Quantum Chemical Study on ·Cl-Initiated Atmospheric Degradation of Monoethanolamine

Abstract

Recent findings on the formation of ·Cl in continental urban areas necessitate the consideration of ·Cl initiated degradation when assessing the fate of volatile organic pollutants. Monoethanolamine (MEA) is considered as a potential atmospheric pollutant since it is a benchmark and widely utilized solvent in a leading CO2 capture technology. Especially, ·Cl may have specific interactions with the N atom of MEA, which could make the MEA + ·Cl reaction have different pathways and products from those of the MEA + ·OH reaction. Hence, ·Cl initiated reactions with MEA were investigated by a quantum chemical method [CCSD(T)/aug-cc-pVTZ//MP2/6-31+G(3df,2p)] and kinetics modeling. Results show that the overall rate constant for ·Cl initiated H-abstraction of MEA is 5 times faster than that initiated by ·OH, and the tropospheric lifetimes of MEA will be overestimated by 6-46% when assuming that [·Cl]/[·OH] = 1-10% if the role of ·Cl is ignored. The MEA + ·Cl reaction exclusively produces MEA-N that finally transforms into several products including mutagenic nitramine and carcinogenic nitrosamine via further reactions with O2/NOx, and the contribution of ·Cl to their formation is about 25-250% of that of ·OH. Thus, it is necessary to consider ·Cl initiated tropospheric degradation of MEA for its risk assessment.

Isocyanic acid (HNCO) and its fate in the atmosphere: a review

“…Second, laboratory experiments have observed HNCO production during the oxidation of amines and amides in the gas phase. [40][41][42][43][44][45] Measurements made in La Jolla, Mohali, and Bode all have similar diurnal proles with early morning minimum (4-6 am) and late morning (10-12 am) maximum mixing ratios. 51,52,55 The summertime data set from the Boulder Atmospheric Observatory tower in Erie, CO 54 shows a diurnal cycle similar to that of Pasadena, with an early morning minimum and early aernoon maximum.…”

“…19,38,39 The secondary production of HNCO, through the oxidation of amines and amides is also a potential source. [40][41][42][43][44][45]65 We rst summarize the studies of HNCO direct emissions in Sections 3.1 and 3.2, and then describe HNCO secondary production in Section 3.3. The contributions of cigarette smoke to HNCO are described in Section 3.4.…”

“…In fact, we know that amines, such as monoethanolamine, oxidize to amides and are subsequently oxidized to isocyanates. [43][44][45]65 In laboratory studies, HNCO is the main oxidation product from the oxidation of formamide with OH, NO 3 , or Cl (common atmospheric oxidants). [40][41][42] Urea also produces HNCO as the sole C-containing oxidation product upon Cl-initiated urea oxidation.…”

“…Secondary sources such as the oxidation of atmospheric amines and amides have also been identied as sources of HNCO. [40][41][42][43][44][45] There is little direct evidence for the loss processes of HNCO in the atmosphere. The atmospheric lifetime of HNCO by photolysis and by oxidation by OH radicals is on the order of months to decades.…”

Atmospheric chemical reaction mechanism and kinetics of 1,2-bis(2,4,6-tribromophenoxy)ethane initiated by OH radical: a computational study

“…46,47 This scheme had been successfully used in our previous study. 48 The details for the reaction rate constant calculations with the restricted Gorin model and long-range transition state theory were presented in the ESI. †…”