Manohar Reddy Poreddy

This work evaluates microwave-assisted calcination as a rapid, energy-efficient alternative to conventional resistive heating for complex oxide synthesis. Ce0.9Gd0.1O1.95 (GDC10) and La0.6Sr0.4Co0.2Fe0.8O3–δ (LSCF6428) were investigated using solid-state and co-precipitated precursors to assess the influence of precursor chemistry on microwave coupling, reaction kinetics, and powder characteristics. Experiments were conducted in a single-mode magnetic-field-extended reactor using a silicon carbide/alumina susceptor–insulation package to ensure uniform and reproducible heating. Microwave processing reduced calcination time to ~1 h, compared to >21 h in a conventional furnace, while yielding powders with 28% higher surface area. High-temperature dielectric measurements of LSCF (450–1000 oC) revealed strong temperature-dependent increases in dielectric constant and loss factor, governing self-heating behavior and distinct microwave-driven reaction pathways. Phase evolution and surface area were characterized by TGA, XRD, and BET. These results clarify microwave–material coupling mechanisms and demonstrate synergistic effects between precursor chemistry and microwave heating in complex oxide synthesis.

Recent advancements in microwave-driven nonoxidative catalytic synthesis of C₂H₄ from CH₄ coupling offer a promising, energy-efficient, and eco-friendly alternative to conventional methods, where selective heating under microwave irradiation enables comparable conversions at substantially lower bulk temperatures and shorter reaction times. This study explores the performance of an MnO_X-based catalyst supported on CeO₂ and HY zeolite (silica-to-alumina ratio = 5.1) for the nonoxidative coupling of CH₄ (NOCM) under microwave irradiation. Inspired by the well-established efficacy of MnO_X catalyst in oxidative CH₄ coupling (OCM), their application in NOCM has also shown significant performance. The catalytic system achieved 15% CH₄ conversion and 99% selectivity toward C₂ hydrocarbons and maintained 64% selectivity toward C₂H₄ surpassing the yields reported in the literature even at higher temperatures (700-1000 °C). Catalyst performance was correlated with measurements by in situ Raman spectroscopy, and additional characterizations were performed using H₂-temperature programmed reduction , NH₃-temperature programmed desorption, and BET surface area analysis to understand structural changes during the reactions. These findings suggested that Mn functions as active sites for CH₄ activation in nonoxidative environments while also promoting efficient C-C coupling under microwave irradiation.