The sidebands in the solid-state
13C NMR spectra of 13 polycyclic aromatic hydrocarboncompounds associated with kerogen structure were suppressed with cross polarization (CP), magic-angle spinning (MAS), and total sideband suppression (TOSS). The chemical shift values of thesemodel compounds were obtained under various chemical circumstances, which were subsequentlyused to determine the chemical shifts of aliphatic and aromatic carbons in kerogen structure viaCP/MAS/TOSS
13C NMR measurements. Dipolar dephasing (DD) was used to obtain the spectraof nonprotonated carbon, discriminating protonated and nonprotonated carbons in the aromaticcluster. Consequently, the structural parameters for different carbons were characterized. High-resolution solid-state
13C NMR measurements were conducted on a suite of kerogen macromolecules isolated from source rocks originated from the
Kuqa depression, Awati River, andKapusaliang River of the Tarim Basin in northwestern China to develop an NMR-associatedmethod for monitoring the thermal alteration of kerogens. These rocks covered a broad maturityrange, as indicated by the
Ro values of 0.52%-1.81%. Our results suggest that the aromaticity(
fa) and aromatic cluster size (
b) are effective parameters for assessment of the thermal evolutionof kerogens that resulted from the geological heating process undergone in the ancient sediments.