Structural and acidity analysis of heteropolyacids supported on faujasite zeolite and its effect in the esterification of oleic acid and n-butanol

Most of the supporting catalytic materials seek to improve classical chemical processes that are less environment -friendly. The association of heteropolyacids (HPA) and zeolites has shown to be interesting for heterogeneous catalysis. In the present study, zeolite Y (faujasite) was modified by the incipient insertion of 12-tungstophos-phoric (HPW) and 12-tungstosilicic (HSiW) acids for application in the esterification reaction of oleic acid with n-butanol. The fine chemical product (butyl oleate) is used in a variety of applications (e.g., plasticizers, lubricants). The catalysts (x%HPA/Y; x = 3, 6 and 12%) were characterized by EDXRF, XRD, FT-IR, multinuclear MAS NMR (27Al, 29Si, and 31P), SEM, low temperature N2 physisorption, thermal methods (TG/DTG), pyridine (Py) gas desorption (Py-TPD) and microcalorimetry of Py adsorption in liquid phase. The resulting acid com-posites showed advantages over both pristine solids with adequate nature, dispersion, stability, accessibility, and strength of active sites. High oleic acid conversions (70% for 12%HSiW/Y and 96% for 12%HPW/Y) with 100% selectivity to butyl oleate were obtained under these conditions: acid: alcohol ratio 1:2; 0.2 g of catalyst; 100 degrees C and 1 h reaction. No leaching of the active phases was detected, and the best catalysts were used three times, keeping fair their initial conversion.