Journal of Petroleum & Environmental Biotechnology

Thermochemistry and kinetics of bioalcohols and bioesters as fossil fuel alternatives Ab initio and DFT studies

2^nd World Congress on Petrochemistry and Chemical Engineering

October 27-29, 2014 Embassy Suites Las Vegas, USA

Ahmed M El-Nahas

Scientific Tracks Abstracts: J Pet Environ Biotechnol

Abstract:

Our concern is devoted to biofuel derived from non-food crops (second- generation biofuel). Accurate thermodynamic and kinetic parameters are needed for detailed mechanism of combustion of fuel. Computational chemistry represents a valuable tool for getting such parameters. The calculations have been performed using ab initio (CCSD(T) and CBS-QB3) and Density Functional Theory (DFT) (BMK, BBIK) procedures. Rate constants and branching ratios for decomposition of bioutanols and bioesters have been calculated. For 2-butanol, the results indicated that the dehydration to 1- and 2-butene through four-center transition states is the most dominant channel at low to moderate temperatures (T ≤ 700 K). The formation of such butenes is kinetically and thermodynamically more favorable than other complex and simple bond scission reactions. Although the C-C bond fission channels require more energy than needed for some complex decomposition reactions, the former pathways predominate at higher temperatures (T ≥ 800 K) due to the higher values of the pre-exponential factors. Isobutanol is oxidized with the OH radical through low energy barriers of -1.0? 2.64 kcal/mol. Rate constants and branching ratios show H-abstraction from Cα as the dominant reaction over the whole temperature range of 200?2000 K, with a competition from Cβ channel at lower temperature up to 600 K. The data obtained reproduce the available experimental findings with good performance of DFT BB1K method compared to high ab initio levels.