Aproveitamento do catalisador de equilíbrio de uma planta de refino de petróleo (FCC) na captura de CO2

Abstract

The large production of catalytic waste, equilibrium catalyst (Ecat), in Fluid Catalytic Cracking Units (FCCU) beds is a potential problem to the environment due to the presence of heavy metals deposited on its surface. Thus, the aim of this study is to propose new technologies for its reuse. Residual USY phase in Ecat were firstly used as zeolitic building blocks to prepare zeolite materials by activation with NaOH solutions. The prepared materials were characterized (XRD, EDX, SEM, FTIR and N2 physisorption) and further tested as CO2 adsorbents. The resulting materials contained zeolites ZK-14 (CHA), P-1 (GIS), ZK-4 (LTA), Analcime (ANA) and -alumina, but the phase distribution mainly depended on the Na/Si atom ratio and reaction temperature. High micropore surface area (> 50 m² g-¹) and high composition of the zeolitic phases in the composite were achieved by the samples with increasingly high ZK-14 (CHA) contents. These factors were associated with the best results on CO2 uptakes by thermogravimetry. After, the 85C-r0.6-7d material, the highest percentage of ZK-14 zeolite (64%) one, now known as CHA-64, was evaluated by CO2 uptake in fixed bed and under the presence of water vapor, methane and carbon monoxide. It was observed, in initial tests without the presence of steam, that the CO2/CHA-64 interaction occurs predominantly by physisorption which gave a high stability in the regeneration test after 12 cycles of adsorption. However, the presence of carbonate species possibly formed by the interaction between CO2 and the surface hydroxyls of the adsorbent confirm the existence of chemisorption in a lesser extent. It was observed that the water contributes to a more negative heat of adsorption by varying the temperature of the adsorption bed (-21.4 e -10.7 KJ mol-1, to the reactions with and without water, respectively). It suggests the existence of mechanisms based on new stronger interactions through water molecules. Thus, the CHA-64 material prepared from waste FCC catalyst proved to be an interesting CO2 adsorbent, being resistant to the presence of steam and other gases.