NICKEL-CATALYSTS centages of 1,3-butanediol found in the reaction mixtures are reported, since these are sufficient to evaluate retention of catalytic activity. The percentage of 1,3-butanediol found in the first product was corrected for the ethyl alcohol (6 grams) added with the catalyst to obtain the value of 55y0 given in the table. Probably the loss in catalytic activity resulted from overexposure of the catalyst to air during recovery between experiments; however, the use of aqueous aldol may have contributed to the loss in activity.
Table
IV.
Expt. 1 2
3
Table
Reaction Time and Yield of I,3-Butanediol
Expt.
Effect of Re-use of Raney N i c k e l o n Reaction Time and Yield of 1,3-Butanediol Reaction Time, Hr./100 G. Aldol 1.4 1.9 3.5
1,a-Butanediol in Reaction Mixture, % 55 51
V. Effect of Re-use of Protected Raney N i c k e l on Temp., O C. 80 80-83 80-83 80-83 81 for 1.9 hr. 91 for 1.4 hr. 81 for 1.4 hr. 91 for 1.6 hr. 81 for 1.4 hr. 91 for 1.9 hr. 81 for 1.3 hr. 91 for 2.0 hr. 90-93
Reaction Time, Hours
1,a-Butanediol in Reaction Mixtuoe,
n
2: 1 2.2 2.5 3.3
64
67 68 68 67
3.0
67
3.3
67
3.3
64
2.0
65
Indeterminate reaction time caused by several mechanical failures d the stirring apparatus. a
47
I n another study of re-use of Raney nickel, a 4-kg. charge of commercial aldol with 150 grams of catalyst was hydrogenated in autoclave B under a hydrogen pressure of 600 pounds per square inch with stirring a t 900 r.p.m. After settling, the majority of the product was decanted, and the residual catalyst, protected in a small portion of the product, plus 120 grams of fresh catalyst were used with the next 4-kg. rharge of commercial aldol. Thereafter, only the residual catalyst from the previous experiment, protected in a small portion of the previous product, was used in succeeding experiments with 4-kg. charges of commercial aldol. The results are shown in Table V. The percentages of 1,3butanediol found are sufficient to compare the relative activities of the re-used catalyst. The percentages found in the first two products were corrected for the ethyl alcohol added with the catalyst to obtain the first t n o values given in the table. It can be seen from the results shown in Table V t h a t Raney nickel retains its catalytic activity quite well when protected as described. ACKNOWLEDGMENT
The author thanks E. P. Schoch, director of the over-all project, for his endorsement and release of this paper for publication. He also thanks H. R. Heme for many helpful suggestions, and
acknowledges the help and part,icipation of Melvin 1.Nobles and C. Weldon Chaffin in the procedures for hydrogenation and analysis. LITERATURE CITED
(1) Bayer and Co., Brit. Patent 940 (Jan. 13, 1913). (2) Carothers, \IT. H., and Adams, R., J . A m . Chern. Soe., 46, 1675 (1924). (3) Covert, L. W., and Adkins, H., Ibid., 54, 4116 (1932). (4) Goldstein, R. F., “The Petroleum Chemicals Industry,” p. 292, New York, John Wiley &- Sons, 1950. (5) Halpern, J. H., Monatsh., 22, 63 (1901). (6) Henson, D. D., Progress Report to Bureau of Industrial Cheniistry, The University of Texas, Austin, Tex., March 28, 1941. (7) I. G. Farbenindustrie -4kt.-Ges., Brit. Patent 328,083 (hlarch 9, 1929). (8) I. G. Farbenindustrie Akt.-Ges., French Patent 668,103 (April 27, 1928). (9) Rlueller-Cunradi, M . (to I. G . Farbenindustrie Akt.-Gee.), U. S. Patent 1,907,855 (May 9, 1933). (10) Mueller-Cunradi, M., and Pieroh, K., Ibid., 1,881,863 (Oct. 11, 1932). (11) Neuberg, C., and Kerb, E., Biochem. Z., 9 2 , 96 (1918). (12) The University of Texas, Austin, Tex., Pub.‘Aro. 5011 (June 1, 1950). (13) U. S. Dept. Commerce, Office Pub. Board, R e p t . S o , 189 (1945). RECEIVED for review January 28, 1932. ACCEPTEDMarch 8, 1952. Presented a t the Seventh Southwest Regional Meeting of !he A a i r : R I c A s CHEXICAL SOCIETY, Austin, Tex., December 1951.
C A T A L Y T I C A C T I V I T Y OF N I C K E L BORIDES RAYMOND PAUL, PAUL BUISSON,
AND
NICOLE JOSEPH
Soci&t& des Usines Chimiques RhOne-Poulenc, Paris B y reacting sodium or potassium borohydride with various nickel salts under various conditions of temperature, pH, and solvents, voluminous black precipitates were produced which invariably comprised one atom of boron to two atoms of nickel. These products are neither magnetic nor pyrophoric and do not dissolve as quickly as Raney nickel in hydrochloric acid or potassium triiodide. Their catalytic activity has been studied in comparison to that of Raney nickel in the hydrogenation of safrole, furfural, and benzonitrile. When prepared from nickel acetate or nickel chloride, these catalysts have an activity equal to or dightly inferior t o that of Raney nickel, Their resistance to fatigue appeared particularly high. O n the other hand, by reacting alkaline borohydride with a nickel salt solution containing small quantities (about 2%) of metals of known promoting activity such as chromium, molybdenum, tungsten, or vanadium, a whole series of complex catalysts was prepared
1006
which in a number of cases clearly proved more active than Raney nickel. The simplicity and rapidity of this technique render it highly suitable to the study of promoters (activators).
N T H E course of his work on borohydrides, Schlesinger (4) observed that although the alkali borohydrides reduced a certain number of salts t o the metallic state (silver, mercury bismuth salts, etc.) they gave only the corresponding bolides with nickel salts or with cobalt salts. Since the products thus obtained have a finely divided form and since on the other hand the atomic volume of boron is small compared t o that of nickel, the authors believed they might possess a certain activity in the reactions for which metallic nickel is usually employed as a catalyst. This hypothesis was found to
I
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44, No. 5
NICKEL-CATALYSTS 800
800
700
700
600
600
.E
dc‘ 500 (Y
m 2 400
4003
P 1 300
300 I
2
200
XK)
100
1w
0
2
0
8
6
4
12
10
14
16
18
200
2
4
6
Minuter
8
10
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18
16
200
5
10
15
Minutes
Figure 1. Safrole
25
30
35
40
45
Figure 3.
I = Raney nickel Catalysts I1 = Ni chloride plus sodium borohydride 111 = Ni chloride plus potassium borohydride
Influence of pH of Mixture
Safrole with: I = Raney nickel Nickel boride catalyst I1 = Acid pH (approx. 5) 111 = Neutral pH IV = Alkaline pH (approx. 10)
800
800
d i
50
Minutes
Figure 2. Safrole
I = Raney nickel Catalysts I1 = Sodium borohydride plus Ni acetate 111 = Sodium borohydride plus Ni sulfate IV = Sodium borohydride plus Ni chloride
20
700
700
6w
600
500
1400 0
I” 3oa 200
200
100
100
0
0
2
4
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14 16
0
15
Minutes
45
60
90
105
120 0
30
15
45
Minuter
C A T A L Y S T S C O N T A I N I N G O N L Y NICKEL
Such catalysts obviously can be prepared either by introduction of the alkali borohydride into the solution of the nickel salt or by introduction of the nickel salt into the solution of the alkali borohydride. Experience has shown that the composition and the activity of the products obtained are identical in both cases. However, the first-mentioned procedure was preferred because it permits much better utilization of the alkali borohydrides. I n fact, the formqtion of nickel boride or borides is always accompanied by a decomposition of the alkali borohydride according to the reaction
60
75
90
105
120
Minutes
1 = Raney nickel Catalysts I1 = Ni chloride i n acid medium (CHaCOOH) 111 = Ni acetate i n neutral medium I V = Ni chloride i n neutral medium (Center lines indieate addition of 5 CC. of 40% NaOH)
be correct and the results of the first ekperiments in this work are yeported here. First the catalytic activity of the precipitates obtained by the action of an alkali borohydride on a pure nickel salt was studied. Then this research was extended to the complex catalysts obtained by treating, in the same fashion, a nickel salt t o which had been added small quantities of elements known t o intensify the catalytic properties of nickel, such as chromium, molybdenum, and vanadium. As will be noted, this addition of promoters was found to be most effective.
May 1952
75
Figure 5. Furfural
Figure 4. Influence of Solvent Safrole with catalysts from sodium borohydride and nickel chloride solution I = 5 % solution i n water IP = 20% solution i n water IEE = 5 % solution i n methanol
30
Figure 6. Benzonitrile I = Raney nickel
Catalysts I1 = Ni acetate I11 = Ni chloride (Center line indicates addition of 5 cc. of 40% NaOH)
BH4Na
+ 2 H 2 0 -+ BO&a + 4H2
This reaction is catalyzed by the nickel borides; therefore, by introducing t h e nickel salt into the alkali borohydride, the greatest portion of this latter reagent is decomposed, without participating in the production of the catalyst. The operating procedure used is very simple: Twenty-seven ml. of a 10% aqueous solution of sodium borohydride are added with stirring, for about 20 minutes, t o 121 ml. of a 5% aqueous solution of nickel chloride hexahydrate (equivalent to 1.5 grams of metallic nickel). Hydrogen is liberated, while a voluminous black precipitate appears; the kmperature may rise t o 40’. When all the nickel has been precipitated, the supernatant liquid is colorless and has a p H approaching 10. The black precipitate is easily collected. It is filtered and washed thoroughly, without exposure of the product t o air. The catalyst is then ready for use and can be kept in stock in loo$& ethyl alcohol without any difficulty. I n contrast t o Raney nickel, this catalyst is neither ferromagnetic nor pyrophoric. The necessity of keeping it from contact with air is not because of any risk of ignition or incandescence, but merely because exposure t o air could considerably diminish its catalytic activity.
INDUSTRIAL AND ENGINEERING CHEMISTRY
1007
NICKEL-CATA LYSTS 800
800
700
700
600
600
Y
.
5
2
>
u'
500
500
400
400
300
3005
200
200
1 00
100
0)
0
2
4
6
8
12
10
14
16
18
2
200
6
4
8
Minutes
10
12
14
16
1 8 0
2
4
6
Minutes
Figure 7 . Safrole
10
12
14
16
18
20
0
Minutes
Figure 8. Safrole
I = Raney nickel I1 = Nickel plus 2 90 molybdenum I11 = Nickel plus 2 % ahromium IV = Nickel without promoter
8
9" D
Figure 9.
I = Raney Nickel 11 = nickel plus 2 % molybdenum III = Nickel plus 2 % vanadium IV = Nickel plus 2 90tungsten
Safrole
I = Raney nickel I1 = Nickel without promoter 111 = Nickel plus 2 % cobalt
(Center lines indicate addition of 5 cc. of 40% NaOH)
Another difference between this catalyst and Raneg nickrl is a much slower rate of decomposition in hydrochloric acid or in aqueous solutions of potassium tri-iodide. Boron and nickel were determined in numerous samples. T h e analytical figures do not total 100% but are always low by about 7%. Schlesinger ( 3 )has already made a similar observation and attributed this fact t o a partial oxidation of the product. However, the average composition of the products obtained under different conditions of preparation deviates very little from a content of 7 to 8% boron and 84 to 85% nickel. The boron t o nickel ratio is virtually constant and always corresponds t o the presence of one boron atom for two nickel atoms; therefore, the authors conclude t h a t the catalyst is nickel boride (NilB). A technique previously described by one of the authors ( 2 )was used for the study of the catalytic activity of these nickel borides. T h e apparatus consists of a shaker (with a reciprocating motion) on which have been mounted four 500-ml. Erlenmeyer flasks connected with four 1200-ml. Bunte burets serving as reservoirs for hydrogen.
This method thus permits the elimination of varying hydi oyenation rates due t o differences in temperature, variations in atmospheric pressure, and changes in the rate of agitation. Hydrogenation of Safrole. For every test a suspension of 1.5 grams of catalyst in 20 ml. of 100% ethyl alcohol was added to 20 nil. of a 30% solution of freshly distilled safrole in ethyl acetate. Theoretically, this quantity of safrole should absorb 830 cc. of hydrogen at 0' and under 7'60 mm. (mercury) for tramformation into dihydrosafrole. Figure 1 shows that the nickel borides prepared from nickel chloride or nickel sulfate have an activity inferior to that of Raneg nickel, whereas if they have been prepared from nickel acetate, their activity is almost e q u J to that of Raney nickel. Figure 2 shows t h a t either sodium borohydride or potassium borohydride can be employed equally well in preparing these nickel borides, in spite of the latter's lower solubility. Figure 3 points out a decrease in the catalytic activity with increase in the pH during the course of the reaction of thc alkali borohydride with the nickel chloride.
800
BM,
700
700
600
m
d. 5 0 0
c
*
0)
Em
4GQ
-0
f
300
300
m
200
100
100
f B
I
0 0
2
4
6
8
10
12
14
16
18
20 0
6
12
18
24
30
36
42
48
Minutes
Minutes
Figure 10. Safrole
Figure 11. Furfural
I Raney nickel I1 Nickel without promoter 111 E Nickel plus 2 9% iron
54
60 0
6
I = Raney nickel 11 = Nickel plus 2 % tungsten I11 = Nickel plus 2 9% molybdenum
12
18
24
30
36
42
48
54
60
Minutes
Figure 12. Furfural I
=
Raneyniekel
11 = Nickel plus 2 % vanadium
IV = Nickel plus 2 %:chromium
(Center liner indicate addition of 5 CC.of 40% NaOH)
Each flask contains the same quantity of the solution t o be hydrogenated, and into each is introduced the same quantity of the catalyst t o be compared. I n practice, therefore, in each run three catalysts are compared with Raney nickel which is used for reference.
1008
Finally, Figure 4 seems t o indicate that the concentration of the reagent and the nature of the reaction medium do not influence t o any extent the activity of the resulting catalyst. Hydrogenation of Furfural. I n every test 1.5 grams of catalyst suspended in 20 ml. of 100% ethyl alcohol were added to 20 ml. of
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44, No. 5
NICKEL-CATALYSTS a 14.4% solution of freshly distilled furfural in ethyl acetate. For such a solution, the hydrogenation t o the furfuryl alcohol stage corresponds to an absorption of 672 cc. of hydrogen measured at 0" and under 760 mm. mercury. Figure 5 confirms the necessity of preparing catalysts in a ' slightly acid medium: the catalyst, corresponding t o curve I1 obtained in an acetic medium at a p H of 5 , is in fact almost as active as Raney nickel.
ann
6w
d;5w m c V 24cQ
5 3w 2m
100
0
6
12
18
24
30
36
42
48
Minutes
54
60 0
6
12
18
24
30
36
occurs very nearly at the same velocity and with the same yield as in the case of Raney nickel. RESISTANCE
TO
FATIGUE
It was important t o examine the resistance t o fatigue of this new type of catalyst. Therefore, under the previously stated conditions, a series of 29 hydrogenations were made, each with 20 ml. of the 3Oy0 safrole solution, using the t same catalyst. In a parallel manner, a series 800 of 29 analogous operations were carried out with the same sample of Raney nickel. Thc results, presented in Table I, show rn that, in this particular case at least, the 500 nickel borides exhibit greater resistance t o 5 fatigue than Raney nickel, since at the end of the twenty-ninth operation, the duration of the hydrogenation had changed from 7 t o 3w I" 10 minutes with nickel boride and from 6 t o 2M 37 minutes with Raney nickel. 100 42
48
54
60
0
C O M P L E X CATALYSTS
Minuter
The technique described here maybe applied quite successfully, as stated, to the preparaI = Raney nickel I = Raney nickel tion of complex Catalysts which contain, in 11 = Nickel plus 2 % manganese 11 = Nickel plus 2 % iron addition to nickel as the basic metal, one or 111 = Nickel plus 2 % cobalt IV = Nickel without promoter more promoter elements such as chromium, (Center lines indicate addition of 5 CC. of 40% NaOH) molybdenum, or tungsten. A nickel-chromium catalyst was prepared On the other hand, from the work of Delepine and Horeau ( 1 ) it by introducing 27 ml. of a 10% solution of sodium borohydride is known t h a t the addition of a small quantity of sodium hydroxide into a mixture of 119 ml. of a 5 % nickel chloride hexahydrate to Raney nickel (as well as t o platinum black) increases the rate of solution and 2.5 ml. of a chromic sulfate solution containing 1.2% hydrogenation of numerous unsaturated functions. chromium. This product is a black powder analyzing 5.3% boron I n this experimeht, 0.5 ml. of a 4070 sodium hydroxide solution and 2% chromium; it also was stored in ethyl alcohol. was added t o each flask after 30 minutes (abscissa 30 of Figure 5). A very definite increase in the hydrogenation rate resulted, and the hydrogenation not only affected the carbonyl group, but also Table 1. Resistance of Catalysts to Fatigue the furan nucleus. Time Necessary for Hydrogenation of 80% of Hydrogenation of Benzonitrile. These tests were carried out Amount of Product Present, Minutes with 20 ml. of a 10.33% solution of benzonitrile in ethyl acetate, 1st 11th 20th 29th Catalyst (1.6 grams) operation operation operation operation t o which was added a suspension of 1.5 grams of catalyst in 20 ml. Raney niokel 6 10 32 37 of 100%ethyl alcohol. Catalyst pre &red from nickel ohlorig and sodium The complete hydrogenation of this quantity of benzonitrile borohydride 7 7 10 10 to benzylamine requires 896 CC. of hydrogen measured at 0 ' under 760 mm. (mercury). The left-hand side of Figure 6 shows that the activity of the I n the same manner, the following catalysts were obtained from catalyst prepared with nickel acetate (curve 11) is slightly sua solution of nickel salt t o which sodium molybdate, sodium perior t o t h a t of the Raney nickel. tungstate, ammonium vanadate, cobalt chloride, manganese Here, too (right-hand side of Figure 6), an addition of 0.5 ml. chloride, and ferrous sulfate were added in calculated quantities: of a 40% sodium hydroxide solution definitely increased the rate Nickel-molybdenum (B, 6.6%; Mo, 1.93%); nickel-tungsten (B, of hydrogenation. The effect, however, is less pronounced for 6.5%; W, 1.8%); nickel-vanadium (B, 7%; V, 1.85%); nickelthe nickel boride catalysts than for the Raney nickel. cobalt (B, 7.2%; Co, 1.95%); nickel-manganese (B, 7.8%; Mn, Isomerization Due to Transfer of Hydrogen. Like Raney 1.3%); and nickel-iron. nickel borides seem capable of causing isomerization by transfer The comparison of the activity of these different catalysts, of hydrogen. I n particular, furfuraldoxime was transformed into with Raney nickel serving as a reference, was carried out under pyromucamide in 80% yield by heating for 1 hour at 100' with the same conditions and for the same hydrogenations as in the about half its weight of catalyst. At room temperature, the yield case of the catalysts containing only nickel. of the transformation product reached 90% at the end of one Hydrogenation of Safrole. Figure 7 shows that the nickelweek. molybdenum and nickel-chromium catalysts are distinctly more active than the catalyst prepared in the same manner but without CH=CH-CH=C-CH=NOH + a promoter. The addition of chromium makes it possible t o obL0 tain a catalyst of a n activity at least equal to that of Raney CH-CH-CH=C-CO-NHz L0 nickel. Figure 8 shows t h a t in this same hydrogenation, tungsten is obviously as active as chromium and slightly more active than I n the same way, the rearrangement of allyl alcohol t o provanadium. pionaldehyde An examination of Figure 9 discloses that, on the contrary, cobalt exercises a clearly unfavorable influence. CH2 = CH-CHzOH +CHr--CH~-CHO Figure 13. Furfural
May 1952
Figure 14. Furfural
INDUSTRIAL AND ENGINEERING CHEMISTRY
1009
NICKELCATALYSTS CONCLUSIONS
ifnd iron, &s may be seen from Figure 10, is practically ineffective. Hydrogenation of Furfural, Figure 11 shows that an addition of chromium makas it possible to obtain a catalyst almost twice as active m Raney nickel. Tungsten and molybdenum, though somewhat lesa effective, also increase the activity of the catalyst. .Is seen from Figure 12, vanadium islan almost equally powerful promoter as chromium.
600
1
I
/ I
I
I I
I
This account is limited to a report of the results obtained with nickel boride catalysts. Xumerous experiments have shown that the same technique also makes it possible to obtain good catalysts .by replacing the nickel with cobalt, Their boron content ( 8 % ) leads to the conclusion that thpy are cobalt boride catalysts (Co2B). Generally speaking, they are less active than the nickel catalysts, but their activity is increased by a certain
I
I600
G
u’
”=. 500
500
400
400
C
2 I 300
;
u 300
200
200
100
100
0
r
5
i5
30
45
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Minutes
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105 120 0
15
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Minuter
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105 120
0
Minuter
R g i i r e 1.5. Benzonitrile
Figure 16. Benzonitrile
I = Raney nickel 11 = Nickel plus 2% molybdenum I11 = Nickel DIUS 2 % chromium 1V = Nickel plus 2”&tungsten
I = Raney Nickel I1 = Nickel plus 2 % molybdenum I11 = Nickel alus 2 % vanadium IV = Nickel 61x1s 2 % cobalt (Center lines indicate addition of 5
I n these two hydrogenation series, a small quantity of sodium hydroxide was added after 30 minutes, and in both cases this addition resulted En a marked increase in the rate of hydrogenation, An examination of Figures 13 and 14 shows that manganese, iion, and cobalt augment the activity of nickel boride, but much less noticeably than do the preceding promoters. With nickel-chromium and nickel-vanadium catalysts, the hydrogenation of furfural continues well beyond the furfuryl alcohol stage, even at normal pressure and a t roem temperature. Under a pressure of 50 atmmpheres and a t 20’ C., the hydrogenation of furfuryl alcohol to tetrahydiofurfuryl alcohol takes place twice a$ fast viith the nickel-chromium catalyst as TT ith Raney nickel. The yield oi pure tetrahydrofurfuryl alcohol is 90%. Hydrogenation of Benzonitrile. In this hydrogenation, the nickel-chromium catalyst was found t o be somewhat more active than Raney nickel. -4dditions of molybdenum and tungsten were less effective, as shown in Figures 15 and 17. Additions of vanadium and cobalt increase the activity of nickel boride, hut do not make it possible to obtain the hydrcgenation rate obtained with Kaney nickel (Figure 16).
60
f
CC.
Figure 17. Benzonitrile I = Raney nickel 11 = Nickel plus 2 7$molghdenum 111 = Nickel without Dromoter
of 40% NaOH)
number of promoters, particularly by chromium, molybdenum and tungsten. From these preliminary experiments, therefore, the authors conclude that the action of alkali borohydrides on nickel salts makes it possible t o obtain rapidly, by a convenient procedure, remarkably active catalysts for hydrogenation reactions. This technique, in addition t o being attractive for the preparation of simple nickle boride catalysts, was found advantageous for obtaining the complex catalysts which, in m o d cases, have shown an activity a t least equal to and often superior t o that of Raney nickel, Contrary to Raney nickel, these catalysts are not pyrophoric and seem t,o offer great, resishnce to fatigue; consequently, they may be useful for indust,rial applications. LITERATURE CITED
( 1 ) Delepine, >I., a n d H o r e a u , A , , Bull. SOC.Chim. [ 5],4,31-49 (1937). (2) P a u l , R., Ibid. [SI, 1946, 13. 208. ( 3 ) Schlesinger, K. I., F i n a l R e p o r t W‘.3434,SC.174.O.P.B., PB6331. ( 4 ) Schlesinger, H. I., C. 8 . Patent 2,461,661 ( J a n . 9 , 1945). RECEIYED for r e v i e x October 17, 1951, hccErTED:February 29, 1952.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44, No. 5
