Phase Relationships in the Cerium-Molybdenum-Tellurium Oxide

Ce2Mo3O12.25, .... Compounds C e 2 M o 2 T e 4 0 1 7 , C e i o M °12 T e l4°79. a n d. C e 6 M ° 8 T ... t e r n a r y compounds ( i n p a r t i c ...
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6 Phase Relationships in the Cerium-Molybdenum-Tellurium Oxide System 1

1

J. C. J. BART , N. GIORDANO , and P. FORZATTI

2

1

Instituto di Chimica Industriale, Universita di Messina, Messina, Italy Dipartimento di ChimicaIndustrialeed Ingegneria Chimica del Politecnico, Piazza Leonardo da Vinci 32, 20133 Milano, Italy

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2

The

complex

solid

state

relations

-molybdenum-tellurium oxide determine the boundaries phase

distributions

system

of

of

of

the cerium­

were

studied

to

single phase regions and a

typical multicomponent

ammoxidation catalyst.

Between

the (Ce,Mo,Te)O system

contains the following phases:

CeO ,

MoO ,

2

TeO ,

3

2

3

4

2

2

3

2

2

Ce (TeO ) ,

6

β-Te MoO , 2

7

α-Ce Mo O

12.25

CeTe O ,

15

and

7

Ce Mo O ,

13

β-Ce Mo O , 2

α-Te MoO

2

β-Ce Mo O ,

400° and 600°C in air

2

4

4

a

3

and

15

solid solution

(Ce,Te)O , Ce Mo Te O , Ce Mo Te O , 2

6

10

Ce Mo Te O , 4

11

4

47

2

2

2

13

Ce Mo Te O ,

59

10

2

2

4

Ce Mo Te O ,

17

10

of primary crystallization of in the (Ce,Mo,Te)O system

12

14

fields

79

each of these compounds

are

indicated.

A typical

active (Ce,Mo,Te)O ammoxidation catalyst is composed of

the

binary

α-Ce Mo O 2

4

and

15

phase the

structure

of

a

highly

2

ternary

(eventually together with

The

β-Ce Mo O 3

oxide

Ce Mo Te O 6

active

10

4

47

and/or

13

Ce Mo Te O 4

11

10

59

and MoO ). 3

cerium-molybdenum-tellurium

a c r y l o n i t r i l e c a t a l y s t Q ) has previously been described i n terms of binary

(Ce,Mo)0

and

ternary

(Ce,Mo,Te)0

phasesC2).

concluded that none of the constituent oxides ( C e 0

2>

It

was

Mo0 and Te0 ) 3

0097-6156/85/0279-0089$06.00/0 © 1985 American Chemical Society

In Solid State Chemistry in Catalysis; Grasselli, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

2

90

S O L I D STATE C H E M I S T R Y IN CATALYSIS

o r compounds o f the b i n a r y (Te,Mo)0 o r ( T e , C e ) 0 systems a r e

present

as the a c t i v e phases i n the ammoxidation c a t a l y s t * We have

recently

ternary oxides

identified

(Ce,Mo,Te)0(3),

compositions c a l c i n e d 600°C.

in

after

air

Combined w i t h the

and

at

characterized studying

( C e , T e ) 0 c h e m i s t r y , w h i c h was developed

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(Ce,Mo,Te)0

identification

the

the

between

4 0 0 ° and

The

active

(Ce,Mo,Te)0 a c r y l o n i t r i l e

in

the l a s t decade, i t

is

complex s o l i d - s t a t e r e l a t i o n s o f the

system.

of

over 100 d i f f e r e n t

temperatures

knowledge o f the ( T e , M o ) 0 , ( C e , M o ) 0 , and

now p o s s i b l e t o d e s c r i b e ternary

s e v e r a l new

results

phase

culminated

composition

of

in

a

the

typical

catalyst.

Experimental

P r e p a r a t i v e methods and samples used previous work(3). (CuKA^ the

r a d i a t i o n ) and

following

systems): and

Samples

P-

2

C e

2

M o

(

C e

materials a-Ce Mo 0

7

0

4 i5 I>

2

2

for

t h i s study were those o f

subjected

M o

3

(

(taken

from

4

3

1 3

2

)

3°l2.25 ~ '

3

binary oxide

1 3

Ce (Mo0 ) (6), 2

4

Te0

2

(ASTM 4-593) and Mo0

the

to

and 0 - C e M o O O 5 ) , O J - C e ^ o ^ O ^

C e ( T e 0 ) a ) , (Ce,Te)0 a) together with 2

to x - r a y d i f f r a c t i o n

s p e c t r a were i n t e r p r e t e d w i t h r e f e r e n c e

support

Te Mo0 (4),

were

2

3

CeTe^C^),

(ASTM 1 1 - 6 9 3 ) , C e 0

2

(ASTM 9 - 2 0 9 ) . T e r n a r y o x i d e s (Ce,Mo,Te)0 were

3

i d e n t i f i e d on the b a s i s o f

previous work(3).

T h e - r e l a t i v e amounts

of the phases formed were e s t i m a t e d by comparison o f the h e i g h t s o f the

characteristic

peaks

e s p e c i a l l y T e 0 ~ and 2

after

heating

in

Mo0 ~rich 3

above

550°C,

non-overlapping samples such

positions.

As

are often n o n - c r y s t a l l i n e

preparations

were

calcined

a d d i t i o n a l l y a t 500°C f o r 8 hours f o l l o w e d by s l o w c o o l i n g i n o r d e r to enhance

crystallinity.

R e s u l t s and D i s c u s s i o n

F i g u r e 1 shows ( C e 0 , Mo0 2

3

the

distribution

and T e 0 ) i n 2

temperatures from 4 0 0 ° to exhibits

the

lowest

of

the t h r e e c o n s t i t u e n t o x i d e s

the v a r i o u s t e r n a r y phase c o m p o s i t i o n s at 600°C.

overall

It

is

reactivity.

c l e a r l y seen t h a t C e 0 Noteworthy

In Solid State Chemistry in Catalysis; Grasselli, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

is

2

the

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BART ET AL.

Cerium-Molybdenum- Tellurium Oxide System

F i g u r e 1. S i n g l e - p h a s e b o u n d a r i e s f o r the component o x i d e s of the (Ce,Mo,Te)0 s y s t e m between 400° and 600° C and r e g i o n s of f o r m a t i o n of n o n - c r y s t a l l i n e r e a c t i o n p r o d u c t s .

In Solid State Chemistry in Catalysis; Grasselli, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

92

S O L I D STATE C H E M I S T R Y IN CATALYSIS

c o n s i d e r a b l e e x t e n s i o n of the

c o m p a t i b i l i t y range f o r TeO^ between

400° and 4 5 0 ° C , w h i c h c o r r e l a t e s H^TeO^

A l s o of i n t e r e s t

is

w i t h the d e c o m p o s i t i o n process of

the

affinity

of Te0

f o r the

2

other

components ( i n p a r t i c u l a r CeC^) above 5 0 0 ° C . The presence of

-Te^MoOy

(Figure

the phase t r i a n g l e i s expected TeC^-MoO^ s y s t e m ( 4 , 8 ) .

2) i n the CeC^-poor a r e a of

based

Noteworthy

on the known b e h a v i o r of

i s the presence o f

the

considerable

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n o n - c r y s t a l l i n e m a t e r i a l i n t h i s p a r t of the d i a g r a m , e s p e c i a l l y a t 550° and

600°C,

which

relates

^-Te^MoO^ g l a s s ( F i g u r e 1 ) . (4,9)

leads

to

an

partly

to

the

formation of

the

The g l a s s - f o r m i n g tendency of Te Mo0^ 2

underestimate

of

the

extension

of

the

c o m p a t i b i l i t y range of the compound. Among the p r o d u c t s of is extensive

found

phase

a

Ce Mo 0^2 25 2

t

3

abundant

more

o

o

minor

up

to

l o

o

with

more

and

product

under

f o r m a t i o n sequence w i t h the phase

600°C

of

is

reaction

the

500°C

2

2).

an

phase

3

25 *

2

At 600°C,

s

a-

i n comparison to

formed a t about 600°C as a conditions.

in

the

Ce Mo 0^

field

cerium-molybdenum found

occupies

o f oi-Ce^Mo^O^ and

(Figure

phase

c

relations

Above

temperatures.

O. L 4 ID

our

compound

formation

restricted

Brown-red

c

500°C.

complex

e s p e c i a l l y at 550°

J il,ZD .

L

4 5 0 ° C.; the

increasingly higher

C e ^ M o ^ O ^ shows a Ce Mo 0

(Ce,Mo)0 s y s t e m , o n l y y e l l o w - g r e e n

below

field

distribution is

the

the

The

observed

o x i d e phases agrees

(Ce,Mo)0 s y s t e m ( 2 ) ,

even

though the b i n a r y compounds are formed at l o w e r temperatures i n the ternary system.

I n f a c t , whereas

550°C i n ( C e , M o ) 0 ,

this

(Ce,Mo,Te)0

system.

a-Ce Mo 0

and

2

4

1 5

respectively,

as

/3-Ce Mo 0 2

compound

forms

Similarly,

Ce Mo 0 2

3

1 2

opposed

forms by about 650°C i n a i r i n

2

to

temperature i n t h i s s t u d y .

the

i s detected

at

in

at

500°-

a t 400°C i n the

binary

formed

system

550°

the

and

ternary

in air 650°C, system.

t r a n s f o r m a t i o n of c v - C e ^ o ^ O ^

binary The

1 3

already

450°C

polymorphic the

in

are

5

3

system absences

s c h e e l i t e C e ^ M o O ^ ) ^ are not s u r p r i s i n g

at

and at a s l i g h t l y l o w e r of y - C e ^ o ^ O ^ and

the

and are i n accordance w i t h

p r e v i o u s d a t a ( 2^). With

regard

to

the

( F i g u r e 3 ) , we n o t i c e t h a t

phases the

of

the

(Te,Ce)0

solid solutions a -

subsystem

and 0 - ( C e , T e ) O

In Solid State Chemistry in Catalysis; Grasselli, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

2

Cerium-Molybdenum-Tellurium Oxide System

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BART ET AL.

F i g u r e 2 . S i n g l e - p h a s e boundaries for (Te,Mo)0 and (Ce,Mo)0 phases i n the (Ce,Mo,Te)0 system between 400° and 6 0 0 ° C .

In Solid State Chemistry in Catalysis; Grasselli, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

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S O L I D STATE C H E M I S T R Y IN CATALYSIS

F i g u r e 3 . S i n g l e - p h a s e boundaries f o r (Ce,Te)0 phases i n the (Ce,Mo,Te)0 system between 400° and 6 0 0 ° C .

In Solid State Chemistry in Catalysis; Grasselli, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

6.

B A R T ET A L .

Cerium-Molybdenum-Tellurium Oxide System

are both formed i n 450° and 5 0 0 ° C .

rather

These

temperatures(7,10). formed at a

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400°C).

r e s t r i c t e d c o m p o s i t i o n a l ranges between

solid

solutions

where

stability

ELTeO.

range

(up

not s t a b l e at

more

( T e , C e ) 0 system. F o r m a t i o n of

CeTe.O. ΔΟ

the

(Te,Ce)0

broad c o m p a t i b i l i t y range. i n c r e a s i n g temperature,

decomposes to

d i s t r i b u t e d phase i s s l i g h t l y

knowledge of

are

The T e ( V I ) - c o n t a i n i n g s c h e e l i t e

temperature The

95

restricted at

system(7). The

550°C)

Ce^(TeO^)^ to Te0

of

is

(above

o

this

widely

than i n the b i n a r y

550°C conforms w i t h our

T h i s phase a l s o o c c u p i e s a

sequence

namely

higher

from

of phase f o r m a t i o n w i t h

(Ce,Te)02

t o Ce^iTeO^)^ and

CeTe^O^, i s i n good agreement w i t h the b i n a r y s y s t e m Ç O . As

may

be

seen

from

Figure

t e l l u r i u m - r i c h t e r n a r y compounds Ce^Mo^Te^O^y

occupy

4,

important

and

C e

10

M o

is

taken

T e

12 14°79>

Also,

some

t

n

e

minor

equilibria

of

up

by

latter

two

and

c o m p o s i t i o n ranges

The c e n t r a l p o r t i o n of t h i s

with

Ce2Mo Te20 , 2

and

13

broad c o m p a t i b i l i t y r a n g e s .

are

(Ce,Mo,Te)0

and/or

Qe^io^Ze^O^,

Ce^Mo^Te^O^,-,

components

the

molybdenum-

extensive

w i t h i n the (Ce,Mo,Te)0 phase t r i a n g l e . diagram

the

Ce^Mo^Te^O^^,

formed

system,

in

the

namely

solid

state

C e 2 M o T e 2 0 ^ and 3

(Ce Mo Te 0 ). 4

1 3

3

5 1

Under our e x p e r i m e n t a l c o n d i t i o n s , t e r n a r y compounds are formed

already

( C e ^ M o ^ T e ^ O ^ ) , which occupies a not observed at h i g h e r Ce^Mo^Te^O^

is

Ce Mo Te 0

over

a

broad

present

ternary

compound

the f u l l

investigated;

1 3

temperature

range

e x t e n s i v e i n the 4 5 0 ° - 5 0 0 ° C temperature Compounds C e M o T e 0 , 2

a l l formed at about CeyMo^&jQ^ ternary

M

2 °3

T e

4

1 7

450°C

M

the

range.

w h i c h i s s t a b l e over phase f i e l d

i s most

interval.

T e

are

400°-550°C

its

io °12 l4°79

and

range

stable

a

n

d

C e

M

6 °8

T e

6°45

up t o at l e a s t

a

r

e

600°C.

e x h i b i t s the most e x t e n s i v e c o m p a t i b i l i t y range o f a l l

compounds

f i n d s i t s major C e

2

C e

temperature

i n the 4 0 0 ° - 4 5 0 ° C r a n g e .

Ce^Mo^Te^QO^g i s the o n l y

2

Amongst these i s

c o m p a t i b i l i t y a r e a and i s

in

2

aforementioned

The molybdenum-rich compound

stable

2

is

400°C.

small

( 4 0 0 ° - 5 5 0 ° C ) , and i s e x t e n s i v e l y Also,

at

temperatures.

stable

f o u r of the

(in

particular

extension

at

above

600°C.

500°C); Finally,

M

T e

C io °12 14^79 e

the minor phase

2 ° i 6 i s formed at 500°C and i s s t a b l e up t o over 6 0 0 ° C .

In Solid State Chemistry in Catalysis; Grasselli, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

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F i g u r e 4 . S i n g l e - p h a s e b o u n d a r i e s f o r (Ce,Mo,Te)0 phases i n the temperature range between 400° and 6 0 0 ° C .

In Solid State Chemistry in Catalysis; Grasselli, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

6.

BART ET AL. As may

be

seen

from

Figure

c r y s t a l l i n e m a t e r i a l was d e t e c t e d phase

97

Cerium-Molybdenum- Tellurium Oxide System

triangle

at

various

1,

in

x-ray

amorphous o r m i c r o -

f a i r l y e x t e n s i v e areas i n the

temperatures.

c e r i u m - p o o r samples c a l c i n e d

at

600°C

s i n t e r e d a s p e c t and are d a r k

in

colour.

In

show

p a r t i c u l a r , many

a v i t r e o u s or h i g h l y However, o n l y i n a few

cases c o m p l e t e l y amorphous samples were observed but the r e g i o n s of g l a s s f o r m a t i o n o b v i o u s l y s t r o n g l y depend on the c o o l i n g r a t e ;

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aspect was not f u r t h e r

investigated.

It

appears t h a t

this

considerable

amounts of (Te,Mo)0 g l a s s - l i k e m a t e r i a l ( o f the 3-Te MoO^ type)

are

2

formed

at

550°

and

s c a t t e r i n g maximum*

600°C. of

max

We

the

c a l c i n e d at 600°C v a r i e s from

Â

in

1 1

1 A

dence t o d=3.34

Â

but

r i c h f r a c t i o n at 500°C but

the

materials with

v a l u e drops to c a . 3.24

Â.

550°C

the

exhibit

7

tellurium-

and

maxima i n c o r r e s p o n -

i n c r e a s i n g cerium concentration

3

conforms

1)

x-ray

samples

this

A l s o , the n o n - c r y s t a l l i n e molybdenum-

molybdenum-poor

temperature ( F i g u r e

the

2

At

c o

molybdenum-rich amorphous

that

f r a c t i o n i n the

s i d e ( c f r . 3.33 À i n 3 - T e M o 0 and

Ce Mo Te O ). 4 11 10 59 /

noticed

d=3.34 Â a t the molybdenum-rich s i d e

t o 3.19 A at the t e l l u r i u m - r i c h 3.29

have

amorphous

microcrystalline is

3

t o g l a s s y (Te,Mo)0 ^ ^ χ * .

different

(d

part =3.15

at

3 3

^) ,

the

A).

same

At lower

max temperatures the presence p a r t l y due starting

to

of

incomplete

products.

non-crystalline material is

decomposition

The e x t e n s i v e

and

probably

interaction

of

the

amorphous phase f o r m a t i o n i n the

c e n t r a l p o r t i o n o f the phase diagram at 450°C may be due t o C e 0 or Ce^Mo^Te^O^ ^ ~ * ^» c e r i u m - p o o r amorphous f r a c t i o n d v a r i e s from c a . 3.36 t o 3.27 Â a t the Mo- and T e - r i c h s i d e s , max 2

d

3

1 5

i

n

t

n

e

m a x

respectively.

At

400°C

respectively.

At

this

these

values

temperature,

are some

3.30

completely

samples were found a t the C e : M o : T e = ( 1 5 - 2 0 ) : 4 5 : ( 3 5 - 4 0 ) D e s p i t e the g r e a t c o m p l e x i t y of phases) a l l x - r a y powder s p e c t r a be a s c e r t a i n e d

from the

c o m p o s i t i o n a l range

w i t h l e s s than about reasonable

5

with at%

and corresponds

to

of

the of the

Â,

amorphous

different

As may e a s i l y

the proposed phase d i s t r i b u t i o n s

p r o p e r l y account f o r the presence full

interpreted.

3.19

ratios.

the system ( w i t h 20

were

figures,

and

each of the c a t i o n s over exception

one

of

the components.

sensitivity

the

of the phase ranges This i s

l i m i t of the

In Solid State Chemistry in Catalysis; Grasselli, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

x-ray

98

SOLID STATE CHEMISTRY IN CATALYSIS

method.

Only i n the

400°C

s e r i e s , e x t e n s i v e a r e a s i n the c e r i u m -

and t e l l u r i u m - r i c h ranges o f the the presence o f Te o r Mo.

phase t r i a n g l e do not account

T h i s i s , however, a consequence o f

complete d a t a a t t h i s t e m p e r a t u r e . a n a l y t i c d a t a f o r the new the TeO^-Ce^iMoO^)^

for

Based on the r e p o r t e d

less

thermo-

t e r n a r y phases(3) , i t appears t h a t below

binary

juncture

steeply; compositions r i c h i n

the

l i q u i d surface T e

MoO^ and

0

m

e

2

^

t

a

t

descends

considerably

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lower t e m p e r a t u r e s . I n some r e a c t a n t m i x t u r e s were

detected,

e.g.

Ce:Mo:Te=7:8:5

after

presence o f more

as

as

in

many the

calcination

phases

than

at

as s i x c r y s t a l l i n e phases case

of

the

550°C

for

composition

8

those p e r m i t t e d under

hours.

thermodynamic

e q u i l i b r i u m i s a consequence o f the i n c o m p l e t e n e s s o f the between the components under also noticed that various sensitive

to

the

s

Ce:Mo:Te 5:8:7

Ce^MOgTe^O^,

areas

composed

experimental of

preparative

is

^-Ce^Mo^O^ after

our

the

of

Ce^Mo^Te^O^^

and

c a l c i n a t i o n at 500°C and 550°C

2

It

is

1 7

the composition

C e ^ M o ^ T e ^ O ^ and

f o r 8 hours but c o n s i s t s o f

an

each

conditions.

e.g.

Ce Mo Te^0 , 2

reactions

phase diagram a r e h i g h l y

conditions;

c a l c i n a t i o n at 550°C

The

amorphous for 8 hours.

fraction

after

Another t y p i c a l

example i s g i v e n i n T a b l e I , but v a r i o u s o t h e r such cases were a l s o encountered.

Without v a r i a t i o n s

r e s u l t s are normally (such

as

reduced

o b s e r v e d , as i n d e e d

in

perfectly

the r e a c t i o n p a r a m - e t e r s ,

reproducible.

molybdenum

oxides

and

the

No reduced phases TeMo^O^)

were

ever

expected.

Conclusions

On the b a s i s o f

the

solid-state

s y s t e m , i t i s now p o s s i b l e t y p i c a l unsupported

to

derive

(Ce,Mo,Te)0

composition of R e f . ( 1 1 ) ,

as

r e l a t i o n s h i p s o f the ( C e , M o , T e ) 0 the phase d i s t r i b u t i o n o f a

acrylonitrile

indicated

in

catalyst

Table

I.

with

the

The r e s u l t s

agree w i t h p r e v i o u s c o n c l u s i o n s w i t h r e g a r d to the r o l e o f (Te,Mo)0 and ( T e , C e ) 0 o x i d e s i n t h i s o f the a c t i v e (Ce,Mo)0 XPS r e s u l t s

system and the most l i k e l y c o m p o s i t i o n

phases

( /?-Ce Mo 0 2

3

1 3

and a - C e ^ o ^ O ^ )

( C e ( I I I ) r a t h e r t h a n Ce(IV) i n the c a t a l y s t )

favour

In Solid State Chemistry in Catalysis; Grasselli, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

02). the

In Solid State Chemistry in Catalysis; Grasselli, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

3

2

3

+

+ +

a+8

8

600

600

+, p r e s e n t ; - , a b s e n t ; s,

Amorphous f r a c t i o n w i t h d

b

c

r

As p r e c e e d i n g

a

max

=3.33 A .

s m a l l amount.

+

a+8

550

line.

+

+

+

+

a+8

llT

500

4

10

59

Ce Mo e 0

+

15

+

4

8

2

-Ce Mo 0

450

M

2 °3°12.25

Ce

8

13

400

Mo0 -Ce Mo 0

Phase d i s t r i b u t i o n

(Ce,Mo,Te)0

t

(h)

conditions

Phase d i s t r i b u t i o n i n the unsupported

Τ (°C)

Activation

Table I .

Ce^o^Te^

catalyst.

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(c) + (c)

+

+ (c)

amorphous

100

S O L I D STATE C H E M I S T R Y IN CATALYSIS

presence of a - C e ^ M o ^ O ^

and

lead

to

oxygen c o n t e n t of the c a t a l y s t Q J . component

i n the phase diagram

the c a t a l y s t

is

essentially

p r o p y l e n e (J12^.

The

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previously

(Table

In f a c t ,

the

presented

range

of

MoO^

catalyst.

active

ternary

phase(s),

and

the

stoichiometry

(Table m a x

I).

is

our

current

study

The p r e v i o u s l y

the

to

reported

by

catalyst,

x-ray

no t e l l u r i u m -

diffraction

of

the (d

fflax

samples

above 500°C

amorphous

fraction

=3.29 A ) , a compound

n o n - c r y s t a l l i n e form above 5 0 0 ° C ( 3 ) .

unknown

i d e n t i f i e d as C e . M o , . Te. O . 4 11 10 59 a c t i v e phase of the

active

maximum

in

and/or

s t a b l e much above 5 0 0 ° C .

Ce^io^e^O^

obtained

n

being

identification

Ce^Mo^Te^O^

the phase d i s t r i b u t i o n o f

the

detected

= 3 . 3 3 A) p o i n t s

which i s e a s i l y

to

of

However,

namely

not

i s noticed that according

c o n t a i n i n g phase

(d

the

T h i s c o n c l u s i o n agrees

results(2)

C e ^ M o ^ T e ^ O ^ w i t h the l a t t e r

with

in

I).

the

It

ammoxidation

the presence o f t h i s compound as

The new f e a t u r e , d e r i v e d from t h i s work, i s the of

to

i t i s w e l l known

inactive i n selective

compatibility

a s i g n i f i c a n t component of

proposed

of s i g n i f i c a n c e w i t h r e s p e c t

( C e , M o , T e ) 0 system c a s t s doubt on

with

r e v i s i o n of the

c o m p o s i t i o n and a c t i v i t y .

t h a t t h i s phase i s of

a

The absence of Ce^iMoO^)^ as a

ternary Therefore,

cn

(Ce,Mo,Te)0

oxide(2) '

it

has

now been

i s l i k e l y that J

ammoxidation c a t a l y s t

the

c o n s i s t s of

an Q f - C e ^ M o ^ O ^ - r i c h m i x t u r e c o n t a i n i n g C e ^ M o ^ T e ^ O ^ g . I n e v a l u a t i n g our r e s u l t s industrial catalystQ), effect and

of the s i l i c a

yet

is

from

that

to

phase of

In

fresh SiO^-supported a c t i v e

the the

a

also

In of

(Te,Ce)0/Si02 the

fact,

as

here shown

the ( T e , C e ) 0 system system

at

the

same effect

r a t e s and s t a b i l i t y ranges

from x - r a y d i f f r a c t i o n d a t a of a

ternary to

taken o f

d i l u t i o n and i n t e r a c t i o n

formation fact,

be

has not been c o n s i d e r e d role.

distribution

the

the r e s p e c t i v e

of the v a r i o u s phases.

c o n c l u s i o n s i n r e l a t i o n to should

which

play

a c t i v a t i o n temperature due t o which a f f e c t s

and

account

support,

likely

p r e v i o u s l y ( 7 , 1 0 ) , the differs

an

the

phase, results

the f o r m a t i o n o f some

CeO^ i s

inferred,

contrary

system.

For these

reasons, a d d i t i o n a l spectroscopic

of

the

unsupported

and

catalytic

In Solid State Chemistry in Catalysis; Grasselli, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

6.

BART ET AL.

Cerium-Molybdenum-Tellurium Oxide System

a c t i v i t y studies regard

to

the

are nature

necessary of

i n d u s t r i a l (Ce,Mo,Te)0/Si0

the

to

confirm

active

101

our suggestions with

phases

contained

i n the

catalyst.

Acknowledgment s

One of us ( P . F . ) acknowledges

support from the I t a l i a n Ministry of

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Education.

Literature Cited 1. 2. 3.

4. 5. 6. 7. 8. 9. 10. 11. 12.

Caporali, G.; Ferlazzo, N.; Giordano, N. German Patent 1.618.685, Nov. 23, 1972. Bart, J. C. J.; Giordano, N. I.&E.C. Prod. Res. Dev., 1984, 23, 56 Bart, J. C. J.; Forzatti, P.; Garbassi, F.; Cariati, F., Proc. Third Intl. Symp. Ind. Uses Selenium & Tellurium, Stockholm, 1984. Bart, J. C. J.; Petrini, G.; Giordano, Ν. Z. Anorg. Allg. Chem., 1975, 412, 258. Castellan, Α.; Bart, J. C. J.; Bossi, Α.; Perissinoto, P.; Giordano, Ν. Z. Anorg. Allg. Chem., 1976, 422, 155. Bart, J. C. J.; Giordano, N. J. Less Common Metals, 1975, 40, 257. Bart, J. C. J.; Giordano, N.; Gianoglio, C. Z. Anorg. Allg. Chem., 1981, 481, 153. Petrini, G.; Bart, J. C. J. Z. Anorg. Allg. Chem., 1981, 474, 229. Dimitriev, Y.; Bart J. C. J.; Dimitrov, V.; Arnaudov, M. Z. Anorg. Allg. Chem., 1981, 479, 229. Bart, J. C. J.; Giordano, N. J. Catal., 1982, 75, 134. Hucknall, D. J. "Selective Oxidation of Hydrocarbons"; Acad. Press: London, 1974, p. 56. Brazdil, J. F.; Grasselli, R. K. J. Catal., 1983, 79, 104.

RECEIVED March 20, 1985

In Solid State Chemistry in Catalysis; Grasselli, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.