Jordanian Dolomite as Potential Catalyst in the Transesterification of Jatropha Oil - Abstract
Jordanian Dolomite was investigated as a heterogeneous catalyst in biodiesel production from Jatropha oil. In order to study the thermal activation process of dolomite, dolomite samples were thermally treated for two hours at 100, 200, 300, 400 500, 600, 700 and 800° C as well as for various time intervals at 800° C. Structural and compositional changes were characterized by x-ray diffraction (XRD) and infra-red spectroscopy (IR). No changes could be observed by heating up to 500o C but heating to 600o C causes the magnesium carbonate (MgCO3 ) to decompose into magnesium oxide while the fraction of calcite (CaCO3 ) grows at the expense of dolomite. The resulting system showed however a rather low activity (~20% transesterification) as a catalyst in the transesterification of Jatropha oil. Highly active catalysts could be produced by heating the dolomite up to 800° C for at least half an hour where the degree of transesterification exceeded 96% at 60° C and a methanol-to-oil molar ratio of 6; the minimum activated dolomite-to-oil mass ratio that gives such a high yield was 1:50 (2%). This high activity was found to correlate with the decomposition of CaCO3 into CaO. Activated dolomite was however found to be non-recyclable as the used catalyst gave when reused a degree of transesterification not higher than 2% suggesting the homogenous nature of the actual catalyst. Nevertheless, activated dolomite can be regarded as a cheaper replacement for the conventionally used potassium hydroxide catalyst.