Solid State Chemistry in Catalysis - American Chemical Society

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

Downloaded by PENNSYLVANIA STATE UNIV on August 5, 2012 | http://pubs.acs.org Publication Date: June 13, 1985 | doi: 10.1021/bk-1985-0279.ch006

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


(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


is

2

the


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 .


92


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


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^MoÔ^ 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


2

Cerium-Molybdenum-Tellurium Oxide System


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 .




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 .


6.

B A R T ET A L .


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

rather

These

temperatures(7,10). formed at a


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 CeîTeO^)^ and

CeTeÔ^, 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^TeÔ^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

Qeîo^ZeÔ^,

Ce^Mo^TeÔ^,-,

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^TeÔ^^,

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^TeÔ^

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 .



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 .


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 ;


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^TeÔ^ ^ ~ * ^» 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


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^-CeîMoO^)^

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


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^MOgTeÔ^,

areas

composed

experimental of

preparative

is

^-Ce^MoÔ^ after

our

the

of

Ce^Mo^TeÔ^^

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 TeMoÔ^)

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


02). the


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 .

Ceô^Te^

catalyst.


(c) + (c)

+

+ (c)

amorphous

100


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


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 .

CeîoêÔ^

obtained

n

being

identification

Ce^Mo^TeÔ^

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 CeîMoO^)^ 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


6.

BART ET AL.


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


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


Solid State Chemistry in Catalysis - American Chemical Society

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