Electrochemical processes of adsorbed chlorobenzene and fluorobenzene on a platinum polycrystalline electrode

2009 ◽  
Vol 74 (4) ◽  
pp. 611-625 ◽  
Author(s):  
Natálie Musilová-Kebrlová ◽  
Pavel Janderka ◽  
Libuše Trnková
Keyword(s):  
Mass Spectrometry ◽  
Sulfuric Acid ◽  
Oxygen Adsorption ◽  
Negative Polarization ◽  
Electrode Processes ◽  
Differential Electrochemical Mass Spectrometry ◽  
Electrochemical Processes ◽  
Polycrystalline Platinum

The electrode processes of chlorobenzene (CB) and fluorobenzene (FB) on polycrystalline platinum (Pt-pc) electrode in sulfuric acid were studied by differential electrochemical mass spectrometry (DEMS). Contrary to the oxidation of adsorbed benzene on Pt surface, the oxidation of adsorbed CB and FB in the oxygen adsorption region does not provide solely CO2 as the final product. At negative polarization potentials CB and FB were desorbed under dehalogenation. While in the case of FB only benzene was detected, CB gave intermediates besides benzene. The final product of stepwise hydrogenation of these species was cyclohexane.

Building a Differential Electrochemical Mass Spectrometry (DEMS): A Powerful Toll for Investigation of (photo)Electrochemical Processes

2021 ◽  
Vol MA2021-01 (46) ◽  
pp. 1873-1873
Author(s):  
Adriana Queiroz ◽  
Wanderson Oliveira da Silva ◽  
Daniel Cantane ◽  
Igor Messias ◽  
Maria Rodrigues Pinto ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Differential Electrochemical Mass Spectrometry ◽  
Electrochemical Processes

scholarly journals Hydrothermal Pretreatment of Wheat Straw: Effects of Temperature and Acidity on Byproduct Formation and Inhibition of Enzymatic Hydrolysis and Ethanolic Fermentation

Agronomy ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 487
Author(s):  
Dimitrios Ilanidis ◽  
Stefan Stagge ◽  
Leif J. Jönsson ◽  
Carlos Martín
Keyword(s):  
Mass Spectrometry ◽  
Sulfuric Acid ◽  
Wheat Straw ◽  
High Performance ◽  
Enzymatic Saccharification ◽  
Hydrothermal Pretreatment ◽  
Gas Chromatography Mass Spectrometry ◽  
Enzymatic Digestibility ◽  
Acid Catalyzed ◽  
Pretreatment Conditions

Biochemical conversion of wheat straw was investigated using hydrothermal pretreatment, enzymatic saccharification, and microbial fermentation. Pretreatment conditions that were compared included autocatalyzed hydrothermal pretreatment at 160, 175, 190, and 205 °C and sulfuric-acid-catalyzed hydrothermal pretreatment at 160 and 190 °C. The effects of using different pretreatment conditions were investigated with regard to (i) chemical composition and enzymatic digestibility of pretreated solids, (ii) carbohydrate composition of pretreatment liquids, (iii) inhibitory byproducts in pretreatment liquids, (iv) furfural in condensates, and (v) fermentability using yeast. The methods used included two-step analytical acid hydrolysis combined with high-performance anion-exchange chromatography (HPAEC), HPLC, ultra-high performance liquid chromatography-electrospray ionization-triple quadrupole-mass spectrometry (UHPLC-ESI-QqQ-MS), and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Lignin recoveries in the range of 108–119% for autocatalyzed hydrothermal pretreatment at 205 °C and sulfuric-acid-catalyzed hydrothermal pretreatment were attributed to pseudolignin formation. Xylose concentration in the pretreatment liquid increased with temperature up to 190 °C and then decreased. Enzymatic digestibility was correlated with the removal of hemicelluloses, which was almost quantitative for the autocatalyzed hydrothermal pretreatment at 205 °C. Except for the pretreatment liquid from the autocatalyzed hydrothermal pretreatment at 205 °C, the inhibitory effects on Saccharomyces cerevisiae yeast were low. The highest combined yield of glucose and xylose was achieved for autocatalyzed hydrothermal pretreatment at 190 °C and the subsequent enzymatic saccharification that resulted in approximately 480 kg/ton (dry weight) raw wheat straw.

Isotopic exchanges in the treatment of cyclobutane with tritiated or deuterated trifluoromethanesulfonic acid or with tritiated sulfuric acid

1980 ◽  
Vol 58 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Choi Chuck Lee ◽  
Eric C. F. Ko
Keyword(s):  
Mass Spectrometry ◽  
Sulfuric Acid ◽  
Trifluoromethanesulfonic Acid ◽  
Isotopic Dilution ◽  
Chain Mechanism

When cyclobutane (1) is shaken at 0 °C with [3H]CF3SO3H (2-t) or with (2H)CF3SO3H (2-d), incorporation of T or D into the hydrocarbon layer readily occurred. All eight H atoms of 1 can be involved in the exchange since polydeuterated species including octadeuterated hydrocarbons were observed by mass spectrometry. In an experiment with 1 and 2-t, quenching of the acid layer with H2O gave a mixture of cyclobutanol, cyclopropylcarbinol, and allylcarbinol in the ratio of 61:37:2, respectively, as estimated by isotopic dilution, while vpc analysis of the hydrocarbon layer showed the presence of 1, methylcyclopropane, and 1-butene in the ratio of 66:30:4. The results are explained by a carbocationic chain mechanism, involving the formation of equilibrating bicyclobutonium ions. Similar but slower incorporation of T into the hydrocarbon layer was observed when 1 was treated with [3H]H2SO4.

scholarly journals Chemical ionization mass spectrometry (CIMS) may not measure all gas-phase sulfuric acid if base molecules are present

2010 ◽  
Vol 10 (12) ◽  
pp. 30539-30568
Author(s):  
T. Kurtén ◽  
T. Petäjä ◽  
J. Smith ◽  
I. K. Ortega ◽  
M. Sipilä ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Sulfuric Acid ◽  
Gas Phase ◽  
Chemical Ionization ◽  
Measurement Data ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Proton Affinities ◽  
Reaction Thermodynamics

Abstract. The state-of-the art method for measuring atmospheric gas-phase sulfuric acid is chemical ionization mass spectrometry (CIMS) based on nitrate reagent ions. Using computed proton affinities and reaction thermodynamics for the relevant charging reactions, we show that in the presence of strong bases such as amines, which tend to cluster with the sulfuric acid molecules, a significant fraction of the total gas-phase sulfuric acid may not be measured by a CIMS instrument. If this is the case, this effect has to be taken into account in the interpretation of atmospheric sulfuric acid measurement data, as well as in intercomparison of different CIMS instruments, which likely have different susceptibilities to amine-sulfuric acid clustering.

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