Preparation and characterization of SO42 −/FexAl1 − xPO4 solid acid catalysts for caprylic acid esterification

A series of SO42 −/FexAl1 − xPO4 solid acid catalysts were prepared and characterized by means of XRD, FE-SEM, elemental analysis, N2 adsorption-desorption, XPS, NH3-TPD, pyridine adsorption FT-IR and ion exchange/titration. Their catalytic performances were evaluated by the esterification of caprylic acid with ethanol. Experimental results revealed that the doping of iron can markedly enhance the acidic properties of the SO42 −/AlPO4, thereby boosting its catalytic activity in esterification. The maximum caprylic acid conversion of 92.4% was achieved over the iron doped catalysts. Moreover, the incorporation of iron has also greatly elevated the stability of SO42 −/AlPO4 during repeated catalytic cycles.