Experiments to measure (i) the reactivity of lithium peroxide and lithium oxide in ambient air as a function of relative humidity and reactant particle size, (ii) the solubility of lithium hydroxide and lithium hydroxide monohydrate in three alcohols, namely methanol, ethanol and 1 and 2-propanol, as a function of time and temperature, (iii) the efficiency of the production of lithium peroxide in alcohol medium as a function of the concentration of LiOH.H 2O in methanol, the concentration of hydrogen peroxide, the kind of alcohol, the kind of feed material, and temperature and the time of mixing, (iv) the analysis of the precipitates, (v) the temperature of the precipitate decomposition in isothermal and non-isothermal conditions in ambient and neutral conditions as function of time, (vi) the activation energy of the precipitate decomposition, (vii) the temperature of the lithium peroxide decomposition in isothermal and non-isothermal conditions as function of time and (viii) the activation energy of lithium peroxide decomposition were performed. / The purpose of the study was to gather the data necessary to evaluate the production of lithium peroxide, Li2O2, and subsequently lithium oxide, Li2O, to be used as a feed for a silicothermic reduction process for the production of metallic lithium. The proposed basis for the production of Li2O2 was the conversion of lithium hydroxide or lithium hydroxide monohydrate by hydrogen peroxide in an alcohol medium. Alcohols were chosen because they are members of a class of non-aqueous solvents that can selectively dissolve the anticipated contaminants while precipitating the desired products. / It was found that the addition of hydrogen peroxide to alcohol solutions containing lithium hydroxide monohydrate resulted in the formation of lithium peroxide as lithium hydroperoxidate trihydrate with eight adduct molecules of methanol, i.e., Li2O2•H2O 2•3H2O•8CH3OH and involved the peroxide group transfer. The optimum conditions for the production of lithium peroxide were found to be (i) the least water concentration in the system (ii) the use of the temperature lower than ambient temperature and (iii) fast separation of the precipitate and raffinate to prevent dissociation of the precipitate or dissolving into the raffinate. / The high solubility of LiOH.H2O and at the same time the low solubility of Li2CO3 and of Li2O2 in methanol resulted in selection of methanol as the best alcohol of those studied for the proposed method of Li2O2 production. It also yielded high purity lithium peroxide. The production of Li2O 2 using H2O2 (35 %wt) required an excess of hydrogen peroxide equal to 2.6 times the stoichiometric amount. / The thermal decomposition of the lithium hydroperoxidate trihydrate precipitate started with the rejection of the adduct methanol molecules, followed by co-evolution of H2O and H2O2 from the resulting Li 2O2•H2O2•H2O. The activation energy of the decomposition reaction of the precipitate was measured as 141 kJ/mol. At temperatures greater than 200°C, lithium peroxide was found to be very reactive with atmospheric air. However, in an argon atmosphere, it rapidly decomposed losing the majority of the oxygen atoms, followed by the gradual slow diffusion of oxygen gas absorbed on the lithium oxide.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.103204 |
| Date | January 2007 |
| Creators | Khosravi, Javad. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Mining, Metals and Materials Engineering.) |
| Rights | © Javad Khosravi, 2007 |
| Relation | alephsysno: 002665338, proquestno: AAINR38597, Theses scanned by UMI/ProQuest. |
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