Salt-assisted acid hydrolysis of starch to D-glucose under microwave irradiation

The effect of inorganic salts on the hydrolysis of starch in a microwave field was investigated and it was found that some inorganic salts can effectively accelerate the acid hydrolysis of starch. The yield of D-glucose reached 111 wt% (equal to the theoretical yield). (C) 2001 Published by Elsevier Science Ltd. All rights reserved.

Discriminating the xanthones in an extract of Swertia franchetiana by retention parameters

The quantitative structure-retention relationship is one of the most actively studied topics in the field of chromatography. In this paper, retention parameters of components were used to discriminate the xanthones in a methanol extract of Swertia franchetiana. The extract was analysed by HPLC under two different multistage linear gradient conditions and the retention parameters calculated from these retention data. It was found that the retention parameters of xanthones are in a specific region in the plot of log k(w) vs. S and the xanthones in the extract could be distinguished from other components by this feature. Furthermore, xanthone aglycones and xanthone glucosides could also be discriminated by retention parameters. Copyright (C) 2005 John Wiley Sons, Ltd.

Heat capacity and thermodynamic properties of N-(2-cyanoethyl) aniline (C9H10N2)

The low temperature heat capacities of N-(2-cyanoethyl)aniline were measured with an automated adiabatic calorimeter over the temperature range from 83 to 353 K. The temperature corresponding to the maximum value of the apparent heat capacity in the fusion interval, molar enthalpy and entropy of fusion of this compound were determined to be 323.33 +/- 0.13 K, 19.4 +/- 0.1 kJ mol(-1) and 60.1 +/- 0.1 J K-1 mol(-1), respectively. Using the fractional melting technique, the purity of the sample was determined to be 99.0 mol% and the melting temperature for the tested sample and the absolutely pure compound were determined to be 323.50 and 323.99 K, respectively. A solid-to-solid phase transition occurred at 310.63 +/- 0.15 K. The molar enthalpy and molar entropy of the transition were determined to be 980 +/- 5 J mol(-1) and 3.16 +/- 0.02 J K-1 mol(-1), respectively. The thermodynamic functions of the compound [H-T - H-298.15] and [S-T - S-298.(15)] were calculated based on the heat capacity measurements in the temperature range of 83-353 K with an interval of 5 K. (c) 2004 Elsevier B.V. All rights reserved.

Microcalorimetric studies of the iridium catalyst for hydrazine decomposition reaction

Microcalorimetric studies of H-2, NH3 and O-2 adsorption, as well as the NH3 decomposition activities evaluation were used to characterize the iridium catalysts for hydrazine decomposition with different supports (Al2O3, SiO,) and iridium contents (1.8, 10.8 and 22.1%). The higher H-2 chemisorption amounts on Ir/Al2O3 catalysts than those on the corresponding Ir/SiO2 counterparts revealed that the strong interaction of iridium and Al2O3 led to higher dispersion of iridium on Ir/Al2O3 catalysts than on Ir/SiO2 catalysts. The larger increase in strong H-2 adsorption sites on highly loaded Ir/Al2O3 than the corresponding Ir/SiO2 ones could be attributed to the interaction not only between iridium atoms but also between iridium and Al2O3. The microcalorimetric results for NH3 adsorption showed that no apparent chemisorption of NH3 existed on Ir/SiO2 catalysts while NH3 chemisorption amounts increased on Ir/Al2O3 catalysts with iridium loadings, which arose from the interaction of the catalysts support of Al2O3 With chloride anion. Both highly dispersed iridium active sites and chloride anion on Ir/Al2O3 catalysts could be beneficial to the intermediate NH3 decomposition in N2H4 decomposition. The similar O-2 plots of differential heat versus normalized coverage on Ir/Al2O3 and Ir/SiO2 catalysts could not be due to the metal-support interaction, but to the formation of strong Ir-O bond. (C) 2005 Elsevier B.V. All rights reserved.

Low temperature heat capacity of (S)-ibuprofen

Molar heat capacities of ( S)-ibuprofen were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range from 80 to 370 K. Experimental heat capacities were fitted into a polynomial equation of heat capacities ( C-p,C- m) with reduced temperature ( X), [ X = f(T)]. The polynomial equations for ( S)-ibuprofen were C-p,C- m(s) = - 39.483 X-4 - 66. 649 X-3 + 95. 196 X-2 + 210. 84 X + 172. 98 in solid state and C-p,C- m(L) = 7. 191X(3) + 4. 2774 X-2 + 56. 365 X + 498. 5 in liquid state. The thermodynamic functions relative to the reference temperature of 298. 15 K, H-T - H-298.15 and S-T - S-298.15, were derived for the( S)-ibuprofen. A fusion transition at T-m = (324. 15 +/- 0. 02) K was found from the C-p - T curve. The molar enthalpy and entropy of the fusion transition were determined to be (18. 05 +/- 0. 31) kJ.mol(-1) and (55. 71 +/- 0. 95) J.mol(-1).K-1, respectively. The purity of the ( S)-ibuprofen was determined to be 99. 44% on the basis of the heat capacity measurement. Finally, the heat capacities of ( S)-ibuprofen and racemic ibuprofen were compared.

Determination of heat capacities and thermodynamic properties of 2-(chloromethylthio)benzothiazole by an adiabatic calorimeter

The molar heat capacities of 2-(chloromethylthio)benzothiazole (molecular formula C8H6ClNS2, CA registry no. 28908-00-1) were measured with an adiabatic calorimeter in the temperature range between (80 and 350) K. The construction and procedures of the calorimeter were described in detail. The performance of the calorimetric apparatus was evaluated by heat capacity measurements on alpha-Al2O3. The deviation of experiment heat capacities from the corresponding smoothed values lies within 0.3%, whereas the uncertainty is within +/-0.5%, compared with that of the recommended reference data over the whole experimental temperature range. A fusion transition was found from the C-p-T curve of 2-(chloromethylthio)benzothiazole. The melting temperature and the molar enthalpy and entropy of fusion of the compound were determined to be T-m = (315.11 +/- 0.04) K, Delta(fus)H(m) = (17.02 +/- 0.03) kJ(.)mol(-1), and Delta(fus)S(m) = (54.04 +/- 0.05) J(.)mol(-1.)K(-1), respectively. The thermodynamic functions (H-T - H-298.15) and (S-T - S-298.15) were also derived from the heat capacity data. The molar fraction purity of the 2-(chloromethylthio)benzothiazole sample used in the present calorimetric study was determined to be 99.21 by fraction melting.

Post-grafting preparation of large-pore mesoporous materials with localized high content titanium doping

A new post-grafting process, consisting of two steps of substrate preparation and sol - gel post-grafting, has been developed to prepare titanium-doped mesoporous SBA-15 material with a double-layered structure and locally concentrated titanium content at the inner pore surface. With this novel technique, the single phased and originally ordered mesostructures can be well conserved; in the conventional direct synthesis they can be partially damaged when the frameworks are doped with high content heteroatoms. Titanium species exist in an isolated, tetrahedral structure and are localized at the pore surface; this is beneficial to both reactant access and product release. Characterization with XRD, N-2 adsorption/desorption isotherms, HREM/ EDS, ICP, UV - Vis, and the newly developed UV - Raman spectroscopy confirm these results. Preliminary catalytic tests with the selective epoxidation of cyclohexene show good catalytic activity. Among them, sample TiSBA-15-10 with a Si : Ti molar ratio of 10 shows a TON value of 75 and a highest product ( epoxide) yield of 55%.

Study of adsorption of methylene blue and new methylene blue in liquid-solid interface by slab optical waveguide spectroscopy

A slab optical waveguide (SOWG) has been used for study of adsorption of both methylene blue (MB) and new methylene blue (NMB) in liquid-solid interface. Adsorption characteristics of MB and NMB on both bare SOWG and silanized SOWG by octadecyltrichlorosilane (ODS) were compared. Effect of pH on adsorption on MB and NMB was investigated. Binding rate constant analysis showed that both MB and NMB on bare SOWG demonstrates larger association constants than those on ODS-SOWG. Interactions of NIB and NMB on bare SOWG and ODS-SOWG were analyzed by molecular mechanics calculation method. The binding energy change was in the following order: ENMB-bare > EMB-bare > ENMB-ODS > EMB-ODS. (c) 2004 Elsevier B.V. All rights reserved.