The present study defines liquid–liquid equilibrium (LLE) data of (water–butyric acid-1-hexyl-3-methylimidazolium hexafluorophosphate [hmim][PF₆]) ternary mixtures at T=298.2, 308.2 and 318.2 K and p=101.3 kPa. The results were then correlated with UNIQUAC and NRTL models. The experimentally obtained tie–line data quality was determined by the Othmer–Tobias and Hand correlations. Distribution coefficients and separation factors were calculated from the experimental data. It was observed that the temperature change has a limited effect on the equilibrium data in the studied temperature range.

The working cycle theory model is the theoretical and important basis for the study of the suction and compression performance of all kinds of vacuum pumps and compressors. Due to large deviation in the actual performance of the liquid ring compressor, it is difficult for the traditional theory based on the “suction–compression–discharge” ideal working cycle to guide practical application. Therefore, an actual working cycle model was established for liquid ring compressors in this paper, which considers the effect of the residual gas after discharge. The rationality of the theoretical model was verified by the external characteristic performance test of a series of liquid ring compressors (Type 2BE1) commonly used in industry. This model provides a theoretical basis and method for analysis of suction compression performance of liquid ring compressors and has a certain scientific research and application value.

Ni/Al hydrotalcite-derived oxides (Ni/Al LDOs) prepared with various Ni/Al ratios at 300°C were used to investigate the removal of gaseous hydrogen cyanide (HCN). The results showed that Ni/Al LDOs exhibited outstanding performance for HCN removal, especially LDO with a Ni/Al ratio of 4 due to the formation of Ni/Al metal oxides (NiO and Al₂O₃) and the disappearance of hydrotalcite after 300°C calcination. Comparison of LDO with other Ni/Al ratios, LDO with a Ni/Al ratio of 4 had a higher surface area of 178 mg²/g and smaller mesopores of 5.46 nm as determined by nitrogen adsorption/desorption isotherms. CO₂ temperature programmed desorption (CO₂-TPD) experiments revealed that the weak basic sites and Ni–O group of the LDO with a Ni/Al ratio of 4 dominated HCN removal. Fourier-transform infrared (FTIR) spectra analysis demonstrated that adsorbed CN⁻ was converted into [Ni(CN)₄]²⁻, implying the occurrence of chemical adsorption. Further experiments found that a relatively low concentration water vapor can promote the removal efficiency of HCN on Ni/Al LDOs, while the inhibiting effect on the removal efficiency of HCN was observed in the presence of water vapor with high concentration due to its competitive adsorption effect. These findings are helpful for the development of innovative technology for the removal of HCN, and also provide a new treatment strategy for HCN based on Ni/Al LDOs.

The effect of a magnetic field on phytosterol crystallization was investigated, and crystals obtained under a magnetic field of 0.6 T were characterized using scanning electron microscopy (SEM), optical rotation analysis, differential scanning calorimetry (DSC), Fourier transform infrared spectrometry (FT-IR), and X-ray diffraction (XRD). The results show that the crystallization rate and purity significantly increased as the strength of the magnetic field increased. The crystallization time decreased from 96.2 min in the absence of a magnetic field to 42.0 min under a magnetic field strength of 0.6 T, and the purity increased from 92.50 to 98.43%. Furthermore, the quality of phytosterol crystals obtained at 0.6 T improved; however, the molecular structure did not change. Overall, these data show that the use of a magnetic field can improve the crystallization rate, purity, and quality of phytosterol crystals.

In this study, hydromagnesite sheets have been prepared under simple hydrothermal process treatment of solution of MgCl₂ and urea. Calcination of the hydromagnesite sheets at 800°C in air for 4 h resulted in porous MgO with polyhedra in the morphology. The high crystalline MgO polyhedra were of side 4–10 µm length and 2–6 µm thickness, and consisted of large number of pores, edges and corners, surface hydroxyl groups and low coordinate O₂⁻ sites which were regarded as active basic sites in heterogeneous base catalysts. The MgO polyhedra can function as a solid base catalyst for the synthesis of propylene carbonate (PC) from CO₂ and propylene oxide (PO). With MgO catalyst calcined at 800°C, the PC yield was 95% and selectivity 99% under mild conditions (1.5 MPa, 10 h). Furthermore, the MgO catalyst can be readily separated and recycled in a test of four cycles.

The development of a base metal catalyst which shows high performance for the ammonia (NH₃) decomposition have been conducted. For the Ni and Co based catalysts using α-Al₂O₃ as a support, the performance of the single metal catalysts was lower than that of the γ-Al₂O₃ supported catalysts. However, its performance was greatly improved by using a binary metal catalyst system. Based on the XRD analysis, it was found that Ni and Co supported on α-Al₂O₃ were alloyed. TEM observation confirmed that the metal particle size in the α-Al₂O₃ supported Ni–Co catalyst is smaller than that of the single metal catalysts (Ni/α-Al₂O₃ or Co/α-Al₂O₃). Furthermore, in-situ XRD and H₂-TPR measurements revealed that the Ni–Co alloy forms during the reduction process. The optimum mixing ratio of Ni and Co components was 1 : 1, and the optimum pre-reduction temperature before the performance test was 600°C. Studies on the differences of support oxides proved that the improvement effect by alloying can be similarly obtained with the SiO₂ supported catalyst, indicating that the catalyst using the support with less interaction between the active metal and the support is more likely to obtain the performance improvement effect by alloying.

For utilization of hydrogen carriers as a hydrogen source at a large scale, development of effective catalysts for hydrogen production is required. Though it is commonly accepted that the activity of catalysts can be enhanced by increasing the metal loading and reducing the metal particle size, the metal particle size is likely to increase with increased metal loading for catalysts prepared by the impregnation method. To obtain highly active catalysts that possess a high metal loading capacity and small metal particle size, we herein employed a preparation method for carbon-supported metal catalysts using ion-exchange resins. Three carbon-supported metal catalysts, Pd/C, Pt/C, and Ni/C, possessing high metal loadings (>10 wt%) and small metal particle sizes (2.7–3.6 nm from transmission electron microscopy (TEM) observations) were successfully prepared. The metal particle sizes estimated from CO or H₂ pulsed chemisorption were larger than those observed by TEM, thus indicating that the small metal particles were embedded in the carbon support. Because of this embedding structure, the size of metal particles in the catalysts was retained at around 3 nm during carbonization at 500°C. Furthermore, dehydrogenation of formic acid was performed over the prepared catalysts at low temperatures. These catalysts exhibited high activity for hydrogen production from formic acid at temperatures in the range of 100–200°C. Pd/C and Pt/C yielded the highest turnover frequencies of 0.35 and 0.49 s⁻¹, respectively, at 100°C, which was attributed to the large amount of small metal particles.

This paper presents a new relay feedback method to guarantee the accuracy of the enhanced relay feedback method. The new method uses the integrals of a process input and output to tune Proportional-Integral-Derivative (PID) controllers automatically even if the process input and output are contaminated by measurement noises and disturbances. This feedback method uses a new disturbance estimator and a new noise magnitude estimator to remove the effects of noises and disturbances on estimates of frequency response data. Simulation and application to a real system to control liquid level demonstrate that the proposed methods provide fairly accurate ultimate data of the process and that the PID controller tuned by the proposed method achieves control faster and with less overshoot than the conventional auto-tuning strategy based on the conventional relay feedback method.

In this study, a carbon monoxide (CO) absorption column model based on the COSORB process was designed for CO separation. We presented a 1-D dynamic simulation model of the CO absorption column using gPROMS. The designed model was validated using actual data from a pilot plant for syngas separation. To illustrate the applicability of the designed model, case studies were conducted for CO separation from blast furnace gas (BFG) and Linz–Donawitz gas (LDG), which are the major by-product gases from the iron and steel industry. The simulation results showed slight difference in the final absorption ratio of CO from the gases (>99% in all cases); however, CO absorption rate of LDG was 4 times larger than other cases because of its high CO concentration. However, the reaction rate of LDG is very high, the absorption of LDG in the column showed a pattern different from those for BFG and syngas absorption. The case studies for the operating pressure and feed temperature showed that the CO concentration [CO] in the feed gas must be higher than 0.16 kmol/m³ to achieve 99% CO absorption.

This paper proposes a practical method to identify the process dynamics for an integral process with dead-time, under continuous self-excited oscillation. It is assumed that the limit cycle is mainly caused by either the nonlinear property, dead-time of the process, or inappropriate PI parameters. Oscillatory PI control loops under inappropriate PI parameter settings are often found in actual plants, particularly in slow-response integral processes. The proposed method identifies not only the integral time constant but also the dead time of processes from their period of oscillation and PI parameters. A simple method to design robust PI parameters on the basis of internal model control (IMC) is also shown, where the IMC filter parameter is derived from the phase/gain margin and dead-time of the process. The process identification method and robust PI design method are successfully applied to an actual approximate integral process with self-excited oscillation. The proposed method does not require a step response test, which are best avoided in actual plant environments.

A practical strategy for the simultaneous control of particle size and shape of active pharmaceutical ingredients has been investigated using ecabet sodium (Na-ECA) hydrate, which tends to generate large plate-like crystals, as a model compound. In conventional batch-cooling crystallization, particle size and relative thickness decreased with increasing cooling rates. However, the particle size was still too large following fast cooling at a rate of 40°C/h. In rapid cooling crystallization with water, achieved by mixing hot Na-ECA solution with cold water, the particle size and relative thickness became 1/3.8 and 1/3, respectively, compared to that under batch-cooling crystallization at a rate of 40°C/h. It was also revealed that both the particle size and relative thickness increased with temperature cycling; however, the morphology of the obtained particles was still plate-like. In rapid cooling crystallization in aqueous NaCl, the particle size was reduced further to 1/4.7, and the relative thickness of the particle increased sixfold over that obtained in water. Moreover, the shape of the particle evolved effectively by temperature cycling. Consequently, granular and smaller particles could be obtained successfully. The mechanism of shape evolution was also discussed with respect to contact angles. Based on the qualitative analysis results obtained using Young’s equation, we propose that shape evolution is induced by surface free energy, which drives the progression towards equilibrium shape during repeated partial dissolution and crystal growth.

An efficient leaching method using citric acid solutions was investigated for the recovery of phosphorus from incineration ash of chicken droppings (IACD). The IACD samples before and after leaching were characterized by energy dispersive X-ray spectroscopy, X-ray diffraction analysis, and infrared spectroscopy. Optimum leaching was achieved using 3% citric acid at a liquid–solid ratio of 0.2 cm³/mg. The leached phosphorus was quantitatively adsorbed on READF-(PG), a commercially available microporous resin containing hydrated zirconium oxide in the pores. Phosphorus adsorption is proposed to occur via anion exchange between the hydroxyl groups of the hydrated zirconium oxide in the resin and the phosphate anions in the aqueous solution. More than 98% of the phosphorus adsorbed on the READF-(PG) resin was successfully desorbed using a NaOH solution. Thus, citric acid leaching followed by adsorption on a READF-(PG) resin is a promising technique for the recovery of phosphorus from IACD.