Pyrolysis and modeling study of methyl lactate based on synchrotron radiation photoionization mass spectrometry

Small esters, including methyl lactate (MELAC) and ethyl lactate (ETLAC), have attracted public attention as potential oxygenated fuel and biodiesel due to their extensive sources, less environmental impacts, and excellent combustion performances. The present work thus set out to perform the pyrolysis study of MELAC with a jet-stirred reactor (JSR) at 1 atm and 690–960 K temperature range. Synchrotron radiation photoionization mass spectrometry (SR-PIMS) was employed to analyse 11 products and intermediates. Based on experimental results and previous work, a kinetic model was developed to predict the MELAC pyrolysis behaviours. The rate-of-production (ROP) and sensitivity analysis at 840 K (57.0 % conversion rate) indicate that the CH 3 OH elimination reaction, MELAC = CH 3 OH + CH 3 COHCO, is the major decomposition pathway of MELAC. Additionally, to explore the influence of the molecular structure, ETLAC pyrolysis experimental data were used to validate the extended model and compared with the newly obtained MELAC pyrolysis results. Despite the structural similarities between the two fuels, their pyrolysis behaviours exhibit significant differences. ETLAC is more reactive than MELAC and generates more C2 intermediates, which indicates that ETLAC could have a stronger soot tendency in the combustion of an engine. Two different thermal decomposition sequences were concluded as MELAC → (CH 3 OH + CH 3 CHOHCO) → (CH 3 CHO + CO) and ETLAC → (C 2 H 4 + LACAC) → (CH 3 CHO + CO + H 2 O), respectively. The findings will be helpful to understand the kinetics of oxygenated fuel and facilitate their applications as biodiesel fuels.