The catalytic performance of anion modified zirconia catalysts, such as sulfated zirconia (SO4/ZrO2) and tungstated zirconia (WO3/ZrO2), was evaluated for the upgrading of oleic acid (OA). In the presence of an aromatic compound, two main reactions occurred on the catalysts: the skeletal isomerization of OA and the arylation of OA with aromatics. The activity of the SO4/ZrO2 was more than triple of that of the WO3/ZrO2. At 250 A degrees C, OA/(SO4/ZrO2)(wt/wt) = 5, the OA conversion and the arylation selectivity reached their maximal values and the isomerization selectivity was the lowest when the toluene to OA (toluene/OA) molar ratio was about 6. When mesitylene was used instead of toluene, the OA conversion and the arylation selectivity decreased, probably because of a steric effect. An attempt to reuse the SO4/ZrO2 by solvent washing after a run was not so successful, while calcination at 630 A degrees C in air recovered the activity completely.