Activated Bauxite as a Catalyst olyrnerization of Olefins HEINZ HEINEMAKN, W. A. LA LANDE, J R . ~AND , W. S. W-. McCARTER Porocel Corporation, Philadelphia, Pa.
T
HE catalytic hroducActivated bauxite is an efficient catalyst for the polyglass beads. A flowmeter tion of dimers, polymers, merization of isobutylene under atmospheric pressure at IVas to measure the rate a t which the gaseous and copolymers of the butyltemperatures of 200 'to 350 F. The activity of the catalyst butvlenes were admitted to enes has been investigated increases with dehydration and the activation temperature the" reactor. The reaction frequently (14, 18, 20, SO) up to a temperature of 1400' F. Rates of polymerization of products were separated by iso- and normal butylenes are sufficiently different to means Of a jvater-jacketed and has assumed commercial condenser and a dry ice import'ance in the producpermit exclusive polymerization of isobutylene from C4 stabilizer. Uncondensed gas t.ion of high octane gasoline olefin mixtures by selecting reaction temperatures of 400 was measured by a wet-test (2, 6 , I S , 19, 29), in the to 600' F. Mixtures of saturated and unsaturated C4 gas meter. hydrocarbons can be polymerized readily by activated For experiments a t elevated removal of isobutylene from pressures a stainless steel the charge stock to dehydrobauxite when employing pressures of 300 to 500 pounds per reactor tVas used, The co?-genation plants producing square inch. After a few hours of operation, the catalyst densing system slmlbutadiene, in t.he production selectively polymerizes isobutylene with yields of 60 to lar to that used a t atmosof high nlolecular weight 70% per pass. Spent catalyst can be restored to full activpheric Pressure* Liquid tylenes were charged with polymers (38),and in the ity by thermal regeneration in a n air stream. a small proportioning pump production of pure isobut'ylcapable of delivering up t o 400 ml. per hour against ene by polymerization and a' pressure of 1000 pounds Per square inch. The flow rate subsequent depolymerization (28). Catalysts used for polywas regulated with a variable speed drive connected to the merization are sulfur.c acid ( 2 , $7, ds), anhydrous aluminum pump and was measured by means of sight glass readings in chloride (39,,401, phosphoric acid (5, 16, 17, 19, 211, boron trithe charge vessel. To start operation, the reactor and condensing fluoride (S), pyrophosphates, and synthetic silica alumina catasystem were brought to the desired pressure by admitting compressed dry nitrogen. The pump was start,ed against a closed dislysts (1, 8,22, 36). Clays and ot,her natural adsorbents have found application charge valve which was opened to the system as soon as the desired pressure was built up. as catalyst carriers and have been studied as catalysts. Gurvich calculated as JTeight per centof feed recovered as yields (10) observed that Florida earth would polymerize gaseous oleliquid polymer. Gas analyses were obtained with the mass spectrograph. fins. This react,ion has been studied at temperatures below 0" C. (26, 34) as well as a t higher temperatures (9, 12, 24, 31, POLYMERIZATION OF ISOBUTYLENE 32). The activity of adsorbent alumina for the polymerization of C4 hydrocarbons has been investigated (16, 36) and bauxite has Isobutylene is readily polymerized by bauxite even a t low been used for the polymerization of diolefins (5, 351,but little is t,eniperat,ures. The react,ion is highly exot.hermic and cooling known about the ability of granular activated bauxite to polyis required to maintain these low temperatures. The act,ivation merizc C4 olefins ( 7 ) . Knowledge of the catalytic properties of temperature of the bauxite is critical (Table I). The lower t,he bauxite for the promotion of such reactions as the CraCkhg (231, residual \x,-ater content of the bauxite (V.11.)the better its polyisomerization (4, s?), and dehydrogenation (33,41) of hydromerizing act,ivity. Material activated i n tmherange 1200" t,o carbons suggested the study of its action in the polymerization of 1400" F. (0.2% 1 T . M . ) is most active. The activity drops slightly C4hydrocarbons. This paper presents the results of a prelimia t higher activation temperatures. The optimum conversion nary investigation of C4 olefins in the presence of activated bauxite teInperat,ure depe& somewhat on t,he activation temperature and the surprising differences in the action of the catalyst on the but generally found to lie betmeen 200" and 350 O F. (Table I). various unsaturated C4 hydrocarbons. The presence of traces of water vapor which is adsorbed by the bauxite will reduce t,he catalyst activity rapidly. Charge stocks MATERIALS
mesh Arkansas low-iron In this study the bauxite used \Vas ore containing 8&.9T0 aluminum oxide, 10.27, silicon dioxide, 3.0Y0titanium dioxide, and 1.9y0ferric oxiQ; its physical properties have been repoited ( 1 1 , 2 5 ) . Indications are that other bauxite ores give similar results. RIatheson Company's isobutylene and 1-butene and Phillips Petroleum Company's 2-butene \\-ere used in the experiments involving pure gases. The B-B feed (caustic washed depropanizer bottoms) was supplied by the Atlantic Refining Company and was representative of the C* fraction charged to its commercial polymerization unit. APPARATUS
A Pyrex tube 3.8 em. in diameter by 120 em. long, enclosed in a n electric tube furnace, was used as the reactor for experiments a t atmospheric pressure. This tube contained a 100- to 200-gram charge of catalyst preceded by a preheating section packed with
TABLE I.
POLYMERS
RECOVERED FROM P U R E I S O B U T Y L E N E
[Space velocity: 250 volumes of gas per volume of catalyst per hour (On C . and atmospheric pressure); 3 volumes of liquid per volume of catalyst per hour a t 350 t o 400 pounds per square inch] yo Polymer Recovered a t 330 to 400 Lb./Sa. In. a n d Bauxite Activation Temp., yo Polymer Recovered a t ktmospheri: Pressure and Bauxite Activation Temp., F. F. 700' 1200' 1400O 1800O 700° 1200° 600D (6% (0.2% (0.1% Reaction (8% (0.2% (0% (6% V.RI.) V.171.) V.M.) V . M . ) V.;11) Temp.,OF. V . M ) V.M.) 100-150 . . . . . . . 82 .O . . . . . . . . 61.5 84.5 200 250 330 450 600 800
Present address, Pennsylvania Salt Manufacturing Company, Philadelphia, Pa. 1
1224
0.0
31.5
90.0 82.0
90.0 90.0 90.0
.......
19.8
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . 54.0 . . . 40.6 . . . . . . .
86.3
45.0 30.6
88.0 85.5 83.8
. . . . . . . .
0.0
.... ....
86.0 85.0
. . . . . . . . . . . . . . . .
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
July 1948
I
too,
must, therefore, be dried carefully. Within certain limits the polymer yield is not influenced by the space velocity. Yields were decreased, however, by operating above 375 volumes of gas (at 0' C. and atmospheric pressure) per volume of catalyst per hour, and 3 volumes of liquid at 400 pounds per square inch, per volume of catalyst, per hour. The average initial conversion yields (5 hours average) and the life of various catalysts at maximum conversion are given in Table 11.
I
1225 I
1
l
l
.
.
TABLE11. ISOBUTYLENE CONVERSION YIELD AND LIFE VARIOUSPOLYMERIZATION CATALYSTS
20 10
OF
(Space velocity: 250 volumes of gas per volume of catalyst per hour; atmospheric pressure operation a t 300° F.) Polymer Yield Catalyst Life, Catalyst % of Isobutylene, Grams Polymers Preheating Average, First per Catalyst Temp., F. 5 Hours Gram Catalyst Bauxite 1200 90 25.0 Supported phosphoric acid 300 90 >25.0 0 0.0 Adsorbent alumina 5000 Silica eel 5000 40 < 1.0 Acid aitivated bentonite 900 78 2.2 Attapulgus clay 900 79 1.0 900 73 1.4 Kaolin Kaolin 1200 72 1.3 a Drying temperature of materials commercially activated to 1% V.M.
Activated bauxite, a thermally treated, naturally occurring alumina containing some clay of the kaolinite type, is superior as a polymerization catalyst to either alumina or kaolin individually. No explanation for this behavior can be advanced a t this time. The rapid deterioration of most catalysts is illustrated in Figure 1. Bauxite catalyst after losing its maximum efficiency can be restored t o full activity by passing air over i t at 1000' F. for 2 hours. This regeneration is an easy process and i t provides a n advantage over supported catalysts which can be restored t o activity only with considerable difficulty. Another advantage of bauxite is its relatively high mechanical strength and the fact t h a t i t does not soften i n service. The polymers obtained from isobutylene vary i n composition, depending on the pressure used during polymerization. Increase in pressure results i n a heavier polymer with larger percentages of material boiling above 400' F. Of the polymer obtained a t atmospheric pressure 6370 boiled below 250' F., 93% between 90" F. and 400' F., and 7% above 400" F. Hydrogenation of this polymer and redistillation t o a 400" F. end point results in a product suitable as a n aviation gasoline stock. Octane numbers ofithis product are given in Table 111.
TABLEIV. WEIGHT PER CENT POLYMER BASED O N GAS CHARGED (Space velocity: 250 volumes of gas per volume of catalyst per hour a t atmospheric pressure; 3 volumes of liquid per volume of catalyst per hour a t 350 Dounds oer inch) - sauare Isobutylene 1-Butene %Butene Atmos350 Atmos350 Atmos350 Reaction pheric 1b.I pheric Ib./ pheric 1b.I Temp., F. pressure sq. in. pressure sq. In. pressure sq. In. 100 to 150 82 84.5 16.0 11.0 0 0 250 90 86.0 13.0 ,... 0 0 350 82 85.0 6.0 7.0 0 .. 450 45 .... 0 0 .. 600 31 .. . ... . , ., ... ..
.
.
TABLEV.
TABLE 111. A.S.T.M. OCTANENUMBERS OF ISOBUTYLENE POLYMERS
. .. .
straights
+
+
+
.... ...
. ..
30% blending value, + 4 . 97.0 cc. T E L a a Blending stock: RMFD-C-45 reference fuel, 71.2 octane. Standards D357-44.)
(A.S.T.M.
.
.
COPOLYMERIZATION OF C4 OLEFINS
POLYMERIZATION OF 1-BUTENE AND 2-BUTENE
+
I
The data in Table IV indicate that when a mixture of unsaturated Cd hydrocarbons is passed over bauxite, isobutylene will be polymerized t o a much larger extent than other C4olefins, and a t higher temperatures the polymerization of 1-butene can be suppressed entirely while i t is still possible to obtain considerable yields of isobutylene polymer (Table V). Some isomerization of 1-butene to 2-butene was observed.
Attempts t o polymerize pure 2-butene over bauxite catalyst were unsuccessful; this indicated that significant polymerization of this hydrocarbon will not occur at temperatures below 400" F. and pressures up to 500 pounds per square inch.
(Produced a t 300° F. and atmospheric pressure) Olefinic Hydrogenated Hydrogenated Bauxite Bauxite Phosphoric Acid Polymer Polymer Polymer Straight 86.7 100.0 95.3 87.7 Iso-octane Iso-octane 2 cc. T E L 1.45 cc. T E L 0 . 3 4 cc. T E L 97.2 84.5 15% blending value, straighta 16% blending value, +4 Iso-octane cc. T E L a 0.035 cc. T E L 30% blending value, 85.8 91.0
.
COPOLYMERIZATION OF MIXTURE OF 50% Iso5070 BUTENE OVER BAUXITE CATALYST
BUTYLENE AND
250 volumes of gas per volume of catalyst per hour) Butylene in Unconverted Gas, Reaction Polymers, % of Charge Temp., F. ,% of Charge Isobutylene n-Butylenes 51 350 5 44 450 21 29 50 600 11 39 50
(Space Velocity:
POLYMERIZATION OF B-B FEED
Polymerization of a refinery C4 cut instead of a mixture of pure unsaturated C4 hydrocarbons changes the picture considerably. The presence of other gases leads to a rapid catalyst deterioration at atmospheric pressure operation, whereas itsdoes not interfere to any great extent at elevated pressures. Careful drying of the B-B feed is most important for the preservation of catalyst activity. With a dry feedstock, polymer yields from a Cd cut increase with pressure and temperature to an opbimum a t about 400 t o 500 pounds per square inch pressure and 350" t o 400" F. At higher temperatures and pressures rapid catalyst deterioration
INDUSTRIAL A N D E N G I N E E R I N G C H E M I S T R Y
1226
caused by carbon deposition on the catalyst becomes noticeable. Variation of space velocities up to 3 volumes of liquid charge per volume of catalyst per hour has little effect; further increases in space velocity decrease the yield. In consideration of these factors standard operating conditions chosen were: 400 pounds per square inch pressure; 350 F.; and a space velocity of 3.
Vol. 40, No. 7
below 400” in either case) were cut to a 400” F. end point, hydrogenated, and evaluated for boiling range and knock characteristics. Performance of the two polymers was about equal. In order to determine the extent of thermal polymerization of the B-B feed under the selected standard conditions, the catalyst was replaced with steel balls. Conversion was found to be negligible (Table VII). Other catalysts showed a considerably lower activity and more rapid deterioration than bauxite or phosphoric acid (Table VII). ACKNOW LEDGRIENT
The authors wish to acknowledge the valuable assistance of
W. E. ICrumm and to thank the Atlantic Refining Company for mas? spectrograph analyses and octane ratings. LITERATURE CITED
Anderson, J. A., and d’Ouville, E. L., U. S. Patent 2,288,872 Figure 2.
Catalytic Polymerization of B-B Feed
0 = phosphoric acid on kieselguhr a t 400 lb./sq. in.; 0 = phosphoric acid on kieselguhr at atmospherio pressure; = bauxite a t 400 lb./sq. in.; X = bauxite at atmospheric pressure. Charge: isobutylene 14.9%; normal butenes 28.7%; butanes 53.4%
+
Figure 2 shows the per cent polymers obtained from a Cd refinery cut containing 14.9y0 isobutylene and 28.7y0 n-butenes polymerized in contact with bauxite and supported phosphoric acid catalyst at both atmospheric and 400 pounds per square inch pressure. Although the conversion in the presence of a supported phosphoric acid catalyst shows that copolymerization of C1 olefins takes place, the yields obtained with a bauxite polymerization catalyst after the first few hours indicate that selective polymerization of isobutylene may occur, This indication is confirmed by mass spectrographic analysis of the unconverted gas; Table V I shows complete recovery of all n-butenes and a conversion of 74.5% of the isobutylene present after the reaction has been in progress for 8 hours. After 25 hours, isobutylene conversion has leveled out a t about 58%. It would, therefore, be possible to increase conversion appreciably by recycling.
TABLE”VI. AKALYSISOF CHARGESTOCKAND PRODUCTS OBTAINED AFTER PASSISG B-B FEED OVER BAUXITE FOR 8 HOURS % Polymer % ’ i-CdHs % n-C4Hs % ’ CiHm 5% Other Charge stock Product
0
10.7
28.7 28.9
14.9 3.8
49.6
51.0
6.8 5.6
After the conversion drops below desirable yields, bauxite catalyst can be restored completely and repeatedly by regeneration in air a t 1000O F. The regenerated bauxite has the same characteristics as freshly activated bauxite and its reuse mill compensate for the longer life of more difficultly regenerable cstzlysts. Polymers from bauxite and phosphoric acid runs (go’% boiling
TABLEVII. CATALYSTS
POLYRIERIZATION OF B-B FEEDTITH VARIOUS 350’ F. A S D 400 P O U N D S PER SQUARE INCH PRESSURE
-4T
(Space velocity: e
Time, Hrs. 1 2 3 4 5 6
3 volumes of liquid per volume of catalyst per hour) Polymers on Charge, % Supported Steel Adsorbent Attapulgus phosphoric balls alumina clay Bauxite acid 0.5 3.2 8.4 17.0 22.7 1.1 0.8 7.6 20.0 26.7 0.6 0.8 6.0 17.2 24.2 0.5 4.9 15.6 25.3 26.8 3.2 13.8 ... ... 12.9 25.7
...
.. .. ..
...
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