Banca de DEFESA: JENNIFER ELLEN LIMA DA COSTA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : JENNIFER ELLEN LIMA DA COSTA
DATE: 27/08/2025
TIME: 09:30
LOCAL: Auditório do LABTAM
TITLE:

Calcium-doped LaNiO₃ Perovskites for Hydrogen Production via Dry Reforming of Methane.

KEY WORDS:

Dry Reforming of Methane; Hydrogen; Perovskite; Dopant; Calcium

PAGES: 90
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Físico-Química
SPECIALTY: Cinética Química e Catálise
SUMMARY:

The growing energy demand, combined with the dependence on fossil fuels, has exacerbated climate change and continuously increased the concentration of greenhouse gases (GHGs) in the atmosphere, making the development of technologies capable of mitigating such environmental impacts urgent. Dry reforming of methane (DRM), which utilizes methane (CH₄) and carbon dioxide (CO₂), two of the main GHGs, stands out as a promising alternative for the production of synthesis gas (H₂ and CO), contributing simultaneously to emission reduction and the generation of energy feedstocks. Nickel-based catalysts, when compared to noble metal catalysts, are widely used in DRM; however, they exhibit limitations related to carbon deposition and sintering, which compromise their stability and catalytic activity. In this study, LaNiO₃ perovskite catalysts were synthesized by microwave-assisted combustion and modified by calcium doping (La₁₋ₓCaₓNiO₃, x = 0.25 and 0.50). The samples were characterized by XRD, SEM, EDS, BET, TPR, TG, and Raman spectroscopy. XRD results of the fresh catalysts revealed that calcium doping significantly altered the phase formation. Instead of the predominance of the pure LaNiO₃ phase (41.75% in the standard), the doped samples formed new complex perovskite phases containing calcium [e.g., (La₁.₅Ca₀.₅)NiO₄ (40.69% in LN-Ca25) and (LaCa)NiO₄ (49.18% in LN-Ca50)], along with increased segregation of NiO (26.43% in LN-Ca25 and 32.09% in LN-Ca50). Textural analyses indicated that Ca doping, especially at 50%, promoted an increase in surface area and porosity (42.46 m²/g for LN-Ca50 vs. 31.99 m²/g for LN). Catalytic evaluation in DRM showed that the doped catalysts exhibited slightly lower conversions and yields than the standard, as well as an induction period for activation, 2 and 6 hours for LN-Ca25 and LN-Ca50, respectively. However, after activation, both doped catalysts exhibited stability during the 15-hour test comparable to the standard LaNiO₃ catalyst. The main innovation lies in the remarkable resistance to carbon deposition. Post-reaction analyses by XRD, TG, and Raman indicated a significant absence of coke. Post-reaction SEM micrographs revealed that the standard catalyst underwent sintering and collapse, while the doped catalysts maintained a more stable morphology. The formation of phases such as CaCO₃ and La₂O₂CO₃ in the doped samples after DRM suggests the role of calcium in coke mitigation.

COMMITTEE MEMBERS:
Presidente - 349770 - DULCE MARIA DE ARAUJO MELO
Externo à Instituição - RODOLFO LUIZ BEZERRA DE ARAÚJO MEDEIROS - UFRN
Externo à Instituição - TIAGO ROBERTO DA COSTA - IFRN
Externo à Instituição - ÂNGELO ANDERSON SILVA DE OLIVEIRA - UFRN