Mechanism studies on thermal dissociation of tri-n-octylamine hydrochloride with FTIR, TG, DSC and quantum chemical methods

Abstract

The thermal dissociation of tri-n-octylamine hydrochloride (TOAHCl) was investigated using both the quantum chemical simulation and experimental methods. The pathway through which a mixture of trin-octylamine (TOA) and hydrogen chloride (HCl), rather than din -octylamine (DOA) and 1-chlorooctane, are produced has been determined through transition state (TS) search with Intrinsic Reaction Coordinate (IRC) calculations. Particularly, strong agreement between the experimental FTIR spectra and that of TOA demonstrates the same result for the first time. Moreover, the thermal dissociation of TOAHCl proceeds in two continuous steps, which is different from the low molecular mass amine hydrochlorides. The experimental enthalpy of the dissociation was 70.793 kJ mol −1 with DSC measurement which is very close to the density functional theory (DFT) calculation result 69.395 kJ mol −1. Furthermore, with the aid of DFT calculations, some other important thermochemical characteristics such as crystal lattice energy with the value of 510.597 kJ mol −1 were evaluated by means of Born-Fajans-Haber cycle.

Insight into thermal dissociation of tri‐n‐octylamine hydrochloride: The key to realizing CO2 mineralization with waste calcium/magnesium chloride liquids

“…Thus, N‐H stretching vibrations are sensitive markers of the chemical environment. Such vibrations are typically strongly infrared active and are assigned in the range between 2700 and 2300 cm −1 region, usually as the summation bands . Red shifts would be observed when electron cloud density moves to nitrogen atom, denoting the decrease in vibration force constant, that is, bond strength or bond energy.…”

“…Coenen, Kosswig et al had made extensive studies on the regeneration of tertiary amines from straight‐chain to branched‐chain through thermal dissociation of its chloride. Also, we have made some basic study on the thermal dissociation of solid TOAHCl . In comparison with branched‐chain tertiary amine tris(2‐ethylhexyl)amine (TEHA), it is much difficult to regenerate straight‐chain tertiary amine TOA by dissociation of their chlorides, with considerable higher temperature (with starting temperature of 170°C vs 100°C) and much longer time (with half‐life of 47 and 2 minutes in certain conditions, respectively).…”

“…Also, we have made some basic study on the thermal dissociation of solid TOAHCl. 21,22 In comparison with branched-chain tertiary amine tris(2-ethylhexyl)amine (TEHA), it is much difficult to regenerate straight-chain tertiary amine TOA by dissociation of their chlorides, with considerable higher temperature (with starting temperature of 170°C vs 100°C) and much longer time (with half-life of 47 and 2 minutes in certain conditions, respectively). The optimal temperature of dissociation of TOAHCl is as high as 215°C with the dodecane as the solvent.…”

Hydrochloric Acid‐Assisted Regeneration of Cobalt Ethylenediamine for NOx Remediation in Flue Gas

“…In general, the lower was the pH, the better was the regeneration. Previous studies have shown that the presence of strong acid can easily dissociate the complex [39,40]. The acid effect reduced the conditional stability constant of the complex.…”

“…Therefore, additives can be used to release metal ions and facilitate the in situ recovery of cobalt ethylenediamine [38]. Previous studies indicated that a strong acid such as hydrochloric acid can dissociate the complex [39,40] using hydrogen chloride as the additive. Also, the denitration effect of original and regenerated of cobalt ethylenediamine is compared.…”