Heat capacity and thermodynamic properties of crystalline ornidazole (C7H10ClN3O3)

The molar heat capacities of 1-(2-hydroxy-3-chloropropyl)-2-methyl-5-nitroimidazole (Ornidazole) (C7H10CIN3O3) with purity of 99.72mol% were measured with an adiabatic calorimeter in the temperature range between 79 and 380K. The melting-point temperature, molar enthalpy Delta(fus)H(m), and entropy, Delta(fus)S(m), of fusion of this compound were determined to be 358.59 +/- 0.04K, 21.38 +/- 0.02 kJ mol(-1) and 59.61 +/- 0.05 J K-1 mol(-1), respectively, from fractional melting experiments. The thermodynamic function data relative to the reference temperature (298.15 K) were calculated based on the heat capacities measurements in the temperature range from 80 to 380 K. The thermal stability of the compound was further investigated by DSC and TG. From the DSC curve an intensive exothermic peak assigned to the thermal decomposition of the compound was observed in the range of 445-590 K with the peak temperature of 505 K. Subsequently, a slow exothermic effect appears when the temperature is higher than 590 K, which is probably due to the further decomposition of the compound. The TG curve indicates the mass loss of the sample starts at about 440K, which corresponds to the decomposition of the sample. (C) 2003 Elsevier B.V. All rights reserved.

Thermodynamic studies of monuron

Monuron (C9H11ClN2O; N,N-dimethyl-N'-(4-chlorophenyl) urea, CAS 150-68-5) was synthesized and the heat capacities of the compound were measured in the temperature range from 79 to 385 K with a high precision automated adiabatic calorimeter. No phase transition or thermal anomaly was observed in this range. The enthalpy and entropy data of the compound relative to the reference temperature 298.15 K were derived based on the heat capacity data. The thermodynamic properties of the compound were further investigated through DSC and TG analysis. The melting point, the molar enthalpy, and entropy of fusion were determined to be 447.6 +/- 0.1 K, 29.3 +/- 0.2 kJ mol(-1), and 65.4 J K-1 mol(-1), respectively. (C) 2004 Elsevier B.V. All rights reserved.

Preparation of Mn substituted La-hexaaluminate catalysts by using supercritical drying

LaMnxAl12-xO19 catalysts were prepared from NH4OH and metal nitrates solutions. Supercritical drying (SCD) and conventional oven drying (CD) methods were used to extract the water in the hydrogel. The effects of drying methods on properties of the catalysts were investigated by means of TEM, N-2-adsorption, thermogravimetry (TG)-differential thermal analysis (DTA) and X-ray diffraction. SCD method is beneficial to maintain high surface area and improving catalytic activity for methane combustion of the catalyst. The specific surface area and pore volume of LaMn1Al11O19 catalyst prepared by SCD method are 28 m(2)/g and 0.23 cm(3)/g, respectively, and the ignition of methane could be carried out at 450degreesC. However, those of the CD catalyst prepared from the same precursor are 15 m(2)/g, 0.11 cm(3)/g and 530 degreesC, respectively. Suitable Mn content (0 less than or equal to x less than or equal to 2) could promote the formation of LaMnAl11O19 hexaaluminate, while further addition of Mn (2 less than or equal to x less than or equal to 6) cause the formation of LaMnO3. (C) 2003 Elsevier B.V All rights reserved.

Hydrothermal synthesis and characterization of microporous crystals of trivalent metal-containing zirconium phosphates

Two organically templated trivalent metal-containing crystalline zirconium phosphate materials FeZrPO-8 and AlZrPO-8 have been prepared hydrothermally by using fluoride as a mineralizer, and 1,6-diaminohexane (DAH) as templates. The powder XRD patterns indicate that the as-synthesized products are new materials. Substitutions of Al3+ or Fe3+ into Zr4+ sites were confirmed by a combination of powder X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) studies. The thermal behavior of the title compounds have been investigated using TG-DTA and X-ray thermodiffractometry, which indicated that the inorganic framework of the compounds are thermally stable up to similar to400 degreesC. (C) 2004 Elsevier B.V. All rights reserved.

Characterization of metal-containing molecular sieves and their catalytic properties in the selective oxidation of cyclohexane

Three types of metal-containing molecular sieves with AFI, AEL and CHA structures (Me = Co, Mn, Cr and V) were synthesized hydrothermally and characterized by XRD, XRF, TG, TPR, NH3-TPD and FT-IR. It was revealed that metals were incorporated into the framework of molecular sieves and induced the presence of charge centers. Both cobalt and manganese in the framework of AIPO-5, AlPO-11 and SAPO-34 were not reducible before the structure collapse. The redox behaviours of these catalysts in cyclohexane oxidation at 403 K using O-2 as oxidant were examined. CoAPO-11 exhibited best activity and good selectivities for the monofunctional oxidation products (88.5%). Cyclohexanol was the major product over most catalysts, whereas for Cr-containing molecular sieves, high selectivity of cyclohexanone was observed. Investigation of reaction mechanism based on CoAPO-11 and CrAPO-5 catalysts indicated that the decomposition of cyclohexyl hydroperoxide (CHHP), the intermediate in cyclohexane oxidation, followed the pathway: cyclohexanone <-- CHHP --> cyclohexanol -->cyclohexanone. (C) 2004 Elsevier B.V. All rights reserved.

Microencapsulation of n-hexadecane as a phase change material in polyurea

For thermal energy storage application, polyurea microcapsules about 2.5 mum in diameter containing phase change material were prepared using interfacial polycondensation method. In the system droplets in microns are first formed by emulsifying an organic phase consisting of a core material ( n-hexadecane) and an oil-soluble reactive monomer, toluene-2, 4-diisocyanate (TDI), in an aqueous phase. By adding water-soluble reactive monomer, diamine, monomers TDI and diamine react with each other at the interface of micelles to become a shell. Ethylenediamine (EDA), 1, 6-hexane diamine (HDA) and their mixture were employed as water-soluble reactive monomers. The effects of diamine type on chemical structure and thermal properties of the microcapsules were investigated by FT-IR and thermal analysis respectively. The infrared spectra indicate that polyurea microcapsules have been successfully synthesized; all the TG thermographs show microcapsules containing n-hexadecane can sustain high temperature about 300 degreesC without broken and the DSC measurements display that all samples possess a moderate heat of phase transition; thermal cyclic tests show that the encapsulated paraffin kept its energy storage capacity even after 50 cycles of operation. The results obtained from experiments show that the encapsulated n-hexadecane possesses a good potential as a thermal energy storage material.

The role of coke in the deactivation of Mo/MCM-22 catalyst for methane dehydroaromatization with CO2

The effect of space velocity on reaction performance and coke deposition over 6Mo/MCM-22 catalyst in methane dehydro-aromatization (MDA) with CO2 were studied. The characterization of catalysts reacted at different space velocity after the same amount of methane feed by TG, TPO and Benzene/NH3-TPD techniques suggested that the inert coke maybe responsible for the deactivation of catalyst because of its blockage effect for pore system.

Investigation of thermodynamic properties of Co2O3 powder

The isobaric molar heat capacities of powder of Co2O3 were determined by an adiabatic calorimeter in the temperature range from 78 to 350 K. No phase transition takes place in this temperature range. The relationship of C-p,C-m with thermodynamic temperature T was established as C-p,C-m = -5 x 10(-6)T(3) + 0.0026T(2) + 0.0325T + 4.2592 (J K-1 mol(-1)), fitting coefficient R-2 = 0.9996. According to this relationship and the relationships between thermodynamic functions, the thermodynamic functions of powder of C2O3 were derived with 298.15 K as reference temperature. Thermal decomposition of Co2O3 powder was studied through thermogravimetry (TG). The possible mechanism of the thermal decomposition reaction was suggested according to the TG result. (C) 2003 Elsevier Science B.V. All rights reserved.

Synthesis and spectroscopic study of mesoporous aluminum methylphosphonate foam templated by dibutyl methylphosphonate

New types of templates and novel interactive mechanisms between template and framework are very important for creating porous materials. In this work, by using neutral dibutyl methylphosphonate as a template, an inorganic-organic hybrid mesoporous material, aluminum methylphosphonate, was prepared. The as-synthesized material was studied by P-31 magnetic angle spinning nuclear magnetic resonance (MAS NMR), Al-27 MAS NMR, C-13 CP/MAS, FT-IR spectroscopy, thermogravimetry (TG), differential thermal analysis (DTA), and transmission electron microscopy. After thermal treatment at 673 K and 10 mmHg for 2 h, hybrid mesoporous foam was obtained. The transformation process was investigated by FT-IR. TG-DTA results indicate that the methyl group bonded to the framework keeps intact up to 792 K under air and 823 K under nitrogen. The characterization results from nitrogen gas adsorption-desorption measurements show that the BET surface area and the Barrett-Joyner-Halenda desorption cumulative pore volume of the foam are 90 m(2) g(-1) and 0.32 cm(3) g(-1) respectively. (C) 2003 Elsevier Inc. All rights reserved.

Shape selectivity in methane dehydroaromatization over Mo/MCM-22 catalysts during a lifetime experiment

Dehydroaromatization of CH4 with 2% CO2 on 6Mo/MCM-22 in a 100-h lifetime test was carried out at 993 K, atmospheric pressure and 1500 mL/gh. The duration of the lifetime test can be divided into an induction stage, stable stage and deactivation stage on the basis of the selectivities of hydrocarbons and coke. The characteristics of deposited coke with different time onstream were studied using TPO and TG techniques. There were two peaks corresponding to two kinds of coke recorded in TPO profiles, and the oxidation temperature of coke shifted to higher values with less hydrogen content with the increase of coke deposits. BET and Benzene-TPD techniques were employed to study the variation of specific surface area of the external and micropore surface versus time onstream. With the accumulation of coke deposits, although the pores became partially blocked and the internal surface decreased, methane could still enter the channel and was converted to benzene with shape selectivity until a critical value of coke deposition was reached.

共轭亚油酸镁硒复方制剂对食高脂饲料肥胖小鼠的减肥作用

目的:探讨共轭亚油酸镁硒复方制剂(CMS)对食高脂饲料小鼠的减肥作用。方法:选昆明种小鼠63只,随机分为5组,正常对照组10只,模型对照组14只,高、中、低剂量组各13只。正常对照组给予基础饲料,模型对照组和实验组给予高脂饲料,实验组同时按0.2mL/10gBW经口灌胃给予1.5%的羧甲基纤维素CMS水溶液,模型对照组和正常对照组给予相同的1.5%的羧甲基纤维素水溶液。实验4周后,称体重和睾丸周围脂肪量,计算饲料利用率,测定血清甘油三酯(TG)、高密度脂蛋白胆固醇(HDL-C)、总胆固醇(CHO)、血糖(GIU)。结果:与模型对照组相比,CMS中剂量组体重明显降低(P<0.05),高剂量组极明显降低(P<0.01);睾丸周围脂肪重量、脂体指数CMS3个剂量组极明显降低(P<0.01),食物摄入量没有明显变化。结论:CMS有降低食高脂饲料胖鼠体重、脂肪的作用。

Controllable synthesis of metal hydroxide and oxide nanostructures by ionic liquids assisted electrochemical corrosion method

Cu(OH)(2) nanowires have been synthesized by anodic oxidation of copper through a simple electrolysis process employing ionic liquid as an electrolyte. Controlling the electrochemical conditions can qualitatively modulate the lengths, amounts, and shapes of Cu(OH)(2) nanostructures. A rational mechanism based on coordination self-assembly and oriented attachment is proposed for the selective formation of the polycrystalline Cu(OH)(2) nanowires. In addition, the FeOOH nanoribbons, Ni(OH)(2) nanosheets, and ZnO nanospheres were also synthesized by this route, indicative of the universality of the electrochemical route presented herein. The morphologies and structures of the synthesized nanostructures have been characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), powder X-ray diffraction (XRD). Fourier transform infrared spectra (FT-IR), and thermogravimetric (TG). (C) 2007 Elsevier Masson SAS. All rights reserved

Structural characterization, stability and electrical properties of strontium niobate ceramic

The double perovskite oxide Sr2CrNbO6 has a cubic structure according to powder X-ray diffraction. After reducing in CO, Sr2CrNbO6 still exhibited a cubic structure refined by Rietveld technique. The TG analysis indicated that Sr2CrNbO6 loses 0.127 oxygen per formula unit from 400 to 700 degrees C in H-2. The morphology and compositions of this ceramic did not significantly change on reduction

Two novel molybdenum complexes containing [Mo2O2S2](2+) fragment: synthesis, crystal structures and catalytic studies

Mo2O2S2(HGly)(GlY)(2) 1 and K-6[Mo2O2S2(nta)(2)][Mo2O2S2(ntaH)(2)]center dot 4H(2)O 2 were synthesized by the reactions of (NH4)(2)MoS4 and amino acids L (L = glycine, nitrilotriacetic acid) in ethanol-water medium at ambient temperature. The two complexes were characterized by elemental analysis, infrared spectra, UV-visible spectra, TG-DTA and XPS.

Preparation and Luminescence Properties of YVO4:Ln and Y(V, P)O-4:Ln (Ln = Eu3+, Sm3+, Dy3+) Nanofibers and Microbelts by Sol-Gel/Electrospinning Process

One-dimensional YVO4:Ln and Y(V, P)O-4:Ln nanofibers and quasi-one-dimensional YVO4:Ln microbelts (Ln = Eu3+, Sm3+, Dy3+) have been prepared by a combination method of sol-gel process and electrospinning. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), low-voltage cathodoluminescence (CL), and time-resolved emission spectra as well as kinetic decays were used to characterize the resulting samples.