Process Hazard Evaluation and Safer Design for Oxidation of Secondary Alcohols to Ketones Using Hydrogen Peroxide

Ketones are industrially produced in large quantities. They find application as solvents and polymer and pharmaceuticals precursors. Substantial efforts have been put towards a green oxidation of alcohols to ketones with aqueous hydrogen peroxide as an oxidant including research for identifying appropriate reaction conditions and employed catalysts. Because of the use of hydrogen peroxide, the study of this reaction from a safety point of view prior to its scale-up is of preponderant importance. Herein, the purpose of this work is to conduct process hazard evaluation of this catalytic reaction and to propose safe process design. Various calorimetric and analytical techniques are used to study the thermal and kinetic behavior, helping identify reaction pathways and safety issues associated with the reaction. Differential scanning calorimetry (DSC) is used to gain insight into the potential reactivity hazards related to the process; Phi-TEC II adiabatic calorimetry measurements is performed to obtain detailed information of the worst reaction runaway scenarios; 100 ml reactor with oil jacket is used to assess the reaction behavior close to normal conditions at minor scale; RC1e heat-flow isothermal calorimetric measurements is conducted for assessing conditions relevant to normal process operations (e.g. stirring rate and heat release) and to evaluate the effect of solvent vaporization on reaction temperature. Gas chromatography-mass spectrometry (GC-MS) were used to analyze the final products. DSC results for 2-octanol and 2-butanol reaction systems were presented, and two highly exothermic reactions are found for both. Especially, for 2-octanol oxidative reaction, Phi-TEC II results again reveal two highly exothermic reactions occurred during testing process. Besides, GC-MS data verify that both exothermic peaks were owing to the alcohol oxidation, thus indicating that in the conditions of the reaction and with the employed catalysts, hydrogen peroxide did not fully decompose at lower temperatures. Non-condensable gas generation measurements through Phi-TEC II validated this argument. The RC1e results verified that 2-octanol conversion was higher at higher stirring rates, while evaporative cooling of solvents tempered the reaction by removing the heat generated, thus improving safety. These findings can be further used to propose safer operating measures for design and scale-up of this reaction process to avert a potential runaway and to probe in the reaction pathways to increase inherently safer conditions for its performance