Size-resolved physico-chemical characterization of diesel exhaust particles and efficiency of exhaust aftertreatment

Abstract

Knowledge of physico-chemical characteristics of particle emissions from combustion engines is essential for various modelling purposes and environmental analysis. It is of particular interest to obtain emission factors of intermediate-volatility organic compounds (IVOC) and semi-volatile organic compounds (SVOC) which have not been comprehensively reported in the literature due to the limitations of characterisation methods. In the current study, a multi-stage Nano impactor and the two-dimensional gas chromatography (GC×GC) mass spectrometry (MS) technique were used to comprehensively characterise size fractionated particle phase emissions from a light-duty diesel engine based on the particle size, compound groups and carbon number. The number size distributions of particles between 1.2-1000 nm were also investigated. Exhaust gas samples were taken before a diesel oxidation catalyst (DOC), after the DOC and after the DOC combined with a catalysed diesel particulate filter (DPF). In samples taken before the DOC (engine-out), the total particulate IVOC+SVOC (I+SVOC) emission factor was approximately 105 milligrams per kilogram of fuel consumed (which was ~49% of the total particle mass) and the peak concentration of different classes of I+SVOC was found in the particle size bins close to 100 nm where most of the total particle mass was found. Alkanes, with maximum abundance at C 24 , were the most dominant class of I+SVOC in samples taken before and after the aftertreatment devices. Total particulate I+SVOC emissions were removed with ~75% efficiency using the DOC and by ~92% using the DOC+DPF. Alkanes, cycloalkanes, bicyclics and monoaromatics were all removed by >90% using the DOC+DPF; however, oxygenates were removed by only ~76% presumably due to the oxidation of different species within the aftertreatment system and reappearance as oxygenates. A high concentration of particles was measured in the sub-2.5 nm range. These particles were efficiently removed by the DOC+DPF due to both the loss of I+SVOC and physical filtration.

Characterization of Gas and Particulate Phase Organic Emissions (C9–C37) from a Diesel Engine and the Effect of Abatement Devices

“…The EF calculated in this study for the three steady-state conditions with and without aftertreatment devices are shown in Table S2, for the gas and particulate phases of all measured groups of compounds in the range C 9 –C 37 . The calculation method for the reported EFs in this study is described in the Supporting Information, S3, and further details are available in a companion paper . Briefly, the EFs are emission concentrations normalized to the actual (measured) engine fuel consumption (kg·fuel) at each engine operating condition.…”

“…Standard European, EN590 specifications, ultralow sulphur diesel (ULSD, S < 10 ppm) and 5W-30 part synthetic engine lubricating oil were used for the experiments. Comprehensive details regarding the engine test rig is described in a companion paper 39 . For S/IVOC characterisation, engine exhaust was diluted (1:50) using a modified TSI 3302A diluter described in detail elsewhere 18 .…”

Lung function and self-rated symptoms in healthy volunteers after exposure to hydrotreated vegetable oil (HVO) exhaust with and without particles

“…Exhaust aftertreatment systems are used in diesel vehicles in order to reduce the environmental and health hazardous emissions of PM (both mass and number concentration), CO, NO x , and organic compounds such as PAHs. An aftertreatment system can, for example, contain a diesel oxidation catalyst (DOC) that oxidizes CO and organic compounds [ 39 , 40 ], and a diesel particle filter (DPF) that oxidizes soot particles which removes significant amounts of PM [ 41 ]. Hence use of aftertreatment systems should reduce exposure to such emissions and their associated health effects.…”

Acute Cardiovascular Effects of Hydrotreated Vegetable Oil Exhaust

“…In order to reduce the environmental and health hazardous emission from diesel vehicles, emission abatement techniques such aftertreatment systems have been enforced in newer vehicles. Such systems are located in the exhaust pipe and can for example contain a diesel oxidation catalyst for removing CO and organic compounds (Zeraati-Rezaei et al, 2020 ), and a diesel particulate filter (DPF) which can remove a large fraction of the PM by oxidizing the soot particles (Reşitoĝlu and K Altinişik K, 2015 ). The impact of such difference in exhaust composition on human health are not completely known (Landwehr et al, 2021 ).…”