Abstract— Prepared zeolite NaX, faujasite was successfully

synthesized from hydrogel solution which prepared by using pure silica powder, aluminum hydroxide, sodium hydroxide and distilled water precursors under hydrothermal condition at atmospheric pressure. Before preparing of hydrogel solution, the amount of raw materials which used in resulting hydrogel with appropriate mole ratio was calculated. In this study, the effect of various factors (agitation temperature, agitation time, aging time and temperature and crystallization time) were extensively investigated. The results show that the product samples for this research work can be prepared with a molar composition of (4.2Na2O: Al2O3: 3SiO2:180H2O) by agitation at room temperature for 1 hr. The mixture was aged for one day at the same temperature, crystallization at 100ºC for 6 hrs. The morphology of SEM image for zeolite (NaX,faujasite) is octahedron shape and the cation exchange capacity (CEC) of the product zeolite NaX, faujasite was found to be 4.9 meq/g.

Keywords—cation exchange capacity, crystallization, faujasite , zeolite NaX

I. INTRODUCTION

EOLITES are crystalline hydrated aluminum silicates with a framework structure containing pores that are occupied

by water and by alkali and alkaline earth cations. Due to their high cation-exchange ability as well as molecular sieve properties, natural zeolites (cheap materials, easily available in large quantities in many parts of the world) show special importance in water and gas purification, adsorption and catalysis [3].

Zeolites are natural minerals that mined in many parts of the world. Most zeolites used commercially are synthetically produced. In hydrocarbon conversion catalysis, these structures of principal interest are the large-pore zeolites type X, Y, L, omega and mordenite [4].

Faujasite was discovered in 1842 by Damour and is named for Barthélemy Faujas de Saint-Fond, a French geologist and volcanologist. The faujasite framework consists of sodalite cages which are connected through hexagonal prisms. The pores are arranged perpendicular to each other. The pore,

Mie Mie Han Htun 1. Mi Mi Han Tun 1 is with the

MandalayTechnology University , Myanmar (corresponding author to provide phone: +9509402575334; e-mail:mimihantun@gmail.com).

Mu Mu Htay 2. was with West Yangon Technological University, Myanmar . She is now with the Department of Chemical Engineering, (e-mail: mu.htay3@gmail.com).

May Zin Lwin 3. is with the Chemical Engineering Department, Mandalay Technological University of Myanmar, (e-mail:mayzinlwin80).

which is formed by a 12-membered ring, has a relatively large diameter of 7.4 Å. The inner cavity has a diameter of 12 Å and is surrounded by 10 sodalite cages. The unit cell is cubic with a length of 24.7 Å.

Faujasite is synthesized as other zeolites from alumina sources such as sodium aluminate and silica sources such as sodium silicate. Other alumosilicates such as kaolin are used as well. The ingredients are dissolved in a basic environment such as sodium hydroxide aqueous solution and crystallized at 70°C to 300°C (usually at 100°C). After crystallization, the faujasite is sodium form and it must be ion exchanged with ammonium to improve stability. The ammonium ion is removed later by calcination which renders the zeolite in its acid form. Depending on the silica-to-alumina ratio of their framework, synthetic faujasite zeolites are divided into X and Y zeolites. In X zeolites that ratio is between 2 and 3, while in Y zeolites it is 3 or higher. The negative charges of the framework are balanced by the positive charges of cations in non-framework positions. Such zeolites have ion-exchange, catalytic and adsorptive properties. The stability of the zeolite increases with the silica-to-alumina ratio of the framework. It is also affected by the type and amount of cations located in non-framework positions [1].

Zeolite X faujasite-type is employed to scavenge the large hardness ions such as hydrated magnesium and iron while A- type zeolite efficiently removes calcium. Today, Zeolite X faujasite-type is used commercially as ion exchanger for water treatment. This zeolite has a high ion exchange capacity (equal to zeolite A) and large pore size which enables it to exchange all significant hardness ions, including hydrated magnesium and iron ions. Zeolite X has a large pore size (7.3Å) and a high CEC (5meq g-1), which make this zeolite as an interesting molecular sieve and a high-cation exchange material [2].

II. MATERIALS AND METHODS

A. Materials

In this study, silica source solution was prepared by using powder form of pure silica (solid amorphous form), deionized (DI) water and sodium hydroxide (analar grade). Alumina trihydroxide (65% Al2O3), deionized (DI) water and sodium hydroxide (analar grade) were also used to prepare alumina source solution. These two source solutions were needed to get synthesis (hydrogel) for the synthesis of zeolites.

Preparation of Zeolite (NaX,Faujasite) from Pure Silica and Alumina Sources

Mie Mie Han Htun1, Mu Mu Htay 2 and May Zin Lwin3

Z

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B. Preparation of Zeolite NaX,Faujasite by using Hydrogel Process

In order to prepare synthetic zeolite by hydrogel process, hydrogel solution (synthesis gel) was prepared by agitation of silica and alumina source solutions with electric stirrer at 250rpm. Hydrogel process for synthetic zeolite was performed as follows. The hydrogel solution which has a molar composition of 4.2Na2O: Al2O3: 3SiO2: 180H2O and the pH range of 13-14 was aged at various temperatures for a desired period to form the nucleation for crystal growth. Then the resulting hydrogel was transferred into the polyethylene container and put into oven to hydrothermally crystallize. In order to prevent contamination, plastic containers such as polypropylene were used for the preparation of all solutions, for the reaction mixture, and for the crystallization at 100˚C. Crystallization was carried out for various times. After completing crystallization, the resultant precipitate was separated from the mother liquor by filtration. The crystalline mass was then washed with deionized water until a pH range of 9-10 and dried at 100˚C for 12-16 hrs.

In the preparation of zeolite (NaX, faujasite), the important parameters such as agitation time, agitation temperature, aging time, aging temperature, crystallization time and crystallization temperature on the zeolite preparation were investigated.

C. Characterization of Prepared Zeolite NaX, Faujasite

Prepared samples were characterized by four ways. These were identified by XRD, investigation of the morphologies were carried by SEM , silica and alumina content were determined by XRF and then the prepared zeolite X were identified by Fourier Transform Infrared Spectrophotometer (FTIR) to know the typical bands in the mid and far infrared. to help you gauge the size of your paper, for the convenience of the referees, and to make it easy for you to distribute preprints.

III. RESULTS AND DISCUSSION

A. Effect of Agitation Temperature on Zeolite Formation

The effect of agitation temperature on zeolite formation is described in Table I. The XRD patterns of the favourable samples are shown in Fig.1, Fig.2 and Fig.3.

TABLE I

EFFECT OF AGITATION TEMPERATURE ON ZEOLITE FORMATION Gel composition: 4.2 Na2O:Al2O3: 3SiO2: 180H2O Agitation time: 1 hr Aging time: 1 day, room temperature Crystallization temperature, time: 100ºC, 8hr

Sample No. Agitation Temperature

Zeolite Phases and Other Synthesis Product

Z-1 32 ºC Faujasite, Zeolite P

Z-2 50 ºC Zeolite zh

Z-3 95 ̊C Zeolite(Na3Al3Si5O166H2O)

Fig.1 The Effect of Agitation Temperature on XRD Pattern of Prepared Zeolite X; Agitation Temperature at 32ºC

Fig.2 The Effect of Agitation Temperature on XRD Pattern of

Prepared Zeolite X; Agitation Temperature at 50ºC

Fig.3 The Effect of Agitation Temperature on XRD Pattern of

Prepared Zeolite X; Agitation Temperature at Steam Temperature

In this investigation of the effect of agitation temperature, it can be observed that when the hydrogel solution was agitated at room temperature for 1hr, the zeolite formation was found faujasite with zeolite P. Then the temperature was increased to 50ºC and kept at temperature for 1hr, the product zeolite was formed zeolite zh. When the temperature was increased to steam temperature and kept at temperature for 1hr, it was found that it posses the formula of Zeolite (Na3Al 3Si5O16.6H2O). From the XRD patterns in Fig.1, the broad peaks at 2θ values 18º, 27º and 36º were confirmed the faujasite. In Fig.2, the broad peaks at 28º, 37º and 40º 2θ values were shown the zeolite zh for sample Z-2. Figure 3 show the XRD pattern of zeolite for sample Z-3.

B. Effect of Agitation Time on Zeolite Formation

The effect of agitation time on zeolite preparation was studied by varing agitation time from 15 min, 30 min, 1hr, 1.5hr and 2hrs. It was shown in Table II. From these investigations, it was found that the agitation time 15min was formed zeolite P as major product and faujasite is minor product. Of the agitation time increased from 30min to 2hrs while other conditions were the same, the products were formed faujasite as major product and zeolite P is minor product.

O. Faujasite (Na2O.Al2O3.2.4SiO2.6.7H2O) ∆. Zeolite, NaP (Na2O.Al2O3 .3.3SiO2 .12H2O)

O. Zeolite (Na3Al 3Si5O16 6H2O)

O. Zeolite zh (Na2O.Al2O3.2.1SiO2. H2O)

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From these results, the agitation time for sample A-3 (1hr) is the highest peak intensity and yield percent.

TABLE II

EFFECT OF AGITATION TIME ON ZEOLITE FORMATION Gel composition: 4.2 Na2O:Al2O3: 3SiO2: 180H2O Agitation temperature: room temperature Aging time: 1 day, room temperature Crystallization temperature, time: 100ºC, 8hr

Sample No. Agitation Time Zeolite Phases and Other Synthesis Product

A-1 15 min Zeolite P, Faujasite

A-2 30 min Faujasite, Zeolite P

A-3 1 hr Faujasite, Zeolite P

A-4 1.5 hr Faujasite, Zeolite P

A-5 2 hr Faujasite, Zeolite P

500

1000

1500

2000

500

500

500

500

1000

1000

1000

1000

1500

1500

1500

1500

2000

2000

2000

2000

15 20 25 30 35

Intensity Count ( a.u)

Two-Theta(deg) F-Faujasite and P-Zeolite P

Fig.4 The Effect of Agitation Time on XRD Pattern of Prepared Zeolite X; Agitation Time for Samples A-1 (15min), A-2 (30min), A-

3 (1hr), A-4 (1.5hr) and A-5 (2hr)

Therefore, the agitation time 1hr was selected for this research. From the XRD patterns in Fig. 4, the broad peaks at 2θ values 18º, 27º and 36º were confirmed the faujasite. According to this experiment, it was found that the higher the agitation temperature can give the disappearance of faujasite zeolite.

C. Effect of Aging Time on Zeolite Formation

The effect of aging time on zeolite preparation was also investigated. It was shown in Table III. The XRD patterns of the favorable samples are shown in Fig. 5 and Fig. 6. According to the XRD results, the aging time was 24hrs for the zeolite formation of faujasite and zeolite P with higher intensity. Without aging step, the prepared zeolite was formed faujasite and zeolite A. The aging time, 8hrs and 16 hrs could give the formation of zeolite. In Fig. 5, the broad peak at 18º, 21º, 23º and 36º give the highest peak intensity of faujasite type zeolite. In Fig. 6, the broad peak at 6º, 11º, 28º was

formed faujasite and 8º, 16º, 19º was formed zeolite A. Therefore, the optimum aging time was 24 hrs for this research.

TABLE III EFFECT OF AGING TIME ON ZEOLITE FORMATION

Gel composition: 4.2 Na2O:Al2O3: 3SiO2: 180H2O Agitation time, temperature: 1 hr, room temperature Aging temperature: room temperature Crystallization temperature, time: 100ºC, 8 hr

Sample No. Aging Time Zeolite Phases and Other Synthesis

Product

A-3= B-1 1 day Faujasite, Zeolite P

B-2 Without aging Faujasite, Zeolite A

B-3 8 hr ∞-Al2O3

B-4 16 hr ∞-Al2O3

Intensity Count(a.u)

Fig.5 The Effect of Aging Time on XRD Pattern of Prepared Zeolite

X; Aging Time for Sample B-1(1day)

Fig. 6 The Effect of Aging Time on XRD Pattern of Prepared Zeolite X; Without Aging Step for Sample B-2

D. Effect of Aging Temperature on Zeolite Formation

The effect of aging temperature on zeolite preparation was studied by varing agitation temperature from 32ºC, 40ºC and 50ºC. It was shown in Table IV . Figure 7 and Fig. 8, it was observed that when the starting slurry was aged at room temperature for 24hrs, the formation of product zeolites were formed as faujasite and zeolite P. Then the temperature increased to 40ºC and kept at this temperature for 24hrs, the major product was only alumina. When the aging temperature was increased to 50ºC and kept at this temperature for 24hrs, it could give the formation of zeolite Y. Therefore, room temperature (32ºC) is become the optimum aging temperature for the formation of zeolite.

A1

A2

A3

A4

A5

O. Faujasite (Na2O.Al2O3.2.4SiO2.6.7H2O) ∆. Zeolite, NaP (Na2O.Al2O3 .3.3SiO2 .12H2O)

O. Faujasite (Na2O.Al2O3.2.4SiO2.6.7H2O) ∆. Zeolite, Na A (Na2O.Al2O3 .2SiO2 .4.5H2O)

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TABLE IV EFFECT OF AGING TEMPERATURE ON ZEOLITE FORMATION

Agitation time, temperature: 1 hr, room temperature Aging time: 1 day Crystallization temperature, time: 100ºC, 8hr

Sample No. Aging Temperature

Zeolite Phases and Other Synthesis Product

B-1= C-1 32 ºC Faujasite, Zeolite P

C-2 40 ºC ∞-Al2O3 C-3 50 ºC Zeolite Y

Therefore, room temperature (32ºC) is become the optimum aging temperature for the formation of zeolite.

Fig. 7 The Effect of Aging Temperature on XRD Pattern of Prepared

Zeolite X; Aging Temperature at 32ºC for Sample C-1

Fig. 8 The Effect of Aging Temperature on XRD Pattern of Prepared Zeolite X; Aging Temperature at 50ºC for Sample C-3

E. Effect of Crystallization Time on Zeolite Formation

From the above investigation, sample A-3 was selected and the effect of crystallization time on zeolite formation was investigated. The results are listed in Table V. The XRD patterns of the favorable samples are shown in Fig. 9, Fig. 10, Fig. 11 and Fig. 12. According to the XRD results, when the crystallization time for 16 hrs the product zeolite were formed faujasite, zeolite zh and zeolite A. Then the crystallization time was decreased from 8 hrs to 4hrs.

TABLE V EFFECT OF CRYSTALLIZATION TIME ON ZEOLITE FORMATION

Agitation time, temperature: 1 hr, room temperature Aging time, temperature: 1 day, room temperature

Sample No.

Crystallization Zeolite Phases and Other Synthesis Product

Temperat

ure Time

C-1=D-1 100 ºC 8 hr Faujasite, Zeolite P

D-2 100 ºC 6 hr Zeolite X(Na), Faujasite

D-3 100 ºC 4 hr Unnamed Zeolite

D-4 100 ºC 16 hr Faujasite, Zeolite zh, Zeolite A

Fig. 9 The Effect of Crystallization Time on XRD Pattern of

Prepared Zeolite X; Crystallization Time for Sample D-1 (8hrs)

Fig. 10 The Effect of Crystallization Time on XRD Pattern of

Prepared Zeolite X; Crystallization Time for Sample D-2 (6hrs)

Fig. 11 The Effect of Crystallization Time on XRD Pattern of

Prepared Zeolite X; Crystallization Time for Sample D-3 (4hrs)

Faujasite and zeolite P were formed at crystallization time for 8 hrs. In crystallization time for 6 hrs, the product samples were formed zeolite X(Na) as major product and faujasite is minor product. When the crystallization time for 4hrs was found unnamed zeolite.

Fig. 12 The Effect of Crystallization Time on XRD

Pattern of Prepared Zeolite X; Crystallization Time for Sample D-4 (16hrs)

In Fig. 10, the broad peaks at 6º, 18º, 27º, 31º and 36º 2θ values give the zeolite X(Na) and faujasite. At the optimum point, the yield percent of product zeolite X(Na) was 48%. The yield % of Zeolite X(Na) is based on the weight of total product.

F.The Prepared Zeolite (NaX,Faujasite) at Optimum Condition

Zeolite X(Na) was prepared from pure silica, alumina hydroxide and sodium hydroxide by hydrogel method. The zeolite X(Na) was prepared at the following conditions. The results are shown in Table VI. The XRD pattern, SEM

O. Faujasite (Na2O.Al2O3.2.4SiO2.6.7H2O) ∆. Zeolite, NaP (Na2O.Al2O3 .3.3SiO2 .12H2O)

O. ZeoliteY (Al48.2 Si143.8O384)

O. Faujasite (Na2O.Al2O3.2.4SiO2.6.7H2O) ∆. Zeolite, NaP (Na2O.Al2O3 .3.3SiO2 .12H2O)

∆. Zeolite X(Na)(Na2O.Al2O3 .2.5SiO2 .6.2H2O) O. Faujasite (Na2O.Al2O3.2.4SiO2.6.7H2O)

O. Unnamed Zeolite

O.Zeolite zh (Na2O.Al2O3.2.1SiO2. H2O) ∆.Faujasite (Na2O.Al2O3.2.4SiO2.6.7H2O) □. Zeolite, Na A (Na2O.Al2O3 .2SiO2 .4.5H2O)

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micrograph and FTIR spectrum of the product sample was shown in Fig.13, Fig. 14 and Fig. 15. The cation exchange capacity (CEC) of the product zeolite NaX was found to be 4.9meq/g. The value of CEC of zeolite NaX was determined by titration method.

From Table VI, it can be observed that the prepared zeolite NaX at optimum condition. The product yield percent of sample 1 was 62.4%. Figure 13 shows the XRD patterns of prepared zeolite X(Na), faujasite. The broad peaks at two theta degrees 6, 10, 27, 30, 36 are the highest peak intensity by using XRD. In Fig. 14 show the Scanning Electron Micrograph SEM image for the prepared zeolite X(Na),faujasite. From these images, the morphology of zeolite X(Na) were also found octahedron shapes. Figure 15 shows the FTIR spectrum of prepared zeolite NaX, faujasite. The mid infrared (IR) region of the spectrum was used 3479 cm-1, OH stretching, 400- 1300 cm-1, aluminosilicate lattice since this region contained the fundamental vibrations of the framework structure. The original assignments of the main IR bands 965-993 cm-1, TO4 Asymmetrical stretching (Internal tetrahedral), 676 cm-1, TO4 Symmetrical stretching (Internal tetrahedral), 566 cm-1 Double ring (External linkage), 462 cm-1, TO bending (Internal tetrahedral).

TABLE VI THE PREPARED ZEOLITE (NAX , FAUJASITE) AT OPTIMUM CONDITION

Raw Materials: pure silica powder, aluminium hydroxide Gel composition: 4.2 Na2O:Al2O3: 3SiO2: 180H2O Agitation time, temperature: 1 hr, room temperature Aging time, temperature: 1 day, room temperature Drying time, temperature: 12 hr, 100ºC

Sample No.

Crystallization Yield % *

Zeolite Phases and Other Synthesis Product

Tempe

rature

Time

1 100ºC

6hr 62.40 Zeolite X(Na), Faujasite

*Weight of final product divided by weight of initial raw

500

1000

1500

2000

5 10 15 20 25 30 35

Intensity Count(a.u)

Two-Theta(deg)

Fig. 13 XRD Pattern of Prepared Zeolite X(Na), Faujasite

Fig. 14 SEM Micrograph of Prepared Zeolite X(Na), Faujasite

Fig. 15 FTIR Spectrum of Prepared Zeolite X(Na), Faujasite

The XRD patterns revealed that the synthesized material exhibits crystalline pattern. The maximum cation exchange capacity (CEC) of the product zeolite X(Na) is equal to 4.9 meq/g.

G. Characterization of Prepared Zeolite X(Na),Faujasite

The prepared zeolite NaX, faujasite was characterized by XRF. The chemical compositions of zeolite NaX, faujasite was shown in Table VII.

TABLE VII CHARACTERIZATION OF PREPARED ZEOLITE NAX, FAUJASITE BY XRF

Chemicals Compositions, % Sample 1

SiO2 49.28

Al2O3 30.17

Na2O 12.41

H2O 8.05

(Si/Al) 1.38

(SiO2/Al2O3) 2.77

IV. CONCLUSION

It is concluded that the prepared zeolite NaX, faujasite could be prepared from hydrogel solution (alumina and silica precursors) under proper hydrothermal conditions. The optimum parameters of this zeolite NaX were molar composition of 3SiO2: Al2O3: 4.2Na2O: 180H2O, agitation time for 1hr at room temperature, aging time at the same temperature for 24hrs, crystallizing at 100°C for 6hrs and drying time for 12hrs at 100°C. According to the XRD results prepared zeolite NaX was formed with faujasite. The morphology of SEM image for zeolite X is octahedron shape. According to the investigation results, the optimum condition of product zeolite NaX with the molar composition of SiO2/Al 2O3 is 2.77.

REFERENCES [1] J. Scherze,: Catalysis Review-Science and Engineering,

1989, vol.3, pp.31 . [2] Y. Traa, and R. W.Thompson,: Controlled Co-

crystallization of Zeolites A and X, Journal of of Stuttgart, Germany, the Royal Society of Chemistry, Institute of Chemical Technology, University, 2002, vol. 12, pp. 496-499.

[3] Anonymous: “Synthesis of Maximum Aluminum X Zeolites,” 2010.

[4] M. M. Htay: “Preparation of Catalyst (Zeolite Y) for Petroleum Cracking,” Ph.D Eng. thesis, Department of Chemical Engineering. Mandalay Technological University, Mandalay, Myanmar 2006.

∆. Zeolite X(Na)(Na2O.Al2O3 .2.5SiO2 .6.2H2O) O. Faujasite (Na2O.Al2O3.2.4SiO2.6.7H2O)

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