RESUMO
Ammonia decomposition has attracted significant attention in recent years due to its ability to produce hydrogen without emitting carbon dioxide and the ease of ammonia storage. This paper reviews the recent developments in ammonia decomposition technologies for hydrogen production, focusing on the latest advances in catalytic materials and catalyst design, as well as the research progress in the catalytic reaction mechanism. Additionally, the paper discusses the advantages and disadvantages of each method and the importance of finding non-precious metals to reduce costs and improve efficiency. Overall, this paper provides a valuable reference for further research on ammonia decomposition for hydrogen production.
Assuntos
Amônia , Metais , Catálise , HidrogênioRESUMO
Hydrogen, ammonia, and methanol are typical carbon-neutral fuels. Combustion characteristics and pollutant formation problems can be significantly improved by their blending. In this paper, reactive molecular dynamics were used to investigate the pollutant formation characteristics of hydrogen/ammonia/methanol blended fuel combustion and to analyze the mechanisms of CO, CO2, and NOX formation at different temperatures and blending ratios. It was found that heating can significantly increase blending and combustion efficiency, leading to more active oxidizing groups and thus inhibiting N2 production. Blended combustion pollutant formation was affected by coupling effects. NH3 depressed the rate of CO production when CH4O was greater than 30%, but the amount of CO and CO2 was mainly determined by CH4O. This is because CH4O provides more OH, H, and carbon atoms for CO and CO2 to collide efficiently. CH4O facilitates the combustion of NH3 by simplifying the reaction pathway, making it easier to form NOX.
RESUMO
Density functional theory is adopted to thoroughly analyze the influence mechanism of Fe on the formation of NH3 and HCN. The structure of Fe adsorbed on the surface of seven-membered zigzag coal containing pyridine nitrogen is selected as the Fe-containing coal model. The effect of Fe on the nitrogen distribution during Zhundong coal pyrolysis is further studied by thermogravimetry-mass spectrometry. The theoretical calculations show that Fe increases the Mulliken charge density on the N5 surface, which increases the rate-determining step energy barrier value of NH3 generated from coal pyrolysis and inhibits the NH3 formation. On the other hand, Fe significantly enhances the bonding energy between σ N5-C6 and π N5-C6, increases the activation energy required for N stripping from the pyridine ring (about 69.14 kJ/mol higher than that without Fe), and inhibits HCN formation. The experimental results show that Fe catalyzes the precipitation peaks of NH3 and CH3CN about 20 K ahead of time and has no obvious catalytic effect on HCN and HNCO. In terms of the nitrogen distribution, Fe significantly promotes the CH3CN formation and shows a significant inhibitory effect on NH3, HCN, and HNCO. Kinetic results show that Fe reduces the precipitation rates of NH3 and HCN, and the inhibitory effect on HCN is more significant.
RESUMO
The combustion experiments of HG micronized coal have been conducted by combining DTG and GC-MS. The effects on NOx emission caused by particle size, oxygen concentration and heating rate were analyzed. The results show that under combustion condition that oxygen concentration is 20%, NOx precipitations of HG coal in difference sizes are single-peaked courses. Particle size impacts NOx emission from coal combustion significantly. Micro-pulverized coal reduces NOx emission. Under heating condition with 5 degrees C/min, 10 degrees C/min and 20 degrees C/min, precipitation of NO and NO2 is increased with heating rate rising, and temperature parallelized with maximum NO precipitation rate is increased with heating rate rising as well. With increasing of oxygen concentration in combustion, NOx precipitation increases correspondingly, and temperature parallelized with maximum NOx precipitation rate is reduced.