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Dive into the research topics where Yasunori Yokomichi is active.

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Applied Catalysis B-environmental | 2000

Theoretical and experimental study on metal-loaded zeolite catalysts for direct NOx decomposition

Yasunori Yokomichi; Tokio Yamabe; Terumitsu Kakumoto; Osamu Okada; Hideyuki Ishikawa; Yasuhisa Nakamura; Hideki Kimura; Isamu Yasuda

Component effects such as a cocation and the zeolite support structure and the preparation condition effect of metal-loaded zeolites for the catalytic activity of direct NOx decomposition were examined using an experimental method. Regarding the cocation effect, the theoretical calculations were performed using a density functional method. The experimental results indicated that ZSM-5 was the best support of all of the zeolite tested such as ZSM-5, ZSM-11, SAPO-5, Y, and MOR. It was also experimentally found that the addition of a cocation such as Ca or Ni to Cu ion-exchanged ZSM-5 zeolite (Cu/ZSM-5) could prevent the catalyst from deactivation caused by O2 or H2O in the reaction gas. Regarding the cocation effect of Ca or Ni on Cu/ZSM-5, the theoretical calculations showed that the addition of these cocations increased the catalytic activity by promoting the desorption of oxygen yielded from NO decomposition and maintained NO adsorption on the catalyst under the coexistence of H2O. These results of the calculations supported the experimental results.


Catalysis Today | 1995

Theoretical study of NO decomposition on Cu-ZSM-5 catalyst models

Yasunori Yokomichi; Hirofumi Ohtsuka; Takeshi Tabata; Osamu Okada; Yasuharu Yokoi; Hideyuki Ishikawa; Ryuichi Yamaguchi; Hisaji Matsui; Akitomo Tachibana; Tokio Yamabe

Abstract The decomposition mechanism of NO on Cu-ZSM-5 catalyst models was investigated using ab initio molecular orbital calculations with Huzinagas MIDI-P basis set [see S. Huzinaga, Gaussian Basic Sets for Molecular Calculations, Elsevier, Amsterdam, 1984]. Two reaction routes were assumed for each model and the geometry of all molecules was optimized.


Catalysis Today | 1996

Fundamental study on the NOx direct decomposition catalysts

Yasunori Yokomichi; Toshiro Nakayama; Osamu Okada; Yasuharu Yokoi; Iruru Takahashi; Hiroshi Uchida; Hideyuki Ishikawa; Ryuichi Yamaguchi; Hisaji Matsui; Tokio Yamabe

Abstract We are developing direct decomposition catalysts to decompose the NO x involved in high temperature exhaust gases to N 2 and O 2 without any reductants such as urea and plan to bring this technology into practice in the 21st century. We expect to create very simple deNO x systems using direct decomposition catalysts applicable to a wide range of fields (co-generation, boilers, automobiles and so on) after overcoming the technical difficulties. Perovskite catalyst and zeolite catalyst are the most promising materials for direct decomposition catalysts. This study focuses on seeking and designing novel NO x direct decomposition catalysts having high activities through theoretical studies using computational chemistry and experimental studies using surface-science techniques.


Tetrahedron | 1979

Synthesis and properties of all members of methylated tropylium ions

Ken'ichi Takeuchi; Yasunori Yokomichi; Takeshi Kurosaki; Yoshihiro Kimura; Kunio Okamoto

Abstract An members of the methylated tropylium perchlorates have been synthesized and their properties (UV absorptions, 1H NMR spectra, and charge-transfer spectra with pyrene) determined. The methylated tropylium ions other than the hexa- and hepta-methyl homologues have been prepared by abstracting a hydride ion with trityl perchlorate from the corresponding methylated tropilidenes. The preparation of the hexa- and hepta-methyltropylium ions has been effected by utilizing phosphorus pentachloride as the hydride-abstraction reagent. The methylated tropilidenes have been prepared via one of the three known routes, i.e. the ring expansion of methylated benzenes with diazomethane (Route 1) or with ethyl diazoacetate (Route 2), and the cycloaddition of cyclopropene or methylcyclopropenes with methylated thiophene 1,1-dioxides accompanied with the exclusion of sulfur dioxide (Route 3). The methyl 1H NMR chemical-shift values have been assigned, partly with the aid of the Me 13C NMR chemical-shift data for the tropylium ions containing the Me groups on contiguous ring-carbons (3a, 4a, 5a, 6 and 7). The transition energy for the charge-transfer band of the tropylium ions with pyrene increases with the increase in the number of the Me group, indicating that the more methylated the tropylium ion, the more stable is the ion.


international conference on software maintenance | 1994

Molecular design and synthesis of poly(azoarylenes)

Yasunori Yokomichi; Kenji Seki; Shinichi Tada; Tokio Yamabe

Abstract The novel conducting polymers such as poly(azopyrrolylene) [II-a] and poly(bis(pyrrolylazo)phenylenes) [III-a,b] were successfully synthesized, and these polymers indicated high conductivity up to 10 0 S/cm after doping. These polymers also showed excellent stability in the air and in high temperature more than poly(pyrrole). We carried out band calculations of azopyrrolylene, azothienylene and bis(pyrrolylazo)-phenylene by using STO-3G basis set. Generally, these poly(azoarylenes) were predicted to have small band gaps. Especially, some of poly(azoarylenes) tend to have quinoid form and very small energy difference between benzenoid and quinoid form.


Tetrahedron | 1980

Alkylated tropylium ions-III: 13C NMR spectra of methylated tropylium ions, correlations among 1H and 13C chemical shifts, and electron density by the hückel mo method

Ken'ichi Takeuchi; Yasunori Yokomichi; Yasuhiro Kubota; Kunio Okamoto

Abstract The 13 C NMR spectra for all seventeen methylated tropylium ions have been obtained in acetonitrile- d 3 and the chemical shifts of the Me- and the ring-carbons assigned. The plots of the 13 C shifts of ring-carbons against charge densities calculated by the simple Huckel MO method by the use of the inductive and the heteroatom models afford linear correlations. The 13 C shifts for the Me-carbons and the 1 H shifts for the Me- and the ring-hydrogens are linearly correlated with the 13 C shifts for the ring-carbons to which they are attached, provided the Me groups or the ring-hydrogens residing in similar steric environments are compared. From the slopes of the correlation lines the dependences of the 13 C shifts of Me-carbons and the 1 H shifts of ring and Me-hydrogens on charge densities of ring-carbons have been estimated to be 35–50, 11–16, and 2.9–5.1 ppm, respectively, by assuming 160 ppm for the charge dependence of the 13 C shifts of the ring-carbons.


Tetrahedron | 1980

Alkylated tropylium ions—IV: Statistical analysis of 13C NMR chemical shifts of methylated tropylium ions by the use of conformational model. Possible out-of-plane distortion o1

Ken'ichi Takeuchi; Yasunori Yokomichi; Kunio Okamoto

Abstract The Me and the ring 13 C chemical shifts for all members of methylated tropylium ions have been statistically analyzed by the application of Grants conformational model for methylated benzenes, and the additive substituent parameters (δ k ) determined. The predicted Me 13 C chemical shifts of highly congested Me groups in 1,2,3,4,5-pentamethyl-, hexamethyl-, and heptamethyl-tropylium ions considerably deviate from experimental Me 13 C chemical shifts, whereas the predicted values for other 33 Me groups are fairly well correlated (multiple R = 0.9910) with experimental values. On the other hand, all the predicted 72 ring 13 C chemical shifts are linearly correlated with experimental values with high precision (multiple R = 0.9991). The results suggest out-of-plane distortion of highly congested Me groups in the above mentioned methylated tropylium ions, with the 7-membered ring being kept planar. Grants valence bond (VB) approach has been applied to the interpretation of conformational dependence of the 13 C chemical shifts of these adjacent Me groups, giving a linear correlation of the substituent parameters reflecting conformational features with the nonbonded H-H repulsive force acting along the C-H bond axis. Smaller sensitivity of the substituent parameters to the steric force than the case of methylated benzenes has been interpreted to suggest leakage of sterically-induced charge polarization to the positively charged tropylium ring.


international conference on software maintenance | 1994

Theoretical studies of the electronic properties of poly(azovinylene)

Yasunori Yokomichi; Tokio Yamabe

Summary form only given. In our previous paper/sup 1)/, it was shown that the doped poly(azovinylene) [PAV] had the similar properties to doped polyacetylene. Recently, some studies on polyazines [PAZ] as a conducting oligomer/sup 2)/ or a non-linear optical material/sup 3)/ have been reported. It is noticed that the structure of PAV is equivalent to that of bond alternated form of PAZ. Electronic structure and properties of PAV are investigated by using ab initio MO calculations on the infinite polymer and the finite oligomer models. The calculations on the infinite polymer model of PAV indicate that PAZ form is more stable than PAV form. The results of calculations on finite models show that the structure of these oligomers of small size strongly depends on the structure of terminal groups. However, the, bond alternation occurs at the range of the chain length between 7 and 10 monomer units from PAV form to PAZ form.


Journal of The Chemical Society-perkin Transactions 1 | 1981

The one-electron reduction of carbonium ions. Part 14. Effect of successive introduction of methyl substituents on the reducibility of tropylium ion in chromium(II) ion and cathodic reductions

Ken'ichi Takeuchi; Takeshi Kurosaki; Yasunori Yokomichi; Yoshihiro Kimura; Yasuhiro Kubota; Hiroshi Fujimoto; Kunio Okamoto

The second-order rate constants (k2) of one-electron reduction with CrII ion of methylated tropylium ions [C7H7 –n(CH3)n+ClO4–, n= 0–7] were determined in 10% hydrochloric acid at 25.0°C. Reduction peak potentials determined by means of triangular wave cyclic voltammetry and charge transfer energies with pyrene were compared with the rates of CrII ion reduction in terms of the effect of methyl substituents. The log k2 values decrease linearly with an increase in the number of methyl groups up to n= 4. However, the decelerating effect per extra methyl substituent becomes smaller when n is 5 or 6, and the seventh methyl substituent accelerates the reduction. The methyl substituent effect on the reduction peak potentials of the carbocations is similar to that found for the CrII ion reduction, giving rise to a linear correlation. A Marcus treatment suggests that CrII ion reduction proceeds through an outer-sphere mechanism. The charge transfer energies with pyrene are linearly correlated with reduction potentials for ions with n= 0–6, but considerable deviation is noted when n is 7. The charge transfer energies are linearly correlated with the LUMO energy levels of the methylated tropylium ions, suggesting that the unexpectedly pronounced reducibilities of hexa- and hepta-methyltropylium ions are attributable to steric factors. The deviation from linearity in the CrII ion reduction and the reduction potential are reasonably explained by assuming that non-bonded repulsive interactions among congested methyl substituents in the carbocations are relieved upon reduction to their corresponding radicals. This explanation is consistent with our previous conclusion from a 13C n.m.r. study that the methyl substituents of 1,2,3,4,5-penta-, hexa-, and hepta-methyltropylium ions are highly congested and distorted out of plane.


The Journal of Physical Chemistry | 1996

THEORETICAL STUDY OF NO DECOMPOSITION ON CU-ZSM-5 CATALYST MODELS USING THE DENSITY FUNCTIONAL METHOD

Yasunori Yokomichi; Tokio Yamabe; Hirofumi Ohtsuka; Terumitsu Kakumoto

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Osamu Okada

Southern California Gas Company

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