Preparation of stable sulfated zirconia by thermal activation from a zirconium doped mesoporous MCM-41 silica: Application to the esterification of oleic acid with methanol

Stable sulfated zirconia can be prepared by impregnation with sulfuric acid of a zirconium doped mesoporous MCM-41 silica and ulterior calcination at 750 °C. Two catalysts with nominal sulfur contents of 1.3 and 4 wt.% were prepared. After the thermal activation at this temperature, some sulfate ions (sulfur content of 0.15 and 0.69 wt.%) are strongly retained onto the superficial zirconia, thus generating acidic catalysts which are able to produce the esterification of oleic acid with methanol at 75 °C in 5 h. The experimental results reveal that the unique way to obtain stable catalysts without leaching of sulfate species to the liquid medium of reaction is by thermal treatment at high temperature as 750 °C. Only with 1 g of this stable catalyst a conversion close to 98% was attained. The conversion of this catalyst is well maintained in a high extend (76%) after three cycles of catalysis without any treatment and is stable in the presence of 5 wt.% of water.