CATALYTIC AmIVITY OF NICKEL TUNQSTATE
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T H E CATALYTIC ACTIVITY OF REDUCED NICKEL TUNGSTATE' C. 9. ROHRER, J. ROOLEY, AND 0 . W. BROWN Departmnt of Chemistry, Indiana University, Bloomington, Indiana
Received January 19, 1060
Numerous investigations have been carried out in the study of the catalytic properties of the metals and their reduced oxides. There are also reviews of the data, classifying the metals in various systems or orders which would aid in attempts to predict the best catalyst for hitherto unexplored systems. Compounds of these metals, such as copper, cobalt, or nickel, with an acid radical containing such metals as chromium, molybdenum, tungsten, etc. have received little attention. The classified effects of these acid radicals as moderators or promoters on the reduced m d d s or compounds should then also be of considerable value. I t is only through a systematic study of all the variables concerned with each of the compound catalysts that one can begin to corre!ate the catalytic activity and selectivity related to these amphoteric anions. The object of this investigation is to study the variables associated with one of the reduced compounds in the series m a hydrogenation catalyst. Some investigations have been reported for compounds of the group VI elements which show their effect in increasing the selectivity of such active metal catalysts as copper, cobalt, and nickel. Reduced copper chromate has been found to be a very good catalyst for reducing complex ethers (1) and nitrobenzene (5). In this laboratory Griffitts and Brown (6) and Brown and Brown (2) have studied the activity of reduced cobalt molybdate in the preparation of aniline. Results from previous preliminary studies on nickel salts of group VI anions, in the reduction of nitrobenzene, led t o this work. APPARATUS
The apparatus was the type usually employed in such studies. A vertical-type electrically heated furnace contained a Pyrex-glass reaction tube 30 in. long and of 18 mm. bore. The heat was controlled by a variable transformer to yield any desired temperature, which was measured by means of a bare thermocouple that extended 1 in. into the catalyst bed from the exit end. The feed was from above, controlled by a.calibrated capillary tube delivering 2.00 ml. of 1-nitropropane and operated under a variable head of mercury. Hydrogen flow was measured in liters per hour through a calibrated flowmeter. EXPERIMENTAL
Preparation of the catalyst
The nickel tungstate catalyst was prepared by a method similar to that of E. F. Smith (9). One hundred and seventy-five grams of C.P. nickel nitrate hexahydrate was dissolved in 500 ml. of boiling distilled water. A solution of 225 g. of Contribution KO.509 from the Department of Chemistry, Indiana University.
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C. R ROHRER, J . ROOLEY, AND 0. W. BROWN
C.P. sodium tungstate dihydrate in 500 ml. of boiling water was slowly added to the nickel nitrate solution with constant stirring. The pale green precipitate was washed repeatedly with boilibg water and then with cold water until the filtrate gave a negative test for both sodium and nitrate ion. The nickel tungstate was then dried for 24 hr. at approximately 100°C. and broken into pieces with an average diameter of 2 in.
Reduction of the catalyst Twenty grams of dried nickel tungstate was placed in the reaction tube and heated slowly in a stream of hydrogen, flowing at the rate of 17 1. per hour, to a temperature of 375°C. and maintained at that temperature for 1 hr. TABLE 1 Reduced nickel tungstate as catalyst in the reduction of 1-nittoptopans Weight of catalyst, 20 g.; temperature of reduction, 375°C.; rate of hydrogen flow,17 1. per hour TI-
PEQUIPJD TO PKAW
min.
30 60 90 120 150
37S-C.
1
1
I
TOTAL T I X I OF PWUCIION
min.
: 1 150 180 210
1
YILy)
or PPoDum IN pxn a m or TEZOPY.
per cmt
74.8 92.5 93.8 87.8 83.7
Though 375°C. was found to be the best temperature for carrying out the reduction, it is also seen from table 1 that the time required to bring the furnace from room temperature to 375°C. was also critical. A total heating time of approximately 140-150 min. gave a catalyst of maximum activity. A rapid decrease in activity was observed with shorter or longer heating time.
Catalytic activity and operating temperature I n a series of preliminary determinations it was found that the reduction of 1-nitropropane at approximately 212°C. gave a maximum yield (figure 1). All yields of propylamine given in this paper are an average of from three to six reductions under constant operating conditions. Catalytic activity as affected by rate of feed of 1-nitropropane It is seen in figure 2 that a feed rate of 6 ml. per hour gives the maximum yield within rather narrow limits, as there are very sharp drops when using higher or lower rates. However, these yields do compare favorably over a considerable range with others previously reported (4, 7).
CATALYTIC ACTIYITY OF NICKEL TUNGSTATE
213
FIQ.1. Effect of operating temperature on the catalytic activity of reduced nickel tungstate. Rate of flow of 1-nitropropane, 6 ml./hr.; rate of flow of hydrogen, 600 per cent of theory.
FIQ.2 FIQ.3 FIQ.2. Effect of rate of feed of 1-nitropropane on the catalytic activity of reduced nickel tungstate. Reduction temperature, 212°C. =t3"; rate of flow of hydrogen, 500 per cent of theory. FIQ. 3. Effect of rate of feed of hydrogen o n the catalytic activity of reduced nickel tungatate. Reduction temperature, 212OC. f 3'; rate of flow of 1-nitropropane, 6 ml./hr.
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C. 8. ROHRER, J. ROOLEY, AND 0. W. BROWN
Catalytic activity MI a f W by rate of feed of hydrogen The ratio of hydrogen to the nitropropane feed is also important, aa seen from figure 3. An excess of 500 per cent of theory of hydrogen waa found to give the maximum yield of product. Dl5CUSSION OF RESULTS
Reduced nickel oxide gave 95.8 per cent reduction (8) of nitrobenzene to aniline, whereas reduced tungstic acid a t 310°C. gave only 50.1 per cent reduction (3). These catalysts have not been used previously in the preparation of propylamine, and in general higher yields are obtained in the reduction of nitrobenzene than of nitropropane. Experimental results in this paper show that the maximum yield of propylamine from 1-nitropropane is 94.5 per cent. From these considerations it is seen that nickel tungstate is a very good hydrogenation catalyst. In contrast to the extreme activity of nickel there is also added selectivity in the intermediate hydrogenation of some nitro compounds to their respective amines. Optimum conditions are given for the reduction of 1-nitropropane and the yields are higher than those previously reported in catalytic preparations. Castner and Lawson (4) reported a yield of 43.1 per cent of n-propylamine from l-nitropropane, using a catalyst composed of a mixture of cobalt, nickel, and cadmium chromates and a feed of nitropropane and ethane. Olin and Schwoegler (7), using a feed of aliphatic aldehydes and ammonia as solvent, reported yields of 81.0 per cent for the preparation of propylamine in the liquid phase. SUMMARY
1. Reduced nickel tungstate was used successfully as a catalyst for the reduction of 1-nitropropane to propylamine. 2. Methods are given for the preparation of the catalyst. 3. Data are given to show the optimum conditions of operation for this catalyst. REFERENCES R . : J. Am. Chem. SOC. 63,1091 (1931). (1) ADKINS,H . AND CONNOR, (2) BROWN, L.J., AND BROWN,0. W . : Unpublished results contained in the thesis of L. J. Brown, Indiana University, September, 1942. (3) BROWN,0. W . , AND HENKE,C . 0 . :J. Phys. Chem. 28, 161-90 (1922). (4) CASTNER, J. B . , AND LAWSON, W. E . : U . S . patent 2,377,071 (March 29,1945). (5) DOYAL, H. A,, AND BROWN,0. W . : J. Phys. Chem. 38, 1549 (1932). (6) GRIFFITTS, F.A , , AND BROWN, 0. W . : J. Phys. Chem. 42, 107-11 (1938). ’ (7) OLIN,J. F., AND SCHWOEGLER, E.J.: U.S . patent 2,373,705 (April 17,1945). (8) SENDERENS, J. B . , AND ABOULENC, J . : Bull. soc. chim. 11,641-6 (1912). (9) SMITH,E . F.: J. Am. Chem. SOC.44, 2027 (1922).
