Theoretical and Experimental Evaluation of Chemical Reactivity

Abstract

Reactive chemicals are presented widely in the chemical and petrochemical process industry. Their chemical reactivity hazards have posed a significant challenge to the industries of manufacturing, storage and transportation. The accidents due to reactive chemicals have caused tremendous loss of properties and lives, and damages to the environment. In this research, three classes of reactive chemicals (unsaturated hydrocarbons, self-reacting chemicals, energetic materials) were evaluated through theoretical and experimental methods. Methylcyclopentadiene (MCP) and Hydroxylamine (HA) are selected as representatives of unsaturated hydrocarbons and self-reacting chemicals, respectively. Chemical reactivity of MCP, including isomerization, dimerization, and oxidation, is investigated by computational chemistry methods and empirical thermodynamic?energy correlation. Density functional and ab initio methods are used to search the initial thermal decomposition steps of HA, including unimolecular and bimolecular pathways. In addition, solvent effects are also examined using water cluster methods and Polarizable Continuum Models (PCM) for aqueous solution of HA. The thermal stability of a basic energetic material, Nitroethane, is investigated through both theoretical and experimental methods. Density functional methods are employed to explore the initial decomposition pathways, followed by developing detailed reaction networks. Experiments with a batch reactor and in situ GC are designed to analyze the distribution of reaction products and verify reaction mechanisms. Overall kinetic model is also built from calorimetric experiments using an Automated Pressure Tracking Adiabatic Calorimeter (APTAC). Finally, a general evaluation approach is developed for a wide range of reactive chemicals. An index of thermal risk is proposed as a preliminary risk assessment to screen reactive chemicals. Correlations are also developed between reactivity parameters, such as onset temperature, activation energy, and adiabatic time to maximum rate based on a limited number, 37 sets, of Differential Scanning Calorimeter (DSC) data. The research shows broad applications in developing reaction mechanisms at the molecular level. The methodology of reaction modeling in combination with molecular modeling can also be used to study other reactive chemical systems.