In this paper, heterogeneous catalysts based on natural dolomite mineral in the transestrification of Jatropha oil into biodiesel. Investigating the applicability of natural basic carbonate minerals as potential catalysts in biodiesel production from Yemeni Jatropha oil. The effect of thermal treatment of these minerals had been addressed and correlating the catalytic behavior with the surface properties of these systems was attempted. XRD measurements show that the dolomite mineral is highly crystalline with small amounts of calcite. Increasing the temperature of thermal treatment up to 500oC has no significant effect on the X-ray diffraction patterns, but upon further increase of the temperature to 600oC the dolomite phase was found to decompose due to the decarbonisation of MgCO3. Temperatures as high as 800oC were found to be necessary to start the thermal decomposition of calcium carbonate, but appreciable amounts of calcite remain even after several hours of thermal treatment at 800oC. The transestrification of Jatropha oil was conducted at 60oC with a methanol-tooil molar ratio of 6:1. Dolomite samples thermally treated up to a temperature of 700oC showed only low activities in the transestrification of Jatropha oil (conversion~20%). Raising the temperature of thermal treatment to 800oC increased the activity significantly to 95%-conversion, apparently due to the formation of strongly basic CaO. It was found that heating the mineral for at least 30 minutes at 800oC is necessary to produce a highly active system. The optimum catalyst-tooil mass ratio was determined to be 1:50.

Keywords : Dolomite, Transestrification, Biodiesel, Thermal Treatment, Heterogeneous, Catalysts.