462
T
H E procedure of alkylation of isoparaffis with olefins in the presence of such catalysts as sulfuric or hydrofluoric acids or aluminum chloride is well known and widely used commercially. The chemistry of this process, however, is very complex. As a matter of fact, the structure of the resulting alkylation products, as a rule, does not correspond to the simple addition of an olefin to the tertiary carbon atom of the isoparaffin. Various theories have been advanced along this line, which, however, are beyond the scope of this article (I, I, 9 , 6 , 7, l a ) . Frey and Hepp (4) and Oberfell and Frey (8) described the noncatalytic alkylation of paraffins with olefins. This is essentially a high pressure-temperature thermal process. The temperature is 500’ C. (932’ F.) or somewhat higher, and the pressure 4500 pounds per square inch or more. I n contrast to catalytic alkylation, normal paraffins and isoparaffins are alkylated thermally with equal ease. Ethane and methane react with difficulty. As to the olefins, the decreasing order of the activity of olefins is: ethene, propene, n-butenes, isobutene. The alkylation of isobutane with ethene was studied more thoroughly and was commercialized. The predominant hydrocarbon in the alkylate is 2,2-&methylbutane or neohexane. In contrast to catalytic alkylation, the structure of the synthetic hydrocarbon corresponds to the expected one, as will be shown. This article describes another method of alkylating paraffins in the presence of homogeneous catalysts such as aliphatic halogenated compounds, nitro compounds, etc. This is also a hightemperature-pressure process, but the conditions are milder than in the noncatalytic method. The average alkylation temperature is about 400 ’C . (752 ’F.) and the presswe is about 3000 pounds gage for the alkylation of isobutane with ethene and about 4500 pounds when propene is the olefin used. Both normal and isoparaffins are alkylated by this method. The structure of the synthetic hydrocarbons in general corresponds to what one would expect, as is also true in the case of the noncatalytic alkylation procedure. The application of homogeneous catalysts to alkylation of aromatics has been disclosed in several patents and is described by one of the authors (11).
.
E X P E R I M E N T A L PROCEDURE
maintained a t this temperature for a given reaction time, cooled finally by dry ice, and then discharged. The discharged material comprising an excess of butane was stabilized by fractionation t o remove the unreacted n-butane or isobutane. The resultant liquid boiling above n-butane or isobutane was considered as total alkylate. It could be fractionated further, producing an aviation alkylate boiling up to 150’ C. (302’ F.), a motor gasoline cut boiling to 200’ C. (392’ F.), and a residuum; or it could be fractionated into narrow fractions comprising predominant hydrocarbons (neohexane, 3-methylpentane, triptane, etc.). The procedure of stabilization and further fractionation of the alkylatewas the same for batch (bomb) and continuous operations. Two units, employed for continuous operation, differed mainly in their respective sizes. The larger unit is shown on the facing page. The high pressure-temperature equipment is in the steel cell. At the left is a fractionating column (equivalent to 100 plates) for separating alkylate components, and the panel board of the column with temperature recorder. The smaller unit is represented schematically in Figure 1. The charge comprising, for example, an excess of isobutane and ethene or propene with the proper catalyst, was pumped by displacement from a cylinder with glycol using a Bosch pump to the reactor.coi1 immersed in a lead bath. Two charging cylinders were provided, one of which could be charged while the other was on stream. The pressure was manually controlled through a needle valve and varied in different experiments from 2000 t o 6000 pounds per square inch at the inlet from the reaction coil. This scheme was employed in order to avoid use of compressors. The lead bath was maintained a t a constant temperature by strip heaters controlled by an intervil timer. The reactor coil was made of ‘/,-inch extra heavy stainless steel tubing, 40 feet long, the total volume being 1700 cc. The charge, upon being released from the reaction coil, passed to a water-cooled condenser, thence to a receiver or gas separator, and on to a pressure fractionating tower of about fifteen theoretical plates (“stabilizer”) which removed isobutane (or n-butane) as well as all lower molecular weight gases formed on alkylation m by-products. The “stabilized” bottoms were considered as total alkylate which could be further fractionated as disclosed above. The procedure described was a once-through operation. I n a series of larger scale experiments on the alkylation of isobutane with ethene, a recycle operation was employed, in which unreacted and separated isobutane was returned (recycled) t o the alkylation coil. An experimental high pressure cracking unit was used for this purpose. The alkylate produced is a result of the above operations contained chiorine since mostly chlorinated compounds were used I
A series of experiments was performed in 2-liter hydrogenation bombs of the American Instrument Company. The bomb was cooled with dry ice and charged with liquid butane and catalyst by pouring in a solution of the latter in the former. The bomb was sealed and charged with olefin by introducing the proper weight of ethene or propene from a lecture-size cylinder. The charged bomb was heated to the reaction temperature, 463
. INDUSTRIAL AND ENGINEERING CHEMISTRY
464
Vol. 38, No. 5
20,000 LB.
0
*
F i g u r e 1. Flow D i a g r a m of Laboratory Triptane U n i t Preheat and reactor coils are 1/4-inch extra heavy stainless steel tubing. All valves and fittings are Amerlean I nstruments Company's high pressure type.
I
TO P R ~ S S U R E STAB1 LI ZER
+SAFETY
DISK
as catalysts. The proportion of chlorine varied from 1 to 2% by weight. As a rule, only an insignificant part of the chlorine could be recovered to the form of the original chlorinated compound used as a catalyst. Thus very little or none of the catalyst was left unchanged after the alkylation. The chlorine in the form of newly formed chlorinated compounds way distributed throughout the raw alkylate with some tendency toward roncentration in a low-boiling fraction in special cases. The alkylate was dechlorinated by many known methods, including the reaction with metallic sodium a t elevated temperatures, treatment over bauxite, adsorption by silica gel, and potassium hydroxide-alcohol treatment. The most practical method seems t o be treatment over bauxite a t atmospheric pressure and temperatures around 500 O F. Under these mild conditions and even a t somewhat higher temperatures the hydrocarbons are not decomposed. The alkylate treated by this process contained traces of chlorine but gave a negative Beilstein test. The dechlorination is a necessary step to remove the nonhydrocarbon impurities from the alkylate and to produce a commercially acceptable motor or aviation fuel. It should be pointed out that the alkylate containing chlorine compounds has a depressed octane value and a negative tetraethyllead response. In many instances the dechlorinated alkylate was fractionated to produce narrow fractions comprising more or less pure hydrocarbons (e.g., neohexane in the isobutane-ethene alkylate or 3,3-dimethylpentane in the isopentane-ethene alkylate) or a mixLure of several hydrocarbons with close boiling points (2,2-dimethylpentane and triptane in propene-isobutane alkylate). The separation of such narrow fractions or fairly pure hydrocarbons was performed in small fractionating packed columns or in a large packed column equivalent to 100 theoreti'cal plates. 2,2-Dimethylpentane, 2-methylhexane, and triptane present in the fractions boiling between 76-86 and 76-92' C. were determined by the infrared absorption method. O
ALKYLATION
OF
BUTANES W I T H ETHENE
The alkylation of paraffins with olefins catalyzed by halogenated and other compounds produces hydrocarbons of the
structure predictable on the basis of the greater reactivity of tertiary and secondary hydrogen atoms. Thus, the alkylation of n-butane and isobutane with ethene may be represented as follows:
CHJ
CHs
I
H--C-H
+ H*C=CHs
+H-k-CH2-CH3
H-&-€II
(1)
H-A-H
I
I
CH,
CH, (3-methylpentane)
CHI
CH, HaC-(&-€I I,
+ H2C=CH2 --+
I
HIC-C-CHz-CHg
CHI
CHa (neohexane)
TABLEI. COMPOSITION BY ALKYL.4TlON
Boiling Range, 25-33 33-44 44-55 55-65 65-150 150-21 0
(2)
II
O F STABILIZED ALKYLATEPRODUCED O F I S O B U T A X E WITH E T H E X E (TABLE
C
x)
Wt. 70 13 8 3 8
43 2 11 2 18 9 9.1
Hydrocarbons Mostly isopentane Mostly n-pentane LIostly neohexane CBisomers, mostly methylpentanee Heavier Heavier
TABI'E 11. (>OMPbSITION O F STABILIZED ALKYL.vrE P R O DUCED BY ALKYLATIONOF OIL FIELD BUTANE(85% TL-BUTANE) TTITII ETmNE
Boiling Range, C . 22-46 45-55 55-65 65-85 85-95 95-105 106-150 >150
TTt. c/a
26.7 6.2 26.4 7.2 2.4 2.3 18.7 10.4
sDistillate p . Gr. of 0 : 664
0.666 0.677 0.709 0.712
Hydrocarbonu Pentanes Mainly neohexane Mainly 3-methylpentane
.... ,...
,...
.... ....
.~
INDUSTRIAL AND ENGINEERING CHEMISTRY
May, 1946
465
relation between temperature and pressure.
I
The actual pres-
TABLE 111. COMPOSITION OF STABILIZED ALKYLATE PRODUCED sures used for the noncatalytic alkylation of isobutane with ethALKYLATION OF ISOPENTANE WITH ETHENE
BY
Boiling Range, C.
Wt. %
59-85.5 85.5-88.5 88.5-90.5 90.5-150 150-210 >210
7.2 54.6 7.8 17.2 9.8 6.0
d:'
'
0.7015
... .., ... ...
n1p
Hydrocarbon
1:392
3,3-Dimethylpentane
.......... .......... .. .. .. .. .. .. .. .. .. ..
... ... ... ...
..........
An analysis of the alkylates resulting in either case (Tables I and 11) shows that the hydrocarbons of reactions 1 and 2 are a t least preponderant. It is obvious that the alkylation process also produces several other hydrocarbons as a result of numerous side and secondary reactions which are probable under the hightemperature conditions of the process. The alkylation of isopentane with ethene follows the same pattern; the reaction takes place between the tertiary hydrogen atom and ethene and produces 3,3-dimethylpentane (Table 111): CHa
1
HrC-C-H
CHs
I + HZC=CH* +HSC-CC-CH,-CHI
I
(3)
I
CH3
CH,
It is interesting to compare the results of the homogeneous hightemperature alkylation with those of the low-temperature alkylation in the presence of the Friedel-Crafts type catalyst; in contrast to the homogeneous alkylation of isobutane-ethene, diisopropyl is formed from isobutane and ethene a t low temperature using aluminum chloride. The calculations of the free energy A F " for the above three reactions give the following simplified equations: Reaction 1: A F o = -22,700 Reaction 2: A F o = -26,500 Reaction 3: AF' = -19,800
++ 33T 36T + 33T
(14
(2-4) (3.4)
The calculations were made on the basis of equations and data derived by Thomas et al. (IS)for normal paraffins and olefins and of data developed by Rossini et al. (IO) for isomeric paraffins. The zero values of free energy for the above reactions are calculated for the temperatures as follows: 415", 463", and 323" C. (779", 865", and 613" F.), respectively. As will be evident later, the alkylation of butanes and pentanes with $bene in the presence of homogeneous catalysts proceeds at about 400" C. or higher. At lower temperatures the rate of the reactions is too slow, although the free energy of the alkylation rapidly decreases with decreasing temperature. Thus the use of high pressures is necessary to decrease the level of free energy at 400" C. or above. The effect of the pressure can be calculated by the equation:
+
AF = -RT log nat P AF" where AF = free energy a t temperature T and under pressure P i n atmospheres In the following approximate calculated pressures are assumed to be equal t o fugacities. Thus an arbitrary substantially negative value of the free energy of alkylation (e.g., -5000 calories), ensuring a shift of the equilibrium predominantly td the alkylation side, corresponds to the following temperature-pressure conditions : n-Butane Isobutane
++ ethene +3-methylpentane ethene +neohexane
700"K. (427' C.) 18 atm. 13 atm.
880' K. (527"C.) 250 atm. 100 atm.
These figures at least indicate the order of pressures to be applied for effecting alkylation at elevated temperatures and the
ene a t temperatures of about 500" C. were close to those calculated above or between 4500 and 6300 pounds per square inch. The effect of pressure on the alkylation of an isobutane-ethene mixture in the presence of chloroform as a homogeneous catalyst a t 400" C. is given in Table IV. At a pressure of 1000 pounds per square inch *he alkylation is insignificant, but it increases rapidly with increasing pressure. The yield of total alkylate a t 3000 pounds pressure is 210% with reference to ethene charged, as compared with theoretical yield of neohexane of 307% from these reactants. Table V summarizes the data on the alkylation of an isobutaneethene mixture noncatalytically and catalytically a t varied temperatures, other conditions being equal. At 330" C. the catalytic alkylation proceeds to a comparatively large extent (141y0 alkylate on ethene), while the noncatalytic alkylation gives only a small yield of a highly olefinic product. With increasing temperature the difference between the catalytic and noncatalytic processes levels off, as the comparative data for 400" C. clearly show. The data for thg catalytic alkylation of isobutane and n-butane with ethene under the same conditions are giveh in Tables VI and VI1 for batch and continuous operations, respectively. The yields of alkylate are practically identical, an indication that normal and isobutane are alkylated with equal ease. The same results were reported by Oberfell and Frey for the noncatalytic high temperature alkylation. It should be remembered that the equations for free energy and the free energy values for alkylation of normal and isobutane are very close. Notwithstanding this, the low-temperature alkylation in the presence of acidic catalysts (strong acids, aluminum chloride, etc.) gives quite different results; only isoparaffins are activated and involved in alkylation reactions, while normal paraffins remain upaffected. Tables VI11 and IX show the effect of various homogeneous catalysts on the alkylation of normal and isobutane with ethene. The conckntration of catalysts varied in a comparatively narrow range from 1.0 to 3.2y0 by weight with reference t o the total charge. A greater part of organic oxygen compounds are inactive, as homogeneous alkylation catalysts. Many halogen compounds and nitro compounds are active. There is an a p proximate relation between the activity and thermal instability of the homogeneous catalysts. Very stable chlorine compounds, e.g., such as chlorobenzene, hexachlorobenzene, chloronaphthalenes, etc., are inactive. Freon 21 (dichlorodifluoromethane), however, is an exception since it is.quite stable and quite active.
TABLEIV. ALKYLATION OF ISOBUTANE WITH ETHENE (CONTINUOUS ONCE-THROUGH OPERATION) (Weight ratio of isobutane t o ethene, 9 to 1; temperature 400' C.; reaction time, approximately 15 minutes; catalyst, 1% chloroiorm b y weight) Pressure, Yield of Total Alkylate Lb./Sq. In. Based on Ethene, % b y Wt.
1000 2000 3000
70 140 210
.
TABLEV. ALKYLATIONOF ISOBUTANE WITH ETHENE (BATCHOPERATION) (Weight ratio of isobutane t o ethene, 7 to 1: ultimate pressure, 3300 lb./sq. in., reaction time, 30 minutes) Yield of Total Iodine No. Tpp., Catalyst Alkylate Based of Alkylate C. Catalyst % ,by Wt. on Ethene up to 160' C. 330 None ... 33.3 90 Chloroform 1.0 141.0 6
370
480
...
53.7 119.2
.. ..
...
155 232
21 14
None Chlorinated naphtha
1.0
None Chloroform
1.0
INDUSTRIAL AND ENGINEERING CHEMISTRY
466
TABLEVI. ALKYLATION OF KORMALA N D ISOBUTAXE WITH ETHENE (BATCH OPERATION) (Catalyst, 1.6% Freon 21 by weight; weight ratio of butane t o ethene, 8 to 1; temperature, 370' C.; ultimate pressure, 3300 Ib./sq. in.; reaction time, 30 minutes) Iodine No. of Alkylate Yield of Total Alkylateup to 2000 C. Based on Ethene, YGby I?.t. Paraffin n-Butane 154 22 Isobutane 145 21
I n addition to the isoheptanes described, Zmethylhexane in appreciable yields is also produced. The formation of this isomer is evidently due to the reaction between the olefin and a primary hydrogen atom:
CHI
I
H-C-CHs
+ H&=CH-CH3 +
AH3
TABLEVII. ALKYLATION OF BUT.4NEs WITH ETHENE (CONTINUOUS ONCE-THROUGH OPER.4TION) [Temperature 427' C.; operation pressure, 3000 lb./sq. in. : reaction time, 10 minutes (2:35 liters/liter coil vol./hour) ; catalyst, chlorinated naphtha, 1% on charge] Oil Field Isob ut a n e Butane Isobutane, 88 5 Hydrocarbon Butane, 8 9 . 4 charge, % by wt. Ethene, 1 0 . 6 Ethene, 11.5 Yields, % by wt. 2.4 CI to Casatd. 4.0 2.5 C2H4 CqHs 3.8 C4Hio CdHa 72.6 73.5 2 1.6 Alkylate 1 9 . 6 __ 100.0 100.0
++
-
OF n-BUTANE TABLE V I I I . ALKYLATION (BATCH OPERATION)
WITH
ETHENE
(Weight ratio of butane t o ethene, 8 to 1 ; temperature, 370' C . ; ultimate pressure, 3300 lb./sq. in.; reaction time, 30 minutes) Yield of Total Iodine No. Catalyst Alkylate Based on of Alkylate Catalyst % by Wt. Etbene, %"by Wt. up to 200' C. 34.0 None 65 41 Hexachlorobenzene 3.2 46.3 20 Phosphorus trichloride 1.3 78.3 8 Benzalchloride 1.6 83.1 Bensylchloride 3.0 104.0 3.5 6 Nitromethane 1.6 124.0 4 Acetylchloride 2.3 127.1 22 Freon 21 1.6 154.0
Vol. 38, No. 5
CHI
HaC-CH-CHz--CHz-CH2--CH3 (2-methylhexane)
(6)
The difference in the results of alkylation in the presence of homogeneous catalysts a t high temperatures and those in the presence of the Friedel-Crafts type catalysts a t low temperatures is as striking for isobutane-propene as for isobutane-ethene. McAllister et al. ( 7 ) investigated the alkylate produced by interaction of isobutane with propene over sulfuric acid, and found 2 , 4 and mostly 2,3-dimethylpentanes as the isoheptanes formed. The same hydrocarbons were determined in the alkylate produced from the same hydrocarbons over aluminum chloride by Pines et al. (9) and over hydrogen fluoride by Linn and Grosse (6).
The calculations of the free energy AF for reactions 4, 5, and 6 gave the simplified equations as follows: Reaction 4: A F " = -22,600 Reaction 5: AF" = -22,000 Reaction 6: AF" = -19,000
+ 392' + 40T + 327'
(W (5N
(6.4)
The zero values of AF" for these three reactions are calculated as 307", 277", and 321' C. (585", 531", 610" F.), respectively. As in the case of butanes ethene, temperatures of the order of 400" C. or higher must be used to effect a reasonable rate of alkylation of isobutane-propene in the presence of homogeneous catalysts. Under these temperature conditions the free energies A.Fo will be positive, and adequately high pressures must be employed to make the reactions thermodynamically possible. The calculations of the pressures required were made in the same
+
The results of continuous catalytic alkylation of isobutaneethene are summarized in Tables VI1 and X. The yields of total alkylate are 188 and 195%, on the average 191%, with reference to ethene charged at 427" C. (801" F.) and 2500-3000 pounds per square inch pressure, for a reaction time of 15minutes in the presence of 1% chlorinated naphtha. The percentage of neohexane in the alkylate is approximately 4070 (Table I ) , and thus the yield of neohexane is calculated as 767. with reference to ethene charged, the theoretical yield being 3077, on the same basis.
TABLE IX. ALKYLATION OB ISOBUTANE WITH ETHENE (BATCH OPERATION) (Weight ratio of butane t o ethene, 8 t o 1 ; . temperature 370° C.; ultimate pressure, 3300 Ib./sq. In.; reactlon time, 30 minutes) Yield of Total Catalyst, Alkvlate Based on Catalyst 70 by Wt. Ethine, % b y Wt. None 53.7 a-Chloronaphthalene 1.0 57.7 a-Chlorophenol 1.6 89.8 1 , l,2-Trichloroethane 1.6 109.7 Benzylchloride 1.6 111.7 Chlorinated naphtha 1.0 119.2 Chlorex 1.6 136.4 (4) Freon 21 1.6 145.0 Trichloroacetaldehgde '1.6 167.3 '
ALKYLATION OF ISOBUTANE W I T H PROPENE
Alkylation of isobutane with propene in the presence of homogeneous catalysts produces the following isoheptanes:
HZC-A-H
+CH~=CH-C~I,-H,C-~-CH~-CHZ-CHI AH, (2,2-dimethylpentanc)
AH3 CHI Hac-C-HI CHI I
CHz
I : + 4H +H3C-C-CH-CHZ CH, I
TABLEX. ALKYIATION OF ISOBUTAKE WITH ETHENE (CONTINUOUS OPERATIOX WITH RECYCLING)
CH3 CH3 (5)
AH, (triptane)
As will be shown later, these isoheptanes are actually formed in moderate yield as the result of alkylation of isobutane-propene in the presence of homogeneous catalysts; as in the case of isobutaneethene, the reactions proceed between the olefin and the tertiary hydrogen.
[Temperature, 427' C.; operation pressure, 2500 Ib./sq. in.; reaction time, 10 minutes (2.4 liters/liter coil vol./hour) catalyst, chlorinated naphtha, 1 % on charge] * Hydrocarbon charge, 7*by wt. 92 Isobutane Ethene 8 Yields, yGby wt. CI to Ca satd. C2H4 CaHs iso-CdHlo n-Cdh n&Ha iso-CaHa Alkylate
+
.
0.5 1.2 0.3 79.2 0.8 1.7 15.6
*
May, 1946
I N D U S T R I A L AND E N G I N E E R I N G CHEMISTRY
467
pene (reaction 4). The extent of the reaction between the tertiary carbon atom and the second unsaturated carbon atom (CONTINUOUS ONCE-THROUGH OPERATION) of propene (reaction 5) is much smaller. The reaction between (Temperature, 413' C.;- 10% by weight propene in charge) the primary carbon atoms of isobutane and the terminal unsaturated ~ ~ " , " , " , ' ~ ~ a ,(&'~ , $ ~ ~ ~ $: & ~ c ~atom~ of ~propene ~ (reaction $ ~ 6~) produces an average of Pressure, Reaction Isoheptane Isoheptane 25% 2-methylhexanes in the fraction. However, it should be Lb./ Time, Total fraction sq. In. Rlln. alkylate (M6-860c.) ( 7 ~ & t ~ o ~ . , kept in mind that the statistical probability of this reaction is much greater than that of the two above reactions since there 3000 13 4 29 5 69 16 105 24 are nine carbon valencies'of isobutane open to this reaction in4000 17 2 30 4 5000 20 9 41 6 125 29 stead of only one open to reactions 4 and 5. 6000 24 5 65 14 150 34 The formation and distribution of the three a Propene chloride, 1.2% on charge, used as catalyst. isomeric heptanes does not correspond to the equilibrium between these isomers. According TABLE XII. ALKYLATION OF ISOBUTANE WITH PROPENE to the data oE Rossini et al. (IO), the equi(BATCHOPERATION) librium between the three isomers. would form (Temperature, 400' C.; reaction time, 15 minutes; ultimate pressure, about 4000 lb./sq. 9.5y0 triptane, 20.5% 2,%dimethylpentene, and in.; 10% by weight of propene in charge) 70.0% 2-methylhexane. Such a result could Yield of Isoheptane . C0mpn.a of'Isoheptane be expected, however, since the homogeneous Fraction, yo Yield of Total Fraction catalysts used are by no means isomerization * Alkylate on (76-92' C.) 2,Z-Di2Propene on Propene TripmethylMeihyl catalysts. Catalyst, % Charged, 73 Charged, % tane pentane hexaneTriptane is by far the most important of Trichloropropane, 0 7 100 30 .. .. .. Trichloropropane, 1.4 170 61 7 60 33 the hydrocarbons produced by homogeneous Trichloropropane, 2 8 170 60 11 66 23 catalytic alkylation of isobutane-propene. As a Tribromopropane, 1 . 4 59 8 82 10 160 Chlorine, 1.1 160 63 11 60 29 matter of fact, the synthesis of triptane was Bromine, 1.2 140 64 8 81 11 the main endeavor in the extended study of a Neglecting the presence of other hydrocarbons as impurities which may amount to 570 of the total fraction. the isobutane-propene alkylation. Table XI11 summarizes the yields of total alkylate, isoheptanes, and triptane under various alkylaTABLE XIIT. L4LKYT.ATJONOF ISOBUTANE \VITH PROPENE tion conditions. The data show that the yield (CONTINUOUS ONCE-THROUGH OPERATION) . of triptane was small, averaging approximately (Pressure, 6000 lb./sq. in.; space rate, 1.5) 5 4 % of the propene charged. In addition, Yield on CsHs Charged, Conthe separation of triptane formed from its iso% by Wt. * tact CaHe in % On Temp., Time, Charge, Total IsoTripmors, particularly from 2,2-dimethylpentane, preCatalyst Charge C. Min. % alkylate heptanes tane sents enormous practical difficulties due to None 413 24 5 9.5 65 14 0 CaHsCln 1 2 413 24 5 10 0 150 34 4 the closeness of the boiling points (80.8' and CsHaCla 1 2 427 24 0 10 9 150 39 5 24 0 5.0 181 52 8 78.9' C.) for triptane and 2,2-dimethylpentane, CsHaCls 1 2 427 12 455 23.0 10.0 153 CsHsCls 39 6 respectively.
TABLEXI. ALKYLATION OF ISOBUTANE WITH PROPENE
..
ACKNOWLEDGMENT
ma?ner as for butanes
+ ethene for an arbitrary negative value
of AF" equal to -5000 Calories with the results as follows:
,
Isobutane Isobutane Isobutane
+ propene + 22-dimothylpentane propene+ triptane + propene 9 2-methylhexane T
700' K. (427'C.) 1100 atm. 2600 atm. 405 atm.
800' K.
(527'C.) 5,000atm.
12,000arm. 1,400atm.
These data show that the efficient homogeneous catalytic alkylation of isobutane-propene a t temperatures of 400" C. or higher requires much higher pressures than the alkylation of butanes ethene. The data on alkylation of isobutane-propene in the ,poncatalytic and catalytic processc)s at various pressures are summarized in Table XI. The yields in the noncatalytic process are very small, and the products consist largely of polymers. The yields of alkylate in the 'catalytic process increase with increasing pressure. The comparison of these data with those of Table IV shows that the degree of alkylation with propene under the same pressures is much lower than that obtained with ethene as could be expected on the basis of the above thermodynamic calculations. Table XI1 gives data on the yields of total alkylate and isoheptane fraction as well as the composition of the latter. 2,2Dimethylpentane is by far the predominant isoheptane formed, followed by 2-methylhexane and then by triptane. Thus the main reaction of alkylation proceeds between the tertiary carbon atom of isobutane and the terminal unsaturated carbon atom of pro-
+
The able assistance of the following members of the staff-
J. W. Brooks, P. D. Caesar, H, D. Chapman, K. F. Hayden, A. N. Joecks, G. Johnson, J. B. Kirkpatrick, C. G. Myers, J. Kellett, G. S. Shrewsbury, J. J. Somers, W. A. Stover, and R. N. Work-in the extensive experimental work, and of F. P. Hochgesang in the infrared analysis of hydrocarbons is hereby acknowledged with appreciation. LITERATURE C I T E D
(1) Birch, 5. F., and Dunstan, A. E., Trans. Faraday SOC.,35, 1013 (1939). (2) Caesar,'P. D.,and Francis, A. W., IND.ENG.CHEM.,33, 1426 (1941). (3) Ciapetta, F. G.,Ibid., 37, 1210 (1945). (4) Frey, F.E.,and Hepp, H. I., IND. ENQ.CHEM.,28,1439 (1936). (5) Grosse, A. V.,and Ipatieff, V. N., J . Org. Chem., 8,438 (1943). ENG.CHEM.,37,924 (1945). (6) Linn, C. B.,and Grosse, A. V., IND. (7) McAllister, 8. H., Anderson, J., Ballard, S. A., and Ross, W. E., J. Org. Chem., 6,847(1941). ( 8 ) Oberfell, C. C., and Frey, F. E.,Oil-Gas J.,38, Nos. 28 and 29 (1939). Grosse, A. V., and Igatieff, V. N., J . Am. Chem. SOC., (9) Pines, H., 64,33(1942).
(10) Rossini, F. D., Prosen, J. R., and Pitser, K. S., J. Research Natl. Bur,&andards, 27,529(1941). (11) Sachanen, A. N., and Caesar, P. D., IND. ENG.CHEM.38, 43 (1946). (12) Schmerling, L.,J. Am. Chem. SOC.,67, 1778 (1945). (13) Thomas, C. L., Egloff, G., and Morrell, J . C., IND. ENG.CHEM., 29,1260(1937). PRESENTED before the Division of Petroleum Chemistry a t the 109th Meetivg of the AXERICAN CHEMICAL SOCIETY in Atlantic City, N. J
