Catalytic Preparation of Aniline. II - The Journal of Physical Chemistry

CATALYTIC PREPARATION O F ANILINE. I1

Temperature of catalyst, "C

200 215 235 260 1

Material yield in yo of theory

25.5 35.4 BO. 1 97.1

Temperatur: of catalyst, C

Material yield in yo of theory

280 300 320 340

98.4 98.7 96.2 90.2

Brown and Henke: Jour. Phys. Chem., 26, 161 (1921).

I

i I

I

I

Catalytic Preparation. of Aniline. I I

273

The results of Table I are plotted in curve Ag of Figure 1. The curve is very similar to the curve for copper which is redrawn from the graph of the previous paper. The best

100

P

0

80

6C

I-

% R 2 c

40

ZG

00 ZOO 300 TEMPERATURE Of CATALYST Fig. 1

temperature for carrying out the reduction with silver as catalyst is seen t o be from 280" to 300". This catalyst was then used t o study the effect of the rates of flow of the hydrogen and nitrobenzene. The results

0.W . Brown and C. 0.Henke

274

Nitrobenzene in grams per hour

Excess of hydrogen in %

Material yield in % of theory

100 190 220 400 710

59.2 77.1 90.2 93.1 98.7

15.5 10.7 9.7

6.3 3.9

PI

I

I

4

8

12

NlTROBENZfNE FLOW- CRAMS P f R H R .

Fig. 2

I

HYnROGEN FLOW- LITERS PER H F

Fig. 3

I n curve Cu-A the rate of flow of hydrogen was 11.4 liters per hour while in all the other curves it was 17 liters per hour. The graph shows that with nickel the speed of reduction of

Catalytic Preparatima o j Awiliuc. 11

275

nitrobenzene is greatest and with copper the least. Silver, though not equal to nickel has a far greater speed of reduction than copper. The temperatures of the different catalysts were not the same, but each one was used at the temperature where it had given the highest yield of aniline with the rate of flow of nitrobenzene at 3.0 to 4 grams per hour and the rate of hydrogen a t 17 liters per hour. Since silver is like copper in that i t does not attack the aromatic ring it appears that i t would be a better catalyst to use than copper in cases where the action of the nickel was too violent, for the silver can be used a t a much greater rate than the copper catalyst. The results of experiments with different rates of flow of hydrogen are given in Table 111. TABLE I11 Catalyst-Silver. Temperature of catalyst-300". Rate of flow of nitrobenzene-;3.9 Hydrogen in liters per hour

grams ?er hour.

Excess o f hydrogen in 9;)

Material yield in Tj of theory

100 300 i10 1310 1940 29'70

96.2 98.1 98.7 94.9 91.2 88.0

The results of Table I11 are plotted in curve Ag of Figure 3 . The curves for nickel and copper are redrawn from the previous paper for purposes of comparison. The temperatures of the different catalysts are the same as in Figure 2. Here again the nickel is capable of effecting the reduction a t the greatest rate with silver second and copper last, although the difference betweensilver and copper is not so great as in Figure 2. An experiment in which the hydrogen was bubbled through water at 50" before being passed into the furnace gave the same result as when it was not bubbled through the water. Likewise passing the hydrogen through an approximately l/zyh ammonia solution did not affect the yield of aniline appreciably.

0.W . Brown

276

aizd C.

0.Henke



TemperatuEe of catalyst, C


305 232 1'70

0.6 5.4 5.0

153 140 125

12.6 23.6 47.6

Catalytic Preparation of Aniline. 11

277

was shown by the fact that the odor of ammonia was strong and at the higher temperatures there was only a small amount of condensate which indicated that the cobalt was reducing some of the nitrobenzene even t o methane. This variance from Sabatier's results may however be due t o the fact that he very carefully freed his nickel from cobalt and his cobalt from nickel, while the cobalt nitrate that we used contained 0.51y0nickel and the nickel nitrate contained 0.386% cobalt. Also Sabatier used a glass tube while we have used these catalysts in an iron pipe. Iron The iron catalyst was prepared from ferric nitrate, which had been repeatedly boiled down with nitric acid to free i t from chlorine. Ferric oxide was precipitated from the ferric nitrate solution by ammonium hydroxide, and then dried in a n oven at about 110'. Twenty six grams of the oxide were used. This was heated in hydrogen to 415' and kept at that temperature for 30 minutes. It was then used in the experiments recorded in'Table V, which show the effect of different temperatures on the yield of aniline secured. TABLE V Catalyst-Iron. Rate of flow of hydrogen-17 liters per hour. Rate of flow of nitrobenzene-3.9 grams per hour. Excess of hydrogen-7100jo. Experiment number

GL1 7L1 SL1

BL1 10L1 11L1 25L1* 17L1** lSLl**

* Prior

Temperatye of catalyst, C

305 305 30.5 2% 268 250 232 250 250


19.4 19.7 17.8 32.0 64.2 70.5 89.9 44.2 13.8

to experiment 25Ll the catalyst was heated in hydrogen a t 415' for 30 minutes. ** For experiments 17L1 and 18L1 the rate of flow of nitrobenzene was 4.9 grams per hour.

0. W . Brawut and C. 0. Henke

278

The first seven results of Table V are plotted in curve Fe of Figure 1. The graph indicates that iron has a high activity. The low results at the higher temperatures are not due to incomplete reduction of the nitrobenzene but to the fact that the iron carried on the reduction too far, as shown by the fact that the product was colorless and there was a very strong odor of ammonia. Even in experiment 25L1 which was carried out at 232" the product was colorless and contained no nitrobenzene indicating that even a t this low temperature the iron has reduced a part of the nitrobenzene farther than the aniline stage. However at the lower temperatures the iron quickly lost its activity as is illustrated by experiments 17L1 and 18L1 which were made under duplicate conditions, one following the other. The second one is about 30y0 lower than the first. However merely heating in hydrogen at 415" for 30 minutes completely restores the activity of the iron. This indicates that a t 250 " metallic iron partially reduces the nitrobenzene and is converted to the oxide. Then a t this low temperature the oxide is not reducible by hydrogen or is only very slowly reduced by hydrogen and as a result the iron is soon converted to the oxide and the catalyst has lost its activity simply because it is no longer metallic iron but iron oxide. Then by heating at 415" the catalyst regains its activity because the iron oxide is reduced and we again have metallic iron as catalyst. Sabatierl states t h a t t h e iron oxide is reduced with difficulty at 400" to 450". He claims that it takes 6 or 7 hours to completely reduce it with hydrogen a t this temperature.

Antimony The antimony catalyst was prepared by reducing 35 grams of the trioxide, which was c. p. material from Kahlbaum, and then heating in hydrogen to 435". The results of experiments carried out at different temperatures with this catalyst are given in Table VI. 1

Sabatier: "La Catalyse," 1st Ed., Paris, 1913, p. 106.

Catalytic Preparation of Aniline. I I

279

TABLE VI Catalyst-Antimony . Rate of flow of hydrogen-17 liters per hour. Rate of flow of nitrobenzene-3.9 grams per hour. Excess of hydrogen-710%. Experiment number

1E1

5E1* 6E1 7E1 8E1

Ternperaturz of catalyst, C

Material yield in % of theofy

242

25.8 85.4

300 300 300

68.7 58.3 300 20.8 9E1** 300 76.9 10E1** 320 95.2 320 llEl 93.3 320 l2El 95.2 260 13E1** 70.6 The results of Table VI are plotted in curve Sb of Figure 1. It will be noted that at 320' the antimony catalyst did not lose its activity while at 300 O its activity decreased steadily with use as the data in the table indicates. However, its. activity was restored by merely heating in hydrogen at 450" for about 25 minutes. This indicates that a t 300 O the metallic antimony partially reduces the nitrobenzene and is converted to the oxide which then is not reduced by the hydrogen at that temperature. However at a higher temperature it is reduced and the catalyst then regains its former activity. The results of the table indicate that a t 320" the antimony catalyst, at the indicated rates of nitrobenzene and hydrogen, does not lose its activity. This action of antimony was very similar to the action of iron except that the metallic iron was a much more vigorous catalyst. (With antimony at 300" the product was colored indicating the presence of azoxybenzene or azobenzene while with iron at this temperature the reduction was carried on farther than the aniline stage.)

* Prior to experiment 5E1 the catalyst was heated in hydrogen at 470' for 30 minutes. ** Prior to each one of these experiments the catalyst was heated in hydrogen at 450" for about 25 minutes.

0. W . Brown and C'. 0. Henkc

280

Both would indicate that the nitrobenzene oxidizes the metal which in turn is reduced by the hydrogen. In experiments 9E1 and 13E1 a small amount of azobenzene was formed. Other catalysts that yielded considerable amounts of azobenzene were lead and bismuth and since the formation of azobenzene with these two catalysts is so marked and peculiar, the results will be given in a separate paper in a later number of this journal.

Molybdenum Oxide The molybdic acid that was used for this catalyst contained 88.03% Mooa,a trace of phosphorus, a trace of insoluble residue and ammonia. No arsenic or copper was present. This was heated in hydrogen a t 405" for about two hours, a few experiments carried out and then after heating in hydrogen a t 405' for another hour the experiments of Table VI1 were carried out. TABLE VI1 Catalyst-Molybdenum Oxide. ' Rate of flow of hydrogen-17 liters per hour. Rate of flow of nitrobenzene-3.0 grams per hour. Excess of hydrogen-710%. Experiment number

llJl 12J1 7J1

8J1

17J1


235 252 290 310 345

I


36.0 26.0 86.5 94.3 93.1

I

Catalytic Preparation of Aniline. 11

Temperature of catalyst, OC

360 340 320 300 280 260 1

Material yield in

'

yo of theory

84.0 85.5 83.1 79.6 67.5 28.2

Brown and Nees: Jour. Ind. Eng. Chemistry, 4, 867 (1912).

281

282

0. W . Brow% and C. 0. Henke

hydroxide. The hydroxide was then dried at about 110" and of course became oxidized to the sesquioxide. Twentyseven grams of the dry sesquioxide were put in the furnace and reduced and heated in hydrogen to 435" and kept a t that temperature for 30 minutes. The results of experiments carried out at different temperatures are given i n Table VIII. The results of Table VI11 are plotted in curve M n of .Figure 4. From the curve the best temperature with manganese as catalyst is seen to be about 340'.

Chromium The chromium catalyst was prepared by precipitating the hydroxide from a solution of the nitrate by ammonium hydroxide. Ten grams of the Fig. 4 dried oxide were put in the furnace and reduced and heated in hydrogen a t 415' for about an hour. The results of experiments a t different temperatures are given in Table IX.

.

The results of Table IX are plotted in curve Cr of Figure 4. The shape of this curve is quite different from those of the other catalysts. The most favorable temperature falls within narrow limits and the decrease with the higher temperatures is very great. Possibly with slower rates of hydrogen and nitrobenzene the optimum temperature range would not have been so narrow and the percentage yield would have been greater.

Catalytic Preparation of Aniline. 11 TABLE IX C atalyst-Chromium. Rate of flow of hydrogen-17 liters per hour. Rate of flow of n i t r o b e n z e n e 4 grams per hour. Excess of hydrogen-680%. Experiment number

, 201 301 101 ti01 60 1 701

so1* 901 1001


340 323 304 286 268 250 250 232 214


64.5 83.0 68.3 65.5 58.0 56.7 56.1 23.8 9.4

Vanadium Oxide

Experiment number

2P1 3P1 4P 1 5P1 6P1 7P 1 SP1 9P1 10P1

Temperature of catalyst, 'C

345 327 310 290 270 252 382 365 345


74.3 66.1 52.0 21.9 14.4 5.6 81.8 88.0 74.3

283

0. W . Brown and C. 0.Henke

284

wise very narrow. The catalyst in this case is probably a lower oxide of vanadium.

Uranium Oxide The uranium oxide catalyst was prepared by precipitating the hydroxide from a solution of the acetate by ammonia. Twenty-seven grams of the dried hydroxide were put in the furnace and heated in hydrogen a t 420' for one hour. The results with this catalyst a t different temperatures are given in Table XI. TABLE XI Catalyst-Uranium Oxide. Rate of flow of hydrogen-17 liters per hour. Rate of flow of nitrobenzene-4.1 grams per hour. Excess of hydrogen-660'%. . Experiment number

8N 1 ON 1 lONl llNl 12N1 13N1 14N1* 15N1 16N1 17N1

Temperaturz of catalyst, C


310 310 290 270 252 235 345 345 327 310 382

33.5 52.6 50.1 16.9 7.5 2.5 49.8 53.9 69.6 55.1 52.3

18N1 The results of Table X I are shown in curve U of Figure 4. It will be noted that each time after heating in hydrogen the first experiment is lower than the second. It thus increases in activity with use. This same behavior was also noted with copper as catalyst. I n the graph the results of experiments 9N1 and 15N1 are plotted instead of the results of 8N1 and 14N1. The curve for uranium is very similar to those for chromium and vanadium. I n fact these three are very similar and are different from the others which are also similar in shape. .

* Prior to experiment 14N1 the catalyst was heated in hydrogen a t 420" for one hour.

Catalytic Preparation of Avziline. 11

285

Other Catalysts Twenty grams tungstic acid were put in the furnace and heated in hydrogen to 420" and kept at that temperature for about two hours. Experiments carried out at 310" with 4 grams nitrobenzene per hour and 17 liters hydrogen per hour gave 50.1% yields of aniline. It was not used a t higher temperatures, although the yield of aniline would probably have increased with increase in temperature. Commercial cerium oxalate was also used as catalyst after heating in hydrogen at 420" for one hour. The cerium oxalate contained some lanthanum and the didymiums. An experiment a t 358 with 3.9 grams nitrobenzene per hour and 17 liters hydrogen per hour gave a yield of 49.5y0 aniline. Calcium and barium oxides were also tried but results were not appreciably higher than those given by the empty iron pipe alone. Commercial tellurium likewise had no appreciable activity. Silica which had been precipitated from a sodium silicate solution with HC1 and then treated repeatedly with H N 0 3 and evaporated with H N 0 3 showed no appreciable activity. With these catalysts the yields obtained were not appreciably more than with the empty iron pipe alone, the results of which were given in the previous paper. An alumina catalyst, prepared by the method described by Johnson,' was used in a glass combustion tube instead of in an iron pipe. Glass is a poorer conductor of heat than iron and as a result the end of the glass combustion tube which extends in the condenser was not kept hot enough t o keep the products from condensing in it. So the end of the glass tube was surrounded by an electric heating jacket about 43/4 inches long and 31/2 inches in diameter. This kept the temperature in the tube near 200" and prevented the products from condensing in the tube. All the other details of the furnace remained the same. Thirteen grams of the alumina were used. The results are given in Table XII. Johnson: Jour. Am. Chem. SOC.,34, 911 (1912).

286

0. W . Brown and C. 0. Henke TABLE XI1 Catalyst-Alumina. Rate of flow of hydrogen-17 liters per hour. Rate of flow of nitrobenzene-3.9 grams per hour. Excess of hydrogen-7 10%. Temperature of catalyst, "C

290

1

Material yield in

70 of theory

2.8

327 5.0 13.2 364 Thus alumina in a glass tube showed some catalytic activity. Its action may be looked upon as one of dehydration, since water is one of the products of the reaction and alumina is known t o be a good dehydrating catalyst. Summary of Results 1. For the reduction of nitrobenzene cobalt was found to be active at a lower temperature than nickel. However the cobalt contained a little nickel and the nickel a little cobalt. 2. Iron was found t o carry the reduction farther than copper but cannot be used below about 300 O and at this temperature its action is too vigorous, the reduction being carried on too far. 3. Silver was found to be an excellent catalyst, even better than copper prepared by ignition of the nitrate, because it can be used at a much higher rate of flow of nitrobenzene. 4. Antimony, manganese and chromium were also found t o act as catalysts in the reduction of nitrobenzene. 5. The lower oxides of molybdenum, vanadium, uranium, tungsten and cerium also acted as catalysts in the reduction. The activity of the oxides of molybdenum and vanadium was greater than that of the other three. 6. Alumina was found to possess a little activity. Its activity is probably that of a dehydrating catalyst as water is one of the products of the reaction. 7. Commercial tellurium and the oxides of calcium, barium and silicon were not found to possess appreciable activity.

Catalytic Preparation of Aniline. IT

287

8. It was pointed out that with iron and antimony a part of the reduction was due to the direct action of the metal, a n oxide being formed. 9. When antimony was used at a low temperature the catalyst lost its activity, which was restored by heating t o 450" in hydrogen. When however antimony was used at about 320" i t did not lose its activity with use. 10. I n choosing a catalyst for any particular reaction that catalyst should be chosen which works best at the temperature a t which the reaction takes place. Laboratory of Physicul Chemistry Indiana University Bloomington

Catalytic Preparation of Aniline. II - The Journal of Physical Chemistry

Recommend Documents