The photocatalytic reduction of Ag+ ions by TiO2 nanoparticles was examined in water under high-temperature high-pressure conditions of T = 25–400°C and P = 30 MPa. The analysis of the reaction by uv-vis absorption spectroscopy, the atomic absorption spectrometry, and TEM observations revealed that the efficient photocatalytic activity compared with that at room temperature remained even under hydrothermal and supercritical conditions. These results could open the way to new applications of TiO2 under extreme environments which have never been explored before.
Polymorphic solid state transition of caffeine anhydrate crystals from a metastable Form I to a stable Form II was conducted to investigate the kinetics as a function of temperature and humidity. The kinetics was expressed well with the penetration model proposed in our previous study. The transition rate was independent of the humidity but was dependent on the temperature. The activation energy was comparable to that for the solid state transition of theophylline anhydrates, indicating a similar mechanism of solid state transition.
In this study we investigated the kinetics of the coagula formation reaction of polymer latex using an extended unreacted core model. Based on the unreacted core model, the diffusion of coagulant molecules into the unreacted core was considered in this model. This phenomenon was confirmed by measuring the coagulant concentration in the unreacted core. The coagulant molecules diffused into the unreacted core, but these did not react with the emulsifier molecules because the coagulant concentration in the unreacted core did not reach the critical coagulation concentration (CAf). This model was in good agreement with the time course of the coagula formation in many conditions. The dependences of the effective diffusion coefficient on polymer latex tube radius, temperature and the coagulant concentration were also examined. The effective diffusion coefficient calculated by this model was independent of the latex tube radius and was explained by molecular diffusion. However, this was strongly dependent on the coagulant concentration. On the other hand, the actual effective diffusion coefficient was not strongly dependent on the coagulant concentration. So we measured the coagulant diffusion rate at the latex tube surface and clarified that the pseudo-steady-state approximation was not held in this reaction system.
In this study we investigated the kinetics of the coagula formation reaction of polymer latex to solve the unsteady equation of diffusion involving the moving boundary. To investigate the kinetics of solid–fluid reactions when the pseudo-steady state approximation is not held, we tried to apply the orthogonal collocation method to an unsteady equation of diffusion involving the moving boundary. This model had good agreement with the reasonable and constant effective diffusion coefficient without the dependence on the coagulant concentration.
A cylindrical methane steam reformer using an electrically heated alumite catalyst (EHAC), i.e., Ni/Al2O3/Alloy catalyst, was introduced in this work. The relevant 2D dynamic model has been developed to reveal the key factors to improve the reformer’s performance in concepts of heat and mass transfer. Various strategies to improve the reformer’s reaction and start-up performance were discussed by numerical investigations. Based on the simulation results, the cylindrical reformer was experimented. The experimental results showed that the reformer has a fast start-up and quick response for the load fluctuation by the internal heating through the EHAC.
Ultrasound was irradiated to an aqueous solution of KI for oxidizing iodide ions in a rectangular-channel type sonoreactor with 14 oscillators mounted in series. The ultrasonic frequency was 133.2 kHz. For different setting conditions with or without a reflector, the reaction was carried out in a batch and continuous operation mode, and the conversion of iodide ions was compared to investigate the characteristics of a reactor. Under the batch operation mode, a reaction rate constant without a reflector was higher than that with a reflector. For a continuous mode, similar rate constants were observed for both conditions with and without a reflector, and the constants were close to that for the batch mode with a reflector. The results indicate that horizontal sweeping flow along the air-liquid interface may have suppressed the cavitation. The effect of the liquid flow should be taken into consideration to design flow-type sonochemical reactors.
An analytical tuning method for a PID controller cascaded with a lead/lag filter is proposed for FOPDT processes based on the IMC design principle. The controller is designed for the rejection of disturbances and a two-degree-of-freedom control structure is used to slacken the overshoot in the set-point response. The simulation study shows that the proposed design method provides better disturbance rejection than the conventional PID design methods when the controllers are tuned to have the same degrees of robustness. A guideline of a single tuning parameter of closed-loop time constant (λ) is provided for several different robustness levels.
Reverse micellar extraction has a potential application in proteins purification. In the process of AOT/isooctane reverse micellar extraction of proteins, a big problem is inactivation of interesting proteins when ionic surfactant AOT was used to form reverse micelles. In this study, it had been found that adding ethanol could stabilize the activity of protein, and it greatly improved extraction recovery of trypsin. When trypsin was extracted from crude material of pig pancreas by using AOT/isooctane reverse micellar system almost 90% and 100% of activity recovery of trypsin could be obtained in forward and backward extraction, respectively. The effects of ethanol concentration, organic salt types, AOT concentration, pH and temperature on the recovery of trypsin were investigated and the extraction process had been optimized. Finally, about 88% of the total yield was obtained, and the specific activity of trypsin purified was increased from 300 U/mg to over 1800 U/mg proteins with purification factor of 5 times more.
Molecular imprinted copolymers, which highly recognized and bound bile acid (BA), were synthesized using a covalently imprinting technique. BA triacrylate (BAA) was a novel monomer targeting the BA imprinting by copolymerizing with a crosslinkable monomer of divinylbenzene (DVB). The resultant copolymer was treated under an acidic condition to form comprehensive BA imprinted sites in the DVB copolymers. The resultant BA imprinted copolymers had less bindings to deoxycholic acid and cholesterol relative to BA. The value of the binding amount of BA for the imprinted copolymer was 22.6 μmol/g, indicating an excellent binding capacity for a template molecule. The recognition ability of the imprinted copolymer was probed with fluorescence of DVB segments in the copolymers: When exposed to the 300 nm light, the fluorescence of the phenyl segments of DVB was observed in the substrate solution. It was found that the BA imprinted copolymer enhanced the monomer fluorescence intensity of the DVB segments near 346 nm, as BA bound. However, when other substrates bound, the segments enhanced the excimer intensity observed near 435 nm. The comparison suggested that the BA binding to the imprinted sites was favorable for the enhanced monomer fluorescence, because comprehensive binding of the molecule into the imprinted DVB segments interfered the excimer formation of the phenyl groups in the copolymer.
Hydrogen peroxide was directly produced from hydrogen and oxygen in a slurry reactor containing a Pd/C catalyst at 5–20°C. Hydrogen and oxygen produced by a solid polymer electrolyte water electrolyzer were fed into the reactor. The effects of reaction temperature, slurry concentration, gas flow rate and solvent on the H2O2 production were investigated. The maximum production rate of H2O2 was obtained at a reaction temperature of 10°C and sharply increased along with the addition of methanol. The results show that H2O2 production is significantly influenced by the solubility of the gas, while excessive catalyst and hydrogen facilitate the decomposition of the accumulated H2O2. Finally, H2O2 production was performed in a catalytic slurry reactor with a pair of platinum electrodes inserted. The in situ feed of hydrogen and oxygen into the reactor improved H2O2 production. This could be due to an increase in gas solubility due to fine bubbles or the electrochemical generation of H2O2.
In order to develop a new process for the production of polylactic acid by adopting rice as material, it is important to find the optimal operational conditions to produce lactic acid as much as possible. In this work, effective liquefaction and saccharification of starch were investigated for the lactic acid fermentation. The states of a sample under the pretreatment were roughly evaluated by measuring the power consumption of an impeller to agitate a solution and the molecular weight of starch.
A single equation of state (EOS) such as the Soave–Redlich–Kwong EOS can accurately describe both the liquid and vapor phase. We present several applications of this equation of state including estimation of pure component properties, computation of vapor–liquid equilibrium (VLE) diagram and phase envelope for binary mixtures. Finally, we solve a flash distillation problem for a mixture of hydrocarbons and show how one can obtain the true vapor pressure (TVP). All these computations are available in the form of notebooks upon request from authors or from the Wolfram Research Information Center (Binous, 2006a). These problems can serve as teaching material for a chemical engineering thermodynamics undergraduate level course.