Development of Isopentanol Reaction Mechanism Reproducing Autoignition Character at High and Low Temperatures

Isopentanol is one of a range of next-generation biofuels that can be produced by advanced biochemical production routes (i.e., genetically engineered metabolic pathways). Isopentanol is a C₅ branched alcohol and is also called 3-methyl-1-butanol. In comparison with the most frequently studied ethanol, the molecular structure of isopentanol has a longer carbon chain and includes a methyl branch. The volumetric energy density of isopentanol is over 30% higher than ethanol. Therefore, isopentanol has the capability to be a better alternative than ethanol to gasoline. In this study, a detailed chemical kinetic model for isopentanol has been developed focusing on autoignition characteristics over a wide range of temperatures. The isopentanol model developed in this study includes high- and low-temperature chemistry. In the isopentanol model, high-temperature chemistry is based on a reaction model for butanol isomers whose reaction paths are quite similar to isopentanol. The low-temperature chemistry is based on a reaction model for isooctane which is a branched molecular structure similar to isopentanol. The model includes a new reaction mechanism for a concerted HO₂ elimination, a process recently examined by da Silva et al. for ethanol (J. Phys. Chem. A2009, 113, 8923). In addition, important reaction mechanisms relevant to low-temperature chemistry were considered in this model. The authors conducted experiments with a shock-tube and a rapid compression machine to evaluate and improve accuracies of this model. The experiments were carried out over a wide range of temperatures, pressures, and equivalence ratios (652–1457 K, 0.7–2.3 MPa, and 0.5–2.0, respectively). Excellent agreement between model calculations and experimental data was achieved under most conditions. Therefore, it is believed that the isopentanol model developed in this study is useful for prediction and analysis of combustion performance involving autoignition processes such as a homogeneous charge compression ignition.