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Catalysis by amorphous Ni0.6Fe0.2P0.2 ribbons
Scripta
METALLURGICA
Vol. 15, pp. 365-368, 1981 Printed in the U.S.A.
CATALYSIS
BY A M O R P H O U S
A. Yokoyama, Department Tokyo 113,
T. M a s u m o t o
Ni0.6Fe0.2P0. 2 RIBBONS
H. K o m i y a m a
of C h e m i c a l Japan
P e r g a m o n Press Ltd. All rights r e s e r v e d
and H.
Engineering,
Inoue University
of Tokyo,
and H. M. Kimura
The R e s e a r c h Institute for Iron, Steel T o h o k u University, Sendai 980, Japan (Received (Revised
November February
and Other
Metals,
26, 1980) 2, 1981)
Introduction It has been r e c e n t l y found that some alloys can be s o l i d i f i e d into the amorphous state by rapid q u e n c h i n g from the melt(l). While several efforts have been d e v o t e d to i n v e s t i g a t i n g the magnetic, electrical, m e c h a n i c a l and c o r r o s i o n p r o p e r t i e s of these new materials(2-5) , no attempts have been r e p o r t e d on the c a t a l y t i c properties. We have p r e s u m e d that the a m o r p h o u s state is more active as c a t a l y s t than the c r y s t a l l i n e state, since the high a c t i v i t i e s of p r a c t i c a l solid catalysts are often c o n s i d e r e d to result from i m p e r f e c t i o n s in the solid state such as dislocations, d i s t o r t i o n s and impurities. Also, the r e c e n t l y dev e l o p e d disk method(6) of p r o d u c i n g amorphous thin ribbons is very a t t r a c t i v e from the p r a c t i c a l as well as the i n v e s t i g a t i v e point of view. The p r e s e n t paper reports a r e m a r k a b l e c a t a l y s i s by a m o r p h o u s Ni 0 6Fen 2P0 2 ribbons showing high act i v i t y and s e l e c t i v i t y in the h y d r o g e n a t i o n reaction o{ carbon monoxide. Experimental The disk m e t h o d was e m p l o y e d to yield amorphous Ni0.6Fe0.2P0. 2 ribbons of 10 to 20 m i c r o n s thick and 3 to 5 m m wide. The ribbons were cut into strips 1 cm long and used in the h y d r o g e n a t i o n reaction of carbon monoxide. The main features of the reaction m e a s u r e m e n t s y s t e m c o n s i s t e d of a tubular reactor of 13 mm I.D. and a g a s - c h r o m a t o g r a p h e q u i p p e d w i t h a P o r a p a c k N column, and a c o m b i n a t i o n of FID and TCD. The s t a n d a r d c o n d i t i o n s for the r e a c t i o n were: i) a t m o s p h e r i c pressure, 2) feed gas c o m p o s i t i o n of 1.26% carbon monoxide, 36.9% H 2 and balance of N 2, and 3) total gas flow rate of 30 m l / m i n (STP) to 1.0 g of the a m o r p h o u s ribbons. Results Tne m a j o r r e a c t i o n p r o d u c t s were methane, ethylene, ethane, p r o p y l e n e .~nd propane, along with a trace of longer chain h y d r o c a r b o n s and CO 2. The c a t a l y t i c act i v i t y of the ribbons v a r i e d in the initial stage of the reaction, but c o n v e r g e d to a c o n s t a n t value after about 10 h from the start of a run. The c o n s t a n t a c t i v i t i e s were m a i n t a i n e d during e x p e r i m e n t s lasting 40 hrs; figure 1 shows these c o n s t a n t activities. The t h e r m o d y n a m i c a l l y u n s t a b l e a m o r p h o u s state is stable against the e x o t h e r m i c reactions, as shown by X-ray d i f f r a c t i o n patterns, (B) , in Figure 2. The r e a c t i o n rates of the a m o r p h o u s state were c o m p a r e d w i t h those of the c r y s t a l l i n e state by p r e c e d i n g heating of the strips under a stream of He for 4 h at 550°C, w h i c h is 180°C higher than the c r y s t a l l i z a t i o n t e m p e r a t u r e of 370°C. As shown in Figure i, the amorphous state is about two orders of m a g n i tude more active than the c r y s t a l l i n e state. Being m e t a s t a b l e , a m o r p h o u s m e t a l s c r y s t a l l i z e with the proper c o m b i n a t i o n of t e m p e r a t u r e and time. The c r y s t a l l i z a t i o n p r o c e e d s in several stages that
365 0036- 9 7 4 8 / 8 1 / 0 4 0 3 6 5 - 04502.00/0 Copyright (c) 1981 Pergamon Press
Ltd.
366
CATALYSIS
BY AMORPHOUS
RIBBONS
Vol.
15, No. 4
often include intermediate metastable crystalline phases; namely, amorphous (Am) MS-I MS-II stable crystalline (ST) (7). The reactions of the intermediate phases, MS-I and MS-II, were also compared with that of the amorphous phase. (C) in Figure 2 is an X-ray diffraction pattern of the ribbon, which was operated under reaction conditions at 250°C to obtain the stable catalytic activity and thereafter operated at 310°C, 60°C below the crystallization temperature. Under these conditions, a small amount of the MS-I phase (fcc Ni particles) appeared in an amorphous matrix, and the activity d e c r e a s e d as seen in Table i. Heating the amorphous ribbon at 500°C for 4 h yielded the MS-II phase (tetragonal M3P type compound) ((D) in Figure 2) and the activity further decreased (Table i). Any treatment which tends to destabilize the amorphous structure decreased the activity. Interestingly, the activation energies of the amorphous, the MS-II and the ST states, 99, 100 and 102 kJ/mol were the same within experimental error. The remarkably high activities of the amorphous state, as high as 210, 18 and 6.8 times greater than those of the ST, the MS-II and the MS-I states respectively, indicate the potential of catalytically active materials. TABLE 1 Catalytic properties
and structure of amorphous Ni0.6Fe0.2P0. 2 ribbons Structure
Property Amorphous
Amorphous+MS-I
MS-II
Stable Crystalline
X-ray pattern (Figure 2)
(B)
(C)
(D)
(E)
Conversion at 260°C,
2.84
0.41
0.16
0.035
(210)
(30)
(12)
(i)
38*
20
18
13
0.37
0.40
0.28
0.33
of CO %
(relative value) Selectivity to C2H4, C2H 6, C3H 6 and C3H8, % BET area, m2/g
* : The selectivity of the amorphous state increased with increasing concentration of CO up to 46%, in the concentration range from 1.26 to 8.0%. The high activity of the amorphous state is not brought about by the difference in the surface area. The BET surface area of the amorphous state, which is about 20 times larger than the geometrical area of the ribbons, is the same as those of the MS-I, MS-II, and the ST states, w i t h i n m e a s u r a b l e uncertainties (Table i). Table 1 also summarizes the selectivity of each phase to ethylene, ethane, propylene and propane; this selectivity was not significantly affected by temperature. Quite interestingly the selectivity of the amorphous state is the highest. Conclusion The catalytic properties of the amorphous Nin ~Fen 2Po.2 ribbons on the h y d r o g e n a t i o n reaction of carbon monoxide were stu~[ed~" The amorphous state was quite stable at reaction temperatures and highly active, as much as 210, 18 and 6.8 times more active than those of the stable crystalline, the MS-II and the MS-I states. The main reaction products were methane, ethylene, ethane, propylene and propane; the amorphous state showed the highest selectivity to C 2 and C 3 hydrocarbons. These results indicate the potential of amorphous alloys as catalysts. More detailed kinetic studies using various amorphous alloys are currently under way.
Vol.
15,
No.
4
CATALYSIS
BY A M O R P H O U S
RIBBONS
367
References
1. 2.
3. 4. 5.
6.
7.
W. K l e m e n t J r . , R. H. W i l l e n s a n d P. Duwez, N a t u r e , 1 8 7 , 869 ( 1 9 6 0 ) . " Rapidly Quenched Metals", e d . b y N. J . G r a n t a n d B. C. G i e s e n , MIT P r e s s , Cambridge, Mass.,1976 and Mater. Sci. Eng., Vol.23, 1976. " Rapidly Quenched Metals", e d . by B. C a n t o r , t h e M e t a l S o c i e t y , London, 1978. " Metallic Glasses", e d . by J . J . G i l m a n a n d H. J . Leamy, Amer. S o c . M e t . , 1978. " Structure and Properties of Amorphous Metals", Vol. Ied. by T. Masumoto a n d K. S u z u k i , S u p p l . t o S c i . R e p . R e s . I n s t . Tohoku U n i v . , A - 2 7 , 1 9 7 8 ; Vol. IIed. by T. Masumoto a n d T. I m u r a , i b i d , A - 2 8 , 1 9 8 0 . H. A. D a v i e s , R a p i d l y Q u e n c h e d M e t a l s I I I ( e d . - E y - B . C a n t o r ) , V o l . 1 , p . l , The M e t a l s S o c i e t y , L o n d o n , 1978. T. Masumoto a n d R. M a d d i n , M a t e r . S c i . E n g . , 1 9 , 1 ( 1 9 7 1 ) .
phous
~M
S-II
N
(J
<
stable crystalline
\
1.8
FIG.
I
2.0 1031T (K-1)
(ST)
2.2
Activity of each phase at different temperatures. The a c t i v i t y refers to the c o n v e r s i o n o f CO u n d e r t h e s t a n d a r d c o n ditions.
368
CATALYSIS BY AMORPHOUS RIBBONS
Vol. 15, No. 4
(A)~ml~ (B)
(C)
(D)
(E)
I 40 °
FIG. 2
I 50 °
I 6 0° 2@
70 °
I 80 °
X-ray diffraction patterns of Ni0.6Fe0.2P0.2 samples; (A) amorphous phase ( as quenched), Am. (B) amorphous phase ( reacted at 250°C for 40 h ), Am. (C) amorphous phase containing a small amount of fcc-Ni particles( reacted at 250°C for i0 h and 310°C for I0 h ), Am + MS-I. (D) tetragonal ~Fe,Ni)3P type compound phase ( reacted at 250°C for 20 h after heating at 500°C for 4 h ), MS-II. (E) stable phase containing fcc-Ni, Fe3P and Ni3P ( reacted at 250°C for 20 h after heating at 550°C for 4 h ), ST.
METALLURGICA
Vol. 15, pp. 365-368, 1981 Printed in the U.S.A.
CATALYSIS
BY A M O R P H O U S
A. Yokoyama, Department Tokyo 113,
T. M a s u m o t o
Ni0.6Fe0.2P0. 2 RIBBONS
H. K o m i y a m a
of C h e m i c a l Japan
P e r g a m o n Press Ltd. All rights r e s e r v e d
and H.
Engineering,
Inoue University
of Tokyo,
and H. M. Kimura
The R e s e a r c h Institute for Iron, Steel T o h o k u University, Sendai 980, Japan (Received (Revised
November February
and Other
Metals,
26, 1980) 2, 1981)
Introduction It has been r e c e n t l y found that some alloys can be s o l i d i f i e d into the amorphous state by rapid q u e n c h i n g from the melt(l). While several efforts have been d e v o t e d to i n v e s t i g a t i n g the magnetic, electrical, m e c h a n i c a l and c o r r o s i o n p r o p e r t i e s of these new materials(2-5) , no attempts have been r e p o r t e d on the c a t a l y t i c properties. We have p r e s u m e d that the a m o r p h o u s state is more active as c a t a l y s t than the c r y s t a l l i n e state, since the high a c t i v i t i e s of p r a c t i c a l solid catalysts are often c o n s i d e r e d to result from i m p e r f e c t i o n s in the solid state such as dislocations, d i s t o r t i o n s and impurities. Also, the r e c e n t l y dev e l o p e d disk method(6) of p r o d u c i n g amorphous thin ribbons is very a t t r a c t i v e from the p r a c t i c a l as well as the i n v e s t i g a t i v e point of view. The p r e s e n t paper reports a r e m a r k a b l e c a t a l y s i s by a m o r p h o u s Ni 0 6Fen 2P0 2 ribbons showing high act i v i t y and s e l e c t i v i t y in the h y d r o g e n a t i o n reaction o{ carbon monoxide. Experimental The disk m e t h o d was e m p l o y e d to yield amorphous Ni0.6Fe0.2P0. 2 ribbons of 10 to 20 m i c r o n s thick and 3 to 5 m m wide. The ribbons were cut into strips 1 cm long and used in the h y d r o g e n a t i o n reaction of carbon monoxide. The main features of the reaction m e a s u r e m e n t s y s t e m c o n s i s t e d of a tubular reactor of 13 mm I.D. and a g a s - c h r o m a t o g r a p h e q u i p p e d w i t h a P o r a p a c k N column, and a c o m b i n a t i o n of FID and TCD. The s t a n d a r d c o n d i t i o n s for the r e a c t i o n were: i) a t m o s p h e r i c pressure, 2) feed gas c o m p o s i t i o n of 1.26% carbon monoxide, 36.9% H 2 and balance of N 2, and 3) total gas flow rate of 30 m l / m i n (STP) to 1.0 g of the a m o r p h o u s ribbons. Results Tne m a j o r r e a c t i o n p r o d u c t s were methane, ethylene, ethane, p r o p y l e n e .~nd propane, along with a trace of longer chain h y d r o c a r b o n s and CO 2. The c a t a l y t i c act i v i t y of the ribbons v a r i e d in the initial stage of the reaction, but c o n v e r g e d to a c o n s t a n t value after about 10 h from the start of a run. The c o n s t a n t a c t i v i t i e s were m a i n t a i n e d during e x p e r i m e n t s lasting 40 hrs; figure 1 shows these c o n s t a n t activities. The t h e r m o d y n a m i c a l l y u n s t a b l e a m o r p h o u s state is stable against the e x o t h e r m i c reactions, as shown by X-ray d i f f r a c t i o n patterns, (B) , in Figure 2. The r e a c t i o n rates of the a m o r p h o u s state were c o m p a r e d w i t h those of the c r y s t a l l i n e state by p r e c e d i n g heating of the strips under a stream of He for 4 h at 550°C, w h i c h is 180°C higher than the c r y s t a l l i z a t i o n t e m p e r a t u r e of 370°C. As shown in Figure i, the amorphous state is about two orders of m a g n i tude more active than the c r y s t a l l i n e state. Being m e t a s t a b l e , a m o r p h o u s m e t a l s c r y s t a l l i z e with the proper c o m b i n a t i o n of t e m p e r a t u r e and time. The c r y s t a l l i z a t i o n p r o c e e d s in several stages that
365 0036- 9 7 4 8 / 8 1 / 0 4 0 3 6 5 - 04502.00/0 Copyright (c) 1981 Pergamon Press
Ltd.
366
CATALYSIS
BY AMORPHOUS
RIBBONS
Vol.
15, No. 4
often include intermediate metastable crystalline phases; namely, amorphous (Am) MS-I MS-II stable crystalline (ST) (7). The reactions of the intermediate phases, MS-I and MS-II, were also compared with that of the amorphous phase. (C) in Figure 2 is an X-ray diffraction pattern of the ribbon, which was operated under reaction conditions at 250°C to obtain the stable catalytic activity and thereafter operated at 310°C, 60°C below the crystallization temperature. Under these conditions, a small amount of the MS-I phase (fcc Ni particles) appeared in an amorphous matrix, and the activity d e c r e a s e d as seen in Table i. Heating the amorphous ribbon at 500°C for 4 h yielded the MS-II phase (tetragonal M3P type compound) ((D) in Figure 2) and the activity further decreased (Table i). Any treatment which tends to destabilize the amorphous structure decreased the activity. Interestingly, the activation energies of the amorphous, the MS-II and the ST states, 99, 100 and 102 kJ/mol were the same within experimental error. The remarkably high activities of the amorphous state, as high as 210, 18 and 6.8 times greater than those of the ST, the MS-II and the MS-I states respectively, indicate the potential of catalytically active materials. TABLE 1 Catalytic properties
and structure of amorphous Ni0.6Fe0.2P0. 2 ribbons Structure
Property Amorphous
Amorphous+MS-I
MS-II
Stable Crystalline
X-ray pattern (Figure 2)
(B)
(C)
(D)
(E)
Conversion at 260°C,
2.84
0.41
0.16
0.035
(210)
(30)
(12)
(i)
38*
20
18
13
0.37
0.40
0.28
0.33
of CO %
(relative value) Selectivity to C2H4, C2H 6, C3H 6 and C3H8, % BET area, m2/g
* : The selectivity of the amorphous state increased with increasing concentration of CO up to 46%, in the concentration range from 1.26 to 8.0%. The high activity of the amorphous state is not brought about by the difference in the surface area. The BET surface area of the amorphous state, which is about 20 times larger than the geometrical area of the ribbons, is the same as those of the MS-I, MS-II, and the ST states, w i t h i n m e a s u r a b l e uncertainties (Table i). Table 1 also summarizes the selectivity of each phase to ethylene, ethane, propylene and propane; this selectivity was not significantly affected by temperature. Quite interestingly the selectivity of the amorphous state is the highest. Conclusion The catalytic properties of the amorphous Nin ~Fen 2Po.2 ribbons on the h y d r o g e n a t i o n reaction of carbon monoxide were stu~[ed~" The amorphous state was quite stable at reaction temperatures and highly active, as much as 210, 18 and 6.8 times more active than those of the stable crystalline, the MS-II and the MS-I states. The main reaction products were methane, ethylene, ethane, propylene and propane; the amorphous state showed the highest selectivity to C 2 and C 3 hydrocarbons. These results indicate the potential of amorphous alloys as catalysts. More detailed kinetic studies using various amorphous alloys are currently under way.
Vol.
15,
No.
4
CATALYSIS
BY A M O R P H O U S
RIBBONS
367
References
1. 2.
3. 4. 5.
6.
7.
W. K l e m e n t J r . , R. H. W i l l e n s a n d P. Duwez, N a t u r e , 1 8 7 , 869 ( 1 9 6 0 ) . " Rapidly Quenched Metals", e d . b y N. J . G r a n t a n d B. C. G i e s e n , MIT P r e s s , Cambridge, Mass.,1976 and Mater. Sci. Eng., Vol.23, 1976. " Rapidly Quenched Metals", e d . by B. C a n t o r , t h e M e t a l S o c i e t y , London, 1978. " Metallic Glasses", e d . by J . J . G i l m a n a n d H. J . Leamy, Amer. S o c . M e t . , 1978. " Structure and Properties of Amorphous Metals", Vol. Ied. by T. Masumoto a n d K. S u z u k i , S u p p l . t o S c i . R e p . R e s . I n s t . Tohoku U n i v . , A - 2 7 , 1 9 7 8 ; Vol. IIed. by T. Masumoto a n d T. I m u r a , i b i d , A - 2 8 , 1 9 8 0 . H. A. D a v i e s , R a p i d l y Q u e n c h e d M e t a l s I I I ( e d . - E y - B . C a n t o r ) , V o l . 1 , p . l , The M e t a l s S o c i e t y , L o n d o n , 1978. T. Masumoto a n d R. M a d d i n , M a t e r . S c i . E n g . , 1 9 , 1 ( 1 9 7 1 ) .
phous
~M
S-II
N
(J
<
stable crystalline
\
1.8
FIG.
I
2.0 1031T (K-1)
(ST)
2.2
Activity of each phase at different temperatures. The a c t i v i t y refers to the c o n v e r s i o n o f CO u n d e r t h e s t a n d a r d c o n ditions.
368
CATALYSIS BY AMORPHOUS RIBBONS
Vol. 15, No. 4
(A)~ml~ (B)
(C)
(D)
(E)
I 40 °
FIG. 2
I 50 °
I 6 0° 2@
70 °
I 80 °
X-ray diffraction patterns of Ni0.6Fe0.2P0.2 samples; (A) amorphous phase ( as quenched), Am. (B) amorphous phase ( reacted at 250°C for 40 h ), Am. (C) amorphous phase containing a small amount of fcc-Ni particles( reacted at 250°C for i0 h and 310°C for I0 h ), Am + MS-I. (D) tetragonal ~Fe,Ni)3P type compound phase ( reacted at 250°C for 20 h after heating at 500°C for 4 h ), MS-II. (E) stable phase containing fcc-Ni, Fe3P and Ni3P ( reacted at 250°C for 20 h after heating at 550°C for 4 h ), ST.