Hydrogenation of carbon monoxide over cobalt containing zeolite catalysts

85

Applied Catalysis, 32 (1987)85-102 Elsevier Science Publishers XV., Amsterdam-Printed

OF CARBON

HYDROGENATION

LEE and Son-Ki

Dong-Keun

of Chemical

Department Technology, *To whom

MONOXIDE

OVER COBALT

Korea Advanced

P.O. Box 131 Cheongryang,

7 August

CONTAINING

ZEOLITE

CATALYSTS

IHM*

Engineering,

all correspondence

(Received

in The Netherlands

should

1986, accepted

Seoul,

Institute

of Science

and

Korea.

be addressed.

24 December

1986)

ABSTRACT Cobalt containing zeolite catalysts were prepared by three different methods: ion exchange (IE), carbonyl complex impregnation (CI), and excess water (EM). They were characterized by hydrogen consumption, chemisorption, TEM, EPR and FMR, temperature programmed desorption (TPD) and temperature programmed surface reaction (TPSR). Kinetics for CO hydrogenation was measured at a temperature of 230-310°C, pressure of 1 atm and H2/CO ratio of 2. The EW catalysts showed a negative reaction order of methanation on CO partial pressure while the IE and CI catalysts showed no dependence. The higher activity of the EW catalysts compared to the IE and CI catalysts was ascribed to the structure sensitive nature of the reaction. The CI catalyst has the highest selectivity to the longer chain hydrocarbons of C3 and C4. The olefin fraction was also affected by the preparation techniques and the extent of ion exchange.

INTRODUCTION Recent mainly

into the hydrogenation

at improving

zeolites highly

research

the product

have great

dispersed

polyfunctional

promise

metals,

pylene

inducing co2+

cobalt

metal

The activity

under

chain

attention,

for well-dispersed study,

ion-exchange

cobalt containing

length

metal

to provide

selectivity,

containing

catalysts

with

and to induce

limitation.

on finely

yielded

[2]. Tkatchenko

Uytterhoeven

pro-

et al.

are prerequisite [5] found

to

that

to reduce. alumina-

or silica-supported have received

has been reported

clusters

the three different

enmeshed

preparation

complex-impregnation

catalysts.

in A zeolite

of carbon monoxide

little data cobalt

are C4 olefins

in NaY zeolite

of conventional

and carbonyl

zeolite

metal

conditions

aggregates

was very difficult

whereas

products

Cobalt

specific

in the hydrogenation

In the Present water,

in NaY zeolite.

and selectivity

catalysts

selectivity

For this purpose

sieving

that the main

that small metallic

a hydrocarbon

siderable

has been aimed

activity.

. Ion in faujasite

cobalt

monoxide

they can be made

to show molecular

as the sole product

C3,41 showed

selectivity.

because

Nazar et al. [I] reported dispersed

of carbon

con-

on the activity

in zeolite methods

and

pores.

of excess-

were employed

to prepare

86 Changes monoxide cobalt

in kinetics,

activity

and selectivity

for the three preparation

catalyst

with zeolite different

was also made

supported

metal

loadings

chemisorption, electron

paramagnetic

programned

In addition

were prepared methods

hydrogen

investigated. technique

ion-exchanged

with

transmission

consumption,

for Comparison

catalysts

kinetic

with

loading.

include

microscopy

(EPR and FMR),

programmed

three

of metal

experiments

electron

resonance

(TPD), and temperature

of carbon

Alumina-supported

to study the influence

together

and ferromagnetic

desorption

for the hydrogenation

were

by the excess-water

ones.

The characterization

methods

(TEM),

temperature

surface

reaction

(TPSR).

CATALYSTS The three preparation carbonyl

complex-impregnation

the NaY zeolite composition

support.

had mean diameter Excess-water supports

of excess-water

)54_9(SiO2),37_,)

catalyst

technique

(T-Al203

catalysts

were

of cobalt

at a concentration

acidic

0.04 N, mixed

deionized

cobalt

water

carbonyl

until the unused

the decomposition

of cobalt

over a period temperature

in vaeuo

(loo3 Torr)

formed

in a glove

All catalysts and holding Hydrogen passing monoxide before

over a period

for another

and helium a deoxo

(Takachiho,

reaching

The different

to cobalt

of water

was dissolved

repetitions.

with

flowing

was removed.

on NaY zeolite,

cell

to room

under

manipulations

by

was dehydrated

sealed

slowly

of 2 h, and was maintained

24 h. All subsequent

The

dispersing followed

NaY zeolite

in an evacuated,

was then warmed

in

of

The extent

by physically

metal.

at

a dynamic

were

per-

box with argon-atmosphere. were reduced

at that temperature

through

in n-pentane

of the

in deionized

for 48 h at 85°C.

were prepared

The mixture

the pores

of ion-exchange

took place

Chemicals)

to a concentration

solution

carbonyl

of 12 h at -10°C.

vacuum

Co(N03)2.6H20

(pH = 4.5-4.8)

of

technique.

by the evaporation

Co(N03)2.6H20

The impregnation

by Strem

dissolved

and washed

dissolved

on or into

mean diameter

by filling

were filtered

catalysts

(Co,(CO),)

in ztac~o at 450°C.

prepared

by the number

the catalysts

complex-impregnated

supplied

(IE) and

had unit cell

by the excess-water

(5 g) and stirred

was controlled

ion exchange

carbonyl

powder

catalyst,

solution

with NaY zeolite

of ion-exchange After

and crystal

of 0.04 N, followed

hydrochloride

cobalt

Chemicals)

salt Co(N03)2.6H20

85°C for 24 h. For the ion-exchanged a weakly

(Strem

of 38 urn and was prepared

with a solution

(EW), ion-exchange

(CI) were used to introduce

The NaY zeolite

of Na54_9((A102

0.74 urn. The Co/y-A1203

water

techniques

with hydrogen

to 500°C at 2°C min

-1

for 18 h.

(Matheson,

99.999%

unit followed

99.99%

by heating

purity)

purity)

were further

by a molecular

was passed

sieve

through

purified

trap.

a molecular

by

Carbon sieve trap

the reactor. catalysts

used in the present

in the rest of the text by the symbols

in Table

investigation 1.

can be identified

87 TABLE

1

Description

of supported

Support

cobalt

catalysts.

Preparation

Metal

method

loading

Symbol

/wt%

NaY

ion-exchange

6

IE-6

NaY

ion-exchange

8

IE-8

NaY

ion-exchange

9

IE-9

NaY

carbonyl

IO

CI-10

complex-

impregnation NaY

excess-water

10

Ze-EW-IO

Y-Al203

excess-water

IO

Al-EW-10

EXPERIMENTAL

AND RESULTS

Chemisorption The adsorption

isotherms

of hydrogen

glass volumetric

adsorption

by extrapolating

the straight

irreversible reversible oxygen

titration

[6] where Co304,

uptake uptake.

consumption. uptake

higher

2 shows

together

between

cobalt

with oxygen

was calculated of reduction.

that the dispersion

for the IE catalysts

by

and Farrauto to proceed

were measured

of cobalt metal the extent

the total and

was assumed

with

and the

were measured

by Bartholomew

of the IE catalysts

Pyrex determined

to zero pressure

of the EW catalysts

to the method

were

to

by hydrogen

from the irreversible

is significantly

than that for the EW catalysts.

Hydrogen

consumption

Hydrogen system

of reduced

The dispersion

of hydrogen

Table

from the difference

of reduction

in a conventional

K. The gas uptakes

of the isotherm

of reduction

at 673 K according

extents

were measured

at 298

portion

was obtained Extents

the reaction

while

apparatus

consumption

at 500°C

to cobalt

metal

by Robertson

in order

with a volumetric

to determine

the extent

for the IE catalysts.

et al. [7]. After

for 6 h, hydrogen reduction

was measured

The apparatus

is similar

0.1 g sample was degassed

was introduced

of cobalt

apparatus

of reductions

at 500°C and hydrogen

ion was measured

from the decrease

in a closed

of cobalt

ion

to that described

at 10q4 Torr

consumption

and 500°C

for the

in pressure.

Assuming cobalt

that hydrogen is consumed stoichiometrically by the reduction of 2+ ion (Co + H2 + Coo + 2H+), the degree of reduction can be calculated

by the ratio of the amount ions in zeolite.

of hydrogen

The reduction

curves

consumed are shown

and the total amount in Figure

1.

of cobalt

88 TABLE Extent

2 of reduction

and dispersion

for supported

50.0

8.Zb

IE-6 IE-8

7.2b

60.0

IE-9

8.7b

60.0

CI-10

1ooc

1ooc

Ze- EW-10

88.gd

0.23

Al-EW-10

59.1d

2.2

aCalculated b Calculated

from the irreversible from hydrogen

uptake

decomposed

metal.

I

I

I

I

I

I

I

I

I

G

8

10

12

14

16

18

20

cobalt

catalysts

consumption

Electron

paramagnetic

The electron ferromagnetic

to 300°C.

cobalt

4

hydrogen

g-factors.

to atomic

I

Reduction

frequencies

completely

2

TIME 1

of hydrogen.

consumption.

'Assuming that cobalt carbonyl d Calculated from O2 titration.

FIGURE

catalysts-

Dispersiona/%

Reduction/%

Catalyst

cobalt

curves

of ion-exchanged

calculated

from

at 500°C.

resonance

paramagnetic

resonance on a Varian

DPPH and weak The quartz

(HR)

(EPR) and ferromagnetic

resonance

(FMR) spectra

(EPR) spectra of cobalt

E-4 spectrometer pitch were

sample

metal

at detection

used as standards

tube was designed

resonance

of cobalt were

(FMR)

ion and the

recorded

temperatures

at X-band of -150°C

for the determination

for the in situ operation.

of

89

IE - C , REDUCED

FIGURE

2

EPR and FMR spectra

FIGURE

3

(Inside

of Co metals

of Figure

in the

cobalt

at -150°C)

ion in the IE-9

(AH = IO Gauss) catalyst nearly value

where

been reduced

peak

looking

up the EPR spectra of cobalt

metal

have been reduced

cobalt

reduction.

of the FMR line-width

are shown

A sharp

exists

metal

stream

to produce

of divalent

(AH = 800 Gauss).

After

cobalt

cobalt

metal,

a very

ion (Signal

(Signal

IE catalysts

metal

(Signals

cobalt

are combined

broad and C). By

EPR peak of cobalt in signal

C. This

E and F). It can be said that

ion coexist

at 500°C for 18 h.

has

A and B) and FMR

D), it seems that the sharp

and the unreduced

This g-

the IE-9 catalyst

with the sharp peak

FMR peak of cobalt

in hydrogen

for the CI-10

and a very broad and

by Iton et al. [8] who identified

in Y zeolite.

together

in Figure

of the divalent

peak of g = 1.99

B. D i's the signal metal

of 2.17 obtained

(Signal

is also true for the other metal

catalysts.

is shown at the g value of 2.15

peak appears

ion and the very broad

before

in spectrum

to the value

spectra

the cobalt

cobalt

‘C

for the IE and CI-IO catalysts

catalyst

in a hydrogen

symmetric

AT 500 ‘C

and B (at IOO'C) are the EPR spectra

it as the FMR peak of cobalt

nearly

AT 500

DEGASSED

2). Temperature-dependence

is observed

symmetric

DEGASSED

[E-Q,

of supported

only zero valent

is similar

IE - 9,

‘C

CI-10 catalyst.

The EPR and FMR spectra 2. A (detected

AT 500

in the IE catalysts

which'

90 O

o CD

~D S. CD

~D N

% r0

% O o xD (D O

O

O O

C, "E cO

~

•r m

•

o 4-

o

o 4~

<

cD

91

The apparent

g-value

IE catalysts

reduced

and line width

did not vary with

from 20 to 300°C. The size of cobalt be small enough

the increase

metal

not to show significant

In the CI-10 catalyst, increase

of the FMR peak of cobalt

the CI-10 catalyst

temperature

has somewhat

in the detection

as shown

larger

seems

to

[8].

decreases

in Figure

cobalt metal

in the

temperature

in the IE catalysts

magnetoanisotropy

the line width

however,

in the detection

formed

metal

slightly

with

the

3. It is believed

crystallites

that

than the IE

catalysts.

Transmission

electron

Transmission scope

using

Ze-EW-10 Large

particles

catalyst

metal

inside

Temperature

programed

The catalyst quartz

tubular

by hydrogen minutes

sample

at the reduction

were carried

temperature

linearly

in cracks

crystal

particles

on a porous

at atmospheric

of carbon

quartz

rapidly.

with helium

The normal

located

immediately

Arthur

light greenish-brown

downstream

of CO was removed H. Thomas

colour

the temperature

using a gas of the catalyst.

before

Co.) which

of Ascarite

of CO2 and the formation when

under

and the

temperature programmed -1 He at 60 cc min by increasing the

(8-20 mesh,

began to appear

reduction for 30

to room temperature monoxide

out in flowing -1 . This gas stream was analyzed

due to the absorption

frit in a

After

carbon monoxide,

from the disproportionation

using Ascarite

possibly

[9].

pressure.

was flushed

and then cooled

the adsorption

with TCD (HP 5710A)

are believed

or holes created

at high temperature

is

(TPD)

operating

adsorbed

to be less

B is for the CI-IO

at 5°C min

the G.C.

change

is thought

nm. The cobalt

crystal,

temperature

Following

of reversibly

CO2 produced

catalysts

were

size were observed.

at 700°C for 18 h. The diameter

at 500°C for 18 h, the catalyst

chromatograph

of detectable

of 0.5 g was supported

desorptions

gradually

of sodium

entering

absorbs

CO2

turned

carbonate.

of the catalysts

This

reached

15OoC.

Figure about

When the IE and CI-10 catalysts

with hydrogen

desorption

of

at 500°C for 18 h.

(g 1.3 nm). Photograph

of zeolite

microreactor

a flow of helium. evacuation

A (Figure 4) is representative

in the IE and CI-IO

the zeolite

by the local destruction

the JEOL 2OOCX micro-

with hydrogen

particles

to be in the range of 2.5-5.0

to be localized

with

in the range of 20-50 nm) are located

crystals.

supercage

which was sintered

estimated

about

(diameter

of the zeolite

than that of faujasite

colour

Photograph

at 500°C for 18 h, no metal

The size of cobalt

white

was performed

that had been reduced

metal

on the outside

(TEM)

microscopy

160 keV electrons.

catalysts

cobalt

reduced

microscopy

electron

5 shows the TPD spectra

of carbon

110°C for the IE and EW catalysts,

30 to 300°C appears

monoxide.

while

for the CI-10 catalyst.

Sharp maxima

a very broad

appear

peak ranging

at from

92

TEMPERATURE FIGURE 5

TPD chromatogram

of CO adsorbed

TEMPERATURE FIGURE

6

TPSR

spectra

of supported

cobalt

("C ) on supported

( "C ) catalysts.

cobalt

catalysts.

93

I

TEMPERATURE FIGURE

Detailed

7

Temperature

lower

400

300

200

100

temperature

( ‘C )

TPSR spectra.

programmed

surface

reaction

Each of the catalyst

samples

of 0.2 g was loaded

treated

(TPSR) in the reactor

in the same way as that for the TPD studies.

After

and pre-

carbon monoxide

was adsorbed,

hydrogen was allowed to flow through the catalyst bed at a -1 . The exit gas stream, mainly methane, was analyzed every rate of 20 cc min two minutes As shown

as the reactor in Figure

very different about

6, catalysts

TPSR spectra

catalyst,

however,

range. The lower temperature to be the most active intensities negligibly temperature

peak appearing

of the lower temperature

exchange.

with

at about of carbon

higher

over a wide

have

at For

temperature

200°C has been sugge~sted monoxide

peak for the IE and CI-IO

are plotted

with the decrease

.

methods

peak appears

those for the EW catalysts.

the lower temperature

temperature

-1

for the IE catalysts.

bands appear

peaks of the IE and CI-10 catalysts

toward

500°C

at 5°C min

different

The main maximum

for the hydrogenation

small when compared

linearly

by the three

and at about

many maximum

7. For the IE catalysts,

is shifted

increased

prepared

of methane.

200°C for the EW catalysts,

the CI-10

Figure

temperature

[TO]. The catalysts

are

The lower

in more

peak becomes

detail smaller

in the extent

in and

of ion-

95

Al - EW - 10

I

I

1.8

1.9

l/T

FIGURE

9

Arrhenius

Arrhenius energies

plots

for methane

plots are shown

for methanation

X

lo3

('K'

2.0 )

formed.

in Figures

9 and IO from which

and for the conversion

activation

energies

the extent

of ion-exchange.

e’

CI-

do not vary significantly

the activation

of CO can be determined.

with

the preparation

The

methods

and

Activity Table different

3 lists the activities definitions

cant variations The turnover

is about

when the mole ratio of H2/C0

in activity frequency

than that of the IE-9 12 times

of all the catalysts

with the preparation

of the Ze-EW-10

catalyst,

higher

in terms of three

is two. There

exist

signifi-

method.

catalyst

and the turnover

at 270°C

is about

frequency

than that of the CI-IO catalyst.

1500 times of the IE-9

The values

higher catalyst

of turnover

96

Eco = 23.29

K CAL/MOLE

1.0

AI-EW

01

0.01

IF = R

t

1.8 l/T X IO3

FIGURE

10

frequency Nazaret cobalt

Arrhenius

,

20

(OK-' )

plots for CO reacted.

of the CI-IO catalyst al, [I] who made cobalt

were of the same order clusters

of magnitude

in NaY zeolite

as those of

via a bis(toluene)

precursor.

Significant depending about

,

1.9

variation

on metal

38 times

higher

than that of the IE-9

Product

in activity

loading.

is also observed

The turnover

frequency

than that of the IE-6

in the IE catalysts

of the IE-8

catalyst

but about

catalyst

is

14 times

lower

catalyst.

distribution

The hydrocarbon

products respective

are represented

molecule

and their

concentrations

fraction

of C2, C3 and C4 hydrocarbons

as the number are listed

was completely

of carbon

as weight

separated

atoms

per

percent.

into olefin

The and

97 TABLE

3

Activity

of supported

Catalyst

cobalt

catalysts

Ratea

0.017

IE-8

1.04

0.283

2.60

1210

Al-EW-10

230

2300

aRate

per weight

bRate per weight

paraffin.

of cobalt/(mole

Although

iso-butane were

of catalyst/(mole

and n-butane

Neither

oxygenated

present

study.

Table

catalyst

of iso-butylene

clusters

and n-butylene

Only iso-butylene

of hydrocarbons, The CI-IO

The hydrocarbon clusters

hydrocarbon.

were detected

olefin

catalyst

product

but the CI-IO

[I] showed catalyst

in the

fraction

and the

is the most

distribution

a pronounced

favorable

of the CI-IO

of Nazar et al. [I] are shown

in NaY zeolite

was possible,

and n-butylene

and linear

than C5 hydrocarbons

to n-butylene.

hydrocarbons.

at 230-26O"C,

set).

the ratio of the branched

and the cobalt

The cobalt olefins

59.4

were not separable.

nor higher

ratio of iso-butylene

1.53 x 10-2 290

CO/g cobalt

4 lists the selectivity

for higher

1.85 x IO-'

CO/g cat set).

the separation

used in calculating

x IO3

1.27 x lO-2

26.0

121

frequency

3.32 x 1o-4

188

Ze-EW-10

= 2).

Turnover

13.1

17.0

CI-10

(H2/C0

Rateb

IE-6

IE-9

at 270°C

in Figure

selectivity

is not so selective

11.

for C4

to C4 hydro-

carbon. The olefin

fraction

of the IE-9 catalyst

is much

smaller

than that of CI-IO

and EW catalysts. It is noted metal

loading.

IE catalysts Even when

that the olefin The amount

fraction

in the IE catalysts

of iso-butylene

in C4 fraction

decreases

with

is significant

for the

but small for the CI-10 and EW catalysts. a relatively

and EW catalysts,

large amount

C5 hydrocarbon

of C5 fraction

was not formed

is observed

for the CI-IO

in the IE catalysts.

DISCUSSION Kinetics The independence

of methanation

IE and CI-10 catalyst strong metal-support

rate on CO partial

was also observed interaction

pressure

on 1.5 wt% Co/Ti02

[II]. Since

over

catalyst,

the size of cobalt

both the showing

crystallite

in

99

f

80 -

**

FIGURE

11

the

: 297

ec

The hydrocarbon

catalysts

::

A : 230 ‘C B : 250 ‘C C 270 ‘C D 290 ‘C x : 247 =C ( Nazar

:

‘: :

: et

aI

)

(Nazar et al.1

product

distributions

of carbonyl

complex-impregnated

(HZ/CO = 2).

IE and CI-10 catalyst

the independence

is small enough

of CO partial

the small size of cobalt

pressure

to show intimate

on methanation

contact

with

rate seems

support,

to be due to

crystallite.

Activity Recently monoxide

Fu and Bartholomew

[IZJ found

on alumina-supported

reaction.

The CO turnover

in cobalt

crystallite

than three times

frequency

that the hydrogenation

catalysts decreased

size C131. Activity

metal

of ion exchange

of the

the metal

with

the decrease

IE and CI-10 catalysts due apparently

activity

is lower than the IE-9, the activity

than that of the IE-9 catalyst.

be explained

by factors

in the activity

for the ion-exchanged

is very small

size of the CI-IO

somewhat

The increase

larger

in the IE catalysts while

believed

should

significantly

is more

to the

nature.

.The size of cobalt

catalysts

of carbon

is a structure-sensitive

lower than that of the EW catalysts

structure-sensitive

the extent

cobalt

palladium

other

difference

Since

Cl43 and ruthenium

the

between

than the metal

for CO hydrogenation

irrespective catalyst

CI-IO

the two

size effect.

with acidity catalysts

of

is

was observed

1151; this was

100 ascribed

to the electron-deficient

nature

of the metals

[16-213. In the IE catalysts with hydrogen,

two Brdnsted

atom. The electronic is modified sites

Na+ cations acid

structure

free electrons

becomes

from metal

sites will

of metal

by the interaction

[22]; the metal

are replaced

2+

cations.

be produced

clusters

of the metal with electron-deficient

atoms

by Co

on the acidic

to the proton

After

reduction

for each cobalt

encaged the

support

in acidic

metal

zeolite

electron-acceptor

Strong

by the Partial

of the strongly

migration

of

acidic

OH groups

is nearly

the same.

[23-251. The extent

of cobalt

More Brdnsted more

acid sites would

ion-exchanged

IE-9)

As the metal

becomes

back-donation

decreases

Hydrogen

then complete

sites,

will

resulting

The TPSR methane

and carbon

becomes

study confirms

to lower temperature of ion-exchange).

be the most

the extent

less strongly

of

on the metal.

for the adsorption

of hydrogen.

the IE catalysts.

the intensity

is very high with

This

Therefore is consistent

of the most

the EW catalysts

With the IE catalysts (or the activity

can originate

by Sachtler

can be made

from either

the active increases

adsorbed

et al. [27] and Rabo et al.

on the origin

of methane

active

but very

low

peak shifts with

the extent

CO or surface

[2B]. No

in the present

study.

distribution

The changes are discussed

in the product

of surface

in the olefin

with

the acidity

hydrogen

olefins

The marked with

between

fraction

with different

preparation

methods

of iso-butylene

the CI-IO and EW catalysts cobalt

metal

support.

enhances

in the decrease

for the ion-exchanged

formation

in the IE catalysts

with the ion-exchange

of zeolite

with acidity

resulting

was also observed

compared

distribution

below.

The decrease is concerned

action

for the

would

electron-deficient,

adsorbs

concentration

among

with the acidity

Methane

as reported

discrimination

formed

surface

hydrogen

metal

with carbon monoxide

these arguments;

200°C

with the IE and CI-IO catalysts.

Product

more

monoxide

the highest

with

[26].

peak at about

carbon

by reduction

and its cobalt

more strongly

in an increased

the IE-9 activity with Vannice

be formed

(i.e.,

catalyst

electron-deficient.

for the IE catalysts

ion reduction

and Brdnsted

The enhanced

the hydrogenation of olefin

ruthenium

fraction.

of the primarily A similar

in Y zeolite

in C4 fraction is attributed acid sites

concentration

result

[15].

on the IE catalysts to their dual functional

[29].

101

CONCLUSIONS Three

different

impregnation catalysts

and excess

(~1)

were

preparation

compared

- ion exchange

methods water

(EW) - for cobalt

Containing

selectivity

for their activity,

carbonyl

(IE),

complex

ZeOlite

and kinetics

in CO

hydrogenation. The higher

activity

the IE and CI-10

of CO hydrogenation

catalysts

was ascribed

for the EW catalysts

to the structure

than that of

sensitive

nature

of CO

hydrogenation. The CI-10 catalyst

was the most

selective

to higher

hydrocarbons

and olefin

hydrocarbons. The reaction partial

orders

pressure

of methanation

and positive

rates for the IE and CI-10 and more

strongly

dependent

AS for the IE catalysts, the olefin with

fraction

the extent

hydrocarbons Br$nsted

for the EW catalysts

to H2 partial

catalysts

were

on H2 partial the increase

with cobalt

of ion exchange.

loading

pressure,

were

negative

to CO

but the methanation

independent

of CO partial

pressure

pressure. in the activity

were explained

Significant

seems due to the dual functional

amounts action

and the decrease

by the acidity

of isobutylene

in C4

between

metal

cobalt

in

change

and

acid sites.

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