained from the carbonization of sawdust consist of wood tar, pyroligneous liquor containing acetic acid, methanol, formic acid, etc., and noncondensable gas comprising mainly COz,CO, Hz, and CHI. The composition of pyroligneous liquor was studied and various methods have been suggested for the recovery of chemicals (Klar, 1925; Piret de Bihain and Padaki, 1978). However, these methods are not economically attractive compared to the synthetic routes unless the processes are carried out on a sufficiently large scale. The pyroligneous liquor which constitutes a major percentage of the volatile products, is highly acidic (pH 4) and its handling poses corrosion problems. Its disposal through biological oxidation is problematic because of the high biological oxygen demand value. Wood tar, which is the next major component of the volatile products, is also acidic and its use as fuel poses corrosion problems. To avoid problems involved in profitable utilization of the tar and pyroligneous liquor, one method that could be adopted is to subject them to cracking before condensation so that a gaseous product of fuel value and negligible 0196-4321/81/ 1220-07 14$01.25/0
amounts of liquid products are obtained. This will be more suitable when the carbonization is done on a small scale. The gas obtained can be used as a fuel in boilers or furnaces. No work appears to have been carried out on the cracking of the volatile products of carbonization of sawdust, before condensation, to get a gas of fuel value. The present paper describes the experiments carried out on carbonization of sawdust followed by the cracking of the resulting vapor and gaseous products before condensation, so that char suitable as smokeless domestic fuel and gas suitable for industrial use are obtained and liquid products are eliminated. Materials and Methods Sawdust collected from different types of locally available wood was used in these studies. The apparatus used for the carbonization experiments was similar to that used for low-temperature carbonization assay of coal (Himus, 1954; Campbell, 1951). It comprises of electrically heated tubular furnace (furnace no.1, Figure 1) a fused silica assay tube 300 mm long and 21 mm in diameter with a side tube 25 mm from the end, a U-shaped glass condenser (cooled externally with ice), and an aspirator of 10-L capacity with arrangement to maintain constant pressure. The procedure adopted for the carbonization experiments on sawdust was the same as that prescribed for coal except that: (i) the initial temperature of the furnace was maintained at 100 "C before it was brought onto the assay tube; (ii) the temperature of the furnace was brought to the desired level at the rate of 5 OC/min and then maintained for 1h; (iii) about 10 g of sample was taken for the experiments instead of 20 g. The temperature of first evolution of gas and the temperature of evolution of the oil vapor were noted. A t the end of the experiment the weight of charcoal, the weight of tar and pyroligneous liquor together collected in the condenser, and the volume of the gas collected in the aspirator, its temperature, and pressure were noted. The mixture of tar and pyroligneous liquor from the condenser were carefully washed with 0 1981 American Chemical Society
Ind. Eng. Chem. Prod. Res. Dev., Vol. 20, No. 4, 1981 715
Table I. Analysis of Samples of Sawdust from Local Wood local name: botanical name:
Teak Mango Neeredu Yegi Tecto na Mangifera Eugenium Pterocarpus grandis indica Jam bolanam indicus Proximate Analysis (Moisture Fkee Basis) ash, % 10.5 2.3 3.2 1.3 volatile matter, % 80.1 79.9 77.1 78.3 fixed carbon, % 9.4 17.8 19.7 20.4 Low-Temperature Carbonization at 600 "C (Yields/100 g of dry sawdust) charcoal, g 31.14 30.40 32.27 32.54 16.92 12.75 12.11 12.47 tar, g pyroligneous liquor, g 33.61 36.36 33.74 34.05 gas, Nm3 0.0141 0.0166 0.0165 0.0163 temperature of first 230 230 230 230 evolution of gas, "C temperature of 280 280 280 280 appearance of oil vapor, "C 33.8 1.2 3.6 22.6 12.6 4.8 21.4 calorific value of gas (calcd) MJ/Nm3
7.107
Composition of Gas, vol 9% 38.0 38.4 1.0 1.4 2.6 2.4 27.4 25.0 6.0 9.8 9.6 9.8 15.4 13.2 8.380
L
6
2
f
300 mm
6dm
'f' 6mm +'
I--l
150mm
Figure 1. Arrangement of apparatus for sawdust carbonization and cracking of vapor products: 1,furnace 1; 2,furnace 2;3,assay tube; 4,thermocouples; 5,sawdust charge; 6, firebrick pieces; 7,asbestos plug; 8,rubber bung; 9, connection to condensation.
several successive portions of toluene and the washings were collected in a microburet (graduated to read 0.05 mL). The organic portion and the pyroligneous liquor separated into two phases. The volume of the lower pyroligneous liquor layer was noted and ita weight was calculated assuming its density to be 1.OOO g/mL. By subtracting this from the total weight of tar and pyroligneous liquor, the weight of tar was obtained. Then the yields of charcoal, tar,pyroligneous liquor, and gas were calculated. In the experiments to get differential yields of liquid products and gas between certain temperature ranges, a modified condensation system to collect the fractions separately was used (Van Chzhao-Syun and Makavav, 1960). For the experiments on carbonization of sawdust and cracking of the vapor and gaseous products, the arrangement of the apparatus used is reproduced in Figure 1. Two separate furances were used for the carbonization and cracking sections. A weighed quantity of sawdust (previously dried a t 108 f 2 "C for 1h) was taken in the fused silica assay tube. Previously ignited and cooled asbestos wool was used for the plugs separating the carbonization and cracking sections. A weighed quantity of (about 30 g) firebrick pieces, 1-3 mm in size previously heated to 950 "C and cooled, was kept in between the plugs in the cracking zone. In some experiments, semicoke/charcoal of the same
8.937
36.4 1.0 2.6 27.0 7.2 9.2 16.6 8.305
Bandaru Adina Cordifolia
0.9 81.2 17.9 30.65 14.70 34.82 0.0153 220 280
41.0 1.2 2.6 26.0 6.0 7.8 15.4 7.710
particle size was used as packing material in the ciacking zone. The assay tube was then connected to the condensation system for condensing the tar and pyroligneous liquor, and the gas was collected in the aspirator. Furnace no. 2 was brought to the required cracking temperature and furnace no. 1 to 100 "C and they were maintained a t the respective temperatures. Furnace no. 2 was moved on to the cracking zone of the assay tube as quickly as possible. Furnace no. 1 was then brought onto the carbonization section of the assay tube. Its temperature was raised to 600 "C at the rate of 5 "C/min. At the end of 1h the heaters in both furnaces were switched off and the furnaces were moved away from the assay tube after the condensation system was disconnected. The weights of charcoal, tar, and pyroligneous liquor together, and the change in weight of the packing material were determined. From the total weight of tar and pyroligneous liquor the weight of pyroligneous liquor was determined adopting the same procedure as in carbonization experiments. The volume of the gas and its temperature and pressure were noted. From these, the yields of different products were calculated. Proximate analysis of sawdust and charcoal was carried out according to standard methods (I.S. 1350, 1965). The gas was analyzed in a modified ORSAT type of apparatus, for C02,C2H4, 02,and CO by the absorption in potassium hydroxide, fuming sulfuric acid, alkaline pyrogallol, and ammoniacal cuprous chloride, respectively, and for H2 and CH4 by combustion over cupric oxide a t 290 to 310 "C and 750 to 770 "C, respectively. The results obtained are presented in Tables I to IV. Results and Discussion Carbonization of Sawdust. Though the composition of individual woods differs to some extent, a general chemical formula and a two-stage decomposition was suggested for the carbonization. The primary decomposition gives rise to primary charcoal, primary tar, acetic acid methanol, liquor, and gases. During the secondary decomposition, the primary tar gives rise to oil, carbon dioxide, and secondary charcoal (Haegglund, 1944). The yields of total charcoal, tar, and pyroligneous liquor cal-
716
Ind. Eng. Chem. Prod. Res. Dev., Vol. 20,No. 4, 1981
Table 11. Carbonization of Teak Wood Sawdust (Yields per 100 g of Dry Sawdust) temp of carbonization, "C products
400
charcoal, g tar, g pyro. liquor, g gas, Nm3
40.7 16.1 29.3 0.0101
COZ C,H, 0 2
co
HZ CH4 N, (by difference) total
450 36.9 16.8 31.6 0.0105
Composition of gas, vol % 43.4 40.6 1.6 2.4 5.0 4.4 22.0 22.0 5.0 6.8 3.6 4.2 19.4 19.6
100.0
calorific value of gas (calcd) MJ/Nm3
33.8 1.2 3.6 22.6 12.6 4.8 21.4
100.0
100.0
5.797
600 31.1 16.9 33.6 0.0141
6.752
7.107
Proximate Analysis of Moisture Free Char ash, % 17.5 18.5 18.2 volatile 25.1 24.1 7.1 matter, % a (30.42) (29.57) (8.48) fixed carbon % 57.4 57.4 74.7 (by difference) 100.0 100.0 100.0 a
Figures in parentheses are on ash free basis.
Table 111. Differential Yields of Liquid and Gaseous Products from Carbonization of Teak Wood Sawdust temperature 100- 300- 400- 500- total range 300 400 500 600 "C "C "C "C charcoal, wt % 31.40 liquid products, 14.8 25.87 6.78 3.07 50.52 wt%
gaseous products, 0.0029 0.0043 0.0031 0.0036 0.0139 ~ m 3 / 1 0 0g of sawdust
culated according to the above do not agree with those obtained in industrial practice. According to another
proposal, the overall reaction of the carbonization of wood is reported as follows (Winnacker and Weingartner, 1952) 2C42H 0 2 8 3C1,jH&2 28H20 (woo8 100%) (charcoal, 34.7%) (liquor, 24.9%) 5C02 + 3CO + 2CH3COOH + CHBOH + C23H2204 (10.9%) (4.1%) (5.9%) (1.6%) (tar,17.9%)
-
The yields of charcoal and tar calculated according to this proposal were reported to be in agreement with those from industrial practice indicating the above reaction to be the correct one. The results of carbonization assay (Table I) of the present investigation are generally in agreement with the latter. Thus the yields are charcoal 30 to 32.5%; tar 12 to 17%;pyroligneous liquor 33 to 35%. The gas is a lean gas characterized by high contents of carbon monoxide and carbon dioxide. Methane and hydrogen contents are low. Detailed investigations were carried out on teak wood sawdust in order to get a charcoal that is suitable for use as smokeless domestic fuel. The temperature of carbonization was varied between 400 and 600 "C. At a carbonization temperature of 600 "C, the charcoal has 7.1% residual volatile matter (Table 11). The differential yields of liquid and gaseous products in the temperature ranges 100-300 "C, 300-400 "C, 400-600 "C, and 500-600 "C are given in Table 111, which show that a major portion of the liquid components are evolved in the temperature range 300-500 "C, while in the region of 500-600 "C more gas is evolved than liquid products. In Figure 2 the residual volatile matter in the charcoal, calculated on moisture and ash free basis, is plotted against the carbonization temperature on a logarithmic scale. The relationship between the two parameters can be expressed by an equation of the type log (VMR= 7.6815 - 2.382 log T. From this equation the temperature at which the residual volatile matter in the char is equal to that of the sawdust is 232 "C, which is also the temperature of initial decomposition of sawdust. This is in agreement with the observed temperature of 230 "C for the first evolution of gas (Table I). It is also in agreement with the finding in the literature which states that the decomposition of wood begins at about 180 "C and becomes rapid from 250 "C onward (Haegglund, 1944; Kollman, 1936; Framer, 1967). This confirms the validity of the relationship between
Table IV. Decomposition of Vapor Products from Carbonization of Teak Wood Sawdust (Carbonization Temperature, 600 "C) packing in cracking zone:
firebrick
firebrick
firebrick firebrick firebrick temp of cracking, "C
600
charcoal, g tar, g pyro. liq. liquor gas, N m 3 carbon deposit, g
cdorific value of gas, MJ/Nm3 thermal value of gas from a ton of dry sawdust (calcd), MJ a
semicoke
charcoal
950
950
950
31.1 16.9 33.6 0.0141 nil
800 850 900 Yields per 100 g Dry Sawdust 30.3 30.3 30.3 30.4 11.8 1.3 0.9 0.5 21.0 18.3 14.0 13.6 0.0303 0.0448 0.0550 0.0571 0.65 0.67 1.29 1.58
30.1 0.3 12.5 0.0621 1.28
28.0 nil 0.18 1.1738
28.4 nil 0.22 1.1574 b
33.8 1.2 3.6 22.6 12.6 4.8 22.4 7.032
Composition of gas, vol % 21.6 20.0 18.4 5.4 1.2 0.9 1.8 1.8 1.4 31.8 28.6 25.0 13.2 21.2 31.9 8.8 9.0 7.8 17.4 18.2 14.6 12.390 10.548 10.799
17.8 0.8 1.4 24.2 34.4 7.4 14.0 10.799
16.8 0.6 1.6 24.2 37.8 7.0 12.0 10.967
4.5
4.0
1.2 39.3 49.2
1.0 40.0 50.0
5.8 11.218
5.0 11.406
989
3752
6168
6775
13104
13138
11.8 g of semicoke was used up.
4723
5942
9.6 g of charcoal was used up.
a
Ind. Eng. Chem. Prod. Res. Dev., Vol. 20, No. 4, 1981 717
Scheme I. Cracking over Firebrick Pieces Corpsillon vel% CO2 15 7 02
05
Y
Hzo( v )
60.4 23
Total
100.0
31 11 Kg Chm coal 6 8 4 9 Kg Vopours and gas 65 25 Kg Combustion products
CRACKER(with fire
bKk)
-
950° C
I
47.78Kg Ai?
66 6 k g Product gas (Cracked gas)
17.47 Kg Product
/
as p
Composition Vd Vol of s u r w product gas 4 6 4 d C V of product gas A0.967MJ
Thermal value of surplus product gas
:505
/"3
MJ
5 Kg Condonvlta
0.22 Kg Tar 02
co H2
37.8
CH4
7.0
H 1m.00
3 0
eo
2 70 b
07
c1 20
\
I
1
3c
I
22
6C
g 5c g 4c
24
1091
26
iS
30
Figure 2. Residual volatile matter in charcoal vs. temperature of carbonization.
carbonization temperature and volatile matter in the charcoal. From this relationship the temperature of carbonization necessary to produce charcoal suitable for smokelew domestic fuel (assuming the m e volatile matter prescribed for semicoke, i.e., 15% on moisture and ash free basis-I.S.4286,1967) from sawdust works out to be 538
"C. Cracking of Vapor and Gaseous Products of Carbonization. Teak wood sawdust was carbonized at 600 O C and the vapor and gaseous products were subjected to cracking. From the results of Table 11,it can be seen that at a carbonization temperature of 600 O C , the yield of charcoal is 31.1% indicating that the balance of 68.9% of the feed material is given out in the form of vapor and gaseous products comprising tar,pyroligneous liquor, and gas. This formed the feedstock for the cracking experiments in which the temperature of the bed of firebrick pieces (packing material for cracking) was varied between 600 and 950 "C.From the results of Table IY,it is inferred that lower hydrocarbons such as ethylene and methane, CO, and H2were formed, as a result of thermal cracking over the firebrick pieces and also partly due to reaction
zc tC I
600
1
700 1
i
800 900 TEMPERATURE O C
I
a00
Figure 3. Degree of cracking vs. temperature.
of the pyroligneous liquor with tar. The formation of ethylene and methane was distinct at a cracking temperature of 600 O C . With increasing cracking temperature, the yield of ethylene and methane decreased. The absence of ethylene and methane in the product gas obtained by cracking over semicoke/charcoal at 950 O C may either be due to their decomposition as they are unstable a t that temperature (Kroeger, 1952) or due to conversion to CO and Hzby reaction with pyrolytic water originating along with tar vapors evolved during carbonization as in the case of carbonization of coal (Hesp and Waters, 1970). In the process of this cracking as well aa gasification, tar and pyroligneous liquor are converted to gaseous products. The intensity of this cracking-gasification (C), which may be defined for the purpose of the present discussion as (100- a ) - ( b + c ) x 100 c, = (100 - a ) where a is the yield of char (%), b is the yield of tar (%I, and c is the yield of pyroligneous liquor (%), which varies with the temperature (2") of cracking. The relationship
I
Corrposltlon Vd 01. CO2
16 4
02
04
N2
646
2 8 0 Kg Charcwl 72 0 Kg Vapwrs and gas
14
oe
-
CRACKER (with semlcoke) 950 O C
86 0
I
1
I
8 productgas ~ ~ (Cracked gas 1
99 15Q Air
0 19 Kg Cadensate V ~ I of . surplus product gas.83
39 3
C V of product g e = 11 218MJ INm3
Thermal value of surplus product gas= 940MJ
Scheme 111. Cracking over Charcoal Pieces
b
100 Kg SAW DUSl
i H20(v>18 7 ~
Total
I
-
I
1a.O
l-zzzZ3
71.6IQ Vapours and gas
124 21 Kg
-
I
9.6 Kg -cod
.
I
CRACKER (with charcoal) 950 O C
9 9 . U Kg Air
81.22Kg Rodrct gcs (cracked gas)
c
I
r L
0.15Kg Condensate
Vol of surplus product gas=eO 4N
Thermal value of surplus product gas= 917 MJ
'
I
N2 HZ
between these two parameters plotted in Figure 3 can be represented by an equation of the type C = 0.0893T 0.700. From this relationship, a complete dtecomposition of the tar and pyroligneous liquor can be expected at 1127 "C in a continuous process. Since the firebricks do not react with the tar and pyroligneous liquor vapors as they are inert, experimenta were conducted at a cracking tamperature of 950 O C using pieces of semicoke and charcoal, respectively, to find out if complete cracking can be achieved at this temperature. The results shown in Table IV gave a value of 99.8 and 99.7 for C, in the case of semicoke and charcoal, respectively. Since cracking and gasification are endothermic processes, an attempt has been made to evaluate the heat requirements for this process if it is to be commercially exploited. For this purpose, the tar, pyroligneous liquor, and gas are considered as feedstock. For the purposes of calculation of the enthalpy of the feedstock, the composition of the tar and liquor was assumed, based on those reported in the literature (Kollman, 1936). The temperature of the feedstock emanating from the carbonizer operating at 600 OC was assumed to be 550 OC €or the purpose
500 50
53 3 K g Surplus prodrdgas
of calculation. Under these conditions, the enthalpy of the feedstock was calculated to be 2258.4 kcal/kg. In a similar way, the enthalpy of the products, for cracking over firebrick pieces at 950 "C,was calculated to be 3025.6 kcal/kg of product. From these, the overall reaction is found to be endothermic and the heat of reaction for the process of cracking-gasification worked out to 767.2 kcal/kg of feedstock. Similarly, when the heat of reaction was calculated for cracking over semicoke and charcoal pieces, they worked out to 1091.6 and 1299.8 kcal/kg of feedstock, respectively. The higher values in the last two cases are probably due to the carbon of the semicoke and charcoal taking part in the water-gas and Boudard reactions resulting in a higher degree of cracking-gasification as reported above. B d on theae calculated heata of reaction, the following conceptual schemes are presented: (i) Scheme I: cracking over firebrick, (ii) Scheme II: cracking over semicoke, and (iii) Scheme 111: cracking over charcoal. In these conceptual schemes, under the steady state the heat requirements of the process are proposed to be met by the combustion of a portion of the product gas, with air. These
Ind. Eng. Chem. Prod. Res. Dev. 1981, 20, 719-721
conceptual schemes indicate that it may be possible to get surplus gas suitable for use in industrial heating. In a similar way, cracking over semicoke and charcoal gives more gas of similar quality. In these cases, however, 14.08 kg of semicoke and 9.6 kg of charcoal, respectively, are to be used for every 100 kg of sawdust carbonized. Conclusions Experiments on carbonization of sawdust showed that charcoal suitable for smokeless domestic fuel can be obtained at 538 OC. Cracking of the vapor and gaseous products of carbonization over firebrick, semicoke, and charcoal showed that the yield and calorific value of the gas can be increased. When semicoke or charcoal is used as packing material, tar and pyroligneous liquor are completely decomposed and the yield and calorific value of the gaseous products obtained are higher than those obtained by cracking over firebrick. Some carbon in semicoke and charcoal was used up. Acknowledgment The authors wish to express their thanks to the Director, Regional Research Laboratory, Hyderabad, for permission to publish the paper.
719
Literature Cited Campbell, J. R. “Methods of Analysis of Fuels and Oils”, Constable and Com pany Ltd.: London, 1951. Framer, R. H. ”Chemistry in the Utilization of Wood”, Pergamon Press: Oxford, 1967. Haeaaiund, E. “Holzchemie”, Akadamlsche Veriaa Geselschaft, M.b.H.: L a i6sg, 1944. Hassler, W. J. “Active Carbon”. Chemical Publishing Co.: Brooklyn, NY, 1951.
Hesp,-W. R.; Waters, P. L. Ind. Eng. Chem. Prod. Res. Dev. 1970, 9 , 195. Himus, G. W. ”Fuel Testing”, Leonard Hili Ltd.: London, 1954. Kiar, M. “The Technology of Wood Distillation”, Chapmann and Hall Ltd.: London, 1925. Kollman, F. “Technoiogle des Hoizes”, Verlag Julius Springer: Berlin. 1936. Kroeger, C. ”Grundrls der technische Chemie”, Part IV, Vanden Hoeck and Ruprecht: Gottingen, 1952. Methods of Test for Coal and Coke, I.S.1350;Indian Standards Institution, New Delhi, 1965. Plret de Bihaln, A.; Padakl, P. B. Chem. Age Indk, 1978, 29, 951. Processed Solid Smokeless Domestic Fuel, I.S. 4286,Indian Standards Institution, New Delhi, 1967. Sadakichl, K. 11th Biennial Conference of the Institute for Brlquetting and Agglomeration Proceedings, Aug 27-29, 1969. Stamm, A.; Harris, E. E. “Chemical Processing of Wood”, Chemical Publishing Co. Inc., 1954. Van Chzhao-Syum; Makavan, G. N. Coke-Si-Chimia, Apr 14, 1960. Wlnnacker, K.; Welngartner, E. “Chemlsche Technologie”, Organlsche Technoiogle, Carl Hamsa Verlag: Munich, 1952.
Receiued for review October 14, 1980 Accepted February 23,1981
Selective Conversion of D-Fructose to 5-Hydroxymethyl-2-furancarboxaldehyde Using a W at er-Solvent-Ion-Exchange Resin Triphasic System Luc Rigal, Antoine Gaset, and Jean-Pierre Gorrichon’ Laborafolre de Chimie Organlque et d‘Agrochimle, €cole Nationale Sup6rleure de Chimie, 118, route de Narbonne 31007 Toulouse Cedex, France
The propounded way of synthesis allows the dehydration of pfructose into 5-hydroxymethyl-2-furancarboxaklehyde (HMF). It implies the use of an ion-exchange resin as catalyst together with an extracting solvent. This system gives satisfactory yields when a macroporous strong acidic resin is used. Therefore, the development of such a system on a larger scale, in a dynamic state, could be considered.
Among biomass resources, carbohydrates are a plant raw material that is liable to be used for various chemical syntheses. 5-Hydroxymethyl-2-furancarboxaldehyde,2, a degradation product of hexoses in acidic media, is commonly occurring at low concentrations in various foods and could be an interesting starting material for the chemical industry. The search for new ways of synthesis of 2 is therefore of major interest, owing to the possible economical value of new processes (Nakamura, 1980;Nakamura and Morikawa, 1979). Previous work generally involved the use of an acid as a catalyst dissolved in the reaction medium. Drastic experimental conditions [temperature above 150 “C,high pressure (Kuster and Van der Steen, 1977;Kuster and Laurens, 1977;Morikawa, 1978; Garber and Jones, 1966)] are required so as to obtain satisfactory yields. The main difficulty lies in the control of the selectivity of the reaction leading to 2. The data reported here concern the dehydration reaction of D-fructose 1 (Scheme I). The procedure considered involves H+ ion-exchange resins as catalysts, together with a water-solvent biphasic 0196-4321/81/1220-0719$01.25/0
Scheme I. Dehydration Reaction of D-Fructose !H,OH
.
ti -C - O H
-
/‘
I
CH,OH
Byproducts
1
H C O O H + C H 3 C 0 CH,CH,COOH 4
-
3
liquid reaction medium: 2 is thus extracted as soon as it is formed; its possible breakdown to byproducts, particularly levulinic acid 3 and formic acid 4, within the aqueous phase, is thus kept to a minimum. The reaction selectivity is markedly improved by the presence of an organic solvent in the reaction medium, as shown by a comparison with the data of Schraufnagel and Rase (1975),who had investigated this reaction in aqueous media, favoring thus the formation of 3. Methyl isobutyl ketone is the extraction solvent; the water-solvent ratio is 1:9 (v/v). The 0 1981 American Chemical Society
