Synthesis of Novel Hypercrosslinked Polymer-Based Solid Acids with Pyridinium Moiety and Their Catalytic Activity in Biodiesel Production
摘要
A novel hypercrosslinked porous polymer-based solid acid with an embedded pyridinium moiety in the polymeric framework was synthesized via the quaternization of 4,4'-bipyridine (BPy) and 4,4'-bis(chloromethyl)-1,1'-biphenyl (BCMBP), followed by polycondensation and sulfonation. This approach represents a key advancement by integrating the pyridinium moiety directly into the rigid polymer skeleton, thereby effectively preventing pore blockage typically encountered with physically immobilized bulky ionic liquids (ILs). The polymer possesses a rigid biphenyl framework, which provides sufficient sulfonation sites for high acidity. The hypercrosslinked structure ensures high stability and a surface area of 1162 m2/g for the solid acid. The ionic liquid moiety in the polymer provides special active sites, and the free coordinating anions make these sites highly accessible to reactants. The novel hypercrosslinked porous polymer-based solid acid with a pyridinium moiety exhibited high catalytic activity in biodiesel synthesis via the esterification of oleic acid (98.7% conversion) and the integrated esterification-transesterification of waste oil (99.1% total yield), respectively. The novel solid acid could be recycled nine times with minimal activity loss (from 99.1 to 97.2%). The pyridinium moiety, high surface area, high acidity (3.4 mmol/g), and rigid aromatic framework were the key factors contributing to the high activity, making the novel solid acid a promising candidate for industrial applications.