Enhanced light olefins production via n-pentane cracking using modified MFI catalysts

Area of Science:

• Catalysis
• Materials Science
• Chemical Engineering

Background:

• Catalytic cracking of n-pentane is crucial for producing light olefins.
• MFI zeolites are widely used catalysts, but their selectivity can be tuned.
• Controlling zeolite properties is key to optimizing hydrocarbon conversion.

Purpose of the Study:

• To investigate n-pentane catalytic cracking over MFI zeolites with varying SiO2/Al2O3 ratios.
• To evaluate the impact of crystal morphology, size, and surface modification (ammonia, phosphorus) on catalytic performance.
• To understand how zeolite modification affects physiochemical properties and selectivity towards light olefins.

Main Methods:

• Synthesis and characterization of MFI zeolites with diverse SiO2/Al2O3 ratios, crystal sizes, and morphologies.
• Catalytic cracking experiments using a fixed-bed reactor at 550-650 °C.
• Surface modification of MFI zeolites using ammonia and phosphorus treatments.

Main Results:

• MFI (SiO2/Al2O3 = 280) showed high light olefin selectivity (51%) but also significant alkane byproducts.
• Surface modification, particularly with phosphorus and large crystal size, improved propylene selectivity (52.2%) and reduced C1-C4 alkanes (8%).
• Phosphorus incorporation created moderate acidic sites, suppressing strong acidity and undesired alkane formation.

Conclusions:

• Phosphorus modification of large-crystal MFI zeolites is an effective strategy to enhance light olefin selectivity in n-pentane cracking.
• Tailoring zeolite acidity and structure through modification is critical for optimizing catalytic performance.
• The study provides insights into designing advanced zeolite catalysts for selective hydrocarbon conversion.