This paper is done to study one particular catalyst which is zeolite supported iron catalyst. Zeolite supported iron catalyst is prepared using a method where it is based on the reaction of a metal exchanged zeolite with a metal containing coordination compound which produces an insoluble compound distributed throughout the zeolite. The metal used will be a specifically a water soluble metal cyanide complex where in this case it is iron. The catalyst is being used in various industries and the two main industries that use it will be the removal of nitrogen oxides in industrial exhaust gas and for the catalytic cracking of heavy oil. Finally this catalyst is being characterized using three methods which are the infrared spectra, X-ray diffraction as well as the TGA and DTA methods.
Catalyst is a substance that causes the change in rate of a chemical reaction. This reaction is known as catalysis and unlike other reagents that take part in a chemical reaction catalyst can be reused again as it will not be consumed by the reaction. Catalyst functions by offering a pathway for a reaction with a lower activation, therefore allowing for an increased rate of reaction. The catalyst that I have chosen to be discussed is iron catalysts. Iron is a transition metal catalysts where the commonly used supports for the groundwork of metal oxides catalysts are inorganic oxides with micropores, mesopores, macropores and a high surface area. In this case the iron catalyst will be supported by zeolite which is widely used as a catalyst as well as a support in various industries such as petroleum industry, nuclear industry and biogas industry. The main reason this support is chosen is due to its highly porous structure. Therefore zeolites are used for variety of applications. Zeolite is a crystalline type support. It has three dimensions structure hence a large surface area and also a micropores type pore dimensions. Zeolites are also known as aluminosilicates.
3.0 Catalyst Preparation
3.1 Support Preparation
In the iron supported zeolite catalyst type Y zeolite is used. To prepare the type Y zeolite the first step taken is to prepare a reaction mixture comprising an aqueous solution of a soluble aluminium compound and an aqueous solution of sodium silicate. The ratio of the reaction solution is obtained from Patent No.US 4540559. The molar ratios of the oxides in the mixture are shown below: SiO2/Al2O3= 5 to 40;
Na2O/SiO2= 0.2 to 2;
H2O/ Na2O= 12 to 200;
All the above preparation is done in ambient temperature. In order to get the highest purity of Type Y zeolite the solution of aluminium compound into the solution of sodium silicate while shaking violently. The second step of this preparation is to introduce a rapid heat transfer to raise the temperature of reaction mixture solution from ambient temperature to the crystallization temperature. The temperature ranges from 50oC to 120oC. There will be no changes of state of the solution during the rapid heat transfer phase but once the heat transfer is completed the solution will transform into gel almost immediately. The third step will be heating the reaction mixture at approximately 100oC. This heating process should be done without agitation in order to avoid the formation of competing zeolites. The heating should be continued till Type Y zeolite crystals are formed. Normally the time taken for the crystallization takes place diverges from 2 hours to 48 hours. The time taken for the crystal formation is determined by the molar ratio of silica to alumina in the Type Y zeolite. The crystallization step is highly recommended to be carried out in the double jacket reactor. The final step will be to separate the Type Y zeolite crystals from mother liquor via filtration where the final products are washed and dried. Tis process shown is very optimum for producing Type Y zeolite having molar ratio SiO2/Al2O3 greater than...
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