Hiroshige Matsumoto

Bio: Hiroshige Matsumoto is an academic researcher from Nagasaki University. The author has contributed to research in topics: Hydrogen & Catalysis. The author has an hindex of 18, co-authored 48 publications receiving 1068 citations. Previous affiliations of Hiroshige Matsumoto include Toyota & University of Connecticut.

CO2 Reforming of CH4 by Atmospheric Pressure ac Discharge Plasmas

Abstract: Partial oxidative reactions of methane by carbon dioxide have been studied using atmospheric pressure alternating current plasmas. The reactions were carried out using a Y-type reactor with metal rods as the inner electrodes inside quartz tubes and aluminum foil wrapped around quartz tubes as the outer electrodes. The waveforms, input voltages, and currents of the reactions were monitored with an oscilloscope. Interactions between excited methane and excited carbon dioxide as well as those between one excited species and the other unexcited species were observed. The products of the reactions include carbon monoxide, hydrogen, ethane, ethylene, propane, and acetylene. The effects of many reaction parameters, including input voltage, total flow rate, mole ratio of methane to carbon dioxide, selective excitation of either reactant, and micro-arc formation, on product distribution and energy efficiency have been investigated. With an increase in the carbon dioxide-to-methane ratio the selectivity to carbon monoxide increased, and less coke formed. Micro-arc formation between excited methane and excited carbon dioxide increased the conversions of both methane and carbon dioxide and favored the production of carbon monoxide. The energy efficiency of the reaction reached a maximum at CH4/CO2=1 with micro-arc formation, but it was minimized at CH4/CO2=1 when no micro-arc formed during the reaction. The reaction with micro-arc formation had a higher energy efficiency than that without micro-arc formation.

Sonochemical Preparation and Catalytic Behavior of Highly Dispersed Palladium Nanoparticles on Alumina.

Abstract: Palladium nanoparticles dispersed on Al2O3 were prepared via the sonochemical reduction of tetrachloropalladate(II) (Pd(II)) in an aqueous solution. The reduction of Pd(II) to metallic Pd successfully proceeded, even in the presence of Al2O3 powder, by ultrasonic irradiation at 200 kHz. The rates of Pd(II) reduction strongly depended on the type of alcohol additive, which acts as an effective accelerator for Pd(II) reduction. The dispersion of metallic Pd particles on the Al2O3 surface was appreciably enhanced by increasing the rate of reduction. By UV−visible, pH, and transmission electron microscopy measurements, the major pathway in the formation of Pd nanoparticles on Al2O3 was speculated to proceed via the following three steps: (1) the reduction of Pd(II) ions proceeds with reducing radicals formed by sonolysis of water and alcohol molecules, resulting in the formation of Pd nuclei, (2) the growth and/or the agglomeration of the Pd nuclei rapidly occurs to form Pd nanoparticles, and (3) the Pd part...

CO2 Decomposition Using Glow Discharge Plasmas

Abstract: Carbon dioxide decomposition has been studied using ac glow discharge plasmas at atmospheric pressure. A tubular reactor with a metal rod inside a quartz tube was wrapped with aluminum foil. The reaction mixture was analyzed by using a mass spectrometer. No coke deposits or other side reactions were observed. A variety of parameters, such as different metals, CO 2 concentrations, flow rate of the CO 2 containing gas, frequency, and power were investigated. The effects of these parameters on CO 2 conversion, reaction rates, and energy efficiency were examined. The initial excitation voltage to produce the plasma is independent of the metal identity on the surface of the rod and the flow rate of CO 2 containing gas, but dependent on the CO 2 concentration and ac frequency used. The maximum energy efficiency was obtained with relatively high CO 2 concentration, high flow rate of CO 2 containing gas, high frequency, as well as low input voltage at the expense of conversion.

Plasma decomposition of CO2 in the presence of metal catalysts

Abstract: The decomposition of CO 2 in fan-type ac glow discharge plasma reactors coated with gold, copper, platinum, palladium, rhodium, and mixed rotor/stator systems (Au/Rh and Rh/Au) was investigated. A high-voltage ac signal was used to produce a plasma between the fins of a turning rotor and an immobile stator, through which a 2.5% CO 2 in He mixture was passed. The analysis of the product gases was achieved using a mass spectrometer equipped with a partial pressure analyzer, and the decomposition of CO 2 was found to proceed to CO and O 2 with >80% selectivity. The percentage conversion of CO 2 increases with decreasing flow rate and increasing input voltage. The opposite trend is obtained when the energy efficiency is evaluated. Spectroscopic data indicate that the diluent gas plays a role in the dissociation of CO 2 , likely via charge and energy transfer from excited state He species to produce vibrationally excited CO 2 + intermediates. The order of reactivity for the different metal catalyst coatings is Rh > Pt ≈ Cu > Pd > Au/Rh ≈ Rh/Au ≈ Au. With the Rh-coated reactor, conversions as high as 30.5%, reaction rates of 8.07×10 −4 mol/h, and energy efficiencies of 3.55% could be obtained. There is a clear relationship between excitation temperature, T ex , of a pure He plasma and the conversion of CO 2 in a CO 2 /He plasma: decreasing T ex corresponds to increasing conversion.

The transient method applied to the methanation and Fischer-Tropsch reactions over a fused iron catalyst

Abstract: In the reduction of carbon monoxide with hydrogen to methane on a commercial iron catalyst, a transient method was used to study the reaction intermediates at 250/sup 0/C and atmospheric pressure. When a stream of the reactant mixture (10% carbon monoxide in hydrogen) flowing over the catalyst in a steady state was suddenly changed to pure hydrogen, a surface intermediate was converted to methane at an initial rate higher than that at the steady state. The intermediate species was deactivated by a similar sudden change to helium. The reactivity of the reaction intermediate was much higher than that of carbon added to the catalyst by carburization by CO in argon. The results indicate that the surface of the active catalyst is covered mostly by a carbon intermediate, whose hydrogenation represents the rate-determining step. The bulk of the catalyst is Hagg carbide, Fe/sub 2/C.

The renaissance of iron-based Fischer-Tropsch synthesis: on the multifaceted catalyst deactivation behaviour.

Abstract: Iron-based Fischer–Tropsch catalysts, which are applied in the conversion of CO and H2 into longer hydrocarbon chains, are historically amongst the most intensively studied systems in heterogeneous catalysis. Despite this, fundamental understanding of the complex and dynamic chemistry of the iron–carbon–oxygen system and its implications for the rapid deactivation of the iron-based catalysts is still a developing field. Fischer–Tropsch catalysis is characterized by its multidisciplinary nature and therefore deals with a wide variety of fundamental chemical and physical problems. This critical review will summarize the current state of knowledge of the underlying mechanisms for the activation and eventual deactivation of iron-based Fischer–Tropsch catalysts and suggest systematic approaches for relating chemical identity to performance in next generation iron-based catalyst systems (210 references).

Plasma technology - a novel solution for CO2 conversion?

Abstract: CO2 conversion into value-added chemicals and fuels is considered as one of the great challenges of the 21st century. Due to the limitations of the traditional thermal approaches, several novel technologies are being developed. One promising approach in this field, which has received little attention to date, is plasma technology. Its advantages include mild operating conditions, easy upscaling, and gas activation by energetic electrons instead of heat. This allows thermodynamically difficult reactions, such as CO2 splitting and the dry reformation of methane, to occur with reasonable energy cost. In this review, after exploring the traditional thermal approaches, we have provided a brief overview of the fierce competition between various novel approaches in a quest to find the most effective and efficient CO2 conversion technology. This is needed to critically assess whether plasma technology can be successful in an already crowded arena. The following questions need to be answered in this regard: are there key advantages to using plasma technology over other novel approaches, and if so, what is the flip side to the use of this technology? Can plasma technology be successful on its own, or can synergies be achieved by combining it with other technologies? To answer these specific questions and to evaluate the potentials and limitations of plasma technology in general, this review presents the current state-of-the-art and a critical assessment of plasma-based CO2 conversion, as well as the future challenges for its practical implementation.

Carbon-Supported Pt and PtRu Nanoparticles as Catalysts for a Direct Methanol Fuel Cell

Abstract: Nanosized Pt and PtRu colloids were prepared by a microwave-assisted polyol process and transferred to a toluene solution of decanthiol Vulcan XC-72 was then added to the toluene solution to adsorb the thiolated Pt and PtRu colloids TEM examinations showed nearly spherical particles and narrow size distributions for both supported and unsupported metals The carbon-supported Pt and PtRu nanoparticles were activated by thermal treatment to remove the thiol stabilizing shell All Pt and PtRu catalysts (except Pt23Ru77) showed the X-ray diffraction pattern of a face-centered cubic (fcc) crystal structure, whereas the Pt23Ru77 alloy was more typical of the hexagonal close-packed (hcp) structure The electro-oxidation of liquid methanol on these catalysts was investigated at room temperature by cyclic voltammetry and chronoamperometry The results showed that the alloy catalyst was catalytically more active than pure platinum The heat-treated catalyst was also expectedly more active than the non-heat-treate

Non-thermal plasmas for non-catalytic and catalytic VOC abatement.

Abstract: This paper reviews recent achievements and the current status of non-thermal plasma (NTP) technology for the abatement of volatile organic compounds (VOCs). Many reactor configurations have been developed to generate a NTP at atmospheric pressure. Therefore in this review article, the principles of generating NTPs are outlined. Further on, this paper is divided in two equally important parts: plasma-alone and plasma–catalytic systems. Combination of NTP with heterogeneous catalysis has attracted increased attention in order to overcome the weaknesses of plasma-alone systems. An overview is given of the present understanding of the mechanisms involved in plasma–catalytic processes. In both parts (plasma-alone systems and plasma–catalysis), literature on the abatement of VOCs is reviewed in close detail. Special attention is given to the influence of critical process parameters on the removal process.