ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT
Nitration of 2-Methylnaphthalene J. A. BRINK, JR.,
AND
R. NORRIS SHREVE
Purdue University, tofayetfe, Ind.
The mononitration of 2-methylnaphthalene produced a mixture of isomers. The chief product of the nitration was 1-nitro-2-methylnaphthalene, which was isolated and purified b y physical means. The other isomers appeared as a by-product oil. The conversion of 2-methylnaphthalene to 1 -nitro-2-rnethylnaphthalene was evaluated over a wide range of conditions. When nitric acid was used as the nitrating agent, the highest conversions (57%) to the 1-nitro isomer were obtained at low temperatures (0" to 30" C.) with a 70% excess of 70% nitric acid. Acetic acid and acetic anhydride were employed as solvents for several nitrations a t low temperatures. Dinitration took place when acetic anhydride was used. Conversions of 57% to the 1 -nitro isomer were obtained with a 15% excess of a mixed acid containing 25y0 nitric acid, 55% sulfuric acid, and 20% water when a cycle acid containing 65% sulfuric acid was employed. Such nitrations were made without the formation of dinitro products.
s
INCE 2-methylnaphthalene has been made available com-
mercially through improvements in coal tar sepaiation methods, considerable interest in the derivatives of this hgdrocarbon has been shown by investigators throughout the world. However, only a few important uses for 2-methylnaphthalene have been commercially exploited. It is the starting material for the synthesis of the antihemorrhagic vitamin IC, and it has minor uses in organic synthesis. l-Nitro-2-methylnaphthalene, which mag be isolated and purified by economical physical operations, has greater commercial possibilities than the other mononitro isomers. If the nitration of 2-methylnaphthalene could be conducted under conditions whereby a predominance of 1-nitro-2-methylnaphthalene is formed, the process would have greater industrial possibilities. I n this investigation the nitration of 2-methylnaphthalenr n as carried out over a wide range of operating conditions. Several different nitrating agents were employed, and the effects of the reaction variables such as temperature, acid concentrations, and the reaction time were investigated. Quantitative determinations of the conversions of 2-methylnaphthalene to l-nitro-2methylnaphthalene were made for all runs. Previous Work
Shulze (9) nitrated 2-methylnaphthalene with nitric and sulfuric acid and reported l-nitro-2-methylnaphthalene, a diiiitro product, and an oil as the products of nitration. Polynitro products were reported by Madinaveitia and DeBuruaga ( 7 ) who also used a mixture of nitric and sulfuric acids. Lesser, Glasser, and Aczel (6) carried out the nitration as a step in the preparation of dyes. These investigators dissolved 2-methylnaphthalene in acetic acid and conducted the nitration at low temperatures with fuming nitric acid. Sah ( 8 ) , Fieser and Fieser (W), and Veldstra and Kiardi ( I O ) have reported nitrations similar to the procedure of Lesser. The nitration of 2-methylnaphthalene with nitric acid a t low temperatures (5" to 15" C.) n-ithouta solvent has beenreported by Vesely and Kapp (11). They obtained 58% of the theoretical amount of the 1-nitroisomer and also an oil containing other niononitro isomers. They separated the isomers by a selective reduction procedure and identified 4-amino-, 6-amino-, and 8amino-2-methylnaphthalene. T'esely and coworkers (18-14) qualitatively identified most of the nitro, amino, acetamino, and hydroxy derivatives of 2-methylnaphthalene. Fierz-David and Mannhart ( I ) prepared a number of com694
pounds from 2-methylnaphthalene. Their first procedure n as similar to that reported by Lesser ( 6 ) , and the second method was a nitration with 60% nitric acid. These previous investigators \yere concerned chiefly with the synthesis oi new compounds, and usually the nitiation reaction was only one step in their researches. Consequently most of the previous work has been qualitative in nature. Experimental Procedures f o r Nitrations
Nitric Acid Nitrations above 35' C. Khen 2-methylnaphthalene was nitrated with nitric acid a t temperatures in excess of 35" C., two liquid phases were present. For these nitrations a 1000-ml., t h r e e - n e c k e d flask Tl-as employed. One side neck was fittcd with a side arm dropping funnel and a reflux condenser, and the other neck n a s fitted with a thermometer. A mercury scal stirrer was used for the center neck, and a flexible, stainless steel, two-blade propeller, 2 inches i n d i a m e t e r , m-as used for agitation. The nitrator as1000 MI sembly i s s h o w n i n REACTW Figure 1. One g r a m mole, ( 1 4 2 g r a m s ) of 2 methy 1n a p h t h a 1en e was melted and then poured into the reacFigure 1. Apparatus for Liquid Phase Nitrations
,"~',c,ti~~\e~~
perature was obtained b y means of a heating mantle that was conThe agitator was turned on during this
trolled with a Variac. warm-up period. The nitric acid was added dropwise via the dropping funnel shown in Figure 1. Since this nitration was exothermic, the acid was added slom-ly in a 30-minute period. .4fter the first 5 ml. of acid had been added the heating mantle v;as removed
INDUSTRIAL A N D E N G I N E E R I N G C H E M I S T R Y
Vol. 46, No. 4
UNIT PROCESSES from the reaction flask, and the flask was cooled in a tap-water bath for the remainder of the acid addition period. During the acid addition the content of the reactor was stirred vigorously and the temperature was controlled within 2' C. of the desired value. The reaction flask was cooled for 5 to 10 minutes after the acid addition was complete. Then the heating mantle was replaced. The content of the reactor was agitated for the remainder of the reaction period (4 t o 6 hours) and controlled within 1" C. of the desired nitration temperature. After the end of the nitration period, the content of the reactor was removed and placed in a sealed container that was placed in an ice bath for 1 hour. During this time 1-nitro-2-methylnaphthalene crystallized from the reaction mass. Then the products of reaction were placed on a 600-cc. fritted disk Bhchnertype filter for 6 to 8 hours. The solid collected was l-nitro-2methylnaphthalene plus some impurities. The filtrate consisted of the spent acid and an oil containing some 1-nitro-%-methylnaphthalene and the other mononitro isomers. The solid was mixed with 200 ml. of 5% sodium bicarbonate. The oil in the filtrate was separated from the spent acid and then placed in a deep freeze set a t -20" F. After 1 to 4 days in the deep freeze, the oil became semisolid and was filtered on a fritted disk filter for 2 to 4 hours. The additional amount of 1-nitro-2-methylnaphthalene recovered in this manner was mixed with the other p r o d k t in the 5% sodium bicarbonate solution. The oil filtrate was returned t o the deep freeze for a 2-month period. The I-nitro-2-methylnaphthalene in the 5% sodium bicarbonate solution was filtered on a fritted disk filter and then washed with 500 ml. of distilled water. It was purified by crystallization from alcohol. Some of the oils that were placed in the deep freeze for 2 months solidified into semisolid mass. Additional 1-nitro-2-methvlnaphthalene was recovered from these oils. Nitric Acid Nitrations below 35" C. When 2-methylnaphthalene was nitrated with nitric acid a t temperatures much below 35' C., it was present as a solid, and agitation was difficult. The apparatus that was used for this type of nitration is shown in Figure 2. The nitric acid was placed in the reactor and was cooled to the desired nitration temperature (0' to 5' C.). An agitated icesalt water bath was used as a cooling agent. Then 142 grams of solid 2-methylnaphthalene was added slowly t o the nitric acid over a 30-minute period. The reaction was agitated vigorously at all times. The temperature was controlled a t the desired value for the remainder of the run. The separation and purification of the products were effected in the same manner as for nitrations with nitric acid a t temperatures above 35' C. Nitrations in Presence of Solvent. 2-Methylnaphthalene may be dissolved in a solvent and nitrated a t low temperatures. Solvents such as acetic acid, glacial acetic acid, and acetic anhydride were used in this investigation. For such a nitration a single liquid phase may be present. The apparatus that was used for these nitrations is shown in Figure 1. The solvent and 142 grams of 2-methylnaphthalene were added to the flask, and the mixture was stirred and heated until a single phase was obtained. Then the temperature was regulated to the desired nitration temperature (0" C.). The nitric acid (fuming nitric acid) was added dropwise via the dropping funnel shown in Figure 1. Usually, a 30-minute acid addition period was required. The content of the reactor was stirred vigorously during the acid addition and for the remainder of the reaction period; the temperature was controlled by the use of the heating mantle or a cooling bath. After the end of the nitration period the content of the reactor was removed and placed in a sealed bottle that was left in a refrigerator (2" to 5" C.) for 12 hours. The 1-nitro-2-methylnaphthalene that crystallized during this time was separated from the solvent by filtration with a fritted disk filter. The filtrate was mixed with 200 grams of crushed ice several times. Additional 1-nitro-2-methylnaphthalene was recovered in this manner. The by-product oil was separated from the diluted solvent, placed in a deep freeze a t -20" F. for 2 to 4 days, and then filtered. The 1-nitro isomer that was recovered from the various fractions was mixed with 200 ml. of 5% sodium bicarbonate, filtered, and
April 1954
purified in the same manner as described for nitrations with nitric acid a t temperatures above 35" C. Mixed Acid Nitrations. The apparatus shown in Figure 2 was used for the mixed acid nitrations; 500 grams of a "cycle" acid, consisting of sulfuric acid, was placed in the nitrator, and 142 grams of 2-methylnaphthalene, which had been pulverized, was added to the cycle acid. The mixed acid was added slowly to the nitrator over a 30-minute period, and the temperature was controlled within 1' C. of the desired temperature (0' C.), Then the reaction was continued for the remainder of the run. The content of the nitrator was agitated during the entire run.
I
I
TO VARIABLE SPEED MOTOR
p9
THERMOMETER
STAINLESS STEEL STIRRER SHAFT
.EEL
IEW
Figure 2. Apparatus for Solid-Liquid Nitrations
At the end of the nitratio? period, the content of the nitrator was removed to a fritted disk Buchner-type filter. The spent acid filtrate was recovered after 5 minutes, and then the filtration was continued for 8 hours. During the 8-hour filtration the byproduct oil and a small amount of spent acid were recovered as filtrate. The by-product oil and the I-nitro product were processed in the same manner as previously described for nitric acid nitrations above 35" C. Crystallization of 1-Nitro-2-methylnaphthalene The 1-nitro-2-methylnaphthalene product was recovered by vacuum filtration as an impure solid. The method of purification of the 1-nitro-2-methylnaphthalene that had been reported in the literature was crystallization from ethyl alcohol. However, the solubilities of 1-nitro-2-methylnaphthalene and the impurities present (other nitro isomers and 2-methylnaphthalene) were not known. The selection of a crystallization procedure should be based on a knowledge of the solubilities of the chemicals present. The solubilities of 2-methylnaphthalene and 1-nitro-2-methylnaphthalene were determined experimentally. The results of this work are shown in Figure 3. Using the solubility data as a basis, the following crystallization procedure was selected: 1. The product was mixed with 300 ml. of 95% ethanol and heated to reflux, with occasional stirring, on a steam cone. 2. The solution was allowed to cool to 45" t o 50' C. a t room temperature and was then placed in an ice bath and cooled t o '8 to 10"
c.
INDUSTRIAL AND ENGINEERING CHEMISTRY
695
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT Since there is no sinnificant difference in the losses for a 50gram or 100-gram sample. the best estimate of the losses is a combination of all the data that is an average of Y
Table Io Results of Crystallization Runs with Impurities Present with 1 -Nitro-2methvlnaDhthane , .
Run
First Crystallization Sintering True Veight, point, g.
0
c.
T.8:
-
Second Crystallization Sintering True Weight, point, ~,p., g.
0
c.
c.
Third Crystallization Sintering True Weight, point, m.p., B.
O
c.
O
c.
20 Grams By-Product Oil 'I 2 3 4 5
97.94 97.10 96.06 97.12 96.50
70
71 73 i1 72
79 i9 79 i S 80
88.87 90.14 88.20 88.80 88.66
78
78 80 78 78
x', and Rb or k 81 81 81 81 81
30 Grams By-product Oil
G
7 8 9
10
100.77 99.78 99.51 99.79 99.60
62 68 69 68
68
78 79 78 78 78
89.10 89.46 89.00 90.93 89.16
76 78
zc
13
77
80 80 80 80 80
3. The solid n-as vacuum filtered with a 600-cc. sintered-glass filter. 4. The product was dried overnight a t 50" C., weighed on a triple beam balance, and its melting point determined. The final temperature for the crystallization (8" to 10' C.) was chosen because the solubility curve for 1-nitro-%methylnaphthalene i8 relatively flat in this region. This selection should result in a lower variability in the results than would be obtained if a higher temperature were selected. Losses of Pure 1-Nitro-2-methylnaphthalene. The solubility data represent the equilibrium concentration of the product in 95% ethanol. The actual crystallization as described in the above procedure is not an equilibrium operation. A calculation of crystallization losses from the solubility data alone would be in error. Pure 1-nitro-2-methylnaphthalene n as used for the initial investigation of crystallization losses. This material was prepared by subjecting the product from some of the early nitration runs to repeated recrystallization. The material prepared in this manner had a melting point of 80' to 81" C. An elemental analysis of this material gave 70.62% carbon, 5.07% hydrogen, and 7.59Yc nitrogen as compared with calculated values of 70.58% carbon, 4.81% hydrogen, and 7.49% nitrogen. The method that n-as used for the determination of the losses consisted of carrying out the crystallization procedure on a known weight of the purified 1-nitro-2-methylnaphthalene. Since the amount of the 1-nitro isomer was expected to vary from run to run, the determination of crystallization losses included an evaluation of this variable. This evaluation was accomplished by carrying out crystallizations with different amounts of the pure 1-nitro-2-methylnaphthalene. It mas expected that for niost of the nitration runs the amount of the 1-nitro isomer would be between 50 and 100 grams. Hence, five crlstallizations were conducted using 50 grams and five were conducted using 100 grame. The mean values for each group of five crystallizatione were
8,= 5,48for 100-gram samples 2 6
= 5.54 for 50-gram samples
An F test showed that the variances were not statistically different at the 5yo level. A simple t test ( 3 ) was made t o determine whether or not the means were statistically different. Calculations gave t = 0.452. Therefore, there is no significant difference in the means. The practical meaning of these results was that the accuracy of the r o r k with a SO-gram sample was shown t o be comparable with that for a 100-gram sample, and there was no measurable difference in the crystallization losses whether 60 or 100 grams of the product were subjected to the Crystallization procedure.
696
82.71 84.39 82.46 82.51 83.26
80 80 80 80 80
81 81 81 81 81
= 5.51 grams
6" = 0.189 grams
(B')2
=
0.0358 grams
Losses of Impure l-Nitro-2methylnaphthalene. The 1nit,ro-2-me t h y 1n a p h t h a1e n e products from nitration runs, which were subjected to the c r y s t a l l i z a t i o n procedure, were not pure. The impuiities that lyere present might affect the losses; therefore, an investigation of the effect of impurities on crystallization losses IT as required before such losses could be accurately estimated. The experimental method that vas used for the investigation of the rffect of impurities on crystallization losses was as follons: 883.08 2.73 82.34 82.41 82.41
80 80 80 80 80
81 81 81 81 81
1. A lrnonn neight of impuritieb (by-product oil) was mixed with 100 grams of pure 1-nitro-2-methylnaphthalene and then cryetalli~edfolloR ing the set procedure. 2. The melting point and w&t of the material after the CI ystallization were determined, 3. Steps 1 and 2 were repeated tnice on the same material.
The impurities (by-product oils) for these experiments were prepared by mising together 10 grams of the oil from each run for nitration runs 12 to 47. Since material balances indicated that t,he amount of impurities was betiveen 20 aud 30 grams, two sets of crystallization runs were conducted, one Tvith 20 and one with 30 grams of impurities present. Five rum of three successive crj-stallizations were made with the two different amounts of impurities. The results of this work are given in Table I. The difference in v-eight of two adjacent values from Table I is the amount of impurities and of 1-nit'ro-2-methylnaphthalene t,hat was removed b y the crystallization. For example, consider the weights reported for the first and second crystallizations for run 1, Table I. The difference value is 97.94 - 88.87, or '3.07 grams. The 9.07 grams is equal to the loss in weight becauv of the second crystallization. Such differences are useful for a statistical analysis of the data. A statistical evaluation of thew differences may be carried out by means of an analysis of variance procedure. A suitable procedure for these data n-as suggested by Irick ( 5 ) . From such an evaluation several practical conclusions were drawn. The crystallizations!, first, second, or third, were shown t o have very significantly different effecte on the loss per crystallization. Also, the interaction of crystallization and impurity had a significant effect. This means that the loss per crystallization was dependent on the impurity level and on the particular crystallization involved. As the result of these conclusioni, the standard error cannot be written on a per c,rystallization basis. However, the data may be analyzed on a basis of the total l o w s for several subsequent crystallizations. The F test for impurities gave F = 0.00834, which is not significant. This means that there is no significant differenve between average losses for the data obhined with 20 grams of impurities initially present as compared with the 3Q-gmm daia. The average total loss for three crystallizations for the 20-gram data \Tas 17.13 grams as compared with 17.17 grams for the 3 0 gram data. These data may be combined to give the best estimate of the losses as 17.15 grams. With a confidence of 90%, i t may be claimed that' the true mean of the accumulated losse: for three crystallizations is 17.15 .i(1.86)(0.224) or 17.15 0.42 grams, where 0.221 is the standard error of the mean. The estimated accumulated losses for three crystallizations of the pure I-nitro-2-methylnaphthalene were
+
INDUSTRIAL, A N D E N G I N E E R I N G CHEMIS'TRY
Vol. 46, No. 4
UNIT PROCESSES (5,51)(3) = 16.53 grama. The losses incurred with the imTable 11. Nitrations of 2-Methylnaphthalene with Nitric Acid purities initially present are S i t r i c .4cid Recovery, Grams elightly, but s i g n i f ic a n t 1y , Reaction ___TheoProduct BySpent higher than for the pure Conversion Acid, Temp., Timea, Actual, retical, ProdCrystal. froin product Grams-% Run O C. hr. % ' % uctb loss oilc oild material. % The standard error of a single 62 46.5 12 70 4.5 60 130 68.2 10.8 8.0 87.0 18.8 45.7 2.5 4.3 85.5 19.8 13 70 130 10.8 60 70.4 60 run of three crystallizations 43.8 2.5 130 7.4 81.9 17.8 63.7 65 14 80 10.8 60 will be greater than the stand43.8 5.4 82.0 15.4 15 4.5 130 10.8 65.8 BO 58 80 43.4 14.3 63.7 ard error of the mean. With 56 80.1 6.5 130 10.8 5.6 80 60 16 42.7 19.6 2.5 none 64 (9.8 10.8 17 60 130 69.0 60 a 90% confidence, it may be 46.6 22.2 61 87.1 10.8 4.5 6.3 18 60 60 130 70.0 claimed that an individual 21.6 54 48.0 4.4 89.8 130 74.6 6.5 60 10.8 19 60 46.3 18.2 86.6 ;9 4.1 71.7 6.5 GO 10.8 20 130 70 run value y will vary as y =k 45.3 81.3 04 16.6 3.5 21 70.5 4.5 130 70 10.8 70 ( 1 . 8 6 ) ( 0 . 7 1 0 ) = y i 1.32 44.8 none 83.8 10.8 50 23.2 22 73.0 2.5 130 70 70 grams, where 0.710 gram is 47.6 2 2 89.0 19.7 44 23 76.0 4.5 130 70 10.8 60 49.3 none 92.4 24.7 46 81.6 4.5 130 10.8 70 24 50 the standard error of an indi98.1 52,5 1.8 15.8 38 10.8 85.5 4.5 130 40 25 70 vidual run. That is. the ob2.3 72.7 85.8 20.0 59 45.9 4.5 130 10.8 60 70 26 served loss may differ as murh 36 5l,5 none 85.5 96.3 28.5 10.8 6.5 130 70 27 40 88.7 25.8 59 47.4 5.2 72.7 130 60 10.8 4.5 50 28 a? 1.32 grams from the actual 87.5 26.5 54 46.8 1.3 75.4 130 60 10.8 4.5 29 true loss. The 1.32 grams 4,0 97.6 21.1 52.2 none 86.8 70 10.8 45 7.5 130 30 may appear large compared 2.3 79.7 26.7 42.6 53 4.5 110 70 10.8 40 66.6 34 3 5 30.9 54.2 17.2 39 101.4 4.5 150 70 40 80.7 35 t o 17.15 grams, but the total 5.2 39.2 54.5 17.2 102.0 33 4.5 170 70 79.6 40 36 amount of 1-nitro-2-methyl.f 2.2 37.7 17.2 70.5 59 4.5 90 51.1 130 39 40 naphthalene product from a i 62 41.8 2.8 10.8 78.2 64.6 80 4.5 41 40 130 27.8 none 10.8 50 88.9 47.5 4.5 42 78.1 40 120 70 nitration run, which is sub31.9 none 1 0 . 8 82 5 9 . 7 20.7 4.5 48.9 40 70 90 43 jected to three subsequent crys36.3 70 67.8 26.6 2.1 4.5 10.8 54.9 50 130 44 40 tallizations, is in the neighborQ 3.6 57.0 39 106.4 43.5 4.25 10.8 91 .9 70 170 48 h 38 107.3 40.7 57.4 1.6 7.67 94.9 70 170 10.8 49 hood.of 100 grams. Percentagewise, then, the 1.32 grams a Acid addition, 0.5 hour except run 26, 0.08 hour. represent about a 1.32% varib Weight of 1-nitro-2-methylnaphthalene after last crystallization. ation in the results. These 1-Nitro-%methylnaphthalene recovered from by-product oils left in deep freeze a t -20' F.for 2 months: conclusions indicate that the corrected for crystallization losses after purification. d Weighed amount of oil after 1-nitro-2-methylnaphthalene was removed, does not represent total amount of errors introduced due to three by-products produced by nitration. crystallizations are probably 8 Temperature was 40° C . for acid addition period and 4 hours thereafter; it was increased t o 50' C. for 1 hour, less than 1.32% for 90% of 60° C. for 1 hour, and 70' C. for 1 hour. i Spent acid oould not be separated for runs 39 and 41. the time. 0 Temperature was ' 0 to 3' C. for addition of 2-methylnaphthalene, 0.5 hr., -5" to 5' C. for 1 hr., 5' t o 30' C. For an evaluation of the for 1 hr., 22O t o 35" C. for 1 hr., and 30° t o 40° C. for remaininn 0.75 hr. accumulated losses for two h Temperature was 0' t o 5' C. for addition of 2 - m e t h y l ~ a p h t ~ a l e n0.5 e , h r . , 0' C . for 3 hr.. 10' C. for 1 hr., 20° C. for 1 hr., 30° C. for 1 hr., and 40° C. for reinainder of reaction. crystallizations, the losses for the third crystallization aTe omitted from the analysis. The conclusions that may be drawn from this analysis were for the 20-gram data was 11.07 grams as compared with 10.47 similar to those discussed for three crystallizationq. The F test grams for the 30-gram data. These data may be combined, for impurities gave an F = 1.28 which is not significant. This and the best estimate of the losses is 10.77 grams. With a means t h a t there is no significant difference between the confidence of 90%, it may be claimed that the true mean of the average loss for two crystallieatione for the data obtained with accumulated losses for two crystallizations is 10.77 f (1.86) 20 grams of impurities initially present as compared with the (0.263) = 10.77 zk 0.49 grams, where 0.263 equals the standard 30-gram data, The average total loss for two crystallizations error of the mean. The estimated accumulated losses for two crystallizations of the pure 1-nitro-2-methylnaphthalene are (5.51)(2) = 11.02 grams. Since the estimate of the mean of 10.77 grams is within 0.49 gram of the 11.02-gram value, there is 160no statistical difference in the two values. With a 90% confidence, it may be claimed that an individual run y may vary as y rt (1.86)(0.833) = y =k 1.55 grams where 0.833 gram equals II the standard error of an individual run. 140The 1.55 grams is slightly greater than the corresponding value of 1.32 grams for the three crystallizations. This difference is small for all practical purposes. Accurate material balances on the main product from the nitration, the l-nitro-2-methylnaphthalene, may be written as a result of this work on crystallization losses. The conversion of 2-METHYL2-methylnaphthalene to the 1-nitro product is equal to the sum NAPHTHALENE of the pure material weighed plus the crystallization losses. Results and Discussion
0
-IO
0
IO
20
30
TEMPERATURE
40
50
( "C. 1
Figure 3. Solubilities of 2-Methylnaphthalene and 1 -Nitro-2-methylnaphthalene as Functions of Temperature
April 1954
Eleven preliminary nitration runs were conducted. During this time, techniques were developed so that quantitative results could be obtained. The 1-nitro-2-methylnaphthalene that was prepared from these early runs m-as purified and then used for the crystallization experiments. Since Fierz-David and Mannhart ( 1 ) and Vesely and Kapp (11 ) had reported yields of 58 to 60% 1-nitro-2-methylnaphthalene from nitrations with nitric acid, the first quantitative runs weie conducted with this nitrating agent. The results of these nitrations are summarized in Table 11. Nitrations with 60% Nitric Acid. Fierz-David and Mannhai t (1)had reported a 60% yield of 1-nitro-2-methylnaphthalene from a nitration at 70" C. with 60% nitric acid. A number of runs were made with 607, nitric acid as the nitrating agent, but the
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
697
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT highest, conversion of 2-methylnaphthalene to the 1-nitro isomer was 4894. The results reported by thew investigators could not be duplicated. Sitrations were carried out at tmnperaturea from 40" t'o 80" C. At 80" C. reddish-bron-n fumes (nitrogen dioxide) evolved from the nitrator toFard the end of the reaction. Some oxidation of the products or react,ants may have t'aken place at t8hehigher temperatures. There was no evidence of oxidation at the lower temperat,ures.
W
z
5
T e E O 0 C.
90-
4
s E! a
60% "03 80-
4 z
-1
E I-
%
7060-
LENGTH OF REACTION
IN H O U R I
Figure 4. Per Cent of 2-Methylnaphthalene Converted to 1 -Nitro-2-methylnaphthalene at 80' C. as Function of Reaction Time
The spent acids weie analyzed for all the nitrations If all the 2-methylnaphthalene that \vas charged v a s converted to mononitio products, the spent acid would be 21% nitric acid (assuming no evaporation losses during the process). '4t highei temperatures such as 80" C. theie would be some evaporation of the nitric acid. Also, some of the acid might be lost in the form of nitrogen dioxide and expended in oxidation reactions. Sincc the separation of the spent acid from the solid product and the by-product oil was a difficult operation. losses of nitric acid may have taken place. The acid analyses ale an indication of the total conversion to mononitro products, but these analyses should not b e used for an accurate quantitative calculation of conversions. These analyses indicate that the total conversions to mononitro products 15-ereclose to 100% for the nitrations at BO", TO",and 80" C. For runs 28 and 29 that were conducted at 50" and 40" C., the acid analyses indicate that the total conversions mere less than 100%. The weights of the by-product oils reported in Table I1 m r e determined on the oils from xhich all the 1-nitro-2-methylnaphthalene had been removed These oils had been placed in a deep freeze for 2 months and then filtered and weighed. Actually this filtration was the third filtration to which the oils mere subjected Oils such as these are difficult to transfer without losses. Also, some by-product oil was always left on the solid 1-nitro-2-methylnaphthalene that was recovered bj- filtration. The total byproduct oil produced by a nitration reaction is equal to the sum of the oil recovered, the oil left on the solid product, and the transfer losses. Therefore, the "By-Product Oil Recovered" values do not represent the total amount of by-products for the nitrations. As is shown in Table 11, nitration runs at BO", TO", and 80' C.
698
were carried out for different reaction times. Curves showing the conversion t'o 1-nitro-2-methylnaphthalene as a function of the react'ion time were prepared. These curves appear in Figures 4: 5 , and 6. At temperatures of TO" and 80' C. (Figures 4 and 5 ) , the reaction was complet'ed in less than 2.5 hours. HoiTever, the runs conducted at' BO" C. indicate that about 6 hours are required for highest conversions to 1-nitro-2-methylnaphthalene. All t'he data given in Table I1 for 609; nit,ric acid are prcsented in Figure 7 , where the per cent conversion to l-nitro-2methylnaphthalene is plotted as a function of the nitration temperature. There appears t o be a slight tendency toward higher conversions at lower t'eniperatures. The rate of nitrat,ion should he lower at the lower temperatures, and t'his might cause lower conversions. However, the conversions, as shown in Figure 7 , increase slightly at IoTT-er temperatures. A straight line is drawn t,hrough a part of the data given in Figure 7. If nitration runs were carried out, for extremely long react'ion times, the conversions would probably lie along this line. Nitrations with 70% Nitric Acid, 30% Excess. Nitrations wit'h an excess of 30% over the theoretical value of 70% nitric acid were carried out at temperatures of 40", SO", BO", and 70" C. The tJ5-o runs at TO" C. for reaction times of 2.5 and 4.5 hours gave essentially the same conversion to the 1-nitro isomer. Three runs iyere conducted at 40" C. at different reaction times. These data show that the reaction at 40" C. was complete in less than 4.5 hours.
T = 70'C. 60% H N O n
c
2 a
z
4z!
80
I
60
0
p
20
W
>
50 E #
3 10 . 0 r
#
0
1
2
3
4
5
6
7
LENGTH OF REACTION IN HOURS
Figure 5 . Per Cent of 2-Methylnaphthalene Converted to T -Nitro-2-methylnaphthalene a t 70" C. as Function of Reaction Time
A11 data given in Table I1 for a 30% excess of 70yonitric acid are presented in Figure 8 where the per cent. conversion t o 1nitro-2-methylnaphthalene is plotted as a function of t.he nitration temperature. A linear correlation coefficient, r, x a s calculat,ed as a test of the relationship between thc conversion and the nitration temperature and vas found to be -0.99. '\\-hen a t test was made, testing the hypothesis that T might actually be zero: it was found that i' was highly significant. It can be concluded that' the nitration temperature does affect the conversion of 2-methylnaphthalene t o 1-nitro-2-methyinaphthalcne. Nitrations with Nitric Acid of Different Compositions. Since the concentration of the nitric acid appeared t o influence the conversion when either 60 or 700/, nitric acid was used, runs with 50,
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Vol. 46, No. 4
UNIT PROCESSES 80, and 90% acid n-ere conducted. These runs were carried out a t 40' C. since lower temperatures were conducive to high conversions. I n Figure 9 the conversion is plotted as a function of the per cent nitric acid used, From this figure, 7Oy0nitric acid appears to be the most effective nitrating agent. If a large excess of 60% nitric acid was used, the conversions might be higher than those obtained with the 30% excess. With a 30% excess, the acid concentration during the reaction falls to about '21%. With such wide variations in the strength of a nitrating agent, it is difficult to maintain optimum operating conditions. The same situation occurs when nitric acids of different concentrations are used. Nitrations with 70% Nitric Acid. The influence of the per cent excess acid on the conversion of 2-methylnaphthalene to the 1-nitro isomer for nitrations a t 40' C. was determined for 70% nitric acid. Figure 10 shows that about a 50% excess of the theoretical amount of nitric acid is iequired for a maxinium conversion to the 1-nitro isomer. The maximum conversion to 1-nitro-2-methylnaphthalene at, 40' C. was obtained for run 36. Nitrations with 70% Nitric Acid below 35" C. When the nitration was conducted without a solvent a t temperatures below 35" C., the 2-methylnaphthalene and the products of reaction were present as solids. Two nitration runs, 48 and 49, were conducted with a 70% excess of 90% nitric acid a t low temperatures. With smaller amounts of acid the solids could not be suspended in a slurry.
w T = 60'C.
60%
"03
2 80 a z
0
1
2
3
4
5
6
7
LENGTH OF REACTION IN H O U R S
Figure 6. Per Cent of 2-Methylnaphthalene Converted to 1 -Nitro-2-methylnaphthalene at 60" C. as Function of Reaction Time
For run 48 the reaction temperature was held below 5" C. for the first 1.5 hours. Then the cooling bath was removed, and the reaction was allowed to run its course. The reaction temperature rose toward the room temperature (22' C.) and then increased to 30' C., an increase of 8' C. above room temperature, without the application of a heating bath. This observation was made after the run had been in progress for 2 hours. The reaction temperature was higher than room temperature for 1 5 hours. These observations indicated that the reaction a t 0' C. with 70% nitric acid would require more than 3 hours. I n run 49 the temperature was held a t or below 10' C. for 4.5 hours and then slowly increased to 40' C. The increase in conversion for run 49 was negligible when compared to run 48.
April 1954
60
I
w
z
REACTION TIME 0 2 5 HOURS 0 4 5 HOURS b 6 5 HOURS
-I W
a
I I +
n
a
z
\
-I
50-
L 7-
$J 0
u
c 7 0 +
40
1 , , , , , -
30
40
50
60
TEMPERATURE
70
80
("C.)
Figure 7. Per Cent of 2-Methylnaphthalene Converted to 1 -Nitro-2-methylnaphthalene with 30% Excess of 60% Nitric Acid at Various Temperatures
The conversions to 1-nitro-2-methylnaphthalene of 57.0 and 57.4%, for runs 48 and 49, check very closely with the 58% conversion reported by Vesely and Kapp ( 1 1 ) . These investigators had used a nitration procedure similar to that reported for runs 48 and 49. They had used an entirely different procedure for the determination of the conversion to the 1-nitro isomer. The conversions obtained for runs 48 and 49 were higher than for the previous runs with nitric acid that were conducted a t 40" C. These runs indicate further the dependence of the conversion on the reaction temperature. For runs 48 and 49 the rates of nitration a t 0" C. were low. The 7041, excess of iOV0 nitric acid is a poor solvent for the nitration. Nitrations in Presence of Solvents. The nitration reaction may be conducted in the liquid phase a t temperatures as low as 0 ' C. when suitable solvents are used. T w o solvents, acetic acid and acetic anhydride, mere used in this investigation. Pure glacial acetic acid melts at 16.7' C. and from this standpoint is a poor solvent. 2-Methylnaphthalene and its nitro derivatives depress the melting point of glacial acetic acid, but some solidification takes place at temperatures of 0' to 1Q' C. Scetic anhydride has a very low melting point (-73" C.), and 2-methyl naphthalene is very soluble in it a t low temperatures. Nine nitration runs were carried out in the presence of solvents. The results of these nitrations are given in Table 111. Runs 31 and 33 indicate that high temperatures are not required for the maximum conversions obtainable with the solvent and nitrating acid employed. There is no real difference between the conversions to the 1-nitro isomer for runs 31, 32, and 33, as the conversions of 48.8, 49.1, and 50.0Vo are essentially the same. Dinitration did not take place for these three runs and the separation of the solid product from the solvent was an easy separation. Since acetic anhydride has better solvent properties for 2methylnaphthalene a t low temperatures than does acetic acid, this material was used for runs 37,38, and 40. The 1-nitro product €or run 37 was very impure. This product was not completely soluble in 95% ethyl alcohol. It was refluxed in 300 ml. of 95% ethyl alcohol and then filtered while it was hot (75' to 80" C.). The melting point of the solid recovered by the filtration was 171' to 202" C. This material had a melting point of
INDUSTRIAL AND ENGINEERING CHEMISTRY
699
ENGINEERING, DESIGN, A N D PROCESS DEVELOPMENT 209" to 213' C. after it had been recrystallized three times from 95% ethyl alcohol. I t analyzed 57.28% carbon, 3.75% hydrogen, and 10.84% nitrogen, as compared with calculated values of 56.907, carbon, 3.4570 hydrogen, and 12.07% nitrogen for dinitro2-methylnaphthalene. The melting point and elemental analysis of this material indicated that dinitration took place in run 37. Similar results were obtained for runs 38 and 40.
1
-
40
20
40
TEMPERATURE
REbCTlON TIME
60
80
1'C.I
Figure 8. Per Cent of 2-Methylnaphthalene Converted to 1 -Nitro2-methylnaphthalene with 30% Excess of 70% Nitric Acid at Various Temperatures
I
the reactants almost to theii boiling point. At lower temperatures, which are desirable for high conversions to the 1-nitro isomer, dinitration might not take place. The mixed acid nitrations carried out in this investigation are presented in Table IV. The acid compositions cho8en for runs 50 and 51 are similar to those reported by Groggins ( 4 ) for the nitration of naphthalene. The conversions to the 1-nitro isomer for runs 50 and 51 are as high as the best runs with nitric acid and are better than any of the result3 obtained by the use of acetic acid as a solvent. There was no evidence of dinitration for runs 5C and 51. The low temperatures were probably the reason that dinitration was absent. These mixed acid nitrations were easily controlled and the products were separated with ease. Since the conversions for runs 50 and 51 were the same, the reaction must have been completed in less than 4.5 hours a t -2' to 3' C. These results indicate that the rate of nitration wae much higher for runs 50 and 51 than for the low temperature 7001, nitric acid runs. The 290 grams of mixed acid was only a 1570 excess above the theoretical amount. These factors indicate that suitable mixed acids are more desirable for the nitration of 2-methylnaphthdcne than the other agents investigated. I n run 52 a dilute (50%) sulfuric acid was used LLP the cvcle acid. The 2-methylnaphthalene did not react undcr these conditions. The Nolid product TWS filtered and purified liy crystallization from 300 ml of 95% ethyl alcohol. This product had a melting point of 34" C., and had the same physical appearance as 2-methylnaphthalene. The high percentage of nitric acid present in the spent acid indicates that nitration did not take place. In runs 53, 54, and 55, cycle acids of different compositions were employed. The separation of the solid product from the by-product oil was difficult for runs 53 and 54; 19 houis weir required for this filtration for run 53 During the acid addition for run 55 the solids present went into solution. The reaction mass became extremely viscous and agitation was difficult. The rate of heat transfer at this time was low, and the temperature increased to 17' C. The product from this run consisted of B thick mass that contained a large part of the spent acid. Thiv product was filtered for 48 hours, but the filtered prodiict was semisolid a t the end of the filtration. Several attempts mere made at crystallizing 1-nitro-2-methylnaphthalene from the product; hotr-ever, this isomer could not be isolated. Run.; 53,
Lesser and cotr7orkers (6:reported that the addition of acetic anliydride did not appear to influence the progress or the yield of the nitration reaction. Runs 37, 38, and 40 show that acetic anhydride does affect both the yield and the type of products. In runs 45, 46, and 4i, 200 grams of glacial acetic acid w r e used as the solvent. I n run 45 a 30% excess of 90% nitric acid was used. The conversion to the I-nitro isomer was 54.4% or higher than had been previously obtained. Since the presence of some mater inTable 111. Nitration of 2-Methylnaphthalene in Presence of Solvents creased the conversion, 70% nitric acid was used for run Recovery, Grams Solvent , 9 0 % " O Prod1 ~ Byh!elt46. T h e conversion de(Glacial Addn. Crys- uct prod- C o n v e r ~ i o n ing Per ?,,ut, creased when this nitrating Acetic) timea, Prod- tal. from uct Grams Grams hr. uct loss oil oil Grams cent C. Run agent was employed. I n run 31. Reaction 2.1 hr. a t 160 SI.3 0.73 74.1 17.2 None 45 91.3 4 8 . 8 81 47 the temperature was in- l o C., 0.6 hr. a t 5 1 . 8 (anhyd.) 0-30° C., 5.3 hr. a t creased at the end of the run, 30' C. but the conversion was essen32. React.ion 2.0 hr. a t 150 91.3 0.7 72.017.24.4 53 9 3 . 0 5 0 . 0 81 6 1 . 8 (anhyd. - l o C., 0.8 hr. a t tially the Bame as for run 45. 0-40' C., 1.0 . :h each a t 40' 50 , Run 47 indicates that tem60°: 70', 80"'C. peratures above 5' C. are 0.7 71.F 1 7 . 2 2 . 9 53 91.749.1 81 150 91.3 33. Reaction 2.0 hr. a t -1; c. 51.8 (anhyd.) not required for good conver0.78 29.8 33.0 None 53 62.8 33.6 78 200 (anhyd.) 91.3 37. Reaction 2.0 hr. a t - 1 ; c. sions in a short reaction time 91.3 0.7 23.0 2 7 . 5 2 . 8 41 53.3 28.5 77 400 (anhyd.) 38. Reaction2.0 hr. a t when acetic and fuming nitric -13 c. 0.6 2 0 . 4 22.0 None 59 42.4 2 2 . 7 7:> 186 (anhyd.) 70 40. Reaction 2.0 hr. a t acids are employed. -20 c. 45. Reaction 2.0 hr. a t 200 91.3 0.6 79.6 2 2 . 0 Xone 2 4 101.6 54,4 81 Mixed A c i d N i t r a t i o n s . -1: c. Since Shulze (Q),in the year 46. Reaction 2.0 hr. a t 200 117.4 0.5 7 4 . 8 1 7 . 2 None 36 9 2 . 0 49.3 81 -1: c. 1884, obtained some dinitro 41 103.7 5 5 . 5 81 (70%) 0.7 9 1 . 4 1 0 . 8 1.5 47. Reaction 2.0 hr. a t 200 91.4 2 O C 1.0 hr. a t 4product from his nitration 2 5 O %., 1.3 hr. a t run, most other investigators 25-60° C., 0.7 hr. a t 60" C. have avoided the use of a a Addition a t 5 O C., except runs 45, 46, and 47 a t 4 ' C. mixed acid. Shulze completed his nitration run by heating
700
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Vol. 46, No. 4
UNIT PROCESSES Table IV.
6W 6 0 -
Nitrations of 2-Methylnaphthalene with Mixed Acids
Run Temperature,
e
C.
Timeb hrs. Cycle Loid (% HnSOr) Mixed acid, % HSO. H SOt HaSOi
i&L;i acid, grams Recovery, grams Product Crystallization losses Product from,oil By-product oil Conversion t o 1-nitro isomer 2ams
50 -2 to 3 4.5 65
52 53 54 55 - 2 t o - 2 t o - 1 t o -1 t o 17 3 4 3 4.5 4.5 4.5 7.7 4.5 60 75 70 65 50
26 5 F, 20 290
25 55
a I
I-
2
5:
zn
290
89.0 10.8 7.1 48
86.6
infi.9 57.2
107.1 57.3
1 .n 64.2 34.8
0.3 64.8 34.9
17.2 3.3 29
25 55 20
25
40
35 290
26 55 20 290
290
63
...
...
49.3 26.4
95.8 51.2
11.3 44.4 44.3
2.9 70.3 26.8
0.6 68.8 30.6
2.2 69.3 28.5
,
,
.
0
-----/C
290
... ... ... ... ... ...
. I .
32.1 17.2
55-
=l z
25 56 20
77.2 17.2 1.4 38
... ...
REACTION TIME 0 4 5 HOURS A 6 5 HOURS
-1
a Temperature for run 51 was same as run 50 for first 4 5 hours, it was increased to l o o and 20° C. for 1 hr. each, and then slowly incrkased t o 40' C . 6 Includes 0 5 hour for addition of mixed acid t o nitrator.
REACTION TIME Q 4.5 HOURS A 6 . 5 HOURS
amount of unreacted 2-methylnaphthalene. If the assumption ia made that the oils contain only 2-methylnaphthalene and mononitro isomers, material balances on the carbon, hydrogen, and nitrogen can be written. Such balances give the per cent mononitro isomers present as 96.7% by the carbon balance, 94.1% by the nitrogen balance, and 97.8% by the hydrogen balance. These results indicate that the by-product oil mixture was approsimately 95% mononitro isomers. Since the three material balances check reasonably close to each other, the above assumption should be valid. Xitrogen analyses were made on the by-product oils from five nitration runs, as follows:
z -I
$
55-
w
I
?
50-
LT 0
k
f 45-
e
*
9
40'
v)
a
Run Nitrogen, wt.
W
1 3 5 0
%
12 7.11
25 7.30
29 6.37
36 8.49
47 7.46
0
e 301
40
I
50
60
70
I
80
I
90
% N I T R I C ACID
Figure 9. Per Cent of 2-Methylnaphthalene Converted to 1 -Nitro-2-rnethylnaphthalene at 40" C. with 30% Excess Nitric Acid at Various Compositions
The analyses indicate that the by-product oils were essentially mononitro isomers of 2-methylnaphthalene. The relative amount of the different mononitro isomers cannot be determined from such analyses, but the results indicate that a mixture of mononitro compounds is produced by the nitration reaction and that the total conversions to mononitro isomers are highprobably above 90%. Acknowledgment
54, and 55 indicate that the concentration of the cycle acid used for nitrations of 2-methylnaphthalene is very important. Analyses of By-product Oils. Previous investigators have reported that the by-product oil from the nitration of 2-methylnaphthalene contained mononitro isomers other than l-nitro2-methylnaphthalene. In the present investigation, the primary objective was the quantitative evaluation of conversions to the 1-nitro isomer; however, a cursory examination of the byproduct oils was made. For this study, elemental analyses were made of some of the oils. A sample of the mixture of by-product oils from runs 12 to 47, which was used for the crystallization experiments, was analyzed for carbon, hydrogen, and nitrogen content. I t analyzed 71.33% carbon, 4.86% hydrogen, and 7.04% nitrogen, as compared with calculated values of 70.58% carbon, 4.81% hydrogen, and 7.49% nitrogen for mononitro-2-methylnaphthalene. The by-product oils are mainly mononitro isomers and probably contain a small
April 1954
The authors wish to thank the Reilly Tar and Chemical Corp. for the generous amounts of specially purified 2-methylnaphthalene that they aupplied. Nomenclature
F = ratio of estimated variances r = linear correlation coefficient s = sample standard deviation 52 = sample variance
,
= estimate of the population standard deviation 2 = estimate of the population variance d = mean value of a sample
literature Cited (1) Fierz-David, H. E., and hlannhart, E. hI., Helv. Chim. Acta, 20, 1024-4.0 (1937). (2) Fieser, L. F., and Fieser, M., "Organic Chemistry," 2nd ed., p. 793, Boston, D. C. Heath & Co., 1950.
INDUSTRIAL AND ENGINEERING CHEMISTRY
70 1
ENGINEERINGr DESIGN, A N D PROCESS DEVELOPMENT (3) Freeman, H. A., "Industrial Statistics," pp. 1-61, New York, John Wiley 6: Sons, Inc., 1947. (4) Groggins, P. H., "Unit Processes in Organic Synthesis," 4th ed., PP. 75-7, New York, McGraw-Hill Book Co., Inc., 1952. (5) Irick, P;, Purdue Vniversity, private communication. ( 6 ) Lesser, R,, Glaser, A,, and Aczel, G., Ann., 402, 1-5 (1914). (7) hladinaveitia, A., and DeBuruaga, 3. S.,Andes. soc. espni2. !is. gutm., 27, 647-58 (1929). (8) Sah, P. T., Rec. trau. chim., 59, 461-70 (1940). (9) Shulze, K. E., Ber., 17, 842 (1884).
(10) Veldstra, H., and Wiardi, P. W., Rec. traa. chim., 62, 75-84 (1943). (11) Vesely, V., and Kapp, J., Ibid., 44, 360-75 (1925). (12) Vesely, V., and Pac, J.,Collection Czeciioslou. Cheni. Communs.,2, 471-85 (1930). (13) Vesely, V., and Stursa, F., Chem. Listy, 29, 361-3 (1935). (14) Vesely, V.,and Stursa, F., Collection Czechoslor. Chem. Cominuns., 6, 137-44 (1934). RECEIVED for review September 14, 1053.
ACCEPTEDDeoembcr 16, 1453,
l o w Temperature Catalytic Oxidation of Ammonia H. F. JOHNSTONE, E. T. HOUVOURASl, w. R. SCHOWALTER
AND
University of Illinois, Urbana, 111.
The oxidation of ammonia at low temperatures is of interest because of the types of products that are formed and because the reactions, which are easily followed, give fundamental information on the mechanism of heterogeneous catalysis. The reactions were studied in the range 180" to 430" C. in fused salt media and in a porous tube impregnated with a rare earth oxide or a manganese oxide-bismuth oxide catalyst. Only those fused salts whose cations form coordination complexes with ammonia act as catalysts. Cuprous chloride-potassium chloride melts rapidly catalyze the oxidation to nitrogen and water at a temperature of 225" C. An equilibrium i s established between cuprous and cupric ions that depends on the ratio of ammonia to oxygen in the gases. With praseodymium oxide as a catalyst, the overall reaction is zero order with respect to ammonia at low oxygen to ammonia ratios and low temperatures. With the more active manganese oxide-bismuth oxide catalyst, the reaction i s first order with respect to ammonia. A mechanism for nitrous oxide formation in the presence of defect oxide catalysts i s proposed. Semiconductors of the Type P defect lattice are more active catalysts than those with Type N lattices.
S
TUDIES on the mechanism of ammonia oxidation a t high
temperatures using a tubular reactor have been reported by Andrussow ( 2 ) . I n this laboratory, the tubular reactor has been used for studies of the oxidation of sulfur dioxide (S), catalytic hydrogenation of ethylene (6, 2 4 , the reaction of carbon monoxide and hydrogen ( 7 ) , and of the reaction of steam with carbon ( I S ) . It has several advantages for studying mechanisnis of heterogeneous reactions, such as ease of temperature control, choice of sampling positions, reproducibility of results, and amenability to mathematical treatment. In this xork, a study v a s made of the reaction of ammonia with oxygen a t relatively low temperatures in two types of reactors-a fused salt media and a poroua tubular reactor impregnated nith oxide catalysts of two types. The n-ork nith fused salts is an extension of the general study of catalysis in these systems made by Norman and Johnstone (19).
A4ndrussow (1) postulates an initial reaction between aninionin and molecular oxygen in which nitroxyl (HKO) is formed. Schlecht and von Sagel (21) oxidized ammonia with e x m s oxygen a t 275' to 300" C. with a mixed catalyst of ferric. oxide-bismuth oxide-manganese dioxide (Fez03-Bi203-Mn02). Postnikov (20) obtained 84% yield of nitrous oxide on a niaiiganese-iron-bismuth catalyst a t 200' t o 300" C. Krauss and Neuhaus (17) used oxides of manganese, bismuth, barium, iron, and nickel, and obtained nitrous oxide, nitric oxide, and nitrogc7n. The relationship between the activity of the catalyst and the amount of adsorbed active oxygen was further shown by K r m s (16). Kobe and Hosman (15) also studied the reaction with the manganese oxide-bismuth oxide catalyst. In general, it appears that crystalline oxide catalysts of the defect-oxide lattice tylx are necessary for the formation of nitrous oxide. Oxidation in Fused Salt Media
Previous Work on Ammonia Oxidation The mechanism of the oxidation of ammonia has been discussed by Zawadski (28). There are a t least three theories of the course of the reaction, Bodenstein (5) and Krauss (16) propose that the initial step is the reaction of ammonia with adsorbed oxygen [ O ]sdS. t o form hydroxylamine, while Zawadski is of the opinion that imide (NH) is formed in the initial step. 1 Present address,
E. I. du Pont de Nemoura & Co., Pna., Benger Labora-
tory, Waynesboro, YE.
702
While the similarity between the catalytic action of finely divided metals and their respective cation melts has been noted in the previous paper (19), t,here are other mechanisms of catalysiP by ionic melts, such as the one involving intermediate compound formation that takes place in the chlorination of light paraffin hydrocarbons with air and hydrogen chloride in the presence of fused copper chloride (11). Thus in the low temperature oxidation of ammonia, the formation of a loose coordinat>ion compound, either with ammonia or with oxygen, might b e t'he mechanism by vhich a fused salt could act as a c:italyst. 4c-
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Vol. 46, No. 4
