Active and durable alkaline earth metal substituted perovskite catalysts for dry reforming of methane

• Published in: Applied catalysis. B, Environmental Vol. 224; pp. 146 - 158
• Main Authors: Dama, Srikanth, Ghodke, Seema R., Bobade, Richa, Gurav, Hanmant R., Chilukuri, Satyanarayana
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.2018; Elsevier BV
• Subjects: Alkaline earth metals; Alkalinity; Basicity; Calcium; Carbon deposition; Carbon dioxide; Carbon nanotubes; Catalysis; Catalysts; Citrate gel method; Citric acid; Coke; Crystal defects; Deactivation; Diffuse reflectance spectroscopy; Dry reforming; Durability; Earth; Fourier transforms; Hydroxyl groups; Infrared spectroscopy; Life assessment; Metals; Methane; Nanotechnology; Nanotubes; Nickel; Nutrient deficiency; Oxygen; Perovskite; Perovskites; Reforming; Spectrum analysis; Studies; Substitutes; Synthesis gas; X ray photoelectron spectroscopy; Citrate gel method; Dry reforming; Carbon deposition; Perovskites; Nickel
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2017.10.048

[Display omitted] •MZr0.8Ni0.2O3-δ (M=Ca, Sr and Ba) perovskite catalysts were prepared by citrate gel method.•Nature of alkaline earth at ‘A’ site of perovskite influences the performance of the catalysts.•CaZr0.8Ni0.2O3-δ has higher oxygen defect sites and stronger metal support interaction.•Surface hydroxyl groups on CaZr0.8Ni0.2O3-δ help to control the coke formation.•CaZr0.8Ni0.2O3-δ is highly active and also stable even after 500h of reaction. Dry reforming of methane is an important process for the utilization of CO2 and to get valuable synthesis gas. Alkaline earth metal substituted MZr1-xNixO3-δ perovskites were synthesized by citrate gel method, characterized and evaluated for dry reforming methane. Characterization results show that the type of alkaline earth substituted at the A site of the perovskite oxide plays an important role in terms of structure, basicity, oxygen deficiency and Ni dispersion. Calcium substituted CaZr0.8Ni0.2O3-δ catalyst shows superior activity in terms of high CH4 and CO2 conversion, while maintaining the activity even after 500h of reaction. Mechanistic investigations were carried out using transient pulse experiments and insitu FTIR-diffuse reflectance spectroscopy. These experiments reveal that redox property and basicity play important role in activation and sustaining the reforming reaction. Insitu FTIR measurements show that surface hydroxyl groups of the support are vital for high activity and durability of CaZr0.8Ni0.2O3-δ catalyst. XRD and TGA analysis of catalysts after reaction show the structures are retained, but peaks pertaining to coke were observed on SrZr0.8Ni0.2O3-δ and BaZr0.8Ni0.2O3-δ catalysts. On the otherhand, CaZr0.8Ni0.2O3-δ catalyst had only amorphous carbon even after 500h of reaction. HRTEM studies revealed that SrZr0.8Ni0.2O3-δ and BaZr0.8Ni0.2O3-δ catalysts deactivated mostly due to the formation of carbon nanotubes with Ni embedded in them. Raman and XPS analysis helped in identifying types of coke precursors present on the catalysts. The investigation also illustrate that type of carbon formed depends on the basicity of perovskite oxide, metal to support interaction, Ni crystallite size, surface hydroxyl groups and oxygen defects. This study clearly demonstrated that CaZr0.8Ni0.2O3-δ is an excellent catalyst for dry reforming reaction with long life.