Catalytic properties of metallosilicates
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言語: English
出版者: 室蘭工業大学
公開日: 2009-03-12
キーワード (Ja):
キーワード (En): metallosilicates, MFI structure,catalytic properties
作成者: 神田, 康晴, PAWLESA, Justyna, KOWALAK,
Stanislaw, 杉岡, 正敏
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http://hdl.handle.net/10258/434

Catalytic properties of metallosilicates
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volumepage range
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KANDA Yasuharu, JANISZEWSKA Ewa, PAWLESA
Justyna, KOWALAK Stanislaw, SUGIOKA
Masatoshi
Memoirs of the Muroran Institute of Technology
58
89‑95
2009‑02‑20
http://hdl.handle.net/10258/434

Mem. Muroran Inst. Tech., 58 (2008) 89㨪95

Catalytic properties of metallosilicates

Yasuharu KANDA*1, Ewa JANISZEWSKA*2, Justyna PAWLESA*2,
Stanisáaw KOWALAK*2 and Masatoshi SUGIOKA*1(Received 20 June 2008, Accepted 7 November 2008)
Abstract
Metallosilicates with MFI structure containing metal atoms such as Ni, Co, Cu, Zn-Cu and Zn in
framework have been synthesized with various metal/silicone (Me/Si) ratios (up to 0.1). The acidities
of H-form metallosilicates were evaluated by some acid-catalyzed reactions (decomposition of
2-propanol, cracking of cumene and isomerization of 1-butene). The Zn-Si catalyst showed the highest
acidities among various metallosilicates. In the metallosilicates-supported noble metal catalysts,
5%Pt/Zn-Si and 0.1%Pd/Cu-Si catalysts showed the highest activities for hydrodesulfurization of
thiophene and hydrodechlorination of chlorobenzene, respectively.
Keywords: Metallosilicates, MFI structure, Catalytic properties,

1

INTRODUCTION

The isomorphous substitution of the frameworkatoms has become very efficient method ofmodification of molecular sieves and manufacturing ofnovel materials. The valence, electronegativity, size,
nature of the introduced metal atom significantly
affects properties and stability of resulting materials.
Although the aluminosilicate zeolites remain still themost important group of the molecular sieves,according to the classification they are only one familyof metallosilicate. The MFI structure is susceptible forisomorphous substitution and quite a number ofmetallosilicates (e.g. Ti-Si, Fe-Si, B-Si, Ge-Si, Ga-Si)
have been obtained(1)(2). Some of the metallosilicatesshow the remarkable catalytic activities and highselectivities for the mild oxidation (Ti-Si)(3) and㧖1

Department of Applied Chemistry, Muroran Instituteof Technology, Muroran, JAPAN.
E-mail address: msugioka@mmm.muroran-it.ac.jp
kanda@mmm.muroran-it.ac.jp
㧖2
Faculty of Chemistry, Adam Mickiewicz University,
PoznaĔ, POLAND.
E-mail address: skowalak@amu.edu.plaromatization of hydrocarbons (Ga-Si)(4). We havereported that catalytic activities of Zn-Si modified withcations for various reactions and the effect of cations
on the activity of supported platinum catalyst forhydrodesulfurization (HDS) of thiophene(5). The
samples that showed the most pronounced acidity
appeared high activity for the HDS reaction.
Furthermore, synthesis of metallosilicates (Cu-Si,
Zn-Si and Zn-Cu-Si) and its catalytic activities for NO
reduction were studied(6). However, catalytic
examinations of metallosilicates for various reactions
are not sufficient to understand catalytic properties ofmetallosilicates.
In the present paper, we studied the synthesis andcharacterization of metallosilicates such as Ni-Si,
Co-Si, Cu-Si, Zn-Cu-Si and Zn-Si. The samples were
examined as catalysts for decomposition of 2-propanol(2-PA), cracking of cumene and isomerization of
1-butene to evaluate the acidity of metallosilicates.
Furthermore, hydrodesulfurization (HDS) of thiopheneand hydrodechlorination (HDC) of chlorobenzene overnoble metal supported on metallosilicates were
examined to obtain information of effect of support on
the catalytic activities of noble metal catalysts. In thecase of the HDS and HDC reactions, the

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Yasuharu KANDA, Ewa JANISZEWSKA, Justyna PAWLESA, Stanisáaw KOWALAK, Masatoshi SUGIOKA

EXPERIMENTAL

2. 1 Preparation of metallosilicates
The conventional hydrothermal preparation
procedure was applied for syntheses, describedearlier(5)(6). The initial gels were formed from solutionsof silica source (water glass, fumed silica, Ludox,
H2SiF6), source of metal (Zn(II), Cu(II), Co(II), Ni(II))
and tetra-n-propylammonium bromide (TPABr) as astructure directing agent (template). The inorganic
acids (H3PO4 or H2SO4) were always admitted into theinitial mixture in order to adjust the pH of the gel to thevalue of 11. The metal(Me)/Si ratio of the initial
mixture varied in the range of 0.0-0.1. The resulted
materials were washed with distilled water till pH=7-8,
then dried overnight at 75 °C and finally calcined at
450 °C to remove the template. The H+ form samples
were prepared by ion-exchange with 0.1 mol/l NH4Cl
solution. The products were characterized by means ofstandard methods such as XRD (Tur M-62 with CuKĮ),SEM (Philips SEM-515), FT-IR (Bruker, Vector 22,
KBr), UV-vis (Varian, Carry 100, diffuse reflectance),
DTA, TG (Setsys 12, Setaram, air atmosphere).
2. 2 Preparation of supported noble metal
catalysts
Supported noble metal catalysts were prepared by
an impregnation method using H2PtCl6•6H2O and
PdCl2 aqueous solution. However, PdCl2 was dissolvedin 1.0 mol/l HCl aqueous solution because PdCl2 dose
not dissolve completely in water. The amount of metalloading was as follows; Pt: 5 wt%, Pd: 0.1 wt%. After
impregnation, the samples were dried at 120 °C
followed by calcination at 450 °C for 4 h. Supported
noble metal catalysts were reduced by hydrogen at
400 °C for 1 h before the reaction.
2. 3 Catalytic activities of metallosilicates
The catalytic activities of metallosilicates were
evaluated by 2-PA decomposition, cumene cracking,
1-butene isomerization, thiophene HDS andchlorobenzene HDC. 2-PA decomposition (250 °C) andcumene cracking (400 °C) were carried out using apulse reactor. In both reactions, the catalysts (0.03 g)
were pretreated at 400 °C for 1 h in helium stream
before the reaction. We used SiO2•Al2O3 (JRC-SAL-2,
13%Al2O3) as a reference acidic catalyst. 1-butene
isomerization was carried out using a Pyrex glass
closed circulation system. 0.05 g of catalyst wasevacuated at 400 °C for 2 h. After evacuation, 1-butene
isomerization was carried out at 100°C and the initialpressure of 5.3 kPa. Thiophene HDS was carried out at
350 °C using a conventional fixed bed flow reactor
under 0.1 MPa. Reaction conditions were as follows:catalyst weight = 0.1 g, H2/thiophene = 30, W/F = 37.9

3

RESULTS AND DISCUSSION

3. 1 XRD patterns of metallosilicatesFig. 1 shows the XRD patterns of metallosilicates.
The XRD patterns indicate that synthesized products
show the MFI structure with good crystallinity ofsamples at low metal loading ((a), Me/Si = 0.01). The
formation of metallosilicate with MFI structure isdifficult at higher Me/Si ratio (Me/Si = 0.05, Zn/Si =0.03) as shown in Fig. 1 (b). The samples with higher
metal content required longer crystallization time andalways contained some admixture of amorphousmaterial. The crystallinity of the samples depends on
the kind of metal. XRD data indicate lower
crystallinity of the samples containing Zn and Co as
substituted heteroatoms.

(a) Me/Si = 0.01
Me/Si=0,01
kind of Me
Intensity [a.u.]2g•h/mol. Chlorobenzene HDC was carried out using apulse reactor at 250 °C. In all reactions, reactants andproducts were analyzed by gas chromatograph.

Co

Co

NiNi
Zn-Cu
Zn,Cu
Cu
Cu
Zn
Zn

4

14

24
2 Theta34

Me/Si=0,05(b) Me/Si = 0.05

90 －
̆－ 90
̆

kind of MeCo
CoIntensity [a.u.]

metallosilicates were used as a support for Pt and Pd
catalysts.

Ni
Ni
Zn-Cu
Zn,Cu
Cu
Cu

Zn
(0,03)
Zn (0.03)
4

14

24
2 Theta

34

Fig. 1 XRD patterns of metallosilicates.

Catalytic properties of metallosilicates

3. 2 FT-IR spectra of metallosilicatesFig. 2 shows the FT-IR spectra of metallosilicates.
The IR spectra of the products do not provide any clear
evidence on the presence of heteroatoms in theframework positions. The bands at ~ 960 cm-1 hardly
noticeable in spectra can reflect the Me-O bondvibrations(16)(17). The shoulder peaks at 960 cm-1 wereobserved in the FT-IR spectra of synthesized
metallosilicates. Instead, we have noticed aninteresting behavior of the asymmetric stretching bandsat ~ 1100cm-1. This band is attributed to the frameworktetrahedral TO4. In the case of zeolites, silicate, AlPO4
and many other zeotypes, the band is sharp and single
without any shoulders. Such shape is also seen inspectra of zincosilicate. However, in the spectra of theother series of metallosilicates under study we cannotice a splitting of this band. Perhaps, it reflects thelower homogeneity of the framework O–Me-O-Si-O
bonds than the analogous bonds (-Al-O-Si-) in zeolites.
The split in main stretching bands can be considered as
an argument supporting the framework position of theheteroatoms. If the metal atoms were sitting in
extra-framework positions, the bands should be similaras that in silicate, i.e. the single ones. These results
indicate that heteroatoms incorporated into frameworkof MFI zeolite.

aggregates. The Co-Si catalyst showed very large
crystallites which could affect their catalytic efficiency.
Furthermore, the Zn-Si showed the larger crystallites
than Cu-Si(6). Thus, low crystallinity of Co-Si and
Zn-Si (Fig. 1) were explained by high metal content in
the SiO2 framework.
3. 4 Thermal analysis of metallosilicates
The thermal analysis in air indicate that thedecomposition of organic template takes place in therange of 350 – 500 °C as shown in Fig 4. In all
samples, it is reflected in very distinctive exothermic
effect (DTA, ~390 °C) and significant weight loss (TG).
However, weight loss was hardly changed withincreasing temperature (~500 °C). This indicates thatmetallosilicates show a good thermal stability. The
exothermic effect is proceeded with an endothermic
effect at ~420 °C, which can be attributed to desorptionof template oxidation products. The differences intemperatures of these effects are significant for the
samples with the same metal loading.
3. 5 Catalytic properties of metallosilicates
3. 5. 1 Acidic properties of metallosilicates
The acidic properties of catalysts can be evaluatedby dehydration of 2-PA, which proceeds on both Lewis
and Brønsted acid sites, and cumene cracking, which
proceeds only on Brønsted acid sites. Fig. 5 shows thecatalytic activities of metallosilicates for 2-PA decomposition at 250 °C. Zn-Si catalyst showed remarkably
high dehydration activity. This indicates that Zn-Si
have higher acidity than other metallosilicates.

3. 3 SEM images of metallosilicatesFig. 3 shows the SEM images of metallosilicates.
The morphology and crystallite size of the products
depended on nature of the introduced metal. Usually
the samples of the metal rich products formed large

NiCokind of Me
960

Co
Intensity [a.u.]

Ni
10 ȝm

Zn,Cu

Cu

Zn-Cu

10 ȝm

Cu

Zn
Si
1400

1200

1000

800

-1

600

10 ȝm

Wavenumber [cm ]Fig. 2 FT-IR spectra of metallosilicates(Me/Si = 0.01).

10 ȝm

Fig. 3 SEM images of metallosilicates (Me/Si = 0.01).
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Yasuharu KANDA, Ewa JANISZEWSKA, Justyna PAWLESA, Stanisáaw KOWALAK, Masatoshi SUGIOKA

Ni/Si=0,01
Ni/Si= 0.01

413 oC

2-PA to propylene
2-PA to acetone

100
80
Conversion [%]However, the activities of other catalysts, except
Zn-Cu-Si, were very low. Furthermore, the products of
2-PA decomposition over Cu-Si catalyst were
propylene and acetone. It is known that 2-PA molecule
is dehydrogenated to acetone on metal particle and/or
basic site. It was reported that, in the 2-PA
dehydrogenation over Cu catalyst, CuO and Cu2O act
as active sites(7).

60
40
20

DTA

0
Ni

500 oC

TG
o

425 C
200

400
600
800
Temperature [oC]

DTA
480 C

0

TG

400
600
800
o
Temperature [ C]

DTA
o

480 C

TG
o

422 C
200

400
600
800
Temperature [oC]1000

Fig. 4 Thermal analysis of metallosilicates.

15
10

0

1000

Cu+Zn/Si=0,01
Cu,Zn/Si= 0.01

o

20

5

419 C

392 C

0

25

o

200

Zn

30

o

exo

Zn-Cu

1000

Cu/Si=0,01
Cu/Si= 0.01387 oC

Cu

Fig. 5 Catalytic activities of metallosilicates (Me/Si =0.01) for 2-propanol decomposition at 250 °C.

Conversion [%]

0

Co

Ni

Co

Cu

Zn-Cu

Zn

Fig. 6 Catalytic activities of metallosilicates (Me/Si =0.01) for cumene cracking at 400 °C.
Thus, small amount of extra framework CuO andCu2O species probably exist in Cu-Si catalyst, or Cu
atom in framework act as active site as well as Cu
oxides. The Co-Si catalyst showed the very low
activity for 2-PA decomposition. The order ofdehydration activities of metallosilicates was asfollows; Zn-Si > Zn-Cu-Si > Cu-Si § Ni-Si >> Co-Si.
Fig. 6 shows the catalytic activities of metallosilicates for cumene cracking. The cracking activity of
Zn-Si catalyst was remarkably higher than that of othermetallosilicates. The order of catalytic activities ofmetallosilicates for cumene cracking was almost thesame as that for 2-PA dehydration. Thus, Zn-Si catalyst
has higher Brønsted acidity than other metallosilicates.
92 －
̆－ 92
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Catalytic properties of metallosilicates100

Conversion [%]

80
60
40
20
0
2-PA

CumeneFig. 7
Catalytic activities of SiO2•Al2O3 for
2-propanol decomposition at 250 °C and cumene
cracking at 400 °C.
3. 5. 2 Catalytic properties of noble metals
supported on metallosilicates
Thiophene HDS(9)(10)(11) and chlorobenzene HDC(18)are proceeded over noble metal catalysts supported onacidic carrier. Thus, we evaluated the catalytic
activities of noble metal supported metallosilicateswith different acidities.

100
80
Conversion [%]It was reported that the Brønsted acidities ofisomorphous substituted ZSM-5 zeolites weretheoretically explained by polarization of incorporated
metal ion and this result was agreed with experimental
data(15). Thus, acidity of metallosilicate would be
explained by polarizability of incorporated metal ion.
However, since we did not evaluate the metal content
in samples, there is a possibility that the metal content
in metallosilicates differ form Me/Si ratio. Therefore,
the polarization and metal content are necessary to
explain the order of acidities of metallosilicatesevaluated by model reactions.
We used SiO2•Al2O3 as reference acidic catalyst tocompare with metallosilicates. The catalytic activities
of SiO2•Al2O3 for 2-PA decomposition and cumene
cracking were remarkable high as shown in Fig. 7.
These activities were higher than those of
metallosilicates. These results indicate that the aciditiesof metallosilicates were weaker than that of
SiO2•Al2O3.
Furthermore, it is well known that 1-butene
isomerization proceeds over both acidic and basic sites.
The order of catalytic activities of 1-butene
isomerization at 100 °C was Zn-Si > Zn-Cu-Si >>Cu-Si > Ni-Si > Co-Si as shown in Fig. 8. This result
also agreed with the results of former reactions.

60
40
20
0
Ni

Co

Cu

Zn-Cu

Zn

Fig. 8 Catalytic activities of metallosilicates (Me/Si =0.01) for 1-butene isomerization at 100 °C.
Fig. 9 shows the catalytic activities of platinum
supported on metallosilicates for thiophene HDS at
350 °C. The HDS activity of Ni-Si catalyst was
remarkably higher than those of other metallosilicates.
In the petroleum industry, sulfided Co(Ni)Mo/Al2O3
catalyst has been widely used in the HDS process(8). In
these catalysts, Co and Ni act as promoter to create
highly active “Co(Ni)-Mo-S” phase. Thus, high HDS
activity of Ni-Si catalyst can be explained bysulfidation of Ni species. However, Co-Si catalyst
showed the very low activity for thiophene HDS. The
crystallite size of Co-Si was larger than those of othermetallosilicates. Thus, since diffusion of reactant into
Co-Si catalyst is difficult, Co-Si catalyst showed low
activities for some acid-catalyzed reactions (2-PA
dehydration, cumene cracking and 1-butene
isomerization) and HDS reaction. In the supported Pt
catalysts, the order of HDS activities was as follows;
Zn-Si > Ni-Si > Cu-Si § Zn-Cu-Si > Co-Si. We havereported that Brønsted acid site plays an important rolein the highly active supported Pt HDS catalyst(9)(10)(11).
However, Pt/Zn-Cu-Si catalyst, which has higher
Brønsted acidity than other catalysts, showed lower
HDS activity than Pt/Ni-Si catalyst. Some methods ofdealumination of zeolites, such as thermal treatment,
steaming, acid treatment and SiCl4 treatment, werereported(12)(13). We used H2PtCl6•6H2O solution (pH =1) as a Pt precursor to prepare supported Pt catalyst.
Thus, in the impregnation of Pt, demetalation frommetallosilicates would be caused in the catalyst
preparation with H2PtCl6•6H2O solution. Thus, sinceacidity of metallosilicates would be changed bydemetalation, the order of HDS activities ofPt/metallosilicate catalysts was not explained simply
by the order of acidity of metallosilicates.

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Yasuharu KANDA, Ewa JANISZEWSKA, Justyna PAWLESA, Stanisáaw KOWALAK, Masatoshi SUGIOKA

Activity of metallosilicate
30

Activity of metallosilicate
50

Activity of supported Pt catalyst

40

20

Conversion [%]Conversion [%]25

Activity of supported Pd catalyst

15
10

30
20
10

5
0

0
Ni

Co

Cu

Zn-Cu

Ni

Zn

Co

Cu

Zn-Cu

Zn

Fig. 9 Catalytic activities of Pt/metallosilicates andmetallosilicates (Me/Si = 0.01) for thiophene HDS at
350 °C.

Fig. 10 Catalytic activities of Pd/metallosilicates andmetallosilicates (Me/Si = 0.01) for chlorobenzene
HDC at 250 °C.

We also examined the catalytic activities of
Pd/metallosilicates for chlorobenzene HDC at 250 °C
as show in Fig. 10. The HDC activity of Ni-Si catalyst
was the highest among those of metallosilicates.
However, in the supported Pd catalyst, Pd/Cu-Si
catalyst was showed the highest HDC activity amongsupported Pd catalysts. It was reported that Cl atom on
Cu surface in Pd-Cu/SiO2 catalyst was removed byhydrogen which is activated on Pd surface(14). Thus,
since Pd and Cu atoms in Pd/Cu-Si catalyst act as
active sites for the HDC of chlorobenzene, the HDC
activity of Pd/Cu-Si catalyst was the highest among
those of Pd/metallosilicate catalysts. However, thePd/Zn-Si and Pd/Zn-Cu-Si catalysts showed lower
HDC activities than other Pd/metallosilicates. This
result may be explained by decrease of acidity which
was caused by poisoning with Cl atom.

REFERENCES

4.

CONCLUSIONS

The metallosilicates with transition metals (Co, Ni,
Cu, Zn-Cu, Zn) in the framework can be obtained byhydrothermal crystallization and the MFI structure canbe attained at as high Me/Si ratio as 0.05. The products
show a good thermal stability. They can be modified
by cation-exchange which confirms the framework
localization of the metal atoms. The order of acidity ofmetallosilicates was as follows; Zn-Si > Zn-Cu-Si >Cu-Si > Ni-Si > Co-Si. On the other hand, in themetallosilicates-supported

noble

metal

catalysts,

5%Pt/Zn-Si and 0.1%Pd/Cu-Si catalysts showed thehighest activities for the HDS of thiophene and HDCof chlorobenzene, respectively.

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94 －
̆－ 94
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ࡔ࠲ࡠࠪ࡝ࠤ࡯࠻ߩ⸅ᇦ․ᕈ

␹↰ ᐽ᥍*1㧘Ewa JANISZEWSKA*2㧘Justyna PAWLESA*2㧘
Stanisáaw KOWALAK*2㧘᧖ጟ ᱜᢅ*1⒳‫ߩޘ‬㊄ዻ/ࠤࠗ⚛(Me/Si)Ყ(0.01-0.1)ߦ߅ߌࠆNi‫ޔ‬Co‫ޔ‬Cu‫ޔ‬Zn-Cu߅ࠃ߮Znࠍ㛽ᩰౝߦ฽߻MFI
ဳࡔ࠲ࡠࠪ࡝ࠤ࡯࠻ࠍวᚑߒߚ‫ޕ‬Hဳߩࡔ࠲ࡠࠪ࡝ࠤ࡯࠻ߩ㉄ᕈ⾰ߪ޿ߊߟ߆ߩ㉄⸅ᇦ෻ᔕ(2-ࡊࡠࡄࡁ࡯࡞ಽ⸃෻ᔕ‫ޔ‬1-ࡉ࠹ࡦ⇣ᕈൻ߅ࠃ߮ࠢࡔࡦಽ⸃෻ᔕ)ߦࠃࠅ⹏ଔߒߚ‫⚿ߩߘޕ‬ᨐ‫ޔ‬
Zn-Si⸅ᇦߪ⒳‫ᦨߡ޿߅ߦ࠻࡯ࠤ࡝ࠪࡠ࠲ࡔߩޘ‬㜞ߩ㉄ᕈ⾰ࠍ␜ߒߚ‫ޔߚ߹ޕ‬⒳‫ࠪࡠ࠲ࡔߩޘ‬࡝ࠤ࡯࠻ᜂᜬ⾆㊄ዻ(Pt, Pd)⸅ᇦߦ߅޿ߡ‫ޔ‬5%Pt/Zn-Si߅ࠃ߮ 0.1%Pd/Cu-Si⸅ᇦߪߘࠇߙࠇ‫࠴ޔ‬ࠝࡈࠚࡦߩ᳓⚛ൻ⣕⎫෻ᔕ߅ࠃ߮ࠢࡠࡠࡌࡦ࠯ࡦߩ᳓⚛ൻ⣕Ⴎ⚛෻ᔕߦኻߒߡᦨ㜞ߩᵴᕈࠍ␜ߒߚ‫ޕ‬
ࠠ࡯ࡢ࡯࠼㧦ࡔ࠲ࡠࠪ࡝ࠤ࡯࠻㧘MFI ᭴ㅧ㧘⸅ᇦ․ᕈ
*1 ቶ⯗Ꮏᬺᄢቇᔕ↪ൻቇ⑼㧘*2Faculty of Chemistry, Adam Mickiewicz University

95 －
̆－ 95
̆