A hydrotreated TiO2 supported potassium catalyst, K/TiHT, was studied on the transesterification reaction of canola oil for the production of biodiesel. It was found that the calcination at different temperatures led to the transformation of the supported potassium catalyst into a titanate form of oxide. This was accompanied by a substantial increase in activity. Leaching studies found that although some potassium and titania was left in the products, the reaction mainly occurred in heterogeneous conditions. The contribution of the leached components to the activity was only minor. The recovered catalyst was then used in successive reactions producing stable conversions. A maximum conversion was achieved with the catalyst calcined at 700 degrees C. Optimum reaction conditions were obtained when using a catalyst loading of 6% (w/w), a methanol to oil ratio of 54:1, and a temperature of reaction of 55 degrees C. (c) 2012 Elsevier B.V. All rights reserved.