Pressure and temperature dependence of the gas‐transport properties of dense poly[2,6‐toluene‐2,2‐bis(3,4‐dicarboxylphenyl)hexafluoropropane diimide] membranes

The gas‐transport properties of poly[2,6‐toluene‐2,2‐bis(3,4‐dicarboxylphenyl)hexafluoropropane diimide] (6FDA‐2,6‐DAT) have been investigated. The sorption behavior of dense 6FDA‐2,6‐DAT membranes is well described by the dual‐mode sorption model and has certain relationships with the critical temperatures of the penetrants. The solubility coefficient decreases with an increase in either the pressure or temperature. The temperature dependence of the diffusivity coefficient increases with an increase in the penetrant size, as the order of the activation energy for the diffusion jump is CH₄ > N₂ > O₂ > CO₂. Also, the average diffusion coefficient increases with increasing pressure for all the gases tested. As a combined contribution from sorption and diffusion, permeability decreases with increases in the pressure and the kinetic diameter of the penetrant molecules. Even up to 32.7 atm, no plasticization phenomenon can be observed on flat dense 6FDA‐2,6‐DAT membranes from their permeability–pressure curves. However, just as for other gases, the absolute value of the heat of sorption of CO₂ decreases with increasing pressure at a low‐pressure range, but the trend changes when the feed pressure is greater than 10 atm. This implies that CO₂‐induced plasticization may occur and reduce the positive enthalpy required to create a site into which a penetrant can be sorbed. Therefore, a better diagnosis of the inherent threshold pressure for the plasticization of a glassy polymer membrane may involve examining the absolute value of the heat of sorption as a function of pressure and identifying the turning point at which the gradient of the absolute value of the heat of sorption against pressure turns from a negative value to a positive one. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 354–364, 2004     

Theoretical kinetic study on the decomposition of 1,5‐diaminotetrazole

1,5‐Daminotetrazole (DAT) is of much interest because of the practical significance and the diversity of characteristics. The study on the decomposition pathway and the kinetics of DAT has been performed based on the quantum chemistry theory. The minimum energy path (MEP) calculation has shown that NH₂N₃ and NH₂CN are the initially detected products of DAT. And the structures of reactant, products and transition state were optimized with MP2 methods using 6‐311G** basis sets, and the energies were refined using CCSD(T)/6‐311G** levels of theory. The calculated rate constants were obtained using the conventional transition‐state theory (TST) and the canonical variational transition‐state theory (CVT) methods. The calculation results indicated that the energy barrier of decomposition reaction is 47.98 kcal mol^?1 and the variational effect is small. In addition, the rate constants and the Arrhenius experience formula of DAT decomposition have been obtained between 200 and 2500 K temperature regions. The fitted three‐parameter expressions calculated using the TST and CVT methods are (TST) and (CVT). This work may provide the theoretical support for further experimental synthesis and testing. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and Characterization of a Novel Energetic Complex [Cd(DAT)6](NO3)2 (DAT = 1,5‐diamino‐tetrazole) with High Nitrogen Content

The novel high nitrogen‐containing energetic complex [Cd(DAT)₆](NO₃)₂ was synthesized by reaction of Cd(NO₃)₂·6H₂O with 1,5‐diamino‐tetrazole (DAT). It was characterized by elemental analysis, FT‐IR spectroscopy and single‐crystal X‐ray diffraction analysis. The central Cd²⁺ ion is coordinated by six nitrogen atoms from six DAT ligand molecules to form a hexacoordinate distorted octahedral compound. The [Cd(DAT)₆](NO₃)₂ molecules are linked together through two types of hydrogen bonds thus forming a stable three‐dimensional net structure. The thermal decomposition mechanism of [Cd(DAT)₆](NO₃)₂ was investigated by DSC and TG/DTG analyses and FT‐IR spectroscopy. The kinetic parameters of the exothermic process were studied by using Kissinger’s and Ozawa–Doyle’s methods.     

Steroselective Hydrolysis of DL‐Beta‐Acetylthioisobutyramide Catalyzed by Genetically Engineered E. Coli Immobilized on Celite 580 in a Packed Bed Bioreactor

Pseudomonas putida IFO12996 catalyzes the stereoselective hydrolysis of methyl dl ‐β‐acetylthioisobutyramide (dl ‐ATIA) to form d ‐β‐acetylthioisobutyric acid (DAT), a key intermediate for synthesis of a series of angiotensin converting enzyme inhibitors. The esterase gene of Pseudomonas putida IFO12996 was cloned and expressed in Escherichia coli which was further immobilized and retained on a packed bed bioreactor filled with Celite 580. The packed bed bioreactor was used to conduct the stereoselective hydrolysis of dl ‐ATIA and to give DAT with a yield of 34.5%, enantiometric excess value of 97% and enantioselectivity value > 150. The optimal pH and temperature for the reaction were 9.0 and 57 °C ～ 67 °C, respectively. The kinetic constants (Km and Vmax) of immobilized cells were found to be 372.5 mM and 285.7 μmol min^?1 (g cell)^?1, respectively. The immobilized cells retained over 60% of the initial catalytic activity after 5 batch cycles of production. This paper presents a simple, practical and economical process of immobilization of genetically engineered E. coli on a novel packed bed bioreactor for production of DAT.     

Synthesis and Crystal Structure of Picrates of 3,5-Diamino-1,2,4-triazole

The title compound C2N5H6+C6N3O7H2-was synthesized by the reaction of 3,5-diamino-1,2,4-triazole and picric acid in the mixture of ethanol and water solution.Single crystals suitable for X-ray measurement were obtained at room temperature.The structure was characterized by elemental analysis and IR and determined by X-ray diffraction analysis.Crystallographic data:C8N8H8O7,Mr = 328.22,monoclinic,space group C2/c with a = 22.815(2),b = 4.8086(5),c = 22.564(2),β = 93.976(2)°,V = 2469.6(4)3,Dc = 1.766 g/cm3,Z = 8,μ = 0.156 mm-1,F(000) = 1344,the final R= 0.0309,wR= 0.0864.     

Synthesis,Performance, and Thermal Behavior of a Novel Insensitive EDNA/DAT Co‐crystal

Due to the acidity and the limited applications of 1,4‐dinitro‐1,4‐diazabutane (EDNA), a novel nitrogen rich energetic co‐crystal based on EDNA and 1,5‐diaminotetrazole (DAT) in a 1:2 molar ratio was synthesized. The formation of the co‐crystal was tested by scanning electron microscope (SEM), powder X‐ray diffraction (PXRD) and Raman spectroscopy. Based on the elemental analysis and the enthalpy of combustion obtained by the calorimetric bomb, the enthalpy of formation was calculated to be 196.9 kJ · mol^–1. Sensitivity to impact was measured and 50 % probability of initiation was 9.7 J for the co‐crystal. In addition, the detonation characteristics were predicted by EXPLO5 Code. The detonation velocity (D) and the detonation pressure (P) of the co‐crystal are 8254.5 m · s^–1 and 26.7 GPa, respectively. The thermal behavior and decomposition kinetics of the co‐crystal and the coformer were described using nonisothermal differential scanning calorimetry (DSC) and thermogravimetry/differential thermogravimetry (TG/DTG) techniques. There is an obvious difference between the thermal behavior of the co‐crystal and the coformer. The activation energy of the co‐crystal (125.3 kJ · mol^–1) is lower than the coformer. The obtained co‐crystal has high nitrogen content and acceptable sensitivity to external stimuli, which makes it promising for expanding the reuse of EDNA in ammunition after overcomeing its acidity problem.