The static relative permittivity εr of carbon dioxide and nitrous oxide has been measured in a temperature range from 273.15 to 353.15 K at pressures up to 30 MPa. The measurements were performed by means of a transformer ratio‐arm bridge with a three‐terminal capacitance cell installed in a pressure vessel at frequencies between 10 to 50 kHz. The newly‐designed capacitance cell and pressure apparatus are described. Experimental εr‐values obtained for the two fluids were estimated to be accurate to within ±0.02%. The critical relative permittivity εr,C, evaluated from the εr‐values of coexisting saturated vapor and saturated liquid, was 1.267±0.001 for carbon dioxide and 1.288±0.003 for nitrous oxide. The density dependence of the εr‐values can be expressed by a quadratic function of density, independent of temperature. The εr‐data for each fluid were combined with available densities from the literature to calculate the molar polarization Pm given by the Clausius‐Mossotti (CM) equation. Some consideration is given for the coefficients of the dielectric virial equation, i.e., the expansion of the CM equation in powers of density.

Noncatalytic conversion of D-cellobiose (at 0.5 M) into 5-hydroxymethyl-2-furaldehyde (5-HMF), a platform chemical for fuels and synthetic materials, was analyzed at 120-200 °C over a wide range of water mole fraction, xw = 0.007-1 in a binary dimethyl sulfoxide (DMSO)-water mixture by means of the in situ (13)C NMR spectroscopy. Effects of the water content were revealed as follows: (i) The tautomerization of the anomeric residue of D-cellobiose from D-glucose to D-fructose type was not initially observed at a lower water content, in contrast to the significant tautomerization into the D-fructose type in a higher water content and pure water. (ii) The lower the water content, the faster the glycosidic-bond cleavage by hydrolysis, because of the high reactivity of solitary water molecules with the large partial charges more naked as in supercritical water clusters due to the isolation by the organic solvent DMSO. (iii) The amount of D-fructose as the intermediate product was larger at the higher xw; despite the increase of D-fructose, the production of 5-HMF from D-fructose was slowed down. (iv) A high 5-HMF yield of 71% was reached at xw = 0.20-0.30 that was 6-10 times the initial D-cellobiose concentration. The best yield of 5-HMF was attained in the low xw region when the polymerization paths into NMR-undetectable species via 5-HMF and anhydromonosaccharides were effectively suppressed. This study provides a new framework to design optimal, noncatalytic reaction process to produce 5-HMF from cellulosic biomass by tuning the water content as well as the temperature and the reaction time.

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Liquid phase static relative permittivities εr of water + acetone and water + dimethyl sulfoxide have been measured over the whole mole-fraction range under pressures up to 300 MPa at 298.15 K. The pressure P dependence of εr values for each mixture was well fitted to the Tait-type equation, and the Tait-type parameters, A and B, were determined. For each aqueous mixture, the composition dependence of (∂ ln εr/∂P) T values at 0.1 MPa evaluated from the static relative permittivity at 0.1 MPa, εr(0.1), and the Tait-type parameters was compared with that of the isothermal compressibility κ T at 0.1 MPa. Values of εr -2(∂εr/∂P) T at 0.1 MPa as a function of composition were also compared for both aqueous mixtures. For pure acetone, (∂ ln εr/∂P) T and εr -2(∂εr/∂P) T values at 0.1 MPa were correlated with temperature by a combination of the present values and the ones evaluated from the literature εr data.