Jin Miyawaki - Profile on Academia.edu (original) (raw)

Papers by Jin Miyawaki

Catalysis Today, Apr 1, 2011

Deep hydrodesulfurization (HDS) was investigated over amorphous silicaalumina (ASA), produced usi... more Deep hydrodesulfurization (HDS) was investigated over amorphous silicaalumina (ASA), produced using various synthetic methods as supports for NiMo catalysts, in single and dual catalytic bed systems. NiMoS active components supported on ASA-2 (ASA from synthetic method 2) achieved S levels of 4.5 and 3.0 ppm at 345 and 360°C, respectively, in single catalytic beds, which was the highest HDS reactivity. Dual catalytic beds were introduced to inhibit excess hydro-cracking of C species in gas oil. For the dual catalytic combination of LX6 (commercial catalyst for reactive S species) and NMASA-2 (NiMoS supported on ASA-2), the S levels were 5.4 and 2 ppm at 345 and 360°C, respectively, indicating that the performance was enhanced at higher temperatures, likely due to improved activity for refractory S species. The increased reactivity for HDS over NMASA-2 was related to the strong acidity of this support due to tetrahedrally-coordinated Al species. In addition, the smaller homogeneous particle size of the support influenced the HDS catalytic performance. Moreover, weaker interactions between the Mo and ASA-2 in NMASA-2 improved the HDS reactivity, as confirmed by laser Raman spectroscopy.

Evergreen, Sep 1, 2016

Influence of pore size and surface functionality of activated carbons on liquid-phase molecular a... more Influence of pore size and surface functionality of activated carbons on liquid-phase molecular adsorption behaviors was carefully investigated both in terms of adsorption capacity and kinetics using indole and amylase as model adsorptive bio-materials by individual single-component experiments to improve adsorptive removal efficiency and selectivity of body wastes. Activated carbon fibers having narrow pore size of about 0.65 nm showed the highest adsorption capability of indole per unit surface area. From the point of view of the adsorption rate, however, a little bit wider micropores of about 0.70 nm considered to be preferable. It was also confirmed that a presence of oxygen-containing surface functional groups induces diffusional inhibitions of indole molecules to deeper pore spaces, giving rise to a lowering both of adsorption capacity and rate of indole. On the other hand, amylase adsorption amount was limited for microporous carbons. Therefore, as for oral applications to selectively remove the wastes in the body such as indole but not for useful molecules such as amylase, the activated carbons having abundant micropores of about 0.7 nm in size and hydrophobic surfaces were found to be suitable from the individual single-component experiments.

Fuel, 2011

Hydro-conversion reactions were carried out at 360°C under 5 MPa of H 2 pressure to study ring-op... more Hydro-conversion reactions were carried out at 360°C under 5 MPa of H 2 pressure to study ring-opening reactions of 1-methyl naphthalene using NiMoS supported on γ-alumina and alumina-coated/mixed USY zeolites. The catalysts were characterized using N 2 -BET, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), pyridine FT-IR, and high-resolution transmission electron microscopy (HRTEM) to study the influence of morphological and acidic properties on hydrogenation (HYD) and hydrocracking (HC) reactions. NMACZ-2 (NiMoS supported on the minimum amount of alumina-coated USY zeolite) showed enhanced reactivity for HC and produced (alkyl)benzenes with the highest yield, of ca. 80%. By-products were tetralin, decalin and cyclo-paraffin species. The tetralin species produced using NMACZ-2 moved into the alumina-coated USY zeolite support before undergoing HYD to produce decalin species, which were rapidly and selectively hydro-cracked into (alkyl)benzenes. A large amount of decalin was produced through the HYD of tetralin without significant cracking, possibly due to the weak acid character of γ-alumina. Bulk-phase Mo oxide species on NMAZ (physical mixture of alumina and USY zeolite), as well as deactivation of the catalysts due to coke formation over the naked zeolite surface, inhibited the ring opening of tetralin, decreasing the yield of (alkyl) benzene. Various morphologies, such as the MoS 2 structure and acidic characteristics of the catalysts, were crucial factors affecting the HC reactivity of 1-methyl naphthalene.

Evergreen, Mar 1, 2017

Highly graphitized carbon with high electric conductivity was successfully prepared from non-grap... more Highly graphitized carbon with high electric conductivity was successfully prepared from non-graphitizable carbon (NGC) via breaking-down and merging of boundaries of microdomains through the potassium hydroxide (KOH) treatment and subsequent graphitization. After the graphitization at 2800°C, the KOH-treated sample showed modified domains having merged boundaries between the microdomains which could be observed in graphitizable carbon (GC). Such a domain-modified carbon showed less than half electric resistivity of graphitized NGC, indicating that macroscopic properties, such as electric conductivity, of carbon materials can be improved via the modification of nanometer-scale microdomain and domain structures.

SN applied sciences, Jan 22, 2019

Journal of Industrial and Engineering Chemistry, Mar 1, 2011

Naphthalene was chosen as a model reactant of PAHs, and its catalytic destruction aimed to reduce... more Naphthalene was chosen as a model reactant of PAHs, and its catalytic destruction aimed to reduce the content of PAHs in diesel fuels was investigated over three different metal (Pt, Ru and Mo) catalysts supported on SBA-15 and γ-alumina. The catalysts were characterized by N 2 -sorption isotherms, CO & NO chemisorptions, temperature programmed desorption of naphthalene & NH 3 , and 27 Al MAS NMR. The SBA-15 supported metal catalysts showed a better activity at lower reaction temperature than the γ-alumina supported ones, most probably due to higher metal dispersion and enhanced meso-accessibility. Pt/SBA-15 catalyst exhibited the highest activity, corresponded to Ru or Mo/SBA-15 catalyst, as reasoned by the temperature programmed desorption of naphthalene. The improved catalytic performances and thermal stability of catalysts could be achieved by incorporation of Al species into SBA-15. The characteristics of Pt states and complex on the surface of acidic supports could lead to the enhanced catalytic activity of naphthalene oxidation, as well as the limited sintering of Pt particles at high temperature, giving rise to thermal stability of catalysts

Chemical Science, 2023

The structural evolution of highly mesoporous templated carbons is examined from temperatures of ... more The structural evolution of highly mesoporous templated carbons is examined from temperatures of 1173 to 2873 K to elucidate the optimal conditions for facilitating graphene-zipping reactions whilst minimizing graphene stacking processes. Mesoporous carbons comprising a few-layer graphene wall display excellent thermal stability up to 2073 K coupled with a nanoporous structure and three-dimensional framework. Nevertheless, advanced temperature-programmed desorption (TPD), X-ray diffraction, and Raman spectroscopy show graphene-zipping reactions occur at temperatures between 1173 and 1873 K. TPD analysis estimates zipping reactions lead to a 1100 fold increase in the average graphene-domain, affording the structure a superior chemical stability, electrochemical stability, and electrical conductivity, while increasing the bulk modulus of the framework. At above 2073 K, the carbon framework shows a loss of porosity due to the development of graphene-stacking structures. Thus, a temperature range between 1873 and 2073 K is preferable to balance the developed graphene domain size and high porosity. Utilizing a neutron pair distribution function and soft X-ray emission spectra, we prove that these highly mesoporous carbons already consist of a well-developed sp 2 -carbon network, and the property evolution is governed by the changes in the edge sites and stacked structures.

Journal of the Society of Rubber Industry,Japan, 2010

Processing and Application of Ceramics, 2018

Nanocrystalline Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ powders were prepared by a cost-effective solve... more Nanocrystalline Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ powders were prepared by a cost-effective solvent-deficient method using metal nitrates and ammonium bicarbonate as precursors. X-ray diffraction (XRD), specific surface determination (BET), thermal analyses (TG-DTA-DSC), dynamic light scattering (DLS) and scanning electron microscopy (SEM) were used to examine the effects of the calcination temperature on the Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) formation. XRD analysis showed that a cubic Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ was obtained after heating for 1 h at 1000 °C. BSCF nanocrystals with a diameter of about 25 nm were obtained. On the other hand, the sample mass was stabilized at 915 °C as recorded by thermogravimetric analysis (TG), indicating a formation of the complex BSCF oxide already at this temperature. The phase transformations during the synthesis of BSCF oxide are defined and confirmed with the note on the instability of the cubic phase. Using the four-point DC measurements between -73 °C and 127 °C, the band gap of 0.84 eV was determined. The solvent-deficient method used in this study to synthesize Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ showed distinct advantages in comparison with other synthesis techniques considering simplicity, rapid synthesis, and quality of the produced nanocrystals.

Carbon, May 1, 2023

This review explores recent research regarding mesophase pitch (MP). Spinnable mesophase pitch (S... more This review explores recent research regarding mesophase pitch (MP). Spinnable mesophase pitch (SMP) was used as a model pitch for MP in all experiments. We explain some phenomenological results of the lyotropic liquid crystalline properties of the SMP, which show that the MP behaves as a typical lyotropic liquid crystal. The mesogenic and solvent components of SMP are defined. We define the threshold concentration (TC) as the minimum amount of mesogenic component necessary for SMP to achieve 100 vol% anisotropy. We also report the TCs of various SMPs and discuss the effects of the solvent component. Concerning the identity of the mesogenic component, we discuss quantitative correlations between the size of the layered molecular stacking units and the anisotropic content of the SMP. Research has shown that a layered molecular stacking unit larger than a specific size corresponds to the mesogenic component of the MP. We discuss a novel method for the manufacture of SMPs using our understanding of MP as a lyotropic liquid crystal, which comprises thermal mixing of optimal amounts of the mesogenic and solvent components that were prepared separately under different conditions. This method enables the properties of each component to be optimized without involving a costly hydrogenation process. Finally, we discuss how this approach can be used to increase SMP yield by modifying the contents of the anisotropic mesogenic and solvent components.

Applied sciences, Dec 18, 2019

The toxic nature of acetaldehyde renders its removal from a wide range of materials highly desira... more The toxic nature of acetaldehyde renders its removal from a wide range of materials highly desirable. Removal of low-concentration acetaldehyde (a group 1 carcinogenic volatile organic compound) using an adsorbent of cellulose-based activated carbon fiber modified by amine functional group (A@CACF-H) is proposed, using 2 ppm of acetaldehyde balanced with N 2 /O 2 (79/21% v/v) observed under continuous flow, with a total flow rate of 100 mL/min over 50 mg of A@CACF-H. The effective removal of the targeted acetaldehyde is achieved by introducing the functionalized amine at optimized content. The removal mechanism of A@CACF-H is elucidated using two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (2D-GC TOF-MS), indicating the efficacy of the proposed acetaldehyde removal method.

Journal of Industrial and Engineering Chemistry, 2014

Chemical Communications, 2011

Journal of Industrial and Engineering Chemistry, Mar 1, 2013

Fluidized bed drying of Loy Yang brown coal with variation of temperature, relative humidity, fluidization velocity and formulation of its drying rate

Fuel, Mar 1, 2013

ABSTRACT The fluidized bed drying of Loy Yang coal, which is one of Australia’s representative Vi... more ABSTRACT The fluidized bed drying of Loy Yang coal, which is one of Australia’s representative Victorian brown coals exhibiting a high moisture content (up to ca. 65 wt.%, as-received base), using air as the bubbling gas was examined by varying temperature, relative humidity, and fluidization velocity at 40–80 °C, 0–40%, and 10.0–35.0 cm/s, respectively. The effects of the three variables on the drying rate and drying time were investigated. Higher temperature, lower relative humidity, and higher fluidization velocity were favorable for drying, i.e., they showed high drying rate. Drying rate was maximum immediately after the set drying temperature was attained; then, it decreased at a roughly constant rate, indicating a falling-rate drying period (constant-decrease drying period) and finally became zero.Drying rate could be described by a simple equation, dw/dt = −k(1−X)n; therefore, it was a function of the drying rate constant k, drying fraction X, and drying rate order n. The drying rate order n could be taken as 0.25; it is independent of temperature, relative humidity or fluidization velocity. The drying rate constant k could be expressed as a function of temperature, relative humidity, fluidization velocity; within the limits of the experimental error, k was a linear function of each variable, and it increased with increasing temperature, decreasing relative humidity, and increasing fluidization velocity.

Two-Dimensional Materials as Emulsion Stabilizers: Interfacial Thermodynamics and Molecular Barrier Properties

Langmuir, Mar 25, 2014

A new application for two-dimensional (2D) materials is emulsification, where they can serve as u... more A new application for two-dimensional (2D) materials is emulsification, where they can serve as ultrathin platelike interfacial stabilizers in two-liquid systems. We present a first detailed thermodynamic analysis of atomically thin 2D materials at organic-aqueous liquid-liquid interfaces and derive expressions for the transfer free energies of emulsion stabilization that account for material geometry, van der Waals transparency or opacity, and variable hydrophobicity. High mass potency is shown to be an intrinsic property of the 2D geometry, which at the atomically thin limit places every atom in contact with both liquid phases, resulting in unit atom efficiency. The thermodynamic model successfully predicts that graphene oxide but not pristine graphene has a favorable hydrophobic-hydrophilic balance for oil-water emulsion stabilization. Multilayer tiling is predicted to occur by the passivation of droplet surface patches left uncovered by packing inefficiencies in the first monolayer, and complete multilayer coverage is confirmed by cryogenic scanning electron microscopy. The molecular barrier function of graphene interfacial films causes a significant suppression of dispersed-phase evaporation rates with potential applications in controlled release. Finally, these emulsions can be used as templates for creating solid graphene foams or graphene microsacks filled with lipophilic cargos. Emerging 2D materials are promising as dispersants or emulsifiers where high mass potency and multifunctional properties are desired.

Efficient Extraction of Alkali and Alkaline Earth Metals from Marine Biomass-Derived Carbon for Use as an Alternative to Traditional Coal or Coke Reductants in Ironmaking

Pore-size-selective-control of surface hydrophilicity of porous carbons by molecular masking

Division of Colloid and Surface Chemistry, Oct 7, 2019

Catalytic Steam Gasification of Waste Palm Tree Trunk Derived Bio-Char

Applied Mechanics and Materials, Apr 1, 2013

Catalytic steam gasification of Malaysia Waste Palm Tree Trunk Derived Bio-char was studied using... more Catalytic steam gasification of Malaysia Waste Palm Tree Trunk Derived Bio-char was studied using alkali metal carbonate (K2CO3) supported perovskite oxide catalysts which showed a favor catalytic activity in the carbon combustion. The bio-char steam gasification reactions were carried out using a fixed reactor under a steam atmosphere with different catalysts, such as K2CO3/LaMn0.8Cu0.2O3, K2CO3/Alumina, Nikel/LaMn0.8Cu0.2O3, Nikel/Alumina, and Alumina, respectively. The effects of temperature, catalyst support and catalysts mixing ratio on the syngas compositions and carbon conversion were carefully investigated. The syngas compositions were analyzed by gas chromatography (GC). K2CO3/LaMn0.8Cu0.2O3 catalyst showed better carbon conversion compared to the other catalysts, which indicated the Perovskite Oxide was more effective as a support for the gasification catalyst. The results showed that the better carbon conversion within short time removed nearly 100% of heavy and light tar.