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Downloaded by KTH ROYAL INST OF TECHNOLOGY on February 15, 2016 | http://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch010

The Structural Form of Cobalt and Nickel Promoters in Oxidic HDS Catalysts R. MONÉ and L. MOSCOU Akzo Chemie Nederland bv, Research Centre Amsterdam, P. O. Box 15, Amsterdam, The Netherlands

H y d r o d e s u l f u r i z a t i o n c a t a l y s t s c o n s i s t of CoO and M o O or NiO and M o O on a -Al O c a r r i e r ( 1 - 3 ) . The c a t a l y s t s are produced i n the o x i d i c form; t h e i r a c t u a l a c t i v e s t a t e is obtained by s u l f i d i n g before or during usage i n the r e a c t o r . Molybdenum oxide - alumina systems have been s t u d i e d i n d e t a i l (4-8). Several authors have pointed out that a molybdate surface l a y e r is formed, due to an i n t e r a c t i o n between molybdenum oxide and the alumina support (9-11). Richardson (12) s t u d i e d the s t r u c t u r a l form of c o b a l t i n s e v e r a l o x i d i c cobalt-molybdenumalumina c a t a l y s t s . The presence of an a c t i v e cobalt-molybdate complex was concluded from magnetic s u s c e p t i b i l i t y measurements. Moreover c o b a l t aluminate and c o b a l t oxide were found. Only the a c t i v e c o b a l t molybdate complex would c o n t r i b u t e to the a c t i v i t y and be c h a r a c t e r i z e d by o c t a h e d r a l l y coordinated c o b a l t . L i p s c h and Schuit (10) s t u d i e d a commercial o x i d i c h y d r o d e s u l f u r i z a t i o n c a t a l y s t , c o n t a i n i n g 12 wt% M o O and 4 wt% CoO. They concluded that a c o b a l t aluminate phase was present and could not f i n d i n d i c a t i o n s f o r an a c t i v e c o b a l t molybdate complex. Recent magnetic s u s c e p t i b i l i t y s t u d i e s of the same type of c a t a l y s t (13) confirmed the c o n c l u s i o n of L i p s c h and Schuit. Schuit and Gates (30 proposed a model f o r the o x i d i c c a t a l y s t , i n which the promotor ions l a y j u s t below the molybdate l a y e r . These c o b a l t ions would s t a b i l i z e the molybdate l a y e r on the c a t a l y s t surface. The promoting a c t i o n of c o b a l t on the a c t i v i t y f o r hydrodesulf u r i z a t i o n has been shown already i n the p i o n e e r i n g work of Byrns, Bradley and Lee ( 1A). This promoting a c t i o n might be l i n k e d with the s u l f i d i n g step, s i n c e the a c t u a l c a t a l y s t i s the s u l f i d e d form of c o b a l t - or nickel-molybdenum-alumina. Voorhoeve and S t u i v e r (15) and Farragher and Cossee (lj3) demonstrated the promoting a c t i o n f o r the unsupported N1-WS2 system. T h e i r i n t e r c a l a t i o n model was based on these experiments. I t i s expected that the a c t i v a t o r system i n the o x i d i c c a t a l y s t has a s t r u c t u r e from which the r i g h t c o n f i g u r a t i o n i s obtained on s u l f i d i n g . We f e e l that the promotor ions have to be 3

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150 In Hydrocracking and Hydrotreating; Ward, John W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.

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present i n the neighbourhood of the surface molybdate l a y e r and that the assumption of a cobalt-aluminate phase might be an i n s u f f i c i e n t d e s c r i p t i o n of the o x i d i c h y d r o d e s u l f u r i z a t i o n c a t a l y s t . Therefore we have examined the presence of i n t e r a c t i o n s between c o b a l t and molybdenum from which a more d e t a i l e d p i c t u r e of the o x i d i c c a t a l y s t can be deduced. We have s t u d i e d t h e r e f o r e UV-VIS r e f l e c t a n c e s p e c t r a of adsorbed p y r i d i n e , a technique that has been used before f o r t h i s type of c a t a l y s t s by K i v i a t and P e t r a k i s (19). Experimental Methods. C a t a l y s t Preparation. The c a t a l y s t s were prepared by impregn a t i o n of îf-alumina extrudates ( SA=253 m /g ). Each impregnation was followed by drying overnight at 120°C and c a l c i n a t i o n at the i n d i c a t e d temperatures during one hour. Molybdenum was brought on the support as an ammonium molybdate s o l u t i o n ; c o b a l t and n i c k e l as n i t r a t e s o l u t i o n s . Each component was impregnated s e p a r a t e l y . The impregnation of c o b a l t on the blanc support took place stepwise (1 wt% CoO i n each s t e p ) . 2

C a t a l y s t s . MoCo-124: Alumina was impregnated f i r s t w i t h molybdenum, then c a l c i n e d at 650°C, followed by the c o b a l t impregn a t i o n . The f i n a l c a l c i n a t i o n was v a r i e d from 400 - 700°C. Composition:

12 wt%

M0O3 and 4 wt%

CoO.

MoCo-122 and MoCo-123 were obtained by impregnation as c a r r i e d out f o r MoCo-124. Only 2 and 3 wt% CoO resp. were brought on the c a t a l y s t . F i n a l c a l c i n a t i o n temperature 650 C. CoMo-124: Alumina was impregnated f i r s t with c o b a l t stepwise. The sample was d r i e d at 120°C and c a l c i n e d at 650 C a f t e r each impregnation step. Afterwards the c a t a l y s t was impregnated w i t h molybdenum. F i n a l c a l c i n a t i o n temperature 650°C. The composition was the same as f o r MoCo-124. CoMo-124 B: Cobalt was brought on uncalcined boehmite, 4 wt% i n one step. Afterwards the sample was c a l c i n e d at 650°C, impregnated w i t h molybdenum oxide (12 wt%) and c a l c i n e d at 650°C f o r a second time. The surface area was 241 m /g. MoCo-153: Alumina was impregnated f i r s t w i t h molybdenum, d r i e d and c a l c i n e d at 650°C. Then the c o b a l t was brought hereupon. Two f i n a l c a l c i n a t i o n temperatures were a p p l i e d , 480 and 650*C. The e

2

composition was

15 wt%

M0O3 and

3 wt%

CoO.

NiMo-124: The c a t a l y s t s were prepared according to the Dutch Patent 123195 (17). The alumina c a r r i e r was impregnated f i r s t w i t h n i c k e l . Two f i n a l c a l c i n a t i o n temperatures were a p p l i e d , 480 and 650°C. These samples were impregnated w i t h molybdenum. F i n a l c a l c i n a t i o n temperatures 480 and 650°C. The composition of the four c a t a l y s t s , which were obtained was 12 wt% M0O3 and 4 wt% NiO, The c a t a l y s t s are i n d i c a t e d by the a p p l i e d c a l c i n a t i o n temperatures a f t e r each impregnation; e.g. NiMo-124 480/480. MoNi-153: Molybdenum was brought on the alumina c a r r i e r f i r s t ,

In Hydrocracking and Hydrotreating; Ward, John W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.

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( c a l c i n a t i o n temperature 650°C), followed by the n i c k e l impregn a t i o n . The f i n a l c a l c i n a t i o n temperature was v a r i e d . The composit i o n was 15 wt% M0O3 and 3 wt% NiO. R e f l e c t i o n Spectroscopy. The r e f l e c t i o n s p e c t r a were r e c o r ded with an O p t i c a Milano CF 4 spectrophotometer, using magnesium oxide as the r e f e r e n c e . The samples were m i l l e d i n a mortar during 20 minutes. The r e f l e c t a n c e d i d not change s i g n i f i c a n t l y when t h i s m i l l i n g time was increased. The s p e c t r a of the c o b a l t c o n t a i n i n g samples are shown, as they have been recorded (% r e f l e c t a n c e against wavelength). The s p e c t r a of the n i c k e l c o n t a i n i n g samples are p l o t t e d as a remission f u n c t i o n (18) against wavenumber. I n f r a r e d Spectroscopy. The procedure of K i v i a t and P e t r a k i s (19) was followed f o r the greater p a r t . The s p e c t r a of adsorbed p y r i d i n e were recorded with a Perkin Elmer 621 spectrophotometer. The d i s c s (15 mg/cm ) were pressed i n a RIIC d i e , using a pressure of 1000 kg/cm . These d i s c s were rehydroxylated f i r s t on standing i n humid a i r during two days before they were placed i n the IR c e l l . Outgassing took place at 420*C. P y r i d i n e was adsorbed at room temperature and the excess was removed by evacuation at 150, 250 and 350°C during one hour. 2

2

Pore s t r u c t u r e . The surface area and pore volume were determined by N2 adsorption. No s i g n i f i c a n t changes were observed when the c a t a l y s t was c a l c i n e d i n the temperature r e g i o n of 400 - 700°C i n d i c a t i n g that no s t r u c t u r a l c o l l a p s e took place i n t h i s temperature range. Results. V i s i b l e R e f l e c t i o n Spectra. The f i n a l c a l c i n a t i o n temperature of MoCo-124 samples has been v a r i e d i n order to study i t s i n f l u e n c e on the c o o r d i n a t i o n of the c o b a l t i o n s . The r e f l e c t i o n s p e c t r a are shown i n F i g u r e 1. The s p e c t r a of MoCo-124, c a l c i n e d at 400 and 500°C show a broad absorption band, covering the whole s p e c t r a l region, with a weak s u p e r p o s i t i o n of the c h a r a c t e r i s t i c t r i p l e t of c o b a l t aluminate. T h i s i n d i c a t e s that the c o b a l t ions are f o r the greater part s t i l l on the c a t a l y s t surface and not i n the alumina l a t t i c e . The s p e c t r a of the MoCo-124 samples, c a l c i n e d at 650-700 °C show a strong increase i n i n t e n s i t y of the t r i p l e t band, while the broad absorption band has disappeared. T h i s i n d i c a tes the formation of a c o b a l t aluminate phase. I n f r a r e d Spectra. F i g u r e 2 shows the s p e c t r a of p y r i d i n e adsorbed on /-alumina. Two types of Lewis a c i d s i t e s are present; strong Lewis a c i d s i t e s , which s t i l l bind p y r i d i n e on evacuation at 350°C and c h a r a c t e r i z e d by the 1622 and 1454 cm" bands and weak Lewis a c i d s i t e s , c h a r a c t e r i z e d by the 1614 and 1450 cm" bands. BrSnsted a c i d s i t e s , which have c h a r a c t e r i s t i c bands around 1

1


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1636 and 1540 cm~l (19,21) are not observed i n t h i s spectrum. The spectrum of p y r i d i n e adsorbed upon cobalt-alumina (4 wt% CoO) i s shown i n F i g u r e 2d. No change i n the p y r i d i n e spectrum i s observed i n comparison with the spectrum of p y r i d i n e on y-alumina, i n d i c a t i n g that the surface a c i d i t y i s not markedly changed. A same behaviour has been observed f o r n i c k e l alumina. These r e s u l t s agree w i t h those o f K i v i a t and P e t r a k i s (19). The adsorption of p y r i d i n e on molybdenum-alumina (12 wt% M0O3) has been i n v e s t i g a t e d f o r samples i n both o r i g i n a l and rehydroxylated form. The s p e c t r a are shown i n F i g u r e 3. I t appears that BriSnsted a c i d s i t e s , c h a r a c t e r i z e d by the 1636 and 1540 cm"" bands are observed only, when the d i s c s are rehydroxylated i n wet a i r before the c a l c i n a t i o n under high vacuum i n the IR c e l l takes p l a c e (Figure 3b). By consequence a l l s p e c t r a have been recorded for such rehydroxylated samples. Only one Lewis band i s observed for the molybdenum-alumina sample, opposite t o the observations of K i v i a t and P e t r a k i s (19), who have observed two Lewis bands f o r t h e i r samples. Spectra of adsorbed p y r i d i n e have been recorded f o r the MoCo-124 c a t a l y s t s , f o r which the f i n a l c a l c i n a t i o n temperature a f t e r the c o b a l t impregnation has been v a r i e d . I t turns out that the 400 and 500°C c a l c i n e d samples and the 650 and 700°C c a l c i n e d samples show very s i m i l a r s p e c t r a . Therefore we show only the s p e c t r a o f the 400°C (low c a l c i n e d ) and the 650°C (high c a l c i n e d ) samples. F i g u r e 4 shows s p e c t r a a f t e r desorption at 150 and 250°C. Few BrSnsted a c i d s i t e s are observed i n the low c a l c i n e d MoCo-124 samples. The r e f l e c t i o n s p e c t r a ( F i g u r e 1) i n d i c a t e f o r these low c a l c i n e d samples the presence of c o b a l t on the c a t a l y s t s u r f a c e , because no c o b a l t aluminate phase could be detected. The high c a l c i n e d samples do show the presence of BrSnsted a c i d s i t e s ; the presence of a c o b a l t aluminate phase i s concluded from the r e f l e c t i o n s p e c t r a (Figure 1) f o r these samples. These experiments i n d i c a t e that at low c a l c i n a t i o n tempera tures the c o b a l t ions are present on the c a t a l y s t surface and n e u t r a l i z e the BrBnsted a c i d s i t e s of the molybdate surface l a y e r . At the higher c a l c i n a t i o n temperatures, the c o b a l t ions move i n t o the alumina l a t t i c e . The BrGnsted a c i d s i t e s reappear, i n d i c a t i n g that the s i t u a t i o n on the molybdate surface i s r e s t o r e d . However, the molybdenum-alumina and the high c a l c i n e d c o b a l t molybdenum-alumina samples s t i l l show an important d i f f e r e n c e . The p y r i d i n e s p e c t r a of MoCo-124 i n d i c a t e a second Lewis a c i d s i t e , c h a r a c t e r i z e d by the 1612 cm" band. T h i s band d i f f e r s from the weak Lewis a c i d s i t e s of the alumina support (1614 cm* ) because the p o s i t i o n i s s i g n i f i c a n t l y d i f f e r e n t . I t a l s o appears that the s t r e n g t h of the bond between p y r i d i n e and the c a t a l y s t i s stronger, for the 1612 cm" band i s s t i l l present a f t e r evacuation at 250°C, w h i l e the weak Lewis band (1614 cm" ) o f the alumina has d i s a p peared at t h i s desorption temperature. Obviously the second Lewis band f o r the MoCo-124 c a t a l y s t i s introduced by the i n t e r a c t i o n of c o b a l t with the surface molybdate l a y e r . T h i s i n t e r a c t i o n i s


1

1

1

1

1




Or

500

600 700 WAVELENGTH (nm)

800

Figure 1. Reflectance spectra of MoCo-124 catalysts, calcined at different temperatures, a) 400°C, b) 500°C, c) 600°C, d) 650°C, and e) 750°C.

170Ô 1600 1500 1400 WAVENUMBER (cm-1)

Figure 2. Spectra of adsorbed pyridine a) on y-Al O evacuated 1 hr, 150°C; b) as a), evacuated 1 hr, 250°C; c) as a), evacuated 1 hr, 350° C; d) on CoO-y-Al O , evacuated 1 hr, 150° C 2

s

z

s

1700 1600 1500 1400 WAVENUMBER (cm-1)

Figure 3. Spectra of adsorbed pyridine a) on MoO -y-Al 0 , evacuated 1 hr, 150°C; b) on rehydroxylated MoCVyAl O , evacuated 1 hr, 150° F; c) as b), evacuated 1 hr, 250°C; d) as b), evacuated 1 hr, 350°C s

z

2

3

s


10.

ΜΟΝΕ AND MOSCOU

155



c l e a r l y s t i l l present i n the high c a l c i n e d c a t a l y s t s , where c o b a l t i s present i n the alumina l a t t i c e . Reversed Impregnation. The reversed impregnation has been s t u d i e d too. Impregnation of 4 wt% CoO on y-alumina i n one step g e n e r a l l y leads t o the formation of C03O4 on c a l c i n a t i o n (black extrudates (22,23)). A stepwise impregnation r e s u l t s i n c o b a l t aluminate formation (blue extrudates), showing i t s c h a r a c t e r i s t i c t r i p l e t i n the r e f l e c t i o n spectrum (Figure 5a). Impregnation of molybdenum on the c o b a l t c o n t a i n i n g support does not i n f l u e n c e the r e f l e c t i o n spectrum of the c o b a l t i o n s , as shown i n F i g u r e 5b. Spectra of p y r i d i n e , adsorbed on t h i s CoMo-124 sample are shown i n F i g u r e 6. The second Lewis band (1612 cm"" ) i s present, i n d i c a t i n g that the i n t e r a c t i o n between the c o b a l t ions and the s u r f a c e molybdate l a y e r i s present too. 1

Boehmite Based .Catalysts. Hedvall (24) has discussed the f o r mation of c o b a l t aluminate from CoO and AI2O3. He has shown that a r e l a t i v e l y f a s t s o l i d s t a t e r e a c t i o n takes place when the alumina undergoes a phase change, v i z . y-Al2C>3-> rt-A^Og. T h i s phenomenon i s known as the Hedvall e f f e c t . Such an e f f e c t might be expected when boehmite supported c o b a l t i s being c a l c i n e d , v i z . during the phase t r a n s i t i o n AIO(OH) - * y - A l 0 3 . F i g u r e 7 shows s p e c t r a of p y r i d i n e , adsorbed on the sample CoMo-124 B, which has been prepared i n t h i s way. Spectra f o r MoCo-122, -123 and -124, c o n t a i n i n g 2, 3 and 4 wt% CoO resp. are shown f o r comparison. A l l these c a t a l y s t s have had a f i n a l c a l c i n a t i o n of 650°C. Comparison of the s p e c t r a of CoMo-124 Β and MoCo-124 i n d i c a t e s that the i n t e n s i t y of the 1612 cm" band, which i s introduced by the i n t e r a c t i o n of the c o b a l t ions and the molybdate l a y e r , i s lower f o r CoMo-124 Β than f o r MoCo-124. The spectrum f o r CoMo-124 Β resembles that of CoMo-123, i n d i c a t i n g that a part of the c o b a l t ions does not p a r t i c i p a t e i n t h i s i n t e r a c t i o n . 2

1

N i c k e l Promoted C a t a l y s t s . N i c k e l c o n t a i n i n g c a t a l y s t s are known to be s e n s i t i v e f o r too high temperatures. The Dutch patent 123195 (17) claims that a c t i v e nickel-molybdenum-alumina c a t a l y s t s are obtained, when n i c k e l i s impregnated f i r s t . The c a l c i n a t i o n i s c r i t i c a l however. According t o t h i s patent, c a t a l y s t s c a l c i n e d at 4 8 0 a r e twice as a c t i v e as c a t a l y s t s , c a l c i n e d at 650°C. C a t a l y s t s NiMo-124 have been prepared according t o t h i s patent and have been i n v e s t i g a t e d . The h y d r o d e s u l f u r i z a t i o n a c t i v i t y showed indeed a pronounced decrease on c a l c i n a t i o n at 650°C i n comparison w i t h the 480°C c a l c i n e d sample. The s p e c t r a of adsorbed p y r i d i n e are shown i n F i g u r e 8. The spectrum of the sample NiMo-124 480/480, which has been c a l c i n e d twice at the lowest c a l c i n a t i o n temperature shows a c l e a r 1612 cm" Lewis band. This band has a f a r weaker i n t e n s i t y f o r the 650/650 c a t a l y s t . The 480/650 sample shows a more intense 1612 cm" band than the 650/650 and 650/480 samples. T h i s might i n d i c a t e that the 1


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HYDROCRACKING A N D H Y D R O T R E A T I N G

1700 1600 1500 1400 WAVENUMBER (cm-1)

Figure 4. Spectra of adsorbed pyridine a) on MoCo-124,finalcalcination 400°C, evacuated 1 hr, 150°C; b) as a), evacuated 1 hr, 250°C; c) on MoCo-124, final calcination 650°C, evacuated 1 hr, 150°C; d) as c), evacuated 1 hr, 250°C

Figure 5. Reflectance spectra: a) CoO-y-Al O , calcined at 650°C; b) of CoMo-124,finalcalcination, 650°C 2

s



ΜΟΝΕ AND MOSCOU


Figure 6. Spectra of adsorbed pyri dine a) on CoMo-124, evacuated 1 hr, 150°C; b) as a) evacuated 1 hr, 1700 250°C

1600 1500 WAVENUMBER (cm-1)

1400

1700 1600 1500 1400 WAVENUMBER (cm-1)

1700 1600 1500 1400 WAVENUMBER (cm-1)

Figure 7. Spectra of ad sorbed pyridine a) MoCo-122; b) MoCo-123; c) MoCo-124; d) CoMo124 B. All after evacua tion 1 hr, 150°C.

Figure 8. Spectra of ad sorbed pyridine NiMo124: a) 480/480; b) 480/ 650; c) 650/480; d) 650/ 650. All after evacuation 1 hr, 150°C.


158


n i c k e l i o n s , which are s t i l l present i n the neighbourhood of the alumina surface a f t e r the f i r s t c a l c i n a t i o n at 480°C, remain t i e d to the molybdate l a y e r to some extent a f t e r the second c a l c i n a t i o n at 650°C. The s p e c t r a of adsorbed p y r i d i n e f o r MoCo-153 and MoNi-153 are compared i n F i g u r e 9. Two f i n a l c a l c i n a t i o n temperatures have been a p p l i e d , 480 and 650 C. The s p e c t r a of the 480°C samples ( F i gure 9a and 9b) are n e a r l y i d e n t i c a l . The Brtfnsted a c i d bands are weak, while the 1612 cm"l Lewis bands are strong. The i n t e n s i t y of the Bro'nsted a c i d bands i n c r e a s e s f o r both 650 °C c a l c i n e d samp l e s (Figure 9c and 9d). The Lewis a c i d bands show a marked d i f f e rence now. The 1612 band remains high i n i n t e n s i t y f o r the MoCo153 c a t a l y s t , but t h i s Lewis band decreases a p p r e c i a b l y i n i n t e n s i t y f o r the MoNi-153 c a t a l y s t . R e f l e c t i o n s p e c t r a f o r the MoNi-153 c a t a l y s t s are shown i n F i g u r e 10. The 480°C c a l c i n e d c a t a l y s t shows the c h a r a c t e r i s t i c a b s o r p t i o n band (25) of o c t a h e d r a l l y coordinated n i c k e l i o n s . The 650°C c a l c i n e d c a t a l y s t shows the c h a r a c t e r i s t i c spectrum of n i c k e l aluminate. These r e f l e c t i o n s p e c t r a i n d i c a t e that the n i c k e l ions migrate from the c a t a l y s t surface i n t o the alumina, as has been observed a l s o f o r the cobalt-molybdenum-alumina c a t a l y s t s .


e

Discussion. R u s s e l l and Stokes (9) and Sonnemans and Mars (11) have presented strong evidence f o r the formation of a molybdate monolayer. I t appears from t h e i r experiments that each molybdate group covers 20-25 Â of the alumina surface.The surface of the alumina support, which has been used i n t h i s study, i s high enough f o r a complete spreading of 15 wt% M 0 O 3 , so no bulk molybdenum oxide i s expected to be present. T h i s has been confirmed by X-ray d i f f r a c t i o n measurements. The molybdate surface l a y e r i n the molybdenum-alumina samples i s c h a r a c t e r i z e d by the presence of Bro'nsted a c i d s i t e s ( 1545 cm" ) and one type of strong Lewis a c i d s i t e s (1622 cm" ). Cobalt or n i c k e l ions are brought on t h i s surface on impregnation of the promotor. The absence of BrSnsted a c i d s i t e s i s observed f o r both c o b a l t and n i c k e l impregnated c a t a l y s t s , c a l c i n e d at the lower temperatures (400-500°C). A l s o a second Lewis band i s observed at 1612 cm" .The r e f l e c t i o n s p e c t r a of these c a t a l y s t s i n d i c a t e that no c o b a l t or n i c k e l aluminate phase has been formed at these temperat u r e s . T h i s i n d i c a t e s that the c o b a l t and n i c k e l ions are s t i l l present on the c a t a l y s t surface and n e u t r a l i z e the BrSnsted a c i d s i t e s of the molybdate l a y e r . These c o n f i g u r a t i o n s w i l l be c a l l e d " c o b a l t molybdate" and " n i c k e l molybdate" and are shown schematica l l y i n F i g u r e 11a. For the high temperature c a l c i n e d cobalt-molybdenum-alumina c a t a l y s t s , the presence of a c o b a l t aluminate phase has been concluded from the r e f l e c t i o n s p e c t r a . The Bro'nsted a c i d s i t e s reappear i n the spectrum of absorbed p y r i d i n e , i n d i c a t i n g that the 2

1

1

1


10.

M O N É

A N D

Moscou



1612

1700 1600 1500 1400 WAVENUMBER (cm-1)

Figure 9. Spectra of adsorbed pyridine on MoC0-153,finalcalcination: a) 480°C; c) 650°C; MoNi-153,finalcalcination: b) 480°C; d) 650°C

1

1

15

10

WAVENUMBER

3

(cm-1)

H Ο ι

/

-Moalumina

-Mo-

Nickel

Cobalt

impregnation Co Cr

calcining 5 0 0 ° C

(5)

2

Ni^

+

-Mo

Hydrocracking and Hydrotreating

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