Liu et al. (Proc. Natl. Acad. Sci. U.S.A, 2019, 116, 24966-24971) showed that at an altitude of 0 km, the reaction of SO3 with CH3OH to form CH3OSO3H reduces the...

The hydrolysis of SO3 plays an important role in atmospheric sulfuric acid formation. It has been found that the neutral (H2O and (H2O)2), basic (NH3), and acidic (HNO3, HCOOH, H2SO4, and C2H2O4) atmospheric species can be involved in and facilitate this reaction. However, the hydrolysis reaction of SO3 assisted by H2SO4···H2O and (H2SO4)2 has not been reported, which will limit the accurate understanding of the H2SO4 formation from the hydrolysis reaction of SO3 in the H2SO4 pollution areas. Herein, the hydrolysis reaction mechanism of SO3 assisted by H2SO4···H2O and (H2SO4)2 has been investigated by using CCSD(T)-F12/cc-pVDZ-F12//M06-2X/6-311+G(2df,2pd) methods and the reaction rate constants were evaluated by the Master Equation/Rice–Ramsperger–Kassel–Marcus model. The results show that the hydrolysis reactions with H2SO4···H2O and (H2SO4)2 are barrierless or nearly barrierless processes and lower the energy barrier at least by 21.6 kcal·mol–1. As compared with the hydrolysis reaction assisted by (H2SO4)2 within the temperature range of 280–320 K, H2SO4···H2O ([H2SO4] in 107 to 108 molecules·cm–3 and [H2O] at 20–100% RH) assisted reaction is more favorable with its effective rate constant larger by 8–10 orders of magnitude. Though H2SO4···H2O assisted reaction cannot compete with the reaction assisted by a neutral H2O (20–100% RH) catalyst due to its relatively lower concentration, it can compete well with the reaction in the presence of NH3 (109 to 1011 molecules·cm–3), HNO3 (109 to 1011 molecules·cm–3), HCOOH (108 to 1011 molecules·cm–3), H2SO4 (106 to 108 molecules·cm–3), and C2H2O4 (107 to 109 molecules·cm–3) within the temperature range of 280–320 K. As H2SO4···H2O is abundant in atmospheric aerosols, this work may suggest that the hydrolysis reaction of SO3 is promoted significantly by pre-existing aerosols, ultimately leading to aerosol growth and particle formation.

Herein, the reaction mechanisms and kinetics for the HO2 + SO3 → HOSO2 + 3O2 reaction catalyzed by water monomer, water dimer and small clusters of sulfuric acid have been...

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The hydrolysis of formaldehyde (HCHO) assisted by bimolecular acidic catalysts of H2SO4●●●H2O and (H2SO4)2 under different concentrations of H2SO4 and H2O were performed by quantum chemical calculations and the Master Equation method. The calculated results show that H2SO4●●●H2O and (H2SO4)2 catalyzed hydrolysis reaction of HCHO can occur through both one-step route and stepwise process. Effective rate coefficients (kt′) within the temperature range of 280-320 K show that H2SO4●●●H2O assisted reaction via stepwise route exerts the strongest catalytic role in increasing the rate of the hydrolysis of HCHO among all the hydrolysis reactions with H2SO4●●●H2O and (H2SO4)2 with its effective rate coefficient larger by at least 1 order of magnitude. As compared with the naked hydrolysis of HCHO, the favorable route of the hydrolysis of HCHO with H2SO4●●●H2O can reduce the energy barrier by 32.0 kcal·mol-1. Meanwhile, this reaction is also lower by another 0.8-17.6 kcal·mol-1 than that with H2SO4, HCOOH, HNO3, CH3COOH, H2O and (H2O)2. The calculated kt′ also reveals that the hydrolysis of HCHO with H2SO4●●●H2O ([H2SO4] =108 molecules∙cm-3 and [H2O] at 20%-100% RH) is more effective than that with H2O and (H2O)2 within 280-320 K, and can compete well with the hydrolysis of HCHO in the presence of HCOOH (2-10 ppbv), HNO3 (1011 molecules●cm-3), CH3COOH (1-5 ppbv) within 280-320 K. So, this work predicts that H2SO4●●●H2O can play a significant role in the hydrolysis of HCHO in the condition of wet areas with relatively high H2SO4-polluted.