Publishing type：Research paper (scientific journal)  

DOI： 10.1039/d0gc01277g

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.apcata.2020.117723

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DOI： 10.1039/d0cc02969f

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DOI： 10.1039/d0re00085j

Publishing type：Research paper (scientific journal)  

DOI： 10.1038/s41598-020-61311-9

Publishing type：Research paper (scientific journal)  

DOI： 10.18942/apg.201913

Publishing type：Research paper (scientific journal)  

<p>It has been reported that the adsorption of 2-cyanopyridine (hereafter 2-cp) on the CeO₂ surface greatly improves the activity as a base catalyst. In order to elucidate the mechanism of the basic site formation, which is thought to improve the catalytic activity, we investigated the adsorption state of 2-cp adsorbed on a CeO₂(111) thin-film surface deposited on Cu(111) using synchrotron radiation based XPS. The XPS measurement suggested that electron donation from the CeO₂ lattice oxygen to the cyano group in 2-cp contributes to the formation of the basic site.</p>

DOI： 10.14886/jvss.2020.0_150

CiNii Article

Publishing type：Research paper (scientific journal)  

DOI： 10.14912/jsmcwm.31.0_149

CiNii Article

Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.jpcc.9b05077

Publishing type：Research paper (scientific journal)  

DOI： 10.7567/1347-4065/ab1b67

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DOI： 10.1136/annrheumdis-2019-eular.4315

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DOI： 10.1063/1.5079306

Publishing type：Research paper (scientific journal)  

DOI： 10.1039/c8cc02697a

Publishing type：Research paper (scientific journal)  

Transformation of sugars, while maintaining the intrinsic stereochemical structure, is desirable. However, such a transformation requires multistep synthesis with protection and deprotection of the OH groups. Herein, a new method for selective transformation of sugar derivatives into chiral building blocks and a diol synthon, with retention of the intrinsic configuration (stereo- and regioselectively), is demonstrated. The method is based on the selective recognition of cis-vicinal OH groups in sugars and leads to the one-pot removal of the cis-vicinal OH groups, without protection of OH groups (except the OH group of the hemiacetal group), over a heterogeneous CeO2 -supported ReOx and Pd (ReOx -Pd/CeO2 ) catalyst by using H2 as a reducing agent.

DOI： 10.1002/anie.201803043

PubMed

Publishing type：Research paper (scientific journal)  

Recent developments in catalytic reduction with H2 of glycerol, which is a by-product of biodiesel manufacture, and the involved chemistry are summarized and reviewed. There are more than ten potential C3 products of glycerol reduction. Among them, 1,2-propanediol can be obtained in very high yield and the production from glycerol is now commercialized. Production of 1,3-propanediol, allyl alcohol and propylene are now possible in &gt
60%, &gt
90% and &gt
80% yield, respectively. Key reaction steps are metal-catalyzed dehydrogenation/hydrogenation, acid-catalyzed dehydration, carbonyl-induced dehydration, metal-catalyzed direct hydrogenolysis and deoxydehydration. The 2-Propanol and small-ring compounds (oxetane, propylene oxide) cannot be produced from glycerol by combinations of these key reaction steps, and no catalytic system is known at present, although the conversion reactions have minus ∆G°.

DOI： 10.1007/s11164-018-3481-2

Publishing type：Research paper (scientific journal)  

Addition effect of 2nd metal to Ru catalysts in hydrogenolysis of squalane was investigated. Addition of V gave lower methane selectivity and higher C14-C16 selectivity and the effect was the most remarkable over SiO2 support. However, addition of V decreased the catalyst activity and increased the deposited amount of carbonaceous species. From hydrogenolysis of n-hexadecane, addition of V suppressed the formation of methane via terminal C–C bond dissociation, but the formation via fragmentation was not suppressed. Ru and V valences in Ru-VOx/SiO2 (V/Ru = 0.25) after reduction were 0 and +III, respectively. The size of Ru particles was about 4 nm from XRD even in changing V/Ru ratio. H2 chemisorption showed that V covered the Ru particles and reduced the size of Ru ensemble. In reuse test, it was difficult to retain the catalyst performance for hydrogenolysis of squalane even with various treatments of the recovered catalyst such as washing with n-hexane, heating in N2 flow or calcination in air. From XAS analysis, the contact of Ru particles with air caused the aggregation of Ru metal especially when calcined in air.

DOI： 10.1016/j.fuproc.2018.03.038

Publishing type：Research paper (scientific journal)  

We found that Pt-modified Ir-ReOx/SiO2 acted as an effective catalyst for aqueous phase reforming (APR) and selective C-O hydrogenolysis of glycerol without external hydrogen sources at low temperature of 463 K, and that 0.5 wt% loaded Ir-ReOx/SiO2 (Pt(0.5)-Ir-ReOx/SiO2) provided 1,2-propanediol (1,2-PrD) and acetol in high total yield of 53% at 81% conversion. The initial activity (TOFinitial) over Pt(0.5)-Ir-ReOx/SiO2 at 463 K was estimated to be 13 h−1. Pt-Ir alloy and Ir-ReOx species in Pt-Ir-ReOx/SiO2 are main active species for APR and selective C-O hydrogenolysis, respectively, and the high yield can be achieved by balancing the APR and hydrogenolysis activities through the optimization of Pt and Ir-ReOx molar ratio.

DOI： 10.1016/j.cattod.2017.07.025

Publishing type：Research paper (scientific journal)  

DOI： 10.1039/c8gc00574e

Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acscatal.7b02879

Publishing type：Research paper (scientific journal)  

The oxidation of 2-hydroxycyclohexanone and carbohydrates to adipic acid and formic acid, respectively, was performed with a combination of a vanadium catalyst, carbon as the cocatalyst, and O-2 in water under mild conditions (353K, 0.1-0.3MPa). The catalytic activity of aqueous V2O5 was increased significantly by the addition of activated carbon (C), whereas the addition of carbon black, graphene oxide, and carbon nanotubes has a much smaller effect. UV/Vis and inductively coupled plasma optical emission spectroscopy were used to show that most V-V species are adsorbed on C at least in a short reaction time. The V-IV species (VO2+) was not adsorbed on C. The order of activity of vanadium species was V-V on C&gt;dissolved free V-V &gt;&gt; dissolved free V-IV. To help the oxidation of V-IV, the further addition of phosphomolybdate (PMo12O403-; PMo) was also tested, and the activity was improved. The selectivity and yield of adipic acid from 2-hydroxycyclohexanone was also improved slightly by the addition of PMo. However, in the oxidation of glucose, the addition of PMo did not improve the final formic acid yield. The oxidation of glucose with the V+C system gave a 42% yield of formic acid, which was comparable to the values reported with a more expensive PVMo polyoxometalate catalyst. A reaction mechanism is proposed in which the reversibly formed biradical state of the vanadium ketol complex reacts with O-2 and accompanying rearrangement dissociates the C-C bond.

DOI： 10.1002/cctc.201700566

Publishing type：Research paper (scientific journal)  

Recent developments on supported Ni-Fe alloy catalysts are reviewed for various reforming reactions such as dry reforming of methane and steam reforming of molecules larger than methane. The catalytic performance greatly depends on the preparation methods, because the control of the composition of the Ni-Fe alloy is critical. Simple co-impregnation is not effective in obtaining uniform Ni-Fe alloy particles. Impregnation of Ni on Fe-containing mixed oxide supports can give Ni-Fe alloy particles by reduction; however, the control of the Fe/Ni ratio is rather difficult. On the other hand, utilization of oxide precursors containing both Ni and Fe ions such as hydrotalcite-like compounds and perovskite is effective in obtaining Ni-Fe alloy particles with controlled composition. The optimized Ni-Fe alloy catalysts show good performance in various reforming reactions in view of activity and resistance to carbon deposition. In addition, catalysts prepared from oxide precursors containing both Ni and Fe ions can show good regeneration ability by redispersion during the oxidation-reduction treatment.

DOI： 10.1039/c7cy01300k

Publishing type：Research paper (scientific journal)  

Intramolecular borrowing hydrogen methodology composed of dehydrogenation and direct hydrogenolysis is proposed. Rh-MoOx/SiO2 substantiated the methodology and acted as an effective catalyst for transformation of diols to the corresponding ketones in water without external hydrogen sources.

DOI： 10.1246/cl.170498

Publishing type：Research paper (scientific journal)  

CeO2-supported Cu (Cu/CeO2) acted as an effective heterogeneous catalyst for N-methylation of aniline with CO2 and H-2, showing higher selectivity to N-methylaniline, mono-Nmethylated aniline, than other catalysts tested. Cu sub-nanoparticles are the main active species, and the CeO2 support plays an important role in suppression of over-N-methylation of N-methylaniline to N, N-dimethylaniline.

DOI： 10.1246/cl.170419

Publishing type：Research paper (scientific journal)  

Selective hydrogenation of alpha,beta-unsaturated ketones to alpha,beta-unsaturated secondary alcohols is a challenging reaction for heterogeneous catalysts because of the nonuniformity of their surface active sites, and high-yield synthesis of the target alpha,beta-unsaturated secondary alcohols has not been achieved by heterogeneous catalysts. Herein, we found that Fe cation modified Ir/MgO acted as an effective heterogeneous catalyst for the reaction, providing high yield (up to 90%) of alpha,beta-unsaturated secondary alcohols. The activity is high (initial TOF = 12 min(-1) and TOFS (TOF per surface Ir site) = 84 min(-1)), and the TOF is more than 10 times higher than those of the reported heterogeneous catalysts. To the best of our knowledge, the TOFS is the highest among the reported homogeneous and heterogeneous catalysts under additional base-free conditions. The catalyst was easily fabricated by only mixing Ir/MgO and Fe cation precursor in the reaction media, and the active sites were proposed to be the interface among Ir metal, Ir4+, and Fe2+ species over MgO support based on kinetic studies and catalyst characterizations such as XPS, TPR, XRD, TEM, and ICP. The cation anion pair sites of Fe2+ and O2- formed at the active sites will bring about formation of active hydrogen species (H- and H+), leading to high selectivity and activity. The catalyst was also applicable to selective hydrogenation of alpha,beta-unsaturated aldehydes, providing the corresponding alpha,beta-unsaturated primary alcohols quantitatively (yield &gt;99%).

DOI： 10.1021/acscatal.7b01055

Publishing type：Research paper (scientific journal)  

Development of new hybrid materials having unique and unprecedented catalytic properties is a challenge for chemists, and heterogeneous-homogeneous hybrid catalysts have attracted much attention because of the preferable and exceptional properties that are highly expected to result from combination of the components. Base catalysts are widely used in organic synthesis as key materials, and a new class of base catalysts has made a large impact from academic and industrial-viewpoints. Here, a principle for creating a new strong base by hybridization of homogeneous and heterogeneous components is presented. It is based on the modification of organic compounds with metal oxides by using the acid-base property of metal oxides. Based on kinetic and DFT studies, combination of CeO2 and 2-cyanopyridine drastically enhanced the basicity of 2-cyanopyridine by a factor of about 10(9) (similar to 9 by pK(a) (in CH3CN)), and the pK(a) was estimated to be similar to 21, which locates it in the superbase category. 2-Cyanopyridine and CeO2 formed a unique adsorption complex-via two interaction modes: (i) coordinative interaction between the Ce atom of CeO2 and the N atom of the pyridine ring in 2-cyanopyridine, and (ii) covalent interaction between the surface O atom of CeO2 and the C atom of the CN group in 2-cyanopyridine by addition of the lattice oxygen of CeO2 to the CN group of 2-cyanopyridine. These interactions established a new, strongly basic site of N- over the CeO2 surface.

DOI： 10.1021/jacs.7b05227

Publishing type：Research paper (scientific journal)  

Production of biomass-derived chemicals requires the decrease of oxygen content in substrates because building blocks in biomass refinery have high oxygen content. C-O hydrogenolysis is one of the useful reactions for decreasing the oxygen content. On the other hand, selective C-O hydrogenolysis is essential in order to obtain a specific product in high yield since the building blocks are over-functionalized and contain a variety of C-O bonds. Recently, selective C-O hydrogenolysis was advanced by the development of surface modification of noble metal particles with metal oxide species. The modified catalysts have been also applied to the selective hydrogenation of carbonyl and carboxyl groups, which are also common functional groups in biomass-derived building blocks. This review deals with the performance, the structure of the active sites, and the reaction mechanism over the catalysts with direct bonds between noble metal particles and metal oxide species.

DOI： 10.1039/c7gc00620a

Publishing type：Research paper (scientific journal)  

Hydrogenolysis of hydrogenated botryococcene (Hy-Bot) was conducted over various supported Ru catalysts, Ir/SiO2, and Pt/SiO2-Al2O3. Ru/CeO2 with very high dispersion showed the highest yield (70%) of gasoline-range (C5-C12) alkanes at 513 K. The main gasoline-range products were dimethylalkanes. This yield is comparable to or higher than the gasoline yields from botryococcene in the literature, which were obtained at much higher temperature. Ir/SiO2 also showed a high fuel yield, but the activity was much lower than that with the Ru catalysts. The reaction over Pt/SiO2-Al2O3 slowed down before total conversion of Hy-Bot was achieved. Ru/CeO2 was stable in the hydrogenolysis of Hy-Bot without loss of activity and selectivity during reuses. The carbon balance was low for the hydrogenolysis of Hy-Bot over all catalysts if the main products are heavy hydrocarbons, whereas for the hydrogenolysis of squalane the carbon balance was kept near 100 %. H-1 NMR spectra of the product mixture and thermogravimetric analyses of the product mixture and the recovered catalyst revealed that the formation of aromatic compounds, polymeric products, and coke was negligible for the carbon balance. In a model reaction using substrate compounds with a substructure of Hy-Bot, only 2,5-dimethylhexane, which has a C6 chain with two C-primary -C-tertiary bonds, produced a cyclic product, 1,4-dimethylcyclohexane, which has a higher boiling point than the substrate. This dehydrocyclization reaction makes the product distribution in the hydrogenolysis of Hy-Bot more complex.

DOI： 10.1002/cctc.201700200

Publishing type：Research paper (scientific journal)  

NbOx-modified Ir/SiO2 catalyst (Ir-NbOx/SiO2) showed high activity and selectivity for gas-phase hydrogenation of crotonaldehyde, and Ir-NbOx/SiO2 with Nb/Ir molar ratio of 0.5 (Ir-NbOJSiO(2) (Nb/Ir = 0.5)) provided high crotyl alcohol yield of 87%. This is the highest crotyl alcohol yield among those in gas-phase over reported heterogeneous catalysts. The activities (TOF per surface lr atom) at low conversion level (40%, W/F = 0.37 g(cat)center dot h center dot mol(-1)) and high conversion level (97%, W/F = 2.2 g(cat)center dot h center dot mol(-1)) were calculated to be 0.21 and 0.08 s(-1), which are more than 3 times higher than those over reported heterogeneous catalysts. High activity and high yield are derived from the combination of Ir metal with NbOx species. Based on the spectroscopic and kinetic studies, the high activity and high selectivity are attributed to strong adsorption of crotonaldehyde on NbOx species by the high Lewis acidity, and suppression of over-hydrogenation of the produced crotyl alcohol at high conversion level. It is suggested that the formation of hydride species at the interface between Ir metal and NbOx species can promote the selective hydrogenation considering the reaction order with respect to hydrogen pressure. High yield and high activity of Ir-NbOx/SiO2 can contribute to energy saving, cost reduction, and waste reduction, which are directly connected to realization of sustainability.

DOI： 10.1021/acssuschemeng.6b03060

Publishing type：Research paper (scientific journal)  

Modification of Ru/SiO2 with metal oxides (MoOx, WOx, and ReOx) improved the activity and selectivity in the hydrogenation of 3-nitrostyrene to 3-aminostyrene under mild conditions such as 0.3 MPa H-2, 303 K, and no solvent. Ru-MoOx/SiO2(Mo/Ru = 1/2) catalyst was applicable to various substituted nitroarenes, providing the corresponding substituted aminoarenes in high yields (85-99%).

DOI： 10.1039/c7cc00653e

Publishing type：Research paper (scientific journal)  

Total hydrogenation of furfural and 5-hydroxymethylfurfural (HMF), both of which are important platform chemicals from biomass, produces tetrahydrofurfuryl alcohol (THFA) and 2,5-bis(hydroxymethyl)tetrahydrofuran (BHTHF), respectively, and these products can be used as solvent or raw material of resin. Ni catalysts can give good yields in these reactions; however the low activity and stability are problems. Supported monometallic Pd and Ru catalysts have been reported to be also active in hydrogenation, although the selectivity for total hydrogenation tends to be lower. Other monometallic catalysts such as Cu and Pt generally have low activity in furan ring hydrogenation of furfuryl alcohol (FOL) and 2,5-bis(hydroxymethyl)furan intermediates. We explored various multicomponent catalysts and found that Ni-Pd/SiO2, Pd-Ir/SiO2 and Rh-Ir-Re0x/SiO2 give good yield of THFA or BHTHF with much higher activity than the mixture of each component supported on SiO2.

DOI： 10.1627/jpi.60.1

Publishing type：Research paper (scientific journal)  

The dependence of the C-C hydrogenolysis activity on reaction parameters and the structure of the substrate alkanes was investigated for Ru/CeO2 catalyst with very small (dispersion: H/Ru=0.89) Ru particles. The substrate concentration and reaction temperature did not have a significant effect on the selectivity pattern, except that methane production was promoted at high temperatures. However, the hydrogen pressure had a marked effect on the selectivity pattern. C-tertiary-C bond dissociation, terminal C-secondary-C-primary bond dissociation, and fragmentation to form excess methane had negative reaction order with respect to hydrogen partial pressure, whereas C-secondary-C-secondary bond dissociation had an approximately zero reaction order. Therefore, a high hydrogen pressure is essential for the regioselective hydrogenolysis of C-secondary-C-secondary bonds in squalane. Ru/SiO2 catalyst with larger Ru particles showed similar changes in the product distribution during the change in hydrogen pressure. The reaction mechanism for each type of C-C bond dissociation is proposed based on reactivity trends and DFT calculations. The proposed intermediate species for the internal C-secondary-C-secondary dissociation, terminal C-secondary-C-primary dissociation, and C-tertiary-C dissociation is alkyls, alkylidynes, and alkenes, respectively.

DOI： 10.1002/cssc.201601204

Publishing type：Research paper (scientific journal)  

2-Furancarboxylic acid (FCA), produced by oxidation of furfural, is rarely used as a platform molecule. Metal-oxide-supported Pt-MoOx catalysts were effective for hydrodeoxygenation of FCA to valeric acid (VA) in water solvent. The highest VA yield is 51% over Pt-MoOx/TiO2 catalyst under 1.5 MPa H-2 at 413 K. Other metal combinations (M-MoOx, M = Rh, Pd, Ru, Ir, Au, none; Pt-M'O-x, M' = V, W, Re, none) showed very low VA yield. This catalyst system was applicable to the hydrodeoxygenation of 2,5-furandicarboxylic acid (FDCA), and adipic acid (AA) was obtained with 21% yield at 473 K.

DOI： 10.1021/acssuschemeng.6b01640

Publishing type：Research paper (scientific journal)  

CeO2 showed higher activity for the direct synthesis of 1,3-dibutylurea (DBU) from CO2 and n-butylamine than the metal oxides tested. The solvent largely influenced the reaction over CeO2, and N-methylpyrrolidone (NMP) was preferable among various solvents tested from the viewpoints of activity and selectivity. The catalyst system composed of CeO2 catalyst and NMP solvent (CeO2 in NMP) was applicable to the reactions of various amines such as linear primary alkylamines or branched primary alkylamines, although tert-butylamine afforded low conversion. In contrast, secondary amines and aniline provided no yield of the ureas. The combination of 2-cyanopyridine with CeO2 in NMP (CeO2 in NMP with 2-cyanopyridine) promoted the transformation of the unreactive amines, showing that tert-butylamine and aniline were converted to the corresponding ureas in 82% and 80% yields, respectively. These yields are much higher than those reported in the previous literatures, indicating that CeO2 in NMP with 2-cyanopyridine drastically promoted transformation of amines with low reactivity. (C) 2015 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcat.2015.11.015

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Gold nanoparticle cocatalyst and ceria support catalyst enabled the use of H-2 as a reductant for Re-catalyzed deoxydehydration (DODH), converting vicinal diols to olefins with higher activity than homogeneous Re catalysts using non-H-2 reductants and with comparable selectivity. The suitable particle size (similar to 10 nm) of Au in ReOx-Au/CeO2 catalyst was especially effective for activating H-2 while retaining the C=C bond in DODH products. Glycerol was converted to ally! alcohol in 91% yield, and the TON per Re atom reached 300. This system is applicable to other substrates such as erythritol (81% yield of 1,3-butadiene).

DOI： 10.1021/acscatal.6b01864

Publishing type：Research paper (scientific journal)  

Production of hydrocarbons from biomass, in which the hydrocarbon molecules have been included in conventional gasoline, becomes attractive, because the products will be compatible with existing gasoline supply infrastructures and can be blended in higher ratios into gasoline than ethanol. The present study proposes a gasoline boiling-range olefin production process, which combines hexanol production from cellulose using Ir-ReOx/SiO2 and acid catalysts, and hexene production from the hexanol using dehydration catalyst (H-ZSM-5). Our previous study found that hexanol can be obtained in relatively high yield of 60 % in depolymerizing cellulose by mechanocatalysis with the aid of H2SO4, and then reacting the cellulose with hydrogen over Ir-ReOx/SiO2. The present study investigated the compositions of the hexene mixture obtained by dehydrating 1-, 2-, and 3-hexanol, and the applicability of the mixture to gasoline based on JIS specifications. About 22 vol% and ca. 7 vol% of the hexene mixture could be blended into regular gasoline in summer and winter, respectively. Therefore, the hexene mixture obtained from cellulose through this pathway is a potential biofuel.

DOI： 10.1627/jpi.59.228

Publishing type：Research paper (scientific journal)  

Rh-MoOx/SiO2 (Mo/Rh=0.13) is an effective catalyst for the hydrogenolysis of 1,4-anhydroerythritol (1,4-AHERY) and provides 2-BuOH in high yield of 51%. This is the first report of the production of 2-BuOH from 1,4-AHERY by hydrogenolysis. 1,4-AHERY was more suitable as a starting material than erythritol because the 2-BuOH yield from erythritol was low (34%). Based on the kinetics and comparison of reactivities of the related compounds using Rh-MoOx/SiO2 and Rh/SiO2 catalysts, the modification of Rh/SiO2 with MoOx leads to the high activity and high selectivity to 2-BuOH because of the generation of reactive hydride species and the strong adsorption of 1,4-AHERY on MoOx species. The reaction proceeds by main two routes, (I)the combination of single C-O hydrogenolysis with the desorption of intermediates, a usual route in hydrogenolysis, and (II)multiple C-O hydrogenolysis without the desorption of intermediates from the active site, and the reaction mechanism for Route(II) is proposed.

DOI： 10.1002/cssc.201600295

Publishing type：Research paper (scientific journal)  

Deoxygenation of sorbitol was carried out over a Pt-modified Ir-ReOx/SiO2 catalyst in biphasic solvent system (n-decane +H2O) without external hydrogen. Good yield of gasoline-ranged products was obtained including C5-C6 alkanes and C2-C6 mono-functionalized compounds such as ketones, alcohols, cyclic ethers and carboxylic acids. The Pt(3 wt%)-Ir-ReOx/SiO2 catalyst showed the best performance in the production of gasoline-ranged products. The maximum yield of gasoline-ranged products was 42%. The distribution of the products can be tuned by the addition of HZSM-5. The main products were C5-C6 alkanes with addition of HZSM-5 while the main products were C2-C6 mono-functionalized compounds without addition of HZSM-5. Characterizations such as TPR, XRD, TEM, XANES, EXAFS, CO adsorption were performed. The results demonstrated that the Pt-Ir-O-x/SiO2 catalyst showed the structure of Pt-Ir alloy particles partially covered with ReO(x)species. The number of surface Pt atoms in Pt(3)-Ir-ReOx/SiO2 was larger than that of Pt/SiO2 or Pt-ReOx/SiO2 because of the small size of Pt-Ir alloy particles. The large number of surface Pt atoms and the synergetic effect of Pt, Ir and ReOx species make the catalyst efficiently generate hydrogen by aqueous phase reforming of sorbitol, and the generated hydrogen is consumed in the hydrogenolysis C-O bonds. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cattod.2015.10.023

Publishing type：Research paper (scientific journal)  

The scope of metal oxide modified noble metal (M+M'Ox) catalysts was scrutinized in the hydrogenation of crotonaldehyde to crotyl alcohol as a model reaction under mild reaction conditions (303 K, 0.8 MPa, water solvent), demonstrating that MoOx, WOx, NbOx, FeOx and ReOx are effective metal oxides for Ir/SiO2 to enhance both the activity and selectivity, although the optimized (metal oxide)/(Ir metal) molar ratio depends on the metal oxide. MoOx modified Ir/SiO2 catalyst (Ir-MoOx/SiO2 (Mo/Ir = 1)) was the most efficient, providing a high yield of crotyl alcohol (90%) and a high TOF (217 h-1). The catalytic activity under such mild reaction conditions is the highest among the reported heterogeneous catalysts. These results showed that modification of active metals with an appropriate amount of metal oxides is an effective method for the development of efficient catalysts for selective hydrogenations. The reaction mechanism over the metal oxide modified Ir catalysts was investigated using Ir-ReOx/SiO2 (Re/Ir = 1) as a model catalyst by means of FTIR studies on H2/D2 adsorption, crotonaldehyde adsorption, and temperature-programmed desorption of crotonaldehyde, and kinetic studies on effects of H-2 pressure and crotonaldehyde concentration, isotopic effect of hydrogen (VH2/VD2), and comparison of reactivities between the aldehyde group and olefin group using various substrates. The reaction proceeds via four steps: (i) adsorption of crotonaldehyde on ReOx species, (ii) generation of hydride species from H-2 on Ir metal species, (iii) hydride attack to the crotonaldehyde adspecies, and (iv) desorption of the produced crotyl alcohol, and the third step is the rate-determining step. Ir metal plays a role in the generation of hydride (H-) species from H-2, leading to the high selectivity to crotyl alcohol, and ReOx plays a role in promotion of crotonaldehyde adsorption, leading to the proximity of crotonaldehyde to the active site and activation of the aldehyde group, which results in high activity and further improvement in the selectivity.

DOI： 10.1021/acscatal.6b00400

Publishing type：Research paper (scientific journal)  

The combination of Pt/C and V2O5 catalysts gave good performance for the oxidative cleavage of trans-1,2-cyclohexanediol into adipic acid via 2-hydroxycyclohexanone. The yield of adipic acid reached 90% in the one-pot oxidative cleavage of trans-1,2-cyclohexanediol. The yield was higher than that obtained in the oxidation of 2-hydroxycyclohexanone with V catalyst, and the higher yield was due to the low 2-hydroxycyclohexanone concentration during the one-pot oxidation of trans-1,2-cyclohexanediol. Cyclic vicinal diols having a six-membered ring and linear vicinal diols having two secondary OH groups were converted into dicarboxylic acids and two carboxylic acids, respectively. The activity of the Pt catalyst decreased during the reaction, and the activity was partially restored by treating the used catalyst with H-2 at 573 K. Even without regeneration, the turnover number based on total Pt could reach approximate to 1000 in a long reaction with an increased amount of trans-1,2-cyclohexanediol.

DOI： 10.1002/cctc.201600153

Publishing type：Research paper (scientific journal)  

The ceria-supported rhenium catalyst modified with palladium (ReOx-Pd/CeO2 (Re = 2 wt %, Pd/Re = 0.25)) is still the best catalyst for simultaneous hydrodeoxygenation. Higher Re loading amount decreased the activity. The simultaneous hydrodeoxygenation of cyclic vicinal diols occurs with high cis-stereoselectivity. ReOx-Pd/CeO2 catalysts were characterized by means of XRD, TEM, H-2-TPR, XAFS, XPS, Raman, and DFT calculations. The Re species on ReOx-Pd/CeO2 (Re = 2 wt %, Pd/Re = 0.25) catalyst after reduction and after stoichiometric reaction of 1,2-hexanediol to 1-hexene were Re-IV and Re-VI, and the Re-IV species were converted to Re-VI through the stoichiometric reaction. The Re species on ReOx-Pd/CeO2 are proposed to be randomly located on the CeO2 surface, and probably only monomeric Re species have catalytic activity for simultaneous hydrodeoxygenation. This model can explain the higher activity of Re = 2 wt % catalyst than those of higher Re loading catalysts. The reaction is proposed to proceed by the tetra/hexavalent redox cycle of the Re center in the catalysis followed by hydrogenation.

DOI： 10.1021/acscatal.6b00491

Publishing type：Research paper (scientific journal)  

Direct polymerization of CO2 and diols is promising as a simple and environmental-benign method in place of conventional processes using high-cost and/or hazardous reagents such as phosgene, carbon monoxide and epoxides, however, there are no reports on the direct method due to the inertness of CO2 and severe equilibrium limitation of the reaction. Herein, we firstly substantiate the direct copolymerization of CO2 and diols using CeO2 catalyst and 2-cyanopyridine promotor, providing the alternating cooligomers in high diol-based yield (up to 99%) and selectivity (up to &gt;99%). This catalyst system is applicable to various diols including linear C4-C10 alpha,omega-diols to provide high yields of the corresponding cooligomers, which cannot be obtained by well-known methods such as copolymerization of CO2 and cyclic ethers and ring-opening polymerization of cyclic carbonates. This process provides us a facile synthesis method for versatile polycarbonates from various diols and CO2 owing to simplicity of diols modification.

DOI： 10.1038/srep24038

Publishing type：Research paper (scientific journal)  

Hydrodeoxygenation of methoxybenzenes such as guaiacol over Ru catalyst was studied. Guaiacol was demethoxylated and then hydrogenated over carbon black supported Ru-MnOx catalyst (Ru-MnOx/C) forming cyclohexanol and methanol in good yield (81% and 86%, respectively) under relatively mild conditions (433 K, H-2 1.5 MPa). Over Ru-MnOx/C, yield of demethoxylated products (cyclohexanol and cyclohexane) was almost the same as that of methanol, suggesting that the methoxy group is eliminated by demethoxylation to form methanol. Other methoxybenzenes such as 2,6-dimethoxyphenol and anisole were also converted to demethoxylated saturated compounds such as cyclohexanol and cyclohexane. The reaction scheme was proposed where demethoxylation and total hydrogenation of aromatic ring from partially-hydrogenated adsorbed guaiacol proceeded in parallel. Lower H2 pressure and higher reaction temperature were advantageous to demethoxylation. Addition of MnOx species slowed down the reaction rate of total hydrogenation of aromatic ring, which increased the relative rate of the elimination of methoxy group to that of total hydrogenation before the elimination. The catalyst can be reused without significant loss of activity. The nanoparticles of Ru and Mn were highly dispersed, and the state of Mn species on Ru-MnOx/C during the reaction was weakly basic MnO. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apcatb.2015.09.021

Publishing type：Research paper (scientific journal)  

Cu/CeO2 works as an effective heterogeneous catalyst for hydrogenation of dimethyl carbonate to methanol at 433 K and even at low H-2 pressure of 2.5 MPa, and it provided 94% and 98% methanol yield based on the carbonyl and total produced methanol, respectively. This is the first report of high yield synthesis of methanol from DMC by hydrogenation with H-2 over heterogeneous catalysts. Characterization of the Cu/CeO2 catalyst demonstrated that reduction of Cu/CeO2 produced Cu metal with &lt;1.0 nm (subnanoparticles). Cu metal subnanopartides are easily formed by the interaction with the CeO2 surface, which is responsible for the high catalytic performance.

DOI： 10.1021/acscatal.5b02258

Publishing type：Research paper (scientific journal)  

n-Pentane, pentanols and xylitol can be separately produced from hemicellulose (xylan) over an Ir-ReOx/SiO2 catalyst combined with acids by simply adjusting the reaction conditions. n-Pentane can be produced by using Ir-ReOx/SiO2 combined with HZSM-5 + H2SO4 in a biphasic solvent system (4 ml n-dodecane + 9.5 ml H2O) with a reaction temperature of 463 K for 24 h. Pentanols can be produced by using Ir-ReOx/SiO2 combined with H2SO4 in a biphasic solvent system (20 ml n-dodecane + 9.5 ml H2O) with a reaction temperature of 413 K for 144 h. Xylitol can be produced by using Ir-ReOx/SiO2 combined with H2SO4 in the aqueous phase with a reaction temperature of 413 K for 12 h. The highest yields of n-pentane, pentanols and xylitol could reach 70%, 32% and 79%, respectively. The reuse of the catalyst was feasible when the catalyst was regenerated by calcination at 773 K for 3 h. The calcination step is for removing the humins which were formed at the hydrolysis + hydrogenation step during conversion of xylan. The humins covered the active site of Ir-ReOx/SiO2 and HZSM-5, and they deactivated Ir-ReOx/SiO2 in C-O hydrogenolysis performance in part. The mineral ions (such as Na+ and K+) in xylan decreased the hydrogenolysis activity of Ir-ReOx/SiO2 significantly since the mineral ions can make the number of hydroxorhenium sites (Re-OH) smaller, which is the active site of Ir-ReOx/SiO2 for C-O hydrogenolysis, by ion exchange. The appropriate amount of H2SO4 addition is very crucial for the production of target products in high yield. The addition of H2SO4 not only neutralized the residual alkali of xylan after being isolated from lignocellulose to make the reaction solution acidic, but also improved the C-O hydrogenolysis activity of Ir-ReOx/SiO2 through increasing the number of hydroxorhenium sites by competitive adsorption on the Re site with mineral ions.

DOI： 10.1039/c5gc02183a

Publishing type：Research paper (scientific journal)  

A Re-Pd/SiO2 (Re/Pd = 8) catalyst was applied to hydrogenation of dicarboxylic acids (succinic acid, glutaric acid and adipic acid) to diols. In the hydrogenation of dicarboxylic acids, ex situ liquid-phase (in only 1,4-dioxane solvent) reduced Re-Pd/SiO2 showed much higher activity than in situ liquid-phase (in the mixture of dicarboxylic acid and 1,4-dioxane) and gas-phase reduced ones, in which the in situ liquid-phase reduced catalyst has been reported to show good activity in the hydrogenation of monocarboxylic acids. High diol yields (71-89%) were achieved in the hydrogenation of dicarboxylic acids on the ex situ liquid-phase reduced catalyst at 413 K. Lactones and hydroxycarboxylic acids were first formed as intermediates in the reaction of C4-C5 and &gt;= C6 dicarboxylic acids, respectively. Characterization using XRD, XPS and XAS indicates that ex situ liquid-phase reduced catalysts with high activity contains comparable amounts of Re-0 and Ren+ species, both of which have been reported to be necessary for good performance. The amount of Ren+ species on the in situ liquid-phase reduced catalysts is much larger than that of surface Re-0 species. This result suggests that the presence of dicarboxylic acids suppresses the reduction of Re species to Re-0 on the calcined catalysts while that of monocarboxylic acids does not, which leads to the low activity in the hydrogenation of dicarboxylic acids on in situ liquid-phase reduced catalysts.

DOI： 10.1039/c6cy00335d