3 Search Results

Microwave absorbing catalysts have the potential to electrify high-temperature thermal reactions such as the dry reforming of methane process (DRM: CO₂ + CH₄ → 2CO + 2 H₂). However, microwave catalysts present unique challenges due to their dual requirements of maintaining microwave absorption in both oxidative and reductive environments and stability across a range of temperatures in inherently non-isothermal reactors. Here, catalyst candidates from the La_0.8Sr_0.2CoO₃-La_0.8Sr_0.2NiO₃-La_0.8Sr_0.2MnO₃ perovskite systems were screened (28 total) to identify promising microwave catalysts free of noble metals for dry reforming methane. The best performing candidates met two main criteria. First, they occurred at crystal phase boundaries,more » giving rise to a pseudocubic perovskite structure. The combined use of Goldschmidt tolerance factor and octahedral tolerance factors appeared to be suitable for predicting pseudocubic perovskites. Second, they provided a balance of reducible metal sites with an irreducible metal oxide support. The best performing catalyst was found to exsolve Ni-Co alloy particles as active sites for the DRM reaction which offered superior resistance to coking for excellent reforming efficiency and stability.« less

Strontium oxide (SrO) is a promising material for CO₂ capture through a reversible cycle of carbonation and calcination, where SrO reacts with CO₂ to form SrCO₃ and can be regenerated by calcination. In the presence of moisture, SrO forms strontium hydroxide and its hydrates (Sr(OH)₂·nH₂O). Here, this study, which employs density functional theory, investigates the CO₂ adsorption mechanism of these processes on various crystal surfaces, including SrO, Sr(OH)₂, Sr(OH)₂·1H₂O, and Sr(OH)₂·8H₂O. A significant finding is that the interaction of CO₂ with these surfaces leads to carbonate/bicarbonate formation via electron transfer, with notable differences in CO₂ orientation and bond characteristics betweenmore » SrO surfaces and its hydroxylated surfaces. To explore the effects of moisture on CO₂ adsorption, H₂O adsorption on these stable surfaces was investigated. The results showed that H₂O reacts with the SrO (100) surface to form hydroxyl (OH) groups while it bonds with the surfaces of Sr(OH)₂·nH₂O (n = 0, 1, 8) with hydrogen bonding. A small amount of H₂O can enhance CO2 adsorption while a large amount of H₂O could decrease the capability of CO₂ adsorption.« less

Here this study reports energy-efficient and water-saving microwave-accelerated regeneration of sorbent (MARS) for dilute carbon capture from the ambient air. The experimental studies indicated that the CO₂ desorption rate from the chemisorbents increased with microwave output under near-isothermal conditions at near room temperature. The reduced activation energy of MARS, i.e., 20–28 kJ/mol, indicated enhanced CO₂ desorption kinetics by microwave-induced rotational–vibrational (rovibrational) coupling transitions, primarily due to the highly polarized feature of the carbamate (CO₂-PEI). The instant and selective delivery of microwave energy to the targeted polarized C–N bonds at room temperature is particularly advantageous for energy-efficient direct air capture. Themore » experimental results also demonstrated a good working capacity of 0.6–1.4 mmol of CO₂/g and a promising rapid MARS-DAC process with microwave swing. As it does not require steam regeneration and heat exchanger, a simple MARS process is attractive for CO₂ capture in water-stressed regions.« less