A Study Of 3-methyl-2-butanone And 3-pentanone On Ignition Delay Time,Ractivity And High-temperature Oxidation Kinetic Models

Searching for renewable energy sources for reducing greenhouse gas emission is regarded as an important approach of dealing with global warming.Pentanone can be converted from cellulosic biomass.Due to the high energy density,impressive knock resistance,and low emissions of soot,pentanone could be suitable for engine applications and has been regarded as a type of promising biofuel.Thus,the kinetic modeling study of pentanone isomers,i.e.,3-methyl-2-butanone(MIPK),3-pentanone(DEK),2-pentanone(MPK),is an important fundamental research of pentanone combustion,it also provides critical theoretical basis for industrial applications.Based on the structural similarity between MIPK and MPK,diisopropyl ketone(DIPK),a high-temperature detailed combustion kinetic model for MIPK was first developed via a hierarchical method,and the model was optimized by the self-adaptive differential evolution(Sa DE)algorithm.The presented high-temperature detailed combustion kinetic model for MIPK consists of the C0-C4 hydrocarbon oxidation model,the C3-C4 ketone submodel and the submodel related to MIPK.The submodel related to MIPK consists of 76 elementary reactions,and the reaction rate coefficients of H-abstraction by H?from the MIPK tertiary carbon were calculated via quantum chemical techniques.The ignition delay times(IDTs)of MIPK were measured in the temperature range from 1150 to 1600 K at pressures from 1 to 5bar and for the equivalence ratios of 0.5,1.0 and 1.5.It was found that the presented MIPK model shows good agreement with all the experimental data.The presented model was used to describe MIPK high temperature oxidation pathways.The IDTs of MIPK were first measured under O₂/CO₂ atmosphere.The experiment was performed at the pressures of 1 and 10 bar for the equivalence ratios of 0.5,1.0 and 1.5,and in the temperature range of 1125-1600 K.OXYMECH 2.0,which was developed by our study group,substituted the C0-C2 submodel of our previous MIPK model and the Sa DE algorithm was used to optimize the updated model.The presented MIPK model was validated against the IDTs of MIPK under O₂/CO₂ and O₂/Ar atmospheres.The effects of CO₂ on the ignition of MIPK were discussed in the pressure range of 1-10 bar in detailed by sensitivity and oxidation pathway analysis.The effects of physical and chemical properties of CO₂ and the total effect of CO₂ inhibit the ignition of MIPK.Oxidization pathway analysis shows that,with the increase of pressure,the ratio of the consumption of MIPK through decomposition reaction decreases,while the ratio of the consumption of MIPK through H-atom abstraction reaction increases.The reaction rate constants of H-atom abstraction by H?and C?H₃ at two sites of 3-pentanone and the subsequent isomerization reaction were calculated using the transition state theory with Eckart tunneling and the multi-structural torsional anharmonicity method,based on the potential energy surfaces calculated at M06-2X/ma-TZVP//M06-2X/6-311+G(2df,2p)level of theory.The results show that the updated rate constants deviate from previous data by up to a few orders of magnitude.Tunneling effect increases the rate constants at low temperatures significantly.Hydrogen from the methylene in 3-pentanone is easier to be abstracted than from the methyl radical.Hydrogen abstraction by H?from the methylene in 3-pentanone is the fastest reaction among them.The calculated rate constants of the five reactions are updated in the Dames-2014 model,and the predictions of the IDTs of the updated model agree better with the experimental data than those of Dames-2014model.The IDTs of MPK were measured in a shock tube over a temperature range of 1227-1571 K at pressures of 1 and 5 bar for equivalence ratios of 0.5,1.0 and 1.5.The IDTs of DEK,MPK and MIPK were compared under the same experimental condition.The results show that DEK has the shortest IDT,followed by MPK and MIPK exhibiting similar IDT.DEK is composed of an carbonyl group symmetrically connecting two ethyl groups.The existence of carbonyl group weakens the bond energy of C-C bonds which is jointed to carbonyl group,leading to the C-C bonds easy to break,so there are more ethyl radicals generated from DEK.Besides,the amount of unsaturated stable fuel-related intermediate products of DEK is less than those of MPK and MIPK.Therefore,the reactivity of DEK is higher than those of MPK and MIPK.The difference of molecular structure between MPK and MIPK is as follows:the carbonyl of MPK connecting with n-propyl,while the carbonyl of MIPK connecting with iso-propyl,but this difference has little effect on the reactivity of MIPK and MPK.