Maceral composition is one of the key factors affecting
the liquefaction
and gasification of coal, which has attracted extensive attention
of researchers working on coal chemical industry. To elucidate the
impact of vitrinite and inertinite in coal on pyrolysis products,
vitrinite and inertinite were extracted from a single coal sample
and mixed to create six samples with varying vitrinite/inertinite
ratios. The samples were subjected to thermogravimetry coupled online
with mass spectrometry (TG–MS) experiments, and the Fourier
transform infrared spectrometry (FITR) experiment was used to determine
the macromolecular structures before and after the TG–MS experiments.
The results show that the maximum mass loss rate is proportional to
the vitrinite content and inversely proportional to the inertinite
content, and increased vitrinite content accelerates the pyrolysis
process and shifts the pyrolysis peak to low temperatures. Based on
FTIR experiments, the sample’s CH2/CH3 content, representing the length of aliphatic side chains, decreases
significantly after pyrolysis, and the greater the loss of CH2/CH3, the greater the intensity of organic molecule
production, indicating that aliphatic side chains are likely to yield
organic molecule products. The aromatic degree (I) of samples rises sharply and steadily with increasing inertinite
content. After high-temperature pyrolysis, the polycondensation degree
of aromatic rings (DOC) and relative abundance of aromatic and aliphatic
hydrogen (Har/Hal) within the sample increased
significantly, indicating the thermal degradation rate of aromatic
hydrogen content is much lower than that of aliphatic hydrogen. When
the pyrolysis temperature is lower than 400 °C, the higher the
inertinite content, the easier it is to produce CO2, whereas
an increase in vitrinite leads to an increase in CO production. At
this stage, the “–C–O–” functional
group is pyrolyzed to produce CO and CO2. When the temperature
exceeds 400 °C, the CO2 output intensity of vitrinite-rich
samples is much higher than that of inertinite-rich samples, while
the CO output intensity of vitrinite-rich samples is lower, and the
higher the vitrinite content, the higher the peak temperature of CO
gas production of samples, indicating that when the temperature exceeds
400 °C, the increase of vitrinite inhibits CO production and
promotes CO2 production. At this stage, the reduction of
each sample’s “–C–O–” functional
group after pyrolysis is positively correlated with the maximum CO
gas production intensity, and the reduction of each sample’s
“–CO” functional group after pyrolysis
is positively correlated with the maximum CO2 gas production
intensity. As a result, the “–C–O–”
functional group is more likely to produce CO, whereas the “–CO”
functional group is more likely to be pyrolyzed to CO2.
Hydrogen is primarily produced during the polycondensation and aromatization
processes, and its production is proportional to the dynamic DOC values
after pyrolysis. The higher the I value after pyrolysis,
the lower the maximu...