Development of cost-effective cellulose-based bilayer hybrid composite membranes for CO₂ separation in biogas...

CO₂ is the main pollutant in biogas, reducing its calorific value. Among various technological methods to eliminate carbon dioxide from biogas, membrane separation technology stands out for large-scale industrial biogas purification due to its advantages. The selection of membrane material and preparation process are key factors in membrane separation technology. In this study, a premixing process was initially used to blend different masses of packed molecular sieves TS-1 (or ZSM-5) and cellulose derivatives (ethyl cellulose, cellulose acetate) separately. These mixtures were then coated onto porous PVDF substrates using a coating process to create various bilayer hybrid composite membranes. Among these, PVDF/EC-ZSM-5 (containing 15 % ZSM-5) bilayer hybrid composite membrane is the most fitting. For CO₂/CH₄ gas mixtures, the gas selectivity of this membrane surpassed Robeson's 1991 standard line (the CO₂ permeability was 597.48 Barrer, and the CO₂/CH₄ selectivity was 9.14). Overall, this composite membrane, made for the first time from PVDF, ZSM-5, and EC, is expected to be a promising CO₂ selective separation membrane material for biogas purification in large-scale industrial processes due to its simple production process.