Mononitration of Benzene No systematic investigation has been reported of the effect of the process variables in the nitration of benzene. Benzene has been nitrated with a yield of over 98qo mononitrobenzene using a sulfuric acid-benzene weight ratio of 1.2, initial sulfuric acid concentration of 84.0aJ,, and the theoretical amount of nitric acid at 60' C. for 40 minutes. The effect of changing the process variables is shown graphically, so that a process can be operated at conditions that are optimum for yield and acid recovery. A method of plotting contour lines of equal yield shows that a broad band of conditions of sulfuric acid concentration and temperature exists in which yields of over 98% can be obtained. AND J. JOHN MILLS' University of Texas, Austin, Tex.
KENNETH A. KOBE
ITROBENZENE has been produced commercially since 1856 when Simpson, Maule, and Nicholson started operations in England. Their nitrators were twenty 1-gallon bottles, each containing a quart of benzene, placed in a pail of cold water. The operator added a few ounces of mixed acid to the bottle, shook it, and returned it to the pail of water, and a t the end of the 12-hour shift he had added 6 pounds of mixed acid to each bottle and had produced altogether 6 gallons of nitrobenzene (8). Now the production in the United States exceeds 100,000,000 pounds per year, the values since 1945 (13)being as follows: Year Production, Pounds 1945 116,203,000 1946 115,109,000 1047 142,198,000 1948 123,764,000 1949 64 ,609,OOOa 1950 132,131,000 1951 164,298,000 a The U.8. Tariff Commission states that this figure is low by 25,000,000 to 30,000,000pounds. PREVIOUS WORK
B
No systematic study has been reported of the effect of the various process variables on the yield of nitrobenzene. A number of papers (1-3, 5, 6) report commercial operations as carried out by some particular plant. The most comprehensive of these are the BIOS reports ( 1 , d ) on operations in Germany. Other commerical operations have been described by Frank (6) and Groggins (6). Fierz-Dayid ( 4 ) described the laboratory production of nitrobenzene in which 100 grams of benzene are nitrated. iMalyarevskir and Kalinchenko (11) nitrated benzene to determine the effect of mixed acid concentrations and amounts, as well as temperature, on the yield of nitrobenzene. They showed that acid concentrations within the ranges sulfuric acid 60.9 to 48.7'%, nitric acid 38.5 to 23.08%, water 14.8 to 12.8'%, and temperatures between 40' and 80' C. gave yields above 97y0 of theoretical. However, they failed to show the limits of concentrations and temperatures that could be used. A summary of the previous work is given in Table I , in which the variables are arranged in terms of those of the present investigation.
The 2-liter kettle had a desiccator-type cover with four openings on top which would receive a standard-taper joint. The large center opening admitted the stirrer, and the three smaller openings admitted the cooling coil, thermometer, and dropping funnel. The agitator shaft was surrounded by a reflux condenser 4 inches long, which condensed any vaporized benzene. The agitator was a three-bladed propeller-type stirrer, 1.5 inches in diameter, with a blade pitch of 35'. The propeller was rotated at 5000 r.p.m. by a variable-speed laboratory stirrer, so that the liquid was forced against the bottom of the kettle. The cooling coil wag made by forming a stainless steel tube 0.25 inch in outside diameter into a loosely wound helical coil 4 inches in diameter and nine turns long. The leads to the coil were bent parallel to the helix and passed up through a stainless steel taper plug fitted into one of the openings in the lid. Tap water was usually used as the coolant, though ice water was pumped through the coil for the nitrations a t 45" C. The thermometer was graduated from -10" to 80" C. in 0.2". It passed through a standard-taper plug and was held in place by Tygon tubing. The mixed acid was added through a thistle tube, the lower end of which was bent to form a loop which was submerged in the liquid contents of the nitrator. A 500-ml. dispensing buret delivered the mixed acid to the thistle tube. With this arrangement the interior of the nitrator was sealed so that no vapors could escape,
TABLE I. SUMMARY OF PREVIOUS WORKON MONONITRATION OF BENZENE
Groggins (6)
Malyarevskii and Kalinchenko (11)
.
1
Final Temp.,
E&?,
HzSOa,
C. 60 60 27 15
G. 258 270 267 266
%b
84 86 85 84.7
96.5 96.6 98.7 96.5
..
40 60 80 40 60 80 40 60 80 40
265 265 265 275 275 275 282 282 282 290 290 290 260 260 260 310 310 310 535 535 535 404
81.4 81.4 81.4 83.8 83.8 83.8 86.0 86.0 86.0 88.5 88.5 88.5 79.1 79.1 79.1 79.2 79.2 70.2 78.5 78.5 78.5 77.8
300 419 515 415
81.5 80.6 79.2 83.4
98.2 99.4 99.1 98.1 99.4 99.6 97.5 98.1 99.1 97.1 97.5 97.2 98.6 99.5 99.5 99.6 98.4 99.7 98.6 98.4 97.9 Almoat theo. 98 99.6 98 95
..
.. .. ..
.. .. .. .. ..
.. .. .. ..
..
.. .. .. .. .. ..
APPARATUS AND MATERIALS
Nitrator. Preliminary work showed that the vapor pressure of benzene is sufficiently high so that 5 to 10% of the benzene was lost by vaporization from a nitrator previously used by Haun and Kobe (7). A new nitrator, shown in Figure 1, was constructed from a borosilicate glass resin reaction kettle.
Total Time, Hours 4 4 6 8
Barnett (3)
..
80
80 40 60 80 40 60 80 40 60 80 70
Adam6 and Harrington (1) 11 45 Avery et aE. (S) 70 Frank (6) '5 52 Fierz-David (4) 2 60 a Grams of HZ804 used for 250 gram8 of benzene. b Concentration of HzS04 on HNOa-free basis.
Yield,
%
Present address, Monsanto Chemical Co., Springfield, Mass.
February 1953
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Steam Distillation Apparatus. The steam distillation apparatus was similar t o that used by Haun and Kobe ( 7 )and Kobe and Pritchett (IO). The Dean and Stark moisture trap was built larger to contain more nitrobenzene, BO it was unnecessary t o drain the trap more than two or three times. A glass tube extended from the upper ground-glass joint to below the surface of the water in the trap in order to prevent nitrobenzene held on the surface of the water from flowing back into the boiling flask. This tube eliminated the need for a piece of rolled copper foil used in previous work.
CONDENSER
ture poured into a 2-liter separatory funnel containing about 400 grams of ice. The remainder of the nitration assembly was washed with 200 ml. of water from a wash bottle and the washings were added to the separatory funnel. The emulsion was broken by vigorous shaking of the funnel, ao that the nitrobenzene and unreacted benzene floated on top of the dilute acid layer and could be separated easily. Both the acid layer and the organic layer were subjected to steam distillation. From the former was recovered from 1 t o 5% of the total nitrobenzene. The initial steam distillation of the organic layer produced material that floated on top of the water. This was removed and weighed as unreacted benzene. The material that sank in the water was removed, dried over Drierite for a t least 3 hours, and weighed as nitrobenzene. Some dinitrobenzene usually steam distilled over near the end of the operation and collected in the trap. The water from each steam distillation was cooled and examined for crystals of dinitrobenzene. If sufficient crystals were found, they were filtered off, dried, and weighed. The material balances were below 100% (except for 3 in 60 nitrations), usually 97 to loo%, so that the yields of nitrobenzene reported are probably somewhat conservative. PROCESS VARIABLES
E%-tco'Ls
The process variables are those adopted by Haun and Kobe (7') as representing the fundamental variables. Based on the concept that the nitryl ion (Not+) is the nitrating agent and the sulfuric acid functions as an ionizing medium for the nitric acid, the fundamental process variables are the sulfuric acid-hydrocarbon ratio and the concentration of the sulfuiic acid on a nitric acid-free basis. The initial concentration of the sulfuric acid is selected because the nitrator and mixed acids can most easily be prepared at the desired concentration. The use of the dehydrating value of the sulfuric acid (D.V.S.) does not give fundamental information because it is based on the final concentration of sulfuric acid, assuming that only the desired reaction went to completion and that no other reactions occurred. This study has used both initial and final concentrations to represent process variables. Because the nitration of benzene gives a high yield of a single nitration product, there is little difference between the two methods. When polynitration and oxidation occur, the use of initial concentration is advantageous.
Figure 1. Nitrator
I
Benzene. The benzene used in this work was produced by the Pan American Refining Corp. The specifications showed a boiling range of 79.2" and 80.2" C., and freezing point of 5.04" C., indicating a purity of 99.3% benzene. When redistilled before use, all of the benzene was found t o distill within 1' C. and 95% within 0.2" C. The refractive index a t 20" C. was 1,50025, compared to a literature value of 1.50144 (9).
. ._
I .
I
I
..
' l h e acids used were 01 reagent grade and were analyzed for acid content before use. Acids.
nrmwnn
OF NITRATION
The total amount of sulfuric acid used was divided between the nitrator acid and the mixed acid, so that 4070 of the acid was placed in the nitrator and 607, was in the mixed acid (6). The concentration of the sulfuric acid, on a nitric acid-free basis was the same for both acids. The water used t o dilute the suifuric acid was measured to the nearest 0.1 ml. in a buret. I n all nitrations 250 grams of benzene was weighed to the nearest 0.1 gram, cooled below 25" C., and then placed in thenitrator. The cooled nitrator acid was added slowly through the thistle tube and emulsified with the benzene. The mixed acid was placed in a 500-ml. dispensing buret and the flow of acid was regulated so that all was added a t a constant rate to the benzene within the desired period of time. The contents of the nitrator reached the desired temperature within 2 or 3 minutes after mixed acid was added and the temperature was maintained within l o C. of the desired value for the remainder of the total time. After all the mixed acid had been added, the reaction mixture was stirred for an additional period of time approximately equal to the time of addition. The time, volume of mixed acid, and temperature n-ere recorded every 5 minutes t o ensure reproducible results. When the additional time of agitation was completed the bottom of the resin kettle was removed and the emulsified mix-
288
34XSULFURIC 0 5OoC
ACID
0 70'C 100
300 GRAMS OF S U L F U R I C
Figure 2.
700
500 ACID
Effect of Amount of Sulfuric Acid o n Yield of Nitrobenzene 250 g r a m s of benzene nitration at 50' or 70' C. Total time of nitration 40 minutes
Other process variables studied were temperature, time, excess nitric acid, and ratio of sulfuric acid in nitrator and mixed acid. The data for all nitrations other than preliminary experiments are given in Table 11. Sulfuric Acid. The amount of sulfuric acid required for the nitration of 250 grams of benzene is shown in Figure 2. The amount was determined for three concentrations of sulfuric acid, 80, 84, and 88%, a t 50" C. It is seen that with 8470 acid
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 45, No. 2
Unit Processes ~~
c
the maximum yield can be obtained with 300 grams of sulfuric acid. At 200 grams of sulfuric acid it is evident that the concentration of acid affects the yield markedly. Here the final concentration of the sulfuric acid is relatively low, so that the lowering of the yield might be interpreted as due to a lower final concentration rather than a smaller amount of sulfuric acid. Thus, the 200 grams of 88% acid have about the same final concentrations as 300 grams of 80% acid, and the yields of nitrobenzene are the same. However, 200 grams of 80% acid give the same final concentration as 150 grams of 88% acid, yet the yield is higher with This indithe 200 grams. cates that the absolute minimum amount of sulfuric acid that will give satisfactory nitration is 200 grams, but that substantially the maximum yield can be obtained with 300 grams of sulfuric acid a t a concentration of 84%. Using 84y0sulfuric acid, the experiments were repeated a t 70" C. The yields were found to be substantially the same as a t 50" C., showing that temperature does not affect the minimum amount of sulfuric acid. Concentration. The effect of concentration of sulfuric acid was studied a t 50' C. with both 300 and 500 grams of sulfuric acid. The results are shown in Figure 3. The maximum yield is seen to be
s.
TABLE 11. SUMMARIZED DATAAND RESULTSFOR NITRATION OF 250 GRAMS OF BENZENE WITH THEORETICAL AMOUNT OF NITRIC ACID H2SOa Concentration, 70 Total Nitrator acid acid Theor. initial initial final Run 1 700 80 80 75 500 2 80 73 300 3 80 69 200 80 4 80 65 100 80 55 5 80 700 88 82 6 88 500 88 88 80 7 300 88 75 8 88 200 88 70 9 88 150 88 65 88 10 11 300 74.5 74.5 65 300 82.5 82.5 71 12 300 77 77 67 13 85 85 300 73 14 73.5 73.5 300 64 15 95.8 300 90.6 77 16 300 77 77 67 17 300 79 79 68 18 700 84 84 78 19 84 84 300 72 20 84 21 200 84 67 150 84 22 84 63 84 23 500 84 76 84 24 300 84 72 25 200 84 67 84 300 74.5 65 74.5 26 88 27 300 88 75 300 80 69 80 28 74.5 29 300 74.5 65 69 80 30 300 80 84 84 72 31 300 88 88 32 300 75 300 88 88 75 33 84 300 34 84 72 80 80 69 35 300 74.5 74.5 65 36 300 300 74.5 65 65 37 74.5 61 65 38 300 74.5 95.8 39 300 65 300 74.5 82 65 40 74.5 70 65 41 300 500 70 70 65 42 86.5 86.5 79 500 43 75 75 69 500 44 83 83 500 76 46 69 69 65 700 46 94 94 300 80 47 94 94 300 80 48 94 94 300 80 49 94 94 300 80 50 94 94 500 84 51 74.5 74.5 300 65 52 74.5 65 74.5 300 53 65 74.5 74.5 54 300 65 74.5 74.5 300 55 72 84 84 300 564 72 84 300 84 57 72 84 84 300 58f 300 65 74.5 74.5 59 300 72 84 84 60 a 10 grams of dinitrobenzene formed. b 14 grams of dinitrobenzene formed. 19 grams of dinitrobenzene formed.
Reaction Temperature,
Time, Min. D.V.S. c. .4dd. Total 3.00 50 25 40 2.70 50 40 25 2.23 50 40 25 1.85 50 25 40 1.22 50 25 40 4.56 50 25 40 3.93 50 25 40 3.00 50 40 25 2.33 50 40 25 1.85 50 40 25 1.85 50 25 40 2.70 50 25 40 2.03 50 25 40 2.70 25 40 50 1.85 50 25 40 3.35 25 50 40 2.03 25 50 40 2.17 25 40 50 3.55 50 25 40 2.57 25 50 40 2.03 50 25 40 1.70 50 25 40 3.00 70 40 25 2.57 70 25 40 1.57 70 25 40 1.85 70 25 40 3.00 40 70 25 2.23 70 25 40 1.86 60 25 40 2.23 40 60 25 2.57 60 25 40 3.00 60 25 40 3.00 35 25 40 2.57 35 25 40 2.23 35 35 40 1.85 35 25 40 1.85 50 25 40 1.85 25 50 40 1.85 25 50 40 1.85 25 40 50 1.85 50 25 40 1.85 25 50 40 3.55 25 40 50 2.23 25 50 40 3.17 25 50 40 1.85 25 40 50 4.00 25 35 40 4.00 25 50 40 4.00 25 60 40 4.00 25 70 40 5.25 50 25 40 50 1.85 30 60 1.85 50 10 20 1.85 60 45 90 1.85 70 50 140 2.57 25 50 40 2.57 25 50 40 2.57 50 25 40 1.85 25 50 40 2.57 25 50 40 d 10'7' excess nitric acid used. e 2 0 g excess nitric acid used. f 95% of theoretical nitric acid used.
&SO&, G.
::*
0 3 0 0 GR. SULFURIC ACID 0 5 0 0 GR. SULFURIC ACID
75
70 INITIAL
Figure 3.
80
85
90
C O N C E N T R A T I O N OF SULFURIC
Effect of Concentration o n Yield of Nitrobenzene
250 grams of benzene nitrated at 50° C. Total time of nitration 40 minutes
February 1953
E ACID
Product Yield Grams % 98.3 387 98.3 397 96.0 378 87.0 343 70.0 276 98.5 388 385 97.5 97.1 382 96.0 378 332 84.1 86.9 342 98.0 396 91.8 351 98.4 388 83.5 329 97.5 385 91.5 361 96.0 378 98.8 389 98.4 387 93.1 367 325 82.5 98 4 388 97.7 385 93.4 368 90.0 354 97.2 383 97.5 384 346 88.0 96.5 380 98.8 389 98.1 386 98.1 386 96.5 380 90.5 357 78.0 302 338 86.0 84.0 330 84.5 333 0 338 .*.86. 333 84.5 81.0 319 99.0 390 96.0 379 99.0 390 82.5 325 96.7a 381 95.la 375 94.5a 372 93.9b 370 361 91.53 86.0 339 80.7 318 89.0 91.7 38i 99.0 390 99.0 390 93.5 368 85.9 338 98.2 387
0 300 OR. SULFURIC ACID 0 500 OR. SULFURIC AClO
80 70
65 FINAL
Figure 4.
75
CONCENTRATION
80 OF SULFURIC
85 ACID
Effect of Concentration o n Yield of Nitrobenzene
250 grams of benzene nitrated at 50° C. Total time of nitration 40 minutes
INDUSTRIAL AND ENGINEERING CHEMISTRY
289
100
I
/
I
/-
I
300 G R . SULFURIC ACID
r -
A
94%
0
8 8 % SULFURIC ACID 8 4 % SULFURIC ACID
0 A
SULFURIC ACID
8 0 % SULFURIC ACID 74.5% SULFURIC ACID
70 30
50
40
TEMPERATURE
-Figure 5.
70
60
'C
Effect of Temperature on Yield of Nitrobenzene
250 grams of bensene nitrated with 300 grams of sulfuric acid Total time of nitration 40 minutes
75
BO
75
85
90
95
CONCENTRATION OF SULFURIC ACID
Figure 6.
Effect of Temperature on Yield of Nitrobenzene
250 grams of benzene nitrated with 300 grams of sulfuric acid Total time of nitration 40 minutes
a t 84% acid. With the larger amount of sulfuric acid the yield is less sensitive to change in concentlation and the maximum yield can be obtained mith acids from 83 to 87% concentration. There is considerable spread between the two curves a t lower concentrations. If the data shown in Figure 3 are replotted so that the final concentration of the acid is used rather than the initial concentration, the results are as shown in Figure 4. Although the curves for the two different amounts of sulfuric acid are pulled together a t lower acid concentrations, the most significant difference is the points a t which maximum yields can be obtained. When initial concentration is used as the process variable, the concentration for maximum yield is seen to be 84 t o 85% on both curves (Figure 3), though nith the larger amount of sulfuric acid the maximum could occur between 83 and 8770. When final concentration is used as the process variable (Figure 4), two different values of concentration are found, depending on the amount of acid used. With 300 grams of sulfuric acid, the maximum yield is obtained at a final concentration of 72 to 73% and with 500 grams of acid the maximum yield is a t 76 to 79%. It is believed that the use of initial concentration is advantageous because the concentration for maximum yield is independent of amount of sulfuric acid used.
290
Temperature. The effect of temperature is shown in Figure 5Temperature has little effect on the yield except a t low concentrations. As has been shown previously, increasing the temperature allows a more dilute acid to be used. This also explains the industrial practice of increasing the temperature of nitration near the end of the reaction when the nitrator acid is more dilute. The maximum yield is seen to occur at 60" C. I n Figure 6 temperature is used as the parameter and concentration of sulfuric acid as the independent variable. The maximum yield of nitrobenzene at 60" C. and 84% concentration is more apparent. The effect of higher temperature in decreaaing the yield due to dinitration is also apparent. These data can also be presented in lines of constant yield on a temperature-concentration diagram (Figure 7 ) . The band of concentrations and temperature within which yields of 98 or over of nitrobenzene can be obtained is a broad one, showing that a wide range of conditions can be employed successfully. As with previous compounds, the concentration of sulfuric acid required decreases as the temperature increases. Concentration of Nitrator Acid. Several nitrations were made to determine the effect of changing the concentration of the nitrator acid. The over-all concentration was held constant a t 74.57,, a lower value than the optimum, because any change due t o nitrator acid concentration would be more pronounced on the steep portion of Figure 3. At one extreme, all water was added to the nitrator acid to give a concentration of 61% a t the start of the nitration. This concentration increased to 65% a t the end of the nitration owing to the more concentrated mixcd acid. At the other extreme, all water was added to the mixed acid, so that the nitrator acid was initially 95% sulfuric acid, decreasing to a final concentration of 65% a t the end of the nitration. The results are shown in Figure 8. The yields are affected little by the concentration of the acid in the nitratox, though better results are obtained if the concentration is not below the final over-all value, 65% in this case. This result is compatible with industrial practice of adding to the nitrator spent acid from a previous nitration, then the benzene, and finally the mixed acid a t the proper initial concentration. Time. The total time required to complete a nitration depends largely on the temperature of the cooling water available and cooling area within the nitrator, except a t low acid concentrations where the reaction is so slow that long periods of time are required to complete the reaction. With 74.5y0 sulfuric acid a t 50' 6 . the yield of nitrobenzene continues to rise, as shown in
I
rU
70
60 0
w a 3 .
5w!
50
L
z Iw
40
85
30 75
90
95 98 YIELD I N PERCENT
98
1
I
I
80
85
90
97 91
95
I N I T I A L CONCENTRATION OF SULFURIC ACID
Figure 7.
Effect of Temperature and Concentration on Yield of Nitrobenzene
250 grams of benzene nitrated with 300 grams of sulfuric acid Total time of nitration 40 minutes
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Vol. 45, No. 2
Unit Processes 100
98
c
z W
a >-
82
0 96 a
l
l
I
I
I
I
I
I
I
65
70
75
80
85
90
60
W
a
J
5
95
a
94
-l
NITRATOR ACID
Figure 8.
w-
C O N C E N T R A T I O N Sb H Z S 0 4
Effect of Varying Nitrator Acid and Concentration
92 90 95
Constant over-all concentration 74.5 yo 250 grams of benzene nitrated with 300 grams of sulfuric acid Total addition t i m e 40 m i n u t e s a t 50‘ C.
100
105
110
115
120
PERCENT EXCESS NITRIC ACID
Figure 10. Effect of Excess Nitric Acid on Yield of Nitrobenzene 250 grams of benzene nitrated with 300 grams of sulfuric acid Concentration 8496, 50’ C .
20
100
60
140
T O T A L TIME I N M I N U T E S
Figure 9. Effect of Time of Reaction on Yield of Nitrobenzene 250 grams o f benzene nitrated with 300 grams of sulfuric acid Concentration 74.596, 50° C.
-
Figure 9. The time of addition of the mixed acid is one half the total time shown. Excess Nitric Acid. Usual industrial practice is to nitrate using the theoretical amount of nitric acid, or slightly less, so that little or no nitric acid remains in the spent acid from the nitrator. The effect of other than the theoretical amount of nitric acid is shown in Figure 10. The amount of nitric acid unused in the reaction is substantially the same whether 95 or 100% of the theoretical amount is used (1.5 and 1.8% unused). Precision of Results. When sulfuric acid of 74.5% concentration is used, the nitration is sensitive to temperature, concentration, and time. Duplicate nitrations gave results that checked within 1.0%. At 84% sulfuric acid concentration the nitration is insensitive to the variables, so that duplicates checked within 0.201,. The deviation a t 74.5% concentration probably represents the maximum, while that a t 84% is probably representative of most nitrations. DISCUSSION
As can be seen from Table I, most of the nitrations of benzene have been done with 260 t o 500 grams of sulfuric acid, for 250 grams of benzene, and acid concentrations from 79 to 85’30. These concentrations are close to the optimum concentration. MalyarevskiI and Kalinchenko (11)used as little as 260 grams of sulfuric acid with good results. Their range of optimum concentrations extended further into the dilute region than shown on Figure 6, but this probably was due to differences in total time. The commercial nitrations mentioned by Groggins (6) yse acid of 84 to 86% concentration and somewhat less than 300 grams of acid, though the longer time may give an improved yield. The German industries ( 1 , 2 ) use from 300 to 400 grams of sulfuric acid a t slightly lower concentrations than the optimum. The grouping of process variables used here makes easier a comparison of the results of various workers on one compound or the work on a number of compounds than when the dehydratFebruary 1953
ing value of sulfuric acid concept is used. Haun and Kobe (‘7) with cumene used 500 grams of sulfuric acid for 250 grams of cumene, or a mole ratio of 2.5. Kobe and Pritchett (10) with o-xylene used 350 grams of sulfuric acid for 170 grams of oxylene, or a mole ratio of 3.4. Benzene requires a mole ratio of sulfuric acid to hydrocarbon of only 1.0. The optimum acid concentration varies with these three compounds: 79.4% for oxylene, 81.0% for cumene, and 84.0y0 for benzene. A graph showing yield contour lines has proved useful to show that a band of temperature-concentration values will give the maximum yields. The narrowness of this band is a measure of the sensitivity of the compound to the conditions of nitration. SUMMARY
Benzene has been nitrated with a yield of over 98% mononitrobenzene using the following conditions: Sulfuric acid-benzene, weight ratio Concentration of sulfuric acid % Nitric acid-benzene, mole ratio Temperature, C., Nitration time, minutes
1.2 84.0 1.0
60 40
The effect of changing these process variables on the yield is shown graphically. A method of plotting contour lines of equal yield shows that a broad band of conditions of sulfuric acid concentration and temperature exists in which yields of over 98% can be obtained. LITERATURE CITED
Adams, D. A., and Harrington, T., British Intelligence Objectives Sub-Committee, Final Rept. 1144, Item No. 22. (2) Avery, J., et al., Ibid., 986, Item No. 2 2 . (3) Barnett, E. D. B., “Coal Tar Dyes and Intermediates,” p. 13, New York, D. Van Nostrand Co., 1919. ( 4 ) Fierz-David, H. E., and Blangcy, L., “Fundamental Processes of Dye Chemistry,” p. 68, New York, Interscience Publishers, (1)
1949.
( 5 ) Frank, G. H., “Manufacture of Intermediates and Dyes,” p. 4 3 , London, Constable and Co., 1950. (6) Groggins, P. H., “Aniline and Its Derivatives,” New York, D. Van Nostrand Co., 1924. (7) Haun, J. W., and Kobe, K. A., IND. ENC.CHEM.,43, 2355-62 (1951).
(8) Hough, A., Savage, W., and Van Morel, D. J., Chem. a n d Met. Eng., 23, 666-71 (1920).
International Critical Tables, Vol. VII, p. 38, New York, McGraw-Hill Book Co., 1930. (10) Kobe, K. A., and Pritchett, P. W., IND.ENC.CHEM., 44, 1398 (9)
(1952). (11)
Malyarevskif, V. I., and Kalinchenko, I. P., J. Chem. I n d . (Moscow), 4, 399 (1927).
Tariff Commission, “Synthetic Organic Chemicals, U. S. Production and Sales,” 1945 to 1951.
(12) U. S.
RECEIVEDfor review April 9, 1952.
INDUSTRIAL AND ENGINEERING CHEMISTRY
ACCEPTED September 16, 1952.
291
