Methyl ketones: a comprehensive study of a novel biofuel

Abstract

For several burning reasons, humanity must rapidly reduce greenhouse gas emissions in the transportation sector. While the vision is to rely on electric vehicles in the future, the existing fleet will depend predominantly on liquid transportation fuels for the decades to come. Here, a blend of saturated and monounsaturated medium-chain length methyl ketones is suggested as a sustainable biofuel that is fully compatible with the existing diesel fleet. These methyl ketones can be produced by genetically modified Pseudomonas taiwanensis VLB120 at high yields from glucose. By performing a comprehensive, reductive solvent screening for in situ extraction of methyl ketones, a bioprocess for methyl ketone production was developed that facilitates simple product purification by decantation. The use of an advanced multiphase loop bioreactor with countercurrent liquid–liquid extraction averted stable emulsion formation in a set-up that can run in continuous mode in the future. The methyl ketones were tested extensively for their applicability in combustion engines. Here, parameters such as the derived cetane number, the flash point, and the kinematic viscosity fit into the diesel fuel specifications. Experiments in a research internal combustion engine showed that methyl ketones as a biofuel combine the efficient combustion of diesel fuel with the clean combustion of other oxygenates. Also, good storability and reduced ecotoxicology compared to common diesel fuel were demonstrated. Accordingly, the presented blend of methyl ketones can serve as an advanced drop-in fuel in the scope of the envisaged sustainable bioeconomy.