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Fast oxide-ion conductivity in Bi3.9Sr0.1NbO8−δCl is reported for the first time, and this oxide is stable under a reducing atmosphere.

Intentionally introducing tensile strain into TiO2 by using a spark plasma sintering process could stabilize reduced Ti species and improve the solid acid activity for acetalization.

The low-temperature activation of methane is highly important as a reaction that can dissociate the strongest C-H bond and convert it into useful compounds. This study demonstrated that supported platinum oxide was found to activate methane near room temperature and selectively afford methanol in the presence of oxygen.

Formic acid is one of the most desirable liquid hydrogen carriers. The selective production of formic acid from monosaccharides in water under mild reaction conditions using solid catalysts was investigated. Calcium oxide, an abundant solid base catalyst available from seashell or limestone by thermal decomposition, was found to be the most active of the simple oxides tested, with formic acid yields of 50 % and 66 % from glucose and xylose, respectively, in 1.4 % H2O2 aqueous solution at 343 K for 30 min. The main reaction pathway is a sequential formation of formic acid from glucose by C−C bond cleavage involving aldehyde groups in the acyclic form. The reaction also involves base‐catalyzed aldose‐ketose isomerization and retroaldol reaction, resulting in the formation of fructose and trioses including glyceraldehyde and dihydroxyacetone. These intermediates were further decomposed into formic acid or glycolic acid. The catalytic activity remained unchanged for further reuse by a simple post‐calcination., Formic acid as a hydrogen carrier was produced via oxidative transformation of various monosaccharides including glucose by using calcium oxide, an abundant solid base catalyst available from seashell or limestone, under mild reaction conditions. While the reaction involves isomerization and retroaldol reaction, the main reaction pathway is a sequential formation of formic acid from glucose by C−C bond cleavage involving aldehyde groups.

From decreasing the cost and the reliability of solid oxide fuel cells (SOFCs), increase in power density is strongly required. In order to achieve these requirements, decrease in operating temperature is the most effective way. However, reduced operating temperature leads to significant decrease in electrode activity, particularly cathode. Therefore, the development of novel and highly active cathode is strongly required for intermediate temperature (873-1073 K). In this study, we studied cathodic performance of double perovskite oxide of PrBaCo2O5 as active cathode of SOFC. Because of delamination of PrBaCo2O5 cathode is easily occurred because of larger thermal expansion coefficient. Mixing effects of PrBaCo2O5 with another perovskite oxide were investigated using a LaGaO3-based electrolyte. The electrochemical performance of the cell was measured using electrolyte-supported single cell at 873, 973 and 1073 K and humidified H2 was used as fuel and O2 as oxidant. Among the oxides mixed with PrBaCo2O5 (PBCO), it was found that mixing Sm0.5Sr0.5CoO3 (SSC)shows the smallest cathodic overpotential and the most suitable for increase in cathodic activity. Therefore, composite oxide of PBCO with SSC is active as cathode for SOFC. However, the cells with composite cathodes show lower performance at 1073 K comparing with PBCO cathode and this could be explained by small cathodic internal resistance at 873 K. On the other hand, the cell with PBCO-SSC (1:1) shows small overpotential at 873 K and much larger power density. Therefore, it was found that mixing PBCO with SSC shows the positive effects on the oxygen dissociation on the cathode at decreased temperature and suitable for low temperature operation SOFC. The optimization of SSC content on the cathodic activity of PBCO-SSC mixed oxide was further studied. The cathodic overpotential at 50 mA/cm2 was decreased with increasing amount of SSC and the smallest overpotential was achieved at 1:1 composition at all temperature studied. Positive effects of mixing PBCO and SSC could be assigned to the increased three phase boundary and increased activity to oxygen dissociation. Since cathodic overpotential was decreased significantly by mixing PBCO-SSC, power density of the cell using PBCO-SSC cathode at 1:1 composition shows 232 mW/cm2 at 873 K which is two times larger than that of the cell using PBCO single oxide cathode. Application of PBCO-SSC composite oxide for anode of steam electrolyser was also studied and it was found that PBCO-SSC is also active to oxygen association under applied voltage. Therefore, this study reveals that PBCO-SSC composite is potential air electrode material for intermediate-temperature solid oxide cells.

The understanding of catalytic mechanisms is enhanced by the observation of surface intermediates at reaction conditions using spectroscopic techniques, but this is insufficient, as the observed species may not be involved in the reaction. This work describes a general method of analysis of hydrogenation or oxidation reactions which uses transient spectroscopic data to determine whether an adsorbed species is a reactive intermediate or a spectator on the surface. The assumptions and limitations of the method are summarized. Although the technique is approximate, it is easy to implement, and provides order-of-magnitude estimates of the rate of reaction of an intermediate. The method consists of measuring the change of coverage of the species with time, dθ/dt, during adsorption in inert gas or at reaction conditions. An example is given with the hydrodeoxygenation of the model compound γ-valerolactone (GVL) using a Ni2 P/MCM-41 catalyst, one of the most effective catalysts reported for the transformation. The reaction is relevant to the upgrading of bio-oil derived from pyrolysis of lignocellulosic feedstocks. The kinetics of the reaction and observation by in situ infrared spectroscopy of adsorbed GVL and its transformation to pentanoic acid are consistent with a Langmuir-Hinshelwood mechanism. Analysis by in situ transient X-ray absorption fine structure shows that the adsorbed GVL is a true reaction intermediate.

A NiO–Y2O3 stabilized ZrO2 (NiO–YSZ) supported tubular solid oxide cell, which consists of a La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) dip-coated electrolyte film and Sm0.5Sr0.5CoO3−δ (SSC) air electrode, was prepared and its power generation and electrolysis performance in the intermediate temperature range were investigated. Compared to other rare earth oxides studied, infiltration of Ce nitrate into the substrate was the most effective for increasing cell performance in the case of 2 M infiltration. Moreover, it was found that the infiltration of a higher concentration of the Ce solution increased the maximum power density, because both IR loss and overpotential were significantly decreased. The maximum power density of the cell was 0.95 and 0.42 W cm−2 at 873 and 773 K, respectively at 3 M Ce nitrate infiltration. The long-term stability of the cell was also measured by using the cell infiltrated with 1.5 M Ce, and a stable power generation performance was demonstrated up to 100 h. The steam electrolysis performance of the cell using Ce infiltration was further studied and it was found that Ce also contributes to higher current density in SOEC operation and 1.07 A cm−2 at 1.6 V was achieved at 873 K using 2 M Ce infiltration.

Photocatalytic water splitting is the most ideal system to harvest solar energy for the production of useful chemicals. There have been many attempts to increase the photocatalytic activity of the TiO2 photocatalyst, such as loading co-catalysts and dopants, and the introduction of oxygen vacancies. Strain effects have also attracted much interest to increase the charge mobility in bulk oxide. Here, we report on the effectiveness of tensile strain in stabilizing the anatase phase of TiO2 at high temperature and increasing the photocatalytic activity by an increase in the charge separation with a unique mixed phase structure. The rate of H2 formation over TiO2 was decreased upon spark plasma sintering (SPS) treatment because of a decrease in the surface area; however, SPS treatment with Au dispersion significantly increased the H2 formation rate to higher than that over commercially available P-25 TiO2 (no SPS treatment) loaded with Au. The O2 formation rate was also increased by strain effects in TiO2. Furthermore, strain effects were effective for visible light sensitivity on TiO2.

The need for sustainable, renewable and low-cost approaches is a driving force behind the development of solar-to-H2 conversion technologies. This study aims to develop a new strategy using a visible-light photocatalyst coupled to a biocatalyst for H2 production. Photocatalytic methyl viologen (MV2+) reduction activity was investigated to discover active oxynitrides. In comparative studies with LaTiO2N, BaTaO2N and Ta3N5, it was revealed that the suitable surface area, band gap and band edge potentials are some physical factors that are responsible for the photocatalytic behaviors of GaN:ZnO in MV2+ reduction. The activity is enhanced at higher concentrations and the alkaline pH of triethanolamine (TEOA). The expression of an active [FeFe]-hydrogenase from Escherichia coli (Hyd+E. coli) as a recombinant biocatalyst was confirmed by its MV˙+-dependent H2 production activity. In the photobiocatalytic system of GaN:ZnO and Hyd+E. coli, the rate of H2 production reached the maximum level in the presence of MV2+ as an electron mediator at neutral pH as a biocompatible condition. The present work reveals a novel hybrid system for H2 production using visible-light active GaN:ZnO coupled to Hyd+E. coli, which shows the feasibility of being developed for photobiocatalytic H2 evolution under solar light.

The direct decomposition of nitrogen oxides (NOX) is an ideal way to remove NOX pollution created by chemical industries and automobiles. Ba3Y4O9 is a promising candidate for the NOX direct decomposition reaction, however, its catalytic activity is not high enough and the stability is insufficient. Here, NO decomposition activity on several metal ion doped Ba3Y4O9 catalysts is reported and it is found that Cu is the most effective for increasing the activity. With 10% Cu doping, the catalytic activity and the stability were improved simultaneously. Temperature programmed desorption (TPD) results indicate that doping with Cu increased the amount of surface oxygen vacancies and mobility of the lattice oxygen resulting in an increase of NO adsorption and the promotion of the decomposition of NOX intermediate species. In situ FT-IR spectra prove that Cu doping weakened the association of NO3− species, thus promoting the decomposition of NO3− species at low temperatures, which resulted in high catalytic activity for NOX decomposition. These results indicate that introducing Cu into the Ba3Y4O9 system is an effective way to achieve high activity and a stable catalyst for the direct decomposition of NOX.

Water-acetonitrile (AN) hybrid electrolyte with high concentration of bis(trifluoromethanesulfonyl) imide (LiTFSI) and Lithium bis(fluorosulfonyl) imide (LiFSI) (LiTFSI-LiFSI=3:1, molar ratio) supporting salts are studied for the high potential and large capacity rechargeable dual-ion battery. Water-acetonitrile hybrid electrolyte (WA) shows a wide electrochemical stability window of 3.1 V in 20 m aqueous electrolyte and 3.6 V in 20 m 9LiFSI-1LiTFSI in water: AN=1:3 molar ratio electrolyte. In particular, high oxidation potential, which can be assigned to the strong solvated ionic cluster formed between AN, water and LiTFSI-LiFSI supporting salts. The dual-ion battery is assembled using the graphitic carbon (KS6) and the activated carbon (AC) as cathode and anode, respectively, and 20 m LiTFSI-LiFSI in hybrid AN-water as electrolyte. It is found that the reasonably large capacity, coulombic efficiency and cycle stability were achieved. The KS6/AC cell shows 86 mAh g−1 at the initial cycle and 50 mAh g−1 at 100th cycle in a voltage range of 0–3.25 V, and the average coulombic efficiency of 85% is sustained over 200 cycles. The solvated structure of water to Li+ is strengthened by addition of AN from ATR-IR and NMR spectrums analysis and this change in the solvated structure is the main reason for the increased performance of the aqueous dual-ion battery.

Spinel oxide (CuFe2O4) has been studied as anode for solid oxide fuel cells. Although CuFe2O4 spinel structure was decomposed by reduction atmosphere observed by SEM-EDX, TEM-EDX and XRD, the decomposed CuFe2O4 became metallic phase with the exsolved nano size alloy particles, which were composite of Cu rich Cu-Fe and Fe rich Fe-Cu metal on anode. According to power generation properties, alloy anode formed from CuFe2O4 showed the maximum power density (MPD) of 611 mW/cm2 at 1073 K and 101 mW/cm2 at 873 K. Comparing to Ni-Fe (9:1 wt.%) alloy anode, alloy anode from CuFe2O4 reduction showed significantly decreased anodic polarization resistance, which was measured by impedance spectroscope and so high power density was assigned to nano alloy particles.

Use of perovskite as a cathode for solid oxide electrolysis cell is limited by its insufficient electrolysis current density or catalytic activity. Most of present perovskites used has a crucial drawback ─ significant segregation of A-site cations (i.e. SrO), likely resulting in the degradation of performance. In this work, spinel oxide of CuFe2O4, which is an alkline earth metal free oxide, is applied as the cathode material to investigate its electrochemical performance, microstructure and chemical composition in the electrolysis of CO2/H2O, steam and CO2. It was found that the exsolution of Cu nanoparticles was observed in CO2/H2O co-electrolysis and the microstructure of CuFe2O4 influenced significantly by operating in different CO2/H2O compositions. Despite the significantly microstructural variation of the CuFe2O4 layer, the cell performs relatively stable electrochemical performance in CO2/H2O and steam electrolysis.

Effects of tensile strain induced by the dispersion of Au nanoparticles in Pr2NiO4-based oxide on the oxygen reduction reaction were investigated. Au-dispersed Pr1.9Ni0.71Cu0.41Ga0.05O4+δ (PNCG) showed a much decreased cathodic overpotential, and a cell using Au-dispersed PNCG showed a significantly higher power density, approximately 2.5 times higher than that of a cell using PNCG without dispersed Au. The smallest overpotential was achieved at 3–5 mol % dispersion of Au nanoparticles, at which the largest tensile strain was observed. Impedance measurements suggested that the impedance arc in the lower frequency range was mainly decreased; therefore, the increased activity to oxygen reduction was attributed to the increased bulk and surface diffusivity of oxide ions. Electron energy loss spectroscopy (EELS) shows that oxygen in the strained region was in a more reduced state and this oxygen could be assigned to interstitial oxygen which is highly mobile. In addition, density functional theory (DFT) analy...

The hydrodeoxygenation (HDO) of the cyclic five-membered ester γ-valerolactone (GVL) was studied on a Ni2P/MCM-41 catalyst. The activation of the passivated catalyst in H2 was followed by in situ near-edge X-ray absorption spectroscopy (NEXAFS) which indicated reduction of the catalyst after 3 h at 550 °C. In situ infrared measurements under reactive H2 and inert N2 showed the presence of adsorbed GVL and pentanoic acid (PA) as the most abundant surface intermediates. The results supported a previous reaction network that showed that ring-opening of GVL to produce pentanoic acid was the rate-determining step. This was confirmed by transient infrared measurements which showed that the number of CH2 groups in the adsorbed species increased under H2 flow, consistent with PA formation but not an alkoxide. The results provide understanding of the key steps in the reaction mechanism.

A variety of silica-supported metal oxide catalysts were prepared by the incipient wetness impregnation method and were used for the conversion of dihydroxyacetone to lactic acid. A titanium oxide catalyst with Bronsted acid sites was selective to an intermediate, pyruvaldehyde and a chromium oxide catalyst with Lewis acid sites was selective to lactic acid. The co-impregnation of chromium- and titanium oxides with different ratios accelerated the reaction rate and improved the lactic acid yield up to 80% at 130 °C. Pyridine-adsorbed Fourier-transform infrared spectroscopy indicated that the silica-supported mixed oxides had both Bronsted acid and Lewis acid sites and the trend of the Lewis/Bronsted ratio was close to that of selectivity to lactic acid. Diffuse reflectance UV–vis spectroscopy showed that the silica-supported chromia-titania catalyst composed of isolated Cr and Ti species in tetrahedral coordination. Kinetic analysis revealed that the two critical rate constants, pyruvaldehyde formation and lactic acid formation, for the chromia-titania catalyst were much higher than those of the titania and chromia catalysts.

Hexagonal boron nitride (h-BN) was ball-milled at various rotation speeds (150–600 rpm) using a planetary ball-mill. Ball-milling disrupted the layered structure of the h-BN, resulting in significant increases of surface area. Ball-milling at 400 rpm gave the highest surface area of 412 m2 g−1 while higher rotation speeds decreased the surface areas due to agglomeration. Moreover, ball-milling resulted in the emergence of amino- and hydroxyl groups on the surface which were observed by Fourier transform infrared spectroscopy, and partial oxidation of the surface boron by the formation of B–OH groups was confirmed by X-ray photoelectron spectroscopy. The appearance of trigonal B–O and tetrahedral B–O was observed by boron-11 magic-angle spinning nuclear magnetic resonance spectroscopy. The number of base sites was increased with the increase of rotation speeds of milling, corresponding to the formation of amino groups. The ball-milled h-BN showed catalytic activity for the nitroaldol reaction between nitromethane and benzaldehyde in which the h-BN milled at 400 rpm exhibited the highest reaction rate and turnover frequency. In addition, the ball-milled h-BN could convert glucose with the formation of fructose at 40 °C whereas pristine h-BN showed no activity. The base sites were mainly responsible for the catalytic activity.

Interlayer composite thin film of Pr2Ni0.71Cu0.24Ga0.05O4-Sm0.2Ce0.8O1.9 (PNCG-SDC) was deposited between the La0.9Sr0.2Ga0.8Mg0.2O3-δ (LSGM) thin film and Sm0.5Sr0.5CoO3-δ (SSC) powder cathode for increasing the cathodic activity for intermediate temperature solid oxide fuel cells (IT-SOFCs). It was found that cathodic overpotential was decreased by introduction of PNCG-SDC composite film resulting in the increased power density on both anode and electrolyte supported LSGM cell. The maximum power density of the anode supported cell using PNCG-SDC film was increased to 2.35 and 0.3 W/cm2 at 700 and 500 °C, respectively, which is higher than that of the cell without PNCG-SDC film. The activation energy estimated by cathodic overpotential indicated that PNCG-SDC film was effective for increasing the activity of active sites. Based on these results, PNCG-SDC composited film, which may be double columnar structure, was highly effective for increasing cathodic performance to oxygen reduction at intermediate temperature.

Ball-milled hexagonal boron nitride (h-BN) involving oxidized boron on the surface was found to catalyze oxidative dehydrogenation of ethane with high selectivity to ethylene (92–96%) whereas prist...

The effect on the gas permeance properties and structural morphology of the presence of methyl functional groups in a silica membrane was studied. Membranes were synthesized via chemical vapor deposition (CVD) at 650 &deg, C and atmospheric pressure using three silicon compounds with differing numbers of methyl- and methoxy-functional groups: tetramethyl orthosilicate (TMOS), methyltrimethoxysilane (MTMOS), and dimethyldimethoxysilane (DMDMOS). The residence time of the silica precursors in the CVD process was adjusted for each precursor and optimized in terms of gas permeance and ideal gas selectivity criteria. Final H2 permeances at 600 &deg, C for the TMOS-, MTMOS-, and DMDMOS-derived membranes were respectively 1.7 &times, 10&minus, 7, 2.4 &times, 7, and 4.4 &times, 8 mol∙m&minus, 2∙s&minus, 1∙Pa&minus, 1 and H2/N2 selectivities were 990, 740, and 410. The presence of methyl groups in the membranes fabricated with the MTMOS and DMDMOS precursors was confirmed via Fourier-transform infrared (FTIR) spectroscopy. From FTIR analysis, an increasing methyl signal in the silica structure was correlated with both an improvement in the hydrothermal stability and an increase in the apparent activation energy for hydrogen permeation. In addition, the permeation mechanism for several gas species (He, H2, Ne, CO2, N2, and CH4) was determined by fitting the gas permeance temperature dependence to one of three models: solid state, gas-translational, or surface diffusion.

This paper deals with a study of the mechanism of hydrodeoxygenation (HDO) at 0.1 MPa and 300–350 °C of 2-methyltetrahydrofuran (2-MTHF) over a Ni2P/SiO2 catalyst. The study was conducted using in situ Fourier transform infrared (FTIR) spectroscopy to monitor the adsorbed species during reaction and in situ X-ray absorption fine structure (XAFS) to probe the oxidation state of the Ni component. The work is relevant to the upgrading of bio-oil derived from the pyrolysis of biomass. It was deduced that the initial interaction of the 2-MTHF was with OH groups on the catalyst surface, followed by adsorption on Ni sites. Ring-opening of the tetrahydrofuran led to the formation of the main products of the reaction, n-pentane by HDO and n-butane + CO by decarbonylation. The CO band appeared with a slight delay in the FTIR spectrum because the reaction to form n-pentane was favored and turned over about four times before one n-butane + CO was formed.

This paper provides some general conclusions about the effects of pressure, contact time, permeance, and selectivity in membrane reactors for the dehydrogenation of ethane. It is demonstrated that elevated pressure is desirable for the operation of membrane reactors even though the equilibrium may be unfavorable because of a net increase in moles (such as occurs in many hydrogen-producing reactions). This is because the increased reactant throughputs at higher pressures more than compensates for the decreased conversion, and because permeance is favored with higher pressure differences. It is also shown that a permeance above 10−7 mol m−2 s−1 Pa−1 is needed for satisfactory operation and that product selectivities above 100 do not substantially improve performance. Finally, it is shown that contact times above 10 s are important for operating membrane reactors. As a model A → B + C reaction, the dehydrogenation of ethane (C2H6 → C2H4 + H2) was studied over a 5 wt% Cr/ZSM-5 catalyst in a conventional packed-bed reactor (PBR) and in a membrane reactor (MR) fitted with hydrogen selective silica membranes at various feed flow rates, total pressures and temperatures. Two types of membranes were used. One was prepared by the chemical vapor deposition (CVD) of vinyltriethoxysilane (VTES) at 873 K and had a high H2 permeance of 4.0 × 10−7 mol m−2 s−1 Pa−1 with a H2/C2H6 selectivity of 240 at 823 K. The other was prepared by the CVD of a mixture of silica and zirconia precursors, and had a lower H2 permeance of 1.9 × 10−7 mol m−2 s−1 Pa−1 but a higher H2/C2H6 selectivity of 4300 at 823 K. At all reaction conditions the conversion of C2H6 and yields of C2H4 and H2 in the MR were higher than those in the PBR. The effect of pressure was studied and an important result was the finding that the productivity in H2 formation increased with increasing pressure even though the conversion of C2H6 decreased for thermodynamic reasons. A one-dimensional model was used to describe the MR, and it’s performance was evaluated by correlating the yield enhancement of C2H4 with the permeance of the membranes and also a parameter called an operability level coefficient (OLC), which is the ratio between the permeation rate and the formation rate of a H2 in the membrane reactor. Another notable finding was that a H2 permeance selectivity of 100 was sufficient to achieve good performance in the MR. Higher selectivities did not improve H2 yields significantly.

Hydrothermally stable silica-alumina composite membranes were synthesized through chemical vapor deposition (CVD) of tetraethylorthosilicate (TEOS) and aluminium tri-sec-butoxide precursor at 923 K on porous alumina supports. The membranes showed high hydrogen permselectivity (order of 10−7 mol m−2 s−1 Pa−1) comparable to that of pure silica membranes but with superior hydrothermal stability, and were used in a membrane reactor. The permeation of small gas species (H2, He, Ne) was well explained by a solid-state diffusion mechanism, involving jumps of the permeating species between solubility sites. The permeation mechanism of large gas molecules (CH4, CO2, N2) was explained by the gas translation mechanism involving large pore defects. Steam methane reforming (SMR) on a Ni/MgO-SiO2 catalyst was carried out at 923 K in the membrane reactor and in a conventional packed-bed reactor. The membrane contributed to an increase in the hydrogen production rate by the selective extraction of hydrogen from the reaction zone.

Hydrogen-selective silica membranes were prepared on a macroporous alumina support by chemical vapor deposition (CVD) of vinyltriethoxysilane (VTES) at 873 K at atmospheric pressure. The membrane had a high H2 permeance of 5.4 × 10−7 mol m−2 s−1 Pa−1 with H2 selectivity over CO2, N2, CO and CH4 of 95, 170, 170 and 480, respectively. In situ Fourier transform infrared (FTIR) measurements after CVD on an alumina disk at the same conditions as for the membrane preparation showed that the vinyl groups remained in the silica structure. The VTES-derived membrane had higher hydrothermal stability than a pure tetraethoxyorthosilicate (TEOS)-derived silica membrane, during exposure to 16 mol% water vapor at 872 K for 72 h. The temperature dependence of the permeance of various molecules (He, Ne, H2, CO2, N2, CO, CH4) before and after hydrothermal treatment gave information about the mechanism of permeance and the structure of the membrane. The membrane was composed of a contiguous silica network through which small species permeated by a solid-state mechanism and a small number of pores through which the large molecules diffused. The silica-based structure became more compact after hydrothermal treatment with decreasing permeance of small molecules (He, Ne, H2), while small pores were enlarged increasing permeance of large molecules (CO2, N2, CO, CH4). Calculation results for the small species based on a mechanism involving jumps of the permeating species between solubility sites showed lower activation energy and larger jump distances than those of a TEOS-derived silica membrane. The retention of the vinyl groups in the structure mostly associated with the defect pores resulted in interactions with CH4 and CO2, so that these species permeated by a surface diffusion mechanism.

Direct depolymerization of crystalline cellulose into water-soluble sugars by solvent-free ball milling was examined in the presence of a strongly acidic layered metal oxide, HNbMoO6 , resulting in full conversion with 72 % yield of water-soluble sugars. Measurements by 13 C cross-polarization magic angle spinning NMR spectroscopy and X-ray diffraction revealed that amorphization of cellulose occurred rapidly within 10 min. Scanning electron microscopy equipped with an energy dispersive X-ray indicated that the substrate and the catalyst were well mixed during milling. The time course of the product distribution showed that most of the resultant water-soluble sugars were produced not by successive degradation of oligosaccharides but by direct depolymerization of cellulose chains. The products included glucose, mannose, and cello-oligomers, as well as anhydrosugars. Addition of small amounts of polar solvents increased the sugar yield, whereas further addition of water decreased the selectivity to anhydrosugars. Calculations of the mechanical energy required for the ball-milling process showed that 0.02 % was utilized for the chemical transformation under the conditions examined in this study.

Two types of Ni2P/SiO2 were prepared by different methods, a conventional method involving temperature-programmed reduction (TPR) and a liquid-phase synthesis (LP). Both methods resulted in phase-pure materials with the Ni2P hexagonal phase, but the sample prepared by TPR had lower particle size (7 nm) than the sample prepared by LP synthesis (25 nm). The samples were tested in the gas-phase hydrodeoxygenation of 2-methylfuran (2-MF) in H2 at 0.5 MPa and 250–450 °C, and it was found that the Ni2P/SiO2-TPR gave higher conversions and turnover frequencies than the Ni2P/SiO2-LP. It was conjectured that the difference in activity was due to the higher phosphorus content of the sample prepared by TPR, and this was confirmed by measurements of the P/Ni ratio by x-ray photoelectron spectroscopy. The main products formed by the two catalysts were 2-pentanone and n-pentane and small amounts of 1-pentanol and 2-pentanol. Contact time measurements on the Ni2P/SiO2-TPR sample indicated that 2-pentanone was a primary product, the pentanols were intermediary compounds, and the n-pentane was a final product. Kinetic measurements on the Ni2P/SiO2-LP revealed orders of 0.6 for the 2-MF and 0.5 for H2, consistent with adsorption of both reactants on the catalyst and a surface reaction between the adsorbed species. TPR was also employed to prepare a Cu3P/SiO2 sample. Although a phase-pure material was formed, the substance showed very low activity for the HDO of 2-MF.

Hydrogenation of furanic compounds is one of the important reactions for upgrading of bio-oils and production of diesel fuels. Platinum catalysts supported on amorphous silica and hexagonal boron nitride (h-BN) were prepared by incipient wetness impregnation and subsequent reduction, and were used for the vapor-phase hydrogenation of 2,5-dimethylfuran in hydrogen at atmospheric pressure and a temperature range of 150–350 °C. For the same amount of Pt loading (1 wt%), the particle size of Pt supported on h-BN was larger than that on silica, resulting in a lower amount of CO chemisorption for Pt/BN than that for Pt/SiO 2 . Using the same amount of active sites, Pt/BN exhibited a 3-fold higher turnover frequency than Pt/SiO 2 for the hydrogenation of 2,5-dimethylfuran whereas both catalysts gave similar product distributions with high selectivity to 2-hexanone at any conversion and low selectivity to n -hexane at high conversion. Contact time studies of 2,5-dimethylfuran hydrogenation on Pt/BN suggested that 2,5-dimethylfuran formed the ring-opening product, 2-hexanone and the ring-saturation product, 2,5-dimethyltetrahydrofuran in parallel, with the rate of the direct furan ring-opening being 9-fold higher than that of the furan ring-saturation.

This work explores the use of hexagonal boron nitride (h-BN), a graphite-like compound, as a novel catalyst with base and acid functionalities. For use as a solid catalyst, the layered structure of h-BN was disrupted by ball-milling, exposing boron and nitrogen edge sites as well as increasing the surface area from 3 to ca. 400 m 2 g −1 . Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and proton magic-angle spinning nuclear magnetic resonance spectroscopy ( 1 H MAS NMR) indicated simultaneous and adjacent formation of amino and hydroxyl groups by milling, which function as Bronsted base and acid sites, respectively. Analysis using color indicator reagents and pyrrole-adsorbed 1 H MAS NMR results revealed that the ball-milled h-BN had basic sites of strength +9.3 > H − ≥ +7.2, comparable to those of KY zeolite. Measurements of 31 P MAS NMR of adsorbed trimethylphosphine oxide indicated that the ball-milled h-BN had weak acid sites, comparable to those in HY zeolite. Despite its weak basicity, the ball-milled h-BN showed high activity and selectivity toward β-nitroalkenes for the nitroaldol reaction (Henry reaction) and the Knoevenagel condensation, whereas nontreated h-BN did not show activity. The nitroaldol reaction was considered to proceed in two steps: the abstraction of a proton from nitromethane by the amino group and the formation of an imine followed by a nucleophilic attack of the deprotonated nitromethane. Kinetic isotope effect experiments using D -substituted nitromethane revealed that the first step was the rate-determining step. Several nitroaldol reactions using a variety of monosubstituted benzaldehydes indicated that electron-donating groups enhanced the activity, suggesting that the formation of adjacent base and acid sites is responsible for it. This study shows the high catalytic activity of BN, a solid catalyst with moderate basicity and weak acidity.

This work reports the electrochemical synthesis of ammonia in solid-state cells at 220 °C and atmospheric pressure. Composites of CsH2PO4 and SiP2O7 were used as the electrolyte, and Pt/C-loaded carbon paper was employed as the anode. Five kinds of electrode materials, including Pt/C-, Pt-Ru/C-, Ru/C-, Ru- and Ag-Pd-loaded carbon paper, were examined as the cathode. Electrochemical activities of the cathode materials were evaluated by cyclic voltammetry. Both H2 and steam were used as the hydrogen source. The successful synthesis of ammonia was confirmed using Nessler's solution. When H2 was used as the hydrogen source, ammonia formation rates higher than 10−10 mol cm−2 s−1 were obtained using Pt/C- or Ru-loaded carbon paper as the cathode. When steam was used as the hydrogen source, ammonia formation rates higher than 10−11 mol cm−2 s−1 were obtained using Pt-Ru/C- or Ru/C- or Ru-loaded carbon paper as the cathode. Ru and Ag-Pd were the most promising noble metal catalysts for electrochemical synthesis of ammonia from N2 and steam.

A series of supported Ni-Mo-P alloy catalysts was studied for the catalytic hydrodeoxygenation (HDO) of the cyclic five-membered ester γ-valerolactone (GVL-C5H8O2) as a model compound for pyrolysis oil. Alloy formation in Ni-Mo-P was indicated by X-ray diffraction analysis and X-ray absorption near-edge spectroscopy, which showed systematic shifts with composition. The number of active sites of each metal species was estimated by factor analysis combining CO-uptake measurements and infrared (IR) spectra of adsorbed CO. It was found that the catalytic activity followed the order: Ni2P/MCM-41 > NiMo(3:1)P/MCM-41 > NiMo(1:1)P/MCM-41 ≅ (Ni2P + MoP)/MCM-41 > NiMo(1:3)P/MCM-41 > MoP/MCM-41, whereas the normalized turnover frequency based on Ni sites were similar for all the catalysts, while retaining the same order. It is concluded that adjacent surface Ni atoms are the main active sites involved in the rate-determining step (rds). The Mo-containing catalysts produced more 1-pentanol and C5 hydrocarbons than Ni2P/MCM-41, indicating that while the exposed Ni sites governed catalytic activity, Mo sites controlled the selectivity to C5 hydrocarbons. Thus, steps following the rds were influenced by Mo sites, leading to preferences for different reaction pathway during the HDO of γ-valerolactone. The study reveals that the catalytic behavior of NiMoP catalysts can be tuned by the relative proportion of Ni and Mo sites.