Transesterification of soybean oil catalyzed by alkylguanidines heterogenized on different substituted polystyrenes

1,5,7-Triazabicyclo[4.4.0]dec-5-ene and 1,1,3,3-tetramethylguanidine were heterogenized on different chloromethylated poly(styrene/divinylbenzene), as well as on linear polystyrene after introduction of a 'spacer-arm'. Furthermore, polymeric 2,3-dicyclohexylguanidines were synthesized by the reaction of 1,3-dicyclohexylcarbodiimide with p-(6-aminohexyl)polystyrenes. The guanidine-containing polymers were used in the transesterification of soybean oil with methanol in several consecutive catalytic cycles. The guanidines heterogenized on gel-type poly(styrene/divinylbenzene) with 1 meq Cl/g showed a slightly lower activity than their homogeneous analogous but reached the same high conversions after prolonged reaction time. On the other hand, they slowly leached from the polymers, allowing only nine catalytic cycles. The guanidines heterogenized on linear polystyrene with the use of a 'spacer-arm' were less active. Furthermore, they suffered substitution reactions during the recycling experiments to form inactive hexasubstituted guanidinium compounds.