Preparation of dimethylaniline R. NORRIS SHREVE, G. N. VRIENS', AND D. A. VOGEL' PURDUE UNIVERSITY, LAFAYETTE, IND.
T h e effect of time, temperature, catalyst concentration, alcohol-amine ratio, and freeboard on the rate of methylation of aniline and methylaniline was determined quantitatively. The equilibrium conversion is high and varies with the temperature and alcohol-amine ratio. Side reactions become noticeable at a temperature of 230' C.
Equation 1 may be combined with Equation 4 or 5, and partly integrated to give, if a # I:
( b - 22)
A
Theory Without speculating on the exact mechanism of the reaction, it might be expected that the rate of alkylation of aniline, or methylaniline, might be proportional to the concentration Of amine, the concentration of alcohol, and some function of the amount of acid present, Since experience has shown that a conversion Of Over 99% is the rate Of the reverse reaction may be Provided the c m ~ e r s i o nis kept substantially below this value. In any single run the amount of catalyst is constant; hence, the alkylation of aniline might be thought to follow a system of consecutive bimolecular reaction equations. Since a mathematical treatment Of this System could not be found, the following analysis was made:
_ dx dt --
* dt
=
k,a(l
- z)(b - z - y)
kza(x - y)(b - 5 - y j
(l)
.
(2)
y a .r
t
= original mole ratio of methanol = =
(1
- Y)
(3)
- 2)
This may be solved directly for y to give, if a # 1:
Y= or, if
(Y
=
(1
- x)a + 011
- 1
0-1
(4)
1 y =
x
+ (1 -z)ln(l
- 5)
(5)
Present address, American Cyanamid Company, Calco Chemical Division, Bound Brook, N. J. 2 Present address, Moore, Olson, and Trexler, Chicago, Ill. 1
'I)
dz (1 - z ) [ ( b- 22) - (1 - z)ln(l - z)]
(7)
The above integrals are of a tYPe which does not, in general, permit a dirert analytical integration. However, if a is known, the appropriate equation may be graphically integrated and a Plot made of h a t versus 5 . Since LY can be obtained experimentally from Equation 4, if the composition of the amine mixture is known a t any time, a direct approach can thus be made to the problem Of verifying the reaction Order*
Techniques The majority of the runs were carried out in a standard high pressure, rocking-bomb-type autoclave, having a capacity of 800 ml. The amount of reaction occurring during the heating period of about 1 hour was found to be equivalent to 0.20 hour a t reaction temperature. The reactions were halted by removing the bomb from the jacket and quenching it. Purification of the product included neutralizing the catalyst, filtering, separating, and distilling. Owing to the closeness of their boiling points, the amines are not separated by a simple distillation. A study was made of a large number of procedures for the quantitative determination of aniline, methylaniline, and dimethylaniline. The picryl chloride method of analysis for aniline ( 6 ) and the freezing point method for dimethylaniline (3,7 ) were chosen as the most practical from the standpoint of accuracy and simplicity of equipment. The freezing point of pure dimethglaniline 1s given as 2.45" C. (6). This figure \\,as checked by repeated fractionation of a sample of material initially freezing a t 2.07" C. After four passes throu h a 30-inch Lecky-Ewe11 column, a fraction was obtained whica froze a t 2.43" C. By means of a series of known mixtures, the following equation was formulated for use over a range of 88 to 92% dimethylaniline, where the percentages are by weight and T i s the freezing point in degrees centigrade.
If Equation 2 is divided by Equation 1, the following result is obtained, where (Y equals the ratio of the rate constants, kz/kl:
9=p
-
= 95.19
+ 1.759T + 0.123(% aniline)
(8)
After having determined the aniline content by reaction with picryl chloride, a weighed sample was diluted to about 90% with a known amount of standard dimethylaniline, to bring the freezing point to a convenient value, and the freezing point was determined. After calculation of the dimethylaniline content, the methylaniline was obtained by difference.
= original concentration of aniline
dx
-
1
% dimethylaniline
= fraction of aniline reacted = fraction of dimethylaniline formed
to aniline time ki reaction rate constant for alkylation of aniline k2 = reaction rate constant for alkylation of methylaniline b
LY =
hiat =
where
z
+ (1 - zj[(l
(6)
or, if LTHOUGH dimethylaniline has been manufactured on a commercial scale by the liquid phase methylation of aniline since 1866 ( d ) , no published account of a laboratory investigation of this reaction has been found. As carried out industrially (1,8 ) , 100 parts of aniline, 110 parts of methano], and 10 parts of 660 Bk, sulfuric acid are charged to a steel autoclave and heated a t 205" C. for 6 hours. The dimethylaniline thus produced should contain less than 1.0% of monomethylaniline. The purpose of this study was t o determine the effectsof various process variables on the alkylation of aniline and methylaniline to dimethylaniline. The five variables investigated were reaction time, catalyst concentration, temperature, alcohol-amine ratio, and amount of freeboard left in the autoclave.
dz
klat =
Effect of Time The first series of runs were made on the methylation of methylaniline, using charges of 2 moles of methanol, 1 mole of water, and 0.0766 equivalent of sulfuric acid per mole of methylaniline. The purpose of the water was to simulate conditions existing during the methylation of aniline after one methyl group had entered and split out an equivalent amount of water. The time was varied from 1 to 8 hours, and the reaction temperature was held a t about 195" C. The purpose was to verify the order of the reaction by studying the variation of composition with time, all other factors being held constant. The results were correlated by means of both a first-order equation and a second-order equation.
791
INDUSTRIAL AND ENGINEERING CHEMISTRY
192
k,"
Vol. 42, No. 5
Figure 2. (ka),,t es. kat for Methylation of Methylaniline
Figure 1. k,,t u5. kt for Methylation of Methylaniline
of a was 1.0, the two rate constants are assumed to hc equal antl the subscripts will be dropped.
where z is the fraction of methyla,niline reacted antl u is the original concentration of methylaniline. I n the first rase the rate of reaction is assumed to bc proportional to the conreiitr:rt~ion of methylaniline only and in t,he second case to both methylaniline and methanol concentrations. The resulting data arc !:thula!ed in Table I. Runs 9 and 10 wrrc made a t a slightly higher teniperature than runs 1 to 8, which accounts for their highe:. rate. In Figures 1 and 2, Lt and kat are plotted against kart and (kn),,,t, rather than agairist t , in order to reduce runs 9 and 10 to R (>ommon basis with runs 1 to 8. The comparison shom that the data are represented better by the first-order equation, Figure 1 , than by the second order equation, Figure 2 . I11 Figure 3, the variation of composition with time is shon-n for thr first-order equation,
Table I.
Methylation of Methylaniline
1,139 1 789 1.236 1.772 0,830 0.815 0.844 1.260 1.326 0,716 o.z;j 0.308 0.458 11.484 0.367 2.23 0.600 o.m 0.973 0.913 4.21 0.622 0.145 o 166 0.270 0,260 1.20 0.237 0.442 0.694 0.417 0,509 0.711 3.20 0.732 o.nn 1.130 0.684 1.132 5.21 1.348 1.976 1.411 0.861 1973 7.20 0.349 0.412 0.604 0.455 0.607 2.20 R u n s 1-8: kav = 0 . 2 1 7 ; (ka)or = 0 , 1 3 8 ; rune 9-10: k m = 0.274: (ka)aa = 0.187 where k = first-order reartion rate constant and ka = product o f second-order reaction rate constant a n d initial inethylaniliire roncpntl'ation. 1
3
8.26 6.11
Table 11. Determination of Ratio of Rate Constants aniline d 0,240 1.00 0.594 0.94 0.98 0.499 0,138 0.99 0.721 0.92 o.ni1 0.589 0.98 0.128 0.422 i on 0.238 0.340 0.295 0.368 0,347 1.01 0,242 1.09 0.407 0.3.il a = I.atio of rate oonhtanis for alkylation of inethylaniline and aniline.
S O .
11 12 13 14 16 16 17 19 20 (1
Aniline 0,394 0.127 0.185 0,522
aniline 0.366 0 . 279 0,316 0,340 0,208 0 283
In order to correlatc the ~.onc!ionr:ttes again by both first- and to integrate graphiotliy ond order. equations, it was neces sl-~+,showninFigure4, uation7. The resultiiig plot of kat served in place of an equatioii relating these variablep. Thc rcsulting data are giveii in Table 111. The first- and second-order correlations are shown in Figures 5 and ti, respectively. It can IE wen that again the first-order equation gives a better straight h i e . i n Figure 7! the variation of cornposition with liiiic is shown for a ;;yslem of consecutivo first-order reactions n.ilh (:qual rate constants.
The nest series of runs comprised i t study of the effecel of time on the methylation of aniline, using charges of 3 moles of methanol and 0.0766 equivalent of sulfuric mid per mole of aniline. After analyzing each product, a determination vias made of the value of a , the ratio of the rate constants of the two cnonsecutive i reactions. For this purpose, Equation 4 may be ivritteri : follows: F ( a ) = (1
--
x)"
+ (.
- y).
- (1
- y)
=
0
(11)
In solving this equation, it should be noted that there is a trivial solution of cy = 1 in addition to the desired root. Tabie I1 shows t,he results of these calculations. Since the average valuc
00
04
,
I
08
I
I2
I
I
16
I
I
2.0
kw'
Figure 3. Effect of Time on Methylation of Methylaniline
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1950
793
Table 111. Methylation of Aniline Mole Fraction Time, DimethylHr. Aniline aniline ktQ 0 . 5 8 9 2.020 7.20 0.128 1.438 0.238 0.422 5.20 0,047 0,390 1.20 0,643 0.347 1.224 4.20 0.295 0.242 0,920 3.20 0.407 k = firat-order reaction rate constant. b ka = product of second-order reaction rate concentration. Run No. 16 17 18 19 20
kast
=
0.285t 2.055 1.484 0.342 1.198 0.913
katb 0.978 0.623 0.139 0.511 0.362
(kQ)@ut = 0.124t 0.986 0.647 0,149 0.523 0.398
constant and initial aniline
Apparently, in the alkylation of both aniline and methylaniline, the equations for a first-order reaction best represent the observed variation of composition rrith time. This is not interpreted to mean that the reactions are truly first order (unimolecular) but only empirically so over the range of concentrations investigated.
O4I /
I
00
04
O O V I
I
I
I
I
12
08
kaVt
I
I 16
I
I
I
20
0285t
Figure 5. kovt vs. kt for Methylation of Aniline
Effect of Catalyst Concentration The probable function of the acid catalyst in this reaction is to furnish hydrogen ions, which are the true catalyst. Since the concentration of hydrogen ions is a function of the fraction of the amine neutralized by the acid, the latter quantity was used to correlate the effect of the amount of catalyst added. A series of runs were made using charges of 2 moles of methanol, 1 mole of water, and from 0.0 to 0.4 equivalent of sulfuric acid per mole of methylaniline. In analyzing the data obtained, shown in Table IV, a first-order rate constant was calculated for each run. These constants could be correlated very well by use of an equation of the form: k = koz(1 - . 0 . 5 ~ )
(12)
where z is the fraction of amine in the form of its sulfate-Le., the equivalents of sulfuric acid used per mole of amine-and ko is a rate constant which is independent of catalyst concentration. Figure 8 shows the variation of reaction rate with amount of catalyst. fko)ov t = 0.1241
Table IV. Effect of Catalyst Concentration
Figure 6. (ka).,f vs. kat for Methylation of Aniline
Conversion,
Time, Mole k, Hr. Fraction Hr.-1 za r(l 0.52) 0.271 0.10 0.095 4.20 0.580 0 . 7 1 6 0 . 3 0 0.255 1.70 0.704 0.896 0.40 0.320 1.20 0.659 0.000 12.3 0.004 0.00 0,000 z = fraction of amine aa sulfate. b Lo = reaction rate constant independent of catalyst.
Run No. 21 23 24 27
0.0 00
-
1
I
0.2
I
I
I
1
04 a6 kat Ji-x)[3-ex-(l-r;)ln 6x
I
I
0.8
I
k/kn = B/2.81b 0.096 0.255 0.319 0,000
I
10
ll-x)]
0
Figure 4. kat vs. 1 - x for Methylation of Aniline
Effect of Temperature
I
The investigation of the effect of temperature on the formation of dimethylaniline was divided into three parts: a study of the side reactions which take place a t high temperatures, determination of the temperature coefficient of the reaction rate, and a study of the effect of temperature on the reaction equilibrium. I t was necessary to carry out the reaction on a considerably larger scale than was used in most of the runs in order to find and identify small amounts of by-products. Hence, two runs were made in an electrically heated, 2-gallon, steel autoclave, the first a t 206" C. for 6 hours and the second a t 230" C. for 3 hours. The products were purified according to the procedure previously described, except that, in place of the h a 1 simple distillation, the crude amine mixtures were fractionated under vacuum through a Lecky-Enell column. The distillates were collected in several fractions and analyzed by the freezing point method, the rise in temperature on acetylation, or by making an appropriate derivative. The analysis of the low temperature product indicated that no material other than methylauiline and dimethylaniline was present in the distillate. The residue was tarry in nature and efforts to isolate a solid material from it failed. In rectifying the product of the run made a t 230" C., the temperature was constant for most of the distillation but rose about 10" during the last few milli-
INDUSTRIAL A N D ENGINEERING CHEMISTRY
194 IO
I
I
I
I
,
I
I
I
I
Vol. 42, No. 5
I
I
0- bNlLlNE
'-METHYLbNlLlNE n - DlMETHYLANlLlNE
-
m 02r
* r , 01
-
kayt =
00
02851
I
I
I
I
I
Figure 7 . Effect of Time on Methylation of Aniline
12 106
(13)
T
01
-12,106 ___
ho = 6.0 X 10"e
'
(14)
Figure 8. Effect of Catalyst Concentration on Reaction Rate
each iun was held a t 220" C. for 2 hours and then lowered to the desired temperature for several hours more. The data are tabulated in Table VI. The analyses were by freezing point, assuming a value of 2.45' C. for the freezing point of pure dimethylaniline, and the equilibrium constants were calculated assuming niethylaniline as the only impurity in the purified products. Figure 11is a plot of the logarithm of the equilibiium constant versuR the reciprocal of the absolute temperature, the equation of the straight line being: 111
Run NO. 33 34 35 36
Temp., 0
c.
201.6 221.8 212.0 190.8
Aniline, Mo1.e Fraction 0.146 0.046 0.068 0.197
37
38 39 40
Thus the activation energy of the reaction is about 24,000 calories per mole. Equation 14 is plotted in Figure 10, which shows the variation of reaction rate with temperature. I t may be seen that a rise of about 13' doubles the rate. A group of runs was next made under conditions calculated to give an equilibrium conversion, using charges of 2 moles of methanol, 1mole of water, and 0.20 equivalent of sulfuric acid per mole of methylaniline. In order to avoid the extremely long reaction times needed to reach equilibrium a t the lower temperatures,
(15)
--
Temp.,
c.
K
219.5 210.3 200.0 189.5
160 177 202 230
Figure 12 gives a plot of the equilibrium constant against the temperature. Oaing t o the fact that the equilibrium conversion is so high, the accuracy of the constants is somelyhat doubtful. A small error in the freezing point of pure dimethylaniline or traces of impurities in the final product could throw off the value of K by a considerable amount. Holyever, it is felt that the foregoing
kQ,
Hr. - 1 4.90 14.35 8.68 2.84
+ 2820 T
= -0.G4
Conversion, Mole % ' 98.76 98.88 99.02 99.14
Run No.
Effect of Temperature on Rate Time, Hr. 2.20 1.20 1.70 3.20
A'
Table VI. Effect of Temperature on Equilibrium
2.16
Table V.
I
1
1
liters of distillate. Anal3 ses shotved that the first fractions contained only methylaniline and dimethylaniline but that the last fraction contained largely a tertiary amine boiling above dimethylaniline. This was identified as dimethyl-p-toluidine by the picrate derivative. This by-product, which amounted to about 0.6%, was presumably formed by a rearrangement, first noted by Hofmann (b), a t the high temperature of the reaction to give a nuclearly alkylated material. The residue from the high temperature run, amounting to 8% of the product, w.s in the form of a moist, dark brown, crystalline solid. By washing with 9570 ethyl alcohol and recrystallizing from the same solvent, leaflets were obtained and identified as p,p'-tetramethyldiaminodiphenylmethane by the dipicrate derivative, tyhich melts a t 190" C. Evidently, then, both rearrangement to nuclearly alkylated products and oxidation to give formaldehyde derivatives occur a t temperatures in the neighborhood of 230' C. The next series of runs was made at various temperatures using 3 moles of methanol and 0.20 equivalent of sulfuric acid per mole of aniline in order to determine the temperature coefficient. Table V shows the resulting data. A plot of the logarithm of the rate constant versus the reciprocal of the absolute temperature is shown in Figure 9. The method of least squares was used to determine the equation of the best straight line, the result being: In ko = 27.114 -
I
I
2.12
I
I
I
I
I
I
I
I\ In
.k
Figure 9. In ku os. 1/T X IO3
I
I
*
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1950
795
ri w
a
c a
HOURS-'
Lo,
In K
Figure 10. Effect of Temperature on Reaction Rate
Table VII. Mole Ratio,
Ale./
Run No.
Amine
41 42 43
1.5 2.0 3.0
Figure 11. In IT us, l / T X 103
Effect of Ratio of Reactants on Rate Time,
Hr. 1.20 1.20 1.20
conversion, Mole Fraction
0.640 0.691 0.694
1st Order
h, Hr.3 4.8 5.5 5.5
2nd Order
koa,
hr.-1 4.34 3.50 2.15
ko
hr.'l mole-11.
0.81 0.73 0.53
Table VIII. Effect of Ratio of Reactants on Equilibrium Run KO. 44 37-40 45
Mole Ratio, Alc./Amine
Conversion, Mole yo
1.50 2.00 3.00
98.50 98.95 99.05
K 263 189 104
results establish the qualitative conclusion that the equilibrium conversion decreases with increasing temperature and show what conversions are attainable in practice.
K
Figure 12. Effect of Temperature on Equilibrium Constant
Effect of Ratio of Reactants The next process variable to be investigated was the ratio of alcohol to amine, or, the per cent excess alcohol used. The effect on both the reaction rate and equilibrium was studied. A group of runs was first made a t 205' C. using charges of 1 mole of water, 0.20 equivalent of sulfuric acid, and from 1.5 to 3.0 moles of methanol per mole of methylaniline. The resulting data are shown in Table VII. The second-order rate constants were calculated from the equation: 1 ( b - 2) kat = __ In b - 1 b ( l - Z) ~
where b is the original mole ratio of alcohol to methylaniline. On comparison of the two sets of rate constants, it may be seen that again those for a first-order equation are more consistent than the second-order constants. The reaction rate appears to be practically independent of the methanol concentration over a wide range and only falls off when the excess alcohol becomes small. A group of runs was then made at 205' C. using similar charges to determine the effect of excess alcohol on the equilibrium conversion. .4s may be seen in Table VIII, the effect was in the expected direction but quite small. Hence, the value of the equilibrium constant appeared to change considerably. An attempt to approach equilibrium from the opposite direction, by making a run with 99.3% dimethylaniline as a reactant, was inconclusive, since very little change took place in the purity of the starting material. This is further evidence that these equilibrium results must be
considered as primarily qualitative in nature due to the fact that the equilibrium conversion is so high that accurate measurement is difficult.
Effect of Freeboard A study was also made of the amount of freeboard left in the autoclave to determine whether the ratio of gaseous to liquid phase had any effect on either the rate or the equilibrium of the reaction. The results, which are tabulated in Tables I X and X, indicate that this variable is without appreciable effect in either case.
Table IX. Run XO,
Freeboard,
%
Table X. Run No. D E
Effect of Freeboard on Rate Time,
Hr.
Aniline, Mole Fraction
Effect of Freeboard on Equilibrium Freeboard,
%
Conversion, Mole %
40 70
99.00 99.00
ko,
Hr. -1
796
INDUSTRIAL AND ENGINEERING CHEMISTRY
Summary The following conclusions can be drawn as to the formation of diniethylaniline by the liquid phase, batch reaction of aniline and methylaniline with methanol, using a sulfuric acid catalyst : 1. The variation in the composition of the amine mixture niih time during t,he methylation of aniline to dimethy1:iniline is represented accurately by R system of first-order, consecutive reactions in which the reaction mte of the first reaction is directly proportional to the concientration of aniline, the reaction rate of the second reaction is directly proportional to the concent ration of methglaniline, and the spcoific- rate constants of thc t\vo reactions are equal. 2. The variation of thr rc ion rate csonstante \\-ith catalyst micentration is represented accurately b y an equation of the form, I; = koe(1 - 0,52), where, z is the fraction of amine present in the form of the sulfuric arid s d t . 3. Temperatures in the neighborhood of 230" C. cause at least two side reactions to occur: rtwrrangement to nuclear1)- alkylated products, such as diniethyl-1J;-toluidine; and oxidation to give formaldehyde derivatives, such as p,p'-tetrameihyldianiinodiphenylmet,hane. 4. The variation of the reaction rate constants with teniperature is represented accurately by the equation: -12,106
k,
=
6.0 X 101k
*
5. The reaction equilibrium becomes less favorablca
:IS
the
t einperature i 9 increased.
Vol. 42, No. 5
6. The reaction rate constant is only slightly decreased -)k dccreasing the mole ratio of methanol to methylaniline from 3.0 t o 1.5. 7. The equilibrium conversion is increased slightly on illcreasing the mole ratio of methanol l o aniline. 8. The equilibrium conversion is over 99% a t 200" C. using 50% excess methanol. 9. The amount of freeboard lelt in the aut,oclavc has no appreciable effect on either the ratc or the equilibrium of the reaction.
Literature Cited ( 1 ) Groggins, P. H., "Unit Processes in Organic. Synthesis," 31.d cd., p. 598, New York, McGraw-Hill Book Co., 1947. ( 2 ) Hofmann, A. IT.,and hlai~tius,C . A , Ber., 4, 742 (1871). (3) Jones, X*.J., J . SOC. Dyer,s C o i o i ~ r i s i s35, . 43 (1919). (4) Poirrier and Chappat, BidL sue. rhim., 6, 502 (1866). ( 5 ) Spencer, G., and Brimley, .J. E., *J. SOC.Chem. I d . , 64, 53 (1943). (6) Timniermans, J., and Hennaut-lioland, Mme., J . chim. picjl~..32,
501, 589 (1935). (7) U. S. Army Specification, No. SO-ll-3OC, June 17, 194:3, (8) Walter, J., Chem-Ztg., 34, 641 (1910). RECEIVEDSoveinbrr 2. 1949. Abstracted from theses subinittrd to the faculty of Purdue Cniversity by G . S . Vriens in rjartial fulfillment of the requirements for t h e degree oi dortor of philosophy. J u n e 194% and by D. A. \'orel in partial fiilfillnient~oi t h e reqiiiwriirntii for the degree of inaster of scicnre in chemical engineering, .lime 1948.
Production of aromatic nitriles WILLIAM I. DENTON, RICHARD B. BISHOP, HAMILTON P. CALDWELL, AND HAROLD D. CHAPMAN RESEARCH AND DEVELOPMENT DEPARTMENT, SOCONY-VACUUM LABORATORIES, PAULSBORO, S. J .
A
process for producing aromatic nitriles from alkyl- or alkenyl-substituted aromatic hydrocarbons and ammonia is described. Operating conditions are: atmospheric pressure, catalyst temperature of 975" to 1025" F. (524" to 552" C.), and catalyst of molybdic oxide on activated alumina. Liquid space velocities and reactant ratios may be varied over a wide range to obtain the desired results. Conversions per pass of 5 to 10 weight YOand ultimate yields of 60 to 85 weight YO of benzonitrile are realized, using toluene as the hydrocarbon charge.
T
HE increased use of nitriles as chcniical intermediates and in
the resin field has result,ed in a demand for cheaper methods of producing these materials. This paper describes a process for the product,ion of aromat,ic nit>iileshy react,ion of ammonia with aromatic hydrocarbons. Known met,hods of preparing aromatic nitriles include: the reaction of an organic acid lvith ammonia over a dchydration catalyst (8); the dehydration of an amide over suitable catalysts or reagents [Japanese acid clay (I ), phosphorus trichloride (0), phosphorus pentachloride ( S ) , and thionyl chloride ( I O ) ] ; and the dehydration of an amnionium salt of an organic acid with heat ( 7 ) or heat plus a catalyst [thoria, silica gel (Sj; phosphorus pentoxide, aluminum sulfate, aluminum phosphate ( 2 ) ; et,c.I. Other methods of preparation are: isomerization of isonitriles by heating to 200" C. ( I O ) , the reaction of cyanogen bromide and an aromatic hydrocarbon in t,he presence of anhydrous aluminum chloride (4), and the condensation of aryl diazonium compounds with potassium cyanide in t,he presence of cuprous cyanide or nickel cyanide ( 5 ) .
Equipment Figure 1 is a schematic flow diagram of the equipment used in this study.
The hydrocarbon was puinped from a graduated cylinder through a preheat,er coil inimersed in a molten salt bath which was maintained at the desired temperature by electric heaters operated by an automatic controller. The ammonia, tho flow rate of which was measured by a rotameter, was prcheatcd in a similar coil and mixed with the vaporized hydrocarbon prior to entering the reactor. The vapors emerging from the reactor w r e passed through an ice condenser and the liquid product \vas separated from the noncondeiised gases. The liquid product \vas water-n-ashed to remove dissolved ammonia, sampled for infrared analysis, and then distilled to recover nitrile and unreacted hytirocarbon. The lioncondensed gases were measured with a gas meter, sampled for mass-spectrometer analysis, and t h e n vented. Stainless steel reactors of 0.33-, 2-, 8-, and 30-liter capacity were used in this worlr, although experiments have shown that. low-carbon steel may also be used. Bot'h adiabatic and isothermal reactors were investigat'ed, but the majority of the work reported herein was done in isothermal reactors. Adiabatic reactors pcrformed as satisfactorily as isothermal reactor?, except that, at low space velocities some difficukies i n maintaining uniform temperatures were experienced.
Analysis I n order to facilitate the investigation of the variables involved in this process, it was necessary to develop routine methods or analysis. The noncondensed gases contained chiefly unreacted ammonia, hydrogen, nitrogen, anti lesser amounts of hydrocarbons and water. Inasmuch as mass-spectrometer analysis of known synthetic mixtures gave satisfactory results, this mcthod was adopted for the anslysis of the noncondensed gases. T o simplify the analysis of the liquid product, toluene was tho only hydrocarbon charged in the runs made for the purposc of evaluating process variables. This resulted in a liquid product consisting of toluene and benzonit,rile. Because benzonitrile boils 1,44' F. (80' C.) above toluene, separation by distillation is relatively simple and analysis of lOO-granl samples gave reproducible results. It was further found that infrared analysis of ltnown mixtures of benzonitrile and toluene gave results of the same
