Abatement of photochemical smog precursors through complete hydrocarbon oxidation over commercial Pd catalysts under fuel-lean conditions with NO promoting effect

Yongwoo Kim; Jonghyun Kim; Michelle H Wiebenga; Se H Oh; Do Heui Kim

doi:10.1016/j.envpol.2023.122721

Abatement of photochemical smog precursors through complete hydrocarbon oxidation over commercial Pd catalysts under fuel-lean conditions with NO promoting effect

Environ Pollut. 2023 Dec 1:338:122721. doi: 10.1016/j.envpol.2023.122721. Epub 2023 Oct 12.

Authors

Yongwoo Kim¹, Jonghyun Kim², Michelle H Wiebenga³, Se H Oh³, Do Heui Kim⁴

Affiliations

¹ School of Chemical and Biological Engineering, Institute of Chemical Processes, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Republic of Korea; Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, Urbana, IL, 61801, USA.
² Corporate R&D, LG Chem R&D Campus Daejeon, 188, Daejeon, 34122, Republic of Korea.
³ General Motors Global R&D, 30470 Harley Earl Blvd, Warren, MI, 48092, USA.
⁴ School of Chemical and Biological Engineering, Institute of Chemical Processes, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Republic of Korea. Electronic address: dohkim@snu.ac.kr.

PMID: 37838319
DOI: 10.1016/j.envpol.2023.122721

Abstract

Currently, severe environmental issues have led to a great transition in the automotive industry from internal combustion engine vehicles to electric vehicles, but this transition will take time more than 10 years, which still requires the use of internal combustion engine vehicles. However, these vehicles emit a significant amount of hydrocarbons, in addition to nitrogen oxides (NO_x), due to incomplete fuel combustion. They contribute to the formation of photochemical smog when they react with NO_x in the presence of sunlight. To effectively remove these hydrocarbons from the exhaust gas of turbo-gasoline engines or diesel engines, we investigated the abatement of propane and iso-pentane, two typical hydrocarbons. In particular, we studied commercial Pd catalysts and revealed how the Pd loading and aging process simulating 4k and 100k mileage affected hydrocarbon abatement abilities, and their phases were identified using characterization technique, including CO chemisorption, X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HR-TEM). We also suggested the reaction pathway for the complete oxidation of propane over Pd catalyst based on the reaction orders of propane and oxygen: Propane adsorbs on O atoms of PdO, and the kinetically relevant C-H bond cleavage step occurs by the interaction with abundant neighboring O atoms of PdO. Finally, the propane and iso-pentane abatement ability of the Pd catalyst aged for 100k mileage were evaluated under realistic exhaust gas conditions, and the effect of each gas component in the realistic exhaust gas was identified; water inhibits the catalytic reaction of hydrocarbons by occupying the active sites, whereas NO catalyzes the hydrocarbon oxidation reaction by either changing the reaction pathway or active sites under fuel-lean conditions. These findings enable us to effectively reduce environmental pollution and facilitate a smoother transition from internal combustion engine vehicles to electric vehicles.

Keywords: Automotive catalysis; Fuel-lean condition; Hydrocarbon oxidation; Palladium; Photochemical smog precursors.

MeSH terms

Gasoline / analysis
Hydrocarbons / analysis
Pentanes*
Propane
Smog*
Vehicle Emissions / analysis

Substances

Smog
pentane
Pentanes
Propane
palladium oxide
Hydrocarbons
Vehicle Emissions
Gasoline