Review of natural gas hydrates as an energy resource: Prospects and challenges ☆

Microwave-assisted preparation of inorganic nanostructures in liquid phase.

ZnO nanowires (or nanorods) have been widely studied due to their unique material properties and remarkable performance in electronics, optics, and photonics. Recently, photocatalytic applications of ZnO nanowires are of increased interest in environmental protection applications. This paper presents a review of the current research of ZnO nanowires (or nanorods) with special focus on photocatalysis. We have reviewed the semiconducting photocatalysts and discussed a variety of synthesis methods of ZnO nanowires and their corresponding effectiveness in photocatalysis. We have also presented the characterization of ZnO nanowires from the literature and from our own measurements. Finally, a wide range of uses of ZnO nanowires in various applications is highlighted in this paper.

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Synthesis, characterization, and applications of ZnO nanowires

Recent progress in synthesis, properties and potential applications of SiC nanomaterials

A review of solidified natural gas (SNG) technology for gas storage via clathrate hydrates

As the foundation of energy industry moves towards gas, flow assurance technology preventing pipelines from hydrate blockages becomes increasingly significant. However, the principle of hydrate inhibition is still poorly understood. Here, we examined natural hydrophobic amino acids as novel kinetic hydrate inhibitors (KHIs), and investigated hydrate inhibition phenomena by using them as a model system. Amino acids with lower hydrophobicity were found to be better KHIs to delay nucleation and retard growth, working by disrupting the water hydrogen bond network, while those with higher hydrophobicity strengthened the local water structure. It was found that perturbation of the water structure around KHIs plays a critical role in hydrate inhibition. This suggestion of a new class of KHIs will aid development of KHIs with enhanced biodegradability, and the present findings will accelerate the improved control of hydrate formation for natural gas exploitation and the utilization of hydrates as next-generation gas capture media.

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Hydrophobic amino acids as a new class of kinetic inhibitors for gas hydrate formation

Hydrophobic amino acids as a new class of kinetic inhibitors for gas hydrate

We have studied the precursor effects of citric acid and various citrates-including triethyl citrate, tripotassium citrate, trisodium citrate and triammonium citrate-on the formation of ZnO crystals in alkaline solution These citrate-related chemicals could be divided into three groups (group A, triethyl citrate; group B, tripotassium citrate and trisodium citrate; and group C, citric acid and triammonium citrate) based on their activity for modifying the ZnO growth direction and solution pH dependency on their concentration We could obtain ZnO structures with various distinct morphologies by simply changing the concentration of citric acid or citrate additive dissolved in the alkaline reaction solution On the basis of the results, we propose the growth mechanisms underlying the formation of the various ZnO structures in the absence and presence of citric acid or citrate additives

Precursor effects of citric acid and citrates on ZnO crystal formation.

The motivation for this work was the potential of hydrophobic amino acids such as glycine, l-alanine, and l-valine to be applied as thermodynamic hydrate inhibitors (THIs). To confirm their capabilities in inhibiting the formation of gas hydrates, three-phase (liquid–hydrate–vapor) equilibrium conditions for carbon dioxide hydrate formation in the presence of 0.1–3.0 mol % amino acid solutions were determined in the range of 273.05–281.45 K and 14.1–35.2 bar. From quantitative analyses, the inhibiting effects of the amino acids (on a mole concentration basis) decreased in the following order: l-valine > l-alanine > glycine. The application of amino acids as THIs has several potential advantages over conventional methods. First, the environmentally friendly nature of amino acids as compared to conventional inhibitors means that damage to ecological systems and the environment could be minimized. Second, the loss of amino acids in recovery process would be considerably reduced because amino acids are nonvol...

Amino acids as natural inhibitors for hydrate formation in CO2 sequestration.

The recovery of gas from natural gas hydrates under the permafrost and in oceanic sediments is of particular interest in energy and environmental fields because of the attractive process to release methane gas through the injection of CO2. The sequestration of CO2, a notorious greenhouse gas, in hydrates has the potential to be used in enhanced gas recovery techniques, while simultaneously releasing CH4 locked within the gas bearing hydrates. In this study, we present quantitative experiments to investigate results of possible CH4–CO2 exchange kinetics from injection of liquid CO2 through CH4 hydrates. The experiments performed use CH4 hydrate formed from ice particles (75–90 or 125–150 microns in diameter) at approximately 10.34 MPa and 263 K. In order to reduce unexpected errors, nearly full conversion (>95%) of ice particles to hydrates is achieved. Liquid CO2 is injected into the pressure cell to sweep the residual CH4 atmosphere, ensuring no free CH4 is left in the gas phase. After soaking the hydrate for several hours, CH4 is produced from the hydrates by injecting liquid CO2. The final composition and analysis of the produced CH4 is measured by using in-line gas chromatography. We also measure the CH4 moles after hydrate dissociation to confirm the closure of the total mass balance of the experiment. From these data, we infer the mechanism for CH4 production, identify the penetration depth of the dissociation/exchange on the hydrate particles, and propose physical models describing the mechanism for CH4 production. These experiments are essential in the quantification of the production of CH4 from CH4 hydrates with the injection of CO2.

Bo Ram Lee

Papers

Hydrophobic amino acids as a new class of kinetic inhibitors for gas hydrate formation

Hydrophobic amino acids as a new class of kinetic inhibitors for gas hydrate

Precursor effects of citric acid and citrates on ZnO crystal formation.

Amino acids as natural inhibitors for hydrate formation in CO2 sequestration.

Quantitative measurement and mechanisms for CH4 production from hydrates with the injection of liquid CO2