Synthesis and characterization Of K-F zeolites

Yomen ATASSI

Plan

• Definition.• Applications.• Structure of K-F zeolite.• Synthesis.• Thermal behavior.• Elemental analysis.• Characterization-XRD patterns.• Characterization-FTIR spectra.

Definition• The zeolites are defined as hydrous

aluminosilicates with complex three-dimensionalstructures .

• Its name is derived from the Greek words:“a boiling stone”.

• Discovered by Crönsted 1756 (stilbite).

• Structural formula: x n 2 2 2x yM AlO SiO mH O.

Definition-continue• Zeolite Structures are crystalline, microporous solids that

contain cavities and channels of molecular dimensions (3 Å to 10 Å ) and sometimes are called molecular sieves.

• The fundamental building block of a zeolite is a tetrahedron of four oxygen atoms surrounding a central silicon or aluminum atom (i.e., (SiO4)4– ) . From the fundamental unit, numerous combinations of secondary building units (polygons) can be formed.

Example

Definition-continue

• About 130 synthetic zeolites.• About 40 natural zeolites (Chapazite,

analcime, phillipsite)

Definition-Synthetic zeolites

• Synthetic zeolites often are cataloged by their Si/Al composition ratios, usually ranging from 1 :1 to 10:500.

• The common reactants are:– silica from sodium silicate (water-glass) or an

aqueous colloidal silica,– aluminum from sodium aluminate, alum, or a

colloidal alumina (boehmite), – sodium or potassium hydroxide.

Applications• Ion exchange. (Detergents), 70% of Z. production.

• Specific adsorption. (Separation- Purification-Molecular sieves)– Separation of n- and iso- alkans (Zeolyst Int.

CBB 901 zeolite)• Heterogeneous catalysis.

– Fluid catalytic cracking (FCC).– MTG Process (Mobil Corp. ) using zeolites

ZSM-5 and ZSM-11.– MTO Process. (methanol to light olefins

process).

Structure of K-F zeolite

• The zeolite synthesized in this work is identified as K-F Zeolite.

• Its structural formula is

• We have used kaolin as source for synthesizing this zeolite.

4 2KAlSiO 1 5H O.

Structure of K-F zeolite-continue(The pictures has been reproduced by courtesy of IZA)

Framework Type Code:EDI

Synthesis

• 1- Enrichment of clay ores.– Dispersion-decantation

• 2- Synthesis of the metakaolin.– Heating kaolin at 6000C.

• 3- Synthesis of the zeolite.– Metakaolin + concentrated KOH at 900C

during 24 hours, under continuous stirring

2p s

2v r g

9

Synthesis-continue

• Kaolin is formed by successive layers.• Each layer consists of a tertahedral sheet

and octahedral sheet .

• Kaolin is chemically inert .• By calcination process we obtain

metakaolin.

4SiO

6MO

Thermal behavior

0 200 400 600 800 1000

-80

-60

-40

-20

0Purified kaolin

DTA

Sign

al (µ

V)

Temperature (0C)

2 2 5 2 2 7 24Si Al O OH Si Al O 2H O

Mullite and cristobalite

Elemental analysis

• For Kaolin: instead of• For zeolite: instead of

2 01 2 03 7 2Si Al O 1 5H O. . . 2 2 7 2Si Al O 2H O

0 758 1 01 1 05 4K Al Si O. . . 4KAlSiO

Sample (gravimetry) (AAS) (gravimetry) (AAS)

Kaolin 48.02 41.23 10.75 N.D.

Zeolite 40.27 32.91 N.D. 22.77

2SiO 2 3Al O 2H O 2K O

Characterization-XRD patterns

10 20 30 40 50 60 700

100

200

300

400

500

600

700

800

900

1000

Q

K

K

Natural kaolin Purified kaolin

Coun

ts

angles (2θ)

Mineral DiagnosticPeak

Reflectance Power

Kaolinite 12.4 2.0

Quartz 26.8 1.5

2

Characterization-XRD patterns

10 20 30 40 50 60 700

50

100

150

200

250

metakaolin

coun

ts

angles 2θ

Characterization-XRD patterns

10 20 30 40 50 60 70

0

50

100

150

200zeolite K-F

coun

ts

angles 2θ

JCPDS file 38-216

Characterization-FTIR spectra

4000 3500 3000 2500 2000 1500 1000 5000.40

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85 kaolin

Tran

smitt

ance

(%)

wavenumber (cm-1)

Al OH

2H O

Si O Si

Al OH Al

Al O Si

Characterization-FTIR spectra

4000 3500 3000 2500 2000 1500 1000 500

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80 Metakaolin

Tran

smitt

ance

(%)

wavenumber (cm-1)

Characterization-FTIR spectra

4000 3500 3000 2500 2000 1500 1000 5000.3

0.4

0.5

0.6

0.7

0.8 K-F zeolite

Tran

smitt

ance

(%)

wavenumber (cm-1)

34201655 1440

985

615

4T O TO

23CO

2H O

2H O4TO

Thank you