At
present, a few chemicals can be separated after further processing
of high-temperature coal tar (HTCT) distillates, which have a lower
utilization. However, hydrogenation to produce clean fuel oil has
not been widely reported in literature. Thus, due to the use of new
feedstocks and the implementation of more severe environmental legislations,
deep hydrodesulfurization (HDS) of HTCT will face formidable challenges.
A series of HDS experiments were performed in a continuous isothermal
trickle bed reactor in which the reactor temperature was varied from
648 to 678 K, the pressure from 12 to 16 MPa, and the liquid hourly
space velocity (LHSV) from 0.25 to 0.35 h–1, and
hydrogen-to-oil ratio kept constant at 2000 L/L. Based on the experimental
data, possible reaction pathways of HDS reaction were investigated,
and a modified Langmuir–Hinshelwood (LH) HTCT desulfurization
kinetic model was established. gPROMS software was used to obtain
optimal kinetic parameters that are as follows: EA = 26,842, K
0 = 93,958, α = −1.14, n = 1.65, and m = 0.86. The model can well
reproduce various working conditions and has better prediction accuracy.
Some characteristics of HTCT HDS reactions were discovered; the reaction
order (n) of HTCT HDS is slightly higher than that
of crude oil and medium/low-temperature coal tar (M/LTCT), but the
activation energy (EA) is relatively smaller. The established reactor
model was used to predict the changes of the concentration of hydrogen,
hydrogen sulfide, and sulfur compounds in the gas, liquid, and solid
phases along the length of the reactor, respectively. The model was
also used to predict the effects of pressure, temperature, and LHSV
on the conversion rate of sulfur and catalyst effectiveness factors.
The results showed that the LHSV has a greater impact on the conversion
rate, and the pressure and temperature are less pronounced at high-severity
operating conditions; the effectiveness factor is significantly smaller
than that of other HDS processes, temperature has a greater effect
on the effectiveness factor, followed by pressure and LHSV. The conclusion
can provide a basis for further understanding the HTCT hydrotreating
process.