The static dielectric constants of aqueous glycol solutions for temperatures 35 to 55°C were measured using a dielectric analyzer. The systems studied are: aqueous ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), tetraethylene glycol (T4EG), propylene glycol (PG), and dipropylene glycol (DPG) solutions. The static dielectric constants of the corresponding pure glycols were also measured for the same temperature range. The measured static dielectric constants of pure glycols were found in a good agreement with the literature values. The measured static dielectric constants of aqueous glycol solutions were correlated by using a Redlich–Kister type equation for the excess static dielectric constants of the solution. The average absolute percentage deviation for the calculations of the static dielectric constants of aqueous glycol solutions is 0.8%.
The aim of this study is to investigate the mass-transfer characteristics of a large paddle impeller by comparing with those of the down-pumping pitched blade turbine and the Rushton turbine, and also to probe the application of surface aeration to batch hydrogenation in polymerization processes and the ethylene oxide additional reaction. Laboratory and industrial data were used for this purpose. As a result, it has been found that, with the large paddle impeller, large kLa values of surface aeration without sparging can be obtained continuously at any liquid level because of the combined effect of surface breakage, bubble entrapment and efficient liquid circulation by axial pumping capacity of the impeller. Using these experimental kLaV data, the improvement in the operation time for a 12 m3 alkoxylation reactor was estimated. The reactor was then retrofitted with a large paddle impeller, and the actual operation time of 17 h was found to be strictly identical to the estimation, that is 75% reduction of the usual 70 h. This result shows the advantage of large paddle impellers in industrial processes and the accuracy of the estimation procedure.
A vacancy solution model based on the NRTL equation was derived and its validity was examined using experimental isotherms for adsorption of krypton and xenon on MS5A and activated charcoal adsorbents. The experimental adsorption isotherms of pure component of Kr and Xe on the adsorbents were successfully correlated with the vacancy solution model based on the NRTL equation. The experimental results for the adsorption equilibrium of Kr–Xe binary component systems on the MS5A and activated charcoal adsorbents were also examined using the model. The binary adsorption equilibria were well predicted by the vacancy solution model without parameter fitting. The optimization of parameters of the model in the binary systems resulted in better correlation of the binary adsorption equilibria.
Activated carbons were prepared from carbonized phenolic resins by steam-activation via a pre-treatment, that is mixing of raw materials with Ca(NO3)2·4H2O and acid-treatment after carbonization. This pre-treatment method has been reported as a method to produce mesoporous activated carbons. In the present work, three different novolak type phenol formaldehyde resins were synthesized under different molar ratio of formaldehyde (F) to phenol (P) (F/P = 0.3, 0.5, and 0.8) and were used as the precursors for activated carbons. It was confirmed that the pre-treatment method effectively enhances mesopores on activated carbons from synthesized phenolic resins prepared by F/P = 0.3 and 0.5, and their pore size distributions depended on the synthesizing conditions (F/P). Namely, it was found that by decreasing the F/P ratio of the precursor resin to the values lower than those usually adopted for commercial phenolic resin production, i.e., less than 0.5, activated carbons with developed mesopores could be obtained. The micropore developments of activated carbons were also influenced by F/P, and the influences were on the formation of pores larger than 0.40 nm. It was suggested that the thermoplastic nature of prepared resins (that can be changed by F/P) influence the porous properties of resultant activated carbons and the effect of the pre-treatments.
The hydroxylation of benzene to phenol with hydrogen peroxide catalyzed by transition metal (Fe(III), Cu(II), and V(V)) on a TiO2 support was performed at room temperature. The Fe(III) catalyst gave the highest conversion and yield but showed the lowest selectivity. At room temperature, the phenol yield was quite low and therefore modifying the system by solvent addition or operation under UV light was examined. Among the various solvents studied, i.e., acetone, acetronitrile and pyridine, acetone gave the highest conversion and yield; however, the selectivity was low. Acetonitrile is a suitable solvent in terms of improved selectivity and yield. Operation under UV light significantly improved the yield with comparatively high selectivity. Ascorbic acid, as a reducing agent, was able to improve the phenol yield. In some solvent systems, an optimum amount of ascorbic acid was observed.
A simple model predictive control strategy based on reduced feedforward neural network (FNN) models is proposed. Under some physical constraint conditions, the short-prediction-horizon predictive control algorithm can carry out the offset-free performance for a class of nonlinear systems with input/output multiplicities. The main issue is to specify the input/output patterns for neural network architecture, and a stable, minimum-phase mode is added to reduce control structures that involve off-line identification algorithms and graphic-based determination. Finally, three examples of chemical reactors exhibiting unstable or nonminimum-phase dynamic behaviors are demonstrated to verify the proposed control scheme.
Experiments of submerged cultivation of Monascus anka were carried out according to the sequential pseudo-uniform design (SPUD) method. Adopting the inputs including cultivation temperature and dissolved oxygen and the outputs of the model such as glucoamylase activity and concentration of extracellular red pigments, a second-order response model was successfully identified from the eleven experiments designed by the initial uniform design (UD) method followed by the SPUD method. The identified model achieved a 2.71% average modeling error for the glucoamylase activity but 12.44% error for the concentration of extracellular red pigments. Considering the resource for the experiments, the optimized operating conditions were determined based on the available experimental data to achieve the maximal overall desirability objective function of glucoamylase activity and concentration of extracellular red pigments of the product. The experimental results shown in this work successfully demonstrated the applicability of the SPUD method for locating minimal experiments that will effectively guide the experimenter toward optimized operating conditions of a new process.
A lot of physiological activities are expected from glucose-1-phosphate (G-1-P) and its derivatives. From the viewpoint that enzymatic phosphorolysis of dextrin is promising as an industrial production of G-1-P, kinetics of the enzymatic reaction in high concentration of substrate was investigated. Phosphorylase with a specific activity of 22.5 U·mg–1-protein was purified from potato. Linear chain dextrin and branched dextrin were used as substrate. For inorganic phosphate (Pi), a mixture of KH2PO4 and K2HPO4 was used. The initial rate of phosphorolysis was a function of the non-reducing-end concentration of α-1,4-glucan, regardless of the chain length and branch ratio of α-1,4-glucan. The inhibitory effects of both dextrin and phosphate were observed. From these experimental results, a possible kinetic model of the enzymatic reaction under high concentration of substrate was proposed. This model could well explain the experimental data obtained up to 18 mM of non-reducing-end of dextrin and 1000 mM of Pi.
Recovery of hexavalent chromium ion from methanol was investigated with commercially available nine ion exchange resins including weak anion, strong anion, weak cation, and strong cation exchangers. The effects of water concentration in water–methanol mixture on the adsorption capacity of resins were investigated. The strong and weak anion exchange resins showed high adsorption capacity for chromium both in methanol and water. The strong cation exchange resins gave relatively high adsorption capacity in methanol, but the capacity drastically decreased as the water concentration in methanol increased. Dowex SBR had the best adsorption capacity both in aqueous and methanol solutions. The adsorption equilibrium was attained within about 30 min at an initial Cr concentration of 10 mg/L with Dowex SBR. The desorption of Cr from the resin was found to be easily carried out with NaCl solution. The adsorption and desorption equilibria predicted that the concentration of Cr from methanol into NaCl eluent was possible. Furthermore, five successive adsorption–desorption cycles were successfully carried out without any decline in adorption nor desorption efficiencies.
We studied the practical use of seaweed to remove inorganic nitrogen, especially ammonia-nitrogen, from the intensive shrimp culture ponds in developing countries. At first, we considered and experimentally evaluated the performance of ammonia-nitrogen uptake by seaweed in terms of parameters essential to the designing of intensive mariculture ponds. Based on the mechanism of ammonia-nitrogen uptake by seaweed, it was predicted that the ammonia-nitrogen concentration in the shrimp culture pond could be controlled by keeping it lower than a certain limit of value using a sufficient amount of seaweed with a condition that the rate of ammonia-nitrogen generation was constant. Experimental ammonia-nitrogen uptake runs confirmed this prediction and gave the parameters essential to design the culture pond with seaweed. Secondly, the control of the pond water quality for the practical shrimp culture batch was simulated by simple calculation based on the material balance of ammonia-nitrogen with parameters obtained from the experiments. The concentration of ammonia-nitrogen could be favorably controlled using seaweed in the practical batch and this method found to be feasible. Consequently, the water quality control using ammonia-nitrogen uptake by seaweed was proposed as a simple and convenient method appropriate for the intensive shrimp culture pond in developing countries.