Thermochemical Water-Splitting for Hydrogen Production by Antimony-Iodine Processes

A new thermochemical water-splitting process named \u22Sb-I Process\u22 was proposed on the basis of thermodynamic considerations and some preliminary experiments. The process consists of three reactions which eventually produce hydrogen from water via HI intermediate. Subsequent examinations, however, showed that this process embraced a difficulty in the separation of HI gas from the reaction system. To overcome this difficulty, the process was subjected to modification in two ways. First the electrolysis of the aqueous HI solution was combined with the original process to eliminate the HI separation step. The overall efficiency for this \u22Sb-I Hybrid Process\u22 was estimated to be 33～37％ when the recovery of heat was assumed to be 80％. The second modification was carried out by introducing calcium as an additional reaction medium. The resulting modified process, \u22Sb-I-Ca Process\u22, consists of five reactions. It was found that all reaction- and separation-steps in this process could be conducted without serious difficulties. From a flow diagram made on the basis of the experimental results, the overall efficiency was estimated to be about 39％ with an assumption of 80％ heat recovery

Hydrogenation of Carbon Monoxide over the Supported Rhodium Catalysts

Hydrogenation of carbon monoxide has been studied at 250℃ under 1 and 10 atm of pressure over rhodium catalysts supported on HY and NaY zeolite, silica, alumina, and titania. The characterization of these supported rhodium catalysts are done by XPS, IR, electron microscopy, and thermal desorption methods. The selectivity and the activity of the catalysts are strongly dependent on the nature of the support and on the state of the rhodium metal on the support surface. Hydrogenation of carbon monoxide at 250℃ under 1 atm gives lower hydrocarbons and carbon dioxide. However, under 10 atm chain growth reaction proceeds with better selectivity for hydrocarbons of carbon atoms 2, 3, and 4, and moreover oxygenated compounds such as ethanol are also produced over Rh-Al_2O_3, Rh-TiO_2, and Rh-SiO_2 catalysts

Humidity Sensors of Mixed Metal Oxides

For the purpose of developing new functional materials, mixed metal oxides were searched as ceramic humidity sensors. The present investigation was conducted to clarify the influence of chemical and physical properties of ceramic material on its electrical conductivity in the presence of adsorbed water. The infrared spectral results of the adsorption structure of water showed that the humidity-impedance characteristics of elements at room temperature was caused by physisorbed water. It has become apparent that the impedance of ceramics are dependent on the composition, degree of sintering, and adsorption amount of water. Good humidity sensors are expected to be obtained by controlling bulk properties, surface area, microstructure, and sintering of ceramic materials

Methylethylketone Oxidation over V_2O_5 Catalysts

The reaction mechanism of methylethylketone (MEK) oxidation to acetaldehyde (AcH) and acetic acid (AcOH) which is characterized by the oxidative splitting of carbon skeleton has been investigated over V_2O_5 catalysts. Kinetics of MEK oxidation at 150℃ over V_2O_5-MoO_3 suggested the participation of molecular oxygen in the reaction. The formation of O_2^- species on the catalyst surface under the reaction conditions was in fact confirmed with temperature programmed desorption and EPR techniques, by using a partially reduced V_2O_5 catalyst supported on silica gel. It was shown that the O_2^- species thus formed reacted with MEK to produce AcH and AcOH selectively, while the lattice oxygen of V_2O_5 converted MEK into CO_2. 0n the basis of these results it was concluded that the O_2^- was the oxygen species reacting with MEK in the oxidative scission reaction