Hypercrosslinked porous polymer as catalyst for efficient biodiesel production

While porous organic polymers (POPs) are known for their unique properties, their application in basic biodiesel catalysis is innovative. This study introduces a novel catalyst, hypercrosslinked polymer (HCP-SB-K), synthesized through mechanochemical polymerization of styrene and benzaldehyde with a cross-linking agent and FeCl₃, followed by calcination of the previous polymer impregnated with KNO₃. The synthesis costs 3.328 euros per gram of catalyst, covering energy and reagent expenses. The catalyst's basic character is explored, demonstrating efficient transesterification with diverse feedstocks. Under optimal conditions, the HCP-SB-K catalyst exhibits exceptional catalytic activity, yielding 99.9% FAME (Fatty Acid Methyl Esters) at 60 °C, 2 h and 3% w/w catalyst. Investigation of free fatty acid (FFA) content highlights the catalyst's effectiveness with oils varying FFA levels: oils with acid value of 0.44 mg_KOH g_oil⁻¹ reached 92.1% FAME at 60 °C, 1 h and 3% w/w catalyst; oils with an acid value of 1.11 mg_KOH g_oil⁻¹, reached 75.9% FAME, under the same conditions. Catalyst leaching evaluation indicates no discharge of basic sites. The regenerated catalyst (impregnation with KNO₃ and calcination, after the first use) exhibits a 98.2% FAME like the fresh catalyst. This suggests that HCP-SB-K can be regenerated without noticeable deactivation, emphasizing its industrial potential.