TITLE:
Hydroisomerization of n-Pentane over Zn-Fe-S2O8-2/ZrO2-Al2O3 Superacid Catalyst: Activity, Surface Analysis and the Investigation of Deactivation and Regeneration
AUTHORS:
Huapeng Cui, Shengnan Li
KEYWORDS:
Zn-Fe, Solid Superacid, Surface Analysis, Deactivation, Regeneration, Hydroisomerization
JOURNAL NAME:
Open Journal of Inorganic Chemistry,
Vol.13 No.3,
July
31,
2023
ABSTRACT: The Zn and Fe modified /ZrO2-Al2O3 catalyst (Zn-Fe-SZA) was prepared and mechanisms of deactivation and methods
for regeneration of as-prepared catalyst were explored with n-pentane isomerization as a probe
reaction. The results indicated that the isopentane yield of the fresh Zn-Fe-SZA-F
catalyst was about 57% at the beginning of the run, and declined gradually to
50% within 1500 min, then fell rapidly from 50% to 40% between 1500 and 2500
minutes. The deactivation of Zn-Fe-SZA catalyst may be caused by carbon
formation on surface of the catalyst, sulfate group attenuation owing to
reduction by hydrogen, removal of sulfur species and the loss of strong acid
sites. It was found that the initial catalytic activity over Zn-Fe-SZA-T
catalyst was 48%, which recovered by 84.3% as compared to that of fresh
catalyst (57%). However, it showed a sharp decrease in isopentane yield from 48%
to 29% within 1500 minutes, showing poor stability. This is associated to the
loss of acidity caused by removal of sulfur species cannot be basically restored
by thermal treatment. Resulfating the calcined catalyst could improve the
acidity of catalyst significantly, especially strong acid sites, as compared
with the calcined sample. The improved stability of the resulfated catalyst can
be explained by: 1) eliminaton of carbon deposition to some extent by calcination
process, 2) formation of improved acidic nature by re-sulfation, favoring isomerization
on acidic sites, 3) restructuring of the acid and metal sites via the
calcination-re-sulfation procedure.