Paraffins in the cracked naphtha can be transformed into aromatics and isoparaffin to improve the octane number. In this article, a series of Ni/HZSM-5 bifunctional catalysts were prepared and were characterized by temperature-programmed desorption of NH 3 (NH 3 -TPD), FT-IR analysis with adsorbed pyridine as well as by x-ray powder diffraction analysis. The monolayer dispersion threshold value of Ni on HZSM-5 was determined and the cracking and aromatization activities of the catalysts were investigated in the transformation of n-heptane. The experimental results show that the catalyst with a monolayer dispersion threshold value of Ni shows the best aromatization and isomerization activity. The products selectivity of n-heptane over different catalysts was analyzed and it was revealed that low hydrogen pressure can reduce the conversion of n-heptane, but at the same time accelerate the production of aromatics. The aromatization activity of the catalysts increases with the elevation of the reaction temperature, and the incorporation of metal in HZSM-5 decreases the cracking reaction on the catalysts, while at the same time increases the reactions that may result in the production of aromatics.
A series of NiMoP(
x
)-Al catalysts with different
phosphorus contents were prepared by the incipient wetness co-impregnation
method. The effects of phosphorus modification on the acidity, active
phase nanostructure, and catalytic properties of the residue hydrodenitrogenation
catalysts were investigated to find the role of phosphorus in the
catalytic mechanism. The results of temperature-programmed desorption
of NH
3
and pyridine IR spectroscopy of the catalysts indicate
that phosphorus modification can increase the total acid and Brønsted
acid. Transmission electron microscopy analysis shows that phosphorus
modification increases the stacking number
N
A
, reduces the slab length
L
A
of
the active MoS
2
phase, and increases the Mo dispersion
f
Mo
, leading to the promotion of the sulfidation
degree of the active Mo phase and thus increasing the denitrification
rate. The catalyst with a 3.4 wt % P
2
O
5
loading
shows the highest Brønsted/Lewis acid ratio, the largest amount
of three-layer active phases, the smallest
L
A
, the highest
f
Mo
, the optimal
sulfurization degree, and the highest denitrification rate, 63.6%,
indicating the correlation between the nanostructure of the active
phase and its catalytic property because of the addition of phosphorus.
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