To investigate sulfur
redistribution in the process of tar catalytic
cracking, nature dolomite, Ni-based dolomite, Fe-based dolomite, and
Ni/Fe-based dolomite catalysts were prepared. The effect of thioanisole,
1-octanethiol, and 1-benzothiophene on sulfur distribution of tar
cracking products was explored in a self-made fixed-bed reactor. The
results showed that sulfur poisoning and carbon deposition had weakened
the activity of Ni-based dolomite. The introduction of Ni decreased
the relative contents of 1-octanethiol and thioanisole in tar. The
additive Fe inhibited the formation of NiS, slowed down the carbon
deposition, and promoted the conversion of thiol to thioether. The
conversion of 1-octanethiol and thioanisole to phenyl disulfide could
be promoted by MgO in dolomite. The relative contents of 1-benzothiophene
in tar products of different modified dolomite catalysts increase
slightly. With 1% Ni/2% Fe-D as the catalyst, high temperature was
beneficial to the transformation from liquid-phase sulfur to gaseous-phase
sulfur. At the temperature of >700 °C, 1-octanethiol and phenyl
disulfide were converted completely. However, the sulfur content fixed
in 1% Ni/2% Fe-D was not promoted by the increasing temperature. This
study had some reference value for the regulation optimization of
sulfur-containing pollutants in coal tar processing.
The 0.5% Ni/1% Fe−dolomite catalyst and 1% Fe−dolomite catalyst were used to explore the wash oil catalytic cracking process on a fixedbed reactor. The experimental results were evaluated by yield distributions of gas, liquid, and solid phases; gas composition distributions; and component varieties of cracked oil. Catalysts were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TG), and an automatic sulfur analyzer. Cracked oil was analyzed by gas chromatography−mass spectrometry (GC−MS). XRD analyses revealed that fresh 0.5% Ni/1% Fe−dolomite catalyst had Ni−Fe and NiO crystal phases, while the used catalyst had CaS and NiS phases when there were sulfur-containing compounds with simple structures in the wash oil. TG results showed that H 2 S contributed to the heavy aromatics adsorption on catalyst, and aggravated carbon deposition. GC−MS showed that cracked oil become lighter as a result of acenaphthene cracking into alkanes, biphenylene, and pyrolysis gas. In addition, catalytic cracking of sulfur-containing compounds did not affect the contents of other liquid components.
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