Banca de QUALIFICAÇÃO: JULIA VIEIRA DA SILVA BERNARDO

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : JULIA VIEIRA DA SILVA BERNARDO
DATE: 25/03/2026
TIME: 14:00
LOCAL: Auditorio do CCET
TITLE:

MESOPOROUS SILICA-BASED MATERIALS AND CARBON REPLICAS FOR CO2 ADSORPTION AND CONVERSION.

KEY WORDS:

SBA-15; KIT-6; CMK-3; CMK-8; Nickel; Adsorption; Conversion; Hydrogenation; Methanation; CO₂.

PAGES: 120
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
SPECIALTY: Cerâmicos
SUMMARY:

Climate change has intensified the search for effective strategies to mitigate carbon dioxide (CO₂) emissions, the main gas associated with global warming. In this context, the development of materials capable of simultaneously capturing and converting CO₂ into value-added products emerges as a high-potential technological alternative. Ordered mesoporous structures stand out due to their high specific surface area, controlled porosity, and structural stability, which are key features for adsorption and catalytic applications. In this work, mesoporous silica-based materials (SBA-15 and KIT-6) and their corresponding carbon replicas (CMK-3 and CMK-8) were synthesized aiming at CO₂ adsorption and conversion. The materials were used as supports for nickel impregnation, employed as the active phase for CO₂ hydrogenation to methane. Commercial activated carbons were also impregnated and characterized for comparison of structural and textural properties, although they were not subjected to catalytic tests. X-ray diffraction confirmed the preservation of the ordered mesoporous structure after impregnation. N₂ adsorption/desorption isotherms showed typical type IV behavior for mesoporous materials and type I behavior for activated carbons, indicating their predominantly microporous nature. The supports exhibited high specific surface areas, with CMK-8 (1187 m² g⁻¹) and CMK-3 (1018 m² g⁻¹) presenting the highest values, while SBA-15 and KIT-6 showed areas close to 640 and 600 m² g⁻¹, respectively. After nickel impregnation, a decrease in surface area was observed due to partial pore occupation, except for KIT-6. CO₂ adsorption tests demonstrated that adsorption capacity is directly related to specific surface area and pore accessibility, being more pronounced in materials with higher surface area. Nickel impregnation caused a slight decrease in CO₂ uptake, indicating a minor contribution of the metallic phase to the adsorption process. Temperature-programmed reduction (TPR) analyses revealed multiple reduction events with maximum temperatures between 336 and 485 °C, indicating varying metal–support interaction strengths. In CO₂ hydrogenation to methane, the SBA-15-Ni catalyst exhibited the highest average conversion (≈5.2%) and high methane selectivity (≈95%), although a slight deactivation was observed over 10 h of reaction. KIT-6-Ni showed lower conversion (≈3.6%) but greater stability over time. CMK-3-Ni presented low conversion (<1%) and lower methane selectivity, highlighting the influence of support nature on metal–support interaction and catalytic performance. Overall, the results demonstrate that structural and textural properties play a decisive role in both CO₂ adsorption and conversion, reinforcing the importance of structural control in the design of catalysts for methanation reactions.

COMMITTEE MEMBERS:
Presidente - 1308577 - SIBELE BERENICE CASTELLA PERGHER
Interno - 1350249 - RUBENS MARIBONDO DO NASCIMENTO
Externa à Instituição - ANNE GABRIELLA DIAS SANTOS - UERN
Externo à Instituição - EDUARDO RIGOTI - UFRN