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Novel CO2 adsorbents were prepared by grafting of various aminosilanes on mesoporous silica SBA-15. CO2 adsorption capacities of aminosilane modified SBA-15 in the presence of water vapor were comparable to those in the absence of water vapor. It was found that efficiency of amine increased with increasing surface density of amine.

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The structure and activity of ReO x -Au/CeO2 catalysts for deoxydehydration (DODH) of polyols to alkenes with H2 were investigated in detail. Based on X-ray diffraction (XRD) and transmission electron microscopy (TEM), the sizes of Au particles are in a similar scale to CeO2 support particles and the number of Au particles is much smaller than that of CeO2 support particles. Nevertheless, the catalytic activity and temperature-programmed reduction (TPR) data of the physical mixture of Re/CeO2 and Au/CeO2 indicate that Re species on all the CeO2 particles can be reduced with H2 and can work as a catalytic center. The H2 activation ability of the catalyst with larger (∼12 nm) Au particles (impAu; “imp” means impregnation for loading) is lower than that with smaller (∼3 nm) Au particles (dpAu; “dp” means deposition–precipitation for loading), and the DODH reaction rate over ReO x -impAu/CeO2 is limited by the H2 activation rate. The CeO2-supported dpAu particles have also higher activity in CC hydrogenation, CC migration, and cis/trans isomerization of diols. The CC hydrogenation and CC migration are side reactions in DODH, and in the DODH reaction of polyols, such as glycerol and erythritol, ReO x -impAu/CeO2 shows higher yield of DODH products than ReO x -dpAu/CeO2. In contrast, in the case of diols, the selectivity decrease by these side reactions is small, and ReO x -dpAu/CeO2 is a better catalyst than ReO x -impAu/CeO2 because of the higher activity. In addition, the cis/trans isomerization activity of ReO x -dpAu/CeO2 enables the DODH of trans-1,2-cyclohexanediol, which is usually unreactive in DODH, into cyclohexene via isomerization to cis-1,2-cyclohexanediol and the subsequent DODH.

Hydrothermal treatment of NH4[NbO­(C2O4)2(H2O)2]·nH2O in water at 448 K for 3 days produced crystalline Nb2O5 with a deformed orthorhombic structure and a high surface area (208 m2 g–1). Fourier-transform infrared spectroscopy measurements of pyridine adsorption revealed that the Nb2O5 catalyst has both high densities of Brønsted and Lewis acid sites that can work in the presence of water. One feature of the Nb2O5 catalyst is its high density of water-compatible Lewis acid sites (0.21 mmol g–1), which is much larger than that of Nb2O5·nH2O (0.03 mmol g–1). The Nb2O5 catalyst was studied as a solid acid catalyst for the formation of lactic acid from 1,3-dihydroxyacetone and pyruvaldehyde in water at 373 K, and was determined to be a highly active and selective catalyst, compared with typical acid catalysts (H2SO4, Sc­(OTf)3, and Nb2O5·nH2O). A high Lewis acid density with moderate acid strength is a crucial factor for the high catalytic performance exhibited for the former reaction. High densities of both Brønsted and Lewis acid sites in the catalyst promote the fast and selective production of lactic acid in the latter reaction. In addition, Such Lewis acidity of the Nb2O5 is also effective over conventional acid catalysts in xylose dehydration to furfural in water, with respect to reaction rate and furfural selectivity. The combination of aqueous-phase dehydration of xylose over the Nb2O5 and the continuous extraction of furfural with an immiscible organic solvent resulted in a high selectivity toward furfural of ∼78.5% with high xylose conversion (97%).

A physical mixture of ReOx–Au/CeO2 and carbon-supported rhenium catalysts effectively converted 1,4-anhydroerythritol to 1,4-butanediol with H2 as a reductant.

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Gasification of lignin in supercritical water was investigated over ruthenium catalysts in the presence of various sulfur contaminants. In the absence of sulfur, lignin was gasified over supported ruthenium catalysts completely to methane, carbon dioxide, and hydrogen. In the presence of sulfur, the gas yield decreased with the amount of sulfur added. The carbon dioxide composition in the presence of sulfur was lager than that in the absence of sulfur, and the methane composition was lower. From X-ray photoelectron spectroscopy characterization of catalysts used for gasification, the sulfur species which poisoned the ruthenium sites were found to be ruthenium sulfide, ruthenium sulfite, and ruthenium sulfate. The gas yield increased with an increase in water density. In addition, the amount of sulfur that remained on the catalyst surface after gasification decreased with increasing water density.