Details of a Researcher - Okamoto, Masaki

Papers - Okamoto, Masaki

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Encapsulation of cytochrome c in hollow mesoporous silica spheres by denaturation

Masaki Okamoto, Yuki Naito, Kiyoyuki Yamazaki, Shunsuke Odai, Hidehiro Ito, Toshiaki Kamachi

Microporous and Mesoporous Materials (Elsevier) 377 113216 2024.06

Research paper (scientific journal), Joint Work, Lead author, Corresponding author, Accepted

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Fabrication and Reinforcement of Macro- and Mesoporous Bimodal Materials from Mesoporous Silica-Alumina Spheres and Their Applications to Acid Catalysts and Adsorbents

Masaki Okamoto, Yuki Takahashi, Yusuke Takanaka

Catalysis Surveys from Asia (Springer Nature) 27 39 - 47 2023

Research paper (scientific journal), Joint Work, Lead author, Corresponding author, Accepted

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Interlayer-expanded MWW-type zeolite catalysts with carbon filler in expanded micropores for efficient microwave heating

Masaki Okamoto, Takahiro Sakatsume, Shuntaro Tsubaki, Yuji Wada

Journal of Materials Chemistry A 10 14585 - 14593 2022

ISSN 20507488

Recently, microwave (MW) heating has been applied to chemical reactions instead of conventional heating because heating only catalysts by MW radiation is more energy-efficient than heating reaction systems by conventional heating. However, zeolites, which are widely used as catalysts in the chemical industry, can hardly be heated by MW radiation. Here, zeolite catalysts suitable for MW heating were prepared by filling carbon in the interlayer-expanded micropores of MWW-type zeolites. The carbon in the pores was readily heated by MW radiation. When the catalyst was heated in a nitrogen stream by MW radiation at 50 W of consumed electric power, the temperature reached 450 °C for 300 s. However, the temperatures of the MWW-type zeolite and the physical mixture of the MWW-type zeolite and graphite powder were 140 °C and 260 °C, respectively. This indicated that the carbon-filled interlayer-expanded MWW was suitable for MW heating. The methylation of toluene with methanol catalyzed using a proton-type C@expanded MWW by MW heating proceeded at a lower reaction temperature, compared with that of the methylation catalyzed using the physical mixture of the MWW-type zeolite and graphite. This indicated that the carbon-incorporated catalysts were suitable for MW heating and that the internal temperature of the catalyst particles was higher than the external temperature. This enhanced the shape selectivity because the reaction preferentially proceeded inside the pores.

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1,3-butadiene production by crotyl alcohol dehydration over solid acids and catalyst deactivation by water adsorption

Atsushi Segawa, Tatsuya Ichijo, Nobuhiro Kimura, Keisuke Tsuruta, Naohiro Yoshida, Masaki Okamoto

Journal of the Japan Petroleum Institute (Journal of the Japan Petroleum Institute) 63 ( 2 ) 70 - 78 2020

ISSN 13468804

The synthesis of 1,3-butadiene via the dehydration of crotyl alcohol (2-buten-1-ol) over solid acids (six silica-alumina catalysts, two zeolite catalysts, and one γ-alumina catalyst) was assessed. Crotyl alcohol conversion and butadiene selectivity were both 95% or more over commercial silica-alumina catalysts. However, a sudden decrease in catalytic activity was observed during the reaction. Since the deactivated catalyst was regenerated by drying at 150°C -200°C, results showed that the main cause of the catalyst deactivation was the adsorption of water formed during the reaction and not the coke formation. An analysis of the deactivated catalyst indicated that, since the formation of Al-OH by the hydrolysis of the Al-O-Al bond increased the hydrophilicity of the catalyst surface, the adsorption of water on the catalyst surface was promoted, while that of crotyl alcohol was probably inhibited. Also, based on the catalyst characterization, the silica-alumina catalysts with few silanol groups, few alumina-rich zones, and a low Si/Al ratio were preferable.

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Synthesis of Short, Needle-Shaped Crystals of TON-Type Zeolite by Addition of Inhibitors of Crystal Growth along the [001] Direction

Masaki Okamoto, Yohei Nishimura, Miyuki Takahashi, Wei Hung Chen

Crystal Growth and Design (Crystal Growth and Design) 18 ( 11 ) 6573 - 6580 2018.11

ISSN 15287483

TON-type zeolite crystals in the shape of short needles were synthesized using inhibitors of crystal growth along the [001] direction. When fluoride was used as a mineralizer, bulky amines incorporating structure-directing agents acted as inhibitors, while nonionic surfactants were more effective as inhibitors for decreasing the crystal length of TON-type zeolite. The amount of surfactant adsorbed on the zeolite increased with the surface area of the face containing pore mouths. This indicates that the surfactant was trapped in the pore mouths to inhibit crystal growth along the long axis of the needle-shaped crystals. By microscopic observation of the crystals, we confirmed inhibition of crystal growth by adsorption of the surfactant. After adsorption of Nile red, a lipophilic stain that is intensely fluorescent in surfactants, on as-synthesized zeolite, only the edges of the needle-shaped crystals were luminous, also indicating adsorption of the surfactant in pore mouths. When hydroxide was used as a mineralizer, the bulky amines acted as inhibitors. Nonionic surfactants, however, did not work. We used the obtained shorter crystals of TON-type zeolites as catalysts for hydroisomerization of n-tetradecane. Use of the shorter crystals improved the selectivity for skeletal isomerization.

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Acetaldehyde Production from Ethanol by Eco-Friendly Non-Chromium Catalysts Consisting of Copper and Calcium Silicate

Atsushi Segawa, Akio Nakashima, Ryoichi Nojima, Naohiro Yoshida, Masaki Okamoto

Industrial and Engineering Chemistry Research (Industrial and Engineering Chemistry Research) 57 ( 35 ) 11852 - 11857 2018.09

ISSN 08885885

The authors developed eco-friendly non-chromium catalysts for acetaldehyde production through bioethanol dehydrogenation, consisting of copper and calcium silicate. Acetaldehyde selectivity was higher over copper calcium silicate catalysts with a CuO content of 40 wt % or more, because the number of acid sites on the calcium silicate was reduced, which helped prevent formation of byproducts. It was found that high ethanol conversion (39%-57%) and high acetaldehyde selectivity (91%-95%) could be achieved simultaneously at high temperature and high weight hourly space velocity conditions. Furthermore, it was shown that stable acetaldehyde production could be maintained over 20 h of time-on-stream. These catalysts were prepared from commercially available precursors and could be used in place of conventional copper chromite catalysts.

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Meerwein-Ponndorf-Verley Reduction of Crotonaldehyde over Supported Zirconium Oxide Catalysts Using Batch and Tubular Flow Reactors

Atsushi Segawa, Keita Taniya, Yuichi Ichihashi, Satoru Nishiyama, Naohiro Yoshida, Masaki Okamoto

Industrial and Engineering Chemistry Research (Industrial and Engineering Chemistry Research) 57 ( 1 ) 70 - 78 2018.01

ISSN 08885885

The authors studied Meerwein-Ponndorf-Verley (MPV) reduction of crotonaldehyde using batch and tubular flow reactors. Various ZrO2/SiO2 catalysts prepared from commercially available carriers and precursors were subjected to activity testing using autoclave batch reactors. To determine the degree of Zr dispersion in the ZrO2/SiO2 catalysts, X-ray photoelectron spectroscopy (XPS) measurements and the benzaldehyde-ammonia titration (BAT) method were carried out. The results suggested a positive correlation between Zr dispersion and crotonaldehyde conversion. Durability tests using tubular flow reactors were performed with the most suitable catalyst, which was selected through batch reactions and catalyst characterizations. Almost no degradation of the catalytic activity was observed over 2,200 h in a liquid-phase reaction, while catalyst durability was short in a gas-phase reaction. It was surmised that in the liquid-phase, 2-propanol (hydrogen donor) in the feed had dissolved the reaction byproducts to purge from the catalyst. In addition, a continuous process flow design that includes 2-propanol regeneration was proposed for industrial production.

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Base-resistant adsorbents prepared using diamino group-grafted mesoporous silica uniformly coated with zirconia

Masaki Okamoto, Haruka Satake, Hiroyuki Seki

Journal of Materials Chemistry A 5 ( 46 ) 24425 - 24432 2017

ISSN 2050-7488

The mesopore walls of ordered mesoporous silicas were coated with zirconia layers at room temperature using zirconia tetra-n-butoxide dissolved in dry toluene. It was found that coating the silicas three times with zirconia layers was sufficient to completely cover their pore walls with zirconia. The coated mesoporous silicas demonstrated high resistance to a 2 M sodium hydroxide solution at 0 °C. Prior to being coated three times with the zirconia layers, the silica walls were partially coated with 3-(2-aminoethylamino)propyltrimethoxysilane so that diamino groups could be grafted onto the pore walls; this was done so that they could be used as base-resistant adsorbents for copper(ii) ions that had been dissolved in basic solutions. The grafted diamino groups, which captured copper(ii) ions, were protected from the basic solution, as the silyl in the diamino groups was covered with zirconia layers.

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Preparation of Mesoporous Silica Uniformly Coated with Titania and Its Application to Hydrodesulfurization Catalyst

H. Satake, M. Okamoto, Y. Sakayori, S. Furudera, T. Kubota, H. Seki

J. Jpn. Inst. Energy 96 144 - 152 2017

Accepted

Synthesis of hollow and rattle-type mesoporous silica spheres by treating layered mesoporous silica with a basic solution, and using the spheres as microreactors for two-phase reactions

Masaki Okamoto, Hiroyuki Tsukada, Syun Fukasawa, Aya Sakajiri

Journal of Materials Chemistry A 3 ( 22 ) 11880 - 11890 2015.06

ISSN 2050-7488

Hollow silica spheres with radially oriented mesopores were synthesized by treating core-shell structured mesoporous silica spheres (pure silica core and propyl group-grafted silica shell) with an ammonia solution in the presence of alkyltrimethylammonium chloride. The pure silica cores dissolved in the basic solution but the propyl groups and the surfactant adsorbed on the shells protected the mesopore walls in the shells from the basic solution. Treating mesoporous silica spheres with three-layered structures (silica with grafted propyl groups, pure silica, and then silica with grafted propyl groups) led to mesoporous spheres with rattle structures being formed. The hollow and rattle-type spheres acted as microreactors when they were added to two-phase reactions, halogen exchange reaction, hydroformylation and esterification, and the reaction rates were increased. Stirring caused the hollow spheres containing the aqueous phase to be transferred into the organic phase, causing the reaction rate to be increased. Modifying the mesopore walls with phenyl groups to make the spheres highly hydrophobic increased the amount of spheres that was present in the organic phase, increasing the reaction rate. A higher reaction rate was achieved using hollow spheres than that using non-hollow mesoporous silica spheres, indicating that the hollow structure was an important factor in increasing the reaction rate.

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Catalytic reactions enhanced under microwave-induced local thermal non-equilibrium in a core-shell, carbon-filled zeolite@zeolite

Dai Mochizuki, Ryo Sasaki, Masato M. Maitani, Masaki Okamoto, Eiichi Suzuki, Yuji Wada

JOURNAL OF CATALYSIS (ACADEMIC PRESS INC ELSEVIER SCIENCE) 323 1 - 9 2015.03

Accepted, ISSN 0021-9517

A core-shell, carbon-filled zeolite@zeolite was created through the epitaxial growth of shell zeolite on a core zeolite filled with carbon. The catalytic dehydrations of alcohols on the core-shell structure were enhanced under microwave irradiation by comparison with conventional heating using an oil bath at the same solution temperatures; however, the dehydrations on the sole core zeolite were not enhanced under microwave irradiation, which indicated the presence of a higher temperature area in the shell near the border with the core. The core-shell structure exhibited thermal non-equilibrium with microwave irradiation because of the extremely different dielectric losses of the core and the shell; that is, the carbon in the core generated much heat from microwaves, but the shell did not. (C) 2014 Elsevier Inc. All rights reserved.

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Skeletal isomerization of tetradecane catalyzed by TON-type zeolites with a fragmented core-shell structure

Masaki Okamoto, Lili Huang, Midori Yamano, Sayuri Sawayama, Yohei Nishimura

APPLIED CATALYSIS A-GENERAL (ELSEVIER SCIENCE BV) 455 122 - 128 2013.03

Accepted, ISSN 0926-860X

TON-type zeolites with a core-shell structure were synthesized by crystal overgrowth of an aluminum-free TON-type zeolite on an aluminum-containing TON-type zeolite in the presence of fluoride ion, which was used as a mineralizing reagent to restrain the formation of defects. The core-shell structured zeolite showed greater selectivity for skeletal isomerization in tetradecane hydroisomerization because the acid sites on the external surface of needle-shaped crystals were passivated to inhibit cracking. Breaking the needle-shaped crystals of the core-shell structure to create shorter crystal pieces effectively enhanced the catalytic activity and selectivity for isomerization because new pore entrances were formed. (c) 2013 Elsevier B.V. All rights reserved.

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Readily recyclable catalysts of zeolite nanoparticles linked with polymer chains

Masaki Okamoto, Satoshi Watanabe, Junya Nitta

Applied Catalysis A: General 467 55 - 60 2013

ISSN 0926-860X

Aggregates of zeolite nanoparticles were linked together with polypropylene oxide or polydimethylsiloxane polymer chains, and were used as catalysts for liquid-phase reactions. The polymer-linked catalysts showed high catalytic activity in esterification of acetic acid with 1-propanol and hydrolysis of ethyl acetate, and were readily separated from reaction mixtures by decantation. Moreover, the linkage with the polymer chains enhanced shape selectivity in esterification of acetic acid with cyclohexanol and dehydration of 1-phenylethanol because of passivating the external acid sites of the zeolite with the polymer. © 2013 Elsevier B.V. All rights reserved.

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Synthesis of core-shell structured porous materials and applications as catalysts and precursors for hollow porous materials

Masaki Okamoto

Journal of the Japan Petroleum Institute 56 ( 4 ) 198 - 205 2013

ISSN 1346-8804

Ordered porous materials such as zeolites and ordered mesoporous silicas have important physical characteristics based on their high surface area and well-defined pore size. Control of the structure or shape of the ordered porous materials will provide new functions. This review focuses on core-shell structure; especially fabrication methods of core-shell structured zeolites with minimal defects are introduced. As an example of applications, MFI and TON-type zeolites with core-shell structure used as catalysts have high shape selectivity in the methylation of toluene with methanol and skeletal isomerization of tetradecane, respectively. As another application, synthesis of hollow porous materials from core-shell porous materials is also described. Decomposition of silica with dimethyl carbonate catalyzed by an alkali metal salt impregnated in the core was an effective method for selective removal of the core from the core-shell structure. Hollow porous materials show promise as vessels for drug delivery, catalyst vessels and microreactors.

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Formation of hollow silica spheres with ordered mesoporous structure by treatment with dimethyl carbonate for selective decomposition of mesoporous silica core

Masaki Okamoto, Huimin Huang

Microporous and Mesoporous Materials 163 102 - 109 2012.11

ISSN 1387-1811

Hollow silica spheres containing ordered mesopores with radial orientation were synthesized from core-shell structured mesoporous silica spheres with pure silica core and propyl group-grafted silica shell. The silica core was selectively impregnated with sodium acetate owing to the hydrophilicity of the core. Sodium acetate acted as a catalyst for silica decomposition with dimethyl carbonate (DMC), and after impregnation, treatment with DMC was performed to remove the core by the reaction of silica with DMC. The obtained hollow spheres contain ordered mesopores with radial orientation and are mono-disperse. The final shell thickness could be controlled by changing the shell thickness of the initial core-shell spheres, as well as by modifying the degree of decomposition of the shell. 9-Phenylanthracene encapsulated in the hollow spheres was gradually released through the mesopores as vapor into an air stream by diffusion limitation. © 2012 Elsevier Inc. All rights reserved.

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MFI-type zeolite with a core-shell structure with minimal defects synthesized by crystal overgrowth of aluminum-free MFI-type zeolite on aluminum-containing zeolite and its catalytic performance

Masaki Okamoto, Yukio Osafune

Microporous and Mesoporous Materials 143 ( 2-3 ) 413 - 418 2011.09

ISSN 1387-1811

MFI-type zeolite with a core-shell structure and minimal defects was synthesized by crystal overgrowth of aluminum-free MFI-type zeolite on aluminum-containing MFI-type zeolite crystals. The purpose of the zeolite shell is to passivate acid sites on the external surface of the zeolite core. When both the shell and the core are synthesized in the presence of fluoride ion, defects are minimal. In the case of synthesizing the shell in the absence of fluoride ion, core growth does not occur. When the core is synthesized in the absence of fluoride ion, significant defects develop and cause mesopores to form in the core-shell zeolite. As catalysts for methylation of toluene with methanol, only the core-shell zeolite with minimal defects shows high selectivity for p-xylene (96%). © 2011 Elsevier Inc. All rights reserved.

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Polymers as novel modifiers for supported metal catalyst in hydrogenation of benzaldehydes

Masaki Okamoto, Tomoyuki Hirao, Tatsuya Yamaai

Journal of Catalysis 276 ( 2 ) 423 - 428 2010.12

ISSN 0021-9517

Polyethylene glycol (PEG) was impregnated on a palladium metal supported on silica gel and used in a catalyst for hydrogenation of benzaldehydes. In the vapor-phase flow reaction, the PEG modification improved catalytic activity and selectivity for a partially hydrogenated product, benzyl alcohol. In isoprene hydrogenation, selectivity for partially hydrogenated products, monoenes, was also enhanced. X-ray photoelectron spectroscopy (XPS) analysis of the modified catalysts revealed that the modification with PEG makes the palladium surface negatively charged, possibly leading to an increase in the selectivity for the partially hydrogenated product caused by enhancement of its desorption from the surface. In the liquid-phase hydrogenation of benzaldehyde, the PEG modification also increased the selectivity for benzyl alcohol. © 2010 Elsevier Inc. All rights reserved.

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東京工業大学・化学系専攻における安全教育

岡本昌樹

触媒 52 ( 1 ) 51 - 56 2010

Effect of addition of alkali metal salts in hydrothermal synthesis and post heat-treatment on porosity of SBA-15

Masaki Okamoto, Yuko Fukukita, Masaki Haga, Kazuhisa Toyofuku, Naoki Mimura

JOURNAL OF POROUS MATERIALS (SPRINGER) 16 ( 2 ) 135 - 140 2009.04

ISSN 1380-2224

SBA-15 was hydrothermally synthesized at 80 A degrees C for 48 h, and then the surfactant template for mesopore formation was removed by extraction with ethanol, washing with nitric acid, and heating at 200 A degrees C. Addition of alkali metal chlorides to a synthesis gel of SBA-15 increased its mesopore diameter in the following order: no added salt < LiCl < KCl < CsCl. The micropore volume did not change with the addition of any alkali metal and was around 0.17 mL g(-1). These results suggest that alkali metal salt is inside the mesopore with a micelle template. When a small amount of potassium chloride was impregnated in SBA-15 after extraction and washing, micropore volume reduced almost to zero with heating at 400 A degrees C in dry air, and the mesopore diameter and pore wall thickness were reduced by a larger amount than for non-impregnated SBA-15. It is likely that the micropores in the mesopore wall vanish due to condensation of silanols and/or reconstruction of siloxane bonds on the micropore wall, which are catalyzed by alkali metal halides.

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Wacker-type oxidation in vapor phase using a palladium-copper chloride catalyst in a liquid polymer medium supported on silica gel

Masaki Okamoto, Yuichi Taniguchi

JOURNAL OF CATALYSIS (ACADEMIC PRESS INC ELSEVIER SCIENCE) 261 ( 2 ) 195 - 200 2009.01

ISSN 0021-9517

Pd(II) chloride and Cu(II) chloride in various liquid polymer media supported on silica gel were prepared and used in a catalyst system for vapor-phase synthesis of acetaldehyde by Wacker-type oxidation of ethylene. This catalyst system supported on silica gel prepared by impregnation was quickly deactivated, while use of polyethylene glycol (PEG) as a liquid polymer medium supported on silica gel showed stable catalytic activity. PEG inhibited the formation of Pd metal particles, which deactivate the catalyst system. Addition of alkali metal salts, especially LiCl, to the PdCl(2)-CuCl(2) catalyst system with PEG enhanced catalytic activity for 22 h, even when the I'd content was high, leading to high activity but poor stability. LiCl also inhibited the formation of metal particles. (C) 2008 Elsevier Inc. All rights reserved.

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