Captura de CO2 de gases de combustão utilizando óxido de cálcio

Abstract

Calcium oxide (CaO) based materials were prepared, characterized and subjected to cyclic carbonation and decomposition reactions in order to evaluate the carbon dioxide capture capacity (CO2) and the stability of the material. The sol-gel method was used for the synthesis of pure CaO and wet mixing and impregnation methods for incorporating CaO into an additive Al2O3, ZrO2, and La2O3. The materials were characterized by X-ray diffraction, temperature programmed desorption, thermogravimetric analysis, scanning electron microscopy and adsorption of N2. The CO2 capture was performed in a looping reaction using thermobalance and fixed bed reactor, with carbonation at 700 °C in CO2 flow and decomposition of calcium carbonate at 800 °C in pure N2 flow. The results showed that pure CaO has decreased the CO2 capture capacity after the first reaction cycle. The materials synthesized by wet mixing showed higher CO2 capture efficiency and stability than the materials prepared by impregnation. Among the materials synthesized by wet mixing, 90CaO10Al2O3, 50CaO50Al2O3 and 50CaO50(Al2O3+La2O3) are the most stable reactivity and highest CO2 capture capacity. The 90CaO10Al2O3 had a CO2 capture capacity of 0.71 g-CO2/g-material up to six cycles, meanwhile, 50CaO50Al2O3 and 50CaO50(Al2O3+La2O3) showed CO2 capture capacity up to six cycles of 0.37 and 0.32 g-CO2/g-material, respectively. However, the materials with the highest amount of additive, 50CaO50Al2O3 and 50CaO50(Al2O3+La2O3), were still the most stable. For the materials prepared by wet mixing, the results of the characterizations suggest that the addiction of additives decreased significantly the amount of unreacted CaO and allowed the accessibility of the CO2 to CaO.