The metastable phase equilibria for the ternary systems K2B4O7–K2SO4–H2O and K2B4O7–KCl–H2O at 273 K were studied using an isothermal evaporation crystallization method. The solubilities of salts and densities of solution in these systems were determined. According to the experimental data and the corresponding equilibrium solid phases, the metastable phase diagrams of the ternary systems K2B4O7–K2SO4–H2O and K2B4O7–KCl–H2O at 273 K were drawn and the density diagrams were constructed, respectively. Experimental results show that the two phase diagrams are both constituted of a eutectic point, two univariate solubility curves and two solid phase crystallization regions. The equilibrium solid phases at the eutectic point are K2SO4 and K2B4O7∙4H2O in the ternary system K2B4O7–K2SO4–H2O, and the equilibrium solid phases at the eutectic point are KCl and K2B4O7∙4H2O in the ternary system K2B4O7–KCl–H2O at 273 K. Therefore, the metastable phase diagrams for ternary systems K2B4O7–K2SO4–H2O and K2B4O7–KCl–H2O at 273 K both belong to a simple co-saturated type and neither double salt nor solid solution was formed.
A new predictive model for dual drops interactions has been formulated, covering four possible situations: namely coalescence, slip & separation, slip & conjunction and non-slip conjunction. The hydrodynamics and motion of a single drop or a conjunct drop rising in stagnant glycerol–water solutions were experimentally investigated. For Morton numbers ranging from 9.68×10−3 to 51.40, the terminal rising velocities, the transverse oscillation frequencies and the wake of the conjunct drop are similar to those for a single drop with the same spherical-equivalent diameter. The rising velocities of a single drop and a conjunct drop were quantified on the basis of the expression for the drag coefficient and the feature size of the drops. The surrounding liquid flow fields for a single drop and a conjunct drop were measured by means of 2-D Particle Image Velocimetry, in order to identify the regions of the wake behind drops, and the similarities and differences between the flow fields were also discussed.
The present study investigates the separation and recovery of the valuable metals in the sintered NdFeB permanent magnets by solvent extraction, in which neodymium, dysprosium and cobalt are contained as valuable metals. Neo-decanoic and naphthenic acids, and 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) and bis(2-ethylhexyl) phosphoric acid (D2EHPA) were used as the metal extractants of carboxylic and organophosphorus acids, respectively, to evaluate the separability of the metals by the liquid–liquid extraction equilibrium. With the single metal ion systems, the distribution ratios of the respective metal ions with D2EHPA were the greatest, followed by those with PC-88A, neo-decanoic acid and naphthenic acid. Although the separation of these metal ions with organophosphorus acids were more effective than those with carboxylic acids, the carboxylic acids showed the sufficient separation efficiency to separate these metal ions. Moreover, the stripping operation with the extractant could be conducted in a relatively high pH range compared to the organophosphorus acid extractants. According to these results, the extraction equilibrium using neo-decanoic acid extractant was measured with binary metal ion systems to study the effects of the coexisting metal ions. While the ferric and rare earth elements had little influence on the extraction equilibrium, cobalt ion was coextracted by the ferric or rare earth element ion, thereby making the separation efficiency lower. Then, based on consideration of these trends of extraction equilibrium, the separation scheme to recover the valuable metals in the sintered NdFeB permanent magnet is suggested.
Forward osmosis (FO) membranes with high water permeation flux are required for FO processes to overcome reverse osmosis energy efficiency and translate the FO process into practical applications. However, in the case of such membranes, convective solute transport has a profound effect on solute permeation flux. The existing solution–diffusion model ignores the convection term and the solute permeation flux cannot be accurately analyzed. To solve this problem, the FO membrane permeation was theoretically modeled via non-equilibrium thermodynamics to introduce the convection effect and by coupling with both the internal and external concentration polarizations. First, the FO desalination process (feed solution was sea water (3.3 wt% NaCl aq.)) was investigated by the model. By slightly decreasing the reflection coefficient, which had minimal influence on water permeation flux, both the convective salt transport and NaCl permeation flux increased significantly. Second, a simplified model system (the feed solution was pure water and the draw solution was NaCl aq.) for the wastewater treatment FO process was analyzed. In this system, water permeated in a direction opposite to that of NaCl, and relevant complex behavior of salt permeation was observed.
Reactive extraction for the esterification of n-butanol with acetic acid was studied using Binary Brønsted Acidic Ionic Liquids (BBAILs) as catalysts. Three [HSO4] based Brønsted Acidic Ionic Liquids (BAILs) were prepared to formulate four bi-component ionic liquid catalysts. The effects of various parameters such as temperature, catalyst loading and catalyst formulation were investigated. The BBAILs were found to have not only good catalytic activity, but also good corrosion resistance and stability. Distribution coefficients were employed in these liquid–liquid biphase systems to interpret the reaction–separation intensification. The kinetics for the esterification of acetic acid with n-butanol using BBAILs as catalysts were also investigated systemically. A variant of the modified Langmuir–Hinshelwood–Hougen–Watson model (MLHHW) was used successfully to correlate the experimental kinetic data.
The present study is an examination of the catalyst deactivation of a silica-supported bismuth–molybdenum complex oxide, and that of catalysts used in the absence of bismuth, for the oxidative dehydrogenation of 1-butene. Due to the detection of deactivation, the molar ratio of 1-butene against oxygen in the reactant gas was adjusted to a ratio similar to that used in industrial processes where reaction temperatures average 100 K higher. Regardless of the presence or absence of bismuth in the catalysts, the conversion of 1-butene was decreased by 6 h on-stream. Both the progress of the coking from the inlet to the outlet of the catalyst and the reduction of molybdenum in the catalysts directly contributed to the deactivation. X-ray photoelectron spectrometry revealed that a greater reduction of molybdenum in the near-surface region and a smaller partial pressure of oxygen (P(O2)) in the reactant gas, although the molybdenum on the surface was not reduced at all. This indicated that the lattice oxygen was pumped from the near-surface region to the surface during the reaction and the oxygen-poor conditions of the near-surface region both in the gas and catalyst phases were formed at a smaller P(O2), which resulted in the enhancements of both the reduction of molybdenum and that of coking. Based on the thermogravimetric analysis, the silica-supported bismuth–molybdenum complex oxide used at P(O2)=4.1 kPa (color of the catalyst=black) was increased in weight while that used at P(O2)=16.4 kPa (color of the catalyst=gray) showed a weight decrease, which indicated that the weight decrease caused by the reduction in molybdenum in the near-surface region used at 4.1 kPa was greater than the weight increase from the coking. It was concluded that the reduction in molybdenum followed by the coking on the catalyst surface were the main factors in the catalyst deactivation.
Modern chemical processes are usually characterized by their large scale and nonlinearity, and the monitoring of such processes is imperative. This paper proposes fault-relevant kernel principal component (KPC) subspace construction integrated with a Bayesian inference method to achieve efficient monitoring of nonlinear chemical processes. First, KPC analysis is performed to deal with process nonlinearity and generate a KPC feature space. Second, a fault-relevant KPC (FRKPC) subspace is constructed for each fault through KPC selection using a stochastic optimization algorithm. Then, a new process measurement is examined in each FRKPC subspace, and the monitoring results from all subspaces are fused in a comprehensive index through Bayesian inference to provide an intuitive indication of the process status. The FRKPC subspace construction method reduces redundancy in monitoring and therefore improves monitoring performance significantly. The proposed method is applied to a numerical example and the Tennessee Eastman benchmark process. These monitoring results demonstrate the efficiency of the proposed method.
We propose a newly designed plate-type reactor, which is in the concept of an assembly-type microreactor and can be varied in the size of the internal reaction space of the depth of catalytic bed or the width of the flow channel by replacement of assembled parts, and where it is possible to set powder catalysts, dp<0.3×10−3 m, without of washcoat or electroless plating process.
Using the plate-type reactor with powder catalysts, we confirmed the advantage of the reactor under dry reforming of methane. Under CH4/CO2/He=1/2/5 at 773 K as a lean methane condition, the plate-type reactor could assume inherent catalyst performance, i.e., the performance of reaction controlled conditions, lower pressure drop and/or friction factor than that of a packed bed reactor, even with coarse particle catalysts at the nearly same or higher methane conversion. Further, these trends became much more pronounced under CH4/CO2/He=1/1/0 at 773 K as a rich methane condition. These results mean that the plate-type reactor allows for prolonged operation time until channel blockage due to carbon deposition.
Moreover, it is suggested that the plate-type reactor can undergo more optimization by replacement of different sized reactor parts to avoid diffusion controlled condition.
In order to obtain high quality crystals, the cooling rate and crystallization temperature are usually adjusted in the manufacturing process. In this study, the temperature dependency of the crystallization process was evaluated using theophylline, noscapine and clotrimazole. The crystallization temperature of theophylline at several concentrations was affected by the cooling rate. With lower concentration, the crystallization temperature decreased, especially at higher cooling rates. In our previous study, the critical supersaturation ratio (Sc) was defined as an index to estimate degree of crystallization difficulty. The Sc of theophylline, noscapine and clotrimazole in several crystallization solvents showed a clear difference around 273 K, but converge to less than 1.0 around 333 K. These results indicate that a higher temperature condition can decrease the Sc value, especially for a compound having a large Sc. Thus, using a high temperature condition could be recommended to crystallize a compound which is difficult to crystallize at room temperature.