Kozo Hirota

The chemisorbed state of propene on metals in reference to the catalytic hydrogenation

Abstract The distributions of all the isotopic isomers of propene produced by its exchange reaction with deuterium oxide and by its hydrogenation reaction with D2 have been investigated with the microwave absorption technique, and the following conclusions have been obtained, assuming that propane is produced via the half-hydrogenated state, C3H7, on nickel and palladium: (1) In both reactions catalyzed by nickel, the methine hydrogen of propene is the most exchangeable, and propene may be chemisorbed mostly as the undissociated C3H6(ads.) state, besides the half-hydrogenated state. (2) On palladium, however, all the hydrogens of three groups show nearly equal exchangeability, and some dissociated species, C3H5(ads.), may exist in addition to the above chemisorbed species. (3) Since water does not poison the formation of the half-hydrogenated state, it can supply such an amount of the chemisorbed hydrogen as can produce the half-hydrogenated state on the surface. Therefore, the exchange reaction can be regarded as a part of the hydrogenation.

On the hyperfine deuterium distribution of the catalytic reaction of propene with deuterium on copper powders

Abstract The hydrogenation mechanism of propene on a copper catalyst was investigated at room temperature, using deuterium as the reactant instead of protium. Thereby, not only distributions of the produced deuteropropenes and deuteropropanes were determined by mass spectrometry, but also distributions of the deuterated positions in both monodeuteropropenes and monodeuteropropanes were determined, respectively, by microwave spectrometry and NMR spectrometry. From these two distributions, an extended associative mechanism could be confirmed by assuming half-hydrogenated intermediates of the types CH 3 -CH 2 - C ∗ H 2 and CH 3 - C ∗ H-CH 3 , even though the deuterium-exchange reaction occurs much more frequently via the former species. Double-bond migration was confirmed during the reaction, as has already been proposed on nickel catalyst. Some caution is pointed out on the use of the random-distribution law in discussing the reaction mechanism on the basis of deuterium distribution.

Infrared study of the adsorption of formic acid on evaporated nickel film and interaction of the chemisorbed species with formic acid

The infrared spectra of HCOOH and DCOOD adsorbed on evaporated nickel film were measured in the 4000- to 400-cm −1 range and the reactivity of the adsorbed species was investigated. Exposure of the nickel surface to HCOOH gave the five bands for the chemisorbed species at 2900, 1583, 1390, 1345, and 795 cm −1 as well as for the physically adsorbed species at 1715 cm −1 . The chemisorbed species of DCOOD gave the bands at 2180, 1575, 1060?, 1325, and 780 cm −1 . The chemisorbed species is assigned to (HCOO −1 ) ads . The chemisorbed (HCOO − ) ads did not change through the exposure of D 2 but it was easily displaced by the (DCOO − ) ads upon addition of DCOOD at room temperature. The changes in the spectra of the adsorbed species caused by heating were studied. The results are discussed in relation to the mechanism of the dehydrogenation reaction of formic acid by metal catalysts and the formation of an intermediate complex from (HCOO − ) ads and (HCOOH) ads is proposed.

Application of microwave spectroscopy to the isotopic analysis of the reaction products of methylacetylene with deuterium on nickel catalysts

Abstract The reaction of methylacetylene with deuterium was investigated in a static system over nickel powders at 25 °C, and the products were analyzed by the mass spectroscopic and microwave spectroscopic methods. The propylene yield in the products was ca. 0.8, similar to the result presented in the literature. In sharp contrast with the reaction of propylene with deuterium, the methyl positions of propylene could not be deuterated, suggesting that the double-bond migration does not occur during the reaction. Of all the propylene- d 2 , cis -dideuteropropylene consisted of more than half the product at the 70% conversion. Protium concentration on the surface was estimated to be very low during the reaction. This is in contrast to the situation in the reaction of olefins with deuterium.

Electronic structure of diborane and hyperconjugation effect

Abstract The ultraviolet spectra of diborane are re-examined and its electronic structure is calculated by the method of LCAO SCF. The hyperconjugation effect of the bridge hydrogens is taken into consideration and the system is treated as a three-center, two-electron problem. The integrals are mainly calculated nonempirically but some of them are evaluated by making some approximation. The transition energies are evaluated to be 6.7 (forbidden) and 10.5 eV (allowed), and they correspond well to the experimental values of 6.9 (weak) and 9.2 eV (strong), respectively. The hyperconjugation effect is proved to play an important role in such a bridge compound. The nature of the bridge bond is discussed.

Desulphurisation of Hydrogen Gas with the Thermal Diffusion Column. II

第一に於て,表題の反應が工業的新脱硫法たる可能性あるを認めたるに鑑み,繊條温度,瓦斯流速,水分の存在を初めとし,反應管の内徑,繊條の種類とその長さ及び無機質硫黄吸收劑の種類等の脱硫能力に及ぼす影響を調べた.斯くて二硫化炭素を33mg/l含む原料瓦斯を最高99.7_??_29.8%迄脱硫するを得,前報の結論を確認した.尚,タングステン繊條は,特に水分の存する時,ニクロム繊條に比し脱硫能力が劣るを認めた.終りに平衡論の立場より脱硫機構の考察を行つた.

Researches on the Reaction Velocity with the Thermal Diffusion Apparatus of Clusius and Dickel

熱擴散管を反應管として使用し,高温部を形成する電熱線をして熱的,接解的又はその兩作用を生ぜしむればある種の化學反應に於て,その遂行に好都合な點のある事は既報せし所である.併し反應管内の温度が均一ならざるがため,壓の減少より簡單に速度恒數及び活性化熱等を算出できぬ難點がある.依て本報にては之等を求むる一般方式を導いた.次にこれな著者等がさきに測定せるアセチレンの重合反應に適用したるに,妥當と思はるる速度恒數と活性化熱とを得た.