Liquid crystal equilibrium application for 2 3 DNT initial

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1376 T Go ofit T Zielenkiewicz, Two nitrate groups in ortho position may react with each is very sensitive for impurities concentration and enables. other forming benzofurazan and benzofuroxan 10 12 studying decomposition process at the initial stage. Nitro group next to the methyl group forms anthranil The aim of this paper is to analyze the initial stage of the. 13 14 Reactions between two DNT molecules may lead thermal decomposition of 2 3 DNT with the application of. to the azoxy bond formation 15 In Duh et al 7 onset liquid crystal equilibrium and partial decomposition. decomposition temperatures of only three DNT isomers method The determination of the influence of process. may be found 2 4 dinitrotoluene 2 4 DNT 2 6 dinitro conditions on products forming is the additional purpose. toluene 2 6 DNT and 3 4 dinitrotoluene 3 4 DNT The. lowest decomposition temperature was denoted for 2 4. DNT 523 K and the highest for 2 6 DNT 563 K This Experimental. temperature equals 553 K for 3 4 DNT Two of DNT iso. mers were studied by Ando 8 and 2 4 DNT onset Materials. decomposition temperature was lower in relation to 3 4. DNT It is assumed that homolytic collapse of C H bond in 2 3 Dinitrotoluene was synthesized in the Technical Mili. methyl group is the first decomposition stage in case of tary Academy in Warsaw in 1960s Physico chemical. ortho nitrotoluenes and the next one hydrogen addition to parameters were determined and compared with literature. the oxygen atom from nitro group 9 16 Then the values melting temperature Tm 332 7 329 7 K 26. number of consequent reactions follows with gaseous melting enthalpy DHm 16 1 17 5 kJ mol 1 26 Purity. products as a result Case s studies 17 indicate that of analyzed compound was determined with cryometric. stable DNT decomposition product in solid phase exists method 99 9 mol and with the application of gaseous. below 573 K which decomposes immediately to gaseous chromatography 99 9. products above this temperature Maksimov 18 calculated. kinetic parameters of the thermal decomposition of 2 4 Method used. DNT 2 6 DNT and 3 5 DNT using manometric SMM, method Decomposition rate constant at 500 K is the Measurements were taken on a heat flux DSC 605 UNI. highest for 2 4 DNT and the lowest for 3 5 DNT PAN calorimeter The calibration was performed with. The analysis of total sample decomposition is the most gallium indium cadmium tin zinc naphthalene and ben. often described method of the analysis of different com zoic acid Purity values of used metals were above. pounds thermal stability 19 21 This method allows 99 999 Purity values of organic substances used were. calculation of kinetic parameters on the basis of calori higher than 99 95 Measurements were taken using. metric measurement performed on the sample with mass of hermetic aluminum pans with heating rate of 2 K min 1. cca 1 mg Unfortunately this method generates problems Samples were sealed under reduced pressure of about. with the proper decomposition enthalpy determination 1 3 kPa Calculations of kinetic parameters were made. Samples with minute masses cca 0 5 mg for hermetic independently with two methods partial decomposition. pans 1 2 mg for pans with the hole should be used to and cryometric method. avoid the destruction of measurement device Additionally Partial decomposition method allows the calculation of. such a sample is unrepresentative because of heterogeneity kinetic parameters on the basis of calorimetric measure. on this mass level Thermal effect of total decomposition ments taken on the sample with mass of over a dozen of. covers mainly temporary decomposition products 94 of mg Disadvantages of total decomposition methods are. TNT disappears until 64 of the decomposition thermal eliminated then The measurement should be terminated at. effect is released 22 From the other hand application of the initial stage of decomposition to avoid device. pans with the hole leads in many cases to the overlapping destruction Kinetic parameters were determined with. of evaporation and decomposition process of the sample Borchardt Daniels method Determined kinetic parameters. for instance DNT do not relate to elementary reaction description because of. Already small conversion degree may cause the thermal high complexity of the decomposition process many. explosion 23 That is why detailed studies of initial stage of competitive and consequent reactions during nitro com. the thermal decomposition are significant Special attention pounds decomposition This is only the mathematic. must be paid on the low temperature decomposition in description of experimental data To emphasize this the. conditions as much as possible similar to technological exponential factor is called as apparent activation energy. operations and storage Cryometry is one of often used aEa in further part of this paper This value may be used for. methods of the analysis of impurities production at the initial the analysis of the hazard related to nitro compounds. stage of decomposition 24 25 Liquid crystal equilibrium thermal decomposition. Liquid crystal equilibrium application for 2 3 DNT initial thermal decomposition analysis 1377. The application of cryometric method to kinetic on the basis of these degrees are also proportional The. parameters calculation consisted on studies of the impuri dependence between reaction rates is presented with. ties concentration increase in consecutive melting pro Eq 2. cesses of the same sample which were conducted up to. da dap DHp Ea RT DHp, arbitrarily chosen temperature Cyclic measurements of the Ae Ap eEa RT 2. dt dt DHt DHt, melting process followed by fast heating to high tempera. tures above 450 K and isothermal conditioning of the where A preexponential factor for real conversion degree. sample were performed Aluminum pan was opened after a and Ap preexponential factor for apparent conversion. cycle of a few to dozens of melting conditioning mea degree. surements to analyze decomposition products As the lit The total decomposition enthalpy DH0t can be obtained. erature data 27 28 indicate the possibility of molecules using DSC measurements of small samples complete. aggregation during conditioning at high temperatures decomposition below 0 5 mg But the loss of initial. reclaimed samples were analyzed with the MALDI TOF substance after the measurement may be observed on the. technique to determine molecular masses of compounds change of the melting enthalpy To calculate the conver. formed as a result of the decomposition Additionally sion degree after DSC measurement af changes of the. thermal conditioning of studied compound in high pressure melting enthalpy should be exploited For this purpose the. tight closed pan was performed at similar temperatures assumption should be made that impurities do not created. These samples were also analyzed with MALDI TOF The solid solution and are totally soluble in the liquid phase. analysis of molecular masses of products was performed in The final conversion degree of the partial decomposition. the Centre of Molecular and Macromolecular Studies in af can be calculated using the following equation. Lodz Kratos Kompact MALDI four device was used with DHm DHn. nitrogen laser wavelength 227 nm 3 ns impulse positive af 3. polarization 20 kV of acceleration voltage 200 impulses. per spectrum Decomposition products were dissolved in where DHm is the melting enthalpy before thermal. the acetone before the analysis decomposition measured in the first DSC run and DHn is. the melting enthalpy in a subsequent measurement made on. Method background the same sample In this case conversion degree equals the. nominal molar ratio of impurities, The method for the analysis of the thermal decomposition X.
af x ixi 4, process at the initial stage sample mass of about dozen of i. mg was developed in High Energetic Materials Division. Faculty of Chemistry Warsaw University of Technology where xi molar ratio of the decomposition product i. 29 31 The measurement of sample decomposition was For the determined value of af the condition ap 1 must. terminated when the calorimetric signal increase exceeded be fulfilled That is why following dependence arises. critical thermal power experimentally determined Above DHp. this critical value calorimeter could be destroyed as the af 5. result of reaction going out of the control Sample reaction. degree during measurement is very low for applied tech and also. nique that is why zero order transition model was assumed A af Ap 6. to determine kinetic parameters Ap i aEa Decomposition. enthalpy DHp is related to ap Conversion degree ap equals where A preexponential factor for the real conversion. 1 at the moment of the measurement termination even degree and Ap preexponential factor for the apparent. though real conversion degree is very small That is why ap conversion degree. is called the apparent conversion degree The dependence Liquid crystal equilibrium is very sensitive for the liquid. of real and apparent conversion degree is as follows phase impurities Small amount of impurities significantly. decreases melting temperature of the substance Molar con. a ap 1 centration of impurities the purity of studied compound. DHt0 may be determined with following cryometric equation. where DH0t decomposition enthalpy of whole sample 2. a 1 Tm Tm x 7, The conversion degree ap is proportional to the real. conversion degree a because the enthalpy ratio in where F sample melting degree x real molar ratio of. brackets is constant It arises that reaction rates determined impurities T0m melting temperature of ideally pure. 1378 T Go ofit T Zielenkiewicz, substance Tm sample melting temperature and DHm 366 K the second at 486 K Results of these analyses are. melting enthalpy Following assumption must be intro presented in Fig 1. duced Components totally mix in the liquid phase and No deviation from DSC curve at high temperatures. totally do not mix in the solid phase melting enthalpy of which would indicate the exothermal decomposition was. components in analyzed temperature range is approxi denoted in case of the run terminated at 486 K Very good. mately independent on the temperature the solution may repeatability of the melting process was obtained for. be described with the perfect solution model Where the measurements taken on the same sample Solid solid. molar ratio of impurities is known the purity of the sample phase transition was observed for this compound with the. may be determined with the following equation melting temperature T 307 2 K and melting enthalpy. P 1 x 100 8 DH 4 58 kJ mol 1, Another series of the melting process after isothermal. The sample is polluted by the decomposition products conditioning at 457 467 and 477 K was performed Results. during thermal analysis When the measurement to the are presented in Fig 2. arbitrarily chosen final temperature Tf is performed Prolonged conditioning at the temperature of 457 K. impurities increase Dx follows It equals the difference 350 min and 467 K 810 min did not cause visible. between the molar impurities ratio of the sample taken for increase in impurities determined with cryometric method. studies x0 and the sample after the decomposition xf The However insignificant but systematic decrease in melting. impurities increase is equal to the real molar impurities enthalpy from 17 6 to 16 6 kJ mol 1 in the 10th run was. ratio x connected with the thermal decomposition observed Significant change in the melting process took. X place only in the 11th It was related to measurement pan. Dx x0 xf xi 9, i decompression and sample mass loss during conditioning.
The last conditioning process performed on the sample. where xi molar ratio of the decomposition product i closed in non hermetical pan caused a significant increase. Making the assumption that one molecule of analyzed in impurities determined with cryometric method but did. substance forms on molecule of the impurity during not cause the decrease in the melting enthalpy Slow. decomposition and the rest of volatile impurities are only decomposition of the sample conditioned at raised tem. in gaseous phase the value of real molar ratio of impurities perature was the reason of the enthalpy decrease in runs. Dx should equal to conversion degree af If the value of 1 10 The lack of purity changes determined with cryo. Dx is higher than af parameter then it means that from metric method indicates that decomposition products at the. one molecule of analyzed compound more than a one initial stage of decomposition form separate phase The. molecule of impurities is formed in liquid phase On the first conditioning process at 477 K caused measurement. other hand when value of Dx is lower than af value then pan decompression related to high vapor pressure and. it means that molecules of decomposition products in the gaseous products of decomposition Following condition. liquid phase join and create compounds with molecular ing process caused the decrease in the sample purity from. mass higher than initial compound Size of these molecules. could be defined with so called mean self aggregation. number k 32 34 which may be calculated on the basis of. following equation 25,Dx 10 1 scan,k k af af 20 2 scan. Heat flow mW,Results and discussion,Initial decomposition 5. In order to verify the usability of liquid crystal equilibrium 0. 305 320 335 350, for impurities production determination at the initial stage. of the decomposition series of three measurements of the Temperature K. Liquid crystal equilibrium application for 2 3 DNT initial thermal decomposition analysis melting process followed by fast heating to high tempera tures above 450 K and isothermal conditioning of the sample were performed Aluminum pan was opened after a cycle of a few to dozens of melting conditioning mea surements to analyze decomposition products As the lit erature data 27 28

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