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Study On Thermal Hazards And Decomposition Mechanisms Of Three Hydroxylamine Compounds

Posted on:2016-11-01Degree:MasterType:Thesis
Country:ChinaCandidate:J J YanFull Text:PDF
GTID:2191330461482951Subject:Safety engineering
Abstract/Summary:PDF Full Text Request
Hydroxylamine and its salts are important chemicals in industry. Since Hydroxylamine is instability at room temperature, it usually exists as the corresponding salts. As accidents caused by them have brought damage to both people and environment, it is important to increase the thermal stability of hydroxylamine and its hydrochloride salts during production, usage and storage. Accelerating Rate Calorimetry -(ARC) and Differential Scanning Calorimetry (DSC) were used to test the thermal decomposition behaviors of hydroxylamine solution (50w% HA) with mass fraction of 50%, hydroxylamine hydrochloride (HH) and N-methyl hydrochloride (NMHH). And the thermal decomposition mechanisms of Hydroxylamine (HA), HH and NMHH were calculated based on quantum chemistry theory.ARC results showed that, the initial decomposition temperature of 50w% HA was 40 ℃, only slightly higher than room temperature, which means that 50w% HA is easy to decompose. The initial decomposition temperature of HH and NMHH were 110.6 ℃,90.7 ℃, both higher than that of 50w% HA, indicating that 50w% HA was more sensitive to heat than HH and NMHH.The thermal decomposition behaviors of HH and NMHH were similar under adiabatic condition. Their temperature and temperature rising rate both appeared sharp increase during exothermic decomposition. Their thermal decomposition reaction time were both shorter than 30min. There’s little time to rescue when runaway reactions happen.Differential scanning calorimetry (DSC) test results showed that both HH and NMHH’s thermal decompositions have autocatalytic properties. By analyzing ARC data of HH, NMHH, and other chemicals from previous researches in our group, it’s found that the time from initial heat release to maximum temperature rise rate (t0-max) for non-autocatalytic decomposition is much longer than that for autocatalytic decomposition, and the thermal inertia 0 has little influence on this phenomenal. Therefore, the adiabatic test parameter, t0-max, can be used to identify autocatalytic decomposition.This paper used density functional theory (DFT), with several different basis sets, to calculate the stable structures, electronic structures, bond dissociation energies, and other informations of HA, HH and NMHH. Besides, the initial decomposition steps of them were calculated by Gaussian09 software. The results showed that in the stable structure of HH and NMHH, the hydrogen bonds were both formed between N atom and H atom. Methyl and hydrogen bond both can increase the molecular polarity. The initial decomposition step of HA was a bimolecular reaction. When HH and NMHH decompose, the hydrogen bond breaks firstly, then their decomposition products react with H+.
Keywords/Search Tags:Hydroxylamine, Hydroxylamine hydrochloride, N-methyl hydroxyiamine hydrochloride, thermal hazard, adiabatic calorimetry, decomposition mechanism, bond dissociation energies
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