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Diesel soot photooxidation enhances the heterogeneous formation of H₂SO₄.

ABSTRACT: Both field observation and experimental simulation have implied that black carbon or soot plays a remarkable role in the catalytic oxidation of SO₂ for the formation of atmospheric sulfate. However, the catalytic mechanism remains ambiguous, especially that under light irradiation. Here we systematically investigate the heterogeneous conversion of SO₂ on diesel soot or black carbon (DBC) under light irradiation. The experimental results show that the presence of DBC under light irradiation can significantly promote the heterogeneous conversion of SO₂ to H₂SO₄, mainly through the heterogeneous reaction between SO₂ and photo-induced OH radicals. The detected photo-chemical behaviors on DBC suggest that OH radical formation is closely related to the abstraction and transfer of electrons in DBC and the formation of reactive superoxide radical (•O₂^-) as an intermediate. Our results extend the known sources of atmospheric H₂SO₄ and provide insight into the internal photochemical oxidation mechanism of SO₂ on DBC.

SUBMITTER: Zhang P

PROVIDER: S-EPMC9467980 | biostudies-literature | 2022 Sep

REPOSITORIES: biostudies-literature

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Diesel soot photooxidation enhances the heterogeneous formation of H2SO4.

Zhang Peng P Chen Tianzeng T Ma Qingxin Q Chu Biwu B Wang Yonghong Y Mu Yujing Y Yu Yunbo Y He Hong H

Nature communications 20220912 1

Both field observation and experimental simulation have implied that black carbon or soot plays a remarkable role in the catalytic oxidation of SO2 for the formation of atmospheric sulfate. However, the catalytic mechanism remains ambiguous, especially that under light irradiation. Here we systematically investigate the heterogeneous conversion of SO2 on diesel soot or black carbon (DBC) under light irradiation. The experimental results show that the presence of DBC under l ...[more]

PMID: 36097270

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Project description:Soot combustion experiments with 5%O2/He were conducted using model soot, and four distinct compositions of CexPr1-xO2-δ oxides of varying nominal cerium compositions (x = 0, 0.2, 0.3, and 1) were prepared. The catalyst samples were comprehensively characterized using techniques such as XRD, Raman spectroscopy, HR-TEM, N2 adsorption at -196 °C, XPS, O2-TPD, H2-TPR, and work function measurements. The Pr-rich compositions, ranging from Ce0.3Pr0.7O2-δ to PrO2-δ, resulted in a significant increase in the total evolved O2 amounts and enhanced catalyst reducibility. However, a decrease in the textural properties of the catalysts was noted, which was particularly important for the pure praseodymia under the synthesis route conducted. The catalytic activity was investigated under the two following contact modes of mixing between soot and catalyst: loose and tight. The results revealed that the catalytic performance is associated with the surface contact in tight contact mode and with the combination of surface/subsurface/bulk oxygen mobility and the BET surface area in loose contact mode. Notably, the temperatures estimated at 10% and 50% of the conversion (T10 and T50) parameters were achieved at much lower temperatures than the uncatalyzed soot combustion, even under loose contact conditions. Specifically, the 50% conversion was achieved at 511 °C and 538 °C for Ce0.3Pr0.7O2 and Ce0.2Pr0.8O2, respectively. While no direct correlation between catalytic activity and work function was observed, a significant relationship emerges between work function values and the formation of oxygen vacancies, whatever the conditions used for these measurements. On the other hand, the ability to generate a high population of oxygen vacancies at low temperatures, rather than the direct activation of gas-phase O2, influences the catalytic performance of Pr-doped ceria catalysts, highlighting the importance of surface/subsurface oxygen vacancy generation, which was the parameter that showed a better correlation with the catalytic activity, whatever the soot conversion value or the mode of contact considered.

Dataset Information

Diesel soot photooxidation enhances the heterogeneous formation of H₂SO₄.

Publications

Diesel soot photooxidation enhances the heterogeneous formation of H<sub>2</sub>SO<sub>4</sub>.

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