山田 泰弘

Vapor-phase intramolecular aldol condensation of 2,5-hexanedione (2,5-HD) to 3-methyl-2-cyclopentenone (MCP) was performed over several rare-earth zirconate catalysts, with yttrium zirconate (YZrO) emerged as the most efficient catalyst. Several parameters, such as Y content, calcination temperature, reaction temperature, and contact time, highly influenced the catalytic performance of the YZrO catalyst: YZrO calcined at 700 °C exhibited the highest catalytic activity but still suffered from catalyst deactivation due to coke formation. Modifying the YZrO with Ag and employing the modified catalyst in an H2 flow effectively reduced the coke accumulation, thus improving the catalytic stability during the aldol condensation of 2,5-HD at 350 °C. The poisoning experiment with the co-fed of acidic CO2 gas and basic molecules of 2,6-, and 3,5-dimethylpyridine suggested that the aldol condensation proceeded via an acid-base concerted mechanism.

Silica-supported Cu (Cu/SiO2) prepared by using an organic additive-assisted impregnation method was employed as a catalyst for the dehydrogenation of 3-methyl-2-butanol (3M2BO) to 3-methyl-2-butanone (methyl isopropyl ketone, MIPK). The utilization of organic additives, especially mannitol, during the impregnation protocol has led to the generation of a Cu/SiO2 catalyst containing highly dispersed Cu nanoparticles, i.e. high Cu surface area (SACu). These properties contributed to the high activity of the mannitol-assisted Cu/SiO2 catalyst, in which the activity was limited only by the equilibrium nature of the reaction. The proportional relationship between the formation rate of the MIPK with the SACu confirmed the benefits of the utilization of organic additives. In addition, the improvement in the SACu of Cu/SiO2 prepared using mannitol only gave a negligible side product originating from the dehydration of 3M2BO; thus, the equilibrium MIPK yield of 99.5% was achieved even at 300 °C.

A highly efficient and stable Cu/SiO2 catalyst was prepared via 12-crown-4-ether (12C4)-assisted impregnation and used in the vapor-phase conversion of glycerol to 1,2-propanediol (propylene glycol, PG) via acetol formation in an ambient hydrogen flow. The 12C4-Cu/SiO2 catalyst gave a PG yield of >97% due to a low rate of C-C cleavage to generate ethylene glycol. Under optimum conditions, the high catalytic performance was maintained for 98 h of time on stream.

Silica-supported Cu (Cu/SiO2) catalyst prepared by using organic additive-assisted impregnation was employed for the chemoselective hydrogenation of a C=O bond in 6-methyl-5-hepten-2-one (1) to produce 6-methyl-5-hepten-2-ol (2) in a vapor phase at a temperature between 140 and 200 °C and an ambient pressure of H2 flow. The Cu was responsible for the selectivity to 2, and the organic additive increased the Cu surface area (SACu), which consecutively enhanced the performance of the Cu/SiO2 catalyst. The proportional correlation between the SACu and the formation rate of 2 further confirmed the benefits of the utilization of organic additives during the impregnation protocol.

Several rare-earth oxides, prepared through a hydrothermal process, were employed as catalysts for vapor-phase dehydration of 3-methyl-1,3-butanediol (3MBDO) to isoprene. Ytterbium oxide (Yb2O3) emerged as the most efficient catalyst for the dehydration of 3MBDO to isoprene. The hydrothermal time and calcination temperature influenced the performance of Yb2O3. The reaction temperature and contact time strongly affect the dehydration of 3MBDO and unsaturated alcohols, while the major side reaction of isobutene formation via decomposition of 3-methyl-3-butene-1-ol was mainly influenced by the reaction temperature. The highest isoprene yield of 92% was achieved at 450 °C and a long contact time of 3.75 h. The poisoning experiment using CO2, 2,6-, and 3,5-dimethylpyridine revealed the importance of base and acid sites of Yb2O3 in the dehydration of 3MBDO, indicating the dehydration of 3MBDO to isoprene proceeded via an acid-base concerted mechanism.

Abstract The deoxydehydration (DODH) of 2,3-butanediol (2,3-BDO) to butene isomers proceeded over silica-supported molybdenum oxide (MoO3/SiO2) catalyst without any external reductants. In the DODH of 2,3-BDO over MoO3/SiO2 catalyst, cis- and trans-2-butene were produced with negligible 1-butene. The MoO3/SiO2 catalyst was inefficient for the hydrogenation of butanone and the dehydrogenation of 3-hydroxy-2-butanone, suggesting that the production of butenes did not proceed via the dehydration of 2-butanol. X-ray photoelectron spectroscopy and energy calculations by density functional theory suggest that the condensation of 2,3-BDO to form Mo(VI) diolate species initiates the DODH of 2,3-BDO. The C–C cleavage of diolate species produces acetaldehyde and Mo(IV). The coordination of 2,3-BDO to Mo(IV) leads to the parallel formation of an alkoxide and diolate species. The alkoxide produces 2-butene via 2-hydroxybutyl radical and Mo(V), while diolate generates only cis-2-butene via concerted scission of (C–O)2Mo(IV) bonds.

Several silica-supported metal oxides (MxOy/SiO2) were employed as catalysts for 1,3-butadiene (BD) production via the dehydration of 1,3-butanediol (1,3-BDO). Among the MxOy/SiO2 catalysts tested, WO3/SiO2 catalyst showed the most promising activity for BD production. Several parameters, such as reaction temperature, contact time, calcination temperature of the catalyst, and W content in the catalyst, influenced the rate of the first-step dehydration of 1,3-BDO to unsaturated alcohols (UOLs), while only contact time significantly affected the consecutive dehydration of UOLs to BD. The poisoning experiment using 2,6- and 3,5-dimethylpyridine revealed that both Brønsted and Lewis acid sites of the WO3/SiO2 catalyst played an essential role in the dehydration of 1,3-BDO to BD. Under optimum conditions at 300 °C and a contact time of 2.65 h, a BD yield as high as 73.4% was attained.

In the published article “Vapor-Phase Oxidant-Free Dehydrogenation of 2,3- and 1,4-Butanediol over Cu/SiO2 Catalyst Prepared by Crown-Ether-Assisted Impregnation“ [1], we came to the realization that we made a mistake in calculating the Cu dispersion, D. Considering that the calculation of Cu surface area, SACu, and the mean particle size of Cu, DCu, are derived from D, this mistake also affected the values of SACu and DCu. The correct D and SACu values should have been twice the values listed in the original publication, whereas the DCu should have been half the values listed in the original publication. It should be noted that the corrections do not change the main finding and conclusion of the research work. This correction was solely done to ensure the transparency, objectivity, and reproducibility of the research work. Following this mistake, several tables and figures need to be revised, and the revisions are as follows. The description in Section 3.6 must also be revised since there was information related to SACu. The corrected description of Section 3.6 is as follows: “Figure 7c depicts the relation between SACu and the formation rate of GBL in the dehydrogenation of 1,4-BDO at 240 °C. The GBL formation rate is proportional to the SACu for SACu values smaller than 30 m2 g−1, while the proportional relation was not observed for SACu values higher than 30 m2 g−1. This phenomenon differed from the results in the dehydrogenation of 2,3-BDO to AC, in which the AC formation rate was proportional to SACu, even for SACu values higher than 30 m2 g−1. This difference can be explained by the mechanism of 1,4-BDO dehydrogenation to GBL. The dehydrogenation of 2,3-BDO to AC is a straightforward reaction, whereas 1,4-BDO dehydrogenation to GBL proceeds via a series of consecutive reactions, including (1) the dehydrogenation of 1,4-BDO to 4-hydroxybutanal, (2) the intramolecular hemiacetal-formed cyclization to 2-hydroxytetrahydrofuran, and (3) the dehydrogenation of 2-hydroxytetrahydrofuran to form GBL (Scheme 2) [41]. The cyclization via an intramolecular hemiacetal reaction was possibly catalyzed by the acid sites of the silanol group in a similar manner to the cyclization of levulinic acid to angelica lactone [71]. Similarly, acidic alumina-supported Cu was also effective for the cyclization of 4-hydroxybutanal; nevertheless, the strong acidity of alumina promoted the dehydration reaction, generating tetrahydrofuran as the side product [41]. For SACu values below 30 m2 g−1, the increment of Cu content did not significantly alter the concentration of silanol sites; thus, the increment of Cu content favored the dehydrogenation of 1,4-BDO to 4-hydroxybutanal but did not hinder the consecutive cyclization of 4-hydroxybutanal to 2-hydroxytetrahydrofuran. However, when the SACu was higher than 30 m2 g−1, the increment of Cu content decreased the contribution of OH to the level that it slightly hindered the cyclization of 4-hydroxybutanal to 2-hydroxytetrahydrofuran and the subsequent GBL formation. As a result, a proportional relation between SACu and GBL formation rate was no longer observed for SACu values above 30 m2 g−1, as shown in Figure 7c.” The D and SACu values are displayed in Table 1; as a result, Table 1 should be corrected as follows: Effect of organic additive on the catalytic performance of 2Cu/SiO2 catalyst in the dehydrogenation of 2,3-BDO. Reaction conditions: Reaction temperature, 200 °C; W/F, 0.18 h. a Average conversion and selectivity at TOS of 0–1 h. The information of SACu is also displayed in Table 3; thus, the revised Table 3 is shown below. In the last entry, the SACu of the 12C4-10Cu/SiO2 catalyst has been corrected. Comparison of the productivity of GBL over various reported Cu catalysts. a Time on stream in a flow system. b Prepared by co-precipitation; Cu content, 41.8 wt.-%. The values of SACu were also displayed in Figure 5b and Figure 7c; therefore, those figures should be revised as follows: (b) Effect of SACu on the formation rate of AC at 200 °C. (c) Relation between Cu surface area and the formation rate of GBL at 240 °C. The D, SACu, and DCu are also depicted in supporting information. The original Table S2 has also been updated. The authors state that the scientific conclusions are unaffected. This correction was approved by the Academic Editor. The original publication has also been updated.

Selective doping of pyridinic nitrogen in carbon materials has attracted attention due to its significant properties for various applications such as catalysts and electrodes. However, selective doping of pyridinic nitrogen together with controlling skeletal structure is challenging in the absence of catalysts. In this work, four precursors including four fused aromatic rings and pyridinic nitrogen were simply carbonized in the absence of catalysts in order to attain mass synthesis at low cost and a high percentage of pyridinic nitrogen in carbon materials with controlled edges. Among four precursors, dibenzo[f,h]quinoline (DQ) showed an extremely high percentage of pyridinic nitrogen (96 and 86%) after heat treatment at 923 and 973 K, respectively. Experimental spectroscopic analyses combined with calculated spectroscopic analyses using density functional theory calculations unveiled that the C-H next to the pyridinic nitrogen in DQ generated gulf edge structures with controlled pyridinic nitrogen after carbonization. By comparing the reactivities among the four precursors, three main factors required for maintaining the pyridinic nitrogen in carbon materials with controlled edges, such as (1) high thermal stability of the pyridinic nitrogen, (2) the presence of one pyridinic nitrogen in one ring, and (3) the formation of gulf edges including pyridinic nitrogen to protect the pyridinic nitrogen by the C-H groups on the gulf edges, were revealed.

A silica-supported copper (Cu/SiO2) catalyst containing highly dispersed Cu nanoparticles was prepared via a crown-ether-assisted impregnation method. A 12-crown-4-ether-assisted Cu/SiO2 catalyst outperformed several Cu/SiO2 catalysts prepared with various organic additives in the dehydrogenation of 2,3- and 1,4-butanediol. It was found that the catalytic activity, i.e., the formation rate of acetoin from 2,3-butanediol and that of γ-butyrolactone from 1,4-butanediol, was proportional to the copper surface area.

Selective doping of nitrogen-containing functional groups of carbon materials is the most essential technique for enhancing properties significantly for various applications such as catalysts and electrodes. Reported carbon materials with controlled pyridinic nitrogen are generally synthesized on substrates, leading to low productivity and high cost. Thus, simple preparation methods for selective doping of nitrogen in carbon materials without substrates are indispensable for mass production. This work discovered that simple heat treatment of 1,7-phenanthroline at 973 K formed carbon material with exceptionally high pyridinic nitrogen content (92%). The selective doping of pyridinic nitrogen was attained by the protection of pyridinic nitrogen due to the steric hindrance by the neighboring C-H group on armchair edges to avoid the formation of N-H bonding on pyridinic nitrogen on armchair edges. Screening techniques of precursors for preparing carbon materials with high pyridinic nitrogen content are also essential to minimize research costs. Screening by 1) formation energy of hydrogenation on pyridinic nitrogen, 2) molecular dynamic simulation with reactive force field, and 3) comparison of structures of precursors revealed that 1,7-phenanthroline was the best precursor to maintain the high percentage of pyridinic nitrogen after carbonization. Thus, strategic synthesis is now possible using screening techniques.

Vapor-phase catalytic dehydration of 2,3-butanediol (2,3-BDO) to form 1,3-butadiene (BD) via 3-buten-2-ol (3B2OL) was studied over various single metal oxide catalysts. Among the catalysts, Sc2O3 prepared under hydrothermal (HT) conditions at 200 °C followed by 800 °C calcination showed the most excellent catalytic activity. The crystallization of precursor ScOOH during HT aging noticeably enhances the catalytic activity of the resulting Sc2O3 for the formation of 3B2OL in the dehydration of 2,3-BDO. The formation rate of 3B2OL from 2,3-BDO over the HT-aged Sc2O3 was twice as high as Sc2O3 without HT aging. Calcination temperatures of Sc2O3 are also important: calcination at 800 °C is efficient for the selective formation of 3B2OL from 2,3-BDO. The HT-aged Sc2O3 also showed an excellent catalytic activity for the formation of BD with the yield higher than 80% in the dehydration of 2,3-BDO at 411 °C.

X-ray photoelectron spectroscopy (XPS) is among the most utilized analytical methods for nitrogen doped carbon materials. Clarifying the assignments of nitrogen-doped carbon materials with different degrees of carbonization, which relates to conjugated systems, is essential to correlate structures with the performance of various applications, but such precise assignments were challenging. In this work, precise analyses were conducted to overcome the difficulty to assign the peaks of carbon materials with different degrees of carbonization, different edges, and various nitrogen-containing functional groups in graphene nanoribbons (GNRs), such as nitrile, pyridinic, primary with/without charges, secondary with/ without charge, tertiary without charges (graphitic nitrogen), and quaternary nitrogen. Electrons donated from hydrogen and Madelung potentials showed a higher correlation to the peak shift of C1s and N1s XPS spectra than Mulliken charges on nitrogen. Zigzag edges showed a greater influence on the peak shift of tertiary amine (graphitic nitrogen) than armchair edges on XPS spectra. Besides, as the degree of carbonization is increased from aromatic compound-like structures to GNRs, the peak positions of C-N in C1s and N1s XPS spectra shifted to higher binding energies. This research proved that XPS could be applied to the precise structural analyses of nitrogen-containing carbon materials. (c) 2021 Elsevier Ltd. All rights reserved.

A metal-free covalent triazine framework (CTF) was synthesized from 2,4,6-tricyano-1,3,5-triazine (TCT) through open-system and liquid-phase synthesis using trifluoromethanesulfonic acid as both a catalyst and a solvent (TCT-CTF). In conventional closed-system methods, metal ions used as catalysts remained even after purification, and large quantities could not be synthesized. The proposed method solved these problems and synthesized higher-quality TCT-CTF with a layered structure and a composition with a C/N ratio of 1, which is close to the ideal value.

Identifying pentagons and heptagons in graphene nanoflake (GNF) structures at the atomic scale is important to completely understand the chemical and physical properties of these materials. Herein, we used X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy to analyze the spectral features of GNFs according to the position of pentagons and heptagons introduced onto their zigzag and armchair edges. The XPS peak maxima were shifted to higher binding energies by introducing the pentagons or heptagons on armchair rather than zigzag edges, and the structures could be distinguished depending on the positions of the introduced pentagons or heptagons. Raman spectroscopic analyses also revealed that the position of edges with introduced pentagons or heptagons could also be identified using Raman spectroscopy, with characteristic bands appearing at 800-1200 cm(-1), following the introduction of either pentagons or heptagons on armchair edges. This precise spectroscopic identification of pentagons and heptagons in GNFs provides the groundwork for the analysis of graphene-related materials.

Oxygen-containing carbon materials have been studied extensively because of their excellent dispersibility, absorptivity, separability, and supportability of catalysts. However, structural control by existing top-down methods is almost impossible. Our group has demonstrated that phloroglucinol (PG, 1,3,5-trihydroxybenzene) can be a promising raw material to synthesize structurally controlled oxygen-containing carbon materials. In this study, in addition to PG, hexahydroxybenzene (HHB), which has more oxygen and high symmetry, was used as the raw material, and a Lewis acid catalyst, tris (pentafluorophenyl) borane (TPB), was used to enhance the structural control rate and the removability of catalysts from the carbonized samples. The solubility of heat-treated HHB was lower than that of heat-treated PG, but the oxygen content of heat-treated HHB was higher than that of heat-treated PG even at 673 K. By adding TPB to PG, dibenzofuran-like structures formed, and the structural control rate increased up to 93.6%. Besides, the content of fluorine in the catalyst was reduced to 0%, indicating that TPB can be a promising recyclable catalyst to promote the structural control rate of carbonized PG.

X-ray photoelectron spectroscopy (XPS) is among the most powerful techniques to analyse structures of nitrogen-doped carbon materials. However, reported assignments of (1) graphitic nitrogen (N)/substitutional N, quaternary N (Q-N), or tertiary amine (T-N) and (2) pyrrolic N/secondary amine or T-N are questionable. Most reports assign peaks at ca. 401 eV as Q-N or graphitic N, whereas raw materials in most of those works contain neither counter anion nor halogen. Besides, the peak at ca. 400 eV has been assigned as pyrrolic N, but the presence of N-H is generally not confirmed. In this work, it was clarified that one of the reasons for the prevailing ambiguous assignments is the presence of N in heptagonal and pentagonal rings. The peaks at 400.1-401.2 eV were determined to be T-N, but not Q-N by analyzing graphitized polyimide (with the oxygen content of 0.01 at% or lower and the hydrogen content of 0 at%) using Raman spectroscopy, XPS, X-ray diffraction, total neutron scattering, elemental analysis, and molecular dynamics simulation. Besides, it was revealed that the peak at 400.1 eV originated from T-N on 5-membered rings or 7- and 5-membered rings, but not pyrrolic N because graphite including no hydrogen was used for analysis.[GRAPHICS].

Long-term stability of catalysts is one of important factors in heterogeneous catalysis. Solid acid catalysts are widely used in various reactions in the chemical industry, whereas they readily deactivate in most cases because of coke deposition on the acid sites. Therefore, efficient methods for controlling deactivation of solid acid catalysts are highly required. A method including both the doping of transition metals and the reaction operation in H2 flow (named as Metal-H2 method) is effective for suppressing coke deposition on solid acids in various cases. Although the Metal-H2 methodology has been utilized in some processes by different research groups, it has not been systematically summarized. In this review, we originally define the Metal-H2 method, and summarize the specific applications of the Metal-H2 method for controlling deactivation in cracking, reforming, dehydration, aldol condensation, and other processes.

Vapor-phase catalytic dehydration of 1,4-butanediol (1,4-BDO) was investigated over Y2O3-ZrO2 catalysts. In the dehydration, 1,3-butadiene (BD) together with 3-buten-1-ol (3B1OL), tetrahydrofuran, and propylene was produced depending on the reaction conditions. In the dehydration over Y2O3-ZrO2 catalysts with different Y contents at 325°C, Y2Zr2O7 with an equimolar ratio of Y/Zr showed high selectivity to 3B1OL, an intermediate to BD. In the dehydration at 360°C, a BD yield higher than 90% was achieved over the Y2Zr2O7 calcined at 700°C throughout 10 h. In the dehydration of 3B1OL over Y2Zr2O7, however, the catalytic activity affected by the calcination temperature is roughly proportional to the specific surface area of the sample. The highest activity of Y2Zr2O7 calcined at 700 °C for the BD formation from 1,4-BDO is explained by the trade-off relation in the activities for the first-step dehydration of 1,4-BDO to 3B1OL and for the second-step dehydration of 3B1OL to BD. The higher reactivity of 3B1OL than saturated alcohols such as 1-butanol and 2-butanol suggests that the C=C double bond of 3B1OL induces an attractive interaction to anchor the catalyst surface and promotes the dehydration. A probable mechanism for the one-step dehydration of 1,4-BDO to BD was discussed.

The vapor-phase catalytic reaction of crotyl alcohol (CRO) was investigated over metal oxide-modified silica catalysts. The isomerization of CRO to 3-buten-2-ol (3B2OL) was found to progress in the reaction of CRO over V2O5-modified SiO2 (V2O5/SiO2) at 200 °C. V2O5/SiO2 showed high 3B2OL yield and stable catalytic activity. The isomerization between CRO and 3B2OL reached an equilibrium without the dehydration to 1,3-butadiene. Poisoning experiments using dimethylpyridines suggested that Lewis acid sites acted as the active centers.

Graphene nanoribbon (GNR) has attracted attention because of the adjustable band gap, depending on the width and functional groups. The introduction of sp3C–H on edges is one of the choices to reduce the agglomeration between GNRs and to change their various properties. Infrared spectroscopy is among the powerful tools to analyze the edge structures of carbon materials, but the number of detailed reports is almost nonexistent for sp3C–H in carbon materials. In this work, the influence of the presence of sp3C–H on the peak position of sp2C–H on zigzag and armchair edges of GNR was revealed by comparing experimental and computational infrared spectra of aromatic compounds. The introduction of methylene and methyl groups next to sp2C–H affected peak positions of in-plane stretching and out-of-plane bending vibration of sp2C–H. The peak position of sp2C–H was further shifted by introducing methylene and methyl groups on both sides of sp2C–H. The presence of either methylene or methyl groups can be clearly distinguished from the difference in coupled vibration of out-of-plane vibration of sp2C–H and quadrant stretching vibration of C=C because the presence of methylene groups affects the conjugated system significantly, whereas methyl groups did not affect the conjugated system.

Carbonization process of pyromellitic dianhydride (PMDA)-4,4′-diaminodiphenyl ether (ODA)-type polyimide has been studied for decades. However, various reaction mechanisms have been proposed and the detailed mechanisms are still controversial. It is essential to understand the carbonized structures of PMDA-ODA-type polyimide before analyzing the defect structures in graphite. In this work, the carbonization mechanisms of polyimide heated at 1273 K or lower were unveiled and the methodology to analyze carbon materials containing nitrogen, oxygen, pentagons, and heptagons using computational spectral analysis combined with molecular dynamics simulation (ReaxFF) are exhibited. For example, the formations of isoimide and cyclic ether were estimated by ReaxFF, and the presence was supported by experimental and calculated X-ray photoelectron spectroscopy (XPS) and carbon-13 nuclear magnetic resonance (13C NMR) spectra of polyimide heated between 813 and 873 K. The formations of pentagons and heptagon, suggested by ReaxFF, were also supported by Raman and 13C NMR spectra of polyimide heated between 833 and 1273 K. This work also revealed that the previously reported structures were unstable and that amine in the basal plane was the most plausible structure in polyimide heated at 1073 K or higher, as clarified by XPS, ReaxFF, and the energy calculation.

The bromination reactivity of various types of polycyclic aromatic hydrocarbons (PAHs) with oxygen atoms and graphene with oxygen atoms was estimated by density functional theory calculation and experimentally clarified by analyzing bromination of PAHs using gas chromatography–mass spectrometry. In the experimental and theoretical bromination reactivity of PAHs, the presence of hydroxyl group increased the reactivity of PAHs because of electron-donating nature of the hydroxyl group but the other oxygen-containing functional groups such as lactone, ether, and ketone decreased the reactivity due to the electron-withdrawing nature of those groups. These effects of functional groups on the reactivity were also confirmed in graphene. The tendency of theoretical bromination reactivity of graphene was graphene with hydroxyl group > graphene with no group > graphene with lactone group > graphene with ether group > graphene with ketone group. Our study on the estimation of bromination reactivity of graphene edges provides the groundwork for the bromination of graphene edges.

The vapor-phase dehydration of 1,3-butanediol (1,3-BDO) to produce 1,3-butadiene (BD) was investigated over yttrium zirconate, Y2Zr2O7, which was prepared through a hydrothermal aging process. 1,3-BDO was initially dehydrated to three unsaturated alcohols, namely 3-buten-2-ol, 3-buten-1-ol, and 2-buten-1-ol, followed by the further dehydration to BD. The catalytic activity of Y2Zr2O7 was strongly dependent on the calcination temperature. Furthermore, the reaction temperature was one of the important factors to produce BD efficiently: the selectivity to BD was increased with increasing reaction temperature up to 375 °C, while coke formation led to catalyst deactivation together with by-product formation at higher temperatures. Y2Zr2O7 catalyst calcined at 900 °C showed a high BD yield of 95% at 375 °C and a time on stream of 10 h.

Vapor-phase hydrogenation of levulinic acid (LA) to ɤ-valerolactone (GVL) was investigated over supported-type Cu-Ni/Al2O3 catalysts in H2 flow at 250 °C. Ni-rich Cu-Ni/Al2O3 catalysts, typically 6 wt.% Cu and 14 wt.% Ni, achieved high LA conversion with high stability and high GVL selectivity. XRD analyses of the catalysts clarified that Cu-Ni alloy nanoparticles were produced on the alumina support by forming a solid solution of CuO-NiO. The Cu-Ni/Al2O3 catalyst showed the highest GVL productivity of 11.0 kg kgcat−1 h−1 with a selectivity of 98.6 %, although the catalyst was gradually deactivated with time on stream under high space velocity conditions. In the characterization of the used catalysts, the catalyst deactivation would be caused by the sintering of active Cu-Ni alloy nanoparticles, which could be induced by the cycle of the oxidation with H2O and the reduction with H2.

Calcia-stabilized zirconia (CSZ) samples were prepared under hydrothermal (HT) conditions for an efficient catalyst in the vapor-phase dehydration of 1,4-butanediol (1,4-BDO). Preparative aspects of CSZ for the efficient catalyst were discussed. Ammonia aqueous media in the HT aging were effective for high crystallinity of tetragonal/cubic CSZ with high specific surface area, which resulted in high catalytic performance in the dehydration of 1,4-BDO while not all Ca in the solution was included in ZrO2 precipitates in the ammonia media. Although almost all Ca was included in ZrO2 in the strong basic KOH/NaOH aqueous solution, the CSZ samples aged in the strong basic media, which were composed of mainly CaZrO3 crystallite, were readily sintered resulting in poor catalytic activity. Sr cations as well as Ca cations were included in ZrO2 to stabilize cubic ZrO2, while small amounts of Mg and Ba cations were included in ZrO2 not to stabilize the cubic ZrO2 structure. Among the alkaline earth cations, Ca was the most effective in enhancement of catalytic activity in the dehydration of 1,4-BDO. CSZ with a Ca content of 9.4 mol% calcined at 900 °C exhibited the highest 3-buten-1-ol selectivity of 89.2 % at a 1,4-BDO conversion of 54.7 % at 325 °C.

Oxygen-containing carbon materials such as graphene oxide have been extensively studied because of their high dispersibility. However, the oxygen-containing functional groups in most carbon materials are not controlled. Uncontrollability of the synthesis is also one of factors that prevent industrialization. Carbon materials derived from phloroglucinol (PG), which show high solubility/dispersibility and controllability of functional groups, have been developed recently by our group. The high performance of carbonized PG originates from the thermally stable backbone structure of the benzene ring with hydroxy groups of PG. However, the degree of carbonization was low. In this study, five heteropoly acids (HPAs), which are thermally stable homogeneous strong acid catalysts, were used to promote carbonization of PG without losing the controllability of functional groups and the dispersibility. HPAs promoted etherification of hydroxy groups followed by C=C coupling reactions (furan cyclization) at 523 K. Furthermore, it was confirmed that particularly furan structures, which contribute to solubility/dispersibility in solvents, and thermal stability in air, could be maintained at 673 K as suggested by spectroscopies and thermogravimetric-differential thermal analysis. Among five HPAs, phosphotungstic acid worked as the excellent catalyst to promote carbonization of PG containing furan structures, exhibiting high solubility/dispersibility and high thermal stability in air.[GRAPHICS].

Pentagons in carbon materials have attracted attentions because of the potential high chemical reactivity, band gap control, and electrochemical activity. However, it is challenging to prepare a carbon film with high pentagon density because of the curvature and the high reactivity caused by the presence of pentagons, and it is also challenging to estimate the percentage of pentagons in carbon materials because of the limitation of current analytical techniques. In this work, the percentage of pentagons in carbon materials was experimentally estimated for the first time using experimental and calculated C1s X-ray photoelectron spectroscopy and elemental analysis. Carbon films with 7% of pentagons (40% of pentagons compared to the raw material) with electrical resistivity of 1.1 x 10(4) Omega meter were prepared by heat treatment of corannulene at 873 K. On the other hand, fluoranthene and fullerene remained as non-film solid and powder without forming films at 873 K. Experimental and calculated Raman and IR spectra revealed the peaks of different types of pentagons. Decrement of pentagons in corannulene and fluoranthene heated at high temperatures can be explained mainly by the scission of C=C bond in pentagons, as suggested by the results of reactive molecular dynamics simulation (ReaxFF).[GRAPHICS].

The performance of graphene-based electronic devices depends critically on the existence of topological defects such as heptagons. Identifying heptagons at the atomic scale is important to completely understand the electronic properties of these materials. In this study, we report an atomic-scale analysis of graphene nanoflakes with two to eight isolated or connected heptagons, using simulated C 1s X-ray photoelectron spectroscopy (XPS) to estimate the XPS profiles depending on the density and the position of the heptagons. The introduction of up to 24% of isolated heptagons shifted the peak position toward high binding energies (284.0 to 284.3 eV), whereas the introduction of up to 39% of connected heptagons shifted the calculated peak position toward low binding energies (284.0 to 283.5 eV). The presence of heptagons also influenced the full width at half-maximum (FWHM). The introduction of 24% of isolated heptagons increased the FWHMs from 1.25 to 1.50 eV. However, the introduction of connected heptagons did not increase the FWHMs above 1.40 eV. The FWHMs increased to 1.40 eV for 19% of connected heptagons, but did not increase further as the percentage of connected heptagons increased to 39%. Based on the calculated results, the XPS profiles of graphene nanoflakes containing heptagons with different densities and positions can be obtained. Our precise identification of heptagons in graphene nanoflakes by XPS lays the groundwork for the analysis of graphene.