Thermodynamic Energy Analysis Research Articles

Theoretical insights into the extraction behaviors of neptunium(VI) and plutonium(IV) based on the structure of organophosphorus ligands

Organophosphorus ligands such as TBP, TiAP, and DMHMP have exhibited excellent performance in recovering actinides from spent fuel. In this work, the molecular geometries and properties of TBP, TiAP and DMHMP were investigated using density functional theory calculations. Furthermore, the extraction mechanism of ligands for actinides (Np(Ⅵ), Pu(Ⅳ)) was further elucidated by simulating the microstructures and extraction reactions of metal–ligand complexes. The results demonstrate that the complexation ability of the three ligands on actinide cations (NpO22+ and Pu4+) follows the order of DMHMP > TiAP > TBP. The electrostatic potential (ESP) analysis indicates that the nucleophilic ability of DMHMP is stronger than that of the other two ligands. The frontier molecular orbital analysis of the three ligands represents that DMHMP has the highest HOMO energy, suggesting that it has the strongest electron-donating capability and is more likely to bond with metal ions. The values of Wiberg bond indices (WBI) suggest that the MO bonds in DMHMP complexes have more covalency. According to the QTAIM analysis, the interactions between actinide cations and the ligands are predominantly ionic in nature. The molecular orbital analysis of the complexes shows that the M(NO3)n·2DMHMP (MNpO22+ and Pu4+) complexes are more stable, which is supported by thermodynamic energy analysis. This work has clarified the complexing properties of actinide cations with three ligands, shedding light on the extraction mechanisms of organophosphorus ligands for actinide cations. It is anticipated to lay the theoretical foundation for the efficient recovery of critical actinide elements in spent fuel reprocessing, which will also provide innovative approaches for the design and development of related separation processes.

Blends of bio-oil/biogas model compounds for high-purity H2 production by sorption enhanced steam reforming (SESR): Experimental study and energy analysis

• SESR of bio-oil/biogas blends leads to renewable high-purity H 2 production. • H 2 yield of 87.1% is experimentally obtained at 625 °C and 2.5 bar. • H 2 purity of 98.6 vol% is achieved at 625 °C and 2.5 bar. • Higher temperature and steam/C molar ratio, but lower pressure, favor H 2 production. • Biogas addition increases the energy efficiency of the bio-oil SESR process by 1.34%. H 2 production by sorption enhanced steam reforming (SESR) of bio-oil/biogas blends was demonstrated in a fluidized bed reactor. It combines steam reforming (SR) with simultaneous CO 2 capture by a solid sorbent. SESR was performed on a Pd/Ni-Co catalyst derived from a hydrotalcite-like material (HT) using dolomite as CO 2 sorbent. Bio-oil from fast pyrolysis of biomass is a carbon–neutral and renewable energy source with great potential for clean H 2 production by steam reforming processes. Biogas is also a promising renewable bio-based resource for hydrogen generation that can be used to increase the H 2 production of a biomass-based plant. In turn, it could improve the energy efficiency of the process due to the exothermic reaction of the CO 2 contained in biogas with the sorbent. Bio-oil composed of acetic acid and acetone (1/1 mol/mol) and biogas composed of CH 4 and CO 2 (60/40 vol%) were used as fuels. They were blended (50 wt% bio-oil + 50 wt% CH 4 ) to study the SESR process. Effects of temperature, steam/C molar ratio, and pressure on the process performance were evaluated. SESR results showed an effective reforming of bio-oil/biogas blends and an enhancement in the H 2 production and fuel conversion compared to conventional SR. Higher temperature and steam/C ratio, but lower pressure, favored H 2 yield and purity. High H 2 yield (87.1%) and H 2 purity (98.6 vol%) were obtained at 625 °C and 2.5 bar (steam/C molar ratio three times higher than the stoichiometric value). The thermodynamic energy analysis of the SESR of bio-oil/biogas blends rendered 1.34% higher cold gas efficiency (CGE) than bio-oil SESR.

Theoretical estimation of efficiency defect in cascade refrigeration system using low global warming potential refrigerant pair

In the presented work, researchers used Efficiency defect as a parameter for deciding the utility of refrigerants in the Cascade refrigeration system. Cascade refrigeration system’s mathematical model is created. Using the first and the second law of thermodynamics energy analysis and exergy analysis are done for different low Global warming potential refrigerant pairs like R134a/CO2, R1234yf/CO2, and R1234ze/CO2. Based on the analysis efficiency defect is calculated for every component of the cascade system individually and the whole system as well. It is found that R1234yf/CO2 has the highest value of efficiency defect, whereas R134a/CO2 has the least efficiency defect for the whole cascade system. Change of efficiency defect in various components with evaporator temperature is presented in form of graphs.

Study of the Redox Potentials of Benzoquinone and Its Derivatives by Combining Electrochemistry and Computational Chemistry

As simple and ubiquitous redox-active organic molecules, quinones participate in diverse electron transfer processes in chemistry and biological systems for energy transformation and signal transduction. We introduce here a practical exercise to study the redox potentials of benzoquinone and its two derivatives by combining the electrochemistry method with quantum chemistry computation. The practical reduction potentials of three quinones were measured by cyclic voltammetry experiment. Quantum chemistry computation, on the other hand, provided theoretical Gibbs free energy change and reduction potentials of the three quinones, which were found to be in line with the experimental results. Detailed thermodynamic energy analysis based on the computation results revealed that the reduction Gibbs free energy changes of the three quinones were mainly contributed from the electronic energies change of the molecules, while thermal energy and entropy played a relatively minor role. The energy levels of the lowest unoccupied molecular orbital (LUMO) of the three quinones, which were modulated by substituent groups and conjugation structures, were further identified as the main origin of the reduction potential. This experiment provides practical and theoretical training on the fundamental ideas involved in major courses like thermodynamics, quantum chemistry, electrochemistry, and organic chemistry, and promotes students to find the tie between macroscopic redox properties of chemicals and their microscopic molecular structures, a key topic in chemistry education.

Potential assessment and experimental analysis of solar vegetable dryer: in case of northern Ethiopia

The traditional vegetable drying (open-air/sun drying) method of harvesting of tomato, potato and onion in the Fogera District in Amhara regional state, Ethiopia, leads to loss of product, reduction in the quality of product and economic loss for the poor farmers. So, this experiment aimed to show the effectiveness of solar dryer technology by increasing the quality of the product in tomato, potato, and onion in Fogera district Northwest Ethiopia, 2018. A simple solar vegetable dryer is experimentally analyzed to alleviate the problem associated with vegetable processing in Woreta city. The first law of thermodynamics energy analysis was carried out to estimate the amount of useful energy gained from solar air dryer and energy utilization ratio of the drying chamber and the energy through drying box. The magnitude of the exergy inflow, outflow and exergy losses in the drying chamber during the drying process was determined by applying the second law of thermodynamics. The average solar drying efficiency was found to be 75.01% to 86.70% for tomato, 75.70% to 87.90% for potato and 58.7% to 85.5% for onion. Regrading the drying period, it took 33 h for tomato, 27 h for potato and 44 h for onion during the experimental test.

A Theoretical Study on the Economic Feasibility of Proton Exchange Membrane Electrolysis Cells for Nitrogen Fixation

The Haber-Bosch process for the thermochemical synthesis of ammonia transformed the fertilizer industry by allowing for ammonia production in industrial scales. Since its invention in the early 1900s, the process has enabled the continuous expansion of the global population. The process operates at high temperatures (700 K) and pressures (100 bar) and takes advantage of economies of scale to produce around 150 million tons of ammonia per year at an efficiency of up to 70%. However, the operating conditions and the massive scale of the process lead to high levels of energy consumption and elevated fertilizer prices due to additional transportation costs from the highly centralized production facilities to the decentralized locations of use. In addition, the process relies on methane reforming as a hydrogen source, making ammonia the commodity chemical with the most significant carbon footprint. One possible strategy to overcome the shortcomings of the Haber-Bosch process is the decentralized production of ammonia-based fertilizers by a proton exchange membrane (PEM) electrolysis plant. Electrochemical ammonia synthesis by a PEM electrolysis cell offers renewable and clean production of ammonia and, consequently, has attracted interest in the scientific community. This technology would be coupled with renewable energy sources to harness nitrogen and water from the air to produce fertilizers near the location of use. This proves advantageous for the agricultural industry because the inexpensive feedstock materials and reduced transportation costs may improve access to fertilizers in the developing regions. However, the efficiencies reported for this technology are still too low to be competitive with the Haber-Bosch process. A detailed theoretical study on the economic feasibility of PEM electrolysis cells for nitrogen fixation is nonexistent, which hinders the development of this technology. A detailed economic analysis is valuable to determine the cost of the technology and the efficiency levels that have to be achieved before the technology is competitive. This work presents a comprehensive economic analysis to investigate the efficiency threshold that would make the technology viable. First, a thermodynamic energy analysis is used to investigate the thermodynamic characteristics of an ammonia production facility while also incorporating the electrochemical characteristics of a PEM electrolysis cell. The model developed is coupled with experimental data to determine the system losses, energy inputs, and the system required size. The system losses and energy inputs are then used to calculate the systems energy and operation costs. Then, a detailed manufacturing cost analysis is used to determine the system capital cost. The model serves to define the optimal manufacturing process to reduce cost. Finally, a life cycle analysis is performed to calculate the systems social and environmental costs. The system performance gathered from the thermodynamic, manufacturing, and life cycle analyses are compared to the current ammonia fertilizer method (Haber-Bosch process) to determine the technology competitive advantage. This work offers a better understanding of the current state of the use of PEM electrolysis cells for ammonia production. In addition, this work highlights the systems threshold values that have to be achieved to provide a competitive advantage of the Haber-Bosch process.

A Metastable Crystalline Phase in Two-Dimensional Metallic Oxide Nanoplates.

A simple method was adopted in which ultrathin cerium oxide nanoplates (<1.4 nm) were synthesized to increase the surface atomic content, allowing transformation from a face-centered cubic (fcc) phase to a body-centered tetragonal (bct) phase. Three types of cerium oxide nanoparticles of different thicknesses (1.2 nm ultrathin nanoplates, 2.2 nm nanoplates, and 5.4 nm nanocubes) were examined using transmission electron microscopy and X-ray diffraction. The metastable bct phase was observed only in ultrathin nanoplates. Thermodynamic energy analysis confirmed that the surface energy of the ultrathin nanoplates is the cause of the remarkable stabilization of the metastable bct phase. The mechanism of surface energy regulation can be expanded to other metallic oxides, thus providing a new means for manipulating and stabilizing novel materials under ambient conditions that otherwise would not be recovered.

Palladium-Mediated Catalysis Leads to Intramolecular Narcissistic Self-Sorting on a Cavitand Platform.

Palladium-catalyzed aminocarbonylation reactions have been used to directly convert a tetraiodocavitand intermediate into the corresponding carboxamides and 2-ketocarboxamides. When complex mixtures of the amine reactants are employed in competition experiments using polar solvents, such as DMF, no "mixed" products possessing structurally different amide fragments are detected either by 1H or 13C NMR. Only highly symmetrical cavitands are sorted out of a large number of potentially feasible products, which represents a rare example of intramolecular, narcissistic self-sorting. Our experimental results along with thermodynamic energy analysis suggest that the observed self-sorting is a symmetry-driven, kinetically controlled process.

New strategy for phase equilibrium and critical point calculations by thermodynamic energy analysis. Part II. Critical point calculations

The thermodynamic energy analysis of Michelsen is reformulated in terms of component molar densities as the primary variables. In this formulation, we can provide analytical expressions for any higher order derivatives for the energy function. This feature enables us to enhance the speed and the reliability of the critical point search method. It is designed to find the critical composition and the critical pressure for fluid mixtures at a fixed temperature (pressure-composition diagram), as well as critical points in the composition space at the specified pressure and temperature (pseudo-ternary diagrams). This has proved to be very useful in finding the miscibility composition for complex and near-critical petroleum reservoir fluids subjected to gas injection. A number of examples illustrate the successful use of this method.

New strategy for phase equilibrium and critical point calculations by thermodynamic energy analysis. Part I. Stability analysis and flash

We have reformulated Michelsen's method of phase stability analysis, which employs the thermodynamic energy minimization in terms of the tangent plane criterion. In our method, we use the component molar densities as the primary variables in place of the mole numbers or mole fractions. Furthermore, we use a modified stability test procedure called the ‘semi-local’ stability test and a higher order initialization procedure in the two-phase region. We believe that these modifications improve the numerical stability and the speed of convergence of the iterative technique, particularly in the near-critical and the liquid-liquid regions. We demonstrate the successful use of this method with well-defined example fluid systems and near-critical and retrograde condensate petroleum reservoir fluids.