Preparation and Characterization of OH/SiO2-TiO2/PES Composite Hollow Fiber Membrane Using Gas-liquid Membrane Contactor for CO2/CH4 Separation

A comprehensive review on zeolite-based mixed matrix membranes for CO2/CH4 separation

Biogas consisting of carbon dioxide/methane (CO₂/CH₄) gas mixtures has emerged as an alternative renewable fuel to natural gas. The presence of CO₂ can decrease the calorific value and generate greenhouse gas. Hence, separating CO₂ from CH₄ is a vital step in enhancing the use of biogas. Zeolite and zeolite-based mixed matrix membrane (MMM) is considered an auspicious candidate for CO₂/CH₄ separation due to thermal and chemical stability. This review initially addresses the development of zeolite and zeolite-based MMM for the CO₂/CH₄ separation. The highest performance in terms of CO₂ permeance and CO₂/CH₄ selectivity was achieved using zeolite and zeolite-based MMM, which exhibited CO₂ permeance in the range of 2.0 × 10^{- 7}-7.0 × 10^{- 6} mol m^{- 2} s^{- 1} Pa^{- 1} with CO₂/CH₄ selectivity ranging from 3 to 300. Current trends directed toward improving CO₂/CH₄ selectivity via modification methods including post-treatment, ion-exchanged, amino silane-grafted, and ionic liquid encapsulated of zeolite-based MMM. Those modification methods improved the defect-free and interfacial adhesions between zeolite particulates and polymer matrices and subsequently enhanced the CO₂/CH₄ selectivity. The modifications via ionic liquid and silane methods more influenced the CO₂/CH₄ selectivity with 90 and 660, respectively. This review also focuses on the possible applications of zeolite-based MMM, which include the purification and treatment of water as well as biomedical applications. Lastly, future advances and opportunities for gas separation applications are also briefly discussed. This review aims to share knowledge regarding zeolite-based MMM and inspire new industrial applications.

Modeling and Simulation of the Impact of Feed Gas Perturbation on CO2 Removal in a Polymeric Hollow Fiber Membrane

A membrane contactor is a device that attains the transfer of gas/liquid or liquid/liquid mass without dispersion of one phase within another. Membrane contactor modules generally provide 30 times more surface area than can be achieved in traditional gas absorption towers and 500 times what can be obtained in liquid/liquid extraction columns. By contrast, membrane contactor design has limitations, as the presence of the membrane adds additional resistance to mass transfer compared with conventional solvent absorption systems. Increasing mass transfer in the gas and solvent phase boundary layers is necessary to reduce additional resistance. This study aims to increase the mass transfer in the gas phase layer without interfering with membrane structure by oscillating the velocity of the feed gas. Therefore, an unsteady state mathematical model was improved to consider feed gas oscillation. The model equation was solved using Comsol Multiphysics version 6.0. The simulation results reveal that the maximum CO₂ removal rate was about 30% without oscillation, and at an oscillation frequency of 0.05 Hz, the CO₂ percent removal was almost doubled.