Al2O3 catalysts prepared byincipient wetness

45

Applied Catalysis, 32 (1987) 45-57 Elsevier Science Publishers B.V., Amsterdam -Printed

THE EFFECT ACTIVITY

OF CATALYST

OF Ni/A1203

PREPARATION

CATALYSTS

in The Netherlands

ON CATALYTIC

PREPARED

ACTIVITY:

BY INCIPIENT

THE CATALYTIC

III.

WETNESS

Y.-J. HUANG and J.A. SCHWARZ* Department

of Chemical

Engineering

and Materials

Science,

Syracuse

University,

Syracuse, New York 13244, U.S.A. * To whom inquiries should be addressed.

(Received

4 August

1986, accepted

19 March

1987)

ABSTRACT A series of nickel catalysts supported on gamma-alumina prepared by incipient wetness procedures was characterized by Hz TPD, CO TPR, steady-state CO hydrogenation, and TPSR. The impregnant pH and nickel concentration were the solution variables used to generate five groups of catalysts ranging in weight loading from 0.9 to 6.23 wt% at initial electrolyte pH's of 1, 3 and 5. The impregnant pH and weight loading independently affected the catalytic performance. The structure, dispersion, activity, selectivity and total carbon deposited during steady-state reaction were found to correlate with the metal weight loading and the initial pH of the impregnant. The results of this study provide the preparation procedures necessary to produce and reproduce Ni/AlzD3 catalysts with In a companion paper the design of catalysts desired catalytic performance. prepared by incipient wetness techniques will be presented.

INTRODUCTION The performance preparation

of catalysts

procedures.

chain of steps are involved includes

procedure

solutions

of catalytic

precursors

weight

under

during

wet impregnation

reproduce

viable

Ni/A1203

cedures.

0166-9834/87/$03.50

activity

catalysts.

catalysts

during

wet

conditions,

based

cata-

and pH of

affect

the amount

impregnation

solely

allow

the

of Ni/A1203

and the carbon

It

[1,2].

to examine

ionic strength

C31. These findings

[I]. for C,,

deposited

during

on the solution

one to produce

and

by wet impregnation.

precursors,

the incipient

metal

as well as selectivity

to be predictable

catalysts

of metal

For example,

on the support

synthesis

variables

Ni/A1203

on their

is that a causal

and passivation

properties

concentration,

dispersion,

have been demonstrated

The impregnation

of supported

activation

step on the catalytic

adsorbed

dependent

for this fact

in our laboratory

used to form these

loading,

C2 and C3 formation

drying,

that the nickel

impregnation

reaction

in the preparation

has been developed

of the impregnation

lysts. We have found

The metal

explanation

the steps of impregnation,

A systematic effect

has been shown to be strongly

A reasonable

however,

wetness

can be achieved

technique

0 1987 Elsevier Science Publishers B.V.

by other

[43 is another

common

proim-

46

pregnation method to prepare Ni/A1203 deposition

enters

into the causal

catalysts.

during wet impregnation and it is expected the finished

catalysts

of the amount

amount

of metal

solution, cedure

deposited

On the other

hand,

concentration alumina

result

support

solution

in lower solution

[5]. Disruption

substitution incipient

than that employed

during

the genesis

gation.

Performance zation

Performance

lattice

state CO hydrogenation

of the

by the pH

and the impregnation

to form NiA1204-like

time is generally

during

prepared

prepared

catalysts

The effect

requires

is, therefore,

by incipient

before

species

not controlled

wet impregnation.

wetness.

under different

techniques

a systematic

For

investi-

the catalytic

Catalyst

characteri-

the differences

in

during incipient

conditions

of temperature-programmed

consist

reaction

and temperature-programmed

[S-S].

but is much of these factors

to examine

[Z] are used to examine

(TPD) of ~2, temperature-programmed

steady-state

of dissolution

will be influenced

of nickel

wetness. These characterization desorption

concent-

in solution

is known to

developed

of catalysts

higher

configuration

of this study

of Catalysts

procedures

[Il. This Pro-

increases

the support

The

in the

on the catalysts.

requires

pH's. The extent catalyst

During

of metal

deposited

loading

time between

of metal-supported

The objective

imptwnation.

to dry completely.

the possibility

the contact

of

design

and this fact affords

into the support

longer

Properties

of the A1203 octahedral

solutions

wetness

salt

than that

for catalyst

impregnation

such as Ni(N03)2,

used to form a Ni/A1203

in acidic

during

loading

the weight

and the contact

basis

by the concentration

weight

salt. For reagents,

of the impregnant

occur

in metal

increasing

of metal

complex

in different

is allowed

from the case of wet

no ambiguity

ration of metal

deposited

solution

is controlled

and is different

leaves

to result

of a scientific

of metal

incipient wetness the impregnation

more

to the former method.

when compared

One component for the development is the control

Here the method

in a manner

chain

(TPR) of co, steady-

surface

reaction

(TPSR) after

reaction.

EXPERIMENTAL' Five groups

of nickel

catalysts

with weight

5%, and 6.23% were prepared

by contacting

electrolyte.

the concentration

For each group

same, but the pH of the impregnation The pH for each solution addition

of acid shaken

suspension

was about

The supported

of 0.9%,

of nickel

solution

group was adjusted

5 cc of

in solution

was the

was different.

to lie in the range of 1 to 5 by suspensions

were

time for each

24 hours.

nickel

atmosphere

1.3%, 2.87%,

with

for each catalyst

[HN03] or base [NH OH]. The A1203/Ni(N0312 4 and dried at room temperature. The drying

constantly

hydrogen

loadings

2 g of gamma-Al203

nitrate

thus formed

and passivated

to yield

was decomposed Ni/A1203

and reduced

catalysts

in a

by the procedures

described

by Bartholomew

C91. For each ClroW'~al1 the catalysts

and Farrauto

were treated at the same time within a reactor to ensure the same activation conditions

were

received

size used in this study metal

profiles

The

the particles

apparatus

as those used in our earlier experimental A fresh

apparatus

catalyst

is 0.225 mm which was small enough

throughout

experimental

The average

by all the catalysts.

to ensure

uniform

ClO,llI.

used to characterize studies

particle

the catalysts

[1,21. A detailed

can be found elsewhere

are the Same

description

of the

C21.

catalyst

sample of 100 mg was dehydrated at 773 K in helium with a -1 -1 was used to for one hour. A heating rate of 5 K min flow rate of 100 cc min reach the dehydration

After

tenpfW?itUre.

the dehydration

stage

the catalyst

was

in flowing helium. The gas stream was then switched -1 at a flow rate of 30 cc min . The catalyst was brought to -1 temperature ramp and was reduced at 773 K for three hours. 773 K at a 20 K min

cooled

to room temperature

to pure hydrogen

The catalyst

was then purged

to room temperature To saturate injected

to complete

the catalyst

into a helium

then flushed

in pure helium the sample

surface,

flow whose

for 10 minutes

procedures.

40 pulses

with,helium

using a flow rate of 30 cc min-'. A H2 -1 heating rate to 773 K in a 30 cc min helium

at a 20 K min

flow rate. During

the TPD experiment,

Subsequently,

pretreatment

and cooled

of hydrogen (0.25 cc/pulse) were -1 flow rate was IO cc min . The system was

TPD was performed

monitored.

at 773 K for 5 minutes

the m/e = 2 and 4 peaks were continuously

the system was cooled

to room temperature

in flowing

helium. Carbon

monoxide

at a flow study

(40 pulses, -1

0.25 cc/pulse)

rate of 10 cc min

showed

that at such

to saturate CO pressures

low

was

injected

the catalyst carbonyl

into a helium

surface.

formation

flow

A previous

was negligible

[121. The system was flushed by helium flow followed by a hydrogen flow. The -1 flow rates were 30 cc min for IO minutes in each gas. A TPR was then performed

at a 20 K min-'

-1 .

30ccmin

heating

the TPR experiment.

sorbed

carbon

For all the catalysts,

oxides was observed.

neither

methane

nor carbon

TPO's and CO TPR's were Performed slight

shifts

Steady-state

carbon

was determined

H2/CO mixture

monoxide over

before

the results

A second

TPR was

Two series

experiments. were

of de-

at 773 K

of ~~

Except

reproducible

for

from run

was established.

hydrogenation

the temperature

reduction

monitored

amount

by helium

was observed.

steady-state

to form

c,, c2 and C3 hydro-

range from 433 to 533 K

rate of 3O cc min -1

intermediate

was purged

monoxide

of the catalyst

with a flow

in steps without experiments,

a flow rate of

a negligible

to room temperature.

in the peak temperatures,

to run and the activity

carbons

The system

one hour of hold time and cooled

performed;

with

The peaks, m/e = 2, 15, 28 and 44, were continuously

during

after

rate to 773 K in hydrogen

. The temperature

of the catalysts.

the peaks, m/e = 2, 15, 28, 30 and 42 were

For

using

a

was increased the

recorded_

steady-state

3:1

48 After

the last measurement

was flushed

with helium

for steady-state

reaction

at 533 K for 5 minutes

was made,

and cooled

the catalyst

to room temperature

in a helium flow. A TPSR spectrum obtained using a hydrogen flow rate of 30 CC -1 -1 was performed up to 773 K to determine and a heating rate of 30 K min min the amount were

of the carbon-containing

recorded

carbon

during

oxides

was observed.

of desorbed

TPSR was performed;

no methane

peak was observed.

AND DISCUSSION

in a single the group

of catalysts

at a temperature

peak shifted increased.

toward

These

lower temperature

as the weight

remained

relatively uptake

was obtained

impregnant

pH. Table

in the TPD

loading

temperature

of the catalyst

from catalysts

with

by integrating

despite

for catalysts

two peaks

of the low temperature

prepared

the same weight

loading,

shifted

toward

pH increased.

for each catalyst

constant

5%

peak had maxima

pH's, the peak temperature

as the impregnant

The H2 uptake

increasing

for catalysts

impregnant

TPD

(about

for the higher

agree with those obtained

[2,3]. However,

The total H2 uptake

5% and 6.23%),

with

temperatures

of the maxima

spectra.

the hydrogen

(2.87%,

than 773 K. For

peak had a small

The temperature

at different

temperature

higher

400 K, and the high temperature

in area and maximum

findings

impregnation

but prepared

of 0.9% and 1.3% resulted

than 773 K. For the catalysts

the difference

peak were negligible.

loadings

The lower temperature

at about

higher

loadings

at a temperature

with higher weight

in two peaks.

of total area) maximum

spectra,

with weight

peak with a peak maximum

of H2 resulted

higher

amount

The system was held at 773 K for one hour to react

A second

H*_J!z TPD of H2 from the catalysts

by wet

The peaks m/2 = 2, 15, 28 and 44

A negligible

the TPSR experiments.

off all the residues.

RESULTS

residues.

prepared

the area under the TPD at the same impregnant

the difference

with

in weight

the same weight

1 summarizes

loading.

loading

pH

However,

decreased

the total H2 uptake

with

for each cata-

lyst. The percentage

of accessible

[4], can be defined adsorption surface

to the total

each catalyst.

H/N1 = 1. Table At a fixed

for H2 adsorption

persion

upon H2 uptake

pH.

with

atoms

as dispersion

accessible

on A1203.

from the total H2 uptake -2

nm2/atm

for H2

The metal by

[I33 and an adsorption

1 also lists the surface area and dispersion ptl, the total

constant

loading,

decreases

is designated

nickel

atoms supported

site of 6 x IO

are relatively

at a fixed weight

based

of nickel

impregnant

H2 adsorption

impregnant

sites, which

can be calculated

an area for a nickel

stoichiometry

However,

number

area and dispersion

assuming

nickel

as the ratio of the surface

number

as the weight

the total number

increasing decreases

impregnant with

either

of accessible

loading

increases.

of accessible

sites for

pH. Consequently increasing

for

sites

weight

the disloading

or

49

TABLE

1

Summary

of H2-TPD

results.

loading/%

Surface

H2 uptake

Impregnant

Nickel weight

/umole

PH

(g catalyst)-'

/m*

area

Dispersiona/% based on H2

g-’

uptake 0.90

1

68.23

5.34

89.0

0.90

3

30.97

2.40

39.8

0.90

5

'a.53

1.45

24.2

1.30

1

59.93

4.69

54.2

1.30

3

30.16

2.36

27.3

1.30

5

20.83

1.63

'8.8

2.87

1

62.48

4.89

25.6

2.87

3

41.53

3.25

17.1

2.87

5

32.58

2.55

13.3

5.00

1

70.15

5.49

16.5

5.00

3

45.23

3.54

9.4

5.00

5

25.68

2.0'

6.' 11.3

6.23

1

58.40

4.57

6.23

3

37.44

2.93

7.1

6.23

5

23.89

1.87

4.5

aSee text for basis of determining

dispersion.

CO TPR TPR of CO from the high weight resulted maxima

in two comparable-sized

in the temperature

peak had maxima catalysts

loading

(0.9% and 1.3%), a major

lower temperature

formation

with

CH4 peak with maxima

peak had

loading

in the range of 530 to inthe

A trend that the peak temperatures

increasing

weight

peak temperature

for each catalyst.

and peak temperature

the TPR experiment,

5.0% and 6.23%)

(less than 5% of total area) with maxima

pH did not influence

shows the TPR spectra

(2.87%,

The low temperature

536 to 555 K. For the low weight

range of 721 to 750 K were observed.

impregnant

peaks.

range from 443 to 482 K, and the high temperature

in the range from

566 K and a very small peak

toward

catalysts

overlapping

maxima.

so the total amount

Table

Neither

loading

was observed.

significantly. 2 tabulates

Figure

The la-o

the total CH4

CO nor CO2 was observed

of CH4 produced

shifted

is assumed

during

to be the

total CO uptake. The dispersion adsorption

and surface

stoichiometry.

as a reference

area can also be calculated

The adsorption

for comparison.

Table

stoichiometry

from CO uptake

of CO/Ni

2 lists the surface

=

and an

1 was chosen

area and dispersion

for

50

c. ._ z

P

WOO_

aJ

s f0

lo 6

th)

. . r-7

aa

“0 a

s ._ P t E

(k

TEMPERATURE FIGURE

1

(a) 0.9%

CO-TPR

spectra

of catalysts

(pH = I), (b) 0.9%

with different

(pH = 3), (c) 0.9%

1.3% (pH = 3), (f) 1.3% (pH = 5), (g) 2.87% 2.87%

1 weight

loadings

and pH's:

(pH = 5), (d) 1.3% (pH = l), (e)

(pH = I), (h) 2.87%

(pH = 31, (i)

(pH = 5), (j) 5% (pH = I), (k) 5% (pH = 3), (1) 5% (pH = 5), (m) 6.23%

(pH = l), (n) 6.23%

(pH = 3), and (0) 6.23%

(pH = 5).

51

TABLE

2

Sunmary Nickel

of CO-TPR weight

results.

Impregnant

loading/%

CO uptake /umole(g

pH

catalyst)-'

Peak

Surface

Dispersiona

tempera-

area

based on CO up-

ture/K

/m2 g-'

take/%

0.90

1

80.2

-

530

3.14

52.3

0.90

3

44.2

-

544

1.73

28.8

0.90

5

33.4

-

536

1.31

21.8

1.30

1

84.4

-

543

3.30

38.1

1.30

3

58.2

-

566

2.28

26.3

-

1.30

5

65.1

540

2.55

29.4

2.87

1

60.9

480 542

2.38

12.5

2.87

3

45.1

482 549

1.76

9.2

2.87

5

73.4

481 555

2.88

15.0

5.00

1

77.5

445 549

3.03

9.1

5.00

3

73.5

449 529

2.88

8.6

5.00

5

93.5

446 543

3.61

11.0

6.23

1

149.9

457 536

5.87

14.1

6.23

3

117.2

449 545

6.93

16.7

6.23

5

121.5

465 554

4.75

11.5

aSee text for basis of determining

different

catalysts

increases

slowly

loading

increases

loading

was further

with

increasing

impregnant

as weight with

reaction

sites

in the low-temperature temperature support

lattice

dominate

increased;

the dispersion

spectra

have been

It has been proposed

the extent

isomorphic

catalysts

species.

the catalytic

CO uptake decreased based on CO uptake

identified

that the sites

as two resulting

time between

of low weight

the solid

of Y-A1203

of nickel

of nickel

is expected

It has been shown that metal-

properties

of dissolution

substitution

16-81. Thus the majority loading

from 0,9 to 2.87% and increases

peak are due to NiO, and the sites for the high-

solution,

This facilitates

pH's the CO uptake

pH was also found.

in the CO-TPR [6,71.

impregnant

from 0.9 to 5%. The trend of decreasing

[73. Due to the long contact

impregnating

weight

increases impregnant

peak are due to NiA1204-like

interactions

catalysts

pH. Consequently

loading

increasing

The two peaks observed different

At fixed

as weight

rapidly

decreases

based on CO uptake.

as the weight

more

dispersion

dispersion.

species

support

loading and

is enhanced

into the octahedral on the support

[5]. alumina

for low

to be in a form of NiAl 0 -like species 24

52 when the catalyst

in both TPO and TPR spectra.

decreases,

the extent

to be valid

dependent

of the disruption

the formation

facilitates

is found

TABLE

by incipient

wetness.

This

proposal

based on the fact that for the 0.9 and 1.3% catalysts

be valid

was evident

further

was prepared

appears

a single

As the pH of the impregnation of the A1203

of NiA1204-like

lattice

species.

for the 0.9 and 1.3% catalysts

based

peak solution

inCreaSeS.

This

to

This

hypothesis

on their

PH-

dispersions.

3

Product Nickel

distribution weight

during

Impregnant

loading/%

steady

CH4a

state CO hydrogenation

C2Hsa

C3H8a

/(10m3 molecule

pH

at 533 K-

site-'

s-l)

C/11~W3mZZ11e

r.lZbl

0.90

1

3.63

0.55

0.032

6.18

0.93

0.90

3

14.28

0.27

0.50

19.81

0.38

0.49

0.90

5

14.84

1.64

0.52

16.43

1.81

0.58

s-l)

0.055

1.30

1

4.79

0.15

0.061

6.81

0.22

0.087

1.30

3

11.36

0.55

0.56

11.76

1.26

0.58

1.30

5

13.36

0.71

0.044

8.54

0.45

0.44

2.87

1

7.17

0.69

0.175

14.72

1.42

0.36

2.87

3

7.95

1.06

0.295

14.68

1.96

0.54

2.87

5

17.79

1.10

0.109

15.75

0.97

0.097

5.00

1

17.53

1.70

0.770

31.77

3.09

1.39

5.00

3

34.93

3.31

1.140

42.93

4.06

1.41

5.00

5

52.17

4.64

0.920

29.05

2.59

0.51

6.23

1

41.45

5.11

2.030

32.37

3.98

1.58

6.23

3

46.34

8.17

3.841

19.59

3.45

1.63

6.23

5

78.35

9.67

4.511

30.84

3.81

1.78

aSite counting

based on H2 uptake.

bSite counting

based on CO uptake.

CO hydrogenation A gas mixture sis reaction. at different reaction

of H2/C0

temperatures

stoichiometry

summarizes K.

were

[2]. The majority

was CH4. The activities

c131. The site counting

tion

= 3/l was used to carry out the steady

C,, C2 and C3 formation

recorded

are reported

is based on either

during

of the product

the reaction

H2 uptake

for Cl, C2 and C3 formation

studies

from the synthesis

in terms of turn-over

for both H/Ni and CO/Ni are chosen

the activities

state synthe-

or CO uptake.

frequency The

to be 1. Table

adsorp-

3

for each catalyst

at 533

53

TABLE

4

Summary

of activation

energy

and pre-exponent

during

steady

state

CO hydro-

genation. Nickel weight

Impregnant

Activation

loadinq/%

PH

/kcal mole-'

energy

Pre-exponenta /molecule

Pre-exponentb

0.90

1

26.0

1.88 x IO8

0.90

3

26.2

8.49 x IO*

1.18 x 10'

0.90

5

25.9

6.17 x IO8

6.82 x IO8

1.30

1

26.5

3.97 x 108

5.64 x IO8

1.30

3

26.4

8.84

x IO8

9.20 x IO8

1.30

5

26.2

9.01 x lo8

5.81 x IO8

site-'

s-l

3.19 x lo8

2.87

1

27.3

1.63 x IO'

3.34 x IO'

2.87

3

26.2

7.02 x IO8

1.29 x IO'

2.87

5

26.0

8.00 x IO8

7.17 x IO8

5.00

1

27.4

2.05 x 10'

3.69 x 10'

5.00

3

27.3

2.09 x IO9

2.58 x IO'

5.00

5

26.8

2.33 x IO'

1.31 x IO9

6.23

1

29.1

3.58 x IO"

2.78 x IO"

6.23

3

28.5

2.23 x 10"

9.46 x IO'

6.23

5

28.4

3.33 x 10"

1.32 x 10"

aSite

counting

based on H2 uptake.

bSite counting

based on CO uptake.

An Arrhenius A "bend over"

plot of methanation in the methanation

plot) was observed mare

severe

prepared

for different

reaction

from 473 to 533 K by linear

activation Arrhenius products

energy

plot could

increasing

weight

centrations with

during

increasing

3 demonstrate

in structure reaction.

regression.

in our previous

energy Table

the

investigators

and pre-exponent

4 lists the

For C2 and C3 a reliable

of the weak

signals

for these

activity

increases

used in this study.

loading.

CO uptake

The activation

because

loading,

[2] and by other

for each catalyst.

not be constructed

in Table

and thus variations

C14-161.

and pre-exponent

at the temperature

The results with

systems

were also reported

impregnation

were obtained

for each catalyst.

in the slope of the Arrhenius

the lower the weight

findings

by wet

was constructed

(change

for all the catalysts;

the bend over. These

study of catalysts

activity

activity

that the methanation

Activity will

is a structure-sensitive

influence

The hypothesis

both H2 and CO surface

that methanation

was found to be valid

property

for catalysts

activity prepared

[I71

conincreases by wet

54

FIGURE

2

Plot of methanation

impregnation

activity

[2]. It was also found

prepared

by incipient

activity

at 533 K increases

to be valid

Figure

wetness.

with

at 533 K vs CO uptake.

for the case of catalysts

2 demonstrates

increasing

that the methanation

CO uptake.

The site counting

is

based on H2 uptake.

TPSR After

steady

state

reaction,

the carbon-containing wet

impregnation,

found

species

a TPSR experiment

left on the surface.

as many as three

[2]. Figure

was carried

For catalysts

types of carbon-containing

3a-o shows the TPSR spectra

wetness.

The carbon

incipient

wetness.

As many as four types of carbon-containing

observed.

At fixed

impregnant

decreases

with

of carbon

residue

decreases

the peak temperatures An average

number

with

per metal

This calculation

and the total carbon

and/or

on the H2 uptake

tabulates

the results

The trend that the average

the metal

or support

activity

loading

for incipient

surface

or decreasing

is independent

surface

number

per metal impregnant

of the average

after by wet

H2 uptake

site was

steady-state impregnation method.

is again

Table

used

with either

pH was observed. number

the amount

5 tabulates

of carbon-containing

site decreases

were

residue

loadings,

per metal

site-counting

wetness;

residues

for each catalyst.

residues

prepared

by

for the case of

pH. Table

deposition

by

were

prepared

of carbon-containing

impregnant

support

site over the catalysts

was based

complicated

At fixed weight

increasing

counting.

weight

the amount

loading.

of four carbon-containing

found to be left on the metal reaction

pH's,

weight

is more

prepared

residues

for each catalyst

incipient

increasing

inventory

out to examine

[2]. 5

in site-

residues

on

increasing

The methanation

of carbon-containing

residues.

55

liii!d L TSIK

40

20

0

100

wn

i

t

aa

8S?K

40

40-

20

20 K 0

(t 1

a0

(d)

00

.od ros

~

0

aoem

400

so0

lOSO

(9)

L!!L as,*

SO

20

20

10

K

0

20,L,

Temperature 3

(a) 0.9%

TPSR spectra

of catalysts

(pH = I), (b) 0.9%

1.3% (pH = 3), (f) 1.3%(pH 2.87%

(pH = 5),

with

LAJ W5K

10

0 . .,

FIGURE

(I)

‘SK

( K)

different

weight

loadings

and pH's:

(pH = 3), (c) 0.9% (pH = 5), (d) 1.3% (pH = I), = 5), (g) 2.87%

(pH = I), (h) 2.87%

(pH = 3), (i)

(j) 5% (pH = 1), (k) 5% (pH = 3), (1) 5% (pH = 5), (m) 6.23%

(pH = I), (n) 6.23%

(pH = 3), and (0) 6.23%

(ptl = 5).

( e)

56 TABLE

5

Summary

of TPSR

results

on each site after

and average

the steady

number

of carbon-containing

state CO hydrogenation.

residues

The site counting

left is

based on H2 uptake. Nickel

weight

Impregnant

loading

Total

temperature

deposition

PH

/umole(g

/%

C/Ni

Peak

carbon

catalyst)-'

/K

0.90

1

750.6

439 654 742 > 773 (shoulder)

5.5

0.90

3

617.4

434 643 735 > 773 (shoulder)

10.1

0.90

5

495.0

444 661

-

> 773 (shoulder)

10.3

1.30

1

751.4

456 647

-

> 773 (shoulder)

6.3

1.30

3

462.8

477 657

-

> 773

1.30

5

427.7

474 654

-

> 773 (shoulder)

2.87

1

556.8

482

623 > 773 (shoulder)

4.5

2.87

3

404.7

465 611 633 > 773 (shoulder)

4.9

2.87

5

327.2

460 615 625 > 773 (shoulder)

5.0 4.1

-

(shoulder) 7.7 10.3

5.00

1

570.0

444 630 730 > 773Ashoulder)

5.00

3

670.1

435 646

> 773 (shoulder)

7.4

5.00

5

595.3

439 586 675 > 773 (shoulder)

11.6

-

6.23

1

433.6

459 599 660 > 773 (shoulder)

3.7

6.23

3

373.8

468 585 688 > 773 (shoulder)

5.0

6.23

5

280.4

462 599 637 > 773 (shoulder)

6.0

CONCLUSION The impregnant catalytic

pH and weight

performance

therefore,

imperative

of the catalysts that when

prepared

under different

variables

are precisely

the comparison confound hand,

of activity

comparison

CO uptake

Ni/A1203

catalyst

reports

1 although will

catalyst.

activity

of the catalyst of the method

the preparation catalyst

pre-

than 100% higher it is likely

conditions

laboratories.

was found

It is,

of catalysts

the methanation

be more

reaction

that

will also

On the other

to increase

of preparation.

rule of thumb to predict

catalysts.

wetness.

the

(based on H2 up-

Furthermore,

from different

regardless

may be used as a reliable different

loading

laboratories

the same dispersion

at a pH of

affect

performance

a 0.9 wt% Ni/A1203

data under different

between

the methanation

increasing

weight

by incipient

in different

loading

to independently

the catalytic

For example,

prepared

for the lower weight

than that of the higher

prepared

have essentially

take) as a 2.9 wt% catalyst

were found

comparing

conditions stated.

pared at a pH of 5 will

activity

loading

with

Thus CO uptake

the methanation

activity

for

57 The findings A1203

catalysts

companion

paper

these catalysts

in this report by incipient

allow

wetness

[18], the development will

us to produce with desired

and reproduce catalytic

of a scientific

viable

Ni/

performance.

In a

basis for the design

of

be presented.

ACKNOWLEDGEMENT This work was supported Energy

Research

The authors

by the Division

under the Department

are indebted

to the experimental

of Chemical

of Energy

contract

to X.-K. Wang and B.T. Barrett

Science,

Office

of Basic

DE-AC02-84ER-13158. for their contributions

work.

REFERENCES

1 2 3 4

Huang, B.T. Barrett and J.A. Schwarz, Appl. Catal., 24 (1986) 241. Y. -J. Huang and J.A. Schwarz, Ap~l. Catal., 30 11987) 239. Y. -J. Huang and J.A. Schwarz, Appl. Catal., 30 (19871 255. C.N. Satterfield, Heterogeneous Catalysis in Practice, McGraw-Hill, New York, 1980. J. Mieth, Y.-J. Huang and J.A. Schwarz, manuscript in preparation. K.B. Kester and J.L. Falconer, J. Catal., 89 (1984) 380. K.B. Kester, E. Zagli and J.L. Falconer, Apol. Catal., 22 (1986) 311. W. Tsai, J.A.Schwarz and C.T. Driscoll, J. Catal., 78 (1982) 88. C.H. Bartholomew and R.J. Farrauto, J. Catal., 45 (1976) 41. M.S. Heise, Master Thesis, Syracuse University (1984). M.S. Heise and J.A. Schwarz, J. Coll. Int. Sci., 107(l) (1985) 237. P.T. Lee, J.A. Schwarz and J.C. Heydweiller, Chem. Eng. Sci., 40 (3) (1985) 509. M.A. Vannice, J. Catal., 40 (1975) 129. S.V. Ho and P. Harriott, 3. Catal., 64 (1980) 272. D.W. Goodman and J-T .Yates, Jr., J. Catal., 82 (1983) 255. Y. -J. Huang and J.A. Schwarz, 1.hE.C. Pro. Res. Dev., 26 (1987) 379. M. Boudart and M.A. McDonald, J. Phy. Chem., 88 (II) (1984) 2185. Y. -J. Huang and J.A. Schwarz, Appl. CataT., 32 (1987) 59.

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