Kohki Ebitani

Gold Nanoparticles Supported on Alumina as a Catalyst for Surface Plasmon-Enhanced Selective Reductions of Nitrobenzene

Co-reporter:Kittichai Chaiseeda, Shun Nishimura, and Kohki Ebitani

ACS Omega October 2017? Volume 2(Issue 10) pp:7066-7066

Publication Date(Web):October 23, 2017

DOI:10.1021/acsomega.7b01248

Au nanoparticles supported on alumina (Au/Al2O3) with average particle size of 3.9 ± 0.7 nm and surface plasmon band centerned at 516.5 nm were prepared by deposition–precipitation method, and their photocatalytic activities for the reduction of nitrobenzene using either formic acid in acetonitrile (method A) or KOH in 2-propanol (method B) were investigated. Even at room temperature, the Au/Al2O3 was found to be highly active and selective for conversion of nitrobenzene to aniline when used with formic acid in acetonitrile or to azobenzene when performed with KOH in 2-propanol under irradiation with green light-emitting diode (517 nm).Topics: Catalysts; Distribution function; Electron transfer; Nanoparticles; Photochemical reduction; Plasmon; Plasmonic and Photonic Structures and Devices; Powder x-ray diffraction; Spectra;

Transfer hydrogenation of furaldehydes with sodium phosphinate as a hydrogen source using Pd-supported alumina catalyst

Co-reporter:Shun Nishimura, Takuma Shimura, Kohki Ebitani

Journal of the Taiwan Institute of Chemical Engineers 2017 Volume 79(Volume 79) pp:

Publication Date(Web):1 October 2017

DOI:10.1016/j.jtice.2017.03.028

•Sodium phosphinate is applied as a hydrogen donor for hydrogenation of furaldehydes.•Furfuryl alcohol, 5-methylfurfuryl alcohol and 2,5-bis(hydroxymethyl)furan are the target product for the reaction.•Reusable Pd/Al2O3 catalyst proceeds the reaction well even at room temperature.•Sodium phosphinate is a cheap and easy-handling hydrogen source.Transformations of furaldehydes to the corresponding furfuryl alcohols via hydrogenation with sodium hypophosphite (NaH2PO2) as a hydrogen donor agent were performed over Pd/Al2O3 catalyst under ambient condition in THF/water solvent. Furfuryl alcohol (FOL), 5-methylfurfuryl alcohol (5-MFOL) and 2,5-bis(hydroxymethyl)furan (BHMF), were produced with 68%, 45% and 63% yield, respectively, from 2-furaldehyde (furfural), 5-methylfulaldehyde (5-MF) and 5-hydroxymethyl-2-furaldehyde (HMF) at room temperature (25 °C). The Pd/Al2O3 catalyst was reusable for all reaction without significant decrease in activity. These results indicated that the NaH2PO2 would be a cheap and an easy-handling hydrogen donor for catalytic hydrogenation reactions under mild conditions.Download high-res image (71KB)Download full-size image

Fine-crystallized LDHs prepared with SiO2 spheres as highly active solid base catalysts

Co-reporter:Mahiro Shirotori;Shun Nishimura

Journal of Materials Chemistry A 2017 vol. 5(Issue 15) pp:6947-6957

Publication Date(Web):2017/04/11

DOI:10.1039/C7TA00984D

Fine-crystallized layered double hydroxides are prepared via the co-precipitation method with the coexistence of SiO2 spheres (SiO2@LDH), and their base catalysis and structural properties are investigated. The as-prepared SiO2@LDHs exhibit higher base catalysis for the Knoevenagel condensation than conventional LDHs prepared via the co-precipitation method in the absence of SiO2 spheres. Such an increase in the activity for base catalysis is also observed in various types of SiO2@LDHs with different metal compositions (M2+: Mg2+ or Ni2+, M3+: Al3+ or Ga3+, and M2+/M3+: 1 or 3). X-ray diffraction (XRD) measurement suggests that the addition of SiO2 induces decreases in the LDH crystallite size. The results of transmission electron microscopy – energy dispersive X-ray spectroscopy (TEM-EDS) and 29Si cross polarization magic angle spinning nuclear magnetic resonance (29Si CP-MAS NMR) on SiO2@Mg–Al LDH suggest that the crystals of Mg–Al LDH are immobilized on the SiO2 surface through Si–O–Al and Si–O–Mg covalent bonds. According to these results, we conclude that the co-precipitation method in the presence of colloidal spherical SiO2 seeds, particularly possessing a 40 nm diameter, result in highly-dispersed points of LDH crystal growth on the SiO2 surface, which lead to the generation of fine-crystallized highly active LDH nanocrystals.

Reductive amination of furfural toward furfurylamine with aqueous ammonia under hydrogen over Ru-supported catalyst

Co-reporter:Shun Nishimura;Kunihiko Mizuhori

Research on Chemical Intermediates 2016 Volume 42( Issue 1) pp:19-30

Publication Date(Web):2016 January

DOI:10.1007/s11164-015-2334-5

Poly(N-vinyl-2-pyrrolidone)-capped ruthenium-supported hydroxyapatite (Ru-PVP/HAP) shows significant activity for the synthesis of furfurylamine (FAM) via the reductive amination of furfural. As-prepared 5 wt% Ru-PVP/HAP affords 50 % yield of FAM in 25 % NH3 aqueous solution under pressurized H2 gas (2.5 atm), and the highest yield approaches 60 % at 4.0 H2 atm. Comparison between the activities over four Ru-supported HAP catalysts prepared with different methods and the results of X-ray absorption spectroscopy suggested that the metallic Ru cluster is the active center for the reductive amination of furfural. Transmission electron microscope and inductively-coupled plasma analysis indicated that the as-prepared 5 wt% Ru-PVP/HAP catalyst possessed 4.0 wt% PVP-capped Ru clusters with average diameter of 1.7 ± 0.3 nm on HAP support. It was also demonstrated that the reductive amination approach with Ru-PVP/HAP catalyst, NH3 aq. and pressurized H2 gas has capability for transformation of aromatic aldehydes to the corresponding aromatic amines. According to these results, it is concluded that Ru(0) cluster supported on HAP will represent a suitable catalyst for widely-usable reductive amination to convert an aldehyde functionality towards an amine.

Synthesis of Formic Acid from Monosaccharides Using Calcined Mg-Al Hydrotalcite as Reusable Catalyst in the Presence of Aqueous Hydrogen Peroxide

Co-reporter:Ryo Sato, Hemant Choudhary, Shun Nishimura, and Kohki Ebitani

Organic Process Research & Development 2015 Volume 19(Issue 3) pp:449-453

Publication Date(Web):March 3, 2015

DOI:10.1021/op5004083

Formic acid (FA) can be synthesized from monosaccharides such as glucose, galactose, xylose, arabinose and lyxose by using both calcined Mg-Al hydrotalcite as a solid catalyst and aqueous H2O2 as an oxidant in ethanol solvent at 343 K for 5 h. For the glucose oxidation, the FA yield and H2O2 utilization efficiency reach 78% and 100%, respectively. The used hydrotalcite catalyst can be easily separated from the reaction mixture and is reusable at least twice.

Hydrothermal Preparation of a Robust Boehmite-Supported N,N-Dimethyldodecylamine N-Oxide-Capped Cobalt and Palladium Catalyst for the Facile Utilization of Formic Acid as a Hydrogen Source

Co-reporter:Hemant Choudhary;Dr. Shun Nishimura ;Dr. Kohki Ebitani

ChemCatChem 2015 Volume 7( Issue 15) pp:2361-2369

Publication Date(Web):

DOI:10.1002/cctc.201500161

Abstract

Bimetallic CoPd nanoparticles (NPs) on boehmite (AlOOH) were synthesized under hydrothermal conditions using three different capping agents for the facile utilization of formic acid (FA) as a hydrogen source. The CoPd NPs capped with N,N-dimethyldodecylamine N-oxide (DDAO) supported on AlOOH (CoPd-DDAO/AlOOH) exhibited superior catalysis and recyclability in the hydrogenation of maleic anhydride (MAn) in water without metal leaching. The formation of monodispersed CoPd-DDAO NPs on AlOOH that contained both cobalt oxides and CoPd alloy in each NP was indicated by TEM with energy-dispersive spectroscopy, XRD, and X-ray absorption spectroscopy (XAS) studies. X-ray photoelectron spectroscopy and XAS supported the partial electron transfer phenomenon in CoPd-DDAO NPs. The as-prepared CoPd-DDAO/AlOOH catalyst showed activity for the utilization of FA formed in situ from biomass for the hydrogenation of MAn. It suggested that the DDAO capping agent contributed strongly to the favorable electronic/geometric changes in CoPd alloy for the facile utilization of FA.

A Convenient Surfactant-Mediated Hydrothermal Approach to Control Supported Copper Oxide Species for Catalytic Upgrading of Glucose to Lactic Acid

Co-reporter:Dr. Hemant Choudhary ;Dr. Kohki Ebitani

ChemNanoMat 2015 Volume 1( Issue 7) pp:511-516

Publication Date(Web):

DOI:10.1002/cnma.201500131

Abstract

Herein, we discuss a convenient surfactant-mediated hydrothermal approach to control supported copper oxide species in a highly reproducible way and investigate their effect on the catalytic upgrading of glucose to lactic acid. Careful characterization using XRD, Raman spectroscopy, and temperature programmed reduction (TPR) studies revealed paramelaconite (Cu₄O₃) loaded on MgO as the catalytically active species. It was also found that the cuprite (Cu₂O) phase can be prepared in the presence of N,N-dimethyldodecylamine N-oxide (DDAO) while the tenorite (CuO) phase was obtained in the absence of surfactant. The use of cetyltrimethylammonium bromide (CTAB) selectively gave the Cu₄O₃ phase as the supported species. The above-mentioned systematic approach demonstrates that substantial improvement in the catalytic activity (or other properties) can be achieved by careful selection of the synthetic conditions for generation of desired Cu species through a simple and inexpensive preparation route.

Selective Oxidation of 1,6-Hexanediol to 6-Hydroxycaproic Acid over Reusable Hydrotalcite-Supported AuPd Bimetallic Catalysts

Co-reporter:Jaya Tuteja;Dr. Shun Nishimura;Hemant Choudhary ;Dr. Kohki Ebitani

ChemSusChem 2015 Volume 8( Issue 11) pp:1862-1866

Publication Date(Web):

DOI:10.1002/cssc.201500255

Abstract

Selective oxidation of 1,6-hexanediol into 6-hydroxycaproic acid was achieved over hydrotalcite-supported Au–Pd bimetallic nanoparticles as heterogeneous catalyst using aqueous H₂O₂. N,N-dimethyldodecylamine N-oxide (DDAO) was used as an efficient capping agent. Spectroscopic analyses by UV/Vis, TEM, XPS, and X-ray absorption spectroscopy suggested that interactions between gold and palladium atoms are responsible for the high activity of the reusable Au₄₀Pd₆₀-DDAO/HT catalyst.

Tailored design of palladium species grafted on an amino functionalized organozinc coordination polymer as a highly pertinent heterogeneous catalyst

Co-reporter:H. Choudhary, S. Nishimura and K. Ebitani

Journal of Materials Chemistry A 2014 vol. 2(Issue 43) pp:18687-18696

Publication Date(Web):08 Sep 2014

DOI:10.1039/C4TA03889D

The design of a highly active and stable heterogeneous palladium catalyst is gaining a lot of attention because of its increasing importance in the organic syntheses of commodity chemicals. Herein, we report the tailored synthesis of palladium species grafted on a highly stable amino functionalized organozinc coordination polymer (denoted as Pd/AZC) and its extraordinary catalytic performances in the Suzuki–Miyaura coupling (SMC) reaction. It achieved the highest turnover number of 2106720 (>99% yield) in air among the most reported palladium catalysts for the SMC reaction of bromobenzene. The as-prepared Pd/AZC composite is also successfully applied for the catalysis of Mizoroki–Heck coupling, hydrogenation of nitro, and –CC– functional groups. Since the developed AZC support has thermal stability at least up to 573 K, it possesses high potential for grafting various metal species as catalytically active centers for a wide range of metal-catalyzed reactions.

One-pot synthesis of furfural derivatives from pentoses using solid acid and base catalysts

Co-reporter:Mahiro Shirotori, Shun Nishimura and Kohki Ebitani

Catalysis Science & Technology 2014 vol. 4(Issue 4) pp:971-978

Publication Date(Web):06 Jan 2014

DOI:10.1039/C3CY00980G

One-pot synthesis of (2-furanylmethylene)malononitrile, a Knoevenagel product of furfural with malononitrile, from xylose efficiently proceeded by combined use of acid Amberlyst-15 and acid-base Cr/hydrotalcites in 44% yield. Structural characterization was carried out using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy, and nitrogen adsorption measurements. The Lewis acidic properties of the highly active Cr/HT were investigated using the Meerwein–Ponndorf–Verley (MPV) reaction. It was confirmed that the prepared Cr/HT possessed the Lewis acid Cr2O3 on the HT surface. Thus, combined use of the dispersed Lewis acid Cr2O3 and the Brønsted base HT facilitated the isomerization step of aldose into ketose and strongly promoted activity for the synthesis of furfural derivatives from aldoses through isomerization, dehydration and Knoevenagel condensation reactions in a one-pot manner.

Production of γ-valerolactone from biomass-derived compounds using formic acid as a hydrogen source over supported metal catalysts in water solvent

Co-reporter:Pham Anh Son, Shun Nishimura and Kohki Ebitani

RSC Advances 2014 vol. 4(Issue 21) pp:10525-10530

Publication Date(Web):31 Jan 2014

DOI:10.1039/C3RA47580H

γ-Valerolactone (GVL) is a key intermediate for production of fuels and chemicals. In this research, GVL is synthesized from biomass-derived compounds using formic acid (FA) as a hydrogen source over various supported metal catalysts which are prepared by a simple impregnation or co-precipitation method. Under optimum conditions, levulinic acid (LA) is almost converted to GVL by Ru/C, Ru/SBA, Au/ZrC and Au/ZrO2 catalysts with above 90% yield in water solvent. Especially, the Au/ZrO2 showed excellent activity and recyclability; the Au/ZrO2 catalyst can decompose completely FA to CO2 and H2, which gives high yield of GVL (ca. 97%) from hydrogenation of LA, and can retain its activity for at least 5 recycle runs. GVL is also obtained from one-pot dehydration/hydrogenation reaction of fructose in water solvent. In this reaction, FA plays two roles: an acid catalyst for dehydration of fructose to LA, and a hydrogen source for hydrogenation of the obtained LA over supported metal catalysts. The Au/ZrO2 is the best catalyst for dehydration/hydrogenation reaction with overall GVL yield of 48% and can be reused several times.

Base-free chemoselective transfer hydrogenation of nitroarenes to anilines with formic acid as hydrogen source by a reusable heterogeneous Pd/ZrP catalyst

Co-reporter:Jaya Tuteja, Shun Nishimura and Kohki Ebitani

RSC Advances 2014 vol. 4(Issue 72) pp:38241-38249

Publication Date(Web):11 Aug 2014

DOI:10.1039/C4RA06174H

A highly efficient, chemoselective, environmentally-benign method is developed for the catalytic transfer hydrogenation (CTH) of nitroarenes using FA as a hydrogen source. Various supported Pd catalysts were examined for this transformation, and Pd supported ZrP (Pd/ZrP) proved to be the best catalyst for CTH of nitrobenzene. Applicability of the Pd/ZrP catalyst is also explored for hydrogenation of various substituted nitroarenes. The Pd/ZrP catalyst showed high specificity for hydrogenation of nitro groups even in the presence of other reducible functional groups such as –CC, –COOCH3, and –CN. To investigate the reaction mechanism, a Hammett plot was obtained for CTH of p-substituted nitroarenes. The active site is thought to be in situ generated Pd(0) species as seen from XRD and TEM data. The Pd/ZrP catalyst is reusable at least up to 4 times while maintaining the same activity and selectivity. To the best of our knowledge, this is one of the best methodologies for CTH of nitroarenes under base-free conditions with high activity and chemoselectivity over heterogeneous Pd-based catalysts.

Preparation of zirconium carbonate as water-tolerant solid base catalyst for glucose isomerization and one-pot synthesis of levulinic acid with solid acid catalyst

Co-reporter:Pham Anh Son;Shun Nishimura

Reaction Kinetics, Mechanisms and Catalysis 2014 Volume 111( Issue 1) pp:183-197

Publication Date(Web):2014 February

DOI:10.1007/s11144-013-0642-6

In this research, zirconium compounds were prepared as water-tolerant solid base catalysts by a simple method. Their catalytic activities were investigated in the aqueous glucose–fructose isomerization reaction. The zirconium carbonate (ZrC) catalyst could work in wide range of reaction temperature (80–140 °C) and the maximum glucose conversion reached 45 % at 120 °C with 76 % selectivity to fructose. The ZrC catalyst was found to retain its activity without significant decrease in the fructose yield after being used for five times. In the one-pot transformation of glucose to levulinic acid (LA), the ZrC could afford 17 % yield of LA after 12 h reaction in water–toluene biphasic solvents in combination with a solid acid catalyst, Amberlyst-15. The proposed reaction system in water–toluene biphasic solvents occurred faster and gave higher LA yield than that in pure water solvent.

Effect of Stabilizing Polymers on Catalysis of Hydrotalcite-Supported Platinum Nanoparticles for Aerobic Oxidation of 1,2-Propanediol in Aqueous Solution at Room Temperature

Co-reporter:Duangta Tongsakul ; Shun Nishimura

The Journal of Physical Chemistry C 2014 Volume 118(Issue 22) pp:11723-11730

Publication Date(Web):May 22, 2014

DOI:10.1021/jp501836a

The effect of stabilizing polymers such as starch, PVP, and PVA on catalysis of hydrotalcite-supported platinum nanoparticles (Pt–polymer/HT) for the base-free aerobic oxidation of 1,2-propanediol (PG) in aqueous solution using molecular oxygen under atmospheric pressure at room temperature (RT), electronic state, and hydrophilicity was investigated. The particle size of supported Pt naoparticles (NPs) was controlled to be the same (ca. 2.2 nm) by changing polymer amount during the preparation of Pt NPs. The Pt–starch/HT exhibited the higher activity than the Pt–PVP/HT and Pt–PVA/HT for oxidation of the primary hydroxyl group of PG toward lactic acid (LA). Pt 4f XPS and Pt L3-edge XANES analyses suggested that Pt atoms in Pt NPs stabilized by starch and PVA were more negative than that stabilized by PVP. Furthermore, the measurement of water contact angle suggested that Pt–starch/HT and Pt–PVA/HT had less hydrophilic nature than that of Pt–PVP/HT. These results indicate that the polymer plays an important role in determining not only the electronic charge on the Pt surface atoms but also wettability of water solvent, and these are strongly attributed to their catalysis. Starch was found to be an appropriate ligand for stabilized Pt NPs in which preserved the abundance of negatively charged to active surface and provided the suitable wettability for water solvent (hydrophilicity), bringing about the high catalytic activity of Pt–starch/HT.

Direct Synthesis of 1,6-Hexanediol from HMF over a Heterogeneous Pd/ZrP Catalyst using Formic Acid as Hydrogen Source

Co-reporter:Jaya Tuteja;Hemant Choudhary;Dr. Shun Nishimura ;Dr. Kohki Ebitani

ChemSusChem 2014 Volume 7( Issue 1) pp:96-100

Publication Date(Web):

DOI:10.1002/cssc.201300832

Abstract

A new approach is developed for hydrogenolytic ring opening of biobased 5-hydroxymethylfurfural (HMF), dehydration product of hexoses, towards 1,6-hexanediol (HDO) under atmospheric pressure. The highest yield of HDO, 43 %, is achieved over reusable Pd/zirconium phosphate (ZrP) catalyst at 413 K in the presence of formic acid as hydrogen source. In comparison with various Brønsted and/or Lewis acidic supports, the specific Brønsted acidity on ZrP support effectively accelerated the cleavage of CO bond in a furan ring.

Platinum/Gold Alloy Nanoparticles-Supported Hydrotalcite Catalyst for Selective Aerobic Oxidation of Polyols in Base-Free Aqueous Solution at Room Temperature

Co-reporter:Duangta Tongsakul, Shun Nishimura, and Kohki Ebitani

ACS Catalysis 2013 Volume 3(Issue 10) pp:2199

Publication Date(Web):August 14, 2013

DOI:10.1021/cs400458k

As-prepared platinum/gold alloy nanoparticles-supported hydrotalcites (PtxAuy–starch/HTs) by using a soluble starch as a green reducing and a stabilizing agent are found to be truly effective heterogeneous catalysts for the selective aerobic oxidation of glycerol (GLY) and 1,2-propanediol (PG) in base-free aqueous solution using molecular oxygen in atmospheric pressure at room temperature. The PtxAuy–starch/HTs exhibited higher selectivities for oxidation of the primary hydroxyl group in GLY and PG toward glyceric acid (GA) and lactic acid (LA), respectively, with molecular oxygen in aqueous solution than those reactions over monometallic Pt–starch/HT or Au–starch/HT. Pt60Au40–starch/HT was found to be the most active catalyst for selective aerobic oxidation of polyols. It showed 73% GLY conversion with 57% GA yield and 63% PG conversion with 47% LA yield and retained high selectivity in recycling experiments. XRD patterns of the PtxAuy–starch NPs indicated the d-spacing of Pt atoms was changed by alloying with Au atoms. XPS and XANES analyses suggested that Pt atoms gained more electrons than Au atoms in PtxAuy–starch/HTs as a result of the two types of electron transfers: (1) from the starch ligand to both Au and Pt atoms and (2) from Au to Pt atoms. We concluded that the high activity and selectivity of PtxAuy–starch/HT can be explained in terms of alterations of geometric and electronic states of the catalytically active surface Pt sites by Au atoms and starch ligand.Keywords: base-free polyol oxidation; electronic effect; geometric effect; heterogeneous catalyst; hydrotalcite; platinum/gold alloy; starch ligand

Characterization, synthesis and catalysis of hydrotalcite-related materials for highly efficient materials transformations

Co-reporter:Shun Nishimura, Atsushi Takagaki and Kohki Ebitani

Green Chemistry 2013 vol. 15(Issue 8) pp:2026-2042

Publication Date(Web):18 Jun 2013

DOI:10.1039/C3GC40405F

This review is intended to introduce recent progress in the characterization, synthesis and catalysis of hydrotalcite (HT) and HT-related materials. NMR, in situ neutron diffraction and TG–DTA techniques have been used to determine the local structure and structural changes of HT. Various synthetic methods of controlling the morphology of HT are introduced together with the crystal formation mechanism. The preparation methods of magnetic HTs are also included. The HT acts as a heterogeneous base catalyst for efficient transformations of organic compounds such as the synthesis of glycerol carbonate, transesterification of oils (biodiesel production) and carbon–carbon bond formations. The HT has also been used as a support for immobilizing various metal species (Ru, Pd, Ag, Au, Pt, Cu, V, Mn etc.), which enables highly selective organic reactions such as dehydrogenation of alcohols and deoxygenation of epoxides. Cooperative actions between basic sites of the HT surface and supported metal species are introduced. It is also shown that the HT can work together with other solid acids and metal catalysts to promote sequential reactions in a one-pot manner, which gives us a very important methodology for environmentally-benign synthesis of value-added chemicals, especially from biomass-derived compounds.

The role of negatively charged Au states in aerobic oxidation of alcohols over hydrotalcite supported AuPd nanoclusters

Co-reporter:Shun Nishimura, Yusuke Yakita, Madoka Katayama, Koichi Higashimine and Kohki Ebitani

Catalysis Science & Technology 2013 vol. 3(Issue 2) pp:351-359

Publication Date(Web):22 May 2012

DOI:10.1039/C2CY20244A

The PVP-protected bimetallic gold–palladium nanoclusters (AuxPdy-PVP NCs) were prepared on the solid base hydrotalcite (HT) with various Au:Pd (x:y) molar ratios. Transmission electron microscopy showed narrow particle size distributions of AuxPdy-PVP NCs with a mean diameter in the range of 2.6–3.0 nm regardless of Pd content. Aerobic oxidations of 1-phenylethanol over the AuxPdy-PVP/HT catalysts showed that their catalytic activities were significantly affected by the Pd content. Correlations between charge transfer between Au and Pd and catalytic activity of the AuxPdy-PVP/HT catalysts were investigated with X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge structure (XANES), Michaelis–Menten kinetic studies for alcohol oxidation, and other analytical techniques. The peaks of Au 4f in the XPS spectra were shifted to the lower energy side with increase of Pd content, indicating the electron transfer from Pd to Au atoms according to Pauling's electronegativity protocol. The electron densities in the Au 5d orbital in the AuxPdy-PVP/HT catalysts estimated by the Au L3-XANES spectra correlated well with their catalytic activities. Moreover, the kinetic studies also proposed that the electron rich Au 5d states, resulting from the intermetallic electron transfer from Pd atoms, strongly contributed to the rate-determining step in the alcohol oxidation. It was concluded that the electronic negativity of the Au 5d states controlled by the Pd content accelerated the rate-determining step in alcohol oxidation through highly active radical-like intermediates.

Synthesis of -Amino Acids from Glucosamine-HCl and its Derivatives by Aerobic Oxidation in Water Catalyzed by Au Nanoparticles on Basic Supports

Co-reporter:Youtaro Ohmi;Dr. Shun Nishimura ;Dr. Kohki Ebitani

ChemSusChem 2013 Volume 6( Issue 12) pp:2259-2262

Publication Date(Web):

DOI:10.1002/cssc.201300303

Hydrotalcite-Supported Platinum Nanoparticles Prepared by a Green Synthesis Method for Selective Oxidation of Glycerol in Water Using Molecular Oxygen

Co-reporter:Duangta Tongsakul, Shun Nishimura, Chuchaat Thammacharoen, Sanong Ekgasit, and Kohki Ebitani

Industrial & Engineering Chemistry Research 2012 Volume 51(Issue 50) pp:16182

Publication Date(Web):November 26, 2012

DOI:10.1021/ie3020507

Hydrotalcite-supported platinum nanoparticles (Pt NPs/HT) prepared by the immobilization method with soluble starch as a reducing and a stabilizing agent were applied as catalysts for the selective oxidation of glycerol using atmospheric molecular oxygen as an oxidant in water. The Pt NPs/HT catalyst achieved a high selectivity (68%) toward glyceric acid (GA) in base-free aqueous solution. The catalyst was removed from the solution by simple filtration after the reaction and could be reused up to three times with a high selectivity (71% in third recycled).

Synthesis of levulinic acid from fructose using Amberlyst-15 as a solid acid catalyst

Co-reporter:Pham Anh Son;Shun Nishimura

Reaction Kinetics, Mechanisms and Catalysis 2012 Volume 106( Issue 1) pp:185-192

Publication Date(Web):2012 June

DOI:10.1007/s11144-012-0429-1

Levulinic acid was obtained from fructose over solid acid catalysts under mild reaction conditions in water. The reaction was carried out at different temperatures and amounts of catalysts to find the best reaction conditions. Among tested heterogeneous catalysts, Amberlyst-15 gave the highest LA yield (52%) with the lowest HMF yield (below 3%) under optimum conditions. Levulinic acid was isolated from the mixture after reaction by rotary vacuum evaporator with 47% isolated yield. The recycling experiments showed that Amberlyst-15 exhibited good activity even after 5 runs, though the LA yield gradually decreased from 52 to 30%.

Catalytic Transformations of Biomass-Derived Materials into Value-Added Chemicals

Co-reporter:Atsushi Takagaki;Shun Nishimura

Catalysis Surveys from Asia 2012 Volume 16( Issue 3) pp:164-182

Publication Date(Web):2012 September

DOI:10.1007/s10563-012-9142-3

This manuscript reviews recent literatures on synthesis of furfurals (5-hydroxymethylfurfural, furfural, 5-methyl-2-furaldehyde) from various sugars (glucose, fructose, d-galactose, d-arabinose, xylose, l-rhamnose, lactose, cellobiose, sucrose) and furfural conversions into other carbonyl compounds (2,5-diformylfuran, 2,5-furandicarboxylic acid, levulinic acid, succinic acid) using catalytic methodology. Our recent achievements on one-pot synthesis of furfurals using solid acid and base catalysts and selective oxidations of furfurals using heterogeneous catalysts are also included.

One-Pot Synthesis of 2,5-Diformylfuran from Carbohydrate Derivatives by Sulfonated Resin and Hydrotalcite-Supported Ruthenium Catalysts

Co-reporter:Atsushi Takagaki, Miho Takahashi, Shun Nishimura, and Kohki Ebitani

ACS Catalysis 2011 Volume 1(Issue 11) pp:1562

Publication Date(Web):October 12, 2011

DOI:10.1021/cs200456t

2,5-Diformylfuran (DFF) was selectively synthesized from 5-hydroxymethylfurfural using a hydrotalcite-supported ruthenium catalyst (Ru/HT) by oxidation with molecular oxygen under mild reaction conditions. A combination of hydrotalcite, Amberlyst-15, and Ru/HT catalysts successfully afforded direct synthesis of DFF from hexoses such as fructose and glucose via isomerization, dehydration, and successive selective oxidation in one pot. Stepwise addition of catalyst improved DFF yield up to 49% from fructose and 25% from glucose, respectively.Keywords: 2,5-diformylfuran; acid−base catalysis; biomass transformation; heterogeneous catalysts; one-pot reaction; selective oxidation;

Hydrotalcite-supported gold-nanoparticle-catalyzed highly efficient base-free aqueous oxidation of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid under atmospheric oxygen pressure

Co-reporter:Navneet Kumar Gupta, Shun Nishimura, Atsushi Takagaki and Kohki Ebitani

Green Chemistry 2011 vol. 13(Issue 4) pp:824-827

Publication Date(Web):14 Feb 2011

DOI:10.1039/C0GC00911C

Green synthesis of 2,5-furandicarboxylic acid, one of the most important chemical building blocks from biomass, viaoxidation of 5-hydroxymethylfurfural has been demonstrated using hydrotalcite-supported gold nanoparticle catalyst in water at 368 K under atmospheric oxygen pressure without addition of homogeneous base.

Role of base in the formation of silver nanoparticles synthesized using sodium acrylate as a dual reducing and encapsulating agent

Co-reporter:Shun Nishimura, Derrick Mott, Atsushi Takagaki, Shinya Maenosono and Kohki Ebitani

Physical Chemistry Chemical Physics 2011 vol. 13(Issue 20) pp:9335-9343

Publication Date(Web):08 Apr 2011

DOI:10.1039/C0CP02985H

The formation mechanism of Ag nanoparticles (NPs) synthesized with a wet-chemical reduction method using sodium acrylate as a dual reducing and capping agent was investigated with various analytical techniques. The time course of the state of the reaction solution was investigated using UV-vis and XAFS spectroscopies which showed that the NP formation rate increased with increasing concentration of sodium hydroxide (NaOH). The detailed kinetic analyses reveal that both the reduction rate of Ag ions and the nucleation rate of Ag NPs are dramatically increased with increasing NaOH concentration. XANES analyses imply that another reaction pathway via alternative Ag+ species, such as Ag(OH)x, was developed in the presence of NaOH. Consequently, NaOH is found to play an important role not only in creating specific intermediates in the reduction of Ag+ to Ag0, but also in accelerating the reduction and nucleation rates by enhancing the oxidation of sodium acrylate, thereby increasing the rate of formation of the Ag NPs.

Selective Oxidation of Glycerol by Using a Hydrotalcite-Supported Platinum Catalyst under Atmospheric Oxygen Pressure in Water

Co-reporter:Akihiro Tsuji;Kasanneni Tirumala Venkateswara Rao;Shun Nishimura;Dr. Atsushi Takagaki; Kohki Ebitani

ChemSusChem 2011 Volume 4( Issue 4) pp:542-548

Publication Date(Web):

DOI:10.1002/cssc.201000359

Abstract

A hydrotalcite-supported platinum (Pt/HT) catalyst was found to be a highly active and selective heterogeneous catalyst for glycerol oxidation in pure water under atmospheric oxygen pressure in a high glycerol/metal molar ratio up to 3125. High selectivity toward glyceric acid (78 %) was obtained even at room temperature under air atmosphere. The Pt/HT catalyst selectively oxidized the primary hydroxyl group of 1,2-propandiol to give the corresponding carboxylic acid (lactic acid) as well as glycerol. The activity of the catalyst was greatly influenced by the Mg/Al ratio of hydrotalcite. Glycerol conversion increased with increasing the Mg/Al ratio of hydrotalcite (from trace to 56 %). X-ray absorption fine structure (XAFS) measurements indicated that the catalytic oxidation activity was proportional to the metallic platinum concentration, and more than 35 % of metallic platinum was necessary for this reaction. TEM measurements and titration analysis by using benzoic acid suggested that the solid basicity of hydrotalcite plays important roles in the precise control of platinum size and metal concentration as well as the initial promotion of alcohol oxidation.

Synthesis of glycerol carbonate from glycerol and dialkyl carbonates using hydrotalcite as a reusable heterogeneous base catalyst

Co-reporter:Atsushi Takagaki, Ken Iwatani, Shun Nishimura and Kohki Ebitani

Green Chemistry 2010 vol. 12(Issue 4) pp:578-581

Publication Date(Web):04 Feb 2010

DOI:10.1039/B925404H

An uncalcined Mg–Al hydrotalcite catalyst involving hydromagnesite with a high surface area acted as a highly active base catalyst for glycerol carbonate synthesis from glycerol and dialkyl carbonates under moderate reaction conditions.

In Situ Time-Resolved XAFS Study on the Formation Mechanism of Cu Nanoparticles Using Poly(N-vinyl-2-pyrrolidone) as a Capping Agent

Co-reporter:Shun Nishimura, Atsushi Takagaki, Shinya Maenosono and Kohki Ebitani

Langmuir 2010 Volume 26(Issue 6) pp:4473-4479

Publication Date(Web):December 29, 2009

DOI:10.1021/la904248z

The formation mechanism of copper nanoparticles (NPs) using poly(N-vinyl-2-pyrrolidone) (PVP) as a capping agent was investigated by measurements of X-ray diffraction (XRD), transmission electron microscopy (TEM), in situ time-resolved X-ray adsorption fine structure (XAFS) analysis, in situ UV−vis spectroscopy, and an indicator method. XAFS analyses, in combination with TEM observations and the indicator method, revealed that the stable intermediates such as Cu(OH)2 and Cu+−PVP intermediate were formed during an induction period of nucleation of Cu NPs, which play a critical role in the Cu NP formation. Our results suggest that the PVP capping agent is important not only to protect NPs from overgrowth and aggregation but also to control the reaction kinetics of NP formation.

A one-pot reaction for biorefinery: combination of solid acid and base catalysts for direct production of 5-hydroxymethylfurfural from saccharides

Co-reporter:Atsushi Takagaki, Mika Ohara, Shun Nishimura and Kohki Ebitani

Chemical Communications 2009 (Issue 41) pp:6276-6278

Publication Date(Web):07 Sep 2009

DOI:10.1039/B914087E

5-Hydroxymethylfurfural (HMF), one of the most important intermediates derived from biomass, was directly produced from monosaccharides (fructose and glucose) and disaccharides (sucrose and cellobiose) by a simple one-pot reaction including hydrolysis, isomerization and dehydration using solid acid and base catalysts under mild conditions.

Fine-crystallized LDHs prepared with SiO2 spheres as highly active solid base catalysts

Co-reporter:Mahiro Shirotori, Shun Nishimura and Kohki Ebitani

Journal of Materials Chemistry A 2017 - vol. 5(Issue 15) pp:NaN6957-6957

Publication Date(Web):2017/03/13

DOI:10.1039/C7TA00984D

Fine-crystallized layered double hydroxides are prepared via the co-precipitation method with the coexistence of SiO2 spheres (SiO2@LDH), and their base catalysis and structural properties are investigated. The as-prepared SiO2@LDHs exhibit higher base catalysis for the Knoevenagel condensation than conventional LDHs prepared via the co-precipitation method in the absence of SiO2 spheres. Such an increase in the activity for base catalysis is also observed in various types of SiO2@LDHs with different metal compositions (M2+: Mg2+ or Ni2+, M3+: Al3+ or Ga3+, and M2+/M3+: 1 or 3). X-ray diffraction (XRD) measurement suggests that the addition of SiO2 induces decreases in the LDH crystallite size. The results of transmission electron microscopy – energy dispersive X-ray spectroscopy (TEM-EDS) and 29Si cross polarization magic angle spinning nuclear magnetic resonance (29Si CP-MAS NMR) on SiO2@Mg–Al LDH suggest that the crystals of Mg–Al LDH are immobilized on the SiO2 surface through Si–O–Al and Si–O–Mg covalent bonds. According to these results, we conclude that the co-precipitation method in the presence of colloidal spherical SiO2 seeds, particularly possessing a 40 nm diameter, result in highly-dispersed points of LDH crystal growth on the SiO2 surface, which lead to the generation of fine-crystallized highly active LDH nanocrystals.

Genesis of a bi-functional acid–base site on a Cr-supported layered double hydroxide catalyst surface for one-pot synthesis of furfurals from xylose with a solid acid catalyst

Co-reporter:Mahiro Shirotori, Shun Nishimura and Kohki Ebitani

Catalysis Science & Technology (2011-Present) 2016 - vol. 6(Issue 23) pp:NaN8211-8211

Publication Date(Web):2016/10/03

DOI:10.1039/C6CY01426G

A Cr-supported Mg–Al layered double hydroxide (Cr/Mg–Al LDH) comprised bi-functional Lewis acid–Brønsted base active sites on the catalyst surface at close boundaries between Cr3+ oxide and Mg–Al LDH. These enabled efficient aldose–ketose isomerization. The combined use of solid Brønsted acid Amberlyst-15 and bi-functional acid–base Cr/Mg–Al LDH exhibits higher activity for one-pot transformation of xylose into furfural via aldose–ketose isomerization and successive dehydration under mild conditions than those exhibited by basic bare Mg–Al LDH, substituted Mg–Cr LDH, and Lewis acidic Cr3+ supported catalysts with Amberlyst-15. The correlation between the activity and the Cr loading amount for Mg–Al LDH was evaluated using several characterization techniques and MPV reduction as a model reaction for Lewis acidity investigation. The results show the following: (1) the monomer of Lewis acidic Cr3+ oxide is supported on the Mg–Al LDH surface below 1 wt%. (2) Thereafter, Cr3+ species form small Lewis acidic Cr3+ oxide dimers and/or trimers up to 5 wt%. Then, they cover the Mg–Al LDH surface to generate highly active bi-functional Lewis acid–Brønsted base sites. (3) Above 5 wt%, the excess Cr3+ species generate inert Mg–Cr and/or Mg–Al–Cr LDH-like composites. They are deposited on some active sites, leading to decreased activity. The results show that furfural yields vary significantly in accordance with Cr loadings and that the 5 wt% Cr/Mg–Al LDH achieved the highest value (59% yield, 18 h) because the most effective interaction between the Lewis acidic Cr3+ oxide and the Mg–Al LDH basic site is observed at 5 wt% Cr loading.

A one-pot reaction for biorefinery: combination of solid acid and base catalysts for direct production of 5-hydroxymethylfurfural from saccharides

Co-reporter:Atsushi Takagaki, Mika Ohara, Shun Nishimura and Kohki Ebitani

Chemical Communications 2009(Issue 41) pp:NaN6278-6278

Publication Date(Web):2009/09/07

DOI:10.1039/B914087E

5-Hydroxymethylfurfural (HMF), one of the most important intermediates derived from biomass, was directly produced from monosaccharides (fructose and glucose) and disaccharides (sucrose and cellobiose) by a simple one-pot reaction including hydrolysis, isomerization and dehydration using solid acid and base catalysts under mild conditions.

Tailored design of palladium species grafted on an amino functionalized organozinc coordination polymer as a highly pertinent heterogeneous catalyst

Co-reporter:H. Choudhary, S. Nishimura and K. Ebitani

Journal of Materials Chemistry A 2014 - vol. 2(Issue 43) pp:NaN18696-18696

Publication Date(Web):2014/09/08

DOI:10.1039/C4TA03889D

The design of a highly active and stable heterogeneous palladium catalyst is gaining a lot of attention because of its increasing importance in the organic syntheses of commodity chemicals. Herein, we report the tailored synthesis of palladium species grafted on a highly stable amino functionalized organozinc coordination polymer (denoted as Pd/AZC) and its extraordinary catalytic performances in the Suzuki–Miyaura coupling (SMC) reaction. It achieved the highest turnover number of 2106720 (>99% yield) in air among the most reported palladium catalysts for the SMC reaction of bromobenzene. The as-prepared Pd/AZC composite is also successfully applied for the catalysis of Mizoroki–Heck coupling, hydrogenation of nitro, and –CC– functional groups. Since the developed AZC support has thermal stability at least up to 573 K, it possesses high potential for grafting various metal species as catalytically active centers for a wide range of metal-catalyzed reactions.

Role of base in the formation of silver nanoparticles synthesized using sodium acrylate as a dual reducing and encapsulating agent

Co-reporter:Shun Nishimura, Derrick Mott, Atsushi Takagaki, Shinya Maenosono and Kohki Ebitani

Physical Chemistry Chemical Physics 2011 - vol. 13(Issue 20) pp:NaN9343-9343

Publication Date(Web):2011/04/08

DOI:10.1039/C0CP02985H

The formation mechanism of Ag nanoparticles (NPs) synthesized with a wet-chemical reduction method using sodium acrylate as a dual reducing and capping agent was investigated with various analytical techniques. The time course of the state of the reaction solution was investigated using UV-vis and XAFS spectroscopies which showed that the NP formation rate increased with increasing concentration of sodium hydroxide (NaOH). The detailed kinetic analyses reveal that both the reduction rate of Ag ions and the nucleation rate of Ag NPs are dramatically increased with increasing NaOH concentration. XANES analyses imply that another reaction pathway via alternative Ag+ species, such as Ag(OH)x, was developed in the presence of NaOH. Consequently, NaOH is found to play an important role not only in creating specific intermediates in the reduction of Ag+ to Ag0, but also in accelerating the reduction and nucleation rates by enhancing the oxidation of sodium acrylate, thereby increasing the rate of formation of the Ag NPs.

The role of negatively charged Au states in aerobic oxidation of alcohols over hydrotalcite supported AuPd nanoclusters

Co-reporter:Shun Nishimura, Yusuke Yakita, Madoka Katayama, Koichi Higashimine and Kohki Ebitani

Catalysis Science & Technology (2011-Present) 2013 - vol. 3(Issue 2) pp:NaN359-359

Publication Date(Web):2012/05/22

DOI:10.1039/C2CY20244A

The PVP-protected bimetallic gold–palladium nanoclusters (AuxPdy-PVP NCs) were prepared on the solid base hydrotalcite (HT) with various Au:Pd (x:y) molar ratios. Transmission electron microscopy showed narrow particle size distributions of AuxPdy-PVP NCs with a mean diameter in the range of 2.6–3.0 nm regardless of Pd content. Aerobic oxidations of 1-phenylethanol over the AuxPdy-PVP/HT catalysts showed that their catalytic activities were significantly affected by the Pd content. Correlations between charge transfer between Au and Pd and catalytic activity of the AuxPdy-PVP/HT catalysts were investigated with X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge structure (XANES), Michaelis–Menten kinetic studies for alcohol oxidation, and other analytical techniques. The peaks of Au 4f in the XPS spectra were shifted to the lower energy side with increase of Pd content, indicating the electron transfer from Pd to Au atoms according to Pauling's electronegativity protocol. The electron densities in the Au 5d orbital in the AuxPdy-PVP/HT catalysts estimated by the Au L3-XANES spectra correlated well with their catalytic activities. Moreover, the kinetic studies also proposed that the electron rich Au 5d states, resulting from the intermetallic electron transfer from Pd atoms, strongly contributed to the rate-determining step in the alcohol oxidation. It was concluded that the electronic negativity of the Au 5d states controlled by the Pd content accelerated the rate-determining step in alcohol oxidation through highly active radical-like intermediates.

One-pot synthesis of furfural derivatives from pentoses using solid acid and base catalysts

Co-reporter:Mahiro Shirotori, Shun Nishimura and Kohki Ebitani

Catalysis Science & Technology (2011-Present) 2014 - vol. 4(Issue 4) pp:NaN978-978

Publication Date(Web):2014/01/06

DOI:10.1039/C3CY00980G

One-pot synthesis of (2-furanylmethylene)malononitrile, a Knoevenagel product of furfural with malononitrile, from xylose efficiently proceeded by combined use of acid Amberlyst-15 and acid-base Cr/hydrotalcites in 44% yield. Structural characterization was carried out using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy, and nitrogen adsorption measurements. The Lewis acidic properties of the highly active Cr/HT were investigated using the Meerwein–Ponndorf–Verley (MPV) reaction. It was confirmed that the prepared Cr/HT possessed the Lewis acid Cr2O3 on the HT surface. Thus, combined use of the dispersed Lewis acid Cr2O3 and the Brønsted base HT facilitated the isomerization step of aldose into ketose and strongly promoted activity for the synthesis of furfural derivatives from aldoses through isomerization, dehydration and Knoevenagel condensation reactions in a one-pot manner.

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