The use of nanostructured membranes in the separation of gases, vapors, and liquids is an innovative and efficient approach compared to conventional processes such as absorption and distillation. This technology is highly attractive to the oil, gas, and petrochemical industries due to its significant advantages, including low cost, low energy consumption, and environmental friendliness. However, its widespread application has been limited by the challenge of accessing membranes with simultaneously high selectivity and permeability. In common polymeric materials used for membrane preparation, increasing selectivity results in a decrease in permeability. This has led to the need for membranes with a combination of desirable properties, including high permeability, high selectivity, and adequate chemical, mechanical, and thermal stability, driving the development of mixed matrix membranes. In this research, polyurethane membranes were chosen due to their suitable permeability and selectivity in the separation of acidic gases and their favorable mechanical properties. The main challenge is the non-permeability of the hard segments; therefore, the aim of this study is to improve their gas separation performance. A polyurethane membrane containing hard segments composed of isophorone diisocyanate (IPDI) and 1,4-butanediol (BDA) and soft segments of polytetramethylene ether glycol (PTMG) with a molecular weight of 2000 g/mol was synthesized. The molar ratio of diisocyanate: chain extender: polyol for polyurethane synthesis was selected as 3:2:1. To prepare mixed matrix membranes based on polyurethane, Mg-based metal-organic framework nanoparticles (Mg-MOF-74) were synthesized and characterized. FTIR and XRD tests were employed to confirm the synthesized structure. Mg-MOF-74 nanoparticles were synthesized via a solvothermal method at 125 °C using 2,5-dihydroxyterephthalic acid (H4DHTP) as the organic ligand and magnesium (Mg) as the metal node. To investigate the effect of Mg-MOF-74 nanoparticles on the gas separation properties of the polyurethane membrane, mixed matrix membranes of polyurethane/Mg-MOF-74 with different loadings of nanoparticles were prepared by the phase inversion method using solvent evaporation. The pure gas permeabilities of N2, O2, CH4, and CO2 were eva‎luated. The influence of nanoparticles on the structure and gas separation properties of the mixed matrix membranes was studied using FTIR, TGA, FE-SEM, and permeability tests. The FE-SEM results indicated a well-dispersed distribution of nanoparticles at the optimal concentration in the polymer matrix. The FTIR results revealed an increase in phase separation in the membrane with 2.5 wt% nanoparticles, followed by a decrease in phase separation in the membrane with 5 wt%. The addition of Mg-MOF-74 nanoparticles (from 0 to 5 wt%) to polyurethane resulted in an increase in permeability in the mixed matrix membranes compared to the pure polymeric membrane. The permeability data for the pure membrane, 2.5 wt% membrane, 5 wt% membrane, and 7.5 wt% membrane were 87.5, 93.5, and 98.8 barrer, respectively. Based on the results, the membrane containing 2.5 wt% nanoparticles was identified as the best option among the studied membranes for carbon dioxide gas separation, exhibiting a 6.5% increase in permeability and a 17% increase in selectivity compared to the pure membrane.

افسانه فخار

محمد ديناري

مرتضي صادقي , سهيل ضرغامي