Preparation of Sulfonated Monomer for Pem Fuel Cell and Solvent Optimization for Recrystallization

2 Abstract: Polymer exchange membrane fuel cells are promising new power sources for vehicles and portable devices. Membranes currently used in PEMFC are perfluorinated polymers such as Nafion®. Even though such membranes have demonstrated good performances and long-term stability, their high cost and methanol crossover makes them unpractical for large-scale production. Sulfonated aromatic polymers based membranes have been studied due to their good mechanical properties, thermal stability and conductivity. In this study, sodium 5, 5 -carbonylbis (2-fluorobenzene- sulfonate) was performed as a sulfonated monomer contained / sulfonic group which is considered as the base for proton exchange process of membrane fuel cell. Sulfonation of 4,4-difluorobenzophenone with 20 % fuming sulfuric acid by adding the SO grouping to an organic molecule 3 in such a way that sulfur is linked to the carbon through an oxygen bridge by the aromatic nucleophilic substitution reaction. Recrystallization of the produced sulfonated monomer was then studied using different types of solvents as methanol, ethanol and isopropanol, as well as, studying the ratio of (water: alcohol) mixtures as solvents.By studying the yield of the produced sulfonated monomer, it was found that 88% yield was obtained using 1:6 (water: ethanol) solvent mixture as an optimum solvent for the re-crystallization process.