Oxidative Reactivity Differences of E0 and E30 Gasoline Direct Injection Particulate Matter

Andrea  Strzelec, Texas A&M University

Exhaust from vehicles is one of the leading contributors of particulate matter (PM) in the atmosphere. PM has been shown to be carcinogenic and to pose a significant risk to human health. [1-4] Therefore, continuously stricter legislation is being implemented for particulate emissions. Diesel engines are the highest emitters of PM in the exhaust [5]. Due to this, diesel particulate matter has been studied since the 1980’s and diesel particulate filters (DPFs) have been in use to reduce diesel PM since 2003 [6, 7]. Gasoline Direct Injection (GDI) engines have penetrated the automotive market due to their increased fuel efficiency and high power output. However, due to incomplete fuel volatilization and partially fuel-rich zones, GDI engines tend to produce more particulate matter as compared to conventional spark ignition engines. [8-11] To aid in reducing PM, GDI engines could benefit from a particulate filter system like diesels have. [12-14] However, adding a filter in the exhaust system is known to increase backpressure in the exhaust, which is especially problematic for GDI operation and can lead to a fuel penalty. [15]

To minimize the fuel penalty associated with these particulate filters, there is ongoing research to improve both the filter media and the regeneration strategy; the second is the focus of this work. To efficiently regenerate a Gasoline Particulate Filter (GPF), the reactivity of GDI particulate matter must be understood. Previous work has shown that diesel particulate matter formation, nanostructure and reactivity is a function of fuel type. [16, 17] With ethanol being the leading and currently deployed biofuel for gasoline engines, there is interest in studying the effect it has on GDI PM reactivity.

This study investigated the reaction kinetics through Temperature Programmed Oxidation (TPO) and Desorption (TPD) experiments, which yield bulk reactivity characterizations and quantified the volatile organic fraction, respectively. Isothermal Pulsed Oxidation (IPO)

experiments determined the effective activation energies to be 171.7 kJ/mol for GDI E0 PM and 227.4 kJ/mol and for GDI E30 PM.  BET total surface area measurements determined the specific surface area to be 81.5 m2/g and 102.25 m2/g for nascent GDI E0 and E30 PM, respectively.

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