I N D U S T R I A L A N D E N G I N E E R I N G ClH E M I S T R Y
March 1950
467
using nonvolatile organic liquids such as the giycols, or by previously suggested salting-out techniques, work on a pilot plant scale will be necessary. This will involve a comparison of the over-all cost of operation, including solvent recovery, with current industrial techniques for the production of the salt. Continuing the investigation of the method proposed in this paper should include a thorough survey of other nonvolatile solvents. The solvent desired should combine the best characteristics of possible reversal of the sodium sulfate solubility curve, corrosiveness, volatility, and cost. LITERATURE CITED
(1) Cole, L. H.,Canadian Dept. Mines, Bull. 646 (1926). Figure 7. Relative Scaling on Heating Surface in Crystallizing (2) Douglass, E. W.,and Anderson, C. O., Chem. & Sodium SuIfate from Aqueous and Ethylene Glycol Solutions Met. Eng., 48,No.5, 135-7 (1941). 3) Gee, E.A., J. Am. Chem. SOC.,67,179-82 (1945). A . Original heating coil 4) Gee, E. A., Cunningham, W. K., and Heindl, B . After 5 hours’ heating in saturated aqueous sodium sulfate solution C. After 5 hours’ heating in aqueous ethylene glycol solution saturated with R.A., IND.ENG.CHEM.,39,1178-88 (1947). sodium sulfate (5) Kobe, K. A.,and Hauge, C. W., Can. Chem. Met., 18,177 (1934). (6) Seidell, A., “Solubilities of Inorganic and Metal-Organic Commenb were carried out in a somewhat larger apparatus. Idenpounds,” 3rd ed., Vol. I, pp. 1300-2,New York, D.Van Nostical 650-watt copper coil-type immersion heaters were subtrand Co., 1940. merged in saturated aqueous and 75% ethylene glycol solutions (7) Smits, A.,and Wuite, J. P., Proc. A m t e r d a m A k a d . , 12,244-57 contained in 5-gallon glass cylinders. Figure 7 shows the extent (1909). of scaling after the solutions had been held a t several degrees (8) Thompson, A. R.. and Molstad, M. C., IND. ENC.CHEM.,37, 1244-8 (1945). below their boiling points for about 5 hours. (9) Trimble, H., and Potts, W., Ibid., 27,66-8 (1935). CONCLUSION (10) Vener, R.E.,and Thompson, A. R., Ibid., 41,2242-7 (1949). (11)Ibid., 42, 171 (1950). These small scale studies indicate that anhydrous sodium sulfate can be crystallized in a variety of forms- by the use of REOBIVED July 26, 1949. Based on a dissertation presented by Raymond organic liquids. To evaluate the economic feasibility of its E. vrnerto the Graduate School, University of Pennsylvania, in partial A
C
B
t
crystallization either by the method proposed by the authors,
fulfillment of the requirements for the degree of doctor of philosophy.
Thiophene from Hydrocarbons and Sulfur Dioxide R. E. CONARY, L. W. DEVANEY’, L. E. RUIDISCH, R. F.
MCCLEARY, AND
K. L. KREUZ
The Texas Company, Beacon, N . Y . Thiophene may be prepared from hydrocarbons and sulfur dioxide over catalysts such as molybdena-alumina, chromia-alumina, vanadia-alumina, molybdenum sulfide-alumina, and activated silica. Production of thiophene is greatest from the normal Ca hydrocarbons especially from the olefins. When using hydrocarbons containing more than 4 carbon atoms in a straight chain, alkyl thiophenes and thiophene itself are formed. The use of a fluidized catalyst system is highly advantageous in handling the exothermic reactions involved in thiophene preparation and catalyst regeneration.
M
ANY different methods for the synthesis of thiophene and
its derivatives have been published. The most important of these methods involves either the reaction of a compound such as sodium succinate with a sulfide of phosphorus or the reaction of sulfur with a hydrocarbon. Morton (6) has stated that reactions of the first type can be carried out with phosphorus trior pentasulfide and any diketone, keto acid] anhydride, or sodium 1
Present address, Baylor University, Waco, Tex.
salt which can theoretically change to a 1,4dienol system. A recent development in the treatment of hydrocarbons with sulfur has been described by Rasmussen, Hansford, and Sachanen (7). No references have been found relating to the preparation of thiophene compounds by the reaction of hydrocarbons and sulfur dioxide. OPERATIONS IN A FIXED BED SYSTEM
In the present work the reaction of hydrocarbons and sulfur dioxide to form various thiophenes was carried out first in a fixed bed catalytic reactor setup (Figure 1). It consisted of a reactor 47 inches in length made from 1-inch stainless steel (18-8) pipe with an axial thermowell of 0.125-inch stainless steel (18-8)pipe extending up from the bottom for 22 inches, and of charge, scrubbing, and collecting systems as shown. The two reactants, completely vaporized by passage through the preheaters, were then mixed and brought to the desired temperature in the upper portion of the reactor tube which was packed with glass wool. Then the mixture was passed through the catalyst bed which occupied the lower portion of the reactor tube. The effluent from the reactor was passed through condensers cooled with ice water which liquefied most of the thio hene and water produced by the reaction. The gaseous effluent 8 o m the product
INDUSTRIAL AND ENGINEERING CHEMISTRY
468
PROPERTIES OF THIOPHCSE ASD ITS HOMOLOGS TABLE I. PHYSICAL B.P., Obsvd. 84.3 112.7
Thiophene 2-Meth 1 thiopxine 3-Methylthiophene
114
Lit. 84.12 112.5
Refractive Index, n2,0 Obsvd. Lit. 1.5288 1.5287 1,5202 1,5203
115.4
1.5195
0
c.
1.5204
~~
Density, G./MI., 20° C. Obsvd. Lit. 1.0652 1.0644 1.0163 1.0194 1.016 1.0195 1.0216
143-4 3,4-Dimetbyl149 145.51.5198 ,, , 0.9993 0 , 9 8 9 thiophene 148.5 2,5-Dimethyl136-7 ... 0,985 thiophene 13&i40a 1.SO92 ,, , 0.9812 2-Ethyl. . . 132-4 . . . ,, . o.'ii2 thiophene 5 Value for mixture of 2,5-dimethylthiophene and 2-ethylthiophene.
i
...
Mercuric Chloride Derivative, M.P., O C. Obsvd. Lit. 183-4 182-3 204-5 204 128
128-9
136
137-8
156-7
ld6-7
iiG7
i4j-8
Vol. 42, No. 3
receiver was taken through a caustic trap where the acidic constituents were absorbed. From the caustic scrubbers the effluent gas passed through a glass wool trap to remove entrained material and through a meter to a storage cylinder or suitable gas sampling apparatus. The well-washed gaseous product was analyzed by mass spectrometry. The total amounts of sulfur dioxide and hydrocarbon charged were determined by the changes in weight of their charge cylinders. Their rates of feed were regulated by suitable flowmeters. At the end of the run nitrogen was passed through to purge the system.
The liquid products were rectified and the principal constituents present were characterized by the properties shown in Table I. In general, the TO VENT yields in this paper are on the basis of products of 95% purity or better. Thiophene has been prepared in varying amounts from many hydrocarbons as shown in Table 11. Best yields of thiophene were obtained from hydrocarbons having 4 carbons in a straight aliphatic chain. In the case of hydrocarbons cont'aining more than 4 carbon atoms per molecule, thiophene was formed in minor amounts, the chief product being a thiophene homolog having the same number of carbon atoms as the parent hydrocarbon. d number of materials were investigated as catalysts for thioW phene production with results as outlined in Table 111. These runs were all made charging n-butane and sulfur dioxide through CONDENSERS O'C. R E C E I V E R BATH 0% a Axed bed catalytic reactor cont,aining 200 cc. of catalyst a t 595" C., liquid butane space velocity of about 1.0 volume per PRODUCT RECEIVER volume per hour for a period of 2 hours each. These data inFigure 1. Fixed Bed Reactor System for dicate t,hat silica, molybdena-alumina, chromia-alumina, vanadiaProduction of Thiophene alumina, and molybdenum sulfide-alumina are all effec~. . tive catalysts for thiophene TABLE11. THIOPHENES FROV SULFUR DIOXIDE ASD VARIOUS€11DROCARBONS production. Carbon, Super HC Filtrol, and alumina are much Lb. Product/ Space 100 Lb. of poorer catalysts. Small yields VklocHydrocarbon Mo!e i t y Vol./ R u n of thiophene are obtained ConTemp., Ratio, ?oL/ Length, Charged sumed Catalysta C. SOz:HC Hr.6 Hr. Product Hydrocarbon (HC) even when the reaction zone 0.3 2.0 Thiophene 0.9 0.8 628c 615 Ethylene is packed with glass wool. 0.2 0.5 Thiophene 1.25 0.8 670° 655 Propylene 2 6 . 7 4 6.0 Thiophene 2 . 0 Runs made with catalysts 1.46 1.0 595 n-Butane ... ... Isobutened 2.0 1.5 1.0 595 Isobutane containing 20% chromia on 40.8 46.2 Thiophene 2.0 1.03 0.91 645 %Butene 34 50 Thiophene 2.0 0.9 1.0 595 %Butene alumina and 12% chromia 39 ... Thiophene 1.4 2.1 1.0 615 1-Butene 23.4 54.4 Thiophene 2.0 on alumina, respectively, 0.63 1.7 600 1,a-Butadiene 2 2 . 2 27.2 Thiophene 1 . 5 676 0.65 1.4 1,a-Butadiene showed the same yields as ... ... ... ... ... ... ... 70% butane 34.2 50.2 Thiophene 2.0 600 1.3 1.2 20% 2-butene those obtained with the ... ... ... ... ... ... 10% 1,3-butadiene 10.7 5 . 3 Thiopgede, 2.0 chromia-alumina catalyst con1.0 1.8 540 n-Pentane %methyl13.2 taining about 10% chromia 6.6 thiophene 12.6 5.3 Thiophene, 2.0 640 1.0 1.2 n-Pentane under the same operating %methyl15.1 6.3 thiowhene conditions. 19.1 3.8 2.0 1.3 1.6 540 CrzOa-AlzOa Iaopentane The reaction of sulfur di51.4 10.3 oxide with hydrocarbons is 1.9 1.0 2.0 1.3 1.6 600 CrzOa-A1203 Iaopentane 3-methylhighly exothermic and soon 10.6 5.6 thiophene 4.8 1.3 it was apparent that control Thiophene, 2 . 0 0.91 1.45 540 1-Pentene 2-methylof heat of reaction was one 15.4 4.3 thio hene Thiopzene 1.5 1.0 3.0 510 CrzOs-AI20a n-Hexane of the most important. prob... 3.1 homologf Thiophene 1.75 lems to be studied. This was 1.1 3.1 515 CrzOa-AhOa 1-Hexene ... 3.2 homologf accomplished in small scale 3-Methyl2.0 1.0 1.2 CrzOa-AlaOae 545 2,3-Dimethylbutane 4.2 2.2 ihiophene, fixed bed apparatus by using 3,4-dimethyl22.4 11.8 thiophene reactor tubes of relatively a 200 cc. of pelleted catalyst used except where noted. small diameter (about 1.0b Volumes of liquid hydrocarbon/volume of catalyst/hour. c Volumes of gaseous hydrocarbon/volume of catalyst/hour. inch inside diameter). HOWd Traces of thiophene formed. e 300 cc. of pelleted catalyst used,in this sun. ever, when larger scale operaI Indicated t o be mixture of 2,5-dimethylthiophene and 2-ethylthiophene. tion was attempted and ap-
March 1950
INDUSTRIAL AND ENG INEERING CHEMISTRY
Figure 2. Fluidized Fixed Bed Reactor System for Production of Thiophene
proximately 3.5-inch diameter reactor tubes were used, it became increasingly difficult to control the heat of reaction adequately even with internal cooling coils. Likewise, it was difficult in the large diameter reactor tube to control the heat of regeneration of the fixed bed of catalyst. Heat control was more difficult with butene than with butane and was particularly difficult with butadiene. The extensive side reactions thereby resulting undoubtedly contributed to lowering of the thiophene yields. OPERATIONS IN A FLUIDIZED FIXED BED SYSTEM
To alleviate these problems, use was made of a different technique which employed a bed of fluidized catalyst. By this means the temperature of the reaction could be controlled to within about 3" C., the catalyst could be regenerated with ease, and the temperatures of regeneration could be much more readily controlled than when using the previously described fixed bed system. These effects appear to result from the fact that in the fluidized state the catalyst particles come into frequent contact with the reactor walls and with one another so that heat transfer through the bed is greatly expedited. The amount of cata-
lyst charged to such a reactor depends upon the volume of the reactor and separator sections, the size of the catalyst particles, and the rate of feed of the charge materials (space velocity of hydrocarbon and mole ratio of sulfur dioxide to hydrocarbon). The setup of this fluidized fixed bed system, illustrated schematically in Figure 2, demonstrates how such a system is used on a relatively small scale. The charge materials in the bombs were completely vaporized by passage through the small preheaters. From thence they passed through flowmeters to a horizontal preheater just prior to the unit proper. This horizontal preheater was constructed of 0.75-inch stainless steel pipe. The reactor proper was arranged in a vertical position and consisted of 4 feet of 2-inch stainless steel pipeand a thermowell of 0.125-inch stainless steel pipe extending upward most of its length. Above the reactor section was a settler section consisting of 4.5-inch stainless steel pipe 21 inches long. In the upper end of this settler section was an Alundum filter which stopped fine particles of catalyst but permitted gaseous materials to pass into the condensing and recovery system. The condenser itself consisted of a vertical pipe with a jacket through which cold water was circulated so as to bring the effluent to temperatures below 40 C. and hence to condense most of the thiophene. The products were treated in substantially the same manner as those obtained in the work done in the fixed bed system. A photographic view showing the preheater and reactor and the split Hevi-Duty furnaces used to heat them is given in Figure 3. The nature of the effluent from the reactor before separation and washing is illustrated by the typical data in Table IV. This run was made charging normal butane and sulfur dioxide to the fluidized fixed bed reactor containing 500 grams of 100to 200-mesh chromia-alumina ,catalyst (containing about 10 chromic oxide). The run was continued until 2.08 weights of nbutane had passed through the reactor per weight of catalyst a t an average temperature of 595" C., a hydrocarbon space velocity of 0.76 weight of charge per hour per weight of catalyst, and a mole ratio of sulfur dioxide to n-butane of 1.5. [In a fluidized O
TABLE 111. THIOPHENE FROM BUTANEAND SULFURDIOXIDE Thiophene Produced, s02: Lb./100 Lb. C4H10t of Butane Mole Ratio Charged Consumed Catalysta 1.45 34.2 51.3 Activated silica 1.47 30.5 43.3 Molybdena-alumina 1.46 26.7 46.0 Chromia-alumina 33.1 1.39 25.6 Vanadia-alumina 1.35 47.3 22.8 Molybdenum, sulfide-alumina 11.0 19.0 1.5 Activated carbon 19.0 1.47 9.8 Su er Filtrol 7.6 1.41 r-Wlumins. ... 0.9 1.46 1.1 Glass wool a Chromia, molybdena, vanadia, and molybdenum sulfide catalysts shown in this table all contain approximately 10% chromia, etc., on an alumina base.
TABLE IV. EFFLUENTCOMPOSITION FROM SULFURDIOXIDE%-BUTANEREACTION Constituent Thiophene Water Hydrogen sulfide Carbon dioxide Carbon monoxide Sulfur Hydrogen %Butane Butenes 1 3-Butadiene hkiscellaneous li h t hydrocarbons (methane, et%ane, ethylene, propylene, etc.) Total
469
Mole % 4.9 15.3 27.3 23.2 2.7 0.3 14.7 5.4 1.2 0.1 4.9 100.0
Figure 3.
View of Fluidized Fixed Bed Reactor
INDUSTRIAL AND ENGINEERING CHEMISTRY
470
z so
u)
p
P
20'0475
5bO
5 TEMPERATbRE,*C. k 5I5 0 ! 6
515
6h5
6kO
Figure 4. Effect of Temperature on Production of Thiophene from Sulfur Dioxide and 2-Butene
system such as this it is necessary to express the space velocity on a gravimetric basis (weight of charge per hour per weight of catalyst) rather than on the volumetric basis used for the fixed bed catalyst.] The production of thiophene was 32.6 pounds per 100 pounds normal butane charged and 48.5 pounds per 100 pounds of normal butane consumed. The total material recovery was 98.0%.
$ 901
:: 80C
I
Vol. 42, No. 3
different amounts of thiophene, the greater vields and conversions being obtained from the 2-butene, but the general trends of the effects of the reaction variables on thiophene production appeared to be the same for both charge stocks. In Figure 4 is shown the effect of variation in temperature on the production of thiophene from sulfur dioxide and 2-butene. These data were obtained at a space velocity of 0.75 weight per hour per weight, a mole ratio of sulfur dioxide to butene of 2.0, and a hydrocarbon-calalyst weight ratio of 1 to 1 using the 100- to 200-mesh chromia-alumina catalyst. It will be seen that change of temperature from 525" to 650" C. had practically no effect on the amount of thiophene produced. The effect of variation in space velocity is shown in Figure 5. In this case the temperature was 540" C. In the range studied variation in space velocity between the limits of 0.50 and 1.50 weight per hour per weight had no significant effect. These runs were made with a 100- to 200-mesh chromia-alumina catalyst and a hydrocarbon-catalyst weight ratio of 1 to 1. By the use of a 40- to 100-mesh catalyst it was possible to extend the space velocity range up to approximately 4.0 weight per hour per weight without significant variation in thiophene production. The effect of variation in mole ratio of sulfur dioxide to normal butane is shown in Figure 6 (595' C., 2.0 weight per hour per weight, average hydrocarbon-catalyst weight ratio 2 to 1). Here there appeared to be some difference in the behavior of the 100- to 200-mesh and the 40- to 100-mesh catalysts. Apparently there was a maximum mole ratio in the neighborhood of 2.0 for the h e r catalyst while in the case of the coarser catalyst no maximum was realized at thelimit of the throughput of the reactor. g
90
a 3
015
I0i
ok
060
u
lk
150
lL5 SPACE VELOCITY W I H R I W
: 80
; I
2670 00
?360 Y O
Figure 5. Effect of Space Velocity on Production of Thiophene from Sulfur Dioxide and 2-Butene
Zg50
hB
g240
+$ 2B3 0 u ) l
Temperature control was so smooth and so simple with the fluidized catalyst as to make operation possible with charge stocks such as butene which were difficult to use in the fixed bed system because of the extremely exothermic nature of their reaction with sulfur dioxide. As a result, both wbutane and 2butene were studied. These charge materials gave substantially so 70
-
40-100
hESH CATALYST CATALYST
z 60m
g
40-
E 300 $ 20 $20-
n
A ULTIMATE(Calc.) 0 PER PASS
100-200MESH CATALYST
w
20
-
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A ULTIMATE(Calc.) 0 PER PASS I
I
2
20
0 0
10
ID
20
40
30
p
50
Y
60 WEIGHT R A~T I O
80
70
~
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Figure 7. Effect of Hydrocarbon-Catalyst Weight Ratio (On-Stream Time) on Production of Thiophene
The activity of the catalyst when operating a t 595' C., 0.75 weight per hour per weight, and a mole ratio of 1.6 varied with the length of on-stream time as shown in Figure 7. In the case of butane, thiophene production remained essentially constant until a hydrocarbon to catalyst weight ratio of about 6 had been reached. Beyond this value the activity of the catalyst dropped off rapidly. In the case of 2-butene under the same conditions initial production was considerably higher but the rate of decline of activity was also greater. These runs were continuous and the cuts were taken by switching from one condenser system to a second one a t the specified hydrocarbon to catalyst weight ratio, In both cases the catalyst could be regenerated back to its initial activity by burning with air. The catalyst used here was 100- to 200-mesh. GENERAL CONSIDERATIONS
The mechanism of the reaction of sulfur dioxide on hydrocarbons to produce thiophene has not been clearly established. There appear to be oxidation, crackjng, and isomerization reactions which occur simultaneously with the dehydrogenationcyclization reactions. Consequently no balanced equation to
~
~
March 1950
INDUSTRIAL AND ENGINEERING CHEMISTRY
represent the over-all process has been written. The hydrocarbon effluent when charging a straight chain C d hydrocarbon always contained butenes and butadiene, suggesting that these materials may be intermediates in the reaction. The somewhat higher yields from butenes than from butane would tend to confirm this. However, these yield data are complicated, especially in fixed bed operation, by the heat effects resulting from the highly exothermic nature of the reactions. ACKNOWLEDGMENT
i
The authors wish to express their appreciation to J. T. Clarke, C. H. Culnane, and B. R. Stanerson for their contributions to the experimental work and to members of the Analytical and Testing Department of the Beacon Laboratories for carrying out much of the analytical work involved.
471
LITERATURE CITED
(1) Auwers, K. V., and KohIhaas, W., J . prakt. Chem., 108,321-31 (1924). (2) Fawcett, F.S., J . Am. Chem. Soc., 68,1420-2 (1946). (3) Fawcett, F.S., and Rasmussen, H. E., Ibid., 67,1705-9 (1945). (4) Lowry, T.,and Nasini, A,, Proc. Roy. SOC.(London), A123, 686-91 (1929). (5) Meyer, V.,and Kreis, H., Bey., 17,1558-63 (1884). (6) Morton, A. A., “The Chemistry of Heterocyclic Compounds,” p. 40,New York, McGraw-HillRook Co., Inc., 1946. (7) Rasmussen, H. E., Hansford, R. C., and Sachanen, A. N., IND. ENO.CHEM.,38,376-82 (1946). (8) Shepard, A. F., Henne, A., and Midgley, T., J . Am. Chem. SOC. 56, 1365-6 (1934). (9) Steinkopf, W., “Die Chemie des Thiophenes,” p. 115,Dresden u., Leipzig, Theodor Steinkopff, 1941 (J. W. Edwards, Ann Arbor, Mich., 1944). RECEIVED August 31,1949.
Diffusion Coefficients in Multicomponent Gas Mixtures D. F. FAIRBANKS AND C. R. WILKE University of Callfornia, Berkeley, Calif.
A n experimental study has been made of the diffusion of vapors into multicomponent gases by vaporization of iiquids in a long tube under conditions such that the theory of diffusion in the semi-infinite column is applicable. The results have verified the relation:
D‘A =
1
- yA
YB + y c f Y D
DAB
DAC
+ * * *
DAD
where D‘A is the effective diffusion coefficient of gas A with respect to the total gas mixture; DAB,DAG,DAD, etc., are the respective binary diffusion coefficients: and yA, ye, ye, etc,, are the mole fractions of the components in the mixture.
’
I
N A binary system the rate of unidirectional diffusion of a gas, A , through a second stagnant gas, B , may be expressed by the equation
where N A
=
DAB =
P
=
R T PA X
=
pi
=
= =
=
rate of diffusion of A , gram moles per second-sq. cm. diffusion coefficient, sq. cm. per second total pressure, atmospheres gas constant, cc.-atmospheres per gram mole-” K. temperature, OK. partial pressure of component A , atmospheres distance in direction of diffusion, cm. pressure of nondiffusing gas B, atmospheres
For diffusion of A into a multicomponent mixture of stagnant gases it is convenient to express the rat,e of diffusion by an equation analogous to Equation l :
Present addresa, Department of Chemical Engineering, Massachusetts InaCitute of Technology, Cambridge, Mass.
where 0;is some proper effective diffusion coefficient for component A , which will be a function of the gas composition. In this case p i is the sum of the partial pressure of all gases other than A . On the basis of the theories of Maxwell (6) and Stefan (8, 9 ) , Wilke (10)has derived an expression given in Equation 3 for the effective diffusion coefficient and discussed its general use in diffusion calculations.
D‘A =
1-
YA
ya+yc + E + . . . .
DAB
DAC
(3)
DAD
where yB, ye, etc., are the mole fractions of components A , B, C, etc., and DAB, DAC,etc., are the respective binary diffusion coefficients of component A with respect to each component of the mixture. The present paper reports the experimental verification of Equation 3 under conditions approximating those assumed in its derivation-namely, the diffusion of one gas into a mixture of stagnant gases. THEORY
On the basis of experimental convenience an apparatus was construeted to operate on the principle of diffusion in the semiinfinite column. I n this method a suitable liquid is allowed to evaporate upward into the gas mixture from the bottom of a long glass tube under conditions such that a negligible quantity of vapor reaches the upper end of the tube during the time of the experiment. This method has been suggested by Arnold ( d ) , who has integrated the differential equations applicable to this case for diffusion in binary systems. These binary equations may be extended to multicomponent systems if the diffusing gas, A , is maintained a t concentrations sufficiently low that the average diffusion coefficient given by Equation 3 remains essentially constant during the diffusion process. This is accomplished in prac-
