Ind. Eng. Chem. Process Des. Dev. 1903, 22, 445-452
and 1 eu, respectively (Benson, 1976). This accuracy leads to an accuracy of the equilibrium constants of about rt50%. For example, a change of 800 cal, less than 1% in the estimate of the free energy of formation of CH30CH20H at 298 K, results in the calculated 65% dissociation rising to about 70% of failing to about 60%. Both values are still in fair agreement with the experimental results of Hall and Piret (1949). In addition, Hall and Piret (1949) argue that water has little effect on the vapor phase equilibrim in reaction 1. Thus, their results for a methanol-formaldehyde system with a very small amount of water are applicable to the vaporized Methyl Formcel used in this study. The approximate agreement between the estimated and measured amounts of vapor phase dissociation products of CH30CH20Hsuggests that the largest hemiformal existing in vaporized methanolic formaldehyde at 403 K is the adduct CH30CH20H. The percentage concentration in the vapor of larger molecules containing methanol and formaldehyde should be small at these temperatures. Thus,each C - 0 4 stretch that contributes to the infrared spectrum found in the vaporized methanolic formaldehyde solution should arise from a different molecule. The conclusion that the majority of the adducts contain only one ether band means that the infrared spectroscopy results should give a direct measure of the vapor phase concentration of CH30CH20H. The data indicate that at 403 K the concentration of CH30CH20H in vaporized Methyl Formcel is about 7 mol % This amount is in good agreement with the equilibrium values shown in Table I11 and the 5 to 10 mol % value determined earlier by gas
.
445
chromatography. Thus, infrared spectroscopy has furnished direct evidence for the presence of the associated species CH30CH20H in vaporized methanolic formaldehyde solutions. From a process design standpoint, formation of this adduct must be considered when a process that handles vapor phase solutions of formaldehyde and methanol is to be designed or modified. Acknowledgment
We wish to thank Dr.George Barker for his assistance in developing the analytical portion of the reactor system. Registry No. Methanol, 67-56-1;formaldehyde, 50-00-0; methoxymethanol, 4461-52-3. L i t e r a t u r e Cited Babushkln, A. A.; Krylova. L. M.; Gorla, A. I. Russ. J . Phys. Chem. 1984, 38(10), 1276. Bellamy, L.J. ”The Infrared Spectra of Complex Molecules”, 3rd ed.; Chapman and Hall, Ltd.: London, 1975; Vol. 1. Benson. S. W. “Thermochemical Klnetlcs”, 2nd ed.; Wlley: New York, 1976. Cothulp, E. N.; Dab, L. H.; Wlberley, S. E. “Introduction to Infrared and Raman Spectroscopy”, 2nd d . ; Academlc Press, Inc.: New York. 1975. Hall, M. W.; Plret. E. L. Ind. Eng. Chem. 1949,40(6), 1277. Hlbben, J. H. J . Am. Chem. Soc. 1953,53, 2418. Lavrova, 0. A.; Matveeva, Zh. A.; Lesteva. T. M.; Pantukh, B. I.Russ. J . Phys. Chem. 1@75a,49(3), 373. Lavrova, 0. A.; Matveeva, Zh. A.; Lesteva, T. M.; Pantukh, B. I.Russ. J . Phys. Chem. 1975b,49(3), 389. Nielsen, H. H.; Ebers, E. S. J . Chem. Phys. 1937,5 , 823. Rekl, R. C.; Prausnltz, J. M.; Sherwood. T. K. “The Properties of Llquids and Gases”; McQraw-HI11 Book Co.: New York, 1977; Chapters 3. 4. Stull, D. R.; Westrum, E. F.; Slnke, G. C. “The Chemical Thermodynamics of Organic Compounds”, Wlley: New York, 1969. Walker, J. F. ”Formaldehyde”, 3rd ed.; Robert E. Krieger Publishlng Co.: Huntington, NY, 1975; and references contained therein.
Received for review June 21, 1982 Accepted November 2, 1982
Kinetics of Donor Solvent Liquefaction of Kentucky No. 6 Coal Edward Leonard and Harry Sllla’ Department of Chemistry and Chemical Enginwlng, Stevens Institute of Technoey, Hoboken, New Jersey 07030
A Kentucky No. 6 coal was liquefied In a well-mixed batch reactor under nonisothermal conditions in a solution of tetralin and decalin at a total pressure up to 7.5 MPa. Liquefied products were separated by liquid-solid chromatography into mixtures of compounds classified as aromatics, ethers, nitrogens, hydroxyls, and multifunctionals. Concentration-time data obtained with these classes of compounds were collected In low (337-390 “C) and hi@ (390-444 “C) temperature ranges. Three kinetic models were ftlted to the concentration-time profiles, but the model that fitted these data the best was the one in which the muttifunctional compounds were considered reaction intermediates which decomposed reversibly into aromatics, ethers, nitrogen, and hydroxyls. Aggregated coal was formed in the high-temperature range. The size and shape of these aggregates were dependent upon the reaction temperature and residence time.
Introduction
It has been shown by Mohan and Silla (1981) that liquid-solid chromatography (LSC)is a reliable and effective method for wparating coal liquefactionproducts for kinetic analysis. They liquefied Illinois No. 6 coal in a temperature range from 330 to 450 “C and separated the liquefied products into five components, namely, aromatics, ethers, nitrogens, hydroxyls, and multifunctionals. The relationship between these compound classes and the definitions of the product fractions based on their solubilities in various solvents, i.e., preasphaltenes, asphaltenes, and oils,
is not clear. An attempt to determine the relationship was made by Mohan and Silla (1981). Because significant qualitative differences in concentration-time profiles for the multifunction compounds were observed at high and low temperatures, the entire experimental range was divided into a high-temperature range (390-450 “C) and a low-temperature range (337-390 “C). It was found that when Illinois No. 6 coal was liquefied in the high-temperature range the multifunctionals reached a peak concentration at a short residence time, but no peak was observed in the low-temperature range. Several kinetic 0 1983 American
Chemlcal Society
448
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 3, 1983
Table I. Chemical Analysis of Kentucky No. 6 and Illinois No. 6 Coals
mass%
(moisture-freebasis)
proximate
component volatile matter fixed carbon ash
ultimate
hydrogen carbon
nitrogen
sulfur (total) oxygen ash
KY
No. 6" 40.1 52.8 7.1 5.2 75.2 1.7 2.6 8.2 7.1
0.24
1
IL No. 6 b 42.3 45.2 12.5 4.8 68.9 1.2 3.7 8.9 12.5
Analysis supplied by the Department of Energy.
Mohan and Silla (1981).
0
-0
0
0
0.06
t
I I 10
1
I
I
i
I
M
I
20
8
50
e4
10
Rmclim Tim, Min
Figure 1. Desulfurization of Kentucky No. 6 coal.
models were tested in order to obtain the best fit to the experimental concentration-time profiles by use of a nonlinear parameter estimation technique. The best fit to the experimental data was obtained when the multifunction& were considered reaction intermediates which then decomposed reversibly into aromatics, ethers, nitrogens, and hydroxyls. The objectives of this investigation were to confiim the presence of the multifunctional peak and to determine the best kinetic model using a significantly different bituminous coal. Kentucky No. 6 coal was selected because it is a bituminous coal having a lower ash and sulfur content than the Illinois No. 6 coal. The composition of both coals is given in Table I.
Experimental Section The reactor system and experimental procedures used in the experiments discussed here are essentially the ones described by Mohan and Silla (1981). Any modification or improvement made in their procedure will be discussed and the reasons for any change will be indicated. As in Mohan and Silla's (1981)work the c d was dried, ball-milled, sieved through a 200 U.S.-standard mesh screen, dried to constant weight, and then stored in a desiccator under a nitrogen atmosphere. The same supply of technical grade tetralin, containing 25 mol % decalin and less than 1.0% naphthalene, was used in these experiments. Significant reaction can occur during the long heat-up and cool-down times in the reactors employed in coal liquefaction kinetic studies. The reactor system used in this work consists of a l-Lvessel, a 15oo-rpm stirrer, and a coal slurry injection system designed to minimize the nonisothermal heat-up time. A typical temperature history for an experiment is given by Mohan and Silla (1981). The temperature histories in these experiments are essentially the same. In spite of the efforts made to eliminate the nonisothermal conditions, a calculation procedure, which is described by Mohan and Silla (1981),was required to account for the nonisothermal conditions. After charging with tetralin and purging with nitrogen, the reador is heated to a steady-state temperature. A coal slurry was then injected into the hot tetralin using nitrogen at 30 atm, and the mixture was allowed to react for a specified time. The pressure rises during the reaction to a final pressure of 44 to 68 atm depending on the experimental conditions. The reaction mixture was then quenched and the liquid mixture was separated from the solids by filtering through a Soxhlet thimble rather than using a centrifuge as employed by Mohan and Silla (1981), which simplifies the procedure somewhat. After filtering,
most of the decalin, tetralin and its reaction products, naphthalene and dihydronapthalene, are removed by vacuum distillation. The bottoms product from the vacuum distillation step is then separated by liquid-solid chromatography using alumina into aromatics, ethers, nitrogens, hydroxyls, and multifunctionals.
Results and Discussion Experimental concentration-time data were collected in high (390-444 "C) and low (337-390"C) temperature ranges because significant qualitative differences in the concentration-time profiles for the multifunctional compounds were observed at high and low temperatures. The temperature range is defined as the minimum temperature the reaction mixture reachea after injection, i.e., 337 or 390 "C,and the final temperature just prior to quenching the reaction, Le., 390 or 444 "C. Reaction times of 5, 10,15, 17.5, 20,25,30,40,50,and 60 min were selected for the experiments. Reaction times of less than 5 min were not considered because of the time required for injection and quenching. After 60 min, the reaction reached steady state. The extent of desulfurization,coal conversion, and product formation for each temperature range is discussed below, and the formation of solids in the high temperature range is described. Coal Desulfurization. The extent of desulfurization is the ratio of the mass of sulfur removed as H2S to the total sulfur content. The maximum desulfurization of 27.8% in the Kentucky No. 6 coal (2.6% sulfur) occurred at the high-temperature range at a residence time of 60 min. Mohan and Silla (1981)report the maximum desulfurization for Illinois No. 6 coal (3.7% sulfur) was 18.8%, which occurred in their high-temperature range (390-450"C) at a residence time of 60 min. The extent of desulfurization for Kentucky No. 6 coal was consistently greater than for Illinois No. 6 coal. The difference in iron pyrite (FeS2)content and other inorganic compounds in these coals may account for the difference in the extent of desulfurization. The mass fraction sulfur removed versus residence time is plotted in Figure 1. Solids Formation. It was found that an excessive quantity of solids was formed in the high-temperature range with the Kentucky No.6 coal. These observations are summarized in Table II. As discussed by Wakeley et al. (1979)and Painter et al. (1979),carbonaceous solids formed during coal liquefaction may be classified as solids obtained from unreacted or partially rea& macer&, and semi-coke formed by retrogressive reactions where soluble compounds polymerize. In addition, inorganic solids
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 3, 1983 447 Table 11. Description of Solids Formation during Liquefaction of Kentucky No. 6 Coal temp residence run no. range,"C times, min remarks
6,12,7,5, 337-390 10,17.5,25, 11,lO 40,50,60 4,8,9,13 356-400 5,10,15,20 3 375-429 40
no aggregation
no aggregation spherical particles, 0.1-2 mm no fine powder4 15,2,18,1, 392-444 5,10,10,16, irregular shaped 16,14,7 15,15,30, 60 particles 0.2 to 1.0 cm fine powdera 16 392444 5 reactor bottom covered with solids fine powdera
Fine powder believed to be unreacted or partially reacted coal.
Figure 2. Cad solids formed in the intermediate temperature range (375-429 "C); run 3; residence time 40 min.
formed from the seed coal consist of unaltered minerals, minerals which undergo fragmentation and changes in hydration, minerals which undergo chemical changes, and minerals which form in the reactor. Three runs were carried out in the low-temperature range (337-390 OF). In these runs the unconverted coal appeared to the naked eye to be a fine powder the same size as the feed coal. Four runs were carried out in an intermediate temperature (355-400 "C) range. The particles in these runs appeared to be a fine powder the same size as the feed coal. Only one 40-minute run (run 3) was carried out in a second intermediate temperature range (375-429 "C) where the particles had aggregated into small somewhat spherical solids as shown in Figure 2. The particle sizes ranged from 0.1 to 2 mm in diameter and no powdered unconverted coal was found. All of the solids had aggregated. In the high-temperature range (390-444 "C) the solids formed were larger and irregular in shape as shown in Figure 3. The particle size of the solids ranged from 0.2 to 1.0 cm and a fine powder. In run 15, having a residence time of 5 min, a solid mass of unconverted coal was found adhering to the bottom of the reactor, but when washed with tetrahydrofuran and stirred a t 1500 rpm, the mass broke apart. In runs of longer residence times this carpet of aggregated coal was absent. In the kinetic analysis all the carbonaceous solids collected were considered unconverted coal, since it would be very difficult or impossible to separate unconverted coal from the solids formed.
Figure 3. Coal solids formed in the high-temperature range (392-444 "C); run 14; residence time 30 min.
R
m Tkw. M h
Figure 4. Conversion of Kentucky No. 6 coal during liquefaction. Table 111. Comparison of Kinetics Parameters for Conversion of Kentucky No. 6 and Illinois No. 6 Coals limiting act. frequency temp conversion, energy, factor, range, "C Xe kcal /g -mol min-' Kentucky No. 6
337-390 392-444
0.70 0.75
330-390 390-450
0.75 0.88
20.0 18.8
3.17 x 1 0 5 2.92 xi05
Illinois No. 6
18.2 19.1
1.86 x 105 3.53 x los
Coal Conversion Kinetics. Coal conversion is determined from the residue, WR,which is insoluble in tetrahydrofuran, on a moisture and ash free (MAF) basis and is given by X =
wC-
wR
WC
where Wc is the mass of feed coal (MAF). If a first-order irreversible reaction for the conversion of the coal is assumed, the kinetic model is
-dx-- -k[x, - x ] dt
x(0) = 0
(3)
where xb, the conversion obtained at long residence times, is a function of temperature. The experimental data are
448
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 3, 1983 1.o 337.392 OC Ky No. 6 Coal 10 kg Solventlkg Coal Solvent: 75% Tetralin, 25% Decalin
0.8
U
9
$
.-
0.6
i
Multifunctionalr
U
I
E
.-c$
0.4
E
EP 0
0.2
r Hydroxyls
-
30
40
--.-.-
I
10
-0
20
50
eo
Reaction Time, Min
Figure 5. Comparison of kinetic model 1 with experimental product concentrations in the low-temperature range. 1.o
337-360 oc Ky No.6 Coal 10 kg Solvent/kg Coal Solvent: 75% Tetralin, 25% Decalin
H(0)
0.8
LL
a H c.-
C(.)-M(Ol
.\
0.6
I
Multifunctionals
U
EI
-
\
0.4
O ~ --O -O -
--
C'
.-
t
4.
f
8
0.2
0 0
10
20
30
40
50
60
Reaction Time, Min
Figure 6. Comparison of kinetic model 2 with experimental product concentrations in the low-temperature range.
treated mathematically by a parameter estimation technique, which is discussed by Mohan and Silla (19811, and are plotted in Figure 4. The parameters that best fit the data are given in Table 111. The values of the kinetic parameters for coal conversion in both temperature regions are compared with Illinois No. 6 coal reported by Mohan and Silla (1981) a~ can be seen in Table III. The activation energies agree reasonably well with the value given by Han et al. (19781, who report an activation energy of 18.7
kcal/g-mol for bituminous coals. Coal Liquefaction Kinetics. As described earlier, the reaction system consists of unreacted coal (C)and the liquid coal products which were separated according to their chemical functionality into mixtures of compounds, classified as aromatics (A), ethers (E), nitrogens (N), hydroxyls (H), and multifunctionals (M). By use of these classes of compounds, three kinetic models, suggested by Mohan and Silla (1981), were tested to obtain the best fit
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 3, 1983 1.o
449
337.392 OC 10 kg Solventlkg Coal Solwnt: 75% Tetralin, 25% Decalin
C(.)
0.8
U
a
I
.d
F
0.0
LL
B
I
Multif unctionals
0.4
i
8
Hydroxyls
0.2
0
0
0
Nitrwns
0
10
0
20
I 30
A
I 50
40
60
Reaction Time, Min
Figure 7. Comparison of kinetic model 3 with experimental product concentrations in the low-temperature range.
to experimental nonisothermal concentration-time profiles using a nonlinear-parameter-estimation technique. The kinetic models were obtained by an instantaneous differential material balance on each class of compounds. In all these modela the reaction steps are assumed first order and the kinetic parameters, the frequency factor, and the activation energy were estimated for each reaction step. T h e minimum sum of squares of the residuals between the models and the experimental data is employed as the criterion of "best fit". The parameter estimation technique used in this work is identical with the one described by Mohan and Silla (1981). Kinetic model one, shown in eq 4, consists of a serieshydroxyls
Table IV. Kinetic Model Discrimination by Use of Remession Analysis sum of squares of residuals high-temp low-temp kinetic scheme
(392444 "C)
(337390 "C)
0.1880
0.0669
0.0279
0.0060
H
1.
C-M,
IN \ E
A H
(HI nitrogen ( N ) k
, coal
(c)
muitifunctionais (M) 'MA
I
y
b.
(4 1
ethers ( E )
1
Multifunctionals are not represented as reaction intermediates; thus the model does not apply.
aromatics ( A )
parallel reaction scheme where the multifunctionals are considered reaction intermediates. In this model each reaction step was assumed first order and irreversible. Kinetic model two, shown in eq 5, is similar to model hydroxyls
the coal degradation step. Again, each step was assumed first order. Finally, kinetic model three (eq 6) was also considered. multifunctionals ( M )
(H) hydroxyls ( H ) coal ( C ) nitrogens (N) ethers ( E )
II aromatics (A)
one except that all the reaction steps are reversible except
aromatics ( A )
This model, consisting of parallel and irreversible firstorder reactions, is proposed to account for the slower rate of formation of multifunctionals in the low-temperature
450
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 3, 1983 1.o
392444 o c Ky No. 6 Coal 10 kg WvenVkg Coal Solvent: 75% Tetralin, 25% Decalin
I f
H(0)
0.8
(0,
&N
c ( 0 ) -M(O)
LL
9
o*6
LL
-\
D
I
i!8
h
r Multifunctionals
F
0'4
Aromatics
-n-
s
0
0.2
n 10
20
40
30
60
50
Reaction Time, Min
Figure 8. Comparison of kinetic model 1 with experimental product concentrations in the high-temperature range. 1.0 &
392444 oc Ky No. 6 Coal 10 kg SolvmVkg Coal Solvent: 75% Tetralin. 25% Decalin
C(.)-M(O) LL
5" ee
0.6
A(.)
U
D
z
I /
s
r Multifunctionals
\Y
\
1
0
d
UnreactedCoal
0.2
0 t
Nitrogenr-)
r Ethers 0 0
10
20
30
I
I
40
50
3n A 80
Reaction Time, Min
Figure 9. Comparison of kinetic model 2 with experimental product concentrations in the high-temperature range.
range. Low-Temperature Liquefaction. AI1 three models were fitted to the experimental concentration-time data, and as can be seen in Table IV,model one does not fit the data as well as models two and three. Model one is compared with the experimental data in Figure 5, model two in Figure 6, and model three in Figure 7. A good fit to the experimental concentration-time data was obtained with both model two and three, but model two fits the data better than model three, as is seen by the lower value of
the s u m of the squares of the residuals given in Table IV. The better fit, however, may be due to the greater number of kinetic constanb in model two. High-TemperatureLiquefaction. Both Illinois No. 6 and Kentucky No. 6 coals show a "peak" in the multifunctional concentration-time experimental data in the high-temperature region at short residence times. The data for Kentucky No. 6 are shown in Figure 8. Mohan and Silla (1981) have suggested that the multifunctionah are reaction intermediateewhich decompose reversibly into
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 3, 1983 451 1.o
0.8
6 0.6
1
U
0
f
EI
0.4
Illinois No. 6 Coal 330.390 %
1 .
(573
0
0 -
5
0
Kentucky No. 6 Coal 337390 OC
0.2
0
I
I
10
20
I 30
I 40
I 50
I 60
Reaction Time, Min
Figure 10. Comparison of kinetic model 2 with experimental multifunctional concentrations in the low-temperature range for Illinois No. 6 and Kentucky No. 6 coals. 1.o
0.8
U
36 0.6
I
-
0
.
U
0
t
$ 0.4
E s5
i o 0
0
0.2
0
L
Kentucky No. 6 Coal 392444 OC
10
20
40
30
50
60
Reaction Time, Min
Figure 11. Comparison of kinetic model 2 with experimental multifunictional concentrations in the high-temperature range for Illinois No. 6 and Kentucky No. 6 coals.
aromatics, ethers, nitrogens, and hydroxyls. Concentration-time profdes are compared with the experimental data for the high-temperature region for model one in Figure 8 and for model two in Figure 9. Model two fib the data best, which is confirmed by a lower value of the minimum sum of squares of the residuals shown in Table IV.
Conclusions It was found by Mohan and Silla (1981), for the liquefaction of Illinois No. 6 coal, that the multifunctional compounds peak in the high-temperature but not in the low-temperatureregion. This observation was also verified for Kentucky No. 6 coal 18.6 can be seen by comparing Figures 10 and 11. Mohan and Silla (1981) proposed that
Ind. Eng. Chem. Process Des. Dev. 1083, 22, 452-457
452
V. Summary of R a t e Parameters Obtained from Kinetic Model 2. Kentucky No. 6 C o a l high-temp range low-temp range (392-444 “C) (337-390 “C) rate parameter Aa Eb A E
Table
kCM kMH kHM kMN kNM
ME
kEM kMA
AM
9.80 2.45 3.35 9.49 1.96 3.27 2.26 6.66 1.04
X
lo5
x 10’ x lo5 X X X
lo4 lo5 10’
lo6 lo4 X lo5 X X
19.6 19.7 19.7 19.8 19.5 19.6 19.6 19.7 19.7
6.02 X l o 5 3.91 x 10’ 8.34 x l o 5 1.10 X105 4.61 X i o 5 3.09 X 10’ 2.86 X l o 6 9.95 X l o 5 4.93 X l o 6
Frequency factor parameter, min-’. energy parameter, kcal/g-mol. a
19.6 19.6 19.4 19.2 18.6 19.8 19.9 19.6 19.4
Activation
the large polar multifunctional compounds are intermediates which are formed by the initial breakup of the “coal molecules”. These multifunctional compounds are later converted into smaller and less polar compounds. Kinetic model two has been shown to describe this observation satisfactorily and to describe the coal liquefaction kinetics in the low-temperature region as well for Kentucky No.
6 coal and by Mohan and Silla (1981) for Illinois No. 6 coal. Model two, which does not account for retrogressive reactions, appears not to be affected by the observed solids formation in the high-temperature region, most likely because the amount of solids formed is small. The optimum kinetic parameters for model two are shown in Table V. The activation energy for all the reaction steps ranges from 18.6 to 19.9 kcal/g-mol. Mohan and Silla (1981) report activation energies of 17.2 to 29.3 kcal(g-mol for Illinois No. 6 coal. Acknowledgment The suggestions and help given by Dr. G . Mohan of Becton Dickinson Co., NJ, are appreciated. Registry No. Tetralin, 119-64-2; decalin, 91-17-8.
Literature Cited Han, K.; Dixit, V. 8.; Wen, C. Y. Ind. Eng. Chem. Process Des. Dev. 1976, 17, 18. Mohan, G.; Silla, H. Ind. Eng. Chem. Process Des, D e v . 1981, 20, 349. Painter, P.; Yamada, Y.; Jenkins, R. G.; Coleman, M. M., Walker, P. L., Jr. Fuel 1979, 58, 293. Wakeby, L. D.; Davis, A.; Jenkins, G.; Mltchell, G. D.; Walker, P. L., Jr. fuel I979* 58, 379.
Received for review December 28, 1981 Accepted September 23, 1982
Recovery of Ethanol from Fermentation Broths by Catalytic Conversion to Gasoline Davld R. Whitcraft,+ Xenophon E. Veryklos, and Rajakkannu Yutharasan’ Depaflment of Chemical Engineering, Drexei Unlversity, Wladeiphia, Pennsylvania 19 104
The technical and economic feasibility of recovering ethanol from fermentationbroths by catalytic conversion to gasollne was investigated. Reactkns of diethyl ether, ethanol, and aqueous 95 wt % ethend over a shapsselecthre zeolite catalyst were studled In terms of product distributions, and the effects of pressure, temperature, and space velocity were established. Higher pressure was found to decrease the amount of gaseous hydrocarbons produced, while increasing the space veioclty had the opposite effect. An optimum temperature of 623 K was found to maximize the amount of liquid paraffins and aromatics with a corresporiding minimum in gaseous hydrocarbons. No significant effect of the presence of water in the feed stream was observed. A prelhninary analysis revealed that the proposed process could offer significant economic advantages over traditional processes of ethanol recovery.
Introduction In view of the national and international critical energy situation, non-petroleum materials are expected to become important energy sources during the next several decades. Particular attention has been directed in recent years tuward the utilization of coal as an alternative energy source. The difficulties and the environmental problems associated with the direct use of coal as a fuel are well-known. A second alternative for energy production from non-petroleum materials is offered by biomass utilization. Biomass represents the only replenishable, environmentally acceptable energy resource which could be developed and become available as a near to mid-term option. Research efforts in this field were undertaken in the period during ‘Joseph E. Seagrams & Sons Inc., Relay, MD 21133.
and after the second World War and have been intensified in recent years of energy scarcity. Thus, today, biomass is looked upon as an abundant, renewable, and attractive feedstock for both direct and indirect production of energy, chemicals, and intermediates. The first step toward the utilization of biomass as an energy source involves the production of ethanol from biomass. This process can be carried out in three steps: (1) pentosan hydrolysis of cellulose to fermentable sugars (glucose), (2) fermentation of pentosans and hexosans to alcohol, and (3) recovery of alcohol from the fermentor broth. The last step is the most energy-intensive one, primarily because ethanol is produced in small concentrations (typically 8-10 w t %) in the fermentor broth and because of the existence of an azeotrope in the ethanolwater system at an ethanol concentration of about 95 w t %. Thus, from the purely economic point of view, the use 0 1983 American Chemical Soclety
