The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Keiichi Tomishige - One of the best experts on this subject based on the ideXlab platform.
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Selective Hydrogenolysis and hydrogenation using metal catalysts directly modified with metal oxide species
Green Chemistry, 2017Co-Authors: Keiichi Tomishige, Yoshinao Nakagawa, Masazumi TamuraAbstract: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.
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role of re species and acid cocatalyst on ir reox sio2 in the c o Hydrogenolysis of biomass derived substrates
Chemical Record, 2014Co-Authors: Keiichi Tomishige, Masazumi Tamura, Yoshinao NakagawaAbstract:: The catalytic performance of ReOx -modified Ir metal catalyst in the Hydrogenolysis of C-O bonds is strongly dependent on the choice of solvent. The acidic property of the Re species becomes obvious in the alkane solvent, and the Hydrogenolysis reaction proceeds mainly by acid-catalyzed dehydration and the subsequent metal-catalyzed hydrogenation. The acidic property of the Re species is weakened in water; however, the Hydrogenolysis reaction proceeds in water via a direct mechanism involving SN 2-like attack of a hydride species at the interface between Ir and ReOx on the adsorbed Re alkoxide species. This mechanism enabled the selective dissociation of the C-O bond neighboring the CH2 OH group.
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one pot conversion of cellulose into n hexane over the ir reox sio2 catalyst combined with hzsm 5
ACS Sustainable Chemistry & Engineering, 2014Co-Authors: Masazumi Tamura, Yoshinao Nakagawa, Keiichi TomishigeAbstract:One-pot conversion of cellulose to n-hexane was carried out over the Ir-ReOx/SiO2 (Re/Ir = 2) catalyst combined with HZSM-5 as cocatalyst in a biphasic reaction system (n-dodecane + H2O). The yield of n-hexane reached 83% from ball-milled cellulose and 78% from microcrystalline cellulose. Even using a high weight ratio of cellulose to water (1:1), a 71% yield of n-hexane could be obtained from ball-milled cellulose. The yield of n-hexane was almost maintained during three repeated tests when the catalyst was calcined again. The transformation of cellulose to n-hexane consists of the hydrolysis of cellulose to glucose via water-soluble oligosaccharides, hydrogenation of glucose to sorbitol, and successive Hydrogenolysis of sorbitol to n-hexane. The Ir-ReOx/SiO2 catalyst promotes a hydrogenation and Hydrogenolysis step. HZSM-5 enhanced the hydrolysis of cellulose in hot water and C–O bond Hydrogenolysis activity of the Ir-ReOx/SiO2 catalyst.
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c o bond Hydrogenolysis of cyclic ethers with oh groups over rhenium modified supported iridium catalysts
Journal of Catalysis, 2012Co-Authors: Kaiyou Chen, Yoshinao Nakagawa, Kazuma Mori, Hideo Watanabe, Keiichi TomishigeAbstract:Hydrogenolysis of tetrahydrofurfuryl alcohol to 1,5-pentanediol and other related substrates such as 3-hydroxytetrahydrofuran and 1,2-cyclohexanediol proceeds over Ir–ReOx/SiO2 catalyst. TOF values are higher than those of Rh–ReOx/SiO2, which has been reported to be an effective catalyst. The selectivity to the product, where the C–O bond neighboring the C–OH group in the substrate is dissociated, is comparable to or higher than that of Rh–ReOx/SiO2. Hydrogenolysis of most substrates except 1,2-cyclohexanediol proceeds via the direct mechanism where hydride species formed from hydrogen molecule attacks the anti-position of C–O bond. In the case of Hydrogenolysis of 1,2-cyclohexanediol where attack of anti-position of C–O bond is unfavorable, indirect mechanism involving dehydrogenation to 2-hydroxycyclohexanone is responsible for the formation of cyclohexanol.
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mechanism of the Hydrogenolysis of ethers over silica supported rhodium catalyst modified with rhenium oxide
Journal of Catalysis, 2011Co-Authors: Shuichi Koso, Yoshinao Nakagawa, Keiichi TomishigeAbstract:Abstract The Rh–ReO x /SiO 2 (Re/Rh = 0.5) exhibited high activity in the Hydrogenolysis of ethers with an OH group. The C O bond neighboring CH 2 OH group was selectively dissociated: The Hydrogenolysis of tetrahydro-5-methyl-2-furfuryl alcohol and 2-isopropoxyethannol gave 1,5-hexanediol and ethanol + isopropanol, respectively. This tendency suggests the regioselective C O dissociation mechanism via anion intermediate formed by the attack of hydride and the subsequent protonation of the anion.
Jeanmarie Basset - One of the best experts on this subject based on the ideXlab platform.
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c h and c c activation of n butane with zirconium hydrides supported on sba15 containing n donor ligands sinh six zrh2 sinh six 2zrh and sin six zrh x nh o a dft study
Organometallics, 2014Co-Authors: F A Pasha, Anissa Bendjeriousedjerari, Kuowei Huang, Jeanmarie BassetAbstract:Density functional theory (DFT) was used to elucidate the mechanism of n-butane Hydrogenolysis (into propane, ethane, and methane) on well-defined zirconium hydrides supported on SBA15 coordinated to the surface via N-donor surface pincer ligands: [(≡SiNH−)(≡SiO−)ZrH2] (A), [(≡SiNH−)2ZrH2] (B), [(≡SiNH−)(≡SiO−)2ZrH] (C), [(≡SiNH−)2(≡SiO−)ZrH] (D), [(≡SiN═)(≡Si–O−)ZrH] (E), and [(≡SiN═)(≡SiNH−)ZrH] (F). The roles of these hydrides have been investigated in C–H/C–C bond activation and cleavage. The dihydride A linked via a chelating [N,O] surface ligand was found to be more active than B, linked to the chelating [N,N] surface ligand. Moreover, the dihydride zirconium complexes are also more active than their corresponding monohydrides C–F. The C–C cleavage step occurs preferentially via β-alkyl transfer, which is the rate-limiting step in the alkane Hydrogenolysis. The energetics of the comparative pathways over the potential energy surface diagram (PES) reveals the Hydrogenolysis of n-butane into propane a...
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efficient Hydrogenolysis of alkanes at low temperature and pressure using tantalum hydride on mcm 41 and a quantum chemical study
Chemcatchem, 2012Co-Authors: Vivek Polshettiwar, F A Pasha, Jean Thivollecazat, A De Mallmann, Sebastien Norsic, Jeanmarie BassetAbstract:Hydrogenolysis of hydrocarbons is of considerable technological importance for applications such as the hydroprocessing of petrochemical feedstocks to generate high-value and useful chemicals and fuels. We studied the catalytic activity of tantalum hydride supported on MCM-41 for the Hydrogenolysis of alkanes at low temperature and low atmospheric pressure in a dynamic reactor. The reactions proceed with good turnover numbers, and the catalyst could be reused for several times, which makes the overall catalytic process sustainable. We derived the plausible mechanism by using DFT calculations and identified the preferred pathways by the analysis of potential energy surface. Our results and the proposed reaction mechanism demonstrate the viability of the “catalyst-by-design” approach.
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Hydrogenolysis of cycloalkanes on a tantalum hydride complex supported on silica and insight into the deactivation pathway by the combined use of 1d solid state nmr and exafs spectroscopies
Chemistry: A European Journal, 2003Co-Authors: Franck Rataboul, Mathieu Chabanas, Aimery De Mallmann, Christophe Coperet, Jean Thivollecazat, Jeanmarie BassetAbstract:Hydrogenolysis of cyclic alkanes is catalysed by [(SiO)2TaH] (1) at 160 °C and leads to lower alkanes and cyclic alkanes including cyclopentane. The turnover number is correlated with the number of carbon atoms of the cyclic alkanes, and therefore while cycloheptane is readily transformed, cyclopentane does not give any product (<1 %). The mechanism of ring contraction probably involves carbene de-insertion as a key carbon–carbon bond-cleavage step. The reluctance of cyclopentane to undergo Hydrogenolysis was further studied: under the reaction conditions cyclopentane reacts with 1 to give the corresponding cyclopentyl derivative [(SiO)2TaC5H9] (13), which evolves towards cyclopentadienyl derivative [(SiO)2Ta(C5H5)] (14) according to both solid-state NMR and EXAFS spectroscopies. This latter complex is inactive in the Hydrogenolysis of alkanes, and therefore the formation of cyclopentane in the Hydrogenolysis of various cyclic alkanes is probably responsible for the de-activation of the catalyst by formation of cyclopentadienyl complexes.
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Hydrogenolysis of cyclohexane over ir sio 2 catalyst a mechanistic study of carbon carbon bond cleavage on metallic surfaces
Journal of the American Chemical Society, 2001Co-Authors: Francois Locatelli, Jeanpierre Candy, Blaise Didillon, Gerald P Niccolai, Denis Uzio, Jeanmarie BassetAbstract:The Hydrogenolysis of cyclohexane catalyzed by supported Ir/SiO(2) has been studied to get mechanistic information on the elementary steps of C--C bond cleavage for cyclic saturated hydrocarbons. The reaction was studied under conditions in which no dehydrogenation to benzene occurs. When a mixture of cyclohexane and H(2) flows over a Ir/SiO(2) catalyst at 200 degrees C and for a H(2)/cyclohexane ratio superior to 40, methane, ethane, propane, n-butane, n-pentane, and n-hexane are identified to be primary products. The Hydrogenolysis of ethane and n-hexane has also been studied to clarify several mechanistic questions. To account for the primary products in the above reactions, a mechanism is proposed in which the key step of the carbon--carbon bond cleavage occurs via concerted electronic transfer in dimetallacyclopentane intermediate. The comparison of product distributions in the Hydrogenolysis of cyclohexane and that observed for n-hexane led to conclusions about the relative ease of carbon--carbon bond cleavage with respect to surface alkyl isomerization.
Yoshinao Nakagawa - One of the best experts on this subject based on the ideXlab platform.
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Selective Hydrogenolysis and hydrogenation using metal catalysts directly modified with metal oxide species
Green Chemistry, 2017Co-Authors: Keiichi Tomishige, Yoshinao Nakagawa, Masazumi TamuraAbstract: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.
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role of re species and acid cocatalyst on ir reox sio2 in the c o Hydrogenolysis of biomass derived substrates
Chemical Record, 2014Co-Authors: Keiichi Tomishige, Masazumi Tamura, Yoshinao NakagawaAbstract:: The catalytic performance of ReOx -modified Ir metal catalyst in the Hydrogenolysis of C-O bonds is strongly dependent on the choice of solvent. The acidic property of the Re species becomes obvious in the alkane solvent, and the Hydrogenolysis reaction proceeds mainly by acid-catalyzed dehydration and the subsequent metal-catalyzed hydrogenation. The acidic property of the Re species is weakened in water; however, the Hydrogenolysis reaction proceeds in water via a direct mechanism involving SN 2-like attack of a hydride species at the interface between Ir and ReOx on the adsorbed Re alkoxide species. This mechanism enabled the selective dissociation of the C-O bond neighboring the CH2 OH group.
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one pot conversion of cellulose into n hexane over the ir reox sio2 catalyst combined with hzsm 5
ACS Sustainable Chemistry & Engineering, 2014Co-Authors: Masazumi Tamura, Yoshinao Nakagawa, Keiichi TomishigeAbstract:One-pot conversion of cellulose to n-hexane was carried out over the Ir-ReOx/SiO2 (Re/Ir = 2) catalyst combined with HZSM-5 as cocatalyst in a biphasic reaction system (n-dodecane + H2O). The yield of n-hexane reached 83% from ball-milled cellulose and 78% from microcrystalline cellulose. Even using a high weight ratio of cellulose to water (1:1), a 71% yield of n-hexane could be obtained from ball-milled cellulose. The yield of n-hexane was almost maintained during three repeated tests when the catalyst was calcined again. The transformation of cellulose to n-hexane consists of the hydrolysis of cellulose to glucose via water-soluble oligosaccharides, hydrogenation of glucose to sorbitol, and successive Hydrogenolysis of sorbitol to n-hexane. The Ir-ReOx/SiO2 catalyst promotes a hydrogenation and Hydrogenolysis step. HZSM-5 enhanced the hydrolysis of cellulose in hot water and C–O bond Hydrogenolysis activity of the Ir-ReOx/SiO2 catalyst.
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c o bond Hydrogenolysis of cyclic ethers with oh groups over rhenium modified supported iridium catalysts
Journal of Catalysis, 2012Co-Authors: Kaiyou Chen, Yoshinao Nakagawa, Kazuma Mori, Hideo Watanabe, Keiichi TomishigeAbstract:Hydrogenolysis of tetrahydrofurfuryl alcohol to 1,5-pentanediol and other related substrates such as 3-hydroxytetrahydrofuran and 1,2-cyclohexanediol proceeds over Ir–ReOx/SiO2 catalyst. TOF values are higher than those of Rh–ReOx/SiO2, which has been reported to be an effective catalyst. The selectivity to the product, where the C–O bond neighboring the C–OH group in the substrate is dissociated, is comparable to or higher than that of Rh–ReOx/SiO2. Hydrogenolysis of most substrates except 1,2-cyclohexanediol proceeds via the direct mechanism where hydride species formed from hydrogen molecule attacks the anti-position of C–O bond. In the case of Hydrogenolysis of 1,2-cyclohexanediol where attack of anti-position of C–O bond is unfavorable, indirect mechanism involving dehydrogenation to 2-hydroxycyclohexanone is responsible for the formation of cyclohexanol.
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mechanism of the Hydrogenolysis of ethers over silica supported rhodium catalyst modified with rhenium oxide
Journal of Catalysis, 2011Co-Authors: Shuichi Koso, Yoshinao Nakagawa, Keiichi TomishigeAbstract:Abstract The Rh–ReO x /SiO 2 (Re/Rh = 0.5) exhibited high activity in the Hydrogenolysis of ethers with an OH group. The C O bond neighboring CH 2 OH group was selectively dissociated: The Hydrogenolysis of tetrahydro-5-methyl-2-furfuryl alcohol and 2-isopropoxyethannol gave 1,5-hexanediol and ethanol + isopropanol, respectively. This tendency suggests the regioselective C O dissociation mechanism via anion intermediate formed by the attack of hydride and the subsequent protonation of the anion.
Shuichi Koso - One of the best experts on this subject based on the ideXlab platform.
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mechanism of the Hydrogenolysis of ethers over silica supported rhodium catalyst modified with rhenium oxide
Journal of Catalysis, 2011Co-Authors: Shuichi Koso, Yoshinao Nakagawa, Keiichi TomishigeAbstract:Abstract The Rh–ReO x /SiO 2 (Re/Rh = 0.5) exhibited high activity in the Hydrogenolysis of ethers with an OH group. The C O bond neighboring CH 2 OH group was selectively dissociated: The Hydrogenolysis of tetrahydro-5-methyl-2-furfuryl alcohol and 2-isopropoxyethannol gave 1,5-hexanediol and ethanol + isopropanol, respectively. This tendency suggests the regioselective C O dissociation mechanism via anion intermediate formed by the attack of hydride and the subsequent protonation of the anion.
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reaction mechanism of the glycerol Hydrogenolysis to 1 3 propanediol over ir reox sio2 catalyst
Applied Catalysis B-environmental, 2011Co-Authors: Yoshinao Nakagawa, Keiichi Tomishige, Shuichi Koso, Takeshi Kubota, Yasushi Amada, Yasunori ShinmiAbstract:Abstract The mechanism of the Hydrogenolysis of glycerol to 1,3-propanediol over Ir–ReO x /SiO 2 catalyst was discussed. We investigated the catalytic performance, structure, reaction kinetics and reactivity trends of various substrates over the catalysts with different amount of Re. The conversion in the glycerol Hydrogenolysis increased with increasing the amount of Re up to Re/Ir = 2, and the high selectivity to 1,3-propanediol (ca. 60%) was almost independent of the Re amount. The average size of Ir metal particle gradually decreased with increasing the amount of Re from XRD and TEM. Characterization results such as CO adsorption, TPR, XANES, EXAFS suggested that Ir metal surface was partially covered with ReO x cluster regardless of the Re amount. The reaction order on H 2 pressure over Ir–ReO x /SiO 2 (Re/Ir = 1) was one, suggesting that one active hydrogen species was produced from one hydrogen molecule. Low reaction order on glycerol concentration represented the strong interaction between glycerol and catalyst surface. This catalyst is also applicable to the selective Hydrogenolysis of the C–O bond neighboring a –CH 2 OH group. These reaction trends and characterization results supported the direct reaction mechanism for the formation of 1,3-propanediol from glycerol via 2,3-dihydroxypropoxide species.
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Hydrogenolysis of 1 2 propanediol for the production of biopropanols from glycerol
Chemsuschem, 2010Co-Authors: Yasushi Amada, Yoshinao Nakagawa, Keiichi Tomishige, Shuichi KosoAbstract:Production of propanols from glycerol, which are known as biopropanols, requires catalysts for the Hydrogenolysis of 1,2-propanediol, which has been easily derived from glycerol. It is found that the Rh/SiO 2 catalysts modified with ReO x species exhibited high activity and selectivity in the Hydrogenolysis of 1,2-propanediol to propanols with low selectivity to degradation products and high stability. The optimized Rh-ReO x/ SiO 2 (Re/Rh = 0.5) catalyst gave high yields of 1-propanol (66%) and propanols (1-propanol + 2-propanol) (85%) in the Hydrogenolysis of 1,2-propanediol. In addition, the catalyst was applicable to the one-pot conversion of glycerol to propanols. The structure of Rh metal particles with attached ReO x clusters is suggested from the catalyst characterization. It is proposed that 1,2-propanediol Hydrogenolysis proceeds by the Hydrogenolysis of the alkoxide species on Re with hydrogen species on the Rh metal surface.
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chemoselective Hydrogenolysis of tetrahydropyran 2 methanol to 1 6 hexanediol over rhenium modified carbon supported rhodium catalysts
Chemcatchem, 2010Co-Authors: Kaiyou Chen, Yoshinao Nakagawa, Keiichi Tomishige, Shuichi Koso, Takeshi KubotaAbstract:Modification of Rh/C with Re species enabled chemoselective Hydrogenolysis of tetrahydropyran-2-methanol to 1,6-hexanediol. In particular, the Rh–ReOx/C (Re/Rh ratio=0.25) catalyst gave a high yield of 1,6-hexanediol (84 %) and showed a very low activity for overHydrogenolysis to 1-hexanol. Using the same catalyst in the Hydrogenolysis of tetrahydrofurfuryl alcohol also gave a high yield of 1,5-pentanediol (94 %). Characterization results indicate the formation of ReOxclusters attached on the surface of Rh metal particles. This can cause the synergy between ReOxand Rh, and the tetrahydropyran-2-methanol Hydrogenolysis proceeds on the interface between Rh metal surface and attached ReOxspecies.
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promoting effect of mo on the Hydrogenolysis of tetrahydrofurfuryl alcohol to 1 5 pentanediol over rh sio2
Journal of Catalysis, 2009Co-Authors: Shuichi Koso, Naoyuki Ueda, Yasunori Shinmi, Kazu Okumura, Tokushi Kizuka, Keiichi TomishigeAbstract:Abstract Addition of Mo to Rh/SiO2 promoted the Hydrogenolysis of tetrahydrofurfuryl alcohol to 1,5-pentanediol drastically. Addition of Re and W to Rh/SiO2 was also effective, but the promoting effect of Mo was more remarkable in terms of catalyst stability and high activity even at low reactant concentrations. Characterization of Rh–MoOx/SiO2 suggests that a partially reduced Mo species is attached to the surface of Rh metal particles. The synergy between the MoOx and the Rh metal surface results in a high chemoselectivity and activity in the Hydrogenolysis of tetrahydrofurfuryl alcohol.
Shuai Wang - One of the best experts on this subject based on the ideXlab platform.
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selective Hydrogenolysis of glycerol to propylene glycol on cu zno composite catalysts structural requirements and reaction mechanism
Chemistry-an Asian Journal, 2010Co-Authors: Shuai Wang, Yichi ZhangAbstract:: Cu-ZnO catalysts were prepared by homogeneous coprecipitation with varying Cu/Zn atomic ratios (0.4-2:1). The catalysts were examined in selective Hydrogenolysis of glycerol to propylene glycol. Although propylene glycol selectivities remained essentially constant (over 93%) on the different Cu-ZnO catalysts, the turnover frequencies changed markedly with the Cu/Zn ratio, and reached the greatest value at the ratio of 1:1. Such activity dependence on the Cu/Zn ratio was in parallel with the change in the interaction between Cu and ZnO and in the Cu microstrain, as a consequence of the effects on the crystalline phases of hydroxycarbonate precursors for the Cu-ZnO catalysts, reflecting the structural requirements for glycerol Hydrogenolysis. The Hydrogenolysis mechanism was also examined and apparently involves kinetically relevant glycerol dehydrogenation to glyceraldehyde on Cu-ZnO and subsequent glyceraldehyde dehydration and hydrogenation to propylene glycol. The mechanism is consistent with the observed superior activities of the more strained Cu particles, and the higher propylene glycol selectivities obtained at higher glycerol and hydrogen concentrations. These findings provide a rationale for the design of more effective Cu-based catalysts in selective Hydrogenolysis of glycerol and other biomass-derived polyols, for example, by synthesis of highly strained Cu particles strongly interacting with ZnO or other oxide supports.
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selective Hydrogenolysis of glycerol to propylene glycol on cu zno catalysts
Catalysis Letters, 2007Co-Authors: Shuai WangAbstract:Hydrogenolysis of biomass-derived glycerol is an alternative route to sustainable production of propylene glycol. Cu–ZnO catalysts were prepared by coprecipitation with a range of Cu/Zn atomic ratio (0.6–2.0) and examined in glycerol Hydrogenolysis to propylene glycol at 453–513 K and 4.2 MPa H2. These catalysts possess acid and hydrogenation sites required for bifunctional glycerol reaction pathways, most likely involving glycerol dehydration to acetol and glycidol intermediates on acidic ZnO surfaces, and their subsequent hydrogenation on Cu surfaces. Glycerol Hydrogenolysis conversions and selectivities depend on Cu and ZnO particle sizes. Smaller ZnO and Cu domains led to higher conversions and propylene glycol selectivities, respectively. A high propylene glycol selectivity (83.6%), with a 94.3% combined selectivity to propylene glycol and ethylene glycol (also a valuable product) was achieved at 22.5% glycerol conversion at 473 K on Cu–ZnO (Cu/Zn = 1.0) with relatively small Cu particles. Reaction temperature effects showed that optimal temperatures (e.g. 493 K) are required for high propylene glycol selectivities, probably as a result of optimized adsorption and transformation of the reaction intermediates on the catalyst surfaces. These preliminary results provide guidance for the synthesis of more efficient Cu–ZnO catalysts and for the optimization of reaction parameters for selective glycerol Hydrogenolysis to produce propylene glycol.
