Exothermic reaction

Abstract: In differential thermal analysis, the temperature at which the maximum deflection is observed varies with heating rate for certain types of reactions. An expression can be derived relating this variation with the kinetics of the reaction. By making a number of differential thermal patterns at different heating rates, the kinetic constants can be obtained directly from the differential thermal data. Measurements of the variation of peak temperature with heating rate have been made for several minerals of the kaolin group, the values of the kinetic constants determined, and these values compared with corresponding values obtained for both the same samples and similar material by conventional isothermal techniques. Some factors affecting the results are discussed. The method of differential thermal analysis (DTA) has been universally accepted by mineralogical laboratories as a rapid and convenient means for recording the thermal effects that occur as a sample is heated. Changes in heat content of the active sample are indicated by deflections shown by a line representing the differential temperature. It is conventional to represent an endothermic effect by a negative deflection and an exothermic effect by a positive deflection. The deflections, whether positive or negative, are called peaks.

Abstract: Summary All technically interesting reactions carried out with vanadium oxide catalysts are marked by their highly exothermic character, which forms an impediment to the investigation of the kinetics of these processes. In the present study use was made of a fluid bed, in which the temperature is uniform. The oxidation of the following substances: benzene, toluene, naphthalene, and anthracene has been studied. The partial pressures of the reacting substances were varied to the greatest possible extent. Both reaction components appeared to influence the reaction rate. A formula depicting this influence is derived. This formula may be interpreted by assuming two successive reactions, namely the reaction between the aromatic and the oxygen on the surface, and the re-oxidation of the partly reduced surface by means of oxygen. The formula may be reduced to an equation by which also the data on the oxidation of sulphur dioxide by means of vanadium oxide catalysts found in the literature are well described. Using kinetic data it is possible to determine the optimum temperature distribution in a fixed bed reactor used for the oxidation of sulphur dioxide and to make calculations of the ratio between the amounts of catalyst to be used in the various stages of a multiple-stage reactor. The results of these calculations have been compared with practical experience.

Abstract: We demonstrate efficient blue electrophosphorescence using exothermic energy transfer from a host consisting of N,N′-dicarbazolyl-3,5-benzene (mCP) to the phosphorescent iridium complex iridium(III)bis[(4,6-difluorophenyl)-pyridinato-N,C2′]picolinate (FIrpic). By examining the temperature dependence of the radiative lifetime and the photoluminescence of a film of mCP doped with FIrpic, we confirm the existence of exothermic energy transfer in contrast to the endothermic transfer characteristic of the N,N′-dicarbazolyl-4-4′-biphenyl and FIrpic system. In employing exothermic energy transfer between mCP and FIrpic, a maximum external electroluminescent quantum efficiency of (7.5±0.8)% and a luminous power efficiency of (8.9±0.9)lm/W are obtained, representing a significant increase in performance over previous endothermic blue electrophosphorescent devices.

Abstract: Intermolecular energy transfer processes typically involve an exothermic transfer of energy from a donor site to a molecule with a substantially lower-energy excited state (trap). Here, we demonstrate that an endothermic energy transfer from a molecular organic host (donor) to an organometallic phosphor (trap) can lead to highly efficient blue electroluminescence. This demonstration of endothermic transfer employs iridium(III)bis(4,6-di-fluorophenyl)-pyridinato-N,C2′)picolinate as the phosphor. Due to the comparable energy of the phosphor triplet state relative to that of the 4,4′-N,N′-dicarbazole-biphenyl conductive host molecule into which it is doped, the rapid exothermic transfer of energy from phosphor to host, and subsequent slow endothermic transfer from host back to phosphor, is clearly observed. Using this unique triplet energy transfer process, we force emission from the higher-energy, blue triplet state of the phosphor (peak wavelength of 470 nm), obtaining a very high maximum organic light-emi...

Abstract: A review of the method of self-propagating high-temperature synthesis (SHS) is presented. The review emphasizes the mechanisms of the rapid, non-isothermal reactions associated with this method. Theoretical analyses pertaining to such reactions are presented and examples of experimental observations on solid-solid and solid-gas interactions are discussed.