MFI Zeolite Membrane with Surface Mo─O Clusters for Inverse CH₄/CO₂ Separation

Area of Science:

• Materials Science
• Chemical Engineering
• Separation Science

Background:

• Industrial separation of methane (CH4) and carbon dioxide (CO2) is crucial for biogas, landfill gas, and natural gas utilization.
• Current CO2-selective membranes limit efficient recovery of methane-rich gases, highlighting the need for CH4-selective alternatives.

Purpose of the Study:

• To develop and demonstrate a novel MFI-type zeolite membrane functionalized with molybdenum-oxygen (Mo─O) clusters for inverse CH4/CO2 gas separation.
• To achieve selective permeation of methane over carbon dioxide, enabling methane purification and recovery.

Main Methods:

• Fabrication of a pure-silica MFI-type zeolite membrane on an alumina support.
• Functionalization of the MFI membrane using impregnation and calcination of sodium molybdate to create Mo─O clusters.
• Gas separation performance evaluation using CH4/CO2 mixtures, measuring separation factor and permeance.

Main Results:

• The Mo─O/MFI membrane exhibited selective permeation of CH4 over CO2.
• Achieved an unprecedented CH4/CO2 separation factor of 11.8.
• Demonstrated a high CH4 permeance of 2.1 × 10^-8 mol s^-1 m^-2 Pa^-1.

Conclusions:

• The Mo─O functionalized MFI zeolite membrane is the first porous membrane capable of inverse CH4/CO2 separation.
• Methane's preferential adsorption onto Mo─O clusters and rapid diffusion through zeolite pores drive the selective separation.
• This research provides a pathway for designing advanced CH4-selective membranes for gas purification applications.