29

Zeolite Based Adsorbents and Catalysts for Environmental
Applications Utilizing a Function of Hydrocarbon-adsorption
Masao NAKANO
Hiroshi OGAWA
Keiji ITABASHI

Hydrothermal stability and hydrophobicity of FAU, MOR, FER, MFI and BEA type zeolites with various
SiO2/Al2O3 ratios have been examined under a variety of conditions. Some of them were found to exhibit highstructural stability at 1000℃ in air containing water vapor and higher hydrophobicity. Adsorption-desorption
properties of toluene, ethene, and n-decane of these siliceous zeolites were studied, and suitable zeolites withmodification were proposed for hydrocarbon trap materials. A combination of the Pt-loaded zeolite with highactivity of NOx conversion and another zeolite with higher adsorption capacity of hydrocarbons for reductant
has been proposed as the effective lean NOx catalyst.

one of the numerous methods that have been

1．Introduction

suggested to meet ULEV hydrocarbon emission

Increasing emission of hazardous compounds has

requirements. It has been reported that theenvironmentalhydrocarbon traps are generally effective forprotection, especially in highly industrialized

trapping aromatics, C4＋ alkanes and alkenes, butcountries. Zeolite adsorbents and catalysts are

ineffective for methane, ethane, and ethene.

recognized as useful and hopeful materials for the

Therefore, further improvements in trapping

become an important problem forremoval of harmful substances.

performance for C2-C3 hydrocarbons are required to

It has been reported that siliceous zeolites are
effective for adsorption of organic

achieve the Super ULEV emission performance [3-5].

compounds

Since Cu-MFI had been reported to be effectivefrom paints, inks and solvents in air [1], and forfor the selective catalytic reduction of NOx even inremoval of organic contaminants in water [2].

oxygen excess conditions [6], several reports wereHigher hydrophobicity of zeolite adsorbents ispublishedrequired for these applications, since organichydrocarbons [7-9]. A new diesel catalyst using

contaminants are extremely dilute in wet gas

zeolite has been reported to reduce SOF (soluble

streams and in aqueous solutions. The use oforganic fraction) and hydrocarbon emissions at lowhydrocarbon traps to reduce cold-start emissions is

exhaust temperature [10]. Higher performance of（ 29 ）

onthelean-NOxcatalysts

with

30

TOSOH Research ＆ Technology Review Vol.45（2001）

NOx conversion may be expected by enhancing

Adsorption-desorption properties of hydrocarbons

the function of zeolites in adsorption and cracking

were measured by temperature programmedof hydrocarbon.

desorption (TPD) method. Samples were pretreated

In this paper, we report useful hydrocarbon trap

at 500℃ for 1h under the stream of dry air.

materials and lean-NOx catalysts based on some

Hydrocarbon adsorption was carried out at room

siliceous zeolites which have high hydrophobicity,temperature by flowing a model gas containing ahydrothermal stability and excellent adsorption-prescribed amount of hydrocarbon and 3％ water,

desorption properties for organic molecules even inthen, the hydrocarbon in gas phase was removed

the presence of water.

by flowing air containing 3％

water. TPD

measurements were carried out from room

2．Experimental

temperature up to 700℃ at the rate of 10℃/min

Commercially available zeolites (Tosoh Corp.) andunder the stream of air containing 3％ water, andsome zeolites prepared in a laboratory scale were

effluent gas was monitored by FID and TCD in

used in this study.

gas chromatography.

Fresh samples

were calcinedin dry air at 500℃ for 1h, andaged samples

Catalytic activities were evaluated in a fixed-bed

were treated in air containing 10％ water at aflow reactor. The gas mixture composed of NO

prescribed temperature for 5h. Hydrothermal(200ppm), hydrocarbon (1000ppmC), SO 2 (25ppm),

stability was evaluated by the measurement ofO2 (10％), H2O (7％), and N2 as a balancing gas

surface area and XRD crystallinity before and after

was passed through the catalyst at 120,000h−1 ofthe hydrothermal treatment. The surface area was

GHSV. C3H6 or n-C10H22 was used as a reactant

measured by BET one-point method of N 2.

hydrocarbon. The reactants and products were

Hydrophobicity was indicated by the adsorbed

analyzed by an on-line gas chromatograph and aamounts of H 2 O and benzene. The adsorbed

chemiluminescence NOx meter.

amount of H2O was measured by TG analysis using
each fresh sample hydrated in relative humidity of
80％ at 25℃. The adsorbed amount of benzene

3．Results and discussion
3.1. Hydrothermal stability and hydrophobicity ofsiliceous zeolites

was obtained from the adsorption isotherm at 25℃
by gravimetric method.

Measured values of surface area before and after

Table１ Surface areas and adsorbed amounts of water and benzene of various
H＋ form zeolites
Structure SiO2/Al2O3 BET surface area[m2/g]a) Adsorbed amount[wt％]
Code
ratio
Fresh
After aging
Fresh
Noteb）
H2Ob) Benzenec)
850℃ 900℃ 1000℃
FAU
14
540 540500 350
5.9
17.6
D
108
640 590
570 420
4.3
18.9
D
260
670 630
630 580
3.6
19.2
D
MOR

26
220
17
67
93

440
450
300
330
290

360
390
280
320
300

330
380
270
310
300

20
330
160
290
290

14.4
8.8
10.6
6.9
4.2

9.5
9.6
1.5
1.5
1.5

D
D
S
S*
S*

MFI

40
390
1900

350
360
360

330
360
360

320
360
350

320
350
350

9.9
4.0
3.2

9.1
8.3
9.0

S
S
S

BEA

26
37
500
1700

590
510
470
460

390
400
450
480

250
330
400
470

20
10
310
390

23.7
18.5
16.0
10.1

18.8
18.8
17.5
19.0

S
S
D*
D*

FER

a）Fresh ; calcined in dry air at 500℃ for 1h.
Aging ; treated in air containing 10％ of water at a given temperature for 5h.
b）at 20torr, 25℃.
c）at 10torr, 25℃d）preparation method ; D : dealuminated, S : synthesized, * : laboratory scale.

（ 30 ）

東ソー研究・技術報告 第45巻（2001）31

the aging, and adsorbed amounts of water andSiO2/Al2O3 ratio. On the other hand, the amount ofbenzene of each sample are summarized in Table

water apparently decreased with increasing

１, and illustrated in Fig. １ and Fig.２. Although

SiO2/Al2O3 ratio in each zeolite. These results show

the decrease of surface areas after the aging wasthat hydrothermal stability and hydrophobicity

observed with the increase of aging temperature,

increase with the increase of SiO2/Al2O3 ratio.

those of siliceous FER and MFI were almost

It is generally understood that the degradation ofmaintained even after the treatment at 1000℃. The

zeolitic structure by hydrothermal treatment is

adsorbed amount of benzene was dependent on theattributed to dealumination from the framework,

structure of zeolites, but independent of theand that structural defects (hydroxyl nests) are

30
Adsorbed Amount[％]

Surface Area[m2/g]

800
600
400

FAU(14)
FAU(108)200

FAU(260)

Water
Benzene

MOR

Water
Benzene

FER

Water
Benzene

MFI

Water
Benzene

BEA

Water
Benzene

20

10

0

0

30
Adsorbed Amount[％]

600
Surface Area[m2/g]

FAU

400
MOR(26)200

MOR(220)

20

10

0

0

30
Adsorbed Amount[％]

Surface Area[m2/g]

500
400
300
FER(17)200

FER(67)100

FER(93)

20

10

0

0

30
Adsorbed Amount[％]

Surface Area[m2/g]

600

400
MFI(40)200

MFI(390)
MFI(1900)

20

10

0

0

30
Adsorbed Amount[％]

Surface Area[m2/g]

600

400

20

BEA(26)
BEA(37)
BEA(500)
BEA(1700)

Fig.１

Aged at
850℃

10

0

0
Fresh

20

Aged at
900℃

1Aged at
1000℃

10

100

1000

10000

SiO2/Al2O3 ratio

Fig.２ Adsorbed amounts of water and benzene ofvarious zeolites.

Hydrothermal stability of various zeolites.

（ 31 ）

32

TOSOH Research ＆ Technology Review Vol.45（2001）

generated. The defects causes structural instability

shown in Fig.３B. Similar results were obtained inand lowers hydrophobicity. Consequently, the key

H-FAU(260), H-MOR(220), and H-BEA(1700). The

points of the base materials are to synthesize

maximum temperature of the desorption of thesesiliceous zeolites without structural defects and tosiliceous zeolites was near the boiling point ofeffectively remove Al atoms from the framework

toluene, 110.6℃. It is easily understood thatpreventing the generation of silanols.

hydrocarbons with a higher boiling point are
adsorbed in channels of siliceous zeolites, and so

3.2. Adsorption-desorption properties of hydrocarbons

the acid sites due to framework Al atoms are notnecessary.

There are many kinds of hydrocarbons with

Siliceouszeolites

with

high

different molecular dimensions and properties inhydrophobicity and hydrothermal stability areautomobile exhaust. It is basically important toeffective for adsorption of toluene.

select a preferred zeolite for each hydrocarbon. In
3.2.2. Ethene

this study, the adsorption-desorption properties oftoluene, ethene, and n-decane on various zeolites

The adsorbed amounts of ethene of various H-

were investigated by TPD method.

zeolites were smaller about three orders ofmagnitude than those of toluene. It is necessary to

3.2.1 Toluene

promote chemical interaction between hydrocarbon

TPD profiles of toluene on H-MFI(40) and H-

molecules and the surface of zeolites to increase

MFI(1900) are illustrated in Fig.３A and B. On theethene adsorption. The metal loading effect on

fresh sample of H-MFI(40), double peaks ofadsorption of ethene was examined with various

desorbed toluene were detected in the absence of

metal loaded zeolites, prepared by impregnationwater (Fig.３ A, b).

temperature

with metal nitrate solution and subsequent thermal

desorption peak was attributed to the adsorbed

treatments. The loading amount of impregnatedspecies at acid sites. However, the corresponding

metal component on each zeolite was adjusted topeak was hardly detected in the presence of water

2wt％. Ag was found to be most effective in(Fig.３A, a). The aged samples of H-MFI(40)various metal loaded FER(17) as shown in Fig.４

showed a single desorption peak of toluene in the[11]. The loading effect of Ag on various zeolites

presence and absence of water (Fig.３A, c and d).

was tested, and siliceous FER showed large

These results indicate that the hydrophobicity isadsorption-desorption capacity as shown in Fig.５.

enhanced by the extraction of Al atoms from the

The effect of hydrophobicity of FER is clearlyframework through the hydrothermal treatment. On

shown in TPD profiles as illustrated in Fig.６. The

the other hand, H-MFI(1900) showed enoughdesorbed amount of H2O decreased while that ofadsorption capacity of toluene in all conditions as

C2H4 increased with increasing SiO2/Al2O3 ratio ofThehigherB : H-MFI(1900)
Desorbed Amount[μmol/g]a : 319b : 523c : 362
d : 438

Intensity[a.u.]

Intensity[a.u.]

A : H-MFI(40)Desorbed Amount[μmol/g]a : 15b : 503c : 282
d : 316
d

d

c
b
a
0

100

200
300
Temperature[℃]

c
b
a
400

0

100

200
300
Temperature[℃]400

Fig.３ TPD profiles of toluene on (A) H−MFI(40) and (B) H-MFI(1900). a : fresh sample with H2O,b ; fresh sample without H2O, c ; aged sample with H2O, d ; aged sample without H2O.

（ 32 ）

東ソー研究・技術報告 第45巻（2001）

33

FER. It was confirmed that the hydrophobic zeolite

capacity of n-C10H22 in our previous study [12]. TPD

was preferable to adsorb light-hydrocarbons in

profiles of n-decane and gas chromatograms at thecoexistence of water even in the case of metal

peak temperature on H-BEA(26) are shown in Fig.

loaded zeolites. It is estimated that small pore size

７. It was measured that n-C10H22 was decomposedof FER is effective to accommodate small

to lower hydrocarbons, mainly C 3 H 6 , in thehydrocarbon molecules.

desorption processes. Fig.８ shows the effect of
SiO2/Al2O3 ratio of H-BEA on adsorption-desorption

3.2.3. n-Decane

property of n-decane. Adsorbed amounts of n-

BEA zeolite showed the largest adsorption

decane in the absence of water are almost
constant. On the other hand, the adsorbed amounts

Desorbed Amount of C2H4[μmol/g]in the presence of water increased with theincrease of SiO2/Al2O3 ratio, because of the increase60

of hydrophobicity. The decomposition rate of n-

Aged at 850℃ for 5h

decane decreased with increasing SiO2/Al2O3 ratio.
40

Namely, if the decomposition of hydrocarbons isdesired, BEA zeolites with lower SiO2/Al2O3 ratio

20

can be selected.
However, after the aging, the decomposition rate

0

Fig.４

of n-decane of H-BEA(26) decreased as shown in

H Mg Ba La Mo W Fe Ir Ni Pd Cu Ag Zn

Effect of metal loading on the adsorption
property of ethene based, on FER(17).
C3H6n-C10H22

n-C10H22
C3H6

FER(67)
Intensity[a.u.]FER(17)
MFI(2100)
MFI(40)
MOR(220)
MOR(26)■ Aged at 850℃ for 5h

BEA(26)□ FreshFresh

Aged at 600℃×500h

FAU(29)
0

Fig.５

20
40
60
80
100
120
Desorbed Amount of C2H4[μmol/g]
100Ag-loading effect of various zeolites.

200

300
400
Temperature[℃]

500

600

Fig.７ TPD profiles of n-decane and gas chromatograms
at the peak temperature on H-BEA(26).

0

100

800

C2H4

200
300
400
Temperature[℃]

500

100
without H2O
80

600

60
400

with H2O
40

200

20
with H2O

0

600

10

100

1000

Decomposition Rate[％]

H2O

H2O
[mmol/g]
1.38(□)
0.48(■)

Desorbed Amount[μmol/g]

Intensity[a.u.]

Ag/FER(17)Ag/FER(67)C2H4[μmol/g]
63(◇)
105(◆)

0
10000

SiO2/Al2O3 ratio

Fig.６

TPD profiles of (◇/◆) C2H4 and (□/■)H2O on
Ag/FER(17) and Ag/FER(67).

（ 33 ）

Fig.８

Effect of SiO2/Al2O3 ratio of H-BEA zeolite on
the adsorption-desorption property of n-C10H22.

34

TOSOH Research ＆ Technology Review Vol.45（2001）

Fig.７. The total amount of desorbed hydrocarbons

thermal treatment result in the enhanced durability

was almost the same in fresh and aged samples.

for cracking activity of hydrocarbons.

The shift of the desorption peak to higher
temperature in the aged sample is due to the3.3. Lean-NOx

catalyst

using

adsorbedhydrocarbons on zeolite

decrease of decomposition because of the decreaseof acid sites caused by dealumination throughLean-NOx catalysts have to possess at least the

aging. Fig.９ shows the total desorbed amounts

following two functions, NOx adsorptive-activation

and

peak

and hydrocarbon adsorptive-activation, because NOxtemperature of n-C10H22. It has been reported thatis catalytically reduced by hydrocarbons. In our

the acidic properties of zeolites after impregnation

previous study [14], a Pt-loaded Al 2O 3 catalyst

with phosphoric acid and subsequent thermal

showed high durability but low activity, because

treatment were changed by dealumination, fomation

Al2O3 adsorbed only small amount of hydrocarbons.

of aluminun phosphates and polyphosphoric acids

The Pt-loaded zeolites generally show higher[13]. The decrease of decomposition rate of H-

conversion of NOx and higher selectivity to N2, but

BEA(37) could be improved by impregnation withlower durability than that of Pt-loaded Al2O3. Pt-(NH4)2HPO4 and subsequent thermal treatment asloaded FER(17) catalyst showed high conversion ofthedecomposition

rates

at

the

shown in P/BEA(37) in Fig.９. It has beenNOx, high selectivity to N2, and good durability insuggested that the acid sites produced by

the case with C3H6, but low conversion of NOx in

impregnation with (NH 4) 2HPO 4 and subsequent

the case with n-C 10 H 22 . These results were
attributed to the small pore size of FER. The

Desorbed Amount of n-C10H22[μmol/g]

hybrid catalyst physically mixed with Pt-loaded
FER(17) and P/BEA(37) was studied in order to□Fresh ■Aged at 600℃

600

19

17
400

68

obtain both high activity and high durability with83

82

n-C10H22. There were large difference in the NOx
conversion with n-C 10H 22 between the Pt-loaded86

FER(17) catalyst and the hybrid one as shown in
200

Fig.10. The NOx conversion could be improved bymixing with P/BEA(37), which has high adsorption

0
H-BEA(26)Fig.９

H-BEA(37)capacity and cracking activity of n-C 10 H 22 as

P-BEA(37)described above.

Adsorption-desorption properties of n-C10H22 on
various BEA zeolites. Numerals in figure referto the decomposition rates of n-C10H22.

4．Conclusion
Fundamental properties of some siliceous zeolites

Conversion of NOx[％]

100

were studied, and adsorptive and catalytic

80

properties

60

b

those

were

investigatedforenvironmental applications. Some siliceous zeolites

cshowed high hydrothermal stability even at the

a

40

of

temperature of 850-1000℃, and high hydrophobicity.
20

Hydrocarbons with high boiling point such as

0toluene and n-decane could be adsorbed in
0

100

200
300
400
Temperature[℃]

500

600

channels of siliceous zeolites and be desorbed

Fig.10 Transient NOx conversions on a ; fresh Pt/FER(17),b ; fresh hybrid catalyst and c ; aged hybrid catalyst
at 600℃ for 50h. Feed composition : 200ppm NO,
1000ppmC n-C10H22, 25ppm SO2, 10％ O2, 7％ H2O,
balance N2 ; GHSV=120,000hr−1.

around their boiling points. Promoting chemicalinteractions between the hydrocarbons and thesurface of zeolites was effective to adsorb lighthydrocarbons with lower boiling point. Ag-loaded（ 34 ）

東ソー研究・技術報告 第45巻（2001）

35

FER, especially siliceous and hydrophobic FER,

〔６〕M. Iwamoto, H.Furukawa, Y. Mine, F. Uemura,showed excellent performance for adsorption of

S. Mikuriya, S. Kagawa, J. Chem. Soc., Chem.

ethene. The hybrid catalyst composed of Pt loaded

Commun., 1272 (1986)

FER(17) and P/BEA(37) showed higher activity〔７〕Y. Traa, B. Burger, J. Weitkamp, Microporousand Mesoporous Materials, 30, 3（1999）

and durability for NOx conversion with n-C10H22.
It was shown that some siliceous zeolites were

〔８〕S. Matsumoto, K. Yokota, H. Doi, M. Kimura,useful for hydrocarbon trap materials and lean-NOx

K. Sekizawa, S. kasahara, Catal. Today 22,

catalyst materials in automobile emission control. It

127（1994）

is also expected that siliceous zeolites will be used

〔９〕A. Takami, T. Takemoto, H. Iwakuni, F. Saito,

for various environmental applications such as

K. Komatsu, SAE Technical Paper 950746, 526

adsorption of volatile organic compounds (VOCs)（1995）

emitted from numerous sources and for removal of〔10〕H. Ueno, T. Furutani, T. Nagami, N. Aono, H.
Goshima, K. Kasahara, SAE Technical Paper

contaminants from water.

980195, 91（1998）

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Zeolite, 143（1997）(Ed.), Fundamentals of Adsorption, Kluwer
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482（1996）〔２〕M. A. Anderson, Environ. Sci. Technol., 34, 725〔13〕J. Caro, M. Bulow, M. Derewinski, J. Harber,
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Zibrowius, J. Catal., 124, 367（1990）〔３〕J. L. Williams, M. D. Patil, W. Hertl, SAE

Technical Paper 960343, 57（1996）〔14〕H. Ogawa, H. Aoyama, K. Ariga, Y. Ito, M.

〔４〕M. R. Montierth, D. F. Thompson, Fortschr Ber

Nakano,VDI Reihe 12, 443（1996）

Proc.

SAE Technical Paper 970741, 27（1997）者

氏名 中 野 雅 雄

Meeting

Association of Zeolite, 98 （1999）〔５〕T. H. Ballinger, W. A. Manning and D. S. Lafyahs,

著

15th

著

者

氏名 小 川著者

宏

氏名 板 橋 慶 治

Masao NAKANO

Hiroshi OGAWA

Keiji ITABASHI

入社 昭和58年４月１日

入社 平成３年４月１日

入社 昭和45年４月１日

所属 南陽研究所

所属 南陽研究所

所属 南陽研究所

ゼオライトグループ

ゼオライトグループ

ゼオライトグループ

グループリーダー

主任研究員

主席研究員

主席研究員

（ 35 ）ofJapan