A new correlation and prediction model for the solubility of metal complexes in supercritical carbon dioxide (scCO2) based on the regular solution theory was developed in this study and the solubilities were calculated for metal(III) acetylacetonates: chromium(III) acetylacetonate (Cr(acac)3), cobalt(III) acetylacetonate (Co(acac)3), iron(III) acetylacetonate (Fe(acac)3), and rhodium(III) acetylacetonate. The physical properties, enthalpies of vaporization, and molar volumes of the metal acetylacetonates that are required to obtain the solubility parameters were estimated using the COSMOtherm program based on the conductor-like screening model for real solvents (COSMO-RS) method. The predicted molar volumes of Co(acac)3 and Fe(acac)3 and the solubility parameter of Cr(acac)3 were in good agreement with the data from the material safety data sheets and the group contribution method, respectively. The binary interaction parameter was introduced into the cross-term of the solubility parameters to calculate solubility. Although some deviations were found in the low-pressure region where the solubility dramatically increased with increasing pressure, the correlated results reproduced the experimental data for all metal acetylacetonates investigated using the physical properties estimated from the COSMOtherm program. The relationship was nearly linear between the values of the interaction parameters optimized by correlation and the pseudo residual chemical potentials of the metal acetylacetonates obtained using the COSMO-RS method. Therefore, the prediction was carried out using the interaction parameters determined from the pseudo residual chemical potentials of the metal acetylacetonates. The predicted results deviated somewhat from the experimental data in the low-pressure region; however, the predicted results reproduced the experimental data in the high-pressure region.
The flowability of coarse particles has been experimentally investigated using the vibrating tube method, to evaluate the applicability of this method to MOX (mixed oxide of PuO2 and UO2) particles which are nuclear fuel used for electric power production. Five sizes of non-radioactive model particles, smaller than 850 μm, made of ZrO2 were prepared, and the experiments were carried out using vibrating tubes with an outlet diameter from 2 to 4 mm. The outlet diameter significantly affected the flowability measurements. When using the tube with a 4-mm-outlet diameter, the flowability of all the model particles was successfully measured. The inclination angle of the tube also affected the flowability measurements. The critical vibration acceleration to make the particles flow, which was a factor for evaluating the flowability, was correlated with Carr’s flowability index. Because of the advantages of high sensitivity, short measurement time, simple structure, and easy operation, the vibrating tube method is expected to be applied to the remote flowability measurement of the MOX particles.
Microwave irradiation is an effective way to regenerate the activated carbon after adsorption and separation of waste. In this work, activated carbon saturated with toluene was efficiently regenerated by microwave irradiation. The maximum regeneration ratio of 77.2% was obtained under the following optimal operation conditions: saturated activated carbon of 5.01 g, microwave power of 500 W, carrier gas N2 flow of 60 mL/min, and microwave irradiation time of 180 s. It was found that the higher microwave power may result in self-burning of activated carbon due to the presence of traces of oxygen, which might slightly deteriorate the pore structures of activated carbon. On the other hand, the lower microwave power cannot start desorption of toluene or might cause re-adsorption. The introduction of N2 flow during regeneration was necessary to release the desorbed toluene from activated carbon, but it might cool the adsorption system under a much higher N2 flow rate.
Many tests should be carried out before launching a new product. By reducing the testing schedule, companies may have the direct financial impact. The sooner the launch of the product is the more likely companies are to maximize the potential profit from them. Recently, some works have been proposed in the literature on minimizing the testing schedule. There is still room for improvement in terms of addressing more practical issues. Particularly, this paper is concerned with test scheduling considering retesting and outsourcing, in addition to parameter uncertainty. These issues are transformed into mathematical programming formulation using scenario based framework. In order to address resource limitations in this problem, the ‘time slot’ is introduced in the formulation. Numerical examples are presented to illustrate the applicability of the proposed methodology.
The segmented flow technique is used for continuous synthesis of ZnO nanoparticles under micro reaction conditions. The experimental setup consisted of syringe pumps and T-type injectors, PTFE tubings as well as PTFE knot mixers in a thermostated bath. ZnO nanoparticles were obtained by generation under strong alkaline conditions and elevated temperature in aqueous solution and by precipitation under moderate alkaline conditions in DMSO solution. In aqueous solution, small compact nanoparticles (diameters below 100 nm) were obtained at high temperature (90°C) and high reactant concentrations. Larger crystals, nanoneedles and nanoflowers (submicron and lower micro range) were obtained at reduced concentrations and reduced temperature (70°C). Compact nanocrystals with diameters of a few hundred nanometers are formed by the reaction of zinc acetate with tetramethylammoniumhydroxide in the presence of polyethylene glycole (at 80°C). In nearly all cases, a strong effect of flow rate on nanoparticle quality was observed. Enhanced flow rates (up to 5000 μL/min) lead to an improvement of shape homogeneity and size distribution.
Molecular dynamics simulations have been performed for the design of operating conditions of liquid–liquid interfacial crystallization and clarifying the crystallization mechanism. It was found that solute ions were dehydrated with diffusion of the hydration ions from solution to organic phase. There were a significant difference of the dehydration behaviour between NaCl solution/1-butanol and /2-butanone. Aggregated ions or clusters were formed by the dehydration near the solution/organic solvent interface. The number of cluster generation near NaCl solution/2-butanone interface was larger than that in the 1-butanol system. This difference originates in the interfacial structure in the NaCl solution/the each organic solvent interface.
For high temperature steam electrolysis (HTSE) applications, the electrical characteristics of electrolyte membranes made by yttria-stabilized zirconia (YSZ) were analyzed with respect to sintering temperature and sintering time. The electrolyte membranes were prepared using dry and wet processes. Microstructure analysis of SEM photographs confirmed that membrane’s grain size increased while the pore size and the porosity decreased with an increase in the sintering temperature. At the sintering temperature of 1400°C, the densities of the electrolyte membranes prepared using the dry and the wet process were 6.13 and 6.25 g/cm3, respectively. The conductivity of the prepared electrolyte membrane was measured by AC impedance analyzer at 800–1000°C. The conductivities of the electrolyte membranes, measured at 1000°C, were 8.8 × 10–2 and 11 × 10–2 S/cm for the dry and the wet process, respectively. When considering conductivity and resistance, results in this study indicate that the wet process of preparing electrolyte membrane is more useful than the dry process.
Algebraic equations of a liquid feed direct methanol fuel cell (DMFC) with co-current channel flow are derived to correlate the literature experimental discharge data with the theoretically predicted polarization curve. Mass conservation of methanol and oxygen normal to the membrane electrode assembly is derived and an averaging procedure over the channel length is carried out to give the overall cell performance. The influence of methanol crossover through the membrane is described as the result of diffusion, electro-osmotic drag, and the pressure difference induced permeation between anode and cathode. The influence of permeated methanol on the cathode electrode potential is demonstrated by the mixed potential theory. That is, the parasitic methanol oxidation reaction consumes part of the oxygen reduction current in the cathode catalyst layer, forming an internal short circuit, so that the resultant cell current density is less than the case without crossover. This model is capable of predicting the concentration depletions of methanol and oxygen within the porous diffusion media of the membrane electrode assembly, and that along the respective flow channels. A nonlinear least square scheme, coupled with an algebraic model, retrieves the parameters of methanol diffusivity in the anode backing layer, exchange current density of methanol on the anode catalyst surface, and proton conductivity in the polymer electrolyte membrane.
Polylactic acid (PLA) was synthesized from l-lactic acid by direct polycondensation under vacuum without the use of catalysts (NC-DP). It was studied in order to adapt it to on-site cell production where safety treatment, compact capacity, and simple operations are required to reduce production costs. Experiments were conducted at polymerization temperatures (Tp) between 150 and 250°C and under reduced pressure. The resulting PLA was characterized using gel permeation chromatography (GPC) to determine the molecular weight as well as by differential scanning calorimetry (DSC) to examine the thermal properties. The maximum weight average molecular weight of PLA obtained was 90 kDa after 89 h at 200°C. Above 200°C, PLA was thermally degraded, and racemization occurred as PLA became atactic. Indeed, PLA only exhibited a glass transition temperature (Tg) and exhibited neither a crystallization temperature nor a melting point. The relations between Tg and the molecular weight were in agreement with the Flory–Fox equation.