Synergistic Reaction of SO2 with NO2 in Presence of H2O and NH3: A Potential Source of Sulfate Aerosol

Abstract

Effect of H2O and NH3 on the synergistic oxidation reaction of SO2 and NO2 is investigated by theoretical calculation using the molecule system SO2-2NO2-nH2O (n = 0, 1, 2, 3) and SO2-2NO2-nH2O-mNH3 (n = 0, 1, 2; m = 1, 2). Calculated results show that SO2 is oxidized to SO3 by N2O4 intermediate. The additional H2O in the systems can reduce the energy barrier of oxidation step. The increasing number of H2O molecules in the systems enhances the effect and promotes the production of HONO. When the proportion of H2O to NH3 is 1:1, with NH3 included in the system, the energy barrier is lower than two pure H2O molecules in the oxidation step. The present study indicates that the H2O and NH3 have thermodynamic effects on promoting the oxidation reaction of SO2 and NO2, and NH3 has a more significant role in stabilizing product complexes. In these hydrolysis reactions, nethermost barrier energy (0.29 kcal/mol) can be found in the system SO2-2NO2-H2O. It is obvious that the production of HONO is energetically favorable. A new reaction mechanism about SO2 oxidation in the atmosphere is proposed, which can provide guidance for the further study of aerosol surface reactions.

A theoretical study on the formation mechanism of carboxylic sulfuric anhydride and its potential role in new particle formation

“…33 M06-2X functional was used with 6-311++G(3df,3pd) basis set for the stationary points calculation of the gas phase reaction of SO 3 to DTAA molecules at 298 K since M06-2X/6-311++G(3df,3pd) has been proved to show good performance in thermochemistry and free energies calculations for atmospheric relevant reactions and clusters formation. [34][35][36][37][38][39] The vibration frequency of the transition state was calculated to ensure that there was only one imaginary frequency. In order to ensure the proper reactant and product sides, intrinsic reaction coordinate (IRC) calculations were further performed.…”

Prediction of Reactive Nitrous Acid Formation in Rare‐Earth MOFs via ab initio Molecular Dynamics

“…[32] NO 2 is known to adsorb to both metal centres and ligands, [20] [34,35] HONO formation has also been identified in atmospheric mixtures of NO 2 ,SO 2 ,and H 2 O; this is the only known environment which shows favourable formation of HONO with the inclusion of H 2 O. [36] Detailed Analysis of AIMD simulations Thec ommonality found in the HONO formation of RE-DOBDC MOFs indicates this is ap redominant occurrence. Them echanisms of HONO formation are essential to reactive gas species formation in MOFs.T his chemical reaction has never been observed experimentally in RE-DOBDC MOFs and is only isolated through the power of AIMD simulations.Therefore,adeep dive into the simulation results is necessary to understand mechanisms of formation that can be applied in future material design.…”

Preparation and Characterization of Metastable trans-Dinitrogen Tetroxide

“…For example, neither the importance nor any potential kinetic limitations arising from dimerization or, alternatively, from isomerization between the multiple dimer’s conformers, as rate-limiting steps in reaction mechanisms, could be addressed nor be demonstrated experimentally in previous work on NO 2 hydrolysis. ,,,− The activation barrier for the isomerization of O 2 N 2 O 2 into t- ONONO 2 and c- ONONO 2 has recently been shown ,, to exceed its binding energy, a limitation which can be circumvented, in the gas phase, through the formation of a so-called roaming transition state . While this phenomenon cannot exist in confinement, for example when O 2 N 2 O 2 is adsorbed onto condensed water, recent computational ,,− ,− and experimental ,,, investigations contributed to the potential catalytic role of water in promoting the isomerization process in small water clusters ,,, and on wet surfaces , to become increasingly recognized, a process further facilitated by SO 2 − and NH 3. ,, In this work, we describe that while the relative abundances of NO 2 and of O 2 N 2 O 2 can be controlled by heating nitrogen dioxide vapors, yielding relative abundances in excellent agreement with the well-known equilibrium constant, the metastable t -ONONO 2 and c -ONONO 2 isomers of dinitrogen tetroxide are observed to display relative abundances that are many orders magnitude greater than those expected from their computationally derived free energies …”