Standard enthalpy of formation of 3,4,5-trimethoxybenzoic acid

The energy of combustion of crystalline 3,4,5-trimethoxybenzoic acid in oxygen at T=298.15 K was determined to be -4795.9±1.3 kJ mol^-1 using combustion calorimetry. The derived standard molar enthalpies of formation of 3,4,5-trimethoxybenzoic acid in crystalline and gaseous states at T=298.15 K, Δ_fH_m ^Θ (cr) and Δ_fH_m ^Θ (g), were -852.9±1.9 and -721.7±2.0 kJ mol^-1, respectively. The reliability of the results obtained was commented upon and compared with literature values. This revised version was published online in August 2006 with corrections to the Cover Date.     

Some thermodynamic aspects of nitrides in materials science

The energies of combustion in fluorine of gallium nitride and indium nitride in wurzite crystalline structure have been measured in a two-compartment calorimetric bomb, and new standard molar enthalpies of formation have been calculated: Δ_fH_m⁰(GaN(cr) 298.15 K)= –(163.7±4.2) kJ mol^–1 and Δ_fH_m⁰(InN(cr) 298.15 K)= –(146.5±4.6) kJ mol^–1 . Comparison with the recommended values of the Δ_fH_m⁰ nitrides from the literature is also presented.     

室温离子液体EMIES的标准生成焓

在(298.15 ±0.01) K下用转动弹热量计测定了离子液体硫酸乙酯-1-甲基-3-乙基咪唑(EMIES)及合成它的原料1-甲基咪唑的恒容燃烧热,通过计算得到它们的标准燃烧焓 分别为(－2671±2) 和(－286.3±0.5) kJ·mol－1;标准生成焓 分别为(－3060±3) kJ·mol－1和(－2145±4) kJ·mol－1.结合文献上硫酸二乙酯的标准生成焓数据,得到了合成离子液体EMIES的反应热(－102.3±1.0) kJ·mol－1,与合成实验中观察到的强烈放热现象是一致的.根据离子液体EMIES的热容数据,计算了不同温度下EMIES的标准生成焓.     

Modulated differential scanning calorimetry in the glass transition region

Temperature-modulated calorimetry (TMC) allows the experimental evaluation of the kinetic parameters of the glass transition from quasi-isothermal experiments. In this paper, model calculations based on experimental data are presented for the total and reversing apparent heat capacities on heating and cooling through the glass transition region as a function of heating rate and modulation frequency for the modulated differential scanning calorimeter (MDSC). Amorphous poly(ethylene terephthalate) (PET) is used as the example polymer and a simple first-order kinetics is fitted to the data. The total heat flow carries the hysteresis information (enthalpy relaxation, thermal history) and indications of changes in modulation frequency due to the glass transition. The reversing heat flow permits the assessment of the first and higher harmonics of the apparent heat capacities. The computations are carried out by numerical integrations with up to 5000 steps. Comparisons of the calculations with experiments are possible. As one moves further from equilibrium, i.e. the liquid state, cooperative kinetics must be used to match model and experiment.On leave from Toray Industries, Inc., Otsu, Shiga 520, Japan.This work was supported by the Division of Materials Research, National Science Foundation, Polymers Program, Grant # DMR 90-00520 and the Division of Materials Sciences, Office of Basic Energy Sciences, U. S. Department of Energy at Oak Ridge National Laboratory, managed by Lockheed Martin Energy Research Corp. for the U. S. Department of Energy, under contract number DE-AC05-96OR22464. Support for instrumentation came from TA Instruments, Inc. Research support was also given by ICI Paints, and Toray Industries, Inc.     

添加剂铜和银离子对MnO2催化燃烧CH4的影响

催化燃烧法，由于起燃温度低、去除率高、适用氧浓度范围大、无二次污染、燃烧缓和等，是国内外治理有机废气时，回收利用能量最有效的方法之一［１］．但目前用于该过程的催化剂中均含有来源有限、价格昂贵的贵金属铂或钯［２］．因此，寻找来源丰富、价格低廉、性能相当...     

Thermochemistry of the solid complex Gd(Et<Subscript>2</Subscript>dtc)<Subscript>3</Subscript>(phen)

Summary A ternary solid complex Gd(Et₂dtc)₃(phen) has been obtained from reactions of sodium diethyldithiocarbamate (NaEt₂dtc), 1,10-phenanthroline (phen) and hydrated gadolinium chloride in absolute ethanol. The title complex was described by chemical and elemental analyses, TG-DTG and IR spectrum. The enthalpy change of liquid-phase reaction of formation of the complex, Δ_rH^Θ_m(l), was determined as (-11.628±0.0204) kJ mol^-1 at 298.15 K by a RD-496 III heat conduction microcalorimeter. The enthalpy change of the solid-phase reaction of formation of the complex, Δ_rH^Θ_m(s), was calculated as (145.306±0.519) kJ mol^-1 on the basis of a designed thermochemical cycle. The thermodynamics of reaction of formation of the complex was investigated by changing the temperature of liquid-phase reaction. Fundamental parameters, the apparent reaction rate constant (k), the apparent activation energy (E), the pre-exponential constant (A), the reaction order (n), the activation enthalpy (Δ_rH^Θ_≠), the activation entropy (Δ_rS^Θ_≠), the activation free energy (Δ_rG^Θ_≠) and the enthalpy (Δ_rH^Θ_≠), were obtained by combination of the thermodynamic and kinetic equations for the reaction with the data of thermokinetic experiments. The constant-volume combustion energy of the complex, Δ_cU, was determined as (-18673.71±8.15) kJ mol^-1 by a RBC-II rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, Δ_cH^Θ_m, and standard enthalpy of formation, Δ_fH^Θ_m, were calculated to be (-18692.92±8.15) kJ mol^-1 and (-51.28±9.17) kJ mol^-1, respectively.     

Surface characterization of Co,K/La2O3 catalysts used for the catalytic combustion of diesel soot

Catalysts of Co,K/La₂O₃ have been prepared by wet impregnation. The samples have been calcined at 400°C and 700°C and have been characterized for phase composition using x‐ray diffraction and Fourier transform infrared spectroscopy. The XPS analysis of the samples has been obtained by examination of the O 1s, K 2p, C 1s and La 3d spectral regions. The XPS data are discussed with respect to the calcination temperatures and the soot combustion performed in the spectrometer reaction chamber. Analysis of the XPS data indicates considerable carbonation of the surfaces of all samples, even after burning the soot. The K/La₂O₃ solid presents the highest content of surface carbonated species, showing the highest catalytic activity for soot combustion. Interaction of the catalysts with CO₂ is studied by temperature‐programmed desorption and microbalance experiments. Kinetic studies and surface characterization of the potassium‐containing samples suggest that an appropriate surface potassium concentration is necessary for a synergetic action between potassium and lanthanum. In the cobalt‐containing catalysts calcined at 700°C, an increase is observed in the concentration of the outer‐layer perovskite species when the potassium content increases, following the same tendency observed in the bulk. Such LaCoO₃ species would limit the reaction of lanthanum with CO₂. Copyright © 2003 John Wiley & Sons, Ltd.     

氧化条件下NOx催化的甲烷均相部分氧化

考察了没有固体催化剂时NOx对甲烷气相氧化的促进作用.实验结果表明，即使在强氧化条件下（O2/CH4=5），NOx对甲烷部分氧化制一氧化碳仍然有明显的催化活性.在CH4-O2体系中加入0.005％～0.2％的NO后，反应温度可降低200-300 ℃.在反应产物中还可观察到甲醛和乙烯，通过改变反应条件可以控制它们的相对浓度.     

Determination of the enthalpy of fusion of K3TaF8 and K3TaOF6

The areas of the fusion and crystallization peaks of K₃TaF₈ and K₃TaOF₆ have been measured using the DSC mode of the high-temperature calorimeter (SETARAM 1800 K). On the basis of these quantities and the temperature dependence of the used calorimetric method sensitivity, the values of the enthalpy of fusion of K₃TaF₈ at temperature of fusion 1039 K: Δ_fusH_m(K₃TaF₈; 1039 K) = (52 ± 2) kJ mol⁻¹ and of K₃TaOF₆ at temperature of fusion 1055 K: Δ_fusH_m(K₃TaOF₆; 1055 K) = (62 ± 3) kJ mol⁻¹ have been determined.     

Conventional hydrothermal process versus microwave-assisted hydrothermal synthesis of La1−xAgxMnO3+δ (x = 0, 0.2) perovskites used in methane combustion

A study on the synthesis of La_1−xAg_xMnO_3+δ (x = 0, 0.2) using a microwave process (MWhyd) has been carried out by comparing the heating time and reaction temperature with the same factor under conventional thermal process (CHhyd). Experiments have been conducted using the hydrothermal method at medium pressure (T = 200 °C, P = 20 atm) followed by a thermal treatment of the precursor at 700 °C (10 h).Structural and physico-chemical properties of the catalysts were investigated using X-ray diffraction (XRD), BET sorption, temperature-programmed reduction or desorption, mass spectrometry (TPR-MS and TPD-MS), and X-ray photoelectron spectroscopy (XPS). While CHhyd and MWhyd powder catalysts exhibited the same XRD patterns indexed as pure perovskite structure, their surface physico-chemical properties were found to be strongly influenced by the preparation method. The effect of the nature of oxygen species, their amount and mobility, evidenced by temperature programmed experiments, on the catalytic properties in methane combustion in the presence and in the absence of hydrogen sulphide has been studied. MWhyd-La_0.8Ag_0.2MnO_3+δ catalysts were found to exhibit a much better performance in methane combustion together with higher resistance to sulphur poisoning than CHhyd catalysts.