Gas-Phase Fragmentation Reactions of Keggin-Type {PW11O39M} (M = Rh, Ir, and Ru) Polyoxometalates as Fingerprints of the Ligands Attached at the Noble Metal Site

2014 ◽  
Vol 2014 (32) ◽  
pp. 5618-5624 ◽  
Author(s):  
Cristian Vicent ◽  
Sergey A. Adonin ◽  
Alexander V. Anyushin ◽  
Dmitry A. Mainichev ◽  
Maxim N. Sokolov
Keyword(s):  
Gas Phase ◽  
Noble Metal ◽  
Metal Site ◽  
Keggin Type ◽  
Fragmentation Reactions ◽  
Gas Phase Fragmentation

scholarly journals Functional Group Selective Derivatization and Gas-Phase Fragmentation Reactions of Plasmalogen Glycerophospholipids

2013 ◽  
Vol 2 (Special_Issue) ◽  
pp. S0015-S0015 ◽  
Author(s):  
Cassie J. Fhaner ◽  
Sichang Liu ◽  
Xiao Zhou ◽  
Gavin E. Reid
Keyword(s):  
Gas Phase ◽  
Functional Group ◽  
Fragmentation Reactions ◽  
Gas Phase Fragmentation

scholarly journals Constraining nucleation, condensation, and chemistry in oxidation flow reactors using size-distribution measurements and aerosol microphysical modelling

2018 ◽  
Author(s):  
Anna L. Hodshire ◽  
Brett B. Palm ◽  
M. Lizabeth Alexander ◽  
Qijing Bian ◽  
Pedro Campuzano-Jost ◽  
...  
Keyword(s):  
Size Distribution ◽  
Gas Phase ◽  
Organic Compounds ◽  
Rate Constants ◽  
Accommodation Coefficient ◽  
Uptake Coefficient ◽  
Flow Reactors ◽  
Reactive Uptake Coefficient ◽  
Fragmentation Reactions ◽  
Gas Phase Fragmentation

Abstract. Oxidation flow reactors (OFRs) allow the concentration of a given atmospheric oxidant to be increased beyond ambient levels in order to study secondary organic aerosol (SOA) formation and aging over varying periods of equivalent aging by that oxidant. Previous studies have used these reactors to determine the bulk OA mass and chemical evolution. To our knowledge, no OFR study has focused on the interpretation of the evolving aerosol size distributions. In this study, we use size distribution measurements of the OFR and an aerosol microphysics model to learn about size-dependent processes in the OFR. Specifically, we use OFR exposures between 0.09–0.9 equivalent days of OH aging from the 2011 BEACHON-RoMBAS and the GoAmazon2014/5 field campaigns. We use simulations in the TOMAS (TwO-Moment Aerosol Sectional) microphysics box model to constrain the following parameters in the OFR: (1) the rate constant of gas-phase functionalization reactions of organic compounds with OH, (2) the rate constant of gas-phase fragmentation reactions of organic compounds with OH, (3) the reactive uptake coefficient for heterogeneous fragmentation reactions with OH, (4) the nucleation rate constants for three different nucleation schemes, and (5) an effective accommodation coefficient that accounts for possible particle diffusion limitations of particles larger than 60 nm in diameter. We find the best model-to-measurement agreement when the accommodation coefficient of the larger particles (Dp > 60 nm) was 0.1 or lower (with an accommodation coefficient of 1 for smaller particles), which suggests a diffusion limitation in the larger particles. When using these low accommodation-coefficient values, the model agrees with measurements when using a published H2SO4-organics nucleation mechanism and previously published values of rate constants for gas-phase oxidation reactions. Further, gas-phase fragmentation was found to have a significant impact upon the size distribution, and including fragmentation was necessary for accurately simulating the distributions in the OFR. The model was insensitive to the value of the reactive uptake coefficient on these aging timescales. Monoterpenes and isoprene could explain 24–95 % of the observed change in total volume of aerosol in the OFR, with ambient semivolatile and intermediate-volatility organic compounds (S/IVOCs) appearing to explain the remainder of the change in total volume. These results provide support to the mass-based findings of previous OFR studies, give insight to important size-distribution dynamics in the OFR, and enable the design of future OFR studies focused on new particle formation and/or microphysical processes.

Mass Spectral Similarity Networking and Gas-Phase Fragmentation Reactions in the Structural Analysis of Flavonoid Glycoconjugates

2019 ◽  
Vol 91 (16) ◽  
pp. 10413-10423 ◽  
Author(s):  
Alan Cesar Pilon ◽  
Haiwei Gu ◽  
Daniel Raftery ◽  
Vanderlan da Silva Bolzani ◽  
Norberto Peporine Lopes ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Gas Phase ◽  
Spectral Similarity ◽  
Mass Spectral ◽  
Fragmentation Reactions ◽  
Gas Phase Fragmentation

scholarly journals Constraining nucleation, condensation, and chemistry in oxidation flow reactors using size-distribution measurements and aerosol microphysical modeling

2018 ◽  
Vol 18 (16) ◽  
pp. 12433-12460 ◽  
Author(s):  
Anna L. Hodshire ◽  
Brett B. Palm ◽  
M. Lizabeth Alexander ◽  
Qijing Bian ◽  
Pedro Campuzano-Jost ◽  
...  
Keyword(s):  
Size Distribution ◽  
Gas Phase ◽  
Organic Compounds ◽  
Rate Constants ◽  
Accommodation Coefficient ◽  
Uptake Coefficient ◽  
Flow Reactors ◽  
Reactive Uptake Coefficient ◽  
Fragmentation Reactions ◽  
Gas Phase Fragmentation

Abstract. Oxidation flow reactors (OFRs) allow the concentration of a given atmospheric oxidant to be increased beyond ambient levels in order to study secondary organic aerosol (SOA) formation and aging over varying periods of equivalent aging by that oxidant. Previous studies have used these reactors to determine the bulk OA mass and chemical evolution. To our knowledge, no OFR study has focused on the interpretation of the evolving aerosol size distributions. In this study, we use size-distribution measurements of the OFR and an aerosol microphysics model to learn about size-dependent processes in the OFR. Specifically, we use OFR exposures between 0.09 and 0.9 equivalent days of OH aging from the 2011 BEACHON-RoMBAS and GoAmazon2014/5 field campaigns. We use simulations in the TOMAS (TwO-Moment Aerosol Sectional) microphysics box model to constrain the following parameters in the OFR: (1) the rate constant of gas-phase functionalization reactions of organic compounds with OH, (2) the rate constant of gas-phase fragmentation reactions of organic compounds with OH, (3) the reactive uptake coefficient for heterogeneous fragmentation reactions with OH, (4) the nucleation rate constants for three different nucleation schemes, and (5) an effective accommodation coefficient that accounts for possible particle diffusion limitations of particles larger than 60 nm in diameter. We find the best model-to-measurement agreement when the accommodation coefficient of the larger particles (Dp > 60 nm) was 0.1 or lower (with an accommodation coefficient of 1 for smaller particles), which suggests a diffusion limitation in the larger particles. When using these low accommodation-coefficient values, the model agrees with measurements when using a published H2SO4-organics nucleation mechanism and previously published values of rate constants for gas-phase oxidation reactions. Further, gas-phase fragmentation was found to have a significant impact upon the size distribution, and including fragmentation was necessary for accurately simulating the distributions in the OFR. The model was insensitive to the value of the reactive uptake coefficient on these aging timescales. Monoterpenes and isoprene could explain 24 %–95 % of the observed change in total volume of aerosol in the OFR, with ambient semivolatile and intermediate-volatility organic compounds (S/IVOCs) appearing to explain the remainder of the change in total volume. These results provide support to the mass-based findings of previous OFR studies, give insight to important size-distribution dynamics in the OFR, and enable the design of future OFR studies focused on new particle formation and/or microphysical processes.

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