328
INDUSTRIAL AND ENGINEERING CHEMISTRY
fiber much more effectively than in the case of a similar product that has been prepared from the corresponding unmercerized wood fiber. On the other hand, a dry mercerized fiber prepared as above will resist the penetration of acetic anhydride and the acetylating catalyst, and demands a special means to reswell the fiber wall in order to facilitate the entry of the acetylating reagent. Otherwise the acetylation is incomplete and unsatisfactory. A dry, alkali-free, mercerized wood fiber swells less rapidly and to a lesser degree when reimmersed in strong alkaline
VOL. 32, NO. 3
solutions than it does the first time the cellulose is mercerized. This fact is sometimes reflected in a less complete xanthation if a purification of wood fiber has been attained by such means. Space does not allow further elaboration of .the behavior of the hardened mercerized wood fiber. Only one additional caution is offered to those who attempt to predict its behavior. Unless they know by what process the wood has been delignified and how the raw fiber has been bleached or refined, prediction becomes nothing more than speculation. PRESENTED before the Division of Cellulose Chemistry a t the 97th Meeting of the Amerioan Chemical Society, Baltimore, Md.
Catalytic Alkylation of Isobutane with Gaseous Olefins J
J
F. H. BLUNCK AND D. R. CARMODY Standard Oil Company (Indiana), Whiting, Ind.
present work, which has been H E union of a paraffin At 1000 pounds per square inch pressure conducted in the vicinity of with a n olefin to produce and about 400" F., isobutane reacts with 400" F., a pressure of 1000 a paraffin has been degaseous olefins under the influence of pounds was sufficient to obtain scribed by several investigators. double chlorides of aluminum and alkali favorable equilibrium conditions. Ruthruff and Kuentzel (6, 7 ) metals, particularly sodium aluminum Practically all the experiments passed refinery mixtures of conto be described were carried out densable gaseous hydrocarbons chloride and lithium aluminum chloride. a t pressures not far from 1000 over certain double halides of The alkylation reaction is accompanied by pounds. aluminum'with other metals a t a varying but considerable amount of 750 pounds per square inch. At polymerization and by extensive rearrangevarious t e m p e r a t u r e s a b o v e Materials ments, which lead to the production of room temperature the liquid The double compounds of product obtained was greater products not explicable on any simple alkali halides and aluminum in amount than the olefins in theory. The life of the catalyst is short, halides were employed as catathe charge, and they concluded and the alkylation reaction declines more lysts. They are not like ort h a t combination of olefins rapidly than polymerization. Higher temdinary double s a l t s ; their and paraffins was taking place. properties differ markedly from perature favors alkylation but further Ipatieff and others (4, 6) althose of the constituents. They kylated isoparaffins with decreases catalyst life. The potassium exhibit none of the volatility olefins a t room temperature compound is not very active. of the aluminum halides, and and above, using boron trithe melting points are generally fluoride, nickel, and water, and in the vicinity of 400" F. or below. As-used in these experialkylated n-hexane and isobutane with ethylene using alumiments they were usually liquids and were suspended on num chloride a t room temperature. Several investigators pumice, which was shown by a blank experiment to have no ( I , $ ) have shown that strong sulfuric acid will produce alkylacatalytic action under the prevailing conditions. tion at low temperatures and pressures. Frey and Hepp The compounds were prepared by heating equal molar (3) effected the paraffin-olefin junction noncatalytically a t quantities of anhydrous aluminum chloride and the halide, high temperature and pressure. The work here described previously mixed, to 500" F. in a glass tube placed inside a utilizes catalysts and conditions generally similar to those sealed steel bomb. A slight excess of aluminum chloride was employed by Ruthruff and Kuentzel, but pure hydrocarbons added t o replace any loss of aluminum chloride due to subwere used as a charge. The paraffin in all cases was isobulimation in the early stages of the heating period, After the tane, and the olefins employed were ethylene, propylene, and temperature of 500" F. had been obtained, the bomb was alisobutylene. lowed t o cool slowly. The complex salt was removed from The alkylation reaction is favored by low temperatures and the bomb and remelted in the glass tube to sublime off any high pressures. At room temperature the equilibrium is in unreacted aluminum chloride. I n most of the experiments favor of the alkylated product even a t atmospheric pressure. the catalyst was prepared by pouring the molten double salt At 900' F. pressures of several thousand pounds per square onto an equal weight of oven-dry 8-mesh pumice. The inch are required to obtain a substantial conversion. I n the
T
INDUSTRIAL AND ENGINEERING CHEMISTRY
MARCH, 1940
double salt-pumice mixture was shaken in a 1-liter flask until cool to obtain uniform distribution of the salt on the carria. Since they are hygroscopic, precaution was taken in all cases t o keep them out of contact with moisture.
329
Behavior of Catalysts The general character of the results obtained is illustrated in Table I, which shows two tests in which a propylene-isobutane mixture was passed over lithium aluminum chloride. The products were collected in two parts in each case and analyzed The reaction is not pure alkylation in any case. The product is somewhat unsaturated, which indic''L t es a considerable amount of polymerization. Also, the products are distributed over the boiling range in a way which cannot be accounted for by alkylation and polymerization combined. It is evident that a considerable rearrangement of the materials occurs which leads to the formation of other products. The amount of alkylation obtained is considerable at the beginning. This is indicated by the low unsaturation and by the prominence of heptanes in the liquid product. The catalyst declines in activity rapidly, especially with regard to its alkylating ability. This is shown by a comparison of the first and second periods in each run, and by I
34 30 26
$22
Y
E
3
18 14
P 10 6
2 c5
'6
c7
'8
CIo
BOTTOMS
ON DISTRIBUTIOX OF FIGURE 1. EFFECTOF AGEOF CATALYST PRODUCTS
1
The isobutane, ethylene, and propylene were purchased materials, used as received. The isobutylene was prepared by dehydrating tert-butyl alcohol over phosphoric acid on coke a t about 450" F.
Apparatus and Procedure The apparatus used was of a simple flow type. Liquid feed was forced into a catalyst chamber from a feed storage system. The liquid was forced out of the top of the storage system by a mercury piston backed by a constant-pressure nitrogen reservoir. The desired pressure was maintained on the catalyst system by a hand-operated back-pressure valve located at the outlet of the catalyst bomb. The catalyst chamber was constructed of double extra heavy seamless steel tubing. Special heads screwed into the ends against copper gaskets effected the pressure seal. It was wound with insulated resistance wire and lagged, The temperature was measured by a thermocouple placed in a thermowell in the catalyst space. The first section of the chamber was empty and served as a preheating section. Pressure was measured with a Bourdon type gage placed just ahead of the chamber. In all runs the amount of catalyst was about 100 cc. After leaving the chamber, the gas and liquid were partially separated by water and solid carbon dioxide-acetone condensers. The liquid was debutanized on a vacuum-jacketed column. The distillation analysis of the debutanized products was carried out in a small helix-packed total reflux column. Because of difficulty in accurately measuring the feed, reliable weight balances were not available, and yields as given are subject to snme uncertainty. For the same reason, it has not seemed worth while t o base results on the olefin consumed. Proportion of Olefin and Paraffin In all alkylation work of this type, pdymerization of the olefin is a competing reaction; therefore it is desirable to keep the olefin concentration low. For this reason it would be advantageous to bleed in the olefin gradually t o the paraffin, either in a static or a flow system. This was not done in the present work; the olefin-paraffin mixture, with the paraffin usually in excess, was passed over the catalyst. It was found that a large ratio of paraffin to olefin was not necessary t o obtain substantial amounts of alkylation, although (Table I1 shows) lower olefin concentrations produced more saturated products.
BOTTOMS
I
80
z60
8
:: Y 3 40
B
20
0 400
450 500 TEMPERATURE OF.
550
FIGURE 2. EFFECTOF TEMPERATURE ON YIELD AND ON PRODUCT DISTRIBUTION WITH PROPYLENE OVER TABLEI. ALKYLATIONOF ISOBUTANE LITHIUMALUMINUM CHLORIDE ON PUMICE
R u n No. Temperature, O F. Pressure Ib./sq in gage Flow ratk (liquid feed vol./vol. oatalyst/hr.) Duration, hr. Feed compn mole % Isobutane" Propylene Catalyst, cc. Yield, yo@ Products, liquid vol. yo on Ca+
cs
42-4 42-B 43-A 43-B 545 548 550 555 1000 1200 1200 1200 1.59 1.59 1.76 1.57 5.0 4.5 6 8 67 33 100
17.0
65 65 85 35 35 35 100 100 100 9.8 17.8 11.0
6.6 0.6 2.5 1.3 1.5 11.6 615 1013 6:O Unsatd. i n CS 1.5 28.2 9.5 48.0 c7 35.6 16.7 25.8 11.2 Unsatd. in Ct 2.5 40.3 14.0 65.7 C8 11.1 15.8 12.9 13.3 Unsstd. in Ca 6.5 52.0 18.5 67.2 CP 12.8 21.0 14.3 24.3 Unsatd. in Cp 35.7 9 . 0 55.7 25.0 ClOC 22.3 39.4 33.2 43.9 a Weight per cent yield based on the weight of heptane t h a t would have been produced b y the uni& of all the olefin in the feed, mole for mole, with isobutane. Unsatd. in Cr Ce
VOL. 32, NO. 3
IXDUSTRIAL AND ENGINEERING CHEMISTRY
330
-
WITH OLEFINSOVER SODIUM ALUMINUXCHLORIDE ox PUMICE TABLE11. ALKYLATIONOF ISOBUTANE
Run No. Feed. mole Tn IsobutankOlefin
1
2
95 5
400 1000 1.5 2.5 93 Products, liquid vol. % on C s i Ca. % Unsatd., % n
sQ
cos %
Unsatd., yo
nT
c7, %
Unsatd., % n?
cs, %
Unsatd.,
nl,c b
90
10
315 1000 4.8 2.5 27
85 15 400 1000 1.6 4.5
6
5
77 23 340 1000 5.0 2.0 GO
14.8 16.8 8.8 4.0 4.0 8.0 1.3695 1.3560 1.3562
17.6 3.0 10.0 30.0 1.3560 1.3583
9.6 10 1.3810
9.6 10 1.3765
7.2 10 1.3769
7.7 16 1.3782
5.5 35 1.3710
6.8 6.0 1.3960
9.3 14.0 1.3920
5.6 9.0 1.3660
7.7 16.0 1.3920
40.8 29.5 10.0 13.4 1.3900 1.4075
29.5 30.0 14.1 13.0 1,4090 1.4060
yo
CSC (bottoms) a For definition, see Table I.
90 10 400 1000 2.1 3.25 83
Isobutylene 3 4
49.3 44.0 37.0 Within the experimental error of 2%.
Figure 1, which gives the relative liquid volume percentage of each fraction a t the end of the first 6 hours and the following 8 hours. After use the catalyst was generally covered with a heavy carbon deposit which penetrated into the interior of the catalyst particles. Because of the rapid decline in activity, the data presented in the latter part of the report are selected from runs of approximately the same length. made on fresh catalvst. CATALYTIC ACTIV~TY.
Most of the experiments were made on sodium aluminum chloride and t o a smaller extent on lithium aluminum chloride. O t h e r a l k a l i halides were also tried. Lithium and sodium aluminum chlorides are the most active. Ammonium aluminum chloride is somewhat less active and requires about 450" F. for any s u b s t a n t i a l activity. Potassium aluminum chloride is nearly inactive, although some polymerization was obFIGURE3. EFFECT OF SPACE VELOCITY OF FEEDON YIELD served a t 600" F. BEHAVIOROF OLEFINS. Table I1 shows the results obtained in various runs alkylating isobutane withisobutylene, propylene, and ethylene, respectively. Generally speaking, the ease of alkylation decreases in the order mentioned, but the specificity of the reaction increases; this indicates that the tendency to polymerize falls off more rapidly than the tendency to alkylate. Regardless of conditions or feed composition, the products are found to contain material with all possible numbers of carbon atoms in the gasoline range. EFFECT OF TEMPERATURE. It was found that temperature had a pronounced effect on the distribution of the hydrocarbon products. A series of runs made using lithium chloroaluminate a t different temperatures was compared, and the data are plotted in Figure 2. The upper portion shows the yield of liquid product from a feed of 35 to 40 mole per cent
37.0
90 10 385 0
1.5 3 0 32.5
-Propylen7 8
so
20 400 1000 3.7 2.2 46
80 20 425 1000 3.6 2.0 56
9 50 50
425 1000 3.8 2.4 25
-Ethylen10 11
12
95 5 310 1000 4.0 2 0 30
85 15 340 1000 1.8 3.0
94 6 340 1000 3.2 2.0 25
11.8 !3.0 11.8 12.0 35.0 Slightb Slight 5 1.3746 1.3560 1.3615 1.3615 8.8 9.3 8.5 10.0 40 0 Slight 7 1.3845 1.3746 1.3740 1.3754
6.2 13.0 12.5 Complete satn. 1.3620 1.3615 1.3620 12.4 29.0 25.0 Complete satn. 1.3680 1.3695 1.3693
1.3920
5,9 35 1.4055
17.1 0 1.3850
15.8 Slight 1.3879
12.0 8 1.3865
12.4 13.0 12.5 Complete satn. 1.3810 1.3850 1.3840
38.0 20.0 1.4110
44.1 30.4 1,4170
14.5 0 1.3890
11.0 Slight 1.3879
11.0 37.2 32.0 25 8 Complete Satn. 1.3990 1.3915 1.3916 1.3917
48.4
29
46.1
52.9
5 1 25
55.0
31.8
13.0
25.0
propylene in isobutane a t 1000 to 1200 pounds per square inch gage pressure. It is apparent that the optimum temperature for the production of liquid hydrocarbons is in the neighborhood of 440" F. The lower portion of the graph indicates the variation in the distribution of the various hydrocarbon cuts with the reaction temperature. The volume per cent of each individual cut is shown as the distance between the solid curves, and the volume per cent of olefins present in any fraction is shown as the distance between the broken line and the solid line immediately below it. The increase in the heptane fraction a t the expense of heavier hydrocarbons with increase in temperature is probably due to the suppression of polymerization. This behavior of lithium chloroaluminate was found to be generally true of sodium chloroaluminate, but the optimum temperature in the latter case was in the neighborhood of 425" F. In general, the life of the catalyst and the yield of liquid products decreased with a rise in temperature while the selectivity of the catalyst towards alkylation increased. EFFECTOF FEEDRATE. Only a brief study was made of the effect of the feed rate on the yield of liquid products in the presence of sodium chloroaluminate on pumice. The experiments were carried out a t 425" F. and 1000 pounds per square inch gage pressure with a feed of 50 mole per cent propylene and 50 mole per cent isobutane. I n Figure 3 the weight per cent yield of liquid products is plotted against the rate expressed as volume of feed per volume of catalyst per hour. With a rate greater than 4.0 the yield fell off rapidly. There was also an indication that high feed rates gave products which were more unsaturated. This fact is in agreement with the observations of other investigators who have found the reaction rate for alkylation considerably slower than that for polymerization.
Literature Cited (1) B a t a a f s c h e P e t r o l e u m M a a t s c h a p p i j , F r e n c h Patent 824,329 (1938). (2) B i r c h , D u n s t a n , F i d l e r , P i m , a n d T d t , Oil Gas J . , 37, NO. 00, 49 (1938). (3) Frey and H e p p , IKD.ENG.CHEM.,23, 1439 (1936). (4) Ipatieff and Grosse, J. Am. Chem. Soc., 5 7 , 1616 (1935). (5) I p a t i e f f , Grosse, P i n e s , and K o m a r e w s k y , Ibid., 58, 913 (1936). (6) R u t h r u f f , U. S. P a t e n t 2,032,518 (1937). (7) Ruthruff a n d K u e n t r e l , Ibid., 2,082,520 (1937). PRESENTED as part of the Symposium on the Role of Catalysis in Petroleum Chemistry before a joint session of the Divisiona of Petroleum Chemistry and of Industrial and Engineering Chemistry a t the 97th Meeting of the American Chemical Society, Baltimore, Md.
