Takanori Miyake

Role of lattice oxygen of metal oxides in the dehydrogenation of ethylbenzene under a carbon dioxide atmosphere.

The mechanism for the dehydrogenation of ethylbenzene over V, Cr, and Fe oxides loaded on activated carbon, powdered diamond, Al(2)O(3), and MgO was studied in the presence of CO(2). Vanadium oxide-loaded catalysts provided higher styrene yields under CO(2) than Ar flow. The transient response method was carried out to understand the reaction behaviors of lattice oxygen of various metal oxides on the support. The results showed that lattice oxygen of vanadium oxide (V=O) was consumed in the dehydrogenation reaction and that reduced vanadium oxide was reoxidized with CO(2). A similar redox cycle was observed on iron oxide-loaded activated carbon catalyst. Spectroscopic characterization revealed that vanadium oxide and iron oxide on the support were reduced to a low valence state during the dehydrogenation reaction, and that CO(2) could oxidize the reduced metal oxides. In contrast, chromium(III) oxide was not reduced during dehydrogenation. From these findings, the redox cycle over vanadium oxide- and iron oxide-loaded catalysts was concluded to be an important factor in promoting the catalytic activity with CO(2).

Cs and Sr removal over highly effective adsorbents ETS-1 and ETS-2

Engelhard titanosilicate-1 (ETS-1) and Engelhard titanosilicate-2 (ETS-2) were prepared. It was the first time their properties were studied for applications in water treatment. The performance of ETS-1 and ETS-2 in Cs and Sr removal was investigated and compared with those of ETS-4, Na-Y and Na-ZSM-5. Characterization revealed successful synthesis of ETS-1 and ETS-2, having layered structures with specific surface areas of about 120 m2 g−1 and 220 m2 g−1, respectively. The compositions of ETS-1 and ETS-2 were analyzed by XRF and TGA, and the theoretical exchange capacities for monovalent cations were calculated to be 6.70 mmol g−1 and 8.12 mmol g−1, respectively, assuming all the alkali metal cations could be exchanged. ETS-1 showed the highest Cs removal performance among the adsorbents studied, whereas ETS-2 was promising in Sr removal. In competitive removal experiments for Cs and Sr, the highest amount of Cs uptake was observed over ETS-1, though ETS-1 did not show specific selectivity to Cs removal.

Oxidative dehydrogenation of propane using lattice oxygen of vanadium oxides on silica

Oxidative dehydrogenation of propane using lattice oxygen of vanadium oxide was carried out with a fix-bed flow reactor at 450 °C under atmospheric pressure. Vanadium oxide loaded on SiO2 from V(t-BuO)3O afforded a high propylene selectivity of 88.3% with a propane conversion of 26.5% based on the lattice oxygen of vanadium oxide. The catalyst prepared with V(t-BuO)3O exhibited higher propane conversion and propylene selectivity than that prepared with NH4VO3. Raman, XPS, and XRD analyses revealed that isolated VO43− species seem to be active sites in the ODHP. For the dehydrogenation of propane, the lattice oxygen of the isolated VO43− species was used to give propylene and H2O. The isolated VO43− species was reduced to the isolated V3+ species and was regenerated by oxidation with oxygen. The activity was maintained for at least 10 repeated cycles, suggesting that VOx/SiO2 would be a promising catalyst for ODHP.

Highly effective K-Merlinoite adsorbent for removal of Cs+ and Sr2+ in aqueous solution

K-Merlinoite or “K-MER” was successfully synthesized and firstly employed as an adsorbent for the removal of Cs+ and Sr2+ cations in aqueous solution by batch operation. The optimum conditions to synthesize K-MER were hydrothermal temperature of 250 °C and a hydrothermal time of 8 h. As revealed by XPS, TG, NMR, and ICP analyses, the composition of K-MER synthesized under optimum conditions was “K10.9Al11.2Si20.9O61.6·17.8H2O”, which corresponded with the typical formula of Merlinoite zeolite. 27Al MAS NMR indicated that no octahedrally coordinated aluminum existed suggesting very high purity of K-MER. The calculated theoretical ion-exchange capacity was 4.2 mmol g−1, assuming exchange of the total amount of potassium. In aqueous solution, K-MER exhibited an excellent Cs+ (≥90%) and Sr2+ (≥65%) removal performance with the maximum exchange capacity of 3.08 meq. g−1 for Cs+ and 2.01 meq. g−1 for Sr2+. K-MER showed higher adsorption for Cs+ than Sr2+ when performed using the same adsorption conditions. Coexisting monovalent cations, Na+ and K+, significantly influenced Cs+ removal more than divalent cations, Ca2+ and Mg2+, and they were in the order of K+ > Na+ > Ca2+ > Mg2+. The most important factor for competitive adsorption between Cs+ and the coexisting cation was the hydrated ionic size. Cs+ became more difficult to adsorb when Cs+ was interfered by a coexisting cation of close size. Although the efficiency of Cs+ removal by K-MER decreased around 50% in artificial seawater compared with that in the aqueous solution, K-MER was a promising material for Cs+ and Sr2+ removal.

Synthesis of one-dimensional microporous todorokite and its catalytic activity in CO oxidation

Synthesis of an octahedral molecular sieve composed of Mn, Mg and O, known as todorokite, was studied in detail. The synthesis procedure is composed of three steps; layered birnessite synthesis, ion-exchange to buserite and final hydrothermal treatment of buserite. To obtain todorokites of different morphological properties, the aging time in the birnessite synthesis was varied. The effects of the aging time on properties of todorokites were studied by XRD, FE-SEM, TG-DTA, N2 adsorption-desorption, FT-IR and CO-TPD. In addition, catalytic activities of various todorokites for CO oxidation were investigated and the correlation between properties and activities was discussed.

Catalytic Performance and Reaction Pathways of Cu/SiO 2 and ZnO/SiO 2 for Dehydrogenation of Ethanol to Acetaldehyde

Ethanol production has significantly increased in the last decade, mainly based on the fermentation of glucose1), and a large amount of the so-called bio-ethanol is used for a transportation fuel or fuel additive2). From a viewpoint of CO2 fixation, other uses of ethanol must be developed. Acetaldehyde is an important bulk chemical used as a raw material for the production of ethyl acetate3). Acetaldehyde is produced by the Wacker process from ethylene as the raw material using PdCl2CuCl2 catalyst4). However, this process has the disadvantages of corrosion of the reactor, chlorinated by-products and deposition of metallic Pd. Therefore, other routes to produce acetaldehyde are desirable. Acetaldehyde can be synthesized by dehydrogenation or oxidative-dehydrogenation of ethanol. Lower cost ethanol production will promote the ethanol-based production of acetaldehyde, and the hydrogen by-product has various uses which will further improve the competitiveness of the acetaldehyde production. Oxidative dehydrogenation of ethanol to acetaldehyde has been studied using metal catalysts5)~7) or oxide catalysts8). AuCuOx/SiO2 catalyst at 200 °C achieved 90 % conversion of ethanol with 80-90 % selectivity for acetaldehyde5). Sobolev et al.6) studied low temperature gas-phase oxidation of ethanol on Au/TiO2. Idriss and Seebauer8) used oxide catalyst such as Fe2O3, CaO and TiO2. Acetaldehyde selectivity was high on CaO catalyst, but the conversion was lower than 15 %. Therefore, acetaldehyde selectivity is not sufficient for oxidative dehydrogenation of ethanol. 205 Journal of the Japan Petroleum Institute, 61, (4), 205-212 (2018)

141 Phenylacetate synthesis by oxyacetoxylation of benzene on Pd-catalyst

Abstract Phenylacetate (PhOAc) synthesis by oxyacetoxylation of benzene on Pd-based binary catalysts was studied in the liquid phase. Among the second components investigated, Sb, Bi and Te had a positive effect for catalytic performance of Pd. Deactivation was observed accompanying the elution of Sb, Bi and Pd. Notably less elution of Pd was observed when Pd was modified with Te. Screening of supports revealed a positive effect of ZrO2 for stability of the Pd-Te catalyst.