Sulphide catalysts on silica as a support. III. x-ray photoelectron spectroscopy study

29

Applied Catcalysis, 11 (1984) 29-34 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands

SULPHIDE

CATALYSTS

ON SILICA

AS A SUPPORT.

III. X-RAY

PHOTOELECTRON

SPECTROSCOPY

STUDY

A.P. SHEPELIN,

P.A. ZHDAN,

Institute

of Catalysis,

(Received

5 July,

V.A. BURMISTROV.

Novosibirsk

1983, accepted

630090,

25 November

A.N. STARTSEV

and Yu. I. YERMAKOV

USSR.

1983)

ABSTRACT Sulphide (Ni,W)/SiO2 and (Ni,Mo)lSiOp catalysts prepared by decomposition of surface orqanometallic complexes in H?S have been studied bv X-rav ohotoelectron spectroscopy. The binding energy of efectrons in the Ni level'has been found to increase simultaneously with decrease of that on W 4f MO 3d5,2) level in bimetallic catalvsts, comoared with the corresoondina va for monometallic sulphide catalysis. This effect is ascribed to'the partial transfer of electron density from nickel atoms onto tungsten (molybdenum) atoms through the formation of mixed surface sulphides. A shift in the binding energies of Ni 2p 2 and W 4f7,2 levels in supported catalysts in comparison with those in bu 7,: sulphides is suggested to be evidence of chemical interaction between the supported sulphides and the silica surface.

INTRODUCTION In the previous

communication

of this series

of sulphide

catalysts

(Ni,W)/Si02

of anchored

complexes

in H2S, has been studied.

the catalyst

composition,

of the surface

by the decomposition

When nickel was introduced typical

of mixed

of layered

nickel-tungsten

into

crystals

(molybdenum)

was suggested.

Mainly

was found

catalysts

prepared

to cause a'shift

(B.E.) as compared

to the initial

oxide.

[5,7]. On sulphidization

ed [6], and it is claimed formation

compounds

[a]. For Ni-W catalysts

by H2S [9]. But the difference was not observed XPS technique,

sulphides

it was found

the complete was observed

possible

to distinguish

Sulphidization

possible

on catalyst

with states

is not form-

is needed

transformation

for cobalt of supp-

treatment

bulk sulphides

CO-MO catalysts

the Cogs8

energies

complies

sulphides

and individual

and unsupported

catalysts

binding

of other

cobalt

of molybdenum

in BE for supported

in [8]. For supported

lower

of the shift

the formation

of Co catalyst

[8] that the presence

into corresponding

towards

The magnitude

but does not exclude

of MoS2.

hydrotreating

were examined.

in XP-spectra

of molybdenum

sulphides

used for studying

by impregnation

of lines

the formation

orted

prepared

of structures

The formation

In recent years XPS has been widely [3-lo].

[2] the morphology

(Ni,Mo)/SiO2,

the formation

of WS2 and MoS2 was observed. sulphide

and

using the

phase from CO metal

[lOI. In the present work an electron

0166-9834/84/$03.00

state of nickel

and tungsten

0 1984 Elsevier Science Publishers B.V.

(molybdenum)

in

1

(0.8 Ni, 311 Mo/Si02

9

228.8

bThe line is widened

in comparison

with NiS and WS2.

after thiophen

hydrogenolysis

at 400°C.

(229.0)

(853.6)

853.8

229.0

229.3 853.9

33.2

32.6 (32.7)

854.1 (853.8)

aIn brackets are values of B.E. in catalysts

IN(C2H5)412CNi(WS4)21

(A-2)

3.9 Mo/Si02

(OM)

MoS2,

7

8

bulk

(B-2)

(1.0 Ni; 5.9W/Si02

6

161Jb

62.3)

62.3

62.4

61.8

62.5)

162.2

162.3 (162.5)

32.7 (32.8)

853.9

162.3

(854.0)

161.8

33.0

7.8 W/Si02

(OM)

32.2

WS2' bulk

(OM)

162.1

S2P

composition

2.4 Ni/Si02

Mo3d5/2

the samples

161.9

(A-4)

10

(B.E./eV)

W4f7/2

energya

entering

853.0

Ni2p3,2

Binding

levels of elements

853.4

index

on various

a-NiS, bulk

Catalyst

energy of electrons

(0.6 Ni,7.8W)/Si02

No.

XPS data on the binding

TABLE

31

,

33.2

853.8

1

W4f

30

40

35

FIGURE

1

Comparison

and of the reference

bimetallic origin

sulphide

compared

855

850 Birlding

of XP-spectra

860

enerqy(ev)

of bimetallic

sulphide

catalysts

(Ni,W)/Si02(0M)

compounds.

catalysts

to individual

(Ni,W)/SiO*

and (Ni,Mo)/Si02

bulk and finely

dispersed

of "organometallic"

sulphides

was studied

using XPS method.

EXPERIMENTAL Catalyst

preparation

done using a VG ESCA-3 with

and their

indexes

spectrometer

are given

with Al Kn radiation.

B.E. = 103.7 eV, was used as an internal

The position

of lines

in XP-spectra

with that of the corresponding [II-121,

in [I]. XPS measurements

levels

standard

in ultradispersed

The line of support

for spectra

of the bimetallic

were

samples

SiZp,

calibration.

was compared

monometallic

catalysts

and bulk sulphides.

RESULTS In Figure levels

NiZp3,*,

metallic noted

1 and Table MO 3dS,2,

catalysts

[Ill,

1 the values W 4f7,2

In (Ni.W)/Si02 in comparison

sulphide

of line W 4f7,2 (OM) catalysts

with

energies

origin

catalysts

is shifted

towards

this value

Similar sulphide

of its position

changes

determination

in the line position

(Ni,Mo)/SiOz

(A-4) catalysts

greater

0.3-0.4

is, however,

and bi-

As was previously

(OM), compared

0.8 eV towards

this line shifts

the B.E. in W/Si02;

W/Si02

in the

and in mono-

are compared.

than that of the B.E. in the case of WS2. The magnitude the accuracy

of electrons

and S 2p in bulk sulphides

of the "organometallic"

in ultradispersed

WSZ' the maximum

of binding

to bulk

values

eV smaller 0.5-0.6

of B.E. values

eV greater

of the line shift

is above

(+ 0.1 eV).

are observed

for MO 3d5,*.

For bimetallic

the value of the B.E. is somewhere

between

32

E,eV

A

1.0

FIGURE

2

Variation

(Ni,Mo)/SiO2

of the binding

(OM) catalysts

energies

in comparison

for bimetallic

(Ni,W)/SiD2

with monometallic

(OM) and

catalysts

and bulk

sulphides.

the values

in bulk MoS2 and ultradispersed

of B.E. Mo3d5,2

sulphide

Mo/Si02

(OM)

samples. In sulphide of electrons

(Ni,W)/SiO2

and 1.0 eV more-than

for ultradispersed 0.7 eV higher

than that

that

As for the level

mono-

in ultra-dispersed

being

and bimetallic

of levels

Ni2p3,2,

W4f,,2.

of the components

A and B) preparation at 400°C

the B.E. values

+ 0.1 eV). This value

sulphide

NilSi

(OM) catalysts

(Table

162.3 f 0.2 eV, remains

catalysts.

than that in the bulk sulphides

The position

(OM) catalysts

(about 854.0

in the bulk a-NiS.

S2p, the B.E. value,

ent of the sequence

rogenolysis

are close

on the level Ni2p3,2

of B.E. is 0.6 eV more

(series

(OM) and (Ni,Mo)/Si02

This value of B.E. is, however,

NiS, WS2 and MoS2. and S2p is practically

Mo3d5,2

supporting

and remains

unchanged

during

practically

bimetallic

unchanged

independ-

catalysts

after thiophen

hyd-

1).

DISCUSSION The significant

increase

Mo3d and S2p of sulphide

in the binding

W/Si02

(OM) and Mo/Si02

with the B.E. of the corresponding earlier

[11,12],

resulting

was ascribed

from the chemical

phenomenon of electron

takes

place

density

energy

levels

is observed

of electron

of a metal

in ultradispersed on nickel

sulphide

in the levels

(OM) catalysts,

for bulk sulphides

to a decrease

interaction

of electrons

in comparison

which was observed

density

on metal

ion with support. Ni/Si02

and sulphur

compared

atoms,

The same

(OM) catalysts:

atoms,

W4f,

a deficit

to a-NiS

33 (Table

1).

The state of metals

in mixed

sulphide

differs

from that in bulk sulphides

Ni2p3,2

level increases

B.E. of W4f7,2

considerably

bulk and ultradispersed B.E. points

levels

and Mo3d5,2

the catalysts

sulphides

composition.

atoms

of this is the formation Thiometallate

the central

feature

or thiomolybdate according

ligands

1, Table

agree with

literature

level

(Figure

1, Table

complex

is higher

complexes

contain

by strong

than that in the catalyst,

to NiS)

(compared

complexes.

(molybdenum)

active

give evidence catalysts

Another origin

important

feature

samples

in the electron

density

the support

in this case [11,12].

the support

seems

ional structures

to prevent

formed

of nickel

on

on the surthiotungstate

density

provides

catalysts

of tungadditional

and in the

was found

by Topsde

Emission

Spectros-

compound

in bimetallic

to Topsde). sulphide

catalysts

(molybdenum)

of "organometallic" ions with

on these atoms The chemical sulphides

silica.

and the B.E. of Mo3d5,2

with that in bulk WS2 and MoS2

at the high temperatures

density

state of Co in CoMo2S4

of tungsten

surface

of tungsten

compound.

value of the B.E. of W4f7,2

as compared

catalysts

(OM) and (Ni,Mo)/Si02

being

of the electron

of a new chemical

of bimetallic

by

in the thiotungstate number

to the data of MHssbauer

phase according

interaction

by a higher

in bimetallic decrease

(CO-MO-S

complex

of the Ni2p3,2

in the electron

(Ni,W)/Si02

on

elements

sulphide

level

compound

hydrodesulphurization

(in addition

density

thiotungstate

of this compound

into the catalyst

of the electronic

for the formation

is the chemical

is supported

of electron

[13]. The

the [N(C2H5)4]2[Ni(WS4)2]

increase

of nickel

transferred

explanation

structure

of chelate

of the structure

of a new chemical

phase of (CO-Mo)/A1203

sulphided

fragments

of

Ni-S-MO(W).

as the oxidation

sulphide

A synchromous

the similarity

et al. [lo]. So XPS data copy)

in their

decrease

in

M' = Fe, Co, Ni, etc.,

and IR-spectra

of a new chemical

upon introduction

for the formation

Recently,

a strong

in bimetallic

gives evidence

face of SiO2, which may contain

support

where

1). The value of the B.E. of the W4f7,2

nickel

(thiomolybdate)

the fragment

to be the same as in bimetallic

is VI [13]. Thus,

sten

to be partially

[15]. The XPS data show the position

complex

(OM), and those change

state of the constituent

analysis

2): B.E. of

ions entering

the most probable

properties

the electronic

in this compound

(OM) catalysts

of metal

is the deficit

acceptor

between

Such a synchronous density

such fragments

[14]. We have prepared

data

values

appears

with

oripin

(Figure

with NiS and NilSjO

atoms;

of type [M'(M"S4)2]2-,

1). The chemical

in thiotungstate

density

(molybdenum)

to [15] and studied

XPS (Figure

of the electron

of these complexes

atom, caused

catalysts

of these metals.

of mixed

compounds

M" = MO, W, are known, which distinguishing

in comparison

The electron

to tungsten

of "organometallic"

take on intermediate

to the redistribution

from nickel

catalysts

and monometallic

(Figure

shows the acceptor interaction

of the catalytic

levels

2). The

properties

of metal

from agglomerating

This

of

ions with

into three-dimens-

reaction,

preserving

34 the high dispersion

of sulphides

As for the electronic S2p level

is practically

metallic"

origin,

and NiS sulphides,

This increase atoms,

on sulphur

interact

with

ed in more detail

considerably

is likely

entering

support

in further

and bimetallic

the B.E. of the

samples

than that

of dispersed

of this

of "organo-

in bulk WS2, MoS2

to be due to the decreasing

The nature

publications

[2].

catalysts,

higher

the composition

surface.

catalysts

in bimetallic

the same both for mono-

but is, however,

density which

in "organometallic"

state of sulphur

electron

sulphide

interaction

particles

will be discuss-

of this series.

CONCLUSION An XPS-study

of the electron

SiO2 and (Ni,Mo)/Si02

catalysts

state of elements

incorporated

of "organometallic"

origin

in sulphide

(Ni,W)/

two main conclusions

may be drawn: 1.

Upon nickel

addition

ment by H2S at 400°C

to W/SiO2

new chemical

are formed

on the surface,

molybdate)

complexes

2.

There

denum)

with

compounds may contain

(OM) catalysts

of nickel fragments

with tungsten

and after treat(molybdenum)

of the thiotungstate

(thio-

of nickel.

is a chemical

compounds

which

(OM) and Mo/Si02

interaction

silica

of the mixed

sulphide

nickel-tungsten

(molyb-

surface.

REFERENCES 1 2 3 4 5 6 7 8 9 10 11

12 13 14 15

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