To enhance the low-temperature activity of monometallic Ni/Al2O3 catalyst for thioetherification, Fe-promoted
Ni/Al2O3 catalysts were prepared. The activity
of the catalysts was evaluated in a fixed-bed reactor, and their physicochemical
properties were characterized. The results showed that the bimetallic
NiFe system had significantly improved activity; in particular sample
14Ni8Fe/Al2O3 exhibited outstanding activity
and stability, with conversions of CH3SH and C2H5SH reaching up to 99.5% and 97.4%, respectively, at
75 °C. The promoting effects of Fe include two aspects: (i) Partial
incorporated Fe species act as textural promoters, preventing the
formation of NiAl2O4, increasing the amount
of nickel oxides (NiO and NiFe2O4) weakly interacting
with Al2O3, and thereby generating more active
sulfides [NiS
x
and NiS(FeS)] after sulfidation,
and (ii) Fe species in a NiS(FeS) phase serving as electron donors
supply electron density to the intimately contacted NiS species and
weaken the Ni–S bonds, promoting the formation of a NiS(FeS)
phase with superior activity.
The poisoning of sulfur oxides and alkali metals emitted from diesel exhaust to active sites of copper ion-exchanged chabazite (Cu-CHA) catalysts is still present and remains a formidable challenge in practical application. Herein, a bifunctional core−shell structural Cu-SSZ-13@Ce 0.75 Zr 0.25 O 2 (Cu-SSZ-13@CZO) catalyst was designed and fabricated via a hydrothermally induced self-assembly protocol, and the catalytic activity of Cu-SSZ-13@ CZO for selective catalytic reduction (SCR) of nitrogen oxides (NO x ) with ammonia was systematically investigated. It unveils that Cu-SSZ-13@CZO features Cu-SSZ-13 as the core and dispersed CZO as the shell and that the CZO shell could not only serve as a sacrificial site protecting the Cu-SSZ-13 active core from SO 2 poisoning by the formation of Ce 2 (SO 4 ) 3 , which could further act as adsorption sites capturing the K + through the strong interaction between K + and cerium sulfate, but also render additional Brønsted acid sites functioning as sacrificial sites to trap K + , thereafter inhibiting the adsorption of K + directly on active Cu species in the Cu-SSZ-13 core. As a result, the as-constructed Cu-SSZ-13@ CZO catalyst, therefore, exhibits perceptibly enhanced coresistance to sulfur and potassium ion poisoning with almost 100% NO x conversion in the temperature window of 275−475 °C as compared to 350−450 °C on pristine Cu-SSZ-13. The finding here may contribute to the fundamental understanding of the coresistance to sulfur oxides and alkali metal poison and thereafter inspire the advancement of a highly efficient NH 3 -SCR catalyst in the future.
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