Conformação de adsorventes: combinando forma, estabilidade e funcionalidade para aplicação industrial

Abstract

Gas drying by adsorption on molecular sieves is a crucial unit operation in natural gas processing. However, the presence of a complex gas mixture and thermal swings can cause early adsorbent fouling, thus reducing process efficiency. To mitigate this issue, shaping the adsorbent materials is essential to avoid/manage large pressure drops and improve thermal and mechanical properties. In this study, we aimed to investigate the effect of shaping on the thermal and mechanical resistance and adsorption properties of three different zeolite powder samples. The molecular sieves were shaped by extrusion into cylindrical beads using a clay binder, followed by calcination at 673 K for 24 hours. The main formulations included 15%, 20%, and 25% of binder. The resulting 2-mm extrudates were compared with commercially available shaped samples for their mechanical and thermal resistances. Then, the shaped samples were submitted to a premature aging protocol that simulated the conditions of TSA drying processes. Before and after the aging process, we performed several analytical characterizations and measured high-resolution H2O isotherms at 313 K. The results indicated that the 20% binder is the composition that led to the lowest decrease in textural properties and water uptake after the premature aging protocol as compared to the pristine zeolite samples. CHA structure (containing potassium) was intrinsically more robust against aging than (sodium) LTA structure in longer aging. SEM images and infrared spectroscopy data strongly suggest that the decrease in adsorption capacity was due to coke occurrence, which is a common cause of deactivation in catalytic applications. However, the coke formation in the present study had somewhat distinct features as compared to those observed in catalysts. These findings provide clear evidence of the protective effect of the clay binder against hydrothermal deactivation. Overall, this study highlights the importance of shaping adsorbent materials for natural gas processing and provides valuable insights into the lifespan of adsorbent and the degree of deactivation.