More Like this

1. Investigation of CO2 and Methanol Solubility at High Pressure and Temperature in the Ionic Liquid [EMIM][BF4] Employed During Methanol Synthesis in a Membrane-Contactor Reactor

   https://doi.org/10.1016/j.ces.2021.116722  

   Zebarjad, Fatemeh; Wang, Zi; Li, Hao; Hu, Sheng; Tang, Yongchun; Tsotsis, Theodore (January 2021, Chemical engineering science)

   In this paper, the solubility properties of the ionic liquid (IL), 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) were studied using a high-pressure, high-temperature set-up employing the pressure-drop technique. [EMIM][BF4] was selected for study because it is used as the sweep liquid in a membrane reactor (MR)-based methanol synthesis (MR-MeS) process recently proposed and studied by our group. The MR-MeS studies indicated high methanol (MeOH) solubilities in the IL under typical MeS reaction conditions, which then motivated this study to measure such solubilities directly under non-reactive conditions to validate the findings of the MR study. In addition, during the MR-MeS studies a concern existed about the solubility of CO2 in [EMIM][BF4], since it is a reactant in the MeS process and its dissolution in the sweep liquid would be detrimental for reactor performance. Studies, therefore, were also carried out to investigate the solubility of CO2, in addition to MeOH, in the IL. Our investigation indicates that though CO2 solubilities in the [EMIM][BF4] are high at room temperature, they become negligible at the typical MeS operating conditions (i.e., temperatures above 200 ⁰C). 

   more » « less
2. Nitrate radical oxidation of <i>γ</i>-terpinene: hydroxy nitrate, total organic nitrate, and secondary organic aerosol yields

   https://doi.org/10.5194/acp-17-8635-2017  

   Slade, Jonathan H.; de Perre, Chloé; Lee, Linda; Shepson, Paul B. (January 2017, Atmospheric Chemistry and Physics)

   Polyolefinic monoterpenes represent a potentially important but understudied source of organic nitrates (ONs) and secondary organic aerosol (SOA) following oxidation due to their high reactivity and propensity for multi-stage chemistry. Recent modeling work suggests that the oxidation of polyolefinic γ-terpinene can be the dominant source of nighttime ON in a mixed forest environment. However, the ON yields, aerosol partitioning behavior, and SOA yields from γ-terpinene oxidation by the nitrate radical (NO₃), an important nighttime oxidant, have not been determined experimentally. In this work, we present a comprehensive experimental investigation of the total (gas + particle) ON, hydroxy nitrate, and SOA yields following γ-terpinene oxidation by NO₃. Under dry conditions, the hydroxy nitrate yield  =  4(+1/−3) %, total ON yield  =  14(+3/−2) %, and SOA yield  ≤  10 % under atmospherically relevant particle mass loadings, similar to those for α-pinene + NO₃. Using a chemical box model, we show that the measured concentrations of NO₂ and γ-terpinene hydroxy nitrates can be reliably simulated from α-pinene + NO₃ chemistry. This suggests that NO₃ addition to either of the two internal double bonds of γ-terpinene primarily decomposes forming a relatively volatile keto-aldehyde, reconciling the small SOA yield observed here and for other internal olefinic terpenes. Based on aerosol partitioning analysis and identification of speciated particle-phase ON applying high-resolution liquid chromatography–mass spectrometry, we estimate that a significant fraction of the particle-phase ON has the hydroxy nitrate moiety. This work greatly contributes to our understanding of ON and SOA formation from polyolefin monoterpene oxidation, which could be important in the northern continental US and the Midwest, where polyolefinic monoterpene emissions are greatest. 

   more » « less
3. Emerging investigator series: deposited particles and human lung lining fluid are dynamic, chemically-complex reservoirs leading to thirdhand smoke emissions and exposure

   https://doi.org/10.1039/D1EA00107H  

   Sheu, Roger; Hass-Mitchell, Tori; Ringsdorf, Akima; Berkemeier, Thomas; Machesky, Jo; Edtbauer, Achim; Klüpfel, Thomas; Filippi, Alexander; Musa Bandowe, Benjamin A.; Wietzoreck, Marco; et al (June 2022, Environmental Science: Atmospheres)

   Thirdhand smoke (THS) persists in locations where smoking previously occurred and can be transported into non-smoking environments, leading to non-smoker exposure. Laboratory experiments using high-resolution mass spectrometry demonstrate that deposited particulate matter (PM) and smoke-exposed surrogate lung lining fluid (LLF) are substantial, chemically-complex reservoirs of gas-phase THS emissions, including hazardous air pollutants, polycyclic aromatic compounds, and nitrogen/oxygen-containing species. Both PM and LLF are persistent real-world THS reservoirs that chemically evolve over time, and can act as vehicles for the transport and emission of reactive pollutants and their reaction byproducts (e.g., acrolein). Deposited PM on clothes, furnishings, bodies, and/or airways will emit volatile to semi-volatile gases over long lifetimes, which can re-partition to other indoor materials and increase their overall persistence. On the other hand, LLF off-gassing consists predominantly of volatile organic compounds in amounts influenced by their aqueous solubilities, and their persistence in breath will be prolonged by re-distribution across internal aqueous reservoirs, as corroborated by multicompartment modeling in this study. 

   more » « less
4. Electrocatalytic redox neutral [3 + 2] annulation of N -cyclopropylanilines and alkenes

   https://doi.org/10.1039/d0sc05665k  

   Wang, Qi; Wang, Qile; Zhang, Yuexiang; Mohamed, Yasmine M.; Pacheco, Carlos; Zheng, Nan; Zare, Richard N.; Chen, Hao (January 2021, Chemical Science)

   null (Ed.)

   Although synthetic organic electrochemistry (EC) has advanced significantly, net redox neutral electrosynthesis is quite rare. Two approaches have been employed to achieve this type of electrosynthesis. One relies on turnover of the product by the reactant in a chain mechanism. The other involves both oxidation on the anode and reduction on the cathode in which the radical cation or the radical anion of the product has to migrate between two electrodes. Herein, a home-built electrochemistry/mass spectrometry (EC/MS) platform was used to generate an N -cyclopropylaniline radical cation electrochemically and to monitor its reactivity toward alkenes by mass spectrometry (MS), which led to the discovery of a new redox neutral reaction of intermolecular [3 + 2] annulation of N -cyclopropylanilines and alkenes to provide an aniline-substituted 5-membered carbocycle via direct electrolysis (yield up to 81%). A chain mechanism, involving the regeneration of the substrate radical cation and the formation of the neutral product, is shown to be responsible for promoting such a redox neutral annulation reaction, as supported by experimental evidence of EC/MS. 

   more » « less
5. Large variability and complexity of isothermal solubility for a series of redox-active phenothiazines

   https://doi.org/10.1039/D2MA00598K  

   Perera, Anton S.; Suduwella, T. Malsha; Attanayake, N. Harsha; Jha, Rahul Kant; Eubanks, William L.; Shkrob, Ilya A.; Risko, Chad; Kaur, Aman Preet; Odom, Susan A. (November 2022, Materials Advances)

   The development of redox-active organic molecules (ROM) with large solubilities in all states of charge in organic electrolytes is imperative to the continued development of non-aqueous redox flow batteries. The capability to a priori predict ROM solubility would be a game changer, allowing for a move away from time and resource consuming trial-and-error approaches to materials design and deployment. However, it is not presently clear that such predictions are generally possible, even for chemically related ROM, given the large number of physicochemical factors in play. Here we use quantitative structure–property relationships (QSPR) to examine solubility trends for a set of thirty phenothiazine derivatives. The solubility in all states of charge (neutral and charged forms) of these molecules were obtained experimentally, and multiple linear regression models were used to correlate these properties with a large set (>100) of molecular descriptors. Minimal QSPR models rationalizing these data include four-to-six molecular descriptors, and cannot be further reduced. However, even such relatively complex models show limited ability to predict solubility of an unknown homologous compound. Thus, even in the controlled experimental environment, “predicting” the solubility may not be easy, suggesting the need for high-throughput measurements to develop the large data sets required for machine-informed materials design. The NMR method presented in this study is promising in this regard as it lends itself to automation. 

   more » « less