Thermal dealumination, modification

Modification of Zeolites. The purpose of any modification is to improve catalytic properties. The most common modification is the dealumination of zeolites which has been shown to increase crystalline thermal stability. Three dealumination procedures can be used (35) chemical dealumination, thermal or hydrothermal dealuminatTon and combination of thermal and chemical dealuminations. 

The Si/Al ratio plays a significant role, since the aluminum atom is directly related to the acidic site and accounts for the formation of carbenium and/or carbonium ions or possibly cation radicals inside the zeolite. Dealumination processes can promote porous structure modifications, which may improve some interesting properties of zeohtes, like thermal and hydrothermal sta-bihty, acidity, catalytic activity, resistance to aging and low coking rate, and... 

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