Skip to main content
U.S. Department of Energy
Office of Scientific and Technical Information

On the role of methyl groups in the molecular architectures of mesophase pitches

Journal Article · · Fuel
The role of methyl groups on the liquid–crystal structure of mesophase pitches was investigated by combining experimental characterizations and atomic-scale computational modeling, using three pitches synthesized from different precursors. Of the three pitches, C-9 alkyl benzene and naphthalene-based pitches have 13 and 7 methyl groups per average polyaromatic hydrocarbon, respectively. By contrast, mesophase produced from a coal-tar pitch has about one methyl group. The coal tar–based mesophase pitch is hydrogen deficient or more aromatic compared with C-9 alkyl benzene- and naphthalene-based pitches. Additionally, X-ray diffraction data showed that average coherent domain sizes of C-9 alkyl benzene (3.7 nm) and naphthalene-based (3.6 nm) pitches with more methyl groups are larger than that of coal tar–based mesophase (2.4 nm). Based on the identified features, the influence of the methyl group on the layering structures was investigated via molecular dynamics simulations. The results revealed that methyl groups are critical in mesophase layering in C-9 alkyl benzene- and naphthalene-based pitches, by reducing CH-π interaction. However, similar alignment could be achieved without the same degree of methyl substitutions for the coal tar-based pitch because of stronger π-π interaction than the other precursors. The insights from this study contribute to our understanding of the formation of conventional mesophase pitch and have implications for the processing of coal-derived materials. In conclusion, this knowledge is vital to produce valuable products like carbon fiber and graphite from pitches.
Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Office of Fossil Energy and Carbon Management (FECM); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
2203829
Journal Information:
Fuel, Journal Name: Fuel Journal Issue: C Vol. 357; ISSN 0016-2361
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

References (44)

Fast, efficient generation of high-quality atomic charges. AM1-BCC model: I. Method journal January 2000
Herringbone Pattern and CH-π Bonding in the Crystal Architecture of Linear Polycyclic Aromatic Hydrocarbons journal September 2016
Development and testing of a general amber force field journal January 2004
Mesoscopic Structure and Properties of Liquid Crystalline Mesophase Pitch and Its Transformation into Carbon Fiber journal March 2002
Fast Parallel Algorithms for Short-Range Molecular Dynamics journal March 1995
Improved understanding of the molecular structure of pyrolysis fuel oil: towards its utilization as a raw material for mesophase pitch synthesis journal January 2019
Preparation of petroleum-based mesophase pitch toward cost-competitive high-performance carbon fibers journal July 2019
Measurement of interlayer spacings and crystal sizes in turbostratic carbons journal October 1963
Preparation and properties of carbonaceous mesophase-II highly soluble mesophase from ethylene tar modified using aluminum chloride as a catalyst journal January 1985
Comparative study of isotropic and mesophase pitches derived from C9 alkylbenzenes journal January 1992
Molecular assembly of mesophase and isotropic pitches at their fused states journal January 1992
Effects of reductively introduced alkyl groups and hydrogen to mesophase pitch on carbonization properties journal January 1993
Reorganization of molecular alignment in naphthalene and methyl-naphthalene derived pitches journal January 1994
The flow properties of mesophase pitches derived from methylnaphthalene and naphthalene in the temperature range of their spinning journal January 1994
Modifying carbonization properties of pitches. 1. Conversion of benzene-insoluble matter of coal-tar pitch into graphitizable carbon journal October 1974
Modifying carbonization properties of pitches. 2. Attempts to improve the yield of fusible material from the quinoline-insoluble fraction of a petroleum pitch journal October 1975
Carbon fibres from mesophase pitch journal September 1981
Average structures of petroleum pitch fractions by 1H13C n.m.r. spectroscopy journal May 1985
Structural characterization of pitch feedstocks for coke making Use of 13C coupled 1H n.m.r. spectroscopy journal August 1985
VMD: Visual molecular dynamics journal February 1996
Structural modification of coal-tar pitch fractions during mild oxidation—relevance to carbonization behavior journal September 2002
Relationships between pitch composition and optical texture of cokes journal January 1997
A study on the effect of heat treatment on functional groups of pitch based activated carbon fiber using FTIR journal January 1997
Structural characterization of milled mesophase pitch-based carbon fibers journal November 1998
Observations on a low-angle X-ray diffraction peak for AR-HP mesophase pitch journal July 2008
The thermotropic liquid crystalline behavior of mesophase pitches with different chemical structures journal January 2015
Molecular characterization of large polycyclic aromatic hydrocarbons in solid petroleum pitch and coal tar pitch by high resolution MALDI ToF MS and insights from ion mobility separation journal December 2015
Activated carbon monoliths with hierarchical pore structure from tar pitch and coal powder for the adsorption of CO2, CH4 and N2 journal July 2016
Analyzing solid fossil-fuel pitches by a combination of Soxhlet extraction and Fourier transform ion cyclotron resonance mass spectrometry journal October 2020
Correlation between molecular stacking and anisotropic texture in spinnable mesophase pitch journal June 2022
Investigation on the development and orientation of mesophase microstructure during the two-stage pyrolysis of FCC decant oil journal March 2020
Modified effect on properties of mesophase pitch prepared from various two-stage thermotreatments of FCC decant oil journal January 2021
Influence of boron trifluoride complex addition on structure and composition of mesophase pitch from FCC decant oil via two-stage thermotreatment journal October 2022
In situ characterization of phase transformations in petroleum pitch by high temperature X-ray diffraction journal January 2023
Moltemplate: A Tool for Coarse-Grained Modeling of Complex Biological Matter and Soft Condensed Matter Physics journal May 2021
Automatic atom type and bond type perception in molecular mechanical calculations journal October 2006
Spinnable Mesophase Pitch Prepared via Co-carbonization of Fluid Catalytic Cracking Decant Oil and Synthetic Naphthalene Pitch journal December 2019
Constructing the Bridge from Isotropic to Anisotropic Pitches for Preparing Pitch-Based Carbon Fibers with Tunable Structures and Properties journal August 2020
NMR:  A Powerful Tool in the Characterization of Coal Tar Pitch journal June 2003
Structural Identification of the Monomeric Constituents of Petroleum Pitch journal July 2010
Depolarized Light Scattering for Study of Heavy Oil and Mesophase Formation Mechanisms journal August 2012
Generation and properties of the new asphalt binder model using molecular dynamics (MD) journal May 2021
Novel Immune Modulators Enhance Caenorhabditis elegans Resistance to Multiple Pathogens journal February 2021
Density, Enthalpy of Vaporization and Local Structure of Neat N-Alkane Liquids journal August 2021