Aerobic oxidation of hydrocarbons using N-hydroxyphthalimide (NHPI) catalysts for cetane enhancement

Abstract

Gasoline compression ignition (GCI) utilizes gasoline-like fuels in low temperature compression ignition (CI) engines. As a result, thermal efficiency is increased compared to that of a conventional spark ignition (SI) engine, while NOx and soot tailpipe emissions are reduced compared to those from a diesel engine. This combustion strategy requires gasoline fuel with a moderate ignition delay for cold start and high load demand conditions. This work proposes an approach to control the ignition characteristics of gasoline to widen GCI engine operation conditions. Aerobic oxidation of gasoline using N-hydroxyphthalimide (NHPI) catalyst has been suggested as an effective method to produce high cetane components, such as hydroperoxide. NHPI catalyzed oxidation reactions of toluene and market gasoline were studied at different reaction conditions using an autoclave batch reactor. The produced hydroperoxide (HP) was quantified by titration using triphenylphosphine (Ph3P) followed by Gas Chromatography (GC) analysis. In addition, an ignition quality tester (IQT) was used to estimate the derived cetane number (DCN) of the oxygenated product. The gasoline cetane number was enhanced by nine digits using gaseous oxygen at moderate conditions (10 bar, 110 °C for 3 h). Aerobic oxidation of gasoline using NHPI catalyst was found to be a promising approach to control the ignition characteristics of fuel and hence an enabler of the GCI engine concept.