Universidade Federal do Ceará
PPGEQ – Programa de Pós-graduação em Engenharia Química

The development of separation processes for CO2 capture has been encouraged by the negative impact of the presence of CO2 on gaseous mixture. The presence of CO2 in natural gas decreases the calorific value and tends to promote corrosion of equipments. Also, after combustion, carbon dioxide emissions to the atmosphere are believed to intensify the greenhouse effect. In this context, the use of porous materials such as molecular sieves to remove CO2 by adsorption-based processes has gained relevance as a clean and economically attractive technology. The aim of this work was to evaluate the use of clinoptilolite to capture CO2 under different scenarios. The characterization was carried out by XRD, Adsorption of N2 at -196 °C and CO2 at 9 °C, and TGA. Single component (CO2, N2 e CH4) and binary (CO2/CH4 e CO2/N2) isotherms were obtained by manometry and gravimetry. A mathematical model using the LDF approach was applied to simulate column dynamics and PSA processes. Results have shown that clinoptilolite is a microporous material, contradicting some literature also reports pointing out mesoporosity. TGA results demonstrated structural stability up to 600 °C. The diffractogram identified the following phases: clinoptilolite, cristobalite and silicon dioxide. Compared to commercial adsorbents, the textural properties of clinoptilolite, as surface area (192 m2 g-1) and total pore volume (0.0953 cm3 g-1), seem to be unfavorable for CO2 capture. The adsorption capacities of CO2, N2 and CH4 at 25 °C and 1 bar were 1.75, 0.43 and 0.78 mmol g-1, respectively. The equilibrium isotherms also revealed low adsorption capacity when compared to commercial adsorbents (ex. zeolite 13X and activated carbons). For 1 bar and 25 °C, the selectivities were 2.70 and 4.10 to CO2 in CO2/CH4 (45 %55 %) and CO2/N2 (15 %85 %), respectively. Simulation results have shown that although the material is selective for CO2, its use in processes such as PSA is not indicated under the studied conditions mainly due to its low working capacity.