1554. Mass spectrometric method for determination of the ratio of effective ionization cross sections of different gases contained in an ionisation chamber

The determination of Li, Be, and B cross sections formed by spallation reactions induced by high-energy protons in C, N, and O targets is of interest for cosmic-ray physics and astrophysics. A mass-spectrometric method has been devised to measure the stable and long-lived isotopes 6Li, 7Li, 9Be, 10Be (τ = 2.5 × 106 yr), 7Be (τ = 54 d), 10B, 11B, formed in oxygen for proton energies of 0.15, 0.60, and 19 GeV. These results have been included in a program of calculations allowing us to determine the quantity of matter traversed by galactic cosmic rays of energy > 1.5 GeV/nucleon; the observed relative abundances are best fitted, in the slab approximation, by passage through 5.4 ± 1 g/cm2 of hydrogen.

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Tandem Mass Spectrometric Evaluation of Core Structures of Aromatic Compounds after Catalytic Deoxygenation

10.26434/chemrxiv.5410807.v1 ◽

2017 ◽

Author(s):

Xueming Dong

Keyword(s):

Aromatic Compounds ◽

Supported Catalyst ◽

Mass Spectrometric ◽

Spectrometric Method ◽

Mass Spectrometric Method ◽

Aromatic Rings ◽

Tandem Mass Spectrometric ◽

Catalytic Deoxygenation ◽

Oxygen Atoms

Catalytic deoxygenation of coal enhances the stability and combustion performance of coal-derived liquids. However, determination of the selectivity of removal of oxygen atoms incorporated in or residing outside of aromatic rings is challenging. This limits the ability to evaluate the success of catalytic deoxygenation processes. A mass spectrometric method, in-source collision-activated dissociation (ISCAD), combined with high resolution product ion detection, is demonstrated to allow the determination of whether the oxygen atoms in aromatic compounds reside outside of aromatic rings or are part of the aromatic system, because alkyl chains can be removed from aromatic cores via ISCAD. Application of this method for the analysis of a subbituminous coal treated using a supported catalyst revealed that the catalytic treatment reduced the number of oxygen-containing heteroaromatic rings but not the number of oxygen atoms residing outside the aromatic rings.<br>

Download Full-text

Tandem Mass Spectrometric Evaluation of Core Structures of Aromatic Compounds after Catalytic Deoxygenation

10.26434/chemrxiv.5410807 ◽

2017 ◽

Author(s):

Xueming Dong

Keyword(s):

Aromatic Compounds ◽

Supported Catalyst ◽

Mass Spectrometric ◽

Spectrometric Method ◽

Mass Spectrometric Method ◽

Aromatic Rings ◽

Tandem Mass Spectrometric ◽

Catalytic Deoxygenation ◽

Oxygen Atoms

Catalytic deoxygenation of coal enhances the stability and combustion performance of coal-derived liquids. However, determination of the selectivity of removal of oxygen atoms incorporated in or residing outside of aromatic rings is challenging. This limits the ability to evaluate the success of catalytic deoxygenation processes. A mass spectrometric method, in-source collision-activated dissociation (ISCAD), combined with high resolution product ion detection, is demonstrated to allow the determination of whether the oxygen atoms in aromatic compounds reside outside of aromatic rings or are part of the aromatic system, because alkyl chains can be removed from aromatic cores via ISCAD. Application of this method for the analysis of a subbituminous coal treated using a supported catalyst revealed that the catalytic treatment reduced the number of oxygen-containing heteroaromatic rings but not the number of oxygen atoms residing outside the aromatic rings.<br>

Download Full-text