The ability to transform fuel hydrocarbons into oxygenated species in a manner that allows for high activity and control over the selectivity would be a break-through in the aftertreatment industry. The invention describe herein is a method to produce specific oxygenates from diesel, natural gas, and other hydrocarbon fuels on-board a vehicle. The process would include three major unit operations: 1) Flash Distillation to remove the light fraction HCs and sulfur from the liquid fuel for further processing to oxygenates, 2) Partial Oxidation to produce syngas (H2+CO) from the light HC fraction, and 3) Synthesis to construct the desired oxygenate, such as dimethyl ether (DME) and methanol (MeOH), form the syngas. The oxygenate product from this method will then be used for NOx reduction in mobile of stationary Lean-NOx or HC-SCR systems.