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Gas Hydrate

Yuying Zhang, Siqi Zhang, Wen Ni, Qihui Yan, Wei Gao, Yunyun Li
The mixture of finely ground blast furnace slag (BFS), basic oxygen furnace (BOF) steel slag (SS), and flue gas desulfurisation (FGD) gypsum could be used as cement to solidify heavy metals. In this study, these cementitious materials were combined with high-arsenic-containing tailings to form cemented backfill material (CBM). The results indicated that the optimal design of CBM was that of specimen CBM2 which showed good early strength (10.09 MPa) at a curing age of 3 days containing 60% BF slag, 30% SS, and 10% gypsum...
February 8, 2019: Chemosphere
Alexandre Mendonça Teixeira, Lara de Oliveira Arinelli, José Luiz de Medeiros, Ofélia de Queiroz F Araújo
Offshore oil/gas productions are power intensive and CO2 emitters from gas-fired power generation. This work investigates supersonic separator as a strategy for affording post-combustion capture backed up by cost reductions. Conventional offshore gas processing usually loses thermodynamic hydrate inhibitor methanol in processing and exported gas. This work analyses a supersonic separator variant gas processing simultaneously reducing methanol losses. Such process dramatically improves gas-plant profitability via cost-reduction of methanol make-up and power-consumption, simultaneously increasing revenues from liquefied-petroleum-gas by-product...
February 13, 2019: Journal of Environmental Management
Christoph G Salzmann
Water's phase diagram displays enormous complexity with currently 17 experimentally confirmed polymorphs of ice and several more predicted computationally. For almost 120 years, it has been a stomping ground for scientific discovery, and ice research has often been a trailblazer for investigations into a wide range of materials-related phenomena. Here, the experimental progress of the last couple of years is reviewed, and open questions as well as future challenges are discussed. The specific topics include (i) the polytypism and stacking disorder of ice I, (ii) the mechanism of the pressure amorphization of ice I, (iii) the emptying of gas-filled clathrate hydrates to give new low-density ice polymorphs, (iv) the effects of acid/base doping on hydrogen-ordering phase transitions as well as (v) the formation of solid solutions between salts and the ice polymorphs, and the effect this has on the appearance of the phase diagram...
February 14, 2019: Journal of Chemical Physics
Fernan Saiz, Leonardo Bernasconi
We investigate the potential use of Fe(iv)oxo species supported on a metal-organic framework in the catalytic hydroxylation of methane to produce methanol. We use periodic density-functional theory calculations at the 6-31G**/B3LYP level of theory to study the electronic structure and chemical reactivity in the hydrogen abstraction reaction from methane in the presence of Fe(iv)O(oxo) supported on MOF-74. Our results indicate that the Fe(iv)O moiety in MOF-74 is characterised by a highly reactive (quintet) ground-state, with a distance between Fe(iv) and O(oxo) of 1...
February 13, 2019: Physical Chemistry Chemical Physics: PCCP
Wafaa Karaki, Rahul, Carlos A Lopez, Diana-Andra Borca-Tasciuc, Suvranu De
Radio-frequency (RF) heating of soft biological tissues during electrosurgical procedures is a fast process that involves phase change through evaporation and transport of intra- and extra-cellular water, and where variations in physical properties with temperature and water content play significant role. Accurately predicting and capturing these effects would improve the modeling of temperature change in the tissue allowing the development of improved instrument design and better understanding of tissue damage and necrosis...
December 2018: International Journal of Heat and Mass Transfer
Hongpeng Cui, Xin Su, Fang Chen, Melanie Holland, Shengxiong Yang, Jinqiang Liang, Pibo Su, Hailiang Dong, Weiguo Hou
Cold seep is a unique habitat for microorganisms in deep marine sediments, and microbial communities and biogeochemical processes are still poorly understood, especially in relation to hydrate-bearing geo-systems. In this study, two cold seep systems were sampled and microbial diversity was studied at Site GMGS2-08 in the northern part of the South China Sea (SCS) during the GMGS2 gas hydrate expedition. The current cold seep system was composed of a sulfate methane transition zone (SMTZ) and an upper gas hydrate zone (UGHZ)...
January 23, 2019: Marine Environmental Research
Chang Wang, Huan Wang, Dan Zhao, Xianqi Wei, Xin Li, Weihua Liu, Hongzhong Liu
A novel hybrid structure sensor based on cobalt carbonate hydroxide hydrate (CCHH) and reduced graphene oxide (RGO) was designed for room temperature NH₃ detection. This hybrid structure consisted of CCHH and RGO (synthesized by a one-step hydrothermal method), in which RGO uniformly dispersed in CCHH, being used as the gas sensing film. The resistivity of the hybrid structure was highly sensitive to the changes on NH₃ concentration. CCHH in the hybrid structure was the sensing material and RGO was the conductive channel material...
February 1, 2019: Sensors
Qian-Zhi Zhou, Yan Li, Fang Chen, Shui-Fu Li, Shu-Jun Dong, Feng-Lin Zhang, Xiao-Ming Xu, Jiang-Hai Wang
Biomarkers from methane hydrate-bearing sediments can provide vital evidence for microbial activities associated with methanogenesis and their relation to the formation of methane hydrates. However, the former mainly focus on intact polar lipids from these microorganisms, and rarely investigate molecular hydrocarbons such as acyclic isoprenoids and hopanes so far. In this work, the composition of biomarkers in the methane hydrate-bearing sediments in cores SH2B and SH7B from the Shenhu area, the South China Sea (SCS) were identified by gas chromatography-mass spectrometry (GC-MS) and comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC×GC-TOFMS)...
January 28, 2019: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Niall J English, Christopher C R Allen
We have conducted non-equilibrium molecular-dynamics (NEMD) simulation to show that externally-applied magnetic fields, including their reversals in direction, have important effects on gas-release dynamics from methane hydrates. In particular, we apply fluctuation-dissipation analysis in the guise of Onsager's hypothesis to study hydrate kinetics at lower applied-field intensities, including temporary hydrate destabilisation in the wake of field-polarity switch; we scale down to the lowest practicable field intensities, of the order of 1 T...
January 6, 2019: Science of the Total Environment
Natalia A Wojas, Agne Swerin, Viveca Wallqvist, Mikael Järn, Joachim Schoelkopf, Patrick A C Gane, Per M Claesson
Understanding the complex and dynamic nature of calcite surfaces under ambient conditions is important for optimizing industrial applications. It is essential to identify processes, their reversibility, and the relevant properties of CaCO3 solid-liquid and solid-gas interfaces under different environmental conditions, such as at increased relative humidity (RH). This work elucidates changes in surface properties on freshly cleaved calcite (topography, wettability and surface forces) as a function of time (≤28 h) at controlled humidity (≤3-95 %RH) and temperature (25...
January 14, 2019: Journal of Colloid and Interface Science
Jean Jules Fifen, Noam Agmon
The sodium cation is ubiquitous in aqueous chemistry and biological systems. Yet, in spite of numerous studies, the (average) distance between the sodium cation and its water ligands, and the corresponding ionic radii, are still controversial. Recent experimental values in solution are notably smaller than those from previous X-ray studies and ab initio molecular dynamics. Here we adopt a "bottom-up" approach of obtaining these distances from quantum chemistry calculations [full MP2 with the 6-31++G(d,p) and cc-pVTZ basis-sets] of gas-phase Na+ (H2 O)n clusters, as a function of the sodium coordination number (CN = 2-6)...
January 21, 2019: Journal of Chemical Physics
Gul Naz Laghari, Ayman Nafady, Sameerah I Al-Saeedi, Syed Tufail H Sherazi, Jan Nisar, Muhammad Raza Shah, Mohammad I Abro, Munazza Arain, Suresh K Bhargava
This study involves environmentally friendly synthesis of copper nanoparticles in aqueous medium without inert gas protection, using ranolazine as a capping material. UV-Visible (UV-Vis) spectrometry showed that ranolazine-derived copper nanoparticles (Rano-Cu NPs) demonstrate a localized surface plasmon resonance (LSPR) band at 573 nm with brick-red color under optimized parameters, including pH, reaction time, and concentrations of copper salt, hydrazine hydrate, and ranolazine. The coating of ranolazine on the surface of Cu NPs was studied via Fourier transform infrared (FTIR) spectroscopy...
January 10, 2019: Nanomaterials
Tomasz Tracz, Tomasz Zdeb
This paper presents the results of comprehensive cement paste porosity and gas permeability tests. The tests conducted concerned ordinary Portland cement (OPC) cement pastes with varying water-cement ratios ranging from 0.3 to 0.6. The tests were conducted after the curing of cement paste for 90 days and two years under laboratory conditions. Open porosity was determined using three methods: helium pycnometry, mercury intrusion porosimetry, and water saturation. Permeability was determined using a modified RILEM-Cembureau method...
January 8, 2019: Materials
Hongjian Tang, Chunfeng Li, Yufeng Duan, Chun Zhu, Liang Cai
Accurate mercury speciation measurements are critical for developing methods for mercury removal from flue gas, but the lack of reliable adsorbents has made Hg2+ selective retention challenging. Calcium oxide (CaO) loaded on porous support is promising for HgCl2 selective adsorption because of its porosity and alkaline nature. The main hypothesis investigated in this paper is if the capacity of CaO sorbent for HgCl2 selective adsorption is attributed to its basic sites, then this will be drastically impacted by the calcium precursors...
March 15, 2019: Science of the Total Environment
Guancong Huang, Ying Liu, Min Shao, Yue Li, Qi Chen, Yan Zheng, Zhijun Wu, Yuechen Liu, Yusheng Wu, Min Hu, Xin Li, Sihua Lu, Chenjing Wang, Junyi Liu, Mei Zheng, Tong Zhu
Naphthalene (Nap) and methylnaphthalene (MN) are the most abundant polycyclic aromatic hydrocarbons (PAHs) in atmosphere, and have been proposed to be important precursors of anthropogenic secondary organic aerosol (SOA) derived from laboratory chamber experiments. In this study, atmospheric Nap/MN and their gas-phase photooxidation products were quantified by a Proton Transfer Reaction-Quadrupole interface Time of Flight Mass Spectrometer (PTR-QiTOF) during the 2016 winter in Beijing. Phthalic anhydride, a late generation product from Nap under high-NOx conditions, appeared to be more prominent than 2-formylcinnamaldehyde (early generation product), possibly due to more sufficient oxidation during the haze...
January 9, 2019: Environmental Science & Technology
C Rondeau-Mouro, C Godfrin, M Cambert, J Rouillac, Y Diascorn, T Lucas, D Grenier
This research aimed to study the effects of using a partial vacuum for bread baking on macromolecules and water distribution in gluten-free bread. Bread baking under partial vacuum results in greater oven-rise and a larger gas fraction in the crumb. Since water's boiling point decreases under reduced pressure, it was expected that its distribution within the dough and its interactions with the others dough's constituents (mainly starch) would differ from those in bread baked under atmospheric pressure. Time-Domain Nuclear Magnetic Resonance (TD-NMR) was used, as it has the rare capacity to quantify both gelatinization and retrogradation of starch...
January 8, 2019: Magnetic Resonance in Chemistry: MRC
Sergey V Gudkovskikh, Mikhail V Kirov
This work is devoted to the study of the mechanical properties of hexagonal ice Ih and gas hydrate frameworks sI, sII and sH, taking into account the disorder in the positions of the hydrogen atoms (protons). The article emphasizes the critical role of the elastic energy for the evaluation of the relative energy of the proton configurations. The calculations are performed with the help of the TINKER package using the AMOEBA polarizable force field. The elastic constants, elastic modulus, and anisotropy indices are calculated...
January 8, 2019: Journal of Molecular Modeling
Thomas M Vlasic, Phillip D Servio, Alejandro D Rey
The infrared spectra of sII gas hydrates have been computed using Density Functional Theory for the first time, at equilibrium, and under pressure. It is also the first account of a full vibrational analysis (both guest and host vibrations) for gas hydrates with hydrocarbon guest molecules. Five hydrate structures were investigated: empty, propane, isobutane, ethane-methane, and propane-methane sII hydrates. The computed IR spectra are in good agreement with available experimental and theoretical results. The OH stretching frequencies were found to increase, while the H-bond stretching, and H2O libration frequencies decreased with an increase in guest size and cage occupancy, and with a decrease in pressure...
January 4, 2019: Journal of Physical Chemistry. B
Prashant Kumar Gupta, Philipp Schienbein, Janos Daru, Dominik Marx
Complementing mid-IR spectroscopy mainly in the OH~stretching region, liquid-state far-IR spectroscopy is successful in elucidating the properties of aqueous solutions by providing direct access to the hallmark of H-bonding at THz~frequencies, namely the H--bond network peak of water at roughly 200~cm$^{-1}$ and its modifications in the hydration shells around solutes. % Here, the idea is scrutinized whether ion hydration can be understood by studying the THz~regime of ``small'' ion-water clusters in the gas phase as a function of size with subsequent extrapolation to the bulk limit...
January 4, 2019: Journal of Physical Chemistry Letters
Daniela Trogolo, J Samuel Arey, Peter R Tentscher
Reactions with ozone transform organic and inorganic molecules in water treatment systems as well as in atmospheric chemistry, either in the aqueous phase, at gas/particle interfaces, or in the gas phase. Computed thermokinetic data can be used to estimate the reactivities of molecules toward ozone in cases where no experimental data are available. Although the gas-phase reactivity of olefins with ozone has been characterized extensively in the literature, this is not the case for the richer chemistry of ozone with polar molecules, which occurs in the aqueous phase or in microhydrated environments...
January 4, 2019: Journal of Physical Chemistry. A
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