Tsutomu Shikada

Oxidative coupling of methane over Y2O3CaO catalysts

Abstract Binary oxides of Y 2 O 3 CaO were evaluated as catalysts in the oxidative coupling of methane to C 2+ (sum of C 2 H 6 , C 2 H 4 , C 3 H 8 , and C 3 H 6 ) hydrocarbons. Passing a mixture of CH 4 /O 2 and He gases (at 6, 3 and 31 ml/min respectively) in a fixed-bed flow reactor 13% and 7.5% of C 2+ yields were achieved at 750°C and 650°C, respectively, over 0.5 g of 10 mol-% Y 2 O 3 CaO catalyst prepared by calcining a coprecipitate of their oxalates at 800°C. The C 2+ yields on 10 mol-% Y 2 O 3 CaO, prepared by physical mixing, were lower than those on the coprecipitated catalyst. With increasing Y 2 O 3 content in the coprecipitated catalyst, the C 2+ selectivity at 700°C was significantly enhanced even at ca. 3 mol-%, whereas at 600°C such a change was not observed. A similar dependence on the Y 2 O 3 content was found in the way both surface areas and basicities decreased. Those changes were attributed to the formation of a solid solution accompanying the production of interstitial oxygen ions. Electron-spin resonance (ESR) studies indicated that the ion is a superoxide ion which is responsible for the generation of methyl radical from methane. At low reaction temperatures, 700°C, it was found that a lattice distortion of Y 2 O 3 in the binary oxides also affected the C 2+ selectivity.

Selective synthesis of C2-C5 hydrocarbons from carbon dioxide utilizing a hybrid catalyst composed of a methanol synthesis catalyst and zeolite

Abstract The synthesis of hydrocarbons from carbon dioxide and hydrogen was studied under pressurized conditions using hybrid catalysts composed of methanol synthesis catalysts and a high-silica zeolite (DAY). Combination of Cu-Zn with DAY gave C 2 -C 5 hydrocarbons with selectivities higher than 90%. Addition of a small amount of CO in the H 2 -CO 2 feed led to a marked increase in yield and selectivity of the C 2 -C 5 hydrocarbons irrespective of reaction conditions such as temperature, contact time and the H 2 /(CO 2 +CO) feed ratio. It was suggested that the major route of hydrocarbon formation was (1) reduction of CO 2 to CO on the methanol synthesis catalyst, (2) methanol formation from CO and H 2 , and (3) methanol conversion to hydrocarbons on the DAY.

Selective oxidation of toluene to benzoic acid catalyzed by modified vanadium oxides

Abstract A variety of oxides were examined as additives to a V 2 O 5 /TiO 2 catalyst in order to enhance the catalytic performance for the vapor phase oxidation of toluene to benzoic acid. It was found that the modification with SeO 2 , TeO 2 or Sb 2 O 3 greatly promoted the title reaction leading to improved catalyst performance in terms of toluene conversion and benzoic acid selectivity. The effect of reaction temperature, O 2 /toluene ratio, steam/toluene ratio and durability were also investigated in order to reveal the catalytic features of the modified catalyst systems.

Vapor phase carbonylation of dimethyl ether and methyl acetate with nickel-active carbon catalysts

Abstract Vapor phase carbonylation of dimethyl ether and methyl acetate on nickel-active carbon catalysts was studied under pressurized conditions in the presence of methyl iodide as a promoter. Methyl acetate was synthesized from dimethyl ether and carbon monoxide with a selectivity of 80 to 90% at 250° C and 11 atm. A small amount of acetic anhydride was obtained at higher pressure which was essential for the acetic anhydride formation from methyl acetate. By-products such as acetic acid, methane and carbon dioxide were formed in both reactions. In particular, fairly large amount of acetic acid was formed in spite of the reaction under water free condition to bring about the decrease in the selectivity to acetic anhydride.

Vapor-phase oxidation of benzoic acid to phenol over Na2O-promoted NiOFe2O3 catalyst

Abstract A NiO Fe 2 O 3 Na 2 O catalyst achieved an extremely high space-time yield (STY) of phenol, while maintaining a high phenol selectivity, as compared with that of a conventional CuO catalyst for the vapor phase oxidation of benzoic acid. The addition of Na 2 O to NiO Fe 2 O 3 catalyst was found to be very effective in increasing the STY of phenol, while maintaining a high phenol selectivity. The effect of temperature, oxygen ratio, H 2 O ratio, and space velocity on the catalyst performance were examined in order to optimize the phenol selectivity and STY of phenol. The reaction route for phenol formation over the Na 2 O-promoted NiO Fe 2 O 3 catalyst was also speculated upon by considering the deactivation of the catalyst.

Structural analysis of NiO—Fe2O3 catalyst for vaporphase oxidation of benzoic acid to phenol

Abstract NiO-Fe 2 O 3 catalyst with an atomic ratio of nickel to iron of one was found to show excellent activity for vapor-phase oxidation of benzoic acid to phenol. The homogeneous distribution profile of NiO and NiFe 2 O 4 on the surface and in the bulk of the catalyst is essential for the formation of phenol.

A highly effective countermeasure for the deactivation of the NiONiFe2O4Na2O catalyst for phenol synthesis

Abstract Durability of the novel catalyst system for phenol synthesis by vapor phase oxidation of benzoic acid was investigated in detail. Although an obvious deactivation was observed using the NiO NiFe 2 O 4 Na 2 O system, prominent results were obtained by the addition of V 2 O 5 to the catalyst. More than 90% both in phenol selectivity and benzoic acid conversion were maintained more than 100 h. The remarkable enhancement of catalytic performance is considered to be derived from the facilitated reoxidation of active species by V 2 O 5 in its redox cycle.

Oxidation of toluene to benzoic acid over modified V2O5-TiO2 catalyst with SeO2, TeO2 and Sb2O3

It was found that the addition of SeO2, TeO2 or Sb2O3 to a V2O5/TiO2 catalyst greatly improved the catalytic activity in the vapor phase oxidation of toluene to selectively form benzoic acid.

Vapor phase carbonylation of methyl chloride with transition metal-active carbon catalysts

Abstract Vapor phase carbonylation of methyl chloride with supported transition metal catalysts was studied under pressurized conditions in the presence of water and alcohols. It was found that Ni, Pd and Rh supported on active carbon were effective for the formation of acetic acid derivatives. The carbonylation activities of these catalysts were promoted by the feed of a small amount of methyl iodide.

Vapour phase oxidation of benzoic acid to phenol over NiO–Fe2O3 catalysts

The NiO–Fe2O3 complex oxide catalysts, which were prepared by precipitation and then calcined at around 800 °C, showed excellent catalytic activity in the vapour phase oxidation of benzoic acid to selectively form phenol.