Effects of Ga Substitution on the Local Structure of Na2Zn2TeO6

In the work presented here, we prepared Ga-substituted NZTO (Na2–xZn2–xGaxTeO6, x = 0.00, 0.05, 0.10, 0.15, 0.20) layered materials with a soft chemical, citric acid-based synthesis method and characterized these by means of X-ray diffraction (XRD), 23Na and 125Te NMR, and by density functional theory (DFT) modeling. The influence of randomly distributed Ga cations on the 125Te NMR spectra confirms the successful synthesis. With DFT-based linear response computations, we show that the local distribution of Na ions in the two neighboring interlayers influences the 125Te chemical shift, consistent with observations. DFT modeling suggests that some of the Na sites are rarely occupied in pure NZTO but become favorable upon Ga substitution. There are clear indications that Ga substitution gives an uneven distribution of Na ions in neighboring interlayers and that the Na structure in one layer affects the adjacent layers.publishedVersio

Low-Viscosity Nonaqueous Sulfolane-Amine-Methanol Solvent Blend for Reversible CO2 Capture

In this work, the absorption–desorption performance of CO2 in six new solvent blends of amine (diisopropylamine (DPA), 2-amino-2-methyl-1-propanol (AMP), methyldiethanolamine (MDEA), diethanolamine (DEA), diisopropanolamine (DIPA), and ethanolamine (MEA)), sulfolane, and methanol has been monitored using ATR-FTIR spectroscopy. Additionally, NMR-based species confirmation and solvent viscosity analysis were done for DPA solvent samples. The identified CO2 capture products are monomethyl carbonate (MMC), carbamate, carbonate, and bicarbonate anions in different ratios. The DPA solvent formed MMC entirely with 0.88 molCO2/molamine capture capacity, 0.48 molCO2/molamine cyclic capacity, and 3.28 mPa·s CO2-loaded solvent viscosity. MEA, DEA, DIPA, and MDEA were shown to produce a low or a negligible amount of MMC while AMP occupied an intermediate position.publishedVersio

Process simulation of Ca-looping processes: review and guidelines☆

Abstract Ca-looping is one of the most promising processes for CO 2 capture in short to medium term plants, which can be applied for both post-combustion and pre-combustion layouts. The recent successful operations of MW-scale pilot plants are leading to an increased interest in this technology. In addition, the particularly advantageous applicability in cement plants, the main industrial contributors to CO 2 emissions worldwide, can further lead to a forthcoming development of the technology. Quite a large amount of scientific papers on reactors and process modeling has been published in the recent years and more studies are expected to be published in the future. According to the experience of the authors in this field and on the basis of a literature review, suggestions and modeling needs for next works are provided in this paper

К уточнению понимания характеристик рынка труда

Рассмотрены основные характеристики рынка труда. Внесены предложения по их уточнению в соответствии с особенностями формирования регионального рынка труда.Розглянуті основні характеристики ринку праці. Внесено пропозиції по їхньому уточненню відповідно до особливостей формування регіонального ринку праці.Basic descriptions of labour-market are considered. Suggestions on their clarification in accordance with the features of forming of regional labour-market are borne

Predicting crystal growth via a unified kinetic three-dimensional partition model

Understanding and predicting crystal growth is fundamental to the control of functionality in modern materials. Despite investigations for more than one hundred years1, 2, 3, 4, 5, it is only recently that the molecular intricacies of these processes have been revealed by scanning probe microscopy6, 7, 8. To organize and understand this large amount of new information, new rules for crystal growth need to be developed and tested. However, because of the complexity and variety of different crystal systems, attempts to understand crystal growth in detail have so far relied on developing models that are usually applicable to only one system9, 10, 11. Such models cannot be used to achieve the wide scope of understanding that is required to create a unified model across crystal types and crystal structures. Here we describe a general approach to understanding and, in theory, predicting the growth of a wide range of crystal types, including the incorporation of defect structures, by simultaneous molecular-scale simulation of crystal habit and surface topology using a unified kinetic three-dimensional partition model. This entails dividing the structure into ‘natural tiles’ or Voronoi polyhedra that are metastable and, consequently, temporally persistent. As such, these units are then suitable for re-construction of the crystal via a Monte Carlo algorithm. We demonstrate our approach by predicting the crystal growth of a diverse set of crystal types, including zeolites, metal–organic frameworks, calcite, urea and L-cystine

<i>CrystalGrower</i>: a generic computer program for Monte Carlo modelling of crystal growth.

From Europe PMC via Jisc Publications RouterHistory: ppub 2020-11-01, epub 2020-11-18Publication status: PublishedA Monte Carlo crystal growth simulation tool, CrystalGrower, is described which is able to simultaneously model both the crystal habit and nanoscopic surface topography of any crystal structure under conditions of variable supersaturation or at equilibrium. This tool has been developed in order to permit the rapid simulation of crystal surface maps generated by scanning probe microscopies in combination with overall crystal habit. As the simulation is based upon a coarse graining at the nanoscopic level features such as crystal rounding at low supersaturation or undersaturation conditions are also faithfully reproduced. CrystalGrower permits the incorporation of screw dislocations with arbitrary Burgers vectors and also the investigation of internal point defects in crystals. The effect of growth modifiers can be addressed by selective poisoning of specific growth sites. The tool is designed for those interested in understanding and controlling the outcome of crystal growth through a deeper comprehension of the key controlling experimental parameters

Continuous hydrogen production by sorption enhanced steam methane reforming (SE-SMR) in a circulating fluidized bed reactor: Sorbent to catalyst ratio dependencies

Continuous hydrogen production by sorption enhanced steam methane reforming (SE-SMR) has been studied using a circulating fluidized bed reactor with calcined natural dolomite as CO2 sorbent and Ni/NiAl2O4 as catalyst. A steam to methane ratio of 4 was used at 575 °C and ambient pressure. Two experiments, each run for 8 h, were carried out using two different volumetric catalyst to sorbent ratios; 20/80 (experiment A) and 50/50 (experiment B) respectively. In experiment A, run at lower than equilibrium conversion, an initial high conversion that dropped significantly after a few hours was observed, while in experiment B, a stable performance throughout the 8 h time-on-stream close to equilibrium conversion of methane was observed. The experiments show that a circulating fluidized bed reactor configuration is suited for SE-SMR for extended time of operation. The sorbent and catalyst materials we have used appear to have quite good mechanical properties at the time scale used (8 h), but only a fraction of the sorbent's CO2 capacity appears to be in use.acceptedVersio

Continuous hydrogen production by sorption enhanced steam methane reforming (SE-SMR) in a circulating fluidized bed reactor: Sorbent to catalyst ratio dependencies

Continuous hydrogen production by sorption enhanced steam methane reforming (SE-SMR) has been studied using a circulating fluidized bed reactor with calcined natural dolomite as CO2 sorbent and Ni/NiAl2O4 as catalyst. A steam to methane ratio of 4 was used at 575 °C and ambient pressure. Two experiments, each run for 8 h, were carried out using two different volumetric catalyst to sorbent ratios; 20/80 (experiment A) and 50/50 (experiment B) respectively. In experiment A, run at lower than equilibrium conversion, an initial high conversion that dropped significantly after a few hours was observed, while in experiment B, a stable performance throughout the 8 h time-on-stream close to equilibrium conversion of methane was observed. The experiments show that a circulating fluidized bed reactor configuration is suited for SE-SMR for extended time of operation. The sorbent and catalyst materials we have used appear to have quite good mechanical properties at the time scale used (8 h), but only a fraction of the sorbent's CO2 capacity appears to be in use