Exploration of the reactivity of N₂O₅ with two Si(OH)₄ monomers using electronic structure methods

Abstract

The heterogeneous uptake of N 2 O 5 on mineral dust particles may play an important role in the removal of nitrogen oxides from the atmosphere. However, the reaction of N 2 O 5 with the mineral particles is not well understood. The reaction of N 2 O 5 with two Si(OH) 4 monomers is explored using theoretical methods. This study represents a first step towards understanding the interaction of N 2 O 5 with the hydroxyl groups of silica particles. Energies are calculated using MP2 single point calculations on the B3LYP optimized geometries and including B3LYP thermodynamic corrections. Four mechanisms are considered for the formation of two HNO 3 and one H 6 Si 2 O 7 . The rate limiting activation barrier of the most favorable path is found to be 12.5 kcal mol À1 . This reaction appears to be more favorable than the hydrolysis of N 2 O 5 with one water molecule. These results are in agreement with experimental observations, which show that N 2 O 5 reacts with OH groups of Saharan dust to form nitrate.

The Role of Hydrates, Competing Chemical Constituents, and Surface Composition on ClNO2 Formation

“…Mitroo et al saw a similar γ N2O5 trend with Black Rock dust where γ N2O5 consequently decreased from 0.072 ± 0.005 to 0.022 ± 0.002 as RH was increased from 29% to 49%. From Figure a, we confirm that this trend can be explained by reactions between N 2 O 5 and clay minerals, which are hypothesized to be more efficient than hydrolysis at low RH. , We also show in Figure b that as 10 Å clay mass concentrations increase, more N 2 O 5 will react with these minerals over Cl – , which results in a high γ N2O5 and low ϕ ClNO2 .…”

“…From Figure 2a, we confirm that this trend can be explained by reactions between N 2 O 5 and clay minerals, which are hypothesized to be more efficient than hydrolysis at low RH. 55,56 We also show in Figure 2b that as 10 Å clay mass concentrations increase, more N 2 O 5 will react with these minerals over Cl − , which results in a high γ N2O5 and low ϕ ClNO2 .…”

ClNO2 Production from N2O5 Uptake on Saline Playa Dusts: New Insights into Potential Inland Sources of ClNO2

“…The decreasing trend in γ N2O5 and increasing trend in φ ClNO2 with increasing evaporite content, shown in Figure , reflects the competition between silicates and evaporites for N 2 O 5 and the impact of this competition on the reaction products formed. Samples with low evaporite content (<20%) have a large mass fraction of silicates that react efficiently with N 2 O 5 resulting in high values of γ N2O5 . ,, For these samples, the scarcity of soluble ions, including chloride (Figure ), coupled with previous observations of the formation of absorbed nitrates when N 2 O 5 reacts with silicates best explain the low yields of ClNO 2 from samples with very low soluble ion (evaporite) content. Conversely, samples with high evaporite content (≥50%) behave similarly to deliquesced, chloride-containing salts with values of γ N2O5 ∼ 0.03 and high values of φ ClNO2 (>0.5).…”

Heterogeneous reaction of N&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt; with illite and Arizona test dust particles

“…Using density functional theory to investigate the reactivity of N 2 O 5 with (Si(OH) 4 ) 2 (a simplified model of a silica surface), Messaoudi et al (2013) concluded that surface reaction of N 2 O 5 with OH groups on the silica surface is more favorable than its hydrolysis. If similar mechanisms also operate for illite, an increase of RH will lead to "deactivation" of surface OH groups by adsorbed surface water and consequently a decrease of the overall surface reactivity towards N 2 O 5 .…”