Avaliação da capacidade de captura de dióxido de carbono do óxido de cálcio suportado em vermiculita

Abstract

Vermiculite samples were impregnated with different amounts of calcium oxide and the products were characterized by thermal analysis (TGA), nitrogen adsorption porosimetry (BET method) and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (DES). The ability of the products to capture carbon dioxide was investigated using thermal analysis experiments, employing a carbon dioxide atmosphere, where the mass gain relates to the amount of carbon dioxide transformed into carbonate. The amount of carbon dioxide captured by the calcium oxide increased from 13 to 16,8g of CO2 per mol of CaO, when the tests were made with pure calcium oxide and vermiculite impregnated with 50% calcium oxide w/w, respectively. The greatest capture value obtained was 32,2g of CO2 per mol of CaO, which represent an increase of 250% from the pure oxide sample. The influence of the vermiculite surface area was evaluated by BET method and the results showed that the material with granulometry smaller than 106 µm has a reduced surface area due to the destruction of the lamellar structure, therefore, less carbon dioxide was captured. Finally, the isoconversionals methods of Kissinger-Akihira-Sunose (KAS) and OsawaFlynn-Wall (OFW) were used for studying the kinetic process. The apparent activation energy values showed that for low conversion (α < 0.3) the controlling step is mixed (20kJ < Ea < 40kJ), the velocity of the chemical step and diffusion step have the same order of magnitude. For greater conversion values (α > 0.3), the apparent activation energy values suggest that the chemical step is the slower step (Ea > 40kJ).