佐藤 智司

© 2020 Elsevier B.V. Vapor-phase hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) was investigated over Al2O3-supported bimetallic Cu-Co catalysts with different Cu/Co weight ratios under ambient H2 pressure. The bimetallic Cu-Co/Al2O3 catalyst with a Cu/Co weight ratio of 8/12 exhibits an excellent catalytic activity and stability: it showed a high GVL productivity of 5.46 kg kgcat.−1 h−1 with a GVL selectivity higher than 99% at 250 °C for 24 h. In the characterization of the catalysts, powder X-ray diffraction suggests that bimetallic Cu-Co particles on the Cu-Co/Al2O3 catalysts are composed of an alloy.

© 2019 Elsevier B.V. Vapor-phase dehydration of 1,3-butanediol was performed over Yb2O3-ZrO2 catalysts in an ambient nitrogen atmosphere. Catalysts were prepared by a hydrothermal (HT) method as well as a coprecipitation method. The Yb2O3-ZrO2 sample prepared by HT was confirmed to be crystallites of oxygen-defected type cubic Yb2Zr2O7, while the as-prepared coprecipitation sample was amorphous. The HT samples had high specific surface areas as ca. 40 m2 g−1 even after calcined at temperatures higher than 800 °C, whereas the coprecipitation samples without HT was readily sintered at the high temperatures. The best catalytic performance was obtained over HT Yb2O3-ZrO2 catalyst calcined at 900 °C: the total selectivity to unsaturated alcohols was higher than 95% at a 1,3-butanediol conversion of 82% at 325 °C. The structure of active sites and the reaction mechanism of the dehydration of 1,3-butanediol were discussed. We proposed that an oxygen defect site on the stable (111) face of cubic Yb2Zr2O7 would provide an active site, and that Zr4+, Yb3+, and O2- exposed on the defect could coordinate with a 1,3-butanediol molecule to form a tridentate coordination structure, which possibly initiate the dehydration to produce unsaturated alcohols through a base-acid concerted mechanism.

© 2019 Elsevier B.V. Vapor-phase dehydrogenation of 1-decanol to form decanal was performed over various supported Cu catalysts such as Cu/SiO2, Cu/ZnO, and Cu/Al2O3. Among the catalysts tested in this work, Cu/SiO2 showed a high and stable catalytic activity for the conversion of 1-decanol to form decanal, and 77.4% conversion of 1-decanol with 98.4% selectivity to decanal was achieved over Cu/SiO2 catalyst in N2 flow at 275 °C. The physical properties of SiO2 support affected the catalytic activity, and the SiO2 with a surface area of 451 m2 g−1 and an averaged pore size of 6 nm was preferable for the formation of decanal. The catalytic reaction was regulated by equilibrium: the pressure equilibrium constant, Kp, was estimated to be 0.30 atm at 275 °C. The deactivation of the catalyst was observed in N2 flow at 325 °C, while it was not observed in H2. The activity of the deactivated catalyst was completely recovered in N2 at 275 °C after calcination in air at 400 °C followed by H2 reduction. Based on the DRIFT and TG analyses, hydrocarbon species were accumulated on the catalyst surface in the initial period of the reaction. In addition, it was found that the dehydrogenation of the hydrocarbon species accumulated on the catalyst mainly caused the catalytic deactivation.

© 2019 Elsevier B.V. Vapor-phase catalytic dehydration of butanediols (BDOs) such as 1,3-, 1,4-, and 2,3-butanediol was investigated over yttria-stabilized tetragonal zirconia (YSZ) catalysts as well as monoclinic zirconia (MZ). BDOs were converted to unsaturated alcohols with some by-products over YSZ and MZ. YSZ is superior to MZ for these reactions in a view point of selective formation of unsaturated alcohols. Calcination temperature of YSZ significantly affected the products selectivity as well as the conversion of BDOs: high selectivity to unsaturated alcohols was obtained over the YSZ calcined at high temperatures over 800 °C. In the conversion of 1,4-butanediol at 325 °C, the highest 3-buten-1-ol selectivity of 75.3% was obtained over the YSZ calcined at 1050 °C, whereas 2,3-butanediol was less reactive than the other BDOs. In the dehydration of 1,3-butanediol at 325 °C, in particular, it was found that a YSZ catalyst with a Y 2 O 3 content of 3.2 wt.% exhibited an excellent stable catalytic activity: the highest selectivity to unsaturated alcohols such as 2-buten-1-ol and 3-buten-2-ol over 98% was obtained at a conversion of 66%. Structures of active sites for the dehydration of 1,3-butanediol were discussed using a crystal model of tetragonal ZrO 2 and a probable model structure of active site was proposed. The well-crystalized YSZ inevitably has oxygen defect sites on the most stable surface of tetragonal ZrO 2 (101). The defect site, which exposes three cations such as Zr 4+ and Y 3+ , is surrounded by six O 2− anions. The selective dehydration of 1,3-butanediol to produce 3-buten-2-ol over the YSZ could be explained by tridentate interactions followed by sequential dehydration: the position-2 hydrogen is firstly abstracted by a basic O 2− anion and then the position-1 hydroxyl group is subsequently or simultaneously abstracted by an acidic Y 3+ cation. Another OH group at position 3 plays an important role of anchoring 1,3-butanediol to the catalyst surface. Thus, the selective dehydration of 1,3-butanediol could proceed via the speculative base-acid-concerted mechanism.

© 2019 Elsevier B.V. Vapor-phase isomerization of 3-pentenal to 2-pentenal was performed over various oxide catalysts. An amorphous SiO2 catalyst with a weak acidity and medium mesopore size showed a conversion over 82% with 2-pentenal selectivity higher than 95% at 250 °C. Several characterizations, such as thermogravimetric analysis, diffuse reflectance infrared Fourier-transform, temperature-programmed desorption of adsorbed NH3, and isotope experiment using deuterated SiO2, were performed to investigate the active sites on SiO2. A SiO2 with a specific pore size showed a stable catalytic activity after a rapid decrease at the initial stage of the reaction. The isomerization of 3-pentenal to 2-pentenal was found to be an equilibrium reaction: the pressure equilibrium constant was estimated to be ca. 5 at 250 °C. The weak acidic silanol groups on SiO2 were proved to be the active sites for the isomerization of 3-pentenal to 2-pentenal. A possible reaction mechanism was proposed: hydrogen of the silanol groups on SiO2 was coordinated to 2-pentenal with a form of six-membered ring, which can explain the primary product of cis isomer.

© 2018 Elsevier Ltd Isotropic pitch-based carbon fiber has been utilized for various applications such as thermal insulation materials for high-temperature furnace and additives for slide member, but the structure of the carbon fiber is still under debate. This is because the precursor pitch contains various aromatic compounds in addition to the complicated oxidation and carbonization reaction during production process of carbon fiber. In this work, oxidation processes of model compounds of pitch such as pyrene (sp2C–H with zigzag-like edges), triphenylene (sp2C–H with armchair edges), fluorene (pentagon with sp3CH2), and 9-methylanthracene (hexagon with sp3CH3) were analyzed using mass spectrometry, elemental analysis, infrared (IR), Raman, and X-ray photoelectron spectroscopy (XPS) in addition to calculation such as molecular dynamic simulation with a reactive force field (ReaxFF) and simulation of IR, Raman, and XPS spectra (Gaussian09). Combination of calculations and experiments revealed that oxidation proceeded in the order of zigzag-like edges > sp3CH3 > sp2CH2 > armchair edges, and the quinone formed by oxidation worked as a precursor for a crosslinking reaction. It is expected that the results of this work, which revealed the origin of the crosslinking, could lead to improve properties as well as to estimate the detailed structures of isotropic pitch-based carbon fiber.

© 2018 Vapor-phase aldol condensation of butanal to form 2-ethyl-2-hexenal was carried out over several oxide catalysts such as SiO2-Al2O3, Al2O3, ZrO2, and SiO2. Catalysts with moderate and strong acid sites such as Al2O3 and SiO2-Al2O3 were active for the reaction in the initial period, whereas they deactivated rapidly. In contrast, SiO2 with weak acidity showed a low but a stable catalytic activity for the formation of 2-ethyl-2-hexenal. Thermogravimetric analyses of the samples used after the reactions indicate that SiO2 has the smallest amount of carbonaceous species that contributed to its stable activity among the tested catalysts. SiO2 catalysts with different pore sizes and specific surface areas were examined: SiO2 with a mean pore diameter of 10 nm and a surface area of 295 m2 g−1 showed the best catalytic performance and gave a 2-ethyl-2-hexenal selectivity of 90% at a conversion of 48% at 240 °C. In the catalytic test using deuterated SiO2, which was prepared by contacting SiO2 with deuterated water before the reaction, it was confirmed by a mass spectrometer that the deuterium atom of SiOD was transferred to a 2-ethyl-2-hexenal molecule during the reaction. It is indicated that silanol groups on the SiO2 surface played a role as an active site.

Copyright © 2018 American Chemical Society. Carbon materials such as graphene and graphene nanoribbon with zigzag and armchair edges have attracted much attention because of various applications such as electronics, batteries, adsorbents, and catalyst supports. Preparation of carbon materials with different edge structures at a large scale is essential for the future of carbon materials, but it is generally difficult and expensive because of the necessity of organic synthesis on metal substrates. This work demonstrated a simple preparation method of carbon materials with zigzag and armchair edges with/without nonmetallic silica supports from aromatic compounds such as tetracene with zigzag edges and chrysene with armchair edges and also determined the edge structures in detail by three types of analyses such as (1) reactive molecular dynamic simulation with a reactive force field, (2) Raman and infrared (IR) spectra combined with calculation of spectra, and (3) reactivity analyzed by oxidative gasification using thermogravimetric analysis. Two different types of carbon materials with characteristic Raman and IR spectra could be prepared. These carbon materials with different edge structures also clearly showed different tendency in oxidative gasification. This work did not only show the simple preparation method of carbon materials with different edge structures, but also contributes to the development of detailed analyses for carbon materials.

© Copyright 2018 American Chemical Society. Edge structures of carbon materials such as zigzag and armchair edges are known to affect their chemical and electronic properties. Although infrared spectroscopy (IR) has been known to be capable of identifying such edge structures, quantitative analysis using IR spectra has been conducted using only out-of-plane sp2C-H bending vibration, and the estimation of the percentage of edges is still challenging. In this work, a novel two-dimensional method to quantify edge structures of carbon materials with and without pentagons was developed by analyzing both out-of-plane sp2C-H bending and in-plane sp2C-H stretching vibration. Calibration factors of sp2C-H on each type of edge were obtained from experimental and simulated IR spectra of various reference compounds. Using the calibration factors, the edge structures of carbonized aromatic compounds with zigzag edges such as tetracene, armchair edges such as chrysene, and zigzag-like edges such as coronene were estimated quantitatively. From tetracene carbonized at 893 K, chrysene carbonized at 933 K, and coronene carbonized at 873 K, carbon materials with 20% of zigzag edges, 38% of armchair edges, and 67% of others edges were prepared, respectively. This method can be utilized as a quantitative analysis to determine edge structures of various carbon materials prepared below 933 K at the lowest.

© 2018 Elsevier B.V. Vapor-phase dehydration of 1,4-butanediol and 3-buten-1-ol to produce 1,3-butadiene was investigated over rare earth oxides such as Lu2O3, Yb2O3, Tm2O3, Er2O3, and Sc1.0Yb1.0O3. In the dehydration of 3-buten-1-ol, heavy rare earth oxides such as Lu2O3, Yb2O3, and Er2O3 showed high catalytic performance for the selective formation of 1,3-butadiene with producing small amount of propylene whereas acidic catalysts such as alumina decomposed 3-buten-1-ol into propylene. In particular, over Yb2O3 calcined at 800 °C, 3-buten-1-ol was converted with a yield of 1,3-butadiene higher than 95% at 340 °C. In the dehydration of 1,4-butanediol, furthermore, we developed an efficient catalytic system: 1,3-butadiene was produced via an intermediate, 3-buten-1-ol, over Yb2O3 with an excellent yield of 96% at 360 °C and a high contact time of 2.26 h. Yb2O3 successfully inhibited the major side reaction such as decomposition of 3-buten-1-ol to propylene and provided the selective production of 1,3-butadiene from 1,4-butanediol.

© 2018 Elsevier B.V. Cu-Ni/SiO2 catalyst was developed by impregnation assisted with citric acid for the vapor-phase hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL). The prepared catalysts were characterized by using X-ray powder diffraction (XRD), transmission electron microscope (TEM), temperature-programed reduction, thermogravimetry analysis, and X-ray fluorescence analysis. The XRD analysis and the TEM observation of the catalyst samples indicate that the usage of citric acid in the preparation process of impregnation improved the dispersion of Cu and Ni metal on SiO2. A Cu-Ni/SiO2 catalyst with Cu loading of 4 wt.% and Ni of 16 wt.% showed the best performance in the hydrogenation of LA to GVL under ambient H2 pressure at a high weight hourly space velocity (WHSV) of 13.2 h−1 and 250 °C: the conversion was 98.2% and the GVL selectivity was 97.6%. The catalyst prepared by citric acid-assisted impregnation showed the resistance to catalyst deactivation.

© 2018 Elsevier B.V. Vapor phase dehydration of 5-amino-1-pentanol to produce piperidine was investigated over various oxide catalysts such as ZrO2, TiO2, Al2O3 and SiO2. Among the tested catalysts, SiO2 selectively produced piperidine at 300 °C. A high 5-amino-1-pentanol conversion of 99.9% with a piperidine selectivity of 94.8% was achieved over weak acidic SiO2. In an experiment using isotope such as deuterated water, surface hydroxy groups of SiO2 are concluded to be the active centers.

Edges of carbon materials have been known to work as active sites for various applications such as catalysts, adsorbent, and electrodes, but selecting precursors for carbon materials with controlled edges in the absence of metallic substrate is challenging. This work developed a method to select the superior precursors instantaneously using molecular dynamic simulation. This simulation predicted that hydrogen in precursors gasified and the hydrogen attacked the active sites in precursors upon carbonization, causing the decrement of active sites. Thus, it is essential to reduce the concentration of hydrogen in precursors and it is also necessary to introduce reactive functional groups near the active site to protect the active sites. We indeed synthesized the selected precursors such as diethynyl anthracene, diethynyl chrysene, divinyl naphthyridine, and divinyl phenanthroline and proved that edges in those precursors were maintained even after carbonization at 773 K using diffuse reflectance infrared Fourier transform and X-ray photoelectron spectroscopy with the aid of spectra simulated by density functional theory calculation. Especially, ca. 100% of edge structures of zigzag edges and armchair edges in diethynyl anthracene and diethynyl chrysene was maintained even after carbonization at 773 K.

Vapor-phase catalytic dehydration of 1,5-pentanediol (1,5-PDO) was investigated over monoclinic ZrO2 catalysts modified with basic oxides. An unsaturated alcohol, 4-penten-1-ol (4P1OL), was produced together with the formation of tetrahydropyran, delta-valerolactone, 1,4-pentadiene, pentanal, 1-pentanol, and 5-hydroxypentanal, etc. Among the modified ZrO2 catalysts, only ZrO2 modified with MgO enhanced the selectivity to 4P1OL efficiently. The most active modified catalyst was found to have 20 mol% MgO and a calcination at 800 degrees C (MgO/ ZrO2), and the selectivity of 4P1OL exceeded 83% at 400 degrees C. A pulse adsorption measurement of several chemicals clarified adsorptive interaction between a reactant and a catalyst at 220 degrees C: the interaction between 1,5-PDO and MgO/ZrO2 was stronger than the other adsorbates and catalysts. Another strong adsorptive interaction between 1,4-butanediol and CaO/ZrO2, which Was effective in the dehydration of 1,4-butanediol to produce 3-buten-1-ol, was also observed.

Vapor-phase hydrogenation of levulinic acid (LA) and methyl levulinate (ML) to gamma-valerolactone (GVL) was performed over non-noble metal-based catalysts such as Cu/Al2O3, Ni/SiO2 and Co/SiO2. The catalytic activity and stability of the Cu-, Ni- and Co-based catalysts for the formation of GVL from ML and LA were investigated and compared at a low contact time of 0.3 h. In the hydrogenation of ML to GVL, the order of the catalytic activity for the conversion of ML was Cu/Al2O3 > Co/SiO2 > Ni/SiO2. Cu/Al2O3 was the most selective for the formation of GVL, whereas it was unstable in contrast to the other catalysts. In the hydrogenation of LA to GVL, the order of the catalytic activity for the conversion of LA was Ni/SiO2 > Cu/Al2O3 > Co/SiO2, which is the same as the order of the catalyst stability, while Cu/Al2O3 was the most selective for the formation of GVL from LA. The reactions were also performed in N-2 atmosphere in order to study the reaction pathways. Methyl 4-hydroxypentanoate was supposed to be the intermediate in the hydrogenation of ML to GVL, whereas the reaction pathways in the hydrogenation of LA to GVL were dependent on the catalyst species. Based on the TG analysis of the used catalysts, it was found that LA led to more severe catalyst deactivation than ML did. (C) 2017 Elsevier B.V. All rights reserved.

Vapor-phase catalytic production of 2,3-butanediol from acetoin and diacetyl was investigated over the supported metal catalysts such as Ni, Co, Cu, and Ag. A yield of 2,3-butanediol higher than 90% can be obtained from both acetoin and diacetyl over Ni/SiO2 catalyst in an 152 flow at 150 degrees C. Since the hydrogenation is an exothermic reaction, a low temperature is favorable to gain a full production of 2,3-butanediol. It was found that the equilibrium among 2,3-butanediol, acetoin, and diacetyl could be achieved at a contact time of the reactants with catalyst longer than 1.67 h. The pressure equilibrium constants in the hydrogenation were calculated by the outlet gas composition.

Vapor-phase hydrogenation of levulinic acid (LA) to gamma-valerolactone (GVL) was performed over SiO2-supported Cu-Ni bimetallic catalysts with different Cu/Ni weight ratios under ambient H-2 pressure. Characterization of the catalysts was carried out using powder X-ray diffraction, temperature-programmed reduction and thermogravimetric analysis. In contrast to the monometallic catalysts i.e. Ni/SiO2 and Cu/SiO2, the Cu-Ni/SiO2 bimetallic catalyst with a Cu/Ni weight ratio of 6/14 exhibits an excellent catalytic activity, and gave a GVL yield higher than 99% with a productivity of 1.64 kg(GvL) kg(cat.)(-1)h(-1) at 250 degrees C and at a high WHSV of 1.65 h(-1) for 50 h.

Hydrogenation of gamma-valerolactone to 1,4-pentanediol was performed over both precious and base metal catalysts in a continuous flow reactor under H-2 pressure. Cu/ZnO catalyst showed the highest catalytic performance for the formation of 1,4-pentanediol from gamma-valerolactone. Low reaction temperatures such as 140 degrees C were preferable for achieving 1,4-pentanediol, and high temperatures led to the further conversion of 1,4-pentanediol to 2-methyltetrahydrofuran and 1-pentanol. High H-2 pressures and moderate H-2 flow rates such as 90 cm(3) min(-1) were effective for the formation of 1,4-pentanediol. Calcination temperature of Cu/ZnO significantly affected its catalytic activity. A Cu/ZnO catalyst with a Cu metal loading of 40 wt.% gave the gamma-valerolactone conversion of 82.3% with the 1,4-pentanediol selectivity of 99.2% at 140 degrees C under 1.5 MPa of H-2 pressure, while no decrease in the catalytic activity was observed for 10 h.

Vapor-phase catalytic dehydration of 1,4-butanediol (1,4-BDO) was investigated over modified ZrO2 catalysts. In the dehydration of 1,4-BDO over monoclinic ZrO2 (m-ZrO2), an unsaturated alcohol, 3-buten-1-ol (3B1OL), was produced together with tetrahydrofuranand-gamma-butyrolactone. Among alkaline earth metal oxide modifiers, CaO with an appropriate content significantly enhanced the 3B1OL selectivity of m-ZrO2. The modification of CaO was more efficient over m-ZrO2 than tetragonal ZrO2. CO2-TPD measurements reveal that CaO supported on m-ZrO2 calcined at 800 degrees C or higher generated new basic sites, which are attributed from Ca-O-Zr hetero-linkages, for the effective formation of 3B1OL from 1,4-BDO. In order to create more Ca-O-Zr hetero-linkages on the m-ZrO2 surface efficiently, additional ZrO2 was loaded on m-ZrO2 together with CaO via a co-impregnation method. At an appropriate weight ratio of CaO/ZrO2 = 7/2 loaded on m-ZrO2, both the 1,4-BDO conversion and the 3B1OL selectivity were enhanced greatly. Especially, the 3B1OL selectivity exceeded 90% at 350 degrees C. (C) 2017 Elsevier B.V. All rights reserved.

Vapor-phase intramolecular aldol condensation of 2,5-hexanedione to produce 3-methylcyclopent-2-enone was performed over several ZrO2-supported alkali and alkali earth metal oxides. Among the tested catalysts, ZrO2 supported Li2O showed a stable catalytic activity. A high 2,5-hexanedione conversion of 99% with a 3methylcyclopent-2-enone selectivity of 96% was achieved over a 20 mol% Li2O-loaded ZrO2 catalyst at 250 degrees C. (C) 2017 Elsevier B.V. All rights reserved.

Vapor-phase dehydration of C4 unsaturated alcohols such as 3-buten-l-ol, 2-buten-1-ol and 3-buten-2-ol were performed to produce 1,3-butadiene over various solid catalysts including ordinary solid acid catalysts such as Al2O3, SiO2-Al2O3, and TiO2 and basic rare earth metal oxides such as Yb2O3 and CeO2. In the reaction of 3-buten-1-ol, 1,3-butadiene could not be selectively produced because the acid catalysts decomposed 3-buten-1-ol into propylene. In contrast to the acid catalysts, CeO2 inhibited the decomposition of 3-buten-1-ol and showed a relatively high performance for the formation of 1,3-butadiene. In the dehydration of 2-buten-1-ol and 3-buten-2-ol, however, acid catalysts were effective for the formation of 1,3-butadiene. Among the tested catalysts, commercial SiO2-Al2O3 showed a relatively high catalytic performance, although it deactivated rapidly. We prepared a series of SiO2/Al2O3 catalysts by depositing SiO2 species onto Al2O3 support, and the SiO2/Al2O3 with a SiO2 content of 10 wt.% showed more stable catalytic activity than the commercial SiO2-Al2O3. Furthermore, modification of SiO2/Al2O3 with Ag at a loading of 3-5 wt.% was found to be efficient for inhibiting the coke formation and improving the catalytic stability of SiO2/Al2O3 in the dehydration of both 2-buten-1-ol and 3-buten-2-ol under hydrogen flow conditions. (C) 2016 Elsevier B.V. All rights reserved.

Vapor-phase catalytic dehydration of 2,3-butanediol (2,3-BDO) to produce 3-buten-2-ol (3B2OL) was investigated over several monoclinic ZrO2 (m-ZrO2) catalysts modified with alkaline earth metal oxides (MOs), such as SrO, BaO, and MgO, to compare with the previously reported CaO/m-ZrO2. It was found that these modifiers enhanced the 3B2OL formation to the same level as CaO did by loading an appropriate MO content. Among all the tested catalysts, the BaO/m-ZrO2 calcined at 800 degrees C with a low BaO content (molar ratio of BaO/ZrO2 = 0.0452) shows the highest 2,3-BDO conversion (72.4%) and 3B2OL selectivity (74.4%) in the initial stage of 5 hat 350 degrees C. In order to characterize those catalysts, their catalytic activities, crystal structures, and basic properties were studied in detail. In X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) experiment, it was elucidated that highly dispersed M-O-Zr (M = Ca, Sr, and Ba) hetero-linkages were formed on the surface by loading these MOs onto m-ZrO2 with an appropriate content and then calcining at 800 degrees C. It can be concluded that the M-O-Zr hetero-linkages generate the proper base-acid balance for the efficient formation of 3B2OL from 2,3-BDO. (C) 2016 Elsevier B.V. All rights reserved.

Nitrogen-doped carbon materials such as graphene and activated carbon have been studied as solid base catalysts. However, active sites of carbon catalysts have long been ambiguous because of the presence of various functional groups. This work clarified the dependence of positions of nitrogen atoms in aromatic hydrocarbons on catalytic activities of well-known Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate to produce ethyl cyanocinnamate (ECC) as one of the examples for catalytic reactions. Catalytic activities of 30 kinds of aromatic hydrocarbons composed of one, two, and three aromatic rings with zero, one, two, and three nitrogen atoms were compared. Phenazine with zigzag edges and pyridinium ion with quaternary nitrogen showed low catalytic activities. On the other hand, 1,10-phenanthroline with armchair edges showed a high ECC selectivity of 99.3% and a high ECC yield of 59.0%. Among various aromatic hydrocarbons carbonized on silica, 1,10-phenanthroline carbonized at 923 K exhibited the highest ECC selectivity of 89.5% and the highest ECC yield of 10.2% because of the highest percentage of 1,10-phenanthroline-like N after carbonization. We believe that this work can serve as a perfect example to examine the performance of carbon catalysts at a molecular level in the future. (C) 2016 Elsevier Ltd. All rights reserved.

Selective doping of nitrogen into carbon materials in the absence of catalysts is a key for various applications of carbon materials. It is well known that most nitrogen-containing raw materials generate unnecessary functional groups during carbonization. Many researchers have noticed the significance of the selective nitrogen doping, whereas only a few works have reported the selective doping. In addition, those few works used catalysts to synthesize nitrogen-doped carbon materials, but the presence of catalysts limits the applications of nitrogen-doped carbon materials. This study found an unusual aromatic compound, imidazo[1,2-a]pyridine (IP), which maintained 88 % of the functional groups of as-received IP even after carbonization at 673 K in the absence of catalysts, and the functional groups were further maintained up to 773 K. The percentage of remaining functional groups was revealed using our state-of-the-art techniques of simulated X-ray photoelectron spectroscopy and Raman spectroscopy combined with transition state calculation using density functional theory. The low carbonization temperature as well as selective doping of nitrogen was achieved because of the low activation energy of dehydrogenation reaction among IP molecules compared to the high activation energy of radical formation for scission of C-N bonding.

Vapor-phase lactonization of levulinic acid to produce angelica lactones, which include alpha-, beta- and gamma-form isomers, was performed in fixed-bed down-flow glass reactors over various oxide catalysts. SiO2 and SiO2-Al2O3 showed relatively high catalytic activity. The lactonization of levulinic acid to angelica lactones was found to be an endothermic equilibrium reaction, and the pressure equilibrium constant was calculated to be 0.2 atm at 275 degrees C. High temperatures and reduced pressures were effective for shifting the equilibrium from levulinic acid to angelica lactones, while the suitable reaction temperature was estimated to be 275 degrees C because temperatures higher than 275 degrees C decreased the selectivity to angelica lactones. The highest angelica lactones yield of 87.5% was achieved at a levulinic acid conversion of 95.3% over SiO2 under reduced pressure conditions of ca. 5 kPa at 275 degrees C. IR, NH3-TPD and TG analyses were performed for characterizing the catalysts used after the reactions together with a silylated SiO2 prepared for studying the active species on SiO2. The silanol groups of SiO2 with weak acidity were proposed to be the active species. (C) 2016 Elsevier B.V. All rights reserved.

Vapor-phase dehydration of several 1,2-alkanediols, such as 1,2-ethanediol, 1,2-propanediol, 1,2-butanediol and 1,2-pentanediol, to produce corresponding aldehydes was investigated over silica-supported WO3 catalyst, which was prepared by impregnation method and then calcined at 320 degrees C. Higher than 90% yield of aldehydes could be achieved over WO3/SiO2 catalyst at 250 degrees C with a feed of 20% aqueous 1,2-alkanediol solution. Both Bronsted and Lewis acid sites exist on WO3/SiO2 catalyst, while Bronsted acid sites are proposed to be the active species for the formation of aldehyde. High concentrations of H2O were effective for inhibiting the intermolecular reaction and improving the selectivity to aldehydes. The dehydration of different 1,2-alkanediols was compared under different reaction conditions. The reactivity of 1,2-ethanediol was low and the product distribution was several comparing with those of the other 1,2-alkanediols. Cyclic acetal, which was generated by the cyclodehydration of the produced aldehyde with another 1,2-alkanediol, was a main by-product, and the formation of acetal was affected by both the temperature and the carbon-chain length of the 1,2-alkanediols. (C) 2016 Elsevier B.V. All rights reserved.

Vapor-phase self-aldol condensation of butanal was performed over various solid catalysts. Among the tested catalysts, SiO2-Al2O3, Nb2O5 and TiO2 showed relatively high catalytic activity for the formation of aldol condensation product, 2-ethyl-2-hexenal, whereas all the catalysts deactivated rapidly. In order to stabilize the catalytic activity, metal-modified catalysts were investigated in hydrogen flow, and it was found that Ag-modified TiO2 showed the best catalytic performance. Characterizations such as XRD, TPD, TPR, TG-DTA, and DRIFT were performed for investigating the effect of the additive Ag and analyzing the coke component. The loaded Ag metal inhibited the formation of carbon accumulated on catalyst surface, and H-2 carrier gas was indispensable in the inhibition. Ag would work as a remover of the products on the catalyst surface together with H-2 to prevent dehydrogenation followed by coke formation. Self-aldol condensation of butanal was stabilized over Ag-modified TiO2 at Ag2O loadings higher than 3 wt.% at 220 degrees C in H-2 flow. TiO2 with Ag2O of 5 wt.% showed the best catalytic performance and gave a 72.2% selectivity to 2-ethyl-2-hexenal at 72.1% conversion in H-2 flow at 220 degrees C. (C) 2016 Elsevier B.V. All rights reserved.

X-ray photoelectron spectroscopy (XPS) is among the most powerful techniques to analyze defective structures of carbon materials such as grapheme and activated carbon. However, reported assignments of defects, especially sp(3)C and sp(2)C, are questionable. Most reports assign sp(3)C peaks to be higher than sp(2)C peaks, whereas a few reports assign sp(3)C peaks to be lower than sp(2)C peaks. Our group previously reported that calculated binding energies of sp(3)C were basically lower than those of sp(2)C. This work clarified that one of the reasons for the prevailing ambiguous assignments of sp(3)C peaks is charging effects of diamond.

A vapor-phase dehydration of acetaldoxime to acetonitrile was investigated over various solid catalysts. Among the tested catalysts, ZrO2, Al2O3 and SiO2 showed high catalytic activity for the formation of acetonitrile from acetaldoxime, while the correlation between catalytic activity and the acid property of the catalysts was not observed. Weak acidic sites such as silanols sufficiently work as catalytic sites for the dehydration, which does not require strong acids such as zeolites. Several SiO2 catalysts with different physical properties were tested, and the SiO2 with the smallest pore size and the highest specific surface area showed the highest catalytic activity for the formation of acetonitrile. Because the dehydration of acetaldoxime to acetonitrile is exothermic, a large amount of reaction heat was generated during the reaction, and the reaction temperature was found to be significantly affected by the feed rate of the reactant and the flow rate of the carrier gas. In order to effectively utilize the in situ generated reaction heat, the dehydration of acetaldoxime to acetonitrile without using the external heat supply was conducted. The temperature was controllable even in the absence of the external heat, and the acetonitrile yield higher than 90% could be achieved in such a green operation under the environment-friendly adiabatic conditions.

Vapor-phase catalytic dehydration of 5-amino-1-pentanol was investigated over various oxide catalysts including rare earth oxides (REOs). Over ordinary acidic oxides such as Al2O3, SiO2, SiO2-Al2O3, TiO2, and ZrO2, a cyclic amine such as piperidine was mainly produced at temperatures of 300 degrees C and higher. In contrast, basic REOs with a cubic bixbyite structure showed the catalytic activity in the conversion of 5-amino-1-pentanol to produce 4-penten-1-amine at 425 degrees C. In REO catalysts, Tm2O3, Yb2O3, and Lu2O3 showed the high conversion of 5-amino-1-pentanol and the high selectivity to 4-penten-1-amine. Especially, Yb2O3 calcined at 800 degrees C showed a high formation rate of 4-penten-1-amine with the selectivity of ca. 90% at 425 degrees C. In comparing the reactivity of several amino alcohols to form the corresponding unsaturated amines, Yb2O3 effectively catalyzed the dehydration of 6-amino-1-hexanol into 5-hexen-1-amine, whereas 3-amino-1-propanol and 4-amino-1-butanol were not effectively dehydrated due to the decomposition of the reactant. (C) 2016 Elsevier B.V. All rights reserved.

C1s X-ray photoelectron spectroscopy (XPS) spectra of graphene with two to eight pentagons and fullerene pentagons were simulated using density functional theory calculation. Peak shifts and full width at half maximum (FWHM) of calculated C1s spectra were compared with those of actual C1s spectra. Introduction of up to four isolated pentagons had no influence on shifts of the calculated peak maxima of graphene (284.0 eV), whereas the introduction of six or more pentagons shifted the calculated peak maximum toward low binding energies because the number of connected pentagons increased. The presence of pentagons also influenced FWHMs. Introduction of six pentagons increased the calculated FWHMs from 1.25 to 1.45 eV, whereas introduction of eight or more pentagons decreased the FWHMs. The FWHM reached at 1.15 eV by introducing twelve pentagons (fullerene). These calculated shifts and FWHMs were close to the actual shifts of graphite (284.0 eV) and fullerene (282.9 eV) and FWHMs of graphite (1.25 eV) and fullerene (1.15 eV). Based on the calculated and the actual results, we proposed peak shifts and FWHMs of graphene with the different number of pentagons, which can be utilized for analyzing actual XPS spectra. Proposed FWHMs can be adjusted by measuring actual FWHMs using each device.

Vapor-phase catalytic conversion of glycerol into propylene was performed over Cu/Al2O3 and acid-loaded Cu/Al2O3 catalysts in an H-2 flow at ambient pressure. Acidic substances such as WO3, MoO3, V2O5 and H3PO4 were loaded on a commercial Cu/Al2O3. The addition of WO3 was found to be effective for promoting the formation of 1-propanol and propylene from glycerol, and 9.3 wt% WO3-loaded Cu/Al2O3(WO3/Cu/Al2O3) catalyst showed the best catalytic performance. WO3/Cu/Al2O3 calcined at a low temperature of 320 degrees C had the largest number of acid sites and gave a 1-proponol selectivity of 38.2% and a propylene selectivity of 47.4% in an H-2 flow at 250 degrees C. The catalytic reaction of glycerol was performed over double-bed catalysts, in which WO3/Cu/Al2O3 was charged in the upper bed and a commercial silica-alumina was charged in the lower bed, to promote the conversion of 1-propanol into propylene. A high propylene selectivity of 84.8% was obtained over the double-bed catalysts at 100% glycerol conversion. An efficient catalytic process for the production of propylene from glycerol was proposed. (C) 2015 Elsevier B.V. All rights reserved.

Vapor-phase cyclodehydration of diethylene glycol (DEG) into 1,4-dioxane (DOX) were performed over several solid acid catalysts, such as Al2O3, Sio(2)-Al2O3, Beta and MFI zeolites. All the catalytic activity gradually decreased with time on stream, especially Beta and MFI zeolites with strong acidic property. The catalysts were modified with silver metal for stabilizing the catalytic activity: Al2O3 modified with 1 wt.% Ag2O showed the best catalytic performance. Characterizations such as XRD, TPD and FIR were performed for analyzing the carbonaceous compound deposited on the catalysts after reaction and investigating the effect of the addition of Ag2O onto Al2O3. Polyethylene glycol was proposed as the carbonaceous compound by FTIR analysis. The modification of Ag was found to decrease the averaged acid strength of Al2O3, which is supposed to be effective for inhibiting carbon deposition and stabilizing the catalytic activity. It was also found that H-2, as a carrier gas, was indispensable for stabilizing the conversion of DEG into DOX. Silver metal would work as a remover of the product on the catalyst surface together with H-2 to prevent carbon deposition. Over Al2O3 modified with 1 wt.% Ag2O, a stable DOX selectivity of 90% with a complete conversion was achieved at 250 degrees C and a contact time of 156.8 g h mol(-1). (C) 2015 Elsevier B.V. All rights reserved.

The bromination reactivity of azulene, naphthalene, and graphene with pentagonal, hexagonal zigzag and armchair, and heptagonal edges was theoretically estimated by density functional theory calculation and experimentally clarified by analyzing bromination of azulene and naphthalene using gas chromatography-mass spectrometry and ultraviolet-visible spectroscopy. The experimental and theoretical bromination reactivity of azulene with one pentagon and one heptagon was higher than that of naphthalene with two hexagons because of electron-rich carbon atoms on the pentagon. On the other hand, the tendency of theoretical bromination reactivity of pentagonal, hexagonal, and heptagonal edges on graphene was totally opposite to that on azulene and naphthalene. The order of the bromination reactivity of graphene edges was hexagonal zigzag > pentagonal > heptagonal and hexagonal armchair edges. The highest reactivity of hexagonal zigzag edges can be explained by the largest amount of electrons of carbon atoms among all of edges of graphene.

Vapor-phase catalytic dehydration of 2,3-butanediol (2,3-BDO) was investigated over rare earth oxide catalysts and In2O3 at around 400 degrees C. In the dehydration of 2,3-BDO over SC2O3, 1,3-butadiene was mainly produced together with butanone, 2-methyl-propanal, 2-methyl-propanol,3-buten-2-ol, and butene isomers. SC2O3 calcined at 800 degrees C showed the highest 1,3-butadiene yield of 88.3% at 411 degrees C in H-2 carrier gas flow. Since 3-buten-2-ol is produced selectively from 2,3-BDO over Sc2O3 at a low temperature of 325 degrees C, 3-buten-2-ol rather than butanone is a probable intermediate from 2,3-BDO to 1,3-butadiene. 3-Buten-2-ol is readily converted into 1,3-butadiene at temperatures lower than 411 degrees C over Sc2O3 and Al2O3. In addition, double-bed catalysts composed of an upper catalyst bed of Sc2O3 and a lower of Al2O3 successfully converted 2,3-BDO directly into 1,3-butadiene with a stable selectivity higher than 94% at 318 degrees C and 100% conversion of 2,3-BDO. (C) 2014 Elsevier B.V. All rights reserved.

Vapor-phase catalytic dehydration of 2,3-butanediol (2,3-BDO) was investigated over rare earth oxide (RHO) catalysts as well as In2O3. In the dehydration of 2,3-BDO, 3-buten-2-ol (3B2OL) was produced together with 3-hydroxy-2-butanone (3H2BO), butanone (MEK), 2-methylpropanal (IBA), 2-methyl-1-propanol (IBO), etc. Sc2O3 and In2O3 showed higher 3B2OL selectivities than other REOs. In particular, Sc2O3 converted 2,3-BDO into 3B2OL with an excellent selectivity of 85.0% at 99.9% conversion.

The vapor-phase dehydration of 1,2-propanediol (1,2-PDO) was performed over various supported acidic oxide catalysts. Silica-supported WO3 catalyst shows the highest catalytic activity for propanal formation than other supported catalysts. A high and stable propanal selectivity of 93.5% was attained in H-2 atmosphere over 18.2%WO3-loaded silica catalyst using 20 wt.% 1,2-PDO aqueous solution as the reactant. The conversion of 1,2-PDO and the selectivity to propanal over the silica-supported WO3 were significantly affected by the calcination temperature of the catalysts. Since the high calcination temperatures decrease both the number of acid sites and the surface area of the catalysts, they decrease both the conversion of 1,2-PDO and the selectivity to propanal. The appropriate calcination temperature for silica-supported WO3 catalysts is 320 degrees C. The conversion of 1,2-PDO and the selectivity to propanal were also affected by the reaction temperature, the concentration of 1,2-PDO and the amount of catalyst used. A high propanal selectivity of 89.1% with a complete 1,2-PDO conversion was obtained at 250 degrees C over 3 g of 18.2% WO3-loaded silica catalyst when pure 1,2-PDO was used as the reactant. (c) 2014 Elsevier B.V. All rights reserved.

Vapor-phase catalytic dehydration of 2,3-butanediol (2,3-BDO) was investigated over several metal oxides loaded on well-crystallized monoclinic ZrO2. In the dehydration of 2,3-BDO, unsaturated alcohol, i.e. 3-buten-2-ol (3B2OL), was preferentially produced together with major by-products such as butanone and 3-hydroxy-2-butanone over ZrO2-based catalysts. The selectivity to 3B2OL over monoclinic ZrO2 was greatly enhanced by the alkaline-earth oxides such as CaO, SrO, and BaO. At a CaO loading of 3 wt% on the monoclinic ZrO2, a Ca-O-Zr hetero-linkage was formed to generate new basic sites, and the selectivity to 3B2OL exceeded 76% at 350 degrees C. Poisoning experiments using CO2 and NH3 strongly suggest that the formation of 3B2OL from 2,3-BDO proceeds over base-acid concerted sites. (c) 2014 Elsevier B.V. All rights reserved.

Catalytic activity of rare earth oxides (REOs) in the vapor-phase dehydration of 1,4-butanediol to produce 3-buten-1-ol varies with lattice parameters of REOs. In order to clarify the adsorption structure and the reaction mechanism, adsorption energy of 1,4-butanediol on bixbyite REO, such as SC2O3, Y2O3, Dy2O3, Ho2O3, and Er2O3, {222} surface was calculated with density functional theory (DFT), and paired interacting orbitals (PIO) calculation of the adsorption state between 1,4-butanediol and Er2O3 was executed. The DFT study elucidates that the catalytic activity is correlated with adsorption energy. The PIO study clarifies the interactions between the reactive atoms of 1,4-butanediol and Er2O3 surface: tridentate interactions between a position-2 hydrogen atom of diol and an oxygen anion on Er2O3 and between each OH group of diol and erbium cations on Er2O3, and an intramolecular repulsive interaction between the position-1 carbon atom and the oxygen atom of OH group are observed. These results suggest that the position-2 hydrogen atom is firstly abstracted by a basic oxygen anion and that the position-1 hydroxyl group is subsequently abstracted by an acidic erbium cation. Another OH group on position 4 plays an important role of anchoring the diol to the Er2O3 surface. Therefore, it is proved that the dehydration of 1,4-butanediol over REOs proceeds via acid-base concerted mechanism. (C) 2013 Elsevier B.V. All rights reserved.

The vapor-phase hydrogenolysis of glycerol was performed at a gradient temperature and ambient hydrogen pressure over a commercial Cu/Al2O3 catalyst modified with silver. Addition of Ag into Cu/Al2O3 catalysts was found to be efficient in inhibiting the decomposition of glycerol to produce ethylene glycol and gave a yield of 1,2-propanediol higher than that of the original Cu/Al2O3 without Ag. To minimize the ethylene glycol formation, the suitable loading of Ag was 1 wt.%. Since the Ag loading decreases the hydrogenation ability of the Cu/Al2O3 catalyst, 1 wt.% Ag-loaded Cu/Al2O3 catalyst was placed on the upper layer of the fixed catalyst bed and the Cu/Al2O3 catalyst was placed on the bottom layer for achieving much higher 1,2-propanediol yield. The effect of temperatures of the top, the interlayer, and the bottom of the catalyst bed on the yield was also examined: a high 1,2-propanediol yield of 98.3%, which is the highest value under ambient H-2 pressure conditions, was achieved at a gradient temperature from 170 to 105 degrees C and a glycerol concentration of 15 wt.%. (C) 2014 Elsevier B.V. All rights reserved.

X-ray photoelectron spectroscopy (XPS) has been commonly used to determine the nitrogen-containing functional groups of graphene. However, reported assignments of C1s shifts of nitrogen-containing functional groups are unclear. Most works discuss peak shifts of only N1s spectra and C1s shifts and the full width at half maximum (FWHM) are excluded. Thus, peak shifts and FWHMs of C1s and N1s XPS spectra of graphene with nitrogen-containing functional groups such as pyridinic, phenanthroline-like, sp(2)C-NH2, sp(3)C-NH2, pyrrolic, imine, pyridazine-like, pyrazole-like, sp(2)C-CN, sp(3)C-CN, and valley quaternary nitrogen (Q-N) on edges and sp(3)C-NH2, center amine, and center Q-N in the basal plane were simulated using density functional theory calculation. Main peaks of C1s spectra were shifted positively and negatively by the electron-withdrawing and electron-donating functional groups, respectively. FWHMs of the main peaks of C1s spectra were influenced by mainly electron-withdrawing functional groups on edges and most functional groups in the basal plane. Sp(2)C-NH2 on zigzag edges is suggested as a reference functional group to adjust the N1s spectra because influence of the functional group on the shift of main peak and the FWHM of C1s spectrum was small. (C) 2013 Elsevier Ltd. All rights reserved.

Vapor-phase catalytic dehydration of 1,2-propanediol was investigated over several solid acid catalysts, such as alumina, silica alumina, HY zeolite, and beta-zeolite. These acids catalyzed the dehydration of 1,2-propanediol to produce propanal (Figure 1), while zeolites were particularly deactivated because of deposition of carbonaceous species. An amorphous silica-alumina was modified with metals such as Ag and Cu to stabilize the catalytic activity under hydrogen flow conditions. Ag-modified silica alumina is a promising catalyst for the production of propanal from 1,2-propanediol.

Vapor-phase dehydration of 3-methyl-1,3-butanediol to 3-methyl-3-buten-l-ol was investigated over carbon-modified alumina, C/Al2O3, which was prepared by depositing carbonaceous species, i.e. coke, on Al2O3 with contacting Al2O3 surface with 3-methyl-1,3-butanediol vapor at 250 C. Temperature-programmed desorption of adsorbed NH3 revealed that the strength of acid sites of fresh Al2O3 was weakened by the coke deposition. It was found that the selectivity to 3-methyl-3-buten-1-01 was increased by the coke deposition over Al2O3 catalysts in the dehydration of 3-methyl-1,3-butanediol at 200 C. Generation of the main by-products such as isobutylene and 4,4-dimethy1-1,3-dioxane were prohibited by the acid sites weakened by the coke deposition. The 13C NMR and IR measurement elucidated that the deposited coke had C=C, C=O, COO, CH2, CH3, and OH groups, which indicates that the coke consisted of polymeric unsaturated alcohol. The coke content that is effective in inhibiting the decomposition of 3-methyl-1,3-butanediol into isobutylene was ca. 15 wt.% of C/Al2O3. (C) 2014 Elsevier B.V. All rights reserved.

Mechanisms for pyrolysis of epoxidized fullerene involving formation of CO, CO2, and O-2 gases were studied using density functional theory calculation. From two oxygen atoms on fullerene, a lactone group is formed through migration of an oxygen atom. The lactone group is transformed into either CO2 gas with a monovacancy defect or a combination of an ether group and a ketone group. The ketone group in the combination of the ether group and the ketone group decomposes into CO gas. All of these mechanisms proceed endothermically, but CO gas tends to form more than CO2 gas because the activation energy required for the formation of CO gas is lower than that of CO2 gas. From three oxygen atoms on fullerene, a combination of a lactone group and a ketone group is generated and decomposes into CO and CO2 gases. CO2 gas tends to form more than CO gas because the activation energy required for the formation of CO2 gas is lower than that of CO gas. O-2 gas is difficult to desorb because of the high activation energy.

Epoxide is one of the simplest functional groups on fullerenes, but mechanisms for migration of oxygen atoms and formations of CO and CO2 gases upon heat treatment are still unclear. In this work, epoxidized fullerenes were heated in helium gas up to 673 K and the pyrolyzed structures of epoxidized fullerenes were analyzed using X-ray photoelectron spectroscopy, infrared spectroscopy, direct-injection mass spectrometry, elemental analysis, and density functional theory calculation. Functional groups such as C=0 and lactone groups were formed by heat treatment of the epoxidized fifflerenes at 523 K. At 673 K, lactone groups were decomposed into CO and CO2 gases. The amount of the CO2 gas was more than that of the CO gas. This suggests that a formation of CO2 gas from lactone groups is energetically more favorable than that of CO gas. Moreover, the ratio of CO2 gas to CO gas increased, as the amount of oxygen atoms on fullerenes increased. The formation of CO and CO2 gases at 673 K indicates that the presence of carbene sites with either vacancy defects or ether groups on fullerenes.

Vapor-phase catalytic dehydration of 2,3-butanediol was investigated over metal oxides such as CeO2, La2O3, Yb(2)O3, ZrO2, Al2O3, TiO2, ZnO, Fe2O3, NiO, and Cr2O3. In the dehydration of 2,3-butanedio13-buten-2-ol was preferentially produced over monoclinic ZrO2 along with major by-products such as butanone and 3-hydroxy-2-butanone. Over ZrO2 calcined at 900 degrees C, 3-buten-2-ol was produced with a maximum selectivity of 59.0% at 300 degrees C without producing 1,3-butadiene. (C) 2014 Elsevier B.V. All rights reserved.