Yasushi Sekine

Reaction mechanism of methane activation using non-equilibrium pulsed discharge at room temperature

Abstract The reaction mechanism of methane activation using non-equilibrium pulsed discharge was largely clarified from the emission spectroscopic study and experiments with higher hydrocarbons and some kinds of isotopes. The strong emission of atomic carbon and C2 swan band system was observed as well as H Balmer series emission. This indicates that methane was highly dissociated into C and H by electron impact, which is consistent with the result of high C2D2 composition in produced acetylene when the mixture of CH4 and D2 was fed into discharge region. High electron energy contributed to produce atomic carbon directly from methane, and high electron density promoted the dehydrogenation from CH3, CH2 and CH to produce atomic carbon consecutively. The reason for the high selectivity to C2H2 was the high concentration of CH or C2 formed from atomic carbon, and the repetition mechanism of decomposition and recombination among C, CH, C2 and C2H2.

Autothermal CO2 reforming of methane over NiO–MgO solid solution catalysts under pressurized condition: Effect of fluidized bed reactor and its promoting mechanism

Abstract The effect of fluidized bed reactor in autothermal CO 2 reforming of methane over NiO–MgO solid solution catalysts was investigated by comparing with fixed bed reactor. Methane conversion to syngas was drastically enhanced by using a fluidized bed reactor. The catalyst was reduced and oxidized repeatedly in fluidized bed reactor during the reaction. The enhancement of methane conversion is related to the catalyst reducibility.

Low-Temperature Hydrogen Production by Highly Efficient Catalytic System Assisted by an Electric Field†

We investigated four catalytic reactions assisted with an electric field to promote catalytic activity, and we could achieve an effective process for hydrogen production at low temperatures, such as 423 K. In the presence of the electric field, four reactions of steam reforming of ethanol, decomposition of ethanol, water gas shift, and steam reforming of methane proceeded at very low temperature, such as 423 K, where a conventional catalytic reaction hardly proceeded. Conversion of reactant was greatly increased by the electric field, and apparent activation energies for these four reactions were lowered by the application of the electric field. This process can produce hydrogen and syngas by using a considerably small energy demand and has quick response.

Direct synthesis of acetylene from methane by direct current pulse discharge

In non-catalytic direct conversion of methane to acetylene by using direct current pulse discharge under conditions of ambient temperature and atmospheric pressure, the selectivity of acetylene from methane was >95% at methane conversion ranging from 16 to 52%; coexisting oxygen was very effective in removing deposited carbon and stabilized the state of discharge.

Low temperature reforming of methane to synthesis gas with direct current pulse discharge method

Synthesis gas was produced by pulsed irradiation of electrons on a mixture of CH4 and CO2 (or H2O) at low temperature and atmospheric pressure without catalysts; especially in the CO2 reforming reaction, the H2∶CO ratio could be controlled and depended on the concentration of CO2 in the feed gas.

Surface Protonics Promotes Catalysis

Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando–IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application. Methane was activated by proton collision at the Pd–CeO2 interface, based on the inverse kinetic isotope effect. Proton conduction on the catalyst surface plays an important role in methane activation at low temperature. This report is the first describing promotion of the catalytic reaction by surface protonics.

One Pot Direct Catalytic Conversion of Cellulose to Hydrocarbon by Decarbonation Using Pt/H-beta Zeolite Catalyst at Low Temperature

We investigated one pot direct catalytic conversion of cellulose to light hydrocarbon selectively at low temperature in the presence of Pt and solid-acid zeolite catalysts. Results revealed that Pt/H-beta zeolite catalyst prepared by ion exchange enabled selective production of C3 and C4 hydrocarbons.

Hydrogen Production by Water Gas Shift Reaction Over Pd–K Impregnated Co Oxide Catalyst

Effects of K and Pd loading on Co3O4 catalyst for the water gas shift (WGS) reaction were investigated. Pd/K/Co3O4 catalyst showed high and stable activity and high selectivity to WGS. Regarding loading amounts of Pd and K, the latter is important for WGS activity and selectivity. XRD, XAFS, and TPR measurements confirmed potassium loading benefits. Supported Pd promoted oxidation of CO with lattice oxygen. The synergetic effect of these functions of K and Pd protected high catalyst activity and stability.Graphical Abstract

High performance methane conversion into valuable products with spark discharge at room temperature

Non-catalytic methane activation with spark discharge showed high energy efficiency and high selectivity to acetylene by the collision of electrons possessing high energy enough to dissociate methane into atomic carbon. The application of spark discharge to steam reforming of methane was effective for hydrogen production at low temperature. The selectivity to desired product was improved by the combination with catalyst.

Low-temperature catalytic oxidative coupling of methane in an electric field over a Ce–W–O catalyst system

We examined oxidative coupling of methane (OCM) over various Ce–W–O catalysts at 423 K in an electric field. Ce2(WO4)3/CeO2 catalyst showed high OCM activity. In a periodic operation test over Ce2(WO4)3/CeO2 catalyst, C2 selectivity exceeded 60% during three redox cycles. However, Ce2(WO4)3/CeO2 catalyst without the electric field showed low activity, even at 1073 K: CH4 Conv., 6.0%; C2 Sel., 2.1%. A synergetic effect between the Ce2(WO4)3 structure and electric field created the reactive oxygen species for selective oxidation of methane. Results of XAFS, in-situ Raman and periodic operation tests demonstrated that OCM occurred as the lattice oxygen in Ce2(WO4)3 (short W–O bonds in distorted WO4 unit) was consumed. The consumed oxygen was reproduced by a redox mechanism in the electric field.