MgCO3CaCO3 (Dolomite) is a magnesium ore widely used in biomass gasification since the tar content of the produced gases during the biomass conversion process is significantly reduced in the presence of Dolomite [8-10]. In addition, this cat­alyst is relatively inexpensive and disposable, so it is possible to use it in bed reactors as primary catalysts as well as in secondary, downstream reactors. The studies related to the catalytic effect of dolomite during biomass gasification are mainly focused on reformation of higher molecular weight hydrocarbons (tar). Steam gasification of biomass in the presence of dolomite leads to the efficient removal of coke formed on the catalyst surface and thus product selectivity is significantly enhanced. On the other hand, olivine [(Mg, Fe)2SiO4], another effective catalyst for biomass gasification, is also an attractive material regarding stability in fluidized bed reactors [11] due to its attrition resistance. Olivines also possess very low surface areas (about 0.4 m2 g-1), normally being an order of magnitude less than those of dolomites. The advantages of both catalysts are their low price and high attrition resistance. However, olivines and dolomites have higher calcination temperatures and this restricts the effective use of both catalysts.

In fact, calcination of both materials leads to several unwanted phenomena such as losing tar conversion activity and catalyst stability, reducing surface area, etc.