STRUKTUR ZEOLIT SINTETIK

Zeolit ZSM 5Zeolit Y Zeolit A Zeolit MFI

Klinoptilolite Mordernite Philipsite

PORE SIZE ENGINEERING IN ZEOLITES

MODIFIKATION BYCATION EXCHANGE

PROCESS

MODIFICATION BYPREADSORPTION

OF POLAR MOLECULES

MODIFICATION OFTHE ZEOLITICFRAMEWORK

MODIFIKATION BYCATION EXCHANGE

PROCESS

MODIFICATION BYPREADSORPTION

OF POLAR MOLECULES

MODIFICATION OFTHE ZEOLITICFRAMEWORK

MODIFICATION BYCATION EXCHANGE PROCESS

1. Changing the exchangeable cations in a zeolite mayeffectively enlarge the pore openings by diminishing thecation diameter, population and/or a resiting of cationswhich are normally located near these openings

2. In the zeolite A, divalent ion exchange opens the apetureto full diameter, where as exchange with a larger univalentIon diminishes the aperture size

1. Changing the exchangeable cations in a zeolite mayeffectively enlarge the pore openings by diminishing thecation diameter, population and/or a resiting of cationswhich are normally located near these openings

2. In the zeolite A, divalent ion exchange opens the apetureto full diameter, where as exchange with a larger univalentIon diminishes the aperture size

In faujasite zeolites, the cations in the beta-cages and the double six-ring(SD6R, the hexagonal prism) (i.e., at sites SI, SI, and SII) are stericallyinaccessible to nitrogen, and so only the supercage cations (i.e., those at SIIand

Diambil dari Adsorbent Fundamental and Application, EBook, Chapter X, hal 287

Unit cell of faujasite-type (X and Y) zeolites, including cation sites.

(Top) Site II cation on six-membered oxygen ring as the basic unit on Aand X zeolites. T denotes Si or Al. (Bottom) Geometry-optimized clustermodel to represent the chemistry of Ag-zeolite.

Diambil dari Adsorbent Fundamental and Application, EBook, Chapter VII, hal 174

(a) Extra-framework cation sites in X- and Y-type zeolites. (b) Far- infrared spectrumof Na-Y with band assignments to cation sites according to [232]. (c) Experimental IR spectrum incomparison to simulated spectra calculated according to the shell model and occupancy ofdifferent cation sites. (d) Experimental spectrum in comparison to power spectra simulated by MDat occupancy of different cation sites (parts c and d from [79] with permission) halaman 67

0,05

0,1

0,15

0,2

0,25

0,3x/m

(g/g)

air

carbon dioxide

etilen

Oksigen

metanol

etana0

0,05

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1extent of K exchange

carbon dioxide

Figure 1a : Effect of Potassium exchange for sodium on the sieving properties ofzeolite-A

(1) Air at 600 Pa, 298 K, (2) metanol at 533 Pa, 298 K,(3) Karbon dioxide at 93,31 kPa 298 K,(4) Etilen pd 93,31 kPa, 298 K,(5) Etana pd 93,31 kPa, 298 K , (6) Oksigen pd 93,31 kPa, 90 K

etana

0,060,080,1

0,120,140,160,180,2

x/m(g/

g)nitrogen

N-heptana

propana

Figure 1b : Effect of Calcium exchange for sodium on the sieving properties ofzeolite-A

(1) Nitrogen 2 kPa, 77 K, (2) n-heptane at 6 kPa, 298 K,(3) Propane at 33,33 kPa 298 K,(4) Isobutane at 53,31 kPa, 298 K,

00,020,04

0 0,1 0,2 0,3 0,4 0,5 0,6extent of Ca exchange

nitrogen n-heptana propana isobutana

Iso butana

0,030,040,050,060,07

Nads (m

mol/g

)Na-mordenit

oksigennitrogen

nitrogen

Figure 2a : Adsorption isotherms of N2, O2 dan Argon at 273 K on dehydratedNa-Mordenite (723 K)

00,010,02

0 5 10 15 20 25 30 35 40

Nads (m

mol/g

)

pressure (kPa)

nitrogen

Oksigen dan Argon

0,030,040,050,060,070,08

Nads (m

mol/g

)Ba-mordenit

oksigen

Figure 2b : Adsorption isotherms of N2, O2 dan Argon at 273 K on dehydratedBa-Mordenite (723 K)

00,010,020,03

0 5 10 15 20 25 30 35 40

Nads (m

mol/g

)

pressure (kPa)

oksigennitrogen

0,06

0,08

0,1

0,12

Nads (m

mol/g

)Ca-mordenit

oksigennitrogenOksigen dan Argon

Nitrogen

Figure 2c : Adsorption isotherms of N2, O2 dan Argon at 273 K on dehydratedCa-Mordenite (723 K)

0

0,02

0,04

0 5 10 15 20 25 30 35 40

Nads (m

mol/g

)

pressure (kPa)

nitrogenOksigen dan Argon

METODA PREADSORPSIMOLEKUL POLAR

Another method for altering the molecular sieving effect of aZeolite is the preadsorption of polar molecules

If small amounts of polar molecules, such amonia,water are preadsorbed in a dehydrated zeolite, the adsorptionof second absorbate can be drastically reduced.

Figure 2 shows the effect of a preadsorption on the adsorptiveproperties of zeolite-A

Another method for altering the molecular sieving effect of aZeolite is the preadsorption of polar molecules

If small amounts of polar molecules, such amonia,water are preadsorbed in a dehydrated zeolite, the adsorptionof second absorbate can be drastically reduced.

Figure 2 shows the effect of a preadsorption on the adsorptiveproperties of zeolite-A

0,1

0,15

0,2

0,25

0,3am

ount

adsorbed

(cc/g

) Nitrogen (CH3NH2)

n-butana (CH3NH2)

Oksigen (water)

n-butana (water)

Figure 2 : Effect of preadsorption on the adsorptive properties of Zeolite-A at 298 K(1) n-butane on Ca-Zeolite-A with preadsorbed water,(2) n-butane on Ca-Zeolite-A with preadsorbed CH3NH2(3) N2 on Ca-Zeolite-A with preadsorbed CH3NH2(4) O2 on Na-Zeolite-A with preadsorbed water(5) O2 on Na-Zeolite-A with preadsorbed ammonia

0

0,05

-0,1 0,1 0,3 0,5 0,7 0,9 1,1 1,3 1,5

amou

nt ad

sorbed

(cc/g

)

amount preadsorbed (cc/g)

Oksigen (amonia)

Oksigen (water)

It is assumed that the strong interactionbetween the zeolite cation and the dipolemoment of the polar molecules producea diffusion block by clustering the polarmolecules arround the exchangeable cationsin the zeolite channels, reduced the amountof adsorption.

It is assumed that the strong interactionbetween the zeolite cation and the dipolemoment of the polar molecules producea diffusion block by clustering the polarmolecules arround the exchangeable cationsin the zeolite channels, reduced the amountof adsorption.

0,30,40,50,60,70,80,9

1

Nad

s (m

mol

/g)N2 (3) Ca

(2) Na

(1) Ba

Figure 4a : Variation of the adsorption capacity of Na, Ca and Ba-Mordenite at 273K andat equilibrium pressure of 26,6 kPa versus the dehydration temperature

00,10,20,3

273 373 473 573 673 773

Nad

s (m

mol

/g)

dehydration Temperature (oK)

0,150,20,250,30,35

Nads (m

mol/g

)O2

1

(1) Ba

(2) Na

00,050,10,15

273 373 473 573 673 773

Nads (m

mol/g

)

Dehydration temperature

23

(3) Ca

Figure 4b : Variation of the adsorption capacity of Na, Ca and Ba-Mordenite at 273K andat equilibrium pressure of 26,6 kPa versus the dehydration temperature

0,10,150,20,250,3

Nads (m

mol/g

)Ar

(3) Ba(3) Ba

(2) Na

00,050,1

273 373 473 573 673 773

Nads (m

mol/g

)

Dehidration temperature

(1) Ca

Figure 4c : Variation of the adsorption capacity of Na, Ca and Ba-Mordenite at 273K andat equilibrium pressure of 26,6 kPa versus the dehydration temperature

MODIFICATION OFTHE ZEOLITIC FRAMEWORK