Epoxycyclopentane hydrate for sustainable hydrate-based energy storage: notable improvements in thermodynamic condition and storage capacity

Geometric and Hydrophilic Effects of Oxirane Compounds with a Four-Carbon Backbone on Clathrate Hydrate Formation

The physicochemical properties of clathrate hydrates are influenced by the chemical nature and three-dimensional (3D) geometry of the added molecules. This study investigates the effects of five oxirane compounds: cis-2,3-epoxybutane (c23EB), trans-2,3-epoxybutane (t23EB), 1,2-epoxybutane (12EB), 1,2,3,4-diepoxybutane (DEB), and 3,3-dimethylepoxybutane (33DMEB) on CH4 hydrate formation. Despite having a four-carbon backbone, these compounds differ in their 3D geometries. The structures and stabilities of CH4 hydrates containing each compound were analyzed using high-resolution powder diffraction, solid-state 13C NMR, and phase equilibrium measurements. The experimental results revealed that c23EB, 12EB, and 33DMEB act as sII/sH hydrate formers and thermodynamic promoters, whereas t23EB and DEB have opposite roles. These results were analyzed in relation to the 3D geometries and relative stabilities of various rotational isomers using DFT calculations. Hydrate structure was influenced by both the length and thickness of the added compounds. Moreover, an appropriate level of (not excessive) hydrophilicity induced by an oxirane group appeared to enhance the thermodynamic stability of the hydrates. This study provides insights into how the chemical nature of additives influences the structure and stability of clathrate hydrates.

Enrichment of gas storage in clathrate hydrates by optimizing the molar liquid water-gas ratio

Natural gas (NG) is considered a modern source of energy. Gas hydrates are anticipated to be an alternative method for gas storage and transportation applications. The process must be handy, rapid, and proficient for scale-up. In the present study, methane (CH₄) and carbon dioxide (CO₂) hydrates are synthesized by varying the guest (gas) to host (water) volume. The experiments are performed in a non-stirred system. The results specify that the maximum storage capacity is achieved when the molar liquid water–gas ratio is about 4.08 and 8.25 for CH₄ and CO₂ hydrates. At the optimal water–gas ratios, the total CH₄ and CO₂ gas uptake capacity is about 14.3 ± 0.4 and 9.1 ± 0.4 liters at standard temperature and pressure (STP) conditions. The gas uptake gradually increases with the solution volume and abruptly falls after a threshold point. The hydrate grows across the reactor's metal surface; when the process fully covers the surface, the growth continues horizontally (increase in thickness). With varying the liquid water–gas ratio (low to high), the formation kinetics (t₉₀) is delayed. The hydrate growth rate gradually decreases and does not significantly influence the hydrate formation temperatures. Optimizing the molar liquid water–gas ratio yields a high gas storage capacity and faster process kinetics.

Methane and carbon dioxide storage in hydrate form.

Modified Ti-MWW Zeolite as a Highly Efficient Catalyst for the Cyclopentene Epoxidation Reaction

The liquid-phase epoxidation of cyclopentene (CPE) was performed in the Ti-zeolite/H₂O₂ catalytic system for the clean synthesis of cyclopentene oxide. Among all the Ti-zeolites (Ti-Beta, Ti-MOR, Ti-MCM-68, TS-1, TS-2, and Ti-MWW) investigated in the present study, Ti-MWW provided relatively lower CPE conversion of 13% due to the diffusion constrains but a higher CPO selectivity of 99.5%. The catalytic performance of Ti-MWW was significantly enhanced by piperidine (PI) treatment, with the CPE conversion and CPO selectivity increased to 97.8 and 99.9%, respectively. The structural rearrangement upon PI treatment converted the 3-dimensional (3D) MWW structure to a 2D lamellar one, which enlarged the interlayer space and greatly alleviated the diffusion constrains of cyclic cyclopentene. Furthermore, the newly constructed “open site” six-coordinated Ti active sites with PI as the ligand exhibited higher catalytic activity. The two factors contributed to more significant enhancement of the activity upon PI-assisted structural arrangement compared to the cases in linear alkenes.