LAUSR

Abstract Novel sulfonated magnetic solid acid catalysts (ZrFe-SA-SO3H) with both Bronsted and Lewis sites were synthesized, which provided both a high density of surface acidity (4.4–8.4 mmol/g) and considerable magnetization (3.7–8.1 Am2/kg). The synthesized catalysts were characterized by elemental analysis, XRD, ICP-OES, FT-IR, BET, SEM-EDX, TEM, TG-DSC, VSM and Boehm titration. The prepared catalysts were tested in the esterification of oleic acid, with high yields of biodiesel (92.7–99.5%) for the first catalytic cycle at 90 °C for 4 h. A High biodiesel yield of 90.3% was still achieved after five cycles of Zr1.0Fe1.0-SA-SO3H. A similar situation was also observed when using sodium carboxymethylcellulose (CMC) to replace SA during catalyst preparation.