Self-Catalytic Reaction of SO₃ and NH₃ To Produce Sulfamic Acid and Its Implication to Atmospheric Particle Formation

Abstract

Sulfur trioxide (SO) is one of the most active chemical species in the atmosphere, and its atmospheric fate has profound implications to air quality and human health. The dominant gas-phase loss pathway for SO is generally believed to be the reaction with water molecules, resulting in sulfuric acid. The latter is viewed as a critical component in the new particle formation (NPF). Herein, a new and competitive loss pathway for SO in the presence of abundant gas-phase ammonia (NH) species is identified. Specifically, the reaction between SO and NH, which produces sulfamic acid, can be self-catalyzed by the reactant (NH). In dry and heavily polluted areas with relatively high concentrations of NH, the effective rate constant for the bimolecular SO-NH reaction can be sufficiently fast through this new loss pathway for SO to become competitive with the conventional loss pathway for SO with water. Furthermore, this study shows that the final product of the reaction, namely, sulfamic acid, can enhance the fastest possible rate of NPF from sulfuric acid and dimethylamine (DMA) by about a factor of 2. An alternative source of stabilizer for acid-base clustering in the atmosphere is suggested, and this new mechanism for NPF has potential to improve atmospheric modeling in highly polluted regions.

Atmospheric Sulfuric Acid‐Dimethylamine Nucleation Enhanced by Trifluoroacetic Acid

“…As a result, the contribution of other atmospheric trace gases to NPF events, in addition to the species that have already been proved to play a key role, remains to be clarified. For example, clusters consisting of SA, DMA, and atmospheric acids have not been detected in field measurements, though a couple of theoretical studies suggest that acidic species (e.g., methane sulfonic acid, Bork et al, ; Dawson et al, ; sulfamic acid, Li, Zhong, et al, ; lactic acid, Li et al, ; and succinic acid, Lin et al, ) can enhance SA‐DMA nucleation due to their acidity via the formation of stabilized clusters. The acidity of perfluorocarboxylic acids is potentially relatively strong due to the electron‐withdrawing inductive effect of the fluorine atoms.…”

Speeding up Viedma Deracemization through Water‐catalyzed and Reactant Self‐catalyzed Racemization

“…[30,31] Moreover, such spontaneous reactantdependent autocatalysis appears to be yet unknown to organic chemists, even though an example was reported very recently for a (non-asymmetric) inorganic reaction and in which only reactant, rather than product, was catalyst in the spontaneous forward reaction step. [32] Autocatalysis is commonly described as a process in which a reaction product catalyzes its own formation. Because product/ catalyst needs to be produced first, before it can exert its catalytic activity, a sigmoidal reaction rate profile with an initiation phase is the consequence.…”

Qualitative Detection Toward Military and Improvised Explosive Vapors by a Facile TiO2 Nanosheet-Based Chemiresistive Sensor Array

“…The room-temperature saturated vapor pressures of all these analytes are extremely low, such as 9 ppb for TNT, 411 ppb for DNT, 647 ppb for PNT, 0.97 ppb for PA, 4.9 ppt for RDX, 2 ppb for S, 9 ppt for urea, and 14.7 ppb for NH 4 NO 3 (Lyons, 2011;Ewing et al, 2013). Meanwhile, the other three explosives, KNO 3 , KClO 3 , and KMnO 4 , owing to their ionic crystal nature, are non-volatile and hard to decompose at room temperature indicating that neither the vapor of themselves nor their decomposition products is responsible for the gas sensing signal ( Supplementary Table 1) However, it has been discovered that microparticulates could be separated from nonvolatile solids and suspended in air (Clark and Shirley, 1973;Samet et al, 2004;Li et al, 2018;Yao et al, 2018). Therefore, we believe that the microparticulates suspended in the vapor of these explosives, which could interact with the surface of sensing materials and hence are responsible for the electric signal changes of the sensors in the array.…”