Catalyst selection for the synthesis of methylpyrazine

161

Applied Catalysis, 29 (1987) 161-174 Elsevier Science Publishers B.V., Amsterdam

CATALYST

Lucia

SELECTION

C.Golgi

(Received

THE

in The Netherlands

SYNTHESIS

Gianemilio

STERN

di

Chimica

Fisica

19,

I-20133

Milano,

FORNI,

Dipartimento Via

FOR

- Printed

18 July 1986, accepted

and

OF

METHYLPYRAZINE

Massimo

ed

GATT1

Elettrochimica,

Universita

di

Milan0

Italy.

15 September

1986)

ABSTRACT An

exploratory

research

programme

and

a glycol

parations

were

tested

in

standard

a mixture

of

ZnO/Zn-chromite,

tained salt, excess

with when

working

steam.

tained at by simple

at

Under

to

on

a diamine

640-700

such

over 90% oxidation

catalysts

methylpyrazine

K,

is

conditions.

The

up

to

conversion. The aged of the carbonaceous

the

mol

catalyst deposits

a few and

%

than

results

with

pressure 60

cyclisation

More

best

promoted

atmospheric

conditions,

for

described.

in

pre-

were wt

ob-

%

Pd

presence

selectivity

was easily in flowing

of

80

of

was

ob-

regenerable, air.

INTRODUCTION An

exploratory

concerning of

research

catalysts

for

2-methyl-pyrazine

reported process

[1,2]. for

programme, the

(MP) Such

teriostatic

and

antitubercular

represented

as:

+

PG

of

is

the

in

(CP),

second

step

2-amido-pyrazine drug.

MP

The

this

vapour-phase

Z-cyano-pyrazine

a reaction

preparation

ED

heterogeneous,

to

the

performed

an

(AP),

process

CP

may

and

ammoxidation

has of

laboratory

been

recently

interesting

a well-known be

bac-

schematically

AP (I)

The

present

catalyst

0166-9834/87/$03.50

for

paper the

step

reports 1

of

01987 Elsevier

on the

our

parallel

scheme,

Science

Publishers

i.e.

B.V.

exploratory the

research

heterogeneous,

of

vapour-

a

162 phase

synthesis

of

pyleneglycol overall

similar

na

[3-51,

it

was

at

of

verifying

based

and

ethylenediamine

the

was

chromite

for

(ED)

practical

reported

on

ZnO

and

pro-

feasibility

to

verify

from

of

the

the

was

silica-alumi-

the

of

effect

of

and

ZnO

Some

of

some

classes,

analysed

preparation

Therefore

behaviour

mentioned Then

precursors.

or

have

respectively. the

three

catalysts

various

recently

the

catalysts

alumina

first

reactions.

such

as

of

[9,10],

different

including

mixtures

or

to

to

classes

such

belonging

promoters

extended,

three

solids,

interesting

sold

some

acidic [6-81,

catalysts,

of

study

on

chromites

considered

prepared

typically

reactions,

on

commercial

were

aiming

(PG),

employed,

tion

cyclisation

process.

For been

by

MP,

or

but the

addi-

finally

of

the

ZnO/Zn-

preliminary

results

[ill.

EXPERIMENTAL Materials "Pro

analysi"

employed the

for

pure

the

reagents

(Merck,

preparation

Fluka,

catalysts

of

and

C. Erba

and

of

solution

the

Ciba)

were fed

to

reactor.

Catalysts More tions

than

were

powder

80

tested

(Ciba):

Zn0302T),

by

acetates, tion

or

adding

by

techniques. (pellets,

ing

the

drying

was and

the

the

mesh done

novo

case

etc.)

obtained

at

with

AlCoA

to

770 after

K.

oxalates,

formates,

was

crushed

In

the

obtained

commercial

catalysts,

from

(HTZ3),

mentioned

commercial

60-80

Zn0308T,

were

impregnation

simply

ZnO

Topsde

(ca.70)

nitrates,

usually

Cu0203T,

(FllO),

the

prepara-

a commercial

CrOZllT,

precipitation, of

commercial

catalysts

from

impregnation

calcination powder

G13/4),

fraction, by

A13996R,

promoter(s)

usual

extrudates,

desired

promoters

ex

Twelve

comparison

remaining

the

the

In

in

G22/4, The

prepared

etc.,

examined.

(Zn0401E,

(G720,

simply

lid

novo,

Harshaw

(SCS79).

substances,

were

as purchased,

Girdler

Rhone-Poulenc either

catalysts

mesh.

or the

calcina-

original

and

sieved,

The

addition

so-

collectof

the

aqueous

solution,

followed

by

case

catalysts

prepared

ex

precipitation

of

and/or

calcination

of

163 the

precursors

was

pressed

were

gently

crushed

tive

to

catalysts

the

Apparatus

and

Catalytic

microreactor,

the

activity

(3

ED

and

of

fresh

ca.2

mm

thick

Some

in

wafers,

essential

Table

24

h.

and

h on-stream, cooled

K and

was

was

which

data,

rela-

1.

by K)

(50

charged

under

standard

0.75

deionised

added

as

carrier

samples

were

of

of

indicated,

an

gas. and

the

usually

withdrawn

liquid

A

In

i.e.

equimolar

water.

reactor

1 g of

ca.

fixed-

conditions,

cm'/h

in

the

a continuous, otherwise

wt%)

into

means

in

Unless

feeding

collecting by

out

[2]. done

by

also

Analytical

(240

were

diluted

PG,

carried

elsewhere

700

catalyst

for

traps,

shown

were

tests

nitrogen

ducted 24

into

mentioned.

are

runs

described

pressure,

of

as

tested,

comparison

cm3/min)

g of

sieved

cyclisation

atmospheric

MPa)

procedure

bed

mixture

and

(300

small

each run

run

was

0.5

con-

after

effluent

flow

1,

in

5

sampling

a cryostat.

Analysis The GC

on

with

condensate a glass

Tenax

After the

final

have

ined

in

AND

of the

Besi,des were

to

an

and

sampling

2 mm

i.d.,

column

gas

at

injecting

was

Analytical

external

670 was

of

K

in

(20

known

by

packed

inert

gas

(8

cm3/min).

factors

flow.

K/min)

up

GC

composition

correction

standard

analysed

and

raised

helium

mixtures

was

silanised

temperature

Carrier

traps

peaks

and

were

to

con-

determ-

(N,N-dimethylformamide).

DISCUSSION of

mol

catalytic

latter

Lesser

of

calculated adopted, in

desired in

activity

% conversion

and,

the

found

acetone.

by

conditions

complete

the

the

pre-conditioned

spectrometry.

results

standard

K,

isotherm.

respect

terms

(Smp),

ly

mass

with

The

K

long

mesh,

identified

by

RESULTS

393

within

3 m

60-80

at

513

been

firmed

column,

GC,

6 min

collected

the

any

case,

product condensate.

amounts

of

ED

comparison

runs

have

(Ced)

and

mol

%

with

respect

to

the

reacted

the

conversion

of

was

higher

it and

always

unconverted

The

most

diethylketone,

PG

expressed

selectivity

was

reagents,

abundant

been

were

ED.

usually

than

that some

pyrazine

isobutyronitrile,

to In

MP

the

practicalof

ED.

byproducts (P)

and

methyl-ethyl-

164 TABLE

1

Chemical

a)

composition

method

of

preparation

Cat.

Producer's code

the

catalysts

employed

(wt

Zn-0401

E

c2 c3

Al-3996 Cr-0211

R T

c4

Cu-0203

T

C5

Zn-0308

T T

C6

Zn-0302

c7

G-72-D

C8

G-22/4

c9

G-13/4 ZnO purum

Cl0

Cl3

Modified

Cr203(19)-A1203(81)

II

;;;(78)-Cr203(20)

II I,

ZnO-ZnChromite ZnO

Girdler

and

II II

Cu(33)-Cr(27)-Ba(ll)-O(Z9) Cu(40)-Cr(25)-O(35)

Ciba

ZnO

AlCoA Topstie

y-alumina ZnO

RhBne-Poul.

y-alumina

(by

calcination

Composition

Cat.no.

y-alumina

II

commercial

drying

M4

G-72-D

M5

Zn-0308

M6

G-72-D

M7 M8

Zn-0308

%)

ZnO

Harshaw II

F-110 HTZ-3 scs-79

Cl1 Cl2

Composition

Producer

Cl

impregnation at

(wt

500°C

%

of

for

added

with 6 h) promoter)

+ PdS04(2) +

PdS04(2)

+ H3P04(3)

+ MnS04(1)

+ H3PO4(3)

+ MnS04(1)

M9

HTZ-3 + PdSOq(2) Zn-0302 + PdS04(2)

Ml0 Ml1

ZnO Ciba + PdS04(2) HTZ-3 + H3P04(3) + MnSO4(1)

Ml2

Zn-0302

Ml5 Ml6

HTZ-3 HTZ-3

+

Ml7 Ml8

HTZ-3

Ml9

HTZ-3

+ Mn02(1), + MgD(l), + Ce02(1),

M20

HTZ-3

+ H3P04(3)

M22

HTZ-3

+

Pd(2),

from

Pd(NH3)4(N03)2

M26

HTZ-3

+

Pt(2),

from

K2PtC14

M27

G-72-D

M28

G-72-D

+

H3P04(3)

+ MnSOq(1)

+ FeS04(2)

HTZ-3

from

Fe203(1),

from from

Fe(N03)3.9H20 Mn(NO3)2.4H20

MgS04.7H20

from

(NH4)2Ce(N03)6

from Fe(N03)3.9H20 + Fe20 (I), + Pd(2 3 , from Pd(NH3)4(N03)2

M30 M31 M33

z

M40

Zn-0308 + Fe203(1), ZnO Ciba + H3P04(3)

M41

of

Commercial

no.

b)

and

;;;:

Zn-0302

: ~~~~3i'~;,Ir~~(~~~~~~~~~~~20 +

Fe203(1),

from

Fe(N03)3.9H20

from Fe(N03)3.9H20 + MnS04(1)

aq.

solution

Of

promoter,

165 TABLE c)

1

(continued)

Prepared

(ZnO-based)

Cat.

Composition

no.

(wt

Sl

ZnO

Method

of

From

hydroxycarbonate, and

Zn(N03)2 500°C 52 s3

for

ZnO

(v.supra, SL) From commercial

ZnO

ZnO ZnO+Fe203(1)

in

commercial

12

From

h

in

freshly drying

3'

prepared

and

from

calcination

acetate,

by

by

calcination

calcination

at

500°C

air freshly

by

precipitated

addition

of

oxalic

from acid

aq.

+ NH40H

and calcination (v.s.,Sl) B)> drying freshly prepared by refluxing From formate, By

aq. at

air hydroxycarbonate,

oxalate,

over 521

h

From

Zn(N0312, s14

6

Na2C0

ZnO

for s13

preparation

%)

stirred

ZnO,

impregnation

drying of

and

calcination

S13

and with

calcination aq.

(pH=

HCOOH

(v.s.,Sl)

Fe(N03)2,

drying

(v.s.,Sl)

S23

ZnO+Ce02(1)

See

S21,

impregnating

solution:

aq.(NH4)2Ce(N03)6

S25

ZnO+PdSO4(2)

See

S21,

impregnating

solution:

aq.

s29

ZnO

See

S3,

but

calcined

S32

ZnO

See

53,

but

preheated

cining s35

ZnO

See

S36

ZnO+Fe203(1)

By

S37

ZnO+PdS04(2)

S3,

at

500°C

but

for

calcined

impregnation

and

calcination

See

S36,

of

for 65 6

14

PdS04

h

h at

260°C

before

for 529

16

with

h aq.

Fe(N03)3,

drying

(v.s.,Sl)

impregnating

cal-

h

solution:

aq.

PdSO

4

166 TABLE d)

1

(continued)

Prepared

Cat.

(ZnO-ZnCr204-based)

Method

of

preparation

no. 542

From Zn- and and at 400°C

543

From "C

S42 4

h at

+

mixed Cr-acetate (lO:l), 5 h in flowing nitrogen

5%

in

CrO

air

(as

aq.solution),

and3reduction

13

h

s44

As

S43,

+

545

As

S43,

reduced

S46

As

S43,

calcined

in

10%

drying, (1:4)

H2

43h

at

at

320°C

As

S46,

reduced

4

h at

320°C

S46,

reduced

6

h at

320°C

s49

From

calcination 2 h at 320°C

+ N2

ZnO+Cr03

(Zn:Cr=6.67:1,

calcined

1 h at

and

2

400°C

15

h at

h at and

3

S49,

Zn:Cr=3.33:1

atomic

4OO"C, h

at

ratio)

pelleted 475"C,

, 2.22:1

s53

As

S51

+

2%

PdS04

554

As

551

+

1%

MnS04

s55-59

As

S51

+ 2.5

S61

From

Zn

and

air

Promoted

and

+

mixed

with

reduced

3%

nitrates

at 360 and

1% in

reduction 1 %

, 4.0

, 0.5

H

a;

%

As

561,

Zn:Cr:Al=3:1:1

S65

As

S61

Zn:Cr:A1=3:1:0.25

S67,69,71

As

S61,

Zn:Cr=l:l

, 2:l

+ N2

2

PdS04,

atomic

slurry, calci-

(1%

H2)

at

calcination

+

% H2)

N2

(4

, 4:l

, respectively

respectively

ratio),

drying,

PdS04.

563

aq.

, respectively

(Zn:Cr=3:1, in

as

graphite,

H3POq

NaHCO

with

with

, 1.6J:l

, 1.0

, 1.5 Cr

precipitation in

1 h

400°C

320°C As

270°C

430°C

As

s50-52

at

CrO

S48

ned

calcined

400°C

547

dried,

and

1

h at

at

by 360°C

320°C.

co4

h

167

TABLE

2

Typical

run

analysis

551

Catalyst:

(0.5

Time-on-stream

g)

;

T

=

43o'C;

feed:

(h)

standard 5

1 wt

%

in

24

condensate

_ 2-methyl-pyrazine

11.80

pyrazine

13.28

1.29

15.98

1.25

0.88

diethyl-ketone iso-butyro-nitrile

0.11

0.13

acetone

7.81

6.36

3.86

methy-ethyl-ketone

0.60

0.53

0.38

propionitrile

0.55

0.29

0.37

mol

C

94.88

ed

Cpg

R

88.84

100.

smp (wt

%)

ketone nal

and

tiny

very

proplonitrile

peaks

low

were

so

is

shown

sis

of

uncondensed

quantity

of as

they

they

ate

pressed

noted

quantity,

trometry,

as

were an

%

could

42.64

48.96

91.00

95.00

97.22

found.

neglected.

not

was

be A

2.

cases,

speed

performed.

.To (R)

condensate,

a

However,

run

To

parameter

collected

some

identified, typical

Table

recovery

In

chromatogram.

not

gas

100.

34.00

the

in

a

of

on

95.20

100.

also

example

losses, wt

were

%

due

additio

to

their

neither

by

mass

spec-

analysis

of

the

condens-

up

the

give

an

has

been

with

few

work,

idea

of

the

analy-

the

overall

calculated,

respect

to

the

ex-

fed

solu-

tion. The the

best

Cl2

and

On

the

to

a

comparison

of

results

are

Cl0 other

lot

selectivity.

of

(see

Table

hand,

with

catalysts

obtained l),

aluminas

unwelcome Work

commercial

with

this

ZnO-based

followed

by

behaved

byproducts, class

(Figure

some

much

of

catalysts

shows

catalysts, chromites,

less

resulting

1)

a was

particularly

drastically then

that

particularly

satisfactorily, in

clearly

leading lowered

immediately

C6.

168 abandoned. The ly

target

of

the

present

work,

reaction It

a dehydration-dehydrogenation.

ting

action

of

while

the

Cr,O,

, etc.

oxide

dehydrogenating and

1 5 22

FIGURE

1

stream

(h)

h/mol);

for

reactions.

fied

catalysts

ing

one

(M19)

and

were

(C5-7

ClO),

and

obtaining tivity ZnO-based tivity,

the data

the

latter

a

M22

M26,

C7,

(M8).

All

little

the

the

M16,

and

extent;

of

of of

other

M27,

M30, i)

C12) ii)

the

both

time-on-

series

the

these

by

of

(g

cat

cata-

the

promotof

substances

previous

addition

com-

modified

The

M40

men-

ZnO-based

Ceaf-

three

commercial

M33,

a re-

previously

(M16),

other

modi-

adding

Fe-oxide

generally onthe

of

for

the

the

,

15

1

evidence

four

in

Fe203

T=19.6

1)

base-catalyst.

well

that:

a

selective

provide

(Mll),

to

Cl0

to

, etc.,

aq.solution.

both

behaviour

MnS04

of

showed

and

dehydra-

1524

5

Table to

active

performed

M4-12,

(C5, to

also

had

catalysts the

prepare

the CeD2

a function %

essential-

effectively

T=430"C,

to

seemed

Pd

as

la).

decided

The

behaviour

added

which

only

1).

1

is

metals,

catalyse

wt

and

, MgO,

noble

50

most

of

(I)

belonging

H3P04+

generally

catalysts but

the

Table

couple

then

of

was

by

1

in

1, that

H3P04

may

(Table

(mol)

M15-20,

of

ZnO

selectivity

conditions

unfavorably

promoters

it

by

14231

1 4 22

promoters,

(C12,

the

that

scheme

[12-141

promoted

catalysts

Mll,

to

of

known

and

known

promoted is

ratio=l:l

of

standard

action

(u)

number

catalyst

fected

1 4 22

Therefore

classes,

in

oxide

1

commercial

(M8,

presentative

lysts

also

feeding

is

action

is

Conversion

such

mercial

it

1 7 24

ED:PG

tioned

catalysts

is

1 of

best

catalysts screening,

and of

M41.

The

promoters

improves

Zn-Chromite-based

the

so acon seleccata-

169

b

a FIGURE

2

sors;

a)

b)

(S25,21,23) as

lyst

(C6),

for

on

acetate 1.

the

based

the

at

24

h

on

Symbols,

ZnO

is

all

for

the

present

by

Natta

iii)

different

on

ZnO

reaction

precur-

from

oxalate

conditions,

on-stream.

improves

of

from

based

PdS04

addition

ZnO

catalyst

(S37,36).

Data

conversion;

to

is

very

of

that

high-pressure

noticed

[15-172

likely

prepared

from

tioned

the less cally

was

catalysts

behaviour

(S13,

and

research of

of

best

these

in

and

useless,

the

selectivity,

cases

the

reaction

is

on

the

then

of

nature

S14,

and the

of

but

key-substance

re-

for

the

as

previous

best

from

promoters

(S3)

that

while

the

most

the

formate

method

Our

exploof

based

on

from

oxalate

others

were

(S14),

or

efficient

ZnO

men-

similarly

(S1,2).

a

The

previously

very the

[15].

techniques.

prepared

hydroxycarbonate to

1)

the

behaved

from

on

preparation

Table

confirmed

series, as

the

H2

hence

employed.

different

catalysts

+

(and

depend

S35,

by

2a)

acetate

such

and

and/or

CO

properties

to

very

practiced

from

precursors

S32

the

from

those

methanol

extended

S29,

surprisingly

extensively

strongly

the

(Figure

selective,

of

ZnO

immediately

catalysts

once

physico-chemical

precursors

of

the

synthesis

properties)

S35)

such of

for

Particularly,

catalysts

active

the

different

s32,

addition

that

the

(Sl-3,

dependence. s29,

for

catalytic

preparation

group

ZnO

process

known

ratory

the

from

behaviour

similar

of

catalysts

performance. The

It

of

promoters

Figure

only

the

good

of

and

etc.

ducing

Behaviour

Effect

to much practi-

Furthermore, of

these

cata-

170 523

and

spectively,

see

Table

lar

observed

lysts

(521,

to

that

mercial is

temperature

extend

the

ZnO/Zn-chromite

ed

for

of

methanol

the

acetates

in

the

Cr03

reduction

It

diate methanol 1)

the

change

were

version

in

rature

was

on

two

of

The

640-700

is

may

consideration. than

leading

attaining

30 K lower.

promoters,

H3P04

to

Furthermore, 546,

temperature

for

(bl ack

These

data

catalyst.

The

such and

as

effect

heavy

it

may

Pd

same

sulfate

symbols, that of

its

Pd

(full same

is

(S42the

[27]

intermefor

the

(S49-52,

Ta-

showed

that

tempe-

chosen

open

symbols)

in

is

show

also

most

that with-

and/or For

T<640

taken

K

551

into

performed

parameters after

Figure

se-

K a higher

be

catalyst

confirmed

con-

obtained

T>700

activity

symbols,

the

conversion

for

must

the

among

temperatures.

of

was

practically

reaction

that

values

of

on

while

noted

was

promoter,

fouling, be

addition

extent.

decrease

behaviour

This

white

confirm

to

Cr

a little

S51),

reasons,

and

to

and

kinetic

by

Zn

re-

only

catalysts

higher

follow-

affect

our

or

based

to

of

any

further

seems

case

strong

of

others

low

S46-48,

behaviour

any

of

and

catalysts

in

lower

the

of

b,

alone

synthesis

in which

Their

and

com-

base-substance

by

ratio)

the

usually

behaviour

group

3a

to

cases

the

simi-

relatively

mixtures

some

2b)

catalysts,

(S4.245

conditions

(546

a

of

re-

ZnO

high-pressure

reported

absence

since

due

rapidly

the

(Figure

the

observed

essentially

rate,

better

in

K range, be

them

results

performance,

in

method.

but

behaviour

ones.

calcining

(ZnO/ZnCr204

the

lectivity

of

slurry

selectivity,

tested

by

third

of

best

decay

composition than

The

the

groups

already

dependence

promising

the

by

two

of

the

techniques

the

preparation

as

catalyst.

for

that

interesting

the

Their

on

modifying

to

groups

+ N2.

depend

(S46-48),

by

followed

H2

of

to

prepared

more

The

this

method

synthesis

ble

air,

flowing

rather

reduced

first

by

owing

acetate,

(Figure

remembering

three

catalyst

obtained of

in

the

seemed

is

were

absence

of

the

from

behaviour

considered

prepared

. The

1)

was

537,

obtained

[18-261

including

mixtures,

Table

independent

it

by

[15,27,28]

in

catalysts

sintering

of

S36,

a consequence,

K),

preparation

spectively,

and

to

and

a change

the As

(674

oxalate

showed

with

exploration,

on

in

1)

prone

Hijttig

the

from

base-substances.

particularly

45).

S25,

3b)

at

the

addition

and

MnS04

a

+

Figure).

very

concentration

likely was

the

best

determined

Promoter by

for preparing

our

171

bl

670

Black

sulfate). MnS04 + recovery

of

reaction

Full and

symbols:

white

Open

temperature. Catalyst

S53

Catalyst

symbols:

as

for

Figure

symbols:

(S51

a)

promoted

S54

(S51

Catalyst with

promoted

2%

S46; Pd

with

1%

; (0,=,0) R (wt % S h o!pstream. Other reaction

3% H3PO ). (().a,@) Ced; (n,A,A) of con d ensed products). Data at 24

conditions

73og K

K

Effect FIGURE 3 b) Catalyst S51.

I ,I,

I

670

730

1.

n_

$6o-< 20 b)

I l/l

3/l

2/l

Effect of 4 coprecipitated

feeding

solution

for

Figure

and

testing

that

the

10

I 1

AI/Cr(atomi

atomic

ratio

(a)

and

of

the

catalysts. T=400"C. Concentration Symbols and other reaction wt%.

presence

of

of ED+PG conditions

Al in as

3.

the

best

was

decided

the

catalysts To

=

Zn/Cr

,

0.5

Zn/Cr hxll)

FIGURE (b) in

I

I

0

4/l

complete

next

series

performance to

limit prepared the

to

of

catalysts

corresponds I %

the

(S55-59). to

l-2

wt

concentration

of

The

results

% PdS04. such

showed

Therefore,

a promoter

it in

thereinafter.

information

about

the

optimal

composition

and

the

all

172

time-on-stream(h) FIGURE

5

as

Figure

for

Reaction-regeneration 3.

Regeneration

most

prepared

by

cases

was

the

solid.

tration molar ed

added,

feeding

effect

(Figure

strength,

4a).

decrease

of

All

results

point

the

whole

set

regeneration and

under

Under in main situ, ous

100

after deposits

bubbling

the

a short in

flowing

outcoming

gas

S61.

670

to

10

are

lowering

wt

but

shown

prepared was

in by

progressive

addition

of

Al,

is

as

may

and

The

then

The

results

are

that

catalyst

note

carried

selectivity

three

K)

Ba(OH)?

by and

out

Zn/

improvement

in

mecha-

accompanied

by

a cor-

(Figure

on

in

activity the

wt

were

oxidation

solution.

4b). among

reaction-

S57,

reported

monitoring

method,

varying

following

and

Compar-

catalyst

regenerations

nitrogen,

(T<720 into

tested.

concenthe

4.

slurry

of

the

selectivity

was

the

in

the

the

Figure

by

some

keeping

the

observed,

In

was

strength

K and %,

series

1).

mechanical

best-performing

The

air

the

557

while

purging

conditions

catalyst

a last Table

and

conditions.

constant.

catalyst,

conversion

run

one

50

the

prepared

h on-stream,

practically

the

to

at

catalysts

expected,

both

reaction

symbols:

(S61-71,

data

selectivity

extended-life

conditions,

from

activity

by

the

tested

on

solids

standard

such

ca.

of

were

the

obtained

full

improving

to

As

responding the

at

solution

relative

of

technique

aiming

The

other

S57,

text.

preparation

catalysts

stronger

nical

of

ED:PG=l:l.

those

ratio

see

T=400"C,

catalyst

coprecipitation

also

the

ratio

a much Cr

the

These

of

with

method

test.

symbols:

conditions:

efficient

Al

Open

at

670

Figure

5.

falls %

K

by

recovery

carried

out

50 rein

of

the

carbonace-

the

COP

formed,

Each

regeneration

by

%

173 took

cd.

K for not

18

2 h

in

taken

It

behaved

of

Hz

into

Figure).

ivity

h and

was

+ Np

(Hz=

account

may

be

the

was

solid

cerning

S61

latter

shows

in

the

after

same

as due

purging

Of

that,

course,

each fresh

to

fouling,

these

dead

in

showing

rather

to

some

h,

see

catalyst the

few

data

that

a quite

act-

modification

indicate

by

T5590 were

that

than

Figure)

accompanied

times

the

comparison,

the

at

(ca.450

sample,

For

selectivity,

reduction

regeneration,

the

symbols

and

time-on-stream

sintering.

(full

a higher

X).

overall

by

catalyst

short

the

essentially

structure

by

4 vol

noted

practically decay

followed

con-

the

fast

activity

decay.

CONCLUSIONS The the MP

information

following may

be

collected

conclusions

carried

out

sintering-inhibitor alumina

should

of

its

in

selectivity;

leading

to

till

the

from

CO

+ Hz;

700

K;

off

the

v)

at

kinetic

a

iv)

very

determining study

properties

and

and

the

the

improve

the

life;

be

easily with

this

study

optimal

looking

for

performance

of

air

in

is

reaction

the

a strong to

be

employed

for

of

the

in

ZnCr

for

synthesis

by

0 2 4'

deca-

methanol

process

situ,

is

640-

burning

conditions. in

conditions between

ii)

decrease

progress

correlations

a

to

controlled

in

which

because

usually

regenerated

to

a promoter,

seems

range

ED+PG

catalyst

or

high-pressure

temperature

of

to

leading

that

permits

catalysts, the

a catalyst

to

study

cyclisation

ZnO-based

to

similar

deposits of

exploratory

sintering-inhibitor

for

may

development

i)

over

either

optimal

catalyst

carbonaceous

drawn:

better

the

present

side-reactions,

mid-sixties,

the

Further aimed

iii)

be

added,

as

favour

a catalyst

des

be

avoided

to

the

effectively

must be

tendency

to

by

our

for

laboratory,

a complete

physico-chemical

catalyst.

ACKNOWLEDGEMENT Thanks Contract,

are

due

by

means

to of

Bracco which

Industria the

Chimica,

present

work

Milano, was

made

for

the

Research

possible.

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