Process hazard evaluation for catalytic oxidation of 2-octanol with hydrogen peroxide using calorimetry techniques

Abstract

Abstract In this work, various calorimetric and analytical techniques were implemented to identify reaction pathways and safety issues associated with the 2-octanol to 2-octanone two liquid phase catalytic reaction oxidative using aqueous hydrogen peroxide as oxidant, sodium tungstate (Na2WO4) as catalyst and methyltri-n-octylammonium hydrogen sulfate [CH3(n-C8H17)3N+HSO4−] as phase transfer catalyst. Differential scanning calorimetry (DSC) was employed to measure the temperature and heat flux of the reactant mixtures under dynamic scanning. Phi-TEC II adiabatic calorimeter was used to track temperature and pressure under worst runaway scenario. Isothermal reaction calorimeter (RC1e) was used to assess conditions relevant to normal process operations. Gas chromatography-mass spectrometry (GC–MS) was utilized to analyze final products of all measurements qualitatively and quantitatively. Data from both DSC and Phi-TEC II show that two highly exothermic reactions were detected with “onset” temperature at ~50 and ~220\u202f°C, respectively. In all cases, only 2-octanol and 2-octanone were the identifiable compounds via GC–MS. 2-Octanol conversion was in the range of 15–50% and it reveals a linear correlation with overall heat generation. Data obtained verify that both exothermic peaks result from 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 validated this argument. Based on those results, possible macroscopic reaction pathway was proposed. Furthermore, pressure and temperature profiles by PHI-TEC II indicated a potential transition to a homogeneous liquid phase at higher temperatures. 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 so as to increase inherently safer conditions for its performance.