In order to convert
low temperature coal tar (LCT) into clean transportation
fuels by hydrotreating (HDT), the changes of asphaltenes properties
during HDT of LCT should be paid more attention. The HDT experiments
were carried out in a trickle-bed reactor unit under various reaction
temperatures, and asphaltenes were extracted from the liquid products.
The properties and structure of asphaltenes were performed by X-ray
diffraction, elemental analysis, size-exclusion chromatography, X-ray
photoelectron spectroscopy, and nuclear magnetic resonance. Structural
units analysis of average molecules and the variation trend of change
in the structural parameters were revealed. The results showed that,
with the temperature increase, the diameter of the aromatic sheet
(L
a), interaromatic layer distance (d
m), total carbon number (C
T), and average alkyl chain length (n) decrease,
while the aromaticity factor (f
A) and
aromatic carbon number (C
A) increase.
Moreover, the mechanism of HDT was studied to make the molecular structure
of asphaltenes easier to understand. At the same time,
the larger condensation degree of the asphaltenes molecules, the larger
aromatic degrees, the removal of the alkyl side chain was more significant.
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