FTIR analysis of surface functionalities on particulate matter produced by off-road diesel engines operating on diesel and biofuel

Fourier transform infrared spectroscopy is applied as a powerful analytic technique for the evaluation of the chemical composition of combustion aerosols emitted by off-road engines fuelled by diesel and biofuels. Particles produced by burning diesel, heated rapeseed oil (RO), RO with ethylhexylnitrate, and heated palm oil were sampled from exhausts of representative in-use diesel engines. Multicomponent composition of diesel and biofuel particles reveal the chemistry related to a variety of functional groups containing carbon, hydrogen, oxygen, sulfur, and nitrogen. The most intensive functionalities of diesel particles are saturated C–C–H and unsaturated C=C–H aliphatic groups in alkanes and alkenes, aromatic C=C and C=C–H groups in polyaromatics, as well as sulfates and nitrated ions. The distinguished features of biofuel particles were carbonyl C=O groups in carboxylic acids, ketones, aldehydes, esters, and lactones. NO2, C–N and -NH groups in nitrocompounds and amines are found to dominate biofuel particles. Group identification is confirmed by complementary measurements of organic carbon (OC), elemental carbon, and water-soluble ion species. The relationship between infrared bands of polar oxygenated and non-polar aliphatic functionalities indicates the higher extent of the surface oxidation of biofuel particles. Findings provide functional markers of organic surface structure of off-road diesel emission, allowing for a better evaluation of relation between engine, fuel, operation condition, and particle composition, thus improving the quantification of environmental impacts of alternative energy source emissions

Combined Nitrogen, Hexane, and Benzene Adsorption Characterization of Pores and Surfaces of Lyophobic Mesoporous Silicas

For lyophobic porous surfaces, structural analysis by vapor adsorption is complicated due to weak adsorbate–adsorbent interactions and limited wetting of the pores (nonzero contact angles). To investigate further, adsorption isotherms of three distinct adsorbates (nitrogen - 77 K, <i>n</i>-hexane and benzene - 298 K) were studied for SBA-15 ordered mesoporous silica where the surface was functionalized with lyophobic perfluoroalkyl groups (C₆F₁₃ termini). The results demonstrated a clear advantage of the combined use of the adsorption isotherms of less surface sensitive (nitrogen) and more surface sensitive (hydrocarbons) adsorbates. The adsorption of nitrogen provided basic structural characteristics like surface area, pore volume, and pore size distribution, while the isotherms of benzene and <i>n</i>-hexane were used to characterize wetting (contact angles) and surface energy of the C₆F₁₃ surfaces within the pores. For the first time, the statistical film thickness for nitrogen, benzene, and <i>n</i>-hexane are being reported for the adsorption on fluorinated surfaces, thereby providing critical data for the pore size and the contact angle determination of the lyophobic materials

Ship particulate pollutants: Characterization in terms of environmental implication

International audienceA major aspect of monitoring the atmosphere is the quantification of man-made pollution and their interactions with the environment. Key physico-chemical characteristics of diesel exhaust particulates of sea-going ship emissions are presented with respect to morphology, microstructure, and chemical composition. Heavy fuel oil (HFO)-derived particles exhibit extremely complex chemistry. They demonstrate three distinct morphological structures with different chemical composition, namely soot, char and mineral/ash. The composition analysis investigates the content of environmentally-dangerous pollutants: metals, inorganic/mineral species, and soluble, volatile organic and ionic compounds. It is found that hazardous constituents from HFO combustion, such as transitional and alkali earth metals (V, Ni, Ca, Fe) and their soluble or insoluble chemical forms (sulfides, sulfates, oxides, carbides), are released together with particles into the atmosphere. The water soluble fraction, more than 27 wt%, is dominated by sulfates and calcium cations. They cause the high hygroscopicity of ship exhaust particles and their possible ability to act as cloud nuclei in humid marine environment