**2. Syntheses of three different types of zeolitic material**

#### **2.1 Materials**

The chemical reagents used are boehmite powder (SASOL, Germany), colloidal silica (Ludox HS- 30, Sigma Aldrich), structure directing agent (SDA) 1-adamantanamine (Sigma Aldrich), ethylene diamine (Merck, Mumbai, India), LiOH flakes (Merck, India), phosphoric acid (Qualigens fine chemicals, India), morpholine (S. D. fine chemicals, India), and deionized water.

### **2.2 Methods**

Three unlike zeolites were synthesized by three different techniques like sonochemical, sonochemical-assisted hydrothermal method, and simple hydrothermal route. In the case of synthesis of the DDR zeolite, the sonochemical synthesis approach was implemented which is assisted by the complete growth of DDR crystal in a shorter crystallization time. The precursor solution containing the molar ratio of 1 silica:0.5 1-adamantanamine:4 ethylene diamine:100 water was used in the synthesis of the DDR crystals. The details of step-by-step synthesis process for DDR zeolite was already described in the previously reported work [40]. Two different mixtures were prepared. It is reported that first the measured amount of Ludox and water were mixed together (mixture-1). Then in another mixture (mixture-2), the ethylene diamine and water were mixed in a beaker followed by addition of 1-adamantanamine. Then the final mother sol (mixture 1 + mixture 2) was sonicated for 1 h. For fast synthesis of DDR zeolite, the ultrasound equipment (UIP1500 hd HIELSCHER Ultrasound Technology) which produces acoustic waves at frequency of 20 kHz was very useful [28]. The energy input for sonication was 250 W, and the mother sol was kept for aging for 1–9 days after sonication. The powdered products were recovered through centrifugation, washed with DI water until pH < 8, and then dried in the oven at 100°C for further characterization.

In the case of Bikitaite zeolite, the molar composition of the sol used for the synthesis was 10 Li2O:0.5 Al2O3:2.5 SiO2:600 H2O [56]. Like the previous protocol, two reactant mixtures were prepared respectively by suspending the measured amount of colloidal silica and lithium hydroxide in deionized water (DI water) in a glass beaker (mixture 1). Mixture 2 was prepared by adding the measured amount of boehmite in lithium hydroxide. Then it was mixed slowly to mixture 1 with constant and vigorous stirring, and the mixture turned into a milky white sol. The resulting mixture was sonicated for 3 h. The energy input of sonication was varied from 150 to 250 W, followed by aging for 72 h. Then the sonicated mixture was poured into Teflonlined stainless steel autoclave. Hydrothermal crystallization was continued under autogenous pressure in a hot air oven at 100°C for 24 h. For comparison, the different Bikitaite samples were synthesized by hydrothermal process similar to the abovementioned condition without sonication treatment. After synthesis, the zeolite powders were washed thoroughly with deionized water until the pH of the washing liquid became neutral and then dried at room temperature for further characterization.

The molar composition of the sol used for the SAPO 34 zeolite synthesis was Al2O3:SiO2:P2O5:H2O 1:0.3:1:66. In a typical synthesis, first boehmite powder, phosphoric acid, and the required amount of water were mixed properly by using the stirrer with 600 rpm. The mixture was stirred overnight (mixture 1).

**99**

*Zeolites: An Emerging Material for Gas Storage and Separation Applications*

Another mixture was prepared by dissolving the calculated amount of silica sol, morpholine, and deionized water (mixture 2). Then the reaction mixture was added slowly with mixture 1, and the resulted mother solution was stirred for another 1 hour at room temperature. The resulting mixture was stirred vigorously for 15–30 min and was kept stirring overnight to produce a homogeneous sol. The prepared homogeneous sol was kept in an autoclave, and the reaction was started at 170°C for 120 h. Finally the zeolite powders were centrifuged at 12,000 rpm for 20 min followed by washing with distilled water and the same washing process repeated four times. The resultant precipitate was dried in the oven at 100°C for 1 h.

An indigenous clay-Al2O3 tube of diameter 10 mm, thickness 3 mm, and 60 mm length was used as support for synthesis of the membrane. The membranes were synthesized by secondary growth hydrothermal techniques. In this technique, first the seed layer was applied on the support by using different intermediate layer in order to attach the seed crystal and prepare a uniform seed layer on the support. Then the membranes were synthesized by secondary growth of the seed layer by hydrothermal process. The membrane synthesis procedure for SAPO 34, DDR, and

Bikitaite zeolites was discussed in details in our previous work [47, 50, 56].

The crystalline structure of the as-synthesized zeolites and membranes was determined by XRD patterns. XRD was carried out on a Philips 1710 diffractometer using CuKα radiation (α =1.541° A). The characteristic vibration bands for zeolite powders were investigated by FTIR (Nicolet 5PC, Nicolet analytical instrument, Madison, WI). Thermogravimetric analyses (TGA) and differential thermal analyses (DTA) were performed in static air using the thermogravimetric analyzer (NETZSCH STA 409 C F3 Jupiter, Germany). The samples were heated at

of different zeolite powder were evaluated on a volumetric gas adsorption analyzer (autosorb-iQ-MP, Quantachrome) at 77 K. The sample used in the adsorption measurement was degassed at 423 K for 6 h before the measurements. Pore size distributions and surface area data of the synthesized powders were collected from N2 adsorption at 77 K. The same apparatus was also used for the measurement of H2 adsorption/desorption isotherms at 77 K up to 1 bar. Prior to adsorption study, the sample was out-gassed appropriately at 250°C for 24 h under high vacuum (106 mbar). In this case, He (99.999%) and N2 (99.999%) were used as carrier gas. Accessible microporous volume has been estimated by using the Dubinin-Radushkevich (DR) method. Transmission electron microscopy (TEM) measurements were carried out with a Tecnai G2 30ST (FEI) operating at 300 kV. The microstructure, elemental mapping with EDAX, and cross-sectional line scanning of the synthesized membranes were examined using field emission scanning electron microscopy (FESEM: model Leo, S430i, UK). X-ray photoelectron spectroscopy (XPS) measurements of support, chemically modified support, and respective membrane were carried out on an XPS system (PHI 5000 VersaProbe II, ULVAC-PHI, INC., USA) using a monochromatic Al Kα X-ray source (1486.6 eV). To identify the bonding between seed crystal and support surface, Raman analysis

The gas permeation experiment was done by a specially designed permeation cell where the membrane was mounted in a stainless steel permeation cell and

under air flow. The N2 adsorption/desorption measurements

**3. Characterization of zeolite powders and membranes**

was carried by Raman microscope (RENISHAW inVia, UK).

*DOI: http://dx.doi.org/10.5772/intechopen.91035*

**2.3 Membrane synthesis**

a rate of 10°C min<sup>−</sup><sup>1</sup>

*Zeolites: An Emerging Material for Gas Storage and Separation Applications DOI: http://dx.doi.org/10.5772/intechopen.91035*

Another mixture was prepared by dissolving the calculated amount of silica sol, morpholine, and deionized water (mixture 2). Then the reaction mixture was added slowly with mixture 1, and the resulted mother solution was stirred for another 1 hour at room temperature. The resulting mixture was stirred vigorously for 15–30 min and was kept stirring overnight to produce a homogeneous sol. The prepared homogeneous sol was kept in an autoclave, and the reaction was started at 170°C for 120 h. Finally the zeolite powders were centrifuged at 12,000 rpm for 20 min followed by washing with distilled water and the same washing process repeated four times. The resultant precipitate was dried in the oven at 100°C for 1 h.

## **2.3 Membrane synthesis**

*Zeolites - New Challenges*

**2.1 Materials**

**2.2 Methods**

After all, the performance of the developed materials was discussed elaborately for

The chemical reagents used are boehmite powder (SASOL, Germany), colloidal silica (Ludox HS- 30, Sigma Aldrich), structure directing agent (SDA) 1-adamantanamine (Sigma Aldrich), ethylene diamine (Merck, Mumbai, India), LiOH flakes (Merck, India), phosphoric acid (Qualigens fine chemicals, India), morpholine

Three unlike zeolites were synthesized by three different techniques like sonochemical, sonochemical-assisted hydrothermal method, and simple hydrothermal route. In the case of synthesis of the DDR zeolite, the sonochemical synthesis approach was implemented which is assisted by the complete growth of DDR crystal in a shorter crystallization time. The precursor solution containing the molar ratio of 1 silica:0.5 1-adamantanamine:4 ethylene diamine:100 water was used in the synthesis of the DDR crystals. The details of step-by-step synthesis process for DDR zeolite was already described in the previously reported work [40]. Two different mixtures were prepared. It is reported that first the measured amount of Ludox and water were mixed together (mixture-1). Then in another mixture (mixture-2), the ethylene diamine and water were mixed in a beaker followed by addition of 1-adamantanamine. Then the final mother sol (mixture 1 + mixture 2) was sonicated for 1 h. For fast synthesis of DDR zeolite, the ultrasound equipment (UIP1500 hd HIELSCHER Ultrasound Technology) which produces acoustic waves at frequency of 20 kHz was very useful [28]. The energy input for sonication was 250 W, and the mother sol was kept for aging for 1–9 days after sonication. The powdered products were recovered through centrifugation, washed with DI water until pH < 8, and then dried in the oven at 100°C for further characterization. In the case of Bikitaite zeolite, the molar composition of the sol used for the synthesis was 10 Li2O:0.5 Al2O3:2.5 SiO2:600 H2O [56]. Like the previous protocol, two reactant mixtures were prepared respectively by suspending the measured amount of colloidal silica and lithium hydroxide in deionized water (DI water) in a glass beaker (mixture 1). Mixture 2 was prepared by adding the measured amount of boehmite in lithium hydroxide. Then it was mixed slowly to mixture 1 with constant and vigorous stirring, and the mixture turned into a milky white sol. The resulting mixture was sonicated for 3 h. The energy input of sonication was varied from 150 to 250 W, followed by aging for 72 h. Then the sonicated mixture was poured into Teflonlined stainless steel autoclave. Hydrothermal crystallization was continued under autogenous pressure in a hot air oven at 100°C for 24 h. For comparison, the different Bikitaite samples were synthesized by hydrothermal process similar to the abovementioned condition without sonication treatment. After synthesis, the zeolite powders were washed thoroughly with deionized water until the pH of the washing liquid became neutral and then dried at room temperature for further characterization. The molar composition of the sol used for the SAPO 34 zeolite synthesis was Al2O3:SiO2:P2O5:H2O 1:0.3:1:66. In a typical synthesis, first boehmite powder, phosphoric acid, and the required amount of water were mixed properly by using the stirrer with 600 rpm. The mixture was stirred overnight (mixture 1).

better understanding and presents the future aspect of these materials.

**2. Syntheses of three different types of zeolitic material**

(S. D. fine chemicals, India), and deionized water.

**98**

An indigenous clay-Al2O3 tube of diameter 10 mm, thickness 3 mm, and 60 mm length was used as support for synthesis of the membrane. The membranes were synthesized by secondary growth hydrothermal techniques. In this technique, first the seed layer was applied on the support by using different intermediate layer in order to attach the seed crystal and prepare a uniform seed layer on the support. Then the membranes were synthesized by secondary growth of the seed layer by hydrothermal process. The membrane synthesis procedure for SAPO 34, DDR, and Bikitaite zeolites was discussed in details in our previous work [47, 50, 56].
