Conversion of Cellobiose to Formic Acid as a Biomass-Derived Renewable Hydrogen Source Using Solid Base Catalysts.

Formic acid is considered a promising hydrogen carrier. Biomass-derived formic acid can be obtained by oxidative decomposition of sugars. This study explored the production of formic acid from cellobiose, a disaccharide consisting of d-glucose linked by β-glycosidic bonds using heterogeneous catalysts under mild reaction conditions.

Low-temperature selective oxidation of methane to methanol over a platinum oxide.

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.

Oxidative Conversion of Glucose to Formic Acid as a Renewable Hydrogen Source Using an Abundant Solid Base Catalyst.

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.

Synthesis of Silica Membranes by Chemical Vapor Deposition Using a Dimethyldimethoxysilane Precursor.

Silica-based membranes prepared by chemical vapor deposition of tetraethylorthosilicate (TEOS) on γ-alumina overlayers are known to be effective for hydrogen separation and are attractive for membrane reactor applications for hydrogen-producing reactions. In this study, the synthesis of the membranes was improved by simplifying the deposition of the intermediate γ-alumina layers and by using the precursor, dimethyldimethoxysilane (DMDMOS). In the placement of the γ-alumina layers, earlier work in our laboratory employed four to five dipping-calcining cycles of boehmite sol precursors to produce high H selectivities, but this took considerable time.

Gas Separation Silica Membranes Prepared by Chemical Vapor Deposition of Methyl-Substituted Silanes.

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 °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.

Fabrication and Evaluation of Trimethylmethoxysilane (TMMOS)-Derived Membranes for Gas Separation.

Gas separation membranes were fabricated with varying trimethylmethoxysilane(TMMOS)/tetraethoxy orthosilicate (TEOS) ratios by a chemical vapor deposition (CVD) method at650 °C and atmospheric pressure. The membrane had a high H permeance of 8.3 × 10 mol m sPa with H2/CH4 selectivity of 140 and H/CH selectivity of 180 at 300 °C.

Mechanochemical Decomposition of Crystalline Cellulose in the Presence of Protonated Layered Niobium Molybdate Solid Acid Catalyst.

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, HNbMoO , resulting in full conversion with 72 % yield of water-soluble sugars. Measurements by 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.

Efficient Epimerization of Aldoses Using Layered Niobium Molybdates.

Both non-acidic LiNbMoO6 and strongly acidic HNbMoO6 efficiently catalyze the epimerization of sugars including glucose, mannose, xylose, and arabinose in water. The reactions over these oxides reached almost equilibrium within a few hours where yields of corresponding epimers from glucose, xylose, and arabinose were 24-29%. The layered mixed oxides functioned as heterogeneous catalysts and could be reused without loss of activity, whereas bulk molybdenum oxide MoO3 was completely dissolved during the reaction.

Intercalation-controlled cyclodehydration of sorbitol in water over layered-niobium-molybdate solid acid.

Layered niobium molybdate (HNbMoO6 ) was used in the aqueous-phase dehydration of sorbitol and was found to exhibit remarkable selectivity toward its monomolecular-dehydrated intermediate 1,4-sorbitan. This was attributed to the selective intercalation of sorbitol within the interlayers with strong Brønsted acid sites.

Role of base in the formation of silver nanoparticles synthesized using sodium acrylate as a dual reducing and encapsulating agent.

The formation mechanism of Ag nanoparticles (NPs) synthesized with a wet-chemical reduction method using sodium acrylate as a dual reducing and capping agent was investigated with various analytical techniques. The time course of the state of the reaction solution was investigated using UV-vis and XAFS spectroscopies which showed that the NP formation rate increased with increasing concentration of sodium hydroxide (NaOH). The detailed kinetic analyses reveal that both the reduction rate of Ag ions and the nucleation rate of Ag NPs are dramatically increased with increasing NaOH concentration.

Selective oxidation of glycerol by using a hydrotalcite-supported platinum catalyst under atmospheric oxygen pressure in water.

A hydrotalcite-supported platinum (Pt/HT) catalyst was found to be a highly active and selective heterogeneous catalyst for glycerol oxidation in pure water under atmospheric oxygen pressure in a high glycerol/metal molar ratio up to 3125. High selectivity toward glyceric acid (78 %) was obtained even at room temperature under air atmosphere. The Pt/HT catalyst selectively oxidized the primary hydroxyl group of 1,2-propandiol to give the corresponding carboxylic acid (lactic acid) as well as glycerol.

In situ time-resolved XAFS study on the formation mechanism of Cu nanoparticles using poly(N-vinyl-2-pyrrolidone) as a capping agent.

The formation mechanism of copper nanoparticles (NPs) using poly(N-vinyl-2-pyrrolidone) (PVP) as a capping agent was investigated by measurements of X-ray diffraction (XRD), transmission electron microscopy (TEM), in situ time-resolved X-ray adsorption fine structure (XAFS) analysis, in situ UV-vis spectroscopy, and an indicator method. XAFS analyses, in combination with TEM observations and the indicator method, revealed that the stable intermediates such as Cu(OH)(2) and Cu(+)-PVP intermediate were formed during an induction period of nucleation of Cu NPs, which play a critical role in the Cu NP formation. Our results suggest that the PVP capping agent is important not only to protect NPs from overgrowth and aggregation but also to control the reaction kinetics of NP formation.

A one-pot reaction for biorefinery: combination of solid acid and base catalysts for direct production of 5-hydroxymethylfurfural from saccharides.

5-Hydroxymethylfurfural (HMF), one of the most important intermediates derived from biomass, was directly produced from monosaccharides (fructose and glucose) and disaccharides (sucrose and cellobiose) by a simple one-pot reaction including hydrolysis, isomerization and dehydration using solid acid and base catalysts under mild conditions.

Glucose production from saccharides using layered transition metal oxide and exfoliated nanosheets as a water-tolerant solid acid catalyst.

The layered transition-metal oxide HNbMoO(6) is demonstrated to exhibit remarkable catalytic performance for the hydrolysis of saccharides such as sucrose, cellobiose, starch, and cellulose, attributable to water tolerance and the facile accessibility of saccharides into the strong acidic interlayer gallery of the solid.

Efficient utilization of nanospace of layered transition metal oxide HNbMoO6 as a strong, water-tolerant solid acid catalyst.

Layered HNbMoO6 was found to function as a strong solid acid catalyst, exceeding the activity of zeolites and ion-exchange resins for Friedel-Crafts alkylation. HNbMoO6 also exhibited high catalytic activity for esterification of hydrocarboxylic acid and hydration. The catalytic performance of layered HNbMoO6 is attributed to the intercalation of reactants into the interlayer and the development of strong acidity.

Photoconductive properties of organic-inorganic hybrid films of layered perovskite-type niobate.

A hybrid film of layered niobate and an organic amphiphile was prepared by the Langmuir-Blodgett (LB) method. Trimethylammonium-exchanged perovskite-type niobates ((CH(3))(3)NHSr(2)Nb(3)O(10)) were exfoliative to form an aqueous suspension. A monolayer of octadecylamine was produced on such an aqueous dispersion as a template for a hybrid film.

Green chemistry: biodiesel made with sugar catalyst.

The production of diesel from vegetable oil calls for an efficient solid catalyst to make the process fully ecologically friendly. Here we describe the preparation of such a catalyst from common, inexpensive sugars. This high-performance catalyst, which consists of stable sulphonated amorphous carbon, is recyclable and its activity markedly exceeds that of other solid acid catalysts tested for 'biodiesel' production.

Exfoliated nanosheets as a new strong solid acid catalyst.

Two-dimensional metal oxide sheets in HTiNbO(5) and HSr(2)Nb(3)O(10), cation-exchangeable layered metal oxides, were examined as solid acid catalysts. Exfoliation of HTiNbO(5) and HSr(2)Nb(3)O(10) in aqueous solutions formed colloidal single-crystal TiNbO(5)(-) and Sr(2)Nb(3)O(10)(-) nanosheets, which precipitated under an acidic condition to form aggregates of HTiNbO(5) nanosheets and HSr(2)Nb(3)O(10) nanosheets. Although esterification of acetic acid, cracking of cumene, and dehydration of 2-propanol were not catalyzed by original HTiNbO(5) because of the narrow interlayer distance, which prevents the insertion of organic molecules, HTiNbO(5) nanosheets functioned as a strong solid acid catalyst for the reactions.