B Catalvs J
rogenation roduction
J
W. H. WOQD AND R. 6. CAPELL Floridin Company, Warren, Pa.
S
HORTLY after the outbreak of World War 11,the country’s dire need for synthetic rubber necessitated large-scale production of styrene for GR-S type rubber. I n the early part of this program Florite ( 1 , g ) , desiccant grade Alabama bauxite, was employed as the catalyst for the dehydrogenation of ethylbenGene to styrene. This naturally occurring bauxite was later placed by a catalyst manufactured under the auspices of the Rubber Reserve Corporation. This company’s research division has investigated various typical bauxites for their catalytic activity in the dehydrogenation react$ion, and the results are reported here. Alabama, Arkansas, Demerara, and Suriname bauxites (the last two from South America) were tested. Activated alumina was also inoluded in the program. Test runs were mnde in the 200-rc. laboratory test unit shown r+b-
in Figure 1. The unit consists, primarily, of a preheater section for the vaporization of water to steam, the catalyst or reactor chamber, product condenser, liquid-gas separator, and gas meter. Both distilled water and ethylbenzene were fed continuously from one-liter calibrated glass burets by means of a dual proportioning pump. The preheater was made from extra strong a/,-inch iron pipe filled with e/,,-mesh cracked porcelain. The catalyst chamber was made from 1-inch, standard stainless steel pipe. Both preheater and catalyst ovens were electrically heated by means of aluminum-bronze cylinders wrapped with chrome1 A wire, the temperature of each being regulated by a suitable temperature controller. The gas-liquid separator consisted of a oneliter glass separatory funnel, fitted with a two-hole stopper accommodating the condenser outlet line and a gas exit line to the meter.
1148
INDUSTRIAL AND ENGINEERING CHEMISTRY
December, 1945
1149
Four n a t u r a l l y occurring bauxites (Alabama, Arkansas, Demerara, and Suriname) and activated alumina were tested for their activity as dehydrogenation catalysts for theproduction of styrene from e'thylbenzene. A t a c o n s t a n t temperature level of 1200' F. for 50 hours of continuous operation, Suriname bauxite gave an over-all yield of 40% styrene (a 3 to 5% advantage over the others). With operation, simulating commercial practice, a t a constant 40% yield, Alabama bauxite was superior since it maintained its activity 25% longer than Suriname bauxite. Arkansas and Demerara bauxites, as well as activated alumina, appear to show excessively long induction periods for the best commercial operation. An Aerial View of a Plant of the Floridin Company, Quinoy, Fla. Here Bauxite, Which Early in the War Was an Important Dehydrogenation Catalyst, Is Milled and Processed -
m
ITEM NO. I
MSCRl PTlON
0
e
e
32
4
5
6
7 8 9
IO
II 12 I3 14 15 16
ii
20
21
Figure 1. Diagram of 200-Cc. Dehydrogenation Unit
OPERATION
For comparative results, a uniform testing procedure was adopted which became standard for this laboratory. Ethylbenzene and water were fed a t rates of 200 and 300 ml. per hour (Le., 1.0 and 1.5 liquid space velocity, respectively) ; this gave a mole ratio of steam to ethylbenzene of 10.2 or a partial pressure of ethylbenzene of about 65 mm. of mercury since atmospheric pressure was employed throughout. Constant-temperature runs were made a t 1200' F. for 50 hours before regeneration. During constant conversion runs, the temperature was varied to maintain the amount of styrene in the hydrocarbon product a t approximately 42% by weight (i,e., about 40% yield on the feed). At constant conversion levels, the runs were terminated when the 42% level could no longer be maintained a t 1250' F. in the case of Suriname bauxite and 1300' F. in the case of Alabama bauxite. Water was pumped from a graduated oneliter buret t o the preheater, where i t was vaporized to steam a t 900" F. Ethyl-benzene was pumped from its buret into the steam stream a t a point just ahead of t t c reactor section where the steam helped
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
1150 1200
Vol. 8, No. 12
data were available, material bttlances were excellent for such a small unit, varying between 99.3 and 100.29r,.
I160 NEAR TOPff BE
ANALYSES
I120
The ethylbenzene was obtained from the Dow Chemical Company. The values of all physical characteristics agreed closely with those reported in the literature (6) 1040 for pure ethylbenzene. Fractional distillation in a packed glass laboratory column, capable of accurately ~1000 evaluating synthetic mixtures of benzene, toluene, and ethylbenzene in the ratio of 2:2:96, indicated the ethyl960 benzene to be 99.6% pure. The hourly product samples were separated from their water layers, dried, and analyied by means of a refrac920 tometer which had been calibrated against synthetic mix880 tures of ethylbenzene and styrene. During the first runs the styrene was also evaluated by bromine number deTIME,MINUTES terminations (3) and fractional distillation of the prodFigure 2. Typical Regeneration Curve (Alabama Jjaudte) uct. All three values a p e d within 1% SO the refractive index method was employed thereafter. This is the same conclusion reached by Ma&y et al. ( 4 ) after an extensive study of t h e vaporize it. The mixture passed into the reactor, over an 8-inch validity of the method. Because of the similarity of the section of glass bans for further preheating then through the refractive indices of benzene, toluene, and ethylbenzene, t h e catalyst bed and condenser, and finally collected in the gaserror in the amount of styrene measured would be only 0.5% liquid separator. The liquid was drawn off hourly and weighed, in the presence of 5% benzene and negligible in the case of 5% the water layer discarded, and the hydrocarbon layer weighed and analyzed for styrene. The product gas was led from the gasliquid separator through a wet-test gas meter from which i t w a s CONVERSION WITH VARIOUS BAUXITES TABLE 11. STYRDNE vented, or periodic samples were taken for analysis. AS CATALYSTS A T 1200° : F Feed rates were kept unusually constant, the maximum deviaWt. % Styrene in tion rarely exceeding 0.5%. Temperature control was of the Hydrocarbon Recovered Wt. % Styrene Yieldb Cycle 1-12 1-25 1-50 1-12 1-25 1-50 order of * Z O F. with the temperature gradient throughout the No. hr. hr. hr. hr. hr. hr. catalyst bed 10" to 15" F. On those runs where sufficient Alabama
s-I080
(Florite)
So. America
(Suriname)
TABLE I. WEIGHTPERCENTANALYSISOF BAUXITES (VOLATILE-FREE BASIS)
AlnOa SiOp FenOa Ti02 65.5 10.1 19.9 2.9 82.3 2.5 12.4 2.8 84.3 9.3 2.1 4.3 91.0 2.3 3.5 3.2 alumina 99.6 0.3 0.1 0.0 bauxite also analyees 0.3% CaO, 0.1% MgO, and 1.2% not
AlabamaSuriname Arkansas Demerara Activated Alabama accounted for.
So. America (Demerara)
2
60.4 59.8
46.5 48.4
35.6 37.3
57 2 56.5
44.8 46.5
34.8 36.4
1 2
62.3 61.4
51.2 53.2
40.4 42.1
58.8 58.4
48.9 51.2
89.8 40.5
1
34.1 41 7 38.0 32.8 40.2 28.1 36.9 36.1 27.4 34.8 37.7 38.2 43.0 37.6 41.3 Arkansas 41.3 38.9 30.7 31.9 39.4 30.4 12.5 18.4 12.3 18.1 Activated 1 10.7 13.5 10.0 alumina 2 10.3 10.6 4 Ethylbenzene feed rate 1.0 v./hr./v.: Hz0 rate, 1.5 v./hr./v.: s t a n t temperature of 1200° F.;atmospheric pressure, 50-hour run. b Rased on ethylbenzene feed.
1 2 1 2
37.2 85.3 36.3 37.4 30.2 13.4
con-
ICA- DEMERAR,
-
Figure 3.
-
.
Comparison of Activities of Various Bauxites over 50-Hour Period at Constant Temperature of 1200" F.
December, 1945
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
l1Sl
purged, and the cycle repeated t o determine the regenerative characteristics of the catalyst. Results of the tests are given in Figure 3 and Table 11. Alabama and Suriname bauxites show a high initial activity (75 and 70% conversion, respectively) with a rapid decline after the first few hours. The high initial activity can probably be attributed t o the high iron content of the bauxites (20and 12%) since the low-iron bauxites did not exhibit this characteristic. Arkansas and Demerara bauxites have a low initial activity, rapidly increasing t o a maximum of a little over 60% conversion some 12-15 hours later. This maximum waa not attained until after 42 hours of operation in the case of activated alumina. The results indicate that within the limits HOURS OF RUN tested, silica has little or no effect on the Figure 4. Temperature Requirement to Maintain Conatant Styrene activity of the bauxite. Yield of 40% The induction period is defined as the time required for the hydrocarbon product t o attain 40% by weight styrene. This definition becomes apparent in the section devoted t o operation at a constant conversion level. Both before and after regeneration, the induction periods of the Alabama and Suriname bauxites were zero, and their catalytic activities did not suffer during the h t cycle or their subsequent regenerations. Arkansas and Demerara bauxites showed induction periods of 7and 8 hours, respectively, during the first cycle, which were increased, after regeneration, t o 10 and 12 hours for the second cycle. For industrial applications, activated alumina, as such, is of little value since it has a 32-hour induction period for the first cycle. Ita activity was so seriously impaired during the first cycle and/or ita regeneration that an induction period for the second cycle can be recorded only as greater than 50 hours. Figure 5. Liquid By-product Formation as a Function of The data for these runs (Table 11) give the yields for Temperature, with Alabama Bauxite as Catalyst toluene, both amounts being greater than those indicated from the curvesin Figure 6 at the most severe conditions. The reproducibility of styrene yields is not closer than 1%. The product gas was analyzed by the use of conventional Burrell equipment. CONSTANT-TEMPERATURE EVALUATION
For the evaluation of their activity as dehydrogenation catalysts, four typical, readily available bauxites were selected (Table I). The Alabama bauxite has both a high silica and iron content; Arkansas, high silica but low iron; Suriname, low silica and high iron; and Demerara, both low silica a n d iron. Activated alumina was also tested as an example of a practically pure alumina. After a few preliminary runs the uniform testing conditions chosen were: ethylbeneene and water liquid space velocities of 1.0 and 1.5 volumes of liquid per hour per volume of catalyst (v./hr./v.), respectively, average catalyst temperature held constant at 1200” F.; atmospheric pressure; length of run, 50 hours. At the end of the first cycle or 50hour period, the catalyst was regenerated in situ by the addition of air and nitrogen to the steam flow. The maximum temperature durjnq regeneration was kept below 1200O F. Figure 2 shows a typical regeneration curve. The system was then adequately
TEMPERATURE,OF.
Figure 6. Exit Gas Composition as a Function of Temperature with Alabama Bauxite as Catalyst
.
INDUSTRIAL AND ENGINEERING CHEMISTRY
1152
TEMPERATURE,-E
Figure 7. Yield-Conversion-Selectivity Variation with Temperature, Using Alabama Bauxite at Constant Yield of 4Q Weight % Styrene
12, 25, and 50 hours, based on the ethylbenzene feed. Data for material balances, gas analyses, and product compositions are available only for the run using Alabama bauxite (Table 111), but it is believed that the material balances for the other runs are equally good. The results show that for the first 12 hours Alabama and Suriname bauxites give styrene yields of approximately 600/00, or about twice as great as those obtained with Arkansas and Demerara bauxites. On the other hand, the over-all yields at 50 hours have become fairly uniform, Suriname perhaps enjoying a 3 to 5% advantage in yield over the other bauxites. Carbon deposition for both Suriname and Alabama bauxites w a p 0.4 yo.
Val. 37, No. 12
practical for commercial operation. Accordingly, for the fist constant conversion run using Suriname bauxite, the end of the run was designated as that point where the conversion dropped below 40% at a maximum average catalyst temperature of 1250" F. All other operating variables were kept constant. Figure 4 shows the temperrtture requirement at a constant 40% yield of styrene for runs employing both Suriname and Alabama bauxites; the latter was continued t o a final operating temperature of 1300' F. Yield and operating data for these runs are reported in Table IV. In the second run employing Alabama bauxite, Figure 5 shows the by-product formation and Figure 6, the product gas composition over the entire temperature range 1100' to 1300' F. The superiority of Suriname bauxite at constant temperature operation is not apparent when operating at constant conversion. The time-temperature curves in Figure 4 show that, for the same maximum operating temperature of 1250" F., Suriname will give a 400/,yield of styrene for 48 hours as compared to 59 hours for Alabama bauxite. Other things being equal, this represents a considerable saving in time between regenerations for large-scale manufacture. If an ultimate styrene yield of 90% is chosen fo? commercial operation, the by-product curves in Figure 5 and selectivity curve in Figure 7would indicate that this yield can no longer be maintained a t temperatures much above 1275" F. Because of their low initial activities observed in constanttemperature operation at 1200' F., it was thought inadvisable to attempt constant-conversion operation with Arkansas and Demerara bauxites. It js probable that temperatures far in excess of 1200" >, would be required to reach an initial yield of 40% styrene; then as the activities of the bauxites increased, the temperature would have to be lowered to maintain the same yield. Finally, the temperature would be gradually increased to compensate for the loss in activity. Such manipulation was deemed inadvisable for commercial operation.
OPERATION A T A CONSTANT CONVERSION LEVEL
ACKNOWLEDGMENT
Because of the considerable variation in styrene yields obtained during constant temperature conditions, this type of operation was believed unsuitable for plant practice. It was decided, therefore, to make a series of runs holding the styrene yield at approximately 40% by varying the temperature. From the data obtained during constant-temperature operation, it was readily seen that i t would be easy to drop the initial temperature of the Alabama and Suriname bauxites to a 40% conversion level and maintain that level by gradually increasing the temperature. At that time it was believed that temperatures much higher than 1250' F. would be either uneconomic or im-
The authors gratefully acknowtedge the assistance of R. C. Amero and W. T. Granquist in the preparation of this paper.
TABLE111. YIELDA N D OPERATINQ DATAFOR CONSTANTTEMPERATURE RUNS WITH ALABAMA. BAVXITE
TABLEIV. YIELDAND OPERATING DATAFOR CONSTANTCONVERSION RUNSWITH ALABAMA AND SURINAME BAUXITDS
Cycle 1 Cycle 2 1200 1200 A v . catalyst temp., F. 1.0 1 .o Ethylbensene rate v./hr./v. Hz0 rate, v./hr./v: 1.5 1.5 10.2 10.2 Mole ratio, Hz@/ethylbeneeno Over-all material balance, wt. % 99.9 100.2 Length of run hr 50 50 Yields (based bn ethylbenzene feed), wt. 7% 34.6 3G.4 Styrene 1.9 1.9 Gas 0.4 0.4 Carbon depoeition 99.6 97.8 Total hydrocarbon product Over-all gas composition, mole % 91.7 ... Hydrogen 2.9 Methane 1.0 ... Ethylene 0.4 ... Ethane 1.6 ... Carhon monoxide 2.4 ... Carbon dioxide 21-30 41-20 1-10 HYDROCARBON ETHYLBENZENE HOCKS H ~ U K E J HOVRB PRODLXT FEED Benzene, wt. yo 0 .. 1 1 1.4 0.6 Toluene, wt. 0 2.6 63.7 29.0 23.6 Stvrene wt. yo Eihyldtkrene, wt. % 99:8$ 32.3 69.7 75.8
...
v7
y::
{
LITERATURE CITED
(1) Capell, Amero, and Moore, Chem. & Met. Eng., 50, 107 (1943). (2) Capell, Hammerschmidt, and Deschner, IND.ENG.CHEM.,36, 779 (1944). (3) Lewis and Bradstreet, IND. ENG. CHEW.,ANAL.ED., 32, 387 (1940). (4) Mavity, Zetterholm, and Hevert, Meeting of Am. Inst. Chem. Engrs., Nov., 1944. (5) Ward and Kurtr, IND.ENG.CHEM., A N ~ LED., . 30, 559 (1938).
Alabama Ethylbenzene rate, v./hr./v. 1.0 H20 rate,, v./hr./v. 1.5 Mole ratio. HzO/ethylbenzene 10.2 99.5 Over-all material balance, wt. 70 Length of run, hr. 90 Max. temp., ' F. 1300 Yields (based on ethylbenzene feed), w t . Yo 40.3 Styrene 2.5 Gas Carhon deposition 0.1 Total hydrocarbon product 96.8 Over-all gas cornposition, mole 70 Hydrogen 86.9 Methane 4.2 3.1 Ethylene 1.1 Ethane Carbon monoxide 2.4 Carbon dioxide 2.3 Hydrocarbon product composition, wt. To Benzene 1.4 1.9 Toluene 41.6 Styrene Ethylbenzene 55.1
Alabama 1 .o 1.5 10 2 99.3 59 1250
Suriname 1.0 1.6 10.2 99.3 48 1250
40.0 1.7
40.7 2.0
97:2
97.0
92.5 2.5 1.1 1.0 1.4 1.5
... ... ...
0.4 1.2 41.2 67.2
...
... ...
...
...
... ... ...
