(260c) Quantitative Analysis and Structural Characterization of Carbonaceous Pitches

Petroleum pitches can serve as precursors for wide range of carbon products, such as high thermal conductivity carbon fibers, carbon electrodes, carbon fibers for fuel cell substrates, and carbon/carbon composites. Research increasingly suggests that the molecular composition of the pitch and the structures present in the pitch have a significant impact on the properties of the final carbon products, but to date this understanding is primarily qualitative because of an inability to isolate the pitches into fractions with narrow mol wt distribution that can be characterized easily. We have recently developed a technique called Dense Gas Extraction (DGE) for the fractionation of petroleum pitches, with the goal of obtaining fractions with relatively narrow mol wt distribution. Such fractions can serve as standards for structural characterization and quantitative analysis.

In this work, we report separation of petroleum pitches into fractions with narrow mol wt distribution using both continuous and semi-batch DGE processes and application of these fractions as standards for structural characterization and quantitative analysis. Matrix-Assisted, Laser Desorption/Ionization time-of-flight mass spectrometry (MALDI) was used for the quantitative analysis of the petroleum pitches. Pitch fractions containing 98% monomer and 97% dimer were isolated by DGE, and were used to study the effect of oligomeric composition on MALDI response. Also, both new and conventional techniques were applied to identify the specific structures that exist in petroleum pitches. Pitch fractions containing 98% monomer and 97% dimer were characterized using MALDI, MALDI-Post Source Decay, and Field Desorption mass spectrometry; and 1H-NMR, UV-Vis, and FT-IR spectroscopy and specific molecular structures that are significant constituents of petroleum pitches were proposed.