COMPARATIVE ACTION O F MIXED CATALYSTS WHEN USED FOR THE JOINT DEHYDRATION OF ETHYL ALCOHOL AND ANILINE. I1 CATALYTIC PREPARATION OF MONOETHYLANILINE N. I. SHUYKIN, A. A. BALANDIN,
AND
F. T. DIMOV
Laboratory o j Organic Chemistry, Section of Catalysis, State University of MOSCOW, Moscow, U.S . S . R. Received J a n u a r y 7, 1936
In our former paper (9) we have investigated the action of mixed catalysts in the joint dehydration of ethyl alcohol and ammonia with the formation of corresponding amines. In connection with this it appeared interesting to test the efficiency of the same catalysts (see below) in the joint dehydration of aniline and ethyl alcohol with the formation of monoand diethylaniline and to compare their action with the activity in this process of pure alumina. We have also tested a catalyst consisting of 95 per cent alumina and 5 per cent nickel oxide, which had proved to be very active in the hydrolysis of diethyl ether under pressure (2). The possibility of obtaining alkylanilines by means of heterogeneous catalysis under ordinary pressure was for the first time established by Mailhe and de Godon (7). These authors passed methyl alcohol and aniline over alumina at 400430°C. and obtained methylaniline and from it, by a further action of methyl alcohol, dimethylaniline. I n the presence of the same catalyst, from o-, m-, and p-toluidines and methyl alcohol a t 350400"C., they obtained (8) a mixture of nearly equal amounts of the corresponding secondary and tertiary amines. Mailhe in his patent (6) concerning the preparation of a series of arylamines, among them ethyl- and diethyl-aniline, recommends the following catalysts: A1203, Tho*, and ZrOz. For the reaction between ethyl alcohol and aniline he proposes alumina a t a temperature of 350400°C. E. and K. Smolensky (10) claim that by passing twice a mixture of methylaniline with methyl alcohol over alumina at 300°C. they obtained dimethylaniline with a yield of 95 per cent. By passing aniline and methyl alcohol over silicon dioxide at 30O-32O0C., monomethylaniline could be obtained. Brown and Reid (3) have investigated the catalytic action of silica gel in the reaction of the ethylation of aniline with alcohol. They found that at a temperature of 385°C. (using a molar ratio aniline: alcohol = 1 :1.05) 1207
1208
N. I. SHUYKIN, A. A. BALANDIN, AND F. T. DIMOV
a mixture of secondary and tertiary amines was obtained with a ratio of 5: 1 and a yield of 41.5 per cent. Using the same temperature but a molar ratio aniline: alcohol = 1 :2.05 they obtained 46.6 per cent of ethylaniline and 13.3 per cent of diethylaniline (ethylaniline :diethylaniline = 77: 2) ; the catalyst rapidly lost its activity. I n later papers the joint dehydration of methyl alcohol and aniline was investigated only in the presence of “Japanese acid earth” (5) (its composition after washing with water and drying in the air: SiOz, 61.67 per cent; A1203,12.28 per cent; Fe203,1.87 per cent; CaO, 0.16 per cent; MgO, 3.44 per cent; loss after drying a t llO”C., 15.66 per cent; loss after heating to incandescence, 4.64 per cent) and in the presence of thorium oxide (4). The joint dehydration of ethyl alcohol and aniline in the presence of mixed catalysts has not as yet been investigated. It must be remarked that the study of mixed catalysts used for the alkylation of aromatic amines has not only a purely theoretical interest, but also a practical one, because it gives the necessary data concerning the influence of impurities upon the action of catalysts in industrial processes. The following catalysts have been tested in our experiments:I (1) AlzOa; (2) A1203(90 per cent) Fe203(10 per cent) ;(3) AL03 (90 per cent) SnO (10 per cent); (4) AlZ03 (90 per cent) ZnO (10 per cent); (5) A1203 (80 per cent) Cr2O3(20 per cent) ; (6) Ala03 (95 per cent) NiO (5 per cent).2
+
+
+
+
+
EXPERIMENTAL PART
Experiments on the joint catalytic dehydration of aniline and ethyl alcohol were performed with each of the above-mentioned catalysts a t temperatures of 350, 375, and 400°C. The apparatus consisted of a tube of hard glass having a 15 mm. interior diameter into which the catalyst was placed. The catalyst was in the form of small lumps dried a t 150OC. The tube was placed in an electric furnace and was provided a t its front end with a special buret (1) for a regular introduction of a mixture of alcohol and aniline, and at the rear end with a receiver that was cooled with ice. The length of the catalyst layer in all experiments was 48 cm. In every experiment the same mixture was used, consisting of 86 g. of pure, freshly distilled aniline (b.p. 182.5-183.5”C., nioo1.5864) and 64 g. of 96 per cent rectified ethyl alcohol (df’0.8056). The inolecular ratio aniline :alcohol was about 2: 2.9. The mixture of aniline and alcohol was introduced into the reaction tube regularly, a t a rate of 12 cc. per hour, and was passed over the catalyst once. As all the
.
1 The description of their preparation is given in the preceding paper by Shuykin, Balandin, and Plotkin (9). All the catalysts were actually hydroxides. 2 For the preparation of this catalyst see reference 9.
1209
COMPARATIVE ACTION O F MIXED CATALYSTS. I1
experiments were of a comparative nature, the same conditions were maintained in all cases where this was possible. In all the experiments a t a temperature of 300°C. the color of the condensate was light yellow; with the rise of the temperature a change of color to orange-yellow was observed. The condensates obtained were separated from the water-alcohol layer and dried over melted sodium hydroxide. The product was fractionated twice with a Vigreux column (sixteen sections, length 58 cm.), which was heated by means of electricity to a constant temperature. An insignificant quantity of the product which distilled up to 16OOC. consisted of ether, of alcohol that had not entered into the reaction, of water, and of traces of aniline. This fore-run was not taken into account. TABLE 1 Indices o j rejraction of mixtures 100
ANILINE
D OF
ETHYLANILINE
MIXTURB
per cent
per cent
100
0 10
90 80 70 60 50 40 30 20 10 0
20 30 40 50 60 70 80 90 100
1
ETHYLANILINE
per cent
,
1.5864 1.5812 1.5781 1,5753 1.5722 1.5693 1.5663 1.5637 1.5607 1 ,5580 1 ,5557
1
~
DIETHYLANILIN
per cent
100
0
90 80
10 20 30 40 50 60 70 80 90 100
70 60
50 40 30 20 10 0
OF THE
MIXTURE
1 .5557 1.5543 1 ,5528 1.5516 1 ,5503 1.5490 1 ,5477 1.5466 1 ,5453 1 ,5440 1,5424
The following fractions were collected: I,160-195°C. ; 11, 195-210°C.; and 111, 210-230°C. In the flask there remained a small quantity of a liquid, boiling above 230"C., which was not investigated furtherea Fraction I (160-195°C.) consisted of a mixture of aniline and ethylaniline; fraction I1 (195-210°C.) of aniline, ethylaniline, and traces of diethylaniline; fraction I11 (210-230°C.) of ethylaniline and diethylaniline. For each fraction the indices of refraction were determined. I n order to determine the composition of these fractions by the indices of refraction, two series of synthetic mixtures were prepared consisting (a) of aniline and ethylaniline and (b) of ethylaniline and diethylaniline, taken in different percentages by weight (see table 1). The initial. substances (Kahl3 The residues from all experiments were collected and fractionated. The product boiled from 230 t o 271°C. and gave a negative reaction for the presence of diphenylamine.
1210
N. I. SHUYKIN, A. A. BALANDIN, AND F. T. DIMOV
FIQ.1. DEPENDENCE OF INDEX OF REFRACTION ON THE COMPOSITION OF THE MIXTURE
DIE THY LANlLlNE
ETHYL ANILINE
FIQ.2. DEPENDENCE OF INDEX OF REFRACTION ON THE COMPOSITION OF THE MIXTURE
-
baum) were previously distilled twice: aniline, b.p. 182.5-183.5' a t 20 751 mm., nEoo1.5864; ethylaniline, b.p. 203-204°C. a t 754 mm., nD 1.5557; diethylaniline, b.p. 214.5-215.5OC. a t 754 mm., nzoe1.5424.
1211
COMPARATIVE ACTION OF MIXED CATALYSTS. I1
TABLE 2 Alkylation of aniline
-
E
- -
2i
2
is
CATALYBTS
!!I 3 !Ii
"C.
A1203..
1
..., .. . . . . . . . . .. . .. .
h
-Per cent
gm.
per cent
per cent
per cent
1 2 3
30 60 7
1.5631 1.5556 64.3 1.5474
3.2
67.526.7
375
1 2 3
19 1.5679 50 1.5581 51.4 7 1.5468
3.5
54.937.4
400
1 2 3
22 1.5728 37 1.5581 41.8 15 1.5471
7.1
48.9 40.1
350
1 2 3
28 39 7
1.5727 1,5556 48.0 1.5502
2.1
50.1 21.4
375
1 2 3
32 42 6
1.5700 1.5576 52.2 1.5528
0.7
52.9 26.7
400
1 52 2 25 3 4
1.5732 1.5595 1.5557
350
1 2 3
25 39 9
1,5748 1,5562 45.6 1.5500
2.8
48.434.7
375
1 2 3
25 46
1,5785 1.5550 1.5486
48.7
1.5
50.2 37.4
1 2 3
40 31 3
1.5703 1.5519 44.0 1.5540
0.3
44.340.1
+
All08 (90 per cent) SnO (10 per cent). . . . . . . . . . . ,
g
2 $ s c s 8 i -
350
+
(90 per cent) FelOa (10 per cent). . . . . . . . . . .
A1203
D m
400
4
--
39.4
39.4 48.1
1212
N. I. SHUYKIN, A. A. BALANDIN, AND F. T. DIMOV
TABLE 2-Concluded
r
BB
-
$
P
R
B
E
E
E
w
0”
CATALY STS
- -
E
B
w
E 1
0 s
8
e
e
M
4
z w
4
8
B P 0 c - - - -
BE
.
“C
ALOa(80 per cent)
7m.
b
ECEI per
cent
1,5750 18 1.5631 31.6 4 1,5556
per cent
per cent
I’races
31 .€ 4.1
1 2 141C 3
60
375
1 1321 2 3
52 14 8
1.5744 1,5646 29.7 1.5586
29.7 8 . 1
400
1 1331 2 3
66 14 4
1,5796 1.5689 18.9 1.5610
18.9 5.4
350
1 132/ 2 3
58 16 3
1.5726 1.5580 34.9 1.5518
0.6
35.5 9 . 1
375
1 136{ 2 3
47 31 2
1,5726 1,5578 43.2 1,5553
I‘races
43.2 7.4
400
4
54 1,5773 16 1,5620 24.4 3 1.5571
350
+
(95 per cent) NiO (5 per cent). . . . , . . . . . . , .
ram
3
I
+
Cr20s (20 per cent). . . . . . . . . . . .
c
U
350
+
A1203 (90 per cent) ZnO (10 per cent). . . . . . . . . . .
$2
E
8
375
400
1 2
3
1 1381 2 3
53 20 5
1,5720 1.5600 38.4 1,5554
1 1321 2
55 6
3
3
1.5785 1,5590 16.3 1,5564
1 1311 2 3
53 1.5779 5 1.5646 15.3 1 1,5605
24.4 $ , 2
0.1
38.5 2.1
16.3 3 . 1
15.3 1.8 -
COMPARATIVE ACTION OF MIXED CATALYSTS. I1
1213
On the basis of the refractometric data obtained, two curves were plotted (figures 1and 2), showing the dependence of the index of refraction on the composition of the mixture expressed in per cent. By means of these curves the content of amines in the fractions was determined (with a certain approximation). When calculating we did not take into consideration the possible presence in every fraction of small amounts of a third component. Such an arbitrary supposition in the determination of the composition of the mixture leads to an error not exceeding 2 to 3 per cent. We used the refractometric curves in order to calculate for every experiment the percentage of the aniline transformed, so that the efficiency of different catalysts in the reaction of the ethylation of aniline could be compared. The percentage of the aniline transformed is easily obtained, knowing the composition of the fractions and taking into account that for the formation of l g. of monoethylaniline and of diethylaniline, respectively, 93/121 and 93,449 g. of aniline are required. The results obtained in all experiments are given in table 2. The loss of alcohol, due to decomposition, shown in the last column of the table, is calculated from the difference in weight between the initial mixture and the crude condensate, taking into consideration that the decomposition leads to the formation of ethylene. DISCUSSION OF RESULTS
Comparing the results obtained, it may be seen'that all the mixed catalysts that were tested in the reaction of the ethylation of aniline with alcohol proved to be less efficient compared with pure alumina. Among the mixed catalysts investigated the most active ones in this Fez03 and A1203 SnO. As well process have been found to be A1203 as in the case 0' the ethylation of ammonia, the first of these catalysts, used a t a temperature of 350 and 375"C., leads to a reaction with a smaller decomposition of alcohol as compared with pure alumina. It is interesting to note that at a temperature of 400°C.the percentage of aniline transformed is in all cases and with all catalysts considerably smaller than a t lower temperatures. In the case of pure A1203, A1208 + NiO, and A1203 ZnO it already attains its maximum value a t 350°C.; in the case of other catalysts at 375°C. As a rule, the loss of alcohol due to decomposition increases with the rise of temperature; an exception is presented by A1203 ZnO at 375"C., but these results are within the limits of a possible error in the experiment. The loss of alcohol in the experiment with A1203 Crz03a t 375°C. may be explained by a comparatively high yield of the products of the principal reaction of ethylation.
+
+
+
+
+
1214
N . I. SHUYKIN, A. A. BALANDIN, AND F. T. DIMOV
It should be noted that under the*conditions of our experiments the mixed catalysts direct the reaction chiefly towards the formation of monoethylaniline. In the presence of pure alumina the relative yield of diethylaniline is considerably higher, which is shown by the determination of the composition of the condensates using the indices of refraction. Thus, for instance, in the case of pure alumina, at 4OO0C.,about 42 per cent of aniline was transformed into monoethylaniline, and 7 per cent into diethylaniline, while a t the same temperature, in the presence of A1203 + Fe203,about 39 per cent was transformed into monoethylaniline, and no transformation whatever into diethylaniline was observed. An insufficient amount of alcohol in comparison with that required by theory for a complete transformation of aniline into diethylaniline (aniline : alcohol = 1:1.5instead of 1:2) was taken with the purpose of promoting the formation of monoethylaniline. However, as the data of the present paper show, this measure was superfluous, as in the presence of the mixed catalysts that were used the secondary amine is formed almost exclusively. It follows from all this, as well as from the consideration of the data of table 2, that in this case (as well as in the investigations concerning the ethylation of ammonia by alcohol) no additivity of the properties of oxides entering into the composition of mixed catalysts is observed. The conclusions we have presented in our preceding paper concerning the specific properties of mixed catalysts when used for similar changes of the systems
-
c-c 1
1
H O I1 K:, 3
N C
I
I
H O U(1 K: 1)
o c I
I
H O I1 K433 1
differing only by the elements cpll (C, N, and 0, which change according to the order of their atomic numbers) remain also valid for the case being investigated, with the only difference that in the catalytic ethylation of aniline one must take into account the influence of the phenyl radical, which increases the rate of this reaction in comparison with a similar reaction, the ethylation of ammonia. The addition to alumina of dehydrogenating oxides investigated by us causes the retardation of the reaction of class I K: 1, contrary to the case of the hydrolysis of diethyl ether (class I1 K:3 1). This conclusion applies not only to the formation of monoethylaniline, but also to the retardation of the next stage-the formation of diethylaniline from monoethylanilinea reaction, which, as one .can easily see, requires the same index with the symbol U (I K: 1). Thus the application of mixed catalysts of the type investigated, decreasing the reaction rate, makes it possible to obtain synthetically mono-
1215
COMPARATIVE ACTION O F MIXED CATALYSTS. I1
alkylanilines, which are more difficult to obtain in a pure state than the dialkylsubstituted anilines (exhaustive alkylation). CONCLUSIONS
1. In the present paper the action of mixed catalysts on the joint dehydration of aniline and ethyl alcohol has been studied; a dehydrating catalyst, alumina, was taken, to which oxides of metals promoting dehydrogenation were added. 2. The alkylating action of the catalysts studied after a single passing of the mixture of aniline with 96 per cent ethyl alcohol having a molecular ratio 1 :1.45, at a rate of 12 cc. per hour, a t 350, 375, and 400°C. may be seen from table 3. TABLE 3 Alkylating action of the calalysts TEMPERATURE
CORRESPONDING TO A
CATALYBT8
MAXIMUEl TRANSFORMATION OF ANILINB
YIELD OF TOTAL PERCENT. AGE OF TRANSFORMBD ANILINE
MONOMETAYLANILINE (RECKONED
FROM ANILINE)
YIELD O F DIETHYLANILINE (RECKONED FROM ANILINE)
--
A1203 ........................... . . . . . . . . . . . . . .. AlnOa (90 per cent) Fez03(10 per cent). . . . . . A1203 (90 per cent) SnO (10 per cent). . . . . . . , A1203 (80 per cent) Cr2Os (20 per cent) . . . . . AlzOs (95 per cent) NiO (5 per cent) .... . . . . , AlzOa (90 per cent) ZnO (10 per cent) .... . . . .
+ + + + +
.
'C.
per cent
350 375 375 375 350 350
67.5 52.9 50.2 43.2 38.5 31.6
64.3 52.2 48.7 43.2 38.4 31.6
3.2 0.7 1.5 Traces 0.1 Traces
3. It has been found that the above-mentioned additions decrease the reaction rate as compared with pure alumina. 4. This leads to the formation of monoethylaniline by preference, and this circumstance can be made use of for synthetic purposes. 5. The substitution of hydrogen by the phenyl radical in the molecule of ammonia increases the reaction rate of the joint dehydration with ethyl alcohol. REFERENCES (1) BALANDIN, A. A.: J. Phys. Chem. U. S. S. R. 4,268 (1933). (2) BALANDIN, A. A., SHUYKIN, N . I., NASVIJSKY, M. P., AND KOSMINSKAYA, T. K.: J. Gen. Chem. U. S. S. R. 2,604 (1932); Ber. 66,1560 (1932). (3) BROWN AND REID:J. Am. Chem. SOC.46, 1836 (1924). (4) CHANDRA, BANKIM: J. Indian Chem. SOC.6,383 (1928).
1216
N . I. SHUYKIN, A. A. BALANDIN, AND F. T. DIMOV
(5) INOUE, HARUSHIQE: Bull. Chem. Soc. Japan 1, 157 (1926). MAILHE:French patent 23,891, August 31, 1918. MAILHEAND DE GODON:Compt. rend. 166, 467 (1918). MAILREAND DE GODON:Compt. rend. 166,564 (1918). SRUYKIN, N. I., BALANDIN, A. A , , AND PLOTKIN, Z. I.: J. Phys. Chem. 39, 1197 (1935). (10) SMOLENSKY, E., AND SMOLENSKY, K.: Roczniki Chemji 1, 232 (1923); Chem. Zentr. 1923,111,204. '
(6) (7) (8) (9)
.
