Theoritical an‎d Experimental Investigation of of Hydrocarbon Cation Exchange Membranes for Chlor-Alkali Process with Emphasizing on Oxidative Stability

3/9/2027 12:00:00 AM

The development of cation exchange membranes (CEMs), as a critical component of the chlor-alkali electrolysis process, plays a decisive role in the performance of these processes. Despite the favorable performance of perfluorinated membranes, challenges such as high production costs an‎d limitations in chemical, mechanical, an‎d thermal stability have highlighted the necessity for alternative hydrocarbon-based membranes. Accordingly, this research employs a hybrid "experimental-computational" approach to design, fabricate, an‎d eva‎luate heterogeneous CEMs based on sulfonated polystyrene-divinylbenzene/polyvinylidene fluoride (PVDF/S(PS@DVB)-X) to achieve an optimal balance between ionic conductivity, structural stability, an‎d chemical durability. In the computational phase, Molecular Dynamics (MD) simulations were conducted to determine the membrane hydration number under saturated conditions (λ), the optimal polymer network structure, the degree of sulfonation (DS), an‎d the composition of the heterogeneous CEM. The results revealed that the saturated hydration state occurs at λ = 3. The optimal polymer network was identified as a structure consisting of five chains an‎d 20 monomers with 2% cross-linking. Furthermore, a 60% degree of sulfonation provided the best balance between transport properties an‎d mechanical/thermal stability (sodium ion diffusion coefficient of 0.5 × 10⁻¹⁶ cm²·s⁻¹, glass transition temperature of 389 K, an‎d Young’s modulus of 3.26 GPa). Ultimately, the PVDF/S(PS@DVB)-70 membrane exhibited the best computational performance with a conductivity of 6.7 mS/cm an‎d a Young’s modulus of 7 GPa. In the experimental phase, the effects of time (3–24) h, temperature (60–100) °C, an‎d the acid-to-solvent ratio (3–7) on the electrochemical properties of the cation exchange resin were investigated through screening tests. The optimal synthesis conditions were determined to be 80 °C, sulfonation time of 3 h, an‎d an acid-to-solvent ratio of 5:1. Subsequently, heterogeneous CEMs were prepared at four different resin-to-base polymer weight ratios (10, 30, 50, an‎d 70 wt%), an‎d their physicochemical, electrochemical, structural, an‎d stability (thermal, chemical, an‎d mechanical) properties were characterized. The results indicated that the PVDF/S(PS@DVB)-70 membrane with a degree of sulfonation of 61.3%, cation exchange capacity (CEC) of 3.3 meq/g, water uptake of 33.4%, an‎d cationic conductivity of 19.6 mS/cm was the optimal membrane. Finally, the performance of the optimized membrane was eva‎luated in a zero-gap cell at 80 °C. At a current density of 4 kA·m⁻², the cell voltage an‎d current efficiency were measured at 4.8 V an‎d 90.1%, respectively. These results demonstrate superior performance compared to the commercial Flemion-316 membrane (4.2 V at 4 kA·m⁻²). Based on both experimental an‎d computational findings, PVDF/S(PS@DVB)-based hydrocarbon CEMs not only serve as cost-effective an‎d stable alternatives to perfluorinated membranes in the chlor-alkali process but also provide a robust framework for molecular-level design.

الكتروليز كلرآلكالي , غشاي تبادل كاتيون , پلي استايرن دي‌وينيل بنزن , پلي وينيليدين فلورايد , هدايت كاتيوني , پايداري ‌اكسايشي

Chlor-alkali electrolysis , cation exchange membrane , polystyrene-divinylbenzene , polyvinylidene fluoride , cation conductivity , oxidative stability

Atieh Sadat Sadat Kachooei

Soosan Rowshanzamir