Water/diesel-cyclopentylamine and water/diesel-cyclopentanone emulsions were used to store natural gas during hydrate formation. First, cyclopentylamine (-amine) and cyclopentanone (-anone) were tested as thermodynamic promoters for CH4 hydrate formation in water/diesel (w/o) emulsions. The kinetics of CH4 hydrate formation in the w/o-amine and w/o-anone emulsions were then investigated. It was found that the promotional effect of both cyclopentylamine and cyclopentanone on CH4 storage in the hydrate phase was much better than that of cyclopentane, with the highest gas storage amount reaching 201.7 m3/m3, which is close to the ideal value (220 m3/m3), and the water-to-hydrate conversion ratio was higher than 90%. The main hydration reaction process was completed in 50 min, with the reaction rate reaching 2.3 mmol/min, which is higher than that reported for aqueous solutions. It should be noted that this was the first time that cyclopentylamine was tested and it showed good thermodynamic and kinetic stimulation effects on gas hydrate formation. The suitable CH4 hydrate formation conditions including the additional amount of promoters, temperature, pressure, and water cut range were determined to be approximately 20 wt %, 274.15–278.15 K, 5.0–6.0 MPa, and 20 wt %, respectively. The storage and transport pressure for the formed hydrate products could be decreased to less than 1 MPa. The significant gas storage amount was further supported by laser Raman analysis, which confirmed that the CH4 molecules were trapped in the small and large cages of the formed SII hydrate. Meanwhile, the formed hydrate/diesel slurries exhibited good dispersion features.
Wanjun Guo,Zhi-Qiang Wang,Shuang Xiang,Yaxuan Jing,Xiaohui Liu,Yong Guo,Xue-Qing Gong,Yanqin Wang
ABSTRACT Owing to the wide application of primary amines, their selective production via reductive amination has become a crucial research topic. Various metal-supported catalysts (Pt, Ru, Rh, Ir, Co, Ni, etc. ) have been investigated, and metallic species have been recognized as active sites in recent years. Herein, we reveal for the first time that CoO species containing oxygen vacancies within a core-shell-structured Co@CoO catalyst accelerate the ammonolysis of Schiff bases, key intermediates in reductive amination, through NH 3 dissociation to hydride-like NH 2 δ – species, delivering an excellent reductive amination performance. The catalyst is highly stable and was utilized in 10 catalytic cycles for the amination of biomass-derived cyclopentanone (CPO) to cyclopentylamine (CPA) without deactivation. Various computational models in combination with spectroscopic measurements indicated that this catalyst not only drives the dissociation of H 2 to the active H δ – species, but also enables the homolytic cleavage of NH 3 to NH 2 δ – . D 2 isotopic tracing experiments provided further evidence of the direct involvement of hydride-like NH 2 δ – species in Schiff base ammonolysis. Theoretical calculations verified the stable co-adsorption of H δ – and NH 2 δ – , which allows the Schiff base to move freely on the surface of the CoO shell and participate extensively in molecular collisions, resulting in exceptional catalytic activity. This is the first study that demonstrates the potential of metal oxide catalysts for the production of primary amines via reductive amination.
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