Efficient hydrogen evolution from decalin by heating at 210°C and cooling at 5°C was attempted in a batch-wise reactor by the use of “superheated liquid-film-type catalysis”. When the carbon-supported metal catalyst 0.75 g was immersed with decalin 3.0 ml under a reactive distillation conditions, a liquid-film state was realized and the catalytic conversion of decalin was remarkably enhanced in contrast to the ordinary suspended state (e.g., 0.75 g/10 ml). Active sites in the liquid-film state were superheated, being higher in temperatures than the boiling point of the substrate solution, which gave the catalytic abilities of both high reaction rates and accelerated desorption of the reaction products from the catalyst surface, as evident from the Langmuir-type analysis. In addition, scarcity of substrate in the liquid-film state improved the utilization efficiency of heat by allotting it more to the endothermic reaction rather than to inevitable evaporation. According to our repetitive reaction test with the same catalyst, reproducible activities were confirmed well. The adoption of superheated liquid-film-type catalysis for decalin dehydrogenation would make the reaction couple with naphthalene hydrogenation useful for mobile storage of hydrogen.
The catalytic activity of Cu-Mn-CeOx/Al2O3/Al alumite catalyst in the selective catalytic reduction of nitric oxide by supplementation with propene (SCR-C3H6) was investigated at temperatures ranging from 473 to 773 K. Oxygen was found to have different effects on NOx removal at low and high temperatures. Introducing a small amount of oxygen could significantly promote the reduction of NOx at low temperatures. However, at high temperatures, the increase in oxygen substantially depressed NOx conversion. When oxygen exceeded the critical concentration point (S > 1.0, i.e. a net oxidizing condition), there was an optimal reaction temperature for maximal NOx conversion, which occurred at the temperature required for complete oxidation of propene. An increase in propene was always favorable in enhancing the reduction of NOx over the entire temperature range.
A catalytic reactor requires an effective exchange of heat energy, a quick load response and a downsized dimension, as is seen for the reformer system that generates hydrogen for fuel cells. A wall-type reactor, which metallic wall is directly catalyzed, is attracting interest as a reactor that would satisfies such demands. This research studied the performance of reaction and heat transfer of a rectangular wall reactor, for decomposing methanol to hydrogen and carbon monoxide. The reactor consists of alternating reaction channels with a plate-fin type nickel catalyst prepared by electroless plating between heat medium channels. Furthermore, the dynamic response of the reactor was also examined when the flow rate of feed gas was rapidly changed. The temperature profiles in the rectangular wall reactor demonstrated that the reactor effectively supplies heat energy to reaction zone, even under the reaction condition with a large amount of energy consumption. In addition, the performance of the reactor to handle the feeding material depended on the channel height and the shape of the plate fins inserted into the reaction channel. The performance increased as the height decreased and when serrated-type fins were used. The overall coefficient of heat transfer estimated from the temperature distribution in the reactor suggests that the performance increased because the heat conductivity of the reactor improved as a result of changing the channel height. The heat conductivity of effluent gas stabilized within a few seconds from when the flow rate of feed gas was changed instantaneously. The time required for the reaction to attain steady state was short. The results suggest that the constructed reactor responds to load fluctuation quickly.
The kinetics of the water gas shift reaction was investigated in supercritical water using the Raman spectroscopic method for in situ quantitative measurement of reactants and relevant products in a stopped flow type reactor. The reaction proceeded according to the stoichiometric reaction as CO + H2O → CO2 + H2, whose rate was first order on the concentration of CO. The dependence on the reactant water was 1.5 ± 0.1 in the water density range from 4 to 25 mol dm–3 at a temperature of 380°C. The steady state concentration of formic acid was in the order of 10–4 against the initial concentration of CO and dependent on a 1.2 ± 0.3 order on the water density. These findings evidence that the rate determining step of the water gas shift reaction is the formation process of formic acid, which subsequently dissociates to CO2 + H2 at a much larger reaction rate. The slightly larger dependence than unity on the water density in the reaction rate as well as in the steady state concentration of the intermediate formic acid suggests that the transition state structure of the formic acid formation process resembles a certain kind of complex formed between a CO molecule and several water molecules such as suggested by Melius et al. (1990) by ab initio calculations.
The purpose of this research is to elucidate the effect of the emulsifier on the dynamic behavior of particle size distribution (PSD) in continuous emulsion polymerization. Emulsion polymerization of vinyl acetate was performed in a continuous stirred tank reactor. An anionic surfactant (sodium dodecyl sulfate: SDS) was used as an emulsifier. The initial emulsifier concentration in the reactor and that in the feed was varied as a control parameter. In order to vary the colloidal stability of latex particles, a nonionic surfactant (polyoxyethylene sorbitan monooleate: Tween80) was added in some cases. It has been found that PSD varies with time even while the constant monomer conversion is maintained at a steady state in all cases. Compared with the case of using only SDS, however, using a mixture of anionic surfactant and nonionic surfactant can effectively suppress this time-dependent behavior.
Monosodium L-glutamate crystals, which are of fragile needle, were obtained by batch crystallization with a natural cooling mode from aqueous solution. The effect of seeding on the product size was examined over a wide range of seed-loadings. The seed-loading ratio Cs, defined as the mass ratio of the added seeds to the theoretical yield per batch, had basically the same effect on the product crystal size as observed previously in cooling crystallization of mechanically strong granular crystals such as potassium alum. At high seed-loading ratios as Cs ≥ Cs*, where Cs* is a critical value of Cs, seed crystals grew with practically no secondary nucleation. Crystal breakage due to mechanical impacts brought by an agitator occurred only slightly for the small products. For the large crystals the breakage was significant. The breakage also depended on the type of stirrers used; the anchor stirrer induced less breakage than the turbine stirrer. The transient supersaturation was measured on-line by an electro-conductivity method.
As a first step to clarify the synergistic extraction mechanism of gallium with the mixed extractant of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester and 5-chloro-8-quinolinol, the initial extraction rate of gallium with 5-chloro-8-quinolinol alone was measured using a stirred transfer cell. As a result, the rate process was found to be limited by a diffusion accompanied by the formation reaction of chelating complex in the aqueous solution. The calculated results based on the model generally explained the experimental data.
In this industry–university collaboration, a soft sensor for measuring a key product quality and an on-line monitoring system for testing the validity of the soft sensor were developed to realize highly efficient operation of the ethylene production plant. To estimate impurity concentration in the ethylene product from on-line measured process variables, a dynamic partial least squares (PLS) model was developed. The developed soft sensor can estimate the product quality very well, but it does not function well when the process is operated under conditions that have never been observed before. Therefore, an on-line monitoring system was developed to judge whether the soft sensor is reliable or not. The monitoring system is based on the dynamic PLS model designed for estimating the product quality. The present research provides a PLS-based framework for developing a soft sensor and monitoring its validity on-line. In addition, simple rules were established for checking the performance of a process gas chromatograph by combining the soft sensor and the monitoring system. The soft sensor and the monitoring system have functioned successfully in the industrial ethylene plant.
A limit cycle test is discussed from the viewpoint of the plant identification, and a practical identification method using the modified limit cycle test is proposed. The limit cycle test is a convenient way to estimate some information of the plant dynamics but only few characteristics are obtained by the conventional way. In this work, the limit cycle test is modified so that the manipulated variable and the process value may contain fractional harmonics, and the plant model is estimated with those fractional harmonic components as well as the basic components. The use of the fractional components enables us to identify the plant model accurately in a noise environment and to handle more sophisticated model: a second order lag plus all-pass filter type one. An experimental example of a thermal plant is illustrated to show the effectiveness of the proposed method where an LQI controller is designed with the identified model of the plant.
Barium titanate (BaTiO3) nanoparticles were prepared by means of a liquid source chemical vapor deposition method under atmospheric pressure. The effects of precursor composition, concentration, operating temperature, and residence time in the hot zone on the surface morphology, composition, and crystallinity of the resulting particles were investigated. By increasing the Ba/Ti ratio in the precursor, the amount of TiO2 particles tended to decrease, while the amount of barium carbonate (BaCO3) particles increased. By decreasing the precursor concentration or the residence time in the hot zone, both particle size and degree of aggregation of the particles produced decreased, but the amount of barium carbonate increased. At a Ba/Ti ratio of 2.3, spherical and highly crystalline cubic BaTiO3 particles 27 nm in size with a narrow size distribution (σg = 1.33) were produced at 900°C.
A system for evaluating dementia of the Alzheimer type (DAT) based on magnetic resonance (MR) imaging by means of fuzzy neural networks (FNNs) was investigated. The T1-weighted head MR transverse section images were obtained by a routinely performed examination. Nine slices including the thalamus were analyzed for each subject. Each MR image (MRI) was divided into four parts. The ratio of the brain area to the intracranial area was defined as the atrophy ratio. DAT severity was assessed by the Mini-Mental State (MMS) examination administered to each patient, and the results were used as teaching values for the FNN models. To construct the FNN model with high accuracy, MRI-based input variables were examined. Using atrophy ratios of 9 MRIs based on thalamically fiducial images and the corresponding areal or volumetric data as input variables, highly accurate FNN models were constructed that gave an average error of 1.29 points out of 30 in the MMS scores.
An active carbon/ammonia AHP with a packed bed type adsorber was used as a low temperature side AHP in a multi AHP for producing cold heat energy at temperatures below 253 K. Its heat and mass transfer characteristics in the adsorber were experimentally investigated in the assumed practical regeneration temperatures (343–363 K) and heat sink temperatures (273–283 K). Then, the heat and mass transfer model in the packed bed was evaluated by the experimental data of adsorption amount and temperatures in the adsorber. The results from the changes of adsorption amount have shown that the amount of ammonia vapor adsorbed in the adsorption process can be completely desorbed, and the reversibility between adsorption and desorption in the AHP has been proven. As in the condition of pressurization (≥0.1 MPa), the adsorption/desorption rate of the active carbon/ammonia AHP is larger than that of the silica gel/water AHP. Subsequently, the results of cold heat output illustrated that the adsorption/desorption can be performed equally in the axial direction of the packed bed even if the packed bed height reaches as high as 100 mm.
In order to enhance the nitrogen removal in the activated sludge process, a rectangular airlift bubble column where aerobic and anaerobic regions coexisted was used, and immobilizing carrier particles were added in the column. The effects of equipment and operation conditions on the liquid circulation flow rate and liquid-phase volumetric mass transfer coefficient were investigated. On the basis of oxygen balance, the distribution of dissolved oxygen concentration in the column was calculated by using these flow characteristics. From the dissolved oxygen distribution the volume fraction of anaerobic region was estimated. The results indicated that the volume fraction of the anaerobic region and the concentration of the immobilizing particles strongly affected the nitrogen removal. The nitrogen removal had a maximum value when the volume fraction of the anaerobic region was about 50%.