Shimpei Matsuda

Superconductivity of Tl-Sr-Ca-Cu-O System in Relation to Tl-Ba-Ca-Cu-O and Bi-Sr-Ca-Cu-O Systems

It was found that Tl-Sr-Ca-Cu-O system gives rise to at least two superconducting phases, a high-Tc phase at 100 K and a low-Tc phase at about 75 K. The two phases are isostructural to those of Bi-Sr-Ca-Cu-O system. Comparing the Tcs and crystal structures of the Tl and Bi systems, it was suggested that Tc is mainly determined by the combination of two alkaline earth elements, i.e., Sr/Ca or Ba/Ca, when the repetition unit in the layered perovskites is equal.

Oxidation and reduction of substances in aqueous solution in presence of water-repel lent catalyst

The surface of a conventional solid catalyst composed mainly of metal oxides such as A1203, SiOz, TiOz, and Fez03 is hydrophilic. When such a catalyst is used in an aqueous solution, the surface is completely covered by water. It has been understood, therefore, that a conventional solid catalyst has little effect on the reaction of a substance in an aqueous solution with an insoluble gas, for example, oxidation of SHion by 02 and reduction of NO3ion by HZ. Since the surface of a hydrophilic catalyst is covered with a layer of water, 02 or H2 gas is not brought into contact with active sites of the catalyst surface. Under such circumstances the reaction rate may be controlled by the dissolution of O2 or H2 gas into the aqueous solution. In order to overcome the drawbacks of a hydrophilic catalyst an attempt has been made in the present study to prepare and utilize a water-repellent or hydrophobic catalyst for a reaction in an aqueous solution involving 02 and Hz gas. It has been discovered that several reactions are greatly accelerated in the presence of a water-repellent catalyst. The term “waterrepellent catalyst” instead of “hydrophobic catalyst” is used in the present paper, since it better represents the nature and function of the catalyst. A water-repellent catalyst is defined as a catalyst whose surface is at least partly water repellent and forms a gas-solid interface when it is in contact with a gas in an aqueous solution. 264 0021-9517/83/020264-07

Continuous gaseous ammonia analyzer by gas titration method

03.00/O Cowi&t Q 1983 by Academic Press, Inc. Au rights of reproduction in any form reserved. Consequently a function of a water-repellent catalyst is to form a three-phase, i.e., gas-liquid-solid interface, which provides reaction sites for the gas and liquid components. A water-repellent catalyst has been used in the HT02 recombiner for a lead-acid battery (1, 2) and in the isotopic exchange between HDO(liquid) and Hz(gas) for the deuterium concentration (3-5). In these applications the catalyst is not used to cause a chemical reaction of a substance in the aqueous solution, but the water repellency is utilized merely to avoid surface wetting. Recently it has been reported in patents that a water-repellent catalyst with an electroconductive support (carbon) has been applied to various chemical reactions in aqueous solutions (6, 7). An electrode catalyst which is used in the HT02 fuel cells with KOH or H3P04 electrolyte can be said to be a water-repellent catalyst with electroconductivity (8, 9). We have prepared a number of waterrepellent catalysts from various support materials (electroconductive and nonconductive) and applied the catalysts to several reactions. The fundamental nature of the water-repellent catalyst is investigated and the preliminary experimental results are reported in this paper.

A New Catalytic Reactor for Nitrogen Oxides Removal

A new instrument for simply and rapidly determining an ammonia concentration in a gaseous mixture has been developed. The principle is based on the fact that ammonia reacts with NO exactly at 1:1 mole ratio in the presence of an appropriate catalyst: NH3+NO+ 1/4 O2=N2+ (3)/(2) H2O. A sample gas containing NH3 is mixed with NO and made to contact with a catalyst capable of promoting reaction of NH3 and NO to form N2 and H2O in an oxidative atmosphere at an elevated temperature, preferably, 300°–400 °C. The catalyst capable of conducting the reaction is composed of TiO2 and at least one of the oxides of V, Fe, Cu, W, Mo. The concentration of NH3 is determined by measuring concentrations of NO before and after the reaction and calculating the consumption of NO. For the analysis of NO in the gas, a chemiluminescence‐type analyzer can be preferably used. According to the present method, ammonia in a sample gas can be analyzed within a few minutes without any influence of various coexisting gas components.

Catalytic process for reducing nitrogen oxides to nitrogen

The body of information presented in this paper is directed to those individuals concerned with the catalytic NOx removal reactor for a dirty (containing dust) flue gas. In the case of treating a dirty flue gas, the concentration of dust is the most important factor. While the dirty gas passes through the catalytic reactor, dust particles deposit and plug up the catalyst causing the reactor pressure loss to rise. As a result, the NOx reduction efficiency decreases more and more, and continuous operation becomes impossible. A new type of NOx removal reactor for dirty flue gas, the intermittent moving bed reactor, has been developed. The following characteristics have been evaluated: (1) method of calculating reactor pressure loss caused by dust particles, (2) static pressure distribution across the catalyst bed in the reactor, (3) method of evaluating uniform movement of catalyst and (4) reentrainment pattern of dust by catalyst movement. After carrying out various successful pilot plant tests, the informa...