Heterogeneous esterification of fatty acids with methanol catalyzed by Lewis acidic organozirconium complexes with Keggin-type mono-aluminum-substituted polyoxotungstates

Two Lewis acidic organozirconium complexes with alpha-Keggin-type mono-aluminum-substituted polyoxotungstates, [(n-C4H9)(4)N](6)[alpha-PW11Al(OH)O39ZrCP2](2) (CP =eta(5)-C5H5-) (TBA-P-Al-Zr) and [(n-C4H9)(4)N](6)[alpha-SiW11Al (OH)(2)O38ZrCP2](2)center dot 2H(2)O (TBA-Si-Al-Zr), were used as heterogeneous catalysts for the esterification of various fatty acids with methanol. For the esterification of linoleic acid at 80 +/- 2 degrees C, TBA-P-Al-Zr exhibited 83% conversion after 6 h, approximately six times higher than that of TBA-Si-Al-Zr. TBA-P-Al-Zr also exhibited 69-90% conversion for the esterification of oleic acid, palmitic acid, myristic acid, and lauric acid with methanol at 80 +/- 2 degrees C.