1. Introduction
It is becoming increasingly difficult to ignore the importance of zeolites, especially aluminum rich ones including A, X and Y types [1]. Y zeolite is widely used as catalyst or catalyst support but a proper post treatment process such as dealumination should be carried out [2, 3] to increase Si to Al molar ratio to values over 3, which is not achievable through direct synthesis [4]. Zeolite dealumination was introduced regarding instability of the framework in acidic and aqueous media [5, 6], and could be conducted by acid extraction [7], Al/Si substitution [8] and thermal treatment of ion exchanged NaY zeolite [9]. Not all zeolites can survive and maintain their framework structure and stability after dealumination [10]. NaY zeolite with Si to Al ratio of …show more content…
Materials
Silica sol (Ludox HS-40, SiO2 40% and H2O 60%) and ammonium chloride (NH4Cl 99.99% in purity) were used as received from Sigma-Aldrich. Sodium hydroxide pellets (NaOH 99% and H2O 1%), Ammonium hydroxide, (NH4OH, 25%) and EDTA (> 99.4% in purity) were used as received from Merck KGaA. Sodium aluminate (Na2O 41%, Al2O3 53% and H2O 6%) was used as received from VWR Co. Tetramethylammonium hydroxide pentahydrate (TMAOH 98% in purity) was used as received from Alfa Aesar GmbH & Co KG.
2.2. Syntheses
2.2.1. NaY Zeolite
The procedure described by Karimi and Rohani was used to synthesize NaY zeolite [30]. 19.2 g of TMAOH was dissolved in 53.5 g deionized water. 4.53 g of NaOH and 4.03 g NaAlO2 were added under stirring to obtain a clear solution. The resulting mixture was added to 18.7 g of silica solution. Afterward, the mixture was aged for two weeks to form synthesis gel with following composition: (1)
PTFE autoclave containing the gel was placed in an oven which was pre-heated to 100 ˚C and kept for two days. After cooling to room temperature, the product was vacuum filtered and washed by deionized water. Finally, the product was dried at 110 °C.
2.2.2. Thermochemical
It is becoming increasingly difficult to ignore the importance of zeolites, especially aluminum rich ones including A, X and Y types [1]. Y zeolite is widely used as catalyst or catalyst support but a proper post treatment process such as dealumination should be carried out [2, 3] to increase Si to Al molar ratio to values over 3, which is not achievable through direct synthesis [4]. Zeolite dealumination was introduced regarding instability of the framework in acidic and aqueous media [5, 6], and could be conducted by acid extraction [7], Al/Si substitution [8] and thermal treatment of ion exchanged NaY zeolite [9]. Not all zeolites can survive and maintain their framework structure and stability after dealumination [10]. NaY zeolite with Si to Al ratio of …show more content…
Materials
Silica sol (Ludox HS-40, SiO2 40% and H2O 60%) and ammonium chloride (NH4Cl 99.99% in purity) were used as received from Sigma-Aldrich. Sodium hydroxide pellets (NaOH 99% and H2O 1%), Ammonium hydroxide, (NH4OH, 25%) and EDTA (> 99.4% in purity) were used as received from Merck KGaA. Sodium aluminate (Na2O 41%, Al2O3 53% and H2O 6%) was used as received from VWR Co. Tetramethylammonium hydroxide pentahydrate (TMAOH 98% in purity) was used as received from Alfa Aesar GmbH & Co KG.
2.2. Syntheses
2.2.1. NaY Zeolite
The procedure described by Karimi and Rohani was used to synthesize NaY zeolite [30]. 19.2 g of TMAOH was dissolved in 53.5 g deionized water. 4.53 g of NaOH and 4.03 g NaAlO2 were added under stirring to obtain a clear solution. The resulting mixture was added to 18.7 g of silica solution. Afterward, the mixture was aged for two weeks to form synthesis gel with following composition: (1)
PTFE autoclave containing the gel was placed in an oven which was pre-heated to 100 ˚C and kept for two days. After cooling to room temperature, the product was vacuum filtered and washed by deionized water. Finally, the product was dried at 110 °C.
2.2.2. Thermochemical