RESUMEN
In order to alleviate the world energy resources crisis, the research and development of natural gas hydrates has a very important economic value and strategic significance. The CH4-CO2 replacement method can not only achieve geological storage of carbon dioxide but also more effectively mine natural gas hydrates. Based on molecular dynamics theory and the properties of natural gas hydrates, this paper delves into the replacement of methane hydrate with carbon dioxide under different temperatures, pressures, and concentrations of ethylene glycol (EG). We established a CO2-Hydrate model and three CO2/EG-Hydrate models with different concentrations of EG, and we simulated the radial distribution function (RDF), mean square displacement (MSD), and relative density distribution of each particle in the system in different conditions. The higher the temperature, the more unstable the methane hydrates are, and the methane hydrates are more prone to decomposition. Compared with 280 and 290 K, the temperature of 270 K is more favorable for carbon dioxide molecules to enter the hydrate layer and form carbon dioxide hydrates. The changes in pressure have little impact on the decomposition of methane hydrates, the rupture of water cages of methane hydrates, and the number of carbon dioxide molecules entering the hydrate layer under temperatures of 280 K and pressures of 1, 4, and 7 MPa. But overall, a pressure of 1 MPa is more conducive for carbon dioxide molecules to enter the hydrate layer and form carbon dioxide hydrates. Adding EG to CO2 molecules can inhibit the decomposition of methane hydrates. However, the higher the concentration of EG, the faster the decomposition of methane hydrates. The degree of fracture of the water cages in methane hydrates is greater under pure CO2 conditions. Adding EG to CO2 molecules is more conducive for CO2 molecules to enter the hydrate layer and form carbon dioxide hydrates. This review is of great significance to improve the mining efficiency and CO2 storage efficiency of the replacement of natural gas hydrates with CO2.
RESUMEN
Nymphaea is a key genus of the ANA grade (Amborellales, Nymphaeales, and Austrobaileyales) of basal flowering plants, which serve as a key model to study the early evolution of floral traits. In this study, we comprehensively investigated the emission, biosynthesis, and biological function of the floral scent in a night-blossoming waterlily Nymphaea prolifera. The headspace volatile collection combined with GC-MS analysis showed that the floral scent of N. prolifera is predominately comprised by methylated benzenoids including anisole, veratrole, guaiacol, and methoxyanisole. Moreover, the emission of these floral benzenoids in N. prolifera exhibited temporal and spatial pattern with circadian rhythm and tissue specificity. By creating and mining transcriptomes of N. prolifera flowers, 12 oxygen methyltransferases (NpOMTs) were functionally identified. By in vitro enzymatic assay, NpOMT3, 6, and 7 could produce anisole and NpOMT5, 7, 9, produce guaiacol, whereas NpOMT3, 6, 9, 11 catalyzed the formation of veratrole. Methoxyanisole was identified as the universal product of all NpOMTs. Expression patterns of NpOMTs provided implication for their roles in the production of the respective benzenoids. Phylogenetic analysis of OMTs suggested a Nymphaea-specific expansion of the OMT family, indicating the evolution of lineage-specific functions. In bioassays, anisole, veratrole, and guaiacol in the floral benzenoids were revealed to play the critical role in repelling waterlily aphids. Overall, this study indicates that the basal flowering plant N. prolifera has evolved a diversity and complexity of OMT genes for the biosynthesis of methylated benzenoids that can repel insects from feeding the flowers. These findings provide new insights into the evolutional mechanism and ecological significance of the floral scent from early-diverged flowering plants.