Non-catalytic gas phase NO oxidation in the presence of decane

Experiments without a catalyst revealed that NO was oxidized in a diesel exhaust gas phase mixture due to the presence of n-C₁₀H₂₂ (decane). This reaction was observed to occur following the low temperature oxidation catalyst test protocol (LTC-D) defined by U.S. DRIVE. The purpose of LTC-D conditions is to simulate an aftertreatment diesel combustion gas mixture in order to test candidate catalyst materials. 100% NO conversion was observed, without a catalyst, after beginning to react at 330 °C accompanied by consumption of decane. After experiments that isolated hydrocarbons, ethylene was also observed to facilitate NO oxidation to a lesser degree (>470 °C). Density functional theory (DFT) calculations were conducted to investigate thermodynamically-possible initiating elementary steps during n-C₁₀H₂₂ consumption and NO oxidation. Two feasible intermediate radicals to oxidize NO to NO₂ are ·C₁₀H₂₁O₂ and ·HO₂.