Structural units of maltenes and asphaltenes from hydrogenation of coal

1982 ◽  
Vol 47 (3) ◽  
pp. 843-852 ◽  
Author(s):  
Ivo Lang
Keyword(s):  
Mass Spectrometry ◽  
Molecular Weight ◽  
Physical Meaning ◽  
Average Molecular Weight ◽  
Condensed System ◽  
Vapour Phase ◽  
Aromatic System ◽  
Structural Units ◽  
Unit Structure ◽  
Nmr Data

The calculation of the unit structure weight (USW) from NMR data is discussed. A comparison with the average molecular weight (Mr) values from vapour phase osmometry and mass spectrometry measurements showed that for the coal maltenes investigated (the fraction from the coal hydrogenation product soluble in pentane), USW can be looked upon as a rapid approximation of Mr. For asphaltenes, the calculation of USW is to a high extent dependent upon the assumed arrangement of the aromatic system. For an approximation of Mr of the asphaltenes studied, the most satisfactory was the calculation of USW from parameters of the Williams method assuming the occurrence of a peri-cata-condensed system. The USW of coal hydrogenation products calculated from NMR (1H and 13C) spectra should not be attributed the physical meaning of their smallest building units.

scholarly journals A straightforward electrospray ionization high resolution mass spectrometry method for underivatized long chain polysaccharides

2015 ◽  
Vol 13 (1) ◽  
Author(s):  
Roxana M. Ghiulai ◽  
Mirela Sarbu ◽  
Constantin Ilie ◽  
Alina D. Zamfir
Keyword(s):  
Mass Spectrometry ◽  
Molecular Weight ◽  
Electrospray Ionization ◽  
High Resolution Mass Spectrometry ◽  
Average Molecular Weight ◽  
Ionization Mass ◽  
Esi Ms ◽  
Singly Charged ◽  
Charged Ions ◽  
Long Chain

AbstractStructural analysis of long chain polysaccharides by electrospray ionization mass spectrometry (ESI-MS) is challenging since these molecules do not contain readily ionizable groups. Their mass spectra are dominated by singly charged ions, limiting the detection of high molecular weight species. Derivatization can enhance ionization, but analyte loss on purification decreases sensitivity. We report a method based on nanoESI-MS and MS/MS by collision induced dissociation (CID) for underivatized long chain polysaccharides. The procedure was tested on underivatized polydisperse dextrans (average molecular weight 4,000) at 2.6 kV ESI voltage and CID MS/MS at energies between 30-60 eV. 113 ions corresponding to species from Glc2 to Glc35 were detected. Ions at m/z 1,409.48, 1,107.35 and 1,438.47, assigned to [G17+2Na]2+,[G20+H+Na+K]3+ and [G35+2H+Na+K]4+, were sequenced and characterized by MS/MS. The component containing 35 Glc repeats is the longest polysaccharide chain detected by ESI-MS and structurally analyzed by MS/MS without prior derivatization and/or separation.

Preparation and Properties of Optically Clear Poly[(Arylenedioxy)(Diphenylsilylene)]s and Poly[(Alkylenedioxy)(Diphenylsilylene)]

2003 ◽  
Vol 15 (3) ◽  
pp. 361-370 ◽  
Author(s):  
S. Tamai ◽  
C. Tanaka ◽  
T. Abe ◽  
T. Kuroki ◽  
J. Ishikawa
Keyword(s):  
Molecular Weight ◽  
Average Molecular Weight ◽  
Structural Units ◽  
Weight Average Molecular Weight ◽  
Glass Transition Temperatures ◽  
Ductile Materials ◽  
Chemical Structures ◽  
High Degree ◽  
Polymerization Method ◽  
Step Polymerization

Several types of poly[(arylenedioxy)(diphenylsilylene)]s and poly[(alkylenedioxy)(diphenylsilylene)] were synthesized from various diols and dichlorodiphenylsilane by the step polymerization method. The thermal properties, solubility in organic solvents and optical properties of the obtained polymers were investigated by focusing on the chemical structures of their repeating structural units. The weight-average molecular weight ( Mw) of the obtained polymers based on polystyrene ranged from 43000 to 194000. High molecular weight, ductile materials with a high degree of optical clarity were obtained. These polymers display glass transition temperatures ( Tg) between 96 and 130°C. The obtained poly[(arylenedioxy) (diphenylsilylene)]s and poly[(alkylenedioxy)(diphenylsilylene)] were soluble in chloroform and toluene. The refractive index ( nd) was 1.64 for a biphenol-based poly[(arylenedioxy)(diphenylsilylene)] and 1.61 for a bisphenol-A based poly[(arylenedioxy)(diphenylsilylene)]. The poly[(arylenedioxy)(diphenylsilylene)]s and poly[(alkylenedioxy)(diphenylsilylene)] display very low birefringence (Δ n) between 0.0005 and 0.0022. The 70 μm thick film transmission of bicyclohexanol-based poly[(alkylenedioxy)(diphenylsilylene)] was 91% at a 350 nm wavelength.

The hydrogenation of olefines - II. The hydrogenation of butene-2 and iso butene

1959 ◽  
Vol 249 (1259) ◽  
pp. 532-546 ◽  
Keyword(s):  
Mass Spectrometry ◽  
Molecular Weight ◽  
Hydrogen Atom ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Room Temperature ◽  
Vapour Phase ◽  
Primary Reaction ◽  
Butyl Radical ◽  
Secondary Reactions

The work on the photosensitized hydrogenation of simple olefines described in part I has been extended to some butenes. The identity of the radicals produced in the primary reaction may be determined by analysis of the octane produced by their combination. The results obtained here agree with previous investigations in that the hydrogenation of iso butene yields tert .-butyl radicals, but disagree in that sec .-butyl radicals are found to be the principal product from butene-2. Disproportionation to combination ratios have been obtained for these radicals by the methods previously described. Vapour-phase chromatography has been used to separate the products of the secondary reactions occurring in these systems and analysis of the fractions attempted by mass spectrometry. The variation of the rate of formation of some of the products with pressure has investigated and from this information hot butyl radicals has been found both to decompose in the system thus C 4 H* 9 →CH 3 + C 3 H 6 , and to abstract from the parent olefine, C 4 H* 9 + C 4 H 8 → C 4 H 10 + C 4 H 7 . Addition of a hydrogen atom to the symmetrical olefine butene-2 can yield only a sec .-butyl radical in the absence of rearrangement. The reaction has previously been studied both at room temperature, and at 300°C (Moore & Wall 1949). The results were remarkable in that only very small traces of 3, 4-dimethyl hexane were detected, while in this work it is one of the major products. The same authors, however, found a considerable amount of 3, 4-dimethyl hexane in the hydrogenation products of butene-1. A few experiments carried out here with butene-1 using v. p. c. analysis indicate that the products from either olefine are similar both with respect to molecular weight distribution and relative quantities. The mercury-photosensitized hydrogenation of iso -butene has been studied by Moore & Wall (1949) who found considerable amounts of 2, 2, 3, 3-tetramethyl butane and iso -butane as well as traces of other hydrocarbons.

scholarly journals A Systematic Study on the Degradation Products Generated from Artificially Aged Microplastics

Polymers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1997
Author(s):  
Greta Biale ◽  
Jacopo La Nasa ◽  
Marco Mattonai ◽  
Andrea Corti ◽  
Virginia Vinciguerra ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Molecular Weight ◽  
Degradation Products ◽  
Average Molecular Weight ◽  
Size Exclusion ◽  
Gas Chromatography Mass Spectrometry ◽  
Low Molecular Weight ◽  
Photo Degradation ◽  
Degradation Processes ◽  
Wide Range

Most of the analytical studies focused on microplastics (MPs) are based on the detection and identification of the polymers constituting the particles. On the other hand, plastic debris in the environment undergoes chemical and physical degradation processes leading not only to mechanical but also to molecular fragmentation quickly resulting in the formation of leachable, soluble and/or volatile degradation products that are released in the environment. We performed the analysis of reference MPs–polymer micropowders obtained by grinding a set of five polymer types down to final size in the 857–509 μm range, namely high- and low-density polyethylene, polystyrene (PS), polypropylene (PP), and polyethylene terephthalate (PET). The reference MPs were artificially aged in a solar-box to investigate their degradation processes by characterizing the aged (photo-oxidized) MPs and their low molecular weight and/or highly oxidized fraction. For this purpose, the artificially aged MPs were subjected to extraction in polar organic solvents, targeting selective recovery of the low molecular weight fractions generated during the artificial aging. Analysis of the extractable fractions and of the residues was carried out by a multi-technique approach combining evolved gas analysis–mass spectrometry (EGA–MS), pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS), and size exclusion chromatography (SEC). The results provided information on the degradation products formed during accelerated aging. Up to 18 wt% of extractable, low molecular weight fraction was recovered from the photo-aged MPs, depending on the polymer type. The photo-degradation products of polyolefins (PE and PP) included a wide range of long chain alcohols, aldehydes, ketones, carboxylic acids, and hydroxy acids, as detected in the soluble fractions of aged samples. SEC analyses also showed a marked decrease in the average molecular weight of PP polymer chains, whereas cross-linking was observed in the case of PS. The most abundant low molecular weight photo-degradation products of PS were benzoic acid and 1,4-benzenedicarboxylic acid, while PET had the highest stability towards aging, as indicated by the modest generation of low molecular weight species.

scholarly journals In situ submicron organic aerosol characterization at a boreal forest research station during HUMPPA-COPEC 2010 using soft and hard ionization mass spectrometry

2013 ◽  
Vol 13 (21) ◽  
pp. 10933-10950 ◽  
Author(s):  
A. L. Vogel ◽  
M. Äijälä ◽  
A. L. Corrigan ◽  
H. Junninen ◽  
M. Ehn ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Molecular Weight ◽  
Organic Acids ◽  
Boreal Forest ◽  
Organic Acid ◽  
Gas Phase ◽  
Biomass Burning ◽  
Average Molecular Weight ◽  
Ionization Mass ◽  
Particle Phase

Abstract. The chemical composition of submicron aerosol during the comprehensive field campaign HUMPPA-COPEC 2010 at Hyytiälä, Finland, is presented. The focus lies on online measurements of organic acids, which were achieved by using atmospheric pressure chemical ionization (APCI) ion trap mass spectrometry (IT-MS). These measurements were accompanied by aerosol mass spectrometry (AMS) measurements and Fourier transform infrared spectroscopy (FTIR) of filter samples, all showing a high degree of correlation. The soft ionization mass spectrometer alternated between gas-phase measurements solely and measuring the sum of gas and particle phase. The AMS measurements of C, H and O elemental composition show that the aerosol during the campaign was highly oxidized, which appears reasonable due to high and prolonged radiation during the boreal summer measurement period as well as the long transport times of some of the aerosol. In order to contrast ambient and laboratory aerosol, an average organic acid pattern, measured by APCI-IT-MS during the campaign, was compared to terpene ozonolysis products in a laboratory reaction chamber. Identification of single organic acid species remains a major challenge due to the complexity of the boreal forest aerosol. Unambiguous online species identification was attempted by the combinatorial approach of identifying unique fragments in the MS2 mode of standards, and then comparing these results with MS2 field spectra. During the campaign, unique fragments of limonene-derived organic acids (limonic acid and ketolimononic acid) and of the biomass burning tracer vanillic acid were detected. Other specific fragments (neutral loss of 28 Da) in the MS2 suggest the occurrence of semialdehydes. Furthermore, an approach to determine the average molecular weight of the aerosol is presented. The campaign average organic molecular weight was determined to be 300 g mol−1. However, a plume of aged biomass burning aerosol, arriving at Hyytiälä from Russia, contained organic compounds up to 800 Da (MWom≈450 g mol−1), showing that the average molecular weight can vary significantly. The high measurement frequency of both AMS and APCI-IT-MS enabled the partitioning of selected organic acids between gas and particle phase as a function of the total particulate mass to be quantified. Surprisingly high fractions of the higher molecular weight organic acids were observed to reside in the gas phase. These observations might be a consequence of large equilibration timescales for semi-solid boreal forest aerosol, as has been recently hypothesized by Shiraiwa and Seinfeld (2012).

scholarly journals In-situ submicron organic aerosol characterization at a boreal forest research station during HUMPPA-COPEC 2010 using soft and hard ionization mass spectrometry

2013 ◽  
Vol 13 (7) ◽  
pp. 17901-17952
Author(s):  
A. L. Vogel ◽  
M. Äijälä ◽  
A. L. Corrigan ◽  
H. Junninen ◽  
M. Ehn ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Molecular Weight ◽  
Organic Acids ◽  
Boreal Forest ◽  
Organic Acid ◽  
Gas Phase ◽  
Biomass Burning ◽  
Average Molecular Weight ◽  
Ionization Mass ◽  
Particle Phase

Abstract. The chemical composition of submicron aerosol during the comprehensive field campaign HUMPPA-COPEC 2010 at Hyytiälä, Finland is presented. The focus lies on online measurements of organic acids, which was achieved by using atmospheric pressure chemical ionization (APCI) ion trap mass spectrometry (IT-MS). These measurements were accompanied by Aerosol Mass Spectrometry (AMS) measurements and Fourier-Transform Infrared Spectroscopy (FTIR) of filter samples, all showing a high degree of correlation. The soft ionization mass spectrometer alternated between gas phase measurements solely and measuring the sum of gas- and particle-phase. The AMS measurements of C, H and O elemental composition show that the aerosol during the campaign was highly oxidized, which appears reasonable due to high and prolonged radiation during the boreal summer measurement period as well as the long transport times of some of the aerosol. In order to contrast ambient and laboratory aerosol, an average organic acid pattern, measured by APCI-IT-MS during the campaign, was compared to terpene ozonolysis products in a laboratory reaction chamber. Identification of single organic acid species remains a major challenge due to the complexity of the boreal forest aerosol. Unambiguous online species identification was attempted by the combinatorial approach of identifying unique fragments in the MS2-mode of standards, and then comparing these results with MS2 field spectra. During the campaign, unique fragments of limonene derived organic acids (limonic acid and ketolimononic acid) and of the biomass burning tracer vanillic acid were detected. Other specific fragments (neutral loss of 28 Da) in the MS2 suggest the occurrence of semialdehydes. Furthermore, an approach to determine the average molecular weight of the aerosol is presented. The campaign average organic molecular weight was determined to be 300 g mol−1. However, a plume of aged biomass burning aerosol, arriving at Hyytiälä from Russia, contained organic compounds up to 800 Da (MWom ≈ 450 g mol−1), showing that the average molecular weight can vary significantly. The high measurement frequency of both, AMS and APCI-IT-MS, enabled the partitioning of selected organic acids between gas- and particle-phase as a function of the total particulate mass to be quantified. Surprisingly high fractions of the higher molecular weight organic acids were observed to reside in the gas phase. These observations might be a consequence of large equilibration timescales for semi-solid boreal forest aerosol, as it has been recently hypothesised by Shiraiwa and Seinfeld (2012).

The Structure of Radiation Cross-Linked Poly (ethylene oxide) Gels

1971 ◽  
Vol 29 ◽  
pp. 76-77
Author(s):  
C. E. Cluthe ◽  
G. G. Cocks
Keyword(s):  
Molecular Weight ◽  
Ethylene Oxide ◽  
Parallel Plate ◽  
Average Molecular Weight ◽  
Radical Reaction ◽  
Free Radical Reaction ◽  
Nitrogen Gas ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene ◽  
Initial Viscosity

Aqueous solutions of a 1 weight-per cent poly (ethylene oxide) (PEO) were degassed under vacuum, transferred to a parallel plate viscometer under a nitrogen gas blanket, and exposed to Co60 gamma radiation. The Co60 source was rated at 4000 curies, and the dose ratewas 3.8x105 rads/hr. The poly (ethylene oxide) employed in the irradiations had an initial viscosity average molecular weight of 2.1 x 106.The solutions were gelled by a free radical reaction with dosages ranging from 5x104 rads to 4.8x106 rads.

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