TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: (I) is obtained from a carbon containing material, preferably prepared or preparable by heat-treatment of at least one carbonate. (I) comprises a particle in which a core comprises at least one metal oxide and a cover, surrounding the core, comprising at least one carbonate, where the cover completely surrounds the core. (I) comprises: at least one earth alkali oxide and at least one carbonate in a weight ratio of 1:100-100:1, preferably 10:1; and particles having average particle size of 0.3-3 (preferably 0.5-1.5) mm, where the particles are porous. The metal oxide has structural formula (MxOy). The metal oxide contains at least one alkaline earth oxide, preferably calcium oxide or a mixture of calcium oxide and magnesium oxide. The metal oxide contains a portion of iron oxide and/or silicium oxide. The carbonate has a structural formula (Mx(CO3)y). The carbonate comprises at least one alkaline earth carbonate, preferably calcium carbonate or a mixture of calcium carbonate and magnesium carbonate. The carbonate is at least one metaloxocarbonate having a structural formula (MxOy(CO3)z). The carbonate particle is particle of natural carbonate (preferably chalk and/or dolomite).M = metal e.g. Mg, Ca, Sr, Ba, La, Mn or Y; andx, y, z = whole numbers.Preferred Process: The heat-treatment is carried out at 1000-1500 (preferably 1100-1300) degrees C. The heat-treatment is carried out until the thermal desorption reaction is complete and the carbonate particle is completely converted into oxide particles. The heat-treatment is interrupted before the thermal desorption reaction is complete so that the carbonate particle is converted into a particle having a core of carbonate and oxide layer surrounding the core. The heat-treated particle is subjected to a surface treatment in a carbon dioxide-containing gas atmosphere, where a thin layer of carbonate is formed on the surface of the particle. The carbon dioxide treatment is carried out at 600-800 degrees C (preferably 650-750 degrees C) and in a gas atmosphere of 100-700 mbar. During the carbon dioxide treatment in the gas atmosphere, water-partial pressure of 100-500 (preferably 100-300) mbar is used. The process parameters for the steps (a) and (b) in the method-2 are selected such that the chemical composition of the core of the particle receives (I). The process parameters in the method-2 are selected depending on the average particle size of the particle and/or the condition of the raw gas, preferably the carbon dioxide content. In the method-2, hydrogen containing synthesis gas, preferably a synthesis gas obtained from biomass, is used as the raw gas and the carbon dioxide content in the raw gas is 10-30 vol.%. The steps (a) and (b) are carried out in a fluidized bed reactor. EXAMPLE - Carbonate (lime stone) was burned at a temperature above 900 degrees C in a first tube reactor, where carbon dioxide was released. In a second tube reactor, carbon dioxide was formed from the intermediary product (oxide) at 650-750 degrees C and particles having a size of less than 100 mu m was removed continuously during or after the completion of the treatment to obtain the material.