A novel method for enhancing the stability of ZSM-5 zeolites used for catalytic cracking of LPG: Catalyst modification by dealumination and subsequent silicon loading

Composite structures of ZSM-5 zeolites were prepared by the synthesis of mesopores and micropores using carbon nanotubes as a template. Dealumination of mesopores was performed selectively using trichloroacetic acid, which could only diffuse into the mesopores and not the micropores owing to the size of the trichloroacetic acid molecules. Empty spaces are created in the catalyst as a result of removal of the Al atoms from the zeolite structure. If Si atoms fill the empty space, then the structure of the mesopores becomes similar to silicates, which do not have any catalytic properties. Silicon containing solution was used to fill the empty spaces, and in doing so, a unique method was developed, by which silicon atoms can directly replace the extracted Al atoms from the mesopore structure. Therefore, by changing the geometry and properties of the mesopores and micropores, the amount of coke reduced from 14% for HZSM-5 to 3% for the modified zeolite.

Graphical AbstractWe have reported the synthesis of mesopores and micropores in ZSM-5 zeolites by changing the geometry and properties of the mesopores using a new method. Selective dealumination of the mesopores by trichloroacetic acid and filling of the empty space with Silicon atoms resulted in inactive mesopore channels with lower production of coke and enhanced catalytic activity for catalytic cracking.Figure optionsDownload full-size imageDownload as PowerPoint slide