Institutional Repository of GuangZhou Institute of Energy Conversion, CAS
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The efficient promoting hydrodeoxygenation of bioderived furans over Pd/ HPW-SiO<sub>2</sub> by phosphotungstic acid
No full textAcidic promoters are significant in the hydrodeoxygenation (HDO) of bioderived furans into alkanes over metal-acid bifunctional catalysts. Here, a supported Pd/HPW-SiO2 catalyst was prepared to investigate the promotion effect of phosphotungstic acid (HPW) on the HDO of HMF-acetone adduct (H-Ac). Characterizations suggested that an intimate contact between Pd and HPW was established in Pd/HPW-SiO2. HPW promoters significantly reduced the reduction temperature of Pd oxides with enhanced hydrogenation and HDO capability. Particularly, in-situ DRIFTS confirmed that Pd-HPW sites significantly weakened the pi(CO) eta(2) adsorption mode (nu(3)(C=O)) of C=O group on Pd surfaces. Thereby, the HDO efficiency was synergistically improved through releasing more Pd metal sites to activate hydrogen for hydrogenation and HDO with HPW promoters. Eventually, >90% yield of nonane was efficiently achieved at 160 degrees C. This work is applicable to explore the structure-activity relationship of bifunctional catalysts in the efficient HDO of complicated oxygenated bioderived furans
Phase Transition Characteristics of Hydrate Formation Process in Microscale Pores
No full textGas hydrates are ubiquitous in nature, with their formation within microscale pores involving intricate physical and chemical process. Recent advancements in visualization methods have propelled further investigations into the formation mechanisms of gas hydrates. The exploration of characteristics pertaining to the hydrate formation process through visual data has emerged as a prominent research avenue. However, it is still difficult to directly point out the relationship between the visual phenomenon and mechanism with a systematic approach. This article focuses on discerning significant temporal changes and categorizes phase transition features of microscale pore hydrate formation into two distinct yet conceptually clear domains: distribution probability and phase transition probability. Then, a statistical discussion of these probabilities has been proposed. Distribution probability elucidates the structural performance and physical attributes of hydrates at the microscale, while phase transition probability offers insights into visualizing kinetic parameters of hydrate reactions, which are conventionally challenging to gauge using traditional sensors. These probabilities linked visual information to physical information. It enabled the quantitative statistical evaluation of various factors during the phase transition process of hydrates, moving beyond a mere visual qualitative analysis. In essence, this innovative methodology furnishes hitherto unexplored concepts and a systematic framework for investigating microscale interface reactions and illuminating their internal mechanisms and evolutionary principles
Experimental and modeling investigations on CH<sub>4</sub> hydrate phase equilibria in multi-ion "Haima" cold seep environment
No full textCH4 hydrate formation represents a primary pathway for CH4 transformation within the deep-sea CH4 seepage environment, holding utmost significance for global carbon budget and marine hydrate resources distribution. As a typical active CH4 seeping, however, the influence characteristics of various ions in in-situ "Haima" cold seep on CH4 hydrate stability remains unclear. In this study, founded on the multiple ion components from the seawater of the "Haima" cold seep, the effects of salt ion categories and concentrations on CH4 hydrate phase equilibrium were investigated, and a thermodynamic model suitable for high-salinity deep-sea environment was proposed. Results indicated that, in higher concentration salt solutions (>3.45 wt%), hydrate stability was no longer solely governed by salinity, and significant differences among ion types were observed. The inhibitory strength of the ions on CH4 hydrate stability followed the order of Mg2+>Na+>Ca2+>Mn2+approximate to K+>Sr2+>Ba2+. The predicted CH4 hydrate phase equilibrium conditions from the proposed model exhibited strong agreement with both experimental results and data reported in the literature. The average absolute deviation of pressure (AADP) from the model prediction was 2.7% and 4.3% compared to the experimental and published literature data, respectively, which outperformed those of the CSMHYD model, Chen-Guo model and Hu-Lee-Sum correlation (4.7%-6.2%). In light of the marine temperature gradient and prediction results, it is estimated that CH4 hydrate could maintain stably below 600 m depth of the seawater in the cold seep area
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