Nobuyuki Gokon

Development of novel magnetic nano-carriers for high-performance affinity purification

We developed novel magnetic nano-carriers around 180 nm in diameter for affinity purification. Prepared magnetic nano-carriers possessed uniform core/shell/shell nano-structure composed of 40 nm magnetite particles/poly(styrene-co-glycidyl methacrylate (GMA))/polyGMA, which was constructed by admicellar polymerization. By utilizing relatively large 40 nm magnetite particles with large magnetization, the magnetic nano-carriers could show good response to permanent magnet. Thanks to uniform polymer shell with high physical/chemical stability, the magnetic nano-carriers could disperse in a wide range of organic solvent without disruption of core/shell structure and could immobilize various kinds of drugs. We examined affinity purification using our prepared magnetic nano-carriers with anti-cancer agent methotrexate (MTX) as ligand. Our magnetic nano-carriers showed higher performance compared to commercially available magnetic beads in terms of purification efficiency of target including extent of non-specific binding protein.

Methane reforming with CO2 in molten salt using FeO catalyst

Abstract Methane dry reforming with CO2 using FeO powder in molten salt has been investigated at various flow rates of CH4/CO2 mixed gases (CH4/CO2=1) between 50 and 400 ml/min at 1223 K in an infrared furnace. This work is carried out to determine the usefulness of this method for the chemical storage of solar energy. The CH4/CO2 mixed gases passing through the molten salt (Na2CO3/K2CO3=1) containing the FeO powder were catalytically decomposed into CO, H2 and H2O. The product gas mole ratios, CO/H2/H2O, were shown to be 3:1:1 for a high flow rate of 200 ml/min and to be CO/H2=2:1 for a low flow rate of 50 ml/min. The results were explained in terms of the kinetics of the CH4-reforming reaction and the thermodynamics of the redox process of FeO powder mixed in the molten salt; CH 4 +2FeO⇒2Fe+H 2 +CO+H 2 O Fe+CO 2 ⇒FeO+CO for a high flow rate, and FeO+CH 4 ⇒Fe+2H 2 +CO Fe+CO 2 ⇒FeO+CO for a low flow rate.

Coal Coke Gasification in a Windowed Solar Chemical Reactor for Beam-Down Optics

Solar thermochemical processes, such as solar gasification of coal, require the development of a high temperature solar reactor operating at temperatures above 1000°C. Direct solar energy absorption by reacting coal particles provides efficient heat transfer directly to the reaction site. In this work, a windowed reactor prototype designed for the beam-down optics was constructed at a laboratory scale and demonstrated for CO2 gasification of coal coke using concentrated visible light from a sun-simulator as the source of energy. Peak conversion of light energy to chemical fuel (CO) of 14% was obtained by irradiating a fluidized bed of 500–710 μm coal coke size fraction with a power input of about 1 kW and a CO2 flow-rate of 6.5 dm3 min−1 at normal conditions.

Iron-Containing Yttria-Stabilized Zirconia System For Two-Step Thermochemical Water Splitting

An iron-containing yttria-stabilized zirconia (YSZ) or Fe-YSZ was found to be a promising working redox material for the thermochemical two-step water-splitting cycle. The Fe-YSZ was formed by a high-temperature reaction between YSZ doped with more than 8 mol % Y 2 O 3 and Fe 3 O 4 supported on the YSZ at 1400°C in an inert atmosphere. The formed Fe-YSZ reacted with steam to generate hydrogen at 1000°C. The oxidized Fe-YSZ was reactivated by a thermal reduction at 1400°C in an inert atmosphere. The alternative O 2 and H 2 generations in the repeated two-step reactions and the X-ray diffraction and chemical analysis studies on the solid materials indicated that the two-step water splitting was associated with a redox transition between Fe 2 +―Fe 3+ ions in the cubic YSZ lattice.

Stoichiometric studies of H2 generation reaction for H2O/Zn/Fe3O4 system

Abstract Water splitting with H2O/Zn/Fe3O4 reaction system is suggested for H2 generation in order to utilize concentrated solar heat. This system has the possibility of generating more H2 per 1 mol of Zn than Zn/H2O reaction system at the same temperature, which is noted recently. When a mixture of Zn and Fe3O4 was heated to 873 K and steam was passed through, H2 was obtained in 93.4% of the theoretical yield. The formation of Zn-ferrites with high content of zinc (ZnxFe3−xO4; 0.2⩽x⩽1) and ZnO was determined by XRD and Mossbauer spectroscopy. The yield of ZnO was 26–29%, which shows that the ratio of the competition-reaction (Zn/H2O system) has less effects on the total H2 yield. The stoichiometry and the reaction mechanism of the system are discussed upon the analyses for the solid product.

New Solar Water-Splitting Reactor With Ferrite Particles in an Internally Circulating Fluidized Bed

The thermal reduction of metal oxides as part of a thermochemical two-step water splitting cycle requires the development of a high temperature solar reactor operating at 1000–1500°C. Direct solar energy absorption by metal-oxide particles provides efficient heat transfer directly to the reaction site. This paper describes experimental results of a windowed thermochemical water-splitting reactor using an internally circulating fluidized bed of the reacting metal-oxide particles under direct solar irradiation. The reactor has a transparent quartz window on the top as aperture. The concentrated solar radiation passes downward through the window and directly heats the internally circulating fluidized bed of metal-oxide particles. Therefore, this reactor needs to be combined with a solar tower or beam down optics. NiFe2 O4 /m-ZrO2 (Ni-ferrite supported on zirconia) particles is loaded as the working redox material in the laboratory scale reactors, and thermally reduced by concentrated Xe-beam irradiation. In a separate step, the thermally-reduced sample is oxidized back to Ni-ferrite with steam at 1000°C. As the results, the conversion of ferrite reached about 44% of maximum value in the reactor by 1kW of incident solar power. The effects of preheating temperature and particle size of NiFe2 O4 /m-ZrO2 were tested for thermal reduction of internally circulating fluidized bed in this paper.Copyright

A Reactive Fe-YSZ Coated Foam Device for Solar Two-Step Water Splitting

A thermochemical two-step water splitting cycle using a redox system of iron-based oxides or ferrites is one of the promising processes for converting solar energy into clean hydrogen in sunbelt regions. An iron-containing YSZ (Yttrium-Stabilized Zirconia) or Fe-YSZ is a promising working redox material for the two-step water splitting cycle. The Fe2+ YSZ is formed by a high-temperature reaction between YSZ, and Fe3 O4 supported on the YSZ at 1400°C in an inert atmosphere. The Fe2+ -YSZ reacts with steam and generate hydrogen at 1000–1100°C, to form Fe3+ -YSZ that is re-activated by a thermal reduction in a separate step at temperatures above 1400°C under an inert atmosphere. In the present work, a ceramic foam coated with the Fe-YSZ particles is examined as the thermochemical water splitting device for use in a solardirectly-irradiated receiver/reactor system. The Fe-YSZ particles were coated on an Mg-partially-stabilized zirconia foam disk and the foam device was tested on the two-step water splitting cycle being performed alternately at temperatures between 1100 and 1400°C. The foam device was irradiated by concentrated visible light from a sun-simulator at the peak flux density of 1000 kW/m2 and the average flux density of 470 kW/m2 in a N2 gas stream, and then, was reacted with steam at 1100°C while heating by an infrared furnace. Hydrogen successfully continued to be produced in the repeated cycles.Copyright

Reaction mechanism of H2 generation for H2O/Zn/Fe3O4 system

Abstract Several ideas on the reaction mechanism of H2O/Zn/Fe3O4 water splitting system were considered from the aspect of Zn mobility. The vapor deposition of Zn onto the Fe3O4 surface was confirmed by H2 generation reaction with Zn and Fe3O4 set separately. XPS measurements suggested that the surface of Fe3O4 is covered by Zn before the reaction with steam. The rapid reaction process has been supported by this Zn deposition, which greatly enlarges the number of sites of Zn/Fe3O4 pair that is ready to react with steam. In order to keep the Zn from vaporizing off the system, the Zn/Fe3O4 mixture was covered with additional Fe3O4 to capture the Zn vapor. This resulted in improved H2 yield of 99.5%.

Internally Circulating Fluidized Bed Reactor Using m-ZrO2 Supported NiFe2O4 Particles for Thermochemical Two-Step Water Splitting

A windowed internally circulating fluidized bed reactor was tested using m-ZrO 2 -supported NiFe 2 O 4 (NiFe 2 O 4 /m-ZrO 2 ) particles as redox material for thermochemical two-step water splitting to produce hydrogen from water. The internally circulating fluidized bed of NiFe 2 O/m-ZrO 2 particles is directly heated by solar-simulated Xe light irradiation through a transparent quartz window mounted on top of the reactor. A sun simulator with three Xe lamps at laboratory scale has been newly installed in our laboratory for testing the fluidized bed reactor. The input power of incident Xe light can be scaled up to 2.6 kW th . Temperature distributions within the fluidized bed are measured under concentrated Xe light irradiation with an input power of 2.6 kW th . Hydrogen productivity and reactivity for the fluidized bed of NiFe 2 O 4 /m-ZrO 2 particles are examined using two different reactors under the N 2 flow rate and flow ratio, which yield a higher bed temperature. The feasibility of successive two-step water splitting using the fluidized bed reactor is examined by switching from N 2 gas flow in the thermal reduction step to a steam/N 2 gas mixture in the water decomposition step. It is confirmed that hydrogen production takes place in the single fluidized bed reactor by successive two-step water splitting.

A Two-Step Water Splitting With Ferrite Particles and Its New Reactor Concept Using an Internally Circulating Fludized-Bed

A thermochemical two-step water splitting cycle using a redox system of iron-based oxides or ferrites is one of the promising processes for converting and storing solar energy into a fuel in sunbelt regions. The ZrO2 -supported ferrite (or the ferrite/ZrO2 ) powders exhibit superior performances on activity and repeatability of the cyclic reactions when compared to conventional unsupported ferrites. In the first step at 1400°C under an inert atmosphere, ferrite on ZrO2 support is thermally decomposed to the reduced phase of wustite that is oxidized back to ferrite on ZrO2 with steam in a separate second step at 1000°C. In this paper, a number of ZrO2 -supporetd ferrites, Mn-, Mg-, Co-, Ni- and Co-Mn-ferrites, are examined on activity. The NiFe2 O4 /ZrO2 powder was found to have a greatest activity between them. This paper also describes a new concept of a windowed solar chemical reactor using an internally circulating fluidized bed of ferrite/ZrO2 particles. In this concept, concentrated solar radiation passes downwards through the transparent window and directly heats the internally circulating fluidized bed. The exploratory experimental studies on this reactor concept are carried out in a laboratory scale for the thermal decomposition of NiFe2 O4 /ZrO2 particle bed as part of two-step water splitting cycle.Copyright