Department of Chemistry, IIT Madras
Research Colloquium

Utilising Single Pulse Shock Tube and Cavity Ring-Down Spectroscopy (CRDS), experiments were conducted to examine the gas phase kinetics of combustion as well as atmospherically relevant reactions.

Name: Subhadarsi Nayak (CY17D063) Date & Time: 24.08.2023 (3 pm)
Guide: Prof.B.Rajakumar Venue: CB310
Abstract: Global population increase and environmental concerns have led the world towards the search for alternative energy sources. Biofuel can be an efficient energy source. The kinetic parameters of the gas phase reactions are necessary to model the atmospheric and combustion processes. The Single pulse shock tube (SPST) technique is a better choice, to study the chemistry happening behind the combustion process1. Pollutants are constituted mostly by polycyclic aromatic hydrocarbons (PAHs) and secondary organic aerosols (SOAs). In recent years, Cavity Ring-Down Spectroscopy (CRDS) has evolved as a viable tool for trace gas sensing and investigate the kinetics of these species.
The overall decomposition kinetics calculation as well as product analysis for the thermal decomposition of Methyl-2-methylbutanoate (M2MB) and 2-methyl-2-butanol (2M2B) were performed in the temperature ranges 959-1392 K and 1011-1303 K respectively2. A comparison of the combustion chemistry of the branched ester M2MB and long-chain ester Methyl butanoate (MB) was also performed. A proposed reaction scheme was simulated for individual experiments to complement the experimental results. A thermo-kinetic theoretical study on the homolytic bond cleavage and the H-abstraction of 1-methoxy butan-2-one, a keto ether fuel additive is performed using the G3B3 quantum composite method as well as the M062X/aug-cc-pvdz method. In another study, the atmospheric fate of a modelled biofuel, 2-methyl tetrahydro furan with the Cl-atom was studied in the temperature range 263-343 K at atmospheric pressure using relative rate technique. The experimentally measured kinetics were verified by performing the computational kinetics calculations using the M062X/aug-cc-pvdz method. Another experiment involved the rate coefficient measurement for the reaction of Butyl peroxy and BrO radicals in the temperature range 253-333K and pressure range 44-63 Torr using the CRDS technique in the presence of N2 as the bath gas. The BrO radicals as well as Butyl peroxy radicals were generated in the CRDS reaction zone by photolyzing the mixture of (CH3CH2CH2CH2Br + O3 +O2) at 248 nm, and the generated BrO radicals were probed at 344 nm. To complement our experimental findings, the kinetics of the title reactions were investigated theoretically using Canonical Variational Transition State Theory (CVT).


References:
[1] Hanson, R.K. and Davidson, D.F., Recent advances in laser absorption and shock tube methods for studies of combustion chemistry. Progress in Energy and Combustion Science, 2014, 44,103-114.
[2] Nayak, S. and Rajakumar, B., An experimental and theoretical kinetic modeling study of the thermal decomposition of methyl-2-methyl butanoate behind shock waves. Combustion and Flame, 2023, 254, 112835.

Signature of Guide Signature of Co-ordinator Signature of HOD