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Abstract <p>The influence of gas-phase fluorination conditions on the gas-selective properties of laboratory-scale hollow fiber membrane modules based on Matrimid 5218<sup>®</sup> for the main components of biogas separation was investigated. The modification was carried out directly in laboratory membrane modules with a F<sub>2</sub>/He gas mixture in the F<sub>2</sub> concentration range of 2–10 vol %. It was found that the interaction with fluorine leads to a change in the chemical structure of the selective membrane layer due to the replacement of hydrogen atoms by fluorine in the polymer structure. Increasing the fluorine concentration in the fluorination mixture and the fluorination time results in a decrease in the permeability of the modules to the target gases. As a result, the CO<sub>2</sub> permeability decreases by a factor of 4-5 and the CH<sub>4</sub> permeability by more than an order of magnitude, leading to an increase in selectivity (from 50 to 136) compared to the original hollow fibers. The high convergence of the ideal selectivity and separation factor of the СО<sub>2</sub>/СН<sub>4</sub> mixture for hollow fibers modified under various conditions has been experimentally demonstrated. The temperature effect on the gas transfer parameters for modified hollow fiber modules based on Matrimid 5218<sup>®</sup> was investigated. In the case of biogas separation under real conditions at <i>T</i> = 50°C (average temperature of vital activity of methanogenic bacteria), the selectivity of СО<sub>2</sub>/СН<sub>4</sub> separation remains at a high level. For example, the CO<sub>2</sub>/CH<sub>4</sub> selectivity for the module modified by 2% F<sub>2</sub> for 2 min was equal to 61, and the СО<sub>2</sub> permeability turns out to be 1.5&#xa0;times higher in comparison with the original membranes. Based on the experimental results, operational schemes have been proposed and modelling of the biogas separation process with release of methane with high recovery rates (up to 99%) and ballast CO<sub>2</sub> using highly selective modified Matrimid 5218<sup>®</sup> membranes has been carried out, moreover, with fluoridation of the modules in “soft” conditions, the indicators improve over time.</p>

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Gas-Phase Fluorination of Hollow Fibers from Matrimid 5218® for Biogas Conditioning

  • 期刊论文

  • 发表日期：

    2025年2月1日

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  • D. A. Syrtsova,
  • M. G. Shalygin,
  • V. V. Teplyakov

摘要

Abstract

The influence of gas-phase fluorination conditions on the gas-selective properties of laboratory-scale hollow fiber membrane modules based on Matrimid 5218® for the main components of biogas separation was investigated. The modification was carried out directly in laboratory membrane modules with a F2/He gas mixture in the F2 concentration range of 2–10 vol %. It was found that the interaction with fluorine leads to a change in the chemical structure of the selective membrane layer due to the replacement of hydrogen atoms by fluorine in the polymer structure. Increasing the fluorine concentration in the fluorination mixture and the fluorination time results in a decrease in the permeability of the modules to the target gases. As a result, the CO2 permeability decreases by a factor of 4-5 and the CH4 permeability by more than an order of magnitude, leading to an increase in selectivity (from 50 to 136) compared to the original hollow fibers. The high convergence of the ideal selectivity and separation factor of the СО2/СН4 mixture for hollow fibers modified under various conditions has been experimentally demonstrated. The temperature effect on the gas transfer parameters for modified hollow fiber modules based on Matrimid 5218® was investigated. In the case of biogas separation under real conditions at T = 50°C (average temperature of vital activity of methanogenic bacteria), the selectivity of СО2/СН4 separation remains at a high level. For example, the CO2/CH4 selectivity for the module modified by 2% F2 for 2 min was equal to 61, and the СО2 permeability turns out to be 1.5 times higher in comparison with the original membranes. Based on the experimental results, operational schemes have been proposed and modelling of the biogas separation process with release of methane with high recovery rates (up to 99%) and ballast CO2 using highly selective modified Matrimid 5218® membranes has been carried out, moreover, with fluoridation of the modules in “soft” conditions, the indicators improve over time.