(131c) Pentanol: A Promissing Fuel and Petrochemical Building Block

The increasing worldwide energy demand and the major environmental constraints on greenhouse gas emissions are strongly driving the search for alternative fuel and base chemical resources. Many studies have reported industrial, experimental and theoretical results on feedstocks derived from non-fossil processes, among which urban waste and biological feedstocks are the most promising. Primary alcohols have already been considered for decades as sustainable fuel; Ethanol, belonging to the first generation biofuels, is widely spread as substitute for conventional diesel. Other alcohols such as propanol and n- and iso-butanol gained significant interest in the past for their higher energy density, higher cetane numbers and lower hygroscopic properties. To increase the energy content even more, the second generation biofuel n-pentanol is now extensively studied.

Optimizing a well-established and well understood chemical process such as combustion or pyrolysis for a new, alternative feedstock requires the knowledge of the underlying chemistry. Alternative feedstocks contain a fundamentally different chemical structure compared to fossil resources, and their chemistry is thus not comparable. In this work, the pyrolysis and combustion chemistry of n-pentanol is studied in two-fold. First, an experimental dataset was obtained on a Bench Scale set-up. N-pentanol was fed to a tubular reactor diluted in a N₂ stream and the reactor effluent was analyzed using two single GC’s and one GC×GC which allows on-line qualification and quantification of the complete product spectrum. Experiments were conducted at several temperature to cover a wide conversion range. Second, a kinetic model was constructed using the automatic kinetic model generation tool Genesys. The resulting model contains solely elementary reaction steps, and most of the kinetic and thermodynamic parameters are estimated using group contribution methods. The chemistry of small molecules is handled by the Aramcomech^1 base mechanism.

The kinetic model has been used in a reactor model to simulate the experimental data. The product fractions of simulations and experiments are compared and a satisfactory agreement is achieved. Rate-of-production analysis allows to identify the important reaction pathways and intermediates under pyrolysis conditions. The initiation reactions are homolytic scissions of C-C and the C-O bond, forming an initial pool of radicals. The C-C bond in beta-position of the alcohol group is the weakest and has the highest contribution to the initial decomposition. Once radicals are created, chain reactions mainly consisting of hydrogen abstraction reactions and β-scission reactions follow each other to form small olefins and oxygenates. Most reactions include radical centers, except for a few such as the direct H₂O elimination from n-pentanol.

 ADDIN EN.REFLIST 1. Metcalfe WK, Burke SM, Ahmed SS, Curran HJ. A Hierarchical and Comparative Kinetic Modeling Study of C-1 - C-2 Hydrocarbon and Oxygenated Fuels. International Journal of Chemical Kinetics. Oct 2013;45(10):638-675.