LPG catalytic cracking over the modified ZSM-5 by activated carbon and carbon nanotube templates: Synthesis, morphology and performance of catalysts

• Investigation of the LPG catalytic cracking process on the synthesized ZSM-5 zeolites.
• Synthesis of ZSM-5 by using the template-free method, which is inexpensive, but difficult.
• Production of mesoporous by activated carbon for the first time in ZSM-5 zeolite and its comparison with carbon nanotubes.

Porous-structured, meso-microporous ZSM-5 zeolite (MZSM5) materials synthesized via in-situ blending of the reaction mixture 40SiO2:Al2O3:4.5Na2O:1500 H2O and carbon-nanotube or activated-carbon powder at certain established conditions were implemented into LPG catalytic cracking. The synthesized catalysts were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), nitrogen adsorption–desorption isotherms, and temperature-programmed desorption of ammonia (NH3-TPD). The impact of type and amount of carbon particles was investigated on properties such as morphology, crystallinity percentage, and the size of synthesized MZSM5 crystals. XRD and SEM measurements revealed that higher amorphous phase was found in MZSM5 synthesized by activated carbon. Applying the activated carbon into carbon nanotubes creates a lot of empty space between the particles in the crystal phase, which is inaccessible with regards to the BET results (not inside the crystal in order to access the active sites). However, the carbon nanotubes create corridor routes to the center of the crystalline particles, providing constant surfaces entirely accessible to the active sites of the catalyst. The experiments of LPG catalytic cracking were implemented by a fixed-bed reactor over the synthesized catalysts. The maximum yield of ethylene plus propylene was found to be 46% over MZSM5 synthesized with 30 wt% carbon nanotube.

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