WITH HYDROGEN SULFIDE AND HYDROGEN. H. Hattori, F.A. Jones, ... potassium-poisoned catalysts were prepared (catalysts 22 and 23). To examine the ...
NEW IRON OXIDE CATALYST REDUCTION ACTIVITIES
WITH HYDROGEN SULFIDE AND HYDROGEN
H. H a t t o r i , F.A. Jones, T. Ogawa, C.L. Knudson, L.J. Radonovich and V.I. Stenberg U n i v e r s i t y o f North Dakota Energy Research Center and the Department o f Chemistry U n i v e r s i t y o f North Dakota, Grand Forks, ND 58202 INTRODUCTION Various types o f c a t a l y s t s have been used f o r coal l i q u e f a c t i o n . these catalysts,
Among
molybdenum and i r o n c a t a l y s t s a r e most f r e q u e n t l y used and
they are u s u a l l y combined w i t h other metal oxides.
Molybdenum c a t a l y s t s ,
in
the form of Co/Mo/A1203 wherein t h i s n o t a t i o n represents some form o f the metal oxides and the l a s t species i s the support,
have been used i n t h e H-Coal
process. I n others, i r o n c a t a l y s t s have been used i n t h e form o f r e d mud which I s mixed w i t h elemental s u l f u r . The a c t i v i t y o f i r o n c a t a l y s t s has generally been regarded as low when compared w i t h t h a t o f molydenum c a t a l y s t s .
However,
i r o n oxide c a t a l y s t s became h i g h l y a c t i v e f o r t h e conversion o f c o a l - r e l a t e d model compounds when used i n t h e presence o f H2S and H2.
For coal l i q u e f a c t i o n
i n t h e absence o f a heterogeneous c a t a l y s t s , the use o f a m i x t u r e o f H2S and H2 instead o f
H2
resulted
i n an increase i n conversion.'
Because o f
the
i n t e r a c t i o n o f H2S w i t h Fe2032 and the f a c t t h a t i r o n i s p r e s e n t l y t h e lowest cost t r a n s i t i o n metal, i r o n was selected as t h e b a s i s metal f o r a new s e t o f heterogeneous c a t a l y s t s s p e c i f i c a l l y designed f o r coal l i q u e f a c t i o n using the H2S-H2 reducing gas medium. I
I 1 k
EX PER IMENTAL A series o f 26 i r o n oxide c a t a l y s t s were designed and synthesized. The supported i r o n c a t a l y s t s prepared are l i s t e d i n Table 1. The s e l e c t i o n o f the supports were based on t h e f o l l o w i n g objectives. 1. To c l a r i f y the e f f e c t of Si02 surface area, Si02 supports f o r c a t a l y s t s 1, 2, and 3 were prepared a t d i f f e r e n t pH's from a Na-free Si02 source.
2. To examine t h e e f f e c t caused by use o f a d i f f e r e n t s t a r t i n g m a t e r i a l t o prepare Si02, c a t a l y s t s 4, 5, and 6 were prepared from sodium m e t a s i l i c a t e a t d i f f e r e n t pH's and can be compared t o c a t a l y s t s 1-3.
287
To examine the e f f e c t of the precipitating reagent, catalysts 7 and 8 were prepared from Si(OC2H5)4 w i t h H2S04 or NaOH, respectively. C a t a l y s t s 7 and 8 results a r e t o be compared w i t h those of catalysts 1 and 3. 4. To examine the e f f e c t of basic supports, metal oxides with basic properties were used f o r the supports of catalysts 9 , 10, 11, 1 2 , 13 and 14. 5. To examine the e f f e c t of t.he s u l f a t e ion on the Ti02 support, i t was prepared in the presence of sulfate ions and the resulting catalyst 15 i s t o be compared w i t h catalyst 14. 6. To examine the e f f e c t of additives t o Fe/Si02, small amounts of Mo, W , Co, and Ni oxides were added ( c a t a l y s t s 16, 17, 18, and 19) t o the Fe203 on the surface of the catalyst. To examine the e f f e c t of the s u l f a t e and n i t r a t e anions on the deposition 7. of the iron layer, catalysts 20 and 21 were prepared. 8. To examine the e f f e c t of acidic s i t e s on the Fe/Si02 c a t a l y s t , sodium- and potassium-poisoned catalysts were prepared (catalysts 22 and 23). 9. To examine the e f f e c t s of the comnercial Ti02 and S i O z supports, catalysts 20 and 24 were prepared t o be compared t o catalysts 1 and 14, respecti vel y. 10. To examine the e f f e c t of activated carbon which posiesses an extremely high surface area as the Fe203 supports, catalyst 26 was prepared t o be compared t o c a t a l y s t 20 (Si02) and 24 (Ti02). 11. To examine the e f f e c t of a simple admixture of Fe20J and Si02, catalyst 28 was prepared t o be compared with catalyst 20. 12. To enable comparison t o a known comnerical hydrogenation catalyst, Co/Mo/A1203 ( c a t a l y s t 29) was included as a p a r t of the series. 3.
The catalysts were subjected t o two reactions: hydrocracking of diphenylmethane t o toluene and benzene, a model compound f o r the Ar-C bond cleavage of t h e coal structure, and hydrocracking of diphenyl ether t o phenol and benzene, a model compound for the Ar-0 bond cleavage of the coal structure. The reaction conditions f o r these reactions are sumnarized i n Table 2. RESULTS AND DISCUSSION The design of the iron oxide catalysts was based on the following experimental findings. 1. For the hydrocracking of diphenylmethane, the e f f e c t of H2S addition was augmented with iron oxide catalysts. 3
288
I I
1
2.
I
The promotional e f f e c t o f the H2S a d d i t i o n on the c a t a l y t i c a c t i v i t y varied w i t h the preparative method f o r i r o n c a t a l y ~ t . ~Among Fe c a t a l y s t s supported on Si02, Zr02, and TiO2, the Fe/Si02 showed t h e highest a c t i v i t y f o r t h e hydrocracking o f diphenylmethane.
3.
The Fe/Ti02 c a t a l y s t was a c t i v e n o t o n l y f o r hydrocracking 3 diphenylmethane b u t also f o r hydrocracking o f diphenyl ether.
of
Besides these f i n d i n g s , i t has been generally observed t h a t t h e c a t a l y t i c behavior o f a c t i v e components vary w i t h t h e types of supports. The t i m e dependence o f t h e diphenylmethane conversion Figure 1.
i s depicted i n
The value of 20 minutes r e a c t i o n time was selected f o r the t u b i n g
bomb t e s t s i n order t o d i f f e r e n t i a t e c a t a l y s t e f f e c t s .
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Fig. 2.
(---)
4
6
8
IO
12
14 16 I8 Catalyst No.
Conversion o f diphenylmethane
(-1
20
22
24
26
28
30
and diphenylether
with v a r i o u s catalysts.
The r e s u l t s o f t h e c a t a l y t i c reactions are given i n Figure 2.
For
hydrocracking o f diphenylmethane, t h e a c t i v i t i e s vary w i t h d i f f e r e n t Supports. This i n d i c a t e s t h a t an i n t e r a c t i o n o f Fe203 w i t h t h e support occurred. The a c t i v i t y increased with an increase i n surface area o f support ( c a t a l y s t s I , 2, and 3). Enhanced c a t a l y t i c a c t i v i t y was observed by a d d i t i o n o f MO (no. 16), w (no. 17), Co (no. 18), and N i (no. 19) oxides t o t h e surface Fe203 as compared t o Fe/SiOp .(no. 20). The i n t r o d u c t i o n o f sodium o r potassium t o Fe/Si02 Similar eliminated t h e c a t a l y t i c a c t i v i t y (nos. 22 and 23 vs. no. 20). phenomena were observed f o r c a t a l y s t s 5, 6, and 8, which possibly contain sodium on the support. The s u l f a t e i o n had a negative i n f l u e n c e on c a t a l y t i c a c t i v i t y , cf. c a t a l y s t 5 with 2.
290
For the hydrocracking of diphenyl ether, the catalyst containing Mo and Fe (catalyst 16) was twice a s active a s the iron oxide catalyst. However, hydrogenated products such as methyl cyclopentane and cyclohexane were produced i n larger quantities w i t h catalyst 16 than w i t h 20. The Fe/Si02 c a t a l y s t a c t i v i t y increased w i t h increased surface area of t h e support (catalysts 1-31, and was poisoned by sodium and potassium ions, cf. catalysts 22 and 23 w i t h 20. The presence of the s u l f a t e ion again retarded the Fe/Si02 a c t i v i t y , cf. nos. 15 t o 14 and 20 t o 21, a s i t did w i t h diphenylmethane. In general the catalysts required the presence of hydrogen sulfide4 and the commercially supplied sample of s i l i c a with i t s high surface area worked very well. The pH of the s i l i c a preparation method proved t o be crucial t o generating high surface area s i l i c a . The c a t a l y s t s i n which the iron oxides were deposited on s i l i c a exceeded o r equaled the a c t i v i t y o f a simple admixture of iron oxide and s i l i c a ( c a t a l y s t 28). The iron oxide c a t a l y s t s were the b e t t e r than the commercial hydrogenation-hydrocracking catalyst Co/Mo/A1203 f o r the hydrocracking of diphenylmethane (e.g., c a t a l y s t 20 vs. 29) b u t the l a t t e r exhibited both hydrocracking and hydrogenation a b i l i t y . However, the Co/Mo/A1203 was more active in the conversion of diphenyl ether. ACKNOWLEDGEMENT We are grateful f o r the financial support of the Department of Energy. REFERENCES 1. (a) Sondreal, E.A.;+Wilson, W.G., and Stenberg, V.I., Mechanisms Leading t o Process Improvements i n Lignite Liquefaction Using CO and H2S, E, 1982, 61, 926. (b) Baldwin, R.M. and Viciguerra, E,1982, 62, 498. (c) Abdel-Baset, M. and Ratcliffe, C.T., Preprints h e r . Chem. SOC. Div. Fuel Chem., 1979, 25, 1. (d) S a t t e r f i e l d , C.M. and Model , M., U.S. NTIS, P.B. Rept., 1975, 248101. 2. ( a ) Ogawa, T.; Stenberg, V.I., and Montano, P.A., 1984, in press. (b) Stenberg, V.I.; Tanabe, K.; Ogawa, T.; Sweeny, P. and Hei, R., Iron-Based Catalysts, H2S and Liquefaction, Preprints, Fuel Division, American Chemical Society, 1983, National Meeting of t h e American Chemical Society, Washington, D.C. 3. Stenberg, V . I . ; Ogawa, T.; Willson, W.G. and Miller, D., Hydrocracking of Dephenylmethane, E,1982, 62, 1487.
w,
291
4.
( a ) Stenberg, V.I.; Srinivas, V.R.; Sweeny, P.; Baltisberger, R.J. and Woolsey, N.F., D e a l k y l a t i o n of N,N-dimethylaniline w i t h Sulphur and Hydrogen Sulphide, K, 1983, 62, 913. (b) Baker, 6.6.; Willson, W.G.; Farnum,
B.W.,
and Stenberg,
V.I.,
L i q u e f a c t i o n with Hydrogen Sulfide,
Homogeneous C a t a l y s i s o f
Lignite
1983 Spring National AlChE Meeting,
U t i l i z i n g Texas L i g n i t e , Session 16D, Fuels and Petrochemicals Division, March 27-31, Houston, Texas.
Table 2.
Reaction c o n d i t i o n s
Temperature
Ratio o f reactant/catalyst
Pressure ( p s i c o l d charge)
Reaction time
Reaction
("IC)
by w t .
H2S
H2
(1 min)
Hydrocracking o f diphenyl methane
425
10/1
100
700
20
Hydrocracking o f diphenyl e t h e r
425
10/1
100
1400
60
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